Harpagide from Scrophularia protects rat cortical neurons from oxygen-glucose deprivation and reoxygenation-induced injury by decreasing endoplasmic reticulum stress

Ethnopharmacological relevance: Harpagide is the main ingredient in Scrophularia ningpoensis Hemsl which is used for the therapeutic purpose of treating encephalopathy. Harpagide has shown promise in the treatment of oxygen-glucose deprivation and reoxygenation (OGD/R)-induced brain injury. However, the underlying mechanisms remain unclear.

Aim of study: In this study, we aimed to determine the neuroprotective effect of harpagide on rat cortical neurons under OGD/R conditions that induce the development of ischaemia-reperfusion (I/R).

Materials and methods: To explore the biological function of harpagide in cerebral ischaemia-reperfusion injury (CIRI), The CIRI model was established by oxygen-glucose deprivation and reoxygenation (OGD/R) on rat cortical neurons. It tested cell survival rate by 3-(4,5-dimethylthiazol-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, apoptosis by flow cytometry, intracellular Ca²⁺ concentration [Ca²⁺] _i by cofocal laser, and expressions related to endoplasmic reticulum stress (ERS) by RT-PCR and Western blot.

Results: We found that pretreatment with harpagide (50 μM) prevented OGD/R-induced apoptotic cell death. Harpagide also significantly decreased the gene expression levels and protein production of ERS-related proteins. We found that harpagide also exerted a neuroprotective effect on TG-induced apoptosis in rat cortical neurons and decreased the gene expression levels and protein production of GRP78, caspase-12 and CHOP. We also measured the intracellular calcium ion concentration ([Ca²⁺]_i) in neurons and found that harpagide significantly decreased the [Ca²⁺]_i induced by OGD/R and TG.

Conclusion: These results suggest that harpagide protects against OGD/R-induced cell apoptosis, likely by decreasing ERS. Collectively, harpagide was demonstrated to be a prominent suppressor of ERS and prevented the apoptosis of rat cortical neurons. Based on the results, harpagide could potentially serve as a therapeutic agent of ischaemia-like injury associated with excessive ERS and apoptosis.