To clarify the significance of immunometabolism in systemic lupus erythematosus (SLE), and to determine the effect of calcium/calmodulin-dependent protein kinase 4 (CaMK4) on T cell metabolism.
Metabolomic profiling was performed using capillary electrophoresis mass spectrometry in naive T cells from MRL/lpr mice treated with anti-CD3/CD28 antibodies in the absence or presence of a CaMK4 inhibitor (KN-93). The expression of GLUT1 and CaMK4 in CD4+ T cells from healthy controls (n = 16), patients with inactive SLE (n = 13), and patients with active SLE (n = 14) was examined by flow cytometry and quantitative polymerase chain reaction. In vitro experiments were performed to determine the effect of KN-93 on the expression of GLUT1 during Th17 cell differentiation in T cells from patients with SLE.
CaMK4 inhibition significantly decreased the levels of glycolytic intermediates such as glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-diphosphate, pyruvate, and lactate (P < 0.05), whereas it did not affect the levels of the pentose phosphate pathway intermediates such as 6-phospho-d-gluconate, ribulose-5-phosphate, ribose-5-phosphate, and phosphoribosyl pyrophosphate. The expression levels of GLUT1 and CaMK4 in effector memory CD4+ T cells were significantly higher in patients with active SLE compared to healthy controls (P < 0.01 and P < 0.05, respectively) and patients with inactive SLE (P < 0.05 and P < 0.01, respectively). A functional analysis revealed that CaMK4 inhibition decreased the expression of GLUT1 during Th17 cell differentiation (P < 0.01), followed by a reduction of interleukin-17 (IL-17) production (P < 0.05).
The results of the study indicate that the activity of CaMK4 could be responsible for glycolysis, which contributes to the production of IL-17, and CaMK4 may contribute to aberrant expression of GLUT1 in T cells from patients with active SLE.