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New insights into the apoptotic process in mollusks: characterization of caspase genes in Mytilus galloprovincialis.

Romero A, Estévez-Calvar N, Dios S, Figueras A, Novoa B - PLoS ONE (2011)

Bottom Line: Caspase proteins constitute the core of the apoptotic machinery and can be categorized as either initiators or effectors of apoptosis.Evaluation of the genes' tissue expression patterns revealed extremely high expression levels within the gland and gills, where the apoptotic process is highly active due to the clearance of damaged cells.Hemocytes also showed high expression values, probably due to of the role of apoptosis in the defense against pathogens.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Investigaciones Marinas, Consejo Superior de Investigaciones Científicas, Vigo, Spain.

ABSTRACT
Apoptosis is an essential biological process in the development and maintenance of immune system homeostasis. Caspase proteins constitute the core of the apoptotic machinery and can be categorized as either initiators or effectors of apoptosis. Although the genes encoding caspase proteins have been described in vertebrates and in almost all invertebrate phyla, there are few reports describing the initiator and executioner caspases or the modulation of their expression by different stimuli in different apoptotic pathways in bivalves. In the present work, we characterized two initiator and four executioner caspases in the mussel Mytilus galloprovincialis. Both initiators and executioners showed structural features that make them different from other caspase proteins already described. Evaluation of the genes' tissue expression patterns revealed extremely high expression levels within the gland and gills, where the apoptotic process is highly active due to the clearance of damaged cells. Hemocytes also showed high expression values, probably due to of the role of apoptosis in the defense against pathogens. To understand the mechanisms of caspase gene regulation, hemocytes were treated with UV-light, environmental pollutants and pathogen-associated molecular patterns (PAMPs) and apoptosis was evaluated by microscopy, flow cytometry and qPCR techniques. Our results suggest that the apoptotic process could be tightly regulated in bivalve mollusks by overexpression/suppression of caspase genes; additionally, there is evidence of caspase-specific responses to pathogens and pollutants. The apoptotic process in mollusks has a similar complexity to that of vertebrates, but presents unique features that may be related to recurrent exposure to environmental changes, pollutants and pathogens imposed by their sedentary nature.

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Related in: MedlinePlus

Modulation of caspase gene expression in hemocytes treated with bezopyrene, phenanthrene and PCBs.Results represent the mean ± SD of 4 experimental hemocyte pools. Data were analyzed using the Student’s t-test. a, b, c, d, e and f indicate significant differences (p<0.05) of caspase-2, -8, 3/7-1, -3/7-2, -3/7-3 and -3/7-4, respectively.
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pone-0017003-g010: Modulation of caspase gene expression in hemocytes treated with bezopyrene, phenanthrene and PCBs.Results represent the mean ± SD of 4 experimental hemocyte pools. Data were analyzed using the Student’s t-test. a, b, c, d, e and f indicate significant differences (p<0.05) of caspase-2, -8, 3/7-1, -3/7-2, -3/7-3 and -3/7-4, respectively.

Mentions: In order to evaluate the effect of different pollutants on the mussel immune system, hemocytes were exposed to high concentrations of PHAs and PCBs. These compounds are some of the most prevalent components of crude oil. Therefore, PHAs and PCBs are some of the chemicals responsible for marine environmental contamination due to oil spills. Both compounds induced changes in the gene expression profiles ranging from a 3-fold-increase to 0.3 times below the controls (Figure 10). Benzopyrene induced a significant down-regulation of all caspase genes by the end of the time course. At 1 h pt, all genes were expressed at least 1.5 times but expression decreased gradually until 6 h pt, when all the genes were expressed at levels less than controls. Opposite results were obtained for hemocytes treated with phenanthrene; the expression of all caspase genes significantly increased during the time course. Caspase-2, -3/7-1, -3/7-2 and -3/7-3 were down-regulated at 1 h pt but expression levels increased to reach levels greater than the control at 6 h pt. The fold-change expression at this sampling point was less than 2 for all genes. The expression of caspase-3/7-4 and caspase-8 increased during the course of the experiment and displayed fold-change values higher than 2.5 by the last time point. Modulation of gene expression was also observed in hemocytes treated with PCBs. Initiator caspase-2 and -8 were significantly down-regulated after 3 h and 6 h pt. Executioner caspase-3/7-1 and -3/7-3 were up-regulated significantly at 3 h and 6 h pt; caspase-3/7-4 was significantly down-regulated. Caspase-3/7-2 showed significant down-regulation after 3 h pt and significant up-regulation after 6 h pt.


New insights into the apoptotic process in mollusks: characterization of caspase genes in Mytilus galloprovincialis.

Romero A, Estévez-Calvar N, Dios S, Figueras A, Novoa B - PLoS ONE (2011)

Modulation of caspase gene expression in hemocytes treated with bezopyrene, phenanthrene and PCBs.Results represent the mean ± SD of 4 experimental hemocyte pools. Data were analyzed using the Student’s t-test. a, b, c, d, e and f indicate significant differences (p<0.05) of caspase-2, -8, 3/7-1, -3/7-2, -3/7-3 and -3/7-4, respectively.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3037946&req=5

pone-0017003-g010: Modulation of caspase gene expression in hemocytes treated with bezopyrene, phenanthrene and PCBs.Results represent the mean ± SD of 4 experimental hemocyte pools. Data were analyzed using the Student’s t-test. a, b, c, d, e and f indicate significant differences (p<0.05) of caspase-2, -8, 3/7-1, -3/7-2, -3/7-3 and -3/7-4, respectively.
Mentions: In order to evaluate the effect of different pollutants on the mussel immune system, hemocytes were exposed to high concentrations of PHAs and PCBs. These compounds are some of the most prevalent components of crude oil. Therefore, PHAs and PCBs are some of the chemicals responsible for marine environmental contamination due to oil spills. Both compounds induced changes in the gene expression profiles ranging from a 3-fold-increase to 0.3 times below the controls (Figure 10). Benzopyrene induced a significant down-regulation of all caspase genes by the end of the time course. At 1 h pt, all genes were expressed at least 1.5 times but expression decreased gradually until 6 h pt, when all the genes were expressed at levels less than controls. Opposite results were obtained for hemocytes treated with phenanthrene; the expression of all caspase genes significantly increased during the time course. Caspase-2, -3/7-1, -3/7-2 and -3/7-3 were down-regulated at 1 h pt but expression levels increased to reach levels greater than the control at 6 h pt. The fold-change expression at this sampling point was less than 2 for all genes. The expression of caspase-3/7-4 and caspase-8 increased during the course of the experiment and displayed fold-change values higher than 2.5 by the last time point. Modulation of gene expression was also observed in hemocytes treated with PCBs. Initiator caspase-2 and -8 were significantly down-regulated after 3 h and 6 h pt. Executioner caspase-3/7-1 and -3/7-3 were up-regulated significantly at 3 h and 6 h pt; caspase-3/7-4 was significantly down-regulated. Caspase-3/7-2 showed significant down-regulation after 3 h pt and significant up-regulation after 6 h pt.

Bottom Line: Caspase proteins constitute the core of the apoptotic machinery and can be categorized as either initiators or effectors of apoptosis.Evaluation of the genes' tissue expression patterns revealed extremely high expression levels within the gland and gills, where the apoptotic process is highly active due to the clearance of damaged cells.Hemocytes also showed high expression values, probably due to of the role of apoptosis in the defense against pathogens.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Investigaciones Marinas, Consejo Superior de Investigaciones Científicas, Vigo, Spain.

ABSTRACT
Apoptosis is an essential biological process in the development and maintenance of immune system homeostasis. Caspase proteins constitute the core of the apoptotic machinery and can be categorized as either initiators or effectors of apoptosis. Although the genes encoding caspase proteins have been described in vertebrates and in almost all invertebrate phyla, there are few reports describing the initiator and executioner caspases or the modulation of their expression by different stimuli in different apoptotic pathways in bivalves. In the present work, we characterized two initiator and four executioner caspases in the mussel Mytilus galloprovincialis. Both initiators and executioners showed structural features that make them different from other caspase proteins already described. Evaluation of the genes' tissue expression patterns revealed extremely high expression levels within the gland and gills, where the apoptotic process is highly active due to the clearance of damaged cells. Hemocytes also showed high expression values, probably due to of the role of apoptosis in the defense against pathogens. To understand the mechanisms of caspase gene regulation, hemocytes were treated with UV-light, environmental pollutants and pathogen-associated molecular patterns (PAMPs) and apoptosis was evaluated by microscopy, flow cytometry and qPCR techniques. Our results suggest that the apoptotic process could be tightly regulated in bivalve mollusks by overexpression/suppression of caspase genes; additionally, there is evidence of caspase-specific responses to pathogens and pollutants. The apoptotic process in mollusks has a similar complexity to that of vertebrates, but presents unique features that may be related to recurrent exposure to environmental changes, pollutants and pathogens imposed by their sedentary nature.

Show MeSH
Related in: MedlinePlus