Enhanced glomerular expression of caldesmon in IgA nephropathy and its suppression by glucocorticoid-heparin therapy

The Crosstalk between Nephropathy and Coagulation Disorder: Pathogenesis, Treatment, and Dilemmas

ABSTRACT

The interaction between the kidney and the coagulation system greatly affects each other because of the abundant vessel distribution and blood perfusion in the kidney. Clinically, the risks of complicated thrombosis and bleeding have become important concerns in the treatment of nephropathies, especially nephrotic syndrome, CKD, ESKD, and patients with nephropathy undergoing RRTs. Adverse effects of anticoagulant or procoagulant therapies in patients with nephropathy, especially anticoagulation-related nephropathy, heparin-induced thrombocytopenia, and bleeding, seriously worsen the prognosis of patients, which have become challenges for clinicians. Over the decades, the interaction between the kidney and the coagulation system has been widely studied. However, the effects of the kidney on the coagulation system have not been systematically investigated. Although some coagulation-related proteins and signaling pathways have been shown to improve coagulation abnormalities while avoiding additional kidney damage in certain kidney diseases, their potential as anticoagulation targets in nephropathy requires further investigation. Here, we review the progression of research on the crosstalk between the coagulation system and kidney diseases and systematically analyze the significance and shortcomings of previous studies to provide new sight into future research. In addition, we highlight the status of clinical treatment for coagulation disorder and nephropathy caused by each other, indicating guidance for the formulation of therapeutic strategies or drug development.

Development of immunoglobulin A nephropathy- like disease in beta-1,4-galactosyltransferase-I-deficient mice

Beta4 galactosylation of glycoproteins plays important roles in protein conformation, stability, transport, and clearance from the circulation. Recent studies have revealed that aberrant glycosylation causes various human diseases. Here we report that mice lacking beta-1,4-galactosyltransferase (beta4GalT)-I, which transfers galactose to the terminal N-acetylglucosamine of N- and O-linked glycans in a beta-1,4 linkage, spontaneously developed human immunoglobulin A nephropathy (IgAN)-like glomerular lesions with IgA deposition and expanded mesangial matrix. beta4GalT-I-deficient mice also showed high serum IgA levels with increased polymeric forms as in human IgAN. IgAN is the most common form of glomerulonephritis, and a significant proportion of patients progress to renal failure. However, pathological molecular mechanisms of IgAN are poorly understood. In humans, abnormal character of serum IgA, especially serum IgA1 with aberrant galactosylation and sialylation of O-glycans in its hinge region is thought to contribute to the pathogenesis of IgAN. Mouse IgA has N-glycans but not O-glycans, and beta4-galactosylation and sialylation of the N-glycans on the serum IgA from beta4GalT-I-deficient mice was completely absent. This is the first report demonstrating that genetic remodeling of protein glycosylation causes IgAN. We propose that carbohydrates of serum IgA are involved in the development of IgAN, whether the carbohydrates are O-glycans or N-glycans.

Blockade of VEGF accelerates proteinuria, via decrease in nephrin expression in rat crescentic glomerulonephritis

Vascular endothelial growth factor (VEGF) is a potent angiogenic factor that maintains the glomerular and peritubular capillary (PTC) network in the kidney. The soluble form of the VEGF receptor-1 (soluble fms-like tyrosine kinase 1 (sFlt-1)) is known to regulate VEGF activity by binding VEGF in the circulation. We hypothesized that VEGF may be beneficial for maintaining glomerular filtration barrier and vascular network in rats with progressive glomerulonephritis (GN). For blockade of VEGF activity in vivo, rats were transfected twice with plasmid DNA encoding the murine sFlt-1 gene into femoral muscle 3 days before and 2 weeks after the induction of antiglomerular basement membrane antibody-induced GN. Inhibition of VEGF with sFlt-1 resulted in massive urinary protein excretion, concomitantly with downregulated expression of nephrin in nephritic rats. Further, blockade of VEGF induced mild proteinuria in normal rats. Administration of sFlt-1 affected neither the infiltration of macrophages nor crescentic formation. In contrast, treatment of sFlt-1 accelerated the progression of glomerulosclerosis and interstitial fibrosis accompanied with renal dysfunction and PTC loss at day 56. VEGF may play a role in maintaining the podocyte function as well as renal vasculature, thereby protecting glomeruli and interstitium from progressive renal insults.

Therapeutic effect of all-trans retinoic acid on rats with anti-GBM antibody glomerulonephritis

BACKGROUND

All-trans retinoic acid (ATRA) has antiproliferative and anti-inflammatory effects and is currently used in the treatment of leukemia and dermatologic diseases. We tested the therapeutic potential of ATRA on anti-glomerular basement membrane (GBM) glomerulonephritis rats.

METHODS

Glomerulonephritis was induced in male Wistar-Kyoto rats on day 0 by an intravenous injection of antirat GBM antibody. On day 14 after the induction of anti-GBM glomerulonephritis, some rats were sacrificed (N = 5). Another 10 rats were divided into two groups: the vehicle group (N = 5) and the ATRA treated group (N = 5). ATRA was orally administrated from day 14 to day 27 after disease induction. Blood pressure, body weight, urinary protein excretion, and blood chemistry was determined on days 1, 14, 21, and 27. Kidney samples were obtained on day 28. The kidneys were examined with periodic acid-Schiff staining (PAS) and immunohistochemistry using antibodies against the proliferative cell nuclear antigen (PCNA), rat monocyte and macrophage (ED-1), and alpha-smooth muscle actin (alpha-SMA). Glomerular RNA was extracted from isolated glomeruli, and reverse transcription (RT) followed by polymerase chain reaction (PCR) was performed.

RESULTS

ATRA administration produced a 55% reduction of proteinuria in glomerulonephritis rats. Light microscopic analysis revealed severe necrosis/crescent formation (>50% of the glomerulus) affecting 34% of glomeruli in vehicle rats, whereas ATRA treatment reduced the glomeruli showing severe change to 14%. ATRA also significantly reduced PCNA-positive cells, ED-1-positive cells and alpha-SMA-positive area in the glomeruli. RT-PCR analyses revealed that a wide variety of genes including inflammation related [tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and CCAAT enhancer-binding protein delta (C/EBPdelta)], cell proliferation-related [platelet-derived growth factor (PDGF)] and fibrosis-related [transforming growth factor-beta1 (TGF-beta1), type I collagen, and alpha-SMA) genes were suppressed in the glomeruli of ATRA-treated rats.

CONCLUSION

ATRA administration significantly reduced severe necrosis/crescent formation and urinary protein excretion in glomerulonephritis rats. Suppression of a wide variety of gene expression may partly explain the mechanism of ATRA's antiproliferative and anti-inflammatory effects. These data suggest a novel therapeutic application of ATRA toward glomerulonephritis.

A clinicopathological study of IgA nephropathy in renal transplant recipients: beneficial effect of angiotensin-converting enzyme inhibitor

BACKGROUND

Prolonging the survival of transplant kidneys is a major task of modern nephrology. It has recently been shown that deteriorating renal function and substantial graft loss were observed in 55% of renal allograft recipients with recurrent IgA nephropathy (IgAN) at long-term follow-up. To gain a useful insight into the therapeutic approach towards protecting allograft kidneys from deteriorating graft function, we compared the histological characteristics of post-transplant IgAN to primary IgAN and investigated the effects of an ACE inhibitor.

METHODS

Twenty-one patients with post-transplant IgAN and 63 patients with primary IgAN were included in the histopathological study. The effectiveness of angiotensin-converting enzyme (ACE) inhibitor treatment in post-transplant IgAN was also studied in 10 patients.

RESULTS

The prevalence of glomeruli with adhesions and/or cellular crescents in primary IgAN was significantly greater than in post-transplant IgAN (P<0.05), but the proportion of glomeruli with segmental sclerosis was similar in both groups. The rate of global obsolescence, and the degree of interstitial fibrosis in post-transplant IgAN were significantly greater than in primary IgAN (P<0.05). The degree of glomerular obsolescence and the severity of interstitial fibrosis correlated with the severity of glomerular lesion in primary IgAN, but not in post-transplant IgAN. In primary IgAN, glomerular diameter significantly correlated with the proportions of glomerular obsolescence, but not in post-transplant IgAN, suggesting that allograft kidneys may be in a hyperfiltration state. Both the blood pressure and the urinary protein excretion significantly improved after ACE-inhibitor treatment (P<0.001).

CONCLUSION

In post-transplant IgAN, histopathological lesions indicative of acute inflammatory insults were suppressed, and glomerular hypertrophy, which may relate to haemodynamic burden such as hyperfiltration, was prominent. Preliminary study of ACE-inhibitor treatment in 10 patients showed favourable effects. A future long-term follow-up study is required to establish the effectiveness of ACE inhibitors in treatment of post-transplant IgAN.

Early treatment with corticosteroids ameliorates proteinuria, proliferative lesions, and mesangial phenotypic modulation in adult diffuse proliferative IgA nephropathy

Diffuse proliferative immunoglobulin A (IgA) nephropathy has the potential risk for end-stage renal disease. However, treatment of IgA nephropathy has not been well established. To determine whether early treatment with corticosteroids ameliorates the proliferative lesions of diffuse proliferative IgA nephropathy, we conducted a prospective, randomized, controlled trial. Inclusion criteria were as follows: duration of abnormal urinalysis results less than 36 months, proteinuria less than 1.5 g/d of protein, serum creatinine level less than 1.5 mg/dL, and mesangial cell proliferation or matrix accumulation involving more than 50% of glomeruli. Twenty-one patients were randomly assigned to two groups: the corticosteroid group and the antiplatelet group. After 1 year of treatment, repeated renal biopsy was performed in 19 patients. We evaluated glomerular filtration rate, blood pressure, proteinuria, and histological parameters, including light microscopic findings and staining of alpha-smooth muscle actin (alphaSMA), as a marker of myofibroblast-like cells and fibronectin EDA (EDA-FN) as an indicator of renal fibrosis. After 1 year of treatment, proteinuria significantly decreased in the corticosteroid group. Histological findings, such as mesangial cell proliferation, mesangial matrix accumulation, and cellular crescents, showed significant improvement in the corticosteroid group but not in the antiplatelet group. Expression of alphaSMA in glomeruli significantly decreased in the corticosteroid group but not in the antiplatelet group. EDA-FN did not change in either group. We conclude that early treatment with corticosteroids for adult diffuse proliferative IgA nephropathy is effective in reducing renal injury.

Role of intron 1 in smooth muscle alpha-actin transcriptional regulation in activated mesangial cells in vivo

BACKGROUND

The activation of glomerular mesangial cells is one of the early, important features of progressive glomerular disease. Smooth muscle alpha-actin (SMalphaA) is an excellent marker of activated mesangial cells. However, the mechanisms of SMalphaA regulation are only available from in vitro investigation.

METHODS

We examined in vivo promoter analysis of the SMalphaA gene-utilizing transgenic mice harboring different promoter regions of the SMalphaA gene fused to chloramphenicol acetyl transferase (CAT). CAT activities were tested in primary cultured mesangial cells and in glomerular legions of Habu venom glomerulonephritis.

RESULTS

The DNA sequence -891 to +3828, which contains exon 1, intron 1, and the first 14 bp of exon 2 in addition to the 5'-flanking sequence of the SMalphaA gene, induced high levels of transcription in activated mesangial cells in in vivo habu venom glomerulonephritis and in cultured mesangial cells derived from transgenic mice. The DNA region -891 to -124 was a positive element in mesangial cells derived from transgenic mice. Deletions (3316 or 137 bp) in intron 1 reduced transcription to undetectable levels. The 137 bp sequence is highly conserved among several species, containing one CArG box element, which is one of the key motifs for transcriptional activation of contractile-related proteins. In vitro transfection analysis failed to demonstrate these positive effects of intron 1 and region -891 to -124. Conclusions. In vivo promoter analysis of the SMalphaA gene provided new information about the transcriptional regulation of SMalphaA in activated mesangial cells. The DNA region -891 to -124 has a positive effect on SMalphaA transcription in cultured mesangial cells. The intron 1 region (+1088 to +1224) plays a pivotal role in SMalphaA transcription in activated mesangial cells in vivo. Further analysis of this conserved region in intron 1, including the CArG motif, will be of great value in understanding the molecular mechanisms of mesangial activation.

High water intake ameliorates tubulointerstitial injury in rats with subtotal nephrectomy: possible role of TGF-beta

BACKGROUND

It has been shown that tubulointerstitial injury correlates well with a decline of renal function. In this study, we investigated the effect of high water intake (HWI) on functional and structural parameters in rats with subtotal nephrectomy.

METHODS

Two weeks after the ablative procedure, rats were divided into two groups. One group received the treatment with HWI (3% sucrose added to drinking water) for eight weeks. Functional parameters were compared with sham-operated control (CONT) or nephrectomized rats without treatment (NX). Remnant kidneys were then assessed histologically for evidence of interstitial fibrosis and glomerulosclerosis.

RESULTS

Creatinine clearance was significantly improved in HWI rats compared with NX rats. Simultaneously, urinary protein was also significantly reduced in HWI rats. HWI predominantly ameliorated interstitial lesions and, to a lesser extent, glomerular lesions. Northern blot analysis demonstrated that transforming growth factor-beta (TGF-beta) mRNA expression was significantly suppressed in HWI rats. In situ hybridization revealed that HWI suppressed TGF-beta mRNA expression mainly in the outer medulla. Fibronectin mRNA was also reduced by the HWI treatment. The changes in TGF-beta and fibronectin mRNA were in parallel with Na+/myo-inositol cotransporter (SMIT) mRNA, which is regulated by extracellular osmolarity. Immunohistochemistry demonstrated that protein expression of TGF-beta and fibronectin coincided with the mRNA expression.

CONCLUSION

These results suggest that HWI reduces TGF-beta mRNA expression in medullary interstitium and ameliorates tubulointerstitial injury in rats with reduced renal mass.