ADP-ribosyl cyclase in rat vascular smooth muscle cells - Properties and regulation

We investigated whether ADP-ribosyl cyclase (ADPR-cyclase) in rat vascular smooth muscle cells (VSMCs) has enzymatic properties that differ from the w ell-characterized CD38-antigen ADPR-cyclase, expressed in HL-60 cells. ADPR -cyclase from VSMCs, but not CD38 ADPR-cyclase from HL-60 cells, was inhibi ted by gangliosides (10 mu mol/L) GT(IB), GD(1), and GM(3). Preincubation o f membranes from CD38 HL-60 cells, but not from VSMCs, with anti-CD38 antib odies increased ADPR-cyclase activity; CD38 antigen was detected both in VS MCs and in HL-60 cells. ADPR-cyclase in VSMC membranes was more sensitive t han CD38 HL-60 ADPR-cyclase to inactivation by N-endoglycosidase F and to t hermal inactivation at 45 degrees C. The specific activity of ADPR-cyclase in membranes from VSMCs was >20-fold higher than in membranes from CD38 HL- 60 cells. Most importantly, VSMC ADPR-cyclase was inhibited by Zn2+ and Cu2 + ions; the inhibition by Zn2+ was dose dependent, noncompetitive, and reve rsible by EDTA. In contrast, Zn2+ stimulated the activity of CD38 HL-60 ADP R-cyclase and other known types of ADPR-cyclases. Retinoids act either via the nuclear receptor retinoic acid receptor or retinoid X receptor, includi ng all-trans retinoic acid (atRA), and panagonist 9-cis-retinoic acid-upreg ulated VSMC ADPR-cyclase; the stimulatory effect of atRA was blocked by act inomycin D and cycloheximide. 1,25(OH)(2)-Vitamin D-3 (calciferol) stimulat ed VSMC ADPR-cyclase dose dependently at subnanomolar concentrations (ED(50 )congruent to 56 pmol/L). Oral administration of atRA to rats resulted in a n increase of ADPR-cyclase activity in aorta (congruent to+60%) and, to a l esser degree, in myocardium of left ventricle (+18%), but atRA had no effec t on ADPR-cyclases in lungs, spleen, intestinal smooth muscle, skeletal mus cle, liver, or testis. Administration of 3,5,3'-triiodothyronine (T-3) to r ats resulted in an increase of ADPR-cyclase activity in aorta (congruent to +89%), but not in liver or brain. We conclude the following: (1) ADPR-cycla se in VSMCs has enzymatic properties distinct from "classic" CD38 ADPR-cycl ase, especially sensitivity to inhibition by Zn2+ and Cu2+;(2) ADPR-cyclase in VSMCs is upregulated by various retinoids, calcitriol, and T-3 in vitro ; and (3) administration of atRA and T-3 increases ADPR-cyclase in aorta in vivo. We suggest that the cADPR signaling system plays an important role i n the regulation of VSMC functions in response to steroid superfamily hormo nes.