(MABP) and heart rate (HR), endothelial dysfunction, and attenuated pressor responses to vasoactive agents. We investigated whether these abnormalities are due to diabetes-associated activation of inducible nitric oxide synthase (iNOS). In addition, the effect of the duration of diabetes on these abnormalities was also evaluated. Diabetes was induced by administration of 60 mg/kg STZ via the tail vein. One, 3, 9, or 12 wk after STZ injection, MABP, HR, and endothelial function were measured in conscious unrestrained rats. Pressor response curves to bolus doses of methoxamine (MTX) and angiotensin II (ANG II) were constructed in the presence of N- [3(aminomethyl)benzyl]-acetamidine, dihydrochloride (1400W), a specific inhibitor of iNOS. Depressed MABP and HR and impairment of endothelial function were observed as early as 3 wk after induction of diabetes. Acute inhibition of iNOS with 1400W (3 mg/kg iv) restored the attenuated pressor responses to both MTX and ANG II without affecting the basal MABP and HR. Immunohistochemical and Western analysis blot studies in cardiovascular tissues revealed decreased expression of endothelial nitric oxide synthase (eNOS) concomitant with increased expression of iNOS and nitrotyrosine with the progression of diabetes. Our findings suggest that induction of iNOS in cardiovascular tissues is dependent on the duration of diabetes and contributes significantly to the depressed pressor responses to vasoactive agents and potentially to endothelial dysfunction. inducible nitric oxide synthase; nitric oxide; cardiovascular abnormalities CHRONIC HYPERGLYCEMIA has been shown to directly affect the composition and structure of cardiac, vascular, and renal tissues, the progressive modification of which results in a deranged cardiovascular homeostasis (8). Cardiovascular depression, characterized by depressed mean arterial blood pressure (MABP), heart rate (HR), and attenuated pressor responses to vasoactive agents is one of the most notable manifestations of this derangement, particularly in animal models of Type 1 diabetes. Although the exact mechanisms by which diabetes contributes to cardiovascular depression are currently unknown, it is likely that hyperglycemia may initiate this abnormality through the activation of protein kinase C, increased activity of the polyol pathway, formation of nonenzymatic advanced glycosylation end products, oxidative stress, and/or possibly by induction of nitric oxide (NO) synthase (NOS) (19,42).The role of NO in the regulation of hemodynamics under hyperglycemic conditions has been controversial. Despite an impairment of endothelial function and reduced bioavailability of endothelium-derived NO, streptozotocin (STZ)-induced diabetic rats are not hypertensive but instead are normotensive or hypotensive (9,14,18,20,23,31,39,44). In addition, an increased dependence on a functional NO system at the onset of diabetes has been reported to prevent the development of hypertension in STZ diabetic rats (12). It has been suggested that increased NO synthesis m...

The cardiac stroma contains multipotent mesenchymal progenitors. However, lineage relationships within cardiac stromal cells are still poorly understood. Here, we identify heartresident PDGFRa + Sca-1 + cells as cardiac Fibro/Adipogenic Progenitors (cFAPs) and show that they respond to ischemic damage by generating fibrogenic cells. Pharmacological blockade of this differentiation step with an anti-fibrotic tyrosine kinase inhibitor decreases post-myocardial infarction (MI) remodeling and leads to improvements in heart function. In the undamaged heart, activation of cFAPs through lineage-specific deletion of the quiescence factor Hic1 reveals additional pathogenic potential, causing fibro-fatty infiltration of the myocardium and driving major pathological features of Arrhythmogenic Cardiomyopathy (AC). Highlights• A subpopulation of PDGFRa + , Sca-1 + cells, previously considered to be a sub-type of cardiac fibroblasts, are multipotent mesenchymal progenitors,• Cardiac damage triggers the differentiation of PDGFRa + Sca-1 + cells into Sca-1cells expressing a fibrogenic transcriptional programme,• Blockade of the cFAP-to-fibroblast transition by Nilotinib ameliorated cardiac dysfunction post-MI and modulated cardiac remodelling.• Studies performed on a model of experimentally-induced AC confirmed that cFAPs are a source of both cardiac fibroblasts and adipocytes in vivo.• Conversely, in the undamaged heart, activation of cFAPs by means of lineage-specific deletion of transcription factor Hic1, resulted in fibro/fatty cardiac degeneration and pathological alterations reminiscent of AC. Collectively, our findings show that a proportion of what are commonly termed "fibroblasts" are actually multipotent .

No abstract

No abstract

Objective: The purpose of the present study was to determine whether increased activation of the RhoA/Rho-kinase (ROCK) pathway occurs in diabetic cardiomyopathy and whether acute inhibition of this pathway improves contractile function of the diabetic heart. Methods: Male Wistar rats were made diabetic with streptozotocin. Twelve to fourteen weeks later, the effects of acute administration of the ROCK inhibitors Y-27632 and H-1152 on cardiac contractile function were measured both in vitro, in isolated working hearts, and in vivo, using echocardiography. Changes in the expression and activity of RhoA, and the effect of ROCK inhibition on changes in the phosphorylation of the downstream target of ROCK, LIM kinase 2, and on actin polymerization in diabetic hearts were also determined. Results: Perfusion of isolated working hearts from diabetic rats with Y-27632 or H-1152 acutely improved left ventricle developed pressure and the rates of contraction and relaxation. Acute administration of H-1152 also significantly improved the percent fraction shortening, an index of left ventricle contractility, in vivo in diabetic rats. The expression and activity of RhoA in cardiomyocytes from diabetic rats were significantly increased, as was the phosphorylation of LIM kinase 2. This was associated with an increase in actin polymerization (the F-actin to G-actin ratio). Both the increase in LIM kinase 2 phosphorylation and actin polymerization were attenuated by ROCK inhibition. Conclusions: These data suggest that activation of the RhoA/ROCK signaling pathway plays a critical role in the development of diabetic cardiomyopathy, and that ROCK is an excellent therapeutic target in the treatment of this condition.

The influence of experimental diabetes induced by streptozotocin on responses of rat isolated aortae and portal veins to noradrenaline, 5-hydroxytryptamine, and KCl was examined 7, 100, 180, and 360 days after the onset of diabetes. No significant changes in reactivity were seen 7 days after the onset of diabetes. After 100 days aortae from diabetic rats were supersensitive (defined as a significant increase in the pD2 value) to noradrenaline. However, 180 days after the onset of diabetes, the sensitivity of diabetic aortae to noradrenaline was not significantly different from control, while the responsiveness (defined as the maximum developed tension divided by cross-sectional area of aorta) to 5-hydroxytryptamine was reduced. A generalized increase in both the sensitivity and responsiveness of diabetic aortae to all three agonists was observed after 360 days of diabetes. In contrast, no changes in either the sensitivity or the responsiveness of portal veins to noradrenaline, 5-hydroxytryptamine, or KCl could be detected at any time after the onset of diabetes. These results indicate that changes in vascular reactivity can be detected with increasing duration of experimental diabetes. However, these changes do not follow a consistent pattern and are not seen in all parts of the vasculature.

The purpose of this study was to investigate the effect of chronic treatment with etanercept (a soluble recombinant fusion protein consisting of the extracellular ligand-binding domain of tumor necrosis factor receptor type 2) on the development of hypertension in fructose-fed rats (FFR). High fructose feeding and treatment with etanercept (0.3 mg/kg, three times per week) was initiated simultaneously in male Wistar rats. Systolic blood pressure, fasted plasma parameters, insulin sensitivity, vascular reactivity, plasma angiotensin II (Ang II), and norepinephrine were determined following 9 weeks of treatment. FFR exhibited insulin resistance, hyperinsulinemia, hypertriglyceridemia, endothelial dysfunction, and hypertension. Treatment with etanercept prevented the rise in blood pressure without affecting insulin levels, insulin sensitivity, triglycerides, or Ang II levels in FFR. Etanercept treatment improved acetylcholine-induced relaxation and normalized endothelial nitric oxide synthase expression in aortas from FFR. The results of this study suggest that treatment with etanercept prevented the development of hypertension by improving vascular function and restoring endothelial nitric oxide synthase expression in FFR.

OBJECTIVEImpaired cardiovascular function in diabetes is partially attributed to pathological overexpression of inducible nitric oxide synthase (iNOS) in cardiovascular tissues. We examined whether the hyperglycemia-induced increased expression of iNOS is protein kinase C-β2 (PKCβ2) dependent and whether selective inhibition of PKCβ reduces iNOS expression and corrects abnormal hemodynamic function in streptozotocin (STZ)-induced diabetic rats.RESEARCH DESIGN AND METHODSCardiomyocytes and aortic vascular smooth muscle cells (VSMC) from nondiabetic rats were cultured in low (5.5 mmol/l) or high (25 mmol/l) glucose or mannitol (19.5 mmol/l mannitol + 5.5 mmol/l glucose) conditions in the presence of a selective PKCβ inhibitor, LY333531 (20 nmol/l). Further, the in vivo effects of PKCβ inhibition on iNOS-mediated cardiovascular abnormalities were tested in STZ-induced diabetic rats.RESULTSExposure of cardiomyocytes to high glucose activated PKCβ2 and increased iNOS expression that was prevented by LY333531. Similarly, treatment of VSMC with LY333531 prevented high glucose–induced activation of nuclear factor κB, extracellular signal–related kinase, and iNOS overexpression. Suppression of PKCβ2 expression by small interference RNA decreased high-glucose–induced nuclear factor κB and extracellular signal–related kinase activation and iNOS expression in VSMC. Administration of LY333531 (1 mg/kg/day) decreased iNOS expression and formation of peroxynitrite in the heart and superior mesenteric arteries and corrected the cardiovascular abnormalities in STZ-induced diabetic rats, an action that was also observed with a selective iNOS inhibitor, L-NIL.CONCLUSIONSCollectively, these results suggest that inhibition of PKCβ2 may be a useful approach for correcting abnormal hemodynamics in diabetes by preventing iNOS mediated nitrosative stress.