The Protective Effect of Notoginsenoside R1 on Isoflurane-Induced Neurological Impairment in the Rats via Regulating miR-29a Expression and Neuroinflammation.

Introduction: Isoflurane inhalation leads to apoptotic neurodegeneration and further results in learning and cognitive dysfunction. Notoginsenoside R1 (NGR1), a major ingredient from Radix notoginseng, has been reported to exert neuroprotective effect during brain or neuron injury. This study aimed to investigate the effect of NGR1 on neurological impairment.

Methods: Sixty-four male Sprague Dawley rat pups (15-20 g) of postnatal day 7 were recruited. Spatial learning and memory were assessed by the Morris water maze test, and the neurological severity score was determined. Real-time quantitative PCR was used to detect the expression levels of microRNA (miR)-29a. Enzyme-linked immunosorbent assay was applied to estimate the levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the hippocampal tissues.

Results: NGR1 attenuated neurological impairment induced by isoflurane, shown by the decrease in neurological function score and escape latency and the increase in staying time in the original quadrant in rats. NGR1 reversed the downregulation of miR-29a expression induced by isoflurane treatment. After the treatment of NGR1, the elevated levels of IL-6, TNF-α, and IL-1β induced by isoflurane were all decreased significantly in the hippocampal tissues of rats. Additionally, the repressive action of NGR1 in neurological impairment and neuroinflammation was eliminated by downregulating miR-29a in rats.

Conclusion: NGR1 protects against isoflurane-induced neurological impairment. The protective effect of NGR1 might be achieved by promoting the expression of miR-29a and preventing inflammatory response.