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This case describes a patient with hypotension, bradycardia, and third-degree atrioventricular block following ingestion of a grayanotoxin-containing Pieris species, or lily of the valley bush. Although unlikely in metropolitan environments, physicians should be aware of the possibility of grayanotoxin ingestion when confronted with new-onset heart block even in nonendemic areas. (Level of Difficulty: Beginner.)

We describe the case of a 36-year-old woman with a past medical history of low grade right frontal lobe glioma and focal epilepsy presenting with subacute, progressive, multifocal myoclonus and neck and back pain. Unlike her typical seizures, the myoclonus exhibited a distinct semiology, involving both positive and negative muscle jerks affecting multiple limb muscles while sparing the face. In addition, neurological examination revealed low-amplitude, arrhythmic movements of the hands and fingers, resembling minipolymyoclonus. There were no other neurological exam findings, including mental status changes, extrapyramidal signs or signs of myelopathy. Brain and spine MRI indicated leptomeningeal and spinal "drop" enhancing lesions, suggesting likely malignant evolution of the glioma. EEG ruled out a cortical origin of the myoclonus. Pharmacological trials with benzodiazepines and other antiepileptic medications were ineffective. The patient's myoclonus was most likely spinal segmental in origin from meningeal spread of glioma. The spinal roots or anterior horns of the spinal cord may have represented a focus of hyperexcitability responsible for generating minipolymyoclonus. Our case expands the etiological spectrum of non-epileptic myoclonus and minipolymyoclonus to encompass meningeal carcinomatosis and drop metastases from glioma. These cases may occur even without overt signs of myelopathy. Recognizing such presentations holds significance due to the poor prognosis associated with meningeal spread of glioma and the limited response of non-epileptic myoclonus to symptomatic treatments., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2024.)

The differentiation and suppressive functions of regulatory CD4 T cells (Tregs) are supported by a broad array of metabolic changes, providing potential therapeutic targets for immune modulation. In this study, we focused on the regulatory role of glycolytic enzymes in Tregs and identified phosphoglycerate mutase (PGAM) as being differentially overexpressed in Tregs and associated with a highly suppressive phenotype. Pharmacologic or genetic inhibition of PGAM reduced Treg differentiation and suppressive function while reciprocally inducing markers of a pro-inflammatory, T helper 17 (Th17)-like state. The regulatory role of PGAM was dependent on the contribution of 3-phosphoglycerate (3PG), the PGAM substrate, to de novo serine synthesis. Blocking de novo serine synthesis from 3PG reversed the effect of PGAM inhibition on Treg polarization, while exogenous serine directly inhibited Treg polarization. Additionally, altering serine levels in vivo with a serine/glycine-free diet increased peripheral Tregs and attenuated autoimmunity in a murine model of multiple sclerosis. Mechanistically, we found that serine limits Treg polarization by contributing to one-carbon metabolism and methylation of Treg-associated genes. Inhibiting one-carbon metabolism increased Treg polarization and suppressive function both in vitro and in vivo in a murine model of autoimmune colitis. Our study identifies a novel physiologic role for PGAM and highlights the metabolic interconnectivity between glycolysis, serine synthesis, one-carbon metabolism, and epigenetic regulation of Treg differentiation and suppressive function.

Acquired demyelinating diseases of the central nervous system (CNS) comprise inflammatory conditions, including multiple sclerosis (MS) and related diseases, as well as noninflammatory conditions caused by toxic, metabolic, infectious, traumatic, and neurodegenerative insults. Here, we review the spectrum of diseases producing acquired CNS demyelination before focusing on the prototypical example of MS, exploring the pathologic mechanisms leading to myelin injury in relapsing and progressive MS and summarizing the mechanisms and modulators of remyelination. We highlight the complex interplay between the immune system, oligodendrocytes and oligodendrocyte progenitor cells (OPCs), and other CNS glia cells such as microglia and astrocytes in the pathogenesis and clinical course of MS. Finally, we review emerging therapeutic strategies that exploit our growing understanding of disease mechanisms to limit progression and promote remyelination., (Copyright © 2024 Cold Spring Harbor Laboratory Press; all rights reserved.)

Protein kinase C (PKC) plays a key role in modulating the activities of the innate immune cells of the central nervous system (CNS). A delicate balance between pro-inflammatory and regenerative activities by microglia and CNS-associated macrophages is necessary for the proper functioning of the CNS. Thus, a maladaptive activation of these CNS innate immune cells results in neurodegeneration and demyelination associated with various neurologic disorders, such as multiple sclerosis (MS) and Alzheimer's disease. Prior studies have demonstrated that modulation of PKC activity by bryostatin-1 (bryo-1) and its analogs (bryologs) attenuates the pro-inflammatory processes by microglia/CNS macrophages and alleviates the neurologic symptoms in experimental autoimmune encephalomyelitis (EAE), an MS animal model. Here, we demonstrate that (2S,5S)-(E,E)-8-(5-(4-(trifluoromethyl)phenyl)-2,4-pentadienoylamino)benzolactam (TPPB), a structurally distinct PKC modulator, has a similar effect to bryo-1 on CNS innate immune cells both in vitro and in vivo , attenuating neuroinflammation and resulting in CNS regeneration and repair. This study identifies a new structural class of PKC modulators, which can therapeutically target CNS innate immunity as a strategy to treat neuroinflammatory and neurodegenerative disorders., Competing Interests: The Johns Hopkins University has filed a patent for the application of PKC modulator bryo-1 and related technology, and PK and MK are co-inventors on the patent. MK has received consulting fees from Biogen, Genentech, Novartis, TG Therapeutics, and OptumRx. Stanford University has filed patents on bryostatin and other PKC modulators which have been licensed by Neurotrope BioScience for the treatment of neurological disorders and by Bryologyx Inc. for use in HIV/AIDS eradication and cancer immunotherapy. PW is an advisor to both companies and a cofounder of the latter. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Shanmukha, Godfrey, Gharibani, Lee, Guo, Deng, Wender, Kornberg and Kim.)

Objectives: While patients with concomitant trigeminal neuralgia (TN) and multiple sclerosis (MS) are understood to experience a more intractable pain phenotype, whether TN pain outcomes differ by the presenting MS subtype is not well characterized. This study's objective is to compare post-operative pain and numbness outcomes following microvascular decompression (MVD) in TN patients with either relapsing-remitting MS (RRMS) or progressive MS., Methods: We retrospectively reviewed all TN patients who underwent MVDs at our institution from 2007 to 2020. Of the 1044 patients reviewed, 45 (4.3%) patients with MS were identified. Patient demographics, procedural characteristics, and post-operative pain and numbness scores were recorded and compared. Factors associated with pain recurrence were assessed using survival analyses and multivariate regressions., Results: Of the resulting 45 MS patients, 34 (75.6%) patients presented with the RRMS subtype, whereas 11 (24.4%) patients exhibited progressive MS. Using an adjusted multivariate ordinal regression, the subtype of MS was not significantly associated with the Barrow Neurological Institute (BNI) pain score at final follow-up. Using a Kaplan-Meier survival analysis and a multivariate Cox proportional hazards regression, respectively, RRMS was significantly associated with a shorter post-operative pain-free interval (p = 0.04) as well as a greater risk for pain recurrence (p = 0.02)., Conclusions: Although the degree of pain at final follow-up may not differ, RRMS patients are at increased risk for pain recurrence following MVD for TN. These results align with a growing understanding that neuroinflammation may play a significant role in TN pain., Competing Interests: Declaration of Competing Interest Dr. Huang owns stock in Longeviti. Dr. Bettegowda is a consultant for DePuy-Synthes, Bionaut Labs, Galectin Therapeutics, Privo Technologies, and Haystack Oncology; and is the co-founder of OrisDX. Dr. Lim is a consultant for Tocagen, VBI, InCephalo Therapeutics, Pyramid Bio, Merck, BMS, Insightec, Biohaven, Sanianoia, Hemispherian, Black Diamond Therapeutics, Novocure, Noxxon, and Stryker; receives research support from Arbor, BMS, Accuray, Tocagen, Biohaven, Kyrin-Kyowa, and Urogen; and owns stock in Egret Therapeutics., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Multiple sclerosis (MS) is a neuroinflammatory disease of the central nervous system (CNS). Although classically considered a demyelinating disease, neuroaxonal injury occurs in both the acute and chronic phases and represents a pathologic substrate of disability not targeted by current therapies. Nitric oxide (NO) generated by CNS macrophages and microglia contributes to neuroaxonal injury in all phases of MS, but candidate therapies that prevent NO-mediated injury have not been identified. Here, we demonstrate that the multifunctional protein glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is robustly nitrosylated in the CNS in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. GAPDH nitrosylation is blocked in vivo with daily administration of CGP3466b, a CNS-penetrant compound with an established safety profile in humans. Consistent with the known role of nitrosylated GAPDH (SNO-GAPDH) in neuronal cell death, blockade of SNO-GAPDH with CGP3466b attenuates neurologic disability and reduces axonal injury in EAE independent of effects on the immune system. Our findings suggest that SNO-GAPDH contributes to neuroaxonal injury during neuroinflammation and identify CGP3466b as a candidate neuroprotective therapy in MS., Competing Interests: MK has received consulting fees from Biogen Idec, Genentech, Janssen Pharmaceuticals, Novartis, OptumRx, and TG Therapeutics on topics unrelated to this manuscript. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Godfrey, Hwang, Cho, Shanmukha, Gharibani, Abramson and Kornberg.)

Background: Intermittent fasting or calorie restriction (CR) diets provide anti-inflammatory and neuroprotective advantages in models of multiple sclerosis (MS); data in humans are sparse., Methods: We conducted a randomised-controlled feeding study of different CR diets in 36 people with MS over 8 weeks. Participants were randomised to 1 of 3 diets: 1) a control diet, in which the participant received 100% of his or her calorie needs 7 days per week, 2) a daily CR diet, in which the participant received 78% of his or her calorie needs 7 days per week, or 3) an intermittent CR diet, in which the participant received 100% of his or her calorie needs on 5 days per week and 25% of his or her calorie needs 2 days per week (i.e., a "5:2" style diet). Untargeted metabolomics was performed on plasma samples at weeks 0, 4 and 8 at Metabolon Inc (Durham, NC). Flow cytometry of cryopreserved peripheral blood mononuclear cells at weeks 0 and 8 were used to identify CD3 + ;CD4 + (CD4 + ) and CD3 + ;CD4 - (as a proxy for CD8 + ) T cell subsets including effector memory, central memory, and naïve cells., Findings: 31 (86%) completed the trial. Over time, individuals randomised to intermittent CR had significant reductions in effector memory (for CD4 - EM : -3.82%; 95%CI: -7.44, -0.21; for CD4 - : -6.96%; 95%CI: -11.96, -1.97) and Th1 subsets (-4.26%; 95% CI: -7.11, -1.40) and proportional increases in naïve subsets (for CD4 - : 10.11%; 95%CI: 3.30, 16.92%). No changes were observed for daily CR or weight-stable diets. Larger within-person changes in lysophospholipid and lysoplasmalogen metabolites in intermittent CR were associated with larger reductions in memory T cell subsets and larger increases in naïve T cell subsets., Interpretation: In people with MS, an intermittent CR diet was associated with reduction in memory T cell subsets and certain biologically-relevant lipid markers., Funding: National MS Society, NIH, Johns Hopkins Catalyst Award., Competing Interests: Declaration of interests Mr. Smith, Ms. Henry-Barron, Ms. Vizthum, Dr. Cassard, Dr. Kappogiannis, Mr. Sullivan, and Dr. Baer report no disclosures. Dr. Fitzgerald and Dr. Bhargava reports grants from NIH, grants from National MS Society, during the conduct of the study. Dr. Kornberg has received consulting fees from Biogen Idec, Janssen Pharmaceuticals, Novartis, OptumRx, and TG Therapeutics and received grants from NIH and the Department of Defense. Dr. Calabresi has received consulting fees from Disarm, NervGen, and Biogen and is PI on grants to JHU from Genentech. Dr. Mowry has grants from Biogen, is site PI for studies sponsored by Biogen and Genentech, has received free medication for a clinical trial from Teva, and receives royalties for editorial duties from UpToDate., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Synapses connect discrete neurons into vast networks that send, receive, and encode diverse forms of information. Synaptic function and plasticity, the neuronal process of adapting to diverse and variable inputs, depend on the dynamic nature of synaptic molecular components, which is mediated in part by cell adhesion signaling pathways. Here, we found that the enzyme biliverdin reductase (BVR) physically links together key focal adhesion signaling molecules at the synapse. BVR -null ( BVR -/- ) mice exhibited substantial deficits in learning and memory on neurocognitive tests, and hippocampal slices in which BVR was postsynaptically depleted showed deficits in electrophysiological responses to stimuli. RNA sequencing, biochemistry, and pathway analyses suggested that these deficits were mediated through the loss of focal adhesion signaling at both the transcriptional and biochemical level in the hippocampus. Independently of its catalytic function, BVR acted as a bridge between the primary focal adhesion signaling kinases FAK and Pyk2 and the effector kinase Src. Without BVR, FAK and Pyk2 did not bind to and stimulate Src, which then did not phosphorylate the N -methyl-d-aspartate (NMDA) receptor, a critical posttranslational modification for synaptic plasticity. Src itself is a molecular hub on which many signaling pathways converge to stimulate NMDAR-mediated neurotransmission, thus positioning BVR at a prominent intersection of synaptic signaling.

Inositol pyrophosphates, such as 5-diphosphoinositol pentakisphosphate (IP7), are generated by a family of inositol hexakisphosphate kinases (IP6Ks), of which IP6K2 has been implicated in various cellular functions including neuroprotection. Absence of IP6K2 causes impairment of oxidative phosphorylation regulated by creatine kinase-B. In the present study, we show that IP6K2 is involved in attenuation of PINK1-mediated mitochondrial autophagy (mitophagy) in the brain. Up-regulation of dynamin-related protein (Drp-1), as well as increased expression of mitochondrial biogenesis markers (PGC1-α and NRF-1) in the cerebella of IP6K2-deleted mice (IP6K2-knockout), point to the involvement of IP6K2 in the regulation of mitochondrial fission. Knockdown of IP6K2 also leads to augmented glycolysis, potentially as a compensatory mechanism for decreased mitochondrial respiration. Overexpressing IP6K2 as well as IP6K2-kinase dead mutant in IP6K2-knockdown N2A cells reverses the expression of mitophagy markers, demonstrating that IP6K2-induced mitoprotection is catalytically/kinase independent. IP6K2 supplementation in K2-PINK1 double-knockdown N2A cells fails to reverse the expression of the mitophagic marker, LC3-II, indicating that the mitoprotective effect of IP6K2 is dependent on PINK1. Overall, our study reveals a key neuroprotective role of IP6K2 in the prevention of PINK1-mediated mitophagy in the brain.

Microglia and CNS-infiltrating macrophages play significant roles in the pathogenesis of neuroinflammatory and neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Prolonged and dysregulated inflammatory responses by these innate immune cells can have deleterious effects on the surrounding CNS microenvironment, which can worsen neurodegeneration and demyelination. However, although chronic activation of pro-inflammatory microglia is maladaptive, other functional microglial subtypes play beneficial roles during CNS repair and regeneration. Therefore, there is a tremendous interest in understanding the underlying mechanism of the activation of these reparative/regenerative microglia. In this review, we focus on the potential role of PKC, a downstream signaling molecule of TREM2 and PLCγ2, and PKC modulators in promoting the activation of reparative/regenerative microglial subtypes as a novel therapy for neuroinflammatory and neurodegenerative diseases., Competing Interests: Conflict of interest statement Johns Hopkins University has filed a patent on the application of bryostatin-1 and its derivatives for multiple sclerosis and other disorders, and P.M.K. and M.D.K. are co-inventors on this patent., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

DICAM, a trafficking molecule preferentially expressed by T H 17 cells, may be a therapeutic target for treating neuroinflammation (Charabati et al. ).

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) characterized by varying degrees of secondary neurodegeneration. Retinal ganglion cells (RGC) are lost in MS in association with optic neuritis but the mechanisms of neuronal injury remain unclear. Complement component C3 has been implicated in retinal and cerebral synaptic pathology that may precede neurodegeneration. Herein, we examined post-mortem MS retinas, and then used a mouse model, experimental autoimmune encephalomyelitis (EAE), to examine the role of C3 in the pathogenesis of RGC loss associated with optic neuritis. First, we show extensive C3 expression in astrocytes (C3 + /GFAP + cells) and significant RGC loss (RBPMS + cells) in post-mortem retinas from people with MS compared to retinas from non-MS individuals. A patient with progressive MS with a remote history of optic neuritis showed marked reactive astrogliosis with C3 expression in the inner retina extending into deeper layers in the affected eye more than the unaffected eye. To study whether C3 mediates retinal degeneration, we utilized global C3 -/- EAE mice and found that they had less RGC loss and partially preserved neurites in the retina compared with C3 +/+ EAE mice. C3 -/- EAE mice had fewer axonal swellings in the optic nerve, reflecting reduced axonal injury, but had no changes in demyelination or T cell infiltration into the CNS. Using a C3-tdTomato reporter mouse line, we show definitive evidence of C3 expression in astrocytes in the retina and optic nerves of EAE mice. Conditional deletion of C3 in astrocytes showed RGC protection replicating the effects seen in the global knockouts. These data implicate astrocyte C3 expression as a critical mediator of retinal neuronal pathology in EAE and MS, and are consistent with recent studies showing C3 gene variants are associated with faster rates of retinal neurodegeneration in human disease., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The circulating metabolome provides unique insights into multiple sclerosis (MS) pathophysiology, but existing studies are relatively small or characterized limited metabolites. We test for differences in the metabolome between people with MS (PwMS; n = 637 samples) and healthy controls (HC; n = 317 samples) and assess the association between metabolomic profiles and disability in PwMS. We then assess whether metabolic differences correlate with changes in cellular gene expression using publicly available scRNA-seq data and whether identified metabolites affect human immune cell function. In PwMS, we identify striking abnormalities in aromatic amino acid (AAA) metabolites (p = 2.77E-18) that are also strongly associated with disability (p = 1.01E-4). Analysis of scRNA-seq data demonstrates altered AAA metabolism in CSF and blood-derived monocyte cell populations in PwMS. Treatment with AAA-derived metabolites in vitro alters monocytic endocytosis and pro-inflammatory cytokine production. We identify shifts in AAA metabolism resulting in the reduced production of immunomodulatory metabolites and increased production of metabotoxins in PwMS., Competing Interests: K.C.F., M.D.S., S.K., M.D., J.G., R.R., L.P., M.C., E.W., and S.G. declare no competing interests. M.D.K. has received consulting fees from OptumRx and Biogen Idec. E.S.S. has served on scientific advisory boards for Viela Bio and Genentech. B.N. received consulting fees from Jazz Pharmaceuticals and research support from Genentech. E.M.M. reports receiving research funding as site principal investigator (PI) or for investigator-initiated studies from Biogen, Sanofi-Genzyme, and Teva, and receives royalties for editorial duties from UpToDate. P.A.C. has received consulting fees from Disarm and Biogen and is PI on grants to Johns Hopkins University from Biogen and Annexon. P.B. reports receiving research funding from Genentech, Amylyx Pharmaceuticals, and EMD Serono and has received honoraria from EMD Serono and Sanofi-Genzyme., (© 2021 The Author(s).)

d-amino acids are increasingly recognized as important signaling molecules in the mammalian central nervous system. However, the d-stereoisomer of the amino acid with the fastest spontaneous racemization ratein vitro in vitro, cysteine, has not been examined in mammals. Using chiral high-performance liquid chromatography and a stereospecific luciferase assay, we identify endogenous d-cysteine in the mammalian brain. We identify serine racemase (SR), which generates the N -methyl-d-aspartate (NMDA) glutamate receptor coagonist d-serine, as a candidate biosynthetic enzyme for d-cysteine. d-cysteine is enriched more than 20-fold in the embryonic mouse brain compared with the adult brain. d-cysteine reduces the proliferation of cultured mouse embryonic neural progenitor cells (NPCs) by ∼50%, effects not shared with d-serine or l-cysteine. The antiproliferative effect of d-cysteine is mediated by the transcription factors FoxO1 and FoxO3a. The selective influence of d-cysteine on NPC proliferation is reflected in overgrowth and aberrant lamination of the cerebral cortex in neonatal SR knockout mice. Finally, we perform an unbiased screen for d-cysteine-binding proteins in NPCs by immunoprecipitation with a d-cysteine-specific antibody followed by mass spectrometry. This approach identifies myristoylated alanine-rich C-kinase substrate (MARCKS) as a putative d-cysteine-binding protein. Together, these results establish endogenous mammalian d-cysteine and implicate it as a physiologic regulator of NPC homeostasis in the developing brain., Competing Interests: The authors declare no competing interest.

Neuroinflammation characterizes multiple neurologic diseases, including primary inflammatory conditions such as multiple sclerosis and classical neurodegenerative diseases. Aberrant activation of the innate immune system contributes to disease progression, but drugs modulating innate immunity, particularly within the central nervous system (CNS), are lacking. The CNS-penetrant natural product bryostatin-1 attenuates neuroinflammation by targeting innate myeloid cells. Supplies of natural bryostatin-1 are limited, but a recent scalable good manufacturing practice (GMP) synthesis has enabled access to it and its analogs (bryologs), the latter providing a path to more efficacious, better tolerated, and more accessible agents. Here, we show that multiple synthetically accessible bryologs replicate the anti-inflammatory effects of bryostatin-1 on innate immune cells in vitro, and a lead bryolog attenuates neuroinflammation in vivo, actions mechanistically dependent on protein kinase C (PKC) binding. Our findings identify bryologs as promising drug candidates for targeting innate immunity in neuroinflammation and create a platform for evaluation of synthetic PKC modulators in neuroinflammatory diseases., Competing Interests: Declaration of interests Johns Hopkins University and Stanford University have filed patent applications on this and related technology. Stanford University patent applications have been licensed by Neurotrope BioScience for the treatment of neurological disorders and by Bryologyx Inc. for use in HIV/AIDS eradication and cancer immunotherapy. P.A.W. is an advisor to both companies and a cofounder of the latter. M.D.K. has received consulting fees from OptumRx and Biogen Idec. The remaining authors declare no competing interests., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Inositol hexakisphosphate kinases (IP6Ks) regulate various biological processes. IP6Ks convert IP6 to pyrophosphates such as diphosphoinositol pentakisphosphate (IP7) and bis-diphosphoinositol tetrakisphosphate (IP8). IP7 is produced in mammals by a family of inositol hexakisphosphate kinases, IP6K1, IP6K2, and IP6K3, which have distinct biological functions. The inositol hexakisphosphate kinase 2 (IP6K2) controls cellular apoptosis. To explore roles for IP6K2 in brain function, we elucidated its protein interactome in mouse brain revealing a robust association of IP6K2 with creatine kinase-B (CK-B), a key enzyme in energy homeostasis. Cerebella of IP6K2-deleted mice (IP6K2-knockout [KO]) produced less phosphocreatine and ATP and generated higher levels of reactive oxygen species and protein oxidative damage. In IP6K2-KO mice, mitochondrial dysfunction was associated with impaired expression of the cytochrome-c1 subunit of complex III of the electron transport chain. We reversed some of these effects by combined treatment with N -acetylcysteine and phosphocreatine. These findings establish a role for IP6K2-CK-B interaction in energy homeostasis associated with neuroprotection., Competing Interests: The authors declare no competing interest.

Immune cells undergo dramatic metabolic reprogramming in response to external stimuli. These metabolic pathways, long considered as simple housekeeping functions, are increasingly understood to critically regulate the immune response, determining the activation, differentiation, and downstream effector functions of both lymphoid and myeloid cells. Within the complex metabolic networks associated with immune activation, several enzymes play key roles in regulating inflammation and represent potential therapeutic targets in human disease. In some cases, these enzymes control flux through pathways required to meet specific energetic or metabolic demands of the immune response. In other cases, key enzymes control the concentrations of immunoactive metabolites with direct roles in signaling. Finally, and perhaps most interestingly, several metabolic enzymes have evolved moonlighting functions, with roles in the immune response that are entirely independent of their conventional enzyme activities. Here, we review key metabolic enzymes that critically regulate inflammation, highlighting mechanistic insights and opportunities for clinical intervention.

Pro-inflammatory signals induce metabolic reprogramming in innate and adaptive immune cells of both myeloid and lymphoid lineage, characterized by a shift to aerobic glycolysis akin to the Warburg effect first described in cancer. Blocking the switch to aerobic glycolysis impairs the survival, differentiation, and effector functions of pro-inflammatory cell types while favoring anti-inflammatory and regulatory phenotypes. Glycolytic reprogramming may therefore represent a selective vulnerability of inflammatory immune cells, providing an opportunity to modulate immune responses in autoimmune disease without broad toxicity in other tissues of the body. The mechanisms by which aerobic glycolysis and the balance between glycolysis and oxidative phosphorylation regulate immune responses have only begun to be understood, with many additional insights expected in the years to come. Immunometabolic therapies targeting aerobic glycolysis include both pharmacologic inhibitors of key enzymes and glucose-restricted diets, such as the ketogenic diet. Animal studies support a role for these pharmacologic and dietary therapies for the treatment of autoimmune diseases, and in a few cases proof of concept has been demonstrated in human disease. Nonetheless, much more work is needed to establish the clinical safety and efficacy of these treatments. This article is categorized under: Biological Mechanisms > Metabolism Translational, Genomic, and Systems Medicine > Translational Medicine Biological Mechanisms > Cell Signaling., (© 2020 The Author. WIREs Systems Biology and Medicine published by Wiley Periodicals, Inc.)

Racial/ethnic disparities have a significant impact on bladder cancer outcomes with African American patients demonstrating inferior survival over European-American patients. We hypothesized that epigenetic difference in methylation of tumor DNA is an underlying cause of this survival health disparity. We analyzed bladder tumors from African American and European-American patients using reduced representation bisulfite sequencing (RRBS) to annotate differentially methylated DNA regions. Liquid chromatography-mass spectrometry (LC-MS/MS) based metabolomics and flux studies were performed to examine metabolic pathways that showed significant association to the discovered DNA methylation patterns. RRBS analysis showed frequent hypermethylated CpG islands in African American patients. Further analysis showed that these hypermethylated CpG islands in patients are commonly located in the promoter regions of xenobiotic enzymes that are involved in bladder cancer progression. On follow-up, LC-MS/MS revealed accumulation of glucuronic acid, S-adenosylhomocysteine, and a decrease in S-adenosylmethionine, corroborating findings from the RRBS and mRNA expression analysis indicating increased glucuronidation and methylation capacities in African American patients. Flux analysis experiments with 13C-labeled glucose in cultured African American bladder cancer cells confirmed these findings. Collectively, our studies revealed robust differences in methylation-related metabolism and expression of enzymes regulating xenobiotic metabolism in African American patients indicate that race/ethnic differences in tumor biology may exist in bladder cancer., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Objective: Identify metabolic changes produced by dimethyl fumarate (DMF) treatment and link them to immunological effects., Methods: We enrolled 18 MS patients and obtained blood prior to DMF and 6 months postinitiation. We also enrolled 18 healthy controls for comparison. We performed global metabolomics on plasma and used weighted correlation network analysis (WGCNA) to identify modules of correlated metabolites. We identified modules that changed with treatment, followed by targeted metabolomics to corroborate changes identified in global analyses. We correlated changes in metabolite modules and individual metabolites with changes in immunological parameters., Results: We identified alterations in lipid metabolism after DMF treatment - increases in two modules (phospholipids, lysophospholipids and plasmalogens) and reduction in one module (saturated and poly-unsaturated fatty acids) eigen-metabolite values (all P  < 0.05). Change in the fatty acid module was greater in participants who developed lymphopenia and was strongly associated with both reduction in absolute lymphocyte counts ( r  =   0.65; P  = 0.005) and change in CD8+ T cell subsets. We also noted significant correlation of change in lymphocyte counts with multiple fatty acid levels (measured by targeted or untargeted methods)., Interpretation: This study demonstrates that DMF treatment alters lipid metabolism and that changes in fatty acid levels are related to DMF-induced immunological changes.

Activated immune cells undergo a metabolic switch to aerobic glycolysis akin to the Warburg effect, thereby presenting a potential therapeutic target in autoimmune disease. Dimethyl fumarate (DMF), a derivative of the Krebs cycle intermediate fumarate, is an immunomodulatory drug used to treat multiple sclerosis and psoriasis. Although its therapeutic mechanism remains uncertain, DMF covalently modifies cysteine residues in a process termed succination. We found that DMF succinates and inactivates the catalytic cysteine of the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in mice and humans, both in vitro and in vivo. It thereby down-regulates aerobic glycolysis in activated myeloid and lymphoid cells, which mediates its anti-inflammatory effects. Our results provide mechanistic insight into immune modulation by DMF and represent a proof of concept that aerobic glycolysis is a therapeutic target in autoimmunity., (Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Multiple sclerosis (MS) is an inflammatory disorder targeting the central nervous system (CNS). The relapsing-remitting phase of MS is largely driven by peripheral activation of autoreactive T-helper (Th) 1 and Th17 lymphocytes. In contrast, compartmentalized inflammation within the CNS, including diffuse activation of innate myeloid cells, characterizes the progressive phase of MS, the most debilitating phase that currently lacks satisfactory treatments. Recently, bryostatin-1 (bryo-1), a naturally occurring, CNS-permeable compound with a favorable safety profile in humans, has been shown to act on antigen-presenting cells to promote differentiation of lymphocytes into Th2 cells, an action that might benefit Th1-driven inflammatory conditions such as MS. In the present study, we show that bryo-1 provides marked benefit in mice with experimental autoimmune encephalomyelitis (EAE), an experimental MS animal model. Preventive treatment with bryo-1 abolishes the onset of neurologic deficits in EAE. More strikingly, bryo-1 reverses neurologic deficits after EAE onset, even when treatment is initiated at a late stage of disease when peak adaptive immunity has subsided. Treatment with bryo-1 in vitro promotes an anti-inflammatory phenotype in antigen-presenting dendritic cells, macrophages, and to a lesser extent, lymphocytes. These findings suggest the potential for bryo-1 as a therapeutic agent in MS, particularly given its established clinical safety. Furthermore, the benefit of bryo-1, even in late treatment of EAE, combined with its targeting of innate myeloid cells suggests therapeutic potential in progressive forms of MS., Competing Interests: The authors declare no conflict of interest.

Opinion Statement: Vitamin D status has been proposed as relevant to many neurological disorders. Data suggest that vitamin D may be important for the development of the nervous system, and it also plays a role in neuroimmunology and neuroprotection. Lower levels of circulating 25-hydroxyvitamin D have been linked with increased risk of multiple sclerosis (MS) and Alzheimer's disease (AD). While people with amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and stroke have lower vitamin D levels than those without the diseases, it is unclear if this is because hypovitaminosis D contributes to disease risk or is a consequence of immobility and other factors caused by the disease. Lower levels of vitamin D have been associated with worse prognosis in MS, PD, ALS, and stroke, while no longitudinal studies have been performed to evaluate such an association in AD. Small pilot trials have been performed to evaluate vitamin D supplementation for some of these diseases, but there have been no phase III studies to support vitamin D supplementation in these patient populations; further, ideal levels of 25-hydroxyvitamin D are not known. Thus, while some expert panels or individuals have suggested routine testing and supplementation for patients with these neurological conditions, it is our opinion that there are currently insufficient data to support high-dose vitamin D supplementation to specifically treat or prevent these conditions.

A 67-year-old man presented with several days of progressive, painless left eye vision loss. He reported mild jaw claudication but denied headache, scalp tenderness or constitutional symptoms. Examination revealed palpable temporal arteries, blurring of the left optic disc, and 20/100 vision in the left eye with mild relative afferent pupillary defect. Inflammatory markers were sent, and methylprednisolone was initiated for presumptive giant cell arteritis (GCA). Erythrocyte sedimentation rate was normal, however, and C reactive protein was only mildly elevated, prompting further investigation. Orbital MRI revealed nodular enhancement of the optic nerve sheaths bilaterally from optic nerve head to chiasm, raising concern for an infiltrative leptomeningeal process such as sarcoidosis or lymphoma. Methylprednisolone was temporarily stopped while a broad work up for inflammatory and neoplastic causes was pursued. Fluorodeoxyglucose-positron emission tomography ultimately revealed hypermetabolism in the temporal, ophthalmic and occipital arteries suggesting GCA, which was confirmed by temporal artery biopsy. Steroids were restarted, and the patient's vision stabilised., (2015 BMJ Publishing Group Ltd.)

S-nitrosylation of proteins by nitric oxide is a major mode of signalling in cells. S-nitrosylation can mediate the regulation of a range of proteins, including prominent nuclear proteins, such as HDAC2 (ref. 2) and PARP1 (ref. 3). The high reactivity of the nitric oxide group with protein thiols, but the selective nature of nitrosylation within the cell, implies the existence of targeting mechanisms. Specificity of nitric oxide signalling is often achieved by the binding of nitric oxide synthase (NOS) to target proteins, either directly or through scaffolding proteins such as PSD-95 (ref. 5) and CAPON. As the three principal isoforms of NOS--neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible NOS (iNOS)--are primarily non-nuclear, the mechanisms by which nuclear proteins are selectively nitrosylated have been elusive. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is physiologically nitrosylated at its Cys 150 residue. Nitrosylated GAPDH (SNO-GAPDH) binds to Siah1, which possesses a nuclear localization signal, and is transported to the nucleus. Here, we show that SNO-GAPDH physiologically transnitrosylates nuclear proteins, including the deacetylating enzyme sirtuin-1 (SIRT1), histone deacetylase-2 (HDAC2) and DNA-activated protein kinase (DNA-PK). Our findings reveal a novel mechanism for targeted nitrosylation of nuclear proteins and suggest that protein-protein transfer of nitric oxide groups may be a general mechanism in cellular signal transduction.

Besides its role in glycolysis, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) initiates a cell death cascade. Diverse apoptotic stimuli activate inducible nitric oxide synthase (iNOS) or neuronal NOS (nNOS), with the generated nitric oxide (NO) S-nitrosylating GAPDH, abolishing its catalytic activity and conferring on it the ability to bind to Siah1, an E3-ubiquitin-ligase with a nuclear localization signal (NLS). The GAPDH-Siah1 protein complex, in turn, translocates to the nucleus and mediates cell death; these processes are blocked by procedures that interfere with GAPDH-Siah1 binding. Nuclear events induced by GAPDH to kill cells have been obscure. Here we show that nuclear GAPDH is acetylated at Lys 160 by the acetyltransferase p300/CREB binding protein (CBP) through direct protein interaction, which in turn stimulates the acetylation and catalytic activity of p300/CBP. Consequently, downstream targets of p300/CBP, such as p53 (Refs 10,11,12,13,14,15), are activated and cause cell death. A dominant-negative mutant GAPDH with the substitution of Lys 160 to Arg (GAPDH-K160R) prevents activation of p300/CBP, blocks induction of apoptotic genes and decreases cell death. Our findings reveal a pathway in which NO-induced nuclear GAPDH mediates cell death through p300/CBP.