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Home > Medical Professionals > Research Initiatives Conference > Poster Abstracts Accepted > Wang Decoupled Syndecan-1 mRNA

Decoupled Syndecan-1 mRNA And Protein Expression Is Differentially Regulated By Angiotensin II In Microphages

Wenli Wang, Carolyn A. Haller, Jing Wen, Peiyi Wang, Elliot L. Chaikof
Emory University, Atlanta, GA

Objective: It has been established that syndecans, a family of cell surface heparan sulfate proteoglycans, are expressed at sites of vascular injury and are important modulators of events relevant to acute tissue repair and chronic injury responses. The current studies were designed to examine syndecan-1 (Sdc1) expression during atherosclerotic lesion formation and whether angiotensin II (AgII) influences Sdc1 expression in macrophages. Methods: ApoE knockout mice were treated for 4 or 8 weeks with an infusion of angiotensin II and/or maintained on an atherogenic diet to induce atherosclerosis. Immunohistochemistry and immunofluorescence microscopy were employed to characterize the expression of Sdc1 in atherosclerotic lesions. Quantitative real-time PCR (QRTPCR) and slot blot analyses were used to define the role of AgII and responsible signaling pathways involved Sdc1 expression and protein shedding in RAW264.7 murine macrophages. Results: Sdc1 was abundantly expressed in macrophages located within early, as well as complex atherosclerotic lesions. Accordingly, we hypothesized that AgII regulates Sdc1 expression in macrophages. A time- and dose-dependent study was performed in RAW264.7 macrophages. QRTPCR demonstrated maximum Sdc1 mRNA up-regulation at 6 h after 500 nM AgII stimulation (3-fold; n=3; p<0.05). Through administration of specific inhibitors, we established that ERK/MAPK, PI3K and JNK signaling pathways mediated this effect, and the AgII-induced Sdc1 mRNA expression levels were dramatically attenuated by blockade of these signaling pathways individually (n=3; P<0.05). As an additional control experiment, we found that P38 and PKC pathways were not involved. Furthermore, FACS and slot blot analyses demonstrated that cAMP induced posttranscriptional Sdc1 protein expression in a dose-dependent manner with or without initial AgII stimulation, and the maximum induction was found with 1mM cAMP after 12 h of administration (~14 to 18 fold; n=3; p<0.05). In particular, AgII induced an increase in cell surface Sdc1 (mean fluorescence intensity: 147.11±5.73 vs. 176.86±4.8; n=3; p<0.05) and significantly accelerated Sdc1 shedding as demonstrated by slot blot analyses. Conclusions: Angiotensin II is a potent regulator of Sdc1 mRNA and protein expression and shedding in atherosclerotic lesions via a specific effect on macrophages.