Impact of house dust mite in vitiligo skin: environmental contribution to increased cutaneous immunity and melanocyte detachment.

BACKGROUND: Vitiligo is an autoimmune skin disorder characterized by loss of melanocytes. Protease-mediated disruption of junctions between keratinocytes and/or keratinocyte intrinsic dysfunction may directly contribute to melanocyte loss. House dust mite (HDM), an environmental allergen with potent protease activity, contributes to respiratory and gut disease but also to atopic dermatitis and rosacea. OBJECTIVES: To verify if HDM can contribute to melanocyte detachment in vitiligo and if so, by which mechanism(s). METHODS: Using primary human keratinocytes, human skin biopsies from healthy donors and patients with vitiligo, and 3D reconstructed human epidermis, we studied the effect of HDM on cutaneous immunity, tight and adherent junction expression and melanocyte detachment. RESULTS: HDM increased keratinocyte production of vitiligo-associated cytokines and chemokines and increased expression of toll-like receptor (TLR)-4. This was associated with increased in situ matrix-metalloproteinase (MMP)-9 activity, reduced cutaneous expression of adherent protein E-cadherin, increased soluble E-cadherin in culture supernatant and significantly increased number of suprabasal melanocytes in the skin. This effect was dose-dependent and driven by cysteine protease Der p1 and MMP-9. Selective MMP-9 inhibitor, Ab142180, restored E-cadherin expression and inhibited HDM-induced melanocyte detachment. Keratinocytes from patients with vitiligo were more sensitive to HDM-induced changes than healthy keratinocytes. All results were confirmed in a 3D model of healthy skin and in human skin biopsies. CONCLUSIONS: Our results highlight that environmental mite may act as an external source of pathogen-associated molecular pattern molecules in vitiligo and topical MMP-9 inhibitors may be useful therapeutic targets. Whether HDM contributes to the onset of flares in vitiligo remains to be tested in carefully controlled trials.

Starvation and antimetabolic therapy promote cytokine release and recruitment of immune cells.

Cellular starvation is typically a consequence of tissue injury that disrupts the local blood supply but can also occur where cell populations outgrow the local vasculature, as observed in solid tumors. Cells react to nutrient deprivation by adapting their metabolism, or, if starvation is prolonged, it can result in cell death. Cell starvation also triggers adaptive responses, like angiogenesis, that promote tissue reorganization and repair, but other adaptive responses and their mediators are still poorly characterized. To explore this issue, we analyzed secretomes from glucose-deprived cells, which revealed up-regulation of multiple cytokines and chemokines, including IL-6 and IL-8, in response to starvation stress. Starvation-induced cytokines were cell type-dependent, and they were also released from primary epithelial cells. Most cytokines were up-regulated in a manner dependent on NF-κB and the transcription factor of the integrated stress response ATF4, which bound directly to the IL-8 promoter. Furthermore, glutamine deprivation, as well as the antimetabolic drugs 2-deoxyglucose and metformin, also promoted the release of IL-6 and IL-8. Finally, some of the factors released from starved cells induced chemotaxis of B cells, macrophages, and neutrophils, suggesting that nutrient deprivation in the tumor environment can serve as an initiator of tumor inflammation.

Lysosomal Cholesterol Hydrolysis Couples Efferocytosis to Anti-Inflammatory Oxysterol Production.

RATIONALE: Macrophages face a substantial amount of cholesterol after the ingestion of apoptotic cells, and the LIPA (lysosomal acid lipase) has a major role in hydrolyzing cholesteryl esters in the endocytic compartment. OBJECTIVE: Here, we directly investigated the role of LIPA-mediated clearance of apoptotic cells both in vitro and in vivo. METHODS AND RESULTS: We show that LIPA inhibition causes a defective efferocytic response because of impaired generation of 25-hydroxycholesterol and 27-hydroxycholesterol. Reduced synthesis of 25-hydroxycholesterol after LIPA inhibition contributed to defective mitochondria-associated membrane leading to mitochondrial oxidative stress-induced NLRP3 (NOD-like receptor family, pyrin domain containing) inflammasome activation and caspase-1-dependent Rac1 (Ras-related C3 botulinum toxin substrate 1) degradation. A secondary event consisting of failure to appropriately activate liver X receptor-mediated pathways led to mitigation of cholesterol efflux and apoptotic cell clearance. In mice, LIPA inhibition caused defective clearance of apoptotic lymphocytes and stressed erythrocytes by hepatic and splenic macrophages, culminating in splenomegaly and splenic iron accumulation under hypercholesterolemia. CONCLUSIONS: Our findings position lysosomal cholesterol hydrolysis as a critical process that prevents metabolic inflammation by enabling efficient macrophage apoptotic cell clearance.

Bax inhibitor-1 protects from nonalcoholic steatohepatitis by limiting inositol-requiring enzyme 1 alpha signaling in mice.

Endoplasmic reticulum (ER) stress is activated in nonalcoholic fatty liver disease (NAFLD), raising the possibility that ER stress-dependent metabolic dysfunction, inflammation, and cell death underlie the transition from steatosis to steatohepatitis (nonalcoholic steatohepatitis; NASH). B-cell lymphoma 2 (BCL2)-associated X protein (Bax) inhibitor-1 (BI-1), a negative regulator of the ER stress sensor, inositol-requiring enzyme 1 alpha (IRE1α), has yet to be explored in NAFLD as a hepatoprotective agent. We hypothesized that the genetic ablation of BI-1 would render the liver vulnerable to NASH because of unrestrained IRE1α signaling. ER stress was induced in wild-type and BI-1-/- mice acutely by tunicamycin (TM) injection (1 mg/kg) or chronically by high-fat diet (HFD) feeding to determine NAFLD phenotype. Livers of TM-treated BI-1-/- mice showed IRE1α-dependent NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation, hepatocyte death, fibrosis, and dysregulated lipid homeostasis that led to liver failure within a week. The analysis of human NAFLD liver biopsies revealed BI-1 down-regulation parallel to the up-regulation of IRE1α endoribonuclease (RNase) signaling. In HFD-fed BI-1-/- mice that presented NASH and type 2 diabetes, exaggerated hepatic IRE1α, X-box binding protein 1 (XBP1), and C/EBP homologous protein (CHOP) expression was linked to activated NLRP3 inflammasome and caspase-1/-11. Rises in interleukin (IL)-1ß, IL-6, monocyte chemoattractant protein 1 (MCP1), chemokine (C-X-C motif) ligand 1 (CXCL1), and alanine transaminase (ALT)/aspartate transaminase (AST) levels revealed significant inflammation and injury, respectively. Pharmacological inhibition of IRE1α RNase activity with the small molecules, STF-083010 or 4µ8c, was evaluated in HFD-induced NAFLD. In BI-1-/- mice, either treatment effectively counteracted IRE1α RNase activity, improving glucose tolerance and rescuing from NASH. The hepatocyte-specific role of IRE1α RNase activity in mediating NLRP3 inflammasome activation and cell death was confirmed in primary mouse hepatocytes by IRE1α axis knockdown or its inhibition with STF-083010 or 4µ8c. CONCLUSION: Targeting IRE1α-dependent NLRP3 inflammasome signaling with pharmacological agents or by BI-1 may represent a tangible therapeutic strategy for NASH. (Hepatology 2018).

Escherichia coli α-hemolysin counteracts the anti-virulence innate immune response triggered by the Rho GTPase activating toxin CNF1 during bacteremia.

The detection of the activities of pathogen-encoded virulence factors by the innate immune system has emerged as a new paradigm of pathogen recognition. Much remains to be determined with regard to the molecular and cellular components contributing to this defense mechanism in mammals and importance during infection. Here, we reveal the central role of the IL-1ß signaling axis and Gr1+ cells in controlling the Escherichia coli burden in the blood in response to the sensing of the Rho GTPase-activating toxin CNF1. Consistently, this innate immune response is abrogated in caspase-1/11-impaired mice or following the treatment of infected mice with an IL-1ß antagonist. In vitro experiments further revealed the synergistic effects of CNF1 and LPS in promoting the maturation/secretion of IL-1ß and establishing the roles of Rac, ASC and caspase-1 in this pathway. Furthermore, we found that the α-hemolysin toxin inhibits IL-1ß secretion without affecting the recruitment of Gr1+ cells. Here, we report the first example of anti-virulence-triggered immunity counteracted by a pore-forming toxin during bacteremia.

Combination of glycolysis inhibition with chemotherapy results in an antitumor immune response.

Most DNA-damaging agents are weak inducers of an anticancer immune response. Increased glycolysis is one of the best-described hallmarks of tumor cells; therefore, we investigated the impact of glycolysis inhibition, using 2-deoxyglucose (2DG), in combination with cytotoxic agents on the induction of immunogenic cell death. We demonstrated that 2DG synergized with etoposide-induced cytotoxicity and significantly increased the life span of immunocompetent mice but not immunodeficient mice. We then established that only cotreated cells induced an efficient tumor-specific T-cell activation ex vivo and that tumor antigen-specific T cells could only be isolated from cotreated animals. In addition, only when mice were immunized with cotreated dead tumor cells could they be protected (vaccinated) from a subsequent challenge using the same tumor in viable form. Finally, we demonstrated that this effect was at least partially mediated through ERp57/calreticulin exposure on the plasma membrane. These data identify that the targeting of glycolysis can convert conventional tolerogenic cancer cell death stimuli into immunogenic ones, thus creating new strategies for immunogenic chemotherapy.

Dependence on mitochondrial respiration of malignant T cells reveals a new therapeutic target for angioimmunoblastic T-cell lymphoma.

Cancer metabolic reprogramming has been recognized as one of the cancer hallmarks that promote cell proliferation, survival, as well as therapeutic resistance. Up-to-date regulation of metabolism in T-cell lymphoma is poorly understood. In particular, for human angioimmunoblastic T-cell lymphoma (AITL) the metabolic profile is not known. Metabolic intervention could help identify new treatment options for this cancer with very poor outcomes and no effective medication. Transcriptomic analysis of AITL tumor cells, identified that these cells use preferentially mitochondrial metabolism. By using our preclinical AITL mouse model, mimicking closely human AITL features, we confirmed that T follicular helper (Tfh) tumor cells exhibit a strong enrichment of mitochondrial metabolic signatures. Consistent with these results, disruption of mitochondrial metabolism using metformin or a mitochondrial complex I inhibitor such as IACS improved the survival of AITL lymphoma-bearing mice. Additionally, we confirmed a selective elimination of the malignant human AITL T cells in patient biopsies upon mitochondrial respiration inhibition. Moreover, we confirmed that diabetic patients suffering from T-cell lymphoma, treated with metformin survived longer as compared to patients receiving alternative treatments. Taking together, our findings suggest that targeting the mitochondrial metabolic pathway could be a clinically efficient approach to inhibit aggressive cancers such as peripheral T-cell lymphoma.

Bax Inhibitor-1 preserves pancreatic ß-cell proteostasis by limiting proinsulin misfolding and programmed cell death.

The prevalence of diabetes steadily increases worldwide mirroring the prevalence of obesity. Endoplasmic reticulum (ER) stress is activated in diabetes and contributes to ß-cell dysfunction and apoptosis through the activation of a terminal unfolded protein response (UPR). Our results uncover a new role for Bax Inhibitor-One (BI-1), a negative regulator of inositol-requiring enzyme 1 (IRE1α) in preserving ß-cell health against terminal UPR-induced apoptosis and pyroptosis in the context of supraphysiological loads of insulin production. BI-1-deficient mice experience a decline in endocrine pancreatic function in physiological and pathophysiological conditions, namely obesity induced by high-fat diet (HFD). We observed early-onset diabetes characterized by hyperglycemia, reduced serum insulin levels, ß-cell loss, increased pancreatic lipases and pro-inflammatory cytokines, and the progression of metabolic dysfunction. Pancreatic section analysis revealed that BI-1 deletion overburdens unfolded proinsulin in the ER of ß-cells, confirmed by ultrastructural signs of ER stress with overwhelmed IRE1α endoribonuclease (RNase) activity in freshly isolated islets. ER stress led to ß-cell dysfunction and islet loss, due to an increase in immature proinsulin granules and defects in insulin crystallization with the presence of Rod-like granules. These results correlated with the induction of autophagy, ER phagy, and crinophagy quality control mechanisms, likely to alleviate the atypical accumulation of misfolded proinsulin in the ER. In fine, BI-1 in ß-cells limited IRE1α RNase activity from triggering programmed ß-cell death through apoptosis and pyroptosis (caspase-1, IL-1ß) via NLRP3 inflammasome activation and metabolic dysfunction. Pharmaceutical IRE1α inhibition with STF-083010 reversed ß-cell failure and normalized the metabolic phenotype. These results uncover a new protective role for BI-1 in pancreatic ß-cell physiology as a stress integrator to modulate the UPR triggered by accumulating unfolded proinsulin in the ER, as well as autophagy and programmed cell death, with consequences on ß-cell function and insulin secretion. In pancreatic ß-cells, BI-1-/- deficiency perturbs proteostasis with proinsulin misfolding, ER stress, terminal UPR with overwhelmed IRE1α/XBP1s/CHOP activation, inflammation, ß-cell programmed cell death, and diabetes.

The caspase-cleaved form of LYN mediates a psoriasis-like inflammatory syndrome in mice.

We showed previously that Lyn is a substrate for caspases, a family of cysteine proteases, involved in the regulation of apoptosis and inflammation. Here, we report that expression of the caspase-cleaved form of Lyn (LynDeltaN), in mice, mediates a chronic inflammatory syndrome resembling human psoriasis. Genetic ablation of TNF receptor 1 in a LynDeltaN background rescues a normal phenotype, indicating that LynDeltaN mice phenotype is TNF-alpha-dependent. The predominant role of T cells in the disease occurring in LynDeltaN mice was highlighted by the distinct improvement of LynDeltaN mice phenotype in a Rag1-deficient background. Using pan-genomic profiling, we also established that LynDeltaN mice show an increased expression of STAT-3 and inhibitory members of the NFkappaB pathway. Accordingly, LynDeltaN alters NFkappaB activity underlying a link between inhibition of NFkappaB and LynDeltaN mice phenotype. Finally, analysis of Lyn expression in human skin biopsies of psoriatic patients led to the detection of Lyn cleavage product whose expression correlates with the activation of caspase 1. Our data identify a new role for Lyn as a regulator of psoriasis through its cleavage by caspases.

Cholesterol efflux pathways hinder KRAS-driven lung tumor progenitor cell expansion.

Cholesterol efflux pathways could be exploited in tumor biology to unravel cancer vulnerabilities. A mouse model of lung-tumor-bearing KRASG12D mutation with specific disruption of cholesterol efflux pathways in epithelial progenitor cells promoted tumor growth. Defective cholesterol efflux in epithelial progenitor cells governed their transcriptional landscape to support their expansion and create a pro-tolerogenic tumor microenvironment (TME). Overexpression of the apolipoprotein A-I, to raise HDL levels, protected these mice from tumor development and dire pathologic consequences. Mechanistically, HDL blunted a positive feedback loop between growth factor signaling pathways and cholesterol efflux pathways that cancer cells hijack to expand. Cholesterol removal therapy with cyclodextrin reduced tumor burden in progressing tumor by suppressing the proliferation and expansion of epithelial progenitor cells of tumor origin. Local and systemic perturbations of cholesterol efflux pathways were confirmed in human lung adenocarcinoma (LUAD). Our results position cholesterol removal therapy as a putative metabolic target in lung cancer progenitor cells.

IRE1α overexpression in malignant cells limits tumor progression by inducing an anti-cancer immune response.

IRE1α is one of the three ER transmembrane transducers of the Unfolded Protein Response (UPR) activated under endoplasmic reticulum (ER) stress. IRE1α activation has a dual role in cancer as it may be either pro- or anti-tumoral depending on the studied models. Here, we describe the discovery that exogenous expression of IRE1α, resulting in IRE1α auto-activation, did not affect cancer cell proliferation in vitro but resulted in a tumor-suppressive phenotype in syngeneic immunocompetent mice. We found that exogenous expression of IRE1α in murine colorectal and Lewis lung carcinoma cells impaired tumor growth when syngeneic tumor cells were subcutaneously implanted in immunocompetent mice but not in immunodeficient mice. Mechanistically, the in vivo tumor-suppressive effect of overexpressing IRE1α in tumor cells was associated with IRE1α RNAse activity driving both XBP1 mRNA splicing and regulated IRE1-dependent decay of RNA (RIDD). We showed that the tumor-suppressive phenotype upon IRE1α overexpression was characterized by the induction of apoptosis in tumor cells along with an enhanced adaptive anti-cancer immunosurveillance. Hence, our work indicates that IRE1α overexpression and/or activation in tumor cells can limit tumor growth in immunocompetent mice. This finding might point toward the need of adjusting the use of IRE1α inhibitors in cancer treatments based on the predominant outcome of the RNAse activity of IRE1α.

Tumoral microenvironment prevents de novo asparagine biosynthesis in B cell lymphoma, regardless of ASNS expression.

Depletion of circulating asparagine with l-asparaginase (ASNase) is a mainstay of leukemia treatment and is under investigation in many cancers. Expression levels of asparagine synthetase (ASNS), which catalyzes asparagine synthesis, were considered predictive of cancer cell sensitivity to ASNase treatment, a notion recently challenged. Using [U-13C5]-l-glutamine in vitro and in vivo in a mouse model of B cell lymphomas (BCLs), we demonstrated that supraphysiological or physiological concentrations of asparagine prevent de novo asparagine biosynthesis, regardless of ASNS expression levels. Overexpressing ASNS in ASNase-sensitive BCL was insufficient to confer resistance to ASNase treatment in vivo. Moreover, we showed that ASNase's glutaminase activity enables its maximal anticancer effect. Together, our results indicate that baseline ASNS expression (low or high) cannot dictate BCL dependence on de novo asparagine biosynthesis and predict BCL sensitivity to dual ASNase activity. Thus, except for ASNS-deficient cancer cells, ASNase's glutaminase activity should be considered in the clinic.

HIF-1alpha mediates the induction of IL-8 and VEGF expression on infection with Afa/Dr diffusely adhering E. coli and promotes EMT-like behaviour.

Microbes regulate a large panel of intracellular signalling events that can promote inflammation and/or enhance tumour progression. Indeed, it has been shown that infection of human intestinal cells with the Afa/Dr diffusely adhering E. coli C1845 strain induces expression of pro-angiogenic and pro-inflammatory genes. Here, we demonstrate that exposure of cryptic-like intestinal epithelial cells to C1845 bacteria induces HIF-1alpha protein levels. This effect depends on the binding of F1845 adhesin to the membrane-associated DAF receptor that initiates signalling cascades promoting translational mechanisms. Indeed, inhibition of MAPK and PI-3K decreases HIF-1alpha protein levels and blocks C1845-induced phosphorylation of the ribosomal S6 protein. Using RNA interference we show that bacteria-induced HIF-1alpha regulates the expression of IL-8, VEGF and Twist1, thereby pointing to a role for HIF-1 in angiogenesis and inflammation. In addition, infection correlates with a loss of E-cadherin and cytokeratin 18 and a rise in fibronectin, suggesting that bacteria may induce an epithelial to mesenchymal transition-like phenotype. Since HIF-1alpha silencing results in reversion of bacteria-induced EMT markers, we speculate that HIF-1alpha plays a key role linking bacterial infection to angiogenesis, inflammation and some aspects of cancer initiation.

The prohibitin-binding compound fluorizoline inhibits mitophagy in cancer cells.

Fluorizoline is a prohibitin-binding compound that triggers apoptosis in several cell lines from murine and human origin, as well as in primary cells from hematologic malignancies by inducing the integrated stress response and ER stress. Recently, it was described that PHB (Prohibitin) 1 and 2 are crucial mitophagy receptors involved in mediating the autophagic degradation of mitochondria. We measured mitophagy in HeLa cells expressing Parkin and in A549, a lung cancer cell line that can undergo mitophagy in a Parkin-independent manner, and we demonstrated that both fluorizoline and rocaglamide A, another PHB-binding molecule, inhibit CCCP- and OA-induced mitophagy. Moreover, we demonstrated that PHBs are mediating Parkin-dependent mitophagy. In conclusion, besides being a potent pro-apoptotic compound, we present fluorizoline as a promising new mitophagy modulator that could be used as anticancer agent.

Pharmacological preconditioning protects from ischemia/reperfusion-induced apoptosis by modulating Bcl-xL expression through a ROS-dependent mechanism.

Myocardial ischemia/reperfusion (I/R) injury is a frequent perioperative threat, with numerous strategies developed to limit and/or prevent it. One interesting axis of research is the anesthetic preconditioning (APc) agent's hypothesis (such as sevoflurane, SEV). However, APc's mode of action is still poorly understood and volatile anesthetics used as preconditioning agents are often not well suited in clinical practice. Here, in vitro using H9C2 cells lines (in myeloblast state or differentiated toward cardiomyocytes) and in vivo in mice, we identified that SEV-induced APc is mediated by a mild induction of reactive oxygen species (ROS) that activates Akt and induces the expression of the anti-apoptotic protein B-cell lymphoma-extra large (Bcl-xL), therefore protecting cardiomyocytes from I/R-induced death. Furthermore, we extended these results to human cardiomyocytes (derived from induced pluripotent stem - IPS - cells). Importantly, we demonstrated that this protective signaling pathway induced by SEV could be stimulated using the antidiabetic agent metformin (MET), suggesting the preconditioning properties of MET. Altogether, our study identified a signaling pathway allowing APc of cardiac injuries as well as a rational for the use of MET as a pharmacological preconditioning agent to prevent I/R injuries.

Escherichia coli Rho GTPase-activating toxin CNF1 mediates NLRP3 inflammasome activation via p21-activated kinases-1/2 during bacteraemia in mice.

Inflammasomes are signalling platforms that are assembled in response to infection or sterile inflammation by cytosolic pattern recognition receptors. The consequent inflammasome-triggered caspase-1 activation is critical for the host defence against pathogens. During infection, NLRP3, which is a pattern recognition receptor that is also known as cryopyrin, triggers the assembly of the inflammasome-activating caspase-1 through the recruitment of ASC and Nek7. The activation of the NLRP3 inflammasome is tightly controlled both transcriptionally and post-translationally. Despite the importance of the NLRP3 inflammasome regulation in autoinflammatory and infectious diseases, little is known about the mechanism controlling the activation of NLRP3 and the upstream signalling that regulates the NLRP3 inflammasome assembly. We have previously shown that the Rho-GTPase-activating toxin from Escherichia coli cytotoxic necrotizing factor-1 (CNF1) activates caspase-1, but the upstream mechanism is unclear. Here, we provide evidence of the role of the NLRP3 inflammasome in sensing the activity of bacterial toxins and virulence factors that activate host Rho GTPases. We demonstrate that this activation relies on the monitoring of the toxin's activity on the Rho GTPase Rac2. We also show that the NLRP3 inflammasome is activated by a signalling cascade that involves the p21-activated kinases 1 and 2 (Pak1/2) and the Pak1-mediated phosphorylation of Thr 659 of NLRP3, which is necessary for the NLRP3-Nek7 interaction, inflammasome activation and IL-1ß cytokine maturation. Furthermore, inhibition of the Pak-NLRP3 axis decreases the bacterial clearance of CNF1-expressing UTI89 E. coli during bacteraemia in mice. Taken together, our results establish that Pak1 and Pak2 are critical regulators of the NLRP3 inflammasome and reveal the role of the Pak-NLRP3 signalling axis in vivo during bacteraemia in mice.

Amplification loop of the inflammatory process is induced by P2X7R activation in intestinal epithelial cells in response to neutrophil transepithelial migration.

Inflammatory bowel diseases (IBD) are characterized during their active phase by polymorphonuclear leukocyte (PMNL) transepithelial migration. The efflux of PMNL into the mucosa is associated with the production of proinflammatory cytokines and the release of ATP from damaged and necrotic cells. The expression and function of purinergic P2X(7) receptor (P2X(7)R) in intestinal epithelial cells (IEC) and its potential role in the "cross talk" between IEC and PMNL have not been explored. The aims of the present study were 1) to examine P2X(7)R expression in IEC (T84 cells) and in human intestinal biopsies; 2) to detect any changes in P2X(7)R expression in T84 cells during PMNL transepithelial migration, and during the active and quiescent phases of IBD; and 3) to test whether P2X(7)R stimulation in T84 monolayers can induce caspase-1 activation and IL-1beta release by IEC. We found that a functional ATP-sensitive P2X(7)R is constitutively expressed at the apical surface of IEC T84 cells. PMNL transmigration regulates dynamically P2X(7)R expression and alters its distribution from the apical to basolateral surface of IEC during the early phase of PMNL transepithelial migration in vitro. P2X(7)R expression was weak in intestinal biopsies obtained during the active phase of IBD. We show that activation of epithelial P2X(7)R is mandatory for PMNL-induced caspase-1 activation and IL-1beta release by IEC. Overall, these changes in P2X(7)R function may serve to tailor the intensity of the inflammatory response and to prevent IL-1beta overproduction and inflammatory disease.

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.

Retraction Note: LAMP2 expression dictates azacytidine response and prognosis in MDS/AML.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

LAMP2 expression dictates azacytidine response and prognosis in MDS/AML.

Chaperone-mediated autophagy (CMA) is a highly selective form of autophagy. During CMA, the HSC70 chaperone carries target proteins endowed with a KFERQ-like motif to the lysosomal receptor LAMP2A, which then translocate them into lysosomes for degradation. In the present study, we scrutinized the mechanisms underlying the response and resistance to Azacytidine (Aza) in MDS/AML cell lines and bone marrow CD34+ blasts from MDS/AML patients. In engineered Aza-resistant MDS cell lines and some AML cell lines, we identified a profound defect in CMA linked to the absence of LAMP2A. LAMP2 deficiency was responsible for Aza resistance and hypersensitivity to lysosome and autophagy inhibitors. Accordingly, gain of function of LAMP2 in deficient cells or loss of function in LAMP2-expressing cells rendered them sensitive or resistant to Aza, respectively. A strict correlation was observed between the absence of LAMP2, resistance to Aza and sensitivity to lysosome inhibitors. Low levels of LAMP2 expression in CD34+ blasts from MDS/AML patients correlated with lack of sensitivity to Aza and were predictive of poor overall survival. We propose that CD34+/LAMP2Low patients at diagnosis or who become CD34+/LAMP2Low during the course of treatment with Aza might benefit from a lysosome inhibitor already used in the clinic.