Increased expression of histamine H1 receptor mRNA in allergic rhinitis

Background Histamine plays an important role in producing nasal symptoms via histamine H₁ receptor (H₁R) 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 H₁R gave divided results on whether the number of H₁Rs is increased in allergic rhinitis or not. Objective The objective of this study was to examine if H₁R 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 suft'ering from allergic rhinitis and 10 control subjects. As the H₁R gene lacks introns. we treated RNA pellets by DNase to distinguish RNA from contaminating genomic DNA. Since amplification of H₁R and β-actin mRNA remained in an exponential phase at 35 cycles. H₁R and β-actin mRNAs were amplified for 35 cycles by reverse transcHption-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 H₁R/β-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 H₁R mRNA is increased in the nasal mucosa of the patients with allergic rhinitis.