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Heart failure with preserved ejection fraction (HFpEF) is a widespread syndrome with limited therapeutic options and poorly understood immune pathophysiology. Using a 2-hit preclinical model of cardiometabolic HFpEF that induces obesity and hypertension, we found that cardiac T cell infiltration and lymphoid expansion occurred concomitantly with cardiac pathology and that diastolic dysfunction, cardiomyocyte hypertrophy, and cardiac phospholamban phosphorylation were T cell dependent. Heart-infiltrating T cells were not restricted to cardiac antigens and were uniquely characterized by impaired activation of the inositol-requiring enzyme 1[alpha]/X-box-binding protein 1 (IRE1[alpha]/XBP1) arm of the unfolded protein response. Notably, selective ablation of XBP1 in T cells enhanced their persistence in the heart and lymphoid organs of mice with preclinical HFpEF. Furthermore, T cell IRE1[alpha]/XBP1 activation was restored after withdrawal of the 2 comorbidities inducing HFpEF, resulting in partial improvement of cardiac pathology. Our results demonstrated that diastolic dysfunction and cardiomyocyte hypertrophy in preclinical HFpEF were T cell dependent and that reversible dysregulation of the T cell IRE1[alpha]/ XBP1 axis was a T cell signature of HFpEF., Introduction Widely regarded as the greatest unmet need in cardiovascular medicine, heart failure with preserved ejection fraction (HFpEF) is a complex and heterogeneous syndrome accounting for roughly 50% of HF [...]

ObjectiveVein graft failure rates resulting from adverse graft remodeling remain high with no effective therapy. The mineralocorticoid receptor (MR) plays a role in pathologic arterial remodeling. We demonstrated recently that the MR is upregulated in venous tissues after grafting and hypothesized that MR inhibition would reduce vein graft remodeling.MethodsReverse transcription polymerase chain reaction and immunoblotting were used to examine the expression of the MR and other components of the renin-angiotensin-aldosterone system in human vein and primary human saphenous vein smooth muscle cells (HSVSMC). Adenoviral reporter gene assays were used to explore MR transcriptional activity in HSVSMC. The effect of MR inhibition on vein graft remodeling in vivo was characterized in a mouse vein graft model.ResultsMessenger RNAs encoding the MR, 11-β-hydroxysteroid dehydrogenase 2, angiotensin type 1 receptor, and the angiotensin-converting enzyme are expressed in whole HSVSMC. MR and 11-β-hydroxysteroid dehydrogenase 2 protein expression is confirmed, and MR-dependent transcriptional regulation is demonstrated at physiologic aldosterone concentrations in HSVSMC. Treatment of mice with the MR antagonist spironolactone, at doses that do not lower blood pressure (20 mg/kg per day), reduces maximal vein graft intima-media thickness by 68%, with an associated reduction in graft inflammatory cell infiltration and fibrosis.ConclusionsMR is expressed in human venous tissue and cells and modulates gene expression in HSVSMC in response to physiologic aldosterone concentrations. In vivo, MR inhibition reduces vein graft thickening and inflammation. These preclinical data support the potential to use MR antagonists as novel treatments to preserve vein graft patency.

In clinical trials, aldosterone antagonists reduce cardiovascular ischemia and mortality by unknown mechanisms. Aldosterone is a steroid hormone that signals through renal mineralocorticoid receptors (MRs) to regulate blood pressure. MRs are expressed and regulate gene transcription in human vascular cells, suggesting that aldosterone might have direct vascular effects. Using gene expression profiling, we identify the pro-proliferative VEGF family member placental growth factor (PGF) as an aldosterone-regulated vascular MR target gene in mice and humans. Aldosterone-activated vascular MR stimulated Pgf gene transcription and increased PGF protein expression and secretion in the mouse vasculature. In mouse vessels with endothelial damage and human vessels from patients with atherosclerosis, aldosterone enhanced expression of PGF and its receptor, FMS-like tyrosine kinase 1 (Flt1). In atherosclerotic human vessels, MR antagonists inhibited PGF expression. In vivo, aldosterone infusion augmented vascular remodeling in mouse carotids following wire injury, an effect that was lost in [Pgf.sup.-/-] mice. In summary, we have identified PGF as what we believe to be a novel downstream target of vascular MR that mediates aldosterone augmentation of vascular injury. These findings suggest a non-renal mechanism for the vascular protective effects of aldosterone antagonists in humans and support targeting the vascular aldosterone/MR/PGF/Flt1 pathway as a therapeutic strategy for ischemic cardiovascular disease., Introduction In heart failure trails, in addition to reducing cardiovascular mortality, aldosterone antagonists have also been unexpectedly shown to significantly reduce atherosclerotic clinical events by mechanisms that remain unclear (1), [...]

Parasympathetic stimulation of the heart, which provides protection from arrhythmias and sudden death, involves activation of the G protein--coupled inward rectifying [K.sup.+] channel GIRK1/4 and results in an acetylcholine-sensitive [K.sup.+] current, [I.sub.KACh]. We describe a unique relationship between lipid homeostasis, the lipid-sensitive transcription factor SREBP-1, regulation of the cardiac parasympathetic response, and the development of ventricular arrhythmia. In embryonic chick atrial myocytes, lipid lowering by culture in lipoprotein-depleted serum increased SREBP-1 levels, GIRK1 expression, and [I.sub.KACh] activation. Regulation of the GIRK1 promoter by SREBP-1 and lipid lowering was dependent on interaction with 2 tandem sterol response elements and an upstream E-box motif. Expression of dominant negative SREBP-1 (DN--SREBP-1) reversed the effect of lipid lowering on [I.sub.KACh] and GIRK1. In SREBP-1 knockout mice, both the response of the heart to parasympathetic stimulation and the expression of GIRK1 were reduced compared with WT. [I.sub.KACh], attenuated in atrial myocytes from SREBP-1 knockout mice, was stimulated by SREBP-1 expression. Following myocardial infarction, SREBP-1 knockout mice were twice as likely as WT mice to develop ventricular tachycardia in response to programmed ventricular stimulation. These results demonstrate a relationship between lipid metabolism and parasympathetic response that may play a role in arrhythmogenesis., Introduction The balance between the response of the heart to sympathetic and parasympathetic stimuli not only determines the rate and force of contraction but also plays a role in regulating [...]

Nitric oxide (NO) inhibits vascular contraction by activating cGMP-dependent protein kinase I-[alpha] (PKGI-[alpha]), which causes dephosphorylation of myosin light chain (MLC) and vascular smooth muscle relaxation. Here we show that PKGI-[alpha] attenuates signaling by the thrombin receptor protease-activated receptor-1 (PAR-1) through direct activation of regulator of G-protein signaling-2 (RGS-2). NO donors and cGMP cause cGMP-mediated inhibition of PAR-1 and membrane localization of RGS-2. PKGI-[alpha] binds directly to and phosphorylates RGS-2, which significantly increases GTPase activity of G[sub.q], terminating PAR-1 signaling. Disruption of the RGS-2-PKGI-[alpha] interaction reverses inhibition of PAR-1 signaling by nitrovasodilators and cGMP. Rgs2[sup.-/-] mice develop marked hypertension, and their blood vessels show enhanced contraction and decreased cGMP-mediated relaxation. Thus, PKGI-[alpha] binds to, phosphorylates and activates RGS-2, attenuating receptor-mediated vascular contraction. Our study shows that RGS-2 is required for normal vascular function and blood pressure and is a new drug development target for hypertension., Author(s): Mary Tang [1]; Guang Wang [1]; Ping Lu [1, 4]; Richard H Karas [1]; Mark Aronovitz [1]; Scott P Heximer [2]; Kevin M Kaltenbronn [2]; Kendall J Blumer [2]; [...]

P-selectin, a glycoprotein, influences the congregation of leukocytes and platelets required to form a thrombus or blood clot. P-selectin is a cell adhesion molecule that controls the interaction of two types of leukocyte, monocytes and neutrophils, with platelets and endothelial cells. Experimental work with the thrombi of baboons added many details to the process by which P-selectin effects leukocyte-platelet adhesion, for instance by inducing the leukocytes to cause the formation of fibrin.

BACKGROUND: Mineralocorticoid receptor (MR) antagonists decrease heart failure (HF) hospitalization and mortality, but the mechanisms are unknown. Preclinical studies reveal that the benefits on cardiac remodeling and dysfunction are not completely explained by inhibition of MR in cardiomyocytes, fibroblasts, or endothelial cells. The role of MR in smooth muscle cells (SMCs) in HF has never been explored. METHODS: Male mice with inducible deletion of MR from SMCs (SMC-MR-knockout) and their MR-intact littermates were exposed to HF induced by 27-gauge transverse aortic constriction versus sham surgery. HF phenotypes and mechanisms were measured 4 weeks later using cardiac ultrasound, intracardiac pressure measurements, exercise testing, histology, cardiac gene expression, and leukocyte flow cytometry. RESULTS: Deletion of MR from SMC attenuated transverse aortic constriction-induced HF with statistically significant improvements in ejection fraction, cardiac stiffness, chamber dimensions, intracardiac pressure, pulmonary edema, and exercise capacity. Mechanistically, SMC-MR-knockout protected from adverse cardiac remodeling as evidenced by decreased cardiomyocyte hypertrophy and fetal gene expression, interstitial and perivascular fibrosis, and inflammatory and fibrotic gene expression. Exposure to pressure overload resulted in a statistically significant decline in cardiac capillary density and coronary flow reserve in MR-intact mice. These vascular parameters were improved in SMC-MR-knockout mice compared with MR-intact littermates exposed to transverse aortic constriction. CONCLUSIONS: These results provide a novel paradigm by which MR inhibition may be beneficial in HF by blocking MR in SMC, thereby improving cardiac blood supply in the setting of pressure overload–induced hypertrophy, which in turn mitigates the adverse cardiac remodeling that contributes to HF progression and symptoms. [ABSTRACT FROM AUTHOR]