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...

Human polymorphonuclear neutrophil (PMN) responses to G protein-coupled chemoattractants are highly dependent upon store-operated Ca2+ entry (SOCE). Recent research suggests that SOCE currents can be mediated by a variety of related channel proteins of the transient receptor potential superfamily. SOCE has been regarded as a specific response to depletion of cell calcium stores. We hypothesized that net SOCE might reflect the contributions of more than one calcium entry pathway. SOCE was studied in normal human PMN using Ca2+ and Sr2+ ions. We found that PMN SOCE depends on at least two divalent cation influx pathways. One of these was nonspecific and Sr2+ permeable; the other was Ca2+ specific. The two pathways show different degrees of dependence on store depletion by thapsigargin and ionomycin, and differential sensitivity to inhibition by 2-aminoethyoxydiphenyl borane and gadolinium. The inflammatory G protein-coupled chemoattractants fMLP, platelet-activating factor, and IL-8 elicit unique patterns of Sr2+ and Ca2+ influx channel activation, and SOCE responses to these agonists displayed differing degrees of linkage to prior Ca2+ store depletion. The mechanisms of PMN SOCE responses to G protein-coupled chemoattractants are physiologically diverse. They appear to reflect Ca2+ transport through a variety of channels that are independently regulated to varying degrees by store depletion and by G protein-coupled receptor activation.

BackgroundInjurious non-microbial factors released from the stressed gut during shocked states contribute to the development of acute lung injury (ALI) and multiple organ dysfunction syndrome (MODS). Since Toll-like receptors (TLR) act as sensors of tissue injury as well as microbial invasion and TLR4 signaling occurs in both sepsis and noninfectious models of ischemia/reperfusion (I/R) injury, we hypothesized that factors in the intestinal mesenteric lymph after trauma hemorrhagic shock (T/HS) mediate gut-induced lung injury via TLR4 activation.Methods/Principal FindingsThe concept that factors in T/HS lymph exiting the gut recreates ALI is evidenced by our findings that the infusion of porcine lymph, collected from animals subjected to global T/HS injury, into naïve wildtype (WT) mice induced lung injury. Using C3H/HeJ mice that harbor a TLR4 mutation, we found that TLR4 activation was necessary for the development of T/HS porcine lymph-induced lung injury as determined by Evan's blue dye (EBD) lung permeability and myeloperoxidase (MPO) levels as well as the induction of the injurious pulmonary iNOS response. TRIF and Myd88 deficiency fully and partially attenuated T/HS lymph-induced increases in lung permeability respectively. Additional studies in TLR2 deficient mice showed that TLR2 activation was not involved in the pathology of T/HS lymph-induced lung injury. Lastly, the lymph samples were devoid of bacteria, endotoxin and bacterial DNA and passage of lymph through an endotoxin removal column did not abrogate the ability of T/HS lymph to cause lung injury in naïve mice.Conclusions/SignificanceOur findings suggest that non-microbial factors in the intestinal mesenteric lymph after T/HS are capable of recreating T/HS-induced lung injury via TLR4 activation.

Background Following severe traumatic injury, critically ill patients have a prolonged hypercatacholamine state that is associated with bone marrow (BM) dysfunction and persistent anemia. However, current animal models of injury and shock result in a transient anemia. Daily restraint stress (CS) has been shown to increase catecholamines. We hypothesize that adding CS following injury or injury and shock in rats will prolong the hypercatecholaminemia, and prolong the initial anemia, despite elevated erythropoietin levels. Methods Male Sprague-Dawley Rats (N=6–8/group) underwent lung contusion (LC) or combined lung contusion/hemorrhagic shock (LCHS) followed by six days of chronic stress (CS). CS consisted of a two hour restraint period interrupted with repositioning and alarms every 30 minutes. At seven days, urine was assessed for norepinephrine (NE) levels, blood for erythropoietin (EPO) and hemoglobin (Hgb), and BM for erythroid progenitor growth. Results Animals undergoing LC or combined LCHS predictably recovered by day seven; urine NE, EPO and Hgb levels were normal. The addition of CS to LC and LCHS models was associated with a significant elevation in NE on day six. The addition of CS to LC led to a persistent 20–25% decrease in the growth of BM HPCs. These findings were further exaggerated when CS was added following LCHS, resulting in a 20–40% reduction in BM erythroid progenitor colony growth and a 20% decrease in Hgb when compared to LCHS alone. Conclusions Exposing injured animals to CS results in prolonged elevation of norepinephrine and erythropoietin which is associated with worsening BM erythroid function and persistent anemia. Chronic restraint stress following injury and shock provides a clinically relevant model to further evaluate persistent injury-associated anemia seen in critically ill trauma patients. Furthermore, alleviating chronic stress after severe injury is a potential therapeutic target to improve BM dysfunction and anemia.

Store-operated calcium entry (SOCE) is required for polymorphonuclear neutrophil (PMN) activation in response to G protein-coupled agonists. Some immunocytes express proteins homologous to the Drosophila transient receptor potential gene (trp) calcium channel. TRP proteins assemble into heterotetrameric ion channels and are known to support SOCE in overexpression systems, but the evidence that TRP proteins support SOCE and are functionally important in wild-type cells remains indirect. We therefore studied the expression and function of TRP proteins in primary human PMN. TRPC1, TRPC3, TRPC4, and TRPC6 were all expressed as mRNA as well as membrane proteins. Immunofluorescence microscopy demonstrated localization of TRPC1, TRPC3, and TRPC4 to the PMN cell membrane and their internalization after cytoskeletal reorganization by calyculin A (CalyA). Either TRPC internalization by CalyA or treatment with the inositol triphosphate receptor inhibitor 2-aminoethoxydiphenyl borane resulted in the loss of PMN SOCE. Cytochalasin D (CytoD) disrupts actin filaments, thus preventing cytoskeletal reorganization, and pretreatment with CytoD rescued PMN SOCE from inhibition by CalyA. Comparative studies of CytoD and 2-aminoethoxydiphenyl borane inhibition of PMN cationic entry after thapsigargin or platelet-activating factor suggested that SOCE occurs through both calcium-specific and nonspecific pathways. Taken together, these studies suggest that the multiple TRPC proteins expressed by human PMN participate in the formation of at least two store-operated calcium channels that have differing ionic permeabilities and regulatory characteristics.

DZ, Semenza GL, Deitch EA, Feinman R. Hypoxia-inducible factor plays a gut-injurious role in intestinal ischemia reperfusion injury. Am J Physiol Gastrointest Liver Physiol 300: G853-G861, 2011. First published December 23, 2010 doi:10.1152/ajpgi.00459.2010.-Gut injury and loss of normal intestinal barrier function are key elements in the paradigm of gutorigin systemic inflammatory response syndrome, acute lung injury, and multiple organ dysfunction syndrome (MODS). As hypoxiainducible factor (HIF-1) is a critical determinant of the physiological and pathophysiological response to hypoxia and ischemia, we asked whether HIF-1 plays a proximal role in the induction of gut injury and subsequent lung injury. Using partially HIF-1␣-deficient mice in an isolated superior mesenteric artery occlusion (SMAO) intestinal ischemia reperfusion (I/R) injury model (45 min SMAO followed by 3 h of reperfusion), we showed a direct relationship between HIF-1 activation and intestinal I/R injury. Specifically, partial HIF-1␣ deficiency attenuated SMAO-induced increases in intestinal permeability, lipid peroxidation, mucosal caspase-3 activity, and IL-1␤ mRNA levels. Furthermore, partial HIF-1␣ deficiency prevented the induction of ileal mucosal inducible nitric oxide synthase (iNOS) protein levels after SMAO and iNOS deficiency ameliorated SMAO-induced villus injury. Resistance to SMAO-induced gut injury was also associated with resistance to lung injury, as reflected by decreased levels of myeloperoxidase, IL-6 and IL-10 in the lungs of HIF-1␣ ϩ/Ϫ mice. In contrast, a short duration of SMAO (15 min) followed by 3 h of reperfusion neither induced mucosal HIF-1␣ protein levels nor caused significant gut and lung injury in wild-type or HIF-1␣ ϩ/Ϫ mice. This study indicates that intestinal HIF-1 activation is a proximal regulator of I/R-induced gut mucosal injury and gut-induced lung injury. However, the duration and severity of the gut I/R insult dictate whether HIF-1 plays a gut-protective or deleterious role.inflammation; inducible nitric oxide synthase; mucosal injury MULTIPLE ORGAN DYSFUNCTION syndrome (MODS) is the major cause of morbidity and mortality in critically ill patients. A key paradigm in the development of the systemic inflammatory response syndrome (SIRS) and acute respiratory distress syndrome (ARDS) that culminates in multiple organ dysfunction syndrome (MODS) is loss of intestinal barrier function (10, 12). Intestinal ischemia reperfusion (I/R) injury occurs in different clinical settings, such as trauma, shock, burn, mesenteric artery occlusion, abdominal, cardiac bypass, and thoracic vascular surgery, as well as small intestinal transplantation.Because the gut acts as the "motor" of SIRS, ARDS, and MODS (6) and therapy for the critically ill patient remains largely supportive, studies identifying the underlying pathophysiological factors in the gut that initiate and propagate SIRS, ARDS, and MODS are of critical importance. To date, studies investigating the gut inflammatory/injurious response have primarily fo...

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.

Recent studies associate cholesterol excess and atherosclerosis with inflammation. The link between these processes is not understood, but cholesterol is an important component of lipid rafts. Rafts are thought to concentrate membrane signaling molecules and thus regulate cell signaling through G protein-coupled pathways. We used methyl β-cyclodextrin to deplete cholesterol from polymorphonuclear neutrophil (PMN) rafts and thus study the effects of raft disruption on G protein-coupled Ca2+ mobilization. Methyl β-cyclodextrin had no effect on Ca2+ store depletion by the G protein-coupled agonists platelet-activating factor or fMLP, but abolished agonist-stimulated Ca2+ entry. Free cholesterol at very low concentrations regulated Ca2+ entry into PMN via nonspecific Ca2+ channels in a biphasic fashion. The specificity of cholesterol regulation for Ca2+ entry was confirmed using thapsigargin studies. Responses to cholesterol appear physiologic because they regulate respiratory burst in a proportional biphasic fashion. Investigating further, we found that free cholesterol accumulated in PMN lipid raft fractions, promoting formation and polarization of membrane rafts. Finally, the transient receptor potential calcium channel protein TRPC1 redistributed to raft fractions in response to cholesterol. The uniformly biphasic relationships between cholesterol availability, Ca2+ signaling and respiratory burst suggest that Ca2+ influx and PMN activation are regulated by the quantitative relationships between cholesterol and other environmental lipid raft components. The association between symptomatic cholesterol excess and inflammation may therefore in part reflect free cholesterol- dependent changes in lipid raft structure that regulate immune cell Ca2+ entry. Ca2+ entry-dependent responses in other cell types may also reflect cholesterol bioavailability and lipid incorporation into rafts.