Zhonggao Xu

Angiotensin II type 1 receptor expression is increased via 12-lipoxygenase in high glucose-stimulated glomerular cells and type 2 diabetic glomeruli

BACKGROUND Angiotensin II type 1 receptor (AT1) plays an important role in the development of diabetic nephropathy (DN). However, the roles played by 12-lipoxygenase (12-LO) in the AT1 expression in glomerular cells exposed to high glucose (HG) and diabetic glomeruli remain unclear. Our objective in the present study was to investigate the role of 12-LO in the AT1 expression in glomerular cells and glomeruli under diabetic conditions. METHODS Mesangial cells (MCs), podocytes and glomeruli isolated from rats were used in this study. The rats fed a high fat diet received low-dose streptozotocin to make type 2 diabetes. The 12-LO product 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] was infused to rats by osmotic mini-pump. Morphometric measurement for glomerular volume, competitive reverse transcription polymerase chain reaction for mRNA expression, western blot and immunohistochemistry for protein expression were performed, respectively. RESULTS Both the 12(S)-HETE and HG increased AT1 protein expression in MCs and podocytes. Furthermore, the levels of the AT1 were significantly higher in glomeruli derived from 12(S)-HETE-treated rats compared with control rats. In addition, HG-induced AT1 expression was significantly reduced by the 12-LO inhibitor cinnamyl-3,4-dihydroxy-alpha-cynanocinnamate (CDC). Compared with the non-diabetic controls, DN rats showed significant glomerular hypertrophy and albuminuria. This was associated with significant increases in AT1 protein expression. These abnormalities were prevented by treatment of the CDC. CONCLUSIONS These results indicate that AT1 expression is enhanced, at least in part, by 12-LO in the type 2 diabetic glomeruli, and 12-LO inhibition can ameliorate DN progression through downregulation of AT1 expression.

Renal Protective Effect of Sirtuin 1

Silent information regulator 2 (Sir2) is a nicotinamide adenine dinucleotide- (NAD+-) dependent deacetylase. The homology of SIRT1 and Sir2 has been extensively studied. SIRT1 deacetylates target proteins using the coenzyme NAD+ and is therefore linked to cellular energy metabolism and the redox state through multiple signalling and survival pathways. During the past decade, investigators have reported that SIRT1 activity is essential in cancer, neurodegenerative diseases, diabetes, cardiovascular disease, and other age-related diseases. In the kidneys, SIRT1 may inhibit renal cell apoptosis, inflammation, and fibrosis. Therefore its activation may also become a new therapeutic target in the patients with chronic kidney disease including diabetic nephropathy. In this paper, we would like to review the protective functions of sirtuins and the role of SIRT1 in the onset of kidney disease based on previous studies, including diabetic nephropathy, acute renal injury, chronic kidney disease as well as lupus nephritis.

Role of 12-lipoxygenase in decreasing P-cadherin and increasing angiotensin II type 1 receptor expression according to glomerular size in type 2 diabetic rats

12-lipoxygenase (12-LO) was implicated in the development of diabetic nephropathy (DN), in which the proteinuria was thought to be associated with a decreased expression of glomerular P-cadherin. Therefore, we investigated the role of 12-LO in the glomerular P-cadherin expression in type 2 diabetic rats according to the glomerular sizes. Rats fed with high-fat diet for 6 wk were treated with low-dose streptozotocin. Once diabetes onset, diabetic rats were treated with 12-LO inhibitor cinnamyl-3,4-dihydroxy-cyanocinnamate (CDC) for 8 wk. Then glomeruli were isolated from diabetic and control rats with a sieving method. RT-PCR, Western blotting, and immunofluorescent staining were used for mRNA and protein expressions of P-cadherin and angiotensin II (Ang II) type 1 receptor (AT1). We found that CDC did not affect the glucose levels but completely attenuated diabetic increases in glomerular volume and proteinuria. Diabetes significantly decreased the P-cadherin mRNA and protein expressions and increased the AT1 mRNA and protein expressions in the glomeruli. These changes were significantly prevented by CDC and recaptured by direct infusion of 12-LO product [12(S)-HETE] to normal rats for 7 days. The decreased P-cadherin expression was similar between large and small glomeruli, but the increased AT1 expression was significantly higher in the large than in the small glomeruli from diabetic and 12(S)-HETE-treated rats. Direct infusion of normal rats with Ang II for 14 days also significantly decreased the glomerular P-cadherin expression. These results suggest that diabetic proteinuria is mediated by the activation of 12-LO pathway that is partially attributed to the decreased glomerular P-cadherin expression.

Combined therapy of low-dose tacrolimus and prednisone in nephrotic syndrome with slight mesangial proliferation

Aim:  Tacrolimus is a calcineurin inhibitor that has been increasingly used in transplant medicine. However, the efficacy and safety of combined therapy of low‐dose tacrolimus and prednisone in the treatment of nephrotic syndrome (NS) with slight mesangial proliferation has not been reported.

Effect of peritoneal dialysis versus hemodialysis on renal anemia in renal in end-stage disease patients: a meta-analysis

Abstract The aim of this meta-analysis was to evaluate the effect of peritoneal dialysis (PD) and hemodialysis (HD) on renal anemia (RA) in renal disease patients by a meta-analysis. Relevant studies published before June 2015 were searched. Pooled odds ratio (OR) with 95% confidence interval (CI) was used to evaluate the effect of HD and PD on RA based on five indexes: hemoglobin, ferritin, transferrin saturation index, serum albumin, and parathyroid hormone. Sensitivity analysis and publication bias assessment were conducted to evaluate the stability and reliability of our results. A total of fourteen eligible studies with 1103 cases underwent HD and 625 cases underwent PD were used for this meta-analysis. There were no significant difference for levels of hemoglobin (SMD = −0.23, 95% CI: −0.74 to 0.28), ferritin (SMD = 0.01, 95% CI: −0.59 to 0.62), parathyroid hormone (SMD = 0.11, 95% CI: −1.53 to 1.75) and transferrin saturation index (SMD = −0.06, 95% CI: −0.67 to 0.56) between HD and PD group. However, the content of serum albumin in HD group was much more than that in PD group (SMD = 1.58, 95% CI: 0.35 to 2.81). Neither of the included studies could reverse the pooled side effect and Egger’s test demonstrated no publication bias. Both of the two dialysis strategies have a similar effect on RA in renal disease patients.

Smoking as a risk factor for diabetic nephropathy: a meta-analysis

BackgroundPrevious studies have investigated the connection between diabetic nephropathy and smoking, and reported widely varying rates. This study aimed to systematically analyze the impact of smoking on diabetic nephropathy.MethodsWe searched the PubMed and EMBASE electronic databases to identify relevant English-language studies published up to March 2016. Eligible studies were selected using inclusion and exclusion criteria. Data for each study were extracted independently by two authors. The homogeneity of the effect size across the studies was tested. Odds ratio (OR) was calculated by using the random-effect model. Sensitivity analysis was performed to reduce heterogeneity, and publication biases were examined.ResultsA total of 21 eligible studies were selected and pooled analyzed. No significant differences in demographic characteristics were found between patients with diabetic nephropathy and those with non-diabetic nephropathy. Significant heterogeneity across studies was found except those of diabetes mellitus controls. The aggregate OR of smoking in the patients with diabetic nephropathy in comparison with those with non-diabetic nephropathy was 1.70 (95% confidence interval 1.48–1.95). No evidence of publication bias was found.ConclusionOur findings indicate that smoking is a significant risk factor for diabetic nephropathy in diabetic patients.

p16ink4a Expression Is Increased through 12-Lipoxygenase in High Glucose-Stimulated Glomerular Mesangial Cells and Type 2 Diabetic Glomeruli

Background/Aims: Arachidonic acid-metabolizing enzyme, 12-lipoxygenase (12-LO), is involved in the glomerular hypertrophy of diabetic nephropathy (DN), in which cyclin-dependent kinase inhibitors (CKIs) play important roles. However, it is unclear whether 12-LO regulates the expression of the CKI p16ink4a in DN. Methods: Primary glomerular mesangial cells (MCs) and glomeruli isolated from rats were used in this study. The rats were fed a high-fat diet and given low-dose streptozotocin to induce type 2 diabetes. The 12-LO product, 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), was infused through an osmotic minipump. Enzyme-linked immunosorbent assay, Western blot, and morphometric analyses were performed. Results: High glucose (HG) increased the p16ink4a protein expression in MCs, but this increase was prevented by the 12-LO inhibitor, cinnamyl-3,4-dihydroxy-α-cynanocinnamate (CDC). The levels of p-p38MAPK and p16ink4a in MCs were significantly elevated after the 12(S)-HETE treatment, whereas the p38MAPK inhibitor SB203580 prevented these increases. Compared with levels in control MCs, marked increases in p38MAPK activation and p16ink4a expression were observed in MCs plated on collagen IV, while the CDC treatment prevented these changes. Subcutaneous injection of CDC did not affect glucose levels, but completely attenuated the diabetes-related increases in the 12(S)-HETE content, p16ink4a expression, p-p38MAPK levels, glomerular volume, and the kidney/body weight ratio. Compared with levels in controls, p16ink4a and p-p38MAPK in the glomeruli derived from 12(S)-HETE-treated rats were significantly higher. Conclusions: 12-LO-p38MAPK mediates the upregulation of p16ink4a in HG-stimulated MCs and type 2-diabetic glomeruli, and new therapies aimed at 12-LO inhibition may prove beneficial in ameliorating diabetes-induced glomerular hypertrophy.

Knockdown of TLR4 attenuates high glucose-induced podocyte injury via the NALP3/ASC/Caspase-1 signaling pathway

Diabetic nephropathy (DN) is one of the most common syndromes of the diabetic mellitus, and is the leading cause of end-stage renal disease. TLR4 (Toll-like receptor 4) has been shown to be implicated in the progression of DN. However, the role of TLR4 in DN and its underlying mechanism remain elusive. In this study, we found that high glucose (HG) activated nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NALP3) inflammasome, as shown by elevated NALP3, apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC) and cleaved caspase-1 protein levels, and increased caspase-1 activity in mouse podocytes in vitro. Simultaneously, HG decreased the mRNA and protein expression of Wilms tumor-1 and synaptopodin, and increased the mRNA and protein expression levels of desmin in podocytes, in a dose-dependent manner. Administration of HG increased the number of TUNEL-positive cells, inhibited the viability of podocytes, elevated the intracellular level of ROS, and increased the levels of IL-1β, IL-18, TNF-α and TGF-β1. Moreover, the effects of HG were effectively blocked by repression of NALP3 or ASC. Furthermore, TLR4 was upregulated in HG-stimulated podocytes. TLR4 knockdown inhibited the activation of NALP3 inflammasome in HG-treated podocytes, as indicated by the decrease in NALP3, ASC and cleaved caspase-1 protein levels and the reduction in caspase-1 activity. Additionally, knockdown of TLR4 attenuated the HG-induced increase of cell apoptosis and reduction of cell viability in podocytes. TLR4 knockdown reduced the intracellular level of ROS in conjunction with reduced IL-1β, IL-18, TNF-α and TGF-β1 levels in podocytes in the presence of HG. In conclusion, knockdown of TLR4 attenuates HG-induced podocyte injury via the NALP3/ASC/Caspase-1 signaling pathway.

Identification of key genes for diabetic kidney disease using biological informatics methods

Diabetic kidney disease (DKD) is a common complication of diabetes, which is characterized by albuminuria, impaired glomerular filtration rate or a combination of the two. The aim of the present study was to identify the potential key genes involved in DKD progression and to subsequently investigate the underlying mechanism involved in DKD development. The array data of GSE30528 including 9 DKD and 13 control samples was downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) in DKD glomerular and tubular kidney biopsy tissues were compared with normal tissues, and were analyzed using the limma package. Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed for DEGs using the GO Function software in Bioconductor. The protein-protein interaction (PPI) network was then constructed using Cytoscape software. A total of 426 genes (115 up- and 311 downregulated) were differentially expressed between the DKD and normal tissue samples. The PPI network was constructed with 184 nodes and 335 edges. Vascular endothelial growth factor A (VEGFA), α-actinin-4 (ACTN4), proto-oncogene, Src family tyrosine kinase (FYN), collagen, type 1, α2 (COL1A2) and insulin-like growth factor 1 (IGF1) were hub proteins. Major histocompatibility complex, class II, DP α1 (HLA-DPA1) was the common gene enriched in the rheumatoid arthritis and systemic lupus erythematosus pathways, and the immune response was a GO term enriched in module A. VEGFA, ACTN4, FYN, COL1A2, IGF1 and HLA-DPA1 may be potential key genes associated with the progression of DKD, and immune mechanisms may serve a part in DKD development.