The major isoforms of Bim contribute to distinct biological activities that govern the processes of autophagy and apoptosis in interleukin-7 dependent lymphocytes

Apoptosis, Autophagy, Necrosis and Their Multi Galore Crosstalk in Neurodegeneration

The progression of neurodegenerative disorders is mainly characterized by immense neuron loss and death of glial cells. The mechanisms which are active and regulate neuronal cell death are namely necrosis, necroptosis, autophagy and apoptosis. These death paradigms are governed by a set of molecular determinants that are pivotal in their performance and also exhibit remarkable overlapping functional pathways. A large number of such molecules have been demonstrated to be involved in the switching of death paradigms in various neurodegenerative diseases. In this review, we discuss various molecules and the concurrent crosstalk mediated by them. According to our present knowledge and research in neurodegeneration, molecules like Atg1, Beclin1, LC3, p53, TRB3, RIPK1 play switching roles toggling from one death mechanism to another. In addition, the review also focuses on the exorbitant number of newer molecules with the potential to cross communicate between death pathways and create a complex cell death scenario. This review highlights recent studies on the inter-dependent regulation of cell death paradigms in neurodegeneration, mediated by cross-communication between pathways. This will help in identifying potential targets for therapeutic intervention in neurodegenerative diseases.

The role of cell signaling in the crosstalk between autophagy and apoptosis in the regulation of tumor cell survival in response to sorafenib and neratinib

The molecular mechanisms by which tumor cells survive or die following therapeutic interventions are complex. There are three broadly defined categories of cell death processes: apoptosis (Type I), autophagic cell death (Type II), and necrosis (Type III). In hematopoietic tumor cells, the majority of toxic stimuli cause these cells to undergo a death process called apoptosis; apoptosis specifically involves the cleavage of DNA into large defined pieces and their subsequent localization in vesicles. Thus, 'pure' apoptosis largely lacks inflammatory potential. In carcinomas, however, the mechanisms by which tumor cells ultimately die are considerably more complex. Although the machinery of apoptosis is engaged by toxic stimuli, other processes such as autophagy ("self-eating") and replicative cell death can lead to observations that do not simplistically correspond to any of the individual Type I-III formalized death categories. The 'hybrid' forms of cell death observed in carcinoma cells result in cellular materials being released into the extracellular space without packaging, which promotes inflammation, potentially leading to the accelerated re-growth of surviving tumor cells by macrophages. Drugs as single agents or in combinations can simultaneously initiate signaling via both apoptotic and autophagic pathways. Based on the tumor type and its oncogene drivers, as well as the drug(s) being used and the duration and intensity of the autophagosome signal, apoptosis and autophagy have the potential to act in concert to kill or alternatively that the actions of either pathway can act to suppress signaling by the other pathway. And, there also is evidence that autophagic flux, by causing lysosomal protease activation, with their subsequent release into the cytosol, can directly mediate killing. This review will discuss the interactive biology between apoptosis and autophagy in carcinoma cells. Finally, the molecular actions of the FDA-approved drugs neratinib and sorafenib, and how they enhance both apoptotic and toxic autophagic processes, alone or in combination with other agents, is discussed in a bench-to-bedside manner.

Irisin and Autophagy: First Update

Aging and sedentary life style are considered independent risk factors for many disorders. Under these conditions, accumulation of dysfunctional and damaged cellular proteins and organelles occurs, resulting in a cellular degeneration and cell death. Autophagy is a conserved recycling pathway responsible for the degradation, then turnover of cellular proteins and organelles. This process is a part of the molecular underpinnings by which exercise promotes healthy aging and mitigate age-related pathologies. Irisin is a myokine released during physical activity and acts as a link between muscles and other tissues and organs. Its main beneficial function is the change of subcutaneous and visceral adipose tissue into brown adipose tissue, with a consequential increase in thermogenesis. Irisin modulates metabolic processes, acting on glucose homeostasis, reduces systemic inflammation, maintains the balance between resorption and bone formation, and regulates the functioning of the nervous system. Recently, some of its pleiotropic and favorable properties have been attributed to autophagy induction, posing irisin as an important regulator of autophagy by exercise. This review article proposes to bring together for the first time the "state of the art" knowledge regarding the effects of irisin and autophagy. Furthermore, treatments on relation between exercise/myokines and autophagy have been also achieved.

The Double-Edge Sword of Autophagy in Cancer: From Tumor Suppression to Pro-tumor Activity

During tumorigenesis, cancer cells are exposed to a wide variety of intrinsic and extrinsic stresses that challenge homeostasis and growth. Cancer cells display activation of distinct mechanisms for adaptation and growth even in the presence of stress. Autophagy is a catabolic mechanism that aides in the degradation of damaged intracellular material and metabolite recycling. This activity helps meet metabolic needs during nutrient deprivation, genotoxic stress, growth factor withdrawal and hypoxia. However, autophagy plays a paradoxical role in tumorigenesis, depending on the stage of tumor development. Early in tumorigenesis, autophagy is a tumor suppressor via degradation of potentially oncogenic molecules. However, in advanced stages, autophagy promotes the survival of tumor cells by ameliorating stress in the microenvironment. These roles of autophagy are intricate due to their interconnection with other distinct cellular pathways. In this review, we present a broad view of the participation of autophagy in distinct phases of tumor development. Moreover, autophagy participation in important cellular processes such as cell death, metabolic reprogramming, metastasis, immune evasion and treatment resistance that all contribute to tumor development, is reviewed. Finally, the contribution of the hypoxic and nutrient deficient tumor microenvironment in regulation of autophagy and these hallmarks for the development of more aggressive tumors is discussed.

Idelalisib promotes Bim-dependent apoptosis through AKT/FoxO3a in hepatocellular carcinoma

Idelalisib, a selective PI3Kδ inhibitor, has been approved by the FDA for chronic lymphocytic leukemia/small lymphocytic lymphoma treatment and for follicular lymphoma treatment when combined with rituximab. However, the mechanisms of effective action of idelalisib in hepatocellular carcinoma (HCC) remain unclear. In the current study, we aimed to investigate how idelalisib inhibits the growth of HCC cells and enhances the effects of other chemotherapeutic drugs. Our results show that idelalisib treatment promotes Bim induction in HCC via the FoxO3a pathway following PI3K/AKT inactivation. Moreover, our results show that Bim is required for idelalisib-mediated apoptosis in HCC. Idelalisib also synergizes with sorafenib or doxorubicin to induce significant apoptosis in HCC, and Bim is also necessary for the induction of apoptosis by cotreatment. Furthermore, a xenograft experiment reveals that the Bim deficiency abolishes apoptosis and antitumor effects of idelalisib in vivo. In summary, our results indicate a key role of Bim in mediating the antitumor effects of idelalisib in HCC. Our results also support the clinical significance of the drug.

IL-7 suppresses macrophage autophagy and promotes liver pathology in Schistosoma japonicum-infected mice

In schistosomiasis japonica and mansoni, parasite eggs trapped in host liver elicit severe liver granulomatous inflammation that subsequently leads to periportal fibrosis, portal hypertension, haemorrhage or even death. Macrophages are critical for granuloma formation and the development of liver fibrosis during schistosomiasis. However, whether the aberrant regulation of macrophage autophagy has an effect on the development of liver immunopathology in schistosomiasis remains to be elucidated. In this study, we showed that Schistosoma japonicum (S. japonicum) egg antigen (SEA)-triggered macrophage autophagy limited the development of pathology in host liver. However, engagement of IL-7 receptor (IL-7R/CD127) on macrophages by S. japonicum infection-induced IL-7 significantly suppressed SEA-triggered macrophage autophagy, which led to an enhanced liver pathology. In addition, anti-IL-7 neutralizing antibody or anti-CD127 blocking antibody treatment increased macrophage autophagy and suppressed liver pathology. Finally, we demonstrated that IL-7 protects macrophage against SEA-induced autophagy through activation of AMP-activated protein kinase (AMPK). Our study reveals a novel role for IL-7 in macrophage autophagy and identifies AMPK as a novel downstream mediator of IL-7-IL-7R signalling and suggests that manipulation of macrophage autophagy by targeting IL-7-IL-7R signalling may have the potential to lead to improved treatment options for liver pathogenesis in schistosomiasis.

Glucocorticoids promote apoptosis of proinflammatory monocytes by inhibiting ERK activity

Glucocorticoids (GCs) are potent anti-inflammatory drugs whose mode of action is complex and still debatable. One likely cellular target of GCs are monocytes/macrophages. The role of GCs in monocyte survival is also debated. Although both granulocyte macrophage-colony stimulating factor (GM-CSF) and macrophage-CSF (M-CSF) are important regulators of macrophage lineage functions including their survival, the former is often associated with proinflammatory functions while the latter is important in lineage homeostasis. We report here that the GC, dexamethasone, induces apoptosis in GM-CSF-treated human monocytes while having no impact on M-CSF-induced monocyte survival. To understand how GCs, GM-CSF, and M-CSF are regulating monocyte survival and other functions during inflammation, we firstly examined the transcriptomic changes elicited by these three agents in human monocytes, either acting alone or in combination. Transcriptomic and Ingenuity pathway analyses found that dexamethasone differentially modulated dendritic cell maturation and TREM1 signaling pathways in GM-CSF-treated and M-CSF-treated monocytes, two pathways known to be regulated by ERK1/2 activity. These analyses led us to provide evidence that the GC inhibits ERK1/2 activity selectively in GM-CSF-treated monocytes to induce apoptosis. It is proposed that this inhibition of ERK1/2 activity leads to inactivation of p90 ribosomal-S6 kinase and Bad dephosphorylation leading in turn to enhanced caspase-3 activity and subsequent apoptosis. Furthermore, pharmacological inhibition of GC receptor activity restored the ERK1/2 signaling and prevented the GC-induced apoptosis in GM-CSF-treated monocytes. Increased tissue macrophage numbers, possibly from enhanced survival due to mediators such as GM-CSF, can correlate with inflammatory disease severity; also reduction in these numbers can correlate with the therapeutic benefit of a number of agents, including GCs. We propose that the ERK1/2 signaling pathway promotes survival of GM-CSF-treated proinflammatory monocytes, which can be selectively targeted by GCs as a novel mechanism to reduce local monocyte/macrophage numbers and hence inflammation.

BAMBI inhibits inflammation through the activation of autophagy in experimental spinal cord injury

Autophagy plays an important role in the progression of spinal cord injury (SCI). In this study, we aimed to examine the effects and potential mechanisms of action of BMP and activin membrane-bound inhibitor (BAMBI) in the progression of SCI. A rat model of SCI was established and the rats were injected with pLentiH1-BAMBI shRNA and pAd-BAMBI in the gray and white matter of the spinal cord at T8. After 14 days, motor function evaluation was measured according to the Basso Beattie Bresnahan (BBB) method and the number of motor neuron cell accounts in the anterior horns was measured by Nissl staining. The protein expression of levels light chain 3B (LC3B), Beclin 1, Bim and p62 were measured by western blot analysis. The concentrations of interleukin (IL)-1β, IL-6 and IL-10 were measured by ELISA. The results revealed that BAMBI expression was significantly decreased in the rats with SCI. The BBB scores and the number of motor neuron cell accounts in the anterior horns were significantly decreased in the pLentiH1-BAMBI shRNA injection group, and were increased in the pAd-BAMBI injection group, suggesting a neuroprotective effect of BAMBI in SCI. Moreover, the increased expression levels of LC3B and Beclin 1, and the decreased expression of Bim and p62 indicated that autophagy was significantly induced in the pAd-BAMBI injection group. Moreover, the overexpression of BAMBI also decreased the expression of transforming growth factor-β (TGF-β) and mammalian target of rapamycin (mTOR), and decreased the concentrations of IL-1β, IL-6 and IL-10. These results indicate that BAMBI plays a neuroprotective role by decreasing inflammation and activating autophagy in rats with SCI.

Regulation of Bim in Health and Disease

The BH3-only Bim protein is a major determinant for initiating the intrinsic apoptotic pathway under both physiological and pathophysiological conditions. Tight regulation of its expression and activity at the transcriptional, translational and post-translational levels together with the induction of alternatively spliced isoforms with different pro-apoptotic potential, ensure timely activation of Bim. Under physiological conditions, Bim is essential for shaping immune responses where its absence promotes autoimmunity, while too early Bim induction eliminates cytotoxic T cells prematurely, resulting in chronic inflammation and tumor progression. Enhanced Bim induction in neurons causes neurodegenerative disorders including Alzheimer's, Parkinson's and Huntington's diseases. Moreover, type I diabetes is promoted by genetically predisposed elevation of Bim in β-cells. On the contrary, cancer cells have developed mechanisms that suppress Bim expression necessary for tumor progression and metastasis. This review focuses on the intricate network regulating Bim activity and its involvement in physiological and pathophysiological processes.

Polycation-mediated integrated cell death processes

One of the major challenges in the field of nucleic acid delivery is the design of delivery vehicles with attributes that render them safe as well as efficient in transfection. To this end, polycationic vectors have been intensely investigated with native polyethylenimines (PEIs) being the gold standard. PEIs are highly efficient transfectants, but depending on their architecture and size they induce cytotoxicity through different modes of cell death pathways. Here, we briefly review dynamic and integrated cell death processes and pathways, and discuss considerations in cell death assay design and their interpretation in relation to PEIs and PEI-based engineered vectors, which are also translatable for the design and studying the safety of other transfectants.

Thymic Atrophy and Apoptosis of CD4+CD8+ Thymocytes in the Cuprizone Model of Multiple Sclerosis

Previous studies on the degenerative animal model of multiple sclerosis suggested that the copper-chelator cuprizone might directly suppress T-cell functions. Peripheral T-cell function in the cuprizone model has already been explored; therefore, in the present study, we investigated, for the first time, how cuprizone feeding affects the thymus, the organ of T-cell maturation and selection. We found that even one week of cuprizone treatment induced significant thymic atrophy, affecting the cortex over the medulla. Fluorescent microscopy and flow-cytometric analyses of thymi from cuprizone- and vehicle-treated mice indicated that eradication of the cluster of the differentiation-4 (CD4)-CD8 double-positive T-cell subset was behind the substantial cell loss. This result was confirmed with CD3-CD4-CD8 triple-staining experiments. Ultrastructurally, we observed degraded as well as enlarged mitochondria, myelin-bodies, large lipid droplets, and large lysosomes in the thymi of cuprizone-treated mice. Some of these features were similar to those in physiological and steroid-induced accelerated aging. According to our results, apoptosis was mainly of mitochondrial origin mediated by both caspase-3- and apoptosis inducing factor-mediated mechanisms. Additionally, mitogen activated protein kinase activation and increased pro-apoptotic B cell lymphoma-2 family protein expression were the major underlying processes. Our results do not indicate a functional relationship between cuprizone-induced thymus involution and the absence of inflammatory responses or the selective demyelination observed in the cuprizone model. On the other hand, due to the reversible nature of cuprizone’s deleterious effects, the cuprizone model could be valuable in studying thymus regeneration as well as remyelination processes.

Targeting T cell immunometabolism for cancer immunotherapy; understanding the impact of the tumor microenvironment

The immune system has a key role to play in controlling cancer initiation and progression. T cell activation, which is central to anti-tumor immune responses, coincides with changes in cellular metabolism. Naïve T cells predominantly require an ATP generating metabolic profile, whereas proliferating effector T cells require anabolic metabolic profiles that promote rapid growth and proliferation. Furthermore, specific T cell subsets require distinct energetic and biosynthetic pathways to match their functional requirements. The often hostile tumor microenvironment can affect T cell immune responses by altering the resulting cellular metabolism. Tailoring immune responses by manipulating cellular metabolic pathways may provide an exciting new option for cancer immunotherapy. T cell responses might also be skewed via metabolic manipulation to treat the complications of obesity-associated inflammation, which is a rapidly growing global health problem and a major risk factor for many malignancies. In this review, the diverse metabolic requirements of T cells in anti-tumor immunity are discussed, as well as the profound influence of the tumor microenvironment and the possible avenues for manipulation to enhance anti-tumor immunity.

Osteolytic bone metastasis is hampered by impinging on the interplay among autophagy, anoikis and ossification

Here we show that the fate of osteolytic bone metastasis depends on the balance among autophagy, anoikis resistance and ossification, and that the hepatocyte growth factor (HGF) signaling pathway seems to have an important role in orchestrating bone colonization. These findings are consistent with the pathophysiology of bone metastasis that is influenced by the cross-talk of supportive and neoplastic cells through molecular signaling networks. We adopted the strategy to target metastasis and stroma with the use of adenovirally expressed NK4 (AdNK4) and Dasatinib to block HGF/Met axis and Src activity. In human bone metastatic 1833 cells, HGF conferred anoikis resistance via Akt and Src activities and HIF-1α induction, leading to Bim isoforms degradation. When Src and Met activities were inhibited with Dasatinib, the Bim isoforms accumulated conferring anoikis sensitivity. The proviability effect of HGF, under low-nutrient stress condition, was related to a faster autophagy deactivation with respect to HGF plus Dasatinib. In the 1833 xenograft model, AdNK4 switched metastasis vasculature to blood lacunae, increasing HIF-1α in metastasis. The combination of AdNK4 plus Dasatinib gave the most relevant results for mice survival, and the following molecular and cellular changes were found to be responsible. In bone metastasis, we observed a hypoxic condition – marked by HIF-1α – and an autophagy failure – marked by p62 without Beclin-1. Then, osteolytic bone metastases were largely prevented, because of autophagy failure in metastasis and ossification in bone marrow, with osteocalcin deposition. The abnormal repair process was triggered by the dysfunctional autophagy/anoikis interplay. In conclusion, the concomitant blockade of HGF/Met axis and Src activity seemed to induce HIF-1α in metastasis, whereas the bone marrow hypoxic response was reduced. As a consequence, anoikis resistance might be hampered favoring, instead, autophagy failure and neoformation of woven bone trabeculae. Mice survival was, therefore, prolonged by overcoming an escape strategy adopted by metastatic cells by disruption of tumor–stroma coevolution, showing the importance of autophagy inhibition for the therapy of bone metastasis.

Lysosomal cell death at a glance

Lysosomes serve as the cellular recycling centre and are filled with numerous hydrolases that can degrade most cellular macromolecules. Lysosomal membrane permeabilization and the consequent leakage of the lysosomal content into the cytosol leads to so-called "lysosomal cell death". This form of cell death is mainly carried out by the lysosomal cathepsin proteases and can have necrotic, apoptotic or apoptosis-like features depending on the extent of the leakage and the cellular context. This article summarizes our current knowledge on lysosomal cell death with an emphasis on the upstream mechanisms that lead to lysosomal membrane permeabilization.

Role of the Crosstalk between Autophagy and Apoptosis in Cancer

Autophagy and apoptosis are catabolic pathways essential for organismal homeostasis. Autophagy is normally a cell-survival pathway involving the degradation and recycling of obsolete, damaged, or harmful macromolecular assemblies; however, excess autophagy has been implicated in type II cell death. Apoptosis is the canonical programmed cell death pathway. Autophagy and apoptosis have now been shown to be interconnected by several molecular nodes of crosstalk, enabling the coordinate regulation of degradation by these pathways. Normally, autophagy and apoptosis are both tumor suppressor pathways. Autophagy fulfils this role as it facilitates the degradation of oncogenic molecules, preventing development of cancers, while apoptosis prevents the survival of cancer cells. Consequently, defective or inadequate levels of either autophagy or apoptosis can lead to cancer. However, autophagy appears to have a dual role in cancer, as it has now been shown that autophagy also facilitates the survival of tumor cells in stress conditions such as hypoxic or low-nutrition environments. Here we review the multiple molecular mechanisms of coordination of autophagy and apoptosis and the role of the proteins involved in this crosstalk in cancer. A comprehensive understanding of the interconnectivity of autophagy and apoptosis is essential for the development of effective cancer therapeutics.

Matched and mismatched metabolic fuels in lymphocyte function

Immunological function requires metabolic support to suit the needs of lymphocytes at a variety of distinct differentiation and activation states. It is now evident that the signaling pathways that drive lymphocyte survival and activity can directly control cellular metabolism. This linkage provides a mechanism by which activation and specific signaling pathways provide a supply of appropriate and required nutrients to support cell functions in a pro-active supply rather than consumption-based metabolic model. In this way, the metabolism and fuel choices of lymphocytes are guided to specifically match the anticipated needs. If the fuel choice or metabolic pathways of lymphocytes are dysregulated, however, metabolic checkpoints can become activated to disrupt immunological function. These changes are now shown in several immunological diseases and may open new opportunities to selectively enhance or suppress specific immune functions through targeting of glucose, lipid, or amino acid metabolism.