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Min L, Zhong F, Gu L, Lee K, He JC. Krüppel-like factor 2 is an endoprotective transcription factor in diabetic kidney disease. Am J Physiol Cell Physiol 2024; 327:C477-C486. [PMID: 38981608 DOI: 10.1152/ajpcell.00222.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Revised: 07/02/2024] [Accepted: 07/02/2024] [Indexed: 07/11/2024]
Abstract
Diabetic kidney disease (DKD) is a microvascular complication of diabetes, and glomerular endothelial cell (GEC) dysfunction is a key driver of DKD pathogenesis. Krüppel-like factor 2 (KLF2), a shear stress-induced transcription factor, is among the highly regulated genes in early DKD. In the kidney, KLF2 expression is mostly restricted to endothelial cells, but its expression is also found in immune cell subsets. KLF2 expression is upregulated in response to increased shear stress by the activation of mechanosensory receptors but suppressed by inflammatory cytokines, both of which characterize the early diabetic kidney milieu. KLF2 expression is reduced in progressive DKD and hypertensive nephropathy in humans and mice, likely due to high glucose and inflammatory cytokines such as TNF-α. However, KLF2 expression is increased in glomerular hyperfiltration-induced shear stress without metabolic dysregulation, such as in settings of unilateral nephrectomy. Lower KLF2 expression is associated with CKD progression in patients with unilateral nephrectomy, consistent with its endoprotective role. KLF2 confers endoprotection by inhibition of inflammation, thrombotic activation, and angiogenesis, and thus KLF2 is considered a protective factor for cardiovascular disease (CVD). Based on similar mechanisms, KLF2 also exhibits renoprotection, and its reduced expression in endothelial cells worsens glomerular injury and albuminuria in settings of diabetes or unilateral nephrectomy. Thus KLF2 confers endoprotective effects in both CVD and DKD, and its activators could potentially be developed as a novel class of drugs for cardiorenal protection in diabetic patients.
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Affiliation(s)
- Lulin Min
- Department of Nephrology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, United States
| | - Fang Zhong
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, United States
| | - Leyi Gu
- Department of Nephrology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Kyung Lee
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, United States
| | - John Cijiang He
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, United States
- Renal Section, James J. Peters Veterans Affair Medical Center, Bronx, New York, United States
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Richfield O, Cortez R, Navar LG. Modeling the interaction between tubuloglomerular feedback and myogenic mechanisms in the control of glomerular mechanics. Front Physiol 2024; 15:1410764. [PMID: 38966231 PMCID: PMC11223525 DOI: 10.3389/fphys.2024.1410764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Accepted: 05/24/2024] [Indexed: 07/06/2024] Open
Abstract
Introduction: Mechanical stresses and strains exerted on the glomerular cells have emerged as potentially influential factors in the progression of glomerular disease. Renal autoregulation, the feedback process by which the afferent arteriole changes in diameter in response to changes in blood pressure, is assumed to control glomerular mechanical stresses exerted on the glomerular capillaries. However, it is unclear how the two major mechanisms of renal autoregulation, the afferent arteriole myogenic mechanism and tubuloglomerular feedback (TGF), each contribute to the maintenance of glomerular mechanical homeostasis. Methods: In this study, we made a mathematical model of renal autoregulation and combined this model with an anatomically accurate model of glomerular blood flow and filtration, developed previously by us. We parameterized the renal autoregulation model based on data from previous literature, and we found evidence for an increased myogenic mechanism sensitivity when TGF is operant, as has been reported previously. We examined the mechanical effects of each autoregulatory mechanism (the myogenic, TGF and modified myogenic) by simulating blood flow through the glomerular capillary network with and without each mechanism operant. Results: Our model results indicate that the myogenic mechanism plays a central role in maintaining glomerular mechanical homeostasis, by providing the most protection to the glomerular capillaries. However, at higher perfusion pressures, the modulation of the myogenic mechanism sensitivity by TGF is crucial for the maintenance of glomerular mechanical homeostasis. Overall, a loss of renal autoregulation increases mechanical strain by up to twofold in the capillaries branching off the afferent arteriole. This further corroborates our previous simulation studies, that have identified glomerular capillaries nearest to the afferent arteriole as the most prone to mechanical injury in cases of disturbed glomerular hemodynamics. Discussion: Renal autoregulation is a complex process by which multiple feedback mechanisms interact to control blood flow and filtration in the glomerulus. Importantly, our study indicates that another function of renal autoregulation is control of the mechanical stresses on the glomerular cells, which indicates that loss or inhibition of renal autoregulation may have a mechanical effect that may contribute to glomerular injury in diseases such as hypertension or diabetes. This study highlights the utility of mathematical models in integrating data from previous experimental studies, estimating variables that are difficult to measure experimentally (i.e. mechanical stresses in microvascular networks) and testing hypotheses that are historically difficult or impossible to measure.
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Affiliation(s)
- Owen Richfield
- Bioinnovation PhD Program, Tulane University, New Orleans, LA, United States
| | - Ricardo Cortez
- Department of Mathematics, Tulane University, New Orleans, LA, United States
| | - L. Gabriel Navar
- Department of Physiology, Tulane School of Medicine, New Orleans, LA, United States
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Friberg N, Arvidsson I, Tontanahal A, Kristoffersson AC, Gram M, Kaplan BS, Karpman D. Red blood cell-derived arginase release in hemolytic uremic syndrome. J Transl Med 2024; 22:17. [PMID: 38178089 PMCID: PMC10765883 DOI: 10.1186/s12967-023-04824-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 12/22/2023] [Indexed: 01/06/2024] Open
Abstract
BACKGROUND Hemolysis is a cardinal feature of hemolytic uremic syndrome (HUS) and during hemolysis excess arginase 1 is released from red blood cells. Increased arginase activity leads to reduced L-arginine, as it is converted to urea and L-ornithine, and thereby reduced nitric oxide bioavailability, with secondary vascular injury. The objective of this study was to investigate arginase release in HUS patients and laboratory models and correlate arginase levels to hemolysis and kidney injury. METHODS Two separate cohorts of patients (n = 47 in total) with HUS associated with Shiga toxin-producing enterohemorrhagic E. coli (EHEC) and pediatric controls (n = 35) were investigated. Two mouse models were used, in which mice were either challenged intragastrically with E. coli O157:H7 or injected intraperitoneally with Shiga toxin 2. An in vitro model of thrombotic microangiopathy was developed in which Shiga toxin 2- and E. coli O157 lipopolysaccharide-stimulated human blood cells combined with ADAMTS13-deficient plasma were perfused over glomerular endothelial cells. Two group statistical comparisons were performed using the Mann-Whitney test, multiple groups were compared using the Kruskal-Wallis test followed by Dunn's procedure, the Wilcoxon signed rank test was used for paired data, or linear regression for continuous variables. RESULTS HUS patients had excessively high plasma arginase 1 levels and activity (conversion of L-arginine to urea and L-ornithine) during the acute phase, compared to remission and controls. Arginase 1 levels correlated with lactate dehydrogenase activity, indicating hemolysis, as well as the need for dialysis treatment. Patients also exhibited high levels of plasma alpha-1-microglobulin, a heme scavenger. Both mouse models exhibited significantly elevated plasma arginase 1 levels and activity. Plasma arginase 1 levels correlated with lactate dehydrogenase activity, alpha-1-microglobulin and urea levels, the latter indicative of kidney dysfunction. In the in vitro model of thrombotic microangiopathy, bioactive arginase 1 was released and levels correlated to the degree of hemolysis. CONCLUSIONS Elevated red blood cell-derived arginase was demonstrated in HUS patients and in relevant in vivo and in vitro models. The excessively high arginase levels correlated to the degree of hemolysis and kidney dysfunction. Thus, arginase inhibition should be investigated in HUS.
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Affiliation(s)
- Niklas Friberg
- Department of Pediatrics, Clinical Sciences Lund, Lund University, 221 85, Lund, Sweden
| | - Ida Arvidsson
- Department of Pediatrics, Clinical Sciences Lund, Lund University, 221 85, Lund, Sweden
| | - Ashmita Tontanahal
- Department of Pediatrics, Clinical Sciences Lund, Lund University, 221 85, Lund, Sweden
| | | | - Magnus Gram
- Department of Pediatrics, Clinical Sciences Lund, Lund University, 221 85, Lund, Sweden
- Skåne University Hospital, Lund, Sweden
| | - Bernard S Kaplan
- Division of Nephrology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Diana Karpman
- Department of Pediatrics, Clinical Sciences Lund, Lund University, 221 85, Lund, Sweden.
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Wang D, Gust M, Ferrell N. Kidney-on-a-Chip: Mechanical Stimulation and Sensor Integration. SENSORS (BASEL, SWITZERLAND) 2022; 22:6889. [PMID: 36146238 PMCID: PMC9503911 DOI: 10.3390/s22186889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 09/07/2022] [Accepted: 09/08/2022] [Indexed: 06/16/2023]
Abstract
Bioengineered in vitro models of the kidney offer unprecedented opportunities to better mimic the in vivo microenvironment. Kidney-on-a-chip technology reproduces 2D or 3D features which can replicate features of the tissue architecture, composition, and dynamic mechanical forces experienced by cells in vivo. Kidney cells are exposed to mechanical stimuli such as substrate stiffness, shear stress, compression, and stretch, which regulate multiple cellular functions. Incorporating mechanical stimuli in kidney-on-a-chip is critically important for recapitulating the physiological or pathological microenvironment. This review will explore approaches to applying mechanical stimuli to different cell types using kidney-on-a-chip models and how these systems are used to study kidney physiology, model disease, and screen for drug toxicity. We further discuss sensor integration into kidney-on-a-chip for monitoring cellular responses to mechanical or other pathological stimuli. We discuss the advantages, limitations, and challenges associated with incorporating mechanical stimuli in kidney-on-a-chip models for a variety of applications. Overall, this review aims to highlight the importance of mechanical stimuli and sensor integration in the design and implementation of kidney-on-a-chip devices.
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Affiliation(s)
- Dan Wang
- Division of Nephrology, Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Matthew Gust
- Division of Nephrology, Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
- Department of Statistics, College of Arts and Sciences, The Ohio State University, Columbus, OH 43210, USA
| | - Nicholas Ferrell
- Division of Nephrology, Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
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Richfield O, Cortez R, Navar LG. Simulations of Glomerular Shear and Hoop Stresses in Diabetes, Hypertension, and Reduced Renal Mass using a Network Model of a Rat Glomerulus. Physiol Rep 2021; 8:e14577. [PMID: 32951361 PMCID: PMC7507384 DOI: 10.14814/phy2.14577] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 08/18/2020] [Accepted: 08/19/2020] [Indexed: 12/15/2022] Open
Abstract
A novel anatomically accurate model of rat glomerular filtration is used to quantify shear stresses on the glomerular capillary endothelium and hoop stresses on the glomerular capillary walls. Plasma, erythrocyte volume, and plasma protein mass are distributed at network nodes using pressure differentials calculated taking into account volume loss to filtration, improving on previous models which only took into account blood apparent viscosity in calculating pressures throughout the network. Filtration is found to be heterogeneously distributed throughout the glomerular capillary network and is determined by concentration of plasma proteins and surface area of the filtering capillary segments. Hoop stress is primarily concentrated near the afferent arteriole, whereas shear stress is concentrated near the efferent arteriole. Using parameters from glomerular micropuncture studies, conditions of diabetes mellitus (DM), 5/6‐Nephrectomy (5/6‐Nx), and Angiotensin II‐induced hypertension (HTN) are simulated and compared to their own internal controls to assess the changes in mechanical stresses. Hoop stress is increased in all three conditions, while shear stress is increased in 5/6‐Nx, decreased in HTN, and maintained at control levels in DM by the hypertrophic response of the glomerular capillaries. The results indicate that these alterations in mechanical stresses and the consequent release of cytokines by or injury of the glomerular cells may play a significant role in the progression of glomerulopathy in these disease conditions.
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Affiliation(s)
- Owen Richfield
- Bioinnovation PhD Program, Tulane University, New Orleans, LA, USA.,Department of Physiology, Tulane School of Medicine, New Orleans, LA, USA
| | - Ricardo Cortez
- Department of Mathematics, Tulane University, New Orleans, LA, USA
| | - L Gabriel Navar
- Department of Physiology, Tulane School of Medicine, New Orleans, LA, USA
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Richfield O, Cortez R, Navar LG. Simulations of increased glomerular capillary wall strain in the 5/6-nephrectomized rat. Microcirculation 2021; 28:e12721. [PMID: 34192389 PMCID: PMC9285434 DOI: 10.1111/micc.12721] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 05/27/2021] [Accepted: 06/22/2021] [Indexed: 12/21/2022]
Abstract
Objective Chronic glomerular hypertension is associated with glomerular injury and sclerosis; however, the mechanism by which increases in pressure damage glomerular podocytes remains unclear. We tested the hypothesis that increases in glomerular pressure may deleteriously affect podocyte structural integrity by increasing the strain of the glomerular capillary walls, and that glomerular capillary wall strain may play a significant role in the perpetuation of glomerular injury in disease states that are associated with glomerular hypertension. Methods We developed an anatomically accurate mathematical model of a compliant, filtering rat glomerulus to quantify the strain of the glomerular capillary walls in a remnant glomerulus of the 5/6‐nephrectomized rat model of chronic kidney disease. In terms of estimating the mechanical stresses and strains in the glomerular capillaries, this mathematical model is a substantial improvement over previous models which do not consider pressure‐induced alterations in glomerular capillary diameters in distributing plasma and erythrocytes throughout the network. Results Using previously reported data from experiments measuring the change of glomerular volume as a function of perfusion pressure, we estimated the Young's modulus of the glomerular capillary walls in both control and 5/6‐nephrectomized conditions. We found that in 5/6‐nephrectomized conditions, the Young's modulus increased to 8.6 MPa from 7.8 MPa in control conditions, but the compliance of the capillaries increased in 5/6‐nephrectomized conditions due to a 23.3% increase in the baseline glomerular capillary diameters. We found that glomerular capillary wall strain was increased approximately threefold in 5/6‐nephrectomized conditions over control, which may deleteriously affect both mesangial cells and podocytes. The magnitudes of strain in model simulations of 5/6‐nephrectomized conditions were consistent with magnitudes of strain that elicit podocyte hypertrophy and actin cytoskeleton reorganization in vitro. Conclusions Our findings indicate that glomerular capillary wall strain may deleteriously affect podocytes directly, as well as act in concert with other mechanical changes and environmental factors inherent to the in vivo setting to potentiate glomerular injury in severe renoprival conditions.
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Affiliation(s)
- Owen Richfield
- Bioinnovation PhD Program, Tulane University, New Orleans, LA, USA.,Department of Physiology, Tulane School of Medicine, New Orleans, LA, USA
| | - Ricardo Cortez
- Department of Mathematics, Tulane University, New Orleans, LA, USA
| | - L Gabriel Navar
- Department of Physiology, Tulane School of Medicine, New Orleans, LA, USA
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