Lixia Xu

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.

Identification and Predicting Short-Term Prognosis of Early Cardiorenal Syndrome Type 1: KDIGO Is Superior to RIFLE or AKIN

Objective Acute kidney injury (AKI) in patients hospitalized for acute heart failure (AHF) is usually type 1 of the cardiorenal syndrome (CRS) and has been associated with increased morbidity and mortality. Early recognition of AKI is critical. This study was to determine if the new KDIGO criteria (Kidney Disease: Improving Global Outcomes) for identification and short-term prognosis of early CRS type 1 was superior to the previous RIFLE and AKIN criteria. Methods The association between AKI diagnosed by KDIGO but not by RIFLE or AKIN and in-hospital mortality was retrospectively evaluated in 1005 Chinese adult patients with AHF between July 2008 and May 2012. AKI was defined as RIFLE, AKIN and KDIGO criteria, respectively. Cox regression was used for multivariate analysis of in-hospital mortality. Results Within 7 days on admission, the incidence of CRS type 1 was 38.9% by KDIGO criteria, 34.7% by AKIN, and 32.1% by RIFLE. A total of 110 (10.9%) cases were additional diagnosed by KDIGO criteria but not by RIFLE or AKIN. 89.1% of them were in Stage 1 (AKIN) or Stage Risk (RIFLE). They accounted for 18.4% (25 cases) of the overall death. After adjustment, this proportion remained an independent risk factor for in-hospital mortality [odds ratios (OR)3.24, 95% confidence interval(95%CI) 1.97–5.35]. Kaplan-Meier curve showed AKI patients by RIFLE, AKIN, KDIGO and [K(+)R(−)+K(+)A(−)] had lower hospital survival than non-AKI patients (Log Rank P<0.001). Conclusion KDIGO criteria identified significantly more CRS type 1 episodes than RIFLE or AKIN. AKI missed diagnosed by RIFLE or AKIN criteria was an independent risk factor for in-hospital mortality, indicating the new KDIGO criteria was superior to RIFLE and AKIN in predicting short-term outcomes in early CRS type 1.

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.

Receptor Activator of NF-kappaB and Podocytes: Towards a Function of a Novel Receptor-Ligand Pair in the Survival Response of Podocyte Injury

Background Glomerulosclerosis correlates with reduction in podocyte number that occurs through mechanisms which include apoptosis. Podocyte injury or podocyte loss in the renal glomerulus has been proposed as the crucial mechanism in the development of glomerulosclerosis. However, the mechanism by which podocytes respond to injury is poorly understood. TNF and TNF receptor superfamilies are important in the pathogenesis of podocyte injury and apoptosis. The ligand of receptor activator of NF-kappaB (RANKL) and receptor activator of NF-kappaB (RANK) are members of the TNF and receptor superfamilies. We investigated whether RANK - RANKL is a receptor - ligand complex for podocytes responding to injury. Methodology/Principal Findings In this study, RANKL and RANK were examined in human podocyte diseases and a rat model of puromycin aminonucleoside nephrosis (PAN). Compared with controls, RANK and RANKL were increased in both human podocyte diseases and the rat PAN model; double immunofluorescence staining revealed that RANK protein expression was mainly attributed to podocytes. Immunoelectron microscopy showed that RANK was localized predominantly at the top of the foot process membrane and the cytoplasm of rat podocyte. In addition, RANK was upregulated in mouse podocytes in vitro after injury induced by puromycin aminonucleoside (PA). Knockdown of RANK expression by small interference RNA (siRNA) exacerbated podocyte apoptosis induced by PA. However, RANKL inhibited significantly the apoptosis of podocytes induced by PA. Conclusions/Significance These findings suggest the increase in RANK–RANKL expression is a response to podocyte injury, and RANK–RANKL may be a novel receptor–ligand complex for the survival response during podocyte injury.

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.

Proteinuria as an independent risk factor for contrast-induced acute kidney injury and mortality in patients with stroke undergoing cerebral angiography.

Background The correlation between proteinuria and contrast-induced acute kidney injury (CI-AKI) in patients with cerebrovascular disease is still unknown. Objective To determine whether proteinuria is a risk factor for CI-AKI and death in patients with stroke undergoing cerebral angiography. Methods Data from 2015 patients with stroke undergoing cerebral angiography between January 2009 and December 2013 were retrospectively collected. Clinical parameters were obtained from the hospitals computerized database. All variables were analyzed by univariate analysis and multivariate logistic regression analysis. Results CI-AKI was seen in 85 patients (4.2%). After adjustment for potential confounding risk factors, patients with proteinuria had a fivefold higher risk of CI-AKI than patients without proteinuria (OR=5.74; 95% CI 2.23 to 14.83; p<0.001). Other independent risk factors for CI-AKI were estimated glomerular filtration rate <60 mL/min/1.73 m2, anemia, and a high National Institute of Health Stroke Scale score. Proteinuria did not increase in-hospital mortality (OR=1.25; 95% CI 0.49 to 3.17; p=0.639) but did increase 1-year mortality (HR=2.30, 95% CI 1.55 to 3.41, p<0.001). Conclusions Proteinuria is an independent risk factor for CI-AKI and 1-year mortality in patients with stroke undergoing cerebral angiography. More attention should be paid to the development of CI-AKI in patients with stroke with proteinuria.

Red blood cell distribution width as a marker of cerebral infarction in hemodialysis patients

Abstract Background: Red blood cell distribution width (RDW) is a cardiovascular biomarker. We evaluated the association between RDW and cerebral stroke risk in hemodialysis patients. Methods: A cohort of 442 adult patients on hemodialysis was studied. Strokes were defined according to ICD-10 diagnosis codes. Routine complete blood counts, evaluated every 3–6 months, were used for RDW values. Results: Among 442 hemodialysis patients, during the 50-month follow-up, there were 62 cases (14.0%) of cerebral stroke: 41 (9.3%) with cerebral infarction and 21 (4.8%) with cerebral hemorrhage. Compared with nonstroke patients, a significantly higher RDW was measured in patients with cerebral stroke and cerebral infarction. However, no significant difference was seen in RDW between patients with cerebral hemorrhage and nonstroke patients. After adjustment by age, hypertension, albumin, Charlson Comorbidity Score, and C-reactive protein in different multivariable Cox regression models, patients with the highest mean RDW quartile had a 2.55-fold (hazard ratio = 3.55; 95% confidence interval: 1.33–9.51) higher risk of developing cerebral infarction relative to those with the lowest mean RDW quartile. RDW was not an independent risk factor for cerebral hemorrhage. Conclusions: Increased RDW is an independent risk factor of cerebral infarction in hemodialysis patients.

NADPH oxidase inhibitor, diphenyleneiodonium prevents necroptosis in HK‑2 cells

The aim of the present study was to investigate the protective effect of the NADPH oxidase inhibitor, diphenyleneiodonium (DPI) against necroptosis in renal tubular epithelial cells. A necroptosis model of HK-2 cells was established using tumor necrosis factor-α, benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone and antimycin A (collectively termed TZA), as in our previous research. The necroptosis inhibitor, necrostatin-1 (Nec-1) or the NADPH oxidase inhibitor, DPI were administered to the necroptosis model. Production of reactive oxygen species (ROS) was detected by dichlorodihydrofluorescein diacetate in the different groups, and the manner of cell death was identified by flow cytometry. Western blot analysis was used to determine the levels of phosphorylation of receptor-interacting protein kinase 3 (RIP-3) and mixed lineage kinase domain-like (MLKL), which are essential to necroptosis. The results revealed that TZA increased the percentages of propidium iodide-positive HK-2 cells from 1.22±0.69 to 8.98±0.73% (P<0.001), and augmented the phosphorylation of RIP-3 and MLKL. ROS levels were increased in the TZA group compared with the control group (27.74±1.60×104 vs. 18.51±1.10×104, respectively; P<0.001), and could be inhibited by Nec-1 (TZA + Nec-1 group, 22.90±2.22×104 vs. TZA group, 27.74±1.60×104; P=0.01). DPI decreased ROS production (TZA + DPI group, 22.13±1.86×104 vs. TZA group, 27.74±1.60×104; P<0.001) and also reduced the proportions of necrosis in the necroptosis model (TZA + DPI group, 4.40±1.51% vs. TZA group, 8.98±0.73%; P<0.001). Phosphorylated RIP-3 and MLKL were also decreased by DPI treatment. The results indicate that ROS production increases in HK-2 cells undergoing necroptosis, and that the NADPH oxidase inhibitor, DPI may protect HK-2 cells from necroptosis via inhibition of ROS production.

Probucol combined with valsartan in immunoglobulin A nephropathy: A multi‐centre, open labelled, randomized controlled study

Angiotensin receptor antagonists (ARBs) and anti‐oxidants reduce urinary protein excretion and delay progression of immunoglobulin A (IgA) nephropathy. We investigated the efficacy and safety of probucol (an anti‐oxidant) combined with valsartan (an ARB) on the progression of IgA nephropathy.