Comparative transcriptome analysis reveals the different roles between hepatopancreas and intestine of Litopenaeus vannamei in immune response to aflatoxin B1 (AFB1) challenge

Chromatin accessibility and transcriptional landscape in PK-15 cells during early exposure to Aflatoxin B1

Aflatoxin B1 (AFB1) not only causes significant losses in livestock production but also poses a serious threat to human health. It is the most carcinogenic among known chemicals. Pigs are more susceptible to AFB1 and experience a higher incidence. However, the molecular mechanism of the toxic effect of AFB1 remains unclear. In this study, we used assay for transposase-accessible chromatin using sequencing (ATAC-seq) and RNA-seq to uncover chromatin accessibility and gene expression dynamics in PK-15 cells during early exposure to AFB1. We observed that the toxic effects of AFB1 involve signaling pathways such as p53, PI3K-AKT, Hippo, MAPK, TLRs, apoptosis, autophagy, and cancer pathways. Basic leucine zipper (bZIP) transcription factors (TFs), including AP-1, Fos, JunB, and Fra2, play a crucial role in regulating the biological processes involved in AFB1 challenge. Several new TFs, such as BORIS, HNF1b, Atf1, and KNRNPH2, represent potential targets for the toxic mechanism of AFB1. In addition, it is crucial to focus on the concentration of intracellular zinc ions. These findings will contribute to a better understanding of the mechanisms underlying AFB1-induced nephrotoxicity and offer new molecular targets.

Cellular and transcriptomic response to pathogenic and non-pathogenic Vibrio parahaemolyticus strains causing acute hepatopancreatic necrosis disease (AHPND) in Litopenaeus vannamei

The shrimp industry has historically been affected by viral and bacterial diseases. One of the most recent emerging diseases is Acute Hepatopancreatic Necrosis Disease (AHPND), which causes severe mortality. Despite its significance to sanitation and economics, little is known about the molecular response of shrimp to this disease. Here, we present the cellular and transcriptomic responses of Litopenaeus vannamei exposed to two Vibrio parahaemolyticus strains for 98 h, wherein one is non-pathogenic (VpN) and the other causes AHPND (VpP). Exposure to the VpN strain resulted in minor alterations in hepatopancreas morphology, including reductions in the size of R and B cells and detachments of small epithelial cells from 72 h onwards. On the other hand, exposure to the VpP strain is characterized by acute detachment of epithelial cells from the hepatopancreatic tubules and infiltration of hemocytes in the inter-tubular spaces. At the end of exposure, RNA-Seq analysis revealed functional enrichment in biological processes, such as the toll3 receptor signaling pathway, apoptotic processes, and production of molecular mediators involved in the inflammatory response of shrimp exposed to VpN treatment. The biological processes identified in the VpP treatment include superoxide anion metabolism, innate immune response, antimicrobial humoral response, and toll3 receptor signaling pathway. Furthermore, KEGG enrichment analysis revealed metabolic pathways associated with survival, cell adhesion, and reactive oxygen species, among others, for shrimp exposed to VpP. Our study proves the differential immune responses to two strains of V. parahaemolyticus, one pathogenic and the other nonpathogenic, enlarges our knowledge on the evolution of AHPND in L. vannamei, and uncovers unique perspectives on establishing genomic resources that may function as a groundwork for detecting probable molecular markers linked to the immune system in shrimp.

Bimetallic nanozyme-bioenzyme hybrid material-mediated ultrasensitive and automatic immunoassay for the detection of aflatoxin B1 in food

Aflatoxin B1 (AFB1) is one of the most prevalent and dangerous biotoxin in crops and feedstuff, which poses a great threat to human health and also cause significant financial losses. Therefore, there is an urgent need to develop an effective method for AFB1 detection. In this work, we developed an automatic reaction equipment and nanozyme-enhanced immunosorbent assay (Auto-NEISA) for sensitive and accurate detection of AFB1 by combining the highly effective signal probes with a self-designed automated immunoreactive equipment. Wherein, polystyrene (PS) nanoparticles were used as signal carriers for loading a massive in situ-synthesized platinum and palladium bimetallic nanozyme, which could enrich horseradish peroxidase-labeled goat anti-mouse antibody (HRP-Ab2) on the nanozyme surface to form a bimetallic nanozyme-bioenzyme hybrid material for multiple signal amplification. The entire reaction could be automatically completed by the self-developed immunoreactive equipment. The Auto-NEISA method realized the sensitive detection of AFB1 with a wide linear detection range of 10-104 pg/mL, at a low limit of detection (LOD) of 5.52 pg/mL. The LOD was 65-fold lower than that of the enzyme-linked immunosorbent assay (ELISA). Additionally, Auto-NEISA was successfully applied to detect AFB1 in real food samples, demonstrating that it has considerable potential for detecting food contaminants with high accuracy and efficiency.

The Dynamics of Gene Expression Unraveling the Immune Response of Macrobrachium rosenbergii Infected by Aeromonas veronii

To further investigate the immune response of Macrobrachium rosenbergii against Aeromonas veronii, comparative transcriptomic analyses of the M. rosenbergii hepatopancreas were conducted on challenge and control groups at 6, 12, and 24 h post-infection (hpi), independently. A total of 51,707 high-quality unigenes were collected from the RNA-seq data, and 8060 differentially expressed genes (DEGs) were discovered through paired comparisons. Among the three comparison groups, a KEGG pathway enrichment analysis showed that 173 immune-related DEGs were considerably clustered into 28 immune-related pathways, including the lysosome, the phagosome, etc. Moreover, the expression levels of the four key immune-related genes (TOLL, PAK1, GSK3β, and IKKα) were evaluated at various stages following post-infection in the hepatopancreas, hemolymph, and gills. Both PAK1 and GSK3β genes were highly up-regulated in all three tissues at 6 hpi with A. veronii; TOLL was up-regulated in the hepatopancreas and hemolymph but down-regulated in the gill at 6 hpi, and IKKα was up-regulated in hemolymph and gill, but down-regulated in the hepatopancreas at 6 hpi. These findings lay the groundwork for understanding the immune mechanism of M. rosenbergii after contracting A. veronii.

Integrated microRNA-mRNA analysis reveals a possible molecular mechanism of enteritis susceptibility in Litopenaeus vannamei

Enteritis is one of the main diseases affecting Pacific whiteleg shrimp (Litopenaeus vannamei) in recent years, and it has resulted in huge losses to the aquaculture industry. Prior to this study, the molecular mechanism underlying enteritis in L. vannamei was unclear, and comprehensive multi-omics analysis had not been conducted. In this study, 1209 differentially expressed genes (DEGs) were identified from the hepatopancreas of L. vannamei with and without enteritis. Kyoto Encyclopedia of Genes and Genomes analysis showed that genes were significantly enriched in immune, metabolic, and endocrine regulatory pathways. Forty-eight significantly different microRNAs (miRNAs) were identified in the miRNA-Seq analysis. Further functional annotation analysis showed that the regulatory pathway of target gene enrichment of differentially expressed miRNAs was consistent with DEGs. Through miRNA-mRNA integration analysis, 47 meaningful miRNA-mRNA pairs were obtained, of which melanogenesis and pancreatic secretion were considered key pathways. Subsequent miRNA-mRNA interaction network analysis revealed that mja-miR-6493-3p, Mja-miR-6494, novel-198, novel-272, novel-261, novel-200, novel-183, novel-184, novel-237, and novel-192 may be key miRNAs involved in the regulation of these two signaling pathways. Finally, the RAS signaling pathway was found to inhibit the translation level of proteins in the hepatopancreas. These results suggest that target gene integration analysis of mRNA-miRNA can reveal the molecular mechanism underlying enteritis in L. vannamei and also provide valuable new insights for resisting enteritis.

Effects of Compound Mycotoxin Detoxifier on Alleviating Aflatoxin B1-Induced Inflammatory Responses in Intestine, Liver and Kidney of Broilers

In order to alleviate the toxic effects of aflatoxins B1 (AFB1) on inflammatory responses in the intestine, liver, and kidney of broilers, the aflatoxin B1-degrading enzyme, montmorillonite, and compound probiotics were selected and combined to make a triple-action compound mycotoxin detoxifier (CMD). The feeding experiment was divided into two stages. In the early feeding stage (1−21 day), a total of 200 one-day-old Ross broilers were randomly divided into four groups; in the later feeding stage (22−42 day), 160 broilers aged at 22 days were assigned to four groups: Group A: basal diet (4.31 μg/kg AFB1); Group B: basal diet with 40 μg/kg AFB1; Group C: Group A plus 1.5 g/kg CMD; Group D: Group B plus 1.5 g/kg CMD. After the feeding experiment, the intestine, liver, and kidney tissues of the broilers were selected to investigate the molecular mechanism for CMD to alleviate the tissue damages. Analyses of mRNA abundances and western blotting (WB) of inflammatory factors, as well as immunohistochemical (IHC) staining of intestine, liver, and kidney tissues showed that AFB1 aggravated the inflammatory responses through NF-κB and TN-α signaling pathways via TLR pattern receptors, while the addition of CMD significantly inhibited the inflammatory responses. Phylogenetic investigation showed that AFB1 significantly increased interleukin-1 receptor-associated kinase (IRAK-1) and mitogen-activated protein kinase (MAPK) activities (p < 0.05), which were restored to normal levels by CMD addition, indicating that CMD could alleviate cell inflammatory damages induced by AFB1.

A Glutathione Peroxidase Gene from Litopenaeus vannamei Is Involved in Oxidative Stress Responses and Pathogen Infection Resistance

In shrimp, several glutathione peroxidase (GPX) genes have been cloned and functionally studied. Increasing evidence suggests the genes’ involvement in white spot syndrome virus (WSSV)- or Vibrio alginolyticus-infection resistance. In the present study, a novel GXP gene (LvGPX3) was cloned in Litopenaeus vannamei. Promoter of LvGPX3 was activated by NF-E2-related factor 2. Further study showed that LvGPX3 expression was evidently accelerated by oxidative stress or WSSV or V. alginolyticus infection. Consistently, downregulated expression of LvGPX3 increased the cumulative mortality of WSSV- or V. alginolyticus-infected shrimp. Similar results occurred in shrimp suffering from oxidative stress. Moreover, LvGPX3 was important for enhancing Antimicrobial peptide (AMP) gene expression in S2 cells with lipopolysaccharide treatment. Further, knockdown of LvGPX3 expression significantly suppressed expression of AMPs, such as Penaeidins 2a, Penaeidins 3a and anti-lipopolysaccharide factor 1 in shrimp. AMPs have been proven to be engaged in shrimp WSSV- or V. alginolyticus-infection resistance; it was inferred that LvGPX3 might enhance shrimp immune response under immune challenges, such as increasing expression of AMPs. The regulation mechanism remains to be further studied.

A IFI27 gene contributes to ER-stress mediated apoptosis and benefits for white spot syndrome virus infection in Litopenaeus vannamei

The interplay between virus and host has been one of the hot spot in virology, and it is also the important aspect of revealing the mechanism of virus infection. Increasing studies revealed that several key molecules took part in the process of virus-host interaction. White spot syndrome virus (WSSV) has been proved to affect several physiological processes of the host cells, especially apoptosis. While the relationship between them still remains unclear. In this study, a IFI27 gene (LvIFI27) of Litopenaeus vannamei was cloned. It is indicated that LvIFI27 was induced upon endoplasmic reticulum (ER)-stress and unfolded protein response activator Thapsigargin. Unlike human IFI27 locating to mitochondria, LvIFI27 lied to ER, and was involved in cell apoptosis process. Moreover, results of cumulative mortality analysis showed that LvIFI27 might contributed to WSSV proliferation by promoting apoptosis during the process of viral infection. Findings in this study enriched our understanding of the relationship between WSSV infection and ER-stress mediated apoptosis.

Aflatoxin B1: metabolism, toxicology, and its involvement in oxidative stress and cancer development

Aflatoxins are a class of carcinogenic mycotoxins produced by Aspergillus fungi, which are widely distributed in nature. Aflatoxin B1 (AFB1) is the most toxic of these compounds and its metabolites have a variety of biological activities, including acute toxicity, teratogenicity, mutagenicity and carcinogenicity, which has been well-characterized to lead to the development of hepatocellular carcinoma (HCC) in humans and animals. This review focuses on the metabolism of AFB1, including epoxidation and DNA adduction, as it concerns the initiation of cancer and the underlying mechanisms. In addition to DNA adduction, inflammation and oxidative stress caused by AFB1 can also participate in the occurrence of cancer. Therefore, the main carcinogenic mechanism of AFB1 related ROS is summarized. This review also describes recent reports of AFB1 exposures in occupational settings. It is hoped that people will pay more attention to occupational health, in order to reduce the incidence of cancer caused by occupational exposure.

Integrated transcriptome analysis of immune-related mRNAs and microRNAs in Macrobrachium rosenbergii infected with Spiroplasma eriocheiris

Macrobrachium rosenbergii (M. rosenbergii), is a major aquaculture species in China and Southeast Asia. However, infection with Spiroplasma eriocheiris (S. eriocheiris) has caused huge economic losses to the cultivation of M. rosenbergii. Currently, there are few reports on the immune response mechanism of M. rosenbergii that are infected with S. eriocheiris. To clarify the immune response mechanism of M. rosenbergii infected with S. eriocheiris, the key immune genes which respond to the infection with the pathogen and the regulation of related microRNAs (miRNAs) on them were identified. In this study, the mRNA and miRNA transcriptome of hepatopancreas of M. rosenbergii at different infection stages were analyzed using high-throughput sequencing and qRT-PCR. In the mRNA transcriptome, 27,703 and 33,402 genes were expressed in healthy and susceptible M. rosenbergii, respectively. By digital gene-expression profiling analysis, 23,929 and 24,325 genes were expressed, and 223 and 373 genes were significantly up-regulated and down-regulated, respectively. A total of 145 key genes related to Toll, IMD, JAK/STAT and MAPK were excavated from the transcriptome. In the miRNA transcriptome, 549 miRNAs (Conserved: 41, PN-type: 83, PC-type: 425) were sequenced, of which 87 were significantly up-regulated and 23 were significantly down-regulated. Among the related immune pathways, there are 259 miRNAs involved in the regulation of target genes in the Toll and IMD pathways, 231 JAK/STAT pathways and 122 MAPK pathways. qRT-PCR differential detection of immune-related miRNAs and mRNAs showed that 22 miRNAs with significant differences (P < 0.05) such as mro-miR-100, PC-mro-3p-27 and PN-mro-miR-316 had corresponding regulatory relationships with 22 important immune genes such as TLR2, TLR3, TLR4, TLR5, MyD88, Pelle and Relish in different stages after infection. In this study, the immune genes and related regulatory miRNAs of M. rosenbergii in response to S. eriocheiris infection were obtained. The results can provide basic data to further reveal the immune defense mechanism of M. rosenbergii against S. eriocheiris infection.

Toxic Effects of Aflatoxin B1 in Chinese Sea Bass (Lateolabrax maculatus)

This study was performed to assess the effects of dietary aflatoxin B₁ (AFB₁) on the growth, antioxidant and immune response, digestive enzyme activities, and intestinal morphology of Lateolabrax maculatus during a 56-day feeding trial. Four diets were formulated including 0, 0.1, 0.5, and 1.0 mg/kg of AFB₁. Each diet was randomly assigned to 3 fish tanks with 40 fish per tank. Results indicated that the fish's final body weight, weight gain rate, specific growth rate, feed intake, condition factor, viscerosomatic index, hepatosomatic index, and intestinesomatic index decreased (p < 0.01) as dietary AFB₁ increased. AFB₁ levels in diets increased (p < 0.05) serum total antioxidant capacity (TAOC), superoxide (SOD), catalase, malondialdehyde (MDA), alkaline phosphatase (AKP), and lysozyme (LZM), and increased (p < 0.05) the TAOC, SOD, MDA, AKP, LZM, and immunoglobulin M in the livers of the fish. Dietary AFB₁ decreased (p < 0.05) intestinal trypsin activity and induced intestinal injury. In summary, dietary AFB₁ up to 1.0 mg/kg was toxic to L. maculatus as judged by reduced growth, enhanced antioxidant and immune response, decreased intestinal trypsin activity, and impaired intestinal morphology.

A new insight to characterize immunomodulation based on hepatopancreatic transcriptome and humoral immune factor analysis of the Cherax quadricarinatus infected with Aeromonas veronii

Cherax quadricarinatus is a type of large freshwater crayfish that is characterized by rapid growth and formidable adaptability. It has also been widely cultured and studied as a model organism. Aeromonas veronii is the dominant pathogen in aquatic environments and the primary threat to aquaculture's economic stability. To better understand the interactions between C. quadricarinatus and A. veronii, high-throughput RNA sequencing of the C. quadricarinatus hepatopancreas was carried out on a control group, susceptible group (6 h after infection), and resistant group (48 h after infection). A total of 65,850,929 genes were obtained. Compared with the control group, 2616 genes were up-regulated and 1551 genes were down-regulated in the susceptible group; while 1488 genes were up-regulated and 1712 genes were down-regulated in the resistant group. GO and KEGG analysis showed that these differentially expressed genes (DEGs) were associated with multiple immune pathways, including Toll-like receptors (TLRs), antigen processing and presentation, NOD-like receptor signaling pathway, phagosome, lysosome, JAK-STAT signaling pathway. qRT-PCR showed that infection by A. veronii changed the expression pattern of the serine proteinase inhibitor (SPI), crustacean hyperglycemic hormone (CHH), anti-lipopolysaccharide factor (ALF), and extracellular copper/zinc superoxide dismutase (SOD1), all of which were significantly higher than in the control group up to 48 h after infection. In addition, detection of superoxide dismutase (SOD), catalase (CAT), lysozyme (LZM), and phenoloxidase (PO) activity, as well as ceruloplasmin (CP) concentration at different times after infection showed diverse trends. Furthermore, pathological sections obtained 24 h after infection show lesions on the hepatopancreas and intestinal tissues caused by A. veronii. The results of this study provide a foundation for analyzing the immune mechanism of C. quadricarinatus infected with A. veronii at the transcriptional level and a theoretical basis for screening disease-resistant individuals to ensure healthy economic development of the aquatic industry.

Agricultural trichothecene mycotoxin contamination affects the life-history and reduced glutathione content of Folsomia candida Willem (Collembola)

There is limited data available concerning the effect of T-2/HT-2 toxin or deoxynivalenol (DON) on invertebrates such as springtails, and no data on their life history and oxidative stress. Control maize and DON or T-2 toxin contaminated maize were fed to Folsomia candida with a toxin content of 16324 mg DON kg–1 or 671 mg T-2 kg–1 maize. Ten to twelve days old animals were investigated in a life-history test and a stress protein test.T-2 toxin did not affect Folsomia candida in any measured parameters. The DON exposed group showed decreased growth and reproduction, and a higher survival rate. DON treatment resulted in lower protein content, while reduced glutathione content was higher than in control. It suggests that DON activated the glutathione-related detoxification pathway, which possibly causes a higher survival rate. The results also suggest that the oral toxicity of DON or T-2 is lower than through physical contact.For that reason, DON and T-2 toxin contaminated maize is not suggested to be used as green manure in the native state. Alternative solutions could be using mycotoxin contaminated maize for biogas production, or after decontamination by bacterial strains, it can be used as organic fertilizer.

The Compromised Intestinal Barrier Induced by Mycotoxins

Mycotoxins are fungal metabolites that occur in human foods and animal feeds, potentially threatening human and animal health. The intestine is considered as the first barrier against these external contaminants, and it consists of interconnected physical, chemical, immunological, and microbial barriers. In this context, based on in vitro, ex vivo, and in vivo models, we summarize the literature for compromised intestinal barrier issues caused by various mycotoxins, and we reviewed events related to disrupted intestinal integrity (physical barrier), thinned mucus layer (chemical barrier), imbalanced inflammatory factors (immunological barrier), and dysfunctional bacterial homeostasis (microbial barrier). We also provide important information on deoxynivalenol, a leading mycotoxin implicated in intestinal dysfunction, and other adverse intestinal effects induced by other mycotoxins, including aflatoxins and ochratoxin A. In addition, intestinal perturbations caused by mycotoxins may also contribute to the development of mycotoxicosis, including human chronic intestinal inflammatory diseases. Therefore, we provide a clear understanding of compromised intestinal barrier induced by mycotoxins, with a view to potentially develop innovative strategies to prevent and treat mycotoxicosis. In addition, because of increased combinatorial interactions between mycotoxins, we explore the interactive effects of multiple mycotoxins in this review.

Transcriptome analysis and immune-related genes expression reveals the immune responses of Macrobrachium rosenbergii infected by Enterobacter cloacae

Macrobrachium rosenbergii is an important cultural species in China and other Southeast Asian countries. However, Enterobacter cloacae infection has caused a great economic loss in M. rosenbergii culture industry. The immune responses of M. rosenbergii to the E. cloacae infection is not fully characterized. To investigate the immune response of M. rosenbergii against E. cloacae, we performed transcriptome analysis of the M. rosenbergii hepatopancreas with and without E. cloacae infection using RNA-seq. After assembly and annotation, 29,731 high quality unigenes were obtained from RNA-seq data. Differential expression analysis revealed the existence of 2498 significantly differently expressed genes (DEGs) at 12 h post infection, with 1365 up-regulated and 1133 down-regulated genes. Among these DEGs, some well-known immune-related genes were up-regulated significantly, including C-type lectin 1, lectin 3, anti-lipopolysaccharide factor 2, Cu/Zn superoxide dismutase and heat shock protein 70. GO analysis demonstrated 24 biological process subcategories, 14 cellular component subcategories, and 12 molecular function subcategories that were enriched among these DEGs, and some DEGs were clustered into immune related subcategories such as immune system process, response to stimulus, biological adhesion, and antioxidant activity. These DEGs were enriched into 216 KEGG pathways including a core set of immune correlated pathways notably in phagosome and lysosome. In addition, 5 up-regulated and 5 down-regulated immune-related DEGs were selected for further validation by quantitative real-time PCR and the results showed consistence with the RNA-seq data. Additionally, the expression level of six selected immune-related genes (ALF2, CLEC1, LEC3, hemocyanin1, HSP70 and SOD) based on the transcriptomic data were monitored at different point of time in hepatopancreas, gill, hemolymph and intestine. Results revealed these immune-related genes were significantly up-regulated in different tissues from 6 to 24 h after E. cloacae infection. Overall, these results provided valuable information for further studying the immune response of M. rosenbergii against E. cloacae infection.

T-2 toxin in the diet suppresses growth and induces immunotoxicity in juvenile Chinese mitten crab (Eriocheir sinensis)

The T-2 toxin is a trichothecene mycotoxin and is highly toxic to aquatic animals, but little is known on its toxic effect in crustaceans. In the present study, the crab juveniles were fed with diets containing four levels of T-2 toxin: 0 (control), 0.6 (T1), 2.5 (T2) and 5.0 (T3) mg/kg diet for 56 days to evaluate its impact on the juvenile of Chinese mitten crab (Eriocheir sinensis). The crabs fed the T-2 toxin diets had significantly lower weight gain and specific growth rate than those fed the control diet. Moreover, crab survival in T3 group was obviously lower than that in the control. Oxidative stress occurred in all the treatment groups as indicated by higher activities of total superoxide dismutase, glutathione peroxidase, and total antioxidant capacity than those in the control. The total hemocyte count, respiratory burst, phenoloxidase in the hemolymph, and phenoloxidase, acid phosphatase and alkaline phosphatase in the hepatopancreas of crabs fed T-2 toxin were significantly lower than those in the control. The transcriptional expressions of lipopolysaccharide-induced TNF-alpha factor, relish, and the apoptosis genes in the hepatopancreas were induced by dietary T-2 toxin. The genes related to detoxication including cytochrome P450 gene superfamily and glutathione S transferase were induced in low concentration, then decreased in high concentration. Dietary T-2 toxin damaged the hepatopancreas structure, especially as seen in the detached basal membrane of hepatopancreatic tubules. This study indicates that dietary T-2 toxin can reduce growth performance, deteriorate health status and cause hepatopancreas dysfunction in crabs.