Regulation of cell death in the lymphoid system by Bcl-2 family proteins

Innovation of the protocol for the application of cryolipolysis: Effects and mechanisms of action

BACKGROUND

In recent years, aesthetic procedures aiming at body remodeling and have grown exponentially. Cryolipolysis (CLL) has stood out as a noninvasive resource that acts directly on the subcutaneous adipose tissue promoting a significant reduction of adipose tissue through of cooling that could lead to the crystallization cytoplasmic lipids, loss of cellular integrity, apoptosis/necrosis of adipocytes, and local inflammation, producing selective loss of adipose tissue. Thus, the objective of the present study was to evaluate the effects of a specific technique of CLL application on the inflammatory reactions of the target tissue in different post-application times.

METHODS

This is a randomized, blind clinical study that evaluated the tissue sample of six patients after 45, 60, and 90 days of an innovative protocol for the application of CLL, with samples collected through abdominoplasty surgeries. The samples were evaluated by immunohistochemical analyses of several markers.

RESULTS

A significantly greater increase in fibroblasts was observed at 45 days and greater phagocytic action at 60 days. Regarding the apoptosis process, the expression of caspase 3 and cleaved caspase 3 markers varied at different times, with cleaved caspase 3 being higher at 45 and 90 days after CLL application.

CONCLUSION

The protocol of the CLL presented in this study was able to induce inflammatory responses in addition to confirming the selective apoptotic action at the different times studied.

Development of Conformational Antibodies to Detect Bcl-xL's Amyloid Aggregates in Metal-Induced Apoptotic Neuroblastoma Cells

Bcl-xL, a member of the Bcl-2 family, is a pro-survival protein involved in apoptosis regulation. We have previously reported the ability of Bcl-xL to form various types of fibers, from native to amyloid conformations. Here, we have mimicked the effect of apoptosis-induced caspase activity on Bcl-xL by limited proteolysis using trypsin. We show that cleaved Bcl-xL (ΔN-Bcl-xL) forms fibers that exhibit the features of amyloid structures (BclxLcf37). Moreover, three monoclonal antibodies (mAbs), produced by mouse immunization and directed against ΔN-Bcl-xL or Bcl-xL fibers, were selected and characterized. Our results show that these mAbs specifically target ΔN-Bcl-xL in amyloid fibers in vitro. Upon metal-stress-induced apoptosis, these mAbs are able to detect the presence of Bcl-xL in amyloid aggregates in neuroblastoma SH-SY5Y cell lines. In conclusion, these specific mAbs directed against amyloidogenic conformations of Bcl-xL constitute promising tools for studying, in vitro and in cellulo, the contribution of Bcl-xL in apoptosis. These mAbs may further help in developing new diagnostics and therapies, considering Bcl-xL as a strategic target for treating brain lesions relevant to stroke and neurodegenerative diseases.

Alpha-Tocotrienol Prevents Oxidative Stress-Mediated Post-Translational Cleavage of Bcl-xL in Primary Hippocampal Neurons

B-cell lymphoma-extra large (Bcl-xL) is an anti-apoptotic member of the Bcl2 family of proteins, which supports neurite outgrowth and neurotransmission by improving mitochondrial function. During excitotoxic stimulation, however, Bcl-xL undergoes post-translational cleavage to ∆N-Bcl-xL, and accumulation of ∆N-Bcl-xL causes mitochondrial dysfunction and neuronal death. In this study, we hypothesized that the generation of reactive oxygen species (ROS) during excitotoxicity leads to formation of ∆N-Bcl-xL. We further proposed that the application of an antioxidant with neuroprotective properties such as α-tocotrienol (TCT) will prevent ∆N-Bcl-xL-induced mitochondrial dysfunction via its antioxidant properties. Primary hippocampal neurons were treated with α-TCT, glutamate, or a combination of both. Glutamate challenge significantly increased cytosolic and mitochondrial ROS and ∆N-Bcl-xL levels. ∆N-Bcl-xL accumulation was accompanied by intracellular ATP depletion, loss of mitochondrial membrane potential, and cell death. α-TCT prevented loss of mitochondrial membrane potential in hippocampal neurons overexpressing ∆N-Bcl-xL, suggesting that ∆N-Bcl-xL caused the loss of mitochondrial function under excitotoxic conditions. Our data suggest that production of ROS is an important cause of ∆N-Bcl-xL formation and that preventing ROS production may be an effective strategy to prevent ∆N-Bcl-xL-mediated mitochondrial dysfunction and thus promote neuronal survival.

Inhibition of Bcl-xL prevents pro-death actions of ΔN-Bcl-xL at the mitochondrial inner membrane during glutamate excitotoxicity

ABT-737 is a pharmacological inhibitor of the anti-apoptotic activity of B-cell lymphoma-extra large (Bcl-xL) protein; it promotes apoptosis of cancer cells by occupying the BH3-binding pocket. We have shown previously that ABT-737 lowers cell metabolic efficiency by inhibiting ATP synthase activity. However, we also found that ABT-737 protects rodent brain from ischemic injury in vivo by inhibiting formation of the pro-apoptotic, cleaved form of Bcl-xL, ΔN-Bcl-xL. We now report that a high concentration of ABT-737 (1 μM), or a more selective Bcl-xL inhibitor WEHI-539 (5 μM) enhances glutamate-induced neurotoxicity while a low concentration of ABT-737 (10 nM) or WEHI-539 (10 nM) is neuroprotective. High ABT-737 markedly increased ΔN-Bcl-xL formation, aggravated glutamate-induced death and resulted in the loss of mitochondrial membrane potential and decline in ATP production. Although the usual cause of death by ABT-737 is thought to be related to activation of Bax at the outer mitochondrial membrane due to sequestration of Bcl-xL, we now find that low ABT-737 not only prevents Bax activation, but it also inhibits the decline in mitochondrial potential produced by glutamate toxicity or by direct application of ΔN-Bcl-xL to mitochondria. Loss of mitochondrial inner membrane potential is also prevented by cyclosporine A, implicating the mitochondrial permeability transition pore in death aggravated by ΔN-Bcl-xL. In keeping with this, we find that glutamate/ΔN-Bcl-xL-induced neuronal death is attenuated by depletion of the ATP synthase c-subunit. C-subunit depletion prevented depolarization of mitochondrial membranes in ΔN-Bcl-xL expressing cells and substantially prevented the morphological change in neurites associated with glutamate/ΔN-Bcl-xL insult. Our findings suggest that low ABT-737 or WEHI-539 promotes survival during glutamate toxicity by preventing the effect of ΔN-Bcl-xL on mitochondrial inner membrane depolarization, highlighting ΔN-Bcl-xL as an important therapeutic target in injured brain.

ΔN-Bcl-xL, a therapeutic target for neuroprotection

The B-cell lymphoma-extra large (Bcl-xL) is a mitochondrial anti-apoptotic protein that plays a role in neuroprotection. However, during excitotoxic stimulation, Bcl-xL undergoes caspase-dependent cleavage and produces a fragmented form, ΔN-Bcl-xL. Accumulation of ΔN-Bcl-xL is associated with mitochondrial dysfunction and neuronal death. Therefore, strategies to inhibit the activity or formation of ΔN-Bcl-xL protect the brain against excitotoxic injuries. Our team found that the pharmacological inhibitor ABT-737 exerts dose dependent effects in primary neurons. When primary hippocampal neurons were treated with 1 μM ABT-737, glutamate-mediated mitochondrial damage and neuronal death were exacerbated, whereas 10 nM ABT-737, a 100-fold lower concentration, protected mitochondrial function and enhanced neuronal viability against glutamate toxicity. In addition, we suggested acute vs. prolonged formation of ΔN-Bcl-xL may have different effects on mitochondrial or neuronal functions. Unlike acute production of ΔN-Bcl-xL by glutamate, overexpression of ΔN-Bcl-xL did not cause drastic changes in neuronal viability. We predicted that neurons undergo adaptation and may activate altered metabolism to compensate for ΔN-Bcl-xL-mediated mitochondrial dysfunction. Although the detailed mechanism of ABT-mediated neurotoxicity neuroprotection is still unclear, our study shows that the mitochondrial membrane protein ΔN-Bcl-xL is a central target for interventions.

Chosen factors of T and B cell apoptosis in hypertrophic adenoid in children with otitis media with effusion

Evaluation of lymphocyte homeostasis within the chronically inflamed adenoid, closely related to the functioning of the immune system, may have a role in qualifying children for adenoidectomy. Apoptosis is a major process maintaining balance between tonsillar lymphocytes. The Fas receptor and Bcl-2 protein family which show pro-apoptotic and anti-apoptotic actions are of particular significance in apoptosis induction. Adenoid excised due to hypertrophy with or without chronic otitis media with effusion was used as study material. Flow cytometry was used to assess the percentages of apoptotic lymphocytes and CD4(+), CD8(+), CD19(+) cells with CD95(+) antigen and Bcl-2 protein in the group of children who underwent adenoidectomy due to adenoid hypertrophy and accompanying otitis media with effusion. The percentages of CD4(+)Bcl-2(+), CD8(+)Bcl-2(+) and CD19(+)Bcl-2(+) lymphocytes in the group of children with adenoid hypertrophy and acute otitis media were lower as compared to the reference group. However, the percentages of CD4(+), CD8(+) and CD19(+) cells with CD95(+) antigen were higher in the study group comparing to the reference group. The tendency of reduced percentages of T and B lymphocytes with Bcl-2 expression and elevated percentages of these cells with CD95(+) expression within the adenoid may reflect local immunity disorders.

Characterization of the effects of Bcl-2 and Bcl-xl deletion mutant expression in cell lines used for antibody production

Strategies to maximize monoclonal antibody (MAb) yields by in vitro production methods entail that hybridoma cells be maintained at high density. Approaches to increase culture density and antibody yields from hybridomas by inhibiting apoptosis through over-expression of exogenous Bcl-2 family genes have produced variable results. In order to determine if expression of mutant forms of Bcl-2 and Bcl-xl could increase viable culture densities and batch MAb yields when compared to parental cell lines, recombinant delta loop deletion mutant of these apoptotic inhibitory genes were expressed in a myeloma and two hybridoma cell lines. Expression of either Bcl-2-delta or Bcl-xl-delta in P3x63Ag8.653 myeloma cells did not significantly increase viable cell densities in cultures over time. However, the rapid post-peak decline in viable cell density was significantly reduced in Bcl-xl-delta-expressing hybridoma cell lines 552 and 7.16.4 and in Bcl-2-expressing hybridoma 7.16.4. Significant increases in MAb yield were only observed in cultures of Bcl-xl-delta-expressing hybridoma 7.16.4. Annexin staining in hybridoma 7.16.4 confirmed that apoptosis was the primary means of cell death in this cell line, and expression of Bcl-2-delta and Bcl-xl-delta inhibited programmed cell death. These results suggest that cell viability in cultures can be improved by transfection and selection of hybridomas that express delta loop deletion mutant forms of Bcl-2 family genes; however, improvements in MAb yields are dependent upon the genetic background of each manipulated cell line.