Suppressor of cytokine signaling 1-derived peptide inhibits Janus kinase/signal transducers and activators of transcription pathway and improves inflammation and atherosclerosis in diabetic mice.

OBJECTIVE: Activation of Janus kinase/signal transducers and activators of transcription (STAT) pathway by hyperglycemia and dislypidemia contributes to the progression of diabetic complications, including atherosclerosis. Suppressor of cytokine signaling (SOCS) proteins negatively regulate Janus kinase/STAT and have emerged as promising target for anti-inflammatory therapies. We investigated whether a cell-permeable lipopeptide corresponding to the kinase inhibitory region of SOCS1 could reduce atherosclerosis in diabetic mice and identified the mechanisms involved. APPROACH AND RESULTS: Streptozotocin-induced diabetic apolipoprotein E-deficient mice (aged 8 and 22 weeks) were given intraperitoneal injections of vehicle, SOCS1-derived peptide, or control mutant peptide for 6 to 10 weeks. SOCS1 therapy suppressed STAT1/STAT3 activation in atherosclerotic plaques of diabetic mice and significantly reduced lesion size at both early and advanced stages of lesion development compared with vehicle group. Plaque characterization demonstrated that SOCS1 peptide decreased the accumulation of lipids, macrophages, and T lymphocytes, whereas increasing collagen and smooth muscle cell content. This atheroprotective effect was accompanied by systemic (reduced proinflammatory Ly6C(high) monocytes and splenic cytokine expression) and local (reduced aortic expression of chemokines and cytokines) mechanisms, without impact on metabolic parameters. In vitro, SOCS1 peptide dose dependently inhibited STAT1/STAT3 activation and target gene expression in vascular smooth muscle cells and macrophages and also suppressed cytokine-induced cell migration and adhesion processes. CONCLUSIONS: SOCS1-based targeting Janus kinase/STAT restrains key mechanisms of atherogenesis in diabetic mice, thereby preventing plaque formation and increasing plaque stability. Approaches to mimic native SOCS1 functions may have a therapeutic potential to retard the progression of diabetic complications.

Intracellular protein therapy with SOCS3 inhibits inflammation and apoptosis.

Suppressor of cytokine signaling (SOCS) 3 attenuates proinflammatory signaling mediated by the signal transducer and activator of transcription (STAT) family of proteins. But acute inflammation can occur after exposure to pathogen-derived inducers staphylococcal enterotoxin B (SEB) and lipopolysaccharide (LPS), or the lectin concanavalin A (ConA), suggesting that physiologic levels of SOCS3 are insufficient to stem proinflammatory signaling under pathogenic circumstances. To test this hypothesis, we developed recombinant cell-penetrating forms of SOCS3 (CP-SOCS3) for intracellular delivery to counteract SEB-, LPS- and ConA-induced inflammation. We found that CP-SOCS3 was distributed in multiple organs within 2 h and persisted for at least 8 h in leukocytes and lymphocytes. CP-SOCS3 protected animals from lethal effects of SEB and LPS by reducing production of inflammatory cytokines and attenuating liver apoptosis and hemorrhagic necrosis. It also reduced ConA-induced liver apoptosis. Thus, replenishing the intracellular stores of SOCS3 with CP-SOCS3 effectively suppresses the devastating effects of acute inflammation.