Forsythiaside inhibits bacterial adhesion on titanium alloy and attenuates Ti-induced activation of nuclear factor-kB signalingmediated macrophage inflammation

Background: Inflammation and biofilm formation by Staphylococcus aureus (S. aureus) are common causes of periprosthetic infection and loosening Recently, we identified that forsythiaside is bacteriostatic for S. aureus and methicillin resistant S. aureus (MRSA). The purpose of the present study was to examine the effect of forsythiaside on S. aureus and MRSA adhesion and biofilm formation on the surface of titanium alloy, which is a populai material for orthopedic joint prostheses. Methods: Two stiains of S aureus and MRSA were used foi in vitio experiments. The spread plate method, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) were used to characterize antimicrobial activity of forsythiaside. Real-time polymerase chain reaction (RT-PCR) and western blotting were used to investigate the inhibitory level of forsythiaside required for titanium-associated inflammation. Results: Direct colony counting showed that 16 mu g/mL forsythiaside significantly inhibited S. aureus and MRSA adhesion on titanium alloy discs in 2 h. CLSM and SEM showed that higher concentrations (> 30 mg/mL) of forsythiaside effectively inhibited the adhesion of S. aureus and MRSA on the surface of the titanium disc in 24 h. Forsythiaside was capable of attenuating Ti-induced activation of nuclear factor-kB signaling, targeting IkB kinase-alpha (IKKa) kinases of macrophages, and influencing the expression of NF-kB downstream cytokines. Conclusions: These observations suggest that forsythiaside is a potential agent for the treatment of Ti implant- associated infection and inflammation.