title: Neuronal damage and functional deficits are ameliorated by inhibition of aquaporin and HIF1α after traumatic brain injury (TBI).
abstract: The present study, using a rodent model of closed-head diffuse traumatic brain injury (TBI), investigated the role of dysregulated aquaporins (AQP) 4 and 9, as well as hypoxia inducible factor -1α(HIF-1α) on brain edema formation, neuronal injury, and functional deficits. TBI was induced in adult (400-425 g), male Sprague-Dawley rats using a modified Marmarou's head impact-acceleration device (450 g weight dropped from 2m height). Animals in each treatment group were administered intravenous anti-AQP4 or -AQP9 antibodies or 2-Methoxyestradiol (2ME2, an inhibitor of HIF-1α) 30 min after injury. At 24h post-TBI, animals (n=6 each group) were sacrificed to examine the extent of brain edema by water content, as well as protein expression of AQP and HIF-1α by Western immune-blotting. At 48-hours post-TBI, neuronal injury (n=8 each group) was assessed by FluoroJade (FJ) histochemistry. Spatial learning and memory deficits were evaluated by radial arm maze (n=8 each group) up to 21 days post-TBI. Compared to non-injured controls, significant (p<0.05) increases in the expression of AQP4 and -9 were detected in the brains of injured animals. In addition, significant (p<0.05) brain edema after TBI was associated with increases (p <0.05) both in neuronal injury (FJ labeling) and neurobehavioral deficits. Selective inhibition of either AQP4 or -9, or HIF-1α significantly (p<0.05) decreased the expression of the proteins. In addition, inhibition of the AQPs and HIF-1α significantly (p<0.05) ameliorated brain edema, as well as the number of injured neurons in cortical layers II/III and V/VI, striatum and hippocampal regions CA1/CA3. Finally, compared to the non-treated TBI animals, AQP or HIF-1α inhibition significantly (p<0.01) improved neurobehavioral outcomes after TBI. Taken together, the present data supports a causal relation between HIF-AQP mediated cerebral edema, secondary neuronal injury, and tertiary behavioral deficits post-TBI. The data further suggests that upstream modulation of the molecular patho-trajectory effectively ameliorates both neuronal injury and behavioral deficits post-TBI.
authors.affiliation: Department of Neurological Surgery, Wayne State University School of Medicine and College of Engineering, Detroit, MI, USA.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Shenaq
authors.forename: Hassan
authors.initials: H
authors.lastname: Kassem
authors.forename: Changya
authors.initials: C
authors.lastname: Peng
authors.forename: Steven
authors.initials: S
authors.lastname: Schafer
authors.forename: Jamie Y
authors.initials: JY
authors.lastname: Ding
authors.forename: Vance
authors.initials: V
authors.lastname: Fredrickson
authors.forename: Murali
authors.initials: M
authors.lastname: Guthikonda
authors.forename: Christian W
authors.initials: CW
authors.lastname: Kreipke
authors.forename: José A
authors.initials: JA
authors.lastname: Rafols
authors.forename: Yuchuan
authors.initials: Y
authors.lastname: Ding
mesh_terms: D000077584:2-Methoxyestradiol; D000818:Animals; D051401:Aquaporin 4 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D020346:Aquaporins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D001925:Brain Damage, Chronic / Q000209:etiology / Q000517:prevention & control / Q000523:psychology; D001929:Brain Edema / Q000209:etiology / Q000517:prevention & control; D001930:Brain Injuries / Q000150:complications / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology / Q000523:psychology; D056547:CA1 Region, Hippocampal / Q000473:pathology; D056654:CA3 Region, Hippocampal / Q000473:pathology; D002463:Cell Membrane Permeability / Q000187:drug effects; D003342:Corpus Striatum / Q000473:pathology; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D005452:Fluoresceins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D007074:Immunoglobulin G / Q000276:immunology / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008569:Memory Disorders / Q000209:etiology / Q000517:prevention & control; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009474:Neurons / Q000473:pathology; D009930:Organic Chemicals / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: C496032:Aqp4 protein, rat; C491637:Aqp9 protein, rat; D051401:Aquaporin 4; D020346:Aquaporins; D005452:Fluoresceins; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007074:Immunoglobulin G; D009419:Nerve Tissue Proteins; D009930:Organic Chemicals; C435731:fluoro jade; D004958:Estradiol; D000077584:2-Methoxyestradiol