Sumoylation of Hypoxia-Inducible Factor-1α Ameliorates Failure of Brain Stem Cardiovascular Regulation in Experimental Brain Death

• Published in: PloS one Vol. 6; no. 3; p. e17375
• Main Authors: Chan, Julie Y. H., Tsai, Ching-Yi, Wu, Carol H. Y., Li, Faith C. H., Dai, Kuang-Yu, Sun, Enya Y. H., Chan, Samuel H. H., Chang, Alice Y. W.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 03.03.2011; Public Library of Science (PLoS)
• Subjects: Animal models; Animals; Biology; Blood pressure; Brain; Brain death; Brain Death - metabolism; Brain Death - pathology; Brain stem; Brain Stem - metabolism; Brain Stem - pathology; Cardiovascular System - metabolism; Cell Nucleus - metabolism; Cerebral blood flow; Coma; Confocal microscopy; Cyclic GMP-Dependent Protein Kinases - metabolism; Death; Deregulation; Disease Models, Animal; Enzyme-linked immunosorbent assay; Heme; Heme oxygenase (decyclizing); Hypoxia; Hypoxia - complications; Hypoxia - metabolism; Hypoxia-inducible factor 1; Hypoxia-inducible factor 1 alpha; Hypoxia-Inducible Factor 1, alpha Subunit - genetics; Hypoxia-Inducible Factor 1, alpha Subunit - metabolism; Hypoxia-inducible factors; Immunoprecipitation; Ischemia; Kinases; Machinery; Machinery and equipment; Male; Medicine; Medulla oblongata; Medulla Oblongata - enzymology; Medulla Oblongata - pathology; Mevinphos; Microscopy; Mortality; Neurons; Nitric oxide; Nitric Oxide Synthase Type I - metabolism; Nitric-oxide synthase; Oxygenase; Protein kinase; Protein kinase G; Proteins; Rats; Rats, Sprague-Dawley; Rodents; Signal Transduction; Signaling; SUMO protein; Sumoylation; Transcription; Transcription, Genetic; Translocation; Ubiquitin; Up-Regulation - genetics; Western blotting; Taiwan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0017375

One aspect of brain death is cardiovascular deregulation because asystole invariably occurs shortly after its diagnosis. A suitable neural substrate for mechanistic delineation of this aspect of brain death resides in the rostral ventrolateral medulla (RVLM). RVLM is the origin of a life-and-death signal that our laboratory detected from blood pressure of comatose patients that disappears before brain death ensues. At the same time, transcriptional upregulation of heme oxygenase-1 in RVLM by hypoxia-inducible factor-1α (HIF-1α) plays a pro-life role in experimental brain death, and HIF-1α is subject to sumoylation activated by transient cerebral ischemia. It follows that sumoylation of HIF-1α in RVLM in response to hypoxia may play a modulatory role on brain stem cardiovascular regulation during experimental brain death. A clinically relevant animal model that employed mevinphos as the experimental insult in Sprague-Dawley rat was used. Biochemical changes in RVLM during distinct phenotypes in systemic arterial pressure spectrum that reflect maintained or defunct brain stem cardiovascular regulation were studied. Western blot analysis, EMSA, ELISA, confocal microscopy and immunoprecipitation demonstrated that drastic tissue hypoxia, elevated levels of proteins conjugated by small ubiquitin-related modifier-1 (SUMO-1), Ubc9 (the only known conjugating enzyme for the sumoylation pathway) or HIF-1α, augmented sumoylation of HIF-1α, nucleus-bound translocation and enhanced transcriptional activity of HIF-1α in RVLM neurons took place preferentially during the pro-life phase of experimental brain death. Furthermore, loss-of-function manipulations by immunoneutralization of SUMO-1, Ubc9 or HIF-1α in RVLM blunted the upregulated nitric oxide synthase I/protein kinase G signaling cascade, which sustains the brain stem cardiovascular regulatory machinery during the pro-life phase. We conclude that sumoylation of HIF-1α in RVLM ameliorates brain stem cardiovascular regulatory failure during experimental brain death via upregulation of nitric oxide synthase I/protein kinase G signaling. This information should offer new therapeutic initiatives against this fatal eventuality.