Systemic Bevacizumab for Treatment of Respiratory Papillomatosis: International Consensus Statement.

OBJECTIVES/HYPOTHESIS: The purpose of this study is to develop consensus on key points that would support the use of systemic bevacizumab for the treatment of recurrent respiratory papillomatosis (RRP), and to provide preliminary guidance surrounding the use of this treatment modality. STUDY DESIGN: Delphi method-based survey series. METHODS: A multidisciplinary, multi-institutional panel of physicians with experience using systemic bevacizumab for the treatment of RRP was established. The Delphi method was used to identify and obtain consensus on characteristics associated with systemic bevacizumab use across five domains: 1) patient characteristics; 2) disease characteristics; 3) treating center characteristics; 4) prior treatment characteristics; and 5) prior work-up. RESULTS: The international panel was composed of 70 experts from 12 countries, representing pediatric and adult otolaryngology, hematology/oncology, infectious diseases, pediatric surgery, family medicine, and epidemiology. A total of 189 items were identified, of which consensus was achieved on Patient Characteristics (9), Disease Characteristics (10), Treatment Center Characteristics (22), and Prior Workup Characteristics (18). CONCLUSION: This consensus statement provides a useful starting point for clinicians and centers hoping to offer systemic bevacizumab for RRP and may serve as a framework to assess the components of practices and centers currently using this therapy. We hope to provide a strategy to offer the treatment and also to provide a springboard for bevacizumab's use in combination with other RRP treatment protocols. Standardized delivery systems may facilitate research efforts and provide dosing regimens to help shape best-practice applications of systemic bevacizumab for patients with early-onset or less-severe disease phenotypes. LEVEL OF EVIDENCE: 5 Laryngoscope, 131:E1941-E1949, 2021.

Biallelic loss-of-function WNT5A mutations in an infant with severe and atypical manifestations of Robinow syndrome.

Robinow syndrome (RS) is a well-recognized Mendelian disorder known to demonstrate both autosomal dominant and autosomal recessive inheritance. Typical manifestations include short stature, characteristic facies, and skeletal anomalies. Recessive inheritance has been associated with mutations in ROR2 while dominant inheritance has been observed for mutations in WNT5A, DVL1, and DVL3. Through trio whole genome sequencing, we identified a homozygous frameshifting single nucleotide deletion in WNT5A in a previously reported, deceased infant with a unique constellation of features comprising a 46,XY disorder of sex development with multiple congenital malformations including congenital diaphragmatic hernia, ambiguous genitalia, dysmorphic facies, shortened long bones, adactyly, and ventricular septal defect. The parents, who are both heterozygous for the deletion, appear clinically unaffected. In conjunction with published observations of Wnt5a double knockout mice, we provide evidence for the possibility of autosomal recessive inheritance in association with WNT5A loss-of-function mutations in RS.

High human herpesvirus 6 viral load in pediatric allogeneic hematopoietic stem cell transplant patients is associated with detection in end organs and high mortality.

Human Herpes Virus 6 (HHV-6) reactivation occurs in approximately half of patients following allogeneic hematopoietic stem cell transplant (HSCT). While encephalitis and delayed engraftment are well-documented complications of HHV-6 following HSCT, the extent to which HHV-6 viremia causes disease in children is controversial. We performed a retrospective review of HHV-6 reactivation and possible manifestations in pediatric allogeneic HSCT patients at a single institution. Of 89 children and young adults who underwent allogeneic HSCT over a three-and-a-half-year period, 34 patients reactivated HHV-6 early post-transplant. Unrelated donor stem cell source and lack of antiviral prophylaxis were risk factors for the development of HHV-6 viremia. Viremia correlated with the presence of acute graft-versus-host disease, but not chronic graft-versus-host disease. We identified two subgroups within the viremic patients-a high-risk viremic and tissue-positive group that reactivated HHV-6 and had suspected end-organ disease and a low-risk viremic but asymptomatic group that reactivated HHV-6 but did not exhibit symptoms or signs of end-organ disease. Peak viral load was found to be strongly associated with mortality. Prospective studies in larger numbers of patients are needed to further investigate the role of HHV-6 in causing symptomatic end-organ disease as well as the association of viral load with mortality.

Mast cells mediate early neutrophil recruitment and exhibit anti-inflammatory properties via the formyl peptide receptor 2/lipoxin A4 receptor.

BACKGROUND AND PURPOSE: In recent years, studies have focused on the resolution of inflammation, which can be achieved by endogenous anti-inflammatory agonists such as Annexin A1 (AnxA1). Here, we investigated the effects of mast cells (MCs) on early LPS-induced neutrophil recruitment and the involvement of the AnxA1-formyl peptide receptor 2/ALX (FPR2/ALX or lipoxin A4 receptor) pathway. EXPERIMENTAL APPROACH: Intravital microscopy (IVM) was used to visualize and quantify the effects of LPS (10 µg per mouse i.p.) on murine mesenteric cellular interactions. Furthermore, the role that MCs play in these inflammatory responses was determined in vivo and in vitro, and effects of AnxA1 mimetic peptide Ac2-26 were assessed. KEY RESULTS: LPS increased both neutrophil endothelial cell interactions within the mesenteric microcirculation and MC activation (determined by IVM and ruthenium red dye uptake), which in turn lead to the early stages of neutrophil recruitment. MC recruitment of neutrophils could be blocked by preventing the pro-inflammatory activation (using cromolyn sodium) or enhancing an anti-inflammatory phenotype (using Ac2-26) in MCs. Furthermore, MCs induced neutrophil migration in vitro, and MC stabilization enhanced the release of AnxA1 from neutrophils. Pharmacological approaches (such as the administration of FPR pan-antagonist Boc2, or the FPR2/ALX antagonist WRW4) revealed neutrophil FPR2/ALX to be important in this process. CONCLUSIONS AND IMPLICATIONS: Data presented here provide evidence for a role of MCs, which are ideally positioned in close proximity to the vasculature, to act as sentinel cells in neutrophil extravasation and resolution of inflammation via the AnxA1-FPR2/ALX pathway.

Targeting the annexin 1-formyl peptide receptor 2/ALX pathway affords protection against bacterial LPS-induced pathologic changes in the murine adrenal cortex.

Hypothalamo-pituitary-adrenocortical dysfunction contributes to morbidity and mortality in a high proportion of patients with sepsis. Here, we provide new insights into the underlying adrenal pathology. Using a murine model of endotoxemia (LPS injection), we demonstrate that adrenal insufficiency is triggered early in the disease. LPS induced a local inflammatory response in the adrenal gland within 4 hours of administration, coupled with increased expression of mRNAs for annexin A1 (AnxA1) and the formyl peptide receptors [(Fprs) 1, 2, and 3], a loss of lipid droplets in cortical cells (index of availability of cholesterol, the substrate for steroidogenesis), and a failure to mount a steroidogenic response to ACTH. Deletion of AnxA1 or Fpr2/3 in mice prevented lipid droplet loss, but not leukocyte infiltration. LPS increased adrenal myeloid differentiation primary response gene 88 and TLR2 mRNA expression, but not lymphocyte antigen 96 or TLR4. By contrast, neutrophil depletion prevented leukocyte infiltration and increased AnxA1, Fpr1, and Fpr3 mRNAs but had no impact on lipid droplet loss. Our novel data demonstrate that AnxA1 and Fpr2 have a critical role in the manifestation of adrenal insufficiency in this model, through regulation of cholesterol ester storage, suggesting that pharmacologic interventions targeting the AnxA1/FPR/ALX pathway may provide a new approach for the maintenance of adrenal steroidogenesis in sepsis.

Leptin fails to blunt the lipopolysaccharide-induced activation of the hypothalamic-pituitary-adrenal axis in rats.

Obesity is a risk factor for sepsis morbidity and mortality, whereas the hypothalamic-pituitary-adrenal (HPA) axis plays a protective role in the body's defence against sepsis. Sepsis induces a profound systemic immune response and cytokines serve as excellent markers for sepsis as they act as mediators of the immune response. Evidence suggests that the adipokine leptin may play a pathogenic role in sepsis. Mouse endotoxaemic models present with elevated leptin levels and exogenously added leptin increased mortality whereas human septic patients have elevated circulating levels of the soluble leptin receptor (Ob-Re). Evidence suggests that leptin can inhibit the regulation of the HPA axis. Thus, leptin may suppress the HPA axis, impairing its protective role in sepsis. We hypothesised that leptin would attenuate the HPA axis response to sepsis. We investigated the direct effects of an i.p. injection of 2 mg/kg leptin on the HPA axis response to intraperitoneally injected 25 µg/kg lipopolysaccharide (LPS) in the male Wistar rat. We found that LPS potently activated the HPA axis, as shown by significantly increased plasma stress hormones, ACTH and corticosterone, and increased plasma interleukin 1ß (IL1ß) levels, 2 h after administration. Pre-treatment with leptin, 2 h before LPS administration, did not influence the HPA axis response to LPS. In turn, LPS did not affect plasma leptin levels. Our findings suggest that leptin does not influence HPA function or IL1ß secretion in a rat model of LPS-induced sepsis, and thus that leptin is unlikely to be involved in the acute-phase endocrine response to bacterial infection in rats.

Role and interactions of annexin A1 and oestrogens in the manifestation of sexual dimorphisms in cerebral and systemic inflammation.

BACKGROUND AND PURPOSE: Gender differences in inflammation are well described, with females often showing more robust, oestrogen-associated responses. Here, we investigated the influence of gender, oestrogen and the anti-inflammatory protein annexin A1 (AnxA1) on lipopolysaccharide (LPS)-induced leukocyte-endothelial cell interactions in murine cerebral and mesenteric microvascular beds. EXPERIMENTAL APPROACH: Intravital microscopy was used to visualize and quantify the effects of LPS (10 µg·per mouse i.p.) on leukocyte-endothelial interactions in male and female wild-type (WT) mice. The effects of ovariectomy ± oestrogen replacement were examined in WT and AnxA1-null (AnxA1(-/-) ) female mice. KEY RESULTS: LPS increased leukocyte adherence in the cerebral and mesenteric beds of both male and female WT mice; females showed exacerbated responses in the brain versus males, but not the mesentery. Ovariectomy further enhanced LPS-induced adhesion in the brain but not the mesentery; its effects were reversed by oestrogen treatment. OVX AnxA1(-/-) mice also showed exaggerated adhesive responses to LPS in the brain. However, these were unresponsive to ovariectomy and, paradoxically, responded to oestrogen with a pronounced increase in basal and LPS-induced leukocyte adhesion in the cerebrovasculature. CONCLUSIONS AND IMPLICATIONS: Our data confirm the fundamental role of AnxA1 in limiting the inflammatory response in the central and peripheral microvasculature. They also (i) show that oestrogen acts via an AnxA1-dependent mechanism to protect the cerebral, but not the mesenteric, vasculature from the damaging effects of LPS and (ii) reveal a paradoxical and potentially toxic effect of the steroid in potentiating the central response to LPS in the absence of AnxA1.

Leukocyte recruitment in the brain in sepsis: involvement of the annexin 1-FPR2/ALX anti-inflammatory system.

Unregulated inflammation underlies many diseases, including sepsis. Much interest lies in targeting anti-inflammatory mechanisms to develop new treatments. One such target is the anti-inflammatory protein annexin A1 (AnxA1) and its receptor, FPR2/ALX. Using intravital videomicroscopy, we investigated the role of AnxA1 and FPR2/ALX in a murine model of endotoxin-induced cerebral inflammation [intraperitoneal injection of lipopolysaccharide (LPS)]. An inflammatory response was confirmed by elevations in proinflammatory serum cytokines, increased cerebrovascular permeability, elevation in brain myeloperoxidase, and increased leukocyte rolling and adhesion in cerebral venules of wild-type (WT) mice, which were further exacerbated in AnxA1-null mice. mRNA expression of TLR2, TLR4, MyD-88, and Ly96 was also assessed. The AnxA1-mimetic peptide, AnxA1(Ac2-26) (100 µg/mouse, ∼33 µmol) mitigated LPS-induced leukocyte adhesion in WT and AnxA1-null animals without affecting leukocyte rolling, in comparison to saline control. AnxA1(Ac2-26) effects were attenuated by Boc2 (pan-FPR antagonist, 10 µg/mouse, ∼12 nmol), and by minocycline (2.25 mg/mouse, ∼6.3 nmol). The nonselective Fpr agonists, fMLP (6 µg/mouse, ∼17 nmol) and AnxA1(Ac2-26), and the Fpr2-selective agonist ATLa (5 µg/mouse, ∼11 nmol) were without effect in Fpr2/3(-/-) mice. In summary, our novel results demonstrate that the AnxA1/FPR2 system has an important role in effecting the resolution of cerebral inflammation in sepsis and may, therefore, provide a novel therapeutic target.

Integrating pharmacology and clinical pharmacology in universities.

Continuing development of safe and effective new medicines is critically important for global health, social prosperity and the economy. The drug discovery-development pipeline depends critically on close partnerships between scientists and clinicians and on educational programmes that ensure that the pharmacological workforce, in its broadest sense, is fit for purpose. Here I consider factors that have influenced the development of basic and clinical pharmacology in UK universities over the past 40 years and discuss ways in which basic pharmacologists, clinical pharmacologists and scientists from different disciplines can work together effectively, while retaining their professional identities and fostering developments in their disciplines. Specifically, I propose the establishment of Institutes of Drug Discovery and Development, whose activities could include development and implementation of a translational pharmacology research strategy, drawing on the collective expertise of the membership and the university as whole; provision of a forum for regular seminars and symposia to promote the discipline, encourage collaboration and develop a cohesive community; provision of a research advisory service, covering, for example, data management, applications for ethics permission, clinical trials design, statistics and regulatory affairs; liaison with potential funders and leadership of major funding bids, including funding for doctoral training; provision of advice on intellectual property protection and the commercialization of research; liaison with corporate partners to facilitate collaboration, knowledge transfer and effective translation; and leadership of undergraduate and postgraduate education in basic and clinical pharmacology and related sciences for medical and science students, including continuing professional development and transferable skills.

Alternative activation in systemic juvenile idiopathic arthritis monocytes.

Systemic juvenile idiopathic arthritis (SJIA) is a chronic autoinflammatory condition. The association with macrophage activation syndrome, and the therapeutic efficacy of inhibiting monocyte-derived cytokines, has implicated these cells in SJIA pathogenesis. To characterize the activation state (classical/M1 vs. alternative/M2) of SJIA monocytes, we immunophenotyped monocytes using several approaches. Monocyte transcripts were analyzed by microarray and quantitative PCR. Surface proteins were measured at the single cell level using flow cytometry. Cytokine production was evaluated by intracellular staining and ELISA. CD14(++)CD16(-) and CD14(+)CD16(+) monocyte subsets are activated in SJIA. A mixed M1/M2 activation phenotype is apparent at the single cell level, especially during flare. Consistent with an M2 phenotype, SJIA monocytes produce IL-1ß after LPS exposure, but do not secrete it. Despite the inflammatory nature of active SJIA, circulating monocytes demonstrate significant anti-inflammatory features. The persistence of some of these phenotypes during clinically inactive disease argues that this state reflects compensated inflammation.

Anti-inflammatory role of the murine formyl-peptide receptor 2: ligand-specific effects on leukocyte responses and experimental inflammation.

The human formyl-peptide receptor (FPR)-2 is a G protein-coupled receptor that transduces signals from lipoxin A(4), annexin A1, and serum amyloid A (SAA) to regulate inflammation. In this study, we report the creation of a novel mouse colony in which the murine FprL1 FPR2 homologue, Fpr2, has been deleted and describe its use to explore the biology of this receptor. Deletion of murine fpr2 was verified by Southern blot analysis and PCR, and the functional absence of the G protein-coupled receptor was confirmed by radioligand binding assays. In vitro, Fpr2(-/-) macrophages had a diminished response to formyl-Met-Leu-Phe itself and did not respond to SAA-induced chemotaxis. ERK phosphorylation triggered by SAA was unchanged, but that induced by the annexin A1-derived peptide Ac2-26 or other Fpr2 ligands, such as W-peptide and compound 43, was attenuated markedly. In vivo, the antimigratory properties of compound 43, lipoxin A(4), annexin A1, and dexamethasone were reduced notably in Fpr2(-/-) mice compared with those in wild-type littermates. In contrast, SAA stimulated neutrophil recruitment, but the promigratory effect was lost following Fpr2 deletion. Inflammation was more marked in Fpr2(-/-) mice, with a pronounced increase in cell adherence and emigration in the mesenteric microcirculation after an ischemia-reperfusion insult and an augmented acute response to carrageenan-induced paw edema, compared with that in wild-type controls. Finally, Fpr2(-/-) mice exhibited higher sensitivity to arthrogenic serum and were completely unable to resolve this chronic pathology. We conclude that Fpr2 is an anti-inflammatory receptor that serves varied regulatory functions during the host defense response. These data support the development of Fpr2 agonists as novel anti-inflammatory therapeutics.

Annexin A1 regulates hormone exocytosis through a mechanism involving actin reorganization.

The glucocorticoid-regulated protein annexin A1 is a potent inhibitor of hormone exocytosis in the neuroendocrine system, acting in a paracrine/juxtacrine manner. The signaling mechanism employed by annexin A1 in this process is uncertain, although we have recently presented evidence for a role of the formyl peptide receptor in vivo. We sought to characterize the mechanism of action of annexin A1 on exocytosis using the release of adrenocorticotrophin from the corticotroph-like cell line AtT20 as an in vitro model system. Through the comparison of adrenocorticotrophin release from cells expressing either wild-type annexin A1 or mutant forms, we show a critical involvement of phosphorylation on serine 27 and 45 in the translocation of the protein to the membrane and its inhibitory action on exocytosis. Moreover, we show, for the first time, that annexin A1-dependent inhibition of adrenocorticotrophin release involves the enhancement of actin polymerization to prevent exocytosis via formyl peptide receptor and Rho kinase signaling pathways. This finding has significant implications for the inhibitory actions of annexin A1 on exocytosis in other endocrine and immune contexts.

Annexin A1 and the formyl peptide receptor family: neuroendocrine and metabolic aspects.

Annexin A1 (ANXA1, formerly termed lipocortin 1 or macrocortin) is an important protein mediator of the feedback actions of glucocorticoids within the hypothalamo-pituitary-adrenocortical (HPA) axis. Here we consider the mechanisms by which ANXA1 exerts these actions, with particular reference to the potential role of the formyl peptide receptors (FPRs), a family of G-protein-coupled receptors which has only very recently been implicated in the regulation of neuroendocrine function. In addition, we discuss evidence that ANXA1 contributes to the regulation of other aspects of endocrine and metabolic function and to the aetiology of sexual dimorphisms.

Annexin A1 in the brain--undiscovered roles?

Annexin A1 (ANXA1) is an endogenous protein known to have potent anti-inflammatory properties in the peripheral system. It has also been detected in the brain, but its function there is still ambiguous. In this review, we have, for the first time, collated the evidence currently available on the function of ANXA1 in the brain and have proposed several possible mechanisms by which it exerts a neuroprotective or anti-neuroinflammatory function. We suggest that ANXA1, its small peptide mimetics and its receptors might be exciting new therapeutic targets in the management of a wide range of neuroinflammatory diseases, including stroke and neurodegenerative conditions.

Membrane-induced folding and structure of membrane-bound annexin A1 N-terminal peptides: implications for annexin-induced membrane aggregation.

Annexins constitute a family of calcium-dependent membrane-binding proteins and can be classified into two groups, depending on the length of the N-terminal domain unique for each individual annexin. The N-terminal domain of annexin A1 can adopt an alpha-helical conformation and has been implicated in mediating the membrane aggregation behavior of this protein. Although the calcium-independent interaction of the annexin A1 N-terminal domain has been known for some time, there was no structural information about the membrane interaction of this secondary membrane-binding site of annexin A1. This study used circular dichroism spectroscopy to show that a rat annexin A1 N-terminal peptide possesses random coil structure in aqueous buffer but an alpha-helical structure in the presence of small unilamellar vesicles. The binding of peptides to membranes was confirmed by surface pressure (Langmuir film balance) measurements using phosphatidylcholine/phosphatidylserine monolayers, which show a significant increase after injection of rat annexin A1 N-terminal peptides. Lamellar neutron diffraction with human and rat annexin A1 N-terminal peptides reveals an intercalation of the helical peptides with the phospholipid bilayer, with the helix axis lying parallel to the surface of membrane. Our findings confirm that phospholipid membranes assist the folding of the N-terminal peptides into alpha-helical structures and that this conformation enables favorable direct interactions with the membrane. The results are consistent with the hypothesis that the N-terminal domain of annexin A1 can serve as a secondary membrane binding site in the process of membrane aggregation by providing a peripheral membrane anchor.

Chemokines as modulators of neuroendocrine functions.

Chemokines are small secreted proteins with chemoattractant properties for immune cells. Besides their role in the immune system, chemokines and their receptors may play important roles in the central nervous system. Neurodegenerative disorders that involve neuroinflammation such as multiple sclerosis, stroke, Alzheimer's disease, Parkinson's disease and HIV-associated dementia are commonly associated with local upregulation and release of chemokines. However, recent work has established that certain chemokines, constitutively expressed in the brain, exert functions in the brain that are distinct from inflammation. These chemokines regulate neuronal migration during brain development, modulate neuronal activity and play a role in various neurodegenerative diseases, pain and more recently in neuroendocrine functions. All these novel aspects, mainly focused on the chemokine stromal cell-derived factor-1/CXCL12 and its receptor CXCR4, were presented by pioneers in the field during the symposium held at the sixth International Congress of Neuroendocrinology in Pittsburgh, Pennsylvania, USA in June 2006.

Expression and externalization of annexin 1 in the adrenal gland: structure and function of the adrenal gland in annexin 1-null mutant 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 hypothalamus and pituitary gland. This study used adrenal gland tissue from ANXA1-null transgenic mice, in which a beta-galactosidase (beta-Gal) reporter gene was controlled by the ANXA1 promoter, and wild-type control mice to explore the potential role of ANXA1 in adrenal function. RT-PCR and Western blotting revealed strong expression of ANXA1 mRNA and protein in the adrenal gland. Immunofluorescence labeling of ANXA1 in wild-type and beta-Gal expression in ANXA1-null adrenals localized intense staining in the outer perimeter cell layers. Immunogold electron microscopy identified cytoplasmic and nuclear ANXA1 labeling in outer cortical cells and capsular cells. Exposure of adrenal segments in vitro to dexamethasone (0.1 mum, 3 h) caused an increase in the amount of ANXA1 in the intracellular compartment and attached to the surface of the cells. The N-terminal peptide ANXA1(Ac2-26) inhibited corticosterone release. Corticosterone release was significantly greater from ANXA1-null adrenal cells compared with wild type in response to ACTH (10 pm to 5 nm). In contrast, basal and ACTH-stimulated aldosterone release from ANXA1-null adrenal cells was not different from wild type. Morphometry studies demonstrated that ANXA1 null adrenal glands were smaller than wild-type, and the cortical/medullary area ratio was significantly reduced. These results suggest ANXA1 is a regulator of adrenocortical size and corticosterone secretion.

Annexin 1, glucocorticoids, and the neuroendocrine-immune interface.

Annexin 1 (ANXA1) was originally identified as a mediator of the anti-inflammatory actions of glucocorticoids (GCs) in the host defense system. Subsequent work confirmed and extended these findings and also showed that the protein fulfills a wider brief and serves as a signaling intermediate in a number of systems. ANXA1 thus contributes to the regulation of processes as diverse as cell migration, cell growth and differentiation, apoptosis, vesicle fusion, lipid metabolism, and cytokine expression. Here we consider the role of ANXA1 in the neuroendocrine system, particularly the hypothalamo-pituitary-adrenocortical (HPA) axis. Evidence is presented that ANXA1 plays a critical role in effecting the negative feedback effects of GCs on the release of corticotrophin (ACTH) and its hypothalamic-releasing hormones and that it is particularly pertinent to the early-onset actions of the steroids that are mediated via a nongenomic mechanism. The paracrine/juxtacrine mode of ANXA1 action is discussed in detail, with particular reference to the significance of the secondary processing of ANXA1, the processes that control the intracellular and transmembrane trafficking of the protein of the molecule and the mechanism of ANXA1 action on its target cells. In addition, the role of ANXA1 in the perinatal programming of the HPA axis is discussed.

Gene deletion reveals roles for annexin A1 in the regulation of lipolysis and IL-6 release in epididymal adipose tissue.

In this study, epididymal adipose tissue from male annexin 1 (ANXA1)-null and wild-type control mice were used to explore the potential role of ANXA1 in adipocyte biology. ANXA1 was detected by Western blot analysis in wild-type tissue and localized predominantly to the stromal-vascular compartment. Epididymal fat pad mass was reduced by ANXA1 gene deletion, but adipocyte size was unchanged, suggesting that ANXA1 is required for the maintenance of adipocyte and/or preadipocyte cell number. Epididymal tissue from wild-type mice responded in vitro to noradrenaline and isoprenaline with increased glycerol release, reduced IL-6 release, and increased cAMP accumulation. Qualitatively similar but significantly attenuated responses to the catecholamines were observed in tissue from ANXA1-null mice, an effect that was not associated with changes in beta-adrenoceptor mRNA expression. Lipopolysaccharide (LPS) also stimulated lipolysis in vitro, but its effects were muted by ANXA1 gene deletion. By contrast, LPS failed to influence IL-6 release from wild-type tissue but stimulated the release of the cytokine from tissue from ANXA1-null mice. ANXA1 gene deletion did not affect glucocorticoid receptor expression or the ability of dexamethasone to suppress catecholamine-induced lipolysis. It did, however, augment IL-6 expression and modify the inhibitory effects of glucocorticoids on IL-6 release. Collectively, these studies suggest that ANXA1 supports aspects of adipose tissue mass and alters the sensitivity of epididymal adipose tissue to catecholamines, glucocorticoids, and LPS, thereby modulating lipolysis and IL-6 release.