The effects of first-line anti-tuberculosis drugs on the actions of vitamin D in human macrophages

Tuberculosis (TB) is a major global health problem. Patients with TB have a high rate of vitamin D deficiency, both at diagnosis and during the course of treatment with anti-tuberculosis drugs. Although data on the efficacy of vitamin D supplementation on Mycobacterium tuberculosis (Mtb) clearance are uncertain from randomized controlled trials (RCTs), vitamin D enhances the expression of the antimicrobial peptide human cathelicidin (hCAP18) in cultured macrophages in vitro. One possible explanation for the mixed (primarily negative) results of RCTs examining vitamin D treatment in TB infection is that anti-TB drugs given to enrolled subjectsmay impact actions of vitamin D to enhance cathelicidin in macrophages. To address this hypothesis, human macrophage-like monocytic (THP-1) cellswere treated with varying doses of first-line anti-tuberculosis drugs in the presence of the active form of vitamin D, 1,25dihydroxyvitamin D-3 (1,25(OH) 2D(3)). The expression of hCAP18 was determined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). 1,25(OH)(2)D-3 strongly induced expression of hCAP18 mRNA in THP-1 cells (fold-change fromcontrol). The combination of the standard 4-drug TB therapy (isoniazid, rifampicin, pyrazinamide and ethambutol) in the cultured THP-1 cells demonstrated a significant decrease in hCAP18 mRNA at the dosage of 10 mu g/ mL. In 31 subjects with newly diagnosed drugsensitive TB randomized to either high-dose vitamin D-3 (1.2 million IU over 8weeks, n = 13) versus placebo (n = 18), there was no change from baseline to week 8 in hCAP18 mRNA levels in peripheral blood mononuclear cells or in plasma concentrations of LL-37, the protein product of hCAP18. These data suggest that first-line anti-TB drugs may alter the vitamin D-dependent increase in hCAP18 and LL-37 human macrophages. Published by Elsevier Inc.