The Ca2+ sensor STIM1 regulates the type I interferon response by retaining the signaling adaptor STING at the endoplasmic reticulum.

Stimulator of interferon genes (STING) is an endoplasmic reticulum (ER) signaling adaptor that is essential for the type I interferon response to DNA pathogens. Aberrant activation of STING is linked to the pathology of autoimmune and autoinflammatory diseases. The rate-limiting step for the activation of STING is its translocation from the ER to the ER-Golgi intermediate compartment. Here, we found that deficiency in the Ca2+ sensor stromal interaction molecule 1 (STIM1) caused spontaneous activation of STING and enhanced expression of type I interferons under resting conditions in mice and a patient with combined immunodeficiency. Mechanistically, STIM1 associated with STING to retain it in the ER membrane, and coexpression of full-length STIM1 or a STING-interacting fragment of STIM1 suppressed the function of dominant STING mutants that cause autoinflammatory diseases. Furthermore, deficiency in STIM1 strongly enhanced the expression of type I interferons after viral infection and prevented the lethality of infection with a DNA virus in vivo. This work delineates a STIM1-STING circuit that maintains the resting state of the STING pathway.

Ca2+ Signaling Augmented by ORAI1 Trafficking Regulates the Pathogenic State of Effector T Cells.

Activation of the Ca2+ release-activated Ca2+ (CRAC) channel is crucial for T cell functions. It was recently shown that naked cuticle homolog 2 (NKD2), a signaling adaptor molecule, orchestrates trafficking of ORAI1, a pore subunit of the CRAC channels, to the plasma membrane for sustained activation of the CRAC channels. However, the physiological role of sustained Ca2+ entry via ORAI1 trafficking remains poorly understood. Using NKD2 as a molecular handle, we show that ORAI1 trafficking is crucial for sustained Ca2+ entry and cytokine production, especially in inflammatory Th1 and Th17 cells. We find that murine T cells cultured under pathogenic Th17-polarizing conditions have higher Ca2+ levels that are NKD2-dependent than those under nonpathogenic conditions. In vivo, deletion of Nkd2 alleviated clinical symptoms of experimental autoimmune encephalomyelitis in mice by selectively decreasing effector T cell responses in the CNS. Furthermore, we observed a strong correlation between NKD2 expression and proinflammatory cytokine production in effector T cells. Taken together, our findings suggest that the pathogenic effector T cell response demands sustained Ca2+ entry supported by ORAI1 trafficking.

SARS-CoV-2 spike protein promotes inflammatory cytokine activation and aggravates rheumatoid arthritis.

BACKGROUND: Coronavirus disease 2019 (COVID-19) induces inflammation, autoantibody production, and thrombosis, which are common symptoms of autoimmune diseases, including rheumatoid arthritis (RA). However, the effect of COVID-19 on autoimmune disease is not yet fully understood. METHODS: This study was performed to investigate the effects of COVID-19 on the development and progression of RA using a collagen-induced arthritis (CIA) animal model. Human fibroblast-like synoviocytes (FLS) were transduced with lentivirus carrying the SARS-CoV-2 spike protein gene in vitro, and the levels of inflammatory cytokine and chemokine expression were measured. For in vivo experiments, CIA mice were injected with the gene encoding SARS-CoV-2 spike protein, and disease severity, levels of autoantibodies, thrombotic factors, and inflammatory cytokine and chemokine expression were assessed. In the in vitro experiments, the levels of inflammatory cytokine and chemokine expression were significantly increased by overexpression of SARS-CoV-2 spike protein in human FLS. RESULTS: The incidence and severity of RA in CIA mice were slightly increased by SARS-CoV-2 spike protein in vivo. In addition, the levels of autoantibodies and thrombotic factors, such as anti-CXC chemokine ligand 4 (CXCL4, also called PF4) antibodies and anti-phospholipid antibodies were significantly increased by SARS-CoV-2 spike protein. Furthermore, tissue destruction and inflammatory cytokine level in joint tissue were markedly increased in CIA mice by SARS-CoV-2 spike protein. CONCLUSIONS: The results of the present study suggested that COVID-19 accelerates the development and progression of RA by increasing inflammation, autoantibody production, and thrombosis. Video Abstract.

Lactobacillus acidophilus and propionate attenuate Sjögren's syndrome by modulating the STIM1-STING signaling pathway.

BACKGROUND: Sjögren's syndrome (SS) is an autoimmune disease characterized by inflammation of the exocrine gland. An imbalance of gut microbiota has been linked to SS. However, the molecular mechanism is unclear. We investigated the effects of Lactobacillus acidophilus (L. acidophilus) and propionate on the development and progression of SS in mouse model. METHODS: We compared the gut microbiomes of young and old mice. We administered L. acidophilus and propionate up to 24 weeks. The saliva flow rate and the histopathology of the salivary glands were investigated, and the effects of propionate on the STIM1-STING signaling pathway were evaluated in vitro. RESULTS: Lactobacillaceae and Lactobacillus were decreased in aged mice. SS symptoms were ameliorated by L. acidophilus. The abundance of propionate-producing bacterial was increased by L. acidophilus. Propionate ameliorated the development and progression of SS by inhibiting the STIM1-STING signaling pathway. CONCLUSIONS: The findings suggest that Lactobacillus acidophilus and propionate have therapeutic potential for SS. Video Abstract.

Effect of IL-10-producing B cells in peripheral blood and tumor tissue on gastric cancer.

BACKGROUND: Interleukin (IL)-10-producing B (B10) cells are generated in response to signals from the tumor microenvironment and promote tumor growth by interacting with B10 cells. We investigated the distributions of immune cells in peripheral blood and tumor tissue samples from patients with gastric cancer (GC). METHODS: Patients with GC who underwent radical gastrectomy in Seoul St. Mary's Hospital between August 2020 and May 2021 were enrolled in this study. Forty-two samples of peripheral blood were collected, and a pair of gastric mucosal samples (normal and cancerous mucosa; did not influence tumor diagnosis or staging) was collected from each patient after surgery. B10 cells in peripheral blood and cancer mucosa samples were investigated by flow cytometry and immunofluorescence. AGS cells, gastric cancer cell line, were cultured with IL-10 and measured cell death and cytokine secretion. Also, AGS cells were co-cultured with CD19 + B cells and measured cytokine secretion. RESULTS: The population of B10 cells was significantly larger in the blood of patients with GC compared with controls. In confocal images of gastric mucosal tissues, cancerous mucosa contained more B10 cells than normal mucosa. The population of B10 cells in cancerous mucosa increased with cancer stage. When AGS cells were cultured under cell-death conditions, cellular necrosis was significantly decreased, and proliferation was increased, for 1 day after IL-10 stimulation. Tumor necrosis factor (TNF)-α, IL-8, IL-1ß, and vascular endothelial growth factor secretion by cancer cells was significantly increased by coculture of AGS cells with GC-derived CD19+ B cells. CONCLUSIONS: B cells may be one of the populations that promote carcinogenesis by inducing the production of inflammatory mediators, such as IL-10, in GC. Targeting B10 cells activity could improve the outcomes of antitumor immunotherapy. Video Abstract.

Inner-Membrane-Bound Gold Nanoparticles as Efficient Electron Transfer Mediators for Enhanced Mitochondrial Electron Transport Chain Activity.

Electron transfer through the mitochondrial electron transport chain (ETC) can be critically blocked by the dysfunction of protein complexes. Redox-active molecules have been used to mediate the electron transfer in place of the dysfunctional complexes; however, they are limited to replacing complex I and are known to be toxic. Here we report artificial mitochondrial electron transfer pathways that enhance ETC activity by exploiting inner-membrane-bound gold nanoparticles (GNPs) as efficient electron transfer mediators. The hybridization of mitochondria with GNPs, driven by electrostatic interaction, is successfully visualized in real time at the level of a single mitochondrion. By observing quantized quenching dips via plasmon resonance energy transfer, we reveal that the hybridized GNPs are bound to the inner membrane of mitochondria irrespective of the presence of the outer membrane. The ETC activity of mitochondria with GNPs such as membrane potential, oxygen consumption, and ATP production is remarkably increased in vitro.

Tripartite motif-containing protein 32 regulates Ca2+ movement in skeletal muscle.

Mutations in tripartite motif-containing protein 32 (TRIM32), especially in NHL repeats, have been found in skeletal muscle in patients with type 2H limb-girdle muscular dystrophy (LGMD2H). However, the roles of the NHL repeats of TRIM32 in skeletal muscle functions have not been well addressed. In the present study, to examine the functional role(s) of the TRIM32 NHL repeats in skeletal muscle, TRIM32-binding proteins in skeletal muscle were first searched using a binding assay and MALDI-TOF/TOF. Sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 1a (SERCA1a) was found to be a TRIM32-binding protein. Next, a deletion mutant of TRIM32 missing the NHL repeats (NHL-Del) was expressed in mouse primary skeletal myotubes during myoblast differentiation into myotubes. Ca2+ movement in the myotubes was examined using single-cell Ca2+ imaging. Unlike wild-type (WT) TRIM32, NHL-Del did not enhance the amount of Ca2+ release from the sarcoplasmic reticulum (SR), Ca2+ release for excitation-contraction (EC) coupling, or extracellular Ca2+ entry via store-operated Ca2+ entry (SOCE). In addition, even compared with the vector control, NHL-Del resulted in reduced SOCE due to reduced expression of extracellular Ca2+ entry channels. Transmission electron microscopy (TEM) observation of the myotubes revealed that NHL-Del induced the formation of abnormal vacuoles and tubular structures in the cytosol. Therefore, by binding to SERCA1a via its NHL repeats, TRIM32 may participate in the regulation of Ca2+ movement for skeletal muscle contraction and the formation of cellular vacuoles and tubular structures in skeletal muscle. Functional defects in TRIM32 due to mutations in NHL repeats may be pathogenic toward LGMD2H.

FK506 and Lactobacillus acidophilus ameliorate acute graft-versus-host disease by modulating the T helper 17/regulatory T-cell balance.

BACKGROUND: Graft-versus-host disease (GvHD) is a critical complication after allogeneic hematopoietic stem cell transplantation (HSCT). The immunosuppressants given to patients undergoing allogeneic HSCT disturb the microbiome and the host immune system, potentially leading to dysbiosis and inflammation, and may affect immune function and bone marrow transplantation. The intestinal microbiome is a target for the development of novel therapies for GvHD. Lactobacillus species are widely used supplements to induce production of antimicrobial and anti-inflammatory factors. METHODS: We determined the effect of the combination of Lactobacillus acidophilus and FK506 on GvHD following major histocompatibility complex-mismatched bone marrow transplantation. RESULTS: The combination treatment suppressed IFN-γ and IL-17-producing T cell differentiation, but increased Foxp3+Treg differentiation and IL-10 production. Also, the combination treatment and combination treated-induced Treg cells modulated the proliferation of murine alloreactive T cells in vitro. Additionally, the combination treatment upregulated Treg-related genes-Nt5e, Foxp3, Ikzf2, Nrp1 and Itgb8-in murine CD4+-T cells. The combination treatment also alleviated GvHD clinically and histopathologically by controlling the effector T cell and Treg balance in vivo. Moreover, the combination treatment decreased Th17 differentiation significantly and significantly upregulated Foxp3 and IL-10 expression in peripheral blood mononuclear cells from healthy controls and liver transplantation (LT) patients. CONCLUSIONS: Therefore, the combination of L. acidophilus and FK506 is effective and safe for patients undergoing allogeneic hematopoietic stem cell transplantation.

Soluble CCR2 gene therapy controls joint inflammation, cartilage damage, and the progression of osteoarthritis by targeting MCP-1 in a monosodium iodoacetate (MIA)-induced OA rat model.

BACKGROUND: Osteoarthritis (OA) is the most common type of degenerative arthritis and affects the entire joint, causing pain, joint inflammation, and cartilage damage. Various risk factors are implicated in causing OA, and in recent years, a lot of research and interest have been directed toward chronic low-grade inflammation in OA. Monocyte chemoattractant protein-1 (MCP-1; also called CCL2) acts through C-C chemokine receptor type 2 (CCR2) in monocytes and is a chemotactic factor of monocytes that plays an important role in the initiation of inflammation. The targeting of CCL2-CCR2 is being studied as part of various topics including the treatment of OA. METHODS: In this study, we evaluated the potential therapeutic effects the sCCR2 E3 gene may exert on OA. The effects of sCCR2 E3 were investigated in animal experiments consisting of intra-articular injection of sCCR2 E3 in a monosodium iodoacetate (MIA)-induced OA rat model. The effects after intra-articular injection of sCCR2 E3 (fusion protein encoding 20 amino acids of the E3 domain of the CCL2 receptor) in a monosodium iodoacetate-induced OA rat model were compared to those in rats treated with empty vector (mock treatment) and full-length sCCR2. RESULTS: Pain improved with expression of the sCCR2 gene. Improved bone resorption upon sCCR2 E3 gene activation was confirmed via bone analyses using micro-computed tomography. Histologic analyses showed that the sCCR2 E3 gene exerted protective effects against cartilage damage and anti-inflammatory effects on joints and the intestine. CONCLUSIONS: These results show that sCCR2 E3 therapy is effective in reducing pain severity, inhibiting cartilage destruction, and suppressing intestinal damage and inflammation. Thus, sCCR2 E3 may be a potential therapy for OA.

Short-chain fatty acid butyrate induces IL-10-producing B cells by regulating circadian-clock-related genes to ameliorate Sjögren's syndrome.

OBJECTIVES: Sjögren's syndrome (SS) is an autoimmune disease caused by inflammation of the exocrine gland. The pathological hallmark of SS is the infiltration of lymphocytes into the salivary glands. Increased infiltration of T and B cells into salivary glands exacerbates symptoms of SS. Several recent studies have identified the role of gut microbiota in SS. Butyrate, one of the metabolites of the gut microbiota, regulates T cells; however, its effects on B cells and SS remain unknown. This study determined the therapeutic effect of butyrate on regulating B cells in SS. METHODS: Various concentrations of butyrate were intraperitoneally injected three times per week in NOD/ShiLtJ (NOD) mice, the prototype animal model for SS, and observed for more than 10 weeks. Whole salivary flow rate and the histopathology of salivary glands were investigated. Human submandibular gland (HSG) cells and B cells in mouse spleen were used to confirm the anti-inflammatory and immunomodulatory effects of butyrate. RESULTS: Butyrate increased salivary flow rate in NOD mice and reduced inflammation of salivary gland tissues. It also regulated cell death and the expression of circadian-clock-related genes in HSG cells. Butyrate induced B cell regulation by increasing IL-10-producing B (B10) cells and decreasing IL-17-producing B cells, through the circadian clock genes RAR-related orphan receptor alpha and nuclear receptor subfamily 1 group D member 1. CONCLUSION: The findings of this study imply that butyrate may ameliorate SS via reciprocal regulation of IL-10- and IL-17-producing B cells.

CRACR2A-Mediated TCR Signaling Promotes Local Effector Th1 and Th17 Responses.

Ca2+ release-activated Ca2+ channel regulator 2A (CRACR2A) is expressed abundantly in T cells and acts as a signal transmitter between TCR stimulation and activation of the Ca2+/NFAT and JNK/AP1 pathways. CRACR2A has been linked to human diseases in numerous genome-wide association studies and was shown to be one of the most sensitive targets of the widely used statin drugs. However, the physiological role of CRACR2A in T cell functions remains unknown. In this study, using transgenic mice for tissue-specific deletion, we show that CRACR2A promotes Th1 responses and effector function of Th17 cells. CRACR2A was abundantly expressed in Th1 and Th17 cells. In vitro, deficiency of CRACR2A decreased Th1 differentiation under nonpolarizing conditions, whereas the presence of polarizing cytokines compensated this defect. Transcript analysis showed that weakened TCR signaling by deficiency of CRACR2A failed to promote Th1 transcriptional program. In vivo, conditional deletion of CRACR2A in T cells alleviated Th1 responses to acute lymphocytic choriomeningitis virus infection and imparted resistance to experimental autoimmune encephalomyelitis. Analysis of CNS from experimental autoimmune encephalomyelitis-induced mice showed impaired effector functions of both Th1 and Th17 cell types, which correlated with decreased pathogenicity. Collectively, our findings demonstrate the requirement of CRACR2A-mediated TCR signaling in Th1 responses as well as pathogenic conversion of Th17 cells, which occurs at the site of inflammation.

Junctophilin-4, a component of the endoplasmic reticulum-plasma membrane junctions, regulates Ca2+ dynamics in T cells.

Orai1 and stromal interaction molecule 1 (STIM1) mediate store-operated Ca(2+) entry (SOCE) in immune cells. STIM1, an endoplasmic reticulum (ER) Ca(2+) sensor, detects store depletion and interacts with plasma membrane (PM)-resident Orai1 channels at the ER-PM junctions. However, the molecular composition of these junctions in T cells remains poorly understood. Here, we show that junctophilin-4 (JP4), a member of junctional proteins in excitable cells, is expressed in T cells and localized at the ER-PM junctions to regulate Ca(2+) signaling. Silencing or genetic manipulation of JP4 decreased ER Ca(2+) content and SOCE in T cells, impaired activation of the nuclear factor of activated T cells (NFAT) and extracellular signaling-related kinase (ERK) signaling pathways, and diminished expression of activation markers and cytokines. Mechanistically, JP4 directly interacted with STIM1 via its cytoplasmic domain and facilitated its recruitment into the junctions. Accordingly, expression of this cytoplasmic fragment of JP4 inhibited SOCE. Furthermore, JP4 also formed a complex with junctate, a Ca(2+)-sensing ER-resident protein, previously shown to mediate STIM1 recruitment into the junctions. We propose that the junctate-JP4 complex located at the junctions cooperatively interacts with STIM1 to maintain ER Ca(2+) homeostasis and mediate SOCE in T cells.

Immunological Disorders: Regulation of Ca2+ Signaling in T Lymphocytes.

Engagement of T cell receptors (TCRs) with cognate antigens triggers cascades of signaling pathways in helper T cells. TCR signaling is essential for the effector function of helper T cells including proliferation, differentiation, and cytokine production. It also modulates effector T cell fate by inducing cell death, anergy (nonresponsiveness), exhaustion, and generation of regulatory T cells. One of the main axes of TCR signaling is the Ca2+-calcineurin-nuclear factor of activated T cells (NFAT) signaling pathway. Stimulation of TCRs triggers depletion of intracellular Ca2+ store and, in turn, activates store-operated Ca2+ entry (SOCE) to raise the intracellular Ca2+ concentration. SOCE in T cells is mediated by the Ca2+ release-activated Ca2+ (CRAC) channels, which have been very well characterized in terms of their electrophysiological properties. Identification of STIM1 as a sensor to detect depletion of the endoplasmic reticulum (ER) Ca2+ store and Orai1 as the pore subunit of CRAC channels has dramatically advanced our understanding of the regulatory mechanism of Ca2+ signaling in T cells. In this review, we discuss our current understanding of Ca2+ signaling in T cells with specific focus on the mechanism of CRAC channel activation and regulation via protein interactions. In addition, we will discuss the role of CRAC channels in effector T cells, based on the analyses of genetically modified animal models.

Interaction between mitsugumin 29 and TRPC3 participates in regulating Ca(2+) transients in skeletal muscle.

Mitsugumin 29 (MG29) is related to the fatigue and aging processes of skeletal muscle. To examine the roles of MG29 in conjunction with its binding protein, the canonical-type transient receptor potential cation channel 3 (TRPC3), in skeletal muscle, the binding region of MG29 to TRPC3 was studied along with the functional relevance of the binding in mouse primary skeletal myotubes using co-immunoprecipitation assays and Ca(2+) imaging experiments. The N-terminus and the I-II loop of MG29 constitute the binding region for TRPC3. The myotubes that expressed the MG29 mutant missing the entire TRPC3-binding region showed a disrupted binding between endogenous MG29 and TRPC3 and a reduction in Ca(2+) transients in response to membrane depolarization without affecting ryanodine receptor 1 activity, the resting cytosolic Ca(2+) level, and the amount of releasable Ca(2+) from the sarcoplasmic reticulum. Among the proteins mediating Ca(2+) movements in skeletal muscle, TRPC4 expression was significantly decreased by the MG29 mutant. Therefore, MG29 could be a new factor for regulating Ca(2+) transients during skeletal muscle contraction possibly via a correlation with TRPC3 and TRPC4.

Stromal interaction molecule 1 (STIM1) regulates sarcoplasmic/endoplasmic reticulum Ca²âº-ATPase 1a (SERCA1a) in skeletal muscle.

Stromal interaction molecule 1 (STIM1) mediates Ca2+ movements from the extracellular space to the cytosol through a store-operated Ca2+ entry (SOCE) mechanism in various cells including skeletal muscle cells. In the present study, to reveal the unidentified functional role of the STIM1 C terminus from 449 to 671 amino acids in skeletal muscle, binding assays and quadrupole time-of-flight mass spectrometry were used to identify proteins binding in this region along with proteins that mediate skeletal muscle contraction and relaxation. STIM1 binds to sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 1a (SERCA1a) via this region (called STIM1-SBR). The binding was confirmed in endogenous full-length STIM1 in rabbit skeletal muscle and mouse primary skeletal myotubes via co-immunoprecipitation assay and immunocytochemistry. STIM1 knockdown in mouse primary skeletal myotubes decreased Ca2+ uptake from the cytosol to the sarcoplasmic reticulum (SR) through SERCA1a only at micromolar cytosolic Ca2+ concentrations, suggesting that STIM1 could be required for the full activity of SERCA1a possibly during the relaxation of skeletal muscle. Various Ca2+ imaging experiments using myotubes expressing STIM1-SBR suggest that STIM1 is involved in intracellular Ca2+ distributions between the SR and the cytosol via regulating SERCA1a activity without affecting SOCE. Therefore, in skeletal muscle, STIM1 could play an important role in regulating Ca2+ movements between the SR and the cytosol.

Heteromeric TRPC3 with TRPC1 formed via its ankyrin repeats regulates the resting cytosolic Ca2+ levels in skeletal muscle.

The main tasks of skeletal muscle are muscle contraction and relaxation, which are mediated by changes in cytosolic Ca(2+) levels. Canonical-type transient receptor potential 3 (TRPC3) contains an ankyrin repeat (AR) region at the N-terminus (38-188 amino acids) and forms extracellular Ca(2+)-entry channels by homo or heteromerization with other TRP subtypes in various cells including skeletal myotubes. However, previous research has not determined which region(s) of TRPC3 is responsible for the heteromerization, whether the AR region participates in the heteromerizations, or what is the role of heteromeric TRPC3s in skeletal muscle. In the present study, the heteromerization of TRPC3 with TRPC1 was first examined by GST pull-down assays of TRPC3 portions with TRPC1. The portion containing the AR region of TRPC3 was bound to the TRPC1, but the binding was inhibited by the very end sub-region of the TRPC3 (1-37 amino acids). In-silico studies have suggested that the very end sub-region possibly induces a structural change in the AR region. Second, the very end sub-region of TRPC3 was expressed in mouse primary skeletal myotubes, resulting in a dominant-negative inhibition of heteromeric TRPC3/1 formation. In addition, the skeletal myotubes expressing the very end sub-region showed a decrease in resting cytosolic Ca(2+) levels. These results suggest that the AR region of TRPC3 could mediate the heteromeric TRPC3/1 formation, and the heteromeric TRPC3/1 could participate in regulating the resting cytosolic Ca(2+) levels in skeletal muscle.

STIM1 negatively regulates Ca²âº release from the sarcoplasmic reticulum in skeletal myotubes.

STIM1 (stromal interaction molecule 1) mediates SOCE (store-operated Ca²âº entry) in skeletal muscle. However, the direct role(s) of STIM1 in skeletal muscle, such as Ca²âº release from the SR (sarcoplasmic reticulum) for muscle contraction, have not been identified. The times required for the maximal expression of endogenous STIM1 or Orai1, or for the appearance of puncta during the differentiation of mouse primary skeletal myoblasts to myotubes, were all different, and the formation of puncta was detected with no stimulus during differentiation, suggesting that, in skeletal muscle, the formation of puncta is a part of the differentiation. Wild-type STIM1 and two STIM1 mutants (Triple mutant, missing Ca²âº-sensing residues but possessing the intact C-terminus; and E136X, missing the C-terminus) were overexpressed in the myotubes. The wild-type STIM1 increased SOCE, whereas neither mutant had an effect on SOCE. It was interesting that increases in the formation of puncta were observed in the Triple mutant as well as in wild-type STIM1, suggesting that SOCE-irrelevant puncta could exist in skeletal muscle. On the other hand, overexpression of wild-type or Triple mutant, but not E136X, attenuated Ca²âº releases from the SR in response to KCl [evoking ECC (excitation-contraction coupling) via activating DHPR (dihydropyridine receptor)] in a dominant-negative manner. The attenuation was removed by STIM1 knockdown, and STIM1 was co-immunoprecipitated with DHRP in a Ca²âº-independent manner. These results suggest that STIM1 negatively regulates Ca²âº release from the SR through the direct interaction of the STIM1 C-terminus with DHPR, and that STIM1 is involved in both ECC and SOCE in skeletal muscle.

Oxidized LDL Accelerates Cartilage Destruction and Inflammatory Chondrocyte Death in Osteoarthritis by Disrupting the TFEB-Regulated Autophagy-Lysosome Pathway.

Osteoarthritis (OA) involves cartilage degeneration, thereby causing inflammation and pain. Cardiovascular diseases, such as dyslipidemia, are risk factors for OA; however, the mechanism is unclear. We investigated the effect of dyslipidemia on the development of OA. Treatment of cartilage cells with low-density lipoprotein (LDL) enhanced abnormal autophagy but suppressed normal autophagy and reduced the activity of transcription factor EB (TFEB), which is important for the function of lysosomes. Treatment of LDL-exposed chondrocytes with rapamycin, which activates TFEB, restored normal autophagy. Also, LDL enhanced the inflammatory death of chondrocytes, an effect reversed by rapamycin. In an animal model of hyperlipidemia-associated OA, dyslipidemia accelerated the development of OA, an effect reversed by treatment with a statin, an anti-dyslipidemia drug, or rapamycin, which activates TFEB. Dyslipidemia reduced the autophagic flux and induced necroptosis in the cartilage tissue of patients with OA. The levels of triglycerides, LDL, and total cholesterol were increased in patients with OA compared to those without OA. The C-reactive protein level of patients with dyslipidemia was higher than that of those without dyslipidemia after total knee replacement arthroplasty. In conclusion, oxidized LDL, an important risk factor of dyslipidemia, inhibited the activity of TFEB and reduced the autophagic flux, thereby inducing necroptosis in chondrocytes.

Gut microbiome-derived butyrate inhibits the immunosuppressive factors PD-L1 and IL-10 in tumor-associated macrophages in gastric cancer.

Early detection and surgical treatment are essential to achieve a good outcome in gastric cancer (GC). Stage IV and recurrent GC have a poor prognosis. Therefore, new treatments for GC are needed. We investigated the intestinal microbiome of GC patients and attempted to reverse the immunosuppression of the immune and cancer cells of GC patients through the modulation of microbiome metabolites. We evaluated the levels of programmed death-ligand 1 (PD-L1) and interleukin (IL)-10 in the peripheral blood immunocytes of GC patients. Cancer tissues were obtained from patients who underwent surgical resection of GC, and stained sections of cancer tissues were visualized via confocal microscopy. The intestinal microbiome was analyzed using stool samples of healthy individuals and GC patients. Patient-derived avatar model was developed by injecting peripheral blood mononuclear cells (PBMCs) from advanced GC (AGC) patients into NSG mice, followed by injection of AGS cells. PD-L1 and IL-10 had higher expression levels in immune cells of GC patients than in those of healthy controls. The levels of immunosuppressive factors were increased in the immune and tumor cells of tumor tissues of GC patients. The abundances of Faecalibacterium and Bifidobacterium in the intestinal flora were lower in GC patients than in healthy individuals. Butyrate, a representative microbiome metabolite, suppressed the expression levels of PD-L1 and IL-10 in immune cells. In addition, the PBMCs of AGC patients showed increased levels of immunosuppressive factors in the avatar mouse model. Butyrate inhibited tumor growth in mice. Restoration of the intestinal microbiome and its metabolic functions inhibit tumor growth and reverse the immunosuppression due to increased PD-L1 and IL-10 levels in PBMCs and tumor cells of GC patients.