Troglitazone Induced Apoptosis via PPARγ Activated POX-induced ROS Formation in HT29 Cells

Objective In order to investigate the potential mechanisms in troglitazone-induced apoptosis in HT29 cells,the effects of PPARγ and POX-induced ROS were explored.Methods [3-（4,5）-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide （MTT） assay,Annexin V and PI staining using FACS,plasmid transfection,ROS formation detected by DCFH staining,RNA interference,RT-PCR RT-QPCR,and Western blotting analyses were employed to investigate the apoptotic effect of troglitazone and the potential role of PPARγ pathway and POX-induced ROS formation in HT29 cells.Results Troglitazone was found to inhibit the growth of HT29 cells by induction of apoptosis.During this process,mitochondria related pathways including ROS formation,POX expression and cytochrome c release increased,which were inhibited by pretreatment with GW9662,a specific antagonist of PPARγ.These results illustrated that POX upregulation and ROS formation in apoptosis induced by troglitazone was modulated in PPARγ-dependent pattern.Furthermore,the inhibition of ROS and apoptosis after POX siRNA used in troglitazone-treated HT29 cells indicated that POX be essential in the ROS formation and PPARγ-dependent apoptosis induced by troglitazone.Conclusion The findings from this study showed that troglitazone-induced apoptosis was mediated by POX-induced ROS formation,at least partly,via PPARγ activation.

Study on the structure and composition of aortic valve calcific deposits:Etiological aspects

The structures and chemical compositions of valve calcific deposits were investigated. The deposits was chosen arbitrarily and subjected to chemical analysis, observation with scanning microscope, semi-quantitative determination of Ca, Mg, Na, K, P and C elements by energy dispersive X-ray, X-ray diffraction and Fourier transform infrared spectroscopy carried out. These deposits were found to have non-uniform internal structures composed of layers of a structureless aspidinic inorganic material, substantial amounts of voluminous organic material and in a few samples small spheres were also present. Two groups of deposits with distinctly different chemical compositions were identified: one group with a low Ca/P molar ratio (1.59) and the other group with a high (1.82) Ca/P molar ratio. The deposits belonging to the group with a low Ca/P molar ratio contain higher concentration of magnesium and consist of increased amount of amorphous calcium phosphate. The deposits with a high Ca/P molar ratio contain low concentration of magnesium and consist predominantly of carbonated hydroxyapatite. The inorganic material was identified as a poorly crystalline carbonate hydroxyapatite containing molecular water of the average formula Ca9.1Mg0.4(Na,K)(PO4)5.8(CO3)0.3(OH)2. The actual chemical composition of the apatitic solid phase varies not only from deposit to deposit but also within the same deposit. The non-uniform internal structure of the deposits, the occasional presence of spherical particles and the variable point composition of the individual deposits indicate that their formation did not proceed under more or less constant conditions.

Cdk2 acts upstream of mitochondrial permeability transition during paclitaxel-induced apoptosis

Sequential activation of cyclin-dependent kinases(Cdks)controls mammalian cell cycle.Here we demonstrate that the upregulation of cyclin-dependent kinase 2(Cdk2)activity coincides with the loss of mitochondrial membrane potential(MMP)in paclitaxel-induced apoptosis.Ectopic expression of the dominant negative Cdk2(Cdk2-dn)and a specific Cdk2 inhibitor,p21WAF1/CIP1,effectively suppresses the loss of MMP,the release of cytochrome c,and subsequent activation of caspase-3 in paclitaxel-treated cells.Whereas forced activation of Cdk2 by overexpression of cyclin A dramatically promotes these events.We further show that Cdk2 activation status does not interfere with a procedure that lies downstream of cytochrome c release induced by Bax protein.These findings suggest that Cdk2 kinase can regulate apoptosis at earlier stages than mitochondrial permeability transition and cytochrome c release.