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Delayed Gelatinase Inhibition Induces Reticulon 4 Receptor Expression in the Peri-Infarct Cortex
Sándor Nardai1, Arpád Dobolyi1, Judit Skopál1
1From the Department Section of Vascular Neurology, Heart and Vascular Center, Semmelweis University, Budapest, Hungary (SN, JS, KL, BM, ZN); National Institute of Clinical Neurosciences, Budapest, Hungary (SN, ZN); and NAP Laboratory of Molecular and Systems Neurobiology, Institute of Biology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary (AD).
Abstract:
Matrix metalloproteinase (MMP) inhibition can potentially prevent hemorrhagic transformation following cerebral infarction; however, delayed-phase MMP activity is also necessary for functional recovery after experimental stroke. We sought to identify potential mechanisms responsible for the impaired recovery associated with subacute MMP inhibition in a transient middle cerebral artery occlusion model of focal ischemia in CD rats. Gelatinase inhibition was achieved by intracerebral injection of the Fn-439 MMP inhibitor 7 days after stroke. Treatment efficacy was determined on day 9 by in situ gelatin zymography. The peri-infarct cortex was identified by triphenyl tetrazolium chloride staining, and tissue samples were dissected for TaqMan array gene-expression study. Of 84 genes known to influence poststroke regeneration, we found upregulation of mRNA for the reticulon 4 receptor (Rtn4r), a major inhibitor of regenerative nerve growth in the adult CNS, and borderline expression changes for 3 additional genes (DCC, Jun, and Ngfr). Western blot confirmed increased Rtn4r protein in the peri-infarct cortex of treated animals, and double immunolabeling showed colocalization primarily with the S100 astrocyte marker. These data suggest that increased Rtn4 receptor expression in the perilesional cortex may contribute to the impaired regeneration associated with MMP inhibition in the subacute phase of cerebral infarction.
Insights
Subacute inhibition of matrix metalloproteinases (MMPs) after stroke impairs functional recovery by increasing the expression of the nerve growth inhibitor reticulon 4 receptor (Rtn4r). This suggests a novel mechanism for post-stroke regeneration challenges.
Area of Science:
- Neuroscience
- Biochemistry
- Regenerative Medicine
Background:
- Matrix metalloproteinase (MMP) activity is crucial for both preventing hemorrhagic transformation and enabling functional recovery after cerebral infarction.
- Subacute inhibition of MMPs has been linked to impaired recovery, but the underlying mechanisms remain unclear.
Purpose of the Study:
- To investigate the molecular mechanisms behind impaired functional recovery following subacute matrix metalloproteinase inhibition in a rat model of focal cerebral ischemia.
- To identify specific genes and pathways affected by MMP inhibition during the subacute phase of stroke.
Main Methods:
- A transient middle cerebral artery occlusion model was used in CD rats.
- Gelatinase inhibition was achieved via intracerebral injection of the Fn-439 MMP inhibitor 7 days post-stroke.
- Gene expression analysis (TaqMan array) and protein validation (Western blot, immunolabeling) were performed on peri-infarct cortex tissue.
Main Results:
- Subacute MMP inhibition led to the upregulation of reticulon 4 receptor (Rtn4r) mRNA and protein in the peri-infarct cortex.
- Rtn4r, a known inhibitor of nerve regeneration, was found to be primarily colocalized with astrocyte markers.
- Borderline expression changes were observed for DCC, Jun, and Ngfr.
Conclusions:
- Increased expression of the Rtn4 receptor in the peri-infarct cortex may be a key mechanism contributing to impaired nerve regeneration after subacute MMP inhibition.
- These findings highlight a potential therapeutic target for enhancing recovery following stroke.
