Expression of transient receptor potential vanilloid 1 (TRPV1) and 2 (TRPV2) in human peripheral blood

The vanilloid receptor family of cation channels includes the capsaicin-sensitive, proton- and heat-activated TRPV1 and noxious heat-activated TRPV2. The present study demonstrates both gene and protein expression of TRPV1 and TRPV2 in human peripheral blood cells (PBCs) using molecular and immunocytochemical techniques. Using reverse-transcription polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR (qRT-PCR), TRPV1 and TRPV2 mRNA was detected in mRNA isolated from human whole peripheral blood. Using qRT-PCR, TRPV2 mRNA was highly expressed in human whole blood isolates (9.33 ± 1.19 × 104 copies per 106 copies of the housekeeping gene GAPDH), whereas TRPV1 message was detected at ≈150-fold lower levels (638 ± 121 copies per 106 copies GAPDH). At the protein level, TRPV1 and TRPV2 activity was determined immunocytochemically in a lymphocyte-enriched mononuclear cell preparation (83 ± 2% lymphocytes). Cells were labelled with rabbit anti-TRPV1 or goat anti-TRPV2 (1:500) and subsequently labelled with goat Texas red- (TRPV1) or FITC-(TRPV2) conjugated secondary antibodies (1:1000). All cells demonstrated punctate TRPV1-immunoreactivity, which appeared to be on the plasma membrane and in the cytoplasm. In contrast, cells within subjects appeared to express the TRPV1 protein at varying intensities. TRPV2-immunoreactivity appeared diffuse. This is the first study to demonstrate the presence of both TRPV1 and TRPV2 in human peripheral lymphocytes. Further studies need to be undertaken in order to determine the role of TRPV channels in these cells.