Non-apoptotic roles of Bcl-2 family: the calcium connection

Transplantation of dorsal root ganglia overexpressing the NaChBac sodium channel improves locomotion after complete SCI

Spinal cord injury (SCI) is a debilitating condition currently lacking treatment. Severe SCI causes the loss of most supraspinal inputs and neuronal activity caudal to the injury, which, coupled with the limited endogenous capacity for spontaneous regeneration, can lead to complete functional loss even in anatomically incomplete lesions. We hypothesized that transplantation of mature dorsal root ganglia (DRGs) genetically modified to express the NaChBac sodium channel could serve as a therapeutic option for functionally complete SCI. We found that NaChBac expression increased the intrinsic excitability of DRG neurons and promoted cell survival and neurotrophic factor secretion in vitro. Transplantation of NaChBac-expressing dissociated DRGs improved voluntary locomotion 7 weeks after injury compared to control groups. Animals transplanted with NaChBac-expressing DRGs also possessed higher tubulin-positive neuronal fiber and myelin preservation, although serotonergic descending fibers remained unaffected. We observed early preservation of the corticospinal tract 14 days after injury and transplantation, which was lost 7 weeks after injury. Nevertheless, transplantation of NaChBac-expressing DRGs increased the neuronal excitatory input by an increased number of VGLUT2 contacts immediately caudal to the injury. Our work suggests that the transplantation of NaChBac-expressing dissociated DRGs can rescue significant motor function, retaining an excitatory neuronal relay activity immediately caudal to injury.

Androgens Modulate Bcl-2 Agonist of Cell Death (BAD) Expression and Function in Breast Cancer Cells

Androgen receptor (AR) expression in estrogen receptor-positive (ER+) breast cancer (BC) correlates with lower tumor grade and a better clinical outcome. Additionally, in normal mammary epithelium or ER+ BC preclinical models, androgens counteract basal/ER-dependent proliferation. Here, we report an additional mechanism, underlining the protective role exerted by AR. Specifically, the activation of intracellular AR upregulates the Bcl-2-family protein BAD, and TCGA database analyses show that in ER+ BC, BAD expression is associated with better disease-free survival. Ligand-activated AR influences its own and BAD cellular compartmentalization by enhancing levels in the nucleus, as well as in mitochondrial fractions. In both compartments, BAD exerts unconventional functions. In the nucleus, BAD and AR physically interact and, upon androgen stimulation, are recruited at the AP-1 and ARE sites within the cyclin D1 promoter region, contributing to explaining the anti-proliferative effect of androgens in BC cells. Androgens cause an enrichment in BAD and AR content in the mitochondria, correlated with a decrease in mitochondrial function. Thus, we have defined a novel mechanism by which androgens modulate BAD expression, its mitochondria localization, and nuclear content to force its ability to act as a cell cycle inhibitor, strengthening the protective role of androgen signaling in estrogen-responsive BCs.

Nrh L11R single nucleotide polymorphism, a new prediction biomarker in breast cancer, impacts endoplasmic reticulum-dependent Ca2+ traffic and response to neoadjuvant chemotherapy

Overexpression of Bcl-2 proteins such as Bcl2L10, also referred to as Nrh, is associated with resistance to therapy and poor survival in various cancers, including breast cancer, lung cancer, and leukemia. The single nucleotide polymorphism (SNP) of BCL2L10 in its BH4 domain at position 11 (BCL2L10 Leu11Arg, rs2231292), corresponding to position 11 in the Nrh open reading frame, is reported to lower resistance towards chemotherapy, with patients showing better survival in the context of acute leukemia and colorectal cancer. Using cellular models and clinical data, we aimed to extend this knowledge to breast cancer. We report that the homozygous status of the Nrh Leu11Arg isoform (Nrh-R) is found in 9.7-11% percent of the clinical datasets studied. Furthermore, Nrh-R confers higher sensitivity towards Thapsigargin-induced cell death compared to the Nrh-L isoform, due to altered interactions with IP3R1 Ca2+ channels in the former case. Collectively, our data show that cells expressing the Nrh-R isoform are more prone to death triggered by Ca2+ stress inducers, compared to Nrh-L expressing cells. Analysis of breast cancer cohorts revealed that patients genotyped as Nrh-R/Nrh-R may have a better outcome. Overall, this study supports the notion that the rs2231292 Nrh SNP could be used as a predictive tool regarding chemoresistance, improving therapeutic decision-making processes. Moreover, it sheds new light on the contribution of the BH4 domain to the anti-apoptotic function of Nrh and identifies the IP3R1/Nrh complex as a potential therapeutic target in the context of breast cancer.

Ca2+ signaling and cell death

Multiple forms of regulated cell death (RCD) have been characterized, each of which originates from the activation of a dedicated molecular machinery. RCD can occur in purely physiological settings or upon failing cellular adaptation to stress. Ca²⁺ions have been shown to physically interact with - and hence regulate - various components of the RCD machinery. Moreover, intracellular Ca²⁺ accumulation can promote organellar dysfunction to degree that can be overtly cytotoxic or sensitize cells to RCD elicited by other stressors. Here, we provide an overview of the main links between Ca²⁺and different forms of RCD, including apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, lysosome-dependent cell death, and parthanatos.

Bcl-xL is required to protect endothelial cells latently infected with KSHV from virus induced intrinsic apoptosis

Kaposi's Sarcoma herpesvirus (KSHV) is the etiologic agent of Kaposi's Sarcoma (KS), a highly vascularized tumor common in AIDS patients and many countries in Africa. KSHV is predominantly in the latent state in the main KS tumor cell, the spindle cell, a cell expressing endothelial cell markers. To identify host genes important for KSHV latent infection of endothelial cells we previously used a global CRISPR/Cas9 screen to identify genes necessary for the survival or proliferation of latently infected cells. In this study we rescreened top hits and found that the highest scoring gene necessary for infected cell survival is the anti-apoptotic Bcl-2 family member Bcl-xL. Knockout of Bcl-xL or treatment with a Bcl-xL inhibitor leads to high levels of cell death in latently infected endothelial cells but not their mock counterparts. Cell death occurs through apoptosis as shown by increased PARP cleavage and activation of caspase-3/7. Knockout of the pro-apoptotic protein, Bax, eliminates the requirement for Bcl-xL. Interestingly, neither Bcl-2 nor Mcl-1, related and often redundant anti-apoptotic proteins of the Bcl-2 protein family, are necessary for the survival of latently infected endothelial cells, likely due to their lack of expression in all the endothelial cell types we have examined. Bcl-xL is not required for the survival of latently infected primary effusion lymphoma (PEL) cells or other cell types tested. Expression of the KSHV major latent locus alone in the absence of KSHV infection led to sensitivity to the absence of Bcl-xL, indicating that viral gene expression from the latent locus induces intrinsic apoptosis leading to the requirement for Bcl-xL in endothelial cells. The critical requirement of Bcl-xL during KSHV latency makes it an intriguing therapeutic target for KS tumors.

Natural compounds regulate the PI3K/Akt/GSK3β pathway in myocardial ischemia-reperfusion injury

The PI3K/Akt/GSK3β pathway is crucial in regulating cardiomyocyte growth and survival. It has been shown that activation of this pathway alleviates the negative impact of ischemia-reperfusion. Glycogen synthase kinase-3 (GSK3β) induces apoptosis through stimulation of transcription factors, and its phosphorylation has been suggested as a new therapeutic target for myocardial ischemia-reperfusion injury (MIRI). GSK3β regulatory role is mediated by the reperfusion injury salvage kinase (RISK) pathway, and its inhibition by Akt activation blocks mitochondrial permeability transition pore (mPTP) opening and enhances myocardial survival. The present article discusses the involvement of the PI3K/Akt/GSK3β pathway in cardioprotective effects of natural products against MIRI.Abbreviations: Akt: protein kinase B; AMPK: AMP-activated protein kinase; ATP: adenosine triphosphate; Bad: bcl2-associated agonist of cell death; Bax: bcl2-associated x protein; Bcl-2: B-cell lymphoma 2; CK-MB: Creatine kinase-MB; CRP: C-reactive-protein; cTnI: cardiac troponin I; EGCG: Epigallocatechin-3-gallate; Enos: endothelial nitric oxide synthase; ER: endoplasmic reticulum; ERK ½: extracellular signal‑regulated protein kinase ½; GSK3β: glycogen synthase kinase-3; GSRd: Ginsenoside Rd; GSH: glutathione; GSSG: glutathione disulfide; HO-1: heme oxygenase-1; HR: hypoxia/reoxygenation; HSYA: Hydroxysafflor Yellow A; ICAM-1: Intercellular Adhesion Molecule 1; IKK-b: IκB kinase; IL: interleukin; IPoC: Ischemic postconditioning; IRI: ischemia-reperfusion injury; JNK: c-Jun N-terminal kinase; Keap1: kelch-like ECH-associated protein- 1; LDH: lactate dehydrogenase; LVEDP: left ventricular end diastolic pressure; LVP: left ventricle pressure; LVSP: left ventricular systolic pressure; MAPK: mitogen-activated protein kinase; MDA: malondialdehyde; MIRI: myocardial ischemia-reperfusion injury; MnSOD: manganese superoxide dismutase; mPTP: mitochondrial permeability transition pore; mtHKII: mitochondria-bound hexokinase II; Nrf-1: nuclear respiratory factor 1; Nrf2: nuclear factor erythroid 2-related factor; NO: nitric oxide; PGC-1α: peroxisome proliferator‑activated receptor γ coactivator‑1α; PI3K: phosphoinositide 3-kinases; RISK: reperfusion injury salvage kinase; ROS: reactive oxygen species; RSV: Resveratrol; SOD: superoxide dismutase; TFAM: transcription factor A mitochondrial; TNF-α: tumor necrosis factor-alpha; VEGF-B: vascular endothelial growth factor B.

Effects of Hydrogen Peroxide-Induced Oxidative Stress on Intestinal Morphology, Redox Status, and Related Molecules in Squabs

The purpose of this study was to evaluate the potential effect of oxidative stress on the intestine of squabs, and to explore the molecular mechanisms. A total of 360 1-day-old squabs were divided evenly into five different groups (n = 72/group): control, negative control, low, medium, and high dose groups. On the 3rd, 5th, and 7th days, squabs in the control group were not effectively treated and the negative control group were intraperitoneally injected with normal saline, whereas the H₂O₂ group was injected with H₂O₂ of 2.0, 2.5, and 3.0 mmol/kg BW respectively. On the 21st day, the serum and duodenum were collected for further analysis. The results indicated that, compared with the control group, H₂O₂ caused squabs weight loss and intestinal morphology damage, and these effects were enhanced with an increase in dose. Further examination revealed that the contents of oxidative stress markers in both the serum and duodenum of the H₂O₂ group were significantly enhanced as the dose was increased. In addition, H₂O₂ exposure also resulted in the lower mRNA expression of Occludin, ZO-1, Beclin1, Atg5, and Caspase-3, but the expression of Claudin2 and Bcl-2 was decreased in comparison to the control group. These findings suggested that duodenal oxidative damage was accompanied by weight loss, changes in intestinal morphology, redox status imbalance, apoptosis as well as autophagy of intestinal cells, with, effects of 3.0 mmol/kg BW of H₂O₂ being the most severe.

Endoplasmic Reticulum-Mitochondria Contacts Modulate Reactive Oxygen Species-Mediated Signaling and Oxidative Stress in Brain Disorders: The Key Role of Sigma-1 Receptor

Significance: Mitochondria-Associated Membranes (MAMs) are highly dynamic endoplasmic reticulum (ER)-mitochondria contact sites that, due to the transfer of lipids and Ca2+ between these organelles, modulate several physiologic processes, such as ER stress response, mitochondrial bioenergetics and fission/fusion events, autophagy, and inflammation. In addition, these contacts are implicated in the modulation of the cellular redox status since several MAMs-resident proteins are involved in the generation of reactive oxygen species (ROS), which can act as both signaling mediators and deleterious molecules, depending on their intracellular levels. Recent Advances: In the past few years, structural and functional alterations of MAMs have been associated with the pathophysiology of several neurodegenerative diseases that are closely associated with the impairment of several MAMs-associated events, including perturbation of the redox state on the accumulation of high ROS levels. Critical Issues: Inter-organelle contacts must be tightly regulated to preserve cellular functioning by maintaining Ca2+ and protein homeostasis, lipid metabolism, mitochondrial dynamics and energy production, as well as ROS signaling. Simultaneously, these contacts should avoid mitochondrial Ca2+ overload, which might lead to energetic deficits and deleterious ROS accumulation, culminating in oxidative stress-induced activation of apoptotic cell death pathways, which are common features of many neurodegenerative diseases. Future Directions: Given that Sig-1R is an ER resident chaperone that is highly enriched at the MAMs and that controls ER to mitochondria Ca2+ flux, as well as oxidative and ER stress responses, its potential as a therapeutic target for neurodegenerative diseases such as Amyotrophic Lateral Sclerosis, Alzheimer, Parkinson, and Huntington diseases should be further explored. Antioxid. Redox Signal. 37, 758-780.

Comparative study of oral versus parenteral crocin in mitigating acrolein-induced lung injury in albino rats

Acrolein (Ac) is the second most commonly inhaled toxin, produced in smoke of fires, tobacco smoke, overheated oils, and fried foods; and usually associated with lung toxicity. Crocin (Cr) is a natural carotenoid with a direct antioxidant capacity. Yet, oral administration of crocin as a natural rout is doubtful, because of poor absorbability. Therefore, the current study aimed to compare the potential protective effect of oral versus intraperitoneal (ip) crocin in mitigating Ac-induced lung toxicity. 50 Adult rats were randomly divided into 5 equal groups; Control (oral-saline and ip-saline) group, Cr (oral-Cr and ip-Cr) group, Ac group, oral-Cr/Ac group, and ip-Cr/Ac group; for biochemical, histopathological, and immunohistochemical investigations. Results indicated increased oxidative stress and inflammatory biomarkers in lungs of Ac-treated group. Histopathological and immunohistochemical examinations revealed lung edema, infiltration, fibrosis, and altered expression of apoptotic and anti-apoptotic markers. Compared to oral-Cr/Ac group, the ip-Cr/Ac group demonstrated remarkable improvement in the oxidative, inflammatory, and apoptotic biomarkers, as well as the histopathological alterations. In conclusion, intraperitoneal crocin exerts a more protective effect on acrolein-induced lung toxicity than the orally administered crocin.

The Bak core dimer focuses triacylglycerides in the membrane

Apoptosis, the intrinsic programmed cell death process, is mediated by the Bcl-2 family members Bak and Bax. Activation via formation of symmetric core dimers and oligomerization on the mitochondrial outer membrane (MOM) leads to permeabilization and cell death. Although this process is linked to the MOM, the role of the membrane in facilitating such pores is poorly understood. We recently described Bak core domain dimers, revealing lipid binding sites and an initial role of lipids in oligomerization. Here we describe simulations that identified localized clustering and interaction of triacylglycerides (TAGs) with a minimized Bak dimer construct. Coalescence of TAGs occurred beneath this Bak dimer, mitigating dimer-induced local membrane thinning and curvature in representative coarse-grain MOM and model membrane systems. Furthermore, the effects observed as a result of coarse-grain TAG cluster formation was concentration dependent, scaling from low physiological MOM concentrations to those found in other organelles. We find that increasing the TAG concentration in liposomes mimicking the MOM decreased the ability of activated Bak to permeabilize these liposomes. These results suggest that the presence of TAGs within a Bak-lipid membrane preserves membrane integrity and is associated with reduced membrane stress, suggesting a possible role of TAGs in Bak-mediated apoptosis.

Environmentally relevant lead (Pb) water concentration induce toxicity in zebrafish (Danio rerio) larvae

Early developmental stages of aquatic organisms including fish are inherently vulnerable to lead (Pb) and other water metal contaminants. However, reports on the deleterious effects of environmentally relevant Pb levels are limited. To this end, we exposed 2.5 h post fertilization (hpf) old zebrafish (Danio rerio) embryos to a range of Pb concentrations encompassing environmentally relevant levels (1, 10, 25, 50 and 100 μg/L Pb) until 96 hpf. Exposure negatively impacted the development and survival of zebrafish embryos by inducing embryo coagulation related mortalities in a concentration-dependent manner. At 24 hpf, the highest level of exposure (100 μg/L Pb) had impaired embryo activity characterized by reduced burst activity and the number of movements per minute made by embryos. At 72 hpf, newly hatched larvae exhibited adverse cardiovascular effects (100 μg/L Pb group) and neuromuscular effects (50 and 100 μg/L Pb groups). The antioxidant system dysregulation evidenced by downregulation of catalase, and upregulation of mRNA expression of glutathione S-transferase and cytochrome oxidase subunit I were observed. The pro-apoptotic tumour protein P53 (TP53) and the anti-apoptotic B cell lymphoma -2 (Bcl-2) mRNA expression levels were also affected. The former was downregulated across exposed groups and the latter was upregulated and downregulated in the groups with Pb concentrations less than 50 μg/L Pb and downregulated in 50 μg/L Pb, respectively. These findings suggest that Pb within environmentally relevant levels may be deleterious to developing zebrafish.

Bcl-2-like protein-10 increases aggressive features of melanoma cells

Aim:

B-cell lymphoma-2 (Bcl-2)-like protein-10 (Bcl2L10) is the less studied member of Bcl-2 family proteins, with the controversial role in different cancer histotypes. Very recently, Bcl2L10 expression in melanoma tumor specimens and its role in melanoma response to therapy have been demonstrated. Here, the involvement of Bcl2L10 on the in vitro and in vivo properties associated with melanoma aggressive features has been investigated.

Methods:

Endogenous Bcl2L10 protein expression was detected by western blotting analysis in a panel of patient-derived and commercially available human melanoma cells. In vitro assays to evaluate clonogenicity, cell proliferation, cell migration, cell invasion, and in vitro capillary-like structure formation [vasculogenic mimicry (VM)] have been performed by using human melanoma cells stably overexpressing Bcl2L10 or transiently transfected for loss/gain function of Bcl2L10, grown under two- or three-dimensional (3D) conditions Xenograft melanoma model was employed to evaluate in vivo tumor growth and angiogenesis.

Results:

Results demonstrated that Bcl2L10 acts as an inducer of in vitro cell migration, invasion, and VM, while in vitro cell proliferation, in vivo tumor growth, as well as colony formation properties were not affected. Dissecting different signaling pathways, it was found that Bcl2L10 positively affects the phosphorylation of extracellular-signal-regulated kinase (ERK) and the expression of markers of cell invasion, such as urokinase plasminogen activator receptor (uPAR) and matrix metalloproteinases (MMPs). Of note, Bcl2L10-dependent in vitro migration, invasion, and VM are linked to uPAR. Bcl2L10 also negatively regulates the intracellular calcium level. Finally, reduced invasion capability in 3D spheroid invasion assay of melanoma cells transiently overexpressing Bcl2L10 was observed after treatment with inhibitors of MMPs and uPAR.

Conclusions:

Overall, data reported in this paper provide evidence supporting a positive role of Bcl2L10 in melanoma aggressive features.

Bcl-2 Family Members and the Mitochondrial Import Machineries: The Roads to Death

The localization of Bcl-2 family members at the mitochondrial outer membrane (MOM) is a crucial step in the implementation of apoptosis. We review evidence showing the role of the components of the mitochondrial import machineries (translocase of the outer membrane (TOM) and the sorting and assembly machinery (SAM)) in the mitochondrial localization of Bcl-2 family members and how these machineries regulate the function of pro- and anti-apoptotic proteins in resting cells and in cells committed into apoptosis.

Mitochondrial inhibitors circumvent adaptive resistance to venetoclax and cytarabine combination therapy in acute myeloid leukemia

Therapy resistance represents a major clinical challenge in acute myeloid leukemia (AML). Here we define a 'MitoScore' signature, which identifies high mitochondrial oxidative phosphorylation in vivo and in patients with AML. Primary AML cells with cytarabine (AraC) resistance and a high MitoScore relied on mitochondrial Bcl2 and were highly sensitive to venetoclax (VEN) + AraC (but not to VEN + azacytidine). Single-cell transcriptomics of VEN + AraC-residual cell populations revealed adaptive resistance associated with changes in oxidative phosphorylation, electron transport chain complex and the TP53 pathway. Accordingly, treatment of VEN + AraC-resistant AML cells with electron transport chain complex inhibitors, pyruvate dehydrogenase inhibitors or mitochondrial ClpP protease agonists substantially delayed relapse following VEN + AraC. These findings highlight the central role of mitochondrial adaptation during AML therapy and provide a scientific rationale for alternating VEN + azacytidine with VEN + AraC in patients with a high MitoScore and to target mitochondrial metabolism to enhance the sensitivity of AML cells to currently approved therapies.

Impact of Concomitant Aberrant CD200 and BCL2 Overexpression on Outcome of Acute Myeloid Leukemia: A Cohort Study from a Single Center

Objective:

CD200 and BCL2 overexpression is independently associated with inferior survival in acute myeloid leukemia (AML), and these two factors are frequently co-expressed; however, no data are available on the role of concomitant aberrant CD200 and BCL2 expression on outcome of AML patients. We aimed to elucidate the prognostic role of CD200/BCL2 co-expression and its association with specific leukemia subsets.

Materials and Methods:

We analyzed 242 adult AML patients uniformly treated with intensive chemotherapy, evaluating the impact of CD200 and BCL2 expression on complete remission (CR), disease-free survival, and overall survival (OS).

Results:

CD200 and BCL2 were expressed in 139 (57.4%) and 137 (56.6%) cases, respectively, with 92 patients (38%) displaying double positivity (DP), 58 (24%) displaying double negativity (DN), and 92 patients expressing only either CD200 (n=47) or BCL2 (n=45). CR was achieved in 71% of cases, being less frequent in DP patients (60%) compared to other groups (76%-81%, p<0.001). In the whole population 3-year OS was 44%, being lower in DP patients (28%) than in patients with single CD200 or BCL2 expression (47%) or DN cases (60%; p=0.004). Other factors associated with worse OS were advanced age, CD34 positivity, secondary AML, and high white blood cell count at diagnosis; combining these 4 factors with CD200/BCL2 DP, we identified 6 groups with significantly different rates of survival (3-year OS ranging from 90% to 0%).

Conclusion:

Our data support a synergistic effect of CD200 and BCL2 in AML cells, conferring an enhanced survival capacity in a permissive microenvironment and resulting in worse prognosis.

Bcl-2 Family of Proteins in the Control of Mitochondrial Calcium Signalling: An Old Chap with New Roles

Bcl-2 family proteins are considered as one of the major regulators of apoptosis. Indeed, this family is known to control the mitochondrial outer membrane permeabilization (MOMP): a central step in the mitochondrial pathway of apoptosis. However, in recent years Bcl-2 family members began to emerge as a new class of intracellular calcium (Ca²⁺) regulators. At mitochondria-ER contacts (MERCs) these proteins are able to interact with major Ca²⁺ transporters, thus controlling mitochondrial Ca²⁺ homeostasis and downstream Ca²⁺ signalling pathways. Beyond the regulation of cell survival, this Bcl-2-dependent control over the mitochondrial Ca²⁺ dynamics has far-reaching consequences on the physiology of the cell. Here, we review how the Bcl-2 family of proteins mechanistically regulate mitochondrial Ca²⁺ homeostasis and how this regulation orchestrates cell death/survival decisions as well as the non-apoptotic process of cell migration.

Balancing ER-Mitochondrial Ca2+ Fluxes in Health and Disease

Organelles cooperate with each other to control cellular homeostasis and cell functions by forming close connections through membrane contact sites. Important contacts are present between the endoplasmic reticulum (ER), the main intracellular Ca²⁺-storage organelle, and the mitochondria, the organelle responsible not only for the majority of cellular ATP production but also for switching on cell death processes. Several Ca²⁺-transport systems focalize at these contact sites, thereby enabling the efficient transmission of Ca²⁺ signals from the ER toward mitochondria. This provides tight control of mitochondrial functions at the microdomain level. Here, we discuss how ER-mitochondrial Ca²⁺ transfers support cell function and how their dysregulation underlies, drives, or contributes to pathogenesis and pathophysiology, with a major focus on cancer and neurodegeneration but also with attention to other diseases such as diabetes and rare genetic diseases.

The Intriguing Clinical Success of BCL-2 Inhibition in Acute Myeloid Leukemia

Over the past several decades numerous preclinical and clinical studies have pursued new approaches for the treatment of acute myeloid leukemia (AML). While some degree of clinical response has been demonstrated for many therapies, for the most part, fundamental changes in the treatment landscape have been lacking. Recently, the use of the BCL-2 inhibitor venetoclax has emerged as a potent therapy for a majority of newly diagnosed AML patients. Venetoclax regimens have shown broad response rates with deep and durable remissions, with a superior toxicity profile compared with traditional intensive chemotherapy agents. Numerous ongoing studies are now using venetoclax in combination with a wide range of other agents as investigators seek even more effective and well-tolerated regimens. Notably, however, while the empirical results of BCL-2 inhibition are encouraging, the mechanisms that have led to these successful clinical outcomes remain unclear. Intriguingly, the activity of venetoclax in AML patients appears to go beyond simply modulating canonical antiapoptosis mechanisms; in addition, the efficacy of venetoclax is linked to its combined use with conventional low-intensity backbone therapies. This article will evaluate the state of the field, provide a summary of key considerations, and propose directions for future studies.

Protective effects of dapagliflozin against oxidative stress-induced cell injury in human proximal tubular cells

Elevated reactive oxygen species (ROS) in type 2 diabetes cause cellular damage in many organs. Recently, the new class of glucose-lowering agents, SGLT-2 inhibitors, have been shown to reduce the risk of developing diabetic complications; however, the mechanisms of such beneficial effect are largely unknown. Here we aimed to investigate the effects of dapagliflozin on cell proliferation and cell death under oxidative stress conditions and explore its underlying mechanisms. Human proximal tubular cells (HK-2) were used. Cell growth and death were monitored by cell counting, water-soluble tetrazolium-1 (WST-1) and lactate dehydrogenase (LDH) assays, and flow cytometry. The cytosolic and mitochondrial (ROS) production was measured using fluorescent probes (H2DCFDA and MitoSOX) under normal and oxidative stress conditions mimicked by addition of H₂O₂. Intracellular Ca²⁺ dynamics was monitored by FlexStation 3 using cell-permeable Ca²⁺ dye Fura-PE3/AM. Dapagliflozin (0.1–10 μM) had no effect on HK-2 cell proliferation under normal conditions, but an inhibitory effect was seen at an extreme high concentration (100 μM). However, dapagliflozin at 0.1 to 5 μM showed remarkable protective effects against H₂O₂-induced cell injury via increasing the viable cell number at phase G0/G1. The elevated cytosolic and mitochondrial ROS under oxidative stress was significantly decreased by dapagliflozin. Dapagliflozin increased the basal intracellular [Ca²⁺]_i in proximal tubular cells, but did not affect calcium release from endoplasmic reticulum and store-operated Ca²⁺ entry. The H₂O₂-sensitive TRPM2 channel seemed to be involved in the Ca²⁺ dynamics regulated by dapagliflozin. However, dapagliflozin had no direct effects on ORAI1, ORAI3, TRPC4 and TRPC5 channels. Our results suggest that dapagliflozin shows anti-oxidative properties by reducing cytosolic and mitochondrial ROS production and altering Ca²⁺ dynamics, and thus exerts its protective effects against cell damage under oxidative stress environment.

Proteome profiling of different rat brain regions reveals the modulatory effect of prolonged maternal separation on proteins involved in cell death-related processes

Background

Early-life stress in the form of maternal separation can be associated with alterations in offspring neurodevelopment and brain functioning. Here, we aimed to investigate the potential impact of prolonged maternal separation on proteomic profiling of prefrontal cortex, hippocampus and cerebellum of juvenile and young adult rats. A special attention was devoted to proteins involved in the process of cell death and redox state maintenance.

Methods

Long-Evans pups were separated from their mothers for 3 h daily over the first 3 weeks of life (during days 2–21 of age). Brain tissue samples collected from juvenile (22-day-old) and young adult (90-day-old) rats were used for label-free quantitative (LFQ) proteomic analysis. In parallel, selected oxidative stress markers and apoptosis-related proteins were assessed biochemically and by Western blot, respectively.

Results

In total, 5526 proteins were detected in our proteomic analysis of rat brain tissue. Approximately one tenth of them (586 proteins) represented those involved in cell death processes or regulation of oxidative stress balance. Prolonged maternal separation caused changes in less than half of these proteins (271). The observed alterations in protein expression levels were age-, sex- and brain region-dependent. Interestingly, the proteins detected by mass spectrometry that are known to be involved in the maintenance of redox state were not markedly altered. Accordingly, we did not observe any significant differences between selected oxidative stress markers, such as the levels of hydrogen peroxide, reduced glutathione, protein carbonylation and lipid peroxidation in brain samples from rats that underwent maternal separation and from the corresponding controls. On the other hand, a number of changes were found in cell death-associated proteins, mainly in those involved in the apoptotic and autophagic pathways. However, there were no detectable alterations in the levels of cleaved products of caspases or Bcl-2 family members. Taken together, these data indicate that the apoptotic and autophagic cell death pathways were not activated by maternal separation either in adolescent or young adult rats.

Conclusion

Prolonged maternal separation can distinctly modulate expression profiles of proteins associated with cell death pathways in prefrontal cortex, hippocampus and cerebellum of juvenile rats and the consequences of early-life stress may last into adulthood and likely participate in variations in stress reactivity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-021-00327-5.

BIRD-2, a BH4-domain-targeting peptide of Bcl-2, provokes Bax/Bak-independent cell death in B-cell cancers through mitochondrial Ca2+-dependent mPTP opening

Anti-apoptotic Bcl-2 critically controls cell death by neutralizing pro-apoptotic Bcl-2-family members at the mitochondria. Bcl-2 proteins also act at the endoplasmic reticulum, the main intracellular Ca²⁺-storage organelle, where they inhibit IP₃ receptors (IP₃R) and prevent pro-apoptotic Ca²⁺-signaling events. IP₃R channels are targeted by the BH4 domain of Bcl-2. Some cancer types rely on the IP₃R-Bcl-2 interaction for survival. We previously developed a cell-permeable, BH4-domain-targeting peptide that can abrogate Bcl-2's inhibitory action on IP₃Rs, named Bcl-2 IP₃ receptor disrupter-2 (BIRD-2). This peptide kills several Bcl-2-dependent cancer cell types, including diffuse large B-cell lymphoma (DLBCL) and chronic lymphocytic leukaemia (CLL) cells, by eliciting intracellular Ca²⁺ signalling. However, the exact mechanisms by which these excessive Ca²⁺ signals triggered by BIRD-2 provoke cancer cell death remain elusive. Here, we demonstrate in DLBCL that although BIRD-2 activates caspase 3/7 and provokes cell death in a caspase-dependent manner, the cell death is independent of pro-apoptotic Bcl-2-family members, Bim, Bax and Bak. Instead, BIRD-2 provokes mitochondrial Ca²⁺ overload that is rapidly followed by opening of the mitochondrial permeability transition pore (mPTP). Inhibiting mitochondrial Ca²⁺ overload using Ru265, an inhibitor of the mitochondrial Ca²⁺ uniporter complex counteracts BIRD-2-induced cancer cell death. Finally, we validated our findings in primary CLL patient samples where BIRD-2 provoked mitochondrial Ca²⁺ overload and Ru265 counteracted BIRD-2-induced cell death. Overall, this work reveals the mechanisms by which BIRD-2 provokes cell death, which occurs via mitochondrial Ca²⁺ overload but acts independently of pro-apoptotic Bcl-2-family members.

Attenuation of Lipopolysaccharide-Induced Acute Lung Injury by Hispolon in Mice, Through Regulating the TLR4/PI3K/Akt/mTOR and Keap1/Nrf2/HO-1 Pathways, and Suppressing Oxidative Stress-Mediated ER Stress-Induced Apoptosis and Autophagy

The anti-inflammatory effect of hispolon has identified it as one of the most important compounds from Sanghuangporus sanghuang. The research objectives were to study this compound using an animal model by lipopolysaccharide (LPS)-induced acute lung injury. Hispolon treatment reduced the production of the pro-inflammatory mediator NO, TNF-α, IL-1β, and IL-6 induced by LPS challenge in the lung tissues, as well as decreasing their histological alterations and protein content. Total cell number was also reduced in the bronchoalveolar lavage fluid (BALF). Moreover, hispolon inhibited iNOS, COX-2 and IκB-α and phosphorylated IKK and MAPK, while increasing catalase, SOD, GPx, TLR4, AKT, HO-1, Nrf-2, Keap1 and PPARγ expression, after LPS challenge. It also regulated apoptosis, ER stress and the autophagy signal transduction pathway. The results of this study show that hispolon regulates LPS-induced ER stress (increasing CHOP, PERK, IRE1, ATF6 and GRP78 protein expression), apoptosis (decreasing caspase-3 and Bax and increasing Bcl-2 expression) and autophagy (reducing LC3 I/II and Beclin-1 expression). This in vivo experimental study suggests that hispolon suppresses the LPS-induced activation of inflammatory pathways, oxidative injury, ER stress, apoptosis and autophagy and has the potential to be used therapeutically in major anterior segment lung diseases.

Endoplasmic reticulum stress mediates resistance to BCL-2 inhibitor in uveal melanoma cells

To address unmet clinical need for uveal melanomas, we assessed the effects of BH3-mimetic molecules, the ABT family, known to exert pro-apoptotic activities in cancer cells. Our results uncovered that ABT-263 (Navitoclax), a potent and orally bioavailable BCL-2 family inhibitor, induced antiproliferative effects in metastatic human uveal melanoma cells through cell cycle arrest at the G0/G1 phase, loss of mitochondrial membrane potential, and subsequently apoptotic cell death monitored by caspase activation and poly-ADP ribose polymerase cleavage. ABT-263-mediated reduction in tumor growth was also observed in vivo. We observed in some cells that ABT-263 treatment mounted a pro-survival response through activation of the ER stress signaling pathway. Blocking the PERK signaling pathway increased the pro-apoptotic ABT-263 effect. We thus uncovered a resistance mechanism in uveal melanoma cells mediated by activation of endoplasmic reticulum stress pathway. Therefore, our study identifies ABT-263 as a valid therapeutic option for patients suffering from uveal melanoma.

The apoptosis inhibitor Bcl-xL controls breast cancer cell migration through mitochondria-dependent reactive oxygen species production

The Bcl-xL apoptosis inhibitor plays a major role in vertebrate development. In addition to its effect on apoptosis, Bcl-xL is also involved in cell migration and mitochondrial metabolism. These effects may favour the onset and dissemination of metastasis. However, the underlying molecular mechanisms remain to be fully understood. Here we focus on the control of cell migration by Bcl-xL in the context of breast cancer cells. We show that Bcl-xL silencing led to migration defects in Hs578T and MDA-MB231 cells. These defects were rescued by re-expressing mitochondria-addressed, but not endoplasmic reticulum-addressed, Bcl-xL. The use of BH3 mimetics, such as ABT-737 and WEHI-539 confirmed that the effect of Bcl-xL on migration did not depend on interactions with BH3-containing death accelerators such as Bax or BH3-only proteins. In contrast, the use of a BH4 peptide that disrupts the Bcl-xL/VDAC1 complex supports that Bcl-xL by acting on VDAC1 permeability contributes to cell migration through the promotion of reactive oxygen species production by the electron transport chain. Collectively our data highlight the key role of Bcl-xL at the interface between cell metabolism, cell death, and cell migration, thus exposing the VDAC1/Bcl-xL interaction as a promising target for anti-tumour therapy in the context of metastatic breast cancer.

A robust TDP-43 knock-in mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is a fatal, adult-onset degenerative disorder of motor neurons. The diseased spinal cord motor neurons of more than 95% of amyotrophic lateral sclerosis (ALS) patients are characterized by the mis-metabolism of the RNA/DNA-binding protein TDP-43 (ALS-TDP), in particular, the presence of cytosolic aggregates of the protein. Most available mouse models for the basic or translational studies of ALS-TDP are based on transgenic overexpression of the TDP-43 protein. Here, we report the generation and characterization of mouse lines bearing homologous knock-in of fALS-associated mutation A315T and sALS-associated mutation N390D, respectively. Remarkably, the heterozygous TDP-43 (N390D/+) mice but not those heterozygous for the TDP-43 (A315T/+) mice develop a full spectrum of ALS-TDP-like pathologies at the molecular, cellular and behavioral levels. Comparative analysis of the mutant mice and spinal cord motor neurons (MN) derived from their embryonic stem (ES) cells demonstrates that different ALS-associated TDP-43 mutations possess critical ALS-causing capabilities and pathogenic pathways, likely modified by their genetic background and the environmental factors. Mechanistically, we identify aberrant RNA splicing of spinal cord Bcl-2 pre-mRNA and consequent increase of a negative regulator of autophagy, Bcl-2, which correlate with and are caused by a progressive increase of TDP-43, one of the early events associated with ALS-TDP pathogenesis, in the spinal cord of TDP-43 (N390D/+) mice and spinal cord MN derived from their ES cells. The TDP-43 (N390D/+) knock-in mice appear to be an ideal rodent model for basic as well as translational studies of ALS- TDP.

miR-636 represses cell survival by targeting CDK6/Bcl-2 in cervical cancer

Cervical cancer is widely known as one of the most common types of cancer diagnosed in women, and microRNAs (miRNAs) has been characterized as an important regulator in tumor progression, such as cervical cancer. MiR-636 was found to play a tumor suppressor role in hepatocellular carcinoma tumorigenesis. However, the tumorigenic mechanism of miR-636 on cervical cancer has not yet been found. In the present study, we first found that miR-636 was significantly downregulated in cervical cancer tissues and cell lines. in vitro gain- and loss-of-function assays revealed that overexpression of miR-636 inhibited cell proliferation and induced cell apoptosis, while knockdown of miR-636 reversed the effect on cervical tumorigenesis. Furthermore, cyclin-dependent kinase 6 (CDK6) and B-cell lymphoma 2 (Bcl-2) were characterized as targets of miR-636. Notably, overexpression of CDK6 or Bcl-2 could reverse the inhibitory effect of miR-636 on cervical cancer progression. Mechanistically, miR-636 repressed cell survival by targeting CDK6/Bcl-2 in cervical cancer, which may be the underlying mechanism of miR-636-inhibited cervical progression. In conclusion, our findings clarified the biologic significance of miR-636/CDK6/Bcl-2 axis in cervical cancer progression and suggested the potential therapeutic target ability of miR-636 in treatment of cervical cancer.

MUC16 facilitates cervical cancer progression via JAK2/STAT3 phosphorylation-mediated cyclooxygenase-2 expression

OBJECTIVES

MUC16 (mucin 16, also known as CA-125, cancer antigen 125, carcinoma antigen 125, or carbohydrate antigen 125) has been predicted as tumor biomarker for therapy. We determined to investigate effects and regulatory mechanism of MUC16 on cervical tumorigenesis.

METHODS

Expression levels of MUC16 in cervical cancer cell lines was analyzed via qRT-PCR (quantitative real-time polymerase chain reaction). Knockdown of MUC16 was conducted via shRNA (Short hairpin RNA) transfection. MTT and colony formation assays were used to investigate effect of MUC16 on cell proliferation. Wound healing assay was utilized to detect migration and transwell assay to detect invasion. The underlying mechanism was demonstrated via western blot analysis.

RESULTS

MUC16 was elevated in cervical cancer cell lines. MUC16 knockdown inhibited cell proliferation, invasion and migration. Gain- and loss-of functional assays revealed that over-expression of MUC16 activated Janus Kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) via phosphorylation, thus facilitating cyclooxygenase-2 (COX-2) expression, while knockdown of MUC16 demonstrated the reverse effect on JAK2/STAT3 activation and COX-2 expression. Moreover, inhibition of JAK2/STAT3 attenuated the regulation of MUC16 on COX-2.

CONCLUSIONS

MUC16 enhanced proliferation and invasion of cervical cancer cells via JAK2/STAT3 phosphorylation-mediated cyclooxygenase-2 expression, suggesting the potential therapeutic target ability of MUC16 to treat cervical cancer.

TNF Induces Pathogenic Programmed Macrophage Necrosis in Tuberculosis through a Mitochondrial-Lysosomal-Endoplasmic Reticulum Circuit

Necrosis of infected macrophages constitutes a critical pathogenetic event in tuberculosis by releasing mycobacteria into the growth-permissive extracellular environment. In zebrafish infected with Mycobacterium marinum or Mycobacterium tuberculosis, excess tumor necrosis factor triggers programmed necrosis of infected macrophages through the production of mitochondrial reactive oxygen species (ROS) and the participation of cyclophilin D, a component of the mitochondrial permeability transition pore. Here, we show that this necrosis pathway is not mitochondrion-intrinsic but results from an inter-organellar circuit initiating and culminating in the mitochondrion. Mitochondrial ROS induce production of lysosomal ceramide that ultimately activates the cytosolic protein BAX. BAX promotes calcium flow from the endoplasmic reticulum into the mitochondrion through ryanodine receptors, and the resultant mitochondrial calcium overload triggers cyclophilin-D-mediated necrosis. We identify ryanodine receptors and plasma membrane L-type calcium channels as druggable targets to intercept mitochondrial calcium overload and necrosis of mycobacterium-infected zebrafish and human macrophages.

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TNF induces mitochondrial ROS to cause necrosis of mycobacterium-infected macrophages

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Mitochondrial ROS activate lysosomal enzymes that lead to BAX activation

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BAX activates ER ryanodine receptors to cause Ca²⁺ flow into the mitochondrion

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Drugs preventing mitochondrial Ca²⁺ overload prevent pathogenic macrophage necrosis in TB

Modulations of Histone Deacetylase 2 Offer a Protective Effect through the Mitochondrial Apoptosis Pathway in Acute Liver Failure

The purpose of this study was to investigate the modulation of histone deacetylase 2 (HDAC2) on mitochondrial apoptosis in acute liver failure (ALF). The cellular model was established with LO2 cells stimulated by tumor necrosis factor alpha (TNF-α)/D-galactosamine (D-gal). Rats were administrated by lipopolysaccharide (LPS)/D-gal as animal model. The cell and animal models were then treated by HDAC2 inhibitor CAY10683. HDAC2 was regulated up or down by lentiviral vector transfection in LO2 cells. The mRNA levels of bcl2 and bax were detected by real-time PCR. The protein levels of HDAC2, bcl2, bax, cytochrome c (cyt c) in mitochondrion and cytosol, apoptosis protease activating factor 1 (apaf1), caspase 3, cleaved-caspase 3, caspase 9, cleaved-caspase 9, acetylated histone H3 (AH3), and histone H3 (H3) were assayed by western blot. Apoptosis was detected by flow cytometry. The serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin (TBIL) levels were also assayed. The openness degree of the mitochondrial permeability transition pore (MPTP) was detected by ultraviolet spectrophotometry. The apoptosis of hepatocytes in liver tissues was determined by tunnel staining. The liver tissue pathology was detected by hematoxylin eosin (HE) staining. The ultrastructure of liver tissue was observed by electron microscopy. Compared with cell and rat model groups, the bax mRNA level was decreased, and bcl2 mRNA was increased in the CAY10683 treatment group. The protein levels of HDAC2, bax, cyt c in cytosol, apaf1, cleaved-caspase 3, and cleaved-caspase 9 were decreased, and the apoptosis rate was decreased (P < 0.05), whereas the protein level of bcl2 and cyt c in the mitochondrion was elevated (P < 0.05) in the CAY10683 treatment group. In the HDAC2 down- or upregulated LO2 cells, the mitochondrial apoptosis pathway was inhibited or activated, respectively. After being treated with TNF-α/D-gal in HDAC2 down- or upregulated LO2 cells, the mitochondrial apoptosis pathway was further suppressed or activated, respectively. The MPTP value was elevated in CAY10683-treated groups compared with the rat model group (P < 0.05). Liver tissue pathological damage and apoptotic index in the CAY10683-treated group were significantly reduced. In addition, AH3 was elevated in both cell and animal model groups (P < 0.05). Downregulated or overexpressed HDAC2 could accordingly increase or decrease the AH3 level, and TNF-α/D-gal could enhance the acetylation effect. These results suggested that modulations of histone deacetylase 2 offer a protective effect through the mitochondrial apoptosis pathway in acute liver failure.

Programmed Cell Death in Immune Defense: Knowledge and Presumptions

Cell-culture studies are our main source of knowledge of the various forms of programmed cell death. Yet genetic perturbations of death-protein function in animal models are almost the only source of our knowledge of the physiological roles of these programs. Shortcomings in the state of knowledge acquired by these two experimental approaches are exemplified in this Perspective by reference to research on the contribution of apoptosis to lymphocyte development, a subject on which there is already much knowledge, and on the role of necroptosis in inflammation, about which information is just beginning to emerge. To address these shortcomings, there is need to find ways to verify the notions obtained through the current experimental approaches by directly monitoring death programs within specific cells in vivo.

BMN 673 (talazoparib): A potent PARP inhibitor for triple negative breast cancer with different genetic profile

The objective of the present study was to elucidate the effect of BMN 673 (talozoparib) on BRCA1 mutant (HCC1937) and wild-type (MDA-MB-231) triple negative breast cancer (TNBC). The in vitro cytotoxicity results indicated that BMN 673 had considerable inhibitory effects on HCC1937 and MDA-MB-231 cell lines by inducing apoptosis, multicaspase activity, G2/M arrest, and altering the expression levels of apoptosis-related genes (P < 0.01). Additionally, BMN 673 indicated no toxicity on MCF-10A control cells until a certain concentration and incubation time. However, BMN 673, a novel and selective poly ADP ribose polymerase inhibitor, was more potent in TNBC cells bearing BRCA1 mutant than those with wild-type BRCA1. In conclusion, our study, for the first time, demonstrated a molecular mechanism of the induction of apoptosis by BMN 673 in TNBC with different genetic profile. However, further investigations regarding the exact molecular mechanisms underlying BMN 673-inducing apoptotic death and gene-cell line associations are required.

Protective Effect and Mechanism of Alprostadil in Acute Respiratory Distress Syndrome Induced by Oleic Acid in Rats

BACKGROUND This study investigated the role and mechanism of alprostadil in acute respiratory distress syndrome (ARDS) induced by oleic acid (OA) in rats. MATERIAL AND METHODS Sprague-Dawley rats were randomly divided into control, OA model, and OA + Alprostadil (2.5, 5, and 10 μg/kg, respectively) groups. The ARDS model was induced by femoral vein injection of OA, and alprostadil was administrated immediately. Lung injury was evaluated by lung wet-dry weight ratio (W/D) and histological analyses. Expressions of ACE, inflammatory mediators, apoptotic-related proteins, and proteins in the MAPKs and NF-κB signaling pathways were determined by Western blot or immunohistochemical staining. RESULTS Compared with the control group, the OA model group had significantly increased W/D, lung injury score, and collagen deposition at 3 h after OA injection. However, alprostadil (10 μg/kg) treatment significantly reduced OA-induced elevation of these indicators. Additionally, OA-induced expression of TNF-α and IL-1β were suppressed by alprostadil. The OA-induced activation of nuclear factor (NF) κB p65 was also reduced by alprostadil. Furthermore, we found that Alprostadil had an inhibitory effect on the phosphorylation of JNK, ERK1/2, and p38 MAPKs. Alprostadil inhibited Bax but increased Bcl-2, indicating a suppressive role in apoptosis. Remarkably increased expression of ACE in the OA model group was observed, which was decreased by alprostadil. CONCLUSIONS Alprostadil has a protective effect on ARDS induced by OA in rats, possibly through inhibiting apoptosis, suppressing the activation of MAPKs and NF-κB signaling pathways, and decreasing ACE protein expression. Therefore, the use of alprostadil in clinical ARDS treatment is promising.

A structural investigation of NRZ mediated apoptosis regulation in zebrafish

Bcl-2 family proteins play a crucial role in regulating apoptosis, a process critical for development, eliminating damaged or infected cells, host-pathogen interactions and in disease. Dysregulation of Bcl-2 proteins elicits an expansive cell survival mechanism promoting cell migration, invasion and metastasis. Through a network of intra-family protein-protein interactions Bcl-2 family members regulate the release of cell death factors from mitochondria. NRZ is a novel zebrafish pro-survival Bcl-2 orthologue resident on mitochondria and the endoplasmic reticulum (ER). However, the mechanism of NRZ apoptosis inhibition has not yet been clarified. Here we examined the interactions of NRZ with pro-apoptotic members of the Bcl-2 family using a combination of isothermal calorimetry and mutational analysis of NRZ. We show that NRZ binds almost all zebrafish pro-apoptotic proteins and displays a broad range of affinities. Furthermore, we define the structural basis for apoptosis inhibition of NRZ by solving the crystal structure of both apo-NRZ and a holo form bound to a peptide spanning the binding motif of the pro-apoptotic zBad, a BH3-only protein orthologous to mammalian Bad. The crystal structure of NRZ revealed that it adopts the conserved Bcl-2 like fold observed for other cellular pro-survival Bcl-2 proteins and employs the canonical ligand binding groove to bind Bad BH3 peptide. NRZ engagement of Bad BH3 involves the canonical ionic interaction between NRZ R86 and Bad D104 and an additional ionic interaction between NRZ D79 and Bad R100, and substitution of either NRZ R86 or D79 to Ala reduces the binding to Bad BH3 tenfold or more. Our findings provide a detailed mechanistic understanding for NRZ mediated anti-apoptotic activity in zebrafish by revealing binding to both Bad and Noxa, suggesting that NRZ is likely to occupy a unique mechanistic role in zebrafish apoptosis regulation by acting as a highly promiscuous pro-apoptotic Bcl-2 binder.

New insights into the role of mitochondrial calcium homeostasis in cell migration

Mitochondria are dynamic organelles involved in numerous physiological functions. Beyond their function in ATP production, mitochondria regulate cell death, reactive oxygen species (ROS) generation, immunity and metabolism. Mitochondria also play a key role in the buffering of cytosolic calcium, and calcium transported into the matrix regulates mitochondrial metabolism. Recently, the identification of the mitochondrial calcium uniporter (MCU) and associated regulators has allowed the characterization of new physiological roles for calcium in both mitochondrial and cellular homeostasis. Indeed, recent work has highlighted the importance of mitochondrial calcium homeostasis in regulating cell migration. Cell migration is a property common to all metazoans and is critical to embryogenesis, cancer progression, wound-healing and immune surveillance. Previous work has established that cytoplasmic calcium is a key regulator of cell migration, as oscillations in cytosolic calcium activate cytoskeletal remodelling, actin contraction and focal adhesion (FA) turnover necessary for cell movement. Recent work using animal models and in cellulo experiments to genetically modulate MCU and partners have shed new light on the role of mitochondrial calcium dynamics in cytoskeletal remodelling through the modulation of ATP and ROS production, as well as intracellular calcium signalling. This review focuses on MCU and its regulators in cell migration during physiological and pathophysiological processes including development and cancer. We also present hypotheses to explain the molecular mechanisms by which MCU may regulate mitochondrial dynamics and motility to drive cell migration.

Mcl-1 regulates reactive oxygen species via NOX4 during chemotherapy-induced senescence

Mcl-1, a Bcl-2 family member, is highly expressed in a variety of human cancers and is believed to enhance tumorigenic potential and chemotherapy resistance through the inhibition of apoptosis and senescence. We previously reported that Mcl-1′s regulation of chemotherapy-induced senescence (CIS) is dependent on its ability to prevent reactive oxygen species (ROS) generation. In this report, we demonstrate that Mcl-1-regulated CIS requires not only ROS, but specifically mitochondrial ROS, and that these events are upstream of activation of the DNA damage response, another necessary step toward senescence. Mcl-1′s anti-senescence activity also involves the unique ability to inhibit ROS formation by preventing the upregulation of pro-oxidants. Specifically, we found that NADPH oxidases (NOXs) are regulated by Mcl-1 and that NOX4 expression in particular is a required step for CIS induction that is blocked by Mcl-1. Lastly, we illustrate that by preventing expression of NOX4, Mcl-1 limits its availability in the mitochondria, thereby lowering the production of mitochondrial ROS during CIS. Our studies not only define the essential role of Mcl-1 in chemoresistance, but also for the first time link a key pro-survival Bcl-2 family member with the NOX protein family, both of which have significant ramifications in cancer progression.

Subcellular Localization and Dynamics of the Bcl-2 Family of Proteins

Bcl-2 family proteins are recognized as major regulators of the mitochondrial pathway of apoptosis. They control the mitochondrial outer membrane permeabilization (MOMP) by directly localizing to this organelle. Further investigations demonstrated that Bcl-2 related proteins are also found in other intracellular compartments such as the endoplasmic reticulum, the Golgi apparatus, the nucleus and the peroxisomes. At the level of these organelles, Bcl-2 family proteins not only regulate MOMP in a remote fashion but also participate in major cellular processes including calcium homeostasis, cell cycle control and cell migration. With the advances of live cell imaging techniques and the generation of fluorescent recombinant proteins, it became clear that the distribution of Bcl-2 proteins inside the cell is a dynamic process which is profoundly affected by changes in the cellular microenvironment. Here, we describe the current knowledge related to the subcellular distribution of the Bcl-2 family of proteins and further emphasize on the emerging concept that this highly dynamic process is critical for cell fate determination.

Breast Cancer Targeting through Inhibition of the Endoplasmic Reticulum-Based Apoptosis Regulator Nrh/BCL2L10

Drug resistance and metastatic relapse remain a top challenge in breast cancer treatment. In this study, we present preclinical evidence for a strategy to eradicate advanced breast cancers by targeting the BCL-2 homolog Nrh/BCL2L10, which we discovered to be overexpressed in >45% of a large cohort of breast invasive carcinomas. Nrh expression in these tumors correlated with reduced metastasis-free survival, and we determined it to be an independent marker of poor prognosis. Nrh protein localized to the endoplasmic reticulum. Mechanistic investigations showed that Nrh made BH4 domain-dependent interactions with the ligand-binding domain of the inositol-1,4,5-triphosphate receptor (IP3R), a type 1/3 Ca2⁺ channel, allowing Nrh to negatively regulate ER-Ca2⁺ release and to mediate antiapoptosis. Notably, disrupting Nrh/IP3R complexes by BH4 mimetic peptides was sufficient to inhibit the growth of breast cancer cells in vitro and in vivo Taken together, our results highlighted Nrh as a novel prognostic marker and a candidate therapeutic target for late stage breast cancers that may be addicted to Nrh.Significance: These findings offer a comprehensive molecular model for the activity of Nrh/BCL2L10, a little studied antiapoptotic molecule, prognostic marker, and candidate drug target in breast cancer. Cancer Res; 78(6); 1404-17. ©2018 AACR.

Genistein Promotes Proliferation of Human Cervical Cancer Cells Through Estrogen Receptor-Mediated PI3K/Akt-NF-κB Pathway

Phytoestrogens are polyphenol compounds which have similar structure to 17β-estradiol (E2), a kind of main estrogen in women. Thus, phytoestrogens may affect the reproductive and endocrine systems, leading to the development of estrogen-related cancers. The effect of genistein (Gen), one of the most studied phytoestrogens, on human cervical cancer cells (HeLa) was investigated in this study. It was found that Gen at concentrations of 0.001, 0.01, 0.1 and 1 µmol·L-1 promoted the proliferation of HeLa cells in a dose-dependent manner. Gen increased the portion of HeLa cells in S phase and decreased the portion of the cells in G1 phase. Besides, apoptosis rate of the cells was significantly lower when treated with Gen compared with the control group. It was also found that the expression of ERα, Akt or nuclear NF-κB p65 protein was activated by Gen. The correlation between these three proteins may be as following: ERα was the upstream, followed by Akt, and then nuclear NF-κB p65 protein. In addition, the downstream genes of activated nuclear NF-κB p65 were found to be associated with cell cycle and apoptosis of cancer cells. Our results suggested that Gen may stimulate cell proliferation partially through the estrogen receptor-mediated PI3K/Akt-NF-κB pathway and the further activation of the downstream genes of nuclear NF-κB p65.

Molecular basis of AKAP79 regulation by calmodulin

AKAP79/150 is essential for coordinating second messenger-responsive enzymes in processes including synaptic long-term depression. Ca²⁺ directly regulates AKAP79 through its effector calmodulin (CaM), but the molecular basis of this regulation was previously unknown. Here, we report that CaM recognizes a ‘1-4-7-8’ pattern of hydrophobic amino acids starting at Trp79 in AKAP79. Cross-linking coupled to mass spectrometry assisted mapping of the interaction site. Removal of the CaM-binding sequence in AKAP79 prevents formation of a Ca²⁺-sensitive interface between AKAP79 and calcineurin, and increases resting cellular PKA phosphorylation. We determined a crystal structure of CaM bound to a peptide encompassing its binding site in AKAP79. CaM adopts a highly compact conformation in which its open Ca²⁺-activated C-lobe and closed N-lobe cooperate to recognize a mixed α/3₁₀ helix in AKAP79. The structure guided a bioinformatic screen to identify potential sites in other proteins that may employ similar motifs for interaction with CaM.

The A-kinase anchoring protein AKAP79 is regulated by calmodulin (CaM). Here, the authors use crosslinking coupled to mass spectrometry to identify the CaM-binding site in AKAP79 and present the structure of CaM bound to an AKAP79 peptide. The structure shows that CaM adopts a highly compact conformation to interact with a mixed α/3₁₀ helix in AKAP79.

Regulation of apoptosis is impaired in atrophic gastritis associated with gastric cancer

BACKGROUND

Gastric premalignant conditions, atrophic gastritis (AG) and intestinal metaplasia (IM) are characterized by an increase of proliferation and a reduction of apoptosis in epithelial cells. The epithelial cell kinetics in AG and IM in gastric mucosa adjacent to gastric cancer is still unclear. The aim of this study was to evaluate the epithelial cell turnover and expression of proliferation and apoptosis-related genes in gastric cancer (GC) and adjacent mucosa with atrophic gastritis or intestinal metaplasia (AG/IM GC+), as well as in atrophic gastritis or intestinal metaplasia mucosa of patients without GC (AG/IM GC-) and in control biopsy samples of non-transformed gastric mucosa (Control).

METHODS

We selected 58 patients (M: F = 34:24; age range 20-84 years, median 61.06 years) with 4 well defined histological conditions: 20 controls with histological finding of non-transformed gastric mucosa, 20 patients with AG or IM (AG/IM GC-), and 18 patients with intestinal type gastric adenocarcinoma (GC) and AG or IM in the adjacent mucosa (3 cm from the macroscopic tumour margin, AG/IM GC+). We performed an immunohistochemical staining of Ki67 and TUNEL and quantitative RT-PCR to determine the expression of PCNA and Bax/Bcl-2.

RESULTS

The immunohistochemical expression of Ki67 and TUNEL in AG/IM GC- was significantly increased compared to not transformed gastric mucosa (p < 0.0001) but not compared to AG/IM in gastric mucosa adjacent to GC. Levels of Bcl-2 were reduced in GC and AG/IM GC- compared to controls as well as in AG/IM GC- compared to AG/IM in mucosa adjacent to GC+ (p < 0.05). Proliferation and apoptosis markers did not correlate with H.pylori status in our study population.

CONCLUSIONS

In AG/IM associated with GC, no significant changes in the epithelial cell turnover were detected. Decreased Bcl-2 gene expression signified atrophic gastritis and IM in presence of cancer, as well as intestinal type gastric adenocarcinoma.

ATP2A3 gene as an important player for resveratrol anticancer activity in breast cancer cells

The Ca²⁺ -ATPases from the Sarco/endoplasmic reticulum (SERCA) are fundamental for maintaining intracellular [Ca²⁺ ] homeostasis by pumping Ca²⁺ into the endoplasmic reticulum (ER) of eukaryotic cells. SERCA enzymes are encoded by three different genes (ATP2A1-3), whose expression occurs in a tissue and development stage-specific manner. It has been reported alterations in the expression of SERCA2 and SERCA3 pumps in different types of cancer: oral, lung, colon, stomach, central nervous system, thyroid, breast, and prostate. Resveratrol (RSV), a phytoalexin produced by a wide variety of plants in response to stress situations can modulate cellular processes involved in all stages of carcinogenesis. In this work, we used breast cancer cell lines (MCF-7 and MDA-MB-231) to evaluate mRNA levels of ATP2A2 and ATP2A3 genes in response to RSV treatment. Our results demonstrate that RSV treatment induced the expression of ATP2A3 gene in both cell lines in a time and concentration-dependent manner, while the expression of ATP2A2 gene remained unaffected. The RSV-induced expression of SERCA3 in these breast cancer cell lines produced decreased cell viability, triggered apoptosis and changes in cytosolic Ca²⁺ levels, as well as changes in the capacity for Ca²⁺ release by the ER. These data suggest an important participation of SERCA3 genes in RSV-mediated anti-tumor effect in breast cancer cell lines. Nevertheless, further research is needed to elucidate the molecular mechanisms underlying this effect.

Bcl-2 family proteins: master regulators of cell survival

The most prominent function of proteins of the Bcl-2 family is regulation of the initiation of intrinsic (mitochondrial) pathways of apoptosis. However, recent research has revealed that in addition to regulation of mitochondrial apoptosis, proteins of the Bcl-2 family play important roles in regulating other cellular pathways with a strong impact on cell survival like autophagy, endoplasmic reticulum (ER) stress response, intracellular calcium dynamics, cell cycle progression, mitochondrial dynamics and energy metabolism. This review summarizes the recent knowledge about functions of Bcl-2 family proteins that are related to cell survival.

Calcium regulates cell death in cancer: Roles of the mitochondria and mitochondria-associated membranes (MAMs)

Until 1972, the term 'apoptosis' was used to differentiate the programmed cell death that naturally occurs in organismal development from the acute tissue death referred to as necrosis. Many studies on cell death and programmed cell death have been published and most are, at least to some degree, related to cancer. Some key proteins and molecular pathways implicated in cell death have been analyzed, whereas others are still being actively researched; therefore, an increasing number of cellular compartments and organelles are being implicated in cell death and cancer. Here, we discuss the mitochondria and subdomains of the endoplasmic reticulum (ER) that interact with mitochondria, the mitochondria-associated membranes (MAMs), which have been identified as critical hubs in the regulation of cell death and tumor growth. MAMs-dependent calcium (Ca²⁺) release from the ER allows selective Ca²⁺ uptake by the mitochondria. The perturbation of Ca²⁺ homeostasis in cancer cells is correlated with sustained cell proliferation and the inhibition of cell death through the modulation of Ca²⁺ signaling. This article is part of a Special Issue entitled Mitochondria in Cancer, edited by Giuseppe Gasparre, Rodrigue Rossignol and Pierre Sonveaux.

IRBIT controls apoptosis by interacting with the Bcl-2 homolog, Bcl2l10, and by promoting ER-mitochondria contact

IRBIT is a molecule that interacts with the inositol 1,4,5-trisphosphate (IP₃)-binding pocket of the IP₃ receptor (IP₃R), whereas the antiapoptotic protein, Bcl2l10, binds to another part of the IP₃-binding domain. Here we show that Bcl2l10 and IRBIT interact and exert an additive inhibition of IP₃R in the physiological state. Moreover, we found that these proteins associate in a complex in mitochondria-associated membranes (MAMs) and that their interplay is involved in apoptosis regulation. MAMs are a hotspot for Ca²⁺ transfer between endoplasmic reticulum (ER) and mitochondria, and massive Ca²⁺ release through IP₃R in mitochondria induces cell death. We found that upon apoptotic stress, IRBIT is dephosphorylated, becoming an inhibitor of Bcl2l10. Moreover, IRBIT promotes ER mitochondria contact. Our results suggest that by inhibiting Bcl2l10 activity and promoting contact between ER and mitochondria, IRBIT facilitates massive Ca²⁺ transfer to mitochondria and promotes apoptosis. This work then describes IRBIT as a new regulator of cell death.

Hypericin in the Dark: Foe or Ally in Photodynamic Therapy?

Photosensitizers (PSs) in photodynamic therapy (PDT) are, in most cases, administered systemically with preferential accumulation in malignant tissues; however, exposure of non-malignant tissues to PS may also be clinically relevant, when PS molecules affect the pro-apoptotic cascade without illumination. Hypericin (Hyp) as PS and its derivatives have long been studied, regarding their photodynamic and photocytotoxic characteristics. Hyp and its derivatives have displayed light-activated antiproliferative and cytotoxic effects in many tumor cell lines without cytotoxicity in the dark. However, light-independent effects of Hyp have emerged. Contrary to the acclaimed Hyp minimal dark cytotoxicity and preferential accumulation in tumor cells, it was recently been shown that non-malignant and malignant cells uptake Hyp at a similar level. In addition, Hyp has displayed light-independent toxicity and anti-proliferative effects in a wide range of concentrations. There are multiple mechanisms underlying Hyp light-independent effects, and we are still missing many details about them. In this paper, we focus on Hyp light-independent effects at several sub-cellular levels—protein distribution and synthesis, organelle ultrastructure and function, and Hyp light-independent effects regarding reactive oxygen species (ROS). We summarize work from our laboratories and that of others to reveal an intricate network of the Hyp light-independent effects. We propose a schematic model of pro- and anti-apoptotic protein dynamics between cell organelles due to Hyp presence without illumination. Based on our model, Hyp can be explored as an adjuvant therapeutic drug in combination with chemo- or radiation cancer therapy.