Macrophage Polarization in Inflammatory Diseases

Liu, Yan-Cun; Zou, Xian-Biao; Chai, Yan-Fen; Yao, Yong-Ming

Analysis of ATM in obese mice revealed that these cells predominantly showed M1 phenotype, which was activated through TLR4/NF-κB and c-jun amino-terminal kinase (JNK) 1 signaling pathways [59] . They secreted pro-inflammatory cytokines with the participation of adipocytes, contributing to insulin resistance. Nevertheless, adipose tissue in lean animals also contains a moderate number of macrophages with a state of alternatively activated. In addition, a recent animal study demonstrated that F4/80 + CD11c -CD301 + macrophages with M2-like characteristics were increased in adipose tissue during chronic weight loss. Those cells might play an essential role in lipolysis and tissue homeostasis by preventing inflammation and promoting insulin sensitivity [60] . Nguyen and colleagues recently confirmed a role for alternatively activated ATM in the orchestration of response to cold [61] . Adaptation to cold temperature promoted the ATM to the alternative activation state, which secreted catecholamines to induce the expression of thermogenic genes including PPARγ coactivator 1a (Ppargc1a), uncoupling protein 1 (Ucp1) and acyl-CoA synthetase long-chain family member 1 (Acsl1) in brown adipose tissue, and the lipolysis in white adipose tissue was also increased [61] . By this way, ATM keeps the cellular functions and physiological processes in the normal state when confronted with cold environments.