Glomerular Capillary Loss Research Articles

Protective Role of Kallistatin in Vascular and Organ Injury.

Kallistatin is an endogenous protein that exerts pleiotropic effects, including vasodilation and inhibition of angiogenesis, inflammation, oxidative stress, apoptosis, fibrosis, and tumor progression. Through its 2 functional domains—an active site and a heparin-binding site—kallistatin regulates differential signaling pathways and a wide spectrum of biological functions. Kallistatin’s active site is key for inhibiting tissue kallikrein activity and stimulating the expression of endothelial nitric oxide (NO) synthase (eNOS), sirtuin 1 (SIRT1), and suppressor of cytokine signaling 3 (SOCS3). Kallistatin via its heparin-binding site blocks signaling pathways mediated by growth factors and cytokines, such as vascular endothelial growth factor (VEGF), tumor necrosis factor-α (TNF-α), high-mobility group box-1 (HMGB1), Wnt, transforming growth factor-β (TGF-β), and epidermal growth factor. Kallistatin gene or protein delivery protects against the pathogenesis of hypertension, heart and kidney damage, arthritis, sepsis, influenza virus infection, tumor growth, and metastasis in animal models. Conversely, depletion of endogenous kallistatin by neutralizing antibody injection exacerbates cardiovascular and renal injury in hypertensive rats. Kallistatin levels are markedly reduced in rodents with hypertension, sepsis, streptozotocin-induced diabetes mellitus, and cardiac and renal injury. Kallistatin levels are also diminished in patients with liver disease, septic syndrome, diabetic retinopathy, severe pneumonia, inflammatory bowel disease, obesity, and prostate, and colon cancer. Therefore, circulating kallistatin levels may serve as a new biomarker for human diseases. This review summarizes kallistatin’s protective roles and mechanisms in vascular and organ injury and highlights the therapeutic potential of kallistatin for multiple disease states. Kallistatin was discovered in human plasma as a tissue kallikrein–binding protein.1 Sequence analysis indicated that tissue kallikrein–binding protein is a novel serine proteinase inhibitor (serpin) and was later designated kallistatin because of its ability to inhibit tissue kallikrein activity.2–9 Tissue kallikrein is a serine proteinase that cleaves low–molecular weight kininogen substrate to release vasoactive kinin peptides.10 The …

Glomerular endothelial cell injury and focal segmental glomerulosclerosis lesion in idiopathic membranous nephropathy.

BackgroundFocal segmental glomerulosclerosis (FSGS) lesions have often been discussed as a negative predictor in idopathic membranous nephropathy (MN). The mechanism of the development of FSGS lesion in MN is still uncertain.MethodsFrom 250 cases of MN, 26 cases contained FSGS lesion. We compared the clinicopathological characteristics between MN cases with FSGS lesion [MN-FSGS(+)] and MN without FSGS lesion [MN-FSGS(−)], matched for gender, age, stage of MN.ResultsThe glomerular filtration rate (eGFR) was significantly lower in MN-FSGS(+) cases compared to MN-FSGS(−), although nephrotic syndrome, hematuria, and systolic blood pressure levels were not significantly different between the two groups. Pathologically, glomeruli in MN-FSGS(+) cases showed narrowing and loss of glomerular capillaries with separating from GBM or disappearance of CD34+ endothelial cells, and accumulation of extracellular matrix (ECM) in capillary walls, indicating the development of glomerular capillary injury. These findings of endothelial injury were seen even in MN-FSGS(−) cases, but they were more prominent in MN-FSGS(+) than MN-FSGS(−) by computer assessed morphometric analysis. In MN-FSGS(+) cases, 44 out of 534 glomeruli (8.2%) contained FSGS lesions (n = 31, NOS lesion; n = 13, perihilar lesion). Significant thickness of GBM with ECM accumulation was evident in MN-FSGS(+) cases. Podocyte injury with effacement of foot processes was also noted, but the expression of VEGF on podocytes was not different between the two groups, which suggests that the significant thickness of capillary walls may influence the function of VEGF from podocyte resulting in the glomerular capillary injury that contribute to the development of FSGS lesion in MN.ConclusionGlomerular capillary injury was seen in all MN cases. Furthermore, the prominent injuries of glomerular capillaries may be associated with the deterioration of eGFR and the formation of FSGS lesions in MN.

Kallistatin attenuates endothelial apoptosis through inhibition of oxidative stress and activation of Akt-eNOS signaling

Kallistatin is a regulator of vascular homeostasis capable of controlling a wide spectrum of biological actions in the cardiovascular and renal systems. We previously reported that kallistatin inhibited intracellular reactive oxygen species formation in cultured cardiac and renal cells. The present study was aimed to investigate the role and mechanisms of kallistatin in protection against oxidative stress-induced vascular injury and endothelial cell apoptosis. We found that kallistatin gene delivery significantly attenuated aortic superoxide formation and glomerular capillary loss in hypertensive DOCA-salt rats. In cultured endothelial cells, kallistatin suppressed TNF-α-induced cellular apoptosis, and the effect was blocked by the pharmacological inhibition of phosphatidylinositol 3-kinase and nitric oxide synthase (NOS) and by the knockdown of endothelial NOS (eNOS) expression. The transduction of endothelial cells with adenovirus expressing dominant-negative Akt abolished the protective effect of kallistatin on endothelial apoptosis and caspase activity. In addition, kallistatin inhibited TNF-α-induced reactive oxygen species formation and NADPH oxidase activity, and these effects were attenuated by phosphatidylinositol 3-kinase and NOS inhibition. Kallistatin also prevented the induction of Bim protein and mRNA expression by oxidative stress. Moreover, the downregulation of forkhead box O 1 (FOXO1) and Bim expression suppressed TNF-α-mediated endothelial cell death. Furthermore, the antiapoptotic actions of kallistatin were accompanied by Akt-mediated FOXO1 and eNOS phosphorylation, as well as increased NOS activity. These findings indicate a novel role of kallistatin in the protection against vascular injury and oxidative stress-induced endothelial apoptosis via the activation of Akt-dependent eNOS signaling.

Involvement of asymmetric dimethylarginine (ADMA) in glomerular capillary loss and sclerosis in a rat model of chronic kidney disease (CKD)

Aims Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, has been reported to be a novel marker for the progression of chronic kidney disease (CKD). We have recently found that accumulation of ADMA could trigger peritubular capillary loss, thus contributing to tubulointerstitial ischemia and fibrosis in a rat model of CKD. However, effects of ADMA on glomerular capillary loss and sclerosis remain to be elucidated. Main methods In this study, we investigated whether lowering of ADMA by overexpression of dimethylarginine dimethylaminohydrolase (DDAH), a main enzyme that degrades ADMA, could ameliorate glomerular capillary loss and sclerosis in a rat model of CKD. Four weeks after 5/6 subtotal nephrectomy (Nx), animals were given tail vein injections with recombinant adenovirus vector encoding DDAH-I (Adv-DDAH) or control vector expressing bacterial β-galactosidase (Adv-LZ), or orally administered with 20 mg/kg/day of hydralazine (Hyz) which served as a blood pressure control model. Key findings Plasma levels of ADMA were associated with decreased number of glomerular capillaries as well as severity of glomerular sclerosis in Nx-rats. These glomerular changes progressed in Adv-LZ- or Hyz-treated Nx-rats, while they were ameliorated by the treatment with DDAH overexpression. Significance Our present data suggest that ADMA may be involved in glomerular capillary loss and sclerosis, thus contributing to the progression of CKD. Substitution of DDAH protein or enhancement of its activity may become a novel therapeutic strategy for the treatment of CKD.

Endothelial injury due to eNOS deficiency accelerates the progression of chronic renal disease in the mouse

The vascular endothelium expresses endothelial nitric oxide synthase (eNOS) that generates nitric oxide (NO) to help maintain vascular integrity due to its anti-inflammatory, antiproliferative, and antithrombogenic effects. Pharmacological blockade of NO production has been shown to exacerbate renal injury in chronic renal disease and induces endothelial cell loss. However, pharmacological inhibition of NO nonspecifically blocks other types of NOS and therefore does not define the specific role of eNOS in kidney disease. We hypothesized that a lack of endothelial eNOS can induce a loss of glomerular and peritubular capillary endothelium and exacerbate renal injury in progressive renal disease. We tested out this hypothesis using remnant kidney (RK) in eNOS knockout (eNOS KO) mice. Systolic blood pressure was significantly higher, and renal function was worse in RK-eNOS KO mice compared with those in RK-C57BL6 mice. eNOS deficiency resulted in more severe glomerulosclerosis, mesangiolysis, and tubular damage. Glomerular and tubular macrophage infiltration and collagen deposition were also greater in RK-eNOS KO mice. Renal injuries in the RK-eNOS KO mice were accompanied by a greater loss of endothelial cells that was shown to be due to both a decrease in endothelial cell proliferation and an increase in apoptosis. A lack of eNOS accelerates both glomerular and tubulointerstitial injury with a loss of glomerular capillaries and peritubular capillaries. Impaired endothelial function is likely a direct risk factor for renal disease.

Angiopoietin correlates with glomerular capillary loss in anti-glomerular basement membrane glomerulonephritis

Emerging evidence suggests that endothelial turnover occurs in several glomerular diseases and correlates with resolution or progression of glomerular lesions. We hypothesized that the growth factors modulating embryonic kidney endothelial cell survival and capillary morphogenesis may be implicated in capillary loss that occurs in immune-mediated glomerulonephritis (GN). GN was induced in C57BL/6 mice by intravenous administration of sheep anti-mouse glomerular basement membrane (GBM) globulin and assessed with markers of vascularity in glomerular lesions, correlating these with expression of specific vascular growth factors. As assessed by periodic acid Schiff staining, 14 +/- 4% (mean +/- SD) glomeruli were affected by sclerosis at 14 days after globulin administration, and 33 +/- 5% were affected at 21 days. By 21 days, a significant increase of plasma creatinine and urinary protein occurred. P-selectin expression was increased in glomerular capillaries 14 days after disease induction, and capillary loss, as assessed by immunohistochemistry for platelet-endothelial cell adhesion molecule, vascular endothelial growth factor (VEGF) receptor 2 and the angiopoietin (Ang) receptor Tie-2, was recorded at 14 and 21 days in glomeruli affected by proliferative crescents and/or sclerosis. VEGF-A immunostaining, evident in control glomeruli, was qualitatively diminished in glomeruli with lesions. Ang-1 immunostaining was detected in control glomeruli and was diminished at 14 days after administration of anti-mouse GBM globulin; instead, Ang-1 was immunolocalized to distal tubules. In contrast, Ang-2 immunostaining was barely detectable in control glomeruli but was prominent in disease glomeruli. In GN mice, rare apoptotic glomerular endothelia were detected by electron microscopy and in situ end-labeling, but such cells were not seen in controls. Loss of glomerular capillaries during the course of anti-GBM GN in mice was temporally associated with decreases in endothelial survival molecules VEGF-A and Ang-1, and with up-regulation of Ang-2, an antagonist of Ang-1. A changing balance of these growth factors may contribute to decreased glomerular vascularity in crescentic GN.