The proliferation marker pKi‐67 organizes the nucleolus during the cell cycle depending on Ran and cyclin B

An overdose of acetaminophen (APAP) (N-acetyl-p-aminophenol) leads to hepatocellular necrosis induced by its metabolite N-acetyl-p-benzoquinone-imine, which is generated during the metabolic phase of liver intoxication. It has been reported that DNA damage occurs during the toxic phase; however, the nucleases responsible for this effect are unknown. In this study, we analyzed the participation of the hepatic endonuclease deoxyribonuclease 1 (DNASE1) during APAP-induced hepatotoxicity by employing a Dnase1 knockout (KO) mouse model. Male CD-1 Dnase1 wild-type (WT) (Dnase1 ؉/؉ ) and KO (Dnase1 ؊/؊ ) mice were treated with 2 different doses of APAP. Hepatic histopathology was performed, and biochemical parameters for APAP metabolism and necrosis were investigated, including depletion of glutathione/glutathione-disulfide (GSH؉GSSG), ␤-nicotinamide adenine dinucleotide (NADH؉NAD ؉ ), and adenosine triphosphate (ATP); release of aminotransferases and Dnase1; and occurrence of DNA fragmentation. As expected, an APAP overdose in WT mice led to massive hepatocellular necrosis characterized by the release of aminotransferases and depletion of hepatocellular GSH؉GSSG, NADH؉NAD ؉ , and ATP. These metabolic events were accompanied by extensive DNA degradation. In contrast, Dnase1 KO mice were considerably less affected. In conclusion, whereas the innermost pericentral hepatocytes of both mouse strains underwent necrosis to the same extent independent of DNA damage, the progression of necrosis to more outwardly located cells was dependent on DNA damage and only occurred in WT mice. Dnase1 aggravates APAP-induced liver necrosis. A cetaminophen, a widely used analgesic, is one of the most commonly overdosed pharmaceuticals. 1 Overdose leads to liver necrosis caused by the electrophilic metabolite N-acetyl-p-benzoquinoneimine (NAPQI), which is generated via oxidation of acetaminophen (APAP) by a microsomal cytochrome P450 containing mixed-function oxidase system. 2 Subsequent detoxication of NAPQI by cellular glutathione leads to depletion of glutathione/glutathione-disulfide (GSHϩGSSG) followed by NAPQI accumulation and induction of necrosis due to protein arylation and severe oxidative stress. 2,3 Nuclear accumulation of Ca 2ϩ and DNA damage have been described to occur during APAPinduced cytotoxicity of murine hepatocytes in vitro and in vivo. 4-6 DNA damage seems to be an important event, because APAP toxicity was prevented by known inhibitors of Ca 2ϩ -dependent endonucleases, including Ca 2ϩ -chelators such as aurintricarboxylic acid, glycol ether diamine tetra-acetic acid, and the Ca 2ϩ -calmodulin antagonist chlorpromazine. 5,7,8 However, the nucleases involved in APAP-induced DNA damage have not yet been identified.Deoxyribonuclease 1 (DNASE1), a Ca 2ϩ /Mg 2ϩ -dependent secreted endonuclease with a pH optimum of approximately 7.5, hydrolyzes double-stranded DNA generating 5Ј-phospho-tri-and/or tetra-oligonucleotides. 9,10 DNASE1 gene expression has been demonstrated in a number of different organs of the urogenital and ...

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“…3B, arrow 7). Furthermore, immunohistochemistry demonstrated upregulation of the proliferation marker pKi-67 22 (data not shown).…”

Section: Quantification Of Apap-induced Liver Necrosis Inmentioning

confidence: 87%

Deoxyribonuclease 1 aggravates acetaminophen-induced liver necrosis in male CD-1 mice

et al. 2006

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“…A recent study showed that Ki-67 played a role in the disintegration and reformation of nucleolus, and thereby in entry into and exit from the Mphase of the cell cycle depending on cyclin B1 expression. 38 Either loss of Rb or p16, or overexpression of cyclin D1 correlated with an increased proliferation fraction in some tumors, 17,33 while no such correlation was seen in others. 39,40 Significantly higher Ki-67 LI was observed in Rb-negative than in Rbpositive tumors within the overall tumors in the present study.…”

Section: Discussionmentioning

confidence: 99%

Divergent cyclin B1 expression and Rb/p16/cyclin D1 pathway aberrations among pulmonary neuroendocrine tumors

et al. 2004

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A total of 111 pulmonary neuroendocrine tumors comprising 13 typical carcinoids, five atypical carcinoids, 44 large-cell neuroendocrine carcinomas and 49 small-cell carcinomas were immunohistochemically studied for dysregulated cyclin B1 expression and disruption of the Rb/p16/cyclin D1 pathway (Rb pathway), and the results were correlated with tumor proliferation activity and clinical outcome. Overexpression of cyclins B1 and D1, respectively, was detected in no and 15% typical carcinoids, 20 and 20% atypical carcinoids, 84 and 32% large-cell neuroendocrine carcinomas, 84 and 10% small-cell carcinomas. Loss of Rb and p16 expression, respectively, was observed in no and 14% typical carcinoids, no and 40% atypical carcinoids, 49 and 18% largecell neuroendocrine carcinomas, 84 and 8% small-cell carcinomas. In summary, 29% typical carcinoids, 20% atypical carcinoids, 78% large-cell neuroendocrine carcinomas and 93% small-cell carcinomas had Rb pathway aberrations. Rb pathway aberration was mostly attributed to Rb loss in small-cell carcinomas, while p16 loss and/or cyclin D1 overexpression besides Rb loss also played an important role in large-cell neuroendocrine carcinomas, while cyclin D1 overexpression was the only cause of Rb pathway aberration in carcinoid tumors. Thus, both cyclin B1-associated G2/M arrest and Rb-mediated G1 arrest are consistently compromised in highgrade large-cell neuroendocrine carcinoma and small-cell carcinoma, but are generally intact or occasionally altered in carcinoid tumor; the mechanisms involved in Rb pathway aberration among the tumor categories are different, reflecting a genetic divergence among the individual tumor categories. Cyclin B1 expression closely correlated with the Ki-67 labeling index either in the individual tumor categories or overall tumors (Po0.0001, r ¼ 0.742), suggesting that cyclin B1 is one of the key factors regulating cell proliferation in pulmonary neuroendocrine tumors. Neither cyclins B1 and D1, Rb, p16, nor Ki-67 correlated with patient survival in individual tumor categories, suggesting that the prognostic significance of these factors is tumor-type specific.

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“…The Ki-67 antigen is present during G 1, S, G2, and M phases, but not in G0 (11). The Ki-67 antigen may play a role in nucleolus organization during the cell cycle (22) and is necessary for nuclear proliferation (8). Cardiac myocytes were dried on Superfrost Plus slides and postfixed in cold acetone for 30 min.…”

Section: Myocyte Analysismentioning

confidence: 99%

Sequential growth of fetal sheep cardiac myocytes in response to simultaneous arterial and venous hypertension

Jonker

Faber

Anderson³

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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Jonker SS, Faber JJ, Anderson DF, Thornburg KL, Louey S, Giraud GD. Sequential growth of fetal sheep cardiac myocytes in response to simultaneous arterial and venous hypertension. Am J Physiol Regul Integr Comp Physiol 292: R913-R919, 2007. First published October 5, 2006; doi:10.1152/ajpregu.00484.2006.-While the fetal heart grows by myocyte enlargement and proliferation, myocytes lose their capacity for proliferation in the perinatal period after terminal differentiation. The relationship between myocyte enlargement, proliferation, and terminal differentiation has not been studied under conditions of combined arterial and venous hypertension, as occurs in some clinical conditions. We hypothesize that fetal arterial and venous hypertension initially leads to cardiomyocyte proliferation, followed by myocyte enlargement. Two groups of fetal sheep received intravascular plasma infusions for 4 or 8 days (from 130 days gestation) to increase vascular pressures. Fetal hearts were arrested in diastole and dissociated. Myocyte size, terminal differentiation (%binucleation), and cell cycle activity cells as a % of mononucleated myocytes) were measured. We found that chronic plasma infusion greatly increased venous and arterial pressures. Heart (but not body) weights were ϳ30% greater in hypertensive fetuses than controls. The incidence of cell cycle activity doubled in hypertensive fetuses compared with controls. After 4 days of hypertension, myocytes were (ϳ11%) longer, but only after 8 days were they wider (ϳ12%). After 8 days, %binucleation was ϳ50% greater in hypertensive fetuses. We observed two phases of cardiomyocyte growth and maturation in response to fetal arterial and venous hypertension. In the early phase, the incidence of cell cycle activity increased and myocytes elongated. In the later phase, the incidence of cell cycle activity remained elevated, %binucleation increased, and cross sections were greater. This study highlights unique fetal adaptations of the myocardium and the importance of experimental duration when interpreting fetal cardiac growth data.hypertrophy; hyperplasia; terminal differentiation; cardiomyocyte THE FETAL HEART GROWS BY PROLIFERATION and enlargement of cardiac myocytes (23). Among mammals, proliferative growth of cardiac myocytes ceases at or soon after birth through a process known as terminal differentiation (18). Thereafter, the postnatal heart grows almost exclusively by cellular enlargement. In the fetal sheep, as in many other species, terminal differentiation is marked by the appearance of two nuclei in cardiac myocytes that were formerly mononucleated. The rate of proliferation during intrauterine life and the occurrence of terminal differentiation in the perinatal period together determine the maximum number of myocytes in the heart for life.Intrauterine conditions affect cardiac myocyte proliferation, enlargement, and terminal differentiation, but myocyte responses to abnormal conditions depend on the level of maturity of the heart. Increased systolic or diastolic hemo...

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The proliferation marker pKi‐67 organizes the nucleolus during the cell cycle depending on Ran and cyclin B

Cited by 37 publications

References 52 publications

Deoxyribonuclease 1 aggravates acetaminophen-induced liver necrosis in male CD-1 mice

Deoxyribonuclease 1 aggravates acetaminophen-induced liver necrosis in male CD-1 mice

Divergent cyclin B1 expression and Rb/p16/cyclin D1 pathway aberrations among pulmonary neuroendocrine tumors

Sequential growth of fetal sheep cardiac myocytes in response to simultaneous arterial and venous hypertension

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