Biomedical subjects

Huda E Tawfik

Publications and source records attributed to Huda E Tawfik.

4 recordsLinked to original sources

PubMed2006

Protection against myocardial ischemia/reperfusion injury by short-term diabetes: enhancement of VEGF formation, capillary density, and activation of cell survival signaling.

The aims of this study were to determine effects of diabetes duration on myocardial ischemia/reperfusion (I/R) injury and test whether time-dependent differences in sensitivity of the streptozotocin diabetic rat heart to I/R are related to differences in vascular density, levels of vascular endothelial growth factor (VEGF) or endothelial nitric oxide synthase (eNOS) expression, NO formation, activation of Akt, and/or oxidative stress. After 2 or 6 weeks of streptozotocin-induced diabetes, I/R injury was induced by occlusion (30 min) and reperfusion of the left descending coronary artery. After 2 weeks of diabetes, infarct size and cleavage of caspase-3, a proapoptosis signal, were decreased as compared with normoglycemic controls or rats that had been diabetic for 6 weeks, whereas capillary density and levels of VEGF and eNOS protein and cardiac NO(x) levels were all increased. Phosphorylation of Akt, a prosurvival signal, was also significantly increased after 2 weeks of diabetes. Cardiac lipid peroxidation was comparable to controls after 2 weeks of diabetes, whereas levels of nitrotyrosine, a peroxynitrite biomarker, were reduced. After 6 weeks of diabetes, lipid peroxidation was increased and levels of VEGF and plasma NO were reduced as compared with controls or rats diabetic for 2 weeks. Our results indicate endogenous cardioprotective mechanisms become transiently activated in this early stage of diabetes and that this may protect the heart from I/R injury through enhancement of VEGF and eNOS expression, NO formation, activation of cell survival signals, and decreased oxidative stress.

Animals↗

PubMed2006

Simvastatin improves diabetes-induced coronary endothelial dysfunction.

3-Hydroxy-3-methylglutaryl CoA reductase inhibitors decrease cardiovascular morbidity in diabetic patients, but the mechanism is unclear. We studied the actions of simvastatin (SIM) in enhancing NO bioavailability and reducing oxidative stress in coronary vessels from diabetic rats and in rat coronary artery endothelial cells (RCAEC) exposed to high glucose. Coronary arteries isolated from diabetic rats showed decreases in acetylcholine (ACh)-mediated maximal relaxation from 81.0 +/- 4.5% in controls to 43.5 +/- 7.6% at 4 weeks and 22.3 +/- 0.6% at 10 weeks of diabetes. This effect was associated with oxidative stress in coronary vessels as shown by dichlorofluorescein (DCF) imaging and nitrotyrosine labeling. Diabetes also reduced trans-coronary uptake of [(3)H]l-arginine. Supplemental l-arginine (50 mg/kg/day p.o.) did not improve coronary vasorelaxation to ACh. However, SIM treatment (5 mg/kg/day subcutaneously) improved maximal ACh relaxation to 65.8 +/- 5.1% at 4 weeks and 47.1 +/- 3.9% at 10 weeks. Coronary arteries from rats treated with both SIM and l-arginine demonstrated the same maximal relaxation to ACh (66.1 +/- 3%) as SIM alone. Mevalonate and l-NAME (N(omega)-nitro-l-arginine methyl ester hydrochloride) inhibited the response to ACh in SIM-treated diabetic rats. Coronary arteries from all groups relaxed similarly to sodium nitroprusside. SIM increased endothelial NO synthase protein levels and blocked diabetes-induced increases in DCF and nitrotyrosine labeling in diabetic coronary vessels. SIM treatment restored normal NO levels in media from high-glucose-treated RCAEC and plasma of diabetic rat. Treatment with SIM or the NADPH oxidase inhibitor apocynin also blocked high-glucose-induced increases in reactive oxygen species and superoxide formation in RCAEC. Taken together, these data suggest that SIM improves diabetes-induced coronary dysfunction by reducing oxidative stress and increasing NO bioavailability.

Animals↗

PubMed2006

Role of A1 adenosine receptor in the regulation of coronary flow.

To determine whether A1 adenosine receptors (AR) participate in adenosine-induced changes of coronary flow, isolated hearts from A1AR(-/-) and A1AR(+/+) mice were perfused under constant pressure, and the effects of nonselective and selective agonists were examined. Adenosine, 5'-N-ethylcarboxamidoadenosine (NECA, nonselective), and the selective A2AAR agonist 2-2-carboxyethylphenethylamino-5'-N-ethylcarboxamidoadenosine (CGS-21680) augmented maximal coronary vasodilation in A1AR(-/-) hearts compared with A1AR(+/+) hearts. Basal coronary flow was increased (P < 0.05) in A1AR(-/-) hearts compared with A1AR(+/+) hearts: 2.548 +/- 0.1 vs. 2.059 +/- 0.17 ml/min. In addition, selective activation of A1AR with 2-chloro-N6-cyclopentyladenosine (CCPA) at nanomolar concentrations (1-100 nM) did not significantly change coronary flow; at higher concentrations, CCPA increased coronary flow in A1AR(-/-) and A1AR(+/+) hearts. Because deletion of A1AR increased basal coronary flow, it is speculated that this effect is due to removal of an inhibitory influence associated with A1AR. Adenosine and NECA at approximately EC50 (100 and 50 nM, respectively) increased coronary flow in A1AR(+/+) hearts to 177.86 +/- 8.75 and 172.72 +/- 17% of baseline, respectively. In the presence of the selective A1AR antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 50 nM), the adenosine- and NECA-induced increase in coronary flow in A1AR(+/+) hearts was significantly augmented to 216.106 +/- 8.35 and 201.61 +/- 21.89% of normalized baseline values, respectively. The adenosine- and NECA-induced increase in coronary flow in A1AR(-/-) hearts was not altered by DPCPX. These data indicate that A1AR may inhibit or negatively modulate coronary flow mediated by other AR subtypes (A2A and A2B).

Adaptation, Physiological↗

PubMed2004

Role of A1 adenosine receptors in regulation of vascular tone.

The vascular response to adenosine and its analogs is mediated by four adenosine receptors (ARs), namely, A(1), A(2A), A(2B), and A(3). A(2A)ARs and/or A(2B)ARs are involved in adenosine-mediated vascular relaxation of coronary and aortic beds. However, the role of A(1)ARs in the regulation of vascular tone is less well substantiated. The aim of this study was to determine the role of A(1)ARs in adenosine-mediated regulation of vascular tone. A(1)AR-knockout [A(1)AR((-/-))] mice and available pharmacological tools were used to elucidate the function of A(1)ARs and the impact of these receptors on the regulation of vascular tone. Isolated aortic rings from A(1)AR((-/-)) and wild-type [A(1)AR((+/+))] mice were precontracted with phenylephrine, and concentration-response curves for adenosine and its analogs, 5'-N-ethyl-carboxamidoadenosine (NECA, nonselective), 2-chloro-N(6)-cyclopentyladenosine (CCPA, A(1)AR selective), 2-(2-carboxyethyl)phenethyl amino-5'-N-ethylcarboxamido-adenosine (CGS-21680, A(2A) selective), and 2-chloro-N(6)-3-iodobenzyladenosine-5'-N-methyluronamide (Cl-IBMECA, A(3) selective) were obtained to determine relaxation. Adenosine and NECA (0.1 microM) caused small contractions of 13.9 +/- 3.0 and 16.4 +/- 6.4%, respectively, and CCPA at 0.1 and 1.0 microM caused contractions of 30.8 +/- 4.3 and 28.1 +/- 3.9%, respectively, in A(1)AR((+/+)) rings. NECA- and CCPA-induced contractions were eliminated by 100 nM of 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, selective A(1)AR antagonist). Adenosine, NECA, and CGS-21680 produced an increase in maximal relaxation in A(1)AR((-/-)) compared with A(1)AR((+/+)) rings, whereas Cl-IBMECA did not produce contraction in either A(1)AR((+/+)) or A(1)AR((-/-)) rings. CCPA-induced contraction at 1.0 microM was eliminated by the PLC inhibitor U-73122. These data suggest that activation of A(1)ARs causes contraction of vascular smooth muscle through PLC pathways and negatively modulates the vascular relaxation mediated by other adenosine receptor subtypes.

Adenosine↗