Expression of functional TRPV1 receptor in primary culture of canine keratinocytes

The interest for the endovanilloid system and for transient receptor potential vanilloid 1 (TRPV1) is continuously increasing, due to their involvement in inflammation, nociception and pruritus. Even if TRPV1 enrolment was highlighted in both physiological and pathological conditions, some aspects remain unclear, mostly in veterinary medicine. This study aimed to verify the expression and functionality of TRPV1 in canine keratinocytes to investigate in vitro the role of TRPV1 in these cells that are involved in different cutaneous pathologies. Keratinocytes primary cultures were isolated from bioptical samples and cultivated. Binding assay (using ³ [H]-resiniferatoxin), displacement assay (in the presence of 1.2 nM ³ [H]-resiniferatoxin) and functional assays (in the presence of 1 μCi/⁴⁵ Ca²⁺ ) with vanilloid agonists and antagonists, specifically addressed to TRPV1 receptor, were performed. Binding assay demonstrated the presence of measurable concentrations of TRPV1 (B_max  = 1,240 ± 120 fmol/mg protein; K_d  = 0.01 ± 0.004 nM). Displacement assay highlighted the highest affinity for resiniferatoxin (RTX) and 5-iodo-resiniferatoxin (5-I-RTX), among agonists and antagonists, respectively. The same compounds results as the most potent in the functional assays. This study demonstrated the identification and the characterization of TRPV1 receptor in primary canine keratinocytes cultures. The results are promising for a clinical use, but further in vivo investigations are required.