Search

Organ failure is a common cause of morbidity and mortality in patients sustaining major trauma, and hence, the pathophysiology of trauma-induced organ injury and dysfunction has been an important line of research.1 Based on these trauma studies, it is clear that shock-induced changes and trauma-induced changes in neutrophil activation are involved in the pathogenesis of the adult respiratory distress syndrome and contribute to the development of the multiple organ dysfunction syndrome.1 Likewise, recent work suggests that impaired red blood cell (RBC) deformability, which occurs in sepsis, after trauma, and during shock states,2–4 contributes to the development of multiple organ dysfunction syndrome by impairing tissue microvascular blood flow.5 Consequently, understanding the factors that modulate the magnitude and extent of neutrophil activation and RBC deformability might provide important insights into ways to limit post-trauma organ dysfunction.1 Because gender and sex hormones have been shown to modulate the development of organ injury as well as the immune system in preclinical models of trauma-hemorrhagic shock (T/HS)6–10 and in some but not all clinical studies,11 we have been interested in investigating the effects of gender and sex hormones on T/HS-induced changes in neutrophil and RBC function. Our earlier studies documented that neutrophil activation12 and RBC rigidification13 were reduced in female as opposed to male rats subjected to T/HS and that estrogen played a protective role in these studies. Because the beneficial effects of estrogen (17β-estradiol) seem to occur through high-affinity estrogen receptors (ER), the major goal of this study was to investigate the relative role that each of the two principal ERs (ER-α and -β) played in protecting against trauma-shock-induced RBC dysfunction, as measured by RBC deformability and neutrophil activation. To accomplish this goal, we administered either the ER-α agonist propyl pyrazole triol (PPT) or the ER-β agonist diarylpropiolnitrile (DPN) to ovariectomized (OVX) rats. These agents were chosen as PPT has a 410-fold higher binding affinity preference for ER-α over ER-β,14 whereas DPN exhibits a 70-fold higher binding affinity to ER-β than ER-α.15

Background Acute lung injury (ALI) and the development of the multiple organ dysfunction syndrome (MODS) is a major cause of death in trauma patients. Earlier studies in trauma hemorrhagic shock (T/HS) have documented that splanchnic ischemia leading to gut inflammation and loss of barrier function is an initial triggering event that leads to gut-induced ARDS and MODS. Since sex hormones have been shown to modulate the response to T/HS and proestrous (PE) females are more resistant to T/HS-induced gut and distant organ injury, the goal of our study was to determine the contribution of estrogen receptor (ER)alpha and ERbeta in modulating the protective response of female rats to T/HS-induced gut and lung injury. Methods/principal findings The incidence of gut and lung injury was assessed in PE and ovariectomized (OVX) female rats subjected to T/HS or trauma sham shock (T/SS) as well as OVX rats that were administered estradiol (E2) or agonists for ERalpha or ERbeta immediately prior to resuscitation. Marked gut and lung injury was observed in OVX rats subjected to T/HS as compared to PE rats or E2-treated OVX rats subjected to T/HS. Both ERalpha and ERbeta agonists were equally effective in limiting T/HS-induced morphologic villous injury and bacterial translocation, whereas the ERbeta agonist was more effective than the ERalpha agonist in limiting T/HS-induced lung injury as determined by histology, Evan's blue lung permeability, bronchoalevolar fluid/plasma protein ratio and myeloperoxidase levels. Similarly, treatment with either E2 or the ERbeta agonist attenuated the induction of the intestinal iNOS response in OVX rats subjected to T/HS whereas the ERalpha agonist was only partially protective. Conclusions/significance Our study demonstrates that estrogen attenuates T/HS-induced gut and lung injury and that its protective effects are mediated by the activation of ERalpha, ERbeta or both receptors.