CEREBROVASCULAR CONTRACTILE RESPONSES TO HIGH ALTITUDE LONG TERM HYPOXIA

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The overall theme of this project is to understand whereby acclimatization to high altitude long-term hypoxia (LTH) alters fundamental mechanisms in the cerebrovasculature of the fetus and adult. We also will examine these mechanisms in association with development from fetus to adult. This project is broadly based, multidisciplinary, and vertically integrated using physiologic, cellular, biochemical, and molecular approaches. Based on two decades of research, we shall test a number of hypotheses in sheep acclimatized to high altitude. The overall hypothesis is that high altitude, long-term hypoxia is associated with changes in cerebrovascular contractile responses secondary to altered alphai-adrenergic-receptor (or AR) subtypes and/or specific protein kinase C isoforms (PKC)-mediated downstream Ca2+-dependent and Ca -independent signal transduction pathways. An associated hypothesis is that LTH significantly alters Oi-AR-subtype- and specific PKC isozyme-mediated expression of proto-oncogenes and genes representing vascular smooth muscle "synthetic" and/or "proliferative" phenotypes, as compared to those of adult "contractile" phenotype. Four specific aims will examine the role of LTH in cerebral artery Or adrenergic-mediated signal tranduction of thin and thick myofilament, e.g., 1) roles of Oi-AR, PKC isoforms, extracellular signal regulated kinases (ERKs), and downstream effector proteins, 2) the role of plasma membrane and sarcoplasmic reticulum Ca2+ channels, 3) gene regulation of vascular phenotypes, and 4) signaling pathways gene/protein discovery. For the studies we will utilize agonist-induced contractility and intracellular [Ca2+], Western immunobiots, RT-PCR, RNAi silencing, confocal microscopy, 2D-gel-mass spectroscopy, and gene microarray/pathways analysis. Scientifically the studies will augment our understanding of basic mechanisms whereby fetal and adult cerebral vessels acclimatize to LTH. They also will illustrate aspects of development from fetus to adult. Clinically the studies relate to at least three critical problems. 1) For the fetus and newborn they relate to responses to prolonged hypoxia as occurs in women who live at high altitude, as well as those who smoke or are anemic, who have heart or lung disease; for the newborn altered cerebrovascular blood flow with intracerebral hemorrhage and pulmonary hypertension. 2) They also will contribute to understanding mechanisms of cardiovascular disorders and renatal "programming" of adult disease. 3) Finally, they are relevant to understanding mechanisms of diseases such as: Acute Mountain Sickness, Preeclampsia, and High Altitude Cerebral and Pulmonary Edema.