Acute hyperglycemia lowers endothelial TRPV4 channel activity

Abstract

Calcium signaling mechanisms regulate endothelium-dependent dilation of small arteries. Endothelial dysfunction has been linked to the clinical symptoms observed in diabetic patients, although the underlying mechanisms behind compromised endothelial health are unclear. The clinical symptoms of hyperglycemia are exacerbated in diabetic patients due to their higher initial spike in blood glucose concentration after food intake. However, the effects of acute increases in glucose levels on endothelial calcium signals have not been studied. Recent studies indicate that transient receptor potential vanilloid 4 (TRPV4) channels, a calcium entry pathway in endothelial cells, promote the dilation of small arteries. Therefore, we hypothesized that hyperglycemia lowers endothelial TRPV4 channel activity to impair the dilation of small arteries. The calcium signal activity of endothelial cells (ECs) was compared in small mesenteric arteries (MA, ~ 100 μm) from C57BL6J mice under normal (5 mM Glucose) and hyperglycemic (25 mM Glucose) conditions using spinning disk confocal microscopy. En face MAs were loaded with fluo-4 AM (10 μM) and images were acquired at 30 frames per second to capture real-time changes in calcium signals. The baseline activity of endothelial calcium signals was lower under hyperglycemic conditions compared to normal and osmotic control (5 mM Glucose/20 mM Mannitol) conditions. In the presence of TRPV4 channel inhibitor GSK2193874 (GSK219, 100 nM), hyperglycemia-induced decrease in endothelial calcium signals was abolished, suggesting that hyperglycemic conditions target endothelial TRPV4 channels. To verify this possibility, we recorded the activity of endothelial TRPV4 channels as unitary calcium influx signals, called TRPV4 sparklets, in the presence of cyclopiazonic acid to eliminate the interference from intracellular calcium release signals. TRPV4 channels were activated using GSK1016790A (GSK101, 3 nM), a selective channel activator. The number of TRPV4 sparklet sites and activity per site were both reduced under hyperglycemic conditions compared to normal conditions. Overall, these data suggest that acute hyperglycemia reduces the activity of endothelial TRPV4 channels, which may attenuate endothelial function. Future work will determine the acute contribution of hyperglycemia-induced decrease of TRPV4 channel activity to impaired endothelium-dependent vasodilation. This work was funded by grants from the NIH (HL142808 and HL147555) to Dr. Sonkusare. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.