Cilostazol inhibits modified low-density lipoprotein uptake and foam cell formation in mouse peritoneal macrophages.

Internalization of modified low-density lipoprotein (LDL) via macrophage scavenger receptors (e.g. scavenger receptor A and CD36) is thought to play a crucial role in the development of atherosclerotic lesions. Cilostazol, an antiplatelet agent with selective phosphodiesterase 3 inhibitory action, has been reported to ameliorate atherosclerosis in mouse models. However, the effect of cilostazol on modified LDL uptake in macrophages is not known. Thus, we investigated the effect of cilostazol on LDL uptake in mouse peritoneal macrophages (MPM). Cilostazol significantly inhibited oxidized and acetylated LDL uptake in MPM, while cyclic AMP (cAMP)-elevating agents, db-cAMP and other phosphodiesterase 3 or 4 inhibitors, did not inhibit the uptake. Cilostazol did not change cytosolic cAMP levels in MPM, and a protein kinase A (PKA) inhibitor did not influence the inhibitory effects of cilostazol. Cilostazol decreased scavenger receptor A but not CD36 expression. Moreover, cilostazol significantly inhibited foam cell formation, which was represented by an increase in esterified cholesterol content. In conclusion, cilostazol significantly inhibits the uptake of modified LDL and foam cell formation in mouse peritoneal macrophages, and the inhibitory effect of cilostazol can be induced in a cAMP- and PKA-independent manner.

Anti-atherosclerotic effect of cilostazol in apolipoprotein-E knockout mice.

To investigate whether cilostazol (CAS 73963-72-1), a selective phosphodiesterase 3 inhibitor, reduces the progression of atherogenic diet-induced atherosclerosis, cilostazol was orally administered twice a day for 4 weeks to male apolipoprotein-E knockout (ApoE KO) mice. In serial sections of the aortic root, the atherosclerotic lesion ratios in the cilostazol-treated groups (32.5 +/- 3.3% for 100 mg/kg, 29.0 +/- 2.9% for 300 mg/kg) were significantly and dose-dependently smaller than that of the control group (40.2 +/- 3.7%). Cilostazol also significantly reduced the expression of vascular cell adhesion molecule-1 (VCAM-1) and monocyte/macrophage accumulation in the aortic root and increased high-density lipoprotein(HDL) cholesterol levels in plasma. These results suggest that cilostazol suppresses the progression of atherosclerosis in ApoE KO mice by inhibiting adhesionand infiltration of monocytes and reducing cholesterol accumulation in atherosclerotic lesion.

Effect of G-1 column (Adacolumn) therapy in rats with adjuvant arthritis on the migration and immunoreactivity of peripheral and splenic leukocytes.

The G-1 column (Adacolumn), a novel extracorporeal adsorption device, is now available for the treatment of such chronic inflammatory diseases as ulcerative colitis and rheumatoid arthritis. G-1 column treatment sometimes results in a rapid decrease in clinical inflammatory parameters and/or has a delayed beneficial effect on disease activity. In order to identify the scientific basis for such clinical benefits, we studied rats with adjuvant arthritis induced by immunization with Mycobacterium butyricum antigen. The potential role of G-1 column treatment on the migratory properties and immunoreactivities of leukocytes was investigated. Treatment of arthritic rats for 60 min with an extracorporeal perfusion through the G-1 column led to the adsorption of a small proportion (20%) of circulating granulocytes and monocytes. However, after G-1 treatment, the migration of radiolabeled blood granulocytes and monocytes to sites of acute dermal inflammatory reactions decreased significantly, in the case of granulocytes, almost by half. The migration of granulocytes to the inflamed hindpaws of severely affected animals was diminished in the G-1 treated group. Granulocytes that have passed through the G-1 column may stay in the bloodstream because of their markedly diminished number of adhesion molecules. A slightly increased accumulation in the liver and a decreased localization in the lung was also observed. These results may be relevant to the rapid clinical anti-inflammatory effect observed in rheumatoid arthritis and possibly also in ulcerative colitis, without any pulmonary complications. In contrast, the adsorption rate by the G-1 column of T lymphocytes was very low, and their migration pattern to sites of dermal inflammatory reactions was not altered after treatment. However, the antigen (Mycobacterium purified protein derivative) reactivity of T lymphocytes in blood was almost completely abolished after G-1 column treatment of arthritic rats. This unexpected qualitative effect on T lymphocytes of G-1 treatment warrants further detailed study.

Nitric oxide (NO) is not involved in accentuated antagonism for chronotropy in the isolated mouse atrium.

Nitric oxide (NO) is reportedly involved in accentuated antagonism in the canine blood-perfused sinoatrial (SA) node, and is thought to modulate cholinergic control of heart rate in rabbits. In the present study, we evaluated the involvement of NO in accentuated antagonism in an isolated preparation of both atria from C57BL/6J mice. Isoprenaline (10(-10) M-10(-7) M) had positive chronotropic effects but decreased rather than increased contraction strength. Carbachol (10(-8) M-3x10(-6) M) had a concentration-dependent, negative chronotropic action. In the presence of a submaximal concentration of isoprenaline (30 nM), the same concentration range of carbachol elicited a larger decrease in heart rate than in the absence of isoprenaline. The larger decrease in heart rate (accentuated antagonism) was not modified by the presence of the NO synthase inhibitor N(omega)-nitro-L-arginine methylester (L-NAME). Similar results were obtained using ICR strain mice. Isoprenaline increased cAMP content but not cGMP; carbachol in the presence of isoprenaline increased cGMP but had no further effects on cAMP. In the presence of L-NAME, the increase in cGMP elicited by carbachol was attenuated. In the isolated mouse atria, it appears that NO is not involved in accentuated antagonism due to lack of coupling between cGMP signalling and chronotropic function.