Heat-shock protein 70 modulates apoptosis signal-regulating kinase 1 in stressed hepatocytes of Mugil cephalus

The Protective Role of Heat Shock Proteins against Stresses in Animal Breeding

Heat shock proteins (HSPs) play an important role in all living organisms under stress conditions by acting as molecular chaperones. The expression of different HSPs during stress varies depending on their protective functions and anti-apoptotic activities. The application of HSPs improves the efficiency and decreases the economic cost of animal breeding. By upregulating the expression of HSPs, feed supplements can improve stress tolerance in farm animals. In addition, high expression of HSPs is often a feature of tumor cells, and inhibiting the expression of HSPs is a promising novel method for killing these cells and treating cancers. In the present review, the findings of previous research on the application of HSPs in animal breeding and veterinary medicine are summarized, and the knowledge of the actions of HSPs in animals is briefly discussed.

Comparative Transcriptome and WGCNA Analysis Reveal Molecular Responses to Salinity Change in Larvae of the Iwagaki Oyster Crassostrea Nippona

The Iwagaki oyster Crassostrea nippona is an important aquaculture species with significant potential for large-scale oyster farming. It is susceptible to the fluctuated salinity in the coastal area. In this study, we compared the transcriptome of Crassostrea nippona larvae under variant conditions with low-salinity stress (28, 20, 15, 10, and 5 practical salinity units (psu)) for 24 h. KEGG enrichment analysis of differentially expressed genes (DEGs) from pairwise comparisons identified several free amino acid metabolism pathway (taurine and hypotaurine, arginine and proline, glycine, and beta-alanine) contributing to the salinity change adaptation and activated "lysosome" and "apoptosis" pathway in response to the low-salinity stress (10 and 5 psu). Trend analysis revealed sustained upregulation of transmembrane transport-related genes (such as SLC family) and downregulation of ribosomal protein synthesis genes faced with decreasing salinities. In addition, 9 biomarkers in response to low-salinity stress were identified through weighted gene co-expression network analysis (WGCNA) and validated by qRT-PCR. Our transcriptome analysis provides a comprehensive view of the molecular mechanisms and regulatory networks underlying the adaptive responses of oyster larvae to hypo-salinity conditions. These findings contribute to our understanding of the complex biological processes involved in oyster resilience and adaptation to changing environmental conditions.

Toxic Effects on Oxidative Stress, Neurotoxicity, Stress, and Immune Responses in Juvenile Olive Flounder, Paralichthys olivaceus, Exposed to Waterborne Hexavalent Chromium

Simple Summary

Metals such as chromium can be exposed at high levels in the marine environment, and exposure to these heavy metals can have a direct effect on marine organisms. High levels of chromium exposure can have a direct impact on organisms in a coastal cage and terrestrial aquaculture. Hexavalent chromium exposure of more than 1.0 and 2.0 mg Cr⁶⁺/L induced physiological responses such as antioxidant, neurotransmitter, immune, and stress indicators in Paralichthys olivaceus. Therefore, this study will provide a reference indicator for stable aquaculture production through reference indicators for toxicity due to chromium exposure that may exist in the marine environment.

Abstract

Juvenile Paralichthys olivaceus were exposed to waterborne hexavalent chromium at various concentrations (0, 0.5, 1.0, and 2.0 mg/L) for 10 days. After chromium exposure, the activities of superoxide dismutase and glutathione S-transferase, which are oxidative stress indicators, were significantly increased; however, the glutathione level was significantly reduced. Acetylcholinesterase activity as a neurotoxicity marker was significantly inhibited upon chromium exposure. Other stress indicators, including plasma cortisol and heat shock protein 70, were significantly increased. The immune response markers (lysozyme and immunoglobulin M) were significantly decreased after chromium exposure. These results suggest that exposure to environmental toxicity in the form of waterborne chromium at concentrations higher than 1.0 mg/L causes significant alterations in antioxidant responses, neurotransmitters, stress, and immune responses in juvenile olive flounders. This study will provide a basis for an accurate assessment of the toxic effects of hexavalent chromium on aquatic organisms.

Exposure of adult sea urchin Strongylocentrotus intermedius to stranded heavy fuel oil causes developmental toxicity on larval offspring

Heavy fuel oil (HFO) spills pose serious threat to coastlines and sensitive resources. Stranded HFO that occurs along the coastline could cause long-term and massive damage to the marine environment and indirectly affect the survival of parental marine invertebrates. However, our understanding of the complex associations within invertebrates is primarily limited, particularly in terms of the toxicity effects on the offspring when parents are exposed to stranded HFO. Here, we investigated the persistent effects on the early development stage of the offspring following stranded HFO exposure on the sea urchin Strongylocentrotus intermedius. After 21 d exposure, sea urchins exhibited a significant decrease in the reproductive capacity; while the reactive oxygen species level, 3-nitrotyrosine protein level, protein carbonyl level, and heat shock proteins 70 expression in the gonadal tissues and gametes significantly increased as compared to the controls, indicating that HFO exposure could cause development toxicity on offspring in most traits of larval size. These results suggested that the stranded HFO exposure could increase oxidative stress of gonadal tissues, impair reproductive functions in parental sea urchins, and subsequently impact on development of their offspring. This study provides valuable information regarding the persistent toxicity effects on the offspring following stranded HFO exposure on sea urchins.

Elevated seasonal temperature disrupts prooxidant-antioxidant homeostasis and promotes cellular apoptosis in the American oyster, Crassostrea virginica, in the Gulf of Mexico: a field study

One of the major impacts of climate change has been the marked rise in global temperature. Recently, we demonstrated that high temperatures (1-week exposure) disrupt prooxidant-antioxidant homeostasis and promote cellular apoptosis in the American oyster. In this study, we evaluated the effects of seasonal sea surface temperature (SST) on tissue morphology, extrapallial fluid (EPF) conditions, heat shock protein-70 (HSP70), dinitrophenyl protein (DNP, an indicator of reactive oxygen species, ROS), 3-nitrotyrosine protein (NTP, an indicator of RNS), catalase (CAT), superoxide dismutase (SOD) protein expressions, and cellular apoptosis in gills and digestive glands of oysters collected on the southern Texas coast during the winter (15 °C), spring (24 °C), summer (30 °C), and fall (27 °C). Histological observations of both tissues showed a notable increase in mucus production and an enlargement of the digestive gland lumen with seasonal temperature rise, whereas biochemical analyses exhibited a significant decrease in EPF pH and protein concentration. Immunohistochemical analyses showed higher expression of HSP70 along with the expression of DNP and NTP in oyster tissues during summer. Intriguingly, CAT and SOD protein expressions exhibited significant upregulation with rising seasonal temperatures (15 to 27 °C), which decreased significantly in summer (30 °C), leaving oysters vulnerable to oxidative and nitrative damage. qRT-PCR analysis revealed a significant increase in HSP70 mRNA levels in oyster tissues during the warmer seasons. In situ TUNNEL assay showed a significant increase in apoptotic cells in seasons with high temperature. These results suggest that elevated SST induces oxidative/nitrative stress through the overproduction of ROS/RNS and disrupts the antioxidant system which promotes cellular apoptosis in oysters.

Effects of elevated temperature on prooxidant-antioxidant homeostasis and redox status in the American oyster: Signaling pathways of cellular apoptosis during heat stress

Increasing seawater temperature affects growth, reproduction, development, and various other physiological processes in aquatic organisms, such as marine invertebrates, which are especially susceptible to high temperatures. In this study, we examined the effects of short-term heat stress (16, 22, 26, and 30 °C for 1-week exposure) on prooxidant-antioxidant homeostasis and redox status in the American oyster (Crassostrea virginica, an edible and commercially cultivated bivalve mollusk) under controlled laboratory conditions. Immunohistochemical and real-time quantitative PCR (qRT-PCR) analyses were performed to examine the expression of heat shock protein-70 (HSP70, a biomarker of heat stress), catalase (CAT, an antioxidant), superoxide dismutase (SOD, an antioxidant), dinitrophenyl protein (DNP, a biomarker of reactive oxygen species, ROS), and 3-nitrotyrosine protein (NTP, an indicator of reactive nitrogen species, RNS), in the gills and digestive glands of oysters. In situ TUNEL assay was performed to detect cellular apoptosis in tissues. Histological analysis showed an increase in mucus secretion in the gills and digestive glands of oysters exposed to higher temperatures (22, 26, and 30 °C) compared to control (16 °C). Immunohistochemical and qRT-PCR analyses showed significant increases in HSP70, DNP and NTP protein, and mRNA expressions in tissues at higher temperatures. Cellular apoptosis was also significantly increased at higher temperatures. Thus, heat-induced oxidative and nitrative stress likely occur due to overproduction of ROS and RNS. Interestingly, expression of CAT and SOD increased in oysters exposed to 22 and 26 °C, but was at or below control levels in the highest temperature exposure (30 °C). Collectively, these results suggest that elevated seawater temperatures cause oxidative/nitrative stress and induce cellular apoptosis through excessive ROS and RNS production, leading to inhibition of the antioxidant defense system in marine mollusks.

Effects of elevated temperature on gonadal functions, cellular apoptosis, and oxidative stress in Atlantic sea urchin Arbacia punculata

Increasing seawater temperature affects growth, reproduction and development in marine organisms. In this study, we examined the effects of elevated temperatures on reproductive functions, heat shock protein 70 (HSP70) and nitrotyrosine protein (NTP, an indicator of reactive nitrogen species) expressions, protein carbonyl (PC, an indicator of oxidative stress) contents, cellular apoptosis, and coelomic fluid (CF) conditions in Atlantic sea urchin. Sea urchins were housed in six aquaria with control (24 °C) and elevated temperatures (28 °C and 32 °C) for a 7-day period. After exposure, sea urchins exhibited decreased percentages of gametes (eggs/sperm), as well as increased HSP70 and NTP expressions in eggs and spermatogenic cells, increased gonadal apoptosis, and decreased CF pH compared to controls. PC contents were also significantly increased in gonadal tissues at higher temperatures. These results suggest that elevated temperature acidifies CF, increases oxidative stress and gonadal apoptosis, and results in impairment of reproductive functions in sea urchins.

Environmental pollution and toxic substances: Cellular apoptosis as a key parameter in a sensible model like fish

The industrial wastes, sewage effluents, agricultural run-off and decomposition of biological waste may cause high environmental concentration of chemicals that can interfere with the cell cycle activating the programmed process of cells death (apoptosis). In order to provide a detailed understanding of environmental pollutants-induced apoptosis, here we reviewed the current knowledge on the interactions of environmental chemicals and programmed cell death. Metals (aluminum, arsenic, cadmium, chromium, cobalt, zinc, copper, mercury and silver) as well as other chemicals including bleached kraft pulp mill effluent (BKME), persistent organic pollutants (POPs), and pesticides (organo-phosphated, organo-chlorinated, carbamates, phyretroids and biopesticides) were evaluated in relation to apoptotic pathways, heat shock proteins and metallothioneins. Although research performed over the past decades has improved our understanding of processes involved in apoptosis in fish, yet there is lack of knowledge on associations between environmental pollutants and apoptosis. Thus, this review could be useful tool to study the cytotoxic/apoptotic effects of different pollutants in fish species.

Proliferation, survival and cell death in fish gills remodeling: From injury to recovery

Pollutants found dispersed in water can cause irritations on the gills, challenge the immune system and prejudice the welfare of the fish. Here we investigated molecules linked to proliferation, survival, and cell death, as well as inflammatory and vascular control, in a model of fish gill remodeling, from injury to recovery. We assessed the gill histology and immunohistochemistry for PCNA, iNOS, HSP70, and Bax in Hypostomus francisci obtained from a river subjected to chronic anthropic influences and then after they were placed in water of good quality. A total of 30 H. francisci adult individuals were collected and distributed into two groups: euthanized on the day of capture (group 1) and maintained for 30 days in an aquarium (group 2). In all the fish from group 1, the primary and secondary lamellae showed hypertrophy of the respiratory epithelium, lamellar fusion, lifting of the epithelium, aneurysm, hyperemia, and vascular congestion. On the other hand, in all the fish from group 2, restoration of gill integrity was observed, and the primary and secondary lamellae showed a simple epithelium, absence of lamellar fusion, hypertrophy, and aneurysm. Gills of fish from group 1 had higher frequency of cells immunopositive for PCNA, iNOS, HSP70, and Bax than those of fish from group 2 (p < 0.05). The molecular and cellular mechanisms from injury to recovery were proposed, with a balance between survival and cell death signals being essential for determining the gill structure. In addition, the findings indicate that recovery of the structural organization of gills is possible if fishes are maintained in good-quality water, indicating the importance of the conservation of aquatic environments.

[The role of heat shock proteins 27 and 70 in redox-dependent regulation of apoptosis in Jurkat tumor cells]

Heat shock proteins Hsp) act as molecular chaperones, protecting enzymes and other proteins against reactive oxygen species. The objective of the study was to investigate the role of Hsp27 in maintaining the balance of the glutathione system and Hsp70 concentrations as well as in implementing Jurkat tumor cell apoptosis. Addition of the Hsp27 inhibitor KRIBB3 (5-(5-ethyl-2-hydroxy-4-methoxyphenyl)-4-(4-methoxyphenyl)-isoxazol) to Jurkat cells resulted in glutathione redox imbalance (increased GSSG and increased glutathione reductase activity), a decrease in Hsp70 concentrations, and also increased cell apoptosis as compared with to the intact cell culture. The proposed selective regulation of chaperone activity is a promising direction in regulating apoptosis at the cellular level.

Differential regulation of pro- and antiapoptotic proteins in fish adipocytes during hypoxic conditions

Worldwide, the frequencies and magnitudes of hypoxic events in estuarine waters have increased considerably over the past two decades. Fish populations are suitable indicators for the assessment of quality of aquatic ecosystems and often comprise a variety of adaptation systems by triggering oxidants, antioxidants and hypoxia-responsive signaling proteins. Signaling pathway may lead to cell survival or cell death which is fine-tuned by both positive and negative factors, which includes hypoxia-inducible factor-1α (HIF1α), heat-shock protein-70 (HSP70), phospho-c-Jun N-terminal kinase 1/2 (p-JNK1/2) and apoptosis signal-regulating kinase-1 (ASK1). In the present study, we attempt to determine stress-mediated signaling changes and molecular mechanism behind the cell survival by comparing adipocytes of fish from field hypoxic condition and laboratory-induced hypoxic condition (in vitro hypoxia). Comparison of field and laboratory studies in fish adipocytes showed differential expression of HIF1α, HSP70, p-JNK1/2 and ASK1 with altered oxidants and antioxidants. Further, the results also suggest that in vitro hypoxic conditions mimic field hypoxic conditions. Trends of hypoxia response were same in in vitro hypoxia of control adipocytes as in Ennore estuary, and hypoxia response was more pronounced in the test adipocytes under in vitro hypoxic condition. Results of the present work suggest that hypoxia is the major crusade of water pollutants affecting fish by differential regulation of pro- and antiapoptotic proteins probably through HSP70. This may play a vital role by providing cytoprotection in pollutant-induced stressed fish adipocytes substantiated by the in vitro hypoxic studies.

Low-level sodium arsenite induces apoptosis through inhibiting TrxR activity in pancreatic β-cells

In our previous study, we reported that sodium arsenite induced ROS-dependent apoptosis through lysosomal-mitochondrial pathway in pancreatic β-cells. Since the thioredoxin (Trx) system is the key antioxidant factor in mammalian cells, we investigate whether the inhibition of Trx system contributes to sodium arsenite-induced apoptosis in this study. After treatment with low-level (0.25-1μM) sodium arsenite for 96h, the thioredoxin reductase (TrxR) activity was decreased significantly in pancreatic INS-1 cells. Following with the inactivation of TrxR, ASK1 was released from combining with Trx, which was evidenced by increased levels of ASK1 in sodium arsenite-treated INS-1 cells. Subsequently, activated ASK1 accelerated the expression of proapoptotic protein Bax and reduced the expression of anti-apoptic protein Bcl-2. Finally, low-level sodium arsenite induced apoptosis via caspase-3 in INS-1 cells. Knockdown of ASK1 alleviated sodium arsenite-induced apoptosis. In summary, the precise molecular mechanisms through which arsenic is related to diabetes have not been completely elucidated, inactivation of Trx system might provide insights into the underlying mechanisms at the environmental exposure levels.