Mechanistic insights of methylcinnamate in improving oxidative stress and inflammation in acetaminophen-induced hepatotoxic mice by upregulating Nrf2 pathway.

Background: Methylcinnamate (MC), a safe flavoring agent naturally found in Occimum basilicum L. is reported to have an anti-inflammatory responses in various disease models. Acetaminophen (APAP) toxicity is a significant contributor to acute liver injury, which leads to oxidative stress and inflammation. The transcriptional factor nuclear factor erythroid 2-related factor 2 (Nrf2) regulated the cellular defense mechanisms aid to antioxidant response facilitation and reduction in inflammation against various disorders.

Methodology: This study evaluated the protective effects of MC in APAP-induced hepatotoxicity in mice and its anti-oxidant, anti-inflammatory, and Nrf2 mechanisms were studied. In-vitro 2,2-diphenyl-1-picrylhydrazyl assay showed the antioxidant capacity of MC. Mice were pretreated with MC (25, 50, 75, and 100 mg/kg) orally for 7 days. After a fasting period of 16 h, hepatotoxicity was induced by injecting APAP 300 mg/kg intraperitoneal on day 7. Liver profile, oxidative test, and histopathological changes were studied. Gene expression of interlukin-1β (IL-1β), interlukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), cytochrome P450 2E1 (CYP2E1), Nrf2, and NAD(P)H dehydrogenase (quinone) 1 (NQO-1) were estimated by real time quantitative polymerase chain reaction (RT-qPCR). IL-1β, IL-6, and TNF-α concentrations were also analyzed by enzyme-linked immunosorbent assay (ELISA).

Results: The MC treatment showed a notable reduction in alanine transaminase, aspartate aminotransferase and alkaline phosphatase activities, and total bilirubin level of serum. Moreover, MC significantly attenuated oxidative stress by rising the antioxidant enzymes catalase, glutathione, and superoxide dismutase and reducing the malondialdehyde and nitric oxide levels in the liver. Furthermore, MC successfully mitigated the levels of IL-1β, IL-6, and TNF-α, which were estimated through RT-qPCR and ELISA. The RT-qPCR revealed a CYP2E1 enzyme inhibition and significant upregulation of hepatic Nrf2 and NQO-1 levels after MC therapy. Histopathological analysis showed improvement in liver injury within the MC treatment groups.

Conclusion: It was concluded from this study that pretreatment of MC had successfully protected the liver through anti-inflammatory, anti-oxidant activity upon subsequent activation of Nrf2.