ABSTRACT
BACKGROUND/PURPOSE: Repetitive hyperbaric oxygen (HBO2) therapy may cause excessive generation of reactive oxygen species. This study assessed whether repetitive or 2-4-day trials of HBO2 therapy (2 treatments daily for 2-4 consecutive days) provides better effects in reducing brain inflammation and oxidative stress caused by middle cerebral artery occlusion (MCAO) in rats than did a 1-day trial of HBO2 therapy (2 treatments for 1 day). METHODS: Rats were randomly divided into four groups: sham; MCAO without HBO2 treatment; MCAO treated with 1-day trial of HBO2; and MCAO treated with 2-4-day trials of HBO2. One treatment of HBO2 (100% O2 at 253 kPa) lasted for 1 hour in a hyperbaric chamber. RESULTS: Therapy with the 2-4-day trials of HBO2 significantly and dose-dependently attenuated the MCAO-induced cerebral infarction and neurological deficits more than the 1-day trial of HBO2 therapy. The beneficial effects of repetitive HBO2 therapy were associated with: (1) reduced inflammatory status in ischemic brain tissues (evidenced by decreased levels of tumor necrosis factor-α, interleukin-1ß, and myeloperoxidase activity); (2) decreased oxidative damage in ischemic brain tissues (evidenced by decreased levels of reactive oxygen and nitrogen species, lipid peroxidation, and enzymatic pro-oxidants, but increased levels of enzymatic antioxidant defenses); and (3) increased production of an anti-inflammatory cytokine, interleukin-10. CONCLUSION: The results provide the apparently contradictory finding that heightened oxygen tension reduced oxidative stress (and inflammation), which was reflected by increased antioxidant and decreased oxidant contents under focal cerebral ischemia.
