Molecular and pharmacological evidence for modulation of kinin B₁ receptor expression by endogenous glucocorticoids hormones in rats

1. The effect of endogenous glucocorticoid hormones on the expression of rat B₁ receptors was examined by means of molecular and pharmacological functional approaches. 2. Rats were adrenalectomized (ADX), and 7 days after this procedure the intradermal injection of B₁ receptor agonist des-Arg⁹-BK produced a significant increase in the paw volume, while only a weak effect was observed in sham-operated animals. A similar increase in the contractile responses mediated by B₁ agonist des-Arg⁹-BK was also observed in the rat portal vein in vitro. 3. Chemical ADX performed with mitotane (a drug that reduces corticosteroid synthesis) produced essentially the same up-regulation of B₁ receptors as that observed in ADX rats. 4. The modulation of B₁ receptor expression was evaluated by ribonuclease protection assay, employing mRNA obtained from the lungs and paw of ADX rats. 5. Additionally, both paw oedema and contraction of portal vein mediated by B₁ agonist des-Arg⁹-BK in ADX rats, were markedly inhibited by treatment with dexamethasone, or COX-2 inhibitor meloxican, or with the NF-κB inhibitor PDTC. Interestingly, the same degree of inhibition was achieved when the animals were treated with a combination of submaximal doses of dexamethasone and PDTC. 6. The involvement of NF-κB pathway was further confirmed by mobility shift assay using nuclear extracts from lung, paw and heart of ADX rats. It was also confirmed that the treatment of ADX rats with dexamethasone, PDTC or dexamethasone plus PDTC completely inhibit NF-κB activation caused by absence of endogenous glucucorticoid. 7. Together, the results of the present study provide, for the first time, molecular and pharmacological evidence showing that B₁ kinin receptor expression can be regulated through endogenous glucocorticoids by a mechanism dependent on NF-κB pathway. Clinical significance of the present findings stem from evidence showing the importance of B₁ kinin receptors in the mediation of inflammatory and pain related responses.