Immunoprotection in proestrus females following trauma-hemorrhage: the pivotal role of estrogen receptors

Parameters influencing health-related quality of life after severe trauma: a systematic review (part II)

INTRODUCTION

It is increasingly recognized that health-related quality of life (HRQoL) is a relevant outcome to study in populations comprising severely injured patients. Although some studies have readily demonstrated a compromised HRQoL in those patients, evidence regarding factors that predict HRQoL is scarce. This hinders attempts to prepare patient-specific plans that may aid in revalidation and improved life satisfaction. In this review, we present identified predictors of HRQoL in patients that have suffered severe trauma.

METHODS

The search strategy included a database search until the 1st of January 2022 in the Cochrane Library, EMBASE, PubMed, and Web of Science, and reference checking. Studies were eligible for inclusion when (HR)QoL was studied in patients with major, multiple, or severe injury and/or polytrauma, as defined by authors by means of an Injury Severity Score (ISS) cut-off value. The results will be discussed in a narrative manner.

RESULTS

A total of 1583 articles were reviewed. Of those, 90 were included and used for analysis. In total, 23 possible predictors were identified. The following parameters predicted reduced HRQoL in severely injured patients and came forward in at least more than three studies: higher age, female gender, lower extremity injuries, higher rate of injury severity, lower achieved educational level, presence of (pre-existing) comorbidities and mental illness, longer duration of hospital stay, and high level of disability.

CONCLUSION

Age, gender, injured body region, and severity of injury were found to be good predictors of health-related quality of life in severely injured patients. A patient-centered approach, based on individual, demographic, and disease-specific predictors, is highly recommended.

Impact of patients' gender on microvascular lower extremity reconstruction

The physiological differences between genders have significant implications for health and disease. With regard to microsurgery, results remain elusive as to whether male or female gender is an independent risk factor for free flap reconstruction. This study evaluated the impact of gender on outcomes of lower-extremity free-flap reconstructions. Within 7 years, 358 patients received 393 microvascular lower limb free flap reconstructions. The cases were divided into two groups according to patients' gender: male vs. female. Retrospective data analysis evaluated patients' demographics, perioperative details, surgical complications and flap outcomes over a 3-month follow-up period. Major and minor surgical complications, including total and partial flap loss, showed no significant differences between the investigated groups (p>.05). In addition, there was no significant difference with regard to the rate of surgical revision surgery, or the incidence of arterial and venous thrombosis (p>.05). Comparison of different flap types (fasciocutaneous ALT vs. gracilis muscle flaps) and type of anastomosis (end-to-end vs. end-to-side) also revealed no difference in outcomes in respect to gender. In conclusion, gender cannot be regarded as an independent risk factor for free flap reconstructions in patients with lower-extremity defects.

Sex-based differences in outcomes after severe injury: an analysis of blunt trauma patients in China

BACKGROUND

Experimental research suggests that females have a higher survival rate after trauma, although this claim is controversial. This study sought to determine the role of sex on mortality among trauma patients in China.

METHODS

The study enrolled 1789 trauma patients who visited the Emergency Intensive Care Unit of the First Affiliated Hospital of Zhengzhou University during 2015 and 2016. A retrospective data analysis was performed to determine sex-based differences after blunt trauma. Patients were stratified by age and injury severity (using the Injury Severity Score). Multiple logistic regression was used to analyze the association between sex and post-injury complications and mortality.

RESULTS

Female trauma patients experienced a significantly lower risk of mortality than males (odds ratio, 0.931; 95% confidence interval, 0.883-0.982). This survival advantage of females was particularly notable in the 'younger than 45 years' age group. Sex-based differences were also found in the occurrence of life-threatening complications after trauma.

CONCLUSION

This study demonstrated that females are more likely to survival after severe blunt trauma and also have less inpatient complications than men, suggesting an important role for sex hormones after severe traumatic injury.

Bioavailable estradiol concentrations are elevated and predict mortality in septic patients: a prospective cohort study

BACKGROUND

Experimental studies demonstrate beneficial immunological and hemodynamic effects of estradiol in animal models of sepsis. This raises the question whether estradiol contributes to sex differences in the incidence and outcomes of sepsis in humans. Yet, total estradiol levels are elevated in sepsis patients, particularly nonsurvivors. Bioavailable estradiol concentrations have not previously been reported in septic patients. The bioavailable estradiol concentration accounts for aberrations in estradiol carrier protein concentrations that could produce discrepancies between total and bioavailable estradiol levels. We hypothesized that bioavailable estradiol levels are low in septic patients and sepsis nonsurvivors.

METHODS

We conducted a combined case-control and prospective cohort study. Venous blood samples were obtained from 131 critically ill septic patients in the medical and surgical intensive care units at the University of Rochester Medical Center and 51 control subjects without acute illness. Serum bioavailable estradiol concentrations were calculated using measurements of total estradiol, sex hormone-binding globulin, and albumin. Comparisons were made between patients with severe sepsis and control subjects and between hospital survivors and nonsurvivors. Multivariable logistic regression analysis was also performed.

RESULTS

Bioavailable estradiol concentrations were significantly higher in sepsis patients than in control subjects (211 [78-675] pM vs. 100 [78-142] pM, p < 0.01) and in sepsis nonsurvivors than in survivors (312 [164-918] pM vs. 167 [70-566] pM, p = 0.04). After adjustment for age and comorbidities, patients with bioavailable estradiol levels above the median value had significantly higher risk of hospital mortality (OR 4.27, 95 % CI 1.65-11.06, p = 0.003). Bioavailable estradiol levels were directly correlated with severity of illness and did not differ between men and women.

CONCLUSIONS

Contrary to our hypothesis, bioavailable estradiol levels were elevated in sepsis patients, particularly nonsurvivors, and were independently associated with mortality. Whether estradiol's effects are harmful, beneficial, or neutral in septic patients remains unknown, but our findings raise caution about estradiol's therapeutic potential in this setting. Our findings do not provide an explanation for sex-based differences in sepsis incidence and outcomes.

Both castration and goserelin acetate ameliorate myocardial ischemia reperfusion injury and apoptosis in male rats

Although reperfusion of an ischemic organ is essential to prevent irreversible tissue damage, it may amplify tissue injury. This study investigates the role of endogenous testosterone in myocardial ischemia reperfusion and apoptosis in male rats. Material and method. Twenty four male rats were randomized into 4 equal groups: Group (1), sham group, rats underwent the same anesthetic and surgical procedure as the control group except for LAD ligation; Group (2), Active control group, rats underwent LAD ligation; Group (3), castrated, rats underwent surgical castration, left 3wks for recovery, and then underwent LAD ligation; and Group (4), Goserelin acetate treated, rats received 3.6 mg of Goserelin 3 wks before surgery and then underwent LAD ligation. At the end of experiment, plasma cTn I, cardiac TNF-α, IL1-β, ICAM-1, and Apoptosis level were measured and histological examination was made. Results. Compared to sham group, the levels of myocardial TNF-α, IL-1β, ICAM-1, apoptosis, and plasma cTn I were significantly increased (P < 0.05) in control group and all rats showed significant myocardial injury (P < 0.05). Castration and Goserelin acetates significantly counteract the increase in myocardial levels of TNF-α, IL-1β, ICAM-1, plasma cTn I, and apoptosis (P < 0.05) and significantly reduce (P < 0.05) the severity of myocardial injury. We conclude that castration and Goserelin acetates ameliorate myocardial I/R injury and apoptosis in rats via interfering with inflammatory reactions.

Effects of trauma-hemorrhage and IL-6 deficiency on splenic immune function in a murine trauma model

Splenic immune function is known to be depressed following hemorrhage. The present study investigates the effects of femoral shaft fracture, isolated or in combination with hemorrhage, on early stage cytokine production capacity of splenocytes and observes the role of IL-6 under these conditions. Male IL-6 knockout (IL-6^−/−) and wild-type mice (WT) were randomly divided into three groups: sham (S), isolated femoral fracture (Fx), and femoral fracture + volume controlled hemorrhage (TH-Fx) (n = 6 per group). Animals were sacrificed four hours after induction of hemorrhage and fracture. Cytokine release (TNF-α, IL-6, and IL-10) of isolated and LPS-stimulated splenocytes was determined by cytometric bead array. Femoral fracture with or without hemorrhage caused a suppression of in vitro cytokine production capacity of splenocytes at an early posttraumatic stage in WT and IL-6^−/−. In the absence of IL-6, the profile of splenic cytokine secretion is significantly altered, identifying this cytokine as a potential therapeutic target to modulate the posttraumatic immune response.

Role of PPARγ in the salutary effects of 17β-estradiol on Kupffer cell cytokine production following trauma-hemorrhage

Studies have shown that administration of 17β-estradiol prevents trauma-hemorrhage-induced increase in proinflammatory cytokine production by Kupffer cells and associated multiple organ injury. Since activation of peroxisome proliferator-activated receptor γ (PPARγ) following ischemic conditions has been shown to be protective, we examined if PPARγ plays any role in the salutary effects of 17β-estradiol on Kupffer cell cytokine production following trauma-hemorrhage. Male mice underwent trauma-hemorrhage (mean blood pressure 40 mmHg for 90 min, then resuscitation). 17β-estradiol (50 µg/kg) or vehicle with or without PPARγ antagonist GW9662 was injected subcutaneously at the middle of resuscitation. At 2 h after trauma-hemorrhage, plasma interleukin (IL)-6 and tumor necrosis factor (TNF)-α levels, Kupffer cell IL-6 and TNF-α production and mRNA expression, and PPARγ, nuclear factor (NF)-κB and activator protein (AP)-1 DNA binding activity were determined. Kupffer cell IL-6 and TNF-α production, as well as plasma IL-6 and TNF-α levels, increased following trauma-hemorrhage. Moreover, NF-κB and AP-1 DNA binding activity and IL-6 and TNF-α mRNA expression were also enhanced under such conditions. However, 17β-estradiol administration normalized all these parameters. Although PPARγ activity decreased after trauma-hemorrhage, administration of 17β-estradiol following trauma-hemorrhage elevated PPARγ activity above the normal level. Inhibition of PPARγ by co-administration of GW9662, however, abolished the salutary effects of 17β-estradiol on plasma cytokine and Kupffer cells. Thus, activation of PPARγ appears to play an important role in mediating the salutary effects of 17β-estradiol on plasma cytokine levels and Kupffer cell cytokine production after trauma-hemorrhage, which are likely mediated via NF-κB and AP-1.

Animal models for trauma research: what are the options?

Even if trauma patients initially avoid death after trauma (due to massive blood volume loss, primary severe brain injury), they are still at risk for multiple organ failure. Thus, it is crucial to elucidate the underlying pathophysiological mechanisms of trauma/hemorrhagic shock and the immune response involved. As of now, many hemorrhagic shock/trauma studies have used various types of animal models. Despite a large number of results from these efforts, some authors have argued that animal model results are difficult to translate directly into the clinical scenario. This review summarizes the advantages and the disadvantages of using animal models in trauma/hemorrhagic shock studies and discusses the relevance of various animal studies to the clinical scenario.

The role of estrogen and receptor agonists in maintaining organ function after trauma-hemorrhage

Sex is increasingly recognized as a major factor in the outcome of patients who have trauma and sepsis. Moreover, sex steroids influence chemokine/adhesion molecule expression and neutrophil accumulation. Heat shock proteins, heat shock factor 1, and peroxisome proliferator-activated receptor [gamma] coactivator 1 are regulated by the estrogen receptors and consequently contribute to organ protection after trauma-hemorrhage. Additionally, sex steroids regulate inflammatory cytokines, leading to increased morbidity and mortality. This article deals with trauma-hemorrhage and examines the following: 1) the evidence for sex differences; 2) the mechanisms by which sex hormones affect organ protection; 3) the tissue-specific effect of sex hormone receptors; and 4) the effect of genomic and nongenomic (i.e. membrane-initiated steroid signaling) pathways of sex hormones after trauma. The available information indicates that sex steroids modulate cardiovascular responses after trauma. Thus, alteration or modulation of the prevailing hormone milieu at the time of injury seems to be a novel therapeutic option for improving outcome after injury

Impact of gender on outcomes after blunt injury: a definitive analysis of more than 36,000 trauma patients

BACKGROUND

The concept that premenopausal female patients are more resistant to shock than male patients has been shown in numerous preclinical models. The more relevant effect of gender on clinically important outcomes after trauma is less clear. Clinical studies have been conflicting, both supporting and refuting the protective effects of gender on outcomes, primarily because of limitations in sample size and patient stratification. In an attempt to resolve this ongoing dispute, we evaluated the effect of gender on various outcomes in the largest single institutional series of trauma patients reported in the literature after blunt injury.

STUDY DESIGN

All patients sustaining blunt trauma during a 10-year period were identified from the trauma registry and stratified by gender, age, and severity of shock and injury. Outcomes included ventilator-associated pneumonia, ARDS, bacteremia, ventilator days, ICU days, hospital length of stay, and mortality. Multivariable logistic regression was performed to determine whether gender was an independent predictor of mortality, morbidity, or both.

RESULTS

There were 36,010 patients identified; 304 died in the resuscitation area, leaving 24,331 men and 11,375 women for analysis. Logistic regression identified gender as an independent predictor of morbidity but failed to show gender as an independent predictor of early (48-hour and 7-day) and overall mortality.

CONCLUSIONS

Multivariable logistic regression analysis of a large trauma cohort definitively establishes that gender is not independently associated with mortality after blunt trauma in humans. In contrast, male gender was shown to be associated with increased morbidity. Unlike rodent studies, gender alone offers no survival advantage in humans after blunt trauma.

Mitogen activated protein kinase (MAPK) mediates non-genomic pathway of estrogen on T cell cytokine production following trauma-hemorrhage

Although studies have shown 17beta-estradiol (E2) administration following trauma-hemorrhage (T-H) attenuates alterations in T cell cytokine production, it remains unknown whether such effects of E2 are mediated via genomic or non-genomic pathways. In this study, we determined the non-genomic effects of E2 on splenic T cell cytokine production and the role of MAPK following T-H. Male Sprague-Dawley rats underwent T-H (mean BP 40 mmHg for 90 min, then resuscitation). E2, E2 conjugated with BSA (E2-BSA, 1 mg/kg E2) with or without an estrogen receptor antagonist (ICI 182 780), or vehicle was administered during resuscitation. Two hours thereafter, T cell production of IL-2 and IFN-gamma and activation of MAPK (p38, ERK-1/2 and JNK) were determined. The effect of selective MAPK inhibitors on cytokine production was also examined in vitro. IL-2 and IFN-gamma production capacity and MAPK activation decreased in T cells following T-H. However, E2 administration normalized these parameters. Although E2-BSA administration also attenuated suppression in cytokine production, the values were lower compared to sham. In contrast, E2-BSA prevented T-H-induced suppression in MAPK activation to the same extent as E2. Co-administration of ICI 182 780 abolished E2-BSA effects. These findings suggest E2 effects on T cell cytokine production following T-H are mediated at least in part via non-genomic pathway and these non-genomic effects are likely mediated via MAPK pathways.

Sex differences and estrogen modulation of the cellular immune response after injury

Cell-mediated immunity is extremely important for resolution of infection and for proper healing from injury. However, the cellular immune response is dysregulated following injuries such as burn and hemorrhage. Sex hormones are known to regulate immunity, and a well-documented dichotomy exists in the immune response to injury between the sexes. This disparity is caused by differences in immune cell activation, infiltration, and cytokine production during and after injury. Estrogen and testosterone can positively or negatively regulate the cellular immune response either by aiding in resolution or by compounding the morbidity and mortality. It is apparent that the hormonal dysregulation is dependent not only on the type of injury sustained but also the amount of circulating hormones. Therefore, it may be possible to design sex-specific therapies to improve immunological function and patient outcome.

Trauma and immune response--effect of gender differences

A major consequence of traumatic injury is immunosuppression. Findings from previous studies suggest that the depression of immune functions is severe in young males, ovariectomised and aged females. In contrast, the immune functions in proestrus females following trauma-haemorrhage are maintained. Studies have also shown that the survival rate in proestrus females following trauma-haemorrhage and the induction of subsequent sepsis is significantly higher than in age-matched males and ovariectomised females. Furthermore, administration of female sex hormone 17beta-oestradiol in males and ovariectomised females after trauma-haemorrhage prevents the suppression of immune response. Thus, these findings suggest that sex hormones play a significant role in shaping the host response following trauma. This article reviews studies delineating the mechanism by which sex hormones regulate immune cell functions in the experimental model of trauma-haemorrhage. The findings from the studies reviewed in this article suggest that sex steroids can be synthesised by the immune cell. The findings further indicate that T cell and macrophages express receptors for androgen and oestrogen. Since these cells are also the cells that produce cytokines, local synthesis of active steroids in these cells may become the significant factor in modulating their cytokine production.

Metabolic modulators following trauma sepsis: Sex hormones

BACKGROUND

The development of metabolic perturbations following severe trauma/sepsis leading to decreased energy production, hyperglycemia, and lipolysis is often rapid. Gender is increasingly recognized as a major factor in the outcome of patients suffering from trauma/sepsis. Moreover, sex hormones influence energy, glucose, and lipid metabolism. Metabolic modulators, such as peroxisome proliferator-activated receptor-gamma coactivator-1 and peroxisome proliferator-activated receptor-alpha, which are required for mitochondrial energy production and fatty acid oxidation, are regulated by the estrogen receptor-beta and consequently contribute to cardioprotection following trauma hemorrhage. Additionally, sex steroids regulate inflammatory cytokines that cause hypermetabolism/catabolism via acute phase response, leading to increased morbidity and mortality.

MEASUREMENTS

This article examines the following: (1) the evidence for gender differences; (2) energy, glucose, and lipid metabolism and the acute phase protein response; (3) the mechanisms by which gender/sex hormones affect the metabolic modulators; and (4) the tissue-specific effect of sex hormone receptors and the effect of genomic and nongenomic pathways of sex hormones following trauma.

RESULTS AND CONCLUSIONS

The available information indicates that sex steroids not only modulate the immune/cardiovascular responses but also influence various metabolic processes following trauma. Thus, alteration or modulation of the prevailing hormone milieu at the time of injury appears to be a novel therapeutic adjunct for improving outcome after injury.

Sexual Dimorphism in Superantigen Shock Involves Elevated TNF-α and TNF-α–induced Hepatic Apoptosis

RATIONALE

There is conflicting evidence regarding sex differences in the outcome from severe sepsis and toxic shock. Superantigen-mediated toxic shock affects a higher proportion of female patients.

OBJECTIVES

The objective of the current study was to investigate sexual dimorphism in superantigen-associated sepsis and in superantigen-mediated shock and to identify the key mechanisms responsible for this sex difference.

METHODS

We measured mortality and serum cytokines after induction of sepsis with isogenic superantigen-positive and superantigen-negative Streptococcus pyogenes in HLA class II transgenics. During superantigen-mediated toxic shock, we measured mortality, T-cell responses, systemic tumor necrosis factor (TNF)-alpha and TNF receptors, TNF-alpha-induced hepatocyte apoptosis, and conditioning of these responses by tamoxifen treatment.

MEASUREMENTS AND MAIN RESULTS

In both superantigen-associated sepsis and in superantigen-mediated shock, serum TNF-alpha was increased in females compared with males. This was not attributable to a detectable difference in splenic TNF-alpha transcription; rather, serum soluble TNF receptors were higher in males. Pretreatment of females with the estrogen receptor modulator tamoxifen increased serum soluble TNF receptors, reduced the early serum TNF-alpha response, and improved mortality in females challenged with staphylococcal enterotoxin B. Lethal superantigen shock was characterized by hepatocyte apoptosis, and was reproduced by injection of TNF-alpha. Females had enhanced susceptibility to TNF-alpha-mediated lethality. TNF-alpha-induced hepatocyte apoptosis was greater in females, and was reduced by tamoxifen pretreatment.

CONCLUSIONS

Sexual dimorphism in experimental superantigen toxic shock results from increased systemic TNF-alpha in females, coupled with an increased susceptibility to TNF-alpha-induced hepatocyte apoptosis. Both processes are abrogated by estrogen receptor modulators.

The complex role of estrogens in inflammation

There is still an unresolved paradox with respect to the immunomodulating role of estrogens. On one side, we recognize inhibition of bone resorption and suppression of inflammation in several animal models of chronic inflammatory diseases. On the other hand, we realize the immunosupportive role of estrogens in trauma/sepsis and the proinflammatory effects in some chronic autoimmune diseases in humans. This review examines possible causes for this paradox. This review delineates how the effects of estrogens are dependent on criteria such as: 1) the immune stimulus (foreign antigens or autoantigens) and subsequent antigen-specific immune responses (e.g., T cell inhibited by estrogens vs. activation of B cell); 2) the cell types involved during different phases of the disease; 3) the target organ with its specific microenvironment; 4) timing of 17beta-estradiol administration in relation to the disease course (and the reproductive status of a woman); 5) the concentration of estrogens; 6) the variability in expression of estrogen receptor alpha and beta depending on the microenvironment and the cell type; and 7) intracellular metabolism of estrogens leading to important biologically active metabolites with quite different anti- and proinflammatory function. Also mentioned are systemic supersystems such as the hypothalamic-pituitary-adrenal axis, the sensory nervous system, and the sympathetic nervous system and how they are influenced by estrogens. This review reinforces the concept that estrogens have antiinflammatory but also proinflammatory roles depending on above-mentioned criteria. It also explains that a uniform concept as to the action of estrogens cannot be found for all inflammatory diseases due to the enormous variable responses of immune and repair systems.

Estrogen receptor-alpha predominantly mediates the salutary effects of 17beta-estradiol on splenic macrophages following trauma-hemorrhage

Although 17beta-estradiol administration following trauma-hemorrhage prevents the suppression in splenic macrophage cytokine production, it remains unknown whether the salutary effects are mediated via estrogen receptor (ER)-alpha or ER-beta and which signaling pathways are involved in such 17beta-estradiol effects. Utilizing ER-alpha- or ER-beta-specific agonists, this study examined the role of ER-alpha and ER-beta in 17beta-estradiol-mediated restoration of macrophage cytokine production following trauma-hemorrhage. In addition, since MAPK and NF-kappaB are known to regulate macrophage cytokine production, we also examined the activation of those signaling molecules. Male rats underwent trauma-hemorrhage (mean arterial pressure of 40 mmHg for 90 min) and fluid resuscitation. The ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), the ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), 17beta-estradiol (50 microg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation. Twenty-four hours thereafter, splenic macrophages were isolated, and their IL-6 and TNF-alpha production and activation of MAPK and NF-kappaB were measured. Macrophage IL-6 and TNF-alpha production and MAPK activation were decreased, whereas NF-kappaB activity was increased, following trauma-hemorrhage. PPT or 17beta-estradiol administration after trauma-hemorrhage normalized those parameters. DPN administration, on the other hand, did not normalize the above parameters. Since PPT but not DPN administration following trauma-hemorrhage was as effective as 17beta-estradiol in preventing the suppression in macrophage cytokine production, it appears that ER-alpha plays the predominant role in mediating the salutary effects of 17beta-estradiol on macrophage cytokine production following trauma-hemorrhage and that such effects are likely mediated via normalization of MAPK but not NF-kappaB signaling pathways.

Salutary effects of 17beta-estradiol on T-cell signaling and cytokine production after trauma-hemorrhage are mediated primarily via estrogen receptor-alpha

Although 17beta-estradiol (E2) administration following trauma-hemorrhage prevents the suppression in splenocyte cytokine production, it remains unknown whether the salutary effects of 17beta-estradiol are mediated via estrogen receptor (ER)-alpha or ER-beta. Moreover, it is unknown which signaling pathways are involved in 17beta-estradiol's salutary effects. Utilizing an ER-alpha- or ER-beta-specific agonist, we examined the role of ER-alpha and ER-beta in E2-mediated restoration of T-cell cytokine production following trauma-hemorrhage. Moreover, since MAPK, NF-kappaB, and activator protein (AP)-1 are known to regulate T-cell cytokine production, we also examined the activation of MAPK, NF-kappaB, and AP-1. Male rats underwent trauma-hemorrhage (mean arterial pressure 40 mmHg for 90 min) and fluid resuscitation. ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), 17beta-estradiol (50 microg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation. Twenty-four hours thereafter, splenic T cells were isolated, and their IL-2 and IFN-gamma production and MAPK, NF-kappaB, and AP-1 activation were measured. T-cell IL-2 and IFN-gamma production was decreased following trauma-hemorrhage, and this was accompanied with a decrease in T-cell MAPK, NF-kappaB, and AP-1 activation. PPT or 17beta-estradiol administration following trauma-hemorrhage normalized those parameters, while DPN administration had no effect. Since PPT, but not DPN, administration following trauma-hemorrhage was as effective as 17beta-estradiol in preventing the T-cell suppression, it appears that ER-alpha plays a predominant role in mediating the salutary effects of 17beta-estradiol on T cells following trauma-hemorrhage, and that such effects are likely mediated via normalization of MAPK, NF-kappaB, and AP-1 signaling pathways.

INFLUENCE OF SEX AND AGE ON MODS AND CYTOKINES AFTER MULTIPLE INJURIES

Although salutary effects of female sex steroids have been demonstrated not only in proestrus females but also in male animals treated with estradiol in different models of trauma, it remains unknown whether sex hormones influence post-traumatic immune response in humans. We therefore investigated the effect of sex and age on organ dysfunction and clinical course in patients with multiple injuries. Polytraumatized patients (injury severity score>16) between 16 and 65 years old admitted to the Hannover Medical School Level 1 trauma center between January 1997 and December 2001 were included. Marshall Score for multiple organ dysfunction syndrome (MODS) was calculated for at least 14 days. The length of stay in intensive care unit and the ventilator days were recorded in addition to the number of transfusions the patient received. A total of 106 males and 37 females were included in the study. Patients with MODS had increased plasma levels of IL-6, IL-8, and IL-10. Furthermore, patients with organ dysfunction had more frequent sepsis and higher mortality rates. In addition, MODS was associated with extended length of stay in the intensive care unit and increased ventilator days. Females not older than 50 years with an injury severity score greater than 25 suffered significantly less MODS and sepsis compared with age-matched males. Moreover, they had significantly lower plasma cytokines. Thus, in this prospective study, sex difference was confirmed in MODS and sepsis, with a benefit observed in females. Although the levels of sex steroids were not measured, it seems that the protective effects may be due to estrogen effects on plasma cytokines. This suggestion is based on the fact that such salutary effects were apparent predominantly in premenopausal females.

Tissue compartment-specific role of estrogen receptor subtypes in immune cell cytokine production following trauma-hemorrhage

Although 17β-estradiol administration following trauma-hemorrhage attenuates plasma cytokines and alteration in immune cell cytokine production, it is not known whether the salutary effects are mediated via estrogen receptor (ER)-α or ER-β. Accordingly, we examined which ER subtype predominantly mediates the salutary effects of 17β-estradiol on systemic inflammatory response/immune cell cytokine production in various tissues following trauma-hemorrhage. Male rats underwent trauma-hemorrhage (mean blood pressure: 40 mmHg for 90 min) and fluid resuscitation. The ER-α agonist propyl pyrazole triol (PPT; 5 μg/kg), the ER-β agonist diarylpropionitrile (DPN; 5 μg/kg), 17β-estradiol (50 μg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation, and various measurements were made 24 h thereafter. 17β-Estradiol or PPT administration following trauma-hemorrhage prevented the increase in plasma IL-6 and IL-10 levels that were observed in vehicle-treated animals. IL-6 and TNF-α production by Kupffer cells increased; however, splenic macrophages (SMΦ), alveolar macrophages (AMΦ), and peripheral blood mononuclear cells (PBMC) had decreased release of these cytokines after trauma-hemorrhage. IL-10 production, however, increased in all macrophage populations. Administration of 17β-estradiol following trauma-hemorrhage prevented all of these alterations. PPT had the same effects as 17β-estradiol on IL-6 and TNF-α production by Kupffer cells and SMΦ, and DPN had the same effects on AMΦ and PBMC. The same effects as 17β-estradiol on IL-10 production were observed by PPT on Kupffer cells and DPN on PBMC. Both agonists were equally effective on SMΦ and AMΦ. Thus ER subtypes have tissue compartment-specific roles in mediating the effects of 17β-estradiol on immune cell functions following trauma-hemorrhage.

17β-estradiol administration following trauma-hemorrhage prevents the increase in Kupffer cell cytokine production and MAPK activation predominately via estrogen receptor-α

BACKGROUND

17 beta-estradiol (E2) administration following trauma-hemorrhage (T-H) attenuates the elevation in plasma cytokines and Kupffer cell (KC) cytokine production; however, it remains unknown whether the salutary effects are mediated via estrogen receptor (ER)-alpha or ER-beta. We hypothesized that E2 mediates its salutary effects via ER-alpha and normalization of MAPK under those conditions.

METHODS

Male rats underwent T-H (mean blood pressure [BP] 40 mmHg for 90 min) and fluid resuscitation. ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), E2 (50 microg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation. Twenty-four hours thereafter, KCs were isolated and their cytokine production (IL-6, TNF-alpha, IL-10) and MAPK activation were measured.

RESULTS

Cytokine production increased after T-H, however, PPT or E2 administration after T-H normalized KC cytokine production. Although DPN attenuated increased production of these cytokines, KC capacity to produce the cytokines remained significantly higher than sham. PPT or E2 also prevented T-H-mediated activation of MAPK in KC. However, DPN did not prevent MAPK activation.

CONCLUSIONS

Since PPT administration after T-H was more effective in decreasing KC cytokine production and MAPK activation than DPN, the salutary effects of E2 on KC functions are mediated predominantly via ER-alpha and normalization of MAPK following T-H.

Traumatic brain injury outcomes in pre- and post- menopausal females versus age-matched males

Gender differences in outcomes from major trauma have been described previously, and exogenous female hormone administration appears to be neuroprotective following traumatic brain injury (TBI). This analysis explored outcomes in pre- and post-menopausal females versus age-matched males. A total of 13,437 patients (n = 3,178 females, n = 10,259 males) with moderate-to-severe TBI (head AIS > or = 3) were identified from our county trauma registry. Overall mortality was similar between males and females (22% for both). Logistic regression was used to compare gender outcome differences, with a separate analysis performed for premenopausal (< 50 years) versus postmenopausal (> or = 50 years) patients, and after stratification by decade of life. No statistically significant difference in outcomes was observed for pre-menopausal females versus males (odds ratio [OR] 1.06; 95% confidence interval [CI] 0.83, 1.35; p = 0.633), but outcomes were significantly better in postmenopausal females versus males (OR 0.63, 95% CI 0.48-0.81, p < 0.001) after adjusting for age, mechanism of injury, Glasgow Coma Scale (GCS), hypotension (SBP < or = 90 mm Hg), head Abbreviated Injury Score (AIS), and Injury Severity Score (ISS). Stratification by decade of life revealed the gender survival differential inflection point to occur between ages 40-49 (OR 1.06, 95% CI 0.66-1.71, p = 0.798) and ages 50-59 (OR 0.38, 95% CI 0.20-0.74, p = 0.005). In addition, Revised Trauma Score and Injury Severity Score (TRISS) was used to calculate probability of survival (PS); all patients were then stratified by decade of life, and males and females were compared with regard to mean survival differential (outcome - PS). The identical pattern of improved outcomes in post-menopausal but not pre-menopausal females versus age-matched males was observed. These data suggest that endogenous female sex hormone production is not neuroprotective.

Gonadal steroids in critical illness

Gonadal steroids are metabolized in target cells and then interact with specific receptors to exert genomic and nongenomic effects. Complex feedback loops that involve the immune-neuroendocrine axis, limbic system, and gonadal steroids play a vital role in the adaptation to critical illness. Preclinical studies demonstrate adverse physiological effects of androgens on the cardiovascular and immune systems despite its purported anabolic effects. Similar models also demonstrate salutary effects of estrogens on these systems. Thus, during the catabolic phases of acute and chronic critical illness, estrogen, and not androgen, therapy may prove to be a valuable intervention. However, during the post-critical illness recovery phase, when anabolism is critical, androgen therapy may still be useful and safe.

Brief exposure to exogenous testosterone increases death signaling and adversely affects myocardial function after ischemia

Chronic endogenous testosterone exposure adversely affects proinflammatory and proapoptotic signaling after ischemia/reperfusion; however, it remains unknown whether a single acute testosterone exposure is equally detrimental. We hypothesized that acute exogenous testosterone infusion before ischemia would worsen myocardial functional recovery, increase the activation of MAPKs and caspase-3, and increase myocardial proinflammatory cytokine production. To study this, isolated-perfused rat hearts (Langendorff) from adult females and castrated males were subjected to 25-min ischemia and 40-min reperfusion with and without acute testosterone infusion (17beta-hydroxy-4-androstenone, 10 ng x ml(-1) x min(-1)) before ischemia. Myocardial contractile function was continuously recorded. After ischemia/reperfusion, hearts were assessed for levels of testosterone (ELISA), expression of proinflammatory cytokines (ELISA), and activation of MAPKs and caspase-3 (Western blot analysis). Data were analyzed with two-way ANOVA or Student's t-test; P < 0.05 was statistically significant. All indices of postischemic functional recovery were decreased with acute exogenous testosterone compared with the untreated groups. Acute testosterone infusion increased activation of MAPKs and caspase-3 following ischemia/reperfusion. However, there were no significant differences in the myocardial proinflammatory cytokine production after brief testosterone infusion. A single acute exposure to exogenous testosterone before ischemia worsens myocardial functional recovery and increases activation of MAPKs and caspase-3. These findings confirm the deleterious effects of testosterone on myocardium, elucidate the nongenomic mechanistic pathways of testosterone, and may have important clinical implications for patients who have acute exposure to exogenous testosterone.

GENDER DIFFERENCES IN ACUTE RESPONSE TO TRAUMA-HEMORRHAGE

To understand the pathogenesis of a disease, experimental models are needed. A good experimental model is the one that simulates responses observed in the clinical setting. In recent years, clinical studies have indicated that gender might be a factor that plays a significant role in the outcome of patients with shock, trauma, and sepsis. These observations are now being evaluated in experimental setting. Studies performed in a rodent model of trauma-hemorrhage have concluded that alterations in immune and cardiac functions after trauma-hemorrhage are more markedly depressed in adult males, and ovariectomized and aged females. However, both are maintained in castrated males and in proestrus females. Moreover, the survival rate of proestrus females subjected to sepsis after trauma-hemorrhage is significantly higher than age-matched males or ovariectomized females. Although these observations suggest gender-specific response after trauma-hemorrhage, the mechanisms responsible for gender specificity remain largely unknown. Furthermore, in other injuries such as burn, experimental studies dealing with sexual dimorphism are limited. Therefore, more studies in clinical and experimental settings are required to determine whether gender-specific responses are global across the injuries or are observed in specific injury situations. Studies are also needed to delineate underlying mechanisms responsible for differences between males and females after trauma-hemorrhage. The information gained from the experimental studies will help in designing innovative therapeutic approaches for the treatment of trauma patients.

Dehydroepiandrosterone restores depressed peripheral blood mononuclear cell function following major abdominal surgery via the estrogen receptors

OBJECTIVE

Peripheral blood mononuclear cell (PBMC) dysfunction occurs following major abdominal surgery and correlates with an increased rate of septic complications. Studies have shown that dehydroepiandrosterone (DHEA) restores cell-mediated immune responses after trauma-hemorrhage in mice. Nonetheless, it remains unknown whether DHEA has any salutary effects on depressed PBMC function in surgical patients.

DESIGN

Laboratory experiment.

SETTING

University laboratory.

PATIENTS

Fifteen patients undergoing major abdominal surgery.

INTERVENTIONS

Blood samples were obtained preoperatively and 2 hrs postoperatively.

MEASUREMENTS AND MAIN RESULTS

PBMCs were cultured with 33% plasma in the presence or absence of DHEA (10(-10) M, 10(-8) M physiologic concentration, 10(-6) M, 10(-5) M). In an additional set of samples, the estrogen receptor antagonist tamoxifen (10(-6) M) was added. The release of proinflammatory cytokines (interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha) was measured in the supernatants by enzyme-linked immunosorbent assay. Abdominal surgery resulted in depressed interleukin-1beta and tumor necrosis factor-alpha release by PBMC. Addition of DHEA to the culture medium, however, significantly improved the release of interleukin-1beta and tumor necrosis factor-alpha and stimulated the interleukin-6 release capacity of PBMC. This effect was most pronounced for a concentration of 10(-5)M DHEA. The immunomodulatory effect of DHEA on PBMC cytokine release was completely blocked by tamoxifen. In contrast, the modulatory effect of DHEA was enhanced by the addition of postoperative plasma.

CONCLUSIONS

DHEA stimulates proinflammatory cytokine release capacities of human PBMCs following major abdominal surgery. The estrogen receptor appears to be involved in mediating the immunomodulatory effect of DHEA. Thus, DHEA might be a useful adjunct for preventing immunosuppression in surgical patients.

Sex differences in the myocardial inflammatory response to ischemia-reperfusion injury

The myocardium generates inflammatory mediators during ischemia-reperfusion (I/R), and these mediators contribute to cardiac functional depression and apoptosis. The great majority of these data have been derived from male animals and humans. Sex has a profound effect over many inflammatory responses; however, it is unknown whether sex affects the cardiac inflammatory response to acute myocardial I/R. We hypothesized the existence of inherent sex differences in myocardial function, expression of inflammatory cytokines, and activation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway after I/R. Isolated rat hearts from age-matched adult males and females were perfused (Langendorff), and myocardial contractile function was continuously recorded. After I/R, myocardium was assessed for expression of TNF-alpha, IL-1beta, and IL-6 (RT-PCR, ELISA); IL-1alpha and IL-10 mRNA (RT-PCR); and activation of p38 MAPK (Western blot). All indexes of postischemic myocardial function [left ventricular developed pressure, left ventricular end-diastolic pressure, and maximal positive (+dP/dt) and negative (-dP/dt) values of the first derivative of pressure] were significantly improved in females compared with males. Compared with males, females had decreased myocardial TNF-alpha, IL-1beta, and IL-6 (mRNA, protein) and decreased activation of p38 MAPK pathway. These data demonstrate that hearts from age-matched adult females are relatively protected against I/R injury, possibly due to a diminished inflammatory response.

SEX DIFFERENCES IN THE MYOCARDIAL INFLAMMATORY RESPONSE TO ACUTE INJURY

Hemorrhage, trauma, ischemia/reperfusion, burn, and sepsis each lead to cardiac dysfunction. These insults lead to an inflammatory cascade, which plays an important role in this process. Gender has been shown to influence the inflammatory response, as well as outcomes after acute injury. The mechanisms by which gender affects the inflammatory response to and the outcome of acute injury are being actively investigated. We searched PubMed for articles in the English language by using the search words sex, gender, estrogen, testosterone, 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. This review will examine evidence for gender differences in the outcome to acute injury, explain the myocardial inflammatory response to acute injury, and elucidate the various mechanisms by which gender affects the myocardial response to acute injury.

Strain-Dependent Vascular Remodeling

Background— Atherosclerosis of the carotid artery, called intima-media thickening (IMT), is a form of vascular remodeling that is an important predictor for cardiovascular events and has a strong genetic component.

Methods and Results— Recently, we established a mouse model of vascular remodeling based on partial ligation of the carotid, which is relevant to the “Glagov phenomenon.” We hypothesized that there would be genetically determined differences in outward remodeling and IMT induced by carotid flow alterations. We compared vascular remodeling among 5 inbred strains of mice. Despite similar changes in flow among the strains in the left carotid artery (LCA), we observed dramatic differences in remodeling of the partially ligated LCA relative to control. The smallest IMT volume (26±3 μm 3 ) was found in C3H/HeJ mice, and the largest were in SJL/J (59±10 μm 3 ) and FVB/NJ (81±6 μm 3 ). Shear stress did not differ after ligation among strains. Lumen area decreased only when stenosis was ≥55%. IMT correlated significantly with outward remodeling among inbred strains (except C3H). There were significant strain-dependent differences in remodeling index (measured as vessel area/IMT), which suggest fundamental alterations in sensing or transducing hemodynamic signals among strains. Among hemodynamic factors, low shear stress and high heart rate were predictive for IMT. Specifically, heart rate (bpm: C3H, 592±6; SJL, 649±6; FVB, 683±7) but not systolic blood pressure (mm Hg: C3H, 116±2; SJL, 119±1; FVB, 136±1) was predictive.

Conclusions— The present study indicates that performing a genetic cross of these strains and total genome scan should identify genes that mediate vascular remodeling.

Female Sex Hormones Protect Red Blood Cells from Damage after Trauma-Hemorrhagic Shock

BACKGROUND

Trauma/hemorrhagic shock (T/HS) is known to cause changes in red blood cell (RBC) deformability and resting shape. Our previous studies have shown that proestrus female rats are more protected from shock-induced RBC damage than diestrus females or males. However, it is unclear whether female or male sex hormones can influence the severity of these alterations.

METHODS

Red blood cell deformability and shape were examined in proestrus female rats, and oophorectomized female rats, as well as in castrated and non-castrated male rats (5-10 animals per group) subjected to T/HS. Red blood cell deformability was measured by laser ektacytometry whereas erythrocyte shape was evaluated by scanning electron microscopy.

RESULTS

Proestrus female rats subjected to T/HS did not show either significant RBC deformability changes (decrease in elongation index) or shape alterations (increase in the percentage of reversibly and irreversibly changed cells). Oophorectomized rats demonstrated more severe RBC changes than did non-oophorectomized rats. The degree of RBC damage was the same in castrated and non-castrated males, which was significantly worse than in proestrus females.

CONCLUSIONS

Removal of female sex hormones increases the severity of T/HS-induced RBC changes, indicating that female sex hormones protect against RBC damage. In contrast, male sex hormones do not appear to modulate T/HS RBC dysfunction.

Estrogen receptor-alpha deficiency promotes increased TNF-alpha secretion and bacterial killing by murine macrophages in response to microbial stimuli in vitro

In this series of studies, we determined the potential role of intracellular estrogen receptors (ER), ERalpha and ERbeta, on macrophage function in response to bacterial stimuli. The sex hormone 17beta-estradiol (E(2)) and ER have been shown to modulate inflammatory responses as well as T helper cell type 1 (TH1)/TH2 responses. The mechanisms E(2) and its receptors use to alter these immune functions remain largely unknown. ERalpha and ERbeta possess complex actions in tissues where they are expressed. We have characterized the receptor repertoire of murine dendritic cells and thioglycollate-elicited peritoneal macrophages (PM). Both cell types express mRNA for ERalpha. Neither cell type expressed detectable amounts of ERbeta mRNA, as determined by reverse transcriptase-polymerase chain reaction using exon-specific primers spanning each of the seven intron/exon junctions. Primary macrophages from ERalpha- and ERbeta-deficient severe combined immunodeficiency mice [ERalpha knockout (KO) and ERssKO, respectively] were used to delineate the effects and potential mechanisms via which steroid receptors modulate macrophage function. ERalpha-deficient PM exposed ex vivo to lipopolysaccharide or Mycobacterium avium exhibited significant increases in tumor necrosis factor alpha (TNF-alpha) secretion as well as reduction in bacterial load when compared with wild-type (WT) PM. In contrast, ERbeta-deficient PM possessed no significant difference in TNF-alpha secretion or in bacterial load when compared with WT littermates. These studies suggest that ERalpha, but not ERbeta, modulates murine PM function.