Rho kinase and protein kinase C involvement in vascular smooth muscle myofilament calcium sensitization in arteries from diabetic rats.

BACKGROUND AND PURPOSE: Diabetes mellitus (DM) causes multiple dysfunctions including circulatory disorders such as cardiomyopathy, angiopathy, atherosclerosis and arterial hypertension. Rho kinase (ROCK) and protein kinase C (PKC) regulate vascular smooth muscle (VSM) Ca(2+) sensitivity, thus enhancing VSM contraction, and up-regulation of both enzymes in DM is well known. We postulated that in DM, Ca(2+) sensitization occurs in diabetic arteries due to increased ROCK and/or PKC activity. EXPERIMENTAL APPROACH: Rats were rendered hyperglycaemic by i.p. injection of streptozotocin. Age-matched control tissues were used for comparison. Contractile responses to phenylephrine (Phe) and different Ca(2+) concentrations were recorded, respectively, from intact and chemically permeabilized vascular rings from aorta, tail and mesenteric arteries. KEY RESULTS: Diabetic tail and mesenteric arteries demonstrated markedly enhanced sensitivity to Phe while these changes were not observed in aorta. The ROCK inhibitor HA1077, but not the PKC inhibitor chelerythrine, caused significant reduction in sensitivity to agonist in diabetic vessels. Similar changes were observed for myofilament Ca(2+) sensitivity, which was again enhanced in DM in tail and mesenteric arteries, but not in aorta, and could be reduced by both the ROCK and PKC blockers. CONCLUSIONS AND IMPLICATIONS: We conclude that in DM enhanced myofilament Ca(2+) sensitivity is mainly manifested in muscular-type blood vessels and thus likely to contribute to the development of hypertension. Both PKC and, in particular, ROCK are involved in this phenomenon. This highlights their potential usefulness as drug targets in the pharmacological management of DM-associated vascular dysfunction.

[Effect of ionising irradiation on outward potassium current in the aorta smooth muscle cells in rats: the role of protein kinase C].

It is known that gamma-irradiation leads to vascular hyperfunction and hypertension development. In this study we tested the hypothesis that ionizing irradiation directly affects vascular smooth muscle cells due to damage in outward K+ channel function. The goal of this study was to evaluate the influence of whole-body ionizing irradiation (6 Gy dose) on Ca(2+) dependent K+ channels and to clarify a possible involvement of protein kinase C in this process. Experiments were conducted on isolated rat aorta smooth muscle cells using whole-cell patch clamp technique. It has been shown that the basic component of outward K+ current in rat aortic smooth muscle cells is a large conductance Ca(2+)-activated K+ current (BK(Ca)). BK(Ca) currents in smooth muscle cells obtained from irradiated animals on the 9th and 30th days post-irradiation demonstrated a significant decrease of K(+)-current density amplitudes. Protein kinase C inhibitor, chelerythrine, effectively restored BK(Ca) current reduced by ionizing irradiation. In conclusion, the results suggest that gamma-irradiation suppressed BK(Ca) current in vascular smooth muscle cells, and this effect is mainly due to activation of protein kinase C.

[Modern conception of protein kinase C role in the vascular smooth muscles tone regulation].

Protein kinase C is an important regulatory enzyme that plays significant role in the vascular tone regulation. Protein kinase C is involved in the vascular smooth muscle cells (SMC) contractility at physiological conditions and its hyperreactivity at different types of pathology. Myogenic and endothelium-dependent pathways of protein kinase C-mediated vascular tone regulation include a variety of cellular mechanisms. The most important protein kinase C-mediated mechanisms in SMC are the increase of myophilament Ca2+-sensitivity; regulation of plasmolema ion permeability, and proliferative changes in SMC. Protein kinase C-related mechanisms in vascular endotheliocytes include regulation of formation and transduction of humoral and electrical signals to SMC that play an important role in the pathological vasospasm development.

[Effect of inhibiting protein kinase C on calcium sensitivity of contractile apparatus of vascular smooth muscle during vasospasms of different origins]. / Vplyv blokady proteïnkinazy C na zminy kal'tsiievoï chutlyvosti skorotlyvoho aparatu sudynnykh gladen'kykh m'iaziv pry vazospastychnykh stanakh riznogo henezu.

The aim of the study was to investigate the role of protein kinase C (PKC) in changes in myofilament Ca(2+)-sensitivity of vascular smooth muscle cells (SMC) in rats at different vasospastic states: hypoxic pulmonary vasoconstriction, genetically determined hypertension, and hypertension resulted from ionizing radiation. All vasospastic states demonstrated rightward shifts in pCa-tension curves suggesting that myofilament Ca(2+)-sensitivity had increased. In chemically (beta-escin) skinned pulmonary artery, hypoxia-induced increase in myofilament Ca(2+)-sensitivity was completely abolished by PKC inhibitor chelerythrine. The similar results were demonstrated in skinned aorta SMC of spontaneously hypertensive rats where an increase in myofilament Ca(2+)-sensitivity was also abolished by PKC inhibitors chelerythrine and staurosporine. The chelerythrine partially inhibited myofilament Ca(2+)-sensitivity that had increased following gamma-radiation. The data suggest the key role of PKC activity in modulation of myofilament Ca(2+)-sensitivity in SMC. We conclude that PKC-mediated increase in myofilament Ca(2+)-sensitivity is one of the main mechanisms which contribute to the vasospasm of different genesis.

[Current concepts on the mechanisms of hypoxic effects on vascular tonus]. / Suchasni uiavlennia pro mekhanizmy vplyvu hipoksiï na tonus krovonosnykh sudyn.

It is well known that hypoxia causes smooth muscle relaxation of the majority of mammalian systemic blood vessels, whereas smooth muscles in the pulmonary and large coronary arteries constrict under hypoxia. The review describes a modern concept of the mechanisms involved in the hypoxic vasoconstriction and vasodilatation. Cationic channels of a plasma membrane, the contractile apparatus, and mitochondria are the main oxygen sensors in the vascular smooth muscle cells. Hypoxic vasodilatation is mediated mainly by a decrease in the voltage-dependent Ca2+ entry, decrease in Ca2+ sensitivity of the contractile apparatus, and activation of ATP-dependent K+ channels. This process also involves endothelium derived nitric oxide. Hypoxic vasoconstriction mechanisms may be related to voltage-gating K+ channels inhibition, Ca2+ release from intracellular stores and inactivation of Ca2+ activated K+ channels each of them leads to increase in intracellular Ca2+ concentration. Platelet-activating factor, prostaglandins F2 alpha, E2, tromboxan B2, leucotriens C4 and D4 also contribute to hypoxic vasoconstriction. Glycolysis which intensity increases in hypoxia, and electron transport chain which generates the reactive oxygen species play the important role in the development of hypoxic pulmonary vasoconstriction. They possess the ability to change redox state in the cells and therefore to modulate the activity of the cationic channels. Hypoxia also leads to a proliferation of smooth muscles in the vascular wall. Better understanding of the underlying hypoxia-related mechanisms is vital for the explanation of enhanced blood flow under hypoxia, and is absolutely necessary for creating new effective antihypoxic drugs.

[Mast cells in a focus of carrageenan-induced acute aseptic inflammation]. / Tuchni klityny u vohnyshchi karahinenovoho hostroho aseptychnoho zapalennia.

On the model of carrageenen-induced acute aseptic peritonitis in rats the regularities of the functional state of mast cells (MC), of the content of free and cellular histamine in exudate and mesenterium and histamine in blood from the 5th minute up to 10th day after injection of phlogogene have been studied. Also as in infectious inflammation, the phasic reaction of MC which is observed at least during 10 days after action of phlogogene has been shown. The quick short first phase during half an hour after induction of inflammation has been observed and the gradual long second phase from the 1st hour up to 10th day has been noted. At least during 1st day the regularities of reaction of MC were extremely similar to the ones in infection peritonitis. Also as in infectious inflammation the second phase of reaction of MC correlates with the accumulation of leukocytes in inflammatory focus. At the same time the dependence of dynamics of functional changes of MC in aseptic inflammation on the properties of phlogogene (irritating or relatively indifferent phlogenes) has been established.