Short-term pretreatment of naringin isolated from Citrus wilsonii Tanaka attenuates rat myocardial ischemia/reperfusion injury

Pretreatment or treatment with anti-apoptotic, anti-inflammatory, or anti-oxidative approaches could be critical for attenuated the severity of myocardial ischemia/reperfusion (I/R) injury. Naringin, a natural flavonoid, plays important roles in inflammation-related diseases. Immature dry fruits of Citrus wilsonii Tanaka (Xiang Yuan) are rich in naringin that can be used as traditional Chinese medicine to treat inflammation-related symptoms. However, its roles in cardioprotective role remain unclear. This study aimed to isolate naringin from Citrus wilsonii Tanaka fruit and tested their cardioprotective effect. The dry fruits of Citrus wilsonii Tanaka were extracted with boiling water and then supernatants were freeze-dried to yield aqueous extract (ZQAE). The extract was chemoprofiled using UPLC-MS/MS to stand for major constituents, and then subjected to different chromatographic separation steps, and naringin was isolated in a high yield. The cardioprotective effects of the aqueous extract of ZQAE and naringin were investigated in a myocardial I/R rat model and to elucidate the mechanism underlying its cardioprotective effect. Our results indicated that 5-day ZQAE and naringin pretreatments both promoted histopathological changes and reduced myocardial enzymes (cTnl, CK-MB, CK and LDH) induced by I/R. Moreover, the 50 mg/kg and 100 mg/kg ZQAE dose pretreatments presented a significantly decreased infarct size as well as myocardial enzyme levels but also inhibited myocardial apoptosis (cleaved-caspase3 protein expression), the inflammatory response (IL-23, IL-6, and TNF-α) and oxidative stress (MDA and SOD). The cardioprotective effect of 5 mg/kg dose of naringin pretreatment is comparable with that of 5 mg/kg drug ditiazem pretreatment. Additionally, naringin pretreatment exhibited striking decreases in the apoptosis index and downregulation of the protein expression levels of cleaved-Caspase3, Bcl2 and Bax. Meanwhile, naringin downregulated HMGB1 expression and upregulated SIRT1 expression in the myocardium. These findings suggest that short-term pretreatments with ZQAE and naringin both protect against myocardial I/R injury by suppressing myocardial apoptosis, the inflammatory response, and oxidative stress. The cardioprotective effect of naringin involves SIRT1 activation and may interact with HMGB1 and inhibit the release of HMGB1.