Exercise-induced oxidative-nitrosative stress is associated with impaired dynamic cerebral autoregulation and blood-brain barrier leakage.

The present study examined whether dynamic cerebral autoregulation and bloodbrain barrier function would become compromised as a result of exercise-induced oxidativenitrosative stress. Eight healthy men were examined at rest and after an incremental bout of semi-recumbent cycling exercise to exhaustion. Changes in a dynamic cerebral autoregulation index were determined during recovery from continuous recordings of blood flow velocity in the middle cerebral artery (MCAv) and mean arterial pressure during transiently induced hypotension. Electron paramagnetic resonance spectroscopy and ozone-based chemiluminescence were employed for direct detection of spin-trapped free radicals and nitric oxide metabolites in venous blood. Neuron-specific enolase, S100 beta and 3-nitrotyrosine were determined by ELISA. While exercise did not alter MCAv, it caused a mild reduction in the autoregulation index (from 6.9 +/- 0.6 to 5.5 +/- 0.9 a.u., P < 0.05) that correlated directly against the exercise-induced increase in the ascorbate radical, 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide and N-tert-butyl-a-phenylnitrone adducts, 3-nitrotyrosine and S100 beta (r=0.66 to 0.76, P < 0.05). In contrast, no changes in neuron-specific enolase were observed. In conclusion, our findings suggest that intense exercise has the potential to increase bloodbrain barrier permeability without causing structural brain damage subsequent to a free radical-mediated impairment in dynamic cerebral autoregulation.