Traumatic brain injury (TBI) induces cerebrovascular oxidative stress, which is associated with neurovascular uncoupling, autoregulatory dysfunction, and persisting
cognitive decline in both pre-clinical models and patients. However, single mild TBI (mTBI), the most frequent form of
brain trauma, increases cerebral generation of
reactive oxygen species (ROS) only transiently. We hypothesized that comorbid conditions might exacerbate long-term ROS generation in cerebral arteries after mTBI. Because
hypertension is the most important cerebrovascular risk factor in populations prone to mild
brain trauma, we induced mTBI in normotensive and spontaneously hypertensive rats (SHR) and assessed changes in cytoplasmic and mitochondrial
superoxide (O2-) production by confocal microscopy in isolated middle cerebral arteries (MCA) 2 weeks after mTBI using
dihydroethidine (DHE) and the mitochondria-targeted redox-sensitive fluorescent
indicator dye MitoSox. We found that mTBI induced a significant increase in long-term cytoplasmic and mitochondrial O2- production in MCAs of SHRs and increased expression of the
nicotinamide adenine dinucleotide phosphate (
NADPH) oxidase subunit Nox4, which were reversed to the normal level by treating the animals with the cell-permeable, mitochondria-targeted
antioxidant peptide SS-31 (5.7 mg kg-1 day-1, i.p.). Persistent mTBI-induced oxidative stress in MCAs of SHRs was significantly decreased by inhibiting vascular
NADPH oxidase (apocyinin). We propose that
hypertension- and mTBI-induced cerebrovascular oxidative stress likely lead to persistent dysregulation of cerebral blood flow (CBF) and
cognitive dysfunction, which might be reversed by SS-31 treatment.