KD may damage the coronary arteries. Intravenous immunoglobulin (IVIG) treatment reduces the incidence of coronary artery aneurysm (CAA) from 25–4% [30]. Some patients are at risk of CAA in adulthood despite systemic treatment [31]. Although the incidence of CAA has decreased dramatically and many treatment options are available, CAA is still not completely preventable, and it can have fatal complications [32–34]. The pathogenesis of KD is not yet clear. Genetic factors might be closely related to KD susceptibility. Genetic variants in ITPKC and CASP3 might promote excessive inflammatory responses by activating the T cell Ca2+/NFAT signaling pathway [35, 36], and a study of cyclosporine, an inhibitor of this pathway, has been carried out in Japan in a randomized, multicenter trial demonstrating that combining cyclosporine with IVIG can reduce the incidence of CAA [37]. Moreover, the symptoms of KD are not specific, so patients are easily misdiagnosed, leading to an increased incidence of CAA. Therefore, the identification of molecular markers for early diagnosis is crucial to KD treatment and CAA prevention.
Autophagy is a conserved lysosomal degradation process that plays a key role in adaptation to metabolic stress, removal of damaged organelles, pathogen defense, and nutrient reutilization [38]. A recent study pointed out that autophagy is linked to many diseases, including cancer, inflammatory diseases, autoimmune diseases, and neurodegenerative diseases. Enhancement of autophagy/mitophagy has been shown to effectively reduce the incidence of vasculitis in KD [39]. Das et al. demonstrated that IVIG may play a role by inducing autophagy in peripheral blood mononuclear cells [40]. Resveratrol alleviates myocardial injury caused by KD by inhibiting autophagy [41]. Some studies have explored the mechanisms underlying the roles of ARGs in KD [6, 42], but no studies have investigated the mechanisms of action of ARGs in KD through bioinformatics analysis. Our bioinformatics analysis identified 20 potential ARGs associated with KD.
GO analysis revealed that these ARGs were mainly involved in biological processes such as autophagy and macro-autophagy. KEGG pathway analysis showed that most DEGs were involved in autophagy—animal. Qi et al. found that ginsenoside Rb1 may inhibit CAL inflammation by regulating the AMPK/mTOR/P70S6 autophagy signaling pathway [43].
We then established a PPI network to analyze the interaction of ARGs in KD and screened the top 10 hub genes (WIPI1, WDFY3, ATP6V0E2, RALB, ATP6V1C1, GBA, C9orf72, LRRK2, GNAI3, and PIK3CB) using Cytoscape software and the cytoHubba plugin. We also detected potential miRNAs, TFs, and drugs associated with KD, analyzed the expression levels of ARGs in tissue-infiltrating immune cells, and evaluated the diagnostic value of ARGs. These data improve our understanding of the etiology of KD.
WIPI1 is a component of the autophagic machinery and is activated downstream of the ULK1 and PI3 kinases to participate in autophagy. WIPI1 mRNA expression can be used as an indicator of autophagosome formation [44, 45], WIPI1 also promotes melanase transcription and melanosome formation by inhibiting TORC1, a process different from starvation-induced autophagy [46]. WDFY3 is essential for macro-autophagy, which is important for brain and neural development, and could also activate the TNFSF11/RANKL–TRAF6 pathway to regulate osteoclastogenesis [47, 48]. ATP6V0E2 is an enzyme transporter that is widely expressed in lysosomes, and Anlotinib can activate lysosomal function. ATP6V0E2 has been identified as the key target of Anlotinib by transcriptome sequencing, and Anlotinib has been applied in the treatment of lung cancer [49]. RALB is a multifunctional GTPase, and the NLRP3 inflammasome promotes RALB activation and autophagosome formation. In turn, autophagy limits interleukin-1β (IL-1β) production [50]. Lee et al. showed that the inflammatory cytokine IL-1β is related to the development of KD in a mouse model [51]. GBA encodes a lysosomal membrane protein. Homozygous mutations in GBA lead to Gaucher disease, and heterozygous GBA mutations lead to Parkinson's disease by inhibiting autophagy [52]. C9orf72 hexanucleotide expansion is the most common genetic cause of familial amyotrophic lateral sclerosis (ALS), and IL-1β levels are increased in the cerebrospinal fluid of ALS patients [53]. In KD, IL-1β decreases the anti-inflammatory effects of IVIG and thus increases drug resistance through activation of the TFs C/EBPβ and C/EBPδ [54]. We speculate that C9orf72 might be related to the occurrence of KD, but this hypothesis requires experimental verification. LRRK2 can participate in inflammatory responses in vivo through the MAPK and NF-κB signaling pathways [55], Zhou et al. found that IVIG may reduce CAL development in KD by inhibiting NF-κB and p38 MAPK activation [56]. Downregulation of the LRRK2 gene in primary microglia or inhibition of its kinase activity reduced the production of tumor necrosis factor-alpha (TNFα) and IL-1β [11, 19]. Gai3 specifically regulates neutrophil chemotaxis through PI3Kγ signaling [57], and neutrophils may mediate vascular endothelial injury, which is the main cause of CAL secondary to KD. Integrin αIIbβ3 mediates atherothrombosis, and the key role of PIK3CB in regulating the formation and stability of adhesion bonds of integrin αIIbβ3 may be a new target for future antithrombotic therapy [58]. In atherosclerosis, inhibition of the PI3K/Akt/mTOR pathway by microRNA-126 attenuates endothelial cell injury [59].
MicroRNAs (miRNAs) are endogenous small, non-coding RNAs. We constructed an mRNA–miRNA network and predicted a total of 72 target miRNAs, some of which have been validated. hsa-miR-19a-3p was suggested by Jone et al. to be a possible biomarker to distinguish KD from other infectious diseases [60]. Another study showed that hsa-miR-222-3p is useful for the early diagnosis of KD [61]. We further constructed TF–mRNA networks and predicted a total of 130 target TFs.
In a rat study, octreotide was shown to exert significant anti-inflammatory effects by reducing the levels of inflammatory cytokines such as TNF-α [62], and another rat study showed that octreotide inhibited the renal inflammatory response after hepatic ischemia and reperfusion injury (HIR) through the autophagic pathway [63]. PI3K inhibitors, such as idelalisib, copanlisib, and alpelisib, are used for the treatment of tumors; in addition, they may have prospects in the treatment of autoimmune diseases, inflammatory diseases, and cardiovascular diseases [64]. Several experimental and clinical studies have shown that statins such as lovastatin also exert anti-inflammatory and immunomodulatory effects [65].
We used the CIBERSORT package to evaluate the types of infiltrated immune cells in KD patients and controls and the correlation with ARG expression. Our analysis showed that SH3GLB1, ATP6V0E2, PLEKHF1, RALB, KLHL3, and TSPO were closely related to CD8 + T cells and neutrophils. A previous study showed that neutrophil counts increased rapidly in the acute phase of KD and decreased significantly in the recovery phase [66], and a mouse study showed that CD8 + T cells played a key role in KD vasculitis [67]. A heatmap of immune cell correlation showed that resting memory CD4 + T cells and CD8 + T cells were closely related to gamma-delta T cells and that CD8 + T cells were closely related to monocytes, M0 macrophages, and neutrophils. The underlying mechanisms require further investigation.
We performed ROC curve analysis of autophagy genes in KD to further verify their diagnostic value in KD. In dataset GSE68004, the genes SH3GLB1, GBA, RALB, DRAM1, GNAI3, TSPO, WIPI1, QSOX1, ATP6V0E2, ATP6V1C1, LRRK2, C9orf72, PIK3CB, PIK3CB, and WDFY3 had a good diagnostic effect for KD. In dataset GSE73461, the genes SH3GLB1, GBA, RALB, DRAM1, GNAI3, TSPO, WIPI1, QSOX1, ATP6V0E2, ATP6V1C1, PIK3CB, WDFY3, and KLHL3 had a good diagnostic effect for KD. We finally examined the expression levels of 10 genes by qRT-PCR. The expression levels of WIPI1 and GBA were consistent with our bioinformatics analysis results.
There are still some limitations in our study. First, the prevalence of KD varies by race, but KD samples in the GSE dataset are limited to KD samples from Europe and America. Second, the sample size of this study was small, which may lead to bias. Our results should be validated by international, multi-center, and large-scale studies. Finally, the prognostic power of the identified ARGs remains unclear.