Proximal-tubule molecular relay from early Protein diaphanous homolog 1 to late Rho-associated protein kinase 1 regulates kidney function in obesity-induced kidney damage.

The small GTPase protein RhoA has two effectors, ROCK (Rho-associated protein kinase 1) and mDIA1 (protein diaphanous homolog 1), which cooperate reciprocally. However, temporal regulation of RhoA and its effectors in obesity-induced kidney damage remains unclear. Here, we investigated the role of RhoA activation in the proximal tubules at the early and late stages of obesity-induced kidney damage. In mice, a three-week high-fat-diet induced proximal tubule hypertrophy and damage without increased albuminuria, and RhoA/mDIA1 activation without ROCK activation. Conversely, a 12-week high-fat diet induced proximal tubule hypertrophy, proximal tubule damage, increased albuminuria, and RhoA/ROCK activation without mDIA1 elevation. Proximal tubule hypertrophy resulting from cell cycle arrest accompanied by downregulation of the multifunctional cyclin-dependent kinase inhibitor p27Kip1 was elicited by RhoA activation. Mice overexpressing proximal tubule-specific and dominant-negative RHOA display amelioration of high-fat diet-induced kidney hypertrophy, cell cycle abnormalities, inflammation, and renal impairment. In human proximal tubule cells, mechanical stretch mimicking hypertrophy activated ROCK, which triggered inflammation. In human kidney samples from normal individuals with a body mass index of about 25, proximal tubule cell size correlated with body mass index, proximal tubule cell damages, and mDIA1 expression. Thus, RhoA activation in proximal tubules is critical for the initiation and progression of obesity-induced kidney damage. Hence, the switch in the downstream RhoA effector in proximal tubule represents a transition from normal to pathogenic kidney adaptation and to body weight gain, leading to obesity-induced kidney damage.

Pre-emptive Short-term Nicotinamide Mononucleotide Treatment in a Mouse Model of Diabetic Nephropathy.

BACKGROUND: The activation of NAD+-dependent deacetylase, Sirt1, by the administration of nicotinamide mononucleotide (NMN) ameliorates various aging-related diseases. METHODS: Diabetic db/db mice were treated with NMN transiently for 2 weeks and observed for effects on diabetic nephropathy (DN). RESULTS: At 14 weeks after the treatment period, NMN attenuated the increases in urinary albumin excretion in db/db mice without ameliorating hemoglobin A1c levels. Short-term NMN treatment mitigated mesangium expansion and foot process effacement, while ameliorating decreased Sirt1 expression and increased claudin-1 expression in the kidneys of db/db mice. This treatment also improved the decrease in the expression of H3K9me2 and DNMT1. Short-term NMN treatment also increased kidney concentrations of NAD+ and the expression of Sirt1 and nicotinamide phosphoribosyltransferase (Nampt), and it maintained nicotinamide mononucleotide adenyltransferase1 (Nmnat1) expression in the kidneys. In addition, survival rates improved after NMN treatment. CONCLUSIONS: Short-term NMN treatment in early-stage DN has remote renal protective effects through the upregulation of Sirt1 and activation of the NAD+ salvage pathway, both of which indicate NMN legacy effects on DN.

ß-hydroxybutyrate attenuates renal ischemia-reperfusion injury through its anti-pyroptotic effects.

Ketone bodies including ß-hydroxybutyrate (ß-OHB) have been shown to protect against ischemic tissue injury when present at low concentrations. We evaluated the impact of ß-OHB on renal ischemia/reperfusion injury (IRI). Mice were treated with a continuous infusion of ß-OHB using an osmotic mini-pump before and after IRI. We also tested the effects of increasing endogenous serum ß-OHB levels by fasting. Renal IRI was attenuated by ß-OHB treatment compared to saline control, with similar results in the fasting condition. ß-OHB treatment reduced the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells and increased expression of forkhead transcription factor O3 (FOXO3), an upstream regulator of pyroptosis. Although ß-OHB treatment did not impact markers of apoptosis, it decreased the expression of caspase-1 and proinflammatory cytokines, indicating that ß-OHB blocked pyroptosis. In a human proximal tubular cell line exposed to hypoxia and reoxygenation, ß-OHB reduced cell death in a FOXO3-dependent fashion. Histone acetylation was decreased in kidneys exposed to IRI and in proximal tubular cells exposed to hypoxia and reoxygenation, and this effect was ameliorated by ß-OHB through the inactivation of histone deacetylases. In vitro, ß-OHB treatment restored histone acetylation at the FOXO3 promoter. Consistent with epigenetic molecular effects, the renoprotective effects of ß-OHB were still observed when the continuous infusion was stopped at the time of IRI. Thus, ß-OHB attenuates renal IRI through anti-pyroptotic effects, likely mediated by an epigenetic effect on FOXO3 expression.

Low birth weight is associated with decline in renal function in Japanese male and female adolescents.

BACKGROUND: Low birth weight (LBW) is a risk factor for chronic kidney disease (CKD) in later life and is becoming increasingly common in developed countries, including Japan. Furthermore, a serial decrease in birth weight has been associated with an increasing prevalence of CKD stage 2 in male Japanese adolescents. Sex-specific differences affect CKD susceptibility, and the association between birth weight and CKD in women, has not been elucidated. In this study, we investigated the sex-specific effect of LBW on renal function. METHODS: Annual cross-sectional data of 2417 Japanese adolescents (males 1736; females 681), aged 15-16 years, were evaluated over 8 years (2007-2014). RESULTS: Over the study period, mean birth weights decreased significantly in males (p < 0.01) and females (p < 0.05). Furthermore, both sexes showed significant decrease in estimated glomerular filtration rates corresponding to the birth weight reduction. The prevalence of CKD stage 2 also increased in males (from 26.0 to 32.4%, p < 0.01) and females (from 6.3 to 18.5%, p < 0.05). The incidence of CKD stage 2 was significantly related to history of LBW (males: odds ratio 1.73; 95% confidence interval 1.06-2.80; p < 0.05; females: odds ratio 3.29; 95% confidence interval 1.25-8.02; p < 0.05). CONCLUSIONS: Our data revealed that renal function and birth weight have decreased over time, in healthy Japanese adolescents. In view of the recent declining trend demonstrated by birth weight in Japan, we speculate that the prevalence of CKD might increase in the future.

Oral adsorbent AST-120 ameliorates gut environment and protects against the progression of renal impairment in CKD rats.

BACKGROUND: Oral charcoal adsorbent AST-120 (AST) is reported to ameliorate renal dysfunction by the absorption of toxic substance in the gut. Recent study revealed that, in CKD, gut environment is disturbed including the decrease in tight junctions and Lactobacillus (Lact). In this study, we examined whether AST improves the renal dysfunction through gut environment. METHOD: Six-week-old spontaneously hypertensive rats (SHR) were rendered CKD by 5/6th nephrectomy (Nx). SHRs were divided into SHR (Sham), SHR with Nx (Nx), and Nx given AST (Nx + AST) (n = 10, each). After 12 weeks, rats were killed and biochemical parameters were explored. The gut flora was analyzed. Furthermore, gut molecular changes in tight junctions and toll-like receptors were examined. We also investigated the effects of the combination therapy with AST and Lact. RESULTS: The increase in serum urea nitrogen and urinary protein excretion in Nx was restored in Nx + AST. The increased renal glomerulosclerosis in Nx was ameliorated in Nx + AST. Increases in serum uremic toxins and IL-6 in Nx were ameliorated in Nx + AST. The gut flora analysis revealed that the decrease in Lact in Nx was restored in Nx + AST. The downregulation in the tight junction and TLR2 in Nx was mitigated by AST. However, combination therapy failed to exhibit additional effects. CONCLUSION: AST ameliorated renal function with the restoration of Lact and tight junction through TLR pathway, which would mitigate systemic inflammation and contributed to their renoprotective effects. Our study provides a novel mechanism of the renoprotective effects by AST.

Gut Lactobacillus protects against the progression of renal damage by modulating the gut environment in rats.

BACKGROUND: The role of gut microbiota in the progression of chronic kidney disease (CKD) has not been fully elucidated. METHODS: Renal failure was induced in 6-week-old spontaneously hypertensive rats by 5/6 nephrectomy (Nx). We analyzed the gut microbiota population to identify the relevant species potentially involved in inducing renal damage. Human colon Caco-2 cells were used to delineate the mechanism involved in the molecular changes in the gut of Nx rats. RESULTS: Nx rats showed an increase in Bacteroides (Bact) and a decrease in Lactobacillus (Lact) species compared with sham-operated rats. Lact, but not Bact, populations were significantly associated with urinary protein excretion. Treatment of Nx rats with 1 × 10(10) CFU/kg/day Lact ameliorated increased urinary protein excretion and higher serum levels of the uremic toxins, indoxyl sulfate and p-cresyl sulfate, and serum urea nitrogen levels. Lact also attenuated systemic inflammation in Nx rats, as evaluated by serum lipopolysaccharide, interleukin-6 and C-reactive protein levels. Histologically, renal sclerosis in Nx rats was restored by Lact treatment. A reduction in the expression of tight junction proteins and the Toll-like receptor 2 (TLR2), a putative Lact receptor, in the colons of Nx rats were mitigated by Lact. Treatment of Caco-2 cells with indole downregulated tight junction protein expression, which was abolished by exposure to Lact. The effects of Lact were reversed by treatment with OxPAPC, a TLR inhibitor. Similarly, the increase in the permeability of the Caco-2 cell monolayer was reversed by the administration of Lact. Lact upregulated TLR2 expression in Caco-2 cells. Lact also attenuated the increase in serum indoxyl sulfate and urea levels and urinary protein excretion in Nx rats even in the pseudogerm-free environment. CONCLUSIONS: Lact supplementation mitigated the systemic inflammation and proteinuria associated with renal failure, suggesting that in the gut microbiota, Lact plays a protective role against the progression of CKD.

The role of adipose tissue asymmetric dimethylarginine/dimethylarginine dimethylaminohydrolase pathway in adipose tissue phenotype and metabolic abnormalities in subtotally nephrectomized rats.

BACKGROUND: The lipodystrophy-like phenotype has been suggested in early chronic kidney disease (CKD). It includes adipose tissue atrophy, systemic insulin resistance (IR), dyslipidemia and ectopic lipid accumulation. To elucidate its pathogenesis, we investigated the role of two uremic toxins that affect insulin sensitivity: an endogenous nitric oxide synthase inhibitor, and asymmetric dimethylarginine (ADMA) and indoxyl sulfate (IS). METHODS: Six-week-old Sprague-Dawley rats were rendered CKD by subtotal nephrectomy (Nx) and compared with sham-operated rats. Cultured 3T3-L1 fibroblasts were differentiated into mature adipocytes with or without ADMA. Transgenic (Tg) mice overexpressing each isoform of ADMA degrading enzyme, dimethylarginine dimethylaminohydrolase 1 (DDAH1) and DDAH2 were subject to Nx and their phenotypes were investigated. RESULTS: In Nx rats, IR was evident and insulin stimulation failed to activate insulin signaling in adipose tissues. Adipose tissue weight, adipocyte size and adipocyte differentiation marker expressions decreased as a consequence of IR in Nx. Tissue lipid content in the liver and muscle increased in Nx rats. Tissue levels of ADMA, IS and oxidative stress increased in the adipose tissue of Nx rats. Both DDAH1 and DDAH2 expressions decreased, and a putative IS receptor, aryl hydrocarbon receptor, expression increased in the adipose tissue of Nx rats. ADMA inhibited adipocyte differentiation, triglyceride accumulation and insulin signaling, which were reversed by pretreatment with cGMP. In each type of Tg mice overexpressing DDAH1 or DDAH2, all lipodystrophy-like phenotypes induced by Nx were reversed. CONCLUSIONS: In mild CKD, dysregulation of the ADMA/DDAH pathway in adipose tissue triggers lipodystrophy-like phenotype changes, including ectopic fat depositions.

Renin-angiotensin blockade resets podocyte epigenome through Kruppel-like Factor 4 and attenuates proteinuria.

Proteinuria is a central component of chronic kidney disease and an independent risk factor for cardiovascular disease. Kidney podocytes have an essential role as a filtration barrier against proteinuria. Kruppel-like Factor 4 (KLF4) is expressed in podocytes and decreased in glomerular diseases leading to methylation of the nephrin promoter, decreased nephrin expression and proteinuria. Treatment with an angiotensin receptor blocker (ARB) reduced methylation of the nephrin promoter in murine glomeruli of an adriamycin nephropathy model with recovery of KLF4 expression and a decrease in albuminuria. In podocyte-specific KLF4 knockout mice, the effect of ARB on albuminuria and the nephrin promoter methylation was attenuated. In cultured human podocytes, angiotensin II reduced KLF4 expression and caused methylation of the nephrin promoter with decreased nephrin expression. In patients, nephrin promoter methylation was increased in proteinuric kidney diseases with decreased KLF4 and nephrin expression. KLF4 expression in ARB-treated patients was higher in patients with than without ARB treatment. Thus, angiotensin II can modulate epigenetic regulation in podocytes and ARB inhibits these actions in part via KLF4 in proteinuric kidney diseases. This study provides a new concept that renin-angiotensin system blockade can exert therapeutic effects through epigenetic modulation of the kidney gene expression.

Insulin resistance in chronic kidney disease is ameliorated by spironolactone in rats and humans.

In this study, we examined the association between chronic kidney disease (CKD) and insulin resistance. In a patient cohort with nondiabetic stages 2-5 CKD, estimated glomerular filtration rate (eGFR) was negatively correlated and the plasma aldosterone concentration was independently associated with the homeostasis model assessment of insulin resistance. Treatment with the mineralocorticoid receptor blocker spironolactone ameliorated insulin resistance in patients, and impaired glucose tolerance was partially reversed in fifth/sixth nephrectomized rats. In these rats, insulin-induced signal transduction was attenuated, especially in the adipose tissue. In the adipose tissue of nephrectomized rats, nuclear mineralocorticoid receptor expression, expression of the mineralocorticoid receptor target molecule SGK-1, tissue aldosterone content, and expression of the aldosterone-producing enzyme CYP11B2 increased. Mineralocorticoid receptor activation in the adipose tissue was reversed by spironolactone. In the adipose tissue of nephrectomized rats, asymmetric dimethylarginine (ADMA; an uremic substance linking uremia and insulin resistance) increased, the expression of the ADMA-degrading enzymes DDAH1 and DDAH2 decreased, and the oxidative stress increased. All of these changes were reversed by spironolactone. In mature adipocytes, aldosterone downregulated both DDAH1 and DDAH2 expression, and ADMA inhibited the insulin-induced cellular signaling. Thus, activation of mineralocorticoid receptor and resultant ADMA accumulation in adipose tissue has, in part, a relevant role in the development of insulin resistance in CKD.

A case of severe osteomalacia caused by Tubulointerstitial nephritis with Fanconi syndrome in asymptomotic primary biliary cirrhosis.

BACKGROUND: Primary biliary cirrhosis (PBC) is an immune-mediated chronic cholestatic liver disease, characterized by increased concentrations of serum IgM and the presence of circulating anti-mitochondrial antibodies. Although bone diseases such as osteoporosis or osteodystrophy are commonly associated with PBC, osteomalacia which is caused by abnormal vitamin D metabolism, mineralization defects, and phosphate deficiency has not been recognized as a complication of PBC. CASE PRESENTATION: We report the case of a 49-year-old Japanese woman who complained of multiple fractures. Hypophosphatemic osteomalacia was diagnosed from a low serum phosphorus level, 1,25-dihydroxyvitamin D3 level, high levels of bone specific alkaline phosphatase and the findings of bone scintigraphy, although a bone biopsy was not performed. Twenty four hour urine demonstrated a low renal fractional tubular reabsorption of phosphate, increased fractional excretion of uric acid and generalized aminoaciduria. An intravenous bicarbonate loading test suggested the presence of proximal renal tubular acidosis (RTA). These biochemical data indicated Fanconi syndrome with proximal RTA. A kidney biopsy demonstrated the features of tubulointerstitial nephritis (TIN). The patient was also suspected as having primary biliary cirrhosis (PBC) because of high levels of alkaline phosphatase, IgM and the presence of anti-mitochondrial M2 antibody, though biochemical liver function was normal. Sequential liver biopsy was compatible with PBC and the diagnosis of PBC was definite. After administration of 1,25 dihydroxyvitamin D3, neutral potassium phosphate, sodium bicarbonate for osteomalacia and subsequent predonizolone for TIN, symptoms of fractures were relieved and renal function including Fanconi syndrome was ameliorated. CONCLUSION: In this case, asymptomatic PBC was shown to induce TIN with Fanconi syndrome with dysregulation of electrolytes and vitamin D metabolism, which in turn led to osteomalacia with multiple fractures. Osteomalacia has not been recognized as a result of the renal involvement of PBC. PBC and its rare complication of TIN with Fanconi syndrome should be considered in adult patients with unexplained osteomalacia even in the absence of liver dysfunction.

The hydrolase DDAH2 enhances pancreatic insulin secretion by transcriptional regulation of secretagogin through a Sirt1-dependent mechanism in mice.

The role of dimethylarginine dimethylaminohydrolase 2 (DDAH2) in glucose metabolism is unknown. Here, we generated DDAH2 transgenic (Tg) mice. These mice had lower plasma glucose levels (60 min: 298±32 vs. 418±35 mg/dl; 120 min: 205±15 vs. 284±20 mg/dl) and higher insulin levels (15 min: 2.1±0.2 vs. 1.5±0.1 ng/ml; 30 min: 1.8±0.1 vs. 1.5±0.1 ng/ml) during intraperitoneal glucose tolerance tests when fed a high-fat diet (HFD) compared with HFD-fed wild-type (WT) mice. Glucose-stimulated insulin secretion (GSIS) was increased in Tg islets by 33%. Pancreatic asymmetrical dimethylarginine, nitric oxide, and oxidative stress levels were not correlated with improvements in insulin secretion in Tg mice. Secretagogin, an insulin vesicle docking protein, was up-regulated by 2.7-fold in Tg mice and in pancreatic MIN-6 cells overexpressing DDAH2. GSIS in MIN-6 cells was dependent on DDAH2-induced secretagogin expression. Pancreatic Sirt1, DDAH2, and secretagogin were down-regulated in HFD-fed WT mice by 70, 75, and 85%, respectively. Overexpression of Sirt1 overexpression by 3.9-fold increased DDAH2 and secretagogin expression in MIN-6 cells by 3.2- and 2.5-fold, respectively. DDAH2 overexpression improved GSIS in pancreas-specific Sirt1-deficient mice. In summary, the Sirt1/DDAH2/secretagogin pathway is a novel regulator of GSIS.

Diagnosis of monoclonal immunotactoid glomerulopathy with positive λ chain by immunoelectron microscopy.

We report the case of a 73-year-old-man who developed immunotactoid glomerulopathy (ITG). ITG is a rare disease characterized by proliferative glomerulonephritis and capillary wall deposits with a 10-60 nm diameter microtubular substructure. In monoclonal ITG, immunofluorescence analysis typically exhibits IgG with light chain restriction. Recent reviews recommend distinguishing monoclonal ITG from polyclonal ITG because monoclonal ITG is associated with a higher incidence of hematological disorders and better responsiveness to clone-directed therapy and renal prognosis. In our case, IgG, IgA, and IgM were negative by routine immunofluorescence; however, immunoelectron microscopy revealed positive λ chain. At 6 months after renal biopsy, the IgG λ chain was detected in the serum and urine, reflecting possible monoclonality. Therefore, it is useful to perform immunoelectron microscopy and follow-up with serum and urine protein electrophoresis and immunofixation to diagnose monoclonal ITG, even when routine immunofluorescence shows negative or nonspecific findings.

A large coronary aneurysm and its probable precursor lesions in a patient with autosomal dominant polycystic kidney disease: an implication for the process of aneurysmogenesis.

Coronary artery aneurysms are rare complications of autosomal dominant polycystic kidney disease (ADPKD), and their pathogenesis remains poorly understood. We report an autopsy case of a 64-year-old ADPKD patient with an asymptomatic, large (4 cm in diameter) saccular aneurysm arising from the left circumflex (LCX) branch of the coronary artery with only mild atherosclerotic changes. Autopsy also revealed small, focal defects of media with or without microaneurysm formation in the LCX, mesenteric and renal arteries, and a fibromuscular dysplasia-like lesion with microaneurysm in the common iliac artery. Since polycystin-1 and -2 are expressed in arterial smooth-muscle cells, these findings imply that abnormal polycystin expression in ADPKD initially causes the focal medial defects, some of which might later progress to microaneurysms and then overt aneurysms. To the best of our knowledge, this is the first description of the pathologic findings of an ADPKD-associated coronary aneurysm and its probable precursor lesions in arteries.

MPO-ANCA associated crescentic glomerulonephritis with numerous immune complexes: case report.

BACKGROUND: Antineutrophil cytoplasmic antibody (ANCA)-associated crescentic glomerulonephritis (CGN) is a major cause of rapidly progressive glomerulonephritis (RPGN). ANCA-associated CGN is generally classified into pauci-immune RPGN, in which there are few or no immune complexes. CASE PRESENTATION: A 78-year-old man presented with RPGN after a 7-year course of chronic proteinuria and hematuria with stable renal function. A blood examination showed a high titer of myeloperoxidase (MPO)-ANCA. A renal biopsy showed crescentic glomerulonephritis with abundant subepithelial, intramenbranous and subendothelial deposits by electron microscopy, leading to the diagnosis of ANCA-associated CGN superimposed on type 3 membranoproliferative glomerulonephritis (MPGN). CONCLUSIONS: This case is unique in that type 3 MPGN and MPO-ANCA-associated CGN coexisted, and no similar case has been reported to date. Because ANCA-associated CGN has a predilection for elderly individuals and primary type 3 MPGN is rarely seen in this age group, coincidental existence appears less likely. This case may confer valuable information regarding the link between immune complex and ANCA-associated CGN.

Fabry disease associated with multiple myeloma: a case report.

Fabry disease (FD) is an X-linked genetic lysosomal disorder caused by alpha-galactosidase A (GLA) deficiency. Multiple myeloma (MM) predominately affects older adults, which ranks as the second commonest hematological malignancy. Their overlap has rarely been reported. We present a case of the coexistence of FD and MM in a patient. We report the case of a 68-year-old woman who was referred to our hospital for the evaluation of thoracic spine tumor with bone destruction. On admission, her serum creatinine (Cr) level was elevated to 12.70 mg/dL from the baseline value of 0.91 mg/dL. Bone marrow aspiration revealed MM. Renal biopsy showed myeloma cast nephropathy, which was the primary cause of acute kidney injury. Renal pathology also showed podocyte swelling and tubule myeloid bodies in a mosaic pattern compatible with female FD. Consequently, the patient was diagnosed as FD based on the germ line mutation in GLA. The patient was treated with bortezomib and dexamethasone therapy, which significantly improved the renal function. This is the second case demonstrating a potential pathogenic relationship between FD and MM. Since FD is one of the few genetic diseases for which there are therapeutic agents with fewer side effects, diagnostic value of FD is high. If an MM patient has multiple organ abnormalities or any familial history, the physician should suspect FD.

The significance of NAD + metabolites and nicotinamide N-methyltransferase in chronic kidney disease.

Dysregulation of nicotinamide adenine dinucleotide (NAD +) metabolism contributes to the initiation and progression of age-associated diseases, including chronic kidney disease (CKD). Nicotinamide N-methyltransferase (NNMT), a nicotinamide (NAM) metabolizing enzyme, regulates both NAD + and methionine metabolism. Although NNMT is expressed abundantly in the kidney, its role in CKD and renal fibrosis remains unclear. We generated NNMT-deficient mice and a unilateral ureter obstruction (UUO) model and conducted two clinical studies on human CKD to investigate the role of NNMT in CKD and fibrosis. In UUO, renal NNMT expression and the degraded metabolites of NAM increased, while NAD + and NAD + precursors decreased. NNMT deficiency ameliorated renal fibrosis; mechanistically, it (1) increased the DNA methylation of connective tissue growth factor (CTGF), and (2) improved renal inflammation by increasing renal NAD + and Sirt1 and decreasing NF-κB acetylation. In humans, along with CKD progression, a trend toward a decrease in serum NAD + precursors was observed, while the final NAD + metabolites were accumulated, and the level of eGFR was an independent variable for serum NAM. In addition, NNMT was highly expressed in fibrotic areas of human kidney tissues. In conclusion, increased renal NNMT expression induces NAD + and methionine metabolism perturbation and contributes to renal fibrosis.

Kidney-specific overexpression of Sirt1 protects against acute kidney injury by retaining peroxisome function.

Sirt1, a NAD-dependent protein deacetylase, is reported to regulate intracellular metabolism and attenuate reactive oxidative species (ROS)-induced apoptosis leading to longevity and acute stress resistance. We created transgenic (TG) mice with kidney-specific overexpression of Sirt1 using the promoter sodium-phosphate cotransporter IIa (Npt2) driven specifically in proximal tubules and investigated the kidney-specific role of Sirt1 in the protection against acute kidney injury (AKI). We also elucidated the role of number or function of peroxisome and mitochondria in mediating the mechanisms for renal protective effects of Sirt1 in AKI. Cisplatin-induced AKI decreased the number and function of peroxisomes as well as mitochondria and led to increased local levels of ROS production and renal tubular apoptotic cells. TG mice treated with cisplatin mitigated AKI, local ROS, and renal tubular apoptotic tubular cells. Consistent with these results, TG mice treated with cisplatin also exhibited recovery of peroxisome number and function, as well as rescued mitochondrial function; however, mitochondrial number was not recovered. Immunoelectron microscopic findings consistently demonstrated that the decrease in peroxisome number by cisplatin in wild type mice was restored in transgenic mice. In HK-2 cells, a cultured proximal tubule cell line, overexpression of Sirt1 rescued the cisplatin-induced cell apoptosis through the restoration of peroxisome number, although the mitochondria number was not restored. These results indicate that Sirt1 overexpression in proximal tubules rescues cisplatin-induced AKI by maintaining peroxisomes number and function, concomitant up-regulation of catalase, and elimination of renal ROS levels. Renal Sirt1 can be a potential therapeutic target for the treatment of AKI.

Rho-kinase inhibition ameliorates peritoneal fibrosis and angiogenesis in a rat model of peritoneal sclerosis.

BACKGROUND: Peritoneal fibrosis (PF) and angiogenesis are typical morphological changes, leading to loss of peritoneal functions in patients undergoing peritoneal dialysis. The small G protein, Rho, and its downstream effector Rho-kinase have been shown to be involved in the tissue fibrosis process. This study was undertaken to investigate the role of Rho-kinase in the pathogenesis of these alterations. METHODS: PF was induced by intraperitoneal administration of chlorhexidine (CHX) in male rats (CHX group). These rats were treated with a Rho-kinase inhibitor, fasudil (Fas group). Human pleural mesothelial cells, MeT-5A cells, were stimulated by glucose with or without another Rho-kinase inhibitor, Y-27632. RESULTS: Peritoneal damage including peritoneal thickening, fibrous changes, macrophage migration and angiogenesis were evident in the CHX group and were ameliorated in the Fas group. The expression of markers of tissue fibrosis, such as transforming growth factor (TGF)-ß, fibronectin and α-smooth muscle cell actin, were increased in the CHX group and were downregulated by fasudil. Similar results were also seen with an inducer of angiogenesis, vascular endothelial growth factor (VEGF). Rho-kinase was activated in the peritoneum of the CHX group, which was inhibited by fasudil. In MeT-5A cells, high glucose increased TGF-ß expression and VEGF secretion, which were blocked by Y-27632. CONCLUSIONS: The activation of Rho-kinase is involved in peritoneal damage at multiple stages including tissue fibrosis and angiogenesis. The inhibition of Rho-kinase constitutes a novel strategy for the treatment of PF.

Renal amyloidosis caused by apolipoprotein A-II without a genetic mutation in the coding sequence.

Although the majority of renal amyloidosis is caused by either acquired monoclonal immunoglobulin light-chain amyloidosis or reactive systemic amyloid A, some cases are caused by hereditary amyloidosis. Apolipoprotein A-II (apoAII) amyloidosis is a rare form of hereditary amyloidosis and cannot be diagnosed by a routine examination. Thus, the prevalence and etiology of apoAII amyloidosis are uncertain. In humans, a genetic mutation in the stop codon of apoAII is considered to be a cause of amyloid fibril formation. We report on a 68-year-old man who presented with proteinuria by apoAII amyloidosis without family history. His proteinuria gradually increased to 6 g/day within 1 year. A renal biopsy showed amyloid deposition in the glomeruli, however, acquired monoclonal immunoglobulin light-chain amyloidosis and reactive systemic amyloid A were ruled out. Immunohistochemistry revealed apoAII deposition in the glomeruli, but DNA sequencing did not identify any genetic mutation in the coding sequence of apoAII. Here, we report a case of apoAII amyloidosis without a genetic mutation in the coding sequence and discuss the etiology of apoAII amyloidosis.

Protein kinase C ß inhibition ameliorates experimental mesangial proliferative glomerulonephritis.

AIM: Activation of protein kinase C (PKC) has been implicated in the pathogenesis of diabetic nephropathy where therapy targeting the ß isoform of this enzyme has been examined. However, PKC-ß is also increased in various forms of human glomerulonephritis, including IgA nephropathy. Accordingly, we sought to examine the effects of PKC-ß inhibition in the Thy1.1 model of mesangial proliferative glomerulonephritis. METHODS: Following administration of monoclonal OX-7, anti-rat Thy-1.1 antibody, Male Wistar rats were randomized to receive either the PKC-ß inhibitor, ruboxistaurin (10 mg/kg per day in chow) or vehicle. Animals were then examined 6 days later. RESULTS: PKC-ß inhibition was associated with reductions in mesangial cellularity and extracellular matrix deposition. Proteinuria was, however, unaffected. In vitro, PKC-ß inhibition showed modest, dose-dependent reductions in mesangial cell (3) H-thymidine and (3) H-proline incorporations, indices of cell proliferation and collagen synthesis, respectively. CONCLUSION: The amelioration of the pathological findings of experimental mesangial proliferative glomerulonephritis by PKC-ß inhibition suggests the potential clinical utility of this approach as a therapeutic strategy in non-diabetic glomerular disease.