Laboratory of P h y d o g i c and Pharmacologit Studies, Nationdl Inctftute on Alrohol Abuse and Alcoholism, Belheda, Marv/dnd 20892
The regulation of P,and 0,-adrenergic receptors @,AR and P,AR) and receptor gene expression by interleukin-1 a (IL-1 a ) was studied in cultured AS49 human lung adenocarcinoma cells. Thc density and affinity of P,AR and PrAR were analyzed by computerized curve fitting of '251-pindolol binding and its displacement by subtype selective antagonists. Steady state levels of receptor mRNAs were quantified by DNA excess solution hybridization assays. A549 cells in preconiluent cultures had fewer P,AR than P,AR (0,: 1.9 5 0.3 vs. P2: 4.0 0.5 fmolimg protein, means 2 SE), but lost most of their b,AR upon reaching confluency (p,: 2.7 2 0.4, Pz: 0.8 -t 0.3 fmolinig). Incubation of preconfluent cells for 24 hr with 20 pM of human recombinant IL-1 LY did not modify the density of either of the PAR subtypes. Similar incubations of confluent cells increased the density of P,AR from 0.8 2 0.3 to 4.2 i 0.9 imolinig, while the density of P,AR and the antagonist affinities of both receptors remained unaltered. The IL-I a-induced increase in PrAR density in confluent cells was antagonized in a concentration-dependent manlier by a recombinant protein antagonist of type I 11--1 receptors (I&: 0.2 nM). The IL-la-induc-ed increase in PrAR density was preceded by an increase in the steady state level of P, AR mRNA, while levels of (J,AK mRNA remained unchanged. IL-la increased the slability as well as the rate of transcription of PLAR mRNA. These findings demonstrate for the first lime that activation of type I IL-1 receptors in A549 cells leads to a ccll d~nsity-dependenl, selective upregulation of P2AR, and that the mechanism of this effect involves increased formation and stability of the PLAR mesage. Q 1992 ~i l e y -i i s 5 , Inc.