Melatonin induces apoptosis in cholangiocarcinoma cell lines by activating the reactive oxygen species-mediated mitochondrial pathway

We previously demonstrated that melatonin could be used as a chemopreventive agent for inhibiting cholangiocarcinoma (CCA) development in a hamster model. However, the cytotoxic activity of melatonin in cancer remains unclear. In the present study, we investigated the effect of melatonin on CCA cell lines. Human CCA cell lines (KKU-M055 and KKU-M214) were treated with melatonin at concentrations of 0.5, 1 and 2 mM for 48 h. Melatonin treatment exerted a cytotoxic effect on CCA cells by inhibiting CCA cell viability in a concentration-dependent manner. Treatment with melatonin, especially at 2 mM, increased intracellular reactive oxygen species (ROS) production and in turn led to increased oxidative DNA damage and 8-oxodG formation. Moreover, melatonin treatment enhanced the production of cytochrome c leading to apoptosis in a concentration-dependent manner, as indicated by increased expression of apoptosis-related proteins caspase-3 and caspase-7. In conclusion, melatonin acts as a pro-oxidant by activating ROS-dependent DNA damage and thus leading to the apoptosis of CCA cells.

Bile canalicular changes and defective bile secretion in Opisthorchis viverrini-infected hamsters

Infection with the liver fluke Opisthorchis viverrini (Digenea) (Poirier, 1886) causes bile duct injury and periductal fibrosis by chronic overproduction of inflammatory-mediators and eventually results in cholangiocarcinoma development. While extensive research works have been done on O. viverrini infection-associated changes of bile ducts and periductal fibrosis, little attention was paid on morphological and biochemical changes of the bile canaliculi (BC), the origin of bile flow. We aimed to investigate the morphological and functional alterations of BC in the liver of hamsters infected with O. viverrini at one and three months post-infection. Ultrastructural changes of BC showed dilatation of BC and significant reduction of the density of microvilli as early as at one month post-infection. Immunohistochemistry revealed that CD10, a BC marker, expression was reduced early as one month post-infection. The mRNA expression of the genes encoding molecules related to bile secretion including bile acid uptake transporters (slc10a1 and slco1a1), bile acid dependent (abcb11) and independent (abcc2) bile flow and bile acid biosynthesis (cyp7a1 and cyp27a1) were significantly decreased at one month post-infection in association with the reduction of bile volume. In contrast, the expression of the mRNA of bile acid regulatory genes (fxr and shp-1) was significantly increased. These changes essentially persisted up to three months post-infection. In conclusion, O. viverrini infection induces morphological and functional changes of BC in association with the decrease of bile volume.

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.

α-Tocopherol and lipid profiles in plasma and the expression of α-tocopherol-related molecules in the liver of Opisthorchis viverrini-infected hamsters

Opisthorchis viverrini infection induces inflammation-mediated oxidative stress and liver injury, which may alter α-tocopherol and lipid metabolism. We investigated plasma α-tocopherol and lipid profiles in hamsters infected with O. viverrini. Levels of α-tocopherol, cholesterol, and low-density lipoprotein increased in the acute phase of infection. In the chronic phase, α-tocopherol decreased, while triglyceride and very low-density lipoprotein increased. Notably, high-density lipoprotein decreased both in the acute and chronic phases. In the liver, cholesteryl oleate, triolein, and oleic acid decreased in the acute phase, and increased in the chronic phase. Such chronological changes were negatively correlated with the plasma α-tocopherol level. The expression of α-tocopherol-related molecules, ATP-binding cassette transporter A1 (ABCA1) and α-tocopherol transfer protein, increased throughout the experiment. These results suggest that O. viverrini infection profoundly affects on lipid and α-tocopherol metabolism in due course of infection.

Proteomic identification of plasma protein tyrosine phosphatase alpha and fibronectin associated with liver fluke, Opisthorchis viverrini, infection

Opisthorchiasis caused by Opisthorchis viverrini induces periductal fibrosis via host immune/inflammatory responses. Plasma protein alteration during host-parasite interaction-mediated inflammation may provide potential diagnostic and/or prognostic biomarkers. To search for target protein changes in O. viverrini-infected hamsters, a 1-D PAGE gel band was trypsin-digested and analyzed by a LC-MS/MS-based proteomics approach in the plasma profile of infected hamsters, and applied to humans. Sixty seven proteins were selected for further analysis based on at least two unique tryptic peptides with protein ID score >10 and increased expression at least two times across time points. These proteins have not been previously identified in O. viverrini-associated infection. Among those, proteins involved in structural (19%), immune response (13%), cell cycle (10%) and transcription (10%) were highly expressed. Western blots revealed an expression level of protein tyrosine phosphatase alpha (PTPα) which reached a peak at 1 month and subsequently tended to decrease. Fibronectin significantly increased at 1 month and tended to increase with time, supporting proteomic analysis. PTPα was expressed in the cytoplasm of inflammatory cells, while fibronectin was observed mainly in the cytoplasm of fibroblasts and the extracellular matrix at periductal fibrosis areas. In addition, these protein levels significantly increased in the plasma of O. viverrini-infected patients compared to healthy individuals, and significantly decreased at 2-months post-treatment, indicating their potential as disease markers. In conclusion, our results suggest that plasma PTPα and fibronectin may be associated with opisthorchiasis and the hamster model provides the basis for development of novel diagnostic markers in the future.

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-1β 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.

Protective effect of melatonin against Opisthorchis viverrini-induced oxidative and nitrosative DNA damage and liver injury in hamsters

The liver fluke, Opisthorchis viverrini, is the risk factor of cholangiocarcinoma, which is a major health problem in northeastern Thailand. Production of reactive oxygen and nitrogen species during the host's response leads to oxidative and nitrosative stress contributing to carcinogenesis. We investigated the protective effect of melatonin against O. viverrini-induced oxidative and nitrosative stress and liver injury. Hamsters were infected with O. viverrini followed by oral administration of various doses of melatonin (5, 10, and 20 mg/kg body weight) for 30 days. Uninfected hamsters served as controls. Compared to the levels in O. viverrini-infected hamsters without melatonin treatment, the indoleamine decreased the formation of oxidative and nitrosative DNA lesions, 8-oxo-7,8-dihydro-2'-deoxyguanosine and 8-nitroguanine, in the nucleus of bile duct epithelium and inflammatory cells, in parallel with a reduction in 3-nitrotyrosine. Melatonin also reduced the expression of heme oxygenase-1 and cytokeratin 19, nitrate/nitrite levels, and bile duct proliferation in the liver. Alanine transaminase activity and the levels of 8-isoprostane and vitamin E were also dose dependently decreased in the plasma of melatonin-treated hamsters. Melatonin reduced the mRNA expression of oxidant-generating genes [inducible nitric oxide synthase, nuclear factor-kappa B (NF-κB), and cyclooxygenase-2] and proinflammatory cytokines (TNF-α and IL-1β), accompanied by an increase in the expression of antioxidant genes [nuclear erythroid 2-related factor 2 (Nrf2) and manganese superoxide dismutase]. Thus, melatonin may be an effective chemopreventive agent against O. viverrini-induced cholangiocarcinoma by reducing oxidative and nitrosative DNA damage via induction of Nrf2 and inhibition of NF-κB-mediated pathways.

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.