Time course of normobaric hyperoxia preconditioning on NCX2, 3 expression

Introduction: the purpose of this study was to determine na-ca exchanger 2, 3 (ncx2, 3) protein level changes during 2, 5, 10, 15 days after induction of normobaric hyperoxia (ho) preconditioning. materials and methods: rats were divided in two experimental groups. the first group was exposed to 95% inspired ho for 4 h/day for 6 consecutive days (ho). the second group acted as control, and was exposed to 21% oxygen in the same chamber. each main group was subdivided to middle cerebral artery occlusion (mcao-operated) and intact (without any surgery) subgroups. after 2, 5, 10 and 15 days from pretreatment, mcao-operated subgroups were subjected to 60 min of right mcao. after 24 hours reperfusion, neurologic deficit score (nds) and infarct volume (iv) were measured in mcao-operated subgroups. the ncx 2, 3 expression levels of core, penumbra and subcortex regions were assessed in sham-operated and intact subgroups. results: expression of ncx 2, 3 proteins were increased in penumbra (p=0.000, p=0.002), core (p=0.001, p=0.033) and just ncx3 was increased in subcortex (p=0.033) during preconditioning with ho. neurologic deficit score and infarct volume were decreased with ho preconditioning. these effects of hyperoxia disappeared gradually during 15 days after pretreatment. conclusion: although further studies are needed to clarify the mechanisms of time course of neuroprotection, ho durable effects on ncx2, 3 expression, iv and nds are consistent with an active role in the genesis of ischemic neuroprotection. abbreviation: anova: analysis of variance; bbb: blood brain barrier; eaat: excitatory amino acid transporter; edta: ethylenediaminetetraacetic acid; ho: normobaric hyperoxia; i: intact; i-ho: intact normobaric hyperoxia subgroup; i-ra: intact normobaric normoxia subgroup; it: ischemic tolerance; lsd: least significant difference; mca: middle cerebral artery; mcao: middle cerebral artery occlusion; ncx: na+-ca2+exchanger; nds: neurologic deficit score; nf-kb: nuclear factor- kappa b; o-ho: mcao-operated normobaric hyperoxia subgroup; o-ra: mcao-operated normobaric normoxia subgroup; p38mapk: p38 mitogen-activated protein kinase; pvdf: polyvinylidenedifluoride; ra: room air (normobaric normoxia); s: sham; sds-page: sodium dodecyl sulfate polyacrylamide gel electrophoresis; sem: standard error of mean; tnf-alpha: tumour necrosis factor- alpha