Over the past decade, significant advancements have been made in understanding asthma’s complex biology. Progress in elucidating the intricate mechanisms underlying asthma inflammation has highlighted the heterogeneous nature of the disease, leading to the identification of numerous asthma phenotypes [1–3], each defined by distinct inflammatory pathways. Epithelial science has emerged as a pivotal frontier in asthma research, with biologists striving to delineate the essential role of the airway epithelium more precisely. However, numerous studies employing cellular, molecular, and animal models have revealed a plethora of interconnected cellular and immunological mechanisms underlying asthma pathogenesis [4–6]. These mechanisms prominently feature increased T helper 2 (Th2) cytokine levels in eosinophilic asthma and Th17 cytokine levels in refractory (neutrophilic) asthma, which recruit inflammatory immune cells to the airways [7, 8].

Despite these advancements, asthma remains a heterogeneous disease [9, 10], encompassing a diverse array of immune and structural cell types [11]. In the epithelial cells of asthmatic lungs, there is an increased synthesis of reactive oxygen species (ROS) associated with mitochondrial dysfunction [12–14]. The interplay between inflammatory cells, mitochondrial dysfunction, and ROS production culminates in epithelial damage, a common feature portraying conditions like asthma [13–16].

Recent advancements in exploring asthma pathogenesis have focused on the pivotal role of mitochondrial dysfunction [17–19]. This dysfunction exerts a profound influence on both bioenergetic metabolism and non-energetic pathogenesis [18]. The disruption of mitochondrial homeostasis results in cellular injury and apoptosis [20]. Key aspects of this dysfunction include the decreased activity of the crucial mitochondrial enzyme adenosine triphosphate (ATP) synthase [17], upregulated oxidative stress [17], initiation of apoptosis, and disrupted calcium homeostasis [17], all instrumental in driving pro-remodeling processes in the asthma-afflicted lung, such as fibrosis of the reticular basement membrane [17] thickening of the airway walls, damage to the epithelial cells, apoptosis of airway cells [17], enlargement and increased number of airway smooth muscle cells, overgrowth of mucus glands, and remodeling and regeneration of blood vessels [17, 21].

Studies have demonstrated an augmentation in Krebs cycle enzyme activity and a reduced reliance on glycolysis in the platelets of individuals diagnosed with asthma [22]. Riou et al. [16] reported that, in the setting of heightened oxidative stress, the oxidative capacity of platelets and peripheral blood mononuclear cells (PBMCs) is increased in individuals with asthma. Alongside these bioenergetic changes observed in platelets and PBMCs, patients have also displayed alterations in their mitochondrial DNA.

IL-4 exacerbates mitochondrial dysfunction in asthma by upregulating 12/15-LOX [20, 40]. This effect, mediated through signal transducer and activator of transcription-6 (STAT-6), leads to increased oxidative stress and damage to mitochondria [20, 42]. IL-4 monoclonal antibody treatment reduces oxidative damage and improves mitochondrial function [14]. IL-4 also influences asymmetric dimethylarginine (ADMA) metabolism, which is linked to oxidative stress and collagen deposition in asthma [43, 44]. Elevated ADMA levels contribute to nitrosative stress and enhanced oxidative responses in asthma [44] (Figure 1).

IL-4 is central to asthma pathogenesis, as evidenced by elevated IL-4 levels in asthma patients, with plasma concentrations of 0.94 ± 0.05 pg/mL compared to 0.75 ± 0.03 pg/mL in healthy controls [45]. It drives inflammation by promoting the differentiation of Th0 cells into Th2 cells, facilitating eosinophilic asthma, and increasing immunoglobulin E (IgE)-mediated immune responses [46, 47]. IL-4 binds to IL-4 receptor α (IL-4Rα), activating signaling pathways involving STAT-6 and insulin receptor substrates, which enhance Th2 responses and mucus production, exacerbate airway obstruction, and induce eotaxin production [47]. It also prevents eosinophil apoptosis and promotes their migration through chemotaxis [47, 48]. Genetically, asthma is linked to the chromosomal region 5q31–33, which houses genes involved in Th2 cytokine synthesis, further implicating IL-4 in asthma pathogenesis [49, 50].

IL-4 significantly influences epithelial cell differentiation and upregulates transcripts like mucin 5AC (MUC5AC), periostin (POSTN), and inducible nitric oxide synthase (INOS) in stromal cells through IL-4Rα signaling, correlating with asthma severity [51, 52]. Dupilumab, an IL-4Rα monoclonal antibody, demonstrates the clinical impact of IL-4Rα-triggered pathways in severe Th2-high asthma [53, 54]. Historically, ALOX15 incubation has been shown to impair mitochondrial function [55, 56]. IL-4-induced peroxidation of lipids, including cardiolipin, disrupts mitochondrial membranes and respiratory enzyme activity [52]. IL-4 and IL-13 upregulate 15-LOX (ALOX15) in human cells and 12-LOX (ALOX15) in murine systems, with IL-4’s effect being STAT-6 dependent [42]. Thus far, the upregulation of human 15-LOX (15-LOX or ALOX15) by IL-4 and IL-13 has been observed solely in vitro [57–60]. In vivo studies with IL-4 transgenic mice show increased 12-LOX activity, linked to STAT-6 activity, suggesting that IL-4 stimulates LOX expression via STAT-6 [42]. This upregulation of LOX enzymes underlines their role in asthma pathogenesis by contributing to mitochondrial dysfunction and inflammation.

Mitochondria, vital for energy production and cellular functions, are integral to immune responses, cellular differentiation, and adaptation to hypoxic stress [61]. Dysfunctional mitochondria contribute to disease progression by increasing ROS, compromising bioenergetics, and impairing mitochondrial biogenesis and mitophagy, leading to epithelial vulnerability and inflammation [62]. In asthma, this dysfunction is marked by reduced ATP synthase activity, elevated oxidative stress, and disrupted calcium balance [62]. In asthmatic lungs, mitochondrial dysfunction manifests through several key disruptions: a decrease in the activity of complex IV of the mitochondrial ETC, an overload of calcium within the mitochondria, a reduction in mitochondrial membrane potential, and an increase in oxidative stress within the mitochondria [14, 40] (Figure 2).

The mitochondrial genome haplogroup “U” correlates with elevated IgE levels and allergic asthma [63]. Asthmatic airway epithelial cells often show mitochondrial swelling, disintegration, and oxidative damage, affecting airway smooth muscle and bronchial epithelium [64, 65]. These abnormalities impact airway contractility, cell proliferation, and calcium regulation, contributing to fibrosis, oxidative stress, and apoptosis [64–67].

Mitochondrial signaling includes anterograde (nuclear control of mitochondrial activity) and retrograde (mitochondria-induced nuclear transcriptional reprogramming) pathways [62–68]. Retrograde signaling involves ABI4- and WRKY-type transcription factors and is linked to ATP generation and cellular proliferation [62, 69]. Increased cytosolic Ca²⁺ enhances mitochondrial function and contributes to airway hyperresponsiveness (AHR) in asthma [66, 70]. Rowlands [66] and Agarwal et al. [71] emphasize the broader impact of mitochondrial dysfunction in asthma, highlighting the role of ubiquinol-cytochrome c reductase complex core protein 2 (UQCRC2) in maintaining mitochondrial function and its deficiency in exacerbating airway inflammation and hyperresponsiveness. Specialized therapies like mitochondrial transfer techniques including microinjection, gap junctions, and tunneling nanotubes (TNTs) are efficacious in alleviating respiratory damage. Mesenchymal stem cells (MSCs), known for their regenerative properties, can transfer mitochondria via TNTs to lung epithelial cells [72–74]. This process has shown promise in treating respiratory conditions like asthma and acute respiratory distress syndrome (ARDS) [72–74]. Studies indicate MSCs enhance cell viability and restore mitochondrial function in injured lung cells. Miro1, a GTPase, regulates this mitochondrial transfer, improving treatment efficacy in asthma models [72].

Mabalirajan et al. [40] showed that 12/15-LOX OE (overexpressed) mice demonstrated elevated caspase 3 activity, decreased cytochrome c oxidase (COX) activity, reduced activity of complex IV, lowered membrane potential of lung mitochondria, heightened lung cytosolic cytochrome c, and an increased number of apoptotic bronchial epithelial cells. These changes, along with mitochondrial architectural modifications like the disappearance of cristae and swollen epithelium of the bronchi, were associated with upregulated oxidative stress and inflammation, ultimately contributing to the pathogenesis of asthma in the 12/15-LOX OE mice [40] (Figure 3).

A promising therapeutic approach for asthma involves evaluating 12/15-LOX inhibitors as potential treatments. 12/15-LOX amplifies oxidative stress, leading to mitochondrial damage, which further exacerbates oxidative stress and cellular injury [75]. Studies have shown that OE of 12/15-LOX leads to mitochondrial dysfunction and bronchial epithelial injury in naive mice [40]. Conversely, knockout or knockdown of 12/15-LOX reduces airway epithelial damage in allergic mice, indicating that 12/15-LOX contributes to such injuries [40]. Notably, OE of 12/15-LOX results in bronchospasm even without allergen exposure, underscoring its role in promoting airway epithelial injury and asthma pathogenesis.

Given that 12/15-LOX induces oxidative stress, which exacerbates inflammatory responses and promotes AHR, antioxidants can play a crucial role in alleviating oxidative stress in asthma by neutralizing oxidants and minimizing lung damage [76]. Antioxidants help prevent radical formation, repair oxidative damage, and remove damaged molecules, thereby protecting lung tissues and improving respiratory health [77].

VIT-E acts as a protective antioxidant, while ALOX15 (12/15-LOX) contributes to inflammation and oxidative stress [92] (Table 1). IL-4 induces 12/15-LOX, promoting epithelial apoptosis and exacerbating asthma [92]. Notably, 12/15-LOX is predominantly found in bronchial epithelial cells and is implicated in mitochondrial degradation. VIT-E complexes inhibit the activity of 12/15-LOX [92].

Maternal intake of VIT-E during pregnancy has been consistently associated with a lower incidence of childhood asthma, inversely correlated with allergen sensitization and total serum IgE levels [107]. VIT-E supplementation reduces airway inflammation and hyperresponsiveness, although the exact mechanisms remain uncertain [92]. Antioxidant deficiency, particularly of VIT-E, leads to mitochondrial dysfunction in neurological and muscular diseases, including asthma [108]. VIT-E derivatives, such as tocopheryl succinate, show promise in combating diseases associated with mitochondrial-derived oxidative stress [4]. Notably, orally administered α-tocopherol predominantly localizes in mitochondrial fractions, with α-tocopherol being the most biologically significant form among natural VIT-E analogs, crucial for maintaining mitochondrial health [109].

Given these findings, it is hypothesized that VIT-E could alleviate mitochondrial dysfunction in asthma. α-Tocopherol’s effects on mitochondrial dysfunction were evaluated using a mouse model of asthma, which mirrors various aspects of human asthma pathology such as goblet cell metaplasia and sub-epithelial fibrosis [92] (Table 1).

Esculetin, a potent antioxidant derived from coumarin, demonstrates significant capabilities in reducing oxidative stress induced by linoleic acid [104]. It operates through multiple mechanisms, including the reduction of oxidative free radicals, scavenging of free radicals, and diminishing lipid peroxidation [104]. Notably, esculetin has shown promise in mitigating mitochondrial dysfunction [104]. Additionally, esculetin acts as a potent nonspecific inhibitor of 12/15-LOX, suggesting its potential in addressing asthma-related features [104]. To explore this hypothesis, researchers administered esculetin to asthmatic mice, evaluating its effects on key mitochondrial structural changes and functions [104].

Derived from various plants, esculetin exhibits broncho-dilating properties in vitro, particularly evident in carbachol-induced airway spasms. However, its clinical efficacy in treating asthma remains unexplored [104]. Furthermore, esculetin demonstrates immunomodulatory properties, potentially contributing to its diverse pharmacological effects [119, 120].

Baicalein, a compound found in the dry roots of “Scutellaria baicalensis” Georgi, is recognized for its diverse biological activities, including antiviral, antioxidant, and anticancer properties [125, 126]. Notably, its inhibition of 12/15-LOX makes it a promising candidate for asthma management. However, it is important to note that baicalein is not a specific ALOX15 inhibitor; it also inhibits other ALOX isoforms, including ALOX5 [127]. Since ALOX5 is responsible for the biosynthesis of leukotrienes, the beneficial effects of baicalein in asthma models might be attributed to its inhibition of ALOX5 also [127]. By targeting multiple ALOX isoforms, baicalein effectively reduces the production of pro-inflammatory metabolites such as HODEs and HETEs, thereby alleviating airway inflammation [91, 128]. Furthermore, baicalein modulates the immune response by decreasing Th2 cytokine levels, which are pivotal in asthma pathogenesis [91, 128].

Baicalein’s antioxidant properties are particularly noteworthy for scavenging ROS, which significantly contributes to mitochondrial damage in asthma [129, 130]. By protecting mitochondria from oxidative stress, baicalein preserves mitochondrial function and stimulates mitochondrial biogenesis via the peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) pathway [131]. This leads to increased ATP production, essential for maintaining cellular energy levels and supporting airway epithelial cell function [131]. Additionally, baicalein safeguards mitochondrial DNA, regulates mitochondrial dynamics, and maintains a healthy mitochondrial network, all of which are crucial for preventing apoptosis and preserving cellular integrity [131].

In conclusion, while baicalein demonstrates promise as a therapeutic agent for asthma through its multifaceted mechanisms targeting inflammation, oxidative stress, and mitochondrial dysfunction, its potential is not without controversy. The non-specific nature of its inhibitory activity and the broad range of its antioxidant effects could lead to adverse side effects if used frequently in clinical settings. Therefore, further clinical investigations are necessary to validate its efficacy, establish optimal treatment protocols, and thoroughly assess its safety profile in asthma management [104].

This review highlights the critical role of 12/15-LOX in asthma pathobiology and the therapeutic potential of targeting this enzyme. However, there are notable limitations to consider. The variability in 12/15-LOX expression and activity among different individuals and asthma phenotypes complicates the generalization of therapeutic strategies. Additionally, while preclinical studies provide valuable insights, the translation of these findings to clinical practice remains challenging due to differences in experimental models, human disease complexity, and pro- and anti-inflammatory properties of 12/15-LOX. The non-specific effects of some inhibitors, such as baicalein, which affects multiple LOX isoforms, further complicate the interpretation of their therapeutic efficacy. Despite these limitations, the strengths of this review lie in its comprehensive analysis of the mechanisms linking 12/15-LOX to mitochondrial dysfunction and oxidative stress in asthma. By integrating recent advancements in understanding the molecular pathways and highlighting promising therapeutic agents, this review provides a solid foundation for future research. The use of multiple antioxidants and their potential to address various aspects of asthma pathology represents a significant strength, offering a multifaceted approach to treatment.

Future research should focus on several key areas to advance the understanding and treatment of asthma. First, further clinical studies are needed to validate the efficacy and safety of 12/15-LOX inhibitors and antioxidants like esculetin, baicalein, and VIT-E in diverse asthma populations. Investigating the long-term effects and optimal dosing regimens will be crucial for translating these findings into effective therapies. Additionally, exploring the mechanisms by which these compounds interact with other signaling pathways and their impact on different asthma phenotypes will help tailor more personalized treatment strategies. Advances in genomic and proteomic technologies could provide deeper insights into individual variations in 12/15-LOX activity and response to treatment. Furthermore, the development of novel delivery systems for these therapeutic agents, including targeted delivery to the lungs, could enhance their effectiveness and minimize side effects. Finally, continued research into mitochondrial dysfunction in asthma could uncover new therapeutic targets and strategies, potentially leading to innovative treatments that address the underlying causes of the disease. By addressing these areas, future studies can build on the current knowledge and significantly improve asthma management and patient outcomes.

This review underscores the pivotal role of 12/15-LOX in the pathogenesis of asthma, emphasizing its significant contribution to mitochondrial dysfunction and oxidative stress. The interplay between 12/15-LOX and mitochondrial dysfunction is central to asthma pathobiology, with 12/15-LOX metabolizing PUFAs like AA into pro-inflammatory mediators such as HODE and HETE. This enzymatic activity exacerbates airway inflammation, epithelial damage, and mitochondrial dysfunction, leading to the exacerbation of asthma symptoms. Recent research highlights the therapeutic potential of targeting 12/15-LOX and its associated pathways. Compounds such as esculetin, baicalein, and VIT-E demonstrate promise in ameliorating the pathophysiological aspects of asthma. Esculetin, a potent antioxidant, not only inhibits 12/15-LOX but also improves mitochondrial function, offering a dual therapeutic approach. Baicalein, derived from “Scutellaria baicalensis”, targets multiple LOX isoforms and reduces inflammatory mediators while promoting mitochondrial biogenesis. VIT-E, known for its antioxidant properties, mitigates 12/15-LOX expression and its metabolites, improving mitochondrial function and reducing asthma symptoms. Despite the insights provided, limitations such as variability in 12/15-LOX activity among individuals, differences between preclinical models and human disease, and the non-specific effects of some inhibitors need to be addressed. Future research should focus on validating the efficacy and safety of these therapeutic agents, exploring their interactions with other signaling pathways, and developing novel delivery systems. Enhanced understanding and targeted therapies could lead to more effective asthma management and improved patient outcomes.