Signals From Inflamed Perivascular Adipose Tissue Contribute to Small Vessel Dysfunction in Women Living With the Human Immunodeficiency Virus

INTRODUCTION

People living with the human immunodeficiency virus (PWH) have microvascular disease. Since perivascular adipose tissue (PVAT) regulates microvascular function and adipose tissue is inflamed in PWH, we tested the hypothesis that PWH have inflamed PVAT that impairs the function of their small vessels.

METHODS

Subcutaneous small arteries were dissected with or without (+ or -) PVAT from a gluteal skin biopsy from 11 women with treated HIV (WWH) aged < 50 years and 10 matched women without HIV and studied on isometric myographs. Nitric oxide (NO) and reactive oxygen species (ROS) were measured by fluorescence microscopy. Adipokines and markers of inflammation and ROS were assayed in PVAT.

RESULTS

PVAT surrounding the small arteries in control women significantly (P < 0.05) enhanced acetylcholine (Ach)-induced endothelium dependent relaxation and NO and reduced contractions to thromboxane and endothelin-1. However, these effects of PVAT were reduced significantly (P < 0.05) in WWH whose PVAT released less adiponectin but more markers of ROS and inflammation. Moderation of contractions by PVAT were correlated positively with adipose adiponectin.

CONCLUSION

PVAT from WWH has oxidative stress, inflammation and reduced release of adiponectin that may contribute to enhanced contractions and therefore could promote small artery dysfunction.

Empagliflozin in Heart Failure: Regional Nephron Sodium Handling Effects

SIGNIFICANCE STATEMENT

The effect of sodium-glucose cotransporter-2 inhibitors (SGLT2i) on regional tubular sodium handling is poorly understood in humans. In this study, empagliflozin substantially decreased lithium reabsorption in the proximal tubule (PT) (a marker of proximal tubular sodium reabsorption), a magnitude out of proportion to that expected with only inhibition of sodium-glucose cotransporter-2. This finding was not driven by an "osmotic diuretic" effect; however, several parameters changed in a manner consistent with inhibition of the sodium-hydrogen exchanger 3. The large changes in proximal tubular handling were acutely buffered by increased reabsorption in both the loop of Henle and the distal nephron, resulting in the observed modest acute natriuresis with these agents. After 14 days of empagliflozin, natriuresis waned due to increased reabsorption in the PT and/or loop of Henle. These findings confirm in humans that SGLT2i have complex and important effects on renal tubular solute handling.

BACKGROUND

The effect of SGLT2i on regional tubular sodium handling is poorly understood in humans but may be important for the cardiorenal benefits.

METHODS

This study used a previously reported randomized, placebo-controlled crossover study of empagliflozin 10 mg daily in patients with diabetes and heart failure. Sodium handling in the PT, loop of Henle (loop), and distal nephron was assessed at baseline and day 14 using fractional excretion of lithium (FELi), capturing PT/loop sodium reabsorption. Assessments were made with and without antagonism of sodium reabsorption through the loop using bumetanide.

RESULTS

Empagliflozin resulted in a large decrease in sodium reabsorption in the PT (increase in FELi=7.5%±10.6%, P = 0.001), with several observations suggesting inhibition of PT sodium hydrogen exchanger 3. In the absence of renal compensation, this would be expected to result in approximately 40 g of sodium excretion/24 hours with normal kidney function. However, rapid tubular compensation occurred with increased sodium reabsorption both in the loop ( P < 0.001) and distal nephron ( P < 0.001). Inhibition of sodium-glucose cotransporter-2 did not attenuate over 14 days of empagliflozin ( P = 0.14). However, there were significant reductions in FELi ( P = 0.009), fractional excretion of sodium ( P = 0.004), and absolute fractional distal sodium reabsorption ( P = 0.036), indicating that chronic adaptation to SGLT2i results primarily from increased reabsorption in the loop and/or PT.

CONCLUSIONS

Empagliflozin caused substantial redistribution of intrarenal sodium delivery and reabsorption, providing mechanistic substrate to explain some of the benefits of this class. Importantly, the large increase in sodium exit from the PT was balanced by distal compensation, consistent with SGLT2i excellent safety profile.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

ClinicalTrials.gov ( NCT03027960 ).

Effect of Sotagliflozin on Early Mortality and Heart Failure-Related Events: A Post Hoc Analysis of SOLOIST-WHF

BACKGROUND

Approximately 25% of patients admitted to hospitals for worsening heart failure (WHF) are readmitted within 30 days.

OBJECTIVES

The authors conducted a post hoc analysis of the SOLOIST-WHF (Effect of Sotagliflozin on Cardiovascular Events in Patients With Type 2 Diabetes Post-WHF) trial to evaluate the efficacy of sotagliflozin versus placebo to decrease mortality and HF-related events among patients who began study treatment on or before discharge from their index hospitalization.

METHODS

The main endpoint of interest was cardiovascular death or HF-related event (HF hospitalization or urgent care visit) occurring within 90 and 30 days after discharge for the index WHF hospitalization. Treatment comparisons were by proportional hazards models, generating HRs, 95% CIs, and P values.

RESULTS

Of 1,222 randomized patients, 596 received study drug on or before their date of discharge. Sotagliflozin reduced the main endpoint at 90 days after discharge (HR: 0.54 [95% CI: 0.35-0.82]; P = 0.004) and at 30 days (HR: 0.49 [95% CI: 0.27-0.91]; P = 0.023) and all-cause mortality at 90 days (HR: 0.39 [95% CI: 0.17-0.88]; P = 0.024). In subgroup analyses, sotagliflozin reduced the 90-day main endpoint regardless of sex, age, estimated glomerular filtration rate, N-terminal pro-B-type natriuretic peptide, left ventricular ejection fraction, or mineralocorticoid receptor agonist use. Sotagliflozin was well-tolerated but with slightly higher rates of diarrhea and volume-related events than placebo.

CONCLUSIONS

Starting sotagliflozin before discharge in patients with type 2 diabetes hospitalized for WHF significantly decreased cardiovascular deaths and HF events through 30 and 90 days after discharge, emphasizing the importance of beginning sodium glucose cotransporter treatment before discharge.

Critical Analysis of the Effects of SGLT2 Inhibitors on Renal Tubular Sodium, Water and Chloride Homeostasis and Their Role in Influencing Heart Failure Outcomes

SGLT2 (sodium-glucose cotransporter 2) inhibitors interfere with the reabsorption of glucose and sodium in the early proximal renal tubule, but the magnitude and duration of any ensuing natriuretic or diuretic effect are the result of an interplay between the degree of upregulation of SGLT2 and sodium-hydrogen exchanger 3, the extent to which downstream compensatory tubular mechanisms are activated, and (potentially) the volume set point in individual patients. A comprehensive review and synthesis of available studies reveals several renal response patterns with substantial variation across studies and clinical settings. However, the common observation is an absence of a large acute or chronic diuresis or natriuresis with these agents, either when given alone or combined with other diuretics. This limited response results from the fact that renal compensation to these drugs is rapid and nearly complete within a few days or weeks, preventing progressive volume losses. Nevertheless, the finding that fractional excretion of glucose and lithium (the latter being a marker of proximal sodium reabsorption) persists during long-term treatment with SGLT2 inhibitors indicates that pharmacological tolerance to the effects of these drugs at the level of the proximal tubule does not meaningfully occur. This persistent proximal tubular effect of SGLT2 inhibitors can be hypothesized to produce a durable improvement in the internal set point for volume homeostasis, which may become clinically important during times of fluid expansion. However, it is difficult to know whether a treatment-related change in the volume set point actually occurs or contributes to the effect of these drugs to reduce the risk of major heart failure events. SGLT2 inhibitors exert cardioprotective effects by a direct effect on cardiomyocytes that is independent of the presence of or binding to SGLT2 or the actions of these drugs on the proximal renal tubule. Nevertheless, changes in the volume set point mediated by SGLT2 inhibitors might potentially act cooperatively with the direct favorable molecular and cellular effects of these drugs on cardiomyocytes to mediate their benefits on the development and clinical course of heart failure.

A kidney-brain neural circuit drives progressive kidney damage and heart failure

Chronic kidney disease (CKD) and heart failure (HF) are highly prevalent, aggravate each other, and account for substantial mortality. However, the mechanisms underlying cardiorenal interaction and the role of kidney afferent nerves and their precise central pathway remain limited. Here, we combined virus tracing techniques with optogenetic techniques to map a polysynaptic central pathway linking kidney afferent nerves to subfornical organ (SFO) and thereby to paraventricular nucleus (PVN) and rostral ventrolateral medulla that modulates sympathetic outflow. This kidney-brain neural circuit was overactivated in mouse models of CKD or HF and subsequently enhanced the sympathetic discharge to both the kidney and the heart in each model. Interruption of the pathway by kidney deafferentation, selective deletion of angiotensin II type 1a receptor (AT1a) in SFO, or optogenetic silence of the kidney-SFO or SFO-PVN projection decreased the sympathetic discharge and lessened structural damage and dysfunction of both kidney and heart in models of CKD and HF. Thus, kidney afferent nerves activate a kidney-brain neural circuit in CKD and HF that drives the sympathetic nervous system to accelerate disease progression in both organs. These results demonstrate the crucial role of kidney afferent nerves and their central connections in engaging cardiorenal interactions under both physiological and disease conditions. This suggests novel therapies for CKD or HF targeting this kidney-brain neural circuit.

Etiology and Management of Edema: A Review

The development of peripheral edema can often pose a significant diagnostic and therapeutic challenge for practitioners due to its association with a wide variety of underlying disorders ranging in severity. Updates to the original Starling's principle have provided new mechanistic insights into edema formation. Additionally, contemporary data highlighting the role of hypochloremia in the development of diuretic resistance provide a possible new therapeutic target. This article reviews the pathophysiology of edema formation and discusses implications for treatment.

Pseudohyperkalemia: Three Cases and a Review of Literature

Hyperkalemia is a potentially fatal complication requiring prompt diagnosis and management. However, pseudohyperkalemia, defined as an artificial rise in serum potassium (S_k), is also an important diagnosis because management differs. Pseudohyperkalemia can result from multiple factors, including excessive potassium leakage from cells of the forearm during blood collection due to release from exercising the muscle during fist clenching, while washout is prevented by tourniquet application, hemolysis, problems with sample transport, preanalysis or contamination, cell damage and metabolic changes, familial conditions that permit excessive potassium ion (K⁺) leak from erythrocytes after blood sampling, and leukocytosis or thrombocytosis. In this review, we will discuss the major causes of pseudohyperkalemia, how to avoid certain diagnostic pitfalls, and comment on the clinical importance of recognizing these false readings. We will review three clinical cases seen in our nephrology and hypertension clinic that illustrate some of these problems.

Activation of Nrf2 in Mice Causes Early Microvascular Cyclooxygenase-Dependent Oxidative Stress and Enhanced Contractility

Nuclear factor erythroid factor E2-related factor 2 (Nrf2) transcribes antioxidant genes that reduce the blood pressure (BP), yet its activation with tert-butylhydroquinone (tBHQ) in mice infused with angiotensin II (Ang II) increased mean arterial pressure (MAP) over the first 4 days of the infusion. Since tBHQ enhanced cyclooxygenase (COX) 2 expression in vascular smooth muscle cells (VSMCs), we tested the hypothesis that tBHQ administration during an ongoing Ang II infusion causes an early increase in microvascular COX-dependent reactive oxygen species (ROS) and contractility. Mesenteric microarteriolar contractility was assessed on a myograph, and ROS by RatioMaster™. Three days of oral tBHQ administration during the infusion of Ang II increased the mesenteric microarteriolar mRNA for p47^phox, the endothelin type A receptor and thromboxane A₂ synthase, and increased the excretion of 8-isoprostane F_2α and the microarteriolar ROS and contractions to a thromboxane A₂ (TxA₂) agonist (U-46,619) and endothelin 1 (ET1). These were all prevented in Nrf2 knockout mice. Moreover, the increases in ROS and contractility were prevented in COX1 knockout mice with blockade of COX2 and by blockade of thromboxane prostanoid receptors (TPRs). In conclusion, the activation of Nrf2 over 3 days of Ang II infusion enhances microarteriolar ROS and contractility, which are dependent on COX1, COX2 and TPRs. Therefore, the blockade of these pathways may diminish the early adverse cardiovascular disease events that have been recorded during the initiation of Nrf2 therapy.

Development and Validation of Prediction Models for Hypertensive Nephropathy, the PANDORA Study

Importance

Hypertension is a leading cause of end-stage renal disease (ESRD), but currently, those at risk are poorly identified.

Objective

To develop and validate a prediction model for the development of hypertensive nephropathy (HN).

Design, Setting, and Participants

Individual data of cohorts of hypertensive patients from Kailuan, China served to derive and validate a multivariable prediction model of HN from 12, 656 individuals enrolled from January 2006 to August 2007, with a median follow-up of 6.5 years. The developed model was subsequently tested in both derivation and external validation cohorts.

Variables

Demographics, physical examination, laboratory, and comorbidity variables.

Main Outcomes and Measures

Hypertensive nephropathy was defined as hypertension with an estimated glomerular filtration rate (eGFR) &lt; 60 ml/min/1.73 m2 and/or proteinuria.

Results

About 8.5% of patients in the derivation cohort developed HN after a median follow-up of 6.5 years that was similar in the validation cohort. Eight variables in the derivation cohort were found to contribute to the risk of HN: salt intake, diabetes mellitus, stroke, serum low-density lipoprotein, pulse pressure, age, hypertension duration, and serum uric acid. The discrimination by concordance statistics (C-statistics) was 0.785 (IQR, 0.770-0.800); the calibration slope was 1.129, the intercept was –0.117; and the overall accuracy by adjusted R2 was 0.998 with similar results in the validation cohort. A simple points scale developed from these data (0, low to 40, high) detected a low morbidity of 7% in the low-risk group (0–10 points) compared with &gt;40% in the high-risk group (&gt;20 points).

Conclusions and Relevance

A prediction model of HN over 8 years had high discrimination and calibration, but this model requires prospective evaluation in other cohorts, to confirm its potential to improve patient care.

Low Dose Chronic Angiotensin II Induces Selective Senescence of Kidney Endothelial Cells

Angiotensin II can cause oxidative stress and increased blood pressure that result in long term cardiovascular pathologies. Here we evaluated the contribution of cellular senescence to the effect of chronic exposure to low dose angiotensin II in a model that mimics long term tissue damage. We utilized the INK-ATTAC (p16^Ink4a–Apoptosis Through Targeted Activation of Caspase 8) transgenic mouse model that allows for conditional elimination of p16^Ink4a -dependent senescent cells by administration of AP20187. Angiotensin II treatment for 3 weeks induced ATTAC transgene expression in kidneys but not in lung, spleen and brain tissues. In the kidneys increased expression of ATM, p15 and p21 matched with angiotensin II induction of senescence-associated secretory phenotype genes MMP3, FGF2, IGFBP2, and tPA. Senescent cells in the kidneys were identified as endothelial cells by detection of GFP expressed from the ATTAC transgene and increased expression of angiopoietin 2 and von Willebrand Factor, indicative of endothelial cell damage. Furthermore, angiotensin II induced expression of the inflammation-related glycoprotein versican and immune cell recruitment to the kidneys. AP20187-mediated elimination of p16-dependent senescent cells prevented physiologic, cellular and molecular responses to angiotensin II and provides mechanistic evidence of cellular senescence as a driver of angiotensin II effects.

Renal negative pressure treatment as a novel therapy for heart failure-induced renal dysfunction

Congestion is the primary pathophysiological lesion in most heart failure (HF) hospitalizations. Renal congestion increases renal tubular pressure, reducing glomerular filtration rate (GFR) and diuresis. Because each nephron is a fluid-filled column, renal negative pressure therapy (rNPT) applied to the urinary collecting system should reduce tubular pressure, potentially improving kidney function. We evaluated the renal response to rNPT in congestive HF. Ten anesthetized ∼80-kg pigs underwent instrumentation with bilateral renal pelvic JuxtaFlow catheters. GFR was determined by iothalamate clearance (mGFR) and renal plasma flow (RPF) by para-aminohippurate clearance. Each animal served as its own control with randomization of left versus right kidney to -30 mmHg rNPT or no rNPT. mGFR and RPF were measured simultaneously from the rNPT and no rNPT kidney. Congestive HF was induced via cardiac tamponade maintaining central venous pressure at 20-22.5 mmHg throughout the experiment. Before HF induction, rNPT increased natriuresis, diuresis, and mGFR compared with the control kidney (P < 0.001 for all). Natriuresis, diuresis, and mGFR decreased following HF (P < 0.001 for all) but were higher in rNPT kidney versus control (P < 0.001 for all). RPF decreased during HF (P < 0.001) without significant differences between rNPT treatments. During HF, the rNPT kidney had similar diuresis and natriuresis (P > 0.5 for both) and higher fractional excretion of sodium (P = 0.001) compared with the non-rNPT kidney in the no HF period. In conclusion, rNPT resulted in significantly increased diuresis, natriuresis, and mGFR, with or without experimental HF. rNPT improved key renal parameters of the congested cardiorenal phenotype.

Compensatory post-diuretic renal sodium reabsorption is not a dominant mechanism of diuretic resistance in acute heart failure

AIMS

In healthy volunteers, the kidney deploys compensatory post-diuretic sodium reabsorption (CPDSR) following loop diuretic-induced natriuresis, minimizing sodium excretion and producing a neutral sodium balance. CPDSR is extrapolated to non-euvolemic populations as a diuretic resistance mechanism; however, its importance in acute decompensated heart failure (ADHF) is unknown.

METHODS AND RESULTS

Patients with ADHF in the Mechanisms of Diuretic Resistance cohort receiving intravenous loop diuretics (462 administrations in 285 patients) underwent supervised urine collections entailing an immediate pre-diuretic spot urine sample, then 6-h (diuretic-induced natriuresis period) and 18-h (post-diuretic period) urine collections. The average spot urine sodium concentration immediately prior to diuretic administration [median 15 h (13-17) after last diuretic] was 64 ± 33 mmol/L with only 4% of patients having low (<20 mmol/L) urine sodium consistent with CPDSR. Paradoxically, greater 6-h diuretic-induced natriuresis was associated with larger 18-h post-diuretic spontaneous natriuresis (r = 0.7, P < 0.001). Higher pre-diuretic urine sodium to creatinine ratio (r = 0.37, P < 0.001) was the strongest predictor of post-diuretic spontaneous natriuresis. In a subgroup of patients (n = 43) randomized to protocol-driven intensified diuretic therapies, the mean diuretic-induced natriuresis increased three-fold. In contrast to the substantial decrease in spontaneous natriuresis predicted by CPDSR, no change in post-diuretic spontaneous natriuresis was observed (P = 0.47).

CONCLUSION

On a population level, CPDSR was not an important driver of diuretic resistance in hypervolemic ADHF. Contrary to CPDSR, a greater diuretic-induced natriuresis predicted a larger post-diuretic spontaneous natriuresis. Basal sodium avidity, rather than diuretic-induced CPDSR, appears to be the predominant determinate of both diuretic-induced and post-diuretic natriuresis in hypervolemic ADHF.

Abstract MP30: Circulating Sars-cov-2 Spike Protein 1 Causes Microarteriolar Oxidative Stress, Endothelial Dysfunction And Enhanced Thromboxane And Endothelin Contractility That Are Prevented By Spironolactone

Introduction and hypothesis: Following bodily entry, the SARS-CoV-2 virus undergoes pulmonary replication with release of circulating viral spike protein 1 (SP1) into the bloodstream. Uptake of SP1 by endothelial cells might provoke vascular dysfunction and thrombosis. We hypothesized that spironolactone could prevent microvascular complications from circulating SP1 in COVID-19.

Methods: male C57Bl/6 mice received spironolactone (100 mg · kg -1 · d -1 PO x 3d) or vehicle and intravenous injections of recombinant full-length human SP1 (10 μg per mouse) or vehicle. They were euthanized after 3 days. Mesenteric resistant arterioles (n=4 per group) were dissected and mounted on isometric myographs. Acetylcholine-induced EDRF responses and L-NAME-inhibitable NO generation (DAF-FM fluorescence) were studied in pre-constricted vessels and contraction to endothelin 1 (ET1) or thromboxane (U-46, 619) and ET1-induced ROS (PEG-SOD inhibitable ethidium: dihydroethidium fluorescence) were studied by fluorescence microscopy in other vessels.

Results: SP1 reduced acetylcholine-induced EDRF (17 ± 3 vs 27 ± 5 % mean ± sem; P < 0.05) and NO generation (0.21 ± 0.03 vs 0.36 ± 0.04, F 1 /F 0 ; P < 0.05) while increasing contraction to ET1 (10 -7 mol·l -1 : 124 ± 13 vs 89 ± 4 %; P < 0.05) and U-46, 619 (10 -6 mol·l -1 :114± 5 vs 87± 6 %; P < 0.05) and ET1-induced ROS generation(0.30± 0.08 vs 0.09± 0.03; P < 0.05). Spironolactone did not modify any of these responses in vessels from normal mice but prevented all the effects of SP1.

Conclusion: these preliminary studies provide a novel model to study COVID-19 vasculopathy. They indicate that spironolactone can provide protection from microvascular oxidative stress, endothelial dysfunction and enhanced contractility and might thereby moderate COVID-19 complications.

Abstract MP16: Perivascular Adipose Tissue Inflammation Impairs Microvascular Endothelial Function In People Living With HIV

Introduction and hypothesis: We had reported that people living with HIV (PLWH) have microvascular endothelial dysfunction and increased ROS. We now tested the hypothesis that perivascular adipose tissue (PVAT) could enhance oxidative stress and inflammation and impair the function of subcutaneous microarterioles (SMAs) in PLWH.

Methods: SMAs were obtained from young, virally-suppressed HIV-infected subjects (n=11) or matched controls (n=11). Subjects were without associated CVD risk factors. Microvascular reactivity and PVAT function were accessed by myograph from isolated subcutaneous vessels with or without PVAT of skin biopsy.

Results: The HIV-infected group had significantly (P<0.05) increased adipose MDA, TNFα, IL-1α, leptin and reduced adiponectin. The PVAT-denuded SMAs from the HIV group had significantly (P<0.05) impaired acetylcholine-induced endothelium-dependent relaxation factor (EDRF, 26±4 vs 38±3%) and NO activity (0.35±0.03 vs 0.58± 0.07 Δfluoresence unit) and significantly (P<0.05) increased contraction to U-46,619 (200±8 vs 141±7%) and endothelin 1 (ET1, 167±12 vs 118±17%) and ROS generation (0.32 ± 0.06 vs 0.1 ± 0.03 (E/DHE fluoresce unit). PVAT enhanced EDRF (50±4 vs 38±3 %) and NO (0.84 ±0.1 vs 0.58±0.07 Δfluoresence unit ) only in controls (P<0.05). The reduction of U46,619 anti-contractivity by PVAT is decreased in HIV (48±7 vs 85±9%, P<0.05).

Conclusion: HIV-infected individuals have intrinsic vascular defects from ROS augmented by extrinsic vascular defects from adipose inflammation that impairs the beneficial microvascular PVAT signaling. Therefore, targets for potential prevention of cardiovascular morbidity in PLWH should include the elimination of ROS and inflammation in both microvessels themselves and the surrounding extravascular PVAT.

Effect of Sotagliflozin on Total Hospitalizations in Patients With Type 2 Diabetes and Worsening Heart Failure : A Randomized Trial

BACKGROUND

In the SOLOIST-WHF (Effect of Sotagliflozin on Cardiovascular Events in Patients With Type 2 Diabetes Post Worsening Heart Failure) trial, sotagliflozin, a sodium-glucose cotransporter-1 and sodium-glucose cotransporter-2 inhibitor, reduced total occurrences of cardiovascular deaths, hospitalizations for heart failure, and urgent visits for heart failure relative to placebo by 33%.

OBJECTIVE

To determine whether sotagliflozin increased the prespecified efficacy outcome of days alive and out of the hospital (DAOH) in the SOLOIST-WHF trial.

DESIGN

Randomized, double-blind, placebo-controlled trial. (ClinicalTrials.gov: NCT03521934).

SETTING

306 sites in 32 countries.

PARTICIPANTS

1222 patients with type 2 diabetes and reduced or preserved ejection fraction who were recently hospitalized for worsening heart failure.

INTERVENTION

200 mg of sotagliflozin once daily (with a possible dose increase to 400 mg) or matching placebo.

MEASUREMENTS

The primary analysis included hospitalizations for any reason on the basis of investigator-reported incidence and duration of admissions after randomization. Days alive and out of the hospital and its converse (days dead and days in the hospital) were analyzed using prespecified Poisson regression models.

RESULTS

Although similar proportions of patients in the sotagliflozin and placebo groups were hospitalized at least once (38.5% vs. 41.4%), fewer patients in the sotagliflozin group were hospitalized more than once (16.3% vs. 22.1%). There were 64 and 76 deaths in the sotagliflozin and placebo groups, respectively. The DAOH rate in the sotagliflozin group was 3% higher than in the placebo group (rate ratio [RR], 1.03 [95% CI, 1.00 to 1.06]; P = 0.027). This difference was primarily driven by a reduction in the rate of days dead (RR, 0.71 [CI, 0.52 to 0.99]; P = 0.041) rather than by a reduction in the rate of days hospitalized for any cause. For every 100 days of follow-up, patients in the sotagliflozin group were alive and out of the hospital for 3% or 2.9 more days than those in the placebo group (91.8 vs. 88.9 days); this difference reflected a 2.6-day difference in days dead (6.3 vs. 8.9 days) and a 0.3-day difference in days in the hospital (1.9 vs. 2.2 days).

LIMITATION

Other than heart failure, the primary reason for each hospitalization was unspecified.

CONCLUSION

Sotagliflozin increased DAOH, a metric that may provide an additional patient-centered outcome to capture the totality of disease burden. Future studies are needed to quantify the consequences of increasing DAOH in terms of health economics and patient quality of life.

PRIMARY FUNDING SOURCE

Sanofi at initiation and Lexicon Pharmaceuticals at completion.

Pathophysiology of Hypertension: The Mosaic Theory and Beyond

Dr Irvine Page proposed the Mosaic Theory of Hypertension in the 1940s advocating that hypertension is the result of many factors that interact to raise blood pressure and cause end-organ damage. Over the years, Dr Page modified his paradigm, and new concepts regarding oxidative stress, inflammation, genetics, sodium homeostasis, and the microbiome have arisen that allow further refinements of the Mosaic Theory. A constant feature of this approach to understanding hypertension is that the various nodes are interdependent and that these almost certainly vary between experimental models and between individuals with hypertension. This review discusses these new concepts and provides an introduction to other reviews in this compendium of Circulation Research.

ADAMTS13 inhibits oxidative stress and ameliorates progressive chronic kidney disease following ischaemia/reperfusion injury

AIMS

Reduced A Disintegrin And Metalloproteinase with a ThromboSpondin type 1 motif member 13 (ADAMTS13) levels are observed in kidney disease. We test whether recombinant human ADAMTS13 (rhADAMTS13) mitigates renal injury in chronic kidney disease (CKD) and the potential mechanisms.

METHODS

CKD was established 3 months after ischaemia/reperfusion (IR). ADAMTS13 and von Willebrand factor (vWF) levels, renal function and morphological changes were analysed. Afferent arteriolar responses to angiotensin II (Ang II) and acetylcholine (ACh) were measured. Oxidative stress-related molecules were detected.

RESULTS

Higher vWF and lower ADAMTS13 levels were observed in CKD mice, which were markedly attenuated by rhADAMTS13. rhADAMTS13 alleviated renal dysfunction, as documented by decreased blood urea nitrogen (BUN), serum creatinine, kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) levels in CKD mice. Moreover, rhADAMTS13 attenuated transforming growth factor (TGF)-β1/Smad3 activation. Plasma vWF: ADAMTS13 ratio showed positive correlations with malondialdehyde (MDA), hydrogen peroxide (H₂ O₂ ) and proteinuria, and correlated inversely with superoxide dismutase (SOD) and catalase (CAT). Finally, rhADAMTS13 inhibited reactive oxygen species (ROS) levels and improved microvascular functional disorders, accompanied by the inhibition of glycogen synthase kinase (GSK) 3β hyperactivity and upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) expression.

CONCLUSIONS

Acute kidney injury (AKI) reduces the expression of ADAMTS13 that contributes to progressive CKD, microvascular dysfunction, oxidative stress, inhibition of Nrf2 activity and renal histopathological damage. All of which can be alleviated by administration of rhADAMTS13.

Sotagliflozin in Patients with Diabetes and Recent Worsening Heart Failure

BACKGROUND

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce the risk of hospitalization for heart failure or death from cardiovascular causes among patients with stable heart failure. However, the safety and efficacy of SGLT2 inhibitors when initiated soon after an episode of decompensated heart failure are unknown.

METHODS

We performed a multicenter, double-blind trial in which patients with type 2 diabetes mellitus who were recently hospitalized for worsening heart failure were randomly assigned to receive sotagliflozin or placebo. The primary end point was the total number of deaths from cardiovascular causes and hospitalizations and urgent visits for heart failure (first and subsequent events). The trial ended early because of loss of funding from the sponsor.

RESULTS

A total of 1222 patients underwent randomization (608 to the sotagliflozin group and 614 to the placebo group) and were followed for a median of 9.0 months; the first dose of sotagliflozin or placebo was administered before discharge in 48.8% and a median of 2 days after discharge in 51.2%. Among these patients, 600 primary end-point events occurred (245 in the sotagliflozin group and 355 in the placebo group). The rate (the number of events per 100 patient-years) of primary end-point events was lower in the sotagliflozin group than in the placebo group (51.0 vs. 76.3; hazard ratio, 0.67; 95% confidence interval [CI], 0.52 to 0.85; P<0.001). The rate of death from cardiovascular causes was 10.6 in the sotagliflozin group and 12.5 in the placebo group (hazard ratio, 0.84; 95% CI, 0.58 to 1.22); the rate of death from any cause was 13.5 in the sotagliflozin group and 16.3 in the placebo group (hazard ratio, 0.82; 95% CI, 0.59 to 1.14). Diarrhea was more common with sotagliflozin than with placebo (6.1% vs. 3.4%), as was severe hypoglycemia (1.5% vs. 0.3%). The percentage of patients with hypotension was similar in the sotagliflozin group and the placebo group (6.0% and 4.6%, respectively), as was the percentage with acute kidney injury (4.1% and 4.4%, respectively). The benefits of sotagliflozin were consistent in the prespecified subgroups of patients stratified according to the timing of the first dose.

CONCLUSIONS

In patients with diabetes and recent worsening heart failure, sotagliflozin therapy, initiated before or shortly after discharge, resulted in a significantly lower total number of deaths from cardiovascular causes and hospitalizations and urgent visits for heart failure than placebo. (Funded by Sanofi and Lexicon Pharmaceuticals; SOLOIST-WHF ClinicalTrials.gov number, NCT03521934.).

Acute Kidney Injury Sensitizes the Brain Vasculature to Ang II (Angiotensin II) Constriction via FGFBP1 (Fibroblast Growth Factor Binding Protein 1)

Acute kidney injury (AKI) causes multiple organ dysfunction. Here, we identify a possible mechanism that can drive brain vessel injury after AKI. We induced 30-minute bilateral renal ischemia-reperfusion injury in C57Bl/6 mice and isolated brain microvessels and macrovessels 24 hours or 1 week later to test their responses to vasoconstrictors and found that after AKI brain vessels were sensitized to Ang II (angiotensin II). Upregulation of FGF2 (fibroblast growth factor 2) and FGFBP1 (FGF binding protein 1) expression in both serum and kidney tissue after AKI suggested a potential contribution to the vascular sensitization. Administration of FGF2 and FGFBP1 proteins to isolated healthy brain vessels mimicked the sensitization to Ang II after AKI. Brain vessels in Fgfbp1-/- AKI mice failed to induce Ang II sensitization. Complementary to this, systemic treatment with the clinically used FGF receptor kinase inhibitor BGJ398 (Infigratinib) reversed the AKI-induced brain vascular sensitization to Ang II. All these findings lead to the conclusion that FGFBP1 is especially necessary for AKI-mediated brain vascular sensitization to Ang II and inhibitors of FGFR pathway may be beneficial in preventing AKI-induced brain vessel injury.

Endothelial prostaglandin D2 opposes angiotensin II contractions in mouse isolated perfused intracerebral microarterioles

Hypothesis:

A lack of contraction of cerebral microarterioles to Ang II (“resilience”) depends on cyclooxygenase (COX) and lipocalin type prostaglandin D sythase L-PGDS producing PGD₂ that activates prostaglandin D type 1 receptors (DP1Rs) and nitric oxide synthase (NOS).

Materials & Methods:

Contractions were assessed in isolated, perfused vessels and NO by fluorescence microscopy.

Results:

The mRNAs of penetrating intraparenchymal cerebral microarterioles versus renal afferent arterioles were >3000-fold greater for L-PGDS and DP1R and 5-fold for NOS III and COX 2. Larger cerebral arteries contracted with Ang II. However, cerebral microarterioles were entirely unresponsive but contracted with endothelin 1 and perfusion pressure. Ang II contractions were evoked in cerebral microarterioles from COX1 –/– mice or after blockade of COX2, L-PGDS or NOS and in deendothelialized vessels but effects of deendothelialization were lost during COX blockade. NO generation with Ang II depended on COX and also was increased by DP1R activation.

Conclusion:

The resilience of cerebral arterioles to Ang II contractions is specific for intraparenchymal microarterioles and depends on endothelial COX1 and two products that are metabolized by L-PGDS to generate PGD₂ that signals via DP1Rs and NO.

Cardiovascular outcome trials in patients with chronic kidney disease: challenges associated with selection of patients and endpoints

Although cardiovascular disease is a major health burden for patients with chronic kidney disease, most cardiovascular outcome trials have excluded patients with advanced chronic kidney disease. Moreover, the major cardiovascular outcome trials that have been conducted in patients with end-stage renal disease have not demonstrated a treatment benefit. Thus, clinicians have limited evidence to guide the management of cardiovascular disease in patients with chronic kidney disease, particularly those on dialysis. Several factors contribute to both the paucity of trials and the apparent lack of observed treatment effect in completed studies. Challenges associated with conducting trials in this population include patient heterogeneity, complexity of renal pathophysiology and its interaction with cardiovascular disease, and competing risks for death. The Investigator Network Initiative Cardiovascular and Renal Clinical Trialists (INI-CRCT), an international organization of academic cardiovascular and renal clinical trialists, held a meeting of regulators and experts in nephrology, cardiology, and clinical trial methodology. The group identified several research priorities, summarized in this paper, that should be pursued to advance the field towards achieving improved cardiovascular outcomes for these patients. Cardiovascular and renal clinical trialists must partner to address the uncertainties in the field through collaborative research and design clinical trials that reflect the specific needs of the chronic and end-stage kidney disease populations, with the shared goal of generating robust evidence to guide the management of cardiovascular disease in patients with kidney disease.

Sympathetic Overactivity in CKD Disrupts Buffering of Neurotransmission by Endothelium-Derived Hyperpolarizing Factor and Enhances Vasoconstriction

BACKGROUND

Hypertension commonly complicates CKD. Vascular smooth muscle cells (VSMCs) of resistance arteries receive signals from the sympathetic nervous system that induce an endothelial cell (EC)-dependent anticontractile response that moderates vasoconstriction. However, the specific role of this pathway in the enhanced vasoconstriction in CKD is unknown.

METHODS

A mouse model of CKD hypertension generated with 5/6-nephrectomy (5/6Nx) was used to investigate the hypothesis that an impaired anticontractile mechanism enhances sympathetic vasoconstriction. In vivo, ex vivo (isolated mesenteric resistance arteries), and in vitro (VSMC and EC coculture) models demonstrated neurovascular transmission and its contribution to vascular resistance.

RESULTS

By 4 weeks, 5/6Nx mice (versus sham) had augmented increases in mesenteric vascular resistance and mean arterial pressure with carotid artery occlusion, accompanied by decreased connexin 43 (Cx43) expression at myoendothelial junctions (MEJs), impaired gap junction function, decreased EC-dependent hyperpolarization (EDH), and enhanced contractions. Exposure of VSMCs to NE for 24 hours in a vascular cell coculture decreased MEJ Cx43 expression and MEJ gap junction function. These changes preceded vascular structural changes evident only at week 8. Inhibition of central sympathetic outflow or transfection of Cx43 normalized neurovascular transmission and vasoconstriction in 5/6Nx mice.

CONCLUSIONS

5/6Nx mice have enhanced neurovascular transmission and vasoconstriction from an impaired EDH anticontractile component before vascular structural changes. These neurovascular changes depend on an enhanced sympathetic discharge that impairs the expression of Cx43 in gap junctions at MEJs, thereby interrupting EDH responses that normally moderate vascular tone. Dysregulation of neurovascular transmission may contribute to the development of hypertension in CKD.

Renal Nerve Deafferentation Attenuates the Fall in GFR during Intravenous Infusion of Furosemide in Anesthetized Rats

INTRODUCTION

Furosemide reduces the glomerular filtration rate (GFR) and increases the renal vascular resistance (RVR) despite inhibiting tubuloglomerular feedback but increases proximal tubule pressure, renin release, and renal nerve activity.

OBJECTIVE

This study tested the hypothesis that the fall in GFR with furosemide is due to volume depletion or activation of angiotensin type 1 (AT1) receptors or renal nerves.

METHODS

Furosemide was infused for 60 min at 1.0 mg·kg-1·h-1 in groups of 5-8 anesthetized rats. Additional groups received intravenous volume replacement to prevent fluid and Na+ losses or volume replacement plus losartan or plus sham denervation or plus renal denervation or renal nerve deafferentation.

RESULTS

At 60 min of infusion, furosemide alone reduced the GFR (-37 ± 4%; p < 0.01). This fall was not prevented by volume replacement or pretreatment with losartan, although losartan moderated the increase in RVR with furosemide (+44 ± 3 vs. +82 ± 7%; p < 0.01). Whereas the GFR fell after furosemide in rats after sham procedure (-31 ± 2%), it was not changed significantly after prior renal deafferentation. Proximal tubule pressure increased significantly but returned towards baseline over 60 min of furosemide, while urine output remained elevated, and GFR and renal blood flow depressed.

CONCLUSIONS

The fall in GFR over 60 min of furosemide infusion is independent of volume depletion or activation of AT1 receptors but is largely dependent on renal afferent nerves.

Rationale and Strategies for Preserving Residual Kidney Function in Dialysis Patients

BACKGROUND

Residual kidney function (RKF) conveys a survival benefit among dialysis patients, but the mechanism remains unclear. Improved volume control, clearance of protein-bound and middle molecules, reduced inflammation and preserved erythropoietin and vitamin D production are among the proposed mechanisms. Preservation of RKF requires techniques to measure it accurately to be able to uncover factors that accelerate its loss and interventions that preserve it and ultimately to individualize therapy. The average of renal creatinine and urea clearance provides a superior estimate of RKF in dialysis patients, when compared with daily urine volume. However, both involve the difficult task of obtaining an accurate 24-h urine sample.

SUMMARY

In this article, we first review the definition and measurement of RKF, including newly proposed markers such as serum levels of beta2-microglobulin, cystatin C and beta-trace protein. We then discuss the predictors of RKF loss in new dialysis patients. We review several strategies to preserve RKF such as renin-angiotensin-aldosterone system blockade, incremental dialysis, use of biocompatible membranes and ultrapure dialysate in hemodialysis (HD) patients, and use of biocompatible solutions in peritoneal dialysis (PD) patients. Despite their generally adverse effects on renal function, aminoglycoside antibiotics have not been shown to have adverse effects on RKF in well-hydrated patients with end-stage renal disease (ESRD). Presently, the roles of better blood pressure control, diuretic usage, diet, and dialysis modality on RKF remain to be clearly established. Key Messages: RKF is an important and favorable prognostic indicator of reduced morbidity, mortality, and higher quality of life in both PD an HD patients. Further investigation is warranted to uncover factors that protect or impair RKF. This should lead to improved quality of life and prolonged lifespan in patients with ESRD and cost-reduction through patient centeredness, individualized therapy, and precision medicine approaches.

NaHCO3 Dilates Mouse Afferent Arteriole Via Na+/HCO3- Cotransporters NBCs

Sodium bicarbonate has long been used to treat chronic kidney disease. It has been demonstrated to slow the decline in glomerular filtration rate in chronic kidney disease patient; however, the mechanisms are not completely understood. We hypothesized that NaHCO₃ dilates afferent arterioles (Af-Art) by stimulating nitric oxide (NO) release mediated by the Na⁺/HCO₃^- cotransporter (NBC) contributing to the elevation in glomerular filtration rate. Isolated microperfused mouse renal Af-Art, preconstricted with norepinephrine (1 µmol/L), dilated 45±2% (n=6, P<0.05) in response to NaHCO₃ (44 mmol/L). Whereas, NaCl solution containing the same Na⁺ concentration was not effective. The mRNA for NBCn1 and NBCe1 were detected in microdissected Af-Art using reverse transcription-polymerase chain reaction and quantitative polymerase chain reaction. The Af-Art intracellular pH measured with 2',7'-bis-(2-carboxyethyl)-5-(and-6) carboxyfluorescein, acetoxymethyl ester increased significantly by 0.29±0.02 (n=6; P<0.05) in the presence of NaHCO₃, which was blunted by N-cyanosulphonamide compound (S0859) that is an inhibitor of the NBC family. After clamping the intracellular pH with 10 μM nigericin, changing the bath solution pH from 7.4 to 7.8 still dilates the Af-Art by 53±4% (n=7; P<0.005) and increases NO generation by 22±3% (n=7; P<0.005). Both pH-induced NO generation and vasodilation were blocked by L-NG-Nitroarginine Methyl Ester. NaHCO₃ increased NO generation in Af-Art by 19±4% (n=5; P<0.005) and elevated glomerular filtration rate in conscious mice by 36% (233 versus 318 ul/min; n=9-10; P<0.0001). S0859 and L-NG-nitroarginine methyl ester blocked NaHCO₃-induced increases in NO generation and vasodilation. We conclude that NBCn1 and NBCe1 are expressed in Af-Art and that NaHCO₃ dilates Af-Art via NBCs mediated by NO that increases the glomerular filtration rate.

Endothelin-1-Induced Microvascular ROS and Contractility in Angiotensin-II-Infused Mice Depend on COX and TP Receptors

(1) Background: Angiotensin II (Ang II) and endothelin 1 (ET-1) generate reactive oxygen species (ROS) that can activate cyclooxygenase (COX). However, thromboxane prostanoid receptors (TPRs) are required to increase systemic markers of ROS during Ang II infusion in mice. We hypothesized that COX and TPRs are upstream requirements for the generation of vascular ROS by ET-1. (2) Methods: ET-1-induced vascular contractions and ROS were assessed in mesenteric arterioles from wild type (+/+) and knockout (−/−) of COX1 or TPR mice infused with Ang II (400 ng/kg/min × 14 days) or a vehicle. (3) Results: Ang II infusion appeared to increase microvascular protein expression of endothelin type A receptors (ETARs), TPRs, and COX1 and 2 in COX1 and TPR +/+ mice but not in −/− mice. Ang II infusion increased ET-1-induced vascular contractions and ROS, which were prevented by a blockade of COX1 and 2 in TPR −/− mice. ET-1 increased the activity of aortic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and decreased superoxide dismutase (SOD) 1, 2, and 3 in Ang-II-infused mice, which were prevented by a blockade of TPRs. (4) Conclusion: Activation of vascular TPRs by COX products are required for ET-1 to increase vascular contractions and ROS generation from NADPH oxidase and reduce ROS metabolism by SOD. These effects require an increase in these systems by prior infusion of Ang II.

High Salt Enhances Reactive Oxygen Species and Angiotensin II Contractions of Glomerular Afferent Arterioles From Mice With Reduced Renal Mass

High salt, Ang II (angiotensin II), and reactive oxygen species enhance progression of chronic kidney disease. We tested the hypothesis that a high salt intake generates specific reactive oxygen species to enhance Ang II contractions of afferent arterioles from mice with reduced renal mass (RRM). C57BL/6 mice were subjected to surgical RRM or sham operations and received 6% or 0.4% NaCl salt diet for 3 months. Ang II contractions were measured in perfused afferent arterioles and superoxide (O₂^-) and hydrogen peroxide (H₂O₂) by fluorescence microscopy. RRM enhanced the afferent arteriolar gene expression for p47^phox and neutrophil oxidase (NOX) 2 and high salt intake in RRM mice enhanced gene expression for angiotensin type 1 receptors, POLDIP2 and NOX4 and reduced catalase. High salt in mice with RRM enhanced arteriolar O₂^- and H₂O₂ generation and maximal contractions to Ang II (10^-6 mol/L) that were dependent on O₂^- because they were prevented by gene deletion of p47^phox and on H₂O₂ because they were prevented by transgenic smooth muscle cell expression of catalase (tg^CAT-SMC) and POLDIP2 gene deletion. Three months of tempol normalized arteriolar reactive oxygen species and Ang II contractions. However, arteriolar contractions to lower concentrations of Ang II (10^-8 to 10^-11 mol/L) were paradoxically inhibited by H₂O₂ and POLDIP2. In conclusion, both O₂^- from p47^phox/NOX2 and H₂O₂ from NOX4/POLDIP2 enhance maximal arteriolar Ang II contractions from RRM mice during high salt, but H₂O₂ and NOX4/POLDIP2 reduce the sensitivity to lower concentrations of Ang II by >100-fold. Tempol prevents all of these changes in function.

A renal-cerebral-peripheral sympathetic reflex mediates insulin resistance in chronic kidney disease

Background

Insulin resistance (IR) complicates chronic kidney disease (CKD). We tested the hypothesis that CKD activates a broad reflex response from the kidneys and the white adipose tissue to impair peripheral glucose uptake and investigated the role of salt intake in this process.

Methods

5/6-nephrectomized rats were administered normal- or high-salt for 3 weeks. Conclusions were tested in 100 non-diabetic patients with stage 3–5 CKD.

Findings

High-salt in 5/6-nephrectomized rats decreased insulin-stimulated 2-deoxyglucose uptake >25% via a sympathetic nervous system (SNS) reflex that linked the IR to reactive oxygen species (ROS) and the renin-angiotensin system (RAS) in brain and peripheral tissues. Salt-loading in CKD enhanced inflammation in adipose tissue and skeletal muscle, and enhanced the impairment of insulin signaling and Glut4 trafficking. Denervation of the kidneys or adipose tissue or deafferentation of adipose tissue improved IR >40%. In patients with non-diabetic CKD, IR was positively correlated with salt intake after controlling for cofounders (r = 0.334, P = 0.001) and was linked to activation of the RAS/SNS and to impaired glucose uptake in adipose tissue and skeletal muscle, all of which depended on salt intake.

Interpretation

CKD engages a renal/adipose-cerebral-peripheral sympathetic reflex that activates the RAS/ROS axes to promote IR via local inflammation and impaired Glut4 trafficking that are enhanced by high-salt intake. The findings point to a role for blockade of RAS or α-and-β-adrenergic receptors to reduce IR in patients with CKD.

Fund

National Natural Science Foundation of China.

Fibroblast Growth Factor Binding Protein 3 (FGFBP3) impacts carbohydrate and lipid metabolism

Secreted FGF binding proteins (FGFBP) mobilize locally-acting paracrine FGFs from their extracellular storage. Here, we report that FGFBP3 (BP3) modulates fat and glucose metabolism in mouse models of metabolic syndrome. BP3 knockout mice exhibited altered lipid metabolism pathways with reduced hepatic and serum triglycerides. In obese mice the expression of exogenous BP3 reduced hyperglycemia, hepatosteatosis and weight gain, blunted de novo lipogenesis in liver and adipose tissues, increased circulating adiponectin and decreased NEFA. The BP3 protein interacts with endocrine FGFs through its C-terminus and thus enhances their signaling. We propose that BP3 may constitute a new therapeutic to reverse the pathology associated with metabolic syndrome that includes nonalcoholic fatty liver disease and type 2 diabetes mellitus.

Abstract 034: Resilience of Isolated, Perfused Cerebral Penetrating Microarterioles to Angiotensin II (Ang II) Contractions Depends on Local Generation of Prostaglandin D 2 (PGD 2 )

The brain depends on a continuous supply of blood for its oxygenation, whereas the kidney is over-perfused for its metabolic needs in order to provide sufficient plasma to form a glomerular filtrate. Thus, the brain requires resilience to vasoconstriction to prevent ischemia and vascular cognitive impairment, but the mechanisms are unclear.

Methods and Results: Single penetrating cerebral microarterioles (CMAs, 12-18μM) were dissected from the frontal cortex and single renal afferent arterioles (RAAs, 8-12μM) from the kidney cortex to investigate the hypothesis that CMAs deploy unique mechanisms to provide resilience to Ang II vasoconstriction. Individual arteriolar genes were assessed by RNAseq or RT-PCR of endothelial cells (ECs). The mRNA for lipocalin type PGD 2 synthase (LPGDS) and the PGD 1 receptor (PD1R) were > 3,000-fold higher in CMAs than RAAs whereas RAAs expressed 3-fold more mRNA for thromboxane A 2 synthase. Both microarterioles had similar expression of AT1Rs. Endothelial cells cultured from these vessels had similar patterns of gene expression. Single isolated perfused RAAs contracted strongly with Ang II (at 10 -6 mol·l -1 ; -47 ± 2%; P<0.005) whereas CMAs were totally resistant to Ang II (0.1 ± 0.1%; NS), yet both contracted similarly to endothelin I or perfusion pressure (n = 6 per group). However, CMAs from COX 1 -/- (vs +/+) mice did contract with Ang II (-15 ± 2 vs 0.1 ± 0.1%; P<0.01) and contracted with Ang II after incubation with parecoxib (vs vehicle) to block COX2 (-7 ± 3 vs 0.1 ± 0.1%; P<0.01) or after dual blockade of COX1 + 2 (-20 ± 2%; P<0.01) or after incubation with AT-56 (vs vehicle) to block LPGDS (-20 ± 3 vs 0.1 ± 0.1%; P<0.01). During LPGDS blockade, incubation of CMAs with BW245c (stable PD1R agonist) reduced Ang II contraction > 65% (-8 ± 2%; P<0.01). In contrast, COX blockade reduced Ang II contractions of RAAs, indicating opposing effects of PGs on cerebral and renal vessels. Measurements of cerebral and renal blood flow and MAP in anesthetized mice confirmed selective renal vasoconstriction with Ang II, yet selective cerebral vasodilation with BW245c.

Perspective: Resilience against Ang II vasoconstriction in cerebral arterioles depends on the generation of PGD 2 and could be a therapeutic target for vascular dementia and stroke.

Enhanced Renal Afferent Arteriolar Reactive Oxygen Species and Contractility to Endothelin-1 Are Associated with Canonical Wnt Signaling in Diabetic Mice

BACKGROUND/AIMS

Canonical Wnt signaling is involved in oxidative stress, vasculopathy and diabetes mellitus but its role in diabetic renal microvascular dysfunction is unclear. We tested the hypothesis that enhanced canonical Wnt signaling in renal afferent arterioles from diabetic mice increases reactive oxygen species (ROS) and contractions to endothelin-1 (ET-1).

METHODS

Streptozotocin-induced diabetes or control C57Bl/6 mice received vehicle or sulindac (40 mg·kg-1·day-1) to block Wnt signaling for 4 weeks. ET-1 contractions were measured by changes of afferent arteriolar diameter. Arteriolar H2O2, O2 -, protein expression and enzymatic activity were assessed using sensitive fluorescence probes, immunoblotting and colorimetric assay separately.

RESULTS

Compared to control, diabetic mouse afferent arteriole had increased O2- (+ 84%) and H2O2 (+ 91%) and enhanced responses to ET-1 at 10-8 mol·l-1 (-72±4% of versus -43±4%, P< 0.05) accompanied by reduced protein expressions and activities for catalase and superoxide dismutase 2 (SOD2). Arteriolar O2 - was increased further by ET-1 and contractions to ET-1 reduced by PEG-SOD in both groups whereas H2O2 unchanged by ET-1 and contractions were reduced by PEG-catalase selectively in diabetic mice. The Wnt signaling protein β-catenin was upregulated (3.3-fold decrease in p-β-catenin/β-catenin) while the glycogen synthase kinase-3β (GSK-3β) was downregulated (2.6-fold increase in p-GSK-3β/ GSK-3β) in preglomerular vessels of diabetic mice. Sulindac normalized the Wnt signaling proteins, arteriolar O2 -, H2O2 and ET-1 contractions while doubling microvascular catalase and SOD2 expression in diabetic mice.

CONCLUSION

Increased ROS, notably H2O2 contributes to enhanced afferent arteriolar responses to ET-1 in diabetes, which is closely associated with Wnt signaling. Antioxidant pharmacological strategies targeting Wnt signaling may improve vascular function in diabetic nephropathy.

Regulation of fluid reabsorption in rat or mouse proximal renal tubules by asymmetric dimethylarginine and dimethylarginine dimethylaminohydrolase 1

Nitric oxide prevents hypertension yet enhances proximal tubule Na⁺ reabsorption. Nitric oxide synthase is inhibited by asymmetric dimethylarginine (ADMA) that is metabolized by dimethylarginine dimethylaminohydrolase (DDAH) whose type 1 isoform is expressed abundantly in the proximal tubule (PT). We hypothesize that ADMA metabolized by DDAH-1 inhibits fluid reabsorbtion (Jv) by the proximal tubule. S2 segments of the PT were microperfused between blocks in vivo to assess Jv in anesthetized rats. Compared with vehicle, microperfusion of ADMA or N^ω-nitro-l-arginine methyl ester (l-NAME) in the proximal tubule reduced Jv dose dependently. At 10^-4 mol/l both reduced Jv by ~40% (vehicle: 3.2 ± 0.7 vs. ADMA: 2.1 ± 0.5, P < 0.01 vs. l-NAME: 1.9 ± 0.4 nl·min^-1·mm^-1, P < 0.01; n = 10). Selective inhibition of DDAH-1 in rats with intravenous L-257 (60 mg/kg) given 2 h before and L-257 (10^-5 mol/l) perfused in the proximal tubule for 5 min reduced Jv by 32 ± 4% (vehicle: 3.2 ± 0.5 vs. L-257: 2.2 ± 0.5 nl·min^-1·mm^-1; P < 0.01) and increased plasma ADMA by ≈50% (vehicle: 0.46 ± 0.03 vs. L-257: 0.67 ± 0.03 µmol/l, P < 0.0001) without changing plasma symmetric dimethylarginine. Compared with nontargeted control small-interference RNA, knock down of DDAH-1 in mice by 60% with targeted small-interference RNAs (siRNA) reduced Jv by 29 ± 5% (nontargeted siRNA: 2.8 ± 0.20 vs. DDAH-1 knockdown: 1.9 ± 0.31 nl·min^-1·mm^-1, P < 0.05). In conclusion, fluid reabsorption in the proximal tubule is reduced by tubular ADMA or by blocking its metabolism by DDAH-1. L-257 is a novel regulator of proximal tubule fluid reabsorption.

Interaction Between the Sodium-Glucose-Linked Transporter 2 Inhibitor Dapagliflozin and the Loop Diuretic Bumetanide in Normal Human Subjects

Background

Dapagliflozin inhibits the sodium‐glucose–linked transporter 2 in the renal proximal tubule, thereby promoting glycosuria to reduce hyperglycemia in type 2 diabetes mellitus. Because these patients may require loop diuretics, and sodium‐glucose–linked transporter 2 inhibition causes an osmotic diuresis, we evaluated the diuretic interaction between dapagliflozin and bumetanide.

Methods and Results

Healthy subjects (n=42) receiving a fixed diet with ≈110 mmol·d⁻¹ of Na⁺ were randomized to bumetanide (1 mg·d⁻¹), dapagliflozin (10 mg·d⁻¹), or both for 7 days, followed by 7 days of both. There were no meaningful pharmacokinetic interactions. Na⁺ excretion increased modestly with the first dose of dapagliflozin (22±6 mmol·d⁻¹; P<0.005) but by more (P<0.005) with the first dose of bumetanide (74±7 mmol·d⁻¹; P<0.005), which was not significantly different from both diuretics together (80±5 mmol·d⁻¹; P<0.005). However, Na⁺ excretion with dapagliflozin was 190% greater (P<0.005) when added after 1 week of bumetanide (64±6 mmol·d⁻¹), and Na⁺ excretion with bumetanide was 36% greater (P<0.005) when added after 1 week of dapagliflozin (101±8 mmol·d⁻¹). Serum urate was increased 4% by bumetanide but reduced 40% by dapagliflozin or 20% by combined therapy (P<0.05).

Conclusions

First‐dose Na⁺ excretion with bumetanide and dapagliflozin is not additive, but the weekly administration of one diuretic enhances the initial Na⁺ excretion with the other, thereby demonstrating mutual adaptive natriuretic synergy. Combined therapy reverses bumetanide‐induced hyperuricemia. This requires further study in diabetic patients with hyperglycemia who have enhanced glycosuria and natriuresis with dapagliflozin.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00930865.

Nitration of TRPM2 as a Molecular Switch Induces Autophagy During Brain Pericyte Injury

AIMS

Dysfunction of neurovascular pericytes underlies breakdown of the blood-brain barrier, but the molecular mechanisms are largely unknown. In this study, we evaluated the role of the transient receptor potential melastatin-related 2 (TRPM2) channel and autophagy during brain pericyte injury both in vitro and in vivo.

RESULTS

A rapid induction in autophagy in human brain vascular pericytes, in the zinc oxide nanoparticles (ZnO-NP)-induced cell stress model, was paralleled with an increase in the expression of the TRPM2-S truncated isoform, which was abolished by treatment with a nitric oxide synthase inhibitor and a peroxynitrite scavenger. Furthermore, Y1485 in the C-terminus of the TRPM2 protein was identified as the tyrosine nitration substrate by mass spectrometry. Overexpression of the Y1485S TRPM2 mutant reduced LC3-II accumulation and pericyte injury induced by ZnO-NP. Consistently, LC3-II accumulation was reduced and pericytes were better preserved in intact brain microvessels of the TRPM2 knockout mice after ZnO-NP-induced vascular injury. Innovation and Conclusions: Our present study has revealed a novel mechanism of autophagy disturbance secondary to nitrosative stress-induced tyrosine nitration of TRPM2 during pericyte injury. Antioxid. Redox Signal. 27, 1297-1316.

NRF2 prevents hypertension, increased ADMA, microvascular oxidative stress, and dysfunction in mice with two weeks of ANG II infusion

Nuclear factor erythyroid factor 2 (Nrf2) transcribes genes in cultured endothelial cells that reduce reactive oxygen species (ROS) and generate nitric oxide (NO) or metabolize asymmetric dimethylarginine (ADMA), which inhibits NO synthase (NOS). Therefore, we undertook a functional study to test the hypothesis that activation of Nrf2 by tert-butylhydroquinone (tBHQ) preserves microvascular endothelial function during oxidative stress. Wild-type CB57BL/6 (wt), Nrf2 wt (+/+), or knockout (-/-) mice received vehicle (Veh) or tBHQ (0.1%; activator of Nrf2) during 14-day infusions of ANG II (to induce oxidative stress) or sham. MAP was recorded by telemetry. Mesenteric resistance arterioles were studied on isometric myographs and vascular NO and ROS by fluorescence microscopy. ANG II increased the mean arterial pressure (112 ± 5 vs. 145 ± 5 mmHg; P < 0.01) and excretion of 8-isoprostane F_2α (2.8 ± 0.3 vs. 3.8 ± 0.3 ng/mg creatinine; P < 0.05) at 12-14 days. However, 12 days of ANG II reduced endothelium-derived relaxation (27 ± 5 vs. 17 ± 3%; P < 0.01) and NO (0.38 ± 0.07 vs. 0.18 ± 0.03 units; P < 0.01) but increased microvascular remodeling, endothelium-derived contractions (7.5 ± 0.5 vs. 13.0 ± 1.7%; P < 0.01), superoxide (0.09 ± 0.03 vs. 0.29 ± 0.08 units; P < 0.05), and contractions to U-46,619 (87 ± 6 vs. 118 ± 3%; P < 0.05), and endothelin-1(89 ± 4 vs. 123 ± 12%; P < 0.05). tBHQ prevented all of these effects of ANG II at 12-14 days in Nrf2^+/+ mice but not in Nrf2^-/- mice. In conclusion, tBHQ activates Nrf2 to prevent microvascular endothelial dysfunction, remodeling, and contractility, and moderate ADMA and hypertension at 12-14 days of ANG II infusion, thereby preserving endothelial function and preventing hypertension.

Blood Pressure Control by a Secreted FGFBP1 (Fibroblast Growth Factor-Binding Protein)

Fibroblast growth factors (FGFs) participate in organ development and tissue maintenance, as well as the control of vascular function. The paracrine-acting FGFs are stored in the extracellular matrix, and their release is controlled by a secreted FGF-binding protein (FGF-BP, FGFBP1, and BP1) that modulates FGF receptor signaling. A genetic polymorphism in the human FGFBP1 gene was associated with higher gene expression and an increased risk of familial hypertension. Here, we report on the effects of inducible BP1 expression in a transgenic mouse model. Induction of BP1 expression in adult animals leads to a sustained rise in mean arterial pressure by >30 mm Hg. The hypertensive effect of BP1 expression is prevented by candesartan, an angiotensin II (AngII) receptor antagonist, or by tempol, an inhibitor of reactive oxygen species. In vivo, BP1 expression sensitizes peripheral resistance vessels to AngII constriction by 20-fold but does not alter adrenergic vasoconstriction. FGF receptor kinase inhibition reverses the sensitization to AngII. Also, constriction of isolated renal afferent arterioles by AngII is enhanced after BP1 expression and blocked by FGF receptor kinase inhibition. Furthermore, AngII-mediated constriction of renal afferent arterioles is abolished in FGF2^-/- mice but can be restored by add-back of FGF2 plus BP1 proteins. In contrast to AngII, adrenergic constriction is not affected in the FGF2^-/- model. Proteomics and gene expression analysis of kidney tissues after BP1 induction show that MAPK (mitogen-activated protein kinase) signaling via MKK4 (MAPK kinase 4), p38, and JNK (c-Jun N-terminal kinase) integrates the crosstalk of the FGF receptor and AngII pathways and thus impact vascular tone and blood pressure.

Melatonin ameliorates hypoglycemic stress-induced brain endothelial tight junction injury by inhibiting protein nitration of TP53-induced glycolysis and apoptosis regulator

Severe hypoglycemia has a detrimental impact on the cerebrovasculature, but the molecular events that lead to the disruption of the integrity of the tight junctions remain unclear. Here, we report that the microvessel integrity was dramatically compromised (59.41% of wild-type mice) in TP53-induced glycolysis and apoptosis regulator (TIGAR) transgenic mice stressed by hypoglycemia. Melatonin, a potent antioxidant, protects against hypoglycemic stress-induced brain endothelial tight junction injury in the dosage of 400 nmol/L in vitro. FRET (fluorescence resonance energy transfer) imaging data of endothelial cells stressed by low glucose revealed that TIGAR couples with calmodulin to promote TIGAR tyrosine nitration. A tyrosine 92 mutation interferes with the TIGAR-dependent NADPH generation (55.60% decreased) and abolishes its protective effect on tight junctions in human brain microvascular endothelial cells. We further demonstrate that the low-glucose-induced disruption of occludin and Caludin5 as well as activation of autophagy was abrogated by melatonin-mediated blockade of nitrosative stress in vitro. Collectively, we provide information on the detailed molecular mechanisms for the protective actions of melatonin on brain endothelial tight junctions and suggest that this indole has translational potential for severe hypoglycemia-induced neurovascular damage.

Sodium and Fluid Excretion With Torsemide in Healthy Subjects is Limited by the Short Duration of Diuretic Action

BACKGROUND

Loop diuretics are highly natriuretic but their short duration of action permits postdiuretic sodium retention, which limits salt loss unless dietary salt is severely restricted. We tested the hypothesis that a more prolonged duration of action would enhance salt loss.

METHODS AND RESULTS

Ten healthy participants were crossed over between 20 mg of oral immediate-release or extended-release (ER) torsemide while consuming a fixed diet with 300 mmol·d^-1 of Na⁺. Compared with immediate-release, plasma torsemide after ER was 59% lower at 1 to 3 hours but 97% higher at 8 to 10 hours as a result of a >3-fold prolongation of time to maximal plasma concentrations. The relationship of natriuresis to log torsemide excretion showed marked hysteresis, but participants spent twice as long with effective concentrations of torsemide after ER, thereby enhancing diuretic efficiency. Compared with immediate-release, ER torsemide did not reduce creatinine clearance and increased fluid (1634±385 versus 728±445 mL, P<0.02) and Na⁺ output (98±15 versus 42±17 mmol, P<0.05) despite an 18% reduction in exposure. Neither formulation increased K⁺ excretion.

CONCLUSIONS

Torsemide ER prolongs urine drug levels, thereby increasing the time spent with effective drug concentrations, reduces postdiuretic Na⁺ retention, and moderates a fall in glomerular filtration rate. It caused significant Na⁺ loss even during very high salt intake. Thus, a short duration of action limits salt loss with loop diuretics. These conclusions warrant testing in subjects with edema and heart failure.

Abstract P344: Nuclear Factor E2-related Factor 2 (nrf2) Causes Early Microvascular Endothelial Dysfunction and Increased Adma by Activation of the Cox2/tp Receptor Pathway in Mice Infused With Angiotensin II for Three Days

Background: Activation of Nrf2 by tert-buthylhydroquinone (tBHQ) prevents hypertension, oxidative stress, endothelial dysfunction and ADMA in mice infused with angiotensin II (Ang II) for 12 days. However, Nrf2 activation with bardoxolone methyl increased cardiovascular events in diabetic patients within one week. Since we found that tBHQ activated cyclooxygenase (COX)-2 within 3 days, we tested the hypothesis that short-term tBHQ administration to Ang II infused mice increases microvascular dysfunction via COX dependent of PGs and TxA 2 that activate thromboxane-prostanoid receptors (TP-Rs).

Methods: Mesenteric resistance arterioles(MRAs)were isolated from mice infused for 3 days with ANG II (400 ng/kg/min) or vehicle and given oral tBHQ (0.1% of water) or vehicle (n=6 mice/group). Endothelial derived relaxation factor (EDRF) was assessed by a myograph and NO and ROS by RatioMaster TM .

Results: Compared to vehicle, Ang II infused mice given tBHQ had increased (P<0.05) conscious mean arterial pressure (135±6 vs 115±7 mmHg), urinary 8-Iso prostane (1.5±0.4 vs 1.1±0.2ng/mg creatinine), and decreased EDRF (17± 3 vs 23± 2%) and NO (0.23 ± 0.02 vs 0.35 ± 0.02 Δunits), and enhanced ( P<0.05, ) cellular ROS (0.27 ± 0.02 vs 0.12 ± 0.03 Δunits), mitochondria ROS (0.24 ± 0.02 vs 0.1 ± 0.02 Δunit) and microvascular asymmetric dimethylarginine (ADMA, 77 ± 6 vs 55 ± 7 nmol/mg protein). All these effects of tBHQ were prevented in COX-1 knockout mice drinking parecoxib (COX-2 inhibitor) and in TPR and Nrf2 knockout mice.

Conclusions: Activation of Nrf2 increases short term Ang II-induced increases in BP, oxidative stress, ADMA and endothelial dysfunction. These depend on signaling via COX 1 + 2 and TP receptors. Our studies reveal novel dual effects of Nrf2 in Ang II infused mice: increased BP, ROS, ADMA and endothelial dysfunction within 3 days secondary to activation of COX/TPR signaling follow by the opposite effects of Nrf2 on BP, ADMA and vascular function within 12 days. Therefore, blockade of COX-2/TPRs pathway during initiation of Nrf2 therapy may prevent the devastating early adverse effects that have prevented its use in hypertension or diabetes.

Abstract P435: Differential Responses of Cerebral Cortical and Renal Cortical Microvessels to Perfusion Pressure and Angiotensin II: Effect of Angiotensin II or DOCA/salt Hypertension

Background: The brain and kidney autoregulate their blood flow well yet both suffer from hypertensive damage. We found that a pressor infusion of angiotensin II (Ang II) reduced renal blood flow yet did not change cerebral blood flow. Therefore, we tested the hypothesis that their myogenic and Ang II responses differed.

Methods: Cerebral cortical microvessels (cerebral) and renal afferent arterioles (afferent) were isolated and perfused from mice after 4 weeks of hypertension from Ang II infusion /high salt/uninephrectomy (Ang II hypertension) or DOCA/high salt/uninephrectomy (DOCA/salt hypertension) or normotensive controls without Ang II or DOCA (n=4-6 per group).

Results: Normal cerebral and afferents had similar myogenic responses (Δ diameter: cerebral -21±3 versus afferent-19±2%, NS), but bath addition of Ang II or norepinephrine contracted afferents strongly (Ang II: -48±5%, P<0.001, NE: -95±2%, P<0.001), yet cerebrals were entirely unresponsive. Myogenic responses in Ang II hypertension were reduced selectively by 40% in cerebral microvessels compared to controls (-13±3 versus -21±3%, P<0.001) yet maintained in afferents (-17±3 versus -19±2%, NS). However, myogenic responses in DOCA/salt hypertension were maintained in both groups. Contractions to Ang II in cerebral microvessels were increased in Ang II hypertension (-5±2 versus 0±1%, P<0.01) and increased in DOCA/salt hypertension (-18±8 versus -2±2%, P<0.01). In contrast, contractions to Ang II in afferent arterioles were reduced 50% in Ang II hypertension (-23±5 versus -48±5%, P<0.001) and reduced 25% in DOCA/salt hypertension (-38±6 versus -50±10%, P=0.05).

Conclusions: The kidney is well protected from hypertension and excessive Ang II vasoconstriction. However, the breakdown of myogenic responses in the cerebral microvessels during Ang II hypertension and the enhanced Ang II responses in the cerebral microvessels during Ang II and DOCA/salt hypertension make the brain especially vulnerable to hypertensive ischemia or damage.

Abstract 070: Canonical Wnt Signaling Mediates Enhanced Renal Afferent Arteriolar Reactive Oxygen Species and Contractility in Diabetic Mice

Background: Canonical Wnt signaling is involved in oxidative stress and diabetes but its role in diabetic renal microvascular dysfunction is unclear. We tested the hypothesis that enhanced canonical Wnt signaling in renal afferent arterioles from diabetic mice increases reactive oxygen species (ROS) and contractions to endothelin-1 (ET-1).

Methods: Diabetic or control C57Bl/6 mice received vehicle or sulindac (40 mg·kg -1 ·day -1 ) to block canonical Wnt signaling for 4 weeks. ET-1 contractions were measured in diameter changes and H 2 O 2 and O 2 .- by fluorescence microscopy. Arteriolar protein expression and enzymatic activity were examined by standard methods.

Results: Compared to control, diabetic mouse afferent arteriole had significantly increased O 2 .- (+84%) and H 2 O 2 (+91%) and enhanced sensitivity to ET-1 at 10 -8 mol·l -1 (-72±4% versus -43±4%, P<0.05) accompanied by significantly (P<0.005) reduced protein expressions and activities for catalase and superoxide dismutase 2 (SOD2). Incubation of afferent arterioles from normal or diabetic mice with PEG-SOD reduced responses to ET-1 whereas incubation with PEG-catalase reduced sensitivity to ET-1 selectively in arterioles from diabetic mice. The arteriolar protein expressions for canonical Wnt signaling indicated overactivation of this pathway in diabetic mice (2.6-fold increase in p-GSK-3β/GSK-3β and 3.3-fold decrease in p-β-catenin/β-catenin). Sulindac given to diabetic mice normalized the canonical Wnt signaling protein and arteriolar O 2 .- , H 2 O 2 and ET-1 contractions while doubling (P<0.05) microvascular catalase and SOD2.

Conclusions: Increased ROS, notably H 2 O 2 , mediated by canonical Wnt signaling contributes to enhanced afferent arteriolar sensitivity to ET-1 in diabetes. Thus, antioxidant pharmacological strategies targeting canonical Wnt signaling may improve vascular function in diabetic nephropathy.

Abstract P506: Deoxycorticosterone Acetate-salt Promotes Endothelial-mesenchymal Transition in Human Glomerular Endothelial Cells

Endothelial cells (ECs) lose their endothelial specification and gain mesenchymal cell features during endothelial-mesenchymal transition (EndMT). Post-developmental EndMT disrupts EC homeostasis, leading to vascular dysfunction. We found that afferent arterioles from deoxycorticosterone acetate (DOCA)-salt treated mice had > 5 fold upregulation of mRNAs for preproendothelin-1, p47phox ,NOX2 and TGF-β accompanied by microvascular dysfunction. Since these may cause EndMT, we investigated the mechanism in human glomerular endothelial cells (HGECs) treated for 7-21 days with high salt and DOCA. Endothelin-1 (ET-1) in the medium was increased 2.8±0.2 fold by day 7 while the cells gained multiple mesenchymal markers with increased mRNA for alpha-smooth muscle actin (1.78±0.19 and 2.96±0.32 fold, P<0.05 and 0.01, n=3) and transgelin ( 1.96±0.14 and 2.91±0.28 fold, p<0.05 and 0.01, n=3) on day 7 and 21, respectively, and markedly downregulated mRNA for endothelial markers with decreased vascular endothelial cadherin ( 1.99± 0.27 and 2.12±0.24 fold, P<0.05 and 0.005, n=3) and platelet endothelial cell adhesion molecule 1 (1.78±0.26 and 1.94±0.23 fold, P<0.05 and 0.005, n=3). There were parallel changes in protein expression. Dihydroethidium and MitSox fluorescence probes were used to determine intracellular and mitochondria ROS. The fluorescent intensities were increased by 1.89±0.27 and 1.62±0.22 fold (P<0.01, N=6) respectively in the cells treated for 7 days with DOCA-salt accompanied by increased expression of TGF-β and phosphorylated-extracellular signal-regulated kinases (P-ERK 1/2). In conclusion, human glomerular endothelial cells treated with high salt and DOCA for 1-3 weeks have increased cellular and mitochondrial ROS, ET-1, TGF-β and P-ERK that could account for adverse changes of endothelial-mesenchymal transition and associated microvascular dysfunction.

Reno-Cerebral Reflex Activates the Renin-Angiotensin System, Promoting Oxidative Stress and Renal Damage After Ischemia-Reperfusion Injury

AIMS

A kidney-brain interaction has been described in acute kidney injury, but the mechanisms are uncertain. Since we recently described a reno-cerebral reflex, we tested the hypothesis that renal ischemia-reperfusion injury (IRI) activates a sympathetic reflex that interlinks the renal and cerebral renin-angiotensin axis to promote oxidative stress and progression of the injury.

RESULTS

Bilateral ischemia-reperfusion activated the intrarenal and cerebral, but not the circulating, renin-angiotensin system (RAS), increased sympathetic activity in the kidney and the cerebral sympathetic regulatory regions, and induced brain inflammation and kidney injury. Selective renal afferent denervation with capsaicin or renal denervation significantly attenuated IRI-induced activation of central RAS and brain inflammation. Central blockade of RAS or oxidative stress by intracerebroventricular (ICV) losartan or tempol reduced the renal ischemic injury score by 65% or 58%, respectively, and selective renal afferent denervation or reduction of sympathetic tone by ICV clonidine decreased the score by 42% or 52%, respectively (all p < 0.05). Ischemia-reperfusion-induced renal damage and dysfunction persisted after controlling blood pressure with hydralazine.

INNOVATION

This study uncovered a novel reflex pathway between ischemic kidney and the brain that sustains renal oxidative stress and local RAS activation to promote ongoing renal damage.

CONCLUSIONS

These data suggest that the renal and cerebral renin-angiotensin axes are interlinked by a reno-cerebral sympathetic reflex that is activated by ischemia-reperfusion, which contributes to ischemia-reperfusion-induced brain inflammation and worsening of the acute renal injury. Antioxid. Redox Signal. 27, 415-432.

Superoxide and hydrogen peroxide counterregulate myogenic contractions in renal afferent arterioles from a mouse model of chronic kidney disease

Myogenic contractions protect kidneys from barotrauma but are impaired in chronic kidney disease (CKD). Since myogenic contractions are enhanced by superoxide but impaired by hydrogen peroxide, we tested the hypothesis that they are counterregulated by superoxide and H2O2 from NOX2/p47phox and/or NOX4/POLDIP2 in CKD. Myogenic contraction in isolated perfused afferent arterioles from mice with surgical 5/6 nephrectomy or sham operations fed a 6% sodium chloride diet was measured directly while superoxide and H2O2 were measured by fluorescence microscopy. Compared to sham-operated animals, an increase in perfusion pressure of arterioles from CKD mice doubled superoxide (21 versus 11%), increased H2O2 seven-fold (29 versus 4%), and reduced myogenic contractions profoundly (-1 versus -14%). Myogenic contractions were impaired further by PEG-superoxide dismutase or in arterioles from p47phox-/- (versus wild type) mice but became supra-normal by PEG-catalase or in mice with transgenic expression of catalase in vascular smooth muscle cells (-11 versus -1%). Single arterioles from mice with CKD expressed over 40% more mRNA and protein for NOX4 and POLDIP2. Myogenic responses in arterioles from POLDIP2 +/- (versus wild type) mice with CKD had over an 85% reduction in H2O2, but preserved superoxide and a normal myogenic response. Tempol administration to CKD mice for 3 months decreased afferent arteriolar superoxide and H2O2 and maintained myogenic contractions. Thus, afferent arteriolar superoxide generated by NOX2/p47phox opposes H2O2 generated by NOX4/POLDIP2 whose upregulation in afferent arterioles from mice with CKD accounts for impaired myogenic contractions.

Inhibition of ROMK blocks macula densa tubuloglomerular feedback yet causes renal vasoconstriction in anesthetized rats

The Na⁺-K⁺-2Cl^- cotransporter (NKCC2) on the loop of Henle is the site of action of furosemide. Because outer medullary potassium channel (ROMK) inhibitors prevent reabsorption by NKCC2, we tested the hypothesis that ROMK inhibition with a novel selective ROMK inhibitor (compound C) blocks tubuloglomerular feedback (TGF) and reduces vascular resistance. Loop perfusion of either ROMK inhibitor or furosemide caused dose-dependent blunting of TGF, but the response to furosemide was 10-fold more sensitive (IC₅₀ = 10^-6 M for furosemide and IC₅₀ = 10^-5 M for compound C). During systemic infusion, both diuretics inhibited TGF, but ROMK inhibitor was 10-fold more sensitive (compound C: 63% inhibition; furosemide: 32% inhibition). Despite blockade of TGF, 1 h of constant systemic infusion of both diuretics reduced the glomerular filtration rate (GFR) and renal blood flow (RBF) by 40-60% and increased renal vascular resistance (RVR) by 100-200%. Neither diuretic altered blood pressure or hematocrit. Proximal tubule hydrostatic pressures (P_PT) increased transiently with both diuretics (compound C: 56% increase; furosemide: 70% increase) but returned to baseline. ROMK inhibitor caused more natriuresis (3,400 vs. 1,600% increase) and calciuresis (1,200 vs. 800% increase) but less kaliuresis (33 vs. 167% increase) than furosemide. In conclusion, blockade of ROMK or Na⁺-K⁺-2Cl^- transport inhibits TGF yet increases renal vascular resistance. The renal vasoconstriction was independent of volume depletion, blood pressure, TGF, or P_PT.

Acute Kidney Injury and In-Hospital Mortality after Coronary Artery Bypass Graft versus Percutaneous Coronary Intervention: A Nationwide Study

BACKGROUND

Post-procedural acute kidney injury (AKI) is associated with significantly increased short- and long-term mortalities, and renal loss. Few studies have compared the incidence of post-procedural AKI and in-hospital mortality between 2 major modalities of revascularization - coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) - and results have been inconsistent.

METHODS

We generated a propensity score-matched cohort that includes a total of 286,670 hospitalizations with multi-vessel coronary disease undergoing CABG or PCI (2004-2012) from the National Inpatient Sample database. We compared incidence of AKI, AKI requiring renal replacement therapy (RRT), in-hospital mortality, hospital stay, and charges between CABG and PCI groups.

RESULTS

The incidence of AKI after CABG was higher than PCI (8.9 vs. 4.5%, OR 2.05, 95% CI 1.99-2.12, p < 0.001). The incidence of AKI requiring RRT was also higher after CABG (1.1 vs. 0.5%, OR 2.14, 95% CI 1.96-2.34, p < 0.001). Likewise, in-hospital mortality was higher after CABG than PCI (2.0 vs. 1.4%, OR 1.44, 95% CI 1.35-1.52, p < 0.001). Among patients with pre-existing chronic kidney disease (stages I-IV), those undergoing CABG was associated with 2.0-2.3-fold higher odds of developing AKI than those undergoing PCI. The patients treated with CABG had a significantly longer hospital stay and higher hospital charges.

CONCLUSIONS

Patients undergoing CABG are associated with (1) increased risk of developing post-procedural AKI, (2) higher likelihood of receiving RRT, and (3) worse short-term survival. Long-term renal outcome remains to be studied.

Patiromer Decreases Serum Potassium and Phosphate Levels in Patients on Hemodialysis

BACKGROUND

Persistent hyperkalemia (serum potassium (K) ≥5.5 mEq/l) is a common condition in hemodialysis (HD) patients, is associated with increased mortality, and treatment options are limited. The effect of patiromer, a gastrointestinal K binder, on serum K was examined in HD patients.

METHODS

Six hyperkalemic HD patients (5 anuric) were admitted to clinical research units for 15 days (1 pretreatment week and 1 patiromer treatment week) and they received a controlled diet with identical meals on corresponding days of pretreatment and treatment weeks. Phosphate (P) binders were discontinued on admission. Patiromer, 12.6 g daily (divided 4.2 g TID with meals), was started on the Monday morning following the last pretreatment week blood sampling. Serum and 24-hour stool samples were collected daily.

RESULTS

Mean ± SE serum K decreased (maximum change per corresponding day, 0.6 ± 0.2 mEq/l, p = 0.009) and fecal K increased 58% on patiromer compared with the pretreatment week. During the pretreatment week, 69.0, 47.6, and 11.9% of patients' serum K values were ≥5.5, ≥6.0, and ≥6.5 mEq/l, respectively. This was reduced to 38.1% (p = 0.009), 11.9% (p < 0.001), and 2.4% (p = 0.2) on patiromer. Following P binder discontinuation, the long interdialytic interval mean ± SE serum P numerically increased from 5.8 ± 0.4 to 7.0 ± 0.5 mg/dl (p = 0.06). On patiromer, P decreased from 7.0 ± 0.5 to 6.2 ± 0.5 mg/dl (p = 0.04). While on patiromer, fecal P numerically increased by 112 ± 72 mg/day (17%; p = 0.1792; range -148 to 344 mg/day). No patient discontinued patiromer because of adverse events (AEs); none had serious AEs.

CONCLUSIONS

In 6 hyperkalemic HD patients, patiromer decreased serum K and P levels and increased fecal K.