Targeting NLRP3 inflammasome attenuates cardiac pyroptosis and fibrosis in estrogen-deficient diabetic rats.

Cardiac diastolic dysfunction is a hallmark of diabetic cardiomyopathy (DCM), particularly in postmenopausal women where estrogen deficiency exacerbates cardiac remodeling. This study investigated the roles of NLRP3 inflammasome activation and cardiac mast cell (CMC) behavior in diabetic ovariectomized (OVX) rat models. Female Wistar rats were divided into five groups: sham-operated, OVX, diabetic (Sham-DM), OVX-diabetic (OVX-DM), and OVX-DM treated with the NLRP3 inhibitor MCC950. Diabetes was induced using a high-calorie quick fat diet (13.8% crude fat, 24.35% crude protein, 25% sucrose; 406.80 kcal/100 g) followed by a single intraperitoneal injection of streptozotocin (30 mg/kg). MCC950 (10 mg/kg BW, intraperitoneally) was administered daily for 4 weeks. Echocardiography revealed significant diastolic dysfunction in OVX-DM rats, with increased left ventricular internal diameter (LVIDd) and reduced mitral valve E/A ratio, while MCC950 treatment partially restored diastolic function (p < 0.05). Masson's trichrome staining showed increased myocardial fibrosis in OVX-DM rats (2.59 ± 0.20%) compared to Sham-DM (1.94 ± 0.16%, p < 0.05), which was reduced with MCC950 treatment (0.88 ± 0.13%, p < 0.05). Western blot analysis demonstrated elevated expression of NLRP3, cleaved caspase-1, IL-1β, and GSDMD-N in OVX-DM hearts. MCC950 significantly reduced cleaved caspase-1, IL-1β, and GSDMD-N expression without altering NLRP3 protein levels. Additionally, mast cell degranulation was markedly increased in OVX-DM rats (62.14%) compared to controls (P < 0.05) and was attenuated by MCC950 (31.06%, P < 0.05). These findings suggest that NLRP3 inflammasome activation under conditions of estrogen deficiency and diabetes contributes to myocardial pyroptosis and mast cell degranulation, driving cardiac remodeling in postmenopausal DCM. Targeting NLRP3 pathways may provide an effective therapeutic strategy to mitigate diastolic dysfunction, fibrosis, and inflammation in diabetic hearts.