Honokiol Inhibits The Oxidative Damage And Inflammatory Response Induced By Staphylococcus Aureus Lipid Teichoic Acid

Staphylococcus aureus?S.aureus?is a main course of pneumonia and septic shock which can express various virulence factors which mediates immune system through different receptors.It's known that lipoteichoic acid?LTA?,component of staphylococcus aureus cell wall,is one of the main virulence factors and affiliated to inflammatory response.LTA as an amphiphile comprised of polyglycerophosphate,could activate Toll-like receptor 2?TLR2?and exhibit similar inflammatory features with lipopolysaccharide?LPS?.There are multiple threats,such as LTA,could arouse prominent generation of reactive oxygen species?ROS?which including the hydroxyl radical?·OH?and other free radicals.It's recorded that the oxidative stress situation will come out when the balance between pro-oxidant and antioxidant is disturbed to be inequitable.And the ROS produced by oxidative stress can be obliterated with enzymes of Superoxide Dismutase?SOD?,catalase?CAT?and Glutathione peroxidase?GSH-Px?.Honokiol?HNK?,an isomeride of magnolol,is one effective component of Magnolia officinalis and chemically named 3,5-di-2-propenyl-1,1-biphenyl-2,4-diol.HNK possesses multiple biological activity such as antioxidant,anti-inflammatory and neuroprotective ability.Therefore,we studied the effect of HNK on LTA-indeced oxidative damage and TLR2 signaling pathway in this paper.Firstly,the ability of HNK to scavenge free radicals was determined in this research.The scavenging rate of radicals DPPH,ABTS⁺·and O₂^-·suggested the good ability of HNK to scavenge free radicals.The scavenging rate of HNK against DPPH,ABTS⁺·and O₂^-·has already reached to 94.57%,90.43%and 91.24%at the concentration of 64?g/mL.Besides,according to the assay of total antioxidant capacity,the total antioxidant capacity value of HNK was 5.94 unit,7.62 unit and 8.16unit when at the concentration of 16?g/mL,32?g/mL and 64?g/mL individually with a dose-dependent relationship.Secondly,it was studied that the inhibition effect of HNK against LTA-induced oxidative damage in cells.The results of fluorescence of dichlorofluorescein showed that HNK could suppressed LTA-mediated increase of ROS in cells.After the stimulation of LTA,the content of MDA increased 7.65 times and the activity of SOD,CAT and GSH-Px decreased to 17.14%,16.90%and 23.21%contrast to control group which can be depressed by HNK with dose-dependent rule.Moreover,based on the results of western blot,HNK could not only improve the expression of SOD,CAT and GSH-Px,but also change the downward trend of antioxidant enzymes induced by LTA.Lastly,it was studied that the effect of HNK on the immune system response induced by LTA in cells.It mainly focused on the expression of TLR2 receptor and other immune mediate factors such as MyD88 and NF-?B,the production of pro-inflammation cytokines IL-1?,IL-6,IL-8 and TNF-?,the expression of related genes in cells.Through the results of western blot,we found that the stimulation of LTA was identified by TLR2 which activates MyD88,NF-?B and other protein in the signaling pathway and eventually leads to immune response.However,the signal transduction could be prevented by HNK with dose-dependent rules.The results of ELISA and qRT-PCR showed that the production of cytokines and the expression of related gene and TLR2 increased apparently after the treatment of LTA.Besides,HNK showed excellent ability to inhibit the gene up-regulation which was positively correlated with the dose of HNK.Above all,we conclude that HNK could inhibit the oxidative damage and immune disease caused by LTA and this study established foundation for HNK to be developed as a safety,natural and effective medicine or health care product.