Minocycline protects against brain injury in a rodent model of subarachnoid hemorrhage

Abstract Background and Purpose: The multifaceted nature of Subarachnoid hemorrhage (SAH) pathogenesis is poorly understood. Despite the high morbidity and disability rate associated with SAH, to date, no pharmacological agent has been found to be efficacious for the prevention of brain injury when used for acute SAH intervention.Methods: We studied SAH brain injury using in vivo pre-chiasmatic subarachnoid hemorrhage rodent model. We analyzed the qualitative and quantitative ultrastructural morphology of capillaries and surrounding neuropil in the rodent brains with SAH and/or minocycline administration. We also performed vast analysis of mRNA, protein and in situ expression of tight junctions proteins, claudin-5 and occludin and matrix metalloproteinases, MMP-2, MMP-9 and their upstream activator EMMPRIN. Lastly, we tested minocycline effect on functional outcomes in tested rats. Results: Here, we report that 1 mg/kg minocycline displayed neuroprotective effects on neurovascular morphology. Using ultrastructural analyses, we found that minocycline protected brain capillaries and surrounding cells from significant SAH-induced changes. Further analysis revealed that the blood-brain barrier in SAH brains is compromised by abnormal vacuole and vesicle production, rather than by tight junction disruptions, which were found to be generally intact. Additionally, our findings suggested that the reported ultrastructural abnormalities as well as minocycline neuroprotective effect during SAH were not directly mediated by the inhibition of MMP-2, MMP-9, or EMMPRIN. However, SAH brain tissue treated with minocycline was protected from development of other kind of morphological features associated with oxidative stress and the presence of immune cells in the perivascular space. Conclusions: These data expand knowledge on the SAH effect on brain tissue as well as functional outcome in the SAH rodent model and minocycline neuroprotective effect when administered in low-doses. Additionally, we showed the multifactorial neuroprotective mechanism of minocycline, as is the pathology associated with SAH.