A novel HIF2A mutation causes dyslipidemia and promotes hepatic lipid accumulation

Targeting Ferroptosis Alleviates Pulmonary Arterial Hypertension, Insights from Transcriptomic and Experimental Analyses

Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling driven by endothelial cell injury. This study investigates the role of ferroptosis in PAH development and its underlying molecular mechanisms. Ferroptosis-related gene expression is analyzed using transcriptomic and single-cell RNA sequencing data. A PAH mouse model is induced by combined hypoxia and Semaxanib (SU5416) treatment. The impact of ferroptosis on pulmonary vascular remodeling is evaluated by measuring right ventricular systolic pressure (RVSP), the Fulton index, vascular wall thickness, and histological changes in pulmonary arteries. Transcriptomic analysis reveals downregulation of SLC7A11 and upregulation of ACSL1 and ACSL4 in PAH patients. Endothelial cells are identified as key mediators of ferroptosis, and inhibiting ferroptosis alleviates endothelial damage and vascular remodeling. Additionally, HIF1α signaling plays a crucial role in ferroptosis induction in PAH. These findings highlight ferroptosis as a critical mechanism of endothelial injury and a key contributor to PAH pathogenesis. Targeting ferroptosis offers promising new strategies for early intervention and targeted therapy in PAH.

The Distinct Role of HIF-1α and HIF-2α in Hypoxia and Angiogenesis

Hypoxia results in a wide range of adaptive physiological responses, including metabolic reprogramming, erythropoiesis, and angiogenesis. The response to hypoxia at the cellular level is mainly regulated by hypoxia-inducible factors (HIFs): HIF1α and HIF2α isoforms. Although structurally similar and overlapping gene targets, both isoforms can exhibit distinct expression patterns and functions in some conditions of hypoxia. The interaction between these isoforms, known as the "HIF switch", determines their coordinated function under varying oxygen levels and exposure time. In angiogenesis, HIF-1α is rapidly stabilized under acute hypoxia, prompting a metabolic shift from oxidative phosphorylation to glycolysis and initiating angiogenesis by activating endothelial cells and extracellular matrix remodeling. Conversely, HIF-2α regulates cell responses to chronic hypoxia by sustaining genes critical for vascular remodeling and maturation. The current review highlights the different roles and regulatory mechanisms of HIF-1α and HIF-2α isoforms, focusing on their involvement in cell metabolism and the multi-step process of angiogenesis. Tuning the specific targeting of HIF isoforms and finding the right therapeutic window is essential to obtaining the best therapeutic effect in diseases such as cancer and vascular ischemic diseases.

Magnolin ameliorates acetaminophen-induced liver injury in mice via modulating the MAPK pathway and lipid metabolism

Acetaminophen (APAP)-induced liver injury (AILI) represents a common yet potentially severe type of drug-induced liver injury with limited available effective therapeutic methods. Magnolin possesses excellent anti-inflammatory and antioxidant properties for treating various diseases. However, its effects against AILI and the fundamental mechanisms still lack comprehensive exploration. This research endeavors to assess magnolin's hepatoprotective properties against AILI. The AILI model was established in male C57BL/6 mice via intraperitoneal injection of 300 mg/kg APAP and in the HepG2 cell line by treating it with 20 mM APAP. The levels of oxidation, liver damage and inflammation were assessed. Transcriptomics and metabolomics were utilized to explore the mechanism underlying magnolin treatment in AILI. We found that 5 mg/kg magnolin effectively mitigated the elevated serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), along with inflammatory factor (IL-6, and TNF-α) levels in vivo. Meanwhile, magnolin relieved oxidative stress by increasing superoxide dismutase activity and reducing malondialdehyde along with oxidized glutathione/reduced glutathione (GSSG/GSH). 6 μM magnolin increased cell viability and reduced the lipid peroxidation in vitro. Furthermore, 5 mg/kg magnolin altered the expression of 413 genes and the levels of 70 metabolites compared with Control group, which were enriched in lipid metabolism, inflammatory responses, and the MAPK signaling pathway. However, 10 mg/kg magnolin tended to exacerbate liver damage. Overall, 5 mg/kg magnolin effectively protects against AILI by modulating inflammatory responses and the MAPK pathway, whereas 10 mg/kg worsens liver injury, underscoring the need for dose optimization. These findings offer a fresh perspective and novel therapy for AILI.

Effect of Rab18 on liver injury and lipid accumulation by regulating perilipin 2 and peroxisome proliferator-activated receptor gamma in non-alcoholic fatty liver disease

BACKGROUND AND AIM

Nonalcoholic fatty liver disease (NAFLD) is currently one of the most common chronic liver diseases worldwide, characterized by the presence of lipid droplets. Rab18 is an important lipid droplet protein; however, its effects and mechanisms of action on NAFLD remain unclear.

METHODS

Free fatty acid-stimulated AML-12 cells and high-fat diet (HFD)-fed mice were used as NAFLD models. Lentiviruses overexpressing Rab18 (Rab18-OE) or knockdown (Rab18-KD) were used to generate stable cell lines for genetic analysis. Blood serum levels of alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, glucose, and leptin were measured using a biochemical autoanalyzer. Hematoxylin and eosin staining was performed to detect pathological damage to the liver. Lipid accumulation in the cells was assessed by Oil Red O staining. Target expression was measured using qPCR, western blotting, and immunocytochemistry.

RESULTS

Rab18 mRNA and protein expression levels increased in free fatty acid-stimulated AML-12 cells and the livers of HFD-fed mice. Rab18-OE increased lipid accumulation in vitro, which was attenuated by Rab18-KD. In vivo, Rab18-OE augmented liver pathological damage, serum alanine aminotransferase/aspartate aminotransferase activity, and triglyceride, total cholesterol, and low-density lipoprotein levels, whereas Rab18-KD decreased these indicators. Rab18-KD also downregulated blood glucose levels in HFD-fed mice. Mechanistically, Rab18-OE and Rab18-KD regulated the mRNA and protein expression levels of perilipin 2 (PLIN2) and peroxisome proliferator-activated receptor gamma (PPARγ) in vitro and in vivo, respectively. Immunocytochemistry revealed that Rab18 colocalized with PLIN2 and PPARγ in AML-12 cells.

CONCLUSION

Rab18 expression was elevated in vitro and in vivo in the NAFLD mouse model. Rab18 regulates PLIN2 and PPARγ expression to exaggerate liver injury and lipid accumulation in patients with NAFLD. Thus, Rab18 may be a crucial protein in this disease and a potential therapeutic target.

Serum metabolomics reveals the effectiveness of human placental mesenchymal stem cell therapy for Crohn's disease

Mesenchymal stem cell (MSC) therapy offers a promising cure for Crohn's disease (CD), however, its therapeutic effects vary significantly due to individual differences. Therefore, identifying easily detectable biomarkers is essential to assess the efficacy of MSC therapy. In this study, SAMP1/Yit mice were used as a model of CD, which develop spontaneous chronic ileitis, closely resembling the characteristics present in CD patients. Serum metabolic alterations during treatment were analyzed, through the application of differential 12C-/13C-dansylation labeling liquid chromatography-mass spectrometry. Based on the significant differences and time-varying trends of serum amine/phenol-containing metabolites abundance between the control group, the model group, and the treatment group, four serum biomarkers were ultimately screened for evaluating the efficacy of MSC treatment for CD, namely 4-hydroxyphenylpyruvate, 4-hydroxyphenylacetaldehyde, caffeate, and N-acetyltryptamine, whose abundances both increased in the serum of CD model mice and decreased after MSC treatment. These metabolic alterations were associated with tyrosine metabolism, which was validated by the dysregulation of related enzymes. The discovery of biomarkers may help to improve the targeting and effectiveness of treatment and provide innovative prospects for the clinical application of MSC for CD.

Effects of Environmental Hypoxia on Serum Hematological and Biochemical Parameters, Hypoxia-Inducible Factor (hif) Gene Expression and HIF Pathway in Hybrid Sturgeon (Acipenser schrenckii ♂ × Acipenser baerii ♀)

Hypoxia is a globally pressing environmental problem in aquatic ecosystems. In the present study, a comprehensive analysis was performed to evaluate the effects of hypoxia on physiological responses (hematology, cortisol, biochemistry, hif gene expression and the HIF pathway) of hybrid sturgeons (Acipenser schrenckii ♂ × Acipenser baerii ♀). A total of 180 hybrid sturgeon adults were exposed to dissolved oxygen (DO) levels of 7.00 ± 0.2 mg/L (control, N), 3.5 ± 0.2 mg/L (moderate hypoxia, MH) or 1.00 ± 0.1 mg/L (severe hypoxia, SH) and were sampled at 1 h, 6 h and 24 h after hypoxia. The results showed that the red blood cell (RBC) counts and the hemoglobin (HGB) concentration were significantly increased 6 h and 24 h after hypoxia in the SH group. The serum cortisol concentrations gradually increased with the decrease in the DO levels. Moreover, several serum biochemical parameters (AST, AKP, HBDB, LDH, GLU, TP and T-Bil) were significantly altered at 24 h in the SH group. The HIFs are transcription activators that function as master regulators in hypoxia. In this study, a complete set of six hif genes were identified and characterized in hybrid sturgeon for the first time. After hypoxia, five out of six sturgeon hif genes were significantly differentially expressed in gills, especially hif-1α and hif-3α, with more than 20-fold changes, suggesting their important roles in adaptation to hypoxia in hybrid sturgeon. A meta-analysis indicated that the HIF pathway, a major pathway for adaptation to hypoxic environments, was activated in the liver of the hybrid sturgeon 24 h after the hypoxia challenge. Our study demonstrated that hypoxia, particularly severe hypoxia (1.00 ± 0.1 mg/L), could cause considerable stress for the hybrid sturgeon. These results shed light on their adaptive mechanisms and potential biomarkers for hypoxia tolerance, aiding in aquaculture and conservation efforts.

MFN2 suppresses the accumulation of lipid droplets and the progression of clear cell renal cell carcinoma

Dissolving the lipid droplets in tissue section with alcohol during a hematoxylin and eosin (H&E) stain causes the tumor cells to appear like clear soap bubbles under a microscope, which is a key pathological feature of clear cell renal cell carcinoma (ccRCC). Mitochondrial dynamics have been reported to be closely associated with lipid metabolism and tumor development. However, the relationship between mitochondrial dynamics and lipid metabolism reprogramming in ccRCC remains to be further explored. We conducted bioinformatics analysis to identify key genes regulating mitochondrial dynamics differentially expressed between tumor and normal tissues and immunohistochemistry and Western blot to confirm. After the target was identified, we created stable ccRCC cell lines to test the impact of the target gene on mitochondrial morphology, tumorigenesis in culture cells and xenograft models, and profiles of lipid metabolism. It was found that mitofusin 2 (MFN2) was downregulated in ccRCC tissues and associated with poor prognosis in patients with ccRCC. MFN2 suppressed mitochondrial fragmentation, proliferation, migration, and invasion of ccRCC cells and growth of xenograft tumors. Furthermore, MFN2 impacted lipid metabolism and reduced the accumulation of lipid droplets in ccRCC cells. MFN2 suppressed disease progression and improved prognosis for patients with ccRCC possibly by interrupting cellular lipid metabolism and reducing accumulation of lipid droplets.

HIF2A mediates lineage transition to aggressive phenotype of cancer-associated fibroblasts in lung cancer brain metastasis

Brain metastasis is the most devasting form of lung cancer. Recent studies highlight significant differences in the tumor microenvironment (TME) between lung cancer brain metastasis (LCBM) and primary lung cancer, which contribute significantly to tumor progression and drug resistance. Cancer-associated fibroblasts (CAFs) are the major component of pro-tumor TME with high plasticity. However, the lineage composition and function of CAFs in LCBM remain elusive. By reanalyzing single-cell RNA sequencing (scRNA-seq) data (GSE131907) from lung cancer patients with different stages of metastasis comprising primary lesions and brain metastasis, we found that CAFs undergo distinctive lineage transition during LCBM under a hypoxic situation, which is directly driven by hypoxia-induced HIF-2α activation. Transited CAFs enhance angiogenesis through VEGF pathways, trigger metabolic reprogramming, and promote the growth of tumor cells. Bulk RNA sequencing data was utilized as validation cohorts. Multiplex immunohistochemistry (mIHC) assay was performed on four paired samples of brain metastasis and their primary lung cancer counterparts to validate the findings. Our study revealed a novel mechanism of lung cancer brain metastasis featuring HIF-2α-induced lineage transition and functional alteration of CAFs, which offers potential therapeutic targets.

BDNF mimetics recover palmitic acid-induced injury in cardiomyocytes by ameliorating Akt-dependent mitochondrial impairments

Cardiac lipotoxicity is a prevalent consequence of lipid metabolism disorders occurring in cardiomyocytes, which in turn precipitates the onset of heart failure. Mimetics of brain-derived neurotrophic factor (BDNF), such as 7,8-dihydroxyflavone (DHF) and 7,8,3'-trihydroxyflavone (THF), have demonstrated significant cardioprotective effects. However, it remains unclear whether these mimetics can protect cardiomyocytes against lipotoxicity. The aim of this study was to examine the impact of DHF and THF on the lipotoxic effects induced by palmitic acid (PA), as well as the concurrent mitochondrial dysfunction. H9c2 cells were subjected to treatment with PA alone or in conjunction with DHF or THF. Various factors such as cell viability, lactate dehydrogenase (LDH) release, death ratio, and mitochondrial function including mitochondrial membrane potential (MMP), mitochondrial-derived reactive oxygen species (mito-SOX) production, and mitochondrial respiration were assessed. PA dose-dependently reduced cell viability, which was restored by DHF or THF. Additionally, both DHF and THF decreased LDH content, death ratio, and mito-SOX production, while increasing MMP and regulating mitochondrial oxidative phosphorylation in cardiomyocytes. Moreover, DHF and THF specifically activated Akt signaling. The protective effects of DHF and THF were abolished when an Akt inhibitor was used. In conclusion, BDNF mimetics attenuate PA-induced injury in cardiomyocytes by alleviating mitochondrial impairments through the activation of Akt signaling.

The Perspective of Using Flow Cytometry for Unpuzzling Hypoxia-Inducible Factors Signalling

Hypoxia-inducible factors (HIFs) are transcription factors that are responsible for adapting to the changes in oxygen levels in the cellular environment. HIF activity determines the expression of cellular proteins that control the development and physiology of the cells and pathophysiology of a disease. Understanding the role of specific HIF (HIF-1-3) in cellular function is essential for development of the HIF-targeted therapies. In this review, we have discussed the use of flow cytometry in analysing HIF function in cells. Proper understanding of HIF-signalling will help to design pharmacological interventions HIF-mediated therapy. We have discussed the role of HIF-signalling in various diseases such as cancer, renal and liver diseases, ulcerative colitis, arthritis, diabetes and diabetic complications, psoriasis, and wound healing. We have also discussed protocols that help to decipher the role of HIFs in these diseases that would eventually help to design promising therapies.