Publications by authors named "Shigeru Shibata"

85 Publications

Renal Involvement as Rare Acute Tubulointerstitial Nephritis in a Patient with Eosinophilic Disorder Treated with Early Add-on Administration of Mepolizumab.

Intern Med 2021 Jun 5. Epub 2021 Jun 5.

Department of Internal Medicine, Teikyo University School of Medicine, Japan.

A 39-year-old man presented with peripheral eosinophilia, pulmonary eosinophilic infiltrate, and renal failure due to acute tubulointerstitial nephritis (TIN). He had experienced childhood asthma and was negative for anti-neutrophil cytoplasmic antibody (ANCA). He was tentatively diagnosed with ANCA-negative eosinophilic granulomatous polyangiitis (EGPA) or idiopathic hypereosinophilic syndrome (HES). Renal involvement of isolated TIN with eosinophil infiltration is rare in EGPA and HES and does not seem to have a good prognosis in the literature. However, his condition improved well with corticosteroids and mepolizumab. The revised classification of EGPA based on the etiology should dictate the proper treatment in suspected EGPA patients with nonsystemic vasculitis.
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http://dx.doi.org/10.2169/internalmedicine.7490-21DOI Listing
June 2021

Activation of Rac1-Mineralocorticoid Receptor Pathway Contributes to Renal Injury in Salt-Loaded Mice.

Hypertension 2021 Jul 1;78(1):82-93. Epub 2021 Jun 1.

Division of Clinical Epigenetics, Research Center for Advanced Science and Technology, The University of Tokyo, Japan (D.H., M.N., N.A., W.K., S.O., S.S., T.M., T.F.).

[Figure: see text].
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http://dx.doi.org/10.1161/HYPERTENSIONAHA.121.17263DOI Listing
July 2021

A Ruptured Jejunal Arterial Aneurysm in a Young Woman Undergoing Chronic Hemodialysis Due to Myeloperoxidase-antineutrophil Cytoplasmic Antibody-associated Vasculitis.

Intern Med 2021 Mar 29. Epub 2021 Mar 29.

Department of Internal Medicine, Teikyo University School of Medicine, Japan.

A 21-year-old woman was admitted to our hospital because of massive intestinal bleeding. She started hemodialysis due to myeloperoxidase antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) at 18 years of age. Her ANCA titers remained stable; however, her C-reactive protein increased on 5 mg/day prednisolone before admission. Computed tomography angiography revealed a ruptured jejunal arterial aneurysm. Transcatheter arterial embolization, blood transfusion and the reinforcement of steroid therapy resolved her symptoms of AAV. Our case of a young patient with AAV and medium-sized arterial vasculitis is rare and emphasizes that the ANCA titer does not always rise, especially in patients with nonrenal vasculitis flare-ups.
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http://dx.doi.org/10.2169/internalmedicine.6721-20DOI Listing
March 2021

Urinary phosphate-containing nanoparticle contributes to inflammation and kidney injury in a salt-sensitive hypertension rat model.

Commun Biol 2020 10 15;3(1):575. Epub 2020 Oct 15.

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, 173-8605, Japan.

Although disturbed phosphate metabolism frequently accompanies chronic kidney disease (CKD), its causal role in CKD progression remains unclear. It is also not fully understood how excess salt induces organ damage. We here show that urinary phosphate-containing nanoparticles promote kidney injury in salt-sensitive hypertension. In Dahl salt-sensitive rats, salt loading resulted in a significant increase in urinary phosphate excretion without altering serum phosphate levels. An intestinal phosphate binder sucroferric oxyhydroxide attenuated renal inflammation and proteinuria in this model, along with the suppression of phosphaturia. Using cultured proximal tubule cells, we confirmed direct pathogenic roles of phosphate-containing nanoparticles in renal tubules. Finally, transcriptome analysis revealed a potential role of complement C1q in renal inflammation associated with altered phosphate metabolism. These data demonstrate that increased phosphate excretion promotes renal inflammation in salt-sensitive hypertension and suggest a role of disturbed phosphate metabolism in the pathophysiology of hypertensive kidney disease and high salt-induced kidney injury.
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http://dx.doi.org/10.1038/s42003-020-01298-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7562875PMC
October 2020

Pyuria without Casts and Bilateral Kidney Enlargement Are Probable Hallmarks of Severe Acute Kidney Injury Induced by Acute Pyelonephritis: A Case Report and Literature Review.

Intern Med 2021 Jan 5;60(2):293-298. Epub 2020 Sep 5.

Department of Internal Medicine, Teikyo University School of Medicine, Japan.

The patient was a 38-year-old man who had experienced nausea and fever for a few days and presented with back pain, oliguria, and pyuria, suggesting acute pyelonephritis (APN). He showed acute kidney injury (AKI) with bilateral kidney enlargement and was using nonsteroidal anti-inflammatory drugs (NSAIDs). AKI-induced by APN was confirmed by kidney biopsy. The AKI was successfully treated with antibiotic therapy. A search of the relevant literature for reports on histopathologically-proven APN-induced severe AKI revealed that the key characteristics were bilateral kidney enlargement with pyuria without casts. Oligoanuria was frequently associated with APN-induced severe AKI, and NSAID use may be a possible risk factor. Prompt antibiotic treatment based on the clinical characteristics of APN-induced AKI can improve the renal outcome.
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http://dx.doi.org/10.2169/internalmedicine.5721-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7872795PMC
January 2021

Hypertension and related diseases in the era of COVID-19: a report from the Japanese Society of Hypertension Task Force on COVID-19.

Hypertens Res 2020 10 31;43(10):1028-1046. Epub 2020 Jul 31.

Department of Endocrinology, Metabolism and Nephrology, Keio University School of Medicine, Tokyo, Japan.

Coronavirus disease-2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected more than seven million people worldwide, contributing to 0.4 million deaths as of June 2020. The fact that the virus uses angiotensin-converting enzyme (ACE)-2 as the cell entry receptor and that hypertension as well as cardiovascular disorders frequently coexist with COVID-19 have generated considerable discussion on the management of patients with hypertension. In addition, the COVID-19 pandemic necessitates the development of and adaptation to a "New Normal" lifestyle, which will have a profound impact not only on communicable diseases but also on noncommunicable diseases, including hypertension. Summarizing what is known and what requires further investigation in this field may help to address the challenges we face. In the present review, we critically evaluate the existing evidence for the epidemiological association between COVID-19 and hypertension. We also summarize the current knowledge regarding the pathophysiology of SARS-CoV-2 infection with an emphasis on ACE2, the cardiovascular system, and the kidney. Finally, we review evidence on the use of antihypertensive medication, namely, ACE inhibitors and angiotensin receptor blockers, in patients with COVID-19.
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http://dx.doi.org/10.1038/s41440-020-0515-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7393334PMC
October 2020

Role of the Ubiquitin Proteasome System in the Regulation of Blood Pressure: A Review.

Int J Mol Sci 2020 Jul 28;21(15). Epub 2020 Jul 28.

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo 173-8605, Japan.

The kidney and the vasculature play crucial roles in regulating blood pressure. The ubiquitin proteasome system (UPS), a multienzyme process mediating covalent conjugation of the 76-amino acid polypeptide ubiquitin to a substrate protein followed by proteasomal degradation, is involved in multiple cellular processes by regulating protein turnover in various tissues. Increasing evidence demonstrates the roles of UPS in blood pressure regulation. In the kidney, filtered sodium is reabsorbed through diverse sodium transporters and channels along renal tubules, and studies conducted till date have provided insights into the complex molecular network through which ubiquitin ligases modulate sodium transport in different segments. Components of these pathways include ubiquitin ligase neuronal precursor cell-expressed developmentally downregulated 4-2, Cullin-3, and Kelch-like 3. Moreover, accumulating data indicate the roles of UPS in blood vessels, where it modulates nitric oxide bioavailability and vasoconstriction. Cullin-3 not only regulates renal salt reabsorption but also controls vascular tone using different adaptor proteins that target distinct substrates in vascular smooth muscle cells. In endothelial cells, UPS can also contribute to blood pressure regulation by modulating endothelial nitric oxide synthase. In this review, we summarize current knowledge regarding the role of UPS in blood pressure regulation, focusing on renal sodium reabsorption and vascular function.
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http://dx.doi.org/10.3390/ijms21155358DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7432568PMC
July 2020

PGI Analog Attenuates Salt-Induced Renal Injury through the Inhibition of Inflammation and Rac1-MR Activation.

Int J Mol Sci 2020 Jun 22;21(12). Epub 2020 Jun 22.

Division of Clinical Epigenetics, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo 153-8904, Japan.

Renal inflammation is known to be involved in salt-induced renal damage, leading to end-stage renal disease. This study aims to evaluate the role of inflammation in anti-inflammatory and renoprotective effects of beraprost sodium (BPS), a prostaglandin I (PGI) analog, in Dahl salt-sensitive (DS) rats. Five-week-old male DS rats were fed a normal-salt diet (0.5% NaCl), a high-salt diet (8% NaCl), or a high-salt diet plus BPS treatment for 3 weeks. BPS treatment could inhibit marked proteinuria and renal injury in salt-loaded DS rats with elevated blood pressure, accompanied by renal inflammation suppression. Notably, high salt increased renal expression of active Rac1, followed by increased Sgk1 expressions, a downstream molecule of mineralocorticoid receptor (MR) signal, indicating salt-induced activation of Rac1-MR pathway. However, BPS administration inhibited salt-induced Rac1-MR activation as well as renal inflammation and damage, suggesting that Rac1-MR pathway is involved in anti-inflammatory and renoprotective effects of PGI. Based upon Rac1 activated by inflammation, moreover, BPS inhibited salt-induced activation of Rac1-MR pathway by renal inflammation suppression, resulting in the attenuation of renal damage in salt-loaded DS rats. Thus, BPS is efficacious for the treatment of salt-induced renal injury.
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http://dx.doi.org/10.3390/ijms21124433DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7353033PMC
June 2020

Cardio-renal protective effect of the xanthine oxidase inhibitor febuxostat in the 5/6 nephrectomy model with hyperuricemia.

Sci Rep 2020 06 9;10(1):9326. Epub 2020 Jun 9.

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo, 173-8605, Japan.

Although hyperuricemia has been shown to be associated with the progression of cardiovascular disorder and chronic kidney disease (CKD), there is conflicting evidence as to whether xanthine oxidase (XO) inhibitors confer organ protection besides lowering serum urate levels. In this study, we addressed the cardio-renal effects of XO inhibition in rodent CKD model with hyperuricemia. Sprague-Dawley rats underwent 5/6 nephrectomy and received a uricase inhibitor oxonic acid for 8 weeks (RK + HUA rats). In some rats, a XO inhibitor febuxostat was administered orally. Compared with control group, RK + HUA group showed a significant increase in albuminuria and renal injury. Febuxostat reduced serum uric acid as well as urinary albumin levels. Histological and immunohistochemical analysis of the kidney revealed that febuxostat alleviated glomerular, tubulointerstitial, and arteriolar injury in RK + HUA rats. Moreover, in the heart, RK + HUA showed individual myofiber hypertrophy and cardiac fibrosis, which was significantly attenuated by febuxostat. We found that renal injury and the indices of cardiac changes were well correlated, confirming the cardio-renal interaction in this model. Finally, NF-E2-related factor 2 (Nrf2) and the downstream target heme oxygenase-1 (HO-1) protein levels were increased both in the heart and in the kidney in RK + HUA rats, and these changes were alleviated by febuxostat, suggesting that tissue oxidative stress burden was attenuated by the treatment. These data demonstrate that febuxostat protects against cardiac and renal injury in RK + HUA rats, and underscore the pathological importance of XO in the cardio-renal interaction.
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http://dx.doi.org/10.1038/s41598-020-65706-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7283314PMC
June 2020

Upregulation of renal Na-K-2Cl cotransporter 2 in obese diabetes mellitus via a vasopressin receptor 2-dependent pathway.

Biochem Biophys Res Commun 2020 04 5;524(3):710-715. Epub 2020 Feb 5.

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, 173-8605, Japan. Electronic address:

Na-K-2Cl cotransporter 2 (NKCC2) in thick ascending limb (TAL) in the kidney plays a central role in tubuloglomerular feedback (TGF) system by sensing NaCl delivery to the distal tubules. Although accumulating data indicate that dysregulated TGF contributes to the progression of diabetic complications, the regulation of NKCC2 in diabetes mellitus (DM) remains unclear. We here show that NKCC2 is overactivated via a vasopressin receptor 2 (V2R)-dependent mechanism in db/db mice, a mouse model of obese DM. Compared with db/+ mice, we found that both aquaporin 2 and NKCC2 levels were significantly increased in the kidney in db/db mice. Immunohistochemical analysis of V2R and NKCC2 in the kidney demonstrated that V2R is present in the TAL, as well as in the collecting duct. Moreover, the administration of tolvaptan, a selective V2R antagonist, sharply decreased aquaporin 2 and NKCC2 in db/db mice, confirming the causal role of V2R signaling in NKCC2 induction in this model. Although tolvaptan reduced aquaporin 2 abundance also in db/+ mice, its effect on NKCC2 was modest compared with db/db mice. In total kidney lysates, uromodulin expression was not altered between db/+ and db/db mice, suggesting that V2R signaling alters NKCC2 without altering uromodulin levels. These data implicate the dysregulation of NKCC2 in the pathophysiology of type 2 DM, and underscore the complex nature of fluid volume disorders in diabetic kidney disease.
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http://dx.doi.org/10.1016/j.bbrc.2020.01.142DOI Listing
April 2020

ABCG2 expression and uric acid metabolism of the intestine in hyperuricemia model rat.

Nucleosides Nucleotides Nucleic Acids 2020 25;39(5):744-759. Epub 2020 Jan 25.

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan.

To elucidate roles of the intestine in uric acid (UA) metabolism, we examined ABCG2 expression, tissue UA content and xanthine oxidoreductase (XOR) activity in different intestinal segments. Male SD rats were assigned to control group or oxonic acid-induced hyperuricemia (HUA) group. In control rats, ABCG2 was present both in villi and crypts in each segment. Tissue UA content and XOR activity were relatively high in duodenum and jejunum. However, in HUA rats, tissue UA content was significantly elevated in the ileum, whereas it remained unaltered in other segments. Moreover, ABCG2 expression in the HUA group was upregulated both in the villi and crypts of the ileum. These data indicate that the ileum may play an important role in the extra-renal UA excretion.
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http://dx.doi.org/10.1080/15257770.2019.1694684DOI Listing
December 2020

Clinicopathological Implications of Proteinuria after Long-Term Isolated Hematuria due to Thin Basement Membrane Nephropathy and Focal Segmental Glomerulosclerosis.

Case Rep Nephrol 2019 17;2019:1627392. Epub 2019 Dec 17.

Department of Internal Medicine, Teikyo University School of Medicine, Itabashi-ku, Tokyo, Japan.

A 45-year-old obese man presented with persistent hematuria for 21 years. At the age of 37, he developed hypertension and proteinuria which later increased up to 1.6 g/g creatinine. Kidney biopsy revealed thin basement membrane nephropathy (TBMN) and focal segmental glomerulosclerosis (FSGS), which explained his urinary abnormalities. Although a subgroup of TBMN can be complicated by FSGS, his FSGS was associated with obesity because of its histological features. Reduction of body weight and increasing a dose of angiotensin-receptor blocker could transiently reduce the amount of proteinuria. Clinicopathological implications of proteinuria after long-term hematuria by TBMN and FSGS were further discussed.
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http://dx.doi.org/10.1155/2019/1627392DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6959157PMC
December 2019

Perfecting a high hypoxanthine phosphoribosyltransferase activity-uricase KO mice to test the effects of purine- and non-purine-type xanthine dehydrogenase (XDH) inhibitors.

Br J Pharmacol 2020 05 18;177(10):2274-2285. Epub 2020 Feb 18.

Department of Human Physiology & Pathology, Faculty of Pharma-Science, Teikyo University, Tokyo, Japan.

Background And Purpose: Purine metabolism in mice and human differ in terms of uricase (Uox) activity as well as hypoxanthine phosphoribosyltransferase (HPRT) activity. The aim of this study was the establishment of high HPRT activity-Uox knockout (KO) mice as a novel hyperuricaemic model. Then to investigate the effects of purine-type xanthine dehydrogenase (XDH) inhibitor, allopurinol, and non-purine-type XDH inhibitor, topiroxostat, on purine metabolism.

Experimental Approach: A novel hyperuricaemic mouse model was established by mating B6-ChrXC mice with uricase KO mice. The pharmacological effects of allopurinol and topiroxostat were explored by evaluating urate, hypoxanthine, xanthine and creatinine in the plasma and urine of these model mice. Furthermore, we analysed the effect of both drugs on erythrocyte hypoxanthine phosphoribosyltransferase activity.

Key Results: Plasma urate level and urinary urate/creatinine ratio significantly decreased after administration of allopurinol 30 mg·kg or topiroxostat 1 mg·kg for 7 days. The urate-lowering effect was equivalent for allopurinol and topiroxostat. However, the urinary hypoxanthine/creatinine ratio and xanthine/creatinine ratio after treatment with topiroxostat were significantly lower than for allopurinol. In addition, the urinary oxypurine/creatinine ratio was significantly lowered after treatment with topiroxostat, but allopurinol elicited no such effect. Furthermore, allopurinol inhibited mouse erythrocyte hypoxanthine phosphoribosyltransferase, while topiroxostat did not.

Conclusions And Implications: High hypoxanthine phosphoribosyltransferase activity- uricase KO mice were established as a novel hyperuricaemic animal model. In addition, topiroxostat, a non-purine-type xanthine dehydrogenase inhibitor, elicited a potent plasma urate-lowering effect. However, unlike allopurinol, topiroxostat did not perturb the salvage pathway, resulting in lowered total oxypurine excretion.
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http://dx.doi.org/10.1111/bph.14978DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7174878PMC
May 2020

25(OH)D stimulates the expression of vitamin D target genes in renal tubular cells when Cyp27b1 is abrogated.

J Steroid Biochem Mol Biol 2020 05 13;199:105593. Epub 2020 Jan 13.

Department of Biochemistry, Teikyo University School of Medicine, Tokyo, Japan.

Recently, it was reported that 25(OH)D (25D3) has physiological bioactivity in certain tissues derived from Cyp27b1 knockout mice. To investigate the function of 25D3 in the kidney as an informational crossroad of various calciotropic substances, we employed the CRISPR-Cas9 system to knock out Cyp27b1 in the mouse renal distal tubular mDCT cell line. Unlike the previously reported mice in which Cyp27b1 was targeted systemically, Cyp27b1 knockout mDCT cells did not produce any measurable 1α,25(OH)D (1,25D3) after 25D3 administration. As was seen with treatment of Cyp27b1 knockout mDCT cells with ≥10 M of 1,25D3, the administration of 10 M of 25D3 translocated the vitamin D receptor (VDR) into the nucleus and promoted the expression of the representative 1,25D3-responsive gene Cyp24a1. The exhaustive target gene profiles of 25D3 were similar to those of 1,25D3. Subsequently, we confirmed that 25D3 induced the expression of the calcium reabsorption-related gene calbindin-D9K, in a way similar to 1,25D3. We also found that 1,25D3 and 25D3 induced the expression of the megalin gene. A chromatin immunoprecipitation assay identified two vitamin D response elements in the upstream region of the megalin gene that seemed to contribute to its expression. Together, we surmise that the ability of 25D3 to stimulate VDR target genes may provide a novel perspective for its role in certain tissues.
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http://dx.doi.org/10.1016/j.jsbmb.2020.105593DOI Listing
May 2020

Role of Pendrin in the Pathophysiology of Aldosterone-Induced Hypertension.

Authors:
Shigeru Shibata

Am J Hypertens 2019 06;32(7):607-613

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan.

The recent advances in genetics and molecular biology have resulted in the characterization of key components that critically regulate renal NaCl transport and blood pressure. Pendrin is a Cl-/HCO3- exchanger that is highly expressed in thyroid, inner ear, and kidney. In the kidney, it is selectively present at the apical membrane in non-α intercalated cells of the connecting tubules and cortical collecting duct. Besides its role in acid/base homeostasis, accumulating studies using various genetically modified animals have provided compelling evidence that pendrin regulates extracellular fluid volume and electrolyte balance at the downstream of aldosterone signaling. We have shown that angiotensin II and aldosterone cooperatively control pendrin abundance partly through mammalian target of rapamycin signaling and mineralocorticoid receptor dephosphorylation, which is necessary for the kidney to prevent extracellular fluid loss and electrolyte disturbances under physiologic perturbations. In line with the experimental observations, several clinical data indicated that the impaired pendrin function can cause fluid and electrolyte abnormalities in humans. The purpose of this review is to provide an update on the recent progress regarding the role of pendrin in fluid and electrolyte homeostasis, as well as in the pathophysiology of hypertension associated with mineralocorticoid receptor signaling.
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http://dx.doi.org/10.1093/ajh/hpz054DOI Listing
June 2019

A Case of Rheumatoid Arthritis Presenting with Renal Thrombotic Microangiopathy Probably due to a Combination of Chronic Tacrolimus Arteriolopathy and Severe Hypertension.

Case Rep Nephrol 2019 6;2019:3923190. Epub 2019 Mar 6.

Department of Internal Medicine, Teikyo University School of Medicine, Itabashi-ku, Tokyo, Japan.

A 51-year-old woman with rheumatoid arthritis presented with mild hypertension 20 months after tacrolimus treatment and developing proteinuria 24 months after the treatment. Tacrolimus was discontinued 27 months after the treatment, followed by heavy proteinuria, accelerated hypertension, and deteriorating renal function without ocular fundus lesions as a clinical sign of malignant hypertension. Renal biopsy revealed malignant nephrosclerosis characterized by subacute and chronic thrombotic microangiopathy (TMA), involving small arteries, arterioles, and glomeruli. Focal segmental glomerulosclerosis, probably secondary to chronic TMA, was identified as a cause of heavy proteinuria. The zonal tubulointerstitial injury caused by subacute TMA may have mainly contributed to deteriorating renal function. The presence of nodular hyalinosis in arteriolar walls was indicative of tacrolimus-associated nephrotoxicity. Together with other antihypertensive drugs, administration of aliskiren stabilized renal function with reducing proteinuria. Owing to the preexisting proteinuria prior to severe hypertension and the complex renal histopathology, we postulated that chronic TMA, which was initially triggered by tacrolimus, was aggravated by severe hypertension, resulting in overt renal TMA.
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http://dx.doi.org/10.1155/2019/3923190DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6431373PMC
March 2019

A Patient with MPO-ANCA-positive IgA Nephropathy Diagnosed with the Clinical Onset of Macrohematuria.

Intern Med 2019 Jul 28;58(14):2051-2056. Epub 2019 Mar 28.

Department of Internal Medicine, Teikyo University School of Medicine, Japan.

A 21-year-old woman presented with renal dysfunction during macrohematuria. A kidney biopsy revealed IgA nephropathy with a small percentage of crescent formation and macrohematuria-associated tubular injury. Macrohematuria-associated acute kidney injury could explain her renal dysfunction. However, she was seropositive for myeloperoxidase (MPO)-anti-neutrophil cytoplasmic antibody (ANCA) and showed fibrin deposition around one arteriole. Corticosteroids and mycophenolate mofetil were administered as for ANCA vasculitis, and the serum creatinine, abnormal urinalysis and MPO-ANCA titer all gradually ameliorated. The presence of extra-glomerular vasculitis, which was probably induced by ANCA, suggested that MPO-ANCA was an exacerbating factor for her prolonged renal dysfunction. This condition has so far only rarely been addressed in ANCA-positive IgA nephropathy.
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http://dx.doi.org/10.2169/internalmedicine.2475-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6702016PMC
July 2019

Inhibition of Sodium Glucose Cotransporter 2 Attenuates the Dysregulation of Kelch-Like 3 and NaCl Cotransporter in Obese Diabetic Mice.

J Am Soc Nephrol 2019 05 26;30(5):782-794. Epub 2019 Mar 26.

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan;

Background: Mechanisms underlying the frequent association between salt-sensitive hypertension and type 2 diabetes remain obscure. We previously found that protein kinase C (PKC) activation phosphorylates Kelch-like 3 (KLHL3), an E3 ubiquitin ligase component, at serine 433. We investigated whether impaired KLHL3 activity results in increased renal salt reabsorption NaCl cotransporter (NCC).

Methods: We used the db/db diabetes mouse model to explore KLHL3's role in renal salt handling in type 2 diabetes and evaluated mechanisms of KLHL3 dysregulation in cultured cells.

Results: We observed PKC activity in the db/db mouse kidney and phosphorylation of serine 433 in KLHL3 (KLHL3). This modification prevents binding of with-no-lysine (WNK) kinases; however, total KLHL3 levels were decreased, indicating severely impaired KLHL3 activity. This resulted in WNK accumulation, activating NCC in distal convoluted tubules. Ipragliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, lowered PKC activity in distal convoluted tubule cells and reduced KLHL3 and NCC levels, whereas the thiazolidinedione pioglitazone did not, although the two agents similarly reduced in blood glucose levels. We found that, in human embryonic kidney cells expressing KLHL3 and distal convoluted tubule cells, cellular glucose accumulation increased KLHL3 levels through PKC. Finally, the effect of PKC inhibition in the kidney of db/db mice confirmed PKC's causal role in KLHL3 and NCC induction.

Conclusions: Dysregulation of KLHL3 is involved in the pathophysiology of type 2 diabetes. These data offer a rationale for use of thiazide in individuals with diabetes and provide insights into the mechanism for cardiorenal protective effects of SGLT2 inhibitors.
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http://dx.doi.org/10.1681/ASN.2018070703DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6493993PMC
May 2019

Group I metabotropic glutamate receptor activation induces TRPC6-dependent calcium influx and RhoA activation in cultured human kidney podocytes.

Biochem Biophys Res Commun 2019 04 16;511(2):374-380. Epub 2019 Feb 16.

Department of Nephrology, The Second Affiliated Hospital of Harbin Medical University, Harbin, China; Institute of Nephrology, Harbin Medical University, Harbin, China. Electronic address:

Researches have shown that mice lacking the metabotropic glutamate receptor 1 (mGluR) showed albuminuria, remodeling of F-actin, with loss of stress fibers. Selective group I mGluRs agonist (S)-3,5-dihydroxyphenylglycine (DHPG) attenuated albuminuria in several rodent models of nephrotic syndrome. However, the molecular mechanism is obscure. Using a human podocyte cell line, we here investigated the molecular mechanisms of group I mGluRs-induced calcium influx and the formation of stress fibers. Our data showed that group I mGluRs activation by DHPG induced a significant calcium influx, and promoted cytoskeletal stress fiber formation and focal adhesions in podocytes. Pre-incubating podocytes with non-selective inhibitor of transient receptor potential channels (TRPC), or the knockdown of TRPC6 attenuated the calcium influx and the stress fiber formation induced by DHPG. Further, DHPG resulted in an increase of active RhoA expression. However, the knockdown of RhoA by siRNA abolished the DHPG-induced increase in stress fibers. Additionally, nonselective inhibitors of TRPC or TRPC6 knockdown clearly inhibited RhoA activation induced by DHPG, as assessed by Glutathione-S-transferase pull-down assay followed by Western blotting. Taken together, our findings suggest TRPC6 regulates actin stress fiber formation and focal adhesions via the RhoA pathway in response to group I mGluRs activation. Our data can potentially explain the mechanism of protective action of group I mGluRs in glomerular podocyte injury.
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http://dx.doi.org/10.1016/j.bbrc.2019.02.062DOI Listing
April 2019

Phosphate binding by sucroferric oxyhydroxide ameliorates renal injury in the remnant kidney model.

Sci Rep 2019 02 11;9(1):1732. Epub 2019 Feb 11.

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan.

Recent clinical studies indicate that the disturbed phosphate metabolism in chronic kidney disease (CKD) may facilitate kidney injury; nonetheless, the causal role of phosphate in CKD progression remains to be elucidated. Here, we show that intestinal phosphate binding by sucroferric oxyhydroxide (SF) ameliorates renal injury in the rat remnant kidney model. Sprague-Dawley rats received 5/6 nephrectomy (RK) and had a normal chow or the same diet containing SF (RK + SF). RK rats showed increased plasma FGF23 and phosphate levels, which were suppressed by SF administration. Of note, albuminuria in RK rats was significantly ameliorated by SF at both 4 and 8 weeks. SF also attenuated glomerulosclerosis and tubulointerstitial injury. Moreover, several different approaches confirmed the protective effects on podocytes, explaining the attenuation of glomerulosclerosis and albuminuria observed in this study. As a possible mechanism, we found that SF attenuated renal inflammation and fibrosis in RK rats. Interestingly, von Kossa staining of the kidney revealed calcium phosphate deposition in neither RK nor RK + SF rats; however, plasma levels of calciprotein particles were significantly reduced by SF. These data indicate that latent positive phosphate balance accelerates CKD progression from early stages, even when overt ectopic calcification is absent.
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http://dx.doi.org/10.1038/s41598-018-38389-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370755PMC
February 2019

Calcineurin dephosphorylates Kelch-like 3, reversing phosphorylation by angiotensin II and regulating renal electrolyte handling.

Proc Natl Acad Sci U S A 2019 02 4;116(8):3155-3160. Epub 2019 Feb 4.

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, 173-8605 Tokyo, Japan;

Calcineurin is a calcium/calmodulin-regulated phosphatase known for its role in activation of T cells following engagement of the T cell receptor. Calcineurin inhibitors (CNIs) are widely used as immunosuppressive agents; common adverse effects of CNIs are hypertension and hyperkalemia. While previous studies have implicated activation of the Na-Cl cotransporter (NCC) in the renal distal convoluted tubule (DCT) in this toxicity, the molecular mechanism of this effect is unknown. The renal effects of CNIs mimic the hypertension and hyperkalemia that result from germ-line mutations in with-no-lysine (WNK) kinases and the Kelch-like 3 (KLHL3)-CUL3 ubiquitin ligase complex. WNK4 is an activator of NCC and is degraded by binding to KLHL3 followed by WNK4's ubiquitylation and proteasomal degradation. This binding is prevented by phosphorylation of KLHL3 at serine 433 (KLHL3) via protein kinase C, resulting in increased WNK4 levels and increased NCC activity. Mechanisms mediating KLHL3 dephosphorylation have heretofore been unknown. We now demonstrate that calcineurin expressed in DCT is a potent KLHL3 phosphatase. In mammalian cells, the calcium ionophore ionomycin, a calcineurin activator, reduces KLHL3 levels, and this effect is reversed by the calcineurin inhibitor tacrolimus and by siRNA-mediated knockdown of calcineurin. In vivo, tacrolimus increases levels of KLHL3, resulting in increased levels of WNK4, phosphorylated SPAK, and NCC. Moreover, tacrolimus attenuates KLHL3-mediated WNK4 ubiquitylation and degradation, while this effect is absent in KLHL3 with S433A substitution. Additionally, increased extracellular K induced calcineurin-dependent dephosphorylation of KLHL3 These findings demonstrate that KLHL3 is a calcineurin substrate and implicate increased KLHL3 phosphorylation in tacrolimus-induced pathologies.
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http://dx.doi.org/10.1073/pnas.1817281116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6386661PMC
February 2019

Mineralocorticoid receptor blockade suppresses dietary salt-induced ACEI/ARB-resistant albuminuria in non-diabetic hypertension: a sub-analysis of evaluate study.

Hypertens Res 2019 04 11;42(4):514-521. Epub 2019 Jan 11.

Division of Clinical Epigenetics, Research Center of Advanced Science and Technology, The University of Tokyo, Tokyo, Japan.

Excessive dietary salt intake can counteract the renoprotective effects of renin-angiotensin system (RAS) blockade in hypertensive patients with chronic kidney disease (CKD). In rodents, salt loading induces hypertension and renal damage by activating the mineralocorticoid receptor (MR) independently of plasma aldosterone levels. Thus, high salt-induced resistance to RAS blockade may be mediated by MR activation. To test this, a post hoc analysis of the Eplerenone Combination Versus Conventional Agents to Lower Blood Pressure on Urinary Antialbuminuric Treatment Effect (EVALUATE) trial was conducted. Thus, 304 non-diabetic hypertensive patients on RAS-blocking therapy were divided into tertiles according to salt intake (estimated 24-h urinary sodium excretion at baseline) and compared in terms of percent reduction in urinary albumin-to-creatinine ratio (UACR) at 52 weeks relative to baseline. The eplerenone-treated patients in the highest sodium excretion tertile exhibited significantly greater reduction in UACR than the placebo subjects in the same tertile (-22.5% vs. +21.8%, p = 0.02). This disparity was not observed in the lowest (-10.2% vs. -0.84%, p = 0.65) or middle (-19.5% vs. +9.5%, p = 0.22) tertiles. Similar systolic blood pressure changes were observed. In the whole cohort, reduction in UACR correlated positively with reduction in systolic blood pressure (r = 0.04, p = 0.02). These results support the hypothesis that excessive salt intake can enhance resistance to RAS blockade by activating MR. They also suggest that eplerenone plus RAS blockade may be effective for CKD in hypertensive patients, especially those with excessive salt intake.
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http://dx.doi.org/10.1038/s41440-018-0201-7DOI Listing
April 2019

Electrolyte transport in the renal collecting duct and its regulation by the renin-angiotensin-aldosterone system.

Clin Sci (Lond) 2019 01 8;133(1):75-82. Epub 2019 Jan 8.

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan

Distal nephron of the kidney plays key roles in fluid volume and electrolyte homeostasis by tightly regulating reabsorption and excretion of Na, K, and Cl Studies to date demonstrate the detailed electrolyte transport mechanisms in principal cells of the cortical collecting duct, and their regulation by renin-angiotensin-aldosterone system (RAAS). In recent years, however, accumulating data indicate that intercalated cells, another cell type that is present in the cortical collecting duct, also play active roles in the regulation of blood pressure. Notably, pendrin in β-intercalated cells not only controls acid/base homeostasis, but is also one of the key components controlling salt and K transport in distal nephron. We have recently shown that pendrin is regulated by the co-ordinated action of angiotensin II (AngII) and aldosterone, and at the downstream of AngII, mammalian target of rapamycin (mTOR) signaling regulates pendrin through inhibiting the kinase unc51-like-kinase 1 and promoting dephosphorylation of mineralocorticoid receptor (MR). In this review, we summarize recent advances in the current knowledge on the salt transport mechanisms in the cortical collecting duct, and their regulation by the RAAS.
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http://dx.doi.org/10.1042/CS20180194DOI Listing
January 2019

ULK1 Phosphorylates and Regulates Mineralocorticoid Receptor.

Cell Rep 2018 07;24(3):569-576

Department of Genetics, Yale University School of Medicine, New Haven, CT 06511, USA; Laboratory of Human Genetics and Genomics, The Rockefeller University, New York, NY 10065, USA. Electronic address:

Mineralocorticoid receptor (MR) signaling regulates both renal Na-Cl reabsorption and K excretion. We previously demonstrated that phosphorylation of S843 in the MR ligand-binding domain in renal intercalated cells is involved in the balance of these activities by regulating ligand binding and signaling. However, the kinase that phosphorylates MR is unknown. Using a high-throughput screen assay of 197 kinases, we found that ULK1 is the principal kinase that is responsible for the phosphorylation of MR. The results were confirmed by in vitro kinase assay, mass spectrometry, and siRNA knockdown experiments. Notably, phosphorylation at MR was markedly reduced in ULK1/2 double knockout mouse embryonic fibroblasts. Upstream, we show that ULK1 activity is inhibited by phosphorylation induced by angiotensin II via mTOR in cell culture and in vivo. These findings implicate mTOR and ULK1 as regulators of MR activity in intercalated cells, a pathway that is critical for maintaining electrolyte homeostasis.
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http://dx.doi.org/10.1016/j.celrep.2018.06.072DOI Listing
July 2018

Tolvaptan for Primary Aldosteronism and Autosomal Dominant Polycystic Kidney Disease: A Case Report.

Case Rep Nephrol Dial 2018 Jan-Apr;8(1):62-69. Epub 2018 Mar 28.

Nephrology Center, Toranomon Hospital Kajigaya, Kawasaki, Japan.

A 59-year-old Japanese woman was admitted for evaluation of muscle weakness. Autosomal dominant polycystic kidney disease had been diagnosed at the age of 47 years, followed by primary aldosteronism at 53 years. At the age of 58, tolvaptan was started (60 mg/day) to treat her renal disease. After 8 months of tolvaptan therapy, hypokalemia-related muscle weakness became prominent, and hypertension became refractory. Finally, treatment with low-dose tolvaptan (30 mg/day) and high-dose spironolactone (100 mg/day) normalized serum potassium and the blood pressure. Tolvaptan can induce urinary excretion of potassium in patients with primary aldosteronism, and possible mechanisms are discussed.
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http://dx.doi.org/10.1159/000487921DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5903093PMC
March 2018

A patient presenting with isolated hematuria and renal dysfunction as rare manifestation of cryoglobulinemic glomerulonephritis in the course of autoimmune diseases including Sjögren's syndrome.

CEN Case Rep 2018 11 18;7(2):211-216. Epub 2018 Apr 18.

Department of Internal Medicine, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo, Japan.

Autoimmune diseases are sometimes associated with immune-mediated renal diseases and cryoglobulinemia is one of the causes. Cryoglobulinemia and cryoglobulinemic glomerulonephritis associated with primary Sjögren's syndrome are most frequent condition among non-hepatitis C virus-related condition. Its typical renal manifestation shows high amount of proteinuria with microscopic hematuria and renal insufficiency. We describe a case of 72-year-old woman with Hashimoto disease, autoimmune hepatitis, Sjögren's syndrome, and immune-related pancytopenia complicated by cryoglobulinemic glomerulonephritis. Before kidney biopsy, tubulointerstitial nephritis probably due to Sjögren's syndrome was suspected because of persistent hematuria without significant proteinuria and developing mild renal dysfunction over 6 months. The developing renal dysfunction associated with isolated hematuria is uncommon in glomerular diseases. Kidney biopsy, however, revealed established membranoproliferative glomerulonephritis with subendothelial deposits consisting of tubular structures with IgM, IgG, and C3 staining. Corticosteroids plus mycophenolate mofetil therapy successfully normalized renal function. Physician should not overlook cryoglobulinemic glomerulonephritis, which is potentially poor prognosis, even if urinalysis shows only persistent isolated hematuria in patients with autoimmune diseases.
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http://dx.doi.org/10.1007/s13730-018-0329-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6181880PMC
November 2018

Time to Target Uric Acid to Retard Chronic Kidney Disease Progression.

Contrib Nephrol 2018 23;192:56-68. Epub 2018 Jan 23.

Uric acid (UA) remains a risk factor for the progression of chronic kidney disease (CKD). Most observational studies showed a slight elevation in the serum UA level and this independently predicts the incidence and development of CKD. The recent meta-analysis, however, did not reach the conclusion that urate-lowering therapy with allopurinol retards the progression of CKD. The target level of serum UA if treated is another issue of debate. Our recent analysis by propensity score analysis has shown that the serum UA should be targeted below 6.0 mg/dL to inhibit the progression towards end-stage renal disease. Underlying mechanisms whereby an increase in serum UA induces kidney injury have been elucidated in animal models. Hyperuricemic models can lead to systemic hypertension, arteriolosclerosis including afferent arteriolopathy as well as albuminuria probably due to the activation of oxidative stress. Discoveries of urate transporters have elucidated the novel mechanism of UA transport in the kidney and intestine. The intestinal ABCG2 may play a compensatory role in light of decreased renal clearance of UA in CKD model rats, the trigger of which is not a uremic toxin but serum UA itself. Insulin directly upregulates URAT1 and downregulates ABCG2 in the kidney tubules, suggesting a possible link between UA and metabolic syndrome. This review summarizes the recent knowledge on the causal effect of serum UA on the kidney injury.
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http://dx.doi.org/10.1159/000484279DOI Listing
April 2019

Uric Acid in the Follow-Up Determines 30% Decline in Estimated GFR Over 2 Years: a Propensity Score Analysis.

Kidney Blood Press Res 2017 4;42(6):1053-1067. Epub 2017 Dec 4.

Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan.

Background/aims: Higher level of serum uric acid (SUA) predicts early entry to dialysis in chronic kidney disease (CKD) patients. However, a short-term effect of SUA remains to be elucidated using a novel surrogate endpoint.

Methods: Japanese CKD stage 3 to 4 patients were retrospectively examined (n= 701). The follow-up level of SUA was estimated as time-averaged uric acid (TA-UA). A propensity score for 6.0, 6.5 or 7.0 mg/dL of TA-UA was respectively calculated using baseline 23 covariates. The time-to-event analysis was performed for 30% decline in estimated GFR over 2 years.

Results: Incidence rates over 2 years were 90 of 440 in men and 36 of 261 in women (p = 0.03). Despite the negative result of baseline SUA, stratified Cox regression on the quintiles of the estimated propensity score showed that higher TA-UA of the three thresholds were all significant (crude HR 2.10 to 2.44) even after adjusting for the confounders. Kaplan-Meier analysis after propensity score matching likewise showed worse survival in the patients with the higher TA-UA (HR 3.11 to 4.26).

Conclusion: Higher SUA increases likelihood of reaching a surrogate endpoint over 2 years. Early intervention for SUA less than 6.0 mg/dL is recommended for slowing CKD progression.
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http://dx.doi.org/10.1159/000485593DOI Listing
August 2018

Remission of Refractory Ascites and Discontinuation of Hemodialysis after Additional Rituximab to Long-term Glucocorticoid Therapy in a Patient with TAFRO Syndrome.

Intern Med 2018 May 11;57(10):1433-1438. Epub 2018 Jan 11.

Department of Internal Medicine, Teikyo University School of Medicine, Japan.

Thrombocytopenia, ascites, myelofibrosis, renal dysfunction, and organomegaly (TAFRO) syndrome is a newly recognized but rare disease, and its treatment has not yet been established. We reported a 50-year-old woman with TAFRO syndrome diagnosed 2 years after the initial symptoms of a fever, fatigue, epigastric pain, edema, ascites, lymphadenopathy, thrombocytopenia and renal insufficiency. The patient showed refractory ascites and required hemodialysis under corticosteroid mono-therapy for suspected immune-mediated disease but was successfully treated with additive rituximab, resulting in improvement in her laboratory data, the withdrawal of hemodialysis and the disappearance of ascites. This case underscores the therapeutic utility of rituximab in patients with corticosteroid-resistant TAFRO syndrome, even long after the onset of the disease.
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http://dx.doi.org/10.2169/internalmedicine.0116-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5995702PMC
May 2018

Emergence of Smoldering ANCA-associated Glomerulonephritis during the Clinical Course of Mixed Connective Tissue Disease and Sjögren's Syndrome.

Intern Med 2018 Jun 21;57(12):1757-1762. Epub 2017 Dec 21.

Department of Internal Medicine, Teikyo University School of Medicine, Japan.

A 67-year-old woman presented with hematuria and proteinuria 16 and 11 months ago, respectively. She had been followed up as mixed connective tissue disease and Sjögren's syndrome for over 19 years. Blood chemistry showed no elevated serum creatinine or C-reactive protein but did reveal myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) of 300 U/dL. A kidney biopsy showed pauci-immune focal necrotizing glomerulonephritis. She was treated with prednisolone and rituximab, resulting in normal urinalysis and decreased MPO-ANCA. The complication of ANCA-associated glomerulonephritis should not be overlooked when abnormal urinalysis findings appear in the course of connective tissue disease, irrespective of the presence of rapidly progressive glomerulonephritis.
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http://dx.doi.org/10.2169/internalmedicine.9844-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6047994PMC
June 2018