Effects of Single and Joint Subacute Exposure of Copper and Cadmium on Heat Shock Proteins in Common Carp (Cyprinus carpio)

Molecular mechanism of selenium against lead-induced apoptosis in chicken brainstem relating to heat shock protein, selenoproteins, and inflammatory cytokines

Extensive application of lead (Pb) brought about environmental pollution and toxic reactions of organisms. Selenium (Se) has the effect of antagonizing Pb poisoning in humans and animals. However, it is still unclear how Pb causes brainstem toxicity. In the present study, we wanted to investigate whether Se can alleviate Pb toxicity in chicken brainstems by reducing apoptosis. One hundred and eighty chickens were randomly divided into four groups, namely the control group, the Se group, the Pb group, and the Se/Pb group. Morphological examination, ultrastructural observation, relative mRNA expressions of genes on heat shock proteins (HSPs); selenoproteins; inflammatory cytokines; and apoptosis-related factors were investigated. The results showed that Pb exposure led to tissue damage and apoptosis in chicken brainstems. Furthermore, an atypical expression of HSPs (HSP27, HSP40, HSP60, HSP70, and HSP90); selenoprotein family glutathione peroxidase (GPx) 1, GPx2, GPx3, and GPx4), thioredoxin reductases (Txnrd) (Txnrd1, Txnrd2, and Txnrd3), dio selenoprotein famliy (diodothyronine deiodinases (Dio)1, Dio2, and Dio3), as well as other selenoproteins (selenoprotein (Sel)T, SelK, SelS, SelH, SelM, SelU, SelI, SelO, Selpb, selenoprotein n1 (Sepn1), Sepp1, Sepx1, Sepw1, 15-kDa selenoprotein (Sep15), and selenophosphate synthetases 2 (SPS2)); inflammatory cytokines (Interleukin 2 (IL-2), IL-4, IL-6, IL-12β, IL-17, and Interferon-γ (IFN-γ)); and apoptosis-related genes (B-cell lymphoma-2 (Bcl-2), tumor protein 53 (p53), Bcl-2 Associated X (Bax), Cytochrome c (Cyt c), and Caspase-3) were identified. An inflammatory reaction and apoptosis were induced in chicken brainstems after exposure to Pb. Se alleviated the abnormal expression of HSPs, selenoproteins, inflammatory cytokines, and apoptosis in brainstem tissues of chickens treated with Pb. The results indicated that HSPs, selenoproteins, inflammatory, and apoptosis were involved in Se-resisted Pb poisoning. Overall, Se had resistance effect against Pb poisoning, and can be act as an antidote for Pb poisoning in animals.

Toxic Effects of Cadmium on Fish

Large amounts of enriched cadmium (Cd) in the environment seriously threatens the healthy and sustainable development of the aquaculture industry and greatly restricts the development of the food processing industry. Studying the distribution and toxic effects of Cd in fish, as well as the possible toxic effects of Cd on the human body, is very significant. A large number of studies have shown that the accumulation and distribution of Cd in fish are biologically specific, cause tissue differences, and seriously damage the integrity of tissue structure and function, the antioxidant defense system, the reproductive regulation system, and the immune system. The physiological, biochemical, enzyme, molecular, and gene expression levels change with different concentrations and times of Cd exposure, and these changes are closely related to the target sites of Cd action and tissues in fish. Therefore, the toxic effects of Cd on fish occur with multiple tissues, systems, and levels.

Effects of Copper Exposure on Oxidative Stress, Apoptosis, Endoplasmic Reticulum Stress, Autophagy and Immune Response in Different Tissues of Chinese Mitten Crab (Eriocheir sinensis)

High concentrations of copper (Cu²⁺) pose a great threat to aquatic animals. However, the mechanisms underlying the response of crustaceans to Cu²⁺ exposure have not been well studied. Therefore, we investigated the alterations of physiological and molecular parameters in Chinese mitten crab (Eriocheir sinensis) after Cu²⁺ exposure. The crabs were exposed to 0 (control), 0.04, 0.18, and 0.70 mg/L of Cu²⁺ for 5 days, and the hemolymph, hepatopancreas, gills, and muscle were sampled. The results showed that Cu²⁺ exposure decreased the antioxidative capacity and promoted lipid peroxidation in different tissues. Apoptosis was induced by Cu²⁺ exposure, and this activation was associated with the mitochondrial and ERK pathways in the hepatopancreas. ER stress-related genes were upregulated in the hepatopancreas but downregulated in the gills at higher doses of Cu²⁺. Autophagy was considerably influenced by Cu²⁺ exposure, as evidenced by the upregulation of autophagy-related genes in the hepatopancreas and gills. Cu²⁺ exposure also caused an immune response in different tissues, especially the hepatopancreas, where the TLR2-MyD88-NF-κB pathway was initiated to mediate the inflammatory response. Overall, our results suggest that Cu²⁺ exposure induces oxidative stress, ER stress, apoptosis, autophagy, and immune response in E. sinensis, and the toxicity may be implicated following the activation of the ERK, AMPK, and TLR2-MyD88-NF-κB pathways.

Effects of cadmium on antioxidant and non-specific immunity of Macrobrachium nipponense

As a non-essential and toxic element, cadmium poses an important threat to aquatic organisms and human food safety. In this study, the effects of cadmium on antioxidant and non-specific immunity of Macrobrachium nipponense were studied from the physiological and biochemical indexes, histology and expression of related genes. These results showed that low concentrations (0.01, 0.02 mg/L) of cadmium have a positive effect on the non-specific immunity of M. nipponense, but high concentration (0.04 mg/L) of cadmium could inhibit or even damage the non-specific immunity of M. nipponense. The cadmium could induce oxidative stress in M. nipponense, and M. nipponense actived the antioxidant defense system to deal with oxidative stress, but high concentration (0.04 mg/L) of cadmium could inhibit the antioxidant defense system of M. nipponense, leading to oxidative damage, and may induce apoptosis in severe case. At the same time, the results of histology showed that cadmium can damage the structure of gill and hepatopancreas tissues of M. nipponense. This study provides theoretical data for evaluating the influences of heavy metal cadmium on M. nipponense and the toxic mechanism of heavy metal cadmium.

Identification of co-chaperone Cdc37 in Penaeus monodon: coordination with Hsp90 can reduce cadmium stress-induced lipid peroxidation

Cell division cycle 37 (Cdc37) is an important cytoplasmic phosphoprotein, which usually functions as a complex with heat shock protein 90 (Hsp90), to effectively reduce the damage caused by heavy metals, such as cadmium (Cd), in aquatic animals. The high toxicity of Cd in aquatic systems generally has a deleterious effect on healthy farming of shrimps. In the present study, a novel Cdc37 gene from Penaeus monodon was identified and designated as PmCdc37. Following exposure to Cd stress, the expression levels of PmCdc37 were upregulated at the transcriptional level in both the hepatopancreas and hemolymph. RNA interference and recombinant protein injection experiments were carried out to determine the function of PmCdc37 in P. monodon following Cd exposure. To clarify the correlations between PmCdc37 and PmHsp90, the respective recombinant proteins were expressed in vitro, and the ATPase activity of PmHsp90, with or without PmCdc37, was assessed. Moreover, a pull-down assay was conducted to detect the correlation between PmCdc37 and PmHsp90. After analyzing the expression patterns of PmHsp90 following Cd challenge, whether PmHsp90 can promote the ability of PmCdc37 to resist Cd stress or not was investigated. The results showed that formation of a PmHsp90/PmCdc37 complex protected shrimp against Cd stress-induced damage. Moreover, we also confirmed that PmSOD is involved in Cd stress, and that the PmHsp90/PmCdc37 complex can regulate SOD enzymatic activity. PmSOD was involved in decreasing the MDA content in shrimp hemolymph caused by Cd stress. We concluded that during exposure to Cd, the PmHsp90/PmCdc37 complex increases SOD enzyme activity, and in turn decreases the MDA content, thereby protecting shrimp against the damage caused by Cd stress. The present studies contribute to understanding the molecular mechanism underlying resistance to Cd stress in shrimp.

Chronic exposure to environmental cadmium affects growth and survival, cellular stress, and glucose metabolism in juvenile channel catfish (Ictalurus punctatus)

Anthropogenic activities have led to the enrichment of cadmium in freshwater systems where it is a contaminant of concern for fisheries and aquaculture as it has no known biological function and is toxic at trace concentrations. Yet, knowledge gaps remain regarding effects of chronic exposure to environmentally relevant concentrations on freshwater fish. Thus, the objectives of the current study were to assess chronic impacts of cadmium on channel catfish (Ictalurus punctatus) including how tissue-specific bioaccumulation patterns relate to functions of those tissues over time. We focused on liver and kidneys, and expression of genes related to cellular stress, glucose metabolism, and steroidogenesis. Catfish were exposed to concentrations of 0.5 (control), 2 (low), and 6 (high) μg L^-1 Cd from fertilization to six months. Cadmium exposure negatively impacted channel catfish growth and was linked to bioaccumulation of tissue Cd, which followed a dose-related response, where concentrations in trunk kidney > liver = head kidney >> muscle. Differences in tissue Ca, Cu, Fe, and Zn concentrations were also observed between treatments. Following 3 months of exposure, expression of metallothionein (MT) and heat shock proteins (HSP) 70 & 90 increased relative to controls; however, no differences were detected at 6 months, suggesting compensation. Conversely, there were no differences in expression patterns for key genes in steroidogenesis, steroidogenic factor 1 (SF1), steroidogenic acute regulatory protein (StAR), and cytochrome P450scc (P450), which supports the observation that Cd did not affect the secondary stress response, evaluated via plasma cortisol and glucose concentrations following a low water stress event. As a function of length and weight, the high Cd treatment yielded fish that were significantly smaller than controls. In addition to the cellular responses in MT and HSPs noted, reduced growth in the high Cd treatment was likely due, at least in part, to elevated energetic demands. This is supported by observations of the upregulation of genes necessary for glucose metabolism. Hexokinase (HK), glucose-6-phosphatase (G6P), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were significantly elevated in the high treatment relative to controls at 3 months of exposure. Over the study period, exposure also reduced survival of channel catfish from 3 to 6 months. Reduced fitness, as a consequence of cadmium exposure, could be visible at the population level through altered life histories and growth patterns.

The protective effects of melatonin on survival, immune response, digestive enzymes activities and intestinal microbiota diversity in Chinese mitten crab (Eriocheir sinensis) exposed to glyphosate

Glyphosate is one of the most widely used pesticides, which can cause toxicity to aquatic animals. In this study, the survival rate, immune response, digestive enzyme activities, and the intestinal microbiota diversity of Chinese mitten crab (Eriocheir sinensis) were evaluated after 14 days of exposure to glyphosate (48.945 mg/L from 50% 96 h LC50 value) and melatonin feeding (80 mg/kg). The results showed that MT significantly improved the survival rate, antibacterial capacity of E. sinensis (P < 0.05). After exposure to glyphosate, the expression of Hsp60, Hsp70 and Hsp90 in cranial ganglia and thoracic ganglia was decreased significantly, but MT significantly raised the expression of these proteins (P < 0.05). Glyphosate significantly decreased lipase activity compared with the control group (P < 0.05), while melatonin significantly increased the lipase, amylase and trypsin activities (P < 0.05). Melatonin significantly increased the Chao1 and Shannon index and the relative abundance of Proteobacteria and Bacteroidetes (P < 0.05). This study shows that melatonin has a protective effect on the glyphosate exposed E. sinensis.

Effects of imidacloprid on the oxidative stress, detoxification and gut microbiota of Chinese mitten crab, Eriocheir sinensis

Imidacloprid (IMI) is used in integrated aquaculture systems for pest control and the toxicity of IMI to non-target aquatic animals such as fish and microcrustaceans has been recognised. However, knowledge about the toxic effect of IMI on commercial crabs is still scarce. In the present study, effects of IMI on the acute toxicity, antioxidative status, detoxification systems and gut microbiota in Chinese mitten crab, Erocheir sinensis were investigated. In the present study, the 96-h LC₅₀ of IMI for E. sinensis was 24.97 mg/L. Under sublethal exposure, superoxide dismutase (SOD) activities increased under low concentration (LC, 5 μg/L) and median concentration (MC, 50 μg/L) exposure, but decreased in high concentration group (HC, 500 μg/L). Activities of catalyse (CAT) decreased in a dose-dependent manner. Detoxification-related enzymes aminopyrine N-demethylase (APND) and erythromycin N-demethylase (ERND) increased in all treatments whereas glutathione-S-transferase (GST) decreased dose-dependently. The relative mRNA expression of the cytochrome P4502 (cyp2) gene was induced significantly in LC and HC groups while no significant change was observed in cytochrome P4503 (cyp3) gene. The expression of gst was also significantly decreased in HC group. Up-regulation of heat shock protein hsp70 and 90 was observed in MC and HC groups whereas hsp60 up-regulated only in LC group. In addition, significant changes of composition of microbial communities at both phylum and genus levels were found in this test. In particular, beneficial bacteria were found to decrease and pathogens increased after exposure to IMI. These results indicate that high concentration of IMI could induce oxidative stress and suppress the detoxification system mainly by down-regulation of gst mRNA expression, inhibition of enzyme activities and dysbiosis of gut microbiota.

Oxidative stress, immunological response, and heat shock proteins induction in the Chinese Mitten Crab, Eriocheir sinensis following avermectin exposure

In this study, the Chinese mitten crabs, Eriocheir sinensis were exposed to avermectin at 0.03, 0.06, 0.12, 0.24, and 0.48 mg/L respectively for 96 hours. The results showed that levels of superoxide dismutase, catalase, and glutathione peroxidase in hepatopancreas were slightly induced at concentration of 0.03 and 0.06 mg/L, but significantly (P < .05) decreased at higher concentrations, meanwhile similar trend of the activities of acid phosphatase, alkaline phosphatase and lysozyme were observed. Significant induction of HSP70 and HSP90 mRNA expression was detected at 24 hours whereas no significant change was found in HSP60. In addition, levels of reactive oxygen species in hepatocytes increased in dose- and time- dependent manners, and cell viabilities of hepatocytes and haemocytes decreased. These results indicated that sublethal concentration exposure of avermectin had a prominent oxidative stress effect on E. sinensis based on the antioxidative and immunological activity inhibition, and HSP60, 70, and 90 perform a protective response during the exposure.

Reference gene selection for quantitative gene expression analysis in black soldier fly (Hermetia illucens)

Hermetia illucens is an important resource insect for the conversion of organic waste. Quantitative PCR (qPCR) is the primary tool of gene expression analysis and a core technology of molecular biology research. Reference genes are essential for qPCR analysis; however, a stability analysis of H. illucens reference genes has not yet been carried out. To find suitable reference genes for normalizing gene expression data, the stability of eight housekeeping genes (including ATP6V1A, RPL8, EF1, Tubulin, TBP, GAPDH, Actin and RP49) was investigated under both biotic (developmental stages, tissues and sex) and abiotic (heavy metals, food, antibiotics) conditions. Gene expression data were analysed by geNorm, NormFinder, BestKeeper, and ΔCt programs. A set of specific reference genes was recommended for each experimental condition using the results of RefFinder synthesis analysis. This study offers a solid foundation for further studies of the molecular biology of H. illucens.

Effect of Bacillus cereus against cadmium induced hematological disturbances and immunosuppression in Carassius auratus gibelio

Cadmium (Cd) is the most common heavy metal and is easily detected in aquatic environments worldwide. The genus Bacillus was one of dominant probiotics, which was commonly used in aquaculture. The present study was undertaken to explore the effects of Bacillus cereus (B. cereus) supplementation on hematological parameters and the immune response of Carassius auratus gibelio (C. gibelio) following Cd exposure. Fish were exposed to waterborne Cd (0, 1 and 2 mg/L) and/or treated with dietary B. cereus at 10⁸ cfu/g for four weeks. The hematological disturbances observed after exposure of waterborne Cd included significant decreases in red blood cell (RBC) count, hemoglobin (Hb) concentration and hematocrit (HCT). While significant elevation (P < 0.05) of RBC count, HCT and Hb levels in the 1 and 2 mg/L Cd-B. cereus administration group at 4 weeks, compared with the Cd-only group. Among serum enzymatic activities, aspartate aminotransferase (AST) and alanine transaminase (ALT) activities by Cd exposure were significantly higher than controls, but this increase was effectively inhibited in Cd-B. cereus administration groups. In the Cd-B. cereus administration group, significant down-regulation of Hsp70, Hsp90, IL-1β, IL-6, IL-10 and TNF-α in conjunction with the up-regulation of IgM and LZM in the spleen indicated that B. cereus alleviated the Cd-induced damage to the immune system to some degree. The results of this study suggested that B. cereus has the potential to countermeasure Cd-induced hematological disturbances and immunosuppression in C. gibelio.

Effects of deltamethrin on the antioxidant defense and heat shock protein expression in Chinese mitten crab, Eriocheir sinensis

In the present study, the status of antioxidant response and molecular regulation in Chinese mitten crab, Eriocheir sinensis under the exposure of synthetic pyrethroid deltamethrin were investigated by means of measuring the antioxidative enzyme activity and relative mRNA expression of heat shock proteins (HSPs) in hepatopancreas. The results showed that activity of superoxide dismutase (SOD) and catalase (CAT) decreased remarkably in all treatments except the SOD activity at concentration of 0.073 μg/L. The oxidative stress products malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) increased significantly at high concentrations while no significant difference was observed at concentrations of 0.073 and 0.146 μg/L throughout the experiment. Meanwhile, the relative mRNA expression of HSP 60, HSP 70 and HSP 90 was significantly up-regulated in all treatments at each time point. All resutls above indicated that deltamethrin has prominent toxic effect on E. sinensis based on antioxidative enzyme inhibition and oxidative products accumulation at environmental related concentrations, and a protective response by up-regulation of HSPs was carried out by animals to mitigate the oxidative stress. In addition, SOD, CAT, MDA, H₂O₂ and the expression of heat shock proteins, especially HSP 70 in hepatopancreas could be sensitive biomarkers in the assessment of toxic effect of deltamethrin on E.sinensis.

Exposure to environmentally relevant cadmium concentrations negatively impacts early life stages of channel catfish (Ictalurus punctatus)

Cadmium is a persistent contaminant of surface waters. The effects of cadmium on early life stages of fish are not well understood, although they are often disproportionately affected by contaminants. The objectives of this study were to examine effects of chronic exposure to environmentally relevant concentrations on growth, development, cellular stress, and glucose metabolism of channel catfish, Ictalurus punctatus. Eggs were wet-fertilized in treatment water at concentrations of 0.4 (control), 2.2 (low), or 8.5 (high) μg L^-1 and monitored through swim-up, black fry stage. Eggs and fry accumulated cadmium dose-dependently. Fertilization rates were unaffected, yet hatch rate was significantly reduced in the high treatment. Survival to black fry and overall size and condition factor were not affected; however, differences in yolk sac size, and presumably energetics of yolk fry, was detected. Physiological pathways were also affected, demonstrated by altered gene expression, most notably in genes related to carbohydrate metabolism. Elevated expression of HK and G6PD, rather than G6P and GADPH, suggests glucose may be shunted towards the pentose-phosphate pathway. Overall, observations indicate cadmium negatively affects development in early life stages of channel catfish, which could lead to shifts in population structure and life history patterns in exposed populations of wild fish.

The protective effect exerted by dietary borax on toxicity metabolism in rainbow trout (Oncorhynchus mykiss) tissues

The aim of this study was to evaluate the effectiveness of borax (BX) against heavy metal exposure on the transcriptional and biochemical reaction in vivo and alleviating effect on gill and liver tissues of rainbow trout. Due to this aim, fish were fed with different level of BX and/or copper (Cu) (1.25, 2.5 and 5 mg/kg of BX; 500 and 1000 mg/kg of Cu) for 21·days in pre- and co-treatment options. The transcriptional parameters [(heat-shock protein 70 (hsp70), and cytochromes P450 (cyp1a), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT))], antioxidant enzyme activities (SOD, CAT and GPx), malondialdehyde (MDA), oxidative DNA damage (8-hydroxy-2'-deoxyguanosine (8-OHdG) and caspase-3 levels were investigated in different tissues samples of treated and control fish. Our results revealed that antioxidant enzyme activity was increased and levels of 8-OHdG, Caspase-3 and MDA were decreased in the BX and BX combined groups as compared to the copper combination group and to copper-only application during pre- and co-treatment (p < 0.05). Similarly, hsp70 and cyp1a gene expressions were decreased after treatment with BX. As conclusion, we suggest that borax itself is not an antioxidant it supportes antioxidant defense mechanism of fish disrupted by heavy metals.

Mytilus galloprovincialis (Lamarck, 1819) spermatozoa: hsp70 expression and protamine-like protein property studies

In this work, we describe results of the reproductive health monitoring studies in Mytilus galloprovincialis following spermatozoa hsp70 expression and protamine-like protein properties. Mussels control (ctr) were released within cages for 30 days in three different marine sites near Naples (Campania, Italy): Bagnoli south (BAs) and Bagnoli north (BAn), both close to a disposal metallurgical factory and in Capo Miseno (CM). Studies of hsp70 gene expression carried out, by RT-qPCR, in mussel spermatozoa have shown varied expression levels, particularly 5, 13, and 15-fold more than ctr in CM, BAs, and BAn, respectively, indicating highest involvement of stress proteins in spermatozoa of mussels in Bagnoli. In order to evaluate the possible risk on Mytilus galloprovincialis sustainability loss, electrophoretic analyses were performed on protamine-like proteins (PL) of collected spermatozoa. The results showed that CM PL were apparently unaltered with respect to ctr PL, while BAs and BAn PL appeared in part in the form of peptides and in part as bands with low mobility. Further, CM and BAs PL showed, by electrophoretic mobility shift assay, a decrease in DNA binding ability and a change in their DNA binding mode. The results of this investigation show the usefulness of the study of alterations of spermatozoa hsp70 expression and protamine-like protein properties for eco-toxicological evaluation using Mytilus galloprovincialis as a bioindicator.

Effect of cadmium on oxidative stress and immune function of common carp (Cyprinus carpio L.) by transcriptome analysis

Cadmium (Cd) is an increasingly important environmental pollutant which causes irreversible toxicity to fish. To understand how Cd impacts the immune response and oxidative stress in common carp, we performed transcriptomic profiles for head kidney, the immune organ of common carp which were underwent Cd exposure. Totally there are 42,489,124 and 48,562,526 high quality clean reads obtained from the Cd exposure groups, and 44,677,578 and 44,106,696 clean reads from the control groups. Among them, 308 genes were differently expressed, including 101 upregulated and 207 down-regulated genes. The identified genes were enriched using databases of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Antioxidant systems and immune function genes and pathways were identified and validated by quantitative real-time RT-PCR. Our results showed that Cd exposure leads to oxidative stress and immunosuppression in head kidney of common carp. These results provide new insights for unveiling the biological effects of Cd in common carp.

Copper or/and arsenic induce oxidative stress-cascaded, nuclear factor kappa B-dependent inflammation and immune imbalance, trigging heat shock response in the kidney of chicken

Excessive amount of copper (Cu) and inorganic arsenic (iAs) coexists in drinking water in many regions, this is associated with high risk of nephropathy, defined as chronic structural and functional disorders of the kidney. However, the underlying mechanisms are not well understood. In this study, a total of 72 day-old Hy-line chickens were exposed to 300 mg/kg copper sulphate or/and 30 mg/kg arsenic trioxide for 12 weeks. Indicators of oxidative stress, inflammation and heat shock proteins (HSPs) production were analyzed in kidney. The results showed that, when the toxicant was administrated alone, there is an antagonism between redox homeostasis during the first 4 weeks, which follows a collapse of antioxidant system manifested by damaged biomembrane structure. What's worse, oxidative damage-cascaded histopathological lesions were accompanied by increases of proinflammatory mediators and an imbalance of "Th1/Th2 drift" (Th, helper T cell) regulated by nuclear factor kappa B (NF-κB). Simultaneously, intense heat shock response went with the organism. The above-mentioned renal lesions and indicators changes were time-dependent, more complex and deteriorated effects were observed in Cu/iAs combined groups compared with the others. This study supports Cu and iAs have a synergistic type on the nephro-toxicological process additively. In conclusion, oxidative stress and inflammatory induced by Cu or/and iAs are potential mechanisms in their nephrotoxicity, increased heat shock response may play a renoprotection function in tissues damage.

Transcriptome Profiling Analysis of Wolf Spider Pardosa pseudoannulata (Araneae: Lycosidae) after Cadmium Exposure

Pardosa pseudoannulata is one of the most common wandering spiders in agricultural fields and a potentially good bioindicator for heavy metal contamination. However, little is known about the mechanisms by which spiders respond to heavy metals at the molecular level. In the present study, high-throughput transcriptome sequencing was employed to characterize the de novo transcriptome of the spiders and to identify differentially expressed genes (DEGs) after cadmium exposure. We obtained 60,489 assembled unigenes, 18,773 of which were annotated in the public databases. A total of 2939 and 2491 DEGs were detected between the libraries of two Cd-treated groups and the control. Functional enrichment analysis revealed that metabolism processes and digestive system function were predominately enriched in response to Cd stress. At the cellular and molecular levels, significantly enriched pathways in lysosomes and phagosomes as well as replication, recombination and repair demonstrated that oxidative damage resulted from Cd exposure. Based on the selected DEGs, certain critical genes involved in defence and detoxification were analysed. These results may elucidate the molecular mechanisms underlying spiders' responses to heavy metal stress.