VIPR1 promoter methylation promotes transcription factor AP-2α binding to inhibit VIPR1 expression and promote hepatocellular carcinoma cell growth in vitro / 南方医科大学学报

OBJECTIVE@#To explore the transcriptional regulation mechanism and biological function of low expression of vasoactive intestinal peptide receptor 1 (VIPR1) in hepatocellular carcinoma (HCC).@*METHODS@#We constructed plasmids carrying wild-type VIPR1 promoter or two mutant VIPR1 promoter sequences for transfection of the HCC cell lines Hep3B and Huh7, and examined the effect of AP-2α expression on VIPR1 promoter activity using dual-luciferase reporter assay. Pyrosequencing was performed to detect the changes in VIPR1 promoter methylation level in HCC cells treated with a DNA methyltransferase inhibitor (DAC). Chromatin immunoprecipitation was used to evaluate the binding ability of AP-2α to VIPR1 promoter. Western blotting was used to assess the effect of AP-2α knockdown on VIPR1 expression and examine the differential expression of VIPR1 in the two cell lines. The effects of VIPR1 overexpression and knockdown on the proliferation, cell cycle and apoptosis of HCC cells were analyzed using CCK8 assay and flow cytometry. We also observed the growth of HCC xenograft with lentivirus-mediated over-expression of VIPR1 in nude mice.@*RESULTS@#Compared with the wild-type VIPR1 promoter group, co-transfection with the vector carrying two promoter mutations and the AP-2α-over-expressing plasmid obviously restored the luciferase activity in HCC cells (P < 0.05). DAC treatment of the cells significantly decreased the methylation level of VIPR1 promoter and inhibited the binding of AP-2α to VIPR1 promoter (P < 0.01). The HCC cells with AP-2α knockdown showed increased VIPR1 expression, which was lower in Huh7 cells than in Hep3B cells. VIPR1 overexpression in HCC cells caused significant cell cycle arrest in G2/M phase (P < 0.01), promoted cell apoptosis (P < 0.001), and inhibited cell proliferation (P < 0.001), while VIPR1 knockdown produced the opposite effects. In the tumor-bearing nude mice, VIPR1 overexpression in the HCC cells significantly suppressed the increase of tumor volume (P < 0.001) and weight (P < 0.05).@*CONCLUSION@#VIPR1 promoter methylation in HCC promotes the binding of AP-2α and inhibits VIPR1 expression, while VIPR1 overexpression causes cell cycle arrest, promotes cell apoptosis, and inhibits cell proliferation and tumor growth.

Role of pyroptosis in bilirubin-induced microglial injury / 中国当代儿科杂志

OBJECTIVE@#To study whether pyroptosis is involved in the bilirubin-induced injury of primary cultured rat cortical microglial cells.@*METHODS@#Primary cultured rat cortical microglial cells were randomly administered with 30 μmol/L bilirubin (bilirubin group), 30 μmol/L bilirubin following 30 μmol/L VX-765 pretreatment (VX-765+bilirubin group), or an equal volume of dimethyl sulfoxide (control group). Modified MTT assay was used to measure the viability of microglial cells. Western blot was used to measure the expression of the pyroptosis-related proteins Caspase-1 and gasdermin D (GSDMD). Lactate dehydrogenase (LDH)-release assay was used to evaluate the cytotoxicity of microglial cells. EtBr/EthD2 with different molecular weights (394 Da/1 293 Da) was used to measure the size of plasma membrane pores. ELISA was used to measure the level of the inflammatory factor interleukin-1β (IL-1β) in culture supernatant.@*RESULTS@#After bilirubin stimulation, the viability of microglial cells decreased and LDH release increased, both in a time-dependent manner. Compared with the control group, the bilirubin group had a significantly higher positive rate of small-molecule EtBr passing through the cell membrane (P0.05). The expression of activated Caspase-1 significantly increased at 0.5 hour after bilirubin stimulation (P<0.05), and that of activated GSDMD significantly increased at 6 hours after bilirubin stimulation (P<0.05). The release of IL-1β significantly increased at 6 hours after bilirubin stimulation and reached the peak at 24 hours (P<0.001). Compared with the bilirubin group, the VX-765+bilirubin group had a significant increase in cell viability (P<0.05) and significant reductions in the expression of activated GSDMD, the pass rate of EtBr, and the release of LDH and IL-1β (P<0.05).@*CONCLUSIONS@#Pyroptosis is involved in bilirubin-induced injury of primary cultured microglial cells.

Role of caspase-1 activation in bilirubin-induced injury in cultured primary rat hippocampal neurons / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the role of caspase-1 activation in bilirubin-induced neuronal injury and the protective effect of VX-765 against bilirubin-induced neurotoxicity in cultured primary rat hippocampal neurons.</p><p><b>METHODS</b>Cultured primary rat hippocampal neurons were exposed to DMSO (control group), 50 µmol/L bilirubin, or 50 µmol/L bilirubin 1 h after 50 µmol/L VX-765 treatment. The expressions of NLRP3 and caspase-1 in the neurons were detected by Western blotting, and the relative cell survival and death rates were assessed with a modified MTT assay, lactate dehydrogenase assay and Typan blue staining. Interleukin-18 (IL-18) concentration in the culture supernatant was measured using enzyme-linked immunosorbent assay (ELISA).</p><p><b>RESULTS</b>In cultured primary rat hippocampal neurons, bilirubin exposure for 3 and 6 h caused significant increases in the expressions of NLRP3 and activated caspase-1 compared with those in the control group (P<0.05). Pretreatment of the cells with VX-765 obviously suppressed bilirubin-induced activation of caspase-1 (P<0.05). The relative survival rate of the neurons was (84.02∓2.31)% in VX-765 intervention group, significantly higher than that in bilirubin group (P<0.05) but lower than that in the control group (P<0.05); LDH release rate in VX-765 intervention group was (10.78∓1.58)%, significantly lower than that in bilirubin group (P<0.05) but higher than that in the control group (P<0.05). The cell death rate in VX-765 intervention group was (5.58∓1.23)%, significantly lower than that in bilirubin group (P<0.05) but higher than that in the control group (P<0.05).</p><p><b>CONCLUSION</b>In cultured primary rat hippocampal neurons, caspase-1 activation plays a role in bilirubin-induced neurotoxicity, and VX-765 treatment provides protection against bilirubin-induced neuronal injury by inhibiting caspase-1 activation.</p>

Relationship between the effect of vascular endothelial growth factor on epithelial-mesenchymal transition of HK-2 cells and the expressions of bone morphogenetic protein-7 and inhibitor of DNA binding/differentiation / 中国医学科学院学报

<p><b>OBJECTIVE</b>To examine the relationship between effect of vascular endothelial growth factor (VEGF) on epithelial-myofibroblast transition (EMT) of HK-2 cells and changes in expressions of bone morphogenetic protein-7 (BMP-7) and inhibitor of DNA binding/differentiation (Id) 2, Id3.</p><p><b>METHODS</b>The cultured HK-2 cells were co-treated with transforming growth factor-beta1 (TGF-beta1) (5 ng/ml) and VEGF165 (0.1, 1, 10, 100 ng/ml), or with TGF-beta1 (5 ng/ml) and VEGF receptor-1 neutralized antibody (10 microg/ ml), and were also co-treated with TGF-beta1 (5 ng/ml) and VEGF165 (100 ng/ml) with or without activin receptor-like kinase 6 (Alk6)/Fc Chimera (2 microg/ml, to neutralize endogenous BMP-7) for 48 hours. mRNA and protein expressions of alpha-smooth muscle actin (alpha-SMA), E-cadherin, BMP-7, Id2 and Id3 of HK-2 cells were assessed with double-stain immunocytochemistry, real-time PCR and Western blot respectively.</p><p><b>RESULTS</b>Compared with normal controls, alpha-SMA expression significantly increased, while E-cadherin, BMP-7, Id2, and Id3 mRNA and protein expressions markedly decreased in HK-2 cells treated with TGF-beta1 (5 ng/ml) (P < 0.05). VEGF165 interrupted TGF-beta1 induced alpha-SMA expression in a dose-dependent manner and upregulated BMP-7, Id2 mRNA and protein expressions of the cells (P < 0.05). alpha-SMA expression increased, while E-cadherin, BMP-7, and Id2 expressions decreased further in HK-2 cells co-treated with TGF-beta1 and VEGFR1 antibody compared with normal controls (P < 0.05). When endogenous BMP-7 was neutralized with Alk6/Fc Chimera in the cells co-treated with TGF-beta1 and VEGF165, alpha-SMA expression upregulated (P < 0.05), while Id2 was not changed.</p><p><b>CONCLUSIONS</b>VEGF165 may partially inhibit TGF-beta1-induced EMT of HK-2 cells in vitro. This effect is related to the upregulated expressions of BMP-7 and Id2. Id2 may be upregulated directly by VEGF165, but not related to BMP-7.</p>