1b). We also examined the kinetics of iNOS expression in BCG-infected macrophages with IL-17A pre-treatment by qPCR and Western blot analysis. From qPCR analysis, we observed that the expression level of iNOS mRNA in BCG-infected macrophages was enhanced by IL-17A over a time course of 24 hr (Fig. 1c). Similar observations could be obtained using Western blot analysis. The production of iNOS protein in BCG-infected macrophages was enhanced by IL-17A as early as 3 hr post-infection and the enhancing effect continued to 12 hr post-infection (Fig. 1d).

At 24 hr post-infection, we observed that the protein levels of iNOS were comparable between BCG-infected macrophages with or without IL-17A pre-treatment. Interleukin-17A alone did not induce detectable level of iNOS protein in Romidepsin macrophages at all time-points being tested (Fig. 1d). Taken together, our data suggest that IL-17A is able to enhance NO production in macrophages by up-regulating iNOS expression during BCG infection. Signalling pathways of MAPK, including JNK, ERK1/2 and p38 MAPK, are activated in macrophages in response to mycobacterial infection, mTOR inhibitor leading to production of pro-inflammatory cytokines.[19, 21, 23] The

expression of iNOS has also been shown to be regulated by those MAPK pathways.[15, 24] To investigate whether IL-17A pre-treatment affects BCG-activated MAPK pathways, we analysed the phosphorylations of various MAPKs. We pre-treated the macrophages with IL-17A for 24 hr, Tyrosine-protein kinase BLK followed by BCG infection for 60, 90, 120 and 150 min. Total cell lysates were harvested for Western blot analysis of phosphorylation of JNK, p38 MAPK

and ERK1/2. Our results showed that phosphorylation of JNK, p38 MAPK and ERK1/2 in macrophages was strongly induced by BCG at 60 and 90 min post-infection (Fig. 2a, lane 2 and lane 6) and became diminished at 120 and 150 min post-infection (Fig. 2a, lane 10 and lane 14). The levels of phosphorylated JNK at 60 min post-infection were found to be similar between BCG-infected macrophages with or without IL-17A pre-treatment (Fig. 2a, lane 2 versus lane 3). However, we observed that in the presence of IL-17A, the BCG-induced phosphorylation of JNK was enhanced at 90, 120 and 150 min (Fig. 2a, lane 7, land 11 and lane 15, respectively). The data suggest that IL-17A is able to prolong BCG-induced phosphorylation of JNK. On the other hand, IL-17A had no effects on BCG-activated ERK1/2 and p38 MAPK at all time-points being tested (Fig. 2a). For verification that JNK was involved in the enhancement of BCG-induced NO production by IL-17A, we blocked the activation of the JNK pathway by using SP600125, which is a reversible ATP competitive inhibitor specific to JNK.[25] Previous studies reported by other groups have shown that the JNK inhibitor SP600125 is able to suppress NO production in macrophages being stimulated by Toll-like receptor agonists including BCG and lipopolysaccharide.