Cultured Porcine Coronary Endothelial Cells Research Articles

0179: Polyphenol-rich blackcurrant juice induces NO-mediated relaxation in porcine coronary artery rings via a copper- and iron-dependent redox-sensitive activation of the Src/PI3-kinase/Akt/eNOS pathway

The beneficial cardiovascular effect of polyphenol-rich food and beverages has been attributed, at least in part, to the improvement of the vascular function through the induction of two major endothelial vasoprotective mechanisms. The aim of the present study is to determine whether a polyphenol-rich blackcurrant juice (PRBJ, 2.7 g/l), improves the vasoprotective endothelial function, and, if so, to characterize the underlying mechanism. The reactivity of porcine coronary artery rings was assessed in organ chambers, and the expression and phosphorylation levels of proteins in cultured porcine coronary endothelial cells by Western blot analysis. PRBJ caused potent endotheliumdependent relaxations that were significantly reduced by an eNOS inhibitor, not affected by inhibition of endothelium-dependent hyperpolarization, and abolished by both treatments. PRBJ-induced NO-mediated relaxations were significantly reduced by chelators of either copper or iron, membrane permeant analogues of superoxide dismutase and catalase, inhibitors of either Src or PI3-kinase, and by calmidazolium, a calmodulin inhibitor. The NO-mediated relaxation was not affected by inhibitors of either PKC, EGFR, IGFR, or of several endogenous enzymes involved in the formation of ROS (NADPH oxidase, xanthine oxidase, mitochondrial respiration chain, cytochrome P450). In cultured endothelial cells, PRBJ increased the formation of NO as assessed by electron paramagnetic resonance spectroscopy. Moreover, PRBJ induced the phosphorylation of Akt and eNOS on activator sites, which were inhibited membrane permeant analogues of superoxide dismutase and catalase and inhibitors of either Src or PI3-kinase. PRBJ is a potent inducer of endothelium- dependent NO-mediated relaxations in porcine coronary artery rings. The NO-mediated relaxation involves an intracellular copper- and iron-dependent redox-sensitive activation the Src/PI3-kinase/Akt pathway leading to activation of eNOS and subsequent formation of NO.

Activation of canonical transient receptor potential channels preserves Ca2+ entry and endothelium-derived hyperpolarizing factor–mediated function in vitro in porcine coronary endothelial cells and coronary arteries under conditions of hyperkalemia

Although membrane depolarization by hyperkalemia is known to reduce Ca2+ influx in endothelial cells, the mechanism by which endothelial Ca2+ channel is affected by hyperkalemia remains poorly studied. We studied the effect of hyperkalemia on canonical transient receptor potential channels, in particular canonical transient receptor potential channel 3, in modulation of endothelial intracellular Ca2+ concentration. Endothelium-derived hyperpolarizing factor-mediated function is Ca2+ dependent, and hyperkalemic cardioplegia/organ preservation solutions impair endothelium-derived hyperpolarizing factor-mediated function. We explored the role of canonical transient receptor potential channel 3 in endothelium-derived hyperpolarizing factor-mediated function and investigated whether modulation of these channels preserves endothelial Ca2+ influx and endothelium-derived hyperpolarizing factor-mediated function under the condition of hyperkalemic/cardioplegic exposure. Intracellular Ca2+ concentration was measured with fluorescent dye in primary cultured porcine coronary endothelial cells exposed to hyperkalemic/cardioplegic solutions containing mild to extreme high K+ concentration. Endothelium-derived hyperpolarizing factor-mediated relaxation under hyperkalemic/cardioplegic exposure was studied in small porcine coronary arteries in a myograph in the presence of cyclooxygenase and nitric oxide synthase inhibitors and nitric oxide scavenger. Canonical transient receptor potential channel 3 blocker inhibited bradykinin-induced Ca2+ influx and attenuated endothelium-derived hyperpolarizing factor-mediated response. Hyperkalemic exposure inhibited canonical transient receptor potential channel 3-mediated Ca2+ influx in a K+ concentration-dependent manner (120>20>10 mmol/L). Ca2+ influx decreased in porcine coronary endothelial cells exposed to histidine-tryptophan-ketoglutarate, St Thomas' Hospital, and University of Wisconsin solutions that contained mild (10 mmol/L), moderate (20 mmol/L), and extreme high (125 mmol/L) K+ concentration, respectively. Canonical transient receptor potential channel activator prevented the reduction of Ca2+ influx in porcine coronary endothelial cells exposed to solutions containing mild to moderate high [K+]o and restored endothelium-derived hyperpolarizing factor-mediated response that was impaired by hyperkalemic exposure. Canonical transient receptor potential channel 3 is involved in endothelium-derived hyperpolarizing factor-mediated function in coronary arteries. Hyperkalemia inhibited canonical transient receptor potential channel 3-mediated Ca2+ influx in endothelial cells. Canonical transient receptor potential channel activation restores Ca2+ influx suppressed by hyperkalemia and prevents dysfunction of endothelium-derived hyperpolarizing factor.

TRPC3 channel contributes to nitric oxide release: significance during normoxia and hypoxia–reoxygenation

Intracellular Ca(2+) ([Ca(2+)](i)) regulation in endothelial cells depends on transient receptor potential channels (TRPs), and the role of canonical TRPs (TRPCs) during hypoxia-reoxygenation (H-R) is unclear. We hypothesized that TRPC3 contributes to endothelial nitric oxide (NO) release and that H-R may reduce TRPC3 activity and the associated endothelial function, including NO release. Measurements of [Ca(2+)](i) and patch-clamp study in primary cultured porcine coronary endothelial cells, measurements of NO and endothelium-dependent relaxation in porcine coronary arteries, and RT-PCR and western blot were conducted. Pre-treatment with SKF96365 (an inhibitor of TRPCs) or the selective TRPC3 inhibitor Pyr3 significantly decreased bradykinin-induced vasorelaxation. One hour of hypoxia followed by reoxygenation significantly reduced the vasorelaxation (70.3 ± 6.4 vs. 88.9 ± 3.5%) and NO concentration (24.0 ± 1.3 vs. 45.2 ± 2.8 nmol/L), and they were restored by pre-incubation with the TRPC3/6/7 activator 1-oleoyl-2-acetyl-sn-glycerol (96.4 ± 1.8% and 41.1 ± 4.7 nmol/L, respectively). In porcine coronary endothelial cells, H-R inhibited bradykinin-activated membrane current (8.6 ± 0.4 vs. 14.0 ± 1.5 pA/pF) and Pyr3-sensitive TRPC3 current (3.8 ± 0.3 vs. 6.3 ± 0.6 pA/pF; P< 0.01). H-R also inhibited bradykinin-induced Ca(2+) influx and the Ca(2+) influx via TRPC3. Cell surface expression of TRPC3 was decreased after H-R. We have, for the first time, demonstrated that Ca(2+) entry via endothelial TRPC3 contributes to NO release and have revealed that H-R is associated with inhibition of TRPC3 activity. Inhibition of channel trafficking to the cell surface is involved in the underlying mechanism of the decrease of TRPC3 current and the reduction in Ca(2+) entry through TRPC3 during H-R. This study suggests that TRPC3 may have the potential to be a new target for endothelial protection during H-R.

A transferable, beta-naphthoflavone-inducible, hyperpolarizing factor is synthesized by native and cultured porcine coronary endothelial cells.

1. The vascular endothelium releases a hyperpolarizing factor (endothelium-derived hyperpolarizing factor, EDHF) tentatively identified as a cytochrome P450-derived arachidonic acid metabolite. However, there is still controversy concerning its transferability and identity. We designed a bioassay system for assessing EDHF release in which the membrane potential was recorded in cultured vascular smooth muscle cells located downstream from donor endothelial cells. 2. Under combined nitric oxide (NO) synthase and cyclo-oxygenase blockade with NG-nitro-L-arginine (100 mumol l-1) and diclofenac (10 mumol l-1), the superfusate from bradykinin (30 mumol l-1)-stimulated, cultured porcine coronary endothelial cells induced a distinct hyperpolarization followed by a depolarization. Direct application of bradykinin to the smooth muscle cells resulted solely in membrane depolarization. Similar results were obtained using bradykinin-stimulated porcine coronary arteries as donor. 3. Single-channel current measurements suggest that this EDHF-induced hyperpolarization was elicited by the activation of Ca(2+)-dependent K+ channels. 4. Increasing the transmural pressure within the donor segment significantly enhanced the duration, but not the amplitude of the hyperpolarization induced by the effluate from bradykinin-stimulated donor segments. 5. Inhibition of P450 oxygenase activity with clotrimazole (3 mumol l-1) or 17-octadecynoic acid (3 mumol l-1) abolished EDHF release from the coronary endothelium, while the P450-derived arachidonic acid metabolite, 5,6-epoxyeicosatrienoic acid, induced a hyperpolarization of detector smooth muscle cells almost identical to that induced by EDHF. Moreover, induction of P450 activity by beta-naphthoflavone (3 mumol l-1, 48 h), significantly increased the bradykinin-induced release of EDHF. 6. These findings suggest that the vascular endothelium releases a transferable hyperpolarizing factor, chemically distinct from NO and prostacyclin, in response to agonists and mechanical stimulation. This beta-naphthoflavone-inducible EDHF appears to be a cytochrome P450-derived metabolite of arachidonic acid, which elicits hyperpolarization by activation of Ca(2+)-dependent K+ channels.

Nitrous Oxide Constricts Epicardial Coronary Arteries in Pigs

Nitrous oxide increases peripheral vascular tone in animals and humans and constricts epicardial coronary arteries in dogs. Current studies sought both to determine whether nitrous oxide caused epicardial coronary artery constriction in a second animal species, pigs, and to investigate mechanisms. Left anterior descending coronary artery diameters were measured by using computer-assisted angiography in intact pigs anesthetized with ketamine and fentanyl. In separate experiments, isolated porcine coronary arteries were used to assess nitrous oxide effects on both vascular tone and norepinephrine overflow. Agonist-induced increases in [Ca2+]i were estimated in cultured porcine coronary endothelial cells. Nitrous oxide caused epicardial coronary artery vasoconstriction in vivo by about 20%. Nitrous oxide did not affect endothelium-dependent relaxations and contractions in isolated vessels. Norepinephrine overflow was increased but only in vessels with endothelium. The anesthetic attenuated Ca2+ mobilization in endothelial cells. We conclude that nitrous oxide induces epicardial coronary artery constriction in pigs and suggest that the mechanism may involve the inhibition of endothelium-dependent norepinephrine turnover. (Anesth Analg 1993;77:232-40)

Nitrous oxide constricts epicardial coronary arteries in pigs: evidence suggesting inhibitory effects on the endothelium.

Nitrous oxide increases peripheral vascular tone in animals and humans and constricts epicardial coronary arteries in dogs. Current studies sought both to determine whether nitrous oxide caused epicardial coronary artery constriction in a second animal species, pigs, and to investigate mechanisms. Left anterior descending coronary artery diameters were measured by using computer-assisted angiography in intact pigs anesthetized with ketamine and fentanyl. In separate experiments, isolated porcine coronary arteries were used to assess nitrous oxide effects on both vascular tone and norepinephrine overflow. Agonist-induced increases in [Ca2+]i were estimated in cultured porcine coronary endothelial cells. Nitrous oxide caused epicardial coronary artery vasoconstriction in vivo by about 20%. Nitrous oxide did not affect endothelium-dependent relaxations and contractions in isolated vessels. Norepinephrine overflow was increased but only in vessels with endothelium. The anesthetic attenuated Ca2+ mobilization in endothelial cells. We conclude that nitrous oxide induces epicardial coronary artery constriction in pigs and suggest that the mechanism may involve the inhibition of endothelium-dependent norepinephrine turnover.