Pentose phosphate pathway inhibition metabolically reprograms CD8+ T cells and disrupts CNS autoimmunity
Ethan M. Grund, Benjamin D.S. Clarkson, Susanna Pucci, Maria S. Westphal, Carolina Muniz Partida, Sara A. Muhammad, Charles L. Howe
Ethan M. Grund, Benjamin D.S. Clarkson, Susanna Pucci, Maria S. Westphal, Carolina Muniz Partida, Sara A. Muhammad, Charles L. Howe
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Research Article Immunology Neuroscience

Pentose phosphate pathway inhibition metabolically reprograms CD8+ T cells and disrupts CNS autoimmunity

Abstract

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.

Authors

Ethan M. Grund, Benjamin D.S. Clarkson, Susanna Pucci, Maria S. Westphal, Carolina Muniz Partida, Sara A. Muhammad, Charles L. Howe

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Figure 6

PPP inhibition in CD8+ T cells prevents antigen-specific antineuronal cytotoxicity.

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PPP inhibition in CD8+ T cells prevents antigen-specific antineuronal cy...
(A) Schematic showing neuron compartment isolated from axon compartment by microgrooves. Neurons were transduced with AAV.hSyn.OVA.GFP; CD8+ OTI T cells were immunomagnetically isolated prior to CD3/28 activation. (B and C) Baseline axonal GFP signal (B) and consequent axon injury (C) at 24 hours after addition of vehicle-treated activated OTI T cells (veh). (D and E) Baseline axonal GFP (D) and preservation of axons (E) at 24 hours after addition of activated OTI T cells pretreated with 6AN (100 μM). (F and G) Live cell imaging of GFP+ axons (F) and cell bodies (G) following addition of OTI T cells ± 6AN (100 μM) to the axon chamber (OTI+6AN, n = 7; OTI+vehicle, n = 6). (H) Spikes per epoch (20 minutes) in mouse cortical neurons exposed to OTI T cells (n = 6/condition); normalized to spike count prior to T cell addition. (I) Number of active electrodes normalized to activity prior to T cell addition. Top graphs in H and I show aggregated data across time tertiles (0–4 hours; 4–9 hours; 9–14 hours). (J–L) Endpoint (48 hours) image of GFP+ neurons following coincubation with nonactivated OTI T cells (J), CD3/28-activated OTI T cells (K), or activated OTI T cells pretreated with 6AN (100 μM) (L); insets show higher-magnification images. (M) Quantitation of neurite and neuron loss using live cell imaging of the conditions in J–L) (OTI+vehicle, n = 15; OTI+6AN, n = 15). Total GFP signal at each time point in wells incubated with nonactivated OTI T cells (J) was used to normalize data collected after addition of activated OTI T cells. One-way or 2-way ANOVA with Tukey’s or Dunnet’s pairwise comparison test was used to assess significance; *P < 0.05, **P < 0.01. Data are shown as 95% CI (F–I) or mean ± SEM (M). Scale bars are 50 μm.