Role of interleukin 8 on leucocyte-endothelial cell adhesion in intestinal inflammation

Monocyte Adhesion and Transmigration Through Endothelium Following Cardiopulmonary Bypass Shearing is Mediated by IL-8 Signaling

Background

The use of cardiopulmonary bypass (CPB) can induce sterile systemic inflammation that contributes to morbidity and mortality, especially in children. Patients have been found to have increased expression of cytokines and transmigration of leukocytes during and after CPB. Previous work has demonstrated that the supraphysiologic shear stresses present during CPB are sufficient to induce proinflammatory behavior in non-adherent monocytes. The interactions between shear stimulated monocytes and vascular endothelial cells have not been well studied and have important translational implications.

Methods

To test the hypothesis that non-physiological shear stress experienced by monocytes during CPB affects the integrity and function of the endothelial monolayer via IL-8 signaling pathway, we have used an in vitro CPB model to study the interaction between THP-1 monocyte-like cells and human neonatal dermal microvascular endothelial cells (HNDMVECs). THP-1 cells were sheared in polyvinyl chloride (PVC) tubing at 2.1 Pa, twice of physiological shear stress, for 2 hours. Interactions between THP-1 cells and HNDMVECs were characterized after coculture.

Results

We found that sheared THP-1 cells adhered to and transmigrated through the HNDMVEC monolayer more readily than static controls. When co-culturing, sheared THP-1 cells also disrupted in the VE-cadherin and led to reorganization of cytoskeletal F-actin of HNDMVECs. Treating HNDMVECs with IL-8 resulted in upregulation of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) while also increasing the adherence of non-sheared THP-1 cells. Preincubating HNDMVECs with Reparixin, an inhibitor of CXCR2/IL-8 receptor inhibited sheared THP-1 cell adhesion to the HNDMVECs.

Conclusions

These results suggested that IL-8 not only increases the endothelium permeability during monocyte migration, but also affects the initial adhesion of monocytes in a CPB setup. This study revealed a novel mechanism of post-CPB inflammation and will contribute to the development of targeted therapeutics to prevent and repair the damage to neonatal patients.

Highlights

Shear stress in a CPB-like environment promoted the adhesion and transmigration of monocytes to and through endothelial monolayer.

Treating endothelial monolayer with sheared monocytes led to disruption of VE-cadherin and reorganization of F-actin.

Interaction between sheared monocytes resulted in a significant increase of IL-8 release.

Inhibiting IL-8 receptor prevented sheared monocyte adhesion, while IL-8 promoted naive monocyte adhesion.

BMP9 signaling promotes the normalization of tumor blood vessels

The presence of an immature tumor vascular network contributes to cancer dissemination and the development of resistance to therapies. Strategies to normalize the tumor vasculature are therefore of significant therapeutic interest for cancer treatments. VEGF inhibitors are used clinically to normalize tumor blood vessels. However, the time frame and dosage of these inhibitors required to achieve normalization is rather narrow, and there is a need to identify additional signaling targets to attain vascular normalization. In addition to VEGF, the endothelial-specific receptor Alk1 plays a critical role in vascular development and promotes vascular remodeling and maturation. Therefore, we sought to evaluate the effects of the Alk1 ligand BMP9 on tumor vascular formation. BMP9 overexpression in Lewis Lung Carcinoma (LLC) tumors significantly delayed tumor growth. Blood vessels in BMP9-overexpressing LLC tumors displayed markers of vascular maturation and were characterized by increased perivascular cell coverage. Tumor vasculature normalization was associated with decreased permeability and increased perfusion. These changes in vascular function in BMP9-overexpressing LLC tumors resulted in significant alterations of the tumor microenvironment, characterized by a decrease in hypoxia and an increase in immune infiltration. In conclusion, we show that BMP9 promotes vascular normalization in LLC tumors that leads to changes in the microenvironment.

Age-dependent variation in innate immune responses to porcine epidemic diarrhea virus infection in suckling versus weaned pigs

Porcine epidemic diarrhea (PED) is an enteric coronaviral infection that causes severe morbidity and mortality in suckling pigs, but less severe disease in older pigs. Consequently, it causes significant economic losses to the pork industry. There are limited studies on the innate immune responses to PED virus (PEDV) in pigs. The aims of our study were to investigate differences in innate immune responses to PEDV infection in suckling and weaned pigs and to examine if disease severity coincides with reduced innate immune responses. Weaned 26-day-old pigs (n = 20) and 9-day-old nursing pigs (n = 20) were assigned to PEDV inoculated or uninoculated control groups. The pigs were observed daily for clinical signs, virus shedding and were euthanized at post-inoculation days (PIDs) 1 and 5 to assay immune responses. Blood samples were collected at PIDs 1, 3 and 5. The natural killer (NK) cell frequencies, NK cell activities (lysis of target K562 tumor cells in vitro), CD3+CD4+ T cell and CD3+CD8+ T cell frequencies were measured in blood and ileum at PIDs 1 and 5. The PEDV infected suckling pigs showed severe diarrhea and vomiting at PID 1, whereas the PEDV infected weaned pigs showed milder clinical signs starting at PID 3. PEDV infected suckling pigs had significantly higher diarrhea scores, earlier fecal PEDV RNA shedding and significantly higher viremia (viral RNA in serum) compared to weaned pigs. There was no mortality in either infected suckling or infected weaned pigs. The control pigs not inoculated with PEDV did not show any clinical signs and no detectable fecal or serum PEDV RNA. Strikingly, PEDV infected suckling pigs had significantly lower NK cell frequencies, undetectable NK cell activity and lower IFNγ producing NK cells in blood and ileum compared to PEDV infected weaned pigs. Pro-inflammatory cytokine profiles of PEDV infected suckling pigs differed from those of PEDV infected weaned pigs and coincided with onset of fecal PEDV RNA shedding and serum PEDV RNA titers. The infected suckling pigs have higher and earlier increases in serum IFNα, but lower serum IL-8 and TNFα levels compared to infected weaned pigs. CD3+CD4+ T cell frequencies were significantly higher in ileum of suckling pigs than in weaned pigs, whereas there was no difference in CD3+CD8+ T cell frequencies. In conclusion, the observations of impaired lytic activity and IFN-γ production by NK cells in suckling pigs coincided with the increased severity of PEDV infection in the suckling pigs compared with the weaned pigs.

Endothelial to Mesenchymal Transition Contributes to Endothelial Dysfunction in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by lung endothelial cell dysfunction and vascular remodeling. Normally, the endothelium forms an integral cellular barrier to regulate vascular homeostasis. During embryogenesis endothelial cells exhibit substantial plasticity that contribute to cardiac development by undergoing endothelial-to-mesenchymal transition (EndoMT). We determined the presence of EndoMT in the pulmonary vasculature in vivo and the functional effects on pulmonary artery endothelial cells (PAECs) undergoing EndoMT in vitro. Histologic assessment of patients with systemic sclerosis-associated PAH and the hypoxia/SU5416 mouse model identified the presence von Willebrand factor/α-smooth muscle actin-positive endothelial cells in up to 5% of pulmonary vessels. Induced EndoMT in PAECs by inflammatory cytokines IL-1β, tumor necrosis factor α, and transforming growth factor β led to actin cytoskeleton reorganization and the development of a mesenchymal morphology. Induced EndoMT cells exhibited up-regulation of mesenchymal markers, including collagen type I and α-smooth muscle actin, and a reduction in endothelial cell and junctional proteins, including von Willebrand factor, CD31, occludin, and vascular endothelial-cadherin. Induced EndoMT monolayers failed to form viable biological barriers and induced enhanced leak in co-culture with PAECs. Induced EndoMT cells secreted significantly elevated proinflammatory cytokines, including IL-6, IL-8, and tumor necrosis factor α, and supported higher immune transendothelial migration compared with PAECs. These findings suggest that EndoMT may contribute to the development of PAH.

RNA-Seq reveals a role for NFAT-signaling in human retinal microvascular endothelial cells treated with TNFα

TNFα has been identified as playing an important role in pathologic complications associated with diabetic retinopathy and retinal inflammation, such as retinal leukostasis. However, the transcriptional effects of TNFα on retinal microvascular endothelial cells and the different signaling pathways involved are not yet fully understood. In the present study, RNA-seq was used to profile the transcriptome of human retinal microvascular endothelial cells (HRMEC) treated for 4 hours with TNFα in the presence or absence of the NFAT-specific inhibitor INCA-6, in order to gain insight into the specific effects of TNFα on RMEC and identify any involvement of NFAT signaling. Differential expression analysis revealed that TNFα treatment significantly upregulated the expression of 579 genes when compared to vehicle-treated controls, and subsequent pathway analysis revealed a TNFα-induced enrichment of transcripts associated with cytokine-cytokine receptor interactions, cell adhesion molecules, and leukocyte transendothelial migration. Differential expression analysis comparing TNFα-treated cells to those co-treated with INCA-6 revealed 10 genes whose expression was significantly reduced by the NFAT inhibitor, including those encoding the proteins VCAM1 and CX3CL1 and cytokines CXCL10 and CXCL11. This study identifies the transcriptional effects of TNFα on HRMEC, highlighting its involvement in multiple pathways that contribute to retinal leukostasis, and identifying a previously unknown role for NFAT-signaling downstream of TNFα.

Combined Effect of 25-Hydroxycholesterol and IL-1β on IL-8 Production in Human Colon Carcinoma Cell Line (Caco-2)

Interleukin-1 beta (IL-1beta) is an important mediator in intestinal inflammation. IL-1beta promotes IL-8 production, which can be modulated by a number of factors, including oxidative stress. Interestingly, oxysterols, which are thought to contribute to inflammation in atherosclerotic plaques, are also produced by intestinal epithelial cells. Thus, we investigated the effect of oxysterols, including 25-hydroxycholesterol and 7beta-hydroxycholesterol, on IL-1beta-induced IL-8 production in Caco-2 cells (a human colon carcinoma cell line). Pre-treatment of Caco-2 cells with 25-hydroxycholesterol significantly enhanced IL-1beta-induced IL-8 expression at both mRNA and protein levels. However, 7beta-hydroxycholesterol showed very little effect on IL-8 production. Furthermore, pre-treatment with 25-hydroxycholesterol, followed by IL-1beta stimulation, enhanced IL-8 promoter activity beyond that observed with IL-1beta alone. These results suggest that 25-hydroxycholesterol enhances IL-1beta-induced IL-8 production, possibly by enhancing promoter activity.

Bosentan, an endothelin receptor antagonist, reduces leucocyte adhesion and inflammation in a murine model of inflammatory bowel disease

BACKGROUND AND AIMS

Endothelins, a group of polyfunctional cytokines, induce the adhesion of circulating leucocytes to venous endothelium, an initial step in the pathogenesis of a cellular infiltrate in inflammatory bowel disease (IBD). The effect of bosentan, a non-selective endothelin receptor antagonist, on leucocyte adhesion and inflammation in a murine model of IBD was studied.

MATERIALS AND METHODS

Thirty BALB/c mice were divided into three groups of 10 animals: untreated controls, chronic colitis [dextran sodium sulphate (DSS), 3% w/v for 30 days], and treatment with bosentan (30 mg/kg i.p. daily on days 26-30). On day 30, adherent and rolling leucocytes and the average rolling velocity were assessed by intravital microscopy. Clinical and histological activity of inflammation were assessed by the disease activity index and modified Dieleman score, respectively.

STATISTICS

Kruskal-Wallis test was used, followed by Dunn's method. A value of p<0.05 was considered significant.

RESULTS

Compared to healthy controls, mice treated with DSS showed pronounced clinical and histological inflammation, and a higher number of rolling and adhering leucocytes in colonic submucosal venules. Therapy with bosentan significantly reduced clinical and histological inflammation. Adherent leucocyte levels were markedly lower (1.2+/-0.3 vs 23.7+/-2.8 adherent cells per 0.01 mm2, p<0.05). The number of rolling leucocytes was lower but not significantly different. However, rolling velocity was significantly higher (91.5+/-14.0 vs 19.0+/-1.6 microm/s, p<0.05).

CONCLUSIONS

Bosentan reduces the adhesion of leucocytes in colonic submucosal venules and reduces inflammation in this mouse model of IBD. By inhibiting leucocyte adhesion, a crucial step in the recruitment of leucocytes to the inflamed tissue, bosentan is a potent therapeutic drug in this animal model. Further studies are necessary to investigate the role of bosentan as a novel drug in human IBD.

Systemic and local cytokine production in quiescent ulcerative colitis and its relationship to future relapse: a prospective pilot study

BACKGROUND

The main aim of this prospective study was to examine whether systemic (plasma) and local (mucosal) cytokine production is a predictor of future relapse in patients with quiescent ulcerative colitis (UC). The impact of other clinical and laboratory parameters on relapse was also studied.

METHODS

Fifty consecutive patients with quiescent UC were included. At enrollment, blood and mucosal (rectal biopsies) samples were collected. All patients were followed up regularly for 1 year after enrollment. Plasma and mucosal cytokine levels were measured by enzyme-linked immunosorbent assay. To identify independent significant predictive factors for relapse, time-dependent analyses using the Kaplan-Meier method and the Cox proportional hazard model were performed.

RESULTS

Thirty-four patients remained in remission, and 16 patients relapsed during the 1-year follow-up. Higher interleukin (IL)-8 levels in the rectal mucosa were significantly associated with relapse. In contrast, IL-1beta, IL-6, and tumor necrosis factor-alpha levels in the rectal mucosa were not associated with relapse. Conventional blood markers and plasma cytokines (IL-1beta, IL-6, IL-8, and tumor necrosis factor-alpha) did not correlate with relapse. Among clinical factors, age and number of prior relapses were significantly associated with relapse. In multivariate analysis, a higher rectal mucosal IL-8 level (> or = 160 pg/mg of tissue; hazard ratio, 4.7), younger age (<30 yr; hazard ratio, 7.3), and a greater number of prior relapses (> or = 5; hazard ratio, 4.3) were independent significant risk factors for future relapse.

CONCLUSIONS

Rectal mucosal IL-8 measurement might be an additional objective diagnostic tool that can predict relapse in patients with quiescent UC.

Effects of anti-tumour necrosis factor, interleukin-10 and antibiotic therapy in the indometacin-induced bowel inflammation rat model

BACKGROUND

The administration of indometacin to rats increases intestinal permeability and induces inflammatory pathology of the small bowel. This represents a potential model for Crohn's disease.

AIMS

To analyse the pathogenic role of T cells, tumour necrosis factor and bacterial flora in indometacin-induced changes in small bowel permeability and inflammation.

METHODS

Rats were given indometacin, 13 mg/kg, on day 1 and day 2. The effects of antibiotic (metronidazole, aztreonam and amoxicillin/clavulanic acid), anti- tumour necrosis factor and interleukin-10 therapy were evaluated. The parameters used were weight change, serum haemoglobin, chromium-51 ethylenediaminetetra-acetate permeability and macro-and microscopic score on day 5. Results in conventionally harboured rats were compared with those in T-cell-free rats. Additional in vitro experiments were carried out to test the effect of metronidazole on tumour necrosis factor production.

RESULTS

Indometacin administration resulted in small bowel ulcers and inflammation, independently of T cells. Metronidazole was more potent than amoxicillin/clavulanic acid and anti-tumour necrosis factor in improving the indometacin-induced small bowel inflammation. Only part of the efficacy was through improvement of increased intestinal permeability. Aztreonam and interleukin-10 had no effect. Metronidazole also suppressed in vitro lipopolysaccharide-induced tumour necrosis factor production, suggesting a therapeutic effect of this drug through the inhibition of tumour necrosis factor.

CONCLUSIONS

These data implicate anaerobic bacteria and tumour necrosis factor production, but not T cells, as essential elements of the pathogenesis of indometacin-induced small bowel inflammation. Tumour necrosis factor is also involved in the change in intestinal permeability. Metronidazole was the most efficacious drug in this model, probably because it suppressed anaerobic bacteria and directly inhibited tumour necrosis factor production.

Thalidomide impairment of trinitrobenzene sulphonic acid-induced colitis in the rat - role of endothelial cell-leukocyte interaction

1. Immune response-modulating drugs such as thalidomide may be of therapeutic value in the treatment of chronic inflammatory bowel diseases including Crohn's disease (CD). In the present study, we have investigated whether thalidomide exerts this effect by impairing endothelial cell-leukocyte interaction through down-regulation of the expression of pro-inflammatory gene products in these cells. 2. Transient CD-like colitis was induced in male Wistar rats by single enema with trinitrobenzene sulphonic acid (TNBS) in ethanol followed by macroscopic scoring, histology, intravital microscopy, RT - PCR and immunohistochemistry (IHC) analyses. Thalidomide or its analogue supidimide were administered in olive oil by intragastric instillation 6 h prior to the induction of colitis and then daily for one week. 3. Both thalidomide and supidimide (200 mg kg(-1) d(-1)) significantly attenuated TNBS-induced colitis as compared to vehicle-treated control animals (44 and 37% inhibition, respectively), and this effect persisted for 7 days post cessation of thalidomide treatment (46% inhibition). 4. Moreover, thalidomide significantly reduced leukocyte sticking to postcapillary venular endothelial cells in the submucosa (by 45%), improved functional capillary density and perfusion, and attenuated endothelial interleukin-8 expression, as judged by IHC analysis. According to RT - PCR analysis, both thalidomide and supidimide also significantly reduced vascular cell adhesion molecule-1 mRNA expression in the affected part of the descending colon. 5. These findings suggest that thalidomide and one of its derivatives impairs CD-like TNBS-induced colitis in the rat by down-regulating endothelial adhesion molecule and chemokine expression and, as a consequence, the interaction of these cells with circulating leukocytes.

Experimental colitis induced by trinitrobenzenesulfonic acid: an ultrastructural and histochemical study

Inflammatory bowel disease (IBD) of humans is a chronic and devastating disease of unknown etiology. Models of acute colitis in animals have been achieved by intrarectal administration of agents such as 2,4,6-trinitrobenzenesulfonic acid (TNBS) into rat colon. This agent induces focal inflammation and alterations in the colon with features similar to those found in chronic inflammatory diseases in humans. The aim of this study was to assess the effect of TNBS administration on histological and ultrastructural features of the rat colon, especially in areas not affected by transmural inflammation. Also in areas without transmural inflammation, we observed a significant increase in crypt diameter and in the number and area of the goblet cells, as well as alterations in the contents of mucin in goblet cells. We conclude that TNBS treatment in rats led to severe changes in normal architecture of the colon and also in damaged areas where no direct inflammation was produced.

Quantitative analysis of small intestinal microcirculation in the mouse

Impairment of intestinal nutritive perfusion and accumulation of inflammatory cells in the intestinal microvasculature are well-known sequelae of mesenteric ischemia/reperfusion, sepsis, and shock. However, the molecular mechanisms underlying these alterations are still not fully understood. The mouse is particularly suitable for the study of these mechanisms since in this species the involvement of, for example, adhesion receptors or pro-/anti-adhesive mediators can be selectively investigated by the use of monoclonal antibodies or gene-targeted strains. The aim of our present study was, therefore, to establish a model to investigate the microcirculation in the mouse small intestine. Under anesthesia by inhalation of isoflurane-N2O, Balb/c mice (n = 16) were laparotomized, and a segment of the jejunum was exteriorized for intrvital fluorescence microscopy. Using FITC-dextran (MW 150,000) as a plasma marker, functional capillary density (FCD) of both the intestinal mucosa and muscle layer was analyzed. Nutritive perfusion was homogeneous in both compartments with values for FCD of 512 +/- 15 cm-1 in mucosa and 226 +/- 21 cm-1 in the muscle layer. No significant changes were observed throughout the observation period of 2 h (FCD values at the end of the observation period: 524 +/- 31 cm-1 and 207 +/- 7 cm-1 in mucosa and muscle, respectively). Besides capillary perfusion, leukocyte-endothelial cell interaction was analyzed in postcapillary venules of the intestinal submucosa using rhodamine-6G as an in vivo leukocyte stain. Under physiological conditions only a few white blood cells were found rolling along or firmly adherent to the microvascular endothelium (number of rolling leukocytes 1 +/- 0.2 cells/mm per second; number of adherent leukocytes: 18 +/- 7 cells/mm2). In a separate group rhodamine-6G-labeled syngeneic platelets were infused to analyze platelet-endothelial cell interactions quantitatively in vivo. Platelets rolled along or attached to the endothelium in a manner similar to leukocytes. However, in contrast to leukocytes the interactions were not restricted to venules, but were also observed in small arterioles. The newly established model allows for the visualization and quantitative assessment of both nutritive perfusion and platelet/leukocytendothelial cell interactions within the distinct layers of the mouse small intestine. Using this model in combination with gene-targeted mice or monoclonal antibodies it is possible to investigate the molecular mechanisms of intestinal inflammation reactions.

Leucocyte endothelial cell adhesion in indomethacin induced intestinal inflammation is correlated with faecal pH

BACKGROUND

Recent studies indicate that faecal pH is acidified in patients with inflammatory bowel disease compared with healthy controls. In healthy volunteers, stool pH, faecal flora, and bile acid concentration could be affected by means of elemental diets.

AIMS

To assess the role of variations of faecal pH on leucocyte endothelial cell adhesion in indomethacin induced long lasting ileitis in rats.

METHODS

Indomethacin (7.5 mg/kg subcutaneously) was injected twice, 24 hours apart. Rats were either fed with the identical diet before and 10 days after the induction of inflammation until the experiment, or the diet was changed at the time of induction. Ten postcapillary mesenteric venules (30 microns diameter) per animal were observed using intravital microscopy. Macroscopic visible intestinal ulceration was scored and faecal pH of different sections of the small bowel was determined.

RESULTS

Small intestinal faecal pH was 8.5 in controls and 8.0 in indomethacin treated animals. Indomethacin significantly changed microcirculatory parameters: there was a 2.3-fold increase in leucocyte adherence, a 3.2-fold increase in leucocyte emigration, and a 20% reduction in shear rate. Application of various diets or diet combinations resulted in variations in faecal pH ranging from 7.8 to 8.8 which were inversely correlated with macroscopic ulcerations (r = -0.67). Leucocyte adherence was attenuated with increased pH and augmented with decreased pH (r = -0.55). Venular wall shear rate was positively correlated with faecal pH (r = 0.48) while leucocyte emigration showed no correlation. Leucocyte rolling velocity was not significantly altered. Normalisation of faecal pH by different alkalising drugs induced a significant decrease in leucocyte adherence in standard fed, indomethacin treated rats.

CONCLUSIONS

Faecal pH is lowered in the indomethacin model of long lasting ileitis in rats, which is similar to human inflammatory bowel disease. Alkalisation of faecal pH due to different diets or alkalising drugs reduces indomethacin induced leucocyte endothelial cell adhesion and macroscopic intestinal damage. These results may provide a rationale for the therapeutic effect of enteral diets in Crohn's disease.