17beta-Estradiol's salutary effects on splenic dendritic cell functions following trauma-hemorrhage are mediated via estrogen receptor-alpha

Immunomodulatory role of estrogen in ischemic stroke: neuroinflammation and effect of sex

Although estrogen is predominantly related to the maintenance of reproductive functioning in females, it mediates various physiological effects in nearly all tissues, especially the central nervous system. Clinical trials have revealed that estrogen, especially 17β-estradiol, can attenuate cerebral damage caused by an ischemic stroke. One mechanism underlying this effect of 17β-estradiol is by modulating the responses of immune cells, indicating its utility as a novel therapeutic strategy for ischemic stroke. The present review summarizes the effect of sex on ischemic stroke progression, the role of estrogen as an immunomodulator in immune reactions, and the potential clinical value of estrogen replacement therapy. The data presented here will help better understand the immunomodulatory function of estrogen and may provide a basis for its novel therapeutic use in ischemic stroke.

POSTHEMORRHAGIC SHOCK MESENTERIC LYMPH IMPAIRS SPLENIC DENDRITIC CELL FUNCTION IN MICE

ABSTRACT

Dendritic cell (DC)-mediated immune dysfunction is involved in the process of severe hemorrhagic shock that leads to sepsis. Although post-hemorrhagic shock mesenteric lymph (PHSML) induces immune organs injuries and apoptosis, whether PHSML exerts adverse effects on splenic DCs remains unknown. In this study, we established a hemorrhagic shock model (40 ± 2 mm Hg for 60 min) followed by fluid resuscitation with the shed blood and equal Ringer's solution and drained the PHSML after resuscitation. At 3 h after resuscitation, we harvested the splenic tissue to isolate DCs using anti-CD11c immunomagnetic beads and then detected the necrotic and apoptotic rates in splenocytes and splenic DCs. We also detected the levels of TNF-α, IL-10, and IL-12 in the culture supernatants and surface marker expressions of MHC-II, CD80, and CD86 of splenic DCs following LPS stimulation for 24 h. Second, we purified the DCs from splenocytes of normal mice to investigate the effects of PHSML treatment on cytokine production and surface marker expression following LPS stimulation. The results showed that PHSML drainage attenuated LPS-induced cell death of splenocytes and DCs. Meanwhile, PHSML drainage enhanced the DC percentage in splenocytes and increased the TNF-α and IL-12 production by DCs and the expressions of CD80, CD86, and MHCII of DCs treated by LPS. Furthermore, PHSML treatment reduced the productions of TNF-α, IL-10, and IL-12 and the expressions of CD80 and CD86 in normal DCs after treatment with LPS. In summary, the current investigation demonstrated that PHSML inhibited the cytokine production and surface marker expressions of DCs stimulated by LPS, suggesting that PHSML plays an important role in hemorrhagic shock-induced immunosuppression through the impairment of DC function and maturation.

Long noncoding RNA MALAT1 in exosomes drives regenerative function and modulates inflammation-linked networks following traumatic brain injury

BACKGROUND

Neuroinflammation is a common therapeutic target for traumatic brain injury (TBI) due to its contribution to delayed secondary cell death and has the potential to occur for years after the initial insult. Exosomes from adipose-derived stem cells (hASCs) containing the long noncoding RNA MALAT1 are a novel, cell-free regenerative approach to long-term recovery after traumatic brain injury (TBI) that have the potential to modulate inflammation at the genomic level. The long noncoding RNA MALAT1 has been shown to be an important component of the secretome of hASCs.

METHODS

We isolated exosomes from hASC containing or depleted of MALAT1. The hASC-derived exosomes were then administered intravenously to rats following a mild controlled cortical impact (CCI). We followed the rats with behavior, in vivo imaging, histology, and RNA sequencing (RNA Seq).

RESULTS

Using in vivo imaging, we show that exosomes migrate into the spleen within 1 h following administration and enter the brain several hours later following TBI. Significant recovery of function on motor behavior as well as a reduction in cortical brain injury was observed after TBI in rats treated with exosomes. Treatment with either exosomes depleted of MALAT1 or conditioned media depleted of exosomes showed limited regenerative effects, demonstrating the importance of MALAT1 in exosome-mediated recovery. Analysis of the brain and spleen transcriptome using RNA Seq showed MALAT1-dependent modulation of inflammation-related pathways, cell cycle, cell death, and regenerative molecular pathways. Importantly, our data demonstrates that MALAT1 regulates expression of other noncoding RNAs including snoRNAs.

CONCLUSION

We demonstrate that MALAT1 in hASC-derived exosomes modulates multiple therapeutic targets, including inflammation, and has tremendous therapeutic potential for treatment of TBI.

The Role and Use of Estrogens Following Trauma

Several lines of evidence indicate that female sex is a protective factor in trauma and hemorrhage. In both clinical and experimental studies, proestrus females have been shown to have better chances of survival and reduced rates of posttraumatic sepsis. Estrogen receptors are expressed in a variety of tissues and exert genomic, as well as nongenomic effects. By improving cardiac, pulmonary, hepatic, and immune function, estrogens have been shown to prolong survival in animal models of hemorrhagic shock. Despite encouraging results from experimental studies, retrospective clinical studies have not clearly pointed to advantages of estrogens following trauma-hemorrhage, which may be due to insufficient study design. Therefore, this review aims to give an overview on the current evidence and emphasizes on the importance of further clinical investigation on estrogens following trauma.

The influence of sex steroid hormones on the response to trauma and burn injury

Trauma and related sequelae result in disturbance of homeostatic mechanisms frequently leading to cellular dysfunction and ultimately organ and system failure. Regardless of the type and severity of injury, gender dimorphism in outcomes following trauma have been reported, with females having lower mortality than males, suggesting that sex steroid hormones (SSH) play an important role in the response of body systems to trauma. In addition, several clinical and experimental studies have demonstrated the effects of SSH on the clinical course and outcomes following injury. Animal studies have reported the ability of SSH to modulate immune, inflammatory, metabolic and organ responses following traumatic injury. This indicates that homeostatic mechanisms, via direct and indirect pathways, can be maintained by SSH at local and systemic levels and hence result in more favourable prognosis. Here, we discuss the role and mechanisms by which SSH modulates the response of the body to injury by maintaining various processes and organ functions. Such properties of sex hormones represent potential novel therapeutic strategies and further our understanding of current therapies used following injury such as oxandrolone in burn-injured patients.

Aromatase Blockade Is Associated With Increased Mortality in Acute Illness in Male Mice

Context:

The increase in circulating estrogen levels with acute illness in humans is accompanied by increased aromatase expression in adipose tissue and increased peripheral aromatization of estrogens to androgens. Animal studies indicate that estrogen may be beneficial in acute illness.

Objective:

We hypothesized that blockade of aromatase in acute illness would decrease survival.

Design:

Prospective sham controlled.

Setting:

Maine Medical Center Research Institute animal facility.

Animals:

Six- to 8-week-old male black 6 mice.

Intervention:

Mice underwent cecal ligation and puncture (CLP) to induce acute illness and were administered letrozole to block aromatase or saline. Mice undergoing sham surgery with or without letrozole served as controls. Adipose and cardiovascular tissue was harvested for preliminary evaluation of aromatase expression.

Main outcome measurements:

Survival was the main outcome measurement. Evidence for aromatase expression in tissue samples was assessed using western blot and/or immunohistochemistry.

Results:

With aromatase blockade, survival in CLP mice was decreased (P = 0.04). The presence of aromatase in adipose tissue was observed by western blot in CLP but not control mice. Similarly, the presence of aromatase was observed in cardiac tissue of CLP but not in control mice.

Conclusions:

The decreased survival during sepsis with aromatase blockade suggests that this response to acute illness may be important both physiologically and clinically. The preliminary observation of aromatase expression in adipose and cardiovascular tissue during acute illness in this mouse model indicates that this model has parallels to human physiology and may be useful for further studying the aromatase response to acute illness.

The brain cytokine levels are modulated by estrogen following traumatic brain injury: Which estrogen receptor serves as modulator?

The present study was designed to explore whether administration of estrogen affects brain cytokine levels in TBI. We also sought determine which one of type of classical estrogen receptors (ERs) is involved. Ovariectomized female rats were divided in to eight groups. Estrogen or vehicle was administered following TBI (E2 and oil groups). Antagonist of ER(ICI 182, 780) or vehicle was also administered following TBI (ICI and DMSO groups). The ICI or vehicle was administered either before induction of TBI and administration of estrogen (ICI+E2 and DMSO+E2 groups). TBI was induced by Marmarou's method. In addition to brain water content, the levels of brain proinflammatory and anti-inflammatory cytokines were measured 24 hours post- TBI. Present results demonstrated that, estrogen reduced TBI- induced brain edema. The antiedema effect of estrogen was attenuated by ICI. The brain measures of IL-1β, IL-6 and TNF-α in TBI were also reduced by estrogen. The anti-inflammatory effect of estrogen was attenuated by ICI. The inhibition level of estrogen by ICI was 53.2%, 12.09% and 48.45% for IL-1β, IL-6 and TNF-α, respectively. Estrogen also elevated IL-10 in TBI. ICI inversely controlled the effect of estrogen on IL-10, by 33.84%. This effect was not observed once ICI was used alone. The estrogen administration following TBI probably results in proinflammatory cytokines reduction, and inversely enhancement of anti-inflammatory cytokines. In our study, the neuroprotective effect of estrogen is proposed to be mediated by both ERα and ERα, and accordingly the inhibition of neuroprotective effect of estrogen by ICI.

Potential therapeutic targets for sepsis in women

INTRODUCTION

Gender is increasingly recognized as a key factor in trauma and sepsis. Multiple clinical and experimental studies on sepsis have shown a distinct advantage of females in the proestrus cycle to survive sepsis compared with age-matched males. In addition, estrogen treatment is beneficial in non-proestrus cycles and also in ovarectomized females. In this manuscript, the effects of gender and sex hormones in sepsis are summarized and potential gender-specific therapeutic strategies in women are evaluated.

AREAS COVERED

This review comprises current clinical studies on the effect of gender in sepsis and gives an overview on gender and sex hormone-related effects on immune cells and organ function. Based on clinical and experimental data, potential therapeutic targets are presented.

EXPERT OPINION

Estrogens and estrogen-receptor agonists have been extensively shown to be beneficial in the setting of sepsis. Clinical data, however, do not clearly support their therapeutic use. This discrepancy appears to be mainly due to insufficient study design in clinical trials conducted up to now. Therefore, improved study protocols with exact analysis of the patients' hormonal status are needed to clarify the role of gender and sex hormones in trauma and sepsis.

Estrogen receptor β agonist diarylpropionitrile inhibits lipopolysaccharide-induced regulated on activation normal T cell expressed and secreted (RANTES) production in macrophages by repressing nuclear factor κB activation

OBJECTIVE

To investigate the effect of the estrogen receptor-β (ERβ) agonist diarylpropionitrile (DPN) on lipopolysaccharide (LPS)-induced regulated on activation normal T cell expressed and secreted (RANTES) production in macrophages and the possible mechanisms.

DESIGN

Cellular and molecular biology experimental study.

SETTING

University-based research laboratory.

PATIENT(S)

None.

INTERVENTION(S)

ERβ mRNA and protein expression determined in murine macrophage cell line RAW264.7 cells using reverse-transcription polymerase chain reaction and Western blot analysis; RANTES production detected by ELISA in LPS-stimulated RAW264.7 cells and ERβ knockdown RAW264.7 cells after the addition of DPN, phosphorylation of p65 and IκB degradation detected by Western blot analysis; and nuclear accumulation of p65 visualized using immunofluorescence.

MAIN OUTCOME MEASURE(S)

LPS-induced RANTES production and phosphorylation of p65 and IκB.

RESULT(S)

ERβ was expressed in RAW264.7 cells, and DPN statistically significantly decreased LPS-induced RANTES production in RAW264.7 cells. Small interfering RNA targeting the ERβ gene inhibited the effect of DPN on RANTES production. In addition, DPN inhibited nuclear translocation and phosphorylation of p65 by inhibiting IκB degradation and thus prohibited the activation of nuclear factor κB (NF-κB).

CONCLUSION(S)

Diarylpropionitrile down-regulates LPS-induced RANTES production via ERβ. This effect of DPN is likely due to repression of nuclear factor κB activation.

Sex, stroke, and inflammation: the potential for estrogen-mediated immunoprotection in stroke

Stroke is the third leading cause of death and the primary cause of disability in the developed world. Experimental and clinical data indicate that stroke is a sexually dimorphic disease, with males demonstrating an enhanced intrinsic sensitivity to ischemic damage throughout most of their lifespan. The neuroprotective role of estrogen in the female brain is well established, however, estrogen exposure can also be deleterious, especially in older women. The mechanisms for this remain unclear. Our current understanding is based on studies examining estrogen as it relates to neuronal injury, yet cerebral ischemia also induces a robust sterile inflammatory response involving local and systemic immune cells. Despite the potent anti-inflammatory effects of estrogen, few studies have investigated the contribution of estrogen to sex differences in the inflammatory response to stroke. This review examines the potential role for estrogen-mediated immunoprotection in ischemic injury.

Estrogens and atherosclerosis: insights from animal models and cell systems

Estrogens not only play a pivotal role in sexual development but are also involved in several physiological processes in various tissues including vasculature. While several epidemiological studies documented an inverse relationship between plasma estrogen levels and the incidence of cardiovascular disease and related it to the inhibition of atherosclerosis, an interventional trial showed an increase in cardiovascular events among postmenopausal women on estrogen treatment. The development of atherosclerotic lesions involves complex interplay between various pro- or anti-atherogenic processes that can be effectively studied only in vivo in appropriate animal models. With the advent of genetic engineering, transgenic mouse models of atherosclerosis have supplemented classical dietary cholesterol-induced disease models such as the cholesterol-fed rabbit. In the last two decades, these models were widely applied along with in vitro cell systems to specifically investigate the influence of estrogens on the development of early and advanced atherosclerotic lesions. The present review summarizes the results of these studies and assesses their contribution toward better understanding of molecular mechanisms underlying anti- and/or pro-atherogenic effects of estrogens in humans.

17β-Estradiol and interferon tau interact in the regulation of the immune response in a model of experimental autoimmune orchitis

Immunoregulatory activity of type I interferons (IFNs) and estrogen is convergent in some cases of autoimmune disorders. The aim of our study was to determine whether a potent interaction of IFN and estradiol (E2) has an influence on immune response and estrogen receptor alpha (ER-?) expression in antigen-presenting cells in a model of experimental autoimmune orchitis (EAO). C3H/He/W male mice were immunized with testicular germ cells (TGCs) and orally treated with interferon tau (IFN-?), E2, or both simultaneously. The delayed-type hypersensitivity reaction was intensified after the administration of either IFN-? or E2, but their co-administration had no effect. IFN-? treatment increased immunoglobulin G2a (IgG2a) and decreased IgG1 levels of TGC-specific antibodies, whereas E2 abolished the effects of the used cytokine. The total splenic cellularity and the number of spleen CD11c+MHC II+ and F4/80+MHC II? cells were increased after IFN-? treatment, whereas E2 antagonized this effect. After IFN-? administration the level of ER-? was significantly higher in F4/80+MHC II? cells, whereas E2 had no effect. However, the administration of E2 significantly reduced the ER-? level in F4/80+MHC II+ and CD11c+MHC II+ cells in comparison with the IFN-??treated groups. In the EAO model, the type I IFN and E2 cooperated at the general and cellular levels of immune response, but E2 treatment usually abolished the effects exerted by the cytokine.

Influence of aging and hemorrhage injury on Sirt1 expression: possible role of myc-Sirt1 regulation in mitochondrial function

Trauma-hemorrhage (T-H) causes hypoxia and organ dysfunction. Mitochondrial dysfunction is a major factor for cellular injury due to T-H. Aging also has been known to cause progressive mitochondrial dysfunction. In order to study the effect of aging on T-H-induced mitochondrial dysfunction, we recently developed a rodent mitochondrial genechip with probesets representing mitochondrial and nuclear genes contributing to mitochondrial structure and function. Using this chip we recently identified signature mitochondrial genes altered following T-H in 6 and 22 month old rats; augmented expression of the transcription factor c-myc was the most pronounced. Based on reports of c-myc-IL6 collaboration and c-myc-Sirt1 negative regulation, we further investigated the expression of these regulatory factors with respect to aging and injury. Rats of ages 6 and 22 months were subjected to T-H or sham operation and left ventricular tissues were tested for cytosolic cytochrome c, mtDNA content, Sirt1 and mitochondrial biogenesis factors Foxo1, Ppara and Nrf-1. We observed increased cardiac cytosolic cytochrome c (sham vs T-H, p<0.03), decreased mitochondrial DNA content (sham vs T-H, p<0.05), and decreased Sirt1 expression (sham vs TH, p<0.05) following T-H and with progressing age. Additionally, expression of mitochondrial biogenesis regulating transcription factors Foxo1 and Nrf-1 was also decreased with T-H and aging. Based upon these observations we conclude that Sirt1 expression is negatively modulated by T-H causing downregulation of mitochondrial biogenesis. Thus, induction of Sirt1 is likely to produce salutary effects following T-H induced injury and hence, Sirt1 may be a potential molecular target for translational research in injury resolution.

Salutary effects of 17beta-estradiol on Peyer's patch T cell functions following trauma-hemorrhage

Although 17beta-estradiol (E2) administration following trauma-hemorrhage (T-H) improves immune functions in male rodents, it remains unclear whether E2 has salutary effects on Peyer's patch (PP) T cell functions. We hypothesized that T-H induces PP T cell dysfunction and E2 administration following T-H will improve PP T cell function. T-H was induced in male C3H/HeN mice (6-8weeks) by midline laparotomy and approximately 90min of hemorrhagic shock (blood pressure 35mmHg), followed by fluid resuscitation (4x the shed blood volume in the form of Ringer's lactate). Estrogen receptor (ER)-alpha agonist propyl pyrazole triol (PPT; 5microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5microg/kg), E2 (50microg/kg), or vehicle was injected subcutaneously at resuscitation onset. Two hours later, mice were sacrificed and PP T cells isolated. PP T cell capacity to produce cytokines in response to in vitro stimulation, PP T cell proliferation and MAPK (p38, ERK-1/2, JNK) activation were measured. Results indicate PP T cell proliferation, cytokine production and MAPK activation decreased significantly following T-H. E2, PPT or DPN administration normalized these parameters. Since PPT or DPN administration following T-H was effective in normalizing PP T cell functions, the salutary effects of E2 are mediated via ER-alpha and ER-beta.

Mechanism of the salutary effects of estrogen on kupffer cell phagocytic capacity following trauma-hemorrhage: pivotal role of Akt activation

Kupffer cells are macrophages in the liver whose major role is to clear circulating pathogens. Decreased phagocytic capacity of Kupffer cells may result in severe systemic infection. We tested the hypothesis that the depressed Kupffer cell phagocytic capacity following trauma-hemorrhage is enhanced by estrogen administration and this occurs due to maintenance of Fc receptor expression and cellular ATP content via the activation of Akt. Male C3H/HeN mice were subjected to sham operation or trauma-hemorrhage and sacrificed 2 h thereafter. Estrogen, with or without an estrogen receptor antagonist (ICI 182,780), a PI3K inhibitor (Wortmannin), or vehicle, was injected during resuscitation. Kupffer cell phagocytic capacity was tested in vivo. The expression of Fc receptors, of Akt phosphorylation, of p38 MAPK phosphorylation, of DNA binding activity of NF-kappaB and ATP content of Kupffer cells were also determined. Trauma-hemorrhage suppressed Kupffer cell phagocytosis by decreasing Fc receptor expression and Akt activation; however, it induced p38 MAPK activation and increased NF-kappaB activity. Cellular ATP levels were also decreased following trauma-hemorrhage. Administration of estrogen following trauma-hemorrhage increased phospho-Akt levels and normalized all the parameters described as well as plasma levels of TNF-alpha, IL-6, and IL-10. Coadministration of ICI 182,780 or Wortmannin abolished the beneficial effects of estrogen in improving the phagocytic capacity of Kupffer cells following trauma-hemorrhage. Thus, activation of Akt plays a crucial role in mediating the salutary effect of estrogen in restoring trauma-hemorrhage-induced suppression of Kupffer cell phagocytosis.

Estradiol's salutary effects on keratinocytes following trauma-hemorrhage are mediated by estrogen receptor (ER)-alpha and ER-beta

Although administration of 17beta-estradiol (estrogen) following trauma-hemorrhage attenuates the elevation of cytokine production and mitogen-activated protein kinase (MAPK) activation in epidermal keratinocytes, whether the salutary effects of estrogen are mediated by estrogen receptor (ER)-alpha or ER-beta is not known. To determine which estrogen receptor is the mediator, we subjected C3H/HeN male mice to trauma-hemorrhage (2-cm midline laparotomy and bleeding of the animals to a mean blood pressure of 35 mmHg and maintaining that pressure for 90 min) followed by resuscitation with Ringer's lactate (four times the shed blood volume). At the middle of resuscitation we subcutaneously injected ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), estrogen (50 microg/kg), or ER antagonist ICI 182,780 (150 microg/kg). Two hours after resuscitation, we isolated keratinocytes, stimulated them with lipopolysaccharide for 24 h (5 microg/mL for maximum cytokine production), and measured the production of interleukin (IL)-6, IL-10, IL-12, and TNF-alpha and the activation of MAPK. Keratinocyte cytokine production markedly increased and MAPK activation occurred following trauma-hemorrhage but were normalized by administration of estrogen, PPT, and DPN. PPT and DPN administration were equally effective in normalizing the inflammatory response of keratinocytes, indicating that both ER-alpha and ER-beta mediate the salutary effects of estrogen on keratinocytes after trauma-hemorrhage.

The effects of estrogen on pulmonary artery vasoreactivity and hypoxic pulmonary vasoconstriction: potential new clinical implications for an old hormone

BACKGROUND AND OBJECTIVES

Recent research recognizes gender as a major factor determining the outcomes in trauma, ischemia/reperfusion, shock, and sepsis. In particular, estrogen has been demonstrated to exert protective effects in these settings. The effects of estrogens on the pulmonary vasculature are potent and complex yet not fully understood. A better mechanistic understanding may allow for future therapeutic interventions in pulmonary hypertensive crises after cardiac surgery and during acute lung injury as well as in patients with pulmonary arterial hypertension.

DATA SOURCES AND STUDY SELECTION

We searched PubMed for articles in the English language by using the search words pulmonary hypertension, hypoxic pulmonary vasoconstriction, estrogen, estradiol, inflammation, acute injury, ischemia reperfusion, sepsis, trauma, and burns. These were used in various combinations. We read the abstracts of the relevant titles to confirm their relevance, and the full articles were then extracted. References from extracted articles were checked for any additional relevant articles.

DATA EXTRACTION AND SYNTHESIS

Estrogen plays a critical role in the improved outcomes in the settings of trauma, shock, sepsis, myocardial ischemia/reperfusion, and acute lung injury. Several new mechanisms of action have been identified. In the pulmonary vasculature, estrogen causes vasodilation and attenuates the vasoconstrictor response to various stimuli, including hypoxia. This is mediated by increased levels of prostacyclin and nitric oxide as well as decreased levels of endothelin-1. In addition, effects on intracellular signaling pathways and several kinases as well as anti-inflammatory mechanisms may contribute as well. Recent studies suggest the importance of acute, nongenomic effects.

CONCLUSION

Estrogen exerts a variety of nongenomic actions, which may allow for future therapeutic interventions in pulmonary vascular disease.

Estrogen: a novel therapeutic adjunct for the treatment of trauma-hemorrhage-induced immunological alterations

Trauma-hemorrhage leads to prolonged immune suppression, sepsis, and multiple organ failure. The condition affects all compartments of the immune system, and extensive studies have been carried out elucidating the immunological events following trauma-hemorrhage. The immune alteration observed following trauma-hemorrhage is gender dependent in both animal models and humans, though some studies in humans are contradictory. Within 30 min after trauma-hemorrhage, splenic and peritoneal macrophages, as well as T-cell function, are depressed in male animals, but not in proestrus females. Studies have also shown that the mortality [corrected] rate and the induction of subsequent sepsis following trauma-hemorrhage are significantly higher in males and ovariectomized females compared with proestrus females. These and other investigations show that sex hormones form the basis of this gender dichotomy, and administration of estrogen can ameliorate the immune depression and increase the survival rate after trauma-hemorrhage. This review specifically elaborates the studies carried out thus far demonstrating immunological alteration after trauma-hemorrhage and its modulation by estrogen. Also, estrogen was shown to produce its salutary effects through nuclear as well as extranuclear receptors. Estrogen rapidly activates several protein kinases and phosphatases, as well as the release of calcium in different cell types. The results of the studies exemplify the promise of estrogen as a therapeutic adjunct in treating adverse pathophysiological conditions following trauma-hemorrhage.

Regulation of dendritic cell differentiation and function by estrogen receptor ligands

Estrogen receptor (ER) ligands can modulate innate and adaptive immunity and hematopoiesis, which may explain the clear sex differences in immune responses during autoimmunity, infection or trauma. Dendritic cells (DC) are antigen presenting cells important for initiation of innate and adaptive immunity, as well as immune tolerance. DC progenitors and terminally differentiated DC express ER, indicating the ER ligands may regulate DC at multiple developmental and functional stages. Although there are profound differences in innate immunity between males and females or upon systemic imposition of sex hormones, studies are just beginning to link these differences to DC. Our and others studies demonstrate that estradiol and other ER ligands regulate the homeostasis of bone marrow myeloid and lymphoid progenitors of DC, as well as DC differentiation mediated by GM-CSF and Flt3 Ligand. Since DC have a brief lifespan, these data suggest that relatively short exposures to ER ligands in vivo will alter DC numbers and intrinsic functional capacity related to their developmental state. Studies in diverse experimental models also show that agonist and antagonist ER ligands modulate DC activation and production of inflammatory mediators. These findings have implications for human health and disease since they suggest that both DC development and functional capacity will be responsive to the physiological, pharmacological and environmental ER ligands to which an individual is exposed in vivo.