ΔΨm compared with controls. This decline inΔΨm was almost completely prevented by 1 g/ml AA. The higher dose not only prevented such decline but slightly increased ΔΨm over control levels, indicating a hyperpolarizing effect. p Trifluoromethoxy carbonyl cyanide phenyl hydrazone, a mitochondrial uncoupler, Volasertib BI6727 added at the end of the experiment to the cultures almost completely diminished TMRE fluorescence within 10 min. DISCUSSION The demonstration that AA and its derivatives are capable of improving neurological function through multiple mechanisms led us to hypothesize that AA could shield the brain from the deleterious effects of stroke. The present data show for the first time that a dose regimen of 75 mg/kg AA administered pre or Krishnamurthy et al. Page 7 J Neurosci Res.
Author manuscript, available in PMC 2010 September 19. NIH PA Author Manuscript NIH PA Author Manuscript NIH PA Author Manuscript postischemia was effective in markedly reducing infarct volume measured by TTC staining at 24 hr after pMCAO. This BMS 777607 1196681-44-3 effect could not be explained by changes in physiological parameters, insofar as no differences in factors such as cerebrovascular blood flow, body weight, pCO2, pO2, or temperature were observed between vehicle and AA treated mice. Although a small, significant decrease in pH values was detected in AA treated mice relative to vehicle treated animals, it cannot account for the AA induced reduction in infarct volume, insofar as tissue acidosis has been shown to exacerbate brain injury.
The neuroprotective effect of AA, however, followed a U shaped concentration response curve, typical of a hormetic response, where lower or higher doses were not effective in reducing the infarct volume significantly, though higher doses were not toxic to animals. AA has been reported to induce cell cycle arrest and to have cytotoxic effects on various cancer cells. This can explain, at least in part, the observed hormetic like response and indicates that it should be taken into consideration when designing experiments aimed at assessing AA neuroprotection against ischemic injury in vivo. Our present data also show that AA associated neuroprotection was maintained for up to 7 days following pMCAO. Compared with the vehicle group, treatment with AA was able to lessen the infarct size with time, suggesting that AA did not simply delay the onset of ischemia but rather protected the brain.
In humans, stroke is associated with deficits in cognitive and sensorimotor functions. After permanent or focal ischemia, rodents also exhibit impaired neurological functions. Neurological scoring is a valuable index to evaluate behavioral performances after ischemia. With the 18 point scale from Garcia et al., deficits in neurological performances were evident in all vehicle treated animals at 24 hr after pMCAOinduced ischemia. In contrast, 75 mg/kg AA treatment significantly ameliorated the neurological functional outcome compared with the control group. No statistical differences in neurological performances were observed between vehicle and AA treated ischemic mice at 7 days after pMCAO.
This can be explained by the observation that, as previously described, infarct volume in the vehicle group decreased overtime so that, by 7 days post pMCAO, no significant deficiency could be observed. Finally, no noticeable adverse behavioral effects were observed in AA treated nonlesioned mice compared with vehicletreated animals. Cerebral ischemia elicits breakdown of the BBB, which leads to the leakage of vascular inflammatory cells and proteins to the brain, the subsequent activation of inflammatory cascades, and further cerebral insult. To gain insights into the mechanisms through which AA exerts its neuroprotective activity, we examined the BBB integrity by lookin