FASEB bioAdvances最新文献

Mutations in the ABCA4 gene in Stargardt disease (STGD1) cause enhanced accumulation of cytotoxic lipofuscin, manifesting in RPE atrophy and photoreceptor dysfunction. One component of lipofuscin is the all-trans-retinal derivative, pyridinium bisretinoid A2E. Since ocular A2E biosynthesis relies on all-trans-retinal, which is obtained from circulating all-trans-retinol bound to retinol binding protein 4 (RBP4-ROL), we hypothesized that modulating vitamin A receptors, such as RBPR2, which regulate serum RBP4-ROL homeostasis, should in principle attenuate A2E production. In silico analysis revealed multiple retinoic acid response element (RARE) binding sites on the murine Rbpr2 gene promoter, which was confirmed in vitro by EMSA and ChIP assays. In vitro luciferase assays showed that Rbpr2 promoter activity was induced by exogenous β-carotene (BC) metabolites. Dietary BC supplementation of Abca4^−/− mice, a mouse model for STGD1, increased hepatic all-trans-retinoic acid and 9-cis-retinoic acid production, which induced Rbpr2 mRNA expression. This mechanism decreased serum RBP4 protein levels, fundus lipofuscin autofluorescence, and ocular A2E accumulation, altogether improving photoreceptor and RPE function. Conversely, such a rescue was not observed in either Abca4^−/− mice fed a diet devoid of BC or in double knockout Rbpr2^−/−; Abca4^−/− mice. Thus, there was a significant inverse correlation between dietary BC supplementation and Rbpr2 gene presence in Abca4^−/− mice, to that of lipofuscin accumulation in Abca4^−/− mice on diets devoid of BC or in Rbpr2^−/−; Abca4^−/− mice. Our results provide impetus to include dietary obtained BC for STGD1 patients with ABCA4 gene mutations and identify a novel role for the vitamin A receptor RBPR2 in this process.

Interest in the endogenous role of methane has grown rapidly over the past decade, driven both by its relevance for disease detection (including intestinal methanogen overgrowth) as well as discoveries that raise the possibility of endogenous sources of methane and suggestive evidence of methane effects relevant to physiology. This review explores both established and emerging origins of breath methane, its physiological relevance, and the evolving landscape of detection methods. We aim to summarize current understanding and provide a platform to outline key directions for future research. Evidence supports the existence of non-microbial, endogenous methane production pathways and potential biological effects beyond the gut. However, the concentrations generated via these pathways and the levels required to elicit physiological responses remain under investigation. Recent technological advances have enabled more accessible and longitudinal breath methane monitoring, opening new avenues for research and clinical application.

Astrocytes play a vital role in maintaining homeostasis and function in the central nervous system, including their involvement in reparative processes. Here, we examined how a common mutation in the homeostatic iron regulatory gene, H67D HFE, impacts the antioxidant mechanism of astrocytes and migration under normal and reparative conditions. Previous data from our group suggested that this mutation may modify disease progression through an antioxidant mechanism involving nuclear factor erythroid 2-related factor 2 (Nrf2), glutathione peroxidase 4 (GPX4), and ferritin. In this study, we used primary murine astrocytes with either the H67D or wild-type HFE genotype to determine whether astrocytes contribute to the antioxidant protective mechanism previously observed. We analyzed their antioxidant profile and migration both at baseline and after a scratch wound injury. We found that H67D HFE astrocytes expressed the HFE protein and exhibited an enhanced antioxidant profile, marked by increased glutathione and GPX4 at baseline, and a reduced migration length into three-dimensional granular hydrogel scaffolds. However, following scratch wound injury, these astrocytes exhibited a shift in migratory behavior, leading to faster wound infiltration. Moreover, their antioxidant response became even more pronounced after injury, with increased expression of Nrf2, GPX4, and H-ferritin (FTH1). These results suggest that the mechanism underlying HFE mutation neuroprotection in disease processes involves an antioxidant profile in astrocytes, which is increased upon insult to activate the astrocytic reparative mechanism.

Osteosarcoma (OS) is highly malignant and easily prone to lung metastasis. The mechanisms of lung metastasis in OS remain unclear. The single-cell RNA sequencing (scRNA-seq) samples in this study included six primary osteosarcoma samples (published in-house data), two lung metastasis samples (GSE152048), and four normal bone tissue samples (GSE169396). To identify potential targets for metastasis, bulk RNA sequencing data from four primary tumors and four lung metastases (in-house data) were also analyzed. scRNA-seq identified five tumor cell subpopulations. CytoTRACE and lung metastasis scores indicated that the C1 subpopulation was most closely associated with lung metastasis. By intersecting lung metastasis-related genes identified via hdWGCNA analysis with differentially expressed genes from bulk RNA sequencing, SEC16B was identified as the key gene influencing lung metastasis. qRT-PCR results revealed that SEC16B expression was significantly downregulated in OS cell lines. Transwell assay demonstrated that overexpression of SEC16B significantly inhibited the invasion and migration capabilities of OS cells. Additionally, analyses using Scissor, CellphoneDB, and CSOmap suggested that fibroblasts, endothelial cells, and OS cells in the tumor microenvironment formed a pre-metastatic niche through mechanisms involving angiogenesis and extracellular matrix remodeling. Overall, this study identifies a new population that may promote lung metastasis by downregulating SEC16B in OS. Moreover, fibroblasts and endothelial cells in the tumor microenvironment play a critical role in OS lung metastasis.

Cover image caption: Cover image adapted from “Signaling Centers Drive Brachyury Dynamics and Lineage Commitment in mESC Aggregates” by Rabeling and Goolam (10.1096/fba.2024-00131).

Extracellular matrix stiffness is enhanced in cancer and fibrosis; however, there is limited knowledge on how matrix mechanics modulate expression and signaling of the methyltransferase G9a. Here, we show that matrix stiffness and transforming growth factor (TGF)-β1 signaling together regulate G9a expression and the levels of the histone mark H3K9me2. Suppressing the activity and expression of G9a attenuates TGFβ1-induced alpha smooth muscle actin (αSMA) and N-cadherin expression and cell morphology changes in mammary epithelial cells cultured on stiff substrata. Knockdown of G9a increases the expression of large tumor suppressor kinase 2 (LATS2) and decreases the nuclear localization of yes associated protein (YAP). Furthermore, inhibition of LATS promotes an increase in YAP nuclear localization and αSMA expression, while inhibition of YAP attenuates αSMA expression. Overall, our findings indicate that a G9a-LATS-YAP signaling cascade regulates mammary epithelial cell response to matrix stiffness and TGFβ1.

Multiple sclerosis (MS) is a debilitating neuroinflammatory disease of the central nervous system (CNS). Approximately 2–3 million people globally are believed to have MS. There is growing interest in the mechanistic link between MS and gut microbiome composition. Experimental autoimmune encephalomyelitis (EAE) is a murine model of inflammatory demyelination of the CNS commonly used to investigate the pathology of MS in relation to the microbiome. Previous research has shown that EAE affects the gut microbiome, and the improvement of EAE can promote microbiome homeostasis. Microbiome homeostasis is crucial for host health, as it contributes to immune regulation and produces bioavailable metabolic products in the digestive tract. Several factors, including diet, genetics, and environment, influence microbiome homeostasis apart from disease state. Our lab previously demonstrated that mice of the same genetic line, sourced from different manufacturers, exhibit differences in microbiome composition despite being housed under similar conditions. Furthermore, these mice showed variations in EAE progression and severity, indicating that differences in the microbiome may contribute to the discrepancies in EAE. Here, we employ PICRUSt2 to estimate functional differences in the microbiomes of EAE mice from various sources at key time points during the EAE disease course. The reanalysis of our microbiome data reveals distinct differences in predicted gene expression of microbiomes that are disproportionately related to the metabolism of amino acids, carbohydrates, lipids, and other metabolites. Our findings support previous observations regarding microbiome alterations in the context of EAE and suggest that evaluating microbiome dynamics would benefit from both taxonomic assessment and metabolic activity, allowing for more effective and comprehensive research strategies.

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), presents a global public health challenge. Although the relationships between gut microbiota, inflammatory proteins, and IBD are recognized, their causal associations and mediating roles remain unclear. Large-scale genome-wide association study data on 473 gut microbiota, 91 circulating inflammatory proteins, and IBD (including CD and UC) were analyzed. Univariable Mendelian randomization (UVMR), Bayesian Weighted MR (BWMR), mediation MR, and sensitivity analyses were used to explore causal associations and quantify mediating effects. MR results indicate that 24, 20, and 22 gut microbiota exhibit causal effects on IBD (nine protective factors, 15 risk factors), CD (nine protective factors, 11 risk factors) and UC (seven protective factors, 15 risk factors). Three inflammatory proteins (one protective factors, two risk factors) have causal effects on IBD, with five having causal effects on CD (one protective factors, four risk factors) and UC (two protective factors, three risk factors). Mediation analysis reveals that Interleukin-17C levels mediate the causal effects of Acetobacterales and Bifidobacterium on IBD. T-cell surface glycoprotein CD6 isoform levels mediate the causal effect of Faecalibacterium prausnitzii E on CD. Interleukin-17C levels also mediate the causal effects of Acetobacterales on UC and Phocea massiliensis on UC. Gut microbiota and circulating inflammatory proteins play key roles in IBD pathogenesis, with Interleukin-17C and T-cell surface glycoprotein CD6 identified as key intermediates in the causal pathway. These findings provide novel biomarkers and potential therapeutic targets for preventing and treating IBD, CD, and UC.

Cell homeostasis and metabolic control require the efficient function of mitochondria and implementation of quality control pathways following damage. Cells have various discrete pathways of mitochondrial quality control (mitoQC) to maintain the healthy network. PINK1 and Parkin are two key players in mitoQC, most highly associated with the ubiquitin-dependent capture and degradation of whole mitochondria by autophagy. However, these proteins have alternative roles in repair routes directing locally damaged cargo to the lysosome, such as the mitochondrial-derived vesicle (MDV) pathway. We aimed to clarify the role of PINK1 and determine how its loss of function impacts mitochondrial dynamics and quality control. Results indicate PINK1 knockout (KO) has little impact on whole mitochondrial turnover in response to damage in SH-SY5Y cells, whereas both PINK1 and Parkin KO cells have healthy mitochondrial networks with efficient ATP production. However, TOM20 positive outer-membrane and damage-induced PDH-positive inner-membrane MDVs are elevated in PINK1 KO cells. Although, in contrast to Parkin KO, this is not due to a defect in trafficking to a LAMP1-positive compartment and may instead indicate increased damage-induced flux. In comparison, loss of Atg5-dependent mitophagy has no effect on whole mitochondrial turnover and only results in a limited elevation in inner-membrane MDVs in response to damage, indicating autophagy-independent mechanisms of whole mitochondrial turnover and a minor compensatory increase in damage-induced MDVs. Therefore, these data suggest PINK1 and Parkin are dispensable for whole mitochondrial turnover, but following their perturbation have disparate effects on the MDV pathway.

Microgravity exposure affects both tissues and cells, and, in this regard, one of the most affected targets is the skeletal muscle system due to the significant loss of bone and muscle mass leading to osteoporosis and sarcopenia, respectively. Several efforts are underway to counteract the effects of microgravity, and recent studies on irisin, a myokine with anabolic effects on the musculoskeletal system, have shown promising results. Due to the practical challenges of conducting experiments in actual microgravity, different devices generating a simulated microgravity condition on Earth have been developed. Here, we exposed myoblasts, osteoblasts, osteocytes to a random position machine (RPM) for five days to assess microgravity effect on the expression of key differentiation factors in cells untreated or treated with irisin. In myoblasts (C2C12), exposure to RPM led to increased expression of early myogenesis maker genes Pax7 (p = 0.0016), Myf5 (p = 0.0005) and MyoD (p = 0.0009). Irisin treatment in the last 8 h of RPM cultures prevented these increases by returning Pax7 (p = 0.0008) and MyoD (p = 0.01) to control values, and only partially Myf5. In bone cells, exposure to RPM for 5 days showed no effect in osteoblasts (MC3T3) but decreased the expression of Pdpn (p = 0.0285) and Dmp-1 (p = 0.0423) genes in osteocytes (MLO-Y4). Irisin treatment completely prevented the decline in Pdpn (p = 0.293) and Dmp-1 (p = 0.0339) levels. Overall, our data showed that the impact of RPM exposure keeps myoblasts and osteocytes in a proliferative state, and irisin treatment restores them to their baseline biological condition, suggesting that irisin can counteract the changes induced by simulated microgravity.