Transcriptomic and behavioural characterisation of a mouse model of burn pain identify the cholecystokinin 2 receptor as an analgesic target

Abstract

Burn injury is a cause of significant mortality and morbidity worldwide and is frequently associated with severe and long-lasting pain that remains difficult to manage throughout recovery. We characterised a mouse model of burn-induced pain using pharmacological and transcriptomic approaches. Mechanical allodynia elicited by burn injury was partially reversed by meloxicam (5 mg/kg), gabapentin (100 mg/kg) and oxycodone (3 and 10 mg/kg), while thermal allodynia and gait abnormalities were only significantly improved by amitriptyline (3 mg/kg) and oxycodone (10 mg/kg). The need for relatively high opioid doses to elicit analgesia suggested a degree of opioid resistance, similar to that shown clinically in burn patients. We thus assessed the gene expression changes in dorsal root ganglion neurons and pathophysiological mechanisms underpinning burn injury-induced pain using a transcriptomic approach. Burn injury was associated with significantly increased expression of genes associated with axon guidance, neuropeptide signalling, behavioural defence response and extracellular signalling, confirming a mixed neuropathic and inflammatory aetiology. Notably, among the pain-related genes that were upregulated post-injury was the cholecystokinin 2 receptor (Cckbr), a G protein-coupled receptor known as a pain target involved in reducing opioid effectiveness. Indeed, the clinically used cholecystokinin receptor antagonist proglumide (30 mg/kg) was effective at reversing mechanical allodynia, with additional analgesia evident in combination with low-dose oxycodone (1 mg/kg), including significant reversal of thermal allodynia. These findings highlight the complex pathophysiological mechanisms underpinning burn injury-induced pain and suggest that cholecystokinin-2 receptor antagonists may be useful clinically as adjuvants to decrease opioid requirements and improve analgesic management.

Isobolographic Analyses of Proglumide–Celecoxib Interaction in Rats with Painful Diabetic Neuropathy

“…In this study, the administration of proglumide and celecoxib ip reduced formalin-induced nociceptive behavior and tactile allodynia in diabetic rats. These data agree with previous studies that showed proglumide reversed mechanical allodynia but not thermal allodynia in a mouse model of burn pain [Yin et al, 2016]. In addition, L365, 260, and CI-988, selective CCK-2 receptor antagonists reduced mechanical allodynia and thermal hyperalgesia in rats [Kovelowski et al, 2000;Kim et al, 2009].…”

Transcriptomic characterisation of the optimised rat model of Walker 256 breast cancer cell‐induced bone pain

“…A total of 26 rats were used in this study as detailed in Figure . As per the standard practice in transcriptomic analysis, three biological replicates were used for all groups for each of the comparisons made. At study commencement, rats in the body weight range of approximately 80–120 g were used.…”

“…The reads were mapped to the Ensembl/Rnor_6.0. Count tables were generated using HTSeq_count from the HTSeq package . Genes were considered to be above the noise level if the read count was ≥ 10.…”

Permanent Photodynamic Activation of the Cholecystokinin 2 Receptor

“…For example, CCK2R has been confirmed as being expressed in dorsal root ganglion neurons to mediate the inhibition of a Kv current (I A ) to increase pain sensation [16]. The CCK2R antagonist is known to reduce the need for opioid administration in relieving pain in a mouse model of burn-induced pain [17], likely by antagonizing CCK2R-µ-opioid receptor (MOR) heterodimerization, which inhibits MOR signaling [18]. CCK infusion into amygdala in rats has been found to activate a descending CCK2R-mediated pathway and to inhibit spinal neuron discharge, leading to hindpaw analgesia [19].…”