Search Results (5,030)

Severe acute pancreatitis (SAP) is a life-threatening inflammatory disorder characterized by high mortality and limited therapeutic options. Alginate oligosaccharide (AOS), a marine-derived bioactive polysaccharide, exhibits prebiotic, anti-inflammatory and antioxidant properties that are effective against various inflammatory diseases. In this study, a mouse model of SAP was established by intraperitoneal injection of cerulein (100 μg/kg) and lipopolysaccharide (5 mg/kg), and the mice were pretreated with AOS (200 mg/kg) by gavage for 4 consecutive weeks to explore the potential protective efficacy and underlying mechanisms. The results shown that AOS attenuated the severity of SAP, as evidenced by reduced serum amylase and lipase levels, as well as alleviated histopathological injury in both pancreatic and ileal tissues. AOS suppressed the overproduction of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) in serum, pancreas, and ileum at protein or mRNA levels. Moreover, AOS effectively diminished pancreatic and ileal inflammatory infiltration and oxidative stress in SAP mice, accompanied by inhibited the TLR4/MyD88/NF-κB pathway and activated the Nrf2/HO-1 antioxidant axis. Furthermore, AOS restored intestinal barrier integrity, as manifested by upregulated expression of tight junction proteins (claudin-1, occludin, ZO-1), reduced serum diamine oxidase, and decreased bacterial translocation from the gut to the pancreas. It was revealed by 16S rRNA sequencing that AOS ameliorated SAP-induced gut dysbiosis by restoring microbial diversity, normalizing the Firmicutes/Bacteroidetes ratio, enriching beneficial genera (Lactobacillus, Blautia), and enhancing cecal short-chain fatty acid (acetic, propionic, butyric acid) production. Collectively, our findings demonstrate that AOS exerts comprehensive protective effects against SAP through suppression of inflammatory signaling and oxidative stress, as well as restoring gut homeostasis. These results suggest that AOS may serve as a promising prebiotic-based nutritional strategy for the management of SAP. Full article

Insulin (Ins) regulates multiple intracellular signalling pathways involved in cell survival, oxidative stress responses, and tau phosphorylation. Dysregulation of these pathways has been implicated in neurodegenerative disorders, including Alzheimer’s disease (AD). The present study evaluated the effects of insulin on protein kinase B/glycogen synthase kinase-3 beta (AKT/GSK-3β) signalling, tau phosphorylation, and oxidative stress-related markers in SH-SY5Y neuroblastoma cells. Cell metabolic activity was assessed using the (diphenyltetrazolium bromide) MTT assay, while cell number and viability were evaluated by Trypan Blue exclusion, necrosis by lactate dehydrogenase (LDH) release, and apoptosis by Caspase-3 activity. Western blot analysis was performed to evaluate the expression of phosphorylated AKT (p-AKT), phosphorylated GSK-3β (p-GSK-3β Ser9), phosphorylated TAU (pTAU), nuclear factor erythroid 2-related factor 2 (NRF2), manganese superoxide dismutase (Mn-SOD), and copper/zinc superoxide dismutase (Cu/Zn-SOD). Lipid peroxidation was determined by measuring malondialdehyde (MDA) levels using a colorimetric/fluorometric assay. Insulin treatment increased MTT reduction (31.25%) and cell metabolic activity (119.15%) while reducing LDH release (19.2%) and Caspase-3 activity (31.26%). In addition, insulin significantly increased p-AKT (34.2%) and p-GSK-3β (Ser9) (19.9%) levels. A reduction in pTAU levels (53.39%) was also observed following insulin treatment. Furthermore, insulin increased NRF2 expression (18.77%), Cu/Zn-SOD (37.29%), and Mn-SOD (50.16%) and reduced MDA levels (13.95%). These findings indicate that insulin modulates signalling pathways associated with tau phosphorylation and cellular redox regulation in SH-SY5Y cells. Insulin treatment was associated with increased AKT and GSK-3β phosphorylation, reduced tau phosphorylation, and changes in oxidative stress-related markers in SH-SY5Y neuroblastoma cells. These findings support a role for insulin in the modulation of molecular pathways implicated in cellular stress responses and tau regulation. Further studies using differentiated neuronal models and disease-relevant conditions are required to determine the relevance of these observations to neurodegenerative disorders. Full article

The roots of Baphicacanthus cusia (Nees) Bremek, commonly known as Nan-Ban-Lan-Gen, have been used for a long time in traditional Chinese medicine to manage inflammatory and infectious diseases. However, the structural features and bioactive potential of its polysaccharides have not been extensively studied. In the present study, a novel homogeneous polysaccharide (BcP-b2) was isolated from the roots of B. cusia, and its bioactivity was evaluated using an activity-guided purification strategy. Multi-dimensional structural analysis identified BcP-b2 as a highly branched galactoarabinan with a molecular weight of ~38.1 kDa, featuring a well-defined backbone and a variety of side chains. In vitro and in vivo assays demonstrated that BcP-b2 attenuated the accumulation of reactive oxygen species (ROS) and enhanced the activities of endogenous antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). Additionally, BcP-b2 activated macrophages under basal conditions and alleviated lipopolysaccharide (LPS)-induced cytotoxicity and inflammatory mediator release. Transcriptomic and Western blot analyses revealed that these dual effects were achieved through the simultaneous suppression of the PI3K/Akt inflammatory axis and activation of the Nrf2/HO-1 antioxidant pathway, concomitant with enhanced nuclear translocation of Nrf2. These findings provide a molecular basis for the ethno-pharmacological use of Nan-Ban-Lan-Gen and identify BcP-b2 as a promising candidate for further investigation as a potential therapeutic agent. Full article

Background: Gentamicin-induced nephrotoxicity limits clinical pharmacotherapy and involves multiple converging stress-response pathways. Ellagic acid (EA) has renoprotective potential, yet its role in coordinating endoplasmic reticulum (ER) stress-mediated apoptosis, autophagy, and inflammation remains unclear. We hypothesized that EA co-treatment would protect the kidney by modulating ER stress-dependent pathways and associated inflammatory and adaptive signaling. Methods: For an integrated mechanistic analysis in a rat model of gentamicin nephrotoxicity, 40 male Sprague-Dawley rats were assigned to control, gentamicin (100 mg/kg), EA (100 mg/kg), and gentamicin + EA groups for 14 days. Renal function, oxidative stress, inflammatory mediators, ER stress markers, apoptosis, autophagy, tubular injury markers, and histopathological changes were assessed. Results: Gentamicin induced renal dysfunction, tubular injury, and ER stress across all unfolded protein response (UPR) branches (IRE1α, PERK, ATF6), C/EBP homologous protein (CHOP)-associated apoptosis, dysregulated autophagy, and upregulated kidney injury molecule-1 (KIM-1). A selective inflammatory signature was observed, with increased cyclooxygenase-2 (COX-2) and interleukin-6 (IL-6), whereas tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) remained unchanged. Co-administration of ellagic acid with gentamicin significantly improved renal function markers compared to the gentamicin group. In contrast, ellagic acid alone did not show significant differences compared to the control group. Notably, gentamicin induced compensatory upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) expression, while ellagic acid co-treatment attenuated this compensatory upregulation, likely secondary to reduced oxidative stress burden. Conclusions: This study provides integrated evidence that ER stress is closely associated with gentamicin nephrotoxicity. The key novel findings include selective suppression of IL-6, modulation of the apoptosis-autophagy balance, and attenuation of Nrf2/HO-1 signaling without direct reactive oxygen species (ROS) scavenging, demonstrating a multi-target framework for EA’s renoprotective effects. These findings suggest that ellagic acid mitigates renal injury in a context-dependent manner rather than confirming a direct causal mechanism. Full article

Chronic kidney disease (CKD) remains a leading cause of premature mortality and global disease burden, yet the molecular mechanisms underlying its progression are still incompletely understood. Accumulating evidence highlights circadian disruption as an underappreciated driver of CKD that warrants systematic re-examination. The kidney harbors an autonomous circadian oscillator, principally regulated by the CLOCK:BMAL1 transcription factor complex, which coordinates glomerular filtration, tubular electrolyte handling, blood pressure rhythmicity, inflammatory tone, and cellular repair. In CKD, retained uremic toxins, sustained oxidative stress, and persistent NF-κB activation collectively suppress this clock machinery, generating a self-reinforcing cycle of renal injury and circadian dysregulation. CKD is also accompanied by progressive attenuation of nocturnal melatonin secretion, weakening a central hormonal cue for peripheral clock entrainment and cytoprotection. Melatonin acts both as a chronobiotic and as a pleiotropic cytoprotective molecule. Through MT1/MT2 receptors, the nuclear receptor RORα, and receptor-independent antioxidant pathways, it may enhance Nrf2/HO-1 signaling, restrain NF-κB and NLRP3 inflammasome activity, suppress TGF-β1/Smad2/3-mediated fibrogenesis, preserve mitochondrial integrity, and engage SIRT1-linked clock regulation. Current clinical studies suggest that nightly melatonin supplementation can improve sleep quality and selected oxidative or circadian surrogate endpoints in hemodialysis patients; however, whether melatonin slows CKD progression or preserves renal function remains unproven. This review synthesizes the molecular interface between circadian dysregulation and CKD progression and articulates a rationale for adequately powered clinical trials evaluating melatonin as a candidate chronotherapeutic adjunct rather than an established renoprotective therapy. Full article

We aimed to investigate the potential antidiabetic effects of an ethanol extract derived from the fruit of Malus floribunda (MF) on insulin resistance, oxidative stress, inflammation, and apoptosis associated with diabetes. In our study, diabetes was induced through the administration of a 10% fructose solution and 40 mg/kg Streptozotocin (STZ). Once diabetes had been induced, metformin (Met) 300 mg/kg and the MF extract (250 mg/kg and 500 mg/kg) were administered orally once daily for 30 days. At the end of the experiment, markers of insulin resistance, oxidative stress, inflammation and apoptosis were evaluated in the serum, muscle and liver tissues of the different groups. The MF extract significantly improved the levels of HOMA-IR, insulin receptor (InR), insulin receptor substrate 1 (IRS-1) and glucose transporter 4 (GLUT4)—key components of peripheral insulin resistance associated with type 2 diabetes. Fructose/streptozotocin induced oxidative stress, inflammation, and apoptosis were mitigated by increasing Nuclear factor erythroid 2-related factor 2 (NRF2) expression, which restored antioxidant levels (Superoxide dismutase (SOD) and Glutathione (GSH)), significantly improved cytokine levels (Tumor necrosis factor alpha (TNF-α) and Interleukin-1 beta (IL-1β)), and downregulated apoptotic proteins (caspase-3 and caspase-9). We demonstrated the antidiabetic effect of MF extract using a fructose/streptozotocin-induced type 2 diabetes model. MF extract shows promise for future use in herbal medicine. Full article

Postoperative inflammation is a necessary response to surgical injury that supports tissue repair and regeneration. However, successful healing depends not only on the initial inflammatory response but also on its timely resolution. Failure to resolve inflammation can impair wound healing, promote fibrosis, and increase the risk of postoperative complications. Increasing evidence suggests that effective recovery is driven by the transition from inflammation to repair and regenerative processes. Diet plays an important role in this transition, as nutrients not only provide metabolic support but also regulate key pathways involved in inflammation, tissue regeneration, redox balance, and immune function. Omega-3 polyunsaturated fatty acids could serve as precursors for specialized pro-resolving mediators that actively terminate inflammation and may promote macrophage-driven tissue repair. Polyphenols and antioxidant micronutrients modulate NF-κB and Nrf2-dependent signalling, attenuating oxidative amplification of inflammatory cascades. Micronutrients and amino acids further regulate enzymatic processes governing collagen synthesis, angiogenesis, and immune competence. Concurrently, diet-driven preservation of gut barrier integrity limits endotoxin-mediated amplification of systemic inflammatory responses. By targeting interconnected molecular networks, including inflammasome activation, mitochondrial redox signalling, and metabolic programming of immune cells, anti-inflammatory dietary patterns may promote immune resolution rather than immunosuppression. This distinction is particularly relevant in the postoperative setting, where balanced inflammation is required for both host defence and regenerative healing. This review synthesizes current molecular and translational evidence linking dietary modulation to postoperative inflammatory control and tissue regeneration. By integrating insights from immunology, metabolism, and nutritional science, it positions diet as an active, biologically grounded component of perioperative management and highlights future directions for precision nutrition strategies aimed at optimizing surgical recovery. Full article

Cisplatin is a widely used platinum-based chemotherapeutic agent that often causes irreversible hair cell loss, leading to hearing impairment. To date, effective strategies for preventing cisplatin-induced ototoxicity remain limited. Corchorus olitorius L. (COL) is rich in bioactive phytochemicals with antioxidant and anti-inflammatory properties; however, the protective role of COL stem against cisplatin-induced hearing loss has not been explored. This study aimed to determine whether COL stem extract treatment could mitigate cisplatin-induced hair cell damage in the lateral line system of zebrafish. Herein, we use 7-day post-fertilization (dpf) transgenic zebrafish larvae as a high-throughput screening platform to assessed COL stem extract against cisplatin-induced hair cell injury. Endpoints included mechanotransduction (MET) function, reactive oxygen species (ROS) production, apoptotic and inflammatory responses, and locomotor behavior. Antioxidant capacity and acute toxicity were also evaluated. Pretreatment with COL stem extract preserved hair cell viability, restored MET function, reduced ROS accumulation, upregulated Nrf-2-dependent cytoprotective genes, suppressed apoptosis, and attenuated macrophage infiltration. The recovery of swimming behavior correlated with hair cell protection, confirming the phenotypic relevance. This study demonstrates, for the first time, that COL stem exerts potent otoprotective effects through antioxidative, anti-apoptotic, and anti-inflammatory mechanisms, contributes to maintain mechanosensory function and swimming behavior. The findings support COL stem as a promising candidate for otoprotection and validate zebrafish-based high-throughput screening for novel therapeutic discovery. Full article

Kidney injury is a major clinical syndrome that can arise from nephrotoxins, ischemia–reperfusion, metabolic disease, infection, and immune dysregulation and can progress from acute kidney injury (AKI) to chronic kidney disease (CKD). Esculetin, a natural 6,7-dihydroxycoumarin derived from Cortex Fraxini, has antioxidant, anti-inflammatory, mitochondrial regulatory, anti-apoptotic, anti-ferroptotic, and anti-fibrotic activities. Preclinical studies report renoprotection in cisplatin-induced AKI, diabetes complicated by ischemia–reperfusion-induced AKI, and adenine-induced chronic renal injury, with changes in Nrf2/HO-1, NF-kappaB/MAPK, PINK1/Parkin-associated mitophagy, endoplasmic reticulum stress, regulated cell death, and fibrotic signaling. However, the evidence is based on a small number of heterogeneous cell and rodent studies, direct molecular targets remain uncertain, and no human studies have validated efficacy, dosing, or safety. Low oral bioavailability, rapid conjugative metabolism, limited long-term toxicology, and the absence of pharmacokinetic–pharmacodynamic relationships are major barriers to translation. This review critically synthesizes the renal evidence for esculetin and identifies the experimental, pharmaceutical, and clinical studies required to determine whether it can progress from a promising multi-target natural product to a renoprotective therapeutic candidate. Full article

Microplastics and nanoplastics (MNPLs) are increasingly recognized as dynamic vectors capable of transporting a wide range of environmental contaminants, as well as acting as physical particulates. Their small size, high surface reactivity and strong sorption capacity allow them to carry metals, pesticides, pharmaceuticals and endocrine-active compounds into biological systems. This narrative review examines how these particle-contaminant complexes influence oxidative stress, inflammatory signaling and endocrine function during early development. Relevant literature was identified through structured searches of PubMed, Scopus, Web of Science and Google Scholar, with a focus on the physicochemical properties of plastics, sorption mechanisms, gut barrier physiology and developmental toxicology. Early developmental stages are particularly sensitive, as immature mucus layers, permeable epithelial junctions and underdeveloped detoxification pathways facilitate the uptake and systemic distribution of MNPLs. Once internalized, these particles and their chemical cargo promote the generation of reactive oxygen species through redox-active contaminants, surface-catalysed reactions and mitochondrial dysfunction. The resulting oxidative imbalance activates stress-responsive pathways, including Nrf2–Keap1 signaling, and promotes lipid peroxidation, DNA damage and cellular dysfunction. MNPLs also stimulate inflammatory cascades by activating pattern-recognition receptors, altering cytokine profiles and disrupting epithelial homeostasis. These responses are intensified in the presence of sorbed pollutants, leading to sustained inflammatory states that can be particularly detrimental during organogenesis and immune maturation. Endocrine function is likewise affected, as MNPLs transport hormonally active chemicals and can interfere with hormone-responsive pathways through oxidative and inflammatory mechanisms. These interactions may disrupt thyroid signaling, metabolic regulation and the development of the reproductive axis, with potential long-term physiological consequences. Integrating evidence from polymer chemistry, contaminant behavior and developmental physiology, this review shows that MNPLs act as biologically active vectors that may increase oxidative, inflammatory and endocrine disturbances during early development. These findings highlight the importance of considering particle–contaminant interactions as a critical component of early-life risk assessment. Full article

Nuclear factor erythroid 2-related factor 2 (NRF2) has traditionally been framed as a Kelch-like ECH-associated protein 1 (KEAP1)-regulated stress-response transcription factor, but three observations now require a broader framework: NRF2 turnover is controlled by parallel E3 ligase systems; transcriptional output can be limited by coactivator assembly despite unchanged NRF2 abundance; and NRF2 activation can be beneficial or harmful depending on disease context, as illustrated by lung cancer models in which NRF2 paradoxically promotes metastasis through BTB and CNC homology 1 (BACH1) stabilization. We synthesize these observations into an NRF2 partner-code framework in which NRF2 acts as a context-dependent transcriptional platform assembled through four partly independent modules: a degradation module (KEAP1; β-transducin repeat-containing protein, β-TrCP; HMG-CoA reductase degradation protein 1/synoviolin 1, Hrd1/SYVN1; WD repeat-containing protein 23/DDB1- and CUL4-associated factor 11, WDR23/DCAF11); a cytoplasmic scaffold module (p62/sequestosome 1, p62/SQSTM1; IQ motif-containing GTPase-activating protein 1, IQGAP1; type I phosphatidylinositol 4-phosphate 5-kinase γ/heat shock protein 27, PIPKIγ–HSP27; peptidyl-prolyl cis-trans isomerase NIMA-interacting 1, PIN1; peptidyl-prolyl isomerase A/cyclophilin A, PPIA); a nuclear coactivator module at Neh4/5 (CREB-binding protein/p300, CBP/p300; receptor-associated coactivator 3/steroid receptor coactivator 3, RAC3/SRC-3; protein arginine methyltransferase 1/coactivator-associated arginine methyltransferase 1, PRMT1/CARM1; Mediator complex subunit 16, MED16); and a DNA/chromatin module at Neh1 (small musculoaponeurotic fibrosarcoma [Maf] proteins, BACH1, and chromodomain helicase DNA-binding protein 6, CHD6). Mapping 22 partners onto the Neh-domain architecture identifies approximately 25 pharmacologically addressable interfaces, stratified into four translational tiers. The framework reframes NRF2 pharmacology around one principle: the most actionable target is often a partner rather than NRF2 itself, with disease context dictating the direction of modulation. We close with five testable hypotheses and a partner-code decision matrix linking disease, biomarker, and candidate target. Full article

Zinc (Zn) is an essential trace element that plays important roles in growth, digestion, antioxidant defense, immunity, and inflammation regulation in fish. This study investigated the effects of graded dietary Zn levels on growth performance, serum biochemistry, digestive enzyme activity, zinc transporter expression, antioxidant capacity, immune responses, and inflammatory regulation in juvenile black carp (Mylopharyngodon piceus). Six isonitrogenous and isoenergetic diets were formulated to contain 27.95, 34.38, 44.90, 66.52, 116.14, and 199.56 mg/kg Zn by supplementing ZnSO₄·7H₂O. Juvenile fish with an initial weight of 2.88 ± 0.12 g were fed the experimental diets for 60 days in triplicate tanks. Growth performance increased with dietary Zn and then plateaued at 44.90–199.56 mg/kg; broken-line regression estimated the optimal dietary Zn requirement at 44.6 mg/kg. Adequate Zn supplementation also reduced whole-body lipid content, increased digestive enzyme activities, improved serum HDL-C and ALP levels, and decreased AST and ALT activities. In addition, adequate dietary Zn (44.90 mg/kg) significantly modulated the expression of zinc transporter genes in the liver and intestine. Adequate dietary Zn supplementation enhanced antioxidant capacity by activating the Nrf2/Keap1 signaling pathway, improved intestinal immunity, and strengthened barrier function by increasing the expression of tight junction proteins and mucins. Moreover, adequate dietary Zn could alleviate inflammatory responses by upregulating anti-inflammatory factors and downregulating pro-inflammatory cytokines via the MAPK14 signaling pathway. These findings suggest that dietary zinc at 44.60 mg/kg is sufficient to promote growth, antioxidant status, immune function, and intestinal health in juvenile black carp. Full article

Neonatal hyperoxia induces oxidative stress that disrupts neurodevelopmental processes. While dexmedetomidine (DEX) exhibits acute neuroprotective properties, its long-term impact on developmental trajectories during recovery remains incompletely understood. This study examined whether a single neonatal dose of DEX modulates hippocampal neurogenesis following hyperoxia across defined postnatal stages. Six-day-old Wistar rats were exposed to 80% oxygen for 24 h and evaluated at postnatal days (P) 9, 11, and 14 after recovery in room air. Mechanistically, hyperoxia permanently triggered apoptotic cascades, evidenced by sustained transcript upregulation and increased histological apoptosis and cell loss across the cortex and hippocampus, while disrupting the hippocampal progenitor niche, suppressing key differentiation factors (Sox2, Tbr2, Prox1, Calb1) and altering mature NeuN expression. Likewise, markers for autophagy (Atg5/12, Beclin1), neurotrophins (BDNF, NGF, NT3), and plasticity markers (Nrp1, Sem3a) showed reduced expression. Proactive treatment with DEX (5 µg/kg) significantly reversed these detrimental patterns. First, DEX elicited a robust antioxidant response (Nrf2, SOD1, SOD3 induction). Second, DEX effectively suppressed hyperoxia-induced programmed cell death and tissue degeneration up to P14. Crucially, this dual protection sustained the neurogenic niche, safeguarding autophagy processes as well as neurotrophic and neuronal plasticity mediators, while showing excellent safety under normoxia. In conclusion, a single dose of DEX mitigates acute oxygen injury and exhibits beneficial, stage-specific effects within hippocampal neurogenic niches during the postnatal phase, highlighting its potential to preserve neurodevelopmental trajectories. Full article

Dynamin-related protein 1 (Drp1) is essential for mitochondrial dynamics in skeletal muscle, particularly in regulating fission, mitophagy, and maintaining mitochondrial function. Exercise is crucial for sustaining muscle function, promoting mitochondrial adaptations that enhance energy metabolism and oxidative capacity in skeletal muscle. In this Review, we discuss the role of Drp1 in exercise-induced mitochondrial adaptations and its potential implications for skeletal muscle health. We first address the evidence that Drp1 activity must be maintained within a narrow physiological range. Both Drp1 deficiency and overabundance provoke muscle atrophy and dysfunction, establishing a Goldilocks principle for mitochondrial fission. We then examine the multi-layered post-translational modification code that governs Drp1 activity, including canonical phosphorylation, redox-sensing modifications, and the receptor selectivity model that may specify distinct fission programs. A three-stage model of exercise-induced mitochondrial adaptation is presented, describing how Drp1 activity is temporally orchestrated from acute fragmentation through short-term remodeling to long-term network optimization, and how these morphological transitions govern substrate metabolism and determine exercise performance. The pathological consequences of Drp1 dysregulation are examined in metabolic disease, where Drp1 is chronically hyperactivated, and in aging, where Drp1 activity is deficient. Finally, we analyze the ROS-Drp1 signaling axis as the mechanistic basis for the bidirectional regulation of Drp1 by exercise. Moderate exercise-induced ROS production activates Nrf2 and AMPK signaling, which suppress excessive fission in metabolic disease while restoring insufficient fission in aging, thereby moving Drp1 activity toward the physiological Goldilocks zone in both contexts. This context-dependent, bidirectional regulation distinguishes exercise from pharmacological inhibitors and identifies the ROS-Drp1 axis as a therapeutic target for conditions at opposite ends of the Drp1 activity continuum, such as sarcopenia and type 2 diabetes. Full article

Naturally fermented tofu whey is a nutrient-rich byproduct of tofu production that harbors diverse lactic acid bacteria (LAB) with potential probiotic properties. However, the antioxidant mechanisms of these LAB, particularly the roles of different cellular fractions and their metabolic basis, remain unclear. This study aimed to isolate LAB from naturally fermented tofu whey and evaluate their antioxidant activities across cellular fractions, combining in vitro assays, 16S rDNA-based identification, metabolomic profiling, and cellular validation to elucidate the underlying mechanisms. Six LAB strains were isolated and screened for 2,2-diphenyl-1-picrylhydrazyl and hydroxyl radical scavenging capacity and environmental stress tolerance. Among the identified isolates, Lactiplantibacillus plantarum MCS1903 exhibited the highest extracellular antioxidant activity. Non-targeted metabolomic analysis of cell-free supernatant revealed distinct metabolic profiles compared with the MRS control, with significant enrichment of antioxidant-related metabolites and pathways. In Caco-2 cells, MCS1903 supernatant (<5%, v/v) showed no significant cytotoxicity and effectively alleviated H₂O₂-induced oxidative stress by modulating the Nrf2/Keap1-HO-1 signaling pathway. These findings indicate that tofu whey is a valuable source of functional LAB, and MCS1903 represents a promising candidate for probiotic and functional food applications, supporting the valorization of tofu whey and development of natural antioxidant probiotics derived from fermented food byproducts. Full article