Atherosclerosis 192 (2007) 313–322 Suppression of hypercholesterolemic atherosclerosis by pentoxifylline and its mechanism Kailash Prasad ∗ , Paul Lee Department of Physiology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, Saskatchewan, Canada S7N 5E5 Received 23 December 2005; received in revised form 19 May 2006; accepted 26 July 2006 Available online 11 September 2006 Abstract Reactive oxygen species (ROS) have been implicated in the development of hypercholesterolemic atherosclerosis. Hypercholesterolemia increases the levels of platelet activating factor (PAF) and cytokines which are known to stimulate granulocytes and endothelial cells to produce ROS. Pentoxifylline (PTX) is an inhibitor of cytokines and PAF and would reduce the generation of ROS by granulocytes and endothelial cells. PTX therefore would be expected to reduce the development of hypercholesterolemic atherosclerosis. New Zealand white female rabbits were assigned to four groups: Group I (n = 12), control; Group II (n = 5), PTX control (40 mg/kg body weight daily orally); Group III (n = 13), 0.5% cholesterol; Group IV (n = 9), 0.5% cholesterol + PTX (40 mg/kg body weight daily orally). Blood samples were collected before (0 time) and after 1 and 2 months on experimental diets for measurement of serum triglycerides (TG), total cholesterol (TC), LDL-C, HDL-C and serum malondialdehyde (MDA), a lipid peroxidation product. At the end of 2 months the aorta was removed for measurement of atherosclerotic plaques, MDA, and aortic tissue chemiluminescence (Ao-CL), a marker for antioxidant reserve. Rabbits in Group III developed atherosclerosis (56.61 ± 6.90% of the intimal surface of aorta was covered with atherosclerotic plaques) which was associated with an increase in the serum TG, TC, LDL-C, HDL-C, TC/HDL-C, MDA and aortic MDA and antioxidant reserve. PTX reduced the development of atherosclerosis by 38.1% and this was associated with decreases in serum MDA by 32%, aortic MDA by 37%, and antioxidant reserve by 17.3% without changes in the serum lipids. These results suggest that ROS generated during hypercholesterolemia via cytokines and PAF may in part contribute to the development of hypercholesterolemic atherosclerosis and that suppression of production and activity of cytokines and PAF may reduce the development of hypercholesterolemic atherosclerosis. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Atherosclerosis; Hypercholesterolemia; Pentoxifylline; Oxygen radicals; Cytokines; Antioxidant reserve; Aortic chemiluminescence 1. Introduction Reactive oxygen species (ROS) have been implicated in the development of hypercholesterolemic atherosclero- sis [1–5]. Hypercholesterolemia could increase the levels of ROS through stimulation of polymorphonuclear leukocytes (PMNLs) and activation of endothelial cells [1,6]. Plasma levels of platelet activating factor (PAF) are elevated in hyper- cholesterolemia [7]. PAF is known to stimulate granulocytes to release cytokines such as tumor necrosis factor (TNF) ∗ Corresponding author. Tel.: +1 306 966 6539; fax: +1 306 966 6532. E-mail address: prasadk@usask.ca (K. Prasad). and interleukin-1 (IL-1) [8,9]. Tumor necrosis factor-alpha (TNF-) [10–12], interferon-gamma (IFN-) [13,14] and interleukin (IL-1, IL-6) [12,13] are elevated in hypercholes- terolemia. In addition TNF- could induce production of IL-6 [14]. IL-1, IL-8 and IL-6 [15–17], TNF- [15–17] and IFN- [18,19] are known to activate granulocytes to generate ROS. TNF- [20,21] stimulates NADPH-oxidase in the endothelial cells to generate ROS. Pentoxifylline (PTX) is a potent inhibitor of IL-1, IL-2, IL-6, TNF- and IFN- [22–24]. PTX down-regulates the release of IL-1, IL-6, IL-8 and TNF- [25]. It also down- regulates the production of TNF- and IFN- [26,27]. PTX inhibits the action of PAF on neutrophils, [28] and production of PAF [29]. 0021-9150/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.atherosclerosis.2006.07.034