Role of innate immunity and altered intestinal motility in LPS- and MnCl2-induced intestinal intussusception in mice.

Intestinal intussusception (ISS) commonly causes intestinal obstruction in children. One mechanism that has been proposed to cause ISS is inflammation-induced alteration of intestinal motility. We investigated whether innate inflammatory factors or altered motility is required for induction of ISS by LPS. We compared rates of ISS among BALB/c and C57BL/6 mice, mice lacking lymphocytes or depleted of phagocytes, or mice with defects in the Toll-like receptor 4 (TLR4) signaling pathway following administration of LPS or the Ca(2+) analog MnCl2. At 6 or 2 h after administration of LPS or MnCl2, respectively, mice underwent image analysis to assess intestinal contraction rate or laparotomy to identify ISS. LPS-induced ISS (LPS-ISS) was observed in BALB/c mice, but not in C57BL/6 mice or any BALB/c mice with disruptions of TLR4 signaling. LPS-induced serum TNF-α, IL-6, and nitric oxide (NO) and intestinal NO levels were similar in BALB/c and C57BL/6 mice. The rate of LPS-ISS was significantly reduced in phagocyte-depleted, but not lymphocyte-deficient, mice. Intestinal contraction rates were reduced in LPS-ISS-susceptible BALB/c mice, but not in LPS-ISS-resistant C57BL/6 or TLR4 mutant mice, suggesting a role for reduced intestinal contraction rate in LPS-ISS susceptibility. This was tested with MnCl2, a Ca(2+) antagonist that reduced intestinal contraction rates and induced ISS, irrespective of mouse strain. Therefore, LPS-ISS is initiated by innate immune signaling that requires TLR4 and phagocytes but may be independent of TNF-α, IL-6, and NO levels. Furthermore, alteration of intestinal motility, specifically, reduced intestinal contraction rate, is a key factor in the development of ISS.

Restoring soluble guanylyl cyclase expression and function blocks the aggressive course of glioma.

The NO and cGMP signaling pathways are of broad physiological and pathological significance. We compared the NO/soluble guanylyl cyclase (sGC)/cGMP pathway in human glioma tissues and cell lines with that of healthy control samples and demonstrated that sGC expression is significantly lower in glioma preparations. Our analysis of GEO databases (National Cancer Institute) further revealed a statistically significant reduction of sGC transcript levels in human glioma specimens. On the other hand, the expression levels of particulate (membrane) guanylyl cyclases (pGC) and cGMP-specific phosphodiesterase (PDE) were intact in the glioma cells that we have tested. Pharmacologically manipulating endogenous cGMP generation in glioma cells through either stimulating pGC by ANP/BNP, or blocking PDE by 3-isobutyl-1-methylxanthine/zaprinast caused significant inhibition of proliferation and colony formation of glioma cells. Genetically restoring sGC expression also correlated inversely with glioma cells growth. Orthotopic implantation of glioma cells transfected with an active mutant form of sGC (sGCα1ß1(Cys105)) in athymic mice increased the survival time by 4-fold over the control. Histological analysis of xenografts overexpressing α1ß1(Cys105) sGC revealed changes in cellular architecture that resemble the morphology of normal cells. In addition, a decrease in angiogenesis contributed to glioma inhibition by sGC/cGMP therapy. Our study proposes the new concept that suppressed expression of sGC, a key enzyme in the NO/cGMP pathway, may be associated with an aggressive course of glioma. The sGC/cGMP signaling-targeted therapy may be a favorable alternative to chemotherapy and radiotherapy for glioma and perhaps other tumors.

Use of fluoroscopy to study in vivo motility in mouse pups.

OBJECTIVES: Few methods exist to noninvasively study in vivo gastrointestinal motility in animal models of enteric infections. None have been used on mouse pups, which often display more severe symptoms during enteric infections than adult mice. This study sought to determine whether digital fluoroscopy could be used to evaluate gastrointestinal motility in mouse pups as well as adult mice. MATERIALS AND METHODS: Fluoroscopic imaging studies were performed on normal 6- to 8-week-old adult mice and 12-day-old pups to develop protocols for evaluating gastric and intestinal wall movements and changes in stomach sizes. These protocols were then applied to evaluate motility in an established rotavirus mouse model. Imaging studies were performed on adult mice at 0, 2, and 4 days postinfection and on 12-day-old pups at 2 days postinfection. RESULTS: Fluoroscopic studies revealed postnatal differences of gastric peristalsis and rates of intestinal contractions between normal mouse pups and adult mice. Studies of the rotavirus mouse model revealed that differences in gastric function occur between rotavirus-infected and control mouse pups, but no discernible difference occurs between infected and control adult mice. In contrast, there were no detectable differences in rates of intestinal wall movements between control pups with normal stools and infected pups with loose stools. CONCLUSIONS: These results demonstrate that fluoroscopy can evaluate in vivo motility in mouse pups and by doing so provide findings that are clinically relevant to the study of enteric infections in young.

Ketamine suppresses LPS-induced bile reflux and gastric bleeding in the rat.

BACKGROUND: Although ketamine has many beneficial effects in a rat model of noninfectious inflammation with lipopolysaccharide (LPS), its effects on gut ileus are unknown. We hypothesized that ketamine would improve LPS-induced ileus and therefore examined its effects on gastric emptying and intestinal transit as well as duodenogastric bile reflux and associated gastric bleeding. METHODS: Male rats received saline or ketamine (7 mg/kg ip) 1 hour before saline or LPS (20 mg/kg ip) for 5 hours. Thirty minutes before killing, rats received orogastric rhodamine B isothiocyanate-labeled dextran and 5 minutes later fluorescein isothiocyanate-labeled dextran via a duodenal catheter. GI contents were collected for dye, bile acid, and hemoglobin (index of bleeding) determinations. RESULTS: LPS significantly impaired intestinal transit and increased duodenogastric bile reflux and gastric luminal hemoglobin content. Ketamine improved intestinal transit, prevented LPS-induced bile reflux, and diminished gastric bleeding. In mechanistic studies, ketamine also attenuated LPS-induced upregulation of the proinflammatory genes inducible nitric oxide synthase and cyclo-oxygenase-2 in the stomach but preserved expression of the anti-inflammatory gene heme-oxygenase-1 (Western blot). CONCLUSIONS: These data suggest that ketamine may prevent LPS-induced gastric bleeding by decreasing bile reflux through improved intestinal transit or by local changes in nitric oxide, prostaglandin, and carbon monoxide metabolism.

Excess adenosine in murine penile erectile tissues contributes to priapism via A2B adenosine receptor signaling.

Priapism, abnormally prolonged penile erection in the absence of sexual excitation, is associated with ischemia-mediated erectile tissue damage and subsequent erectile dysfunction. It is common among males with sickle cell disease (SCD), and SCD transgenic mice are an accepted model of the disorder. Current strategies to manage priapism suffer from a poor fundamental understanding of the molecular mechanisms underlying the disorder. Here we report that mice lacking adenosine deaminase (ADA), an enzyme necessary for the breakdown of adenosine, displayed unexpected priapic activity. ADA enzyme therapy successfully corrected the priapic activity both in vivo and in vitro, suggesting that it was dependent on elevated adenosine levels. Further genetic and pharmacologic evidence demonstrated that A2B adenosine receptor-mediated (A2BR-mediated) cAMP and cGMP induction was required for elevated adenosine-induced prolonged penile erection. Finally, priapic activity in SCD transgenic mice was also caused by elevated adenosine levels and A2BR activation. Thus, we have shown that excessive adenosine accumulation in the penis contributes to priapism through increased A2BR signaling in both Ada -/- and SCD transgenic mice. These findings provide insight regarding the molecular basis of priapism and suggest that strategies to either reduce adenosine or block A2BR activation may prove beneficial in the treatment of this disorder.

Hypertonic saline reverses stiffness in a Sprague-Dawley rat model of acute intestinal edema, leading to improved intestinal function.

INTRODUCTION: Acute edema induced by resuscitation and mesenteric venous hypertension impairs intestinal transit and contractility and reduces intestinal stiffness. Pretreatment with hypertonic saline (HS) can prevent these changes. Changes in tissue stiffness have been shown to trigger signaling cascades via stress fiber formation. We proposed that acute intestinal edema leads to a decrease in intestinal transit that may be mediated by changes in stiffness, leading to stress fiber formation and decreased intestinal transit. Furthermore, HS administration will abolish these detrimental effects of edema. RESULTS: Intestinal edema causes a significant increase in tissue water and a significant decrease in intestinal transit and stiffness compared with sham. HS reversed these changes to sham levels. In addition, tissue edema led to significant stress fiber formation and decreased numbers of focal contacts. HS preserved tissue stiffness, prevented stress fiber formation, and was associated with improved intestinal function. CONCLUSION: HS eliminates intestinal tissue edema formation and improves intestinal transit. In addition, the action of HS may be mediated through its preservation of tissue stiffness, which leads to prevention of signaling via stress fiber formation, leading to preserved intestinal function. Finally, intestinal edema may provide a novel physiologic model for examining stiffness and stress fiber signaling.

Measurement of intestinal edema using an impedance analyzer circuit.

BACKGROUND: Acute intestinal edema adversely affects intestinal transit, permeability, and contractility. Current resuscitation modalities, while effective, are associated with development of acute intestinal edema. Knowledge of levels of tissue edema would allow clinicians to monitor intestinal tissue water and may help prevent the detrimental effects of edema. However, there is no simple method to measure intestinal tissue water without biopsy. We sought to develop a tissue impedance analyzer to measure tissue edema, without the need for invasive biopsy. METHODS: Oscillating voltage input was applied to the analyzer circuit and an oscilloscope measured the voltage output across any load. Rats were randomized to three groups: sham, mild edema (80 mL/kg of NS resuscitation), and severe edema (80 mL/kg of NS resuscitation with intestinal venous hypertension). Intestinal edema was measured by wet-to-dry tissue weight ratio. Bowel impedance was measured and converted to capacitance using a standard curve. RESULTS: Acute intestinal edema causes a significant increase in bowel capacitance. This capacitance can be used to predict tissue water concentration. CONCLUSION: Using an impedance analyzer circuit, it is possible to measure intestinal edema reliably and quickly. This may prove to be a useful tool in the resuscitation of critically ill patients.

Conventional dose hypertonic saline provides optimal gut protection and limits remote organ injury after gut ischemia reperfusion.

BACKGROUND: Hypertonic saline (HS) resuscitation prevents neutrophil mediated injury after shock. The optimal dose is not known, but appears as a result of osmotic stress. We hypothesized that a dose dependent effect exists related to increasing tonicity and that the optimal gut protective dose would provide better protection against remote organ injury than large volume isotonic crystalloids. METHODS: In experiment 1, rats were assigned to controls (sham/no resuscitation, sham/4 mL/kg 7.5% HS, superior mesenteric artery occlusion [SMAO]/no resuscitation), SMAO/equal volume (4 mL/kg 0.9% NS, 4 mL/kg 2.5% HS, 4 mL/kg 5% HS, 4 mL/kg 7.5% HS and 4 mL/kg 10% HS) or SMAO/equal sodium (33 mL/kg 0.9% NS, 12 mL/kg 2.5% HS, 6 mL/kg 5% HS, 4 mL/kg 7.5% HS, and 3 mL/kg 10% HS). In experiment 2, rats were assigned to the same control groups, and to either SMAO/NS (33 mL/kg 0.9% NS, equal salt load) or SMAO/HS (4 mL/kg 7.5% HS). The SMAO was clamped for 60 minutes and boluses given 5 minutes before clamp removal. After 6 hours of reperfusion, ileum and lungs were harvested for analysis of histologic injury, myeloperoxidase (MPO) as an index of neutrophil mediated injury, and serum ALT and AST drawn as markers of liver injury. RESULTS: In experiment 1, equal volume and equal sodium decreased injury and inflammation with increasing tonicity in a dose dependent fashion, with the optimal effect seen at 7.5%. In experiment 2, NS resuscitation resulted in minimal improvement of SMAO-induced lung injury and inflammation or increases in serum ALT and AST whereas HS resuscitation significantly decreased these parameters. CONCLUSION: The protective effect of HS is related to increased tonicity. While NS had little effect on SMAO-induced remote organ injury, optimal dose HS resuscitation was quite protective. This supports the growing evidence that HS protection may be because of its gut protective effects.

Hypertonic saline resuscitation prevents hydrostatically induced intestinal edema and ileus.

OBJECTIVE: We have shown that acute edema induced by mesenteric venous hypertension (MV-HTN) impairs intestinal transit and reduces the standardized engineering measures of intestinal stiffness (elastic modulus) and residual stress (opening angle). We hypothesized that hypertonic saline (7.5%) would reverse these detrimental effects of acute edema. DESIGN: Laboratory study. SETTING: University laboratory. SUBJECTS: Male Sprague Dawley rats (270-330 g). INTERVENTIONS: Rats were randomized to five groups: sham, MV-HTN alone, MV-HTN with 4 mL/kg normal saline resuscitation (equal volume), MV-HTN with 33 mL/kg normal saline resuscitation (equal salt), and MV-HTN with 4 mL/kg hypertonic saline. Intestinal edema was measured by wet to dry tissue weight ratio. A duodenal catheter was placed and, 30 mins before death, fluorescein isothiocyanate Dextran was injected. At death, dye concentrations were measured to determine intestinal transit. Segments of distal ileum were hung to a fixed point in a tissue bath and to a force displacement transducer and stretched in increments of 1 mm; we recorded the new length and the corresponding force from the force displacement transducer to determine elastic modulus. Next, two transverse cuts were made yielding a 1- to 2-mm thick ring-shaped segment of tissue which was then cut radially to open the ring. Then the opening angle was measured. MEASUREMENTS AND MAIN RESULTS: MV-HTN, MV-HTN with 4 mL/kg normal saline, and MV-HTN with 33 mL/kg normal saline caused a significant increase in tissue edema and a significant decrease in intestinal transit, stiffness, and residual stress compared with sham. Hypertonic saline significantly lessened the effect of edema on intestinal transit and prevented the changes in stiffness and residual stress. CONCLUSIONS: Hypertonic saline prevented intestinal tissue edema. In addition, hypertonic saline improved intestinal transit, possibly through more efficient transmission of muscle force through stiffer intestinal tissue.

The effect of morphine on mast cell-mediated mucosal permeability.

BACKGROUND: The late phase of post-traumatic multisystem organ failure is associated with sepsis from organisms that normally reside within the gut's lumen. Morphine, a commonly employed analgesic in injured patients, is associated with intestinal stasis, bacterial overgrowth, and translocation when administered to rats. N-formyl-methionyl-leucyl-phenylalanine (FMLP), a toxic product of gram-negative organisms, provokes an increase in mucosal permeability when infused into the ileal lumen of this species. The current study was designed to examine the effects of morphine on FMLP perturbation of the mucosal barrier of the ileum of rats and mice to an impermeant macromolecule, dextran 4400. The potential role of mucosal mast cells in the response to either agent alone or in combination was examined. METHODS: Intact and isolated segments of distal ileum of naïve and sensitized (Trichinella spiralis and egg albumin) Sprague-Dawley rats were exposed to FMLP with or without morphine or doxantrazole, a mast cell-stabilizing agent. Isolated segments of distal ileum of mast cell-deficient mice also were studied. RESULTS: Mucosal exposure of distal ileal mucosa (intact and isolated, and naive and sensitized) to FMLP was associated with an increase in permeability to dextran 4400, which was completely ablated by morphine and doxantrazole. Sensitization was associated with a prolongation of the FMLP response. Ilea of mast cell-deficient mice (but not their wild type litter mates) were unresponsive to FMLP. CONCLUSIONS: Morphine antagonizes the provocative effect of FMLP on the mucosal barrier to dextran 4400 of the ilea of rats and mice. Intestinal mucosal mast cells play a central role in the process.

Hypertonic saline resuscitation after mesenteric ischemia/reperfusion induces ileal apoptosis.

BACKGROUND: We have previously demonstrated that hypertonic saline (HS) resuscitation decreased inflammation and mucosal injury after mesenteric ischemia/reperfusion (I/R). In contrast to I/R cell necrosis, apoptosis provides controlled cell death that minimizes inflammation. We therefore hypothesized that HS resuscitation after mesenteric I/R would induce apoptosis and decrease mucosal injury. METHODS: Rats underwent 60 minutes of superior mesenteric artery occlusion (SMAO) and then received no resuscitation or resuscitation with 4 mL/kg of HS, 4 mL/kg of lactated Ringer's (LR) solution (equal volume), or 32 mL/kg of LR solution (equal salt load). Rats were killed at 6 hours of reperfusion, and ileum was harvested for analysis. DNA fragmentation (apoptosis) was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) and mucosal injury by histology (Chiu score 0-5). Caspase-3 (proapoptotic mediator) and Bcl-xL (antiapoptotic mediator) protein expression were analyzed by Western immunoblot. RESULTS: SMAO with no resuscitation, SMAO with 4 mL/kg of LR, and SMAO with 32 mL/kg of LR increased apoptosis (quantitated by TUNEL) and I/R-induced mucosal injury (quantitated by Chiu score). This was associated with an increase to similar levels in both proapoptotic caspase-3 and antiapoptotic Bcl-xL protein expression. Moreover, SMAO with 4 mL/kg of HS further increased apoptosis but decreased mucosal injury. This was associated with a differential expression of proapoptotic caspase-3 over antiapoptotic Bcl-xL. CONCLUSION: HS resuscitation after mesenteric I/R significantly increased ileal mucosal apoptosis while decreasing mucosal injury and may represent a novel mechanism by which HS resuscitation after mesenteric I/R reduces inflammation and imparts protection to the gut.

Peroxisome proliferator-activated receptor gamma mediates protection against cyclooxygenase-2-induced gut dysfunction in a rodent model of mesenteric ischemia/reperfusion.

Cyclooxygenase (COX)-2 has been identified as an important mediator elaborated during ischemia/reperfusion, with pro- and anti-inflammatory properties having been reported. As the role of COX-2 in the small intestine remains unclear, we hypothesized that COX-2 expression would mediate mesenteric ischemia/reperfusion-induced gut injury, inflammation, and impaired transit and that these deleterious effects could be reversed by the selective COX-2 inhibitor, N-[2-(cyclohexyloxy)-4-nitrophenyl] methanesulphanamide (NS-398). Additionally, we sought to determine the role of peroxisome proliferator-activated receptor gamma (PPARgamma) in mediating protection by NS-398 in this model. Rats underwent sham surgery or were pretreated with NS-398 (3, 10, or 30 mg/kg) intraperitoneally 1 h before 60 min of superior mesenteric artery occlusion and 30 min to 6 h of reperfusion. In some experiments, NS-398 (30 mg/kg) was administered postischemia. Ileum was harvested for COX-2 mRNA and protein, PGE2, myeloperoxidase (inflammation), histology (injury), intestinal transit and PPARgamma protein expression, and DNA-binding activity. COX-2 expression and PGE2 production increased after mesenteric ischemia/reperfusion and were associated with gut inflammation, injury, and impaired transit. Inhibition of COX-2 by NS-398 (30 mg/kg, but not 3 or 10 mg/kg) not only reversed the deleterious effects of COX-2, but additionally induced expression and nuclear translocation of PPARgamma. NS-398 given postischemia was equally protective. In conclusion, COX-2 may function as a proinflammatory mediator in a rodent model of mesenteric ischemia/reperfusion. Reversal of gut inflammation, injury, and impaired transit by high-dose NS-398 is associated with PPAR activation, suggesting a potential role for PPAR-gamma in shock-induced gut protection.

Resuscitation-induced intestinal edema decreases the stiffness and residual stress of the intestine.

We have shown that acute edema impairs intestinal transit and we wanted to know whether this could be from changes in the physical characteristics of the intestine. Our hypothesis was that acute edema will change the physical characteristics of the intestine, which were measured by standardized engineering measures of elastic modulus, to determine stiffness and opening angle, and to determine residual stress. Rats were randomized to sham, mild edema (80 mL/ kg of normal saline resuscitation), and severe edema groups (80 mL/kg of normal saline resuscitation with intestinal venous hypertension). Segments of distal ileum were hung to a fixed point in a tissue bath and to a tensiometer and were stretched in increments of 1 mm, recording the new length and the corresponding force from the tensiometer to determine elastic modulus. Next, two transverse cuts were made yielding a 1- to 2-mm-thick ring-shaped segment of tissue and were then cut radially to open the ring. The opening angle was measured. Acute intestinal edema led to a decrease in transit, elastic modulus, and opening angle of the intestine in the absence of ischemic injury. Acute intestinal edema leads to a significant loss in stiffness and residual stress and is a plausible explanation for how acute edema impairs intestinal transit.

Ketamine inhibits lipopolysacharide (LPS) induced gastric luminal fluid accumulation.

INTRODUCTION: Lipopolysacharide (LPS) causes gastrointestinal ileus and gastric luminal fluid accumulation. Ketamine, an anti-inflammatory anesthetic agent attenuates accumulation of luminal fluid. However, its effects on gastrointestinal transit induced by endotoxemia are unknown. The purpose of this study was to determine if the anti-inflammatory properties of ketamine improve impaired gastric emptying and gastrointestinal transit because of LPS. MATERIALS AND METHODS: Rats were given ketamine (70 mg/kg i.p.) or saline 1 h before LPS (20 mg/kg, i.p.) or saline injection. Five hours after LPS injection, rats were gavaged with 1 cc consisting of 0.1 ml of 5 mm FITC Dextran added to 0.9 ml of saline. After 30 min, rats were sacrificed, and gastric emptying, gastrointestinal transit, and gastric fluid accumulation determined. Gastric and ileal mucosa were harvested for analysis of inducible nitric oxide synthase (iNOS) (Western immunoblot). Results are reported as mean +/- SE (n > or = 5 per group; ANOVA). RESULTS: Ketamine did not prevent LPS induced gastrointestinal ileus, nor did it improve gastric emptying. More importantly, it did not worsen gastrointestinal function or gastric emptying when compared to saline controls. However, it did decrease LPS induced gastric luminal fluid accumulation and blunted iNOS expression in both the stomach and ileum. CONCLUSION: These data indicate that the ability of ketamine to attenuate gastric fluid accumulation is not because of improved gastric emptying or improved gastrointestinal transit. Moreover, while iNOS may play a role in LPS induced gastric luminal fluid accumulation, it does not appear to be a major mediator of the gastrointestinal ileus caused by LPS.

Helminth regulation of host IL-4Ralpha/Stat6 signaling: mechanism underlying NOS-2 inhibition by Trichinella spiralis.

Gastrointestinal nematode infection is known to alter host T cell activation and has been used to study immune and inflammatory reactions in which nitric oxide (NO) is a versatile player. We previously demonstrated that Trichinella spiralis infection inhibits host inducible NO synthase (NOS-2) expression. We now demonstrate that (i) an IL-4 receptor alpha-subunit (IL-4Ralpha)/Stat6-dependent but T cell-independent pathway is the key for the nematode-induced host NOS-2 inhibition; (ii) endogenous IL-4 and IL-13, the only known IL-4Ralpha ligands, are not required for activating the pathway; and (iii) treatment of RAW264.7 cells with parasite-cultured medium inhibits NOS-2 expression but not cyclooxygenase 2 expression. We propose that a yet-unidentified substance is released by the nematode during the host-parasite interaction.

Resuscitation-induced gut edema and intestinal dysfunction.

BACKGROUND: Mesenteric venous hypertension and subsequent gut edema play a pivotal role in the development of intra-abdominal hypertension. Although gut edema is one cause of intra-abdominal hypertension, its impact on gut function is unknown. The purpose of this study was to create a model of acute hydrostatic gut edema and to evaluate its effect on gut motility and barrier function. METHODS: The first study, group A, evaluated the effect of gut edema on transit over time using 20 mL/kg 0.9% saline. The second study, group B, focused on the 12-hour time period using 80 mL/kg 0.9% saline. Rats were randomized to superior mesenteric vein partial occlusion (venous hypertension) or sham surgery. At 6, 12, and 24 hours, group A underwent intestinal transit and tissue water weight measurements. At 12 hours, group B underwent tissue water, transit, ileal permeability and resistance, lactate and myeloperoxidase activity, and mucosal injury measurements. RESULTS: Venous hypertension with fluid resuscitation caused acute hydrostatic gut edema, delayed intestinal transit, increased mucosal permeability to macromolecules, and decreased tissue resistance over time. Mucosal injury was minimal in mesenteric venous hypertension. CONCLUSION: Acute mesenteric venous hypertension and resuscitation-induced gut edema, in the absence of ischemia/reperfusion injury, is associated with delayed intestinal transit and altered gut barrier function.

Mechanisms of intestinal dysmotility in morphine dependence: whether central or peripheral?

Changes of intestinal motility and transit due to morphine administration are attributed to its central and peripheral action, however coexistence of both central and peripheral mu receptors in morphine dependence hasn't been clearly demonstrated so far. Our purpose was the evaluation of the effect of either CNS or ENS mu receptor blockade on intestinal motility in morphine dependent rats. Twenty male rats were subjected to chronic subcutaneous morphine infusions for 72 hrs. On each day motility indices (MI) were analysed in the animals' duodenum and ascending colon before and after either intraperitoneal (IP) or intracerebroventricular (ICV) mu antagonist (CTOP) administration. Tolerance of the intestinal motility to morphine developed in both the duodenum and the ascending colon after 72 hrs of the infusion. Dependence was observed at 24 hrs and maintained at 48 and 72 hrs of morphine administration. On each day no differences of MI reaction to mu blockade were visible regarding the IP or ICV CTOP administration. Our results suggest the involvement of both the CNS and the ENS mu opioid receptors in mechanisms of the intestinal tolerance to and dependence upon morphine.

Hypertonic saline prevents inflammation, injury, and impaired intestinal transit after gut ischemia/reperfusion by inducing heme oxygenase 1 enzyme.

BACKGROUND: Hypertonic saline (HTS) has been shown to modulate the inflammatory response after shock. We have previously demonstrated that heme oygenase-1 (HO-1) induction is protective against gut dysfunction in models of shock-induced gut ischemia/reperfusion (I/R). We therefore hypothesized that HTS prevents gut inflammation, injury, and impaired transit by inducing HO-1 in a model of gut I/R. METHODS: Rats underwent 60 minutes of superior mesenteric artery occlusion (SMAO) and then were resuscitated with 4 mL/kg of HTS, an equal volume of lactated Ringer's (LR) solution (4 mL/kg, low volume), or equal salt LR solution (32 mL/kg, high volume) and compared with SMAO alone or shams. A separate group was pretreated with the HO-1 blocker Sn protoporphyrin IX (SNP IX) before SMAO plus HTS. At 6 hours of reperfusion, transit was determined and ileum harvested for HO-1 (anti-inflammatory) and inducible nitric oxide synthase (proinflammatory) immunoreactivity, myeloperoxidase (MPO) activity, and histologic injury. Data are expressed as mean +/- SEM (analysis of variance). RESULTS: Intestinal transit was severely impaired after SMAO (2.5 +/- 0.1), improved with low- and high-volume LR solution (3.2 +/- 0.2 and 3.1 +/- 0.1, not significant), but returned to sham (4.6 +/- 0.2) with HTS (4.8 +/- 0.2). Pretreatment with SNP abrogated this protective effect. Myeloperoxidase activity was significantly increased by SMAO (SMAO, 2.3 +/- 0.3; sham, 0.4 +/- 0.05), lessened by low- and high-volume LR solution (1.5 +/- 0.3 and 1.7 +/- 0.4), but returned to sham levels with HTS (1.0 +/- 0.01). Activity with SNP IX pretreatment was significantly increased (4.04 +/- 0.8). Mucosal injury followed a similar pattern. Inducible nitric oxide synthase was increased by SMAO and low- and high-volume LR solution (0.8 +/- 0.2, 0.8 +/- 0.03, and 0.8 +/- 0.02, respectively; sham, 0.5 +/- 0.02), but significantly reduced by HTS (0.7 +/- 0.02). HO-1 was induced by SMAO and low- and high-volume LR solution (0.33 +/- 0.02, 0.32 +/- 0.03, and 0.37 +/- 0.4, respectively; sham, 0.0 +/- 0.0), but was further increased with HTS (0.49 +/- 0.04). CONCLUSION: HTS resuscitation protects against inflammation, injury, and impaired intestinal transit after gut I/R in part by inducing HO-1. This is a novel mechanism of HO-1 protection.

Abdominal compartment syndrome: the cause or effect of postinjury multiple organ failure.

Abdominal compartment syndrome (ACS) has emerged to be a significant problem in patients who develop postinjury multiple organ failure (MOF). Current laboratory research suggests that ACS could be a second hit for the development of MOF. Recent studies demonstrate that ACS is an independent predictor of MOF and that the prevention of ACS decreases the incidence of MOF. The Trauma Research Centers at the University of Colorado and the University of Texas-Houston Medical School are focused on defining the role of the gut in postinjury MOF. Because ACS is a plausible modifiable risk factor, our interest has been to 1) describe the epidemiology of ACS, 2) build prediction models, 3) provide strategies for prevention and treatment of ACS, and 4) develop relevant laboratory models. This review summarizes our findings.

Hypothermia protects against gut ischemia/reperfusion-induced impaired intestinal transit by inducing heme oxygenase-1.

PURPOSE: Gut ischemia/reperfusion (I/R) elicits an inflammatory response that impairs intestinal transit. We have previously shown that regional intraischemic hypothermia (IH) protects against moderate gut I/R-induced mucosal injury, is associated with decreased NF-kappaB activity and inducible nitric oxide synthase induction and preserves heme oxygenase-1 (HO-1) expression. HO-1 provides cytoprotection in various models of oxidant stress. We, therefore, tested the hypothesis that IH protects against gut I/R-induced impaired intestinal transit via HO-1 induction. MATERIALS AND METHODS: At laparotomy (lap), Sprague-Dawley rats had duodenal catheters placed followed by sham or gut I/R (superior mesenteric artery occlusion for 75 min) with or without regional IH (15 degrees C). Each animal was placed on a heating blanket maintaining systemic normothermia (37 degrees C). At 12 or 24 h of reperfusion, small intestinal transit was determined by quantitating the distribution of a tracer (FITC dextran) in the intestine 30 min after instillation (expressed as geometric center of distribution). Ileal samples were obtained for histology and HO-1 expression, assessed by Western immunoblot at 12 and 24 h of reperfusion. In separate experiments, rats were pretreated with an HO-1 inhibitor Sn protoporphyrin IX (25 mumol/kg, ip), 1 h before superior mesenteric artery occlusion and transit measured as above. RESULTS: Rats treated with I/R had increased histological injury and impaired intestinal transit at both 12 and 24 h compared with sham. Rats treated with I/R+IH exhibited histological injury and transit comparable with sham controls. I/R induced HO-1 expression at 12 and 24 h of reperfusion and IH augmented this I/R-induced HO-1 expression. Sn protoporphyrin IX abrogated IH protection against histological injury and impaired transit. CONCLUSION: We conclude that intraischemic regional hypothermia protects against histological injury and impaired intestinal transit caused by severe gut I/R injury. Hypothermic protection under these conditions is in part due to HO-1 expression.