Chronic hyperglycemia induces hepatocyte pyroptosis via Gα12/Gα13-associated endoplasmic reticulum stress: Effect of pharmacological intervention.

Abstract

Aims: Hyperglycemia induces pathophysiological changes. Endoplasmic reticulum (ER) stress with Gα₁₂ overexpression may promote hepatocyte death. This study investigated whether sustained hyperglycemia triggers ER stress-associated pyroptosis and fibrosis in the liver alongside an overexpression of Gα₁₂, and examined the potential link with VEGF-A levels.

Main methods: Mice were subjected to a high-fat diet (60 kcal% fat) with streptozotocin (50 mg/kg body weight, three consecutive times, between 12-13^th weeks). AZ2 (a functional Gα₁₂ inhibitor) was treated at 10 mg/kg body weight (5 times/week, 3 weeks). Immunoblotting and immunohistochemistry analyses were performed.

Key findings: Hepatic Gα₁₂/Gα₁₃ were overexpressed in the diabetic mice. The following proteins downstream from the Gα₁₂ axis were upregulated: PGC1α, PPARα, and SIRT1. Sustained hyperglycemia promoted ER stress marker levels. Histopathological and biochemical assays showed large-sized lipid droplet accumulation, hepatocyte degeneration, and damage as blood transaminase activities increased. Moreover, the diabetic condition increased IL-1β, caspase-1, and NLRP3 levels, which were supportive of pyroptosis. Consistently, the intensities of Masson's trichrome, collagen-1A1, α-SMA, vimentin, and fibronectin all increased. VEGF-A and VEGFR2 levels also increased in the liver and/or sera. The levels of hepatic pigment epithelial-derived factor (PEDF), a physiological antagonist of VEGF-A, decreased with its reciprocal increase in serum. These events were reversed by AZ2 treatment, supporting the role of Gα₁₂ in hyperglycemic stress in the liver.

Significance: Chronic hyperglycemia causes hepatic pyroptosis and fibrosis related to ER stress with Gα₁₂/Gα₁₃ and VEGF overexpression, which may be overcome by AZ2 treatments.