Abstract
Trifluoperazine, a knowm calmodulin antagonist, belongs to a class of phenothiazine compounds that have multiple sites of action in mycobacteria including lipid synthesis, DNA processes, protein synthesis and respiration. The objective of this study is to evaluate the potential of TFP to be used as a lead molecule for development of novel TB drugs by showing its efficacy on multiple drug resistant (MDR) Mycobacterium tuberculosis (M.tb) and non-replicating dormant M.tb. Wild type and MDR M.tb were treated with TFP under different growth conditions of stress like low pH, starvation, presence of nitric oxide and in THP-1 infection model. Perturbation in growth kinetics of bacilli at different concentrations of TFP was checked to determine the MIC of TFP for active as well as dormant bacilli. Results show that TFP is able to significantly reduce the actively replicating as well as non-replicating bacillary load. It has also shown inhibitory effect on the growth of MDR M.tb. TFP has shown enhanced activity against intracellular bacilli, presumably because phenothiazines are known to get accumulated in macrophages. This concentration was, otherwise, found to be non-toxic to macrophage in vitro. Our results show that TFP has the potential to be an effective killer of both actively growing and non-replicating bacilli including MDR TB. Further evaluation and in vivo studies with Trifluoperazine can finally help us know the feasibility of this compound to be used as either a lead compound for development of new TB drugs or as an adjunct in the current TB chemotherapy.
Highlights
M. tuberculosis has been significantly contributing to the worldwide human infectious disease burden since long
Bacterial Strains and Culture Conditions To prepare bacterial stocks, Mycobacterium tuberculosis (H37Rv), M.tbJAL2287 and M.tb1934 were grown to logarithmic phase (OD600,0.6) in Middlebrook 7H9 broth supplemented with 10% albumin dextrose complex (ADC); 0.5% glycerol and 0.02% Tween 80 were added to the media
Many groups have reported the Minimum Inhibitory Concentration (MIC) of various phenothiazines against mycobacteria in the range of 4–32 mg/ml [19]
Summary
M. tuberculosis has been significantly contributing to the worldwide human infectious disease burden since long. The global TB crisis is further convoluted by the presence of MDRand XDR-TB, being resistant to current antibiotics and hard to treat. It is a known fact that TB therapy has remained unchanged for nearly four decades [1]. The existence of dormant TB in 90% of the TB affected individuals, poses a major hindrance in eradication of this dreadful disease. A number of promising new classes of compounds are currently in pipeline at various stages of discovery and clinical development [2]. An ideal therapy should consist of drugs that are active against the drug resistant varieties of M.tb they as well as can effectively target the sleeping bacilli lying within tubercular lesions
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