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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

Protein expression of CDK1 and p-CDK1 in rat spleens.(A) Western blot determination of CDK1 and p-CDK1 protein expression in control and aniline-treated rats. (B) Densitometric analysis of protein expressions. Values are mean ± SD; *p < 0.05.
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pone.0131457.g003: Protein expression of CDK1 and p-CDK1 in rat spleens.(A) Western blot determination of CDK1 and p-CDK1 protein expression in control and aniline-treated rats. (B) Densitometric analysis of protein expressions. Values are mean ± SD; *p < 0.05.

Mentions: CDKs are central components of the cell cycle regulatory machinery and play a key role in driving cell cycle progression [27,29,34,35]. CDK1 is the master regulatory kinase of G2 checkpoint and plays pivotal role in transition from G2 to M. Phosporylation of the conserved Thr161 in the T-loop of CDK1 is required for activation of the cyclin B/CDK1 complex [27,29]. To evaluate the roles of CDK1 in regulating splenocyte proliferation, CDK1 and p-CDK1 expression was thus analyzed by Western blot and data are presented in Fig 3. The protein expression of CDK1 and p-CDK1 in aniline-treated rats showed remarkable increases of 200% and 577%, respectively, as compared to the control rats. The results further suggest that aniline treatment stimulates the expression of cell cycle regulatory proteins.


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

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

Protein expression of CDK1 and p-CDK1 in rat spleens.(A) Western blot determination of CDK1 and p-CDK1 protein expression in control and aniline-treated rats. (B) Densitometric analysis of 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.g003: Protein expression of CDK1 and p-CDK1 in rat spleens.(A) Western blot determination of CDK1 and p-CDK1 protein expression in control and aniline-treated rats. (B) Densitometric analysis of protein expressions. Values are mean ± SD; *p < 0.05.
Mentions: CDKs are central components of the cell cycle regulatory machinery and play a key role in driving cell cycle progression [27,29,34,35]. CDK1 is the master regulatory kinase of G2 checkpoint and plays pivotal role in transition from G2 to M. Phosporylation of the conserved Thr161 in the T-loop of CDK1 is required for activation of the cyclin B/CDK1 complex [27,29]. To evaluate the roles of CDK1 in regulating splenocyte proliferation, CDK1 and p-CDK1 expression was thus analyzed by Western blot and data are presented in Fig 3. The protein expression of CDK1 and p-CDK1 in aniline-treated rats showed remarkable increases of 200% and 577%, respectively, as compared to the control rats. The results further suggest that aniline treatment stimulates the expression of cell cycle regulatory proteins.

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