Protein S100B as a reliable tool for early prognostication after cardiac arrest.

PURPOSE: Early and reliable prognostication after cardiac arrest (CA) remains crucial. We hypothesized that protein-S100B (PS100B) could predict more accurately outcome in the early phase of CA compared with other current biomarkers. METHODS: This prospective single-center study included 330 adult comatose non-traumatic successfully resuscitated CA patients, treated with targeted temperature management but not extra-corporeal life support. Lactate, pH, creatinine, NSE, and PS100B were sampled in ICU early after return of spontaneous circulation (ROSC) corresponding to admission (Adm). Serial measurements were also performed at H24 and H48. PS100B was the sole biomarker blinded to physicians. MEASUREMENTS AND MAIN RESULTS: The median delay between ROSC and first PS100B sampling was 220 min. At admission, all biomarkers were significantly associated with good outcome (CPC1-2; 109 patients) at 3-month follow-up (P ≤ 0.001, except for NSE: P = 0.03). PS100B-Adm showed the best AUC of ROC curves for outcome prediction at 3-month (AUC 0.83 [95%-CI: 0.78-0.88]), compared with other biomarkers (P < 0.0001), while AUC for lactate-Adm was higher than for NSE-Adm. AUC for PS100B-H24 was significantly higher than for other biomarkers except NSE-H24 (P ≤ 0.0001), while AUC for NSE-H24 was higher than for lactate-H24 and pH-H24. AUCs for PS100-H48 and NSE-H48 were significantly higher than for all other biomarkers (P < 0.001). Compared to patients with decreased PS100B values over time, an increasing PS100B value between admission and H24 was significantly associated with poor outcome at 3 months (P = 0.001). No-flow, initial non-shockable rhythm, PS100B-Adm, lactate-Adm, pH-Adm, clinical seizures, and absence of therapeutic hypothermia were independent predictors associated with poor outcome at 3-month in multivariate analysis. Net-Reclassification-Index was 70%, 64%, and 81% when PS100B-Adm was added to the clinical model, to clinical model with NSE-Adm, and to clinical model with standard biological parameters, respectively. CONCLUSIONS: Early PS100B compared with other biomarkers was independently correlated with outcome after CA, with an interesting added value.

Acute Kidney Injury Induces Remote Cardiac Damage and Dysfunction Through the Galectin-3 Pathway.

Acute kidney injury is associated with increased risk of heart failure and mortality. This study demonstrates that acute kidney injury induces remote cardiac dysfunction, damage, injury, and fibrosis via a galectin-3 (Gal-3) dependent pathway. Gal-3 originates from bone marrow-derived immune cells. Cardiac damage could be prevented by blocking this pathway.

QSOX1, a novel actor of cardiac protection upon acute stress in mice.

QSOX1, a sulfhydryl oxidase, was shown to be upregulated in the heart upon acute heart failure (AHF). The aim of the study was to unravel QSOX1 roles during AHF. We generated and characterized mice with QSOX1 gene deletion. The QSOX1-/- mice were viable but adult male exhibited a silent dilated cardiomyopathy. The QSOX1-/- hearts were characterized by low protein SERCA2a levels associated with a calcium homeostasis alteration, high levels of the endoplasmic reticulum (ER) chaperone proteins Grp78/Bip, and of the ER apoptosis sensor CHOP, indicating a chronic unfolded protein response (UPR). Importantly the QSOX1invalidation led to overexpression of two ER oxidases, ERO1-α and PRDX4. Acute stress was induced by isoproterenol injection (ISO, 300 mg/kg/12 h) for 2 days. In both groups, the PERK UPR pathway was transiently activated 6 h after the first ISO injection as indicated by eIF2 phosphorylation. By day-3 after the onset of stress, both WT and QSOX1-/- mice exhibited AHF profile but while high cardiac QSOX1 level was induced in WT hearts, ERO1-α and PRDX4 levels drop down in QSOX1-/-. At that time, QSOX1-/- hearts exhibited an enhanced inflammation (CD68+ cells and Galectin-3 expression) and oxidative stress (DHE staining and oxyblot) when compared to WT ones. In conclusion, the lack of QSOX1 promotes the upregulation of two ER oxidases ERO1α and PRDX4 that likely rescues oxidative protein folding in the hearts. However, signs of chronic ER stress remained present and were associated with a dilated cardiomyopathy. The superimposition of acute stress allowed us to propose that QSOX1 participate to the early response to cardiac stress but not to immediate UPR response. Taken altogether, the data indicated that QSOX1 is required 1) for a proper protein folding in the endo/sarcoplasmic reticulum (ER/SR) and 2) for resolution and protective response during acute stress.

Beneficial effects of exercise training in heart failure are lost in male diabetic rats.

Exercise training has been demonstrated to have beneficial effects in patients with heart failure (HF) or diabetes. However, it is unknown whether diabetic patients with HF will benefit from exercise training. Male Wistar rats were fed either a standard (Sham, n = 53) or high-fat, high-sucrose diet ( n = 66) for 6 mo. After 2 mo of diet, the rats were already diabetic. Rats were then randomly subjected to either myocardial infarction by coronary artery ligation (MI) or sham operation. Two months later, heart failure was documented by echocardiography and animals were randomly subjected to exercise training with treadmill for an additional 8 wk or remained sedentary. At the end, rats were euthanized and tissues were assayed by RT-PCR, immunoblotting, spectrophotometry, and immunohistology. MI induced a similar decrease in ejection fraction in diabetic and lean animals but a higher premature mortality in the diabetic group. Exercise for 8 wk resulted in a higher working power developed by MI animals with diabetes and improved glycaemia but not ejection fraction or pathological phenotype. In contrast, exercise improved the ejection fraction and increased adaptive hypertrophy after MI in the lean group. Trained diabetic rats with MI were nevertheless able to develop cardiomyocyte hypertrophy but without angiogenic responses. Exercise improved stress markers and cardiac energy metabolism in lean but not diabetic-MI rats. Hence, following HF, the benefits of exercise training on cardiac function are blunted in diabetic animals. In conclusion, exercise training only improved the myocardial profile of infarcted lean rats fed the standard diet. NEW & NOTEWORTHY Exercise training is beneficial in patients with heart failure (HF) or diabetes. However, less is known of the possible benefit of exercise training for HF patients with diabetes. Using a rat model where both diabetes and MI had been induced, we showed that 2 mo after MI, 8 wk of exercise training failed to improve cardiac function and metabolism in diabetic animals in contrast to lean animals.

Loss of Notch3 Signaling in Vascular Smooth Muscle Cells Promotes Severe Heart Failure Upon Hypertension.

Hypertension, which is a risk factor of heart failure, provokes adaptive changes at the vasculature and cardiac levels. Notch3 signaling plays an important role in resistance arteries by controlling the maturation of vascular smooth muscle cells. Notch3 deletion is protective in pulmonary hypertension while deleterious in arterial hypertension. Although this latter phenotype was attributed to renal and cardiac alterations, the underlying mechanisms remained unknown. To investigate the role of Notch3 signaling in the cardiac adaptation to hypertension, we used mice with either constitutive Notch3 or smooth muscle cell-specific conditional RBPJκ knockout. At baseline, both genotypes exhibited a cardiac arteriolar rarefaction associated with oxidative stress. In response to angiotensin II-induced hypertension, the heart of Notch3 knockout and SM-RBPJκ knockout mice did not adapt to pressure overload and developed heart failure, which could lead to an early and fatal acute decompensation of heart failure. This cardiac maladaptation was characterized by an absence of media hypertrophy of the media arteries, the transition of smooth muscle cells toward a synthetic phenotype, and an alteration of angiogenic pathways. A subset of mice exhibited an early fatal acute decompensated heart failure, in which the same alterations were observed, although in a more rapid timeframe. Altogether, these observations indicate that Notch3 plays a major role in coronary adaptation to pressure overload. These data also show that the hypertrophy of coronary arterial media on pressure overload is mandatory to initially maintain a normal cardiac function and is regulated by the Notch3/RBPJκ pathway.

Inhibition of Galectin-3 Pathway Prevents Isoproterenol-Induced Left Ventricular Dysfunction and Fibrosis in Mice.

Galectin-3 (Gal-3) is involved in inflammation, fibrogenesis, and cardiac remodeling. Previous evidence shows that Gal-3 interacts with aldosterone in promoting macrophage infiltration and vascular fibrosis and that Gal-3 genetic and pharmacological inhibition prevents remodeling in a pressure-overload animal model of heart failure. We aimed to explore the contribution of Gal-3 and aldosterone in mechanisms leading to heart failure in a murine model. Male mice with cardiac-specific hyperaldosteronism underwent isoproterenol subcutaneous injections, to be then randomized to receive placebo, a Gal-3 inhibitor (modified citrus pectin [MCP]), an aldosterone antagonist (potassium canrenoate), or MCP+canrenoate for 14 days. Isoproterenol induced a rapid and persistent decrease in left ventricular fractional shortening (-20% at day 14); this was markedly improved by treatment with either MCP or canrenoate (both P<0.001 versus placebo). MCP and canrenoate also reduced cardiac hypertrophy and fibrosis and the expression of genes involved in fibrogenesis (Coll-1 and Coll-3) and macrophage infiltration (CD-68 and MCP-1). After isoproterenol, Gal-3 gene expression (P<0.05 versus placebo) and protein levels (-61% and -69% versus placebo) were decreased by both canrenoate and MCP. The combined use of antagonists of Gal-3 and aldosterone resulted in more pronounced effects on cardiac hypertrophy, inflammation, and fibrosis, when compared with either MCP or canrenoate alone. Inhibition of Gal-3 and aldosterone can reverse isoproterenol-induced left ventricular dysfunction, by reducing myocardial inflammation and fibrogenesis. Gal-3 likely participates in mechanisms of aldosterone-mediated myocardial damage in a heart failure murine model with cardiac hyperaldosteronism. Gal-3 inhibition may represent a new promising therapeutic option in heart failure.

Aldosterone promotes cardiac endothelial cell proliferation in vivo.

BACKGROUND: Experimentally, aldosterone in association with NaCl induces cardiac fibrosis, oxidative stress, and inflammation through mineralocorticoid receptor activation; however, the biological processes regulated by aldosterone alone in the heart remain to be identified. METHODS AND RESULTS: Mice were treated for 7 days with aldosterone, and then cardiac transcriptome was analyzed. Aldosterone regulated 60 transcripts (51 upregulated and 9 downregulated) in the heart (fold change ≥1.5, false discovery rate <0.01). To identify the biological processes modulated by aldosterone, a gene ontology analysis was performed. The majority of aldosterone-regulated genes were involved in cell division. The cardiac Ki-67 index (an index of proliferation) of aldosterone-treated mice was higher than that of nontreated mice, confirming microarray predictions. Costaining of Ki-67 with vinculin, CD68, α-smooth muscle actin, CD31, or caveolin 1 revealed that the cycling cells were essentially endothelial cells. Aldosterone-induced mineralocorticoid receptor-dependent proliferation was confirmed ex vivo in human endothelial cells. Moreover, pharmacological-specific blockade of mineralocorticoid receptor by eplerenone inhibited endothelial cell proliferation in a preclinical model of heart failure (transverse aortic constriction). CONCLUSIONS: Aldosterone modulates cardiac gene expression and induces the proliferation of cardiac endothelial cells in vivo.

Akt-mediated cardioprotective effects of aldosterone in type 2 diabetic mice.

Studies have shown that aldosterone would have angiogenic effects and therefore would be beneficial in the context of cardiovascular diseases. We thus investigated the potential involvement of aldosterone in triggering a cardiac angiogenic response in the context of type-2 diabetes and the molecular pathways involved. Male 3-wk-old aldosterone synthase (AS)-overexpressing mice and their control wild-type (WT) littermates were fed a standard or high-fat, high-sucrose (HFHS) diet. After 6 mo of diet treatment, mice were euthanized, and cardiac samples were assayed by RT-PCR, immunoblotting, and immunohistology. HFHS diet induced type-2 diabetes in WT (WT-D) and AS (AS-D) mice. VEGFa mRNAs decreased in WT-D (-43%, P<0.05 vs. WT) and increased in AS-D mice (+236%, P< 0.01 vs. WT-D). In WT-D mouse hearts, the proapoptotic p38MAPK was activated (P<0.05 vs. WT and AS-D), whereas Akt activity decreased (-64%, P<0.05 vs. WT). The AS mice, which exhibited a cardiac up-regulation of IGF1-R, showed an increase in Akt phosphorylation when diabetes was induced (P<0.05 vs. WT and AS-D). Contrary to WT-D mice, AS-D mouse hearts did not express inflammatory markers and exhibited a normal capillary density (P<0.05 vs. WT-D). To our knowledge, this is the first study providing new insights into the mechanisms whereby aldosterone prevents diabetes-induced cardiac disorders.

AT1 blockade abolishes left ventricular hypertrophy in heterozygous cMyBP-C null mice: role of FHL1.

This research investigated the impact of angiotensin AT1 receptor (Agtr1) blockade on left ventricular (LV) hypertrophy in a mouse model of human hypertrophic cardiomyopathy (HCM), which carries one functional allele of Mybpc3 gene coding cardiac myosin-binding protein C (cMyBP-C). Five-month-old heterozygous cMyBP-C knockout (Het-KO) and wild-type mice were treated with irbesartan (50 mg/kg/day) or vehicle for 8 weeks. Arterial blood pressure was measured by tail cuff plethysmography. LV dimension and function were accessed by echocardiography. Myocardial gene expression was evaluated using RT-qPCR. Compared with wild-type littermates, Het-KO mice had greater LV/body weight ratio (4.0 ± 0.1 vs. 3.3 ± 0.1 mg/g, P < 0.001), thicker interventricular septal wall (0.70 ± 0.02 vs. 0.65 ± 0.01 mm, P < 0.02), lower Mybpc3 mRNA level (-43%, P < 0.02), higher four-and-a-half LIM domains 1 (Fhl1, +110%, P < 0.01), and angiotensin-converting enzyme 1 (Ace1, +67%, P < 0.05), but unchanged Agtr1 mRNA levels in the septum. Treatment with irbesartan had no effect in wild-type mice but abolished septum-predominant LV hypertrophy and Fhl1 upregulation without changes in Ace1 but with an increased Agtr1 (+42%) in Het-KO mice. Thus, septum-predominant LV hypertrophy in Het-KO mice is combined with higher Fhl1 expression, which can be abolished by AT1 receptor blockade, indicating a role of the renin-angiotensin system and Fhl1 in cMyBP-C-related HCM.

Effects of biological sex on the pathophysiology of the heart.

Cardiovascular diseases are the leading causes of death in men and women in industrialized countries. While the effects of biological sex on cardiovascular pathophysiology have long been known, the sex-specific mechanisms mediating these processes have been further elucidated over recent years. This review aims at analysing the sex-based differences in cardiac structure and function in adult mammals, and the sex-based differences in the main molecular mechanisms involved in the response of the heart to pathological situations. It emerged from this review that the sex-based difference is a variable that should be dealt with, not only in basic science or clinical research, but also with regards to therapeutic approaches.

Aldosterone mediates cardiac fibrosis in the setting of hypertension.

Cardiac remodeling is a deleterious consequence of arterial hypertension. This remodeling results from cardiac transcriptomic changes induced by mechanical and hormonal factors. Angiotensin II and aldosterone often collaborate in pathological situations to induce hypertrophy of cardiomyocytes, vascular inflammation, perivascular and interstitial fibrosis, and microvascular rarefaction. Experimental models of transgenic mice overexpressing renin in liver, leading to increased plasma angiotensin II and severe hypertension, and mice overexpressing aldosterone-synthase in cardiomyocytes, leading to a doubling of intracardiac aldosterone concentration have shown that cardiac fibrosis in the heart depends on a balance between pro-fibrotic (TGF-ß, galectin-3) and anti-fibrotic (BNP, ANP) factors. Recent studies using cell-specific deletion of the mineralocorticoid receptor indicate that its activation in macrophages is a key step in the development of cardiac fibrosis in the setting of hemodynamic or hormonal challenges. This review focuses on the impact of inappropriate stimulation of aldosterone in the development of cardiac fibrosis.

Aldosterone-specific activation of cardiomyocyte mineralocorticoid receptor in vivo.

Inappropriate mineralocorticoid receptor (MR) activation is involved in cardiac diseases. Whether and how aldosterone is involved in the deleterious effects of cardiac mineralocorticoid activation is still unclear. Mice overexpressing MR in cardiomyocytes and their controls were treated for 7 days with aldosterone, and cardiac transcriptome was analyzed. Aldosterone regulated 265 genes in cardiomyocyte-targeted MR overexpression mice. Forty three of these genes were also differentially expressed between untreated cardiomyocyte-targeted MR overexpression and controls mice, thus representing putative aldosterone-regulated genes in cardiomyocytes. Among these genes, we focused on connective tissue growth factor (CTGF). In vivo, in cardiomyocyte-targeted MR overexpression mice, aldosterone (but not corticosterone) induced CTGF expression (mRNA and protein) in cardiomyocytes. Ex vivo, aldosterone induced the binding of mineralocorticoid receptor to CTGF promoter and increased the expression of its transcript. Aldosterone induction of CTGF synthesis in cardiomyocytes seems pathologically relevant as the increase in CTGF observed in a model of heart failure (transverse aortic constriction) in rats was prevented by eplerenone, a mineralocorticoid receptor blocker. This study demonstrates that aldosterone specifically regulates gene expression in cardiomyocytes despite large prevalence of glucocorticoids in plasma.

Glatiramer Acetate administration does not reduce damage after cerebral ischemia in mice.

Inflammation plays a key role in ischemic stroke pathophysiology: microglial/macrophage cells and type-1 helper cells (Th1) seem deleterious, while type-2 helper cells (Th2) and regulatory T cells (Treg) seem protective. CD4 Th0 differentiation is modulated by microglial cytokine secretion. Glatiramer Acetate (GA) is an immunomodulatory drug that has been approved for the treatment of human multiple sclerosis by means of a number of mechanisms: reduced microglial activation and pro-inflammatory cytokine production, Th0 differentiation shifting from Th2 to Th2 and Treg with anti-inflammatory cytokine production and increased neurogenesis. We induced permanent (pMCAo) or transient middle cerebral artery occlusion (tMCAo) and GA (2 mg) or vehicle was injected subcutaneously immediately after cerebral ischemia. Mice were sacrificed at D3 to measure neurological deficit, infarct volume, microglial cell density and qPCR of TNFα and IL-1ß (pro-inflammatory microglial cytokines), IFNγ (Th2 cytokine), IL-4 (Th2 cytokine), TGFß and IL-10 (Treg cytokines), and at D7 to evaluate neurological deficit, infarct volume and neurogenesis assessment. We showed that in GA-treated pMCAo mice, infarct volume, microglial cell density and cytokine secretion were not significantly modified at D3, while neurogenesis was enhanced at D7 without significant infarct volume reduction. In GA-treated tMCAo mice, microglial pro-inflammatory cytokines IL-1ß and TNFα were significantly decreased without modification of microglial/macrophage cell density, cytokine secretion, neurological deficit or infarct volume at D3, or modification of neurological deficit, neurogenesis or infarct volume at D7. In conclusion, Glatiramer Acetate administered after cerebral ischemia does not reduce infarct volume or improve neurological deficit in mice despite a significant increase in neurogenesis in pMCAo and a microglial pro-inflammatory cytokine reduction in tMCAo.

Effects of spironolactone alone and in addition to a ß-blocker on myocardial histological and electrical remodeling in chronic severe failing rat hearts.

BACKGROUND: Aldosterone antagonists (AAs) have beneficial effects on ventricular histological and electrical remodeling and improve noradrenaline uptake. Adding an AA to a beta-blocker (BB) further improves cardiac mortality in heart failure patients. We investigated if adjunction of a BB modifies beneficial effects of spironolactone on different parameters of the ventricular remodeling. METHODS: A severe myocardial infarction (MI) was produced in rats. Three months after surgery, left ventricular (LV) function was assessed by echocardiography. Fifty-five rats with heart failure were then randomized in 5 groups: sham, MI, and MI treated for 4 weeks with spironolactone (10 mg·kg·d), atenolol (1 mg·kg·d), or both. Holter transducers were implanted to record 24-hour ventricular electrical parameters, mean cycle length (RR) and SD of RR. Before killing, invasive left ventricular end diastolic pressure (LVEDP) was recorded. LV samples were used for histological analysis and catecholamine assay. RESULTS: Rats with MI had significantly increased LVEDP (32 ± 3 vs. 14 ± 1 mm Hg), LV, collagen content (5.8% ± 1.4% vs. 3.6% ± 0.7%), ventricular premature complexes (2.5 10 ± 10 vs. 30 ± 13), and decreased meanRR (164 ± 2 vs. 169 ± 1 milliseconds) and SDRR (3.9 ± 0.2 vs. 5.4 ± 0.2 milliseconds) compared with sham. At nonhypotensive doses, spironolactone and atenolol similarly improved LVEDP. Compared with MI, although spironolactone significantly decreased ventricular premature complexes, LV collagen and noradrenaline contents, and improved meanRR and SDRR, atenolol had effects only on meanRR and SDRR. Addition of atenolol to spironolactone further improved spironolactone effects on all these parameters. CONCLUSIONS: AA improved, independently of the cardiac function, histological and electrical remodeling after MI. A BB added to an AA did not blunt these beneficial effects; furthermore, it improved these effects related to spironolactone.

Aldosterone inhibits the fetal program and increases hypertrophy in the heart of hypertensive mice.

BACKGROUND: Arterial hypertension (AH) induces cardiac hypertrophy and reactivation of "fetal" gene expression. In rodent heart, alpha-Myosin Heavy Chain (MyHC) and its micro-RNA miR-208a regulate the expression of beta-MyHC and of its intronic miR-208b. However, the role of aldosterone in these processes remains unclear. METHODOLOGY/PRINCIPAL FINDINGS: RT-PCR and western-blot were used to investigate the genes modulated by arterial hypertension and cardiac hyperaldosteronism. We developed a model of double-transgenic mice (AS-Ren) with cardiac hyperaldosteronism (AS mice) and systemic hypertension (Ren). AS-Ren mice had increased (x2) angiotensin II in plasma and increased (x2) aldosterone in heart. Ren and AS-Ren mice had a robust and similar hypertension (+70%) versus their controls. Anatomical data and echocardiography showed a worsening of cardiac hypertrophy (+41%) in AS-Ren mice (P<0.05 vs Ren). The increase of ANP (x 2.5; P<0.01) mRNA observed in Ren mice was blunted in AS-Ren mice. This non-induction of antitrophic natriuretic peptides may be involved in the higher trophic cardiac response in AS-Ren mice, as indicated by the markedly reduced cardiac hypertrophy in ANP-infused AS-Ren mice for one month. Besides, the AH-induced increase of ßMyHC and its intronic miRNA-208b was prevented in AS-Ren. The inhibition of miR 208a (-75%, p<0.001) in AS-Ren mice compared to AS was associated with increased Sox 6 mRNA (x 1.34; p<0.05), an inhibitor of ßMyHC transcription. Eplerenone prevented all aldosterone-dependent effects. CONCLUSIONS/SIGNIFICANCE: Our results indicate that increased aldosterone in heart inhibits the induction of atrial natriuretic peptide expression, via the mineralocorticoid receptor. This worsens cardiac hypertrophy without changing blood pressure. Moreover, this work reveals an original aldosterone-dependent inhibition of miR-208a in hypertension, resulting in the inhibition of ß-myosin heavy chain expression through the induction of its transcriptional repressor Sox6. Thus, aldosterone inhibits the fetal program and increases cardiac hypertrophy in hypertensive mice.

Aldosterone inhibits antifibrotic factors in mouse hypertensive heart.

The renin-angiotensin-aldosterone system is involved in the arterial hypertension-associated cardiovascular remodeling. In this context, the development of cardiac fibrosis results from an imbalance between profibrotic and antifibrotic pathways, in which the role of aldosterone is yet not established. To determine the role of intracardiac aldosterone in the development of myocardial fibrosis during hypertension, we used a double transgenic model (AS-Ren) of cardiac hyperaldosteronism (AS) and systemic hypertension (Ren). The 9-month-old hypertensive mice had cardiac fibrosis, and hyperaldosteronism enhanced the fibrotic level. The mRNA levels of connective tissue growth factor and transforming growth factor-ß1 were similarly increased in Ren and AS-Ren mice compared with wild-type and AS mice, respectively. Hyperaldosteronism combined with hypertension favored the macrophage infiltration (CD68(+) cells) in heart, and enhanced the mRNA level of monocyte chemoattractant protein 1, osteopontin, and galectin 3. Interestingly, in AS-Ren mice the hypertension-induced increase in bone morphogenetic protein 4 mRNA and protein levels was significantly inhibited, and B-type natriuretic peptide expression was blunted. The mineralocorticoid receptor antagonist eplerenone restored B-type natriuretic peptide and bone morphogenetic protein 4 levels and decreased CD68 and galectin 3 levels in AS-Ren mice. Finally, when hypertension was induced by angiotensin II infusion in wild-type and AS mice, the mRNA profiles did not differ from those observed in Ren and AS-Ren mice, respectively. The aldosterone-induced inhibition of B-type natriuretic peptide and bone morphogenetic protein 4 expression was confirmed in vitro in neonatal mouse cardiomyocytes. Altogether, we demonstrate that, at the cardiac level, hyperaldosteronism worsens hypertension-induced fibrosis through 2 mineralocorticoid receptor-dependent mechanisms, activation of inflammation/galectin 3-induced fibrosis and inhibition of antifibrotic factors (B-type natriuretic peptide and bone morphogenetic protein 4).

Aldosterone, mineralocorticoid receptor, and heart failure.

Several large clinical studies have demonstrated the important benefit of mineralocorticoid receptor (MR) antagonists in patients with heart failure, left ventricular dysfunction after myocardial infarction, hypertension or diabetic nephropathy. Aldosterone adjusts the hydro-mineral balance in the body, and thus participates decisively to the control of blood pressure. This traditional view of the action of aldosterone restricted to sodium reabsorption in epithelial tissues must be revisited. Clinical and experimental studies indicated that chronic activation of the MR in target tissues induces structural and functional changes in the heart, kidneys and blood vessels. These deleterious effects include cardiac and renal fibrosis, inflammation and vascular remodeling. It is important to underscore that these effects are due to elevated MR activation that is inadequate for the body salt requirements. Aldosterone is generally considered as the main ligand of MR. However, this is a matter of debate especially in heart. Complexity arises from the glucocorticoids with circulating concentrations much higher than those of aldosterone, and the fact that the MR has a high affinity for 11ß-hydroxyglucocorticoids. Nevertheless, the beneficial effects of MR inhibition in patients with heart failure emphasize the importance of this receptor in cardiovascular tissue. Diverse experimental models and strains of transgenic mice have allowed to dissect the effects of aldosterone and the MR in the heart. Taken together experimental and clinical data clearly highlight the deleterious cardiovascular effects of MR stimulation.

Muscle creatine kinase deficiency triggers both actin depolymerization and desmin disorganization by advanced glycation end products in dilated cardiomyopathy.

Alterations in the balance of cytoskeleton as well as energetic proteins are involved in the cardiac remodeling occurring in dilated cardiomyopathy (DCM). We used two-dimensional DIGE proteomics as a discovery approach to identify key molecular changes taking place in a temporally controlled model of DCM triggered by cardiomyocyte-specific serum response factor (SRF) knock-out in mice. We identified muscle creatine kinase (MCK) as the primary down-regulated protein followed by α-actin and α-tropomyosin down-regulation leading to a decrease of polymerized F-actin. The early response to these defects was an increase in the amount of desmin intermediate filaments and phosphorylation of the αB-crystallin chaperone. We found that αB-crystallin and desmin progressively lose their striated pattern and accumulate at the intercalated disk and the sarcolemma, respectively. We further show that desmin is a preferential target of advanced glycation end products (AGE) in mouse and human DCM. Inhibition of CK in cultured cardiomyocytes is sufficient to recapitulate both the actin depolymerization defect and the modification of desmin by AGE. Treatment with either cytochalasin D or glyoxal, a cellular AGE, indicated that both actin depolymerization and AGE contribute to desmin disorganization. Heat shock-induced phosphorylation of αB-crystallin provides a transient protection of desmin against glyoxal in a p38 MAPK-dependent manner. Our results show that the strong down-regulation of MCK activity contributes to F-actin instability and induces post-translational modification of αB-crystallin and desmin. Our results suggest that AGE may play an important role in DCM because they alter the organization of desmin filaments that normally support stress response and mitochondrial functions in cardiomyocytes.

Myocardial fibrosis and TGFB expression in hyperhomocysteinemic rats.

Hyperhomocysteinemia, characterized by an elevated plasma homocysteine concentration, leads to several clinical manifestations and particularly cardiovascular diseases. Experimental models of hyperhomocysteinemia revealed several tissue injuries including heart fibrosis and ventricular hypertrophy. In order to analyze the molecular mechanisms link to these morphological alterations, a mild hyperhomocysteinemia was induced in rats via a chronic methionine administration. Effects of methionine administration were examined by histological analysis with Sirius red staining, histomorphometric analysis, zymography, and immunoblotting. Hyperhomocysteinemia due to methionine administration produces an interstitial myocardial fibrosis and a ventricular cardiomyocyte hypertrophy, which were associated with increased expression of transforming growth factor-beta1 (TGFß1), tissue inhibitors of metalloproteinase (TIMP) 2, and JNK activation. However, the matrix metalloproteinase 2 activity was decreased in the hearts of hyperhomocysteinemic rats. Moreover, the TIMP1 protein expression was decreased, and the TIMP1-MMP1 balance was shifted. Remodeling in cardiac tissue observed in rat model of mild hyperhomocysteinemia is associated with a dysregulation in extracellular matrix degradation which results, at least in part, from enhancement of TGFß1 level.