Truncated thioredoxin (Trx‐80) promotes pro‐inflammatory macrophages of the M1 phenotype and enhances atherosclerosis

Vascular cells are particularly susceptible to oxidative stress that is believed to play a key role in the pathogenesis of cardiovascular disorders. Thioredoxin‐1 (Trx‐1) is an oxidative stress‐limiting protein with anti‐inflammatory and anti‐apoptotic properties. In contrast, its truncated form (Trx‐80) exerts pro‐inflammatory effects. Here we analyzed whether Trx‐80 might exert atherogenic effects by promoting macrophage differentiation into the M1 pro‐inflammatory phenotype. Trx‐80 at 1 µg/ml significantly attenuated the polarization of anti‐inflammatory M2 macrophages induced by exposure to either IL‐4 at 15 ng/ml or IL‐4/IL‐13 (10 ng/ml each) in vitro, as evidenced by the expression of the characteristic markers, CD206 and IL‐10. By contrast, in LPS‐challenged macrophages, Trx‐80 significantly potentiated the differentiation into inflammatory M1 macrophages as indicated by the expression of the M1 cytokines, TNF‐α and MCP‐1. When Trx‐80 was administered to hyperlipoproteinemic ApoE2.Ki mice at 30 µg/g body weight (b.w.) challenged either with LPS at 30 µg/30 g (b.w.) or IL‐4 at 500 ng/30 g (b.w.), it significantly induced the M1 phenotype but inhibited differentiation of M2 macrophages in thymus and liver. When ApoE2.Ki mice were challenged once weekly with LPS for 5 weeks, they showed severe atherosclerotic lesions enriched with macrophages expressing predominantly M1 over M2 markers. Such effect was potentiated when mice received daily, in addition to LPS, the Trx‐80. Moreover, the Trx‐80 treatment led to a significantly increased aortic lesion area. The ability of Trx‐80 to promote differentiation of macrophages into the classical proinflammatory phenotype may explain its atherogenic effects in cardiovascular diseases. J. Cell. Physiol. 228: 1577–1583, 2013. © 2013 Wiley Periodicals, Inc.