Search Results (1,308)

Chronic hyperglycemia and excessive reactive oxygen species (ROS) production are defining features of endothelial dysfunction, a key driver of diabetic vascular complications such as diabetic nephropathy. Microvesicles (MV-enriched fraction), a subtype of extracellular vesicles, and the stress-responsive antioxidant protein Sestrin2 (SESN2) have emerged as important contributors to these processes. This study investigated the role of the MV-enriched fraction in endothelial cell communication under diabetic conditions, with a particular focus on oxidative stress signaling. To model diabetic injury, EA.hy926 endothelial cells were treated with methylglyoxal (MGO), and the resulting MV-enriched fraction was isolated and then applied to two recipient models: naïve endothelial cells and SESN2 knockdown (KD) cells. Protein expression of key antioxidant markers, including endothelial nitric oxide synthase (eNOS), was assessed by Western blot. Nitric oxide (NO) bioavailability was quantified via nitrite measurement using 2,3-diaminonaphthalene (DAN), while mitochondrial and cytosolic ROS levels were evaluated using MitoSOX and dihydroethidium (DHE), respectively. Results demonstrated that the MV-enriched fraction derived from diabetic conditions triggers a complex antioxidant response in healthy endothelial cells, characterized by upregulation of SESN2, superoxide dismutase 1 (SOD1), and heme oxygenase-1 (HO-1). This suggests a compensatory mechanism that mitigates oxidative stress. Notably, SESN2 KD cells exhibited increased ROS production and reduced NO levels upon MV treatment, underscoring the essential role of SESN2 in maintaining redox homeostasis. Overall, this study highlights the dual role of the MV-enriched fraction as a mediator of both protective and detrimental redox signaling in diabetic endothelial dysfunction and suggests potential therapeutic targets for managing diabetic vascular complications. Full article

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. Full article

Nanoplastics (NPs) and heavy metal cadmium (Cd) are common co-existing pollutants in freshwater environments, but their combined toxic effects on the liver of herbivorous economic fish remain unclear. In this study, grass carp (Ctenopharyngodon idella) were exposed to polystyrene nanoplastics (PS-NPs, 100 nm) and/or Cd to investigate their individual and combined effects on hepatic toxicity. The results revealed that co-exposure interactively suppressed interleukin-10 (IL-10) expression and heme oxygenase-1 (HO-1) antioxidant response, and induced more severe hepatic necrosis, melanization, and fibrinoid necrosis, with the highest integrated biomarker response index and extensive disruption of lipid and steroid metabolism pathways. This study clarified the toxicological interaction of NPs and Cd on the liver of grass carp, and provided a theoretical basis for understanding the combined toxicity of NPs and heavy metal pollution in extreme contamination scenarios or accidental pollution events. Full article

Coordinated responses of intestinal epithelial and immune cells are essential for maintaining barrier integrity and immune homeostasis in dogs, yet our mechanistic understanding of probiotic-derived metabolites remains limited due to reliance on non-canine experimental models, highlighting the need for studies in canine-derived systems. Here, we investigated the effects of metabolites derived from Limosilactobacillus reuteri strain ATCC PTA6127 (Lr6127), delivered as a cell-free supernatant (CFS), on canine epithelial MCA-B1 cells and macrophage-like DH82 cells subjected to lipopolysaccharide (LPS)-induced inflammatory stress. Lr6127 CFS significantly reduced epithelial permeability, decreasing FITC–dextran leakage to 94.9 ± 1.9% (normalized relative to LPS-treated control, which was set as 100%) (p < 0.001), despite no detectable transcriptional changes in tight junction, adherens junction, or mucin genes. Barrier effects were instead associated with changes in markers of cellular stress responses, with heme oxygenase expression decreasing from 0.9 ± 0.1 to 0.7 ± 0.1 (p < 0.05). In DH82 immune cells, Lr6127-derived metabolites altered LPS-induced stress- and inflammation-related gene expression patterns; enhanced anti-apoptotic responses, as reflected by the increased BCL2 expression (1.4 ± 0.1 vs. 1.0 ± 0.0; p < 0.01) and elevated BCL2/BAX ratios (p < 0.01); and reduced expression of pro-inflammatory mediators including IL-6 and CCL2 (p < 0.05–0.001). Proteomic analysis corroborated that Lr6127-derived metabolites reduced the abundance of inflammatory and STAT-associated signaling proteins under LPS challenge, while indicating context-dependent changes in immune-related protein profiles under resting condition. Collectively, these results suggest that Lr6127-derived metabolites improved epithelial barrier function, which was accompanied by coordinated changes in cellular stress-related and inflammatory pathways, highlighting their potential to positively influence host responses. 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

Carbon monoxide (CO) is a gasotransmitter generated by heme oxygenase (HO) isoforms during heme catabolism. The inducible HO-1 produces CO under conditions of redox imbalance, such as oxidative stress and inflammation. On the other hand, HO-2 constitutively generates CO, primarily during the physiological turnover of heme. Extensive evidence indicates that CO exerts autocrine effects by targeting hemoproteins, including soluble guanylyl cyclase, cyclooxygenase, and cytochromes. Furthermore, CO regulates many biological processes within the brain, including mitochondrial biogenesis, potassium channel activity, mitogen-activated protein kinase and phosphatidylinositol-3-kinase/Akt signaling. It also controls the activity of transcription factors, such as hypoxia-inducible factor-1 and peroxisome proliferator-activated receptor-γ. Through these mechanisms, CO modulates inflammatory gene expression, promotes anti-apoptotic signaling, and contributes to local stress responses. Conversely, CO produced in the hypothalamus inhibits the stress-induced release of corticotropin-releasing hormone and arginine vasopressin under pro-inflammatory conditions, resulting in reduced adrenocorticotropin hormone release and cortisol secretion from the anterior pituitary and adrenal cortex, respectively. Moreover, hypothalamic CO acts in a paracrine manner to modulate glucocorticoid release during psychological stress, including restraint or water deprivation. Together, these findings support the view that endogenous CO is a key modulator of the stress axis, exerting pleiotropic effects that integrate neuroendocrine, immune, and metabolic responses. Full article

Oxidative stress, caused by excessive reactive oxygen species (ROS) accumulation, is a major factor in muscle cell damage and muscle atrophy-related disorders. Although Stanniocalcin 2 (STC2) is involved in cellular stress and exhibits cytoprotective effects in various cell types, its role in skeletal muscle cells during oxidative stress is unclear. This study investigated the effects of STC2 overexpression in quail muscle (QM7) cells exposed to H₂O₂-induced oxidative stress. STC2 expression was upregulated in non-transfected QM7 cells following H₂O₂ treatment. Stable STC2-overexpressing cells were differentiated for 4 days, and then assessed for cell viability, ROS accumulation, cell death, and myotube morphology following H₂O₂ treatment. Compared with control cells, STC2-overexpressing cells exhibited higher cell viability, reduced ROS accumulation, and decreased cell death. STC2 overexpression also attenuated the H₂O₂-induced reduction in MyHC protein expression. Antioxidant-related genes, including Superoxide Dismutase 1, Glutathione Peroxidase 1, Heme Oxygenase 1, and NAD(P)H Quinone Dehydrogenase 1, were significantly upregulated in STC2-overexpressing cells. Compared with the control cells, nuclear factor erythroid 2-related factor 2 protein levels were not increased in STC2-overexpressing cells under oxidative stress conditions. These findings suggest that STC2 overexpression alleviates oxidative stress-induced cellular damage and may contribute to protective antioxidant responses in muscle cells. Full article

Associated with high morbidity and mortality, cisplatin-induced acute kidney injury (AKI) is a common clinical complication characterized by oxidative stress, inflammation, and mitochondria-associated signaling. Although multiple signaling pathways have been implicated in AKI progression, effective interventions targeting these complex mechanisms are still lacking. As a medicinal fungus with antioxidant and anti-inflammatory properties, Schizophyllum commune (SC) has shown potential biological activities; however, its renoprotective effects in cisplatin-induced AKI remain unclear. Therefore, this study aimed to investigate SC’s protective effects and underlying mechanisms in a cisplatin-induced AKI mouse model. SC treatment improved renal function and attenuated histopathological damage. It reduced oxidative stress and inflammatory responses, as evidenced by the modulation of malondialdehyde (MDA), glutathione (GSH), nitric oxide (NO), and pro-inflammatory cytokines. Mechanistically, SC regulated multiple signaling pathways, including mitogen-activated protein kinase (MAPK), toll-like receptor 4/nuclear factor kappa B (TLR4/ NF-κB), PI3K/AKT, nuclear factor erythroid 2–related factor 2/heme oxygenase-1 (Nrf2/HO-1), and the calcium/calmodulin-dependent protein kinase kinase–AMP-activated protein kinase–sirtuin 1 (CaMKK–AMPK–Sirt1) axis. In addition, SC modulated apoptosis, autophagy, and PTEN-induced kinase 1 (PINK1)/Parkin-mediated mitophagy, suggesting improved mitochondrial homeostasis. These findings indicate that SC exerts renoprotective effects and may contribute to cisplatin-induced nephrotoxicity mitigation strategies. Full article

Although previous studies have indicated that heme oxygenase 1 (HO1/HY1) regulates the flowering time via the photoperiod pathway, the specific mechanism is still elusive. Here, we found that the Arabidopsis hy1-100 mutant displayed early flowering, and the characteristic expression patterns of several master genes involved in the autonomous pathway were altered. Notably, the transcript levels of FLOWERING LOCUS C (AtFLC) gene declined developmentally in both wild-type and hy1-100 mutant, with a more pronounced fold reduction observed in the mutant. Genetic evidence further underlined that hy1-100/FLCOE plants partially reversed the early flowering phenomenon of hy1-100 mutant, suggesting that AtHO1 regulated flowering at least partially through the AtFLC-involved autonomous pathway, as supported by changes in FLOWERING LOCUS T (AtFT) and SUPPRESSOR OF OVEREXPRESSION OF CO1 (AtSOC1) transcripts. Further analysis of hy1-100/ft mutants revealed that hy1-100/ft and ft mutants displayed similar late flowering phenotypes, accompanied by downregulated APETALA1 (AtAP1) and AtSOC1, indicating that AtFT played a crucial role in AtHO1-regulated flowering. Two key conclusions are drawn: first, the loss of AtHO1 function promotes early flowering in Arabidopsis, which was genetically linked to the autonomous pathway regulating AtFLC expression; second, AtFT was an essential downstream factor mediating AtHO1-regulated flowering. Full article

Ultraviolet A (UVA) radiation disrupts the redox balance of melanocytes and may lead to the development of melanoma, highlighting the need for new skin protection strategies. This study assessed the effect of phytocannabinoids [cannabigerol (CBG), cannabidiol (CBD), and CBG + CBD] on redox homeostasis in control and UVA-exposed melanocytes and in melanoma cells (SK-Mel-5). UVA radiation increased the activity of prooxidant enzymes in both melanocytes and SK-Mel-5 cells and, consequently, the level of reactive oxygen species (ROS) (approx. 2-fold). It also activated nuclear factor erythroid 2 (Nrf2), as reflected by increased expression of heme oxygenase 1 (HO-1) (melanocytes approx. 2-fold; SK-Mel-5 approx. 7-fold). Concomitantly, antioxidant mechanisms were impaired, as demonstrated by reduced superoxide dismutase (SOD1/SOD2) activity and impaired glutathione and thioredoxin function. These changes were accompanied by increased levels of oxidative damage markers (isoprostanes, 4-hydroxynonenal-4-HNE, and 4-HNE-protein adducts) (43–100%) and increased inflammatory signaling, including increased expression of nuclear factor kappa B (NF-κB) subunits (melanocytes: p52 ~2-fold, p65 ~75%; SK-Mel-5: ~4–4.5-fold) and tumor necrosis factor alpha (TNF-α; ~30%). Phytocannabinoid treatment modulated these UVA-induced changes. In SK-Mel-5 cells, phytocannabinoids normalized the activity of prooxidant enzymes and consequently reduced ROS levels (~30%). They also reduced Nrf2 activation and HO-1 expression; however, CBG increased HO-1 level in melanocytes (~25–40%). Furthermore, phytocannabinoids enhanced antioxidant defense by increasing SOD activity, particularly in melanocytes (~10–40%), and restoring the glutathione and thioredoxin systems. Markers of oxidative damage were reduced by approximately 23–37% after treatment. Furthermore, phytocannabinoids attenuated NF-κB activation (p52 ~18–28%, p65 ~25–29% in melanocytes; ~20% in SK-Mel-5), while TNF-α levels remained unchanged. The effects in non-irradiated cells were modest (<15%). These results suggest that phytocannabinoid-mediated modulation of redox balance may stabilize melanocytes exposed to UVA radiation and potentially reduce the risk of neoplastic transformation. However, the observed protective effects in SK-Mel-5 cells require further investigation and detailed molecular analysis. Full article

Premature ovarian insufficiency (POI) poses a serious risk to the reproductive health and psychological well-being of women. Here, the protective effects of hydroxytyrosol (HT), the primary phenolic component of olive oil, on POI were investigated. In vitro, human ovarian granulosa-like tumour cell lines (KGN cells) were challenged by D-galactose (D-gal) with or without HT. HT administration effectively alleviated KGN cell damage, decreased the number of senescence-associated β-galactosidase (SA-β-gal)-positive cells, increased superoxide dismutase (SOD) activity, reduced reactive oxygen species (ROS) and malondialdehyde (MDA) levels, enhanced the expression level of Bcl-2, inhibited the expression level of Bax, and inhibited cell apoptosis in D-gal-treated KGN cells. In vivo, HT administration reversed the decreased ovarian index, oestrous cycle disruption, and abnormal sex hormone levels observed in D-gal-induced POI mice. HT administration increased glutathione (GSH) levels, reduced the MDA levels, and attenuated apoptosis in ovarian tissues, as evidenced by a decreased number of TUNEL-positive cells, upregulated Bcl-2 expression, and downregulated Bax expression. Mechanistically, HT downregulated the expression level of Kelch-like ECH-associated protein 1 (Keap1) and enhanced the expression levels of heme oxygenase-1 (HO-1) and nuclear factor erythroid 2-related factor 2 (Nrf2) in vitro and in vivo. In conclusion, HT ameliorates D-gal-induced POI in vitro and in vivo by activating the Nrf2/HO-1 signalling pathway. Full article

Biomolecular condensates in the cytoplasm and nucleus contribute to carcinogenesis through aberrant signaling by assorted transcription factors and fusion oncoproteins. Oral cancer, which is highly prevalent worldwide, frequently occurs in a U-shaped “high-risk” zone (floor of mouth, side of tongue, and anterior fauces) which forms the path of liquid transit through the mouth. We previously reported that environmental stresses of saliva-like hypotonicity and beverage-like temperature changes triggered cycles of disassembly/reassembly of biomolecular condensates of GFP-tagged human myxovirus resistance protein (MxA; alias Mx1) in oral cancer cells. In the present study, we identified some of the constituents of GFP-MxA cytoplasmic condensates in oral cells. These condensates were isolated from interferon (IFN)-λ1-treated GFP-MxA expressing OECM1 human oral cancer cells using magnetic bead-based immunoisolation. Unbiased peptide identification confirmed the presence of MxA/Mx1 peptides; however, the strongest intensity was for the BACH1 transcription factor family. Immunofluorescence analyses confirmed the association of BACH1 and the family member Nrf2 with cytoplasmic human GFP-MxA condensates. Moreover, GFP-BACH1 and GFP-Nrf2 colocalized with cytoplasmic human HA-MxA condensates in transiently transfected OECM1 cells. Western blot assays confirmed the presence of BACH1 and Nrf2 proteins in complexes isolated using anti-MxA pAb. As much as BACH1 and Nrf2 regulate oxidative stress response genes, it was remarkable that immunofluorescence assays revealed the presence of heme oxygenase 1 (HO1)—a downstream redox regulator—in GFP-MxA condensates. However, these condensates were devoid of p62, KEAP1 and Cul3. In terms of aberrant function, in live cells, the Nrf2 transcription factor underwent rapid disassembly and reassembly cycles driven by saliva-like hypotonicity, and was also disassembled by sulforaphane. The data highlight the unexpected intersections in oral cells between MxA condensates and BACH1, Nrf2 and HO1—proteins well known to be involved in pathways regulating cellular responses to environmental and oxidative stresses, antiviral defense, oral epithelial dysplasia, and cancer progression and metastases. Full article

Zearalenone (ZEA) is a common contaminant in crops and animal feed. However, research on the effects of ZEA on animal mammary tissue is relatively limited. Sulforaphane (SFN) is a naturally active compound mainly derived from cruciferous vegetables (such as broccoli), with significant antioxidant and cytoprotective effects. The purpose of this study is the effect of SFN on ZEA-induced toxicity in bovine mammary epithelial cells (MAC-T). By treating MAC-T cells with different concentrations of ZEA and SFN for 24 h, the results showed that different concentrations of ZEA (10, 20, 40, 60, 80, or 100 μM) could inhibit MAC-T cell viability. Treatment with SFN at concentrations of 1, 2.5, and 5 μM had no significant effect on cell viability. The results of combined treatment with 10 μM ZEA and 1, 2.5, or 5 μM SFN showed that SFN could significantly reverse the decrease in cell viability caused by ZEA; reduce the increase in lactate dehydrogenase (LDH) release, reactive oxygen species (ROS), and malondialdehyde (MDA) content induced by ZEA; and increase the levels of glutathione (GSH), superoxide dismutase (SOD), and mitochondrial membrane potential that were decreased by ZEA. SFN can significantly inhibit the upregulation of interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), and interleukin 1 beta (IL-1β) induced by ZEA exposure and markedly reverse the increase in cell apoptosis rate caused by ZEA. Compared with the control group, the expression of genes nuclear factor erythroid 2–related factor 2 (Nrf2), heme oxygenase 1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO1), glutamate-cysteine ligase modifier subunit (GCLM), and glutathione peroxidase 1 (GPX1) was significantly reduced in the ZEA group, while the addition of SFN effectively increased the expression levels of these genes. Corresponding protein detection results were consistent with the trends in gene expression. This study demonstrated that SFN alleviates ZEA-induced damage to MAC-T cells by activating the Nrf2 pathway, providing a theoretical basis for the subsequent application of SFN in dairy farming to prevent and control breast health risks related to mycotoxins. Full article

Citrus flavonoid intake is associated with beneficial effects on endothelial function. Our previous randomized control trial demonstrated that the concentration of Hesperetin-7-O-glucuronide (H7G) was positively correlated with the improvement in endothelial function in overweight and obese participants following blood orange juice consumption. To explore the underlying mechanism by which H7G improves endothelial function, we investigated the regulation of H7G on endothelial function in a permanent human endothelial cell line (EA. hy926 cells) under normal and oxidative conditions treated with high-oxidation low-density lipoprotein. The results indicated that H7G improved the expression of nitric oxide synthase 3 (NOS3), heme oxygenase 1 (HMOX1) ad glutamate cysteine ligase catalytic (GCLC), and inhibited the expression of endothelin-1 (EDN1), through the upregulation of miR-660-5p and inhibition of miR-21-5p. In summary, H7G improves endothelial cell function via the upregulation of miR-660-5p and the inhibition of miR-21-5p. Full article

Heme metabolism in the liver has traditionally been described as a linear pathway that supports oxygen utilization, redox balance, and detoxification. Here, we synthesize recent evidence and propose a framework in which heme functions as a system-level regulator, the “queen” of metabolism, whereas its upstream intermediate protoporphyrin IX (PPIX) represents a chemically reactive “dark twin” that emerges when metabolic flux fails to resolve. In this view, metabolic state is defined not only by end products but also by the behavior of pathway intermediates. This system is spatially organized. Hepatocytes dominate heme synthesis and utilization. In contrast, liver stromal compartments, particularly Kupffer cells, play a central role in heme degradation through heme oxygenase-1 (HMOX1), linking heme turnover to iron recycling and stress adaptation. The metabolic state of the liver therefore reflects not only pathway flux but also the degree of coupling between these cellular compartments. We propose a state model of hepatic heme metabolism. In the resolution state, most evident during inflammation, coordinated hepatocyte–macrophage activity maintains flux and limits intermediate accumulation. In contrast, the expansion state, exemplified in cancer, is defined by impaired flux completion, leading to PPIX accumulation, metabolic heterogeneity, and oxidative stress. This framework reframes liver disease through intermediate behavior rather than pathway presence: porphyrias reflect direct overload, metabolic liver diseases partial expansion, and hepatocellular carcinoma a fully developed expansion state. By focusing on the “intermediate space,” this model links biochemistry, spatial organization, and disease pathogenesis, while suggesting new opportunities for diagnosis and therapy based on metabolic state. Full article