Papers of the Week

Despite the available knowledge on underlying mechanisms and the development of several therapeutic strategies, optimal management of postoperative pain remains challenging. This pre-clinical study hypothesizes that, by promoting an anti-inflammatory scenario, pre-emptive administration of IMT504, a non-coding, non-CpG oligodeoxynucleotide with immune modulating properties, will reduce postincisional pain, also facilitating therapeutic opioid-sparing. Male adult Sprague-Dawley rats with unilateral hindpaw skin-muscle incision received pre-emptive (48 h and 24 h prior to surgery) or postoperative (6h after surgery) subcutaneous vehicle (saline) or IMT504. Various groups of rats were prepared for pain-like behaviour analyses, including subgroups receiving morphine or naloxone, as well as for flow-cytometry or quantitative RT-PCR analyses of the spleen and hindpaws (for analysis of inflammatory phenotype). Compared to vehicle-treated rats, pre-emptive IMT504 significantly reduced mechanical allodynia by 6 h after surgery, and accelerated recovery of basal responses from 72 h after surgery and onwards. Cold allodynia was also reduced by IMT504. Postoperative administration of IMT504 resulted in similar positive effects on pain-like behaviour. In IMT504-treated rats, 3 mg/kg morphine resulted in comparable blockade of mechanical allodynia as observed in vehicle-treated rats receiving 10 mg/kg morphine. IMT504 significantly increased hindpaw infiltration of mesenchymal stem cells, CD4+T and B cells, and caused upregulated or downregulated transcript expressions of interleukin-10 and interleukin-1β, respectively. Also, IMT504 treatment targeted the spleen, with upregulated or downregulated transcript expressions, 6 h after incision, of interleukin-10 and interleukin-1β, respectively. Altogether, pre-emptive or postoperative IMT504 provides protection against postincisional pain, through participation of significant immunomodulatory actions, and exhibiting opioid-sparing effects.