Role of recombinant mitogen-activated protein kinases JNK and p38 in the regulation of apoptosis in blood mononuclear cells under conditions of oxidative stress in vitro

Apoptosis: Activation and Inhibition in Health and Disease

There are many types of cell death, each involving multiple and complex molecular events. Cell death can occur accidentally when exposed to extreme physical, chemical, or mechanical conditions, or it can also be regulated, which involves a genetically coded complex machinery to carry out the process. Apoptosis is an example of the latter. Apoptotic cell death can be triggered through different intracellular signalling pathways that lead to morphological changes and eventually cell death. This is a normal and biological process carried out during maturation, remodelling, growth, and development in tissues. To maintain tissue homeostasis, regulatory, and inhibitory mechanisms must control apoptosis. Paradoxically, these same pathways are utilized during infection by distinct intracellular microorganisms to evade recognition by the immune system and therefore survive, reproduce and develop. In cancer, neoplastic cells inhibit apoptosis, thus allowing their survival and increasing their capability to invade different tissues and organs. The purpose of this work is to review the generalities of the molecular mechanisms and signalling pathways involved in apoptosis induction and inhibition. Additionally, we compile the current evidence of apoptosis modulation during cancer and Leishmania infection as a model of apoptosis regulation by an intracellular microorganism.

2-Alkylsulfanyl-4(5)-aryl-5(4)-heteroarylimidazoles: An Overview on Synthetic Strategies and Biological Activity

2-Alkylsulfanyl-4(5)-aryl-5(4)-heteroarylimidazoles represent an important class of ATP-competitive protein kinase inhibitors, offering the possibility of multiple interactions with different regions of the target enzyme. The necessity of exploring the effects of diverse chemical decorations around the imidazole core prompted the design of several synthetic routes aimed at achieving both efficiency and flexibility. Additionally, the optimization of established protocols and the extensive use of transition metal-catalyzed cross-coupling reactions have been broadening the spectrum of preparative methodologies within the last decade. This review summarizes the progress in the development of synthetic strategies leading to 2-alkylsulfanyl-4(5)-aryl-5(4)-heteroarylimidazoles and 1-alkyl-2-alkylsulfanyl-4(5)-aryl-5(4)-heteroarylimidazoles and offers a glance at the biological activities of this class of compounds.

Inhibition of p38 mitogen-activated protein kinase phosphorylation decreases H₂O₂-induced apoptosis in human lens epithelial cells

BACKGROUND

Oxidative damage resulting from ROS is a known causal factor for cataractogenesis. The mitogen-activated protein kinases (MAPK) pathway plays an important role in the apoptosis of HLE cells. The purpose of this study was to investigate the role of phosphorylated p38 mitogen-activated protein kinase in H2O2-induced apoptosis in cultured human lens epithelial (HLE) cells.

METHODS

The effect of SB203580 on HLE cells treated with H2O2 was determined by various assays. Cell viability was monitored by the MTT assay. The rates of apoptosis and ROS generation were determined by flow cytometric analysis. The numbers of mitotic and apoptotic cell nuclei were determined after staining with Hoechst 33342. The protein level of phospho-p38 was measured using western blot analysis.

RESULTS

SB203580 reduced H2O2-induced cellular apoptosis and inhibited the generation of reactive oxygen species (ROS); it also delayed the progression of H2O2-induced opacification of lenses. The level of p-p38 was increased when cells were exposed to H2O2 and significantly SB203580-inhibited phosphorylation of p38. The p38MAPK pathway plays an important role in H2O2-induced apoptosis of HLE cells.

CONCLUSIONS

The study demonstrates that activation of p38MAPK plays an important role in H2O2-induced apoptosis of HLE cells. SB203580 may potentially be exploited as a useful tool for cataract prevention.

Defective nuclear translocation of stress-activated signaling in senescent diploid human fibroblasts: a possible explanation for aging-associated apoptosis resistance

In order to study the nature of aging-dependent apoptosis resistance, we compared the activation pattern of mitogen-activated protein kinases (MAPK) in response to three different stress modalities: hydrogen peroxide (H(2)O(2)), staurosporine, and thapsigargin. We observed the agonist-specific activation pattern of MAP kinases in human diploid fibroblasts (HDFs). When young HDFs were treated with PD98059, a specific inhibitor of extracellular signal-regulated kinase (ERK), H(2)O(2)-induced apoptosis was blocked, whereas staurosporine-induced apoptosis was inhibited by treatment with SB203580, a specific inhibitor of p38. In addition, the levels of anti-apoptotic protein Bcl-2 (B-cell lymphoma protein-2) were restored by PD98059 or SB239063 in cells treated with H(2)O(2) or staurosporine, respectively. We also found that inhibition of the nuclear import of p-Erk and p-p38 using wheat germ agglutinin induced apoptosis resistance in young HDF cells in response to H(2)O(2) or staurosporine. These data indicate a potential role of the nuclear translocation of apoptotic signals in the induction of apoptosis. Moreover, the nuclear translocation of activated ERK1/2 and p38 in response to H(2)O(2) or staurosporine was significantly compromised in senescent HDFs, compared with young cells. Taken together, we propose that the apoptosis resistance of senescent HDFs might be related to the defective nuclear translocation of stress-activated signals in an agonist-specific manner, which would imply the operation of an aging-dependent functional nucleo-cytoplasmic trafficking barrier.