Sara Amor

Effects of Coronary Ischemia-Reperfusion in a Rat Model of Early Overnutrition. Role of Angiotensin Receptors

Background Obesity during childhood has dramatically increased worldwide in the last decades. Environmental factors acting early in life, including nutrition, play an important role in the pathogenesis of obesity and cardiovascular diseases in adulthood. Aims To analyze the effects of early overfeeding on the heart and coronary circulation, the effect of ischemia-reperfusion (I/R) and the role of the renin-angiotensin system (RAS) were studied in isolated hearts from control and overfed rats during lactation. Methods and Results On the day of birth litters were adjusted to twelve pups per mother (control) or to three pups per mother (overfed). At weaning (21 days) the rats were killed and the heart perfused in a Langendorff system and subjected to 30 min of ischemia followed by 15 min of reperfusion. The contractility (left developed intraventricular pressure) was lower in the hearts from overfed rats, and was reduced by I/R in hearts from control but not from overfed rats. I/R also reduced the coronary vasoconstriction to angiotensin II more in hearts from control than from overfed rats, and the vasodilatation to bradykinin similarly in both experimental groups. The expression of both angiotensin AGTRa and AGTR2 receptors was increased in the myocardium of overfed rats, and I/R increased the expression of both receptors in control rats but reduced it in overfed rats. The expression of apoptotic and antiapoptotic markers was increased in hearts of overfed rats compared with control, and further increased by I/R. Conclusions These results suggest that both overfeeding and I/R impair cardiac and coronary function due, at least in part, to activation of the angiotensin pathway. However, overfeeding may reduce the impairment of ventricular contractility by I/R.

Altered expression of P2Y2 and P2X7 purinergic receptors in the isolated rat heart mediates ischemia-reperfusion injury.

The aim of this study is to analyze the expression of purinergic receptors in the heart after ischemia-reperfusion, and their possible role in ischemia-reperfusion injury. Rat hearts were perfused according to the Langendorff technique and subjected to 30 min ischemia followed by 15 min reperfusion. Ischemia-reperfusion reduced the gene expression and protein content of purinergic receptors of the P2Y2 subtype, and increased the gene expression and protein content of the P2X7 subtype. Treatment with the agonist of the P2Y2 subtype 2-thio-UTP and with the antagonist of the P2X7 subtype Brilliant Blue improved myocardial function parameters, reduced cell death and increased the myocardial expression of antiapoptotic markers after ischemia-reperfusion. These results suggest that the myocardial expression of the protective P2Y2 subtype of purinergic receptors is reduced, whereas that of the harmful subtype P2X7 subtype is increased during coronary ischemia-reperfusion. This may contribute to myocardial injury in this condition.

Effects of age and caloric restriction on the cardiac and coronary response to endothelin-1 in rats

BACKGROUND AND AIMS Aging is associated with alterations in the cardiovascular system such as increased vasoconstriction and decreased vasodilatation. Some of these changes are partially reversed by caloric restriction. Endothelin-1 is a potent vasoconstrictor which levels increased with age. The aim of this study is to analyze the role of endothelin-1 in the cardiac and coronary changes induced by age and whether these changes may be attenuated by a three-month caloric restriction. METHODS AND RESULTS Hearts from young (3 months old), aged (24 months old) and aged rats after 3 months of caloric restriction were perfused according to the Langendorff technique. Coronary vasoconstriction to endothelin-1 was reduced in old rats, and endothelin-1 increased myocardial contractility (dP/dt) and heart rate in old but not in young rats. These changes observed in old rats were partly reversed by caloric restriction. Also, in the myocardial tissue of old rats the gene expression of endothelin-1, inducible nitric oxide synthase (iNOS) and tumor necrosis factor alpha (TNF-a) was increased, and the gene expression of endothelin ETB receptors and endothelial nitric oxide syntase (eNOS) was reduced, compared with young rats. Aging induced changes in the expression of ETB receptors and eNOS were reversed by caloric restriction. CONCLUSIONS These results suggest that aging produces alterations in myocardial and coronary responses to endothelin-1, that may be related to changes in expression of nitric oxide synthases and/or endothelin receptor subtypes, with some of these changes being prevented by caloric restriction.

Long-Term Effects of Early Overnutrition in the Heart of Male Adult Rats: Role of the Renin-Angiotensin System

To analyze the long-term effects of early overfeeding on the heart and coronary circulation, the effect of ischemia-reperfusion (I/R) and the role of the renin-angiotensin system (RAS) was studied in isolated hearts from control and overfed rats during lactation. On the day of birth litters were adjusted to twelve pups per mother (controls) or to three pups per mother (overfed). At 5 months of age, the rats from reduced litters showed higher body weight and body fat than the controls. The hearts from these rats were perfused in a Langendorff system and subjected to 30 min of ischemia followed by 15 min of reperfusion (I/R). The myocardial contractility (dP/dt) and the coronary vasoconstriction to angiotensin II were lower, and the expression of the apoptotic marker was higher, in the hearts from overfed rats compared to controls. I/R reduced the myocardial contractily, the coronary vasoconstriction to angiotensin II and the vasodilatation to bradykinin, and increased the expression of (pro)renin receptor and of apoptotic and antiapoptotic markers, in both experimental groups. I/R also increased the expression of angiotensinogen in control but not in overfed rats. In summary, the results of this study suggest that early overnutrition induces reduced activity of the RAS and impairment of myocardial and coronary function in adult life, due to increased apoptosis. Ischemia-reperfusion produced myocardial and coronary impairment and apoptosis, which may be related to activation of RAS in control but not in overfed rats, and there may be protective mechanisms in both experimental groups.

Effects of age and caloric restriction in the vascular response of renal arteries to endothelin-1 in rats

&NA; Cardiovascular alterations are the most prevalent cause of impaired physiological function in aged individuals with kidney being one the most affected organs. Aging‐induced alterations in renal circulation are associated with a decrease in endothelium‐derived relaxing factors such as nitric oxide (NO) and with an increase in contracting factors such as endothelin‐1(ET‐1). As caloric restriction (CR) exerts beneficial effects preventing some of the aging‐induced alterations in cardiovascular system, the aim of this study was to analyze the effects of age and caloric restriction in the vascular response of renal arteries to ET‐1 in aged rats. Vascular function was studied in renal arteries from 3‐month‐old Wistar rats fed ad libitum (3 m) and in renal arteries from 8‐and 24‐month‐old Wistar rats fed ad libitum (8 m and 24 m), or subjected to 20% caloric restriction during their three last months of life (8 m‐CR and 24 m‐CR). The contractile response to ET‐1 was increased in renal arteries from 8 m and 24 m compared to 3 m rats. ET‐1‐induced contraction was mediated by ET‐A receptors in all experimental groups and also by ET‐B receptors in 24 m rats. Caloric restriction attenuated the increased contraction to ET‐1 in renal arteries from 8 m but not from 24 m rats possibly through NO release proceeding from ET‐B endothelial receptors. In 24 m rats, CR did not attenuate the aging‐increased response of renal arteries to ET‐1, but it prevented the aging‐induced increase in iNOS mRNA levels and the aging‐induced decrease in eNOS mRNA levels in arterial tissue. In conclusion, aging is associated with an increased response to ET‐1 in renal arteries that is prevented by CR in 8 m but not in 24 m rats. HighlightsRenal arteries response to ET‐1 is increased in 8‐ and 24‐month‐old ratsET‐A and ET‐B receptors are involved in ET‐1‐induced contraction of renal arteriesThe effect of caloric restriction differs depending on rat age

Vascular reactivity profile of novel KCa3.1‐selective positive‐gating modulators in the coronary vascular bed

Opening of intermediate‐conductance calcium‐activated potassium channels (KCa3.1) produces membrane hyperpolarization in the vascular endothelium. Here, we studied the ability of two new KCa3.1‐selective positive‐gating modulators, SKA‐111 and SKA‐121, to (1) evoke porcine endothelial cell KCa3.1 membrane hyperpolarization, (2) induce endothelium‐dependent and, particularly, endothelium‐derived hyperpolarization (EDH)‐type relaxation in porcine coronary arteries (PCA) and (3) influence coronary artery tone in isolated rat hearts. In whole‐cell patch‐clamp experiments on endothelial cells of PCA (PCAEC), KCa currents evoked by bradykinin (BK) were potentiated ≈7‐fold by either SKA‐111 or SKA‐121 (both at 1 μM) and were blocked by a KCa3.1 blocker, TRAM‐34. In membrane potential measurements, SKA‐111 and SKA‐121 augmented bradykinin‐induced hyperpolarization. Isometric tension measurements in large‐ and small‐calibre PCA showed that SKA‐111 and SKA‐121 potentiated endothelium‐dependent relaxation with intact NO synthesis and EDH‐type relaxation to BK by ≈2‐fold. Potentiation of the BK response was prevented by KCa3.1 inhibition. In Langendorff‐perfused rat hearts, SKA‐111 potentiated coronary vasodilation elicited by BK. In conclusion, our data show that positive‐gating modulation of KCa3.1 channels improves BK‐induced membrane hyperpolarization and endothelium‐dependent relaxation in small and large PCA as well as in the coronary circulation of rats. Positive‐gating modulators of KCa3.1 could be therapeutically useful to improve coronary blood flow and counteract impaired coronary endothelial dysfunction in cardiovascular disease.

Purinergic Component in the Coronary Vasodilatation to Acetylcholine after Ischemia-Reperfusion in Perfused Rat Hearts

To determine the involvement of purinergic receptors in coronary endothelium-dependent relaxation, the response to acetylcholine (1 × 10^-8 to 3 × 10^-7<smlcap>M</smlcap>) was recorded in isolated rat hearts perfused according to the Langendorff procedure before and after 30 min of ischemia and 15 min of reperfusion and after the inhibition of nitric oxide synthesis with <smlcap>L</smlcap>-NAME (10^-4<smlcap>M</smlcap>), in the absence and presence of the antagonist of purinergic P2X receptors, PPADS (3 × 10^-6<smlcap>M</smlcap>), and of the antagonist of purinergic P2Y receptors, Reactive Blue 2 (3 × 10^-7<smlcap>M</smlcap>). In control conditions, the relaxation to acetylcholine was not altered by PPADS or Reactive Blue 2. The relaxation to acetylcholine was reduced after ischemia-reperfusion, and, in this condition, it was further reduced by treatment with PPADS or Reactive Blue 2. Likewise, the relaxation to acetylcholine was reduced by <smlcap>L</smlcap>-NAME, and reduced further by Reactive Blue 2 but not by PPADS. These results suggest that the relaxation to acetylcholine may be partly mediated by purinergic receptors after ischemia-reperfusion, due to the reduction of nitric oxide release in this condition.

Effects of early overnutrition on the renal response to Ang II and expression of RAAS components in rat renal tissue

BACKGROUND AND AIMS The aim of this study was to analyze the effects of early overnutrition (EON) on the expression of the renin angiotensin aldosterone system (RAAS) components in renal cortex, renal arteries and renal perivascular adipose tissue (PVAT), as well as the vascular response of renal arteries to Angiotensin II (Ang II). METHODS AND RESULTS On birth day litters were adjusted to twelve (L12-control) or three (L3-overfed) pups per mother. Half of the animals were sacrificed at weaning (21 days old) and the other half at 5 months of age. Ang II-induced vasoconstriction of renal artery segments increased in young overfed rats and decreased in adult overfed rats. EON decreased the gene expression of angiotensinogen (Agt), Ang II receptors AT1 and AT2 and eNOS in renal arteries of young rats, while it increased the mRNA levels of AT-2 and ET-1 in adult rats. In renal PVAT EON up-regulated the gene expression of COX-2 and TNF-α in young rats and the mRNA levels of renin receptor both in young and in adult rats. On the contrary, Ang II receptors mRNA levels were downregulated at both ages. Renal cortex of overfed rats showed increased gene expression of Agt in adult rats and of AT1 in young rats. However the mRNA levels of AT1 were decreased in the renal cortex of overfed adult rats. CONCLUSION EON is associated with alterations in the vascular response of renal arteries to Ang II and changes in the gene expression of RAAS components in renal tissue.

Study of insulin vascular sensitivity in aortic rings and endothelial cells from aged rats subjected to caloric restriction: Role of perivascular adipose tissue

ABSTRACT The prevalence of metabolic syndrome is dramatically increasing among elderly population. Metabolic syndrome in aged individuals is associated with hyperinsulinemia and insulin resistance both in metabolic tissues and in the cardiovascular system, with this fact being associated with the cardiometabolic alterations associated to this condition. Caloric restriction (CR) improves insulin sensitivity and is one of the dietetic strategies most commonly used to enlarge life and to prevent aging induced cardiovascular alterations. The aim of this study was to analyze the possible beneficial effects of CR in aging‐induced vascular insulin resistance both in aortic rings and in primary culture of endothelial cells. In addition, the inflammatory profile of perivascular adipose tissue (PVAT) and its possible role in the impairment of vascular insulin sensitivity associated with aging was also assessed. Three experimental groups of male Wistar rats were used: 3 (3 m), 24 (24 m) fed ad libitum and 24 months old rats subjected to 20% CR during their three last months of life (24 m–CR). Aorta rings surrounded or not by PVAT were mounted in an organ bath and precontracted with phenylephrine (10− 7.5 M). Changes in isometric tension were recorded in response to cumulative insulin concentrations (10− 8–10− 5.5 M) in the presence or absence of L‐NAME (10− 4 M). Aortic rings and primary aortic endothelial cells were incubated in presence/absence of insulin (10− 7 M) and the activation of the PI3K/Akt and MAPK pathways as well as nitrite and nitrates concentrations and the mRNA levels of eNOS, insulin receptor, and GLUT‐4 were assessed. CR prevented the aging‐induced decrease in the vasodilator response to insulin and the aging‐induced increase in the vasoconstrictor response to high insulin concentrations. Changes between 24 m and 24 m–CR aorta rings were abolished in the presence of L‐NAME. CR induced‐improvement in insulin vascular sensitivity was related with activation of the PI3K/Akt both in aortic rings and in aortic endothelial cells in response to insulin. CR attenuated the overexpression of iNOS, TNF‐&agr; and IL‐1&bgr; in the PVAT of aged rats although aortic rings surrounded by PVAT from 24 m rats showed and increased vasorelaxation in response to insulin compared to aortic rings from 3 m and 24 m–CR rats. In conclusion, a moderate protocol of CR improves insulin vascular sensitivity and prevents the aging induced overexpression of pro‐inflammatory cytokines in PVAT. HighlightsModerate caloric restriction attenuates aging‐induced insulin vascular resistanceCaloric restriction improves insulin sensitivity in aortic endothelial cellsCaloric restriction prevents aging‐induced inflammation in perivascular adipose tissue