Classical and Alternative Activation of Rat Microglia Treated with Ultrapure Porphyromonas gingivalis Lipopolysaccharide In Vitro

Abstract

The possible relationship between periodontal disease resulting from the infection of gingival tissue by the Gram-negative bacterium Porphyromonas gingivalis (P. gingivalis) and the development of neuroinflammation remains under investigation. Recently, P. gingivalis lipopolysaccharide (LPS) was reported in the human brain, thus suggesting it might activate brain microglia, a cell type participating in neuroinflammation. We tested the hypothesis of whether in vitro exposure to ultrapure P. gingivalis LPS may result in classical and alternative activation phenotypes of rat microglia, with the concomitant release of cytokines and chemokines, as well as superoxide anion (O2−), thromboxane B2 (TXB2), and matrix metalloprotease-9 (MMP-9). After an 18-h exposure of microglia to P. gingivalis LPS, the concentration-dependent responses were the following: 0.1–100 ng/mL P. gingivalis LPS increased O2− generation, with reduced inflammatory mediator generation; 1000–10,000 ng/mL P. gingivalis LPS generated MMP-9, macrophage inflammatory protein 1α (MIP-1α/CCL3), macrophage inflammatory protein-2 (MIP-2/CXCL2) release and significant O2− generation; 100,000 ng/mL P. gingivalis LPS sustained O2− production, maintained MMP-9, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) release, and triggered elevated levels of MIP-1α/CCL3, MIP-2/CXCL2, and cytokine-induced neutrophil chemoattractant 1 (CINC-1/CXCL-1), with a very low release of lactic dehydrogenase (LDH). Although P. gingivalis LPS was less potent than Escherichia coli (E. coli) LPS in stimulating TXB2, MMP-9, IL-6 and interleukin 10 (IL-10) generation, we observed that it appeared more efficacious in enhancing the release of O2−, TNF-α, MIP-1α/CCL3, MIP-2/CXCL2 and CINC-1/CXCL-1. Our results provide support to our research hypothesis because an 18-h in vitro stimulation with ultrapure P. gingivalis LPS resulted in the classical and alternative activation of rat brain microglia and the concomitant release of cytokines and chemokines.

Perinatal Gram-Positive Bacteria Exposure Elicits Distinct Cytokine Responses In Vitro

“…Importantly, in our settings, cytokine secretion evoked by increasing levels of bacteria lysates presented a bimodal response, with stabilization or reduction of cytokine levels in stimulations with higher concentrations of bacteria lysates. Such a bimodal response has been already reported in multiple settings [ 63 , 64 , 65 , 66 , 67 ]. Suppression of cytokine production in high stimulatory conditions may rely on auto/paracrine and intracellular negative feedback pathways [ 63 , 68 ].…”

Lipopolysaccharide’s Cytotoxicity on Human Umbilical Cord Mesenchymal Stem Cells

“…The assessments were conducted and performed in triplicates with regard to previous studies [16,17] and sample size determination formula for controlled laboratory experiments. Data were provided as mean + standard deviation.…”

“…Ultrapure Porphyromonas gingivalis lipopolysaccharide (InvivoGen, San Diego, CA, USA) was used [17]. The LPS powder was diluted with MEM alpha medium into different concentrations.…”

Interaction between genetic factors, Porphyromonas gingivalis and microglia to promote Alzheimer’s disease

“…initiated AD inflammation involving the comple-ment cascade of ApoE −/- brains [ 25 ] LPS Initiates neuroinflammation through microglia activation [ 68 ] Migroglia were ‘primed’ inducing increased responses to subsequent challenges [ 68 ] When located in brains microglia can be activated by P.g . LPS [ 4 , 76 ] P.g . causes imbalance in the M1/M2 phenotype of microglia [ 78 ] Leptomeningeal cells P.g .…”

“…Last, but not least, P. gingivalis LPS has been reported in the human brain, thus suggesting it might activate brain microglia participating in brain inflammation [ 4 ]. This idea was supported in an 18-h in vitro stimulation study with ultrapure P. gingivalis LPS in rats that resulted in classical and alternative activation of rat brain microglia and the concomitant release of cytokines and chemokines [ 76 ].…”