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Thrombin induces ischemic LTP (iLTP): implications for synaptic plasticity in the acute phase of ischemic stroke.

Stein ES, Itsekson-Hayosh Z, Aronovich A, Reisner Y, Bushi D, Pick CG, Tanne D, Chapman J, Vlachos A, Maggio N - Sci Rep (2015)

Bottom Line: Upon OGD, thrombin activity increased in hippocampal slices.A robust potentiation of excitatory synaptic strength was detected, which occluded the ability to induce further LTP.Inhibition of either thrombin or its receptor PAR1 blocked iLTP and restored the physiological, stimulus induced LTP.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, The Chaim Sheba Medical Center, Tel HaShomer, Israel.

ABSTRACT
Acute brain ischemia modifies synaptic plasticity by inducing ischemic long-term potentiation (iLTP) of synaptic transmission through the activation of N-Methyl-D-aspartate receptors (NMDAR). Thrombin, a blood coagulation factor, affects synaptic plasticity in an NMDAR dependent manner. Since its activity and concentration is increased in brain tissue upon acute stroke, we sought to clarify whether thrombin could mediate iLTP through the activation of its receptor Protease-Activated receptor 1 (PAR1). Extracellular recordings were obtained in CA1 region of hippocampal slices from C57BL/6 mice. In vitro ischemia was induced by acute (3 minutes) oxygen and glucose deprivation (OGD). A specific ex vivo enzymatic assay was employed to assess thrombin activity in hippocampal slices, while OGD-induced changes in prothrombin mRNA levels were assessed by (RT)qPCR. Upon OGD, thrombin activity increased in hippocampal slices. A robust potentiation of excitatory synaptic strength was detected, which occluded the ability to induce further LTP. Inhibition of either thrombin or its receptor PAR1 blocked iLTP and restored the physiological, stimulus induced LTP. Our study provides important insights on the early changes occurring at excitatory synapses after ischemia and indicates the thrombin/PAR1 pathway as a novel target for developing therapeutic strategies to restore synaptic function in the acute phase of ischemic stroke.

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Related in: MedlinePlus

Previous exposures to thrombin or PAR1-AP occlude the induction of later iLTP.Either (a) 1 U thrombin or (b) 1 μM PAR1-AP induce a slow onset LTP and saturate the induction of further potentiation upon brief exposure (3 minutes) to OGD. Averaged EPSPs are plotted versus time. Representative traces at indicated times (a, b) are shown for each section.
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f3: Previous exposures to thrombin or PAR1-AP occlude the induction of later iLTP.Either (a) 1 U thrombin or (b) 1 μM PAR1-AP induce a slow onset LTP and saturate the induction of further potentiation upon brief exposure (3 minutes) to OGD. Averaged EPSPs are plotted versus time. Representative traces at indicated times (a, b) are shown for each section.

Mentions: In order to gain further evidences on the role of thrombin and PAR1 on iLTP induction, we hypothesized that previous exposure of the slice to either thrombin or a specific PAR1 agonist will occlude further potentiation following OGD, due to the earlier recruitment of the PAR1 signaling pathway. This assumption was tested in an experimental setting using an additional stimulating electrode in order to examine two parallel pathways in the same slice28. Exposure to either 1 U thrombin or 1 μM of the specific PAR1 agonist-activating peptide SFLLRN (PAR1-AP, Fig. 3a and 3b) resulted in a slow onset LTP, as shown previously17. When potentiation levels reached asymptote, stimulation intensity at one pathway was reduced to the level before drug application and OGD was then applied. In this condition, a transient depression of transmission was still evoked in both pathways following exposure to OGD. However, no iLTP was induced in the previously depotentiated path, indicating that prior exposure to either thrombin or PAR1-AP saturated the ability to induce further iLTP. At the alternate path, EPSP slopes reached the same levels of potentiation previously accomplished (Fig. 3a and 3b). These experiments concluded that thrombin induces iLTP in hippocampal slices exposed to OGD through the activation of PAR1.


Thrombin induces ischemic LTP (iLTP): implications for synaptic plasticity in the acute phase of ischemic stroke.

Stein ES, Itsekson-Hayosh Z, Aronovich A, Reisner Y, Bushi D, Pick CG, Tanne D, Chapman J, Vlachos A, Maggio N - Sci Rep (2015)

Previous exposures to thrombin or PAR1-AP occlude the induction of later iLTP.Either (a) 1 U thrombin or (b) 1 μM PAR1-AP induce a slow onset LTP and saturate the induction of further potentiation upon brief exposure (3 minutes) to OGD. Averaged EPSPs are plotted versus time. Representative traces at indicated times (a, b) are shown for each section.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4300504&req=5

f3: Previous exposures to thrombin or PAR1-AP occlude the induction of later iLTP.Either (a) 1 U thrombin or (b) 1 μM PAR1-AP induce a slow onset LTP and saturate the induction of further potentiation upon brief exposure (3 minutes) to OGD. Averaged EPSPs are plotted versus time. Representative traces at indicated times (a, b) are shown for each section.
Mentions: In order to gain further evidences on the role of thrombin and PAR1 on iLTP induction, we hypothesized that previous exposure of the slice to either thrombin or a specific PAR1 agonist will occlude further potentiation following OGD, due to the earlier recruitment of the PAR1 signaling pathway. This assumption was tested in an experimental setting using an additional stimulating electrode in order to examine two parallel pathways in the same slice28. Exposure to either 1 U thrombin or 1 μM of the specific PAR1 agonist-activating peptide SFLLRN (PAR1-AP, Fig. 3a and 3b) resulted in a slow onset LTP, as shown previously17. When potentiation levels reached asymptote, stimulation intensity at one pathway was reduced to the level before drug application and OGD was then applied. In this condition, a transient depression of transmission was still evoked in both pathways following exposure to OGD. However, no iLTP was induced in the previously depotentiated path, indicating that prior exposure to either thrombin or PAR1-AP saturated the ability to induce further iLTP. At the alternate path, EPSP slopes reached the same levels of potentiation previously accomplished (Fig. 3a and 3b). These experiments concluded that thrombin induces iLTP in hippocampal slices exposed to OGD through the activation of PAR1.

Bottom Line: Upon OGD, thrombin activity increased in hippocampal slices.A robust potentiation of excitatory synaptic strength was detected, which occluded the ability to induce further LTP.Inhibition of either thrombin or its receptor PAR1 blocked iLTP and restored the physiological, stimulus induced LTP.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, The Chaim Sheba Medical Center, Tel HaShomer, Israel.

ABSTRACT
Acute brain ischemia modifies synaptic plasticity by inducing ischemic long-term potentiation (iLTP) of synaptic transmission through the activation of N-Methyl-D-aspartate receptors (NMDAR). Thrombin, a blood coagulation factor, affects synaptic plasticity in an NMDAR dependent manner. Since its activity and concentration is increased in brain tissue upon acute stroke, we sought to clarify whether thrombin could mediate iLTP through the activation of its receptor Protease-Activated receptor 1 (PAR1). Extracellular recordings were obtained in CA1 region of hippocampal slices from C57BL/6 mice. In vitro ischemia was induced by acute (3 minutes) oxygen and glucose deprivation (OGD). A specific ex vivo enzymatic assay was employed to assess thrombin activity in hippocampal slices, while OGD-induced changes in prothrombin mRNA levels were assessed by (RT)qPCR. Upon OGD, thrombin activity increased in hippocampal slices. A robust potentiation of excitatory synaptic strength was detected, which occluded the ability to induce further LTP. Inhibition of either thrombin or its receptor PAR1 blocked iLTP and restored the physiological, stimulus induced LTP. Our study provides important insights on the early changes occurring at excitatory synapses after ischemia and indicates the thrombin/PAR1 pathway as a novel target for developing therapeutic strategies to restore synaptic function in the acute phase of ischemic stroke.

Show MeSH
Related in: MedlinePlus