Effects of 15-deoxy-Delta12, 14 prostaglandin J2 and ciglitazone on human cancer cell cycle progression and death: the role of PPARgamma.

The role of PPARgamma in ciglitazone and 15-d PGJ(2)-induced apoptosis and cell cycle arrest of Jurkat (before and after PPARgamma gene silencing), U937 (express high levels of PPARgamma) and HeLa (that express very low levels of PPARgamma) cells was investigated. PPARgamma gene silencing, per se, induced a G2/M cell arrest, loss of membrane integrity and DNA fragmentation of Jurkat cells, indicating that PPARgamma is important for this cell survival and proliferation. Ciglitazone-induced apoptosis was abolished after knockdown of PPARgamma suggesting a PPARgamma-dependent pro-apoptotic effect. However, ciglitazone treatment was toxic for U937 and HeLa cells regardless of the presence of PPARgamma. This treatment did not change the cell cycle distribution corroborating with a PPARgamma-independent mechanism. On the other hand, 15-d PGJ(2) induced apoptosis of the three cancer cell lines regardless of the expression of PPARgamma. These results suggest that PPARgamma plays an important role for death of malignant T lymphocytes (Jurkat cells) and PPARgamma agonists exert their effects through PPARgamma-dependent and -independent mechanisms depending on the drug and the cell type.

Beneficial Role of Low-Intensity Laser Irradiation on Neural ß-tubulin III Protein Expression in Human Bone Marrow Multipotent Mesenchymal Stromal Cells.

The purpose of the present study was to evaluate the neural protein expression pattern of human multipotent mesenchymal stromal cells (hMSCs) treated with forskolin (free-form/FF). The study investigated forskolin's capacity to enhance intracellular levels of cyclic adenosine monophosphate (cAMP) by activating adenylate cyclase and probably by inducing neuron-like cells in vitro. In addition, because nanotechnology is a growing field of tissue engineering, we also assessed the action of a new system called the nanostructured-forskolin (NF) to examine the improvement of drug delivery. Afterwards, the cells were submitted to low-level laser irradiation to evaluate possible photobiostimulatory effects. Investigations using the immunofluorescence by confocal microscopy and Western blot methods revealed the expression of the neuronal marker ß-tubulin III. Fluorescence intensity quantification analysis using INCell Analyzer System for ß-tubulin III was used to examine significant differences. The results showed that after low-level laser irradiation exposure, there was a tendency to increase the ß-tubulin III expression in all groups, as expected in the photobiostimulation process. Notably, this process induced for irradiation was more pronounced in irradiated nanoforskolin cells (INF) compared to non-irradiated free-forskolin control cells (NFFC). However, there was also an increase in ß-tubulin III protein expression in the groups: irradiated nanocontrol cells (INC) compared to non-irradiated free-forskolin control cells (NFF) and after treatment with non-irradiated free-forskolin (NFF) and non-irradiated nanoforskolin (NNFC). We concluded that the methods using low-level laser irradiation and/or nanoparticles showed an up-regulation of neural-protein expression in hMSCs that could be used to facilitate cellular therapy protocols in the near future.

Tumor necrosis factor-á signaling cascades in apoptosis, necrosis, necroptosis and cell proliferation

Tumor necrosis factor-á (TNF-á) is a multifunctional cytokine involved in host defense, inflammation, apoptosis, autoimmunity, organogenesis and lymphoid microarchitecture. Many of these activities may be explained by the ability of this cytokine to induce distinct signal transduction pathways that recruit regulatory proteins involved in differentiation, cell death or cell proliferation. In this review, we discuss the contribution of caspases -3, -6, -7 and -8, and of cyclin-dependent kinases (CDKs), cyclin B and cyclin-dependent kinase inhibitors (CKI p21 and p27), as well as retinoblastoma tumor suppressor in the signaling cascades triggered by TNF-á to induce apoptosis, necrosis and cellular proliferation in the murine cell lines NIH3T3 and WEHI-164 and the human cervical carcinoma cell line HeLa-S3. Based on the findings of many literature reports and our own data, we discussed a model in which caspases are continuously activated throughout the cell cycle and kept at a critical threshold level by IAP (inhibitor of apoptosis) antagonists. Following the release of Smac/Diablo and HtrA2/OMI from mitochondria in response to diverse stimuli, this threshold is overcome and results in amplified caspase activation and cell death. An alternative, caspase-independent mechanism of cell death is induced in NIH3T3 fi broblasts by a combination of TNF and the pan-caspase inhibitor z-VADfmk. This cell death phenotype, known as necroptosis, displays some morphological features of apoptosis and necrosis. Although caspases are critical regulators of the TNF signaling pathway during cellular life and death, the mechanisms involved in the fine regulation of their dual effects remain to be fully elucidated.