Tissue-type plasminogen activator is a neuroprotectant in the mouse hippocampus
Ramiro Echeverry, … , Johanna Guzman, Manuel Yepes
Ramiro Echeverry, … , Johanna Guzman, Manuel Yepes
Published May 3, 2010
Citation Information: J Clin Invest. 2010;120(6):2194-2205. https://doi.org/10.1172/JCI41722.
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Research Article Neuroscience

Tissue-type plasminogen activator is a neuroprotectant in the mouse hippocampus

Abstract

The best-known function of the serine protease tissue-type plasminogen activator (tPA) is as a thrombolytic enzyme. However, it is also found in structures of the brain that are highly vulnerable to hypoxia-induced cell death, where its association with neuronal survival is poorly understood. Here, we have demonstrated that hippocampal areas of the mouse brain lacking tPA activity are more vulnerable to neuronal death following an ischemic insult. We found that sublethal hypoxia, which elicits tolerance to subsequent lethal hypoxic/ischemic injury in a natural process known as ischemic preconditioning (IPC), induced a rapid release of neuronal tPA. Treatment of hippocampal neurons with tPA induced tolerance against a lethal hypoxic insult applied either immediately following insult (early IPC) or 24 hours later (delayed IPC). tPA-induced early IPC was independent of the proteolytic activity of tPA and required the engagement of a member of the LDL receptor family. In contrast, tPA-induced delayed IPC required the proteolytic activity of tPA and was mediated by plasmin, the NMDA receptor, and PKB phosphorylation. We also found that IPC in vivo increased tPA activity in the cornu ammonis area 1 (CA1) layer and Akt phosphorylation in the hippocampus, as well as ischemic tolerance in wild-type but not tPA- or plasminogen-deficient mice. These data show that tPA can act as an endogenous neuroprotectant in the murine hippocampus.

Authors

Ramiro Echeverry, Jialing Wu, Woldeab B. Haile, Johanna Guzman, Manuel Yepes

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Figure 6

Akt phosphorylation mediates tPA-induced delayed tolerance.

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Akt phosphorylation mediates tPA-induced delayed tolerance. (A) Represen...
(A) Representative image of Western blot analysis for Akt phosphorylated at serine 473 (pAkt), total Akt (tAkt), and β-actin in lysates from WT hippocampal neurons incubated during 60 minutes with 60 nM tPA, 60 nM itPA, or a combination of tPA and 10 μM MK-801. (B) Mean MTT reduction in hippocampal neurons incubated with tPA either alone or in combination with wortmannin 20 nM while exposed to OGD conditions for 55 minutes. n = 10. Error bars denote SD. *P < 0.05 compared with other experimental groups. (C) Mean MTT reduction in hippocampal neurons incubated with 60 nM tPA, 100 nM plasmin, or 20 nM wortmannin or with a combination of tPA and wortmannin or wortmannin and plasmin, followed 24 hours later by exposure to OGD conditions for 55 minutes. n = 12. Lines denote SD. *P < 0.05 compared with neurons treated with a combination of wortmannin and tPA; **P < 0.05 compared with neurons treated with a combination of wortmannin and plasmin. “PREC.” denotes the moment of incubation with each compound. MTT, quantification of cell survival by MTT assay.