Oral naftidrofuryl prevents platelet hyperreactivity ex vivo and inhibits functional desensitization to prostacyclin in hypercholesterolemic rabbits

Comparison of Cilostazol and Naftidrofuryl in an Experimental Acute Ischemia-Reperfusion Model

INTRODUCTION

Naftidrofuryl and cilostazol are drugs with proven efficacy in the treatment of claudication in peripheral vascular disease. In this experimental study, we evaluated the effects of naftidrofuryl and cilostazol in ischemia-reperfusion (IR) injury on various tissues.

MATERIALS AND METHODS

40 male albino Wistar rats (8-12 weeks old, 250-350 g.) are randomly divided into 4 groups: Control (Group 1), sham (group 2), cilostazol pre-treatment (group 3), naftidrofuryl pre-treatment (group 4). During 21 days placebo is given to group 2, 12 mg/kg/day cilostazol is given to group 3, 50 mg/kg/day naftidrofuryl is given to group 4 orally. Ischemia and reperfusion are induced at the lower hind limb in Groups 2, 3 and 4. Ischemic muscle, kidney, liver, heart, brain and blood samples are obtained. The total antioxidant capacity, oxidant levels and oxidative stress index are studied for each group.

RESULTS

Both drugs have protective effects of remote organ injury following IR. Systemic effects are similar to each other, both have protective effects of IR injury. It showed no statistical significance in the total antioxidant capacity. Total oxidant levels are significantly affected by cilostazol in the heart (p < 0.01) and by naftidrofuryl in the liver (p < 0.01). The effect on oxidative stress was only significant with cilostazol on the heart (p < 0.01).

CONCLUSION

Cilostazol and naftidrofuryl had beneficial effects in all tissues against tissue damage caused by IR injury. In ischemic muscle, kidney and heart cilostazol had improved outcomes comparing to naftidrofuryl. Naftidrofuryl had benefits over cilostazol in liver tissue.

Hypercholesterolemia enhances thromboembolism in arterioles but not venules: complete reversal by L-arginine

We investigated in vivo the effect of cholesterol diet-induced hypercholesterolemia (HC) on thromboembolism in nonatherosclerotic rabbit mesenteric arterioles and venules (diameter 21 to 45 micrometer). After mechanical vessel wall injury, the ensuing thromboembolic reaction was studied by intravital videomicroscopy. A dramatic prolongation of embolization duration (median >600 seconds) was observed in the arterioles of the HC group compared with the arterioles of a normal chow-fed (NC) control group (142 seconds, P<0.0001); concomitantly, relative thrombus height increased (thrombus height/vessel diameter was 68% for the HC group and 58% for the NC group; P<0.05). By contrast, in venules, cholesterol did not affect embolization duration (42 seconds for HC group, 34 seconds for NC group) and thrombus height (66% for HC group, 64% for NC group). Furthermore, the role of endothelial NO synthesis was studied. In arterioles, stimulation of endogenous NO synthesis through mesenteric superfusion of L-arginine (1 mmol/L) completely reversed cholesterol-enhanced embolization (152 seconds) but did not influence thrombus height (63%). L-Arginine had no effect in venules of the HC group (51 seconds) and nor in the arterioles and venules of the NC group (177 seconds for arterioles, 43 seconds for venules). This study indicates that hypercholesterolemia selectively enhances thrombus formation and embolization in arterioles but not in venules and that stimulation of endogenous NO production antagonizes this enhancement of arteriolar thromboembolism.

Naftidrofuryl exerts antiserotonergic but no endothelin-receptor blocking effects in AS4.1 cells, juxtaglomerular cells and isolated perfused rat kidneys

Naftidrofuryl, a 5-hydroxytryptamine 2 (5-HT 2 ) serotonergic receptor antagonist with vasodilator effects, has successfully been used for intermittent claudication, some forms of dementia, and glaucoma. Recently, an additional mode of action of naftidrofuryl (i.e., mixed endothelin receptor antagonism) has been suggested. However, in the current study naftidrofuryl was unable to block endothelin-3-induced free intracellular calcium increases, in contrast to a mixed endothelin receptor antagonist, bosentan. The inhibition of forskolin-induced renin secretion by endothelin-3 in primary cultures of mouse juxtaglomerular cells and by endothelin-1 in the isolated perfused rat kidney could not be blocked by naftidrofuryl. Naftidrofuryl was unable to block marked endothelin-1-induced renal vasoconstriction in isolated perfused rat kidney. In contrast, naftidrofuryl markedly attenuated serotonin-induced renal vasoconstriction and nearly completely blocked serotonin's renin inhibitory properties in isolated perfused rat kidney. The present results suggest that naftidrofuryl is a potent antagonist of serotonin's renal effects, but has no endothelin receptor-blocking properties.

Cardiovascular dysfunction in hypercholesterolemia associated with enhanced formation of AT1-receptor and of eicosanoids

BACKGROUND

In hypercholesterolemia with or without atherosclerosis cardiovascular dysfunction and altered signalling of angiotensin (Ang II), nitric oxide (NO), or prostanoids are intimately related to enhanced oxidant stress and concomitant changes in gene expression. We analyzed cardiac angiotensin receptor (AT1) expression and metabolism of Ang II, eicosanoids, and NO in hypercholesterolemic animals.

METHODS

Guinea pigs were fed a 1% cholesterol diet for 8 weeks (Chol). Hemodynamics were analyzed in Langendorff hearts. Spectrophotometric determination of plasma lipids and radioimmunological detection of eicosanoids/cyclic guanosine monophosphate (cGMP). Activities of NO synthase III (NOS-III) or angiotensin converting enzyme (ACE) were determined by enzymatic assays. AT1 receptor density was assessed by radioligand binding assay. NOS-III mRNAs were quantitated by reverse transcription polymerase chain reaction.

RESULTS

Hypercholesterolemia was associated with fatty degeneration of the liver and profound myocardial and coronary (e.g., endothelial) dysfunction. In Chol Langendorff hearts we observed significant increases in coronary flow (26.0 +/- 1.0 vs. 17.5 +/- 0.5 mL/min/g tissue) but diminished coronary responses to bradykinin (Bk, 250 ng bolus) or adenosine (Ado, 250 micrograms bolus) (delta CPPBk/Ado: 5 +/- 0.5 vs. 7.2 +/- 1/0.9 +/- 0.1 vs. 1.9 +/- 0.3 cm2 (area under the curve)). AT1 receptor expression was significantly increased in Chol hearts (72 +/- 6.8 vs. 45 +/- 5.6 fmol/mg protein), whereas marked suppression of cardiac activities of ACE (1.96 +/- 0.34 vs. 4.90 +/- 0.20 nmol/min/mg tissue) and of the entire cardiac nitric oxide-cGMP axis (e.g., NOS-III activity: 1.9 +/- 0.4 vs. 3.1 +/- 0.1 pmol/min/mg tissue; NOS-III mRNA: 0.82 +/- 0.16 vs. 1.20 +/- 0.12 arbitrary units; cGMP release: 0.41 +/- 0.02 vs. 0.54 +/- 0.04 pmol/min/g tissue) were shown in Chol. Finally, cardiac release of eicosanoids prostacyclin (PGI2) and thromboxane (TxA2) were significantly enhanced (0.48 +/- 0.05 vs. 0.38 +/- 0.05 and 0.60 +/- 0.10 vs. 0.24 +/- 0.10 ng/min/g tissue, respectively). Enhanced cardiac PGI2 release and suppression of cGMP synthesis in Chol were even more pronounced on stimulation with Bk (38.2 +/- 3.0 vs. 28.2 +/- 2.0 ng/min/g tissue and 1.9 +/- 0.3 vs. 3.0 +/- 0.3 pmol/min/g tissue, respectively).

CONCLUSIONS

Altered angiotensin-mediated signal transduction probably related to augmented eicosanoid formation does not compensate for the limited endogenous NO production and for cardiovascular dysfunction in hypercholesterolemic guinea pigs. In this context, changes in redox-sensitive regulation of gene expression (AT1 receptor, NOS-III--caused by enhanced oxidant stress--could play a pivotal role.

In vivo effect of naftidrofuryl on 5-hydroxytryptamine-mediated constriction in rat peripheral microcirculation

Naftidrofuryl is commonly used in treatment of peripheral vascular disease. Its vasodilator action has been partly explained by its inhibitory effect of 5-HT2 receptors on peripheral arteries in vitro. The purpose of this study was to test in vivo whether naftidrofuryl selectively inhibits 5-hydroxytryptamine (5-HT)-mediated constriction of large arterioles in the peripheral microcirculation. This constriction appears to be 5-HT2 receptor-mediated. Three separate protocols were used to test the effects of naftidrofuryl: chronic injection (15 mg/kg, i.p., twice daily for 5-6 days; n = 7), acute intravenous (i.v.) infusion (15 mg/kg over 30 min; n = 7), or topical application (5 x 10(-8) M, n = 6; 5 x 10(-7) M, n = 5; 5 x 10(-6) M, n = 5; 10(-5) M, n = 7). Male Sprague-Dawley rats (145-185 g body weight) were anesthetized with sodium pentobarbital (50 mg/kg) and the cremaster muscle was prepared for intravital video microscopy. Diameter response of arterioles (70-120 microns) to increasing concentrations of locally applied 5-HT (10(-8)-10(-4) M) was assessed. In rats receiving no drug treatment, 5-HT caused vasoconstriction of arterioles beginning at 10(-6) M and reaching approximately 40% constriction at 10(-4) M. These vasoactive responses were not altered by chronic daily doses or an acute infusion of naftidrofuryl. 5-HT responses obtained with and without naftidrofuryl applied directly into the cremaster-bath also had little effect on the arteriole response at each of the four concentrations tested.(ABSTRACT TRUNCATED AT 250 WORDS)