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Published on: August 17, 2021
Clec7a promotes hippocampal microglial activation in rats with status epilepticus via inducing the TLR4/MyD88/NF-κB
1Department of Pediatrics, Fujian Medical University Union Hospital, Fuzhou 350001, Fujian, China.
Abstract:
Microglial polarization imbalance between pro-inflammatory M1 and anti-inflammatory M2 phenotypes is a key mechanism in epilepsy-related neuroinflammation. This study explores the role of C-type lectin domain containing 7A (Clec7a) in M1 microglial polarization in epilepsy. An AAV-shClec7a was injected intra-hippocampally into Sprague-Dawley rats prior to induction of status epilepticus (SE) using lithium-pilocarpine. CLEC7A expression was assessed via qRT-PCR and Western blot. Histopathology was evaluated using H&E and Nissl staining. M1 markers and cytokines were analyzed by qRT-PCR/Western blot. The effects of Clec7a silencing were examined in kainic acid-stimulated BV2 cells and primary microglia. CLEC7A was significantly upregulated in epileptic models. AAV-shClec7a reduced Racine score, seizure frequency and duration, alleviated hippocampal damage, and suppressed M1 polarization and neuroinflammation, evidenced by decreased IBA1, iNOS, IL-1β, IL-6, and TNF-α, and increased IL-10 levels. Silencing Clec7a in vitro also inhibited M1 polarization and inflammation, and suppressed TLR4/MyD88/NF-κB pathway activation. Overexpression of Nfkb reversed the inhibition of M1 polarization induced by Clec7a silencing. Meanwhile, TLR4 inhibitor TAK-242 reversed Clec7a-induced M1 polarization. Clec7a is upregulated in epilepsy and promotes M1 polarization and neuroinflammation, mediated at least partially through the TLR4/MyD88/NF-κB signaling pathway.
Insights
C-type lectin domain containing 7A (Clec7a) promotes M1 microglial polarization and neuroinflammation in epilepsy. Silencing Clec7a reduced seizures and hippocampal damage by inhibiting the TLR4/MyD88/NF-κB pathway.
Area of Science:
- Neuroscience
- Immunology
- Pathology
Background:
- Microglial polarization imbalance, specifically M1 (pro-inflammatory) vs. M2 (anti-inflammatory) phenotypes, is central to epilepsy-related neuroinflammation.
- C-type lectin domain containing 7A (Clec7a) is implicated in microglial activation, but its specific role in M1 polarization within epilepsy remains unclear.
Purpose of the Study:
- To investigate the role of Clec7a in M1 microglial polarization and its contribution to neuroinflammation and seizures in an epilepsy model.
- To elucidate the signaling pathway involved in Clec7a-mediated M1 polarization.
Main Methods:
- An in vivo epilepsy model was established in Sprague-Dawley rats using lithium-pilocarpine, with intra-hippocampal injection of AAV-shClec7a to silence Clec7a expression.
- CLEC7A expression, histopathology, M1 markers (IBA1, iNOS), and inflammatory cytokines (IL-1β, IL-6, TNF-α, IL-10) were assessed.
- In vitro studies utilized kainic acid-stimulated BV2 cells and primary microglia to examine the effects of Clec7a silencing on M1 polarization and the TLR4/MyD88/NF-κB pathway.
Main Results:
- CLEC7A expression was significantly upregulated in epileptic models.
- Clec7a silencing reduced seizure severity (Racine score), frequency, and duration, and alleviated hippocampal damage.
- Clec7a silencing suppressed M1 polarization and neuroinflammation, decreasing pro-inflammatory markers (IBA1, iNOS, IL-1β, IL-6, TNF-α) and increasing anti-inflammatory IL-10.
- In vitro, Clec7a silencing inhibited M1 polarization and inflammation, suppressing the TLR4/MyD88/NF-κB pathway. NF-κB overexpression reversed this inhibition, while TLR4 inhibition (TAK-242) reversed Clec7a-induced M1 polarization.
Conclusions:
- Clec7a is upregulated in epilepsy and promotes M1 microglial polarization and associated neuroinflammation.
- The pro-inflammatory effects of Clec7a in epilepsy are mediated, at least partially, through the TLR4/MyD88/NF-κB signaling pathway.
- Targeting Clec7a may represent a novel therapeutic strategy for mitigating neuroinflammation and seizures in epilepsy.
