Comparative roles of free fatty acids with reactive nitrogen intermediatesand reactive oxygen intermediates in expression of the anti-microbial activity of macrophages against Mycobacterium tuberculosis

We assessed the role of free fatty acids (FFA) in the expression of the act ivity of macrophages against Mycobacterium tuberculosis in relation to the roles of two major anti-microbial effectors, reactive nitrogen intermediate s (RNI) and reactive oxygen intermediates (ROI). Intracellular growth of M. tuberculosis residing inside macrophages was accelerated by treatments of macrophages with either quinacrine (phospholipase A(2) (PLA(2)) inhibitor), arachidonyl trifuloromethylketone (type IV cytosolic PLA(2) inhibitor), N- G-monomethyl-l-arginine (nitric oxide synthase inhibitor), and superoxide d ismutase plus catalase (ROI scavengers). In addition, M. tuberculosis-infec ted macrophages produced and/or secreted these effectors sequentially in th e order ROI (0-3 h), FFA (0-48 h), and RNI (3 to at least 72 h). Notably, m embranous FFA (arachidonic acid) of macrophages translocated to M. tubercul osis residing in the phagosomes of macrophages in phagocytic ability- and P LA(2)-dependent fashions during cultivation after M. tuberculosis infection . FFA, RNI and H2O2-mediated halogenation system (H2O2-halogenation system) displayed strong activity against M. tuberculosis in cell-free systems, wh ile ROI alone exerted no such effects. Combinations of 'FFA + RNI' and 'RNI + H2O2-halogenation system' exhibited synergistic and additive effects aga inst M. tuberculosis, respectively, while 'FFA + H2O2-halogenation system' had an antagonistic effect. Moreover, a sequential attack of FFA followed b y RNI exerted synergistic activity against M. tuberculosis. Since M. tuberc ulosis-infected macrophages showed simultaneous production of RNI with FFA secretion for relatively long periods (approx. 45 h) and prolonged RNI prod uction was seen thereafter, RNI in combination with FFA appear to play crit ical roles in the manifestation of the activity of macrophages against M. t uberculosis.