Effect of proteins from the coelomic fluid of superficially wounded holothurians on the activity of phagocytes

Holothurians are among the most capable of regenerating animals. Their phagocytes are analogues of macrophages, but the mechanisms of their participation in wound healing have not been studied. The aim of the work is to determine the effect of individual protein components isolated from the coelomic fluid of holothurians with superficial damage to the body wall on the functional activity of the two types of phagocytes (P1 and P2) in holothurian Eupentacta fraudatrix.

Protein components of the coelomic fluid of holothurians with superficial wounds of the body wall were analyzed and collected by gel permeation chromatography. We used proteins whose content changed significantly during the wound healing period in preliminary experiments. Two proteins and a peptide were added to phagocytes, isolated by gradient centrifugation, simultaneously with the thermostable toxin of Yersinia pseudotuberculosis and incubated for 24 h. The production of superoxide anion radical was determined by the reduction of nitroblue tetrazolium (NBT) using a colorimetric method. To assess the specificity of the proteins, bovine serum albumin (BSA) was used as an internal control. In one-day in vivo experiments, proteins were administered to wounded animals.

Two proteins, when compared with the effect of BSA, did not show a specific effect on the production of reactive oxygen species in phagocytes in vitro. However, a comparison of the effect of the peptide on the oxidative activity and viability of phagocytes with those of BSA revealed the specificity of its action. The peptide reduced the oxidative activity of P1 phagocytes and increased it in P2 phagocytes in a direct concentration-dependent manner. One of the two proteins being administered to wounded holothurians caused a multidirectional concentration-dependent effect on the oxidative activity of the two types of phagocytes, with a predominant suppression of the P1 phenotype activity. The ability of protein components to cause a shift in the ratio of oxidative activity of the two types of phagocytes towards the preferential activation of P2 phagocytes, which are considered as functional analogues of M2 macrophages, suggests that they act as anti-inflammatory agents.