Sivaram Pillarisetti

HDL elevators and mimetics--emerging therapies for atherosclerosis.

High plasma levels of LDL cholesterol, triglycerides and low levels of HDL cholesterol are strong and independent risk factors of coronary heart disease (CHD). The first two abnormalities are addressed by a variety of drugs including statins, cholesterol absorption inhibitors, fibrates and niacin. Some of these drugs also elevate HDL albeit weakly. Thus treatments optimized for HDL elevation are still an unmet medical need. Low HDL-C is the most common lipoprotein abnormality in patients with CHD and the body of evidence showing an inverse relationship between HDL-C levels and risk for CHD has grown large. Research in the past decade not only greatly enhanced our understanding of HDL metabolism but also offered potential therapeutic targets to address low HDL syndrome. There are two classes of these HDL drugs--those that elevate plasma HDL (e.g. cholesteryl ester transfer protein--CETP and ligands of transcription factors such as peroxisome proliferator activated receptor PPARalpha/delta, liver X receptor (LXR)) and those that mimic HDL and facilitate reverse cholesterol transport (RCT) a key function of plasma HDL. HDL mimetics, which include ApoA1 mutants and peptide mimetics of ApoA1, are thought to be fast acting and may show greater benefits especially in acute coronary syndromes. The purpose of this review is to examine key players in HDL metabolism and therapeutics that modulate/mimic these targets. The prospect of these approaches in the prevention of cardiovascular disease is also discussed.

A perlecan-inducing compound significantly inhibits smooth muscle cell function and in-stent intimal hyperplasia: novel insights into the diverse biological effects of perlecan.

AIMS Perlecan is the major heparan sulfate proteoglycan in the arterial wall. Previous studies have suggested that perlecan is a potent inhibitor of smooth muscle cell (SMC) activity. Therefore, perlecan overexpression may serve as a therapeutic modality to prevent in-stent restenosis (ISR). We have investigated a novel compound (RUS3108), identified in a SMC based screen to induce perlecan synthesis in SMC. The aims of this study were to assess the in vitro effects of RUS3108 and the effects of RUS3108-eluting stents in preventing ISR. METHODS AND RESULTS Rabbit aortic SMC and bovine aortic endothelial cells (EC) were used in this study. Immunohistochemistry showed that RUS3108-treated SMC over-expressed perlecan indicating the drug effects. Furthermore, RUS3108 induced a SMC differentiated phenotype by SMembryonic staining. RUS3108 (1 microM) inhibited 3H-thymidine incorporation by >50%, which was completely reversed by a perlecan antibody. RUS3108 also inhibited SMC migration (Boyden chamber) and MMP-9 activity. In contrast, RUS3108 (100nM) modestly stimulated EC 3H-thymidine incorporation by 22% (p<0.02). In vivo, a total of 30 stents were deployed in rabbit iliac arteries as follows: 1) bare metal stents (n=10), 2) polymer onlycoated stents (n=10), and 3) polymer-coated stents containing RUS3108 (n=10). Rabbits were sacrificed at four weeks and stented segments were subjected to morphometric analysis. Intimal cross sectional area was significantly lower in the RUS3108-eluting stent group (0.31+ or -0.27 mm(2) versus 1.0 + or - 0.31 and 1.25 + or - 0.51 in the bare metal stents and polymer only coated stents groups, respectively, p<0.0001). CONCLUSIONS RUS3108 is a novel perlecan-inducing compound, which is a potent inhibitor of SMC activity and a modest stimulator of EC proliferation. RUS3108-eluting stents may serve as an excellent modality for the prevention of ISR.

Selected players in the inflammation cascade and drugs that target these inflammation genes against metastasis.

Despite many recent advances the prognosis of cancer patients with metastasis still remains poor. In metastatic invasion, tumor cells interact with endothelial cells through several distinct adhesion molecules. Adherent tumor cells extravasate into tissues by degrading basement membranes with matrix degrading enzymes such as heparanases and matrix metalloproteinases. Endothelial expression of matrix degrading enzymes and adhesion molecules are under the control of inflammatory cytokines. These inflammatory proteins and the signaling pathways involved in the expression of these genes are under intense investigation as therapeutic targets to prevent tumor growth and metastasis. The current review focuses on selected players of the inflammation cascade and drugs that target these inflammatory genes.

Heparan sulfate side chains have a critical role in the inhibitory effects of perlecan on vascular smooth muscle cell response to arterial injury

Perlecan is a proteoglycan composed of a 470-kDa core protein linked to three heparan sulfate (HS) glycosaminoglycan chains. The intact proteoglycan inhibits the smooth muscle cell (SMC) response to vascular injury. Hspg2(Δ3/Δ3) (MΔ3/Δ3) mice produce a mutant perlecan lacking the HS side chains. The objective of this study was to determine differences between these two types of perlecan in modifying SMC activities to the arterial injury response, in order to define the specific role of the HS side chains. In vitro proliferative and migratory activities were compared in SMC isolated from MΔ3/Δ3 and wild-type mice. Proliferation of MΔ3/Δ3 SMC was 1.5× greater than in wild type (P < 0.001), increased by addition of growth factors, and showed a 42% greater migratory response than wild-type cells to PDGF-BB (P < 0.001). In MΔ3/Δ3 SMC adhesion to fibronectin, and collagen types I and IV was significantly greater than wild type. Addition of DRL-12582, an inducer of perlecan expression, decreased proliferation and migratory response to PDGF-BB stimulation in wild-type SMC compared with MΔ3/Δ3. In an in vivo carotid artery wire injury model, the medial thickness, medial area/lumen ratio, and macrophage infiltration were significantly increased in the MΔ3/Δ3 mice, indicating a prominent role of the HS side chain in limiting vascular injury response. Mutant perlecan that lacks HS side chains had a marked reduction in the inhibition of in vitro SMC function and the in vivo arterial response to injury, indicating the critical role of HS side chains in perlecan function in the vessel wall.