Epidemiologic studies have previously suggested that premenopausal females have reduced incidence of cardiovascular disease (CVD) when compared to age-matched males, and the incidence and severity of CVD increases postmenopause. The lower incidence of cardiovascular disease in women during reproductive age is attributed at least in part to estrogen (E2). E2 binds to the traditional E2 receptors (ERs), estrogen receptor alpha (ERα), and estrogen receptor beta (ERβ), as well as the more recently identified G-protein-coupled ER (GPR30), and can exert both genomic and non-genomic actions. This review summarizes the protective role of E2 and its receptors in the cardiovascular system and discusses its underlying mechanisms with an emphasis on oxidative stress, fibrosis, angiogenesis, and vascular function. This review also presents the sexual dimorphic role of ERs in modulating E2 action in cardiovascular disease. The controversies surrounding the clinical use of exogenous E2 as a therapeutic agent for cardiovascular disease in women due to the possible risks of thrombotic events, cancers, and arrhythmia are also discussed. Endogenous local E2 biosynthesis from the conversion of testosterone to E2 via aromatase enzyme offers a novel therapeutic paradigm. Targeting specific ERs in the cardiovascular system may result in novel and possibly safer therapeutic options for cardiovascular protection.

Rationale: Pulmonary hypertension (PH) is characterized by progressive increase in pulmonary artery pressure leading to right ventricular (RV) hypertrophy, RV failure, and death. Current treatments only temporarily reduce severity of the disease, and an ideal therapy is still lacking. Objectives: Estrogen pretreatment has been shown to attenuate development of PH. Because PH is not often diagnosed early, we examined if estrogen can rescue preexisting advanced PH. Methods: PH was induced in male rats with monocrotaline (60 mg/kg). At Day 21, rats were either treated with 17-b estradiol or estrogen (E2, 42.5 mg/kg/d), estrogen receptor-b agonist (diarylpropionitrile, 850 mg/kg/d), or estrogen receptor a-agonist (4,4',4"-[4-Propyl-(1H)-pyrazole-1,3,5-triyl] trisphenol, 850 mg/kg/d) for 10 days or left untreated to develop RV failure. Serial echocardiography, cardiac catheterization, immunohistochemistry, Western blot, and real-time polymerase chain reaction were performed. Measurements and Main Results: Estrogen therapy prevented progression of PH to RV failure and restored lung and RV structure and function. This restoration was maintained even after removal of estrogen at Day 30, resulting in 100% survival at Day 42. Estradiol treatment restored the loss of blood vessels in the lungs and RV. In the presence of angiogenesis inhibitor TNP-470 (30 mg/kg) or estrogen receptor-b antagonist (PHTPP, 850 mg/kg/d), estrogen failed to rescue PH. Estrogen receptor-b selective agonist was as effective as estrogen in rescuing PH. Conclusions: Estrogen rescues preexisting severe PH in rats by restoring lung and RV structure and function that are maintained even after removal of estrogen. Estrogen-induced rescue of PH is associated with stimulation of cardiopulmonary neoangiogenesis, suppression of inflammation, fibrosis, and RV hypertrophy. Furthermore, estrogen rescue is likely mediated through estrogen receptor-b.Keywords: pulmonary hypertension; estrogen; neoangiogenesis; estrogen receptors; inflammation Pulmonary hypertension (PH) is a chronic lung disease characterized by pulmonary vascular remodeling and progressive increase in pulmonary artery pressure leading to right ventricular (RV) hypertrophy and RV failure (RVF). End-stage RVF has long been regarded as a terminal state of pathological cardiopulmonary remodeling, including fibrosis and chamber dilation, being unresponsive to available therapies. Advanced PH is most often treated with aggressive nonpharmacological therapies, such as lung transplantation, but this approach is only feasible for a fraction of patients. In the past decade, cell and gene therapies have shown great potential for treatment of PH in animal models (1, 2) and humans (3). However, effective pharmacological therapy for treatment of patients with advanced PH would be much more practical and much more cost effective. Several agents have been identified to attenuate the development of PH when the therapy is started before the initiating stimuli (4-6). Unfortunately, up to now, there has been no id...

Background Intralipid, a brand name for the first safe fat emulsion for human use, has been shown to be cardioprotective. However, the mechanism of this protection is not known. Here we investigated the molecular mechanism(s) of Intralipid-induced cardioprotection against ischemia/reperfusion injury, particularly the role of GSK-3β and mitochondiral permeability transition pore in this protective action. Methods In-vivo rat hearts or isolated Langendorff-perfused mouse hearts were subjected to ischemia followed by reperfusion with Intralipid (1% in ex-vivo and one bolus of 20% in in-vivo) or vehicle. The hemodynamic function, infarct size, threshold for the opening of mitochondiral permeability transition pore and phosphorylation levels of Akt/ERK/GSK-3β were measured. Results Administration of Intralipid at the onset of reperfusion resulted in ~70% reduction in infarct size in the in-vivo rat model. Intralipid also significantly improved functional recovery of isolated Langendorff-perfused mouse hearts as the rate pressure product was increased from 2999±863mmHg*beats/min in control to 13676±611 mmHg*beats/min (Mean±SEM) and the infarct size was markedly smaller (18.3±2.4% vs. 54.8±2.9% in control, P<0.01). The Intralipid-induced cardioprotection was fully abolished by LY294002, a specific inhibitor of PI3K, but only partially by PD98059, a specific ERK inhibitor. Intralipid also increased the phosphorylation levels of Akt/ERK1/GSK-3β by 8, 3 and 9 fold, respectively. The opening of mitochondiral permeability transition pore was inhibited by Intralipid as calcium retention capacity was higher in Intralipid group (274.3±8.4nM/mg vs. 168.6±9.6nM/mg control). Conclusions Postischemic treatment with Intralipid inhibits the opening of mitochondiral permeability transition pore and protects the heart through GSK-3β via PI3K/Akt/ERK pathways.

Nitric oxide (NO) produced in the heart by nitric oxide synthase (NOS) is a highly reactive signaling molecule and an important modulator of myocardial function. NOS catalyzes the conversion of L: -arginine to L: -citrulline and NO but under particular circumstances reactive oxygen species (ROS) can be formed instead of NO (uncoupling). In the heart, three NOS isoforms are present: neuronal NOS (nNOS, NOS1) and endothelial NOS (eNOS, NOS3) are constitutively present enzymes in distinct subcellular locations within cardiomyocytes, whereas inducible NOS (iNOS, NOS2) is absent in the healthy heart, but its expression is induced by pro-inflammatory mediators. In the tissue, NO has two main effects: (i) NO stimulates the activity of guanylate cyclase, leading to cGMP generation and activation of protein kinase G, and (ii) NO nitrosylates tyrosine and thiol-groups of cysteine in proteins. Upon nitrosylation, proteins may change their properties. Changes in (i) NOS expression and activity, (ii) subcellular compartmentation of NOS activity, and (iii) the occurrence of uncoupling may lead to multiple NO-induced effects, some of which being particularly evident during myocardial overload as occurs during aortic constriction and myocardial infarction. Many of these NO-induced effects are considered to be cardioprotective but particularly if NOS becomes uncoupled, formation of ROS in combination with a low NO bioavailability predisposes for cardiac damage.

OBJECTIVES Lipid Emulsion (LE) has been shown to be effective in resuscitating bupivacaine-induced cardiac arrest but its mechanism of action is not clear. Here we investigated whether fatty acid oxidation is required for rescue of bupivacaine induced cardiotoxicity by LE in rats. We also compared the mitochondrial function and calcium threshold for triggering of mitochondrial permeability transition pore (mPTP) opening in bupivacaine-induced cardiac arrest before and after resuscitation with LE. DESIGN Prospective, randomized, animal study. SETTING University Research Laboratory. SUBJECTS Adult male Sprague-Dawley rats. INTERVENTIONS Asystole was achieved with a single dose of bupivacaine (10mg/kg over 20seconds, i.v.) and 20% LE infusion (5ml/kg bolus, and 0.5ml/kg/min maintenance) with cardiac massage started immediately. The rats in CVT group were pretreated with a single dose of fatty acid oxidation inhibitor CVT (0.5, 0.25, 0.125 or 0.0625mg/kg bolus i.v.) 5min prior to inducing asystole by bupivacaine overdose. Heart rate (HR), ejection fraction (EF), fractional shortening (FS), the threshold for opening of mPTP, oxygen consumption and membrane potential were measured. The values are Mean±SEM. MEASUREMENTS AND MAIN RESULTS Administration of bupivacaine resulted in asystole. ILP infusion improved the cardiac function gradually as the EF was fully recovered within 5min (EF=64±4% and FS=36±3%, n=6) and heart rate increased to 239±9 beats/min (71% recovery, n=6) within 10min. LE was only able to rescue rats pretreated with low dose of CVT (0.0625mg/kg) (HR=~181±11 beats/min at 10 min, recovery of 56%; EF=50±1%; FS=26±0.6% at 5min, n=3) but was unable to resuscitate rats pretreated with higher doses of CVT (0.5, 0.25 or 0.125mg/kg). The calcium retention capacity in response to Ca2+ overload was significantly higher in cardiac mitochondria isolated from rats resuscitated with 20% LE compared to the group that did not receive ILP after bupivacaine-overdose (330±42 vs. 180±8.2 nmol/mg-mitochondrial protein, p<0.05, n=3 in each group). The mitochondrial oxidative rate and membrane potential were similar in bupivacaine group before and after resuscitation with LE infusion. CONCLUSIONS Fatty acid oxidation is required for successful rescue of bupivacaine induced cardiotoxicity by LE. This rescue action is associated with inhibition of mitochondrial permeability transition pore opening.