The Effect of Neutrophil-Derived Products on the Function of Leukocytes Obtained after Titanium Implantation in the Ovine Model

Simple Summary

Titanium is one of the most commonly used biomaterials for implantation as a part of the orthopedic procedures. However, this biomaterial can cause an excessive inflammatory response, even leading to rejection of the implant. Therefore, the aim of our study was to assess the overall organism response after insertion of Ti implant and the activity of neutrophils and monocyte-derived macrophages (MDM), to evaluate the possible negative effect of this biomaterial on the host cells. Our study revealed that insertion of the Ti implant did not evoke systemic inflammatory response or activation of leukocytes. Additionally, we evaluated the activity of neutrophils and MDM after stimulation with autologous neutrophil products, namely, antimicrobial neutrophil extract and neutrophil degranulation product as two potential regulators of inflammatory response. Antimicrobial neutrophil extract appeared to be a factor causing the decrease of secretory neutrophil response and polarization of MDM towards pro-resolving phenotype, whereas the neutrophil degranulation product acted as pro-inflammatory.

Abstract

Titanium (Ti) is currently the most common biomaterial used for orthopedic implants; however, these implants may cause deleterious immune response. To investigate the possible mechanisms involved in excessive inflammation, we assessed the activity of neutrophils and monocyte-derived macrophages (MDMs) during the insertion of the Ti implant in a sheep model. The study was conducted on 12 sheep, 4 of which were control animals and 8 were in the experimental group with inserted Ti implant. Neutrophil secretory response was estimated at two time points T0 before surgery and T1 1 h after implantation and was based on the release of enzymes from neutrophil granules and reactive oxygen and nitrogen species (RONS) generation. MDM function was evaluated 5 months after implantation, on the basis of RONS generation arginase activity and morphological changes. Moreover, the influence of some autologous neutrophil derived products, namely, antimicrobial neutrophil extract (ANE) and neutrophil degranulation products (DGP) on leukocytes was estimated. Our study revealed that Ti implant insertion did not cause any adverse effects up to 5 months after surgical procedure. Stimulation of neutrophil cultures with ANE decreased the enzyme release as well as superoxide generation. Treatment of MDM with ANE diminished superoxide and NO generation and increased arginase activity. On the other hand, MDM stimulated with DGP showed elevated superoxide and NO generation as well as decreased arginase activity. To summarize, ANE exerted an anti-inflammatory and pro-resolving effect on studied leukocytes, whereas DGP acted as pro-inflammatory.

Evaluation of Platelet-Rich Plasma and Neutrophil Antimicrobial Extract as Two Autologous Blood-Derived Agents

The platelet-rich plasma (PRP) and antimicrobial peptides neutrophil extract (AMP extract) were prepared from rabbit neutrophils as two autologous blood-derived preparations, which could be applied locally to enhance healing process of tissues. Both preparations were analyzed using the MALDI TOF method for accurate qualitative assay. Growth factors (PDGF and VEGF) and microbicidal protein were reported in PRP. In AMP extract α-defensins, namely; NP-1, -2, -3a, -3b, -4, and -5 and cathelicidins represented among other by 15-kDa antibacterial protein (p15s) were detected. In the second part of our study the influence of antimicrobial extract on macrophages in vitro was tested. Then, degranulation of neutrophils in vitro and generation of reactive intermediates by these cells under the influence of AMP extract were assessed. As estimated, the addition of AMP extract into cultures of macrophages decreased superoxide anion generation after 5 days of incubation. Furthermore, AMP extract inhibited degranulation and respiratory burst in neutrophils, therefore in this regard it suppress proinflammatory effect of two studied populations of leukocytes.

Response of antimicrobial peptides from porcine neutrophils to pentoxifylline and antigens from Gram negative and Gram positive bacteria

Neutrophils, the main component of the defense against invading organisms have also been implicated in tissue damage in numerous inflammatory conditions. Neutrophil products can degrade the extracellular matrix and when excessively released are thought to cause some disorders. As it is known, pentoxifylline (PTX) can suppress a range of neutrophil responses. Cathelicidins are components of the early host defenses against infection, however, in most cases cleavage with elastase is necessary to obtain active forms. Thus, the aim of our study was to assess the usage of PTX as a factor which could inhibit some neutrophil functions, and to assess if PTX can lead to the impairment of the release from these cells active cathelicidins. For these purposes we determined neutrophil activity as well as expression of cathelicidins from porcine neutrophils in cultures under the influence of PTX. PTX exerted an inhibitory effect on elastase and MPO release from neutrophils. At lower concentrations of PTX, ALP release was inhibited both in cultures stimulated with PTX+fMLP and with PTX+LPS. Inhibition of superoxide generation was insignificant, whereas a decrease of NO production was noted. The MALDI TOF analysis revealed that in all cultures stimulated with PTX+fLMP and PTX+LPS there was no inhibition of the release of cathelicidins in comparison with cultures stimulated only with fMLP and only with LPS. Our study proved that although PTX in porcine neutrophils is able to suppress many neutrophil functions, the expression of cathelicidins is maintained.