Yersinia pseudotuberculosis (Yptb) causes intestinal infection and can spread to the liver, where the bacterium induces hemosiderosis, abscesses, and hepatitis. To evade the immune response of the host organism, Yptb expresses at least six plasmid-encoded Yersinia outer proteins belonging to the Type III secretion system, which suppress phagocytic activity. Recently, evidence has accumulated that chromosome-encoded protein toxins are also involved in the anti-phagocytic defense of Yptb. Most of these toxins have been found in isolates from patients with Far East scarlet-like fever, often accompanied by liver pathology. Yersinia proteins contribute to bacterial colonization of lymphoid organs through their effects on immune cells. A thorough understanding of the immunomodulatory effects of these toxic proteins on bacterial dissemination and colonization in the liver will contribute to the development of novel approaches to cure hepatic pathology during Yptb infection. The review aimed to summarize the current data on the mechanisms of effects of Yptb plasmid- and chromosome-encoded toxins on bacterial colonization in the liver. The review highlights the fine-tuning of immune system activity by toxins encoded by both a 70-kb plasmid and chromosomes, through various mechanisms of action of individual proteins and their interactions. The focus is on mechanisms that promote bacterial survival in macrophages, including those that facilitate bacterial-induced macrophage polarization towards the M2 phenotype. The role of a type of phagocyte death in bacterial dissemination and colonization in the organs is also discussed.

Phagocytes of the Far Eastern holothurian Eupentacta fraudatrix are separatedby gradient centrifugation into two fractions (P1 and P2 phagocytes)having different functional markers. The aim of the work was toidentify morphological features of P1 and P2 phagocytes, their basic oxidant/antioxidantstatus and phenotype. Various methods, including light and fluorescence microscopy,cytometric analysis, and flow imaging microscopy, revealed morphological differencesbetween the two types of E. fraudatrix phagocytes.Phagocytes differ in their dimensional characteristics, granularity,nuclear/cytoplasmic ratio, and cell circularity parameters. Theobtained data support both the idea that P1 and P2 phagocytes representdifferent levels of differentiation and our previous findings onthe different role of these cells in the immune response. Differentialpatterns of seasonal changes in the number of these cells also arguein favor of the concept of different functional roles of the twotypes of phagocytes. The largest changes in the number of P1 phagocyteswere observed during the period of temperature-dependent metabolic alterationsin E. fraudatrix, while thosein P2 phagocytes occurred during the periods corresponding to tissuerearrangements. The study of the basic parameters of functionalactivity revealed no significant differences in levels of reactiveoxygen species in both P1 and P2 phagocytes, while there was a tendencytoward a higher level of reduced glutathione in P1 compared to P2phagocytes, suggesting ​​a higher antioxidant activity in the former. Dexamethasonehad a multidirectional effect on the level of binding of plant lectinsderived from Canavalia ensiformis (conA) and Glycin max (SBA) byto surface receptors in two types of phagocytes, further supportingthe assumption of different differentiation/activity levels and functionalroles of these cells.

— The impact of a heat-stable toxin of Yersinia pseudotuberculosis (HSTYp) on the markers of functional activity and phenotypes of P1- and P2-type phagocytes was studied in the holothurian Eupentacta fraudatrix. In the control, P1 and P2 phagocytes differed in the levels of apoptosis and reduced glutathione, as well as in the surface receptor binding to some plant lectins. HSTYp (0.2–2 μg/mL) caused a shift in the functional activity and phenotype of P1 phagocytes toward the prevalence of those characteristic of the P2 type, which has a lower bactericidal activity. It is supposed that HSTYp is an important factor in the reprogramming of holothurian phagocytes toward the predominance of the anti-inflammatory type, which may increase the virulence of Y. pseudotuberculosis for holothurians.

Echinoderms are one of the most ancient groups of invertebrates. The study of their genomes has made it possible to conclude that these animals have a wide variety of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). The phylogenetic analysis shows that the MMPs and TIMPs underwent repeated duplication and active divergence after the separation of Ambulacraria (Echinodermata+Hemichordata) from the Chordata. In this regard the homology of the proteinases and their inhibitors between these groups of animals cannot be established. However, the MMPs of echinoderms and vertebrates have a similar domain structure. Echinoderm proteinases can be structurally divided into three groups—archetypal MMPs, matrilysins, and furin-activatable MMPs. Gelatinases homologous to those of vertebrates were not found in genomes of studied species and are probably absent in echinoderms. The MMPs of echinoderms possess lytic activity toward collagen type I and gelatin and play an important role in the mechanisms of development, asexual reproduction and regeneration. Echinoderms have a large number of genes encoding TIMPs and TIMP-like proteins. TIMPs of these animals, with a few exceptions, have a structure typical for this class of proteins. They contain an NTR domain and 10–12 conservatively located cysteine residues. Repeated duplication and divergence of TIMP genes of echinoderms was probably associated with an increase in the functional importance of the proteins encoded by them in the physiology of the animals.

Tumor-associated macrophages (TAMs) are M2 phenotype dominant and promote tumor growth and metastasis. The new cancer treatment strategy includes TAM targeting and is aimed primarily at reprogramming TAMs toward the M1 phenotype or reducing the number and activity of M2 macrophages. Several marine invertebrate-derived drugs, combining efficacy and a low level of side effects, were approved for use in the cancer therapy. The mechanisms of action of some of them include TAM targeting. The review includes data showing immunomodulatory properties of these already approved anticancer drugs and drug candidates in clinical development which additionally incorporate data from screening studies of new substances from marine invertebrates. Based on screening data, the most promising marine compounds for cancer immunotherapy are supposed.

Data on temporal (July and September) and interannual variations in the content of several heavy metals are presented for the body wall, gonad, and gut of the sea cucumber Eupentacta fraudatrix from coastal waters of two inlets of Peter the Great Bay (Sea of Japan) with different levels of anthropogenic pollution. The gonads mostly accumulate Zn, Fe, Cu and Cd, while the body wall, presumably, Mn and Pb. Moreover, an increase in the heavy metal content in the gut below a certain threshold is asynchronous with changes in the content of most of them in the body wall and/or gonads, which are caused mainly by physiological factors during the spawning period. However, the influence of environmental pollution is significant during the postspawning period. When the heavy metal content in the gut exceeds a certain limit, synchronous variations in concentrations of heavy metals in the gut and tissues were recorded, which highlight impaired control of the heavy metal distribution in the organism. A correlation between the lead content in the gut and gonad indicates the possibility of determining this metal in the gonads as a bioindicator of environmental pollution.

Macrophages play a fundamental role in the immune system. Depending on the microenvironment stimuli, macrophages can acquire distinct phenotypes characterized with different sets of the markers of their functional activities. Polarization of macrophages towards M1 type (classical activation) is involved in inflammation and the related progression of diseases, while, in contrast, alternatively activated M2 macrophages are associated with the anti-inflammatory mechanisms. Reprogramming macrophages to switch their phenotypes could provide a new therapeutic strategy, and targeting the M1/M2 macrophage balance is a promising current trend in pharmacology. Marine invertebrates are a vast source of the variety of structurally diverse compounds with potent pharmacological activities. For years, a large number of studies concerning the immunomodulatory properties of the marine substances have been run with using some intracellular markers of immune stimulation or suppression irrespective of the possible application of marine compounds in reprogramming of macrophage activation, and only few reports clearly demonstrated the macrophage-polarizing activities of some marine compounds during the last decade. In this review, the data on the immunomodulating effects of the extracts and pure compounds of a variety of chemical structure from species of different classes of marine invertebrates are described with focus on their potential in shifting M1/M2 macrophage balance towards M1 or M2 phenotype.

The effect of a thermostable toxin of Yersinia pseudotuberculosis (in comparison with that of dexamethasone) on the functional activities of two types of phagocytes (P1 and P2) was studied in the holothurian Eupentacta fraudatrix. A high level of NO was shown to be a marker of intact P1 cells, while the high activity of arginase was a marker of P2 cells. The antioxidant defense in the P1 type was more pronounced than that of the P2 type. At the same time, the toxin inhibited the functional activity (generation of reactive oxygen species) of P1 phagocytes after 1 h of incubation and induced primarily the activity of P2 phagocytes, compared to that of P1 cells, after 24 h. In contrast to dexamethasone, which induced the transformation of the P1 phenotype into the P2 phenotype, the toxin promoted the mutual acquisition of the phenotype features by these two types of phagocytes. An analogy between the P1 and P2 phagocytes of the holothurian and M1 and M2 macrophages is discussed.

The influence of humoral products of morula cells on apoptosis, the concentration of cytokinin-like compounds, and expression of cell-surface receptors specific to plant lectins from Arachis hypogaea, Glycine max, and concanavalin A (Con A) were studied in two types of phagocytes (P1 and P2) of the Far Eastern sea cucumber Eupentacta fraudatrix (Djakonov et Baranova, 1958). Our data show that morula cell supernatant reduced the level of apoptosis and concentration of interleukin-1α-like factors (IL-1α-LF) in P1 phagocytes, while it increased them in P2 phagocytes. We hypothesize that an increase in IL-1α-LF concentration stimulates apoptosis in E. fraudatrix P2 cells under the effect of treatment with morula cell supernatant. Moreover, opposite changes in apoptosis levels in P1 and P2 phagocytes in response to morula cell supernatant correlate with the expression of receptors of different types: N-acetyl-D-galactosamine- and β-D-galactose-containing receptors in P1 phagocytes and α-D-mannose-containing receptors in P2 phagocytes. Taken together, our results support the idea of differential roles of P1 and P2 phagocytes in the holothurian immune response. The study suggests that the differences in the binding of lectins to P1 and P2 cell-surface receptors is a distinctive feature and can be used in phenotyping of these immunocytes.

In view of increasing lead pollution (Pb2+) of coastal waters, the compensatory abilities of holothurians need to be assessed. The goal of the work is to clarify the functional and phenotypical differences between two types of phagocytes (P1 and P2) in Eupentacta fraudatrix exposed to Pb(NO3)2. It has been shown that 2 mg L−1 lead exposure for 48 h increases the number of P2 phagocytes as compared to P1 cells, does not significantly affect cell viability in both P1 and P2 phagocyte fractions, and significantly enhances chromatin condensation in P2 but not in P1 phagocytes. A lead concentration of 4 mg L−1 increases the number of P1 phagocytes compared to that of P2 type, and does not change cell viability and chromatin condensation in P1 phagocytes. In the P2 type, it decreases cell viability and does not influence the level of apoptosis. The protection against lead-induced apoptosis is apparently mediated by the activities of antioxidant enzymes, especially glutathione S-transferase. The differences in labeling cell surface receptors of P1 and P2 phagocytes by plant lectins also indicate the specific phenotypic properties of these cells. The results clarify the potential and GSH-dependent mechanisms of immune adaptation in holothurians that have been shortly exposed to lead at concentrations close to the maximum environmentally relevant level in coastal waters. Additionally, P1 and P2 phagocytes are first shown to have different functions and phenotypes during the response to lead, which indicates the complexity of the phagocytic system in holothurians and contributes to understanding the immunity evolution.

Data on the changes in heavy metal concentrations in tissues of the sea cucumber Eupentacta fraudatrix from Alexeev Bay and Vityaz Bay (Peter the Great Bay) since 2008-2009 to 2016-2017 are presented.The increase in heavy metal contents in the sea cucumber tissues was not determined in both bays except the cadmium concentration in the sea cucumber from Alexeev Bay.The total heavy metal pollution except cadmium is supposed to decrease in the seawater.

This study examines the interaction between two types of phagocytes (P1 and P2) of the holothurian Eupentacta fraudatrix and its in vitro modulation by dexamethasone. Our results indicate that inhibition of apoptosis in P1 phagocytes by P2 phagocytes was accompanied by increased activities of antioxidant enzymes and reduced synthesis of interleukin-1α-like substances. We hypothesize that P1-phagocyte-related effects occurred in response to a high level of hydrogen peroxide produced by P2 phagocytes. The reduced anti-apoptotic effect of P2-phagocyte supernatant during prolonged incubation (24 h) was accompanied by a decline in defense reactions in P1 phagocytes due to depletion of antioxidant enzymes (catalase, glutathione reductase, and glutathione transferase). Inhibition of apoptotis in P1 phagocytes associated with upregulation of antioxidant enzyme defense in response to P2 phagocytes preincubated with dexamethasone (100 µM) indicates that P2 phagocytes affect P1 phagocytes via a ROS-associated mechanism. Thus, our data provide evidence that P1 and P2 phagocytes exhibit their maximum activity at different stages of the immune response, thus causing inhibition of activity in target cells during prolonged exposure. Dexamethasone enhances these effects.

This work aims at the comparable study on the markers of response of two phagocyte fractions (P1 and P2) of the holothurian Eupentacta fraudatrix to the treatment with a thermostable toxin of bacteria Yersinia pseudotuberculosis in vitro and in vivo. The phagocyte fractions were isolated using a ficoll-verographine discontinous gradient. The cells were incubated with ТsТYp (0.2 and 0.5 μg/ml) at 22°C for 48 h. In the series of in vivo experiments ТsТYp was used at the doses of 0.5 и 1.25 μg/ml. Phagocytes were isolated in 5 h. The nitroblue tetrazolium level was measured by the colorimetric method. Apoptosis was evaluated with using both methods of DNA agarose gel electrophoresis and Hoechst 33342 staining. Cell viability was estimated with a trypan blue exclusion test. The level of IL-1α-like substances was determined using kit for immune enzyme analysis. The results obtained indicate that ТsТYp induced differently directed changes in the markers studied in the two types of phagocytes in the holothurian E. fraudatrix. It suggests different roles of those two types in antibacterial defense.

Echinoderm phagocytes are considered to be analogues to vertebrate macrophages. Previously, the phagocytes of some echinoderm species were divided into two fractions with unclearly identified functional properties. This study aims at modeling the immune response of two phagocyte fractions (P1 and P2) of the holothurian Eupentacta fraudatrix to the synthetic glucocorticoid hormone dexamethasone (Dex) in vitro and at comparison of the effects of such pretreatment on humoral cooperation of each phagocyte fraction with another type of immunocytes, morula cells. During 48-h incubation, Dex (0.1–100 μM) induced apoptosis in a direct (in the P1 fraction) or reverse (in the P2 fraction) concentration-dependent manner. In addition, 100 μM Dex differently affected the cytokin-like substance level in the P1 and P2 phagocyte fractions. Moreover, the supernatants of the Dex(100 μM)-pretreated phagocytes induced opposite changes in the IL-1-like substance level in morula cells. These results indicate a striking functional difference between the two phagocyte fractions. The data obtained provide a new insight into the evolution of macrophage response and into the prospects of the use of in vitro holothurian phagocyte model.