N-acetylcysteine modulates markers of oxidation, inflammation and infection in tuberculosis

Half the global tuberculosis health burden is due to post-tuberculosis lung disease. Host-directed therapies have been proposed to reduce this burden. N-acetylcysteine (NAC) provides the conditionally essential amino acid cysteine required for synthesis of glutathione, an antioxidant thiol. We recently reported clinical outcomes of a trial of adjunctive NAC in patients with pulmonary tuberculosis, finding that NAC improved the secondary endpoint of recovery of lung function. Here we report the effects of NAC on biomarkers of oxidation, inflammation, and infection in that trial.

140 adults with moderate or far-advanced pulmonary tuberculosis were randomly assigned to standard tuberculosis treatment with or without NAC 1200 mg twice daily for months 1-4. Sputum and blood samples were obtained at specified intervals to measure total glutathione, MTB-induced cytokines, hemoglobin, whole blood mycobactericidal activity (WBA), and sputum MTB burden.

NAC treatment rapidly increased total glutathione (P<.0001), but levels did not reach those of healthy volunteers (P<.001). NAC reduced MTB-induced TNF-α (P =.011) without affecting IL-10, and accelerated the recovery of hemoglobin in participants with low values on entry. NAC did not affect killing in ex vivo whole blood culture but did slow the clearance of MTB from sputum (P=0.003).

Adjunctive NAC showed antioxidant and anti-inflammatory effects consistent with the amelioration of immunopathology seen in preclinical models. Two biomarkers of antimicrobial activity showed discordant results; neither demonstrated the enhanced antimicrobial effects seen preclinically. The reduction of oxidative stress and inflammation by NAC may explain its effects on the recovery of lung function post-TB.