Jeongmin Lee

Studies of allergic rhinitis (AR) have increasingly recognized that reactive oxygen species (ROS) are not simply byproducts of oxidative metabolism but function as modulators of the type 2 inflammatory network during the pathogenesis of this disease. This narrative review summarizes the role of ROS in the pathophysiology of AR by analyzing studies that examined markers of systemic oxidative stress, dysfunction of the epithelial barrier, ROS derived from immune cells, mitochondrial redox signaling, and inflammasome-related pathways. Our structured search of the literature reviewed five major databases (PubMed, Scopus, EMBASE, Cochrane Library, and Google Scholar) and identified 17 eligible studies published between 2000 and 2026. Clinical studies suggest that patients with AR exhibit altered systemic redox homeostasis, including thiol–disulfide imbalance and increased lipid peroxidation. However, these findings are primarily from measurements of markers in peripheral blood, not nasal mucosa. Experimental studies consistently demonstrated that allergen exposure increased the levels of ROS in nasal epithelial and immune cells, disrupted the epithelial barrier, downregulated tight junction proteins, and activated inflammatory signaling pathways. Although direct nasal tissue data remain limited, evidence extrapolated from peripheral blood and bronchial challenge models suggests that eosinophils and neutrophils contribute to the generation of ROS during the late phase of the allergic response, thereby potentially amplifying and sustaining airway inflammation. There is also evidence that mitochondrial ROS and DUOX-dependent signaling contribute to epithelial dysfunction, including the release of damage-associated molecular patterns and activation of inflammasome pathways. In parallel, antioxidant defense mechanisms, such as the KEAP1/NRF2 axis and mitophagy-related pathways, appear to modulate disease severity by maintaining redox homeostasis. Experimental strategies such as ROS scavengers and oxidative stress-responsive drug delivery systems have shown early proof-of-concept potential in preclinical and pilot studies, but rigorous and large-scale clinical support is strictly required before any clinical application can be considered. Overall, current evidence indicates that ROS function in AR as context-dependent redox mediators rather than as primary causes. The biological effects of ROS appear to depend on site of synthesis, subcellular localization, and the balance between oxidant generation and antioxidant defenses. Further studies that directly assess the dynamics of nasal mucosal ROS and well-designed clinical trials are needed to clarify the translational relevance of these studies and the therapeutic potential of different treatments for AR.

Chronic rhinosinusitis (CRS) is an inflammatory disease of the sinonasal mucosa whose pathogenesis is characterized by complex interactions of immunological and environmental factors. The maintenance of normal sinonasal function requires a balance of sinus ostial patency, mucociliary clearance, and mucus secretion, and disruption of this balance can lead to CRS. Although many studies have examined the pathophysiology of CRS, the role of reactive oxygen species (ROS) remains incompletely understood. In this review, we analyzed 22 studies of CRS that examined the effects of ROS on epithelial barrier function, local immune responses, and tissue remodeling. The results from in vitro studies, animal models, and human tissue analyses suggest that ROS are not merely by-products of inflammation, but appear to function as key mediators in the pathophysiology of CRS, particularly in the formation and persistence of the CRS phenotype with nasal polyps (CRSwNP). In particular, CRSwNP is characterized by increased activity of enzymes in the dual oxidase (DUOX) and NADPH oxidase (NOX) families, mitochondrial dysfunction, and decreased activity of superoxide dismutase (SOD) and peroxiredoxin 2 (PRDX2). At the molecular level, these alterations increase the generation of ROS and impair antioxidant defense. At the cellular level, these alterations disrupt the epithelial barrier, activate inflammasomes, increase pyroptosis, and induce the formation of neutrophilic and eosinophilic extracellular traps. These changes culminate in the epithelial–mesenchymal transition (EMT), with the formation of nasal polyps and tissue remodeling. Increased oxidative stress can also occur in CRS without nasal polyps (CRSsNP), but this phenotype appears to have relatively preserved antioxidant defense systems, which may partly explain the more limited structural remodeling. External stimuli, such as fungal proteases, bacterial toxins, and certain antibiotics, can also increase the production of ROS and may contribute to disease chronicity. Taken together, the level and pathophysiological roles of ROS differ in the two primary phenotypes of CRS. Further mechanistic studies are needed to clarify the specific alterations of redox pathways in these two phenotypes and to develop novel therapeutic strategies that target ROS.

In ovarian cancer, reactive oxygen species (ROS) are both toxic byproducts and mediators of signaling and stress adaptation, such that the same “ROS change” can suppress or promote tumors in vivo. Here, we integratively summarize how ROS modulation reshapes tumor growth, metastasis, and treatment response in ovarian cancer, based on 22 original in vivo-containing studies that were selected from a five-database search of papers published from January 1990 to December 2025. On the antitumor axis, ROS amplification in xenograft models is accompanied by reduced tumor burden and increased markers of cell death, and can operate through diverse death programs beyond apoptosis, including pyroptosis and ferroptosis. ROS-based anticancer effects may vary depending on whether cytoprotective autophagy is co-induced. For example, in models treated with daphnetin, ROS-dependent cell death occurs together with induction of cytoprotective autophagy and the anticancer effect is strengthened when an autophagy inhibitor is added. In a therapeutic context, autophagy may thus function as an adaptive response in tumor cells to partially buffer ROS-induced stress. Conversely, on the pro-tumor axis, ROS can serve as an upstream signal driving inflammatory and metastatic processes. In a peritoneal metastasis model, GPX1 inhibition-induced ROS elevation was linked to increased metastatic burden. In the context of drug resistance, platinum resistance is proposed to be an adaptive state shaped not by the absolute level of ROS alone, but by integrated ROS-sensing and buffering circuits, the DNA damage response (DDR), and NF-κB networks. In vivo, AMPK–ROS axis activation through ACLY inhibition or resetting of drug responsiveness can be connected to tumor suppression and increased sensitivity. Furthermore, ROS modulation is not limited to tumor cell-intrinsic targets: it can also be linked to therapeutic response reprogramming at the tumor microenvironment (TME) level, such as via regulation of acidity/ROS conditions and coupling to macrophage polarization in immunocompetent syngeneic models. Taken together, these lines of in vivo evidence indicate that, in ovarian cancer, ROS should not be interpreted in a binary “increase/decrease” manner, but rather in terms of redox-buffering capacity, the engaged signaling axes (cell death, DDR, metastasis/inflammation), and interactions with TME factors.

This review explores the dual role of reactive oxygen species (ROS) and free radicals in the pathogenesis of endometriosis, aiming to deepen our understanding of these processes through a systematic literature review. To assess the induction and involvement of ROS in endometriosis, we conducted a comprehensive literature review using Cochrane Libraries, EMBASE, Google Scholar, PubMed, and SCOPUS databases. Of 30 qualifying papers ultimately reviewed, 28 reported a significant contribution of ROS to the pathogenesis of endometriosis, while two found no association. The presence of ROS in endometriosis is associated with infertility, irregular menstrual cycles, painful menstruation, and chronic pelvic discomfort. Among individual ROS types studied, hydrogen peroxide was most frequently investigated, followed by lipid peroxides and superoxide radicals. Notable polymorphisms associated with ROS in endometriosis include those for AT-rich interactive domain 1A (ARID1A) and quinone oxidoreductase 1 (NQO1) isoforms. Key enzymes for ROS scavenging and detoxification include superoxide dismutase, glutathione, and glutathione peroxidase. Effective inhibitors of ROS related to endometriosis are vitamins C and E, astaxanthin, fatty acid-binding protein 4, cerium oxide nanoparticles (nanoceria), osteopontin, sphingosine 1-phosphate, N-acetyl-L-cysteine, catalase, and a high-antioxidant diet. Elevated levels of ROS and free radicals are involved in the pathogenesis of endometriosis, suggesting that targeting these molecules could offer potential therapeutic strategies.

Facial nerve injury (FNI) induces complex molecular and cellular responses, with reactive oxygen species (ROS) and free radicals (FRs) playing pivotal roles in nerve degeneration and regeneration. However, to date, no systematic review has specifically investigated the involvement of ROS and FRs in FNI. To address this unmet need, we reviewed the literature on the subject, comprehensively searching SCOPUS, PubMed, Cochrane Library, EMBASE, and Google Scholar to identify studies that assessed the roles of FRs and ROS in FNI and summarize their findings. A total of 15 studies that satisfied search criteria were identified. Key findings showed that excessive ROS and FR lead to mitochondrial dysfunction, lipid peroxidation, and ferroptosis, exacerbating nerve degeneration after facial nerve injury. These effects are modulated by antioxidants, including alpha-lipoic acid, edaravone, N(ω)-nitro-L-arginine methyl ester (L-NAME), glutathione peroxidase 4, glutathione, methylprednisolone sodium succinate, Si-based agents, superoxide dismutase, and tirilazad mesylate. The insights gained from this review suggest that levels of FRs and ROS are strongly associated with the pathophysiology of facial nerve injury and underscore the therapeutic potential of targeting ROS and FR pathways in facial nerve injuries.

Many studies have evaluated the roles of free radicals and reactive oxygen species (ROS) in various diseases. To date, however, no systematic review has specifically investigated the involvement of free radicals and ROS in acute otitis media (OM), OM with effusion, and chronic OM. The present study therefore assessed the roles of free radicals and ROS in OM. SCOPUS, PubMed, Cochrane Library, EMBASE, and Google Scholar were comprehensively searched to identify studies assessing the roles of free radicals and ROS in OM. Relevant studies were identified and their findings summarized. The literature search identified 21 studies. A review of their findings showed that the concentrations of hydrogen peroxide (H₂O₂), lipid hydroperoxide (LPO), and myeloperoxidase (MPO) were elevated in patients with acute OM; that the concentrations of H₂O₂, LPO, MPO, xanthine oxidase (XO), superoxide dismutase (SOD), glutathione peroxidase (GPX), malondialdehyde (MDA), hydroxyl radical (·OH), and nitrotyrosine were elevated in patients with OM with effusion; and that the levels of nitric oxide (NO), MPO, 4-hydroxynonenal (4-HNE), and malondialdehyde (MDA) were elevated in patients with chronic OM. Although some studies reported that SOD levels were increased in patients with OM with effusion, decreases in antioxidants such as SOD and catalase, as well as total antioxidant capacity, were observed across all types of OM. Although the levels of free radicals and ROS varied by type of OM, study design, control group selection, sample type, ROS and free radical markers, and antioxidant types, most studies showed increased ROS and decreased antioxidants in OM patients. These findings suggest that levels of free radicals and ROS are strongly associated with the pathophysiology of OM.

Although several methods are being applied to treat peripheral nerve injury, a perfect treatment that leads to full functional recovery has not yet been developed. SMAD (Suppressor of Mothers Against Decapentaplegic Homolog) plays a crucial role in nerve regeneration by facilitating the survival and growth of nerve cells following peripheral nerve injury. We conducted a systematic literature review on the role of SMAD in this context. Following peripheral nerve injury, there was an increase in the expression of SMAD1, -2, -4, -5, and -8, while SMAD5, -6, and -7 showed no significant changes; SMAD8 expression was decreased. Specifically, SMAD1 and SMAD4 were found to promote nerve regeneration, whereas SMAD2 and SMAD6 inhibited it. SMAD exerts its effects by promoting neuronal survival and growth through BMP/SMAD1, BMP/SMAD4, and BMP/SMAD7 signaling pathways. Furthermore, it activates nerve regeneration programs via the PI3K/GSK3/SMAD1 pathway, facilitating active regeneration of nerve cells and subsequent functional recovery after peripheral nerve damage. By leveraging these mechanisms of SMAD, novel strategies for treating peripheral nerve damage could potentially be developed. We aim to further elucidate the precise mechanisms of nerve regeneration mediated by SMAD and explore the potential for developing targeted nerve treatments based on these findings.

No matter what treatment is used after nerve transection, a complete cure is impossible, so basic and clinical research is underway to find a cure. As part of this research, autophagy is being investigated for its role in nerve regeneration. Here, we review the existing literature regarding the involvement and significance of autophagy in peripheral nerve injury and regeneration. A comprehensive literature review was conducted to assess the induction and role of autophagy in peripheral nerve injury and subsequent regeneration. Studies were included if they were prospective or retrospective investigations of autophagy and facial or peripheral nerves. Articles not mentioning autophagy or the facial or peripheral nerves, review articles, off-topic articles, and those not written in English were excluded. A total of 14 peripheral nerve studies that met these criteria, including 11 involving sciatic nerves, 2 involving facial nerves, and 1 involving the inferior alveolar nerve, were included in this review. Studies conducted on rats and mice have demonstrated activation of autophagy and expression of related factors in peripheral nerves with or without stimulation of autophagy-inducing factors such as rapamycin, curcumin, three-dimensional melatonin nerve scaffolds, CXCL12, resveratrol, nerve growth factor, lentinan, adipose-derived stem cells and melatonin, basic fibroblast growth factor, and epothilone B. Among the most studied of these factors in relation to degeneration and regeneration of facial and sciatic nerves are LC3II/I, PI3K, mTOR, Beclin-1, ATG3, ATG5, ATG7, ATG9, and ATG12. This analysis indicates that autophagy is involved in the process of nerve regeneration following facial and sciatic nerve damage. Inadequate autophagy induction or failure of autophagy responses can result in regeneration issues after peripheral nerve damage. Animal studies suggest that autophagy plays an important role in peripheral nerve degeneration and regeneration.

Objective: There are currently no known treatment methods for ensuring complete recovery from facial nerve damage. Thus, various basic and clinical studies continue to be conducted to achieve this end. As part of this research, autophagy is being investigated for its role in nerve regeneration. Here, we review the existing literature regarding the involvement and signifi-cance of autophagy in facial nerve injury and regeneration. Methods: A comprehensive litera-ture review was conducted to assess the induction and role of autophagy in facial nerve injury and subsequent regeneration. Results: Studies conducted on rats and mice have demonstrated activation of autophagy and expression of related factors in facial and sciatic nerves. Among the most studied of these factors in relation to degeneration and regeneration of facial and sciatic nerves are LC3II/I, PI3K, mTOR, Beclin-1, ATG3, ATG5, ATG7, ATG9, and ATG12. Conclusion: This analysis indicates that autophagy is involved in the process of nerve regeneration follow-ing facial and sciatic nerve damage. Inadequate autophagy induction or failure of autophagy re-sponses can result in regeneration issues after facial or sciatic nerve damage. Animal studies suggest that autophagy plays an important role in facial and sciatic nerve degeneration and re-generation.