Background: Gut microbiome dysbiosis is related to the pathogenesis of nonalcoholic fatty liver disease (NAFLD), and the role of toll-like receptor 2 (TLR2) in its molecular mechanism is controversial. Here, we investigated the effects and mechanisms of Escherichia coli-derived lipopolysaccharide (LPS) on lipid accumulation and lipotoxicity in palmitic acid (PA)-treated L02 cell as an NAFLD cell model, and the role of TLR2 in this process.Methods: Oil red O staining assay and free fatty acid (FFA) content test were performed to determine the effects of LPS on lipid accumulation in a PA-induced NAFLD cell model with or without TLR2 inhibition.The levels of IL-6 and TNF-α were measured to investigate inflammation conditions. Hoechst 33342 staining assay and Caspase-3 activity assay were used to test cell apoptosis, and the expression levels of proteins in the IRS1/PI3K/AKT signaling pathway, TLR2/MyD88/IKKα/NF-κB signaling pathway, and mitochondrion-dependent apoptotic signaling pathway were detected using Western blot.Results: Lipid accumulation, pro-inflammatory cytokine release, and cell apoptosis with high levels were observed in the PA-induced NAFLD cell model, and LPS aggravated these processes. Whereas TLR2 inhibition could significantly ameliorate PA-induced and LPS-amplified lipid accumulation, inflammatory, and cell apoptosis, it had no significant effect on L02 cells treated with LPS alone.Conclusions: These results were confirmed by activation or inhibition of the IRS1/PI3K/AKT signaling pathway, TLR2/MyD88/IKKα/NF-κB signaling pathway, and mitochondrion-dependent apoptotic signaling pathway, and were reflected by changes on their proteins expression. TLR2 is involved in PA-induced lipid accumulation and lipotoxicity in L02 cells, which could be aggravated by LPS, although LPS-induced amplification might not be through direct interaction with TLR2.
Objective: Periodontal ligament cells (PDLCs) are critical for wound healing and regenerative capacity of periodontal diseases. Within an inflammatory periodontal pocket, a hypoxic environment can aggravate periodontal inflammation, where PDLCs response to the inflammation would change. Resolvin D1 (RvD1) is an endogenous lipid mediator, which can impact intracellular inflammatory pathways of periodontal/oral cells and periodontal regeneration. It is not clear how hypoxia and RvD1 impact the inflammatory responses of pro-inflammatory PDLCs phenotype. Therefore, this study aimed to test hypoxia could induce changes in pro-inflammatory phenotype of PDLCs and RvD1 could reverse it. Methods: Human PDLCs were cultured from periodontal tissues from eight healthy individuals and were characterized by immunofluorescence staining of vimentin and cytokeratin. Cell viability was examined by Methyl-thiazolyl-tetrazolium (MTT) assay. To examine the effects of hypoxia and RvD1 on the inflammatory responses of proinflammatory PDLCs phenotype, protein levels and gene expressions of inflammatory cytokines and signal transduction molecules were measured by enzyme-linked immunosorbent assay (ELISA), western blotting (WB), and real-time quantitative reverse transcription PCR (real-time qRT-PCR). Alizarin red S staining and real-time qRT-PCR were employed to study the effects of hypoxia and RvD1 on the osteogenic differentiation of pro-inflammatory PDLCs phenotype. Results: It was found that hypoxia increases the expression of inflammatory factors at the gene level (p < .05). RvD1 reduced the expression of IL-1β (p < .05) in PDLCs under hypoxia both at the protein and RNA levels. There were increases in the expression of p38 mitogen-activated protein kinase (p38 MAPK, p < .01) and protein kinase B (Akt, p < .05) in response to RvD1. Also, a significantly higher density of calcified nodules was observed after treatment with RvD1 for 21 days under hypoxia. Conclusion: Our results indicate that hypoxia up-regulated the inflammatory level of PDLCs. RvD1 can reduce under-hypoxia-induced pro-inflammatory cytokines in the inflammatory phenotype of PDLCs. Moreover, RvD1 promotes the calcium nodules in PDLCs, possibly by affecting the p38 MAPK signaling pathway through Akt and HIF-1α.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.