Salutary effects of estrogen receptor-β agonist on lung injury after trauma-hemorrhage

Sirtinol attenuates hepatic injury and pro-inflammatory cytokine production following trauma-hemorrhage in male Sprague-Dawley rats

BACKGROUND

Although studies have demonstrated that sirtinol administration following adverse circulatory conditions is known to be protective, the mechanism by which sirtinol produces the salutary effects remains unknown. We hypothesized that sirtinol administration in male rats following trauma-hemorrhage decreases cytokine production and protects against hepatic injury.

METHODS

Male Sprague-Dawley rats underwent trauma-hemorrhage (mean blood pressure 40 mmHg for 90 min, then resuscitation). A single dose of sirtinol (1 mg/kg of body weight) or vehicle was administered intravenously during resuscitation. Twenty-four hours thereafter, tissue myeloperoxidase (MPO) activity (a marker of neutrophil sequestration), cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-3, intercellular adhesion molecule (ICAM)-1, and interleukin (IL)-6 levels in the liver and plasma alanine aminotransferase (ALT) concentrations were measured (n=6 Sprague-Dawley rats/group).

RESULTS

Trauma-hemorrhage increased hepatic MPO activity, CINC-1, CINC-3, ICAM-1, and IL-6 levels and plasma ALT concentrations. These parameters were significantly improved in the sirtinol-treated rats subjected to trauma-hemorrhage.

CONCLUSION

The salutary effects of sirtinol administration on attenuation of hepatic injury following trauma-hemorrhage are, at least in part, related to reduction of pro-inflammatory mediators.

Male gender is associated with excessive IL-6 expression following severe injury

OBJECTIVE

An important and persistent laboratory finding has been that males and females respond differently after traumatic injury and hemorrhagic shock. We have previously presented clinical data showing that male gender is independently associated with a 40% higher rate of multiple organ failure (MOF) and a 25% higher rate of nosocomial infection (NI) after injury; however, the mechanism responsible for this dimorphic response after injury has not been adequately characterized clinically.

METHODS

Data were obtained from a multicenter prospective cohort study evaluating clinical outcomes in severely injured adults with blunt hemorrhagic shock. Proteomic analysis of serum inflammatory cytokines, on days 0, 1, and 4 postinjury, was performed on 46 males and 34 females. Repeated measures ANOVA were used to compare serial IL-1beta, TNF-alpha, IL-6, IL-8, and IL-10 serum levels across gender, while controlling for important confounders. Logistic regression modeling was then used to analyze the independent risk of MOF and NI associated with gender.

RESULTS

IL-6 serum levels were statistically higher in males relative to females (p = 0.008). This higher level of IL-6 expression in males remained statistically significant over time even after controlling for differences in age, initial base deficit, ISS, and 12-hour blood transfusion requirements (p = 0.025). No differences in IL-1beta serum levels (p = 0.543), TNF-alpha, (p = 0.200) IL-8 (p = 0.107), and IL-10 (p = 0.157) were found. Males had a higher crude incidence of MOF and an 11-fold higher independent risk of MOF.

CONCLUSIONS

Persistently elevated IL-6 levels in males are associated with a higher rate of MOF. It is not known if this excessive IL-6 expression in males is causal or only a marker for poor outcome. Further studies are required to elucidate if this early, persistent IL-6 expression is responsible for the gender-based differential outcomes after injury.

Age differences in inflammatory and hypermetabolic postburn responses

OBJECTIVE

The aim of this study was to identify contributors to morbidity and death in severely burned patients <4 years of age.

METHODS

A total of 188 severely burned pediatric patients were divided into 3 age groups (0-3.9 years, 4-9.9 years, and 10-18 years of age). Resting energy expenditure was measured through oxygen consumption, body composition through dual-energy x-ray absorptiometry, liver size and cardiac function through ultrasonography, and levels of inflammatory markers, hormones, and acute-phase proteins through laboratory chemistry assays.

RESULTS

Resting energy expenditure was highest in the 10- to 18-year-old group, followed by the 4- to 9.9-year-old group, and was lowest in the 0- to 3.9-year-old group. Children 0 to 3.9 years of age maintained lean body mass and body weight during acute hospitalization, whereas children >4 years of age lost body weight and lean body mass. The inflammatory cytokine profile showed no differences between the 3 age groups, whereas liver size increased significantly in the 10- to 18-year-old group and was lowest in the 0- to 3.9-year-old group. Acute-phase protein and cortisol levels were significantly decreased in the toddler group, compared with the older children. Cardiac data indicated increased cardiac work and impaired function in the toddler group, compared with the other 2 age groups.

CONCLUSIONS

Increased mortality rates for young children are associated with increased cardiac work and impaired cardiac function but not with the inflammatory and hypermetabolic responses.

Estrogen signaling through the transmembrane G protein-coupled receptor GPR30

Steroids play an important role in the regulation of normal physiology and the treatment of disease. Steroid receptors have classically been described as ligand-activated transcription factors mediating long-term genomic effects in hormonally regulated tissues. It is now clear that steroids also mediate rapid signaling events traditionally associated with growth factor receptors and G protein-coupled receptors. Although evidence suggests that the classical steroid receptors are capable of mediating many of these events, more recent discoveries reveal the existence of transmembrane receptors capable of responding to steroids with cellular activation. One such receptor, GPR30, is a member of the G protein-coupled receptor superfamily and mediates estrogen-dependent kinase activation as well as transcriptional responses. In this review, we provide an overview of the evidence for the cellular and physiological actions of GPR30 in estrogen-dependent processes and discuss the relationship of GPR30 with classical estrogen receptors.

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.

17beta-Estradiol: a novel hormone for improving immune and cardiovascular responses following trauma-hemorrhage

17beta-Estradiol (i.e., estrogen or E2) is a female sex steroid, which plays an essential role in female reproductive physiology. However, several lines of evidence indicate that in addition to its role in reproductive physiology, E2 is critical for maintaining many other organ functions in stress conditions. These include immune, cardiovascular, and neuronal functions, as well as regulation of skin, bone, and lipid metabolism. Studies have examined the role of E2 as an adjunct in post-trauma responses, and this article will review whether E2 as an adjunct to fluid resuscitation following trauma-hemorrhage plays any role in improving/restoring immune and cardiovascular functions.

Protective effect of raloxifene on lipopolysaccharide and acid- induced acute lung injury in rats

AIM

To evaluate the protective effect of oral raloxifene on acute lung injury.

METHODS

Thirty adult, male Sprague-Dawley rats each weighing 180-210 g were used and divided into 3 groups: the raloxifene-lipopolysaccharide (LPS)-HCl group (n=10), the LPS-raloxifene-HCl group (n=10), and the placebo group (n=10). All the rats were injected intraperitoneally (ip) with 5 mg/kg LPS, and raloxifene (30 mg/kg) was orally administered 1 h before and 14 h after LPS injection into the raloxifene-LPS-HCl and the LPS-raloxifene-HCl groups, respectively; the placebo group received nothing. Sixteen hours after LPS injection, all the animals were anesthetized and the femoral artery was cannulated. All the rats received a direct intratracheal (IT) injection of HCl (pH 1.2; 0.5 mL/kg). The mean arterial pressure (MAP) and blood gas concentrations were measured. Fifteen rats (5 in each group, respectively) underwent a micro positron emission tomography (microPET) scan of the thorax 4 h after HCl instillation. The wet/dry (W/D) weight ratio determination and histopathological examination were also performed.

RESULTS

The rats in the LPS-raloxifene-HCl group had a lower [18F]fluorodeoxyglucose uptake compared with the rats in the placebo group (4.67+/-1.33 vs 9.01+/-1.58, respectively, P<0.01). The rats in the LPS-raloxifene-HCl group also had a lower histological lung injury score (8.20+/-1.23 vs 12.6+/-0.97, respectively, P<0.01) and W/D weight ratio (5.335+/-0.198 vs 5.886+/-0.257, respectively, P<0.01) compared to the placebo group. The rats in this group also showed better pulmonary gas exchange and more stable mean arterial pressure (MAP) compared to the placebo group.

CONCLUSION

Raloxifene provides a significant protective effect on acute lung injury in rats induced first by LPS ip injection and then by HCl IT instillation.

Gender dimorphism following injury: making the connection from bench to bedside

Despite ongoing prevention efforts, injury remains the leading cause of mortality over the first three decades of life in the United States. Those who survive their initial injury continue to be plagued with the development of sepsis and multiple organ failure and their attributable morbidity and mortality. An important and persistent finding has been that males and females respond differently following traumatic injury and hemorrhagic shock. A significant advancement in the experimental understanding of the gender dimorphism in response to trauma-hemorrhage and sepsis has occurred. Experimental evidence for the differential effects of sex hormones on cell-mediated immunity and organ system tolerance of shock continues to expand. Clinical studies, however, have been unable to reproduce these laboratory bench findings consistently. There continues to be a divide between the "bench and bedside" in regard to our understanding of gender-based differences following injury. Relative to controlled animal experiments, predisposing comorbidities, injury characteristics, and a lack of information about the hormone milieu of the trauma patient disallow reproducible results from clinical analyses. Continued clinical research into potential sex hormone-based differences, genetic differences, and the cellular and molecular mechanisms responsible for these gender-based differential responses is required to close this gap. This may ultimately promote therapeutic interventions, which will allow for improved outcomes for males and females in the near future.

The critical role of vascular endothelial growth factor in pulmonary vascular remodeling after lung injury

The pulmonary vascular endothelial cell plays a crucial role in the regulation of the pulmonary vascular tone and in the maintenance of the barrier function and integrity of the alveolar-capillary membrane. It also plays a major role in coagulation, fibrinolysis, and angiogenesis and participates in inflammatory reactions. Vascular endothelial growth factor (VEGF) is a central growth and survival factor for the endothelial cell. Particularly high levels of VEGF are expressed in the lungs, reflecting the critical role of VEGF for lung development and structural integrity of the adult lung. Vascular endothelial growth factor exerts a variety of physiological and pathophysiological actions in the lung. Recent evidence suggests its involvement in the pathogenesis of lung diseases such as bronchopulmonary dysplasia, acute lung injury, emphysema, and pulmonary hypertension. To summarize the critical effects of VEGF on the pulmonary endothelial cell in the pathogenesis of these diseases, the purposes of this review are to (1) discuss the biological activities and intracellular signaling pathways of VEGF in the lung; (2) summarize the regulatory mechanisms involved in VEGF expression; (3)address the effects of VEGF on endothelial cells in hyperoxia-induced and other forms of lung injury; (4) highlight the endothelial effects of VEGF in the pathogenesis of emphysema; and (5) explore the role of VEGF in the pathogenesis of pulmonary arterial hypertension.

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.

Endogenous estrogen attenuates pulmonary artery vasoreactivity and acute hypoxic pulmonary vasoconstriction: the effects of sex and menstrual cycle

Sex differences exist in a variety of cardiovascular disorders. Sex hormones have been shown to mediate pulmonary artery (PA) vasodilation. However, the effects of fluctuations in physiological sex hormone levels due to sex and menstrual cycle on PA vasoreactivity have not been clearly established yet. We hypothesized that sex and menstrual cycle affect PA vasoconstriction under both normoxic and hypoxic conditions. Isometric force displacement was measured in isolated PA rings from proestrus females (PF), estrus and diestrus females (E/DF), and male (M) Sprague-Dawley rats. The vasoconstrictor response under normoxic conditions (organ bath bubbled with 95% O(2)-5% CO(2)) was measured after stimulation with 80 mmol/l KCl and 1 mumol/l phenylephrine. Hypoxia was generated by changing the gas to 95% N(2)-5% CO(2). PA rings from PF demonstrated an attenuated vasoconstrictor response to KCl compared with rings from E/DF (75.58 +/- 3.2% vs. 92.43 +/- 4.24%, P < 0.01). Rings from M also exhibited attenuated KCl-induced vasoconstriction compared with E/DF (79.34 +/- 3.2% vs. 92.43 +/- 4.24%, P < 0.05). PA rings from PF exhibited an attenuated vasoconstrictor response to phenylephrine compared with E/DF (59.61 +/- 2.98% vs. 70.03 +/- 4.61%, P < 0.05). While the maximum PA vasodilation during hypoxia did not differ between PF, E/DF, and M, phase II of hypoxic pulmonary vasoconstriction was markedly diminished in the PA from PF (64.10 +/- 7.10% vs. 83.91 +/- 5.97% in M, P < 0.05). We conclude that sex and menstrual cycle affect PA vasoconstriction in isolated PA rings. Even physiological increases in circulating estrogen levels attenuate PA vasoconstriction under both normoxic and hypoxic conditions.

The impact of sex and sex hormones on lung physiology and disease: lessons from animal studies

Numerous animal studies have revealed significant effects of sex and sex hormones on normal lung development, lung physiology, and various lung diseases. The primary goal of this review is to summarize knowledge to date on the effects of sex and sex hormones on lung development, physiology, and disease in animals. Specific emphasis will be placed on fibrosis, allergic airway disease, acute lung injury models, respiratory infection, and lung toxicology studies.

Estrogen modulates TNF-α-induced inflammatory responses in rat aortic smooth muscle cells through estrogen receptor-β activation

We have previously shown that 17β-estradiol (E2) attenuates responses to endoluminal injury of the rat carotid artery, at least in part, by decreasing inflammatory mediator expression and neutrophil infiltration into the injured vessel, with a major effect on the neutrophil-specific chemokine cytokine-induced neutrophil chemoattractant (CINC)-2β. Current studies tested the hypothesis that activated rat aortic smooth muscle cells (RASMCs) express these same inflammatory mediators and induce neutrophil migration in vitro and that E2 inhibits these processes by an estrogen receptor (ER)-dependent mechanism. Quiescent RASMCs treated with E2, the ERα-selective agonist propyl pyrazole triol (PPT), the ERβ-selective agonist diarylpropiolnitrile (DPN), or vehicle for 24 h were stimulated with tumor necrosis factor (TNF)-α and processed for real-time RT-PCR, ELISA, or chemotaxis assays 6 h later. TNF-α stimulated and E2 attenuated mRNA expression of inflammatory mediators, including P-selectin, intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, monocyte chemoattractant protein (MCP)-1, and CINC-2β. DPN dose dependently attenuated TNF-α-induced mRNA expression of CINC-2β, whereas PPT had no effect. The anti-inflammatory effects of DPN and E2 were blocked by the nonselective ER-inhibitor ICI-182,780. ELISA confirmed the TNF-α-induced increase and E2-induced inhibition of CINC-2β protein secretion. TNF-α treatment of RASMCs produced a twofold increase in neutrophil chemotactic activity of conditioned media; E2 and DPN treatment markedly inhibited this effect. E2 inhibits activated RASMC proinflammatory mediator expression and neutrophil chemotactic activity through an ERβ-dependent mechanism.

Estrogen receptor-beta: recent lessons from in vivo studies

The unexpected discovery of a second form of the estrogen receptor (ER), designated ERbeta, surprised and energized the field of estrogen research. In the 9 yr since its identification, the remarkable efforts from academic and industrial scientists of many disciplines have made significant progress in elucidating its biology. A powerful battery of tools, including knockout mice as well as a panel of receptor-selective agonists, has allowed an investigation into the role of ERbeta. To date, in vivo efficacy studies are limited to rodents. Current data indicate that ERbeta plays a minor role in mediating estrogen action in the uterus, on the hypothalamus/pituitary, the skeleton, and other classic estrogen target tissues. However, a clear role for ERbeta has been established in the ovary, cardiovascular system, and brain as well as in several animal models of inflammation including arthritis, endometriosis, inflammatory bowel disease, and sepsis. The next phase of research will focus on elucidating, at a molecular level, how ERbeta exerts these diverse effects and exploring the clinical utility of ERbeta-selective agonists.