BCL-xL, a Mitochondrial Protein Involved in Successful Aging: From C. elegans to Human Centenarians

Parthenolide improves sepsis-induced coagulopathy by inhibiting mitochondrial-mediated apoptosis in vascular endothelial cells through BRD4/BCL-xL pathway

BACKGROUND

Sepsis is a systemic inflammatory syndrome that can cause coagulation abnormalities, leading to damage in multiple organs. Vascular endothelial cells (VECs) are crucial in the development of sepsis-induced coagulopathy (SIC). The role of Parthenolide (PTL) in regulating SIC by protecting VECs remains unclear.

METHODS

The study utilized septic rats and lipopolysaccharide (LPS)-stimulated VECs to simulate a SIC model and observe the therapeutic effects of PTL. Additionally, nanotechnology was employed to produce Nano-PTL (N-PTL), to observe whether it has advantages over PTL in treating SIC.

RESULTS

PTL has been shown to mitigate lung injury in septic rats, significantly reduce tumor necrosis factor-α (TNF-α) levels, and increase survival rates. PTL treatment also enhances coagulation function, augments vascular endothelial cell (VEC) function, reduces mitochondrial fragmentation, and increases both mitochondrial oxygen consumption rate (OCR) and mitochondrial membrane potential (MMP), while inhibiting reactive oxygen species (ROS) production. By increasing BRD4/BCL-xL levels, PTL can prevent mitochondrial-mediated apoptosis in VECs, improve VEC function, and consequently ameliorate SIC. Additionally, nanotechnology-synthesized N-PTL further enhances the protective effects on VECs and coagulation function.

CONCLUSIONS

This study clarifies the therapeutic effects and mechanisms of PTL on SIC, offering new strategies and directions for the treatment of sepsis.

GATDE: A graph attention network with diffusion-enhanced protein-protein interaction for cancer classification

Cancer classification is crucial for effective patient treatment, and recent years have seen various methods emerge based on protein expression levels. However, existing methods oversimplify by assuming uniform interaction strengths and neglecting intermediate influences among proteins. Addressing these limitations, GATDE employs a graph attention network enhanced with diffusion on protein-protein interactions. By constructing a weighted protein-protein interaction network, GATDE captures the diversity of these interactions and uses a diffusion process to assess multi-hop influences between proteins. This information is subsequently incorporated into the graph attention network, resulting in precise cancer classification. Experimental results on breast cancer and pan-cancer datasets demonstrate that GATDE surpasses current leading methods. Additionally, in-depth case studies further validate the effectiveness of the diffusion process and the attention mechanism, highlighting GATDE's robustness and potential for real-world applications.

The Role of JAK/STAT Signaling Pathway and Its Downstream Influencing Factors in the Treatment of Atherosclerosis

Atherosclerosis is now widely considered to be a chronic inflammatory disease, with increasing evidence suggesting that lipid alone is not the main factor contributing to its development. Rather, atherosclerotic plaques contain a significant amount of inflammatory cells, characterized by the accumulation of monocytes and lymphocytes on the vessel wall. This suggests that inflammation may play a crucial role in the occurrence and progression of atherosclerosis. As research deepens, other pathological factors have also been found to influence the development of the disease. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway is a recently discovered target of inflammation that has gained attention in recent years. Numerous studies have provided evidence for the causal role of this pathway in atherosclerosis, and its downstream signaling factors play a significant role in this process. This brief review aims to explore the crucial role of the JAK/STAT pathway and its representative downstream signaling factors in the development of atherosclerosis. It provides a new theoretical basis for clinically affecting the development of atherosclerosis by interfering with the JAK/STAT signaling pathway.

Reversing and modulating cellular senescence in beta cells, a new field of opportunities to treat diabetes

Diabetes constitutes a world-wide pandemic that requires searching for new treatments to halt its progression. Cellular senescence of pancreatic beta cells has been described as a major contributor to development and worsening of diabetes. The concept of reversibility of cellular senescence is critical as is the timing to take actions against this "dormant" senescent state. The reversal of cellular senescence can be considered as rejuvenation of the specific cell if it returns to the original "healthy state" and doesn't behave aberrantly as seen in some cancer cells. In rodents, treatment with senolytics and senomorphics blunted or prevented disease progression, however their use carry drawbacks. Modulators of cellular senescence is a new area of research that seeks to reverse the senescence. More research in each of these modalities should lead to new treatments to stop diabetes development and progression.

Senolytic and senomorphic interventions to defy senescence-associated mitochondrial dysfunction

The accumulation of senescent cells in the aging individual is associated with an increase in the occurrence of age-associated pathologies that contribute to poor health, frailty, and mortality. The number and type of senescent cells is viewed as a contributor to the body's senescence burden. Cellular models of senescence are based on induction of senescence in cultured cells in the laboratory. One type of senescence is triggered by mitochondrial dysfunction. There are several indications that mitochondria defects contribute to body aging. Senotherapeutics, targeting senescent cells, have been shown to induce their lysis by means of senolytics, or repress expression of their secretome, by means of senomorphics, senostatics or gerosuppressors. An outline of the mechanism of action of various senotherapeutics targeting mitochondria and senescence-associated mitochondria dysfunction will be here addressed. The combination of geroprotective interventions together with senotherapeutics will help to strengthen mitochondrial energy metabolism, biogenesis and turnover, and lengthen the mitochondria healthspan, minimizing one of several molecular pathways contributing to the aging phenotype.

Involvement of Bcl-2 Family Proteins in Tetraploidization-Related Senescence

The B-cell lymphoma 2 (Bcl-2) family of proteins is the main regulator of apoptosis. However, multiple emerging evidence has revealed that Bcl-2 family proteins are also involved in cellular senescence. On the one hand, the different expression of these proteins determines the entry into senescence. On the other hand, entry into senescence modulates the expression of these proteins, generally conferring resistance to apoptosis. With some exceptions, senescent cells are characterized by the upregulation of antiapoptotic proteins and downregulation of proapoptotic proteins. Under physiological conditions, freshly formed tetraploid cells die by apoptosis due to the tetraploidy checkpoint. However, suppression of Bcl-2 associated x protein (Bax), as well as overexpression of Bcl-2, favors the appearance and survival of tetraploid cells. Furthermore, it is noteworthy that our laboratory has shown that the joint absence of Bax and Bcl-2 antagonist/killer (Bak) favors the entry into senescence of tetraploid cells. Certain microtubule inhibitory chemotherapies, such as taxanes and vinca alkaloids, induce the generation of tetraploid cells. Moreover, the combined use of inhibitors of antiapoptotic proteins of the Bcl-2 family with microtubule inhibitors increases their efficacy. In this review, we aim to shed light on the involvement of the Bcl-2 family of proteins in the senescence program activated after tetraploidization and the possibility of using this knowledge to create a new therapeutic strategy targeting cancer cells.

BCL-XL Overexpression Protects Pancreatic β-Cells against Cytokine- and Palmitate-Induced Apoptosis

Diabetes is a chronic disease that affects glucose metabolism, either by autoimmune-driven β-cell loss or by the progressive loss of β-cell function, due to continued metabolic stresses. Although both α- and β-cells are exposed to the same stressors, such as proinflammatory cytokines and saturated free fatty acids (e.g., palmitate), only α-cells survive. We previously reported that the abundant expression of BCL-XL, an anti-apoptotic member of the BCL-2 family of proteins, is part of the α-cell defense mechanism against palmitate-induced cell death. Here, we investigated whether BCL-XL overexpression could protect β-cells against the apoptosis induced by proinflammatory and metabolic insults. For this purpose, BCL-XL was overexpressed in two β-cell lines-namely, rat insulinoma-derived INS-1E and human insulin-producing EndoC-βH1 cells-using adenoviral vectors. We observed that the BCL-XL overexpression in INS-1E cells was slightly reduced in intracellular Ca2+ responses and glucose-stimulated insulin secretion, whereas these effects were not observed in the human EndoC-βH1 cells. In INS-1E cells, BCL-XL overexpression partially decreased cytokine- and palmitate-induced β-cell apoptosis (around 40% protection). On the other hand, the overexpression of BCL-XL markedly protected EndoC-βH1 cells against the apoptosis triggered by these insults (>80% protection). Analysis of the expression of endoplasmic reticulum (ER) stress markers suggests that resistance to the cytokine and palmitate conferred by BCL-XL overexpression might be, at least in part, due to the alleviation of ER stress. Altogether, our data indicate that BCL-XL plays a dual role in β-cells, participating both in cellular processes related to β-cell physiology and in fostering survival against pro-apoptotic insults.

Swimming exercise and nano-l-arginine supplementation improve oxidative capacity and some autophagy-related genes in the soleus muscle of aging rats

The present research aims to evaluate the effect of swimming exercise and chitosan-coated l-arginine on mitochondrial oxidation, BCL2 Interacting Protein 3 (Bnip3), NIP-like protein × (Nix), B-cell lymphoma-extra-large (Bcl-xL) and autophagy-related protein light chain 3(LC3) expression in soleus muscle of aging rats. In this experimental research, 25 male Wistar rats were assigned into five groups randomly: young, old, old + Nano l-arginine (Nano L-a), old + exercise (Ex), and old + Nano l-arginine (Nano L-a) + exercise (Ex) (n = 5 in each). They performed a swimming exercise program five days a week for six weeks. To determine the relative strength for rats before and after performing these interventions, the 1repetition maximum (1RM) test was done as a pre and post-test. The exercise program started with 20 min and after four sessions, gradually increased to 60 min and this time was maintained until the completion of the training period. l-arginine coated with chitosan nanoparticles was given to the rats in the l-arginine-supplemented group via gavage at a dosage of 500 mg/kg/day, five days a week, for six weeks. Additionally, the rats in all groups were fed a normal diet (2.87 kcal/g and 15 % energy from fat). Upon the completion of the protocol implementation, the rats were sacrificed and the soleus muscle was fixed and frozen to determine hematoxylin and eosin (H&E) staining, immunohistochemistry (IHC), gene expression analysis, levels of reactive oxygen species (ROS), and total antioxidant capacity (TAC). The results from the present research indicated that swimming exercise and Nano l-arginine improve the strength and histology of muscle tissue in old rats (p < 0.05). Aging significantly increased the expression of Nix and Bnip3 (p < 0.05) and reduced the Bcl-xL gene expression (p < 0.05). The expression of LC3 protein also increased with aging (p < 0.05). Therapeutic interventions, such as combined treatment (old + Nano L-a + Ex) for old animals, reduced the amount of this protein in soleus muscle (p < 0.05). The ROS values also showed a significant reduction only in the old + Nano L-a + Ex group compared to the old group. Moreover, TAC values show a significant decrease in the old and old + Ex groups in comparison to the young group. The use of arginine supplement, especially in nano form, along with swimming exercise seems to reduce the oxidative damage to the elderly muscle tissue, which has a positive effect on the structure and function of the soleus muscle. Since these interventions only had a significant effect on LC3 protein, further studies with more diverse measurement methods for autophagy are suggested.

Targeting Mitochondria to Control Ageing and Senescence

Ageing is accompanied by a progressive impairment of cellular function and a systemic deterioration of tissues and organs, resulting in increased vulnerability to multiple diseases. Here, we review the interplay between two hallmarks of ageing, namely, mitochondrial dysfunction and cellular senescence. The targeting of specific mitochondrial features in senescent cells has the potential of delaying or even reverting the ageing process. A deeper and more comprehensive understanding of mitochondrial biology in senescent cells is necessary to effectively face this challenge. Here, we discuss the main alterations in mitochondrial functions and structure in both ageing and cellular senescence, highlighting the differences and similarities between the two processes. Moreover, we describe the treatments available to target these pathways and speculate on possible future directions of anti-ageing and anti-senescence therapies targeting mitochondria.

Involvement of Akt and the antiapoptotic protein Bcl-xL in the inhibition of apoptosis of dendritic cells by Leishmania mexicana

The intracellular parasite Leishmania mexicana inhibits camptothecin (CPT)-induced apoptosis of monocyte-derived dendritic cells (moDC) through the down-regulation of p38 and JNK phosphorylation, while the kinase Akt is maintained active for 24 hours. In addition, the infection of moDC with L. mexicana promastigotes increases the protein presence of the antiapoptotic protein Bcl-xL. In the present work we aimed to investigate the role of Akt in the inhibition of apoptosis of moDC by L. mexicana and in the modulation of the expression of the antiapoptotic proteins Bcl-2, Mcl-1, and Bcl-xL. moDC were infected with L. mexicana metacyclic promastigotes and treated with CPT, an Akt inhibitor, or both and the MOMP and protein presence of active caspase 3, Bcl-2, Mcl-1, and Bcl-xL were evaluated. Our results show that the specific inhibition of Akt reverts the apoptosis protective effect exerted by L. mexicana on moDC reflected by a reduction in MOMP, caspase 3 activation, and upregulation of Bcl-xL. Interestingly, we also found that the infection of moDC with L. mexicana promastigotes induces a decrease in Bcl-2 along with an isoform change of Mcl-1, this independently to Akt activity. We demonstrated that Akt is deeply involved in the inhibition of apoptosis of moDC by L. mexicana.

An Activatable NIR Probe for the Detection and Elimination of Senescent Cells

Cellular senescence is involved in diverse physiological processes. Accumulation of senescent cells can lead to numerous age-related diseases. Therefore, it is of great significance to develop chemical tools to effectively detect and eliminate senescent cells. Till date, a dual functional probe that could detect and eliminate senescent cells has yet been accomplished. Herein, a β-gal-activated probe, MB-βgal, based on the methylene blue (MB) fluorophore, was designed to detect and eliminate senescent cells. In the absence of β-gal, the probe showed no fluorescence and its ¹O₂ production efficiency was suppressed simultaneously. On the other hand, MB-βgal could be specifically activated by the high level of β-gal in senescent cells, thus, releasing free MB with near-infrared (NIR) fluorescence and high ¹O₂ production efficiency under light irradiation. MB-βgal demonstrated a fast response, high sensitivity, and high selectivity in detecting β-gal in an aqueous solution and was further applied to visualization and ablation of senescent cells. As a proof of concept, the dual functions of MB-βgal were successfully demonstrated in senescent HeLa cells and mouse embryonic fibroblast cells.

Alterations in hippocampal mitochondrial dynamics are associated with neurodegeneration and recognition memory decline in old male mice

Mitochondrial dynamics is a key process that modulates the ultrastructure, quality and function of mitochondria. It is disrupted in numerous major neurodegenerative disorders including Parkinson's, Alzheimer's and Huntington's disease. Mitochondrial dysfunction has been correlated with the loss of memory. Previous studies suggest the involvement of Vdac1 and Drp1 in outer mitochondrial membrane permeabilization and promotion of mitochondrial fragmentation through Drp1 phosphorylation at S616. However, alterations in mitochondrial dynamics with respect to aging, memory loss and neurodegeneration remain unexplored. Therefore, the present study focuses on the involvement of mitochondrial dynamics in neurodegeneration and recognition memory decline during aging. The recognition memory decline was validated by the novel object recognition test and measurement of hippocampal Arc protein level during aging. The ultrastructure analysis revealed a decline in mitochondrial length and area, while an increase in the number of fragmented, round and disrupted mitochondria in the hippocampus during aging. Disruption was also evident in mitochondrial cristae and membrane with advancing age. The change in mitochondrial morphology was corroborated by an increase in the expression of phospho-Drp1 (S616) and Cyt-c proteins but decline in Mfn2, LC3B, Vdac1, Bcl-XL and Bcl-2 proteins in the hippocampus during aging. Taken together, our findings reveal that an increase in the expression of phospho-Drp1 (S616) and decrease in Mfn2 and LC3B proteins in the hippocampus bring about a reduction in mitochondrial length and area, and rise in mitochondrial fragmentation leading to reduced neuronal cell density, increased neurodegeneration and recognition memory decline in old male mice. Diagram depicts the increase in hippocampal mitochondrial fragmentation during aging of mice. Increased mitochondrial fragmentation causes distorted mitochondrial function such as decrease in ATP/ADP transportation due to decrease in Vdac1 protein level and increase in oxidative damage. These alterations result in hippocampal neurodegeneration and consequently impairment in recognition memory during aging.

Roles and Regulation of BCL-xL in Hematological Malignancies

Members of the Bcl-2 family are proteins that play an essential role in the regulation of apoptosis, a crucial process in development and normal physiology in multicellular organisms. The essential mechanism of this family of proteins is given by the role of pro-survival proteins, which inhibit apoptosis by their direct binding with their counterpart, the effector proteins of apoptosis. This family of proteins was named after the typical member Bcl-2, which was named for its discovery and abnormal expression in B-cell lymphomas. Subsequently, the structure of one of its members BCL-xL was described, which allowed one to understand much of the molecular mechanism of this family. Due to its role of BCL-xL in the regulation of cell survival and proliferation, it has been of great interest in its study. Due to this, it is important to research its role regarding the development and progression of human malignancies, especially in hematologic malignancies. Due to its variation in expression in cancer, it has been suggested that BCL-xL can or cannot play a role in cancer depending on the cellular or tissue context. This review discusses recent advances in its transcriptional regulation of BCL-xL, as well as the advances regarding the activities of BCL-xL in hematological malignancies, its possible role as a biomarker, and its possible clinical relevance in these malignancies.

Suppression of NSCLC A549 tumor growth by a mtDNA mutation-targeting pyrrole-imidazole polyamide-TPP and a senolytic drug

Certain somatic mutations in mtDNA were associated with tumor progression and frequently found in a homoplasmic state. We recently reported that pyrrole‐imidazole polyamide conjugated with the mitochondria‐delivering moiety triphenylphosphonium (PIP‐TPP) targeting an mtDNA mutation efficiently induced apoptosis in cancer cells with the mutation but not normal cells. Here, we synthesized the novel PIP‐TPP, CCC‐021‐TPP, targeting ND6 14582A > G homoplasmic missense mutation that is suggested to enhance metastasis of non‐small‐cell lung cancer A549 cells. CCC‐021‐TPP did not induce apoptosis but caused cellular senescence in the cells, accompanied by a significant induction of antiapoptotic BCL‐XL. Simultaneous treatment of A549 cells with CCC‐021‐TPP and the BCL‐XL selective inhibitor A‐1155463 resulted in apoptosis induction. Importantly, the combination induced apoptosis and suppressed tumor growth in an A549 xenografted model. These results highlight the potential of anticancer therapy with PIP‐TPPs targeting mtDNA mutations to induce cell death even in apoptosis‐resistant cancer cells when combined with senolytics.

[Mechanisms of age-related changes in the morphology of the pulp system of the first lower molars]

OBJECTIVE

To study the coupling of age-related systemic changes in inflammation-mediated apoptosis with the features of the anatomy of the pulp system of the first mandibular molars in patients with chronic pulpitis and periodontitis.

MATERIAL AND METHODS

The study included 55 patients of both sexes from 18 to 75 years of age in three age groups - young (18-44 years) (n=17), middle (45-59 years) (n=18), elderly (60-74 years) (n=20) with indications for endodontic treatment. Diagnostic measures were supplemented with New Tom 3G cone-beam tomography. The concentration of anitapoptotic protein Bcl-XL and tumor necrosis factor-a (TNF-a) was determined in the blood, and the level of the nuclear transcription factor NF-KB subunit p65 was determined in the lysates of mononuclear cells.

RESULTS

As a result of the analysis of the sections, significant obliteration of the pulp was revealed throughout and an increase in the frequency of occurrence of slit-shaped channels in the distal root of the first molar of the mandible in elderly patients.

CONCLUSION

The pathogenetic factors leading to a change in the morphology of the pulp system include old age and an imbalance in the system of anti-inflammatory cytokine transcription mechanisms, which contributes to increased apoptosis and the protracted nature of inflammation.

Impact of Deamidation on the Structure and Function of Antiapoptotic Bcl-xL

Bcl-x_L is an antiapoptotic mitochondrial trans-membrane protein, which is known to play a crucial role in the survival of tumor cells. The deamidation of Bcl-x_L is a pivotal switch that regulates its biological function. The potential impact of deamidation on the structure and dynamics of Bcl-x_L is directly linked to the intrinsically disordered region (IDR), which is the main site for post-translational modifications (PTMs). In this study, we explored deamidation-induced conformational changes in Bcl-x_L to gain insight into its loss of function by performing microsecond-long molecular dynamics (MD) simulations. MD simulation outcomes showed that the IDR motion and interaction patterns have changed notably upon deamidation. Principal component analysis (PCA) demonstrates significant differences between wild-type and deamidated Bcl-x_L and suggests that deamidation affects the structure and dynamics of Bcl-x_L. The combination of clustering analysis, H-bond analysis, and PCA revealed changes in conformation, interaction, and dynamics upon deamidation. Differences in contact patterns and essential dynamics that lead to a narrowing in the binding groove (BG) are clear indications of deamidation-induced allosteric effects. In line with previous studies, we show that the IDR plays a very important role in the loss of apoptotic functions of Bcl-x_L while providing a unique perspective on the underlying mechanism of Bcl-x_L deamidation-induced cell death.

Apoptosis and Cell Proliferation Markers in Inflammatory-Fibroproliferative Diseases of the Vessel Wall (Review)

Apoptosis is the main feature of inflammatory-fibroproliferative disorders of the vessel wall. Studies in animal models have shown that smooth muscle cells (SMCs) cultured from endarterectomy specimens from the affected area proliferate more slowly and display higher apoptotic indices than SMCs derived from the normal vessel wall. Apoptotic cells were found in the destabilized atherosclerotic plaques, as well as in the samples with restenosis of the reconstruction area.

Injury to the vessel wall causes two waves of apoptosis. The first wave is the rapid apoptosis in the media that occurs within a few hours after injury and leads to a marked reduction in the number of vascular wall cells. The second wave of apoptosis occurs much later (from several days to weeks) and is limited by the SMCs within the developing neointima. Up to 14% of the neointimal SMCs undergo apoptosis 20 days after balloon angioplasty. Ligation of the external carotid artery in a rabbit model led to a marked decrease in blood flow in the common carotid artery, which correlated with the increased apoptosis of endothelial cells and SMCs.

Angioplasty-induced death of SMCs is regulated by a redox-sensitive signaling pathway, and topical administration of antioxidants can minimize vascular cell loss. On the whole, studies show that apoptosis is prevalent in vascular lesions, controlling the viability of both inflammatory and vascular cells, determining the cellular composition of the vessel wall. The main markers of apoptosis (Fas, Fas ligand, p53, Bcl-2, Bax) and cell proliferation (toll receptor) have been considered in the current review.

TFEB promotes BCL-2 expression by upregulating its promoter activity in the t(6;11) translocation renal cell carcinomas

t(6;11) translocation renal cell carcinoma (RCC) is classified as a subset of the MiT family translocation RCCs and characterized by harboring the Alpha-TFEB fusion gene. However, the development mechanism of this tumor and its effective treatment have not been fully identified yet. The purpose of this study was to explore the relationship between TFEB and BCL-2 in Alpha-TFEB stably transfected cell lines and in t(6;11) RCC tumor tissue. An Alpha-TFEB eukaryotic expression vector was constructed and stably transfected into CaKi-2 and HK-2 cells. RT-PCR and real-time RT-PCR were used to measure the mRNA expressions of TFEB and BCL-2, and immunohistochemistry, Western blot and dual immunofluorescence assays were used to evaluate the TFEB and BCL-2 protein expressions. MTT proliferation assays and flow cytometry were also performed. Furthermore, luciferase reporter assays were used to evaluate the BCL-2 promoter activity. An Alpha-TFEB eukaryotic expression vector was successfully constructed and stably transfected into CaKi-2 and HK-2 cells (named CaKi-2-TFEB and HK-2-TFEB cells). Compared with the CaKi-2 and HK-2 groups, the TFEB and BCL-2 mRNA expression levels were significantly upregulated in the CaKi-2-TFEB and HK-2-TFEB groups respectively. The TFEB and BCL-2 protein expressions showed a similar result. The overexpression of TFEB and BCL-2 promoted cell proliferation and inhibited cell apoptosis. Moreover, the overexpression of TFEB upregulated the promoter activity of BCL-2. Our data suggest that the overexpression of TFEB promotes BCL-2 expression by upregulating its promoter activity and ultimately results in the development of t(6;11) translocation RCC. BCL-2 inhibitors may serve as potential therapeutic targets for t(6;11) translocation RCC.

Methods for Studying Myofibroblast Apoptotic Pathways

Evasion of apoptosis by myofibroblasts is a hallmark of fibrotic diseases, ultimately leading to persistent myofibroblast activation, extracellular matrix (ECM) deposition, and remodeling. Targeting myofibroblast apoptosis is emerging as a novel therapeutic strategy to reverse established fibrosis. We have recently discovered that in the process of fibroblast-to-myofibroblast transdifferentiation driven by matrix stiffness, the "mitochondrial priming" (readiness to undergo apoptosis) is dramatically increased in stiffness-activated myofibroblasts. Thus, myofibroblasts, traditionally viewed as apoptosis-resistant cells, appear poised to die when survival pathways are blocked, a cellular state we call "primed for death." This apoptosis-prone phenotype is driven by high levels of pro-apoptotic proteins loaded in myofibroblast's mitochondria, which require concomitant upregulation of pro-survival BCL-2 proteins to suppress mitochondrial apoptosis and ensure survival. Here, we describe a method called BH3 profiling which measures myo/fibroblast apoptotic priming as well as their antiapoptotic dependencies for survival. In addition, we describe how BH3 profiling can be used to predict myofibroblast responses to therapeutic agents targeting pro-survival BCL-2 proteins, also known as BH3 mimetic drugs. Finally, we describe methods to assess myofibroblast sensitivity to extrinsic apoptosis via Annexin V staining.

Aberrant Bcl-x splicing in cancer: from molecular mechanism to therapeutic modulation

Bcl-x pre-mRNA splicing serves as a typical example to study the impact of alternative splicing in the modulation of cell death. Dysregulation of Bcl-x apoptotic isoforms caused by precarious equilibrium splicing is implicated in genesis and development of multiple human diseases, especially cancers. Exploring the mechanism of Bcl-x splicing and regulation has provided insight into the development of drugs that could contribute to sensitivity of cancer cells to death. On this basis, we review the multiple splicing patterns and structural characteristics of Bcl-x. Additionally, we outline the cis-regulatory elements, trans-acting factors as well as epigenetic modifications involved in the splicing regulation of Bcl-x. Furthermore, this review highlights aberrant splicing of Bcl-x involved in apoptosis evade, autophagy, metastasis, and therapy resistance of various cancer cells. Last, emphasis is given to the clinical role of targeting Bcl-x splicing correction in human cancer based on the splice-switching oligonucleotides, small molecular modulators and BH3 mimetics. Thus, it is highlighting significance of aberrant splicing isoforms of Bcl-x as targets for cancer therapy.

Bcl-xL: A Focus on Melanoma Pathobiology

Apoptosis is the main mechanism by which multicellular organisms eliminate damaged or unwanted cells. To regulate this process, a balance between pro-survival and pro-apoptotic proteins is necessary in order to avoid impaired apoptosis, which is the cause of several pathologies, including cancer. Among the anti-apoptotic proteins, Bcl-xL exhibits a high conformational flexibility, whose regulation is strictly controlled by alternative splicing and post-transcriptional regulation mediated by transcription factors or microRNAs. It shows relevant functions in different forms of cancer, including melanoma. In melanoma, Bcl-xL contributes to both canonical roles, such as pro-survival, protection from apoptosis and induction of drug resistance, and non-canonical functions, including promotion of cell migration and invasion, and angiogenesis. Growing evidence indicates that Bcl-xL inhibition can be helpful for cancer patients, but at present, effective and safe therapies targeting Bcl-xL are lacking due to toxicity to platelets. In this review, we summarized findings describing the mechanisms of Bcl-xL regulation, and the role that Bcl-xL plays in melanoma pathobiology and response to therapy. From these findings, it emerged that even if Bcl-xL plays a crucial role in melanoma pathobiology, we need further studies aimed at evaluating the involvement of Bcl-xL and other members of the Bcl-2 family in the progression of melanoma and at identifying new non-toxic Bcl-xL inhibitors.

Bcl-xL as a Modulator of Senescence and Aging

Many features of aging result from the incapacity of cells to adapt to stress conditions. When cells are overwhelmed by stress, they can undergo senescence to avoid unrestricted growth of damaged cells. Recent findings have proven that cellular senescence is more than that. A specific grade of senescence promotes embryo development, tissue remodeling and wound healing. However, constant stresses and a weakening immune system can lead to senescence chronicity with aging. The accumulation of senescent cells is directly related to tissue dysfunction and age-related pathologies. Centenarians, the most aged individuals, should accumulate senescent cells and suffer from their deleterious effects, however, they enjoy a compression of morbidity. We have shown that they overexpress B-cell lymphoma-extra large (Bcl-xL). Bcl-xL could avoid an excessive burden of senescent cells through the regulation of intrinsic apoptosis, mitochondrial bioenergetics and oxidative stress. On the other hand, Bcl-xL maintains a fully functional immune system that ensures an efficient clearance of senescent cells. Moreover, there is a paradox, as inhibitors of Bcl-xL have been employed as senolytic agents, which have been shown to protect from aging in animal models. In this review, we aim to discuss how Bcl-xL could modulate senescence-associated harmful effects in centenarians, protecting them from the burden of accumulation of senescent cells.

Bcl-xL represents a therapeutic target in Philadelphia negative myeloproliferative neoplasms

Myeloproliferative neoplasms are divided into essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF). Although ruxolitinib was proven to be effective in reducing symptoms, patients rarely achieve complete molecular remission. Therefore, it is relevant to identify new therapeutic targets to improve the clinical outcome of patients. Bcl‐xL protein, the long isoform encoded by alternative splicing of the Bcl‐x gene, acts as an anti‐apoptotic regulator. Our study investigated the role of Bcl‐xL as a marker of severity of MPN and the possibility to target Bcl‐xL in patients. 129 MPN patients and 21 healthy patients were enrolled in the study. We analysed Bcl‐xL expression in leucocytes and in enriched CD34+ and CD235a+ cells. Furthermore, ABT‐737, a Bcl‐xL inhibitor, was tested in HEL cells and in leucocytes from MPN patients. Bcl‐xL was found progressively over‐expressed in cells from ET, PV and PMF patients, independently by JAK2 mutational status. Moreover, our data indicated that the combination of ABT‐737 and ruxolitinib resulted in a significantly higher apoptotic rate than the individual drug. Our study suggests that Bcl‐xL plays an important role in MPN independently from JAK2 V617F mutation. Furthermore, data demonstrate that targeting simultaneously JAK2 and Bcl‐xL might represent an interesting new approach.