Effect of endotoxemia on hepatic portal and sinusoidal blood flow in rats

Betulinic acid mitigates zearalenone-induced liver injury by ERS/MAPK/Nrf2 signaling pathways in mice

Zearalenone (ZEA) is a mycotoxin commonly found in cereals and feedstuffs, which can induce oxidative stress and inflammation to cause liver damage in humans and animals. Betulinic acid (BA) is extracted from pentacyclic triterpenoids of many natural plants and has anti-inflammatory, and anti-oxidation biological activities in many studies. However, the protective effect of BA on liver injury induced by ZEA has not been reported. Therefore, this study aims to explore the protective effect of BA on ZEA-induced liver injury and its possible mechanism. In the mice experiment, ZEA exposure increased the liver index and caused histopathological impairment, oxidative damage, hepatic inflammatory responses, and increased hepatocyte apoptosis. However, when combined with BA, it could inhibit the production of ROS, up-regulate the proteins expression of Nrf2 and HO-1 and down-regulate the expression of Keap1, and alleviate oxidative damage and inflammation in the liver of mice. In addition, BA could alleviate ZEA-induced apoptosis and liver injury in mice by inhibiting the endoplasmic reticulum stress (ERS) and MAPK signaling pathways. In conclusion, this study revealed the protective effect of BA on the hepatotoxicity of ZEA for the first time, providing a new perspective for the development of ZEA antidote and the application of BA.

Liver perfusion MRI in a rodent model of cirrhosis: Agreement with bulk-flow phase-contrast MRI and noninvasive evaluation of inflammation in chronic liver disease using flow-sensitive alternating inversion recovery arterial spin labelling and tissue T1

Noninvasive measurements of liver perfusion and fibrosis in cirrhotic small animals can help develop treatments for haemodynamic complications of liver disease. Here, we measure liver perfusion in cirrhotic rodents using flow-sensitive alternating inversion recovery arterial spin labelling (FAIR ASL), evaluating agreement with previously validated caval subtraction phase-contrast magnetic resonance imaging (PCMRI) total liver blood flow (TLBF). Baseline differences in cirrhotic rodents and the haemodynamic effects of acute inflammation were investigated using FAIR ASL and tissue T1. Sprague-Dawley rats (nine bile duct ligated [BDL] and ten sham surgery controls) underwent baseline hepatic FAIR ASL with T1 measurement and caval subtraction PCMRI (with two-dimensional infra-/supra-hepatic inferior vena caval studies), induction of inflammation with intravenous lipopolysaccharide (LPS) and repeat liver FAIR ASL with T1 measurement after ~90 minutes. The mean difference between FAIR ASL hepatic perfusion and caval subtraction PCMRI TLBF was -51 ± 30 ml/min/100 g (Bland-Altman 95% limits-of-agreement ±258 ml/min/100 g). The FAIR ASL coefficient of variation was smaller than for caval subtraction PCMRI (29.3% vs 50.1%; P = .03). At baseline, FAIR ASL liver perfusion was lower in BDL rats (199 ± 32 ml/min/100 g vs sham 316 ± 24 ml/min/100 g; P = .01) but liver T1 was higher (BDL 1533 ± 50 vs sham 1256 ± 18 ms; P = .0004). Post-LPS FAIR ASL liver perfusion response differences were observed between sham/BDL rats (P = .02), approaching significance in sham (+78 ± 33 ml/min/100 g; P = .06) but not BDL rats (-49 ± 40 ml/min/100 g; P = .47). Post-LPS differences in liver tissue T1 were nonsignificant (P = .35). FAIR ASL hepatic perfusion and caval subtraction PCMRI TLBF agreement was modest, with significant baseline FAIR ASL liver perfusion and tissue T1 differences in rodents with advanced cirrhosis compared with controls. Following inflammatory stress, differences in hepatic perfusion response were detected between cirrhotic/control animals, but liver T1 was unaffected. Findings underline the potential of FAIR ASL in the assessment of vasoactive treatments for patients with chronic liver disease and inflammation.

Effects of Probiotics BaSC06 on Intestinal Digestion and Absorption, Antioxidant Capacity, Microbiota Composition, and Macrophage Polarization in Pigs for Fattening

This study aimed to compare the effects of BaSC06 and antibiotics on growth, digestive functions, antioxidant capacity, macrophage polarization, and intestinal microbiota of pigs for fattening. A total of 117 pigs for fattening with similar weight and genetic basis were divided into 3 groups: Anti group (containing 40 g/t Kitasamycin in the diet), Anti+Ba group (containing 20 g/t Kitasamycin and 0.5 × 108 CFU/kg BaSC06 in the diet) and Ba group (containing 1 × 108 cfu/Kg BaSC06 in the diet without any antibiotics). Each treatment was performed in three replicates with 13 pigs per replicate. Results showed that BaSC06 replacement significantly improved the ADG (P < 0.05), intestinal digestion and absorption function by increasing the activity of intestinal digestive enzymes and the expression of glucose transporters SGLT1 (P < 0.05) and small peptide transporters PEPT1 (P < 0.05). Besides, BaSC06 supplementation enhanced intestinal and body antioxidant capacity by activating the Nrf2/Keap1 antioxidant signaling pathway due to the increased expression of p-Nrf2 (P < 0.05). Notably, BaSC06 alleviated intestinal inflammation by inhibiting the production of pro-inflammatory cytokines, IL-8, IL-6, and MCP1 (P < 0.05), and simultaneously increasing the expression of M1 macrophage marker protein iNOS (P < 0.05) and M2 macrophage marker protein Arg (P < 0.05) in the intestinal mucosa. Moreover, BaSC06 promoted the polarization of macrophages to M2 phenotype by stimulating the STAT3 signaling pathway. It was also noted that BaSC06 improved microbiota composition by enhancing the proportion of Firmicutes, and reducing that of Bacteroidetes and Proteobacteria. Taken together, our results indicate that dietary supplementation of BaSC06 in pigs for fattening improves the growth, mucosal structure, antioxidative capacity, immune functions (including increasing M1 and M2 polarization of macrophage) and composition of intestinal microbiota, which is much better than antibiotics, suggesting that it is an effective alternative to antibiotics in the preparation of pig feed.

The Role of Nrf2 Signaling Pathway in Eucommia ulmoides Flavones Regulating Oxidative Stress in the Intestine of Piglets

Eucommia ulmoides flavones (EUF) have been demonstrated to alleviate oxidative stress and intestinal damage in piglets, but their effect target is still poorly understood. NF-E2-related factor 2 (Nrf2) pathway plays a very important role in the defense mechanism. This study was designed to investigate the regulation of EUF on the Nrf2 pathway and inhibition of Nrf2 on oxidative stress in the intestine of piglets. An in vivo study was conducted in weaned piglets treated with basal diet, basal diet+diquat, and 100 mg/kg EUF diet+diquat for 14 d to determine Nrf2 and Keap1 protein expressions, as well as downstream antioxidant gene mRNA expression. An in vitro study was performed in a porcine jejunal epithelial cell line to investigate the effect of inhibiting Nrf2 on cell growth and intracellular oxidative stress parameters. The results showed that the supplementation of EUF decreased the oxidized glutathione (GSSG) concentration and the ratio of GSSG to glutathione (GSH) but increased the protein expressions of nuclear Nrf2 and Kelch-like ECH-associated protein 1 (Keap1) as well as mRNA expression of heme oxygenase 1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO-1), and glutamate cysteine ligase catalytic subunit (GCLC) in the small intestinal mucosa of diquat-challenged piglets. When Nrf2 was inhibited by using ML385, cell viability, cellular antioxidant activities, expressions of nuclear Nrf2 and Keap1 protein, and downstream antioxidant enzyme (HO-1, NQO-1, and GCLC) mRNA were decreased in paraquat-treated enterocytes. These results showed that the Nrf2 signaling pathway played an important role in EUF-regulating oxidative stress in the intestine of piglets.

Multiorgan Development of Oxidative and Nitrosative Stress in LPS-Induced Endotoxemia in C57Bl/6 Mice: DHE-Based In Vivo Approach

Detection of free radicals in tissues is challenging. Most approaches rely on incubating excised sections or homogenates with reagents, typically at supraphysiologic oxygen tensions, to finally detect surrogate, nonspecific end products. In the present work, we explored the potential of using intravenously (i.v.) injected dihydroethidine (DHE) to detect superoxide radical (O₂ ^∙-) abundance in vivo by quantification of the superoxide-specific DHE oxidation product, 2-hydroxyethidium (2-OH-E⁺), as well as ethidium (E⁺) and DHE in multiple tissues in a murine model of endotoxemia induced by lipopolysaccharide (LPS). LPS was injected intraperitoneally (i.p.), while DHE was delivered via the tail vein one hour before sacrifice. Tissues (kidney, lung, liver, and brain) were harvested and subjected to HPLC/fluorescent analysis of DHE and its monomeric oxidation products. In parallel, electron spin resonance (EPR) spin trapping was used to measure nitric oxide (^∙NO) production in the aorta, lung, and liver isolated from the same mice. Endotoxemic inflammation was validated by analysis of plasma biomarkers. The concentration of 2-OH-E⁺ varied in the liver, lung, and kidney; however, the ratios of 2-OH-E⁺/E⁺ and 2-OH-E⁺/DHE were increased in the liver and kidney but not in the lung or the brain. An LPS-induced robust level of ^∙NO burst was observed in the liver, whereas the lung demonstrated a moderate yet progressive increase in the rate of ^∙NO production. Interestingly, endothelial dysfunction was observed in the aorta, as evidenced by decreased ^∙NO production 6 hours post-LPS injection that coincided with the inflammatory burden of endotoxemia (e.g. elevated serum amyloid A and prostaglandin E₂). Combined, these data demonstrate that systemic delivery of DHE affords the capacity to specifically detect O₂ ^∙- production in vivo. Furthermore, the ratio of 2-OH-E⁺/E⁺ oxidation products in tissues provides a tool for comparative insight into the oxidative environments in various organs. Based on our findings, we demonstrate that the endotoxemic liver is susceptible to both O₂ ^∙--mediated and nonspecific oxidant stress as well as nitrosative stress. Oxidant stress in the lung was detected to a lesser extent, thus underscoring a differential response of liver and lung to endotoxemic injury induced by intraperitoneal LPS injection.

The pharmacokinetics of dexmedetomidine in patients with obstructive jaundice: A clinical trial

OBJECTIVES

Dexmedetomidine, a highly selective central α2-agonist, undergoes mainly biotransformation in the liver. The pharmacokinetics of dexmedetomidine were significantly affected by hepatic insufficiency. The clearance of dexmedetomidine in patients with severe hepatic failure decreased by 50% compared with controls. We tested the hypothesis that the pharmacokinetics of dexmedetomidine would be affected by obstructive jaundice. The prospective registration number of clinical trial is ChiCTR-IPR-15007572.

METHODS

18 patients with obstructive jaundice and 12 non-jaundiced patient controls received dexmedetomidine, 1 μg/kg, over 10 min. Arterial blood samples were drawn before, during, and up to 5 h after the infusion. Plasma dexmedetomidine concentrations were determined by 1290 infinity high performance liquid chromatography coupled with 6470 tandem mass spectrometry. The relevant pharmacokinetic parameters were calculated by non-compartmental analysis using Phoenix WinNonlin 7.0.

RESULTS

Plasma clearance of dexmedetomidine was decreased by 33.3% in the obstructive jaundice group as compared with the control group (0.0068±0.0017 vs. 0.0102±0.0033 L/kg/min; P = 0.002). Volume of distribution was decreased by 29.2% in the obstructive jaundice group as compared with the control group (1.43±0.58 vs. 2.02±0.84 L/kg; P = 0.041).

CONCLUSIONS

This study demonstrates that the clearance and distribution volume of dexmedetomidine were decreased in patients with obstructive jaundice. It may be advisable to adjust the dose of dexmedetomidine in those patients.

Simulated altitude exercise training damages small intestinal mucosa barrier in the rats

This study investigated the effect of simulated altitude training on the changes of small intestinal mucosa barrier, bacterial overgrowth and inflammatory response in the small intestine of rat. Male 8-week-old Sprague-Dawley rats were randomly divided into four groups: normal oxygen sedentary group (n=30), normal oxygen exercise group (n=30), low oxygen sedentary group (n=30) and low oxygen exercise group (n=30). Exercise training was on a treadmill for 1 hr per day on days 3, 6, and 9 in the hypoxia condition. Hematological profiles, hematolxylin and eosin staining, fluorescence in situ hybridization, reverse transcription-polymerase chain reaction and Western blot were used to analyze the effect of simulated altitude training on the amount of bacteria, and expression of mRNA and protein. Simulated exercise training significantly increased red blood cells and hematocrit. The small intestinal mucosa barrier was significantly injured by the simulated altitude exercise training. Comparatively more bacterial growth was evident in the small intestine by the simulated altitude exercise training. mRNA levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) and protein expression of nuclear factor-kappa B (NF-κB) were significantly elevated by simulated altitude exercise training. These results suggest that the simulated altitude exercise training may impair the small intestinal mucosa barrier via elevation of bacterial growth and inflammatory cytokines (IL-6, TNF-α) and the up-regulation of NF-κB in the rats.

Review: The role of the liver in the response to LPS: experimental and clinical findings

The liver plays an important physiological role in lipopolysaccharide (LPS) detoxification and, in particular, hepatocytes are involved in the clearance of endotoxin of intestinal derivation. In experimental shock models, tumor necrosis factor (TNF)-α induces hepatocyte apoptosis and lethal effects are due to secreted TNF-α and not to cell-associated TNF-α. An exaggerated production of TNF-α has been reported in murine viral infections, in which mice become sensitized to low amounts of LPS and both interferon (IFN)-γ and IFN-α/β are involved in the macrophage-induced release of TNF-α. The prominent role of LPS and TNF-α in liver injury is also supported by studies of ethanol-induced hepatic damage. In humans, evidence of LPS-induced hepatic injury has been reported in cirrhosis, autoimmune hepatitis, and primary biliary cirrhosis and a decreased phagocytic activity of the reticulo-endothelial system has been found in these diseases. The origin of endotoxemia in hepatitis C virus (HCV) infected patients seems to be multifactorial and LPS may be of exogenous or endogenous derivation. In endotoxemic HCV-positive patients responsive to a combined treatment with IFN-α/ribavirin (RIB), endotoxemia was no longer detected at the end of the therapeutic regimen. By contrast, 48% of the non-responders to this treatment were still endotoxemic and their monocytes displayed higher intracellular TNF-α and interleukin (IL)-1β levels than responders. Moreover, in responders, an equilibrium between IFN-γ and IL-10 serum levels was attained. In the non-responders, serum levels of IL-10 did not increase following treatment. This may imply that an imbalance between T helper (Th)1 and Th2 derived cytokines could be envisaged in the non-responders.

Role of transforming growth factor-β1 (TGF-β1) in endotoxin-induced hepatic failure after extensive hepatectomy in rats

Postoperative infections after hepatectomy sometimes lead to fatal hepatic failure, but the mechanism of the hepatic failure is unclear. Wistar rats underwent 90% hepatectomy, and were then divided into three groups: (i) the SAL group, injected with normal saline; (ii) the LPS group, injected with lipopolysaccharide (LPS) every day for 1 week; and (iii) the LPS plus TGF-Ab (LPS+TGF-Ab) group, injected with LPS with anti-transforming growth factor-β1 (TGF-β1) antibody. We investigated survival rates, TGF-β1 expression in the liver, liver regeneration by proliferating cell nuclear antigen labeling index, hepatocyte apoptosis by single stranded DNA labeling index, and perisinusoidal fibrosis using Masson's trichrome staining. The LPS group (30.4%) had a significantly lower survival rate than the SAL group (84%) and tended to be lower than the LPS+TGF-Ab group (49.4%). Liver regeneration in the LPS group was significantly lower than in the other groups. In the LPS group, hepatocyte apoptosis and perisinusoidal fibrosis was significantly more remarkable, and TGF-β1 expression was significantly higher than in the SAL group. TGF-β1 enhanced by LPS plays an important role in the mechanism of hepatic failure by infections after hepatectomy, especially in inhibition of liver regeneration, and induction of hepatocyte apoptosis and perisinusoidal fibrosis.

Protective effect of heme oxygenase-1 on Wistar rats with heart failure through the inhibition of inflammation and amelioration of intestinal microcirculation

BACKGROUND

Myocardial infarction (MI) has likely contributed to the increased prevalence of heart failure (HF). As a result of reduced cardiac function, splanchnic blood flow decreases, causing ischemia in villi and damage to the intestinal barrier. The induction of heme oxygenase-1 (HO-1) could prevent, or lessen the effects of stress and inflammation. Thus, the effect and mechanism thereof of HO-1 on the intestines of rats with HF was investigated.

METHODS

Male Wistar rats with heart failure through ligation of the left coronary artery were identified with an left ventricular ejection fraction of < 45% through echocardiography and then divided into various experimental groups based on the type of peritoneal injection they received [MI: saline; MI + Cobalt protoporphyrin (CoPP): CoPP solution; and MI + Tin mesoporphyrin IX dichloride (SnMP): SnMP solution]. The control group was comprised of rats without coronary ligation. Echocardiography was performed before ligation for a baseline and eight weeks after ligation in order to evaluate the cardiac function of the rats. The bacterial translocation (BT) incidence, mesenteric microcirculation, amount of endotoxins in the vein serum, ileum levels of HO-1, carbon oxide (CO), nitric oxide (NO), interleukin (IL)-10, tumour necrosis factor-α (TNF-α), and the ileum morphology were determined eight weeks after the operation.

RESULTS

The rats receiving MI + CoPP injections exhibited a recovery in cardiac function, an amelioration of mesenteric microcirculation and change in morphology, a lower BT incidence, a reduction in serum and ileac NO and TNF-α levels, and an elevation in ileac HO-1, CO, and interleukin-10 (IL-10) levels compared to the MI group (P < 0.05). The rats that received the MI + SnMP injections exhibited results inverse to the MI (P < 0.05) group.

CONCLUSIONS

HO-1 exerted a protective effect on the intestines of rats with HF by inhibiting the inflammation and amelioration of microcirculation through the CO pathway. This protective effect could be independent from the recovery of cardiac function.

Obstructive jaundice and perioperative management

The causes of obstructive jaundice are varied, but it is most commonly due to choledocholithiasis; benign strictures of the biliary tract; pancreaticobiliary malignancies; and metastatic disease. Surgery in patients with obstructive jaundice is generally considered to be associated with a higher incidence of complications and mortality. Therefore, it poses a considerable challenge to the anesthesiologist, surgeons, and the intensive care team. However, appropriate preoperative evaluation and optimization can greatly contribute to a favorable outcome for perioperative jaundiced patients. This article outlines the association between obstructive jaundice and perioperative management, and reviews the clinical and experimental studies that have contributed to our knowledge of the underlying pathophysiologic mechanisms. Pathophysiology caused by obstructive jaundice involving coagulopathies, infection, renal dysfunction, and other adverse events should be fully assessed and reversed preoperatively. The depressed cardiovascular effects of obstructive jaundice are worth noticing because it has complicated mechanisms and needs to be further explored. Alterations of anesthesia-related drugs induced by obstructive jaundice are varied and clinicians should be aware of the possible need for a decrease in the anesthetic dose. Recommendations concerning the perioperative management of the patients with obstructive jaundice including preoperative biliary drainage, anti-infection, nutrition support, coagulation reversal, cardiovascular evaluation, perioperative fluid therapy, and hemodynamic optimization should be taken.

Role of gaseous signal molecules in the development of hepatic cirrhosis with portal hypertension

Nitrogen monoxide, carbon monoxide and hydrogen sulfide are three types of endogenous gas molecules that are able to exert diverse biological effects. As they can dilate blood vessels and suppress platelet aggregation and cell multiplication, the research on these gas signal molecules has become active. Their role in the development of hepatic cirrhosis with portal hypertension has gradually attracted more attention. Here, we will review the role of these gas signal molecules in the development of hepatic cirrhosis with portal hypertension.

Advance in causes and mechanisms of intestinal injury

New evidence suggests that intestinal barrier injury contributes to many diseases' occurrence, development and outcome in clinics. Therefore, the causes and mechanisms of intestinal mucosal barrier damage are attracting more and more attention from clinicians. Many causes may induce damages of the intestinal mucosal membrane barrier, including ischemia, anoxia, ischemia/reperfusion, inflammatory mediator infiltration, bacterial endotoxin release, imbalance of intestinal flora, immune abnormity, nutritional disturbance, total parenteral nutrition, severe trauma, general and gastrointestinal infection and so on. This article gives a review on the above causes and mechanisms.

Fasting exacerbates and feeding diminishes LPS-induced liver injury in the rat

INTRODUCTION

Enteral nutrition improves clinical outcomes. The effects of feeding on LPS induced liver injury are unknown. We hypothesized that feeding would attenuate liver injury from LPS.

METHODS

Fasted or fed rats were given LPS (20 mg/kg i.p.) or saline for 5 h and sacrificed. Serum aminotransferases and cytokines (immunoassay) were measured. Oxidative stress protein (iNOS, COX2, and HO1) assessments (Western immunoblot) were also obtained.

RESULTS

In fasted rats, LPS significantly increased serum aminotransferase levels, enhanced hepatic COX2, iNOS, and HO1 immunoreactivity, and increased serum cytokine levels when compared to controls. While feeding diminished liver enzymes, attenuated expression of COX2 and iNOS, and blunted production of pro-inflammatory cytokines, it did not modulate LPS-induced expression of the anti-inflammatory markers HO1 and IL-10.

CONCLUSION

These data suggest that feeding decreases liver injury by attenuating expression of pro-inflammatory mediators while maintaining expression of anti-inflammatory mediators, both systemically and locally.

Heat-stress-induced damage to porcine small intestinal epithelium associated with downregulation of epithelial growth factor signaling

Extreme heat during certain days of the summer renders pigs susceptible to severe heat stress, which negatively affects their growth performance. We hypothesized that such heat stress impaired the small intestinal mucosa, a site responsible for nutrient absorption. To simulate heat stress, Chinese experimental mini-pigs were treated with 5 h of continual 40 degrees C temperature each day for 10 d in succession. Pigs were killed at 1, 3, 6 and 10 d after treatment, and small intestinal epithelia were sampled for histochemical examination and biochemical analyses. The duodenum and jejunum were seriously damaged within 3 d of initiation of treatment. Subsequent study of the process of jejunum recovery showed that the initiation of recovery started within 6 d following heat stress. Such damage was associated with the downregulation of epithelial growth factor signaling. In conclusion, heat stress induced short-term damage to the epithelium of porcine intestine. Because the intestinal epithelium is crucial for nutrient uptake, such damage should partially account for the impairment of growth performance of pigs under heat stress.

Influencing factors for gastric emptying rate during oral fluid resuscitation of hemorrhagic shock in rats with 40% blood volume loss

AIM: To observe the changes of plasma nitrogen monoxidum (NO), motilin (MTL) content and gastric emptying (GE) rate and to investigate the relationship between NO, MTL content and GE during early oral fluid resuscitation of hemorrhagic shock in rats with 40% blood volume loss.

METHODS: Twenty-four SD rats were randomly divided into three groups: sham operation group (GES group, n = 8), hemorrhage with no resuscitation group (H group, n = 8) and hemorrhage with oral administration of a glucose-electrolyte solution group (H + GES group, n = 8). Rats of H group and H + GES group were subjected to a 40% hemorrhagic injury from the right common carotid artery, while GES group only to a ligation of the artery. GES was intragastrically administrated with a total amount double of blood loss at 0.5 h and 1 h post-hemorrhage in GES group and H + GES group. Rats were sacrificed 4 h after hemorrhage/operation and blood samples were harvested for evaluation of plasma NO and MTL contents. Gastric emptying rates (GE) were determined using method of phenol red emptying.

RESULTS: Gastric emptying rate was significantly lower in H + GES group than in GES group. (62.4% ± 11.4% vs 92.4% ± 12.5%, P < 0.01). The plasma NO level was significantly higher (105.7 ± 13.2 μmol/L vs 53.6 ± 6.9 μmol/L, 75.4 ± 10.5 μmol/L, both P < 0.01) but plasma MTL content was significantly lower in H + GES group than in GES group or than in H group (72.5 ± 14.3 ng/L vs 132.3 ± 24.1 ng/L, 95.7 ± 15.5 ng/L, both P < 0.01). Gastric emptying rate was negatively correlated with plasma NO content but positively correlated with plasma MTL content (P < 0.01).

CONCLUSION: The results indicate that gastric emptying rate is lowered after early oral fluid resuscitation of hemorrhagic shock in rats with 40% blood volume loss, which might be caused by the increased plasma No content and decreased plasma MTL content during hemorrhagic shock.

Prevention and treatment of gastrointestinal dysfunction following severe burns: A summary of recent 30-year clinical experience

AIM: To sum up the recent 30-year experience in the prevention and treatment of gastrointestinal dysfunction in severe burn patients, and propose practicable guidelines for the prevention and treatment of gastrointestinal (GI) dysfunction.

METHODS: From 1980 to 2007, a total of 219 patients with large area and extraordinarily large area burns (LAB) were admitted, who were classified into three stages according the therapeutic protocols used at the time: Stage 1 from 1980 to 1989, stage 2 from 1990 to 1995, and stage 3 from 1996 to 2007. The occurrence and mortality of GI dysfunction in patients of the three stages were calculated and the main causes were analyzed.

RESULTS: The occurrence of stress ulcer in patients with LAB was 8.6% in stage 1, which was significantly lower than that in stage 1 (P < 0.05). No massive hemorrhage from severe stress ulcer and enterogenic infections occurred in stages 2 and 3. The occurrence of abdominal distension and stress ulcer and the mortality in stage 3 patients with extraordinarily LAB was 7.1%, 21.4% and 28.5%, respectively, which were significantly lower than those in stage 1 patients (P < 0.05 or P < 0.01), and the occurrence of stress ulcer was also significantly lower than that in stage 2 patients (P < 0.05).

CONCLUSION: Comprehensive fluid resuscitation, early excision of necrotic tissue, staged food ingestion, and administration of specific nutrients are essential strategies for preventing gastrointestinal complications and lowering mortality in severely burned patients.

Hepatic gene expression during endotoxemia

PURPOSE

During the course of sepsis, endotoxins and cytokines activate Kupffer cells, induce the liberation and synthesis of adhesion molecules, and damage hepatocytes, which leads to septic liver failure. The interaction of the different hepatic cell types during these processes is not completely understood and may be clarified by microarray technology.

MATERIALS AND METHODS

Seven Sprague Dawley rats received either an intraperitoneal injection of lipopolysaccharides (LPS) of 3 mg/kg body weight (n = 4) or sodium chloride (SC) 0.9% (n = 3). Animals were sacrificed 24 h after LPS or SC injection. RNA from liver tissue was isolated and hybridized on GeneChips (RAE 230A; Affymetrix, Santa Clara, CA). Expression of interleukin-1beta, tumor necrosis factor-alpha, and signal transducer and activator of transcription 3 was controlled by reverse transcription-polymerase chain reaction analysis. Immunohistochemical staining for intercellular adhesion molecule-1 of liver tissue was performed.

RESULTS

We detected 508 differentially expressed genes between LPS and SC. Two hundred forty-eight genes were up-regulated and 260 genes were down-regulated in the LPS versus the SC group. Mainly genes involved in immune response and receptor activity were up-regulated in the LPS group. Genes enrolled in catalytic, transferase activity, and metabolisms were down-regulated in the LPS group. The microarray findings could be verified by reverse transcription-polymerase chain reaction analysis and immunohistochemical staining.

CONCLUSIONS

The contemporaneous differential regulation of genes involved in metabolism, hepatocellular synthesis, and immune response reflect the liver's central role as immune organ during the course of sepsis. A switch from metabolic to immunological activity is obvious, which aggravates the hepatic damage. The functional interaction of the single genes identified during this process must be further clarified.

Hepatic platelet and leukocyte adherence during endotoxemia

INTRODUCTION

Liver microcirculation disturbances are a cause of hepatic failure in sepsis. Increased leukocyte-endothelial interaction, platelet adherence and impaired microperfusion cause hepatocellular damage. The time course and reciprocal influences of ongoing microcirculatory events during endotoxemia have not been clarified.

METHODS

Male Wistar rats (232 +/- 17 g) underwent cecal ligation and puncture (CLP). Intravital microscopy (IVM) was performed 0, 1, 3, 5, 10 and 20 hours after CLP. Mean erythrocyte velocity, leukocyte and platelet rolling in postsinusoidal venules and sticking of leukocytes and platelets in postsinusoidal venules and hepatic sinusoids were determined. Heart rate (HR), mean arterial pressure (MAP) and portal venous blood flow (PBF) were measured. Blood count and investigation of hepatic enzyme release was performed after each IVM time point.

RESULTS

Hepatic platelet-endothelial adherence in liver sinusoids and postsinusoidal venules occurred one hour after the induction of endotoxemia. Leukocyte-endothelial interaction started three to five hours after CLP. A decrease of hepatic microperfusion could be observed at three hours in sinusoids and ten hours in postsinusoidal venules after CLP, although PBF was reduced one hour after CLP. HR remained stable and MAP decreased ten hours after CLP. Hepatic enzymes in blood were significantly elevated ten hours after CLP.

CONCLUSION

Hepatic platelet-endothelial interaction is an early event during endotoxemia. Leukocyte adherence occurs later, which underlines the probable involvement of platelets in leukocyte recruitment. Although PBF is reduced immediately after CLP, the later onset of hepatic microperfusion decrease makes the existence of autoregulatory liver mechanisms likely.

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Expression of endothelin receptors in the gastric mucosa of portal hypertensive rats

BACKGROUND

Portal hypertensive gastropathy is an abnormal circulatory state in gastric mucosa with vascular dilatation due to portal hypertension. The aim of the present study was to evaluate expression of endothelin receptors and their roles in the portal hypertensive gastric mucosa.

METHODS

Portal hypertensive rats were generated by staged portal vein occlusion. Expression of endothelin-A receptor and endothelin-B receptor mRNA was examined by reverse transcriptase-polymerase chain reaction, and protein were examined by immunohistochemistry. The changes of mucosal microcirculation by endothelin receptor antagonists were measured with in vivo microscope.

RESULTS

Expression of endothelin-A receptor mRNA was increased significantly in portal hypertensive rats in comparison with sham-operated control rats (P < 0.05). There was no significant difference between the two groups in endothelin-B receptor mRNA expression. Vessels of the gastric mucosa were dilated, and intravessel blood flow was increased significantly in the portal hypertensive group (P < 0.05). Diameters of mucosal vessels and blood flow were increased significantly by endothelin-A receptor antagonist (BQ-485) in the portal hypertensive rats. Endothelin-B receptor antagonist (IRL-1038) had no significant effect on mucosal microcirculation.

CONCLUSION

These data suggest that increased expression of endothelin-A receptor in the portal hypertensive gastric mucosa may be related to the regulation of gastric microcirculation.

Amelioration of microcirculatory damage by an endothelin A receptor antagonist in a rat model of reversible acute liver failure

BACKGROUND/AIMS

Hepatocellular damage in acute liver failure (ALF) is aggravated by proinflammatory and cytotoxic mediators released from sinusoidal-lining cells. We studied a selective endothelin A receptor (ETAR) antagonist for its potential influence on the microcirculation in the setting of ALF.

METHODS

Seventy Wistar rats were divided into five groups: (I) induction of ALF by a 70% liver resection combined with injection of 400 microg/kg endotoxin, (II) ALF treated with the ETAR antagonist LU 135252 (1 mg/kg b.w. i.v.), (III) sham operation, (IV) injection of endotoxin, (V) 70% liver resection. Liver microcirculation was measured by intravital microscopy. Parenchymal injury, growth fractions, endothelin (ET)-1 and ETAR were studied by histology and immunohistology. Survival, liver function, and morphology were followed up to 14 days.

RESULTS

100% mortality, impaired liver function, widespread endothelial lesions, highest ET-1 and ETAR levels, a decreased perfusion rate, reduced sinusoidal diameter, as well as an increase in both leukocyte-endothelium interactions and sinusoidal blood flow were observed after induction of ALF. ETAR antagonist-treated rats showed decreased ET-1 and ETAR levels as well as improved microcirculatory function, morphology, liver function, and 85% survival.

CONCLUSIONS

Microcirculatory disturbances correlate with liver dysfunction in ALF. ETAR blockade represents a new therapeutic approach to ALF by reducing microcirculatory lesions and their sequelae.

Intravenous glycine after cecal ligation and puncture has no effect on impaired hepatic microperfusion, leukocyte adhesion, and mortality in septic rats

Recent studies indicated that prefeeding of a glycine supplemented diet reduces the hepatic inflammatory response and liver damage in sepsis. We investigated the effect of a glycine-enriched infusion on hepatic microcirculatory disturbances and mortality in a rat model of sepsis after the onset of the disease. Male Wistar rats (240 +/- 13 g) underwent cecal ligation and puncture (CLP) or laparotomy (LAP). A glycine (CLP + Gly, n = 24), valine (CLP + Val, n = 24), or sodium chlorid (CLP + Sc, n = 24) infusion was started 2 h after CLP. The LAP group received sodium chloride intravenously (LAP + Sc, n = 18 ). Five hours, 10 h, and 20 h after CLP or LAP intravital microscopy (IVM) was performed to investigate leukocyte-endothelial interaction (LEI) and mean erythrocyte velocity in liver sinusoids (sMEV) and postsinosoidal venules (vMEV). The portal blood flow (PBF), hepatic enzyme liberation, and glycine values in blood were measured. Immunohistochemical staining for ICAM-1 in liver tissue was performed and survival was observed. Glycine values were significantly elevated in the CLP + Gly vs. the CLP + Val and the CLP + Sc group at every timepoint of investigation. Glycine infusion had no beneficial effects on sMEV, vMEV, LEI, hepatic enzyme liberation, and survival. Heart rate and mean arterial pressure remained stable but PBF decreased significantly in all groups 20 h after CLP. Although glycine reduces the hepatic inflammatory response and liver damage in pretreatment of septic rats, there was no effect of intravenous glycine after the onset of sepsis in our experiments. Our animal model does not support the use of glycine in patients.

C1-inhibitor reduces hepatic leukocyte-endothelial interaction and the expression of VCAM-1 in LPS-induced sepsis in the rat

INTRODUCTION

Increased leukocyte-endothelial interaction (LEI) leading to hepatic microperfusion disorders is proposed as major contributor for hepatic failure during sepsis. Recently it has been demonstrated that complement inhibition by C1-inhibitor (C1-INH) is an effective treatment against microcirculatory disturbances in various diseases. The purpose of this study was to investigate the influence of C1-INH on microcirculation and LEI in the liver in a rat model of sepsis.

MATERIALS AND METHODS

Rats received lipopolysaccharides (LPS) from Escherichia coli intravenously. Controls received Ringer solution only. Ninety minutes after LPS infusion some animals were treated with C1-INH intravenously (LPS + C1-INH). Others (LPS + SC) and controls (Ringer + SC) received sodium chloride (SC). Hepatic LEI and mean erythrocyte velocity (MEV) were quantified by intravital microscopy (IVM) 90 min after LPS or Ringer infusion (0) and 30, 60, 90 and 120 min following treatment. VCAM-1 m-RNA in hepatic tissue, C3a, TNF-alpha and hepatic enzyme liberation in blood was analysed.

RESULTS

Leukocyte sticking to the endothelial wall in postsinusoidal venules was significantly reduced in the LPS + C1-INH vs. the LPS + SC group 30, 60, 90 and 120 min after treatment. VCAM-1 m-RNA expression in the hepatic tissue was markedly and C3a levels in plasma were significantly reduced in the LPS + C1-INH vs. the LPS + SC group. No differences in TNF-alpha levels were detected between these two groups. MEV was improved in the LPS + C1-INH vs. the LPS + SC group.

CONCLUSIONS

Our results indicate that even upon delayed treatment hepatic adhesion molecule expression and LEI can be reduced by C1-INH. The multifunctional regulator may reduce hepatic microcirculatory disturbances during sepsis under clinical conditions.

Effects of Portal Vein Arterialization on Regeneration and Morphology in Liver Transplantation: Investigations Using the Rat Model

BACKGROUND

Portal vein arterialization (PVA) has been proposed as a technical variant in liver transplantation in the case of non-recanalizable thrombosis. The present study investigates the effects of the arterialized portal vein on the function, morphology, and regenerative behavior of the liver.

METHODS

Different PVA techniques, including orthotopic liver transplantation, were used in a rat model. Portal blood flow was measured using a ultrasonic flowmeter. The regeneration capacity was determined on the basis of the increase of liver weight and the proliferating cell nuclear antigen index. The amount of hydroxyproline and the transcript levels of procollagen I were measured to determine the degree of fibrosis. The extracellular matrix was visualized with Picro-Sirius staining.

RESULTS

The measurements obtained with an ultrasonic probe revealed a significant increase in portal blood flow after PVA. The regeneration capacity in the groups after PVA with no flow reduction was comparable to that of the control. Liver transplantation and PVA with no flow reduction was followed by a significant increase (four- to sixfold) in the amount of hydroxyproline and the level of the mRNA for procollagen I. In the Picro-Sirius staining, periportal and perivascular fibrosis with incipient formation of septa was seen. After reduction of the portal blood flow, these effects were significantly less pronounced.

CONCLUSIONS

These operative techniques represent an excellent small animal model for studying the mechanism of liver regeneration and the genesis of fibrosis in liver and vessel tissue. The presenting findings indicate that the negative effects of "overarterialization" may be largely avoided by reducing portal blood flow. This implies that permanent PVA in clinical liver transplantation should be performed only in conjunction with a down-regulation of portal flow.

Estradiol's effect on portal response to endothelin-1 after trauma-hemorrhage

BACKGROUND

The fine balance between vasoconstrictors and vasodilators maintains portal circulation. Studies have shown that portal response to endothelin-1 (ET-1), a potent vasoconstrictor, is enhanced following hemorrhagic-shock, which subsequently leads to the impaired hepatic circulation and hepatic damage. Although protective effects of 17beta-estradiol (E(2)) against hepatic damage following trauma-hemorrhage have been observed, it remains unknown whether E(2) directly improves hepatic circulation. We hypothesized that the salutary effects of E(2) are mediated, at least in part, by the attenuation of portal response to ET-1 following trauma-hemorrhage.

MATERIALS AND METHODS

Male adult Sprague-Dawley rats were randomly assigned to sham operation or trauma-hemorrhage with or without in vivo E(2) treatment. Trauma-hemorrhage included midline laparotomy and approximately 90 min of hemorrhagic shock (35 mmHg), then resuscitation with four times the shed blood volume with Ringer's lactate solution over 60 min. For the E(2) treatment group, 1 mg/kg of E(2) was added to the Ringer's lactate solution. At 5 h after the end of resuscitation, the liver was isolated and perfused in vitro to measure portal pressure responses to exogenous ET-1 (60 pmol in 150 ml perfusate, bolus) with or without E(2) (1,500 pg/ml).

RESULTS

Peak portal pressure after the administration of ET-1 was significantly higher in vehicle-treated trauma-hemorrhage group compared with the sham group. This effect was significantly attenuated in the E(2) treatment group. Furthermore, E(2) treatment restored bile production and prevented hepatic damage following trauma-hemorrhage.

CONCLUSIONS

The beneficial effects of estradiol observed following trauma-hemorrhage, at least partly, are caused by the attenuation of portal pressure response to increased ET-1.

Development and evaluation of an experimental model for investigating the pathogenesis and therapeutic strategies of acute liver failure

Because of the various etiologies of acute liver failure (ALF) a clinically relevant model must fulfill four criteria--reversibility, reproducibility, ALF-induced death, and a sufficient time interval for diagnosis and therapy between induction and death. In this study an experimental model was evaluated for these criteria. A total of 49 rats were randomized into seven groups: First, a pilot study was performed regarding the survival rate after different treatments: In group I, animals underwent a 70% liver resection. In group II, 70% liver resection was combined with ascending doses of postoperative endotoxin administration up to 400 microg/kg (group IIc). In group III, animals only underwent liver mobilization. In group IV, ALF was induced according to the protocol of group IIc, but with additional treatment of an endothelin-A-receptor (ETAR) antagonist. Animals in group V received only 400 microg endotoxin. After induction of ALF, all animals died within the first day, showing significantly elevated bilirubin and ammonium levels and severe damage to hepatocellular integrity. Application of the ETAR antagonist resulted in the survival of 6/7 animals until the 14th day; the biochemical and histomorphological changes were reversible. All other animals survived to the 14th day. A clinically relevant model of ALF in rats can be created by the combination of 70% liver resection and endotoxin application to produce an inflammatory component.

Hepatic ischemia-reperfusion syndrome after partial liver resection (LR): hepatic venous oxygen saturation, enzyme pattern, reduced and oxidized glutathione, procalcitonin and interleukin-6

The hepatic ischemia-reperfusion syndrome was investigated in 28 patients undergoing elective partial liver resection with intraoperative occlusion of hepatic inflow (Pringle maneuver) using the technique of liver vein catheterization. Hepatic venous oxygen saturation (ShvO2) was monitored continuously up to 24 hours after surgery. Aspartate aminotransferase, glutamate dehydrogenase, gamma-glutamyl transpeptidase, pseudocholinesterase, alpha-glutathione S-transferase, reduced and oxidized glutathione, procalcitonine, and interleukin-6 were serially measured both before and after Pringle maneuver during the resection and postoperatively in arterial and/or hepatic venous blood. ShvO2 measurement demonstrated that peri- and postoperative management was suitable to maintain an optimal hepatic oxygen supply. As expected, we were able to demonstrate a typical enzyme pattern of postischemic liver injury. There was a distinct decrease of reduced glutathione levels both in arterial and hepatic venous plasma after LR accompanied by a strong increase in oxidized glutathione concentration during the phase of reperfusion. We observed increases in procalcitonin and interleukin-6 levels both in arterial and hepatic venous blood after declamping. Our data support the view that liver resection in man under conditions of inflow occlusion resulted in ischemic lesion of the liver (loss of glutathione synthesizing capacity with disturbance of protection against oxidative stress) and an additional impairment during reperfusion (liberation of reactive oxygen species, local and systemic inflammation reaction with cytokine production). Additionally, we found some evidence for the assumption that the liver has an export function for reduced glutathione into plasma in man.

Procalcitonin following elective partial liver resection--origin from the liver?

BACKGROUND

The origin of the inflammatory peptide procalcitonin (PCT) is still unknown. In the present study PCT concentrations in arterial and hepatic-venous blood were examined in patients undergoing elective partial liver resection (LR) using a fiberoptic pulmonary arterial catheter placed in a liver vein to obtain further information on the origin of PCT.

METHODS

In 28 patients (21 male/7 female; average age of 58.8+/-8.8 years) undergoing LR, arterial and hepatic venous PCT concentrations were measured during 24 h perioperatively. The parallel blood withdrawals occurred immediately before the Pringle maneuver (Hx), 2 min, 1, 2, 6, 12, and 24 h after Hx. Over the whole period, the oxygen saturation in hepatic venous blood (ShvO2) was monitored. PCT concentrations were assayed by immunoluminometry.

RESULTS

We observed a significant increase in PCT concentration already 6 h after Hx compared to the values before Hx. Twenty-four hours after Hx we found the highest plasma concentrations. It was conspicuous that hepatic venous PCT concentrations were always higher than the arterial ones (significantly from the 6th hour after Hx). There was no correlation between the courses of ShvO2 and PCT rise. A significant correlation was verified between Hx duration and PCT concentration measured 24 h after Hx both in the hepatic venous and arterial blood.

CONCLUSIONS

The results of our investigation can be interpreted as evidence that liver (or the hepatosplanchnicus?) is a source of PCT. The mechanism of PCT induction cannot be clarified by our study: whether the induction of PCT was caused by an endotoxin translocation during the impeded splanchnic outflow or by the direct surgery-induced lesion (hypoxia) of the liver remains unclear. However, the latter appears more probable because of the observed correlation between Hx duration and PCT concentration rise.

Effects of dobutamine and dopexamine on hepatic micro- and macrocirculation during experimental endotoxemia: an intravital microscopic study in the rat

OBJECTIVE

To test the effects of dobutamine and dopexamine on hepatic portal and sinusoidal blood flow in a model of normodynamic endotoxemia.

DESIGN

Randomized, controlled trial.

SETTING

Experimental laboratory.

SUBJECTS

Male Wistar rats (250-350 g).

INTERVENTIONS

A total of 40 male Wistar rats were randomized into four groups: a control group, which only received Ringer's solution; an endotoxin group, which received a continuous infusion of 2 mg/kg body weight (bw)/hr of endotoxin; a dobutamine group, which received endotoxin and a continuous infusion of dobutamine (3 microg/kg bw/min); and a dopexamine group, which received endotoxin and dopexamine (2 microg/kg bw/min). The experimental period was 120 min.

MEASUREMENTS AND MAIN RESULTS

Mean arterial blood pressure (MAP), heart rate (HR), and cardiac output (CO) were detected. Portal blood flow was measured using an ultrasonic flow probe positioned around the portal vein, and sinusoidal blood flow was detected in the left liver lobe using intravital microscopy. All detected variables remained stable in the control group. In the endotoxin group, HR increased significantly and MAP decreased significantly from 111 +/- 10 mm Hg to 95 +/- 8 mm Hg at 120 mins, whereas CO remained unchanged. Both in the dobutamine and the dopexamine group HR increased and MAP decreased more than in the endotoxin group. CO increased in both groups significantly. Portal blood flow (23 +/- 4 mL/min to 16 +/- 3 mL/min) and sinusoidal blood flow (38.6 +/- 2.5 to 22.8 +/- 1.2 10(3) microm(3)/sec) decreased significantly in the endotoxin group. In the dobutamine and the dopexamine group portal and sinusoidal blood flow remained at baseline values.

CONCLUSIONS

In our model of endotoxemia, dobutamine and dopexamine preserved systemic and hepatic blood flow. These preservations of hepatic blood flow during endotoxemia could portend beneficial effects but need to be studied further.