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Published on: January 30, 2014
Porphyromonas gingivalis promote microglia M1 polarization through the NF-кB signaling pathway
Xue Li1,2,3, Chao Yao2, Dongmei Lan2
1Department of Oral Prosthodontics, Shanghai Stomatological Hospital, Fudan University, Shanghai, 200001, China.
Background:
Porphyromonas gingivalis (P.gingivalis) is associated with the onset of Alzheimer's disease (AD), but the underlying molecular mechanism is unclear. Neuroinflammation in the brain from the microglial immune response induces the pathological progression of AD. In this study, the roles and molecular mechanism of P.gingivalis in microglial inflammation in vitro were investigated.
Methods:
In this study, a P.gingivalis oral administration mouse model was generated, and microglia were stimulated with P.gingivalis in vitro. The viability of the microglia after P.gingivalis treatment was evaluated through CCK-8 and live/dead cell staining. Inflammation in brain tissue after P.gingivalis treatment and the immune response of microglia in vitro were detected by RT‒PCR, Western blotting and IF. Moreover, the RNA sequence was used, and the role of the NF-κB signalling pathway in microglial activation was analysed after P.gingivalis stimulation.
Results:
The mRNA and protein levels of IL-6 and IL-17 were increased, and the expression of IL-10 was decreased in brain tissue after P.gingivalis oral administration. The viability of the HMC3 cells significantly decreased with 5% P.gingivalis after stimulation. The results of live/dead cell staining also showed the inhibitory effect of 5% P.gingivalis supplementation on cell viability. Moreover, 5% P.gingivalis supplementation increased the mRNA and protein levels of IL-6 and IL-17 and decreased IL-10 expression in HMC3 cells. P.gingivalis supplementation increased the mRNA and protein levels of iNOS and CD86 and decreased CD206 expression in HMC3 cells. RNA sequencing revealed that the NF-κB signalling pathway was involved in this process. Furthermore, p-P65 was upregulated and p-IKBα was downregulated in brain tissue and HMC3 cells after P.gingivalis stimulation, and an NF-κB signalling pathway inhibitor (QNZ) reversed the viability, M1 polarization and inflammatory factors of microglia in HMC3 cells in vitro.
Conclusions:
In conclusion, P.gingivalis induced neuroinflammation in the brain, possibly through promotion of M1 polarization of microglia via activation of the NF-κB signalling pathway during the progression of AD.
Insights
Porphyromonas gingivalis infection triggers neuroinflammation in Alzheimer's disease by activating the NF-κB pathway in microglia. This leads to increased inflammatory markers and reduced cell viability, contributing to AD progression.
Area of Science:
- Neuroscience
- Immunology
- Microbiology
Background:
- Porphyromonas gingivalis (P. gingivalis) is linked to Alzheimer's disease (AD) onset.
- Microglial neuroinflammation exacerbates AD pathology.
- The molecular mechanisms linking P. gingivalis to microglial inflammation remain unclear.
Purpose of the Study:
- Investigate the role of P. gingivalis in microglial inflammation.
- Elucidate the molecular mechanisms underlying P. gingivalis-induced neuroinflammation in vitro.
- Determine the involvement of the NF-κB signaling pathway.
Main Methods:
- Generated a P. gingivalis oral administration mouse model.
- Stimulated HMC3 microglial cells with P. gingivalis in vitro.
- Assessed cell viability, inflammatory markers (IL-6, IL-17, IL-10, iNOS, CD86, CD206), and NF-κB pathway activation (p-P65, p-IKBα) using RT-PCR, Western blotting, IF, and RNA sequencing.
- Utilized an NF-κB inhibitor (QNZ) to validate pathway involvement.
Main Results:
- P. gingivalis increased IL-6 and IL-17, decreased IL-10, and promoted M1 polarization (increased iNOS, CD86; decreased CD206) in microglia.
- P. gingivalis reduced microglial viability.
- Activated the NF-κB pathway, evidenced by increased p-P65 and decreased p-IKBα.
- NF-κB inhibition reversed P. gingivalis-induced effects on viability, M1 polarization, and inflammation.
Conclusions:
- P. gingivalis induces neuroinflammation in the brain.
- This occurs possibly through promoting M1 polarization of microglia.
- Activation of the NF-κB signaling pathway is a key mechanism in P. gingivalis-associated AD progression.
