Effect of cilostazol on the neuropathies of streptozotocin-induced diabetic rats

Topical combinations aimed at treating microvascular dysfunction reduce allodynia in rat models of CRPS-I and neuropathic pain

Growing evidence indicates that various chronic pain syndromes exhibit tissue abnormalities caused by microvasculature dysfunction in the blood vessels of skin, muscle, or nerve. We tested whether topical combinations aimed at improving microvascular function would relieve allodynia in animal models of complex regional pain syndrome type I (CRPS-I) and neuropathic pain. We hypothesized that topical administration of either α(2)-adrenergic (α(2)A) receptor agonists or nitric oxide (NO) donors combined with either phosphodiesterase (PDE) or phosphatidic acid (PA) inhibitors would effectively reduce allodynia in these animal models of chronic pain. Single topical agents produced significant dose-dependent antiallodynic effects in rats with chronic postischemia pain, and the antiallodynic dose-response curves of PDE and PA inhibitors were shifted 2.5- to 10-fold leftward when combined with nonanalgesic doses of α(2)A receptor agonists or NO donors. Topical combinations also produced significant antiallodynic effects in rats with sciatic nerve injury, painful diabetic neuropathy, and chemotherapy-induced painful neuropathy. These effects were shown to be produced by a local action, lasted up to 6 hours after acute treatment, and did not produce tolerance over 15 days of chronic daily dosing. The present results support the hypothesis that allodynia in animal models of CRPS-I and neuropathic pain is effectively relieved by topical combinations of α(2)A or NO donors with PDE or PA inhibitors. This suggests that topical treatments aimed at improving microvascular function may reduce allodynia in patients with CRPS-I and neuropathic pain.

PERSPECTIVE

This article presents the synergistic antiallodynic effects of combinations of α(2)A or NO donors with PDE or PA inhibitors in animal models of CRPS-I and neuropathic pain. The data suggest that effective clinical treatment of chronic neuropathic pain may be achieved by therapies that alleviate microvascular dysfunction in affected areas.

Neuroprotective effect of the glucagon-like peptide-1 receptor agonist, synthetic exendin-4, in streptozotocin-induced diabetic rats

BACKGROUND AND PURPOSE

Glucagon-like peptide-1 (GLP-1) receptors are widely expressed in neural tissues and diminish neuronal degeneration or induce neuronal differentiation. The aim of this study was to investigate the effect of the GLP-1 pathway on peripheral nerves in streptozotocin-induced diabetic rats.

EXPERIMENTAL APPROACH

Diabetic and nondiabetic rats were treated with the GLP-1 receptor agonist, synthetic exendin-4 (i.p., 1 nmol·kg(-1)·day(-1)) or placebo for 24 weeks, and current perception threshold values, cAMP levels and nerve fibre size in the sciatic nerve were measured. We also investigated GLP-1 receptor expression, quantitative changes in PGP9.5-positive intraepidermal nerve fibres and cleaved caspase 3-stained Schwann cells by immunohistochemistry.

KEY RESULTS

GLP-1 receptor expression was detected in the sciatic nerve and skin. After exendin-4 treatment, the increase seen in current perception threshold values at 2000 and 250 Hz in diabetic rats was reduced. Also, the decrease in myelinated fibre size or axon/fibre area ratio in the sciatic nerve and the loss of intraepidermal nerve fibre in the skin of diabetic rats were ameliorated. These responses were closely associated with the attenuation of Schwann cell apoptosis and improvement in the cAMP level in exendin-4-treated diabetic rats, compared with placebo-treated animals.

CONCLUSION AND IMPLICATIONS

Synthetic exendin-4 may prevent peripheral nerve degeneration induced by diabetes in an animal model, supporting the hypothesis that GLP-1 may be useful in peripheral neuropathy. The neuroprotection is probably attributable to GLP-1 receptor activation, antiapoptotic effects and restoration of cAMP content.

Cilostazol in Diabetic Neuropathy

Peripheral neuropathy remains a major chronic complication of diabetes mellitus. Its pathogenesis mainly involves chronic glucose toxicity and nerve ischemia. Preclinical studies have shown that cilostazol, a reversible selective inhibitor of phosphodiesterase-3A with antiplatelet, antithrombotic, and vasodilatory properties, exerts beneficial effects on nerve function in experimental diabetes. Clinical data, however, is sparse. Two recent randomized placebo-controlled clinical trials showed that cilostazol did not improve diabetic neuropathy in humans. Hence, more data is needed to confirm or refute the poor clinical efficacy of cilostazol. Importantly, future studies should include larger patient series, provide longer follow-up data, and employ more accurate diagnostic tools.

Cilostazol: a pilot study on safety and clinical efficacy in neuropathies of diabetes mellitus type 2 (ASCEND)

BACKGROUND

Diabetic polyneuropathy may have vascular and metabolic components in its pathophysiologic mechanism. Cilostazol, aside from its antiplatelet and vasodilatory properties, may increase nerve blood flow and potentially improve neuropathy.

OBJECTIVE

To assess the efficacy and safety of cilostazol in diabetic polyneuropathy.

METHODS

Forty-seven diabetic patients were randomized into placebo, low-dose (100 mg/d), and high-dose (200 mg/d) cilostazol groups. Primary efficacy parameter was a change in neuropathy symptom scores and secondary efficacy parameter was a change in walking speed from baseline to week 12. Safety parameters were changes in nerve conduction studies as well as reporting of adverse events.

RESULTS/CONCLUSION

Despite significant improvement in the neuropathy symptom scores in the overall motor and sensory categories of the 3 arms of the study from baseline to week 12, no significant differences were found among the groups, indicating nonsuperiority of cilostazol in regard to improvement of neuropathy symptoms over the short study span. However, cilostazol, at low dose, was effective in improving walking speed from baseline to week 12, implying an improved blood flow. No significant worsening nor improvement in motor and sensory nerve conduction parameters were observed, comparing the 3 study arms from baseline to weeks 4, 12, and 16, supporting cilostazol's safety. Overall, the adverse events of the 3 study arms did not significantly differ, and neither were there serious adverse events reported, also signifying safety and tolerability in our Filipino cohort of patients with neuropathy in diabetes mellitus treated with cilostazol.

The Effects of Cilostazol on Peripheral Neuropathy in Diabetic Patients With Peripheral Arterial Disease

Background Evidence from diabetic animal models suggests that cilostazol, a cyclic AMP phosphodiesterase inhibitor used in the treatment of claudication, is efficacious in the treatment of peripheral neuropathy, although this is unproven in humans. The main aim of this study was to assess the effects of cilostazol on neuropathic symptomatology in diabetic patients with peripheral arterial disease (PAD). Methods Diabetic patients with PAD were prospectively recruited to a randomized double-blinded placebo-controlled trial. Baseline clinical data were recorded prior to trial commencement following medical optimization. Neurological assessment included the Toronto Clinical Neuropathy Scoring system (TCNS) and vibration perception thresholds (VPT) with a neurothesiometer at baseline, 6 weeks, and 24 weeks. Results Twenty-six patients were recruited from December 2004 to January 2006, which included 20 males. Baseline patient allocation to treatment arms was matched for age, sex, and medical comorbidities. There was no significant difference in neurological assessment between the treatment groups using the TCNS and VPT at 6 and 24 weeks. Conclusions Despite extensive animal-based evidence that cilostazol attenuates neuropathic symptomatology, our results do not support this effect in human diabetic PAD patients.

Effects of Shenmai Huoxue Decoction on early diabetic peripheral neuropathy in rats

OBJECTIVE

To evaluate the effects of Shenmai Huoxue Decoction (SMHXD) on early diabetic peripheral neuropathy (DPN) in rats.

METHODS

The rats were randomly divided into 3 groups: normal group, diabetic model group and SMHXD-treated diabetic group. The diabetic rats were induced by streptozotocin (STZ) intraperitoneally. After the treatment, sensory nerve conduction velocity (SNCV) of caudal nerve was detected with evoked electromyography, and the activity of aldose reductase (AR) in erythrocytes and the concentration of endothelin (ET) in plasma were measured.

RESULTS

It was showed that the SNCV reduced significantly and the activity of AR in erythrocytes and the concentration of ET in plasma were increased significantly in diabetic group as compared with those in the normal group. The SNCV was increased, and the activity of AR in erythrocytes and the concentration of ET in plasma were improved significantly in SMHXD-treated diabetic group after the treatment.

CONCLUSION

The results indicate that SMHXD can alleviate the lesion of DPN in the early stage of diabetic rats.