Endothelial factors and diabetic nephropathy

GPR56 Promotes Diabetic Kidney Disease Through eNOS Regulation in Glomerular Endothelial Cells

Although glomerular endothelial dysfunction is well recognized as contributing to the pathogenesis of diabetic kidney disease (DKD), the molecular pathways contributing to DKD pathogenesis in glomerular endothelial cells (GECs) are only partially understood. To uncover pathways that are differentially regulated in early DKD that may contribute to disease pathogenesis, we recently conducted a transcriptomic analysis of isolated GECs from diabetic NOS3-null mice. The analysis identified several potential mediators of early DKD pathogenesis, one of which encoded an adhesion G protein-coupled receptor-56 (GPR56), also known as ADGRG1. Enhanced glomerular expression of GPR56 was observed in human diabetic kidneys, which was negatively associated with kidney function. Using cultured mouse GECs, we observed that GPR56 expression was induced with exposure to advanced glycation end products, as well as in high-glucose conditions, and its overexpression resulted in decreased phosphorylation and expression of endothelial nitric oxide synthase (eNOS). This effect on eNOS by GPR56 was mediated by coupling of Gα12/13-RhoA pathway activation and Gαi-mediated cAMP/PKA pathway inhibition. The loss of GPR56 in mice led to a significant reduction in diabetes-induced albuminuria and glomerular injury, which was associated with reduced oxidative stress and restoration of eNOS expression in GECs. These findings suggest that GPR56 promotes DKD progression mediated, in part, through enhancing glomerular endothelial injury and dysfunction.

ARTICLE HIGHLIGHTS

Transplantation of Human Amniotic Mesenchymal Stem Cells Up-Regulates Angiogenic Factor Expression to Attenuate Diabetic Kidney Disease in Rats

BACKGROUND AND AIMS

Diabetic kidney disease (DKD) is a prevalent and intractable microvascular complication of diabetes mellitus (DM), the process of which is closely related to abnormal expression of angiogenesis-regulating factors (ARFs). Stem cell transplantation might be a novel strategy for treating DKD. This study aims to explore the effect of transplantation of human amniotic mesenchymal stem cells (hAMSCs) on renal microangiopathy in a type 1 DKD rat model (T1DRM).

METHODS

Seventy-two rats were randomly divided into three groups, including normal control group, DKD group, and hAMSCs transplantation group. T1DRM was established using a rat tail vein injection of streptozotocin (STZ) (55 mg/kg). hAMSCs were obtained from placental amniotic membranes during cesarean delivery and transplanted at 3 and 4 weeks through penile veins. At 6, 8, and 12 weeks following transplantation, blood glucose levels, renal function, pathological kidney alterations, and the expressions of ARFs' mRNA and protein were analyzed.

RESULTS

In T1DRM, transplanted hAMSCs that were homed at the injured site of kidneys increased ARFs' expression and decreased blood glucose levels. Compared to the DKD group, the levels of 24-h urinary protein, serum creatinine, urea, and kidney injury molecule-1 (KIM-1) were reduced in hAMSCs transplantation group. In terms of renal pathology such as the degree of basement membrane thickening, hAMSCs transplantation was also less severe than the DKD group, thereby alleviating kidney injury.

CONCLUSION

hAMSCs transplantation might ameliorate STZ-induced chronic kidney injury through increasing ARFs' expression in kidneys and lowering blood glucose levels.

Late renal toxicity in patient with radioiodine-refractory differentiated thyroid cancer treated with lenvatinib: A case report and literature review

Introduction

Thyroid carcinoma is the most common endocrine neoplasm. Multimodal therapy including surgery, radioactive iodine (RAI) therapy, and indefinite suppression of thyroid-stimulating hormone has led to an 85% cure rate in differentiated thyroid tumors (DTT). Approximately 5–10% of patients will have recurrence or metastases that have the potential to become resistant to RAI treatment. 1 10-year overall survival rates are reported to be 10% in these patients versus 56% in patients with RAI avid disease. 2 Lenvatinib, a multi-tyrosine-kinase inhibitor (TKI), was shown to have a 65% overall response rate in addition to a significant improvement in progression-free survival (PFS), approved to treat RAI-resistant DTTs. 3 , 4

Case Report

We are reporting a very rare case of late renal toxicity in a 68-year-old woman with a history of type 2 diabetes and metastatic RAI-resistant follicular thyroid carcinoma (Hurthle cell variant) who developed thrombotic microangiopathy 21 months after initiation of treatment.

Management & Outcome

It was determined that LEN should be held, due to worsening renal function secondary to TKI-induced kidney injury. Although the patient's renal function eventually improved and returned to her baseline after discontinuation of LEN, there was marked disease progression after drug cessation.

Discussion

Renal toxicity is a rare adverse event (AE) that tends to occur typically within three weeks of initiation of treatment. The utilization of TKIs can lead to glomerulosclerosis, and careful considerations and precautions should be taken by clinicians who intend to initiate TKI therapy in patients with pre-existing diabetes to prevent renal toxicity.

Association of eNOS and MCP-1 Genetic Variants with Type 2 Diabetes and Diabetic Nephropathy Susceptibility: A Case-Control and Meta-Analysis Study

Type 2 diabetes (T2D) and its secondary complications result from the complex interplay of genetic and environmental factors. To understand the role of these factors on disease susceptibility, the present study was conducted to assess the association of eNOS and MCP-1 variants with T2D and diabetic nephropathy (DN) in two ethnically and geographically different cohorts from North India. A total of 1313 subjects from two cohorts were genotyped for eNOS (rs2070744, rs869109213 and rs1799983) and MCP-1 (rs1024611 and rs3917887) variants. Cohort-I (Punjab) comprised 461 T2D cases (204 T2D with DN and 257 T2D without DN) and 315 healthy controls. Cohort-II (Jammu and Kashmir) included 337 T2D (150 T2D with DN and 187 T2D without DN) and 200 controls. Allele, genotype and haplotype frequencies were compared among the studied participants, and phenotype-genotype interactions were determined. Meta-analysis was performed to investigate the association between the selected variants and disease susceptibility. All three eNOS variants were associated with 1.5-4.0-fold risk of DN in both cohorts. MCP-1 rs1024611 conferred twofold risk towards DN progression in cohort-II, while rs3917887 provided twofold risk for both T2D and DN in both cohorts. eNOS and MCP-1 haplotypes conferred risk for T2D and DN susceptibility. Phenotype-genotype interactions showed significant associations between the studied variants and anthropometric and biochemical parameters. In meta-analysis, all eNOS variants conferred risk towards DN progression, whereas no significant association was observed for MCP-1 rs1024611. We show evidences for an association of eNOS and MCP-1 variants with T2D and DN susceptibility.

Peri-renal adipose inflammation contributes to renal dysfunction in a non-obese prediabetic rat model: Role of anti-diabetic drugs

Diabetic nephropathy is a major health challenge with considerable economic burden and significant impact on patients' quality of life. Despite recent advances in diabetic patient care, current clinical practice guidelines fall short of halting the progression of diabetic nephropathy to end-stage renal disease. Moreover, prior literature reported manifestations of renal dysfunction in early stages of metabolic impairment prior to the development of hyperglycemia indicating the involvement of alternative pathological mechanisms apart from those typically triggered by high blood glucose. Here, we extend our prior research work implicating localized inflammation in specific adipose depots in initiating cardiovascular dysfunction in early stages of metabolic impairment. Non-obese prediabetic rats showed elevated glomerular filtration rates and mild proteinuria in absence of hyperglycemia, hypertension, and signs of systemic inflammation. Isolated perfused kidneys from these rats showed impaired renovascular endothelial feedback in response to vasopressors and increased flow. While endothelium dependent dilation remained functional, renovascular relaxation in prediabetic rats was not mediated by nitric oxide and prostaglandins as in control tissues, but rather an upregulation of the function of epoxy eicosatrienoic acids was observed. This was coupled with signs of peri-renal adipose tissue (PRAT) inflammation and renal structural damage. A two-week treatment with non-hypoglycemic doses of metformin or pioglitazone, shown previously to ameliorate adipose inflammation, not only reversed PRAT inflammation in prediabetic rats, but also reversed the observed functional, renovascular, and structural renal abnormalities. The present results suggest that peri-renal adipose inflammation triggers renal dysfunction early in the course of metabolic disease.

LRG1 Promotes Diabetic Kidney Disease Progression by Enhancing TGF-β-Induced Angiogenesis

BACKGROUND

Glomerular endothelial dysfunction and neoangiogenesis have long been implicated in the pathogenesis of diabetic kidney disease (DKD). However, the specific molecular pathways contributing to these processes in the early stages of DKD are not well understood. Our recent transcriptomic profiling of glomerular endothelial cells identified a number of proangiogenic genes that were upregulated in diabetic mice, including leucine-rich α-2-glycoprotein 1 (LRG1). LRG1 was previously shown to promote neovascularization in mouse models of ocular disease by potentiating endothelial TGF-β/activin receptor-like kinase 1 (ALK1) signaling. However, LRG1's role in the kidney, particularly in the setting of DKD, has been unclear.

METHODS

We analyzed expression of LRG1 mRNA in glomeruli of diabetic kidneys and assessed its localization by RNA in situ hybridization. We examined the effects of genetic ablation of Lrg1 on DKD progression in unilaterally nephrectomized, streptozotocin-induced diabetic mice at 12 and 20 weeks after diabetes induction. We also assessed whether plasma LRG1 was associated with renal outcome in patients with type 2 diabetes.

RESULTS

LRG1 localized predominantly to glomerular endothelial cells, and its expression was elevated in the diabetic kidneys. LRG1 ablation markedly attenuated diabetes-induced glomerular angiogenesis, podocyte loss, and the development of diabetic glomerulopathy. These improvements were associated with reduced ALK1-Smad1/5/8 activation in glomeruli of diabetic mice. Moreover, increased plasma LRG1 was associated with worse renal outcome in patients with type 2 diabetes.

CONCLUSIONS

These findings identify LRG1 as a potential novel pathogenic mediator of diabetic glomerular neoangiogenesis and a risk factor in DKD progression.

The effect of resveratrol on the histologic characteristics of the cochlea in diabetic rats

OBJECTIVES/HYPOTHESIS

The aim of this study was to investigate changes in the cochlea and the potential dose-dependent effects of resveratrol (RSV) against diabetes mellitus (DM) ototoxicity.

STUDY DESIGN

Animal model.

METHODS

Twenty-four male Wistar albino rats were divided into four groups. Baseline distortion product otoacoustic emission (DPOAE) measurements were evaluated. Group I was the control group, group II was made diabetic with single-dose streptozotocin, and groups III and IV were rendered diabetic as group II and administered 10 and 20 mg RSV, respectively, intraperitoneally for 4 weeks. All animals were sacrificed after repeated DPOAE measurement. Apoptosis was investigated using caspase-3, Bax (Bcl-associated X protein), and TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) staining.

RESULTS

The DPOAE values in the diabetic group were found to be significantly lower compared with the other groups at 5,714 Hz and 8,000 Hz (P < .05). No significant difference in otoacoustic emission was detected in the comparison of the RSV doses (P > .05). The histopathologic investigation using caspase-3, Bax, and TUNEL staining showed that the mean rank of the diabetic group was significantly higher compared with the RSV10, RSV20, and control groups (DM > RSV10 > RSV20 > control) (P < .05).

CONCLUSIONS

These results imply that RSV administration offered statistically significant protection for the cochleas of rats against diabetes. This protective effect improved histologically with higher doses.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E1-E6, 2019.

Microvascular endothelial function is an independent predictor for albuminuria progression among Asians with type 2 diabetes-A prospective cohort study

OBJECTIVE

We aim to investigate whether microvascular endothelial dysfunction is an independent predictor for future albuminuria progression in T2DM cohort.

METHODS

A total of 1098 patients with T2DM were clinically assessed at baseline and 3.2-year follow-up. Progression was defined as transition from normoalbuminuria (ACR <30 mg/g) to microalbuminuria (ACR = 30-299 mg/g) or macroalbuminuria (ACR >300 mg/g), or microalbuminuria to macroalbuminuria. Microvascular endothelial vasodilation at baseline was quantified using LDF. The increase in perfusion in response to ACh and NaNP was calculated. Logistic regression model was used to estimate the OR for albuminuria progression.

RESULTS

Albuminuria progression occurred in 226 (20.6%) patients. Baseline ACh was significantly higher in nonprogression than progression group (80.0 ± 53.2% vs 72.0 ± 49.7%, P = .04). There is no significant difference in NaNP between the two groups (111.1 ± 80.3% vs 121.1 ± 87.4%, P = .12). After multivariable adjustment, 1-SD increase in ACh was marginally associated with albuminuria progression (OR = 0.87, 95% CI, 0.72-1.02, P = .08) in all patients. When stratified by baseline albuminuria, 1-SD increase in ACh was significantly associated with albuminuria progression in normoalbuminuria (OR = 0.76, 95% CI, 0.59-0.97, P = .03), but not in microalbuminuria patients (OR = 1.18, 95% CI, 0.81-1.70, P = .39).

CONCLUSIONS

Impaired endothelial-dependent microvascular reactivity predicts the onset of albuminuria progression among T2DM patients with normoalbuminuria.

Preliminary study of hypoxia-related cardiovascular mediator-markers in patients with end-stage renal disease with and without diabetes and the effects of haemodialysis

BACKGROUND

Evidence points to activation of pro-inflammatory and pro-thrombotic stimuli during the haemodialysis process in end-stage renal disease (ESRD) with potential to predispose to cardiovascular events. Diabetes is associated with a higher incidence of cardiovascular disease in haemodialysis patients. We tested the hypothesis that a range of mediators and markers that modulate cardiovascular risk are elevated in haemodialysis patients with diabetes compared to those without.

METHODS

Men and women with diabetes (n = 6) and without diabetes (n = 6) aged 18-90 years receiving haemodialysis were recruited. Blood samples were collected and analysed pre- and post-haemodialysis sessions for (platelet-monocyte conjugates (PMC), oxidised LDL (Ox-LDL), endothelin 1 (ET-1) and vascular endothelial growth factor (VEGF-A).

RESULTS

PMC levels significantly increased after haemodialysis in both groups (diabetes p = 0.047; non-diabetes p = 0.005). Baseline VEGF-A was significantly higher in people with diabetes (p = 0.009) and post-dialysis levels were significantly reduced in both groups (P = 0.002). Ox-LDL and CRP concentrations were not significantly different between groups nor affected in either group post-dialysis. Similarly, ET-1 concentrations were comparable in all patients at baseline, with no change post-dialysis in either group.

CONCLUSIONS

In this pilot study, we have confirmed that circulating PMCs are increased following dialysis irrespective of diabetes status. This is likely to be a mechanistic process and offers a potential explanation for high rates of vascular events associated with haemodialysis. The higher VEGF-A concentrations between patients with and without diabetes is a previously unreported finding in diabetic ESRD. Further research is merited to establish whether VEGF-A is a marker or mediator (or both) of cardiovascular risk in haemodialysis.

Renal endothelial protein C receptor expression and shedding during diabetic nephropathy

Essentials Endothelial protein C receptor (EPCR) promotes diabetic nephropathy (DN) outcome improvement. Renal expression and shedding of EPCR were measured in diabetic patients with or without DN. Inhibition of metalloproteinase-driven EPCR shedding restored glomerular endothelium phenotype. EPCR shedding through metalloproteinase ADAM17 contributes to the worsening of DN.

SUMMARY

Background Diabetic nephropathy (DN) represents the leading cause of end-stage renal disease. The endothelial protein C receptor (EPCR) and its ligand (activated protein C) have been shown to ameliorate the phenotype of DN in mice. EPCR activity can be regulated by proteolytic cleavage involving ADAMs, yielding a soluble form of EPCR (sEPCR). Objective To characterize the renal expression and shedding of EPCR during DN. Methods EPCR levels were measured in plasma, urine and biopsy samples of diabetic patients with (n = 73) or without (n = 63) DN. ADAM-induced cleavage of EPCR was investigated in vitro with a human glomerular endothelium cell line. Results DN patients showed higher plasma and urinary levels of sEPCR than diabetic controls (112.2 versus 135.2 ng mL(-1) and 94.35 versus 140.6 ng mL(-1) , respectively). Accordingly, glomerular endothelial EPCR expression was markedly reduced in patients with DN, and this was associated with increased glomerular expression of ADAM-17 and ADAM-10. In vitro, EPCR shedding was induced by incubation of glomerular endothelium in high-glucose medium, and this shedding was suppressed by ADAM-17 inhibition or silencing, which led to improved vascular endothelial cadherin (VE-cadherin) expression and reduced mRNA expression of transforming growth factor (TGF)-β. In addition, EPCR silencing led to minor effects on VE-cadherin but to a significant increase in TGF-β mRNA expression. Conclusion Inhibition of ADAM-driven glomerular EPCR shedding restored the endothelial phenotype of glomerular endothelium, whereas EPCR silencing led to enhanced expression of TGF-β, a marker of endothelial-mesenchymal transition. These findings demonstrate that EPCR shedding driven by ADAMs contributes to the worsening of DN.

Urinary biomarkers for early diabetic nephropathy: beyond albuminuria

Diabetic nephropathy (DN) is the most common cause of end-stage kidney disease in the USA and accounts for a significant increase in morbidity and mortality in patients with diabetes. Early detection is critical in improving clinical management. Although microalbuminuria is regarded as the gold standard for diagnosing the onset of DN, its predictive powers are limited. Consequently, great efforts have been made in recent years to identify better strategies for the detection of early stages of DN and progressive kidney function decline in diabetic patients. Here, we review the various urinary biomarkers that have emerged from these studies which hold promise as more sensitive diagnostic tools for the earlier detection of diabetic kidney disease and the prediction of progression to end-stage kidney disease. A number of key biomarkers present in the urine have been identified that reflect kidney injury at specific sites along the nephron, including glomerular/podocyte damage and tubular damage, oxidative stress, inflammation and activation of the intrarenal renin-angiotensin system. We also describe newer approaches, including urinary microRNAs, which are short noncoding mRNAs that regulate gene expression, and urine proteomics, that can be used to identify potential novel biomarkers in the development and progression of diabetic kidney disease.

Vascular cell adhesion molecule-1, but not intercellular adhesion molecule-1, is associated with diabetic kidney disease in Asians with type 2 diabetes

BACKGROUND AND AIMS

The association of adhesion molecules ICAM-1 and VCAM-1 with cardiovascular diseases has been well-studied. However, their roles in diabetic kidney disease (DKD) are incompletely understood. We aim to study the association of plasma ICAM-1 and VCAM-1 with DKD in Asians with type 2 diabetes (T2DM).

SUBJECTS AND METHODS

A total of 1950 Asians with T2DM were included in this cross-sectional study. Plasma ICAM-1 and VCAM-1 were measured by immunoassays.

RESULTS

Renal filtration function (eGFR) declined and urinary albumin-to-creatinine ratio (ACR) levels increased progressively with the increase in plasma VCAM-1 levels. In contrast, no significant changes in eGFR and ACR were observed in subjects across different plasma ICAM-1 levels. Both ICAM-1 and VCAM-1 were correlated with ACR (rho = 0.153, p < 0.001 for VCAM-1 and ACR; rho = 0.053, p = 0.020 for ICAM-1 and ACR) in bivariate correlation analysis. However, only VCAM-1 was correlated with eGFR (rho = -0.228, p < 0.001). Multivariable linear regression models revealed that VCAM-1, but not ICAM-1, was independently associated with eGFR and albuminuria. Backward linear regression suggested that plasma VCAM-1 variability was mainly determined by eGFR whereas plasma ICAM-1 level was mainly determined by C-reactive protein in patients with T2DM.

CONCLUSIONS

Plasma VCAM-1 level, but not ICAM-1 level, was independently associated with prevalent DKD in Asians with T2DM. High level of ICAM-1 may be indicative of systemic inflammation and portends increase risk of incipient DKD.

Effect of uncontrolled hyperglycemia on levels of adhesion molecules in patients with diabetes mellitus type 2

OBJECTIVE

Uncontrolled diabetes has become a major cause of mortality and morbidity by reason of vascular angiopathy. The aim of this study was to evaluate the concentrations of soluble forms of vascular adhesion molecule-1 (sVCAM-1), intercellular adhesion molecule-1 (sICAM-1), E-selectin, and thrombomodulin in patients with well-controlled and uncontrolled diabetes type 2.

METHODS

The study was conducted on 62 patients with diabetes. Group I consisted of 35 patients with well-controlled diabetes. The second group included 27 patients with uncontrolled diabetes with micro-albuminuria. A control group was made up of 25 healthy volunteers. The concentrations of sVCAM-1, sICAM-1, sE-selectin, and soluble thrombomodulin were assayed in plasma. Serum concentration of creatinine was measured and the plasma concentrations of fasting glucose and glycated hemoglobin (HbA1c) determined.

RESULTS

Lower concentrations of ICAM-1 were found in the group of uncontrolled diabetes patients compared with those with well-controlled disease. In patients with uncontrolled diabetes, VCAM-1 levels were significantly higher compared with the group with well-controlled diabetes. In patients with uncontrolled diabetes a positive correlation was obtained between glomerular filtration rate and sE-selectin and a negative correlation between the levels of creatinine and ICAM-1, although there was a positive correlation between (HbA1c) and ICAM-1.

CONCLUSIONS

The study confirmed the participation of the inflammatory process associated with impaired vascular endothelial function in the pathogenesis of type 2 diabetes. The opposite effect of uncontrolled hyperglycemia on adhesion molecules suggests different functions of VCAM-1 and ICAM-1 in complications of diabetes.

Endothelial and platelet markers in diabetes mellitus type 2

Diabetes mellitus (DM) is an extremely common disorder which carries a risk of vascular impairment. DM type 2 (DM2) can be characterized by the dysfunction of haemostasis manifesting by stimulated coagulation process, disorder of platelet function and decreased fibrinolytic activity. These all are the reasons why DM2 is the most common acquired thrombophilia. Endothelial dysfunction along with platelet hyperactivity are unquestionably involved in the hyperactivation of platelets and clotting factors in DM. As a natural consequence of continuous investigation, many markers of endothelial dysfunction and diabetic thrombocytopathy have been identified and considered for implementation in clinical practice. Endothelial function can be assessed by the evaluation of endothelial markers, circulating molecules synthesised in various amounts by the endothelium. These markers precede the signs of evident microangiopathy. Platelets have an ethiopathogenic relation to the microangiopathy in DM. Their increased activity was confirmed in both types of DM. Predictors of endothelial and platelet disorder could improve the screening of individuals at increased risk, thus leading to the early diagnosis, appropriate treatment, as well as to the effective prevention of the complications of DM2. In the article we deal with the mechanisms involved in the pathogenesis of endothelial and platelet functional abnormalities, endothelial and platelet markers of DM2 considered for implementation in clinical practice and possibilities of their detection.

Finasteride reduces microvessel density and expression of vascular endothelial growth factor in renal tissue of diabetic rats

BACKGROUND

Vascular endothelial growth factor (VEGF) plays a critical role in the pathogenesis of diabetic microvascular complications. Finasteride has been confirmed to decrease VEGF expression in prostate and prostatic suburethral tissue resulting in limiting hematuria from human benign prostatic hyperplasia. The purpose of this study was to evaluate the effects of finasteride on microvessel density (MVD), VEGF protein and mRNA expressions in the renal tissue of diabetic rats.

METHODS

Diabetic rats induced by streptozotocin were intragastrically given finasteride at 30 mg/kg body weight once a day for 4 weeks. Histomorphologic changes in kidney were observed under light microscope. Immunohistochemistry for CD34 and VEGF on kidney sections was performed to assess MVD and VEGF protein expression in glomeruli of rats, respectively. The VEGF mRNA expression in the renal tissue was examined using reverse transcription polymerase chain reaction analysis.

RESULTS

The glomerular tuft area, glomerular volume, MVD, VEGF protein expression in glomeruli and VEGF mRNA expression in the renal cortex tissue were significantly increased in diabetic rats and finasteride-treated rats when compared with controls (P < 0.01, P < 0.05). When compared with diabetic rats, the glomerular tuft area, glomerular volume, MVD, VEGF protein expression in glomeruli and VEGF mRNA expression in the renal cortex tissue of finasteride-treated rats were significantly decreased (P < 0.05, P < 0.01).

CONCLUSIONS

Finasteride reduces the VEGF expression and decreases the MVD in the renal tissue of diabetic rats, suggesting the therapeutic potential of finasteride on diabetic microvascular complications.

Role of the potassium channel KCa3.1 in diabetic nephropathy

There is an urgent need to identify novel interventions for mitigating the progression of diabetic nephropathy. Diabetic nephropathy is characterized by progressive renal fibrosis, in which tubulointerstitial fibrosis has been shown to be the final common pathway of all forms of chronic progressive renal disease, including diabetic nephropathy. Therefore targeting the possible mechanisms that drive this process may provide novel therapeutics which allow the prevention and potentially retardation of the functional decline in diabetic nephropathy. Recently, the Ca2+-activated K+ channel KCa3.1 (KCa3.1) has been suggested as a potential therapeutic target for nephropathy, based on its ability to regulate Ca2+ entry into cells and modulate Ca2+-signalling processes. In the present review, we focus on the physiological role of KCa3.1 in those cells involved in the tubulointerstitial fibrosis, including proximal tubular cells, fibroblasts, inflammatory cells (T-cells and macrophages) and endothelial cells. Collectively these studies support further investigation into KCa3.1 as a therapeutic target in diabetic nephropathy.

Elevated soluble VEGF receptor sFlt-1 correlates with endothelial injury in IgA nephropathy

BACKGROUND

Endothelial injury, which may present clinically as hypertension, proteinuria and increased von Willebrand Factor (vWF) level, is a common manifestation in IgA nephropathy (IgAN). However, causal factors for endothelial injury in IgAN are not completely understood. An imbalance of vascular endothelial growth factor/Soluble fms-like tyrosine kinase-1 (VEGF/sFlt-1) has been observed in many diseases with endothelial dysfunction, including pre-eclampsia and diabetic retinopathy, but whether it contributes to endothelial injury in IgAN requires further exploration.

METHODS

Initially, 96 IgAN patients and 22 healthy volunteers were enrolled as a discovery cohort. VEGF/sFlt-1, sFlt-1 and VEGF levels were compared between patients with IgAN and healthy volunteers to explore the underlying factors that contribute to endothelial injury in IgAN. The identified contributor (sFlt-1) was further confirmed in a replication cohort, which included 109 IgAN patients and 30 healthy volunteers. Correlations of sFlt-1 with hypertension, proteinuria, Oxford-E score and plasma vWF were further evaluated in the combined 205 patients with IgAN.

RESULTS

VEGF/sFlt-1 levels were significantly lower in IgAN patients than healthy volunteers (0.33±0.27 vs. 0.43±0.22, p = 0.02) in the discovery cohort. Within the ratio, plasma sFlt-1 levels were significantly elevated (101.18±25.19 vs. 79.73±18.85 pg/ml, p<0.001), but plasma VEGF levels showed no significant differences. Elevated sFlt-1 levels in the replication cohort were confirmed in IgAN patients (93.40±39.78 vs. 71.92±15.78 pg/ml, p<0.001). Plasma sFlt-1 levels in IgAN patients correlated with proteinuria (severe (>3.5 g/d) vs. moderate (1-3.5 g/d) vs. mild (<1 g/d) proteinuria: 115.95±39.09 vs. 99.89±28.55 vs. 83.24±33.92 pg/ml; severe vs. mild: p<0.001, moderate vs. mild p = 0.001, severe vs. moderate: p = 0.014), hypertension (with vs. without hypertension: 107.87±31.94 vs. 87.32±32.76 pg/ml, p = 0.015) and vWF levels (r = 0.161, p = 0.021).

CONCLUSIONS

The present study found elevated sFlt-1 in IgAN patients and further identified its correlation with proteinuria, hypertension and vWF levels. These results suggested that elevated sFlt-1 contributes to endothelial injury in IgAN.

Vascular endothelial growth factor-receptor 1 inhibition aggravates diabetic nephropathy through eNOS signaling pathway in db/db mice

The manipulation of vascular endothelial growth factor (VEGF)-receptors (VEGFRs) in diabetic nephropathy is as controversial as issue as ever. It is known to be VEGF-A and VEGFR2 that regulate most of the cellular actions of VEGF in experimental diabetic nephropathy. On the other hand, such factors as VEGF-A, -B and placenta growth factor bind to VEGFR1 with high affinity. Such notion instigated us to investigate on whether selective VEGFR1 inhibition with GNQWFI hexamer aggravates the progression of diabetic nephropathy in db/db mice. While diabetes suppressed VEGFR1, it did increase VEGFR2 expressions in the glomerulus. Db/db mice with VEGFR1 inhibition showed more prominent features with respect to, albuminuria, mesangial matrix expansion, inflammatory cell infiltration and greater numbers of apoptotic cells in the glomerulus, and oxidative stress than that of control db/db mice. All these changes were related to the suppression of diabetes-induced increases in PI3K activity and Akt phosphorylation as well as the aggravation of endothelial dysfunction associated with the inactivation of FoxO3a and eNOS-NOx. In cultured human glomerular endothelial cells (HGECs), high-glucose media with VEGFR1 inhibition induced more apoptotic cells and oxidative stress than did high-glucose media alone, which were associated with the suppression of PI3K-Akt phosphorylation, independently of the activation of AMP-activated protein kinase, and inactivation of FoxO3a and eNOS-NOx pathway. In addition, transfection with VEGFR1 siRNA in HGECs also suppressed PI3K-Akt-eNOS signaling. In conclusion, the specific blockade of VEGFR1 with GNQWFI caused severe renal injury related to profound suppression of the PI3K-Akt, FoxO3a and eNOS-NOx pathway, giving rise to the oxidative stress-induced apoptosis of glomerular cells in type 2 diabetic nephropathy.

Podocyte-specific VEGF-a gain of function induces nodular glomerulosclerosis in eNOS null mice

VEGF-A and nitric oxide are essential for glomerular filtration barrier homeostasis and are dysregulated in diabetic nephropathy. Here, we examined the effect of excess podocyte VEGF-A on the renal phenotype of endothelial nitric oxide synthase (eNOS) knockout mice. Podocyte-specific VEGF(164) gain of function in eNOS(-/-) mice resulted in nodular glomerulosclerosis, mesangiolysis, microaneurysms, and arteriolar hyalinosis associated with massive proteinuria and renal failure in the absence of diabetic milieu or hypertension. In contrast, podocyte-specific VEGF(164) gain of function in wild-type mice resulted in less pronounced albuminuria and increased creatinine clearance. Transmission electron microscopy revealed glomerular basement membrane thickening and podocyte effacement in eNOS(-/-) mice with podocyte-specific VEGF(164) gain of function. Furthermore, glomerular nodules overexpressed collagen IV and laminin extensively. Biotin-switch and proximity ligation assays demonstrated that podocyte-specific VEGF(164) gain of function decreased glomerular S-nitrosylation of laminin in eNOS(-/-) mice. In addition, treatment with VEGF-A decreased S-nitrosylated laminin in cultured podocytes. Collectively, these data indicate that excess glomerular VEGF-A and eNOS deficiency is necessary and sufficient to induce Kimmelstiel-Wilson-like nodular glomerulosclerosis in mice through a process that involves deposition of laminin and collagen IV and de-nitrosylation of laminin.

[Medical significance of endothelial glycocalyx]

Endothelial glycocalyx is a layer composed by glycosaminoglycans, proteoglycans and glycoproteins attached to the vascular endothelial luminal surface. It has several physiological roles: shear stress mechanotransduction to the endothelial cells, regulation of fluids and macromolecules vascular permeability, of coagulation cascade activation and fibrinolysis, and protects the endothelium from platelets and leukocytes adhesion. In general, glycocalyx protects vascular wall against pathogenic insults. The glycocalyx may be damaged by abnormal shear stress, reactive oxygen species, hypernatremia, hyperglycemia, hypercholesterolemia and inflammatory molecules, resulting in endothelial dysfunction, enhanced vascular permeability, lipoproteins leakage to subendothelial space, activation of plasma coagulation, and increased adherence of platelets and leukocytes to the endothelial cells. Shredding of glycocalyx appears as an important initial step in the pathophysiology of vascular diseases.

The angiopoietin:Tie 2 interaction: a potential target for future therapies in human vascular disease

Angiopoietin-1 and -2 are endogenous ligands for the vascular endothelial receptor tyrosine kinase Tie2. Signalling by angiopoietin-1 promotes vascular endothelial cell survival and the sprouting and reorganisation of blood vessels, as well as inhibiting activation of the vascular endothelial barrier to reduce leakage and leucocyte migration into tissues. Angiopoietin-2 generally has an opposing action, and is released naturally at times of vascular growth and inflammation. There is a significant body of emerging evidence that promoting the actions of angiopoietin-1 through Tie2 is of benefit in pathologies of vascular activation, such as sepsis, stroke, diabetic retinopathy and asthma. Similarly, methods to inhibit the actions of angiopoietin-2 are emerging and have been demonstrated to be of preclinical and clinical benefit in reducing tumour angiogenesis. Here the author reviews the evidence for potential benefits of modulation of the interaction of angiopoietins with Tie2, and the potential applications. Additionally, methods for delivery of the complex protein angiopoietin-1 are discussed, as well as potentially deleterious consequences of administering angiopoietin-1.

Blockade of CCL2/CCR2 signalling ameliorates diabetic nephropathy in db/db mice

BACKGROUND

CCL2/C-C chemokine receptor 2 (CCR2) signalling is suggested to play a significant role in various kidney diseases including diabetic nephropathy. We investigated the renoprotective effect of a CCR2 antagonist, RS102895, on the development of diabetic nephropathy in a type 2 diabetic mouse model.

METHODS

Six-week-old diabetic db/db and non-diabetic db/m mice were fed either normal chow or chow mixed with 2 mg/kg/day of RS102895 for 9 weeks. We investigated the effects of CCR2 antagonism on blood glucose, blood pressure, albuminuria and the structure and ultrastructure of the kidney.

RESULTS

Diabetes-induced albuminuria was significantly improved after CCR2 antagonist treatment, and glucose intolerance was improved in the RS102895-treated diabetic mice. RS102895 did not affect blood pressure, body weight or kidney weight. Mesangial expansion, glomerular basement membrane thickening and increased desmin staining in the diabetic kidney were significantly improved after RS102895 treatment. The up-regulation of vascular endothelial growth factor mRNA expression and the down-regulation of nephrin mRNA expression were markedly improved in the kidneys of RS102895-treated diabetic mice. Increased renal CD68 and arginase II and urinary malondialdehyde in diabetes were effectively attenuated by RS102895 treatment.

CONCLUSION

Blockade of CCL2/CCR2 signalling by RS102895 ameliorates diabetic nephropathy not only by improving blood glucose levels but also by preventing CCL2/CCR2 signalling from altering renal nephrin and VEGF expressions through blocking macrophage infiltration, inflammation and oxidative stress in type 2 diabetic mice.

Effects of Zishentongluo in Patients with Early-Stage Diabetic Nephropathy

The purpose of this study was to assess the efficacy of zishentongluo (ZSTL) for the treatment of diabetic nephropathy (DN) and its related mechanisms. Forty-five patients with DN were randomized to receive either ZSTL (n = 25) or benazepril (n = 20), an angiotensin converting enzyme inhibitor, for 12 weeks. Conventional biochemical tests were performed to determine fasting blood glucose (FBG), glycated hemoglobin (HbA1c), serum creatinine (SCr), endogenous creatinine clearance rate (Ccr), total cholesterol (TC), and triglyceride (TG) levels. The urinary albumin excretion rate (UAER), and endothelin 1 (ET-1), and atrial natriuretic peptide (ANP) levels were determined with a radioimmunoassay, and vascular endothelial growth factor (VEGF) was detected using an enzyme-linked immunosorbent assay. The primary endpoint was change from the baseline to post-treatment in HbA1c. Secondary endpoints were change from baseline to post-treatment in FBG, TC, TG, UAER, SCr, Ccr, VI-C, ANP, ET-1, and VEGF. ZSTL was significantly more effective at improving the primary (i.e., HbA1c) and secondary (i.e., FBG, TC, TG, UAER, SCr, ANP, ET-1, and VEGF) outcomes than benazepril (p < 0.05). These findings suggest that ZSTL is superior to benazepril at improving the metabolic and renal functioning in patients with early-stage DN, in part, by modifying ANP, ET-1, and VEGF.

VEGF and podocytes in diabetic nephropathy

Vascular endothelial growth factor-A (VEGF-A) is a protein secreted by podocytes that is necessary for survival of endothelial cells, podocytes, and mesangial cells. VEGF-A regulates slit-diaphragm signaling and podocyte shape via VEGF-receptor 2-nephrin-nck-actin interactions. Chronic hyperglycemia-induced excess podocyte VEGF-A and low endothelial nitric oxide drive the development and the progression of diabetic nephropathy. The abnormal cross-talk between VEGF-A and nitric oxide pathways is fueled by the diabetic milieu, resulting in increased oxidative stress. Recent findings on these pathogenic molecular mechanisms provide new potential targets for therapy for diabetic renal disease.

VEGF and angiopoietins in diabetic glomerulopathy: how far for a new treatment?

Diabetic nephropathy (DN) is the major cause of end-stage renal disease in Western countries and its prevalence continues to increase (United States Renal Data System 2010, http://www.usrds.org/). Treatments currently utilised for DN provide only partial renoprotection, hence the need to identify new targets for therapeutic intervention. Metabolic and haemodynamic abnormalities have been implicated in the pathogenesis of DN, triggering the activation of intracellular signaling molecules that lead to the dysregulation of vascular growth factors and cytokines, such as vascular endothelial growth factor (VEGF) and angiopoietins, important players in the functional and structural regulation of the glomerular filtration barrier. This review focuses on the importance of VEGF-A and angiopoietins in kidney physiology and in the diabetic kidney, exploring their potential therapeutic role in the prevention and delay of diabetic glomerulopathy.

Increased inner ear susceptibility to noise injury in mice with streptozotocin-induced diabetes

We aimed to investigate the pathophysiology of diabetes-associated hearing impairment in type 1 diabetes using mice with streptozotocin-induced diabetes (C57BL/6J; male). Hearing function was evaluated 1, 3, and 5 months after induction of diabetes (five diabetic and five control animals per time point) using auditory-evoked brain stem responses (ABRs). Mice (four diabetic and four control) were exposed to loud noise (105 dB) 5 months after induction of diabetes. ABRs were measured before and after noise exposure. Cochlear blood flows were measured by laser-Doppler flowmeter. Spiral ganglion cells (SGCs) were counted. Vessel endothelial cells were observed by CD31 immunostaining. Chronologic changes in the ABR threshold shift were not significantly different between the diabetic and control groups. However, vessel walls in the modiolus of the cochleae were significantly thicker in the diabetic group than the control group. Additionally, recovery from noise-induced injury was significantly impaired in diabetic mice. Reduced cochlea blood flows and SGC loss were observed in diabetic mice cochleae after noise exposure. Our data suggest that diabetic cochleae are more susceptible than controls to loud noise exposure, and decreased cochlear blood flow due to sclerosis of the vessels and consequent loss of SGCs are possible mechanisms of hearing impairment in diabetic patients.