Neutrophilic granule protein (NGP) attenuates lipopolysaccharide-induced inflammatory responses and enhances phagocytosis of bacteria by macrophages

• Published in: Cytokine (Philadelphia, Pa.) Vol. 128; p. 155001
• Main Authors: Liu, Kuan, Tian, Li-xing, Tang, Xin, Wang, Jing, Tang, Wan-qi, Ma, Zhong-fu, Chen, Tao, Liang, Hua-ping
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2020
• Subjects: Inflammation; Lipopolysaccharide; Macrophages; Neutrophilic granule protein; NF-κB; Phagocytosis; Lipopolysaccharide; Neutrophilic granule protein; NF-κB; Inflammation; Macrophages; Phagocytosis
• ISSN: 1043-4666; 1096-0023
• DOI: 10.1016/j.cyto.2020.155001

•A positive feedback loop existed between NGP and TLR4 in response to multiple bacterial infection or LPS stimulation.•NGP played a critical role in the anti-inflammatory response by targeting the NF-κB signaling pathway and IL-10 secretion.•Endogenous NGP elevated IL-10 expression but exogenous NGP was not elevated.•NGP may be a novel anti-infectious agent by enhancing macrophage phagocytosis. Neutrophilic granule protein (NGP) belongs to the cystatin superfamily. Even though this superfamily is critically involved in cancer biology and adaptive immunity, the relationship of macrophage NGP to inflammation and phagocytosis remains poorly understood. In this study, we observed a significant increase of NGP in peritoneal macrophages (PMs) isolated from mice challenged with E. coli or lipopolysaccharide (LPS), as judged by NGP mRNA microarray. We also found changes in NGP to be mainly Toll-like receptor 4 (TLR4)-dependent. By western blot and electrophoretic mobility shift assay, we demonstrated NGP overexpression to reduce TNF-α and IL-1β production by LPS-induced RAW264.7 cells (RAW) via suppression of the NF-κB (p65 and p50) signalling pathway, rather than the JNK1/AP-1 (fos and jun) signalling pathway. NGP overexpression by LPS-induced RAW also induced IL-10, an anti-inflammatory cytokine, which was partially involved in the anti-inflammatory effect produced by NGP overexpression. Moreover, upregulated NGP enhanced the phagocytosis of E. coli by RAW. Taken together, these results demonstrated NGP to be an important host defense component that regulates inflammatory responses and phagocytosis by activated macrophages. As such, NGP may be useful for the treatment of inflammatory based disease.