Interleukin-1beta mediates the extra-intestinal thrombosis associated with experimental colitis

Exosomes-transferred LINC00668 Contributes to Thrombosis by Promoting NETs Formation in Inflammatory Bowel Disease

Epidemiological studies show an association between inflammatory bowel disease (IBD) and increased risk of thrombosis. However, how IBD influences thrombosis remains unknown. The current study shows that formation of neutrophil extracellular traps (NETs) significantly increased in the dextran sulfate sodium (DSS)-induced IBD mice, which in turn, contributes to thrombus formation in a NETs-dependent fashion. Furthermore, the exosomes isolated from the plasma of the IBD mice induce arterial and venous thrombosis in vivo. Importantly, proinflammatory factors-exposed intestinal epithelial cells (inflamed IECs) promote neutrophils to release NETs through their secreted exosomes. RNA sequencing revealed that LINC00668 is highly enriched in the inflamed IECs-derived exosomes. Mechanistically, LINC00668 facilitates the translocation of neutrophil elastase (NE) from the cytoplasmic granules to the nucleus via its interaction with NE in a sequence-specific manner, thereby inducing NETs release and thrombus formation. Importantly, berberine (BBR) suppresses the nuclear translocation of NE and subsequent NETs formation by inhibiting the interaction of LINC00668 with NE, thus exerting its antithrombotic effects. This study provides a novel pathobiological mechanism linking IBD and thrombosis by exosome-mediated NETs formation. Targeting LINC00668 can serve as a novel molecular treatment strategy to treat IBD-related thrombosis.

IEC-intrinsic IL-1R signaling holds dual roles in regulating intestinal homeostasis and inflammation

Intestinal epithelial cells (IECs) constitute a critical first line of defense against microbes. While IECs are known to respond to various microbial signals, the precise upstream cues regulating diverse IEC responses are not clear. Here, we discover a dual role for IEC-intrinsic interleukin-1 receptor (IL-1R) signaling in regulating intestinal homeostasis and inflammation. Absence of IL-1R in epithelial cells abrogates a homeostatic antimicrobial program including production of antimicrobial peptides (AMPs). Mice deficient for IEC-intrinsic IL-1R are unable to clear Citrobacter rodentium (C. rodentium) but are protected from DSS-induced colitis. Mechanistically, IL-1R signaling enhances IL-22R-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation in IECs leading to elevated production of AMPs. IL-1R signaling in IECs also directly induces expression of chemokines as well as genes involved in the production of reactive oxygen species. Our findings establish a protective role for IEC-intrinsic IL-1R signaling in combating infections but a detrimental role during colitis induced by epithelial damage.

Platelet-Covered Nanocarriers for Targeted Delivery of Hirudin to Eliminate Thrombotic Complication in Tumor Therapy

Most patients are at high risk of thrombosis during cancer treatment. However, the major discrepancy in the therapeutic mechanisms and microenvironment between tumors and thrombosis makes it challenging for a panacea to treat cancer while being able to eliminate the risk of thrombosis. Herein, we developed a biomimetic MnOx/Ag₂S nanoflower platform with platelet membrane modification (MnOx@Ag₂S@hirudin@platelet membrane: MAHP) for the long-term release of anticoagulant drugs to treat thrombosis together with tumor therapy. This MAHP platform could achieve the targeted delivery of hirudin to the thrombus site and perform the controlled release under the irradiation of near-infrared light, demonstrating effective removal of the thrombus. Moreover, MAHP could inhibit tumor progression and prolong the survival time of mice with thromboembolic complications.

Experimental and Clinical Evidence of Endothelial Dysfunction in Inflammatory Bowel Disease

The endothelium has a crucial role in proper hemodynamics. Inflammatory bowel disease (IBD) is mainly a chronic inflammatory condition of the gastrointestinal tract. However, considerable evidence points to high cardiovascular risk in patients with IBD. This review positions the basic mechanisms of endothelial dysfunction in the IBD setting (both clinical and experimental). Furthermore, we review the main effects of drugs used to treat IBD in endothelial (dys)function. Moreover, we leave challenging points for enlarging the therapeutic arsenal for IBD with new or repurposed drugs that target endothelial dysfunction besides inflammation.

Neutrophil Extracellular Traps Induce Intestinal Damage and Thrombotic Tendency in Inflammatory Bowel Disease

BACKGROUND AND AIMS

Despite the presence of neutrophil extracellular traps [NETs] in inflamed colon having been confirmed, the role of NETs, especially the circulating NETs, in the progression and thrombotic tendency of inflammatory bowel disease [IBD] remains elusive. We extended our previous study to prove that NETs constitute a central component in the progression and prothrombotic state of IBD.

METHODS

In all 48 consecutive patients with IBD were studied. Acute colitis was induced by the treatment of C57BL/6 mice with 3.5% dextran sulphate sodium [DSS] in drinking water for 6 days. Peripheral blood neutrophils and sera were collected from IBD patients and murine colitis models. Exposed phosphatidylserine [PS] was analysed with flow cytometry and confocal microscopy. Procoagulant activity was evaluated using clotting time, purified coagulation complex, and fibrin formation assays.

RESULTS

We observed higher plasma NET levels and presence of NETs in colon tissue in patients with active IBD. More importantly, NETs were induced in mice with DSS colitis, and inhibition of NET release attenuated colitis as well as colitis-associated tumorigenesis. NET degradation through DNase administration decreased cytokine levels during DSS-induced colitis. In addition, DNase treatment also significantly attenuated the accelerated thrombus formation and platelet activation observed in DSS-induced colitis. NETs triggered PS-positive microparticle release and PS exposure on platelets and endothelial cells partially through TLR2 and TLR4, converting them to a procoagulant phenotype.

CONCLUSIONS

NETs exacerbate colon tissue damage and drive thrombotic tendency during active IBD. Strategies directed against NET formation may offer a potential therapeutic approach for the treatment of IBD.

Venous thromboembolism in IBD: Increased risk for women in CD?

Although coagulation disturbances have been described in inflammatory bowel disease (IBD), it remains unclear how common venous thromboembolism (VTE) is in IBD, and what factors influence VTE frequency. We evaluated VTE in Crohn's disease (CD) and ulcerative colitis (UC) at LSUHSC-S, a southern US medical center with an approximately equal White: African-American (AA) (1.12:1) patient base. This retrospective study evaluated VTE as a co-morbidity in IBD as a function of age, gender and race based on ICD-10 coding (2011-2015.) Results. Of 276 IBD diagnostic records, 213 were for CD (77.17%) and 63 for UC (22.8%). 52% of the CD patients were white, 42% were AA, and 6% were other. 42% of CD patients were male, with 58% were female. 6.1% (13 patients) of the 213 CD patients had a VTE. Of these 13 CD patients, 9 had active disease and 4 were in remission. 9 of 13 were female and 4 were male, with 5 white patients and 4 A A patients. 63 patients were diagnosed with UC, 3.38-fold fewer cases than CD. 25 UC patients were white, 25 were AA and 13 were in other ethnic groups. Of 63 UC cases, 2 UC patients had a VTE, both with active disease. At our institution, VTE appears to be 3x more frequently associated with CD than UC and was more common in white female patients. The recognition of VTE risk in CD, particularly in women, may be an important observation which may guide therapy and limit potentially life-threatening consequences.

Novel Role of T Cells and IL-6 (Interleukin-6) in Angiotensin II-Induced Microvascular Dysfunction

Hypertension is an established risk factor for subsequent cardiovascular diseases, with Ang II (angiotensin II) playing a major role in mediating thrombotic and inflammatory abnormalities. Although T cells and IL-6 (interleukin-6) play an important role in adaptive immune responses, little is known about their role(s) in the thromboinflammatory responses associated with Ang II. Here we show using intravital microscopy coupled with the light/dye injury model that Rag-1 deficient (Rag-1-/-) and IL-6 deficient (IL-6-/-) mice are afforded protection against Ang II-induced thrombosis. Blocking IL-6 receptors (using CD126 and gp130 antibodies) significantly diminished Ang II-mediated thrombosis and inflammatory cell recruitment in mice. Furthermore, the adoptive transfer of IL-6-/--derived T cells into Rag-1-/- mice failed to accelerate Ang II-induced thrombosis compared with Rag-1-/- mice reconstituted with wild-type-derived T cells, suggesting T cell IL-6 mediates the thrombotic abnormalities associated Ang II hypertension. Interestingly, adoptive transfer of WT T cells into Rag-1-/-/Ang II mice resulted in increased numbers of immature platelets, which constitutes a more active platelet population, that is, prothrombotic and proinflammatory. To translate our in vivo findings, we used clinical samples to demonstrate that IL-6 also predisposes platelets to an interaction with collagen receptors, thereby increasing the propensity for platelets to aggregate and cause thrombosis. In summary, we provide compelling evidence for the involvement of IL-6, IL-6R, and T-cell-dependent IL-6 signaling in Ang II-induced thromboinflammation, which may provide new therapeutic possibilities for drug discovery programs for the management of hypertension.

Neonatal Colonic Inflammation Epigenetically Aggravates Epithelial Inflammatory Responses to Injury in Adult Life

BACKGROUND & AIMS

Early life adversity is considered a risk factor for the development of gastrointestinal diseases, including inflammatory bowel disease. We hypothesized that early life colonic inflammation causes susceptibility to aggravated overexpression of interleukin (IL)1β.

METHODS

We developed a 2-hit rat model in which neonatal inflammation (NI) and adult inflammation (AI) were induced by trinitrobenzene sulfonic acid.

RESULTS

Aggravated immune responses were observed in NI + AI rats, including a sustained up-regulation of IL1β and other cytokines. In parallel with exacerbated loss of inhibitor of kappa B alpha expression, NI + AI rats showed hyperacetylation of histone H4K12 and increased V-Rel Avian Reticuloendotheliosis Viral Oncogene Homolog A binding on the IL1B promoter, accompanied by high levels of norepinephrine/epinephrine. Propranolol, a β-blocker, markedly ameliorated the inflammatory response and IL1β overexpression by mitigating against epigenetic modifications. Adrenalectomy abrogated NI-induced disease susceptibility whereas yohimbine sensitized the epithelium for exacerbated immune response. The macrophages of NI rats produced more IL1β than controls after exposure to lipopolysaccharide (LPS), suggesting hypersensitization; incubation with LPS plus Foradil (Sigma, St. Louis, MO), a β2-agonist, induced a greater IL1β expression than LPS alone. Epinephrine and Foradil also exacerbated LPS-induced IL1β activation in human THP-1-derived macrophages, by increasing acetylated H4K12, and these increases were abrogated by propranolol.

CONCLUSIONS

NI sensitizes the colon epithelium for exacerbated IL1β activation by increasing stress hormones that induce histone hyperacetylation, allowing greater access of nuclear factor-κB to the IL1B promoter and rendering the host susceptible to aggravated immune responses. Our findings suggest that β blockers have a therapeutic potential for inflammatory bowel disease susceptibility and establish a novel paradigm whereby NI induces epigenetic susceptibility to inflammatory bowel disease.

Fibrinogen-like protein 2 prothrombinase may contribute to the progression of inflammatory bowel disease by mediating immune coagulation

Inflammation and coagulation are interdependent processes that enable each process to activate and propagate the other in inflammatory bowel disease (IBD). Thus, we investigated the role of a novel immune coagulant, fibrinogen-like protein 2 prothrombinase (FGL2), in patients and mice with IBD. 83 IBD patients and 40 normal controls were enrolled, and trinitro-benzene-sulfonic acid (TNBS)-induced colitis mice were used. Expression of FGL2 in the intestine was detected by immunohistochemistry. Using serial sections, staining was performed to detect tumor necrosis factor α (TNF-α) expression, and to demonstrate co-localization of FGL2 with macrophages and fibrin. Correlations between FGL2 expression with some common laboratory parameters were examined. FGL2 was seen primarily in inflammatory infiltrating cells, mainly macrophages, and microvascular vessels and had a strong co-localization with fibrin deposition. IBD patients and mice had increased expression of FGL2 compared with controls. Furthermore, FGL2 expression was correlated with intestinal and plasmatic TNF-α expression, mean platelet volume (MPV), platelet count (PLT), platelet-crit (PCT), and fibrinogen. Our data indicate that FGL2 may mediate immune coagulation in IBD patients. It may be considered as a novel molecule that contributes to the onset and development of IBD.

Targeting factor VIII expression to platelets for hemophilia A gene therapy does not induce an apparent thrombotic risk in mice

Essentials Platelet-Factor (F) VIII gene therapy is a promising treatment in hemophilia A. This study aims to evaluate if platelet-FVIII expression would increase the risk for thrombosis. Targeting FVIII expression to platelets does not induce or elevate thrombosis risk. Platelets expressing FVIII are neither hyper-activated nor hyper-responsive.

SUMMARY

Background Targeting factor (F) VIII expression to platelets is a promising gene therapy approach for hemophilia A, and is successful even in the presence of inhibitors. It is well known that platelets play important roles not only in hemostasis, but also in thrombosis and inflammation. Objective To evaluate whether platelet-FVIII expression might increase thrombotic risk and thereby compromise the safety of this approach. Methods In this study, platelet-FVIII-expressing transgenic mice were examined either in steady-state conditions or under prothrombotic conditions induced by inflammation or the FV Leiden mutation. Native whole blood thrombin generation assay, rotational thromboelastometry analysis and ferric chloride-induced vessel injury were used to evaluate the hemostatic properties. Various parameters associated with thrombosis risk, including D-dimer, thrombin-antithrombin complexes, fibrinogen, tissue fibrin deposition, platelet activation status and activatability, and platelet-leukocyte aggregates, were assessed. Results We generated a new line of transgenic mice that expressed 30-fold higher levels of platelet-expressed FVIII than are therapeutically required to restore hemostasis in hemophilic mice. Under both steady-state conditions and prothrombotic conditions induced by lipopolysaccharide-mediated inflammation or the FV Leiden mutation, supratherapeutic levels of platelet-expressed FVIII did not appear to be thrombogenic. Furthermore, FVIII-expressing platelets were neither hyperactivated nor hyperactivatable upon agonist activation. Conclusion We conclude that, in mice, more than 30-fold higher levels of platelet-expressed FVIII than are required for therapeutic efficacy in hemophilia A are not associated with a thrombotic predilection.

IL-6 Mediates the Intestinal Microvascular Thrombosis Associated with Experimental Colitis

Inflammatory bowel diseases are associated with increased risk for thrombus formation both within the inflamed bowel and at distant sites. Although the increased propensity for distant organ thrombus development has been recapitulated in animal models of colitis and linked to interleukin-6 (IL-6), it remains unclear whether experimental colitis results in accelerated thrombus development within the inflamed bowel and whether IL-6 contributes to a local thrombogenic response. These issues related to thrombus formation within the inflamed bowel were addressed in mice with dextran sodium sulfate-induced colitis. Wild-type (WT) mice, IL-6 deficient (IL-6(-/-)) mice, and bone marrow chimeras (WT→WT and IL-6(-/-)→WT) were used. The effects of treatment with either an IL-6-blocking, IL-6Rα-blocking or gp130-blocking antibody were also evaluated. Disease activity index and colonic weight-to-length ratio (W/L) were used to monitor the development of colitis. Intravital videomicroscopy was used to study thrombus development (induced with the light/dye method) in mucosal vessels of the ascending colon. Thrombus development was significantly enhanced in WT colitic mice. Neither genetic deficiency nor immunoblockade of IL-6 significantly altered the disease activity index and W/L responses to dextran sodium sulfate treatment. However, colitis-induced thrombogenesis was attenuated in IL-6(-/-) mice and in WT mice treated with either the IL-6-blocking, IL-6Rα-blocking or gp130-blocking antibody. IL-6(-/-)→WT, but not WT→WT chimeras, exhibited a blunted thrombosis response to dextran sodium sulfate. These results indicate that experimental colitis is associated with accelerated thrombus development within the inflamed colon and that IL-6, derived from bone marrow-derived blood cells, is largely responsible for this response.

Retrospective comparison of thromboelastography results to postmortem evidence of thrombosis in critically ill dogs: 39 cases (2005-2010)

OBJECTIVE

To determine whether there is an association between thromboelastography (TEG) data and necropsy evidence of thrombosis in a cohort of critically ill dogs.

DESIGN

Retrospective study (2005-2010).

SETTING

University teaching hospital.

ANIMALS

Thirty-nine client-owned critically ill dogs for which TEG was performed within 7 days of complete necropsy.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Thrombi were found in 26 (67%) dogs. Spayed females (n = 20) were significantly more likely to have thrombosis (P = 0.0127). No significant association was found between presence of thrombosis and any TEG parameter, the calculated coagulation index, results of coagulation testing, type of vascular access, or clinical diagnosis. D-dimers were significantly higher in dogs with thrombosis (P = 0.0207) and a weak positive correlation was found between D-dimer value and number of sites of thrombosis (ρ = 0.18, P = 0.0045). Dogs with WBC > 16 × 10(3) /μL were more likely to have thrombosis compared to others (odds ratio 5.56, 95% confidence interval 1.2-25.7, P = 0.025).

CONCLUSIONS

This study found no association between any TEG parameter and the presence of thrombosis on postmortem examination.

MyD88 mediates the protective effects of probiotics against the arteriolar thrombosis and leukocyte recruitment associated with experimental colitis

Several studies in patients with IBD and in animal models of IBD have revealed a protective effect of probiotics in reducing clinical symptoms of disease and in blunting the gut inflammation that accompanies this condition. However, the mechanism underlying the therapeutic effect of probiotics is currently unknown. Furthermore, the ability of probiotics to influence the enhanced thrombus development that accompanies IBD has not been studied. This study addresses whether the enhanced extraintestinal thrombosis (induced by light/dye injury) associated with experimental colitis is altered by oral treatment with the probiotic preparation VSL#3 or by the absence of microbiota. Colitis was induced by DSS 3% in Swiss Webster mice, germ-free mice, C57BL/6 WT, or Myd88 mice. In some experiments, mice received VSL#3 for 8 days before and during DSS feeding. Swiss Webster mice were also subjected to a chronic model of DSS colitis, and the effect of VSL#3 was evaluated. VSL#3 treatment significantly attenuated the accelerated thrombus formation observed in both acute and chronic models of colitis. VSL#3-treated mice also exhibited attenuated inflammatory response and injury in the colon. The protective effects of VSL#3 on colitis-associated thrombogenesis and inflammation were not evident in MyD88-deficient mice. Our results suggest that improved control of the enteric microflora in IBD may afford protection against the hypercoagulable prothrombotic state that follows this condition.

The relationship between coagulation state and inflammatory bowel disease: current understanding and clinical implications

Inflammatory bowel disease (IBD) is associated with a hypercoagulable state and subsequently with an increased risk for venous thromboembolism (VTE). VTE in IBD is characterized by a high recurrence rate and is associated with the disease activity. Acquired endothelial dysfunction, abnormalities of platelets, activation of coagulation system and impaired fibrinolysis are the main changes in the coagulation state in IBD. The development of VTE in IBD has been considered to be the result of multiple interactions between acquired and inherited risk factors. The treatment of VTE in IBD patients is recommended to be similar and to follow the same protocols as for non-IBD patients. In the clinical practice, the management of IBD patients and especially the hospitalized patients should include thromboprophylaxis.

Venous thrombosis and prothrombotic factors in inflammatory bowel disease

Patients with inflammatory bowel disease (IBD) may have an increased risk of venous thrombosis (VTE). PubMed, ISI Web of Knowledge and Scopus were searched to identify studies investigating the risk of VTE and the prevalence of acquired and genetic VTE risk factors and prothrombotic abnormalities in IBD. Overall, IBD patients have a two- to fourfold increased risk of VTE compared with healthy controls, with an overall incidence rate of 1%-8%. The majority of studies did not show significant differences in the risk of VTE between Crohn’s disease and ulcerative colitis. Several acquired factors are responsible for the increased risk of VTE in IBD: inflammatory activity, hospitalisation, surgery, pregnancy, disease phenotype (e.g., fistulising disease, colonic involvement and extensive involvement) and drug therapy (mainly steroids). There is also convincing evidence from basic science and from clinical and epidemiological studies that IBD is associated with several prothrombotic abnormalities, including initiation of the coagulation system, downregulation of natural anticoagulant mechanisms, impairment of fibrinolysis, increased platelet count and reactivity and dysfunction of the endothelium. Classical genetic alterations are not generally found more often in IBD patients than in non-IBD patients, suggesting that genetics does not explain the greater risk of VTE in these patients. IBD VTE may have clinical specificities, namely an earlier first episode of VTE in life, high recurrence rate, decreased efficacy of some drugs in preventing further episodes and poor prognosis. Clinicians should be aware of these risks, and adequate prophylactic actions should be taken in patients who have disease activity, are hospitalised, are submitted to surgery or are undergoing treatment.

Platelet activation and platelet-leukocyte aggregation elicited in experimental colitis are mediated by interleukin-6

There is growing evidence for an interdependence of inflammation, coagulation, and thrombosis in acute and chronic inflammatory diseases. Inflammatory bowel diseases (IBD) are associated with a hypercoagulable state and an increased risk of thromboembolism. Although the IBD-associated prothrombogenic state has been linked to the inflammatory response, the mediators that link these 2 conditions remain unclear. Recent evidence suggests that interleukin-6 (IL-6) may be important in this regard. The objective of this study was to more fully define the contribution of IL-6 to the altered platelet function that occurs during experimental colitis. The number of immature and mature platelets, activated platelets, and platelet-leukocyte aggregates were measured in wild-type and IL-6 mice with dextran sodium sulfate (DSS)-induced colonic inflammation. DSS treatment of WT mice was associated with significant increases in the number of both immature and mature platelets, activated platelets, and platelet-leukocyte aggregates. These platelet responses to DSS were not observed in IL-6 mice. Chronic IL-6 infusion (through an Alzet pump) in WT mice reproduced all of the platelet abnormalities observed in DSS-colitic mice. IL-6-infused mice also exhibited an acceleration of thrombus formation in arterioles, similar to DSS. These findings implicate IL-6 in the platelet activation and enhanced platelet-leukocyte aggregate formation associated with experimental colitis, and support a role for this cytokine as a mediator of the enhanced thrombogenesis in IBD.

Decreases in colonic and systemic inflammation in chronic HIV infection after IL-7 administration

Despite antiretroviral therapy (ART), some HIV-infected persons maintain lower than normal CD4(+) T-cell counts in peripheral blood and in the gut mucosa. This incomplete immune restoration is associated with higher levels of immune activation manifested by high systemic levels of biomarkers, including sCD14 and D-dimer, that are independent predictors of morbidity and mortality in HIV infection. In this 12-week, single-arm, open-label study, we tested the efficacy of IL-7 adjunctive therapy on T-cell reconstitution in peripheral blood and gut mucosa in 23 ART suppressed HIV-infected patients with incomplete CD4(+) T-cell recovery, using one cycle (consisting of three subcutaneous injections) of recombinant human IL-7 (r-hIL-7) at 20 µg/kg. IL-7 administration led to increases of both CD4(+) and CD8(+) T-cells in peripheral blood, and importantly an expansion of T-cells expressing the gut homing integrin α4β7. Participants who underwent rectosigmoid biopsies at study baseline and after treatment had T-cell increases in the gut mucosa measured by both flow cytometry and immunohistochemistry. IL-7 therapy also resulted in apparent improvement in gut barrier integrity as measured by decreased neutrophil infiltration in the rectosigmoid lamina propria 12 weeks after IL-7 administration. This was also accompanied by decreased TNF and increased FOXP3 expression in the lamina propria. Plasma levels of sCD14 and D-dimer, indicative of systemic inflammation, decreased after r-hIL-7. Increases of colonic mucosal T-cells correlated strongly with the decreased systemic levels of sCD14, the LPS coreceptor - a marker of monocyte activation. Furthermore, the proportion of inflammatory monocytes expressing CCR2 was decreased, as was the basal IL-1β production of peripheral blood monocytes. These data suggest that administration of r-hIL-7 improves the gut mucosal abnormalities of chronic HIV infection and attenuates the systemic inflammatory and coagulation abnormalities that have been linked to it.

Inflammatory cytokine gene expression in mesenteric adipose tissue during acute experimental colitis

BACKGROUND

Production of inflammatory cytokines by mesenteric adipose tissue (MAT) has been implicated in the pathogenesis of inflammatory bowel disease (IBD). Animal models of colitis have demonstrated inflammatory changes within MAT, but it is unclear if these changes occur in isolation or as part of a systemic adipose tissue response. It is also unknown what cell types are responsible for cytokine production within MAT. The present study was designed to determine whether cytokine production by MAT during experimental colitis is depot-specific, and also to identify the source of cytokine production within MAT.

METHODS

Experimental colitis was induced in 6-month-old C57BL/6 mice by administration of dextran sulfate sodium (2% in drinking water) for up to 5 days. The induction of cytokine mRNA within various adipose tissues, including mesenteric, epididymal, and subcutaneous, was analyzed by qRT-PCR. These adipose tissues were also examined for histological evidence of inflammation. The level of cytokine mRNA during acute colitis was compared between mature mesenteric adipocytes, mesenteric stromal vascular fraction (SVF), and mesenteric lymph nodes.

RESULTS

During acute colitis, MAT exhibited an increased presence of infiltrating mononuclear cells and fibrotic structures, as well as decreased adipocyte size. The mRNA levels of TNF-α, IL-1β, and IL-6 were significantly increased in MAT but not other adipose tissue depots. Within the MAT, induction of these cytokines was observed mainly in the SVF.

CONCLUSIONS

Acute experimental colitis causes a strong site-specific inflammatory response within MAT, which is mediated by cells of the SVF, rather than mature adipocytes or mesenteric lymph nodes.

Inflammatory bowel disease: mechanisms, redox considerations, and therapeutic targets

Oxidative stress is thought to play a key role in the development of intestinal damage in inflammatory bowel disease (IBD), because of its primary involvement in intestinal cells' aberrant immune and inflammatory responses to dietary antigens and to the commensal bacteria. During the active disease phase, activated leukocytes generate not only a wide spectrum of pro-inflammatory cytokines, but also excess oxidative reactions, which markedly alter the redox equilibrium within the gut mucosa, and maintain inflammation by inducing redox-sensitive signaling pathways and transcription factors. Moreover, several inflammatory molecules generate further oxidation products, leading to a self-sustaining and auto-amplifying vicious circle, which eventually impairs the gut barrier. The current treatment of IBD consists of long-term conventional anti-inflammatory therapy and often leads to drug refractoriness or intolerance, limiting patients' quality of life. Immune modulators or anti-tumor necrosis factor α antibodies have recently been used, but all carry the risk of significant side effects and a poor treatment response. Recent developments in molecular medicine point to the possibility of treating the oxidative stress associated with IBD, by designing a proper supplementation of specific lipids to induce local production of anti-inflammatory derivatives, as well as by developing biological therapies that target selective molecules (i.e., nuclear factor-κB, NADPH oxidase, prohibitins, or inflammasomes) involved in redox signaling. The clinical significance of oxidative stress in IBD is now becoming clear, and may soon lead to important new therapeutic options to lessen intestinal damage in this disease.

Interleukin-6 mediates the platelet abnormalities and thrombogenesis associated with experimental colitis

Clinical studies and animal experimentation have shown that colonic inflammation is associated with an increased number and reactivity of platelets, coagulation abnormalities, and enhanced thrombus formation. The objective of this study was to define the contribution of IL-6 to the thrombocytosis, exaggerated agonist-induced platelet aggregation, and enhanced extra-intestinal thrombosis that occur during experimental colitis. The number of mature and immature platelets, platelet life span, thrombin-induced platelet aggregation response, and light/dye-induced thrombus formation in cremaster muscle arterioles were measured in wild-type (WT) and IL-6-deficient (IL-6(-/-)) mice with dextran sodium sulfate (DSS)-induced colitis. DSS colitis in WT mice was associated with thrombocytosis with an elevated number of both mature and immature platelets and no change in platelet life span. The thrombocytosis response was absent in IL-6(-/-) mice. DSS treatment also enhanced the platelet aggregation response to thrombin and accelerated thrombus development in WT mice, but not in IL-6(-/-) mice. Exogenous IL-6 administered to WT mice elicited a dose-dependent enhancement of thrombus formation. These findings indicate that IL-6 mediates the thrombocytosis, platelet hyperreactivity, and accelerated thrombus development associated with experimental colitis. The IL-6-dependent colitis-induced thrombocytosis appears to result from an enhancement of thrombopoiesis because platelet life span is unchanged.

Platelet abnormalities during colonic inflammation

Patients with inflammatory bowel disease are susceptible to microvascular thrombosis and thromboembolism. The increased incidence of thrombosis is accompanied by enhanced coagulation and abnormalities in platelet function. Clinical studies have revealed thrombocytosis, alterations in platelet activation, enhanced platelet-leukocyte interactions, and elevated plasma levels of prothrombotic cytokines. This study was directed toward determining whether the thrombocytosis, altered platelet functions, and enhanced platelet-leukocyte interactions observed in patients with inflammatory bowel disease can be recapitulated in the dextran sodium sulfate and T-cell transfer models of murine colonic inflammation. Flow cytometry was used to characterize platelet function in heparin-anticoagulated whole blood of control mice and in mice with colonic inflammation. Platelets were identified by characteristic light scattering and membrane expression of CD41. Thiazole orange labeling was used to differentiate between immature and mature platelets. Platelet activation was monitored using the expression of an activation epitope of GPIIb/IIIa integrin. The combination of CD41, CD45.2, Gr-1, F4/80, and isotype control antibodies was used to detect and quantify aggregates of leukocytes, neutrophils, and monocytes with platelets. Our results indicated that colonic inflammation is associated with thrombocytosis, leukocytosis, and the appearance of immature platelets. An increased number of circulating activated platelets was detected in colitic mice, along with the formation of aggregates of leukocytes (PLA), neutrophils (PNA), and monocytes (PMA) with platelets. Selectin blockade with fucoidin inhibited dextran sodium sulfate-induced PLA formation. The findings of this study indicate that many features of the altered platelet function detected in human inflammatory bowel disease can be reproduced in animal models of colonic inflammation.

Increased procoagulant function of microparticles in pediatric inflammatory bowel disease: role in increased thrombin generation

OBJECTIVES

Patients with inflammatory bowel disease (IBD) have a higher risk for venous thromboembolism compared with non-IBD subjects. The pathogenic mechanisms of the thrombotic events are not fully understood. We investigated levels of circulating microparticles and their influence on thrombin generation in pediatric patients with IBD during active and quiescent disease compared with healthy controls.

METHODS

Plasma samples were collected from 33 pediatric patients with Crohn disease (CD), 20 pediatric patients with ulcerative colitis (UC), and 60 healthy controls. Microparticles' procoagulant activity was measured by enzyme-linked immunosorbent assay, and the dependency of thrombin generation on microparticles-derived tissue factor was determined by means of calibrated automated thrombography.

RESULTS

The procoagulant function of microparticles was significantly increased in patients with active and inactive CD, and active UC compared with controls. Endogenous thrombin potential was significantly higher in patients with CD and UC compared with controls. A minor influence of microparticles on thrombin generation was only observed for patients with active UC.

CONCLUSIONS

Our study shows increased procoagulant function of microparticles in pediatric patients with active and quiescent CD and active UC compared with controls, but demonstrates that they are not a major cause for the higher thrombin generation in pediatric patients with IBD.

Platelet-derived Toll-like receptor 4 (Tlr-4) is sufficient to promote microvascular thrombosis in endotoxemia

Endotoxin (lipopolysaccharide, LPS) produced by gram-negative bacteria initiates a host of pro-inflammatory effects through Toll-like receptor 4 (TLR-4). We reported previously that LPS enhances microvascular thrombosis in cremaster venules of wild-type mice, but had no effect in mice deficient in TLR-4. Since TLR-4 is expressed on various cell types, the cellular origin of TLR-4 responsible for the LPS-enhanced thrombosis remains undetermined. Platelets are known to express functional TLR-4. Platelet-derived TLR-4 has been suggested to mediate various inflammatory responses in endotoxemia, including production of tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β), two cytokines reported to enhance microvascular thrombosis. We determined whether platelet-derived TLR-4 was sufficient to mediate the enhanced thrombosis induced by endotoxin and whether these responses were accompanied by systemic increases in TNF-α and IL-1β. We isolated platelets from wild-type mice and transfused them into either of two strains of TLR-4-deficient mice (C57BL/10ScN and B6.B10ScN-TLR-4^lps-del/Jth). The mice were then injected with LPS or saline, and the kinetics of thrombosis were studied 4 hours later. Transfusion of wild-type platelets restored responsiveness to LPS in TLR-4-deficient mice with regards to microvascular thrombosis but not to plasma levels of TNF-α or IL-1β. The accelerated rates of microvascular thrombosis induced by platelet transfusions were specific to TLR-4, since isolation and transfusion of platelets derived from TLR-4-deficient donors did not restore responsiveness to LPS. These studies demonstrate that platelet-derived TLR-4 is sufficient to promote microvascular thrombosis in endotoxemia, independent of systemic increases in TNF-α or IL-1β.

Mechanism of interleukin-1β induced-increase in mouse intestinal permeability in vivo

Interleukin-1β (IL-1β) has been shown to play an essential role in mediating intestinal inflammation of Crohn's disease and other inflammatory conditions of the gut. Previous studies from our laboratory have shown that IL-1β causes an increase in intestinal tight-junction permeability in Caco-2 monolayers in vitro. However, the IL-1β effect on the intestinal epithelial barrier in vivo remains unclear.

AIMS

the major aims of this study were to examine the effect of IL-1β on mouse intestinal epithelial barrier in vivo and to delineate the mechanisms involved using an in vivo model system consisting of a recycling perfusion of mouse small intestine. Intraperitonial injection of IL-1β at varying doses (0-10 μg) caused a concentration-dependent increase in mouse intestinal permeability to the paracellular marker dextran (10 KD), and the maximal increase in dextran flux occurred at IL-1β dose of 5 μg. IL-1β treatment caused an increase in myosin light-chain kinase (MLCK) mRNA and protein expression in the small intestinal tissue starting at 24 h, which continued up to 72 h. Additionally, IL-1β did not cause an increase in intestinal permeability in MLCK-deficient mice (C57BL/6 MLCK(-/-)). MLCK inhibitor ML-7 (2 mg/kg body weight) also inhibited the IL-1β-induced increase in small intestinal permeability. The IL-1β-induced increase in mouse intestinal permeability was associated with an increase in NF-κB activation. The intestinal tissue-specific silencing of NF-κB p65 inhibited the IL-1β-induced increase in intestinal permeability and increase in MLCK expression. These data show for the first time that IL-1β causes an increase in mouse intestinal permeability in vivo. These data suggested that the mechanism of IL-1β-induced increase in mouse intestinal permeability in vivo involved NF-κB p65-induced activation of the mouse enterocyte MLCK gene.

Role of tumor necrosis factor-α in the extraintestinal thrombosis associated with colonic inflammation

BACKGROUND

Inflammatory bowel diseases (IBDs) are associated with a hypercoagulable state and an increased risk of thromboembolism, with accelerated thrombus formation occurring both within the inflamed bowel and in distant tissues. While the IBD-associated prothrombogenic state has been linked to the inflammatory response, the mediators that link inflammation and thrombosis remain poorly defined. The objective of this study was to assess the role of tumor necrosis factor alpha (TNF-α) in the enhanced extraintestinal microvascular thrombosis that accompanies colonic inflammation.

METHODS

TNF-α concentration was measured in plasma, colon, and skeletal muscle of control mice and in mice with dextran sodium sulfate (DSS)-induced colitis. A light/dye injury method was used to induce microvascular thrombosis in cremaster microvessels. The effects of exogenous TNF-α on thrombus formation were determined in control mice. DSS-enhanced thrombus formation was evaluated in wildtype (WT) mice treated with an anti-TNF-α antibody (±an anti-IL-1β antibody) and in TNF-α receptor-deficient (TNFr(-/-) ) mice.

RESULTS

DSS colitis enhanced thrombus formation in cremaster arterioles. A similar response was produced by TNF-α administration in control mice. TNF-α concentration was elevated in plasma, colon, and skeletal muscle. Immunoblockade of TNF-α or genetic deficiency of the TNF-α receptor blunted the thrombotic response of arterioles to DSS colitis. Additional protection was noted in mice receiving antibodies to both TNF-α and IL-1β.

CONCLUSIONS

Our findings implicate TNF-α in the enhanced microvascular thrombosis that occurs in extraintestinal tissue during colonic inflammation, and suggests that the combined actions of TNF-α and IL-1β accounts for most of the colitis-enhanced thrombotic response.

Role of T lymphocytes in angiotensin II-mediated microvascular thrombosis

Clinical trials and animal studies have revealed a role for the renin-angiotensin system in the enhanced thrombus development that is associated with hypertension. Because T lymphocytes have been implicated in the vascular dysfunction and blood pressure elevation associated with increased angiotensin II (Ang II) levels, we evaluated the role of the adaptive immune system in mediating the enhanced thrombosis during Ang II-induced hypertension. Light/dye-induced thrombosis was induced in cremaster arterioles of wild-type, immunodeficient Rag-1(-/-), CD8(+), or CD4(+) lymphocyte-deficient and NADPH oxidase (gp91(phox))-deficient mice implanted with an Ang II-loaded pump for 2 weeks. Chronic Ang II infusion enhanced arteriolar thrombosis in wild-type mice but not in Rag-1(-/-), CD4(+) T-cell-deficient, or gp91(phox-/-) mice. CD8(+) T-cell(-/-) mice exhibited partial protection. Adoptive transfer of T cells derived from wild-type or gp91(phox-/-) mice into Rag-1(-/-) restored the prothrombotic phenotype induced by Ang II. T lymphocytes (CD4(+) and, to a lesser extent, CD8(+)) play a major role in mediating the accelerated microvascular thrombosis associated with Ang II-induced hypertension. NADPH oxidase-derived reactive oxygen species, produced by cells other than T lymphocytes, also appear critical for the Ang II-enhanced, T cell-dependent thrombosis response.