Bank, She eld, ST10 2TN and 4 8 Palace Garden, Royston, Hertfordshire, S68 5AD1 It has been hypothesized that in patients with benign prostatic hyperplasia, selective antagonism of the a 1A -adrenoceptor-mediated contraction of lower urinary tract tissues may, via a selective relief of outlet obstruction, lead to an improvement in symptoms. 2 The present study describes the a 1 -adrenoceptor (a 1 -AR) subtype selectivities of two novel a 1 -AR antagonists, Ro 70-0004 (aka RS-100975) and a structurally-related compound RS-100329, and compares them with those of prazosin and tamsulosin. Radioligand binding and second-messenger studies in intact CHO-K1 cells expressing human cloned a 1A -, a 1B -and a 1D -AR showed nanomolar a nity and signi®cant a 1A -AR subtype selectivity for both Ro 70-0004 (pK i 8.9: 60 and 50 fold selectivity) and RS-100329 (pK i 9.6: 126 and 50 fold selectivity) over the a 1B -and a 1D -AR subtypes respectively. In contrast, prazosin and tamsulosin showed little subtype selectivity. 3 Noradrenaline-induced contractions of human lower urinary tract (LUT) tissues or rabbit bladder neck were competitively antagonized by Ro 70-0004 (pA 2 8.8 and 8.9), RS-100329 (pA 2 9.2 and 9.2), tamsulosin (pA 2 10.4 and 9.8) and prazosin (pA 2 8.7 and 8.3 respectively). A nity estimates for tamsulosin and prazosin in antagonizing a 1 -AR-mediated contractions of human renal artery (HRA) and rat aorta (RA) were similar to those observed in LUT tissues, whereas Ro 70-0004 and RS-100329 were approximately 100 fold less potent (pA 2 values of 6.8/6.8 and 7.3/7.9 in HRA/RA respectively). 4 The a 1A -AR subtype selectivity of Ro 70-0004 and RS-100329, demonstrated in both cloned and native systems, should allow for an evaluation of the clinical utility of a`uroselective' agent for the treatment of symptoms associated with benign prostatic hyperplasia.

NO is a cell-derived radical reported to inhibit mast cell degranulation and subsequent allergic inflammation, although whether its action is nonspecific or occurs via specific molecular mechanisms remains unknown. To examine this question, we set out to determine whether NO inhibits mast cell cytokine production, and, if so, whether it also alters FcεRI-dependent signal transduction. As hypothesized, the radical inhibited IgE/Ag-induced IL-4, IL-6, and TNF production. Although NO did not influence phosphorylated JNK, p38 MAPK, or p44/42 MAPK, it did inhibit phosphorylation of phospholipase Cγ1 and the AP-1 transcription factor protein c-Jun, but not NF-κB or CREB. NO further completely abrogated IgE/Ag-induced DNA-binding activity of the nuclear AP-1 proteins Fos and Jun. These results show that NO is capable of inhibiting FcεRI-dependent mast cell cytokine production at the level of gene regulation, and suggest too that NO may contribute to resolution of allergic inflammation.

SUMMARYActivated mast cells generate multiple cytokines but it is not known if these can be differentially regulated by pharmacological agents. We report here that the glucocorticoid dexamethasone (DEX) preferentially inhibited Ag-induced expression of IL-4 and IL-6 mRNA relative to TNF-a mRNA in RBL-2H3 cells. Likewise, the drug more readily inhibited release of IL-4 than TNF-a protein. SB203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK), enhanced Ag-induced TNFa mRNA expression without affecting IL-4 or IL-6 mRNA. At the protein level, SB203580 exerted little effect on TNF-a release but inhibited IL-4 release; notably, the ratio of TNF-a : IL-4 increased markedly with the concentration of SB203580, confirming the differential regulation of these cytokines. PD98059, an inhibitor of MAPK kinase (MEK), a component of the p44/42 MAPK pathway, partially inhibited Ag-induced expression of mRNA for all three cytokines while cyclosporin A inhibited Aginduced IL-4 and IL-6 mRNA more readily than TNF-a mRNA. Ag activation of the cells led to phosphorylation of p38 and p44/42 MAPK but this was not influenced by DEX. In conclusion, mast cell cytokines can be differentially regulated pre-and post-translationally by DEX and SB203580 but there does not appear to be a direct mechanistic link between the actions of these two drugs.

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