Dihydro-stilbene gigantol relieves CCl4-induced hepatic oxidative stress and inflammation in mice via inhibiting C5b-9 formation in the liver.

In general, anti-inflammatory treatment is considered for multiple liver diseases despite the etiology. But current drugs for alleviating liver inflammation have defects, making it necessary to develop more potent and safer drugs for liver injury. In this study, we screened a series of (dihydro-)stilbene or (dihydro-)phenanthrene derivatives extracted from Pholidota chinensis for their potential biological activities. Among 31 compounds, the dihydro-stilbene gigantol exerted most potent protective effects on human hepatocytes against lithocholic acid toxicity, and exhibited solid antioxidative and anti-inflammatory effect in vitro. In mice with CCl4-induced acute liver injury, pre-administration of gigantol (10, 20, 40 mg· kg-1· d-1, po, for 7 days) dose-dependently decreased serum transaminase levels and improved pathological changes in liver tissues. The elevated lipid peroxidation and inflammatory responses in the livers were also significantly alleviated by gigantol. The pharmacokinetic studies showed that gigantol was highly concentrated in the mouse livers, which consisted with its efficacy in preventing liver injury. Using a label-free quantitative proteomic analysis we revealed that gigantol mainly regulated the immune system process in liver tissues of CCl4-treated mice, and the complement and coagulation cascades was the predominant pathway; gigantol markedly inhibited the expression of complement component C9, which was a key component for the formation of terminal complement complex (TCC) C5b-9. These results were validated by immunohistochemistry (IHC) or real time-PCR. Confocal microscopy analysis showed that gigantol significantly inhibited the vascular deposition of TCC in the liver. In conclusion, we demonstrate for the first time that oral administration of gigantol potently relieves liver oxidative stress and inflammation, possibly via a novel mechanism of inhibiting the C5b-9 formation in the liver.

Characterization of the metabolites of gigantol in rat, dog, monkey, and human hepatocytes using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry.

RATIONALE: Gigantol (3',4-dihydroxy-3,5'-dimethoxybibenzyl) is a bibenzyl compound isolated from Dendrobii Caulis that has been widely used as a medicinal herb in China. To fully understand the mechanism of action of gigantol, it is necessary to determine its metabolic profile. METHODS: Gigantol at a concentration of 20 µM was incubated with hepatocytes (rat, dog, monkey, and human) at 37°C. After 120 min incubation, the samples were analyzed using liquid chromatography coupled with electrospray ionization tandem mass spectrometry. The structures of the metabolites were characterized by their molecular masses, product ions, and retention times. RESULTS: A total of 17 metabolites were detected and structurally identified. The metabolism involved the following pathways: (a) oxidation to form quinone-methide species and subsequently conjugation with glutathione (GSH); (b) demethylation to form demethylated gigantol, which was further conjugated with GSH; (c) hydroxylation to yield hydroxyl-gigantol followed by glucuronidation or GSH conjugation; and (d) glucuronidation to form glucuronide conjugates. Glucuronidation was the primary metabolic pathway in all tested species. CONCLUSIONS: Hydroxylation, demethylation, glucuronidation, and GSH conjugation were the major metabolic pathways of gigantol. This study provides new information on the metabolic profiles of gigantol and helps us understand the disposition of the compound.

The role of mitochondria-mediated intrinsic death pathway in gingerdione derivative I6-induced neuronal apoptosis.

Neuronal death induced by I6 displayed apoptotic characteristics but the precise mechanism has not been fully elucidated. In the present studies, I6 at 24 h after intraperitoneal administration significantly decreased the density of surviving neurons and increased caspase-3 activity in frontal cortex, suggesting that peripherally administered I6 may cross BBB to induce CNS toxicity. In rat embryonic primary cortical cells, I6-induced reduction of mitochondrial viability and neuronal apoptosis was inhibited by vitamin E. In addition, I6-induced reactive oxygen species (ROS) caused the disruption of mitochondria membrane potential (MMP), the release of cytochrome c, the activation of caspase-9 and caspase-3, and cleavage of poly(ADP-ribose) polymerase (PARP), resulting in activation of mitochondrial-mediated intrinsic death pathway. Pre-treatment with antioxidant vitamin E or N-acetylcysteine (NAC) completely abolished the I6-induced generation of ROS, loss of MMP, release of cytochrome c, activation of caspase-9 and caspase-3, and cleavage of PARP. Carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), a mitochondrial uncoupler, significantly reduced I6-induced neuronal death as well as caspase-3 activation and PARP cleavage. These results suggest that I6 induces neuronal death by promoting intracellular ROS production to cause a loss of MMP that result in release of cytochrome c and activation of mitochondria-mediated intrinsic death pathway.