Mode of action of pyrazinamide: disruption of Mycobacterium tuberculosis membrane transport and energetics by pyrazinoic acid

Abstract

Pyrazinamide is an important sterilizing drug that shortens tuberculosis (TB) therapy. However, the mechanism of action of pyrazinamide is poorly understood because of its unusual properties. Here we show that pyrazinoic acid, the active moiety of pyrazinamide, disrupted membrane energetics and inhibited membrane transport function in Mycobacterium tuberculosis. The preferential activity of pyrazinamide against old non-replicating bacilli correlated with their low membrane potential and the disruption of membrane potential by pyrazinoic acid and acid pH. Inhibitors of membrane energetics increased the antituberculous activity of pyrazinamide. These findings shed new light on the mode of action of pyrazinamide and may help in the design of new drugs that shorten therapy.

A New Approach for Pyrazinamide Susceptibility Testing inMycobacterium tuberculosis

“…1,7,9,10 PZA is a pro-drug that enters bacteria by passive diffusion and is converted to its active form, pyrazinoic acid (POA), by bacterial pyrazinamidase (PZAse). 6,12,19 POA is expelled from the mycobacterium by an efflux pump, it is protonated in the acidic extracellular space, and the protonated form is then reabsorbed into the bacilli, where the proton is released. This cycle is repeated, resulting in a lethal combination of POA accumulation and intracellular acidification, causing disruption of membrane permeability and cellular damage.…”

“…This cycle is repeated, resulting in a lethal combination of POA accumulation and intracellular acidification, causing disruption of membrane permeability and cellular damage. 3,17,19 The major mechanism of PZA resistance in M. tuberculosis arises from mutations in the PZAse, resulting in a loss of enzymatic activity, preventing conversion of PZA to POA. 17 The same mechanism is responsible for the natural resistance to PZA of Mycobacterium bovis and Mycobacterium kansasii.…”

“…Mycobacterium smegmatis, naturally PZA resistant, has a much more active POA efflux mechanism than M. tuberculosis, which prevents intracellular POA accumulation. 15,18,19 M. tuberculosis strains exhibit a range of POA efflux rates, associated with different PZA-susceptibility levels. Recently, POA efflux rates from susceptible M. tuberculosis strains were found to fall within a critical range, with strains with rates below this range showing resistance.…”

A New Hope in TB Treatment: The Development of the Newest Drugs

“…In fact, TMC207 is also active against MDR-TB strains. Based on transposon mutagenesis analysis, F1F0 ATP synthase seems to be an essential enzyme in M. tuberculosis although the enzyme is not essential for E. coli because mutants of F1F0 were viable but grew at a reduced rate and were attenuated for virulence in mice Zhang, 2003). TMC207 was more active than INH and RIF in the mouse model (Andries et al, 2005) and could shorten TB therapy from four months to two months in mice with an established infection model.…”

New potentially active pyrazinamide derivatives synthesised under microwave conditions

“…This molecule gets into the mycobacterial cell and causes the inner cell compartment acidification in the train of the ionic efflux. These consequences lead to cellular death [2,3].…”