Rupatadine prevents histamine-induced gene expression of B1 and B2 bradykinin receptors in the rat paw

B Kokkas1, D Molyva1, K Kalokasidis3, A Tsartalis1, C Poulios2, H Dedi1, A Goulas1,2. 1Aristotle University of Thessaloniki Medical School, Department of Pharmacology, Greece, 2Aristotle University of Thessaloniki Medical School, Department of Anatomical Pathology, Greece, 3Aristotle University of Thessaloniki Medical School, 2nd Department of Dermatology, Papageorgiou Hospital, Greece

Introduction/ Aim: The gene expression of B1 and B2 bradykinin receptors (B1R, B2R) is known to be induced by a variety of proinflammatory stimuli, such as activators of Toll-like receptors, cytokines, platelet-activating factor (PAF) and kinins. In many instances this upregulation was shown to be dependent on or facilitated by TNF action and neutrophil migration. In this study we examine the effect of histamine on bradykinin receptor gene expression, in the rat paw. The effect of rupatadine, a second generation antihistamine and PAF receptor antagonist, was also examined.

Methods: Hydrochloric histamine (5mM, in 100 μl normal saline) was injected in the hind paw of Wistar rats and, three hours later, the animals were sacrificed and their paw tissue excised and either immediately frozen for RNA extraction or added to a solution of formalin for histopathological examination with standard eosin-haematoxylin staining. Gene expression of the B1 and B2 bradykinin receptors as well as the H1 histamine receptor (H1R) was assessed by reverse transcription followed by real-time PCR. GAPDH was used as the housekeeping gene. Rupatadine fumarate, dissolved in DMSO (20 mg/kg), was administered intraperitoneally, 1 hour prior to histamine injection into the paw. PCR-based estimates of gene expression were compared using non-parametric statistical analysis (Kruskal-Wallis, Mann-Whitney).

Results: Under our experimental conditions, a statistically significant increase of gene expression was recorded for all three receptors; an approximate 10xfold induction for B1R (p = 0.001) and a 6xfold induction for either B2R or H1R (p = 0.036 and 0.006, respectively). Parenteral administration of rupatadine prior to histamine injection into the paw, managed to largely prevent the up-regulation of the three receptors (p = 0.003, 0.001 and <0.001 for the histamine-induced expression of H1R, B1R and B2R respectively, in presence/absence of rupatadine). In addition, we observed a considerable infiltration of lymphocytes (but not of neutrophils) following the injection of histamine into the paw, which was similarly prevented by rupatadine.

Conclusions: Histamine is able to stimulate a neutrophil–independent induction of the B1R, B2R and H1R gene expression, in the rat paw. Rupatadine, administered systemically prior to histamine is able to prevent this effect, an observation which may be of use when considering future uses for this drug.