Heminephrectomy causes the progression of glomerulosclerosis and apoptosis in high IgA strain ddY mice

Targeting C3a/C5a receptors inhibits human mesangial cell proliferation and alleviates immunoglobulin A nephropathy in mice

Complement activation has a deep pathogenic influence in immunoglobulin (Ig)A nephropathy (IgAN). C3a and C5a, small cleavage fragments generated by complement activation, are key mediators of inflammation. The fragments exert broad proinflammatory effects by binding to specific receptors (C3aR and C5aR, respectively). However, no studies thus far have investigated the effects of C3a, C5a and their receptors on IgAN. We observed that C3aR and C5aR antagonists repressed IgA-induced cell proliferation and interleukin (IL)-6 and monocyte chemotactic protein 1 (MCP-1) production in cultured human mesangial cells (HMCs). Furthermore, an IgAN mouse model induced by Sendai virus infection was employed to investigate the effects of C3aR and C5aR on IgAN in vivo for the first time. Wild-type (WT) and several knock-out mouse strains (C3aR^-/- or C5aR^-/- ) were immunized intranasally with increasing doses of inactivated virus for 14 weeks and were subjected to two intravenous viral challenges during the time-period indicated. In the Sendai virus-induced IgAN model, C3aR/C5aR-deficient mice had significantly reduced proteinuria, lower renal IgA and C3 deposition, less histological damage and reduced mesangial proliferation compared with WT mice. Both C3aR deficiency and C5aR deficiency, especially C3aR deficiency, inhibited renal tumour necrosis factor (TNF)-α, transforming growth factor (TGF)-β, IL-1β, IL-6 and MCP-1 expression significantly. However, C3aR/C5aR-deficient and WT mice with IgAN did not differ with respect to their blood urea nitrogen (BUN) and serum creatinine levels. Our findings provide further support for the idea that C3aR and C5aR are crucially important in IgAN, and suggest that pharmaceutically targeting C3aR/C5aR may hold promise for the treatment of IgAN.

(E)-N-[(3,4-dimethoxyphenethyl)]-N-methyl-3-(3-pyridyl)-2-propenamide (TJN-331) inhibits mesangial expansion in experimental IgA nephropathy in ddY mice

BACKGROUND

TJN-331 is an inhibitor of transforming growth factor β1 (TGF-β1) production that has similar structural features to the natural product acteoside. This study was performed to examine the antinephritic effects of TJN-331 in a mouse model of experimental IgA nephropathy.

MATERIALS AND METHODS

IgA nephropathy was induced in ddY mice by oral administration of bovine γ globulin, followed by reticuloendothelial blocking by colloidal carbon injection and heminephrectomy. Effects of TJN-331 were examined over oral administration periods from 10 to 15 weeks after the third colloidal carbon injection. Intravenous administration of a TGF-β1-neutralizing antibody was used to investigate the role of TGF-β1 in IgA nephropathy.

RESULTS

Administration of TJN-331 or captopril prevented elevation of serum creatinine. Histopathological examination after both experimental periods showed that TJN-331 inhibited increases in the mesangial matrix index and the number of nuclei per glomerular cross-section, compared with in untreated ddY mice with IgA nephropathy. TJN-331 prevented increase in glomerular TGF-β1 staining without affecting IgA. In the in vitro study, TJN-331 prevented total TGF-β1 production from splenocytes stimulated with concanavalin A. A neutralizing antibody against TGF-β1 prevented increase in the mesangial matrix index and the number of glomerular cells per cross-sectional area.

CONCLUSION

These results suggest that TJN-331 is effective against IgA nephropathy in ddY mice and acts via suppression of TGF-β1 production in glomeruli.

Protective role of γ-aminobutyric acid against chronic renal failure in rats

The protective effect of γ-aminobutyric acid (GABA) against chronic renal failure (CRF) was investigated using a remnant kidney model with 5/6 nephrectomized rats. Nephrectomy led to renal dysfunction, which was evaluated via several parameters including serum urea nitrogen, creatinine (Cr) and Cr clearance. However, the administration of GABA ameliorated renal dysfunction, and a longer administration period of GABA increased its protective effect. In addition, nephrectomized control rats showed an elevation in the fractional excretion of sodium (FENa) with an increase in urinary sodium, while GABA led to a significant decline in FENa. Moreover, nephrectomy resulted in a decrease of serum albumin and an increase of urinary protein with a change in the urinary protein pattern, whereas the rats administered GABA showed improvement in these changes associated with CRF caused by nephrectomy. This suggests that GABA would inhibit the disease progression and have a protective role against CRF. As one of the risk factors for CRF progression, hypertension was also regulated by GABA. The results also indicate that GABA may play a protective role against CRF through improvement of the serum lipid profile, with reductions in triglyceride and total cholesterol. Furthermore, nephrectomy led to renal oxidative stress with a decrease in the activity of antioxidative enzymes and elevation of lipid peroxidation. The administration of GABA attenuated oxidative stress induced by nephrectomy through an increase in superoxide dismutase and catalase, and decrease in lipid peroxidation. The histopathological lesions, including glomerular, tubular and interstitial lesions, under nephrectomy were also improved by GABA with the inhibition of fibronectin expression. This study demonstrated that GABA attenuated renal dysfunction via regulation of blood pressure and lipid profile, and it also ameliorated the oxidative stress induced by nephrectomy, suggesting the promising potential of GABA in protecting against renal failure progression.

TJN-259 improves mesangial lesions in experimental immunoglobulin A nephropathy in ddY mice

TJN-259 is a chemical substance based on the structural features of the botanically derived ingredient acteoside. This study was performed in order to elucidate the antinephritic effects of TJN-259 in experimental immunoglobulin A (IgA) nephropathy. In this study, 28-week-old ddY mice were used as a spontaneous model of IgA nephropathy. With regard to spontaneous IgA nephropathy, we investigated the effects of TJN-259 administered from 28 to 40 weeks. In addition, an accelerated model of IgA nephropathy was experimentally induced in ddY mice by oral administration of bovine serum albumin, followed by reticuloendothelial blocking by colloidal carbon injection and heminephrectomy. At 10 weeks after the 3rd carbon injection, we also examined the effects of TJN-259 on accelerated IgA nephropathy. To investigate the effects of TJN-259 on transforming growth factor (TGF)-beta1 production in accelerated IgA nephropathy, kidneys were isolated and measured TGF-beta1 by the enzyme-linked immunosorbent assay (ELISA) method. The administration of TJN-259 to mice with spontaneous IgA nephropathy decreased the incidence of mesangial expansion as well as the number of nuclei per glomerular cross-section in comparison with that of non-treated mice. In addition, TJN-259 treatment prevented the increase in the incidence of mesangial expansion, crescent formation, and segmental sclerosis in glomeruli in accelerated IgA nephropathy. TJN-259 also inhibited the increased immunostaining score of collagen type IV and TGF-beta1 in glomeruli of accelerated IgA nephropathy. Treatment with TJN-259 inhibited the increases in renal total and mature TGF-beta1 protein levels in accelerated type IgA nephropathy. TJN-259 failed to inhibit the increase in serum IgA levels in both models. These results suggest that TJN-259 was an effective treatment against IgA nephropathy in ddY mice, acting via the suppression of TGF-beta1 production in glomeruli.

Angiotensin II type 1 receptor blockade inhibits the development and progression of HIV-associated nephropathy in a mouse model

HIV-associated nephropathy (HIVAN) is characterized by a collapsed glomerular capillary tuft with hyperplasia and hypertrophy of podocytes. Recently generated were conditional transgenic mice (podocin/Vpr) that express one of the HIV-1 accessory genes, vpr, selectively in podocytes using podocin promoter and Tet-on system. These transgenic mice developed renal injury similar to HIVAN when treated with doxycycline for 8 to 12 wk. This study demonstrated that nephron reduction by heminephrectomy markedly enhanced phenotypic changes of podocytes and led to severe FSGS within 4 wk. Nephrotic-range proteinuria was observed already at 2 wk, together with dedifferentiation and dysregulation of podocytes, indicated by decreased expression of nephrin, synaptopodin, and Wilms' tumor 1 protein and increased expression of Ki-67. The acceleration of phenotypic changes of podocytes, proteinuria, and subsequent glomerulosclerosis by heminephrectomy was almost completely inhibited by angiotensin II type 1 receptor (AT1R) blocker olmesartan. In contrast, the renoprotective effect of the calcium channel antagonist azelnidipine was minimal, although it lowered systemic BP to the same level as olmesartan, demonstrating that the inhibitory effect of AT1R blocker was independent of systemic BP. Olmesartan also reduced proteinuria and prevented glomerulosclerosis even by the delayed treatment, which was initiated after the podocyte injury appeared. These data suggest that nephron reduction exaggerates podocyte injury and subsequent glomerulosclerosis, possibly through glomerular hypertension, in the mouse model of HIVAN. AT1R blockade could be beneficial in the treatment of HIVAN by ameliorating podocyte injury by avoiding the vicious cycle of nephron reduction and glomerular hypertension.

Renal effects of Coxsackie B4 virus in hyper-IgA mice

For clarification of the pathogenetic role of viral infection in chronic glomerulonephritis, the renal effects of Coxsackie B4 virus (CB4) were examined in hyper-IgA (HIGA) mice. In experiment 1, HIGA mice (n = 75) were inoculated intravenously with live CB4 and inactivated CB4 once a month from 1 to 12 mo of age. In experiment 2, HIGA mice (n = 45) were inoculated intravenously with live CB4 and inactivated CB4 once at 6 wk of age. In experiment 3, 60 mice were inoculated intravenously with carbon and live or inactivated CB4 once at 6 wk of age. Mice in the control group were inoculated with vehicle. The kidneys were extirpated from five mice of each group killed with time after inoculation for histologic evaluation. The scores for mesangial IgA deposition, PCNA-positive cells, and matrix at 20 wk were higher in mice with live CB4 than in mice with inactivated CB4 or without CB4. On electron microscopic examination, swelling and detachment of endothelial cells from 24 h after inoculation and increase of serum IFN-gamma concentration were found in mice with live CB4. Many carbon particles were present in peripheral and central zones of the mesangium from 5 to 10 d in mice with carbon and live CB4. These results suggest that CB4 provokes exacerbation of renal pathologic findings in HIGA mice via endothelial injury, IFN-gamma production, and dysfunction of the mesangial pathway.

Prorenin receptor blockade inhibits development of glomerulosclerosis in diabetic angiotensin II type 1a receptor-deficient mice

Blockade of the renin-angiotensin system slows the progression of diabetic nephropathy but fails to abolish the development of end-stage nephropathy of diabetes. The prorenin-to-active renin ratio significantly increases in diabetes, and prorenin binding to its receptor in diabetic animal kidney induces the nephropathy without its conventional proteolytic activation, suggesting that angiotensin II (AngII) may not be the decisive factor causing the nephropathy. For identification of an AngII-independent mechanism, diabetes was induced in wild-type mice and AngII type 1a receptor gene-deficient mice by streptozotocin treatment, and their development and progression of diabetic nephropathy were assessed. In addition, prolonged inhibition of angiotensin-converting enzyme and prolonged prorenin receptor blockade were compared for their efficacy in preventing the nephropathy that occurred in diabetic AngII type 1a receptor gene-deficient mice. Only the prorenin receptor blockade with a short peptide of prorenin practically abolished the increased mitogen-activated protein kinase (MAPK) activation and nephropathy despite unaltered increase in AngII in diabetic kidney. These results indicate that the MAPK activation signal leads to the diabetic nephropathy but not other renin-angiotensin system-activated mechanisms in the glomeruli. It is not only AngII but also intraglomerular activation of MAPK by the receptor-associated prorenin that plays a pivotal role in diabetic nephropathy.

Accelerated Glomerular Injury in Hemi-Nephrectomized Transgenic Mice of Mesangial Cell-Predominant Serpin, Megsin

Mesangial cells play a critical role in the maintenance of normal glomerular functions such as matrix remodeling and immune complex disposal. We recently identified a novel human mesangium-predominant gene, megsin, which is a new member of the serine protease inhibitor (serpin) superfamily. While our previous studies demonstrated progressive mesangial matrix expansion and an increase in the number of mesangial cells in megsin transgenic mice, it took 40 weeks to develop these manifestations. Here we performed hemi-nephrectomy to accelerate glomerular injury in megsin transgenic mice. Hemi-nephrectomized transgenic mice developed focal segmental mesangial expansion, which was associated with proteinuria. Megsin has thus a biologically relevant influence on the development of glomerular damage. The hemi-nephrectomized model of this transgenic mouse might serve as a tool to investigate the mechanisms of glomerular disease.

Frequent vaccination and immune complex deposition in unilateral nephrectomized mice

The aim of this study was to investigate the effect of increased number and frequency of vaccination on immune complex deposition in the choroid plexus and glomeruli of non-nephrectomized and unilateral nephrectomized mice. Fifty-five non-nephrectomized, 40 nephrectomized, and 7 control Swiss albino mice were used. Half of each group was vaccinated only with diphtheria-tetanus and the other half with multiple vaccines, which are used in pediatric practice. Each group was divided into subgroups, which were vaccinated with increasing frequency. No immune deposits were detected in the choroid plexus of any vaccinated mice. There were immune deposits in glomeruli in 2 of 55 (3.6%) of the non-nephrectomized and in 3 of 40 (7.5%) of the nephrectomized mice (P=0.199). The difference between the diphtheria-tetanus and multiple vaccine groups in non-nephrectomized (P=0.236) and nephrectomized (P=1.000) mice was not significant. A significant positive correlation between increased frequency of vaccination and glomerular immune complex deposition 8 weeks after the last immunization was detected in the multiple vaccine group of nephrectomized mice (P=0.048, r=0.447). Our results suggest that the large number and frequent doses of vaccines would not lead to immune complex deposition in choroid plexus and do not significantly increase the deposition of immune complexes in glomeruli in unilateral nephrectomized mice compared with non-nephrectomized mice.