HO-1 dependent antioxidant effects of ethyl acetate fraction from Physalis alkekengi fruit ameliorates scopolamine-induced cognitive impairments

Abstract

Physalis alkekengi var. francheti is an indigenous herb well known for its anti-inflammatory, sedative, antipyretic, and expectorant properties. However, the information regarding the impacts of P. alkekengi fruits (PAF) in modulation of oxidative stress and learning memory are still unknown. This study therefore evaluated the antioxidant properties of ethyl acetate (EA) fraction of PAF and its impacts on learning and memory. The antioxidant activities of PAF were evaluated in LPS-induced BV2 microglial cells. The potent EA fraction then investigated and confirmed for its involvement of HO-1 pathway using hemin (HO-1 inducer) and ZnPP (HO-1 inhibitor) through Western blotting, DCFH-DA, and/or Griess assay. The involvements of PI3K/Akt, MEK, and p38 MAPK also investigated. Furthermore, we applied EA fraction to the animals at 100 and 200 mg/kg doses to check if the extract could improve scopolamine-induced memory deficits in passive avoidance and elevated plus maze tests. Our results demonstrated that the fractions from PAF significantly inhibited the generation of intracellular reactive oxygen species (ROS) induced by LPS in concentration-dependent manners. In comparison to other fractions, the EA fraction exhibited potent effect in suppressing intracellular ROS generation. Besides, EA fraction also induced the expression of HO-1 in time- and concentration-dependent manners. ZnPP significantly reversed the suppressive effect of EA fraction on LPS-induced ROS generation and NO production, which confirm the involvement of HO-1 signaling in EA-fraction-mediated antioxidant activities. Consistently, blocking of PI3K/Akt, MEK, and p38 MAPK pathways by PAF-EA suppressed the production of intracellular ROS, indicating their potential participation. In addition, one of the major constituents of EA fraction, luteolin-7-O-β-D-glucoside, also demonstrated HO-1-dependent antioxidant effects in BV2 cells. Further, the EA fraction significantly (p < 0.05) improves scopolamine-induced memory deficits in mice. Taken together, our findings highlight the antioxidant effects of EA fraction of PAF which may be beneficial in treatment of different neurodegenerative diseases associated with free radicals.