Emerging evidence for glucagon-like peptide-1 agonists in slowing chronic kidney disease progression.

PURPOSE OF REVIEW: Diabetic kidney disease continues to increase, and several novel therapeutic agents have been shown to slow the progression of chronic kidney disease in those with diabetes. This review summarizes more recent data on the role of glucagon-like peptide-1 (GLP-1) receptor agonists and kidney outcomes. RECENT FINDINGS: Posthoc analysis of cardiovascular outcome trials, as well as several retrospective studies, demonstrate benefits of GLP-1 receptor agonist therapy for chronic kidney disease progression in diabetics. Although limited randomized clinical trials evidence assessing the effects of GLP-1 receptor agonists on kidney outcomes in diabetic chronic kidney disease patients have been published, FLOW-CKD trial was halted based on interim data for efficacy, and results are awaited. SUMMARY: GLP-1 receptor agonism is a promising therapy for slowing the progression of diabetic chronic kidney disease. Recent studies support kidney benefits GLP-1 receptor agonists over insulin and dipeptidyl peptidase-4-inhibitors, and the FLOW-CKD trial would inform the potential benefits for reducing the need for dialysis and kidney-disease related mortality in those with kidney disease.

Chronic Interstitial Nephritis in Agricultural Communities: Observational and Mechanistic Evidence Supporting the Role of Nephrotoxic Agrochemicals.

Chronic interstitial nephritis in agricultural communities (CINAC) is an epidemic of kidney disease affecting specific tropical and subtropical regions worldwide and is characterized by progressive CKD in the absence of traditional risk factors, such as hypertension and diabetes. CINAC prevalence is higher among young, male agricultural workers, but it also affects women, children, and nonagricultural workers in affected areas. Biopsies from patients with CINAC across regions commonly demonstrate tubular injury with lysosomal aggregates, tubulointerstitial inflammation, and fibrosis and variable glomerular changes. Each endemic area holds environmental risk factors and patient/genetic milieus, resulting in uncertainty about the cause(s) of the disease. Currently, there is no specific treatment available for CINAC. We highlight survey findings of Houston-based migrant workers with CINAC and draw similarities between kidney injury phenotype of patients with CINAC and mice treated chronically with paraquat, an herbicide used worldwide. We propose potential pathways and mechanisms for kidney injury in patients with CINAC, which may offer clues for potential therapies.

Discovery and Clinical Proof-of-Concept of RLY-2608, a First-in-Class Mutant-Selective Allosteric PI3Kα Inhibitor That Decouples Antitumor Activity from Hyperinsulinemia.

PIK3CA (PI3Kα) is a lipid kinase commonly mutated in cancer, including ∼40% of hormone receptor-positive breast cancer. The most frequently observed mutants occur in the kinase and helical domains. Orthosteric PI3Kα inhibitors suffer from poor selectivity leading to undesirable side effects, most prominently hyperglycemia due to inhibition of wild-type (WT) PI3Kα. Here, we used molecular dynamics simulations and cryo-electron microscopy to identify an allosteric network that provides an explanation for how mutations favor PI3Kα activation. A DNA-encoded library screen leveraging electron microscopy-optimized constructs, differential enrichment, and an orthosteric-blocking compound led to the identification of RLY-2608, a first-in-class allosteric mutant-selective inhibitor of PI3Kα. RLY-2608 inhibited tumor growth in PIK3CA-mutant xenograft models with minimal impact on insulin, a marker of dysregulated glucose homeostasis. RLY-2608 elicited objective tumor responses in two patients diagnosed with advanced hormone receptor-positive breast cancer with kinase or helical domain PIK3CA mutations, with no observed WT PI3Kα-related toxicities. SIGNIFICANCE: Treatments for PIK3CA-mutant cancers are limited by toxicities associated with the inhibition of WT PI3Kα. Molecular dynamics, cryo-electron microscopy, and DNA-encoded libraries were used to develop RLY-2608, a first-in-class inhibitor that demonstrates mutant selectivity in patients. This marks the advance of clinical mutant-selective inhibition that overcomes limitations of orthosteric PI3Kα inhibitors. See related commentary by Gong and Vanhaesebroeck, p. 204 . See related article by Varkaris et al., p. 227 . This article is featured in Selected Articles from This Issue, p. 201.

Simulation-based workshop for emergency preparedness in otolaryngology.

Objectives: This study aimed to evaluate the outcomes of a hands-on simulation-based course with emphasis on procedural techniques, clinical reasoning, and communication skills developed to improve junior Otolaryngology - Head and Neck Surgery (OHNS) residents' preparedness in managing otolaryngologic emergencies. Methods: Junior OHNS residents and faculty from residency programs in California, Nevada, and Arizona participated in this workshop in 2020 and 2021. The stations featured airway management techniques, ultrasound-guided needle aspiration, nasoseptal hematoma evacuation, and facial fracture repair using various models and cadavers. Participants completed a pre-workshop survey, post-workshop survey, and 2-month follow-up survey that assessed resident anxiety and confidence in three OHNS emergency situations across knowledge, manual skills, and teamwork using a 5-point Likert scale. Results: Pre-workshop surveys reported the least anxiety and most confidence in teamwork, but the most anxiety and least confidence in technical skills and knowledge related to foreign body retrieval and airway management. Immediately post-workshop participants reported significant reductions in anxiety and increases in confidence, largest in the manual skills domain, in foreign body retrieval (anxiety: -0.99, confidence: +0.95, p < .01) and airway management stations (anxiety: -0.68, confidence: +1.07, p < .01). Data collected for the epistaxis station showed decreasing confidence and increasing anxiety following the workshop. Conclusion: Our findings demonstrate the effectiveness of a workshop in preparing junior residents in potentially lifesaving otolaryngologic techniques that residents will encounter. Optimizing use of simulation centered training can inform the future of residency education, improving confidence and decreasing anxiety in residents responsible for the safety of patients. Level of Evidence: III.

Treatment of Severe COVID-19 Infection With Remdesivir in Peritoneal Dialysis.

End-stage kidney disease (ESKD) has been shown to be correlated with an increased risk of COVID-19 infection and mortality. Remdesivir is an effective non-EUA U.S. Food and Drug Administration (FDA)-approved antiviral agent for the treatment of COVID-19 in hospitalized adult and pediatric patients, though a lack of data has prevented its use in patients with severe kidney disease including dialysis patients. Some observational studies report the use of remdesivir in hemodialysis patients, but there are no reports of patients treated with remdesivir on peritoneal dialysis. Dialysis modalities may affect drug pharmacokinetics, and safety and efficiency of remdesivir in peritoneal dialysis is unknown. We report the first case, to our knowledge, of using remdesivir in a patient treated with peritoneal dialysis with no significant adverse events. This case illustrates the potential for remdesivir to be considered in peritoneal dialysis patients with severe COVID infection. Proper risk analysis and careful monitoring should be done, given the unpredictable clearance of the drug.

Evaluation of an Academic Detailing Program to Improve Blood Pressure Measurement and Hypertension Treatment in Urban Community Health Centers.

INTRODUCTION: Hypertension is estimated at a prevalence of 30 to 50% in the United States. Only 54% of patients with hypertension have their condition adequately controlled. This study aimed to use academic detailing (AD) to improve practice team knowledge and confidence in blood pressure (BP) management, specifically in low-income, underresourced patient populations. METHODS: AD was developed for five practices that care for high percentages of Medicaid-eligible patients. A needs assessment was administered to each site's practice champion to determine high-yield AD sessions for their team. Presession and postsession evaluations were completed by practice team members. RESULTS: Fifty providers and eight staff member participants completed evaluations over nine sessions for two AD topics at four practice sites. Statistical significance was found for several items within sessions including accurately choosing cuff sizes and identifying barriers to home BP monitoring. DISCUSSION: AD is a potentially financially efficient model to improve knowledge and confidence in hypertension care at the practice level. Tailoring session content to specific needs of a practice site, along with an identified practice champion, facilitated implementation of the program. This replicable model is one way to deliver evidence-based information to those who serve Medicaid-eligible patients.

Postoperative Gabapentin's Effect on Opioid Consumption and Pain Control Following Sinonasal Surgery.

OBJECTIVE: This study investigates the impact of postoperative gabapentin on opioid consumption and pain control following endoscopic sinus surgery (ESS) and/or septoplasty. METHODS: Patients who underwent ESS and/or septoplasty at a single institution from 2021 to 2022 were enrolled. All patients received postoperative hydrocodone-acetaminophen for pain control. Half of the patients were also prescribed gabapentin for the first postoperative day in addition to hydrocodone-acetaminophen. Subjects completed the Revised American Pain Society Patient Outcome Questionnaire 24 h and 7 days after surgery. We conducted a multivariable regression analysis to assess opioid consumption and improvement in pain scores in the first week between gabapentin and non-gabapentin groups. RESULTS: A total of 102 subjects, 51 in each arm, were enrolled. The mean age was 52 years and 53% of participants were female. Controlling for important baseline demographic, clinical, and surgically related variables, the addition of postoperative gabapentin was associated with a 44% (9.5 mg from 21.6 mg) reduction in opioids consumed in the first postoperative week (B = -9.54, 95% C.I. = [-17.84, -1.24], p = 0.025). In addition, patients in both arms exhibited similar improvement in pain severity and sleep interference in the first 7 days (B = -1.59, 95% C.I. = [-5.03, 1.84], p = 0.36). CONCLUSION: To the best of our knowledge, this is the first study to investigate the impact of postoperative gabapentin on opioid consumption and pain control following ESS and/or septoplasty. Our analysis demonstrated that postoperative gabapentin effectively reduced opioid use during the first postoperative week without compromising pain control. LEVEL OF EVIDENCE: 3 Laryngoscope, 133:1065-1072, 2023.

A Multifaceted Hit-Finding Approach Reveals Novel LC3 Family Ligands.

Autophagy-related proteins (Atgs) drive the lysosome-mediated degradation pathway, autophagy, to enable the clearance of dysfunctional cellular components and maintain homeostasis. In humans, this process is driven by the mammalian Atg8 (mAtg8) family of proteins comprising the LC3 and GABARAP subfamilies. The mAtg8 proteins play essential roles in the formation and maturation of autophagosomes and the capture of specific cargo through binding to the conserved LC3-interacting region (LIR) sequence within target proteins. Modulation of interactions of mAtg8 with its target proteins via small-molecule ligands would enable further interrogation of their function. Here we describe unbiased fragment and DNA-encoded library (DEL) screening approaches for discovering LC3 small-molecule ligands. Both strategies resulted in compounds that bind to LC3, with the fragment hits favoring a conserved hydrophobic pocket in mATG8 proteins, as detailed by LC3A-fragment complex crystal structures. Our findings demonstrate that the malleable LIR-binding surface can be readily targeted by fragments; however, rational design of additional interactions to drive increased affinity proved challenging. DEL libraries, which combine small, fragment-like building blocks into larger scaffolds, yielded higher-affinity binders and revealed an unexpected potential for reversible, covalent ligands. Moreover, DEL hits identified possible vectors for synthesizing fluorescent probes or bivalent molecules for engineering autophagic degradation of specific targets.

Forming Cardi-OH: A Statewide Collaborative to Improve Cardiovascular Health in Ohio.

Background Cardiovascular risk factor control is challenging, especially in disadvantaged populations. However, few statewide efforts exist to tackle this challenge. Therefore, our objective is to describe the formation of a unique statewide cardiovascular health collaborative so others may learn from this approach. Methodology With funding from the Ohio Department of Medicaid's Ohio Medicaid Technical Assistance and Policy Program, we used a collective impact model to link the seven medical schools in Ohio, primary care clinics across the state, the Ohio Department of Medicaid, and Ohio's Medicaid Managed Care Plans in a statewide health improvement collaborative for expanding primary care capacity to improve cardiovascular health in Ohio. Results Initial dissemination activities for primary care teams included a virtual case-based learning series focused on hypertension and social determinants of health, website resources, a monthly newsletter with clinical tips, webinars, and in-person conferences. The collaborative is aligned with a separately funded hypertension quality improvement project for paired implementation. Conclusions The collective impact model is a useful framework for developing a statewide collaborative focused on the dissemination and implementation of evidence-based best practices for cardiovascular health improvement and disparity reduction. Statewide collaboratives bringing payers, clinicians, and academic partners together have the potential to substantially impact cardiovascular health.

Potential Mechanisms Involved in Chronic Kidney Disease of Unclear Etiology.

BACKGROUND AND OBJECTIVES: The etiology of chronic kidney disease of unclear etiology, also known as Mesoamerican nephropathy, remains unclear. We investigated potential etiologies for Mesoamerican nephropathy in an immigrant dialysis population. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Migrants with Mesoamerican nephropathy kidney failure (n=52) were identified by exclusion of known causes of kidney disease and compared using a cross-sectional survey with demographically similar patients with kidney failure from other causes (n=63) and age/sex/place of origin-matched healthy participants (n=16). Survey results were extended to the bench; C57BL/6 mice (n=73) received 10-15 weekly intraperitoneal injections of paraquat (a reactive oxygen species-generating herbicide) or vehicle. Kidney function, histology, and expression of organic cation transporter-2 (proximal tubule entry for paraquat) and multidrug and toxin extrusion 1 (extrusion pathway) were examined. Kidney biopsies from Nicaraguan patients with acute Mesoamerican nephropathy were stained for the above transporters and compared with patients with tubulointerstitial nephritis and without Mesoamerican nephropathy. RESULTS: Patients with Mesoamerican nephropathy and kidney failure were young agricultural workers, almost exclusively men; the majority were from Mexico and El Salvador; and they had prior exposures to agrochemicals, including paraquat (27%). After adjustment for age/sex, exposure to any agrochemical or paraquat was associated with Mesoamerican nephropathy kidney failure (odds ratio, 4.86; 95% confidence interval, 1.82 to 12.96; P=0.002 and odds ratio, 12.25; 95% confidence interval, 1.51 to 99.36; P=0.02, respectively). Adjusted for age/sex and other covariates, 1 year of agrochemical exposure was associated with Mesoamerican nephropathy kidney failure (odds ratio, 1.23; 95% confidence interval, 1.04 to 1.44; P=0.02). Compared with 16 matched healthy controls, Mesoamerican nephropathy kidney failure was significantly associated with exposure to paraquat and agrochemicals. Paraquat-treated male mice developed kidney failure and tubulointerstitial nephritis consistent with Mesoamerican nephropathy. Organic cation transporter-2 expression was higher in male kidneys versus female kidneys. Paraquat treatment increased organic cation transporter-2 expression and decreased multidrug and toxin extrusion 1 expression in male kidneys; similar results were observed in the kidneys of Nicaraguan patients with Mesoamerican nephropathy. CONCLUSIONS: Exposure to agrochemicals is associated with Mesoamerican nephropathy, and chronic exposure of mice to paraquat, a prototypical oxidant, induced kidney failure similar to Mesoamerican nephropathy.

SIRPα Mediates IGF1 Receptor in Cardiomyopathy Induced by Chronic Kidney Disease.

BACKGROUND: Chronic kidney disease (CKD) is characterized by increased myocardial mass despite near-normal blood pressure, suggesting the presence of a separate trigger. A potential driver is SIRPα (signal regulatory protein alpha)-a mediator impairing insulin signaling. The objective of this study is to assess the role of circulating SIRPα in CKD-induced adverse cardiac remodeling. METHODS: SIRPα expression was evaluated in mouse models and patients with CKD. Specifically, mutant, muscle-specific, or cardiac muscle-specific SIRPα KO (knockout) mice were examined after subtotal nephrectomy. Cardiac function was assessed by echocardiography. Metabolic responses were confirmed in cultured muscle cells or cardiomyocytes. RESULTS: We demonstrate that SIRPα regulates myocardial insulin/IGF1R (insulin growth factor-1 receptor) signaling in CKD. First, in the serum of both mice and patients, SIRPα was robustly secreted in response to CKD. Second, cardiac muscle upregulation of SIRPα was associated with impaired insulin/IGF1R signaling, myocardial dysfunction, and fibrosis. However, both global and cardiac muscle-specific SIRPα KO mice displayed improved cardiac function when compared with control mice with CKD. Third, both muscle-specific or cardiac muscle-specific SIRPα KO mice did not significantly activate fetal genes and maintained insulin/IGF1R signaling with suppressed fibrosis despite the presence of CKD. Importantly, SIRPα directly interacted with IGF1R. Next, rSIRPα (recombinant SIRPα) protein was introduced into muscle-specific SIRPα KO mice reestablishing the insulin/IGF1R signaling activity. Additionally, overexpression of SIRPα in myoblasts and cardiomyocytes impaired pAKT (phosphorylation of AKT) and insulin/IGF1R signaling. Furthermore, myotubes and cardiomyocytes, but not adipocytes treated with high glucose or cardiomyocytes treated with uremic toxins, stimulated secretion of SIRPα in culture media, suggesting these cells are the origin of circulating SIRPα in CKD. Both intracellular and extracellular SIRPα exert biologically synergistic effects impairing intracellular myocardial insulin/IGF1R signaling. CONCLUSIONS: Myokine SIRPα expression impairs insulin/IGF1R functions in cardiac muscle, affecting cardiometabolic signaling pathways. Circulating SIRPα constitutes an important readout of insulin resistance in CKD-induced cardiomyopathy.

Interactions between leucines within the signal peptides of megalin and stanniocalcin-1 are crucial for regulation of mitochondrial metabolism.

The mitochondrial intracrine Stanniocalcin 1 (STC1) activates mitochondrial anti-oxidant defenses. LRP2 (megalin) shuttles STC1 to the mitochondria through retrograde early endosome-to-Golgi- and Rab32-mediated pathway, and LRP2 KO impairs mitochondrial respiration and glycolysis. We determined STC1-LRP2 interaction domains using HA- and FLAG-tagged fragments of STC1 and LRP2, respectively, co-expressed in HEK293T cells. The trans-membrane domain of LRP2 is required for trafficking to the mitochondria. STC1-FLAG expressed in LRP2 KO cells fails to reach the mitochondria; thus, mitochondrial STC1 is extracellularly-derived via LRP2-mediated trafficking. Tri-leucines L12-14 in LRP2's signal peptide interact with STC1's signal peptide. Mutant LRP2 (L(12-14)A) does not bind STC1, while hSTC1 lacking signal peptide or Leucines L8/9/11 does not bind LRP2. STC1 fails to induce respiration or glycolysis in megalin KO mouse embryonal fibroblasts (MEF) expressing mutant LRP2, while mutant hSTC1 (L8/L9/L11 - > A8/A9/A11) fails to reach the mitochondria or induce respiration and glycolysis in WT MEF. Our data suggest direct regulation of mitochondrial metabolism by extracellular cues and reveal an important role for signal peptides' leucines in protein-protein interactions and mitochondrial biology.

Structures of the ApoL1 and ApoL2 N-terminal domains reveal a non-classical four-helix bundle motif.

Apolipoprotein L1 (ApoL1) is a circulating innate immunity protein protecting against trypanosome infection. However, two ApoL1 coding variants are associated with a highly increased risk of chronic kidney disease. Here we present X-ray and NMR structures of the N-terminal domain (NTD) of ApoL1 and of its closest relative ApoL2. In both proteins, four of the five NTD helices form a four-helix core structure which is different from the classical four-helix bundle and from the pore-forming domain of colicin A. The reactivity with a conformation-specific antibody and structural models predict that this four-helix motif is also present in the NTDs of ApoL3 and ApoL4, suggesting related functions within the small ApoL family. The long helix 5 of ApoL1 is conformationally flexible and contains the BH3-like region. This BH3-like α-helix resembles true BH3 domains only in sequence and structure but not in function, since it does not bind to the pro-survival members of the Bcl-2 family, suggesting a Bcl-2-independent role in cytotoxicity. These findings should expedite a more comprehensive structural and functional understanding of the ApoL immune protein family.

Sirtuin-3 mediates sex differences in kidney ischemia-reperfusion injury.

Studies suggest that biological sex influences susceptibility to kidney diseases with males demonstrating greater risk for developing ischemic acute kidney injury (AKI). Sex-related differences in mitochondrial function and homeostasis exist, likely contributing to sexual dimorphism in kidney injury, but the mechanisms are not well characterized. Our observations reveal lower baseline expression of Sirtuin-3 (Sirt3, a major mitochondrial acetyltransferase) in the kidneys of male mice versus females. We tested the hypothesis that differential expression of kidney Sirt3 may mediate sexual dimorphism in AKI using a bilateral kidney ischemia-reperfusion injury (IRI) model and three transgenic mouse models: (1) mice with global transgenic overexpression of Sirt3; (2) mice with inducible, kidney tubule-specific Sirt3 knockdown (iKD); and (3) mice with global Sirt3 knockout. Low mitochondrial Sirt3 (mtSirt3) in males versus females is associated with development of kidney tubular epithelium vacuoles, increased mitochondrial ROS and susceptibility to IRI. Transgenic overexpression of Sirt3 in males protects against kidney IRI and development of tubular epithelium vacuoles. In both sexes, mice with partial kidney tubular epithelium-specific Sirt3 knockdown display intermediate - while global Sirt3 knockout mice display the highest susceptibility to IRI. Female Sirt3 iKD mice demonstrate decreased survival and kidney function after IRI indistinguishable from control males, abolishing the protective effects observed in females. Mechanistically, observed differences in kidney mtSirt3 are sex hormone-dependent; estradiol increases - while testosterone decreases mtSirt3 protein. Our results demonstrate that Sirt3 is an important contributor to the observed sex-related differences in IRI susceptibility, and a potential therapeutic target in the clinical management of AKI.

Megalin-Mediated Trafficking of Mitochondrial Intracrines: Relevance to Signaling and Metabolism.

The multi-ligand binding protein megalin (LRP2) is ubiquitously expressed and facilitates cell uptake of hormones, nutrients and vitamins. We have recently shown megalin is present in the mitochondria of cultured epithelial and mesenchymal cells, as well as many organs and tissues. Mitochondrial megalin associates with stanniocalcin-1 and SIRT3; two proteins that promote anti-oxidant defenses. Megalin shuttles mitochondrial intracrines (angiotensin II, stanniocalcin-1 and TGF-ß) from the cell surface to the mitochondria through the retrograde early endosome to Golgi pathway and requires Rab32. Deletion of megalin impairs mitochondrial respiration and glycolysis. This pathway overlaps molecular and vesicular trafficking defects common to Donai Barrow and Lowe syndromes, suggesting that mitochondrial intracrine signaling defects may contribute to the pathogenesis of these diseases.

Decontamination Methods for Reuse of Filtering Facepiece Respirators.

Importance: The novel coronavirus disease 2019 (COVID-19) has proven to be highly infectious, putting health care professionals around the world at increased risk. Furthermore, there are widespread shortages of necessary personal protective equipment (PPE) for these individuals. Filtering facepiece respirators, such as the N95 respirator, intended for single use, can be reused in times of need. We explore the evidence for decontamination or sterilization of N95 respirators for health care systems seeking to conserve PPE while maintaining the health of their workforce. Observations: The filtration properties and fit of N95 respirators must be preserved to function adequately over multiple uses. Studies have shown that chemical sterilization using soap and water, alcohols, and bleach render the respirator nonfunctional. Decontamination with microwave heat and high dry heat also result in degradation of respirator material. UV light, steam, low-dry heat, and commercial sterilization methods with ethylene oxide or vaporized hydrogen peroxide appear to be viable options for successful decontamination. Furthermore, since the surface viability of the novel coronavirus is presumed to be 72 hours, rotating N95 respirator use and allowing time decontamination of the respirators is also a reasonable option. We describe a protocol and best practice recommendations for redoffing decontaminated N95 and rotating N95 respirator use. Conclusions and Relevance: COVID-19 presents a high risk for health care professionals, particularly otolaryngologists, owing to the nature of viral transmission, including possible airborne transmission and high viral load in the upper respiratory tract. Proper PPE is effective when used correctly, but in times of scarce resources, institutions may turn to alternative methods of preserving and reusing filtering facepiece respirators. Based on studies conducted on the decontamination of N95 respirators after prior outbreaks, there are several options for institutions to consider for both immediate and large-scale implementation.

Soluble Urokinase Receptor and Acute Kidney Injury.

BACKGROUND: Acute kidney injury is common, with a major effect on morbidity and health care utilization. Soluble urokinase plasminogen activator receptor (suPAR) is a signaling glycoprotein thought to be involved in the pathogenesis of kidney disease. We investigated whether a high level of suPAR predisposed patients to acute kidney injury in multiple clinical contexts, and we used experimental models to identify mechanisms by which suPAR acts and to assess it as a therapeutic target. METHODS: We measured plasma levels of suPAR preprocedurally in patients who underwent coronary angiography and patients who underwent cardiac surgery and at the time of admission to the intensive care unit in critically ill patients. We assessed the risk of acute kidney injury at 7 days as the primary outcome and acute kidney injury or death at 90 days as a secondary outcome, according to quartile of suPAR level. In experimental studies, we used a monoclonal antibody to urokinase plasminogen activator receptor (uPAR) as a therapeutic strategy to attenuate acute kidney injury in transgenic mice receiving contrast material. We also assessed cellular bioenergetics and generation of reactive oxygen species in human kidney proximal tubular (HK-2) cells that were exposed to recombinant suPAR. RESULTS: The suPAR level was assessed in 3827 patients who were undergoing coronary angiography, 250 who were undergoing cardiac surgery, and 692 who were critically ill. Acute kidney injury developed in 318 patients (8%) who had undergone coronary angiography. The highest suPAR quartile (vs. the lowest) had an adjusted odds ratio of 2.66 (95% confidence interval [CI], 1.77 to 3.99) for acute kidney injury and 2.29 (95% CI, 1.71 to 3.06) for acute kidney injury or death at 90 days. Findings were similar in the surgical and critically ill cohorts. The suPAR-overexpressing mice that were given contrast material had greater functional and histologic evidence of acute kidney injury than wild-type mice. The suPAR-treated HK-2 cells showed heightened energetic demand and mitochondrial superoxide generation. Pretreatment with a uPAR monoclonal antibody attenuated kidney injury in suPAR-overexpressing mice and normalized bioenergetic changes in HK-2 cells. CONCLUSIONS: High suPAR levels were associated with acute kidney injury in various clinical and experimental contexts. (Funded by the National Institutes of Health and others.).

Structures of autoinhibited and polymerized forms of CARD9 reveal mechanisms of CARD9 and CARD11 activation.

CARD9 and CARD11 drive immune cell activation by nucleating Bcl10 polymerization, but are held in an autoinhibited state prior to stimulation. Here, we elucidate the structural basis for this autoinhibition by determining the structure of a region of CARD9 that includes an extensive interface between its caspase recruitment domain (CARD) and coiled-coil domain. We demonstrate, for both CARD9 and CARD11, that disruption of this interface leads to hyperactivation in cells and to the formation of Bcl10-templating filaments in vitro, illuminating the mechanism of action of numerous oncogenic mutations of CARD11. These structural insights enable us to characterize two similar, yet distinct, mechanisms by which autoinhibition is relieved in the course of canonical CARD9 or CARD11 activation. We also dissect the molecular determinants of helical template assembly by solving the structure of the CARD9 filament. Taken together, these findings delineate the structural mechanisms of inhibition and activation within this protein family.