A novel fibroblast activation inhibitor attenuates left ventricular remodeling and preserves cardiac function in heart failure.

Cardiac fibroblasts are critical mediators of fibrotic remodeling in the failing heart and transform into myofibroblasts in the presence of profibrotic factors such as transforming growth factor-ß. Myocardial fibrosis worsens cardiac function, accelerating the progression to decompensated heart failure (HF). We investigated the effects of a novel inhibitor (NM922; NovoMedix, San Diego, CA) of the conversion of normal fibroblasts to the myofibroblast phenotype in the setting of pressure overload-induced HF. NM922 inhibited fibroblast-to-myofibroblast transformation in vitro via a reduction of activation of the focal adhesion kinase-Akt-p70S6 kinase and STAT3/4E-binding protein 1 pathways as well as via induction of cyclooxygenase-2. NM922 preserved left ventricular ejection fraction ( P < 0.05 vs. vehicle) and significantly attenuated transverse aortic constriction-induced LV dilation and hypertrophy ( P < 0.05 compared with vehicle). NM922 significantly ( P < 0.05) inhibited fibroblast activation, as evidenced by reduced myofibroblast counts per square millimeter of tissue area. Picrosirius red staining demonstrated that NM922 reduced ( P < 0.05) interstitial fibrosis compared with mice that received vehicle. Similarly, NM922 hearts had lower mRNA levels ( P < 0.05) of collagen types I and III, lysyl oxidase, and TNF-α at 16 wk after transverse aortic constriction. Treatment with NM922 after the onset of cardiac hypertrophy and HF resulted in attenuated myocardial collagen formation and adverse remodeling with preservation of left ventricular ejection fraction. Future studies are aimed at further elucidation of the molecular and cellular mechanisms by which this novel antifibrotic agent protects the failing heart. NEW & NOTEWORTHY Our data demonstrated that a novel antifibrotic agent, NM922, blocks the activation of fibroblasts, reduces the formation of cardiac fibrosis, and preserves cardiac function in a murine model of heart failure with reduced ejection fraction.

Detrimental role of lysyl oxidase in cardiac remodeling.

A key feature of heart failure is adverse extracellular matrix (ECM) remodeling, which is associated with increases in the collagen cross-linking enzyme, lysyl oxidase (LOX). In this study, we assess the progression of cardiovascular remodeling from the compensatory to decompensatory phase, with a focus on the change in LOX expression and activity as it relates to alterations in ECM composition and changes in cardiac function. Adult male Sprague-Dawley rats were studied after 4, 14, or 21weeks of aortocaval fistula-induced volume overload (VO). Progressive increases in the left and right ventricular mass indicated biventricular hypertrophy. Echocardiography revealed significant increases in the posterior wall thickness and internal diameter of the left ventricle as early as 3weeks, which persisted until the 21week endpoint. There were also significant decreases in eccentric index and fractional shortening in VO animals. Hemodynamic measurements showed progressive decreases in contractility, indicative of systolic dysfunction. There were progressive VO-induced increases in LOX expression and activity, collagen, and collagen cross-linking during the course of these experiments. We observed a negative correlation between LOX activity and cardiac function. Additional rats were treated with an inhibitor of LOX activity starting at 2weeks post-surgery and continued to 14weeks. LOX inhibition prevented the cardiac dysfunction and collagen accumulation caused by VO. Overall these data suggest a detrimental role for the chronic increase of cardiac LOX expression and activity in the transition from compensated remodeling to decompensated failure.

Zofenopril Protects Against Myocardial Ischemia-Reperfusion Injury by Increasing Nitric Oxide and Hydrogen Sulfide Bioavailability.

BACKGROUND: Zofenopril, a sulfhydrylated angiotensin-converting enzyme inhibitor (ACEI), reduces mortality and morbidity in infarcted patients to a greater extent than do other ACEIs. Zofenopril is a unique ACEI that has been shown to increase hydrogen sulfide (H2S) bioavailability and nitric oxide (NO) levels via bradykinin-dependent signaling. Both H2S and NO exert cytoprotective and antioxidant effects. We examined zofenopril effects on H2S and NO bioavailability and cardiac damage in murine and swine models of myocardial ischemia/reperfusion (I/R) injury. METHODS AND RESULTS: Zofenopril (10 mg/kg PO) was administered for 1, 8, and 24 hours to establish optimal dosing in mice. Myocardial and plasma H2S and NO levels were measured along with the levels of H2S and NO enzymes (cystathionine ß-synthase, cystathionine γ-lyase, 3-mercaptopyruvate sulfur transferase, and endothelial nitric oxide synthase). Mice received 8 hours of zofenopril or vehicle pretreatment followed by 45 minutes of ischemia and 24 hours of reperfusion. Pigs received placebo or zofenopril (30 mg/daily orally) 7 days before 75 minutes of ischemia and 48 hours of reperfusion. Zofenopril significantly augmented both plasma and myocardial H2S and NO levels in mice and plasma H2S (sulfane sulfur) in pigs. Cystathionine ß-synthase, cystathionine γ-lyase, 3-mercaptopyruvate sulfur transferase, and total endothelial nitric oxide synthase levels were unaltered, while phospho-endothelial nitric oxide synthase(1177) was significantly increased in mice. Pretreatment with zofenopril significantly reduced myocardial infarct size and cardiac troponin I levels after I/R injury in both mice and swine. Zofenopril also significantly preserved ischemic zone endocardial blood flow at reperfusion in pigs after I/R. CONCLUSIONS: Zofenopril-mediated cardioprotection during I/R is associated with an increase in H2S and NO signaling.

Therapeutic potential of sustained-release sodium nitrite for critical limb ischemia in the setting of metabolic syndrome.

Nitrite is a storage reservoir of nitric oxide that is readily reduced to nitric oxide under pathological conditions. Previous studies have demonstrated that nitrite levels are significantly reduced in cardiovascular disease states, including peripheral vascular disease. We investigated the cytoprotective and proangiogenic actions of a novel, sustained-release formulation of nitrite (SR-nitrite) in a clinically relevant in vivo swine model of critical limb ischemia (CLI) involving central obesity and metabolic syndrome. CLI was induced in obese Ossabaw swine (n = 18) by unilateral external iliac artery deployment of a full cross-sectional vessel occlusion device positioned within an endovascular expanded polytetrafluoroethylene-lined nitinol stent-graft. At post-CLI day 14, pigs were randomized to placebo (n = 9) or SR-nitrite (80 mg, n = 9) twice daily by mouth for 21 days. SR-nitrite therapy increased nitrite, nitrate, and S-nitrosothiol in plasma and ischemic skeletal muscle. Oxidative stress was reduced in ischemic limb tissue of SR-nitrite- compared with placebo-treated pigs. Ischemic limb tissue levels of proangiogenic growth factors were increased following SR-nitrite therapy compared with placebo. Despite the increases in cytoprotective and angiogenic signals with SR-nitrite therapy, new arterial vessel formation and enhancement of blood flow to the ischemic limb were not different from placebo. Our data clearly demonstrate cytoprotective and proangiogenic signaling in ischemic tissues following SR-nitrite therapy in a very severe model of CLI. Further studies evaluating longer-duration nitrite therapy and/or additional nitrite dosing strategies are warranted to more fully evaluate the therapeutic potential of nitrite therapy in peripheral vascular disease.

Hydrogen sulfide cytoprotective signaling is endothelial nitric oxide synthase-nitric oxide dependent.

Previous studies have demonstrated that hydrogen sulfide (H2S) protects against multiple cardiovascular disease states in a similar manner as nitric oxide (NO). H2S therapy also has been shown to augment NO bioavailability and signaling. The purpose of this study was to investigate the impact of H2S deficiency on endothelial NO synthase (eNOS) function, NO production, and ischemia/reperfusion (I/R) injury. We found that mice lacking the H2S-producing enzyme cystathionine γ-lyase (CSE) exhibit elevated oxidative stress, dysfunctional eNOS, diminished NO levels, and exacerbated myocardial and hepatic I/R injury. In CSE KO mice, acute H2S therapy restored eNOS function and NO bioavailability and attenuated I/R injury. In addition, we found that H2S therapy fails to protect against I/R in eNOS phosphomutant mice (S1179A). Our results suggest that H2S-mediated cytoprotective signaling in the setting of I/R injury is dependent in large part on eNOS activation and NO generation.

Cigarette smoke exacerbates ventricular remodeling and dysfunction in the volume overloaded heart.

Cigarette smoking is an independent risk factor for heart disease and is linked to sudden cardiac death. In this study, we examined the effects of cigarette smoke (CS) on the volume overload stressed heart. Our hypothesis was that CS exacerbates volume overload (VO)-induced cardiac dysfunction by accelerating ventricular remodeling. VO stress was surgically induced in male Sprague-Dawley rats by abdominal aortocaval fistula (ACF). Rats, with and without ACF, were exposed to either room air or CS (6 cigarettes/day) for 6 weeks. Temporal echocardiogram measurements indicated that CS significantly increased VO-induced left ventricular dilatation, prevented compensatory wall thickening, and depressed fractional shortening. Morphological analysis of ventricular collagen revealed that CS blunted compensatory collagen expression (45% decrease versus ACF alone). CS exacerbated the VO-induced increase of MMP-9 and TIMP-1 expression in the heart. CS also blocked the compensatory increases of HIF-1α, VEGF, and TGF-ß in the VO-stressed heart. These data indicate that CS worsens VO remodeling by disrupting compensatory mechanisms, thereby promoting eccentric dilation and dysfunction.

Estrogen attenuates chronic volume overload induced structural and functional remodeling in male rat hearts.

We have previously reported gender differences in ventricular remodeling and development of heart failure using the aortocaval fistula model of chronic volume overload in rats. In contrast to males, female rats exhibited no adverse ventricular remodeling and less mortality in response to volume overload. This gender-specific cardioprotection was lost following ovariectomy and was partially restored using estrogen replacement. However, it is not known if estrogen treatment would be as effective in males. The purpose of this study was to evaluate the structural and functional effects of estrogen in male rats subjected to chronic volume overload. Four groups of male rats were studied at 3 days and 8 wk postsurgery as follows: fistula and sham-operated controls, with and without estrogen treatment. Biochemical and histological studies were performed at 3 days postsurgery, with chronic structural and functional effects studied at 8 wk. Measurement of systolic and diastolic pressure-volume relationships was obtained using a blood-perfused isolated heart preparation. Both fistula groups developed significant ventricular hypertrophy after 8 wk of volume overload. Untreated rats with fistula exhibited extensive ventricular dilatation, which was coupled with a loss of systolic function. Estrogen attenuated left ventricular dilatation and maintained function in treated rats. Estrogen treatment was also associated with a reduction in oxidative stress and circulating endothelin-1 levels, as well as prevention of matrix metalloproteinase-2 and -9 activation and breakdown of ventricular collagen in the early stage of remodeling. These data demonstrate that estrogen attenuates ventricular remodeling and disease progression in male rats subjected to chronic volume overload.