Hypoxic pulmonary vasoconstriction (HPV) is a unique physiological response of the lung that acts to optimize gas exchange by diverting blood flow from poorly ventilated regions. The endothelium has been thought to play a mostly modulatory role in this phenomenon through the synthesis of vasoactive agents such as nitric oxide (NO), prostacyclin, and endothelin. Data is provided showing that acute hypoxia induces increases in NO biosynthesis, promoting S-nitrosation of the metal binding protein metallothionein (MT), which resulted in intracellular release of zinc. Hypoxia released zinc induced contraction of pulmonary endothelial cells and contributed to vasoconstriction of small, non-muscularized intra-acinar arteries in isolated perfused mouse lungs (IPL). The relevance of this NO/MT/Zn pathway in HPV was illustrated by pharmacological inhibition of NO synthesis and analysis of the response in MT knockout (MT-/-) mice, both of which resulted in a blunted pressure response to hypoxia in IPL. Signaling pathways were delineated, indicating how changes in intracellular zinc can alter the actin cytoskeleton and promote cellular contraction. It was found that either hypoxia or exogenous zinc resulted in increases in the formation and alignment of actin stress fibers. These changes were mediated through the inhibition of myosin light chain phosphatase (MLCP), which promoted phosphorylation of myosin light chain (MLC) and tension generation. Activation of PKC appeared to play a role in this process, as indicated by activation and translocation of the enzyme in response to both hypoxia and/or increases in labile zinc, and by the blunted contractile response in isolated endothelial cells following pharmacological inhibition of PKC or utilization of a PCKε dominant negative construct. These data suggest that the NO released in response to hypoxia promotes increases in MLC phosphorylation through zinc-dependent pathways, which in turn are responsible for the force induction and cell stability necessary to elicit an active contractile response in pulmonary endothelium.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-08172010-192901 |
| Date | 19 August 2010 |
| Creators | Bernal, Paula Jimena |
| Contributors | Linton M Traub, Daniel C Devor, Claudette M St Croix, Simon C Watkins, Bruce R Pitt |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-08172010-192901/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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