At present, there have been few studies on asthma and mitochondria-related genes. Therefore, the aim of our research is of great significance to as we explore mitochondrial related biomarkers in CAS. In this study, we investigated the hub genes (NDUFAF7, MTIF3, MRPS26, NDUFAF1) that can be used for accurate diagnosis of CAS. Significantly, we detected the expression of each hub gene and obtained the corresponding score. The incidence of CAS could be determined based on the total score.
Over-expression of the target protein amyloid precursor protein (APP) gene caused by exon variants of NDUFAF7 is associated with the risk of Alzheimer's disease [29]. Mammalian mitochondrial ribosomal protein MRPS26 expression levels are correlated with tumor purity in non-small cell lung cancer (NSCLC). MRPS26 has been observed to participate in mitochondrial activity of muscle stem cells [30]. MTIF3 encodes 29 kDa proteins that promote the formation of initiation complexes on mitochondrial 55S ribosomes and play an active role in translation initiation. The MTIF3 gene may influence Parkinson's disease by causing mitochondrial dysfunction [31]. In our study, in the GSE40888 dataset, the expression of MTIF3 in the CAS sample was lower than that in the normal sample. This suggested that, similar to Parkinson's disease, MTIF3 may trigger CAS by causing mitochondrial dysfunction. A Study [32] has demonstrated that NDUFAF1 is an crucial mitochondrial protein involved in complex I assembly and stabilization, with important functions in electron transport and proton pumping. Expression levels of NDUFAF1 in two central nodes involved in epidermal growth factor (EGF) and Olfactomedin 4 (OLFM4) have been associated with acute kidney injury and septic shock [33]. It is suggested that NDUFAF1 is involved in the cellular inflammatory response pathway.
Some scholars have found that [14] MT function also has a positive effect on the inflammatory response of asthma patients, suggesting that inflammatory response may affect the occurrence and progression of asthma. Wu et al. [34] found that an iron chelator could relieve allergic airway inflammation. CAMKK2 and CISD1 are key suppressors of iron-induced cell death in asthma. CAMKK2 is down-regulated in patients with asthma. Interestingly, the negative correlation between CISD1 gene expression and Tregs suggests a potential role of CISD1 in regulating immune cell infiltration [35]. Tregs are viable targets of airway allergic inflammatory responses and play an integral role in maintaining immune tolerance in asthma [36]. By up regulating immunosuppressive molecules and suppressor genes, the Tregs portion of CD4 T cells prevents the development of pro-inflammatory activity and reduces inflammation [37, 38]. In our study, an analysis to examine the correlation between the hub gene and immune cells. The results revealed that the immune system's response to asthma is negatively affected, mainly due to the high the abundance of B-cell naive cells. MTIF3 had the strongest negative correlation with B cell naive. The activation of B cells in the airway during the inflammatory response is quite different from the classical B cell activation observed in secondary lymphoid organs, and has been demonstrated [39]. In addition, the expression of the MTIF3 and MRPS26 genes negatively affects the immune system's response to asthma, impacting mitochondrial-related functions.
Lin et al. [40] showed that CAMKK2 participated in mitochondrial autophagy and promoted iron death. Autophagy may play a key role in chronic airway inflammation [41]. Increased autophagy plays an important role in airway remodeling, extracellular matrix deposition and fibrosis in asthma [42]. In addition, genetic mutations in autophagy genes were associated with asthma [43]. Particulate matter 2.5 (PM2.5) has been reported [44] to drive mitochondrial autophagy and induce cell cycle arrest and senescence. Our KEGG enrichment results indicate that differentially expressed mitochondria-related genes are associated with thermogenesis, mitochondrial phagocytosis - animal, diabetic cardiomyopathy, citric acid cycle (TCA cycle), propionic acid metabolism, Parkinson's disease, oxidative phosphorylation, nonalcoholic fatty liver, valine, leucine, and isoleucine degradation. Additionally, these genes are correlated with chemo-9 - Carcinogenic effects - reactive oxygen species and other pathways. GSEA enrichment analysis based on KEGG gene set showed that the enrichment results of four hub genes were enriched in a total of one cell cycle pathway. Four hub genes regulate the occurrence of autophagy through some mitochondrial signaling pathways, resulting in cell cycle arrest and cell senescence, which contribute to the development of asthma phenotype. This is in line with some studies suggesting that cell senescence in the lung may be an important risk factor for asthma [45, 46]. And mitochondrial dysfunction has been shown to drive premature cellular aging, consistent with its impact on airway diseases [47, 48].
This study is similar to previous research protocols, but is different in that it is a biomarker related to mitochondrial function in CAS, simple and straightforward. The results of this study were obtained from a dataset of blood samples. The chronic inflammation, vasoconstriction, and hyperresponsiveness of CAS often lead to systemic inflammatory changes. Therefore, it is possible to collect blood samples of CAS. Screening out dysregulated mitochondria could be a promising way to prevent or stop the development of these chronic lung diseases. The clinical application of the results of bioinformatics analysis requires more sample data support and further clinical experiments. It also shows that we will continue to pay attention to the role of these genes.