Nucleolin Mediates LPS-induced Expression of Inflammatory Mediators and Activation of Signaling Pathways
Li Fang , Kang-kai Wang , Qing Huang , Feng Cheng , Fang Huang , Wei-wei Liu
Current Medical Science ›› 2020, Vol. 40 ›› Issue (4) : 646 -653.
In this study, we investigated the effects of nucleolin on lipopolysaccharide (LPS)-induced activation of MAPK and NF-KappaB (NF-κB) signaling pathways and secretion of TNF-α, IL-1β and HMGB1 in THP-1 monocytes. Immunofluorescence assay and Western blotting were used to identify the nucleolin expression in cell membrane, cytoplasm and nucleus of THP-1 monocytes. Inactivation of nucleolin was induced by neutralizing antibody against nucleolin. THP-1 monocytes were pretreated with anti-nucleolin antibody for 1 h prior to LPS challenge. The irrelevant IgG group was used as control. Secretion of inflammatory mediators (TNF-α, IL-1β and HMGB1) and activation of MAPK and NF-κB/I-κB signaling pathways were examined to assess the effects of nucleolin on LPS-mediated inflammatory response. Nucleolin existed in cell membrane, cytoplasm and nucleus of THP-1 monocytes. Pretreatment of anti-nucleolin antibody significantly inhibited the LPS-induced secretion of TNF-α, IL-1β and HMGB1. P38, JNK, ERK and NF-κB subunit p65 inhibitors could significantly inhibit the secretion of IL-1β, TNF-α and HMGB1 induced by LPS. Moreover, the phosphorylation of p38, JNK, ERK and p65 (or nuclear translocation of p65) was significantly increased after LPS challenge. In contrast, pretreatment of anti-nucleolin antibody could significantly inhibit the LPS-induced phosphorylation of p38, JNK, ERK and p65 (or nuclear translocation of p65). However, the irrelevant IgG, as a negative control, had no effect on LPS-induced secretion of TNF-α and IL-1β and phosphorylation of p38, JNK, ERK and p65 (or nuclear translocation of p65). We demonstrated that nucleolin mediated the LPS-induced activation of MAPK and NF-κB signaling pathways, and regulated the secretion of inflammatory mediators (TNF-α, IL-1β and HMGB1).
nucleolin / THP-1 monocytes / lipopolysaccharide / MAPK / NF-κB signaling pathway / inflammatory mediators
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