Rapid activation of NF-kappaB and AP-1 and target gene expression in postischemic rat intestine

Genome-wide gene expression profiling of ischemia-reperfusion injury in rat kidney, intestine and skeletal muscle implicate a common involvement of MAPK signaling pathway

The mechanisms of ischemia‑reperfusion (I/R) injury have not been fully elucidated to date. In order to determine the genetic involvement across different organs during I/R injury, a DNA microarray approach was used to analyze the gene expression profiles of the kidney, intestine, and skeletal muscle in a rat model of I/R injury. Fifteen male Lewis rats were divided randomly into three different organ groups; a sham operation (control group), 60‑min‑ischemia (Is group) only, and 60‑min‑ischemia plus 60‑min‑reperfusion (I/R group), respectively. The target genes were identified by DNA microarray and studied by quantitative polymerase chain reaction (qPCR). By comparing the I/R group with the control group, a 2‑fold upregulation of 467, 172, and 3932 and a 2‑fold downregulation of 437, 416, and 4203 genes were identified in the kidney, small intestine, and skeletal muscle, respectively. Several commonly upregulated genes associated with mitogen‑activated protein kinase (MAPK) pathways, including Jun, Atf3, junB, Fos, Adm and Dusp 1, were differentially expressed in the I/R group. The mRNA expression levels of the target genes were confirmed by qPCR. The present study hypothesized that the MAPK pathway may function in a common pathway of I/R injury and regulate the pathogenesis through activator protein 1. The findings of the present study contributed to the understanding of the molecular pathways associated with I/R injury.

Multidirectional and simultaneous evaluation of gastroschisis-related intestinal damage in chick embryos

PURPOSE

In a chick model of gastroschisis, we aimed to investigate the morphological/cellular, molecular, and ultrastructural changes taking place in gastroschisis-related intestinal damage (GRID).

METHODS

13-Day fertilized eggs were divided into two groups.

CONTROL GROUP

chorio-amnio-allontoic membranes opened and abdominal wall exposed. Gastroschisis group: an anterior abdominal wall defect created after opening membranes. Embryos from both groups were surgically removed on post-fertilization day 19. Intestinal samples were obtained for histopathology, immunohistochemistry, molecular biology, and electron microscopy.

RESULTS

The histopathological grade of intestinal damage which primarily involved mucosal structures was significantly higher in the gastroschisis group when compared to the control group (p<0.001). Immunohistochemically, E-cadherin and synaptophysin immunoreactivity in the gastroschisis group was significantly lower than control group (p<0.05 and p<0.01, respectively), whereas there was no significant difference in laminin and type-4 collagen immunoreactivity between the groups (p>0.05). Molecular analyses indicated a significant decrease in NFκB and IκB expression in the gastroschisis group (p<0.05 and p=0.001, respectively). Electron microscopy showed that the gastroschisis group had considerable ultrastructural damage, manifested by apoptosis in all layers.

CONCLUSIONS

GRID affected all layers but was more prominent in mucosa. The damage may depend on E-cadherin and synaptophysin downregulation. Increased apoptotic activity, associated with decreased NFκB and IκB expression, may be an important component of this multifactorial damaging process.

Protective effects of icariin-mediated SIRT1/FOXO3 signaling pathway on intestinal ischemia/reperfusion-induced acute lung injury

Acute lung injury (ALI) is a common complication following intestinal ischemia/reperfusion (I/R) and is a major contributing factor to its high mortality rate. Sirtuin 1 (SIRT1), a NAD+-dependent deacetylase, has been reported to have an important role in apoptosis inhibition, oxidative stress resistance and cell lifespan extension through its deacetylation of forkhead box protein O3 (FOXO3). It has been demonstrated that icariin (ICA), a flavonoid extracted from Epimedium, upregulates SIRT1 expression. The aim of the present study was to examine whether ICA-mediated SIRT1/FOXO3 signaling pathway activation had a protective effect on intestinal I/R-induced ALI. The effects of ICA on intestinal I/R-induced ALI and its regulation of the SIRT1/FOXO3 signaling pathway on intestinal I/R-induced ALI were investigated in rats. The results demonstrated that ICA pretreatment markedly reduced intestinal I/R-induced ALI as indicated by histological alterations, including decreased tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), reduced oxidative stress, acetylated FOXO3 and B-cell lymphoma 2 (Bcl-2)-interacting mediator of cell death levels, and increased glutathione (GSH), GSH peroxidase, SIRT1, manganese superoxide dismutase and Bcl-2 levels in rat lung tissues. Furthermore, ICA pretreatment upregulated SIRT1 expression, which then downregulated FOXO3 acetylation. In conclusion, ICA exhibited significant protective effects in intestinal I/R-induced ALI. The protective effect of ICA may be attributed to the upregulation of SIRT1, which contributed to FOXO3 deacetylation and the modulation of downstream antioxidative and anti-apoptotic factors.

VSL#3 probiotics provide protection against acute intestinal ischaemia/reperfusion injury

Acute intestinal ischaemia/reperfusion injury (AII/R) is an adaptive physiologic response during critical illness, involving mesenteric vasoconstriction and hypoperfusion. Prevention of AII/R in high risk patient populations would have a significant impact on morbidity and mortality. The purpose of this study was to investigate the protective effects of VSL#3 probiotic treatment in a murine model of AII/R. Adult 129/SvEv mice were subjected to an experimental AII/R model using superior mesenteric artery occlusion. Animals were pre-treated with either three days or two weeks of VSL#3 probiotics. Local tissue injury markers were assessed by levels of myeloperoxidase and activation of nuclear factor kappa B (NFкB). Systemic and local cytokines, including interleukin (IL)-1β, IL- 10, TNFα, and interferon gamma were measured by ELISA and multiplex fluorescent detection. VSL#3 probiotics reduced local tissue inflammation and injury due to AII/R. A two-week course of VSL#3 was more effective than a shorter three-day course. The reduction in local inflammation from the two-week course of VSL#3 is correlated to a significant reduction in levels of active IL-1β, and tissue levels of myeloperoxidase. Levels of active NFкB were significantly elevated in the vehicle-fed AII/R mice, corroborating with tissue inflammation, which were attenuated by VSL#3 administrations. VSL#3 did not cause any systemic inflammation or lung injury. VSL#3 probiotics are effective in reducing local tissue injury from AII/R by down-regulating pro-inflammatory mediators and immune cell recruitment. This study highlights a potential role for VSL#3 in management of patients at high risk for AII/R.

Hypoxia-inducible factor-2α and iron absorptive gene expression in Belgrade rat intestine

The divalent metal transporter (DMT1, Slc11a2) is an important molecule for intestinal iron absorption. In the Belgrade (b/b) rat, the DMT1 G185R mutation markedly decreases intestinal iron absorption. We used b/b rats as a model to examine the genes that could be compensatory for decreased iron absorption. When tissue hypoxia was assayed by detecting pimonidazole HCl adducts, the b/b liver and intestine exhibited more adducts than the +/+ rats, suggesting that hypoxia might signal altered gene expression. Total RNA in the crypt-villus bottom (C-pole) and villus top (V-pole) of +/+, b/b, and iron-fed b/b rats was isolated for gene array analyses. In addition, hepatic hepcidin and intestinal hypoxia-inducible factor-α (Hifα) expression were examined. The results showed that expression of hepatic hepcidin was significantly decreased and intestinal Hif2α was significantly increased in b/b and iron-fed b/b than +/+ rats. In b/b rats, the expression of Tfrc mRNA in the C-pole and of DMT1, Dcytb, FPN1, Heph, Hmox1, and ZIP14 mRNAs in the V-pole were markedly enhanced with increases occurring even in the C-pole. After iron feeding, the increased expression found in b/b rats persisted, except for Heph and ZIP14, which returned to normal levels. Thus in b/b rats depressed liver hepcidin production and activated intestinal Hif2α starting at the C-pole resulted in increasing expression of iron transport genes, including DMT1 G185R, in an attempt to compensate for the anemia in Belgrade rats.

Hypoxia-inducible factor plays a gut-injurious role in intestinal ischemia reperfusion injury

Gut injury and loss of normal intestinal barrier function are key elements in the paradigm of gut-origin systemic inflammatory response syndrome, acute lung injury, and multiple organ dysfunction syndrome (MODS). As hypoxia-inducible factor (HIF-1) is a critical determinant of the physiological and pathophysiological response to hypoxia and ischemia, we asked whether HIF-1 plays a proximal role in the induction of gut injury and subsequent lung injury. Using partially HIF-1α-deficient mice in an isolated superior mesenteric artery occlusion (SMAO) intestinal ischemia reperfusion (I/R) injury model (45 min SMAO followed by 3 h of reperfusion), we showed a direct relationship between HIF-1 activation and intestinal I/R injury. Specifically, partial HIF-1α deficiency attenuated SMAO-induced increases in intestinal permeability, lipid peroxidation, mucosal caspase-3 activity, and IL-1β mRNA levels. Furthermore, partial HIF-1α deficiency prevented the induction of ileal mucosal inducible nitric oxide synthase (iNOS) protein levels after SMAO and iNOS deficiency ameliorated SMAO-induced villus injury. Resistance to SMAO-induced gut injury was also associated with resistance to lung injury, as reflected by decreased levels of myeloperoxidase, IL-6 and IL-10 in the lungs of HIF-1α(+/-) mice. In contrast, a short duration of SMAO (15 min) followed by 3 h of reperfusion neither induced mucosal HIF-1α protein levels nor caused significant gut and lung injury in wild-type or HIF-1α(+/-) mice. This study indicates that intestinal HIF-1 activation is a proximal regulator of I/R-induced gut mucosal injury and gut-induced lung injury. However, the duration and severity of the gut I/R insult dictate whether HIF-1 plays a gut-protective or deleterious role.

Role of transcription factors in small intestinal ischemia-reperfusion injury and tolerance induced by ischemic preconditioning

BACKGROUND

Small intestinal ischemia-reperfusion (I/R) injury, a clinically important condition, induces severe organ damage. Ischemic preconditioning (IPC) produces tolerance to long-term I/R by inducing a short-term I/R. Herein, we have examined the reduction in the extent of injury by IPC.

METHODS

Small intestinal I/R injury was induced in rats by clamping the superior mesenteric artery (SMA) for 30 minutes followed by reperfusion for various 30 minutes. The IPC + I/R group underwent a short-term I/R (IPC) prior to long-term I/R. Nuclear factor-κB (NF-κB) activity was analyzed by an electrophoretic mobility shift assay and cytokine mRNA levels, by reverse transcription-polymerase chain reaction. Apoptosis-related genes were analyzed by Western blotting and immunohistochemistry, and apoptotic cells, by TUNEL staining.

RESULTS

The animals were subjected to 30 minutes of ischemia followed by 30 minutes of reperfusion. NF-κB activity increased in the I/R group and decreased in the IPC + I/R group. The IPC + I/R group showed decreased cytokine in mRNA levels. Expression of the proapoptotic gene caspase-3 was increased in the I/R and decreased in the IPC + I/R group. Expression of the antiapoptotic gene Bcl-xL was increased in the IPC + I/R group. The number of apoptotic cells was increased in the I/R and decreased in the IPC + I/R group.

CONCLUSION

Small intestinal I/R injury was reduced by IPC produced by clamping the SMA; thus, IPC may have potential clinical applications in the future.

Claude H. Organ, Jr. memorial lecture: splanchnic hypoperfusion provokes acute lung injury via a 5-lipoxygenase-dependent mechanism

Postinjury multiple organ failure (MOF) is the net result of a dysfunctional immune response to injury characterized by a hyperactive innate system and a suppressed adaptive system. Acute lung injury (ALI) is the first clinical manifestation of organ failure, followed by renal and hepatic dysfunction. Circulatory shock is integral in the early pathogenesis of MOF, and the gut has been invoked as the motor of MOF. Mesenteric lymph is recognized as the mechanistic link between splanchnic ischemia/reperfusion and distant organ dysfunction, but the specific mediators remain to be defined. Current evidence suggests the lipid fraction of postshock mesenteric lymph is central in the etiology of ALI. Specifically, our recent work suggests that intestinal phospholipase A2 generated arachidonic acid and its subsequent 5-lipoxygenase products are essential in the pathogenesis of ALI. Proteins conveyed via postshock mesenteric lymph also may have an important role. Elucidating these mediators and the timing of their participation in pulmonary inflammation is critical in translating our current knowledge to new therapeutic strategies at the bedside.

HIF-1 mediates pathogenic inflammatory responses to intestinal ischemia-reperfusion injury

Acute lung injury (ALI) and the development of the multiple organ dysfunction syndrome (MODS) are major causes of death in trauma patients. Gut inflammation and loss of gut barrier function as a consequence of splanchnic ischemia-reperfusion (I/R) have been implicated as the initial triggering events that contribute to the development of the systemic inflammatory response, ALI, and MODS. Since hypoxia-inducible factor (HIF-1) is a key regulator of the physiological and pathophysiological response to hypoxia, we asked whether HIF-1 plays a proximal role in the induction of gut injury and subsequent lung injury. Utilizing partially HIF-1α-deficient mice in a global trauma hemorrhagic shock (T/HS) model, we found that HIF-1 activation was necessary for the development of gut injury and that the prevention of gut injury was associated with an abrogation of lung injury. Specifically, in vivo studies demonstrated that partial HIF-1α deficiency ameliorated T/HS-induced increases in intestinal permeability, bacterial translocation, and caspase-3 activation. Lastly, partial HIF-1α deficiency reduced TNF-α, IL-1β, cyclooxygenase-2, and inducible nitric oxide synthase levels in the ileal mucosa after T/HS whereas IL-1β mRNA levels were reduced in the lung after T/HS. This study indicates that prolonged intestinal HIF-1 activation is a proximal regulator of I/R-induced gut mucosal injury and gut-induced lung injury. Consequently, these results provide unique information on the initiating events in trauma-hemorrhagic shock-induced ALI and MODS as well as potential therapeutic insights.

Intestinal ischemia/reperfusion injury: defining the role of the gut microbiome

Intestinal ischemia/reperfusion (I/R) injury initiates a systemic inflammatory response syndrome with a high associated mortality rate. Early diagnosis is essential for reducing surgical mortality, yet current clinical biomarkers are insufficient. Metabonomics is a novel strategy for studying intestinal I/R, which may be used as part of a systems approach for quantitatively analyzing the intestinal microbiome during gut injury. By deconvolving the mammalian–microbial symbiotic relationship systems biology thus has the potential for personalized risk stratification in patients exposed to intestinal I/R. This review describes the mechanism of intestinal I/R and explores the essential role of the intestinal microbiota in the initiation of systemic inflammatory response syndrome. Furthermore, it analyzes current and future approaches for elucidating the mechanism of this condition.

Post-ischaemic restituted intestinal mucosa is more resistant to further ischaemia than normal mucosa in the pig

OBJECTIVE

Ischaemic preconditioning may protect the intestine from subsequent prolonged ischaemia. This study evaluates whether a much longer initial ischaemia, encountered clinically, may modify intestinal resistance to further ischaemia in a pig model.

MATERIAL AND METHODS

After cross-clamping of the superior mesenteric artery for 1 h, the intestine was either reperfused for 8 h or a second cross-clamping for 1 h was performed at 4 h of reperfusion. Based on microarray analysis of intestinal samples at 1, 4 and 8 h of reperfusion, mRNA of selected genes was measured with QRT-PCR.

RESULTS

The first ischaemic period caused exfoliation of surface epithelial cells from the basement membrane comprising about 90 % of the villi tips, a marked increase in permeability and depletion of ATP. The second ischaemic challenge caused about 30 % less denudation of the basement membrane (p = 0.008), no increase in permeability (p = 0.008) and less depletion of ATP (p = 0.039). mRNAs for superoxide dismutase 2, heat shock proteins and signal transducer and activator of transcription 3, which may protect against ischaemia/reperfusion injury, were up-regulated throughout the reperfusion period. mRNAs for matrix metalloproteinase 1, connexin 43 and peripheral myelin 22, which may be associated with cell migration or tight junctions, showed a particular up-regulation at 4 h of reperfusion.

CONCLUSION

One hour of initial ischaemia followed by 4 h of reperfusion is associated with increased intestinal resistance to further ischaemia. The differential regulation of genes identified in this study provides working hypotheses for mechanisms behind this observation.

Natural IgM-mediated innate autoimmunity: a new target for early intervention of ischemia-reperfusion injury

Recent studies showed that innate autoimmunity is an early mechanism for ischemia-reperfusion (I/R) injury. Results from different animal models showed that reperfusion of ischemic tissues elicits an acute inflammatory response involving a complement system, which is activated by autoreactive natural IgM. Moreover, ischemia-specific self-targets were identified. In contrast to the unsuccessful attempts in the past to treat I/R injury, targeting natural IgM-mediated innate autoimmunity may open a new avenue for early intervention.

The effect of remote ischemic preconditioning on healing of colonic anastomoses

BACKGROUND

We aimed to investigate the potential protective effect of remote ischemic preconditioning (IPC) on delayed colonic anastomotic healing induced by remote ischemia and reperfusion (I/R) injury.

MATERIALS AND METHODS

Forty male Wistar rats were randomly assigned into four groups, each consisting of 10 rats: the control group (C), the remote I/R group [I/R, 40 min of superior mesenteric artery (SMA) occlusion], the preconditioned I/R group (IPC, two cycles of 5 min temporary occlusion of SMA before an ischemic insult of 40 min), and the preconditioned group (PC, two cycles of 5 min temporary occlusion of SMA). Colonic anastomosis was performed immediately after the ischemic insult. Anastomotic healing was assessed on postoperative day 7 by determining anastomotic bursting pressure (ABP), tissue hydroxyproline content, histopathological examination, malondialdehyde (MDA), and nitric oxide levels.

RESULTS

Remote I/R injury resulted with significant impairment in anastomotic healing in terms of mean ABP (P = 0.004), hydroxyproline content (P = 0.002), histopathological healing score (P = 0.001), nitric oxide level (P = 0.010), and MDA levels (P = 0.0001) when compared with the control group, but remote IPC did not improve all above mentioned parameters (P = NS for all), except MDA level (P = 0.011) when compared with I/R group. PC alone impaired the ABP (P = 0.0001), but it did not significantly change the other parameters measured (P = NS).

CONCLUSIONS

The results of this study showed that remote IPC did not prevent I/R-induced delaying in colonic anastomotic healing.

Role of neuropeptides in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, relapsing condition involving complex interactions between genes and the environment. The mechanisms triggering the initial attack and relapses, however, are not well understood. In the past several years the enteric nervous system (ENS) has been implicated in the pathophysiology of IBD. Both the ENS and the central nervous system (CNS) can amplify or modulate aspects of intestinal inflammation through secretion of neuropeptides that serve as a link between the ENS and CNS. Neuropeptides are defined as any peptide released from the nervous system that serves as an intercellular signaling molecule. Neuropeptides thought to play a potentially key role in IBD include substance P, corticotropin-releasing hormone, neurotensin, vasoactive intestinal peptide, mu-opioid receptor agonists, and galanin. This review focuses on the role of these neuropeptides in the pathophysiology of IBD and discusses the cell types and mechanisms involved in this process. The available evidence that neuropeptide blockade may be considered a therapeutic approach in both Crohn's disease and ulcerative colitis will also be discussed.

Donor pretreatment with FK506 reduces reperfusion injury and accelerates intestinal graft recovery in rats

BACKGROUND

FK506 alleviates warm ischemia-reperfusion injury, but it remains unknown if such protection is manifest after cold storage and transplantation. We studied the early outcome after transplantation of intestines from donors pretreated with FK506 compared to grafts from controls treated with saline (154 mM NaCl).

METHODS

Sprague-Dawley rats received 0.3 mg/kg FK506 or saline intravenously 6 hours before graft retrieval. The small bowel was harvested, stored for 3 hours, and then transplanted heterotopically. Samples were taken after preservation and at 20 minutes, 6 hours, 12 hours, and 24 hours after reperfusion. Heat shock protein 72 (Hsp72) and iintercellular adhesion molecule (ICAM)-1 expression and nuclear factor kappaB (NF-kappaB) activation were assessed via Western blots and eelectrophoretic mobility shift assay (EMSA), respectively. Dissacharidase activity and enterocyte proliferation rate were also studied.

RESULTS

Preservation injury was similar between groups, but pretreated grafts had better morphology already 20 minutes after reperfusion. Control grafts always had thinner mucosa and more PMN infiltration. Hsp72 expression was greater in pretreated grafts. ICAM-1 was absent after harvesting, preservation, and immediately after reperfusion but increased in control grafts at the later time points. Control grafts showed a biphasic NF-kappaB activation pattern, whereas NF-kappaB activation was inhibited effectively in pretreated grafts. Dissacharidase activity decreased during the first 6 hours after reperfusion but recovered within 24 hours in pretreated grafts but not in control grafts. Earlier enterocyte proliferation was observed in pretreated grafts.

CONCLUSIONS

FK506 donor pretreatment reduced graft proinflammatory activation and neutrophil inflammation. Pretreated groups revealed a milder reperfusion injury and accelerated morphologic and functional recovery. The mechanisms involved appear to involve Hsp72 upregulation and NF-kappaB inhibition.

Natural antibody mediated innate autoimmune response

Recent advance in autoimmunity research reveals that the innate immune system is able to recognize self-targets and initiate inflammatory response in a similar way as with pathogens. This review describes one novel example of this innate autoimmunity, ischemia-reperfusion (I/R) injury. Studies of intestinal, skeletal muscle, and heart I/R models showed that reperfusion of ischemic tissues elicits an acute inflammatory response involving serum complement system which is activated by natural IgM. The recent identification of a monoclonal natural IgM that initiates I/R led to the identification of non-muscle myosin heavy chain type II A and C as the self-targets in two different tissues. New evidence further suggests that IgM binds initially to ischemic antigen providing a binding site for mannan binding lectin (MBL) which subsequently leads to activation of complement and results in tissue injury. Therefore, natural IgM mediated innate autoimmunity is likely responsible for the detrimental consequences in ischemic diseases.

Human colonic myocytes are involved in postischemic inflammation through ADAM17-dependent TNFalpha production

The aim of this study was to identify human colonic resident cells able to initiate an inflammatory response in postischemic injury. Postischemic colonic injury, a condition relevant to various clinical settings, involves an inflammatory cascade in intestinal tissues through the recruitment of circulating inflammatory cells. However, there is no information on the nature of resident cells of the different intestinal layers able to initiate a postischemic inflammatory response. It is however an important issue in the context of a pharmacological approach of the early phase of intestinal ischemia. We reasoned that maintaining the different colonic layers as explant cultures in an oxygenated medium immediately after colonic resection, that is, after an ischemic period, would allow one to identify the resident cells able to initiate an inflammatory cascade, without interference of recruited inflammatory/immune cells. To this end, we designed an explant culture system that operationally defines three compartments in surgical specimens of the human colon, based on the microdissected layers, that is, mucosa, submucosa (containing muscularis mucosae) and muscularis propria. To validate the results obtained in explant cultures in the clinical setting of ischemic colitis, eight cases of sigmoid volvulus were examined. Only the myocytes-containing explants produced tumor necrosis factor alpha (TNFalpha), via an ADAM17 (a disintegrin and metalloproteinase-17)-dependent pathway, as shown by the abrogation of TNFalpha production by the inhibitor Tapi-2. Immunofluorescence studies identified nonvascular and vascular myocytes as resident cells coexpressing TNFalpha and ADAM17, both in our postischemic explant system and in surgical specimens from ischemic colitis patients. Finally, time-course experiments on explanted tissues showed that TNFalpha production by myocytes was an early event triggered by a postischemic oxidative stress involving nuclear factor kappa B (NF-kappaB). In conclusion, this study identifies human intestinal myocytes as resident cells able to initiate an inflammatory reaction through TNFalpha production in postischemic conditions, and delineates two points of control in TNFalpha production, NF-kappaB and ADAM17, which can be targeted by pharmacological manipulation.

Diverse patterns of cell-specific gene expression in response to glucocorticoid in the developing small intestine

Although glucocorticoids are known to elicit functional maturation of the gastrointestinal tract, the molecular mechanisms of glucocorticoid action on the developing intestine have not been fully elucidated. Our previous microarray studies identified 66 transcripts as being rapidly induced in the jejunum following dexamethasone (Dex) administration to suckling mice. Now we report the specific cellular location of a subset of these transcripts. Mouse pups at P8 received Dex or vehicle and intestinal segments were collected 3-4 h later. Robotic-based in situ hybridization (ISH) was performed with digoxygenin-labeled riboprobes. Transcripts studied included Ndrg1, Sgk1, Fos, and two unknown genes (Gene 9 and Gene 36). As predicted, ISH revealed marked diversity of cellular expression. In small intestinal segments, Sgk1 mRNA was in all epithelial cells; Fos mRNA was confined to epithelial cells at the villus tip; and Ndrg1 and Gene 36 mRNAs were localized to epithelial cells of the upper crypt and villus base. The remaining transcript (Gene 9) was induced modestly in villus stroma and strongly in the muscle layers. In the colon, Ndrg1, Sgk1, and Gene 36 were induced in all epithelial cells; Gene 9 was in muscle layers only; and Fos was not detectable. For jejunal segments, quantitation of ISH signals in tissue from Dex-treated and vehicle-treated mice demonstrated mRNA increases very similar to those measured by Northern blotting. We conclude that glucocorticoid action in the intestine reflects diverse molecular mechanisms operating in different cell types and that quantitative ISH is a valuable tool for studying hormone action in this tissue.

Hibernation confers resistance to intestinal ischemia-reperfusion injury

The damaging effects of intestinal ischemia-reperfusion (I/R) on the gut and remote organs can be attenuated by subjecting the intestine to a prior, less severe I/R insult, a process known as preconditioning. Because intestines of hibernating ground squirrels experience repeated cycles of hypoperfusion and reperfusion, we examined whether hibernation serves as a model for natural preconditioning against I/R-induced injury. We induced intestinal I/R in either the entire gut or in isolated intestinal loops using rats, summer ground squirrels, and hibernating squirrels during natural interbout arousals (IBA; body temperature 37-39 degrees C). In both models, I/R induced less mucosal damage in IBA squirrels than in summer squirrels or rats. Superior mesenteric artery I/R increased MPO activity in the gut mucosa and lung of rats and summer squirrels and the liver of rats but had no effect in IBA squirrels. I/R in isolated loops increased luminal albumin levels, suggesting increased gut permeability in rats and summer squirrels but not IBA squirrels. The results suggest that the hibernation phenotype is associated with natural protection against intestinal I/R injury.

Effects of NT on gastrointestinal motility and secretion, and role in intestinal inflammation

It is well established that interactions of neuropeptides with several cell types at various parts of the intestine are critically involved in intestinal pathophysiology. Among them, neurotensin has been identified as an important mediator in the development and progress of several gastrointestinal functions and disease conditions, exerting its effects by interacting with specific receptors that exert direct and indirect effects on nerves, epithelial cells, and cells of the immune and inflammatory systems. This review summarizes our recent understanding on the participation of neurotensin in the physiology and pathophysiology of the small and large intestine, and discusses various mechanisms that could be involved in these actions.

Xanthohumol, a prenylflavonoid derived from hops induces apoptosis and inhibits NF-kappaB activation in prostate epithelial cells

There is increasing evidence that certain natural compounds found in plants may be useful as cancer chemopreventive or chemotherapeutic agents. Limited in vitro studies indicate that several prenylated flavonoids present in the hop plant (Humulus lupulus) possess anticarcinogenic properties. The purpose of this study was to investigate the anti-tumorigenic effects of xanthohumol (XN), the major prenylflavonoid in hops, on prostate cancer and benign prostate hyperplasia. BPH-1 and PC3 cell lines were used in our study to represent both non-tumorigenic hyperplasia and malignant prostate cancer. In both BPH-1 and PC3 cells, XN and its oxidation product, XAL, decreased cell viability in a dose dependent manner (2.5-20 microM) as determined by MTT assay and caused an increase in the formation of early and late apoptotic cells as determined by Annexin V staining and multicaspase assays. XN and its oxygenated derivative also induced cell cycle changes in both cells lines, seen in an elevated sub G1 peak at 48h treatment. Western blot analysis was performed to confirm the activation of proapoptotic proteins, Bax and p53. XN and its derivative caused decreased activation of NFkappaB. This work suggests that XN and its oxidation product, XAL, may be potentially useful as a chemopreventive agent during prostate hyperplasia and prostate carcinogenesis, acting via induction of apoptosis and down-regulation of NFkappaB activation in BPH-1 cells.

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.

Heme oxygenase-1 (Hsp32) is involved in the protection of small intestine by whole body mild hyperthermia from ischemia/reperfusion injury in rat

AIM

The aim of the present study was to explore whether heme oxygenase-1 (HO-1) is involved in the hyperthermia-provided protection of the small intestine from ischemia/reperfusion injury in rats.

METHODS

Intestinal damage was induced in male Sprague-Dawley rats by clamping both the superior mesenteric artery and the celiac trunk for 30 min, followed by reperfusion. Whole-body hyperthermia was induced in anesthetized rats by placement in a temperature-controlled water bath. Whole-body hyperthermia to a core temperature of 42-43 degrees C for 15 min was followed by passive cooling. We started the hyperthermic treatment 6 h before the vascular clamping. The severity of the mucosal injury was evaluated by several biochemical markers and histological findings. Hyperthermia-induced heat-shock proteins were detected by Western blotting. We also investigated the effect of zinc protoporphyrin IX (an HO-1 inhibitor) on the protective effect of hyperthermia.

RESULTS

The rats, which were killed after ischemia/reperfusion, had severe intestinal inflammation. Hyperthermia significantly induced the production of Hsp70 and HO-1 in intestinal mucosa and significantly reduced ischemia/reperfusion-induced mucosal injury. The combination of zinc protoporphyrin IX with hyperthermia extinguished the protective effects of hyperthermia on ischemia/reperfusion injury.

CONCLUSION

Hyperthermia protects against ischemia/reperfusion injury in rat small intestine through the expression of heat-shock proteins, especially HO-1.

NF-kappaB plays a major role during the systemic and local acute inflammatory response following intestinal reperfusion injury

1 The nuclear translocation of transcription factors may be a critical factor in the intracellular pathway involved in ischaemia/reperfusion (I/R) injury. Here, we examined whether NF-kappaB and AP-1 participated in the cascade of events leading to TNF-alpha production, neutrophil recruitment, tissue injury and lethality following intestinal I/R. 2 The superior mesenteric artery (SMA) of mice was made ischaemic for 60 min followed by 30 min of reperfusion. The effects of NF-kappaB and AP-1 were studied by the administration of the thioredoxin inhibitor, MOL-294 (methyl 4-hydroxy-4-(8-methyl-1,3-dioxo-2-phenyl-2,3,5,8-tetrahydro-1H-[1,2,4]triazolo[1,2-a]pyridazin-5-yl)but-2-ynoate), and the AP-1 inhibitor, PNRI-299 (N-benzyl-2-(3-cyanophenyl)-1,3,7-trioxo-2,3,7,8-tetrahydro-1H-[1,2,4]triazolo[1,2-a]pyridazine-5-carboxamide). After I/R, there was increase of translocation of NF-kappaB, but not of AP-1, in the intestine and lungs, as assessed by a gel shift assay. 3 Treatment with MOL-294 inhibited the increase in vascular permeability, neutrophil accumulation, hemorrhage and proinflammatory cytokine levels, induced by intestinal I/R injury in the intestine. In the lungs, MOL-294 partially inhibited edema formation, TNF-alpha production, but did not alter neutrophil recruitment. 4 Treatment with MOL-294 inhibited reperfusion-associated lethality, an effect likely to be secondary to the inhibition of systemic TNF-alpha levels. PNRI-299 had no effects on the inflammatory changes or lethality induced by I/R injury. 5 Our results point to an important role for NF-kappaB in triggering endogenous proinflammatory networks during intestinal I/R injury. Inhibition of NF-kappaB prevents tissue injury and lethality, and this was associated with inhibition of TNF-alpha production and decrease in neutrophil recruitment.

Immune-enhancing enteral nutrients differentially modulate the early proinflammatory transcription factors mediating gut ischemia/reperfusion

BACKGROUND

Recent reports suggest that enteral diets enriched with arginine may be harmful by enhancing inflammation. This is consistent with our gut ischemia/reperfusion (I/R) model in which arginine induced the proinflammatory mediator inducible nitric oxide synthase and resulted in injury and inflammation whereas glutamine was protective. We now hypothesize that arginine and glutamine differentially modulate the early proinflammatory transcription factors activated by gut I/R.

METHODS

At laparotomy, jejunal sacs were filled with either 60 mmol/L glutamine, arginine, or an iso-osmotic control followed by 60 minutes of superior mesenteric artery occlusion and 6 hours of reperfusion and compared with shams. Jejunum was harvested for nuclear factor (NF)-kappaB and activator protein-1 (AP-1) measured by electrophoretic mobility shift assay and c-jun and c-fos (AP-1 family) by supershift.

RESULTS

Both NF-kappaB and AP-1 were activated by gut I/R. Arginine and glutamine had no differential effect on NF-kappaB, whereas AP-1 expression (c-jun but not c-fos) was markedly enhanced by arginine and significantly lessened by glutamine.

CONCLUSION

Arginine enhanced expression of the early proinflammatory transcription factor AP-1 but not NF-kappaB. This represents a novel mechanism by which arginine may be harmful when administered to critically ill patients.

Differential subcellular targeting of PKC-epsilon in response to pharmacological or ischemic stimuli in intestinal epithelia

Ischemia is the central pathogenic factor underlying a spectrum of intestinal disorders. The study of the cellular signaling responses to ischemic stress in nonepithelial cells has progressed substantially in the previous several years, but little is known about the response in epithelial cells. Unique features of the epithelial response to ischemic stress suggest differential regulation with regards to signaling. The PKC family of proteins has been implicated in ischemic stress in nonepithelial systems. The role of PKC isoforms in chemical ischemia in intestinal epithelial cells is evaluated in this study. Additionally, the phosphorylation of the F-actin cross-linking protein myristoylated alanine-rich C kinase substrate (MARCKS) is also studied. Chemical ischemia resulted in the transient activation of only the isoform PKC-epsilon as detected by translocation employing the subcellular fractionation technique. The pharmacological agonists phorbol 12-myristate 13-acetate and carbachol also led to the translocation of PKC-epsilon. By immunofluoresence, MARCKS is noted to be located at the lateral membrane under control conditions. In response to carbachol, MARCKS translocates to the cytosol, indicating its phosphorylation, which is additionally confirmed biochemically. Consistent with this observation, carbachol induces the translocation of PKC-epsilon to proximity with MARCKS at the lateral membrane. In response to chemical ischemia, MARCKS fails to translocate and phosphorylation does not increase. Additionally, the translocation of PKC-epsilon is not to the lateral membrane but rather basally. The data suggest that the differential translocation of PKC-epsilon in response to pharmacological agonists versus ischemic stress may lead to different effects on downstream targets.

NF-kappaB p65 involves in reperfusion injury and iNOS gene regulation in skeletal muscle

This study investigated the effects of inhibition of NF-kappaB activation on microcirculation and inducible NOS expression in reperfused rat cremaster muscle. The muscle from 16 rats underwent 5-h ischemia and 90-min reperfusion. Each rat received NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC, 150 mg/kg) or phosphate-buffered saline 15 min before reperfusion. Results showed that PDTC treatment had a significant overall increase in muscle blood flow during reperfusion. Blood flow more rapidly recovered to and over baseline in the PDTC-treated group than in controls, with a significant difference at 10-30 min and 70-90 min. Expression of iNOS mRNA had a 167-fold increase from normal in controls, but was significantly (P < 0.05) reduced to a 63-fold increase in PDTC-treated muscles. In addition, PDTC treatment significantly (P < 0.05) decreased a reperfusion-induced increase in activated NF-kappaB p65 and nuclear p65 protein. Our results suggest that NF-kappaB is involved in I/R injury and that inhibition of NF-kappaB p65 activation affords protection against I/R injury, perhaps via downregulating expression of iNOS transcription.

Activation of nuclear factor kappaB In vivo selectively protects the murine small intestine against ionizing radiation-induced damage

Exposure of mice to total body irradiation induces nuclear factor kappaB (NFkappaB) activation in a tissue-specific manner. In addition to the spleen, lymph nodes, and bone marrow, the tissues that exhibit NFkappaB activation now include the newly identified site of the intestinal epithelial cells. NFkappaB activated by total body irradiation mainly consists of NFkappaB p50/RelA heterodimers, and genetically targeted disruption of the NFkappaB p50 gene in mice significantly decreased the activation. By comparing tissue damage and lethality in wild-type and NFkappaB p50 knockout (p50-/-) mice after they were exposed to increasing doses of total body irradiation, we additionally examined the role of NFkappaB activation in total body irradiation-induced tissue damage. The results show that p50-/- mice are more sensitive to total body irradiation-induced lethality than wild-type mice (LD50/Day 7: wild-type = 13.12 Gy versus p50-/- = 7.75 Gy and LD50/Day 30: wild-type = 9.31 Gy versus p50-/- = 7.81 Gy). The increased radiosensitivity of p50-/- mice was associated with an elevated level of apoptosis in intestinal epithelial cells and decreased survival of the small intestinal crypts compared with wild-type mice (P < 0.01). In addition, RelA/TNFR1-deficient (RelA/TNFR1-/-) mice also exhibited a significant increase in intestinal epithelial cell apoptosis after they were exposed to total body irradiation as compared with TNFR1-deficient (TNFR1-/-) mice (P < 0.01). In contrast, no significant increase in total body irradiation-induced apoptosis or tissue injury was observed in bone marrow cells, spleen lymphocytes, and the liver, heart, lung, and kidney of p50-/- mice in comparison with wild-type mice. These findings indicate that activation of NFkappaB selectively protects the small intestine against ionizing radiation-induced damage.

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.

Heme oxygenase-1 induction by hemin protects against gut ischemia/reperfusion injury

BACKGROUND

We have shown that both intraischemic hypothermia and hypertonic saline resuscitation provide dramatic protection against gut ischemia/reperfusion (I/R) injury that is in part mediated by heme oxygenase-1 (HO-1). We therefore hypothesized that induction of HO-1 by hemin would lessen damage and improve function after gut I/R.

MATERIALS AND METHODS

Male Sprague-Dawley rats were treated with 50 micromol/kg hemin (HO-1 inducer ferric protoporphyrin IX chloride) sq or vehicle 2 h before superior mesenteric artery occlusion for 60 min or sham laparotomy. After 6 h of reperfusion, transit was determined by quantitation of percentage of tracer in 10 equal segments of small intestine 30 min following injection into the duodenum (expressed as mean geometric center). Ileum was harvested for assessment of mucosal histologic injury (Chiu score 0-5 by blinded observer), myeloperoxidase activity (MPO, index of inflammation), and HO-1 protein expression.

RESULTS

Hemin treatment was associated with increased HO-1 protein expression, lessened mucosal injury, decreased MPO activity, and improved intestinal transit following gut I/R.

CONCLUSION

These data corroborate that HO-1 plays an important role in protecting the gut against I/R-induced injury.

Inhibition of c-Jun NH2-terminal kinase activity improves ischemia/reperfusion injury in rat lungs

Although c-Jun NH(2)-terminal kinase (JNK) has been implicated in the pathogenesis of transplantation-induced ischemia/reperfusion (I/R) injury in various organs, its significance in lung transplantation has not been conclusively elucidated. We therefore attempted to measure the transitional changes in JNK and AP-1 activities in I/R-injured lungs. Subsequently, we assessed the effects of JNK inhibition by the three agents including SP600125 on the degree of lung injury assessed by means of various biological markers in bronchoalveolar lavage fluid and histological examination including detection of apoptosis. In addition, we evaluated the changes in p38, extracellular signal-regulated kinase, and NF-kappaB-DNA binding activity. I/R injury was established in the isolated rat lung preserved in modified Euro-Collins solution at 4 degrees C for 4 h followed by reperfusion at 37 degrees C for 3 h. We found that AP-1 was transiently activated during ischemia but showed sustained activation during reperfusion, leading to significant lung injury and apoptosis. The change in AP-1 was generally in parallel with that of JNK, which was activated in epithelial cells (bronchial and alveolar), alveolar macrophages, and smooth muscle cells (bronchial and vascular) on immunohistochemical examination. The change in NF-kappaB qualitatively differed from that of AP-1. Protein leakage, release of lactate dehydrogenase and TNF-alpha into bronchoalveolar lavage fluid, and lung injury were improved, and apoptosis was suppressed by JNK inhibition. In conclusion, JNK plays a pivotal role in mediating lung injury caused by I/R. Therefore, inhibition of JNK activity has potential as an effective therapeutic strategy for preventing I/R injury during lung transplantation.

Heparin-binding epidermal growth factor-like growth factor and intestinal ischemia-reperfusion injury

Intestinal ischemia/reperfusion (I/R) injury affects patients of different ages, especially premature babies and the elderly. The outcome after intestinal I/R is often dismal, which may be attributed to loss of the barrier and immune functions of the intestines, as well as development of secondary injury in remote organs. The available treatment for advanced gut ischemia mandates extensive resection, which may cause growth retardation in infants and nutritional problems in the elderly. Throughout the past decade we have been investigating the potential therapeutic role of heparin-binding epidermal growth factor-like factor (HB-EGF) in intestinal I/R. The mitogenic and chemoattractant functions of HB-EGF formed the initial rationale for our investigations. In addition, HB-EGF is a potent antiapoptotic protein that enables cells and tissues exposed to different apoptotic stimuli to survive hypoxic, oxidative, and nutritional stresses. HB-EGF is known to have a vital role in wound healing and postischemic regeneration in different organs. In the current review, we summarize the results of our findings of the beneficial effects of HB-EGF in intestinal I/R, supported by additional evidence from the literature and an explanation of different possible mechanisms of its actions. Collectively, the data strongly suggest a potential therapeutic role for the use of HB-EGF to treat intestinal ischemic diseases such as I/R and necrotizing enterocolitis.

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.

Regional hypothermia reduces mucosal NF-kappaB and PMN priming via gut lymph during canine mesenteric ischemia/reperfusion

BACKGROUND

Mesenteric ischemia/reperfusion (I/R) activates pro-inflammatory mediators that exacerbate gut reperfusion injury and prime circulating neutrophils that cause remote organ injury. We have shown that regional intraischemic hypothermia protects the intestinal mucosa during I/R in rats. In this study, we examined the effects of regional hypothermia on I/R-induced transvascular protein clearance, NF-kappaB DNA binding activity, and polymorphonuclear neutrophil (PMN) priming via gut lymph in a canine mesenteric lymphatic fistula model.

MATERIALS AND METHODS

Conditioned dogs underwent 60 min of mesenteric ischemia, with or without regional intraischemic hypothermia, and 3 h reperfusion. A mesenteric lymphatic fistula model was used to measure transvascular protein clearance and harvest lymph. Biopsies of distal ileum were obtained at baseline and 0, 180 min of reperfusion for NF-kappaB DNA binding activity using electrophoretic mobility shift assay (EMSA). A kinetic spectrophotometric assay was used to determine fMLP stimulated PMN superoxide production after priming by gut lymph obtained at baseline and 180 min reperfusion.

RESULTS

Transvascular protein clearance increased during reperfusion compared to baseline, and hypothermia had no significant effect on this I/R-induced protein clearance. NF-kappaB activity increased three-fold at the end of ischemia and hypothermia prevented this early activation. PMN superoxide production increased 19-fold during I/R (0.06 +/- 0.04 versus 1.14 +/- 0.50 nmol O(2), P < 0.05), but only 2.5-fold during I/R + hypothermia (0.28 +/- 0.09 versus 0.70 +/- 0.32 nmol O(2), P = 0.2).

CONCLUSIONS

Regional intraischemic hypothermia prevented early intestinal NF-kappaB activation, partially abrogated PMN priming via gut lymph, but had no significant effect on increased transvascular protein clearance during mesenteric I/R in dogs.

Abdominal irradiation increases inflammatory cytokine expression and activates NF-kappaB in rat ileal muscularis layer

The small bowel is an important dose-limiting organ in abdominal radiotherapy because irradiation can cause acute enteritis that, in turn, leads to progressively reduced motility and finally, in a later phase, to fibrosis. Because these clinical symptoms may be caused by the early stage of an inflammatory process, we characterized the radiation-induced intestinal inflammation in rats. Abdominal gamma-irradiation (10-Gy) induced a cascade of inflammatory events characterized by an early (6 h after exposure) increase in IL-1beta, TNF-alpha, and IL-6 mRNA levels in the rat ileal muscularis layer. IL-8 [a cytokine-induced neutrophil chemoattractant (CINC)] mRNA appeared later (at 3 days). The expression of TGF-beta (a profibrotic cytokine) was higher in irradiated than control tissue at day 1, whereas IL-10 (an anti-inflammatory cytokine) expression vanished completely. Despite strong IL-1ra expression, the IL-1ra/IL-1beta ratio, which is an indicator of inflammatory balance, was -41% at day 1 in irradiated compared with control tissue. The nuclear transcription factors NF-kappaB and activator protein-1 (AP-1) govern transcription of these genes, directly or indirectly. Although expression of the subunits of NF-kappaB (p65, p50) and AP-1 (c-fos, c-jun) did not increase, irradiation caused a rapid and persistent translocation of p65 and p50. An imbalance between proinflammatory and anti-inflammatory mediators may contribute to perpetuating intestinal inflammation, thus making it chronic.

Role for complement in mediating intestinal nitric oxide synthase-2 and superoxide dismutase expression

Inducible nitric oxide synthase (iNOS) and superoxide dismutase (SOD) play an important role in the pathology of ischemia-reperfusion. This study sought to determine if the proinflammatory effects of complement modulate iNOS and SOD in the rat after gastrointestinal ischemia and reperfusion (GI/R). An inhibitory or noninhibitory anti-complement component 5 (C5) monoclonal antibody (18A or 16C, respectively) was administered before GI/R. RT-PCR revealed a significant increase in intestinal iNOS mRNA compared with sham after GI/R that was attenuated significantly by 18A. Immunohistochemistry demonstrated increased iNOS protein expression within the intestinal crypts after GI/R. Cu/Zn SOD (mRNA and protein) was unaffected by GI/R, whereas Cu/Zn SOD activity was reduced significantly. Mn SOD protein expression was decreased significantly by GI/R. Anti-C5 preserved Cu/Zn SOD activity and Mn SOD protein expression. Staining for nitrotyrosine showed that anti-C5 treatment reduced protein nitration in the reperfused intestine. Immunohistochemistry demonstrated prominent phosphorylated (p) inhibitory factor-kappaB (IkappaB)-alpha staining of intestinal tissue after GI/R, whereas anti-C5 reduced p-IkappaB-alpha expression. These data indicate that complement may mediate tissue damage during GI/R by increasing intestinal iNOS and decreasing the activity and protein levels of Cu/Zn SOD and Mn SOD, respectively.

IL-10 increases tissue injury after selective intestinal ischemia/reperfusion

OBJECTIVE This study focused on the effect of immunoregulatory cytokines on tissue injury after intestinal ischemia/reperfusion (IR). Furthermore, the role of nitric oxide, heme oxygenase-1 (HO-1) and the transcription factor NF-kappaB/Rel in the disease process was evaluated.SUMMARY BACKGROUND DATA Oxidative stress and inflammatory gene products contribute to ischemia/reperfusion injury (IRI). However, expression of stress proteins such as the inducible nitric oxide synthase (NOS-2) and HO-1 might also provide protection against IRI. METHODS IR was achieved in Lewis rats by selective clamping of the superior mesenteric artery. IL-2 or IL-10 was administered intravenously before reperfusion. Animals were killed 1 hour, 4 hours, and 24 hours after reperfusion. Tissue destruction was assessed by hyaluronic acid (HA) and aminoaspartate-transaminase (AST) serum levels, whereas reduction of glutathione (GSH) tissue levels was used as a marker for oxidative stress. Furthermore, the activation of NF-kappaB/Rel and the expression of NOS-2 and HO-1 were analyzed.RESULTS IR resulted in tissue destruction and significantly reduced GSH tissue levels in the intestines and liver. In addition, NF-kappaB/Rel activation and increased NOS-2 and HO-1 mRNA expression were detected in both organs after IR. IL-2 administration resulted in clinical improvement of the animals and was associated with increased NF-kappaB/Rel activation and enhanced NOS-2 and HO-1 mRNA expression. In contrast, IL-10 resulted in increased tissue destruction in both organs and sustained reduction of GSH levels in the intestines. Furthermore, IL-10 administration failed to enhance NF-kappaB/Rel activity, NOS-2 mRNA, or HO-1 mRNA expression after IR. CONCLUSION IL-10 resulted in increased tissue damage after intestinal IR. This detrimental effect of IL-10 might have been the result of reduced NOS-2 and HO-1 mRNA expression. In contrast, the beneficial effect of IL-2 might have relied on increased HO-1 expression and NOS-2 activity. These controversial effects of IL-2 and IL-10 might have been mediated through transcriptional regulation of NOS-2 and HO-1 gene expression.

Alterations in the DNA binding activity of transcriptional factors activator protein-1, Sp1, and hepatocyte nuclear factor-1 in rat jejunum during starvation and refeeding

BACKGROUND

The molecular processes leading to mucosal atrophy, regrowth, and functional changes with starvation and refeeding are largely unknown. There are many transcriptional factors that might be related to mucosal atrophy and proliferation. In contrast, we previously reported that H+/peptide transporter and aminopeptidase N messenger RNA in the intestinal mucosa were upregulated during starvation. Therefore, we selected and studied three transcriptional factors: activator protein (AP)-1, Sp1, and hepatocyte nuclear factor (HNF)-1, which not only play important roles for enterocytes proliferation, but also exist in promoter lesions of the brush border enzymes and peptide transporter.

METHODS

In the present study, we performed electrophoretic mobility shift assays employing AP-1, Sp1, and HNF-1, and evaluated the changes in the DNA binding activities in rat jejunum during starvation and refeeding.

RESULTS

Two days after starvation, the Sp1 binding activity was significantly decreased to 61.8% as compared with the control level, whereas AP-1 was 121.4% and HNF-1 was 77.5%. Two hours after refeeding, the AP-1 activity was significantly increased to 175.0% as compared with the control level, and the HNF-1 activity was significantly increased to 180.2%. In contrast, the decreased SP1 level did not recover until 24 h after refeeding.

CONCLUSIONS

The DNA binding activities of these three transcriptional factors were significantly changed in the rat jejunum during starvation and refeeding. Our results provide insight into the molecular mechanisms of the transcriptional regulations associated with mucosal atrophy, regrowth, and functional changes of the jejunal epithelium in response to starvation and refeeding.

NF-kappa B activation by oxidative stress and inflammation suppresses contractility in colonic circular smooth muscle cells

BACKGROUND & AIMS

Transcription factor nuclear factor kappa B (NF-kappa B) plays a critical role in transcriptional changes in several diseases, including inflammation. The aim of this study was to investigate whether NF-kappa B is activated by inflammation and oxidative stress in colonic circular smooth muscle cells and whether that leads to suppression of their contractility.

METHODS

The experiments were performed on freshly dissociated single cells using electrophoretic mobility shift assay, Western immunoblotting, and immunofluorescence imaging.

RESULTS

The NF-kappa B DNA binding was approximately 6-fold greater in cells from the inflamed colon vs. those from the normal colon. Supershift assay indicated that the antibodies to p65, p50, and c-Rel, but not that to p52, shifted the NF-kappa B band. Western immunoblotting and immunofluorescence imaging also demonstrated the presence of p65, p50, and c-Rel proteins in the cytoplasm and their translocation to the nucleus by H(2)O(2)-induced oxidative stress. H(2)O(2) treatment degraded I kappa B(beta), but not I kappa B(alpha), to translocate NF-kappa B to the nucleus. Hydrogen peroxide concentration and time dependently activated NF-kappa B DNA binding and suppressed cell contraction to acetylcholine. NF-kappa B inhibitors significantly inhibited these effects. Inhibition of NF-kappa B prior to and during inflammation in intact dogs also reversed the suppression of contractility.

CONCLUSIONS

Transcription factor NF-kappa B is activated in colonic circular muscle cells by inflammation and oxidative stress. This activation of NF-kappa B mediates the suppression of cell contractility.

Gabexate mesilate, a synthetic protease inhibitor, inhibits lipopolysaccharide-induced tumor necrosis factor-alpha production by inhibiting activation of both nuclear factor-kappaB and activator protein-1 in human monocytes

Gabexate mesilate, a synthetic protease inhibitor, was shown to be effective in treating patients with sepsis-associated disseminated intravascular coagulation in which tumor necrosis factor-alpha (TNF-alpha) plays a critical role. We demonstrated that gabexate mesilate reduced lipopolysaccharide (LPS)-induced tissue injury by inhibiting TNF-alpha production in rats. In the present study, we analyzed the mechanism(s) by which gabexate mesilate inhibits LPS-induced TNF-alpha production in human monocytes in vitro. Gabexate mesilate inhibited the production of TNF-alpha in monocytes stimulated with LPS. Gabexate mesilate inhibited both the binding of nuclear factor-kappaB (NF-kappaB) to target sites and the degradation of inhibitory kappaBalpha. Gabexate mesilate also inhibited both the binding of activator protein-1 (AP-1) to target sites and the activation of mitogen-activated protein kinase pathways. These observations strongly suggest that gabexate mesilate inhibited LPS-induced TNF-alpha production in human monocytes by inhibiting activation of both NF-kappaB and AP-1. Inhibition of TNF-alpha production by gabexate mesilate might explain at least partly its therapeutic effects in animals given LPS and those in patients with sepsis.

Effects of NF-kappa B inhibition on mesenteric ischemia-reperfusion injury

Mesenteric ischemia-reperfusion injury is a serious complication of shock. Because activation of nuclear factor-kappaB (NF-kappaB) has been implicated in this process, we treated rats with vehicle or the IkappaB-alpha inhibitor BAY 11-7085 (25 mg/kg ip) 1 h before mesenteric ischemia-reperfusion (45 min of ischemia followed by reperfusion at 30 min or 6 h) and examined the ileal injury response. Vehicle-treated rats subjected to ischemia-reperfusion exhibited severe mucosal injury, increased myeloperoxidase (MPO) activity, increased expression of interleukin-6 and intercellular adhesion molecule 1 protein, and a biphasic peak of NF-kappaB DNA-binding activity during the 30-min and 6-h reperfusion courses. In contrast, BAY 11-7085-pretreated rats subjected to ischemia-reperfusion exhibited less histological injury and less interleukin-6 and intercellular adhesion molecule 1 protein expression at 30 min of reperfusion but more histological injury at 6 h of reperfusion than vehicle-treated rats subjected to ischemia-reperfusion. Studies with phosphorylation site-specific antibodies demonstrated that IkappaB-alpha phosphorylation at Ser(32),Ser(36) was induced at 30 min of reperfusion, whereas tyrosine phosphorylation of IkappaB-alpha was induced at 6 h of reperfusion. BAY 11-7085 inhibited the former, but not the latter, phosphorylation pathway, whereas alpha-melanocyte-stimulating hormone, which is effective in limiting late ischemia-reperfusion injury to the intestine, inhibited tyrosine phosphorylation of IkappaB-alpha. Thus NF-kappaB appears to play an important role in the generation and resolution of intestinal ischemia-reperfusion injury through different activation pathways.

Heparin-binding EGF-like growth factor downregulates expression of adhesion molecules and infiltration of inflammatory cells after intestinal ischemia/reperfusion injury

BACKGROUND/PURPOSE

This study examined whether heparin-binding epidermal growth factor (EGF) like growth factor (HB-EGF), a proven intestinal cytoprotective molecule, exerts its protective effects through modulation of adhesion molecule expression and inflammatory cell infiltration, important pathogenic mediators of ischemia/reperfusion (I/R) injury.

METHODS

Total midgut I/R injury in rats was achieved by occlusion of the superior mesenteric artery for 90 minutes followed by reperfusion. Rats were treated intraluminally with 600 microg/kg HB-EGF or with PBS 45 minutes after the onset of ischemia. Four- or 24-hours post-I/R, ileum was harvested and processed for immunhistochemical detection of P-/E-selectins, intercellular adhesion molecule-1 (ICAM-1)/vascular cell adhesion molecule-1 (VCAM-1), and polymorphonuclear cells (PMN)/macrophages (MPhi).

RESULTS

P-/E-selectins were significantly induced in vascular endothelia 4 hours after I/R injury compared with normal intestine. HB-EGF treatment significantly down-regulated the expression of P-/E-selectins. I/R-injured intestine displayed overexpression of ICAM-1 and VCAM-1, which were significantly down-regulated by HB-EGF treatment. Lastly, I/R injury caused significant infiltration of PMN and MPhi into wounded tissue 24 hours after I/R compared with normal intestine. HB-EGF treatment significantly decreased PMN and MPhi infiltration into the injured tissue.

CONCLUSIONS

HB-EGF intestinal cytoprotection is mediated, in part, by down-regulation of expression of adhesion molecules and infiltration of PMN and MPhi after intestinal I/R injury.

The heat shock response and cytoprotection of the intestinal epithelium

Following heat stress, the mammalian intestinal epithelial cells respond by producing heat shock proteins that confer protection under stressful conditions, which would otherwise lead to cell damage or death. Some of the noxious processes against which the heat shock response protects cells include heat stress, infection, and inflammation. The mechanisms of heat shock response-induced cytoprotection involve inhibition of proinflammatory cytokine production and induction of cellular proliferation for restitution of the damaged epithelium. This can mean selective interference of pathways, such as nuclear factor kappa B (NF-kappaB) and mitogen-activated protein kinase (MAPK), that mediate cytokine production and growth responses. Insight into elucidating the exact protective mechanisms could have therapeutic significance in treating intestinal inflammations and in aiding maintenance of intestinal integrity. Herein we review findings on heat shock response-induced intestinal epithelial protection involving regulation of NF-kappaB and MAPK cytokine production.

Pyrrolidinedithiocarbamate inhibits NF-kappaB activation and IL-8 production in intestinal epithelial cells

During inflammatory bowel disease and intestinal ischemia, epithelial cells of the gut mucosa produce various inflammatory mediators, including the chemokine interleukin (IL-8). This IL-8 produced by intestinal epithelial cells has recently been implicated as a contributory factor to the deleterious inflammatory process resulting in colitis during inflammatory bowel disease or multiple organ failure following shock and trauma. Recent evidence suggests that the transcription factor nuclear factor kappaB (NF-kappaB) is a central regulator of IL-8 gene expression. In the present paper we investigated the effect of pharmacological inhibition of NF-kappaB with pyrrolidinedithiocarbamate (PDTC) on IL-1beta-induced IL-8 production by the human intestinal epithelial cell line HT-29. Pretreatment of cells with PDTC (3-1000 microM) dose-dependently attenuated IL-8 production. Furthermore, PDTC (100 microM) suppressed the accumulation of IL-8 mRNA. PDTC inhibited the activation of NF-kappaB, because PDTC suppressed both NF-kappaB DNA binding and NF-kappaB-dependent transcriptional activity. Taken together, our data demonstrate that NF-kappaB inhibition with PDTC decreases IL-8 production by intestinal epithelial cells.

Activation time course of activator protein-1 and effect of proline dithiocarbamate during ischemia-reperfusion in rat skeletal muscle

Activator protein 1 (AP-1) is thought to play an important role in the expression of genes expressed in response to ischemia-reperfusion injury. In this report, the activation of AP-1 in rat skeletal muscle during reperfusion after a 4-hour ischemic period was studied. AP-1 activation displayed a biphasic pattern, showing peak activities at 1 hour after perfusion and from 4 hours to 12 hours after perfusion. Inhibition of AP-1 activation was investigated using a potent nuclear factor kappa B inhibitor, proline dithiocarbamate (Pro-DTC). AP-1 binding activity at 1 hour of reperfusion was significantly reduced (29.0 +/- 10.1% SEM; p < 0.05) after intravenous administration of Pro-DTC (n = 7 animals in each group). Further elucidation of the role of AP-1 is warranted in hopes of developing strategies to reduce the deleterious effects of ischemia-reperfusion injury.

Supplementation of N-acetylcysteine normalizes lipopolysaccharide-induced nuclear factor kappaB activation and proinflammatory cytokine production during early rehabilitation of protein malnourished mice

Increased sensitivity to septic shock has been reported in protein malnourished patients. In this study, we used an animal septic shock model to investigate effects of glutathione (GSH) levels on nuclear factor kappaB (NFkappaB) activation and proinflammatory cytokine production in protein malnutrition. We further investigated molecular mechanisms by which protein malnutrition influenced inflammatory responses. CD-1 mice were fed for 3 wk a normal protein (150 g/kg) diet or a protein-deficient (5 g/kg) diet, or for 2 wk a protein-deficient diet followed by 1 wk of N-acetylcysteine (NAC) supplementation. Lipopolysaccharide (LPS) was injected intravenously, and liver was collected at 0, 15 min, 1, 4, 24 and 48 h after LPS administration. Protein malnutrition significantly increased the activation of NFkappaB and transcription levels of its downstream genes interleukin-1beta and tumor necrosis factor-alpha. Peak NFkappaB activation was inversely associated with GSH levels (r = -0.939, P < 0.0001) but positively correlated with the GSH disulfide/2GSH reduction potential (r = 0.944 P < 0.0001). We noted unusual NFkappaB p50/p50 homodimer translocation that was significantly elevated in tissue from protein malnourished mice, along with decreased peak levels of normal p65/p50 heterodimer translocation. Interestingly, mRNA levels of IkappaB-alpha were not affected by protein malnutrition. However, early supplementation of NAC to protein malnourished mice without replenishing with dietary protein restored GSH levels and reduction potential, and normalized NFkappaB activation and proinflammatory cytokine production. Taken together, these findings provide evidence supporting the role of GSH in NFkappaB activation and inflammatory response in protein malnutrition, and the use of NAC in early rehabilitation of protein malnutrition without a high protein diet.

The effects of preconditioning on the oxidative stress in small-bowel autotransplantation

BACKGROUND

One determining factor in intestinal transplantation is the extreme sensitivity of the small bowel to ischemia-reperfusion injury. This study investigated the effect of ischemic preconditioning prior to autotransplantation.

METHODS

Total orthotopic intestinal autotransplantation was performed in 40 mongrel dogs. In 4 groups (GI-GIV), grafts were stored for 3 hours in cold Euro Collins (GI,GIII) and University of Wisconsin (GII,GIV) solutions. In GIII and GIV, before preservation, preconditioning was induced by 4 cycles (5-min ischemia + 10-min reperfusion). Bowel samples were collected after laparotomy (control), at the end of preservation and reperfusion periods. We determined oxidative stress markers (reduced glutathione [GSH], superoxide dismutase [SOD]), production of oxygen free radicals, activity of nuclear factor-kappaB (NF-kappaB), and DNA damage.

RESULTS

In the non-preconditioned groups, GSH concentration increased slightly, while SOD activity decreased significantly during reperfusion. In the preconditioned groups, GSH increased markedly, and better preservation of SOD was observed. The number of oxygen free radicals increased during reperfusion mainly in non-preconditioned groups. Activation of NF-kappaB peaked by 1 hour, and decreased 3 hours after preconditioning. We observed DNA-damaged cells in all groups.

CONCLUSIONS

Our findings confirm that preconditioning prior to preservation can moderate the severity of oxidative stress and activate the endogenous cellular adaptation in bowel tissue.