Identification of potent small-molecule inhibitors of STAT3 with anti-inflammatory properties in RAW 264.7 macrophages

摘要

Signal transducer and activator of transcription 3 (STAT3) is a key mediator of the inflammatory response by macrophages and other immune cell types. The naturally occurring polyphenol resveratrol is associated with anti-proliferative and anti-inflammatory properties via mechanisms implicating inhibition of STAT3 signaling. Here, we report that the small-molecule analogs of resveratrol, RSVA314 and RSVA405, are potent inhibitors of STAT3. RSVA314 and RSVA405 inhibited both constitutive and stimulated STAT3 in HEK293 cells and lipopolysaccharide (LPS)-activated RAW 264.7 macrophages, respectively. The small-molecule analogs inhibited STAT3 nearly 50 times more potently than did resveratrol (apparent IC50 ~ 0.5 μM). We further show that RSVA405 interfered with the inflammatory response by RAW 264.7 cells upon LPS stimulation by inhibiting IKK and IκBα phosphorylation and by decreasing the expression of several cytokines, including the NF-κB target genes, tumor necrosis factor-α and interleukin-6. Downstream activation of STAT1 upon LPS stimulation was also inhibited by RSVA405. Consequently, RSVA405 significantly interfered with the phagocytotic activity and proliferation of LPS-activated RAW 264.7 macrophages. Finally, we found that the effect of the two small-molecule analogs on STAT3 phosphorylation could be prevented by inhibitors of protein tyrosine phosphatases (PTPs), indicating that the small-molecules acted by promoting the dephosphorylation of STAT3 by PTPs.