Erythropoietin-derived peptide (HBSP) inhibits caspase-3/GSDME through HMGB1 to regulate pyroptosis and reduce diabetic retinopathy.

BACKGROUND: Pyroptosis exerts an important effect on the development of diabetic retinopathy (DR). Helix B surface peptide (HBSP) is derived from erythropoietin (EPO) and has a special role in diabetes. This study explored effect of HBSP on retinal pigment epithelium (RPE) cell pyroptosis in DR and its mechanism. METHODS: ARPE-19 cells were treated with high-glucose (HG) and HBSP. Mice were injected with streptozotocin (STZ) and treated with HBSP. HE staining analyzed pathological changes. EB staining tested integrity of blood-retinal barrier (BRB). RT-qPCR determined HMGB1 mRNA. Western blot detected HMGB1 and pyroptosis-related proteins (NLRP3, caspase-1, GSDMD, caspase-3, GSDME). CCK-8 determined viability of ARPE-19 cells. Changes of cell pyroptosis were observed by transmission electron microscopy. RESULTS: In STZ-induced diabetic mice, retinal tissue exhibited typical DR lesion, BRB breakdown and increased pyroptosis-related proteins. HG reproduced these events in ARPE-19 cells: viability loss, ultrastructural pyroptotic morphology and activation of both canonical (caspase-1/GSDMD) and non-canonical (caspase-3/GSDME) pyroptotic pathways, with the latter being most pronounced. HBSP dose-dependently rescued retinal architecture, restored BRB integrity in vivo, and normalized HG-lowered cell viability in vitro. HBSP ameliorated HG-triggered pyroptosis, primarily by suppressing caspase-3/GSDME signaling pathway. HBSP alleviated HG-stimulated pyroptosis via downregulating HMGB1. HMGB1 knockdown alleviated HG-triggered pyroptosis, primarily by inhibiting caspase-3/GSDME signaling pathway. In vivo, overexpression of HMGB1 could reverse the therapeutic effect of HBSP and increase pyroptosis. CONCLUSION: HBSP suppresses RPE cell pyroptosis by disrupting the HMGB1-caspase-3/GSDME axis, thereby mitigating DR. These findings could illuminate a promising therapeutic avenue for DR.