Epigenetic regulatory pathways involving microRNAs may modulate the host immune response following major trauma.
BACKGROUND
Posttraumatic nosocomial pneumonia is a common complication resulting in significant morbidity. Trauma-induced immunocompromise is associated with an enhanced susceptibility to pneumonia. In this study, we explore the hypothesis that posttranscriptional epigenetic regulation of gene expression may be an important factor in determining this immune phenotype. We describe the pattern of production of microRNAss (miRs) and their association with nosocomial pneumonia following severe trauma.


METHODS
A convenience sample of 30 ventilated polytrauma patients (
5637) and 16 healthy controls were recruited. Messenger RNA and protein levels of key cytokines were quantified within 2 hours of the injury and at 24 hours. Three miRs per cytokine were then selected based on miRBase target prediction scores and quantified using polymerase chain reaction. Nosocomial pneumonia was defined using the Centers for Disease Control and Prevention definitions.


RESULTS
Median Injury Severity Score (ISS) was 29, and 47% of the patients developed nosocomial pneumonia. miR-125a and miR-202 decreased by 34% and 77%, respectively, immediately following injury, whereas their target, IL-10, increased messenger RNA levels 3-fold and protein levels 180-fold. Tumor necrosis factor α (TNF-α) and IL-12 gene expression decreased by 68% and 43%, respectively, following injury, and this was mirrored by a 10-fold increase in miR-181, an miR predicted to target TNF-α transcripts. Lower levels of miR-125a and miR-374b were associated with the later acquisition of hospital-acquired pneumonia.


CONCLUSIONS
Alteration in the expression of miRs with highly predicted complementarity to IL-10 and TNF-α may be an important mechanism regulating the posttraumatic immunosuppressive phenotype in intensive care unit patients.


METHODS
Retrospective observational study, level III.
From the Centre for Translational Medicine and Therapeutics (H.C.O., H.D.T.T., T.F.J., R.M.P., C.J.H., M.J.O.), William Harvey Research Institute, and Centre for Trauma Sciences (H.D.T.T., T.F.J., K.B.), Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London; and Adult Critical Care Unit (H.D.T.T, R.M.P., C.J.H., M.J.O.), Royal London Hospital, Barts Health NHS Trust, London, United Kingdom.
Helen C
HC
Owen
Hew D T
HD
Torrance
Timothy F
TF
Jones
Rupert M
RM
Pearse
Charles J
CJ
Hinds
Karim
K
Brohi
Michael J
MJ
O'Dwyer
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003428:Cross Infection / Q000453:epidemiology / Q000235:genetics; D004636:Emergency Service, Hospital; D044127:Epigenesis, Genetic; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D016867:Immunocompromised Host / Q000235:genetics*; D015601:Injury Severity Score; D016753:Interleukin-10 / Q000378:metabolism; D018664:Interleukin-12 / Q000378:metabolism; D008297:Male; D035683:MicroRNAs / Q000235:genetics*; D008875:Middle Aged; D009104:Multiple Trauma / Q000235:genetics / Q000276:immunology / Q000628:therapy; D011014:Pneumonia / Q000453:epidemiology / Q000235:genetics; D011237:Predictive Value of Tests; D011379:Prognosis; D012121:Respiration, Artificial; D012189:Retrospective Studies; D015398:Signal Transduction; D014193:Trauma Centers; D016896:Treatment Outcome; D006113:United Kingdom; D014947:Wounds and Injuries / Q000235:genetics / Q000276:immunology* / Q000628:therapy
D035683:MicroRNAs; D016753:Interleukin-10; D018664:Interleukin-12