title: Acute mountain sickness, inflammation, and permeability: new insights from a blood biomarker study.
abstract: The pathophysiology of acute mountain sickness (AMS) is unknown. One hypothesis is that hypoxia induces biochemical changes that disrupt the blood-brain barrier (BBB) and, subsequently, lead to the development of cerebral edema and the defining symptoms of AMS. This study explores the relationship between AMS and biomarkers thought to protect against or contribute to BBB disruption. Twenty healthy volunteers participated in a series of hypobaric hypoxia trials distinguished by pretreatment with placebo, acetazolamide (250 mg), or dexamethasone (4 mg), administered using a randomized, double-blind, placebo-controlled, crossover design. Each trial included peripheral blood sampling and AMS assessment before (-15 and 0 h) and during (0.5, 4, and 9 h) a 10-h hypoxic exposure (barometric pressure = 425 mmHg). Anti-inflammatory and/or anti-permeability [interleukin (IL)-1 receptor agonist (IL-1RA), heat shock protein (HSP)-70, and adrenomedullin], proinflammatory (IL-6, IL-8, IL-2, IL-1β, and substance P), angiogenic, or chemotactic biomarkers (macrophage inflammatory protein-1β, VEGF, TNF-α, monocyte chemotactic protein-1, and matrix metalloproteinase-9) were assessed. AMS-resistant subjects had higher IL-1RA (4 and 9 h and overall), HSP-70 (0 h and overall), and adrenomedullin (overall) compared with AMS-susceptible subjects. Acetazolamide raised IL-1RA and HSP-70 compared with placebo in AMS-susceptible subjects. Dexamethasone also increased HSP-70 and adrenomedullin in AMS-susceptible subjects. Macrophage inflammatory protein-1β was higher in AMS-susceptible than AMS-resistant subjects after 4 h of hypoxia; dexamethasone minimized this difference. Other biomarkers were unrelated to AMS. Resistance to AMS was accompanied by a marked anti-inflammatory and/or anti-permeability response that may have prevented downstream pathophysiological events leading to AMS. Conversely, AMS susceptibility does not appear to be related to an exaggerated inflammatory response.
authors.affiliation: Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, 12469 East 17 Place, Bldg 400, Aurora, CO 80045-0508, USA.
authors.forename: Colleen Glyde
authors.initials: CG
authors.lastname: Julian
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Subudhi
authors.forename: Megan J
authors.initials: MJ
authors.lastname: Wilson
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Dimmen
authors.forename: Travis
authors.initials: T
authors.lastname: Pecha
authors.forename: Robert C
authors.initials: RC
authors.lastname: Roach
mesh_terms: D000086:Acetazolamide / Q000627:therapeutic use; D000208:Acute Disease; D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000097:blood* / Q000188:drug therapy / Q000473:pathology*; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use; D015415:Biomarkers; D001812:Blood-Brain Barrier / Q000187:drug effects; D001929:Brain Edema / Q000188:drug therapy / Q000209:etiology; D002257:Carbonic Anhydrase Inhibitors / Q000627:therapeutic use; D002463:Cell Membrane Permeability / Q000502:physiology*; D003907:Dexamethasone / Q000627:therapeutic use; D004311:Double-Blind Method; D005260:Female; D006261:Headache / Q000188:drug therapy / Q000209:etiology; D006801:Humans; D007249:Inflammation / Q000473:pathology*; D008297:Male; D009051:Mountaineering; D055815:Young Adult
chemical_list: D000893:Anti-Inflammatory Agents; D015415:Biomarkers; D002257:Carbonic Anhydrase Inhibitors; D003907:Dexamethasone; D000086:Acetazolamide