Curcumin suppresses epithelial-to-mesenchymal transition of peritoneal mesothelial cells (HMrSV5) through regulation of transforming growth factor-activated kinase 1 (TAK1).

OBJECTIVE: Peritoneal fibrosis remains a serious complication of long-term peritoneal dialysis (PD) leading to peritoneal membrane ultrafiltration failure. Epithelial-mesenchymal transition (EMT) of peritoneal mesothelial cells (PMCs) is a key process of peritoneal fibrosis. Curcumin has been previously shown to inhibit EMT of renal tubular epithelial cells and prevent renal fibrosis. There are only limited reports on inhibition of PMCs-EMT by curcumin. This study aimed to investigate the effect of curcumin on the regulation of EMT and related pathway in PMCs treated with glucose-based PD. METHODS: EMT of human peritoneal mesothelial cells (HMrSV5) was induced with glucose-based peritoneal dialysis solutions (PDS). Cells were divided into a control group, PDS group, and PDS group receiving varied concentrations of curcumin. Cell Counting Kit-8 (CCK-8) assay was used to measure cell viability, and a transwell migration assay was used to verify the capacity of curcumin to inhibit EMT in HMrSV5 cells. Real-time quantitative PCR and western blot were used to detect the expression of genes and proteins associated with the EMT. RESULTS: High glucose PDS decreased cell viability and increased migratory capacity. Curcumin reversed growth inhibition and migration capability of human peritoneal mesothelial cells (HPMCs). In HMrSV5 cells, high glucose PDS also decreased expression of epithelial markers, and increased expression of mesenchymal markers, a characteristic of EMT. Real-time RT-PCR and western blot revealed that, compared to the 4.25% Dianeal treated cells, curcumin treatment resulted in increased expression of E-cadherin (epithelial marker), and decreased expression of α-SMA (mesenchymal markers) (P < 0.05). Furthermore, curcumin reduced mRNA expression of two extracellular matrix protein, collagen I and fibronectin. Curcumin also reduced TGF-ß1 mRNA and supernatant TGF-ß1 protein content in the PDS-treated HMrSV5 cells (P < 0.05). Furthermore, it significantly reduced protein expression of p-TAK1, p-JNK and p-p38 in PDS-treated HMrSV5 cells. CONCLUSIONS: Our results demonstrate that curcumin showed an obvious protective effect on PDS-induced EMT of HMrSV5 cells and suggest implication of the TAK1, p38 and JNK pathway in mediating the effects of curcumin in EMT of MCs.

Curcumin ameliorates peritoneal fibrosis via inhibition of transforming growth factor-activated kinase 1 (TAK1) pathway in a rat model of peritoneal dialysis.

BACKGROUND: Peritoneal fibrosis (PF) remains a serious complication of long-term peritoneal dialysis (PD). The goal of this study was to investigate the anti-fibrotic effects of curcumin on the PF response to PD and its' mechanism. METHODS: Male Sprague-Dawley rats were infused with 20 mL of 4.25% glucose-based standard PD fluid for 8 consecutive weeks to establish PF model and then divided into five groups: Control, received sham operation and 0.9% physiological saline; PD, received 4.25% standard PD fluid; Curcumin, PD rats injected intraperitoeally with curcumin for 8 weeks at doses of 10, 20 or 40 mg/kg. Masson's staining was performed to evaluate the extent of PF. Peritoneal Equilibration Test (PET) was conducted to assess ultrafiltration volume (UFV) and mass transfer of glucose (MTG), quantitative RT-PCR, and immunohistochemistry or western blotting were performed to measure the expression levels of inflammation and fibrosis-associated factors. We also detected the TGF-ß1 in peritoneal fluid by ELISA. RESULTS: Compared with the control group, the PD rats showed decreased UFV (2.54 ± 0.48 to 9.87 ± 0.78 mL, p < 0.05] and increased MTG (18.99 ± 0.86 to 10.85 ± 0.65 mmol/kg, p < 0.05) as well as obvious fibroproliferative response, with markedly increased peritoneal thickness (178.33 ± 4.42 to 25.26 ± 0.32um, p < 0.05) and higher expression of a-SMA, collagen I and TGF-ß1. Treatment with curcumin significantly increased UFV, reduced MTG and peritoneal thickness of PD rats. The elevated TGF-ß1 in peritoneal fluid of PD rats was significantly decreased by curcumin. It attenuated the increase in protein and mRNA of TGF-ß1, α-SMA and collagen I in peritoneum of PD rats. The mRNA expressions of TAK1, JNK and p38, as well as the protein expressions of p-TAK1, p-JNK and p-p38 in peritoneum of PD rats were reduced by curcumin. CONCLUSIONS: Present results demonstrate that curcumin showed a protective effect on PD-related PF and suggest an implication of TAK1, p38 and JNK pathway in mediating the benefical effects of curcumin.

[Effect of Rhein on the development of hepatic fibrosis in rats].

OBJECTIVE: To investigate the effect of rhein on the development of hepatic fibrosis. METHODS: The animal models were made with carbon tetrachloride (CCl(4)) mixed with vegetable oil (3/2, v/v), which was injected subcutaneously twice a week for 6 weeks, and with 5% ethanol for free drinking water. At the same time, Rhein was administrated at the dose of 25 mg/kg or 100 mg/kg once a day for 6 weeks. The changes of both biochemical markers, such as the levels of alanine aminotransferase (ALT), hyaluronic acid (HA), procollagen type III (PCIII) in serum and SOD, malondialdehyde (MDA) in liver, and related histopathological parametres were determined. RESULTS: Compared with the model group, there were three kinds of changes in the larger quantity of rhein treated group. (1) The levels of ALT, HA, PCIII in serum and MDA in liver homogenate were decreased significantly (from 150 U/L +/- 16 U/L to 78 U/L +/- 18 U/L, 321 microg/L +/- 97 microg/L to 217 microg/L +/- 75 microg/L, 31 microg/L +/- 14 microg/L to 16 microg/L +/- 6 microg/L and 3.67 nmol/mg +/- 0.68 nmol/mg to 1.88 nmol/mg +/- 0.34 nmol/mg, respectively, t > or 2.977, P<0.01). However the level of SOD in liver was increased (from 62.45 NU/mg +/- 8.74 NU/mg to 91.26 NU/mg +/- 14.04 NU/mg, t=4.453, P<0.01). (2) The expressions of transforming growth factor beta 1 (TGF-beta 1) and alpha-smooth muscle actin (alpha-SMA) in liver were markedly reduced (P<0.05 and P<0.01). (3) The collagen staining positive area was decreased and the grade of fibrosis was reduced significantly in liver (P<0.05 and P<0.01). CONCLUSION: Rhein can protect hepatocyte from injury and prevent the progress of hepatic fibrosis in rats, which may associate with that rhein plays a role in antioxidation, anti-inflammation, inhibiting the expression of TGF-beta1 and suppressing the activation of hepatic stellate cells (HSCs).

Rhein inhibits liver fibrosis induced by carbon tetrachloride in rats.

AIM: To investigate the effect of rhein on liver fibrosis induced by the exposure of carbon tetrachloride (CCl4)/ethanol in rats. METHODS: Male Wistar rats were divided into four study groups (n=10 each group): healthy controls, CCl4/ethanol-injured rats left untreated, and CCl4/ethanol-injured rats treated with rhein of low-dose (25 mg/kg) and high-dose (100 mg/kg). Rhein was given once a day since rat received CCl4/ethanol injury. After administration of rhein for 6 weeks rats were killed. The following parameters were determined: the activity of alanine aminotransferase (ALT), hyalauronic acid (HA) and procollagen type III (PC-III) concentrations in serum, liver malondialdehyde (MDA) level, the degree of liver fibrosis, and the expression of alpha-smooth muscle actin (alpha-SMA) and transforming growth factor-beta1 (TGF-beta1) in liver tissue. RESULTS: The treatment of rhein markedly reduced the ALT activity, HA and PC-III concentrations, and liver MDA level in CCl4/ethanol-injured rats (P<0.01). It also improved significantly histological changes of fibrosis and decreased the expression of alpha-SMA and TGF-beta1 in liver of these rats (P<0.05 or P<0.01). CONCLUSION: Rhein has protective effect on liver injury and can inhibit liver fibrosis induced by CCl4/ethanol in rats. The mechanisms possibly contribute to its action of antioxidant and anti-inflammatory activity, also associated with its effect of inhibiting TGF-beta1 and suppressing the activation of hepatic stellate cells.