Changes in the expression of four heat shock proteins during the aging process in Brachionus calyciflorus (rotifera)

Toxic effects of combined exposure to homoyessotoxin and nitrite on the survival, antioxidative responses, and apoptosis of the abalone Haliotis discus hannai

Homoyessotoxin (homo-YTX) and nitrite (NO2-N), released during harmful dinoflagellate cell lysis adversely affect abalones. However, their toxicity mechanisms in shellfish remain unclear. This study investigated the economic abalone species Haliotis discus hannai exposed to varying concentrations of homo-YTX (0, 2, 5, and 10 µg L-1) and NO2-N (0, 3, and 6 mg L-1) on the basis of their 12 h LC50 values (5.05 µg L-1 and 4.25 mg L-1, respectively) and the environmentally relevant dissolved concentrations during severe dinoflagellate blooms, including mixtures. The test abalones were exposed to homo-YTX and NO2-N for 12 h. The mortality rate (D), reactive oxygen species (ROS) levels, antioxidant defense capabilities, and expression levels of antioxidant-related, Hsp-related, and apoptosis-related genes in abalone gills were assessed. Results showed that the combined exposure to homo-YTX and NO2-N increased the D and ROS levels and upregulated B-cell lymphoma-2 (BCL2)-associated X (BAX) and caspase3 (CASP3) expression levels while reducing glutathione peroxidase (GPx) activity and GPx, CuZnSOD, and BCL2 expression levels. High concentrations of homo-YTX (10 µg L-1) and NO2-N (6 mg L-1) solutions and the combinations of these toxicants inhibited the activities of superoxide dismutase (SOD) and catalase (CAT) and downregulated the expression levels of MnSOD, CAT, Hsp70, and Hsp90. The ROS levels were negatively correlated with the activities of SOD, CAT, and GPx and the expression levels of MnSOD, CuZnSOD, CAT, GPx, Hsp70, Hsp90, and BCL2. These results suggest that homo-YTX, in conjunction with NO2-N, induces oxidative stress, disrupts antioxidant defense systems, and triggers caspase-dependent apoptosis in the gills of abalone. ROS-mediated antioxidative and heat-shock responses and apoptosis emerge as potential toxicity mechanisms affecting the survival of H. discus hannai due to homo-YTX and NO2-N exposure.

A genome-wide screening of the 70 kDa heat shock protein (HSP70) genes in the rotifer Brachionus plicatilis sensu stricto with a characterization of two heat-inducible HSP70 genes

The 70 kDa heat shock proteins (HSP70s) and the constitutive members of the HSP70 family (heat shock cognates; HSC70s) play essential roles in various biological processes. The number of hsp70/hsc70 in the database is rapidly increasing because of their importance and the automatic annotation of newly sequenced genomes. However, accumulating evidence indicates that neither hsp70 nor hsc70 forms a monophyletic gene family, raising the need to reconsider the annotation strategy based on the traditional concept of the inducible HSP70 and constitutive HSC70s. The main aim of this study is to establish a systematic scheme to annotate hsp70-like genes taking the latest phylogenetic insights into account. We cloned two hsp70s from the rotifer Brachionus plicatilis sensu stricto (s.s.), an emerging model in evolutionary genetics, and conducted a genome-wide screening of B. plicatilis s.s. hsp70s using the two sequences as queries. A total of 15 hsp70-like genes were found, and 7 of them encoded distant members of the HSP70 family, the function of which largely remains unknown. Eight canonical hsp70s were annotated according to a recently proposed nomenclature based on the molecular evolution: e.g., HSP70cA1/B1 for the cytosolic lineage, HSP70er1 for the endoplasmic reticulum lineage, and HSP70m1 for the mitochondrial lineage. The two cloned hsp70s, HSP70cB1 and HSP70cB2, ubiquitously increased their mRNA levels up to 7.5 times after heat treatment as assessed by semi-quantitative PCR, real-time PCR, and in situ hybridization. This systematic screening incorporating a reasonable update to the annotation strategy would provide a useful example for future HSP70 studies, especially those in non-traditional model organisms.

Variation in heat shock protein 40 kDa relates to divergence in thermotolerance among cryptic rotifer species

Genetic divergence and the frequency of hybridization are central for defining species delimitations, especially among cryptic species where morphological differences are merely absent. Rotifers are known for their high cryptic diversity and therefore are ideal model organisms to investigate such patterns. Here, we used the recently resolved Brachionus calyciflorus species complex to investigate whether previously observed between species differences in thermotolerance and gene expression are also reflected in their genomic footprint. We identified a Heat Shock Protein gene (HSP 40 kDa) which exhibits cross species pronounced sequence variation. This gene exhibits species-specific fixed sites, alleles, and sites putatively under positive selection. These sites are located in protein binding regions involved in chaperoning and may therefore reflect adaptive diversification. By comparing three genetic markers (ITS, COI, HSP 40 kDa), we revealed hybridization events between the cryptic species. The low frequency of introgressive haplotypes/alleles suggest a tight, but not fully impermeable boundary between the cryptic species.

Heat Shock Proteins (Hsps) in Cellular Homeostasis: A Promising Tool for Health Management in Crustacean Aquaculture

Heat shock proteins (Hsps) are a family of ubiquitously expressed stress proteins and extrinsic chaperones that are required for viability and cell growth in all living organisms. These proteins are highly conserved and produced in all cellular organisms when exposed to stress. Hsps play a significant role in protein synthesis and homeostasis, as well as in the maintenance of overall health in crustaceans against various internal and external environmental stresses. Recent reports have suggested that enhancing in vivo Hsp levels via non-lethal heat shock, exogenous Hsps, or plant-based compounds, could be a promising strategy used to develop protective immunity in crustaceans against both abiotic and biotic stresses. Hence, Hsps as the agent of being an immune booster and increasing disease resistance will present a significant advancement in reducing stressful conditions in the aquaculture system.

Variable heat shock response in Antarctic biofouling serpulid worms

The classical heat shock response (HSR) with up-regulation of hsp70 in response to warming is often absent in Antarctic marine species. Whilst in Antarctic fish, this is due to a mutation in the gene promoter region resulting in permanent constitutive expression of the inducible form of hsp70; there are further questions as to whether evolution to life below 0 °C has resulted in a generalised alteration to the HSR in Antarctic marine invertebrates. However, the number of species investigated to date is limited. In the first evaluation of the HSR in two spirorbid polychaetes Romanchella perrieri and Protolaeospira stalagmia, we show highly variable results of HSR induction depending on warming regimes. These animals were subjected to in situ warming (+ 1 °C and + 2 °C above ambient conditions) using heated settlement panels for 18 months, and then the HSR was tested in R. perrieri using acute and chronic temperature elevation trials. The classic HSR was not induced in response to acute thermal challenge in this species (2 h at 15 °C) and significant down-regulation of hsp90 occurred during chronic warming at 4 °C for 30 days. Analysis of heat shock protein (HSP) genes in a transcriptome study of P. stalagmia, which had been warmed in situ for 18 months, showed up-regulation of HSP70 and HSP90 family members, thus further emphasising the complexity of the response in Antarctic marine species. It is increasingly apparent that the Antarctic HSR has evolved in a species-specific manner to life in the cold.

Brachionus rotifers as a model for investigating dietary and metabolic regulators of aging

Because every species has unique attributes relevant to understanding specific aspects of aging, using a diversity of study systems and a comparative biology approach for aging research has the potential to lead to novel discoveries applicable to human health. Monogonont rotifers, a standard model for studies of aquatic ecology, evolutionary biology, and ecotoxicology, have also been used to study lifespan and healthspan for nearly a century. However, because much of this work has been published in the ecology and evolutionary biology literature, it may not be known to the biomedical research community. In this review, we provide an overview of Brachionus rotifers as a model to investigate nutritional and metabolic regulators of aging, with a focus on recent studies of dietary and metabolic pathway manipulation. Rotifers are microscopic, aquatic invertebrates with many advantages as a system for studying aging, including a two-week lifespan, easy laboratory culture, direct development without a larval stage, sexual and asexual reproduction, easy delivery of pharmaceuticals in liquid culture, and transparency allowing imaging of cellular morphology and processes. Rotifers have greater gene homology with humans than do established invertebrate models for aging, and thus rotifers may be used to investigate novel genetic mechanisms relevant to human lifespan and healthspan. The research on caloric restriction; dietary, pharmaceutical, and genetic interventions; and transcriptomics of aging using rotifers provide insights into the metabolic regulators of lifespan and health and suggest future directions for aging research. Capitalizing on the unique biology of Brachionus rotifers, referencing the vast existing literature about the influence of diet and drugs on rotifer lifespan and health, continuing the development of genetic tools for rotifers, and growing the rotifer research community will lead to new discoveries a better understanding of the biology of aging.

Heat Shock Protein 40 (HSP40) in Pacific White Shrimp (Litopenaeus vannamei): Molecular Cloning, Tissue Distribution and Ontogeny, Response to Temperature, Acidity/Alkalinity and Salinity Stresses, and Potential Role in Ovarian Development

Heat shock proteins (HSPs), a family of conserved proteins that are produced by cells in response to stresses, are known as molecular chaperones with a range of housekeeping and cellular protective functions. The 40 kD heat shock protein (HSP40) is a co-chaperone for HSP70 in the regulation of ATP hydrolysis. Unlike its well-documented cofactor HSP70, little is currently known regarding the biological functions of HSP40 in crustacean species such as penaeid shrimp. In the present study, the cDNA encoding HSP40 (Lv-HSP40) was identified from the Pacific white shrimp Litopenaeus vannamei, a highly significant commercial culture species. The structural organization indicates that Lv-HSP40 belongs to the type-I HSP40s. The muscle, gill, and hepatopancreas are the main sites of Lv-HSP40 transcript expression. Within these tissues, Lv-HSP40 mRNA were predominantly exhibited in the myocytes, epithelial cells and hepatopancreatic cells, respectively. Under acute thermal stress in the culture environment, Lv-HSP40 transcript levels are significantly induced in these three tissues, while low pH stress only upregulates Lv-HSP40 mRNA in the hepatopancreas and gill. During ontogenesis, Lv-HSP40 transcript levels are high at early embryonic stages and drop sharply at late embryonic and early larval stages. The ovary is another major organ of Lv-HSP40 mRNA expression in female shrimp, and Lv-HSP40 transcripts were mainly presented in the follicle cells but only weekly detected in the oocytes. Ovarian Lv-HSP40 mRNA levels increase continuously during gonadal development. Silencing of the Lv-HSP40 gene by RNA interference may effectively delay ovarian maturation after unilateral eyestalk ablation. The roles of Lv-HSP40 in ovarian development are speculated to be independent of its cofactor HSP70, and the vitellogenesis factor vitellogenin (Vg) and vitellogenin receptor (VgR). Our study, as a whole, provides new insights into the roles of HSP40 in multiple physiological processes in L. vannamei: (1) HSP40 is a responding factor during stressful conditions; and (2) HSP40 participates in embryonic and ovarian development.

Transcriptome analysis on chlorpyrifos detoxification in Uronema marinum (Ciliophora, Oligohymenophorea)

Chlorpyrifos (CPF) pollution has drawn widespread concerns in aquatic environments due to its risks to ecologic system, however, the response mechanisms of ciliates to CPF pollution were poorly studied. In our current work, the degradation of CPF by ciliates and the morphological changes of ciliates after CPF exposure were investigated. In addition, the transcriptomic profiles of the ciliate Uronema marinum, with and without exposure with CPF, were detected using digital gene expression technologies. De novo transcriptome assembly 166,829,634 reads produced from three groups (untreated, CPF treatment at 12 h and 24 h) by whole transcriptome sequencing (RNA-Seq). Gene ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathways were analyzed in all unigenes and different expression genes to identify their biological functions and processes. Furthermore, the results indicated that genes related to the stress response, cytoskeleton and cell structure proteins, and antioxidant systems might play an important role in the resistance mechanism of ciliates. The enzyme activities of SOD and GST after CPF stress were also analyzed, and the result showed the good antioxidant capacity of SOD and GST in ciliates inferred from the increase of the activities of the two enzymes. The ciliate Uronema marinum showed a resistance response to chlorpyrifos stress at the transcriptomic level in the present work, which indicates that ciliates can be considered as a potential bioremediation agent.

Adverse effects of the insecticides chlordecone and fipronil on population growth and expression of the entire cytochrome P450 (CYP) genes in the freshwater rotifer Brachionus calyciflorus and the marine rotifer Brachionus plicatilis

Chlordecone and fipronil are used as an insecticide and have been widely detected in the aquatic environments. However, their toxicity is still poorly investigated in aquatic invertebrates. In this study, we examined effects of chlordecone and fipronil on population growth and transcriptional regulation of the entire cytochrome P450 (CYP) genes in the freshwater rotifer Brachionus calyciflorus and the marine rotifer B. plicatilis. In B. calyciflorus, a 24 h-no observed effect concentration (NOEC-24 h) and a 24 h-median lethal concentration (LC50-24 h) of chlordecone were determined as 100 μg/L and 193.8 μg/L, respectively, while NOEC-24 h and LC50-24 h of fipronil were determined as 1000 μg/L and 2033.0 μg/L, respectively. In B. plicatilis, NOEC-24 h and LC50-24 h of chlordecone were 100 μg/L and 291.0 μg/L, respectively, while NOEC-24 h and LC50-24 h of fipronil were determined as 1000 μg/L and 5735.0 μg/L, respectively. Moreover, retardation in the population growth were observed in response to chlordecone and fipronil in both rotifer species, suggesting that chlordecone and fipronil have a potential adverse effects on life cycle parameters of two rotifer species. Additionally, modulation in the expressions of the entire CYP genes were demonstrated in response to chlordecone and fipronil at 24 h period. These results provide the better understanding on how chlordecone and fipronil can affect in population growth of two rotifers and CYP gene expressions in chlordecone- and fipronil-exposed rotifers.

Regulation of heat shock protein 70 (Hsp70) levels in the bdelloid rotifer Rotaria rotatoria under temperature stress

The bdelloid rotifer is an important component of freshwater zooplankton, exhibiting the features of parthenogenesis and anhydrobiotic capability. Heat shock proteins (Hsps), acting as molecular chaperones, are a highly conserved, ubiquitously expressed family of stress response proteins. In this study, the thermal optimums for heat-shock response and the levels of Hsp70 in Rotaria rotatoria (bdelloid rotifer) under different stress conditions were evaluated using survival assays and western blotting with fluorescent detection. The results showed that: (1) The survivorship in R. rotatoria were 100% throughout the temperature range of 12°C to 40°C, and the population growth rate reached its culmination at 28°C, suggesting the retardation of growth and reproduction at the other temperatures; (2) While stressed under 40°C, the levels of Hsp70 in R. rotatoria increased significantly over time, correlating with the duration of the stress; (3) As responses to different temperatures, the synthesis of Hsp70 could be induced significantly in R. rotatoria under both of high (40°C) and low (16°C) temperatures; (4) After removal of the thermal stress and recovery at 28°C, the levels of Hsp70 continued to rise for a period of time, peaked at 12 h, and then slowly declined with the extension of recovery duration, until there is no significant difference of Hsp70 levels. Summarily, with the fluctuations of stress duration and temperature, the rotifers could adapt to the environments sensitively by regulating the synthesis of Hsp70.

Moderately lower temperatures greatly extend the lifespan of Brachionus manjavacas (Rotifera): Thermodynamics or gene regulation?

Environmental temperature greatly affects lifespan in a wide variety of animals, but the exact mechanisms underlying this effect are still largely unknown. A moderate temperature decrease from 22°C to 16°C extends the lifespan of the monogonont rotifer Brachionus manjavacas by up to 163%. Thermodynamic effects on metabolism contribute to this increase in longevity, but are not the only cause. When rotifers are exposed to 16°C for four days and then transfered to 22°C, they survive until day 13 at nearly identical rates as rotifers maintained at 16°C continuously. This persistence of the higher survival for nine days after transfer to 22°C suggests that low temperature exposure alters the expression of genes that affect the rate of aging. The relative persistence of the gene regulation effect suggests that it may play an even larger role in slowing aging than the thermodynamic effects. The life extending effects of these short-term low temperature treatments are largest when the exposure happens early in the life cycle, demonstrating the importance of early development. There is no advantage to lowering the temperature below 16°C to 11° or 5°C. Rotifers exposed to 16°C also displayed increased resistance to heat, starvation, oxidative and osmotic stress. Reproductive rates at 16°C were lower than those at 22°C, but because they reproduce longer, there is no significant change in the lifetime fecundity of females. To investigate which genes contribute to these effects, the expression of specific temperature sensing genes was knocked down using RNAi. Of 12 genes tested, RNAi knockdown of four eliminated the survival enhancing effects of the four-day cold treatment: TRP7, forkhead box C, Y-box factor, and ribosomal protein S6. This demonstrates that active gene regulation is an important factor in temperature mediated life extension, and that these particular genes play an integral role in these pathways. As a thermoresponsive sensor, TRP7 may be responsible for triggering the signaling cascade contributing to temperature mediated life extension. The TRP genes may also provide especially promising candidates for targeted gene manipulations or pharmacological interventions capable of mimicking the effects of low temperature exposure. These results support recent theories of aging that claim rate of aging is determined by an actively regulated genetic mechanism rather than an accumulation of molecular damage.

Identification and expression analysis of a heat-shock protein 70 gene in Polycelis sp

Heat-shock protein 70 (HSP70) is ubiquitously found in a variety of organisms and plays an important role in cytoprotection, environmental monitoring, and disease resistance. In this study, the full-length complementary DNA (cDNA) of hsp70 from planarian Polycelis sp. was first cloned using rapid amplification of cDNA ends (RACE). The expression levels of Pyhsp70 were analyzed in the presence of various stressors by real-time PCR, and its temporal-spatial expression patterns were also examined in both intact and regenerative animals by whole-mount in situ hybridization. The results show that (1) the deduced amino acid sequence of Pyhsp70 includes three typical HSP70 family signature motifs and is highly conserved during evolution; (2) Pyhsp70 expression is induced by prolonged starvation, tissue damage, and ionic liquid but inhibited by high or low temperatures; and (3) Pyhsp70 mRNA is mainly expressed in the head peripheral region and in the regenerating blastema during regeneration. These results suggest that the highly expressed Pyhsp70 gene may contribute to enhance cytoprotection and tolerance against stress-induced molecular damage, and the migration of neoblasts to the wound, which might also be involved in the proliferation and differentiation of neoblasts. Our work provides basic data for the study of stress responses and regenerative mechanism in freshwater planarians.

The Cardioprotective Effect of Vitamin E (Alpha-Tocopherol) Is Strongly Related to Age and Gender in Mice

Vitamin E (VitE) only prevented cardiovascular diseases in some patients and the mechanisms remain unknown. VitE levels can be affected by aging and gender. We hypothesize that age and gender can influence VitE’s cardioprotective effect. Mice were divided into 4 groups according to age and gender, and each group of mice were divided into a control group and a VitE group. The mice were administered water or VitE for 21 days; Afterward, the cardiac function and myocardial infarct size and cardiomyocyte apoptosis were measured after myocardial ischemia reperfusion(MI/R). VitE may significantly improved cardiac function in young male mice and aged female mice by enhancing ERK1/2 activity and reducing JNK activity. Enhanced expression of HSP90 and Bcl-2 were also seen in young male mice. No changes in cardiac function and cardiac proteins were detected in aged male mice and VitE was even liked to exert a reverse effect in cardiac function in young mice by enhancing JNK activity and reducing Bcl-2 expression. Those effects were in accordance with the changes of myocardial infarction size and cardiomyocyte apoptosis in each group of mice. VitE may reduce MI/R injury by inhibiting cardiomyocyte apoptosis in young male mice and aged female mice but not in aged male mice. VitE was possibly harmful for young female mice, shown as increased cardiomyocyte apoptosis after MI/R. Thus, we speculated that the efficacy of VitE in cardiac protection was associated with age and gender.

Inhibitors of eicosanoid biosynthesis influencing the transcripts level of sHSP21.4 gene induced by pathogen infections, in Antheraea pernyi

Small heat shock proteins (sHSPs) can regulate protein folding and protect cells from stress. To investigate the role of sHSPs in the silk-producing insect Antheraea pernyi response to microorganisms, a sHsp gene termed as Ap-sHSP21.4, was identified. This gene encoded a 21.4 kDa protein which shares the conserved structure of insect sHsps and belongs to sHSP21.4 family. Ap-sHSP21.4 was highly expressed in fat body and up-regulated in midgut and fat body of A. pernyi challenged with Escherichia coli, Beauveria bassiana and nuclear polyhedrosis virus (NPV), which was determined by quantitative real-time PCR. Meanwhile, knock down of Ap-sHSP21.4 with dsRNA result in the decrease at the expression levels of several immune response-related genes (defensin, Dopa decarboxylase, Toll1, lysozyme and Kazal-type serine protease inhibitor). Additionally, the impact of eicosanoid biosynthesis on the expression of Ap-sHSP21.4 response to NPV was determined using qPCR, inhibitors of eicosanoid biosynthesis significantly suppress Ap-HSP21.4 expression upon NPV challenge. All together, Ap-sHSP21.4 was involved in the immunity of A. pernyi against microorganism and possibly mediated by eicosanoids pathway. These results will shed light in the understanding of the pathogen-host interaction in A. pernyi.

Joint inhibition of TOR and JNK pathways interacts to extend the lifespan of Brachionus manjavacas (Rotifera)

The TOR kinase pathway is central in modulating aging in a variety of animal models. The target of rapamycin (TOR) integrates a complex network of signals from growth conditions, nutrient availability, energy status, and physiological stresses and matches an organism's growth rate to the resource environment. Important remaining problems are the identification of the pathways that interact with TOR and their characterization as additive or synergistic. One of the most versatile stress sensors in metazoans is the Jun-N-terminal kinase (JNK) signaling pathway. JNK is an evolutionarily conserved stress-activated protein kinase that is induced by a range of stressors, including UV irradiation, reactive oxygen species, DNA damage, heat, and bacterial antigens. JNK is thought to interact with the TOR pathway, but its effects on TOR are poorly understood. We used the rotifer Brachionus manjavacas as a model animal to probe the regulation of TOR and JNK pathways and explore their interaction. The effect of various chemical inhibitors was examined in life table and stressor challenge experiments. A survey of 12 inhibitors revealed two, rapamycin and JNK inhibitor, that significantly extended lifespan of B. manjavacas. At 1 μM concentration, exposure to rapamycin or JNK inhibitor extended mean rotifer lifespan by 35% and maximum lifespan by 37%. Exposure to both rapamycin and JNK inhibitor simultaneously extended mean rotifer lifespan by 65% more than either alone. Exposure to a combination of rapamycin and JNK inhibitors conveyed greater protection to starvation, UV and osmotic stress than either inhibitor alone. RNAi knockdown of TOR and JNK gene expression was investigated for its ability to extend rotifer lifespan. RNAi knockdown of the TOR gene resulted in 29% extension of the mean lifespan compared to control and knockdown of the JNK gene resulted in 51% mean lifespan extension. In addition to the lifespan, we quantified mitochondria activity using the fluorescent marker MitoTracker and lysosome activity using LysoTracker. Treatment of rotifers with JNK inhibitor enhanced mitochondria activity nearly 3-fold, whereas rapamycin treatment had no significant effect. Treatment of rotifers with rapamycin or JNK inhibitor reduced lysosome activity in 1, 3 and 8 day old animals, but treatment with both inhibitors did not produce any additive effect. We conclude that inhibition of TOR and JNK pathways significantly extends the lifespan of B. manjavacas. These pathways interact so that inhibition of both simultaneously acts additively to extend rotifer lifespan more than the inhibition of either alone.