Increased expression of histamine H-1 receptor mRNA in allergic rhinitis

Background Histamine plays an important role in producing nasal symptoms via histamine H-1 receptor (H(1)R) in allergic rhinitis. It is reported that the minimum histamine concentration that induces sneezing is lower in allergic patients than in normal control subjects. Previous studies by binding assay on H(1)R gave divided results on whether the number of H(1)Rs is increased in allergic rhinitis or not. Objective The objective of this study was to examine if H(1)R mRNA expression is increased in patients with allergic rhinitis compared with normal healthy volunteers. Methods We extracted RNA from scrapings of inferior turbinate mucosa of 10 patients suffering from allergic rhinitis and 10 control subjects. As the H(1)R gene lacks introns, we treated RNA pellets by DNase to distinguish RNA from contaminating genomic DNA. Since amplification of H(1)R and beta-actin mRNA remained in an exponential phase at 35 cycles, H(1)R and beta-actin mRNAs were amplified for 35 cycles by reverse transcription-polymerase chain reaction (RT-PCR). The PCR products were hybridized with internal probes and band intensities were quantitated by a densitometer. Results The mean +/- SD of H(1)R/beta-actin ratio was 0.88 +/- 0.62 for the patients with allergic rhinitis and 0.29 +/- 0.17 for the normal subjects; the difference was statistically significant (P < 0.01). Conclusions These data suggest that expression of H(1)R mRNA is increased in the nasal mucosa of the patients with allergic rhinitis.