In this study, we extracted GCF samples from KD patients and healthy volunteers, and performed DIA quantitative proteomics identification and MRM validation for DEPs between the two groups. We identified 197 DEPs from a total of 3353 proteins, of which 174 were significantly up-regulated, and 23 were significantly down-regulated. Then, 46 potential alternative protein markers were found in the GCF of KD using PPI network analysis. Subsequently, we performed quantitative protein detection by MRM-MS to validate 12 DEPs, which were consistent with the results we acheived from DIA detection.
The results of GO enrichment analysis showed that the DEPs in GCF of KD were mainly enriched in the biological processes including cell proliferation, immune system process and cellular process. The main signaling pathways involved in DEPs were cell growth and death, post-transport catabolism, cell motility, cardiovascular diseases, infectious diseases: bacteria, immune diseases. Based on previous published data, we found that cell proliferation, migration, death and immune processes played a key role in the pathogenesis of KD and the occurance of vascular injury(7, 8). The presents of related protein in GCF samples suggested that GCF would be used as a biomarker resource for KD diagnose. The GCF could be used as samples to investigate the pathomechanisms of periodontitis(9). The present research revealed that bacterial infection pathway was also enriched in GCF in patients with KD, which indicated that pathogen infection may be involved in the pathogenesis of KD and periodontitis. In order to screen the key protein markers in GCF for KD, we selected 12 DEPs detected by DIA to verify by MRM-MS, which included SAA1,FKBP4, IFIT3, UB2L6, HPT, A1AT, HS90A, HNRPC, HS90B, MX1, B2MG, and TRAP1. Interestingly, these results were all consistent with the data of DIA.
SAA1 is one of the major proteins of amyloid A (AA), which plays an important role in lipid metabolism, bacterial infection, arterial inflammation and tumor(10, 11). Chen et al. reported the association between genetic locus polymorphisms of SAA1 and coronary artery disease in KD, which indicated that SAA1 may be involved in the process of coronary artery injury (12). The Increased levels of SAA1 protein in human periodontal lesion tissues are positively correlated with periodontal inflammation, and SAA1 may induce inflammatory cell infiltration and release of inflammatory factors through Toll-like receptor 2 (TLR2) and Toll-like receptor 4 (TLR4)(13). The present study showed that the protein expression of SAA1 was significantly increased in the GCF of patients with KD, which suggests that SAA1 may be closely related to the pathogenesis of periodontal tissue and vessel inflammation.
The dynein-associated immunoaffinity FKBP52 (FKBP4) belongs to the immunoaffinity protein family and plays an important role in immunoregulatory processes, protein folding and trafficking activities associated with heat shock protein 90 (HSP90)(14). FKBP4 interacts with HSP90 to regulate the activity of the steroid receptor axis. Data have showed that FKBP4-deficient mice could develope specialized phenotypes associated with androgen, progesterone, and glucocorticoid insensitivity(15, 16). HSP90 is a chaperone protein that regulates protein maturation, and is involved in the regulation of atherosclerotic lesions through various pathways such as lipid metabolism disorders, vascular smooth muscle cell proliferation and migration, glucocorticoid receptor axis, and oxidative stress(7, 17–20). Xu 's study has confirmed that the traditional Chinese medicine berberine can protect against oxidative stress damage to coronary endothelial cells in Kawasaki disease by inhibiting HSP90B(7). HSP90 has also been demonstrated to be involved in the immune response to periodontal inflammation due to P. gingivalis infection(21, 22). The results of this study suggested that FKBP4 and HSP90A/B expression were synergistically increased in KD, which revealed that FKBP4 and HSP90A/B may involve in the regulatory process of gingival injury in patients with KD.
Interferon-induced protein repeats with tetratricopeptide 3 (IFIT3) is an interferon-inducible protein with antiviral and proinflammatory effects. IFIT3 can be used as a biomarker of macrophage polarizing proinflammatory phenotype (M1) and is up-regulated in the arterial tissue of atherosclerotic mice(23). MX1 has anti-pathogen and proinflammatory functions, which has been reported to be associated with the depletion of vascular endothelial progenitor cells and endothelial dysfunction(24). Studies have shown that MX1 is also involved in the regulation of pathogen defense mechanisms in gingival tissues(25). IFIT3 and MX1 are important mediators for inflammation and vascular diseases, which may be involved in the pathogenesis of KD and periodontal diseases.
E2 ubiquitin-conjugating enzyme UB2L6 (UB2L6) belongs to the ubiquitin-proteasome system and is used to transport ubiquitin and promote substrate proteins to complete ubiquitin labeling, which is associated with the regulation of both apoptosis and cell cycle(26). The increased expression level of UB2L6 in the present experiment suggested an increased level of ubiquitination in the gingival tissue of KD, but the molecular regulatory mechanism involved was still unclear. Tumor necrosis factor receptor-associated protein 1 (TRAP1, or HSP75) is a major member of the HSP90 family, which can prevent cardiomyocyte injury induced by hypoxia via maintaining mitochondrial activity(27). Increased TRAP1 expression may indicate a protective function in gingival tissue in patients with KD.
Studies have confirmed that the expression of α1-antitrypsin (A1AT) was increased in the plasma in patients with KD,which can inhibit neutrophil elastase activity associated with coronary artery damage induced by KD(28). Published data have also confirmed that A1AT is also associated with periodontal inflammation, which may identify the severity of periodonatal status(29). Data have also shown that A1AT has antiviraland protective effects in lung diseases, while the role of A1AT in the cardiovascular system has not yet been clearly reported(30, 31). In the present study, the expression of A1AT was up-regulated as mentioned above. Further experiments should be performed to investigate the role of A1AT in the pathogenesis of KD and periodontal diseases.