Grund, Ethan M.

Multiple sclerosis is characterized by CNS infiltration of autoreactive immune cells that drive both acute inflammatory demyelination and chronic progressive axonal and neuronal injury. Expanding evidence implicates CD8 + antineural T cells in the neurodegeneration that underlies irreversible clinical progression in multiple sclerosis, yet therapies specifically targeting this cell population are limited. CD8 + T cells from patients with MS exhibit increased engagement of the pentose phosphate pathway. Pharmacologic inhibition of the pentose phosphate pathway reduced glycolysis, glucose uptake, NADPH production, ATP production, proliferation, and proinflammatory cytokine secretion in CD8 + T cells activated by ligation of CD3 and CD28. Pentose phosphate pathway inhibition also prevented CD8 + T cell–mediated antigen-specific neuronal injury in vitro and in both an adoptive transfer–based cuprizone model of demyelination and in mice with experimental autoimmune encephalomyelitis. Notably, transcriptional profiling of CNS-infiltrating CD8 + T cells in patients with MS indicated increased pentose phosphate pathway engagement, suggesting that this pathway is involved in CD8 + T cell–mediated injury of axons and neurons in the demyelinated CNS. Inhibiting the pentose phosphate pathway disrupts CD8 + T cell metabolic reprogramming and effector functions, suggesting that such inhibition may serve as a therapeutic strategy to prevent neurodegeneration in patients with progressive MS.

AbstractMetabolic pathways are known to generate byproducts—some of which have no clear metabolic function and some of which are toxic. Nicotinamide adenine dinucleotide phosphate hydrate (NAD(P)HX) is a toxic metabolite that is produced by stressors such as a fever, infection, or physical stress. Nicotinamide adenine dinucleotide phosphate hydrate dehydratase (NAXD) and nicotinamide adenine dinucleotide phosphate hydrate epimerase (NAXE) are part of the nicotinamide repair system that function to break down this toxic metabolite. Deficiency of NAXD and NAXE interrupts the critical intracellular repair of NAD(P)HX and allows for its accumulation. Clinically, deficiency of NAXE manifests as progressive, early onset encephalopathy with brain edema and/or leukoencephalopathy (PEBEL) 1, while deficiency of NAXD manifests as PEBEL2. In this report, we describe a case of probable PEBEL2 in a patient with a variant of unknown significance (c.362C>T, p.121L) in the NAXD gene who presented after routine immunizations with significant skin findings and in the absence of fevers.

Abstract In diseases such as multiple sclerosis and autoimmune encephalitides, activated CD8+ cytotoxic T cells infiltrate the brain and are found in clonally expanded clusters that outnumber CD4+ cells in progressive stages of disease. At present, the pathophysiological role of these cells is poorly understood and therapeutic strategies for preventing or ameliorating autoinflammatory disease progression are limited. T cells exhibit profound metabolic reprogramming that facilitates the energetic and proliferative demands of effector T cells. Key metabolic pathways in this reprogramming include upregulation of glycolysis and the pentose phosphate pathway (PPP). Here we show that 1) pharmacologic inhibition of the PPP suppresses effector phenotype acquisition and proinflammatory cytokine secretion by CD8+ T cells; 2) engagement of the PPP is enhanced by pharmacologic Nrf2 activation, implicating reactive oxygen species-induced activation as a transcriptional regulator of PPP-dependent immune activation; 3) Nrf2-driven PPP flux promotes the acquisition of specific CD8+ effector phenotypes; 4) limiting the metabolic flux of glucose-derived metabolites through the PPP prevents CD8+ T cell-mediated injury of neurons expressing cognate antigen and preserves their electrophysiological function; and 5) pharmacologic inhibition of the PPP in B6 mice at symptom onset is sufficient to delay and ameliorate motor disability in the MOG EAE preclinical model of MS. Overall, these results underscore the potential of immunometabolic therapies to limit T cell mediated injury in autoinflammatory and autoimmune diseases across organ systems including the prevention of neurologic deficits in patients with T cell driven neurologic disease. This work was supported by the NIH (R01NS115126 to CLH; T32GM065841 to EMG), the Mayo Clinic Graduate School of Biomedical Sciences, the Mayo Clinic Center for MS and Autoimmune Neurology, and generous donations from Eugene and Marcia Applebaum, Donald J. and Frances I. Herdrich, Bob and Loralee Marvin, and Rob and Debbie Mudge.

Abstract New strategies to preserve cognitive function could broadly benefit the aging population. Cellular senescence is a hypothesized mediator of inflammation-related tissue dysfunction in aging. Using single-cell RNA-sequencing, we discovered an age-related brain myeloid population exhibiting overlapping senescent and disease-associated activation signatures, including upregulation of chemoattractant factors. We confirmed senescent brain myeloid cells promote peripheral immune cell chemotaxis in vitro. Through mass cytometry, we demonstrate age- and sex-dependent increases in activated resident and infiltrating brain immune cells are reduced through systemic targeting of p16-positive senescent cells, which is associated with improvements in executive function and spatial learning tasks. Our high-dimensional results reveal dynamic remodeling of the age-dependent brain immune cell landscape and implicate senescent cell targeting as a strategy to counter inflammatory changes and cognitive decline.

Background and ObjectivesWe sought to determine clinical significance of neuronal septin autoimmunity and evaluate for potential IgG effects.MethodsSeptin‐IgGs were detected by indirect immunofluorescence assays (IFAs; mouse tissue and cell based) or Western blot. IgG binding to (and internalization of) extracellular septin epitopes were evaluated for by live rat hippocampal neuron assay. The impact of purified patient IgGs on murine cortical neuron function was determined by recording extracellular field potentials in a multielectrode array platform.ResultsSeptin‐IgGs were identified in 23 patients. All 8 patients with septin‐5‐IgG detected had cerebellar ataxia, and 7 had prominent eye movement disorders. One of 2 patients with co‐existing septin‐7‐IgG had additional psychiatric phenotype (apathy, emotional blunting, and poor insight). Fifteen patients had septin‐7 autoimmunity, without septin‐5‐IgG detected. Disorders included encephalopathy (11; 2 patients with accompanying myelopathy, and 2 were relapsing), myelopathy (3), and episodic ataxia (1). Psychiatric symptoms (≥1 of agitation, apathy, catatonia, disorganized thinking, and paranoia) were prominent in 6 of 11 patients with encephalopathic symptoms. Eight of 10 patients with data available (from 23 total) improved after immunotherapy, and a further 2 patients improved spontaneously. Staining of plasma membranes of live hippocampal neurons produced by patient IgGs (subclasses 1 and 2) colocalized with pre‐ and post‐synaptic markers. Decreased spiking and bursting behavior in mixed cultures of murine glutamatergic and GABAergic cortical neurons produced by patient IgGs were attributable to neither antigenic crosslinking and internalization nor complement activation.InterpretationSeptin‐IgGs are predictive of distinct treatment‐responsive autoimmune central nervous system (CNS) disorders. Live neuron binding and induced electrophysiologic effects by patient IgGs may support septin‐specific pathophysiology. ANN NEUROL 2022;92:1090–1101