Abstract:

Exposure to hypoxic conditions can result in significant brain damage, such as that experienced during an ischemic stroke. Thus, finding ways to mitigate ischemia/hypoxia-induced brain tissue damage is a critical issue that needs addressing. HH-A, a derivative of honokiol, has demonstrated potent pharmacological activities and medicinal properties in treating brain ischemia/reperfusion injury. However, its effect on anti-hypoxic responses during stroke remains largely unexplored. In the present study, we subjected male Sprague-Dawley rats to 24 h of hypoxia (oxygen content at 11%) or to 7 d of permanent middle cerebral artery occlusion. We discovered that both 1 mg/kg (i.v.) and 40 mg/kg (i.g.) of HH-A elevated arterial oxygen saturation after 24 h of hypoxia and significantly reduced the infarct volume after 7 d of ischemia. Furthermore, fluorescence staining with hypoxyprobe-1 indicated that HH-A significantly mitigated the severity of hypoxia in brain tissue. Hematoxylin and eosin staining, along with neuronal nuclei immunofluorescent staining, further revealed that HH-A curbed the death of brain cells. To identify potential protein partners of HH-A, we used a molecular fishing approach based on surface plasmon resonance technology. A high binding affinity was detected between HH-A and the hemoglobin subunit beta, with an estimated binding free energy of –8.7 kcal/mol. These findings suggested that HH-A was capable of enhancing hypoxia tolerance and alleviating brain injury caused by ischemia.

Key words: Hypoxia, Stroke, Brain ischemic injury, Permanent middle cerebral artery occlusion