Finerenone Reduces Renal RORγt γδ T Cells and Protects against Cardiorenal Damage.

INTRODUCTION: Chronic activation of the mineralocorticoid receptor (MR) leads to pathological processes like inflammation and fibrosis during cardiorenal disease. Modulation of immunological processes in the heart or kidney may serve as a mechanistic and therapeutic interface in cardiorenal pathologies. In this study, we investigated anti-inflammatory/-fibrotic and immunological effects of the selective nonsteroidal MR antagonists finerenone (FIN) in the deoxycorticosterone acetate (DOCA)-salt model. METHODS: Male C57BL6/J mice were uninephrectomized and received a DOCA pellet implantation (2.4 mg/day) plus 0.9% NaCl in drinking water (DOCA-salt) or received a sham operation and were orally treated with FIN (10 mg/kg/day) or vehicle in a preventive study design. Five weeks after the procedure, blood pressure (BP), urinary albumin/creatinine ratio (UACR), glomerular and tubulointerstitial damage, echocardiographic cardiac function, as well as cardiac/renal inflammatory cell content by FACS analysis were assessed. RESULTS: BP was significantly reduced by FIN. FACS analysis revealed a notable immune response due to DOCA-salt exposure. Especially, infiltrating renal RORγt γδ-positive T cells were upregulated, which was significantly ameliorated by FIN treatment. This was accompanied by a significant reduction of UACR in FIN-treated mice. In the heart, FIN reduced DOCA-salt-induced cardiac hypertrophy, cardiac fibrosis and led to an improvement of the global longitudinal strain. Cardiac actions of FIN were not associated with a regulation of cardiac RORγt γδ-positive T cells. DISCUSSION/CONCLUSION: The present study shows cardiac and renal protective effects of FIN in a DOCA-salt model. The cardiorenal protection was accompanied by a reduction of renal RORγt γδ T cells. The observed actions of FIN may provide a potential mechanism of its efficacy recently observed in clinical trials.

Immune mechanisms in arterial hypertension. Recent advances.

Increasing evidence indicates that hypertension and hypertensive end-organ damage are not only mediated by hemodynamic injury. Inflammation also plays an important role in the pathophysiology and contributes to the deleterious consequences of this disease. Cells of the innate immune system including monocyte/macrophages and dendritic cells can promote blood pressure elevation via effects mostly on kidney and vascular function. Moreover, convincing evidence shows that T and B cells from the adaptive immune system are involved in hypertension and hypertensive end-organ damage. Skin monocyte/macrophages, regulatory T cells, natural killer T cells, and myeloid-derived suppressor cells have been shown to exert blood pressure controlling effects. Sodium intake is undoubtedly indispensable for normal body function but can be detrimental when taken in excess of dietary requirements. Sodium levels also modulate the function of monocyte/macrophages, dendritic cells, and different T cell subsets. Some of these effects are mediated by changes in the microbiome and metabolome that can be found after high salt intake. Modulation of the immune response can reduce severity of blood pressure elevation and hypertensive end-organ damage in several animal models. The purpose of this review is to briefly summarize recent advances in immunity and hypertension as well as hypertensive end-organ damage.

A pathogenic role of complement in arterial hypertension and hypertensive end organ damage.

The self-amplifying cascade of messenger and effector molecules of the complement system serves as a powerful danger-sensing system that protects the host from a hostile microbial environment, while maintaining proper tissue and organ function through effective clearance of altered or dying cells. As an important effector arm of innate immunity, it also plays important roles in the regulation of adaptive immunity. Innate and adaptive immune responses have been identified as crucial players in the pathogenesis of arterial hypertension and hypertensive end organ damage. In line with this view, complement activation may drive the pathology of hypertension and hypertensive injury through its impact on innate and adaptive immune responses. It is well known that complement activation can cause tissue inflammation and injury and complement-inhibitory drugs are effective treatments for several inflammatory diseases. In addition to these proinflammatory properties, complement cleavage fragments of C3 and C5 can exert anti-inflammatory effects that dampen the inflammatory response to injury. Recent experimental data strongly support a role for complement in arterial hypertension. The remarkably similar clinical and histopathological features of malignant nephrosclerosis and atypical hemolytic uremic syndrome, which is driven by complement activation, suggest a role for complement also in the development of malignant nephrosclerosis. Herein, we will review canonical and noncanonical pathways of complement activation as the framework to understand the multiple roles of complement in arterial hypertension and hypertensive end organ damage.

Role of the anaphylatoxin receptor C5aR2 in angiotensin II induced hypertension and hypertensive end organ damage.

BACKROUND: Complement activation may facilitate hypertension through its effects on immune responses. The anaphylatoxin C5a, a major inflammatory effector, binds to the C5a receptor 1 and 2 (C5aR1, C5aR2). We have recently shown that C5aR1-/- mice have reduced hypertensive renal injury. The role of C5aR2 in hypertension is unknown. METHODS: For examination of C5aR2 expression on infiltrating and resident renal cells a tandem dye Tomato-C5aR2 knock-in reporter mouse was used. Human C5aR2 expression was analyzed in a single cell RNAseq data set from kidneys of hypertensive patients. Finally, we examined the effect of Ang II induced hypertension in C5aR2-deficient mice. RESULTS: Flow cytometric analysis of leukocytes isolated from kidneys of the reporter mice showed that dendritic cells are the major C5aR2-expressing population (34%) followed by monocyte/macrophages (30%) and neutrophils (14%). Using confocal microscopy C5aR2 was not detected in resident renal or cardiac cells. In the human kidney C5aR2 was also mainly found in monocytes, macrophages and dendritic cells with a significantly higher expression in hypertension (p<0,05). Unilateral nephrectomy was performed followed by infusion of Ang II (0.75 ng/g/min) and a high salt diet in wildtype (n=18) and C5aR2-deficient mice (n=14). Blood pressure, renal injury (albuminuria, glomerular filtration rate, glomerular and tubulointerstitial injury, inflammation) and cardiac injury (cardiac fibrosis, heart weight, gene expression) did not differ between hypertensive wildtype and C5aR2-/- mice. CONCLUSION: In summary, C5aR2 is mainly expressed on myeloid cells in the kidney in mice and humans but its deficiency has no effect in Ang II induced hypertensive injury.

Deficiency of Complement C3a and C5a receptors Does Not Prevent Angiotensin II-Induced Hypertension and Hypertensive End-Organ Damage.

BACKGROUND: Complement may drive the pathology of hypertension through effects on innate and adaptive immune responses. Recently an injurious role for the anaphylatoxin receptors C3aR (complement component 3a receptor) and C5aR1 (complement component 5a receptor) in the development of hypertension was shown through downregulation of Foxp3+ (forkhead box protein 3) regulatory T cells. Here, we deepen our understanding of the therapeutic potential of targeting both receptors in hypertension. METHODS: Data from the European Renal cDNA Bank, single cell sequencing and immunohistochemistry were examined in hypertensive patients. The effect of C3aR or C3aR/C5aR1 double deficiency was assessed in two models of Ang II (angiotensin II)-induced hypertension in knockout mice. RESULTS: We found increased expression of C3aR, C5aR1 and Foxp3 cells in kidney biopsies of patients with hypertensive nephropathy. Expression of both receptors was mainly found in myeloid cells. No differences in blood pressure, renal injury (albuminuria, glomerular filtration rate, glomerular and tubulointerstitial injury, inflammation) or cardiac injury (cardiac fibrosis, heart weight, gene expression) between control and mutant mice was discerned in C3aR-/- as well as C3aR/C5aR1-/- double knockout mice. The number of renal Tregs was not decreased in Ang II as well as in DOCA salt induced hypertension. CONCLUSIONS: Hypertensive nephropathy in mice and men is characterized by an increase of renal regulatory T cells and enhanced expression of anaphylatoxin receptors. Our investigations do not corroborate a role for C3aR/C5aR1 axis in Ang II-induced hypertension hence challenging the concept of anaphylatoxin receptor targeting in the treatment of hypertensive disease.

Complement component C3 as a new target to lower albuminuria in hypertensive kidney disease.

BACKGROUND AND PURPOSE: Complement activation may drive hypertension through its effects on immunity and tissue integrity. EXPERIMENTAL APPROACH: We examined expression of C3, the central protein of the complement cascade, in hypertension. KEY RESULTS: Increased C3 expression was found in kidney biopsies and micro-dissected glomeruli of patients with hypertensive nephropathy. Renal single cell RNA sequence data from normotensive and hypertensive patients confirmed expression of C3 in different cellular compartments of the kidney. In angiotensin II (Ang II) induced hypertension renal C3 expression was up-regulated. C3-/- mice revealed a significant lower albuminuria in the early phase of hypertension. However, no difference was found for blood pressure, renal injury (histology, glomerular filtration rate, inflammation) and cardiac injury (fibrosis, weight, gene expression) between C3-/- and wildtype mice after Ang II infusion. Also, in deoxycorticosterone acetate (DOCA) salt hypertension, a significantly lower albuminuria was found in the first weeks of hypertension in C3 deficient mice but no significant difference in renal and cardiac injury. Down-regulation of C3 by C3 targeting GalNAc (n-acetylgalactosamine) small interfering RNA (siRNA) conjugate decreased C3 in the liver by 96% and lowered albuminuria in the early phase but showed no effect on blood pressure and end-organ damage. Inhibition of complement C5 by siRNA showed no effect on albuminuria. CONCLUSION AND IMPLICATIONS: Increased C3 expression is found in the kidneys of hypertensive mice and men. Genetic and therapeutic knockdown of C3 improved albuminuria in the early phase of hypertension but did not ameliorate arterial blood pressure nor renal and cardiac injury.

The role of the mineralocorticoid receptor in immune cells in cardiovascular disease.

Chronic low-grade inflammation and immune cell activation are important mechanisms in the pathophysiology of cardiovascular disease (CVD). Therefore, targeted immunosuppression is a promising novel therapy to reduce cardiovascular risk. In this review, we identify the mineralocorticoid receptor (MR) on immune cells as a potential target to modulate inflammation. The MR is present in almost all cells of the cardiovascular system, including immune cells. Activation of the MRs in innate and adaptive immune cells induces inflammation which can contribute to CVD, by inducing endothelial dysfunction and hypertension. Moreover, it accelerates atherosclerotic plaque formation and destabilization and impairs tissue regeneration after ischaemic events. Identifying the molecular targets for these non-renal actions of the MR provides promising novel cardiovascular drug targets for mineralocorticoid receptor antagonists (MRAs), which are currently mainly applied in hypertension and heart failure. LINKED ARTICLES: This article is part of a themed issue on Emerging Fields for Therapeutic Targeting of the Aldosterone-Mineralocorticoid Receptor Signaling Pathway. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.13/issuetoc.

The role of complement in arterial hypertension and hypertensive end organ damage.

Increasing evidence indicates that hypertension and hypertensive end organ damage are not only mediated by haemodynamic injury but that inflammation also plays an important role. The complement system protects the host from a hostile microbial environment and maintains tissue and cell integrity through the elimination of altered or dead cells. As an important effector arm of innate immunity, it plays also central roles in the regulation of adaptive immunity. Thus, complement activation may drive the pathology of hypertension through its effects on innate and adaptive immune responses, aside from direct effects on the vasculature. Recent experimental data strongly support a role for complement in all stages of arterial hypertension. The remarkably similar clinical and histopathological features of malignant nephrosclerosis and atypical haemolytic uraemic syndrome suggest also a role for complement in the development of malignant nephrosclerosis. Here, we review the role of complement in hypertension and hypertensive end organ damage. LINKED ARTICLES: This article is part of a themed issue on Canonical and non-canonical functions of the complement system in health and disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.14/issuetoc.

B6.Rag1 Knockout Mice Generated at the Jackson Laboratory in 2009 Show a Robust Wild-Type Hypertensive Phenotype in Response to Ang II (Angiotensin II).

A key finding supporting a causal role of the immune system in the pathogenesis of hypertension is the observation that RAG1 knockout mice on a C57Bl/6J background (B6.Rag1-/-), which lack functional B and T cells, develop a much milder hypertensive response to Ang II (angiotensin II) than control C57Bl/6J mice. Here, we report that we never observed any Ang II resistance of B6.Rag1-/- mice purchased directly from the Jackson Laboratory as early as 2009. B6.Rag1-/- mice displayed nearly identical blood pressure increases monitored via radiotelemetry and hypertensive end-organ damage in response to different doses of Ang II and different levels of salt intake (0.02%, 0.3%, and 3% NaCl diet). Similarly, restoration of T-cell immunity by adoptive cell transfer did not affect the blood pressure response to Ang II in B6.Rag1-/- mice. Full development of the hypertension-resistant phenotype in B6.Rag1-/- mice appears to depend on the action of yet unidentified nongenetic modifiers in addition to the absence of functional T cells.

Salt, inflammation, IL-17 and hypertension.

Traditionally, arterial hypertension and subsequent end-organ damage have been attributed to haemodynamic factors, but increasing evidence indicates that inflammation also contributes to the deleterious consequences of this disease. The immune system has evolved to prevent invasion of foreign microorganisms and to promote tissue healing after injury. However, this beneficial activity comes at a cost of collateral damage when the immune system overreacts to internal injury, such as prehypertension. Over the past few years, important findings have revolutionized hypertension research. Firstly, in 2007, a seminal paper showed that adaptive immunity is involved in the pathogenesis of hypertension. Secondly, salt storage in the skin and its consequences for cardiovascular physiology were discovered. Thirdly, after the discovery that salt promotes the differentiation of CD4+ T cells into TH 17 cells, it was demonstrated that salt directly changes several cells of the innate and adaptive immune system and aggravates autoimmune disease but may improve antimicrobial defence. Herein, we will review pathways of activation of immune cells by salt in hypertension as the framework for understanding the multiple roles of salt and immunity in arterial hypertension and autoimmune disease. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Adaptive immunity and IL-17A are not involved in the progression of chronic kidney disease after 5/6 nephrectomy in mice.

BACKGROUND AND PURPOSE: The adaptive immune response and IL-17A contribute to renal damage in several experimental models of renal injury. EXPERIMENTAL APPROACH: To evaluate the role of the adaptive immune response, 5/6 nephrectomy was performed in wildtype DBA/1J mice and in recombination-activating gene-1 (RAG-1) deficient mice that lack B and T-cells. To assess the role of IL-17A, we carried out 5/6 nephrectomy in IL-17A deficient mice. Flow cytometric analysis, immunohistochemistry and RT-PCR were used. KEY RESULTS: Infiltration of CD3+ T-cells in the remnant kidney was increased after 5/6 nephrectomy in wildtype mice, along with a robust induction of IL-17A production in CD4+ T and γδ T-cells. After 5/6 nephrectomy, wildtype mice developed albuminuria in the nephrotic range over 10 weeks. This was accompanied by severe glomerular sclerosis and tubulointerstitial injury, and as well as renal mRNA expression of markers of inflammation and fibrosis (the chemokine CCL2, plasminogen activator inhibitor-1; PAI-1 and neutrophil gelatinase-associated lipocalin; NGAL). Unexpectedly, RAG-1 deficient mice and IL-17A deficient mice developed renal injury, similar to that in wildtype mice. No differences were found for albuminuria, glomerular sclerosis, tubulointerstitial injury and mRNA expression of CCL2, PAI-1 and NGAL. Mortality did not differ between the three groups. CONCLUSIONS AND IMPLICATIONS: Numbers of CD3+ T-cells and IL-17A+ lymphocytes infiltrating the kidney were increased after 5/6 nephrectomy. In contrast to other experimental models of renal injury, genetic deficiency of the adaptive immune system or of IL-17A did not attenuate induction or progression of chronic kidney disease after 5/6 nephrectomy. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.