Session Type: Abstract Submissions (ACR)
Background/Purpose: In RA, autoimmunity precedes clinical symptoms by a decade and persists unabated even when downstream inflammation is well controlled; exposing lymphocytes to chronic stimulation and enforcing adaptation to persistent stress. T cells undergo rapid and extensive clonal expansion with a fairly unique need to greatly enhance metabolic activities and fulfill their energy needs by up-regulating aerobic glycolysis as well as autophagy. Glycolytic flux is mainly controlled by 6-phosphofructo-1-kinase, with its allosteric activator fructose 2,6-bisphosphate as a key regulator of the glycolytic pathway. The enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase isoform 3 (PFKFB3) generates fructose-2,6-bisphosphate and, hence, critically regulates the glycolytic rate under normal and pathophysiological conditions.
Methods: CD4+CD45RO– T cells purified from the blood of RA patients (n=77) and age-matched controls were stimulated by TCR crosslinking. Glucose consumption, intracellular ATP and lactate production were quantified. Expression of 33 glycolysis-associated genes was profiled by RT-PCR. Protein levels of PFKFB3 and the autophagy marker LC3II were measured by Western blotting. Glycolytic flux and autophagic signaling were blocked through the PFKFB3 inhibitor N-BrEt or the autophagy inhibitor 3-methyladenine.
Results: Compared to control CD4 T cells, RA CD4 T cells respond to stimulation-induced metabolic needs with impaired glucose consumption (p=0.015), diminished ATP production (p<0.001)and reduced lactate release (p<0.001); all indicative of a defect in glycolytic flux. RA T cells express normal densities of glucose receptors but consistently fail to up-regulate PFKFB3 (p=0.012) and induce insufficient amounts of LC3II (p=0.032). Deficiency in glucose metabolism and autophagy is associated with increased apoptosis (p=0.003). This phenotype is reproduced in control T cells by knockdown of PFKFB3 or blocking autophagic signaling. Overexpression of ectopic PFKFB3 in RA T cells restores intracellular ATP (p=0.009) and lactate production (p=0.024) and conveys apoptotic resistance. Restoring PFKFB3 in RA T cells also rectifies the autophagic defect (p=0.024). Energy deprivation is a stable phenotype of RA T cells, independent from disease activity and duration.
Conclusion: The inducible glycolytic rate-limiting enzyme PFKFB3 is repressed in RA T cells, resulting in deficient glucose utilization. The energy deprivation is aggravated by insufficient access to cell-internal energy resources and renders RA T cells apoptosis sensitive. Resetting the immune system in RA will require the repair of these metabolic abnormalities as they strain immune homeostasis and sustain chronic immune stress.
J. J. Goronzy,
C. M. Weyand,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/metabolic-reprogramming-of-autoimmune-t-cells-in-rheumatoid-arthritis/