TNFalpha-induced macrophage death via caspase-dependent and independent pathways

Aging modulates homeostatic leukocyte trafficking to the peritoneal cavity in a sex-specific manner

Aging is associated with exacerbated systemic inflammation (inflammaging) and the progressive loss of immune system function (immunosenescence). Leukocyte migration is necessary for effective immunity; however, dysregulated trafficking of leukocytes into tissue contributes to inflammaging and the development of age-related inflammatory diseases. Aging modulates leukocyte trafficking under inflammatory conditions; however, whether aging modulates leukocyte trafficking under homeostatic conditions remains to be elucidated. Although immune responses are evidently sexually dimorphic, limited studies have investigated the effect of sex on age-related changes to leukocyte trafficking processes. Here, we investigated age-related and sex-specific changes to the leukocyte populations within the peritoneal cavity of young (3-mo), middle-aged (18-mo) and old (21-mo) male and female wild-type mice in the steady state. We found an age-related increase in the number of leukocytes within the peritoneal cavity of female mice, predominantly B cells, which may reflect increased trafficking through this tissue with age. This was accompanied by an increased inflammatory environment within the aged cavity, including increased levels of chemoattractants, including B cell chemoattractants CXCL13 and CCL21, soluble adhesion molecules, and proinflammatory cytokines, which was more pronounced in aged female mice. Intravital microscopy techniques revealed altered vascular structure and increased vascular permeability within the peritoneal membrane of aged female mice, which may support increased leukocyte trafficking to the cavity with age. Together, these data indicate that aging affects homeostatic leukocyte trafficking processes in a sex-specific fashion.

Engineer a double team of short-lived and glucose-sensing bacteria for cancer eradication

Rationally designed and engineered bacteria represent an emerging unique approach for cancer treatment. Here, we engineer a short-lived bacterium, mp105, that is effective against diverse cancer types and safe for intravenous administration. We reveal that mp105 combats cancer by direct oncolysis, depletion of tumor-associated macrophages, and elicitation of CD4⁺ T cell immunity. We further engineer a glucose-sensing bacterium named m6001 that selectively colonizes solid tumors. When intratumorally injected, m6001 clears tumors more efficiently than mp105 due to its post-delivery replication in tumors and potent oncolytic capacity. Finally, we combine intravenous injection of mp105 and intratumoral injection of m6001, forming a double team against cancer. The double team enhances cancer therapy compared with single treatment for subjects carrying both intratumorally injectable and uninjectable tumors. The two anticancer bacteria and their combination are applicable to different scenarios, turning bacterial therapy for cancer into a feasible solution.

Lysosomal membrane permeabilization mediated apoptosis involve in perphenazine-induced hepatotoxicity in vitro and in vivo

Antipsychotic drugs represent a class of lysosomotropic drugs widely used in clinical practice. However, the hepatotoxicity of these drugs has been reported in recent years. Therefore, understanding the changes in cellular homeostasis mediated by these drugs is of great significance for revealing the true mechanisms underlying hepatotoxicity. Perphenazine is a classical antipsychotic drug that can reportedly induce extrapyramidal and sympatholytic side effects. The present research focuses on the toxicity effect of perphenazine on normal human hepatocytes. To assess the hepatotoxicity of continuous administration of perphenazine and investigate potential mechanisms related to apoptosis, human normal L02 hepatocytes were exposed to 10-40μM perphenazine in vitro. The results showed that perphenazine inhibited cell viability in a concentration and time-dependent manner. Furthermore, 30μM perphenazine induced intense lysosome vacuolation, impaired lysosomal membrane, and induced lysosomal membrane permeabilization (LMP), ultimately triggering lysosomal cell death in L02 cells. Knockdown cathepsin D(CTSD) also ameliorated perphenazine-induced liver injury via the inhibition of LMP. In vivo, ICR mice received intragastric administration of 10-180mg/kg B.W. perphenazine every other day for 21 days. 180mg/kg perphenazine significantly increased histological injury and aminotransferases compared with control. Taken together, our findings suggest that perphenazine can trigger hepatotoxicity through lysosome disruption both in vitro and in vivo.

Development of (4-Phenylamino)quinazoline Alkylthiourea Derivatives as Novel NF-κB Inhibitors

For many inflammatory diseases, new effective drugs with fewer side effects are needed. While it appears promising to target the activation of the central pro-inflammatory transcription factor NF-κB, many previously discovered agents suffered from cytotoxicity. In this study, new alkylthiourea quinazoline derivatives were developed that selectively inhibit the activation of NF-κB in macrophage-like THP−1 cells while showing low general cytotoxicity. One of the best compounds, 19, strongly inhibited the production of IL-6 (IC50 = 0.84 µM) and, less potently, of TNFα (IC50 = 4.0 µM); in comparison, the reference compound, caffeic acid phenethyl ester (CAPE), showed IC50s of 1.1 and 11.4 µM, respectively. Interestingly, 19 was found to block the translocation of the NF-κB dimer to the nucleus, although its release from the IκB complex was unaffected. Furthermore, 19 suppressed the phosphorylation of NF-κB-p65 at Ser468 but not at Ser536; however, 19 did not inhibit any kinase involved in NF-κB activation. The only partial suppression of p65 phosphorylation might be associated with fewer side effects. Since several compounds selectively induced cell death in activated macrophage-like THP−1 cells, they might be particularly effective in various inflammatory diseases that are exacerbated by excess activated macrophages, such as arteriosclerosis and autoimmune diseases.

Intratumoral administration of the antisecretory peptide AF16 cures murine gliomas and modulates macrophage functions

Glioblastoma has remained the deadliest primary brain tumor while its current therapy offers only modest survival prolongation. Immunotherapy has failed to record notable benefits in routine glioblastoma treatment. Conventionally, immunotherapy relies on T cells as tumor-killing agents; however, T cells are outnumbered by macrophages in glioblastoma microenvironment. In this study, we explore the effect of AF16, a peptide from the endogenous antisecretory factor protein, on the survival of glioma-bearing mice, the tumor size, and characteristics of the tumor microenvironment with specific focus on macrophages. We elucidate the effect of AF16 on the inflammation-related secretome of human and murine macrophages, as well as human glioblastoma cells. In our results, AF16 alone and in combination with temozolomide leads to cure in immunocompetent mice with orthotopic GL261 gliomas, as well as prolonged survival in immunocompromised mice. We recorded decreased tumor size and changes in infiltration of macrophages and T cells in the murine glioma microenvironment. Human and murine macrophages increased expression of proinflammatory markers in response to AF16 treatment and the same effect was seen in human primary glioblastoma cells. In summary, we present AF16 as an immunomodulatory factor stimulating pro-inflammatory macrophages with a potential to be implemented in glioblastoma treatment protocols.

IL-1β/MMP9 activation in primary human vascular smooth muscle-like cells: Exploring the role of TNFα and P2X7

BACKGROUND

Vascular smooth muscle cells exhibit phenotypic plasticity in response to microenvironmental stimuli and contribute to vascular remodelling through mechanisms only partially understood. In atherosclerosis, P2X-purinoceptor7 (P2X7) has been related to interleukin-1β (IL-1β) and metalloproteinase 9 (MMP9). The hypoxia-inducible factor-1alpha (HIF1α) was associated to remodelling. Here the activation of IL-1β and MMP9 was studied in relationship to P2X7 and HIF1α in cells exploited from human carotid plaque and internal mammary artery.

METHODS AND RESULTS

Migrating cells expressed HIF1α-regulated canopy FGF-signalling regulator 2 and CD117, and led to primary cells with SMC-like phenotype (VSMC), P2X7⁺. We investigated in VSMC the effects of hypoxia, of treatment with tumour necrosis factor-α (TNFα) and/or with P2X7 antagonist, A740003. Quantitative RT-PCR showed that hypoxia unaffected IL-1β and down-regulated MMP9 mRNAs, without activating HIF1α. TNFα increased IL-1β mRNA via NLR Family Pyrin Domain-Containing 3, with production of proIL-1β but no rise of mature IL-1β. Zymography demonstrated that A740003 triggered MMP9 secretion from VSMC. Combination of A740003 with TNFα abrogated this effect. Combination was ineffective on IL-1β activation elicited by TNFα, but down-regulated HIF1α mRNA. A740003 induced the intracellular P2X7 aggregation and differently perturbed lysosome and mitochondria network compared to TNFα.

CONCLUSIONS

Cells migration from human arteries leads to partially differentiated VSMC analogous to neointimal cells within atherosclerotic lesions. Down-regulated HIF1α in stimulated VSMC translates in resilience in atherosclerotic lesions. P2X7-independent partial activation of IL-1β elicited by TNFα underlines complexity of the cytokine secretion. Data also supported P2X7 as modulator of MMP9 secretion, important for atherosclerosis progression.

Patulin Induces Autophagy-Dependent Apoptosis through Lysosomal-Mitochondrial Axis and Impaired Mitophagy in HepG2 Cells

Patulin (PAT) is a compound produced by fungi including those of the Aspergillus, Penicillium, and Byssochlamys species. PAT has been linked with negative outcomes in certain microorganisms and animal species, but how it causes hepatotoxicity is poorly understood. In this study, we determined that, by treating HepG2 cells using PAT, these cells could be induced to rapidly undergo autophagy, and this was followed within 12 h of treatment by lysosomal membrane permeabilization (LMP) and cathepsin B release. We were able to block these outcomes if cells were treated with 3-methyladenine (3MA), an inhibitor of autophagy, prior to PAT treatment. Moreover, PAT-induced collapse of mitochondrial membrane potential (ΔΨm) depended both on cathepsin B and autophagy. 3MA was further able to reduce the induction of apoptosis in response to PAT, suggesting that autophagy is a driving mechanism for this apoptotic induction. Inhibiting cathepsin B using CA-074 Me further reduced PAT-induced collapses of ΔΨm, mitochondiral cytochrome c release, and apoptosis. We also found that extended treatment of HepG2 cells using PAT over a period of 24 h led to the impairment of mitophagy such that morphologically swollen mitochondria accumulated within cells, and PINK1 failed to colocalize with LC3. Together these data reveal that PAT treatment can promote the induction of apoptosis in HepG2 cells in a manner dependent upon autophagy that progresses via the lysosomal-mitochondrial axis. This study thereby affords new insights into the mechanisms by which PAT drives hepatotoxicity.

Effects of TNF receptor blockade on in vitro cell survival and response to negative energy balance in dairy cattle

Background

Associative data and some controlled studies suggest that the inflammatory cytokine tumor necrosis factor (TNF) α can induce fatty liver in dairy cattle. However, research demonstrating that TNFα is a necessary component in the etiology of bovine fatty liver is lacking. The aim of this work was to evaluate whether blocking TNFα signaling with a synthetic cyclic peptide (TNF receptor loop peptide; TRLP) would improve liver metabolic function and reduce triglyceride accumulation during feed restriction.

Results

Capability of TRLP to inhibit TNFα signaling was confirmed on primary bovine hepatocytes treated with recombinant bovine TNFα and 4 doses of TRLP (0, 1, 10, 50 μmol/L) over 24 h. Next, 4 lactating Holstein cows (parity 1.4 ± 0.5, 433 ± 131 d in milk) in an incomplete Latin rectangle design (3 × 2) were subcutaneously administered with different TRLP doses (0, 1.5, 3.0 mg/kg BW) every 4 h for 24 h, followed by an intravenous injection of TNFα (5 μg/kg BW). Before and for 2 h after TNFα injection, TRLP decreased plasma non-esterified fatty acid (NEFA) concentration (P ≤ 0.05), suggesting an altered metabolic response to inflammation. Finally, 10 non-pregnant, non-lactating Holstein cows (3.9 ± 1.1 yr of age) were randomly assigned to treatments: control (carrier: 57% DMSO in PBS) or TRLP (1.75 mg TRLP /kg BW per day). Treatments were administrated every 4 h for 7 d by subcutaneous injection to feed-restricted cows fed 30% of maintenance energy requirements. Daily blood samples were analyzed for glucose, insulin, β-hydroxybutyrate, NEFA, and haptoglobin concentrations, with no treatment effects detected. On d 7, cows completed a glucose tolerance test (GTT) by i.v. administration of a dextrose bolus (300 mg glucose/kg BW). Glucose, insulin, and NEFA responses failed to demonstrate any significant effect of treatment during the GTT. However, plasma and liver analyses were not indicative of dramatic lipolysis or hepatic lipidosis, suggesting that the feed restriction protocol failed to induce the metabolic state of interest. Injection site inflammation, assessed by a scorer blinded to treatment, was enhanced by TRLP compared to control.

Conclusions

Although the TRLP inhibited bovine TNFα signaling and altered responses to i.v. administration of TNFα, repeated use over 7 d caused apparent local allergic responses and it failed to alter metabolism during a feed restriction-induced negative energy balance. Although responses to feed restriction seemed atypical in this study, side effects of TRLP argue against its future use as a tool for investigating the role of inflammation in metabolic impacts of negative energy balance.

Tumor control by hypoxia-specific chemotargeting of iron-oxide nanoparticle - Berberine complexes in a mouse model

AIM

To evaluate the therapeutic efficacy of hypoxic cell-sensitizer Sanazole (SAN) -directed targeting of cytotoxic drug Berberine (BBN) and Iron-oxide nanoparticle (NP) complexes, to solid tumor in Swiss albino mice.

MAIN METHODS

NP-BBN-SAN complexes were characterized by FTIR, XRD, TEM and Nano-size analyzer. This complex was orally administered to mice-bearing solid tumor in hind limb. Tumor regression was analysed by measuring tumor volume. Cellular DNA damages were assessed by comet assay. Transcriptional expression of genes related to tumor hypoxia and apoptosis was evaluated by quantitative real-time PCR and morphological changes in tissues were analysed by histopathology. Also levels of antioxidants and tumor markers in tissues and serum biochemical parameters were analysed.

KEY FINDINGS

Administration of NP-BBN-SAN complexes reduced tumor volume and studies were focussed on the underlying mechanisms. Extensive damage to cellular-DNA; down-regulated transcription of hif-1α, vegf, akt and bcl2; and up-regulated expression of bax and caspases, were observed in tumor. Results on tumor markers, antioxidant-status and serum parameters corroborated the molecular findings. Histopathology of tumor, liver and kidney revealed the therapeutic specificity of NP-BBN-SAN.

SIGNIFICANCE

Thus SAN and NP can be used for specific targeting of drugs, to hypoxic solid tumor, to improve therapeutic efficacy.

IUGR induced by maternal chronic inflammation: long-term effect on offspring's ovaries in rat model-a preliminary report

PURPOSE

Excess maternal inflammation and oxidative stress while in utero have been known to affect gross fetal development. However, an association between the inflammatory process in utero and the effects on ovarian development and future fertility has not yet been demonstrated. This study focused on LPS-induced chronic inflammation in early pregnancy and its effect on ovarian development and reserves of the offspring, using a rat model. Our aim was to determine whether maternal inflammation in utero disturbs reproductive system development in the offspring, given that maternal inflammation and oxidative stress has been shown to affect gross fetal development.

METHODS

Prospective case control rat model. Sprague-Dawley pregnant rats (n = 11) received intraperitoneal lipopolysaccharide (LPS group) (50 µg/kg bodyweight) or saline solution (control group) on day 14, 16, and 18 of gestation. Pups were delivered spontaneously. At 3 months, female offspring were weighed and killed. Ovaries were harvested for (1) follicle count using hematoxylin and eosin staining, (2) apoptosis: ovaries were stained for caspase, and (3) serum CRP and AMH levels were determined.

RESULTS

Birth weights of pups were significantly lower in the LPS group compared to the control group (6.0 ± 0.6 vs. 6.6 ± 0.4 gr; P = 0.0003). The LPS group had fewer preantral follicles, and increased intensity of Caspase 3 staining (510 vs. 155.5 u; P = 0.007). AMH levels were significantly lower in the LPS group (4.15 ± 0.46 vs 6.08 ± 1.88 ng/ml; P = 0.016). There was no significant difference in the CRP and MCP-1 levels between the two groups.

CONCLUSIONS

Chronic maternal inflammation induced intrauterine growth restriction in offspring and a decrease in the proportion of follicles. This change might be due to premature apoptosis. These preliminary results suggest that maternal inflammation has a detrimental effect on the development of the female reproductive system of the offspring and thus, future fertility.

MicroRNA: Dynamic Regulators of Macrophage Polarization and Plasticity

The ability of a healthy immune system to clear the plethora of antigens it encounters incessantly relies on the enormous plasticity displayed by the comprising cell types. Macrophages (MΦs) are crucial member of the mononuclear phagocyte system (MPS) that constantly patrol the peripheral tissues and are actively recruited to the sites of injury and infection. In tissues, infiltrating monocytes replenish MΦ. Under the guidance of the local micro-milieu, MΦ can be activated to acquire specialized functional phenotypes. Similar to T cells, functional polarization of macrophage phenotype viz., inflammatory (M1) and reparative (M2) is proposed. Equipped with diverse toll-like receptors (TLRs), these cells of the innate arm of immunity recognize and phagocytize antigens and secrete cytokines that activate the adaptive arm of the immune system and perform key roles in wound repair. Dysregulation of MΦ plasticity has been associated with various diseases and infection. MicroRNAs (miRNAs) have emerged as critical regulators of transcriptome output. Their importance in maintaining health, and their contribution toward disease, encompasses virtually all aspects of human biology. Our understanding of miRNA-mediated regulation of MΦ plasticity and polarization can be utilized to modulate functional phenotypes to counter their role in the pathogenesis of numerous disease, including cancer, autoimmunity, periodontitis, etc. Here, we provide an overview of current knowledge regarding the role of miRNA in shaping MΦ polarization and plasticity through targeting of various pathways and genes. Identification of miRNA biomarkers of diagnostic/prognostic value and their therapeutic potential by delivery of miRNA mimics or inhibitors to dynamically alter gene expression profiles in vivo is highlighted.

Association of Increased F4/80high Macrophages With Suppression of Serum-Transfer Arthritis in Mice With Reduced FLIP in Myeloid Cells

OBJECTIVE

Macrophages are critical in the pathogenesis of rheumatoid arthritis (RA). We recently demonstrated that FLIP is necessary for the differentiation and/or survival of macrophages. We also showed that FLIP is highly expressed in RA synovial macrophages. This study was undertaken to determine if a reduction in FLIP in mouse macrophages reduces synovial tissue macrophages and ameliorates serum-transfer arthritis.

METHODS

Mice with Flip deleted in myeloid cells (Flip^f/f LysM^c/+ mice) and littermate controls were used. Arthritis was induced by intraperitoneal injection of K/BxN serum. Disease severity was evaluated by clinical score and change in ankle thickness, and joints were examined by histology and immunohistochemistry. Cells were isolated from the ankles and bone marrow of the mice and examined by flow cytometry, real-time quantitative reverse transcriptase-polymerase chain reaction, or Western blotting.

RESULTS

In contrast to expectations, Flip^f/f LysM^c/+ mice developed more severe arthritis early in the clinical course, but peak arthritis was attenuated and the resolution phase more complete than in control mice. Prior to the induction of serum-transfer arthritis, the number of tissue-resident macrophages was reduced. On day 9 after arthritis induction, the number of F4/80^high macrophages in the joints of the Flip^f/f LysM^c/+ mice was not decreased, but increased. FLIP was reduced in the F4/80^high macrophages in the ankles of the Flip^f/f LysM^c/+ mice, while F4/80^high macrophages expressed an antiinflammatory phenotype in both the Flip^f/f LysM^c/+ and control mice.

CONCLUSION

Our observations suggest that reducing FLIP in macrophages by increasing the number of antiinflammatory macrophages may be an effective therapeutic approach to suppress inflammation, depending on the disease stage.

B-cell-specific depletion of tumour necrosis factor alpha inhibits atherosclerosis development and plaque vulnerability to rupture by reducing cell death and inflammation

AIMS

B2 lymphocytes promote atherosclerosis development but their mechanisms of action are unknown. Here, we investigated the role of tumour necrosis factor alpha (TNF-α) produced by B2 cells in atherogenesis.

METHODS AND RESULTS

We found that 50% of TNF-α-producing spleen lymphocytes were B2 cells and ∼20% of spleen and aortic B cells produced TNF-α in hyperlipidemic ApoE(-/-) mice. We generated mixed bone marrow (80% μMT/20% TNF-α(-/-)) chimeric LDLR(-/-) mice where only B cells did not express TNF-α. Atherosclerosis was reduced in chimeric LDLR(-/-) mice with TNF-α-deficient B cells. TNF-α expression in atherosclerotic lesions and in macrophages were also reduced accompanied by fewer apoptotic cells, reduced necrotic cores, and reduced lesion Fas, interleukin-1β and MCP-1 in mice with TNF-α-deficient B cells compared to mice with TNF-α-sufficient B cells. To confirm that the reduced atherosclerosis is attributable to B2 cells, we transferred wild-type and TNF-α-deficient B2 cells into ApoE(-/-) mice deficient in B cells or in lymphocytes. After 8 weeks of high fat diet, we found that atherosclerosis was increased by wild-type but not TNF-α-deficient B2 cells. Lesions of mice with wild-type B2 cells but not TNF-α-deficient B2 cells also had increased apoptotic cells and necrotic cores. Transferred B2 cells were found in lesions of recipient mice, suggesting that TNF-α-producing B2 cells promote atherosclerosis within lesions.

CONCLUSION

We conclude that TNF-α produced by B2 cells is a key mechanism by which B2 cells promote atherogenesis through augmenting macrophage TNF-α production to induce cell death and inflammation that promote plaque vulnerability.

TRAF3IP2 mediates atherosclerotic plaque development and vulnerability in ApoE(-/-) mice

BACKGROUND AND AIMS

Atherosclerosis is a major cause of heart attack and stroke. Inflammation plays a critical role in the development of atherosclerosis. Since the cytoplasmic adaptor molecule TRAF3IP2 (TRAF3-Interacting Protein 2) plays a causal role in various autoimmune and inflammatory diseases, we hypothesized that TRAF3IP2 mediates atherosclerotic plaque development.

METHODS

TRAF3IP2/ApoE double knockout (DKO) mice were generated by crossing TRAF3IP2(-/-) and ApoE(-/-) mice. ApoE(-/-) mice served as controls. Both DKO and control mice were fed a high-fat diet for 12 weeks. Plasma lipids were measured by ELISA, atherosclerosis by en face analysis of aorta and plaque cross-section measurements at the aortic valve region, plaque necrotic core area, collagen and smooth muscle cell (SMC) content by histomorphometry, and aortic gene expression by RT-qPCR.

RESULTS

The plasma lipoprotein profile was not altered by TRAF3IP2 gene deletion in ApoE(-/-) mice. While total aortic plaque area was decreased in DKO female, but not male mice, the plaque necrotic area was significantly decreased in DKO mice of both genders. Plaque collagen and SMC contents were increased significantly in both female and male DKO mice compared to respective controls. Aortic expression of proinflammatory cytokine (Tumor necrosis factor α, TNFα), chemokine (Chemokine (C-X-C motif) Ligand 1, CXCL1) and adhesion molecule (Vascular cell adhesion molecule 1, VCAM1; and Intercellular adhesion molecule 1, ICAM1) gene expression were decreased in both male and female DKO mice. In addition, the male DKO mice expressed markedly reduced levels of extracellular matrix (ECM)-related genes, including TIMP1 (Tissue inhibitor of metalloproteinase 1), RECK (Reversion-Inducing-Cysteine-Rich Protein with Kazal Motifs) and ADAM17 (A Disintegrin And Metalloproteinase 17).

CONCLUSIONS

TRAF3IP2 plays a causal role in atherosclerotic plaque development and vulnerability, possibly by inducing the expression of multiple proinflammatory mediators. TRAF3IP2 could be a potential therapeutic target in atherosclerotic vascular diseases.

HIV-infected microglia mediate cathepsin B-induced neurotoxicity

HIV-1-infected mononuclear phagocytes release soluble factors that affect the homeostasis in tissue. HIV-1 can prompt metabolic encephalopathy with the addition of neuronal dysfunction and apoptosis. Recently, we reported that HIV-1 enhances the expression and secretion of bioactive cathepsin B in monocyte-derived macrophages, ultimately contributing to neuronal apoptosis. In this research, we asked if microglia respond to HIV infection similarly by modifying the expression, secretion, and neurotoxic potential of cathepsin B and determined the in vivo relevance of these findings. HIV-1ADA-infected human primary microglia and CHME-5 microglia cell line were assessed for expression and activity of cathepsin B, its inhibitors, cystatins B and C, and the neurotoxicity associated with these changes. Human primary neurons were exposed to supernatants from HIV-infected and uninfected microglia in the presence of cathepsin B inhibitors and apoptosis was assessed by TUNEL. Microglial expression of cathepsin B was validated in brain tissue from HIV encephalitis (HIVE) patients. HIV-infected microglia secreted significantly greater levels of cathepsin B, cystatin B, and cystatin C compared to uninfected cells. Increased apoptosis was observed in neurons exposed to supernatants from HIV-1 infected microglia at day 12 post-infection. The cathepsin B inhibitor CA-074 and cathepsin B antibody prevented neuronal apoptosis. Increased microglia-derived cathepsin B, cystatin B, and cystatin C and caspase-3+ neurons were detected in HIVE brains compared to controls. Our results suggest that HIV-1-induced cathepsin B production in microglia contributes to neuronal apoptosis and may be an important factor in neuronal death associated with HIVE.

Tumor necrosis factor-alpha-converting enzyme activities and tumor-associated macrophages in breast cancer

The role of the tumor microenvironment especially of tumor-associated macrophages (TAMs) in the progression and metastatic spread of breast cancer is well established. TAMs have primarily a M2 (wound-healing) phenotype with minimal cytotoxic activities. The mechanisms by which tumor cells influence TAMs to display a pro-tumor phenotype are still debated although the key roles of immunomodulatory cytokines released by tumor cells, including colony-stimulating factor 1, tumor necrosis factor (TNF) and soluble TNF receptors 1/2, soluble vascular cell adhesion molecule 1, soluble interleukin 6 receptor and amphiregulin, have been demonstrated. Importantly, these factors are released through ectodomain shedding by the activities of the tumor necrosis factor-alpha-converting enzyme (TACE/ADAM17). The role of TACE activation leading to autocrine effects on tumor progression has been extensively studied. In contrast, limited information is available on the role of tumor cell TACE activities on TAMs in breast cancer. TACE inhibitors, currently in clinical trials, will certainly affect TAMs and subsequently treatment outcomes based on the substrates it releases. Furthermore, whether targeting a subset of the molecules shed by TACE, specifically those leading to TAMs with altered functions and phenotype, holds greater therapeutic promises than past clinical trials of TACE antagonists' remains to be determined. Here, the potential roles of TACE ectodomain shedding in the breast tumor microenvironment are reviewed with a focus on the release of tumor-derived immunomodulatory factors shed by TACE that directs TAM phenotypes and functions.

A20 expressing tumors and anticancer drug resistance

Resistance to anticancer drugs is a major impediment to treating patients with cancer. The molecular mechanisms deciding whether a tumor cell commits to cell death or survives under chemotherapy are complex. Mounting evidence indicates a critical role of cell death and survival pathways in determining the response of human cancers to chemotherapy. Nuclear factor-kappaB (NF-kappaB) is a eukaryotic transcription factor on the crossroad of a cell's decision to live or die. Under physiological conditions, NF-kappaB is regulated by a complex network of endogenous pathway modulators. Tumor necrosis factor alpha induced protein 3 (tnfaip3), a gene encoding the A20 protein, is one of the cell's own inhibitory molecule, which regulates canonical NF-kappaB activation by interacting with upstream signaling pathway components. Interestingly, A20 is also itself a NF-kappaB dependent gene, that has been shown to also exert cell-type specific anti- or pro-apoptotic functions. Recent reports suggest that A20 expression is increased in a number of solid human tumors. This likely contributes to both carcinogenesis and response to chemotherapy. These data uncover the complexities of the mechanisms involved in A20's impact on tumor development and response to treatment, highlighting tumor and drug-type specific outcomes. While A20-targeted therapies may certainly add to the chemotherapeutic armamentarium, better understanding of A20 regulation, molecular targets and function(s) in every single tumor and in response to any given drug is required prior to any clinical implementation. Current renewed appreciation of the unique molecular signature of each tumor holds promise for personalized chemotherapeutic regimen hopefully comprising specific A20-targeting agents i.e., both inhibitors and enhancers.

The deubiquitinase A20 mediates feedback inhibition of interleukin-17 receptor signaling

The proinflammatory cytokine interleukin-17 (IL-17) is the signature cytokine of the T helper 17 (TH17) subset of CD4(+) T cells, and antibodies targeting IL-17 or the IL-17 receptor (IL-17R) show clinical efficacy in several autoimmune diseases. Although important for protective immunity against microorganisms, IL-17 causes collateral damage in inflammatory settings. TNFAIP3 encodes the deubiquitinase A20 and is genetically linked to numerous autoimmune syndromes. A20, a potent inhibitor of tumor necrosis factor-α signaling, removes ubiquitin from signaling intermediates upstream of nuclear factor κB (NF-κB), thereby dampening NF-κB-mediated inflammation. We demonstrated that IL-17 stimulates TNFAIP3 expression. Enhanced IL-17-mediated induction of genes encoding proinflammatory factors, including IL-6 and various chemokines, occurred upon knockdown of A20 with short inhibitory RNA or in A20(-/-) cells. A20 associated with the E3 ubiquitin ligase TRAF6 (tumor necrosis factor receptor-associated factor 6) in an IL-17-dependent manner and restricted the IL-17-dependent activation of NF-κB and mitogen-activated protein kinases. A20 interacted directly with the distal domain of IL-17RA, a previously defined inhibitory domain. Together, these data describe a mechanism of restraining IL-17 signaling and reveal an aspect of A20 activity that may help to explain its role in autoimmunity in humans.

NFκB and ubiquitination: partners in disarming RIPK1-mediated cell death

The mechanisms regulating cell survival and thus its corollary, cell death, have been intensively studied over the last two decades. Recent studies have shed new light into how non-degradative ubiquitination of the kinase RIPK1 is critical in determining this cell fate. In this review, we summarize recent findings on how ubiquitination of RIPK1 constitutes a survival signal through both NFκB-independent and NFκB-dependent mechanisms. However, in the absence of ubiquitination, RIPK1 becomes a death-signaling molecule capable of engaging both the caspase-dependent apoptosis machinery and the recently described RIPK3-dependent necroptosis machinery. Another layer of complexity is now emerging in that components of the ubiquitin-modifying machinery are themselves regulated by proteolytic processing. This survival/death regulatory mechanism has been best analyzed in the context of TNF receptor signaling, but it is likely that principles learned from TNFR may be applicable to other immune receptors including the antigen and Toll-like receptors.

p38 MAPK/PP2Acα/TTP pathway on the connection of TNF-α and caspases activation on hydroquinone-induced apoptosis

This study investigated tumor necrosis factor-α (TNF-α)-mediated death pathway contribution to hydroquinone (HQ) cytotoxicity in human leukemia U937 cells. HQ-induced apoptosis of human leukemia U937 cells was characterized by the increase in mitochondrial membrane depolarization, procaspase-8 degradation and tBid production. Downregulation of Fas-associated death domain protein (FADD) blocked HQ-induced procaspase-8 degradation and rescued the viability of HQ-treated cells, suggesting the involvement of a death receptor-mediated pathway in HQ-induced cell death. HQ induced increased TNF-α mRNA stability led to TNF-α protein expression upregulation, whereas HQ suppressed TNF-α-mediated NFκB pathway activation. HQ elicited protein phosphatase 2A catalytic subunit α (PP2Acα) upregulation via p38 mitogen-activated protein kinase (MAPK)-mediated CREB/c-Jun/ATF-2 phosphorylation, and PP2Acα upregulation was found to promote tristetraprolin (TTP) degradation. Suppression of p38 MAPK activation and protein phosphatase 2A (PP2A) activity abrogated TNF-α upregulation and procaspase degradation in HQ-treated cells. Overexpression of TTP suppressed HQ-induced TNF-α upregulation and restored the viability of HQ-treated cells. Moreover, TTP overexpression increased TNF-α mRNA decay in HQ-treated cells. Taken together, our data indicate that HQ elicits TNF-α upregulation via p38 MAPK/PP2A-mediated TTP downregulation, and suggest that the TNF-α-mediated death pathway is involved in HQ-induced U937 cell death. The same pathway was also proven to be involved in the HQ-induced death of human leukemia HL-60 and Jurkat cells.

Serglycin proteoglycan promotes apoptotic versus necrotic cell death in mast cells

The mechanisms that govern whether a cell dies by apoptosis or necrosis are not fully understood. Here we show that serglycin, a secretory granule proteoglycan of hematopoietic cells, can have a major impact on this decision. Wild type and serglycin(-/-) mast cells were equally sensitive to a range of cell death-inducing regimens. However, whereas wild type mast cells underwent apoptotic cell death, serglycin(-/-) cells died predominantly by necrosis. Investigations of the underlying mechanism revealed that cell death was accompanied by leakage of secretory granule compounds into the cytosol and that the necrotic phenotype of serglycin(-/-) mast cells was linked to defective degradation of poly(ADP-ribose) polymerase-1. Cells lacking mouse mast cell protease 6, a major serglycin-associated protease, exhibited similar defects in apoptosis as observed in serglycin(-/-) cells, indicating that the pro-apoptotic function of serglycin is due to downstream effects of proteases that are complex-bound to serglycin. Together, these findings implicate serglycin in promoting apoptotic versus necrotic cell death.

TNF-induced necroptosis in L929 cells is tightly regulated by multiple TNFR1 complex I and II members

TNF receptor 1 signaling induces NF-κB activation and necroptosis in L929 cells. We previously reported that cellular inhibitor of apoptosis protein-mediated receptor-interacting protein 1 (RIP1) ubiquitination acts as a cytoprotective mechanism, whereas knockdown of cylindromatosis, a RIP1-deubiquitinating enzyme, protects against tumor necrosis factor (TNF)-induced necroptosis. We report here that RIP1 is a crucial mediator of canonical NF-κB activation in L929 cells, therefore questioning the relative cytoprotective contribution of RIP1 ubiquitination versus canonical NF-κB activation. We found that attenuated NF-κB activation has no impact on TNF-induced necroptosis. However, we identified A20 and linear ubiquitin chain assembly complex as negative regulators of necroptosis. Unexpectedly, and in contrast to RIP3, we also found that knockdown of RIP1 did not block TNF cytotoxicity. Cell death typing revealed that RIP1-depleted cells switch from necroptotic to apoptotic death, indicating that RIP1 can also suppress apoptosis in L929 cells. Inversely, we observed that Fas-associated protein via a death domain, cellular FLICE inhibitory protein and caspase-8, which are all involved in the initiation of apoptosis, counteract necroptosis induction. Finally, we also report RIP1-independent but RIP3-mediated necroptosis in the context of TNF signaling in particular conditions.

Deubiquitinating enzyme A20 negatively regulates NF-κB signaling in skeletal muscle in mdx mice

Duchenne muscular dystrophy (DMD) is caused by the lack of a functional dystrophin protein that results in muscle fiber membrane disruption and, ultimately, degeneration. Regeneration of muscle fibers fails progressively, and muscle tissue is replaced with connective tissue. As a result, DMD causes progressive limb muscle weakness and cardiac and respiratory failure. The absence of dystrophin from muscle fibers triggers the chronic activation of the nuclear factor of kappa B (NF-κB). Chronic activation of NF-κB in muscle leads to infiltration of macrophages, up-regulation of the ubiquitin-proteosome system, and down-regulation of the helix-loop-helix muscle regulatory factor, MyoD. These processes, triggered by NF-κB activation, promote muscle degeneration and failure of muscle regeneration. A20 (TNFAIP3) is a critical negative regulator of NF-κB. In this study, we characterize the role of A20 in regulating NF-κB activation in skeletal muscle, identifying a novel role in muscle regeneration. A20 is highly expressed in regenerating muscle fibers, and knockdown of A20 impairs muscle differentiation in vitro, which suggests that A20 expression is critically important for regeneration of dystrophic muscle tissue. Furthermore, down-regulation of the classic pathway of NF-κB activation is associated with up-regulation of the alternate pathway in regenerating muscle fibers, suggesting a mechanism by which A20 promotes muscle regeneration. These results demonstrate the important role of A20 in muscle fiber repair and suggest the potential of A20 as a therapeutic target to ameliorate the pathology and clinical symptoms of DMD.

A role for serglycin proteoglycan in mast cell apoptosis induced by a secretory granule-mediated pathway

Mast cell secretory granules (secretory lysosomes) contain large amounts of fully active proteases bound to serglycin proteoglycan. Damage to the granule membrane will thus lead to the release of serglycin and serglycin-bound proteases into the cytosol, which potentially could lead to proteolytic activation of cytosolic pro-apoptotic compounds. We therefore hypothesized that mast cells are susceptible to apoptosis induced by permeabilization of the granule membrane and that this process is serglycin-dependent. Indeed, we show that wild-type mast cells are highly sensitive to apoptosis induced by granule permeabilization, whereas serglycin-deficient cells are largely resistant. The reduced sensitivity of serglycin(-/-) cells to apoptosis was accompanied by reduced granule damage, reduced release of proteases into the cytosol, and defective caspase-3 activation. Mechanistically, the apoptosis-promoting effect of serglycin involved serglycin-dependent proteases, as indicated by reduced sensitivity to apoptosis and reduced caspase-3 activation in cells lacking individual mast cell-specific proteases. Together, these findings implicate serglycin proteoglycan as a novel player in mast cell apoptosis.

Adenovirus membrane penetration activates the NLRP3 inflammasome

Adenovirus type 5 (Ad5) infection of macrophages results in rapid secretion of interleukin-1β (IL-1β) and is dependent on the inflammasome components NLRP3 and ASC and the catalytic activity of caspase-1. Using lentivirus-expressed short hairpin RNA (shRNA) and competitive inhibitors, we show that Ad-induced IL-1β release is dependent upon Toll-like receptor 9 (TLR9) sensing of the Ad5 double-stranded DNA (dsDNA) genome in human cell lines and primary monocyte-derived macrophages but not in mouse macrophages. Additionally, a temperature-sensitive mutant of Ad5 unable to penetrate endosomal membranes, ts1, is unable to induce IL-1β release in TLR2-primed THP-1 cells, suggesting that penetration of endosomal membranes is required for IL-1β release. Disruption of lysosomal membranes and the release of cathepsin B into the cytoplasm are required for Ad-induced NLRP3 activation. Ad5 cell entry also induces reactive oxygen species (ROS) production, and inhibitors of ROS prevent Ad-induced IL-1β release. Ad5 activation of NLRP3 also induces necrotic cell death, resulting in the release of the proinflammatory molecule HMGB1. This work further defines the mechanisms of virally induced inflammasome activation.

Apoptosis in chondrogenesis of human mesenchymal stem cells: effect of serum and medium supplements

Apoptosis is an inevitable process during development and is evident in the formation of articular cartilage and endochondral ossification of growth plate. Mesenchymal stem cells (MSCs) can serve as alternative sources for cell therapy in focal chondral lesions or diffuse osteoarthritis. But there are few, if any, studies investigating apoptosis during chondrogenesis by MSCs. The aim of this study was to find the better condition to prevent apoptosis during chondrogenesis by MSCs. Apoptosis were evaluated in MSCs induced in different chondrogenic media by the use of Annexin V, TUNEL staining, lysosomal labeling with lysotracker and immunostaining of apoptotic markers. We found apparent apoptosis was demonstrated by Annexin V, TUNEL staining and lysosomal labeling during chondrogenesis. Meanwhile, the degree of apoptosis was related to the reagents of the defined chondrogenic medium. Adding serum in medium increased apoptosis, however, TGF-beta1 inhibited apoptosis. The apoptosis was associated with the activation of caspase-3, the increase in the Bax/Bcl-2 ratio, the loss of lysosomal integrity, and the increase of PARP-cleavage. Pro-inflammatory cytokines, IL-1alpha, IL-1beta and TNFalpha did not induce any increase in apoptosis. Interestingly, the inhibition of apoptosis by serum free medium supplemented with ITS was also associated with an increase in the expression of type II collagen, and a decrease in the expression of type X collagen, Runx2, and other osteogenic genes, while TGF-beta1 increased the expression of Sox9, type II and type X collagen and decreased the expression of osteogenic genes. These data suggest apoptosis occurs during chondrogenesis by MSCs by cell death intrinsic pathway activation and this process may be modulated by culture conditions.

Expression, biological activities and mechanisms of action of A20 (TNFAIP3)

A20 (also known as TNFAIP3) is a cytoplasmic protein that plays a key role in the negative regulation of inflammation and immunity. Polymorphisms in the A20 gene locus have been identified as risk alleles for multiple human autoimmune diseases, and A20 has also been proposed to function as a tumor suppressor in several human B-cell lymphomas. A20 expression is strongly induced by multiple stimuli, including the proinflammatory cytokines TNF and IL-1, and microbial products that trigger pathogen recognition receptors, such as Toll-like receptors. A20 functions in a negative feedback loop, which mediates its inhibitory functions by downregulating key proinflammatory signaling pathways, including those controlling NF-κB- and IRF3-dependent gene expression. Activation of these transcription factors is controlled by both K48- and K63- polyubiquitination of upstream signaling proteins, respectively triggering proteasome-mediated degradation or interaction with other signaling proteins. A20 turns off NF-κB and IRF3 activation by modulating both types of ubiquitination. Induction of K48-polyubiquitination by A20 involves its C-terminal zinc-finger ubiquitin-binding domain, which may promote interaction with E3 ligases, such as Itch and RNF11 that are involved in mediating A20 inhibitory functions. A20 is thought to promote de-ubiquitination of K63-polyubiquitin chains either directly, due to its N-terminal deubiquitinase domain, or by disrupting the interaction between E3 and E2 enzymes that catalyze K63-polyubiquitination. A20 is subject to different mechanisms of regulation, including phosphorylation, proteolytic processing, and association with ubiquitin binding proteins. Here we review the expression and biological activities of A20, as well as the underlying molecular mechanisms.

Endolysosomal proteases and their inhibitors in immunity

The cellular endolysosomal compartment is dynamic, complex and incompletely understood. Its organelles and constituents vary between different cell types, but endolysosomal proteases are key components of this compartment in all cells. In immune cells, these proteases function in pathogen recognition and elimination, signal processing and cell homeostasis, and they are regulated by dedicated inhibitors. Pathogens can produce analogous proteases to subvert the host immune response. The balance in activity between a protease and its inhibitor can tune the immune response or cause damage as a result of mislocalized proteolysis. In this Review, we highlight recent developments in this area and emphasize the importance of studying the role of endolysosomal proteases, and their natural inhibitors, in the initiation and regulation of immune responses.