Background: Thermal therapy, namely Waon therapy, has previously been reported to regulate nitric oxide (NO) and endothelial NO synthase (eNOS) and augment ischemia-induced angiogenesis in mice and improve limb ischemia in patients with peripheral artery disease. The aim of this study was to clarify the precise mechanism by which Waon therapy augments angiogenesis in mice with hindlimb ischemia.
Methods and results: Unilateral hindlimb ischemia was induced in apolipoprotein E-deficient mice and Waon therapy was performed for 5 weeks. Heat shock protein 90 (Hsp90), phosphorylated-Akt, and phosphorylated-eNOS were detected in arterial endothelial cells of ischemic hindlimbs and all were upregulated by Waon therapy compared to controls. Waon therapy also increased serum concentrations of nitrite and nitrate. Capillary density and the ischemic limb/normal side blood perfusion ratio monitored by laser Doppler perfusion imaging in the Waon therapy group were significantly increased beyond those in the control group. The effect of Waon therapy on angiogenesis through the activation of the Hsp90/Akt/eNOS pathway was attenuated by the administration of a Hsp90 inhibitor.
Conclusions: It is suggested that Waon therapy upregulates Hsp90, which contributes to the activation of the Akt/eNOS/NO pathway, and induces angiogenesis in mice with hindlimb ischemia.