Genome-Wide Association Analysis of Protein-Coding Variants in IgA Nephropathy.

SIGNIFICANCE STATEMENT: Genome-wide association studies have identified nearly 20 IgA nephropathy susceptibility loci. However, most nonsynonymous coding variants, particularly ones that occur rarely or at a low frequency, have not been well investigated. The authors performed a chip-based association study of IgA nephropathy in 8529 patients with the disorder and 23,224 controls. They identified a rare variant in the gene encoding vascular endothelial growth factor A (VEGFA) that was significantly associated with a two-fold increased risk of IgA nephropathy, which was further confirmed by sequencing analysis. They also identified a novel common variant in PKD1L3 that was significantly associated with lower haptoglobin protein levels. This study, which was well-powered to detect low-frequency variants with moderate to large effect sizes, helps expand our understanding of the genetic basis of IgA nephropathy susceptibility. BACKGROUND: Genome-wide association studies have identified nearly 20 susceptibility loci for IgA nephropathy. However, most nonsynonymous coding variants, particularly those occurring rarely or at a low frequency, have not been well investigated. METHODS: We performed a three-stage exome chip-based association study of coding variants in 8529 patients with IgA nephropathy and 23,224 controls, all of Han Chinese ancestry. Sequencing analysis was conducted to investigate rare coding variants that were not covered by the exome chip. We used molecular dynamic simulation to characterize the effects of mutations of VEGFA on the protein's structure and function. We also explored the relationship between the identified variants and the risk of disease progression. RESULTS: We discovered a novel rare nonsynonymous risk variant in VEGFA (odds ratio, 1.97; 95% confidence interval [95% CI], 1.61 to 2.41; P = 3.61×10 -11 ). Further sequencing of VEGFA revealed twice as many carriers of other rare variants in 2148 cases compared with 2732 controls. We also identified a common nonsynonymous risk variant in PKD1L3 (odds ratio, 1.16; 95% CI, 1.11 to 1.21; P = 1.43×10 -11 ), which was associated with lower haptoglobin protein levels. The rare VEGFA mutation could cause a conformational change and increase the binding affinity of VEGFA to its receptors. Furthermore, this variant was associated with the increased risk of kidney disease progression in IgA nephropathy (hazard ratio, 2.99; 95% CI, 1.09 to 8.21; P = 0.03). CONCLUSIONS: Our study identified two novel risk variants for IgA nephropathy in VEGFA and PKD1L3 and helps expand our understanding of the genetic basis of IgA nephropathy susceptibility.

[Effect of application at Shu-Mu acupoint on serum uric acid in hyperuricemic rats].

OBJECTIVE: To observe the effect of application at Back-Shu with Front-Mu acupoints on serum uric acid (SUA) and kidney uric acid transport related proteins in hyperuricemia rats, so as to explore the mechanism of Shu-Mu acupoint application on treatment of hyperuricemia. METHODS: SD rats were randomly divided into blank control, model, vaseline application and medication application groups, with 8 rats in each group. The hyperuricemia rat model was established by gavage of potassium oxonate. Rats in the vaseline application group received application of vaseline at bilateral "Ganshu"(BL18) and "Qimen"(LI14), "Pishu"(BL20) and "Zhangmen"(LR13), "Shenshu" (BL23) and "Jingmen"(GB25). Rats in the medication application group received application of traditional Chinese medicine at the same acupoints. The contents of SUA and creatinine (SCr) were detected by automatic biochemical analyzer. H.E. staining was used to observe the pathological changes of kidney. And the protein expression levels of organic anion transporter 1(OAT1) and adenosine triphosphate binding cassette transporter G2(ABCG2) were detected by immunohistochemistry. RESULTS: Rats in the model group showed symptoms such as polydipsia, polyuria, loose stools, fatigue, weakness, etc. The renal tubules atrophied, and urate crystals can be seen in the lumen. Compared with the control group. the SUA content in the model group increased (P<0.01)and the expressions of OAT1 and ABCG2 protein in kidney decreased (P<0.01). After intervention and in comparison with the model group showed that, the diet, excretion function, and mental state of the rats in the medication application group returned to normal, and the pathological changes of the kidney tissue were alleviated, the SUA content was down-regulated(P<0.01)and the expression levels of OAT1 and ABCG2 in the kidney up-regulated (P<0.01). There was no statistically significant difference in the SCr content among the 4 groups (P＞0.05). CONCLUSION: Medication application at Shu-Mu points can effectively reduce the SUA level of hyperuricemia rats, which may be related to its effects in up-regulating the protein expressions of OAT1 and ABCG2 in the kidney and reducing the damage to the kidneys.

The changes in the levels of IL-6, IL-17, and IL-21 in the acute stage of childhood asthma.

BACKGROUND: Asthma is the most common disease in children, and its pathogenesis is highly complicated. METHODS: CD4+ cells and CD4+ IL-17+ cells were analysed by flow cytometry, and the ratio of CD4+ cells to the peripheral blood mononuclear cells (PBMCs) and CD4+ IL-17+ cells to PMBCs were calculated from the control group, acute group, and moderate group. The levels of protein expression of IL-6, IL-17, and IL-21 were detected by ELISA in the plasma and culture supernatants of PBMCs of the three groups. The correlations between IL-7 and IL-6, IL-7 and IL-21 were analysed in culture supernatants of PBMCs of the three groups. RESULTS: The mean ratio of CD4+ IL-17+ cells/peripheral blood mononuclear cells (PBMCs) was 4.32% in the acute group, which was higher than in the control group and moderate group. The levels of IL-6 and IL-17 were elevated, and the levels of IL-21 were decreased in the acute group. The levels of IL-17 and IL-6 were positively correlated (r = 0.182, p = 0.03), and the levels of IL-17 and IL-21 were negatively correlated (r = -0.834, p = 0.02). CONCLUSIONS: The results suggest that the levels of IL-17 and IL-6 are related to the severity of asthma. Furthermore, IL-17 may play a role in the development of childhood asthma.

A genome-wide association study in Han Chinese identifies multiple susceptibility loci for IgA nephropathy.

We performed a two-stage genome-wide association study of IgA nephropathy (IgAN) in Han Chinese, with 1,434 affected individuals (cases) and 4,270 controls in the discovery phase and follow-up of the top 61 SNPs in an additional 2,703 cases and 3,464 controls. We identified associations at 17p13 (rs3803800, P = 9.40 × 10(-11), OR = 1.21; rs4227, P = 4.31 × 10(-10), OR = 1.23) and 8p23 (rs2738048, P = 3.18 × 10(-14), OR = 0.79) that implicated the genes encoding tumor necrosis factor (TNFSF13) and α-defensin (DEFA) as susceptibility genes. In addition, we found multiple associations in the major histocompatibility complex (MHC) region (rs660895, P = 4.13 × 10(-20), OR = 1.34; rs1794275, P = 3.43 × 10(-13), OR = 1.30; rs2523946, P = 1.74 × 10(-11), OR = 1.21) and confirmed a previously reported association at 22q12 (rs12537, P = 1.17 × 10(-11), OR = 0.78). We also found that rs660895 was associated with clinical subtypes of IgAN (P = 0.003), proteinuria (P = 0.025) and IgA levels (P = 0.047). Our findings show that IgAN is associated with variants near genes involved in innate immunity and inflammation.

Suppression of tumor necrosis factor receptor associated factor (TRAF)-2 attenuates the proinflammatory and proliferative effect of aggregated IgG on rat renal mesangial cells.

Immune-complex (IC) mediated glomerulonephritis (GN) is a common cause of chronic kidney disease associated with increased levels of tumor necrosis factor (TNF)-alpha in renal cells. TNF-alpha signaling pathways involve complicated interactions between multiple proteins including TNF-receptor-associated factor (TRAF)-2. We have previously found markedly up-regulated expression of TRAF-2 in renal tissues from IC mediated lupus nephritis patients. Here we investigated the effect of TRAF-2 on inflammatory response in rat mesangial cells (MCs). The results showed that treatment with soluble aggregated IgG (AIgG) resulted in a time- and dose-dependent increase in the expression of interleukin (IL)-1beta and IL-6. Significant cell proliferation was also observed after the treatment with soluble AIgG. Knockdown TRAF-2 by siRNA significantly suppressed soluble AIgG induced up-regulation of TRAF-2, IL-1beta, and IL-6. Meanwhile the cell proliferation was inhibited and apoptotic cells were increased. It was concluded that TRAF-2 could induce the proinflammatory and proliferative effects of soluble AIgG on rat MCs. Thus, TRAF-2 may represent a future target for therapy of IC mediated GN.