Piezo1 activates nitric oxide synthase in red blood cells via protein kinase C with increased activity in diabetes.

Nitric oxide (NO) is a key signaling molecule in maintaining cardiovascular health. While endothelial cells were initially thought to exclusively contain endothelial nitric oxide synthase (eNOS), an enzyme that produces NO, recent evidence suggests that red blood cells (RBC) also contain functional eNOS that impacts cardiovascular function. However, the mechanisms driving RBC eNOS activation are not well understood. Like endothelial cells, RBC are mechanosensitive via the stretch-activated piezo1 Ca(2+) channel. Therefore, we investigated how piezo1 stimulation induced RBC and endothelial eNOS phosphorylation. We further examined how this mechanism is affected during diabetes, a condition known to impair vascular NO bioavailability. Our results reveal that piezo1 stimulation activated RBC eNOS via protein kinase C (PKC) and endothelial eNOS partially via protein kinase B (Akt). Surprisingly, piezo1-stimulation increased eNOS phosphorylation at the Ser1177 activation site nearly 20-fold in RBC from diabetic patients compared to 5.5-fold in RBC from non-diabetic patients. These findings highlight important differences in eNOS activation between RBC and endothelial cells and suggest potential biomolecular markers for targeting vascular NO bioavailability in health and disease.