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Although melatonin treatment following trauma-hemorrhage or ischemic reperfusion prevents organs from dysfunction and injury, the precise mechanism remains unknown. This study tested whether melatonin prevents liver injury following trauma-hemorrhage involved the protein kinase B (Akt)-dependent heme oxygenase (HO)-1 pathway. After a 5-cm midline laparotomy, male rats underwent hemorrhagic shock (mean blood pressure approximately 40 mmHg for 90 min) followed by fluid resuscitation. At the onset of resuscitation, rats were treated with vehicle, melatonin (2 mg/kg), or melatonin plus phosphoinositide 3-kinase (PI3K) inhibitor wortmannin (1 mg/kg). At 2 hr after trauma-hemorrhage, the liver tissue myeloperoxidase activity, malondialdehyde, adenosine triphosphate, serum alanine aminotransferase, and aspartate aminotransferase levels were significantly increased compared with sham-operated control. Trauma-hemorrhage resulted in a significant decrease in the Akt activation in comparison with the shams (relative density, 0.526 ± 0.031 versus 1.012 ± 0.066). Administration of melatonin following trauma-hemorrhage normalized liver Akt phosphorylation (0.993 ± 0.061), further increased mammalian target of rapamycin (mTOR) activation (5.263 ± 0.338 versus 2.556 ± 0.225) and HO-1 expression (5.285 ± 0.325 versus 2.546 ± 0.262), and reduced cleaved caspase-3 levels (2.155 ± 0.297 versus 5.166 ± 0.309). Coadministration of wortmannin abolished the melatonin-mediated attenuation of the shock-induced liver injury markers. Our results collectively suggest that melatonin prevents hemorrhagic shock-induced liver injury in rats through an Akt-dependent HO-1 pathway. [ABSTRACT FROM AUTHOR]

1. Oxidative stress induced by reactive oxygen species (ROS) is a key mediator of haemorrhagic shock (HS)-induced vascular hyperpermeability. In the present study, curcumin, a natural anti-oxidant obtained from turmeric ( Curcuma longa), was tested against HS-induced hyperpermeability and associated ROS formation in rat mesenteric post-capillary venules in vivo and in rat lung microvascular endothelial cells (RLMEC) in vitro. 2. In rats, HS was induced by withdrawing blood to reduce mean arterial pressure to 40 mmHg for 60 min, followed by resuscitation for 60 min. To investigate vascular permeability, rats were given fluorescein isothiocyanate (FITC)–albumin (50 mg/kg, i.v.). The FITC–albumin flux was measured in mesenteric post-capillary venules by determining optical intensity intra- and extravascularly under intravital microscopy. Mitochondrial ROS formation was determined using dihydrorhodamine 123 in vivo. Parallel studies were conducted in vitro using serum collected after HS. The serum was tested on rat lung microvascular endothelial cell RLMEC monolayers. 3. In rats, HS induced a significant increase in vascular hyperpermeability and ROS formation in vivo ( P < 0.05). Treatment with curcumin (20 μmol/L) attenuated both these effects ( P < 0.05). In RLMEC in vitro, HS serum induced monolayer permeability and ROS formation. Curcumin (10 μmol/L) attenuated HS serum-induced monolayer hyperpermeability and ROS formation. Curcumin (2–100 μmol/L) scavenged 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) and 1,1-diphenyl-2-picrylhydrazyl radicals in vitro, indicating its potential as a free radical scavenger. 4. The present study demonstrates that curcumin is an inhibitor of vascular hyperpermeability following HS, with its protective effects mediated through its anti-oxidant properties. [ABSTRACT FROM AUTHOR]

To determine whether parenterall-arginine supplementation enhances the impaired wound healing of rats subjected to trauma/hemorrhagic shock. Impaired wound healing after trauma and shock has been documented experimentally and clinically.l-arginine has been shown to enhance wound strength and collagen synthesis in rodents and humans. Its efficacy under conditions of impaired wound healing is less well defined. Forty-eight male Lewis rats were used in this study. Using a well-defined model, 24 rats underwent trauma/hemorrhagic shock before wounding. Twenty-four untreated rats served as controls. All animals underwent a dorsal skin incision with implantation of polyvinyl-alcohol sponges. Half of the animals in each group were assigned to receive 1 g/kg/day ofl-arginine by intraperitoneal injection in three divided doses, while the other half received saline injections only. Animals were sacrificed 10 days postwounding, and wound-breaking strength (WBS) and wound sponge total hydroxyproline (OHP) and nitrite/nitrate (NO x) content were determined. Wound sponge RNA was collected and subjected to Northern blot analysis for procollagens I and III. Trauma/hemorrhage greatly decreased WBS with a concomitant diminution in collagen (OHP) deposition.l-arginine significantly enhanced WBS (19%) and increased OHP (21%) levels in control animals as well as in rats subjected to trauma/hemorrhage (WBS +29%, OHP 40%) compared with their saline-treated counterparts. Procollagen I and III mRNA levels were elevated byl-arginine treatment in both trauma/hemorrhage and control rats. Arginine treatment had no effect on wound fluid and plasma NO x. The data demonstrate that the impaired healing subsequent to trauma/hemorrhage can be greatly alleviated byl-arginine supplementation. [ABSTRACT FROM AUTHOR]

Discusses a study which determined whether heme oxygenase-1 (HO-1) induction restores cyclic adenosine monophosphate-dependent lung epithelial fluid transport following severe hemorrhage in rats. Role of hemorrhagic shock in the decrease of alveolar epithelial fluid transport; Restoration of normal alveolar epithelial fluid transport by HO-1; Role of HO-1 in the attenuation of nitric oxide release by alveolar macrophages.

Previous studies from our laboratory demonstrated a positive correlation between hemorrhagic shock (HS)-induced vascular hyperpermeability and endothelial cell reactive oxygen species (ROS) generation. We hypothesized that curcumin a known antioxidant obtained from turmeric (Curcuma longa), would attenuate vascular hyperpermeability following HS. The objective of this study was to determine if curcumin prevents ROS production and vascular hyperpermeability following HS in rat mesentric vasculature in vivo. In rats, HS was induced by withdrawing blood to reduce the MAP to 40 mmHg for 60 minutes followed by resuscitation to 90 mmHg with the shed blood and saline. To study vascular permeability, the rats were injected intravenously with FITC-albumin (50 mg/kg) and the FITC-albumin flux was measured by determining the changes in integrated optical intensity obtained intra and extra vascularly using intravital microscopy. ROS production was determined by using the fluorescent dye dihydrorhodamine 123, that was superfused on the exposed mesenteric vasculature. The results showed that, HS induced hyperpermeability in rat mesenteric vasculature. Curcumin pre-treatment (20 µM) attenuated HS-induced hyperpermeability (p < 0.05). HS was followed by a significant rise in intracellular ROS generation. Hemorrhagic shock-induced ROS rise was inhibited by curcumin (20 µM; p < 0.05). Together, these findings show that curcumin is effective in maintaining endothelial cell barrier integrity following hemorrhagic shock. The protective effects of curcumin may be mediated through its antioxidant properties. [ABSTRACT FROM AUTHOR]

Acute blood loss triggers heightened vasoconstriction which contributes to maintenance of the blood pressure. Hemorrhage also induces shock proteins, including heme oxygenase (HO)-1. HO metabolizes heme to form carbon monoxide (CO), which inhibits nitric oxide synthase to promote endothelial dysfunction. This study examines the hypothesis that hemorrhage induces HO-1, to enhance CO production and promote endothelial dysfunction which contributes to the restoration of blood pressure. Male Sprague-Dawley rats (300-350g) with chronic femoral arterial catheters were subjected to a 45% hemorrhage (shock). Hemorrhage produced vasodepression from 117±2 mmHg to 78±6 mmHg in 1 hour. At 36hrs, vascular HO-1 was induced (shock: 2.7±0.3 vs unbled: 1.1±0.2 ng/mg Pr), which was accompanied by a 25% increase in expired CO and restoration of arterial pressures to 106±2 mmHg. First order gracilis muscle arterioles, isolated from each group, were mounted in a microvessel chamber, superfused with oxygenated Krebs buffer and exposed to constant midpoint, but altered endpoint pressures to establish graded levels of luminal flow (0-50µL/min). Flow-induced dilation was abolished in shock arterioles (Δmax 0±0µm vs Δmax18±1µm, shock vs unbled; P<0.05). Acute pretreatment with an inhibitor of HO, chromium mesoporphyrin (15µmol/L) restored flow-induced dilation to control levels (Δmax 30±1µm). These data show that hemorrhagic shock can induce HO-1 to increase CO formation and promote endothelial dysfunction. Accordingly it suggests that shock induced increases in CO formation may contribute to the restoration of blood pressure via its well established ability to inhibit nitric oxide synthase. [ABSTRACT FROM AUTHOR]

WHPC extends the survival of mice exposed to lethal environmental hypoxia by preserving structural and functional integrity of key organs. We now examined whether WHPC would also prolong survival in response to hemorrhagic shock. Conscious male rats were subjected to bleeding of 60% of their estimated blood volume (∼37.2 ml/kg) over 30 min. We found that naïve rats died 76+9 min after the completion of bleeding (n=15) and this process was associated with progressively increasing metabolic acidosis and cell/organ injury. In contrast, more than 80% of rats treated with WHPC (6 cycles of 8% O2x10-min/21% O2x10-min) 2 h before bleeding survived >6 h without fluid resuscitation (n=14, p<0.001) and displayed significantly reduced acidosis and cell/organ injury. Although it decreased drastically following bleeding in all rats, Oz consumption in those treated with WHPC was significantly higher, suggesting better tissue perfusion in these animals. Furthermore, surviving animals appeared to be recovering from the initial impact of massive blood loss, with accelerated compensation and sustained maintenance of key variables above critical levels (mean arterial pressure >60 mmHg, blood base excess >-6 mmol/L, and plasma lactate <5 mmol/L). WHPC treatment 8 h before bleeding was associated with similar beneficial effects. We conclude that WHPC provides a robust protective mechanism against acute hemorrhagic shock. [ABSTRACT FROM AUTHOR]

Microvascular observations and measurements of the oxygen partial pressure (PO2) distribution are essential to understand tissue oxygenation. Longitudinal PO2 gradients have been reported previously, but few attempts have been made to investigate factors that can alter such a gradient. Despite its importance in hemorrhagic shock, the mesenteric microvascular PO2 distribution has never been evaluated during HH. We tested the hypothesis that the diverse hemodynamic responses of arterioles to HH would lead to changes in longitudinal PO2 gradients. The mesenteric microcirculation of anesthetized rats was studied under normovolemia (baseline) and during HH (mean arterial pressure = 50 mmHg). Diameter and blood flow of arterioles and venules of different orders were studied using intravital videomicroscopy. PO2 was determined using the phosphorescence quenching technique. During HH, blood flow was uniformly reduced in arterioles and venules, while PO2 showed a wider distribution. In arterioles, the small longitudinal PO2 gradient recorded during baseline was enhanced during HH. Two groups of vessels were observed with regard to PO2: large vessels showed PO2 levels similar to or above baseline, while small vessels showed reduced PO2. Changes in blood flow did not explain this variability, since the reduction in flow was similar for all vessels, irrespective of vessel order or type. [ABSTRACT FROM AUTHOR]

Hemorrhagic shock reflects low tissue perfusion that is inadequate to maintain normal metabolic functions. Often associated with this condition are impairments in cellular oxygen utilization. Rats bred for high (HCR) vs low (LCR) aerobic running capacity have greater O2 uptake and improved cardiovascular function (Gonzalez et al., J Appl Physiol 101: 1288, 2006). Hence, it was hypothesized that HCR would be more tolerant to global ischemia than LCR. To address this hypothesis, survival time to a severe controlled hemorrhage was measured. Male rats (generation 12) were catheterized and, ∼ 24 hours later, 55% of the calculated blood volume was removed during a 26 min period from conscious unrestrained animals. Rats were observed for 6 hr or until death. Contrary to our hypothesis, survival time in HCR (173 ± 55 min; n=8) did not differ (P = 0.24) from that in LCR (254 ± 52 min; n=8). Similarly, there were no differences between strains in blood pH, lactate, and base deficit values pre or post-hemorrhage. Since oxygen uptake and cardiac function are different in these rat strains, these results suggest that other mechanisms must play a more dominant role in determining survival time to hemorrhage. [ABSTRACT FROM AUTHOR]