Theacrine protects vascular endothelial cells against oxidative damage after ischemic stroke by inhibiting Rac1 and activating Nrf2 pathway.

Ischemic stroke is a leading global health issue without a definitive treatment. Theacrine (TC), a purine alkaloid extracted from Chinese tea kucha (Camellia assamica var. kucha), has shown potential in brain health and is under investigation for its medicinal benefits. However, its neuroprotective mechanisms and role in preventing endothelial damage are unclear. This study aims to evaluate the protective property and mechanism of TC against oxidative stress-induced vascular endothelial cell injury and middle cerebral artery occlusion (MCAO)-induced ischemic injury. An MCAO rat model and a tert-butyl hydroperoxide (TBHP) induced oxidative damage model in human umbilical vein endothelial cells (HUVECs) were used to assess the effect of TC. Mechanistically, approaches that test Rac activity as well as Rac inhibitor and agonist were used. In vitro experiments revealed that TC treatment significantly reduced TBHP-induced oxidative stress by enhancing cell functions and reducing oxidative levels, apoptosis, and vascular injury markers. In vivo, TC protected against MCAO-induced ischemic injury by improving neurological function, reducing infarct size, and restoring mitochondrial function. Mechanically, TC inhibited Ras-related C3 botulinum toxin substrate 1 (Rac1) activity and activated the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, promoting Nrf2's nuclear translocation. Nevertheless, these protective effects were reversed by phorbol 12-myristate 13-acetate (PMA), an agonist of Rac1. Overall, TC alleviates oxidative stress in endothelial cells and protects against cerebral I/R injury by activating Nrf2 and suppressing Rac1. The present findings can enhance the use of kucha as a common beverage in health care and promote the development of TC as a potential treatment agent for ischemic stroke.