Human endothelial cells (EC) play a critical role in vascular homeostasis and their function is influenced by oxygen tension. This study investigates for the first time the effects of long-term adaptation (5 days) of two major EC types to physiological oxygen tension (5 kPa) on basal and nitric oxide (NO)-modulated K+ channel activities. Whole-cell patch clamp experiments demonstrate that human umbilical vein EC (HUVEC) exhibit larger basal K+ outward and smaller inward currents under 5 kPa O2 compared to standard hyperoxic (18 kPa) culture conditions. Outward currents were potentiated by NO only under hyperoxia. Human cerebral microvascular EC (hCMEC/D3) showed larger outward currents under 5 kPa O2 which were further potentiated by NO. Pharmacological isolation of different K+ currents using tetraethylammonium, TRAM-34 and apamin revealed differential effects in EC adapted to 5 kPa or 18 kPa O2. Under 5 kPa O2, both cell types show greater contributions of TEA-sensitive currents and in addition hCMEC/D3 cells exhibit higher proportions of TRAM-34 and apamin-sensitive currents under 5 kPa O2. In HUVEC, changes in half-activation voltage and hyperpolarized membrane potentials were detected only under hyperoxic conditions following NO exposure, with both cell types exhibiting altered current activation kinetics of outward and inward currents. Notably, expression of KCa3.1, KCa1.1, KCa2.3 and Kir6.1 channels was unaffected by O2, suggesting that changes in whole-cell currents in both EC types were due to channel modulation. Thus, our findings reveal that physiological O2 tension shapes the electrophysiological phenotype of human EC by modulating K+ channel function and NO responsiveness. The novel insights into the modulation of EC K+ channels by O2 has implications for the regulation of vascular tone and design and use of experimental models in vitro for high throughput drug discovery and clinical translation.

BackgroundMyocarditis is an inflammatory disease of the myocardium that can progress to chronic inflammatory cardiomyopathy and heart failure. Aberrant activation and metabolic reprogramming of macrophages drive myocardial inflammation and injury, yet effective targeted therapies remain limited.MethodsExperimental autoimmune myocarditis (EAM) was induced in BALB/c mice by α-myosin heavy chain immunization. Rapamycin was administered during the inflammatory phase. Cardiac function and injury were evaluated by echocardiography, Millar catheterization, histology, qPCR, and ELISA. Single-cell RNA sequencing (scRNA-seq) of cardiac CD45+ cells, coupled with pseudotime trajectory, SCENIC regulon, and NicheNet analyses, was performed to delineate macrophage heterogeneity, lineage dynamics, and macrophage–cardiomyocyte communication. Functional validation included Seahorse metabolic assays and Cebpb-overexpressing bone marrow–derived macrophage (BMDM)–cardiomyocyte co-culture experiments, along with in vivo OSM-neutralizing antibody (OSM-nAb) intervention.ResultsRapamycin preserved cardiac function and alleviated myocardial inflammation and fibrosis in EAM mice, accompanied by reduced cytokine release and cardiac injury markers. scRNA-seq revealed that rapamycin reprogrammed cardiac monocyte–macrophages by inhibiting mTOR signaling, restoring mitochondrial metabolism, and suppressing inflammatory, glycolytic, and senescence pathways. It specifically targeted pathogenic Cxcl9+ macrophages by disrupting the mTORC1–C/EBPβ axis and limiting their differentiation from Plac8+ monocytes. Rapamycin further protected cardiomyocytes by blocking C/EBPβ-dependent OSM-mediated macrophage–cardiomyocyte crosstalk. Therapeutic OSM neutralization in vivo similarly mitigated myocardial inflammation and fibrosis while preserving ventricular contractility.ConclusionRapamycin preserves cardiac function in autoimmune myocarditis by reprogramming Cxcl9+ macrophages via the mTORC1–C/EBPβ–OSM axis. Targeting OSM provides mechanistic validation and highlights a translational therapeutic strategy for myocarditis and chronic inflammatory cardiomyopathy.

Monoamine oxidases (MAOA and MAOB) are mitochondrial enzymes that degrade various monoamine neurotransmitters, which have been recognized as important regulators of tumor progression. Recently, conflicting roles of both enzymes were identified in several cancer types. However, their potential involvement in the progression of clear cell renal cell carcinoma (ccRCC) remains unclear. In this study, in silico analysis of the TCGA-KIRC dataset revealed that MAOB has a more significant prognostic impact than MAOA and serves as an independent prognostic factor for overall survival in ccRCC. Lower MAOB transcript and protein levels were observed in RCC tissues compared to normal tissues and were associated with larger tumor sizes. Enzymatically active MAOB promoted reactive oxygen species (ROS)-induced DNA damage, subsequently enhancing the stability and transcriptional activity of p53, which induced G1 cell cycle arrest, mitochondria apoptosis, and lipid peroxidation-triggered ferroptosis, ultimately suppressing tumor growth both in vitro and in vivo. Molecular studies showed that MAOB stabilizes and activates p53 through post-translational modifications (PTMs), including increased phosphorylation at Ser15 and acetylation at Lys382, as well as activation of the hepatocyte nuclear factor 1 homeobox A (HNF1A)–p53-binding protein 1 (53BP1) axis. Activated p53, in turn, regulated MAOB through positive feedback. Clinically, ccRCC samples revealed a positive correlation between MAOB and HNF1A expression, with patients expressing high levels of both having the best prognoses. Regarding therapeutic aspects, we discovered that DNA methyltransferase inhibitors serve as potential MAOB inducer in ccRCC. The current findings reveal novel mechanisms by which MAOB suppresses the malignancy of ccRCC and suggest that MAOB may serve as a valuable prognostic marker in the management of ccRCC.

Diabetic bone regeneration is significantly affected by reactive oxygen species (ROS)-induced oxidative stress (OS), which disrupts the balance between osteoclast (OC)-mediated resorption and osteoblast (OB)-mediated formation of bone tissue. This review synthesizes current understanding of how hyperglycemia-driven ROS overproduction dysregulates OB and OC functions, leading to pathological bone remodeling and compromised healing. The key molecular mechanisms involved, such as RANK/RANKL, NF-κB, and MAPK, are discussed, highlighting their role in the ROS-mediated feedback loop that promotes OC differentiation while inhibiting OB survival, differentiation, and activity, worsening bone degeneration. Furthermore, the review addresses ROS-induced cell death pathways (apoptosis, ferroptosis, necroptosis, pyroptosis) along with the pathophysiological changes in the bone marrow microenvironment. Emerging therapeutic strategies to reduce oxidative damage, including antioxidant (AO) therapies and innovative drug delivery systems, offer promise for restoring bone regenerative capacity in diabetic conditions. These innovations aim to restore redox homeostasis, mitigate OS damage, and reactivate endogenous bone regenerative capacity. Understanding these mechanisms provides a foundation for developing targeted interventions to improve clinical outcomes in diabetic bone disease.