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Inhibition of mitogen-activated protein kinase phosphatase-1 (MKP-1) increases experimental stroke injury
Lin Liu1, Sarah Doran1, Yan Xu1
1Department of Neuroscience, University of Connecticut Health Center, Farmington, CT, United States.
Background And Purpose:
Activation of mitogen-activated protein kinases (MAPKs), particularly c-jun-N-terminal kinases (JNK) and p38 exacerbates stroke injury by provoking pro-apoptotic and pro-inflammatory cellular signaling. MAPK phosphatase-1 (MKP-1) restrains the over-activation of MAPKs via rapid de-phosphorylation of the MAPKs. We therefore examined the role of MKP-1 in stroke and studied its inhibitory effects on MAPKs after experimental stroke.
Methods:
Male mice were subjected to transient middle cerebral artery occlusion (MCAO). MKP-1 knockout (KO) mice and a MKP-1 pharmacological inhibitor were utilized. We utilized flow cytometry, immunohistochemistry (IHC), and Western blots analysis to explore MKP-1 signaling and its effects on apoptosis/inflammation in the brain and specifically in microglia after stroke.
Results:
MKP-1 was highly expressed in the nuclei of both neurons and microglia after stroke. MKP-1 genetic deletion exacerbated stroke outcome by increasing infarct, neurological deficits and hemorrhagic transformation. Additionally, delayed treatment of the MKP-1 pharmacological inhibitor worsened stroke outcome in wild type (WT) mice but had no effect in MKP-1 KO mice. Furthermore, MKP-1 deletion led to increased c-jun-N-terminal kinase (JNK) activation and microglial p38 activation after stroke. Finally, MKP-1 deletion or inhibition increased inflammatory and apoptotic response as evidenced by the increased levels of interleukin-6 (IL-6), tumor necrosis factor α (TNFα), ratio of p-c-jun/c-jun and cleaved caspase-3 following ischemia.
Conclusions:
We have demonstrated that MKP-1 signaling is an endogenous protective mechanism in stroke. Our data imply that MKP-1 possesses anti-apoptotic and anti-inflammatory properties by simultaneously controlling the activities of JNK and microglial p38.
Insights
MAPK Phosphatase-1 (MKP-1) protects the brain after stroke by reducing inflammation and apoptosis. Inhibiting MKP-1 worsens stroke outcomes, highlighting its crucial protective role.
Area of Science:
- Neuroscience
- Molecular Biology
- Immunology
Background:
- Mitogen-activated protein kinases (MAPKs), including JNK and p38, worsen stroke injury through pro-apoptotic and pro-inflammatory pathways.
- MAPK Phosphatase-1 (MKP-1) deactivates MAPKs, acting as a crucial regulator of cellular signaling.
Purpose of the Study:
- To investigate the role of MKP-1 in experimental stroke.
- To evaluate the effects of MKP-1 on MAPK activation, apoptosis, and inflammation post-stroke.
Main Methods:
- Transient middle cerebral artery occlusion (MCAO) model in male mice.
- Utilized MKP-1 knockout (KO) mice and a pharmacological inhibitor.
- Analyzed brain tissue using flow cytometry, immunohistochemistry, and Western blots for MKP-1, MAPKs, apoptosis, and inflammatory markers.
Main Results:
- MKP-1 was upregulated in neurons and microglia post-stroke.
- MKP-1 deletion or inhibition worsened stroke outcomes, increasing infarct size and neurological deficits.
- MKP-1 deficiency elevated JNK and microglial p38 activation, alongside increased inflammatory cytokines (IL-6, TNFα) and apoptosis markers (cleaved caspase-3).
Conclusions:
- MKP-1 functions as an endogenous protective mechanism in stroke.
- MKP-1 exhibits anti-apoptotic and anti-inflammatory properties by regulating JNK and microglial p38 activity.