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Published on: January 7, 2014
RIPK1 Regulates Microglial Activation in Lipopolysaccharide-Induced Neuroinflammation and MPTP-Induced Parkinson's
Do-Yeon Kim1, Yea-Hyun Leem1, Jin-Sun Park1
1Department of Molecular Medicine and Inflammation-Cancer Microenvironment Research Center, School of Medicine, Ewha Womans University, Seoul 07804, Republic of Korea.
Abstract:
Increasing evidence suggests a pivotal role of receptor-interacting protein kinase 1 (RIPK1), an initiator of necroptosis, in neuroinflammation. However, the precise role of RIPK1 in microglial activation remains unclear. In the present study, we explored the role of RIPK1 in lipopolysaccharide (LPS)-induced neuroinflammation and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model mice by using RIPK1-specific inhibitors necrostatin-1 (Nec-1) and necrostatin-1 stable (Nec-1s). Nec-1/Nec-1s or RIPK1 siRNA inhibited the production of proinflammatory molecules and the phosphorylation of RIPK1-RIPK3-MLKL and cell death in LPS-induced inflammatory or LPS/QVD/BV6-induced necroptotic conditions of BV2 microglial cells. Detailed mechanistic studies showed that Nec-1/Nec-1s exerted anti-inflammatory effects by modulating AMPK, PI3K/Akt, MAPKs, and NF-κB signaling pathways in LPS-stimulated BV2 cells. Subsequent in vivo studies showed that Nec-1/Nec-1s inhibited microglial activation and proinflammatory gene expression by inhibiting the RIPK1 phosphorylation in the brains of LPS-injected mice. Furthermore, Nec-1/Nec-1s exert neuroprotective and anti-inflammatory effects in MPTP-induced PD mice. We found that p-RIPK1 is mainly expressed in microglia, and thus RIPK1 may contribute to neuroinflammation and subsequent cell death of dopaminergic neurons in MPTP-induced PD model mice. These data suggest that RIPK1 is a key regulator of microglial activation in LPS-induced neuroinflammation and MPTP-induced PD mice.
Insights
Receptor-interacting protein kinase 1 (RIPK1) drives neuroinflammation and microglial activation. Inhibiting RIPK1 reduces inflammatory responses and offers neuroprotection in Parkinson's disease models.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Receptor-interacting protein kinase 1 (RIPK1) is implicated in necroptosis and neuroinflammation.
- The specific role of RIPK1 in microglial activation is not fully understood.
Purpose of the Study:
- To investigate the role of RIPK1 in lipopolysaccharide (LPS)-induced neuroinflammation and a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) model.
- To evaluate the therapeutic potential of RIPK1 inhibitors.
Main Methods:
- Utilized RIPK1 inhibitors necrostatin-1 (Nec-1) and necrostatin-1 stable (Nec-1s) in BV2 microglial cells and MPTP-induced PD mouse models.
- Assessed inflammatory molecule production, cell death, and signaling pathway modulation (AMPK, PI3K/Akt, MAPKs, NF-κB).
- Examined RIPK1 phosphorylation in LPS-injected and MPTP-treated mice.
Main Results:
- Nec-1/Nec-1s and RIPK1 siRNA inhibited pro-inflammatory molecule production and cell death in LPS-stimulated BV2 cells.
- RIPK1 inhibition modulated key inflammatory signaling pathways in microglia.
- In vivo, Nec-1/Nec-1s reduced microglial activation and neuroinflammation in LPS-injected and MPTP-treated mice.
- RIPK1 inhibition demonstrated neuroprotective effects in the MPTP-induced PD model.
Conclusions:
- RIPK1 is a critical regulator of microglial activation in neuroinflammatory conditions.
- Targeting RIPK1 with inhibitors like Nec-1/Nec-1s offers a potential therapeutic strategy for neuroinflammation and PD.
