Interleukin-13 induction of 15-lipoxygenase gene expression requires p38 mitogen-activated protein kinase-mediated serine 727 phosphorylation of Stat1 and Stat3

Latexin deficiency limits foam cell formation and ameliorates atherosclerosis by promoting macrophage phenotype differentiation

Latexin (LXN) is abundant in macrophages and plays critical roles in inflammation. Much is known about macrophages in atherosclerosis, the role of macrophage LXN in atherosclerosis has remained elusive. Here, the expression of LXN in human and mouse atherosclerotic lesions was examined by immunofluorescence and immunohistochemistry. LXN knockout and LXN/ApoE double-knockout mice were generated to evaluate the functions of LXN in atherosclerosis. Bone marrow transplantation (BMT) experimentation was carried out to determine whether macrophage LXN regulates atherosclerosis. We found that LXN is enriched in human and murine atherosclerotic lesions, mainly localized to macrophages. LXN deletion ameliorated atherosclerosis in ApoE-/- mice. BMT demonstrate that deletion of LXN in bone marrow protects ApoE-/- mice against atherosclerosis. Mechanistically, we found that LXN targets and inhibits JAK1 in macrophages. LXN deficiency stimulates the JAK1/STAT3/ABC transporter pathway, thereby enhancing the anti-inflammatory and anti-oxidant phenotype, cholesterol efflux, subsequently minimizing foam cell formation and atherosclerosis. Gene therapy by treatment of atherosclerotic mice with adeno-associated virus harbouring LXN-depleting shRNA attenuated the disease phenotype. In summary, our study provides new clues for the role of LXN in the pathological regulation of atherosclerosis, and determines that LXN is a target for preventing atherosclerosis, which may be a potential new anti-atherosclerosis therapeutic target.

AMPK activation reduces cancer cell aggressiveness via inhibition of monoamine oxidase A (MAO-A) expression/activity

AIM

AMPK can be considered as an important target molecule for cancer for its unique ability to directly recognize cellular energy status. The main aim of this study is to explore the role of different AMPK activators in managing cancer cell aggressiveness and to understand the mechanistic details behind the process.

MAIN METHODS

First, we explored the AMPK expression pattern and its significance in different subtypes of lung cancer by accessing the TCGA data sets for LUNG, LUAD and LUSC patients and then established the correlation between AMPK expression pattern and overall survival of lung cancer patients using Kaplan-Meire plot. We further carried out several cell-based assays by employing different wet lab techniques including RT-PCR, Western Blot, proliferation, migration and invasion assays to fulfil the aim of the study.

KEY FINDINGS

SIGNIFICANCE: This study identifies the importance of AMPK activators as a repurposing agent for combating lung and colon cancer cell aggressiveness. It also suggests SRT-1720 as a potent repurposing agent for cancer treatment especially in NSCLC patients where a point mutation is present in LKB1.

ROS-mediated MAPK activation aggravates hyperoxia-induced acute lung injury by promoting apoptosis of type II alveolar epithelial cells via the STAT3/miR-21-5p axis

Inhibition of type II alveolar epithelial (AE-II) cell apoptosis is a critical way to cure hyperoxia-induced acute lung injury (HALI). It has been reported that miR-21-5p could reduce H2O2-induced apoptosis in AE-II cells. However, the upstream molecular mechanism remains unclear. Herein, we established a cellular model of HALI by exposing AE-II cells to H2O2 treatment. It was shown that miR-21-5p alleviated H2O2-induced apoptosis in AE-II cells. ROS inhibition decreased apoptosis of H2O2-evoked AE-II cells via increasing miR-21-5p expression. In addition, ROS induced MAPK and STAT3 phosphorylation in H2O2-treated AE-II cells. MAPK inactivation reduces H2O2-triggered AE-II cell apoptosis. MAPK activation inhibits miR-21-5p expression by promoting STAT3 phosphorylation in H2O2-challenged AE-II cells. Furthermore, STAT3 activation eliminated MAPK deactivation-mediated inhibition on the apoptosis of AE-II cells under H2O2 condition. In conclusion, ROS-mediated MAPK activation promoted H2O2-triggered AE-II cell apoptosis by inhibiting miR-21-5p expression via STAT3 phosphorylation, providing novel targets for HALI treatment.

Bergapten ameliorates combined allergic rhinitis and asthma syndrome after PM2.5 exposure by balancing Treg/Th17 expression and suppressing STAT3 and MAPK activation in a mouse model

Combined allergic rhinitis and asthma syndrome (CARAS) causes chronic respiratory inflammation in allergic individuals. Long-term exposure to particulate matter 2.5 (PM2.5; particles 2.5 µm or less in diameter) can aggravate respiratory damage. Bergapten (5-methoxysporalen) is a furocoumarin mostly found in bergamot essential oil and has significant antioxidant, anticancer, and anti-inflammatory activity. This study created a model in which CARAS was exacerbated by PM2.5 exposure, in BALB/c mice and explored the potential of bergapten as a therapeutic agent. The bergapten medication increased ovalbumin (OVA)-specific immunoglobulin (Ig) G2a level in serum and decreased OVA-specific IgE and IgG1 expression. Clinical nasal symptoms diminished significantly, with weakened inflammatory reaction in both the nasal mucosa and lungs. Furthermore, bergapten controlled the T helper (Th)1 to Th2 ratio by increasing cytokines associated with Th1-like interleukin (IL)-12 and interferon gamma and decreasing the Th2 cytokines IL-4, IL-5, and IL-13. Factors closely related to the balance between regulatory T cells and Th17 (such as IL-10, IL-17, Forkhead box protein P3, and retinoic-related orphan receptor gamma) were also regulated. Notably, pro-inflammatory cytokines IL-6, IL-1β, and tumor necrosis factor-alpha were reduced by bergapten, which suppressed the activation of both the signal transducer and activator of transcription 3 signaling pathway and the mitogen-activated protein kinase signaling pathway. Therefore, bergapten might have potential as a therapeutic agent for CARAS.

Sensitization of colonic nociceptors by IL-13 is dependent on JAK and p38 MAPK activity

The effective management of visceral pain is a significant unmet clinical need for those affected by gastrointestinal diseases, such as inflammatory bowel disease (IBD). The rational design of novel analgesics requires a greater understanding of the mediators and mechanisms underpinning visceral pain. Interleukin-13 (IL-13) production by immune cells residing in the gut is elevated in IBD, and IL-13 appears to be important in the development of experimental colitis. Furthermore, receptors for IL-13 are expressed by neurons innervating the colon, though it is not known whether IL-13 plays any role in visceral nociception per se. To resolve this, we used Ca²⁺ imaging of cultured sensory neurons and ex vivo electrophysiological recording from the lumbar splanchnic nerve innervating the distal colon. Ca²⁺ imaging revealed the stimulation of small-diameter, capsaicin-sensitive sensory neurons by IL-13, indicating that IL-13 likely stimulates nociceptors. IL-13-evoked Ca²⁺ signals were attenuated by inhibition of Janus (JAK) and p38 kinases. In the lumbar splanchnic nerve, IL-13 did not elevate baseline firing, nor sensitize the response to capsaicin application, but did enhance the response to distention of the colon. In line with Ca²⁺ imaging experiments, IL-13-mediated sensitization of the afferent response to colon distention was blocked by inhibition of either JAK or p38 kinase signaling. Together, these data highlight a potential role for IL-13 in visceral nociception and implicate JAK and p38 kinases in pronociceptive signaling downstream of IL-13.

IL-13 and the hydroperoxy fatty acid 13(S)HpODE play crucial role in inducing an apoptotic pathway in cancer cells involving MAO-A/ROS/p53/p21 signaling axis

This study depicted the effect of IL-13 and 13(S)HpODE (the endogenous product during IL-13 activation) in the process of cancer cell apoptosis. We examined the role of both IL-13 and 13(S)HpODE in mediating apoptotic pathway in three different in vitro cellular models namely A549 lung cancer, HCT116 colorectal cancer and CCF52 GBM cells. Our data showed that IL-13 promotes apoptosis of A549 lung carcinoma cells through the involvement of 15-LO, PPARγ and MAO-A. Our observations demonstrated that IL-13/13(S)HpODE stimulate MAO-A-mediated intracellular ROS production and p53 as well as p21 induction which play a crucial role in IL-13-stimulated A549 cell apoptosis. We further showed that 13(S)HpODE promotes apoptosis of HCT116 and CCF52 cells through the up-regulation of p53 and p21 expression. Our data delineated that IL-13 stimulates p53 and p21 induction which is mediated through 15-LO and MAO-A in A549 cells. In addition, we observed that PPARγ plays a vital role in apoptosis as well as in p53 and p21 expression in A549 cells in the presence of IL-13. We validated our observations in case of an in vivo colon cancer tumorigenic study using syngeneic mice model and demonstrated that 13(S)HpODE significantly reduces solid tumor growth through the activation of apoptosis. These data thus confirmed that IL-13 > 15-LO>13(S)HpODE > PPARγ>MAO-A > ROS > p53>p21 axis has a major contribution in regulating cancer cell apoptosis and further identified 13(S)HpODE as a potential chemo-preventive agent which can improve the efficacy of cancer treatment as a combination compound.

Role of arachidonic acid lipoxygenase pathway in Asthma

The arachidonic acid (AA) metabolism pathways play a key role in immunological response and inflammation diseases, such as asthma, etc. AA in cell membranes can be metabolized by lipoxygenases (LOXs) to a screen of bioactive substances that include leukotrienes (LTs), lipoxins (LXs), and eicosatetraenoic acids (ETEs), which are considered closely related to the pathophysiology of respiratory allergic disease. Studies also verified that drugs regulating AA LOXs pathway have better rehabilitative intervention for asthma. This review aims to summarize the physiological and pathophysiological importance of AA LOXs metabolism pathways in asthma and to discuss its prospects of therapeutic strategies.

Arachidonic Acid 15-Lipoxygenase: Effects of Its Expression, Metabolites, and Genetic and Epigenetic Variations on Airway Inflammation

Arachidonic acid 15-lipoxygenase (ALOX15) is an enzyme that can oxidize polyunsaturated fatty acids. ALOX15 is strongly expressed in airway epithelial cells, where it catalyzes the conversion of arachidonic acid to 15-hydroxyeicosatetraenoic acid (15-HETE) involved in various airway inflammatory diseases. Interleukin (IL)-4 and IL-13 induce ALOX15 expression by activating Jak2 and Tyk2 kinases as well as signal transducers and activators of transcription (STATs) 1/3/5/6. ALOX15 up-regulation and subsequent association with phosphatidylethanolamine-binding protein 1 (PEBP1) activate the mitogen-activated extracellular signal-regulated kinase (MEK)-extracellular signal-regulated kinase (ERK) pathway, thus inducing eosinophil-mediated airway inflammation. In addition, ALOX15 plays a significant role in promoting the migration of immune cells, such as immature dendritic cells, activated T cells, and mast cells, and airway remodeling, including goblet cell differentiation. Genome-wide association studies have revealed multiple ALOX15 variants and their significant correlation with the risk of developing airway diseases. The epigenetic modifications of the ALOX15 gene, such as DNA methylation and histone modifications, have been shown to closely relate with airway inflammation. This review summarizes the role of ALOX15 in different phenotypes of asthma, chronic obstructive pulmonary disease, chronic rhinosinusitis, aspirin-exacerbated respiratory disease, and nasal polyps, suggesting new treatment strategies for these airway inflammatory diseases with complex etiology and poor treatment response.

Surfactant Protein-A Protects against IL-13-Induced Inflammation in Asthma

The lung surfactant proteins are recognized as critical not only for their role in lowering lung surface tension but also in innate host defense. Reports have shown that some asthmatic patients have decreased levels of one member of this protein family in particular, surfactant protein-A (SP-A). Our studies set out to determine the contribution of SP-A to the response of a key effector cytokine in asthma, IL-13. Our studies employ both animal models sufficient and deficient in SP-A challenged with IL-13 and primary epithelial cells from participants with asthma that are exogenously treated with SP-A in the context of IL-13 challenge. The inflammatory response and mucin production were assessed in both model systems. As compared with WT mice, we show that the activity of IL-13 is dramatically augmented in SP-A-/- mice, which have significantly increased neutrophil and eosinophil recruitment, mucin production and asthma-associated cytokines in the bronchoalveolar lavage fluid. In parallel, we show asthma-associated factors are attenuated in human cells from asthma subjects when exogenous SP-A is added during IL-13 challenge. Although many of these phenotypes have previously been associated with STAT6 signaling, SP-A inhibited IL-13-induced STAT3 phosphorylation in mice and in human epithelial cells while having little effect on STAT6 phosphorylation. In addition, when either STAT3 or IL-6 were inhibited in mice, the phenotypes observed in SP-A-/- mice were significantly attenuated. These studies suggest a novel mechanism for SP-A in asthma as a modulator of IL-13-induced inflammation via mediating downstream IL-6/STAT3 signaling.

Emerging cellular functions of the lipid metabolizing enzyme 15-Lipoxygenase-1

The oxygenation of polyunsaturated fatty acids such as arachidonic and linoleic acid through lipoxygenases (LOXs) and cyclooxygenases (COXs) leads to the production of bioactive lipids that are important both in the induction of acute inflammation and its resolution. Amongst the several isoforms of LOX that are expressed in mammals, 15-LOX-1 was shown to be important both in the context of inflammation, being expressed in cells of the immune system, and in epithelial cells where the enzyme has been shown to crosstalk with a number of important signalling pathways. This review looks into the latest developments in understanding the role of 15-LOX-1 in different disease states with emphasis on the emerging role of the enzyme in the tumour microenvironment as well as a newly re-discovered form of cell death called ferroptosis. We also discuss future perspectives on the feasibility of use of this protein as a target for therapeutic interventions.

Regulation of monoamine oxidase A (MAO-A) expression, activity, and function in IL-13-stimulated monocytes and A549 lung carcinoma cells

Monoamine oxidase A (MAO-A) is a mitochondrial flavoenzyme implicated in the pathogenesis of atherosclerosis and inflammation and also in many neurological disorders. MAO-A also has been reported as a potential therapeutic target in prostate cancer. However, the regulatory mechanisms controlling cytokine-induced MAO-A expression in immune or cancer cells remain to be identified. Here, we show that MAO-A expression is co-induced with 15-lipoxygenase (15-LO) in interleukin 13 (IL-13)-activated primary human monocytes and A549 non-small cell lung carcinoma cells. We present evidence that MAO-A gene expression and activity are regulated by signal transducer and activator of transcription 1, 3, and 6 (STAT1, STAT3, and STAT6), early growth response 1 (EGR1), and cAMP-responsive element-binding protein (CREB), the same transcription factors that control IL-13-dependent 15-LO expression. We further established that in both primary monocytes and in A549 cells, IL-13-stimulated MAO-A expression, activity, and function are directly governed by 15-LO. In contrast, IL-13-driven expression and activity of MAO-A was 15-LO-independent in U937 promonocytic cells. Furthermore, we demonstrate that the 15-LO-dependent transcriptional regulation of MAO-A in response to IL-13 stimulation in monocytes and in A549 cells is mediated by peroxisome proliferator-activated receptor γ (PPARγ) and that signal transducer and activator of transcription 6 (STAT6) plays a crucial role in facilitating the transcriptional activity of PPARγ. We further report that the IL-13-STAT6-15-LO-PPARγ axis is critical for MAO-A expression, activity, and function, including migration and reactive oxygen species generation. Altogether, these results have major implications for the resolution of inflammation and indicate that MAO-A may promote metastatic potential in lung cancer cells.

Structural and functional biology of arachidonic acid 15-lipoxygenase-1 (ALOX15)

Lipoxygenases (LOX) form a family of lipid peroxidizing enzymes, which have been implicated in a number of physiological processes and in the pathogenesis of inflammatory, hyperproliferative and neurodegenerative diseases. They occur in two of the three domains of terrestrial life (bacteria, eucarya) and the human genome involves six functional LOX genes, which encode for six different LOX isoforms. One of these isoforms is ALOX15, which has first been described in rabbits in 1974 as enzyme capable of oxidizing membrane phospholipids during the maturational breakdown of mitochondria in immature red blood cells. During the following decades ALOX15 has extensively been characterized and its biological functions have been studied in a number of cellular in vitro systems as well as in various whole animal disease models. This review is aimed at summarizing the current knowledge on the protein-chemical, molecular biological and enzymatic properties of ALOX15 in various species (human, mouse, rabbit, rat) as well as its implication in cellular physiology and in the pathogenesis of various diseases.

Aryl hydrocarbon receptor agonists upregulate VEGF secretion from bronchial epithelial cells

Chronic airway diseases, such as asthma and chronic obstructive pulmonary disease, are characterized by airway remodeling. Vascular endothelial growth factor (VEGF) is a critical regulator of angiogenesis and vascular remodeling, important components of airway remodeling. The aryl hydrocarbon receptor (AhR) is the principle receptor for many environmental toxicants, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which may contribute to the pathogenesis of asthma and chronic obstructive pulmonary disease. However, the regulatory role of AhR on the expression of VEGF in bronchial epithelial cells (BECs) remains elusive. This study was conducted to determine the role of AhR in regulating bronchial epithelial VEGF expression, which might contribute to angiogenesis of airway remodeling. The plasma VEGF levels of asthmatic patients and healthy subjects were compared. By treating HBE-135, Beas-2B, and primary human BECs with AhR agonists, the mechanisms through which AhR modulated VEGF expression in human BECs were investigated. The plasma VEGF level was significantly higher in asthmatic patients than in healthy subjects. AhR agonists significantly upregulated VEGF secretion from human BECs, which promoted the migratory and tube-forming ability of human umbilical vein endothelial cells. The secretion of VEGF was increased via a canonical AhR pathway, followed by the 15-LOX/15-HETE/STAT3 pathway. C57BL/6JNarl mice treated with TCDD intratracheally also showed increased VEGF expression in BECs. This hitherto unrecognized pathway may provide a potential target for the treatment of airway remodeling in many pulmonary diseases, especially those related to environmental toxicants.

KEY MESSAGE

AhR agonists increase VEGF secretion from bronchial epithelial cells. The mechanism involves the canonical AhR pathway and 15-LOX/15-HETE/STAT3 pathway. Asthmatic patients have higher plasma VEGF level. Mice treated with intratracheal TCDD show increased VEGF expression in BECs. This novel regulatory pathway is a potential target for treating asthma and COPD.

IL-27 and type 2 immunity in asthmatic patients: association with severity, CXCL9, and signal transducer and activator of transcription signaling

BACKGROUND

Severe asthma (SA) can involve both innate and type 2 cytokine-associated adaptive immunity. Although IL-27 has been reported to potentiate TH1 responses (including the chemokine CXCL9) and suppress TH2 responses, its function in asthmatic patients is unknown.

OBJECTIVE

We sought to evaluate IL-27 expression in human asthma alone and in combination with type 2 immunity to determine the relationship to disease severity and CXCL9 expression. We also sought to model these interactions in vitro in human bronchial epithelial cells.

METHODS

Bronchoalveolar lavage cells from 87 participants were evaluated for IL-27 mRNA and protein alone and in association with epithelial CCL26 (a marker of type 2 activation) in relation to asthma severity and CXCL9 mRNA. Human bronchial epithelial cells cultured at the air-liquid interface and stimulated with IL-27 (1-100 ng/mL) with or without IL-13 (1 ng/mL) were evaluated for CXCL9 expression by using quantitative real-time PCR and ELISA. Phosphorylated and total signal transducer and activator of transcription (STAT) 1/3 were detected by means of Western blotting. Small interfering RNA knockdown of STAT1 or STAT3 was performed.

RESULTS

Bronchoalveolar lavage cell IL-27 mRNA and protein levels were increased in asthmatic patients. Patients with evidence for type 2 pathway activation had higher IL-27 expression (P = .02). Combined IL-27 and CCL26 expression associated with more SA and higher CXCL9 expression (P = .004 and P = .007 respectively), whereas IL-27 alone was associated with milder disease. In vitro IL-13 augmented IL-27-induced CXCL9 expression, which appeared to be due to augmented STAT1 activation and reduced STAT3 activation.

CONCLUSIONS

IL-27, in combination with a type 2/CCL26 signature, identifies a more SA phenotype, perhaps through combined effects of IL-27 and IL-13 on STAT signaling. Understanding these interactions could lead to new targets for asthma therapy.

Hyper-inflammation and skin destruction mediated by rosiglitazone activation of macrophages in IL-6 deficiency

Injury initiates recruitment of macrophages to support tissue repair; however, excessive macrophage activity may exacerbate tissue damage causing further destruction and subsequent delay in wound repair. Here we show that the peroxisome proliferation–activated receptor-γ agonist, rosiglitazone (Rosi), a medication recently reintroduced as a drug to treat diabetes and with known anti-inflammatory properties, paradoxically generates pro-inflammatory macrophages. This is observed in both IL-6-deficient mice and control wild-type mice experimentally induced to produce high titers of auto-antibodies against IL-6, mimicking IL-6 deficiency in human diseases. IL-6 deficiency when combined with Rosi-mediated upregulation of suppressor of cytokine signaling 3 leads to an altered ratio of nuclear signal transducer and activator of transcription 3/NF-κB that allows hyper-induction of inducible nitric oxide synthase (iNOS). Macrophages activated in this manner cause de novo tissue destruction, recapitulating human chronic wounds, and can be reversed in vivo by recombinant IL-6, blocking macrophage infiltration, or neutralizing iNOS. This study provides insight into an unanticipated paradoxical role of Rosi in mediating hyper-inflammatory macrophage activation significant for diseases associated with IL-6 deficiency.

Monoamine oxidase A (MAO-A): a signature marker of alternatively activated monocytes/macrophages

Monocytes/macrophages are versatile cells centrally involved in host defense and immunity. Th1 cytokines induce a classical activation program in monocytes/macrophages leading to a proinflammatory M1 macrophage phenotype while Th2 cytokines IL-4 and IL-13 promote monocyte differentiation into an alternatively activated, anti-inflammatory M2 macrophage phenotype. Although monoamine oxidase A (MAO-A) is primarily known for its action in the nervous system, several recent studies have identified MAO-A as a signature marker of alternative activation of monocytes/macrophages. In this brief review we explore the signaling pathways/molecules that regulate MAO-A expression in alternatively activated monocytes/macrophages. We further discuss the contribution of MAO-A to the resolution of inflammation and identify potential therapeutic targets for controlling inflammation. Altogether this review provides deeper insight into the role of MAO-A in alternative activation of monocytes/macrophages and their participation in the inflammatory response.

Global discovery of high-NaCl-induced changes of protein phosphorylation

High extracellular NaCl, such as in the renal medulla, can perturb and even kill cells, but cells mount protective responses that enable them to survive and function. Many high-NaCl-induced perturbations and protective responses are known, but the signaling pathways involved are less clear. Change in protein phosphorylation is a common mode of cell signaling, but there was no unbiased survey of protein phosphorylation in response to high NaCl. We used stable isotopic labeling of amino acids in cell culture coupled to mass spectrometry to identify changes in protein phosphorylation in human embryonic kidney (HEK 293) cells exposed to high NaCl. We reproducibly identify >8,000 unique phosphopeptides in 4 biological replicate samples with a 1% false discovery rate. High NaCl significantly changed phosphorylation of 253 proteins. Western analysis and targeted ion selection mass spectrometry confirm a representative sample of the phosphorylation events. We analyze the affected proteins by functional category to infer how altered protein phosphorylation might signal cellular responses to high NaCl, including alteration of cell cycle, cyto/nucleoskeletal organization, DNA double-strand breaks, transcription, proteostasis, metabolism of mRNA, and cell death.

Cyclin-dependent kinase 5 modulates STAT3 and androgen receptor activation through phosphorylation of Ser⁷²⁷ on STAT3 in prostate cancer cells

Cyclin-dependent kinase 5 (Cdk5) is known to regulate prostate cancer metastasis. Our previous results indicated that Cdk5 activates androgen receptor (AR) and supports prostate cancer growth. We also found that STAT3 is a target of Cdk5 in promoting thyroid cancer cell growth, whereas STAT3 may play a role as a regulator to AR activation under cytokine control. In this study, we investigated the regulation of Cdk5 and its activator p35 on STAT3/AR signaling in prostate cancer cells. Our results show that Cdk5 biochemically interacts with STAT3 and that this interaction depends on Cdk5 activation in prostate cancer cells. The phosphorylation of STAT3 at Ser⁷²⁷ (p-Ser⁷²⁷-STAT3) is regulated by Cdk5 in cells and xenograft tumors. The mutant of STAT3 S727A reduces its interaction with Cdk5. We further show that the nuclear distribution of p-Ser⁷²⁷-STAT3 and the expression of STAT3-regulated genes (junB, c-fos, c-myc, and survivin) are regulated by Cdk5 activation. STAT3 mutant does not further decrease cell proliferation upon Cdk5 inhibition, which implies that the role of STAT3 regulated by Cdk5 correlates to cell proliferation control. Interestingly, Cdk5 may regulate the interaction between STAT3 and AR through phosphorylation of Ser⁷²⁷-STAT3 and therefore upregulate AR protein stability and transactivation. Correspondingly, clinical evidence shows that the level of p-Ser⁷²⁷-STAT3 is significantly correlated with Gleason score and the levels of upstream regulators (Cdk5 and p35) as well as downstream protein (AR). In conclusion, this study demonstrates that Cdk5 regulates STAT3 activation through Ser⁷²⁷ phosphorylation and further promotes AR activation by protein-protein interaction in prostate cancer cells.

IL-4 and IL-13 employ discrete signaling pathways for target gene expression in alternatively activated monocytes/macrophages

Monocytes/macrophages are innate immune cells that play a crucial role in the resolution of inflammation. In the presence of the Th2 cytokines interleukin-4 (IL-4) and interleukin-13 (IL-13), they display an anti-inflammatory profile and this activation pathway is known as alternative activation. In this study we compare and differentiate pathways mediated by IL-4 and IL-13 activation of human monocytes/macrophages. Here we report differential regulation of IL-4 and IL-13 signaling in monocytes/macrophages starting from IL-4/IL-13 cytokine receptors to Jak/Stat-mediated signaling pathways that ultimately control expression of several inflammatory genes. Our data demonstrate that although the receptor-associated tyrosine kinases Jak2 and Tyk2 are activated after the recruitment of IL-13 to its receptor (containing IL-4Rα and IL-13Rα1), IL-4 stimulates Jak1 activation. We further show that Jak2 is upstream of Stat3 activation and Tyk2 controls Stat1 and Stat6 activation in response to IL-13 stimulation. In contrast, Jak1 regulates Stat3 and Stat6 activation in IL-4-induced monocytes. Our results further reveal that although IL-13 utilizes both IL-4Rα/Jak2/Stat3 and IL-13Rα1/Tyk2/Stat1/Stat6 signaling pathways, IL-4 can use only the IL-4Rα/Jak1/Stat3/Stat6 cascade to regulate the expression of some critical inflammatory genes, including 15-lipoxygenase, monoamine oxidase A (MAO-A), and the scavenger receptor CD36. Moreover, we demonstrate here that IL-13 and IL-4 can uniquely affect the expression of particular genes such as dual-specificity phosphatase 1 and tissue inhibitor of metalloprotease-3 and do so through different Jaks. As evidence of differential regulation of gene function by IL-4 and IL-13, we further report that MAO-A-mediated reactive oxygen species generation is influenced by different Jaks. Collectively, these results have major implications for understanding the mechanism and function of alternatively activated monocytes/macrophages by IL-4 and IL-13 and add novel insights into the pathogenesis and potential treatment of various inflammatory diseases.

From macrophage interleukin-13 receptor to foam cell formation: mechanisms for αMβ2 integrin interference

IL-13 is a potent stimulator of alternative monocyte/macrophage activation. During alternative activation, the expression of several proteins is induced including 15-lipoxygenase (15-LO), a lipid-peroxidating enzyme and the scavenger receptor CD36. We previously reported that α(M)β(2) integrin activation or clustering suppresses the expression of both 15-LO and CD36. In this study we focused on exploring the molecular mechanisms that down-regulate CD36 expression and CD36-mediated foam cell formation in IL-13-stimulated monocytes/macrophages after α(M)β(2) activation. Our studies reveal that α(M)β(2) integrin activation inhibits the IL-13 activation of several critical pathways that are required for macrophage alternative activation; namely, blocking Jak2 and Tyk2 phosphorylation, which bind to the cytoplasmic tails of the IL-4Rα/IL-13Rα1 complex. This leads to the inhibition of tyrosine phosphorylation of Stats (Stat1, Stat3, and Stat6) and prevents the formation of a signaling complex (containing p38MAPK, PKCδ, and Stat3) that are critical for the expression of both 15-LO and CD36. Jak2-mediated Hck activation is also inhibited, thereby preventing Stats serine phosphorylation, which is essential for downstream Stat-dependent gene transcription. Moreover, inhibition of Jak2, Tyk2, or their downstream target 15-LO with antisense oligonucleotides profoundly inhibits IL-13-induced CD36 expression and CD36-dependent foam cell formation, whereas13(S) Hydroperoxyoctadecadienoic acid (HPODE), a 15-LO product and peroxisome proliferator-activated receptor-γ ligand, completely restores CD36 expression in monocytes treated with 15-LO antisense. α(M)β(2) integrin activation controls CD36 expression and foam cell formation in alternatively activated monocyte/macrophages by blocking Tyk2/Jak2 phosphorylation via a 15-LO-dependent pathway. The discovery of this mechanism helps our understanding of the potential role of alternatively activated macrophages in atherogenesis and highlights the impact of integrin α(M)β(2) on this process.

12/15-lipoxygenase during the regulation of inflammation, immunity, and self-tolerance

12/15-Lipoxygenase (12/15-LO) catalyzes the oxidation of free and esterified fatty acids thereby generating a whole spectrum of bioactive lipid mediators. This enzyme is involved in the regulation of various homeostatic processes as well as in the pathogenesis of multiple diseases. During the innate and adaptive immune response, 12/15-LO and its products exert both pro- and anti-inflammatory effects. Likewise, this enzyme has been implicated in the pathogenesis of autoimmune disease as well as in the maintenance of self-tolerance. This review will summarize our current knowledge about the role of 12/15-LO and will try to examine the two faces of this enzyme within the context of inflammation and immunity.

Inhibition of signal transducer and activator of transcription 3 (STAT3) attenuates interleukin-6 (IL-6)-induced collagen synthesis and resultant hypertrophy in rat heart

IL-6 has been shown to play a major role in collagen up-regulation process during cardiac hypertrophy, although the precise mechanism is still not known. In this study we have analyzed the mechanism by which IL-6 modulates cardiac hypertrophy. For the in vitro model, IL-6-treated cultured cardiac fibroblasts were used, whereas the in vivo cardiac hypertrophy model was generated by renal artery ligation in adult male Wistar rats (Rattus norvegicus). During induction of hypertrophy, increased phosphorylation of STAT1, STAT3, MAPK, and ERK proteins was observed both in vitro and in vivo. Treatment of fibroblasts with specific inhibitors for STAT1 (fludarabine, 50 μM), STAT3 (S31-201, 10 μM), p38 MAPK (SB203580, 10 μM), and ERK1/2 (U0126, 10 μM) resulted in down-regulation of IL-6-induced phosphorylation of specific proteins; however, only S31-201 and SB203580 inhibited collagen biosynthesis. In ligated rats in vivo, only STAT3 inhibitors resulted in significant decrease in collagen synthesis and hypertrophy markers such as atrial natriuretic factor and β-myosin heavy chain. In addition, decreased heart weight to body weight ratio and improved cardiac function as measured by echocardiography was evident in animals treated with STAT3 inhibitor or siRNA. Compared with IL-6 neutralization, more pronounced down-regulation of collagen synthesis and regression of hypertrophy was observed with STAT3 inhibition, suggesting that STAT3 is the major downstream signaling molecule and a potential therapeutic target for cardiac hypertrophy.

Epigenetic and transcriptional control of the 15-lipoxygenase-1 gene in a Hodgkin lymphoma cell line

Lipoxygenases oxidatively metabolize polyunsaturated fatty acids to a rich spectrum of biologically active metabolites. The present study aimed at delineating the transcriptional and epigenetic mechanisms leading to 15-lipoxygenase-1 (15-LOX-1) expression in the Hodgkin lymphoma (HL) cell line L1236. Examination of the 15-LOX-1 5' promoter region demonstrated three putative binding sites for signal transducer and activator of transcription (STAT6) within the proximal 1200 base pairs relative to the start codon. Analysis by serial promoter deletions and STAT6 binding site mutations indicated that all three STAT6 binding sites are required for full activation of the 15-LOX-1 promoter. Chromatin immunoprecipitation assay demonstrated that these regions were occupied by STAT6 in L1236 (15-LOX-1 positive) but not in L428 (15-LOX-1 negative) cultured HL cells. Furthermore, DNA hypomethylation and histone hyperacetylation were detectable within the core promoter region of 15-LOX-1 only in L1236 cells but not L428 cells. Taken together, our data indicate that STAT6 activation and chromatin remodeling by DNA demethylation and histone acetylation are crucial for transcriptional activation of 15-LOX-1 in cultured HL cells. These prerequisites are fulfilled in the L1236 cell line, but not in the L428 cell line.

p38α and p38β mitogen-activated protein kinases determine cholinergic transdifferentiation of sympathetic neurons

Although the p38 mitogen-activated protein kinases are active in many neuronal populations in the peripheral and central nervous systems, little is known about the physiological functions of p38 in postmitotic neurons. We report that p38 activity determines in vitro and in vivo the switch from noradrenergic to cholinergic neurotransmission that occurs in sympathetic neurons on exposure to the neuropoietic cytokines CNTF and LIF. This transdifferentiation serves as a model for the plastic mechanisms that enable mature neurons to change some of their central functions without passing through the cell cycle. We demonstrate that in postmitotic neurons, p38 and STAT pathways are concurrently activated by neuropoietic cytokine treatment for at least 12 h overlapping with changes in neurotransmitter marker gene expression. Inhibition of p38 blocks the upregulation of the nuclear matrix protein Satb2 and of cholinergic markers by CNTF without affecting STAT3 phosphorylation. Conversely, overexpression of p38α or β in the absence of cytokines stimulates cholinergic marker expression. The neurotransmitter switch in vitro is impaired in neurons isolated from p38β(-/-) mice. Consistent with these in vitro results, a substantial loss of cells expressing cholinergic properties is observed in vivo in the stellate ganglion of mature mice deficient in the p38β isoform.

Hck is a key regulator of gene expression in alternatively activated human monocytes

IL-13 is a Th2 cytokine that promotes alternative activation (M2 polarization) in primary human monocytes. Our studies have characterized the functional IL-13 receptor complex and the downstream signaling events in response to IL-13 stimulation in alternatively activated monocytes/macrophages. In this report, we present evidence that IL-13 induces the activation of a Src family tyrosine kinase, which is required for IL-13 induction of M2 gene expression, including 15-lipoxygenase (15-LO). Our data show that Src kinase activity regulates IL-13-induced p38 MAPK tyrosine phosphorylation via the upstream kinases MKK3 or MKK6. Our findings also reveal that the IL-13 receptor-associated tyrosine kinase Jak2 is required for the activation of both Src kinase as well as p38 MAPK. Further, we found that Src tyrosine kinase-mediated activation of p38 MAPK is required for Stat1 and Stat3 serine 727 phosphorylation in alternatively activated monocytes/macrophages. Additional studies identify Hck as the specific Src family member, stimulated by IL-13 and involved in regulating both p38 MAPK activation and p38 MAPK-mediated 15-LO expression. Finally we show that the Hck regulates the expression of other alternative state (M2)-specific genes (Mannose receptor, MAO-A, and CD36) and therefore conclude that Hck acts as a key regulator controlling gene expression in alternatively activated monocytes/macrophages.

Monocyte and macrophage dynamics during atherogenesis

Vascular inflammation is associated with and in large part driven by changes in the leukocyte compartment of the vessel wall. Here, we focus on monocyte influx during atherosclerosis, the most common form of vascular inflammation. Although the arterial wall contains a large number of resident macrophages and some resident dendritic cells, atherosclerosis drives a rapid influx of inflammatory monocytes (Ly-6C(+) in mice) and other monocytes (Ly-6C(-) in mice, also known as patrolling monocytes). Once in the vessel wall, Ly-6C(+) monocytes differentiate to a phenotype consistent with inflammatory macrophages and inflammatory dendritic cells. The phenotype of these cells is modulated by lipid uptake, Toll-like receptor ligands, hematopoietic growth factors, cytokines, and chemokines. In addition to newly recruited macrophages, it is likely that resident macrophages also change their phenotype. Monocyte-derived inflammatory macrophages have a short half-life. After undergoing apoptosis, they may be taken up by surrounding macrophages or, if the phagocytic capacity is overwhelmed, can undergo secondary necrosis, a key event in forming the necrotic core of atherosclerotic lesions. In this review, we discuss these and other processes associated with monocytic cell dynamics in the vascular wall and their role in the initiation and progression of atherosclerosis.

Silencing IL-13Rα2 promotes glioblastoma cell death via endogenous signaling

Glioblastoma multiforme (GBM) is one of the most lethal forms of cancer, with a survival rate of only 13% to 27% within 2 years of diagnosis despite optimal medical treatment. We hypothesize that the presence of a unique IL-13Rα2 decoy receptor prevents GBM apoptosis. This receptor has a high affinity for interleukin-13 (IL-13), binds the cytokine, and competitively inhibits the intracellular signaling cascade initiated by IL-13. In cells lacking the IL-13Rα2 decoy receptor, IL-13 initiates the production of 15-lipoxygenase-1 (15-LOX-1), which has been implicated in cellular apoptosis. Our group and others have shown that induction of 15-LOX-1 correlates with tumor cell death in colorectal, pancreatic, and prostate cancer. How 15-LOX-1 induces apoptosis remains unclear. Preliminary evidence in GBM cells implicates an apoptotic process mediated by PPARγ. 15-LOX-1 metabolites can modulate PPARγ and activation of PPARγ can suppress tumor growth. We hypothesize that in GBM, IL-13 can induce 15-LOX-1, which regulates cell apoptosis via signaling through PPARγ and that expression of IL-13Rα2 prevents apoptosis and contributes to tumor growth. Our in vitro and in vivo data support this. Knocking down IL-13Rα2 with short interfering RNA dramatically induces 15-LOX-1 expression, promotes apoptosis, and reduces GBM tumor growth in vivo. These findings identify a mechanism for eliminating the blockade of endogenous IL-13 signaling and for promotion of apoptosis, and characterize a role for 15-LOX-1 in GBM apoptosis. Identifying a mechanistic pathway that can be targeted for pharmacologic intervention will have applied implications to developing novel and effective treatments of GBM.

αMβ₂ integrin activation prevents alternative activation of human and murine macrophages and impedes foam cell formation

RATIONALE

The alternative activation of monocytes by interleukin (IL)-13 and IL-4 is a significant component of the inflammatory response. The consequences of alternative activation in inflammatory diseases remain to be determined.

OBJECTIVE

In this report, we explored how integrins, receptors important for monocyte migration to inflammatory sites, regulate IL-13-mediated monocyte activation. We focused on the analysis of 2 proteins, which are upregulated during the alternative activation and are important for the development of atherosclerosis, an oxidative enzyme 15-lipoxygenase (15-LO) and a scavenger receptor CD36.

METHODS AND RESULTS

We found that adhesion of resting monocytes through β(2) integrins and inside-out activation of β(2) integrins by monocyte chemoattractant protein-1 did not change IL-13-stimulated 15-LO upregulation; however, preincubation of monocytes with the antibody MEM48, which generates full activation of β(2) integrins, significantly inhibited 15-LO mRNA and protein expression. In contrast, activation of β(1) integrins had no effect on 15-LO expression. Analysis of integrin clustering through α(M), α(L), α(X), and α(D) subunits demonstrated the pivotal role for integrin α(M)β(2) in inhibiting 15-LO expression. IL-13 treatment upregulates 15-LO-dependent CD36 expression on human monocytes; our studies showed that β(2) integrin activation and α(M) integrin clustering significantly inhibited IL-13-dependent CD36 mRNA and protein expression, as well as CD36-related foam cell formation. Moreover, IL-13 stimulation of α(M)-deficient peritoneal macrophages demonstrated an upregulated level of 15-LO induction, CD36 expression, and lipid accumulation as compared with wild-type controls.

CONCLUSIONS

The adhesion of monocytes/macrophages through activated integrin α(M)β(2) has a regulatory and potential atheroprotective function during the alternative activation of macrophages.

Monocyte 15-lipoxygenase gene expression requires ERK1/2 MAPK activity

IL-13 induces profound expression of 15-lipoxygenase (15-LO) in primary human monocytes. Our studies have defined the functional IL-13R complex, association of Jaks with the receptor components, and the tyrosine phosphorylation of several Stat molecules in response to IL-13. Furthermore, we identified both p38MAPK and protein kinase Cδ as critical regulators of 15-LO expression. In this study, we report an ERK1/2-dependent signaling cascade that regulates IL-13-mediated 15-LO gene expression. We show the rapid phosphorylation/activation of ERK1/2 upon IL-13 exposure. Our results indicate that Tyk2 kinase is required for the activation of ERK1/2, which is independent of the Jak2, p38MAPK, and protein kinase Cδ pathways, suggesting bifurcating parallel regulatory pathways downstream of the receptor. To investigate the signaling mechanisms associated with the ERK1/2-dependent expression of 15-LO, we explored the involvement of transcription factors, with predicted binding sites in the 15-LO promoter, in this process including Elk1, early growth response-1 (Egr-1), and CREB. Our findings indicate that IL-13 induces Egr-1 nuclear accumulation and CREB serine phosphorylation and that both are markedly attenuated by inhibition of ERK1/2 activity. We further show that ERK1/2 activity is required for both Egr-1 and CREB DNA binding to their cognate sequences identified within the 15-LO promoter. Furthermore, by transfecting monocytes with the decoy oligodeoxyribonucleotides specific for Egr-1 and CREB, we discovered that Egr-1 and CREB are directly involved in regulating 15-LO gene expression. These studies characterize an important regulatory role for ERK1/2 in mediating IL-13-induced monocyte 15-LO expression via the transcription factors Egr-1 and CREB.

Interleukin-25 fails to activate STAT6 and induce alternatively activated macrophages

Interleukin-25 (IL-25), a T helper type 2 (Th2) -related factor, inhibits the production of inflammatory cytokines by monocytes/macrophages. Since Th2 cytokines antagonize classically activated monocytes/macrophages by inducing alternatively activated macrophages (AAMs), we here assessed the effect of IL-25 on the alternative activation of human monocytes/macrophages. The interleukins IL-25, IL-4 and IL-13 were effective in reducing the expression of inflammatory chemokines in monocytes. This effect was paralleled by induction of AAMs in cultures added with IL-4 or IL-13 but not with IL-25, regardless of whether cells were stimulated with lipopolysaccharide or interferon-γ. Moreover, pre-incubation of cells with IL-25 did not alter the ability of both IL-4 and IL-13 to induce AAMs. Both IL-4 and IL-13 activated signal transducer and activator of transcription 6 (STAT6), and silencing of this transcription factor markedly reduced the IL-4/IL-13-driven induction of AAMs. In contrast, IL-25 failed to trigger STAT6 activation. Among Th2 cytokines, only IL-25 and IL-10 were able to activate p38 mitogen-activated protein kinase. These results collectively indicate that IL-25 fails to induce AAMs and that Th2-type cytokines suppress inflammatory responses in human monocytes by activating different intracellular signalling pathways.

[Roles of PPAR and p21WAF1/CIP1 in monocyte/macrophage differentiation: are circulating monocytes able to proliferate?]

Macrophages are involved in the immune and the inflammatory response. The deregulation of their physiological properties is associated with several pathologies such as atherosclerosis and some cancers. Cytokines action on this blood lineage modulates p21WAF1/CIP1 expression. It appears that this protein may play a role in the inflammation regulation through PPAR (peroxysome proliferator-activated receptors) transcription factors, strongly linked to lipid metabolism. It could also be involved in the control of the proliferation of monocytes/macrophages, even if these cells are classically described as devoided of any proliferative capacity.

p38 MAP kinase inhibits neutrophil development through phosphorylation of C/EBPalpha on serine 21

Many extracellular stimuli regulate growth, survival, and differentiation responses through activation of the dual specificity mitogen activated protein kinase (MAPK) kinase three (MKK3) and its downstream effector p38 MAPK. Using CD34+ hematopoietic progenitor cells, here we describe a novel role for MKK3-p38MAPK in the regulation of myelopoiesis. Inhibition of p38MAPK utilizing the pharmacological inhibitor SB203580, enhanced neutrophil development ex vivo, but conversely reduced eosinophil differentiation. In contrast, constitutive activation of MKK3 dramatically inhibited neutrophil differentiation. Transplantation of beta2-microglobulin(-/-) nonobese diabetic/severe combined immune deficient (NOD/SCID) mice with CD34+ cells ectopically expressing constitutively active MKK3 resulted in reduced neutrophil differentiation in vivo, whereas eosinophil development was enhanced. Inhibitory phosphorylation of CCAAT/enhancer binding protein alpha (C/EBPalpha) on serine 21 was induced upon activation of p38MAPK. Moreover, ectopic expression of a non-phosphorylatable C/EBPalpha mutant was sufficient to abrogate MKK3-induced inhibition of neutrophil development. Furthermore, treatment of CD34+ progenitors from patients with severe congenital neutropenia with SB203580 restored neutrophil development. These results establish a novel role for MKK3-p38MAPK in the regulation of lineage choices during myelopoiesis through modulation of C/EBPalpha activity. This signaling module may thus provide an important therapeutic target in the treatment of bone marrow failure.

Functional proteomics identifies targets of phosphorylation by B-Raf signaling in melanoma

Melanoma and other cancers harbor oncogenic mutations in the protein kinase B-Raf, which leads to constitutive activation and dysregulation of MAP kinase signaling. In order to elucidate molecular determinants responsible for B-Raf control of cancer phenotypes, we present a method for phosphoprotein profiling, using negative ionization mass spectrometry to detect phosphopeptides based on their fragment ion signature caused by release of PO(3)(-). The method provides an alternative strategy for phosphoproteomics, circumventing affinity enrichment of phosphopeptides and isotopic labeling of samples. Ninety phosphorylation events were regulated by oncogenic B-Raf signaling, based on their responses to treating melanoma cells with MKK1/2 inhibitor. Regulated phosphoproteins included known signaling effectors and cytoskeletal regulators. We investigated MINERVA/FAM129B, a target belonging to a protein family with unknown category and function, and established the importance of this protein and its MAP kinase-dependent phosphorylation in controlling melanoma cell invasion into three-dimensional collagen matrix.

Phosphatidylethanolamine-esterified eicosanoids in the mouse: tissue localization and inflammation-dependent formation in Th-2 disease

In this study, murine peritoneal macrophages from naïve lavage were found to generate four phospholipids that contain 12-hydroxyeicosatetraenoic acid (12-HETE). They comprise three plasmalogen and one diacyl phosphatidylethanolamines (PEs) (16:0p, 18:1p, 18:0p, and 18:0a at sn-1) and are absent in macrophages from 12/15-lipoxygenase (12/15-LOX)-deficient mice. They are generated acutely in response to calcium mobilization, are primarily cell-associated, and are detected on the outside of the plasma membrane. Levels of 12-HETE-PEs in naïve lavage are in a similar range to those of free 12-HETE (5.5 ± 0.2 ng or 18.5 ± 1.03 ng/lavage for esterified versus free, respectively). In healthy mice, 12/15-LOX-derived 12-HETE-PEs are found in the peritoneal cavity, peritoneal membrane, lymph node, and intestine, with a similar distribution to 12/15-LOX-derived 12-HETE. In vivo generation of 12-HETE-PEs occurs in a Th2-dependent model of murine lung inflammation associated with interleukin-4/interleukin-13 expression. In contrast, in Toll receptor-dependent peritonitis mediated either by live bacteria or bacterial products, 12-HETE-PEs are rapidly cleared during the acute phase then reappear during resolution. The human homolog, 18:0a/15-HETE-PE inhibited human monocyte generation of cytokines in response to lipopolysaccharide. In summary, a new family of lipid mediators generated by murine macrophages during Th2 inflammation are identified and structurally characterized. The studies suggest a new paradigm for lipids generated by 12/15-LOX in inflammation involving formation of esterified eicosanoids.

MAPK signaling pathways in the regulation of hematopoiesis

The MAPKs are a family of serine/threonine kinases that play an essential role in connecting cell-surface receptors to changes in transcriptional programs. MAPKs are part of a three-component kinase module consisting of a MAPK, an upstream MEK, and a MEKK that couples the signals from cell-surface receptors to trigger downstream pathways. Three major groups of MAPKs have been characterized in mammals, including ERKs, JNKs, and p38MAPKs. Over the last decade, extensive work has established that these proteins play critical roles in the regulation of a wide variety of cellular processes including cell growth, migration, proliferation, differentiation, and survival. It has been demonstrated that ERK, JNK, and p38MAPK activity can be regulated in response to a plethora of hematopoietic cytokines and growth factors that play critical roles in hematopoiesis. In this review, we summarize the current understanding of MAPK function in the regulation of hematopoiesis in general and myelopoiesis in particular. In addition, the consequences of aberrant MAPK activation in the pathogenesis of various myeloid malignancies will be discussed.

House dust mite allergen Der f 2-induced phospholipase D1 activation is critical for the production of interleukin-13 through activating transcription factor-2 activation in human bronchial epithelial cells

The purpose of this study was to identify the role of phospholipase D1 (PLD1) in Der f 2-induced interleukin (IL)-13 production. The major house dust mite allergen, Der f 2, increased PLD activity in human bronchial epithelial cells (BEAS-2B), and dominant negative PLD1 or PLD1 siRNA decreased Der f 2-induced IL-13 expression and production. Treatment of Der f 2 activated the phospholipase Cgamma (PLCgamma)/protein kinase Calpha (PKCalpha)/p38 MAPK pathway. Der f 2-induced PLD activation was attenuated by PLCgamma inhibitors (U73122 and PAO), PKCalpha inhibitors (RO320432 and GO6976), and p38 MAPK inhibitors (SB203580 and SB202190). These results indicate that PLCgamma, PKCalpha, and p38 MAPK act as upstream activators of PLD in Der f 2-treated BEAS-2B cells. Furthermore, expression and production of IL-13 increased by Der f 2 were also blocked by inhibition of PLCgamma, PKCalpha, or p38 MAPK, indicating that IL-13 expression and production are related to a PLCgamma/PKCalpha/p38 MAPK pathway. We found that activating transcription factor-2 (ATF-2) was activated by Der f 2 in BEAS-2B cells and activation of ATF-2 was controlled by PLD1. When ATF-2 activity was blocked with ATF-2 siRNA, Der f 2-induced IL-13 expression and production were decreased. Thus, ATF-2 might be one of the transcriptional factors for the expression of IL-13 in Der f 2-treated BEAS-2B cells. Taken together, PLD1 acts as an important regulator in Der f 2-induced expression and production of IL-13 through activation of ATF-2 in BEAS-2B cells.

IL-18 and IL-33 elicit Th2 cytokines from basophils via a MyD88- and p38alpha-dependent pathway

IL-4 and IL-13 are instrumental in the development and progression of allergy and atopic disease. Basophils represent a key source of these cytokines and produce IL-4 and IL-13 when stimulated with IL-18, a member of the IL-1 family of cytokines. Comparative analyses of the effects of caspase-1-dependent IL-1 family cytokines on basophil IL-4 and IL-13 production have not been performed, and the signaling pathway proteins required for FcepsilonRI-independent Th2 cytokine production from basophils remain incompletely defined. Using mouse bone marrow-derived cultured basophils, we found that IL-4 and IL-13 are produced in response to IL-18 or IL-33 stimulation. IL-18- or IL-33-mediated Th2 cytokine production is dependent on MyD88 and p38alpha signaling proteins. In addition, basophil survival increased in the presence of IL-18 or IL-33 as a result of increased Akt activation. Studies in vivo confirmed the potency of IL-18 and IL-33 in activating cytokine release from mouse basophils.

Modulation of PKCdelta signaling alters the shear stress-mediated increases in endothelial nitric oxide synthase transcription: role of STAT3

We have previously shown that the regulation of endothelial nitric oxide synthase (eNOS) in endothelial cells isolated from fetal lamb under static conditions is positively regulated by PKCdelta. In this study, we explore the role of PKCdelta in regulating shear-induced upregulation of eNOS. We found that shear caused a decrease in PKCdelta activation. Modulation of PKCdelta before shear with a dominant negative mutant of PKCdelta (DN PKCdelta) or bryostatin (a known PKCdelta activator) demonstrated that PKCdelta inhibition potentiates the shear-mediated increases in eNOS expression and activity, while PKCdelta activation inhibited these events. To gain insight into the mechanism by which PKCdelta inhibits shear-induced eNOS expression, we examined activation of STAT3, a known target for PKCdelta phosphorylation. We found that shear decreased the phosphorylation of STAT3. Further the transfection of cells with DN PKCdelta reduced, while PKCdelta activation enhanced, STAT3 phosphorylation in the presence of shear. Transfection of cells with a dominant negative mutant of STAT3 enhanced eNOS promoter activity and nitric oxide production in response to shear. Finally, we found that mutating the STAT3 binding site sequence within the eNOS promoter increased promoter activity in response to shear and that this was no longer inhibited by bryostatin. In conclusion, shear decreases PKCdelta activity and, subsequently, reduces STAT3 binding to the eNOS promoter. This signaling pathway plays a previously unidentified role in the regulation of eNOS expression by shear stress.

Chronic hypoxia enhances 15-lipoxygenase-mediated vasorelaxation in rabbit arteries

15-Lipoxygenase (15-LO-1) metabolizes arachidonic acid (AA) to 11,12,15-trihydroxyeicosatrienoic acids (THETAs) and 15-hydroxy-11,12-epoxyeicosatrienoic acids (HEETA) that dilate rabbit arteries. Increased endothelial 15-LO-1 expression enhances arterial relaxations to agonists. We tested the effect of hypoxia on 15-LO-1 expression, THETA and HEETA synthesis, and relaxations in rabbit arteries. The incubation of rabbit aortic endothelial cells and isolated aortas in 0.7% O(2) increased 15-LO-1 expression. Rabbits were housed in a hypoxic atmosphere of 12% O(2) for 5 days. 15-LO-1 expression increased in the endothelium of the arteries of rabbits in 12% O(2) compared with room air. THETA and HEETA synthesis was also enhanced in aortas and mesenteric arteries. AA hyperpolarized the smooth muscle cells in indomethacin- and phenylephrine-treated mesenteric arteries of hypoxic rabbits from -29.4 +/- 1 to -50.1 +/- 3 mV. The hyperpolarization to AA was less in arteries of normoxic rabbits (from -26.0 +/- 2 to -37 +/- 2 mV). This AA-induced hyperpolarization was inhibited by the 15-LO inhibitor BW-755C. Nitric oxide and prostaglandin-independent maximum relaxations to acetylcholine (79.7 +/- 2%) and AA (38.3 +/- 4%) were enhanced in mesenteric arteries from hypoxic rabbits compared with the normoxic rabbits (49.7 +/- 6% and 19.9 +/- 2%, respectively). These relaxations were inhibited by BW-755C and nordihydroguaiaretic acid. Therefore, hypoxia increased the relaxations to agonists in the rabbit mesenteric arteries by enhancing endothelial 15-LO-1 expression and synthesis of the hyperpolarizing factors THETA and HEETA.

The chemokine CCL2 activates p38 mitogen-activated protein kinase pathway in cultured rat hippocampal cells

Emerging evidence indicates that chemokines can regulate both the physiology and biochemistry of CNS neurons and glia. In the current study, Western blot analysis showed that in rat hippocampal neuronal/glial cultures the signal transduction pathway activated by CCL2, a chemokine expressed in the normal brain and at elevated levels during neuroinflammation, involves a G-protein coupled receptor, p38 MAPK as well as its immediate upstream kinase MKK3/6, and the downstream transcription factor CREB. ERK 1/2 and the transcription factors STAT1 and STAT3 do not play a prominent role. CCL2 also altered Ca(2+) influx and synaptic network activity in the hippocampal neurons. These results suggest an important role for p38 MAPK and CREB in hippocampal actions of CCL2.

The Roles of Dietary PPARgamma Ligands for Metastasis in Colorectal Cancer

Dietary peroxisome proliferator-activated receptor (PPAR)gamma ligands, linoleic acid (LA) and conjugated linoleic acid (CLA), showed anticancer effects in colorectal carcinoma cells. LA is metabolized by two pathways. Cyclooxygenase (COX)-2 produces procarcinogenic prostaglandin E2, whereas 15-lipoxygenase (LOX)-1 produces PPARgamma ligands. The 15LOX-1 pathway, which is dominant in colorectal adenomas, was downregulated and inversely COX-2 was upregulated in colorectal cancer. LA and CLA inhibited peritoneal metastasis of colorectal cancer cells in nude mice. The inhibitory effect was abrogated by PPARgamma antisense treatment. A continuous LA treatment provided cancer cells quiescence. These quiescent cells formed dormant nests in nude mice administrated LA. The quiescent and dormant cells showed downregulated PPARgamma and upregulated nucleostemin. Thus, short-term exposure to dietary PPARgamma ligands inhibits cancer metastasis, whereas consistent exposure to LA provides quiescent/dormant status with possible induction of cancer stem and/or progenitor phenotype. The complicated roles of dietary PPARgamma ligands are needed to examine further.

In vivo validation of signaling pathways regulating human monocyte chemotaxis

Identification of novel signal transduction pathways regulating monocyte chemotaxis can indicate unique targets for preventive therapies for treatment of chronic inflammatory diseases. To aid in this endeavor we report conditions for optimal transfection of primary human monocytes coupled with a new model system for assessing their chemotactic activity in vivo. This method can be used as a tool to identify the relevant signal transduction pathways regulating human monocyte chemotaxis to MCP-1 in the complex in vivo environment that were previously identified to regulate chemotaxis in vitro. MCP-1-dependent chemotaxis of monocytes is studied in an adoptive transfer model where human monocytes transfected with mutant cDNAs are transferred to mice followed by initiation of peritonitis. Harvesting peritoneal cells at 24 h diminishes the contribution of immunologic responses to the cross-species transfer. Validation of relevant regulatory molecules in vivo is critical for understanding the most relevant therapeutic targets for drug development.

In vivo inhibition of angiogenesis by interleukin-13 gene therapy in a rat model of rheumatoid arthritis

OBJECTIVE

Interleukin-13 (IL-13) is a pleiotropic cytokine that can affect vessel formation, an important component of the rheumatoid arthritis (RA) synovial tissue pannus. The purpose of this study was to use a gene therapy approach to investigate the role of IL-13 in angiogenesis in vivo, using a rat adjuvant-induced arthritis model of RA.

METHODS

Ankle joints of female rats were injected preventatively with an adenovirus vector containing human IL-13 (AxCAIL-13), a control vector with no insert (AxCANI), or phosphate buffered saline (PBS). Joints were harvested at the peak of arthritis, and histologic and biochemical features were evaluated.

RESULTS

AxCAIL-13-treated joint homogenates had lower hemoglobin levels, suggesting reduced joint vascularity, and both endothelial cell migration and tube formation were significantly inhibited (P < 0.05). Similarly, AxCAIL-13 inhibited capillary sprouting in the rat aortic ring assay and vessel growth in the Matrigel plug in vivo assay. IL-13 gene delivery resulted in up-regulation and association of phosphorylated ERK-1/2 and protein kinase Calpha/betaII, suggesting a novel pathway in IL-13-mediated angiostasis. The angiostatic effect of AxCAIL-13 was associated with down-regulation of proangiogenic cytokines (IL-18, cytokine-induced neutrophil chemoattractant 1/CXCL1, lipopolysaccharide-induced CXC chemokine/CXCL5) and up-regulation of the angiogenesis inhibitor endostatin. The expression and activity of matrix metalloproteinases 2 and 9, which participate in angiogenesis, was impaired in response to IL-13 as compared with AxCANI and PBS treatment.

CONCLUSION

Our findings support a role for IL-13 as an in vivo antiangiogenic factor and provide a rationale for its use in RA to control pathologic neovascularization.

Reversal of expression of 15-lipoxygenase-1 to cyclooxygenase-2 is associated with development of colonic cancer

AIMS

Two different pathways of linoleic acid (LA) metabolism have opposite effects on the development of colonic cancer: a protumoral prostaglandin cascade metabolized by cyclooxygenase (COX)-2, and an antitumoral peroxisome proliferator-activated receptor (PPAR)-gamma ligands metabolized by 15-lipooxygenase (LOX)-1. The aim was to examine the switching of the two LA metabolic pathways in colonic adenomas and carcinomas.

MATERIALS AND METHODS

The expression of 15LOX-1 mRNA and COX-2 protein was examined in 54 adenomas, 21 pTis carcinoma-in-adenoma lesions and 36 pT3/p Stage II carcinomas of the colon by in-situ hybridization and immunohistochemistry, respectively.

RESULTS

15LOX-1 expression was found in 89% (48 of 54) of adenomas, 43% (nine of 21) of adenomas and 10% (two of 21) of carcinomas in carcinoma-in-adenoma lesions, but not in pT3 carcinomas (P < 0.0001). In contrast, COX-2 production was found in 11% (six of 54) of adenomas, 52% (11 of 21) of adenomas and 71% (15 of 21) of carcinomas in carcinoma-in-adenoma lesions, and 92% (33 of 36) of pT3 carcinomas (P < 0.0001). Concurrence of 15LOX-1 down-regulation and COX-2 up-regulation was found in 6% (three of 54) of adenomas, 33% (seven of 21) of adenomas and 71% (15 of 21) of carcinomas in carcinoma-in-adenoma lesions, and 92% (33 of 36) of pT3 carcinomas (P < 0.0001).

CONCLUSIONS

These results suggest that switching of LA metabolism by reversal of the expression of 15LOX-1 and COX-2 is associated with acquisition of malignant potential in colonic neoplasia.

The role of p38 mitogen-activated protein kinase in regulating interleukin-10 gene expression in Burkitt's lymphoma cell lines

In malignant B lymphoma cells interleukin-10 (IL-10) expression is frequently upregulated. This effect is thought to support to the malignant transformation of these cells and to be a potential target for pharmacotherapy. To define better the mechanism for upregulation of the IL-10 gene, we tested the association between IL-10 and p38 mitogen-activated protein kinase (MAPK) in several Epstein-Barr virus (EBV) infected and non-infected Burkitt's lymphoma (BL) cell lines. The all BL cell lines expressed IL-10 and IL-10 receptor mRNAs, and produced IL-10. p38 MAPK was constitutively phosphorylated in the cytoplasm of the BL cell lines. We further analyzed molecular effects of p38 MAPK on IL-10 expression in Akata cells. Exogenous IL-10 lead rapidly to phosphorylation of Jak1 and Tyk2 as transducers of signals of IL-10, and promoted growth of Akata cells in a dose-dependent manner. The phosphorylation of cytoplasmic p38 MAPK in Akata cells was reduced by the serine/threonine kinase inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7). A specific inhibitor of p38 MAPK, SB203580, blocked simultaneously STAT3 DNA-binding activity, and IL-10 mRNA expression, IL-10 production, and then the cell growth was inhibited. These results indicate that the p38 MAPK pathway is functionally linked to IL-10 gene expression and supports the view that the constitutive activation of cytoplasmic p38 MAPK in BL cells is a step in the upregulation of IL-10 gene expression and lymphomagenesis.

Signal transducer and activator of transcription 1 is required for optimal foam cell formation and atherosclerotic lesion development

BACKGROUND

Signal transducer and activator of transcription 1 (Stat1) potently regulates gene expression after stimulation by certain cytokines involved in tumorigenesis and host defenses. The present study investigated a novel role for Stat1 in foam cell formation and atherosclerosis.

METHODS AND RESULTS

Inhibition of Stat1 activity by a Stat1-specific DNA "decoy" oligomer transfected into differentiated human THP-1 cells, and deficiency of stat1 in mouse macrophages significantly inhibited foam cell formation assessed by lipid staining and cholesteryl ester accumulation compared with control cells. The mechanism of Stat1 regulation of foam cell formation was uniquely dependent on the scavenger receptor CD36. Blunted Stat1 activity and stat1 deficiency significantly decreased expression of CD36 but not of scavenger receptor-A compared with controls, as assessed by immunoblotting and flow cytometry. Deficiency of CD36 but not scavenger receptor-A in mouse macrophages removed any dependency of foam cell formation on Stat1. In an intraperitoneal model of foam cell formation in which foam cells form in vivo independently of the model ligands used in vitro, stat1 deficiency significantly inhibited foam cell formation and CD36 expression. Transplantation of bone marrow from apolipoprotein e-/- x stat1-/- mice into lethally irradiated, atherosclerosis-susceptible apolipoprotein e-/- recipients significantly reduced both en face aortic lesion coverage and aortic root lesions compared with recipients of bone marrow from genetically matched apolipoprotein e-/- mice.

CONCLUSIONS

Stat1 regulates CD36 expression and foam cell formation in macrophages in vitro; the Stat1 regulation of foam cell formation requires CD36. The regulation of CD36 expression by Stat1 may be important in other pathophysiological CD36-dependent events. Stat1 deficiency reduces atherosclerosis in an apolipoprotein e-/- atherosclerosis-susceptible bone marrow transplantation model.

Involvement of enzymes other than CYPs in the oxidative metabolism of xenobiotics

Although the majority of oxidative metabolic reactions are mediated by the CYP superfamily of enzymes, non-CYP-mediated oxidative reactions can play an important role in the metabolism of xenobiotics. The (major) oxidative enzymes, other than CYPs, involved in the metabolism of drugs and other xenobiotics are: the flavin-containing monooxygenases, the molybdenum hydroxylases (aldehyde oxidase and xanthine oxidase), the prostaglandin H synthase, the lipoxygenases, the amine oxidases (monoamine, polyamine, diamine and semicarbazide-sensitive amine oxidases) and the alcohol and aldehyde dehydrogenases. In a similar manner to CYPs, these oxidative enzymes can also produce therapeutically active metabolites and reactive/toxic metabolites, modulate the efficacy of therapeutically active drugs or contribute to detoxification. Many of them have been shown to be important in endobiotic metabolism, and, consequently, interactions between drugs and endogenous compounds might occur when they are involved in drug metabolism. In general, most non-CYP oxidative enzymes appear to be noninducible or much less inducible than the CYP system, although some of them may be as inducible as some CYPs. Some of these oxidative enzymes exhibit polymorphic expression, as do some CYPs. It is possible that the contribution of non-CYP oxidative enzymes to the overall metabolism of xenobiotics is underestimated, as most investigations of drug metabolism in discovery and lead optimisation are performed using in vitro test systems optimised for CYP activity.