Nicotine Suppresses Phagocytic Ability of Macrophages by Regulating the miR-296-3p-SIRP alpha Axis

Phagocytic ability of macrophage is responsible for tuberculosis infection. Nicotine has been shown to attenuate the phagocytic ability of macrophage; however, the underlying mechanism remains unclear. Here, we demonstrated that nicotine increased the message RNA (mRNA) and protein expression of signal regulatory protein alpha (SIRP alpha) and enhanced the stability of SIRP alpha mRNA in macrophage. Nicotine decreased the expression of microRNA (miR)-296-3p, which directly targeted the 3 '-untranslated region (3 '-UTR) of SIRP alpha mRNA in macrophage. Furthermore, nicotine inhibited the phagocytic ability of macrophage by regulating the miR-296-3p-SIRP alpha axis. Moreover, nicotine decreased miR-296-3p expression via increasing c-Myc expression in macrophage. Together, we found that nicotine attenuate the phagocytic ability of macrophage by regulating the c-Myc-miR-296-3p-SIRP alpha signal.