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Peripheral serotonin (5-hydroxytryptamine: 5-HT) synthesized in the intestine by enterochromaffin cells (ECs),plays an important role in the regulation of peristaltic of the gut,epithelial secretion and promotes the development and maintenance of the enteric neurons. Recent studies showed that the indigenous gut microbiota modulates 5-HT signalling and that ECs use sensory receptors to detect dietary and microbiota-derived signals from the lumen to subsequently transduce the information to the nervous system. We hypothesized that Clostridium ramosum by increasing gut 5-HT availability consequently contributes to high-fat diet-induced obesity. Using germ-free mice and mice monoassociated with C. ramosum,intestinal cell lines and mouse organoids,we demonstrated that bacterial cell components stimulate host 5-HT secretion and program the differentiation of colonic intestinal stem progenitors toward the secretory 5-HT-producing lineage. An elevated 5-HT level regulates the expression of major proteins involved in intestinal fatty acid absorption in vitro,suggesting that the presence of C. ramosum in the gut promotes 5-HT secretion and thereby could facilitates intestinal lipid absorption and the development of obesity. View Publication

The therapeutic monoclonal antibody (mAb) TGN1412 (anti-CD28 superagonist) caused near-fatal cytokine release syndrome (CRS) in all six volunteers during a phase-I clinical trial. Several cytokine release assays (CRAs) with reported predictivity for TGN1412-induced CRS have since been developed for the preclinical safety testing of new therapeutic mAbs. The whole blood (WB) CRA is the most widely used,but its sensitivity for TGN1412-like cytokine release was recently criticized. In a comparative study,using group size required for 90% power with 5% significance as a measure of sensitivity,we found that WB and 10% (v/v) WB CRAs were the least sensitive for TGN1412 as these required the largest group sizes (n = 52 and 79,respectively). In contrast,the peripheral blood mononuclear cell (PBMC) solid phase (SP) CRA was the most sensitive for TGN1412 as it required the smallest group size (n = 4). Similarly,the PBMC SP CRA was more sensitive than the WB CRA for muromonab-CD3 (anti-CD3) which stimulates TGN1412-like cytokine release (n = 4 and 4519,respectively). Conversely,the WB CRA was far more sensitive than the PBMC SP CRA for alemtuzumab (anti-CD52) which stimulates FcγRI-mediated cytokine release (n = 8 and 180,respectively). Investigation of potential factors contributing to the different sensitivities revealed that removal of red blood cells (RBCs) from WB permitted PBMC-like TGN1412 responses in a SP CRA,which in turn could be inhibited by the addition of the RBC membrane protein glycophorin A (GYPA); this observation likely underlies,at least in part,the poor sensitivity of WB CRA for TGN1412. The use of PBMC SP CRA for the detection of TGN1412-like cytokine release is recommended in conjunction with adequately powered group sizes for dependable preclinical safety testing of new therapeutic mAbs. View Publication

A well-balanced maternal immune system is crucial to maintain fetal tolerance in case of infections during pregnancy. Immune adaptations include an increased secretion of soluble mediators to protect the semi-allogeneic fetus from excessive pro-inflammatory response. B lymphocytes acquire a higher capacity to express CD83 and secrete soluble CD83 (sCD83) upon exposure to bacteria-derived components such as LPS. CD83 possesses immune modulatory functions and shows a promising therapeutic potential against inflammatory conditions. The administration of sCD83 to pregnant mice reduces LPS-induced abortion rates. The increased CD83 expression by endometrial B cells as compared to peripheral blood B cells suggests its modulatory role in the fetal tolerance,especially in the context of infection. We postulate that in pregnancy,CD83 expression and release is controlled by pregnancy-related hormones. The intra- and extracellular expression of CD83 in leukocytes from peripheral blood or decidua basalis and parietalis at term were analyzed by flow cytometry. After treatment with pregnancy-related hormones and LPS,ELISA and qPCR were performed to study sCD83 release and CD83 gene expression,respectively. Cleavage prediction analysis was used to find potential proteases targeting CD83. Expression of selected proteases was analyzed by ELISA. Higher levels of CD83 were found in CD11c+ dendritic cells,CD3+ T cells and CD19+ B cells from decidua basalis and decidua parietalis after LPS-stimulation in vitro. An increase of intracellular expression of CD83 was also detected in CD19+ B cells from both compartments. Stimulated B cells displayed significantly higher percentages of CD83+ cells than dendritic cells and T cells from decidua basalis and peripheral blood. Treatment of B lymphocytes with pregnancy-related molecules (E2,P4,TGF-β1 and hCG) enhanced the LPS-mediated increase of CD83 expression,while dexamethasone led to a reduction. Similarly,the release of sCD83 was increased under TGF-β1 treatment but decreased upon dexamethasone stimulation. Finally,we found that the hormonal regulation of CD83 expression is likely a result from a balance between gene transcription from CD83 and the modulation of the metalloproteinase MMP-7. Thus,data supports and complements our previous murine studies on hormonal regulation of CD83 expression,reinforcing its immunomodulatory relevance in anti-bacterial responses during pregnancy. View Publication

In dynamic systems like the circulatory system,establishing localized cytokine gradients is challenging. Upon lipopolysaccharide (LPS) stimulation,we observed that monocytes release numerous migrasomes enriched with inflammatory cytokines,such as TNF-α and IL-6. These cytokines are transported into migrasomes via secretory carriers,leading to their immediate exocytosis or eventual release from detached migrasomes. We successfully isolated TNF-α and IL-6-enriched,monocyte-derived migrasomes from the blood of LPS-treated mice. Total secretion analysis revealed a substantial amount of TNF-α and IL-6 released in a migrasome-packaged form. Thus,detached,monocyte-derived migrasomes represent a type of extracellular vesicle highly enriched with cytokines. Physiologically,these cytokine-laden migrasomes rapidly accumulate at local sites of inflammation,effectively creating a concentrated source of cytokines. Our research uncovers novel mechanisms for cytokine release and delivery,providing new insights into immune response modulation. View Publication

Early cognitive deficits in Alzheimer's disease (AD) seem to be correlated to dysregulation of glutamate receptors evoked by amyloid-beta (Aβ) peptide. Aβ interference with the activity of N-methyl-d-aspartate receptors (NMDARs) may be a relevant factor for Aβ-induced mitochondrial toxicity and neuronal dysfunction. To evaluate the role of mitochondria in NMDARs activation mediated by Aβ,we followed in situ single-cell simultaneous measurement of cytosolic free Ca(2+)(Cai(2+)) and mitochondrial membrane potential in primary cortical neurons. Our results show that direct exposure to Aβ + NMDA largely increased Cai(2+) and induced immediate mitochondrial depolarization,compared with Aβ or NMDA alone. Mitochondrial depolarization induced by rotenone strongly inhibited the rise in Cai(2+) evoked by Aβ or NMDA,suggesting that mitochondria control Ca(2+) entry through NMDARs. However,incubation with rotenone did not preclude mitochondrial Ca(2+) (mitCa(2+)) retention in cells treated with Aβ. Aβ-induced Cai(2+) and mitCa(2+) rise were inhibited by ifenprodil,an antagonist of GluN2B-containing NMDARs. Exposure to Aβ + NMDA further evoked a higher mitCa(2+) retention,which was ameliorated in GluN2B(-/-) cortical neurons,largely implicating the involvement of this NMDAR subunit. Moreover,pharmacologic inhibition of endoplasmic reticulum (ER) inositol-1,4,5-triphosphate receptor (IP3R) and mitCa(2+) uniporter (MCU) evidenced that Aβ + NMDA-induced mitCa(2+) rise involves ER Ca(2+) release through IP3R and mitochondrial entry by the MCU. Altogether,data highlight mitCa(2+) dyshomeostasis and subsequent dysfunction as mechanisms relevant for early neuronal dysfunction in AD linked to Aβ-mediated GluN2B-composed NMDARs activation. View Publication

Peroxynitrite toxicity is a major cause of neuronal injury in stroke and neurodegenerative disorders. The mechanisms underlying the neurotoxicity induced by peroxynitrite are still unclear. In this study,we observed that TPEN [N,N,N',N'-tetrakis (2-pyridylmethyl)ethylenediamine],a zinc chelator,protected against neurotoxicity induced by exogenous as well as endogenous (coadministration of NMDA and a nitric oxide donor,diethylenetriamine NONOate) peroxynitrite. Two different approaches to detecting intracellular zinc release demonstrated the liberation of zinc from intracellular stores by peroxynitrite. In addition,we found that peroxynitrite toxicity was blocked by inhibitors of 12-lipoxygenase (12-LOX),p38 mitogen-activated protein kinase (MAPK),and caspase-3 and was associated with mitochondrial membrane depolarization. Inhibition of 12-LOX blocked the activation of p38 MAPK and caspase-3. Zinc itself induced the activation of 12-LOX,generation of reactive oxygen species (ROS),and activation of p38 MAPK and caspase-3. These data suggest a cell death pathway triggered by peroxynitrite in which intracellular zinc release leads to activation of 12-LOX,ROS accumulation,p38 activation,and caspase-3 activation. Therefore,therapies aimed at maintaining intracellular zinc homeostasis or blocking activation of 12-LOX may provide a novel avenue for the treatment of inflammation,stroke,and neurodegenerative diseases in which the formation of peroxynitrite is thought to be one of the important causes of cell death. View Publication

SorLA,encoded by the gene SORL1,is an intracellular sorting receptor of the VPS10P domain receptor gene family. Although SorLA is best recognized for its ability to shuttle target proteins between intracellular compartments in neurons,recent data suggest that also its microglial expression can be of high relevance for the pathogenesis of brain diseases,including glioblastoma (GBM). Here,we interrogated the impact of SorLA on the functional properties of glioma-associated microglia and macrophages (GAMs). In the GBM microenvironment,GAMs are re-programmed and lose the ability to elicit anti-tumor responses. Instead,they acquire a glioma-supporting phenotype,which is a key mechanism promoting glioma progression. Our re-analysis of published scRNA-seq data from GBM patients revealed that functional phenotypes of GAMs are linked to the level of SORL1 expression,which was further confirmed using in vitro models. Moreover,we demonstrate that SorLA restrains secretion of TNFα from microglia to restrict the inflammatory potential of these cells. Finally,we show that loss of SorLA exacerbates the pro-inflammatory response of microglia in the murine model of glioma and suppresses tumor growth. View Publication

The persistence of HIV-1 in long-lived latent reservoirs during suppressive antiretroviral therapy (ART) remains one of the principal barriers to a functional cure. Blocks to transcriptional elongation play a central role in maintaining the latent state,and several latency reversal strategies focus on the release of positive transcription elongation factor b (P-TEFb) from sequestration by negative regulatory complexes,such as the 7SK complex and BRD4. Another major cellular reservoir of P-TEFb is in Super Elongation Complexes (SECs),which play broad regulatory roles in host gene expression. Still,it is unknown if the release of P-TEFb from SECs is a viable latency reversal strategy. Here,we demonstrate that the SEC is not required for HIV-1 replication in primary CD4+ T cells and that a small molecular inhibitor of the P-TEFb/SEC interaction (termed KL-2) increases viral transcription. KL-2 acts synergistically with other latency reversing agents (LRAs) to reactivate viral transcription in several cell line models of latency in a manner that is,at least in part,dependent on the viral Tat protein. Finally,we demonstrate that KL-2 enhances viral reactivation in peripheral blood mononuclear cells (PBMCs) from people living with HIV (PLWH) on suppressive ART,most notably in combination with inhibitor of apoptosis protein antagonists (IAPi). Taken together,these results suggest that the release of P-TEFb from cellular SECs may be a novel route for HIV-1 latency reactivation. Author summarySince the start of the HIV pandemic,it is estimated that nearly 86 million people have been infected with the virus,and about 40 million people have died. Modern antiretroviral therapies potently restrict viral replication and prevent the onset of AIDS,saving millions of lives. However,these therapies are not curative due to the persistence of the virus in a silenced or ‘latent’ state in long-lived cells of the body. One proposed strategy to clear this latent reservoir,termed “shock and kill”,is to activate these silenced viruses such that the infected cells can be cleared from the body by the immune system. While several drugs have been developed that can activate latent viruses,none have proven effective at reducing the size of the latent reservoir in patients in clinical trials. Here,we describe a new method for latency reactivation using a small molecule inhibitor of a human protein complex called the Super Elongation Complex (SEC). Inhibiting the SEC enhances viral transcription during active infection and triggers the reactivation of latent viruses,especially when in combination with other latency reversing agents. These results pave the way for developing more effective strategies to reactivate latent viruses towards a functional cure. View Publication

Glatiramer acetate (GA or Copaxone) is a drug used to treat experimental autoimmune encephalomyelitis in mice and multiple sclerosis in human. Here,we describe a new mechanism of action for this drug. GA enhanced the cytolysis of human NK cells against autologous and allogeneic immature and mature monocyte-derived dendritic cells (DCs). This drug reduced the percentages of mature DCs expressing CD80,CD83,HLA-DR or HLA-I. In contrast,it did not modulate the percentages of NK cells expressing NKG2D,NKp30,or NKp44. Nonetheless,anti-NKp30 or anti-CD86 inhibited GA-enhanced human NK cell lysis of immature DCs. Hence,CD86,and NKp30 are important for NK cell lysis of immature DCs,whereas CD80,CD83,HLA-DR and HLA-I are important for the lysis of mature DCs when GA is used as a stimulus. Further,GA inhibited the release of IFN-gamma 24 h but increased the release of TNF-alpha 48 h after incubation with NK cells. View Publication

BackgroundAnti-CD19 chimeric antigen receptor T (CAR-T) cell therapy has proven effective for treating relapsed or refractory acute B cell leukemia. However,challenges such as cytokine release syndrome,T cell dysfunction,and exhaustion persist. Enhancing CAR-T cell efficacy through changing CAR internalization and recycling is a promising approach. The transmembrane domain is the easiest motif to optimize for modulating CAR internalization and recycling without introducing additional domains,and its impact on CAR internalization and recycling has not yet been thoroughly explored. In this study,we aim to enhance CAR-T cell function by focusing on the solely transmembrane domain design.MethodsUtilizing plasmid construction and lentivirus generation,we get two different transmembrane CAR-T cells [19CAR-T(1a) and 19CAR-T(8α)]. Through co-culture with tumor cells,we evaluate CAR dynamic change,activation levels,exhaustion markers,mitochondrial function,and differentiation in both CAR-T cells. Furthermore,immunofluorescence microscopy analysis is performed to reveal the localization of internalized CAR molecules. RNA sequencing is used to detect the transcriptome of activated CAR-T cells. Finally,a mouse study is utilized to verify the anti-tumor efficacy of 19CAR-T(1a) cells in vivo.ResultsOur findings demonstrate that 19CAR-T(1a) has lower surface CAR expression,faster internalization,and a higher recycling rate compared to 19CAR-T(8α). Internalized 19CAR(1a) co-localizes more with early and recycling endosomes,and less with lysosomes than 19CAR(8α). These features result in lower activation levels,less cytokine release,and reduced exhaustion markers in 19CAR-T(1a). Furthermore,CAR-T cells with CD1a transmembrane domain also exhibit a superior anti-tumor ability and reduced exhaustion in vivo.ConclusionOverall,we demonstrate that the transmembrane domain plays a critical role in CAR-T cell function. An optimized transmembrane domain can alleviate cytokine release syndrome and reduce CAR-T cell exhaustion,providing a direction for CAR design to enhance CAR-T cell function. View Publication

Leukocyte trafficking to sites of inflammation follows a defined temporal pattern,and evidence suggests that initial neutrophil transendothelial migration modifies endothelial cell phenotype. We tested the hypothesis that preconditioning of human umbilical vein endothelial cells (HUVEC) by neutrophils would also modify the subsequent transendothelial migration of T lymphocytes across cytokine-stimulated HUVEC in an in vitro flow assay. Using fluorescence microscopy,preconditioning of HUVEC by neutrophils was observed to significantly reduce the extent of subsequent stromal cell-derived factor-1alpha (SDF-1alpha [CXCL12])-mediated T lymphocyte transendothelial migration,without reducing accumulation. In contrast,recruitment of a second wave of neutrophils was unaltered. Conditioned medium harvested after transendothelial migration of neutrophils or supernatants from stimulated neutrophils mediated a similar blocking effect,which was negated using a specific neutrophil elastase inhibitor. Furthermore,T lymphocyte transendothelial migration was inhibited by treatment of HUVEC with purified neutrophil elastase,which selectively cleaved the amino terminus of HUVEC-bound SDF-1alpha,which is required for its chemotactic activity. The reduction in T lymphocyte transendothelial migration was not observed using a different chemokine,ELC (CCL19),and was not reversed by replenishment of SDF-1alpha,indicating endothelial retention of the inactivated chemokine. In summary,transmigrating neutrophils secrete localized elastase that is protected from plasma inhibitors,and thereby modulate trafficking of other leukocyte subsets by altering the endothelial-associated chemotactic activities. View Publication

A two-step separation procedure is described for the positive selection of cells based on their reactivity with mouse monoclonal antibodies. In the first step cells are specifically cross-linked to hapten-modified glass beads using tetrameric monoclonal antibody complexes. In the second step bound cells are selectively eluted by reductive cleavage of the tetrameric antibody complexes. The latter are comprised of two mouse IgG1 monoclonal antibodies (one recognizing a cell surface antigen on target cells and the other a hapten coupled to the glass beads) bound together by two F(ab')2 fragments of rat anti-mouse IgG1 monoclonal antibody. The complexes provide a specific cleavable cross-link between cell and bead because the disulfide bonds between the two Fab' arms of the F(ab')2 fragments can be broken under relatively mild conditions using dithiothreitol. This specific cleavage of the cross-linker allows elution of the specifically absorbed cells without co-elution of non-specifically bound cells. This is shown in the purification of CD3+ T cells from human peripheral blood,where the removed fractions were over 90% pure and approximately 50% of the positive cells were recovered. Separation of cells labelled with limiting amounts of tetrameric antibody complexes demonstrated that this separation technique was also effective for the purification of cells expressing low amounts of antigens. This was confirmed by the purification of CD34-positive cells from human bone marrow. With this approach,colony-forming cells were enriched 15-24-fold over density separated marrow. View Publication