Gene expression changes in the human diaphragm after cardiothoracic surgery

Abstract

We examined the effects of cardiothoracic surgery, including cardiopulmonary bypass and controlled mechanical ventilation, on messenger RNA gene expression in human diaphragm. We hypothesized that genes responsible for stress response, redox regulation, protein turnover, energy metabolism, and contractile function would be altered by cardiothoracic surgery. Paired diaphragm biopsy samples were obtained from 5 male patients (67 ± 11 years) during cardiothoracic surgery, the first as soon as the diaphragm was exposed and the second as late in surgery as possible (4.9 ± 1.8 hours between samples). We profiled messenger RNA from 5 specimen pairs with microarray analysis (Hu U133 plus 2.0; Affymetrix UK Ltd, High Wycombe, UK). Quantitative reverse transcriptase polymerase chain reaction was performed with a select set of genes exhibiting differential expression for validation. Microarray analysis identified 779 differentially expressed (early vs late samples) unique gene products (P < .005). Postoperatively, genes related to stress response and redox regulation were upregulated. Additionally, we found significantly upregulated expression of cathepsin C (2.7-fold), cathepsin L1 (2.0-fold), various ubiquitin-conjugating enzymes (E2, approximately 1.8-fold), proinflammatory cytokine interleukin 6 (15.6-fold), and muscle-specific ubiquitin ligase (MuRF-1, 2.6-fold). Comparison of fold change values obtained by quantitative reverse transcriptase polymerase chain reaction and microarray yielded significant correlation (r = 0.95, P < .0001). Cardiothoracic surgery results in rapid changes in human diaphragm gene expression in the operating room, including genes related to stress response, inflammation, redox regulation, and proteolysis. These results may provide insight into diaphragm muscle biology after prolonged cardiothoracic procedures.