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Disorder of G2-M Checkpoint Control in Aniline-Induced Cell Proliferation in Rat Spleen.

Wang J, Wang G, Khan MF - PLoS ONE (2015)

Bottom Line: Despite our demonstration that cell proliferation was associated with deregulation of G1 phase cyclins and increased expression of G1 phase cyclin-dependent kinases (CDKs), molecular mechanisms, especially the regulation of G2 phase and contribution of epigenetic mechanisms in aniline-induced splenic cellular proliferation remain largely unclear.Aniline treatment resulted in significant increases in cell cycle regulatory proteins, including cyclins A, B and CDK1, particularly phosphor-CDK1, and decreases in CDK inhibitors p21 and p27, which could promote the splenocytes to go through G2/M transition.More importantly, we observed lower expression of miRNAs including Let-7a, miR-15b, miR24, miR-100 and miR-125, and greater expression of CDK inhibitor regulatory miRNAs such as miR-181a, miR-221 and miR-222 in the spleens of aniline-treated animals.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, United States of America.

ABSTRACT
Aniline, a toxic aromatic amine, is known to cause hemopoietic toxicity both in humans and animals. Aniline exposure also leads to toxic response in spleen which is characterized by splenomegaly, hyperplasia, fibrosis and the eventual formation of tumors on chronic in vivo exposure. Previously, we have shown that aniline exposure leads to iron overload, oxidative DNA damage, and increased cell proliferation, which could eventually contribute to a tumorigenic response in the spleen. Despite our demonstration that cell proliferation was associated with deregulation of G1 phase cyclins and increased expression of G1 phase cyclin-dependent kinases (CDKs), molecular mechanisms, especially the regulation of G2 phase and contribution of epigenetic mechanisms in aniline-induced splenic cellular proliferation remain largely unclear. This study therefore, mainly focused on the regulation of G2 phase in an animal model preceding a tumorigenic response. Male Sprague-Dawley rats were given aniline (0.5 mmol/kg/day) in drinking water or drinking water only (controls) for 30 days, and expression of G2 phase cyclins, CDK1, CDK inhibitors and miRNAs were measured in the spleen. Aniline treatment resulted in significant increases in cell cycle regulatory proteins, including cyclins A, B and CDK1, particularly phosphor-CDK1, and decreases in CDK inhibitors p21 and p27, which could promote the splenocytes to go through G2/M transition. Our data also showed upregulation of tumor markers Trx-1 and Ref-1 in rats treated with aniline. More importantly, we observed lower expression of miRNAs including Let-7a, miR-15b, miR24, miR-100 and miR-125, and greater expression of CDK inhibitor regulatory miRNAs such as miR-181a, miR-221 and miR-222 in the spleens of aniline-treated animals. Our findings suggest that significant increases in the expression of cyclins, CDK1 and aberrant regulation of miRNAs could lead to an accelerated G2/M transition of the splenocytes, and potentially to a tumorigenic response on chronic aniline exposure.

No MeSH data available.


Related in: MedlinePlus

Cyclins A and B1 protein expression in rat spleens following aniline exposure (A) Western blot determination of cyclins A and B1 protein expression in control or aniline-treated rats. (B) Densitometric analysis of cyclin protein expressions. Values are mean ± SD; *p < 0.05.
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pone.0131457.g001: Cyclins A and B1 protein expression in rat spleens following aniline exposure (A) Western blot determination of cyclins A and B1 protein expression in control or aniline-treated rats. (B) Densitometric analysis of cyclin protein expressions. Values are mean ± SD; *p < 0.05.

Mentions: Cyclins are key component of the cell cycle machinery controlling cell cycle progression [34–36]. Only after binding of cyclins, CDKs become active kinases, and those specific CDK-cyclin complexes are responsible for appropriate and ordered cell cycle transit [35,36]. CDKs are selectively activated as a result of binding of a specific cyclin. CDK1 is activated via association with cyclin A at the end of interphase to facilitate the onset of mitosis. CDK1-cyclin A complex remains into late G2 phase until replaced by CDK1-cyclin B complex and is implicated in activation and stabilization of CDK1-cyclin B which is responsible for driving cells through mitosis [34–36]. There are two different cyclin B proteins in mammalian cells. Cyclin B2 is non-essential protein during mitosis, but cyclin B1 is an essential protein that is thought to be responsible for most of action of CDK1 in the cytoplasm and nucleus [36,37]. Therefore, cyclins A and B1 were the major focus of the study and thus, analyzed. As evident from Fig 1, cyclins A and B1 protein expression in aniline-treated rat spleens showed significant increases of 412% and 280%, respectively, than the controls.


Disorder of G2-M Checkpoint Control in Aniline-Induced Cell Proliferation in Rat Spleen.

Wang J, Wang G, Khan MF - PLoS ONE (2015)

Cyclins A and B1 protein expression in rat spleens following aniline exposure (A) Western blot determination of cyclins A and B1 protein expression in control or aniline-treated rats. (B) Densitometric analysis of cyclin protein expressions. Values are mean ± SD; *p < 0.05.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507860&req=5

pone.0131457.g001: Cyclins A and B1 protein expression in rat spleens following aniline exposure (A) Western blot determination of cyclins A and B1 protein expression in control or aniline-treated rats. (B) Densitometric analysis of cyclin protein expressions. Values are mean ± SD; *p < 0.05.
Mentions: Cyclins are key component of the cell cycle machinery controlling cell cycle progression [34–36]. Only after binding of cyclins, CDKs become active kinases, and those specific CDK-cyclin complexes are responsible for appropriate and ordered cell cycle transit [35,36]. CDKs are selectively activated as a result of binding of a specific cyclin. CDK1 is activated via association with cyclin A at the end of interphase to facilitate the onset of mitosis. CDK1-cyclin A complex remains into late G2 phase until replaced by CDK1-cyclin B complex and is implicated in activation and stabilization of CDK1-cyclin B which is responsible for driving cells through mitosis [34–36]. There are two different cyclin B proteins in mammalian cells. Cyclin B2 is non-essential protein during mitosis, but cyclin B1 is an essential protein that is thought to be responsible for most of action of CDK1 in the cytoplasm and nucleus [36,37]. Therefore, cyclins A and B1 were the major focus of the study and thus, analyzed. As evident from Fig 1, cyclins A and B1 protein expression in aniline-treated rat spleens showed significant increases of 412% and 280%, respectively, than the controls.

Bottom Line: Despite our demonstration that cell proliferation was associated with deregulation of G1 phase cyclins and increased expression of G1 phase cyclin-dependent kinases (CDKs), molecular mechanisms, especially the regulation of G2 phase and contribution of epigenetic mechanisms in aniline-induced splenic cellular proliferation remain largely unclear.Aniline treatment resulted in significant increases in cell cycle regulatory proteins, including cyclins A, B and CDK1, particularly phosphor-CDK1, and decreases in CDK inhibitors p21 and p27, which could promote the splenocytes to go through G2/M transition.More importantly, we observed lower expression of miRNAs including Let-7a, miR-15b, miR24, miR-100 and miR-125, and greater expression of CDK inhibitor regulatory miRNAs such as miR-181a, miR-221 and miR-222 in the spleens of aniline-treated animals.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, United States of America.

ABSTRACT
Aniline, a toxic aromatic amine, is known to cause hemopoietic toxicity both in humans and animals. Aniline exposure also leads to toxic response in spleen which is characterized by splenomegaly, hyperplasia, fibrosis and the eventual formation of tumors on chronic in vivo exposure. Previously, we have shown that aniline exposure leads to iron overload, oxidative DNA damage, and increased cell proliferation, which could eventually contribute to a tumorigenic response in the spleen. Despite our demonstration that cell proliferation was associated with deregulation of G1 phase cyclins and increased expression of G1 phase cyclin-dependent kinases (CDKs), molecular mechanisms, especially the regulation of G2 phase and contribution of epigenetic mechanisms in aniline-induced splenic cellular proliferation remain largely unclear. This study therefore, mainly focused on the regulation of G2 phase in an animal model preceding a tumorigenic response. Male Sprague-Dawley rats were given aniline (0.5 mmol/kg/day) in drinking water or drinking water only (controls) for 30 days, and expression of G2 phase cyclins, CDK1, CDK inhibitors and miRNAs were measured in the spleen. Aniline treatment resulted in significant increases in cell cycle regulatory proteins, including cyclins A, B and CDK1, particularly phosphor-CDK1, and decreases in CDK inhibitors p21 and p27, which could promote the splenocytes to go through G2/M transition. Our data also showed upregulation of tumor markers Trx-1 and Ref-1 in rats treated with aniline. More importantly, we observed lower expression of miRNAs including Let-7a, miR-15b, miR24, miR-100 and miR-125, and greater expression of CDK inhibitor regulatory miRNAs such as miR-181a, miR-221 and miR-222 in the spleens of aniline-treated animals. Our findings suggest that significant increases in the expression of cyclins, CDK1 and aberrant regulation of miRNAs could lead to an accelerated G2/M transition of the splenocytes, and potentially to a tumorigenic response on chronic aniline exposure.

No MeSH data available.


Related in: MedlinePlus