Nociceptive sensitization by the secretory protein Bv8

Abstract

1. The small protein Bv8, isolated from amphibian skin, belongs to a novel family of secretory proteins (Bv8-Prokineticin family, SWISS-PROT: Q9PW66) whose orthologues have been conserved throughout evolution, from invertebrates to humans. 2. When injected intravenously or subcutaneously (from 0.06 to 500 pmol kg -1) or intrathecally (from 6 fmol to 250 pmol) in rats, Bv8 produced an intense systemic nociceptive sensitization to mechanical and thermal stimuli applied to the tail and paws. 3. Topically delivered into one rat paw, 50 fmol of Bv8 decreased by 50% the nociceptive threshold to pressure in the injected paw without affecting the threshold in the contralateral paw. 4. The two G-protein coupled prokineticin receptors, PK-R1 and PK-R2, were expressed in rat dorsal root ganglia (DRG) and in dorsal quadrants of spinal cord (DSC) and bound Bv8 and the mammalian orthologue, EG-VEGF, with high affinity. In DSC, PK-R1 was more abundant than PK-R2, whereas both receptors were equally expressed in DRG. IC 50 of Bv8 and EG-VEGF to inhibit [ 125I]-Bv8 binding to rat DRG and DSC were 4.1±0.4 nM Bv8 and 76.4±7.6 nM EG-VEGF, in DRG; 7.3±0.9 nM Bv8 and 330±41 nM EG-VEGF, in DSC. 5. In the small diameter neurons (< 30 μm) of rat DRG cultures, Bv8 concentrations, ranging from 0.2 to 10 nM, raised [Ca 2+] i in a dose-dependent manner. 6. These data suggest that Bv8, through binding to PK receptors of DSC and primary sensitive neurons, results in intense sensitization of peripheral nociceptors to thermal and mechanical stimuli.