Nonepithelial mineralocorticoid receptor activation as a determinant of kidney disease

Mineralocorticoid receptor antagonists in kidney transplantation

BACKGROUND

The fundamental role of the renin-angiotensin-aldosterone system in the pathophysiology of chronic kidney disease, congestive heart failure, hypertension and proteinuria is well established in pre-clinical and clinical studies. Mineralocorticoid receptor antagonists are among the primary options for renin-angiotensin-aldosterone system blockage, along with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers.

METHODS

In this narrative review, we aim to evaluate the efficiency and safety of mineralocorticoid receptor antagonists in kidney transplant recipients, including the potential underlying pathophysiology.

RESULTS

The efficiency and safety of mineralocorticoid receptor antagonists in managing chronic kidney disease and proteinuria, either non-nephrotic or nephrotic range, have been demonstrated among nontransplanted patients, though studies investigating the role of mineralocorticoid receptor antagonists among kidney transplant recipients are scarce. Nevertheless, promising results have been reported in pre-clinical and clinical studies among kidney transplant recipients regarding the role of mineralocorticoid receptor antagonists in terms of ischaemia-reperfusion injury, proteinuria, or calcineurin inhibitor-mediated nephrotoxicity without considerable adverse events such as hypotension, hyperkalaemia or worsening renal functions.

CONCLUSION

Even though initial results regarding the role of mineralocorticoid receptor antagonist therapy for kidney transplant recipients are promising, there is clear need for large-scale randomized clinical trials with long-term follow-up data.

Effectiveness and safety of finerenone in Chinese CKD patients without diabetes: a retrospective, real-world study

BACKGROUND

Finerenone, a non-steroidal mineralocorticoid receptor antagonist, has previously demonstrated its efficacy and safety in chronic kidney disease (CKD) associated with diabetes mellitus. Given its therapeutic potential, finerenone has been preliminarily explored in clinical practice for non-diabetic CKD patients. The effectiveness and safety in this population require further investigation in a real-world setting.

METHODS

This retrospective, real-world analysis included non-diabetic CKD patients receiving finerenone. The main clinical outcomes assessed were changes in urinary albumin-to-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR). Serum potassium (sK+) levels were also monitored. Data were collected at baseline, and then at 1 month and 3 months following treatment initiation.

RESULTS

Totally, 16 patients were included. There was a notable decrease in UACR from 1-month post-treatment, with a further reduction at 3 months, resulting in a median reduction of 200.41 mg/g (IQR, 84.04-1057.10 mg/g; P = 0.028; percent change, 44.52% [IQR, 31.79-65.42%]). The average eGFR at baseline was 80.16 ml/min/1.73m2, with no significant change after 1 month (80.72 ml/min/1.73m2, P = 0.594) and a slight numerical increase to 83.45 ml/min/1.73m2 (P = 0.484) after 3 months. During the 3-month follow-up, sK+ levels showed only minor fluctuations, with no significant differences compared to baseline, and remained within the normal range throughout the treatment period. No treatment discontinuation or hospitalization due to hyperkalemia was observed.

CONCLUSION

In non-diabetic CKD patients, finerenone showed good effectiveness and safety within a 3-month follow-up period. This study provides valuable real-world evidence supporting the use of finerenone in non-diabetic CKD and highlights the need for future large-scale prospective research to further validate its efficacy.

An in Vitro triple screen model for human mineralocorticoid receptor activity

The mineralocorticoid receptor (MR, NR3C2) mediates ion and water homeostasis in epithelial cells of the distal nephron and other tissues. Aldosterone, the prototypical mineralocorticoid, regulates electrolyte and fluid balance. Cortisol binds to MR with equal affinity to aldosterone, but many MR-expressing tissues inactivate cortisol to cortisone via 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2). Dysregulated MR activation contributes to direct cardiovascular tissue insults. Besides aldosterone and cortisol, a variety of MR agonists and/or HSD11B2 inhibitors are putative players in the pathophysiology of low-renin hypertension (LRH), and cardiovascular and metabolic pathology. We developed an in vitro human MR (hMR) model, to facilitate screening for MR agonists, antagonists, and HSD11B2 inhibitors. The CV1 monkey kidney cells were transduced with lentivirus to stably express hMR and an MR-responsive gaussia luciferase gene. Clonal populations of MR-expressing cells (CV1-MRluc) were further transduced to express HSD11B2 (CV1-MRluc-HSD11B2). CV1-MRluc and CV1-MRluc-HSD11B2 cells were treated with aldosterone, cortisol, 11-deoxycorticosterone (DOC), 18-hydroxycorticosterone (18OHB), 18-hydroxycortisol (18OHF), 18-oxocortisol (18oxoF), progesterone, or 17-hydroxyprogesterone (17OHP). In CV1-MRLuc cells, aldosterone and DOC displayed similar potency (EC50: 0.45 nM and 0.30 nM) and maximal response (31- and 23-fold increase from baseline) on hMR; 18oxoF and 18OHB displayed lower potency (19.6 nM and 56.0 nM, respectively) but similar maximal hMR activation (25- and 27-fold increase, respectively); cortisol and corticosterone exhibited higher maximal responses (73- and 52-fold, respectively); 18OHF showed no MR activation. Progesterone and 17OHP inhibited aldosterone-mediated MR activation. In the MRluc-HSD11B2 model, the EC50 of cortisol for MR activation increased from 20 nM (CV1-MRLuc) to ∼2000 nM, while the EC50 for aldosterone remained unchanged. The addition of 18β-glycyrrhetinic acid (18β-GA), a HSD11B2 inhibitor, restored the potency of cortisol back to ∼70 nM in CV1-hMRLuc-HSD11B2 cells. Together, these two cell models will facilitate the discovery of novel MR-modulators, informing MR-mediated pathophysiology mechanisms and drug development efforts.

Alport Syndrome

Alport syndrome (AS) is characterized by progressive kidney failure, hematuria, sensorineural hearing loss, and ocular abnormalities. Pathogenic variants in the COL4A3-5 genes result in a defective deposition of the collagen IV α3α4α5 protomers in the basement membranes of the glomerulus in the kidney, the cochlea in the ear and the cornea, lens capsule and retina in the eye. The presence of a large variety of COL4A3-5 gene(s) pathogenetic variants irrespective of the mode of inheritance (X-linked, autosomal recessive, autosomal dominant, or digenic) with and without syndromic features is better defined as the "Alport spectrum disorder", and represents the most common cause of genetic kidney disease and the second most common cause of genetic kidney failure. The clinical course and prognosis of individuals with AS is highly variable. It is influenced by gender, mode of inheritance, affected gene(s), type of genetic mutation, and genetic modifiers. This review article will discuss the epidemiology, classification, pathogenesis, diagnosis, clinical course with genotype-phenotype correlations, and current and upcoming treatment of patients with AS. It will also review current recommendations with respect to when to evaluate for hearing loss or ophthalmologic abnormalities.

Mineralocorticoid receptor promotes cardiac macrophage inflammaging

Inflammaging, a pro-inflammatory status that characterizes aging and primarily involving macrophages, is a master driver of age-related diseases. Mineralocorticoid receptor (MR) activation in macrophages critically regulates inflammatory and fibrotic processes. However, macrophage-specific mechanisms and the role of the macrophage MR for the regulation of inflammation and fibrotic remodeling in the aging heart have not yet been elucidated. Transcriptome profiling of cardiac macrophages from male/female young (4 months-old), middle (12 months-old) and old (18 and 24 months-old) mice revealed that myeloid cell-restricted MR deficiency prevents macrophage differentiation toward a pro-inflammatory phenotype. Pathway enrichment analysis showed that several biological processes related to inflammation and cell metabolism were modulated by the MR in aged macrophages. Further, transcriptome analysis of aged cardiac fibroblasts revealed that macrophage MR deficiency reduced the activation of pathways related to inflammation and upregulation of ZBTB16, a transcription factor involved in fibrosis. Phenotypic characterization of macrophages showed a progressive replacement of the TIMD4+MHC-IIneg/low macrophage population by TIMD4+MHC-IIint/high and TIMD4-MHC-IIint/high macrophages in the aging heart. By integrating cell sorting and transwell experiments with TIMD4+/TIMD4-macrophages and fibroblasts from old MRflox/MRLysMCre hearts, we showed that the inflammatory crosstalk between TIMD4- macrophages and fibroblasts may imply the macrophage MR and the release of mitochondrial superoxide anions. Macrophage MR deficiency reduced the expansion of the TIMD4- macrophage population and the emergence of fibrotic niches in the aging heart, thereby protecting against cardiac inflammation, fibrosis, and dysfunction. This study highlights the MR as an important mediator of cardiac macrophage inflammaging and age-related fibrotic remodeling.

Finerenone cardiovascular and kidney outcomes by age and sex: FIDELITY post hoc analysis of two phase 3, multicentre, double-blind trials

OBJECTIVES

This study aimed to evaluate the efficacy and safety of finerenone, a selective, non-steroidal mineralocorticoid receptor antagonist, on cardiovascular and kidney outcomes by age and/or sex.

DESIGN

FIDELITY post hoc analysis; median follow-up of 3 years.

SETTING

FIDELITY: a prespecified analysis of the FIDELIO-DKD and FIGARO-DKD trials.

PARTICIPANTS

Adults with type 2 diabetes and chronic kidney disease receiving optimised renin-angiotensin system inhibitors (N=13 026).

INTERVENTIONS

Randomised 1:1; finerenone or placebo.

PRIMARY AND SECONDARY OUTCOME MEASURES

Cardiovascular (cardiovascular death, non-fatal myocardial infarction, non-fatal stroke or hospitalisation for heart failure (HHF)) and kidney (kidney failure, sustained ≥57% estimated glomerular filtration rate (eGFR) decline or renal death) composite outcomes.

RESULTS

Mean age was 64.8 years; 45.2%, 40.1% and 14.7% were aged <65, 65-74 and ≥75 years, respectively; 69.8% were male. Cardiovascular benefits of finerenone versus placebo were consistent across age (HR 0.94 (95% CI 0.81 to 1.10) (<65 years), HR 0.84 (95% CI 0.73 to 0.98) (65-74 years), HR 0.80 (95% CI 0.65 to 0.99) (≥75 years); Pinteraction=0.42) and sex categories (HR 0.86 (95% CI 0.77 to 0.96) (male), HR 0.89 (95% CI 0.35 to 2.27) (premenopausal female), HR 0.87 (95% CI 0.73 to 1.05) (postmenopausal female); Pinteraction=0.99). Effects on HHF reduction were not modified by age (Pinteraction=0.70) but appeared more pronounced in males (Pinteraction=0.02). Kidney events were reduced with finerenone versus placebo in age groups <65 and 65-74 but not ≥75; no heterogeneity in treatment effect was observed (Pinteraction=0.51). In sex subgroups, finerenone consistently reduced kidney events (Pinteraction=0.85). Finerenone reduced albuminuria and eGFR decline regardless of age and sex. Hyperkalaemia increased with finerenone, but discontinuation rates were <3% across subgroups. Gynaecomastia in males was uncommon across age subgroups and identical between treatment groups.

CONCLUSIONS

Finerenone improved cardiovascular and kidney composite outcomes with no significant heterogeneity between age and sex subgroups; however, the effect on HHF appeared more pronounced in males. Finerenone demonstrated a similar safety profile across age and sex subgroups.

TRIAL REGISTRATION NUMBERS

NCT02540993, NCT02545049.

Macrophages polarization in renal inflammation and fibrosis animal models (Review)

Chronic kidney disease (CKD) is a significant public health concern. Renal fibrosis is the final common pathway in the progression of kidney diseases, irrespective of the initial injury. Substantial evidence underscores the pivotal role of renal inflammation in the genesis of renal fibrosis. The presence of macrophages within normal renal tissue is significantly increased within diseased renal tissue, indicative of their crucial regulatory function in inflammation and fibrosis. Macrophages manifest a high degree of heterogeneity, exhibiting distinct phenotypic and functional traits in response to diverse stimuli within the local microenvironment in various types of kidney diseases. Broadly, macrophages are categorized into two principal groups: Classically activated, designated as M1 macrophages and alternatively activated, designated as M2 macrophages. A number of experimental models are widely used to study the underlying mechanisms driving renal inflammation and fibrosis progression. The present review delineated the phenotypic and functional attributes of macrophages present in diverse induced models, analyzing their disposition in relation to M1 and M2 polarization states.

Biomarkers to Guide Medical Therapy in Primary Aldosteronism

Primary aldosteronism (PA) is an endocrinopathy characterized by dysregulated aldosterone production that occurs despite suppression of renin and angiotensin II, and that is non-suppressible by volume and sodium loading. The effectiveness of surgical adrenalectomy for patients with lateralizing PA is characterized by the attenuation of excess aldosterone production leading to blood pressure reduction, correction of hypokalemia, and increases in renin-biomarkers that collectively indicate a reversal of PA pathophysiology and restoration of normal physiology. Even though the vast majority of patients with PA will ultimately be treated medically rather than surgically, there is a lack of guidance on how to optimize medical therapy and on key metrics of success. Herein, we review the evidence justifying approaches to medical management of PA and biomarkers that reflect endocrine principles of restoring normal physiology. We review the current arsenal of medical therapies, including dietary sodium restriction, steroidal and nonsteroidal mineralocorticoid receptor antagonists, epithelial sodium channel inhibitors, and aldosterone synthase inhibitors. It is crucial that clinicians recognize that multimodal medical treatment for PA can be highly effective at reducing the risk for adverse cardiovascular and kidney outcomes when titrated with intention. The key biomarkers reflective of optimized medical therapy are unsurprisingly similar to the physiologic expectations following surgical adrenalectomy: control of blood pressure with the fewest number of antihypertensive agents, normalization of serum potassium without supplementation, and a rise in renin. Pragmatic approaches to achieve these objectives while mitigating adverse effects are reviewed.

[The role of mineralocorticoid receptors hyperactivation in the development of cardiorenal complications in patients with diabetes mellitus, perspective of the selective nonsteroidal mineralocorticoid receptors antagonist's treatment: A review]

The renin-angiotensin-aldosterone system (RAAS) activation plays a key role in the chronic kidney disease (CKD) progression and in the cardiovascular complications (CVC) development in patients with diabetes mellitus (DM). RAAS blockers alone are not sufficient to prevent CVC and CVC progression. RAAS upregulation in CKD associated with DM triggers the mineralocorticoid receptors (MCR) hyperactivation which results in fibrosis and inflammation in the heart and kidneys. This review presents the current data about the variety of MCR hyperactivation manifestations, as well as about of multiplicity of MCR hyperactivation ways in DM. The efficacy and safety of finerenone, a new MCR nonsteroidal selective antagonist, are discussed.

Diabetic Nephropathy: Update on Pillars of Therapy Slowing Progression

Management of diabetic kidney disease (DKD) has evolved in parallel with our growing understanding of the multiple interrelated pathophysiological mechanisms that involve hemodynamic, metabolic, and inflammatory pathways. These pathways and others play a vital role in the initiation and progression of DKD. Since its initial discovery, the blockade of the renin-angiotensin system has remained a cornerstone of DKD management, leaving a large component of residual risk to be dealt with. The advent of sodium-glucose cotransporter 2 inhibitors followed by nonsteroidal mineralocorticoid receptor antagonists and, to some extent, glucagon-like peptide 1 receptor agonists (GLP-1 RAs) has ushered in a resounding paradigm shift that supports a pillared approach in maximizing treatment to reduce outcomes. This pillared approach is like that derived from the approach to heart failure treatment. The approach mandates that all agents that have been shown in clinical trials to reduce cardiovascular outcomes and/or mortality to a greater extent than a single drug class alone should be used in combination. In this way, each drug class focuses on a specific aspect of the disease's pathophysiology. Thus, in heart failure, β-blockers, sacubitril/valsartan, a mineralocorticoid receptor antagonist, and a diuretic are used together. In this article, we review the evolution of the pillar concept of therapy as it applies to DKD and discuss how it should be used based on the outcome evidence. We also discuss the exciting possibility that GLP-1 RAs may be an additional pillar in the quest to further slow kidney disease progression in diabetes.

Diabetic Kidney Disease: An Update

Diabetes is a major public health challenge and diabetic kidney disease (DKD), a broader diagnostic term than diabetic nephropathy, is the leading cause of chronic kidney disease and end-stage kidney disease in the United States and worldwide. A better understanding of the underlying pathophysiological mechanisms of DKD, and recent clinical trials testing new therapeutic interventions, have shown promising results to curb this epidemic. Given the global health burden of DKD, it is extremely important to prioritize prevention, early recognition, referral, and aggressive management of DKD in the primary care setting.

Finerenone: Questions and Answers-The Four Fundamental Arguments on the New-Born Promising Non-Steroidal Mineralocorticoid Receptor Antagonist

Chronic kidney disease (CKD) is one of the most common complications of diabetes mellitus and an independent risk factor for cardiovascular disease. Despite guideline-directed therapy of CKD in patients with type 2 diabetes, the risk of renal failure and cardiovascular events still remains high, and diabetes remains the leading cause of end-stage kidney disease in affected patients. To date, current medications for CKD and type 2 diabetes mellitus have not reset residual risk in patients due to a high grade of inflammation and fibrosis contributing to kidney and heart disease. This question-and-answer-based review will discuss the pharmacological and clinical differences between finerenone and other mineralocorticoid receptor antagonists and then move on to the main evidence in the cardiovascular and renal fields, closing, finally, on the potential role of therapeutic combination with sodium-glucose cotransporter 2 inhibitors (SGLT2is).

Mineralocorticoid Receptor Antagonists for Preventing Chronic Kidney Disease Progression: Current Evidence and Future Challenges

Regulation and action of the mineralocorticoid receptor (MR) have been the focus of intensive research over the past 80 years. Genetic and physiological/biochemical analysis revealed how MR and the steroid hormone aldosterone integrate the responses of distinct tubular cells in the face of environmental perturbations and how their dysregulation compromises fluid homeostasis. In addition to these roles, the accumulation of data also provided unequivocal evidence that MR is involved in the pathophysiology of kidney diseases. Experimental studies delineated the diverse pathological consequences of MR overactivity and uncovered the multiple mechanisms that result in enhanced MR signaling. In parallel, clinical studies consistently demonstrated that MR blockade reduces albuminuria in patients with chronic kidney disease. Moreover, recent large-scale clinical studies using finerenone have provided evidence that the non-steroidal MR antagonist can retard the kidney disease progression in diabetic patients. In this article, we review experimental data demonstrating the critical importance of MR in mediating renal injury as well as clinical studies providing evidence on the renoprotective effects of MR blockade. We also discuss areas of future investigation, which include the benefit of non-steroidal MR antagonists in non-diabetic kidney disease patients, the identification of surrogate markers for MR signaling in the kidney, and the search for key downstream mediators whereby MR blockade confers renoprotection. Insights into these questions would help maximize the benefit of MR blockade in subjects with kidney diseases.

From Ligands to Behavioral Outcomes: Understanding the Role of Mineralocorticoid Receptors in Brain Function

Stress is a normal response to situational pressures or demands. Exposure to stress activates the hypothalamic-pituitary-adrenal (HPA) axis and leads to the release of corticosteroids, which act in the brain via two distinct receptors: mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Persistent HPA axis overactivation or dysregulation can disrupt an individual's homeostasis, thereby contributing to an increased risk for mental illness. On the other hand, successful coping with stressful events involves adaptive and cognitive processes in the brain that render individuals more resilient to similar stressors in the future. Here we review the role of the MR in these processes, starting with an overview of the physiological structure, ligand binding, and expression of MR, and further summarizing its role in the brain, its relevance to psychiatric disorders, and related rodent studies. Given the central role of MR in cognitive and emotional functioning, and its importance as a target for promoting resilience, future research should investigate how MR modulation can be used to alleviate disturbances in emotion and behavior, as well as cognitive impairment, in patients with stress-related psychiatric disorders.

Chronic kidney disease in patients with type 2 diabetes: new targets of medicine action

Diabetes mellitus type 2 (DM2) is socially important disease, becoming non-infectious epidemic due to increasing prevalence. Chronic kidney disease (CKD) is one of the most common diabetic complications. Kidney injury signs and/or estimated glomerular filtration rate (eGFR) decrease are seen in 40-50% of patients with DM2. Three groups of factors are considered to be the basis of CKD development and progression in DM2: metabolic, hemodynamic, inflammation and fibrosis. Existing drugs that are used in patients with CKD and DM2 first of all target hemodynamic and metabolic disturbances, but their action against inflammation and fibrosis is indirect. Hyperactivation of mineralocorticoid receptors (MR) is considered as one of the main trigger factors of end-organ damage in patients with DM2 due to inflammation and fibrosis. Development of selective nonsteroidal MR antagonists (MRA) as a new class of medications is directed to demonstrate positive effects from blocking this pathophysiological pathway of CKD development and overcome the steroidal MRAs’ shortcomings. Hence pathophysiological hyperactivation of MR with subsequent inflammation and fibrosis in patients with CKD in DM2 is considered a promising therapeutic target for the new drugs with cardionephroprotective effect.

Impaired negative feedback and death following acute stress in glucocorticoid receptor knockout Xenopus tropicalis tadpoles

Blood glucocorticoid levels are regulated by the hypothalamo-pituitary-adrenal/interrenal axis (HPA axis in mammals, HPI axis in amphibians), and negative feedback by glucocorticoid signaling is a key player in that regulation. Glucocorticoid and mineralocorticoid receptors (GR and MR) mediate negative feedback in mammals, but little is known about nuclear receptor-mediated feedback in amphibians. Because amphibians have only one corticosteroidogenic cell type responsible for glucocorticoid and mineralocorticoid production, we hypothesized that GR knockout (GRKO) tadpoles have elevated levels of glucocorticoids and mineralocorticoids as well as axis components regulating their production. We also examined the response to stress and potential for increased aldosterone signaling in GRKO tadpoles. We found that GRKO tadpoles have severe hyperactivity of the HPI axis, namely high mRNA expression levels of pomc, cyp17a1, cyp21a2, cyp11b2, and star, and high tissue content of corticosterone, aldosterone, 17-hydroxyprogesterone, 21-deoxycortisol, and progesterone. Such aberrant HPI activity was accompanied by reduced survival after acute temperature shock and shaking stress. Like mammalian models of HPA hyperactivity, GRKO tadpoles have high MR mRNA expression levels in brain, kidney, heart, and skin and high levels of the inflammatory cytokine tnf-α and the profibrotic factor tgf-β in kidneys. This study showed GR is critical for negative feedback to the amphibian HPI axis and for survival from acute stressors. This study also showed GRKO tadpoles exhibit altered expression/overproduction of regulators of salt-water homeostasis and associated biomarkers of kidney disease.

The innate immune response, microenvironment proteinases, and the COVID-19 pandemic: pathophysiologic mechanisms and emerging therapeutic targets

The coronavirus disease 2019 (COVID-19) pandemic, causing considerable mortality and morbidity worldwide, has fully engaged the biomedical community in attempts to elucidate the pathophysiology of COVID-19 and develop robust therapeutic strategies. To this end, the predominant research focus has been on the adaptive immune response to COVID-19 infections stimulated by mRNA and protein vaccines and on the duration and persistence of immune protection. In contrast, the role of the innate immune response to the viral challenge has been underrepresented. This overview focuses on the innate immune response to COVID-19 infection, with an emphasis on the roles of extracellular proteases in the tissue microenvironment. Proteinase-mediated signaling caused by enzymes in the extracellular microenvironment occurs upstream of the increased production of inflammatory cytokines that mediate COVID-19 pathology. These enzymes include the coagulation cascade, kinin-generating plasma kallikrein, and the complement system, as well as angiotensin-generating proteinases of the renin–angiotensin system. Furthermore, in the context of several articles in this Supplement elucidating and detailing the trajectory of diverse profibrotic pathways, we extrapolate these insights to explore how fibrosis and profibrotic pathways participate importantly in the pathogenesis of COVID-19. We propose that the lessons garnered from understanding the roles of microenvironment proteinases in triggering the innate immune response to COVID-19 pathology will identify potential therapeutic targets and inform approaches to the clinical management of COVID-19. Furthermore, the information may also provide a template for understanding the determinants of COVID-19–induced tissue fibrosis that may follow resolution of acute infection (so-called “long COVID”), which represents a major new challenge to our healthcare systems.