JAC Advance Access originally published online on April 2, 2007
Journal of Antimicrobial Chemotherapy 2007 59(6):1271-1279; doi:10.1093/jac/dkm071
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Special section: Efflux |
Reversal of resistance in microorganisms by help of non-antibiotics
1 International Non-Antibiotic Research Group, Department of Research and Department of Microbiology, University of Southern Denmark, Sønderborg, Denmark 2 Department of Microbiology, University of Southern Denmark, Odense, Denmark 3 Chemical Laboratory II, University of Copenhagen, Copenhagen, Denmark 4 Department of Chemistry and Biochemistry, California State University, Los Angeles, CA, USA
* Corresponding author. Tel: +45-74182876; Fax: +45-74182743; E-mail: malthe{at}dadlnet.dk
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Abstract |
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 Top Abstract 1. Introduction2. Experimental3. Results and discussion4. Targets and tissues5. Putative non-antibiotic...6. Summary and conclusionsTransparency declarationsReferences |
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Intracellular efflux pumps have been largely the research focus in multidrug-resistant (MDR) Gram-positive and Gram-negative microorganisms and parasites including cancers. However, drug efflux mechanisms other than pumps per se have been observed, supported by the effects of isomeric, non-antibiotic depressant (DPR), phenothiazines and thixenes, and antidepressant (ADPR) phenylpiperidine neurotropic drugs, alone or in combination with classical antimicrobials on MDR Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Streptococcus pyogenes and Streptococcus pneumoniae. Of the non-antibiotics we investigated, the DPR L-thioridazine, trans-clopenthixol and isomers of phenylpiperidines NNC 20-4962 (isomer of femoxetine) and NNC 20-7052 (isomer of paroxetine) were potent antimicrobials with the least neurotropic activity, pointing to a possible general isomeric structure–activity relationship. These compounds may be regarded as new efflux inhibitors. Moreover, these isomers have considerably reduced, in some cases absent, neurotropism and reduced mammalian toxicity. This may alleviate concerns about adverse effects and therapeutic safety for infected patients in life-threatening situations where the non-antibiotic dosage would be in the lower, non-chronic dosage ranges generally prescribed for individuals with mild mental health problems. The results point to the prokaryotic and eukaryotic microorganisms' phospholipid/protein domain involvement of the cationic, amphiphilic, non-antibiotic DPR and ADPR, with the phospholipids being the initial sites attracting and concentrating the neurotropes to induce a form of suspended animation, followed by gross changes of cell wall and membrane structure, and thereby potentiating their destructive or immobilizing effects on various as yet only hinted at resistance and efflux mechanisms. Combination of appropriate isomeric non-antibiotic DPR and ADPR of low neurotropism and toxicity with conventional and classical antimicrobials promises early, new therapeutic strategies salutary against microbial resistance, resistance development, pathogenicity and virulence.
Keywords: depressants , antidepressants , drug efflux , multidrug resistance
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1. Introduction |
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TopAbstract1. Introduction2. Experimental3. Results and discussion4. Targets and tissues5. Putative non-antibiotic...6. Summary and conclusionsTransparency declarationsReferences |
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Genetic manipulation supports the current belief that the rise of resistance to classical drugs,1 including multidrug resistance (MDR), generated by deleterious prokaryotes and malignant eukaryotes, involves efflux pumps.2 Danø3 pioneered the concept that Ehrlich tumour cells pumped out daunomycin and that the toxic Vinca plant extract inhibited the efflux system competitively. Subsequently, the presence of efflux pumps, Tet and NorA, was demonstrated in the prokaryotes Staphylococcus aureus and Escherichia coli.4 Inhibitors of passive ion effluxes of eukaryotic cells, e.g. amphiphilic anaesthetics, barbiturates and the antimalarial chloroquine,5,6 were found by various research groups to apply to prokaryotes.6,7 Thus, the multifaceted nature of efflux mechanisms8 may preclude simple pharmacological targeting.
The combining of antibiotic drugs for disease treatment is failing, the trend worsening worldwide,7,9 but the combination of antibiotic drugs with non-antibiotics, such as the neuroleptics and their isomers, appears promising. Non-antibiotics are classed as therapeutic agents not originally designed for antibiotic or chemotherapeutic purposes, but subsequently exhibited such properties. Among the non-antibiotics are the depressant (DPR) and antidepressant (ADPR) neurotropes, antihistamines with neurotropic properties, to name a few. These, and other kinds mentioned in this review, share physico-chemical traits, particularly cationic amphiphilicity, surfaction and membrane activity.10,11
Our searches have been directed especially to serious MDR microorganisms in extra- and intracellular infections difficult to treat today. In view of the antibiotic efficacy of non-antibiotics, we wish: (i) to identify in more detail their properties, particularly those of neurotropes and their isomers, as antimicrobial resistance inhibitors and modifiers; (ii) to suggest the use of selected non-antibiotics in the treatment of specific infections in those parts of the body open to the necessary accumulation of the drug; and (iii) to draw attention to the neurotropic non-antibiotics as potentiators or ‘helper’ compounds in combination with conventional antibiotics for infectious disease treatments, and possible adverse effects that may be encountered.
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2. Experimental |
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TopAbstract1. Introduction2. Experimental3. Results and discussion4. Targets and tissues5. Putative non-antibiotic...6. Summary and conclusionsTransparency declarationsReferences |
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Standard diagnostic tests shown in the legends of the following tables yielded examples of growth inhibition and resistance reversal effects of non-antibiotics and their combination with antibiotics on serious intra- and extracellular infectious Gram-positive bacteria. The new results supplement and confirm previously published data essential for discussion.
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3. Results and discussion |
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TopAbstract1. Introduction2. Experimental3. Results and discussion4. Targets and tissues5. Putative non-antibiotic...6. Summary and conclusionsTransparency declarationsReferences |
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3.1. Gram-positive bacteria
The MICs of a panel of phenothiazines in Table 1 show that highest activity resides in the isomers and racemate of thioridazine. The growth-inhibiting concentrations generally may be efficacious in specific infected human organs such as the phospholipid-rich, lungs, skin and the urinary tract.12 In 2002, Ordway et al.13 demonstrated that thioridazine inhibited intracellular growth of S. aureus in human macrophages at a concentration of 0.1 mg/L. The MIC value in that study was 18 mg/L corresponding to our value in Table 1. The antimicrobial actions of the neurotropic non-antibiotics are of special interest because these drugs accumulate mainly on the cellular membrane and to some extent in the cytosol. However, intracellular localization plays an important clinical role in infections of several S. aureus, Streptococcus pyogenes and Staphylococcus epidermidis disorders and by Mycobacterium tuberculosis.
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Tables 2 and 3 present resistance reversal effects for methicillin-resistant S. aureus tested with oxacillin and erythromycin-resistant S. pyogenes. Note that resistance reversal by the phenothiazines in combination with the antibiotics is at concentrations much less than required for growth inhibition by these compounds. The stereoisomeric phenothiazine derivatives inhibit growth of S. aureus and other Gram-positive bacteria directly, these non-antibiotics being characterized by activity reversing microbial resistance.14–18
Tables 4 and 5 show that efflux mechanisms of Gram-positive bacteria are influenced directly by the ADPR phenylpiperidines characterized as serotonin-re-uptake inhibitors in common with similar ADPR:10,19,20 NNC 20-4963 (D-trans or D-E), femoxetine; NNC 20-4962 (L-trans or L-E), femoxetine analogue; NNC 20-7051 (L-trans or L-E), paroxetine and NNC 20-7052 (D-trans), paroxetine analogue. Of this group, D-E-femoxetine, D-E-paroxetine and L-E-paroxetine are the most effective efflux inhibitors on strain S. aureus SA-1199B, a strong NorA overproducer. Kaatz et al.21 demonstrated similar activity for a series of DPR phenothiazines and thioxanthenes that inhibit the NorA-mediated fluoroquinolone efflux of S. aureus.
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Tables 6–8 show the influence of thioridazine and prochlorperazine on vancomycin- and ampicillin-resistant Enterococcus faecalis. Thioridazine is the most effective. In combinations of the antibiotics with these phenothiazines, the MICs are reduced significantly for the individual drugs, in some cases dramatically, depending on the E. faecalis strain.
Phenothiazines reduce efflux-mediated fluoroquinolone resistance in vitro,21 and the same derivatives reduce oxacillin resistance in vitro and in an intracellular model, with oxacillin resistance involving target alteration.22 Thus, the phenothiazine effect at present must be viewed as multifaceted because they block NorA-related efflux21 and non-NorA-related efflux in a concentration-dependent manner. Hence, phenothiazines interact with bacterial efflux mechanisms and/or mechanisms not yet fully identified as in the case of methicillin resistance.
The multifaceted resistance-modifying behaviour of membrane-active, stereoisomeric DPR and ADPR and some other non-antibiotics with respect to Gram-positive bacteria has been extended to Gram-negative and mycobacterial microorganisms.
Köhler (personal communication) showed that the resistance of Pseudomonas aeruginosa to tetracycline efflux was reduced from MIC 32 to 4 mg/L by the phenothiazine fluphenazine, this drug proving as potent as Phe-Arg-naphthylamide.23 In 2002, Chen et al.24 showed that nizatidine, an H2-receptor antagonist used as an anti-ulcerative with anticholinergic effects at overdose,19 counteracted Helicobacter pylori resistance to metronidazole in vitro, despite exhibiting no growth-inhibiting effect. This agrees with earlier findings that drugs capable of reversing antibiotic resistance do not necessarily inhibit growth. Nizatidine also inhibited fumarate reductase dose-dependently like metronidazole but unlike the anti-ulcerative omeprazole which is ineffective against that enzyme.24 The latter drug's effect may be due to a proton pump of H. pylori.25 Omeprazole inhibits the H+/K+-ATPase enzyme system at the secretory surface of gastric parietal cells.10 Note that in large doses, it induces sedation and hypothermia like the antihistaminic, isomeric phenothiazine promethazine.10,19 Another similarity to the phenothiazines is that omeprazole alters the cell wall of H. pylori (Figure 1). Gross changes of cell walls and membranes of pathogenic microorganisms attend exposure to non-antibiotics, almost invariably mimicking antibiotics;26,27 in S. aureus, chlorpromazine produces frayed cell walls, thickened cross-walls and bizarre progeny cells, some devoid of cytoplasmic content. Chlorpromazine causes significant elongation of E. coli.26 salmonellae, resistant to chlorpromazine, lose the ‘rough’ texture of their cell walls.26 Of interest is that like other agents that elevate gastric pH, omeprazole produces a significant increase in intragastric concentrations of viable bacteria, but the pattern of the species remains unchanged from that found in saliva.10 Electron micrographs of E. faecalis cells growing in vancomycin and L-thioridazine show abortive cell division planes and elongation.18
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In 2002, Tegos et al.28 showed that Rhein, an anthraquinone plant extract, was almost ineffective against P. aeruginosa, MIC >500 mg/L, but in combination with efflux inhibitors, it reduced the MIC to 5 mg/L. Like phenothiazines and thioxanthenes, Rhein has a fused tricyclic aromatic system.
The alarming rise of tuberculosis, particularly in HIV and AIDS epidemics since the 1980s, is a result of the emergence of M. tuberculosis strains exhibiting MDR to treatment with classical drugs even in combinations. In 1985, classical antimicrobials and the phenothiazines were re-assessed against resistant and susceptible typical and atypical mycobacteria, the latter drugs and the thioxanthenes being scrutinized in depth.29 From 1992 onwards, Crowle et al.30 demonstrated clearly that non-toxic concentrations of phenothiazines in the lung achieved complete elimination of M. tuberculosis from human macrophages, confirming previous in vivo results.31 As early as 1969, Manion et al.32 described the delay of resistance development of mycobacteria to isoniazid by phenothiazines and their analogue quinacrine. At that time, little was known about efflux inhibition or direct inhibition of membrane sensors (quorum sensing) by these membrane-active amphiphiles. Intensive thioridazine investigations by Amaral et al.7,33 and others34 have confirmed the importance of the DPR phenothiazines against susceptible and MDR M. tuberculosis and also MDR S. aureus in vitro.
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4. Targets and tissues |
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TopAbstract1. Introduction2. Experimental3. Results and discussion4. Targets and tissues5. Putative non-antibiotic...6. Summary and conclusionsTransparency declarationsReferences |
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Neurotropes act on malign prokaryotes and eukaryotes, including cancers, as if they had ‘nervous’ systems. One only has to reflect on the biologically similar actions of these organisms and nervous systems with respect to signalling, chemotaxis, motility and phototropism.15,35 The distinction then blurs between these different classes of organisms in terms of possible rejection of unwanted molecules. Other similarities obtrude. Saier36 reviews in detail the unifying concepts of solute permeation of prokaryotes and eukaryotes, pointing to the evolution-based similarities, and also the differences in the nature of specific substrate-binding interactions, gating and energy-coupling mechanisms when these are present.
An important feature of treatment failure is ascribed to P-glycoprotein (PGP)-mediated cellular MDR identified in the early 1970s, reviewed by Higgins,37 and characterized by PGP increase and reversal of phenotype resistance by a variety of drugs.38 PGP is a member of the ABC transporters that feature a variety of bacterial efflux transporters as well as the P. falciparum resistance mechanism. Saier36 points out that PGP is an ATP-dependent pump that functions to reduce the cytoplasmic levels of cytotoxic drugs. Consequently, the parallel between bacterial permeases and the mammalian MDR transporters extends beyond the structural to the functional level. In addition to the MDR permeases of mammals, other proteins from eukaryotic cells tend to be homologous with bacterial-binding protein-dependent systems. These systems include the protein defective in cystic fibrosis patients, which is genetically linked to defective Cl– transport.36 Another is the CQR protein responsible for chloroquine resistance in the malaria parasite. Still another is an export protein of yeast that mediates the secretion of the mating pheromone from the cell.36 Further similarities are the responses of these organisms to the cationic, amphiphilic DPR and ADPR non-antibiotics,15,39,40 which share physico-chemical traits, structural features, lipophilicity, surfactant (micelle-forming) and microbuffering capacity.11
Although the developing resistance and efflux processes of microorganisms against drugs involve proteins, one recalls that very few water-soluble proteins and lipoproteins in their native state contain binding sites for amphiphilic ligands, among the exceptions being serum albumin that interacts with many amphiphiles but most strongly with those containing normal alkyl chains and anionic head groups.41 The interaction of only proteins with molecules unwanted by a biological cell as an entity is an untenable view.
4.2. Phospholipid and neurotropes
Some workers contend that the cationic DPR and ADPR neurotropes act largely in the biological membrane rather than the cytosol.11 Cationic amphiphilic neurotrope accumulation at the membrane and attendant activity are characterized by a suspended-animation effect,11 sometimes culminating in membrane disruption (Figure 1 and Section 3.2), and/or secretory (efflux) process modification, as our results and those of others have shown repeatedly. Surfactant neurotropes, DPR and ADPR alike, share similar tissue/plasma concentration ratios increasing in order of about 10–50 for muscle, brain and fat, 100 or more for lung, liver, kidney and some other organs rich in phospholipid with negatively charged head groups,42 and of course the nervous system. For example, the DPR phenothiazines can reach concentrations in the lung in excess of the perfused dose,43 matched by nearly quantitative extraction of the ADPR imipramine.42 Pulmonary total lipid is increased at the alveolar surface by imipramine and the DPR chlorpromazine43; lung fluid is also increased by 
2.5%.43 Increased phosphatidylcholine metabolism has been noted in the brain.43 Phospholipid increases have also been observed in some other tissues of mice, rats and dogs after chronic administration of the ADPR fluoxetine, an effect shared by many cationic amphiphilic drugs including fenfluramine, a chiral anorexic; ranitidine, an isomeric anti-ulcerative used against H. pylori and the tricyclic phenothiazine analogue imipramine.10 One should therefore expect that a spectrum of activities, not as yet fully elucidated, is involved in the interplay between phospholipid and intrinsic as well as cytosolic proteins, and other components of biological cells insulted with unwanted compounds, such as the neurotropes.
4.3. Structural features of non-antibiotics
Molecules that affect the membrane (or cell walls) may generate sufficient conditions for growth inhibition or trigger secretion (efflux) modification processes of organs or microorganisms. Prime candidates for such effects are the neurotropes with well-known structures.19
The neurotropes in our study have generally a so-called ‘phenalkylamine’ pattern (PAP) signifying an aromatic or pseudo-aromatic system several carbon atoms distant from a quaternizable nitrogen atom.11 DPR phenothiazines and thioxanthenes are characterized by a fused tricyclic aromatic system with a rigid central pseudo-aromatic bridge from which depends a propylamine side-chain. In phenothiazines, the side-chain is attached to the bridge N and is capable of dextro (D) or laevo (L) chirality depending on chain substituents, e.g. thioridazine. In thioxanthenes, the bridge N of the phenothiazines is replaced by a carbon atom double bonded to the C atom of the side-chain, conferring trans (E) and cis (Z) configurations on these molecules. In ADPR imipramine analogues of phenothiazines, the S atom is replaced by a flexible ethyl group conferring upon these molecules a bridge that allows the aromatic rings to twist with respect to each other, albeit somewhat hindered. Ring substituents direct quantitative characteristics, and side-chain configurations direct qualitative properties of these compounds.11 Twistability of aromatic rings, often quite free, is also present in the ADPR phenylpiperidines that can have four types of isomer combinations: D-E, L-E, D-Z and L-Z.19 PAP compounds with two carbons in the side-chain tend to have pronounced antihistaminic properties, e.g. enantiomeric promethazine.11,19
In addition to the isomer types mentioned earlier, DPR perazine phenothiazines and thioxanthenes possess a quaternizable piperazinyl side-chain terminus, e.g. prochlorperazine and trifluoperazine, yielding pH-dependent boat/chair conformations.44 The piperazinyl bases and the dihydrochlorides have the chair form and the monohydrochlorides the boat form.11 Their conformations may be so influenced by localized pH regions of cell and microbe membranes. Hendrich et al.45 have observed that trifluoperazine, differing from prochlorperazine only in its 2'-substituent, induced domain formation in zwitterionic phosphatidylcholines but not in phosphatidylglycerol bilayers, ascribed to the dissimilar interactions of trifluoperazine's two protonated forms with phosphatidylcholines. Caetano and Tabak46 have also noted such trifluoperazine dual behaviour on a variety of synthetic compound micelles. Plasmodia increase acidity of erythrocytes by 0.4 U, altering them to adhere to capillary walls.47 Chlorpromazine, as a function of increasing concentration, as in its micelles acting as microbuffers, drops pH by as much as 1.2 U,48 similar to other phenothiazines, e.g. prochlorperazine, and may be a reason for its antiparasitic effect by driving the microbial environmental pH well beyond the optimum required.
Of the chiral DPR phenothiazines currently in use, the L drugs, exemplified by L-thioridazine, have reduced or absent neurotropism. When either racemates or isomers in combination with antibiotics were presented to microorganisms, they invariably lowered the MICs of the antibiotics (Tables 2, 3, 6, 7 and 8). However, L-enantiomers reversed more effectively the resistance of streptococcal strains to erythromycin.18 Moreover, L-thioridazine concentrates in human tissue more than the D form.49 L-Thioridazine is therefore clearly superior as a helper compound in conjunction with antibiotic treatments. We used S. aureus in macrophages as an intracellular model to gauge the effect of the non-antibiotics alone and combined with antibiotics. L-Thioridazine was also applied to different epithelial cell lines infected with Klebsiella pneumoniae, Salmonella typhimurium and S. pyogenes, strains chosen for high-level antibiotic resistance based on well-described efflux pumps. Preliminary results showed reduction of invasiveness of both Gram-positive and Gram-negative species.50 L-Thioridazine may well come to be regarded as a novel antireversal drug.
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E-Thiothixenes exhibit quite decreased neurotropism when compared with the Z conformers. The additional benefit is that, for example, E-clopenthixol is more antimicrobially potent than the Z isomer.15 Often the E isomers have a significantly higher LD50, e.g. E-chlorprothixene 235 mg/kg when compared with 100 mg/kg for the Z isomer for mice injected intraperitoneally.15,19
The ADPR phenylpiperidines inhibit serotonin re-uptake mechanisms.10,15,19 The racemic fluoxetine, not a phenylpiperidine but an antidepressant analogous to the L-E-phenylpiperidine, paroxetine, and L-E-femoxetine,19 also has isomers equivalent as specific and potent serotonin re-uptake inhibitors, but the L isomer is metabolized more slowly and is the predominant isomer in plasma at the steady state.10 The major metabolite, norfluoxetine, is also a potent and selective serotonin re-uptake inhibitor, the L-norfluoxetine being more potent than D-norfluoxetine.10 The ADPR femoxetine has been pressed into service as a migraine prophylactic, which unlike similar prophylactics did not influence platelet aggregation in vitro10; E-femoxetine was generally shown to be twice as effective as Z-femoxetine for growth inhibition of 20 enterobacteria.51
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5. Putative non-antibiotic therapy |
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TopAbstract1. Introduction2. Experimental3. Results and discussion4. Targets and tissues5. Putative non-antibiotic...6. Summary and conclusionsTransparency declarationsReferences |
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The following is not a polemic for non-antibiotic therapy but an attempt to lessen scruples for the use of ‘older’ drugs, specifically non-antibiotic isomers, in a new way in life-threatening situations.
Isomeric reserpine, one of the oldest sedatives, has strong antiresistant activity.20 Racemic thalidomide, introduced as a sedative in the 1960s, was teratogenic, but now finds use as a selective inhibitor of tumour necrosis factor 
, and for aphthous ulceration related to HIV infection, immunological disorders and leprosy.19 Re-introduction of ‘older’ drugs for new treatments has often met with skepticism, fuelled by the discredited belief that only a specific class of drugs applies to a specific class of disease. Even the ancient analgesic aspirin has found a new use as a mild anticoagulant prescribed for patients at risk for heart disease. It is a truism that the longer a drug is in use, even a ‘safe’ one, more side effects emerge, varying widely from individual to individual. Thus, the so-called side effects of ‘old’ drugs for new treatments may need critical re-examination.
Since the 1970s, several excellent reviews have been available that address the possible toxicity, drug interactions and genetic and interspecies differences in drug metabolism of psychotherapeutics and will not be considered here in detail.52,53 The following represents a severely truncated commentary on possible adverse side effects of neurotropes.
Keeping in mind that neither DPR nor ADPR is usually prescribed for mentally normal patients, the following statements apply to patients ordinarily under mental health management and may also apply to patients in antiretroviral therapy for HIV and HIV/AIDS.54 Prolonged therapy with antimicrobial neurotropes alone or in combination with antibiotics for psychologically normal, infected patients is not envisaged, so that toxic and other adverse effects may not obtrude. Indeed, adverse reactions, except those allergenically and/or genetically contraindicated for individuals, are likely to be no more than a nuisance.
Toxicity has been alluded to previously for Z-thiothixene. On the basis of animal studies, the neuroleptic therapeutic index (LD50/ED50) of the DPR is relatively high: thioridazine 20, chlorpromazine 200, for the more potent agents >1000 and for the ADPR imipramine, it is 5.42 The reader is referred to several excellent articles on this topic.52,53
For humans, a neurotropic minimum dose of 10 mg/day for months is usually satisfactory for the relief of mild mental health problems, considerably more for severe cases.10 A not uncommon dose of 50 mg/L for an adult human with 5 L of blood translates to a 10 mg/L plasma concentration, close to the 8–32 mg/L microbial inhibitory concentrations observed in our in vitro studies. At even the smaller subgrowth-inhibitory concentrations of appropriate neurotropes that we observed, microbes are still open to the onslaught of added antimicrobials. This is especially important because observations indicate that (i) growth inhibition is not necessarily dependent on the influence of efflux pumps and (ii) antimicrobials require different killing concentrations for free bacteria versus those adherent or in microcolonies.55 For schizophrenic patients responding to treatment who have a 50 nM equilibrium plasma concentration of a neurotrope, say chlorpromazine, this yields an approximate 10–5 M concentration (in the critical micelle range) on membranes, based on a water/lipid distribution coefficient of about 2000.11 However, in view of the fact that chlorpromazine and related compounds tend to accumulate ultimately at a limited number of cellular sites, and at those sites further concentrate by micelle formation, localized concentration in relevant organ membranes and microorganisms would likely be increased by several orders of magnitude,11,48 depending of course on the drug's half-life. Similar calculations apply to all the DPR and ADPR in our study.
Recently, phenothiazines, as possible resistance modifiers, were shown to co-micellize a wide variety of poorly soluble antifungal, antibacterial and anticancer drugs.56 This feature also promises neurotrope/antibiotic efficacy for antimicrobe and anticancer treatment. Taking into account the combination of the non-antibiotic helper compounds, especially the appropriate isomers, with classical antibiotics, promises early introduction of prospective new therapies7,15,18,26 and may allow guidance for treatment of seriously ill patients, particularly those requiring intensive care. Isomeric non-antibiotic drugs combined with classical antibiotics therefore offer intriguing possibilities.
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6. Summary and conclusions |
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TopAbstract1. Introduction2. Experimental3. Results and discussion4. Targets and tissues5. Putative non-antibiotic...6. Summary and conclusionsTransparency declarationsReferences |
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Gram-positive and Gram-negative bacteria and parasites resistant to classical antibiotic treatment are on the rise worldwide, some alarmingly so. Much of the current research has focused myopically on intracellular efflux pumps. However, microorganisms including cancers that have efflux pump mechanisms in common also have blocking and efflux mechanisms different from efflux pumps per se, as scattered observations and our results have implied for the non-antibiotic depressants and antidepressants alone and in their combination with classical antibiotics. Our work, confirming other reports, indicated that the non-antibiotics accumulating at phospholipid domains containing intrinsic proteins act by means of a suspended animation effect followed by membrane disruption. Thus, they may potentiate as helper compounds destructive or immobilizing effects on resistance mechanisms and efflux-mediating enzymes, as yet poorly understood. They act alone or with antibiotics, often synergistically, on a considerable range of microorganisms. The non-antibiotics we investigated have isomers with quite different, well-established neurotropic characteristics and toxicities. This suggested that isomers with diminished neurotropic properties and toxicity could be beneficial in infection therapies. Of course, each case requires critical examination prior to a selected therapy. Pure isomers may be imperative for research and may be appropriate in putative medicinal practice. Examples with the least neurotropic activity in each group we examined were L-thioridazine, E-clopenthixol and the isomers of phenylpiperidines, NNC 20-4963 femoxetine and NNC 20-7051, 20-7052 PRT. The above isomers, appropriately chosen, alone or in combination with classical antibiotics should receive consideration as low-dose candidates for antimicrobial treatment, especially in life-threatening situations marked by a poor response to classical antimicrobials. We surveyed briefly possible adverse effects of low-dose neurotropic non-antibiotics for mentally normal patients and suggested that, in appropriate cases, these may present no more than a nuisance. The use of relevant neurotropic isomers with classical antibiotics may revitalize the latter in the protracted battle against MDR microorganisms. This approach has exciting prospects and may lead to new concepts of infectious containment while shedding light on resistance and efflux mechanisms. Our observations that growth inhibition is not necessarily dependent on efflux pumps may lead to a more integrated view of various resistance mechanisms exhibited by microbes and cancers. Finally, isomeric neurotropes as research tools have value as vital as conventional probes and dyes in molecular biology studies.
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Transparency declarations |
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TopAbstract1. Introduction2. Experimental3. Results and discussion4. Targets and tissues5. Putative non-antibiotic...6. Summary and conclusionsTransparency declarationsReferences |
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All authors confirm that there are no conflicting financial interests.
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Acknowledgements |
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We are grateful for helpful discussions with members of the EU COST Action B16.
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References |
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1 Heinemann J. Do antibiotics maintain antibiotic resistance? Drug Discov Today (2000) 5:195–204.[CrossRef][Web of Science][Medline]
2
Levy SB. Active efflux mechanisms for antimicrobial resistance. Antimicrob Agents Chemother (1992) 36:695–703.
3 Danø K. Cross resistance between vinca alkaloids and anthracyclines in Ehrlich ascites tumor in vivo. Cancer Chemother Rep (1972) 56:701–8.[Web of Science][Medline]
4 Nikaido H. Preventing drug access to targets: cell surface permeability barriers and active efflux in bacteria. Semin Cell Dev Biol (2001) 12:215–23.[CrossRef][Web of Science][Medline]
5 Clausen T, Harving H, Dahl-Hansen AB. The relationship between the transport of glucose and cations across cell membranes in isolated tissues. 8. The effect of membrane stabilizers on the transport of K+, Na+ and glucose in muscle, adipocytes and erythrocytes. Biochim Biophys Acta (1973) 298:393–411.[Medline]
6 Kristiansen JE. Experiments to illustrate the effect of chlorpromazine on the permeability of the bacterial cell wall. Acta Pathol Microbiol Scand [B] (1979) 87:317–9.[Web of Science][Medline]
7 Amaral L, Viveiros M, Kristiansen JE. "Non-Antibiotics": alternative therapy for the management of MDRTB and MRSA in economically disadvantaged countries. Curr Drug Targets (2006) 7:887–91.[CrossRef][Web of Science][Medline]
8 Kristiansen JE, Mortensen I, Nissen B. Membrane stabilizers inhibit potassium efflux from Staphylococcus aureus strain No. U2275. Biochim Biophys Acta (1982) 685:379–82.[Medline]
9
Van Bambeke F, Glupczynski Y, Plesiat P, et al. Antibiotic efflux pumps in prokaryotic cells: occurrence, impact on resistance and strategies for the future of antimicrobial therapy. J Antimicrob Chemother (2003) 51:1055–65.
10 Physicians Desk Reference. (1996) 11th. Montvale, New Jersey: Medical Economics.
11 Dea PK, Keyzer H, Maurer JS B. Structure-activity relationships of phenothiazines and 1,4-benzophenothiazines. In: Phenothiazines and 1,4-Benzothiazines—RR Gupta, ed. (1988) New York: Elsevier. 587–625.
12 Forrest FM, Forrest IS, Roizin L. Clinical, biochemical and post mortem studies on a patient treated with chlorpromazine. Agressologie (1963) 4:259–65.[Medline]
13
Ordway D, Viveiros M, Leandro C, et al. Clinical concentrations of thioridazine kill intracellular multidrug-resistant Mycobacterium tuberculosis. Antimicrob Agents Chemother (2003) 47:917–22.
14 Kristiansen JE. Chlorpromazine non-antibiotics with antimicrobial activity-new insight in managing resistance? Curr Opin Invest Drugs (1993) 2:587–91.
15 Kristiansen JE. The antimicrobial activity of psychotropic drugs and stereo-isomeric analogues. In: Dan Med Bull (1990) 37. Denmark: University of Copenhagen. 165–82. DrSci Thesis.[Web of Science][Medline]
16 Hendricks O, Molnár A, Butterworth TS, et al. In vitro activity of phenothiazine derivatives in Enterococcus faecalis and Enterococcus faecium. Basic Clin Pharmacol Toxicol (2005) 96:33–6.[CrossRef][Web of Science][Medline]
17 Hendricks O, Butterworth TS, Kristiansen JE. The in vitro antimicrobial effect of non-antibiotics and putative inhibitors of efflux pumps on Pseudomonas aeruginosa and Staphylococcus aureus. Int J Antimicrob Agents (2003) 22:262–64.[CrossRef][Web of Science][Medline]
18 Hendricks O. Antimicrobial effects of selected non-antibiotics on sensitivity and invasion of Gram-positive bacteria. (2007) January. University of Southern Denmark. PhD Thesis.
19 Budavari S, ed. The Merck Index (1996) 12th Edition. Whitehouse Station, New Jersey: Merck and Co.
20 Kaatz GW, Moudgal VV, Seo SM, et al. Phenylpiperidine selective serotonin reuptake inhibitors interfere with multidrug efflux pump activity in Staphylococcus aureus. Int J Antimicrob Agents (2003) 22:254–61.[CrossRef][Web of Science][Medline]
21 Kaatz GW, Moudgal VV, Seo SM, et al. Phenothiazines and thioxanthenes inhibit multidrug efflux pump activity in Staphylococcus aureus. Antimicrob Agents Chemother (2002) 47:719–26.[CrossRef][Web of Science]
22 Kristiansen MM, Leandro C, Ordway D, et al. Phenothiazines alter resistance methicillin-resistant strains of Staphylococcus aureus (MRSA) to oxacillin in vitro. Int J Antimicrob Agents (2003) 22:250–3.[CrossRef][Web of Science][Medline]
23 Lomovskaya O, Watkins WJ. Efflux pumps: their role in antibacterial drug discovery. Curr Med Chem (2001) 8:1699–711.[Web of Science][Medline]
24 Chen M, Jensen B, Zhai L, et al. Nizatidine and omeprazole enhance the effect of metronidazole in Helicobacter pylori in vitro. Int J Antimicrob Agents (2002) 19:195–200.[CrossRef][Web of Science][Medline]
25 Sadijan M, Bettaney KE, Szakonyi G, et al. Active membrane transport and receptor proteins from bacteria. Biochem Soc Trans (2005) 3:867–72.
26 Kristiansen JE, Amaral L. The potential management of resistant infections with non-antibiotics. J Antimicrob Chemother (1995) 40:319–27.[CrossRef]
27 Gemmel GG, Lorian V. Effects of low antibiotic concentrations on bacteria: effect on ultrastructure. Their virulence and susceptibility to immuno-defences. In: Antibiotics in Laboratory Medicine—Lorian V, ed. (1991) Baltimore, Maryland: Williams and Wilkins. 397–452.
28 Tegos G, Stermitz FR, Lomovskaya O, et al. Multidrug pump inhibitors uncover the remarkable activity of plant antimicrobials. Antimicrob Agents Chemother (2002) 46:313–41.
29 Kristiansen JE, Vergmann B. The antibacterial effect of selected phenothiazines and thioxanthenes on slow-growing mycobacteria. Acta Pathol Microbiol Immunol Scand [B] (1986) 94:393–8.[Web of Science][Medline]
30 Crowle AJ, Douvas SG, May MH. Chlorpromazine: a drug potentially useful for treating mycobacterial infections. Chemotherapy (1992) 38:410–9.[Web of Science][Medline]
31 Geiger H, Finkelstein BA. Largactil in the treatment of tuberculosis. Schweiz Med Wochenschr (1954) 84:1063–4.[Web of Science][Medline]
32 Manion RE, Bradley SG, Hall WH. Retardation of the emergence of isoniazid-resistant mycobacteria by phenothiazines and quinacrine. Proc Soc Exp Biol Med (1969) 130:206–9.[CrossRef][Medline]
33 Amaral L, Viveiros M, Molnar J. Antimicrobial activity of phenothiazines. Vivo (2004) 18:725–31.
34
Kristiansen MM, Leandro C, Ordway D, et al. Thioridazine reduces resistance of methicillin-resistant Staphylococcus aureus by inhibiting a reserpine-sensitive efflux pump. In Vivo (2006) 20:361–6.
35 Pechère J-C. Emotion, intelligence and ethics in bacteria. Abstracts of the Seventh European Congress of Chemotherapy and Infection, 2005: Florence, Italy. Abstract EL 1, p. 21.
36 Saier MH. Mechanisms of carbohydrate transport in bacteria and comparison with those in eukaryotes. In: The Structure of Biological Membranes—Yeagle R, ed. (1992) Boca Raton, Florida: CRC Press. 833–91.
37 Higgins CF. ABC transporters: from microorganisms to man. Annu Rev Cell Biol (1992) 8:67–113.[CrossRef][Web of Science][Medline]
38 Schmitt L, Tampe R. Structure and mechanisms of ABC transporters. Curr Opin Struct Biol (2002) 12:754–60.[CrossRef][Web of Science][Medline]
39 Motohashi N. Antitumor activities of phenothiazines. In: Phenothiazines and 1,4-Benzothiazines—Gupta RR, ed. (1988) New York: Elsevier. 705–74.
40 Allen MJ. The electrochemical aspects of some biochemical systems. The anomalous behaviour of Escherichia coli with mixed substrates. X. Electrochim Acta (1967) 12:563–8.[CrossRef][Web of Science]
41 Reynolds JA. Interactions between proteins and amphiphiles. In: Lipid-Protein Interactions—Jost PC, Griffith OH, eds. (1982) New York: Wiley. 193–224.
42 Bickel MH. Imipramine series. In: Psychotherapeutic Drugs, Part II—Usdin E, Forrest IS, eds. (1977) New York: Marcel Dekker. 1131–72.
43 Keyzer H, Kim HK, Varkey C. An animal lung experiment involving thiazines and structurally related compounds. In: Thiazines and Structurally Related Compounds—Keyzer H exec, ed. (1992) Malabar: Krieger. 213–8. Florida.
44 Duncan Q, Keyzer H, Young KL. [Di]piperazinyl phenothiazine amphiphiles. In: Biological and Chemical Aspects of Thiazines and Analogs—Barbe J, Keyzer H, Soyfer JC, eds. (1995) San Gabriel: Enlight Assoc. 131–9.
45 Hendrich AB, Wesolowska O, Michalak K. Trifluoperazine induces domains formation in zwitterionic phosphatidylcholine but not in charged phosphatidylglycerol bilayers. Biochim Biophys Acta (2001) 10:414–25.
46 Caetano W, Tabak M. Interaction of chlorpromazine and trifluoperazine with ionic micelles: electronic absorption spectroscopy studies. Spectrochim Acta Part A (1999) 55:2513–28.[CrossRef]
47 Voet D, Voet JG. Biochemistry (1995) New York: Wiley.
48 Gutmann F, Johnson C, Keyzer H, et al. Charge Transfer Complexes in Biological Systems (1997) New York: Marcel Dekker.
49 Jortani SA, Valentour JC, Poklis A. Thioridazine enantiomers in human tissues. Forensic Sci Int (1994) 64:165–70.[CrossRef][Web of Science][Medline]
50 Hendricks O, Sahly H, Podschun R, et al. Anti-microbial effects of nonantibiotics: influence of phenothiazine-derivatives on bacterial invasion of epithelial cells. (2004) Proceedings of the European Conference of Chemotherapeutics. Paris, France. Poster 613.
51 Kristiansen JE, Mortensen I, Gaarslev K. The antibiotic effect of the anti-depressive drug femoxetine and its stereo-isomeric analogs on diarrhoea producing enterobacteriaceae. Acta Pathol Microbiol Immunol Scand [B] (1986) 94:103–6.[Web of Science][Medline]
52 Usdin E, Forrest IS. Psychotherapeutic Drugs, Part I (1977) New York: Marcel Dekker.
53 Miyata T, Takahama K, Irie T, et al. Toxicological properties of phenothiazines. In: Phenothiazines and 1,4-Benzothiazines—Gupta RR, ed. (1988) New York: Elsevier. 665–703.
54 Treismana GJ, Kaplina AI. Depression, cognitive impairment, neurologic and psychiatric complications in HIV and antiretroviral drugs. AIDS (2002) 16:1201–15.[CrossRef][Web of Science][Medline]
55 Naylor PT, Jennings R, Myrvik Q, et al. Antibiotic sensitivity of biomaterial adherent Staphylococcus epidermidis. Orthop Trans (1988) 12:524–5.
56 Flores VC, Keyzer H, Kristiansen JE. Micellar thiazine interaction with water-insoluble medicinals. Abstracts of the Seventh European Conference on Chemotherapy and Infection, 2005: Florence, Italy. Abstract S16.5, p. 97.
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