Caspase-mediated apoptosis in crustaceans: cloning and functional characterization of EsCaspase-3-like protein from Eriocheir

Ginger polysaccharide promotes myeloid-derived suppressor cell apoptosis by regulating lipid metabolism

Recently, targeting myeloid-derived suppressor cells (MDSCs) which mainly play an immunosuppressive role in tumor microenvironment has become a hot spot in tumor immunotherapy. This study focuses on biological effect of ginger polysaccharide extracted from natural plants on promoting apoptosis of MDSCs by regulating lipid metabolism. An MTT assay was used to detect the inhibitory effect of ginger polysaccharide on the growth of an MDSC-like cell line (MSC-2). The apoptosis-promoting effect of ginger polysaccharide on MSC-2 cells was detected by flow cytometry. Expression levels of apoptosis proteins (caspase 9 and Bcl-2) and lipid metabolism enzymes (fatty acid synthase (FASN) and diacylglycerol acyltransferase 2) in MSC-2 cells treated with different concentrations of ginger polysaccharide were detected by western blot assay. Nile red staining was used to quantitatively detect the effect of ginger polysaccharide on lipid droplet synthesis. Ginger polysaccharide inhibited proliferation of MSC-2 cells and promoted their apoptosis by upregulating pro-apoptotic caspase 9 protein, downregulating anti-apoptotic Bcl-2 protein, inhibiting expression of FASN and diacylglycerol acyltransferase 2 (key enzymes in fatty acid synthesis and lipid droplet formation, respectively). Ginger polysaccharide promoted apoptosis of MDSCs by regulating key lipid metabolism enzymes, inhibiting fatty acid synthesis and lipid droplet accumulation, and reducing the energy supply of cells.

Pathogenicity of Plesiomonas shigelloides causing mass mortalities of largemouth bass (Micropterus salmoides) and its induced host immune response

The outbreak of mass mortality of M. salmoides occurred in an aquaculture farm in Jiangsu province of China, showing signs of skin ulceration and haemorrhages. The bacteria were isolated from diseased largemouth bass, and identified as Plesiomonas shigelloides based on morphological, physiological and biochemical features, as well as 16S rRNA gene sequence analysis. The pathogenicity of P. shigelloides was determined by challenge experiments, and the median lethal dosage (LD₅₀) of the isolate NJS1 for M. salmoides was calculated as 1.6 × 10⁵ CFU/mL at 7 d post-infection. Histopathological analysis revealed that extensive necrosis, vacuolization and inflammation were presented in the kidney, liver and gill of the diseased fish. Detection of virulence-related genes showed that P. shigelloides NJS1 was positive for astA, astB, astD, astE, actP and 6 ahpA. Additionally, the host defensive response of M. salmoides infected by P. shigelloides was analyzed by quantitive real-time PCR (qRT-PCR), and the results showed that the expression levels of Cas3, Hep1, HIF, IgM, IL15 and TGF were significantly up-regulated in head kidney, liver and spleen in different hours post-infection, which revealed varying expression profiles and clear transcriptional activation of immune related genes. The results suggested that P. shigelloides was an etiological element in the mass mortalities of M. salmoides and this study provided deeper insights for the pathogenesis and host defensive system in P. shigelloides invasion.

Integrinβ1/FAK/ERK signalling pathway is essential for Chinese mitten crab Eriocheir sinensis hemocyte survival

Integrins are cellular adhesion molecules that mediate cell-cell, cell-extracellular matrix, and cell-pathogen interactions. Integrins can stimulate various signaling pathways by binding to different ligands, thereby exerting immunological functions. While integrins have been found to primarily play a role in bacterial agglutination, phagocytosis, and inhibition of apoptosis in invertebrates, the specific signaling pathway and mechanism of action remain unclear. In vertebrates, β1 integrin and extracellular matrix interactions can associate with focal adhesion kinase (FAK) to initiate MAPK/ERK signaling and regulate cell survival; however, in invertebrates (e.g., Chinese mitten crab), the mechanisms of integrins are poorly understood. The purpose of this study was to investigate whether integrinβ1/FAK activation of the MAPK/ERK pathway regulates hemocyte survival and the associated mechanism. Treatment with an integrinβ1 inhibitor RGD (a conserved tripeptide Arg-Gly-Asp), decreased the levels of FAK and ERK expression and phosphorylation, followed by an intensification of apoptosis. Similar results were obtained following siRNA knockdown of integrinβ1 expression. We further found that the attenuation of ERK phosphorylation enhanced the level of Caspase-3 expression. Together, these findings suggest that integrinβ1 activates the FAK/ERK signaling cascade and is involved in the survival of Chinese mitten crab hemocytes.

Comparative transcriptomic analysis revealed dynamic changes of distinct classes of genes during development of the Manila clam (Ruditapes philippinarum)

Background

The Manila clam Ruditapesphilippinarum is one of the most economically important marine shellfish. However, the molecular mechanisms of early development in Manila clams are largely unknown. In this study, we collected samples from 13 stages of early development in Manila clam and compared the mRNA expression pattern between samples by RNA-seq techniques.

Results

We applied RNA-seq technology to 13 embryonic and larval stages of the Manila clam to identify critical genes and pathways involved in their development and biological characteristics. Important genes associated with different morphologies during the early fertilized egg, cell division, cell differentiation, hatching, and metamorphosis stages were identified. We detected the highest number of differentially expressed genes in the comparison of the pediveliger and single pipe juvenile stages, which is a time when biological characteristics greatly change during metamorphosis. Gene Ontology (GO) enrichment analysis showed that expression levels of microtubule protein-related molecules and Rho genes were upregulated and that GO terms such as ribosome, translation, and organelle were enriched in the early development stages of the Manila clam. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the foxo, wnt, and transforming growth factor-beta pathways were significantly enriched during early development. These results provide insights into the molecular mechanisms at work during different periods of early development of Manila clams.

Conclusion

These transcriptomic data provide clues to the molecular mechanisms underlying the development of Manila clam larvae. These results will help to improve Manila clam reproduction and development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08813-0.

Effect of infection with Aeromonas hydrophila on antioxidant capacity, inflammation response, and apoptosis proteins in Chinese mitten crab (Eriocheir sinensis)

Aeromonas hydrophila (A. hydrophila) as a serious bacterial disease endangering aquaculture and the Chinese mitten crabs (Eriocheir sinensis) industry. The present study was conducted to investigate the effects of A. hydrophila on the antioxidant, inflammation, immunity and apoptosis of the E. sinensis. The E. sinensis (female: 150 crabs and male: 150 crabs; 67.11 ± 0.76 g) were randomly divided into the control group (Foot injection with 200 μl PBS) and infection group (Foot injection with 200 μl A. hydrophila of 10⁶ cfu/mL). The hepatopancreas and serum was collected to detect the related indicators after injection 24 h. The results showed that A. hydrophila significantly reduced the malondialdehyde (MDA) level and gamma-glutamyl-cysteine synthetase (γ-GCS) activity in the hepatopancreas of male and female crabs (P < 0.05). A.hydrophila also significantly decreased the total-superoxide dismutase (T-SOD) activity while the levels of total antioxidant capacity (T-AOC) and total glutathione (T-GSH) were significantly increased in the hepatopancreas and serum of male crabs (P < 0.05). At the transcriptional level, the expression of catalase (CAT) and glutathione peroxidases (GPx), Glutathione S-transferase (GST) in the hepatopancreas of male and female crabs was significantly reduced compared to the control group (P < 0.05). However, A. hydrophila could not significantly change the Kelch-like ECH-associated protein 1 (Keap1) gene expression level in both of male and female carbs. A. hydrophila injection for 24 h, the lysozyme (LZM) and phenoloxidase (PO) activity was significantly increased in the hepatopancreas and serum of the male and female crabs (P < 0.05). Simultaneous increase of immune-related enzyme activity (acid phosphatase and alkaline phosphatase) was found in the serum of male and female crabs (P < 0.05). However, the acid phosphatase (ACP) and alkaline phosphatase (ALP) activity was significantly decreased in the hepatopancreas of male and female crabs (P < 0.05). Meanwhile, the LZM mRNA level was significantly decreased in the hepatopancreas of E. sinensis (P < 0.05). Furthermore, A. hydrophila significantly inhibited the mRNA expression of immune regulated factors (Interleukin enhancer binding factor 2: ILF2, interleukin-16: IL-16, Toll-like receptor: TLR) in the male and female crabs. The levels of inflammatory cytokines (interleukin-1β: IL-1β, interleukin-6: IL-6, interleukin-8: IL-8, interleukin-10: IL-10) were significantly increased in the hepatopancreas of male and female crabs. Moreover, A.hydrophila increased the mRNA expression of apoptosis - related genes in male crabs (p38 mitogen-activated protein kinase: p38, adamalysin 17: ADAM17, Cysteine-aspartic acid protease 3: Caspase 3, and Bcl-2-associated X: BAX), but reduced the expression of p38, ADAM17, Caspase 3 and BAX genes in female crabs. In conclusion, A. hydrophila could induce oxidative stress and the response of inflammation and immunity, and also trigger the mRNA expression changes of apoptosis related-genes in E. sinensis. This study provides a theoretical basis for the study of E. sinensis diseases.

The Eriocheir sinensis calcium/calmodulin-dependent protein kinase II activates apoptosis to resist Spiroplasma eriocheiris infection

Calcium/calmodulin-dependent protein kinase II is a downstream mediator of calcium signalling and participates in the regulation of various cellular physiological functions. In previous studies, the expression of Eriocheir sinensis CaMKII (EsCaMKII) was significantly decreased in the thoracic ganglion after Spiroplasma eriocheiris infection, as shown using TMT-based quantitative proteomic analysis; however, the specific functions of EsCaMKII are still unclear. In this study, the full-length cDNA of EsCaMKII was 3314 bp long, consisting of a 1605 bp open reading frame encoding a protein of 535 amino acids, including a 258 aa serine/threonine protein kinase catalytic domain (EsCaMKII-CD). EsCaMKII is highly transcribed in haemocytes, nerves (thoracic ganglion), gills, and muscles, but lowly transcribed in the hepatopancreas, heart, and intestines. The transcription levels of EsCaMKII were altered in E. sinensis haemocytes after S. eriocheiris infection. After the over-expression of EsCaMKII-CD in RAW264.7 cells, the apoptosis rate of RAW264.7 cells was significantly increased. After the over-expression of EsCaMKII-CD, the morphology of RAW264.7 cells became worse after being infected with S. eriocheiris. Meanwhile, the copy number of S. eriocheiris in RAW264.7 cells was significantly decreased. From 48 h to 96 h after EsCaMKII RNA interference, the transcription levels of EsCaMKII decreased significantly. The transcription of apoptosis genes and cell apoptosis were also inhibited in haemocytes after EsCaMKII RNAi. The knockdown of EsCaMKII by RNAi resulted in significant increases in the copy number of S. eriocheiris and in the mortality of crabs during S. eriocheiris infection. These results indicate that EsCaMKII could promote the apoptosis of E. sinensis and enhance its ability to resist S. eriocheiris infection.

The role of caspase 3 in the mud crab (Scylla paramamosain) after Vibrio parahaemolyticus infection

Apoptosis plays essential roles in the immune defense mechanism against pathogen infection. Caspase 3 is a family of cysteine proteases involved in apoptosis and the immune response. In this study, the full-length of mud crab (Scylla paramamosain) caspase 3 (designated as Sp-caspase 3) was cloned and characterized. The open reading frame of Sp-caspase 3 was comprised a 1035 bp, which encoded a putative protein of 344 amino acids. Sp-caspase 3 was ubiquitously expressed in various tissues with a high-level expression in hemocytes. Cellular localization analysis revealed that Sp-caspase 3 was located in the cytoplasm and nucleus. Over-expression of Sp-caspase 3 could induce cell apoptosis. In addition, V. Parahaemolyticus infection induced the relative expression of caspase-3 mRNA and increased caspase-3 activity. Knocking down Sp-caspase 3 in vivo significantly reduced cell apoptosis and increased mortality of mud crab after V. parahaemolyticus infection. These results indicated that Sp-caspase 3 played important roles in the immune response and apoptosis against bacterial infection.

Expression levels of caspase-3 and gasdermin E and their involvement in the occurrence and prognosis of lung cancer

Background

Pyroptosis plays a dual role in the development of cancer and malignancy; as such, it may potentially be a new target for cancer treatment. However, the inflammatory response to pyroptosis may have adverse effects on the body. The roles of gasdermin E (GSDME), caspases, and related proteins associated with pyroptosis in cancer remain controversial.

Aim

The goal of this study was to determine whether the expression levels of caspase‐3 and GSDME affect the clinical stage, pathological grade, or survival prognosis of patients with lung cancer.

Methods

We examined the protein levels of GSDME, caspase‐3, caspase‐8, and caspase‐9 in lung tissue samples from 100 patients with lung cancer by using immunohistochemistry.

Results

We found that GSDME, caspase‐3, and caspase‐8 were more highly expressed in tumor tissues than in adjacent normal tissues. Moreover, we found that GSDME could serve as a prognostic factor as there was a positive correlation between its expression level and the postoperative survival rate of patients with lung cancer.

Conclusions

GSDME may be an independent factor affecting the prognosis of patients with lung cancer. However, the role of GSDME and its related proteins in cancer requires further research.

Carboplatin and epigallocatechin-3-gallate synergistically induce cytotoxic effects in esophageal cancer cells

Background and purpose:

We aimed at evaluating the effects of combinatorial treatments with carboplatin and epigallocatechin-3-gallate (EGCG) on the KYSE-30 esophageal cancer (EC) cell line and elucidate the underlying mechanisms.

Experimental approach:

EC cells were harvested and exposed to increasing concentrations of carboplatin and EGCG to construct a dose-response plot. Cell inhibitory effects were assessed by the MTT method and apoptosis-related gene expression levels (caspases 8 and 9) and Bcl-2 mRNA were detected using real-time polymerase chain reaction. The lactate levels in the various treated cases were analyzed using the colorimetric assay kit. In addition, total antioxidant capacity was measured.

Findings/Results:

The results indicated that, following treatments with carboplatin in IC₂₀, IC₂₅, and IC₁₀ concentrations when combined with EGCG in similar concentrations, synergistically decreased cell viability versus single treatments of both agents. Also, in combined treatments at IC₂₀ and IC₂₅ of both agents the gene expression ratio of caspases 8 and 9 upregulated significantly compared to monotherapies (P < 0.05). Bcl-2 gene expression ratios were decreased in double agents treated cells versus monotherapies. Following treatment of KYSE-30 cells with carboplatin and EGCG in double combinations, lactate levels were significantly decreased compared with the untreated cells and single treatments (P < 0.05). Also, in IC₂₅, IC₂₀, and IC₁₀ concentrations of both agents the total antioxidant capacity levels were decreased versus monotherapies and untreated cells.

Conclusion and implications:

The presented study determined that treatment with carboplatin and EGCG was capable of promoting cytotoxicity in EC cells and inhibits the cancer progress. Combined treatments with low concentrations of carboplatin and EGCG may promote apoptosis induction and inhibit cell growth. These results confirmed the anticancer effects of carboplatin and EGCG and providing a base for additional use of EGCG to the EC treatment.

The TSPO Ligands MGV-1 and 2-Cl-MGV-1 Differentially Inhibit the Cigarette Smoke-Induced Cytotoxicity to H1299 Lung Cancer Cells

Simple Summary

In this study, we investigated the impact of CS on various TSPO-related mitochondrial processes, and the protective ability of our novel TSPO ligands against such CS-induced cellular damages. Our results support the previously reported role of TSPO in apoptotic cell death. Moreover, the present data demonstrate the protective effect of our TSPO ligands against CS-induced cellular damage.

Abstract

TSPO is involved in cigarette smoke (CS)-induced cellular toxicity, which may result in oral and pulmonary diseases and lung cancer. H1299 lung cancer cells were exposed directly to CS. The H1299 cells were pretreated with our TSPO ligands MGV-1 and 2-Cl-MGV-1 (Ki = 825 nM for both) at a concentration of 25 µM 24 h prior to CS exposure. Cell death and apoptotic markers were measured, in addition to TSPO expression levels, ATP synthase activity, generation of reactive oxygen species (ROS), depolarization of mitochondrial membrane potential (ΔΨm), cAMP and LDH levels. Pretreatment with MGV-1 and 2-Cl-MGV-1 (25 µM), 24 h prior to CS exposure, differentially attenuated the CS-induced cellular insult as well as cell death in H1299 lung cancer cells. These protective effects included prevention of ATP synthase reversal, ROS generation, depolarization of the mitochondrial membrane and elevation in LDH. The preventive efficacy of 2-Cl-MGV-1 was superior to that achieved by MGV-1. Both ligands did not prevent the elevation in cAMP. These findings may indicate a mild protective effect of these TSPO ligands in CS-related pulmonary and keratinocyte cellular pathology.

Acceleration of α-synuclein fibril formation and associated cytotoxicity stimulated by silica nanoparticles as a model of neurodegenerative diseases

A wide range of biophysical and theoretical analysis were employed to explore the formation of (α-syn) amyloid fibril formation as a model of Parkinson's disease in the presence of silica oxide nanoparticles (SiO₂ NPs). Also, different cellular and molecular assays such as MTT, LDH, caspase, ROS, and qPCR were performed to reveal the α-syn amyloid fibrils-associated cytotoxicity against SH-SY5Y cells. Fluorescence measurements showed that SiO₂ NPs accelerate the α-syn aggregation and exposure of hydrophobic moieties. Congo red absorbance, circular dichroism (CD), and transmission electron microscopy (TEM) analysis depicted the SiO₂ NPs accelerated the formation of α-syn amyloid fibrils. Molecular docking study showed that SiO₂ clusters preferably bind to the N-terminal of α-syn as the helix folding site. We also realized that SiO₂ NPs increase the cytotoxicity of α-syn amyloid fibrils through a significant decrease in cell viability, increase in membrane leakage, activation of caspase-9 and -3, elevation of ROS, and increase in the ratio of Bax/Bcl2 mRNA. The cellular assay indicated that α-syn amyloid fibrils formed in the presence of SiO₂ NPs induce their cytotoxic effects through the mitochondrial-mediated intrinsic apoptosis pathway. We concluded that these data may reveal some adverse effects of NPs on the progression of Parkinson's disease.

An effector caspase Sp-caspase first identified in mud crab Scylla paramamosain exhibiting immune response and cell apoptosis

Apoptosis plays a key role in the immune defense against pathogen infection, and caspase is one of the most important protease enzyme families, which could initiate and execute apoptosis. Among crustaceans, several caspase genes have been reported. However, caspase in mud crab Scylla paramamosain, have not been identified yet. Here, in the present study, we characterized a new caspase, named as Sp-caspase, from S. paramamosain. The full-length cDNA sequence of Sp-caspase contained 966 bp open reading frame, encoding 322 amino acids, and its molecular weight was 36 kDa. This gene has three conserved domains of the caspase family, a prodomain, a large subunit P20 and a small subunit P10. Phylogenetic analysis showed that Sp-caspase was clustered into an effector caspase group. Sp-caspase mainly distributed in midgut, hepatopancreas, hemocytes and female ovaries, and the transcript was significantly regulated in different tissues after being challenged with Vibrio parahaemolyticus, Vibrio alginolyticus or LPS. After infection with V. alginolyticus, the apoptosis rate of hemocytes notably increased, while the mRNA level of Sp-caspase and hydrolysis activity of caspase 3/7 significantly decreased. Furthermore, in vitro assays showed that the recombinant protein tSp-caspase (deletion of Sp-caspase prodomain) could efficiently recognize and cleave human caspase 3/7 substrate Ac-DEVD-pNA, functioning as an effector caspase. Meanwhile, heterologous expression of Sp-caspase in several cell lines (HEK293T cells, HeLa cells and HighFive cells) could specifically induce cell apoptosis. Taken together, these data demonstrated that Sp-caspase could perform apoptosis as an effector caspase. In addition, it might be a negative regulator of hemocytes apoptosis under pathogen infection, which would contribute to homeostasis and immune defense of hemocytes in S. paramamosain.

Polyphenolic Composition and Anti-Melanoma Activity of White Forsythia (Abeliophyllum distichum Nakai) Organ Extracts

Abeliophyllum distichum Nakai, commonly called white forsythia, is a monotypic genus endemic to Korea. Although A. distichum is mainly used as an ornamental plant because of its horticultural value, recent studies have demonstrated its bioactivities, including antioxidant and anti-inflammatory activities, prompting us to investigate the potential anticancer effect of A. distichum organ extracts (leaves, fruit, and branches) against human melanoma SK-MEL-2 cells. The methanol extract of A. distichum leaves (AL) exhibited dose- and time-dependent cytotoxicities against SK-MEL-2 cells but not against HDFa human dermal fibroblasts. Based on high-performance liquid chromatography analysis, we identified 18 polyphenolic compounds from A. distichum organ extracts and suggest that differences in anticancer activity between organ extracts should be caused by different compositions of polyphenolic compounds. Additionally, the Annexin V/propidium iodide staining assay and analysis of caspase activity and expression indicated that AL induced cell death, including early and late apoptosis, as well as necrosis, by inducing the extrinsic pathway. Furthermore, we analyzed the differentially expressed genes between mock- and AL-treated cells using RNA-seq technology, suggesting that the anti-melanoma action of AL is mediated by down-regulation of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. Taken together, these results shed light on the potential use of A. distichum as a green resource with potent anti-melanoma activity.

Characterization and functional analysis of a caspase 3 gene: Evidence that ChCas 3 participates in the regulation of apoptosis in Crassostrea hongkongensis

Caspase 3 plays an important role in apoptotic pathways and contributes to maintaining the homeostasis of the immune system in organisms. The structure, functions, and characteristics of caspase 3 have been extensively investigated in many species, but the research is scarce when it comes to bivalves, particularly oysters. In this study, we identified and cloned a previously unknown caspase 3 gene, named ChCas 3, in C. hongkongensis. The full-length cDNA of ChCas 3 was 1562 bp and included a 175 bp 5'-untranslated region (UTR), a 141 bp 3'-UTR and a 1245 bp open reading frame (ORF) that encoded a polypeptide of 415 amino acids. Similar to caspase 3 in other species, ChCas 3 has a pro-domain, a conserved cysteine active site, a large p20 subunit and a small p10 subunit. Our findings demonstrated the expression of ChCas 3 in all the eight tissues via tissue-specific expression assays with the highest expression in haemocytes. ChCas 3 was confirmed to be expressed throughout the larval development stages, and fluorescence from pEGFP-N1-ChCas 3 was found to be distributed throughout the entire HEK293T cell. In addition, the relative expression of ChCas 3 significantly enhanced in hemocytes post bacterial stimulation, and overexpression of ChCas 3 led to upregulation of the transcriptional activity of NF-κB and p53 reporter genes in HEK293T cells, which indicated that it was involved in innate immune responses. Finally, the apoptosis rate of the haemocytes declined considerably compared with that of the control group after the expression of ChCas 3 was successfully silenced by dsRNA, corroborating its sentinel role in apoptosis. This study provides comprehensive underpinning evidences, affirming caspase 3 crucial role against bacterial infection and apoptosis in C. hongkongensis.

In vitro effects of PNP and PNMC on apoptosis and proliferation in the hen ovarian stroma and prehierarchal follicles

This study aimed to examine the mRNA expression, activity, and immunolocalisation of apoptosis/proliferation regulating factors following in vitro exposure of the stroma, white (WFs), and yellowish (YFs) follicles of the chicken ovary to 4-nitrophenol (PNP) or 3-methyl-4-nitrophenol (PNMC). PNMC increased the mRNA expression of caspase-3, -8, Apaf-1, and cytochrome c in the ovarian stroma. The activity of caspase-3, -8, and -9 decreased in WFs in both nitrophenol-treated groups. PNP reduced the number of caspase-3-positive cells in the stromal connective tissue (CT) and the theca interna and externa layers of WFs. In the stroma, the proliferating index decreased in the wall of primary follicles in both nitrophenol-treated groups, however, in the CT, the effect of PNMC was opposite. In the theca interna of WFs, PNP diminished the proliferating index. These results suggest that nitrophenols might impact the development of chicken ovarian follicles by affecting cell death and proliferation.

An inhibitor of apoptosis protein (EsIAP1) from Chinese mitten crab Eriocheir sinensis regulates apoptosis through inhibiting the activity of EsCaspase-3/7-1

Inhibitor of apoptosis proteins (IAPs) maintain the balance between cell proliferation and cell death by inhibiting caspase activities and mediating immune responses. In the present study, a homolog of IAP (designated as EsIAP1) was identified from Chinese mitten crab Eriocheir sinensis. EsIAP1 consisted of 451 amino acids containing two baculoviral IAP repeat (BIR) domains with the conserved Cx2 Cx6 Wx3 Dx5 Hx6 C motifs. EsIAP1 mRNA was expressed in various tissues and its expression level in hemocytes increased significantly (p < 0.01) at 12–48 h after lipopolysaccharide stimulation. In the hemocytes, EsIAP1 protein was mainly distributed in the cytoplasm. The hydrolytic activity of recombinant EsCaspase-3/7-1 against the substrate Ac-DEVD-pNA decreased after incubation with rEsIAP1. Moreover, rEsIAP1 could directly combine with rEsCaspase-3/7-1 in vitro. After EsIAP1 was interfered by dsRNA, the mRNA expression and the hydrolytic activity of EsCaspase-3/7-1 increased significantly, which was 2.26-fold (p < 0.05) and 1.71-fold (p < 0.05) compared to that in the dsGFP group, respectively. These results collectively demonstrated that EsIAP1 might play an important role in apoptosis pathway by regulating the activity of EsCaspase-3/7-1 in E. sinensis.

Caspase-3C gene from red swamp crayfish, Procambarus clarki: Characterization and expression in response to pathogenic infection

The caspase is an essential module in the Drosophila immune deficiency (IMD) pathway, which plays a crucial role in countering pathogen infection. In this study, a gene named PcCaspase-3C was found in Procambarus clarkia with a full-length of 4684 bp, including a 1572 bp opening reading frame, which encoded a putative protein of 523 amino acids. PcCaspase-3C contained a CASc domain constituted of 237 amino acids. The PcCaspase-3C gene was primarily expressed in heart, stomach, and intestine, while less in gonad, hepatopancreas, gills, and hemocytes, with the least expression in muscle. Infection with Staphyloccocus aureus, Vibrio parahaemolyticus or white spot syndrome virus (WSSV) induced an up-regulated expression of PcCaspase-3C in intestine or stomach to varying degrees. When PcCaspase-3C was silenced by double-stranded RNA, the expression of some antimicrobial peptides such as ALF2, ALF5, ALF6, Cru3, Cru4, and Lys was significantly inhibited. In addition, silencing of PcCaspase-3C accelerated infection with WSSV in vivo. According to these results, we suggest that PcCaspase-3C might play a crucial role in the immune response of P. clarkia against pathogenic bacterial and viral infections.

Cinnamaldehyde causes apoptosis of myeloid-derived suppressor cells through the activation of TLR4

Malignant tumors are among the most life-threatening diseases in the world. Although many different types of antitumor agents are available, severe side effects and toxicity limit their applications. Myeloid-derived suppressor cells (MDSCs) inhibit the antitumor immune response by suppressing the proliferation of T cells, the production of cytokines and the killing of tumor cells. As MDSCs have become novel targets in cancer therapy, this research focused on the anti-MDSC function of cinnamaldehyde (CA), which is extracted from cinnamon, a traditional Chinese spice. In the present study, MDSCs isolated from the spleens of mice with colon cancer were used as an in vitro model to assess the efficacy of CA. Treatment of MDSCs with CA significantly decreased cell proliferation and induced apoptotic cell death. Subsequent experiments demonstrated that CA treatment enhanced the expression of Bax and caspase-9 and inhibited the expression of Bcl-2, suggesting that CA induced apoptosis in the MDSCs via the intrinsic pathway. Taken together, the results demonstrated that CA exhibited significant anti-MDSC activity and attenuated the suppression of the antitumor immune response, indicating a potential use for CA in cancer therapy.

Identification of a CqCaspase gene with antiviral activity from red claw crayfish Cherax quadricarinatus

Caspase, an aspartate specific proteinase mediating apoptosis, plays a key role in immune response. In our previous study, the expression of a caspase gene was up-regulated in a transcriptome library from the haematopoietic tissue (Hpt) cells of red claw crayfish Cherax quadricarinatus post white spot syndrome virus (WSSV) infection. To further reveal the effect of caspase on WSSV infection, we cloned this caspase gene (denominated as CqCaspase) with an open reading frame of 1062 bp, which encoded 353 amino acids with a caspase domain (CASc) containing a p20 subunit and a p10 subunit. Tissue distribution analysis indicated that the mRNA transcript of CqCaspase was widely expressed in all tested tissues with the highest expression in Hpt, while the lowest expression in muscle. To further explore the effect of CqCaspase on WSSV replication, recombinant protein of CqCaspase (rCqCaspase) was delivered into Hpt cells followed by WSSV infection, which resulted in a significantly decreased expression of both an immediate early gene IE1 and a late envelope protein gene VP28 of WSSV, suggesting that CqCaspase, possibly by the enhanced apoptotic activity, had a strong negative effect on the WSSV replication. These data together indicated that CqCaspase was likely to play a vital role in immune defense against WSSV infection in a crustacean C. quadricarinatus, which shed a new light on the mechanism study of WSSV infection in crustaceans.

A novel effector caspase (Caspase-3/7-1) involved in the regulation of immune homeostasis in Chinese mitten crab Eriocheir sinensis

Caspases are a conserved family of cysteine proteases characterized by specificity for aspartic acid and play an essential role in cell apoptosis. In the present study, a novel effector caspase (designated as EsCaspase-3/7-1) was identified from Chinese mitten crab Eriocheir sinensis. The open reading frame of EsCaspase-3/7-1 cDNA was of 972 bp, encoding a polypeptide of 323 amino acids. EsCaspase-3/7-1 contained an N-terminal prodomain and a conservative C-terminal CASc domain, with the conserved active site "QACRG". The mRNA transcripts of EsCaspase-3/7-1 were constitutively expressed in all the examined tissues with high expression level in hemocytes, hepatopancreas and gill. The EsCaspase-3/7-1 protein was mainly distributed in the cytoplasm of hemocytes. After Aeromonas hydrophila and lipopolysaccharide (LPS) stimulations, the mRNA expression level of EsCaspase-3/7-1 in hemocytes increased significantly. The mRNA expression level of EsCaspase-3/7-1 in hemocytes was significantly up-regulated after H₂O₂ treatment in vitro. The recombinant EsCaspase-3/7-1 protein (rEsCaspase-3/7-1) was capable of hydrolyzing the substrate Ac-DEVD-pNA rather than Ac-YVAD-pNA and Ac-VEID-pNA in vitro, and exhibited binding activity to LPS. These results demonstrated that EsCaspase-3/7-1 might act as an LPS receptor, and play an important role in the regulation of immune homeostasis of E. sinensis.

Toxic effects of cyhalofop-butyl on embryos of the Yellow River carp (Cyprinus carpio var.): alters embryos hatching, development failure, mortality of embryos, and apoptosis

As a universal environmental contaminant, the herbicide cyhalofop-butyl is considered to have infested effects on the embryonic development of aquatic species. The present study focused on an assessment of the impacts of cyhalofop-butyl on Yellow River carp embryos. It was found that cyhalofop-butyl inhibited the hatching of the embryos, and the hatching rate decreased with higher concentrations of the herbicide. The mortality rate was increased on exposure to cyhalofop-butyl and was significantly higher in the 1.6 and 2 mg/L treatment groups over 48 h. All of the embryos of the 2 mg/L treatment group died within the 48 h post-hatching stage. And the transcription of several embryos related to apoptosis was also influenced by cyhalofop-butyl exposure. Further, cyhalofop-butyl exposure leads to a series of morphological changes (pericardial edema, tail deformation, and spine deformation) in embryos, which were consistent with significant modifications in the associated genes. These results provided a scientific basis for further studies into the effects of cyhalofop-butyl on aquatic organisms.

Eugenol triggers CD11b+Gr1+myeloid-derived suppressor cell apoptosisviaendogenous apoptosis pathway

To study the effect and underlying molecular mechanism of eugenol on CD11b⁺Gr1⁺ myeloid-derived suppressor cells (MDSCs). The effect of eugenol on the inhibition of immortalized MDSC cell line MSC-2 and murine peritoneal macrophages was detected by MTT. Flow cytometry was used to detect the pro-apoptosis effect of eugenol on MDSCs. The expression levels of apoptosis-related proteins were detected by western blot. Eugenol has a selective inhibitory effect on MDSCs in a dose-dependent manner, which activates an endogenous apoptosis pathway, leading to apoptosis. Eugenol promotes the apoptosis of MDSCs via the intrinsic pathway.

To study the effect and underlying molecular mechanism of eugenol on CD11b⁺Gr1⁺ myeloid-derived suppressor cells (MDSCs).

The self-activation and LPS binding activity of executioner caspase-1 in oyster Crassostrea gigas

Executioner caspases play important roles in apoptotic pathway and immune defense, which is considered to coordinate the execution phase of apoptosis by cleaving multiple structural and repair proteins. However, the knowledge about the activation mechanism and function of executioner caspases in mollusks, especially marine bivalves is limited. In the present study, the full-length cDNA sequence of caspase-1 was cloned from oyster Crassostrea gigas, which encoded a predicted protein containing a small subunit (p10) and large subunit (p20) with a conserved caspase active site QACRG similar to that of human executioner caspase-3/7. SDS-polyacrylamide gel electrophoresis and western blot results demonstrated that the CgCaspase-1 zymogen could be cleaved into p20p10, p20 and p10 in prokaryotic expression systems, and the C-terminus of CgCaspase-1 was also cleaved into p20 and p10. Both of the recombinant CgCaspase-1 (rCgCaspase-1) and the C-terminus of CgCaspase-1 (rCgCaspase-1-C) exhibited similar caspase activity towards proteolytic substrate Ac-DMQD-pNA and Ac-DEVD-pNA. However, the recombinant N-terminus of CgCaspase-1 (rCgCaspase-1-N) did not display any caspase activity. Moreover, the inhibitor of both caspase-3/7 and pan-caspase could significantly inhibit the proteolytic activity of rCgCaspase-1. The strong binding activities towards lipopolysaccharide (LPS) of both rCgCaspase-1 and rCgCaspase-1-C were revealed by ELISA techniques and western blotting. A high level of CgCaspase-1 mRNA transcripts was detected in the gills and hemocytes by quantitative real-time PCR, and the CgCaspase-1 protein was mainly located in the cytoplasm of oyster hemocytes by immunofluorescence assay. These results collectively suggested that CgCaspase-1 was a homolog of executioner caspase-3/7, which could be self-activated through proteolytic cleavage in prokaryotic expression systems, and performed caspase and LPS binding activities in the innate immune response of oyster.

Effect of UVB radiation exposure in the expression of genes and proteins related to apoptosis in freshwater prawn embryos

Our previous studies showed that embryos of the freshwater prawn Macrobrachium olfersii exposed to ultraviolet B (UVB) radiation exhibited DNA damage, excessive ROS production, mitochondrial dysfunction and increased hsp70 expression, which are able, independently or together, to induce apoptosis. Thus, we attempted to elucidate some key apoptosis-related genes (ARG) and apoptosis-related proteins (ARP) and their expression during different stages of embryonic development, as well as to characterize the chronology of ARG expression and ARP contents after UVB radiation insult. We demonstrate that p53, Bax and Caspase3 genes are active in the embryonic cells at early embryonic developmental stages, and that the Bcl2 gene is active from the mid-embryonic stage. After UVB radiation exposure, we found an increase in ARP such as p53 and Bak after 3h of exposure. Moreover, an increase in ARG transcript levels for p53, Bax, Bcl2 and Caspase3 was observed at 6h after UVB exposure. Then, after 12h of UVB radiation exposure, an increase in Caspase3 gene expression and protein was observed, concomitantly with an increased number of apoptotic cells. Our data reveal that ARG and ARP are developmentally regulated in embryonic cells of M. olfersii and that UVB radiation causes apoptosis after 12h of exposure. Overall, we demonstrate that embryonic cells of M. olfersii are able to active the cell machinery against environmental changes, such as increased incidence of UVB radiation in aquatic ecosystems.

Molecular cloning, characterization and expression analysis of caspase-3 from the oriental river prawn, Macrobrachium nipponense when exposed to acute hypoxia and reoxygenation

Caspases are present in the cytosol as inactive proenzymes but become activated when apoptosis is initiated, playing an essential role at various stages of the process. In this study, a caspase-3 (Mncaspase-3c) was cloned from gill of the oriental river prawn Macrobrachium nipponense by reverse-transcription polymerase chain reaction and rapid amplification of cDNA ends, and its properties were characterized. The 1730-bp cDNA contained an open reading frame of 1566 bp, a 123-bp 5'-untranslated region (UTR), and a 41-bp 3'-UTR containing a poly(A) tail. The molecular mass of the deduced amino acid (aa) sequence (521 aa) was 56.3 kDa with an estimated pI of 5.01. The MnCaspase-3c sequence contained a predicted caspase family p20 domain and a caspase family p10 domain at positions 236-367 and 378-468 respectively. Recombinant MnCaspase-3c protein was expressed in Escherichia coli and purified. In vitro activity assays indicated that the recombinant MnCaspase-3c hydrolyzed the substrate Ac-DEVD-pNA, suggesting a physiological role as a caspase-3. Caspase-3c gene transcripts were distributed in all M. nipponense tissues tested by quantitative RT-PCR, being especially abundant in hemocytes. Comet assays in gill tissues showed an obvious time-dependent response to hypoxia. Furthermore, Mncaspase-3c, at both the mRNA and protein levels, was demonstrated to participate in the apoptotic process in gill after stimulation by acute hypoxia. Overall, these results indicate that hypoxia triggers apoptosis in shrimp gill tissues.

Chemosensitizing Effect of Astragalus Polysaccharides on Nasopharyngeal Carcinoma Cells by Inducing Apoptosis and Modulating Expression of Bax/Bcl-2 Ratio and Caspases

Background

Platinum-based chemotherapy is the most effective regimen for nasopharyngeal carcinoma, which presents highly invasive and metastatic activity. However, the dose-related toxicity of chemotherapy agents limits the dose administration. Astragalus polysaccharide (APS) is the major active ingredient extracted from Chinese herb Radix Astragali and is proven to be active against carcinomas. We aimed to assess the chemosensitizing effects of Astragalus polysaccharides on nasopharyngeal carcinoma in vitro and in vivo and to explore the underlying mechanism.

Material/Methods

We used BALB/c nu/nu mice and human nasopharyngeal carcinoma cell lines CNE-1, CNE-2, and SUNE-1. MTT, Annexin V/PI, Western blot analysis, and TUNEL assay were carried out.

Results

APS significantly promoted anti-proliferative and apoptotic effects of cisplatin on nasopharyngeal carcinoma cells. APS also enhanced the anti-tumor effects and cisplatin-induced apoptosis in the xenograft model. The level of Bcl-2 decreased, while the levels of Bax, caspase-3, and caspase-9 increased in cisplatin combined with APS treatment compared to cisplatin only treatment. The ratio of Bax to Bcl-2 was significantly enhanced by the APS to cisplatin.

Conclusions

APS enhanced the anti-proliferative and apoptotic effect of cisplatin by modulating expression of Bax/Bcl-2 ratio and caspases on nasopharyngeal carcinoma cells and in the xenograft model.

Caspase-8 and Caspase-9 Functioned Differently at Different Stages of the Cyclic Stretch-Induced Apoptosis in Human Periodontal Ligament Cells

Background

Human periodontal ligament (PDL) cells underwent apoptosis after mechanical stretch loading. However, the exact signalling pathway remains unknown. This study aimed to elucidate how the apoptotic caspases functioned in the cyclic stretch-induced apoptosis in human PDL cells.

Materials and Methods

In the present study, 20% cyclic stretch was selected to load the cells for 6 or 24 h. The following parameters were analyzed: apoptotic rates, the protein levels of caspase-3, -7, -8 and -9 and the activities of caspase-8 and -9. Subsequently, the influences of caspase-8 and caspase-9 inhibitors on the apoptotic rate and the protein level of the activated caspase-3 were assessed as well.

Results

The apoptotic rates increased in response to cyclic stretch, but the cells entered different apoptotic stages after 6 and 24 h stretches. Caspase-3, -7, -8 and -9 were all activated after stretch loading. The stretch-induced apoptosis and the protein level of the activated caspase-3 were inhibited after inhibiting both caspase-8 and caspase-9 in both 6 and 24 h stretched cells and after inhibiting caspase-9 in 24 h stretched cells.

Conclusion

Caspase-8 and -9 functioned differently at different apoptotic stages in human PDL cells after cyclic stretch.

Internalization of a novel, huge lectin from Ibacus novemdentatus (slipper lobster) induces apoptosis of mammalian cancer cells

An N-acetyl sugar-binding lectin (termed iNoL) displaying cytotoxic activity against human cancer cells was isolated from the slipper lobster Ibacus novemdentatus (family Scyllaridae). iNoL recognized monosaccharides containing N-acetyl group, and glycoproteins (e.g., BSM) containing oligosaccharides with N-acetyl sugar. iNoL was composed of five subunits (330, 260, 200, 140, and 30 kDa), which in turn consisted of 70-, 40-, and 30-kDa polypeptides held together by disulfide bonds. Electron microscopic observations and gel permeation chromatography indicated that iNoL was a huge (500-kDa) molecule and had a polygonal structure under physiological conditions. iNoL displayed cytotoxic (apoptotic) effects against human cancer cell lines MCF7 and T47D (breast), HeLa (ovarian), and Caco2 (colonic), through incorporation (internalization) into cells. The lectin was transported into lysosomes via endosomes. Its cytotoxic effect and incorporation into cells were inhibited by the co-presence of N-acetyl-D-mannosamine (ManNAc). Treatment of HeLa cells with iNoL resulted in DNA fragmentation and chromatin condensation, through activation of caspase-9 and -3. In summary, the novel crustacean lectin iNoL is incorporated into mammalian cancer cells through glycoconjugate interaction, and has cytotoxic (apoptotic) effects.

Interaction study of a novel Macrobrachium rosenbergii effector caspase with B2 and capsid proteins of M. rosenbergii nodavirus reveals their roles in apoptosis

Apoptosis is an essential immune response to protect invertebrates from virus infected cells. In shrimp, virus infection has been reported to induce apoptosis. Macrobrachium rosenbergii (Mr) was considered to be a disease-resistant host when compared to penaeid shrimps. Caspase-3 was classified as an executioner caspase which played a key role in virus-induced apoptosis. In this study, an effector caspase gene of M. rosenbergii (Mrcasp) was cloned and characterized. The open reading frame (ORF) of Mrcasp was 957 nucleotide encoding 318 amino acid with a deduced molecular mass of 35.87 kDa. RT-PCR analysis showed the presence of Mrcasp in all examined tissues. The phylogenetic tree indicated that Mrcasp was closely related with caspase 3 of shrimp. The functions of the Mrcasp, B2 and capsid proteins of M. rosenbergii nodavirus (MrNV) were assayed in Sf-9 cells. The results showed that Mrcasp induce apoptotic morphology cells; however, capsid protein of MrNV could inhibit apoptotic cells whereas B2 could neither induce nor inhibit apoptotic cells by DAPI staining. The protein interaction between Mrcasp and viral MrNV structure revealed that Mrcasp did not bind to B2 or capsid protein whereas B2 and capsid proteins could bind directly to each other. This study reported a novel sequence of a full-length Mrcasp and its functional studies indicated that Mrcasp could induce apoptotic cells. Our data is the first report demonstrating the direct protein-protein interaction between capsid protein and B2 protein of MrNV.