Unlocking the Role of Exercise on CD4+ T Cell Plasticity

Respiratory and Metabolic Responses of CD4 + T Cells to Acute Exercise and Their Association with Cardiorespiratory Fitness

INTRODUCTION

The study aimed to investigate to what extent acute endurance exercise, especially eccentric exercise and cardiorespiratory fitness, affects the metabolic profile of CD4 + cells.

METHODS

Fifteen male, healthy adults aged between 20 and 33 yr with a maximal oxygen uptake (V̇O 2max ) between 44 and 63 mL·kg -1 ·min -1 performed a downhill run (DR) and a level run (LR) for 45 min at 70% of their V̇O 2max on a treadmill in a crossover design. Blood samples were taken before (T0), directly after (T1), 3 h after (T3), and 24 h (T24) after each exercise for analyzing leukocyte numbers and cytokine levels. Isolated CD4 + cells were incubated for 4 h in autologous resting versus 3 h after exercise serum (T3 DR and T3 LR), and subsequently, cellular respiration, transcriptomic, and metabolomics profiles were measured.

RESULTS

The systemic immune inflammation index increased significantly after DR and LR at T1 and T3 ( P < 0.001). In contrast, the transcriptomic and metabolic profile of CD4 + cells showed no significant alterations after incubation in T3 exercise serum. However, cardiorespiratory fitness positively correlated with the maximal mitochondrial respiration in CD4 + cells after incubation with T3 LR serum ( r = 0.617, P = 0.033) and with gene expression of oxidative phosphorylation and levels of different metabolites. Similarly, V̇O 2max was associated with an anti-inflammatory profile on RNA level. Lower lactate, methylmalonic acid, and d -gluconic acid levels were found in CD4 + cells of participants with a high V̇O 2max ( P < 0.001).

CONCLUSIONS

Acute exercise leads to a mild proinflammatory milieu with only small changes in the metabolic homeostasis of CD4 + cells. High cardiorespiratory fitness is associated with a metabolic shift to oxidative phosphorylation in CD4 + cells. Functional relevance of this metabolic shift needs to be further investigated.

Single-Molecule DNA Methylation Reveals Unique Epigenetic Identity Profiles of T Helper Cells

Both identity and plasticity of CD4 T helper (Th) cells are regulated in part by epigenetic mechanisms. However, a method that reliably and readily profiles DNA base modifications is still needed to finely study Th cell differentiation. Cytosine methylation in CpG context (5mCpG) and cytosine hydroxymethylation (5hmCpG) are DNA modifications that identify stable cell phenotypes, but their potential to characterize intermediate cell transitions has not yet been evaluated. To assess transition states in Th cells, we developed a method to profile Th cell identity using Cas9-targeted single-molecule nanopore sequencing. Targeting as few as 10 selected genomic loci, we were able to distinguish major in vitro polarized murine T cell subtypes, as well as intermediate phenotypes, by their native DNA 5mCpG patterns. Moreover, by using off-target sequences, we were able to infer transcription factor activities relevant to each cell subtype. Detection of 5mCpG and 5hmCpG was validated on intestinal Th17 cells escaping transforming growth factor β control, using single-molecule adaptive sampling. A total of 21 differentially methylated regions mapping to the 10-gene panel were identified in pathogenic Th17 cells relative to their nonpathogenic counterpart. Hence, our data highlight the potential to exploit native DNA methylation profiling to study physiological and pathological transition states of Th cells.