Characterization of the heat shock response in the gills of sea lampreys and a brook lamprey at different intervals of their life cycles

Molecular evolution of the heat shock protein family and the role of HSP30 in immune response and wound healing in lampreys (Lethenteron reissneri)

Heat shock proteins (HSPs) are molecular chaperones that ubiquitously exist in various organisms and play essential roles in protein folding, transport, and expression. While most HSPs are highly conserved across species, a few HSPs are evolutionarily distinct in some species and may have unique functions. To explore the evolutionary history of the vertebrate HSP family, we identify members of the HSP family at the genome-wide level in lampreys (Lethenteron reissneri), a living representative of jawless vertebrates diverged from jawed vertebrates over 500 million years ago. The phylogenetic analysis reveals that the lamprey HSP family contains HSP90a1, HSP90a2, HSC70, HSP60, HSP30, HSP27, HSP17, and HSP10, which have a primitive status in the molecular evolution of vertebrate HSPs. Transcriptome analysis reveals the expression distribution of members of the HSP family in various tissues of lampreys. It is shown that HSP30, normally found in birds, amphibians, and fish, is also present in lampreys, with remarkable expansion of HSP30 gene copies in the lamprey genome. The transcription of HSP30 is significantly induced in leukocytes and heart of lampreys during various pathogens or poly(I:C) stimulation, indicating that HSP30 may be involved in the immune defense of lampreys in response to bacterial or viral infection. Immunohistochemistry demonstrates significantly increased HSP30 expression in subcutaneous muscle tissue after skin injury in lamprey models of wound repair. Furthermore, transcriptome analysis shows that ectopic expression of HSP30 in 3T3-L1 fibroblasts affect the expression of genes related to the PI3K-AKT signaling pathway, suggesting that HSP30 could serves as a negative regulator of fibrosis. These results indicate that HSP30 may play a critical role in facilitating the process of lamprey skin repair following injury. This study provides new insights into the origin and evolution of the HSP gene family in vertebrates and offers valuable clues to reveal the important role of HSP30 in immune defense and wound healing of lampreys.

Post-translational protein deimination signatures in sea lamprey (Petromyzon marinus) plasma and plasma-extracellular vesicles

Lampreys are a jawless vertebrate species belonging to an ancient vertebrate lineage that diverged from a common ancestor with humans ~500 million years ago. The sea lamprey (Petromyzon marinus) has a filter feeding ammocoete larval stage that metamorphoses into a parasitic adult, feeding both on teleost and elasmobranch fish. Lampreys are a valuable comparative model species for vertebrate immunity and physiology due to their unique phylogenetic position, unusual adaptive immune system, and physiological adaptions such as tolerance to salinity changes and urea. Peptidylarginine deiminases (PADs) are a phylogenetically conserved enzyme family which catalyses post-translational deimination/citrullination in target proteins, enabling proteins to gain new functions (moonlighting). The identification of deiminated protein targets in species across phylogeny may provide novel insights into post-translational regulation of physiological and pathophysiological processes. Extracellular vesicles (EVs) are membrane vesicles released from cells that carry cargos of small molecules and proteins for cellular communication, involved in both normal and pathological processes. The current study identified deimination signatures in proteins of both total plasma and plasma-EVs in sea lamprey and furthermore reports the first characterisation of plasma-EVs in lamprey. EVs were poly-dispersed in the size range of 40-500 nm, similar to what is observed in other taxa, positive for CD63 and Flotillin-1. Plasma-EV morphology was confirmed by transmission electron microscopy. Assessment of deimination/citrullination signatures in lamprey plasma and plasma-EVs, revealed 72 deimination target proteins involved in immunity, metabolism and gene regulation in whole plasma, and 37 target proteins in EVs, whereof 24 were shared targets. Furthermore, the presence of deiminated histone H3, indicative of gene-regulatory mechanisms and also a marker of neutrophil extracellular trap formation (NETosis), was confirmed in lamprey plasma. Functional protein network analysis revealed some differences in KEGG and GO pathways of deiminated proteins in whole plasma compared with plasma-EVs. For example, while common STRING network clusters in plasma and plasma-EVs included Peptide chain elongation, Viral mRNA translation, Glycolysis and gluconeogenesis, STRING network clusters specific for EVs only included: Cellular response to heat stress, Muscle protein and striated muscle thin filament, Nucleosome, Protein processing in endoplasmic reticulum, Nucleosome and histone deacetylase complex. STRING network clusters specific for plasma were: Adipokinetic hormone receptor activity, Fibrinogen alpha/beta chain family, peptidase S1A, Glutathione synthesis and recycling-arginine, Fructose 1,6-bisphosphate metabolic process, Carbon metabolism and lactate dehydrogenase activity, Post-translational protein phosphorylation, Regulation of insulin-like growth factor transport and clotting cascade. Overall, for the EV citrullinome, five STRING network clusters, 10 KEGG pathways, 15 molecular GO pathways and 29 Reactome pathways were identified, compared with nine STRING network clusters, six KEGG pathways, two Molecular GO pathways and one Reactome pathway specific for whole plasma; while further pathways were shared. The reported findings indicate that major pathways relevant for immunity and metabolism are targets of deimination in lamprey plasma and plasma-EVs, with some differences, and may help elucidating roles for the conserved PAD enzyme family in regulation of immune and metabolic function throughout phylogeny.

Extracellular Vesicle Signatures and Post-Translational Protein Deimination in Purple Sea Urchin (Strongylocentrotus purpuratus) Coelomic Fluid-Novel Insights into Echinodermata Biology

The purple sea urchin (Strongylocentrotus purpuratus) is a marine invertebrate of the class Echinoidea that serves as an important research model for developmental biology, cell biology, and immunology, as well as for understanding regenerative responses and ageing. Peptidylarginine deiminases (PADs) are calcium-dependent enzymes that mediate post-translational protein deimination/citrullination. These alterations affect protein function and may also play roles in protein moonlighting. Extracellular vesicles (EVs) are membrane-bound vesicles that are released from cells as a means of cellular communication. Their cargo includes a range of protein and RNA molecules. EVs can be isolated from many body fluids and are therefore used as biomarkers in physiological and pathological responses. This study assessed EVs present in the coelomic fluid of the purple sea urchin (Strongylocentrotus purpuratus), and identified both total protein cargo as well as the deiminated protein cargo. Deiminated proteins in coelomic fluid EVs were compared with the total deiminated proteins identified in coelomic fluid to assess putative differences in deiminated protein targets. Functional protein network analysis for deiminated proteins revealed pathways for immune, metabolic, and gene regulatory functions within both total coelomic fluid and EVs. Key KEGG and GO pathways for total EV protein cargo furthermore showed some overlap with deimination-enriched pathways. The findings presented in this study add to current understanding of how post-translational deimination may shape immunity across the phylogeny tree, including possibly via PAD activity from microbiota symbionts. Furthermore, this study provides a platform for research on EVs as biomarkers in sea urchin models.

The effect of hyperthermia on liver histology, oxidative stress and disease resistance of the Wuchang bream, Megalobrama amblycephala

This study aimed to investigate the effects of hyperthermia on serum hormones, hepatic oxidization indices, hepatic heat shock protein (HSP60, 70, and 90) mRNA expression levels and liver cell ultrastructure in Megalobrama amblycephala before and after high temperature stress. Fish were exposed to the optimal temperature (25 ± 1 °C) or high temperature (32 ± 1 °C) and then challenged with Aeromonas hydrophila. The results showed that hyperthermic stress significantly increased serum adrenocorticotropic hormone (ACTH) at 0.5 and 2 d, serum cortisol (COR) at 0.5, 14, and 21 d and serum 3,5,3'-triiodothyronine (T3) at 1, 14, and 21 d after stress. Additionally, hyperthermia led to oxidative stress, as evidenced by a significant decrease in the hepatic anti-superoxide anion free radical concentration (ASAFER) at 1, 2, 7, and 21 d and in hepatic superoxide dismutase (SOD) activity at 1, 2, 14 and 21 d after stress; however, hepatic malondialdehyde content (MDA) increased at 1, 2, and 7 d after stress. Moreover, the expression of HSP60 at 1 d, HSP70 at 1 and 2 d, and HSP90 at 0.25, 0.5, 1 and 2 d after stress was higher in the stress group compared with the control group. The histological results clearly showed that hyperthermia resulted in fat and glycogen accumulation and structural alterations of the hepatocytes, mitochondria, and nuclei. The cumulative mortality increased in the high temperature stress group at 1 d after acute stress and at 2 and 7 d after chronic stress compared with the control group. Overall, 1 d or 2 d after hyperthermia stress damaged the hepatic ultrastructure and impaired mitochondrial bioenergetics. Dysfunction of the mitochondria subsequently mediated oxidative stress and improved HSP expression modulated the cellular anti-stress response, which in turn led to reduced efficacy of the immune system and increased mortality from Aeromonas hydrophila infection in Megalobrama amblycephala.

Effect of heat stress and recovery on viability, oxidative damage, and heat shock protein expression in hepatic cells of grass carp (Ctenopharyngodon idellus)

In this study, we investigated the effects of hyperthermia and recovery on cell viability, lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity, malondialdehyde (MDA), total antioxidant capacity (T-AOC), and heat shock protein (HSP60, 70, and 90) mRNA expression in the hepatic cells of the grass carp, Ctenopharyngodon idellus. Triplicate groups of cultured cells were exposed to 30, 32, or 34 °C for 0.5 h and then immediately incubated at 27 °C in 5 % CO2 for 6, 12, 24, or 48 h. Hyperthermia stress greatly reduced cell viability and increased LDH release. Cell damage declined after recovery. Hyperthermia stress increased the lipid peroxide levels and reduced the antioxidant capacity (e.g., reduced SOD and T-AOC) of the cells. However, oxidative damage declined as the recovery period increased, and the levels of MDA, SOD, and T-AOC were restored. After cells were exposed to 32 °C, the expression of HSP60 after recovery for 1, 2, and 4 h (P < 0.05), the expression of HSP70 after recovery for 0.5 and 1 h (P < 0.01), and the expression of HSP90 throughout recovery were significantly higher (P < 0.01) than the prestress levels. During the recovery period, the variations in HSP gene expression reflected the transition period from a state of cellular growth to one of the cellular repairs. In conclusion, hyperthermia depresses cell viability, induces oxidative damage, and increases HSP expression, which plays an important role during hyperthermic stress in grass carp hepatic cells.

The value of stress protein 70 as an environmental biomarker of fish health under field conditions

Hsp70 protein in three tissue types (gill, liver, and muscle) from black bream (Acanthopagrus butcheri) collected in a highly variable estuarine environment was investigated to determine which tissue provides better intersite discrimination. The usefulness of hsp70 expression to identify anthropogenic stress under field conditions was evaluated. Intersite differences were detected in hsp70 levels in gill and white muscle of black bream while liver showed no spatial difference. There was high interfish variability in hsp70 levels in each tissue group. A post hoc power analysis of the datasets for each tissue found that in black bream, white muscle provided the best discriminatory power to elucidate spatial variability. Only 11 fish per site are required to identify significant intersite differences in white muscle whereas for gill and liver tissues 14 and 21 fish per site, respectively, would be required. Because of high intertissue and interindividual variability, field measurement of hsp70 should be complemented by evidence of changes in other biomarkers of fish health.

Bacterial infection and tissue-specific Hsp72, -73 and -90 expression in western painted turtles

Heat shock proteins (Hsps) are molecular chaperones that assist intracellular folding, assembly and translocation of proteins in prokaryotic and eukaryotic cells. A variety of stresses including hyperthermia, radiation, heavy metals, ischemia, anoxia and reoxygenation have been shown to increase the expression of Hsps. Likewise, bacterial infection represents a stress for the host cell. In this study, expression of the constitutive (Hsp73) and inducible (Hsp72) isoforms of Hsp70 and Hsp90 was monitored in brain, heart, liver and skeletal muscle from the western painted turtle Chrysemys picta bellii diagnosed with Septicemic Cutaneous Ulcerative Dermatitis (SCUD). This disease is caused by a gram-negative bacterium probably belonging to the Citrobacter spp. The expression of Hsp73 increased 1.8-fold in brain and liver, 2.2-fold in heart but did not change in skeletal muscle; Hsp72 expression increased 5.5-fold in brain and 3-fold in liver but did not change in heart or skeletal muscle; Hsp90 expression increased 9-fold in brain, 2.7-fold in heart and 2.4-fold in skeletal muscle but did not change in liver. These results suggest a tissue-specific Hsp response during bacterial infection and a role for Hsps in immunopathological events in reptiles.

Organization and nucleotide sequence of the European flat oyster Ostrea edulis heat shock cognate 70 (hsc70) and heat shock protein 70 (hsp70) genes

The heat shock protein 70 family is composed of both environmentally inducible (Hsp) and constitutively expressed (Hsc) members. We sequenced two genes encoding Hsp70 and Hsc70 in the European flat oyster Ostrea edulis. The Oehsc70 gene contained introns, while the Oehsp70 gene did not. The corresponding amino acid sequences contained the characteristic motifs of the HSP70 family.