T cells from patients with type 1 diabetes fail to upregulate mitochondrial genes upon activation

Background: Mitochondrial function and metabolism are fundamental for T-cell physiology and function. Upon T-cell activation genes encoding proteins that regulate mitochondrial ATP production undergo changes. Mitochondrial dysfunction in the T-cell compartment has been associated with human autoimmune diseases. We recently reported that T-cells from T1D patients exhibit mitochondrial hyperpolarization that was associated with enhanced activation-induced ROS and inflammatory cytokine production. To test our hypothesis that T-cell mitochondrial dysfunction is intrinsic, we performed mitochondria-related gene array analysis and compared activation-induced gene regulation in T-cells from patients and healthy controls.

Methods: T cells enriched from fresh PBMC of 5 T1D patients and 5 age-matched controls were stimulated with plate-bound anti-CD3+anti-CD28 or isotype control antibodies for 24hr. RNA was extracted and cDNA synthesized. Qiagen RT2 expression array for 168 mitochondria-related genes was used.

Results: After polyclonal activation, genes encoding proteins involved in mitochondrial ATP production were elevated while those decrease ATP production were reduced in control T-cells. Elevated networks included Oxidative Phosphorylation proteins (subunits of Oxidative-Phosphorylation complexes I, III, IV, and V) as well as Adenine Nucleotide Translocases. Alternatively, genes (i.e. uncoupling proteins) that decrease ATP synthesis were reduced. When compared to healthy controls, T-cells from T1D patients failed to exhibit activation-induced upregulation of mitochondrial-related genes. Forty-two genes showed significant fold changes between control and T1D groups (upregulated 1.2-4.7 fold in controls, p-values ranged from 0.048 to 0.0001 vs T1D). The majority of these differentially regulated genes were members of Oxidative Phosphorylation complexes. Genes that regulate mitochondrial transport and outer membrane translocation were also differentially expressed. Of significant note, no genes were observed to be upregulated in T1D T-cells versus control T-cells .

Conclusion: These results suggest there is intrinsic mitochondrial abnormality in T-cells from patients with T1D. These mitochondrial abnormalities may result in T-cell metabolism and functional changes and participate in autoimmunity.