Targeting mitogen-activated protein kinase in acute ischaemic stroke

Caryocar brasiliense peel ethanolic extract has neuroprotective potential and reduces the activation of ERK1/2 in the ischemia and reperfusion brain acute phase in the rat

Oxidative stress induced by ischemia and reperfusion (I/R) injury results in cell death by necrosis or apoptosis and triggers the activation of different intracellular pathways, such as mitogen-activated protein activated kinases. Pequi (Caryocar brasiliense) peel, residue of a fruit from Brazilian savannah-like vegetation, has phenolic compounds that have been demonstrated to have antioxidant effects in vitro. The present study aimed to evaluate the neuroprotective effects of C. brasiliense peel ethanolic extract (CBPE) against transient global I/R injury in the rat brain. Global ischemia for 5, 20, and 45 min followed by 2 h of reperfusion caused a significant time-dependent increase in the number of ischemic neurons (p ≤ 0.05); increased immunoreactivity of cleaved caspase-3 (CASP3); and activated extracellular signal-regulated kinase (ERK) 1/2. Pretreatment with CBPE (600 mg/kg, oral) or vitamin E (0.6 mg, oral) for 30 days showed significant protection against acute brain injury induced by 20 and 45 min or 5 min of ischemia, respectively, by reducing the cortical ischemic neuron count (p ≤ 0.05) and p-ERK1/2 immunoreactivity. In addition, active c-Jun N-terminal kinase (JNK) immunoreactivity was reduced in animals not subjected to ischemia. Therefore, we suggest an association between vitamin E and CBPE, which may generate a better neuroprotective response. Interestingly, mainly in the hippocampus and oligodendrocytes, high dose CBPE increase the number of isquemic neurons and of CASP3 immunoreactive cells in animals subjected or not to ischemia, which was not verified in the vitamin E group. Therefore, additional studies are recommended to verify the safety of the continuous use of CBPE.

Deregulated Protein Kinases: Friend and Foe in Ischemic Stroke

Ischemic stroke is the third leading cause of mortality worldwide, but its medical management is still limited to the use of thrombolytics as a lifesaving option. Multiple molecular deregulations of the protein kinase family occur during the period of ischemia/reperfusion. However, experimental studies have shown that alterations in the expression of essential protein kinases and their pharmacological modulation can modify the neuropathological milieu and hasten neurophysiological recovery. This review highlights the role of key protein kinase members and their implications in the evolution of stroke pathophysiology. Activation of ROCK-, MAPK-, and GSK-3β-mediated pathways following neuronal ischemia/reperfusion injury in experimental conditions aggravate the neuropathology and delays recovery. Targeting ROCK, MAPK, and GSK-3β will potentially enhance myelin regeneration, improve blood-brain barrier (BBB) function, and suppress inflammation, which ameliorates neuronal survival. Conversely, protein kinases such as PKA, Akt, PKCα, PKCε, Trk, and PERK salvage neurons post-ischemia by mechanisms including enhanced toxin metabolism, restoring BBB integrity, neurotrophic effects, and apoptosis suppression. Certain protein kinases such as ERK1/2, JNK, and AMPK have favourable and unfavourable effects in salvaging ischemia-injured neurons. Targeting multiple protein kinase-mediated pathways simultaneously may improve neuronal recovery post-ischemia.