Melatonin inhibits cholangiocarcinoma and reduces liver injury in Opisthorchis viverrini-infected and N-nitrosodimethylamine-treated hamsters.

The human liver fluke Opisthorchis viverrini infection and N-nitrosodimethylamine (NDMA) administration induce cholangiocarcinoma (CCA) and liver injury in hamsters. Melatonin protects against liver injury and reduces the alteration of mitochondrial structure, mitochondrial membrane potential, and mitochondrial pro- and anti-apoptotic pathways in various cancer types. To investigate the chemopreventive effect of melatonin on CCA genesis and liver injury, hamsters were treated with a combination of O. viverrini infection and NDMA concurrently administered with melatonin (10 mg/kg and 50 mg/kg) for 120 days. Melatonin treatment at 50 mg/kg caused a significant reduction in liver/body weight ratios and decreased tumor volumes leading to an increase in the survival of animals. In the tumorous tissues, the high-dose melatonin reduced DNA fragmentation and mitochondrial apoptosis by inducing anti-apoptotic protein (Bcl-2) in the mitochondrial fraction and down-regulating cytochrome c, pro-apoptotic protein (Bax), and caspase-3 in tumor cytosol. Moreover, a high-dose melatonin treatment significantly increased mitochondrial antioxidant enzymes and prevented mitochondrial ultrastructure changes in the tumor. Overall, melatonin has potent chemopreventive effects in inhibiting CCA genesis and also reduces liver injury in hamster CCA, which, in part, might involve in the suppression of CCA by reducing tumor mitochondria alteration.

Curcumin induces a nuclear factor-erythroid 2-related factor 2-driven response against oxidative and nitrative stress after praziquantel treatment in liver fluke-infected hamsters.

Praziquantel has been used for the treatment of liver fluke infection, but an oxidative/nitrative stress may occur after a short-term treatment and participate in side effects. In an attempt to reduce the adverse effects, we administered curcumin, an anti-inflammatory agent, to Opisthorchis viverrini-infected hamsters treated with praziquantel. At 12h after treatment, curcumin decreased eosinophil infiltration and increased mononuclear cell infiltration in parallel with nuclear factor-erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 expression at the transcriptional and protein levels. Curcumin also enhanced the expression of genes involved in the Nrf2-regulated stress pathway (Kelch-like ECH-associated protein 1, NAD(P)H:quinine oxidoreductase 1, glutamate cysteine ligase, and activating transcription factor 3, peroxiredoxin 3, peroxiredoxin 6, manganese superoxide dismutase, and catalase), leading to increased ferric antioxidant capacity in the plasma. In contrast, curcumin decreased the level of oxidative and nitrative stress markers such as urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine, plasma levels of malondialdehyde and nitrate/nitrite, and activity of plasma alanine transaminase, a liver injury marker. This correlated with the suppression of nuclear factor-kappaB (NF-κB) and related molecules (cyclooxygenase-2 and inducible nitric oxide synthase) and pro-inflammatory cytokines (IL-1ß and TNF-α). In conclusion, curcumin may be an effective chemopreventive agent against oxidative and nitrative stress derived from praziquantel treatment during O. viverrini infection via induction of Nrf2 and suppression of NF-κB-mediated pathways. Nrf2 may also be a novel therapeutic target for not only parasitic diseases but other types of inflammation-mediated diseases.

Reduction of periductal fibrosis in liver fluke-infected hamsters after long-term curcumin treatment.

Chronic infection with the liver fluke, Opisthorchis viverrini, induces advanced periductal fibrosis and is a relative risk factor for cholangiocarcinoma in Southeastern Asia. We examined the reducing effect of curcumin on hepatobiliary fibrosis using O. viverrini-infected hamsters supplemented with dietary 1% curcumin (w/w) as an animal model. The expression profile of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs), cytokines, and collagens was assessed in relation to liver fibrosis. Histopathological studies revealed that curcumin had no effect on fibrosis at the short-term infection (21 days and 1 month); however, peribiliary fibrosis was significantly reduced after the long-term curcumin treatment for 3 months, compared to the untreated group. Expression of alpha-smooth muscle actin was associated with the reduction of liver fibrosis. A decrease in hepatic hydroxyproline level and mRNA expression of collagen I and III supported the reduction of fibrosis. The expression of TIMP-1, TIMP-2, and tumor necrosis factor-alpha genes was also decreased after curcumin treatment. In contrast, curcumin increased mRNA expression of MMP-13, MMP-7 (at 6 months), interleukin-1 beta, and transforming growth factor beta, implying that increased MMPs activity contributes to extracellular matrix degradation. These results suggest that curcumin reduces periductal fibrosis after long-term treatment by tissue resorption via inhibition of TIMPs expression and enhancement of MMPs expression mediated by cytokines. In conclusion, curcumin may serve as a promising nutraceutical agent exerting antifibrotic effect in O. viverrini-infected patients and contribute to cholangiocarcinoma prevention.