Effects of the nitric oxide synthase inhibitors N(G)-nitro-L-arginine methyl ester and aminoethyl-isothiourea on the liver microcirculation in rat endotoxemia

Selective inhibition of PKR by C16 accelerates diabetic wound healing by inhibiting NALP3 expression in mice

OBJECTIVE AND DESIGN

To understand the expression of dsRNA-dependent protein kinase R (PKR) in impaired diabetic wounds, hyperglycemia was induced in C57/BL6 mice with streptozotocin. Murine macrophage cell line, Raw 264.7, stimulated with high glucose and LPS was used to mimic diabetic wound environment in in-vitro.

MATERIALS

Macrophages stimulated with HG + LPS, in presence and absence of PKR inhibitor (C16) and wound tissue samples from topically treated mice with C16, were analyzed for the expression of PKR, NALP3, active caspase-1, mature IL-1β and phosphorylation of PKR and eIF2α. Wounds tissues were also analyzed for inflammatory cell infiltration by immunohistochemistry, angiogenesis by CD31 staining, collagen expression by western blotting, expression of CD206+ macrophages by flow cytometry and wound strength by texture analyzer.

RESULTS

PKR and NALP3 were found to be upregulated in macrophages stimulated with HG + LPS as well as in impaired diabetic wounds. PKR inhibition using C16 ameliorated expression of NALP3, caspase-1, IL-1β and phosphorylation of PKR and eIF2α, in macrophages and also in diabetic wounds. Treatment with C16 promoted the wound healing in diabetic mice by increasing collagen synthesis, reducing infiltration of F4/80⁺ macrophages and MPO⁺ neutrophil cells, increased angiogenesis, and increased number of M2 macrophages.

CONCLUSION

PKR inhibition using C16 accelerates the wound healing process in diabetic mice by decreasing NALP3-mediated IL-1β maturation.

Long-term binge and escalating ethanol exposure causes necroinflammation and fibrosis in rat liver

BACKGROUND

To investigate whether "binge" and escalating alcohol exposure in the rat influences the development of pathological liver injury.

METHODS

Time courses for the formation of eicosanoids by cyclooxygenase (COX), oxidative stress and nitrosative stress production, expression of hypoxia-inducible factor 1 (HIF-1), cytokines, hepatic tissue necroinflammation, and fibrosis were assessed in rats during 16 weeks of daily alcohol gavage.

RESULTS

In this model of binge and escalating levels of alcohol, hepatic steatosis, necrosis, and inflammation as well as fibrosis were increased over the 16-week period. The levels of COX-2, oxidative stress, nitrosative stress, HIF-1, proinflammatory mediators (tumor necrosis factor-α, interleukin 1(β) [IL-1(β) ], IL-6), and procollagen-I were increased over the 16-week period. The content of IL-10 in rat serum increased at the end of 4 and 8 weeks but decreased thereafter and was significantly decreased at 12 and 16 weeks.

CONCLUSIONS

A rat model of alcoholic liver disease (ALD) with long-term binge and escalating ethanol exposure was developed. Our data support the hypothesis that enhanced eicosanoid production by COX, oxidative stress and nitrosative stress, HIF-1, and the imbalance between pro- and anti-inflammatory cytokines plays an important role in the pathogenesis of ALD.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Pyrazole induced oxidative liver injury independent of CYP2E1/2A5 induction due to Nrf2 deficiency

Pyrazole can induce CYP2E1 and 2A5, which produce reactive oxygen species (ROS). Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates important antioxidant enzymes to remove ROS. In this study, we applied Nrf2 knockout mice to test the hypothesis that pyrazole will cause hepatotoxicity and elevate oxidative stress to a greater extent in Nrf2 knockout mice compared to wild type mice. Pyrazole induced severe oxidative liver damage in Nrf2 knockout mice but not in wild type mice. Activities and levels of CYP2E1 and 2A5 were elevated by pyrazole in the wild type mice but not in the Nrf2 knockout mice. However, expression or activity of Nrf2-regulated antioxidant enzymes, such as gamma-glutamylcysteine synthetase (GCS), heme oxygenase-1 (HO-1) and glutathione-S-transferase (GST), were upregulated in the pyrazole-treated wild type mice, but to a lesser extent or not at all in the pyrazole-treated Nrf2 knockout mice. Treatment with antioxidants such as vitamin C or S-adenosyl-l-methionine (SAM) or an inhibitor of iNOS prevented the pyrazole-induced oxidative liver damage, thus validating the role of oxidative/nitrosative stress in the pyrazole induced liver injury to the Nrf2 knockout mice. In summary, even though ROS-producing CYP2E1/2A5 were not elevated by pyrazole, impaired antioxidant capacity resulting from Nrf2 deficiency appear to be sufficient to promote pyrazole-induced oxidative liver injury.

Resuscitating the microcirculation in sepsis: the central role of nitric oxide, emerging concepts for novel therapies, and challenges for clinical trials

Microcirculatory dysfunction is a critical element of the pathogenesis of severe sepsis and septic shock. In this Bench-to-Bedside review, we present: 1) the central role of the microcirculation in the pathophysiology of sepsis; 2) new translational research techniques of in vivo video microscopy for assessment of microcirculatory flow in human subjects; 3) clinical investigations that reported associations between microcirculatory dysfunction and outcome in septic patients; 4) the potential role of novel agents to "rescue" the microcirculation in sepsis; 5) current challenges facing this emerging field of clinical investigation; and 6) a framework for the design of future clinical trials aimed to determine the impact of novel agents on microcirculatory flow and organ failure in patients with sepsis. We specifically focus this review on the central role and vital importance of the nitric oxide (NO) molecule in maintaining microcirculatory homeostasis and patency, especially when the microcirculation sustains an insult (as with sepsis). We also present the scientific rationale for clinical trials of exogenous NO administration to treat microcirculatory dysfunction and augment microcirculatory blood flow in early sepsis therapy.

Lipopolysaccharide-induced liver injury in rats treated with the CYP2E1 inducer pyrazole

Elevated LPS and elevated cytochrome P-450 2E1 (CYP2E1) in liver are two major independent risk factors in alcoholic liver disease. We investigated possible synergistic effects of the two risk factors in causing oxidative stress and liver injury. Sprague-Dawley rats were injected intraperitoneally with pyrazole (inducer of CYP2E1) for 2 days, and then LPS was injected via tail vein. Other rats were treated with pyrazole alone or LPS alone or saline. Eight hours later, blood was collected and livers were excised. Pathological evaluation showed severe inflammatory responses and necroses only in liver sections from rats in the pyrazole plus LPS group; blood transaminase levels were significantly elevated only in the combination group. Activities of caspase-3 and -9 and positive terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining were highest in the LPS alone and the LPS plus pyrazole group, with no significant difference between the two groups. Lipid peroxidation and protein carbonyls in liver homogenate as well as in situ superoxide production were maximally elevated in the LPS plus pyrazole group. Levels of nitrite plus nitrate and inducible nitric oxide (NO) synthase (iNOS) content were comparably elevated in LPS alone and the LPS plus pyrazole group; however, 3-nitrotyrosine adducts were elevated in the combined group but not the LPS group. It is likely that LPS induction of iNOS, which produces NO, coupled to pyrazole induction of CYP2E1 which produces superoxide, sets up conditions for maximal peroxynitrite formation and production of 3-nitrotyrosine adducts. CYP2E1 activity and content were elevated in the pyrazole and the LPS plus pyrazole groups. Immunohistochemical staining indicated that distribution of CYP2E1 was in agreement with that of necrosis and production of superoxide. These results show that pyrazole treatment enhanced LPS-induced necrosis, not apoptosis. The enhanced liver necrosis appears to involve an increase in oxidative and nitrosative stress generated by the combination of LPS plus elevated CYP2E1 levels.

Role of nitric oxide in hepatic microvascular injury elicited by acetaminophen in mice

Nitric oxide (NO) is suggested to play a role in liver injury elicited by acetaminophen (APAP). Hepatic microcirculatory dysfunction also is reported to contribute to the development of the injury. As a result, the role of NO in hepatic microcirculatory alterations in response to APAP was examined in mice by in vivo microscopy. A selective inducible NO synthase (iNOS) inhibitor,l-N6-(1-iminoethyl)-lysine (L-NIL), or a nonselective NOS inhibitor, NG-nitro-l-arginine methyl ester (L-NAME), was intraperitoneally administered to animals 10 min before APAP gavage. L-NIL suppressed raised alanine aminotransferase (ALT) values 6 h after APAP, whereas L-NAME increased those 1.7-fold. Increased ALT levels were associated with hepatic expression of iNOS. L-NIL, but not L-NAME, reduced the expression. APAP caused a reduction (20%) in the numbers of perfused sinusoids. L-NIL restored the sinusoidal perfusion, but L-NAME was ineffective. APAP increased the area occupied by infiltrated erythrocytes into the extrasinusoidal space. L-NIL tended to minimize this infiltration, whereas L-NAME further enhanced it. APAP caused an increase (1.5-fold) in Kupffer cell phagocytic activity. This activity in response to APAP was blunted by L-NIL, whereas L-NAME further elevated it. L-NIL suppressed APAP-induced decreases in hepatic glutathione levels. These results suggest that NO derived from iNOS contributes to APAP-induced parenchymal cell injury and hepatic microcirculatory disturbances. L-NIL exerts preventive effects on the liver injury partly by inhibiting APAP bioactivation. In contrast, NO derived from constitutive isoforms of NOS exerts a protective role in liver microcirculation against APAP intoxication and thereby minimizes liver injury.

The role of nitric oxide in systemic and hepatic haemodynamics in the rat in vivo

The physiological role of nitric oxide (NO) in portal venous and hepatic arterial haemodynamics in the rat in vivo during healthy and diseased conditions remains unclear. The present study determined the physiological role of nitric oxide in hepatic haemodynamics in the rat in vivo during healthy conditions as a basis for future pharmacological work. Male Wistar rats (300-350 g) were anaesthetised with fentany/fluanisone (0.3 mg/kg s.c.) and midazolam (0.3 mg/kg s.c.) and heparinised (30 U/100 g i.v.) via a cannulated left carotid artery for measurement of heart rate, mean arterial pressure, and the difference between systolic and diastolic blood pressures (P(S-D)). Following laparotomy, two distal ileocolic veins were cannulated, one catheter introduced to a distance of 1 cm and used for intraportal drug injections and the other to the main trunk of the portal vein for continuous measurement of portal venous pressure. The portal venous trunk and hepatic artery were carefully isolated and electromagnetic probes placed around each of them for measurement of portal venous flow and hepatic arterial flow. Augmentation of NO production was achieved by intraportal injection of 0.2, 0.4, 0.6 and 0.8 g/kg L-arginine and the NO donor, 3-morpholinosydnonimine (SIN-1), was injected intraportally at 0.2, 0.4, 0.6 and 0.8 mg/kg. L-NAME, the non-selective NOS inhibitor, was injected intraportally in increasing doses of 5, 10, 15 and 20 mg/kg in the absence or presence of L-arginine in doses of 0.2 and 0.5 g/kg. L-arginine increased portal blood flow by 25% without significant changes in systemic haemodynamics. SIN-1 decreased mean arterial pressure by 33% with no effect on portal blood flow. Both L-arginine and SIN-1 reduced portal venous pressure by 25% in a dose-dependent manner. L-NAME had no effect on portal haemodynamics despite a significant increase in systemic arterial pressure of 60% that was reduced dose-dependently by L-arginine. Hepatic arterial flow increased by 88% and 49% at the second and third doses of L-arginine and by 68% and 27% at the first two doses of L-NAME. No significant changes in hepatic arterial flow were found when L-NAME and L-arginine were given together. It is concluded that augmented endogenous NO production increased portal flow. Inhibition of endogenous NO had no effect on portal haemodynamics. Endogenous NO may not play a major role in regulation of portal haemodynamics in the rat in vivo.

Bench-to-bedside review: microvascular dysfunction in sepsis--hemodynamics, oxygen transport, and nitric oxide

The microcirculation is a complex and integrated system that supplies and distributes oxygen throughout the tissues. The red blood cell (RBC) facilitates convective oxygen transport via co-operative binding with hemoglobin. In the microcirculation oxygen diffuses from the RBC into neighboring tissues, where it is consumed by mitochondria. Evidence suggests that the RBC acts as deliverer of oxygen and 'sensor' of local oxygen gradients. Within vascular beds RBCs are distributed actively by arteriolar tone and passively by rheologic factors, including vessel geometry and RBC deformability. Microvascular oxygen transport is determined by microvascular geometry, hemodynamics, and RBC hemoglobin oxygen saturation. Sepsis causes abnormal microvascular oxygen transport as significant numbers of capillaries stop flowing and the microcirculation fails to compensate for decreased functional capillary density. The resulting maldistribution of RBC flow results in a mismatch of oxygen delivery with oxygen demand that affects both critical oxygen delivery and oxygen extraction ratio. Nitric oxide (NO) maintains microvascular homeostasis by regulating arteriolar tone, RBC deformability, leukocyte and platelet adhesion to endothelial cells, and blood volume. NO also regulates mitochondrial respiration. During sepsis, NO over-production mediates systemic hypotension and microvascular reactivity, and is seemingly protective of microvascular blood flow.

Is nitric oxide overproduction the target of choice for the management of septic shock?

Sepsis is a heterogeneous class of syndromes caused by a systemic inflammatory response to infection. Septic shock, a severe form of sepsis, is associated with the development of progressive damage in multiple organs, and is a leading cause of patient mortality in intensive care units. Despite important advances in understanding its pathophysiology, therapy remains largely symptomatic and supportive. A decade ago, the overproduction of nitric oxide (NO) had been discovered as a potentially important event in this condition. As a result, great hopes arose that the pharmacological inhibition of NO synthesis could be developed into an efficient, mechanism-based therapeutic approach. Since then, an extraordinary effort by the scientific community has brought a deeper insight regarding the feasibility of this goal. Here we present in summary form the present state of knowledge of the biological chemistry and physiology of NO. We then proceed to a systematic review of experimental and clinical data, indicating an up-regulation of NO production in septic shock; information on the role of NO in septic shock, as provided by experiments in transgenic mice that lack the ability to up-regulate NO production; effects of pharmacological inhibitors of NO production in various experimental models of septic shock; and relevant clinical experience. The accrued evidence suggests that the contribution of NO to the pathophysiology of septic shock is highly heterogeneous and, therefore, difficult to target therapeutically without appropriate monitoring tools, which do not exist at present.

Potentiation by aminoethylisothiourea of the extra-cellular Ca(2+) component of norepinephrine-induced contraction in rat femoral arteries

Aminoethylisothiourea (AET) is a potent inhibitor of inducible nitric oxide synthase (NOS). The present study was performed to investigate whether AET and its rearrangement products might modulate vascular contraction independently of its effects as a NOS inhibitor in rat small femoral arteries. AET caused an endothelium-independent increase in contraction induced by norepinephrine (NE). This effect was not affected by either N(omega)-nitro-L-arginine methyl ester, nitro-L-arginine, indomethacin or propanolol, but it was suppressed in Ca(2+)-free medium. AET enhanced extracellular Ca(2+) component of NE-induced contraction, and this effect was prevented by the receptor-mediated Ca(2+) entry blocker, 1-{beta-[3-(p-methoxyphenyl)-propyloxyl]-p-methoxyphenetyl}- 1H-imidaz ole hydrochloride (SK&F 96365), but not by the voltage-dependent Ca(2+) channel blocker, nitrendipine. AET did not alter the response to CaCl(2) in vessels exposed to KCl depolarization. The protein kinase C (PKC) inhibitor, 2-[1-(3-dimethylaminopropyl)indol-3-yl]-3-(indol-3-yl) (GF 109203X), prevented the potentiating effect of AET on the NE response. AET failed to produce an increase in tone in the presence of NE and GTP in permeabilized arteries. Among the AET rearrangement products, mercaptoethylguanidine produced an endothelium-independent increase in the NE response. 2-aminothiazoline had no effect, and guanidinoethyldisulphide produced relaxation. The effect of mercaptoethylguanidine was dependent on extracellular Ca(+) and was prevented by GF 109203X. These results indicate that AET is able to potentiate the contraction to NE in rat femoral resistance arteries independently of its inhibitory effect on either NOS or cyclo-oxygenase. Its effect occurs via an enhancement of SK&F 96365-sensitive Ca(2+) entry. A PKC inhibitor-sensitive mechanism also appears to be involved in the AET effect. Mercaptoethylguanidine potentiates NE response through a mechanism similar to AET.

Preventive effect of preoperative portal vein ligation on endotoxin-induced hepatic failure in hepatectomized rats is associated with reduced tumour necrosis factor alpha production

BACKGROUND

Preoperative portal vein embolization successfully reduces the incidence of postoperative hepatic failure in which endotoxin is postulated to be involved. To identify the mechanism of this preventive effect, the relationship of endotoxin-induced liver injury with tumour necrosis factor (TNF) alpha and nitric oxide production in the peripheral blood, liver and spleen of rats subjected to preoperative portal vein branch ligation (PVL) was compared with that in rats undergoing sham operation.

METHODS

Rats with PVL and those that underwent sham operation were subjected to resection of ligated liver lobes (PVL-Hx rats) and two-thirds hepatectomy (noPVL-Hx rats) respectively at day 5, followed by intravenous administration of endotoxin 200 microgram/kg body-weight at day 7. At various time intervals after endotoxin injection, the peripheral blood, liver and spleen tissues were harvested and analysed for TNF-alpha and nitric oxide production.

RESULTS

The survival rates of noPVL-Hx and PVL-Hx rats at 48 h after endotoxin administration were 40 and 100 per cent respectively. The former rats showed more extensive liver injury as represented by higher serum aminotransferase and hyaluronate levels than the latter. Plasma concentrations of TNF-alpha at 1.5 h after endotoxin treatment were significantly higher in noPVL-Hx rats (mean(s.e.m.) 22 125(2175) pg/ml; n = 6) than PVL-Hx rats (8344(4076) pg/ml; n = 6) (P < 0.01). Consistent with this, expression of TNF-alpha messenger RNA in the liver and spleen was suppressed in PVL-Hx rats. In two-thirds hepatectomized rats, plasma TNF-alpha concentrations after endotoxin administration at 1, 2 and 3 days (14 350(2186), 26 375(2478) and 23 000(3745) pg/ml respectively; n = 6 each) were significantly higher than that before operation (9067(1559) pg/ml; n = 6) (P < 0.05), whereas those at 5 and 7 days (10 102(3616) and 8580(1427) pg/ml respectively; n = 6 each) showed no significant increase. Furthermore, nitric oxide production in peripheral blood and liver was suppressed by preoperative PVL.

CONCLUSION

Prevention of endotoxin-induced liver failure by preoperative PVL is associated with reduced production of TNF-alpha in the later phase of liver regeneration.

Suppression of lipopolysaccharide-induced nitric oxide synthase expression by platelet-activating factor receptor antagonists in the rat liver and cultured rat Kupffer cells

Excessive nitric oxide (NO) generated by hepatic cells in response to lipopolysaccharide (LPS) and inflammatory substances (e.g., platelet-activating factor [PAF]) is a key contributor to the pathophysiological outcomes observed in the liver during sepsis. In rats subjected to liver-focused endotoxemia, inducible nitric oxide synthase (iNOS) levels in the intact liver were elevated by 6 hours; cell-specific expression of iNOS messenger RNA (mRNA) was Kupffer cells (KCs), endothelial cells, and hepatocytes. Elevated serum alanine transaminase (ALT) levels at 6 hours confirmed hepatic damage. Pretreatment of endotoxemic rats with PAF receptor antagonists BN 50739 or WEB 2170 reduced serum ALT and iNOS mRNA levels in the intact liver. Pretreatment of cultured KCs with BN 50739 or WEB 2170 inhibited both LPS and PAF-induced iNOS mRNA formation. In addition, LPS-induced iNOS protein levels in KCs pretreated with BN 50739 or WEB 2170 were decreased. Exposure of KCs to either LPS or PAF caused the translocation of the p65 subunit of nuclear factor kappa B (NF-kappaB) into the nucleus and this process was attenuated by BN 50739 and WEB 2170. There was concomitant inhibition of LPS-dependent degradation of the inhibitory protein IkappaBalpha and increase in intracellular Ca(2+) in KC treated with BN 50739 or WEB 2170. Also, in KCs, LPS was able to induce iNOS mRNA expression independent of CD14. This response was inhibited by pretreatment of KCs with either BN 50739 or WEB 2170. Our findings indicate that PAF receptor antagonists convey protection against hepatocellular injury accompanied by a decrease in nitric oxide (NO) formation in the livers of endotoxemic rats.

Effects of calcium channel antagonists on LPS-induced hepatic iNOS expression

The onset of liver injury is a pivotal event during endotoxemia. Lipopolysaccharide (LPS) activates the Kupffer cells (KC), the resident macrophages of the liver, to generate an abundance of inflammatory substances, including nitric oxide (NO). Elevated levels of NO are thought to contribute to the propagation of liver injury during sepsis. Calcium, a major second messenger in several cellular signaling events, is required by the KC for the generation of inducible nitric oxide synthase (iNOS). The purpose of this study was to determine whether calcium channel antagonists limit hepatic injury and iNOS expression in vivo following LPS exposure and to evaluate their effects on the regulation of iNOS expression in cultured KC. In rats subjected to LPS for 6 h, the serum alanine aminotransferase (ALT) level was elevated significantly; this response was accompanied by an increase in iNOS mRNA formation in the intact liver. Pretreatment of rats with calcium channel antagonists (i.e., diltiazem, nifedipine, or verapamil) before LPS exposure attenuated the serum ALT level and iNOS mRNA expression in the liver. Pretreatment of cultured KC with calcium channel antagonists for 1 h followed by the addition of LPS markedly repressed iNOS protein and mRNA expression. Time-course studies revealed that calcium channel antagonists were most effective at inhibiting LPS-induced iNOS mRNA formation by KC when added before LPS. Treatment of KC with calcium channel antagonists prior to the addition of LPS decreased nuclear levels of the p65 subunit of nuclear factor-kappaB and prevented the LPS-dependent degradation of the inhibitory protein IkappaBalpha. Thus our findings indicate that under endotoxemic conditions calcium channel antagonists limit hepatocellular injury that is accompanied by an inhibition of LPS-mediated iNOS expression in rat liver KC.

Hypertonic saline dextran attenuates leukocyte accumulation in the liver after hemorrhagic shock and resuscitation

BACKGROUND

Hemorrhagic shock and resuscitation triggers a global ischemia/reperfusion phenomenon, in which activated leukocytes are considered strong contributors to the ensuing tissue damage.

METHODS

The aim of the study was to investigate the effects of hypertonic saline dextran (HSD) on the early leukocyte/endothelial interactions (intravital fluorescence microscopy) in a rat model of hemorrhagic shock (1 hour at mean arterial pressure of 40 mm Hg). The resuscitation was performed with lactated Ringer's solution (RL, four times shed blood/20 minutes, n = 6), 6% dextran 60 (DEX, 100% shed blood/5 minutes, n = 8), and 7.2% NaCl/10% dextran 60 (HSD, 10% shed blood/2 minutes, n = 8).

RESULTS

After 1 hour of resuscitation, shock-induced stasis/adherence of leukocytes was further enhanced with RL (sinusoids 17.6+/-6.9%; venules 33.9+/-8.5%), whereas DEX and HSD attenuated leukocyte stagnation in sinusoids (DEX -7.4+/-6,1%; HSD -14.7+/-2.9%, p<0.01 vs. RL) and leukocyte adherence in postsinusoidal venules (DEX -12.2+/-8.6%, p<0.05 vs. RL; HSD -27+/-7.4%, p<0.01 vs. RL).

CONCLUSION

HSD reduced significantly the number of leukocytes accumulated in the liver after resuscitation of hemorrhagic shock, probably due to a combination of mechanisms of both components.

Resuscitation with hypertonic saline dextran reduces endothelial cell swelling and improves hepatic microvascular perfusion and function after hemorrhagic shock

BACKGROUND

Hemorrhagic shock severely compromises hepatic microcirculation and function with tendency to promote hepatic insufficiency and multiple organ failure.

MATERIAL AND METHODS

The aim of the study was to evaluate the effects of small volume resuscitation on liver microcirculation (intravital fluorescence microscopy and electron microscopy) and function (arterial ketone body ratio (AKBR) and bile flow), in a rat model of traumatic-hemorrhagic shock. One hour after hemorrhage (MAP 40 mm Hg) the rats were resuscitated with HSD (7.2% NaCl/10% dextran 60, 10% of shed blood/2 min, n = 8); DEX (6% dextran 60, 100% of shed blood/5 min, n = 8); or RL (Ringer lactate, 400% of shed blood/20 min, n = 6).

RESULTS

HSD yielded a better recovery of sinusoidal perfusion (17.8 +/- 0.8% nonperfused sinusoids) than DEX (21.8 +/- 0. 7%, P < 0.05) and RL (23.9 +/- 0.9%, P < 0.01). Hemorrhagic shock produced a moderate increase of mean sinusoidal endothelial cell thickness, which was further enhanced by DEX and RL (P < 0.05 vs baseline), whereas HSD reduced the mean endothelial cell thickness toward baseline (P < 0.05 vs DEX and RL). Both AKBR and bile flow were profoundly reduced after 1 h shock. Resuscitation with DEX and RL produced a weak recovery, still remaining at shock level, while HSD infusion allowed a significant improvement of AKBR and bile flow (P < 0.05 vs shock).

CONCLUSION

Reduction of mean endothelial cell thickness after HSD is very likely the mechanism for the amelioration of sinusoidal perfusion, resulting in a significant improvement of hepatic energetic status and excretory function.