Cholesterol restricts lymphotoxin β receptor-triggered NF-κB signaling

Comprehensive analysis reveals that LTBR is a immune-related biomarker for glioma

Glioma is a common malignant brain tumor with great heterogeneity and huge difference in clinical outcomes. Although lymphotoxin (LT) beta receptor (LTBR) has been linked to immune system and response development for decades, the expression and function in glioma have not been investigated. To confirm the expression profile of LTBR, integrated RNA-seq data from glioma and normal brain tissues were analyzed. Functional enrichment analysis, TMEscore analysis, immune infiltration, the correlation of LTBR with immune checkpoints and ferroptosis, and scRNAseq data analysis in gliomas were in turn performed, which pointed out that LTBR was pertinent to immune functions of macrophages in gliomas. In addition, after being trained and validated in the tissue samples of the integrated dataset, an LTBR DNA methylation-based prediction model succeeded to distinguish gliomas from non-gliomas, as well as the grades of glioma. Moreover, by virtue of the candidate LTBR CpG sites, a prognostic risk-score model was finally constructed to guide the chemotherapy, radiotherapy, and immunotherapy for glioma patients. Taken together, LTBR is closely correlated with immune functions in gliomas, and LTBR DNA methylation could serve as a biomarker for diagnosis and prognosis of gliomas.

Systematic analysis of the prognostic value and immunological function of LTBR in human cancer

Lymphotoxin beta receptor (LTBR) is a positive T cell proliferation regulator gene. It is closely associated with the tumor immune microenvironment. However, its role in cancer and immunotherapy is unclear. Firstly, the expression level and prognostic value of LTBR were analyzed. Secondly, the expression of LTBR in clinical stages, immune subtypes, and molecular subtypes was analyzed. The correlation between LTBR and immune regulatory genes, immune checkpoint genes, and RNA modification genes was then analyzed. Correlations between LTBR and immune cells, scores, cancer-related functional status, tumor stemness index, mismatch repair (MMR) genes, and DNA methyltransferase were also analyzed. In addition, we analyzed the role of LTBR in DNA methylation, mutational status, tumor mutation burden (TMB), and microsatellite instability (MSI). Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) were used to explore the role of LTBR in pan-cancer. Finally, the drugs associated with LTBR were analyzed. The expression of LTBR was confirmed using quantitative real-time PCR and Western blot. LTBR is significantly overexpressed in most cancers and is associated with low patient survival. In addition, LTBR expression was strongly correlated with immune cells, score, cancer-related functional status, tumor stemness index, MMR genes, DNA methyltransferase, DNA methylation, mutational status, TMB, and MSI. Enrichment analysis revealed that LTBR was associated with apoptosis, necroptosis, and immune-related pathways. Finally, multiple drugs targeting LTBR were identified. LTBR is overexpressed in several tumors and is associated with a poor prognosis. It is related to immune-related genes and immune cell infiltration.

Membrane contact sites orchestrate cholesterol homeostasis that is central to vascular aging

Chronological age causes structural and functional vascular deterioration and is a well-established risk factor for the development of cardiovascular diseases, leading to more than 40% of all deaths in the elderly. The etiology of vascular aging is complex; a significant impact arises from impaired cholesterol homeostasis. Cholesterol level is balanced through synthesis, uptake, transport, and esterification, the processes executed by multiple organelles. Moreover, organelles responsible for cholesterol homeostasis are spatially and functionally coordinated instead of isolated by forming the membrane contact sites. Membrane contact, mediated by specific protein-protein interaction, pulls opposing organelles together and creates the hybrid place for cholesterol transfer and further signaling. The membrane contact-dependent cholesterol transfer, together with the vesicular transport, maintains cholesterol homeostasis and has intimate implications in a growing list of diseases, including vascular aging-related diseases. Here, we summarized the latest advances regarding cholesterol homeostasis by highlighting the membrane contact-based regulatory mechanism. We also describe the downstream signaling under cholesterol homeostasis perturbations, prominently in cholesterol-rich conditions, stimulating age-dependent organelle dysfunction and vascular aging. Finally, we discuss potential cholesterol-targeting strategies for therapists regarding vascular aging-related diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology.

Silencing of TRAF5 enhances necroptosis in hepatocellular carcinoma by inhibiting LTBR-mediated NF-κB signaling

Background

Hepatocellular carcinoma (HCC) is a common malignancy with poor prognosis and high mortality. This study aimed to explore the oncogenic mechanisms of TRAF5 in HCC and provide a novel therapeutic strategy for HCC.

Methods

Human HCC cell lines (HepG2, HuH7, SMMC-LM3, and Hep3B), normal adult liver epithelial cells (THLE-2), and human embryonic kidney cells (HEK293T) were utilized. Cell transfection was performed for functional investigation. qRT-PCR and western blotting were used to detect mRNA expression of TRAF5, LTBR, and NF-κB and protein expression of TRAF5, p-RIP1(S166)/RIP1, p-MLKL(S345)/MLKL, LTBR, and p-NF-κB/NF-κB. Cell viability, proliferation, migration, and invasion were evaluated using CCK-8, colony formation, wound healing, and Transwell assays. Cell survival, necrosis, and apoptosis were assessed using flow cytometry and Hoechst 33342/PI double staining. Co-immunoprecipitation and immunofluorescence were performed to determine the interaction between TRAF5 and LTBR. A xenograft model was established to validate the role of TRAF5 in HCC.

Results

TRAF5 knockdown inhibited HCC cell viability, colony formation, migration, invasion, and survival but enhanced necroptosis. Additionally, TRAF5 is correlated with LTBR and TRAF5 silencing down-regulated LTBR in HCC cells. LTBR knockdown inhibited HCC cell viability, while LTBR overexpression eliminated the effects of TRAF5 deficiency on inhibiting HCC cell proliferation, migration, invasion, and survival. LTBR overexpression abolished the promotive function of TRAF5 knockdown on cell necroptosis. LTBR overexpression undid the suppressive effect of TRAF5 knockdown on NF-κB signaling in HCC cells. Moreover, TRAF5 knockdown suppressed xenograft tumor growth, inhibited cell proliferation, and promoted tumor cell apoptosis.

Conclusions

TRAF5 deficiency facilitates necroptosis in HCC by suppressing LTBR-mediated NF-κB signaling.

Integrative Analysis of Bioinformatics and Machine Learning Algorithms Identifies a Novel Diagnostic Model Based on Costimulatory Molecule for Predicting Immune Microenvironment Status in Lung Adenocarcinoma

Costimulatory molecules are an indispensable signal for activating immune cells. However, the features of many costimulatory molecule genes (CMGs) in lung adenocarcinoma (LUAD) are poorly understood. This study systematically explored expression patterns of CMGs in the tumor immune microenvironment (TIME) status of patients with LUAD. Their expression profiles were downloaded from The Cancer Genome Atlas and the Gene Expression Omnibus databases. Two robust TIME subtypes ("hot" and "cold") were classified by K-means clustering and estimation of stromal and immune cells in malignant tumor tissues using expression data. The "hot" subtype presented higher infiltration in activated immune cells and enrichments in the immune cell receptor signaling pathway and adaptive immune response. Three CMGs (CD80, LTB, and TNFSF8) were screened as final diagnostic markers by means of Least Absolute Shrinkage Selection Operator and Support Vector Machine-Recursive Feature Elimination algorithms. Accordingly, the diagnostic nomogram for predicting individualized TIME status showed satisfactory diagnostic accuracy in The Cancer Genome Atlas training cohort as well as GSE31210 and GSE180347 validation cohorts. Immunohistochemistry staining of 16 specimens revealed an apparently positive correlation between the expression of CMG biomarkers and pathologic response to immunotherapy. Thus, this diagnostic nomogram provided individualized predictions in TIME status of LUAD patients with good predictive accuracy, which could serve as a potential tool for identifying ideal candidates for immunotherapy.

CREB1 Transcriptionally Activates LTBR to Promote the NF-κB Pathway and Apoptosis in Lung Epithelial Cells

Bronchopulmonary dysplasia (BPD) is a prevalent chronic pediatric lung disease. Aberrant proliferation and apoptosis of lung epithelial cells are important in the pathogenesis of BPD. Lymphotoxin beta receptor (LTBR) is expressed in lung epithelial cells. Blocking LTBR induces regeneration of lung tissue and reverts airway fibrosis in young and aged mice. This study is aimed at revealing the role of LTBR in BPD. A mouse model of BPD and two in vitro models of BPD using A549 cells and type II alveolar epithelial (ATII) cells were established by exposure to hyperoxia. We found that LTBR and CREB1 exhibited a significant upregulation in lungs of mouse model of BPD. LTBR and CREB1 expression were also increased by hyperoxia in A549 and ATII cells. According to results of cell counting kit-8 assay and flow cytometry analysis, silencing of LTBR rescued the suppressive effect of hyperoxia on cell viability and its promotive effect on cell apoptosis of A549 and ATII cells. Bioinformatics revealed CREB1 as a transcriptional factor for LTBR, and the luciferase reporter assay and ChIP assay subsequently confirmed it. The NF-κB pathway was regulated by LTBR. CREB1 induced LTBR expression at the transcriptional level to regulate NF-κB pathway and further modulate A549 and ATII cells viability and apoptosis. In conclusion, this study revealed the CREB1/LTBR/NF-κB pathway in BPD and supported the beneficial role of LTBR silence in BPD by promoting viability and decreasing apoptosis of lung epithelial cells.

Trametenolic Acid Ameliorates the Progression of Diabetic Nephropathy in db/db Mice via Nrf2/HO-1 and NF-κB-Mediated Pathways

Diabetic nephropathy (DN) is a fatal complication of diabetes and the main cause of end-stage renal disease. Due to the suboptimal effects of current treatments, there is an urgent need to develop new therapeutic strategies for DN. Trametenolic acid (TA), a lanostane-type tetracyclic triterpenoid, is one of the main active ingredients extracted from the natural product Inonotus obliquus. Our study was aimed at clarifying the potential protective effects of TA on DN and its underlying mechanism. In this research, C57BLKS/db (db/db) mice were used as the spontaneous DN model, and TA (10 mg/kg/d) was intraperitoneally injected for 4 consecutive weeks. Ratio of right kidney weight/body weight was calculated, and the contents of serum creatinine (Scr), blood urea nitrogen (BUN), and urine albumin were detected. The activities of superoxide dismutase (SOD) and catalase (CAT) and the contents of reductive glutathione (GSH) and malondialdehyde (MDA) were measured. The histopathological changes of renal tissues were observed by hematoxylin and eosin (HE), periodic acid-Schiff (PAS), and Masson staining. The protein expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), NAD(P)H:quinone oxidoreductase-1 (NQO-1), nuclear factor kappa B (NF-κB), proinflammation cytokine tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), Nephrin, and Podocin were detected by western blot assay. Immunohistochemistry was utilized to detect expressions of collagen III (COL-III) and fibronectin (FN). Our results showed that TA administration significantly reduced the ratio of right kidney weight/body weight, BUN, Scr, and urine albumin levels and alleviated the histopathological changes of DN mice. Moreover, TA administration remarkably increased GSH content and SOD and CAT activities and decreased MDA content. Western blot assay demonstrated that TA activated Nrf2 signaling and increased the expression of downstream antioxidant enzymes HO-1 and NQO-1. Further studies illustrated that NF-κB signaling was inhibited, and downstream proinflammation cytokine expressions of TNF-α, IL-6, and IL-1β were also downregulated. In addition, we also found that TA administration significantly increased the expression of nephrin and podocin proteins and reduced the protein expression of COL-III and FN. These findings suggested that TA exhibited a renoprotective effect by ameliorating oxidative stress and inflammation via Nrf2/HO-1 and NF-κB signaling pathways.

Asiaticoside ameliorates osteoarthritis progression through activation of Nrf2/HO-1 and inhibition of the NF-κB pathway

Osteoarthritis has become the fourth cause of disability in the world and its occurrence and development are caused by apoptosis and extracellular matrix (ECM) degradation of chondrocytes. Asiaticoside (ASI) is a triterpene saponin compound obtained from Centella Asiatica and has anti-inflammatory and anti-apoptotic effects in various diseases. However, its effects on OA are not clear. In this study, we reported that ASI has a protective effect on the occurrence and progression of OA in vivo and in vitro, and demonstrated its potential molecular mechanism. In vitro, ASI treatment inhibited the release of pro-apoptotic factors induced by TBHP and promoted the release of the anti-apoptotic proteins. In addition, ASI promotes the expression of Aggrecan and Collagen II, while inhibiting the expression of thrombospondin motifs 5 (ADAMTS5) and matrix metalloproteinase-13 (MMP-13), which causes extracellular matrix (ECM) degradation. Mechanistically, ASI exerts its anti-apoptotic effect by activating the Nrf2/HO-1 pathway and preventing p65 from binding to DNA. Similarly, in vivo, ASI has been shown to have a protective effect in a mouse OA model. The conclusion is that our research shows that ASI can be used as a potential drug for the treatment of OA.

TRPV6 Regulation by Cis-22a and Cholesterol

The highly calcium-selective transient receptor potential vanilloid-type channel TRPV6 is important for epithelial Ca²⁺ transport. Proper regulation of the inherently constitutively active TRPV6 channels is intricate in preserving Ca²⁺ homeostasis, whereby structural and functional data suggest that lipids hold an essential role. Altered expression levels or specific TRPV6 mutations may lead to diseases, hence, TRPV6 represents an interesting target for pharmacological modulation. Recent cryo-EM data identified that the specific TRPV6 blocker cis-22a binds, apart from the pore, to a site within the tetrameric channel that largely matches a lipid binding pocket, LBS-2. Therein, cis-22a may replace a lipid such as cholesterol that is bound in the open state. Based on site-directed mutagenesis and functional recordings, we identified and characterized a series of residues within LBS-2 that are essential for TRPV6 inhibition by cis-22a. Additionally, we investigated the modulatory potential of diverse cholesterol depletion efforts on TRPV6 activity. While LBS-2 mutants exhibited altered maximum currents, slow Ca²⁺-dependent inactivation (SCDI) as well as less inhibition by cis-22a, TRPV6 activity was resistant to cholesterol depletion. Hence, lipids other than cholesterol may predominate TRPV6 regulation when the channel is expressed in HEK293 cells.

Effects of Statins on Renin-Angiotensin System

Statins, a class of drugs for lowering serum LDL-cholesterol, have attracted attention because of their wide range of pleiotropic effects. An important but often neglected effect of statins is their role in the renin–angiotensin system (RAS) pathway. This pathway plays an integral role in the progression of several diseases including hypertension, heart failure, and renal disease. In this paper, the role of statins in the blockade of different components of this pathway and the underlying mechanisms are reviewed and new therapeutic possibilities of statins are suggested.

Dimethyl fumarate improves cognitive deficits in chronic cerebral hypoperfusion rats by alleviating inflammation, oxidative stress, and ferroptosis via NRF2/ARE/NF-κB signal pathway

Cerebrovascular disease and its risk factors cause persistent decrease of cerebral blood flow, chronic cerebral hypoperfusion (CCH) is the major foundation of vascular cognitive impairment (VCI). The hippocampus is extremely vulnerable to cerebral ischemia and hypoxia. Oxidative stress and neuroinflammation injury are important pathophysiological mechanisms of this process, which is closely related to hippocampal neurons damage and loss. Dimethyl fumarate (DMF), an FDA-approved therapeutic for multiple sclerosis (MS), plays a protective role in multiple neurological disorders. Studies have shown that DMF exerts anti-inflammatory and antioxidant effects via the NRF2/ARE/NF-κB signaling pathway. Thus, this study aimed to evaluate the neuroprotective effect of DMF in the CCH rat model. Ferroptosis, a novel defined iron-dependent cell death form, were found to be strongly associated with the pathophysiology of CCH. Emerging evidences have shown that inhibition of ferroptosis by targeting NRF2 exerted neuroprotective effect in neurodegeneration diseases. We also investigated whether DMF can alleviate cognitive deficits through inhibition of ferroptosis by the NRF2 signaling pathway in this study. DMF was intragastric for consecutive five weeks (100 mg/kg/day). Then behavior test and histological, molecular, and biochemical analysis were performed. We found that DMF treatment significantly improved cognitive deficits and partially reversed hippocampus neuronal damage and loss caused by CCH. And DMF treatment decreased hippocampus IL-1β, TNF-α, and IL-6 pro-inflammatory cytokines concentration, and mediated the NF-κB signaling pathway. And DMF also alleviated hippocampus oxidative stress through reducing MDA, and increasing GSH and SOD levels, which are also closely associated with ferroptosis. Besides, DMF treatment reduced the expression of PTGS2, and increased the expression of FTH1 and xCT, and the iron content is also reduced, which were the important features related to ferroptosis. Furthermore, DMF activated the NRF2/ARE signaling pathway and upregulated the expression of HO-1, NQO1 and GPX4. These outcomes indicated that DMF can improve cognitive impairment in rats with CCH, possibly through alleviating neuroinflammation, oxidative stress damage and inhibiting ferroptosis of hippocampal neurons. Overall, our results provide new evidence for the neuroprotective role of DMF.

LTβR Signaling Controls Lymphatic Migration of Immune Cells

The pleiotropic functions of lymphotoxin (LT)β receptor (LTβR) signaling are linked to the control of secondary lymphoid organ development and structural maintenance, inflammatory or autoimmune disorders, and carcinogenesis. Recently, LTβR signaling in endothelial cells has been revealed to regulate immune cell migration. Signaling through LTβR is comprised of both the canonical and non-canonical-nuclear factor κB (NF-κB) pathways, which induce chemokines, cytokines, and cell adhesion molecules. Here, we focus on the novel functions of LTβR signaling in lymphatic endothelial cells for migration of regulatory T cells (Tregs), and specific targeting of LTβR signaling for potential therapeutics in transplantation and cancer patient survival.

Bioinformatics analysis of common key genes and pathways of intracranial, abdominal, and thoracic aneurysms

Background

Aneurysm is a severe and fatal disease. This study aims to comprehensively identify the highly conservative co-expression modules and hub genes in the abdominal aortic aneurysm (AAA), thoracic aortic aneurysm (TAA) and intracranial aneurysm (ICA) and facilitate the discovery of pathogenesis for aneurysm.

Methods

GSE57691, GSE122897, and GSE5180 microarray datasets were downloaded from the Gene Expression Omnibus database. We selected highly conservative modules using weighted gene co‑expression network analysis before performing the Gene Ontology, Kyoto Encyclopedia of Genes and Genomes pathway and Reactome enrichment analysis. The protein–protein interaction (PPI) network and the miRNA-hub genes network were constructed. Furtherly, we validated the preservation of hub genes in three other datasets.

Results

Two modules with 193 genes and 159 genes were identified as well preserved in AAA, TAA, and ICA. The enrichment analysis identified that these genes were involved in several biological processes such as positive regulation of cytosolic calcium ion concentration, hemostasis, and regulation of secretion by cells. Ten highly connected PPI networks were constructed, and 55 hub genes were identified. In the miRNA-hub genes network, CCR7 was the most connected gene, followed by TNF and CXCR4. The most connected miRNAs were hsa-mir-26b-5p and hsa-mir-335-5p. The hub gene module was proved to be preserved in all three datasets.

Conclusions

Our study highlighted and validated two highly conservative co-expression modules and miRNA-hub genes network in three kinds of aneurysms, which may promote understanding of the aneurysm and provide potential therapeutic targets and biomarkers of aneurysm.

Clathrin- and dynamin-dependent endocytosis limits canonical NF-κB signaling triggered by lymphotoxin β receptor

Background

Lymphotoxin β receptor (LTβR) is a member of tumor necrosis factor receptor (TNFR) superfamily which regulates the immune response. At the cellular level, upon ligand binding, the receptor activates the pro-inflammatory NF-κB and AP-1 pathways. Yet, the intracellular distribution of LTβR, the routes of its endocytosis and their connection to the signaling activation are not characterized. Here, we investigated the contribution of LTβR internalization to its signaling potential.

Methods

Intracellular localization of LTβR in unstimulated and stimulated cells was analyzed by confocal microscopy. Endocytosis impairment was achieved through siRNA- or CRISPR/Cas9-mediated depletion, or chemical inhibition of proteins regulating endocytic routes. The activation of LTβR-induced signaling was examined. The levels of effector proteins of the canonical and non-canonical branches of the NF-κB pathway, and the phosphorylation of JNK, Akt, ERK1/2, STAT1 and STAT3 involved in diverse signaling cascades, were measured by Western blotting. A transcriptional response to LTβR stimulation was assessed by qRT-PCR analysis.

Results

We demonstrated that LTβR was predominantly present on endocytic vesicles and the Golgi apparatus. The ligand-bound pool of the receptor localized to endosomes and was trafficked towards lysosomes for degradation. Depletion of regulators of different endocytic routes (clathrin-mediated, dynamin-dependent or clathrin-independent) resulted in the impairment of LTβR internalization, indicating that this receptor uses multiple entry pathways. Cells deprived of clathrin and dynamins exhibited enhanced activation of canonical NF-κB signaling represented by increased degradation of IκBα inhibitor and elevated expression of LTβR target genes. We also demonstrated that clathrin and dynamin deficiency reduced to some extent LTβR-triggered activation of the non-canonical branch of the NF-κB pathway.

Conclusions

Our work shows that the impairment of clathrin- and dynamin-dependent internalization amplifies a cellular response to LTβR stimulation. We postulate that receptor internalization restricts responsiveness of the cell to subthreshold stimuli.

Lipid metabolism in astrocytic structure and function

Astrocytes are the most abundant glial cell in the central nervous system and are involved in multiple processes including metabolic homeostasis, blood brain barrier regulation and neuronal crosstalk. Astrocytes are the main storage point of glycogen in the brain and it is well established that astrocyte uptake of glutamate and release of lactate prevents neuronal excitability and supports neuronal metabolic function. However, the role of lipid metabolism in astrocytes in relation to neuronal support has been until recently, unclear. Lipids play a fundamental role in astrocyte function, including energy generation, membrane fluidity and cell to cell signaling. There is now emerging evidence that astrocyte storage of lipids in droplets has a crucial physiological and protective role in the central nervous system. This pathway links β-oxidation in astrocytes to inflammation, signalling, oxidative stress and mitochondrial energy generation in neurons. Disruption in lipid metabolism, structure and signalling in astrocytes can lead to pathogenic mechanisms associated with a range of neurological disorders.

Akebia Saponin D ameliorated kidney injury and exerted anti-inflammatory and anti-apoptotic effects in diabetic nephropathy by activation of NRF2/HO-1 and inhibition of NF-KB pathway

Diabetic nephropathy (DN), a common microvascular complication of type 2 diabetes mellitus (T2DM), causes increasing mortality and morbidity due to its high prevalence and severe consequences. Hence, it is urgent to search for effective agents that provide new insights into novel molecular therapeutic targets for DN. This study was designed to investigate the critical role of Akebia saponin D (ASD) in kidney damage, inflammation and apoptosis of renal tubular cells in DN. To probe the protective effects of ASD on DN in vivo, diabetes mellitus model was established by intraperitoneal (ip) injection of STZ (60 mg/kg) for 5 days consecutively. Besides, HG-induced human renal tubular cells (HK-2) were used to analyze the defined effects and underlying mechanism of ASD on DN in vitro. Blood glucose, insulin, serum creatinine (Scr), blood urea nitrogen (BUN), renal injury, inflammation, oxidative stress and apoptosis of renal tubular cells were respectively measured and evaluated. ASD prevented kidney damage, improved renal function and inflammatory reaction, ameliorated oxidative stress and inhibited apoptosis of renal tubular cells in DN mice via activation of NRF2/HO-1 pathway and inhibition of NF-KB pathway.

Akebia Saponin D suppresses inflammation in chondrocytes via the NRF2/HO-1/NF-κB axis and ameliorates osteoarthritis in mice

Akebia Saponin D promotes the translocation of NRF2 into nucleus, activates NRF2/HO-1 pathway and inhibits NF-κB pathway in chondrocytes, and ultimately alleviates osteoarthritis development.