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:  Melatonin exhibits a wide variety of biological effects, including antioxidant and anti‐inflammatory functions. Its antioxidant role impedes the etiopathogenesis of pancreatitis, but little is known about the signaling pathway of melatonin in the induction of antioxidant enzymes in acute pancreatitis (AP). The aim of this study was to determine whether melatonin could prevent cerulein‐induced AP through nuclear factor erythroid 2‐related factor 2 (Nrf2) and curtail inflammation by inhibition of NF‐κB. AP was induced by two intraperitoneal (i.p.) injections of cerulein at 2 h intervals (50 μg/kg) in Sprague‐Dawley rats. Melatonin (10 or 50 mg/kg/daily, i.p.) was administered 24 h before each injection of cerulein. The rats were killed 12 h after the last injection. Acinar cell degeneration, pancreatic edema, and inflammatory infiltration were significantly different in cerulein‐ and melatonin‐treated rats. Melatonin significantly reduced amylase, lipase, MPO, and MDA levels, and increased antioxidant enzyme activities including SOD and GPx, which were decreased in AP (P < 0.05). Melatonin increased the expression of NQO1, HO‐1, and SOD2 when compared with the cerulein‐induced AP group (P < 0.05). In addition, melatonin increased Nrf2 expression, and reduced expressions of tumor necrosis factor‐alpha, IL‐1β, IL‐6, IL‐8, and iNOS. The elevated nuclear binding of NF‐κB in the cerulein‐induced pancreatitis group was inhibited by melatonin. These results show that melatonin increases antioxidant enzymes and Nrf2 expression, and limits inflammatory mediators in cerulein‐induced AP. It is proposed that melatonin may play an important role in oxidative stress via the Nrf2 pathway in parallel with reduction of inflammation by NF‐κB inhibition.

Melatonin has potent hepatoprotective effects as an antioxidant. However, the signaling pathway of melatonin in the induction of antioxidant enzymes against acute liver injury is not fully understood. The study aimed to determine whether melatonin could prevent dimethylnitrosamine (DMN)-induced liver injury through nuclear erythroid 2-related factor 2 (Nrf2) and inflammation. Liver injury was induced in rats by a single injection of DMN (30 mg/kg, i.p.). Melatonin treatment (50 mg/kg/daily, i.p.) was initiated 24 hr after DMN injection for 14 days, after which the rats were killed and samples were collected. Serum and antioxidant enzyme activities improved in melatonin-treated rats, compared with DMN-induced liver injury group (P < 0.01). Melatonin reduced the infiltration of inflammatory cells and necrosis in the liver, and increased the expression of NADPH: quinone oxidoreductase-1, heme oxygenase-1, and superoxide dismutase-2, which were decreased by DMN. Melatonin increased expression of novel transcription factor, Nrf2, and decreased expression of inflammatory mediators including tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, and inducible nitric oxide synthase. The increased nuclear binding of nuclear factor-kappa B (NF-kappaB) in the DMN-induced liver injury group was inhibited by melatonin. Our results show that melatonin increases antioxidant enzymes and Nrf2 expression in parallel with the decrease of inflammatory mediators in DMN-induced liver injury, suggesting that melatonin may play a role of antioxidant defense via the Nrf2 pathway, by reducing inflammation by NF-kappaB inhibition.

Oxidative stress in liver injury is a major pathogenetic factor in progress of liver fibrosis. Resveratrol, a representative antioxidant derived from grapes, has been reported to show widespread pharmacological properties. In this study, we investigated the protective effects of resveratrol on dimethylnitrosamine (DMN)-induced liver fibrosis in rats. Rats were treated with resveratrol daily by oral gavage for seven days after a single intraperitoneal injection of DMN (40 mg/kg). Resveratrol remarkably recovered body and liver weight loss due to DMN-induced liver fibrosis. Liver histology showed that resveratrol alleviated the infiltration of inflammatory cells and fibrosis of liver tissue. Resveratrol decreased the level of malondialdehyde and increased the levels of glutathione peroxidase and superoxide dismutase. Also, resveratrol significantly inhibited the mRNA expression of inflammatory mediators including inducible nitric oxide, tumor necrosis factor-alpha and interleukin-1beta. In addition, resveratrol showed not only reduced mRNA expression of fibrosis-related genes such as transforming growth factor beta 1, collagen type I, and alpha-smooth muscle actin, but also a significant decrease of hydroxyproline in rats with DMN-induced liver fibrosis. Our results suggest that resveratrol could be used to treat liver injury and fibrosis and be useful in preventing the development of liver fibrosis and cirrhosis.

Fucoidan, a sulfated polysaccharide extracted from various brown seaweeds, possesses a wide range of pharmacological properties. In this study, we investigated the protective effect of fucoidan on acetaminophen-induced acute liver injury in rats. Liver injury was induced by administration of acetaminophen (800 mg/kg, i.p.) and fucoidan was administered (100 mg kg, p.o.) 2 h before and after acetaminophen administration. After 24 h, co-treatment of fucoidan ameliorated liver damage and cell death induced by acetaminophen. Acetaminophen induced the overexpression of CYP2E1, one of the metabolizing enzymes of acetaminophen, but cotreatment with fucoidan suppressed its increased expression of CYP2E1. Fucoidan also reduced the hepatic apoptosis induced by acetaminophen exposure as shown in the protein expression of Bax, Bcl-2, and cleaved caspase-3. The anti-oxidative effect of fucoidan was observed from the increase of the production and expression of glutathione, superoxide dismutase, and glutathione peroxidase, both of which were decreased by acetaminophen. Also, fucoidan decreased the expression of inflammatory mediators, including tumor necrosis factoralpha, interleukin 1 beta, and inducible nitric oxide synthase. Taken together, the data demonstrate the hepato-protective effects of fucoidan against acetaminophen-induced liver injury via anti-oxidant, anti-inflammatory, and anti-apoptotic mechanisms.

Identification of small molecules that safely inhibit cancer progression is critical for cancer therapeutics. Saponins exhibit cytostatic and cytotoxic activity against various cancer cells, but the mechanism is not well understood. Here, we investigated whether saponin D (designated SB365), an active component isolated from Pulsatilla koreana, could inhibit the progression of hepatocellular carcinoma (HCC) and considered its mechanism. SB365 strongly suppressed the growth of HCC cells in a dosedependent manner and induced apoptosis by increasing the proportion of sub G1 apoptotic cells from 8% to 21% through induction of expression of Bax and cleaved caspase-3. In addition, SB365 exhibited potent anti-angiogenic activity and decreased the expression of hypoxia-inducible factor-1a (HIF-1a) and vascular endothelial growth factor, a key molecule for angiogenesis. Furthermore, SB365 suppressed the tube formation and migration of HUVEC, as well as in vivo neovascularization in a mouse Matrigel plug assay. In vivo study showed that SB365 significantly inhibited tumor growth in an HCC xenograft model, inducing apoptosis by increasing the expression of the cleaved caspase-3 and DNA fragmentation. The expressions of vascular endothelial growth factor and CD34 in the tumor tissue were decreased by SB365 treatment. In examining its mechanism, SB365 was found to effectively suppress the phosphorylation of PI3K downstream factors, such as Akt, mTOR and p70S6K both in vitro and in vivo. Our study demonstrates that SB365 not only induces apoptosis but also inhibits cell growth and angiogenesis through modulation of the PI3K/Akt/mTOR pathway in human HCC. We suggest that SB365 may be a new chemotherapeutic candidate against

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