The bradykinin B 1 -receptor is strongly upregulated under chronic inflammatory conditions. However, the mechanism and reason are not known. Because a better understanding of the mechanism of the upregulation will help in understanding its potential importance in inflammation, we have studied the molecular mechanism of B 1 -receptor upregulation in cultured human lung fibroblasts (

Estradiol is known to exert a protective effect against the development of atherosclerosis, but the mechanism by which this protection is mediated is unclear. Since animal studies strongly suggest that production of endothelium-derived relaxing factor is enhanced by estradiol, we The incidence of cardiovascular disease, the leading cause of mortality in western societies, is higher in men than in premenopausal women but increases in postmenopausal women. An abundance of epidemiological data supports a role for estrogens in this atheroprotective effect, prompting recommendations for their widespread use in postmenopausal replacement therapy (1, 2). However, the mechanism whereby this protection is mediated remains obscure. It is traditionally thought to be due to potentially favorable changes in blood lipids and lipoproteins (1), but a number of human (3) as well as animal studies strongly suggest a direct effect on the vascular system (4-6) and more specifically that basal endotheliumderived relaxing factor is enhanced in estradiol-treated females compared with oophorectomized controls (7-11).The endothelium-derived relaxing factor has been identified as nitric oxide (NO) or a closely related compound derived from the amino acid L-arginine, able to induce stimulation of the soluble guanylate cyclase enzyme contained in vascular smooth muscle cells (12)(13)(14) Because the molecular mechanisms of the endotheliumderived relaxing factor-enhanced activity observed in estradiol-treated animals has not yet been precisely elucidated, we sought to determine the effects of estradiol on NO production and simultaneously on NOS mRNA, protein, and activity in a well-characterized culture system of endothelial cells. MATERIALS AND METHODSCell Culture and Materials. Bovine aortic endothelial cells (BAEC) were obtained and grown as described (25,26)

We investigated the possible presence of bradykinin (BK) B1 receptor on rat mesangial cells (MC) by binding studies and by the effect of the B1 agonist des-Arg9-BK on intracellular calcium concentration ([Ca2+]i) and DNA synthesis in comparison with the effects of BK. Binding studies demonstrated specific, saturable binding for des-Arg9-[3H]BK inhibited by B1 but not by B2 antagonists. Scatchard analysis revealed a single class of B1 binding site with a maximum density of 15 fmol/mg protein and an affinity of 8.7 +/- 2.4 nM. Saturation and competition studies of 125I-[Tyr0]BK demonstrated the presence of two classes of B2 binding sites [dissociation constant (Kd) = 0.1 and 4 nM, respectively]. On fura-2-loaded adherent MC, both des-Arg9-BK and BK induced a biphasic increase (a transient enhancement followed by a sustained phase) in [Ca2+]i, both in primary culture and in cloned MC. Both the transient and sustained phases of [Ca2+]i induced by des-Arg9-BK were dose dependent, whereas BK induced a transient dose-dependent rise in [Ca2+]i, but the sustained phase remained constant. The increases in [Ca2+]i induced by des-Arg9-BK and BK were specifically abolished by B1 and B2 receptor antagonists, respectively, and showed homologous but not heterologous desensitization. Des-Arg9-BK and BK induced a significant proliferation (tested by cell counting and [3H]thymidine incorporation) of quiescent MC. Furthermore, the effects of des-Arg9-BK and BK were additive on Ca2+ mobilization but not on mitogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Background-The physiological effects of ACE inhibitors may act in part through a kinin-dependent mechanism. We investigated the effect of chronic ACE-inhibitor treatment on functional kinin B 1 -and B 2 -receptor expression, which are the molecular entities responsible for the biological effects of kinins. Methods and Results-Rats were subjected to different 6-week treatments using various mixtures of the following agents:ACE inhibitor, angiotensin AT 1 -receptor antagonist, and B 1 -and B 2 -receptor antagonists. Chronic ACE inhibition induced both renal and vascular B 1 -receptor expression, whereas B 2 -receptor expression was not modified. Furthermore, with B 1 -receptor antagonists, it was shown that B 1 -receptor induction was involved in the hypotensive effect of ACE inhibition. Using microdissection, we prepared 10 different nephron segments and found ACE-inhibitor-induced expression of functional B 1 -receptors in all segments. ACE-inhibitor-induced B 1 -receptor induction involved homologous upregulation, because it was prevented by B 1 -receptor antagonist treatment. Finally, using B 2 -receptor knockout mice, we showed that ACE-inhibitor-induced B 1 -receptor expression was B 2 -receptor independent. Conclusions-This study provides the first evidence that chronic ACE-inhibitor administration is associated with functional vascular and renal B 1 -receptor induction, which is involved in ACE-inhibitor-induced hypotension. The observed B 1 -receptor induction in the kidney might participate in the known renoprotective effects of ACE inhibition.

These studies show a functional induction of the B1-kinin receptor along the rat nephron, which should be taken in account to address the effects of kinins under inflammatory conditions in the kidney.