mediates pathogenic inflammatory responses to intestinal ischemia-reperfusion injury. Am J Physiol Gastrointest Liver Physiol 299: G833-G843, 2010. First published August 5, 2010 doi:10.1152/ajpgi.00065.2010.-Acute lung injury (ALI) and the development of the multiple organ dysfunction syndrome (MODS) are major causes of death in trauma patients. Gut inflammation and loss of gut barrier function as a consequence of splanchnic ischemia-reperfusion (I/R) have been implicated as the initial triggering events that contribute to the development of the systemic inflammatory response, ALI, and MODS. Since hypoxia-inducible factor (HIF-1) is a key regulator of the physiological and pathophysiological response to hypoxia, we asked whether HIF-1 plays a proximal role in the induction of gut injury and subsequent lung injury. Utilizing partially HIF-1␣-deficient mice in a global trauma hemorrhagic shock (T/HS) model, we found that HIF-1 activation was necessary for the development of gut injury and that the prevention of gut injury was associated with an abrogation of lung injury. Specifically, in vivo studies demonstrated that partial HIF-1␣ deficiency ameliorated T/HS-induced increases in intestinal permeability, bacterial translocation, and caspase-3 activation. Lastly, partial HIF-1␣ deficiency reduced TNF-␣, IL-1␤, cyclooxygenase-2, and inducible nitric oxide synthase levels in the ileal mucosa after T/HS whereas IL-1␤ mRNA levels were reduced in the lung after T/HS. This study indicates that prolonged intestinal HIF-1 activation is a proximal regulator of I/R-induced gut mucosal injury and gut-induced lung injury. Consequently, these results provide unique information on the initiating events in trauma-hemorrhagic shock-induced ALI and MODS as well as potential therapeutic insights. hemorrhagic shock; inflammation; multiple organ dysfunction syndrome; acute lung injury IN PATIENTS SUSTAINING major trauma, the development of the systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction (MODS) is a major clinical problem resulting in 50 -80% of all deaths in surgical intensive care units. Since the pathophysiology of this syndrome remains incompletely understood and therapy remains largely supportive (16), studies focusing on the basic biology of traumainduced SIRS, organ injury/dysfunction, and MODS have been major areas of investigation. These mechanistic studies have generated several working hypotheses, one of which is the gut hypothesis of MODS. A key element in the gut hypothesis of MODS is that a splanchnic ischemia-reperfusion (I/R) insult leading to gut inflammation and loss of barrier function is the initial triggering event that turns the gut into the "motor" of MODS (19). However, the exact mechanisms by which gut I/R leads to intestinal injury and how an intestinal ischemic insult is transduced into a systemic inflammatory response remains incomplete. To date, the majority of the molecular and cellular studies investigating shock-induced gut injury and gut-induced MODS have focused pr...

Unilateral LC results in the rapid mobilization of a significant number of HPC from the BM to the site of injury. BM function is maintained under this condition. The addition of HS increases HPC mobilization from the BM and sequestration at the site of injury as well as decreasing BM HPC growth. We postulate that the accumulation of progenitor cells in the injured tissue combined with an alteration of normal BM homing, as exemplified by the decrease in progenitor cells from the lung without restoration of BM function, plays a role in posttraumatic BM suppression. The mechanism of shock-mediated mobilization from the BM and the exact role and fate of these cells at the site of injury requires further investigation.

BackgroundAcute 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)α and ERβ in modulating the protective response of female rats to T/HS-induced gut and lung injury.Methods/Principal FindingsThe 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 ERα or ERβ 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 ERα and ERβ agonists were equally effective in limiting T/HS-induced morphologic villous injury and bacterial translocation, whereas the ERβ agonist was more effective than the ERα 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 ERβ agonist attenuated the induction of the intestinal iNOS response in OVX rats subjected to T/HS whereas the ERα agonist was only partially protective.Conclusions/SignificanceOur study demonstrates that estrogen attenuates T/HS-induced gut and lung injury and that its protective effects are mediated by the activation of ERα, ERβ or both receptors.