Forsythia suspensa extract attenuates lipopolysaccharide-induced inflammatory liver injury in rats via promoting antioxidant defense mechanisms.

Reactive oxygen species (ROS) have been shown to have a role in inflammation. We investigated whether Forsythia suspensa extract (FSE) could exert its antioxidant potential against lipopolysaccharide (LPS)-induced inflammatory liver injury in rats. Rats were orally fed FSE once daily for 7 consecutive days prior to LPS (Escherichia coli, serotype O55:B5) injection. LPS treatment caused liver dysfunction as evidenced by massive histopathological changes and increased serum alanine aminotransferase and aspartate aminotransferase activities which were ameliorated by FSE pretreatment. FSE attenuated LPS-induced depletion of cytosolic nuclear factor-erythroid 2-related factor 2 (Nrf2) and suppression of Nrf2 nuclear translocation in liver, and the generation of ROS and malondialdehyde in serum and liver. FSE increased the Nrf2-mediated induction of heme oxygenase-1 in liver, as well as superoxide dismutase and glutathione peroxidase activities in serum and liver. Importantly, FSE attenuated LPS-induced nuclear factor-кB (NF-кB) nuclear translocation in liver, and subsequently decreased tumor necrosis factor-α, interleukin (IL)-1β and IL-6 levels in serum and liver, which were associated with FSE-induced activation of Nrf2 in liver. These results indicate that the protective mechanisms of FSE may be involved in the attenuation of oxidative stress and the inhibition of the NF-кB-mediated inflammatory response by modulating the Nrf2-mediated antioxidant response against LPS-induced inflammatory liver injury.