Maturation and long-term hypoxia-induced acclimatization responses in PKC-mediated signaling pathways in ovine cerebral arterial contractility.
In the developing fetus, cerebral arteries (CA) show striking differences in signal transduction mechanisms compared with the adult, and these differences are magnified in response to high-altitude long-term hypoxia (LTH). In addition, in the mature organism, cerebrovascular acclimatization to LTH may be associated with several clinical problems, the mechanisms of which are unknown. Because PKC plays a key role in regulating CA contractility, in fetal and adult cerebral arteries, we tested the hypothesis that LTH differentially regulates the PKC-mediated Ca(2+) sensitization pathways and contractility. In four groups of sheep [fetal normoxic (FN), fetal hypoxic (FH), adult normoxic (AN), and adult hypoxic (AH)], we examined, simultaneously, responses of CA tension and intracellular Ca(2+) concentration and measured CA levels of PKC, ERK1/2, RhoA, 20-kDa myosin light chain, and the 17-kDa PKC-potentiated myosin phosphatase inhibitor CPI-17. The PKC activator phorbol 12,13-dibutyrate (PDBu) produced robust contractions in all four groups. However, PDBu-induced contractions were significantly greater in AH CA than in the other groups. In all CA groups except AH, in the presence of MEK inhibitor (U-0126), the PDBu-induced contractions were increased a further 20-30%. Furthermore, in adult CA, PDBu led to increased phosphorylation of ERK1, but not ERK2; in fetal CA, the reverse was the case. PDBu-stimulated ERK2 phosphorylation also was significantly greater in FH than FN CA. Also, although RhoA/Rho kinase played a significant role in PDBu-mediated contractions of FN CA, this was not the case in FH or either adult group. Also, whereas CPI-17 had a significant role in adult CA contractility, this was not the case for the fetus. Overall, in ovine CA, the present study demonstrates several important maturational and LTH acclimatization changes in PKC-induced contractile responses and downstream pathways. The latter may play a key role in the pathophysiologic disorders associated with acclimatization to high altitude.
Goyal
Ravi
R
Center for Perinatal Biology and Department of Physiology, Loma Linda University, School of Medicine, Loma Linda, California 92350, USA.
Mittal
Ashwani
A
Chu
Nina
N
Arthur
Rebecca Afiba
RA
Zhang
Lubo
L
Longo
Lawrence D
LD
D000064:Acclimatization; D000367:Age Factors; D000375:Aging; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D002536:Cerebral Arteries / Q000187:drug effects / Q000196:embryology / Q000201:enzymology* / Q000254:growth & development / Q000503:physiopathology; D004195:Disease Models, Animal; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000494:pharmacology; D005311:Fetal Hypoxia / Q000201:enzymology* / Q000503:physiopathology; D005865:Gestational Age; D000860:Hypoxia / Q000201:enzymology* / Q000503:physiopathology; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D018994:Myosin Light Chains / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012756:Sheep; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects; D054460:rho-Associated Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D020536:Enzyme Activators; D018994:Myosin Light Chains; D047428:Protein Kinase Inhibitors; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020930:MAP Kinase Kinase Kinases; D010749:Phosphoprotein Phosphatases; D020742:rhoA GTP-Binding Protein