Molecular and cellular biochemistry
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Mol. Cell. Biochem. · May 2002
Control of mitochondrial membrane potential and ROS formation by reversible phosphorylation of cytochrome c oxidase.
Phosphorylation of isolated cytochrome c oxidase from bovine kidney and heart, and of the reconstituted heart enzyme, with protein kinase A, cAMP and ATP turns on the allosteric ATP-inhibition at high ATP/ADP ratios. Also incubation of isolated bovine liver mitochondria only with cAMP andATP turns on, and subsequent incubation with Ca2+ turns off the allosteric ATP-inhibition of cytochrome c oxidase. ⋯ The results support the 'molecular-physiological hypothesis' [29], which proposes a low mitochondrial membrane potential through the allosteric ATP-inhibition. A hormone- or agonist-stimulated increase of cellular [Ca2+] is suggested to activate a mitochondrial protein phosphatase which dephosphorylates cytochrome c oxidase, turns off the allosteric ATP-inhibition and results in increase of mitochondrial membrane potential and ROS formation.
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Mol. Cell. Biochem. · Mar 2001
Comparative StudySerial changes in the myocardial beta-adrenergic signalling system in two models of non-insulin dependent diabetes mellitus.
Since it was reported in 1991 by Schaffer et al. that myocardial contractile responsiveness was altered in NIDDM in the absence of alterations in the beta-adrenergic receptor population, researchers have been seeking a post-receptor defect to account for this. The present study addresses this issue by comparing alterations occurring in the myocardial beta-receptor signalling pathway in two different models of rat NIDDM, as well as the response of the pathway after stimulation with isoproterenol in the presence or absence of insulin. The characteristics of the beta-receptor population, adenylyl cyclase activity and cAMP levels were determined at three different ages. The main results demonstrate that: (i) the two models of NIDDM myocardium differ biochemically; (ii) the beta-adrenergic signalling system of the insulin deficient model was altered more than the hyperinsulinemic model and (iii) the observed exaggerated cAMP response of NIDDM hearts after stimulation with a beta-adrenergic agonist is in contrast with lower responsivity.
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Mol. Cell. Biochem. · Sep 1998
Ischemic preconditioning and superoxide dismutase protect against endothelial dysfunction and endothelium glycocalyx disruption in the postischemic guinea-pig hearts.
The effect of ischemic preconditioning and superoxide dismutase (SOD) on endothelial glycocalyx and endothelium-dependent vasodilation in the postischemic isolated guinea-pig hearts was examined. Seven groups of hearts were used: group 1 underwent sham aerobic perfusion; group 2 was subjected to 40 min global ischemia without reperfusion; group 3, 40 min ischemia followed by 40 min reperfusion; group 4 was preconditioned with three cycles of 5 min global ischemia followed by 5 min of reperfusion (IPC), prior to 40 min ischemia; group 5 was subjected to IPC prior to standard ischemia/ reperfusion; group 6 underwent standard ischemia/reperfusion and SOD infusion (150 U/ml) was begun 5 min before 40 min ischemia and continued during the initial 5 min of the reperfusion period; group 7 was subjected to 80 min aerobic perfusion with NO-synthase inhibitor, L-NAME, to produce a model of endothelial dysfunction independent from the ischemia/reperfusion. Coronary flow responses to acetylcholine (ACh) and sodium nitroprusside (SNP) were used as measures of endothelium-dependent and endothelium-independent vascular function, respectively. Reduction in coronary flow caused by NO-synthase inhibitor, L-NAME, served as a measure of a basal endothelium-dependent vasodilator tone. After completion of each experimental protocol, the hearts were stained with ruthenium red or lanthanum chloride for electron microscopy evaluation of the endothelial glycocalyx. While ischemia led only to a slightly flocculent appearance of the glycocalyx, in ischemia/reperfused hearts the glycocalyx was disrupted, suggesting that it is the reperfusion injury which leads to the glycocalyx injury. Moreover, the coronary flow responses to ACh and L-NAME were impaired, while the responses to SNP were unchanged in the ischemia/reperfused hearts. The disruption of the glycocalyx and the deterioration of ACh and L-NAME responses was prevented by IPC. In addition, the alterations in the glycocalyx and the impairment of ACh responses were prevented by SOD. The glycocalyx appeared to be not changed in the hearts subjected to 80 min aerobic perfusion with L-NAME. ⋯ (1) the impairment of the endothelium-dependent coronary vasodilation is paralleled by the endothelial glycocalyx disruption in the postischemic guinea-pig hearts; (2) both these changes are prevented by SOD, suggesting the role of free radicals in the mechanism of their development; (3) both changes are prevented by IPC. We hypothesize, therefore, that alterations in the glycocalyx contribute to the mechanism of the endothelial dysfunction in the postischemic hearts.
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Mol. Cell. Biochem. · Sep 1998
Opioid receptor contributes to ischemic preconditioning through protein kinase C activation in rabbits.
Recent studies have reported that protection from ischemic preconditioning (PC) is blocked by the opioid receptor antagonist naloxone (NAL). We tested whether an opioid agonist could mimic PC in the rabbit heart, whether that protection involved protein kinase C (PKC) activation, and whether opioid receptors act in concert with other PKC-coupled receptors. Rabbit hearts were subjected to 30 min coronary occlusions and were reperfused for either 3 (in situ) or 2 (in vitro) h. ⋯ Neither chelerythrine nor NAL by itself modified infarction in non-PC hearts. NAL could not block protection from one cycle of PC in isolated hearts indicating that an intact innervation may be required for endogenous opioid production. Thus, opioid receptors, like other PKC-coupled receptors, participate in the triggering of PC in the rabbit heart.
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Mol. Cell. Biochem. · Jun 1998
Expression and localization of insulin-like growth factor-1 in normal and post-burn hypertrophic scar tissue in human.
The migration of epithelial cells from dermal appendages toward the wound surface is essential for re-epithelialization of partial thickness burn injuries. This study provides evidence that these cells in vivo synthesize a mitogenic and fibrogenic factor, insulin-like growth factor-1 (IGF-1), which may promote the development of the post-burn fibroproliferative disorder, hypertrophic scarring (HSc). An evaluation of 7 post-burn hypertrophic scars, 7 normal skin samples obtained from the same patients and 4 mature scars revealed that IGF-1 expressing cells from the disrupted sweat glands tend to reform small sweat glands of 4-10 cells/gland in post-burn HSc. ⋯ By in situ hybridization, IGF-1 mRNA was localized to both epithelial and infiltrated immune cells. Collectively, these findings suggest that in normal skin, fibroblasts have little or no access to diffusible IGF-1 expressed by epithelial cells of the epidermis, sweat and sebaceous glands; while following dermal injury when these structures are disrupted, IGF-1 may contribute to the development of fibrosis through its fibrogenic and mitogenic functions. Reformation of sweat glands during the later stages of healing may, therefore, limit this accessibility, and lead to scar maturation.