Background: Histologic study of inflamed coronary arteries from the Kawasaki disease (KD) patients shows infiltration by immune effector cells, IL-17-producing myofibroblasts, and breaks in the internal elastic lamina. Transcripts from genes associated with cell trafficking (e.g. paxillin) are elevated in whole blood from acute KD patients. Lysyl oxidase (LOX) is a multifunctional protein affecting affecting “monocyte and smooth muscle cell migration, elastogenesis, and endothelial-to-mesenchymal transition. LOX promotes cell motility through paxillin phosphorylation, which influences T-cell trafficking via the calcium signaling pathway. We investigated the role of LOX in the pathogenesis of KD.
Methods: Agilent microarray data using whole blood were analyzed for differential expression of enzymes in the LOX family (LOX, LOX-like (L)1-4) in acute and convalescent KD samples (n=19). LOXL1 results were validated using RT-PCR in an independent cohort (n=20). LOXL1 transcripts levels were measured in KD whole blood, peripheral blood mononuclear cells (PBMC), T-cell clones, B-cell lines, and myeloid dendritic cells from acute KD patients. Immunohistochemical staining for LOXL1 was performed on coronary arteries from a KD patient who died on illness day 7.
Result: LOXL1 expression by microarray was 3.2-fold higher in acute than convalescent samples (p<0.001) and was validated in an independent cohort by RT-PCR (5.4-fold higher, p<0.001). LOXL1 transcripts levels were 2-35 times higher in PBMC compared to whole blood (n=8). KD T cell clones had higher LOXL1 transcript levels than B-cells and dendritic cells. Immunohistochemical staining showed LOXL1-expressing inflammatory cells and smooth muscle cells in the coronary artery walls.
Conclusion: LOXL1 may increase inflammation in acute KD by promoting the motility of infiltrating T cells and smooth muscle cells through focal adhesion formation. However, LOXL1 may also participate in arterial wall repair by crosslinking collagen and elastin. Statins inhibit focal adhesion formation and thus cell trafficking but not the crosslinking mediated by LOXL1. Studies of LOXL1 protein levels and paxillin phosphorylation in PBMC may further our understanding of their role in KD pathogenesis.