The Involvement of Bax in Zinc-Induced Mitochondrial Apoptogenesis in Malignant Prostate Cells

<p>Abstract</p> <p>Background</p> <p>The development and progression of prostate cancer requires the transformation of normal zinc-accumulating epithelial cells to malignant cells that have lost the ability to accumulate zinc. This metabolic transformation is essential so that the tumor suppressive effects of zinc can be eliminated and the malignant process can proceed. One of the major effects of zinc is its prevention of prostate cell growth by its induction of apoptosis. The accumulation of cellular zinc has a direct effect on the mitochondria that results in the release of cytochrome c, which initiates the caspase cascade that leads to apoptosis. This effect is associated with the mitochondrial pore-forming process, but the mechanism by which zinc induces the release of cytochrome c and induces mitochondrial apoptogenesis has not been resolved. The present report provides for the first time information that implicates Bax in the zinc induction of mitochondrial apoptogenesis.</p> <p>Results</p> <p>The effects of zinc treatment on the Bax levels of PC-3 cells and on the mitochondria were determined. The exposure of isolated mitochondria to zinc results in an increase in membrane bound Bax, which is due to the mitochondrial insertion of endogenous resident Bax. The mitochondrial Bax/Bcl-2 ratio is increased by zinc treatment. Zinc treatment of PC-3 cells also increases the mitochondrial level of Bax. In addition, zinc treatment increases the cellular level of Bax and the cellular Bax/Bcl2 ratio. Down regulation of Bax in PC-3 cells eliminates the zinc induction of apoptosis. The increase in cellular Bax level appears to involve zinc induction of Bax gene expression.</p> <p>Conclusion</p> <p>This report extends and confirms that physiological levels of zinc induce apoptosis in prostate cells. The study provides evidence that zinc is directly involved in facilitating a Bax-associated pore formation process that initiates mitochondrial apoptogenesis. This is enhanced by an additional effect of zinc on increasing the cellular level of Bax. To avoid the anti-tumor apoptogenic effects of zinc, the malignant cells in prostate cancer posses genetic/metabolic adaptations that prevent the cellular accumulation of zinc.</p

Regional remodeling strain and its association with myocardial apoptosis after myocardial infarction in an ovine model

ObjectiveProgressive left ventricular remodeling after myocardial infarction has been viewed as an important contributor to progressive heart failure. The objective of this study was to investigate the relationship between myocardial apoptosis and strain during progressive cardiac remodeling.MethodsBefore creation of an anterolateral left ventricular infarction by ligation of diagonal arteries, 16 sonomicrometry transducers were placed in the left ventricular free wall of 8 sheep to assess regional deformation in the infarct, adjacent, and normally perfused remote myocardial regions over 8 weeks' duration. Hemodynamic, echocardiographic and sonomicrometric data were collected before infarction and then 30 minutes and 2, 6, and 8 weeks after infarction. At the end of the study, regional myocardial tissues were collected for apoptotic signaling proteins.ResultsAt terminal study, an increase in left ventricular end-diastolic pressure of 8.1 ± 0.1 mm Hg, a decrease in ejection fraction from 54.19% ± 5.68% to 30.55% ± 2.72%, and an end-diastolic volume increase of 46.08 ± 5.02 mL as compared with the preinfarct values were observed. The fractional contraction at terminal study correlated with the relative abundance of apoptotic protein expressions: cytochrome c (r2 = 0.02, P < .05), mitochondrial Bax (r2 = 0.27, P < .05), caspase-3 (r2 = 0.31, P < .05), and poly (adenosine diphosphate–ribose) polymerase (r2 = 0.30, P < .05). These myocardial apoptotic activities also correlated with remodeling strain: cytochrome c (r2 = 0.02, P < .05), mitochondrial Bax (r2 = 0.28, P < .05), caspase-3 (r2 = 0.43, P < .05), and poly (adenosine diphosphate–ribose) polymerase (r2 = 0.37, P < .05).ConclusionIncrease in regional remodeling strain led to an increase in myocardial apoptosis and regional contractile dysfunction in heart failure

The cells were treated with medium supplemented with 15 μM zinc for 180 minutes versus no zinc treatment

<p><b>Copyright information:</b></p><p>Taken from "The Involvement of Bax in Zinc-Induced Mitochondrial Apoptogenesis in Malignant Prostate Cells"</p><p>http://www.molecular-cancer.com/content/7/1/25</p><p>Molecular Cancer 2008;7():25-25.</p><p>Published online 10 Mar 2008</p><p>PMCID:PMC2329666.</p><p></p

PC-3 cells were cultured in serum-free medium for 24 h and then treated with or without cycloheximide (CHX, 5 μg/ml) for 1 hour prior to zinc (15 μM) exposure for 6 hours

<p><b>Copyright information:</b></p><p>Taken from "The Involvement of Bax in Zinc-Induced Mitochondrial Apoptogenesis in Malignant Prostate Cells"</p><p>http://www.molecular-cancer.com/content/7/1/25</p><p>Molecular Cancer 2008;7():25-25.</p><p>Published online 10 Mar 2008</p><p>PMCID:PMC2329666.</p><p></p

PC-3 cells were transfected with Bax siRNA or with empty vector and cultured for 72 hours; followed by treatment of the cells with 15 μM zinc for 24 hours

<p><b>Copyright information:</b></p><p>Taken from "The Involvement of Bax in Zinc-Induced Mitochondrial Apoptogenesis in Malignant Prostate Cells"</p><p>http://www.molecular-cancer.com/content/7/1/25</p><p>Molecular Cancer 2008;7():25-25.</p><p>Published online 10 Mar 2008</p><p>PMCID:PMC2329666.</p><p></p

The isolated mitochondria were exposed to medium supplemented with 15 μM zinc for 15 minutes or with unsupplemented medium (control)

<p><b>Copyright information:</b></p><p>Taken from "The Involvement of Bax in Zinc-Induced Mitochondrial Apoptogenesis in Malignant Prostate Cells"</p><p>http://www.molecular-cancer.com/content/7/1/25</p><p>Molecular Cancer 2008;7():25-25.</p><p>Published online 10 Mar 2008</p><p>PMCID:PMC2329666.</p><p></p

Strain-related regional alterations of calcium-handling proteins in myocardial remodeling

BackgroundCardiac remodeling has been shown to have deleterious effects at both the global and local levels. The objective of this study is to investigate the role of strain in the initiation of structural and functional changes of myocardial tissue and its relation to alteration of calcium-handling proteins during cardiac remodeling after myocardial infarction.MethodsSixteen sonomicrometry transducers were placed in the left ventricular free wall of 9 sheep to measure the regional strain in the infarct, adjacent, and remote myocardial regions. Hemodynamic, echocardiographic, and sonomicrometry data were collected before myocardial infarction, after infarction, and 2, 6, and 8 weeks after infarction. Regional myocardial tissues were collected for calcium-handling proteins at the end study.ResultsAt time of termination, end-systolic strains in 3 regionally distinct zones (remote, adjacent, and infarct) of myocardium were measured to be −14.65 ± 1.13, −5.11 ± 0.60 (P ≤ .05), and 0.92 ± 0.56 (P ≤ .05), respectively. The regional end-systolic strain correlated strongly with the abundance of 2 major calcium-handling proteins: sarcoplasmic reticulum Ca2+ adenosine triphosphatase subtype 2a (r2 = 0.68, P ≤ .05) and phospholamban (r2 = 0.50, P ≤ .05). A lesser degree of correlation was observed between the systolic strain and the abundance of sodium/calcium exchanger type 1 protein (r2 = 0.17, P ≤ .05).ConclusionsRegional strain differences can be defined in the different myocardial regions during postinfarction cardiac remodeling. These differences in regional strain drive regionally distinct alterations in calcium-handling protein expression

Mesenchymal Stem Cell Transplantation Improves Regional Cardiac Remodeling Following Ovine Infarction

Progressive cardiac remodeling, including the myopathic process in the adjacent zone following myocardial infarction (MI), contributes greatly to the development of cardiac failure. Cardiomyoplasty using bone marrow-derived mesenchymal stem cells (MSCs) has been demonstrated to protect cardiomyocytes and/or repair damaged myocardium, leading to improved cardiac performance, but the therapeutic effects on cardiac remodeling are still under investigation. Here, we tested the hypothesis that MSCs could improve the pathological remodeling of the adjacent myocardium abutting the infarct. Allogeneic ovine MSCs were transplanted into the adjacent zone by intracardiac injection 4 hours after infarction. Results showed that remodeling and contractile strain alteration were reduced in the adjacent zone of the MSC-treated group. Cardiomyocyte hypertrophy was significantly attenuated with the normalization of the hypertrophy-related signaling proteins phosphatidylinositol 3-kinase α (PI3Kα), PI3Kγ, extracellular signal-regulated kinase (ERK), and phosphorylated ERK (p-ERK) in the adjacent zone of the MSC-treated group versus the MI-alone group. Moreover, the imbalance of the calcium-handling proteins sarcoplasmic reticulum Ca(2+) adenosine triphosphatase (SERCA2a), phospholamban (PLB), and sodium/calcium exchanger type 1 (NCX-1) induced by MI was prevented by MSC transplantation, and more strikingly, the activity of SERCA2a and uptake of calcium were improved. In addition, the upregulation of the proapoptotic protein Bcl-xL/Bcl-2-associated death promoter (BAD) was normalized, as was phospho-Akt expression; there was less fibrosis, as revealed by staining for collagen; and the apoptosis of cardiomyocytes was significantly inhibited in the adjacent zone by MSC transplantation. Collectively, these data demonstrate that MSC implantation improved the remodeling in the region adjacent to the infarct after cardiac infarction in the ovine infarction model

A Novel Large Animal Model of Acute Respiratory Distress Syndrome Induced by Mitochondrial Products

Objective: We aimed to create a reproducible lung injury model utilizing injection of mitochondrial damage-associated molecular products. Our goal was to characterize the pathophysiologic response to damage-associated molecular pattern mediated organ injury. Summary Background Data: There remain significant gaps in our understanding of acute respiratory distress syndrome, in part due to the lack of clinically applicable animal models of this disease. Animal models of noninfectious, tissue damage-induced lung injury are needed to understand the signals and responses associated with this injury. Methods: Ten pigs (35-45 kg) received an intravenous dose of disrupted mitochondrial products and were followed for 6 hours under general anesthesia. These animals were compared to a control group (n = 5) and a model of lung injury induced by bacterial products (lipopolysaccharide n = 5). Results: Heart rate and temperature were significantly elevated in the mitochondrial product (204 +/- 12 and 41 +/- 1) and lipopolysaccharide groups (178 +/- 18 and 42 +/- 0.5) compared with controls (100 +/- 13 and 38 +/- 0.5) (P < 0.05). Lung oxygenation (PaO2/FiO(2)) was significantly lower 6 hours after injection in the mitochondrial products and lipopolysaccharide groups compared with controls (170 +/- 39, 196 +/- 27, and 564 +/- 75mmHgrespectively, P = 0.001). Lung injury scoring of histological sections was significantly worse in mitochondrial and lipopolysaccharide groups compared with controls (mitochondrial- 64 +/- 6, lipopolysaccharide-54 +/- 8, control-14 +/- 1.5, P = 0.002). Conclusions: Our data demonstrated that the presence of mitochondrial products in the circulation leads to systemic inflammatory response and lung injury. In its acute phase lung injury induced by tissue or bacterial products is clinically indistinguishable