Candesartan restores pressure-induced vasodilation and prevents skin pressure ulcer formation in diabetic mice

Abstract

Background: Angiotensin II type 1 receptor (AT1R) blockers have beneficial effects on neurovascular complications in diabetes and in organ's protection against ischemic episodes. The present study examines whether the AT1R blocker candesartan (1) has a beneficial effect on diabetes-induced alteration of pressure-induced vasodilation (PIV, a cutaneous physiological neurovascular mechanism which could delay the occurrence of tissue ischemia), and (2) could be protective against skin pressure ulcer formation.

Methods: Male Swiss mice aged 5-6 weeks were randomly assigned to four experimental groups. In two groups, diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ, 200 mg.kg(-1)). After 6 weeks, control and STZ mice received either no treatment or candesartan (1 mg/kg-daily in drinking water) during 2 weeks. At the end of treatment (8 weeks of diabetes duration), C-fiber mediated nociception threshold, endothelium-dependent vasodilation and PIV were assessed. Pressure ulcers (PUs) were then induced by pinching the dorsal skin between two magnetic plates for three hours. Skin ulcer area development was assessed during three days, and histological examination of the depth of the skin lesion was performed at day three.

Results: After 8 weeks of diabetes, the skin neurovascular functions (C-fiber nociception, endothelium-dependent vasodilation and PIV) were markedly altered in STZ-treated mice, but were fully restored by treatment with candesartan. Whereas in diabetes mice exposure of the skin to pressure induced wide and deep necrotic lesions, treatment with candersartan restored their ability to resist to pressure-induced ulceration as efficiently as the control mice.

Conclusion: Candesartan decreases the vulnerability to pressure-induced ulceration and restores skin neurovascular functions in mice with STZ-induced established diabetes.

Figure 1

Schematic representation of study design. PU: pressure ulcer, STZ: streptozotocin.

Figure 2

Effects of candesartan on nociceptive, skin microcirculation and neurovascular function. (a) Randall-Sellito tail pressure test. Mechanical withdrawal thresholds to nociceptive tail pressure. (b) Endothelium-dependent vasodilation. Maximal percentage of vasodilation from baseline in response to iontophoretic delivery of Ach. (c) Cutaneous typical laser Doppler blood flow response during a progressive increase of pressure in a control mice (black) and in a diabetic mice (red). P: start of pressure, a.u.: arbitrary units. (d) Pressure-induced vasodilation. Maximal percentage of vasodilation from baseline during localpressure application. (n = 10 in each group,non-parametric Kruskal-Wallis test followed by Dunn’s post-hoc test, *P < 0.05, **P < 0.01, ***P < 0.001)Ach: Acetylcholine, LDF:Laser Doppler Flowmetry.

Figure 3

Effect of candesartan on cutaneous macroscopic findings following 3 hours of pressure. (a) Representative photographs of skin compressed areas, one day and three days after pressure release. Scale bar = 2 mm (b) Time course of macroscopic stage 2 ulcer area. (n = 20 in each group, non-parametric Kruskal-Wallis test followed by Dunn’s post-hoc test, ***P < 0.001).

Figure 4

Effect of candesartan on histological findings following 3 hours of pressure. (a) Representative photographs of central histological skin compressed section, one day and three days after pressure release. Ischemic skin lesions were removed 24 h and 72 h after pressure release and stained with hematoxylin and eosin. ep: epidermis, d.pl: dermis-papillary layer, d.rl: dermis-reticular layer. Scale bar = 100 μm. (b) Central histological pressure score (n = 6 in each group, *P < 0.05).