Attenuation of vascular endothelial dysfunction by testosterone receptor blockade after trauma and hemorrhagic shock

Therapeutic interventions to restore microcirculatory perfusion following experimental hemorrhagic shock and fluid resuscitation: A systematic review

Objective

Microcirculatory perfusion disturbances following hemorrhagic shock and fluid resuscitation contribute to multiple organ dysfunction and mortality. Standard fluid resuscitation is insufficient to restore microcirculatory perfusion; however, additional therapies are lacking. We conducted a systematic search to provide an overview of potential non‐fluid‐based therapeutic interventions to restore microcirculatory perfusion following hemorrhagic shock.

Methods

A structured search of PubMed, EMBASE, and Cochrane Library was performed in March 2020. Animal studies needed to report at least one parameter of microcirculatory flow (perfusion, red blood cell velocity, functional capillary density).

Results

The search identified 1269 records of which 48 fulfilled all eligibility criteria. In total, 62 drugs were tested of which 29 were able to restore microcirculatory perfusion. Particularly, complement inhibitors (75% of drugs tested successfully restored blood flow), endothelial barrier modulators (100% successful), antioxidants (66% successful), drugs targeting cell metabolism (83% successful), and sex hormones (75% successful) restored microcirculatory perfusion. Other drugs consisted of attenuation of inflammation (100% not successful), vasoactive agents (68% not successful), and steroid hormones (75% not successful).

Conclusion

Improving mitochondrial function, inhibition of complement inhibition, and reducing microvascular leakage via restoration of endothelial barrier function seem beneficial to restore microcirculatory perfusion following hemorrhagic shock and fluid resuscitation.

6β-Hydroxytestosterone, a metabolite of testosterone generated by CYP1B1, contributes to vascular changes in angiotensin II-induced hypertension in male mice

Background

Previously, we showed that 6β-hydroxytestosterone (6β-OHT), a cytochrome P450 1B1 (CYP1B1)-derived metabolite of testosterone, contributes to angiotensin II (Ang II)-induced hypertension in male mice. This study was conducted to test the hypothesis that 6β-OHT contributes to increased vascular reactivity, endothelial dysfunction, vascular hypertrophy, and reactive oxygen species production associated with Ang II-induced hypertension.

Methods

Eight- to 10-week-old intact or castrated C57BL/6 J (Cyp1b1^+/+ and Cyp1b1^−/−) mice were anesthetized for implantation of a micro-osmotic pump which delivered Ang II (700 ng/kg/day) or saline for 14 days. Mice were injected with 6β-OHT (15 μg/g b.w every third day), flutamide (8 mg/kg every day), or its vehicle. Blood pressure was measured via tail-cuff. Vascular reactivity, endothelial-dependent and endothelial-independent vasodilation, media to lumen ratio, fibrosis by collagen deposition, and reactive oxygen species production by dihydroethidium staining were determined in the isolated thoracic aorta.

Results

The response of thoracic aorta to phenylephrine and endothelin-1 was increased in Ang II-infused Cyp1b1^+/+ mice compared to intact Cyp1b1^−/− or castrated Cyp1b1^+/+ and Cyp1b1^−/− mice; these effects of Ang II were restored by treatment with 6β-OHT. Ang II infusion caused endothelial dysfunction, as indicated by decreased relaxation of the aorta to acetylcholine in Cyp1b1^+/+ but not Cyp1b1^−/− or castrated Cyp1b1^+/+ and Cyp1b1^−/− mice. 6β-OHT did not alter Ang II-induced endothelial dysfunction in Cyp1b1^+/+ mice but restored it in Cyp1b1^−/− or castrated Cyp1b1^+/+ and Cyp1b1^−/− mice. Ang II infusion increased media to lumen ratio and caused fibrosis and reactive oxygen species production in the aorta of Cyp1b1^+/+ mice. These effects were minimized in the aorta of Cyp1b1^−/− or castrated Cyp1b1^+/+ and Cyp1b1^−/− mice and restored by treatment with 6β-OHT. Treatment with the androgen receptor antagonist flutamide reduced blood pressure and vascular hypertrophy in castrated Ang II-infused mice injected with 6β-OHT.

Conclusions

6β-OHT is required for the action of Ang II to increase vascular reactivity and cause endothelial dysfunction, hypertrophy, and increase in oxygen radical production. The effect of 6β-OHT in mediating Ang II-induced hypertension and associated hypertrophy is dependent on the androgen receptor. Therefore, CYP1B1 could serve as a novel target for the development of therapeutics to treat vascular changes in hypertensive males.

Mitochondrial targeting by dichloroacetate improves outcome following hemorrhagic shock

Hemorrhagic shock is a leading cause of death in people under the age of 45 and accounts for almost half of trauma-related deaths. In order to develop a treatment strategy based on potentiating mitochondrial function, we investigated the effect of the orphan drug dichloroacetate (DCA) on survival in an animal model of hemorrhagic shock in the absence of fluid resuscitation. Hemorrhagic shock was induced in rats by withdrawing 60% of the blood volume and maintaining a hypotensive state. The studies demonstrated prolonged survival of rats subjected to hemorrhagic injury (HI) when treated with DCA. In separate experiments, using a fluid resuscitation model we studied mitochondrial functional alterations and changes in metabolic networks connected to mitochondria following HI and treatment with DCA. DCA treatment restored cardiac mitochondrial membrane potential and tissue ATP in the rats following HI. Treatment with DCA resulted in normalization of several metabolic and molecular parameters including plasma lactate and p-AMPK/AMPK, as well as Ach-mediated vascular relaxation. In conclusion we demonstrate that DCA can be successfully used in the treatment of hemorrhagic shock in the absence of fluid resuscitation; therefore DCA may be a good candidate in prolonged field care following severe blood loss.

Hepatoprotective effect of casodex after trauma hemorrhage in a rodent model

Casodex (bicalutamide), an androgen receptor antagonist, is used for the treatment of prostate cancer. Recent evidences show that Akt signaling pathway exerts organ-protective effects after injury. The aim of this study was to investigate whether Akt plays any role in the casodex-mediated attenuation of hepatic injury after trauma-hemorrhagic shock. Male Sprague-Dawley rats underwent trauma hemorrhage (mean blood pressure kept at approximately 35-40 mm Hg for 90 min), followed by fluid resuscitation. During resuscitation, a single dose of casodex (5 mg/kg, intravenous) with and without a phosphatidylinositol 3-kinase inhibitor wortmannin (1 mg/kg, intravenous), wortmannin or vehicle was administered. Plasma aspartate aminotransferase and alanine aminotransferase levels and various hepatic parameters were measured at 24 h after resuscitation. One-way analysis of variance and the Tukey test were used for statistical analysis. These results showed that trauma hemorrhage increased hepatic myeloperoxidase activity, interleukin 6 and intercellular adhesion molecule 1 levels, and plasma aspartate aminotransferase and alanine aminotransferase concentrations. In the trauma hemorrhage rats treated with casodex, these parameters were significantly improved. Casodex treatment also increased hepatic phospho-Akt expression compared with vehicle-treated trauma hemorrhaged rats. Coadministration of wortmannin with casodex abolished the casodex-induced advantageous effects on the aforementioned parameters and hepatic injury. Our results suggest that the protective effect of casodex administration on attenuation of hepatic injury after trauma hemorrhage, which is, at least in part, through Akt-dependent pathway.

Low Testosterone Levels are Frequent in Patients with Acute Respiratory Failure and are Associated with Poor Outcomes

OBJECTIVE

Low testosterone level is a common finding in critically ill patients with trauma, shock, and sepsis. However, its prevalence and outcomes in patients with primary acute respiratory failure is unknown; low testosterone could contribute to respiratory muscle weakness and further compromise ventilation in these patients.

METHODS

We aimed to determine the prevalence, severity, and effects of hypotestosteronemia in patients with acute respiratory failure in a 16-bed single academic center medical intensive care unit (ICU). We studied 30 men who required mechanical ventilation for ≥24 hours for a primary diagnosis of acute respiratory failure. Blood samples were drawn on ICU day 1 and day 3 to measure serum levels of total and free testosterone.

RESULTS

Hypotestosteronemia (level below the lower reference limit) was present on day 1 in 93.1% (total testosterone) and 76.7% (free testosterone) of patients and on day 3 in 94.4% (total testosterone) and 100% (free testosterone) of patients. Sex hormone-binding globulin, dehydroepiandrosterone sulfate, follicle-stimulating hormone, luteinizing hormone, and thyroid function levels were all within stated reference ranges. Total and free testosterone levels correlated inversely with ventilator days and ICU length of stay.

CONCLUSION

Hypotestosteronemia is common in mechanically ventilated patients with primary acute respiratory failure and may contribute to longer ICU stay. Further studies are needed to determine the effect of testosterone replacement on short- and long-term outcomes in these patients.

Time-dependent effect of orchidectomy on vascular nitric oxide and thromboxane A2 release. Functional implications to control cell proliferation through activation of the epidermal growth factor receptor

This study analyzes whether the release of nitric oxide (NO) and thromboxane A2 (TXA2) depends on the time lapsed since gonadal function is lost, and their correlation with the proliferation of vascular smooth muscle cells (VSMC) mediated by the epidermal growth factor receptor (EGFR). For this purpose, aortic and mesenteric artery segments from control and 6-weeks or 5-months orchidectomized rats were used to measure NO and TXA2 release. The results showed that the basal and acetylcholine (ACh)-induced NO release were decreased 6 weeks post-orchidectomy both in aorta and mesenteric artery, but were recovered 5 months thereafter up to levels similar to those found in arteries from control rats. The basal and ACh-induced TXA2 release increased in aorta and mesenteric artery 6 weeks post-orchidectomy, and was maintained at high levels 5 months thereafter. Since we previously observed that orchidectomy, which decreased testosterone level, enlarged the muscular layer of mesenteric arteries, the effect of testosterone on VSMC proliferation was analyzed. The results showed that treatment of cultured VSMC with testosterone downregulated mitogenic signaling pathways initiated by the ligand-dependent activation of the EGFR. In contrast, the EGFR pathways were constitutively active in mesenteric arteries of long-term orchidectomized rats. Thus, the exposure of mesenteric arteries from control rats to epidermal growth factor (EGF) induced the activation of EGFR signaling pathways. However, the addition of EGF to arteries from orchidectomized rats failed to induce a further activation of these pathways. In conclusion, this study shows that the release of NO depends on the time lapsed since the gonadal function is lost, while the release of TXA2 is already increased after short periods post-orchidectomy. The alterations in these signaling molecules could contribute to the constitutive activation of the EGFR and its downstream signaling pathways after long period post-orchidectomy enhancing the proliferation of the vascular muscular layer.

Ischemic and oxidative damage to the hypothalamus may be responsible for heat stroke

The hypothalamus may be involved in regulating homeostasis, motivation, and emotional behavior by controlling autonomic and endocrine activity. The hypothalamus communicates input from the thalamus to the pituitary gland, reticular activating substance, limbic system, and neocortex. This allows the output of pituitary hormones to respond to changes in autonomic nervous system activity. Environmental heat stress increases cutaneous blood flow and metabolism, and progressively decreases splanchnic blood flow. Severe heat exposure also decreases mean arterial pressure (MAP), increases intracranial pressure (ICP), and decreases cerebral perfusion pressure (CPP = MAP - ICP), all of which lead to cerebral ischemia and hypoxia. Compared with normothermic controls, rodents with heatstroke have higher hypothalamic values of cellular ischemia (e.g., glutamate and lactate-to-pyruvate ratio) and damage (e.g., glycerol) markers, pro-oxidant enzymes (e.g., lipid peroxidation and glutathione oxidation), proinflammatory cytokines (e.g., interleukin-1β and tumor necrosis factor-α), inducible nitric oxide synthase-dependent nitric oxide, and an indicator for the accumulation of polymorphonuclear leukocytes (e.g., myeloperoxidase activity), as well as neuronal damage (e.g., apoptosis, necrosis, and autophagy) after heatstroke. Hypothalamic values of antioxidant defenses (e.g., glutathione peroxidase and glutathione reductase), however, are lower. The ischemic, hypoxic, and oxidative damage to the hypothalamus during heatstroke may cause multiple organ dysfunction or failure through hypothalamic-pituitary-adrenal axis mechanisms. Finding the link between the signaling and heatstroke-induced hypothalamic oxidative and ischemic damage might allow us to clinically attenuate heatstroke. In particular, free radical scavengers, heat shock protein-70 inducers, hypervolemic hemodilution, inducible nitric oxide synthase inhibitors, progenitor stem cells, flutamide, estrogen, interleukin-1 receptor antagonists, glucocorticoid, activated protein C, and baicalin mitigate preclinical heatstroke levels.

Flutamide fails to reduce resuscitation requirements in a porcine ischemia-reperfusion model

BACKGROUND

Hemorrhagic shock and subsequent resuscitation can lead to ischemia-reperfusion injury, followed by multiorgan failure and death. Flutamide, a vasoactive nonsteroidal antiandrogen compound, is thought to improve tissue and organ perfusion. We tested whether administration of flutamide-cyclodextrin (FLU-CYD) alters physiologic parameters or resuscitation requirements in a porcine model of severe acidosis and shock secondary to combined hemorrhage + ischemia-reperfusion injury.

METHODS AND MATERIALS

Fifteen male pigs underwent a 35% blood-volume hemorrhage. Ischemia was induced by cross-clamping the supraceliac aorta for 50 min followed by reperfusion and resuscitation. FLU-CYD complex was administered during aortic clamping. Fluid resuscitation and epinephrine were titrated by protocol to maintain mean arterial pressure ≥40 mm Hg for 6 h. Sequential laboratory results were obtained and serum levels of FLU and 2-hydroxy-flutamide (FLUOH) were measured by mass spectrometry.

RESULTS

Mean requirements for injured control swine were 14.6 (± 1.21 standard error of the mean [SEM]) L crystalloid saline and 0.59 (± 0.29 SEM) g epinephrine, compared with 16.30 (± 1.33 SEM) L and 0.54 (± 0.16 SEM) g, respectively, in the FLU-CYD group (both P > 0.05). There were no significant differences in central hemodynamics between control and experimental groups. No significant differences for pH, bicarbonate, fibrinogen, or international normalized ratio were evident. FLU-CYD resuscitation was associated with a significant increase in lactate levels compared with controls (10.1 versus 5.7 mmol/L, P < 0.05). Histologic injury was significantly increased in the livers of FLU-CYD compared with sham (P = 0.022). High serum levels of FLU and the active metabolite FLUOH were measurable throughout the resuscitation period.

CONCLUSIONS

Flutamide failed to show any benefit to resuscitation in a model of severe injury and was associated with increased acidosis, hemodilution, and liver injury compared with standard crystalloid resuscitation.

Antiandrogen pretreatment alters cocaine pharmacokinetics in men

Among cocaine users, men experience more adverse brain and vascular effects than their female counterparts. This could be caused by testosterone, which may potentiate some of cocaine's effects. We examined whether antiandrogen (flutamide, FL) pretreatment alters cocaine's acute behavioral, physiologic, and pharmacokinetic effects in men with histories of occasional cocaine use. Participants (N = 8) were pretreated with oral FL (250 mg) and placebo on separate study days followed by intravenous (IV) cocaine (0.4 mg/kg). Vital signs, subjective ratings, and blood samples for cocaine and metabolites were obtained at baseline and for 90 minutes after cocaine administration. FL, itself, had no effects on physiologic or subjective responses; however, after cocaine, heart rate recovered faster with FL pretreatment. Flutamide reduced peak plasma cocaine levels (Wilcoxon signed-rank z = 2.1, P < 0.04) and area under the curve (AUC; z = 1.96, P < 0.05). Additionally, FL reduced EME levels (z = 1.96, P < 0.05) and AUC for BE and EME (z = 2.38, P < 0.02 and z = 1.96, P < 0.05, respectively). These results suggest that FL may alter cocaine pharmacokinetics in men. Because cocaine and BE are vasoconstrictive, the data imply that FL might reduce some of cocaine's cardiovascular effects.

Flutamide, an androgen receptor antagonist, improves heatstroke outcomes in mice

Flutamide has been used as an adjunct for decreasing the mortality from subsequent sepsis. Heatstroke resembles septic shock in many aspects. We hypothesized that heat-induced multiple organ dysfunction syndromes and lethality could be reduced by flutamide therapy. In heatstroke groups, mice were exposed to whole body heating (41.2°C, for 1h) in a controlled-environment chamber. The heat-stressed mice were returned to normal room temperature (24°C) after whole body heating. Mice still alive on day 4 of WBH treatment were considered survivors. Physiological and biochemical parameters were monitored for 2.5h post-WBH. Heatstroke mice were subcutaneously treated with flutamide (12.5-50mg/kg body weight in 0.05 ml) or vehicle solution (0.05 ml/kg body weight) once daily for 3 consecutive days post-WBH. We evaluated the effect of flutamide in heatstroke mice and showed that flutamide significantly (i) attenuated hypothermia, (ii) reduced the number of apoptotic cells in the hypothalamus, the spleen, the liver, and the kidney, (iii) attenuated the plasma index of toxic oxidizing radicals (e.g., nitric oxide metabolites and hydroxyl radicals), (iv) diminished the plasma index of the organ injury index (e.g., lactate dehydrogenase), (v) attenuated plasma systemic inflammation response molecules (e.g., tumor necrosis factor-α and interleukin-6), (vi) reduced the index of infiltration of polymorphonuclear neutrophils in the lung (e.g., myeloperoxidase activity), and (vii) allowed three times the fractional survival compared with vehicle. Thus, flutamide appears to be a novel agent for the treatment of mice with heatstroke or patients in the early stage of heatstroke.

Microarray and functional cluster analysis implicates transforming growth factor beta1 in endothelial cell dysfunction in a swine hemorrhagic shock model

BACKGROUND

Trauma leading to massive hemorrhage results in widespread tissue hypoxia, anaerobic metabolism, and production of inflammatory cytokines and oxidative molecules injurious to the vascular endothelium. Although trauma-related endothelial cell pathophysiology has been extensively studied, very little is known regarding gene transcriptional changes that occur during the event, particularly in endothelia. Thus, we employed fluorescent microarray analysis of gene transcription to elucidate critical pathways and gene products involved in endothelial dysfunction.

MATERIALS AND METHODS

A trauma-hemorrhage/shock (T-H/S) model mimicking the physiologic changes seen in human trauma was performed on 10 Yorkshire swine, consisting of 35% blood volume hemorrhage followed by 6 h of full resuscitation. Aortic endothelium was analyzed by microarray and functional clusters were identified through the use of Database for Annotation, Visualization, and Integrated Discovery (DAVID) software.

RESULTS

Injured swine developed profound acidosis, coagulopathy, massive resuscitative fluid requirements, and microscopic changes of ischemia/reperfusion injury. While 1007 transcripts were down-regulated, 529 transcripts were up-regulated. DAVID functional clustering analysis revealed 21 significantly altered biological processes that were grouped into 12 distinct functional categories. The transforming growth factor beta (TGFβ) family of genes was the most interrelated. In addition, vascular endothelial growth factor (VEGF) signaling members and leukocyte chemoattractants were also altered.

CONCLUSIONS

Our model identified two major signaling pathways, TGFβ and VEGF, which undergo early transcriptional changes in injured endothelial cells. Our results suggest that TGFβ and VEGF may play a crucial role in the development of endothelial cell injury leading to increased vascular permeability during shock-trauma.

Sex differences in vasoconstrictor reserve during 70 deg head-up tilt

Women are generally recognized to be less orthostatically tolerant than men. We hypothesized that during head-up tilt (HUT), women would demonstrate less splanchnic vasoconstriction, leading to splanchnic pooling, lower blood pressure and lower orthostatic tolerance. Mean arterial blood pressure (MAP), heart rate (HR), cardiac output ((.)Q(c), assessed by C2H2 rebreathing), stroke volume, splanchnic blood flow (SpBF, assessed by Indocyanine Green clearance) and vascular conductance (systemic, SVC = (.)Qc/MAP; splanchnic, SpVC = SpBF/MAP; non-splanchnic, non-SpVC = SVC - SpVC) were measured during supine baseline conditions, 70 deg HUT and recovery in 14 healthy women (23 +/- 6 years old; mean +/- S.D.) and 16 men (23 +/- 5 years old). The proportion of sexes surviving 45 min of HUT trended towards significance (chi(2) = 2.92, P = 0.09). The MAP was lower in women than in men (supine, 77 +/- 5 versus 86 +/- 9 mmHg, P < 0.01; tilt, 72 +/- 8 versus 83 +/- 10 mmHg, P < 0.01), while HR and cardiac index ( /body surface area) were not different between the sexes (heart rate supine, 66 +/- 6 versus 64 +/- 8 beats min(-1); heart rate tilt, 96 +/- 13 versus 94 +/- 10 beats min(-1); cardiac index supine, 3.8 +/- 0.9 versus 3.7 +/- 0.7 l min(-1) m(2); cardiac index tilt, 2.7 +/- 0.8 versus 2.3 +/- 0.5 l min(-1) m(2)). The SpBF and SpVC were lower in women at rest but not during tilt (SpBF supine, 1174 +/- 243 versus 1670 +/- 391 ml min(-1), P < 0.01; SpVC supine, 14.83 +/- 3.61 versus 19.59 +/- 4.95 ml min(-1) mmHg(1), P < 0.01; SpBF tilt, 884 +/- 300 versus 1094 +/- 271 ml min(-1); SpVC tilt, 13.14 +/- 4.28 versus 14.82 +/- 4.16 ml min(-1) mmHg(-1)). However, in the women the SpVC did not decrease from baseline to tilt (SpVC, in women, 1.70 +/- 3.19 ml min(-1) mmHg(-1), n.s.; in men, 4.81 +/- 3.44 ml min(-1) mmHg(-1), P < 0.01), suggesting a blunted vasoconstrictor response. In conclusion, women tended to have lower tilt-table tolerance associated with a smaller splanchnic vasoconstrictor reserve than men.

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.

Flutamide attenuates pro-inflammatory cytokine production and hepatic injury following trauma-hemorrhage via estrogen receptor-related pathway

OBJECTIVE

To determine the mechanism by which flutamide administration following trauma-hemorrhage (T-H) decreases cytokine production and hepatic injury under those conditions.

SUMMARY BACKGROUND DATA

Although studies have demonstrated that flutamide administration following T-H improves hepatic and immune functions, the mechanism by which flutamide produces the salutary effects remains unknown.

METHODS

Male Sprague-Dawley rats underwent a 5-cm laparotomy and hemorrhagic shock (40 mm Hg for approximately 90 minutes), followed by resuscitation with 4 times the shed blood volume in the form of Ringer's lactate. Flutamide (25 mg/kg body weight, sc) was administered at the middle of resuscitation and animals were killed 2 hours thereafter. To block estrogen receptor (ER), ER antagonist ICI 182,780 was administrated with flutamide.

RESULTS

Hepatic injury, myeloperoxidase activity, nuclear factor-kappaB (NF-kappaB) DNA binding activity and protein expression of intercellular adhesion molecule-1, and cytokine-induced neutrophil chemoattractant (CINC-1 and CINC-3) markedly increased following T-H. Hepatic mRNA and plasma IL-6 levels were also elevated following T-H. The alterations in these parameters induced by T-H were significantly attenuated by flutamide administration. The decreased plasma estradiol levels following T-H were restored to sham levels in the flutamide-treated T-H animals. Coadministration of ICI 182,780 prevented those salutary effects of flutamide administration on pro-inflammatory responses and hepatic injury following T-H.

CONCLUSION

These findings suggest that the reduction in the production of pro-inflammatory mediators and hepatic injury produced by flutamide administration following T-H is likely due to the down-regulation in hepatic NF-kappaB DNA binding activity. Moreover, the salutary effects of flutamide administration appear to be mediated at least in part via ER-related pathway.

Gonadal steroids in critical illness

Gonadal steroids are metabolized in target cells and then interact with specific receptors to exert genomic and nongenomic effects. Complex feedback loops that involve the immune-neuroendocrine axis, limbic system, and gonadal steroids play a vital role in the adaptation to critical illness. Preclinical studies demonstrate adverse physiological effects of androgens on the cardiovascular and immune systems despite its purported anabolic effects. Similar models also demonstrate salutary effects of estrogens on these systems. Thus, during the catabolic phases of acute and chronic critical illness, estrogen, and not androgen, therapy may prove to be a valuable intervention. However, during the post-critical illness recovery phase, when anabolism is critical, androgen therapy may still be useful and safe.

PGC-1 upregulation via estrogen receptors: a common mechanism of salutary effects of estrogen and flutamide on heart function after trauma-hemorrhage

Flutamide, an androgen receptor antagonist, is thought to improve cardiovascular function by blocking the androgen receptor after trauma-hemorrhage (T-H). Although 17β-estradiol (E2) and flutamide improve cardiac function after T-H, whether E2 and flutamide produce their salutary effect via the same or a different mechanism is unknown. We hypothesized that E2 and flutamide mediate their effects via estrogen receptor (ER)-mediated upregulation of peroxisome proliferator-activated receptor coactivator 1 (PGC-1). PGC-1, a key regulator of cardiac mitochondrial function, induces mitochondrial genes by activating transcription factors such as nuclear respiratory factor 2 (NRF-2), which regulates mitochondrial proteins [i.e., mitochondrial transcription factor A (Tfam), cytochrome- c oxidase subunit IV, and β-ATP synthase]. Adult male rats underwent T-H [5-cm midline incision and hemorrhage (blood pressure = 40 mmHg for ∼90 min)] and resuscitation. At the onset of resuscitation, rats received vehicle, flutamide (25 mg/kg), or E2 (50 μg/kg). Another group received the ER antagonist ICI-182780 (3 mg/kg) with or without flutamide. Flutamide or E2 administration after T-H restored depressed cardiac function. Moreover, E2 and flutamide normalized expression of cardiac PGC-1, NRF-2, Tfam, cytochrome- c oxidase subunit IV, and the mitochondrial DNA-encoded gene cytochrome- c oxidase subunit I and β-ATP synthase, mitochondrial ATP, and cytochrome- c oxidase activity. However, if the ER antagonist ICI-182780 was administered with flutamide, flutamide-mediated PGC-1 upregulation was totally abolished. These results indicate that E2 and flutamide upregulate PGC-1 via the ER. Thus PGC-1 upregulation appears to be the common mechanism by which E2 and flutamide mediate their salutary effects on cardiac function after T-H.

Current Understanding of Gender Dimorphism in Hepatic Pathophysiology1

Studies have shown gender dimorphic response of the liver for various hepatic stresses including ischemia/reperfusion, hemorrhagic shock-resuscitation, hepatectomy, liver cirrhosis, endotoxemia, and chronic alcoholic consumption. The mechanisms responsible for the gender dimorphic response include differences in pro-inflammatory cytokine release, production of reactive oxygen species, and alteration in hepatic vasoregulatory action. These effects were shown to be modulated by circulating sex steroid levels. In this regard, modulation of sex steroid levels by agents/drugs has been proposed as a therapeutic option for preventing hepatic damage in various hepatic stress models. Further elucidation of precise mechanisms responsible for the gender-related differences in the hepatic pathophysiology is essential for the potential clinical application of sex hormone modulation therapy. In this article, current progress in our understanding the gender difference in the hepatic pathophysiology under the condition of hepatic stress is reviewed and discussed.

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.

Testosterone as a modulator of vascular behavior

Male sex is an acknowledged risk factor for many forms of cardiovascular disease, and vascular disease prevalence patterns appear to be different in men versus women. The vascular properties of the principal mammalian androgen, testosterone, are complex and linked to dose, duration of exposure, presence of underlying vascular disease, and, possibly, biological sex. Data from isolated vessels and animal models suggest that pharmacological doses of testosterone, or its potent intracellular metabolite dihydrotestosterone, produce vasodilation. Testosterone's major effect on vascular beds at physiologic concentrations remains unclear, with documentation of both vasodilatory and vasoconstrictive actions. Results of various studies suggest that testosterone can alter vascular tone through both endothelium-dependent and endothelium-independent mechanisms in a variety of vascular beds and vessel types. Testosterone's endothelium-dependent effects are likely mediated at least in part through nitric oxide (NO) elaboration, whereas mechanisms of endothelium-independent effects involve 1 or more types of smooth muscle ion conductance channels. Data from clinical studies indicate that, in men, androgen replacement may provide beneficial effects when coronary artery disease is present. Conversely, in women, testosterone may augment existing hypertension, increase risk for cardiovascular events, or promote atherogenesis. However, it should be emphasized that most of these observations are anecdotal or come from small-scale clinical studies, and limited information is available in women. New research is required to understand the potential efficacy of androgen therapy, or lack thereof. This review focuses on current understanding of testosterone's physiological effects on vascular behavior and of testosterone's putative role in vascular health and disease.

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.

Superior mesenteric artery occlusion models shock-induced gut ischemia-reperfusion

INTRODUCTION

Superior mesenteric artery occlusion (SMAO) is a simple and reproducible model of shock-induced gut ischemia/reperfusion, but some argue that it is not clinically relevant. The purpose of the current study was to compare SMAO to a standard model of controlled hemorrhage (CH) and uncontrolled hemorrhage (UH).

METHODS

Rats had femoral lines and a jejunal mucosal laser Doppler placed followed by SMAO (60 min of ischemia, no resuscitation), controlled hemorrhage (40 mm Hg for 60 min, 2:1 resuscitation shed blood and lactated Ringers), or uncontrolled hemorrhage (liver injury, 3:1 resuscitation with lactated Ringers). Base deficit, lactate, and jejunal mucosal flow (as a percentage of baseline) were recorded during ischemia and for 120 min after reperfusion. Jejunal tissue was harvested for morphological evaluation. Comparison among groups was by analysis of variance (ANOVA), and significance was set at P < 0.05.

RESULTS

Mucosal blood flow was similar among groups at the onset of reperfusion (CH, 16.9 +/- 5.0% versus UH, 10.9 +/- 3.1% versus SMAO, 13.9 +/- 6.2%) and during the initial period of reperfusion. By 120 min, however, flow in CH (75.4 +/- 2.5%) was significantly higher that in either UH (36.4 +/- 13.1%) or SMAO (31.7 +/- 8.4%). Histological injury was less with CH, while base deficit was significantly higher in CH at the onset of reperfusion (-24 +/- 2 versus UH, -10 +/- 3 and SMAO, -6 +/- 3 mM/L) but comparable by the end (CH, -17 +/- 4 versus UH, -16 +/- 3 and SMAO, -17 +/- 2 mM/L).

CONCLUSIONS

SMAO is a clinically relevant model of shock-induced gut ischemia/reperfusion.

Metabolic disturbances in shock, and the role of ATP-MgCl2 and sex steroids

Hemorrhage following accidental injuries is a common cause of death in the industrialized world. Moreover, the impact of elective surgery and solid organ transplantation sometimes results in low flow conditions similar to those seen following hemorrhagic shock. A shortage in O(2) availability, or hypoxia, leads to sequential changes in cell metabolism and morphology, including inflammatory responses and the expression of hypoxia-inducible transcription factor-1, which controls the cellular adaptation to hypoxia. These endogenous adaptive responses show that O(2) deprivation is not an unforeseen event for cells. The purpose of this review article is to discuss the pathophysiologic principles of shock and the metabolic alterations that cells undergo during low flow conditions. Moreover, the rationale for therapeutic intervention by administering ATP-MgCl(2) and sex steroids following shock and trauma will also be discussed.

Gender differences in large artery stiffness pre- and post puberty

Age-related large artery stiffening is more pronounced in women compared with men and is an important cause of isolated systolic hypertension. This study aimed to investigate whether such gender differences are inherent or the result of sex steroid influences. Healthy children prepuberty [26 female (10.3 +/- 0.1 yr), 32 male (10.3 +/- 0.1 yr), mean age +/- SD] and post puberty [30 female (15.9 +/- 0.2 yr), 22 male (15.9 +/- 0.4 yr)] were studied. Large artery stiffness was assessed globally via systemic arterial compliance and regionally via pulse wave velocity. Prepubertal males and females did not differ in body size, cardiac output, or heart rate. Prepubertal females had stiffer large arteries and higher pulse pressure than age-matched males (P < 0.05). Postpubertal males were taller and heavier and had a greater cardiac output and lower heart rate compared with similarly aged females. In relation to pubertal status, females developed more distensible large arteries post puberty whereas males developed stiffer large vessels (P < 0.05). These changes where such that central large artery stiffness was similar between genders in the postpubertal group. Together these data suggest that large artery stiffness varies intrinsically between genders but is also modulated by both male and female sex steroids.

Androgens and cardiovascular disease

Globally, cardiovascular disease will continue causing most human deaths for the foreseeable future. The consistent gender gap in life span of approximately 5.6 yr in all advanced economies must derive from gender differences in age-specific cardiovascular death rates, which rise steeply in parallel for both genders but 5-10 yr earlier in men. The lack of inflection point at modal age of menopause, contrasting with unequivocally estrogen-dependent biological markers like breast cancer or bone density, makes estrogen protection of premenopausal women an unlikely explanation. Limited human data suggest that testosterone exposure does not shorten life span in either gender, and oral estrogen treatment increases risk of cardiovascular death in men as it does in women. Alternatively, androgen exposure in early life (perinatal androgen imprinting) may predispose males to earlier onset of atherosclerosis. Following the recent reevaluation of the estrogen-protection orthodoxy, empirical research has flourished into the role of androgens in the progression of cardiovascular disease, highlighting the need to better understand androgen receptor (AR) coregulators, nongenomic androgen effects, tissue-specific metabolic activation of androgens, and androgen sensitivity. Novel therapeutic targets may arise from understanding how androgens enhance early plaque formation and cause vasodilatation via nongenomic androgen effects on vascular smooth muscle, and how tissue-specific variations in androgen effects are modulated by AR coregulators as well as metabolic activation of testosterone to amplify (via 5alpha-reductase to form dihydrotestosterone acting on AR) or diversify (via aromatization to estradiol acting upon estrogen receptor alpha/beta) the biological effects of testosterone on the vasculature. Observational studies show that blood testosterone concentrations are consistently lower among men with cardiovascular disease, suggesting a possible preventive role for testosterone therapy, which requires critical evaluation by further prospective studies. Short-term interventional studies show that testosterone produces a modest but consistent improvement in cardiac ischemia over placebo, comparable to the effects of existing antianginal drugs. By contrast, testosterone therapy has no beneficial effects in peripheral arterial disease but has not been evaluated in cerebrovascular disease. Erectile dysfunction is most frequently caused by pelvic arterial insufficiency due to atherosclerosis, and its sentinel relationship to generalized atherosclerosis is insufficiently appreciated. The commonality of risk factor patterns and mechanisms (including endothelial dysfunction) suggests that the efficacy of antiatherogenic therapy is an important challenge with the potential to enhance men's motivation for prevention and treatment of cardiovascular diseases.

Effect of estradiol administration on splanchnic perfusion after trauma-hemorrhage and sepsis

PURPOSE OF REVIEW

This review focuses on the latest mechanistic understanding of the effects of estradiol on the splanchnic circulation and the possibility of estradiol treatment as an adjunct for the treatment of trauma-hemorrhage and sepsis.

RECENT FINDINGS

Systemic hypotension induced by shock accompanies marked alterations in blood flow to various organs. Decreased splanchnic perfusion is frequently observed after insults, such as severe hemorrhage or sepsis, which leads to the destruction of the intestinal mucosal barrier and hepatic dysfunction. Studies suggest that estradiol acts as a facilitator of the intestinal blood flow via the increased production of nitric oxide, decreased production of vasoconstrictors, attenuated neutrophil adhesion, and decreased formation of oxygen free radicals.

SUMMARY

Trauma-hemorrhage results in decreased circulating blood volume. In contrast, sepsis is an inflammatory state mainly mediated by bacterial products. However, these divergent insults show similar pathophysiologic alterations in terms of the splanchnic circulation. Because estradiol effectively protects the organs from circulatory failure after various adverse circulatory conditions, many studies are being performed to clarify the molecular mechanism of estradiol action with regard to tissue circulation. Estradiol improves the macro- and microcirculation of the splanchnic organs by multiple mechanisms. Nonetheless, it remains unclear which mechanism plays the most important role in the treatment of trauma-hemorrhage and sepsis. Additional studies are required to elucidate the precise mechanism of estradiol action and to determine the usefulness of estradiol treatment for severe hemorrhage and sepsis in patients.

Hemorrhage induces the rapid development of hepatic insulin resistance

Hyperglycemia is an early metabolic response to trauma and hemorrhage. The role of hepatic insulin resistance to the development of this hyperglycemia is not well understood. The aim of this study was to determine whether the liver becomes insulin resistant and to identify the particular hepatic insulin signaling pathways that may be compromised following trauma and hemorrhage. Male adult rats were bled to a mean arterial pressure of 40 mmHg and maintained at that pressure for 90 min followed by resuscitation with Ringer lactate. Data showed that trauma and hemorrhage rapidly induced profound hyperinsulinemia in combination with significant hyperglycemia, suggesting the development of insulin resistance. After trauma and hemorrhage, hepatic insulin signaling via the insulin-induced phosphatidylinositol 3 (PI3)-kinase-Akt pathway was abolished, whereas ERK1/2 signaling was relatively normal. The regulation (inhibition) of a hepatic-, insulin-, and the PI3-kinase-dependent gene, IGF binding protein-1, was also lost. The present study provides convincing evidence of a rapid onset hepatic insulin resistance following a combination of trauma and hemorrhage.

Resuscitation regimens for hemorrhagic shock must contain blood

Endothelial cell dysfunction occurs during hemorrhagic shock (HS) and persists despite adequate resuscitation (RES) that restores and maintains hemodynamics. We hypothesize that RES from HS with crystalloid solutions alone aggravate the endothelial cell dysfunction. To test this hypothesis, anesthetized nonheparinized rats were monitored for hemodynamics, and the terminal ileum was studied with intravital video microscopy. HS was 50% of mean arterial pressure (MAP) for 60 min. Four hemorrhaged groups (10 animals in each group) were randomized for RES: group I with shed blood returned + equal volume of normal saline (NS); group II with shed blood returned + 2x NS; group III with 2x NS only; and group IV with 4x NS only. Two hours post-RES, endothelial cell function was assessed with the endothelial-dependent agonist acetylcholine (ACh, 10(-9)-10(-4) M). Maximum arteriolar diameter was elicited by the endothelial-independent agonist sodium nitroprusside (NTP, 10(-4) M). HS caused a selective vasoconstriction associated with low blood flow in inflow A1 arterioles in all hemorrhaged groups. Post-RES vasoconstriction developed in A1 and premucosal arterioles (pA3 and dA3) In all hemorrhaged groups regardless of the RES regimen. However, A1 vasoconstriction and flow were significantly worst in the animals RES with NS alone (-43% and -75%, respectively) compared with those resuscitated with blood and NS (-27% and -57%). Impaired dilation response to ACh was noted in all hemorrhaged animals. However, a significant shift to the right of the dose-response curve (decreased sensitivity) was observed in the animals resuscitated with NS alone irrespective of the RES volume. These animals required at least two orders of magnitude greater ACh concentration to produce a 20% dilation response. For all vessel types, Group II had the best preservation of endothelial cell function. In conclusion, HS causes a selective vasoconstriction of A1 arterioles, which was not observed in A3 vessels. RES from HS results in progressive vasoconstriction in all intestinal arterioles irrespective of the RES regimen. Crystalloid RES after HS does not restore hemodynamics to baseline and is associated with a marked endothelial cell dysfunction. Blood-containing RES regimens preserve and maintain hemodynamics and are associated with the least microvascular dysfunction. Therefore, regimens for RES from HS must contain blood. Endothelial cell dysfunction is not the sole etiologic factor of post-RES microvascular impairment.

Sexual dimorphism in the spontaneous recovery from spinal cord injury: a gender gap in beneficial autoimmunity?

Immune cells have been shown to contribute to spontaneous recovery from central nervous system (CNS) injury. Here we show that adult female rats and mice recover significantly better than their male littermates from incomplete spinal cord injury (ISCI). This sexual dimorphism is wiped out and recovery is worse in adult mice deprived of mature T cells. After spinal cord contusion in adult rats, functional recovery (measured by locomotor scores in an open field) was significantly worse in females treated with dihydrotestosterone prior to the injury than in placebo-treated controls, and significantly better in castrated males than in their noncastrated male littermates. Post-traumatic administration of the testosterone receptor antagonist flutamide promoted the functional recovery in adult male rats. These results, in line with the known inhibitory effect of testosterone on cell-mediated immunity, suggest that androgen-mediated immunosuppression plays a role in ISCI-related immune dysfunction and can therefore partly explain the worse outcome of ISCI in males than in female. We suggest that females, which are more prone to develop autoimmune response than males, benefit from this response in cases of CNS insults.

Vascular reactivity in hypogonadal men is reduced by androgen substitution

The effect of testosterone (T) substitution therapy on blood vessel functions in relation to cardiovascular disease has not been fully elucidated. In 36 newly diagnosed nonsmoking hypogonadal men (37.5 +/- 12.7 yr) endothelium-dependent flow-mediated vasodilatation (FMD; decreased in atherosclerosis) of the brachial artery was assessed before treatment and after 3 months of T substitution therapy (250 mg testosterone enanthate im every 2 wk in 19 men, human chorionic gonadotropin sc twice per week in 17 men). Twenty nonsmoking controls matched for age, low-density lipoprotein cholesterol (LDL-C), body height, and baseline diameter of the artery were selected for repeated measurements from a larger eugonadal control group (n = 113). In hypogonadal men, basal FMD (17.9 +/- 4.5%) was significantly higher than in the large (11.9 +/- 6.4%) and matched control (11.8 +/- 7.1%, both P < 0.001) groups. Grouped multiple linear regression analysis revealed a significant negative association of T levels with FMD within the hypogonadal range, but no significant association was seen within the eugonadal range. During substitution therapy, T levels increased from 5.8 +/- 2.3 to 17.2 +/- 5.1 nmol/liter and FMD decreased significantly to 8.6 +/- 3.1% (P < 0.001, analysis for covariance for repeated measurements including matched controls). LDL-C and advanced age contributed significantly to decrease FMD (P = 0.01, P = 0.04, respectively). Because T substitution adversely affects this important predictor of atherosclerosis, other contributing factors (such as smoking, high blood glucose, and LDL-C) should be eliminated or strictly controlled during treatment of hypogonadal men.