Effects of Asiaticoside on Nitric Oxide induced injuries in Neuronal cell line cultures

Abstract

Asiaticoside, a main triterpene of Centalla asiatica, was well known for wound healing effect. In traditional medicine, Centella asiatica have been used in the management of central nervous system disorders including neurodegenerative diseases and memory deficit. The present research was designed to investigate the potential ability of asiaticoside and Centella asiatica extract to prevent or attenuate the process of neurodegeneration in the in vitro model of nitric oxide-induced injuries in cultured neuroblastoma N1E-115 cells. Cell viability (assessed by MTT reduction and LDH release), levels of lipid peroxidation, and glutathione content, were used as the measuring endpoints. Treatment of cultured N1E-115 cells with 1-100 µM of asiaticoside or 1-100 µg/ml of Centella asiatica extract for 24 or 48 hr had no apparent effect on cell viability whereas treatment with 200-500 µM of asiaticoside under the same condition revealed cytotoxic effects. SNAP, a NO donor, induced neuronal injury and death in a concentration-dependent manner with approximately 50% cell injury occurred after an exposure to 1 mM SNAP for 24 hr. Pre-treatment with asiaticoside or Centella asiatica extract, and co-treatment with asiaticoside, had no protective effect against SNAP-induced neurotoxicity. However, co-treatment of 25-100 µg/ml Centella asiatica extract with 1 mM SNAP for 24 hr attenuated SNAP-induced suppression of mitochondrial metabolic activity and successive cell death in spite of no apparent effects on SNAP-induced nitrite accumulation. In addition, at a concentration of 100 µg/ml, Centella asiatica extract elevated SNAP-induced decrease of total glutathione content while exerted ambiguous effects on levels of lipid peroxidation. In conclusion, the present study suggested that Centella asiatica extract, but not asiaticoside, may possess the marginal in vitro cytoprotective property against NO-induced neuronal damages. Antioxidant activity of Centella asiatica extract may not be directly responsible for this beneficial effect. However, the detailed mechanisms are not fully understood and remain to be further elucidated.