Evidence for microRNA involvement in exercise-associated neutrophil gene expression changes

Abstract

Exercise leads to a rapid change in the profile of gene expression in circulating neutrophils. MicroRNAs (miRNAs) have been discovered to play important roles in immune function and often act to attenuate or silence gene translation. We hypothesized that miRNA expression in circulating neutrophils would be affected by brief exercise. Eleven healthy men (19-30 yr old) performed 10, 2-min bouts of cycle ergometer exercise interspersed with 1-min rest at a constant work equivalent to approximately 76% of maximal oxygen uptake (Vo(2 max)). We used the Agilent Human miRNA V2 Microarray. A conservative statistical approach was used to determine that exercise significantly altered 38 miRNAs (20 had lower expression). Using RT-PCR, we verified the expression level changes from before to after exercise of seven miRNAs. In silico analysis showed that collectively 36 miRNAs potentially targeted 4,724 genes (2 of the miRNAs had no apparent gene targets). Moreover, when we compared the gene expression changes (n = 458) in neutrophils that have been altered by exercise, as previously reported, with the miRNAs altered by exercise, we identified three pathways, Ubiquitin-mediated proteolysis, Jak-STAT signaling pathway, and Hedgehog signaling pathway, in which an interaction of miRNA and gene expression was plausible. Each of these pathways is known to play a role in key mechanisms of inflammation. Brief exercise alters miRNA profile in circulating neutrophils in humans. These data support the hypothesis that exercise-associated changes in neutrophil miRNA expression play a role in neutrophil gene expression in response to physical activity.

Figures

Fig. 1.

An intersecting analysis of the specific neutrophil microRNAs (miRNAs) whose expression was significantly altered by exercise and genes whose expression was also significantly altered by exercise. This approach identified 3 significant pathways, providing direction for further investigations of how miRNAs altered by exercise regulate neutrophil function.

Fig. 2.

Relationship between exercise-associated changes in miRNA expression and their targeted genes whose expression was also significantly altered by exercise. Top: individual miRNAs that were downregulated by exercise and the proportion of their targeted genes that were upregulated. Previous studies suggest that, in general, downregulated miRNAs will lead to upregulation of targeted genes. As seen in the figure, this phenomenon is corroborated by the data from neutrophils as ∼80% of the targeted mRNAs were upregulated when their associated miRNA was downregulated. Bottom: individual miRNAs that were upregulated by exercise and the proportion of their targeted genes that were downregulated. In contrast to the downregulated miRNAs, upregulation of miRNAs did not lead to downregulation of their targeted genes.