Purinergic P2X4 receptors and mitochondrial ATP production regulate T cell migration

Mitochondrial control of lymphocyte homeostasis

Mitochondria play a multitude of essential roles within mammalian cells, and understanding how they control immunity is an emerging area of study. Lymphocytes, as integral cellular components of the adaptive immune system, rely on mitochondria for their function, and mitochondria can dynamically instruct their differentiation and activation by undergoing rapid and profound remodelling. Energy homeostasis and ATP production are often considered the primary functions of mitochondria in immune cells; however, their importance extends across a spectrum of other molecular processes, including regulation of redox balance, signalling pathways, and biosynthesis. In this review, we explore the dynamic landscape of mitochondrial homeostasis in T and B cells, and discuss how mitochondrial disorders compromise adaptive immunity.

Sympathetic hyperinnervation drives abdominal aortic aneurysm development by promoting vascular smooth muscle cell phenotypic switching

INTRODUCTION

Sympathetic hyperinnervation plays an important role in modulating the vascular smooth muscle cell (VSMC) phenotype and vascular diseases, but its role in abdominal aortic aneurysm (AAA) is still unknown.

OBJECTIVES

This study aimed to investigate the role of sympathetic hyperinnervation in promoting AAA development and the underlying mechanism involved.

METHODS

Western blotting and immunochemical staining were used to detect sympathetic hyperinnervation. We performed sympathetic denervation through coeliac ganglionectomy (CGX) and 6-OHDA administration to understand the role of sympathetic hyperinnervation in AAA and investigated the underlying mechanisms through transcriptome and functional studies. Sema4D knockout (Sema4D-/-) mice were utilized to determine the involvement of Sema4D in inducing sympathetic hyperinnervation and AAA development.

RESULTS

We observed sympathetic hyperinnervation, the most important form of sympathetic neural remodeling, in both mouse AAA models and AAA patients. Elimination of sympathetic hyperinnervation by CGX or 6-OHDA significantly inhibited AAA development and progression. We further revealed that sympathetic hyperinnervation promoted VSMC phenotypic switching in AAA by releasing extracellular ATP (eATP) and activating eATP-P2rx4-p38 signaling. Moreover, single-cell RNA sequencing revealed that Sema4D secreted by osteoclast-like cells induces sympathetic nerve diffusion and hyperinnervation through binding to Plxnb1. We consistently observed that AAA progression was significantly ameliorated in Sema4D-deficient mice.

CONCLUSIONS

Sympathetic hyperinnervation driven by osteoclast-like cell-derived Sema4D promotes VSMC phenotypic switching and accelerates pathological aneurysm progression by activating the eATP/P2rx4/p38 pathway. Inhibition of sympathetic hyperinnervation emerges as a potential novel therapeutic strategy for preventing and treating AAA.

Crosstalk between P2Y receptors and cyclooxygenase activity in inflammation and tissue repair

The role of extracellular nucleotides as modulators of inflammation and cell stress is well established. One of the main actions of these molecules is mediated by the activation of purinergic receptors (P2) of the plasma membrane. P2 receptors can be classified according to two different structural families: P2X ionotropic ion channel receptors, and P2Y metabotropic G protein-coupled receptors. During inflammation, damaged cells release nucleotides and purinergic signaling occurs along the temporal pattern of the synthesis of pro-inflammatory and pro-resolving mediators by myeloid and lymphoid cells. In macrophages under pro-inflammatory conditions, the expression and activity of cyclooxygenase 2 significantly increases and enhances the circulating levels of prostaglandin E2 (PGE2), which exerts its effects both through specific plasma membrane receptors (EP1-EP4) and by activation of intracellular targets. Here we review the mechanisms involved in the crosstalk between PGE2 and P2Y receptors on macrophages, which is dependent on several isoforms of protein kinase C and protein kinase D1. Due to this crosstalk, a P2Y-dependent increase in calcium is blunted by PGE2 whereas, under these conditions, macrophages exhibit reduced migratory capacity along with enhanced phagocytosis, which contributes to the modulation of the inflammatory response and tissue repair.

Mitochondrial metabolism sustains CD8+ T cell migration for an efficient infiltration into solid tumors

The ability of CD8+ T cells to infiltrate solid tumors and reach cancer cells is associated with improved patient survival and responses to immunotherapy. Thus, identifying the factors controlling T cell migration in tumors is critical, so that strategies to intervene on these targets can be developed. Although interstitial motility is a highly energy-demanding process, the metabolic requirements of CD8+ T cells migrating in a 3D environment remain unclear. Here, we demonstrate that the tricarboxylic acid (TCA) cycle is the main metabolic pathway sustaining human CD8+ T cell motility in 3D collagen gels and tumor slices while glycolysis plays a more minor role. Using pharmacological and genetic approaches, we report that CD8+ T cell migration depends on the mitochondrial oxidation of glucose and glutamine, but not fatty acids, and both ATP and ROS produced by mitochondria are required for T cells to migrate. Pharmacological interventions to increase mitochondrial activity improve CD8+ T cell intratumoral migration and CAR T cell recruitment into tumor islets leading to better control of tumor growth in human xenograft models. Our study highlights the rationale of targeting mitochondrial metabolism to enhance the migration and antitumor efficacy of CAR T cells in treating solid tumors.

Time-resolved role of P2X4 and P2X7 during CD8+ T cell activation

CD8+ T cells are a crucial part of the adaptive immune system, responsible for combating intracellular pathogens and tumor cells. The initial activation of T cells involves the formation of highly dynamic Ca2+ microdomains. Recently, purinergic signaling was shown to be involved in the formation of the initial Ca2+ microdomains in CD4+ T cells. In this study, the role of purinergic cation channels, particularly P2X4 and P2X7, in CD8+ T cell signaling from initial events to downstream responses was investigated, focusing on various aspects of T cell activation, including Ca2+ microdomains, global Ca2+ responses, NFAT-1 translocation, cytokine expression, and proliferation. While Ca2+ microdomain formation was significantly reduced in the first milliseconds to seconds in CD8+ T cells lacking P2X4 and P2X7 channels, global Ca2+ responses over minutes were comparable between wild-type (WT) and knockout cells. However, the onset velocity was reduced in P2X4-deficient cells, and P2X4, as well as P2X7-deficient cells, exhibited a delayed response to reach a certain level of free cytosolic Ca2+ concentration ([Ca2+]i). NFAT-1 translocation, a crucial transcription factor in T cell activation, was also impaired in CD8+ T cells lacking P2X4 and P2X7. In addition, the expression of IFN-γ, a major pro-inflammatory cytokine produced by activated CD8+ T cells, and Nur77, a negative regulator of T cell activation, was significantly reduced 18h post-stimulation in the knockout cells. In line, the proliferation of T cells after 3 days was also impaired in the absence of P2X4 and P2X7 channels. In summary, the study demonstrates that purinergic signaling through P2X4 and P2X7 enhances initial Ca2+ events during CD8+ T cell activation and plays a crucial role in regulating downstream responses, including NFAT-1 translocation, cytokine expression, and proliferation on multiple timescales. These findings suggest that targeting purinergic signaling pathways may offer potential therapeutic interventions.

The Role and Mechanism of Metformin in Inflammatory Diseases

Metformin is a classical drug used to treat type 2 diabetes. With the development of research on metformin, it has been found that metformin also has several advantages aside from its hypoglycemic effect, such as anti-inflammatory, anti-aging, anti-cancer, improving intestinal flora, and other effects. The prevention of inflammation is critical because chronic inflammation is associated with numerous diseases of considerable public health. Therefore, there has been growing interest in the role of metformin in treating various inflammatory conditions. However, the precise anti-inflammatory mechanisms of metformin were inconsistent in the reported studies. Thus, this review aims to summarize various currently known possible mechanisms of metformin involved in inflammatory diseases and provide references for the clinical application of metformin.

Intercellular Communication in Airway Epithelial Cell Regeneration: Potential Roles of Connexins and Pannexins

Connexins and pannexins are transmembrane proteins that can form direct (gap junctions) or indirect (connexons, pannexons) intercellular communication channels. By propagating ions, metabolites, sugars, nucleotides, miRNAs, and/or second messengers, they participate in a variety of physiological functions, such as tissue homeostasis and host defense. There is solid evidence supporting a role for intercellular signaling in various pulmonary inflammatory diseases where alteration of connexin/pannexin channel functional expression occurs, thus leading to abnormal intercellular communication pathways and contributing to pathophysiological aspects, such as innate immune defense and remodeling. The integrity of the airway epithelium, which is the first line of defense against invading microbes, is established and maintained by a repair mechanism that involves processes such as proliferation, migration, and differentiation. Here, we briefly summarize current knowledge on the contribution of connexins and pannexins to necessary processes of tissue repair and speculate on their possible involvement in the shaping of the airway epithelium integrity.

Maladaptive T-Cell Metabolic Fitness in Autoimmune Diseases

Immune surveillance and adaptive immune responses, involving continuously circulating and tissue-resident T-lymphocytes, provide host defense against infectious agents and possible malignant transformation while avoiding autoimmune tissue damage. Activation, migration, and deployment of T-cells to affected tissue sites are crucial for mounting an adaptive immune response. An effective adaptive immune defense depends on the ability of T-cells to dynamically reprogram their metabolic requirements in response to environmental cues. Inability of the T-cells to adapt to specific metabolic demands may skew cells to become either hyporesponsive (creating immunocompromised conditions) or hyperactive (causing autoimmune tissue destruction). Here, we review maladaptive T-cell metabolic fitness that can cause autoimmune diseases and discuss how T-cell metabolic programs can potentially be modulated to achieve therapeutic benefits.

Metabolic regulation of γδ intraepithelial lymphocytes

Elucidating the relationship between cellular metabolism and T cell function has substantially advanced our understanding of how T cells are regulated in response to activation. The metabolic profiles of circulating or peripheral T cells have been well-described, yet less is known regarding how complex local microenvironments shape or modulate the bioenergetic profile of tissue-resident T lymphocytes. Intraepithelial lymphocytes expressing the γδ T cell receptor (γδ IEL) provide immunosurveillance of the intestinal epithelium to limit tissue injury and microbial invasion; however, their activation and effector responses occur independently of antigen recognition. In this review, we will summarize the current knowledge regarding γδ T cell and IEL metabolic profiles and how this informs our understanding of γδ IEL metabolism. We will also discuss the role of the gut microbiota in shaping the metabolic profile of these sentinel lymphocytes, and in turn, how these bioenergetics contribute to regulation of γδ IEL surveillance behavior and effector function. Improved understanding of the metabolic processes involved in γδ IEL homeostasis and function may yield novel strategies to amplify the protective functions of these cells in the context of intestinal health and disease.

The interplay between the DNA damage response and ectonucleotidases modulates tumor response to therapy

The extracellular nucleoside adenosine reduces tissue inflammation and is generated by irreversible dephosphorylation of adenosine monophosphate (AMP) mediated by the ectonucleotidase CD73. The pro-inflammatory nucleotides adenosine triphosphate, nicotinamide adenine dinucleotide, and cyclic guanosine -monophosphate-AMP (cGAMP), which are produced in the tumor microenvironment (TME) during therapy-induced immunogenic cell death and activation of innate immune signaling, can be converted into AMP by ectonucleotidases CD39, CD38, and CD203a/ENPP1. Thus, ectonucleotidases shape the TME by converting immune-activating signals into an immunosuppressive one. Ectonucleotidases also hinder the ability of therapies including radiation therapy, which enhance the release of pro-inflammatory nucleotides in the extracellular milieu, to induce immune-mediated tumor rejection. Here, we review the immunosuppressive effects of adenosine and the role of different ectonucleotidases in modulating antitumor immune responses. We discuss emerging opportunities to target adenosine generation and/or its ability to signal via adenosine receptors expressed by immune and cancer cells in the context of combination immunotherapy and radiotherapy.

Therapeutic targeting of P2X4 receptor and mitochondrial metabolism in clear cell renal carcinoma models

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cancer. Large-scale metabolomic data have associated metabolic alterations with the pathogenesis and progression of renal carcinoma and have correlated mitochondrial activity with poor survival in a subset of patients. The aim of this study was to determine whether targeting mitochondria-lysosome interaction could be a novel therapeutic approach using patient-derived organoids as avatar for drug response.

METHODS

RNAseq data analysis and immunohistochemistry were used to show overexpression of Purinergic receptor 4 (P2XR4) in clear cell carcinomas. Seahorse experiments, immunofluorescence and fluorescence cell sorting were used to demonstrate that P2XR4 regulates mitochondrial activity and the balance of radical oxygen species. Pharmacological inhibitors and genetic silencing promoted lysosomal damage, calcium overload in mitochondria and cell death via both necrosis and apoptosis. Finally, we established patient-derived organoids and murine xenograft models to investigate the antitumor effect of P2XR4 inhibition using imaging drug screening, viability assay and immunohistochemistry.

RESULTS

Our data suggest that oxo-phosphorylation is the main source of tumor-derived ATP in a subset of ccRCC cells expressing P2XR4, which exerts a critical impact on tumor energy metabolism and mitochondrial activity. Prolonged mitochondrial failure induced by pharmacological inhibition or P2XR4 silencing was associated with increased oxygen radical species, changes in mitochondrial permeability (i.e., opening of the transition pore complex, dissipation of membrane potential, and calcium overload). Interestingly, higher mitochondrial activity in patient derived organoids was associated with greater sensitivity to P2XR4 inhibition and tumor reduction in a xenograft model.

CONCLUSION

Overall, our results suggest that the perturbed balance between lysosomal integrity and mitochondrial activity induced by P2XR4 inhibition may represent a new therapeutic strategy for a subset of patients with renal carcinoma and that individualized organoids may be help to predict drug efficacy.

Tissue- and temporal-specific roles of extracellular ATP on T cell metabolism and function

The activation and function of T cells is fundamental for the control of infectious diseases and cancer, and conversely can mediate several autoimmune diseases. Among the signaling pathways leading to T cell activation and function, the sensing of extracellular adenosine triphosphate (eATP) has been recently appreciated as an important component. Through a plethora of purinergic receptors, most prominently P2RX7, eATP sensing can induce a wide variety of processes in T cells, such as proliferation, subset differentiation, survival, or cell death. The downstream roles of eATP sensing can vary according to (a) the T cell subset, (b) the tissue where T cells are, and (c) the time after antigen exposure. In this mini-review, we revisit the recent findings on how eATP signaling pathways regulate T-cell immune responses and posit important unanswered questions on this field.

Transcriptomic analysis reveals novel age-independent immunomodulatory proteins as a mode of cerebroprotection in P2X4R KO mice after ischemic stroke

Identification of new potential drug target proteins and their plausible mechanisms for stroke treatment is critically needed. We previously showed that genetic deletion and short-term pharmacological inhibition of P2X4R, a purinergic receptor for adenosine triphosphate ATP, provides acute cerebroprotection. However, potential mechanisms remain unknown. Therefore, we employed RNA-seq technology to identify the gene expression profiles, pathway analysis, and qPCR validation of differentially expressed genes (DEGs). This analysis identified roles of DEGs in certain biological processes responsible for P2X4R-dependent cerebroprotection after stroke. We subjected both young and aged male and female global P2X4 KO and littermate WT mice to ischemic stroke. After 3 days, mice were sacrificed, total RNA was isolated using Trizol, and subjected to RNA-seq and Nanostring-mediated qPCR. DESeq2, Gene Ontology (GO), and Ingenuity Pathway Analysis (IPA) were used to identify mRNA transcript expression profiles and biological pathways. We found 2246 DEGs in P2X4R KO vs WT tissue after stroke. Out of these DEGs, 1920 gene were downregulated, and 325 genes were upregulated in KO. GO/IPA analysis of the top 300 DEGs suggests an enrichment of inflammation and extracellular matrix component genes. qPCR validation of the top 30 DEGs revealed downregulation of two common age-independent genes in P2X4R KO mice: Interleukin-6 ( IL-6) , an inflammatory cytokine, and Cytotoxic T Lymphocyte-Associated Protein 2 alpha ( Ctla2a ), an immunosuppressive factor. These data suggest that P2X4R-mediated cerebroprotection after stroke is initiated by attenuation of immune modulatory pathways in both young and aged mice of both sexes.

The role of the ATP-adenosine axis in ischemic stroke

In ischemic stroke, the primary neuronal injury caused by the disruption of energy supply is further exacerbated by secondary sterile inflammation. The inflammatory cascade is largely initiated by the purine adenosine triphosphate (ATP) which is extensively released to the interstitial space during brain ischemia and functions as an extracellular danger signaling molecule. By engaging P2 receptors, extracellular ATP activates microglia leading to cytokine and chemokine production and subsequent immune cell recruitment from the periphery which further amplifies post-stroke inflammation. The ectonucleotidases CD39 and CD73 shape and balance the inflammatory environment by stepwise degrading extracellular ATP to adenosine which itself has neuroprotective and anti-inflammatory signaling properties. The neuroprotective effects of adenosine are mainly mediated through A₁ receptors and inhibition of glutamatergic excitotoxicity, while the anti-inflammatory capacities of adenosine have been primarily attributed to A_2A receptor activation on infiltrating immune cells in the subacute phase after stroke. In this review, we summarize the current state of knowledge on the ATP-adenosine axis in ischemic stroke, discuss contradictory results, and point out potential pitfalls towards translating therapeutic approaches from rodent stroke models to human patients.

Metabolic Challenges in Anticancer CD8 T Cell Functions

Cancer immunotherapies continue to face numerous obstacles in the successful treatment of solid malignancies. While immunotherapy has emerged as an extremely effective treatment option for hematologic malignancies, it is largely ineffective against solid tumors due in part to metabolic challenges present in the tumor microenvironment (TME). Tumor-infiltrating CD8⁺ T cells face fierce competition with cancer cells for limited nutrients. The strong metabolic suppression in the TME often leads to impaired T-cell recruitment to the tumor site and hyporesponsive effector functions via T-cell exhaustion. Growing evidence suggests that mitochondria play a key role in CD8⁺ T-cell activation, migration, effector functions, and persistence in tumors. Therefore, targeting the mitochondrial metabolism of adoptively transferred T cells has the potential to greatly improve the effectiveness of cancer immunotherapies in treating solid malignancies.

Arming a killer: mitochondrial regulation of CD8+ T cell cytotoxicity

While once regarded as ATP factories, mitochondria have taken the spotlight as important regulators of cellular homeostasis. The past two decades have witnessed an intensifying interest in the study of mitochondria in cells of the immune system, with many new and unexpected roles for mitochondria emerging. Immune cells offer intriguing insights as mitochondria appear to play different roles at different stages of T cell development, matching the changing functions of the cells. Here we briefly review the multifaceted roles of mitochondria during T cell differentiation, focusing on CD8⁺ cytotoxic T lymphocytes (CTLs) and we consider how mitochondrial dysfunction can contribute to CTL exhaustion. In addition, we highlight a newly appreciated role for mitochondria as homeostatic regulators of CTL-mediated killing and explore the emerging literature describing mechanisms linking cytosolic and mitochondrial protein synthesis.

Purinergic signalling in graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation is used to treat blood cancers, but often results in lethal graft-versus-host disease (GVHD). GVHD is an inflammatory disorder mediated by donor leukocytes that damage host tissues. Purinergic signalling plays important roles in GVHD development in mice but studies of these pathways in human GVHD remain limited. P2X7 receptor activation by ATP on host antigen presenting cells contributes to the induction of GVHD, while activation of this receptor on regulatory T cells, myeloid-derived suppressor cells and possibly type 3 innate lymphoid cells results in their loss to promote GVHD progression. In contrast, A_2A receptor activation by adenosine on donor T cells serves to restrict GVHD development. These and other purinergic signalling molecules remain potential biomarkers and therapeutic targets in GVHD.

Extracellular mitochondria drive CD8 T cell dysfunction in trauma by upregulating CD39

RATIONALE

The increased mortality and morbidity seen in critically injured patients appears associated with systemic inflammatory response syndrome (SIRS) and immune dysfunction, which ultimately predisposes to infection. Mitochondria released by injury could generate danger molecules, for example, ATP, which in turn would be rapidly scavenged by ectonucleotidases, expressed on regulatory immune cells.

OBJECTIVE

To determine the association between circulating mitochondria, purinergic signalling and immune dysfunction after trauma.

METHODS

We tested the impact of hepatocyte-derived free mitochondria on blood-derived and lung-derived CD8 T cells in vitro and in experimental mouse models in vivo. In parallel, immune phenotypic analyses were conducted on blood-derived CD8 T cells obtained from trauma patients.

RESULTS

Isolated intact mitochondria are functional and generate ATP ex vivo. Extracellular mitochondria perturb CD8⁺ T cells in co-culture, inducing select features of immune exhaustion in vitro. These effects are modulated by scavenging ATP, modelled by addition of apyrase in vitro. Injection of intact mitochondria into recipient mice markedly upregulates the ectonucleotidase CD39, and other immune checkpoint markers in circulating CD8⁺ T cells. We note that mice injected with mitochondria, prior to instilling bacteria into the lung, exhibit more severe lung injury, characterised by elevated neutrophil influx and by changes in CD8⁺ T cell cytotoxic capacity. Importantly, the development of SIRS in injured humans, is likewise associated with disordered purinergic signalling and CD8 T cell dysfunction.

CONCLUSION

These studies in experimental models and in a cohort of trauma patients reveal important associations between extracellular mitochondria, aberrant purinergic signalling and immune dysfunction. These pathogenic factors with immune exhaustion are linked to SIRS and could be targeted therapeutically.

The role of extracellular ATP in homeostatic immune cell migration

Antigen stimulation induces adenosine triphosphate (ATP) release from naïve lymphocytes in lymphoid tissues. However, previous studies indicated that the non-lytic release of ATP also occurs in most tissues and cell types under physiological conditions. Here, we show that extracellular ATP (eATP) is indeed constitutively produced by naïve T cells in response to lymphoid chemokines in uninflamed lymph nodes and is involved in the regulation of immune cell migration. In this review, we briefly summarize the homeostatic role of extracellular ATP in immune cell migration in vivo.

β1 Integrin induces adhesion and migration of human Th17 cells via Pyk2-dependent activation of P2X4 receptor

Integrin-mediated T-cell adhesion and migration is a crucial step in immune response and autoimmune diseases. However, the underlying signalling mechanisms are not fully elucidated. In this study, we examined the implication of purinergic signalling, which has been associated with T-cell activation, in the adhesion and migration of human Th17 cells across fibronectin, a major matrix protein associated with inflammatory diseases. We showed that the adhesion of human Th17 cells to fibronectin induces, via β1 integrin, a sustained release of adenosine triphosphate (ATP) from the mitochondria through the pannexin-1 hemichannels. Inhibition of ATP release or its degradation with apyrase impaired the capacity of the cells to attach and migrate across fibronectin. Inhibition studies identified a major role for the purinergic receptor P2X4 in T-cell adhesion and migration but not for P2X7 or P2Y₁₁ receptors. Blockade of P2X4 but not P2X7 or P2Y₁₁ receptors reduced cell adhesion and migration by inhibiting activation of β1 integrins, which is essential for ligand binding. Furthermore, we found that β1 integrin-induced ATP release, P2X4 receptor transactivation, cell adhesion and migration were dependent on the focal adhesion kinase Pyk2 but not FAK. Finally, P2X4 receptor inhibition also blocked fibronectin-induced Pyk2 activation suggesting the existence of a positive feedback loop of activation between β1 integrin/Pyk2 and P2X4 purinergic signalling pathways. Our findings uncovered an unrecognized link between β1 integrin and P2X4 receptor signalling pathways for promoting T-cell adhesion and migration across the extracellular matrix.

The Flavonoid Naringenin Alleviates Collagen-Induced Arthritis through Curbing the Migration and Polarization of CD4+ T Lymphocyte Driven by Regulating Mitochondrial Fission

Rheumatoid arthritis (RA) is a progressive autoimmune disease. Due to local infiltration and damage to the joints, activated CD4⁺ T cells play a crucial role in the progression of RA. However, the exact regulatory mechanisms are perplexing, which makes the effective management of RA frustrating. This study aimed to investigate the effect of mitochondria fission on the polarization and migration of CD4⁺ T cells as well as the regulatory mechanism of NAR, so as to provide enlightenment on therapeutic targets and novel strategies for the treatment of RA. In this study, a collagen-induced arthritis (CIA) model was established, and rats were randomly given saline or naringenin (NAR, 10 mg/kg, 20 mg/kg, 50 mg/kg, i.p.) once a day, before being euthanized on the 42nd day of primary immunization. The pain-like behavior, articular index scores, account of synovial-infiltrated CD4⁺ T cells, and inflammatory factors were investigated in each group. In vitro, spleen CD4⁺ T lymphocytes were derived from each group. In addition, mitochondrial division inhibitor 1 (Mdivi-1) or NAR was added to the cell medium containing C-X-C motif chemokine ligand 12 (CXCL12) in order to induce CD4⁺ T lymphocytes, respectively. The polarization capacity of CD4⁺ T cells was evaluated through the immunofluorescence intensity of the F-actin and myosin light chain phosphorylated at Ser19 (pMLC S19), and the mitochondrial distribution was determined by co-localization analysis of the translocase of outer mitochondrial membrane 20 (TOM20, the mitochondrial marker) and intercellular adhesion molecule 1 (ICAM1, the uropod marker). The mitochondrial fission was investigated by detecting dynamin-related protein 1 (Drp1) and mitochondrial fission protein 1 (Fis1) using Western blot and immunofluorescence. This study revealed that high-dose NAR (50 mg/kg, i.p.) alleviated pain-like behavior and articular index scores, reduced the serum level of interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α), and accounted for CD4⁺ T lymphocytes that infiltrated into the synovial membrane of the CIA group. Meanwhile, NAR (50 mg/kg, i.p.) suppressed the polarization of spleen CD4⁺ T lymphocytes, reduced the redistribution of mitochondria in the uropod, and inhibited the expression of Drp1 and Fis1 in the CIA model. Furthermore, the in vitro experiments confirmed that NAR reduced mitochondrial fission, which in turn inhibited the CXCL12-induced polarization and migration of CD4⁺ T lymphocytes. Our results demonstrated that the flavonoid NAR was a promising drug for the treatment of RA, which could effectively interfere with mitochondrial fission, thus inhibiting the polarization and migration of CD4⁺ T cells in the synovial membrane.

Effector Memory-Expressing CD45RA (TEMRA) CD8+ T Cells from Kidney Transplant Recipients Exhibit Enhanced Purinergic P2X4 Receptor-Dependent Proinflammatory and Migratory Responses

BACKGROUND

The mechanisms regulating CD8+ T cell migration to nonlymphoid tissue during inflammation have not been fully elucidated, and the migratory properties of effector memory CD8+ T cells that re-express CD45RA (TEMRA CD8+ T cells) remain unclear, despite their roles in autoimmune diseases and allotransplant rejection.

METHODS

We used single-cell proteomic profiling and functional testing of CD8+ T cell subsets to characterize their effector functions and migratory properties in healthy volunteers and kidney transplant recipients with stable or humoral rejection.

RESULTS

We showed that humoral rejection of a kidney allograft is associated with an accumulation of cytolytic TEMRA CD8+ T cells in blood and kidney graft biopsies. TEMRA CD8+ T cells from kidney transplant recipients exhibited enhanced migratory properties compared with effector memory (EM) CD8+ T cells, with enhanced adhesion to activated endothelium and transmigration in response to the chemokine CXCL12. CXCL12 directly triggers a purinergic P2×4 receptor-dependent proinflammatory response of TEMRA CD8+ T cells from transplant recipients. The stimulation with IL-15 promotes the CXCL12-induced migration of TEMRA and EM CD8+ T cells and promotes the generation of functional PSGL1, which interacts with the cell adhesion molecule P-selectin and adhesion of these cells to activated endothelium. Although disruption of the interaction between functional PSGL1 and P-selectin prevents the adhesion and transmigration of both TEMRA and EM CD8+ T cells, targeting VLA-4 or LFA-1 (integrins involved in T cell migration) specifically inhibited the migration of TEMRA CD8+ T cells from kidney transplant recipients.

CONCLUSIONS

Our findings highlight the active role of TEMRA CD8+ T cells in humoral transplant rejection and suggest that kidney transplant recipients may benefit from therapeutics targeting these cells.

Purinergic regulation of mast cell function: P2X4 receptor-mediated enhancement of allergic responses

Adenosine triphosphate (ATP) initially attracted attention as a neurotransmitter, with much research conducted on the regulation of neurotransmission in the autonomic and central nervous systems. ATP is also abundant as an energy currency in all living cells and is released into extracellular spaces by various regulated mechanisms. The role of ATP and related purine and pyrimidine nucleotides as extracellular signaling molecules in the regulation of immune cell functions has been reported as evidence for purinergic signaling and has become the focus of attention as therapeutic targets for various diseases. Mast cells (MCs) are distributed in tissues in contact with the outside environment and are the first immune cells to respond to non-microbial environmental antigens. Although extracellular ATP is known as an activator of MCs, the details remain to be investigated. Based on our series of studies, this review describes the unique features of ionotropic P2X4 receptor signals in MC functions. The role of purinergic signaling may exist in combination with various physiological, chemical and physical stimuli. The characteristics of P2X4 receptor-mediated action in MCs described in this article may provide clues to reveal the previously unknown effects induced by purinergic signaling.

Reprogramming T-Cell Metabolism for Better Anti-Tumor Immunity

T cells play central roles in the anti-tumor immunity, whose activation and differentiation are profoundly regulated by intrinsic metabolic reprogramming. Emerging evidence has revealed that metabolic processes of T cells are generally altered by tumor cells or tumor released factors, leading to crippled anti-tumor immunity. Therefore, better understanding of T cell metabolic mechanism is crucial in developing the next generation of T cell-based anti-tumor immunotherapeutics. In this review, we discuss how metabolic pathways affect T cells to exert their anti-tumor effects and how to remodel the metabolic programs to improve T cell-mediated anti-tumor immune responses. We emphasize that glycolysis, carboxylic acid cycle, fatty acid oxidation, cholesterol metabolism, amino acid metabolism, and nucleotide metabolism work together to tune tumor-reactive T-cell activation and proliferation.

P2 Receptors: Novel Disease Markers and Metabolic Checkpoints in Immune Cells

Extracellular ATP (eATP) and P2 receptors are novel emerging regulators of T-lymphocyte responses. Cellular ATP is released via multiple pathways and accumulates at sites of tissue damage and inflammation. P2 receptor expression and function are affected by numerous single nucleotide polymorphisms (SNPs) associated with diverse disease conditions. Stimulation by released nucleotides (purinergic signalling) modulates several T-lymphocyte functions, among which energy metabolism. Energy metabolism, whether oxidative or glycolytic, in turn deeply affects T-cell activation, differentiation and effector responses. Specific P2R subtypes, among which the P2X7 receptor (P2X7R), are either up- or down-regulated during T-cell activation and differentiation; thus, they can be considered indexes of activation/quiescence, reporters of T-cell metabolic status and, in principle, markers of immune-mediated disease conditions.

IL-4 prevents adenosine-mediated immunoregulation by inhibiting CD39 expression

The ectonucleotidase CD39 functions as a checkpoint in purinergic signaling on effector T cells. By depleting eATP and initiating the generation of adenosine, it impairs memory cell development and contributes to T cell exhaustion, thereby causing defective tumor immunity and deficient T cell responses in older adults who have increased CD39 expression. Tuning enzymatic activity of CD39 and targeting the transcriptional regulation of ENTPD1 can be used to modulate purinergic signaling. Here, we describe that STAT6 phosphorylation downstream of IL-4 signaling represses CD39 expression on activated T cells by inducing a transcription factor network including GATA3, GFI1, and YY1. GATA3 suppresses ENTPD1 transcription through prevention of RUNX3 recruitment to the ENTPD1 promoter. Conversely, pharmacological STAT6 inhibition decreases T cell effector functions via increased CD39 expression, resulting in the defective signaling of P2X receptors by ATP and stimulation of A2A receptors by adenosine. Our studies suggest that inhibiting the STAT6 pathway to increase CD39 expression has the potential to treat autoimmune disease while stimulation of the pathway could improve T cell immunity.

Immune Checkpoint Proteins, Metabolism and Adhesion Molecules: Overlooked Determinants of CAR T-Cell Migration?

Adoptive transfer of T cells genetically engineered to express chimeric antigen receptors (CAR) has demonstrated striking efficacy for the treatment of several hematological malignancies, including B-cell lymphoma, leukemia, and multiple myeloma. However, many patients still do not respond to this therapy or eventually relapse after an initial remission. In most solid tumors for which CAR T-cell therapy has been tested, efficacy has been very limited. In this context, it is of paramount importance to understand the mechanisms of tumor resistance to CAR T cells. Possible factors contributing to such resistance have been identified, including inherent CAR T-cell dysfunction, the presence of an immunosuppressive tumor microenvironment, and tumor-intrinsic factors. To control tumor growth, CAR T cells have to migrate actively enabling a productive conjugate with their targets. To date, many cells and factors contained within the tumor microenvironment have been reported to negatively control the migration of T cells and their ability to reach cancer cells. Recent evidence suggests that additional determinants, such as immune checkpoint proteins, cellular metabolism, and adhesion molecules, may modulate the motility of CAR T cells in tumors. Here, we review the potential impact of these determinants on CAR T-cell motility, and we discuss possible strategies to restore intratumoral T-cell migration with a special emphasis on approaches targeting these determinants.

The P2X4 Receptor: Cellular and Molecular Characteristics of a Promising Neuroinflammatory Target

The adenosine 5′-triphosphate-gated P2X4 receptor channel is a promising target in neuroinflammatory disorders, but the ability to effectively target these receptors in models of neuroinflammation has presented a constant challenge. As such, the exact role of P2X4 receptors and their cell signalling mechanisms in human physiology and pathophysiology still requires further elucidation. To this end, research into the molecular mechanisms of P2X4 receptor activation, modulation, and inhibition has continued to gain momentum in an attempt to further describe the role of P2X4 receptors in neuroinflammation and other disease settings. Here we provide an overview of the current understanding of the P2X4 receptor, including its expression and function in cells involved in neuroinflammatory signalling. We discuss the pharmacology of P2X4 receptors and provide an overview of P2X4-targeting molecules, including agonists, positive allosteric modulators, and antagonists. Finally, we discuss the use of P2X4 receptor modulators and antagonists in models of neuroinflammatory cell signalling and disease.

Effects of Hormone, NEFA and SCFA on the Migration of Neutrophils and the Formation of Neutrophil Extracellular Traps in Dairy Cows

Simple Summary

Perinatal dairy cows face the challenge of maintaining the resilience of defense against invading pathogens. During the perinatal period, hormonal or metabolic changes cause the decline of immune function of dairy cows and further lead to varying degrees of immunosuppression. The results of this study indicate that, hormones, nonesterified fatty acids (NEFAs) and short-chain fatty acids (SCFAs) can regulate neutrophil migration and the NETs formation of dairy cows in vitro. These results help to further explain the effects of changes in hormone secretion and metabolites on immunosuppression and the increased risk of disease in perinatal dairy cows.

Abstract

Polymorphonuclear neutrophils (PMN) are the first line of defense against the invasion of foreign pathogenic microorganisms and play an essential role in the immune system of dairy cows. The changes in hormone secretion and metabolites of dairy cows during the perinatal period are the key factors that cause immunosuppression and increased risk of diseases. However, the effects of the hormone, nonesterified fatty acid (NEFA), and short-chain fatty acid (SCFA) on the transmammary epithelial migration of dairy cows and the formation of neutrophil extracellular traps (NETs) have rarely been studied. This study explored the effects of hormones, NEFAs and SCFAs on the neutrophil migration and NETs formation of dairy cows in vitro. It was found that P₄ and Ac can regulate the transepithelial migration of PMN; SA and Pr can regulate the formation of NETs; E₂, OA and Bt can regulate PMN transepithelial migration and NET formation. These results help to further explain the effects of changes in hormone secretion and metabolites on immunosuppression and the increased risk of disease in perinatal dairy cows.

The Purinergic Receptor P2X4 Promotes Th17 Activation and the Development of Arthritis

Purinergic signaling plays a major role in T cell activation leading to IL-2 production and proliferation. However, it is unclear whether purinergic signaling contributes to the differentiation and activation of effector T cells. In this study, we found that the purinergic receptor P2X4 was associated with human Th17 cells but not with Th1 cells. Inhibition of P2X4 receptor with the specific antagonist 5-BDBD and small interfering RNA inhibited the development of Th17 cells and the production of IL-17 by effector Th17 cells stimulated via the CD3/CD28 pathway. Our results showed that P2X4 was required for the expression of retinoic acid-related orphan receptor C, which is the master regulator of Th17 cells. In contrast, inhibition of P2X4 receptor had no effect on Th1 cells and on the production of IFN-γ and it did not affect the expression of the transcription factor T-bet (T-box transcription factor). Furthermore, inhibition of P2X4 receptor reduced the production of IL-17 but not of IFN-γ by effector/memory CD4⁺ T cells isolated from patients with rheumatoid arthritis. In contrast to P2X4, inhibition of P2X7 and P2Y₁₁ receptors had no effects on Th17 and Th1 cell activation. Finally, treatment with the P2X4 receptor antagonist 5-BDBD reduced the severity of collagen-induced arthritis in mice by inhibiting Th17 cell expansion and activation. Our findings provide novel insights into the role of purinergic signaling in T cell activation and identify a critical role for the purinergic receptor P2X4 in Th17 activation and in autoimmune arthritis.

Pannexin Channel Regulation of Cell Migration: Focus on Immune Cells

The role of Pannexin (PANX) channels during collective and single cell migration is increasingly recognized. Amongst many functions that are relevant to cell migration, here we focus on the role of PANX-mediated adenine nucleotide release and associated autocrine and paracrine signaling. We also summarize the contribution of PANXs with the cytoskeleton, which is also key regulator of cell migration. PANXs, as mechanosensitive ATP releasing channels, provide a unique link between cell migration and purinergic communication. The functional association with several purinergic receptors, together with a plethora of signals that modulate their opening, allows PANX channels to integrate physical and chemical cues during inflammation. Ubiquitously expressed in almost all immune cells, PANX1 opening has been reported in different immunological contexts. Immune activation is the epitome coordination between cell communication and migration, as leukocytes (i.e., T cells, dendritic cells) exchange information while migrating towards the injury site. In the current review, we summarized the contribution of PANX channels during immune cell migration and recruitment; although we also compile the available evidence for non-immune cells (including fibroblasts, keratinocytes, astrocytes, and cancer cells). Finally, we discuss the current evidence of PANX1 and PANX3 channels as a both positive and/or negative regulator in different inflammatory conditions, proposing a general mechanism of these channels contribution during cell migration.

Single-cell eQTL analysis of activated T cell subsets reveals activation and cell type-dependent effects of disease-risk variants

The impact of genetic variants on cells challenged in biologically relevant contexts has not been fully explored. Here, we activated CD4⁺ T cells from 89 healthy donors and performed a single-cell RNA sequencing assay with >1 million cells to examine cell type-specific and activation-dependent effects of genetic variants. Single-cell expression quantitative trait loci (sc-eQTL) analysis of 19 distinct CD4⁺ T cell subsets showed that the expression of over 4000 genes is significantly associated with common genetic polymorphisms and that most of these genes show their most prominent effects in specific cell types. These genes included many that encode for molecules important for activation, differentiation, and effector functions of T cells. We also found new gene associations for disease-risk variants identified from genome-wide association studies and highlighted the cell types in which their effects are most prominent. We found that biological sex has a major influence on activation-dependent gene expression in CD4⁺ T cell subsets. Sex-biased transcripts were significantly enriched in several pathways that are essential for the initiation and execution of effector functions by CD4⁺ T cells like TCR signaling, cytokines, cytokine receptors, costimulatory, apoptosis, and cell-cell adhesion pathways. Overall, this DICE (Database of Immune Cell Expression, eQTLs, and Epigenomics) subproject highlights the power of sc-eQTL studies for simultaneously exploring the activation and cell type-dependent effects of common genetic variants on gene expression (https://dice-database.org).

Extracellular ATP Limits Homeostatic T Cell Migration Within Lymph Nodes

Whereas adenosine 5'-triphosphate (ATP) is the major energy source in cells, extracellular ATP (eATP) released from activated/damaged cells is widely thought to represent a potent damage-associated molecular pattern that promotes inflammatory responses. Here, we provide suggestive evidence that eATP is constitutively produced in the uninflamed lymph node (LN) paracortex by naïve T cells responding to C-C chemokine receptor type 7 (CCR7) ligand chemokines. Consistently, eATP was markedly reduced in naïve T cell-depleted LNs, including those of nude mice, CCR7-deficient mice, and mice subjected to the interruption of the afferent lymphatics in local LNs. Stimulation with a CCR7 ligand chemokine, CCL19, induced ATP release from LN cells, which inhibited CCR7-dependent lymphocyte migration in vitro by a mechanism dependent on the purinoreceptor P2X7 (P2X7R), and P2X7R inhibition enhanced T cell retention in LNs in vivo. These results collectively indicate that paracortical eATP is produced by naïve T cells in response to constitutively expressed chemokines, and that eATP negatively regulates CCR7-mediated lymphocyte migration within LNs via a specific subtype of ATP receptor, demonstrating its fine-tuning role in homeostatic cell migration within LNs.

P2X4 and P2X7 are essential players in basal T cell activity and Ca2+ signaling milliseconds after T cell activation

Initial T cell activation is triggered by the formation of highly dynamic, spatiotemporally restricted Ca²⁺ microdomains. Purinergic signaling is known to be involved in Ca²⁺ influx in T cells at later stages compared to the initial microdomain formation. Using a high-resolution Ca²⁺ live-cell imaging system, we show that the two purinergic cation channels P2X4 and P2X7 not only are involved in the global Ca²⁺ signals but also promote initial Ca²⁺ microdomains tens of milliseconds after T cell stimulation. These Ca²⁺ microdomains were significantly decreased in T cells from P2rx4^-/- and P2rx7^-/- mice or by pharmacological inhibition or blocking. Furthermore, we show a pannexin-1-dependent activation of P2X4 in the absence of T cell receptor/CD3 stimulation. Subsequently, upon T cell receptor/CD3 stimulation, ATP release is increased and autocrine activation of both P2X4 and P2X7 then amplifies initial Ca²⁺ microdomains already in the first second of T cell activation.

Metabolic adaptation of lymphocytes in immunity and disease

Adaptive immune responses mediated by T cells and B cells are crucial for protective immunity against pathogens and tumors. Differentiation and function of immune cells require dynamic reprogramming of cellular metabolism. Metabolic inputs, pathways, and enzymes display remarkable flexibility and heterogeneity, especially in vivo. How metabolic plasticity and adaptation dictate functional specialization of immune cells is fundamental to our understanding and therapeutic modulation of the immune system. Extensive progress has been made in characterizing the effects of metabolic networks on immune cell fate and function in discrete microenvironments or immunological contexts. In this review, we summarize how rewiring of cellular metabolism determines the outcome of adaptive immunity in vivo, with a focus on how metabolites, nutrients, and driver genes in immunometabolism instruct cellular programming and immune responses during infection, inflammation, and cancer in mice and humans. Understanding context-dependent metabolic remodeling will manifest legitimate opportunities for therapeutic intervention of human disease.

Modulation of Cell Energy Metabolism by the P2X7 Receptor

For many years the P2X7 receptor (P2X7R) was considered the prototypic cytolytic receptor due to its ability to cause dramatic changes in plasma membrane permeability, eventually leading to cell death. However, later studies revealed that controlled P2X7R activation has beneficial effects on cell metabolism and nowadays our perception of the physiological role of this receptor has radically changed. Some of the biochemical pathways underlying the trophic effect of the P2X7R are being unveiled, thus disclosing an unanticipated role of P2X7Rs in mitochondrial and glycolytic metabolism. We provide here an update of the effects of the P2X7R on cell energy metabolism.

Pannexin-1 channel opening is critical for COVID-19 pathogenesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapidly rampaged worldwide, causing a pandemic of coronavirus disease (COVID -19), but the biology of SARS-CoV-2 remains under investigation. We demonstrate that both SARS-CoV-2 spike protein and human coronavirus 229E (hCoV-229E) or its purified S protein, one of the main viruses responsible for the common cold, induce the transient opening of Pannexin-1 (Panx-1) channels in human lung epithelial cells. However, the Panx-1 channel opening induced by SARS-CoV-2 is greater and more prolonged than hCoV-229E/S protein, resulting in an enhanced ATP, PGE₂, and IL-1β release. Analysis of lung lavages and tissues indicate that Panx-1 mRNA expression is associated with increased ATP, PGE₂, and IL-1β levels. Panx-1 channel opening induced by SARS-CoV-2 spike protein is angiotensin-converting enzyme 2 (ACE-2), endocytosis, and furin dependent. Overall, we demonstrated that Panx-1 channel is a critical contributor to SARS-CoV-2 infection and should be considered as an alternative therapy.

A novel definition and treatment of hyperinflammation in COVID-19 based on purinergic signalling

Hyperinflammation plays an important role in severe and critical COVID-19. Using inconsistent criteria, many researchers define hyperinflammation as a form of very severe inflammation with cytokine storm. Therefore, COVID-19 patients are treated with anti-inflammatory drugs. These drugs appear to be less efficacious than expected and are sometimes accompanied by serious adverse effects. SARS-CoV-2 promotes cellular ATP release. Increased levels of extracellular ATP activate the purinergic receptors of the immune cells initiating the physiologic pro-inflammatory immune response. Persisting viral infection drives the ATP release even further leading to the activation of the P2X7 purinergic receptors (P2X7Rs) and a severe yet physiologic inflammation. Disease progression promotes prolonged vigorous activation of the P2X7R causing cell death and uncontrolled ATP release leading to cytokine storm and desensitisation of all other purinergic receptors of the immune cells. This results in immune paralysis with co-infections or secondary infections. We refer to this pathologic condition as hyperinflammation. The readily available and affordable P2X7R antagonist lidocaine can abrogate hyperinflammation and restore the normal immune function. The issue is that the half-maximal effective concentration for P2X7R inhibition of lidocaine is much higher than the maximal tolerable plasma concentration where adverse effects start to develop. To overcome this, we selectively inhibit the P2X7Rs of the immune cells of the lymphatic system inducing clonal expansion of Tregs in local lymph nodes. Subsequently, these Tregs migrate throughout the body exerting anti-inflammatory activities suppressing systemic and (distant) local hyperinflammation. We illustrate this with six critically ill COVID-19 patients treated with lidocaine.

T-cell Immunometabolism: Therapeutic Implications in Organ Transplantation

Although solid-organ transplantation has evolved steadily with many breakthroughs in the past 110 y, many problems remain to be addressed, and advanced therapeutic strategies need to be considered. T-cell immunometabolism is a rapidly advancing field that has gathered much attention recently, providing ample mechanistic insight from which many novel therapeutic approaches have been developed. Applications from the field include antitumor and antimicrobial therapies, as well as for reversing graft-versus-host disease and autoimmune diseases. However, the immunometabolism of T cells remains underexplored in solid-organ transplantation. In this review, we will highlight key findings from hallmark studies centered around various metabolic modes preferred by different T-cell subtypes (categorized into naive, effector, regulatory, and memory T cells), including glycolysis, glutaminolysis, oxidative phosphorylation, fatty acid synthesis, and oxidation. This review will discuss the underlying cellular signaling components that affect these processes, including the transcription factors myelocytomatosis oncogene, hypoxia-inducible factor 1-alpha, estrogen-related receptor alpha, and sterol regulatory element-binding proteins, along with the mechanistic target of rapamycin and adenosine monophosphate-activated protein kinase signaling. We will also explore potential therapeutic strategies targeting these pathways, as applied to the potential for tolerance induction in solid-organ transplantation.

Involvement of the miR-363-5p/P2RX4 Axis in Regulating Schwann Cell Phenotype after Nerve Injury

Although microRNAs (miRNAs or miRs) have been studied in the peripheral nervous system, their function in Schwann cells remains elusive. In this study, we performed a microRNA array analysis of cyclic adenosine monophosphate (cAMP)-induced differentiated primary Schwann cells. KEGG pathway enrichment analysis of the target genes showed that upregulated miRNAs (mR212-5p, miR335, miR20b-5p, miR146b-3p, and miR363-5p) were related to the calcium signaling pathway, regulation of actin cytoskeleton, retrograde endocannabinoid signaling, and central carbon metabolism in cancer. Several key factors, such as purinergic receptors (P2X), guanine nucleotide-binding protein G(olf) subunit alpha (GNAL), P2RX5, P2RX3, platelet-derived growth factor receptor alpha (PDGFRA), and inositol 1,4,5-trisphosphate receptor type 2 (ITPR2; calcium signaling pathway) are potential targets of miRNAs regulating cAMP. Our analysis revealed that miRNAs were differentially expressed in cAMP-treated Schwann cells; miRNA363-5p was upregulated and directly targeted the P2X purinoceptor 4 (P2RX4)-UTR, reducing the luciferase activity of P2RX4. The expression of miRNA363-5p was inhibited and the expression of P2RX4 was upregulated in sciatic nerve injury. In contrast, miRNA363-5p expression was upregulated and P2RX4 expression was downregulated during postnatal development. Of note, a P2RX4 antagonist counteracted myelin degradation after nerve injury and increased pERK and c-Jun expression. Interestingly, a P2RX4 antagonist increased the levels of miRNA363-5p. This study suggests that a double-negative feedback loop between miRNA363-5p and P2RX4 contributes to the dedifferentiation and migration of Schwann cells after nerve injury.

H2 O2 -induced oxidative stress disrupts mitochondrial functions and impairs migratory potential of human epidermal melanocytes

Reactive oxygen species (ROS) have already been demonstrated to impede the migratory ability in non-melanocytic cell lines by depleting mitochondrial ATP production. Therefore, understanding the mitochondrial metabolic response to migration in the presence of ROS should be a key to understanding repigmentation in vitiligo. This study aimed to investigate the energy mechanism associated with the ROS-mediated attenuation of melanocyte migration. After melanocytes were pretreated with H₂ O₂ , their ATP production, migratory ability, ultrastructural changes and Mitochondrial Permeability Potential were analysed. The results showed that, in parallel with the decreased ATP production, the migratory ability of melanocytes was significantly inhibited by oxidative stress. Supplementation with exogenous ATP reversed the suppressed ATP-dependent migration of melanocytes. Melanocytes were then stressed with H₂ O₂ and Agilent Whole Human Genome microarray analysis identified 763 up-regulated mRNAs and 1117 down-regulated mRNAs. Among them, 11 of the encoded proteins were involved in mitochondrial ATP production and their expression levels were verified. The decreased expression of NADH dehydrogenase 2(ND₂₎ , cytochrome c oxidase 1(COX1) and cytochrome c oxidase 3(COX3) was shown to be involved in the depletion of mitochondrial ATP production, which was coupled with the impaired migratory potential. These results indicate that the migration of melanocytes relies heavily on an inexhaustible supply of ATP from mitochondria.

The ATP-hydrolyzing ectoenzyme E-NTPD8 attenuates colitis through modulation of P2X4 receptor-dependent metabolism in myeloid cells

Extracellular adenosine triphosphate (ATP) released by mucosal immune cells and by microbiota in the intestinal lumen elicits diverse immune responses that mediate the intestinal homeostasis via P2 purinergic receptors, while overactivation of ATP signaling leads to mucosal immune system disruption, which leads to pathogenesis of intestinal inflammation. In the small intestine, hydrolysis of luminal ATP by ectonucleoside triphosphate diphosphohydrolase (E-NTPD)7 in epithelial cells is essential for control of the number of T helper 17 (Th17) cells. However, the molecular mechanism by which microbiota-derived ATP in the colon is regulated remains poorly understood. Here, we show that E-NTPD8 is highly expressed in large-intestinal epithelial cells and hydrolyzes microbiota-derived luminal ATP. Compared with wild-type mice, Entpd8 ^-/- mice develop more severe dextran sodium sulfate-induced colitis, which can be ameliorated by either the depletion of neutrophils and monocytes by injecting with anti-Gr-1 antibody or the introduction of P2rx4 deficiency into hematopoietic cells. An increased level of luminal ATP in the colon of Entpd8 ^-/- mice promotes glycolysis in neutrophils through P2x4 receptor-dependent Ca²⁺ influx, which is linked to prolonged survival and elevated reactive oxygen species production in these cells. Thus, E-NTPD8 limits intestinal inflammation by controlling metabolic alteration toward glycolysis via the P2X4 receptor in myeloid cells.

IL-6 enhances CD4 cell motility by sustaining mitochondrial Ca2+ through the noncanonical STAT3 pathway

Interleukin 6 (IL-6) is known to regulate the CD4 T cell function by inducing gene expression of a number of cytokines through activation of Stat3 transcription factor. Here, we reveal that IL-6 strengthens the mechanics of CD4 T cells. The presence of IL-6 during activation of mouse and human CD4 T cells enhances their motility (random walk and exploratory spread), resulting in an increase in travel distance and higher velocity. This is an intrinsic effect of IL-6 on CD4 T-cell fitness that involves an increase in mitochondrial Ca²⁺ Although Stat3 transcriptional activity is dispensable for this process, IL-6 uses mitochondrial Stat3 to enhance mitochondrial Ca²⁺-mediated motility of CD4 T cells. Thus, through a noncanonical pathway, IL-6 can improve competitive fitness of CD4 T cells by facilitating cell motility. These results could lead to alternative therapeutic strategies for inflammatory diseases in which IL-6 plays a pathogenic role.

Brd4 Regulates the Homeostasis of CD8+ T-Lymphocytes and Their Proliferation in Response to Antigen Stimulation

CD8+ T cells are major components of adaptive immunity and confer robust protective cellular immunity, which requires adequate T-cell numbers, targeted migration, and efficient T-cell proliferation. Altered CD8+ T-cell homeostasis and impaired proliferation result in dysfunctional immune response to infection or tumorigenesis. However, intrinsic factors controlling CD8+ T-cell homeostasis and immunity remain largely elusive. Here, we demonstrate the prominent role of Brd4 on CD8+ T cell homeostasis and immune response. By upregulating Myc and GLUT1 expression, Brd4 facilitates glucose uptake and energy production in mitochondria, subsequently supporting naïve CD8+ T-cell survival. Besides, Brd4 promotes the trafficking of naïve CD8+ T cells partially through maintaining the expression of homing receptors (CD62L and LFA-1). Furthermore, Brd4 is required for CD8+ T cell response to antigen stimulation, as Brd4 deficiency leads to a severe defect in clonal expansion and terminal differentiation by decreasing glycolysis. Importantly, as JQ1, a pan-BRD inhibitor, severely dampens CD8+ T-cell immune response, its usage as an anti-tumor agent or latency-reversing agent for human immunodeficiency virus type I (HIV-1) should be more cautious. Collectively, our study identifies a previously-unexpected role of Brd4 in the metabolic regulation of CD8+ T cell-mediated immune surveillance and also provides a potential immunomodulation target.

On the mechanism of anti-CD39 immune checkpoint therapy

With the coming of age of cancer immunotherapy, the search for new therapeutic targets has led to the identification of immunosuppressive adenosine as an important regulator of antitumor immunity. This resulted in the development of selective inhibitors targeting various components of the adenosinergic pathway, including small molecules antagonists targeting the high affinity A2A adenosine receptor and low affinity A2B receptor, therapeutic monoclonal antibodies (mAbs) and small molecules targeting CD73 and therapeutic mAbs targeting CD39. As each regulator of the adenosinergic pathway present non-overlapping biologic functions, a better understanding of the mechanisms of action of each targeted approach should accelerate clinical translation and improve rational design of combination treatments. In this review, we discuss the potential mechanisms-of-action of anti-CD39 cancer therapy and potential toxicities that may emerge from sustained CD39 inhibition. Caution should be taken, however, in extrapolating data from gene-targeted mice to patients treated with blocking anti-CD39 agents. As phase I clinical trials are now underway, further insights into the mechanism of action and potential adverse events associated with anti-CD39 therapy are anticipated in coming years.

Lysosome purinergic receptor P2X4 regulates neoangiogenesis induced by microvesicles from sarcoma patients

The tumor microenvironment modulates cancer growth. Extracellular vesicles (EVs) have been identified as key mediators of intercellular communication, but their role in tumor growth is largely unexplored. Here, we demonstrate that EVs from sarcoma patients promote neoangiogenesis via a purinergic X receptor 4 (P2XR4) -dependent mechanism in vitro and in vivo. Using a proteomic approach, we analyzed the protein content of plasma EVs and identified critical activated pathways in human umbilical vein endothelial cells (HUVECs) and human progenitor hematopoietic cells (CD34+). We then showed that vessel formation was due to rapid mitochondrial activation, intracellular Ca²⁺ mobilization, increased extracellular ATP, and trafficking of the lysosomal P2XR4 to the cell membrane, which is required for cell motility and formation of stable branching vascular networks. Cell membrane translocation of P2XR4 was induced by proteins and chemokines contained in EVs (e.g. Del-1 and SDF-1). Del-1 was found expressed in many EVs from sarcoma tumors and several tumor types. P2XR4 blockade reduced EVs-induced vessels in angioreactors, as well as intratumor vascularization in mouse xenografts. Together, these findings identify P2XR4 as a key mediator of EVs-induced tumor angiogenesis via a signaling mediated by mitochondria-lysosome-sensing response in endothelial cells, and indicate a novel target for therapeutic interventions.

The Nlrp3 inflammasome - the evolving story of its positive and negative effects on hematopoiesis

PURPOSE OF REVIEW

Hematopoiesis is co-regulated by innate immunity, which is an ancient evolutionary defense mechanism also involved in the development and regeneration of damaged tissues. This review seeks to shed more light on the workings of the Nlrp3 inflammasome, which is an intracellular innate immunity pattern recognition receptor and sensor of changes in the hematopoietic microenvironment, and focus on its role in hematopoieisis.

RECENT FINDINGS

Hematopoietic stem progenitor cells (HSPCs) are exposed to several external mediators of innate immunity. Moreover, since hemato/lymphopoietic cells develop from a common stem cell, their behavior and fate are coregulated by intracellular innate immunity pathways. Therefore, the Nlrp3 inflammasome is functional both in immune cells and in HSPCs and affects hematopoiesis in either a positive or negative way, depending on its activity level. Specifically, while a physiological level of activation regulates the trafficking of HSPCs and most likely maintains their pool in the bone marrow, hyperactivation may lead to irreversible cell damage by pyroptosis and HSPC senescence and contribute to the origination of myelodysplasia and hematopoietic malignancies.

SUMMARY

Modulation of the level of Nrp3 inflammasome activation will enable improvements in HSPC mobilization, homing, and engraftment strategies. It may also control pathological activation of this protein complex during HSPC senescence, graft-versus-host disease, the induction of cytokine storms, and the development of hematopoietic malignancies.

Optical Control of CD8+ T Cell Metabolism and Effector Functions

Although cancer immunotherapy is effective against hematological malignancies, it is less effective against solid tumors due in part to significant metabolic challenges present in the tumor microenvironment (TME), where infiltrated CD8+ T cells face fierce competition with cancer cells for limited nutrients. Strong metabolic suppression in the TME is often associated with impaired T cell recruitment to the tumor site and hyporesponsive effector function via T cell exhaustion. Increasing evidence suggests that mitochondria play a key role in CD8+ T cell activation, effector function, and persistence in tumors. In this study, we showed that there was an increase in overall mitochondrial function, including mitochondrial mass and membrane potential, during both mouse and human CD8+ T cell activation. CD8+ T cell mitochondrial membrane potential was closely correlated with granzyme B and IFN-γ production, demonstrating the significance of mitochondria in effector T cell function. Additionally, activated CD8+ T cells that migrate on ICAM-1 and CXCL12 consumed significantly more oxygen than stationary CD8+ T cells. Inhibition of mitochondrial respiration decreased the velocity of CD8+ T cell migration, indicating the importance of mitochondrial metabolism in CD8+ T cell migration. Remote optical stimulation of CD8+ T cells that express our newly developed "OptoMito-On" successfully enhanced mitochondrial ATP production and improved overall CD8+ T cell migration and effector function. Our study provides new insight into the effect of the mitochondrial membrane potential on CD8+ T cell effector function and demonstrates the development of a novel optogenetic technique to remotely control T cell metabolism and effector function at the target tumor site with outstanding specificity and temporospatial resolution.