Extracellular heat shock protein 70 has novel functional effects on sea urchin eggs and coelomocytes

Molecular Aspects of Regeneration Mechanisms in Holothurians

Holothurians, or sea cucumbers, belong to the phylum Echinodermata. They show good regenerative abilities. The present review provides an analysis of available data on the molecular aspects of regeneration mechanisms in holothurians. The genes and signaling pathways activated during the asexual reproduction and the formation of the anterior and posterior parts of the body, as well as the molecular mechanisms that provide regeneration of the nervous and digestive systems, are considered here. Damage causes a strong stress response, the signs of which are recorded even at late regeneration stages. In holothurian tissues, the concentrations of reactive oxygen species and antioxidant enzymes increase. Furthermore, the cellular and humoral components of the immune system are activated. Extracellular matrix remodeling and Wnt signaling play a major role in the regeneration in holothurians. All available morphological and molecular data show that the dedifferentiation of specialized cells in the remnant of the organ and the epithelial morphogenesis constitute the basis of regeneration in holothurians. However, depending on the type of damage, the mechanisms of regeneration may differ significantly in the spatial organization of regeneration process, the involvement of different cell types, and the depth of reprogramming of their genome (dedifferentiation or transdifferentiation).

Stress and immune response to bacterial LPS in the sea urchin Paracentrotus lividus (Lamarck, 1816)

The immune system of the sea urchin species Paracentrotus lividus is highly complex and, as yet, poorly understood. P. lividus coelomocytes mediate immune response through phagocytosis and encapsulation of non-self particles, in addition to the production of antimicrobial molecules. Despite this understanding, details of exactly how these processes occur and the mechanisms which drive them are still in need of clarification. In this study, we show how the bacterial lipopolysaccharides (LPS) is able to induce a stress response which increases the levels of the heat shock proteins HSP70 and HSP90 only a few hours after treatment. This study also shows that LPS treatment increases the expression of the β-thymosin-derivated protein paracentrin, the precursor of antimicrobial peptides.

Thermal resistances and acclimation potential during coral larval ontogeny in Acropora pulchra

Rising temperature can adversely affect specific functions of corals. Coral gametes and planulae of Acropora pulchra were evaluated to determine their temperature resistances, and the potential of developmental thermal acclimation was examined on gametes. Results highlight that fertilization success displays a relatively high thermal resistance at ET₅₀ (median effective temperature) 31.5 ± 0.5 °C after 4 h and 30 min. Additionally, probability of larval survival is halved at LT₅₀ (median lethal temperature) 28.4 ± 0.42 °C after 14 days. The pre-exposure of oocytes to 30 °C and 32 °C for 1 h increases the cell development pace during fertilization at ambient temperature. Pre-exposure of gametes, separately at 32 °C for 1 h, increases fertilization success rate by 63% at 32°C, conversely, pre-exposure to 30 °C induces more variable results. These results evidenced the occurrence of developmental thermal acclimation as a result of thermal pre-exposure of oocytes.

Silver nanoparticles and dissolved silver activate contrasting immune responses and stress-induced heat shock protein expression in sea urchin

Using immune cells of sea urchin Strongylocentrotus droebachiensis in early development as a model, the cellular protective mechanisms against ionic and poly(allylamine)-coated silver nanoparticle (AgNPs; 14 ± 6 nm) treatments at 100 μg L^-1 were investigated. Oxidative stress, heat shock protein expression, and pigment production by spherulocytes were determined as well as AgNP translocation pathways and their multiple effects on circulating coelomocytes. Sea urchins showed an increasing resilience to Ag over time because ionic Ag is accumulated in a steady way, although nanoAg levels dropped between 48 h and 96 h. A clotting reaction emerged on tissues injured by dissolved Ag (present as chloro-complexes in seawater) between 12 h and 48 h. Silver contamination and nutritional state influenced the production of reactive oxygen species. After passing through coelomic sinuses and gut, AgNPs were found in coelomocytes. Inside blood vessels, apoptosis-like processes appeared in coelomocytes highly contaminated by poly(allylamine)-coated AgNPs. Increasing levels of Ag accumulated by urchins once exposed to AgNPs pointed to a Trojan-horse mechanism operating over 12-d exposure. However, under short-term treatments, physical interactions of poly(allylamine)-coated AgNPs with cell structures might be, at some point, predominant and responsible for the highest levels of stress-related proteins detected. The present study is the first report detailing nano-translocation in a marine organism and multiple mechanisms by which sea urchin cells can deal with toxic AgNPs. Environ Toxicol Chem 2017;36:1872-1886. © 2016 SETAC.

Biochemical characterization of the interaction between HspA1A and phospholipids

Seventy-kilodalton heat shock proteins (Hsp70s) are molecular chaperones essential for maintaining cellular homeostasis. Apart from their indispensable roles in protein homeostasis, specific Hsp70s localize at the plasma membrane and bind to specific lipids. The interaction of Hsp70s with lipids has direct physiological outcomes including lysosomal rescue, microautophagy, and promotion of cell apoptosis. Despite these essential functions, the Hsp70-lipid interactions remain largely uncharacterized. In this study, we characterized the interaction of HspA1A, an inducible Hsp70, with five phospholipids. We first used high concentrations of potassium and established that HspA1A embeds in membranes when bound to all anionic lipids tested. Furthermore, we found that protein insertion is enhanced by increasing the saturation level of the lipids. Next, we determined that the nucleotide-binding domain (NBD) of the protein binds to lipids quantitatively more than the substrate-binding domain (SBD). However, for all lipids tested, the full-length protein is necessary for embedding. We also used calcium and reaction buffers equilibrated at different pH values and determined that electrostatic interactions alone may not fully explain the association of HspA1A with lipids. We then determined that lipid binding is inhibited by nucleotide-binding, but it is unaffected by protein-substrate binding. These results suggest that the HspA1A lipid-association is specific, depends on the physicochemical properties of the lipid, and is mediated by multiple molecular forces. These mechanistic details of the Hsp70-lipid interactions establish a framework of possible physiological functions as they relate to chaperone regulation and localization.

Sea urchin immune cells as sentinels of environmental stress

Echinoderms, an ancient and very successful phylum of marine invertebrates, play a central role in the maintenance of ecosystem integrity and are constantly exposed to environmental pressure, including: predation, changes in temperature and pH, hypoxia, pathogens, UV radiation, metals, toxicants, and emerging pollutants like nanomaterials. The annotation of the sea urchin genome, so closely related to humans and other vertebrate genomes, revealed an unusually complex immune system, which may be the basis for why sea urchins can adapt to different marine environments and survive even in hazardous conditions. In this review, we give a brief overview of the morphological features and recognized functions of echinoderm immune cells with a focus on studies correlating stress and immunity in the sea urchin. Immune cells from adult Paracentrotus lividus, which have been introduced in the last fifteen years as sentinels of environmental stress, are valid tools to uncover basic molecular and regulatory mechanisms of immune responses, supporting their use in immunological research. Here we summarize laboratory and field studies that reveal the amenability of sea urchin immune cells for toxicological testing.

Cellular responses and HSP70 expression during wound healing in Holothuria tubulosa (Gmelin, 1788)

Wound repair is a key event in the regeneration mechanisms of echinoderms. We studied, at the behavioural, cellular and molecular levels, the wound healing processes in Holothuria tubulosa after injuries to the body wall. The experiments were performed for periods of up to 72 h, and various coelomocyte counts, as well as the expression of heat shock proteins (HS27, HSP70 and HSP90), were recorded. Dermal wound healing was nearly complete within 72 h. In the early stages, we observed the injured animals twisting their bodies to keep their injuries on the surface of the water for the extrusion of the buccal pedicles. At the cellular level, we found time-dependent variations in the circulating coelomocyte counts. After injury, in particular, we observed a significant increase in spherule cells at 2.5 h post-injury. Using the western blot method, we observed and reported that the wounds produced, compared with controls, a significant increase in HSP27 and HSP70 expression in coelomocytes, whereas HSP70 was increased in scar tissue and HSP90 was increased only in cell-free coelomic fluid. These results highlight that the wounds were responsible for the stress condition with the induction of cellular and biochemical responses.

Heat-shock protein A8 restores sperm membrane integrity by increasing plasma membrane fluidity

The constitutive 70  kDa heat-shock protein, HSPA8, has previously been shown to contribute to the long-term survival of spermatozoa inside the mammalian female reproductive tract. Here, we show that a recombinant form of HSPA8 rapidly promotes the viability of uncapacitated spermatozoa, the ability of spermatozoa to bind to oviductal epithelial cells, enhances IVF performance, and decreases sperm mitochondrial activity. Fluorescence recovery after photobleaching revealed that the repair of membrane damage is achieved by an almost instantaneous increase in sperm membrane fluidity. The ability of HSPA8 to influence membrane stability and fluidity, as well as its conserved nature among mammalian species, supports the idea that this protein protects sperm survival through membrane repair mechanisms. Free Persian abstract A Persian translation of the abstract is freely available online at http://www.reproduction-online.org/content/147/5/719/suppl/DC1.

Shotgun proteomics of coelomic fluid from the purple sea urchin, Strongylocentrotus purpuratus

The purple sea urchin has a complex immune system that is likely mediated by gene expression in coelomocytes (blood cells). A broad array of potential immune receptors and immune response proteins has been deduced from their gene models. Here we use shotgun mass spectrometry to describe 307 proteins with possible immune function in sea urchins including proteins involved in the complement pathway and numerous SRCRs. The relative abundance of dual oxidase 1, ceruloplasmin, ferritin and transferrin suggests the production of reactive oxygen species in coelomocytes and the sequestration of iron. Proteins such as selectin, cadherin, talin, galectin, amassin and the Von Willebrand factor may be involved in generating a strong clotting reaction. Cell signaling proteins include a guanine nucleotide binding protein, the Rho GDP dissociation factor, calcium storage molecules and a variety of lipoproteins. However, based on this dataset, the expression of TLRs, NLRs and fibrinogen domain containing proteins in coelomic fluid and coelomocytes could not be verified.

The effect of hot-tub therapy on serum Hsp70 level and its benefit on diabetic rats: a preliminary report

PURPOSE

To carry out a preliminary study examining the efficacy of long-term hot-tub therapy (HTT) in the improvement of diabetic complications on streptozotocin-induced diabetic rats.

MATERIALS AND METHODS

Male Wistar rats were immersed mid-sternum in a circulating water bath (42 degrees C for 30 min) to obtain a core body temperature of 41 degrees C; this process was repeated three times a week for 5 months. The blood was collected every month. Multiple parameters were examined for all rats including heat shock protein (Hsp70) level, serum glucose and insulin concentrations, advanced glycation end product (AGE) and glycated haemoglobin (HbA1c) formation, lipid profile and antioxidant defence system. Additionally, the chaperoning capacity of glycated Hsp70 was evaluated based on in vitro studies in which the refolding of denatured luciferase was compared to refolding by native Hsp70.

RESULTS

HTT-treated diabetic rats showed a significant improvement in lipid profile, antioxidant capacity, insulin secretion and serum Hsp70 level and a significant decrease in AGE formation compared to the untreated diabetic rats. However, HTT had a borderline significant effect on weight and fasting blood glucose. Glycated Hsp70 lost its chaperoning ability to reactivate the denatured luciferase.

CONCLUSION

A decrease in complications in diabetic rats after hot-tub therapy is shown here. An increase in the extracellular Hsp70 level due to HTT was observed. This increase may serve to protect the structure of proteins (e.g. preventing AGE formation), and the observed beneficial effects may be related to it.