Resuscitation of hemorrhagic shock attenuates intrapulmonary nitric oxide formation

[Erythrocytes and microvascular tone during acute traumatic haemorrhagic shock]

Haemorrhagic shock remains a leading cause of death in trauma patients. The concept of haematologic damage control is gradually taking place in the management of traumatic haemorrhagic shock. It is based primarily on the early implementation of a quality blood transfusion involving erythrocytes, plasmas and platelets transfusion. Red blood cell transfusion is mainly supported by the oxygen carrier properties of erythrocytes. However, it appears that erythrocytes ability to modulate the bioavailability of nitric oxide (NO) plays a major role in capillary opening and perfusion. Erythrocytes are also actively involved in the processes of hemostasis and coagulation. In this context, it seems difficult to define a threshold of hemoglobin concentration to determine the implementation of a blood transfusion in traumatic haemorrhagic shock.

Measuring exhaled nitric oxide in animal models: methods and clinical implications

Animal models such as rats and mice are useful for studying the multiple roles of nitric oxide (NO) in various respiratory disorders. The production of NO is catalyzed by the three isoforms of the enzymes (NO synthases; NOS). Indirect assessment of NOS gene or protein expression only provides partial information on the role of NO in health and lung disease. NO can also be measured in exhaled air by invasive or non-invasive approaches as a direct and quantitative marker of NO production in animal models. Whilst addressing the different methods of exhaled NO analysis in small animals (rats and mice), this review also focuses on the possible clinical implications, and discusses the advantages and limitations of these methods.

Minocycline ameliorates lung and liver dysfunction in a rodent model of hemorrhagic shock/resuscitation plus abdominal compartment syndrome

BACKGROUND

We sought to elucidate whether minocycline, a broad-spectrum tetracycline antibiotic with potent anti-inflammation capacity, could mitigate inflammatory response and organ dysfunction in the lungs and liver induced by hemorrhagic shock/resuscitation (HS) plus abdominal compartment syndrome (ACS).

MATERIALS AND METHODS

Adult male rats were randomized to receive HS plus ACS or HS plus ACS plus minocycline (denoted as the HS/A and HS/A-M group, respectively; n = 12). Sham-instrumentation groups were employed to serve as the controls. Hemorrhagic shock/resuscitation was induced by blood drawing (mean arterial pressure: 40-45 mm Hg for 60 min) followed by shed blood/saline mixture reinfusion. Subsequently, intra-abdominal pressure (IAP) was increased to 25 mm Hg by injecting air into the preplaced intraperitoneal latex balloon to induce ACS. Minocycline (20 mg/kg) was intravenously administered immediately after resuscitation. IAP was maintained at 25 mm Hg for 6 h. Then, all rats were euthanized.

RESULTS

The levels of polymorphonuclear leukocyte infiltration, the wet/dry weight ratio, and the concentrations of inflammatory molecules (e.g., chemokine, cytokine, and prostaglandin E2) in lung and liver tissues of the HS/A group were significantly higher than those of the HS/A-M groups (all P < 0.05). Moreover, the levels of lung dysfunction (assayed by arterial blood gas) and liver dysfunction (assayed by plasma concentrations of bilirubin, aspartate aminotransferase, and alaninine aminotransferase) of the HS/A group were significantly higher than those of the HS/A-M group (all P < 0.05).

CONCLUSIONS

Minocycline ameliorates inflammatory response and organ dysfunction in the lungs and liver induced by hemorrhagic shock/resuscitation plus abdominal compartment syndrome.

Dexmedetomidine-ketamine combination mitigates acute lung injury in haemorrhagic shock rats

AIM OF THE STUDY

Upregulation of pulmonary inflammatory molecules is crucial in mediating the development of acute lung injury induced by haemorrhagic shock. Dexmedetomidine and ketamine possess potent anti-inflammatory capacity. We sought to elucidate whether dexmedetomidine, ketamine, or dexmedetomidine-ketamine combination could mitigate acute lung injury in haemorrhagic shock rats.

METHODS

Fifty adult male Sprague-Dawley rats were randomized to the sham-instrumented, haemorrhagic shock (HS), HS plus dexmedetomidine (HS-D), HS plus ketamine (HS-K), or HS plus dexmedetomidine-ketamine (HS-D+K) group (n=10 in each group). Haemorrhagic shock was induced by blood withdrawing and the mean blood pressure was maintained at 40-45mmHg for 120min. Resuscitation was then performed by infusion of shed blood/saline mixtures. After monitoring for another 8h, rats were sacrificed.

RESULTS

Histology findings and lung injury score analysis revealed moderate lung injury in rats of the HS, HS-D, and HS-K groups, whereas those of the HS-D+K group revealed mild lung injury. The effects of haemorrhagic shock on increasing cell number and protein concentration in bronchoalveolar lavage fluid as well as water content, leukocyte infiltration, and myeloperoxidase activity of lung tissues were significantly attenuated by dexmedetomidine-ketamine combination but not by dexmedetomidine or ketamine alone. Dexmedetomidine-ketamine combination, but not dexmedetomidine or ketamine alone, also significantly inhibited haemorrhagic shock-induced upregulation of pulmonary inflammatory molecules, including nitric oxide, prostaglandin E(2), chemokine (e.g., macrophage inflammatory protein-2), and cytokines [e.g., interleukin (IL)-1beta, and IL-6].

CONCLUSIONS

Dexmedetomidine-ketamine combination mitigates acute lung injury in haemorrhagic shock rats.

Lipoic acid decreases exhaled nitric oxide concentrations in anesthetized endotoxemic rats

We recently demonstrated that lipoic acid suppresses endotoxin-stimulated expression of inducible nitric oxide synthase and nitric oxide production in mouse macrophages. In this study, we tested whether lipoic acid suppresses these inflammatory mediators in the lungs of rats. Rats were assigned to receive either no special treatment, endotoxin alone, or pretreatment with lipoic acid followed by endotoxin. After anesthetizing the rats and injecting them intraperitoneally with lipoic acid (100 mg/kg) at 4 h and again at 1 h before treatment, the rats then received either endotoxin (0.01 mg/kg) or its vehicle solution. Exhaled gas was sampled every 15 min and concentrations of nitric oxide in the samples were measured using a chemiluminescence analyzer. After 150 min of exposure to endotoxin, the lungs were harvested and snap-frozen in liquid nitrogen for subsequent analysis. Lipoic acid attenuated endotoxin-induced increases in exhaled nitric oxide concentrations (P<0.001) and iNOS (P<0.05). These findings support the hypothesis that lipoic acid inhibits endotoxin-stimulated formation of intrapulmonary nitric oxide.

Hyperbaric oxygen attenuation of lipopolysaccharide-induced acute lung injury involves heme oxygenase-1

BACKGROUND

Hyperbaric oxygen (HBO) attenuates lipopolysaccharide (LPS)-induced acute lung injury. This beneficial effect of HBO involves inhibition of inducible nitric oxide synthase (iNOS) expression and subsequent nitric oxide (NO) biosynthesis. We sought to investigate the role of heme oxygenase-1 (HO-1) on this HBO inhibition of iNOS induction and acute lung injury in septic rat lungs.

METHODS

Before the experiment, 72 rats were randomly allocated to receive HBO or air treatment. With or without HBO pre-treatment, the rats were further divided into the following subgroups (n = 6): (i) LPS injection, (ii) normal saline (N/S) injection, (iii) hemin (a HO-1 inducer) plus LPS, (iv) hemin alone, (v) tin protoporphyrin (SnPP; a HO-1 inhibitor) plus LPS, and (vi) SnPP alone. All rats were maintained for 6 h and then sacrificed with a high-dose pentobarbital injection. Lung injuries and relevant enzymes expression were thus assayed.

RESULTS

Histological analysis, PMNs/alveoli ratio, and wet/dry weight ratio measurements demonstrated that LPS caused significant lung injury and HBO and/or hemin significantly attenuated this LPS-induced lung injury. Increased pulmonary iNOS expression and NO production were associated with lung injury. Induction of HO-1, by HBO and/or hemin, significantly attenuated this LPS-induced iNOS expression and acute lung injury. SnPP, on the contrary, offset the effects of HBO and worsened the LPS-induced lung injury.

CONCLUSIONS

HBO may act through inhibiting pulmonary iNOS expression to attenuate LPS-induced acute lung injury in septic rats. Furthermore, this HBO attenuation of iNOS expression involves HO-1 induction.

Endothelial Dysfunction After Lactated Ringerʼs Solution Resuscitation for Hemorrhagic Shock

BACKGROUND

Endothelial dysfunction is presumed to occur after hemorrhagic shock and resuscitation. This study uses a novel large-animal model to evaluate the effects of diverse resuscitation regimens on endothelial function.

METHODS

Twenty-seven adult domestic pigs (Sus scrofa) were used in this study. Control pigs (n = 3) underwent instrumentation alone. The remaining pigs experienced controlled hemorrhagic shock to a mean arterial blood pressure of 30 +/- 5 mm Hg for 45 minutes. Pigs were resuscitated to their baseline mean arterial blood pressure +/-5 mm Hg with either shed blood (SB; n = 8), lactated Ringers solution (40 mL/kg) followed by shed blood (LRSB; n = 8), or lactated Ringers solution alone (LR; n = 8). At baseline, 1 and 4 hours after resuscitation, acetylcholine (5, 10, and 15 microg/min) was infused into the proximal iliac artery to measure endothelial dependent relaxation (EDR). Sodium nitroprusside was infused to determine endothelial independent relaxation at the end of the study to insure smooth muscle vasomotor integrity. External iliac artery luminal diameter was measured using motion-mode ultrasonography. Statistical analysis was performed using repeated-measures analysis of variance with Tukey's post-hoc analysis.

RESULTS

All pigs survived the experiment. Pigs required ninefold more resuscitation with LR (370.58 +/- 29 mL/kg) versus SB (41.45 +/- 3.5 mL/kg) or LRSB (76.4 +/- 1.1 mL/kg) (p < 0.05). EDR for LR pigs 1 hour after initiation of resuscitation (R1) was 70.4 +/- 14.4% compared with 94.2 +/- 13.4% for SB and 106.1 +/- 8.2% for LRSB (p < 0.05). At 4 hours after resuscitation (R4), systolic luminal diameters were larger in the SB (0.45 +/- 0.01 cm) and LRSB (0.51 +/- 0.02 cm) groups compared with LR (0.41 +/- 0.03 cm) (LRSB versus LR; p = 0.01). At R4, EDR for the LR group was 78.3 +/- 10.7% compared with SB (101.4 +/- 8.3%) and LRSB (106.4 +/- 7.4%) (p < 0.05). Infusion of sodium nitroprusside confirmed integrity of smooth muscle vasorelaxation. Analysis of serum nitric oxide levels revealed decreased values after resuscitation with LR (9.44 +/- 0.76 mol/L) compared with SB (26.3 +/- 7.8 mol/L) and LRSB (16.3 +/- 1.0 mol/L) (p = not significant).

CONCLUSION

This is the first description of a large-animal model to evaluate EDR after hemorrhagic shock. Resuscitation with LR requires significantly larger volumes than SB or LRSB. LR resuscitation leads to endothelial dysfunction, as determined by decreased EDR, versus SB or LRSB. Resuscitation with blood products may preserve nitric oxide bioactivity when compared with crystalloid resuscitation in the setting of hemorrhagic shock.

Microdialysis for measurement of hepatic and systemic nitric oxide biosynthesis in septic rats

BACKGROUND

We sought to compare two techniques, microdialysis and repeated blood withdrawal, for serial assessment of hepatic and systemic nitric oxide (NO) biosynthesis in septic rats.

METHODS

Rats were randomly allocated to either microdialysis or blood withdrawal groups. Two microdialysis probes, one in liver and the other in right atrium, were placed in rats in the microdialysis group. Half of the rats from each group were then given lipopolysaccharide (LPS) to induce NO production. The other half of the rats from each group were injected with vehicle (normal saline) to serve as controls. In the microdialysis group, dialysate (30 microl) was collected every 30 min. In the blood withdrawal group, 0.3 ml of blood was drawn every 30 min. Sampling was performed up to 6 h after injection of LPS or vehicle. Hemodynamics, hepatic and systemic NO concentrations, and iNOS expression in harvested liver tissues were assayed.

RESULTS

Repeated blood withdrawal by itself caused a significant decrease in blood pressure and induced hepatic iNOS expression. Microdialysis, on the contrary, reliably detected LPS-induced NO production without resulting either in hemodynamic changes or in iNOS induction in liver tissue.

CONCLUSIONS

Microdialysis provides serial measure of hepatic and systemic NO concentrations in LPS-treated rats without the need for removal of tissue.

Pulmonary transcription of CAT-2 and CAT-2B but not CAT-1 and CAT-2A were upregulated in hemorrhagic shock rats

Hemorrhagic shock stimulates nitric oxide (NO) biosynthesis through upregulation of inducible NO synthase (iNOS) expression. Trans-membrane l-arginine transportation mediated by the isozymes of cationic amino acid transporters (e.g. CAT-1, CAT-2, CAT-2A, and CAT-2B) is one crucial regulatory mechanism that regulates iNOS activity. We sought to assess the effects of hemorrhage and resuscitation on the expression of these regulatory enzymes in hemorrhage-stimulated rat lungs. Twenty-four rats were randomized to a sham-instrumented group, a sustained shock group, a shock with blood resuscitation group, or a shock with normal saline resuscitation group. Hemorrhagic shock was induced by withdrawing blood to maintain MAP between 40 and 45mmHg for 60min. Resuscitation by infusing blood/saline mixtures (blood resuscitation group) or saline alone (saline resuscitation group) was then performed. At the end of the experiment (300min after hemorrhage began), rats were sacrificed and enzymes expression as well as pulmonary NO biosynthesis and lung injuries were assayed. Our data revealed that hemorrhage-induced pulmonary iNOS, CAT-2, and CAT-2B transcription which was associated with pulmonary NO overproduction and subsequent lung injury. Resuscitation significantly attenuated the hemorrhage-induced enzyme upregulation, pulmonary NO overproduction, and lung injury. Blood/saline mixtures were superior to saline as a resuscitation solution in treating hemorrhage-induced pulmonary NO overproduction and lung injury. Hemorrhage and/or resuscitation, however, did not affect the expression of pulmonary CAT-1 and CAT-2A. It is, therefore, concluded that the expression of pulmonary iNOS, CAT-2, and CAT-2B is inducible and that of CAT-1 and CAT-2A is constitutive in hemorrhagic shock rat lungs.

NF-kappaB involvement in the induction of high affinity CAT-2 in lipopolysaccharide-stimulated rat lungs

BACKGROUND

Endotoxemia stimulates nitric oxide (NO) biosynthesis through induction of inducible NO synthase (iNOS). Cellular uptake of L-arginine, the sole substrate for iNOS, is an important mechanism regulating NO biosynthesis by iNOS. The isozymes of type-2 cationic amino acid transporters, including CAT-2, CAT-2A, and CAT-2B, constitute the most important pathways responsible for trans-membrane L-arginine transportation. Therefore, regulation of CAT-2 isozymes expression may constitute one of the downstream regulatory pathways that control iNOS activity. We investigated the time course of enzyme induction and the role of nuclear factor-kappaB (NF-kappaB) in CAT-2 isozymes expression in lipopolysaccharide-(LPS) treated rat lungs.

METHODS

Adult male Sprague-Dawley rats were randomly given intravenous injections of normal saline (N/S), LPS, LPS plus NF-kappaB inhibitor pre-treatment (PDTC, dexamethasone, or salicylate), or an NF-kappaB inhibitor alone. The rats were sacrificed at different times after injection and enzyme expression and lung injury were examined. Pulmonary and systemic NO production were also measured.

RESULTS

LPS co-induced iNOS, CAT-2, and CAT-2B but not CAT-2A expression in the lungs. Furthermore, NF-kappaB actively participated in LPS-induction of iNOS, CAT-2, and CAT-2B. LPS induced pulmonary and systemic NO overproduction and resulted in lung injuries. Attenuation of LPS-induced iNOS, CAT-2, and CAT-2B induction significantly inhibited NO biosynthesis and lessened lung injury.

CONCLUSION

NF-kappaB actively participates in the induction of CAT-2 and CAT-2B in intact animals. Our data further support the idea that CAT-2 and CAT-2B are crucial in regulating iNOS activity.

Influence of selective nitric oxide synthetase inhibitor for treatment of refractory haemorrhagic shock

OBJECTIVE

Haemorrhagic shock (HS) is implicated in the induction of inducible nitric oxide synthase that leads to increased production of nitric oxide (NO). We investigated the influence of aminoguanidine (AG), a selective iNOS inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), a non-selective inhibitor and S-Nitroso-N-acetylpenicillamine (SNAP), a NO donor, each of which was given with (+) or without (-) angiotensin II (ANGII), a vasoconstrictor, on the survival rate of HS decompensatory phased (HSDP) rats.

MATERIALS AND METHODS

HSDP was achieved via a constant pressure method. Organs were harvested and analyzed from rats sacrificed 72 h after HSDP or upon death. Plasma collected from HSDP rats were used to measure nitrate/nitrite, GOT and creatinine levels.

RESULTS

AG+ANGII-treated rats had significantly higher survival rates compared to the other treatment groups, 72 h following HSDP. A marked increase in MABP level was observed in AG+ANGII-treated rats when compared to other treatment groups. Histological examinations also showed a reduction of organ damage in AG+ANGII-treated rats compared to other treatment groups. Nitrate/nitrite level, glutamic oxalacetic transaminase (GOT) level and creatinine level were also significantly improved in AG+ANGII-treated rats compared to the other groups.

CONCLUSIONS

A greater beneficial effect was achieved with treatment by the AG+ANGII combination. Our experiments showed that the inhibition of excessive NO formation that occurred during HSDP, had augmented the vascular responsiveness effect of ANGII following protracted HS.

Renal transcription of high-affinity type-2 cationic amino acid transporter is up-regulated in LPS-stimulated rodents

OBJECTIVE

Sepsis stimulates renal nitric oxide (NO) biosynthesis through up-regulation of inducible NO synthase (iNOS) expression. Type-2 cationic amino acid transporter (CAT-2) mediation of trans-membrane L-arginine (L-Arg) transportation has been identified as one of the crucial regulatory mechanisms involved in the formation of NO by iNOS. We had previously shown that CAT-2B, a high-affinity alternative-spliced transcript of the CAT-2, is involved in induced NO biosynthesis by iNOS (Nitric Oxide, 2002). In this present study, we sought to assess the effects of sepsis on the expression of CAT-2B in lipopolysaccharide (LPS)-stimulated rat kidney.

METHODS

Forty rats were randomized to either a normal saline (N/S)-treated group or a LPS-treated group. Renal NO production was determined using chemiluminescence. Semi-quantitative RT-PCR was used to determine the mRNA concentrations of iNOS and L-Arg transporters (CAT-1, CAT-2 and CAT-2B) in kidney.

RESULTS

Lipopolysaccharide-coinduced iNOS, CAT-2 and CAT-2B mRNA expression in kidney and caused renal NO overproduction. A significant linear regression relationship was defined between renal NO concentrations and iNOS, CAT-2 and CAT-2B, respectively. On the contrary, CAT-1 expression was not affected by LPS-stimulation.

CONCLUSIONS

We provide the first evidence to illustrate that sepsis/septic shock induces the transcription of high-affinity CAT-2B in renal tissues. Transcription of iNOS, CAT-2 and CAT-2B correlates well with renal NO biosynthesis. Regulation of L-Arg uptake by modulating the expression regulation of induced CAT-2 and CAT-2B might be a potential target for therapies against renal pathologic conditions related to NO overproduction.