TNFα Induces Multidrug Resistance-Associated Protein 4 Expression through p38-E2F1-Nrf2 Signaling in Obstructive Cholestasis

PURPOSE: To explore the molecular mechanism of the upregulation of multidrug resistance-associated protein 4 (MRP4) in cholestasis. MATERIALS AND METHODS: The mRNA and protein levels of MRP4 in liver samples from cholestatic patients were determined by quantitative real-time PCR and Western blot. In human hepatoma HepG2 cells, electrophoretic mobility shift assay (EMSA) was used to determine the affinity of nuclear factor-E2-related factor (Nrf2) binding to MRP4 promoter. Dual-luciferase reporter assay was used to detect the binding of tumor necrosis factor α (TNFα) to the promotor of E2F1. The bile duct ligation mouse models were established using male C57BL/6 mice. RESULTS: The mRNA and protein levels of MRP4 were significantly increased in cholestatic patients. TNFα treatment induced the expression of MRP4 and Nrf2 and enhanced cell nuclear extract binding activity to MRP4 promoter, as demonstrated by EMSA. Nrf2 knockdown reduced MRP4 mRNA levels in both HepG2 and Hep-3B cells. In addition, TNFα increased Rb phosphorylation and expression of MRP4 and Nrf2 and activated E2F1 and phosphorylated p38 in HepG2 and Hep-3B cells. These effects were markedly inhibited by pretreatment with E2F1 siRNA. Dual-luciferase reporter assay validated that TNFα induces the transcription of E2F1. Furthermore, the expression of MRP4, Nrf2, E2F1, and p-p38 proteins was improved with treatment of TNFα in a mouse model of cholestasis. E2F1 siRNA lentivirus or SB 203580 (p38 inhibitor) inhibited these positive effects. CONCLUSION: Our findings indicated that TNFα induces hepatic MRP4 expression through activation of the p38-E2F1-Nrf2 signaling pathway in human obstructive cholestasis.

Effects of MRP4 gene on lipopolysaccharide-induced endothelial permeability and the cytoskeleton of endothelial cells changes / 中华急诊医学杂志

Objective To investigate the effects of multidrug resistance-associated protein 4 (MRP4) on the cytoskeleton and cellular permeability of rat pulmonary microvascular endothelial cells (PMVECs) induced by lipopolysaccharide (LPS).Methods PMVECs were cultured for 3 to 6 generations were randomly divided into 4 groups:control group,LPS group,Ad-shMRP4 group (adenoviral expression of a short-hairpin RNA directed against MRP4),Ad-shRNA group.The infection rate of cells was detected by fluorescence microscope observation.The level of MRP4 was assayed by Western botting.Monolayer permeability was determined by the Transwell assay.The morphological characteristic and distribution of Factin was measured by laser confocal fluorescence microscope.Results Compared with control group,the expression of MRP4 protein was up-regulated (P ＜ 0.05) and the significant increase in the permeability of endothelial cells (2 h,6 h,12 h and 24 h respectively:0.28 ±0.02 vs.0.41 ±0.04,0.32 ±0.02,0.30 ±0.01 vs.0.53±0.04,0.39±0.03,0.33 ±0.04 vs.1.12±0.17,0.70 ±0.07,0.32±0.03 vs.0.79 ± 0.02,0.57 ± 0.05,P ＜ 0.05),the F-actin was remodeled,and the stress fibers were formed in LPS group and Ad-shMRP4 group.However,compared with LPS group,the expression of MRP4 protein was down-regulated (P ＜ 0.05) and the markedly decrease in the permeability of endothelial ceils (2 h,6 h,12 h and 24 h respectively:0.41 ± 0.04 vs.0.32 ± 0.02,0.53 ± 0.04 vs.0.39 ± 0.03,1.12 ± 0.17 vs.0.70 ± 0.07,0.79 ± 0.02 vs.0.57 ± 0.05,P ＜ 0.05) was found,and the remodeling of F-actin,and the formation of stress fibers were observed in Ad-shMRP4 group.Conclusions Silencing of MRP4 gene can effectively attenuates LPS-induced increase in the endothelial cell permeability and the destruction of cytoskeleton,thus playing an important role in the protection of endothelial cell barrier.

Effects of MRP4 gene on lipopolysaccharide-induced endothelial permeability and the cytoskeleton of endothelial cells changes / 中华急诊医学杂志

Objective To investigate the effects of multidrug resistance-associated protein 4 (MRP4) on the cytoskeleton and cellular permeability of rat pulmonary microvascular endothelial cells (PMVECs) induced by lipopolysaccharide (LPS).Methods PMVECs were cultured for 3 to 6 generations were randomly divided into 4 groups:control group,LPS group,Ad-shMRP4 group (adenoviral expression of a short-hairpin RNA directed against MRP4),Ad-shRNA group.The infection rate of cells was detected by fluorescence microscope observation.The level of MRP4 was assayed by Western botting.Monolayer permeability was determined by the Transwell assay.The morphological characteristic and distribution of Factin was measured by laser confocal fluorescence microscope.Results Compared with control group,the expression of MRP4 protein was up-regulated (P ＜ 0.05) and the significant increase in the permeability of endothelial cells (2 h,6 h,12 h and 24 h respectively:0.28 ±0.02 vs.0.41 ±0.04,0.32 ±0.02,0.30 ±0.01 vs.0.53±0.04,0.39±0.03,0.33 ±0.04 vs.1.12±0.17,0.70 ±0.07,0.32±0.03 vs.0.79 ± 0.02,0.57 ± 0.05,P ＜ 0.05),the F-actin was remodeled,and the stress fibers were formed in LPS group and Ad-shMRP4 group.However,compared with LPS group,the expression of MRP4 protein was down-regulated (P ＜ 0.05) and the markedly decrease in the permeability of endothelial ceils (2 h,6 h,12 h and 24 h respectively:0.41 ± 0.04 vs.0.32 ± 0.02,0.53 ± 0.04 vs.0.39 ± 0.03,1.12 ± 0.17 vs.0.70 ± 0.07,0.79 ± 0.02 vs.0.57 ± 0.05,P ＜ 0.05) was found,and the remodeling of F-actin,and the formation of stress fibers were observed in Ad-shMRP4 group.Conclusions Silencing of MRP4 gene can effectively attenuates LPS-induced increase in the endothelial cell permeability and the destruction of cytoskeleton,thus playing an important role in the protection of endothelial cell barrier.

Protective effect of multidrug resistant associated protein 4 inhibitor on rats with sepsis-induced acute lung ;injury / 中华危重病急救医学

Objective To investigate the protective effect of multidrug resistant associated protein 4 (MRP4) inhibitor on rats with sepsis-induced acute lung injury (ALI). Methods Sixty Sprague-Dawley (SD) rats were randomly divided into sham group, sepsis group and MRP4 inhibitor MK571 treatment group, with 20 rats in each group. Sepsis model was reproduced by cecal ligation and puncture operation (CLP), and the rats in sham group were only received celiotomy without ligation and puncture. Rats in MK571 treatment group were intraperitoneally injected with MRP4 inhibitor MK571 (20 mg/kg) 30 minutes before model reproduction, while rates in sham group and sepsis group were given the same amount of normal saline. Twenty-four hours later, the femoral artery blood of mice was collected, and arterial blood gas analysis was measured. Serum tumor necrosis-α (TNF-α) was determined by enzyme-linked immunosorbent assay (ELISA). The lung tissues were collected, and the wet/dry weight ratio (W/D) was calculated. The expression of MRP4 protein in lung tissue was determined by Western Blot. Results Compared with sham group, arterial blood pH value and arterial partial pressure of oxygen (PaO2) were significantly lowered [pH value: 7.18±0.03 vs. 7.40±0.03; PaO2 (mmHg, 1 mmHg = 0.133 kPa): 63.15±6.24 vs. 98.05±2.58], while arterial partial pressure of carbon dioxide (PaCO2) was dramatically higher in the sepsis group (mmHg: 56.60±8.30 vs. 37.85±3.18), serum TNF-α level in the sepsis group was significantly increased (ng/L: 146.24±19.99 vs. 25.77±9.83), the W/D ratio of lung tissue was significantly increased (7.75±0.47 vs. 4.09±0.58), and the expression of MRP4 protein was up-regulated in the sepsis group (gray value: 0.153±0.006 vs. 0.087±0.005, all P < 0.05). Compared with the sepsis group, arterial blood pH value (7.30±0.02 vs. 7.18±0.03) and PaO2 (mmHg: 80.30±5.34 vs. 63.15±6.24) were significantly elevated in the MK571 treatment group, while PaCO2 was dramatically decreased (mmHg: 29.25±3.24 vs. 56.60±8.30), the serum level of TNF-α was significantly decreased (ng/L: 97.96±16.72 vs. 146.24±19.99), the W/D ratio of lung tissue was significantly reduced (5.89±0.51 vs. 7.75±0.47), and MRP4 protein expression was significantly down-regulated (gray value: 0.124±0.006 vs. 0.153±0.006, all P < 0.05). Conclusion MRP4 inhibitor may improve lung function in rats with sepsis-induced ALI by down-regulating MRP4 protein expression and reducing levels of inflammatory cytokines, which exerts protective effect on ALI.

Inhibition of multidrug resistance-associated protein 4 protects against pulmonary vascular endothelial barrier dysfunction in septic rats / 中华急诊医学杂志

Objective To explore the effects of multidrug resistance-associated protein 4 (MRP4) inhibition on pulmonary vascular endothelial barrier dysfunction in septic rats.Methods Sixty Sprague Dawley rats were randomly (random number) divided into three groups:sham-operated group,sepsis group,and sepsis plus MRP4 inhibitor treatment group,with 20 rats in each group.Sepsis was induced by cecal ligation and puncture.MRP4 inhibitor MK571 (20 mg/kg) was administrated by intraperitoneal injection 30 minutes before induction of sepsis.Twenty-four later,serum interlukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) levels were measured by enzyme-linked immunosorbent assay.Lung injury was assessed by histopathological examination.Lung vascular permeability was evaluated by quantitation of Evans blue dye extravasation from vascular space to lung parenchyma.Results Compared with sham group,serum IL-6 and TNF-α levels were significantly higher in sepsis group.In addition,lung injury and lung vascular permeability were elevated in sepsis group compared to sham group.Importantly,MRP4 inhibitor treatment significantly decreased serum IL-6 and TNF-α levels,improved lung injury and reduced lung vascular permeability in septic rats.Conclusions Inhibition of MRP4 protects against pulmonary vascular endothelial barrier dysfunction in septic rats.