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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 gene expression in rat spleens following aniline exposure.The fold change in mRNA expression (2−ΔΔCT) was determined by real-time PCR analysis. Values are means ± SD (n = 3). *p < 0.05 vs. respective controls.
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pone.0131457.g002: Cyclins A and B1 gene expression in rat spleens following aniline exposure.The fold change in mRNA expression (2−ΔΔCT) was determined by real-time PCR analysis. Values are means ± SD (n = 3). *p < 0.05 vs. respective controls.

Mentions: As mentioned above, cyclins A and B play key role in regulating cell cycle transitions and controlling cell cycle progression via assembling with CDK1 to form cyclin-CDK complexes [34,36]. Since our Western analysis data showed that aniline exposure led to increases in protein expression of cyclins A and cyclin B1 in spleens, it was important to evaluate if aniline exposure also affected the expression of cyclins at gene levels. Therefore, the mRNA expression of cyclins A and B1 was measured by using real-time PCR and the results are presented in Fig 2. Aniline treatment led to 16 and 12 fold increases, respectively, in the mRNA expression of cyclins A and B1 in comparison to the controls, providing further support to the observed increases in protein expression.


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 gene expression in rat spleens following aniline exposure.The fold change in mRNA expression (2−ΔΔCT) was determined by real-time PCR analysis. Values are means ± SD (n = 3). *p < 0.05 vs. respective controls.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0131457.g002: Cyclins A and B1 gene expression in rat spleens following aniline exposure.The fold change in mRNA expression (2−ΔΔCT) was determined by real-time PCR analysis. Values are means ± SD (n = 3). *p < 0.05 vs. respective controls.
Mentions: As mentioned above, cyclins A and B play key role in regulating cell cycle transitions and controlling cell cycle progression via assembling with CDK1 to form cyclin-CDK complexes [34,36]. Since our Western analysis data showed that aniline exposure led to increases in protein expression of cyclins A and cyclin B1 in spleens, it was important to evaluate if aniline exposure also affected the expression of cyclins at gene levels. Therefore, the mRNA expression of cyclins A and B1 was measured by using real-time PCR and the results are presented in Fig 2. Aniline treatment led to 16 and 12 fold increases, respectively, in the mRNA expression of cyclins A and B1 in comparison to the controls, providing further support to the observed increases in protein expression.

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