MCT1-governed pyruvate metabolism is essential for antibody class-switch recombination through H3K27 acetylation.

Monocarboxylate transporter 1 (MCT1) exhibits essential roles in cellular metabolism and energy supply. Although MCT1 is highly expressed in activated B cells, it is not clear how MCT1-governed monocarboxylates transportation is functionally coupled to antibody production during the glucose metabolism. Here, we report that B cell-lineage deficiency of MCT1 significantly influences the class-switch recombination (CSR), rendering impaired IgG antibody responses in Mct1f/fMb1Cre mice after immunization. Metabolic flux reveals that glucose metabolism is significantly reprogrammed from glycolysis to oxidative phosphorylation in Mct1-deficient B cells upon activation. Consistently, activation-induced cytidine deaminase (AID), is severely suppressed in Mct1-deficient B cells due to the decreased level of pyruvate metabolite. Mechanistically, MCT1 is required to maintain the optimal concentration of pyruvate to secure the sufficient acetylation of H3K27 for the elevated transcription of AID in activated B cells. Clinically, we found that MCT1 expression levels are significantly upregulated in systemic lupus erythematosus patients, and Mct1 deficiency can alleviate the symptoms of bm12-induced murine lupus model. Collectively, these results demonstrate that MCT1-mediated pyruvate metabolism is required for IgG antibody CSR through an epigenetic dependent AID transcription, revealing MCT1 as a potential target for vaccine development and SLE disease treatment.

Magnifying image-enhanced endoscopy-only mode boosted early cancer diagnostic efficiency: a multicenter randomized controlled trial.

BACKGROUND AND AIMS: Magnifying image-enhanced endoscopy (MIEE) is an advanced endoscopy with image enhancement and magnification used in preoperative examination. However, its impact on the detection rate is unknown. METHODS: We conducted an open-label, randomized, parallel (1:1:1), controlled trial in 6 hospitals in China. Patients were recruited between February 14, 2022 and July 30, 2022. Eligible patients were aged ≥18 years and undergoing gastroscopy in outpatient departments. Participants were randomly assigned to the MIEE-only mode (o-MIEE) group, white-light endoscopy-only mode (o-WLE) group, and MIEE when necessary mode (n-MIEE) group (initial WLE followed by switching to another endoscope with MIEE if necessary). Biopsy sampling of suspicious lesions of the lesser curvature of the gastric antrum was performed. Primary and secondary aims were to compare detection rates and positive predictive value (PPV) of early cancer and precancerous lesions in these 3 modes, respectively. RESULTS: A total of 5100 recruited patients were randomly assigned to the o-MIEE (n = 1700), o-WLE (n = 1700), and n-MIEE (n = 1700) groups. In the o-MIEE, o-WLE, and n-MIEE groups, 29 (1.51%; 95% confidence interval [CI], 1.05-2.16), 4 (.21%; 95% CI, .08-.54), and 8 (.43%; 95% CI, .22-.85) early cancers were found, respectively (P < .001). The PPV for early cancer was higher in the o-MIEE group compared with the o-WLE and n-MIEE groups (63.04%, 33.33%, and 38.1%, respectively; P = .062). The same trend was seen for precancerous lesions (36.67%, 10.00%, and 21.74%, respectively). CONCLUSIONS: The o-MIEE mode resulted in a significant improvement in diagnosing early upper GI cancer and precancerous lesions; thus, it could be used for opportunistic screening. (Clinical trial registration number: ChiCTR2200064174.).

Embigin facilitates monocarboxylate transporter 1 localization to the plasma membrane and transition to a decoupling state.

Cell-surface ancillary glycoproteins basigin or embigin form heterodimeric complexes with proton-coupled monocarboxylate transporters (MCTs), facilitating the membrane trafficking of MCTs and regulating their transport activities. Here, we determine the cryoelectron microscopy (cryo-EM) structure of the human MCT1-embigin complex and observe that embigin forms extensive interactions with MCT1 to facilitate its localization to the plasma membrane. In addition, the formation of the heterodimer effectively blocks MCT1 from forming a homodimer through a steric hindrance effect, releasing the coupling between two signature motifs and driving a significant conformation change in transmembrane helix 5 (TM5) of MCTs. Consequently, the substrate-binding pocket alternates between states of homodimeric coupling and heterodimeric decoupling states and exhibits differences in substrate-binding affinity, supporting the hypothesis that the substrate-induced motion originating in one subunit of the MCT dimer could be transmitted to the adjacent subunit to alter its substrate-binding affinity.

Ablation of Proton/Glucose Exporter SLC45A2 Enhances Melanosomal Glycolysis to Inhibit Melanin Biosynthesis and Promote Melanoma Metastasis.

Sequence variation in SLC45A2 are responsible for oculocutaneous albinism type 4 in many species and are associated with melanoma susceptibility, but the molecular mechanism is unclear. In this study, we used Slc45a2-deficient melanocyte and mouse models to elucidate the roles of SLC45A2 in melanogenesis and melanoma metastasis. We found that the acidified cellular environment impairs the activity of key melanogenic enzyme tyrosinase in Slc45a2-deficient melanocytes. SLC45A2 is identified as a proton/glucose exporter in melanosomes, and its ablation increases the acidification of melanosomal pH through enhanced glycolysis. Intriguingly, 13C-glucose-labeled metabolic flux and biochemical assays show that melanosomes are active glucose-metabolizing organelles, indicating that elevated glycolysis mainly occurs in melanosomes owing to Slc45a2 deficiency. Moreover, Slc45a2 deficiency significantly upregulates the activities of glycolytic enzymes and phosphatidylinositol 3-kinase/protein kinase B signaling to promote glycolysis-dependent survival and metastasis of melanoma cells. Collectively, our study reveals that the proton/glucose exporter SLC45A2 mediates melanin synthesis and melanoma metastasis primarily by modulating melanosomal glucose metabolism.

Spatial distribution, geochemical behaviors and risk assessment of antimony in rivers around the antimony mine of Xikuangshan, Hunan Province, China.

Pollutants derived from antimony (Sb) mining can easily cause pollution of surrounding water bodies. However, qualitative source analysis of river pollution is mostly conducted, and quantitative source analysis is still lacking. A total of 21 water samples were collected to analyze the pollution status of the heavy metal element Sb, explore the Xikuangshan (XKS) area river heavy metals pollution mechanism, undertake quantitative analysis of the sources of pollution, and carry out irrigation water suitability assessment and potential ecological risk assessment. The results showed that, compared with the mining non-affected area, the maximum excess multiple of Sb in surface water and rivers in Hunan XKS area is 411.31. When the river fluid flows through the mining-affected area, the heavy metal element Sb content increases rapidly, and then decreases due to dilution process. Positive matrix factorization (PMF) source analysis showed that the main source of Sb pollution in the rivers is the impact of mining and smelting (83.60%), followed by the role of waste rock leaching (16.40%). After irrigation, 27.78% of the river water had strong ecological risks, and 16.67% had extremely strong ecological risks. This achievement provides a theoretical basis and technical guarantee for protecting and using the local water body of the mining area.

Amino Acid Solute Carrier Transporters in Inflammation and Autoimmunity.

The past decade exposed the importance of many homeostasis and metabolism related proteins in autoimmunity disease and inflammation. Solute carriers (SLCs) are a group of membrane channels that can transport amino acids, the building blocks of proteins, nutrients, and neurotransmitters. This review summarizes the role of SLCs amino acid transporters in inflammation and autoimmunity disease. In detail, the importance of Glutamate transporters SLC1A1, SLC1A2, and SLC1A3, mainly expressed in the brain where they help prevent glutamate excitotoxicity, is discussed in the context of central nervous system disorders such as multiple sclerosis. Similarly, the cationic amino acid transporter SLC7A1 (CAT1), which is an important arginine transporter for T cells, and SLC7A2 (CAT2), essential for innate immunity. SLC3 family proteins, which bind with light chains from the SLC7 family (SLC7A5, SLC7A7 and SLC7A11) to form heteromeric amino acid transporters, are also explored to describe their roles in T cells, NK cells, macrophages and tumor immunotherapies. Altogether, the link between SLC amino acid transporters with inflammation and autoimmunity may contribute to a better understanding of underlying mechanism of disease and provide novel potential therapeutic avenues. Significance Statement SIGNIFICANCE STATEMENT In this review, we summarize the link between SLC amino acid transporters and inflammation and immune responses, specially SLC1 family members and SLC7 members. Studying the link may contribute to a better understanding of related diseases and provide potential therapeutic targets and useful to the researchers who have interest in the involvement of amino acids in immunity.

[Mechanism of histone deacetylase inhibitor tubastatin A promoting autophagy of Legionella pneumophila infected RAW264.7 cells].

Objective To investigate the role of HDAC6 in the interference of Legionella pneumophila on the autophagy of macrophages and its mechanism. Methods RAW264.7 macrophages were treated with 10 µmol/L, 5 µmol/L, and 2.5 µmol/L tubastatin A (TubA). CCK-8 assay was used to detect the proliferative activity of RAW264.7 macrophages, and the half maximal inhibitory concentration (IC50) of TubA was determined. A model of RAW264.7 macrophages infected with Legionella pneumophila was established and divided into TubA free groups (further divided into cell control group, inactivated bacteria group, and live bacteria group) and TubA treatment groups (10 µmol/L, 5 µmol/L, 2.5 µmol/L, each further divided into cell control group, inactivated bacteria group, and live bacteria group). The cells were collected at 6, 12, 24, and 48 h after Legionella pneumophila infection. The bacterial proliferation assay was conducted to detect the proliferation of Legionella pneumophila in RAW264.7 macrophages; RAW264.7 macrophages were transfected with pmCherry-C1-EGFP-LC3B plasmid to detect autophagic flux changes in each group; real-time quantitative PCR and Western blot were used respectively to detect the mRNA and protein expression levels of histone deacetylase 6 (HDAC6), sequestosome 1(SQSTM1/P62), microtubule associated protein 1 light chain 3 (LC3), α-tubulin, valosin containing protein (p97/VCP), heat shock protein 90 (HSP90), HSP70, heat shock transcription factor 1 (HSF1), and filamentous actin (F-actin). Results IC50 of TubA was 50 µmol/L. Compared with those in the RAW264.7 normal control group, the proliferation of Legionella pneumophila in mouse macrophages was significantly reduced after the addition of TubA. In the groups without the HDAC6 inhibitor, the live bacteria group had a stronger inhibiting effect on autophagic flux than the inactivated bacteria group compared with the normal control group. In the TubA groups with the HDAC6 inhibitor, the green fluorescence bright spots decreased and the autophagic flux increased in the live bacteria group. After the RAW264.7 macrophages were treated with inactivated and live Legionella pneumophila for 6, 12, 24, and 48 h, the mRNA and protein expression levels of HDAC6, α-tubulin, p97-VCP, and P62 decreased in the TubA group interfered with the Legionella pneumophila compared with the RAW264.7 normal control group. Conclusion The interference of Legionella pneumophila on the autophagy of macrophages is associated with the signal pathways of HDAC6/P62/LC3B and HDAC6/p97/HSF1.

Overexpression of FcγRIIB regulates downstream protein phosphorylation and suppresses B cell activation to ameliorate systemic lupus erythematosus.

The present study aimed to examine the effects of FcγRIIB on systemic lupus erythematosus (SLE) and to investigate the underlying mechanisms. For this purpose, lentiviral vector carrying the membrane­bound type FcγRIIB gene (mFcγRIIB lentivirus) and soluble FcγRIIB (sFcγRIIB) protein were used to treat B cells from patients with SLE. The B cells were treated with calf thymus DNA (ctDNA) and anti­calf thymus DNA­immune complexes (anti­ctDNA­IC). mFcγRIIB lentivirus and sFcγRIIB protein were also injected into MRL/lpr SLE mice. The results revealed that anti­ctDNA­IC treatment significantly downregulated the IgG antibody secretion of B cells treated with mFcγRIIB lentivirus. mFcγRIIB and sFcγRIIB decreased the phosphorylation level of Bruton's tyrosine kinase (BTK) in B cells, and increased the phosphorylation level of Lyn proto­oncogene (Lyn), docking protein 1 (DOK1) and inositol polyphosphate­5­phosphatase D (SHIP). mFcγRIIB promoted the apoptosis of B cells. Following the treatment of MRL/lpr SLE mice with mFcγRIIB lentivirus, the levels of urinary protein, serum anti­nuclear and anti­dsDNA antibodies were decreased, while the levels of mFcγRIIB in B cells were increased. mFcγRIIB ameliorated the pathologies of the kidneys, liver and lymph node tissues of the MRL/lpr SLE mice. Following treatment of the MRL/lpr SLE mice with sFcγRIIB, the levels of urinary protein, serum anti­dsDNA antibody and BTK and SHIP phosphorylation levels in B cells were decreased, while the serum sFcγRIIB and sFcγRIIB­IgG levels were increased. On the whole, the findings of the present study demonstrate that recombinant FcγRIIB inhibits the secretion of IgG antibody by B cells from patients with SLE, ameliorates the symptoms of SLE in mice, and alters the phosphorylation levels of downstream proteins of the FcγRIIB signaling pathway in B cells. These results suggest that FcγRIIB may play preventive and therapeutic roles in SLE by inhibiting B cell activation via the FcγRIIB signaling pathway, which provides a novel theory and strategy for the prevention and treatment of SLE.

[Legionella pneumophila activates Nrf2-Keap1 pathway to inhibit autophagy of mouse RAW264.7 macrophages].

Objective To investigate the effect of Legionella pneumophila (LP) on the autophagy flux of RAW264.7 macrophages and explore the molecular mechanism of the expression changes of autophagy-related factors. Methods Live LP and inactivated LP (MOI=10, 50, 100) were separately used to affect RAW264.7 for 1, 2 and 3 hours so as to screen the optimum condition of LP infection. The optimal condition for LP infection was MOI=50 and the infection time was 2 hours. After affected by rapamycin (RAPA) for 12 hours, RAW264.7 cells were then treated by live and inactivated LP for another 2 hours. Normal control group, RAPA group, live LP group, inactivated LP group, RAPA-treated live LP group, RAPA-treated inactivated LP group were designed. The pmCherry-C1-EGFP-LC3B double fluorescent labeling protein method was used to monitor the changes of autophagy flux. The relevant factor CLN3, histone deacetylase 6 (HDAC6), regulator of G protein signaling 19 (RGS19), tumor necrosis factor (TNF), cathepsin B (CTSB), GABA type A receptor associated protein like 2 (GABARAPL2), P62, microtubule-related protein 1 light chain 3 (LC3) were screened by gene array analysis. In order to validate the results of gene array, real-time quantitative PCR (RT-qPCR) was used to detect the mRNA levels of nuclear factor erythroid derived 2 like 2 (Nrf2), beclin1 and kelch like ECH associated protein 1 (Keap1); Western blot analysis was performed to measure the protein levels of Nrf2, beclin1 and Keap1. Results Both the live LP group and the inactivated LP group inhibited the autophagy flux compared with the normal control group and the RAPA group. Gene array analysis showed that in the live LP and inactivated LP groups, LC3 expression was down-regulated and P62 expression was up-regulated. The results of RT-qPCR and Western blot analysis were consistent with the gene array. The mRNA and protein levels of Keap1, beclin1, and Nrf2 significantly decreased, while the mRNA and protein levels of Nrf2 significantly increased. Conclusion LP can inhibit the autophagy of macrophage via activating Nrf2-Keap1 signaling pathway.