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AlphaB crystallin (αB-crystallin) is a key protein for maintaining the long-term transparency of the eye lens. In the eye lens, αB-crystallin is a “dynamical” oligomer regulated by subunit exchange between the oligomers. To elucidate the unsettled mechanism of subunit exchange in αB-crystallin oligomers, the study was carried out at two different protein concentrations, 28.5 mg/mL (dense sample) and 0.45 mg/mL (dilute sample), through inverse contrast matching small-angle neutron scattering. Interestingly, the exchange rate of the dense sample was the same as that of the dilute sample. From analytical ultracentrifuge measurements, the coexistence of small molecular weight components and oligomers was detected, regardless of the protein concentration. The model proposed that subunit exchange could proceed through the assistance of monomers and other small oligomers; the key mechanism is attaching/detaching monomers and other small oligomers to/from oligomers. Moreover, this model successfully reproduced the experimental results for both dense and dilute solutions. It is concluded that the monomer and other small oligomers attaching/detaching mainly regulates the subunit exchange in αB-crystallin oligomer.

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.

Summary: Nicotinamide adenine dinucleotide (NAD+) metabolism plays a critical role in kidneys. We previously reported that decreased secretion of a NAD+ precursor, nicotinamide mononucleotide (NMN), from proximal tubules (PTs) can trigger diabetic albuminuria. In the present study, we investigated the role of NMN-producing enzyme nicotinamide phosphoribosyltransferase (Nampt) in diabetic nephropathy. The expression of Nampt in PTs was downregulated in streptozotocin (STZ)-treated diabetic mice when they exhibited albuminuria. This albuminuria was ameliorated in PT-specific Nampt-overexpressing transgenic (TG) mice. PT-specific Nampt-conditional knockout (Nampt CKO) mice exhibited TBM thickening and collagen deposition, which were associated with the upregulation of the profibrogenic gene TIMP-1. Nampt CKO mice also exhibited the downregulation of sirtuins, particularly in Sirt6. PT-specific Sirt6-knockout mice exhibited enhanced fibrotic phenotype resembling that of Nampt CKO mice with increased Timp1 expression. In conclusion, the Nampt-Sirt6 axis in PTs serves as a key player in fibrogenic extracellular matrix remodeling in diabetic nephropathy. : Muraoka et al. reveal that the Nampt-Sirt6 axis in proximal tubules serves as a key player in fibrogenic extracellular matrix remodeling in diabetic nephropathy. Keywords: NAD, Nampt, Sirt6, metabo-fibrosis, NMN, TBM thickening, diabetic nephropathy

Cardiac hypertrophy is a life-threatening disorder and is frequently observed in patients with chronic kidney disease (CKD). Much attention has been focused on the derangement in hormonal factors, including aldosterone and FGF23, as novel causes of cardiac hypertrophy in CKD. Plasma aldosterone concentrations are elevated as renal function declines. Although aldosterone antagonists are available for the treatment of hypertension with cardiac hypertrophy, concern remains regarding the possible occurrence of serious hyperkalemia. Alternatively, certain types of calcium channel blockers suppress aldosterone synthesis or exert blocking action for mineralocorticoid receptors and could halt the progression of cardiac dysfunction. Recently, FGF23 is shown to be elevated as CKD progresses and may be responsible for the development of cardiac hypertrophy and heart failure. Furthermore, FGF23 not only inhibits the renal expression of angiotensin converting enzyme 2 but also enhances renin gene transcription, both of which could accelerate renin-angiotensin-aldosterone system. Although the increase in serum phosphate concentrations is a pivotal stimulus for FGF23 production, recent studies suggest that reduced iron status and elevated aldosterone levels, frequently seen in patients with CKD or on dialysis, might also contribute to the elevation in serum FGF23 levels. Conversely, phosphate binders and appropriate iron status could reduce serum FGF23, potentially leading to the alleviation of cardiac hypertrophy and heart failure. In conclusion, novel therapeutic strategies associated with aldosterone and FGF23 may confer a benefit in the management of cardiac disorders in CKD.

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.

Summary: Altered DNA methylation plays an important role in the onset and progression of kidney disease. However, little is known about how the changes arise in disease states. Here, we report that KAT5-mediated DNA damage repair is essential for the maintenance of kidney podocytes and is associated with DNA methylation status. Podocyte-specific KAT5-knockout mice develop severe albuminuria with increased DNA double-strand breaks (DSBs), increased DNA methylation of the nephrin promoter region, and decreased nephrin expression. Podocyte KAT5 expression is decreased, whereas DNA DSBs and DNA methylation are increased in diabetic nephropathy; moreover, KAT5 restoration by gene transfer attenuates albuminuria. Furthermore, KAT5 decreases DNA DSBs and DNA methylation at the same nephrin promoter region, which indicates that KAT5-mediated DNA repair may be related to DNA methylation status. These results suggest a concept in which an environment of DNA damage repair, which occurs with decreased KAT5, may affect DNA methylation status. : Hishikawa et al. reveal that KAT5-mediated DNA repair is essential for podocyte maintenance and is related to changes in DNA methylation status. Decreased podocyte KAT5 expression may contribute to the pathophysiology of diabetic nephropathy, suggesting a therapeutic target. Keywords: podocyte, DNA damage repair, DNA methylation, diabetic nephropathy

The patient was a 48-year-old Japanese woman diagnosed as having systemic lupus erythematosus at the age of 21 years when she presented with fever and an erythematous skin rash on her face and extremities. Prednisolone was initiated at that time. Thirteen days before admission to our hospital, she was referred to us by her family physician. Upon admission, blood tests showed pancytopenia, hypocomplementemia, and renal dysfunction, as well as the presence of lupus anticoagulant. Urinalysis showed abundant proteinuria and heavy microscopic hematuria. After performing a renal biopsy, we initiated immunosuppressive therapy and an anticoagulant. On the 22nd hospital day, microangiopathic hemolytic anemia appeared with the progression of thrombocytopenia and renal failure, and the patient subsequently underwent ten sessions of plasma exchange. After the commencement of the plasma exchange, her general condition improved. Her renal dysfunction, however, continued to progress, and hemodialysis was started on the 36th hospital day. The light microscopy showed severe endo- and extra-capillary proliferative glomerulonephritis with abundant crescents, and massive thrombi in the capillary lumen of the glomeruli. The arterioles contained occlusive hyaline materials. An immunofluorescence study showed granular staining of immunoglobulins and complements along the glomerular capillary wall. An electron microscopy examination revealed the presence of electron-dense deposits in the subepithelial and intramembranous areas of the glomeruli, but subendothelial deposits were absent. For cases with lupus nephritis (LN), immunosuppressive therapy based on corticosteroid remains the mainstay of treatment. However, immunosuppression alone may be insufficient when antiphospholipid antibody syndrome and thrombotic microangiopathy (TMA) are also present, and other treatment modalities including antiplatelet therapy, anticoagulation, and plasma exchange are likely to be necessary, as illustrated by the present case. Although the mechanism responsible for LN remains uncertain, we report a case of LN suggesting that TMA is associated with renal dysfunction.

Background/Aims: The role of matrix metalloproteinases (MMPs) in the pathogenesis of glomerular injury appears to be complex. To investigate the role of individual MMPs, we examined the course of Adriamycin-induced albuminuria and glomerulosclerosis in mice lacking either a gelatinase (MMP-9) or a collagenase (MMP-13). Methods: Adriamycin was administered to MMP-9 or MMP-13 knockout (KO) mice. Glomerular injury was assessed by the quantification of albuminuria, the glomerular injury score and type IV collagen immunostaining. Results: Treatment of mice with Adriamycin (18 mg/kg i.v.) resulted in marked albuminuria and glomerulosclerosis reaching a peak at 4–8 weeks. The albuminuria and glomerulosclerosis were significantly (p < 0.05) attenuated in both the MMP-9 KO and MMP-13 KO mice compared to controls. In contrast, treatment of wild-type mice with the broad-spectrum MMP inhibitor doxycycline did not have a beneficial effect on the albuminuria and glomerulosclerosis. Conclusion: These results support a role for both gelatinase (MMP-9) and collagenase (MMP-13) in the pathogenesis of glomerular injury in the Adriamycin-induced glomerulosclerosis model. MMP inhibitors with high specificity towards MMP-9 and/or MMP-13 may be potential future candidates to provide more effective therapies to inhibit the development of glomerulosclerosis.

One ultimate goal of hypertension therapy is to cause permanent reversal (“regression”) of already established hypertension. Our aim was to examine whether high-dose “pulse” treatment with a renin-angiotensin system inhibitor could cause regression of established hypertension and to link this action to reversal of arteriolar hypertrophy and changes in vascular matrix metalloproteinase activities. First, 16-week-old male spontaneously hypertensive rats (n=60) were pulse treated for 2 weeks with high-dose angiotensin-converting enzyme inhibitor (enalapril), angiotensin receptor blocker (candesartan), calcium channel blocker (nifedipine), or vasodilator (hydralazine) with or without salt restriction, and the long-term effects on blood pressure were examined. Second, spontaneously hypertensive rats were treated with angiotensin receptor blocker or calcium channel blocker, and the effects on renal gene expressions, arteriolar structure, and vascular matrix metalloproteinase were compared. Treatment of spontaneously hypertensive rats with different antihypertensive agents caused apparently similar reductions in blood pressure during the course of the pulse treatment, within the limitations of the tail-cuff method. After cessation of medications, blood pressure in the rats treated with renin-angiotensin system inhibitor remained reduced by >30 to 40 mm Hg for 4 months. No such effect was seen with calcium channel blocker or vasodilator. The 2-week angiotensin receptor blocker treatment induced a marked reversal of the arteriolar hypertrophy specifically in the small (30 to 100 μm) renal arterioles, together with increased expression and activity of matrix metalloproteinase-13. In conclusion, transient high-dose pulse treatment with angiotensin receptor blocker caused changes in vascular matrix metalloproteinase activity, specific reversal of renal arteriolar hypertrophy, and regression of hypertension in spontaneously hypertensive rats.

We have recently published that tubular epithelial cells affect the podocyte epigenome though nicotinic acid metabolism in diabetic nephropathy (DN), and we have named this relationship "proximal tubule-podocyte communication". In this review, we describe this novel mechanism in the early stage of DN, focusing on the function of renal tubular Sirt1 and Sirt1-related nicotinic acid metabolism. Mainly, we discuss the following three findings. First, we described the details of proximal tubule-podocyte communication. Second, we explained how Sirt1 regulates albuminuria via epigenetic mechanisms. This means that repeated high glucose stress triggers the initial changes in proximal tubules, which lead to the epigenetically irreversible glomerular damages. However, proximal tubular Sirt1 overexpression can rescue these changes. Our previous data indicated that the decrease in Sirt1 expression in proximal tubules caused the reduction in glomerular Sirt1 and the subsequent increase in glomerular Claudin-1. It seemed plausible that some humoral mediator is released from proximal tubules, migrates to podocytes and glomeruli, and affects Sirt1 expression in podocytes. Third, we mentioned a mediator connecting this communication, nicotinamide mononucleotide (NMN). We suggest the potential of Sirt1 or NMN as not only a therapeutic target but also as a prognostic marker of very early stage DN.

Hypertension is prevalent in over 25% of populations in developed countries, and poses an increasing economic burden on health resources. Therefore it is predicted that future medical treatment of hypertension will be increasingly affected by cost considerations. Several classes of antihypertensive drugs are used as first-line agents for the treatment of hypertension, but the economic impact of using these agents in different countries remains to be addressed. In this study, we compared health costs associated with treatment of hypertension using the calcium channel blocker amlodipine and the angiotensin-converting enzyme inhibitor enalapril in the US and Japan. Pharmaceutical costs and hospitalization costs were analyzed from established databases. The data for the prevalence of myocardial infarction and stroke were derived from the Framingham study and the Hisayama study. Analysis of the economic impacts using relative risk differences between the calcium channel blocker and angiotensin-converting enzyme inhibitor together with regional hospitalization costs resulted in an apparent 11.2 billion yen health cost reduction in favor of the calcium channel blocker in the case of Japan, in contrast to an apparent 5.7 billion yen reduction in favor of the angiotensin-converting enzyme inhibitor in the case of the US. The trends in Japan for 2000 and 2004 were similar. These results suggest that there are regional differences in the health costs associated with different classes of hypertensive agents, which could affect national policies on the choice of antihypertensive drugs. It is predicted that future treatment of hypertension will be increasingly tailored to the epidemiologic profiles and medical costs of individual communities.

Sirtuin 1 (Sirt1), a NAD[superscript +]-regulated deacetylase with numerous known positive effects on cellular and whole-body metabolism, is expressed in the renal cortex and medulla. It is known to have protective effects against age-related disease, including diabetes. Here we investigated the protective role of Sirt1 in diabetic renal damage. We found that Sirt1 in proximal tubules (PTs) was downregulated before albuminuria occurred in streptozotocin-induced or obese (db/db) diabetic mice. PT-specific SIRT1 transgenic and Sirt1 knockout mice showed prevention and aggravation of the glomerular changes that occur in diabetes, respectively, and nondiabetic knockout mice exhibited albuminuria, suggesting that Sirt1 in PTs affects glomerular function. Downregulation of Sirt1 and upregulation of the tight junction protein Claudin-1 by SIRT1-mediated epigenetic regulation in podocytes contributed to albuminuria. We did not observe these phenomena in 5/6 nephrectomized mice. We also demonstrated retrograde interplay from PTs to glomeruli using nicotinamide mononucleotide (NMN) from conditioned medium, measurement of the autofluorescence of photoactivatable NMN and injection of fluorescence-labeled NMN. In human subjects with diabetes, the levels of SIRT1 and Claudin-1 were correlated with proteinuria levels. These results suggest that Sirt1 in PTs protects against albuminuria in diabetes by maintaining NMN concentrations around glomeruli, thus influencing podocyte function., Japan. Ministry of Education, Culture, Sports, Science and Technology (Grant 22790800)

The transcription factor Kruppel-like factor 4 (KLF4) has the ability, along with other factors, to reprogram somatic cells into induced pluripotent stem (iPS) cells. Here, we determined that KLF4 is expressed in kidney glomerular podocytes and is decreased in both animal models and humans exhibiting a proteinuric. Transient restoration of KLF4 expression in podocytes of diseased glomeruli in vivo, either by gene transfer or transgenic expression, resulted in a sustained increase in nephrin expression and a decrease in albuminuria. In mice harboring podocyte-specific deletion of Klf4, adriamycin-induced proteinuria was substantially exacerbated, although these animals displayed minimal phenotypical changes prior to adriamycin administration. KLF4 overexpression in cultured human podocytes increased expression of nephrin and other epithelial markers and reduced mesenchymal gene expression. DNA methylation profiling and bisulfite genomic sequencing revealed that KLF4 expression reduced methylation at the nephrin promoter and the promoters of other epithelial markers; however, methylation was increased at the promoters of genes encoding mesenchymal markers, suggesting selective epigenetic regulation of podocyte gene expression. Together, these results suggest that KLF4 epigenetically modulates podocyte phenotype and function and that the podocyte epigenome can be targeted for direct intervention and reduction of proteinuria.

We report a case of membranous nephropathy with primary biliary cirrhosis (PBC). A 76-year-old Japanese man had been treated for PBC and was referred to our department because of acute severe proteinuria (10 g/day). Renal biopsy was performed and was compatible with a diagnosis of membranous nephropathy. The patient was treated with cyclosporine A (CsA; Neoral®), which was followed by normalization of liver function and partial remission of proteinuria (0.68 g/day) within six months without any significant side effects. This case suggests that CsA monotherapy is effective for the treatment of both liver dysfunction and membranous nephropathy associated with PBC.

Background/Aims: We have previously shown that treatment of spontaneously hypertensive rats (SHR) with an angiotensin receptor blocker (ARB) during the ‘critical period’ from age 3 to 10 weeks confers protection against L-NAME-induced renal injury later in life. The aim of this study was to examine the effects of transient prepubertal exposure to ARB on the development of nephropathy in streptozotocin-induced diabetic SHR and to compare the results with other antihypertensive agents including a mineralocorticoid receptor antagonist (MR-ant). Methods: Male SHR (n = 43) were transiently treated with candesartan (ARB), potassium canreonate (the active metabolite of the MR-ant spironolactone) or hydralazine (vasodilator) between 3 and 10 weeks of age with untreated rats serving as controls. An additional group was treated continuously with candesartan throughout the study. Rats were injected with streptozotocin to induce diabetes at age 16 weeks and followed until age 8 months. Results: Diabetic control rats showed signs of diabetic nephropathy including albuminuria and mesangial expansion. These changes were significantly suppressed in rats exposed to ARB or MR-ant. Systolic blood pressure was significantly reduced compared to controls in the ARB (transient) and ARB (sustained) groups, but not in the MR-ant or vasodilator groups. Conclusion: Transient prepubertal exposure to ARB or MR-ant, but not vasodilator, confers protection against the later development of diabetic nephropathy and involves blood pressure-independent protective mechanisms.

The incidence of hypertension and hypertensive renal disease is increasing worldwide, and new strategies to prevent these diseases need to be investigated. The aims of this study were 1) to examine if transient exposure to an angiotensin receptor blocker (ARB) during an early period in hypertension development confers protection against subsequent worsening of hypertension and renal injury induced by the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME), and 2) conversely, to examine the effects of transient exposure to angiotensin II (Ang II) during the same period. First, spontaneously hypertensive rats (SHR) were treated transiently from age 3 to 10 weeks with an ARB (candesartan cilexetil), a calcium channel antagonist or a vasodilator, then taken off treatment for 2 months. Administration of L-NAME at age 18 weeks caused severe hypertension and renal injury. However, the rats that had been exposed to the ARB not only had a lower blood pressure, but also failed to show signs of renal injury or increase of oxidative stress. Furthermore, the elevation of components of the renin-angiotensin-aldosterone system was also suppressed in these rats. In the second study, Wistar-Kyoto rats (WKY) and SHR were exposed to Ang II from age 4 to 8 weeks. The follow-up showed that the blood pressures in the WKY remained elevated compared to controls, while the SHR had heightened increases in blood pressure, renal renin mRNA, and urinary 8-hyroxydeoxyguanosine after L-NAME administration. Together, these experiments demonstrate that transient treatment of rats during an early phase in the development of hypertension with an ARB suppresses the renin-angiotensin-aldosterone system and confers long-term protection against subsequent L-NAME-induced renal injury and increases in renal oxidative stress. Conversely, developmental exposure to Ang II during this "critical" period had the opposite effect, predisposing rats to higher blood pressure, renal injury, and oxidative stress after L-NAME administration.

Understanding mechanisms that contribute to the regression of glomerulosclerosis is important for developing new strategies to treat chronic kidney disease. We reported that transient high-dose treatment with an angiotensin receptor blocker causes regression of renal arteriolar hypertrophy and hypertension in spontaneously hypertensive rats. To extend those findings to another form of kidney disease, we examined the short- and long-term effects of transient high-dose angiotensin receptor blocker treatment in a mouse model of adriamycin-induced glomerulosclerosis. A 2-week course of candesartan caused a dose-dependent regression of established glomerulosclerotic lesions sustained for over 6 months following cessation of treatment. Highly sensitive in situ zymography and activity assays showed that glomerular matrix metalloproteinase (MMP)-2 activity was increased after high-dose angiotensin blocker therapy. Treatment of cultured podocytes with candesartan resulted in an increase in MMP-2 activity. The regression of glomerulosclerosis was partially attenuated in mice pretreated with the MMP inhibitor doxycycline, as well as in MMP-2 knockout mice. Our results suggest that transient high-dose angiotensin receptor blocker treatment effectively induced sustained regression of glomerulosclerosis by a mechanism mediated, in part, by changes in MMP-2 activity.