A randomized study to compare oral potassium binders in the treatment of acute hyperkalemia.

BACKGROUND: The KBindER (K+ Binders in Emergency Room and hospitalized patients) clinical trial is the first head-to-head evaluation of oral potassium binders (cation-exchange resins) for acute hyperkalemia therapy. METHODS: Emergency room and hospitalized patients with a blood potassium level ≥ 5.5 mEq/L are randomized to one of four study groups: potassium binder drug (sodium polystyrene sulfonate, patiromer, or sodium zirconium cyclosilicate) or nonspecific laxative (polyethylene glycol). Exclusion criteria include recent bowel surgery, ileus, diabetic ketoacidosis, or anticipated dialysis treatment within 4 h of treatment drug. Primary endpoints include change in potassium level at 2 and 4 h after treatment drug. Length of hospital stay, next-morning potassium level, gastrointestinal side effects and palatability will also be analyzed. We are aiming for a final cohort of 80 patients with complete data endpoints (20 per group) for comparative statistics including multivariate adjustment for kidney function, diabetes mellitus, congestive heart failure, metabolic acidosis, renin-angiotensin-aldosterone system inhibitor prescription, and treatment with other agents to lower potassium (insulin, albuterol, loop diuretics). DISCUSSION: The findings from our study will inform decision-making guidelines on the role of oral potassium binders in the treatment of acute hyperkalemia. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04585542 . Registered 14 October 2020.

Thrombotic Microangiopathy Syndromes-Common Ground and Distinct Frontiers.

Thrombotic microangiopathies (TMAs) have in common a terminal phenotype of microangiopathic hemolytic anemia with end-organ dysfunction. Thrombotic thrombocytopenic purpura results from von Willebrand factor multimerization, Shiga toxin-mediated hemolytic uremic syndrome causes toxin-induced endothelial dysfunction, while atypical hemolytic uremic syndrome results from complement system dysregulation. Drug-induced TMA, rheumatological disease-induced TMA, and renal-limited TMA exist in an intermediate space that represents secondary complement activation and may overlap with atypical hemolytic uremic syndrome clinically. The existence of TMA without microangiopathic hemolytic features, renal-limited TMA, represents an undiscovered syndrome that responds incompletely and inconsistently to complement blockade. Hematopoietic stem cell transplant-TMA represents another more resistant form of TMA with different therapeutic needs and clinical course. It has become apparent that TMA syndromes are an emerging field in nephrology, rheumatology, and hematology. Much work remains in genetics, molecular biology, and therapeutics to unravel the puzzle of the relationships and distinctions apparent between the different subclasses of TMA syndromes.

Is It Time to Utilize Genetic Testing for Living Kidney Donor Evaluation?

Living donor kidney transplantation is an effective strategy to mitigate the challenges of solid organ shortage. However, being a living kidney donor is not without risk, as donors may encounter short- and long-term complications including the risk of developing chronic kidney disease, end-stage kidney disease, hypertension, and possible pregnancy-related complications. Although the evaluation of potential living donors is a thorough and meticulous process with the intention of decreasing the chance of complications, particularly in donors who have lifetime risk projection, risk factors for kidney disease including genetic predispositions may be missed because they are not routinely investigated. This type of testing may not be offered to patients due to variability and decreased penetrance of symptoms and lack of availability of appropriate genetic testing and genetic specialists. We report a case of a middle-aged woman with a history of gestational diabetes and preeclampsia who underwent an uneventful living kidney donation. She developed postdonation nonnephrotic range proteinuria and microscopic hematuria. Given the risk of biopsy with a solitary kidney, genetic testing was performed and revealed autosomal dominant Alport syndrome. Our case underscores the utility of genetic testing. Hopefully, future research will examine the incorporation of predonation genetic testing into living kidney donor evaluation.

Review of intravitreal VEGF inhibitor toxicity and report of collapsing FSGS with TMA in a patient with age-related macular degeneration.

Intravitreal vascular endothelial growth factor (VEGF) receptor blockade is used for a variety of retinal pathologies. These include age-related macular degeneration (AMD), diabetic macular edema (DME) and central retinal vein obstruction. Reports of absorption of intravitreal agents into systemic circulation have increased in number and confirmation of depletion of VEGF has been confirmed. Increasingly there are studies and case reports showing worsening hypertension, proteinuria, renal dysfunction and glomerular disease. The pathognomonic findings of systemic VEGF blockade, thrombotic microangiopathies (TMAs), are also being increasingly reported. One lesion that occurs in conjunction with TMAs that has been described is collapsing focal segmental glomerulosclerosis (cFSGS). cFSGS has been postulated to occur due to TMA-induced chronic glomerular hypoxia. In this updated review we discuss the mechanistic, pharmacological, epidemiological and clinical evidence of intravitreal VEGF toxicity. We review cases of biopsy-proven toxicity presented by our group and other investigators. We also present the third reported case of cFSGS in the setting of intravitreal VEGF blockade with a chronic TMA component that was crucially found on biopsy. This patient is a 74-year-old nondiabetic male receiving aflibercept for AMD. Of the two prior cases of cFSGS in the setting of VEGF blockade, one had AMD and the other had DME. This case solidifies the finding of cFSGS and its association with chronic TMA as a lesion that may be frequently encountered in patients receiving intravitreal VEGF inhibitors.

Refractory scleroderma renal crisis precipitated after high-dose oral corticosteroids and concurrent intravitreal injection of bevacizumab.

Scleroderma renal crisis is a serious complication that can develop in certain patients with systemic sclerosis. Some risks have been identified as potential triggers of scleroderma renal crisis, including the high-dose oral corticosteroids. Here, we present a patient who developed clinically severe systemic sclerosis and scleroderma renal crisis after exposure to oral corticosteroids and intravitreal vascular endothelial growth factor blockade with bevacizumab for cotton wool spots. The patient's scleroderma renal crisis was severe, progressive, and refractory to the standard of care therapy: oral captopril. Biopsy showed a diffuse thrombotic microangiopathy and findings consistent with scleroderma renal crisis. We hypothesize that depletion of systemic vascular endothelial growth factor with intravitreal anti-vascular endothelial growth factor injections likely contributed to the particularly severe presentation seen in this case. Though the finding of a monoclonal gammopathy of undetermined significance is another complicating factor, this case suggests that vascular endothelial growth factor inhibition may be a newly recognized trigger of scleroderma renal crisis.

Finding of pathological thrombomodulin gene variant in a patient with idiopathic nodular glomerulosclerosis and chronic thrombotic microangiopathy-like changes.

Idiopathic nodular glomerulosclerosis is an unusual histopathological finding that has commonly been observed in male smokers with hypertension. It has remained an enigmatic condition and is best described as a diabetic pattern of glomerular injury seen in non-diabetic patients. It is also one of the few nicotine (smoking)-associated/smoking-associated patterns of renal injury. We present an even more unusual manifestation of this pathological finding in a 59-year-old Hispanic female who presented with chronic kidney disease approaching need for renal replacement therapy. The patient had idiopathic nodular glomerulosclerosis on kidney biopsy, despite no prior history of diabetes, nor smoking history, including no secondhand smoking exposure. The patient did have hypertension. The renal biopsy also showed evidence of chronic thrombotic-microangiopathic changes within arteries and arterioles. Genetic testing of the alternative pathway revealed an unusual and likely pathological variant of thrombomodulin supporting complement dysfunction as having a role in the presentation.

Cell proliferation in the absence of E2F1-3.

E2F transcription factors regulate the progression of the cell cycle by repression or transactivation of genes that encode cyclins, cyclin dependent kinases, checkpoint regulators, and replication proteins. Although some E2F functions are independent of the Retinoblastoma tumor suppressor (Rb) and related family members, p107 and p130, much of E2F-mediated repression of S phase entry is dependent upon Rb. We previously showed in cultured mouse embryonic fibroblasts that concomitant loss of three E2F activators with overlapping functions (E2F1, E2F2, and E2F3) triggered the p53-p21(Cip1) response and caused cell cycle arrest. Here we report on a dramatic difference in the requirement for E2F during development and in cultured cells by showing that cell cycle entry occurs normally in E2f1-3 triply-deficient epithelial stem cells and progenitors of the developing lens. Sixteen days after birth, however, massive apoptosis in differentiating epithelium leads to a collapse of the entire eye. Prior to this collapse, we find that expression of cell cycle-regulated genes in E2F-deficient lenses is aberrantly high. In a second set of experiments, we demonstrate that E2F3 ablation alone does not cause abnormalities in lens development but rescues phenotypic defects caused by loss of Rb, a binding partner of E2F known to recruit histone deacetylases, SWI/SNF and CtBP-polycomb complexes, methyltransferases, and other co-repressors to gene promoters. Together, these data implicate E2F1-3 in mediating transcriptional repression by Rb during cell cycle exit and point to a critical role for their repressive functions in cell survival.

E2f1-3 switch from activators in progenitor cells to repressors in differentiating cells.

In the established model of mammalian cell cycle control, the retinoblastoma protein (Rb) functions to restrict cells from entering S phase by binding and sequestering E2f activators (E2f1, E2f2 and E2f3), which are invariably portrayed as the ultimate effectors of a transcriptional program that commit cells to enter and progress through S phase. Using a panel of tissue-specific cre-transgenic mice and conditional E2f alleles we examined the effects of E2f1, E2f2 and E2f3 triple deficiency in murine embryonic stem cells, embryos and small intestines. We show that in normal dividing progenitor cells E2f1-3 function as transcriptional activators, but contrary to the current view, are dispensable for cell division and instead are necessary for cell survival. In differentiating cells E2f1-3 function in a complex with Rb as repressors to silence E2f targets and facilitate exit from the cell cycle. The inactivation of Rb in differentiating cells resulted in a switch of E2f1-3 from repressors to activators, leading to the superactivation of E2f responsive targets and ectopic cell divisions. Loss of E2f1-3 completely suppressed these phenotypes caused by Rb deficiency. This work contextualizes the activator versus repressor functions of E2f1-3 in vivo, revealing distinct roles in dividing versus differentiating cells and in normal versus cancer-like cell cycles.