Shuangxin Liu

1,25-Dihydroxyvitamin D(3) prevents puromycin aminonucleoside-induced apoptosis of glomerular podocytes by activating the phosphatidylinositol 3-kinase/Akt-signaling pathway.

Background: Accumulating evidence suggests that vitamin D and its analogs reduce proteinuria and slow the decline in kidney function in chronic kidney disease. Given a rich literature identifying podocyte apoptosis as an early step in the pathophysiological progression to proteinuria and glomerulosclerosis, we hypothesized that vitamin D protects podocytes from undergoing apoptosis. Methods: A rat model of podocyte apoptosis was created by a single intravenous injection of 100 mg·kg–1 puromycin aminonucleoside (PAN) and received either solvent or 1,25(OH)2D3 treatment. Proteinuria, podocyte apoptosis, the expression of nephrin protein and mRNA, TGF-β/Smad and phosphatidylinositol 3-kinase (PI3K)/Akt-signaling pathway were evaluated, respectively. Results: PAN induced massive proteinuria, serum creatinine elevation and podocyte apoptosis in PAN nephropathy rats, which was associated with the loss of nephrin, an adhesion molecule specific for the glomerular slit and the reduced of p-Akt/Akt ratio. Moreover, PAN induced foot process retraction, redistribution of nephrin and the activation of TGF-β/Smad-signaling pathway. Compared with PAN nephropathy rats, 1,25(OH)2D3 significantly prevented loss of nephrin, foot process retraction and podocyte apoptosis by stimulating Akt phosphorylation and suppressing TGF-β/Smad-signaling pathway. Conclusion: 1,25(OH)2D3 reduced the PAN-induced podocyte apoptosis and loss of nephrin in PAN nephropathy rat. The anti-apoptotic effects of 1,25(OH)2D3 on podocytes may be partly attributable to activation of a PI3K/Akt survival pathway.

Combination of urinary kidney injury molecule-1 and interleukin-18 as early biomarker for the diagnosis and progressive assessment of acute kidney injury following cardiopulmonary bypass surgery: a prospective nested case–control study

The aim of this nested case–control study was to assess the combined use of urinary kidney injury molecule (KIM)-1 and interleukin (IL)-18 for acute kidney injury (AKI) after cardiopulmonary bypass surgery (CPB). From a cohort of 122 subjects who underwent CPB, serial urinary KIM-1 and IL-18 concentrations were determined in 30 AKI and 92 non-AKI patients. An increased level of urinary KIM-1 was associated with the occurrence of AKI, whereas an increased level of IL-18 was related to progressive AKI. The combination of these two biomarkers facilitates the early diagnosis and assessment of the likely progression of AKI after CPB.

Necrostatin-1 Attenuates Ischemia Injury Induced Cell Death in Rat Tubular Cell Line NRK-52E through Decreased Drp1 Expression

Necrostatin-1 (Nec-1) inhibits necroptosis and is usually regarded as having no effect on other cell deaths. Here, this study explored whether the addition of Nec-1 has an effect on cell death induced by simulated ischemia injury in rat tubular cell line NRK-52E. In addition, we also investigated the mechanism of Nec-1 attenuates cell death in this renal ischemia model. The NRK-52E cells were incubated with TNF-α + antimycinA (TA) for 24 h with or without Nec-1. Cell death was observed under fluorescent microscope and quantified by flow cytometry. Cell viabilities were detected by MTT assay. The protein expression of dynamin-related protein 1 (Drp1) was detected by Western blotting and immunofluorescence assay. Increased cell death in simulated ischemia injury of NRK-52E cells were markedly attenuated in the Nec-1 pretreated ischemia injury group. Meanwhile, cell viability was significantly improved after using Nec-1. In addition, we also observed that the protein expression of Drp1, a mediator of mitochondrial fission, was significantly increased in simulated ischemia injury group. Increased Drp1 expression in the ischemia injury group can be abolished by Nec-1 or Drp1-knock down, accompanied with decreased cell death and improved cell viabilities. These results suggest that Nec-1 may inhibit cell death induced by simulated ischemia injury in the rat tubular cell line NRK-52E through decreased Drp1 expression.

NFAT2 inhibitor ameliorates diabetic nephropathy and podocyte injury in db/db mice.

Podocyte injury plays a key role in the development of diabetic nephropathy (DN). We have recently shown that 11R‐VIVIT, an inhibitor of cell‐permeable nuclear factor of activated T‐cells (NFAT), attenuates podocyte apoptosis induced by high glucose in vitro. However, it is not known whether 11R‐VIVIT has a protective effect on DN, especially podocyte injury, under in vivo diabetic conditions. Hence, we examined the renoprotective effects of 11R‐VIVIT in diabetic db/db mice and the possible mechanisms underlying its protective effects on podocyte injury in vivo and in vitro.

Role of impaired peritubular capillary and hypoxia in progressive interstitial fibrosis after 56 subtotal nephrectomy of rats

Aim:  To investigate the potential role of peritubular capillary (PTC) loss and subsequent hypoxia as a pathogenic factor in interstitial fibrosis after renal ablation in rats.

NFAT2 mediates high glucose-induced glomerular podocyte apoptosis through increased Bax expression

BACKGROUND Hyperglycemia promotes podocyte apoptosis and plays a key role in the pathogenesis of diabetic nephropathy. However, the mechanisms that mediate hyperglycemia-induced podocyte apoptosis is still far from being fully understood. Recent studies reported that high glucose activate nuclear factor of activated T cells (NFAT) in vascular smooth muscle or pancreatic β-cells. Here, we sought to determine if hyperglycemia activates NFAT2 in cultured podocyte and whether this leads to podocyte apoptosis. Meanwhile, we also further explore the mechanisms of NFAT2 activation and NFAT2 mediates high glucose-induced podocyte apoptosis. METHODS Immortalized mouse podocytes were cultured in media containing normal glucose (NG), or high glucose (HG) or HG plus cyclosporine A (a pharmacological inhibitor of calcinerin) or 11R-VIVIT (a special inhibitor of NFAT2). The activation of NFAT2 in podocytes was detected by western blotting and immunofluorescence assay. The role of NFAT2 in hyperglycemia-induced podocyte apoptosis was further evaluated by observing the inhibition of NFAT2 activation by 11R-VIVIT using flow cytometer. Intracellular Ca(2+) was monitored in HG-treated podcocytes using Fluo-3/AM. The mRNA and protein expression of apoptosis gene Bax were measured by real time-qPCR and western blotting. RESULTS HG stimulation activated NFAT2 in a time- and dose-dependent manner in cultured podocytes. Pretreatment with cyclosporine A (500nM) or 11R-VIVIT (100nM) completely blocked NFAT2 nuclear accumulation. Meanwhile, the apoptosis effects induced by HG were also abrogated by concomitant treatment with 11R-VIVIT in cultured podocytes. We further found that HG also increased [Ca(2+)]i, leading to activation of calcineurin, and subsequent increased nuclear accumulation of NFAT2 and Bax expression in cultured podocytes. CONCLUSION Our results identify a new finding that HG-induced podocyte apoptosis is mediated by calcineurin/NFAT2/Bax signaling pathway, which may present a promising target for therapeutic intervention.

PODOCYTE INJURY IS SUPPRESSED BY 1,25-DIHYDROXYVITAMIN D3 VIA MODULATION OF TRANSFORMING GROWTH FACTOR-β1/BONE MORPHOGENETIC PROTEIN-7 SIGNALLING IN PUROMYCIN AMINONUCLEOSIDE NEPHROPATHY RATS

1 Accumulating evidence suggests that vitamin D and its analogues are renoprotective. However, the precise mechanisms and the molecular targets by which active vitamin D exerts its beneficial effects remain obscure. The objective of the present study was to evaluate the effect of active vitamin D on rats with puromycin aminonucleoside (PAN) nephropathy, a model that is characterized by predominant podocyte injury. 2 The PAN nephropathy rats were created by a single intravenous injection of 100 mg/kg PAN. Changes in renal pathology and podocyte numbers were observed. Real‐time polymerase chain reaction (PCR) was performed to examine mRNA expression of nephrin, transforming growth factor (TGF)‐β1 and bone morphogenetic protein (BMP)‐7. Protein expression of nephrin, TGF‐β1, BMP‐7 and p‐Smad2/3 and p‐Smad1/5/8 was examined by immunofluorescence, immunohistochemistry and western blotting, respectively. Rats were treated with 1,25(OH)2D3 by gastric gavage at a dose of 2.5 µg/kg per day, starting 2 days before PAN injection and continuing throughout the experiment. 3 A single injection of PAN induced massive proteinuria and elevated serum creatinine on Day 7, both of which were significantly suppressed by 1,25‐dihydroxyvitamin D3 (1,25(OH)2D3). Immunofluorescence and real‐time PCR of the podocyte‐associated protein nephrin revealed reduced and discontinuous staining and this change was reversed by 1,25(OH)2D3. In PAN nephropathy rats, TGF‐β1 and p‐Smad2/3 expression was upregulated, whereas that of BMP‐7 and p‐Smad1/5/8 was downregulated. Treatment with 1,25(OH)2D3 significantly restored BMP‐7/Smad signalling while suppressing TGF‐β1/Smad signalling. 4 In conclusion, 1,25(OH)2D3 can ameliorate podocyte damage and proteinuria induced by PAN. The beneficial effects of 1,25(OH)2D3 on podocytes may be attributable, in part, to direct modulation of TGF‐β1/BMP‐7 signalling.

Coupled plasma filtration adsorption combined with continuous veno-venous hemofiltration treatment in patients with severe acute pancreatitis.

Background: Severe acute pancreatitis (SAP) still has a high mortality rate. Coupled plasma filtration adsorption (CPFA) and continuous veno-venous hemofiltration (CVVH) are 2 extracorporeal blood purification techniques. We hypothesized that CPFA combined with CVVH could preferentially improve prognosis and suppress clinical manifestations of SAP. Methods: In this observational cohort study, 25 patients with SAP were enrolled, in which 12 received CPFA plus CVVH treatment (group 1), and 13 received CVVH therapy (group 2). All the patients underwent a successive 10-day intervention. Clinical indicators were detected before or after the intervention and the results were compared between the 2 groups. The feasibility and the survival rate were evaluated on day 28. Results: Compared with group 2, oxygenation index (PaO2/FiO2), mean arterial pressure, serum amylase, and blood urine nitrogen showed significant differences (all P<0.01) and serum TNF-&agr;, IL-1&bgr;, IL-6 were reduced and IL-10 was elevated with time in group 1 (all P<0.01). Liver functions, electrolyte, and acid-base balance did not show significant difference before and after the 10-day treatment with CPFA plus CVVH compared with CVVH (P>0.05). No therapy-related adverse reactions were noted in both groups. Twenty-eight-day survival rate of group 1 was higher than that in group 2 [91.7% (11/12) vs. 53.8% (7/13), P<0.05]. Conclusions: CPFA combined with CVVH was an effective and safe method for treatment of SAP patients, the mechanism being related to its effect on regulating the level of cytokines and serum amylase.

1,25-Dihydroxyvitamin D(3) Inhibits Podocyte uPAR Expression and Reduces Proteinuria

Background Accumulating studies have demonstrated that 1,25-Dihydroxyvitamin D(3) (1,25(OH)2D3) reduces proteinuria and protects podocytes from injury. Recently, urokinase receptor (uPAR) and its soluble form have been shown to cause podocyte injury and focal segmental glomerulosclerosis (FSGS). Here, our findings showed that 1,25(OH)2D3 did inhibit podocyte uPAR expression and attenuate proteinuria and podocyte injury. Methodology/Principal Findings In this study, the antiproteinuric effect of 1,25(OH)2D3 was examined in the lipopolysaccharide mice model of transient proteinuria (LPS mice) and in the 5/6 nephrectomy rat FSGS model(NTX rats). uPAR protein expression were tested by flow cytometry, immune cytochemistry and western blot analysis, and uPAR mRNA expression by real-time quantitative PCR in cultured podocytes and kidney glomeruli isolated from mice and rats. Podocyte motility was observed by transwell migration assay and wound healing assay. Podocyte foot processes effacement was identified by transmission electron microscopy. We found that 1,25(OH)2D3 inhibited podocyte uPAR mRNA and protein synthesis in LPS-treated podocytes, LPS mice and NTX rats, along with 1,25(OH)2D3 reducing proteinuria in NTX rats and LPS mice.1,25(OH)2D3 reduced glomerulosclerosis in NTX rats and alleviated podocyte foot processes effacement in LPS mice. Transwell migration assay and wound healing assay showed that LPS-induced podocyte motility, irrespective of random or directed motility, were substantially reduced by 1,25(OH)2D3. Conclusions/Significance Our results demonstrated that 1,25(OH)2D3 inhibited podocyte uPAR expression in vitro and in vivo, which may be an unanticipated off target effect of 1,25(OH)2D3 and explain its antiproteinuric effect in the 5/6 nephrectomy rat FSGS model and the LPS mouse model of transient proteinuria.

Cellulose Triacetate Dialyzer Reduces Platelet Loss during Continuous Veno-Venous Hemofiltration

Thrombocytopenia is a common complication in patients receiving continuous veno-venous hemofiltration (CVVH) in the intensive care unit. The hemofilter itself plays an important role in the genesis of thrombocytopenia. The present study was undertaken to test whether there were differences in platelet loss and activation during CVVH with a polysulfone (PS) hemofilter or a cellulose triacetate (CTA) dialyzer. 96 patients with thrombocytopenia and acute kidney injury requiring CVVH were randomly assigned to four groups receiving low-molecular-weight heparin (LMWH) PS (n = 24), LMWH CTA (n = 24), no anticoagulation PS (n = 24), and no anticoagulation CTA (n = 24), respectively. We found a significant decrease in platelet counts, but an increased platelet activation with the PS hemofilter in patients who received no anticoagulation. There was no significant decrease in platelet counts and activation in the CTA group. The cellulose membranes could be an effective alternative to the standard synthetic membranes in patients at high risk for thrombocytopenia during CVVH.