It is well known that glomerulonephritis can occur after streptococcal infection, which is classically referred to as acute poststreptococcal glomerulonephritis (APSGN). The pathogenic mechanism of APSGN has been described by so-called immune complex theory, which involves glomerular deposition of nephritogenic streptococcal antigen and subsequent formation of immune complexes in situ and/or the deposition of circulating antigen-antibody complexes. However, the exact entity of the causative antigen has remained a matter of debate. We isolated a nephritogenic antigen for APSGN from the cytoplasmic fractions of group A streptococcus (GAS) depending on the affinity for IgG of APSGN patients. The amino acid and the nucleotide sequences of the isolated protein revealed to be highly identical to those of reported plasmin(ogen) receptor of GAS. Thus, we termed this antigen nephritis-associated plasmin receptor (NAPlr). Immunofluorescence staining of the renal biopsy tissues with anti-NAPlr antibody revealed glomerular NAPlr deposition in essentially all patients with early-phase APSGN. Furthermore, glomerular plasmin activity was detected by in situ zymography in the distribution almost identical to NAPlr deposition in renal biopsy tissues of APSGN patients. These data suggest that NAPlr has a direct, nonimmunologic function as a plasmin receptor and may contribute to the pathogenesis of APSGN by maintaining plasmin activity.
Patients with chronic renal failure often have hypertension, but the cause of hypertension, other than an excess of body fluid, is not well known. We hypothesized that the bulbospinal neurons in the rostral ventrolateral medulla (RVLM) are stimulated by uremic toxins in patients with chronic renal failure. To investigate whether RVLM neurons are sensitive to uremic toxins, such as uric acid, indoxyl sulfate, or methylguanidine, we examined changes in the membrane potentials (MPs) of bulbospinal RVLM neurons of Wister rats using the whole-cell patch-clamp technique during superfusion with these toxins. A brainstem-spinal cord preparation that preserved the sympathetic nervous system was used for the experiments. During uric acid, indoxyl sulfate, or methylguanidine superfusion, almost all the RVLM neurons were depolarized. To examine the transporters for these toxins on RVLM neurons, histological examinations were performed. The uric acid-, indoxyl sulfate-, and methylguanidine-depolarized RVLM neurons showed the presence of urate transporter 1 (URAT 1), organic anion transporter (OAT)1 or OAT3, and organic cation transporter (OCT)3, respectively. Furthermore, the toxin-induced activities of the RVLM neurons were suppressed by the addition of an anti-oxidation drug (VAS2870, an NAD(P)H oxidase inhibitor), and a histological examination revealed the presence of NAD(P)H oxidase (nox)2 and nox4 in these RVLM neurons. The present results show that uric acid, indoxyl sulfate, and methylguanidine directly stimulate bulbospinal RVLM neurons via specific transporters on these neurons and by producing oxidative stress. These uremic toxins may cause hypertension by activating RVLM neurons.
Although the effects of dipeptidyl peptidase 4 (DPP-4) inhibitors beyond their hypoglycemic action have been reported, whether these inhibitors have renoprotective effects in nondiabetic chronic kidney disease (CKD) is unclear. We examined the therapeutic effects of DPP-4 inhibition in mice with unilateral ureteral obstruction (UUO), a nondiabetic model of progressive renal fibrosis. After UUO surgery, mice were administered either the DPP-4 inhibitor alogliptin or a vehicle by oral gavage once a day for 10 days. Physiological parameters, degrees of renal fibrosis and inflammation, and molecules related to renal fibrosis and inflammation were then evaluated using sham-operated mice as controls. Positive area of α-smooth muscle actin was significantly smaller and expression of transforming growth factor β messenger RNA was significantly lower in the alogliptin-treated group than in the vehicle-treated group. Renal total collagen content was also significantly lower in the alogliptin-treated group than in the vehicle-treated group. These results suggest that alogliptin exerted renoprotective antifibrotic effects. The positive area of F4/80 was significantly smaller and expression of CD68 messenger RNA was significantly lower in the alogliptin-treated group than in the vehicle-treated group, suggesting an anti-inflammatory action by the DPP-4 inhibitor. Compared to the results for the vehicle-treated group, expression of markers for M1 macrophages tended to be lower in the alogliptin-treated group, and the relative expression of M2 macrophages tended to be higher. These data indicate the various protective effects of DPP-4 inhibition in nondiabetic mice with UUO. DPP-4 inhibitors may therefore be promising therapeutic choices even for nondiabetic CKD patients.
The protective effects of Rho kinase inhibitor fasudil against renal diseases have recently been reported. We compared the therapeutic effects of fasudil on the spontaneously hypercholesterolemic (SHC) rat, a model of chronic kidney disease (CKD) with proteinuria, with those of the angiotensin receptor blocker olmesartan (OL) by paying attention to the proteinuria and the macrophage phenotype. SHC rats were allocated to six treatment groups: a vehicle (Ve) group, a low-dose fasudil (FL) group, a high-dose fasudil (FH) group, an OL group, a combination of low-dose fasudil and OL (CL) group, and a combination of high-dose fasudil and OL (CH) group. Sprague-Dawley rats treated with vehicle served as a control (n = 7/each). The rats were treated for 24 wk. Compared with the Ve group, proteinuria was significantly decreased in the FH, OL, and CL groups, and it completely disappeared in the CH group. Glomerular stainings of nephrin and F-actin were focally impaired in the Ve group but were restored in the CH group. Western blotting showed that the CH group had significantly increased renal nephrin expression compared with the Ve group. Interstitial infiltration of macrophages was significantly increased in the Ve group, which was significantly attenuated in all treatment groups. The ratio of CD206 (M2 macrophage marker) to CD68 mRNA was significantly greater in the CH group than in the Ve group. These results indicate that fasudil with OL reduces proteinuria by protecting podocyte integrity and alters the interstitial macrophage density/phenotype, thereby exerting renoprotective effects against CKD.
BackgroundThe therapeutic effect of tonsillectomy for immunoglobulin A nephropathy (IgAN) has been widely recognized, but the mechanism by which tonsillar immunity leads to glomerulonephritis has been unclear. We investigated subtypes and localization of dendritic cells (DCs) in tonsils and looked for relationships between the tonsillar DCs and the clinical features and renal histological changes of patients with IgAN.MethodsWe examined tonsils from 33 IgAN patients, using as control tonsillar specimens from subjects without glomerulonephritis. Five distinct markers of DCs (CD303, CD1c, CD209, CD208 and CD1a) were analyzed by immunohistochemistry and flow cytometry. The mRNA levels of these DC markers were evaluated using real-time polymerase chain reaction. The clinical data and histological results obtained evaluating renal biopsy tissues were statistically compared with immunological data.ResultsOf the five subtypes of DCs, CD208+ DCs were significantly increased in the tonsils of IgAN patients compared with that of controls. Furthermore, the number of CD208+ DCs in the tonsils was positively and linearly correlated with the proportion of crescentic glomeruli in renal biopsy tissues and with the urinary protein level. Only few CD208+ cells, however, were found in the kidney biopsy specimens of IgAN patients.ConclusionsThese observations suggest that increased CD208+ DCs in tonsils may play a directive role in the pathogenesis of IgAN. The present results support the therapeutic significance of tonsillectomy for IgAN patients.
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