Murine Model Of Kawasaki Disease Research Articles

MTOR signalling controls the formation of smooth muscle cell-derived luminal myofibroblasts during vasculitis

The accumulation of myofibroblasts within the intimal layer of inflamed blood vessels is a potentially catastrophic complication of vasculitis, which can lead to arterial stenosis and ischaemia. In this study, we have investigated how these luminal myofibroblasts develop during Kawasaki disease (KD), a paediatric vasculitis typically involving the coronary arteries. By performing lineage tracing studies in a murine model of KD, we reveal that luminal myofibroblasts develop independently of adventitial fibroblasts and endothelial cells, and instead derive from smooth muscle cells (SMCs). Notably, the emergence of SMC-derived luminal myofibroblasts—in both mice and patients with KD, Takayasu’s arteritis and Giant Cell arteritis—coincided with activation of the mechanistic target of rapamycin (mTOR) signalling pathway. Moreover, SMC-specific deletion of mTOR signalling, or pharmacological inhibition, abrogated the emergence of luminal myofibroblasts. Thus, mTOR is an intrinsic and essential regulator of luminal myofibroblast formation that is activated in vasculitis patients and therapeutically tractable. These findings provide molecular insight into the pathogenesis of coronary artery stenosis and identify mTOR as a therapeutic target in vasculitis.

Inhibition of IL-1 Ameliorates Cardiac Dysfunction and Arrhythmias in a Murine Model of Kawasaki Disease.

Kawasaki disease (KD) is an acute febrile illness and systemic vasculitis often associated with cardiac sequelae, including arrhythmias. Abundant evidence indicates a central role for IL (interleukin)-1 and TNFα (tumor necrosis factor-alpha) signaling in the formation of arterial lesions in KD. We aimed to investigate the mechanisms underlying the development of electrophysiological abnormalities in a murine model of KD vasculitis. Lactobacillus casei cell wall extract-induced KD vasculitis model was used to investigate the therapeutic efficacy of clinically relevant IL-1Ra (IL-1 receptor antagonist) and TNFα neutralization. Echocardiography, in vivo electrophysiology, whole-heart optical mapping, and imaging were performed. KD vasculitis was associated with impaired ejection fraction, increased ventricular tachycardia, prolonged repolarization, and slowed conduction velocity. Since our transcriptomic analysis of human patients showed elevated levels of both IL-1β and TNFα, we asked whether either cytokine was linked to the development of myocardial dysfunction. Remarkably, only inhibition of IL-1 signaling by IL-1Ra but not TNFα neutralization was able to prevent changes in ejection fraction and arrhythmias, whereas both IL-1Ra and TNFα neutralization significantly improved vasculitis and heart vessel inflammation. The treatment of L casei cell wall extract-injected mice with IL-1Ra also restored conduction velocity and improved the organization of Cx43 (connexin 43) at the intercalated disk. In contrast, in mice with gain of function of the IL-1 signaling pathway, L casei cell wall extract induced spontaneous ventricular tachycardia and premature deaths. Our results characterize the electrophysiological abnormalities associated with L casei cell wall extract-induced KD and show that IL-1Ra is more effective in preventing KD-induced myocardial dysfunction and arrhythmias than anti-TNFα therapy. These findings support the advancement of clinical trials using IL-1Ra in patients with KD.

Mechanistic Target of Rapamycin Inhibition Prevents Coronary Artery Remodeling in a Murine Model of Kawasaki Disease.

Remodeling of the coronary arteries is a common feature in severe cases of Kawasaki disease (KD). This pathology is driven by the dysregulated proliferation of vascular fibroblasts, which can lead to coronary artery aneurysms, stenosis, and myocardial ischemia. We undertook this study to investigate whether inhibiting fibroblast proliferation might be an effective therapeutic strategy to prevent coronary artery remodeling in KD. We used a murine model of KD (induced by the injection of the Candida albicans water-soluble complex [CAWS]) and analyzed patient samples to evaluate potential antifibrotic therapies for KD. We identified the mechanistic target of rapamycin (mTOR) pathway as a potential therapeutic target in KD. The mTOR inhibitor rapamycin potently inhibited cardiac fibroblast proliferation in vitro, and vascular fibroblasts up-regulated mTOR kinase signaling in vivo in the CAWS mouse model of KD. We evaluated the in vivo efficacy of mTOR inhibition and found that the therapeutic administration of rapamycin reduced vascular fibrosis and intimal hyperplasia of the coronary arteries in CAWS-injected mice. Furthermore, the analysis of cardiac tissue from KD fatalities revealed that vascular fibroblasts localizing with inflamed coronary arteries up-regulate mTOR signaling, confirming that the mTOR pathway is active in human KD. Our findings demonstrate that mTOR signaling contributes to coronary artery remodeling in KD, and that targeting this pathway offers a potential therapeutic strategy to prevent or restrict this pathology in high-risk KD patients.

PROGRESSION OF VASCULAR FUNCTION AND BLOOD PRESSURE IN A MOUSE MODEL OF KAWASAKI DISEASE.

Kawasaki disease (KD) is a systemic vasculitis of childhood characterized by vascular damage in the acute stage, which can persist into the late stage. The vascular mechanisms in the cardiovascular risk of KD are not fully studied. We investigated the vascular function and blood pressure in a murine model of KD. We used the Candida albicans water-soluble (CAWS) fraction model. Mice were injected with 4 mg CAWS for 5 consecutive days and separated into three groups. Control, CAWS 7 days (C7), and CAWS 28 days (C28). Hearts and arteries were harvested for vascular characterization. Rat aortic smooth muscle cells were used to studies in vitro. C7 presented elevated inflammatory markers in the coronary area and abdominal aortas, whereas C28 showed severe vasculitis. No difference was found in blood pressure parameters. Vascular dysfunction characterized by higher contractility to norepinephrine in C7 and C28 in aortic rings was abolished by blocking nitric oxide (NO), reactive oxygen species, and cyclooxygenase (COX)-derived products. The CAWS complex increased COX2 expression in rat aortic smooth muscle cells, which was prevented by Toll-like receptor 4 antagonist. Our data indicate that the murine model of KD is associated with vascular dysfunction likely dependent on COX-derived products, oxidant properties, and NO bioavailability. Furthermore, vascular smooth muscle cell may present an important role in the genesis of vascular dysfunction and vasculitis via the Toll-like receptor 4 pathway. Finally, the CAWS model seems not to be appropriate to study KD-associated shock. More studies are necessary to understand whether vascular dysfunction and COXs are triggers for vasculitis.

Characterization of Inflammatory Factors and T Cell Subpopulations in a Murine Model of Kawasaki Disease Induced by Candida albicans Cell Wall Extracts (CAWS).

BackgroundKawasaki disease (KD) is an acute vasculitis in children, which ranks as the main cause of acquired heart disease in children in developed countries. The etiopathogenesis of KD remains to be clarified. Our study constructed a KD murine model and monitored the alterations of inflammatory factors and T cell subpopulations.Material/MethodsCandida albicans cell wall extracts (CAWS) were utilized for inducing KD murine models. After 5 days, the mice were subcutaneously injected with rhG-CSF lasting 5 consecutive days. At 4 weeks, histopathology of hearts and arteries was observed via H&E staining. Inflammatory cytokine, chemokine, and adhesion molecule expression in serum specimens was detected via RT-qPCR and ELISA. T cell subpopulations in cardiac tissues were labeled through immunofluorescence and flow cytometry.ResultsCAWS induced cardiac dysfunction (reduced fraction shortening, increased left ventricle end-diastolic diameter and heart weight/body weight ratio) and cardiac and vascular inflammation, which were ameliorated by rhG-CSF treatment. CAWS-induced mice had increased levels of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α), chemokine (RANTES), and adhesion molecules (MCP-1, VCAM-1, ICAM-1, E-selectin), as well as the decreased levels of anti-inflammatory cytokines (IL-10, G-CSF). Their levels were decreased following rhG-CSF administration. There were decreased CD3+, CD4+, CD8+, CD8+CD45+, Foxp3+, CD25+ and Foxp3+CD25+ T lymphocyte subpopulations and an increased CD45+ T lymphocyte subpopulation in cardiac tissues of CAWS-induced mice, which were ameliorated by rhG-CSF administration.ConclusionsOur findings reveal the characteristics of inflammatory factors and T cell subpopulations in CAWS-induced KD. Moreover, rhG-CSF might be an effective therapeutic regimen against KD.

Crucial role of NLRP3 inflammasome in a murine model of Kawasaki disease

Kawasaki disease (KD) is a systemic febrile syndrome during childhood that is characterized by coronary arteritis. The etiopathogenesis of KD remains to be elucidated. NLRP3 inflammasome is a large multiprotein complex that plays a key role in IL-1β-driven sterile inflammatory diseases. In the present study, we investigated the role of NLRP3 inflammasome in a murine model of KD induced by Candida albicans water-soluble fraction (CAWS) and found that NLRP3 inflammasome is required for the development of CAWS-induced vasculitis. CAWS administration induced IL-1β production, caspase-1 activation, leukocyte infiltration, and fibrotic changes in the aortic root and coronary arteries, which were significantly inhibited by a deficiency of IL-1β, NLRP3, and ASC. In vitro experiments showed that among cardiac resident cells, macrophages, but not endothelial cells or fibroblasts, expressed Dectin-2, but did not produce IL-1β in response to CAWS. In contrast, CAWS induced caspase-1 activation and IL-1β production in bone marrow-derived dendritic cells (BMDCs), which were inhibited by a specific caspase-1 inhibitor and a deficiency of NLRP3, ASC, and caspase-1. CAWS induced NLRP3 and pro-IL-1β expression through a Dectin-2/Syk/JNK/NF-κB pathway, and caspase-1 activation and cleavage of pro-IL-1β through Dectin-2/Syk/JNK-mediated mitochondrial ROS generation, indicating that CAWS induces the priming and activation of NLRP3 inflammasome in BMDCs. These findings provide new insights into the pathogenesis of KD vasculitis, and suggest that NLRP3 inflammasome may be a potential therapeutic target for KD.

TNF and IL-1 Play Essential but Temporally Distinct Roles in Driving Cardiac Inflammation in a Murine Model of Kawasaki Disease.

Kawasaki disease (KD) is a leading cause of pediatric heart disease, characterized by the emergence of life-threatening coronary vasculitis. Identifying which cytokines drive KD has been a major research goal, and both TNF and IL-1 have been identified as potential candidates. Using a murine model of KD induced by the injection of the water-soluble component of Candida albicans, we therefore undertook a mechanistic study to determine how and when these two cytokines mediate cardiac inflammation. In this study, we show that TNF signaling is active in the acute phase of cardiac inflammation, which is characterized by a diffuse myocarditis that precedes the development of coronary vasculitis. Mechanistically, TNF is produced by the myeloid cells and triggers acute cardiac inflammation by stimulating both stromal and immune compartments of the heart. In contrast to this early involvement for TNF, IL-1 signaling is dispensable for the development of acute myocarditis. Critically, although mice deficient in IL-1 signaling have extensive acute inflammation following C. albicans water-soluble complex challenge, they do not develop coronary vasculitis. Thus, TNF and IL-1 appear to play temporally distinct roles in KD, with TNF being active in acute cardiac inflammation and IL-1 in the subsequent development of coronary vasculitis. These observations have important implications for understanding the progression of cardiac pathology in KD and the relative therapeutic use of targeting these cytokines.

Adeno-associated Virus Vector-mediated Interleukin-10 Induction Prevents Vascular Inflammation in a Murine Model of Kawasaki Disease

Kawasaki disease (KD), which is the leading cause of pediatric heart disease, is characterized by coronary vasculitis and subsequent aneurysm formation. Although intravenous immunoglobulin therapy is effective for reducing aneurysm formation, a certain number of patients are resistant to this therapy. Because interleukin-10 (IL-10) was identified as a negative regulator of cardiac inflammation in a murine model of KD induced by Candida albicans water-soluble fraction (CAWS), we investigated the effect of IL-10 supplementation in CAWS-induced vasculitis. Mice were injected intramuscularly with adeno-associated virus (AAV) vector encoding IL-10, then treated with CAWS. The induction of AAV-mediated IL-10 (AAV-IL-10) significantly attenuated the vascular inflammation and fibrosis in the aortic root and coronary artery, resulting in the improvement of cardiac dysfunction and lethality. The predominant infiltrating inflammatory cells in the vascular walls were Dectin-2+CD11b+ macrophages. In vitro experiments revealed that granulocyte/macrophage colony-stimulating factor (GM-CSF) induced Dectin-2 expression in bone marrow-derived macrophages and enhanced the CAWS-induced production of tumor necrosis factor-α (TNF-α) and IL-6. IL-10 had no effect on the Dectin-2 expression but significantly inhibited the production of cytokines. IL-10 also inhibited CAWS-induced phosphorylation of ERK1/2, but not Syk. Furthermore, the induction of AAV-IL-10 prevented the expression of TNF-α and IL-6, but not GM-CSF and Dectin-2 at the early phase of CAWS-induced vasculitis. These findings demonstrate that AAV-IL-10 may have therapeutic application in the prevention of coronary vasculitis and aneurysm formation, and provide new insights into the mechanism underlying the pathogenesis of KD.

Calcineurin inhibitors exacerbate coronary arteritis via the MyD88 signalling pathway in a murine model of Kawasaki disease.

Calcineurin inhibitors (CNIs) have been used off-label for the treatment of refractory Kawasaki disease (KD). However, it remains unknown whether CNIs show protective effects against the development of coronary artery lesions in KD patients. To investigate the effects of CNIs on coronary arteries and the mechanisms of their actions on coronary arteritis in a mouse model of KD, we performed experiments with FK565, a ligand of nucleotide-binding oligomerization domain-containing protein 1 (NOD1) in wild-type, severe combined immunodeficiency (SCID), caspase-associated recruitment domain 9 (CARD9)-/- and myeloid differentiation primary response gene 88 (MyD88)-/- mice. We also performed in-vitro studies with vascular and monocytic cells and vascular tissues. A histopathological analysis showed that both cyclosporin A and tacrolimus exacerbated the NOD1-mediated coronary arteritis in a dose-dependent manner. Cyclosporin A induced the exacerbation of coronary arteritis in mice only in high doses, while tacrolimus exacerbated it within the therapeutic range in humans. Similar effects were obtained in SCID and CARD9-/- mice but not in MyD88-/- mice. CNIs enhanced the expression of adhesion molecules by endothelial cells and the cytokine secretion by monocytic cells in our KD model. These data indicated that both vascular and monocytic cells were involved in the exacerbation of coronary arteritis. Activation of MyD88-dependent inflammatory signals in both vascular cells and macrophages appears to contribute to their adverse effects. Particular attention should be paid to the development of coronary artery lesions when using CNIs to treat refractory KD.

Echocardiographic Evaluation of Coronary Abnormalities and Cardiac Function in a Murine Model of Kawasaki Disease Using High-frequency Ultrasound.

Background:Murine model of coronary arterial inflammation has been widely accepted as an animal model of and used in Kawasaki disease (KD). This study sought to evaluate the developmental changes of coronary arteries and cardiac function in a murine model of KD with a high-frequency ultrasound system and to provide evidence for the preparation of the model of KD.Methods:Lactobacillus casei cell wall extract was prepared and injected into C57BL/6 mice intraperitoneally (i.p.) to induce KD. A total of 120 mice were grouped into three groups. The intravenous immunoglobulin (IVIG) treatment group was i.p. injected with IVIG (2 g/kg), while the KD model and normal control groups were i.p. injected with 0.5 ml of phosphate buffered solution on day 5. All high-resolution echocardiography detection of mouse heart was performed by the same senior technician. Animal echocardiography was performed by measuring the coronary artery dimensions and cardiac function on days 0, 7, 14, 28, and 56 (high-resolution small animal ultrasound [Vevo770 pattern; VisualSonic, Canada] with broadband probe [RMVTM707B; frequency, 30 mHz; depth of focus, 1.2 cm]) which were measured and analyzed with Vevo770 software.Results:Pathological studies revealed focal inflammatory infiltrate asymmetrically distributed around the coronary artery trunk in the KD model group. Echocardiographic study including coronary dimension and cardiac function measurements was successfully performed in all subjects. The KD model and IVIG treatment groups showed left coronary artery dilation on days 7, 14, 28, and 56. The diameter of left coronary artery in the KD model group (0.53 ± 0.09 mm; 0.36 ± 0.07 mm; 0.34 ± 0.05 mm; 0.34 ± 0.04 mm) was significantly larger than those of IVIG treatment group (0.22 ± 0.02 mm; 0.28 ± 0.03 mm; 0.26 ± 0.03 mm; 0.27 ± 0.05 mm; 0.26 ± 0.03 mm; all P < 0.01) and the normal control group (0.21 ± 0.02 mm; 0.22 ± 0.03 mm; 0.22 ± 0.02 mm; 0.23 ± 0.02 mm; 0.27 ± 0.04 mm; all P < 0.01) on days 7, 14, 28, and 56. No significant differences were observed in the measurements of cardiac function among the groups on days 0, 7, 14, 28, and 56 (all P > 0.05).Conclusions:Echocardiography could identify the consecutive changes of coronary artery in KD mice. Echocardiography is more convenient and direct in evaluating the coronary abnormalities in this animal model.

Losartan attenuates the coronary perivasculitis through its local and systemic anti-inflammatory properties in a murine model of Kawasaki disease

Kawasaki disease is a common systemic vasculitis that leads to coronary artery lesions. Besides its antihypertensive effects, losartan can modulate inflammation in cardiovascular disease. We examined whether losartan can attenuate coronary inflammation in a murine model of Kawasaki disease. Five-wk-old C57/BL6J male mice were intraperitoneally injected with Lactobacillus casei cell wall extract to induce coronary inflammation and divided into four groups: placebo, intravenous immunoglobulin (IVIG), losartan, and IVIG+losartan. After 2 wk, mice were harvested. The coronary perivasculitis was significantly attenuated by losartan but not by IVIG alone, and further dramatic attenuation by IVIG+losartan was observed. The frequency of Lactobacillus casei cell wall extract-induced myocarditis (80%) was markedly lowered by losartan (22%) and IVIG+losartan (0%). Furthermore, interleukin (IL)-6 mRNA was markedly attenuated by IVIG+losartan. Serum levels of IL-6, TNF-α, MCP-1, and IL-10 after Lactobacillus casei cell wall extract injection were slightly decreased by IVIG or losartan. Moreover, IL-1β, IL-10, and MCP-1 levels were significantly decreased by IVIG+losartan. The addition of losartan to IVIG strongly attenuated the severity of coronary perivasculitis and the incidence of myocarditis, along with suppressing systemic/local cytokines as well as the activated macrophage infiltration. Therefore, losartan may be a potentially useful additive drug for the acute phase of Kawasaki disease to minimize coronary artery lesions.

Abstract O.26: Angiotensin Receptor Blocker, Losartan suppresses coronary arteritis in a Murine Model of Kawasaki Disease. -Effectiveness of IVIG versus Losartan-

Background: Although intravenous immunoglobulin (IVIG) is an established treatment for Kawasaki disease (KD), 5 % of KD patients treated with IVIG still have coronary involvement. Angiotensin receptor blockers (ARBs), beside their antihypertensive effects, also suppress cell infiltration in atherosclerosis. However, the efficacy of ARB for KD has not been established. Objective: We aimed to elucidate if ARB ameliorates coronary arteritis (CA) in a murine model of KD, introduced by Lactobacillus casei wall extract (LCWE). We also aimed to verify whether ARB’s effects are different from those of IVIG. Method: 4-week-old male mice were intraperitoneally injected with LCWE (L, n=15) or PBS (P, n=15). 5 days later, those mice were given IVIG (1g/kg, L+IVIG, n=8), or ARB (losartan 100mg/L in drinking water for 2 wks, L+ARB, n=18). 2 weeks after LCWE injection, histological assessment of the heart and measurement of plasma cytokine levels were performed. IL-6 and mannose receptor (MR) mRNA expressions in the aortic root were studied (n=5 each group) in an additional experiment. Results: CA score was significantly increased by LCWE (L: 8.3±0.5 vs. P: 2.9±0.5, p&lt;0.0001). ARB significantly ameliorated CA (L+ARB: 5.1±0.7 vs. L, p=0.008). The effect of IVIG on CA was milder and not significant (L+IVIG: 6.0±0.9 vs. L). Of note, macrophage infiltration was dramatically decreased by ARB but not by IVIG. IVIG treatment ameliorated serum levels of IL-1β, IL-10 and TNF-α in a milder fashion than ARB. Interestingly, serum IL-6 level was suppressed by ARB, but not by IVIG. Locally up-regulated mRNAs of IL-6 and MR were significantly ameliorated by ARB, with milder effects by IVIG. Conclusions: ARB, rather than IVIG, exerts powerful anti-CA effects with suppressing local macrophage infiltration and systemic/local inflammatory cytokines. Thus, ARB potentially exerts additive anti-CA effects in KD under IVIG treatment.

PO-0022 Assessment Of Coronary Artery In A Murine Model Of Kawasaki Disease By Echocardiography

Introduction This study sought to assess the changes of coronary artery complications and cardiac function in the murine model of Kawasaki disease (KD) with a high frequency ultrasound system. Methods Lactobacillus casei cell wall extract (LCWE) was prepared, and injected to C57BL/6 mice intraperitoneally to induce KD. Totally 40 mice were categorised into KD model group and the control group randomly. On days 10, 21 and 60, coronary artery were measured by echocardiography. Left ventricular end-diastolic diameter (LVIDd), end-systolic diameter (LVIDs), ejection fraction (EF), fractional shortening (FS) and blood flow velocity of atrio-ventricular valve during early diastole (E)/atrial contraction (A) were also assessed. Results Echocardiography detected coronary artery and measured cardiac function in all mice. There was a high density echo images around the coronary artery wall at 10 days and 21 days in the KD group, 4(20%) presented local coronary artery aneurysm at 14 days and 21 days. The diameter of left coronary artery in KD group (0.46 ± 0.11 mm on D10, 0.47 ± 0.09 mm on D21) was larger than controls (0.32 ± 0.14 mm on D 10, 0.36 ± 0.06 mm on D21, all p Conclusions Coronary artery and cardiac function could be assessed easily by echocardiography in murine model of KD. Murine model of KD established by LCWE was shown similar natural progression on coronary artery abnormalities with KD patient.

Effects of intravenous immunoglobulin upon the overexpression and over-activation of nuclear factor-κB and matrix metalloproteinase-9 in murine model of Kawasaki disease

To explore the changes of expression and biological activity of nuclear factor-kappa B (NF-κB) and matrix metalloproteinase-9 (MMP-9) after using intravenous immunoglobulin (IVIG) in a murine model of Kawasaki disease (KD) and elucidate the therapeutic mechanism of IVIG for the treatment of KD. A total of 72 mice were categorized randomly into IVIG, KD and control groups.Lactobacillus casei cell wall extract (LCWE) was prepared and injected intraperitoneally into C57BL/6 mice to induce KD (0.5 mg single injection).IVIG group received an intraperitoneal injection of IVIG (2 mg/g) while KD model group had an intraperitoneal injection of normal saline. At Days 14, 28 and 56, the diameter of coronary artery was by echocardiography in 8 mice of each group. At the same time, the stains of hematoxylin & eosin and elastic fiber were used to observe the pathological damage of coronary artery. Western blot was used to evaluate the expressions of NF-κB and MMP-9, electrophoretic mobility shift assay (EMSA) was used to measure the activity of NF-κB and Gelatin zymography was used to evaluate the activity of MMP-9 in heart samples of murine model of KD. The local inflammatory infiltrate, composed predominantly of mononuclear lymphocytes, of coronary artery trunk and branches was observed at Days 14 and 28 while broken elastin was observed at Day 56. And the inflammatory cell infiltrate was less severe and no apparent broken elastin was observed in IVIG and control groups. On echocardiography, the average value of diameter of left coronary artery in KD model group was higher than that in IVIG and control groups (28 d:(0.48 ± 0.07) vs (0.41 ± 0.03) and (0.35 ± 0.02) mm, all P < 0.01). Compared with the other two groups, the result of Western blot showed that the expressions of NF-κB and MMP-9 in KD model group were markedly higher than those in IVIG treatment group and that in control group at each time point (28 d: (58 ± 14) vs (25 ± 14) & (19 ± 11) µg/L, (100 ± 41) vs (39 ± 19) & (35 ± 19) µg/L, all P < 0.01). The activity of NF-κB by EMSA and the result from KD model group were much higher than those from the control and IVIG groups (28 d: (84 788 ± 2 081) vs (27 220 ± 4 990) & (50 192 ± 1 586) µg/L, all P < 0.01]. And it was in accord with the expression of NF-κB. The outcome of gelatin zymography demonstrated that the activity of MMP-9 had similar change with the expression of MMP-9(18 560 ± 7 963) vs (9 112 ± 3 398) & (11 834 ± 4 996) µg/L, all P < 0.05). NF-κB/MMP-9 is overexpressed and over-activated in the heart of KD mouse models. IVIG may inhibit the inflammatory cell infiltration and alleviate coronary artery. And such a therapeutic effect is possibly achieved by a suppression of the overexpression and over-activation of NF-κB/MMP-9 pathway.

The role of TNF-α in a murine model of Kawasaki disease arteritis induced with a Candida albicans cell wall polysaccharide

Objectives Various inflammatory cytokines, including tumor necrosis factor-α (TNF-α), have been reported to play roles in Kawasaki disease (KD). Recently, anti-TNF-α therapy was reported to show efficacy in patients who do not respond to high-dose intravenous immunoglobulin therapy. However, there are many gaps in our understanding of the role that TNF-α plays in the development of KD arteritis as well as whether anti-TNF-α therapy causes any histological changes in the arteritis. Accordingly, the present histopathological study was carried out to elucidate the inhibitory effect of anti-TNF-α therapy on vasculitis as well as the role of TNF-α in the development of vasculitis in a murine model of KD vasculitis.Methods We used two anti-TNF-α drugs (etanercept and infliximab) to treat a Candida albicans-induced murine model of KD vasculitis. We investigated the histopathological changes in terms of the incidence of vasculitis, the scope of lesions and the degree of inflammation.Results Administration of etanercept to the mice reduced not only the incidence of vasculitis but also the scope of lesions and the degree of inflammation.Conclusion Based on the histological findings, TNF-α is deeply involved in the development of vasculitis.

Etanercept Suppresses Arteritis in a Murine Model of Kawasaki Disease: A Comparative Study Involving Different Biological Agents

Coronary arteritis, a complication of Kawasaki disease (KD), can be refractory to immunoglobulin (IVIG) treatment. To determine the most effective alternative therapy, we compared the efficacy of different agents in a mouse model of KD. Vasculitis was induced by injection of Candida albicans water-soluble fractions (CAWS) into a DBA/2 mouse, followed by administration of IVIG, etanercept, methylprednisolone (MP), and cyclosporine-A (CsA). At 2 and 4 weeks, the mice were sacrificed, and plasma cytokines and chemokines were measured. CAWS injection induced active inflammation in the aortic root and coronary arteries. At 2 weeks, the vasculitis was reduced only by etanercept, and this effect persisted for the subsequent 2 weeks. At 4 weeks, IVIG and CsA also attenuated the inflammation, but the effect of etanercept was more significant. MP exerted no apparent effect at 2 or 4 weeks. The suppressive effect exerted by etanercept on cytokines, such as interleukin- (IL-)6, IL-12, IL-13, and tumor necrosis factor-α (TNF-α), was more evident than that of others. The extent of arteritis correlated with the plasma TNF-α levels, suggesting a pivotal role of TNF-α in KD. In conclusion, etanercept was most effective in suppressing CAWS-induced vasculitis and can be a new therapeutic intervention for KD.

Status of endothelial progenitor cell in murine model of Kawasaki disease

To assess whether the occurrence of coronary artery lesion was correlated with the changes of endothelial progenitor cell (EPC) number and function in murine model of Kawasaki disease (KD). Lactobacillus casei cell wall extract (LCWE) was prepared and then C57BL/6 mice received a single intraperitoneal injection of LCWE for inducing KD. Twenty-four mice were categorized randomly into 3 groups: KD model group at Day 14 post-injection, KD model group at Day 56 post-injection and control group with an intraperitoneal injection of phosphate buffered solution (n = 8 each). The number of circulating EPC was defined as CD34(+)Flk-1(+)CD45(-) from mice. Meanwhile, bone marrow mononuclear cells were cultured in vitro to expand EPC for functional analysis. After 7 days of culturing, EPC were inoculated onto culture plate and thiazolyl blue assay was used to measure the absorbance value by enzyme labeling instrument to evaluate the proliferation. The adhesion of EPC was performed by replating cells on fibronectin coated dishes and then counting the number of adherent cells. The migration of EPC was assayed by Transwell. Focal inflammatory infiltrate was evident in coronary artery trunk and a series of branches at Day 14 post-injection. The inflammatory cell infiltrate consisted of mononuclear lymphocytes. The number of circulating EPC were significantly lower in the Day 14 LCWE-treating murine model versus the controls (0.017% ± 0.008% vs 0.028% ± 0.007%, P < 0.01). Disruption of elastin was consistently observed at Day 56 post-injection. And there was no apparent recovery in number of EPC (0.016% ± 0.007%, P < 0.01). When bone marrow mononuclear cells were cultured in vitro, the colony-forming ability of EPC decreased in the KD model group at Day 14 post-injection versus the controls. Test of proliferating ability showed that the absorbance was 0.39 ± 0.11 in MTT experiment and decreased than the controls (0.61 ± 0.14, P < 0.01). Adhesion and migration were also down-regulated versus the controls ((3.1 ± 0.6) and (3.2 ± 0.6) vs (6.4 ± 1.2) and (6.2 ± 0.5) cells/HPF, both P < 0.01). In the KD model group at Day 56 post-injection, the colony-forming ability of EPC was not recovered significantly. Proliferation ability, adhesion and migration were still decreased compared to the controls (0.38 ± 0.09, (3.12 ± 0.56) cells/HPF and (3.29 ± 0.63) cells/HPF, all P < 0.01). The occurrence of coronary artery lesion may be correlated with the down-regulation of EPC number and function in murine model of KD.

Interleukin-1β Is Crucial for the Induction of Coronary Artery Inflammation in a Mouse Model of Kawasaki Disease

Kawasaki disease (KD) is the most common cause of acute vasculitis and acquired cardiac disease in US children. Untreated, children may develop coronary artery aneurysms, myocardial infarction, and sudden death as a result of the illness. Up to a third of KD patients fail to respond to intravenous immunoglobulin, the standard therapy, and alternative treatments are being investigated. Genetic studies have indicated a possible role for interleukin (IL)-1β in KD. We therefore explored the role of IL-1β in a murine model of KD. Using an established mouse model of KD that involves injection of Lactobacillus casei cell wall extract (LCWE), we investigated the role of IL-1β and caspase-1 (activated by the inflammasome and required for IL-1β maturation) in coronary arteritis and evaluated the efficacy of IL-1 receptor antagonist as a potential treatment. LCWE-induced IL-1β maturation and secretion were dependent on the NLRP3 inflammasome in macrophages. Both caspase-1-deficient and IL-1 receptor-deficient mice were protected from LCWE-induced coronary lesions. Injection of recombinant IL-1β into caspase-1-deficient mice restored the ability of LCWE to cause coronary lesions in response to LCWE. Furthermore, daily injections of the IL-1 receptor antagonist prevented LCWE-mediated coronary lesions up to 3 days after LCWE injection. Our results strongly suggest that caspase-1 and IL-1β play critical roles in the development of coronary lesions in this KD mouse model, blocked by IL-1 receptor antagonist. Therefore, anti-IL-1β treatment strategies may constitute an effective, more targeted treatment of KD to prevent coronary lesions.

Vasculitis: Molecular Imaging by Targeting the Inflammatory Enzyme Myeloperoxidase

To determine if a molecular imaging approach targeting the highly oxidative enzyme myeloperoxidase (MPO) can help noninvasively identify and confirm sites of vascular wall inflammation in a murine model of vasculitis. Animal experiments were approved by the institutional animal care committee. Twenty-six mice were studied, including eight MPO-deficient and six sham-operated mice as controls. Vasculitis was induced with intraperitoneal injection of Candida albicans water-soluble fraction (CAWS). Aortic root magnetic resonance imaging was performed after intravenous injection of the activatable MPO sensor (bis-5-hydroxytryptamide-diethylenetriaminepentatacetate gadolinium) (n = 23), referred to as MPO-Gd, or gadopentetate dimeglumine (n = 10). Seven mice were randomly assigned to receive either MPO-Gd or gadopentetate dimeglumine first. Aortic root specimens were collected for biochemical and histopathologic analyses to validate imaging findings. Statistical significance was calculated for contrast-to-noise ratios (CNRs) by using the paired t test. In the aortic root, the mean MPO-Gd CNRs after agent injection (CNR = 28.1) were more than 2.5-fold higher than those of sham-operated mice imaged with MPO-Gd and vasculitis mice imaged with gadopentetate dimeglumine (CNR = 10.6) (P < .05). MPO-Gd MR imaging helped identify areas of vasculitis that were not seen at unenhanced and contrast material-enhanced imaging with gadopentetate dimeglumine. Histopathologic and biochemical analyses for MPO and myeloid cells confirmed imaging findings. In MPO-deficient mice, injection of CAWS did not result in a vasculitis phenotype, implying a key role of the imaging target in disease cause. Molecular imaging targeting MPO can be a useful biomarker to noninvasively detect and confirm inflammation in vasculitis by using a murine model of Kawasaki disease.

Inhibition of Transforming Growth Factor β Worsens Elastin Degradation in a Murine Model of Kawasaki Disease

Kawasaki disease (KD) is an acute inflammatory illness marked by coronary arteritis. However, the factors increasing susceptibility to coronary artery lesions are unknown. Because transforming growth factor (TGF) β increases elastin synthesis and suppresses proteolysis, we hypothesized that, in contrast to the benefit observed in aneurysms forming in those with Marfan syndrome, inhibition of TGF-β would worsen inflammatory-induced coronary artery lesions. By using a murine model of KD in which injection of Lactobacillus casei wall extract (LCWE) induces coronary arteritis, we show that LCWE increased TGF-β signaling in the coronary smooth muscle cells beginning at 2 days and continuing through 14 days, the point of peak coronary inflammation. By 42 days, LCWE caused fragmentation of the internal and external elastic lamina. Blocking TGF-β by administration of a neutralizing antibody accentuated the LCWE-mediated fragmentation of elastin and induced an overall loss of medial elastin without increasing the inflammatory response. We attributed these increased pathological characteristics to a reduction in the proteolytic inhibitor, plasminogen activator inhibitor-1, and an associated threefold increase in matrix metalloproteinase 9 activity compared with LCWE alone. Therefore, our data demonstrate that in the coronary arteritis associated with KD, TGF-β suppresses elastin degradation by inhibiting plasmin-mediated matrix metalloproteinase 9 activation. Thus, strategies to block TGF-β, used in those with Marfan syndrome, are unlikely to be beneficial and could be detrimental.