CD14 recycling modulates LPS‐induced inflammatory responses of murine macrophages

Abstract

TLR4 is activated by the bacterial endotoxin lipopolysaccharide (LPS) and triggers two proinflammatory signaling cascades: a MyD88-dependent one in the plasma membrane, and the following TRIF-dependent one in endosomes. An inadequate inflammatory reaction can be detrimental for the organism by leading to sepsis.Therefore, novel approaches to therapeutic modulation of TLR4 signaling are being sought after. The TLR4 activity is tightly connected with the presence of CD14, a GPI-anchored protein that transfers LPS monomers to the receptor and controls its endocytosis. In this study we focused on CD14 trafficking as a still poorly understood factor affecting TLR4 activity. Two independent assays were used to show that after endocytosis CD14 can recycle back to the plasma membrane in both unstimulated and stimulated cells. This route of CD14 trafficking can be controlled by sorting nexins (SNX) 1, 2 and 6, and is important for maintaining the surface level and the total level of CD14, but can also affect the amount of TLR4. Silencing of these SNXs attenuated especially the CD14-dependent endosomal signaling of TLR4, making them a new target for therapeutic regulation of the inflammatory response of macrophages to LPS.

Machine learning and deep learning to identifying subarachnoid haemorrhage macrophage‐associated biomarkers by bulk and single‐cell sequencing

“…By applying various machine learning algorithms, we or inflammation, initiates inflammatory responses through recognition of pathogen-associated molecular patterns like LPS. [27][28][29] CD14's wide expression on macrophages, coupled with its involvement in phagocytosis, clearance of debris and regulation of cytokine production, underscores its hallmark status in macrophage function. 30 Investigating the intricate interplay between CD14 and macrophages unveils opportunities for leveraging their immunological functions in the context of inflammation and immune-related disorders.…”

“…Understanding the crucial role of CD14 in immune responses is imperative. As a glycoprotein primarily residing on the cell membrane, its release into body fluids, triggered by bacterial infection or inflammation, initiates inflammatory responses through recognition of pathogen‐associated molecular patterns like LPS 27–29 . CD14's wide expression on macrophages, coupled with its involvement in phagocytosis, clearance of debris and regulation of cytokine production, underscores its hallmark status in macrophage function 30 .…”

Flotillins affect LPS-induced TLR4 signaling by modulating the trafficking and abundance of CD14

“…Raw264.7 (further Raw264) cells and J774 cells (both from ATTC) were cultured in DMEM containing 10% FBS (Thermo Fisher Scientific) with 4.5 and 1 g/l glucose, respectively. Thioglycolate-elicited macrophages were isolated from 8- to 14-week-old male C57BL/6 mice, as described previously [22]. The procedure had been reviewed and approved by the Local Animal Ethics Committee (permission No.…”

“…Thus, the involvement of flotillins in LPS-induced signaling is manifested in conditions that require the engagement of CD14 for TLR4 activation and endocytosis [16,18,53]. For this reason, we decided to establish whether flotillins take part in determining the cell surface level of CD14 known to condition the extent of the TRIF-dependent signaling of TLR4 [22]. Flotillin depletion reduces the surface level of CD14.…”

Association analysis between CD14 gene polymorphisms and peri‐implantitis susceptibility in a Chinese population

“…It is involved in primary immune and inflammatory responses 6,7 . Additionally, LPS has been reported to be associated with the deterioration of gram‐positive bacteria induce 8 . CD14 can proportionally regulate the subsequent production of pro‐inflammatory cytokines, eventually resulting in LPS‐stimulated bone resorption 7,9 .…”