Search Results (464)

Background/Objectives: Alzheimer’s disease (AD), one of the most prevalent neurodegenerative disorders in the elderly, is characterized by progressive cognitive loss, amyloid-β (Aβ) plaque deposition, and neurofibrillary tangle formation. Cerebral hypoxia has been reported as a complex modulator of AD pathology, with hypoxia-inducible factor-1 (HIF-1) emerging as a central molecular marker associated with neurodegeneration. This review aims to comprehensively report the roles of HIF-1 signaling in AD pathogenesis, emphasizing its neuroprotective and neurotoxic mechanisms along with demonstrating the therapeutic potential and challenges of translating this pathway for AD therapeutics. Methods: A comprehensive literature search was conducted across PubMed, Scopus, Web of Science, Embase, and Google Scholar databases for articles published between January 2000 and December 2025 on the context. Results: Under mild hypoxic conditions, HIF-1 activation enhances neuronal survival through upregulation of glucose transporters, glycolytic enzymes, angiogenic factors, erythropoietin, and antioxidant defense mechanisms. In contrast, chronic hypoxia modulates HIF-1 into a pathogenic marker through transcriptional activation of β-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) and γ-secretase, facilitating amyloidogenic APP processing, along with tau hyperphosphorylation. Moreover, HIF-1 exacerbates neuroinflammation through microglial activation and pro-inflammatory cytokine release. The cell-type-specific expression patterns of HIF-1α and the temporal dynamics of its activation regulate whether the pathway exerts neuroprotective or neurodegenerative effects. Conclusions: This review discusses the current understanding of HIF-1-mediated mechanistic insights in AD pathology and impacts of existing HIF-1 modulators on AD pathology, along with the therapeutic implications of targeting this pathway for translational application in AD therapeutics. Full article

Feline mammary tumors are the third most common neoplasms in female cats and they are characterized by high aggressiveness and high metastatic rates. Given the pivotal role of iron in human breast cancer development, in this study, we preliminarily explore the immunohistochemical expression of proteins involved in iron uptake, storage and efflux [Transferrin Receptor 1 (TfR1), Transferrin Receptor 2 (TfR2), ferritin (FTH1), and ferroportin (SLC40A1)] in non-metastatic and metastatic feline mammary carcinomas and their tributary lymph node and the possible correlation with hypoxia-inducible factor-1 (HIF-1). Our results showed an increased expression of TfR1 and TfR2 in relation to tumor progression. FTH1 immunolabeling was mainly observed in cancer cells delimiting necrotic areas and in lymph node metastasis, indicating greater iron storage possibly associated with hypoxic environments, as suggested by increased expression of HIF-1α. Also, an increase in SLC40A1 labeling in tumoral cells suggested greater iron efflux. Although preliminary, our results underline interesting differences between feline normal and tumoral mammary tissues, which could pave the way to further in vitro studies to better understand the role of iron in the progression of feline mammary tumors. Full article

Acute myeloid leukemia (AML) persistence is sustained by leukemic stem cells (LSCs) that survive metabolic deprivation, oxidative stress, hypoxia, proteotoxic burden, and therapeutic pressure. The integrated stress response (ISR) has emerged as a central adaptive network in this process. Through phosphorylation of a subunit of eukaryotic initiation factor 2 (eIF2α) and selective translation of activating transcription factor 4 (ATF4), the ISR coordinates stress-responsive transcriptional programs that may either preserve cellular fitness or promote apoptotic commitment, depending on the intensity, duration, and biological context of activation. In AML, ATF4 occupies a critical position at the interface between stemness, metabolic adaptation, redox control, ferroptosis resistance, and treatment response. In primitive leukemic compartments, ISR–ATF4 signaling appears to support stress tolerance, amino acid metabolism, serine biosynthesis, autophagy, and leukemic persistence. At the same time, pharmacologic or sustained ISR activation may lower the apoptotic threshold by inducing pro-apoptotic mediators such as CHOP, PUMA, and NOXA, thereby modulating MCL-1 dependency and enhancing sensitivity to venetoclax-based strategies. Conversely, adaptive ISR signaling may promote resistance through mechanisms such as ATP-binding cassette subfamily B member 1 (ABCB1) enhancer activation and mitochondrial stress tolerance. This duality creates a therapeutic paradox: ISR–ATF4 signaling may need to be inhibited in adaptive, resistance-promoting states but amplified in apoptosis-permissive contexts. This review discusses the biological and therapeutic relevance of ISR–ATF4 dysregulation in AML and highlights the need for biomarkers capable of distinguishing adaptive ATF4 dependency from inducible apoptotic vulnerability. Full article

Short episodes of intradialytic hypoxemia (IDH) are a common but still under-recognized complication of hemodialysis with clinically significant consequences. The aim of the study was to analyze the effect of IDH on the secretion of hypoxia-inducible factors 1 and 2 and sirtuin 1. The study group consisted of 49 chronic hemodialysis patients, mean age 58.8 ± 15.3 years. Pulse oximetry was continuously recorded throughout hemodialysis. Blood was collected three times during a single mid-week hemodialysis session and at the start of the next mid-week session to assess levels of sirtuin 1 (SIRT1), hypoxia-inducible factor 1 (HIF-1), and hypoxia-inducible factor 2 (HIF-2). IDH, defined as a decrease in blood oxygen saturation below 90%, occurred in 22 (45%) patients. The mean time of hypoxemia during dialysis was 0.52% of the total hemodialysis session time. Plasma SIRT1 and HIF-2 concentrations did not change significantly during hemodialysis, whereas plasma HIF-1 levels decreased significantly. Multiple regression analysis showed that pre-dialysis plasma SIRT1 and HIF-1 explained a significant portion of the variability of blood oxygen saturation during hemodialysis. Pre-dialysis plasma levels of sirtuin 1 and HIF-1 could be considered predictors of the decline in blood oxygen saturation during hemodialysis sessions; they also determine the degree of variability of this parameter during the procedure. Full article

The blood–brain barrier (BBB) carefully regulates the transport of molecules between the blood and the nervous tissue. Obstructive sleep apnea (OSA) is a chronic condition that induces structural and functional changes in the BBB. These include alterations in its permeability and in protein expression in the BBB capillary endothelium. Moreover, OSA alters blood levels of transcription factors, such as hypoxia-inducible factor 1 (HIF-1), which are suggested to be responsible for these changes. As a review article, this paper focuses on the most significant effects of OSA on the BBB, including deviations in barrier morphology, particularly changes in the expression of tight junction and adherens junction proteins and membrane channels, as well as their impact on transport across the barrier. Moreover, particular attention is given to emerging evidence for the differential regulation of major BBB efflux transporters, including P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), as well as the role of the HIF-1 pathway. Additionally, we summarize the current state of knowledge regarding the contribution of these BBB alterations to the development of neurodegenerative diseases. At the same time, altered transport is being investigated as a possibility for delivering new drugs to the central nervous system. Thus, this review aims to summarize the current knowledge about OSA’s impact on the BBB. Full article

Existing diagnostic markers of sepsis indicate already developed inflammatory complications, whereas predictors enable preoperative identification of high-risk patients for preventive measures. This study aimed to evaluate the prognostic value of preoperative inflammatory biomarkers for postoperative complications in cardiac surgery patients. Preoperatively, we assessed age, body mass index, EuroSCORE II (European System for Cardiac Operative Risk Evaluation II), complete blood count with hematological indices including neutrophil-to-lymphocyte ratio (NLR), serum cytokines, HIF1A (hypoxia-inducible factor 1-alpha), and EPAS1 (endothelial PAS domain protein 1) expression in peripheral blood leukocytes. During surgery, cardiopulmonary bypass time, myocardial ischemia time, and blood loss were recorded. Postoperatively, complications, intensive care unit (ICU) stay, and total hospitalization were documented. No differences were found in non-modifiable risk factors or perioperative parameters between groups, except for longer ICU stay in the complications group. Preoperatively, absolute neutrophil count and NLR were higher in patients without complications, while eosinophil count, HIF1A expression, and HIF1A/EPAS1 ratio were higher in those with it. The HIF1A/EPAS1 ratio demonstrated the best diagnostic characteristics. Thus, preoperative predictors of postoperative inflammatory complications include low neutrophil count and NLR, as well as high HIF1A expression and HIF1A/EPAS1 ratio. These markers may facilitate early risk stratification and preventive strategies before surgery. Full article

Gemcitabine-based chemotherapy has long served as a standard treatment for urothelial carcinoma (UC), particularly in perioperative and metastatic settings. However, therapeutic efficacy is frequently limited by intrinsic or acquired resistance. Gemcitabine functions as a prodrug whose activity depends on coordinated processes involving cellular uptake, intracellular activation, metabolic inactivation, and nucleotide metabolism. Increasing evidence suggests that resistance in UC is mediated by multiple interconnected mechanisms beyond alterations in gemcitabine transport, activation, and inactivation alone. Key molecular determinants include human equilibrative nucleoside transporter 1 (hENT1), deoxycytidine kinase (dCK), cytidine deaminase (CDA), and ribonucleotide reductase regulatory subunit M1 (RRM1), which is involved in nucleotide pool maintenance and DNA synthesis. In addition, replication stress responses, apoptosis evasion pathways, and tumor microenvironment-associated factors also contribute to gemcitabine resistance. Stress-adaptive pathways involving Y-box binding protein 1 (YB-1), hypoxia-inducible factor-1 alpha (HIF-1α), and autophagy-related mechanisms may further promote survival under chemotherapy-induced stress conditions. In addition, extracellular mucin-associated mechanisms may alter intratumoral drug accessibility and contribute to resistance. In this review, we summarize UC-specific evidence regarding gemcitabine resistance and discuss how these pathways collectively shape an integrated resistant phenotype. Full article

The canonical transsulfuration (TSS) pathway enzymes cystathionine β-synthase (CBS) and cystathionine γ-lyase (CTH) are traditionally recognized for their roles in the sequential conversion of homocysteine to cysteine and in endogenous hydrogen sulfide (H₂S) production. Increasing evidence, however, suggests that these enzymes may also exhibit non-canonical (“moonlighting”) functions that extend beyond metabolic regulation. In this review, we evaluate the hypothesis that CTH may participate in translational regulation, particularly in the control of hypoxia-inducible factor-1α (HIF-1α) expression in clear cell ovarian carcinoma (CCOC). We first highlight limitations of the prevailing H₂S- and cysteine-centric view of the TSS pathway, which may not fully explain emerging context-dependent functions of CTH in cancer biology. Current evidence suggests that CTH enhances HIF-1α protein expression through mechanisms independent of transcription, protein stability, or H₂S production, implicating a potential role in translational regulation, although direct mechanistic evidence remains limited. To critically evaluate this emerging hypothesis, we categorize evidence according to its level of experimental support, ranging from direct experimental evidence to indirect mechanistic observations and computational predictions. Within this framework, we examine three non-mutually exclusive models: (1) regulation through PI3K/AKT/mTOR-dependent translational signaling; (2) modulation of translational control through interaction with translation-associated proteins and RNA-binding proteins (RBPs) involved in HIF1A mRNA regulation; and (3) the more speculative possibility of direct interaction between CTH and HIF1A mRNA. Collectively, these observations support a model in which CTH contributes to selective translational regulation beyond its canonical metabolic functions, potentially linking sulfur metabolism to stress-adaptive gene expression in cancer. Full article

Succinate, a tricarboxylic acid (TCA) cycle intermediate, is the essential signal molecule that links metabolic signals and inflammation. Dietary succinate supplementation has been reported to prevent obesity induced by a high-fat diet (HFD). However, the underlying mechanism remains elusive. Here, we found that dietary succinate elevated the serum succinate levels. Meanwhile, we found succinate increased methyltransferaselike 3 (METTL3) protein expression in brown adipocytes, thereby elevating N⁶-methyladenosine (m⁶A) levels in Hypoxia-inducible factor1-alpha (Hif1a) mRNA. Hif1a mRNA is recognized by the m⁶A-binding protein YTH domain-containing family protein 1 (YTHDF1), facilitating HIF1A protein expression. HIF1A activates the transcription of thermogenic genes, ultimately increasing brown adipose energy expenditure. Together, our research provided new insights into the effect of succinate on m⁶A modification in brown adipose tissue thermogenesis. Full article

Statins are commonly used cholesterol-lowering drugs, but their effects on astrocyte oxidative metabolism are poorly understood. To investigate this, rat astrocytes were exposed to 200 nM atorvastatin or simvastatin for 6 days and then assessed for changes in coenzyme Q (CoQ) homeostasis, mitochondrial function, and energy metabolism. Both statins comparably decreased cellular CoQ9 and CoQ10 levels (~35%), with greater losses of their reduced antioxidant forms (60–75%). Lower intracellular and mitochondrial levels of reactive oxygen species (ROS) were accompanied by the upregulation of nuclear factor erythroid 2-related factor 2 (NRF2)-dependent antioxidant pathways (superoxide dismutase 1 and glutathione reductase) and metabolic stress response factors, including hypoxia-inducible factor 1-alpha (HIF1α) and brain-derived neurotrophic factor (BDNF). Both statins promoted glycolytic reprogramming, mitochondrial fission, and biogenesis while impairing oxidative phosphorylation, as evidenced by reduced ATP-linked respiration, increased proton leak, and lower ATP levels. These findings suggest that statin-treated astrocytes adapt by prioritizing redox homeostasis over ATP production. CoQ10 supplementation increased cellular CoQ10 levels and restored ATP levels without further decreasing ROS, suggesting that its primary benefit is bioenergetic support, not additional antioxidant protection. Overall, statin-induced CoQ deficiency induces adaptive metabolic remodeling of astrocytes, while CoQ10 supplementation may help maintain energy metabolism under these conditions. Full article

Clear cell renal cell carcinoma (ccRCC) is increasingly recognized as a lipid-addicted malignancy in which de novo lipogenesis (DNL) supports tumor growth, survival, and treatment resistance. ccRCC-specific genetic alterations, particularly loss of VHL and activation of hypoxia-inducible factor (HIF) signaling, promote SREBP-mediated upregulation of key lipogenic enzymes, including ATP-citrate lyase (ACLY), acetyl-CoA carboxylase (ACC), fatty acid synthase (FASN), and stearoyl-CoA desaturase 1 (SCD1). These pathways support membrane biogenesis and redox balance while also promoting metabolic flexibility, enabling adaptation to therapeutic and microenvironmental stresses. Emerging preclinical studies suggest that pharmacological inhibition of lipogenic enzymes, either alone or in combination with tyrosine kinase inhibitors, mTOR inhibitors, HIF-2α antagonists, or immune checkpoint blockade, may suppress ccRCC progression. However, most therapeutic data remain limited to preclinical models, and clinical validation is still lacking. This review synthesizes recent advances in molecular regulation and therapeutic targeting of DNL in ccRCC and discusses the challenges and future opportunities to improve mechanistic understanding and explore potential therapeutic applications. Full article

This study investigated the association between serum hypoxia-inducible factor 1-alpha (HIF-1α) levels and clinical severity in patients with coronavirus disease 2019 (COVID-19). This prospective case–control study included 91 patients with confirmed COVID-19, of whom 51 had severe-critical disease with pneumonia and 40 had mild disease without pneumonia, as well as 39 healthy controls. Vital signs, including body temperature, pulse rate, respiratory rate, oxygen saturation, and blood pressure, were recorded. Biochemical parameters such as complete blood count, D-dimer, ferritin, creatinine, urea, and high-sensitivity cardiac troponin T were analyzed. Serum HIF-1α levels were measured using ELISA. Median HIF-1α levels were 132.9 pg/mL (IQR: 131.7–138.0) in the severe-critical disease group, 137.35 pg/mL (IQR: 131.65–152.75) in the mild disease group, and 136.6 pg/mL (IQR: 132.2–162.2) in controls. Significant differences were observed between groups (p = 0.012). ROC analysis showed a discriminatory performance for HIF-1α, with a sensitivity of 89.01% and specificity of 35.90% at a cut-off value of ≤154 pg/mL for distinguishing mild disease from controls, and a sensitivity of 86.3% and specificity of 42.5% at a cut-off value of ≤141.1 pg/mL for distinguishing severe-critical disease from mild disease. HIF-1α levels decreased with increasing disease severity. HIF-1α levels were found to be associated with disease severity; however, the low AUC values indicate that this parameter has limited discriminative ability for clinical use when used alone. Full article

Background: Hepatocellular carcinoma (HCC) shows a high rate of early recurrence after curative resection, indicating a critical contribution of tumor microenvironment-driven molecular mechanisms. Early recurrence of hepatocellular carcinoma is defined as recurrence within 6 months after curative resection, with a prevalence exceeding 30%. Hypoxia signaling and immune dysregulation have been implicated, yet their compartment-specific relevance remains unclear. Methods: This multicenter nested case–control study included 49 HCC patients to evaluate associations between hypoxia-inducible factor-1 alpha (HIF-1α), vascular endothelial growth factor (VEGF), tumor-infiltrating lymphocytes (TILs), CD4⁺ T cells, CD8⁺ T cells, regulatory T cells (Tregs), programmed cell death protein 1 (PD-1), and programmed death-ligand 1 (PD-L1) and early recurrence after resection. TIL density was assessed using hematoxylin and eosin staining, while immunohistochemistry was performed to quantify intratumoral and peritumoral expression of the studied markers. Receiver operating characteristic (ROC) curve analysis was used to evaluate the predictive performance. Recurrence-free survival (RFS) was analyzed using the Kaplan–Meier, and independent predictors were identified using multivariate Cox proportional hazards regression. Results: Early recurrence occurred in 11 of 49 patients (22.4%) of Child–Pugh A patients. Recurrent tumors were characterized by elevated VEGF expression despite absent HIF-1α, alongside significant depletion of intratumoral TILs (HR 5.02; 95% CI 1.09–23.26), CD4⁺ (HR 7.68; 95% CI 1.66–35.60) and CD8⁺ cells (HR 6.68; 95% CI 1.77–25.23) and reduced peritumoral CD8⁺ infiltration (HR 4.20; 95% CI 1.11–15.91). Multivariable analysis identified low intratumoral CD4⁺ (HR 7.98; 95% CI 1.63–39.07) and reduced peritumoral CD8⁺ expression (HR 4.98; 95% CI 1.14–21.70) as independent predictors, whereas HIF-1α, VEGF, Treg, PD-1, and PD-L1 were not significantly associated. Conclusions: Early HCC recurrence shows HIF-1α-independent angiogenesis alongside spatial immune depletion, supporting integrated immune profiling over single angiogenic markers. Full article

Epicardial mesothelium plays a pivotal role in postinfarction cardiac repair by generating fibroblasts, producing extracellular matrix, and releasing paracrine mechanisms. However, interspecies differences have not been sufficiently studied, particularly in in vivo models of scar-free healing such as the African spiny mouse (Acomys cahirinus). This study aimed to compare the profibrotic response of epicardial mesothelial cells (MCs) from Acomys and C57BL/6 mice to hypoxic stress, a key factor in postinfarction recovery. We isolated epicardial MCs from the African spiny mouse (Acomys cahirinus), a species with documented cardiac regenerative capabilities, and from C57BL/6 laboratory mice. Using a CoCl₂-induced hypoxia model in vitro, we assessed cell viability, morphological changes, and expression of epithelial and fibroblast markers. In vivo, following experimental myocardial infarction (MI), we evaluated tissue hypoxia (pimonidazole adducts), epicardial activation (layer thickness, Wt1⁺ and TBX18⁺ progenitor cells), and collagen accumulation. The study was conducted using real-time PCR, Western blotting, immunohistochemical analysis and microscopic examination. In vitro, MCs from both species exhibited an epithelial-like phenotype under normoxic conditions, expressing E-cadherin and cytokeratin 18. Hypoxia (200 µM CoCl₂) induced a comparable response in both Acomys and C57BL/6 cells, characterized by a shift to a spindle-shaped, fibroblast-like morphology, decreased E-cadherin expression, and increased pro-collagen 1 and α-SMA expression. Following MI, both species exhibited similarly extensive hypoxic areas affecting the epicardial zone. Epicardial activation dynamics were comparable: from day 3 post-MI, epicardial thickness increased significantly, and Wt1⁺ and TBX18⁺ progenitor cells accumulated, peaking during the first week. Collagen accumulation in the epicardial region was similar between species, although the number of Wt1⁺ cells was higher in C57BL/6 on day 7. Despite the well-known superior regenerative capacity of spiny mice, epicardial MCs from Acomys and C57BL/6 demonstrated similar signs of profibrotic responses to hypoxic stimulation both in vitro and following MI. These findings suggest that species-specific regenerative outcomes may not be attributable to differential acute epicardial sensitivity to hypoxia, but rather to downstream mechanisms or additional factors influencing the cardiac repair process. This study provides the first characterization of Acomys epicardial MCs and establishes a foundation for further investigation of evolutionarily conserved and species-specific mechanisms of cardiac regeneration. Full article

Chronic exposure to fine particulate matter (${\mathrm{PM}}_{2.5}$) derived from residential wood combustion is a major environmental health concern in southern Chile and other cold-climate regions. Although ${\mathrm{PM}}_{2.5}$ has been linked to adverse reproductive outcomes, it remains unclear whether sustained exposure induces pregestational uterine alterations that compromise reproductive competence before the first pregnancy. This study evaluated the effects of chronic wood smoke-derived ${\mathrm{PM}}_{2.5}$ exposure on uterine morphology and molecular markers in nulliparous rats. A two-generation exposure model was used to assess cumulative effects. Second-generation (G2) female Sprague Dawley rats continuously exposed from conception were housed in filtered air (FA, control; $n=12$) or ${\mathrm{PM}}_{2.5}$-containing ambient air (NFA; $n=12$) until reproductive maturity (82 days). Uterine horns were analyzed by histology, planimetry, immunohistochemistry, immunofluorescence, and second harmonic generation microscopy. Markers of hypoxia, inflammation, extracellular matrix remodeling, angiogenesis, proliferation, apoptosis, and DNA repair were quantified. Chronic ${\mathrm{PM}}_{2.5}$ exposure increased hypoxia-inducible factor 1$\alpha$, tumor necrosis factor-$\alpha$, vascular endothelial growth factor A, and collagen types I, III, and IV, while transforming growth factor-$\beta$ expression and Ki-67-positive proliferating cells were reduced. Exposed rats showed increased apoptosis and decreased nuclear expression of ${\mathrm{O}}^6$-methylguanine-DNA methyltransferase, indicating impaired DNA repair capacity. Second harmonic generation imaging demonstrated increased collagen deposition with marked fibrillar disorganization. These findings indicate that chronic wood smoke-derived ${\mathrm{PM}}_{2.5}$ exposure induces hypoxia-driven structural and molecular alterations in the uterus of nulliparous rats before first pregnancy, including extracellular matrix remodeling, inflammatory imbalance, angiogenic dysregulation, reduced proliferation, and compromised DNA repair, suggesting early disruption of uterine homeostasis and increased susceptibility to adverse reproductive outcomes. Full article