Allergic rhinitis, a chronic IgE-mediated inflammation of the nasal mucosa, continues to pose challenges for current treatment methods, thereby negatively impacting the quality of life for patients. Consequently, identifying suitable targets and treatment strategies has become a focal point in allergic rhinitis research. Mitochondrial dysfunction is increasingly recognized as a potential mechanism underlying various inflammatory and autoimmune diseases, including cancer, atherosclerosis, neurodegenerative diseases, diabetes, and both autoimmune and allergic conditions (23–26). The progression of these diseases is often exacerbated when systemic inflammation and oxidative stress are present, due in part to the impairment of normal mitochondrial function and subsequent programmed cell death (27). Mutations in mitochondrial genes have been linked to the pathogenesis and local inflammation associated with allergic rhinitis (28). However, the role of mitochondrial function and the mechanism of PCD in AR remain unclear, with limited related studies available. Therefore, this study employed a series of bioinformatics analyses, integrating MitoRGs and PCDRGs, to investigate key biomarkers of MitoRGs - PCDRGs in AR. This research aims to provide new directions for the clinical diagnosis and treatment of AR.
This study employs bioinformatics methodologies to investigate the mtPCD gene in AR and identify potential biomarkers, including HPDL, PLEKHF1, PFKFB3, and TNFAIP3. The aim is to understand the influence of these biomarkers on AR development, pinpoint effective ones, and elucidate their significant roles in this process. Subsequently, the transcription factors (TF) associated with these biomarkers were predicted using NetworkAnalyst to establish an mRNA-TF regulatory network. Furthermore, predictions of drugs corresponding to these biomarkers, based on the DSigDB database, offer a foundational framework for future clinical research endeavors.
Evidence suggests that the activation of NF-κB signaling plays a significant role in the pathogenesis of Ankylosing Spondylitis (AR), with inappropriate NF-κB activity implicated in numerous autoimmune and inflammatory diseases (29). Tumor Necrosis Factor α Inducing Protein 3 (TNFAIP3), a variant of Tumor Necrosis Factor α (TNF-α), is crucial for modulating immune responses and cell apoptosis (30). TNFAIP3 encodes ubiquitin-modifying enzyme (A20) as a negative regulator of TNF-induced NF-κB activity, thereby playing a key role in managing inflammatory responses across various biological environments (31–33). Li et al. identified the rs9494885SNPTNFAIP3 gene as a significant risk factor for Behcet's disease in Han Chinese population (34). Recent research has demonstrated that PFK15, a small molecule inhibitor of PFKFB3, can impede RAFLS migration, MAPK and NF-κB signaling, lactate secretion, and alleviate collagen-induced arthritis inflammation (35). Consequently, targeting TNFAIP3 to inhibit the inappropriate activation of the NF-κB signaling pathway may offer a potential treatment for AR.
The coding gene PFKFB3, also known as 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3, plays a significant role in the regulation of the glycolysis process. While its involvement in the pathological progression of allergic rhinitis remains unconfirmed, PFKFB3 is implicated in the advancement of inflammation and glucose metabolism via Toll-like receptor 4 (TLR4). Furthermore, PFKFB3 can modulate LPS (lipopolysaccharide)-induced inflammation through the NF-κB signaling pathway. This influence can alter the functions of trophoblast cells, including adhesion, oxidative stress, apoptosis, and migration. Such changes may lead to mitochondrial dysfunction, thereby potentially inducing allergic rhinitis (36).
PLEKHF1, an endosomal protein comprising PH and FYVE membrane-bound domains, plays a crucial role in endosomal trafficking, lysosomal targeting, and autophagosome formation (37). Its expression is notably upregulated during the progression of various pathological conditions. An increase in PLEKHF1 expression may trigger AR by modulating macrophages. In AR patients, macrophages in the nasal cavity and peripheral blood are predominantly of the M2 type. These M2 type macrophages can enhance the Th2 immune response by releasing specific molecules such as YKL-40 and a series of chemokines, including CCL17, CCL18, and CCL26. This suggests that PLEKHF1 plays a significant role in the pathogenesis of AR (38). Mendelian randomization (MR) analysis and in vivo experiments have shown a causal relationship between AR and idiopathic pulmonary fibrosis (IPF). Inhibiting the expression of PLEKHF1 in the lungs could increase the inhibition of PI3K/Akt signaling and reduce pulmonary fibrosis in mice (39–40). The present study demonstrated that PLEKHF1 was differentially expressed in AR. We hypothesize that it is possible to attenuate AR and reduce the level of pulmonary fibrosis by regulating the expression of PLEKHF1. However, the specific mechanism requires further investigation.
HPDL, a single-exon intronless gene situated in the nuclear genome of N2a cells, is located within mitochondria. Its deletion influences the mitochondrial oxygen consumption rate and encodes a 4-hydroxyphenylpyruvate dioxygenase-like protein integral to the tyrosine metabolic pathway (41). In WTHeLa cells, HPDL is isotopically present in the cytoplasm alongside the mitochondrial protein HSP60 and exhibits slight dispersion in the nucleus. Western blotting of HeLa cell subcellular fractions reveals that HPDL can be identified in mitochondria, mirroring the mitochondrial marker TOM20. In conclusion, variants of HPDL induce mitochondrial neuropathy with diverse features such as DD/ID, spasticity, and hypertonia. A deficiency in HPDL impairs mitochondrial respiration processes, potentially leading to a spectrum of inflammatory diseases, including AR (42). Furthermore, our study discovered that both HPDL and PFKB3 upregulate AR, while PLEKHF1 downregulates it. Notably, HPDL was initially identified as a potential biomarker for AR and is involved in classical AR pathways such as the Toll receptor signaling pathway and pattern recognition receptor signaling pathway. These biomarkers are likely implicated in the inflammatory process of AR, suggesting that developing clinical tests targeting these biomarkers could enhance the diagnosis and treatment of AR.
Immune cells, a type of white blood cell, primarily function to safeguard the human body from foreign pathogens such as bacteria and viruses, and also to eliminate abnormal or dead cells. Innate immune cells, including neutrophils, dendritic cells, and natural killer (NK) cells, are born within humans and offer rapid non-specific immune responses to pathogens (43). A growing body of research indicates that immune cell infiltration is closely linked to the efficacy of immunotherapy and patient prognosis (44). Our study suggests that the aforementioned biomarkers are strongly correlated with activated CD4 + T cells, NK cells, and T follicular helper cells. CD4 + T cells, innate immune cells involved in allergic reactions, differentiate into two subsets, Th1 and Th2 cells, upon activation (45). An imbalance between Th1 and Th2 cells has been identified in AR, where Th2 promotes allergic reactions while Th1 counteracts them (46). This imbalance can be mitigated by ameliorating the disproportion between the two cell types, thereby alleviating AR. Furthermore, allergic respiratory diseases are associated with a decrease in natural killer cells and impaired function, which exacerbates the inflammatory response (47). T follicular helper (Tfh) cells are derived from T cells (48). In AR, alterations in the number and activity of Tfh cells have been observed. Some research posits that the quantity of Tfh cells in AR patients may be diminished (49). Tfh cells significantly contribute to AR pathogenesis by secreting cytokines such as IL-4, which encourage the differentiation of B cells into plasma cells, thereby escalating IgE production. Allergen-specific immunotherapy (AIT) could potentially influence the number and function of Tfh cells, thereby mitigating the inflammatory response in AR patients (50). In conclusion, Tfh cells may enhance the inflammatory response and participate in immunoglobulin production in AR. Conversely, immunotherapy might reduce this inflammatory response by modulating Tfh cells. Given our findings that four biomarkers were strongly associated with three immune cells, and considering these biomarkers' involvement in previous studies on inflammatory responses, we hypothesize that HPDL, PLEKHF1, PFKFB3, and TNFAIP3 may directly or indirectly impact the function of CD4 + T cells, NK cells, and trifollicular helper cells. Their activity is crucial for regulating B cell survival, T cell function, and the inflammatory response. Targeting these biomarkers can regulate the function and infiltration degree of immune cells, thereby effectively ameliorating AR.
Currently, the only approved AR-targeted therapies are omalizumab and dupilumab. These drugs target proliferating adaptive immune cells, the interleukin-6 receptor (IL-6R), and CD20 + B cells, respectively. Our research has identified that PFKFB1 and HPDL both utilize the transcription factor KDM5B. KDM5B is a histone lysine demethylase that suppresses gene transcription and functions as an oncogenic factor in cancer initiation and progression (51). Currently, researchers have developed an inhibitor for KDM5B (52). Furthermore, KDM5B may inhibit the expression of NF-κB pathway mRNA in immune diseases. Its congener, KDM5A, is necessary for NK cell activation by suppressing the expression of cytokine signaling inhibitor 1 (SOCS1) (53). However, the differences between KDM5B and other members of the KDM5 family remain largely undefined. Emerging therapies and targeted agents have shown positive effects in treating immune diseases such as AR (54). Given the complexity of pharmacological effects, these epigenetic targets and inhibitors are being evaluated for the treatment of autoimmune diseases (55). These studies suggest that these epigenetic factors are under investigation for the treatment of immune-related diseases, and targeting KDM5B holds significant potential for the treatment of AR.