Expression Profiles of Fatty Acid Transporters and the Role of n-3 and n-6 Polyunsaturated Fatty Acids in the Porcine Endometrium.

Fatty acids (FAs) are important for cell membrane composition, eicosanoid synthesis, and metabolic processes. Membrane proteins that facilitate FA transport into cells include FA translocase (also known as CD36) and FA transporter proteins (encoded by SLC27A genes). The present study aimed to examine expression profiles of FA transporters in the endometrium of cyclic and early pregnant gilts on days 3 to 20 after estrus and the possible regulation by conceptus signals and polyunsaturated FAs (PUFAs). The effect of PUFAs on prostaglandin (PG) synthesis and transcript abundance of genes related to FA action and metabolism, angiogenesis, and immune response was also determined. Day after estrus and reproductive status of animals affected FA transporter expression, with greater levels of CD36, SLC27A1, and SLC27A4 observed in pregnant than in cyclic gilts. Conceptus-conditioned medium and/or estradiol-17ß stimulated SLC27A1 and CD36 expression. Among PUFAs, linoleic acid decreased SLC27A1 and SLC27A6 mRNA expression, while arachidonic, docosahexaenoic, and eicosapentaenoic acids increased SLC27A4 transcript abundance. Moreover, arachidonic acid stimulated ACOX1, CPT1A, and IL1B expression and increased PGE2 and PGI2 secretion. In turn, α-linolenic acid up-regulated VEGFA, FGF2, FABP4, and PPARG mRNA expression. These results indicate the presence of an active transport of FAs in the porcine endometrium and the role of PUFAs as modulators of the uterine activity during conceptus implantation.

[Preparation and preliminary identification of Fc-silent anti-human CD36 chimeric antibody].

Objective To prepare a Fc-silent chimeric antibody against human CD36 and analyse its bioactivity and phagocytic effect on CD36(+) platelets. Methods The genes encoding VH and VL fragments of the monoclonal antibody (mAb) 32-106 were obtained through RNA extraction from hybridoma cell lines, PCR amplification and sequence analysis. By using gene synthesis and recombination techniques, the vectors expressing light and heavy chains of the chimeric antibody against human CD36 were constructed. Stable cell lines secreting the chimeric antibody were established by selective culture using Zeocin and Blasticidin. Antibodies were purified by an affinity chromatography column. The purity and molecular weight of the chimeric antibody were detected by SDS-PAGE. The activity of the antibody binding to CD36 antigen was determined by ELISA and flow cytometry. The ability of the chimeric antibody to participate in CD36(+) platelet phagocytosis was analyzed by a platelet phagocytosis assay. Results The vectors expressing light and heavy chains of chimeric antibody were successfully constructed. After co-transfection into HEK293 cells, stable cell lines secreting chimeric antibody were obtained by screening and cloning. The high purity and correct molecular weight of the chimeric antibody were confirmed by protein silver staining. The results of Flow cytometry and ELISA showed that the chimeric antibody had the activity of binding to human CD36 antigen. Platelet phagocytosis assay showed that the Fc-silent chimeric antibody against human CD36 basically lost the ability of mediating monocyte phagocytosis of CD36(+) platelets. Conclusion In this study, the Fc-silent chimeric antibody against human CD36 was successfully prepared, and its loss of ability to mediate CD36(+) platelet clearance was confirmed in vitro, which provides a preliminary basis for the study of modified antibodies for the therapy of CD36-antibody-mediated fetal and neonatal alloimmune thrombocytopenia(FNAIT).

SPA Promotes Atherosclerosis Through Mediating Macrophage Foam Cell Formation-Brief Report.

BACKGROUND: Atherosclerosis is a progressive inflammatory disease in which macrophage foam cells play a central role in disease pathogenesis. SPA (surfactant protein A) is a lipid-associating protein involved with regulating macrophage function in various inflammatory diseases. However, the role of SPA in atherosclerosis and macrophage foam cell formation has not been investigated. METHODS: SPA expression was assessed in healthy and atherosclerotic human coronary arteries and the brachiocephalic arteries of wild-type or ApoE-deficient mice fed high-fat diets for 4 weeks. Hypercholesteremic wild-type and SPA-deficient mice fed a high-fat diet for 6 weeks were investigated for atherosclerotic lesions in vivo. In vitro experiments using RAW264.7 macrophages, primary resident peritoneal macrophages extracted from wild-type or SPA-deficient mice, and human monocyte-derived macrophages from the peripheral blood of healthy donors determined the functional effects of SPA in macrophage foam cell formation. RESULTS: SPA expression was increased in atherosclerotic lesions in humans and ApoE-deficient mice and in response to a proatherosclerotic stimulus in vitro. SPA deficiency reduced the lipid profiles induced by hypercholesterolemia, attenuated atherosclerosis, and reduced the number of lesion-associated macrophage foam cells. In vitro studies revealed that SPA deficiency reduced intracellular cholesterol accumulation and macrophage foam cell formation. Mechanistically, SPA deficiency dramatically downregulated the expression of scavenger receptor CD36 (cluster of differentiation antigen 36) cellular and lesional expression. Importantly, SPA also increased CD36 expression in human monocyte-derived macrophages. CONCLUSIONS: Our results elucidate that SPA is a novel factor promoting atherosclerosis development. SPA enhances macrophage foam cell formation and atherosclerosis by increasing scavenger receptor CD36 expression, leading to increasing cellular OxLDL influx.

METTL3-mediated m6A modification of CD36: Implications for glucose metabolism and inflammatory dysregulation in follicles of polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder that affects women of reproductive age and is characterized by menstrual irregularities, metabolic imbalances and infertility. The pathogenesis of PCOS is complex and not fully understood, and chronic inflammation and insulin resistance are implicated in its progression. In this study, we investigated the role of m6A methylation, an important epigenetic modification, in the pathogenesis of PCOS. Using methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq), we mapped the m6A methylation profile in granulosa cells from patients with PCOS and identified a significant regulatory effect on gene expression. CD36 is a novel m6A-regulated gene that may facilitate the progression of PCOS. We demonstrated that METTL3, an m6A methyltransferase, modulated CD36 expression and influenced glucose metabolism and inflammatory responses in PCOS. Employing KGN cells as a model of insulin resistance, we observed that CD36 knockdown ameliorated the impaired glucose uptake and significantly reduced the production of pro-inflammatory cytokines. These findings are consistent with the results of CD36 inhibition in a mouse model of PCOS, indicating a role of CD36 in modulating the disease phenotype. Our study delineates a previously unrecognized epigenetic mechanism involving m6A methylation in PCOS, highlighting the potential of targeting the METTL3-CD36 axis as a therapeutic strategy for managing ovarian inflammation and metabolic dysregulation in patients with PCOS.

SUN1 inhibits osteogenesis and promotes adipogenesis of human adipose-derived stem cells by regulating α-tubulin and CD36 expression.

Sad and UNC84 domain 1 (SUN1) is a kind of nuclear envelope protein with established involvement in cellular processes, including nuclear motility and meiosis. SUN1 plays an intriguing role in human adipose-derived stem cells (hASCs) differentiation; however, this role remains largely undefined. This study was undertaken to investigate the role of SUN1 in hASCs differentiation, as well as its underlying mechanisms. Employing siRNAs, we selectively downregulated SUN1 and CD36 expression. Microtubules were depolymerized using nocodazole, and PPARγ was activated using rosiglitazone. Western blotting was performed to quantify SUN1, PPARγ, α-tubulin, CD36, OPN, and adiponectin protein expression levels. Alkaline phosphatase and Oil red O staining were used to assess osteogenesis and adipogenesis, respectively. Downregulated SUN1 expression increased osteogenesis and decreased adipogenesis in hASCs, concomitant with upregulated α-tubulin expression and downregulated CD36 expression, alongside reduced nuclear localization of PPARγ. Microtubule depolymerization increased CD36 expression. Rescue experiments indicated that microtubule depolymerization counteracted the downregulated SUN1-induced phenotypic changes. This study demonstrates that SUN1 influences the differentiation of hASCs towards osteogenic and adipogenic lineages, indicating its essential role in cell fate.

Single-cell landscape of innate and acquired drug resistance in acute myeloid leukemia.

Deep single-cell multi-omic profiling offers a promising approach to understand and overcome drug resistance in relapsed or refractory (rr) acute myeloid leukemia (AML). Here, we combine single-cell ex vivo drug profiling (pharmacoscopy) with single-cell and bulk DNA, RNA, and protein analyses, alongside clinical data from 21 rrAML patients. Unsupervised data integration reveals reduced ex vivo response to the Bcl-2 inhibitor venetoclax (VEN) in patients treated with both a hypomethylating agent (HMA) and VEN, compared to those pre-exposed to chemotherapy or HMA alone. Integrative analysis identifies both known and unreported mechanisms of innate and treatment-related VEN resistance and suggests alternative treatments, like targeting increased proliferation with the PLK inhibitor volasertib. Additionally, high CD36 expression in VEN-resistant blasts associates with sensitivity to CD36-targeted antibody treatment ex vivo. This study demonstrates how single-cell multi-omic profiling can uncover drug resistance mechanisms and treatment vulnerabilities, providing a valuable resource for future AML research.

[The effect and mechanism of exposure to polystyrene nanoplastics on lipid metabolism in mice liver].

Objective: To investigate the effect and potential mechanism of exposure to 20 nm polystyrene nanoplastics (PS-NPs) on lipid metabolism in mice liver. Methods: An animal experimental model was designed, which was completed from September 2022 to July 2023 on the exposure omics platform of the School of Public Health at Capital Medical University and the Key Laboratory of Environment and Population Health at the Chinese Center for Disease Control and Prevention.1 mg/kg and 10 mg/kg PS-NPs tail vein mice exposure models were constructed. After exposure 7 d, serum was collected to measure the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and air flow assisted desorption electrospray ionization-mass spectrometry imaging (AFADESI-MSI) analysis were used to analyze the mRNA levels of fatty acid esterification related genes (Dgat1 and Dgat2) and lipid transport related genes (ApoB, Cd36, ApoE and Mttp) and metabolites' spatial changes in liver tissue. In vivo imaging system (IVIS) and tissue shake sections were employed to observe the fluorescence biological distribution of PS-NPs. t-test or one-way ANOVA was used to explore the difference between groups. Results: The serum ALT levels were (83.97±4.58), (91.17±13.69) and (142.43±6.09) U/L in the control group, 1 mg/kg PS-NPs exposure group and 10 mg/kg PS-NPs exposure group respectively (F=37.281, P<0.05). The relative mRNA levels of Dgat1, Dgat2, ApoB, Cd36 and ApoE were (1.49±0.63, 2.53±0.32, 2.45±0.54), (1.07±0.38, 1.86±0.83, 2.23±0.73), (1.01±0.13, 1.58±0.43, 2.03±0.52), (1.01±0.14, 1.55±0.37, 1.52±0.51), (1.01±0.17, 2.11±0.27, 2.39±0.93) in these three groups respectively. The differences were statistically significant (F=11.54, 6.95, 14.90, 5.98 and 14.68, P<0.05). AFADESI-MSI analysis found that PS-NPs exposure led to a significant decrease in the levels of glutarylcarnitine and O-Linoleoylcarnitine (t=4.12 and 3.35, P<0.05), which were associated with lipid beta oxidation. The content of triglycerides (TG) (m/z 921.726 4, t=8.69, P<0.05; m/z 919.711 4, t=3.20, P<0.05), phosphatidylic acid (PA) (m/z 895.712 3, t=3.60, P<0.05; m/z 821.526 6, t=3.36, P<0.05), lysophosphatidylcholine (LysoPC) (m/z 560.310 6, t=3.35, P<0.05; m/z 582.295 3, t=6.28, P<0.05), phosphatidylcholine (PC) (m/z 778.533 9, t=3.53, P<0.05; m/z 804.549 6, t=3.60, P<0.05; m/z 820.523 1, t=3.37, P<0.05), phosphatidylethanolamine (PE) (m/z 772.523 3, t=3.08, P<0.05) showed a significant increase in the PS-NPs exposure group. In vivo and in vitro imaging and in situ cell localization revealed that PS-NPs were mainly enriched in hepatic stellate cells and hepatic Kupffer cells in liver tissue. Conclusion: Exposure to PS-NPs induces disorder of liver lipid metabolism, which may be related to the accumulation of PS-NPs in hepatic stellate cells and hepatic Kupffer cells, providing basis for searching early biomarkers of PS-NPs exposure and further mechanism research.

Haplotypes analysis reveals the genetic basis of type I CD36 deficiency.

CD36, also known as glycoprotein IV, is classified into two distinct subgroups based on the presence or absence of its expression on monocytes. The CD36 gene spans approximately 50,000 base pairs. Historically, research has focused on identifying CD36 mutations through Sanger sequencing and next-generation sequencing (NGS), with limited exploration of haplotypes. In this study, we collected blood samples from donors with type I and type II CD36 deficiencies as well as from healthy controls, and employed single-molecule long-read sequencing (also known as Third-Generation Sequencing) of genomic DNA to analyze the genetic basis of CD36. The study identified 180 genetic variants, 12 of which were found to alter the amino acid sequence. Notably, four of these mutations (c.220 C > T; c.329_330delAC; c.430-1 G > C; c.1006 + 2 T > G) are premature termination mutations that lead to protein truncation. Using Fisher's exact test, we statistically analyzed a specific haplotype, c.-132A > C and c.329_330delAC, along with their clinical phenotypes, revealing a strong association between these variants in the 5' block and type I CD36 deficiency. We analyzed the CD36 gene sequences in platelet donors and patients with PTR (platelet transfusion refractoriness) and FNAIT (fetal and neonatal alloimmune thrombocytopenia), conducting a detailed haplotype analysis associated with type I CD36 deficiency and FNAIT.

Serum amyloid A1 induced dysfunction of airway macrophages via CD36 pathway in allergic airway inflammation.

Previous studies showed that serum amyloid A (SAA) and macrophages were associated with allergic airway inflammation. However, the interaction between SAA1 and macrophages in allergic airway inflammation remains to be further elucidated. In this study, the levels of SAA1 were measured in nasal tissues from patients with eosinophilic chronic rhinosinusitis with nasal polyps (CRSwNP), house dust mite (HDM)-treated BEAS-2B cells and the tissues of mice of HDM-induced allergic airway inflammation. Human monocytes-derived macrophages and mouse bone marrow-derived macrophages (BMDMs) were exposed to SAA1, and CCL17 and the other M1/M2-related factors were evaluated using RT-PCR and/or ELISA. To test the effects of SAA1-treated BMDMs on chemotaxis and differentiation of CD4+ T cells, number of migrated cells and the levels of Th1 and Th2 were measured using flow cytometry. SAA1 receptors were examined in BMDMs and lung macrophages of model mice. CD36 neutralizing antibody was applied to explore the mechanisms of SAA1 in regulating BMDMs using RT-PCR and/or ELISA. We found that SAA1 was expressed in epithelial cells, and was increased in the nasal tissues of patients with eosinophilic CRSwNP and HDM-treated BEAS-2B- cells as well as the bronchoalveolar lavage fluid and lung tissues of mice exposed to HDM. We also found that the level of CCL17 was increased in M2 macrophages, more CD4+ T cells were recruited and proportion of Th2 was increased after the treatment of SAA1. The treatment of CD36 neutralizing antibody decreased CCL17 level in SAA1-treated M2 BMDMs. In summary, our results showed that SAA1 was increased in allergic airway inflammation, and the administration of SAA1 upregulated the expression of CCL17 in M2 macrophages via CD36 and promoted the chemotaxis of CD4+ T cells and differentiation of Th2. It may provide a new therapeutic strategy that could mediate allergic airway inflammation via suppressing SAA1 to reduce recruitment of CD4+ T cells and activation of Th2.

Interleukin-34-orchestrated tumor-associated macrophage reprogramming is required for tumor immune escape driven by p53 inactivation.

As the most frequent genetic alteration in cancer, more than half of human cancers have p53 mutations that cause transcriptional inactivation. However, how p53 modulates the immune landscape to create a niche for immune escape remains elusive. We found that cancer stem cells (CSCs) established an interleukin-34 (IL-34)-orchestrated niche to promote tumorigenesis in p53-inactivated liver cancer. Mechanistically, we discovered that Il34 is a gene transcriptionally repressed by p53, and p53 loss resulted in IL-34 secretion by CSCs. IL-34 induced CD36-mediated elevations in fatty acid oxidative metabolism to drive M2-like polarization of foam-like tumor-associated macrophages (TAMs). These IL-34-orchestrated TAMs suppressed CD8+ T cell-mediated antitumor immunity to promote immune escape. Blockade of the IL-34-CD36 axis elicited antitumor immunity and synergized with anti-PD-1 immunotherapy, leading to a complete response. Our findings reveal the underlying mechanism of p53 modulation of the tumor immune microenvironment and provide a potential target for immunotherapy of cancer with p53 inactivation.

FABP4 facilitates epithelial-mesenchymal transition via elevating CD36 expression in glioma cells.

Glioblastoma multiforme (GBM) is the most aggressive brain tumor with poor prognosis. A better understanding of mechanisms concerned in glioma invasion might be critical for treatment optimization. Given that epithelial-mesenchymal transition in tumor cells is closely associated with glioma progression and recurrence, identifying pivotal mediators in GBM EMT process is urgently needed. As a member of Fatty acid binding protein (FABP) family, FABP4 serves as chaperones for free fatty acids and participates in cellular process including fatty acid uptake, transport, and metabolism. In this study, our data revealed that FABP4 expression was elevated in human GBM samples and correlated with a mesenchymal glioma subtype. Gain of function and loss of function experiments indicated that FABP4 potently rendered glioma cells increased filopodia formation and cell invasiveness. Differential expression genes analysis and GSEA in TCGA dataset revealed an EMT-related molecular signature in FABP4-mediated signaling pathways. Cell interaction analysis suggested CD36 as a potential target regulated by FABP4. Furthermore, in vitro mechanistic experiments demonstrated that FABP4-induced CD36 expression promoted EMT via non-canonical TGFß pathways. An intracranial glioma model was constructed to assess the effect of FABP4 on tumor progression in vivo. Together, our findings demonstrated a critical role for FABP4 in the regulation invasion and EMT in GBM, and suggest that pharmacological inhibition of FABP4 may represent a promising therapeutic strategy for treatment of GBM.

Glucagon-like peptide-1 analog, liraglutide, regulates Sertoli cell energy metabolism.

Liraglutide, an analog of the incretin hormone glucagon-like peptide 1 (GLP-1), is widely used for obesity and type 2 diabetes treatment. However, there is scarce information about its effects on testicular function. Within the testis, Sertoli cells (SCs) provide nutritional support for germ cells; they metabolize glucose to lactate, which is delivered to germ cells to be used as a preferred energy substrate. Besides, SCs use fatty acids (FAs) as an energy source and store them as triacylglycerols (TAGs) within lipid droplets (LDs), which serve as an important energy reserve. In the present study, 20-day-old rat SC cultures were used to assess whether liraglutide affects their metabolic functions related to nutritional support and lipid storage. The results show that liraglutide does not modify glucose consumption or lactate production. However, it increases TAG levels and LD content. These effects are accompanied by an increase in the mRNA levels of the fatty acid transporter FAT/CD36, glycerol-3-phosphate-acyltransferase 3, and perilipins 1 and 4. The participation of the cAMP/PKA signaling pathway was explored. We observed that H89 (a PKA inhibitor) decreases the LD upregulation elicited by liraglutide, and that dibutyryl cAMP increases LD content and the expression of related genes. In summary, liraglutide promotes lipid storage in SCs through the regulation of key regulatory genes involved in FA transport, TAG synthesis, and LD formation. Considering the importance of lipid storage in SC energetic homeostasis maintenance, we postulate that liraglutide might improve the overall energetic status of the seminiferous tubule.

Eicosatrienoic acid inhibits estradiol synthesis through the CD36/FOXO1/CYP19A1 signaling pathway to improve PCOS in mice.

Polycystic ovary syndrome (PCOS) is a common metabolic and endocrine disorder characterized by abnormal elevation in hormone levels, with currently lacking effective treatment options. N-3 polyunsaturated fatty acids (PUFA) have broad pharmacological activity and play a beneficial role in the development of PCOS. In this study, we observed that n-3 PUFA-eicosatrienoic acid (ETA) improves the estrous cycle and ovarian morphology in dehydroepiandrosterone (DHEA)-induced PCOS mice, particularly serum hormone levels. Additionally, it suppresses the expression of CYP19A1 and E2 synthesis in human granulosa-like tumor cell line (KGN) cells. Further investigation revealed that ETA significantly upregulates the expression of CD36, cAMP, P-PKA, and FOXO1 in KGN cells and mouse ovaries to lower E2 levels. This conclusion was supported by inhibiting CD36 and FOXO1 at both the mouse and cellular levels. Additionally, ETA treatment decreased the expression of ESR1, Kiss1, Gnrh in the hypothalamus, and GnRHR, Lhß, Egr1, Pitx1, Sf1 in the pituitary of PCOS mice. No differences were observed after ETA treatment in the CD36 and FOXO1 inhibitor groups, indicating that ETA improves PCOS mice by regulating the hypothalamic-pituitary axis through E2 synthesis inhibition. In summary, we have elucidated for the first time the mechanism by which CD36 regulates E2 synthesis in ovarian granulosa cells and demonstrated that ETA activates the CD36 receptor to inhibit E2 synthesis through the cAMP/PKA/FOXO1/CYP19A1 signaling pathway, thereby improving hormonal imbalance and treating PCOS. This provides a new strategy for the effective prevention and treatment of PCOS.

Glucose-Dependent Insulinotropic Polypeptide Inhibits AGE-Induced NADPH Oxidase-Derived Oxidative Stress Generation and Foam Cell Formation in Macrophages Partly via AMPK Activation.

Glucose-dependent insulinotropic polypeptide (GIP) of the incretin group has been shown to exert pleiotropic actions. There is growing evidence that advanced glycation end products (AGEs), senescent macromolecules formed at an accelerated rate under chronic hyperglycemic conditions, play a role in the pathogenesis of atherosclerotic cardiovascular disease in diabetes. However, whether and how GIP could inhibit the AGE-induced foam cell formation of macrophages, an initial step of atherosclerosis remains to be elucidated. In this study, we address these issues. We found that AGEs increased oxidized low-density-lipoprotein uptake into reactive oxygen species (ROS) generation and Cdk5 and CD36 gene expressions in human U937 macrophages, all of which were significantly blocked by [D-Ala2]GIP(1-42) or an inhibitor of NADPH oxidase activity. An inhibitor of AMP-activated protein kinase (AMPK) attenuated all of the beneficial effects of [D-Ala2]GIP(1-42) on AGE-exposed U937 macrophages, whereas an activator of AMPK mimicked the effects of [D-Ala2]GIP(1-42) on foam cell formation, ROS generation, and Cdk5 and CD36 gene expressions in macrophages. The present study suggests that [D-Ala2]GIP(1-42) could inhibit the AGE-RAGE-induced, NADPH oxidase-derived oxidative stress generation in U937 macrophages via AMPK activation and subsequently suppress macrophage foam cell formation by reducing the Cdk5-CD36 pathway.

Loss of embryonically-derived Kupffer cells during hypercholesterolemia accelerates atherosclerosis development.

Hypercholesterolemia is a major risk factor for atherosclerosis and associated cardiovascular diseases. The liver plays a key role in the regulation of plasma cholesterol levels and hosts a large population of tissue-resident macrophages known as Kupffer cells (KCs). KCs are located in the hepatic sinusoids where they ensure key functions including blood immune surveillance. However, how KCs homeostasis is affected by the build-up of cholesterol-rich lipoproteins that occurs in the circulation during hypercholesterolemia remains unknown. Here, we show that embryo-derived KCs (EmKCs) accumulate large amounts of lipoprotein-derived cholesterol, in part through the scavenger receptor CD36, and massively expand early after the induction of hypercholesterolemia. After this rapid adaptive response, EmKCs exhibit mitochondrial oxidative stress and their numbers gradually diminish while monocyte-derived KCs (MoKCs) with reduced cholesterol-loading capacities seed the KC pool. Decreased proportion of EmKCs in the KC pool enhances liver cholesterol content and exacerbates hypercholesterolemia, leading to accelerated atherosclerotic plaque development. Together, our data reveal that KC homeostasis is perturbed during hypercholesterolemia, which in turn alters the control of plasma cholesterol levels and increases atherosclerosis.

The senescent marker p16INK4a enhances macrophage foam cells formation.

BACKGROUND: The senescence marker p16INK4a, which constitutes part of the genome 9p21.3 cardiovascular disease (CVD) risk allele, is believed to play a role in foam cells formation. This study aims to unravel the role of p16INK4a in mediating macrophage foam cells formation, cellular senescence, and autophagy lysosomal functions. METHODS: The mammalian expression plasmid pCMV-p16INK4a was used to induce p16INK4a overexpression in THP-1 macrophages. Next, wild-type and p16INK4a-overexpressed macrophages were incubated with oxidized LDL to induce foam cells formation. Lipids accumulation was evaluated using Oil-red-O staining and cholesterol efflux assay, as well as expression of scavenger receptors CD36 and LOX-1. Cellular senescence in macrophage foam cells were determined through analysis of senescence-associated ß-galactosidase activity and other SASP factors expression. Meanwhile, autophagy induction was assessed through detection of autophagosome formation and LC3B/p62 markers expression. RESULTS: The findings showed that p16INK4a enhanced foam cells formation with increased scavenger receptors CD36 and LOX-1 expression and reduced cholesterol efflux in THP-1 macrophages. Besides, ß-galactosidase activity was enhanced, and SASP factors such as IL-1α, TNF-α, and MMP9 were up-regulated. In addition, p16INK4a is also shown to induce autophagy, as well as increasing autophagy markers LC3B and p62 expression. CONCLUSIONS: This study provides insights on p16INK4a in mediating macrophages foam cells formation, cellular senescence, and foam cells formation.

CD36-mediated ferroptosis destabilizes CD4+ T cell homeostasis in acute Stanford type-A aortic dissection.

Acute type A aortic dissection (ATAAD) is a lethal pathological process within the aorta with high mortality and morbidity. T lymphocytes are perturbed and implicated in the clinical outcome of ATAAD, but the exact characteristics of T cell phenotype and its underlying mechanisms in ATAAD remain poorly understood. Here we report that CD4+ T cells from ATAAD patients presented with a hypofunctional phenotype that was correlated with poor outcomes. Whole transcriptome profiles showed that ferroptosis and lipid binding pathways were enriched in CD4+ T cells. Inhibiting ferroptosis or reducing intrinsic reactive oxygen species limited CD4+ T cell dysfunction. Mechanistically, CD36 was elevated in CD4+ T cells, whose blockade effectively alleviated palmitic acid-induced ferroptosis and CD4+ T cell hypofunction. Therefore, targeting the CD36-ferroptosis pathway to restore the functions of CD4+ T cells is a promising therapeutic strategy to improve clinical outcomes in ATAAD patients.

Lipolysis engages CD36 to promote ZBP1-mediated necroptosis-impairing lung regeneration in COPD.

Lung parenchyma destruction represents a severe condition commonly found in chronic obstructive pulmonary disease (COPD), a leading cause of morbidity and mortality worldwide. Promoting lung regeneration is crucial for achieving clinical improvement. However, no therapeutic drugs are approved to improve the regeneration capacity due to incomplete understanding of the underlying pathogenic mechanisms. Here, we identify a positive feedback loop formed between adipose triglyceride lipase (ATGL)-mediated lipolysis and overexpression of CD36 specific to lung epithelial cells, contributing to disease progression. Genetic deletion of CD36 in lung epithelial cells and pharmacological inhibition of either ATGL or CD36 effectively reduce COPD pathogenesis and promote lung regeneration in mice. Mechanistically, disruption of the ATGL-CD36 loop rescues Z-DNA binding protein 1 (ZBP1)-induced cell necroptosis and restores WNT/ß-catenin signaling. Thus, we uncover a crosstalk between lipolysis and lung epithelial cells, suggesting the regenerative potential for therapeutic intervention by targeting the ATGL-CD36-ZBP1 axis in COPD.

Enhanced ECCD36 signaling promotes skeletal muscle insulin resistance in female mice.

Consumption of a Western diet (WD) increases CD36 expression in vascular, hepatic, and skeletal muscle tissues promoting lipid metabolic disorders and insulin resistance. We further examined the role of endothelial cell-specific CD36 (ECCD36) signaling in contributing to skeletal muscle lipid metabolic disorders, insulin resistance, and their underlying molecular mechanisms. Female ECCD36 wild-type (ECCD36+/+) and knock-out (ECCD36-/-) mice, aged 6 wk, were provided with either a WD or a standard chow diet for a duration of 16 wk. ECCD36+/+ WD mice were characterized by elevated fasting plasma glucose and insulin levels, increased homeostatic model assessment for insulin resistance, and glucose intolerance that was blunted in ECCD36-/- mice. Improved insulin sensitivity in ECCD36-/- mice was characterized by increased phosphoinositide 3-kinases/protein kinase B signaling that further augmented glucose transporter type 4 expression and glucose uptake. Meanwhile, 16 wk of WD feeding also increased skeletal muscle free fatty acid (FFA) and lipid accumulation, without any observed changes in plasma FFA levels. These lipid metabolic disorders were blunted in ECCD36-/- mice. Moreover, ECCD36 also mediated in vitro palmitic acid-induced lipid accumulation in cultured ECs, subsequently leading to the release of FFAs into the culture media. Furthermore, consumption of a WD increased FFA oxidation, mitochondrial dysfunction, impaired mitochondrial respiratory, skeletal muscle fiber type transition, and fibrosis. These WD-induced abnormalities were blunted in ECCD36-/- mice. These findings demonstrate that endothelial-specific ECCD36 signaling participates in skeletal muscle FFA uptake, ectopic lipid accumulation, mitochondrial dysfunction, insulin resistance, and associated skeletal muscle dysfunction in diet-induced obesity.NEW & NOTEWORTHY ECCD36 exerts "extra endothelial cell" actions in skeletal muscle insulin resistance. ECCD36 is a major mediator of Western diet-induced lipid metabolic disorders and insulin resistance in skeletal muscle. Mitochondrial dysfunction is associated with diet-induced CD36 activation and related skeletal muscle insulin resistance.

A novel peptide encoded by circ-SLC9A6 promotes lipid dyshomeostasis through the regulation of H4K16ac-mediated CD36 transcription in NAFLD.

BACKGROUND: As the leading cause of end-stage liver disease, nonalcoholic fatty liver disease (NAFLD) is mainly induced by lipid dyshomeostasis. The translation of endogenous circular RNAs (circRNAs) is closely related to the progression of various diseases, but the involvement of circRNAs in NAFLD has not been determined. METHODS: Combined high-throughput circRNA profiles were used to identify circRNAs with translational potential. The underlying molecular mechanisms were investigated by RNA sequencing, pull-down/MS and site-specific mutagenesis. RESULTS: In this study, we focused on circ-SLC9A6, an abnormally highly expressed circRNA in human and mouse liver tissue during NAFLD development that exacerbates metabolic dyshomeostasis in hepatocytes by encoding a novel peptide called SLC9A6-126aa in vivo and in vitro. YTHDF2-mediated degradation of m6A-modified circ-SLC9A6 was found to be essential for the regulation of SLC9A6-126aa expression. We further found that the phosphorylation of SLC9A6-126aa by AKT was crucial for its cytoplasmic localization and the maintenance of physiological homeostasis, whereas high-fat stress induced substantial translocation of unphosphorylated SLC9A6-126aa to the nucleus, resulting in a vicious cycle of lipid metabolic dysfunction. Nuclear SLC9A6-126aa promotes transcriptional activation of the target gene CD36 and enhances its occupancy of the CD36 promoter locus by regulating MOF-mediated histone H4K16 acetylation. Hepatic CD36 depletion significantly ameliorated hyperactivated MAPK signalling and lipid disturbance in SLC9A6-126aa transgenic mice. Clinically, increasing levels of SLC9A6-126aa were observed during NAFLD progression and were found to be positively correlated with the CD36 and MAPK cascades. CONCLUSION: This study revealed the role of circ-SLC9A6-derived SLC9A6-126aa in the epigenetic modification-mediated regulation of lipid metabolism. Our findings may provide promising therapeutic targets for NAFLD and new insights into the pathological mechanisms of metabolic diseases. HIGHLIGHTS: Under normal circumstances, driven by m6A modification, YTHDF2 directly recognizes and degrades circ-SLC9A6, thereby inhibiting the translation of SLC9A6-126aa. Additionally, AKT1 phosphorylates and inhibits the nuclear translocation of SLC9A6-126aa. In NAFLD, lipid overload leads to YTHDF2 and AKT1 deficiency, ultimately increasing the expression and nuclear import of SLC9A6-126aa. Nuclear SLC9A6-126aa binds directly to the CD36 promoter and initiates CD36 transcription, which induces lipid dyshomeostasis.