Kinin B1receptors contributes to acute pain following minor surgery in humans

Abstract

Background: Kinins play an important role in regulation of pain and hyperalgesia after tissue injury and inflammation by activating two types of G-protein-coupled receptors, the kinin B1and B2receptors. It is generally accepted that the B2receptor is constitutively expressed, whereas the B1receptor is induced in response to inflammation. However, little is known about the regulatory effects of kinin receptors on the onset of acute inflammation and inflammatory pain in humans. The present study investigated the changes in gene expression of kinin receptors and the levels of their endogenous ligands at an early time point following tissue injury and their relation to clinical pain, as well as the effect of COX-inhibition on their expression levels.Results: Tissue injury resulted in a significant up-regulation in the gene expression of B1and B2receptors at 3 hours post-surgery, the onset of acute inflammatory pain. Interestingly, the up-regulation in the gene expression of B1and B2receptors was positively correlated to pain intensity only after ketorolac treatment, signifying an interaction between prostaglandins and kinins in the inflammatory pain process. Further, the gene expression of both B1and B2receptors were correlated. Following tissue injury, B1ligands des-Arg9-BK and des-Arg10-KD were significantly lower at the third hour compared to the first 2 hours in both the placebo and the ketorolac treatment groups but did not differ significantly between groups. Tissue injury also resulted in the down-regulation of TRPV1 gene expression at 3 hours post-surgery with no significant effect by ketorolac treatment. Interestingly, the change in gene expression of TRPV1 was correlated to the change in gene expression of B1receptor but not B2receptor.Conclusions: These results provide evidence at the transcriptional level in a clinical model of tissue injury that up-regulation of kinin receptors are involved in the development of the early phase of inflammation and inflammatory pain. The up-regulation of B1receptors may contribute to acute inflammatory pain through TRPV1 activation. © 2010 Hamza et al; licensee BioMed Central Ltd.