Altered Protein Kinase C Regulation of Pulmonary Endothelial Store- and Receptor-Operated Ca²⁺Entry after Chronic Hypoxia

Abstract

Chronic hypoxia (CH)-induced pulmonary hypertension is associated with decreased basal pulmonary artery endothelial cell (EC) Ca 2ϩ , which correlates with reduced storeoperated Ca 2ϩ (SOC) entry. Protein kinase C (PKC) attenuates SOC entry in ECs. Therefore, we hypothesized that PKC has a greater inhibitory effect on EC SOC and receptoroperated Ca 2ϩ entry after CH. To test this hypothesis, we assessed SOC in the presence or absence of the nonselec-in freshly isolated, Fura-2-loaded ECs obtained from intrapulmonary arteries of control and CH rats (4 weeks at 0.5 atm). We found that SOC entry and 1-oleoyl-2-acetyl-sn-glycerol (OAG)-and ATP-induced Ca 2ϩ influx were attenuated in ECs from CH rats versus controls, and GF109203X restored SOC and OAG responses to the level of controls. In contrast, nonselective PKC inhibition with GF109203X or the selective PKC inhibitor myristoylated V1-2 attenuated ATP-induced Ca 2ϩ entry in ECs from control but not CH pulmonary arteries. ATP-induced Ca 2ϩ entry was also attenuated by the T-type voltage-gated Ca 2ϩ channel (VGCC) inhibitor mibefradil in control cells. Consistent with the presence of endothelial T-type VGCC, we observed depolarization-induced Ca 2ϩ influx in control cells that was inhibited by mibefradil. This response was largely absent in ECs from CH arteries. We conclude that CH enhances PKC-dependent inhibition of SOC-and OAG-induced Ca 2ϩ entry. Furthermore, these data suggest that CH may reduce the ATP-dependent Ca 2ϩ entry that is mediated, in part, by PKC and mibefradil-sensitive Ca 2ϩ channels in control cells.

PICK1/calcineurin suppress ASIC1-mediated Ca2+ entry in rat pulmonary arterial smooth muscle cells

“…The effect of PKC on ASIC1 has been shown to be either stimulatory or inhibitory, depending on the PKC isoform and phosphorylation site (3,4,16,50). Consistent with previous data from our laboratory in isolated pulmonary arteries and pulmonary arterial endothelial sheets (32,39), activation of PKC suppressed SOCE in PASMC. These data are in line with reports that PKC activation reduces current amplitude of human ASIC1 in glioma cells and Xenopus oocytes (3,4).…”

Regulation of Ca2+Signaling in Pulmonary Hypertension

“…Ca(v)3.1 has been specifically linked to the expression and activation of cyclin D further supporting its importance in regulating cell cycle suppressing [14]. In pulmonary artery endothelial cells (PAEC), isolated from the CH induced experimental model of PH, a decreased ATP-dependent and depolarization induced Ca 2+ entry via mibefradil-sensitive T-type channels has been observed [15]. Such function regulation would imply a potential role in PH and in particular in pulmonary vascular remodeling.…”

Role of impaired endothelial cell Ca2+signaling in uteroplacental vascular dysfunction during diabetic rat pregnancy

“…Recent data have demonstrated that PKC-␣ mediates ACh-induced activation of TRPV4-dependent Ca 2ϩ influx in vascular ECs (1). On the other hand, chronic hypoxia enhances PKC-dependent inhibition of Ca 2ϩ entry in ECs of rat intrapulmonary arteries (56). The role of enhanced PKC activity in impaired EC Ca 2ϩ signaling in uteroplacental arteries of diabetic pregnant rats requires further investigation.…”