Synergistic effect of adrenal steroids and angiotensin II on plasminogen activator inhibitor-1 production

Chronic unpredictable mild stress increases serum aldosterone without affecting corticosterone levels and induces hepatic steatosis and renal injury in young adult male rats

Stress is often associated with anxiety and depressive symptoms in adolescents. Stress is associated with components of metabolic syndrome and inflammation. The present study hypothesizes that aldosterone, more than corticosterone, promotes chronic stress-hepatic steatosis and fibrosis, as well as renal inflammation and fibrosis in young adult rats. Thirty-two young adult male Wistar rats of 51 days old were divided into four groups (n = 8 per group): Control (C), chronic unpredictable mild stress (CUMS), control plus vehicle (C plus veh), CUMS plus eplerenone, a selective aldosterone blocker (CUMS plus EP). On postnatal day 51, eplerenone was administered orally through a gastric tube two hours before the start of the stress test. The CUMS paradigm was administered once daily at different times, with no repetition of the stressor sequence for four weeks. Renal inflammation and fibrosis were measured, as well as liver glycogen, triacylglycerol, and fibrosis levels. The serum concentrations of corticosterone, aldosterone, sodium, and creatinine were measured in urine and serum. The CUMS group showed a high level of serum aldosterone without affecting the level of corticosterone, increased urinary sodium, tubular atrophy, glomerular sclerosis, the presence of inflammation, and fibrosis, without affecting creatinine, increased glycogen content, triacylglycerol, and moderate fibrosis in the liver, and treatment with eplerenone prevented the inflammation, fibrosis, glycogen, and triacylglycerol. Our results show that chronic stress-induced aldosterone promotes hepatic steatosis and renal injury more than corticosterone. The prevention by eplerenone supports our hypothesis.

Mineralocorticoid Receptors in Vascular Smooth Muscle: Blood Pressure and Beyond

After half a century of evidence suggesting the existence of mineralocorticoid receptors (MR) in the vasculature, the advent of technology to specifically knockout the MR from smooth muscle cells (SMCs) in mice has elucidated contributions of SMC-MR to cardiovascular function and disease, independent of the kidney. This review summarizes the latest understanding of the molecular mechanisms by which SMC-MR contributes to (1) regulation of vasomotor function and blood pressure to contribute to systemic and pulmonary hypertension; (2) vascular remodeling in response to hypertension, vascular injury, obesity, and aging, and the impact on vascular calcification; and (3) cardiovascular pathologies including aortic aneurysm, heart valve dysfunction, and heart failure. Data are reviewed from in vitro studies using SMCs and in vivo findings from SMC-specific MR-knockout mice that implicate target genes and signaling pathways downstream of SMC-MR. By regulating expression of the L-type calcium channel subunit Cav1.2 and angiotensin II type-1 receptor, SMC-MR contributes to myogenic tone and vasoconstriction, thereby contributing to systemic blood pressure. MR activation also promotes SMC proliferation, migration, production and degradation of extracellular matrix, and osteogenic differentiation by regulating target genes including connective tissue growth factor, osteopontin, bone morphogenetic protein 2, galectin-3, and matrix metallopeptidase-2. By these mechanisms, SMC-MR promotes disease progression in models of aging-associated vascular stiffness, vascular calcification, mitral and aortic valve disease, pulmonary hypertension, and heart failure. While rarely tested, when sexes were compared, the mechanisms of SMC-MR-mediated disease were sexually dimorphic. These advances support targeting SMC-MR-mediated mechanisms to prevent and treat diverse cardiovascular disorders.

Angiotensin II and post-streptococcal glomerulonephritis

BACKGROUND

Post-streptococcal glomerulonephritis (PSGN) is a consequence of the infection by group A beta-hemolytic streptococcus. During this infection, various immunological processes generated by streptococcal antigens are triggered, such as the induction of antibodies and immune complexes. This activation of the immune system involves both innate and acquired immunity. The immunological events that occur at the renal level lead to kidney damage with chronic renal failure as well as resolution of the pathological process (in most cases). Angiotensin II (Ang II) is a molecule with vasopressor and pro-inflammatory capacities, being an important factor in various inflammatory processes. During PSGN some events are defined that make Ang II conceivable as a molecule involved in the inflammatory processes during the disease.

CONCLUSION

This review is focused on defining which reported events would be related to the presence of this hormone in PSGN.

Direct Blood Pressure-Independent Anti-Fibrotic Effects by the Selective Nonsteroidal Mineralocorticoid Receptor Antagonist Finerenone in Progressive Models of Kidney Fibrosis

INTRODUCTION

The nonsteroidal mineralocorticoid receptor (MR) antagonist finerenone and sodium-glucose cotransporter-2 (SGLT2) inhibitors have demonstrated clinical benefits in chronic kidney disease patients with type 2 diabetes. Precise molecular mechanisms responsible for these benefits are incompletely understood. Here, we investigated potential direct anti-fibrotic effects and mechanisms of nonsteroidal MR antagonism by finerenone or SGLT2 inhibition by empagliflozin in 2 relevant mouse kidney fibrosis models: unilateral ureter obstruction and sub-chronic ischemia reperfusion injury.

METHODS

Kidney fibrosis was induced in mice via unilateral ureteral obstruction or ischemia. In a series of experiments, mice were treated orally with the MR antagonist finerenone (3 or 10 mg/kg), the SGLT2 inhibitor empagliflozin (10 or 30 mg/kg), or in a direct comparison of both drugs. Interstitial myofibroblast accumulation was quantified via alpha-smooth muscle actin and interstitial collagen deposition via Sirius Red/Fast Green staining in both models. Secondary analyses included the assessment of inflammatory cells, kidney mRNA expression of fibrotic markers as well as functional parameters (serum creatinine and albuminuria) in the ischemic model. Blood pressure was measured via telemetry in healthy conscious compound-treated animals.

RESULTS

Finerenone dose-dependently decreased pathological myofibroblast accumulation and collagen deposition with no effects on systemic blood pressure and inflammatory markers in the tested dose range. Reduced kidney fibrosis was paralleled by reduced kidney plasminogen activator inhibitor-1 (PAI-1) and naked cuticle 2 (NKD2) expression in finerenone-treated mice. In contrast, treatment with empagliflozin strongly increased urinary glucose excretion in both models and reduced ischemia-induced albuminuria but had no effects on kidney myofibroblasts or collagen deposition.

DISCUSSION/CONCLUSION

Finerenone has direct anti-fibrotic properties resulting in reduced myofibroblast and collagen deposition accompanied by a reduction in renal PAI-1 and NKD2 expression in mouse models of progressive kidney fibrosis at blood pressure-independent dosages.

Hyperinflammation and derangement of renin-angiotensin-aldosterone system in COVID-19: A novel hypothesis for clinically suspected hypercoagulopathy and microvascular immunothrombosis

Early clinical evidence suggests that severe cases of coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), are frequently characterized by hyperinflammation, imbalance of renin-angiotensin-aldosterone system, and a particular form of vasculopathy, thrombotic microangiopathy, and intravascular coagulopathy. In this paper, we present an immunothrombosis model of COVID-19. We discuss the underlying pathogenesis and the interaction between multiple systems, resulting in propagation of immunothrombosis, which through investigation in the coming weeks, may lead to both an improved understanding of COVID-19 pathophysiology and identification of innovative and efficient therapeutic targets to reverse the otherwise unfavorable clinical outcome of many of these patients.

Tβ4-Ac-SDKP pathway: Any relevance for the cardiovascular system?

The last 20 years witnessed the emergence of the thymosin β4 (Tβ4)-N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) pathway as a new source of future therapeutic tools to treat cardiovascular and renal diseases. In this review article, we attempted to shed light on the numerous experimental findings pertaining to the many promising cardiovascular therapeutic avenues for Tβ4 and (or) its N-terminal derivative, Ac-SDKP. Specifically, Ac-SDKP is endogenously produced from the 43-amino acid Tβ4 by 2 successive enzymes, meprin α and prolyl oligopeptidase. We also discussed the possible mechanisms involved in the Tβ4-Ac-SDKP-associated cardiovascular biological effects. In infarcted myocardium, Tβ4 and Ac-SDKP facilitate cardiac repair after infarction by promoting endothelial cell migration and myocyte survival. Additionally, Tβ4 and Ac-SDKP have antifibrotic and anti-inflammatory properties in the arteries, heart, lungs, and kidneys, and stimulate both in vitro and in vivo angiogenesis. The effects of Tβ4 can be mediated directly through a putative receptor (Ku80) or via its enzymatically released N-terminal derivative Ac-SDKP. Despite the localization and characterization of Ac-SDKP binding sites in myocardium, more studies are needed to fully identify and clone Ac-SDKP receptors. It remains promising that Ac-SDKP or its degradation-resistant analogs could serve as new therapeutic tools to treat cardiac, vascular, and renal injury and dysfunction to be used alone or in combination with the already established pharmacotherapy for cardiovascular diseases.

Vascular Mineralocorticoid Receptor: Evolutionary Mediator of Wound Healing Turned Harmful by Our Modern Lifestyle

The mineralocorticoid receptor (MR) is indispensable for survival through its critical role in maintaining blood pressure in response to sodium scarcity or bleeding. Activation of MR by aldosterone in the kidney controls water and electrolyte homeostasis. This review summarizes recent advances in our understanding of MR function, specifically in vascular endothelial and smooth muscle cells. The evolving roles for vascular MR are summarized in the areas of (i) vascular tone regulation, (ii) thrombosis, (iii) inflammation, and (iv) vascular remodeling/fibrosis. Synthesis of the data supports the concept that vascular MR does not contribute substantially to basal homeostasis but rather, MR is poised to be activated when the vasculature is damaged to coordinate blood pressure maintenance and wound healing. Specifically, MR activation in the vascular wall promotes vasoconstriction, inflammation, and exuberant vascular remodeling with fibrosis. A teleological model is proposed in which these functions of vascular MR may have provided a critical evolutionary survival advantage in the face of mechanical vascular injury with bleeding. However, modern lifestyle is characterized by physical inactivity and high fat/high sodium diet resulting in diffuse vascular damage. Under these modern conditions, diffuse, persistent and unregulated activation of vascular MR contributes to post-reproductive cardiovascular disease in growing populations with hypertension, obesity, and advanced age.

The Vasculature in Prediabetes

The frequency of prediabetes is increasing as the prevalence of obesity rises worldwide. In prediabetes, hyperglycemia, insulin resistance, and inflammation and metabolic derangements associated with concomitant obesity cause endothelial vasodilator and fibrinolytic dysfunction, leading to increased risk of cardiovascular and renal disease. Importantly, the microvasculature affects insulin sensitivity by affecting the delivery of insulin and glucose to skeletal muscle; thus, endothelial dysfunction and extracellular matrix remodeling promote the progression from prediabetes to diabetes mellitus. Weight loss is the mainstay of treatment in prediabetes, but therapies that improved endothelial function and vasodilation may not only prevent cardiovascular disease but also slow progression to diabetes mellitus.

Plasminogen Activator Inhibitor-1 and Pericardial Fat in Individuals with Type 2 Diabetes Mellitus

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) is implicated in the pathophysiology of cardiovascular disease (CVD) and increased in individuals with type 2 diabetes mellitus (T2DM). Adipose tissue produces PAI-1, and pericardial fat is a CVD risk factor. We sought to determine the relationship between PAI-1 and pericardial fat in males and females with well-controlled T2DM.

METHODS

The study population consisted of 32 males and 19 females, aged 35-70 years with T2DM, without clinical evidence of CVD or other active medical problems except for hypertension. Subjects were studied under good cardiometabolic control. Study procedures included fasting blood work and cardiovascular imaging. Cardiac magnetic resonance imaging of the heart was used to identify and quantify pericardial fat from the bifurcation of the pulmonary trunk to the last slice containing cardiac tissue.

RESULTS

PAI-1 was positively correlated with pericardial fat (β = 0.72, r = 0.72, P < 0.001) as well as with homeostatic model assessment of insulin resistance (r = 0.31, P = 0.03) and serum triglycerides (r = 0.27, P = 0.05). In a multivariable regression model, controlling for insulin sensitivity, triglycerides, and body mass index, pericardial fat was independently associated with PAI-1 (β = 0.80, P < 0.001).

CONCLUSIONS

PAI-1 is positively associated with pericardial fat in individuals with T2DM.

Coagulation and mental disorders

The neurovascular unit is a key player in brain development, homeostasis, and pathology. Mental stress affects coagulation, while severe mental illnesses, such as recurrent depression and schizophrenia, are associated with an increased thrombotic risk and cardiovascular morbidity. Evidence indicates that the hemostatic system is involved to some extent in the pathogenesis, morbidity, and prognosis of a wide variety of psychiatric disorders. The current review focuses on emerging data linking coagulation and some psychiatric disorders.

Peptidergic regulation of plasminogen activator inhibitor-1 gene expression in vivo

BACKGROUND

The mechanisms by which PAI-1 biosynthesis is altered during stress have not been fully elucidated. Studies suggest a major role for neuro-peptidergic modulation of the stress response by PACAP (pituitary adenylate cyclase-activating polypeptide), a member of the VIP/secretin/glucagon family.

OBJECTIVE

We tested the hypothesis that PACAP regulates PAI-1 biosynthesis during stress in vivo.

METHODS

PAI-1 gene expression was monitored by RT-PCR in adrenal glands harvested from C57BL/6J mice that were unstressed, or subjected to restraint stress for 2 h, or treated with PACAP.

RESULTS

PAI-1 mRNA expression was markedly increased in adrenals from stressed mice. Restraint stress resulted in much smaller increments in adrenal tPA mRNA, suggesting that local adrenal tPA/PAI-1 biosynthetic balance is markedly altered by stress. The observed increases in PAI-1mRNA during stress were substantially blunted (55 ± 4%, P < 0.001) by pretreatment with the specific PACAP receptor antagonist, PACAP6-38, compared with pretreatment with vehicle. Administration of the agonist PACAP1-38 alone resulted in a dose-dependent increase in tissue PAI-1 mRNA. PACAP1-38 administration also resulted in substantial increases in plasma PAI-1 antigen and active PAI-1 concentrations that were significantly greater in male mice than in female mice.

CONCLUSIONS

We conclude that adrenal PAI-1 mRNA expression is markedly increased by stress, and that the PACAP peptidergic signaling pathway plays a major role in mediating the stress-induced increase in PAI-1 biosynthesis.

Contribution of aldosterone to cardiovascular and renal inflammation and fibrosis

The steroid hormone aldosterone regulates sodium and potassium homeostasis. Aldosterone and activation of the mineralocorticoid receptor also causes inflammation and fibrosis of the heart, fibrosis and remodelling of blood vessels and tubulointerstitial fibrosis and glomerular injury in the kidney. Aldosterone and mineralocorticoid-receptor activation initiate an inflammatory response by increasing the generation of reactive oxygen species by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and mitochondria. High salt intake potentiates these effects, in part by activating the Rho family member Rac1, a regulatory subunit of reduced NADPH oxidase that activates the mineralocorticoid receptor. Studies in mice in which the mineralocorticoid receptor has been deleted from specific cell types suggest a key role for macrophages in promoting inflammation and fibrosis. Aldosterone can exert mineralocorticoid-receptor-independent effects via the angiotensin II receptor and via G-protein-coupled receptor 30. Mineralocorticoid-receptor antagonists are associated with decreased mortality in patients with heart disease and show promise in patients with kidney injury, but can elevate serum potassium concentration. Studies in rodents genetically deficient in aldosterone synthase or treated with a pharmacological aldosterone-synthase inhibitor are providing insight into the relative contribution of aldosterone compared with the contribution of mineralocorticoid-receptor activation in inflammation, fibrosis, and injury. Aldosterone-synthase inhibitors are under development in humans.

Loss of heparin-binding protein prevents necrotizing glomerulonephritis: first clues hint at plasminogen activator inhibitor-1

The orchestration of acute inflammatory kidney injury is subject to widespread influences and involves cytokines as well as chemokines released by resident as well as infiltrating cells. Although intense research efforts have been made in the field, it still unravels yet novel key molecules involved in the pathogenesis of this kidney disease. A heparin-binding growth factor denoted midkine is expressed by various cell types following stress of tissue damage. Specific functions relate to orchestration of reparative and inflammatory processes by promoting migration of leucocytes and release of chemokines with ensuing angiogenesis. Midkine appears as a double-edged sword with beneficial or harmful effects in injured tissues. Here, we discuss a recent publication that provides evidence for the beneficial role of midkine in progressive glomerulonephritis, most likely due to blockade of plasminogen activator inhibitor-1 release.

Role of BCL2-associated athanogene 1 in differential sensitivity of human endothelial cells to glucocorticoids

OBJECTIVE

Chronic therapy with synthetic glucocorticoids has been associated with cardiovascular side effects, although differential interindividual susceptibility to glucocorticoids has been observed. The objective of this study was to identify the molecular mechanisms leading to differential glucocorticoid responses in endothelial cells.

APPROACH AND RESULTS

We tested the sensitivity of 42 human umbilical vein endothelial cells (HUVECs) to dexamethasone as determined by changes in gene expression, promoter transactivation, and procoagulant activity. We identified that 16 HUVECs were sensitive in every test, 14 HUVECs were sensitive in at least 1 test and 12 HUVECs were resistant in every test to dexamethasone. Nuclear translocation assays revealed that Dex-sensitive HUVECs have higher basal and Dex-stimulated levels of nuclear glucocorticoid receptor compared with Dex-resistant HUVECs. Cycloheximide assays revealed that Dex-resistant HUVECs have significantly shorter glucocorticoid receptor protein half-lives than Dex-sensitive HUVECs. Dex-resistant HUVECs have a stronger interaction of glucocorticoid receptor with the proteasomal recruiting protein, BCL2-associated athanogene 1 (BAG1), as shown by immunoprecipitation assays. Silencing BAG1 expression increased Dex-sensitivity in resistant HUVECs, whereas BAG1 overexpression decreased Dex-sensitivity in sensitive HUVECs. Finally, Dex-resistant HUVECs presented higher BAG1 expression than Dex-sensitive HUVECs.

CONCLUSIONS

In vitro endothelial sensitivity to Dex varies within individuals and is inversely proportional to BAG1 protein expression and glucocorticoid receptor protein turnover.

Aldosterone and cardiovascular disease: the heart of the matter

Aldosterone contributes to the endocrine basis of heart failure, and studies on cardiac aldosterone signaling have reinforced its value as a therapeutic target. Recent focus has shifted to new roles of aldosterone that appear to depend on coexisting pathologic stimuli, cell type, and disease etiology. This review evaluates recent advances in mechanisms underlying aldosterone-induced cardiac disease and highlights the interplay between aldosterone and Ca(2+)/calmodulin dependent protein kinase II, whose hyperactivity during heart failure contributes to disease progression. Increasing evidence implicates aldosterone in diastolic dysfunction, and there is a need to develop more targeted therapeutics such as aldosterone synthase inhibitors and molecularly specific antioxidants. Despite accumulating knowledge, many questions still persist and will likely dictate areas of future research.

Aldosterone in the pathogenesis of chronic kidney disease and proteinuria

There has been much recent interest in the role of aldosterone as an independent contributor to the progression of chronic kidney disease. Despite treatment with agents such as angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, many studies have shown that there is incomplete blockade of the renin-angiotensin cascade evidenced by persistent or rising plasma aldosterone levels despite therapeutic renin-angiotensin blockade. This phenomenon is commonly referred to as "aldosterone escape" and is thought to be one of the main contributors to chronic kidney disease progression despite conventional therapeutics. Animal models of the effects of exposure to exogenous aldosterone demonstrate the development of inflammation and fibrosis in both the myocardium and renal parenchyma. In limited human studies, aldosterone receptor antagonism is associated with decreased proteinuria and improved glomerular filtration rate. Although data support the addition of an aldosterone antagonist to conventional therapy when treating patients with chronic kidney disease, more studies are needed to determine the precise clinical indications and the appropriate safety monitoring.

Aldosterone and inflammation

PURPOSE OF REVIEW

Aldosterone causes tissue inflammation leading to fibrosis and remodeling in the heart, vasculature, and kidney. We summarize recent data regarding the mechanism(s) through which aldosterone stimulates inflammation.

RECENT FINDINGS

Studies elucidate the cell-specific effects of mineralocorticoid receptor activation on inflammatory cell infiltration and adhesion, and highlight the role of the macrophage in the development of vascular collagen deposition and hypertension. Activation of nuclear factor-kappaB in vascular smooth muscle cells involves a complex interplay between the angiotensin subtype 1 (AT1) receptor and the mineralocorticoid receptor. Activation of the mineralocorticoid receptor by aldosterone stimulates an inflammatory phenotype in adipocytes and contributes to insulin resistance by increasing oxidative stress.

SUMMARY

Mechanistic studies of aldosterone-induced inflammation provide the rationale for an expanded therapeutic role for mineralocorticoid receptor antagonists and aldosterone synthase inhibitors.

Insulin acts through FOXO3a to activate transcription of plasminogen activator inhibitor type 1

Plasminogen activator inhibitor-1 (PAI-1) is an important regulator of fibrinolysis. PAI-1 levels are elevated in type 2 diabetes, and this elevation correlates with macro- and microvascular complications of diabetes. However, the mechanistic link between insulin and up-regulation of PAI-1 is unclear. Here we demonstrate that overexpression of Forkhead-related transcription factor (Fox)O1, FoxO3a, and FoxC1 augment insulin's ability to activate the PAI-1 promoter. In addition, insulin treatment promotes the phosphorylation of nuclear and cytoplasmic Fox03a and an increase of cytoplasmic Fox03a. In contrast, insulin treatment led to the accumulation of phospho-Fox01 only in the cytoplasm. Furthermore, insulin also increased the ability of chimeric LexA-FoxO1, LexA-FoxO3a, and LexA-FoxC1 proteins to increase the activity of a LexA reporter, suggesting that the effect of insulin on FoxO3a was direct. Using small interfering RNA to specifically deplete each of the Fox transcription factors tested, we demonstrate that only reduction of FoxO3a inhibits insulin-increased PAI-1-Luc expression and PAI-1 mRNA accumulation. Finally, chromatin immunoprecipitation assays confirm the presence of FoxO3a on the PAI-1 promoter. These results suggest that FoxO3a mediates insulin-increased PAI-1 gene expression.

The role of plasminogen activator inhibitor 1 in renal and cardiovascular diseases

The 50 kDa glycoprotein plasminogen activator inhibitor 1 (PAI-1) is the major physiological inhibitor of tissue-type and urokinase-type plasminogen activator. These two molecules convert inactive plasminogen into its fibrin-degrading form, plasmin. Plasma and tissue concentrations of PAI-1 are extremely low under normal circumstances but increase under pathologic conditions. This increase is mediated by many factors, including reactive oxygen species. Increased PAI-1 activity is associated with an increased risk of ischemic cardiovascular events and tissue fibrosis. Whereas the antifibrinolytic property of PAI-1 derives mainly from its inhibition of serine proteases, its profibrotic actions seem to derive from a capacity to stimulate interstitial macrophage recruitment and increase transcription of profibrotic genes, as well as from inhibition of serine proteases. Despite studies in mice that lack or overexpress PAI-1, the biological effects of this molecule in humans remain incompletely understood because of the complexity of the PAI-1-plasminogen-activator-plasmin system. The cardioprotective and renoprotective properties of some currently available drugs might be attributable in part to inhibition of PAI-1. The development of an orally active, high-affinity PAI-1 inhibitor will provide a potentially important pharmacological tool for further investigation of the role of PAI-1 and might offer a novel therapeutic strategy in renal and cardiovascular diseases.

Endogenous aldosterone contributes to acute angiotensin II-stimulated plasminogen activator inhibitor-1 and preproendothelin-1 expression in heart but not aorta

To test the hypothesis that angiotensin (Ang) II induces profibrotic gene expression through endogenous aldosterone, we measured the effect of 4 h infusion (600 ng/kg x min) of Ang II on tissue mRNA expression of plasminogen activator inhibitor 1 (PAI-1), preproendothelin-1 (ppET-1), TGF-beta, and osteopontin in wild-type (WT), aldosterone synthase-deficient (AS(-/-)), and AS(-/-) mice treated with aldosterone (either 500 ng/d for 7 d or 250 ng as a concurrent 4 h infusion). Ang II increased aldosterone in WT (P < 0.001) but not in AS(-/-) mice. Aldosterone (7 d) normalized basal aldosterone concentrations in AS(-/-) mice; however, there was no further effect of Ang II on aldosterone (P = NS). Basal cardiac and aortic PAI-1 and ppET-1 expression were similar in WT and AS(-/-) mice. Ang II-stimulated PAI-1 (P < 0.001) and ppET-1 expression (P = 0.01) was diminished in the heart of AS(-/-) mice; treatment with aldosterone for 4 h or 7 d restored PAI-1 and ppET-1 mRNA responsiveness to Ang II in the heart. Ang II increased PAI-1 (P = 0.01) expression in the aorta of AS(-/-) as well as WT mice. In the kidney, basal PAI-1, ppET-1, and TGF-beta mRNA expression was increased in AS(-/-) compared with WT mice and correlated with plasma renin activity. Ang II did not stimulate osteopontin or TGF-beta expression in the heart or kidney. Endogenous aldosterone contributes to the acute stimulatory effect of Ang II on PAI-1 and ppET-1 mRNA expression in the heart; renin activity correlates with basal profibrotic gene expression in the kidney.

PAI-1 and kidney fibrosis

Substantial evidence demonstrates a link of increased plasminogen activator inhibitor-1 (PAI-1) and glomerulosclerosis and kidney fibrosis, providing a novel therapeutic option for prevention and treatment of chronic kidney diseases. Several mechanisms contributing to increased PAI-1 will be addressed, including classic key profibrotic factors such as the renin-angiotensin-system (RAS) and transforming growth factor-beta (TGF-b???and novel molecules identified by proteomic analysis, such as thymosin- b4. The fibrotic sequelae caused by increased PAI-1 in kidney depend not only on its classic inhibition of tissue-type and urokinase-type plasminogen activators (tPA and uPA), but also its influence on cell migration.

Aldosterone activates NF-kappaB in the collecting duct

Besides its classical effects on salt homeostasis in renal epithelial cells, aldosterone promotes inflammation and fibrosis and modulates cell proliferation. The proinflammatory transcription factor NF-kappaB has been implicated in cell proliferation, apoptosis, and regulation of transepithelial sodium transport. The effect of aldosterone on the NF-kappaB pathway in principal cells of the cortical collecting duct, a major physiologic target of aldosterone, is unknown. Here, in both cultured cells and freshly isolated rat cortical collecting duct, aldosterone activated the canonical NF-kappaB signaling pathway, leading to increased expression of several NF-kappaB-targeted genes (IkappaBalpha, plasminogen activator inhibitor 1, monocyte chemoattractant protein 1, IL-1beta, and IL-6). Small interfering RNA-mediated knockdown of the serum and glucocorticoid-inducible kinase SGK1, a gene induced early in the response to aldosterone, but not pharmacologic inhibition of extracellular signal-regulated kinase and p38 kinase, attenuated aldosterone-induced NF-kappaB activation. Pharmacologic antagonism or knockdown of the mineralocorticoid receptor prevented aldosterone-induced NF-kappaB activity. In addition, activation of the glucocorticoid receptor inhibited the transactivation of NF-kappaB by aldosterone. In agreement with these in vitro findings, spironolactone prevented NF-kappaB-induced transcriptional activation observed in cortical collecting ducts of salt-restricted rats. In summary, aldosterone activates the canonical NF-kappaB pathway in principal cells of the cortical collecting duct by activating the mineralocorticoid receptor and by inducing SGK1.

Aldosterone, but not angiotensin II, increases profibrotic factors in kidney of adrenalectomized stroke-prone spontaneously hypertensive rats

An increase in angiotensin II (ANG II) under conditions of high salt intake can result in renal damage. The extent to which ANG II does this directly or by way of stimulating aldosterone (Aldo) secretion is a subject of some debate. In the present study, we sought to determine the separate effects of Aldo and ANG II on the expression of plasminogen activator inhibitor-1 (PAI-1) and other factors related to renal fibrosis in the stroke-prone spontaneously hypertensive rat (SHRSP). Saline-drinking male SHRSPs underwent adrenalectomy (ADX) or sham operation (Sham). Treatment groups consisted of ADX + ANG II (25 ng/min sc) and ADX + Aldo (40 microg.kg(-1).day(-1) sc). After 2 wk of treatment, circulating Aldo levels were reduced to the limit of detection, renal PAI-1, transforming growth factor-beta1 (TGF-beta1), and osteopontin expression, and phospho-Smad2 (p-Smad2) level were decreased severalfold, and Smad7 (an inhibitory regulator of TGF-beta1 action) expression was increased in ADX compared with Sham rats. Infusion of Aldo into ADX SHRSPs restored the renal mRNA expression of PAI-1, TGF-beta1 (along with restored p-Smad2 level), and osteopontin and reduced that of Smad7, whereas ANG II had no or a lesser effect. The findings were confirmed by histological examination of renal tissue. In summary, in the saline-drinking SHRSP, Aldo increased renal profibrotic factors and produced renal injury whereas ANG II in the absence of the adrenals had no effect.

Aldosterone and TGF-beta1 synergistically increase PAI-1 and decrease matrix degradation in rat renal mesangial and fibroblast cells

Aldosterone is thought to modulate renal fibrosis, in part, through increasing plasminogen activator inhibitor type 1 (PAI-1), a major inhibitor of ECM degradation. The present study investigated aldosterone effects on PAI-1 and transforming growth factor (TGF)-beta(1) and asked whether PAI-1 effects were TGF-beta mediated and whether aldosterone and TGF-beta(1) acted synergistically to increase PAI-1 and decrease ECM degradation. Rat mesangial cells (MCs) and fibroblast cells [normal rat kidney (NRK)-49F] were used. (3)H-labeled ECM was produced by MCs. The effect of aldosterone and TGF-beta on ECM degradation by newly plated MCs or NRK-49F was measured by the release of (3)H into medium. Aldosterone markedly increased PAI-1 mRNA and protein in both cell types, increases completely blocked by spironolactone and partially blocked by TGF-beta neutralizing antibody. Adding both aldosterone and TGF-beta(1) produced PAI-1 mRNA and protein increases higher than the sum of increases seen with either compound alone. Aldosterone or TGF-beta(1) alone inhibited matrix degradation by 39 and 49% in MCs and 21 and 23% in NRK-49F, respectively. When both compounds were added, matrix degradation was further decreased by 93% in MCs and 61% in NRK-49F. The results indicate that aldosterone-induced PAI-1 increases are partially mediated by TGF-beta(1) and lead to decreased ECM degradation. While aldosterone alone induced TGF-beta(1) weakly, aldosterone and TGF-beta(1) added together produced dramatic synergistic effects on PAI-1 production and subsequent ECM accumulation. Thus the elevated aldosterone induced by renin-angiotensin-aldosterone system activation may amplify renin-angiotensin-aldosterone system profibrotic actions.

Changes in the haemostatic system after thermoneutral and hyperthermic water immersion

Warm water bathing is a popular recreational activity and is frequently used in rehabilitation medicine. Although well tolerated in most cases, there are reports indicating an increased risk of thrombotic events after hot tub bathing. The effects of a 45 min thermoneutral bath followed by a 50 min bath with increasing water temperature (maximum 41 degrees C) until reaching a body core temperature of 39 degrees C on factors of blood coagulation and fibrinolysis were studied in eight healthy male volunteers. Blood was obtained after a 45-min resting period as control and after the thermoneutral and hyperthermic bath as well as after another 45 min recovery period at the end of the study. Hyperthermic immersion (HI) lead to a shortening of activated partial thromboplastin time (aPTT) (P < 0.05). Fibrinogen concentration decreased immediately after HI (P < 0.05) but increased during recovery (P < 0.05). Plasminogen activator inhibitor (PAI) activity decreased during HI (P < 0.05), D-dimer concentration was not found to change. Thrombocyte count increased (P < 0.05) during HI. The increases in tissue-type plasminogen activator concentration as well as leucocyte count during HI were due to haemoconcentration. Prothrombin time, PAI-activity and granulocyte count decreased during thermoneutral immersion (P < 0.05). Warm water bathing leads to haemoconcentration and minimal activation of coagulation. The PAI-1 activity is decreased. A marked risk for thrombotic or bleeding complications during warm water bathing in healthy males could not be ascertained.

Mechanisms of progression of chronic kidney disease

Chronic kidney disease (CKD) occurs in all age groups, including children. Regardless of the underlying cause, CKD is characterized by progressive scarring that ultimately affects all structures of the kidney. The relentless progression of CKD is postulated to result from a self-perpetuating vicious cycle of fibrosis activated after initial injury. We will review possible mechanisms of progressive renal damage, including systemic and glomerular hypertension, various cytokines and growth factors, with special emphasis on the renin-angiotensin-aldosterone system (RAAS), podocyte loss, dyslipidemia and proteinuria. We will also discuss possible specific mechanisms of tubulointerstitial fibrosis that are not dependent on glomerulosclerosis, and possible underlying predispositions for CKD, such as genetic factors and low nephron number.

Transforming growth factor-beta-dependent and -independent pathways of induction of tubulointerstitial fibrosis in beta6(-/-) mice

Transforming growth factor-beta1 (TGF-beta1) and the renin-angiotensin-aldosterone system are key mediators in kidney fibrosis. Integrin alphavbeta6, a heterodimeric matrix receptor expressed in epithelia, binds and activates latent TGF-beta1. We used beta6 integrin-null mice (beta6(-/-)) to determine the role of local TGF-beta1 activation in renal fibrosis in the unilateral ureteral obstruction (UUO) model. Obstructed kidneys from beta6(-/-) mice showed less injury than obstructed kidneys from wild-type (WT) mice, associated with lower collagen I, collagen III, plasminogen activator inhibitor (PAI-1), and TGF-beta1 mRNA levels and lower collagen content. Infusion with either angiotensin II (Ang II) or aldosterone (Aldo) or combination in beta6(-/-) UUO mice significantly increased collagen contents to levels comparable to those in identically treated WT. Active TGF-beta protein expression in beta6(-/-) mice was less in UUO kidneys with or without Ang II infusion compared to matched WT mice. Activated Smad 2 levels in beta6(-/-) obstructed kidneys were lower than in WT UUO mice, and did not increase when fibrosis was induced in beta6(-/-) UUO mice by Ang II infusion. Anti-TGF-beta antibody only partially decreased this Ang II-stimulated fibrosis in beta6(-/-) UUO kidneys. In situ hybridization and immunostaining showed low expression of PAI-1 mRNA and protein in tubular epithelium in beta6(-/-) UUO kidneys, with increased PAI-1 expression in response to Ang II, Aldo, or both. Our results indicate that interruption of alphavbeta6-mediated activation of TGF-beta1 can protect against tubulointerstitial fibrosis. Further, the robust induction of tubulointerstitial fibrosis without increase in activated Smad 2 levels in obstructed beta6(-/-) mice by Ang II suggests the existence of a TGF-beta1-independent pathway of induction of fibrosis through angiotensin.

Cardiometabolic syndrome: pathophysiology and treatment

The cardiometabolic syndrome, an interesting constellation of maladaptive cardiovascular, renal, metabolic, prothrombotic, and inflammatory abnormalities, is now recognized as a disease entity by the American Society of Endocrinology, National Cholesterol Education Program, and World Health Organization, among others. These cardiovascular and metabolic derangements individually and interdependently lead to a substantial increase in cardiovascular disease (CVD) morbidity and mortality, making the cardiometabolic syndrome an established and strong risk factor for premature and severe CVD and stroke. Established and evolving treatment strategies including moderate physical activity, weight reduction, rigorous blood pressure control, correction of dyslipidemia, and glycemic control have proven beneficial in reversing these abnormal responses and decreasing the CVD risk.

Renal fibrosis: not just PAI-1 in the sky

A delicate balance exists between ECM synthesis and degradation such that interruption of the corresponding pathways results in increased plasminogen activator inhibitor-1 (PAI-1), pathological matrix accumulation, and glomerulosclerosis. A new study demonstrates that therapy with a mutant PAI-1 increases matrix turnover and reduces glomerulosclerosis by competing with endogenous PAI-1, suggesting therapeutic utility in the treatment of fibrotic renal disease.

Aldosterone: a risk factor for vascular disease

Blockade of the renin-angiotensin-aldosterone system with angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor antagonists has resulted in beneficial effects in essential hypertensive patients. However, occurrence of cardiovascular events has not been appropriately controlled beyond a certain percentage. One reason could be the effects of aldosterone, the final component of the system. The aldosterone escape phenomenon could explain undesirable outcomes observed in hypertensive patients even under treatment with ACE inhibitors or angiotensin antagonists. Aldosterone has direct effects on the vasculature and has been associated with vascular smooth muscle cell hypertrophy, endothelial dysfunction, cardiac fibrosis, proteinuria, and renal vascular injury. Animal models and clinical trials have proven the benefit of aldosterone receptor antagonism. With increased recognition of the prevalence of hyperaldosteronism in patients thought to have "essential" hypertension, the use of drugs that block aldosterone action may become more widespread and protect the vasculature from the deleterious effects of aldosterone.