The Effects of Cilostazol on Tissue Oxygenation upon an Ischemic-reperfusion Injury in the Mouse Cerebrum

Cilostazol promotes blood vessel formation and bone regeneration in a murine non-union model

Non-unions represent a major complication in trauma and orthopedic surgery. Many factors contribute to bone regeneration, out of which an adequate vascularization has been recognized as crucial. The phosphodiesterase-3 (PDE-3) inhibitor cilostazol has been shown to exert pro-angiogenic and pro-osteogenic effects in a variety of preclinical studies. Hence, we herein investigated the effects of cilostazol on bone regeneration in an atrophic non-union model in mice. For this purpose, a 1.8 mm femoral segmental defect was stabilized by pin-clip fixation and the animals were treated daily with 30 mg/kg body weight cilostazol or saline (control) per os. At 2, 5 and 10 weeks after surgery the healing of femora was analyzed by X-ray, biomechanics, photoacoustic imaging, and micro-computed tomography (µCT). To investigate the cellular composition and the growth factor expression of the callus tissue additional histological, immunohistochemical and Western blot analyses were performed. Cilostazol-treated animals showed increased bone formation within the callus, resulting in an enhanced bending stiffness when compared to controls. This was associated with a more pronounced expression of vascular endothelial growth factor (VEGF), a higher number of CD31-positive microvessels and an increased oxygen saturation within the callus tissue. Furthermore, cilostazol induced higher numbers of tartrate-resistant acidic phosphate (TRAP)-positive osteoclasts and CD68-positive macrophages. Taken together, these findings demonstrate that cilostazol is a promising drug candidate for the adjuvant treatment of atrophic non-unions in clinical practice.

The Treatment Algorithm in Diabetic Foot: An Alternative Against Amputation?

This clinical treatment modality was applied to 62 diabetic ulcers on lower extremities for which surgeons had been advised amputation. Total healing was achieved in 53 of them and was achieved through this treatment in a 3-month period. The remaining nine cases also showed improvement in healing at different levels, but they were not accepted as a ‘satisfactory result’. This treatment modality contains a synthetic prostacyclin analogue, two different phosphodiesterase inhibitors, a peripheral revascularisation agent, another agent increasing peripheral resistance to ischaemia, and a polysaccharide with positive rheologic properties on capillary circulation. Therefore, this treatment was found to be effective on circulation of the extremities, with radiologically-proven insufficient blood supply. The treatment also had a positive effect on recirculation and effects on collateral revascularisation through mechanical vacuum application, modified from standard vacuum treatments. With this combination, this technique was found extremely effective by application, according to the algorithm explained below, and should be an alternative to the current therapy applications in diabetic ulcers.

Cilostazol protects against myocardial ischemia and reperfusion injury by activating transcription factor EB (TFEB)

Although cilostazol was proved to have antitumor biological effects, its function in myocardial ischemia and reperfusion (I/R) injury and the underlying mechanisms were not fully illustrated yet. In this study, a rat model of I/R injury was constructed and quantitative real-time PCR, Western blot, and immunofluorescence (IF) assay were performed. Our results showed that cilostazol increased LC3 II/LC3 I ratio, reduced p62 abundance, and promoted the expressions of LAMP1, LAMP2, cathepsin B, and cathepsin D, indicating that cilostazol could activate autophagy and elevated lysosome activation. Following analysis showed that cilostazol enhanced nuclear protein expression of transcription factor EB (TFEB), an important regulator of autophagy-lysosome pathway. Furthermore, CCI-779, an inhibitor of TFEB, could reverse the effects of cilostazol on autophagic activity and lysosome activation. Importantly, cilostazol suppressed I/R injury-induced apoptosis by decreasing the cleavage of caspase 3 and PARP. Enzyme-linked immunosorbent assay showed that cilostazol reduced the serum levels of CTn1 and CK-MB and decreased infract size caused by I/R injuries. Altogether this study suggested that cilostazol protects against I/R injury by regulating autophagy, lysosome, and apoptosis in a rat model of I/R injury. The protective mechanism of cilostazol was partially through increasing the transcriptional activity of TFEB.

Cilostazol protects mice against myocardium ischemic/reperfusion injury by activating a PPARγ/JAK2/STAT3 pathway

Myocardial ischemia/reperfusion (MIR) injury causes severe arrhythmias and a high lethality. The present study is designed to investigate the effect of cilostazol on MIR injury and the underlying mechaism. We measured the effects of cilostazol on heart function parameters in a mouse model of MIR. Proinflammatory cytokines and apoptosis proteins in the myocardium were examined to investigate the anti-inflammatory and anti-apoptosis ability of cilostazol. The participation of PPARγ/JAK2/STAT3 pathway was investigated. Results showed that the impairment of hemodynamic parameters caused by MIR was attenuated by cilostazol. The IL-6, IL-1β and TNF-a levels were all decreased by cilostazol. Cilostazol also significantly inhibited Bax and cleaved caspase-3 levels and restored the Bcl-2 levels. PPARγ, JAK2 and STAT3 were all activated by cilostazol. Treatment of inhibitors of them abolished the protective effects of cilostazol on cardiac function, myocardial inflammation and apoptosis. In summary, cilostazol alleviated the cardiac function impairment, myocardial inflammation and apoptosis induced by MIR. The results present a novel signaling mechanism that cilostazol protects MIR injury by activating a PPARγ/JAK2/STAT3 pathway.

Oral administration of cilostazol improves survival rate after rat liver ischemia/reperfusion injury

BACKGROUND

Cilostazol is a type III phosphodiesterase inhibitor used to treat the symptoms of intermittent claudication. Recent studies have shown that cilostazol decreases ischemia/reperfusion (I/R) injury in several organs.

MATERIALS AND METHODS

We evaluated the effects of cilostazol in a rat model of liver I/R injury. Thirty male Wistar rats with liver I/R injury were divided into a cilostazol or saline (control) group (n = 15 each). Each rat was orally administered cilostazol or saline for 3 d before I/R injury. Liver I/R injury was induced via 1 h of warm ischemia of the median and left lateral liver lobes, followed by 3 h of reperfusion. The rats were then euthanized. Serum aspartate aminotransferase, alanine aminotransferase, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α levels were measured. The Mann-Whitney U test was used to compare the differences between the treatment groups. Histologic examination was performed on the liver tissues. We also conducted a survival study to confirm the effect of cilostazol on the mortality rate in rats. For the survival study, a liver I/R injury model with an ischemia time of 1.5 h was used, and the rats were observed for 1 wk.

RESULTS

Serum aspartate aminotransferase, alanine aminotransferase, IL-1β, and IL-6 levels were significantly lower in the cilostazol group than in the saline group. Treatment with cilostazol significantly improved pathological findings associated with liver I/R injury and increased survival rate compared to that in controls.

CONCLUSIONS

Cilostazol reduced mortality and alleviated the effects of liver I/R injury in Wistar rats.

Stimulation of angiogenesis by cilostazol accelerates fracture healing in mice

Cilostazol, a selective phosphodiesterase-3 inhibitor, is known to control cyclic adenosine monophosphate (c-AMP) and to stimulate angiogenesis through upregulation of pro-angiogenic factors. There is no information, however, whether cilostazol affects fracture healing. We, therefore, studied the effect of cilostazol on callus formation and biomechanics during fracture repair. Bone healing was analyzed in a murine femur fracture stabilized with an intramedullary screw. Radiological, biomechanical, histomorphometric, histochemical, and protein biochemical analyses were performed at 2 and 5 weeks after fracture. Twenty-five mice received 30 mg/kg body weight cilostazol p.o. daily. Controls (n=24) received equivalent amounts of vehicle. In cilostazol-treated animals radiological analysis at 2 weeks showed an improved healing with an accelerated osseous bridging compared to controls. This was associated with a significantly higher amount of bony tissue and a smaller amount of cartilage tissue within the callus. Western blot analysis showed a higher expression of cysteine-rich protein 61 (CYR61), bone morphogenetic protein (BMP)-4, and receptor activator of NF-kappaB ligand (RANKL). At 5 weeks, improved fracture healing after cilostazol treatment was indicated by biomechanical analyses, demonstrating a significant higher bending stiffness compared to controls. Thus, cilostazol improves fracture healing by accelerating both bone formation and callus remodeling.

Diabetes augments cognitive dysfunction in chronic cerebral hypoperfusion by increasing neuronal cell death: implication of cilostazol for diabetes mellitus-induced dementia

Many patients with diabetes are at increased risk of cognitive dysfunction and dementia. Diabetes mellitus is a vascular risk factor that may increase the risk of dementia through its associations with vascular dementia. We tested whether cognitive impairment could be exacerbated in combined injury using a rat model of chronic cerebral hypoperfusion with diabetes. We also determined whether a potent inhibitor of type III phosphodiesterase could prevent the cognitive decline caused by this combined injury. We used Otsuka Long-Evans Tokushima Fatty (OLETF) rats as a model of type II diabetes (T2DM) and Long-Evans Tokushima Otsuka (LETO) rats as a control. Chronic cerebral hypoperfusion was modeled by permanent bilateral common carotid artery occlusion (BCCAO). At 24weeks, the non-diabetic and T2DM rats were randomly assigned into groups for the following experiments: analysis I (1) sham non-diabetic rats (n=8); (2) hypoperfused non-diabetic rats (n=9); (3) sham T2DM rats (n=8); (4) hypoperfused T2DM rats (n=9); analysis II- (1) sham T2DM rats without treatment (n=8); (2) cilostazol-treated T2DM rats (n=8); (3) hypoperfused T2DM rats (n=9); and (4) hypoperfused T2DM rats and cilostazol treatment (n=9). The rats were orally administered cilostazol (50mg/kg) or vehicle once a day for 2weeks after 24weeks. Rats performed Morris water maze tasks, and neuronal cell death and neuroinflammation were investigated via Western blots and histological investigation. Spatial memory impairment was exacerbated synergistically in the hypoperfused T2DM group compared with the hypoperfused non-diabetic group and sham T2DBM group (P<0.05). Compared with the control group, neuronal cell death was increased in the hippocampus of the hypoperfused T2DM group. Cilostazol, a PDE-3 inhibitor, improved the memory impairments through inhibition of neuronal cell death, activation of CREB phosphorylation and BDNF expression in the hypoperfused T2DM group. Our experimental results support the hypothesis that there are deleterious interactions between chronic cerebral hypoperfusion and T2DM. That is, metabolic diseases such as diabetes may exacerbate cognitive impairment in a rat model of vascular dementia. We also suggest that surprisingly, the phosphodiesterase III inhibitor, cilostazol may be useful for the treatment of cognitive impairment in diabetes mellitus-induced dementia. In conclusion, diabetes can aggravate cognitive dysfunction in vascular dementia, and PDE-3 inhibitors, such as cilostazol, may form the basis of a novel therapeutic strategy for diabetes-associated cognitive impairment or vascular dementia.

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.

Phosphodiesterase inhibitor modulation of brain microvascular endothelial cell barrier properties

BACKGROUND AND PURPOSE

Brain microvascular disorders, including cerebral microscopic hemorrhage, have high prevalence but few treatment options. To develop new strategies for these disorders, we analyzed the effects of several phosphodiesterase (PDE) inhibitors on human brain microvascular endothelial cells (HBECs).

METHODS

We modified barrier properties and response to histamine of HBECs using cilostazol (PDE3 inhibitor), rolipram (PDE4 inhibitor), and dipyridamole (non-specific PDE inhibitor).

RESULTS

Cilostazol and dipyridamole altered the distribution of endothelial F-actin. Cilostazol increased expression of tight junction protein claudin-5 by 118% compared to control (p<.001). Permeability to albumin was decreased by cilostazol (21% vs control, p<.05), and permeability to dextran (70Kd) was decreased by both cilostazol (37% vs control, p<.001) and dipyridamole (44% vs control, p<.0001). Cilostazol increased trans-endothelial electrical resistance (TEER) after 12h by 111% compared to control (p<.0001). Protein kinase A (PKA) inhibitors H89 and KT5720 attenuated the TEER increase by cilostazol. Transient increased permeability in response to histamine was significantly mitigated by cilostazol, but not by other PDE inhibitors.

CONCLUSIONS

These findings demonstrate distinctive effects of cilostazol and other PDE inhibitors on HBECs, including enhanced barrier characteristics and mitigation of response to histamine. PKA-mediated effects of cilostazol were prominent in this model. These in vitro findings are consistent with therapeutic potential of PDE inhibitors in human brain microvascular disorders.