title: tPA promotes cortical neuron survival via mTOR-dependent mechanisms.
abstract: Tissue plasminogen activator (tPA) is a thrombolytic agent commonly used in the treatment of ischemic stroke. While the thrombolytic effects of tPA have been well established, the impact of this blood-brain barrier (BBB) crossing drug on neurons is not known. Given the widespread use of tPA in the clinical setting and the strict therapeutic window established for effective use of the drug, we examined the molecular mechanisms mediating the impact of tPA on postnatal cortical neurons isolated from the mouse brain. Dissociated postnatal primary cortical neurons were treated with tPA and the effects on neuron survival were evaluated. Pharmacological inhibitors of several signaling pathways previously implicated in neuroprotection (mTOR, JAK/STAT, MAPK and PKA-dependent mechanisms) were used to pinpoint the mechanistic effectors of tPA on neuron survival in vitro. We report here that tPA treatment results in a time-dependent neuroprotective effect on postnatal cortical neurons that relies predominantly on Janus kinase (JAK) and mammalian target of rapamycin (mTOR) signaling mechanisms. Taken together, these data suggest that tPA promotes neuroprotection in a temporally-regulated manner and that both JAK and mTOR signaling effectors are critical mediators of this neuroprotective effect. The results suggest the possibility of targeting these defined mechanisms to potentially expand the therapeutic window for tPA.
authors.affiliation: Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada. Electronic address: Julia.Grummisch@carleton.ca.
authors.forename: Julia A
authors.initials: JA
authors.lastname: Grummisch
authors.affiliation: Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada. Electronic address: Nafisa.Jadavji@carleton.ca.
authors.forename: Nafisa M
authors.initials: NM
authors.lastname: Jadavji
authors.affiliation: Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada. Electronic address: Patrice.Smith@carleton.ca.
authors.forename: Patrice D
authors.initials: PD
authors.lastname: Smith
mesh_terms: D000818:Animals; D002470:Cell Survival; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D053612:Janus Kinases / Q000037:antagonists & inhibitors; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D010959:Tissue Plasminogen Activator / Q000494:pharmacology*
chemical_list: D018696:Neuroprotective Agents; D047428:Protein Kinase Inhibitors; D053612:Janus Kinases; D058570:TOR Serine-Threonine Kinases; D010959:Tissue Plasminogen Activator
keywords: Cell survival; Cellular and molecular mechanisms; JAK/STAT; Neuroprotection; Primary postnatal cortical neurons; Tissue plasminogen activator (tPA); mTOR