OBJECTIVES: To investigate the effects of quercetin on cuproptosis and L-type calcium currents in the myocardium of diabetic rats. METHODS: Forty SD rats were randomized into control group and diabetic model groups. The rat models of diabetes mellitus (DM) induced by high-fat and high-sugar diet combined with streptozotocin (STZ) injection were further divided into DM model group, quercetin treatment group, and empagliflozin treatment group (n=10). Blood glucose and body weight were measured every other week, and cardiac function of the rats was evaluated using echocardiography. HE staining, Sirius red staining, and wheat germ agglutinin (WGA) analysis were used to observe the changes in myocardial histomorphology, and serum copper levels and myocardial FDX1 expression were detected. In cultured rat cardiomyocyte H9c2 cells with high-glucose exposure, the effects of quercetin and elesclomol, alone or in combination, on intracellular CK-MB and LDH levels and FDX1 expression were assessed, and the changes in L-type calcium currents were analyzed using patch-clamp technique. RESULTS: The diabetic rats exhibited elevated blood glucose, reduced body weight, impaired left ventricular function, increased serum copper levels and myocardial FDX1 expression, decreased L-type calcium currents, and prolonged action potential duration. Quercetin and empagliflozin treatment significantly lowered blood glucose, improved body weight, and restored cardiac function of the diabetic rats, and compared with empagliflozin, quercetin more effectively reduced serum copper levels, downregulated FDX1 expression, and enhanced myocardial L-type calcium currents in diabetic rats. In H9c2 cells, high glucose exposure significantly increased myocardial expressions of FDX1, CK-MB and LDH, which were effectively lowered by quercetin treatment; Elesclomol further elevated FDX1, CK-MB and LDH levels in the exposed cells, and these changes were not significantly affected by the application of quercetin. CONCLUSIONS Quercetin ameliorates myocardial injury in diabetic rats possibly by suppressing myocardial cuproptosis signaling and restoring L-type calcium channel activity.
Animals ; Quercetin/pharmacology* ; Calcium Channels, L-Type/metabolism* ; Diabetes Mellitus, Experimental/metabolism* ; Rats, Sprague-Dawley ; Rats ; Myocytes, Cardiac/drug effects* ; Myocardium/pathology* ; Male

Alzheimer's disease (AD), a progressive dementia, is one of the most common neurodegenerative diseases. Clinical trial results of amyloid-β (Aβ) and tau regulators based on the pretext of straightforward amyloid and tau immunotherapy were disappointing. There are currently no effective strategies for slowing the progression of AD. Herein, we spotlight the dysregulation of lipid metabolism, particularly the elevation of ceramides (Cers), as a critical yet underexplored facet of AD pathogenesis. Our study delineates the role of Cers in promoting microglial pyroptosis, a form of programmed cell death distinct from apoptosis and necroptosis, characterized by cellular swelling, and membrane rupture mediated by the NLRP3 inflammasome pathway. Utilizing both in vivo experiments with amyloid precursor protein (APP)/presenilin 1 (PS1) transgenic mice and in vitro assays with BV-2 microglial cells, we investigate the activation of microglial pyroptosis by Cers and its inhibition by icariin (ICA), a flavonoid with known antioxidant and anti-inflammatory properties. Our findings reveal a significant increase in Cers levels and pyroptosis markers (NOD-like receptor family, pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase recruitment domain, caspase-1, gasdermin D (gasdermin D (GSDMD)), and interleukin-18 (IL-18)) in the brains of AD model mice, indicating a direct involvement of Cers in AD pathology through the induction of microglial pyroptosis. Conversely, ICA treatment effectively reduces these pyroptotic markers and Cer levels, thereby attenuating microglial pyroptosis and suggesting a novel therapeutic mechanism of action against AD. This study not only advances our understanding of the pathogenic role of Cers in AD but also introduces ICA as a promising candidate for AD therapy, capable of mitigating neuroinflammation and pyroptosis through the cyclooxygenase-2 (COX-2)-NLRP3 inflammasome-gasdermin D (GSDMD) axis. Our results pave the way for further exploration of Cer metabolism disorders in neurodegenerative diseases and highlight the therapeutic potential of targeting microglial pyroptosis in AD.

Methods: (i) Animal experiments. This study conducted experiments using specific pathogen-free (SPF) grade male C57BL/6J wild-type (WT) mice and APP/PS1 double transgenic mice. The animals were divided into three groups: WT group (WT mice, n = 5, receiving distilled water daily), APP/PS1 group (APP/PS1 double transgenic mice, n = 5, receiving distilled water daily), and BSTSD group [APP/PS1 double transgenic mice, n = 5, treated with BSTSD suspension at a dosage of 27 g/(kg·d) for 90 d]. Cognitive function was assessed using the Morris water maze (MWM). Post-experiment, hippocampal tissues were collected for analysis of pyramidal cell and synaptic morphology through hematoxylin-eosin (HE) staining and transmission electron microscopy (TEM). (ii) Cell experiments. The HT-22 cells were divided into control group (untreated), Aβ25-35 group (treated with 20 μmol/L Aβ25-35 for 24 h), icariin group (pre-treated with 20 μmol/L icariin for 60 min, followed by 20 μmol/L Aβ25-35 for an additional 24 h), and icariin + LY294002 group [treated with 20 μmol/L icariin and 20 μmol/L LY294002 (an inhibitor of the phosphoinostitide 3-kinases (PI3K) signaling pathway) for 60 min, then exposed to 20 μmol/L Aβ25-35 for 24 h], and cell viability was measured. Western blot was used to detect the expression levels of synapse-associated proteins [synaptophysin (SYP) and postsynaptic density-95 (PSD-95)] and PI3K signaling pathway associated proteins [phosphorylated (p)-PI3K/PI3K, p-protein kinase B (Akt)/Akt, and p-mechanistic target of rapamycin (mTOR)/mTOR]. Results: (i) Animal experiments. Compared with APP/PS1 group, BSTSD group showed that escape latency was significantly shortened (P < 0.01) and the frequency of crossing the original platform was significantly increased (P < 0.01). Morphological observation showed that pyramidal cells in the hippocampal CA1 region were arranged more regularly, nuclear staining was uniform, and vacuole-like changes were reduced after BSTSD treatment. TEM showed that the length of synaptic active zone in BSTSD treatment group was increased compared with APP/PS1 group (P < 0.01), and the width of synaptic gap was decreased (P < 0.01). (ii) Cell experiments. Icariin had no obvious toxicity to HT-22 cells when the concentration was not more than 20 μmol/L (P > 0.05), and alleviated the cell viability decline induced by Aβ25-35 (P < 0.01). Western blot results showed that compared with Aβ25-35 group, the ratios of p-PI3K/PI3K, p-Akt/Akt and p-mTOR/mTOR in icariin group were significantly increased (P < 0.01), while the protein expression levels of SYP and PSD-95 were increased (P < 0.01). These effects were blocked by LY294002 (P < 0.01). Conclusion BSTSD and icariin enhance cognitive function and synaptic integrity in AD models and provide potential therapeutic strategies through activation of the PI3K/Akt/mTOR pathway.