SummaryKawasaki disease (KD) is an acute systemic vasculitis of childhood that does not have a known cause or aetiology. The epidemiological features (existence of epidemics, community outbreaks and seasonality), unique age distribution and clinical symptoms and signs of KD suggest that the disease is caused by one or more infectious environmental triggers. However, KD is not transmitted person-to-person and does not occur in clusters within households, schools or nurseries. KD is a self-limited illness that is not associated with the production of autoantibodies or the deposition of immune complexes, and it rarely recurs. Regarding the underlying pathophysiology of KD, innate immune activity (the inflammasome) is believed to play a role in the development of KD vasculitis, based on the results of studies with animal models and the clinical and laboratory findings of KD patients. Animal studies have demonstrated that innate immune pathogen-associated molecular patterns (PAMPs) can cause vasculitis independently of acquired immunity and have provided valuable insights regarding the underlying mechanisms of this phenomenon. To validate this concept, we recently searched for KD-specific PAMPs and identified such molecules with high specificity and sensitivity. These molecules have structures similar to those of microbe-associated molecular patterns (MAMPs), as shown by liquid chromatography-tandem mass spectrometry. We propose herein that KD is an innate immune disorder resulting from the exposure of a genetically predisposed individual to microbe-derived innate immune stimulants and that it is not a typical infectious disease.

Recent linkage analyses of nondiabetic African-American patients with focal segmental glomerulosclerosis (FSGS) have identified MYH9, encoding nonmuscle myosin heavy chain IIA (NMMHC-IIA), as a gene having a critical role in this disease. Abnormalities of the MYH9 locus also underlie rare autosomal dominant diseases such as May-Hegglin anomaly, and Sebastian, Epstein (EPS), and Fechtner (FTNS) syndromes that are characterized by macrothrombocytopenia and cytoplasmic inclusion bodies in granulocytes. Among these diseases, patients with EPS or FTNS develop progressive nephritis and hearing disability. We analyzed clinical features and pathophysiological findings of nine EPS-FTNS patients with MYH9 mutations at the R702 codon hot spot. Most developed proteinuria and/or hematuria in early infancy and had a rapid progression of renal impairment during adolescence. Renal histopathological findings in one patient showed changes compatible with FSGS. The intensity of immunostaining for NMMHC-IIA in podocytes was decreased in this patient compared with control patients. Thus, MYH9 R702 mutations display a strict genotype-phenotype correlation, and lead to the rapid deterioration of podocyte structure. Our results highlight the critical role of NMMHC-IIA in the development of FSGS.

Objective-The goal of this study was to investigate the effects of stimulants for a nucleotide-binding domain, leucine-rich repeat-containing (NLR) protein family on human artery endothelial cells and murine arteries. Methods and Results-Human coronary artery endothelial cells were challenged in vitro with microbial components that stimulate NLRs or Toll-like receptors. We found stimulatory effects of NLR and Toll-like receptor ligands on the adhesion molecule expression and cytokine secretion by human coronary artery endothelial cells. On the basis of these results, we examined the in vivo effects of these ligands in mice. Among them, FK565, 1 of the nucleotide-binding oligomerization domain (Nod)-1 ligands induced strong site-specific inflammation in the aortic root. Furthermore, coronary arteritis/valvulitis developed after direct oral administration or ad libitum drinking of FK565. The degree of the respective vascular inflammation was associated with persistent high expression of proinflammatory chemokine/ cytokine and matrix metallopeptidase (Mmp) genes in each tissue in vivo by microarray analysis. Conclusion-This is the first coronary arteritis animal model induced by oral administration of a pure synthetic Nod1ligand. The present study has demonstrated an unexpected role of Nod1 in the development of site-specific vascular inflammation, especially coronary arteritis. These findings might lead to the clarification of the pathogenesis and pathophysiology of coronary artery disease in humans. Key Words: coronary artery disease Ⅲ immune system Ⅲ Kawasaki disease Ⅲ pathology Ⅲ coronary arteritis Ⅲ inflammation G erm-line encoded pattern-recognition receptors of the innate immune system sense exogenous microbial components and endogenous danger signals to protect the host. [1][2][3][4] The pattern-recognition receptors include Toll-like receptors (TLRs), retinoic acid-inducible gene (RIG)-I-like receptors, the leucine-rich repeat-containing (NLR) protein family, and as-yet-unidentified pattern-recognition receptors that recognize double-stranded DNA. 1,3 The TLR, RIG-I-like receptor, and NLR families consist of 10 (human), 3, and more than 20 members, respectively. 1,3,4 In the cardiovascular system, endothelial cells are usually the first among the structural cells to sense microbial components through pattern-recognition receptors. Human endothelial cells express functional innate immune receptors, such as TLRs and NLRs. 5,6 There is a line of evidence that activation of TLRs, especially TLR4 and TLR2, contributes to the development and progression of cardiovascular diseases, including atherosclerosis, cardiac dysfunction in sepsis, and congestive heart failure. 7 With respect to NLRs, only a limited number of studies have shown that human endothelial cells express functional NLRs, nucleotide-binding oligomerization domain 1 (NOD1) and NOD2. Chlamydophila pneumoniae and Listeria monocytogenes elicited NOD1-dependent interleukin (IL)-8 production in endothelial cells. 8,9 A selective NOD1 ligand, FK565, ...

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Objective— Nod1 is an intracellular pattern recognition receptor for bacterial peptidoglycan fragments. We previously reported that a synthetic Nod1 ligand, FK565, induced acute coronary arteritis in mice similar to that of Kawasaki disease. However, the molecular mechanisms underlying this characteristic inflammation have remained elusive. Approach and Results— We found that CD11c + MHC class II + cells accumulated in the heart of FK565-treated mice before arteritis development. Morphological features and gene expression signatures of the cardiac CD11c + MHC class II + cells suggested that this population is closely related to macrophages, and thus, we designated them cardiac CD11c + macrophages. Nod1 in nonhematopoietic cells, rather than hematopoietic cells, was required for the increase of cardiac CD11c + macrophages and arteritis development. Among nonhematopoietic cells, cardiac endothelial cells produced a large amount of chemokines in response to FK565. Endothelial cell–specific blockade of Nod1 signaling suppressed FK565-induced expression of these chemokines, accumulation of cardiac CD11c + macrophages, and subsequent coronary arteritis development. We also found that CCR2 + Ly6C hi inflammatory monocytes in peripheral blood supplied precursors of cardiac CD11c + macrophages. CCR2-deficient mice or pertussis toxin–treated mice exhibited decreased numbers of cardiac CD11c + macrophages and reduced arteritis. Conclusions— These results suggest that Ly6C hi monocytes are recruited to FK565-activated endothelial cells to generate cardiac CD11c + macrophages, which play a pivotal role in the pathogenesis of acute coronary arteritis.

BackgroundKawasaki disease (KD) is a systemic vasculitis of unknown etiology. The innate immune system is involved in its pathophysiology at the acute phase. We have recently established a novel murine model of KD coronary arteritis by oral administration of a synthetic microbe-associated molecular pattern (MAMP). On the hypothesis that specific MAMPs exist in KD sera, we have searched them to identify KD-specific molecules and to assess the pathogenesis.MethodsWe performed liquid chromatography-mass spectrometry (LC-MS) analysis of fractionated serum samples from 117 patients with KD and 106 controls. Microbiological and LC-MS evaluation of biofilm samples were also performed.ResultsKD samples elicited proinflammatory cytokine responses from human coronary artery endothelial cells (HCAECs). By LC-MS analysis of KD serum samples collected at 3 different periods, we detected a variety of KD-specific molecules in the lipophilic fractions that showed distinct m/z and MS/MS fragmentation patterns in each cluster. Serum KD-specific molecules showed m/z and MS/MS fragmentation patterns almost identical to those of MAMPs obtained from the biofilms formed in vitro (common MAMPs from Bacillus cereus, Yersinia pseudotuberculosis and Staphylococcus aureus) at the 1st study period, and from the biofilms formed in vivo (common MAMPs from Bacillus cereus, Bacillus subtilis/Bacillus cereus/Yersinia pseudotuberculosis and Staphylococcus aureus) at the 2nd and 3rd periods. The biofilm extracts from Bacillus cereus, Bacillus subtilis, Yersinia pseudotuberculosis and Staphylococcus aureus also induced proinflammatory cytokines by HCAECs. By the experiments with IgG affinity chromatography, some of these serum KD-specific molecules bound to IgG.ConclusionsWe herein conclude that serum KD-specific molecules were mostly derived from biofilms and possessed molecular structures common to MAMPs from Bacillus cereus, Bacillus subtilis, Yersinia pseudotuberculosis and Staphylococcus aureus. Discovery of these KD-specific molecules might offer novel insight into the diagnosis and management of KD as well as its pathogenesis.

Our study shows that R702 mutations result in especially large platelets and inclusion bodies being faint and mostly invisible on conventionally stained blood smears. We further demonstrated that poly(A)+ RNA content but not NMMHC-IIA accumulation is responsible for the morphological appearance/stainability of inclusion bodies on stained blood smears and the amount of poly(A)+ RNA is decreased in those with R702 mutations.

Atherosclerosis is essentially a vascular inflammatory process in the presence of an excess amount of lipid. We have recently reported that oral administration of a nucleotide-binding oligomerization domain (Nod)-1 ligand, FK565, induced vascular inflammation in vivo. No studies, however, have proven the association between Nod1 and atherosclerosis in vivo. To investigate a potential role of NOD1 in atherogenesis, we orally administered FK565 to apolipoprotein E knockout (Apoe−/−) mice for 4 wk intermittently and performed quantification of atherosclerotic lesions in aortic roots and aortas, immunohistochemical analyses, and microarray-based gene expression profiling of aortic roots. FK565 administration accelerated the development of atherosclerosis in Apoe−/− mice, and the effect was dependent on Nod1 in non–bone marrow origin cells by bone marrow transplantation experiments. Immunohistochemical studies revealed the increases in the accumulation of macrophages and CD3 T cells within the plaques in aortic roots. Gene expression analyses of aortic roots demonstrated a marked upregulation of the Ccl5 gene during early stage of atherogenesis, and the treatment with Ccl5 antagonist significantly inhibited the acceleration of atherosclerosis in FK565-administered Apoe−/− mice. Additionally, as compared with Apoe−/− mice, Apoe and Nod1 double-knockout mice showed reduced development of atherosclerotic lesions from the early stage as well as their delayed progression and a significant reduction in Ccl5 mRNA levels at 9 wk of age. Data in the present study show that the Nod1 signaling pathway in non–bone marrow-derived cells contributes to the development of atherosclerosis.