Novel plasminogen activator inhibitor-1-derived peptide protects against impairment of cerebrovasodilation after photothrombosis through inhibition of JNK MAPK

Abstract

The sole FDA-approved treatment for acute stroke is recombinant tissue-type plasminogen activator (rtPA). However, rtPA aggravates the impairment of cerebrovasodilation induced by global hypoxia/ischemia; this impairment is attenuated by the preinjury treatment with the plasminogen activator inhibitor derivative EEIIMD. MAPK (a family of kinases, p38, and JNK) is upregulated after cerebral ischemia. In this study, we determined whether the novel plasminogen activator inhibitor-derived peptide, Ac-RMAPEEIIMDRPFLYVVR-amide, (PAI-1-DP) given 30 min before or 2 h after, focal central nervous system injury induced by photothrombosis would preserve responses to cerebrovasodilators and the role of p38 and JNK MAPK in such effects. Cerebrospinal fluid JNK and p38 levels were elevated by photothrombotic injury, an effect potentiated by rtPA. Cerebrovasodilation was blunted by photothrombosis and reversed to vasoconstriction by rtPA but restored to dilation by PAI-1-DP pre- and posttreatment. PAI-1-DP blocked JNK, but preserved p38 MAPK upregulation after photothrombosis. The JNK MAPK antagonist SP600125 prevented, and the p38 antagonist SB203580 potentiated, impaired cerebrovasodilation after photothrombosis. These data indicate that rtPA impairs cerebrovasodilation after injury by activating JNK, while p38 MAPK is protective, and that the novel peptide PAI-1-DP protects by inhibiting activation of JNK by rtPA. JNK MAPK inhibitors, including PAI-1-DP, may offer a novel approach to increase the benefit-to-risk ratio of thrombolytic therapy and enable its use in central nervous system ischemic disorders.

Tissue-Type Plasminogen Activator-A 296–299 Prevents Impairment of Cerebral Autoregulation After Stroke Through Lipoprotein-Related Receptor–Dependent Increase in cAMP and p38

“…The JNK isoform is upregulated robustly and contributes to tPA-mediated impairment of autoregulation after thrombotic stroke in the pig. 6,7 Indeed, results of the present study show that co-administration of the NMDA-R antagonist with wt-tPA prevented impairment of cerebral autoregulation after stroke, supporting the predominance of the pathway shown on the right side in Figure 5, wherein wt-tPA acts primarily on NMDA-Rs to contribute to damage after stroke, presumably, in part, via upregulation of JNK MAPK. 6,7 …”

“…In contrast, standard of care administration of wt-tPA in the same timeframe only transiently restores CBF 6,7 and blood flow values are in the ischemic range when determined at 1h post drug administration. Further, wt-tPA did not prevent impairment of cerebral autoregulation after stroke.…”

“…The concentrations of substances in CSF reflects those in brain parenchyma. 6,7 Thrombotic stroke reduced the concentration of cAMP, which was further reduced by administration of wt-tPA, but cAMP was augmented above levels in sham (control) animals after treatment with tPA-A 296-299 (Fig 3). In contrast, p38 MAPK was robustly augmented in animals given tPA-A 296-299 (Fig 3).…”

“…Pial artery reactivity was determined in small pial arteries close to the area of injury (peri-ischemic area) using the closed cranial window technique. 18 …”

“…wt-tPA, given in a clinically relevant timeframe after stroke in the pig, disrupts CBF autoregulation by impairing vasodilation. 6,7 In pigs with traumatic brain injury (TBI), we have shown that tPA impairs autoregulation by activating NMDA-Rs, 8 but the contribution of NMDA-R activation by tPA to neurotoxicity after ischemic stroke, identification of the pathogenic intracellular signaling pathway and means to limit this damage are unknown. Although the NMDA-R antagonist MK 801 protects against cerebral dysregulation after TBI, 9 its toxicity limits usage in humans indicating the need for novel approaches.…”