Gender dimorphic tissue perfusion response after acute hemorrhage and resuscitation: role of vascular endothelial cell function

Sex as Biological Variable in Cardiac Mitochondrial Bioenergetic Responses to Acute Stress

Cardiac dysfunction/damage following trauma, shock, sepsis, and ischemia impacts clinical outcomes. Acute inflammation and oxidative stress triggered by these injuries impair mitochondria, which are critical to maintaining cardiac function. Despite sex dimorphisms in consequences of these injuries, it is unclear whether mitochondrial bioenergetic responses to inflammation/oxidative stress are sex-dependent. We hypothesized that sex disparity in mitochondrial bioenergetics following TNFα or H2O2 exposure is responsible for reported sex differences in cardiac damage/dysfunction. Methods and Results: Cardiomyocytes isolated from age-matched adult male and female mice were subjected to 1 h TNFα or H2O2 challenge, followed by detection of mitochondrial respiration capacity using the Seahorse XF96 Cell Mito Stress Test. Mitochondrial membrane potential (ΔΨm) was analyzed using JC-1 in TNFα-challenged cardiomyocytes. We found that cardiomyocytes isolated from female mice displayed a better mitochondrial bioenergetic response to TNFα or H2O2 than those isolated from male mice did. TNFα decreased ΔΨm in cardiomyocytes isolated from males but not from females. 17β-estradiol (E2) treatment improved mitochondrial metabolic function in cardiomyocytes from male mice subjected to TNFα or H2O2 treatment. Conclusions: Cardiomyocyte mitochondria from female mice were more resistant to acute stress than those from males. The female sex hormone E2 treatment protected cardiac mitochondria against acute inflammatory and oxidative stress.

Anti-Inflammatory and Organ-Protective Effects of Resveratrol in Trauma-Hemorrhagic Injury

Resveratrol, a natural polyphenolic compound of grape and red wine, owns potential anti-inflammatory effects, which results in the reduction of cytokines overproduction, the inhibition of neutrophil activity, and the alteration of adhesion molecules expression. Resveratrol also possesses antioxidant, anti-coagulation and anti-aging properties, and it may control of cell cycle and apoptosis. Resveratrol has been shown to reduce organ damage following traumatic and shock-like states. Such protective phenomenon is reported to be implicated in a variety of intracellular signaling pathways including the activation of estrogen receptor, the regulation of the sirtuin 1/nuclear factor-kappa B and mitogen-activated protein kinases/hemeoxygenase-1 pathway, and the mediation of proinflammatory cytokines and reactive oxygen species formation and reaction. In the recent studies, resveratrol attenuates hepatocyte injury and improves cardiac contractility due to reduction of proinflammatory mediator expression and ameliorates hypoxia-induced liver and kidney mitochondrial dysfunction following trauma and hemorrhagic injuries. Moreover, through anti-inflammatory effects and antioxidant properties, the resveratrol is believed to protect organ function in trauma-hemorrhagic injury. In this review, the organ-protective and anti-inflammatory effects of resveratrol in trauma-hemorrhagic injury will be discussed.

Organ-Protective Effects of Red Wine Extract, Resveratrol, in Oxidative Stress-Mediated Reperfusion Injury

Resveratrol, a polyphenol extracted from red wine, possesses potential antioxidative and anti-inflammatory effects, including the reduction of free radicals and proinflammatory mediators overproduction, the alteration of the expression of adhesion molecules, and the inhibition of neutrophil function. A growing body of evidence indicates that resveratrol plays an important role in reducing organ damage following ischemia- and hemorrhage-induced reperfusion injury. Such protective phenomenon is reported to be implicated in decreasing the formation and reaction of reactive oxygen species and pro-nflammatory cytokines, as well as the mediation of a variety of intracellular signaling pathways, including the nitric oxide synthase, nicotinamide adenine dinucleotide phosphate oxidase, deacetylase sirtuin 1, mitogen-activated protein kinase, peroxisome proliferator-activated receptor-gamma coactivator 1 alpha, hemeoxygenase-1, and estrogen receptor-related pathways. Reperfusion injury is a complex pathophysiological process that involves multiple factors and pathways. The resveratrol is an effective reactive oxygen species scavenger that exhibits an antioxidative property. In this review, the organ-protective effects of resveratrol in oxidative stress-related reperfusion injury will be discussed.

The role of biological sex in severely traumatized patients on outcomes: a matched-pair analysis

OBJECTIVE

Analyze sex differences in TraumaRegister DGU (TR-DGU).

BACKGROUND

Sex differences are considered to influence trauma outcomes. However, clinical study results are controversial.

METHODS

Of 29,353 prospectively recorded cases of TR-DGU, we included primary trauma room admissions with Injury Severity Score of 9 or more into the analysis. Pairs (n = 3887) were formed from 1 male and 1 female according to age, mechanism, injury severity by Abbreviated Injury Scale (for head, thorax, abdomen, extremities), and occurrence of prehospital shock. Biochemical markers, treatment modalities, length of stay, and outcome (multiple organ failure, sepsis, mortality rates) were assessed. Statistical significance was accepted at P < 0.05. Odds ratios (ORs) are given with 95% confidence interval (CI).

RESULTS

Females had less multiple organ failure [OR: 1.18 (95% CI, 1.05-1.33); P = 0.007], particularly in age group of 16 to 44 years; sepsis [OR: 1.45 (95% CI, 1.21-1.74); P < 0.001]), particularly at age more than 45 years; and mortality [OR: 1.14 (95% CI, 1.01-1.28); P = 0.037]. Prehospital chest tube insertions (214 vs 158) and surgical procedures before intensive care unit admission were more often performed in males (79.7% vs 76.4%). Females had lower mean hemoglobin levels [10.7 ± 2.6 vs 11.9 ± 2.8 (mg/dL)]. There were no sex differences in fluid resuscitation, shock index, coagulation, and base excess.

CONCLUSIONS

Males are more susceptible to multiple organ failure, sepsis, and mortality after trauma. Differences were not exclusively related to reproductive age and thus cannot be attributed to sex hormones alone. Females aged 16 to 44 years seem to tolerate shock better. Higher susceptibility to sepsis might be explained by male immune function or increased systemic burden from higher rates of surgical interventions.

Female sex protects from organ failure and sepsis after major trauma haemorrhage

INTRODUCTION

Biological sex is considered a risk factor for adverse outcome after major trauma. We hypothesized that female sex is protective against organ failure, sepsis and mortality in patients with traumatic haemorrhage.

PATIENTS AND METHODS

We selected patients from TraumaRegister DGU(®) (TR-DGU) with primary admission for blunt trauma with an injury severity score ≥ 16 and an ICU stay ≥ 3 days that presented with relevant bleeding in the years 2007-2012. Relevant bleeding was defined as Abbreviated Injury Scale (AIS) ≥ 3 with an estimated blood loss exceeding 20%, any femoral shaft fracture, any pelvic clamp as surrogate for unstable pelvic fracture or the presence of at least one criteria of haemorrhagic shock: shock index of 0.8-1.4; base excess of -2.0 to -10.0 mmol/L; body temperature ≤ 34°C; transfusion of ≥ 4 units of packed red blood cells; application of recombinant activated factor VII; any embolization during trauma room phase and pre-hospital resuscitation volume ≥ 3000 ml or any catecholamine use during pre-hospital care in the absence of cardiopulmonary resuscitation. A total of 7560 males and 2774 females were selected and analyzed for sex differences.

RESULTS

Higher rates of multiple organ failure (24.4 vs. 21.3%, Odds ratio [OR] 1.19 (95% confidence interval [95%CI] 1.07-1.33), p=0.001*) and sepsis (16.5 vs. 11.3%, OR 1.55 (95%CI 1.35-1.77), p<0.001*) were observed in males. Organ function of lung, cardio-circulatory system, liver and kidney were better in females, however, there was no difference in mortality. Stratification by age group revealed that in particular age-group 16-44 years was related to improved organ function which may indicate effects of sex hormones in females at reproductive age. Increased rates of sepsis in males were observed throughout virtually all age groups starting at 16 years of age, except in age group 54-64 years. This may suggest suppressive effect of testosterone on immune function.

CONCLUSIONS

Our study supports the hypothesis that female sex is associated with improved organ function following traumatic injury and haemorrhagic shock, in particular in age groups that are at reproductive age. However, further studies are warranted before sex steroids can be deployed as therapeutic intervention in critically ill trauma patients.

Oxidative metabolism of dehydroepiandrosterone (DHEA) and biologically active oxygenated metabolites of DHEA and epiandrosterone (EpiA)--recent reports

Dehydroepiandrosterone (DHEA) is a multifunctional steroid with a broad range of biological effects in humans and animals. DHEA can be converted to multiple oxygenated metabolites in the brain and peripheral tissues. The mechanisms by which DHEA exerts its effects are not well understood. However, evidence that the effects of DHEA are mediated by its oxygenated metabolites has accumulated. This paper will review the panel of oxygenated DHEA metabolites (7, 16 and 17-hydroxylated derivatives) including a number of 5α-androstane derivatives, such as epiandrosterone (EpiA) metabolites. The most important aspects of the oxidative metabolism of DHEA in the liver, intestine and brain are described. Then, this article reviews the reported biological effects of oxygenated DHEA metabolites from recent findings with a specific focus on cancer, inflammatory and immune processes, osteoporosis, thermogenesis, adipogenesis, the cardiovascular system, the brain and the estrogen and androgen receptors.

Resveratrol prevents endothelial dysfunction and aortic superoxide production after trauma hemorrhage through estrogen receptor-dependent hemeoxygenase-1 pathway

OBJECTIVE

To determine whether resveratrol provides vasculoprotection in trauma-hemorrhaged animals and whether the effects are mediated via estrogen receptor-dependent hemeoxygenase-1.

DESIGN

Prospective, multiexperimental, randomized, controlled studies.

SETTING

University research laboratory.

SUBJECTS

Male Sprague-Dawley rats weighing 300-350 g.

INTERVENTIONS

Male Sprague-Dawley rats underwent trauma hemorrhage (mean arterial pressure 40 mm Hg for 90 min, then resuscitation). Resveratrol (30 mg/kg) with or without an estrogen receptor antagonist (ICI 182,780), a hemeoxygenase enzyme inhibitor (chromium-mesoporphyrin), or vehicle was injected during resuscitation. At 24 hrs after trauma hemorrhage with resuscitation or sham operation, the animals were euthanized for further evaluation.

MEASUREMENTS AND MAIN RESULTS

Acetylcholine-induced endothelium-dependent relaxation decreased, whereas nicotinamide adenine dinucleotide-stimulated superoxide radical production in the aorta and aortic p22phox, p47phox, gp91phox, NOX1, and NOX4 mRNA concentrations increased in trauma-hemorrhaged rats vs. sham rats. All altered parameters were normalized in resveratrol-treated trauma-hemorrhaged rats. Furthermore, there was a significant increase in hemeoxygenase-1 after trauma hemorrhage, and resveratrol treatment further increased hemeoxygenase-1 expression in trauma-hemorrhaged rats. However, administration of ICI 182,780 or chromium-mesoporphyrin abolished the resveratrol-induced prevention of shock-induced oxidative stress and endothelial damage. In the resveratrol-treated rats subjected to trauma hemorrhage, there were significant improvements in plasma aspartate aminotransferase and alanine aminotransferase levels, and mortality rate, and there was lesser damage in histology.

CONCLUSIONS

Resveratrol treatment prevented the overproduction of superoxide radical/NADPH oxidase expression and restored the trauma-hemorrhage-impaired endothelium-dependent relaxation via estrogen receptor-dependent stimulation of hemeoxygenase-1 expression.

Intestinal mucus layer preservation in female rats attenuates gut injury after trauma-hemorrhagic shock

BACKGROUND

We tested the hypothesis that females are more resistant to trauma-hemorrhagic shock (T/HS)-induced gut injury than males, and this is related to better preservation of their intestinal mucus layer, which is influenced in turn by the estrus cycle stage at the time of injury.

METHODS

Male, proestrus and diestrus female rats underwent a laparotomy (trauma) and 90 minutes of shock ( approximately 35 mm Hg). At 3 hours after reperfusion, terminal ileum was harvested and stained with Carnoy's Alcian Blue for mucus assessment, hematoxylin and eosin, and periodic acid schiff for villous and goblet cell morphology and injury. Ileal permeability was measured in separate intestinal segments using the ex vivo everted gut sac technique.

RESULTS

When compared with males, proestrus female rats were significantly more resistant to T/HS-induced morphologic gut injury, as reflected in both a lower incidence of villous injury (14% vs. 22%; p < 0.05) and a lesser grade of injury (1.0 vs. 2.8; p < 0.05) as well as preservation of gut barrier function (17.9 vs. 32.2; p < 0.05). This resistance to gut injury was associated with significant preservation of the mucus layer (87% vs. 62%; p < 0.05) and was influenced by the estrus cycle stage of the female rats. There was a significant inverse correlation between mucus layer coverage and the incidence (r = 0.9; p < 0.0001) and magnitude (r = 0.89; p < 0.0001) of villous injury and gut permeability (r = 0.74; p < 0.001).

CONCLUSIONS

The resistance of female rats to T/HS-induced intestinal injury and dysfunction was associated with better preservation of the intestinal mucus barrier and was to some extent estrus cycle-dependent. Preservation of the mucus barrier may protect against shock-induced gut injury and subsequent distant organ injury by limiting the ability of luminal contents such as bacteria and digestive enzymes from coming into direct contact with the epithelium.

Estrogen receptor hormone agonists limit trauma hemorrhage shock-induced gut and lung injury in rats

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.

Organ blood flow and the central hemodynamic response are better preserved in female, as opposed to the male rats, after trauma-hemorrhagic shock

The objective of this study was to test the hypotheses that the better resistance of proestrus female than male rats to trauma-hemorrhagic shock (T/HS)-induced gut and other organ injury, and it is associated with better preservation of central hemodynamics and organ blood flow including blood flow to the intestine. Male and female proestrus rats were subjected to T/HS (laparotomy and 90 minutes of shock at a mean arterial blood pressure of 35-40 mm Hg) or trauma sham-shock after that cardiac index, systemic vascular resistance, and organ blood flow was measured 15 minutes before the end of the shock period and at 15 minutes, 60 minutes, and 180 minutes after volume resuscitation. The hemodynamic response to T/HS was better preserved during the shock period in the female than male rats and this was manifest as better maintenance of central hemodynamics (cardiac output and systemic vascular resistance) and intestinal as well as other organ microcirculatory blood flow. Cardiac output had returned toward normal at 15 minutes after volume resuscitation in both the male and female rats, however only in the female rats was there a consistent increase in organ blood flow after volume resuscitation. In contrast, in the male T/HS rats, the level of organ blood flow, especially to the splanchnic organs, remained similar to that observed during the shock period. These results indicate that the greater resistance of female than male rats to gut and other organ injury after T/HS is associated with better preservation of central hemodynamics and organ blood flow during the shock and postshock periods.

Sex steroids/receptor antagonist: their use as adjuncts after trauma-hemorrhage for improving immune/cardiovascular responses and for decreasing mortality from subsequent sepsis

Studies in human as well as animal models demonstrate that females in the proestrus cycle (i.e., with high estrogen) tolerate trauma-hemorrhage and sepsis far better than males. The female sex steroid, estrogen, is the significant factor contributing to this observed gender difference in outcome. One reason for the lack of significant gender association in some clinical studies is the possibility of heterogeneity of the population in terms of their hormonal status at the time of injury. Several experimental investigations have revealed that androgens produce immune and cardiovascular depression after trauma-hemorrhage. However, the use of an androgen receptor antagonist after trauma-hemorrhage has salutary effects of immune and cardiovascular function. Likewise, estrogen produces beneficial effects on immune and cardiovascular function after trauma-hemorrhage and significantly decreases mortality rates from subsequent sepsis. The salutary effects of estrogen after trauma-hemorrhage have been shown to be due to both genomic and nongenomic effects. Thus, the use of an estrogen or androgen receptor antagonist as an adjunct after trauma-hemorrhage is a safe and novel approach for restoring immune and cardiovascular function after trauma-hemorrhage and for decreasing the mortality from subsequent sepsis.

RESISTANCE OF THE FEMALE, AS OPPOSED TO THE MALE, INTESTINE TO I/R-MEDIATED INJURY IS ASSOCIATED WITH INCREASED RESISTANCE TO GUT-INDUCED DISTANT ORGAN INJURY

We tested the hypothesis that the female intestine is more resistant to gut I/R injury than the male intestine by comparing the effects of the isolated pure gut I/R superior mesenteric artery occlusion (SMAO) model on gut morphology and whether SMAO-induced distant organ injury (lung, bone marrow [BM], neutrophils, and red blood cells [RBCs]) would differ between male and proestrus female rats. At 6 or 24 h after SMAO or sham SMAO, gut injury, lung permeability, pulmonary neutrophil sequestration, RBC deformability, and BM RBC and white blood cell progenitor growth were measured, as was the ability of the plasma from these rats to activate naive rat neutrophils. At both 6 and 24 h after SMAO, the female rats had significantly less intestinal injury and reduced gut-induced lung injury, BM suppression, RBC dysfunction, and neutrophil activation than male rats subjected to SMAO. These results indicate that the resistance of proestrus female rats to gut injury and gut-induced distant organ injury is greater than that observed in male rats.

Hormonally active women tolerate shock-trauma better than do men: a prospective study of over 4000 trauma patients

OBJECTIVE

To test the hypothesis that comparably injured women, especially those in the hormonally active age groups, would manifest a better preserved hemodynamic response and tissue perfusion after major trauma than do men.

SUMMARY BACKGROUND DATA

The notion that premenopausal women are more resistant than men to shock and trauma has been shown in numerous preclinical models. However, human studies on the effects of gender on outcome after shock-trauma are less clear, and none has examined the effect of gender on the immediate postinjury response to major trauma.

METHODS

Prospective series of all patients at a Level I trauma center from January 2000 to December 2005. Study patients were all patients arriving to the trauma area of the emergency department and having a serum lactate drawn within 30 minutes of arrival. Demographic data, injury severity indices, blood utilization, and lactate levels were recorded. Lactate was used as a marker of the hemodynamic response to injury, because it has been shown to be an excellent and accurate indicator of inadequate tissue perfusion.

RESULTS

: A total of 5192 patients were eligible for the study of which 4106 fulfilled the study requirements and were enrolled. Initial serum lactate levels were significantly lower in premenopausal (age 14-44) and perimenopausal (age 45-54) women than in men of the same age groups (P < 0.001), even though the Injury Severity Score of the women was significantly higher than that of the men (24 vs. 18; P < 0.1). When patients were stratified into major injury groups as well as groups receiving blood transfusions, the premenopausal women were also found to have lower initial serum lactate levels and receive less blood, while having a greater magnitude of injury as reflected in their Injury Severity Score.

CONCLUSION

The data firmly establishes a proof of principle that hormonally active human women have a better physiologic response to similar degrees of shock and trauma than do their male counterparts. These gender-based differences should be taken into account in designing studies evaluating the response to shock-trauma.

Effects of candesartan and enalaprilat on the organ-specific microvascular permeability during haemorrhagic shock in rats

BACKGROUND

To counteract the contribution of angiotensin II to shock-induced ischaemic organ damage pharmacologic blockade of the renin-angiotensin-system (RAS) is currently under investigation. To evaluate potential side-effects of RAS blockade regarding capillary leak, we studied alterations in microvascular permeability in various organs during haemorrhagic shock (HS) in rats pretreated with candesartan (AT(1)-receptor antagonism) or enalaprilat (ACE-inhibition).

METHODS

Thirty-eight instrumented and anaesthetized animals received either candesartan, enalaprilat or placebo. Within each of the three groups 6-7 animals were exposed to HS and 6 animals of each group served as normovolaemic controls. After 30 min of shock, 50 mg kg(-1) Evans blue (EB) was injected i.v. followed by a distribution period of 20 min. Exsanguination was performed with saline, before harvesting organs to quantify albumin-bound EB extravasation.

RESULTS

To reduce cardiac output from 37.5 (1.3) to 20.4 (1.1) ml min(-1) [mean (SEM)] in the shock groups, withdrawal of 4.0 (0.25) ml [mean (SEM)] blood was necessary. Simultaneously mean arterial pressure decreased from 77.5 (3.2) to 36.1 (2) mm Hg. Serum lactate increased significantly from 1.3 (0.1) to 3.5 (0.24) mmol litre(-1). Treatment with candesartan increased EB extravasation in the kidney in normovolaemic controls. Specific AT(1) and ACE-blockade before acute non-resuscitated HS significantly increased EB extravasation in the rat ileum by 53 and 66%, respectively.

CONCLUSION

This observation of increased microvascular albumin extravasation should be borne in mind for any interventional use of candesartan or enalaprilat during circulatory stress.

Plasma protein and blood volume restitution after hemorrhage in conscious pregnant and ovarian steroid-replaced rats

We have previously shown that both plasma protein restitution and plasma volume restitution are significantly enhanced in female rats hemorrhaged during the proestrus phase of the estrous cycle. Estradiol and progesterone levels are markedly elevated during proestrus and also increase during pregnancy. The present studies were therefore designed to determine whether the ability to restore plasma protein and blood volume after hemorrhage is augmented during pregnancy and by chronically elevated estradiol levels. The response to moderate hemorrhage (22–23% blood loss) was evaluated in conscious pregnant rats during early and midgestation and compared with that of virgin female rats studied during metestrus. At 22 h posthemorrhage, plasma volume had increased to greater than basal levels, and blood volume was restored to 93 ± 1% (metestrus), 91 ± 2% (early pregnancy), and 98 ± 2% (midgestation) of control ( P > 0.05). Animals hemorrhaged during metestrus or early pregnancy restored the same amount of protein to the plasma as had been removed, whereas those hemorrhaged during midgestation restored nearly 50% more plasma protein than had been removed ( P < 0.01). In ovariectomized animals with chronic steroid replacement that maintained plasma progesterone at metestrus levels (15 ± 2 ng/ml) but raised plasma estradiol to twofold that of midgestation (22 ± 3 pg/ml), the blood volume and plasma protein restitution responses to hemorrhage did not differ from those of ovariectomized animals with no steroid replacement. In summary, posthemorrhage restoration of plasma protein content is significantly augmented during midgestation, but not during early pregnancy. This augmented response cannot be attributed to chronic elevation of plasma estradiol levels alone.

Mechanisms responsible for vascular hyporesponsiveness to adrenomedullin after hemorrhage: the central role of adrenomedullin binding protein-1

OBJECTIVE

Irreversible hypovolemia remains a major clinical problem. Preliminary studies indicate that administration of adrenomedullin and adrenomedullin binding protein-1 in combination (AM/AMBP-1) after hemorrhage, improves cardiovascular function despite the increased levels of AM. Our aim was to determine whether vascular responsiveness to AM is reduced after hemorrhage and, if so, to elucidate the possible mechanism responsible for such hyporesponsiveness.

METHODS

Male rats were bled to and maintained at a mean arterial pressure of 40 mm Hg for 90 minutes. The animals were then resuscitated with 4 times the volume of shed blood with lactated Ringer's solution over 60 minutes. At 1.5 hours postresuscitation, vascular responses to AM and AMBP-1, plasma levels of AM and AMBP-1, AMBP-1 and AM receptor gene expression were measured. In additional animals, AM and AMBP-1 were administered intravenously at 15 minutes after resuscitation over 45 minutes. Serum levels of liver enzymes, lactate, creatinine, TNF-alpha, IL-6, and IL-10 were measured at 1.5 hours postresuscitation.

RESULTS

AM-induced vascular relaxation decreased significantly after hemorrhage and resuscitation, which was markedly improved by AMBP-1. However, AM receptor gene expression did not change under such conditions. Hemorrhage-induced AM hyporesponsiveness was accompanied by the decreased expression and release of AMBP-1. Moreover, AM/AMBP-1 treatment down-regulated TNF-alpha and IL-6, up-regulated IL-10, and attenuated organ injury.

CONCLUSIONS

The decreased AMBP-1 levels rather than alterations in AM receptors are responsible for producing AM hyporesponsiveness after hemorrhage. Thus, administration of AMBP-1 in combination with AM can be useful to reduce organ injury after severe hypovolemia.

Gender differences in small intestinal perfusion following trauma hemorrhage: the role of endothelin-1

Although gender differences in intestinal perfusion exist following trauma-hemorrhage (T-H), it remains unknown whether endothelin-1 (ET-1) plays any role in these dimorphic responses. To study this, male, proestrus female (female), and 17 beta-estradiol (E2)-treated male rats underwent midline laparotomy, hemorrhagic shock (blood pressure 40 mmHg, 90 min), and resuscitation (Ringer lactate, 4X shed blood volume, 1 h). Two hours thereafter, intestinal perfusion flow (IPF) was measured using isolated intestinal perfusion. The IPF in sham-operated males was significantly lower than those in other groups and decreased markedly following T-H. In contrast, no significant decrease in IPF was observed in females and E2 males following T-H. The lower IPF in sham-operated males was significantly elevated by ET(A) receptor antagonist (BQ-123) administration and was similar to that seen in sham-operated females. The decreased IPF in males after T-H was also attenuated by BQ-123 administration. The intestinal ET-1 levels in sham-operated males were significantly higher than in other groups. Although plasma and intestinal ET-1 levels increased significantly after T-H in all groups, they were highest in males. Plasma E2 levels in females and E2 males were significantly higher than in males; however, they were not affected by T-H. There was a negative correlation between plasma ET-1 and E2 following T-H. Thus ET-1 appears to play an important role in intestinal perfusion failure following T-H in males. Because E2 can modulate this vasoconstrictor effect of ET-1, these findings may partially explain the previously observed salutary effect of estrogen in improving intestinal perfusion following T-H in males.

A novel approach to maintaining cardiovascular stability after hemorrhagic shock: beneficial effects of adrenomedullin and its binding protein

BACKGROUND

Vascular responsiveness to adrenomedullin (AM), a recently discovered vasodilator peptide, is depressed after hemorrhage and resuscitation. Downregulation of AM binding protein-1 (ie, AMBP-1) appears to be responsible for this hyporesponsiveness. Therefore, we hypothesize that administration of AM/AMBP-1 improves cardiovascular responses after hemorrhagic shock and resuscitation.

METHODS

Male rats were bled to and maintained at a mean blood pressure of 40 mm Hg for 90 minutes. The animals were then resuscitated with 4 times the volume of shed blood with Ringer's lactate over 60 minutes. At 15 minutes after the beginning of resuscitation in hemorrhaged animals, AM alone, AMBP-1 alone, AM in combination with AMBP-1, or vehicle (phosphate-buffered saline solution) was administered intravenously over 45 minutes. At 4-hour postresuscitation, in vivo left ventricular contractility parameters, maximal rates of ventricular pressure increase (+dP/dt max ) and decrease (-dP/dt max ), were determined. Cardiac output and organ blood flow were measured with the use of radioactive microspheres. In an additional group of animals, cardiac tumor necrosis factor-alpha (TNF-alpha) levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

Four hours after resuscitation, +dP/dt max , -dP/dt max , cardiac output, and organ blood flow in the liver, small intestine, and kidneys were decreased while treatment with AM/AMBP-1 increased these parameters ( P < .05). Moreover, cardiac TNF-alpha levels were elevated at 4 hours after hemorrhage and resuscitation, while AM/AMBP-1 treatment reduced them to sham levels ( P < .05).

CONCLUSIONS

Administration of AM/AMBP-1 appears to be a useful approach for restoring and maintaining cardiovascular stability after severe hemorrhagic shock and crystalloid resuscitation.

Sex hormones modulate distant organ injury in both a trauma/hemorrhagic shock model and a burn model

BACKGROUND

Emerging data suggest a gender dimorphism in resistance and susceptibility to distant organ injury after mechanical and thermal trauma. The aim of this study was to determine the role that testosterone and estradiol play in modulating resistance or susceptibility to distant organ injury, and whether their effects were associated with differences in the production of nitric oxide.

METHODS

Adult male, female, castrated male, and ovariectomized female Sprague-Dawley rats were given intraperitoneal pentobarbital sodium anesthesia and subjected to trauma/sham shock or trauma/hemorrhagic shock (T/HS). A second set of animals were subjected to a 40% total body surface area, third-degree burn or sham burn. At 3 hours after resuscitation, plasma levels of nitrite/nitrate were measured, and the extent of lung injury (permeability to Evans Blue dye and neutrophil sequestration by myeloperoxidase) and intestinal injury (morphology) were determined.

RESULTS

Proestrus females showed resistance to lung and gut injury after both T/HS and burns, and had low levels of nitrite/nitrate production. This resistance to injury was abrogated by ovariectomy with an associated increase in nitric oxide production. Males showed increased lung and gut injury after both T/HS and burns associated with increased production of nitrite/nitrate. Castration decreased susceptibility to both lung and gut injury, and decreased production of nitrite/nitrate. A correlation was noted between intestinal and lung injury, and both intestinal and lung injury correlated with plasma nitrite/nitrate levels.

CONCLUSIONS

Male sex hormones potentiate, while female hormones reduce T/HS and burn-induced lung and gut injury. Production of nitric oxide is associated with increased lung and gut injury after T/HS and burns.

Insights into the role of interleukin-6 in the induction of hepatic injury after trauma-hemorrhagic shock

Although systemic interleukin-6 (IL-6) level is elevated, hepatocellular function is impaired and liver injury occurs after trauma-hemorrhage (T-H), it remains unknown whether a causal relationship exists between elevated IL-6 levels and liver injury after T-H. We hypothesized that IL-6 is causative in the development of hepatic dysfunction and injury after T-H. To examine this, adult male Sprague-Dawley rats underwent a 5-cm midline laparotomy and were subjected to hemorrhagic shock (blood pressure = 35 mmHg for ∼90 min), followed by resuscitation (Ringer lactate, 4 times the shed blood volume). At 2, 5, and 24 h thereafter, blood samples were collected and the liver isolated and perfused for 60 min. Portal inflow pressure was measured, and perfusate samples were collected to measure IL-6, alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) levels. A significant positive correlation between plasma levels of IL-6 and ALT and perfusate levels of IL-6 and LDH levels was observed. In a second series of experiments, rats were treated with immunoglobulin G (IgG) or antibodies against rat IL-6 (anti-IL-6) at the onset of resuscitation. At 5 h after resuscitation, anti-IL-6 treatment attenuated the T-H induced increases in plasma ALT and thromboxane B2 (a thromboxane A2 metabolite) levels, and bile flow was normalized to sham levels. Perfusion of livers from normal rats with IL-6 did not alter portal pressure; however, perfusion of a stable thromboxane A2 analog dose dependently increased portal pressure. Thus IL-6 plays a significant role in the induction of hepatic dysfunction and liver injury after T-H that appears to be in part mediated by increased thromboxane A2 levels.

Sexual dimorphism in the permeability response of coronary microvessels to adenosine

Gender influences volume regulation via several mechanisms; whether these include microvascular exchange, especially in the heart, is not known. In response to adenosine (Ado), permeability (P(s)) to protein of coronary arterioles of female pigs decreases acutely. Whether Ado induces similar P(s) changes in arterioles from males or whether equivalent responses occur in coronary venules of either sex has not been determined. Hypotheses that 1) basal P(s) properties and 2) P(s) responses to vasoactive stimuli are sex independent were evaluated from measures of P(s) to two hydrophilic proteins, alpha-lactalbumin and porcine serum albumin (PSA), in arterioles and venules isolated from hearts of adult male and female pigs. Consistent with hypothesis 1, basal P(s) values of both microvessel types were independent of sex. Contrary to hypothesis 2, P(s) responses to Ado varied with sex, protein, and vessel type. Confirming earlier studies, Ado induced a approximately 20% decrease in P(s) to both proteins in coronary arterioles from females. In arterioles from males, Ado did not change P(s) for alpha-lactalbumin (P(s)(alpha-lactalb), 3 +/- 13%), whereas P(s) for PSA (P(s)(PSA)) decreased by 27 +/- 8% (P < 0.005). In venules from females, Ado elevated P(s)(PSA) by 44 +/- 20% (P < 0.05), whereas in those from males, Ado reduced P(s)(PSA) by 24 +/- 5% (P < 0.05). The variety of outcomes is consistent with transvascular protein and protein-carried solute flux being regulated by multiple sex-dependent mechanisms in the heart and provides evidence of differences in exchange homeostasis of males and females in health and, likely, disease.

Salutary effects of androstenediol on cardiac function and splanchnic perfusion after trauma-hemorrhage

Recent studies have shown that dehydroepiandrosterone (DHEA) administration after trauma-hemorrhage (T-H) improves cardiovascular function and decreases cytokine production in male animals. Although androstenediol, one of the metabolites of DHEA, is reported to have estrogen-like activity, it remains unknown whether androstenediol per se has any salutary effects on cytokines and cardiovascular function after T-H. To examine this effect, male Sprague-Dawley rats underwent laparotomy and were bled to and maintained at a mean arterial blood pressure of 35–40 mmHg for ∼90 min. The animals were resuscitated with four times the volume of maximal bleedout volume in the form of Ringer lactate. Androstenediol (1 mg/kg body wt iv) or vehicle was administered at the end of resuscitation. Twenty-four hours after resuscitation, cardiac function and organ blood flow were measured by using 85Sr-microspheres. Circulating levels of nitrate/nitrite and IL-6 were also determined. Cardiovascular function and organ blood flow were significantly depressed after T-H. However, these parameters were restored by androstenediol treatment. The elevated plasma IL-6 levels after T-H were also lowered by androstenediol treatment. In contrast, plasma levels of nitrate/nitrite were the highest in the androstenediol-treated T-H animals. Because androstenediol administration after T-H decreases cytokine production and improves cardiovascular function, this agent appears to be a novel and useful adjunct for restoring the depressed cardiovascular function and for cytokine production in males after adverse circulatory conditions.

Gender differences in small intestinal endothelial function: inhibitory role of androgens

Although gender differences exist in cardiovascular endothelial function, it remains unclear whether such differences are also seen in small intestinal endothelial function. To determine this, untreated male, age-matched proestrus female, castrated male, and 17beta-estradiol (E2)-treated noncastrated male rats were studied. Dose response curves to ACh and nitroglycerin (NTG) were determined by measuring changes in perfusion pressure by using an isolated small intestinal perfusion model. Endothelium-derived nitric oxide (NO) production/release was indirectly determined by the ability of intact endothelium to suppress serotonin (10(-5) M)-induced perfusion pressure changes. Intestinal tissue levels of NO were also measured. Moreover, plasma levels of androgen and E2 were determined and correlated with ACh (10(-8) M)-induced perfusion pressure reductions. ACh-induced intestinal perfusion pressure reductions in proestrus females, castrated males, and E2-treated noncastrated males were significantly higher than in untreated males. NTG-induced perfusion pressure reductions were not significantly different among groups. Perfusion pressures after administration of serotonin (10(-5) M) and intestinal tissue levels of NO in proestrus females, castrated males, and E2-treated noncastrated males were also significantly higher than in untreated males. Plasma androgen levels in proestrus females, castrated males, and in E2-treated noncastrated males were significantly lower compared with untreated males. There was a positive correlation between plasma androgen and ACh-reduced perfusion pressure; however, E2 levels did not show a similar relationship. Thus androgens appear to play an inhibitory role in small intestinal endothelial function. These properties in male vessels can be modulated by decreasing the level of circulating androgens or by E2 treatment.