Protein N-glycans in Healthy and Sclerotic Glomeruli in Diabetic Kidney Disease.

BACKGROUND: Diabetes is expected to directly impact renal glycosylation, yet to date, there has not been a comprehensive evaluation of alterations in N-glycan composition in the glomeruli of patients with diabetic kidney disease (DKD). METHODS: We used untargeted mass spectrometry imaging to identify N-glycan structures in healthy and sclerotic glomeruli in FFPE sections from needle biopsies of five patients with DKD and three healthy kidney samples. Regional proteomics was performed on glomeruli from additional biopsies from the same patients to compare the abundances of enzymes involved in glycosylation. Secondary analysis of single nuclei transcriptomics (snRNAseq) data was used to inform on transcript levels of glycosylation machinery in different cell types and states. RESULTS: We detected 120 N-glycans, and among them identified twelve of these protein post-translated modifications that were significantly increased in glomeruli. All glomeruli-specific N-glycans contained an N-acetyllactosamine (LacNAc) epitope. Five N-glycan structures were highly discriminant between sclerotic and healthy glomeruli. Sclerotic glomeruli had an additional set of glycans lacking fucose linked to their core, and they did not show tetra-antennary structures that are common in healthy glomeruli. Orthogonal omics analyses revealed lower protein abundance and lower gene expression involved in synthesizing fucosylated and branched N-glycans in sclerotic podocytes. In snRNAseq and regional proteomics analyses, we observed that genes and/or proteins involved in sialylation and LacNAc synthesis were also downregulated in DKD glomeruli, but this alteration remained undetectable by our spatial N-glycomics assay. CONCLUSIONS: Integrative spatial glycomics, proteomics, and transcriptomics revealed protein N-glycosylation characteristic of sclerotic glomeruli in DKD.

Pragmatic Trial of Hospitalization Rate in Chronic Kidney Disease.

BACKGROUND: Despite the availability of effective therapies for patients with chronic kidney disease, type 2 diabetes, and hypertension (the kidney-dysfunction triad), the results of large-scale trials examining the implementation of guideline-directed therapy to reduce the risk of death and complications in this population are lacking. METHODS: In this open-label, cluster-randomized trial, we assigned 11,182 patients with the kidney-dysfunction triad who were being treated at 141 primary care clinics either to receive an intervention that used a personalized algorithm (based on the patient's electronic health record [EHR]) to identify patients and practice facilitators to assist providers in delivering guideline-based interventions or to receive usual care. The primary outcome was hospitalization for any cause at 1 year. Secondary outcomes included emergency department visits, readmissions, cardiovascular events, dialysis, and death. RESULTS: We assigned 71 practices (enrolling 5690 patients) to the intervention group and 70 practices (enrolling 5492 patients) to the usual-care group. The hospitalization rate at 1 year was 20.7% (95% confidence interval [CI], 19.7 to 21.8) in the intervention group and 21.1% (95% CI, 20.1 to 22.2) in the usual-care group (between-group difference, 0.4 percentage points; P = 0.58). The risks of emergency department visits, readmissions, cardiovascular events, dialysis, or death from any cause were similar in the two groups. The risk of adverse events was also similar in the trial groups, except for acute kidney injury, which was observed in more patients in the intervention group (12.7% vs. 11.3%). CONCLUSIONS: In this pragmatic trial involving patients with the triad of chronic kidney disease, type 2 diabetes, and hypertension, the use of an EHR-based algorithm and practice facilitators embedded in primary care clinics did not translate into reduced hospitalization at 1 year. (Funded by the National Institutes of Health and others; ICD-Pieces ClinicalTrials.gov number, NCT02587936.).

Intrinsic endothelial hyperresponsiveness to inflammatory mediators drives acute episodes in models of Clarkson disease.

Clarkson disease, or monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome (ISCLS), is a rare, relapsing-remitting disorder featuring the abrupt extravasation of fluids and proteins into peripheral tissues, which in turn leads to hypotensive shock, severe hemoconcentration, and hypoalbuminemia. The specific leakage factor(s) and pathways in ISCLS are unknown, and there is no effective treatment for acute flares. Here, we characterize an autonomous vascular endothelial defect in ISCLS that was recapitulated in patient-derived endothelial cells (ECs) in culture and in a mouse model of disease. ISCLS-derived ECs were functionally hyperresponsive to permeability-inducing factors like VEGF and histamine, in part due to increased endothelial nitric oxide synthase (eNOS) activity. eNOS blockade by administration of N(γ)-nitro-l-arginine methyl ester (l-NAME) ameliorated vascular leakage in an SJL/J mouse model of ISCLS induced by histamine or VEGF challenge. eNOS mislocalization and decreased protein phosphatase 2A (PP2A) expression may contribute to eNOS hyperactivation in ISCLS-derived ECs. Our findings provide mechanistic insights into microvascular barrier dysfunction in ISCLS and highlight a potential therapeutic approach.

Designer high-density lipoprotein particles enhance endothelial barrier function and suppress inflammation.

High-density lipoprotein (HDL) nanoparticles promote endothelial cell (EC) function and suppress inflammation, but their utility in treating EC dysfunction has not been fully explored. Here, we describe a fusion protein named ApoA1-ApoM (A1M) consisting of apolipoprotein A1 (ApoA1), the principal structural protein of HDL that forms lipid nanoparticles, and ApoM, a chaperone for the bioactive lipid sphingosine 1-phosphate (S1P). A1M forms HDL-like particles, binds to S1P, and is signaling competent. Molecular dynamics simulations showed that the S1P-bound ApoM moiety in A1M efficiently activated EC surface receptors. Treatment of human umbilical vein ECs with A1M-S1P stimulated barrier function either alone or cooperatively with other barrier-enhancing molecules, including the stable prostacyclin analog iloprost, and suppressed cytokine-induced inflammation. A1M-S1P injection into mice during sterile inflammation suppressed neutrophil influx and inflammatory mediator secretion. Moreover, systemic A1M administration led to a sustained increase in circulating HDL-bound S1P and suppressed inflammation in a murine model of LPS-induced endotoxemia. We propose that A1M administration may enhance vascular endothelial barrier function, suppress cytokine storm, and promote resilience of the vascular endothelium.

Mitochondrial genetic variation and risk of chronic kidney disease and acute kidney injury in UK Biobank participants.

Experimental models suggest an important role for mitochondrial dysfunction in the pathogenesis of chronic kidney disease (CKD) and acute kidney injury (AKI), but little is known regarding the impact of common mitochondrial genetic variation on kidney health. We sought to evaluate associations of inherited mitochondrial DNA (mtDNA) variation with risk of CKD and AKI in a large population-based cohort. We categorized UK Biobank participants who self-identified as white into eight distinct mtDNA haplotypes, which were previously identified based on their associations with phenotypes associated with mitochondrial DNA copy number, a measure of mitochondrial function. We used linear and logistic regression models to evaluate associations of these mtDNA haplotypes with estimated glomerular filtration rate by serum creatinine and cystatin C (eGFRCr-CysC, N = 362,802), prevalent (N = 416 cases) and incident (N = 405 cases) end-stage kidney disease (ESKD), AKI defined by diagnostic codes (N = 14,170 cases), and urine albumin/creatinine ratio (ACR, N = 114,662). The mean age was 57 ± 8 years and the mean eGFR was 90 ± 14 ml/min/1.73 m2. MtDNA haplotype was significantly associated with eGFR (p = 2.8E-12), but not with prevalent ESKD (p = 5.9E-2), incident ESKD (p = 0.93), AKI (p = 0.26), or urine ACR (p = 0.54). The association of mtDNA haplotype with eGFR remained significant after adjustment for diabetes mellitus and hypertension (p = 1.2E-10). When compared to the reference haplotype, mtDNA haplotypes I (ß = 0.402, standard error (SE) = 0.111; p = 2.7E-4), IV (ß = 0.430, SE = 0.073; p = 4.2E-9), and V (ß = 0.233, SE = 0.050; p = 2.7E-6) were each associated with higher eGFR. Among self-identified white UK Biobank participants, mtDNA haplotype was associated with eGFR, but not with ESKD, AKI or albuminuria.

The chromatin landscape of healthy and injured cell types in the human kidney.

There is a need to define regions of gene activation or repression that control human kidney cells in states of health, injury, and repair to understand the molecular pathogenesis of kidney disease and design therapeutic strategies. Comprehensive integration of gene expression with epigenetic features that define regulatory elements remains a significant challenge. We measure dual single nucleus RNA expression and chromatin accessibility, DNA methylation, and H3K27ac, H3K4me1, H3K4me3, and H3K27me3 histone modifications to decipher the chromatin landscape and gene regulation of the kidney in reference and adaptive injury states. We establish a spatially-anchored epigenomic atlas to define the kidney's active, silent, and regulatory accessible chromatin regions across the genome. Using this atlas, we note distinct control of adaptive injury in different epithelial cell types. A proximal tubule cell transcription factor network of ELF3, KLF6, and KLF10 regulates the transition between health and injury, while in thick ascending limb cells this transition is regulated by NR2F1. Further, combined perturbation of ELF3, KLF6, and KLF10 distinguishes two adaptive proximal tubular cell subtypes, one of which manifested a repair trajectory after knockout. This atlas will serve as a foundation to facilitate targeted cell-specific therapeutics by reprogramming gene regulatory networks.

Clinical Evaluation and Management of Thrombotic Microangiopathy.

Thrombotic microangiopathy (TMA) refers to a diverse group of diseases that share clinical and histopathologic features. TMA is clinically characterized by microangiopathic hemolytic anemia, consumptive thrombocytopenia, and organ injury that stems from endothelial damage and vascular occlusion. There are several disease states with distinct pathophysiological mechanisms that manifest as TMA. These conditions are associated with significant morbidity and mortality and require urgent recognition and treatment. Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome are traditionally considered to be primary forms of TMA, but TMA more commonly occurs in association with a coexisting condition such as infection, pregnancy, autoimmune disease, or malignant hypertension, among others. Determining the cause of TMA is a diagnostic challenge because of limited availability of disease-specific testing. However, identifying the underlying etiology is imperative as treatment strategies differ. Our understanding of the conditions that cause TMA is evolving. Recent advances have led to improved comprehension of the varying pathogenic mechanisms that drive TMA. Development of targeted therapeutics has resulted in significant improvements in patient outcomes. In this article, we review the pathogenesis and clinical features of the different TMA-causing conditions. We outline a practical approach to diagnosis and management and discuss empiric and disease-specific treatment strategies.

Bile acid-induced IRF3 phosphorylation mediates cell death, inflammatory responses, and fibrosis in cholestasis-induced liver and kidney injury via regulation of ZBP1.

BACKGROUND AND AIMS: Cell death and inflammation play critical roles in chronic tissue damage caused by cholestatic liver injury leading to fibrosis and cirrhosis. Liver cirrhosis is often associated with kidney damage, which is a severe complication with poor prognosis. Interferon regulatory factor 3 (IRF3) is known to regulate apoptosis and inflammation, but its role in cholestasis remains obscure. In this study. APPROACH AND RESULTS: We discovered increased IRF3 phosphorylation in the liver of patients with primary biliary cholangitis and primary sclerosing cholangitis. In the bile duct ligation model of obstructive cholestasis in mice, we found that tissue damage was associated with increased phosphorylated IRF3 (p-IRF3) in the liver and kidney. IRF3 knockout ( Irf3-/- ) mice showed significantly attenuated liver and kidney damage and fibrosis compared to wide-type mice after bile duct ligation. Cell-death pathways, including apoptosis, necroptosis, and pyroptosis, inflammasome activation, and inflammatory responses were significantly attenuated in Irf3-/- mice. Mechanistically, we show that bile acids induced p-IRF3 in vitro in hepatocytes. In vivo , activated IRF3 positively correlated with increased expression of its target gene, Z-DNA-Binding Protein-1 (ZBP1), in the liver and kidney. Importantly, we also found increased ZBP1 in the liver of patients with primary biliary cholangitis and primary sclerosing cholangitis. We discovered that ZBP1 interacted with receptor interacting protein 1 (RIP1), RIP3, and NLRP3, thereby revealing its potential role in the regulation of cell-death and inflammation pathways. In conclusion. CONCLUSIONS: Our data indicate that bile acid-induced p-IRF3 and the IRF3-ZBP1 axis play a central role in the pathogenesis of cholestatic liver and kidney injury.

Safety and Efficacy of Long-Term Voclosporin Treatment for Lupus Nephritis in the Phase 3 AURORA 2 Clinical Trial.

OBJECTIVE: AURORA 2 evaluated the long-term safety, tolerability, and efficacy of voclosporin compared to placebo in patients with lupus nephritis (LN) receiving an additional two years of treatment following completion of the one-year AURORA 1 study. METHODS: Enrolled patients continued their double-blinded treatment of voclosporin or placebo randomly assigned in AURORA 1, in combination with mycophenolate mofetil and low-dose glucocorticoids. The primary objective was safety assessed with adverse events (AEs) and biochemical and hematological assessments. Efficacy was measured by renal response. RESULTS: A total of 216 patients enrolled in AURORA 2. Treatment was well tolerated with 86.1% completing the study and no unexpected safety signals. AEs occurred in 86% and 80% of patients in the voclosporin and control groups, respectively, with an AE profile similar to that seen in AURORA 1, albeit with reduced frequency. Investigator reported AEs of both glomerular filtration rate (GFR) decrease and hypertension occurred more frequently in the voclosporin than the control group (10.3% vs 5.0%, and 8.6% vs 7.0%, respectively). Mean corrected estimated GFR (eGFR) was within the normal range and stable in both treatment groups. eGFR slope over the two-year period was -0.2 mL/min/1.73 m2 (95% confidence interval [CI] -3.0 to 2.7) in the voclosporin group and -5.4 mL/min/1.73 m2 (95% CI -8.4 to -2.3) in the control group. Improved proteinuria persisted across three years of treatment, leading to more frequent complete renal responses in patients treated with voclosporin (50.9% vs 39.0%; odds ratio 1.74; 95% CI 1.00-3.03). CONCLUSION: Data demonstrate the safety and efficacy of long-term voclosporin treatment over three years of follow-up in patients with LN.

Hepatocyte nuclear factor 4α mediated quinolinate phosphoribosylltransferase (QPRT) expression in the kidney facilitates resilience against acute kidney injury.

Nicotinamide adenine dinucleotide (NAD+) levels decline in experimental models of acute kidney injury (AKI). Attenuated enzymatic conversion of tryptophan to NAD+ in tubular epithelium may contribute to adverse cellular and physiological outcomes. Mechanisms underlying defense of tryptophan-dependent NAD+ production are incompletely understood. Here we show that regulation of a bottleneck enzyme in this pathway, quinolinate phosphoribosyltransferase (QPRT) may contribute to kidney resilience. Expression of QPRT declined in two unrelated models of AKI. Haploinsufficient mice developed worse outcomes compared to littermate controls whereas novel, conditional gain-of-function mice were protected from injury. Applying these findings, we then identified hepatocyte nuclear factor 4 alpha (HNF4α) as a candidate transcription factor regulating QPRT expression downstream of the mitochondrial biogenesis regulator and NAD+ biosynthesis inducer PPARgamma coactivator-1-alpha (PGC1α). This was verified by chromatin immunoprecipitation. A PGC1α - HNF4α -QPRT axis controlled NAD+ levels across cellular compartments and modulated cellular ATP. These results propose that tryptophan-dependent NAD+ biosynthesis via QPRT and induced by HNF4α may be a critical determinant of kidney resilience to noxious stressors.

Targeted Therapeutics for Transthyretin Amyloid Cardiomyopathy.

BACKGROUND: Deposition of wild-type or mutant transthyretin (TTR) amyloid fibrils in the myocardium causes TTR amyloid cardiomyopathy (ATTR-CM). Targeted therapeutics for ATTR-CM include TTR stabilizers (tafamidis and diflunisal) and oligonucleotide drugs (revusiran, patisiran, and inotersen). TTR stabilizers prevent dissociation of transthyretin tetramers. Transthyretin monomers can misfold and form amyloid fibrils. TTR stabilizers thereby limit amyloid fibrils development and deposition. Oligonucleotide drugs inhibit hepatic synthesis of transthyretin, which decreases transthyretin protein levels and thus the amyloid fibril substrate. AREAS OF UNCERTAINTY: To study the safety and efficacy of targeted therapeutics in patients with ATTR-CM, we performed a pooled analysis. A random-effects model with the Mantel-Haenszel method was used to pool the data. DATA SOURCES: A literature search was performed using PubMed, Cochrane CENTRAL, and Embase databases using the search terms "cardiac amyloidosis" AND "tafamidis" OR "patisiran" OR "inotersen" OR "revusiran" OR "diflunisal." THERAPEUTIC ADVANCES: We identified 6 studies that compared targeted therapeutics with placebo. One study was stopped prematurely because of increased mortality in the targeted therapeutics arm. Pooled analysis included 1238 patients, of which 738 patients received targeted therapeutics and 500 patients received placebo. When compared with placebo, targeted therapeutics significantly reduced all-cause mortality [OR 0.39, 95% confidence interval (CI): 0.16-0.97, P = 0.04]. Only 2 studies reported the effect on cardiovascular-related hospitalizations. There was a trend toward an improvement in global longitudinal strain (mean difference -0.69, 95% CI: -1.44 to 0.05, P = 0.07). When compared with placebo, there was no increase in serious adverse events with targeted therapeutics (OR 1.06, 95% CI: 0.78-1.44, P = 0.72). CONCLUSION: Evidence from the pooled analysis revealed targeted therapeutics improve survival and are well-tolerated. These findings suggest a potential role for targeted therapeutics in the treatment of patients with ATTR-CM.

Hypoxia-inducible factor 1 signaling drives placental aging and can provoke preterm labor.

Most cases of preterm labor have unknown cause, and the burden of preterm birth is immense. Placental aging has been proposed to promote labor onset, but specific mechanisms remain elusive. We report findings stemming from unbiased transcriptomic analysis of mouse placenta, which revealed that hypoxia-inducible factor 1 (HIF-1) stabilization is a hallmark of advanced gestational timepoints, accompanied by mitochondrial dysregulation and cellular senescence; we detected similar effects in aging human placenta. In parallel in primary mouse trophoblasts and human choriocarcinoma cells, we modeled HIF-1 induction and demonstrated resultant mitochondrial dysfunction and cellular senescence. Transcriptomic analysis revealed that HIF-1 stabilization recapitulated gene signatures observed in aged placenta. Further, conditioned media from trophoblasts following HIF-1 induction promoted contractility in immortalized uterine myocytes, suggesting a mechanism by which the aging placenta may drive the transition from uterine quiescence to contractility at the onset of labor. Finally, pharmacological induction of HIF-1 via intraperitoneal administration of dimethyloxalyl glycine (DMOG) to pregnant mice caused preterm labor. These results provide clear evidence for placental aging in normal pregnancy, and demonstrate how HIF-1 signaling in late gestation may be a causal determinant of the mitochondrial dysfunction and senescence observed within the trophoblast as well as a trigger for uterine contraction.

NAD+ precursor nutritional supplements sensitize the brain to future ischemic events.

Nicotinamide adenine dinucleotide (NAD+) is a redox cofactor critical for oxidative phosphorylation. Nicotinamide (NAM) and nicotinamide riboside (NR) are NAD+ precursors widely used as nutritional supplements to augment oxidative phosphorylation. Indeed, NAD+ precursors have been reported to improve outcomes in ischemic stroke when administered as a rescue therapy after stroke onset. However, we have also reported that enhanced reliance on oxidative phosphorylation before ischemia onset might worsen outcomes. To address the paradox, we examined how NAD+ precursors modulate the outcome of middle cerebral artery occlusion in mice, when administered either 20 minutes after reperfusion or daily for three days before ischemia onset. A single post-ischemic dose of NAM or NR indeed improved tissue and neurologic outcomes examined at 72 hours. In contrast, pre-ischemic treatment for three days enlarged the infarcts and worsened neurological deficits. As a possible explanation for the diametric outcomes, a single dose of NAM or NR augmented tissue AMPK, PGC1α, SIRT1, and ATP in both naïve and ischemic brains, while the multiple-dose paradigm failed to do so. Our data suggest that NAD+ precursor supplements may sensitize the brain to subsequent ischemic events, despite their neuroprotective effect when administered after ischemia onset.

The chromatin landscape of healthy and injured cell types in the human kidney.

There is a need to define regions of gene activation or repression that control human kidney cells in states of health, injury, and repair to understand the molecular pathogenesis of kidney disease and design therapeutic strategies. However, comprehensive integration of gene expression with epigenetic features that define regulatory elements remains a significant challenge. We measured dual single nucleus RNA expression and chromatin accessibility, DNA methylation, and H3K27ac, H3K4me1, H3K4me3, and H3K27me3 histone modifications to decipher the chromatin landscape and gene regulation of the kidney in reference and adaptive injury states. We established a comprehensive and spatially-anchored epigenomic atlas to define the kidney's active, silent, and regulatory accessible chromatin regions across the genome. Using this atlas, we noted distinct control of adaptive injury in different epithelial cell types. A proximal tubule cell transcription factor network of ELF3 , KLF6 , and KLF10 regulated the transition between health and injury, while in thick ascending limb cells this transition was regulated by NR2F1 . Further, combined perturbation of ELF3 , KLF6 , and KLF10 distinguished two adaptive proximal tubular cell subtypes, one of which manifested a repair trajectory after knockout. This atlas will serve as a foundation to facilitate targeted cell-specific therapeutics by reprogramming gene regulatory networks.

Thiamine for Renal Protection in Septic Shock (TRPSS): A Randomized, Placebo-controlled, Clinical Trial.

Rationale: Kidney injury is common and associated with worse outcomes in patients with septic shock. Mitochondrial resuscitation with thiamine (vitamin B1) may attenuate septic kidney injury. Objectives: To assess whether thiamine supplementation attenuates kidney injury in septic shock. Methods: The TRPSS (Thiamine for Renal Protection in Septic Shock) trial was a multicenter, randomized, placebo-controlled trial of thiamine versus placebo in septic shock. The primary outcome was change in serum creatinine between enrollment and 72 hours after enrollment. Measurements and Main Results: Eighty-eight patients were enrolled (42 patients received the intervention, and 46 received placebo). There was no significant between-groups difference in creatinine at 72 hours (mean difference, -0.57 mg/dl; 95% confidence interval, -1.18, 0.04; P = 0.07). There was no difference in receipt of kidney replacement therapy (14.3% vs. 21.7%, P = 0.34), acute kidney injury (as defined by stage 3 of the Kidney Disease: Improving Global Outcomes acute kidney injury scale; 54.7% vs. 73.9%, P = 0.07), or mortality (35.7% vs. 54.3%, P = 0.14) between the thiamine and placebo groups. Patients who received thiamine had more ICU-free days (median [interquartile range]: 22.5 [0.0-25.0] vs. 0.0 [0.0-23.0], P < 0.01). In the thiamine-deficient cohort (27.4% of patients), there was no difference in rates of kidney failure (57.1% thiamine vs. 81.5% placebo) or in-hospital mortality (28.6% vs. 68.8%) between groups. Conclusions: In the TRPSS trial, there was no statistically significant difference in the primary outcome of change in creatinine over time. Patients who received thiamine had more ICU-free days, but there was no difference in other secondary outcomes. Clinical trial registered with www.clinicaltrials.gov (NCT03550794).

A Rare Case of Recurrent Immunotactoid Glomerulonephritis.

Immunotactoid glomerulopathy is an uncommon cause of glomerular disease that results from deposits derived from immunoglobulins. This rare disease can occur in native kidneys and in transplant patients. They are present only in 0.5% to 1.4% of native kidney biopsies. Treatment of this disease is directed at the underlying monoclonal gammopathy, infection, and B-cell lymphoproliferative disorders. Prognosis is very guarded with 50% of people developing ESRD within five years of diagnosis. We present an interesting, rare case of recurrent immunotactoid glomerulonephritis which responded appropriately to rituximab therapy.