Background: We recently reported that hesperetin-5,7,3'-O-triacetate (HTA) dually inhibited phosphodiesterase (PDE)3/4 with a therapeutic ratio of 20.8. The application and development of PDE4 inhibitors for treating asthma or COPD are limited by their side effects, such as nausea, vomiting and gastric hypersecretion. PDE4 inhibitors were reported to reverse xylazine/ketamine-induced anesthesia in rats and triggered vomiting in ferrets. Thus the reversing effect of HTA on xylazine/ketamine-induced anesthesia in mice was studied to assess emetic effect of HTA. The aim of this study was to prove the therapeutic effect of HTA without vomiting effect at an effective dose for treating COPD. Methods: Ten female BALB/c mice in each group were sensitized by ovalbumin (OVA) on days 0 and 14. On day 21, these mice were emphasized the sensitization by Freund's complete adjuvant. Mice were challenged by 1% OVA nebulization on days 28, 29, and 30. Airway hyperresponsiveness (AHR) was assessed on day 32 in each group, using the FlexiVent system to determine airway resistance (RL) and lung dynamic compliance (Cdyn) in anesthetized ovalbumin (OVA)-sensitized and challenged mice. Each group was orally administered HTA (10 ~ 100 μmol/kg), roflumilast (1 and 5 mg/kg) or vehicles (controls) 2 h before and 6 and 24 h after OVA provocation. For comparison, sham-treated mice were challenged with saline instead of 1% OVA. The ability to reverse xylazine/ketamine-induced anesthesia by HTA or roflumilast for 3 h was determined in normal mice. We used roflumilast, a selective PDE4 inhibitor and bronchodilator for severe COPD approved by the US Food and Drug Administration, as a reference drug. Results: In the results, HTA (100 μmol/kg, p.o.) or roflumilast (5 mg/kg, p.o.) significantly suppressed all RL values of MCh at 0.78 ~ 25 mg/mL and enhanced Cdyn values of MCh at 3.125 ~ 25 mg/mL compared to OVA-sensitized and -challenged control mice. Orally administered 1, 3 or 10 mg/kg roflumilast, but not 30 or 100 μmol/kg HTA, significantly reversed xylazine/ketamine-induced anesthesia. Conclusions: In contrast to roflumilast, HTA may ameliorate COPD but induce few side effects of nausea, vomiting and gastric hypersecretion at an effective dose for treating COPD, because HTA did not reverse xylazine/ketamine-induced anesthesia in mice.
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