The aim of this review is to assess the role of the JNK signaling pathway in the disruption of the structural integrity of the BBB in animal models of stroke (MCAO/R, middle cerebral artery occlusion with reperfusion), Alzheimer’s disease, and brain tumors and to analyze the effects of compounds of various natures that directly or indirectly affect the activity of the JNK signaling pathway. This evidence concerns the gene MAPK8 and early-onset autosomal dominant Alzheimer disease.