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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

Real-time PCR analysis of miRNAs Let-7a, miR-15b, miR24, miR-100 and miR-125 (A), and miRNAs miR-181a, miR-221 and miR-222 (B) expression in rat spleens following aniline exposure.Values are means ± SD (n = 3). *p < 0.05 vs. respective controls.
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pone.0131457.g007: Real-time PCR analysis of miRNAs Let-7a, miR-15b, miR24, miR-100 and miR-125 (A), and miRNAs miR-181a, miR-221 and miR-222 (B) expression in rat spleens following aniline exposure.Values are means ± SD (n = 3). *p < 0.05 vs. respective controls.

Mentions: miRNAs are functionally linked to many crucial cell-cycle control pathways. Many miRNAs are anti-proliferative and this function may be mediated by the control of different mitogenic pathways including the routes that lead to activation of cyclins and CDKs. On the other hand, several miRNAs can induce proliferation by targeting CDK inhibitors. Some miRNA may target both positive and negative regulators of the cell cycle [30–32]. To investigate whether miRNAs have a role in the cell cycle regulation of splenocytes following aniline exposure, the expression of miRNAs, including Let-7a, miR-15b, miR24, miR-100, miR-125, miR-181a, miR-221 and miR-222 which are known to mainly control G2/M phase regulators [30–32], was analyzed by using real-time PCR and the results are presented in Fig 7. Aniline exposure led to significantly decreased expression of Let-7a (decreased 82%), miR-15b (decreased 62%), miR24 (decreased 78%), miR-100 (decreased 63%), miR-125 (decreased 86%), whereas miR-181a, miR-221 and miR-222 increased by 155%, 78% and 56%, respectively, in comparison to controls (Fig 7).


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

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

Real-time PCR analysis of miRNAs Let-7a, miR-15b, miR24, miR-100 and miR-125 (A), and miRNAs miR-181a, miR-221 and miR-222 (B) expression in rat spleens following aniline exposure.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.g007: Real-time PCR analysis of miRNAs Let-7a, miR-15b, miR24, miR-100 and miR-125 (A), and miRNAs miR-181a, miR-221 and miR-222 (B) expression in rat spleens following aniline exposure.Values are means ± SD (n = 3). *p < 0.05 vs. respective controls.
Mentions: miRNAs are functionally linked to many crucial cell-cycle control pathways. Many miRNAs are anti-proliferative and this function may be mediated by the control of different mitogenic pathways including the routes that lead to activation of cyclins and CDKs. On the other hand, several miRNAs can induce proliferation by targeting CDK inhibitors. Some miRNA may target both positive and negative regulators of the cell cycle [30–32]. To investigate whether miRNAs have a role in the cell cycle regulation of splenocytes following aniline exposure, the expression of miRNAs, including Let-7a, miR-15b, miR24, miR-100, miR-125, miR-181a, miR-221 and miR-222 which are known to mainly control G2/M phase regulators [30–32], was analyzed by using real-time PCR and the results are presented in Fig 7. Aniline exposure led to significantly decreased expression of Let-7a (decreased 82%), miR-15b (decreased 62%), miR24 (decreased 78%), miR-100 (decreased 63%), miR-125 (decreased 86%), whereas miR-181a, miR-221 and miR-222 increased by 155%, 78% and 56%, respectively, in comparison to controls (Fig 7).

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