Access Type

Open Access Dissertation

Date of Award

January 2017

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Biochemistry and Molecular Biology

First Advisor

Chunying Li

Abstract

Objective: p120 catenin (p120ctn) has been reported to play a critical role in maintenance of the stability of adherens junctions. It also has potential anti-inflammatory effects in epithelial and endothelial cells. This research was designed to evaluate the effects of p120ctn on inflammatory responses in human macrophages upon LPS stimulation, as well as the possible mechanism by which p120ctn regulates LPS-induced proinflammatory response in macrophages. Methods: THP-1 cells were induced to differentiate into macrophages by PMA. The isoforms of p120ctn were identified via RT-PCR and Western blot. The expression of p120ctn was examined by Western blot in THP-1 derived macrophages after LPS challenge. p120ctn was knocked down in THP-1 cells by using shRNA lentivirus particles. mRNA level of proinflammatory cytokines were evaluated by RT-PCR. The autophagy pathway was analyzed by Western blot in macrophages after LPS stimulation with or without Bafilomycin A1 treatment. Results: THP-1 derived macrophages expressed p120ctn isoform 1A and 3A. E. coli LPS could downregulate p120ctn expression in macrophage via autophagy pathway, which was suppressed by Src signaling inhibitor PP2. mRNA levels of proinflammatory cytokines including IL-1β, IL-8, IL-6 and TNF-α were elevated in p120ctn-delpeted macrophages in response to LPS stimulation, as compared with control cells. The activation of NF-κB signaling pathway was more rapid in p120ctn knockdown macrophages in response to LPS treatment. Decreased autophagy and downregulation of conjugated Atg12-Atg5 were observed in p120ctn knockdown macrophages after LPS challenge. Conclusions: The downregulation of p120ctn in the macrophages in response to E. coli LPS stimulation is regulated by Src signaling and autophagy. p120ctn has anti-inflammatory functions in macrophages. NF-κB signaling pathway might be the regulatory target. The loss of p120ctn results in the decreased activity of LPS-induced autophagy and downregulation of conjugated Atg12-Atg5 in macrophages upon LPS stimulation, which might contribute to the over-activation of LPS-induced inflammation in p120ctn knockdown macrophages.

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