ORAL ADMINISTRATION OF DOXYCYCLINE PREVENTS VULNERABLE PLAQUES FROM RUPTURE INDEPENDENT OF SERUM LIPID LEVELS (AN ANIMAL EXPERIMENT WITH RABBITS)

Objectives Chronic inflammatory responses have been implicated in the process of atherosclerosis. Doxycycline, as a broad spectrum antibiotic, has also proven effective in inhibiting MMP. The aim of this study was to evaluate the effect of doxycycline treatment on stabilising the vulnerable plaque in the New Zealand white rabbits. Methods Thirty New Zealand white rabbits were then randomly divided into group A (n=10), group B (n=10), group C (n=10).All underwent balloon-induced abdominal aortic endothelial injury and were fed a diet of 1% cholesterol for 8 weeks. The rabbits in Group A were given doxycycline (10 mg/kg/d). The rabbits in Group B were given simvastatin (5 mg/kg/d). The rabbits in Group C were the control group. All three groups were given high cholesterol food. 12 weeks later, pharmacological triggering was performed with the injection of Chinese Russell9s viper venom and histamine in both groups. The concentration of doxycycline in rabbit9s plasma was determined by HPLC. Serum lipids and inflammatory markers were measured and high frequency ultrasonography and intravascular ultrasound (IVUS) imaging were performed to measure the intimal media thickness (IMT), the external elastic membrane area (EEMA), the plaque area (pA) and the plaque burden (PB) of the abdominal aorta. Plaque contents were evaluated by immunohistochemistry and the vulnerability index (VI) was calculated. The mRNA expressions of inflammatory markers in the plaques were assessed by RT-PCR. Results The results showed that doxycycline resulted in a significant inhibition of IMT (p Conclusions Doxycycline effectively inhibits plaque inflammation and prevents vulnerable plaques from rupture. These therapeutic effects are independent of serum lipid levels and demonstrate the concept that inhibition of plaque inflammation alone without lipid lowering can stabilise vulnerable plaques.