N-terminal peptide fragments of lipocortin-1 inhibit A549 cell growth and block EGF-induced stimulation of proliferation

Reciprocal regulation of pro-inflammatory Annexin A2 and anti-inflammatory Annexin A1 in the pathogenesis of rheumatoid arthritis

Annexin A2 has been implicated in several immune modulated diseases including Rheumatoid arthritis (RA) pannus formation. The most relied treatment option for RA pathogenesis is glucocorticoids. Glucocorticoids regulate the synthesis, phosphorylation and cellular deposition of Annexin A1. This annexin mediates the anti-inflammatory actions of glucocorticoids. These two first characterized members of annexin superfamily proteins acts reciprocally, one as an anti-inflammatory and the other proinflammatory in nature. The possibility of these molecules as soluble biomarkers and as an upstream regulator of major cytokine devastation at RA microenvironment has not been previously explored. Current study elucidates the reciprocal regulation of these two annexins in RA pathogenesis. These Annexin A2/A1 and downstream cytokines in RA serum were analysed by ELISA. Western blot, Immunocytochemistry, immunoprecipitation and Immunohistochemistry were adapted to analyse these molecules in tissue and synovial fibroblasts and also in different experimental conditions. Significant increase in the level of Annexin A2 was noticed in naïve RA patients compared to controls (14.582 ± 1.766 ng/ml vs. 7.37 ± 1.450 ng/ml; p ≤ 0.001). In remission cases significant low levels was detected. On the contrary, significant decrease in the level of Annexin A1 was noticed in naïve RA patients compared to healthy controls (12.322 ± 2.91 vs. 16.998 ± 4.298 ng/ml; p ≤ 0.001), wherein remission cases serum Annexin A1 was significantly high. The knockdown of proinflammatory Annexin A2 by siRNA/antibody treatment could mimic the glucocorticoid treatment as which induced cellular Annexin A1 and membrane translocation resulting in the terminal action. Current data elucidating the regulatory interplay between Annexin A2 and Annexin A1 in RA pathogenesis.

Annexin A1 mimetic peptide controls the inflammatory and fibrotic effects of silica particles in mice

BACKGROUND AND PURPOSE

Endogenous glucocorticoids are pro-resolving mediators, an example of which is the endogenous glucocorticoid-regulated protein annexin A1 (ANXA1). Because silicosis is an occupational lung disease characterized by unabated inflammation and fibrosis, in this study we tested the therapeutic properties of the N-terminal ANXA1-derived peptide annexin 1-(2-26) (Ac2-26) on experimental silicosis.

EXPERIMENTAL APPROACH

Swiss-Webster mice were administered silica particles intranasally and were subsequently treated with intranasal peptide Ac2-26 (200 μg per mouse) or dexamethasone (25 μg per mouse) for 7 days, starting 6 h post-challenge. Ac2-26 abolished the leukocyte infiltration, collagen deposition, granuloma formation and generation of pro-inflammatory cytokines evoked by silica; these variables were only partially inhibited by dexamethasone.

KEY RESULTS

A clear exacerbation of the silica-induced pathological changes was observed in ANXA1 knockout mice as compared with their wild-type (WT) littermate controls. Incubation of lung fibroblasts from WT mice with Ac2-26 in vitro reduced IL-13 or TGF-β-induced production of CCL2 (MCP-1) and collagen, but this peptide did not affect the production of CCL2 (MCP-1) by stimulated fibroblasts from formyl peptide receptor type 1 (FPR1) knockout mice. Ac2-26 also inhibited the production of CCL2 (MCP-1) from fibroblasts of FPR2 knockout mice.

CONCLUSIONS AND IMPLICATIONS

Collectively, our findings reveal novel protective properties of the ANXA1 derived peptide Ac2-26 on the inflammatory and fibrotic responses induced by silica, and suggest that ANXA1 mimetic agents might be a promising strategy as innovative anti-fibrotic approaches for the treatment of silicosis.

Mass spectrometry based quantitative proteomics and integrative network analysis accentuates modulating roles of annexin-1 in mammary tumorigenesis

Annexin-1 (ANXA1) is known to be involved in important cellular processes and implicated in cancer. Our previous study showed its roles in cell migration and DNA-damage response processes in breast cancer initiation. In order to understand its roles in tumorigenesis, we extended our studies to analyze tumors derived from polyomavirus middle T-antigen ANXA1 heterozygous (ANXA1(+/-) ) and ANXA1 null (ANXA1(-/-) ) mice. We performed quantitative comparison of ANXA1(+/-) and ANXA1(-/-) tumors employing reductive dimethyl labeling quantitative proteomics. We observed 253 differentially expressed proteins (DEPs) with high statistical significance among over 5000 quantified proteins. Combinatorial use of pathway and network-based computational analyses of the DEPs revealed that ANXA1 primarily modulates processes related to cytoskeletal remodeling and immune responses in these mammary tumors. Of particular note, ANXA1(-/-) tumor showed reduced expression of a known epithelial-to-mesenchymal transition (EMT) marker vimentin, as well as myosin light-chain kinase, which has been reported to induce Rho-kinase mediated assembly of stress fibers known to be implicated in EMT. Integrative network analysis of established interactome of ANXA1 alongside with DEPs further highlights the involvement of ANXA1 in EMT. Functional role of ANXA1 in tumorigenesis was established in invasion assay where knocking down ANXA1 in murine mammary tumor cell line 168FARN showed lower invasive capability. Altogether, this study emphasizes that ANXA1 plays modulating roles contributing to invasion-metastasis in mammary tumorigenesis, distinctive to its roles in cancer initiation.

Overexpression of ANXA1 confers independent negative prognostic impact in rectal cancers receiving concurrent chemoradiotherapy

Neoadjuvant concurrent chemoradiation therapy (CCRT) is an increasingly common therapeutic strategy for rectal cancer. Clinically, it remains a major challenge to predict therapeutic response and patient outcomes after CCRT. Annexin I (ANXA1), encoded by ANXA1, is a Ca(2+)/phospholipid-binding protein that mediates actin dynamics and cellular proliferation, as well as suggesting tumor aggressiveness and predicting therapeutic response in certain malignancies. However, expression of ANXA1 has never been reported in rectal cancer receiving CCRT. This study examined the predictive and prognostic impact of ANXA1 expression in patients with rectal cancer following neoadjuvant CCRT. We identified ANXA1 as associated with resistance to CCRT through data mining from a published transcriptomic dataset. Its immunoexpression was retrospectively assessed using H scores on pre-treatment biopsies from 172 rectal cancer patients treated with neoadjuvant CCRT followed by curative surgery. Results were correlated with clinicopathological features, therapeutic response, tumor regression grade (TRG), and metastasis-free survival (MeFS), as well as local recurrent-free survival (LRFS) and disease-specific survival (DSS). High expression of ANXA1 was associated with advanced pre-treatment tumor status (T3, T4, p = 0.022), advanced pre-treatment nodal status (N1, N2, p = 0.004), advanced post-treatment tumor status (T3, T4, p < 0.001), advanced post-treatment nodal status (N1, N2, p = 0.001) and inferior TRG (p = 0.009). In addition, high expression of ANXA1 emerged as an adverse prognosticator for DSS (p < 0.0001), LRFS (p = 0.0001) and MeFS (p = 0.0004). Moreover, high expression of ANXA1 also remained independently prognostic of worse DSS (hazard ratio [HR] = 3.998; p = 0.007), LRFS (HR = 3.206; p = 0.028) and MeFS (HR = 3.075; p = 0.017). This study concludes that high expression of ANXA1 is associated with poor therapeutic response and adverse outcomes in rectal cancer patients treated with neoadjuvant CCRT.

Green tea inhibits cycolooxygenase-2 in non-small cell lung cancer cells through the induction of Annexin-1

Elevated cyclooygenase-2 (COX-2) expression is frequently observed in human non-small cell lung cancer (NSCLC) and associated with poor prognosis, indicating critical involvement of the inflammatory pathway in lung carcinogenesis. Recently, we found that green tea extract (GTE) induced Annexin-1 (ANX1) in the lung adenocarcinoma A549 cells. ANX1 is a glucocorticoid-inducible 37kDa protein involved in a wide range biological function and is an important anti-inflammatory mediator. The present study further examines the interplay between the expressions and production of ANX1, COX-2, phospholipase A(2) (cPLA(2)) and prostaglandin E(2) (PGE(2)) following the treatment of NSCLC cell lines with GTE. We found that GTE induced ANX1 and inhibited COX-2 expression in lung cancer A549, H157 and H460 cell lines. Addition of pro-inflammatory cytokine IL-1β diminished GTE-induced ANX1. Silence of ANX1 in cells abrogates the inhibitory activity on COX-2, indicating that the anti-inflammatory activity of GTE is mediated at least partially by the up-regulation of ANX1. However, differential pattern of inhibitory effects of ANX1 on cPLA(2) expression was observed among various cell types, suggesting that the anti-inflammatory activity mediated by ANX1 is cell type specific. Our study may provide a new mechanism of GTE on the prevention of lung cancer and other diseases related to inflammation.

Proteomic investigation of anti-tumor activities exerted by sinularin against A2058 melanoma cells

The extracts from soft corals have been increasingly investigated for biomedical and therapeutic purposes. The aim of this study is to examine and analyze the anti-tumor effects of the genus Sinularia extract sinularin on A2058 melanoma cells using MTT assay, cell migration assay, wound healing assay, flow cytometric analysis, and proteomic analysis. Sinularin dose-dependently (1-5 μg/mL) inhibited melanoma cell proliferation while the treatment at identical concentrations suppressed cell migration. Sinularin dose-dependently enhanced apoptotic melanoma cells and caused tumor cell accumulation at G2/M phase, indicating that sinularin exerts apoptosis-induced and cell cycle-delayed activities in A2058 melanoma cells. Comparative proteomic analysis was conducted to investigate the effects of sinularin at the molecular level by comparison between the protein profiling of melanoma cells treated with sinularin and without the treatment. Thirty-five differential proteins (13 upregulated and 22 downregulated) concerning the treatment were identified by liquid chromatography-tandem mass spectrometry. Proteomic data and Western blot displayed the levels of several tumor inhibitory or apoptosis-associated proteins including annexin A1, voltage-dependent anion-selective channel protein 1 and prohibitin (upregulated), heat shock protein 60, heat shock protein beta-1, and peroxiredoxin-2 (downregulated) in A2058 melanoma cells exposed to sinularin. Increased expression of p53, cleaved-caspase-3, cleaved-caspase-8, cleaved-caspase-9, p21, and Bax and decreased expression of Bcl-2 in sinularin-treated melanoma cells suggest that the anti-tumor activities of sinularin against melanoma cells are particularly correlated with these pro-apoptotic factors. These data provide important information for the mechanisms of anti-tumor effects of sinularin on melanoma cells and may be helpful for drug development and progression monitoring of human melanoma.

Up-regulation of Annexin-A1 and lipoxin A(4) in individuals with ulcerative colitis may promote mucosal homeostasis

Background

One of the characteristics of an active episode of ulcerative colitis (UC) is the intense mucosal infiltration of leukocytes. The pro-resolution mediators Annexin-A1 (AnxA1) and lipoxin A₄ (LXA₄) exert counter-regulatory effects on leukocyte recruitment, however to date, the dual/cumulative effects of these formyl peptide receptor-2 (FPR2/ALX) agonists in the context of human intestinal diseases are unclear. To define the contribution of these mediators, we measured their expression in biopsies from individuals with UC.

Methods

Colonic mucosal biopsies were collected from two broad patient groups: healthy volunteers without (‘Ctrl’ n = 20) or with a prior history of UC (‘hx of UC’ n = 5); individuals with UC experiencing active disease (‘active’ n = 8), or in medically-induced remission (‘remission’ n = 16). We assessed the mucosal expression of LXA₄, AnxA1, and the FPR2/ALX receptor in each patient group using a combination of fluorescence microscopy, biochemical and molecular analyses.

Results

Mucosal expression of LXA₄ was elevated exclusively in biopsies from individuals in remission (3-fold, P<0.05 vs. Ctrl). Moreover, in this same group we observed an upregulation of AnxA1 protein expression (2.5-fold increase vs. Ctrl, P<.01), concurrent with an increased level of macrophage infiltration, and an elevation in FPR2/ALX mRNA (7-fold increase vs. Ctrl, P<.05). Importantly, AnxA1 expression was not limited to cells infiltrating the lamina propria but was also detected in epithelial cells lining the intestinal crypts.

Conclusions

Our results demonstrate a specific up-regulation of this pro-resolution circuit in individuals in remission from UC, and suggest a significant role for LXA₄ and AnxA1 in promoting mucosal homeostasis.

Annexin-I overexpression is associated with tumour progression and independently predicts inferior disease-specific and metastasis-free survival in urinary bladder urothelial carcinoma

AIMS

In our previous studies, comparative proteomics and immunohistochemistry (IHC) demonstrated that annexin-I (ANXA1) is up-regulated in high grade urinary bladder urothelial carcinoma (UBUC) as compared to non-high grade carcinomas. However, the small sample size prohibited further correlation of ANXA1 expression to tumour progression. Therefore, in the present study, 81 primary localised UBUC specimens of various grades and primary tumour (pT) status were examined for ANXA1 expression to further confirm the proteomics data and to clarify the relevance of ANXA1 expression level to the prognosis of UBUC.

METHODS

IHC was implemented to investigate ANXA1 protein expression in 81 primary localised UBUC specimens. The association of ANXA1 expression with tumour progression and prognosis was analysed.

RESULTS

Our data demonstrated that the ANXA1 expression level was strongly associated with an escalated pT status (p < 0.001) and a higher histological grade (p < 0.001), suggesting that ANXA1 might be related to tumour progression. Moreover, at the univariate level, ANXA1 overexpression, along with higher pT status and histological grade, significantly predicted disease-specific survival (DSS) and metastasis-free survival (MFS). More importantly, multivariate analyses revealed that the association of ANXA1 overexpression and prognosis remained significant for both DSS and MFS.

CONCLUSION

The above results reinforced the comparative proteomics results and confirmed the prognostic role of ANXA1 in UBUC.

Annexin-1 regulates growth arrest induced by high levels of estrogen in MCF-7 breast cancer cells

Estrogen, a naturally occurring female steroid growth hormone, has been implicated as a major risk factor for the development of breast cancer. Recent research into this disease has also correlated Annexin-1 (ANXA1), a glucocorticoid-inducible protein, with the development of breast tumorigenesis. ANXA1 is lost in many cancers, including breast cancer, and this may result in a functional promotion of tumor growth. In this study, we investigated the expression of ANXA1 in MCF-7 cells treated with estrogen and the regulation of estrogen functions by ANXA1. Exposure of MCF-7 breast cancer cells to high physiologic levels (up to 100 nmol/L) of estrogen leads to an up-regulation of ANXA1 expression partially through the activation of cyclic AMP-responsive element binding protein and dependency on activation of the estrogen receptor. In addition, treatment of MCF-7 cells with physiologic levels of estrogen (1 nmol/L) induced proliferation, whereas high pregnancy levels of estrogen (100 nmol/L) induced a growth arrest of MCF-7 cells, associated with constitutive activation of extracellular signal-regulated kinase 1/2 and up-regulation of cell cycle arrest proteins such as p21(waf/cip). Silencing of ANXA1 with specific small interfering RNA reverses the estrogen-dependent proliferation as well as growth arrest and concomitantly modulates extracellular signal-regulated kinase 1/2 phosphorylation. We confirm that ANXA1 is lost in clinical breast cancer, indicating that the antiproliferative protective function of ANXA1 against high levels of estrogen may be lost. Finally, we show that ANXA1-deficient mice exhibit faster carcinogen-induced tumor growth. Our data suggest that ANXA1 may act as a tumor suppressor gene and modulate the proliferative functions of estrogens.

Decreased expression of annexin A1 during the progression of cervical neoplasia

The aim of this study was to evaluate whether the expression of annexin A1 (ANXA1) is associated with the progression of cervical neoplasia. ANXA1 expression was examined by immunohistochemistry in paraffin-embedded cervical tissue samples (n = 234), comprising 52 samples of normal cervical epithelia, 30 of cervical intraepithelial neoplasia (CIN) I, 27 of CIN II, 32 of CIN III, and 93 of invasive squamous cell carcinoma (ISCC). ANXA1 expression was strong in normal cervical squamous epithelium and significantly reduced with increasing progression of cervical neoplasia. Moreover, a close association was observed between ANXA1 expression and tumour cell differentiation in ISCC. These preliminary results indicate that ANXA1 may be an effective candidate for detecting CIN lesions and for evaluating tumour cell differentiation in squamous cell carcinoma of the cervix.

Differences in the protein expression in limbal versus central human corneal epithelium--a search for stem cell markers

In the search for potential limbal stem cell protein markers, the purpose of this study was to characterize differences in protein expression between human central and limbal corneal epithelium by a proteomic approach using two-dimensional polyacrylamide gel electrophoresis (2D PAGE) combined with mass spectrometry (LC-MS/MS). The results were subsequently confirmed by Western blotting and immunohistochemistry. We detected more than 1000 protein spots in each gel. Thirty-two spots were significantly over-expressed in the central part and 70 spots were significantly over-expressed in the limbal part. We identified 25 different proteins. Among these 11 proteins representing different cellular locations and functions were selected for further investigations. Most interestingly, superoxide dismutase 2 (SOD2), was expressed in clusters of cells in the basal limbal epithelium. Heat shock protein 70 protein 1 (HSP70.1) and annexin I were highly abundant in limbal epithelium, although they were also present in the central epithelium to a minor extent. Among the proteins primarily expressed in the limbal fraction we further identified cytokeratin (CK) 15, CK19 and alpha enolase, which have been reported previously to be related to the limbal basal epithelium. The basal limbal epithelium consists of clusters of slow cycling limbal stem cells and rapid cycling transient amplifying cells. Ideally, proteins exclusively expressed in the limbal part of the epithelium may serve as markers for the basal limbal cells. SOD2 and CK15 identify clusters of limbal basal cells and therefore they may serve as markers for limbal stem cells in conjunction with the earliest transient amplifying cells.

Annexin 1: the new face of an old molecule

The annexin superfamily consists of 13 calcium or calcium and phospholipid binding proteins with a significant degree of biological and structural homology (40-60%). First described in the late 1970s and subsequently referred to as macrocortin, renocortin, lipomodulin, lipocortin-1, and more recently Annexin 1, this 37 kDa calcium and phospholipid binding protein is a strong inhibitor of glucocorticoid-induced eicosanoid synthesis and PLA2. Recent interest in the biological activity of this intriguing molecule has unraveled important functional attributes of Annexin 1 in a variety of inflammatory pathways, on cell proliferation machinery, in the regulation of cell death signaling, in phagocytic clearance of apoptosing cells, and most importantly in the process of carcinogenesis. Here we attempt to present a short review on these diverse biological activities of an interesting and important molecule, which could be a potential target for novel therapeutic intervention in a host of disease states.

Lack of annexin 1 results in an increase in corticotroph number in male but not female mice

Annexin 1 (ANXA1) is a member of the annexin family of phospholipid- and calcium-binding proteins with a well demonstrated role in early delayed (30 min to 3 h) inhibitory feedback of glucocorticoids in the pituitary. We have examined corticotrophs in wild-type and ANXA1 knockout mice to determine the effects of lack of ANXA1 in male and female animals. Anterior pituitary tissue from ANXA1 wild-type, heterozygote and null mice was fixed and examined (i) by confocal immunocytochemistry to determine the number of corticotrophs and (ii) by electron microscopy to examine the size, secretory granule population and secretory machinery of corticotrophs. No differences in these parameters were detected in female mice. In male ANXA1 null mice, there were approximately four-fold more corticotrophs than in wild-type animals. However, the corticotrophs in ANXA1 null mice were smaller and had reduced numbers of secretory granules (the reduction in granules paralleled the reduction in cell size). No differences in the numerical density of folliculo-stellate, gonadotroph, lactotroph or somatotroph cells were detected in male ANXA1 null mice. Plasma corticosterone, adrenocorticotrophic hormone (ACTH) and pituitary pro-opiomelanocortin mRNA were unchanged but pituitary ACTH content was increased in male ANXA1 null mice. Interleukin (IL)-6 pituitary content was significantly elevated in male and reduced in female ANXA1 null mice compared to wild-type. In conclusion, these data indicate that ANXA1 deficiency is associated with gender-specific changes in corticotroph number and structure, via direct actions of ANXA1 and/or indirect changes in factors such as IL-6.

The Clever Fetus: Responding to Inflammation to Minimize Lung Injury

Clinical and experimental information indicate that fetal exposure to inflammation can induce lung maturation. This inflammation may be chronic and indolent. We present clinical and experimental information that challenge assumptions about chorioamnionitis associated infection/inflammatory exposures to the fetus. We question the assumption that the fetal compartment is sterile, and that delivery is inevitable if chronic infection/inflammation is present. We demonstrate that the preterm fetus can develop a brisk and adequate inflammatory response, and the fetus also can quickly modulate and downregulate inflammation to prevent injury. The fetus at risk of early preterm delivery may be exposed to both chorioamnionitis and glucocorticoids. Both exposures can either increase or decrease fetal inflammatory responses depending on the timing of the exposures. The immunomodulatory ability of the fetus to fetal exposures remains an unexplored research field.

An overview of the effects of annexin 1 on cells involved in the inflammatory process

The concept of anti-inflammation is currently evolving with the definition of several endogenous inhibitory circuits that are important in the control of the host inflammatory response. Here we focus on one of these pathways, the annexin 1 (ANXA1) system. Originally identified as a 37 kDa glucocorticoid-inducible protein, ANXA1 has emerged over the last decade as an important endogenous modulator of inflammation. We review the pharmacological effects of ANXA1 on cell types involved in inflammation, from blood-borne leukocytes to resident cells. This review reveals that there is scope for more research, since most of the studies have so far focused on the effects of the protein and its peptido-mimetics on neutrophil recruitment and activation. However, many other cells central to inflammation, e.g. endothelial cells or mast cells, also express ANXA1: it is foreseen that a better definition of the role(s) of the endogenous protein in these cells will open the way to further pharmacological studies. We propose that a more systematic analysis of ANXA1 physio-pharmacology in cells involved in the host inflammatory reaction could aid in the design of novel anti-inflammatory therapeutics based on this endogenous mediator.

Kinase-dependent regulation of the secretion of thyrotrophin and luteinizing hormone by glucocorticoids and annexin 1 peptides

Our previous studies have identified a role for annexin 1 (ANXA1), a protein produced by the pituitary folliculostellate cells, as a paracrine/juxtacrine mediator of the acute regulatory effects of glucocorticoids on the release of adrenocorticotropic hormone and other pituitary hormones. In the present study, we focused on the secretion of thyroid stimulating hormone (TSH) and luteinizing hormone (LH) and used a battery of ANXA1-derived peptides to identify the key domains in the ANXA1 molecule that are critical to the inhibition of peptide release. In addition, as ANXA1 is a substrate for protein kinase C (PKC) and tyrosine kinase, we examined the roles of these kinases in the manifestation of the ANXA1-dependent inhibitory actions of dexamethasone on TSH and LH release. Dexamethasone suppressed the forskolin-induced release of TSH and LH from rat anterior pituitary tissue in vitro. Its effects were mimicked by human recombinant ANXA1 (hrANXA1) and a truncated protein, ANXA1(1-188). ANXA1(Ac2-26), also suppressed stimulated peptide release but it lacked both the potency and the efficacy of the parent protein. Shorter N-terminal ANXA1 sequences were without effect. The PKC inhibitor PKC(19-36) abolished the inhibitory actions of dexamethasone on the forskolin-evoked release of TSH and LH; it also attenuated the inhibitory actions of ANXA1(Ac2-26). Similar effects were produced by annexin 5 (ANXA5) which sequesters PKC in other systems. By contrast, the tyrosine kinase inhibitors, p60v-src (137-157) and genistein, had no effect on the secretion of TSH or LH alone or in the presence of forskolin and/or dexamethasone. Dexamethasone caused the translocation of a tyrosine-phosphorylated species of ANXA1 to the surface of pituitary cells. The total amount of ANXA1 exported from the cells in response to the steroid was unaffected by tyrosine kinase blockade. However, the degree of tyrosine-phosphorylation of the exported protein was markedly reduced by genistein. These results suggest that (i) the ANXA1-dependent inhibitory actions of dexamethasone on the release of TSH and LH require PKC and sequences in the N-terminal domain of ANXA1, but are independent of tyrosine kinase, and (ii) while dexamethasone induces the cellular exportation of a tyrosine-phosphorylated species of ANXA1, tyrosine phosphorylation per se is not critical to the steroid-induced passage of ANXA1 across the membrane.

Annexin A1 processing is associated with caspase-dependent apoptosis in BZR cells

Annexins are widely distributed and have been described in lung as well as in other cells and tissues. Annexin I (ANX AI) is a member of the calcium-dependent phospholipid binding protein family. Besides its anti-inflammatory function, ANX AI has been involved in several mechanisms such as the Erk repression pathway or apoptosis. To investigate the role of ANX AI on apoptosis in broncho-alveolar cells, we have constructed a plasmid containing the ANX AI full length cDNA. Transfected BZR cells displayed a higher level of both forms of ANX AI (37 and 33 kDa) as well as a decrease in cell viability (two-fold versus cells transfected with an empty vector). In order to analyse the endogenous ANX AI processing during stimulus-induced apoptosis, BZR cells were treated with a commonly used inducer, i.e. C2 ceramides. In these conditions, microscopic analysis revealed chromatin condensation in dying cells and the Bcl-2, Bcl-x(L)/Bax mRNA balance was altered. Caspase-3 is one of the key executioners of apoptosis, being responsible for the cleavage of many proteins such as the nuclear enzyme poly(ADP-ribose) polymerase (PARP). We demonstrate that caspase-3 was activated after 4 h treatment in the presence of ceramide leading to the cleavage of PARP. Dose-response experiments revealed that cell morphology and viability modifications following ceramide treatment were accompanied by an increase in endogenous ANX AI processing. Interestingly, in both ceramide and transfection experiments, the ANX AI cleaved form was enhanced whereas pre-treatment with the caspase inhibitor Z-VAD-fmk abolished ANX AI cleavage. In conclusion, this study demonstrates a complex regulatory role of caspase-dependent apoptosis where ANX AI is processed at the N-terminal region which could give susceptibility to apoptosis upon ceramide treatment.

Evidence for a role of the adenosine 5'-triphosphate-binding cassette transporter A1 in the externalization of annexin I from pituitary folliculo-stellate cells

Annexin 1 (ANXA1) has a well-demonstrated role in early delayed inhibitory feedback of glucocorticoids in the pituitary. ANXA1 is located in folliculo-stellate (FS) cells, and glucocorticoids act on these cells to externalize and stimulate the synthesis of ANXA1. However, ANXA1 lacks a signal sequence so the mechanism by which ANXA1 is externalized from FS cells was unknown and has been investigated. The ATP-binding cassette (ABC) transporters are a large group of transporters with varied roles that include the externalization of proteins. Glucocorticoid-induced externalization of ANXA1 from an FS cell line (TtT/GF) and rat anterior pituitary was blocked by glyburide, which inhibits ABC transporters. Glyburide also blocked the glucocorticoid inhibition of forskolin-stimulated ACTH release from pituitary tissue in vitro. RT-PCR revealed mRNA and Western blotting demonstrated protein for the ATP binding cassette A1 (ABCA1) transporter in mouse FS, TtT/GF, and A549 lung adenocarcinoma cells from which glucocorticoids also induce externalization of ANXA1. In TtT/GF cells, immunofluorescence labeling revealed a near total colocalization of cell surface ANXA1 and ABCA1. We conclude that ANXA1, which mediates the early delayed feedback of glucocorticoids in the anterior pituitary, is externalized from FS cells by an ABC transporter and that the ABCA1 transporter is a likely candidate.

Inhibition of cytosolic phospholipase A2 by annexin I. Specific interaction model and mapping of the interaction site

Annexins (ANXs) display regulatory functions in diverse cellular processes, including inflammation, immune suppression, and membrane fusion. However, the exact biological functions of ANXs still remain obscure. Inhibition of phospholipase A(2) (PLA(2)) by ANX-I, a 346-amino acid protein, has been observed in studies with various forms of PLA(2). "Substrate depletion" and "specific interaction" have been proposed for the mechanism of PLA(2) inhibition by ANX-I. Previously, we proposed a specific interaction model for inhibition of a 100-kDa porcine spleen cytosolic form of PLA(2) (cPLA(2)) by ANX-I (Kim, K. M., Kim, D. K., Park, Y. M., and Na, D. S. (1994) FEBS Lett. 343, 251-255). Herein, we present an analysis of the inhibition mechanism of cPLA(2) by ANX-I in detail using ANX-I and its deletion mutants. Deletion mutants were produced in Escherichia coli, and inhibition of cPLA(2) activity was determined. The deletion mutant ANX-I-(1-274), containing the N terminus to amino acid 274, exhibited no cPLA(2) inhibitory activity, whereas the deletion mutant ANX-I-(275-346), containing amino acid 275 to the C terminus, retained full activity. The protein-protein interaction between cPLA(2) and ANX-I was examined using the deletion mutants by immunoprecipitation and mammalian two-hybrid methods. Full-length ANX-I and ANX-I-(275-346) interacted with the calcium-dependent lipid-binding domain of cPLA(2). ANX-I-(1-274) did not interact with cPLA(2). Immunoprecipitation of A549 cell lysate with anti-ANX-I antibody resulted in coprecipitation of cPLA(2). These results are consistent with the specific interaction mechanism rather than the substrate depletion model. ANX-I may function as a negative regulator of cPLA(2) in cellular signal transduction.

Investigation into the involvement of phospholipases A(2) and MAP kinases in modulation of AA release and cell growth in A549 cells

1. We have investigated the contribution of specific PLA(2)s to eicosanoid release from A549 cells by using specific inhibitors of secretory PLA(2) (ONO-RS-82 and oleyloxyethylphosphocholine), cytosolic PLA(2) (AACOCF(3) and MAFP) and calcium-independent PLA(2) (HELSS, MAFP and PACOCF(3)). Similarly, by using specific inhibitors of p38 MAPK (SB 203580), ERK1/2 MAPK (Apigenin) and MEK1/2 (PD 98059) we have further evaluated potential pathways of AA release in this cell line. 2. ONO-RS-82 and oleyloxyethylphosphocholine had no significant effect on EGF or IL-1beta stimulated (3)H-AA or PGE(2) release or cell proliferation. AACOCF(3), HELSS, MAFP and PACOCF(3) significantly inhibited both EGF and IL-1beta stimulated (3)H-AA and PGE(2) release as well as cell proliferation. Apigenin and PD 98509 significantly inhibited both EGF and IL-1beta stimulated (3)H-AA and PGE(2) release and cell proliferation whereas, SB 203580 had no significant effect on EGF or IL-1beta stimulated (3)H-AA release, or cell proliferation but significantly suppressed EGF or IL-1beta stimulated PGE(2) release. 3. These results confirm that the liberation of AA release, generation of PGE(2) and cell proliferation is mediated largely through the actions of cPLA(2) whereas, sPLA(2) plays no significant role. We now also report a hitherto unsuspected contribution of iPLA(2) to this process and demonstrate that the stimulating action of EGF and IL-1beta in AA release and cell proliferation is mediated in part via a MEK and ERK-dependent pathway (but not through p38MAPK). We therefore propose that selective inhibitors of MEK and MAPK pathways may be useful in controlling AA release, eicosanoid production and cell proliferation.

Glucocorticoids act within minutes to inhibit recruitment of signalling factors to activated EGF receptors through a receptor-dependent, transcription-independent mechanism

Recruitment to activated tyrosine kinase growth factor receptors of Grb2 and p21(ras) leads to downstream activation of the kinases Raf, MAPK/Erk kinase (Mek) and, subsequently, extracellular signal-regulated kinase (Erk). Activated Erk phosphorylates specific serine residues within cytosolic phospholipase A(2) (PLA(2)), promoting enzyme translocation to membranes and facilitating liberation of arachidonic acid (AA). In the A549 human adenocarcinoma cell line dexamethasone inhibited epidermal growth factor (EGF)-stimulated cytosolic PLA(2) (cPLA(2)) activation and AA release by blocking the recruitment of Grb2 to the activated EGF receptor (EGF-R) through a glucocorticoid receptor (GR)-dependent (RU486-sensitive), transcription-independent (actinomycin-insensitive), mechanism. The dexamethasone-induced block of Grb2 recruitment was parallelled by changes in phosphorylation status and subcellular localization of lipocortin 1 (LC1) and an increase in the amount of the tyrosine phosphoprotein co-localized with EGF-R. Like dexamethasone, peptides containing E-Q-E-Y-V from the N-terminal domain of LC1 also blocked ligand-induced association of Grb2, p21(ras) and Raf. Our results point to an unsuspected rapid effect of glucocorticoids, mediated by occupation of GR but not by changes in gene transcription, which is brought about by competition between LC1 and Grb2 leading to a failure of recruitment off signalling factors to EGF-R

Lipocortin 1 (annexin 1) in patches associated with the membrane of a lung adenocarcinoma cell line and in the cell cytoplasm

Lipocortin 1 (annexin I) is a calcium- and phospholipid-binding annexin protein which can be externalised from cells despite the lack of a signal sequence. To determine its cellular distribution lipocortin 1 in A549 human lung adenocarcinoma cells was localised by light- and electron-microscopic immunocytochemistry and by cell fractionation and western blotting. Lipocortin 1 immunoreactivity is concentrated in prominent patches associated with the plasma membrane. The intensity of these patches varied with the confluence and duration of the culture and was not detectably diminished by an EDTA wash before fixation. Tubulin and cytokeratin 8 were colocalized with lipocortin 1 in the patches. Within the cells lipocortin 1 was distributed throughout the cytoplasm. Electron microscopy revealed prominent immunoreactivity along the plasma membrane with occasional large clusters of gold particles in contact with the membrane surface of the cells; within the cytoplasm the membrane of some vesicle/vacuole structures and some small electron-dense bodies was immunoreactive, but no immunogold particles were associated with the multilamellar bodies. Subcellular fractionation, extraction and western blotting showed that lipocortin 1 in the membrane pellet was present as two distinct fractions; one, intimately associated with the lipid bilayer, which behaved like an integral membrane protein and one loosely attached which behaved like a peripheral membrane protein. The results show that a substantial amounts of lipocortin 1 is concentrated in focal structures associated with and immediately beneath the plasma membrane. These might form part of the mechanism by which lipocortin 1 is released from the cells.

Inhibitory effect of peptides derived from the N-terminus of lipocortin 1 on arachidonic acid release and proliferation in the A549 cell line: identification of E-Q-E-Y-V as a crucial component

1. The ability of the glucocorticoid-induced protein lipocortin 1 (LC1) to inhibit arachidonic acid release and cell proliferation in A549 cells may be mimicked by a sequence taken from the N-terminal, LC1(13-25) (FIENEEQEYVQTV). We have now synthesized and tested for biological activity a library of 25 smaller peptides derived from this sequence. 2. Peptides were tested in two assays: A549 cells were prelabelled with tritiated arachidonic acid and thapsigargin (50 nM) and EGF (10 nM) used to stimulate the release of this fatty acid. Cell proliferation was determined by counting cell numbers following 3 day incubation with these peptides, or controls. 3. Many of the peptides were highly insoluble but could be more readily dissolved in aqueous solution in the presence of commercial liposomes or phosphatidyl serine (5 microM). Since neither of these agents alone had any effect on arachidonic acid release or cell proliferation, all peptides were tested in the presence of 5 microM phosphatidyl serine. Under these conditions LC1(13-25) was active in both assay systems with an IC40 of 40.7 and 57.0 microM respectively. 4. Deletion of amino acids from the C-terminus of the peptide progressively diminished (2-3 fold) the molar potency of LC1(13-25) in both assays: after the removal of Val22 biological activity was virtually undetectable or very weak (< 30% of LC1[13-25]). 5. Removal of amino acids from the N-terminus also lead to a progressive reduction (3-5 fold) in the molar potency of the peptides and biological activity became undetectable, or very weak, after the removal of Glu18. 6. All active peptides contained the core sequence EQEYV(Glu-Gln-Glu-Tyr-Val) which seems to represent a crucial component of the pharmacophore, although this sequence on its own was inactive and the shortest peptide with significant activity was LC1(18-25) (EQEYVQTV). 7. Methoxylation of Tyr21 abolished the ability of LC1(18-25) to inhibit cell proliferation and arachidonic acid release. A cyclized version of LC1(18-25) was also tested and found to be inactive. 8. LC1(18-25) (178 microM) inhibits cPLA2 activation in A549 cells as judged by a band-shift assay, whereas equimolar concentrations of an inactive peptide LC1(19-25) were without effect in this assay system. 9. Several possible mechanisms whereby these peptides act are discussed in the light of LC1 biology and of the effect of glucocorticoids on cell function.

Lipocortin 1 co-associates with cytokeratins 8 and 18 in A549 cells via the N-terminal domain

An affinity chromatography strategy was used to search for proteins in A549 cells which interact with the N-terminus of lipocortin 1 (annexin 1). Using the biologically active fragment Lc13-25 as the affinity ligand, two proteins of molecular weight (m.w.) 52 and 48kDa were extracted. Affinity blots of these proteins bound iodinated Lc13-25. Partial tryptic digests of these proteins were analysed by matrix assisted laser desorption mass spectrometry and found to display fragmentation patterns with a strong similarity to those of cytokeratin 8 and 18 respectively. Subsequent blotting with a panel of specific cytokeratin antibodies strongly supported the idea that the two proteins were cytokeratin 8 and cytokeratin 18. Cytokeratin 8 was isolated from A549 cells in intermediate filament (IF) preparations which were also found to contain lipocortin 1 as a potential intermediate filament associated protein (IFAP). This association persisted throughout cycles of IF assembly and disassembly. Dual-labelling immuno-histochemistry in A549 cells showed strong co-localization of lipocortin 1 and cytokeratin 8. The implications of this finding are discussed in the light of the biological activity and possible function of lipocortin 1.

Tamoxifen inhibits the release of arachidonic acid stimulated by thapsigargin in estrogen receptor-negative A549 cells

In pre-labelled A549 cells the tumour promoter thapsigargin (50 nM) stimulates the release of [5,6,8,9,11,12,14,15-3H(N)]-arachidonic acid (3H-AA) by ca. 300% above basal levels. A549 cells are estrogen receptor negative (ER-), yet this stimulation by thapsigargin is inhibited in a dose-dependent manner by a 3 h pre-treatment with the anti-estrogen tamoxifen (1-20 microM). Moreover, the presence of excess (100 microM) estradiol does not reverse this effect of tamoxifen. Thapsigargin stimulated 3H-AA release is not inhibited over the same concentration range by 4 hydroxy-tamoxifen nor by the steroidal anti-estrogen ICI 164384. However, the steroidal anti-estrogen ICI 182780 inhibits thapsigargin stimulated 3H-AA release in a similar manner to tamoxifen and this effect is also not reversed by the presence of excess estradiol. Stimulation of 3H-AA release by EGF (10 nM), IL-1beta (1 ng ml-1) and bradykinin (100 nM) was unaffected by these concentrations of tamoxifen. Ionomycin (10 microM) stimulates 3H-AA release by ca. 700% and A23187 (10 microM) by ca. 300% above basal levels. Pre-treatment with tamoxifen (1-20 microM) inhibits 3H-AA release stimulated by both these agents and again the presence of excess estradiol does not reverse this effect. Unlike the effects of glucocorticoids on 3H-AA release in A549 cells the effects of tamoxifen are not reversed by neutralizing anti-bodies to lipocortin 1. Arachidonic acid release is central to cell proliferation in A549 cells and we propose that this action of tamoxifen could explain the anti-proliferative effect seen in these cells and could have important implications for control of cell proliferation of ER- cells in general.

In vivo modulation of annexins I, II and V expression by thyroxine and methylthiouracil

Regulation of annexin concentration and localization were investigated in thyroid tissues of hypothyroid [methylthiouracil (MeSur) treatment], euthyroid (control) and hyperthyroid [thyroxine (T4) treatment] rats. A low level of circulating thyroid hormones induces a decrease of total thyroid calcium-binding protein concentration when compared with the concentration in unstimulated animals. Conversely, concentrations of annexins I, II and V increase. The accumulation of these proteins in two subcellular compartments (cytosolic and particulate fractions) can be reversed by addition of thyroid hormones. The finding of a specific increase in annexins concentration in thyroid-hormone-deficient rats, with a general decrease of the total calcium-binding protein content points to a very important role of these proteins in the cells. Furthermore, hyperthyroidisnt gives opposite results. To investigate the transduction pathway of annexins I-, II- and V-induced biosynthesis by thyroid hormones in thyroid glands, we used cultured pig thyroid cells as in vitro model system. In previous work [16], we have shown that annexin concentrations and localization are under TSH control via the adenylate cyclase pathway. In the presence of MeSur (in the culture medium), the protein-binding iodine remains low, indicative of weak thyroid hormone synthesis (data not shown) and that the annexins content is unchanged. These results suggest that, in thyroid tissue, an indirect mechanism links thyroid hormones to annexin expressions via the TSH feed-back loop, and excludes autocrine regulation.

The hepatocyte growth factor receptor kinase-mediated phosphorylation of lipocortin-1 transduces the proliferating signal of the hepatocyte growth factor

Hepatocyte growth factor (HGF), which is identical to scatter factor (SF) through coupling to its receptor the product of c-met oncogene, was found to induce proliferation of A549 lung carcinoma cell line, accompanied by release of prostaglandin E2 (PGE2). This activity was sensitive to 0.1-100 microM indomethacin and to 5-50 nM of verapamil. Lipocortin-1, a dexamethasone-inducible inhibitor of phospholipase A2, was shown to be phosphorylated on tyrosine 10 min upon addition of HGF and to translocate to the membrane fraction for up to 6 h upon ligand stimulation. Lipocortin-1 was found to associate in vivo with the HGF receptor species, and this association was independent of the phosphorylation state of the beta-subunit of the HGF receptor (p145betaMET. Immobilized HGF receptor kinase species associated and phosphorylated in vitro lipocortin-1, thus providing evidence that lipocortin-1 is directly phosphorylated by the p145betaMET. Incubation of A549 cells with antisense 21-mer lipocortin-1 oligonucleotides reduced the synthesis and the HGF-stimulated phosphorylation of lipocortin-1 as well as the HGF-stimulated cell proliferation. In processes where the HGF receptor tyrosine kinase is activated, phosphorylation of lipocortin-1 may function as a "signal amplifier" promoting the release of intercellular messengers (PGE2) with pluripotent roles in cell proliferation, chemotaxis, and vascular remodeling.

Lipocortin 1 and the control of cPLA2 activity in A549 cells. Glucocorticoids block EGF stimulation of cPLA2 phosphorylation

Epidermal growth factor (EGF) rapidly stimulates the release of arachidonic acid in A549 cells by a mechanism that is sensitive to pertussis toxin [1]. We show that EGF treatment of A549 cells stimulates phosphorylation of cytosolic phospholipase A2 (cPLA2) through a mechanism that is similarly inhibited by pertussis toxin. The level of cPLA2 expression is, apparently, not changed during this period. Pretreatment of cells with dexamethasone (10-100 nM) for 3 hr prevents this activation of cPLA2 by EFG, without changing the level of cPLA21 expression. The effect of dexamethasone is reversed in the presence of the neutralizing antilipocortin Mab 1A but not by the nonneutralizing antilipocortin 1 control Mab 1B. This strongly suggests that lipocortin 1 mediates the effect of dexamethasone by inhibiting activation of cPLA2. This concept is supported by the fact that a peptide Lc13-25 (10-200 micrograms/mL), derived from the N-terminus of lipocortin 1, also inhibits activation of cPLA2 by EGF in these cells.

Lipocortin-1 and the control of arachidonic acid release in cell signalling. Glucocorticoids (changed from glucorticoids) inhibit G protein-dependent activation of cPLA2 activity

In pre-labelled A549 cells epidermal growth factor (EGF) (10 nM) stimulates the release of [5,6,8,9,11,12,14,15-3H(N)]-arachidonic acid (3H-AA) by approximately 70%. Increasing Ca2+i with thapsigargin (50 nM) stimulates 3H-AA release by approximately 120%. However, the combined use of these two agents results in a synergistic stimulation of 3H-AA release by over 700%. The EGF stimulated release is sensitive to pertussis toxin (10 ng/mL) and guanosine 5'-O-(2-thiodiphosphate) suggesting a G protein-mediated event. This is supported by the fact that the G protein activators AlF-4 and guanosine 5'-O-(2-thiotriphosphate) both stimulate 3H-AA release. The stimulation of 3H-AA release by both EGF or direct G protein activation is completely blocked following pre-treatment for 3 hr with 1 nM dexamethasone. This effect is reversed with a neutralizing antibody to lipocortin-1 (1 microgram/mL) suggesting that this protein mediates the inhibitory effects of glucocorticoids on agonist activated 3H-AA release. Thapsigargin stimulation of 3H-AA release is insensitive to dexamethasone treatment. A peptide fragment from the N-terminus of lipocortin-1-Lc13-25 (20-200 micrograms/mL) mimics the effect of glucocorticoid in suppressing both EGF and G protein activated 3H-AA release. A peptide with Me-Tyr substituting Tyr21 is much reduced in activity suggesting that the presence of this residue is essential. As peptide Lc13-25 is not derived from the Ca2+/phospholipid binding domain of the native protein then sequestration of phospholipid substrate for PLA2 remains an unlikely mechanism of action for this peptide.

Expression and activation of erbB-2 and epidermal growth factor receptor in lung adenocarcinomas

ErbB-2 and EGFR (epidermal growth factor receptor) are expressed in lung adenocarcinomas and associated with a poor prognosis. Immunocytochemical analysis revealed erbB-2 and EGFR coexperession as a characteristic feature of most lung adenocarcinomas, and at levels of receptor expression present in bronchial epithelial cells. In primary lung tumours and cell lines, erbB-2 detected using Western blot analysis demonstrated low-level phosphotyrosine staining of the 185 kDa band, as compared with breast cancer cell lines. A549 and A427 lung adenocarcinoma cells treated with neu differentiation factor (NDF) showed increased erbB-2 phosphotyrosine staining, but to a much lesser extent than breast cancer cells. The lung cells were examined for expression of the potential autocrine growth factors NDF and transforming growth factor alpha (TGF-alpha) by Northern blot analysis. Both NDF and TFG-alpha mRNA were abundantly expressed in the A549 cells. NDF mRNA was highest during active cell proliferation and decreased in confluent cells or after treatment with the growth-inhibitory steroid dexamethasone. Primary tumours and cell lines expressed EGFR, showing higher basal level phosphotyrosine staining than erbB-2. Treatment with NDF and EGF (epidermal growth factor) stimulated cell growth, and in A549 cells the presence of both factors provided an additive increase in cell growth. The growth stimulus that ligand-activated erbB-2 and EGFR provides to lung adenocarcinoma cells may establish a background of continued cell proliferation over which other critical transforming events may occur.

Induction of cyclo-oxygenase-2 by cytokines in human pulmonary epithelial cells: regulation by dexamethasone

1. Cyclo-oxygenase metabolizes arachidonic acid to prostaglandin H2 (PGH2) and exists in at least two isoforms. Cyclo-oxygenase-1 (COX-1) is expressed constitutively whereas COX-2 is induced by lipopolysaccharide (LPS) and some cytokines in vitro and at the site of inflammation in vivo. Epithelial cells may be an important source of prostaglandins in the airways and we have, therefore, investigated the expression of COX-1 or COX-2 isoforms in primary cultures of human airway epithelial cells or in a human pulmonary epithelial cell line (A549). 2. COX-1 or COX-2 protein was measured by western blot analysis using specific antibodies to COX-2 and selective antibodies to COX-1. The activity of COX was assessed by the conversion of either endogenous or exogenous arachidonic acid to four metabolites, PGE2, PGF2 alpha, thromboxane B2 or 6-oxo PGF1 alpha measured by radioimmunoassay. Thus, COX-1 or COX-2 activity was measured under two conditions; initially the accumulation of the COX metabolites formed from endogenous arachidonic acid was measured after 24 h. In other experiments designed to measure COX activity directly, cells were treated with cytokines for 12h before fresh culture medium was added containing exogenous arachidonic acid (30 microM) for 15 min after which COX metabolites were measured. 3. Untreated primary cells or A549 cells contained low amounts of COX-1 or COX-2 protein. Bacterial LPS (1 micro g ml-1 for 24 h) induced COX-2 protein in the primary cells, a process which was enhanced by interferon-gamma, with no further increase in the presence of a mixture of cytokines (interleukin-1 beta, tumour necrosis factor-alpha and interferon-gamma, 10 ng ml-1 for all). In contrast, A549 cells contained only low levels of COX-2 protein after exposure to LPS or LPS plus interferon-y, but contained large amounts of COX-2 protein after exposure to the mixture of cytokines.4. Untreated human pulmonary primary cells or A549 cells released low levels of all COX metabolites measured over a 24 h incubation period. This release was enhanced by treatment of either cell type with the mixture of cytokines (interleukin-1 beta , tumour necrosis factors- and interferon-gamma, 10 ng ml-1 for all).PGE2 was the principal COX metabolite released by cytokine-activated epithelial cells. The release of PGE2 induced by cytokines occurred after a lag period of more than 6 h.5. The glucocorticosteroid, dexamethasone (1 micro M; 30 min prior to cytokines) completely suppressed the cytokine-induced expression of COX-2 protein and activity in both primary cells and A549 cells.6. In experiments where COX-2 activity was supported by endogenous stores of arachidonic acid,treatment of A549 cells with interleukin-l beta but not tumour necrosis factor a or interferon-gamma alone caused a similar release of PGE 2 to that seen when the cytokines were given in combination. However, both interleukin-l beta and necrosis factor- alone produced similar increases in COX-2 activity (measured in the presence of exogenous arachidonic acid) as seen when the mixture of interleukin-l beta, tumour necrosis factor- alpha and interferon-gamma were used to stimulate the cells.7. These findings show that COX-2 expression correlates with the exaggerated release of prostaglandins from cytokine-activated human pulmonary epithelial cells and that the induction of the enzyme is suppressed by a glucocorticosteroid. These findings may be relevant to inflammatory diseases of the lung, such as asthma.

Tamoxifen inhibits growth of oestrogen receptor-negative A549 cells

The non-steroidal anti-oestrogen tamoxifen inhibits proliferation of the A549 human lung adenocarcinoma cell line (EC50 congruent to 10 nM) yet there was no evidence of oestrogen receptor expression as determined by ligand binding assay and northern blotting. 17-beta-Oestradiol had no effect on A549 cell proliferation (1 pM-1 microM) and moreover a 100-fold excess failed to reverse the effect of 10 nM tamoxifen as did a 100-fold excess of the steroidal anti-oestrogens ICI 164384 and ICI 182780. However, 4-hydroxytamoxifen which had no significant effect on A549 cell growth (1 pM-1 microM) completely antagonized the effect of 10 nM tamoxifen when used at a 100-fold excess. In the presence of oleic acid and stearic acid (10 microM) the growth inhibitory effect of tamoxifen in A549 cells was greatly enhanced, unlike effects mediated by the anti-oestrogen binding protein described in other cells where these fatty acids had no effect. These results indicate the presence of a unique and highly sensitive mechanism in A549 cells whereby concentrations of tamoxifen relevant to classical receptor binding can inhibit cell growth in the absence of the oestrogen receptor.

Phospholipase A2-induced stimulation of A549 lung adenocarcinoma cell line proliferation

Phospholipase A2 (PLA2) activity was found in the cytosolic fraction of the A549 human lung adenocarcinoma line. This PLA2 had a molecular mass of approximately 70 kDa as assessed by gel filtration chromatography and required submicromolar concentrations of calcium concentrations for optimal activity. These characteristics are consistent with the cytosolic PLA2 recently reported in other cell types, such as U937 cells. We have now demonstrated that A549 cell PLA2 (PLA2 activity: 1 unit/ml) partially purified by gel filtration stimulated proliferation of A549 cells by 50% after 3 days of culture. Similarly, porcine pancreatic PLA2 (0.1 unit/ml) also promoted proliferation of A549 cell cultures by 42%. Furthermore, A549 cell PLA2 stimulated prostaglandin E2 release (approx. 7-fold increase). Both PLA2s lost activity when treated with p-bromophenacyl bromide. Neither porcine pancreatic PLA2 nor A549 cell PLA2 reversed the inhibitory activities of dexamethasone and indomethacin on cell growth. These results suggest that both of these PLA2s stimulate A549 cell growth, and that this is likely to be mediated by increased eicosanoid production.