Journal of Cellular Biochemistry 101:753–766 (2007) Interleukin-1b Selectively Decreases the Synthesis of Versican by Arterial Smooth Muscle Cells Joan M. Lemire, 1 Christina K. Chan, 2 Steven Bressler, 2 John Miller, 2,3 Richard G. LeBaron, 4 and Thomas N. Wight 2,5 * 1 Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts 2 Hope Heart Program, Benaroya Research Institute at Virginia Mason, Seattle, Washington 3 University of Nebraska Medical Center, Nebraska Medical Center, Omaha, Nebraska 4 Division of Life Sciences, University of Texas at San Antonio, San Antonio, Texas 5 Department of Pathology, School of Medicine, University of Washington, Seattle, Washington Abstract Proteoglycans accumulate in lesions of atherosclerosis but little is known as to which factors regulate the synthesis of these molecules. Interleukin-1b (IL-1b) is a cytokine involved in vascular lesion development but it is not clear whether it has specific effects on proteoglycan synthesis by arterial smooth muscle cells (ASMC). Monkey ASMC were treated with IL-1b and proteoglycan synthesis assessed using [ 35 S]-sulfate and [ 35 S]-Trans amino acid labeling. Four prominent size populations of proteoglycans, as determined by SDS – PAGE gradient gel electrophoresis, were observed in the culture medium and identified as versican, biglycan, decorin, and an unknown population that migrated to the gel interface. IL-1b treatment decreased significantly the synthesis of versican, while increasing the synthesis of decorin, but having no effect on biglycan synthesis. Northern blot analyses confirmed this selective effect on versican and decorin mRNA transcripts. Nuclear run-on and RNA inhibition studies showed that decreased mRNA for versican was due to increased mRNA degradation and not to changes in transcription. In addition, IL-1b increased the synthesis of the population of proteoglycans that separated at the SDS–PAGE gel interface. Chondroitinase ABC lyase digestion of this population revealed a complex of proteins composed of versican (350 kDa), an unidentified protein (215 kDa), and a 23 kDa protein identified by sequence analyses as serglycin. These data demonstrate that IL-1b selectively downregulates versican synthesis by ASMC, while positively regulating the synthesis of other proteoglycans. J. Cell. Biochem. 101: 753–766, 2007. ß 2007 Wiley-Liss, Inc. Key words: versican; interleukin-1b; decorin; serglycin; smooth muscle cells Versican is an extracellular matrix proteo- glycan that accumulates in vascular diseases such as atherosclerosis and restenosis [Geary et al., 1996; Halpert et al., 1996; Matsuura et al., 1996; Lin et al., 1996a; Gutierrez et al., 1997; Wight et al., 1997; Evanko et al., 1998; O’Brien et al., 1998; Geary et al., 2002]. The principal source of vascular versican in these lesions is the arterial smooth muscle cell (ASMC) [Chang et al., 1983; Scho ¨nherr et al., 1991; Yao et al., 1994; Scho ¨nherr et al., 1997; Lemire et al., 1999]. Versican influences the phenotype of ASMCs [Evanko et al., 1999; Lemire et al., 2002; Merrilees et al., 2002] and endothelial cells [Cattaruzza et al., 2002] and may regulate key events associated with lipid retention [Camejo et al., 1998; Williams and Tabas, 1998; Chait and Wight, 2000] and plaque thrombosis [Kolodgie et al., 2002; Mazzucato et al., 2002; McGee and Wagner, 2003]. The inhibition of versican synthesis by antisense modulates tropoelastin synthesis and elastic fiber forma- tion [Huang et al., 2006], possibly affecting intima or plaque stability. For these reasons, it becomes important to understand those factors that regulate versican synthesis by ASMC. Studies to date have identified a number of growth factors such as platelet-derived growth factor (PDGF) and transforming growth ß 2007 Wiley-Liss, Inc. Grant sponsor: National Institutes of Health; Grant number: HL 18645. *Correspondence to: Dr. Thomas N. Wight, Benaroya Research Institute at Virginia Mason, Hope Heart Pro- gram, 1201 Ninth Avenue, Seattle, WA 98101-2795. E-mail: twight@benaroyaresearch.org Received 17 August 2006; Accepted 16 November 2006 DOI 10.1002/jcb.21235