A Multilevel Redox-Based Prognostic Model for Asthma Severity: From Genotype to Serum Biomarkers

Asthma is a heterogeneous chronic airway disease in which oxidative stress (OS) plays a central mechanistic role beyond classical immune-mediated inflammation. Reactive oxygen and nitrogen species (ROS/RNS), generated by recruited inflammatory cells and activated airway structural cells, drive epithelial injury, mucus hypersecretion, airway remodeling, and modulate key transcription factors including nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. This review synthesizes current evidence on the multilevel redox-based determinants of asthma severity, spanning from genetic polymorphisms to circulating biomarkers. We examine serum antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), peroxiredoxins (PRDXs), and the thioredoxin (Trx) system as dynamic indicators of systemic redox status and disease severity, alongside oxidative enzymes including NADPH oxidases and dual oxidases (NOX/DUOX), xanthine oxidase (XO), and myeloperoxidase (MPO) that serve as upstream sources of airway oxidant burden. Functional genetic polymorphisms in antioxidant genes (SOD2, CAT, glutathione S-transferase mu 1/glutathione S-transferase theta 1 (GSTM1/GSTT1), heme oxygenase-1 (HO-1), NAD(P)H quinone dehydrogenase 1 (NQO1), nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (Nrf2/KEAP1)) and oxidative enzyme genes including nitric oxide synthase 1/2/3 (NOS1/2/3), MPO, cytochrome b-245 alpha chain (CYBA), and xanthine dehydrogenase (XDH) are reviewed as modulators of individual redox capacity and asthma susceptibility, with particular attention to gene–environment interactions. We further discuss oxidative damage biomarkers, including malondialdehyde (MDA), 8-isoprostanes, 4-hydroxynonenal, 8-oxo-7, 8-dihydro-2′-deoxyguanosine, protein carbonyls, 3-nitrotyrosine, and advanced oxidation protein products as indicators of lipid, DNA, and protein oxidation that correlate with disease activity and control. The roles of micronutrient cofactors in modulating antioxidant enzyme function and their potential as contextual biomarkers are also addressed. Additionally, emerging evidence on microRNAs (miRNAs) linked to OS biology in asthma is presented. Finally, we critically evaluate the challenges limiting clinical translation, including biomarker non-specificity, analytical variability, gene–environment complexity, and the absence of standardized reference ranges. This integrated framework supports the development of multilevel redox prognostic panels combining genetic, enzymatic, and oxidative damage readouts for improved asthma phenotyping, severity stratification, and personalized therapeutic approaches.