Renal NLRP3 Inflammasome Research Articles

EARLY FLUID PLUS NOREPINEPHRINE RESUSCITATION DIMINISHES KIDNEY HYPOPERFUSION AND INFLAMMATION IN SEPTIC NEWBORN PIGS.

Sepsis is the most frequent risk factor for acute kidney injury (AKI) in critically ill infants. Sepsis-induced dysregulation of kidney microcirculation in newborns is unresolved. The objective of this study was to use the translational swine model to evaluate changes in kidney function during the early phase of sepsis in newborns and the impact of fluid plus norepinephrine resuscitation. Newborn pigs (3-7-day-old) were allocated randomly to three groups: 1) sham, 2) sepsis (cecal ligation and puncture) without subsequent resuscitation, and 3) sepsis with lactated Ringer plus norepinephrine resuscitation. All animals underwent standard anesthesia and mechanical ventilation. Cardiac output and glomerular filtration rate were measured noninvasively. Mean arterial pressure, total renal blood flow, cortical perfusion, medullary perfusion, and medullary tissue oxygen tension (mtPO 2 ) were determined for 12 h. Cecal ligation and puncture decreased mean arterial pressure and cardiac output by more than 50%, with a proportional increase in renal vascular resistance and a 60-80% reduction in renal blood flow, cortical perfusion, medullary perfusion, and mtPO 2 compared to sham. Cecal ligation and puncture also decreased glomerular filtration rate by ~79% and increased AKI biomarkers. Isolated foci of tubular necrosis were observed in the septic piglets. Except for mtPO 2 , changes in all these parameters were ameliorated in resuscitated piglets. Resuscitation also attenuated sepsis-induced increases in the levels of plasma C-reactive protein, proinflammatory cytokines, lactate dehydrogenase, alanine transaminase, aspartate aminotransferase, and renal NLRP3 inflammasome. These data suggest that newborn pigs subjected to cecal ligation and puncture develop hypodynamic septic AKI. Early implementation of resuscitation lessens the degree of inflammation, AKI, and liver injury.

VEGFC ameliorates salt-sensitive hypertension and hypertensive nephropathy by inhibiting NLRP3 inflammasome via activating VEGFR3-AMPK dependent autophagy pathway.

Salt-sensitivity hypertension (SSHTN) is an independent predictor for cardiovascular mortality. VEGFC has been reported to be a protective role in SSHTN and hypertensive kidney injury. However, the underlying mechanisms remain largely unclear. The current study aimed to explore the protective effects and mechanisms of VEGFC against SSHTN and hypertensive nephropathy. Here, we reported that VEGFC attenuated high blood pressure as well as protected against renal inflammation and fibrosis in SSHTN mice. Moreover, VEGFC suppressed the activation of renal NLRP3 inflammasome in SSHTN mice. In vitro, we found VEGFC inhibited NLRP3 inflammasome activation, meanwhile, upregulated autophagy in high-salt-induced macrophages, while these effects were reversed by an autophagy inhibitor 3MA. Furthermore, in vivo, 3MA pretreatment weakened the protective effects of VEGFC on SSHTN and hypertensive nephropathy. Mechanistically, VEGF receptor 3 (VEGFR3) kinase domain activated AMPK by promoting the phosphorylation at Thr183 via binding to AMPK, thus enhancing autophagy activity in the context of high-salt-induced macrophages. These findings indicated that VEGFC inhibited NLRP3 inflammasome activation by promoting VEGFR3-AMPK-dependent autophagy pathway in high-salt-induced macrophages, which provided a mechanistic basis for the therapeutic target in SSHTN and hypertensive kidney injury.

Abstract 009: Age-related Clonal Hematopoiesis Predisposes To Hypertension In Mice Through An Inflammasome Mechanism

Hypertension incidence increases with age and represents one of the most prevalent risk factors for cardiovascular disease (CVD). Clonal events in the hematopoietic system resulting from somatic mutations in “driver” genes such as Tet2 are prevalent in elderly individuals in the absence of overt hematologic disorders. This condition is referred to as age-related clonal hematopoiesis (ARCH), and it is a newly recognized risk factor for CVD. It is unknown whether ARCH and hypertension in the elderly are causally related and, if so, what are the mechanistic features. Objective: Given that the aging process increases the prevalence of hypertension and ARCH, the current experimental study was designed to test the effect of ARCH in hypertension incidence. Methods and Results: A murine model of adoptive bone marrow transplantation to nonconditioned mice was employed to examine the interplay between ARCH and hypertension. Mice carrying Tet2-deficiency in hematopoietic cells resulted in elevated systolic (SBP) and diastolic blood pressure (DBP) as early as one day after challenge with a sub-pressure dose of angiotensin II (Ang II) 200ng/kg/min; SBP (day 1 Tet2 -/- : 148 mmHg± 4 vs. WT: 129±2 mmHg, P=0.002); day 9 Tet2 -/- 159±7 mmHg vs. WT: 139±5 mmHg, P<0.05), and DBP (day 1, Tet2 -/- : 108 ±3 mmHg vs. WT: 100±1 mmHg, P<0.005; day 9, Tet2 -/- : 111 ±4 mmHg vs. WT 107±3 mmHg). The ARCH Tet2 model of CH led to greater macrophage infiltration in the kidney, aorta and mesentery after Ang II compared with WT-treated mice. The Tet2-/- CH condition led to renal NLRP3 inflammasome activation and elevated renal levels of IL (interleukin)-1β (Tet2 -/- 1.4 vs. WT: 0.96, P<0.005) and IL-18 (Tet2 -/- 1.56 vs. WT: 1.18, P<0.005) after Ang II administration. Interestingly, administration of the inflammasome inhibitor MCC950 reversed hypertension seen in the mouse model of Tet2 -/- CH. Conclusion: Our data show that a sub-pressor dose of Ang II promotes hypertension due to elevated renal immune cell infiltration in a Tet2-CH model, promoting IL1-β and IL-18. These data suggest that Tet2 -/- CH carriers could be at elevated risk for the development of hypertension, and that NLRP3 inhibitors could be useful for treating hypertension in this population.

Early fluid and norepinephrine resuscitation in septic acute kidney injury diminishes pro-inflammatory cytokine levels and kidney hypoperfusion in newborn pigs

Background and Objective: Sepsis is the most frequent risk factor for acute kidney injury (AKI) in critically ill infants. Whereas sepsis-induced AKI has been studied in several animal models, alterations in renal microcirculation are unclear. The objective of this study was to use the translational swine model to evaluate the changes in renal hemodynamics during the early phase of sepsis in the first week of life. We also examined the impact of early fluid and norepinephrine (NE) resuscitation on renal hemodynamics in newborn septic AKI. Methodology: Newborn pigs (3-7 days old) were randomly allocated to three groups; 1) Sham, 2) Sepsis (cecal ligation and puncture; CLP) without subsequent resuscitation, and 3) CLP-induced sepsis with fluid and vasopressor NE resuscitation. All animals underwent standard anesthesia induction, mechanical ventilation, and intravenous fluid. Cardiac output (COP) and GFR were measured non-invasively using electrical velocimetry and a transdermal system. The pigs were instrumented to measure the mean arterial pressure (MAP), total renal blood flow (tRBF), cortical perfusion (coPf), and medullary perfusion (mePf). Also, a fiber-optic probe was placed in the medulla to measure medullary tissue oxygen tension (tPO2). Baseline values were recorded for the above indices in all groups. In resuscitated animals, fluid bolus and NE infusion were started at the 4-h to maintain MAP within 15 mmHg from baseline. The pigs were euthanized after twelve hours. Results: Compared to baseline values, MAP and COP decreased by more than two-thirds in non-resuscitated sepsis, with a proportional increase in RVR and reduction in tRBF, coPf, mePf, and tPO2 in contrast to sham. CLP also decreased GFR and increased serum creatinine, BUN, and NGAL. A few tubular coagulative necroses were observed in the septic pigs. Changes in all these parameters, except tPO2, were ameliorated in resuscitated pigs. Resuscitation also attenuated sepsis-induced increase in the levels of serum C-reactive protein, inflammatory cytokines (IL-6, IL-8, IL-12, and IL-18), liver enzymes (aspartate aminotransferase and alanine aminotransferase), and renal NLRP3 inflammasome. Conclusions: Early implementation of resuscitation to maintain MAP, COP, and kidney perfusion lessens the degree of inflammation, AKI, and liver injury in newborn pigs. The discrepancy between medullary perfusion and oxygenation indicates that optimizing perfusion and blood flow does not always correlate with improved medullary oxygen delivery in newborns, especially in cases of increased metabolic demand, as in sepsis. Sepsis is a dynamic illness with phases of hypodynamic and hyperdynamic renal perfusion; therefore, management strategies would differ based on hemodynamic status. NIH R01DK120595 and R01DK127625 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

PROPHYLACTIC n CMT-3 ATTENUATES SEPSIS-INDUCED ACUTE KIDNEY INJURY IN ASSOCIATION WITH NLRP3 INFLAMMASOME ACTIVATION AND APOPTOSIS.

Background: The kidney is the most common extrapulmonary organ injured in sepsis. The current study examines the ability of aerosolized nanochemically modified tetracycline 3 (nCMT-3), a pleiotropic anti-inflammatory agent, to attenuate acute kidney injury (AKI) caused by intratracheal LPS. Methods: C57BL/6 mice received aerosolized intratracheal nCMT-3 (1 mg/kg) or saline, followed by intratracheal LPS (2.5 mg/kg) to induce acute lung injury-induced AKI. Tissues were harvested at 24 h. The effects of nCMT-3 and LPS on AKI were assessed by plasma/tissue levels of serum urea nitrogen, creatinine, neutrophil gelatinase-associated lipocalin, kidney injury molecule 1, and renal histology. Renal matrix metalloproteinase (MMP) level/activity, cytochrome C, Bax, Bcl-2, caspase-3, p38 mitogen-activated protein kinase activation, NLRP3, and caspase-1 were also measured. Apoptotic cells in kidney were determined by TUNEL assay. Renal levels of IL-1β and IL-6 were measured to assess inflammation. Results: Acute lung injury-induced AKI was characterized by increased plasma blood urea nitrogen, creatinine, injury biomarkers (neutrophil gelatinase-associated lipocalin, kidney injury molecule 1), and histologic evidence of renal injury. Lipopolysaccharide-treated mice demonstrated renal injury with increased levels of inflammatory cytokines (IL-1β, IL-6), active MMP-2 and MMP-9, proapoptotic proteins (cytochrome C, Bax/Bcl-2 ratio, cleaved caspase-3), apoptotic cells, inflammasome activation (NLRP3, caspase-1), and p38 signaling. Intratracheal nCMT-3 significantly attenuated all the measured markers of renal injury, inflammation, and apoptosis. Conclusions: Pretreatment with aerosolized nCMT-3 attenuates LPS-induced AKI by inhibiting renal NLRP3 inflammasome activation, renal inflammation, and apoptosis.

Renal NLRP3 Inflammasome activation is associated with disease activity in lupus nephritis

The current study was initiated to comprehensively evaluate renal NLRP3 inflammasome pathway activation in lupus nephritis (LN) patients and their clinicopathological significances based on a Chinese LN cohort. We found that the expressions of NLRP3, ASC, caspase-1, IL-1β and IL-18 were all significantly higher in the kidneys of LN patients and were predominantly expressed in glomerular mesangial cells, podocytes, renal tubular epithelial cells and macrophages. The expressions of NLRP3, ASC, caspase-1 and IL-1β were positively correlated to SLEDAI scores and several renal pathological activity indices, while the expression of NLRP3 was negatively associated with chronicity scores. Moreover, the foot process width was positively correlated with glomerular caspase-1 levels, and several podocyte injury markers were decreased significantly in LN patients with higher caspase-1 expression compared with those with lower expression. Our findings indicated that renal NLRP3 inflammasome was activated in LN patients and correlated with disease activity, which needs further explorations.

Empagliflozin Attenuates Obesity-Related Kidney Dysfunction and NLRP3 Inflammasome Activity Through the HO-1-Adiponectin Axis.

Empagliflozin (EMPA) is a novel sodium-glucose cotransporter 2 inhibitor (SGLT2i) that produces protective cardiovascular-renal outcomes in patients with diabetes. However, the effects of EMPA on obesity-related kidney disease have not been determined. The heme oxygenase-1 (HO-1)–adiponectin axis is an essential antioxidant system with anti-apoptotic and anti-inflammatory properties. This study explored whether EMPA improves obesity-related kidney disease through regulation of the renal HO-1-mediated adiponectin axis. C57BL/6J mice were assigned to control, high-fat diet (HFD) groups, and EMPA (10 mg/kg) groups. HFD mice showed metabolic abnormality and renal injury, including increased urinary albumin excretion, morphologic changes, and lipid accumulation. EMPA treatment improved metabolic disorders and attenuated lipotoxicity-induced renal injury. Furthermore, EMPA treatment ameliorated renal NLRP3 inflammasome activity and upregulated the HO-1–adiponectin axis. Our findings indicate that EMPA improves obesity-related kidney disease through reduction of NLRP3 inflammasome activity and upregulation of the HO-1–adiponectin axis, suggesting a novel mechanism for SGLT2i-mediated renal protection in obesity.

6-Paradol alleviates Diclofenac-induced acute kidney injury via autophagy enhancement-mediated by AMPK/AKT/mTOR and NLRP3 inflammasome pathways

Diclofenac (DIC)-induced acute kidney injury (AKI) causes high morbidity and mortality. With the absence of satisfactory treatment, we investigated the protective effects of 6-Paradol (PDL) against DIC-induced AKI, with focus on renal autophagy and NLRP3 inflammasome pathways . PDL has anti-inflammatory, antioxidant and AMPK-activation properties. PDL was administered to DIC-challenged rats. Nephrotoxicity, oxidative stress, inflammatory, and autophagy markers and histopathological examinations were evaluated. Compared to DIC, PDL restored serum nephrotoxicity, renal oxidative stress and pro-inflammatory markers. PDL almost restored renal architecture, upregulated renal Nrf2 pathway via enhancing Nrf2 mRNA expression and HO-1 levels. PDL suppressed renal NF-κB mRNA expression, and NLRP3 inflammasome pathway expression. Moreover, PDL enhanced renal autophagy through upregulating LC3B, AMPK and SIRT-1, and suppressed mTOR, p-AKT mRNA expressions and phosphorylated-p62 levels. Our study confirmed that autophagy suppression mediates DIC-induced AKI via AMPK/mTOR/AKT and NLRP3-inflammasome pathways. Also, PDL’s nephroprotective effects could provide a promising therapeutic approach against DIC-induced AKI.

The role of uric acid in inflammasome-mediated kidney injury.

Uric acid is produced after purine nucleotide degradation, upon xanthine oxidase catalytic action. In the evolutionary process, humans lost uricase, an enzyme that converts uric acid into allantoin, resulting in increased serum uric acid levels that may vary according to dietary ingestion, pathological conditions, and other factors. Despite the controversy over the inflammatory role of uric acid in its soluble form, crystals of uric acid are able to activate the NLRP3 inflammasome in different tissues. Uric acid, therefore, triggers hyperuricemic-related disease such as gout, metabolic syndrome, and kidney injuries. The present review provides an overview on the role of uric acid in the inflammasome-mediated kidney damage. Hyperuricemia is present in 20-35% of patients with chronic kidney disease. However, whether this increased circulating uric acid is a risk factor or just a biomarker of renal and cardiovascular injuries has become a topic of intense discussion. Despite these conflicting views, several studies support the idea that hyperuricemia is indeed a cause of progression of kidney disease, with a putative role for soluble uric acid in activating renal NLRP3 inflammasome, in reprograming renal and immune cell metabolism and, therefore, in promoting kidney inflammation/injury. Therapies aiming to decrease uric acid levels prevent renal NLRP3 inflammasome activation and exert renoprotective effects in experimental kidney diseases. However, further clinical studies are needed to investigate whether reduced circulating uric acid can also inhibit the inflammasome and be beneficial in human conditions.

Effect of Quamoclit angulata Extract Supplementation on Oxidative Stress and Inflammation on Hyperglycemia-Induced Renal Damage in Type 2 Diabetic Mice.

Type 2 diabetes mellitus (T2DM) is caused by abnormalities of controlling blood glucose and insulin homeostasis. Especially, hyperglycemia causes hyper-inflammation through activation of NLRP3 inflammasome, which can lead to cell apoptosis, hypertrophy, and fibrosis. Quamoclit angulata (QA), one of the annual winders, has been shown ameliorative effects on diabetes. The current study investigated whether the QA extract (QAE) attenuated hyperglycemia-induced renal inflammation related to NLRP inflammasome and oxidative stress in high fat diet (HFD)-induced diabetic mice. After T2DM was induced, the mice were treated with QAE (5 or 10 mg/kg/day) by gavage for 12 weeks. The QAE supplementation reduced homeostasis model assessment insulin resistance (HOMA-IR), kidney malfunction, and glomerular hypertrophy in T2DM. Moreover, the QAE treatment significantly attenuated renal NLRP3 inflammasome dependent hyper-inflammation and consequential renal damage caused by oxidative stress, apoptosis, and fibrosis in T2DM. Furthermore, QAE normalized aberrant energy metabolism (downregulation of p-AMPK, sirtuin (SIRT)-1, and PPARγ-coactivator α (PGC-1 α)) in T2DM mice. Taken together, the results suggested that QAE as a natural product has ameliorative effects on renal damage by regulation of oxidative stress and inflammation in T2DM.

Abstract P3034: Female Mice are Protected Against Renal Inflammation and Salt-Sensitive Hypertension During Diabetes

Introduction: Diabetic nephropathy is characterized by renal inflammation and impaired kidney function that predisposes to salt-sensitive hypertension. However, the prevalence of diabetic kidney disease is lower in females compared to males. Here, we aim to study the sexual differences associated with the progression of diabetic nephropathy and the response to a high salt diet. Methods: Four- and seven-month old male and female diabetic (db/db) and non-diabetic (db/+) mice received either a high-salt (4% NaCl w/w) or a control (0.4% NaCl w/w) diet for four weeks (n=4). Mean arterial pressure (MAP) was measured by telemetry. To evaluate sodium handling, mice were challenged with an intraperitoneal injection of saline solution (0.9% NaCl) in a volume equivalent to 10% of the mouse body weight and hourly sodium excretion was evaluated by flame photometry. Finally, mice were euthanized, and kidneys were preserved to assess renal inflammation. Results: At 4 months, a high salt diet did not modify blood pressure in any experimental group. However, male diabetic mice showed higher abundance of renal TNFα (1.8-fold increase, P <0.01), IL-6 (1.9 fold-increase, P <0.01) and IL-1β (2.1-fold increase, P <0.05) compared to equally treated diabetic females. Further, male diabetic mice displayed higher levels of renal NLRP3 inflammasome components such as pro-caspase-1 (3.9-fold increase) and NLRP3 (4.5-fold increase) compared to female diabetic mice ( P <0.01). After an acute sodium challenge, diabetic male mice retained more sodium than diabetic females. Five hours after the saline injection, diabetic females eliminated 32 ± 3% of injected sodium while diabetic males eliminated only 23 ± 2% ( P <0.01). Another set of mice at 7 months of age were exposed to a 4-week high salt diet. Now, diabetic males develop salt-sensitivity (MAP: 122 ± 2 mmHg) while females remained normotensive (MAP: 99 ± 3 mmHg) ( P <0.01). Conclusion: Even in the absence of salt sensitivity, 4-month old diabetic males display renal inflammation and sodium retention. This is associated with the development of salt-sensitive hypertension at 7 months. Diabetic female mice are protected against the progression of diabetic nephropathy and do not develop salt sensitivity.

NLRP3 Inflammasome Modulation by Melatonin Supplementation in Chronic Pristane-Induced Lupus Nephritis.

Lupus nephritis (LN) is a kidney inflammatory disease caused by systemic lupus erythematosus (SLE). NLRP3 inflammasome activation is implicated in LN pathogenesis, suggesting its potential targets for LN treatment. Melatonin, an endogenous indoleamine, is considered an important multitasking molecule that has been reported to have anti-inflammatory effects by inhibiting nuclear factor-kappa B (NF-κB)-mediated inflammatory responses in vivo. This molecule has also protective effects against the activation of the inflammasomes and, in particular, the NLRP3 inflammasome. Thus, this work evaluated the effect of melatonin on morphological alteration and NLRP3 inflammasome activation in LN pristane mouse models. To evaluate the melatonin effects in these mice, we studied the renal cytoarchitecture by means of morphological analyses and immunohistochemical expression of specific markers related to oxidative stress, inflammation and inflammasome activation. Our results showed that melatonin attenuates pristane-induced LN through restoring of morphology and attenuation of oxidative stress and inflammation through a pathway that inhibited activation of NLRP3 inflammasome signaling. Our data clearly demonstrate that melatonin has protective activity on lupus nephritis in these mice that is highly associated with its effect on enhancing the Nrf2 antioxidant signaling pathway and decreasing renal NLRP3 inflammasome activation.

Compound K inhibits priming and mitochondria-associated activating signals of NLRP3 inflammasome in renal tubulointerstitial lesions.

Renal tubulointerstitial lesions (TILs), a key pathological hallmark for chronic kidney disease to progress to end-stage renal disease, feature renal tubular atrophy, interstitial mononuclear leukocyte infiltration and fibrosis in the kidney. Our study tested the renoprotective and therapeutic effects of compound K (CK), as described in our US patent (US7932057B2), on renal TILs using a mouse unilateral ureteral obstruction (UUO) model. Renal pathology was performed and renal draining lymph nodes were subjected to flow cytometry analysis. Mechanism-based experiments included the analysis of mitochondrial dysfunction, a model of tubular epithelial cells (TECs) under mechanically induced constant pressure (MICP) and tandem mass tags (TMT)-based proteomics analysis. Administration of CK ameliorated renal TILs by reducing urine levels of proinflammatory cytokines, and preventing mononuclear leukocyte infiltration and fibrosis in the kidney. The beneficial effects clearly correlated with its inhibition of: (i) NF-κB-associated priming and the mitochondria-associated activating signals of the NLRP3 inflammasome; (ii) STAT3 signalling, which in part prevents NLRP3 inflammasome activation; and (iii) the TGF-β-dependent Smad2/Smad3 fibrotic pathway, in renal tissues, renal TECs under MICP and/or activated macrophages, the latter as a major inflammatory player contributing to renal TILs. Meanwhile, TMT-based proteomics analysis revealed downregulated renal NLRP3 inflammasome activation-associated signalling pathways in CK-treated UUO mice. The present study, for the first time, presents the potent renoprotective and therapeutic effects of CK on renal TILs by targeting the NLRP3 inflammasome and STAT3 signalling.

Female mice are protected against the renal pro‐inflammatory effects of a high‐salt diet during diabetes

IntroductionHigh‐salt diet and hypertension are major contributors to diabetic nephropathy and predispose to end‐stage renal disease. In addition, studies in both humans and animal models of diabetes demonstrated that males have higher incidence of diabetic kidney disease compared to females.ObjectiveWe aim to determine the contribution of a high salt diet to the development of renal inflammation associated with diabetes in female versus male diabetic mice.MethodsFour‐month‐old female and male db/db mice (a model of type 2 diabetes) and non‐diabetic controls were exposed to either a high (4% NaCl w/w) or control (0.4% NaCl w/w) diet for 3 weeks (n=4). Systolic blood pressure (SBP) was measured by the tail‐cuff method. At the end of the protocol, mice were euthanized, and kidneys were preserved to assess renal inflammation.ResultsA high salt diet did not modify the blood pressure in any experimental group. At the beginning of the high salt diet, SBP was 99 ± 8 mmHg in diabetic females and 100 ± 3 mmHg in diabetic males. After 3 weeks of high salt, SBP was 101 ± 4 mmHg in diabetic females and 106 ± 2 mmHg in diabetic males (P=NS). However, male diabetic mice exposed to high salt displayed higher abundance of renal TNFα (1.8‐fold increase, P<0.001), IL‐6 (1.9 fold‐increase, P<0.01) and IL‐1β (2.1‐fold increase, P<0.05) compared to equally treated diabetic females. Further, male diabetic mice displayed higher expression of renal NLRP3 inflammasome components such as Pro‐caspase‐1 (2.6‐fold increase, P<0.01), caspase‐1 (2.2‐fold increase, P<0.05) and the adaptor protein ASC (2.3‐fold increase, P<0.05) compared to female diabetic mice. Finally, the anti‐inflammatory cytokine IL‐10 was decreased in diabetic males exposed to a high salt diet compared to diabetic males receiving a control diet (from 563 ± 23 to 411 ± 21 pg/mg kidney protein, P<0.05). In female diabetic mice, IL‐10 remained unchanged. Both female and male non‐diabetic mice displayed no changes in response to a 3‐week high salt diet.ConclusionEven in the absence of salt‐sensitive hypertension, male diabetic mice are more susceptible to the renal pro‐inflammatory effects of a high‐salt diet compared to female diabetic mice.Support or Funding InformationThis study was supported by NIH R01HL142672, AHA 16SDG30130015, and P30 DK063491 (JFG); NIH R01HL110353 and AHA 17GRNT32580000 (KEB).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Salt‐Responsive Metabolite, beta‐Hydroxybutyrate, Attenuates Hypertension

Dietary salt reduction and exercise are lifestyle modifications for salt‐sensitive hypertensives. While exercise has prominent metabolic effects, salt has an adverse effect on metabolic syndrome, of which hypertension is a hallmark. We hypothesized that dietary salt impacts metabolism in a salt‐sensitive model of hypertension. An untargeted metabolomics approach demonstrates lower circulating levels of the ketone body, beta‐hydroxybutyrate (βOHB), in high salt‐fed hypertensive rats. Despite the high salt intake, specific rescue of βOHB levels by nutritional supplementation of its precursor, 1,3‐butanediol, attenuates hypertension and protects kidney function. This beneficial effect of βOHB was likely independent of gut‐microbiotal and Th17‐mediated effects of salt and instead facilitated by βOHB inhibiting the renal Nlrp3 inflammasome. The juxtaposed effects of dietary salt and exercise on salt‐sensitive hypertension, which decrease and increase βOHB respectively, indicate that nutritional supplementation of a precursor of βOHB provides a similar benefit to salt‐sensitive hypertension as exercise.Support or Funding InformationFunding from this work to BJ from the NHLBI (NIH) (HL143082) is gratefully acknowledged.Declaration of interests: Bina Joe and Saroj Chakraborty have an interest in U.S. Patent Application Serial No.: 62/665,690 filed on May 2, 2018 in this paper regarding nutritional intervention for salt‐sensitive hypertension for 1,3‐butanediol.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Salt-Responsive Metabolite, β-Hydroxybutyrate, Attenuates Hypertension

SUMMARYDietary salt reduction and exercise are lifestyle modifications for salt-sensitive hypertensives. While exercise has prominent metabolic effects, salt has an adverse effect on metabolic syndrome, of which hypertension is a hallmark. We hypothesized that dietary salt impacts metabolism in a salt-sensitive model of hypertension. An untargeted metabolomic approach demonstrates lower circulating levels of the ketone body, beta-hydroxybutyrate (βOHB), in high salt-fed hypertensive rats. Despite the high salt intake, specific rescue of βOHB levels by nutritional supplementation of its precursor, 1,3-butanediol, attenuates hypertension and protects kidney function. This beneficial effect of βOHB was likely independent of gut-microbiotal and Th17-mediated effects of salt and instead facilitated by βOHB inhibiting the renal Nlrp3 inflammasome. The juxtaposed effects of dietary salt and exercise on salt-sensitive hypertension, which decrease and increase βOHB respectively, indicate that nutritional supplementation of a precursor of βOHB provides a similar benefit to salt-sensitive hypertension as exercise.

RIPK3-MLKL-mediated necroinflammation contributes to AKI progression to CKD

Necroptosis predominates functionally over apoptosis in the pathophysiology of renal ischemia-reperfusion injury (IRI). Inhibition of the core components of the necroptotic pathway—receptor-interacting protein kinase 1 (RIPK1), RIPK3 or mixed lineage kinase domain-like protein (MLKL) reduced renal injury after ischemia/reperfusion (IR). Necrosis can initiate inflammation, which enhances necrosis in a positive feedback loop, subsequently leading to triggering more inflammation, termed as necroinflammation. However, the mechanisms underlying necroinflammation driven by renal tubular cell necroptosis in progression of AKI to CKD are still largely unknown. Here we showed that the upregulated expression and interactions between RIPK3 and MLKL induced necroptosis of renal proximal tubular cells and contributed to NLRP3 inflammasome activation under the conditions of IRI. Gene deletion of Ripk3 or Mlkl ameliorated renal tubular cell necroptosis, macrophage infiltration and NLRP3 inflammasome activation with a reduction in caspase-1 activation and maturation of IL-1β, and then finally reduced interstitial fibrogenesis in the long term after IRI. Bone marrow chimeras confirmed that RIPK3-MLKL-dependent necroptosis is responsible for the initiation of the early renal injury after IRI, and then necroptosis triggered NLRP3 inflammasome activation, which subsequently accelerates necroptosis and triggers more inflammation in an auto-amplification loop. These data indicate that necroinflammation driven by RIPK3-MLKL-dependent necroptosis plays a crucial role in the progression of IRI to CKD.

BCL6 attenuates renal inflammation via negative regulation of NLRP3 transcription

Renal inflammation contributes to the pathogeneses of hypertension. This study was designed to determine whether B-cell lymphoma 6 (BCL6) attenuates renal NLRP3 inflammasome activation and inflammation and its underlying mechanism. Male spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were used in the present study. Angiotensin (Ang) II or lipopolysaccharides (LPS) was used to induce inflammation in HK-2 cells, a human renal tubular epithelial (RTE) cell line. NLRP3 inflammasome was activated and BCL6 was downregulated in the kidneys of SHR. Either Ang II or LPS suppressed BCL6 expression in HK-2 cells. BCL6 overexpression in HK-2 cells attenuated Ang II-induced NLRP3 upregulation, inflammation and cell injury. The inhibitory effects of BCL6 overexpression on NLRP3 expression and inflammation were also observed in LPS-treated HK-2 cells. BCL6 inhibited the NLRP3 transcription via binding to the NLRP3 promoter. BCL6 knockdown with shRNA increased NLRP3 and mature IL-1β expression levels in both PBS- or Ang II-treated HK-2 cells but had no significant effects on ASC, pro-caspase-1 and pro-IL-1β expression levels. BCL6 overexpression caused by recombinant lentivirus expressing BCL6 reduced blood pressure in SHR. BCL6 overexpression prevented the upregulation of NLRP3 and mature IL-1β expression levels in the renal cortex of SHR. The results indicate that BCL6 attenuates Ang II- or LPS-induced inflammation in HK-2 cells via negative regulation of NLRP3 transcription. BCL6 overexpression in SHR reduced blood pressure, NLRP3 expression and inflammation in the renal cortex of SHR.

Siwu decoction attenuates oxonate-induced hyperuricemia and kidney inflammation in mice

The aim of the study was to investigate the effects of Siwu decoction on hyperuricemia, kidney inflammation, and dysfunction in hyperuricemic mice. Siwu decoction at 363.8, 727.5, and 1 455 mg·kg−1 was orally administered to potassium oxonate-induced hyperuricemic mice for 7 days. Serum urate, creatinine, and blood urea nitrogen levels and hepatic xanthine oxidase (XOD) activity were measured. The protein levels of hepatic XOD and renal urate transporter 1 (URAT1), glucose transporter 9 (GLUT9), organic anion transporters 1 (OAT1), ATP-binding cassette subfamily G member 2 (ABCG2), organic cation transporter 1 (OCT1), OCT2, organic cation/carnitine transporter 1 (OCTN1), OCNT2, Nod-like receptor family, pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein (ASC), Caspase-1, and interleukin-1β (IL-1β) were determined by Western blotting. Renal histopathology change was obtained following hematoxylin-eosin staining. Our results indicated that Siwu decoction significantly reduced serum urate, creatinine and blood urea nitrogen levels and increased fractional excretion of uric acid in hyperuricemic mice. It effectively reduced hepatic XOD activity and protein levels in this animal model. Furthermore, Siwu decoction down-regulated URAT1 and GLUT9 protein levels, and up-regulated the protein levels of OAT1, ABCG2, OCT1, OCT2, OCTN1, and OCTN2 in the kidney of the hyperuricemic mice. Additionally, Siwu decoction remarkably reduced renal protein levels of NLRP3, ASC, Caspase-1, and IL-1β in the hyperuricemic mice. These results suggested that Siwu decoction exhibited anti-hyperuricemic and anti-inflammatory effects by inhibiting hepatic XOD activity, regulating renal organic ion transporter expression, and suppressing renal NLRP3 inflammasome activation, providing the evidence for its use in the treatment of hyperuricemia and associated kidney inflammation.

Resveratrol inhibits NLRP3 inflammasome activation by preserving mitochondrial integrity and augmenting autophagy.

The NLRP3 inflammasome is a caspase-1-containing multi-protein complex that controls the release of IL-1β and plays important roles in the development of inflammatory disease. Here, we report that resveratrol, a polyphenolic compound naturally produced by plants, inhibits NLRP3 inflammasome-derived IL-1β secretion and pyroptosis in macrophages. Resveratrol inhibits the activation step of the NLRP3 inflammasome by suppressing mitochondrial damage. Resveratrol also induces autophagy by activating p38, and macrophages treated with an autophagy inhibitor are resistant to the suppressive effects of resveratrol. In addition, resveratrol administration mitigates glomerular proliferation, glomerular sclerosis, and glomerular inflammation in a mouse model of progressive IgA nephropathy. These findings were associated with decreased renal mononuclear leukocyte infiltration, reduced renal superoxide anion levels, and inhibited renal NLRP3 inflammasome activation. Our data indicate that resveratrol suppresses NLRP3 inflammasome activation by preserving mitochondrial integrity and by augmenting autophagy.