The bradykinin B1 receptor antagonist BI113823 reverses inflammatory hyperalgesia by desensitization of peripheral and spinal neurons.

BACKGROUND: Bradykinin is a neuropeptide released after tissue damage which plays an important role in inflammatory pain. The up-regulation of the bradykinin B1 receptor in response to inflammation makes it an attractive target for drug development. Aim was to investigate if the selective B1 receptor antagonist BI113823 reduces inflammation-induced mechanical hyperalgesia and if the effect is mediated via peripheral and/or spinal B1 receptor antagonism. METHODS: Electrophysiological recordings of peripheral afferents and spinal neurons were combined with behavioural experiments to better understand the underlying mechanisms of B1 receptor antagonism. Experiments were performed 24 h after injection of complete Freund's adjuvant (CFA) or saline into the paw of Wistar rats. A gene expression analysis for the B1 receptor was performed in different tissues. BI113823 was administered orally or intrathecally to assess effects on CFA-induced hyperalgesia. Peripheral afferents of the saphenous nerve as well as spinal wide dynamic range (WDR) and nociceptive-specific (NS) neurons were recorded, and mechanosensitivity was measured before and after BI113823 administration. RESULTS: BI113823 reduced CFA-induced mechanical hyperalgesia when administered orally or intrathecally. An increased B1 receptor gene expression was found in peripheral and spinal neural tissue. BI113823 significantly reduced mechanosensitivity of peripheral afferents and spinal NS neurons, but had no effect on WDR neurons. CONCLUSION: The selective bradykinin B1 receptor antagonist BI113823 reduces CFA-induced mechanical hyperalgesia which is mediated via antagonism of peripheral as well as spinal bradykinin B1 receptors. The selective modulation of CFA-sensitized spinal NS neurons by BI113823 could be a promising property for the treatment of inflammatory pain.

Reduced toxicity of F-deficient Sendai virus vector in the mouse fetus.

Current concerns over insertional mutagenesis by retroviral vectors mitigate investigations into alternative, potentially persistent gene therapy vector systems not dependent on genomic integration, such as Sendai virus vectors (SeVV). Prenatal gene therapy requires efficient gene delivery to several tissues, which may not be achievable by somatic gene transfer to the adult. Initially, to test the potential and tropism of the SeVV for gene delivery to fetal tissues, first-generation (replication- and propagation-competent) recombinant SeVV, expressing beta-galactosidase was introduced into late gestation immunocompetent mice via the amniotic and peritoneal cavities and the yolk sac vessels. At 2 days, this resulted in very high levels of expression particularly in the airway epithelium, mesothelium and vascular endothelium, respectively. However, as expected, substantial vector toxicity was observed. The efficiency of gene transfer and the level of gene expression were then examined using a second-generation SeVV. The second generation was developed to be still capable of cytoplasmic RNA replication and therefore high-level gene expression, but incapable of vector spread due to lack of the gene for viral F-protein. Vector was introduced into the fetal amniotic and peritoneal cavities, intravascularly, intramuscularly and intraspinally; at 2 days, expression was observed in the airway epithelia, peritoneal mesothelia, unidentified cells in the gut wall, locally at the site of muscle injection and in the dorsal root ganglia, respectively. Mortality was dramatically diminished compared with the first-generation vector.