Iridoid glycosides from Radix Scrophulariae attenuates focal cerebral ischemia-reperfusion injury via inhibiting endoplasmic reticulum stress-mediated neuronal apoptosis in rats

Iridoid glycosides of Radix Scrophulariae (IGRS) are a group of the major bioactive components from Radix Scrophulariae with extensive pharmacological activities. The present study investigated the effects of IGRS on cerebral ischemia-reperfusion injury (CIRI) and explored its potential mechanisms of action. A CIRI model in rats was established by occlusion of the right middle cerebral artery for 90 min, followed by 24 h of reperfusion. Prior to surgery, 30, 60 or 120 mg/kg IGRS was administered to the rats once a day for 7 days. Then, the neurological scores, brain edema and volume of the cerebral infarction were measured. The apoptosis index was determined by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling. The effects of IGRS on the histopathology of the cortex in brain tissues and the endoplasmic reticulum ultrastructure in the hippocampus were analyzed. Finally, the expression of endoplasmic reticulum stress (ERS)-regulating mediators, endoplasmic reticulum chaperone BiP (GRP78), DNA damage-inducible transcript 3 protein (CHOP) and caspase-12, were detected by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. The volume of cerebral infarction and brain water content in the IGRS-treated groups treated at doses of 60 and 120 mg/kg were decreased significantly compared with the Model group. The neurological scores were also significantly decreased in the IGRS-treated groups. IGRS treatment effectively decreased neuronal apoptosis resulting from CIRI-induced neuron injury. In addition, the histopathological damage and the endoplasmic reticulum ultrastructure injury were partially improved in CIRI rats following IGRS treatment. RT-qPCR and western blot analysis data indicated that IGRS significantly decreased the expression levels of GRP78, CHOP and caspase-12 at both mRNA and protein levels. The results of the present study demonstrated that IGRS exerted a protective effect against CIRI in brain tissue via the inhibition of apoptosis and ERS.