Vitamin D modulates innate immunity in pulmonary tuberculosis

Abstract

Abstract Vitamin D and vitamin D receptor (VDR) may play role in altering host defence against Mtb via cathelicidin production and regulating nitric oxide (NO) production through inducible nitric oxide synthase (iNOS). 100 active pulmonary tuberculosis (PTB) patients, 75 household contacts and 70 healthy controls were recruited. Serum Vitamin D and NO levels were measured using CLIA and colorimetry based kit respectively. VDR and iNOS mRNA was studied in monocytes using qPCR. Serum VDR, cathelicidin and iNOS levels were measured using ELISA. Lower serum levels of vitamin D was found in PTB group compared to household contacts and healthy controls (P<0.001). VDR (both mRNA and protein) and iNOS mRNA levels were also lower in PTB group compared to household contacts and healthy controls (P<0.005)probably due to decreased levels of vitamin D. However, despite low serum vitamin D, serum cathelicidin levels were higher in PTB group compared to household contacts and healthy controls (p<0.01) which could be attributed to direct trigger via toll like receptors where Mtb is multiplying actively. Serum iNOS and NO levels were higher in PTB group compared to household contacts and healthy controls (p< 0.05), despite decreased iNOS expression which needs further evaluation. Increased VDR and iNOS expression in household contacts compared to both PTB and healthy controls could be due to optimum levels of vitamin D along with some exposure to Mtb as evident by increased levels of cathelicidin and NO compared to healthy controls. Adequate levels of vitamin D, VDR and iNOS that in turn promote production of antimicrobial cathelicidin and NO might have protective role against TB among household contacts and needs further investigation for its therapeutic potential.