title: Endogenous opioids in wound-site neutrophils of sternotomy patients.
abstract: BACKGROUND
  Postoperative pain management is a critical aspect of patient care. The inflammatory state of the post-sternotomy surgical wound sensitizes nerve endings, causing pain. Unrelieved or improperly managed pain compromises wound healing. Peripheral opioid receptors play a major role in analgesia, particularly under inflammatory conditions where both opioid receptor expression and efficacy are increased. Leukocytic opioid peptides include β-endorphin (END), met-enkephalin (ENK), and dynorphin-A (DYN), with END and ENK being predominant.
  
  
  RESULTS
  This work represents the first study of inflammatory cells collected from post-sternotomy wounds of patients undergoing cardiac surgery including coronary artery bypass grafting (CABG). Wound fluid (WF) and cells were collected from sternal wounds using a JP Blake drain at 24, 48, and 72 hours post sternum closure. Anti-CD15 staining and flow cytometry revealed that polymorphonuclear neutrophils (PMN) are the predominant cells present in wound fluid collected post-surgery. Compared to peripheral blood (PB) derived PMN, significant increases in CD177+/CD66b+ PMN were observed suggesting activation of wound-site PMN. Such activation was associated with higher levels of opioid peptide expression in PMN derived from WF. Indeed, increased level of opioid peptides in sternal wound environment was noted 72 h post-surgery. We demonstrate that WF contains factors that can significantly induce POMC transcription in human PMNs. IL-10 and IL-4 were abundant in WF and both cytokines significantly induced POMC gene expression suggesting that WF factors such as IL-10 and IL-4 contribute towards increased opioid peptide expression in wound-site PMN.
  
  
  CONCLUSIONS
  This approach provided a unique opportunity to study the cross-talk between inflammation and opioid peptides in PMN at a sternotomy wound-site. Wound-site PMN exhibited induction of END and ENK. In addition, sternal wound fluid significantly induced END expression in PMN. Taken together, these data constitute first clinical evidence that human wound-site PMNs are direct contributors of opioids at the sternal wound-site.
authors.affiliation: Comprehensive Wound Center and Davis Heart and Lung Research Institute, Department of Anesthesiology, Wexner Medical Center at the Ohio State University, Columbus, Ohio, United States of America.
authors.forename: Hamdy
authors.initials: H
authors.lastname: Awad
authors.forename: Motaz
authors.initials: M
authors.lastname: Abas
authors.forename: Haytham
authors.initials: H
authors.lastname: Elgharably
authors.forename: Ravi
authors.initials: R
authors.lastname: Tripathi
authors.forename: Tykie
authors.initials: T
authors.lastname: Theofilos
authors.forename: Sujatha
authors.initials: S
authors.lastname: Bhandary
authors.forename: Chittoor
authors.initials: C
authors.lastname: Sai-Sudhakar
authors.forename: Chandan K
authors.initials: CK
authors.lastname: Sen
authors.forename: Sashwati
authors.initials: S
authors.lastname: Roy
mesh_terms: D000368:Aged; D004399:Dynorphins / Q000097:blood; D004744:Enkephalin, Methionine / Q000097:blood; D005260:Female; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D016753:Interleukin-10 / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000378:metabolism*; D059408:Pain Management; D011184:Postoperative Period; D056346:Sternotomy / Q000379:methods; D014945:Wound Healing; D001615:beta-Endorphin / Q000097:blood
chemical_list: D016753:Interleukin-10; D015847:Interleukin-4; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D004399:Dynorphins