Distinct Regulation of Th17 and Th1 Cell Differentiation by Glutaminase-Dependent Metabolism.

Activated T cells differentiate into functional subsets with distinct metabolic programs. Glutaminase (GLS) converts glutamine to glutamate to support the tricarboxylic acid cycle and redox and epigenetic reactions. Here, we identify a key role for GLS in T cell activation and specification. Though GLS deficiency diminished initial T cell activation and proliferation and impaired differentiation of Th17 cells, loss of GLS also increased Tbet to promote differentiation and effector function of CD4 Th1 and CD8 CTL cells. This was associated with altered chromatin accessibility and gene expression, including decreased PIK3IP1 in Th1 cells that sensitized to IL-2-mediated mTORC1 signaling. In vivo, GLS null T cells failed to drive Th17-inflammatory diseases, and Th1 cells had initially elevated function but exhausted over time. Transient GLS inhibition, however, led to increased Th1 and CTL T cell numbers. Glutamine metabolism thus has distinct roles to promote Th17 but constrain Th1 and CTL effector cell differentiation.

MTHFD2 is a metabolic checkpoint controlling effector and regulatory T cell fate and function.

Antigenic stimulation promotes T cell metabolic reprogramming to meet increased biosynthetic, bioenergetic, and signaling demands. We show that the one-carbon (1C) metabolism enzyme methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) regulates de novo purine synthesis and signaling in activated T cells to promote proliferation and inflammatory cytokine production. In pathogenic T helper-17 (Th17) cells, MTHFD2 prevented aberrant upregulation of the transcription factor FoxP3 along with inappropriate gain of suppressive capacity. MTHFD2 deficiency also promoted regulatory T (Treg) cell differentiation. Mechanistically, MTHFD2 inhibition led to depletion of purine pools, accumulation of purine biosynthetic intermediates, and decreased nutrient sensor mTORC1 signaling. MTHFD2 was also critical to regulate DNA and histone methylation in Th17 cells. Importantly, MTHFD2 deficiency reduced disease severity in multiple in vivo inflammatory disease models. MTHFD2 is thus a metabolic checkpoint to integrate purine metabolism with pathogenic effector cell signaling and is a potential therapeutic target within 1C metabolism pathways.

T cells specific for α-myosin drive immunotherapy-related myocarditis.

Immune-related adverse events, particularly severe toxicities such as myocarditis, are major challenges to the utility of immune checkpoint inhibitors (ICIs) in anticancer therapy1. The pathogenesis of ICI-associated myocarditis (ICI-MC) is poorly understood. Pdcd1-/-Ctla4+/- mice recapitulate clinicopathological features of ICI-MC, including myocardial T cell infiltration2. Here, using single-cell RNA and T cell receptor (TCR) sequencing of cardiac immune infiltrates from Pdcd1-/-Ctla4+/- mice, we identify clonal effector CD8+ T cells as the dominant cell population. Treatment with anti-CD8-depleting, but not anti-CD4-depleting, antibodies improved the survival of Pdcd1-/-Ctla4+/- mice. Adoptive transfer of immune cells from mice with myocarditis induced fatal myocarditis in recipients, which required CD8+ T cells. The cardiac-specific protein α-myosin, which is absent from the thymus3,4, was identified as the cognate antigen source for three major histocompatibility complex class I-restricted TCRs derived from mice with fulminant myocarditis. Peripheral blood T cells from three patients with ICI-MC were expanded by α-myosin peptides. Moreover, these α-myosin-expanded T cells shared TCR clonotypes with diseased heart and skeletal muscle, which indicates that α-myosin may be a clinically important autoantigen in ICI-MC. These studies underscore the crucial role for cytotoxic CD8+ T cells, identify a candidate autoantigen in ICI-MC and yield new insights into the pathogenesis of ICI toxicity.

Cell-programmed nutrient partitioning in the tumour microenvironment.

Cancer cells characteristically consume glucose through Warburg metabolism1, a process that forms the basis of tumour imaging by positron emission tomography (PET). Tumour-infiltrating immune cells also rely on glucose, and impaired immune cell metabolism in the tumour microenvironment (TME) contributes to immune evasion by tumour cells2-4. However, whether the metabolism of immune cells is dysregulated in the TME by cell-intrinsic programs or by competition with cancer cells for limited nutrients remains unclear. Here we used PET tracers to measure the access to and uptake of glucose and glutamine by specific cell subsets in the TME. Notably, myeloid cells had the greatest capacity to take up intratumoral glucose, followed by T cells and cancer cells, across a range of cancer models. By contrast, cancer cells showed the highest uptake of glutamine. This distinct nutrient partitioning was programmed in a cell-intrinsic manner through mTORC1 signalling and the expression of genes related to the metabolism of glucose and glutamine. Inhibiting glutamine uptake enhanced glucose uptake across tumour-resident cell types, showing that glutamine metabolism suppresses glucose uptake without glucose being a limiting factor in the TME. Thus, cell-intrinsic programs drive the preferential acquisition of glucose and glutamine by immune and cancer cells, respectively. Cell-selective partitioning of these nutrients could be exploited to develop therapies and imaging strategies to enhance or monitor the metabolic programs and activities of specific cell populations in the TME.

Motivated with joy or anxiety: Does approach-avoidance goal framing elicit differential reward-network activation in the brain?

Psychological research on human motivation repeatedly observed that approach goals (i.e., goals to attain success) increase task enjoyment and intrinsic motivation more strongly than avoidance goals (i.e., goals to avoid failure). The present study sought to address how the reward network in the brain-including the striatum and ventromedial prefrontal cortex-is involved when individuals engage in the same task with a focus on approach or avoidance goals. Participants reported stronger positive emotions when they focused on approach goals, but stronger anxiety and disappointment when they focused on avoidance goals. The fMRI analyses revealed that the reward network in the brain showed similar levels of activity to cues predictive of approach and avoidance goals. In contrast, the two goal states were associated with different patterns of activity in the visual cortex, hippocampus, and cerebellum during success and failure outcomes. Representation similarity analysis further revealed shared and different representations within the striatum and vmPFC between the approach and avoidance goal states, suggesting both the similarity and uniqueness of the mechanisms behind the two goal states. In addition, the distinct patterns of activation in the striatum were associated with distinct subjective experiences participants reported between the approach and the avoidance conditions. These results suggest the importance of examining the pattern of striatal activity in understanding the mechanisms behind different motivational states in humans.

Motivated for near impossibility: How task type and reward modulate task enjoyment and the striatal activation for extremely difficult task.

Economic and decision-making theories suppose that people would disengage from a task with near zero success probability, because this implicates little normative utility values. However, humans often are motivated for an extremely challenging task, even without any extrinsic incentives. The current study aimed to address the nature of this challenge-based motivation and its neural correlates. We found that, when participants played a skill-based task without extrinsic incentives, their task enjoyment increased as the chance of success decreased, even if the task was almost impossible to achieve. However, such challenge-based motivation was not observed when participants were rewarded for the task or the reward was determined in a probabilistic manner. The activation in the ventral striatum/pallidum tracked the pattern of task enjoyment. These results suggest that people are intrinsically motivated to challenge a nearly impossible task but only when the task requires certain skills and extrinsic rewards are unavailable.

Six-dimensional dynamic tractography atlas of language connectivity in the developing brain.

During a verbal conversation, our brain moves through a series of complex linguistic processing stages: sound decoding, semantic comprehension, retrieval of semantically coherent words, and overt production of speech outputs. Each process is thought to be supported by a network consisting of local and long-range connections bridging between major cortical areas. Both temporal and extratemporal lobe regions have functional compartments responsible for distinct language domains, including the perception and production of phonological and semantic components. This study provides quantitative evidence of how directly connected inter-lobar neocortical networks support distinct stages of linguistic processing across brain development. Novel six-dimensional tractography was used to intuitively visualize the strength and temporal dynamics of direct inter-lobar effective connectivity between cortical areas activated during each linguistic processing stage. We analysed 3401 non-epileptic intracranial electrode sites from 37 children with focal epilepsy (aged 5-20 years) who underwent extra-operative electrocorticography recording. Principal component analysis of auditory naming-related high-gamma modulations determined the relative involvement of each cortical area during each linguistic processing stage. To quantify direct effective connectivity, we delivered single-pulse electrical stimulation to 488 temporal and 1581 extratemporal lobe sites and measured the early cortico-cortical spectral responses at distant electrodes. Mixed model analyses determined the effects of naming-related high-gamma co-augmentation between connecting regions, age, and cerebral hemisphere on the strength of effective connectivity independent of epilepsy-related factors. Direct effective connectivity was strongest between extratemporal and temporal lobe site pairs, which were simultaneously activated between sentence offset and verbal response onset (i.e. response preparation period); this connectivity was approximately twice more robust than that with temporal lobe sites activated during stimulus listening or overt response. Conversely, extratemporal lobe sites activated during overt response were equally connected with temporal lobe language sites. Older age was associated with increased strength of inter-lobar effective connectivity especially between those activated during response preparation. The arcuate fasciculus supported approximately two-thirds of the direct effective connectivity pathways from temporal to extratemporal auditory language-related areas but only up to half of those in the opposite direction. The uncinate fasciculus consisted of <2% of those in the temporal-to-extratemporal direction and up to 6% of those in the opposite direction. We, for the first time, provided an atlas which quantifies and animates the strength, dynamics, and direction specificity of inter-lobar neural communications between language areas via the white matter pathways. Language-related effective connectivity may be strengthened in an age-dependent manner even after the age of 5.

Dynamic tractography: Integrating cortico-cortical evoked potentials and diffusion imaging.

INTRODUCTION: Cortico-cortical evoked potentials (CCEPs) are utilized to identify effective networks in the human brain. Following single-pulse electrical stimulation of cortical electrodes, evoked responses are recorded from distant cortical areas. A negative deflection (N1) which occurs 10-50 â€‹ms post-stimulus is considered to be a marker for direct cortico-cortical connectivity. However, with CCEPs alone it is not possible to observe the white matter pathways that conduct the signal or accurately predict N1 amplitude and latency at downstream recoding sites. Here, we develop a new approach, termed "dynamic tractography," which integrates CCEP data with diffusion-weighted imaging (DWI) data collected from the same patients. This innovative method allows greater insights into cortico-cortical networks than provided by each method alone and may improve the understanding of large-scale networks that support cognitive functions. The dynamic tractography model produces several fundamental hypotheses which we investigate: 1) DWI-based pathlength predicts N1 latency; 2) DWI-based pathlength negatively predicts N1 voltage; and 3) fractional anisotropy (FA) along the white matter path predicts N1 propagation velocity. METHODS: Twenty-three neurosurgical patients with drug-resistant epilepsy underwent both extraoperative CCEP recordings and preoperative DWI scans. Subdural grids of 3 â€‹mm diameter electrodes were used for stimulation and recording, with 98-128 eligible electrodes per patient. CCEPs were elicited by trains of 1 â€‹Hz stimuli with an intensity of 5 â€‹mA and recorded at a sample rate of 1 â€‹kHz. N1 peak and latency were defined as the maximum of a negative deflection within 10-50 â€‹ms post-stimulus with a z-score > 5 relative to baseline. Electrodes and DWI were coregistered to construct electrode connectomes for white matter quantification. RESULTS: Clinical variables (age, sex, number of anti-epileptic drugs, handedness, and stimulated hemisphere) did not correlate with the key outcome measures (N1 peak amplitude, latency, velocity, or DWI pathlength). All subjects and electrodes were therefore pooled into a group-level analysis to determine overall patterns. As hypothesized, DWI path length positively predicted N1 latency (R2 â€‹= â€‹0.81, ߠ​= â€‹1.51, p â€‹= â€‹4.76e-16) and negatively predicted N1 voltage (R2 â€‹= â€‹0.79, ߠ​= â€‹-0.094, p â€‹= â€‹9.30e-15), while FA predicted N1 propagation velocity (R2 â€‹= â€‹0.35, ߠ​= â€‹48.0, p â€‹= â€‹0.001). CONCLUSION: We have demonstrated that the strength and timing of the CCEP N1 is dependent on the properties of the underlying white matter network. Integrated CCEP and DWI visualization allows robust localization of intact axonal pathways which effectively interconnect eloquent cortex.

Four-dimensional map of direct effective connectivity from posterior visual areas.

Lower- and higher-order visual cortices in the posterior brain, ranging from the medial- and lateral-occipital to fusiform regions, are suggested to support visual object recognition, whereas the frontal eye field (FEF) plays a role in saccadic eye movements which optimize visual processing. Previous studies using electrophysiology and functional MRI techniques have reported that tasks requiring visual object recognition elicited cortical activation sequentially in the aforementioned posterior visual regions and FEFs. The present study aims to provide unique evidence of direct effective connectivity outgoing from the posterior visual regions by measuring the early component (10-50 â€‹ms) of cortico-cortical spectral responses (CCSRs) elicited by weak single-pulse direct cortical electrical stimulation. We studied 22 patients who underwent extraoperative intracranial EEG recording for clinical localization of seizure foci and functionally-important brain regions. We used animations to visualize the spatiotemporal dynamics of gamma band CCSRs elicited by stimulation of three different posterior visual regions. We quantified the strength of CCSR-defined effective connectivity between the lower- and higher-order posterior visual regions as well as from the posterior visual regions to the FEFs. We found that effective connectivity within the posterior visual regions was larger in the feedforward (i.e., lower-to higher-order) direction compared to the opposite direction. Specifically, connectivity from the medial-occipital region was largest to the lateral-occipital region, whereas that from the lateral-occipital region was largest to the fusiform region. Among the posterior visual regions, connectivity to the FEF was largest from the lateral-occipital region and the mean peak latency of CCSR propagation from the lateral-occipital region to FEF was 26 â€‹ms. Our invasive study of the human brain using a stimulation-based intervention supports the model that the posterior visual regions have direct cortico-cortical connectivity pathways in which neural activity is transferred preferentially from the lower-to higher-order areas. The human brain has direct cortico-cortical connectivity allowing a rapid transfer of neural activity from the lateral-occipital region to the FEF.

Metabolic Barriers to T Cell Function in Tumors.

The metabolic programs that drive T cell functions are exquisitely sensitive to cell intrinsic and extrinsic factors, allowing T cells to respond in a fine-tuned manner to a variety of immune challenges and conditions. However, many of the factors essential for effector T cell function are perturbed in the tumor microenvironment, where oncogenic mutations drive unrestrained cancer cell growth that leads to excess nutrient consumption, excess waste excretion, and insufficient oxygen delivery. This imposes metabolic constraints on infiltrating cells that result in dysfunction and loss of potential antitumor activity in both naturally occurring as well as tailored T cells introduced as part of immunotherapy. In this review, we highlight the metabolic properties that characterize tumor-infiltrating T cells, the barriers within the metabolic landscape of the tumor microenvironment, and the opportunities and challenges they present in development of new cancer therapeutics.

Four-dimensional functional cortical maps of visual and auditory language: Intracranial recording.

OBJECTIVE: The strength of presurgical language mapping using electrocorticography (ECoG) is its outstanding signal fidelity and temporal resolution, but the weakness includes limited spatial sampling at an individual patient level. By averaging naming-related high-gamma activity at nonepileptic regions across a large number of patients, we provided the functional cortical atlases animating the neural dynamics supporting visual-object and auditory-description naming at the whole brain level. METHODS: We studied 79 patients who underwent extraoperative ECoG recording as epilepsy presurgical evaluation, and generated time-frequency plots and animation videos delineating the dynamics of naming-related high-gamma activity at 70-110 Hz. RESULTS: Naming task performance elicited high-gamma augmentation in domain-specific lower-order sensory areas and inferior-precentral gyri immediately after stimulus onset. High-gamma augmentation subsequently involved widespread neocortical networks with left hemisphere dominance. Left posterior temporal high-gamma augmentation at several hundred milliseconds before response onset exhibited a double dissociation; picture naming elicited high-gamma augmentation preferentially in regions medial to the inferior-temporal gyrus, whereas auditory naming elicited high-gamma augmentation more laterally. The left lateral prefrontal regions including Broca's area initially exhibited high-gamma suppression subsequently followed by high-gamma augmentation at several hundred milliseconds before response onset during both naming tasks. Early high-gamma suppression within Broca's area was more intense during picture compared to auditory naming. Subsequent lateral-prefrontal high-gamma augmentation was more intense during auditory compared to picture naming. SIGNIFICANCE: This study revealed contrasting characteristics in the spatiotemporal dynamics of naming-related neural modulations between tasks. The dynamic atlases of visual and auditory language might be useful for planning of epilepsy surgery. Differential neural activation well explains some of the previously reported observations of domain-specific language impairments following resective epilepsy surgery. Video materials might be beneficial for the education of lay people about how the brain functions differentially during visual and auditory naming.

Phase-amplitude coupling between interictal high-frequency activity and slow waves in epilepsy surgery.

OBJECTIVE: We hypothesized that the modulation index (MI), a summary measure of the strength of phase-amplitude coupling between high-frequency activity (>150 Hz) and the phase of slow waves (3-4 Hz), would serve as a useful interictal biomarker for epilepsy presurgical evaluation. METHODS: We investigated 123 patients who underwent focal cortical resection following extraoperative electrocorticography recording and had at least 1 year of postoperative follow-up. We examined whether consideration of MI would improve the prediction of postoperative seizure outcome. MI was measured at each intracranial electrode site during interictal slow-wave sleep. We compared the accuracy of prediction of patients achieving International League Against Epilepsy class 1 outcome between the full multivariate logistic regression model incorporating MI in addition to conventional clinical, seizure onset zone (SOZ), and neuroimaging variables, and the reduced logistic regression model incorporating all variables other than MI. RESULTS: Ninety patients had class 1 outcome at the time of most recent follow-up (mean follow-up = 5.7 years). The full model had a noteworthy outcome predictive ability, as reflected by regression model fit R2 of 0.409 and area under the curve (AUC) of receiver operating characteristic plot of 0.838. Incomplete resection of SOZ (P < 0.001), larger number of antiepileptic drugs at the time of surgery (P = 0.007), and larger MI in nonresected tissues relative to that in resected tissue (P = 0.020) were independently associated with a reduced probability of class 1 outcome. The reduced model had a lower predictive ability as reflected by R2 of 0.266 and AUC of 0.767. Anatomical variability in MI existed among nonepileptic electrode sites, defined as those unaffected by magnetic resonance imaging lesion, SOZ, or interictal spike discharges. With MI adjusted for anatomical variability, the full model yielded the outcome predictive ability of R2 of 0.422, AUC of 0.844, and sensitivity/specificity of 0.86/0.76. SIGNIFICANCE: MI during interictal recording may provide useful information for the prediction of postoperative seizure outcome.

How self-determined choice facilitates performance: a key role of the ventromedial prefrontal cortex.

Recent studies have documented that self-determined choice does indeed enhance performance. However, the precise neural mechanisms underlying this effect are not well understood. We examined the neural correlates of the facilitative effects of self-determined choice using functional magnetic resonance imaging (fMRI). Participants played a game-like task involving a stopwatch with either a stopwatch they selected (self-determined-choice condition) or one they were assigned without choice (forced-choice condition). Our results showed that self-determined choice enhanced performance on the stopwatch task, despite the fact that the choices were clearly irrelevant to task difficulty. Neuroimaging results showed that failure feedback, compared with success feedback, elicited a drop in the vmPFC activation in the forced-choice condition, but not in the self-determined-choice condition, indicating that negative reward value associated with the failure feedback vanished in the self-determined-choice condition. Moreover, the vmPFC resilience to failure in the self-determined-choice condition was significantly correlated with the increased performance. Striatal responses to failure and success feedback were not modulated by the choice condition, indicating the dissociation between the vmPFC and striatal activation pattern. These findings suggest that the vmPFC plays a unique and critical role in the facilitative effects of self-determined choice on performance.

Social equality in the number of choice options is represented in the ventromedial prefrontal cortex.

A distinct aspect of the sense of fairness in humans is that we care not only about equality in material rewards but also about equality in nonmaterial values. One such value is the opportunity to choose freely among many options, often regarded as a fundamental right to economic freedom. In modern developed societies, equal opportunities in work, living, and lifestyle are enforced by antidiscrimination laws. Despite the widespread endorsement of equal opportunity, no studies have explored how people assign value to it. We used functional magnetic resonance imaging to identify the neural substrates for subjective valuation of equality in choice opportunity. Participants performed a two-person choice task in which the number of choices available was varied across trials independently of choice outcomes. By using this procedure, we manipulated the degree of equality in choice opportunity between players and dissociated it from the value of reward outcomes and their equality. We found that activation in the ventromedial prefrontal cortex (vmPFC) tracked the degree to which the number of options between the two players was equal. In contrast, activation in the ventral striatum tracked the number of options available to participants themselves but not the equality between players. Our results demonstrate that the vmPFC, a key brain region previously implicated in the processing of social values, is also involved in valuation of equality in choice opportunity between individuals. These findings may provide valuable insight into the human ability to value equal opportunity, a characteristic long emphasized in politics, economics, and philosophy.

Prognostic Factors for Japanese Adults With Acute Community-Acquired Bacterial Meningitis: A Retrospective Study.

Background This study aimed to determine if the cerebrospinal fluid (CSF) cell count is useful for predicting the infection severity or prognosis in Japanese adults with community-acquired bacterial meningitis. Methodology This study retrospectively evaluated the prognosis of patients diagnosed with community-acquired bacterial meningitis at our hospital from January 2004 to December 2021 using the modified Rankin scale (mRs) (Showa General Hospital; N = 39). Patients were classified into the following two groups: (i) favorable (mRs: 0-3) and (ii) unfavorable (mRs: 4-6). Eight factors were selected and compared with outcomes, and then two factors were evaluated from those, and a multivariate logistic regression was used to determine the significant variables. Results CSF cell count was observed to be associated with poor prognoses (odds ratio (OR) = 0.86, 95% confidence interval (CI) = 0.99995-0.99999, p = 0.0012). Glasgow coma scale (GCS) score on admission was also observed to be associated with poor prognoses (OR = 0.93, 95% CI = 0.89145-0.97290, p = 0.0029). Conclusions Low CSF cell count and low GCS on admission were observed as risk factors for poor prognoses in patients with bacterial meningitis.

Functional Overlap of Inborn Errors of Immunity and Metabolism Genes Define T Cell Immunometabolic Vulnerabilities.

Inborn Errors of Metabolism (IEM) and Immunity (IEI) are Mendelian diseases in which complex phenotypes and patient rarity can limit clinical annotations. Few genes are assigned to both IEM and IEI, but immunometabolic demands suggest functional overlap is underestimated. We applied CRISPR screens to test IEM genes for immunologic roles and IEI genes for metabolic effects and found considerable crossover. Analysis of IEM showed N-linked glycosylation and the de novo hexosamine synthesis enzyme, Gfpt1 , are critical for T cell expansion and function. Interestingly, Gfpt1 -deficient T H 1 cells were more affected than T H 17 cells, which had increased Nagk for salvage UDP-GlcNAc synthesis. Screening IEI genes showed the transcription factor Bcl11b promotes CD4 + T cell mitochondrial activity and Mcl1 expression necessary to prevent metabolic stress. These data illustrate a high degree of functional overlap of IEM and IEI genes and point to potential immunometabolic mechanisms for a previously unappreciated set of these disorders. HIGHLIGHTS: Inborn errors of immunity and metabolism have greater overlap than previously known Gfpt1 deficiency causes an IEM but also selectively regulates T cell subset fate Loss of Bcl11b causes a T cell deficiency IEI but also harms mitochondrial function Many IEM may have immune defects and IEI may be driven by metabolic mechanisms.

Tissue-Specific Dependence of Th1 Cells on the Amino Acid Transporter SLC38A1 in Inflammation.

Amino acid (AA) uptake is essential for T cell metabolism and function, but how tissue sites and inflammation affect CD4+ T cell subset requirements for specific AA remains uncertain. Here we tested CD4+ T cell AA demands with in vitro and multiple in vivo CRISPR screens and identify subset- and tissue-specific dependencies on the AA transporter SLC38A1 (SNAT1). While dispensable for T cell persistence and expansion over time in vitro and in vivo lung inflammation, SLC38A1 was critical for Th1 but not Th17 cell-driven Experimental Autoimmune Encephalomyelitis (EAE) and contributed to Th1 cell-driven inflammatory bowel disease. SLC38A1 deficiency reduced mTORC1 signaling and glycolytic activity in Th1 cells, in part by reducing intracellular glutamine and disrupting hexosamine biosynthesis and redox regulation. Similarly, pharmacological inhibition of SLC38 transporters delayed EAE but did not affect lung inflammation. Subset- and tissue-specific dependencies of CD4+ T cells on AA transporters may guide selective immunotherapies.

Elevated transferrin receptor impairs T cell metabolism and function in systemic lupus erythematosus.

T cells in systemic lupus erythematosus (SLE) exhibit multiple metabolic abnormalities. Excess iron can impair mitochondria and may contribute to SLE. To gain insights into this potential role of iron in SLE, we performed a CRISPR screen of iron handling genes on T cells. Transferrin receptor (CD71) was identified as differentially critical for TH1 and inhibitory for induced regulatory T cells (iTregs). Activated T cells induced CD71 and iron uptake, which was exaggerated in SLE-prone T cells. Cell surface CD71 was enhanced in SLE-prone T cells by increased endosomal recycling. Blocking CD71 reduced intracellular iron and mTORC1 signaling, which inhibited TH1 and TH17 cells yet enhanced iTregs. In vivo treatment reduced kidney pathology and increased CD4 T cell production of IL-10 in SLE-prone mice. Disease severity correlated with CD71 expression on TH17 cells from patients with SLE, and blocking CD71 in vitro enhanced IL-10 secretion. T cell iron uptake via CD71 thus contributes to T cell dysfunction and can be targeted to limit SLE-associated pathology.

Acly Deficiency Enhances Myelopoiesis through Acetyl Coenzyme A and Metabolic-Epigenetic Cross-Talk.

Hematopoiesis integrates cytokine signaling, metabolism, and epigenetic modifications to regulate blood cell generation. These processes are linked, as metabolites provide essential substrates for epigenetic marks. In this study, we demonstrate that ATP citrate lyase (Acly), which metabolizes citrate to generate cytosolic acetyl-CoA and is of clinical interest, can regulate chromatin accessibility to limit myeloid differentiation. Acly was tested for a role in murine hematopoiesis by small-molecule inhibition or genetic deletion in lineage-depleted, c-Kit-enriched hematopoietic stem and progenitor cells from Mus musculus. Treatments increased the abundance of cell populations that expressed the myeloid integrin CD11b and other markers of myeloid differentiation. When single-cell RNA sequencing was performed, we found that Acly inhibitor-treated hematopoietic stem and progenitor cells exhibited greater gene expression signatures for macrophages and enrichment of these populations. Similarly, the single-cell assay for transposase-accessible chromatin sequencing showed increased chromatin accessibility at genes associated with myeloid differentiation, including CD11b, CD11c, and IRF8. Mechanistically, Acly deficiency altered chromatin accessibility and expression of multiple C/EBP family transcription factors known to regulate myeloid differentiation and cell metabolism, with increased Cebpe and decreased Cebpa and Cebpb. This effect of Acly deficiency was accompanied by altered mitochondrial metabolism with decreased mitochondrial polarization but increased mitochondrial content and production of reactive oxygen species. The bias to myeloid differentiation appeared due to insufficient generation of acetyl-CoA, as exogenous acetate to support alternate compensatory pathways to produce acetyl-CoA reversed this phenotype. Acly inhibition thus can promote myelopoiesis through deprivation of acetyl-CoA and altered histone acetylome to regulate C/EBP transcription factor family activity for myeloid differentiation.

A guide to interrogating immunometabolism.

The metabolic charts memorized in early biochemistry courses, and then later forgotten, have come back to haunt many immunologists with new recognition of the importance of these pathways. Metabolites and the activity of metabolic pathways drive energy production, macromolecule synthesis, intracellular signalling, post-translational modifications and cell survival. Immunologists who identify a metabolic phenotype in their system are often left wondering where to begin and what does it mean? Here, we provide a framework for navigating and selecting the appropriate biochemical techniques to explore immunometabolism. We offer recommendations for initial approaches to develop and test metabolic hypotheses and how to avoid common mistakes. We then discuss how to take things to the next level with metabolomic approaches, such as isotope tracing and genetic approaches. By proposing strategies and evaluating the strengths and weaknesses of different methodologies, we aim to provide insight, note important considerations and discuss ways to avoid common misconceptions. Furthermore, we highlight recent studies demonstrating the power of these metabolic approaches to uncover the role of metabolism in immunology. By following the framework in this Review, neophytes and seasoned investigators alike can venture into the emerging realm of cellular metabolism and immunity with confidence and rigour.