ADP-Ribosyl Cyclase in Rat Vascular Smooth Muscle Cells

Abstract

Abstract —We investigated whether ADP-ribosyl cyclase (ADPR-cyclase) in rat vascular smooth muscle cells (VSMCs) has enzymatic properties that differ from the well-characterized CD38-antigen ADPR-cyclase, expressed in HL-60 cells. ADPR-cyclase from VSMCs, but not CD38 ADPR-cyclase from HL-60 cells, was inhibited by gangliosides (10 μmol/L) GT 1B , GD 1 , and GM 3 . Preincubation of membranes from CD38 HL-60 cells, but not from VSMCs, with anti-CD38 antibodies increased ADPR-cyclase activity; CD38 antigen was detected both in VSMCs and in HL-60 cells. ADPR-cyclase in VSMC membranes was more sensitive than CD38 HL-60 ADPR-cyclase to inactivation by N- endoglycosidase F and to thermal inactivation at 45°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 Zn 2+ and Cu 2+ ions; the inhibition by Zn 2+ was dose dependent, noncompetitive, and reversible by EDTA. In contrast, Zn 2+ stimulated the activity of CD38 HL-60 ADPR-cyclase and other known types of ADPR-cyclases. Retinoids act either via the nuclear receptor retinoic acid receptor or retinoid X receptor, including all- trans retinoic acid (atRA), and panagonist 9- cis -retinoic acid–upregulated VSMC ADPR-cyclase; the stimulatory effect of atRA was blocked by actinomycin D and cycloheximide. 1,25(OH) 2 –Vitamin D 3 (calciferol) stimulated VSMC ADPR-cyclase dose dependently at subnanomolar concentrations (ED 50 ≅56 pmol/ l ). Oral administration of atRA to rats resulted in an increase of ADPR-cyclase activity in aorta (≅+60%) and, to a lesser degree, in myocardium of left ventricle (+18%), but atRA had no effect on ADPR-cyclases in lungs, spleen, intestinal smooth muscle, skeletal muscle, liver, or testis. Administration of 3,5,3′-triiodothyronine (T 3 ) to rats resulted in an increase of ADPR-cyclase activity in aorta (≅+89%), but not in liver or brain. We conclude the following: (1) ADPR-cyclase in VSMCs has enzymatic properties distinct from “classic” CD38 ADPR-cyclase, especially sensitivity to inhibition by Zn 2+ and Cu 2+ ; (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 in the regulation of VSMC functions in response to steroid superfamily hormones.