Effects of cilostazol, a selective cyclic AMP phosphodiesterase inhibitor on isolated rabbit spinal arterioles

Two Cases Showing That Cilostazol Administration Leads to an Increase in Cerebral Blood Flow and Has a Positive Effect on Rehabilitation

Cilostazol is a drug that has both antiplatelet and vasodilatory effects. To examine the effects of cilostazol on cerebral blood flow and rehabilitation following stroke, cilostazol was administered to two patients with chronic atherothrombotic cerebral infarction. In both patients, cilostazol administration effectively increased cerebral blood flow and promoted rehabilitation. Therefore, cilostazol was considered to be a useful agent for improving the clinical condition of patients suffering from chronic cerebral infarction. Further clinical studies on the effective use of cilostazol for rehabilitation in stroke patients are needed.

Cilostazol induces vasorelaxation through the activation of the eNOS/NO/cGMP pathway, prostanoids, AMPK, PKC, potassium channels, and calcium channels

OBJECTIVE

This study aimed to investigate vasoactive effect mechanisms of cilostazol in rat thoracic aorta.

MATERIALS AND METHODS

The vessel rings prepared from the thoracic aortas of the male rats were placed in the chambers of the isolated tissue bath system. The resting tone was adjusted to 1 g. Following the equilibration phase, potassium chloride or phenylephrine was used to contract the vessel rings. When achieving a steady contraction, cilostazol was applied cumulatively (10-8-10-4 M). In the presence of potassium channel blockers or signaling pathway inhibitors, the same experimental procedure was performed.

RESULTS

Cilostazol exhibited a significant vasorelaxant effect in a concentration-dependent manner (pD2: 5.94 ± 0.94) (p < .001). The vasorelaxant effect level of cilostazol was significantly reduced by the endothelial nitric oxide synthase inhibitor L-NAME (10-4 M), soluble guanylate cyclase inhibitor methylene blue (10 µM), cyclooxygenase 1/2 inhibitor indomethacin (5 µM), adenosine monophosphate-activated protein kinase inhibitor compound C (10 µM), non-selective potassium channel blocker tetraethylammonium chloride (10 mM), large-conductance calcium-activated potassium channel blocker iberiotoxin (20 nM), voltage-gated potassium channel blocker 4-Aminopyridine (1 mM), and inward-rectifier potassium channel blocker BaCl2 (30 µM) (p < .001). Moreover, incubation of cilostazol (10-4 M) significantly reduced caffeine (10 mM), cyclopiazonic acid (10 µM), and phorbol 12-myristate 13-acetate-induced (100 µM) vascular contractions (p < .001).

CONCLUSIONS

In the rat thoracic aorta, the vasodilator action level of cilostazol is quite noticeable. The vasorelaxant effects of cilostazol are mediated by the eNOS/NO/cGMP pathway, prostanoids, AMPK pathway, PKC, potassium channels, and calcium channels.

Phosphodiesterase as a Target for Cognition Enhancement in Schizophrenia

Schizophrenia is a severe mental disorder that affects more than 1% of the population worldwide. Dopamine system dysfunction and alterations in glutamatergic neurotransmission are strongly implicated in the aetiology of schizophrenia. To date, antipsychotic drugs are the only available treatment for the symptoms of schizophrenia. These medications, which act as D2-receptor antagonist, adequately address the positive symptoms of the disease, but they fail to improve the negative symptoms and cognitive impairment. In schizophrenia, cognitive impairment is a core feature of the disorder. Therefore, the treatment of cognitive impairment and the other symptoms related to schizophrenia remains a significant unmet medical need. Currently, phosphodiesterases (PDEs) are considered the best drug target for the treatment of schizophrenia since many PDE subfamilies are abundant in the brain regions that are relevant to cognition. Thus, this review aims to illustrate the mechanism of PDEs in treating the symptoms of schizophrenia and summarises the encouraging results of PDE inhibitors as anti-schizophrenic drugs in preclinical and clinical studies.

Cilostazol strengthens the endothelial barrier of postcapillary venules from the rat mesentery in situ

Objective

Although cilostazol, a phosphodiesterase 3 inhibitor, has been suggested to strengthen the endothelial barrier using cultured endothelial monolayers, its effect has not been tested in vivo. We, therefore, investigated effects of cilostazol on barrier properties of postcapillary venules of the rat in situ.

Methods

Cilostazol was administered to the rats through oral gavage at 4 hours before the measurements. The hydraulic permeability ( Lp) and the effective osmotic pressure (σΔπ), molecular sieving properties of microvascular walls, were estimated in single mesenteric postcapillary venules by a micro-occlusion technique, first during control perfusion and then in the presence of histamine.

Results

When the vessels were inflamed with histamine, cilostazol attenuated a transient increase in Lp and prevented σΔπ from falling. Furthermore, it reduced baseline Lp under a control state.

Conclusion

Cilostazol appears to tighten the endothelial barrier in situ, at least in part by inhibiting the cAMP-degrading enzyme in the endothelium.

Effect of cilostazol administration on cerebral hemodynamics and rehabilitation outcomes in poststroke patients

PRIMARY OBJECTIVE

Cilostazol is an antiplatelet agent that inhibits phosphodiesterase III in platelets and the vascular endothelium. We assessed the effects of cilostazol on human cerebral hemodynamics and rehabilitation outcomes.

RESEARCH DESIGN

Prospective, consecutive, observational trial with pretreatment and posttreatment evaluations.

EXPERIMENTAL INTERVENTIONS

Cilostazol (200 mg/day) administered for 8 weeks.

METHODS AND PROCEDURES

Cerebral blood flow at rest, cerebrovascular reserve capacity, and rehabilitation outcomes (Brunnstrom stage, Barthel index score, modified Rankin Scale score, and Mini-Mental State Examination score) were measured in 104 poststroke patients with an average age ± standard deviation of 60.8 ± 9.2 years.

MAIN OUTCOMES AND RESULTS

The cerebral blood flow increased by 23.8% on the affected side of the brain and by 16.9% on the nonaffected side. The cerebrovascular reserve capacity increased by 19.0% on the affected side of the brain and by 13.3% on the nonaffected side. Improvements were observed in the Brunnstrom stage, Barthel index score, modified Rankin Scale score, and Mini-Mental State Examination score.

CONCLUSIONS

Cilostazol appeared to have beneficial effects in poststroke patients with cerebral ischemia and might improve cerebral circulation and rehabilitation outcome.

Effect of cilostazol on cerebral arteries in secondary prevention of ischemic stroke

OBJECTIVE

To compare the effects of cilostazol on cerebral arteries and cerebrovascular blood flow in secondary prevention of ischemic stroke, with those of aspirin.

METHODS

Sixty-eight patients who had ischemic stroke during the recent 1-6 months were recruited and randomized into cilostazol or aspirin group. Cerebrovascular condition was assessed by magnetic resonance angiography (MRA) and transcranial doppler ultrasonography (TCD) at the beginning of the study and after 12-month medication.

RESULTS

During the clinical follow-up, ischemic stroke recurred in 2 patients in cilostazol group, while in aspirin group, one case of ischemic stroke recurrence and one case of acute myocardial infarction were found. MRA revealed that in aspirin group, the percentages of patients experiencing aggravation and attenuation of cerebrovascular condition were 3.3% and 6.7%, respectively, while in aspirin group, they were 3.3% and 10%, respectively. Moreover, TCD revealed that 26.9% of the patients in aspirin group and 14.3% of the patients in cilostazol group experienced aggravation of cerebrovascular condition. However, the systolic peak flow velocity of the previously abnormal arteries increased by 42.9% after 12-month medication of cilostazol, which was significantly higher than that after aspirin medication (27.5%) (P = 0.04). Furthermore, as a major side effect of antiplatelet therapy, the frequency of bleeding was much less in cilostazol group (0 case in cilostazol group vs 5 in aspirin, P< 0.05).

CONCLUSION

Cilostazol is as effective as aspirin in preventing the aggravation of cerebral arteries in secondary prevention of ischemic stroke. Besides, it is more safe. Cilostazol can increase the systolic peak flow velocity of cerebral arteries, which may improve the blood supply of focal ischemia.

An oral administration of cilostazol before focal ischemia reduces the infarct volume with delayed cerebral blood flow increase in rats

We studied the acute brain protection provided by an antiplatelet agent, cilostazol, in rat experimental focal ischemia model. We administered 30 mg/kg of cilostazol or vehicle orally 2 hours before transient middle cerebral artery (MCA) occlusion (MCAO) by the intraluminal thread method. We measured the absolute cerebral blood flow (CBF) 2 hours after cilostazol administration, the regional CBF (rCBF) of MCA territory during MCAO, and neurologic deficits and the infarct volume at 22 hours after reperfusion. We found that cilostazol did not increase absolute CBF just before MCAO. rCBF in the MCA territory was reduced to the same degree in both groups up to 60 minutes post-MCAO. A significant increase of rCBF was observed in cilostazol-treated rats at 90 minutes and maintained until reperfusion compared with the controls (P = .031 and P = .047). The average neurologic score and the infarct volume, determined by 2,3,5-triphenyltetrazolium chloride monohydrate staining, were significantly lower in cilostazol-treated rats (P = .010). The single oral administration of cilostazol before transient ischemia in healthy adult rats induced a delayed penumbral CBF increase and resulted in a significant reduction of stroke damage.

NT-702, a selective phosphodiesterase 3 inhibitor, dilates rabbit spinal arterioles via endothelium-dependent and endothelium-independent mechanisms

We investigated the effects of NT-702, a selective phosphodiesterase (PDE) 3 inhibitor, on arterioles isolated from rabbit lumbar spinal cords. NT-702 caused a dose-dependent dilation of the isolated spinal arterioles. The disruption of endothelium produced a significant reduction of higher concentrations (10(-7) and 10(-6) M), but not lower concentrations (less than 10(-8) M), of NT-702-induced vasodilation. The NT-702-induced vasodilation of the arterioles with endothelium was not affected by pretreatment with an inhibitor of nitric oxide, cyclooxygenase, or cytochrome P-450 monooxygenase. In contrast, catalase reduced significantly the higher concentrations of NT-702-induced vasodilation only. Tetraethylammonium (TEA) completely reduced the lower concentrations of NT-702-induced vasodilation, but decreased only partially the higher concentrations of NT-702-induced vasodilation of the arterioles with endothelium. Hydrogen peroxide dilated significantly the isolated arterioles with endothelium, the response of which was reduced significantly by TEA. KT5720 (a selective protein kinase inhibitor) significantly decreased both the lower and higher concentrations of NT-702-induced vasodilation of the arterioles with endothelium. The findings suggest that NT-702 dose-dependently dilated the isolated spinal arterioles of rabbits via endothelium-dependent and endothelium-independent mechanisms. Protein kinase A (PKA)- and TEA-sensitive K(+) channels may be involved in the NT-702-induced vasodilation. Moreover, hydrogen peroxide may contribute in part to the endothelium-dependent higher concentrations of NT-702-induced vasodilation.

Cilostazol Attenuates Gray and White Matter Damage in a Rodent Model of Focal Cerebral Ischemia

Background and Purpose— To evaluate whether delayed treatment with the antiplatelet agent cilostazol reduces the volume of infarction in the gray and white matter in a rodent model of permanent focal cerebral ischemia and to explore the mechanism of the neuroprotective effect in vivo.

Methods— Cilostazol (30 or 50 mg/kg) or vehicle was administered by gavage 30 minutes and 4 hours after the induction of cerebral ischemia by permanent occlusion of the left middle cerebral artery (MCA). Animals were euthanized 24 hours after MCA occlusion, and the volume of gray matter damage was evaluated by quantitative histopathology. Axonal damage was determined with amyloid precursor protein immunohistochemistry. Dynamic susceptibility contrast MRI was used to assess regional cerebral blood volume (CBV) and cerebral blood flow (CBF).

Results— Treatment with the higher dose of cilostazol (50 mg/kg) significantly reduced the volume of gray matter damage and axonal damage in the cerebral hemisphere by 45.0% ( P <0.02) and 42.4% ( P <0.002), respectively, compared with the control group. Relative CBV in the peri-infarct area after MCA occlusion was significantly increased in the cilostazol-treated group (50 mg/kg) compared with the control group ( P <0.05). Relative CBF tended to be higher in the cilostazol-treated group compared with the control group.

Conclusions— Treatment with cilostazol significantly reduced the gray and white matter damage associated with permanent focal ischemia. Cilostazol improved CBV and CBF in the peri-infarct area. The major action of cilostazol is to increase perfusion in the ischemic penumbra.

Cilostazol, an Inhibitor of Type 3 Phosphodiesterase, Produces Endothelium-Independent Vasodilation in Pressurized Rabbit Cerebral Penetrating Arterioles

We investigated the effects of cilostazol, a potent inhibitor of cGMP-inhibited cAMP phosphodiesterase, on mechanical activity of isolated pressurized rabbit cerebral penetrating arterioles with special reference to the function of the endothelium. Both cilostazol and milrinone, another inhibitor of cAMP phosphodiesterase, produced vasodilation of the cerebral penetrating arterioles in a dose-dependent manner. Pretreatment with selective inhibitors of cyclooxygenase or nitric oxide synthase, or chemical denudation of the endothelial cells caused no significant effect on the cilostazol-mediated vasodilation of the cerebral arterioles. A selective large-conductance calcium-activated potassium channel inhibitor, iberiotoxin, and a selective protein kinase A inhibitor, H-89, caused no significant effect on the cilostazol-mediated vasodilation. In the cerebral arterioles, low concentration (10(-6)M) of cilostazol or milrinone caused a significant shift of the dose-vasodilatory response curve for adenosine to the left. These findings suggest that cilostazol produces vasodilation independent of the presence of the endothelium or activation of endogenous vasodilative prostaglandins, nitric oxide, calcium-activated potassium channel and protein kinase A. In conclusion, the vasodilator action of cilostazol may, in part, contribute to the beneficial effect of preventing lacunar cerebral infarction in patients with functional damage of the endothelium in cerebral penetrating arterioles.

Age-Dependent Changes in the Regulatory Roles of Nitric Oxide and Vasodilator Prostanoids on the Mechanical Activities of Isolated Rabbit Spinal Arterioles

The developmental changes in acetylcholine (ACh)-induced vasodilator response in isolated rabbit spinal arterioles were investigated with special reference to endogenous nitric oxide (NO) and vasodilator prostaglandins. Spinal arterioles from juvenile (1-3 months) and adult (12-14 months) Japanese white rabbits were dissected, cannulated, and perfused. In both age groups, ACh produced a comparable vasodilation of the arterioles preconstricted with KCl (20-40 mM). In juveniles, a major part of the ACh-induced vasodilation was eliminated by the cyclo-oxygenase inhibitor indomethacin (10 microM), whereas the effect of the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 30 microM) was smaller. In contrast, L-NAME completely eliminated the ACh-induced vasodilation in the adult group, which was partially restored with additional treatment with L-arginine (1 mM). Vasodilations induced by isocarbacyclin (a prostacyclin analogue) and cilostazol (a cAMP-phosphodiesterase inhibitor) was attenuated in the adult, whereas that induced by sodium nitroprusside was unaltered. These results suggest that the mechanisms of ACh-induced vasodilation of rabbit spinal arterioles change with the development: prostanoid-associated in juveniles and NO-associated in the adult. Such age-related modulation of the mediator roles of prostanoids and NO might represent an increase in NO production and a decreased sensitivity of the vascular smooth muscle to cAMP-mediated responses with age.