Exploring of the ameliorative effects of Nerium (Nerium oleander L.) ethanolic flower extract in streptozotocin induced diabetic rats via biochemical, histological and molecular aspects

Oleander attenuates hepatic inflammation in a TLR4-independent manner and by favorable modulation of hepatocellular global metabolome that supports cytoprotection

ETHNOPHARMACOLOGICAL RELEVANCE

Nerium oleander is used to treat liver-associated chronic metabolic diseases in traditional medicinal systems across the globe. The hepatoprotective effects of oleander are mentioned in Indian and Chinese traditional medicinal literature.

AIM OF THE STUDY

The present study aimed to investigate the cellular mechanisms behind the hepatoprotective effects of a non-toxic dose of oleander (NO).

MATERIALS AND METHODS

The hepatoprotective effects of NO were tested against lipopolysaccharide (LPS)-treated HepG2 cells. Oxidative stress response was studied using cellular enzymatic assays, and gene expression was analyzed using qRT-PCR. HepG2 cells were pretreated with TAK-242 (pharmacological inhibitor of TLR4) to decipher the anti-inflammatory mechanisms of NO. Cell-free metabolites were analyzed using GCMS and were subjected to pathway enrichment analysis.

RESULTS

NO reduced systemic inflammation, serum lipid peroxidation byproducts, and glucose without affecting serum transaminase levels and hepatic histopathological features. NO attenuated the inflammation-induced loss of antioxidant enzyme activities and mRNA expressions of toll-like receptor-4 (TLR4)/nuclear factor κβ (NFκβ)-dependent inflammatory genes. In TAK-242 pretreated cells, LPS was unable to induce inflammatory and oxidative responses. However, NO treatment in TAK-242 pretreated cells with LPS stimulation further reduced the signs of inflammation and improved hepatoprotective activities. A comparative analysis of the intracellular global metabolome from HepG2 cells with and without NO treatment indicated NO-mediated favorable modulation of intracellular metabolic pathways that support cytoprotective activities.

CONCLUSION

NO protects HepG2 cells from LPS-induced oxidative and inflammatory injury. The hepatoprotective effects of NO are mediated by a TLR4-independent process and through a favorable modulation of the intracellular global metabolome that supports cytoprotection.