Apoptotic effects of rhein through the mitochondrial pathways, two death receptor pathways, and reducing autophagy in human liver L02 cells.

Rhein (4,5-dihydroxyanthraquinone-2-carboxylic acid) is a major component of many medicinal herbs such as Rheum palmatum L. and Polygonum multiflorum. Despite being widely used, intoxication cases associated with rhein-containing herbs are often reported. Currently, there are no available reports addressing the effects of rhein on apoptosis in human liver L02 cells. Thus, the aim of this study is to determine the cytotoxic effects and the underlying mechanism of rhein on human normal liver L02 cells. In the present study, the methyl thiazolyl tetrazolium assay demonstrated that rhein decreased the viability of L02 cells in dose-dependent and time-dependent ways. Rhein was found to trigger apoptosis in L02 cells as shown by Annexin V-fluoresceine isothiocyanate (FITC) apoptosis detection kit and cell mitochondrial membrane potential (MMP) assay, with nuclear morphological changes demonstrated by Hoechst 33258 staining. Detection of intracellular superoxide dismutase activity, lipid oxidation (malondialdehyde) content, and reactive oxygen species (ROS) levels showed that apoptosis was associated with oxidative stress. Moreover, it was observed that the mechanism implicated in rhein-induced apoptosis was presumably via the death receptor pathway and the mitochondrial pathway, as illustrated by upregulation of TNF-α, TNFR1, TRADD, and cleaved caspase-3, and downregulation of procaspase-8, and it is suggested that rhein may increase hepatocyte apoptosis by activating the increase of TNF-α level. Meanwhile, rhein upregulates the expression of Bax and downregulates the expression of procaspase-9 and -3, and it is suggested that the mitochondrial pathway is activated and rhein-induced apoptosis may be involved. In addition, we also want to explore whether rhein-induced apoptosis is related to the autophagic changes induced by rhein. The results showed that rhein treatment increased P62 and decreased LC3-II and beclin-1, which means that autophagy was weakened. The results of our studies indicated that rhein induced caspase-dependent apoptosis via both the Fas death pathway and the mitochondrial pathway by generating ROS, and meanwhile the autophagy tended to weaken.

[Paeoniflorin ameliorates liver injury of MRL/lpr mice through inhibition of NF-κB pathway].

Objective To investigate the effects of paeoniflorin (PF) on liver injury of MRL/lpr mice and its underlying mechanisms. Methods The research included 10 normal control C57BL/6 mice and 40 MRL/lpr mice. MRL/lpr mice were randomly assigned equally to a blank control group, a dexamethasone (1.5 mg/kg) group, and two PF (20, 40 mg/kg) groups. The serum levels of alanine transaminase (ALT) and aspartate transaminase (AST) were tested with microplate assay. Inflammatory cytokines in the serum and liver were also detected using ELISA. Liver pathological changes were observed using HE staining. The protein levels of receptor interacting protein140 (RIP140), Toll-like receptor 4 (TLR4), p-NF-κBp65, NF-κBp65, p-IκBα and IκBα in the liver were detected by Western blot analysis. Results PF significantly decreased the serum levels of AST and ALT, obviously decreased the expressions of the inflammatory cytokines IL-1ß, IL-6 and TNF-α in the serum and liver, alleviated liver pathological changes and inhibited the expressions of RIP140, TLR4, p-NF-κBp65, p-IκBα proteins in the MRL/lpr mice. Conclusion PF has protective effects against liver injury in MRL/lpr mice by inhibiting NF-κB pathway.