NF-kappa B activation plays an important role in the IL-4-induced protection from apoptosis

Ethanol Extract of Ampelopsis brevipedunculata Rhizomes Suppresses IgE-Mediated Mast Cell Activation and Anaphylaxis

More than 20% of the world's population suffers from allergic diseases, including allergic asthma, rhinitis, and atopic dermatitis that severely reduce the patient's quality of life. The treatment of allergy has been developed, but there are still unmet needs. Ampelopsis brevipedunculata (Maxim.) Trautv. is a traditional medicinal herb with beneficial bioactivities, such as antioxidant, anti-hypertension, anti-viral, anti-mutagenic, and skin and liver (anti-hepatotoxic) protective actions. However, its anti-allergic effect has not been addressed. This study designed to investigate the pharmacological effect of an ethanol extract of A. brevipedunculata rhizomes (ABE) on mast cell and anaphylaxis models. For in vivo studies, we used ovalbumin-induced active systemic anaphylaxis (ASA) and immunoglobulin (Ig) E-mediated passive cutaneous anaphylaxis (PCA) models. In ASA model, oral administration of ABE (1, 10, and 100 mg/kg) attenuated the anaphylactic responses, such as hypothermia, serum histamine, and IgE productions. In PCA model, ABE also suppressed the plasma extravasation and swelling. The underlying mechanisms of action were identified in various mast cell types. In vitro, ABE (10, 30, and 60 µg/mL) inhibited the release of essential allergic mediators, such as histamine and β-hexosaminidase, in a concentration-dependent manner. ABE prevented the rapid increase in intracellular calcium levels induced by the DNP-HSA challenge. In addition, ABE downregulated the tumor necrosis factor-α and interleukin-4 by suppressing the activation of nuclear factor-κB. Collectively, this study is the first to identify the anti-allergic effect of ABE, suggesting that ABE is a promising candidate for treating allergic diseases.

Exploring association of melanoma-specific Bcl-xL with tumor immune microenvironment

BACKGROUND

Macrophages take center stage in the tumor microenvironment, a niche composed of extracellular matrix and a heterogeneous group of cells, including immune ones. They can evolve during tumor progression and acquire Tumor-Associated Macrophage (TAMs) phenotype. The release of cytokines by tumor and stromal cells, influence the secretion of cytokines by TAMs, which can guarantee tumor progression and influence the response to therapy. Among all factors able to recruit and polarize macrophages, we focused our attention on Bcl-xL, a multifaceted member of the Bcl-2 family, whose expression is deregulated in melanoma. It acts not only as a canonical pro-survival and anti-apoptotic protein, but also as a promoter of tumor progression.

METHODS

Human melanoma cells silencing or overexpressing Bcl-xL protein, THP-1 monocytic cells and monocyte-derived macrophages were used in this study. Protein array and specific neutralizing antibodies were used to analyze cytokines and chemokines secreted by melanoma cells. qRT-PCR, ELISA and Western Blot analyses were used to evaluate macrophage polarization markers and protein expression levels. Transwell chambers were used to evaluate migration of THP-1 and monocyte-derived macrophages. Mouse and zebrafish models were used to evaluate the ability of melanoma cells to recruit and polarize macrophages in vivo.

RESULTS

We demonstrated that melanoma cells overexpressing Bcl-xL recruit macrophages at the tumor site and induce a M2 phenotype. In addition, we identified that interleukin-8 and interleukin-1β cytokines are involved in macrophage polarization, and the chemokine CCL5/RANTES in the macrophages recruitment at the tumor site. We also found that all these Bcl-xL-induced factors are regulated in a NF-kB dependent manner in human and zebrafish melanoma models.

CONCLUSIONS

Our findings confirmed the pro-tumoral function of Bcl-xL in melanoma through its effects on macrophage phenotype.

Elevated GRO-α and IL-18 in serum and brain implicate the NLRP3 inflammasome in frontotemporal dementia

Neuroinflammation is a hallmark of frontotemporal dementia (FTD), a heterogeneous group of proteinopathies characterized by the progressive degeneration of the frontal and temporal lobes. It is marked by microglial activation and subsequent cytokine release. Although cytokine levels in FTD brain and CSF have been examined, the number of cytokines measured in each study is limited and knowledge on cytokine concentrations in FTD serum is scarce. Here, we assessed 48 cytokines in FTD serum and brain. The aim was to determine common cytokine dysregulation pathways in serum and brain in FTD. Blood samples and brain tissue samples from the superior frontal cortex (SFC) were collected from individuals diagnosed with behavioral variant FTD (bvFTD) and healthy controls, and 48 cytokines were measured using a multiplex immunological assay. The data were evaluated by principal component factor analysis to determine the contribution from different components of the variance in the cohort. Levels of a number of cytokines were altered in serum and SFC in bvFTD compared to controls, with increases in GRO-α and IL-18 in both serum and SFC. These changes could be associated with NLRP3 inflammasome activation or the NFκB pathway, which activates NLRP3. The results suggest the possible importance of the NLRP3 inflammasome in FTD. An improved understanding of the role of inflammasomes in FTD could provide valuable insights into the pathogenesis, diagnosis and treatment of FTD.

Acupoint Catgut-Embedding Therapy Inhibits NF-κB/COX-2 Pathway in an Ovalbumin-Induced Mouse Model of Allergic Asthma

Allergic asthma is associated with T helper (Th) 2 cell-biased immune responses and characterized by the airway hyperresponsiveness (AHR). Studies have shown that the acupoint catgut-embedding therapy (ACE) has a therapeutic effect on allergic asthma. However, the relevant mechanism is poorly understood. In present study, female BALB/c mice were sensitized and challenged with ovalbumin (OVA) to establish a model of allergic asthma. AHR was evaluated by using airway resistance ( $R_L$ ) and lung dynamic compliance (Cdyn). Airway inflammation and mucus hypersecretion were observed by HE and PAS staining. Inflammatory cells were counted, and related cytokines in bronchoalveolar lavage fluid (BALF) were detected by enzyme-linked immunosorbent assay (ELISA). Pulmonary group 2 innate lymphoid cell (ILC2s) proportions were analyzed by flow cytometry. The expression of nuclear factor κB (NF-κB) and cyclooxygenase-2 (COX-2) was detected by immunostaining. Our results showed that OVA induction resulted in a significant increase in $R_L$ , accompanied by a significant decrease in Cdyn. The levels of interleukin- (IL-) 4, IL-13, OVA-specific IgE in BALF, and the percentage of ILC2 in the lungs were markedly increased accompanied by a significant decreased in interferon-γ (IFN-γ). Furthermore, the expressions of p-NF-κB p65 and COX-2 in airways were significantly upregulated. After ACE treatment, the indicators above were significantly reversed. In conclusion, ACE treatment inhibited the secretion of Th2 cytokines and the proliferation of ILC2s in the lungs, thereby dampening the inflammatory activity in allergic asthma. The underlying mechanism might be related to the inhibition of NF-κB/COX-2 pathway.

MicroRNA 21 Elicits a Pro-inflammatory Response in Macrophages, with Exosomes Functioning as Delivery Vehicles

MicroRNAs can regulate inflammatory responses by modulating macrophage polarization. Although microRNA miR-21 is linked to crucial processes involved in inflammatory responses, its precise role in macrophage polarization is controversial. In this study, we investigated the functional relevance of endogenous miRNA-21 and the role of exosomes. RAW 264.7 macrophages were transfected with miR-21 plasmid, and the inflammatory response was evaluated by flow cytometry, phagocytosis, and real-time PCR analysis of inflammatory cytokines. To understand the signaling pathways' role, the cells were treated with inhibitors specific for PI3K or NFĸB. Exosomes from transfected cells were used to study the paracrine action of miR-21 on naive macrophages. Overexpression of miR-21 resulted in significant upregulation of pro-inflammatory cytokines, pushing the cells towards a pro-inflammatory phenotype, with partial involvement of PI3K and NFĸB signal pathways. The cells also secreted miR-21 rich exosomes, which, on delivery to naive macrophages, caused them to exhibit pro-inflammatory activity. The presence of miR-21 inhibitor quenched the inflammatory response. This study validates the pro-inflammatory property of miR-21 with a tendency to foster an inflammatory milieu. Our findings also reinforce the dual importance of exosomal miR-21 as a biomarker and therapeutic target in inflammatory conditions.

Environmental pollutants modulate RNA and DNA virus-activated miRNA-155 expression and innate immune system responses: Insights into new immunomodulative mechanisms

Many persistent organic pollutants, such as polychlorinated biphenyls (PCBs), have high immunomodulating potentials. Exposure to them, in combination with virus infections, has been shown to aggravate outcomes of the infection, leading to increased viral titers and host mortality. Expression of immune-related microRNA (miR) signaling pathways (by host and/or virus) have been shown to be important in determining these outcomes; there is some evidence to suggest pollutants can cause dysregulation of miRNAs. It was thus hypothesized here that modulation of miRNAs (and associated cytokine genes) by pollutants exerts negative effects during viral infections. To test this, an in vitro study on chicken embryo fibroblasts (CEF) exposed to a PCB mixture (Aroclor 1260) and then stimulated with a synthetic RNA virus (poly(I:C)) or infected with a lymphoma-causing DNA virus (Gallid Herpes Virus 2 [GaHV-2]) was conducted. Using quantitative real-time PCR, expression patterns for mir-155, pro-inflammatory TNFα and IL-8, transcription factor NF-κB1, and anti-inflammatory IL-4 were investigated 8, 12, and 18 h after virus activation. The study showed that Aroclor1260 modulated mir-155 expression, such that a down-regulation of mir-155 in poly(I:C)-treated CEF was seen up to 12 h. Aroclor1260 exposure also increased the mRNA expression of pro-inflammatory genes after 8 h in poly(I:C)-treated cells, but levels in GaHV-2-infected cells were unaffected. In contrast to with Aroclor1260/poly(I:C), Aroclor1260/GaHV-2-infected cells displayed an increase in mir-155 levels after 12 h compared to levels seen with either individual treatment. While after 12 h expression of most evaluated genes was down-regulated (independent of treatment regimen), by 18 h, up-regulation was evident again. In conclusion, this study added evidence that mir-155 signaling represents a sensitive pathway to chemically-induced immunomodulation and indicated that PCBs can modulate highly-regulated innate immune system signaling pathways important in determining host immune response outcomes during viral infections.

IL-27 regulates IL-4-induced chemokine production in human bronchial epithelial cells

IL-4 coordinates the Th2-type immune response in inflammatory diseases such as asthma. IL-27 can inhibit the development of both Th2 and Th1 cells. However, IL-27 can also drive naïve T cells to differentiate toward the Th1 phenotype. In this study, we investigated the effects of IL-27 on the activation of IL-4-induced human bronchial epithelial cells (BEAS-2B). Compared to controls, both IL-4 and IL-27 (25-100 ng/mL) increased the concentrations of CCL2 and IL-8 in a dose-dependent manner. However, compared to cells stimulated individually with IL-4 or IL-27, treatment with a combination of both cytokines reduced CCL2 and IL-8 concentrations in a dose- and time-dependent manner. IL-4 increased the activation of p38 MAPK, ERK1/2, STAT6 and NF-κB, while IL-27 increased the activation of p38 MAPK and ERK1/2 but not STAT6 and NF-κB. Compared to IL-4-stimulated cells, cells treated with both IL-27 and IL-4 displayed decreased activation of STAT6 and NF-κB but not ERK1/2 and p38 MAPK. Taken together, these results suggest that IL-27 plays a pro-inflammatory role when administered alone but downregulates bronchial epithelial cell activation when combined with IL-4. Therefore, IL-27 may be an interesting target for the treatment of Th2 inflammatory diseases.

Clinico-Biological Implications of Modified Levels of Cytokines in Chronic Lymphocytic Leukemia: A Possible Therapeutic Role

B-cell chronic lymphocytic leukemia (B-CLL) is the main cause of mortality among hematologic diseases in Western nations. B-CLL is correlated with an intense alteration of the immune system. The altered functions of innate immune elements and adaptive immune factors are interconnected in B-CLL and are decisive for its onset, evolution, and therapeutic response. Modifications in the cytokine balance could support the growth of the leukemic clone via a modulation of cellular proliferation and apoptosis, as some cytokines have been reported to be able to affect the life of B-CLL cells in vivo. In this review, we will examine the role played by cytokines in the cellular dynamics of B-CLL patients, interpret the contradictions sometimes present in the literature regarding their action, and evaluate the possibility of manipulating their production in order to intervene in the natural history of the disease.

The transcriptional response of mouse spleen B cells to IL-4: Comparison to the response of human peripheral blood B cells

The Th2 cytokine IL-4 triggers a signaling cascade which activates transcription by STAT6. The goals of the present study are to define the transcriptomic response of mouse spleen B cells (mSBC) to IL-4 used as single stimulus, its specificity compared to human peripheral blood B cells (hPBBC) and to mouse spleen T cells (mSTC), and the pathways affected. Oligonucleotide-based microarrays were performed using two references, the untreated sample and the cells cultured without IL-4, an experimental design which reduces the potential confounding effect of cellular stress during culture. Specificity was addressed by comparing the response of mSBC and our previously published study on hPBBC, of similar design, and a study by other authors on mSTC. We detected an mSBC-specific response (including novel genes, e.g., Sertad4, Lifr, Pmepa1, Epcam, Tbxas1; and common genes, e.g., Usp2, Cst7, Grtp1, and Casp6), an hPBBC-specific response (e.g., CCL17, MTCL1, GCSAM, HOMER2, IL2RA), and a common mSBC/hPBBC response (e.g., CISH, NFIL3, SOCS1, VDR, CDH1). In contrast, the mSBC and mSTC responses were largely divergent. Gene set enrichment analysis (GSEA) was applied for the first time to identify the pathways affected. Both in mSBC and hPBBC, IL-4 activated Myc, the transcriptional machinery itself, cell cycle, mitochondria and respiratory chain, ribosome, proteasome and antigen presentation, and Wnt signaling, and inhibited GPCR signaling. However, significant differences were found in histone demethylation, Nod signaling, and Rho signaling, which were downregulated in mSBC, and in chromatin condensation, which was downregulated in hPBBC. These findings may have therapeutic implications for the treatment of allergic diseases and parasitic infections.

IL-4 Up-Regulates MiR-21 and the MiRNAs Hosted in the CLCN5 Gene in Chronic Lymphocytic Leukemia

Interleukin 4 (IL-4) induces B-cell differentiation and survival of chronic lymphocytic leukemia (CLL) cells. MicroRNAs (miRNAs) regulate mRNA and protein expression, and several miRNAs, deregulated in CLL, might play roles as oncogenes or tumor suppressors. We have studied the miRNA profile of CLL, and its response to IL-4, by oligonucleotide microarrays, resulting in the detection of a set of 129 mature miRNAs consistently expressed in CLL, which included 41 differentially expressed compared to normal B cells (NBC), and 6 significantly underexpressed in ZAP-70 positive patients. IL-4 stimulation brought about up-regulation of the 5p and 3p mature variants of the miR-21 gene, which maps immediately downstream to the VMP1 gene, and of the mature forms generated from the miR-362 (3p and 5p), miR-500a (3p), miR-502 (3p), and miR-532 (3p and 5p) genes, which map within the third intron of the CLCN5 gene. Both genes are in turn regulated by IL-4, suggesting that these miRNAs were regulated by IL-4 as passengers from their carrier genes. Their levels of up-regulation by IL-4 significantly correlated with cytoprotection. MiR-21 has been reported to be leukemogenic, associated to bad prognosis in CLL, and the miRNA more frequently overexpressed in human cancer. Up-regulation by IL-4 of miR-21 and the miRNAs hosted in the CLCN5 locus may contribute to evasion of apoptosis of CLL cells. These findings indicate that the IL-4 pathway and the miRNAs induced by IL-4 are promising targets for the development of novel therapies in CLL.

The gene expression response of chronic lymphocytic leukemia cells to IL-4 is specific, depends on ZAP-70 status and is differentially affected by an NFκB inhibitor

Interleukin 4 (IL-4), an essential mediator of B cell development, plays a role in survival of chronic lymphocytic leukemia (CLL) cells. To obtain new insights into the function of the IL-4 pathway in CLL, we analyzed the gene expression response to IL-4 in CLL and in normal B cells (NBC) by oligonucleotide microarrays, resulting in the identification of 232 non-redundant entities in CLL and 146 in NBC (95 common, 283 altogether), of which 189 were well-defined genes in CLL and 123 in NBC (83 common, 229 altogether) (p<0.05, 2-fold cut-off). To the best of our knowledge, most of them were novel IL-4 targets for CLL (98%), B cells of any source (83%), or any cell type (70%). Responses were significantly higher for 54 and 11 genes in CLL and NBC compared to each other, respectively. In CLL, ZAP-70 status had an impact on IL-4 response, since different sets of IL-4 targets correlated positively or negatively with baseline expression of ZAP-70. In addition, the NFκB inhibitor 6-Amino-4-(4-phenoxyphenethylamino)quinazoline, which reversed the anti-apoptotic effect of IL-4, preferentially blocked the response of genes positively correlated with ZAP-70 (e.g. CCR2, SUSD2), but enhanced the response of genes negatively correlated with ZAP-70 (e.g. AUH, BCL6, LY75, NFIL3). Dissection of the gene expression response to IL-4 in CLL and NBC contributes to the understanding of the anti-apoptotic response. Initial evidence of a connection between ZAP-70 and NFκB supports further exploration of targeting NFκB in the context of the assessment of inhibition of the IL-4 pathway as a therapeutic strategy in CLL, especially in patients expressing bad prognostic markers.

Caspase mediated synergistic effect of Boswellia serrata extract in combination with doxorubicin against human hepatocellular carcinoma

The study investigated the growth-inhibiting and apoptosis mediating effects of B. serrata extract as monotherapy and combination therapy with DOX against hepatocellular carcinoma cell lines. Boswellic acid rich fraction of B. serrata extract was prepared. MTT assay on HepG2 and Hep3B cells was carried out using B. serrata alone and in combination with DOX. Further, caspase-3 activity, TNF-α level, and IL-6 level were estimated. Isobolographic analysis was carried out to evaluate the effect of combination therapy. Additionally, protective effect of B. serrata extract on DOX induced hepatic toxicity was also evaluated in Wistar rats. B. serrata extract inhibited growth of HepG2 (IC50 value of 21.21 ± 0.92 μg/mL) as well as HepG2 (IC50 value of 18.65 ± 0.71 μg/mL). DOX inhibited growth in HepG2 and Hep3B cells with an IC50 of 1.06 ± 0.04 μg/mL and 1.92 ± 0.09 μg/mL. Isobolographic analysis showed combination index (CI) of DOX and B. serrata extract of 0.53 ± 0.03 to 0.79 ± 0.02 suggesting synergistic behavior against the two cell lines. B. serrata extract also caused dose dependent increase in caspase-3 activity, TNF-α level, and IL-6 level which was higher (P < 0.001) with DOX (1 μM) and B. serrata extract (20 μg/mL) combination. B. serrata extract also protected Wistar rats against DOX induced hepatic toxicity.

NF-κB signaling participates in both RANKL- and IL-4-induced macrophage fusion: receptor cross-talk leads to alterations in NF-κB pathways

NF-κB activation is essential for receptor activator for NF-κB ligand (RANKL)-induced osteoclast formation. IL-4 is known to inhibit the RANKL-induced osteoclast differentiation while at the same time promoting macrophage fusion to form multinucleated giant cells (MNG). Several groups have proposed that IL-4 inhibition of osteoclastogenesis is mediated by suppressing the RANKL-induced activation of NF-κB. However, we found that IL-4 did not block proximal, canonical NF-κB signaling. Instead, we found that IL-4 inhibited alternative NF-κB signaling and induced p105/50 expression. Interestingly, in nfκb1(-/-) bone marrow-derived macrophages (BMM), the formation of both multinucleated osteoclast and MNG induced by RANKL or IL-4, respectively, was impaired. This suggests that NF-κB signaling also plays an important role in IL-4-induced macrophage fusion. Indeed, we found that the RANKL-induced and IL-4-induced macrophage fusion were both inhibited by the NF-κB inhibitors IκB kinase 2 inhibitor and NF-κB essential modulator inhibitory peptide. Furthermore, overexpression of p50, p65, p52, and RelB individually in nfκb1(-/-) or nfκb1(+/+) BMM enhanced both giant osteoclast and MNG formation. Interestingly, knockdown of nfκb2 in wild-type BMM dramatically enhanced both osteoclast and MNG formation. In addition, both RANKL- and IL-4-induced macrophage fusion were impaired in NF-κB-inducing kinase(-/-) BMM. These results suggest IL-4 influences NF-κB pathways by increasing p105/p50 and suppressing RANKL-induced p52 translocation and that NF-κB pathways participate in both RANKL- and IL-4-induced giant cell formation.

Interleukin(IL)-4 promotion of CXCL-8 gene transcription is mediated by ERK1/2 pathway in human pulmonary artery endothelial cells

Interleukin-4 is central to allergic pulmonary inflammatory responses, but its contribution to airway neutrophilia remains controversial. The endothelium plays a critical role in regulating leukocyte recruitment and migration during inflammation. However, its response to IL-4 is reported to either increase or decrease the production of neutrophil chemotactic factors. We hypothesized that these conflicting findings may be due to the tissue and the size of the vessels from which endothelial cells have been derived. The expression of CXCL-8 by human primary culture umbilical veins endothelial cells (HUVECs), human pulmonary artery endothelial cells (HPAECs), and human pulmonary microvascular endothelial cells (HPMECs) when stimulated with recombinant human IL-4 (rhIL-4) was studied. The chemoattractant property of the cells' supernatants for neutrophils was evaluated using Boyden chambers. The role of the nuclear factor-κB (NF-κB), and mitogen-activated protein kinases (MAPK) in IL-4-induced HPAECs was studied using Western blotting and electrophoretic mobility shift assay (EMSA). We demonstrated that IL-4 increased the mRNA expression and the protein production of CXCL-8 in HPAECs, but not in HUVECs and HPMECs. The supernatants of HAPECs stimulated by IL-4 significantly promoted neutrophils migration in a dose-dependent manner, and was significantly attenuated by an inhibitor of CXCL-8. We also found that extracellular-regulated protein kinase1/2 (ERK1/2) is activated by IL-4 in HPAECs, but not JUN-N-terminal protein kinase (JNK) or p38 MAPK pathway. Furthermore, NF-κB-DNA binding activity, phosphorylation of IκBα and p65 levels were not affected by rhIL-4 in HAPECs. These findings indicate marked functional differences in the response of micro and macro-ECs to IL-4. ERK1/2, rather than NF-κB, JNK and p38 MAPK signaling, plays a role in IL-4 induced chemokine activation. Our results suggest that inhibition of ERK1/2 may be a possible target for airway neutrophilia in allergic lung diseases.

Antitumor activity of Noscapine in combination with Doxorubicin in triple negative breast cancer

Background

The aim of this study was to investigate the anticancer activity and mechanism of action of Noscapine alone and in combination with Doxorubicin against triple negative breast cancer (TNBC).

Methods

TNBC cells were pretreated with Noscapine or Doxorubicin or combination and combination index values were calculated using isobolographic method. Apoptosis was assessed by TUNEL staining. Female athymic Nu/nu mice were xenografted with MDA-MB-231 cells and the efficacy of Noscapine, Doxorubicin and combination was determined. Protein expression, immunohistochemical staining were evaluated in harvested tumor tissues.

Results

Noscapine inhibited growth of MDA-MB-231 and MDA-MB-468 cells with the IC₅₀ values of 36.16±3.76 and 42.7±4.3 µM respectively. The CI values (<0.59) were suggestive of strong synergistic interaction between Noscapine and Doxorubicin and combination treatment showed significant increase in apoptotic cells. Noscapine showed dose dependent reduction in the tumor volumes at a dose of 150–550 mg/kg/day compared to controls. Noscapine (300 mg/kg), Doxorubicin (1.5 mg/kg) and combination treatment reduced tumor volume by 39.4±5.8, 34.2±5.7 and 82.9±4.5 percent respectively and showed decreased expression of NF-KB pathway proteins, VEGF, cell survival, and increased expression of apoptotic and growth inhibitory proteins compared to single-agent treatment and control groups.

Conclusions

Noscapine potentiated the anticancer activity of Doxorubicin in a synergistic manner against TNBC tumors via inactivation of NF-KB and anti-angiogenic pathways while stimulating apoptosis. These findings suggest potential benefit for use of oral Noscapine and Doxorubicin combination therapy for treatment of more aggressive TNBC.

Chemical Complexity and the Genetics of Aging

We examine how aging is impacted by various chemical challenges that organisms face and by the molecular mechanisms that have evolved to regulate lifespan in response to them. For example, environmental information, which is detected and processed through sensory systems, can modulate lifespan by providing information about the presence and quality of food as well as presence and density of conspecifics and predators. In addition, the diverse forms of molecular damage that result from constant exposure to damaging chemicals that are generated from the environment and from metabolism pose an informatic and energetic challenge for detoxification systems, which are important in ensuring longevity. Finally, systems of innate immunity are vital for recognizing and combating pathogens but are also seen as of increasing importance in causing the aging process. Integrating ideas of molecular mechanism with context derived from evolutionary considerations will lead to exciting new insights into the evolution of aging.

Differential expression of RANK, RANK-L, and osteoprotegerin by synovial fluid neutrophils from patients with rheumatoid arthritis and by healthy human blood neutrophils

Functional links between bone remodeling and the immune system in chronic inflammatory arthritis are mediated, in part, by the ligand of receptor activator of nuclear factor-kappa-B (RANK-L). Because neutrophils play a crucial role in chronic inflammation, the goal of this study was to determine whether proteins of the RANK/RANK-L pathway are expressed by synovial fluid (SF) neutrophils from patients with rheumatoid arthritis (RA) and to characterize this pathway in normal human blood neutrophils. The expression of RANK-L, osteoprotegerin (OPG), RANK, and tumor necrosis factor receptor-associated factor 6 (TRAF6) was determined by polymerase chain reaction, enzyme-linked immunosorbent assay, Western blotting, and cytofluorometry. RANK signaling was analyzed by the degradation of inhibitor of kappaB-alpha (I-κB-α). SF neutrophils from patients with RA express and release OPG and express the membrane-associated forms of RANK-L and RANK. In contrast, normal blood neutrophils express only the membrane-associated form of RANK-L. They do not express the mRNAs encoding OPG and RANK. SF neutrophils from RA patients and normal blood neutrophils release no soluble RANK-L. They express the mRNA for TRAF6. The expression of OPG and RANK by normal human blood neutrophils, however, can be induced by interleukin-4 + tumor necrosis factor-alpha and by SFs from patients with RA. In contrast, SFs from patients with osteoarthritis do not induce the expression of OPG and RANK. Moreover, the addition of RANK-L to normal blood neutrophils pretreated by SF from patients with RA decreased I-κB-α, indicating that RANK signaling by neutrophils stimulated with SF is associated with nuclear factor-kappa-B activation. In summary, RANK-L is expressed by inflammatory and normal neutrophils, unlike OPG and RANK, which are expressed only by neutrophils exposed to an inflammatory environment. Taken together, these results suggest that neutrophils may contribute to bone remodeling at inflammatory sites where they are present in significantly large numbers.

The role of IL-6 in inhibition of lymphocyte apoptosis by mesenchymal stem cells

Mesenchymal stem cells (MSCs) are widely distributed throughout the body. Despite intensive studies on the immunosuppressive effect of MSCs, little is known about whether MSCs affect lymphocyte apoptosis. We investigated the effect of MSCs on the spontaneous death of lymphocytes and found that MSCs inhibit the apoptosis of splenocytes and thymocytes as well as purified T and B cells. The protective effect of MSCs was absent when lymphocytes were not in contact with MSCs, indicating that the anti-apoptotic effect is exerted through direct interaction between MSCs and lymphocytes. Interestingly, this anti-apoptotic effect could be inhibited by neutralization of IL-6. Consequently, we found that the expression of IL-6 by MSCs was augmented by contact with lymphocytes. Taken together, these results demonstrate that IL-6 plays an important role in the inhibition of lymphocyte apoptosis by MSCs.

IL-4 suppresses UVB-induced apoptosis in skin

In this study, cutaneous role of IL-4 in UVB-induced apoptosis was investigated using transgenic mice with skin-specific expression of IL-4 (IL-4 Tg mice). The transgenic mice did not show any gross clinical abnormalities. However, epidermis was thickened and increased MHC class II positive cells were detected as well as enhanced expression of inflammatory cytokines such as IL-1 and TNF-alpha in skin. In addition, histological analysis revealed increased infiltration of lymphocytes, acanthosis, hyperkeratosis, and parakeratosis in skin of IL-4 Tg mice. The physiological effect of IL-4 overexpression in skin against environmental stimulus such as UVB was investigated by irradiating wild-type and IL-4 Tg mice with UVB followed by evaluation of apoptosis. The result demonstrated suppressed apoptosis in epidermis of IL-4 Tg mice compared with wild-type mice. To further assess anti-apoptotic function of IL-4 in keratinocytes, stable cell clones were made where IL-4 was constitutively overexpressed and examined for UVB-induced apoptosis. The results showed that apoptosis was remarkably decreased in IL-4 over-expressing cell clones compared with that in mock transfected cells. Collectively, data presented here shows that IL-4 has an inhibitory effect against UVB-induced apoptosis in keratinocytes, suggesting that IL-4 may be an important regulator in cutaneous immunity against UVB.

IL-4-induced upregulation of adenine nucleotide translocase 3 and its role in Th cell survival from apoptosis

We have identified mitochondrial adenine nucleotide translocase (ANT)3 as a novel target up-regulated by IL-4 in human T cells. The IL-4-induced ANT3 expression is dependent on tyrosine kinase, NF-kappaB, PI3K/Akt, and Erk pathways. In fact, IL-4 induced specific activation of NF-kappaB, Akt, and Erk in Jurkat T cells and partially rescued these cells from dexamethasone-induced apoptosis. The IL-4-mediated T cell survival was blocked by inhibitors of tyrosine kinase, NF-kappaB, PI3K/Akt, and Erk. During the IL-4-induced T cell rescue, there was a concomitant increase in ANT3, nuclear NF-kappaB, and Bcl-2 and a decrease in ANT1, I-kappaB, and mitochondrial Bax-alpha levels. Importantly, overexpression of ANT3 effectively protected T cells from dexamethasone-induced apoptosis, while forced expression of ANT1 caused apoptosis. In contrast, siRNA knock-out of ANT3 expression induced T cell apoptosis and blocked the IL-4-mediated cell survival. Together these results suggest that ANT3 has a potential role in Th cell survival and immune cell homeostasis.

Recruitment of insulin receptor substrate-1 and activation of NF-kappaB essential for midkine growth signaling through anaplastic lymphoma kinase

Anaplastic lymphoma kinase (ALK) is a transmembrane receptor tyrosine kinase in the insulin receptor superfamily. We recently demonstrated that the growth factors pleiotrophin (PTN) and midkine (MK) are ligands for ALK and that upon ALK activation, insulin receptor substrate-1 (IRS-1) and other substrates are phosphorylated. Here, the role of IRS-1 in ligand-mediated ALK signaling is investigated in interleukin-3 (IL-3)-dependent 32D murine myeloid cells. These cells do not express ALK and IRS family members, and do not respond to exogenously added PTN or MK. We show that expression of ALK plus IRS-1 renders these cells independent of IL-3 owing to the activation of ALK by endogenous MK. Mutational analysis reveals that this transformed phenotype of 32D cells requires kinase-active ALK as well as the interaction of ALK with IRS-1. Furthermore, 32D/IRS-1/ALK cells display an enhanced activation of mitogen-activated protein kinase and PI3-kinase pathways, and a selective transcriptional activation of nuclear factor (NF)-kappaB. Small interfering RNA-mediated knockdown of the endogenous MK or p65/NF-kappaB revealed that both these are rate limiting for the transformed phenotype induced by ALK plus IRS-1. We conclude that the recruitment of IRS-1 to activated ALK and the activation of NF-kappaB are essential for the autocrine growth and survival signaling of MK.

Expression of the adaptor protein hematopoietic Src homology 2 is up-regulated in response to stimuli that promote survival and differentiation of B cells

Analysis of hematopoietic Src homology 2 (HSH2) protein expression in mouse immune cells demonstrated that it is expressed at low levels in resting B cells but not T cells or macrophages. However, HSH2 expression is up-regulated within 6-12 h in response to multiple stimuli that promote activation, differentiation, and survival of splenic B cells. HSH2 expression is increased in response to anti-CD40 mAb, the TLR ligands LPS and CpG DNA, and B lymphocyte stimulator (BLyS), a key regulator of peripheral B cell survival and homeostasis. Stimulation of B cells with anti-CD40 mAb, LPS, CpG DNA, or BLyS has previously been shown to induce activation of NF-kappaB. In agreement with this finding, up-regulation of HSH2 expression in response to these stimuli is blocked by inhibitors of NF-kappaB activation and is potentiated by stimulation with PMA, suggesting that HSH2 expression is dependent on NF-kappaB activation. In contrast to CD40, BAFF receptor, TLR4, and TLR9 mediated signaling, stimulation of splenic B cells via the BCR was not observed to induce expression of HSH2 unless the cells had been stimulated previously through CD40. Finally, HSH2 expression is down-regulated in splenic B cells in response to stimulation with IL-21, which has been shown to induce apoptosis, even in the presence of anti-CD40 mAb, LPS, or CpG DNA. IL-21 stimulation also results in down-regulation of antiapoptotic proteins such as Bcl-x(L) and up-regulation of proapoptotic proteins like Bim. Therefore, HSH2 expression is coordinately up-regulated with known antiapoptotic molecules and directly correlates with B cell survival.

Effects of interleukin 4 on CD25+CD4+ regulatory T cell function

CD25+CD4+ regulatory T cells (Tregs) contribute to the maintenance of peripheral tolerance against self and non-self. The modulatory effects of cytokines, such as interleukin 4 (IL-4) on the function of Tregs have not been explored in detail. We here report that IL-4 prevents spontaneous apoptosis and the decline of foxp3 mRNA which were found to occur during culture of isolated Tregs. Tregs exposed to IL-4 were more potent in suppressing the proliferation of naïve CD4+ T cells and they better inhibited IFN-gamma production by CD4+ T cells as compared to Tregs cultured in medium. IL-4 also enhanced membrane IL-2Ralpha (CD25) expression on Tregs above the levels observed on freshly isolated cells. IL-4-mediated effects on Treg function persisted in Tregs from Stat6-/- mice, pointing to a Stat6-independent intracellular transduction pathway. In conclusion, our data suggest that the anti-inflammatory function of IL-4 could partly be mediated by effects on Tregs function.

Requirement for NF-(kappa)B in interleukin-4-induced androgen receptor activation in prostate cancer cells

BACKGROUND

Accumulating evidence suggest a critical role of activation of androgen receptor (AR) by nonandrogen in the development of androgen independent prostate cancer. Previous study identified that interleukin-4 (IL-4) enhances AR activation in the absence of androgen or in the very low levels of androgen in prostate cancer cells. In this study, the mechanism of IL-4-induced AR activation was investigated.

METHODS & RESULTS

The induction of AR activation by IL-4 can be suppressed by expression of the I(kappa)B(alpha), an inhibitor of NF-(kappa)B. The enhanced expression of AR-mediated prostate-specific antigen (PSA) by IL-4 was blocked by the expression of I(kappa)B(alpha). IL-4 increases NF-(kappa)B transcriptional activity in prostate cancer cells which can be blocked by the addition of IL-4 antibody. IL-4 can also rapidly activate NF-kappaB. Furthermore, the IL-4-induced NF-kappaB activation and nuclear translocation can be blocked by LY294002, a PI3K/Akt specific inhibitor, suggesting that IL-4-induced NF-(kappa)B activation is mediated by activation of PI3K/Akt pathway.

CONCLUSION

In combination with previous study that IL-4 activates PI3K/Akt pathway, activation of PI3K/Akt > NF-(kappa)B pathways may be responsible for IL-4-induced AR activation in prostate cancer cells. Taken together, these studies suggest that IL-4 > PI3K/Akt > NF-(kappa)B signaling pathways, which activate AR signaling, may play an important role during the progression of androgen independent prostate cancer cells.

Proteolytic regulation of activated STAT6 by calpains

The transcription factor STAT6 plays an important role in cell responses to IL-4. Its activation is tightly regulated. STAT6 phosphorylation is associated with JAKs, whereas dephosphorylation is associated with specific phosphatases. Several studies indicate that proteases can also regulate STAT6. The aim of this study was to investigate the nature of these proteases in mouse T cell lines. We found that STAT6 was degraded in cell extracts by calcium-dependent proteases. This degradation was specifically prevented by calpain inhibitors, suggesting that STAT6 was a target for these proteases. This was supported by the cleavage of STAT6 by recombinant calpains. The proteolytic regulation of STAT6 was more complex in vivo. Calcium signaling was not sufficient to induce STAT6 degradation. However, treatment of IL-4-stimulated cells with calcium ionophores resulted in the absence of phosphorylated STAT6. This effect correlated with the loss of STAT6 protein and was prevented by calpain inhibitors. Cytoplasmic calpains seemed to be responsible for STAT6 degradation. Calpains can target signaling proteins; in this study we found that they can negatively regulate activated STAT6.

Signaling pathways in Th2 development

In order for an immune response to be successful, it must be of the appropriate type and magnitude. Intracellular residing pathogens require a cell-mediated immune response, whereas extracellular pathogens evoke a humoral immune response. T-helper (Th) cells orchestrate the immune response and are divided into two subsets, Th1 and Th2 cells. Here, we discuss the mechanisms of Th2 development with a focus on signal transduction pathways that influence Th2 differentiation.

Differential effect of interleukin-10 on hepatocyte apoptosis

Current data suggests that hepatocyte apoptosis is an essential feature contributing to several chronic liver diseases. It has been shown that IL-10 has diverse and potentially pleiotropic actions that suggest that it may have a direct effect on apoptosis. It has been established that NF-kappaB activation is essential to protect hepatocytes from apoptosis. The purpose of the present work is to evaluate the effect of the anti-inflammatory cytokine, IL-10 on the activation of NF-kappaB in primary cultured rat hepatocytes and hepatoblastoma (HepG2) cell line and explore its consequences on apoptosis. Apoptosis was induced by TNF-alpha and cicloheximide in HepG2 hepatoblastoma cells and by ethanol and a glutathione depletor in primary cultured rat hepatocytes. NF-kappaB activation was determined by EMSA. IL-10 increased ethanol induced apoptosis in primary culture rat hepatocytes (28%). These effects were enhanced when the cells were pre-treated with IL-10 under conditions of oxidative stress (glutathione depletion). The effects of IL-10 on primary cultured hepatocytes were independent of NF-kappaB activation. When apoptosis was induced by cicloheximide and TNF-alpha in hepatoblastoma cells, pretreatment with IL-10 was accompanied by a decrease of 38% in apoptosis. IL-10 did not have any effect on the signaling cascade of apoptosis but caused a significant increase in NF-kappaB activation. When NF-kappaB activation was inhibited by sulfazalazine the decrease in apoptosis was reversed. The present study demonstrates the importance of differential cell marking when trying to characterize the effects of cytokines in their contribution to liver cell apoptosis. The study provides insight into the mechanisms by which IL-10 affects apoptosis through a differential effect on NF-kappaB activation.

IL-10 induces regulatory T cell apoptosis by up-regulation of the membrane form of TNF-alpha

Numerous studies have demonstrated the role of regulatory T (Treg) cells in peripheral tolerance. Nevertheless, how the survival and death of Treg cells is controlled is largely unknown. In this study, we investigated the mechanisms involved in regulating the homeostasis of a subset of Ag-specific alphabetaTCR+ CD4-CD8- double negative (DN) Treg cells. We demonstrate that DN Treg cells are naturally resistant to TCR cross-linking-induced apoptosis. Administration of exogenous IL-10 renders DN Treg cells susceptible to apoptosis, and abolishes their suppressive function. Furthermore, TCR cross-linking of DN Treg cells in the presence of IL-10 leads to the up-regulation of the membrane-bound but not the soluble form of TNF-alpha. Interaction of membrane bound TNF-alpha with TNFR2 sends death signals to DN Treg cells. Blocking their interaction can reverse the effects of IL-10 on DN Treg cells. These results provide insights into the mechanisms that regulate the function and homeostasis of DN Treg cells.

Phosphatidylcholine-Specific Phospholipase C Activity Is Necessary for the Activation of STAT6

It is well established that Janus kinase (JAK) tyrosine kinases play a key role in the activation of STAT6 by IL-4. In this study, we investigated additional molecules involved in this process. We previously found that IL-4 and TNF-alpha cooperate in the activation of STAT6 and NF-kappaB, suggesting that these transcription factors are regulated by common intracellular signaling pathways. To test this hypothesis, we analyzed the effect of known inhibitors of NF-kappaB on the activation of STAT6. We discovered that inhibitors of phosphatidylcholine-specific phospholipase C (PC-PLC), but not other lipases, blocked the activation of STAT6 by IL-4. The activation of PC-PLC seems to be an early event in IL-4 signaling, because its inhibition abrogated JAK activation and STAT6 tyrosine phosphorylation. Interestingly, we found that the effects of pervanadate and sodium orthovanadate on STAT6 activation correspond to their effect on PC-PLC. Thus, pervanadate by itself activated PC-PLC, JAK, and STAT6, whereas sodium orthovanadate suppressed PC-PLC, JAK, and STAT6 activation by IL-4. We further found that PC-PLC activation is necessary but not sufficient to promote STAT6 activation, and therefore, additional intracellular pathways regulated by IL-4 and pervanadate may collaborate with PC-PLC to signal STAT6 activation. It has been reported that IL-4 signals PC-PLC activation; in this study, we provide evidence that this phospholipase plays a key role in IL-4 signaling.

IL-4 suppresses osteoclast development and mature osteoclast function by a STAT6-dependent mechanism: irreversible inhibition of the differentiation program activated by RANKL

Numerous reports have described the effects of interleukin-4 (IL-4) on bone biology. Previous studies, performed using complex coculture systems, demonstrated the effects of IL-4 on osteoblasts and osteoclasts. To directly test the effect of IL-4 on osteoclasts, we took advantage of a simplified system using recombinant receptor activator of nuclear factor kappaB ligand (RANKL) as the osteoclast differentiation factor. We analyzed the ability of IL-4 to directly regulate osteoclast differentiation and mature osteoclast function. We found that IL-4 inhibited the differentiation of osteoclasts from bone marrow precursors in an irreversible manner and also inhibited the resorptive capacity of mature osteoclasts. In the presence of IL-4, we detected the appearance of tartrate-resistant acid phosphatase (TRAP)-negative multinucleated giant (MNG) cells. Both IL-4 effects were dependent on signal transducer and activator of transcription 6 (STAT6). We found that IL-4 suppresses RANK mRNA expression in the developing precursor cells. When RANK was ectopically expressed under the cytomegalovirus (CMV) promoter in RAW264.7 macrophages, IL-4 treatment did not inhibit osteoclast development. Furthermore, when osteoclastogenesis was induced independently of RANKL by using tumor necrosis factor-alpha (TNF-alpha), IL-4 inhibited osteoclast differentiation through a STAT6-dependent mechanism. These results suggest that IL-4 regulates osteoclast development by regulating gene expression, including RANK. We propose that IL-4 irreversibly regulates the lineage commitment of precursor cells by regulating gene expression, resulting in the suppression of osteoclast development and the generation of MNG cells as an alternative pathway of differentiation.

IKK beta is required for peripheral B cell survival and proliferation

NF-kappaB activity in mammalian cells is regulated through the IkappaB kinase (IKK) complex, consisting of two catalytic subunits (IKKalpha and IKKbeta) and a regulatory subunit (IKKgamma). Targeted deletion of Ikkbeta results in early embryonic lethality, thus complicating the examination of IKKbeta function in adult tissues. Here we describe the role of IKKbeta in B lymphocytes made possible by generation of a mouse strain that expresses a conditional Ikkbeta allele. We find that the loss of IKKbeta results in a dramatic reduction in all peripheral B cell subsets due to associated defects in cell survival. IKKbeta-deficient B cells are also impaired in mitogenic responses to LPS, anti-CD40, and anti-IgM, indicating a general defect in the ability to activate the canonical NF-kappaB signaling pathway. These findings are consistent with a failure to mount effective Ab responses to T cell-dependent and independent Ags. Thus, IKKbeta provides a requisite role in B cell activation and maintenance and thus is a key determinant of humoral immunity.

Inhibition of NF-kappa B activity in T and NK cells results in defective effector cell expansion and production of IFN-gamma required for resistance to Toxoplasma gondii

To define the role of NF-kappa B in the development of T cell responses required for resistance to Toxoplasma gondii, mice in which T cells are transgenic for a degradation-resistant (Delta N) form of I kappa B alpha, an inhibitor of NF-kappa B, were challenged with T. gondii and their response to infection compared with control mice. I kappa B alpha(Delta N)-transgenic (Tg) mice succumbed to T. gondii infection between days 12 and 35, and death was associated with an increased parasite burden compared with wild-type (Wt) controls. Analysis of the responses of infected mice revealed that IL-12 responses were comparable between strains, but Tg mice had a marked reduction in systemic levels of IFN-gamma, the major mediator of resistance to T. gondii. In addition, the infection-induced increase in NK cell activity observed in Wt mice was absent from Tg mice and this correlated with NK cell expression of the transgene. Infection-induced activation of CD4(+) T cells was similar in Wt and Tg mice, but expansion of activated CD4(+)T cells was markedly reduced in the Tg mice. This difference in T cell numbers correlated with a reduced capacity of these cells to proliferate after stimulation and was associated with a major defect in the ability of CD4(+) T cells from infected mice to produce IFN-gamma. Together, these studies reveal that inhibition of NF-kappa B activity in T and NK cells results in defective effector cell expansion and production of IFN-gamma required for resistance to T. gondii.

IL-4 induces the proteolytic processing of mast cell STAT6

IL-4 is a potent, pleiotropic cytokine that, in general, directs cellular activation, differentiation, and rescue from apoptosis. However, in mast cells, IL-4 induces the down-regulation of activation receptors and promotes cell death. Mast cells have been shown to transduce IL-4 signals through a unique C-terminally truncated isoform of STAT6. In this study, we examine the mechanism through which STAT6 is processed to generate this isoform. We demonstrate that STAT6 processing in mast cells is initiated by IL-4-induced phosphorylation and nuclear translocation of full-length STAT6 and subsequent cleavage by a nuclear serine-family protease. The location of the protease in the nucleus ensures that the truncated STAT6 has preferential access to bind DNA. IL-4-responsive target genes in mast cells are identified by chromatin immunoprecipitation of STAT6, including the IL-4 gene itself. These results suggest a molecular explanation for the suppressive effects of IL-4 on STAT6-regulated genes in mast cells.