Inhibition of IL-6 in the LCWE Mouse Model of Kawasaki Disease Inhibits Acute Phase Reactant Serum Amyloid A but Fails to Attenuate Vasculitis

Objective

Kawasaki disease (KD) is the most common cause of acquired pediatric heart disease in the developed world. 10% of KD patients are resistant to front-line therapy, and no interventions exist to address secondary complications such as myocardial fibrosis. We sought to identify proteins and pathways associated with disease and anti-IL-1 treatment in a mouse model of KD.

Methods

Vasculitis was induced via Lactobacillus casei cell wall extract (LCWE) injection in 5-week-old male mice. Groups of mice were injected with LCWE alone, LCWE and IL-1 receptor antagonist anakinra, or saline for controls. Upper heart tissue was assessed by quantitative mass spectrometry analysis. Expression and activation of STAT3 was assessed by immunohistochemistry, immunofluorescence and Western blot, and IL-6 expression by RNA-seq and ELISA. A STAT3 small molecular inhibitor and anti-IL-6R antibody were used to evaluate the role of STAT3 and IL-6 in disease development.

Results

STAT3 was highly expressed and phosphorylated in cardiac tissue of LCWE-injected mice, and reduced following anakinra treatment. Il6 and Stat3 gene expression was enhanced in abdominal aorta of LCWE-injected mice and reduced with Anakinra treatment. IL-6 serum levels were enhanced in LCWE-injected mice and normalized by anakinra. However, neither inhibition of STAT3 nor blockade of IL-6 altered disease development.

Conclusion

Proteomic analysis of cardiac tissues demonstrates differential protein expression between KD-like, control and anakinra treated cardiac tissue. STAT3 and IL-6 were highly upregulated with LCWE and normalized by anakinra treatment. However, both STAT3 and IL-6 were dispensable for disease development indicating they may be bystanders of inflammation.

MicroRNA-223 Regulates the Development of Cardiovascular Lesions in LCWE-Induced Murine Kawasaki Disease Vasculitis by Repressing the NLRP3 Inflammasome

Kawasaki disease (KD), an acute febrile childhood illness and systemic vasculitis of unknown etiology, is the leading cause of acquired heart disease among children. Experimental data from murine models of KD vasculitis and transcriptomics data generated from whole blood of KD patients indicate the involvement of the NLRP3 inflammasome and interleukin-1 (IL-1) signaling in KD pathogenesis. MicroRNA-223 (miR-223) is a negative regulator of NLRP3 activity and IL-1β production, and its expression has been reported to be upregulated during acute human KD; however, the specific role of miR-223 during KD vasculitis remains unknown. Here, using the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis, we demonstrate increased miR-223 expression in LCWE-induced cardiovascular lesions. Compared with control WT mice, LCWE-injected miR-223-deficient mice (miR223 ^-/y ) developed more severe coronary arteritis and aortitis, as well as more pronounced abdominal aorta aneurysms and dilations. The enhanced cardiovascular lesions and KD vasculitis observed in LCWE-injected miR223 ^-/y mice correlated with increased NLRP3 inflammasome activity and elevated IL-1β production, indicating that miR-223 limits cardiovascular lesion development by downmodulating NLRP3 inflammasome activity. Collectively, our data reveal a previously unappreciated role of miR-223 in regulating innate immune responses and in limiting KD vasculitis and its cardiovascular lesions by constraining the NLRP3 inflammasome and the IL-1β pathway. These data also suggest that miR-223 expression may be used as a marker for KD vasculitis pathogenesis and provide a novel therapeutic target.

Endothelial Nlrp3 inflammasome activation associated with lysosomal destabilization during coronary arteritis

Inflammasomes play a critical role in the development of vascular diseases. However, the molecular mechanisms activating the inflammasome in endothelial cells and the relevance of this inflammasome activation is far from clear. Here, we investigated the mechanisms by which an Nlrp3 inflammasome is activated to result in endothelial dysfunction during coronary arteritis by Lactobacillus casei (L. casei) cell wall fragments (LCWE) in a mouse model for Kawasaki disease. Endothelial dysfunction associated with increased vascular cell adhesion protein 1 (VCAM-1) expression and endothelial-leukocyte adhesion was observed during coronary arteritis in mice treated with LCWE. Accompanied with these changes, the inflammasome activation was also shown in coronary arterial endothelium, which was characterized by a marked increase in caspase-1 activity and IL-1β production. In cultured endothelial cells, LCWE induced Nlrp3 inflammasome formation, caspase-1 activation and IL-1β production, which were blocked by Nlrp3 gene silencing or lysosome membrane stabilizing agents such as colchicine, dexamethasone, and ceramide. However, a potassium channel blocker glibenclamide or an oxygen free radical scavenger N-acetyl-l-cysteine had no effects on LCWE-induced inflammasome activation. LCWE also increased endothelial cell lysosomal membrane permeability and triggered lysosomal cathepsin B release into cytosol. Silencing cathepsin B blocked LCWE-induced Nlrp3 inflammasome formation and activation in endothelial cells. In vivo, treatment of mice with cathepsin B inhibitor also abolished LCWE-induced inflammasome activation in coronary arterial endothelium. It is concluded that LCWE enhanced lysosomal membrane permeabilization and consequent release of lysosomal cathepsin B, resulting in activation of the endothelial Nlrp3 inflammasome, which may contribute to the development of coronary arteritis.