C-Terminal Fibronectin Exerts Beneficial Effects in Reducing Tissue Damage and Modulating Macrophage Function in a Murine Septic Model

Abstract

Background: Fibronectin (FN) can improve organ function and slow the progression of sepsis, but full-length FN is hard to be exacted as a therapeutic.Objective: This study aimed to investigate the beneficial effects of C-terminal heparin-binding domain polypeptide of FN (rhFNHC-36) in a cecal ligation and puncture (CLP)-mediated murine septic model and explore its regulatory effects on macrophages. Methods: Mice were randomly assigned to four groups: unoperated control (Normal), sham operation control (Sham), CLP-operation with intravenous injection of phosphate-buffered saline (CLP+PBS), and CLP-operation with rhFNHC-36 treatment (CLP+rhFNHC-36). Blood and abdominal fluid samples were subjected to bacterial colony formation assays. Organs (liver, spleen, and lung) were undergone histopathological analyses and/or weighed to obtain organ indices. Serum interleukin-6 (IL-6) levels, nitric oxide (NO) release from isolated abdominal macrophages, and chemotactic effect of macrophages were measured with commercial kits. Surface programmed death ligand 1 (PD-L1) expression on macrophages was measured by flow cytometry. Results: Mice in the CLP+PBS group showed a lower survival rate than that in the CLP+rhFNHC-36 group. Improved survival was associated with better clearance of bacterial pathogens, as evidenced by colony formation assays. The CLP-induced decrease in thymus and spleen indices was attenuated by rhFNHC-36 treatments. rhFNHC-36 alleviated sepsis-associated tissue damage in liver, spleen, and lung. CLP-mediated increases in plasma IL-6 levels were reversed by rhFNHC-36 treatment. NO levels in peritoneal macrophages after lipopolysaccharides (LPS)-stimulation in the CLP+rhFNHC-36 group were lower than that in the CLP+PBS group. Notably, macrophages from the CLP+rhFNHC-36 group retained better chemotaxis ability. After LPS challenge, these macrophages had a reduced percentage of PD-L1-positive cells compared to those in the CLP+PBS group. Conclusion: rhFNHC-36 improved survival of mice with CLP-induced sepsis by reducing tissue damage and modulating macrophage function. Our work provides critical insight for developing FN-based and macrophages-targeted therapeutics for treating sepsis.

Long-term treatment with Alcaligenes faecalis A12C improves host resistance to pathogens in septic rats: possible contribution of curdlan-like immune-trainer

“…However, most studies report these damages 24h after CLP when our evaluation is 20h post-CLP, even though other studies shown early damage in mice before 20h post-CLP [11,17].…”

Fibronectin extra domain a limits liver dysfunction and protects mice during acute inflammation

“…In humans, although contradictory findings have been reported, a general reduction of FN plasma levels was observed during acute inflammation associated with sepsis [ 13 ] coupled with increased production of circulating FN containing EDA [ 46 , 47 ]. Despite this, the concentration of plasma FN_EDA+ in patients with sepsis who survived was significantly lower than that in non-survivors [ 13 ].…”

“…In humans, although contradictory findings have been reported, a general reduction of FN plasma levels was observed during acute inflammation associated with sepsis [ 13 ] coupled with increased production of circulating FN containing EDA [ 46 , 47 ]. Despite this, the concentration of plasma FN_EDA+ in patients with sepsis who survived was significantly lower than that in non-survivors [ 13 ]. Whether this is indirectly marking the ability of FN_EDA + to opsonize bacteria and favour the elimination of the complex or increased deposition in tissues during acute and severe inflammation is unclear.…”

“…Among the acute phase proteins modulated during sepsis, changes in fibronectin (FN) levels were proposed as a prognostic marker of sepsis severity in humans and the injection of the FN fragment was shown to protect from sepsis [ [13] , [14] , [15] , [16] , [17] , [18] ]. Previous reports have shown that FN or its fragments can potentially interact with host pathogens during normal and pathological conditions [ 19 , 20 ].…”

The implication of targeting PD-1:PD-L1 pathway in treating sepsis through immunostimulatory and anti-inflammatory pathways

“…Zusanli (ST36), Guanyuan (CV4), and Qihai (CV6) acupoint electroacupuncture modulated the immune function of sepsis patients through the PD-1/PD-L1 pathway and improved clinical symptoms (169). Furthermore, adoptive transfer of bone marrow-derived dendritic cells (BMDCs), niacinamide nucleoside supplementation, fibronectin FN C-terminal heparin-binding domain polypeptide (rhFNHC-36), glutamine (GLN), recombinant enhancer of zeste homolog 2 (EZH2) inhibitor GSK343, mitogen-activated protein kinase phosphatase 1 (Mkp-1), mycophenolate mofetil (MMF), anti-ICAM (intercellular adhesion molecule)-1 antibody and other methods have shown improved survival rates in septic mice (178)(179)(180)(181)(182)(183)(184). Notably, downregulation of PD-L1 expression has been observed in these approaches.…”