PS-BPB01-1: SPARC IS INDUCED AT THE EARLY STAGE OF VASCULAR ENDOTHELIAL DYSFUNCTION TO COMPENSATE INFLAMMATION IN DOCA-SALT HYPERTENSIVE RATS

Abstract

Objective: Extracellular matrix (ECM) regulates various cellular functions as well as provides structural support. SPARC (secreted protein acidic and rich in cysteine) is one of the ECM components, which participates in various cellular functions, especially during morphogenesis and tissue remodeling. We have reported that 1) SPARC, which increases in accordance with renal injury, causes collagen deposition through ADAMTS1 (a disintegrin and metalloproteinase with thrombospondin type 1 motif) production, and 2) renin-angiotensin system is placed in the upstream of SPARC overexpression in the hypertensive rat kidney. The present study investigated the roles for SPARC in vascular endothelial cell dysfunction and inflammation in the setting of hypertension. Design and method: Rats were treated with deoxycorticosterone acetate (DOCA) and 1% salt water for 0, 1, 2 or 3 weeks. Blood pressure was measured by tail-cuff methods, and thoracic aorta was isolated to examine acetylcholine-induced vasodilatory response, macrophage infiltration by immunohistochemistry, and protein expression of SPARC and ADAMTS1 by Western blotting. In the separate experiment, angiotensin II (10–7mol/L, 6hr) or SPARC recombinant protein (100nmol/L, 24hr) was treated to cultured rat aortic endothelial cells (RAECs) with/without siRNA targeting SPARC and ADAMTS1. MCP-1 and LOX-1 mRNA levels were measured by real-time RT-PCR. Result: DOCA-salt caused time-dependent increases in systolic blood pressure, impairment of endothelium-dependent vasodilation, and macrophage infiltration into the adventitial area of the aorta. The expression of SPARC in the DOCA-salt rat aorta was enhanced at week1 and week2 compared to week0. ADAMTS1 expression tended to increase from week1 and showed significant increases at week3. In RAECs, SPARC and ADAMTS1 gene knockdown aggravated angiotensin II-induced overexpression of LOX-1 and MCP-1 mRNA, indicating anti-inflammatory effects of SPARC. On the other hand, SPARC recombinant protein treatment induced the upregulation of LOX-1 and MCP-1. Conclusions: SPARC may be induced at the early stage of vascular injury to compensate inflammation under the existence of angiotensin II. We need further investigation into the diverse effects of SPARC and the relationship between SPARC and ADAMTS1.