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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 p27 and p21 in the rat spleens following aniline exposure.(A) Western blot detection of p27 and p21 in the spleens of control and aniline-treated rats. (B) Densitometric analysis of the protein bands. Values are mean ± SD; *p < 0.05.
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pone.0131457.g004: Protein expression of p27 and p21 in the rat spleens following aniline exposure.(A) Western blot detection of p27 and p21 in the spleens of control and aniline-treated rats. (B) Densitometric analysis of the protein bands. Values are mean ± SD; *p < 0.05.

Mentions: CDK inhibitors p21 and p27 are two important cell cycle regulators. Loss of expression or function of p21 and p27 has been implicated in the genesis or progression of many human malignancies [35,38]. In addition to the role of p21 and p27 as efficient inhibitors of CDK2, CDK4 and CDK6, which also explains their ability to block cell cycle at the G1/S boundary, they have also been shown to inhibit cyclin A- and cyclin B-associated kinase activity in G2 phase [27,30,38]. Therefore, to evaluate the potential of p21 and p27 in aniline-mediated cell proliferation, the expression of p21 and p27 was also determined. As evident from Figs 4 and 5, aniline treatment resulted in significant decreases in protein expression of p21 (64%) and p27 (73%) in the spleens, whereas 67% decrease in p21 mRNA and 71% decrease in p27 mRNA expression were also observed, suggesting aniline-induced down-regulation of p21 and p27, and thus, their potential role in cell cycle progression.


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 p27 and p21 in the rat spleens following aniline exposure.(A) Western blot detection of p27 and p21 in the spleens of control and aniline-treated rats. (B) Densitometric analysis of the protein bands. Values are mean ± SD; *p < 0.05.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4507860&req=5

pone.0131457.g004: Protein expression of p27 and p21 in the rat spleens following aniline exposure.(A) Western blot detection of p27 and p21 in the spleens of control and aniline-treated rats. (B) Densitometric analysis of the protein bands. Values are mean ± SD; *p < 0.05.
Mentions: CDK inhibitors p21 and p27 are two important cell cycle regulators. Loss of expression or function of p21 and p27 has been implicated in the genesis or progression of many human malignancies [35,38]. In addition to the role of p21 and p27 as efficient inhibitors of CDK2, CDK4 and CDK6, which also explains their ability to block cell cycle at the G1/S boundary, they have also been shown to inhibit cyclin A- and cyclin B-associated kinase activity in G2 phase [27,30,38]. Therefore, to evaluate the potential of p21 and p27 in aniline-mediated cell proliferation, the expression of p21 and p27 was also determined. As evident from Figs 4 and 5, aniline treatment resulted in significant decreases in protein expression of p21 (64%) and p27 (73%) in the spleens, whereas 67% decrease in p21 mRNA and 71% decrease in p27 mRNA expression were also observed, suggesting aniline-induced down-regulation of p21 and p27, and thus, their potential role in cell cycle progression.

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