Effect of autophagy on necroptosis of renal tubular epithelial cells in subtotal nephrectomy rats

AIM: To explore whether autophagy is involved in the excessive death of renal tubular epithelial cells in subtotal nephrectomy(SNx) rats and the relationship between autophagy and necroptosis in the kidney of SNx rats. METHODS: Male Sprague-Dawley rats were randomly assigned to control group(n=6) and SNx group(n=42). The rats in SNx group were subjected to SNx. Sham surgery was performed in the rats in control group. The rats in SNx group were divided into subgroups at 0, 4, 8 and 12 weeks(n=6) and the other rats in SNx group were divided into SNx+vehicle group, SNx+necrostatin-1(Nec-1) group and SNx+3-methyladenine(3-MA) group. The expression of RIP1, RIP3, LC3 and beclin-1 at mRNA and protein levels was measured at 0, 4, 8 and 12 weeks by qPCR and immunohistochemistry. The effects of Nec-1 or 3-MA on the protein expression of LC3-I, LC3-II and beclin-1, and production of reactive oxygen species(ROS) in the rat kidney were determined by Western blot and DCFH-DA staining. The death of renal tubular epithelial cells in the SNx rats was observed by TUNEL staining and electron microscopy. Finally, the effects of Nec-1 and 3-MA on blood urea nitrogen(BUN), serum creatinine(SCr) and the pathological changes of the renal tissues were analyzed. RESULTS: The highest mRNA and protein levels of RIP1, RIP3, LC3 and beclin-1 appeared at the 8th week after SNx(P<0.01). Compared with the rats in SNx+vehicle group, the protein over-expression of LC3-II/I and beclin-1, renal tubular epithelial cells with typical morphological features of necroptotic cell death and TUNEL-positive renal tubular cells were decreased in the SNx rats treated with Nec-1 and 3-MA(P<0.01), but 3-MA did not reduce the increased concentration of ROS. In addition, treatment with Nec-1 and 3-MA obviously reduced BUN, SCr(P<0.05), glomerulosclerosis index and tubulointerstitial injury score(P<0.01). CONCLUSION: Autophagy participates in the excessive death of renal tubular epithelial cells in SNx rats. Inhibition of autograph prevents necroptotic cell death of renal tubular cells, and alleviates chronic renal injury in SNx rats.     

C-reactive protein induces apoptosis in human renal tubular epithelial cells

ATM: To explore whether the C-reactive protein (CRP) level in microinflammation state induces the apoptosis of renal tubular epithelial cells. METHODS: HK-2 cells were stimulated with recombinant human CRP. Annexin-FITC-PI staining and flow cytometry were used to detect the percentage of apoptotic cells. Morphology observation of apoptosis was assessed by Hoechst 33258 staining. Caspase-3 activity was measured by a colorimetric assay. The expression of apoptotic gene bax and anti-apoptotic gene bcl-2 at mRNA levels was determined by real-time PCR. RESULTS: CRP induced apoptosis of HK-2 cells in a time- and dose-dependent manner. The maximal apoptotic effect of CRP concentration was 10 mg/L CRP at concentration of 20 mg/L. CRP treatment was associated with the characteristic morphological features of apoptosis such as condensation, fragmentation or margination of nuclear chromatin. CRP exposure increased caspase-3 activity, up-regulated the mRNA expression of Bax and down-regulated the mRNA expression of Bcl-2. CONCLUSION: Slightly increased CRP level has the potential to induce apoptosis of renal tubular cells.     

Effect of VDUP-1 on apoptosis of renal tubular epithelial cells induced by high glucose

AIM: To investigate the effect of vitamin D3 up-regulated protein 1 (VDUP-1) on apoptosis of renal tubular epithelial cells induced by high glucose and its mechanism. METHODS: Human renal proximal tubular epithelial cell line HK-2 was treated with high glucose. The mRNA and protein levels of VDUP-1 in HK-2 cells were detected by real-time PCR and Western blot. HK-2 cells were transfected with VDUP-1 small interfering RNA (siRNA). Real-time PCR and Western blot were used to detect the inhibitory effect. The HK-2 cells were treated with high glucose, and the change of VDUP-1 expression was detected. The apoptosis was analyzed by flow cytometry. The activities of caspase-3 and caspase-9 in the cells were measured. The tumor necrosis factor-α (TNF-α) content in the culture supernatant was examined by ELISA. The key proteins of Sonic hedgehog (Shh) signaling pathway, Patched 1 (Ptch1), Smoothened (Smo), zinc finger protein Gli2 and Shh, were determined by Western blot. The HK-2 cells were treated with exogenous Shh, and the levels of Ptch1, Smo and Gli2 were detected by Western blot. After the HK-2 cells with VDUP-1 silencing were treated with exogenous Shh and high glucose, the apoptosis was analyzed by flow cytometry, the activities of caspase-3 and caspase-9 in the cells were examined, and the TNF-α content in culture supernatant was measured by ELISA. RESULTS: High levels of VDUP-1 mRNA and protein were observed in the HK-2 cells treated with high glucose. The mRNA and protein levels of VDUP-1 were decreased in the HK-2 cells transfected with VDUP-1 siRNA(P<0.05). Compared with the normally cultured cells, the apoptotic rate of HK-2 cells was increased after high glucose treatment, and the activities of caspase-3 and caspase-9 and the content of TNF-α were also significantly increased (P<0.05). After down-regulation of VDUP-1 expression by siRNA transfection, the apoptotic rate of HK-2 cells decreased after high glucose treatment, and the activities of caspase-3 and caspase-9, and the content of TNF-α were also significantly decreased (P<0.05). The protein levels of Ptch1, Smo, Gli2 and Shh were decreased after high glucose culture, while down-regulation of VDUP-1 partly antagonized the effect of high glucose on the expression of Ptch1, Smo, Gli2 and Shh in the HK-2 cells. Exogenous Shh promoted the expression of Ptch1, Smo and Gli2, and inhibited the apoptosis of the HK-2 cells induced by high glucose. Exogenous Shh and down-regulation of VDUP-1 synergistically inhibited high glucose-induced apoptosis of the HK-2 cells. CONCLUSION: Down-regulation of VDUP-1 expression inhibits high glucose-induced apoptosis and release of TNF-α in renal tubular epithelial cells by activating Shh signaling pathway.     

Types of transdifferentiation of renal tubular epithelial cells and its role in kidney diseases

The normal shape and functions of renal tubular epithelial cells are very important for keeping renal function. Under pathological conditions, renal tubular epithelial cells transform to myofibroblast or immunocytes. The transdifferentiation of renal tubular epithelial cells acts in the progresses of many kidney diseases, such as diabetic nephropathy and lupus nephritis. In this review, we summarize the types of transdifferentiation of renal tubular epithelial cells and its roles in kidney diseases.     

Effect of CHOP expression knock-down on apoptosis of renal tubular epithelial cells

AIM:To study the effect of C/EBP homologous protein (CHOP) on the apoptosis of renal tubular epithelial HK2 cells. METHODS:The serum mRNA levels of CHOP in the patients with acute kidney injury and healthy controls were detected by qPCR. In vitro, renal tubular epithelial HK2 cells were divided into control group, negative group (transfected with negative control siRNA), si-CHOP group (transfected with CHOP siRNA), and induced by transforming growth factor-β1 (TGF-β1). The viability of the cells was measured by MTT assay, and the apoptotic rate was analyzed by flow cytometry. The protein levels of nuclear antigen Ki-67, proliferating cell nuclear antigen (PCNA), caspase-3 and cleaved caspase-3 were determined by Western blot. RESULTS:Compared with the healthy controls, the serum mRNA levels of CHOP in the patients with acute kidney injury were increased significantly (P<0.05). Transfection with CHOP siRNA significantly decreased the expression of CHOP in the renal tubular epithelial HK2 cells (P<0.05). Knock-down of CHOP expression by siRNA significantly increased the viability of renal tubular epithelial HK2 cells (P<0.05), decreased the apoptotic rate (P<0.05), increased the expression of Ki-67 and PCNA (P<0.05), and down-regulated the protein level of cleaved caspase-3 (P<0.05). CONCLUSION:The serum mRNA levels of CHOP were increased in the patients with acute kidney injury. Knock-down of CHOP expression inhibits the apoptosis of renal tubular epithelial cells by regulating the expression of proliferation-and apoptosis-related proteins.     

Effects of uremic serum on the proliferation and trans-differentiation of human renal tubular epithelial cells

AIM: To explore the effects of uremic serum on proliferation and trans-differentiation of human renal tubular epithelial cells. METHODS: Human renal tubular epithelial cell line (HK-2) was cultured in RPMI-1640 medium. The proliferation effects of uremic serum at different concentrations were evaluated by methylene blue assay (MTT method) and flow cytometry. The positive cells percentage of α-smooth muscle actin(α-SMA)in different concentration uremic serum medium was also measured by flow cytometry in vitro. RESULTS: Absorbance 490 (A₄₉₀) was increased in 5%-20% uremic serum groups compared with that in normal controls with the use of MTT. Cells in G₁ phase were decreased, but proliferation index (PI) was increased in 10%-20% uremic serum groups compared with that in normal controls with the use of flow cytometry. No significant difference of cell proliferation index was found among uremic serum groups. The positive percentage of α-SMA cells was increased significantly in uremic serum groups compared with that in normal controls, and increased in parallel with the increasing of uremic serum concentration. CONCLUSION:These data suggest that AGEs could induce a high expression of MIP-1αm RNA and protein in cultured HUVECs in a dose-dependent and time-dependent manner.     

Oxidative stress and P53 involve in fluctuant high glucose-induced apoptosis of renal tubular epithelial cells

AIM: To explore the mechanism of fluctuant high blood glucose-induced apoptosis of renal tubular epithelial cells. METHODS: Cultured human renal tubular epithelial cells (HK-2) were treated with stable high glucose or fluctuant high glucose. Antioxidant and specific inhibitor of P53 were applied for identifying the role of oxidative stress and P53 in fluctuant high glucose-induced apoptosis of renal tubular epithelial cells. Additionally, SD rats were randomly divided into normal control group (A), stable high blood glucose group (B) and fluctuant high blood glucose group (C). Diabetic rats were induced by intraperitoneal injection of streptozocin(STZ,65 mg/kg), and the fluctuant high blood glucose animal model was induced by intraperitoneal injection of ordinary insulin and glucose at different time points every day. The activity of superoxide dismutase (SOD) and the content of malonaldehyde (MDA) were detected by the method of colorimetry. The protein expression of NADPH oxidase 4(Nox4) and P53 were examined by immunohistochemistry and Western blotting. Apoptosis was assessed by flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). RESULTS: The cultured HK-2 cells treated with fluctuant high glucose had significantly higher apoptotic rate and expression level of P53 protein than those in the cells treated with stable high glucose. Compared with the culture solution of the cels treated with stable high glucose, the SOD activity was decreased and the concentration of MDA was increased in the culture solution of the cells treated with fluctuant high glucose. The antioxidant and specific inhibitor of P53 significantly inhibited the p-P53 expression and decreased the apoptotic rate. After 12 experimental weeks, the cell apoptotic index and protein expression of Nox4 and p-P53 in the kidney tubular epithelial cells isolated from the diabetic rats were significantly increased in C group as compared with B group. CONCLUSION: Oxidative stress and P53 are involved in fluctuant high glucose-induced apoptosis of renal tubular epithelial cells.     

TAK1 regulates fibrosis of renal tubular epithelial cells by regulating p38 MAPK signaling pathway

AIM:To investigate the effect of transforming growth factor-β (TGF-β) activated kinase 1(TAK1) on renal tubular epithelial fibrosis. METHODS:The renal tubular epithelial cell line HK-2 was used as the research object. After induced by TGF-β1, real-time PCR and Western blot were used to detect the expression of TAK1 in the HK-2 cells. TAK1 shRNA lentivirus was used to infect HK-2 cells, real-time PCR and Western blot were used to determine the interference effect on TAK1 expression in the HK-2 cells with TGF-β1 stimulation. Under the condition of treating with p38 MAPK activator anisomycin, the levels of type I collagen and type Ⅲ collagen in the supernatant, and the protein levels of α-smooth muscle actin (α-SMA), connective tissue growth factor (CTGF) and p-p38MAPK^{Thr 180/Tyr 182} in the HK-2 cells with TAK1 knock-down were determined by ELISA and Western blot, respectively. RESULTS:TGF-β1 significantly increased the expression of TAK1 in the HK-2 cells(P<0.05). TAK1 shRNA significantly decreased the expression of TAK1 in the HK-2 cells with TGF-β1 stimulation. Type I collagen and type Ⅲ collagen secreted by the HK-2 cells after treatment with TGF-β1 were increased, the protein levels of α-SMA, CTGF and p-p38MAPK^{Thr 180/Tyr 182} were also increased(P<0.05). Knock-down of TAK1 expression significantly inhibited the secretion of type I and type Ⅲ collagen, reduced the protein levels of α-SMA, CTGF and p-p38MAPK^{Thr 180/Tyr 182} in the TGF-β1-induced HK-2 cells(P<0.05). Treatment with p38 MAPK activator reversed the inhibitory effect of TAK1 knock-down on the secretion of type I and type Ⅲ collagens, and the protein levels of α-SMA, CTGF and p-p38 MAPK^{Thr 180/Tyr 182} in the HK-2 cells(P<0.05). CONCLUSION:Knock-down of TAK1 expression attenuates the TGF-β1 induced fibrosis of renal tubular epithelial cells by inhibiting p38 MAPK signaling pathway.     

Effects of uremic serum of different molecular weight groups ongene and protein expression of connective tissue growth factor gene and proteinexpression in human renal tubular epithelial cells

AIM:To investigate the effects of uremic serum of different molecular weight groups on gene and protein expression of connective tissue growth factor (CTGF) in human renal tubular epithelial cells.METHODS:The serum from 40 chronic renal failure patients and 20 healthy volunteers were collected and uremic serum was segregated to three groups: >10 000 D,5 000-10 000 D,<5 000 D by 10 000 D and 5 000 D molecular weight Centricon Plus 20 Centrifugal Filter Devices.The protein expression of CTGF was examined by Western blotting.The mRNA expression of CTGF was detected by RT-PCR.RESULTS:CTGF gene expression were increased in 2.5%-20% uremic serum groups compared with that in normal control group,and it was the highest in 10% uremic serum groups.CTGF gene expression was increased significantly in molecular weight >10 000 D and 5 000-10 000 D groups,and the highest was in >10 000 D group,but it was no significant difference in <5 000 D group compared with that in normal control group.CTGF protein was increased in different molecular weight uremic serum groups compared with that in normal control group,and gradually increased following the increasing of uremic serum concentration and it was the highest in molecular weight >10 000 D group.CONCLUSION:Human renal tubulointerstitial fibrosis was accelerated significantly by uremic toxin,especially molecular weight >10 000 D uremic toxin through promoting the gene and protein expression of CTGF in renal tubular epithelial cells in patients with chronic renal failure.     

Effect of netrin-1 on high glucose induced injury of renal tubular epithe-lial cells

AIM:To study the effect of netrin-1 on the damage of renal tubular epithelial cells induced by high glucose. METHODS:Human renal tubular epithelial HK-2 cells were treated with high glucose. Real-time PCR and Western blot were used to detect the expression level of netrin-1 in the cells. HK-2 cells were infected with netrin-1-over-expressing lentivirus, and the effect of netrin-1 over-expression on the HK-2 cells treated with high glucose was observed. The apoptosis rate was analyzed by flow cytometry. The protein level of cleaved caspase-3 was determined by Western blot. lactate dehydrogenase (LDH) activity in the culture medium was measured by 2,4-binitrobenzene hydrazine method. The content of malondialdehyde (MDA) in the culture medium was detected by thiobarbituric acid method. The concentrations of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the culture medium were measured by ELISA. RESULTS:The expression of netrin-1 at mRNA and protein levels in the HK-2 cells after high glucose treatment was significantly lower than that in the control cells (P<0.05). Infection with netrin-1-over-expressing lentivirus up-regulated the expression of netrin-1 in the HK-2 cells treated with high glucose. High glucose promoted the secretion of IL-1β and TNF-α, decreased the levels of LDH and MDA in the cell culture supernatant, and induced apoptosis and activation of caspase-3 in renal tubular epithelial cells (P<0.05). After the HK-2 cells with up-regulation of netrin-1 were induced by high glucose, the IL-1β and TNF-α secretion, the levels of LDH and MDA in the culture medium, the apoptosis, and the level of activated caspase-3 protein in the cells were all decreased, as compared with the control cells (P<0.05). CONCLUSION:Up-regulation of netrin-1 expression attenuates oxidative damage and inflammatory injury, and reduces apoptosis induced by high glucose in renal tubular epithelial cells.     

Effect of SnoN protein on high-glucose-induced expression of fibronectin in primary cultured rat renal tubular cells

AIM: To investigate the effect of Ski-related novel protein N(SnoN) on high-glucose-induced expression of fibronetin (FN) in primary cultured rat renal tubular cells (RTECs). METHODS: The primary renal cells were cultured, and the cell types were indentified to be RTECs. The cells were divided into 3 groups: normal-glucose group (DMEM+2% FBS), high-glucose group (19.5 mmol/L D-glucose+DMEM+2% FBS) and high-osmotic group (19.5 mmol/L D-mannitol+DMEM+2% FBS). The cells were harvested at 30 min, 2 h, 12 h, 24 h, 48 h, 72 h and 96 h. SnoN expression in primary cultured RTECs was knocked down by RNA interference, then the cells were divided into 4 groups: normal-glucose group, high-glucose group, control siRNA group and SnoN siRNA group. The protein expressions of SnoN and FN in RTECs was examined by the methods of Western blotting, immunocytochemistry staining and immunofluorescence cytochemistry. RT-PCR was used to examine the mRNA expression of FN and SnoN. RESULTS: The RTECs constituted the major cell type of cultured cells. SnoN protein was decreased in a time-dependent manner in RTECs under high-glucose condition. The FN protein and mRNA levels raised in high-glucose group and sustained through entire experiment. Moderate reduction of SnoN in RTECs was observed by RNAi strategy, which greatly up-regulated the expression of FN (P<0.05). CONCLUSION: The down-regulation of SnoN participates high-glucose-induced expression of FN in RTECs.     

miR-10b promotes high glucose-stimulated epithelial-mesenchymal transition of renal tubular epithelial cells by repressing KLF10 expression

AIM:To explore the effect and the underlying mechanisms of microRNA-10b (miR-10b) on high glucose-stimulated epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells. METHODS:The expression level of miR-10b was examined by RT-qPCR in the kidney tissues of the type 2 diabetes patients with kidney fibrosis. The EMT model of HK-2 cells was induced by high glucose stimulation and the miR-10b expression in the process was detected by RT-qPCR. The morphological changes of the HK-2 cells were observed using a microscope. EMT markers, such as fibronectin and N-cadherin, were examined by Western blot. The online database predicted that the 3'-UTR of KLF10 bound to miR-10b and their direct interaction was confirmed by dual luciferase report assay. RESULTS:Compared with the para-carcinoma normal tissues, the expression level of miR-10b was up-regulated in the tissues of type 2 diabetes patients with kidney fibrosis (P<0.01). In high glucose-stimulated HK-2 cells, the expression level of miR-10b was increased in a time-dependent manner (P<0.01). miR-10b inhibitor reversed the morphological changes and the increases expression of the EMT markers including fibronectin, SLUG, N-cadherin and SNAI1 induced by high glucose stimulation. Online database showed miR-10b was able to bind with the 3'-UTR in the promoter region of KLF10, thus negatively regulating its expression. Meanwhile, over-expression of KLF10 inhibited the EMT induced by high glucose. Inhibition of TGF-β/Smad3 activation was observed during the process of KLF10-repressed EMT. CONCLUSION:miR-10b promotes high glucose-stimulated epithelial-mesenchymal transition of renal tubular epithelial cells may through repressing KLF10 expression.     

Establishment of autophagy model of rat gastric interstitial cells of Cajal induced by glutamic acid

AIM: To establish an autophagy model of glutamic acid-induced rat gastric interstitial cells of Cajal (ICCs) in vitro. METHODS: Glutamic acid was added to the medium of cultured ICCs in vitro at different concentrations (high, medium and low concentrations were 10 mmol/L, 5 mmol/L and 2.5 mmol/L, respectively) for different periods (3 h, 6 h and 24 h). The cell viability was measured by CCK-8 assay. The protein expression of microtubule-associated protein 1 light chain 3 (LC3) in the ICCs after cultured with glutamic acid at different concentrations for different periods was determined by Western blot. The ultrastructure and autophagic vacuoles of ICCs were observed under electron microscope, and immunofluorescence technique was used to measure the fluorescence intensity of autophagic protein LC3 after co-cultured with glutamic acid at medium concentration. RESULTS: Compared with control group, glutamic acid significantly inhibited the viability of ICCs (P<0.01). The ratios of LC3-Ⅱ/LC3-I in medium and high concentration groups at 3 h, 6 h and 24 h were significantly increased as compared with control group and low concentration group (P<0.01), and that in medium concentration group at 3 h was the best to increased the ratio of LC3-Ⅱ/LC3-I (P<0.01). Under electron microscope, the ICCs in glutamic acid group showed obvious autophagic vacuoles and cytoplasmic vacuoles. The fluorescence intensity of autophagic protein LC3 in the ICCs of glutamic acid group was significantly enhanced (P<0.01). CONCLUSION: Glutamic acid successfully induces autophagy in ICCs. The optimum condition of glutamic acid was 5 mmol/L for 3 h.     

Effect of HMGA2 gene on high glucose-induced apoptosis of renal tubular epithelial cells by regulating Notch signaling pathway

AIM:To investigate the effect of HMGA2 down-regulation on apoptosis and Notch signaling pathway in renal tubular epithelial cells exposed to high glucose (HG). METHODS:D-glucose at 5, 10, 20 and 30 mmol/L was used to stimulate human renal tubular epithelial HK-2 cells for 2 h, and D-glucose at 30 mmol/L was used to stimulate the HK-2 cells for 10 min, 60 min and 120 min. The protein expression of HMGA2 was determined by Western blot. The HK-2 cells were divided into normal glucose (NG) group, HG group, HG+si-HMGA2 group and HG+NC group, in which siRNA was transfected by Lipofectamine^TM 2000 for 48 h. Flow cytometry was used to analyze the apoptotic rate, reactive oxygen species (ROS) assay kit was used to detect ROS content, and Western blot was used to detect the protein levels of Notch1, Hes1 and Bcl-2. The HK-2 cells were treated with the Notch signaling pathway inhibitor DAPT, and then the cells were divided into HG group, HG+DAPT group and HG+si-HMGA2+DAPT group. The apoptotic rate was analyzed by flow cytometry. RESULTS:Exposure of the HK-2 cells to D-glucose at different concentrations for different time significantly increased the expression of HMGA2 (P<0.05). Compared with NG group, the protein expression of HMGA2, Notch1 and Hes1 in HG group was increased, the expression of Bcl-2/Bax was decreased, the apoptotic rate was increased, and the content of ROS was increased obviously (P<0.05). Compared with HG group, the protein expression of HMGA2, Notch1 and Hes1 of HG+si-HMGA2 group was decreased, the expression of Bcl-2/Bax was increased, the apoptotic rate was decreased, and the content of ROS was decreased significantly (P<0.05). The apoptotic rate in HG+DAPT group was significantly lower than that in HG group, while the apoptotic rate in HG+si-HMGA2+DAPT group was significantly lower than that in HG+DAPT group (P<0.05). CONCLUSION:Down-regulation of HMGA2 expression inhibits the apoptosis of renal tubular epithelial cells by regulating Notch signaling pathway and decreasing ROS production.     

TNF-α induces PIP3-mediated necroptosis in MLO-Y4 cells

AIM: To explore whether tumor necrosis factor-α (TNF-α) induces necroptosis in murine long bone osteocyte-like cell line MLO-Y4 and the possible mechanism. METHODS: The MLO-Y4 cells were divided into control group, TNF-α group, TNF-α+necrostatin-1 (Nec-1) group, TNF-α+Z-VAD group and TNF-α+receptor-interacting protein 3 (RIP3)-siRNA group. The death rate of MLO-Y4 cells was assessed by flow cytometry with Annexin V-FITC/PI staining. The morphological features of the cells were observed under transmission electron microscope (TEM). The protein levels of RIP1, RIP3 and cleaved caspase-3 were determined by Western blot. Finally, the numbers of total cells and RIP1-RIP3-positive cells were observed under laser scanning confocal microscope. The production of reactive oxygen species (ROS) in the cells was measured by DCFH-DA staining. RESULTS: Compared with control group, the apoptotic or necroptotic rate of the cells induced by TNF-α was increased significantly (P<0.01). The increased apoptotic or necroptotic rate was dramatically reduced by treating with Nec-1, Z-VAD or RIP3-siRNA transfection (P<0.01). In TNF-α group and TNF-α+Z-VAD group, a lot of MLO-Y4 cells with typical necroptotic morphological features were observed under TEM. However, obvious necroptotic cells were not found in Nec-1 or RIP3-siRNA treatment group. The protein level of RIP1 in the cells treated with Nec-1 was sharply lower than that in TNF-α group (P<0.01). However, Z-VAD did not reduce the elevated levels of RIP1 and RIP3. RIP3-siRNA effectively down-regulated the protein level of RIP3 compared with TNF-α group (P<0.01). Nec-1 effectively down-regulated the protein levels of RIP1 colocalized with RIP3 compared with TNF-α group (P<0.01). However, Z-VAD did not reduce the levels of RIP1 colocalized with RIP3. Nec-1, Z-VAD and RIP3 siRNA significantly decreased the ROS levels (P<0.01). CONCLUSION: TNF-α induces the necroptosis of MLO-Y4 cells. RIP3 play vital roles in the cell necroptotic signal pathway. ROS may be the executor of necroptosis of MLO-Y4 cells.     

Effect of HIPK2 gene on viability,apoptosis and JAK2/STAT3 signaling pathway in NRK-52E renal tubular epithelial cells induced by hypoxia and reoxygenation

AIM: To investigate the effect of homeodomain-interacting protein kinase 2 (HIPK2) on the viabi-lity, apoptosis and JAK2/STAT3 signaling pathway in NRK-52E renal tubular epithelial cells induced by hypoxia and reoxygenation (H/R). METHODS: HIPK2 small interfering RNA (siRNA) was transfected into NRK-52E cells by Lipofectamine^TM 2000, and normal control group (control group) and negative control group (HIPK2-NC group) were set up. After H/R, the cell viability was measured by CCK-8 assay, the apoptotic rate and Ca²⁺ fluorescence intensity were analyzed by flow cytometry, and the protein levels of Ki67, cleaved caspase-3, caspase-12, Bcl-2, Bax, p-JAK2 and p-STAT3 were determined by Western blot. RESULTS: Compared with control group, the protein expression of HIPK2 in the NRK-52E cells was significantly decreased after transfection with HIPK2 siRNA (P<0.05). Compared with control group, the cell viability and the protein expression of Ki67 and Bcl-2 in H/R group were also significantly decreased, and the apoptotic rate, the Ca²⁺ fluorescence intensity and the protein levels of cleaved caspase-3, caspase-12, Bax, p-JAK2 and p-STAT3 were significantly increased (P<0.05). Compared with H/R group, the cell viability and the protein expression of Ki67 and Bcl-2 in HIPK2-siRNA+H/R group were significantly increased, while the apoptotic rate, the Ca²⁺ fluorescence intensity and the protein levels of cleaved caspase-3, caspase-12, Bax, p-JAK2 and p-STAT3 were significantly decreased (P<0.05). CONCLUSION: Inhibition of HIPK2 gene expression promotes H/R-induced growth of NRK-52E renal tubular epithelial cells, and reduces the apoptosis. The mechanism is related to down-regulating the JAK2/STAT3 signaling pathway.     

Necroptosis mediates high glucose-induced injury in human umbilical vein endothelial cells

AIM: To explore whether necroptosis contributes to the high glucose (HG)-induced damage in human umbilical vein endothelial cells (HUVECs). METHODS: The protein levels of receptor-interacting protein 3 (RIP3) and cleaved caspase-3 were detected by Western blot. The intracellular levels of reactive oxygen species (ROS) were determined by DCFH-DA staining followed by photofluorography. Mitochondrial membrane potential (MMP) was measured by rhodamine 123 staining followed by photofluorography. RESULTS: Treatment of HUVECs with HG at different concentrations (10, 20 and 40 mmol/L glucose) for 24 h gradually enhanced the expression levels of RIP3. Treatment of HUVECs with HG (40 mmol/L glucose) for different time (3 h, 6 h, 9 h, 12 h and 24 h) also up-regulated the expression levels of RIP3, peaking at 9 h. Pretreatment of HUVECs with 20 μmol/L Z-VAD-FMK (an inhibitor of caspase) for 30 min before exposure to HG enhanced the expression level of RIP3. Pretreatment of HUVECs with 100 μmol/L necrostatin-1 (an inhi-bitor of necroptosis) for 1 h before exposure to HG alleviated the HG-induced injuries, such as a decrease in cell viability, an increase in ROS generation and dissipation of MMP, but up-regulated the protein level of cleaved caspase-3. CONCLUSION: Necroptosis mediates HG-induced injury in HUVECs. There is a negative interacting between necroptosis and apoptosis.