Nitroglycerin attenuates ischemic neuronal injury via PKG-dependent regulation of endoplasmic reticulum (ER) stress and glucose metabolism

Nitroglycerin (GTN), a widely used anti-anginal drug, has emerged as a potential alternative therapy for acute ischemic stroke. However, the underlying protective mechanisms of GTN in neuronal ischemic injury remain unclear. This study investigates the neuroprotective effects of GTN on glucose metabolism and endoplasmic reticulum (ER) stress during oxygen-glucose deprivation followed by reoxygenation (OGD/R). Primary rat cortical neurons were subjected to 2 hours of OGD, followed by either 6 or 24 hours of reoxygenation (OGD/R) or no reoxygenation (OGD only). GTN was administered at reoxygenation onset or at the end of the OGD. The PKG inhibitor KT5823 was administered at the onset of OGD. Cell viability and neuronal apoptosis were assessed using CCK-8 assays, TUNEL staining, and Western blotting. Reactive oxygen species (ROS), lactate, and cyclic guanosine monophosphate (cGMP) levels were measured via ELISA, and nitric oxide (NO) levels were determined using the Griess method. ER stress-related proteins, glycolytic/gluconeogenic enzymes, and signaling molecules were analyzed by qRT-PCR and Western blotting. GTN significantly improved neuronal survival, preserved cell integrity, and reduced apoptosis under OGD/R conditions. It restored ROS, lactate, NO, and cGMP levels, but not in the OGD-only group. GTN markedly reduced glycolytic enzymes, gluconeogenic enzymes, and ERS-related proteins. It also enhanced PKG expression while suppressing phosphorylated AMPK, effects observed only under OGD/R conditions. The neuroprotective effects of GTN were abolished by the PKG inhibitor KT5823. GTN confers neuroprotection in OGD/R injury by activating PKG signaling, alleviating ER stress, and modulating glucose metabolism by suppressing hyperglycolysis and gluconeogenesis.