Honokiol inhibitsVibrio harveyihemolysin virulence by reducing its haemolytic activity

Abstract

Vibrio harveyi, as one of the main pathogens of vibriosis, has serious multidrug resistance, which has been a focus for domestic and foreign researchers. Vibrio harveyi hemolysin (VHH), an important virulence determinant of V. harveyi, causes cell necrosis and tissue damage by lysing cell membranes, which is essential for V. harveyi invasion of the host. The critical role of VHH in the virulence of V. harveyi renders it an ideal target for designing novel anti-virulence therapeutics. We found that honokiol, a natural compound, could act as a potent antagonist of VHH-mediated haemolysis at non-bacteriostatic concentrations. Honokiol can effectively inhibit the damage caused by VHH and V. harveyi both in vitro and in vivo. qRT-PCR and molecular docking analysis showed that although honokiol up-regulated the transcription level of vhh, it could block the active centre of VHH directly and forcefully, thereby reducing the catalytic activity of VHH. The results suggest that HNK could have great potential in the development of new aquaculture drugs. K E Y W O R D S anti-virulence, honokiol, VHH, Vibrio harveyi

Screening and evaluating honokiol from Magnolia officinalis against Nocardia seriolae infection in largemouth bass (Micropterus Salmoides)

“…Honokiol is an isomer of magnolol, they are major phenolic substances derived from the root and bark of M. officinalis (Ho et al, 2001). Recently studies have shown that honokiol reduced Vibrio harveyi haemolysin virulence, with the MIC of 16 μg/ ml (Guo et al, 2019b), magnolol inhibited the haemolytic activity of Aeromonas hydrophila, and the MICs ranged from 32 to 64 μg/ml (Dong et al, 2017). Despite different bacteria species, the reported MICs are higher than our results, which may be attributed to the fact that honokiol and magnolol are more effective in inhibition The MRA method is a simple, accurate and reliable bioassay that is widely used in evaluating natural products and synthetic compounds for antimycobacterial activity (O'Neill et al, 2014;Palomino et al, 2002).…”