Activation of human monocytes by LPS and DHEA

Androgen and Androgen Receptors as Regulators of Monocyte and Macrophage Biology in the Healthy and Diseased Lung

Androgens, the predominant male sex hormones, drive the development and maintenance of male characteristics by binding to androgen receptor (AR). As androgens are systemically distributed throughout the whole organism, they affect many tissues and cell types in addition to those in male sexual organs. It is now clear that the immune system is a target of androgen action. In the lungs, many immune cells express ARs and are responsive to androgens. In this review, we describe the effects of androgens and ARs on lung myeloid immune cells-monocytes and macrophages-as they relate to health and disease. In particular, we highlight the effect of androgens on lung diseases, such as asthma, chronic obstructive pulmonary disease and lung fibrosis. We also discuss the therapeutic use of androgens and how circulating androgens correlate with lung disease. In addition to human studies, we also discuss how mouse models have helped to uncover the effect of androgens on monocytes and macrophages in lung disease. Although the role of estrogen and other female hormones has been broadly analyzed in the literature, we focus on the new perspectives of androgens as modulators of the immune system that target myeloid cells during lung inflammation.

Peripheral Immunity, Immunoaging and Neuroinflammation in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder among elderly population, characterized by the progressive degeneration of dopaminergic neurons in the midbrain. To date, exact cause remains unknown and the mechanism of neurons death uncertain. It is typically considered as a disease of central nervous system (CNS). Nevertheless, numerous evidence has been accumulated in several past years testifying undoubtedly about the principal role of neuroinflammation in progression of PD. Neuroinflammation is mainly associated with presence of activated microglia in brain and elevated levels of cytokine levels in CNS. Nevertheless, active participation of immune system as well has been noted, such as, elevated levels of cytokine levels in blood, the presence of auto antibodies, and the infiltration of T cell in CNS. Moreover, infiltration and reactivation of those T cells could exacerbate neuroinflammation to greater neurotoxic levels. Hence, peripheral inflammation is able to prime microglia into pro-inflammatory phenotype, which can trigger stronger response in CNS further perpetuating the on-going neurodegenerative process. In the present review, the interplay between neuroinflammation and the peripheral immune response in the pathobiology of PD will be discussed. First of all, an overview of regulation of microglial activation and neuroinflammation is summarized and discussed. Afterwards, we try to collectively analyze changes that occurs in peripheral immune system of PD patients, suggesting that these peripheral immune challenges can exacerbate the process of neuroinflammation and hence the symptoms of the disease. In the end, we summarize some of proposed immunotherapies for treatment of PD.

Dehydroepiandrosterone and Bone

In humans, dehydroepiandrosterone (DHEA), secreted mainly from the adrenal cortex, and its sulfate ester, DHEAS, are the most abundant circulating steroids. DHEA/DHEAS possess pleiotropic effects in human aging, bone, metabolic diseases, neurologic function/neurodegenerative diseases, cancer, immune system and disorders, cardiovascular diseases, diabetes, muscle function, sexual dysfunction, and other health conditions. The age-related reduced levels of DHEA and DHEAS are associated with bone mineral density measures of osteopenia and osteoporosis. Clinical, epidemiological, and experimental studies indicate that DHEA replacement therapy may be beneficial for bone health through its inhibition of skeletal catabolic IL-6 and stimulation of osteoanabolic IGF-I-mediated mechanisms. Studies with primary cultures of human bone marrow-derived mesenchymal stem cells (hMSCs) were used to show that DHEA stimulates osteoblastogenesis. The in vitro stimulation of both osteoblastogenesis and IGF-I gene expression by DHEA in hMSCs requires IGF-I receptor, PI3K, p38 MAPK, or p42/44 MAPK signaling pathways. The in vitro inhibition of IL-6 secretion in hMSCs by DHEA was more consistent and extensive than by estradiol or dihydrotestosterone. In summary, evidence from us and others indicates that DHEA may be useful for treating bone diseases through its inhibition of skeletal catabolic IL-6 and stimulation of anabolic IGF-I-mediated mechanisms.

Neuroendocrine effects of stress on immunity in the elderly: implications for inflammatory disease

Age-related changes in immune function leave older adults at risk for a host of inflammatory diseases. Immune-mediated inflammatory processes are regulated by neuroendocrine hormones, including glucocorticoids, dehydroepiandrosterone, and the catecholamines, epinephrine, and norepinephrine. This regulation, however, becomes impaired in older adults in light of age-related changes in endocrine function. Chronic stress shows similarly harmful effects on neuroendocrine and immune function and may, therefore, combine with age to further increase disease risk in older adults. This article highlights evidence for the impact of age and stress on neuroendocrine regulation of inflammatory processes that may substantially increase risk for inflammatory disease at older ages.

Dehydroepiandrosterone as a regulator of immune cell function

Dehydroepiandrosterone (DHEA) is a C19 steroid of adrenal origin. Notably, its secretion declines with age, a phenomenon referred to as the "adrenopause". For many years, the physiological significance of DHEA remained elusive. However, many studies have now shown that DHEA has significant immune modulatory function, exhibiting both immune stimulatory and anti-glucocorticoid effects. Although several of these studies are limited by the fact that they were carried out in rodents, who are incapable of adrenal DHEA production, and therefore have very low circulating levels of this steroid, evidence from the study of immune cells is now accumulating to suggest a role for DHEA in regulating human immunity. This ability to regulate immune function has raised interest in the therapeutic potential of DHEA as a treatment for the immunological abnormalities that arise in subjects with low circulating levels of this hormone. This has included attempts at reversing the impaired immune response of older individuals to vaccination and restoring immune regulation in patients with chronic autoimmune disease. This review summarises the reported effects of DHEA on immune function and discusses the therapeutic potential of this steroid in geriatric medicine and particularly in age-related disease with an immune component.

Dehydroepiandrosterone in systemic lupus erythematosus

Dehydroepiandrosterone (DHEA) is a weak androgen that exerts pleomorphic effects on the immune system. The hormone has no known receptor, and consequently, its mechanism of action on immunocompetent cells remains poorly understood. Interestingly, serum levels of DHEA are decreased in patients with inflammatory diseases including lupus, and these levels seem to correlate inversely with disease activity. Following encouraging studies demonstrating beneficial effects of DHEA supplementation in murine lupus models, several clinical studies have tested the effect of DHEA in lupus patients. DHEA treatment could improve overall quality-of-life assessment measures and glucocorticoid requirements in some lupus patients with mild to moderate disease; however, DHEA's effect on disease activity in lupus patients remains controversial. Long-term safety studies are required in light of the reported effect of DHEA supplementation in lowering high-density lipoprotein cholesterol in lupus patients.

Might DHEA be considered a beneficial replacement therapy in the elderly?

Dehydroepiandrosterone (DHEA) [prasterone] is typically secreted by the adrenal glands and its secretory rate changes throughout the human lifespan. When human development is completed and adulthood is reached, DHEA and DHEA sulphate (DHEAS) [PB-008] levels start to decline so that at 70-80 years of age, peak DHEAS concentrations are only 10-20% of those in young adults. This age-associated decrease has been termed 'adrenopause', and since many age-related disturbances have been reported to begin with the decline of DHEA/DHEAS levels, this provides a potential opportunity for use of DHEA as replacement therapy. For these reasons, use of DHEA as a replacement therapy in aging men and women has been proposed and this paper outlines the reported beneficial effects of such treatment in humans. Many interesting results have been obtained in experimental animals suggesting that DHEA positively modulates most age-related disturbances. However, renewed interest in DHEA has arisen as a result of recent studies suggesting that DHEA appears to be beneficial in hypoandrogenic men as well as in postmenopausal and aging women. Menopause is the event in a woman's life that induces a dramatic change in the steroid milieu, and use of DHEA as 'replacement treatment' has been reported to restore both the androgenic and estrogenic environment and reduce most of the symptoms of this change. As menopause is the beginning of the biological transition of women towards senescence, it is of great interest to better understand how DHEA might help to solve and/or overcome the problems of this complex stage of life. In men with adrenal insufficiency and hypogonadism without androgen replacement, DHEA administration results in a significant increase in circulating androgens. Though most data are suggestive for use of DHEA as hormonal replacement treatment, more defined and specific clinical trials are needed to uncover all of the 'secrets' and features of this steroid before it can be used as a standard treatment. Furthermore, DHEA is perceived differently around the world, being considered only a 'dietary supplement' in the US, while in many European countries it is considered a 'true hormone' that has not been approved for use as a hormonal treatment by the European health authorities. This overview offers some points of view on use of DHEA as an experimental hormonal replacement therapy.

From rodent reagents to human therapeutics using antibody guided selection

Guided selection is a method of producing a human version of a rodent or any other non-human antibody. The process is a serial transition from rodent to human via rodent-human chimaerics, through to a panel of human antibodies with similar characteristics to those of the starting rodent antibody. The guided selection process can be undertaken using either phage display or ribosome display, and chimaeric antibodies can be made either in series or parallel, with or without the retention of the original rodent CDR3s. Guided selection has successfully been used for the generation of a number of human versions of rodent antibodies, including HUMIRA, an inhibitor of tumour necrosis factor-alpha which is approved for the treatment of moderate to severe rheumatoid arthritis in over 40 countries.

Stress responses and innate immunity: aging as a contributory factor

Evolutionary pressure has selected individuals with traits that allow them to survive to reproduction, without consideration of the consequences for the post-child rearing years and old age. In the 21st century, society is populated increasingly by the elderly and with the falling birth rate and improved health care this trend is set to continue for the foreseeable future. To minimize the potential burden on health services one would hope that 'growing old gracefully' should also mean 'growing old healthily'. However, for too many the aging process is accompanied by increasing physical and mental frailty producing an elevated risk of physical and psychological stress in old age. Stress is a potent modulator of immune function, which in youth can be compensated for by the presence of an optimal immune response. In the elderly the immune response is blunted as a result of the decline in several components of the immune system (immune senescence) and a shifting to a chronic pro-inflammatory status (the so-called 'inflamm-aging' effect). We discuss here what is known of the effects of both stress and aging upon the innate immune system, focusing in particular upon the age-related alterations in the hypopituitary-adrenal axis. We propose a double hit model for age and stress in which the age-related increase in the cortisol/sulphated dehydroepiandrosterone ratio synergizes with elevated cortisol during stress to reduce immunity in the elderly significantly.

[Recent development of new drugs for the treatment of allergic diseases]

Due to the prevalence of allergic diseases such as bronchial asthma, allergic rhinoconjunctivitis and dermallergosis, efforts at the discovery of novel and effective medications for prevention and treatment of these conditions have been reinforced. Recently, it has been recognized that these allergic diseases are a chronic inflammatory disorder of the lower and upper airways and skin. In this article, we reviewed the recent development of the following new antiallergic therapies: anti-Th2 cytokine antibodies, decoy receptors, receptor antibodies, anti-IgE antibodies, anti-cell adhesion molecules antibodies, antisense oligonucleotides, keratinocyte modulators, inhibitors of phosphodiesterase 4, tachykinin receptor antagonists, and anti-histaminic drugs. Most of these new agents are aimed to inhibit various components of allergic inflammation. The future use of allergic disease therapies hold great promise and excitement.

Adrenocortical hormones in survivors and nonsurvivors of severe sepsis: diverse time course of dehydroepiandrosterone, dehydroepiandrosterone-sulfate, and cortisol

OBJECTIVE

Activation and suppression of immune responses are crucial events during sepsis. Based on substantial new data, a complex picture of differential immune-enhancing and immunosuppressive actions of adrenocortical steroids is emerging. The adrenal androgen dehydroepiandrosterone and its precursor, dehydroepiandrosterone-sulfate, show a considerable decrease with increasing age and serve as functional antagonists to endogenous glucocorticoids. Therefore, we examined time-dependent changes in dehydroepiandrosterone, dehydroepiandrosterone-sulfate, cortisol, adrenocorticotropin, and inflammatory variables in surviving and nonsurviving patients with severe sepsis.

DESIGN

Prospective observational study in consecutive patients.

SETTING

Medical and interdisciplinary intensive care units in two university hospitals and one city hospital.

PATIENTS

Thirty nonsurgical patients (25 men and 5 women) with severe sepsis (American College of Chest Physicians/Society of Critical Care Medicine criteria); 15 survivors (mean age, 54 +/- 14 yrs; Acute Physiology and Chronic Health Evaluation III score, 59 +/- 35) and 15 nonsurvivors (mean age, 63 +/- 15 yrs; Acute Physiology and Chronic Health Evaluation III score, 67 +/- 24) were included. Hormones were compared individually and between survivors/nonsurvivors by sequential blood drawings from early sepsis till time of recovery/death.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

During early sepsis, cortisol (nmol/L) was not significantly higher in survivors than nonsurvivors (750 +/- 121 vs. 454 +/- 92, p <.08) and decreased in survivors (p <.01) during late sepsis. During early sepsis, dehydroepiandrosterone-sulfate (percentage of age-matched normal levels) was higher in survivors than nonsurvivors (85 +/- 19 vs. 22 +/- 7, p <.01). Dehydroepiandrosterone-sulfate decreased in survivors (p =.0001) but remained low in nonsurvivors during late sepsis. Dehydroepiandrosterone (percentage of age-matched normal levels) was not significantly elevated in survivors compared to nonsurvivors during early sepsis (282 +/- 42 vs. 214 +/- 63, p <.08). Dehydroepiandrosterone decreased in survivors (p <.01) but not in nonsurvivors during late sepsis. Linear regression for dehydroepiandrosterone levels showed a reconstitution of age dependence only in survivors during recovery. Adrenocorticotropin levels did not change. The dehydroepiandrosterone-sulfate/cortisol ratio decreased significantly in both survivors and nonsurvivors, whereas dehydroepiandrosterone/cortisol ratio only decreased in survivors during course of sepsis.

CONCLUSIONS

During sepsis, adrenal androgens and glucocorticoids show a diverse time-dependent course in survivors and nonsurvivors.

Adalimumab - a new TNF-alpha antibody for treatment of inflammatory joint disease

Tumour necrosis factor alpha (TNF-alpha) is a pro-inflammatory cytokine with various roles in inflammatory processes. Several TNF blockers are currently approved for use in rheumatoid arthritis (RA) as well as in other inflammatory arthropathies. The latest of these compounds is the human monoclonal antibody, adalimumab, which was obtained using phage display technology and successfully produced in a mammalian expression system. Clinical application of this compound led to significant improvement in patients suffering from RA, both as monotherapy and in combination with various disease modifying antirheumatic drugs (DMARDs), including methotrexate (MTX). Moreover, radiographic progression is significantly inhibited and quality of life improved. This article summarises the available information.

DHEA treatment: myth or reality?

Dehydroepiandrosterone (DHEA) and its sulfate ester are major secretory products of the human adrenal. Serum DHEA concentrations decline with advancing age and DHEA supplementation in elderly people has been advertized as anti-aging medication. However, such claims are based on experiments in rodents with a fundamentally different DHEA physiology. In humans, DHEA is a crucial precursor of sex steroid biosynthesis and exerts indirect endocrine and intracrine actions following conversion to androgens and estrogens. In addition, it acts as a neurosteroid via effects on neurotransmitter receptors in the brain. DHEA has considerable effects on mood, well-being and sexuality in patients with adrenal insufficiency, and also in those with mood disorders. However, subjects with a physiological, age-related decline in DHEA secretion show little benefit from DHEA administration. Future research should focus on DHEA treatment for adrenal insufficiency, and DHEA administration in both patients receiving chronic glucocorticoid treatment and women with androgen deficiency.

Increased serum interferon alpha in HIV-1 associated lipodystrophy syndrome

BACKGROUND

A syndrome of lipodystrophy (LD) associated with peripheral lipoatrophy and central/visceral adiposity has been reported in HIV-1-infected patients treated by combined antiretroviral therapy (ART). Lipid metabolism is partly regulated by both steroid hormones and cytokines and we have previously reported that dyslipidaemia in LD-positive men is correlated to an increase in cortisol : DHEA ratio (Christeff et al., AIDS 1999;13:2251). In this study we questioned whether it is also related to cytokine perturbations.

MATERIALS AND METHODS

A cross-sectional study was performed on 42 HIV-1-positive men on ART, 27 of whom had symptoms of LD, defined by computed tomography scan. Serum cytokines (IFN-alpha, TNF-alpha, sTNF-RI, sTNF-RII, IL-6, IL-1beta and IL-2) and lipids [cholesterol, triglycerides (TG) and their subclasses], and apolipoproteins (Apo), were determined.

RESULTS

Serum IFN-alpha was markedly increased in LD-positive compared with LD-negative men and controls. IL-6 and TNF-alpha concentrations were also significantly elevated in HIV-positive men compared to controls but the levels of these cytokines did not differ between the two groups of patients. A significant positive correlation was found between accumulation of IFN-alpha and increased levels of cholesterol, TG, VLDL cholesterol, VLDL TG, ApoB and ApoB-ApoA1 ratio. A multivariate forward-performed analysis revealed that IFN-alpha is the best marker for lipid perturbations associated to LD, followed by insulin and cortisol : DHEA ratio.

CONCLUSIONS

This study demonstrates an association between serum IFN-alpha and lipid alterations in LD-positive men. The concomittant action of IFN-alpha and cortisol : DHEA ratio is probably one of the mechanisms responsible for hyperlipidaemia in LD syndrome.

Signal transduction system for interleukin-6 synthesis stimulated by lipopolysaccharide in human osteoblasts

Lipopolysaccharide (LPS) is a bacterial cell component that plays multifunctional roles in inflammatory reactions, and one of the roles is as a powerful stimulator of bone resorption. LPS stimulated bone resorption via CD14 in mouse calvaria and was reported to function as a receptor for bacterial LPS complexed with serum proteins. Interleukin-6 (IL-6) is capable of stimulating the differentiation of osteoclasts from their hematopoietic precursors, and LPS elevates IL-6 synthesis in human osteoblastic cells. However, the signaling pathway of LPS-induced IL-6 synthesis in osteoblasts is unknown. In the present study, we could detect the existence of CD14 in human osteoblastic cells by RT-PCR analysis and show that LPS increased IL-6 mRNA and synthesis via CD14 in human osteoblastic cells. In human osteoblasts (SaM-1 cells) treated with 10 microg/ml LPS, increases in IL-6 mRNA and synthesis were inhibited by anti-CD14 antibody (MEM-18), PD98059 (an inhibitor of classic mitogen-activated protein kinase [MAPK]), or SB203580 (an inhibitor of p38 MAPK) but were not inhibited by H-89 (an inhibitor of protein kinase A [PKA]) and calphostin C (an inhibitor of protein kinase C [PKC]). Furthermore, LPS-induced IL-6 synthesis was inhibited by curcumin (an inhibitor of activating protein-1 [AP-1]) but not by pyrrolidine dithiocarbamate (PDTC) (an inhibitor of nuclear factor kappa B [NF-kappaB]). The findings of the present study suggest that the LPS receptor CD14, existent in human osteoblastic cells, and IL-6 synthesis in response to LPS probably occur via CD14, p38 MAPK, and MAP kinase/extracellular-regulated kinase kinase (MEK), leading to the transcriptional activation of AP-1 in human osteoblastic cells.

In vitro secretion of cytokines and prostaglandin-E2 by monocytes from lung cancer patients

Monocytes (MO) from cancer patients present functional abnormalities, such as an altered secretion of soluble factors. In the present study, our aim was to evaluate the levels of interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha) and prostaglandin-E2 (PGE2) secreted in vitro by MO from lung cancer patients (LCP), spontaneously or after stimulation with lipopolysaccharide (LPS). Results showed that cytokine secretion was higher for MO from LCP than for MO from healthy controls, while in the 25% of the patients analysed, an absence of response to LPS treatment was found.

Preliminary studies on the effect of dehydroepiandrosterone (DHEA) on both constitutive and phytohaemagglutinin (PHA)-inducible IL-6 and IL-2 mRNA expression and cytokine production in human spleen mononuclear cell suspensions in vitro

In order to gain further insight into the potential immunological benefits of oral administration of DHEA we have examined its effects on the constitutive and PHA-inducible expression by human spleen cell suspensions in vitro of IL-6 and IL-2. This was studied at both the mRNA and protein levels. The quantification of specific mRNA was undertaken using commercially available quantitative polymerase chain reaction kits. These studies, which were performed on suspensions from six individual spleens, revealed that 10(-5) M DHEA did not impair the expression of IL-6 at either the mRNA or protein level, but may have slightly enhanced the latter. In contrast, IL-2 mRNA levels were increased on most occasions, whilst IL-2 secretion was decreased, albeit slightly. Additional studies revealed that cyclosporin (approx. 10(-5) M) and dexamethasone (10(-7) M) readily inhibited these responses and the production of other cytokines, including interferon-gamma and tumour necrosis factor-alpha. These preliminary studies suggest that high doses of DHEA do not readily inhibit the production of IL-6, and indeed other cytokines, by PHA-stimulated secondary human lymphoid tissue suspensions in vitro. They may also partially explain the meagre immunomodulatory effects noted in some DHEA replacement studies in humans.

Pravastatin down-regulates inflammatory mediators in human monocytes in vitro

There is experimental evidence that pravastatin, which is designed to inhibit the rate-limiting enzyme of cholesterol synthesis, can affect cell metabolism and proliferation. We therefore studied the effects of pravastatin on the generation of inflammatory mediators in non-stimulated and stimulated primary human monocytes in vitro. In our experimental model, pravastatin induced a dose-dependent inhibition of monocyte cholesterol synthesis (up to 67%), up-regulation of low density lipoprotein receptor mRNA (by about 35%) and reduction in intracellular cholesterol accumulation. In parallel, exposure of non-stimulated monocytes to various doses of pravastatin resulted in inhibition of monocyte chemoattractant protein-1 protein expression (up to 15-fold), reduction of tumour necrosis factor alpha (TNF-alpha) levels (up to 2.4-fold) and a total loss of metalloproteinase-9 activity in stimulated cells. Pravastatin at concentrations of 5, 100 and 500 microM caused an inhibition of TNF-alpha-induced cellular oxygen consumption from 2. 4- to 5.5-fold. These data extend the findings of potential anti-inflammatory actions of statins and also suggest the possibility for pravastatin use in a broader spectrum of inflammatory situations.

Dehydroepiandrosterone inhibits microglial nitric oxide production in a stimulus-specific manner

Dehydroepiandrosterone (DHEA) is a steroid that circulates in abundance in the form of a sulfated reserve (DHEA-S). The levels of DHEA decline with age and further in age-related neuropathologies, including Alzheimer disease. Because of their reported anti-inflammatory effects, we tested the actions of these compounds on microglia. At concentrations of 3(-9) to 1(-6) M, DHEA and DHEA-S inhibited the production of nitrite and morphological changes stimulated by lipopolysaccharide. DHEA and DHEA-S also inhibited LPS induction of iNOS protein, but neither inhibited LPS-induced iNOS mRNA or the activation of NF-kappaB. These data suggest that the hormone regulates nitrite production through a post-transcriptional mechanism. Interestingly, microglial nitrite production in response to a secreted form of the beta-amyloid precursor protein (sAPP) was unaffected by DHEA. Another Alzheimer-related factor, amyloid beta-peptide, also stimulated microglial nitrite production but in a manner dependent on the co-stimulus interferon-gamma. DHEA was found to inhibit only the interferon-gamma component of the microglial response. These data add to a growing body of evidence for differences in the profiles of mononuclear phagocytes activated by distinct stimuli.

Regulation of murine interleukin-10 production by dehydroepiandrosterone

Dehydroepiandrosterone (DHEA), one of the predominant androgens secreted by the adrenal cortex, is a potential immunologic regulator. In this report, the effect of DHEA on interleukin-10 (IL-10) production was studied in vivo. Mice were injected s.c. with DHEA or DHEA-sulfate (DHEAS) ranging from 50 microg to 500 microg/g body weight. The serum was collected, and the spleen cells were isolated 48 h after treatment. Results indicate that treatment with DHEA or DHEAS significantly increases the serum level of IL-10. The spleen cells isolated from the DHEA-treated or DHEAS-treated mice also showed an increase in IL-10 secretion and mRNA expression after the cells were activated by concanavalin A (ConA). The maximal dose of DHEA for inducing IL-10 production was 250 microg/g body weight. As IL-10 is a potent differentiation factor of B lymphocytes, the possible role of DHEA in regulation of immunoglobulin (Ig) production was studied in vivo. Results indicated a significant increase in both serum level of Ig (IgG, IgM, IgA) and Ig secretion by spleen cells after the mice were treated with DHEA or DHEAS. Mice injected with both DHEA (250 microg/g body weight) and anti-IL-10 antibody (0.5 mg/g body weight) showed a significantly reduced DHEA-mediated increase in Ig production. Thus, DHEA might affect the function of B lymphocytes via stimulating IL-10 production.

Lipopolysaccharide enhances the production of vascular endothelial growth factor by human pulp cells in culture

We investigated whether vascular endothelial growth factor (VEGF) production by human pulp cells (HPC) is regulated by lipopolysaccharide (LPS) in relation to the pathogenesis of pulpitis. Although HPC incubated with medium alone only marginally expressed VEGF mRNA and produced a low level of VEGF as detected by enzyme-linked immunosorbent assay, the VEGF mRNA expression and VEGF production were markedly enhanced upon stimulation with LPS from Escherichia coli. Prevotella intermedia LPS, phorbol 12-myristate 13-acetate, and interleukin-6 also induced VEGF mRNA expression in HPC. A simian virus 40-infected HPC line also exhibited increased VEGF mRNA expression in response to E. coli LPS, but lung and skin fibroblasts did not. Fetal bovine serum (FBS) increased the sensitivity of HPC to LPS in a dose-dependent manner. HPC did not express membrane CD14 on their surfaces. However, the anti-CD14 monoclonal antibody MY4 inhibited VEGF induction upon stimulation with LPS in HPC cultures in the presence of 10% FBS but not in the absence of FBS. LPS augmented the VEGF production in HPC cultures in the presence of recombinant human soluble CD14 (sCD14). To clarify the mechanisms of VEGF induction by LPS, we examined the possible activation of the transcription factor AP-1 in HPC stimulated with LPS, by a gel mobility shift assay. AP-1 activation in HPC was clearly observed, whereas that in skin fibroblasts was not. The AP-1 inhibitor curcumin strongly inhibited LPS-induced VEGF production in HPC cultures. In addition, a protein synthesis inhibitor, cycloheximide, inhibited VEGF mRNA accumulation in response to LPS. These results suggest that the enhanced production of VEGF in HPC induced by LPS takes place via an sCD14-dependent pathway which requires new protein synthesis and is mediated in part through AP-1 activation.