Jörg C. Kalff

Role of inducible nitric oxide synthase in postoperative intestinal smooth muscle dysfunction in rodents

BACKGROUND & AIMSnWe have shown that intestinal manipulation leads to a significant inhibition of circular muscle contraction. We hypothesized that the inflammatory mediator inducible nitric oxide (NO) plays a role in surgically induced ileus.nnnMETHODSnRats and inducible NO synthase (iNOS) knockout and wild-type mice underwent a simple intestinal manipulation. Reverse-transcription polymerase chain reaction and immunohistochemistry were used to detect and localize iNOS expression. Nitrite and NO production were measured in muscularis cultures. Spontaneous and bethanechol-stimulated jejunal circular muscle contractions were measured in an organ bath.nnnRESULTSnIntestinal manipulation resulted in significant iNOS messenger RNA induction in mucosa and muscularis. Immunohistochemistry localized iNOS in phagocytes within the muscularis. Nitrite and NO production increased 59.8-fold 24 hours after manipulation. L-n(6)-(1-iminoethyl) lysine (L-NIL) inhibited this response. In control rats, selective iNOS inhibition did not increase spontaneous muscle activity, but after manipulation L-NIL significantly improved spontaneous activity. iNOS knockout mice showed a significant 81% decrease in neutrophil infiltration into the muscularis after intestinal manipulation compared with wild-types. Contractile activity was normal in knockout mice after intestinal manipulation.nnnCONCLUSIONSnThese results show that leukocyte-derived inducible NO inhibits gastrointestinal motility after manipulation and plays an essential role in the initiation of intestinal inflammation.

Intra-Abdominal Activation of a Local Inflammatory Response Within the Human Muscularis Externa During Laparotomy

ObjectiveTo investigate the initiation of a complex inflammatory response within the human intestinal muscularis intraoperatively so as to determine the clinical applicability of the inflammatory hypothesis of postoperative ileus. Summary Background DataMild intestinal manipulation in rodents initiates the activation of transcription factors, upregulates proinflammatory cytokines, and increases the release of kinetically active mediators (nitric oxide and prostaglandins), all of which results in the recruitment of leukocytes and a suppression in motility (i.e., postoperative ileus). MethodsHuman small bowel specimens were harvested during abdominal procedures at various times after laparotomy. Histochemical and immunohistochemical techniques were applied to intestinal muscularis whole-mounts. Reverse transcriptase–polymerase chain reaction (RT-PCR) was performed for interleukin (IL)-6, IL-1&bgr;, tumor necrosis factor (TNF)-&agr;, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). Signal transducers and activators of transcription (STAT) protein phosphorylation was determined by electromobility shift assay. Organ bath experiments were performed on jejunal circular smooth muscle strips. GW274150C and DFU were used in vitro as iNOS and COX-2 inhibitors. ResultsNormal human muscularis externa contained numerous macrophages that expressed increased lymphocyte function associated antigen-1 (LFA-1) immunoreactivity as a function of intraoperative time. RT-PCR demonstrated a time-dependent induction of IL-6, IL-1&bgr;, TNF-&agr;, iNOS, and COX-2 mRNAs within muscularis extracts after incision. Mediators were localized to macrophages with STAT protein activation in protein extracts demonstrating local IL-6 functional activity. DFU alone or in combination with GW274150C increased circular muscle contractility. Specimens harvested after reoperation developed leukocytic infiltrates and displayed diminished in vitro muscle contractility. ConclusionsThese human data demonstrate that surgical trauma is followed by resident muscularis macrophage activation and the upregulation, release, and functional activity of proinflammatory cytokines and kinetically active mediators.

Biphasic response to gut manipulation and temporal correlation of cellular infiltrates and muscle dysfunction in rat

BACKGROUNDnSurgical manipulation of the intestine results in the massive movement of leukocytes into the intestinal muscularis at 24 hours. This is associated with muscle inhibition. The aim of this study was to temporally associate leukocyte extravasation with ileus after surgical manipulation.nnnMETHODSnRats underwent a simple manipulation of the small bowel and were killed at various times (0, 0.25, 0.5, 1, 3, 6, 12, and 24 hours) postoperatively. Jejunal circular-muscle contractile activity was assessed in a standard organ bath. Both extravasating and resident leukocytes were immunohistochemically stained in muscularis whole mounts.nnnRESULTSnContractile activity was significantly reduced immediately after surgery, but rapidly returned to control levels at 3 hours. After recovery, muscle function decreased at 12 and 24 hours (41% and 81%, respectively). The resident muscularis macrophage network demonstrated cellular activation 1 hour postoperatively. The number of leukocytes increased over time (neutrophils, 67.5-fold; monocytes, 98.2-fold; and mast cells, 47-fold at 24 hours).nnnCONCLUSIONSnThe functional results demonstrate a biphasic response in the suppression of muscle activity after surgical manipulation. Regression analysis (r2 = 0.998) of the temporal development of leukocyte infiltration and the protracted phase of muscle inhibition provides evidence for a correlation between cellular inflammation and postoperative dysmotility.

LPS-induced muscularis macrophage nitric oxide suppresses rat jejunal circular muscle activity.

Cellular mechanisms of sepsis-induced ileus remain an enigma. The study aim was to determine the role of nitric oxide (NO) in mediating the suppression of rat jejunal circular smooth muscle activity during endotoxemia. Isolated muscularis inducible NO synthase (iNOS) mRNA was measured by RT-PCR, immunohistochemistry was employed to localize iNOS protein, and contractile activity was measured in an organ bath. The low basal expression of muscularis iNOS mRNA expression was increased in a time-dependent fashion after lipopolysaccharide (LPS), resulting in a 20-fold increase over controls 3 h after injection. Immunohistochemistry of muscularis whole mounts and dissociated muscularis cells for iNOS revealed staining only in the muscularis macrophages 12 h after LPS. LPS caused a 68% reduction in spontaneous muscle activity 12 h after injection, which improved by 53% after the in vitro application of the selective iNOS inhibitorl- N 6-(1-iminoethyl)lysine. Similar results were obtained in C57BL/6 mice but not in iNOS knockout mice. These data demonstrate that macrophage iNOS plays an important role in mediating LPS-induced intestinal circular muscle suppression.

Interleukin-6 production in hemorrhagic shock is accompanied by neutrophil recruitment and lung injury

Hemorrhagic shock (HS) initiates an inflammatory cascade that includes the production of cytokines and recruitment of neutrophils (PMN) and may progress to organ failure, inducing acute respiratory distress syndrome (ARDS). To examine the hypothesis that interleukin-6 (IL-6) contributes to PMN infiltration and lung damage in HS, we examined the lungs of rats subjected to unresuscitated and resuscitated HS for the production of IL-6 and activation of Stat3. Using semiquantitative RT-PCR, we found a striking increase in IL-6 mRNA levels only in resuscitated HS, with peak levels observed 1 h after initiation of resuscitation. Increased IL-6 protein expression was localized to bronchial and alveolar cells. Electrophoretic mobility shift assay of protein extracts from shock lungs exhibited an increase in Stat3 activation with kinetics similar to IL-6 mRNA. In situ DNA binding assay determined Stat3 activation predominantly within alveoli. Intratracheal instillation of IL-6 alone into normal rats resulted in PMN infiltration into lung interstitium and alveoli, marked elevation of bronchoalveolar lavage cellularity, and increased wet-to-dry ratio. These findings indicate that IL-6 production and Stat3 activation occur early in HS and may contribute to PMN-mediated lung injury, including ARDS after HS.Hemorrhagic shock (HS) initiates an inflammatory cascade that includes the production of cytokines and recruitment of neutrophils (PMN) and may progress to organ failure, inducing acute respiratory distress syndrome (ARDS). To examine the hypothesis that interleukin-6 (IL-6) contributes to PMN infiltration and lung damage in HS, we examined the lungs of rats subjected to unresuscitated and resuscitated HS for the production of IL-6 and activation of Stat3. Using semiquantitative RT-PCR, we found a striking increase in IL-6 mRNA levels only in resuscitated HS, with peak levels observed 1 h after initiation of resuscitation. Increased IL-6 protein expression was localized to bronchial and alveolar cells. Electrophoretic mobility shift assay of protein extracts from shock lungs exhibited an increase in Stat3 activation with kinetics similar to IL-6 mRNA. In situ DNA binding assay determined Stat3 activation predominantly within alveoli. Intratracheal instillation of IL-6 alone into normal rats resulted in PMN infiltration into lung interstitium and alveoli, marked elevation of bronchoalveolar lavage cellularity, and increased wet-to-dry ratio. These findings indicate that IL-6 production and Stat3 activation occur early in HS and may contribute to PMN-mediated lung injury, including ARDS after HS.

Hemorrhagic shock results in intestinal muscularis intercellular adhesion molecule (ICAM-1) expression, neutrophil infiltration, and smooth muscle dysfunction

Abstract Intestinal stasis followed by mucosal barrier breakdown and the generation of locally produced cytokines has been proposed as the cause of systemic infection and multiple organ failure following hemorrhagic shock. The aim of this study was to investigate the underlying mechanisms of impaired intestinal muscle function leading to ileus following hemorrhagic shock. Rats were subjected to severe hemorrhagic shock (mean arterial pressure 40 mmu2002Hg) followed by resuscitation and were killed early at 4 h or late at 24 h. Other groups consisted of control and sham animals. Intercellular adhesion molecule (ICAM-1) mRNA levels were significantly elevated in the muscularis but not in the mucosa using the semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR). There was a marked infiltration of neutrophils into the muscularis early and late after shock. Furthermore, smooth muscle contractility in response to bethanechol was significantly decreased, being more pronounced in the early group. Immunohistochemistry revealed signal for ICAM-1 in the muscularis microvasculature and on infiltrating cells. These results suggest that the expression of ICAM-1 within the muscularis vasculature after hemorrhagic shock promotes the local recruitment of leukocytes and that this inflammatory response is accompanied by a subsequent impairment of intestinal contractility.

Impaired Gut Contractility Following Hemorrhagic Shock is Accompanied by IL-6 and G-CSF Production and Neutrophil Infiltration

Recovery from hemorrhagic shock (HS) is frequently accompanied by bowel stasis. The aim of this study was to examine whether or not HS initiates an inflammatory response that includes production of cytokines, specifically G-CSF and interleukin-6 (IL-6), and recruitment of leukocytes within the intestinal muscularis which contribute to impaired muscle contractility. Sprague-Dawley rats were subjected to HS (MAP 40 mm Hg for 156 min) followed by resuscitation, and then they were killed at 4 hr. Shock animals demonstrated accumulation of PMNs in the jejunal muscularis and decreased spontaneous and bethanechol-stimulated muscle contractility. Semiquantitative RT-PCR demonstrated elevated levels of IL-6 and G-CSF mRNA in shock animals in full-thickness jejunum and in mucosa and muscularis layers compared to sham controls. Immunostaining demonstrated increased IL-6 protein production within the muscularis externa and submucosa. In situ hybridization studies localized G-CSF mRNA production to the submucosa. Gel shift assays revealed increased NF-κB and Stat3 activity in full-thickness jejunum and jejunal layers of shock animals. Activation of Stat3 also was demonstrated in normal muscularis tissue exposed to IL-6 and G-CSF in vitro. IL-6 and G-CSF are produced in the muscularis and mucosa layers of the gut in HS where they may contribute to PMN recruitment and smooth muscle dysfunction.

Activation of STAT proteins in the lung of rats following resuscitation from hemorrhagic shock.

Abstract Hemorrhagic shock (HS) initiates a series of inflammatory processes, including the production of proinflammatory cytokines at critical sites such as the lung. We have previously shown that granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6) mRNA are produced in the lungs of rats subjected to resuscitated HS and that both the ischemic and reperfusion phases of resuscitated HS were required. G-CSF and IL-6 activate STAT (signal transducers and activators of transcription) proteins which may sustain the inflammatory response that follows resuscitation in HS. We tested the hypothesis that STAT proteins are activated in the lungs of rats subjected to resuscitated HS and examined the factors contributing to their activation including duration of shock and duration of resuscitation. Sprague-Dawley rats were subjected to compensated (66.1 ± 1.1 min) or decompensated (157.3 ± 2.3 min) HS (mean arterial pressure 40 mmHg) followed by resuscitation and sacrifice at 4 or 8 h. The amount of activated Stat3 was increased 2.3- to 7-fold compared with sham control animals in all four experimental groups of resuscitated HS. Levels of Stat3 activation increased with increase in duration of shock but did not demonstrate differences at the 4 or 8 h time point of killing. These results indicate that resuscitated HS results in the activation of the intracellular signaling cascade that includes that activation of STAT proteins driven by cytokines such as G-CSF and IL-6.

Selective coinduction of cyclooxygenase-2 and inducible nitric oxide synthase in human intestinal smooth muscle during abdominal surgery

Postoperative ileus continues to be a major cause of prolonged hospitalization and morbidity after laparotomy. We have previously demonstrated that endotoxin-activation of the dense network of resident macrophages in the small bowel muscularis modulates muscle function through the rapid release of prostanoids and nitric oxide. Furthermore, in vitro activation of mouse macrophages by endotoxin has been shown to increase the inducible enzymes cyclonxygenase (COX-2) and nitric oxide synthase (iNnS). The aim of this study was to investigate the coinduction of these enzymes in the human gut after surgical manipulation. We obtained human small bowel specimens at two time points during common abdominal surgical procedures: early less than 60 minutes and late greater than three hours after incision. The mucosa and muscularis layers was isolated, rapidly frozen in liquid nitroge n and stored for RNA extraction. Semi-quantitative RT-PCR was used to measure COX-2 and iNnS mRNA levels in the separated layers. Fixed museularis whole-mounts were stained immunnhistochemically using monoclonal antibodies against COX-2, iNnS, macrnphages and the activation marker LFA-Ic~. Both inducible enzymes were strongly expressed in the separated layers at both time points. COX-2 and iNnS mRNA-levels were significantly increased in late compared to early specimens only in the muscularis (COX-2 3.4 fold, iNnS 2.2 fold, p<0.05), mucosal levels did not change. Immunohistochemistry showed a dense network of resident macrophages within the muscularis. LFA-la and iNnS positive cells were increased in late specimens, whereas early specimens were either negative or displayed only a weak signal. Morphologically, LFA-I~ and iNnS positive cells appeared to be macrophages. These results demonstrate that common abdominal surgical procedures activate resident macrophages in the muscularis extema and upregulate COX-2 and iNnS within human intestinal smooth muscle. The data suggest that the production of prnstaglandins and nitric oxide by muscularis macrophages could play a major role in the development of postoPerative ileus.

Bacterial Toxin N-Formyl-Methionyl-Leucyl-Phenylalanine Acutely Contracts Human and Rabbit Detrusor Through the Release of Eicosanoids

PURPOSEnUropathogenic bacteria that secrete N-formylmethionyl oligopeptides such as N-formyl-methionyl-leucyl-phenylalanine (f-MLP) are a common cause of urinary tract infections. We determined the in vitro effects of f-MLP on human and rabbit detrusor as well as its mechanism and site of action.nnnMATERIALS AND METHODSnReverse transcriptase-polymerase chain reaction was used to investigate cyclooxygenase-2 messenger RNA within the rabbit detrusor. Standard mechanical organ bath recording techniques were used to measure contractile activity from rabbit and human detrusor muscle strips. Immunohistochemistry was performed using macrophage specific antibodies (human BerMAC3 and rabbit RAM11) on detrusor whole mount specimens.nnnRESULTSnMuscle activity recorded from human and rabbit detrusor showed that f-MLP caused contracture of the detrusor, which was completely blocked by indomethacin and partially blocked by individual cyclooxygenase-1 and cyclooxygenase-2 selective inhibitors. Exposure of the detrusor to exogenous prostaglandins indicated that f-MLP released an effective concentration of more than 1 microM. from an endogenous source. Immunohistochemical staining of the human (BerMAC3) and rabbit (RAM11) bladder demonstrated a dense network of resident macrophages lying within the detrusor muscle bundles, which are known to secrete prostaglandins during the activation of specific f-MLP receptors.nnnCONCLUSIONSnBacterial derived f-MLP contracts the detrusor through the release of eicosanoids from resident macrophages. These data suggest that bacterial activation of the resident macrophage network could participate in causing the symptoms of bacterial cystitis.