Nephrology
Abstract
Urinary obstruction causes injury to the renal medulla, impairing the ability to concentrate urine, and increasing the risk of progressive kidney disease. However, the regenerative capacity of the renal medulla after reversal of obstruction is poorly understood. To investigate this, we developed a mouse model of reversible urinary obstruction. Despite robust regeneration and complete histological recovery of the renal medulla, these mice exhibited a permanent defect in urinary concentrating capacity. However, there were lasting changes in the composition, organization, and transcriptional profiles of epithelial, endothelial, and interstitial cells. Persistent inflammatory responses were also seen in patients with renal stone disease, but there were also adaptive responses to the increasingly hypoxic environment of the renal medulla that only occurred after reversal of obstruction. These findings indicate that while partial repair occurs after reversal of urinary obstruction, there are lasting structural and functional changes across all major cellular compartments of the renal medulla. These changes reflect shared and distinct responses to different renal medullary injuries in humans and mice.
Authors
Thitinee Vanichapol, Alex Gonzalez, Rachel Delgado, Maya Brewer, Kelly A. Clouthier, Anna A. Menshikh, William E. Snyder, Teebro Rahman, Veronika Sander, Haichun Yang, Alan Davidson, Mark Caestecker
Abstract
Disrupted feeding and fasting cycles as well as chronic high fat diet (HFD)-induced obesity are associated with cardiovascular disease risk factors. We designed studies that determined whether two weeks of time-restricted feeding (TRF) intervention in mice fed a chronic HFD would reduce cardiovascular disease risk factors. Mice were fed a normal diet (ND; 10% fat) ad libitum or HFD (45% fat) for 18 weeks ad libitum to establish diet-induced obesity. ND or HFD mice were continued on ad libitum diet or subjected to TRF (limiting food availability to 12 hr only during the dark phase) during the final two weeks of the feeding protocol. TRF improved whole-body metabolic diurnal rhythms without a change in body weight. HFD mice showed reduced blood pressure dipping compared to ND, which was restored by TRF. Further, TRF reduced aortic wall thickness, decreased aortic stiffness, as well as increased kidney tubular brush border integrity, decreased renal medullary fibrosis, and reduced renal medullary T cell inflammation in HFD mice. These findings indicate that TRF may be an effective intervention for improving vascular and kidney health in a model of established diet-induced obesity.
Authors
Paramita Pati, Carmen De Miguel, Jodi R. Paul, Dingguo Zhang, Jackson Colson, John Miller Allan, Claudia J. Edell, Megan K. Rhoads, Luke S. Dunaway, Sara N. Biswal, Yihan Zhong, Randee Sedaka, Telisha Millender-Swain, Shannon M. Bailey, Karen L. Gamble, David M. Pollock, Jennifer S. Pollock
Abstract
The role played by anionic channels in diabetic kidney disease (DKD) is not known. Chloride channel accessory 1 (CLCA1) facilitates the activity of TMEM16A (Anoctamin-1), a Ca2+-dependent Cl– channel. We examined if CLCA1/TMEM16A had a role in DKD. In mice with type 2 diabetes, renal cortical CLCA1 and TMEM16A content was increased. CLCA1 and TMEM16A content was associated with hydrogen sulfide (H2S) deficiency, mTOR complex 1 (mTORC1) activation, albuminuria, and matrix increase. Administering sodium hydrosulfide (NaHS), a source of H2S, mitigated these changes. In proximal tubular epithelial (MCT) cells, high glucose rapidly increased CLCA1 by recruiting the IL-6/STAT3 axis and augmented TMEM16A expression by stimulating its mRNA translation; these changes were abolished by NaHS. Patch clamp experiments showed that high glucose increased Cl– current in MCT cells that was ameliorated by NaHS and a TMEM16A chemical inhibitor. siRNA against CLCA1 or TMEM16A and TMEM16A inhibitor abolished high glucose–induced mTORC1 activation and matrix protein increase. Tubular expression of TMEM16A correlated with albuminuria in kidney biopsies from people with type 2 diabetes. We report a pathway for DKD in which H2S deficiency results in kidney injury by the recruitment of the CLCA1/TMEM16A/Cl– current system.
Authors
Hak Joo Lee, Yuyang Sun, Falguni Das, Wenjun Ju, Viji Nair, Christopher G. Kevil, Shankara Varadarajan, Guanshi Zhang, Goutam Ghosh Choudhury, Brij B. Singh, Matthias Kretzler, Robert G. Nelson, Kumar Sharma, Balakuntalam S. Kasinath
Abstract
Diabetic patients have increased susceptibility to acute kidney injury (AKI), and AKI could progress to chronic tubulointerstitial injury and fibrosis, referred to as AKI-to–chronic kidney disease (AKI-to-CKD) transition. However, whether diabetes directly promotes AKI-to-CKD transition is not known. We previously showed that reticulon-1A (RTN1A), a gene highly upregulated in injured renal tubular epithelial cells (RTECs), promotes AKI-to-CKD transition in nondiabetic settings. Therefore, we also examined whether reducing RTN1A expression could attenuate diabetes-induced AKI-to-CKD transition. Diabetes was induced by a high-fat diet and streptozotocin injections, and unilateral ischemic reperfusion injury was created as an AKI model in control, diabetic, and RTEC-specific Rtn1a-knockdown diabetic mice. AKI induced greater renal function decline, tubulointerstitial injury, and fibrosis in diabetic mice than in nondiabetic mice. Reduction of RTN1A markedly reduced the CKD development following AKI in diabetic mice, which was associated with reduced ER stress and mitochondrial dysfunction in RTECs. These findings indicate that diabetes markedly accelerates AKI-to-CKD transition and that RTN1A is a crucial mediator of diabetes-induced AKI-to-CKD transition. The development of RTN1A inhibitors could potentially attenuate AKI-to-CKD transition in diabetic patients.
Authors
Lulin Min, Ya Chen, Yixin Chen, Fang Zhong, Zhaohui Ni, Leyi Gu, Kyung Lee, John Cijiang He
Abstract
With the aging of society, the incidence of chronic kidney disease (CKD), a common cause of death, has been increasing. Transcription factor EB (TFEB), the master transcriptional regulator of the autophagy–lysosomal pathway, is regarded as a promising candidate for preventing various age-related diseases. However, whether TFEB in the proximal tubules plays a significant role in elderly CKD patients remains unknown. First, we found that nuclear TFEB localization in proximal tubular epithelial cells (PTECs) declined with age in both mice and humans. Next, we generated PTEC-specific Tfeb-deficient mice and bred them for up to 24 months. We found that TFEB deficiency in the proximal tubules caused metabolic disorders and occasionally led to apolipoprotein A4 (APOA4) amyloidosis. Supporting this result, we identified markedly decreased nuclear TFEB localization in the proximal tubules of elderly patients with APOA4 amyloidosis. The metabolic disturbances were accompanied with mitochondrial dysfunction due to transcriptional changes involved in fatty acid oxidation and oxidative phosphorylation pathways, as well as decreased mitochondrial clearance reflected by the accumulation of mitochondria–lysosome-related organelles, which depends on lysosomal function. These results shed light on the presumptive mechanisms of APOA4 amyloidosis pathogenesis and provide a therapeutic strategy for CKD-related metabolic disorders and APOA4 amyloidosis.
Authors
Jun Nakamura, Takeshi Yamamoto, Yoshitsugu Takabatake, Tomoko Namba-Hamano, Atsushi Takahashi, Jun Matsuda, Satoshi Minami, Shinsuke Sakai, Hiroaki Yonishi, Shihomi Maeda, Sho Matsui, Hideaki Kawai, Isao Matsui, Tadashi Yamamuro, Ryuya Edahiro, Seiji Takashima, Akira Takasawa, Yukinori Okada, Tamotsu Yoshimori, Andrea Ballabio, Yoshitaka Isaka
Abstract
Diabetes mellitus (DM) is acknowledged as an independent risk factor for acute kidney injury. Ras guanine nucleotide-releasing protein-4 (RasGRP4) exerts a notable role in modulating immune-inflammatory responses and kidney disease progression in diabetes. Herein, we delved into the specific role and mechanism of RasGRP4 in diabetic renal ischemia-reperfusion injury. Diabetes was induced by a high-fat diet and STZ injections, followed by creating an ischemia-reperfusion kidney injury via renal pedicle clamping and reperfusion. In vitro, a high glucose and hypoxia-reoxygenation modeled cellular inflammatory injury. We found RasGRP4 knockout (KO) mice, compared to C57BL/6J (WT) mice, showed markedly less renal dysfunction and fibrosis in diabetic ischemia-reperfusion injury. There was a significant decrease in the renal infiltration of M1 macrophages and Th17 cells, along with downregulated IL17 pathway proteins and effectors. In vitro, RasGRP4 deletion restrained M1 macrophage polarization and Th17 cell differentiation, inhibiting the IL17 signaling pathway in HK-2 cells. Hyperglycemia intensified renal inflammation state. Together, RasGRP4, through the regulation of interactions among M1 macrophages, CD4+ T cells and HK-2 cells, formed a cascade that intensified the inflammatory storm activity, ultimately exacerbating the inflammatory injury of diabetic ischemia-reperfusion kidneys. DM intensified this inflammatory injury mechanism, worsening the injury from renal ischemia-reperfusion.
Authors
Li Zhang, Zhanglong Wang, Yunqi Wu, Binshan Zhang, Zhongli Wang, Sisi Chen, Mengxu Ying, Pei Yu, Saijun Zhou
Abstract
Diabetic kidney disease (DKD) is the leading cause of chronic renal pathology. Understanding the molecular underpinnings of DKD is critical to designing tailored therapeutic approaches. Here we focused on sex differences and the contribution of aging towards the progression of DKD. To explore these questions, we utilized young (12 weeks old) and aged (approximately 50 weeks old) type 2 diabetic nephropathy (T2DN) rats. We revealed that the cyclic GMP-AMP synthase (cGAS)-Stimulator of Interferon Genes (STING) pathway was upregulated in T2DN rats compared to non-diabetic Wistar rats and in type 2 diabetic human kidneys. The activation of the cGAS-STING signaling pathway exhibited distinct protein expression profiles between male and female T2DN rats, with these differences becoming more pronounced with aging. RNA-Seq analysis of the kidney cortex in both male and female T2DN rats, at both younger and older ages, revealed several key molecules, highlighting crucial genes within the cGAS-STING pathway. Thus, our study delved deep into understanding the intricate sexual differences in the development and progression of DKD and proposed the cGAS-STING pathway as an essential contributor to disease development.
Authors
Sherif Khedr, Lashodya V. Dissanayake, Ammar J. Alsheikh, Adrian Zietara, Denisha R. Spires, Romica Kerketta, Angela J. Mathison, Raul Urrutia, Oleg Palygin, Alexander Staruschenko
Abstract
Many circulating proteins are associated with risk of ESKD, but their source and the biological pathways/disease processes they represent are unclear. Using OLINK proteomics platform, concentrations of 455 proteins were measured in plasma specimens obtained at baseline from 399 individuals with diabetes. Elevated concentrations of 46 circulating proteins were associated (P < 1 × 10–5) with development of ESKD (n = 143) during 7–15 years of follow-up. Twenty of these proteins enriched apoptosis/TNF receptor signaling pathways. A subset of 20 proteins (5–7 proteins), summarized as an apoptosis score, together with clinical variables accurately predicted risk of ESKD. Expression of genes encoding the 46 proteins in peripheral WBCs showed no difference between cells from individuals who did or did not develop ESKD. In contrast, plasma concentration of many of the 46 proteins differed by this outcome. In single-nucleus RNA-Seq analysis of kidney biopsies, the majority of genes encoding for the 20 apoptosis/TNF receptor proteins were overexpressed in injured versus healthy proximal tubule cells. Expression of these 20 genes also correlated with the overall index of apoptosis in these cells. Elevated levels of circulating proteins flagging apoptotic processes/TNF receptor signaling pathways — and likely originating from kidney cells, including injured/apoptotic proximal tubular cells — preceded the development of ESKD.
Authors
Katsuhito Ihara, Eiichiro Satake, Parker C. Wilson, Bozena Krolewski, Hiroki Kobayashi, Zaipul I. Md Dom, Joseph Ricca, Jonathan Wilson, Jonathan M. Dreyfuss, Monika A. Niewczas, Alessandro Doria, Robert G. Nelson, Marcus G. Pezzolesi, Benjamin D. Humphreys, Kevin Duffin, Andrzej S. Krolewski
Abstract
Mutations in the CLCNKB gene (1p36), encoding a basolateral chloride channel, ClC-Kb, cause type 3 Bartter’s syndrome. We identified a family with a mixed Bartter’s / Gitelman’s phenotype and early-onset kidney failure and employing a candidate gene approach, discovered a homozygous mutation (CLCNKB c.499G>T [p.Gly167Cys]) in exon 6 of CLCNKB in the index patient. We then validated these results with Sanger and whole exome sequencing. Compared to wild-type ClC-Kb, the Gly167Cys mutant conducted less current and impaired, complex N-linked glycosylation in vitro. We demonstrated that loss of Gly-167, rather than gain of a mutant Cys, impairs complex glycosylation but that surface expression remains intact. Moreover, Asn364 was necessary for channel function and complex glycosylation. Morphologic evaluation of human kidney biopsies revealed typical basolateral localization of mutant Gly167Cys ClC-Kb in cortical distal tubular epithelia. However, we detected attenuated expression of distal sodium transport proteins, changes in abundance of distal tubule segments, and hypokalemia-associated intracellular condensates from the index patient compared to control nephrectomy specimens. The present data establish what we believe, are novel regulatory mechanisms of ClC-Kb activity and demonstrate nephron remodeling in man, caused by mutant ClC-Kb, with implications for renal electrolyte handling, blood pressure control, and kidney disease.
Authors
Yogita Sharma, Robin Lo, Viktor N. Tomilin, Kotdaji Ha, Holly Deremo, Aishwarya V. Pareek, Wuxing Dong, Xiaohui Liao, Svetlana Lebedeva, Vivek Charu, Neeraja Kambham, Kerim Mutig, Oleh Pochynyuk, Vivek Bhalla
Abstract
Urinary concentration is an energy-dependent process that minimizes body water loss by increasing aquaporin-2 (AQP2) expression in collecting duct (CD) principal cells. To investigate the role of mitochondrial (mt) ATP production in renal water clearance, we disrupted mt electron transport in CD cells by targeting ubiquinone (Q) binding protein QPC (UQCRQ), a subunit of mt complex III essential for oxidative phosphorylation. QPC-deficient mice produced less concentrated urine than controls, both at baseline and after type 2 vasopressin receptor stimulation with desmopressin. Impaired urinary concentration in QPC-deficient mice was associated with reduced total AQP2 protein levels in CD tubules, while AQP2 phosphorylation and membrane trafficking remained unaffected. In cultured inner medullary CD cells treated with mt complex III inhibitor antimycin A, the reduction in AQP2 abundance was associated with activation of 5′ adenosine monophosphate-activated protein kinase (AMPK) and was reversed by treatment with AMPK inhibitor SBI-0206965. In summary, our studies demonstrated that the physiological regulation of AQP2 abundance in principal CD cells was dependent on mt electron transport. Furthermore, our data suggested that oxidative phosphorylation in CD cells was dispensable for maintaining water homeostasis under baseline conditions, but necessary for maximal stimulation of AQP2 expression and urinary concentration.
Authors
Joshua S. Carty, Ryoichi Bessho, Yvonne Zuchowski, Jonathan B. Trapani, Olena Davidoff, Hanako Kobayashi, Joseph T. Roland, Jason A. Watts, Andrew S. Terker, Fabian Bock, Juan Pablo Arroyo, Volker H. Haase
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