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Increases in apoptosis, caspase activity and expression of p53 and bax, and the transition between two types of mitochondrion-rich cells, in the gills of the climbing perch, Anabas testudineus, during a progressive acclimation from freshwater to seawater.

Ching B, Chen XL, Yong JH, Wilson JM, Hiong KC, Sim EW, Wong WP, Lam SH, Chew SF, Ip YK - Front Physiol (2013)

Bottom Line: Seawater acclimation apparently activated both the extrinsic and intrinsic pathways, as reflected by significant increases in branchial caspase-8 and caspase-9 activities.The involvement of the intrinsic pathway was confirmed by the significant increase in branchial mRNA expression of bax between day 4 (salinity 20) and day 6 (seawater).Western blotting results revealed the presence of a freshwater Na(+)/K(+)-ATPase (Nka) α-isoform, Nka α1a, and a seawater isoform, Nka α1b, the protein abundance of which decreased and increased, respectively, during seawater acclimation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Science, National University of Singapore Kent Ridge, Singapore, Singapore.

ABSTRACT
This study aimed to test the hypothesis that branchial osmoregulatory acclimation involved increased apoptosis and replacement of mitochdonrion-rich cells (MRCs) in the climbing perch, Anabas testudineus, during a progressive acclimation from freshwater to seawater. A significant increase in branchial caspase-3/-7 activity was observed on day 4 (salinity 20), and an extensive TUNEL-positive apoptosis was detected on day 5 (salinity 25), indicating salinity-induced apoptosis had occurred. This was further supported by an up-regulation of branchial mRNA expression of p53, a key regulator of cell cycle arrest and apoptosis, between day 2 (salinity 10) and day 6 (seawater), and an increase in branchial p53 protein abundance on day 6. Seawater acclimation apparently activated both the extrinsic and intrinsic pathways, as reflected by significant increases in branchial caspase-8 and caspase-9 activities. The involvement of the intrinsic pathway was confirmed by the significant increase in branchial mRNA expression of bax between day 4 (salinity 20) and day 6 (seawater). Western blotting results revealed the presence of a freshwater Na(+)/K(+)-ATPase (Nka) α-isoform, Nka α1a, and a seawater isoform, Nka α1b, the protein abundance of which decreased and increased, respectively, during seawater acclimation. Immunofluorescence microscopy revealed the presence of two types of MRCs distinctly different in sizes, and confirmed that the reduction in Nka α1a expression, and the prominent increases in expression of Nka α1b, Na(+):K(+):2Cl(-) cotransporter 1, and cystic fibrosis transmembrane conductance regulator Cl(-) channel coincided with the salinity-induced apoptotic event. Since modulation of existing MRCs alone could not have led to extensive salinity-induced apoptosis, it is probable that some, if not all, freshwater-type MRCs could have been removed through increased apoptosis and subsequently replaced by seawater-type MRCs in the gills of A. testudineus during seawater acclimation.

No MeSH data available.


Related in: MedlinePlus

Apoptotic cells indicated by TUNEL-positive nuclei (green) in gill sections of Anabas testudineus kept in (A) freshwater on day 1 (FW; control), or after 24 h of exposure to (B) salinity 15 on day 3, (C) salinity 25 on day 5 or (D) salinity 30 on day 6 after a progressive increase in salinity. All sections were counterstained with nuclear stain DAPI (blue). Magnification: 200×. Reproducible results were obtained from three individuals for each of the four conditions. Micrographs for (E) salinity 15 and (F) salinity 25 were enlarged (Magnification: 400×) for clearer visualization of apoptotic nuclei.
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Figure 1: Apoptotic cells indicated by TUNEL-positive nuclei (green) in gill sections of Anabas testudineus kept in (A) freshwater on day 1 (FW; control), or after 24 h of exposure to (B) salinity 15 on day 3, (C) salinity 25 on day 5 or (D) salinity 30 on day 6 after a progressive increase in salinity. All sections were counterstained with nuclear stain DAPI (blue). Magnification: 200×. Reproducible results were obtained from three individuals for each of the four conditions. Micrographs for (E) salinity 15 and (F) salinity 25 were enlarged (Magnification: 400×) for clearer visualization of apoptotic nuclei.

Mentions: TUNEL positive apoptosis was undetectable in gills of A. testudineus kept in freshwater, but was detected weakly and strongly in gills of fish exposed to salinity 15 (day 3) and salinity 25 (day 5), respectively, during a 6-day progressive acclimation from freshwater to seawater (Figure 1). By day 6, TUNEL positive apoptosis was no longer detectable in the gills of fish that had been exposed to seawater for 24 h (Figure 1).


Increases in apoptosis, caspase activity and expression of p53 and bax, and the transition between two types of mitochondrion-rich cells, in the gills of the climbing perch, Anabas testudineus, during a progressive acclimation from freshwater to seawater.

Ching B, Chen XL, Yong JH, Wilson JM, Hiong KC, Sim EW, Wong WP, Lam SH, Chew SF, Ip YK - Front Physiol (2013)

Apoptotic cells indicated by TUNEL-positive nuclei (green) in gill sections of Anabas testudineus kept in (A) freshwater on day 1 (FW; control), or after 24 h of exposure to (B) salinity 15 on day 3, (C) salinity 25 on day 5 or (D) salinity 30 on day 6 after a progressive increase in salinity. All sections were counterstained with nuclear stain DAPI (blue). Magnification: 200×. Reproducible results were obtained from three individuals for each of the four conditions. Micrographs for (E) salinity 15 and (F) salinity 25 were enlarged (Magnification: 400×) for clearer visualization of apoptotic nuclei.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3675322&req=5

Figure 1: Apoptotic cells indicated by TUNEL-positive nuclei (green) in gill sections of Anabas testudineus kept in (A) freshwater on day 1 (FW; control), or after 24 h of exposure to (B) salinity 15 on day 3, (C) salinity 25 on day 5 or (D) salinity 30 on day 6 after a progressive increase in salinity. All sections were counterstained with nuclear stain DAPI (blue). Magnification: 200×. Reproducible results were obtained from three individuals for each of the four conditions. Micrographs for (E) salinity 15 and (F) salinity 25 were enlarged (Magnification: 400×) for clearer visualization of apoptotic nuclei.
Mentions: TUNEL positive apoptosis was undetectable in gills of A. testudineus kept in freshwater, but was detected weakly and strongly in gills of fish exposed to salinity 15 (day 3) and salinity 25 (day 5), respectively, during a 6-day progressive acclimation from freshwater to seawater (Figure 1). By day 6, TUNEL positive apoptosis was no longer detectable in the gills of fish that had been exposed to seawater for 24 h (Figure 1).

Bottom Line: Seawater acclimation apparently activated both the extrinsic and intrinsic pathways, as reflected by significant increases in branchial caspase-8 and caspase-9 activities.The involvement of the intrinsic pathway was confirmed by the significant increase in branchial mRNA expression of bax between day 4 (salinity 20) and day 6 (seawater).Western blotting results revealed the presence of a freshwater Na(+)/K(+)-ATPase (Nka) α-isoform, Nka α1a, and a seawater isoform, Nka α1b, the protein abundance of which decreased and increased, respectively, during seawater acclimation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Science, National University of Singapore Kent Ridge, Singapore, Singapore.

ABSTRACT
This study aimed to test the hypothesis that branchial osmoregulatory acclimation involved increased apoptosis and replacement of mitochdonrion-rich cells (MRCs) in the climbing perch, Anabas testudineus, during a progressive acclimation from freshwater to seawater. A significant increase in branchial caspase-3/-7 activity was observed on day 4 (salinity 20), and an extensive TUNEL-positive apoptosis was detected on day 5 (salinity 25), indicating salinity-induced apoptosis had occurred. This was further supported by an up-regulation of branchial mRNA expression of p53, a key regulator of cell cycle arrest and apoptosis, between day 2 (salinity 10) and day 6 (seawater), and an increase in branchial p53 protein abundance on day 6. Seawater acclimation apparently activated both the extrinsic and intrinsic pathways, as reflected by significant increases in branchial caspase-8 and caspase-9 activities. The involvement of the intrinsic pathway was confirmed by the significant increase in branchial mRNA expression of bax between day 4 (salinity 20) and day 6 (seawater). Western blotting results revealed the presence of a freshwater Na(+)/K(+)-ATPase (Nka) α-isoform, Nka α1a, and a seawater isoform, Nka α1b, the protein abundance of which decreased and increased, respectively, during seawater acclimation. Immunofluorescence microscopy revealed the presence of two types of MRCs distinctly different in sizes, and confirmed that the reduction in Nka α1a expression, and the prominent increases in expression of Nka α1b, Na(+):K(+):2Cl(-) cotransporter 1, and cystic fibrosis transmembrane conductance regulator Cl(-) channel coincided with the salinity-induced apoptotic event. Since modulation of existing MRCs alone could not have led to extensive salinity-induced apoptosis, it is probable that some, if not all, freshwater-type MRCs could have been removed through increased apoptosis and subsequently replaced by seawater-type MRCs in the gills of A. testudineus during seawater acclimation.

No MeSH data available.


Related in: MedlinePlus