Arginase 2 Promotes Cisplatin-Induced Acute Kidney Injury by the Inflammatory Response of Macrophages.

Acute kidney injury (AKI) is a complex clinical syndrome with a rapid decrease in renal function caused by several different etiologies, including sepsis, ischemia, and the administration of nephrotoxic drugs. Tubular arginase 2 (ARG2), an arginine-metabolic enzyme, is a potential therapeutic target for AKI, but it has not been confirmed under various AKI conditions. The aim of this study was to investigate ARG2 as a therapeutic target for cisplatin-induced AKI. Cisplatin-treated mice with a genetic deficiency in Arg2 had significant amelioration of renal dysfunction, characterized by decreased acute tubular damage and apoptosis. In contrast, cisplatin-induced tubular toxicity was not ameliorated in proximal tubule cells derived from Arg2-deficient mice. Immunohistochemical analysis demonstrated the increased infiltration of ARG2-positive macrophages in kidneys damaged by cisplatin. Importantly, cisplatin-treated Arg2 knockout mice exhibited a significant reduction in kidney inflammation, characterized by the decreased infiltration of inflammatory macrophages and reduced gene expression of interleukin (IL)-6 and IL-1ß. The secretion of IL-6 and IL-1ß induced by lipopolysaccharides was decreased in bone marrow-derived macrophages isolated from Arg2-deficient mice. Furthermore, the lipopolysaccharide-induced elevation of mitochondrial membrane potential and production of reactive oxygen species were reduced in bone marrow-derived macrophages lacking Arg2. These findings indicate that ARG2 promotes the inflammatory responses of macrophages through mitochondrial reactive oxygen species, resulting in the exacerbation of AKI. Therefore, targeting ARG2 in macrophages may constitute a promising therapeutic approach for AKI.

Acrolein produced during acute kidney injury promotes tubular cell death.

Acute kidney injury is an important global health concern as it is associated with high morbidity and mortality. Polyamines, essential for cell growth and proliferation, are known to inhibit cardiovascular disease. However, under conditions of cellular damage, toxic acrolein is produced from polyamines by the enzyme spermine oxidase (SMOX). We used a mouse renal ischemia-reperfusion model and human proximal tubule cells (HK-2) to investigate whether acrolein exacerbates acute kidney injury by renal tubular cell death. Acrolein visualized by acroleinRED was increased in ischemia-reperfusion kidneys, particularly in tubular cells. When HK-2 cells were cultured under 1% oxygen for 24 h, then switched to 21% oxygen for 24 h (hypoxia-reoxygenation), acrolein accumulated and SMOX mRNA and protein levels were increased. Acrolein induced cell death and fibrosis-related TGFB1 mRNA in HK-2 cells. Administration of the acrolein scavenger cysteamine suppressed the acrolein-induced upregulation of TGFB1 mRNA. Cysteamine also inhibited a decrease in the mitochondrial membrane potential observed by MitoTrackerCMXRos, and cell death induced by hypoxia-reoxygenation. The siRNA-mediated knockdown of SMOX also suppressed hypoxia-reoxygenation-induced acrolein accumulation and cell death. Our study suggests that acrolein exacerbates acute kidney injury by promoting tubular cell death during ischemia-reperfusion injury. Treatment to control the accumulation of acrolein might be an effective therapeutic option for renal ischemia-reperfusion injury.

Protective Roles of Xenotropic and Polytropic Retrovirus Receptor 1 (XPR1) in Uremic Vascular Calcification.

Cellular phosphate transporters play critical roles in the pathogenesis of vascular calcification (VC) in chronic kidney disease (CKD). However, the mechanistic link between VC and xenotropic and polytropic receptor 1 (XPR1), a newly identified phosphate exporter, remains unknown. We developed a new mouse model with rapidly progressive uremic VC in C57BL/6 mice and examined the roles of XPR1. The combination of surgical heminephrectomy and 8 weeks of feeding a customized warfarin and adenine-based diet induced extensive aortic VC in almost all mice. The XPR1 mRNA level in the aorta of CKD mice was significantly lower than those in control mice as early as week 2, when there was no apparent VC, which progressively declined thereafter. Dietary phosphate restriction increased XPR1 mRNA expression in the aorta but reduced aortic VC in CKD mice. In cultured vascular smooth muscle cells (VSMCs), a calcifying medium supplemented with high phosphate and calcium did not affect XPR1 mRNA expression. The XPR1 mRNA expression in cultured VCMCs was also unaffected by administration of indoxyl sulfate or calcitriol deficiency but was decreased by 1-34 parathyroid hormone or fibroblast growth factor 23 supplementation. Furthermore, XPR1 deletion in the cultured VSMCs exacerbated calcification of the extracellular matrix as well as the osteogenic phenotypic switch under the condition of calcifying medium. Our data suggest that XPR1 plays protective roles in the pathogenesis of VC and its decrease in the aorta may contribute to the progression of VC in CKD.

Glucose degradation products in peritoneal dialysis solution impair angiogenesis by dysregulating angiogenetic factors in endothelial and vascular smooth muscle cells.

BACKGROUND: The accumulation of glucose degradation products (GDPs) during peritoneal dialysis (PD) can lead to immature angiogenesis in the peritoneum. However, the effect of GDPs on angiogenesis, at concentrations observed in dialysate effluent, has not been widely investigated. We do not know how the inflammation observed in PD-related peritonitis affects angiogenesis of the peritoneum. METHODS: Human umbilical vessel endothelial cells (HUVEC) and human umbilical aortic smooth muscle cells (HUASMC) were used to examine the response to the three main GDPs found in peritoneal dialysate (methylglyoxal (MGO), 3-deoxyglucosone (3-DG), and 5-hydroxymethylfurfural (5-HMF). Supernatant from lipopolysaccharide (LPS)-activated murine macrophage cell lines (RAW 264.7 cells) were used to stimulate angiogenesis in the peritoneum. Changes in the expression of vascular endothelial growth factor-A (VEGF-A) and platelet-derived growth factor B (PDGFB) in HUVEC, and PDGF-receptor beta (PDGF-Rß) in HUASMC, were examined by real-time PCR, Western blot, and ELISA. RESULTS: In HUVECs, the expression of PDGFB mRNA and protein were decreased by exposure to MGO, 3-DG, and 5-HMF at concentrations observed in dialysate effluent. A subsequent decrease in secreted PDGF-BB was observed. In HUASMCs, MGO and 5-HMF increased the expression of VEGF-A mRNA and protein, while 5-HMF decreased the expression of PDGF-Rß. VEGF-A is upregulated, and PDGF-Rß is downregulated, by conditioned medium of LPS-stimulated macrophages in HUASMCs. CONCLUSIONS: The GDPs of PD effluent cause an imbalance of angiogenic factors in endothelial cells and vascular smooth muscle cells that may lead to immature angiogenesis in the peritoneum.

Autophagy gene ATG7 regulates albumin transcytosis in renal tubule epithelial cells.

Receptor-mediated albumin transport in proximal tubule epithelial cells (PTECs) is important to control proteinuria. Autophagy is an evolutionarily conserved degradation pathway, and its role in intracellular trafficking through interactions with the endocytic pathway has recently been highlighted. Here, we determined whether autophagy regulates albumin transcytosis in PTECs and suppresses albumin-induced cytotoxicity using human proximal tubule (HK-2) cells. The neonatal Fc receptor (FcRn), a receptor for albumin transcytosis, is partially colocalized with autophagosomes. Recycling of FcRn was attenuated, and FcRn accumulated in autophagy-related 7 (ATG7) knockdown HK-2 cells. Colocalization of FcRn with RAB7-positive late endosomes and RAB11-positive recycling endosomes was reduced in ATG7 knockdown cells, which decreased recycling of FcRn to the plasma membrane. In ATG7 or autophagy-related 5 (ATG5) knockdown cells and Atg5 or Atg7 knockout mouse embryonic fibroblasts, albumin transcytosis was significantly reduced and intracellular albumin accumulation was increased. Finally, the release of kidney injury molecule-1, a marker of tubule injury, from ATG7 or ATG5 knockdown cells was increased in response to excess albumin. In conclusion, suppression of autophagy in tubules impairs FcRn transport, thereby inhibiting albumin transcytosis. The resulting accumulation of albumin induces cytotoxicity in tubules.NEW & NOTEWORTHY Albumin transport in proximal tubule epithelial cells (PTECs) is important to control proteinuria. The neonatal Fc receptor (FcRn), a receptor for albumin transcytosis, is partially colocalized with autophagosomes. Recycling of FcRn to the plasma membrane was decreased in autophagy-related 7 (ATG7) knockdown cells. In addition, albumin transcytosis was decreased in ATG7 or autophagy-related 5 (ATG5) knockdown PTECs. Finally, release of kidney injury molecule-1 from ATG7 or ATG5 knockdown cells was increased in response to excess albumin.

Stronger Effect of Azilsartan on Reduction of Proteinuria Compared to Candesartan in Patients with CKD: A Randomized Crossover Trial.

INTRODUCTION: Angiotensin receptor blockers (ARBs) are preferably used in hypertensive patients with CKD. Azilsartan is a strong antihypertensive ARB, but its antiproteinuric effects are not well understood. We compared the antiproteinuric effect of azilsartan and candesartan in CKD patients in an open-label, randomized, crossover trial. METHODS: A total of 111 patients were treated with 20 mg of azilsartan daily for 2 months as a run-in period. After the run-in period, patients were randomized into 2 arms and received either 20 mg of azilsartan or 8 mg of candesartan daily for 3 months in a crossover trial. The primary outcome was the percent change in urinary protein-to-Cr ratio (UPCR). RESULTS: Ninety-five patients completed the trial. The mean age was 64.3 years. The estimated glomerular filtration rate (eGFR) and UPCR were 41.5 mL/min/1.73 m2 and 1.8 g/gCr, respectively. The baseline systolic and diastolic blood pressures were 131.4 and 71.0 mm Hg, respectively. The mean percent change in the UPCR was -3.8% in the azilsartan group and 30.8% in the candesartan group at the 1st endpoint (p = 0.0004), and 6.1% in the azilsartan group and 25.8% in the candesartan group at the 2nd (final) endpoint (p = 0.029). The incidence of adverse events, including eGFR levels and serum potassium levels, was not significantly different between the groups. CONCLUSION: A 20 mg azilsartan dose had potent antiproteinuric effects compared with an 8 mg candesartan dose, without an increase in adverse events. Azilsartan may provide renal protection in addition to antihypertensive effects in CKD patients.

Non-invasive fibrosis assessments of non-alcoholic fatty liver disease associated with low estimated glomerular filtration rate among CKD patients: the Fukuoka Kidney disease Registry Study.

BACKGROUND: A growing body of evidence has shown that non-alcoholic fatty liver disease (NAFLD) is associated with chronic kidney disease (CKD). Non-invasive fibrosis assessments of NAFLD such as Fibrosis-4 (FIB-4) index and NAFLD fibrosis score (NFS) have been developed to substitute liver biopsy. Little is known about the association between FIB-4 index or NFS and the components of CKD. METHODS: In the present cross-sectional study, we assessed of 3640 Japanese CKD patients. We examined the association between FIB-4index or NFS and the odds of having low estimated glomerular filtration rate (eGFR) defined as eGFR < 60 mL/min/1.73 m2 or albuminuria defined as urinary albumin-to-creatinine ratio (UACR) ≥ 30 mg/g. Patients were divided into quartiles according to their baseline FIB-4 index and NFS levels. Linear and logistic regression analysis were conducted, with adjustment for potential confounding factors. RESULTS: FIB-4 index and NFS were negatively associated with eGFR, but not UACR, after adjustment for potential confounding factors. Both FIB-4 index and NFS were significantly associated with low eGFR after adjustment for potential confounding factors. Meanwhile, in the multivariable-adjusted model, no associations were found between FIB-4 index or NFS and albuminuria. The addition of FIB-4 index or NFS to the established clinical CKD risk factors improved diagnostic accuracy of prevalence of low eGFR. We also found that there was a significant trend of higher FIB-4 index and NFS with more advanced renal fibrosis using the kidney biopsy data. CONCLUSIONS: Higher non-invasive fibrosis assessments of NAFLD were associated with higher odds of decreased eGFR.

Arginase 2 is a mediator of ischemia-reperfusion injury in the kidney through regulation of nitrosative stress.

Kidney ischemia-reperfusion injury is a major cause of acute kidney injury (AKI). Following reduced kidney perfusion, the pathological overproduction of reactive oxygen and reactive nitrogen species play a substantial role in the development of kidney ischemia-reperfusion injury. Arginase 2 (ARG2) competes with nitric oxide synthase for the same substrate, L-arginine, and is implicated in the regulation of reactive nitrogen species. Therefore, we investigated the role of ARG2 in kidney ischemia-reperfusion injury using human proximal tubule cells (HK-2) and a mouse model of kidney ischemia-reperfusion injury. ARG2 was predominantly expressed in kidney tubules of the cortex, which was increased after ischemia-reperfusion injury. In HK-2 cells, ARG2 was expressed in punctate form in the cytoplasm and upregulated after hypoxia-reoxygenation. ARG2 knockdown reduced the level of reactive oxygen species and 3-nitrotyrosine after hypoxia-reoxygenation injury compared with control siRNA. Consistent with these results, in Arg2 knockout mice, abnormal kidney function and the increased acute tubular necrosis score induced by ischemia-reperfusion injury was significantly reduced without any obvious blood pressure changes. Additionally, an accumulation of 3-nitrotyrosine and apoptosis of renal tubule cells were attenuated in Arg2 knockout mice compared with wild-type mice. Inhibition of arginase by Nω-hydroxy-nor-L-arginine alleviated kidney ischemia-reperfusion injury like the results found in Arg2 knockout mice. Thus, ARG2 plays a pivotal role in ischemia-reperfusion-induced AKI by means of nitrosative stress. Hence, an ARG2-specific inhibitor may effectively treat kidney ischemia-reperfusion injury.

Hemoglobin concentration and the risk of hemorrhagic and ischemic stroke in patients undergoing hemodialysis: the Q-cohort study.

Background: The contribution of the hemoglobin concentration to the incidence of hemorrhagic or ischemic stroke in patients undergoing hemodialysis is unclear. Methods: In total, 3436 patients undergoing prevalent hemodialysis were followed up for 4 years. The primary outcome was the first development of hemorrhagic or ischemic stroke. The baseline hemoglobin concentration was divided into quartiles [hemoglobin (g/dL): Q1, ≤9.7; Q2, 9.8-10.5; Q3, 10.6-11.1; Q4, ≥11.2]. The association between the hemoglobin concentration and each type of stroke was examined using the Kaplan-Meier method and a Cox proportional hazards model. Results: During the follow-up period, 76 (2.2%) patients developed hemorrhagic stroke and 139 (4.0%) developed ischemic stroke. The 4-year incidence rate of hemorrhagic stroke was significantly higher in patients with lower hemoglobin concentrations. Compared with the quartile of patients with the highest hemoglobin concentrations (Q4), the multivariable-adjusted hazard ratios for hemorrhagic stroke were 1.18 (95% confidence interval, 0.56-2.51), 1.59 (0.82-3.21) and 2.31 (1.16-4.73) in patients in Q3, Q2 and Q1, respectively. No association was identified between the 4-year incidence rate of ischemic stroke and the hemoglobin concentration. Compared with the quartile of patients with the lowest hemoglobin concentrations (Q1), the multivariable-adjusted hazard ratios for ischemic stroke were 1.17 (95% confidence interval, 0.73-1.89), 0.88 (0.51-1.51) and 1.10 (0.66-1.83) in patients in Q2, Q3 and Q4, respectively. Conclusions: Our results suggest that low hemoglobin concentrations are associated with a high risk of hemorrhagic stroke, but not of ischemic stroke, in patients undergoing hemodialysis.

Vascular endothelial growth factor-C ameliorates renal interstitial fibrosis through lymphangiogenesis in mouse unilateral ureteral obstruction.

Renal fibrosis is the final common pathway of chronic kidney diseases. Lymphatic vessel (LV) proliferation is found in human renal diseases and other fibrotic diseases, suggesting that lymphangiogenesis is associated with the progression or suppression of kidney diseases. However, the purpose of LV proliferation is not completely understood. We investigated the effect of vascular endothelial growth factor (VEGF)-C on lymphangiogenesis, inflammation, and fibrosis in the mouse kidney using the unilateral ureteral obstruction (UUO) model. In UUO mice, significant proliferation of LVs was accompanied by tubulointerstitial nephritis and fibrosis. We continuously administered recombinant human VEGF-C to UUO model mice using an osmotic pump (UUO+VEGF-C group). Lymphangiogenesis was significantly induced in the UUO+VEGF-C group compared with the vehicle group, despite similar numbers of capillaries in both groups. The number of infiltrating macrophages, and levels of inflammatory cytokines and transforming growth factor-ß1 were reduced in the UUO+VEGF-C group compared with the vehicle group. Renal fibrosis was consequently attenuated in the UUO+VEGF-C group. In cultured lymphatic endothelial cells, administration of VEGF-C increased the activity and proliferation of lymphatic endothelial cells (LECs) and expression of adhesion molecules such as vascular cell adhesion molecule-1. These findings suggest that induction of lymphangiogenesis ameliorates inflammation and fibrosis in the renal interstitium. Enhancement of the VEGF-C signaling pathway in LECs may be a therapeutic strategy for renal fibrosis.

PKCη deficiency improves lipid metabolism and atherosclerosis in apolipoprotein E-deficient mice.

Genomewide association studies have shown that a nonsynonymous single nucleotide polymorphism in PRKCH is associated with cerebral infarction and atherosclerosis-related complications. We examined the role of PKCη in lipid metabolism and atherosclerosis using apolipoprotein E-deficient (Apoe-/- ) mice. PKCη expression was augmented in the aortas of mice with atherosclerosis and exclusively detected in MOMA2-positive macrophages within atherosclerotic lesions. Prkch+/+ Apoe-/- and Prkch-/- Apoe-/- mice were fed a high-fat diet (HFD), and the dyslipidemia observed in Prkch+/+ Apoe-/- mice was improved in Prkch-/- Apoe-/- mice, with a particular reduction in serum LDL cholesterol and phospholipids. Liver steatosis, which developed in Prkch+/+ Apoe-/- mice, was improved in Prkch-/- Apoe-/- mice, but glucose tolerance, adipose tissue and body weight, and blood pressure were unchanged. Consistent with improvements in LDL cholesterol, atherosclerotic lesions were decreased in HFD-fed Prkch-/- Apoe-/- mice. Immunoreactivity against 3-nitrotyrosine in atherosclerotic lesions was dramatically decreased in Prkch-/- Apoe-/- mice, accompanied by decreased necrosis and apoptosis in the lesions. ARG2 mRNA and protein levels were significantly increased in Prkch-/- Apoe-/- macrophages. These data show that PKCη deficiency improves dyslipidemia and reduces susceptibility to atherosclerosis in Apoe-/- mice, showing that PKCη plays a role in atherosclerosis development.

Cardiothoracic Ratio and All-Cause Mortality and Cardiovascular Disease Events in Hemodialysis Patients: The Q-Cohort Study.

BACKGROUND: Cardiothoracic ratio by chest radiography is commonly used to assess volume status. Little is known about the relationships between cardiothoracic ratio and the incidence of clinical outcomes in patients undergoing hemodialysis (HD). STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: 3,436 participants in the Q-Cohort Study 18 years or older who underwent maintenance HD in Japan. PREDICTOR: Cardiothoracic ratio. OUTCOMES & MEASUREMENTS: All-cause mortality and cardiovascular disease (CVD) events. RESULTS: During a 4-year follow-up period, 564 (16.4%) patients died of any cause and 590 (17.2%) developed CVD events. From baseline cardiothoracic ratios, participants were categorized into sex-specific quartiles because cardiothoracic ratio distribution differed by sex. The 4-year event-free survival rate, in terms of all-cause mortality and CVD events, was significantly lower with higher cardiothoracic ratios. Compared to the lowest cardiothoracic ratio (quartile 1), multivariable-adjusted HRs for all-cause mortality were 0.89 (95% CI, 0.66-1.20), 1.41 (1.08-1.86), and 1.52 (1.17-2.00) in patients from quartiles 2, 3, and 4, respectively. Similarly, in comparison to quartile 1, multivariable-adjusted HRs for CVD events were 1.00 (95% CI, 0.77-1.31), 1.18 (0.92-1.53), and 1.37 (1.07-1.76) in patients from quartiles 2, 3, and 4, respectively. Furthermore, the combination of higher cardiothoracic ratio and normohypotension (systolic blood pressure < 140mmHg and diastolic blood pressure < 90mmHg) was associated with higher risk for CVD events. LIMITATIONS: Single measurement of all variables, potentially less-heterogeneous patient population, and limited ascertainment of cardiac parameters and the outcomes. CONCLUSIONS: Higher cardiothoracic ratio is associated with higher risk for both all-cause mortality and CVD events in patients undergoing HD.

Assessment of urinary angiotensinogen as a marker of podocyte injury in proteinuric nephropathies.

Urinary protein (UP) is widely used as a clinical marker for podocyte injury; however, not all proteinuric nephropathies fit this model. We previously described the elevation of urinary angiotensinogen (AGT) accompanied by AGT expression by injured podocytes in a nitric oxide inhibition rat model (Eriguchi M, Tsuruya K, Haruyama N, Yamada S, Tanaka S, Suehiro T, Noguchi H, Masutani K, Torisu K, Kitazono T. Kidney Int 87: 116-127, 2015). In this report, we performed the human and animal studies to examine the significance and origin of urinary AGT. In the human study, focal segmental glomerulosclerosis (FSGS) patients presented with higher levels of urinary AGT, corrected by UP, than minimal-change disease (MCD) patients. Furthermore, AGT was evident in podocin-negative glomerular segmental lesions. We also tested two different nephrotic models induced by puromycin aminonucleoside in Wistar rats. The urinary AGT/UP ratio and AGT protein and mRNA expression in sieved glomeruli from FSGS rats were significantly higher than in MCD rats. The presence of AGT at injured podocytes in FSGS rats was detected by immunohistochemistry and immunoelectron microscopy. Finally, we observed the renal tissue and urinary metabolism of exogenous injected human recombinant AGT (which is not cleaved by rodent renin) in FSGS and control rats. Significant amounts of human AGT were detected in the urine of FSGS rats, but not of control rats. Immunostaining for rat and human AGT identified that only rat AGT was detected in injured podocytes, and filtered human AGT was seen in superficial proximal tubules, but not in injured podocytes, suggesting AGT generation by injured podocytes. In conclusion, the urinary AGT/UP ratio represents a novel specific marker of podocyte injury.

Spironolactone ameliorates arterial medial calcification in uremic rats: the role of mineralocorticoid receptor signaling in vascular calcification.

Vascular calcification (VC) is a critical complication in patients with chronic kidney disease (CKD). The effects of spironolactone (SPL), a mineralocorticoid receptor (MR) antagonist, on VC have not been fully investigated in CKD. The present in vivo study determined the protective effects of SPL on VC in CKD rats. Rats were divided into a control group and four groups of rats with adenine-induced CKD. Three groups were treated with 0, 50, and 100 mg·kg(-1)·day(-1) SPL for 8 wk, and one group was treated with 100 mg·kg(-1)·day(-1) SPL for the last 2 wk of the 8-wk treatment period. After 8 wk, CKD rats developed azotemia and hyperphosphatemia, with increases in the expression of serum and glucocorticoid-regulated kinase-1 and sodium-phosphate cotransporter, in inflammation and oxidative stress level, in osteogenic signaling and apoptosis, and in aortic calcification, compared with control rats. SPL dose dependently decreased these changes in the aortas, concomitant with improvements in renal inflammation, tubulointerstitial nephritis, and kidney function. SPL neither lowered blood pressure level nor induced hyperkalemia. Treatment of CKD rats for the last 2 wk with 100 mg·kg(-1)·day(-1) SPL attenuated VC compared with CKD rats with the same degree of kidney function and hyperphosphatemia. In conclusion, SPL dose dependently inhibits the progression of VC by suppressing MR signaling, local inflammation, osteogenic transition, and apoptosis in the aortas of CKD rats.

Renal denervation has blood pressure-independent protective effects on kidney and heart in a rat model of chronic kidney disease.

We elucidate the underlying mechanisms of bidirectional cardiorenal interaction, focusing on the sympathetic nerve driving disruption of the local renin-angiotensin system (RAS). A rat model of N(ω)-nitro-L-arginine methyl ester (L-NAME; a nitric oxide synthase inhibitor) administration was used to induce damage in the heart and kidney, similar to cardiorenal syndrome. L-NAME induced sympathetic nerve-RAS overactivity and cardiorenal injury accompanied by local RAS elevations. These were suppressed by bilateral renal denervation, but not by hydralazine treatment, despite the blood pressure being kept the same between the two groups. Although L-NAME induced angiotensinogen (AGT) protein augmentation in both organs, AGT mRNA decreased in the kidney and increased in the heart in a contradictory manner. Immunostaining for AGT suggested that renal denervation suppressed AGT onsite generation from activated resident macrophages of the heart and circulating AGT excretion from glomeruli of the kidney. We also examined rats treated with L-NAME plus unilateral denervation to confirm direct sympathetic regulation of intrarenal RAS. The levels of urinary AGT and renal angiotensin II content and the degrees of renal injury from denervated kidneys were less than those from contralateral innervated kidneys within the same rats. Thus, renal denervation has blood pressure-independent beneficial effects associated with local RAS inhibition.

Membranoproliferative glomerulonephritis with predominant IgG2 and IgG3 deposition in a patient with IgG4-related disease.

BACKGROUND: IgG4-related disease is a novel disease entity characterized by elevated serum IgG4 and tissue infiltration by IgG4-positive plasma cells. Typical renal pathology is tubulointerstitial nephritis with storiform fibrosis, although the co-existence of various glomerular lesions has been described. Here, we present the first report of a case of IgG4-related kidney disease and membranoproliferative glomerulonephritis showing the discrepancy in IgG subclasses between the kidney interstitium and glomeruli. CASE PRESENTATION: A 70-year-old Japanese woman was diagnosed with membranoproliferative glomerulonephritis and focal tubulointerstitial nephritis with IgG4-positive plasma cells. Immunofluorescence studies revealed predominant deposition of IgG3 and IgG2, but not IgG4 in the glomeruli. We administered oral prednisolone at 30 mg/day, and the abnormalities in urine and blood tests gradually resolved. CONCLUSION: In this case, different patterns of IgG subclasses detected in the glomeruli and interstitial plasma cells suggest overlapping immunologic abnormalities. The favorable clinical course in our patient suggests that steroid therapy is promising in cases of IgG4-related kidney disease accompanied by glomerulonephritis.

More rapid progression of brain atrophy in patients on peritoneal dialysis compared with hemodialysis: The VCOHP Study.

We previously reported that brain atrophy was more severe and progressed more rapidly in patients with end-stage kidney disease on peritoneal dialysis (PD) than those with non-dialysis-dependent chronic kidney disease. However, it remains unknown whether there is a difference between patients on PD and hemodialysis (HD). In total, 73 PD and 34 HD patients who underwent brain magnetic resonance imaging (MRI) were recruited for a cross-sectional analysis. Among them, 42 PD and 25 HD patients who underwent a second brain MRI after 2 years were recruited for a longitudinal analysis. T1-weighted MRI images were analyzed. Total gray matter volume (GMV), total white matter volume, and cerebrospinal fluid volume were segmented, and each volume was quantified using statistical parametric mapping software. The ratio of GMV (GMR) was calculated by dividing GMV by intracranial volume, to adjust for variations in head size. We compared GMR between PD and HD patients in the cross-sectional analysis and the annual change in GMR (AC-GMR) in the longitudinal analysis. In the cross-sectional analysis, age- and sex-adjusted GMR was significantly lower in PD than HD patients [least square mean (LSM): 39.2% vs. 40.0%, P = 0.018]. AC-GMR was significantly greater in PD than HD patients and this difference remained significant even after adjustment for potential confounding factors (LSM: -0.68 vs. -0.28 percentage-points/year, P = 0.011). In conclusion, the present study demonstrated a more rapid progression of brain atrophy in PD patients compared with HD patients. We demonstrated that decline in GMR progressed significantly more rapidly in PD than HD patients independent of potential confounding factors. GMR gray matter volume ratio, HD hemodialysis, PD peritoneal dialysis.

Spermidine from arginine metabolism activates Nrf2 and inhibits kidney fibrosis.

Kidney metabolism may be greatly altered in chronic kidney disease. Here we report that arginine metabolism is the most altered in unilateral ureteral obstruction (UUO)-induced fibrosis of the kidneys in metabolomic analysis. Spermidine is the most increased metabolite of arginine. In human glomerulonephritis, the amount of spermidine shown by immunostaining is associated with the amount of fibrosis. In human proximal tubule cells, spermidine induces nuclear factor erythroid 2-related factor 2 (Nrf2). Subsequently, fibrotic signals, such as transforming growth factor ß1 secretion, collagen 1 mRNA, and oxidative stress, represented by a decrease in the mitochondrial membrane potential is suppressed by spermidine. UUO kidneys of Arg2 knockout mice show less spermidine and significantly exacerbated fibrosis compared with wild-type mice. Nrf2 activation is reduced in Arg2 knockout UUO kidneys. Spermidine treatment prevents significant fibrotic progression in Arg2 knockout mice. Spermidine is increased in kidney fibrosis, but further increases in spermidine may reduce fibrosis.

Indoxyl sulfate induces left ventricular hypertrophy via the AhR-FGF23-FGFR4 signaling pathway.

Background: Patients with chronic kidney disease (CKD) have a high risk of left ventricular hypertrophy (LVH). Fibroblast growth factor 23 (FGF23) and indoxyl sulfate (IS) are associated with LVH in patients with CKD, but the interactions between these molecules remain unknown. We investigated whether IS contributes to LVH associated with FGF23 in cultured cardiomyocytes and CKD mice. Methods and results: In cultured rat cardiac myoblast H9c2 cells incubated with IS, mRNA levels of the LVH markers atrial natriuretic factor, brain natriuretic peptide, and ß-myosin heavy chain were significantly upregulated. Levels of mRNA of the polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3), which regulates FGF23 O-glycosylation, and FGF23 were also upregulated in H9c2 cells. Intact FGF23 protein expression and fibroblast growth factor receptor 4 (FGFR4) phosphorylation were increased in cell lysates by IS administration. In C57BL/6J mice with heminephrectomy, IS promoted LVH, whereas the inhibition of FGFR4 significantly reduced heart weight and left ventricular wall thickness in IS-treated groups. While there was no significant difference in serum FGF23 concentrations, cardiac FGF23 protein expression was markedly increased in IS-injected mice. GALNT3, hypoxia-inducible factor 1 alpha, and FGF23 protein expression was induced in H9c2 cells by IS treatment and suppressed by the inhibition of Aryl hydrocarbon receptor which is the receptor for IS. Conclusion: This study suggests that IS increases FGF23 protein expression via an increase in GALNT3 and hypoxia-inducible factor 1 alpha expression, and activates FGF23-FGFR4 signaling in cardiomyocytes, leading to LVH.