Investigations Into The Functional Mechanism Of Emodin Against Staphylococcus Aureus Using ITRAQ-LC-MS/MS Proteomic Analysis

ObjectiveStaphylococcus aureus (SA) is a serious pathogen associated with severe infection and the clinic methicillin-resistant isolates are almostly multidrug resistant Staphylococcus aureus (MRSA). The aim of the present study was to confirm the inhibitory activity of emodin against SA and explore the functional mechanism thereof.Methods①A micro-twofold dilution method was performed to detect the minimum inhibitory concentration (MIC) of Emodin against SA and the clinical isolate MRSA133630.②The growth curve of bacteria incubated with Emodin at0.25X MIC was recorded by measuring OD595successively for24hours and the protein expression profile was mapped by SDS-PAGE.③A high throughput method, iTRAQ-LC-MS/MS, was applied to analyze the altered proteins after Emodin exposure.Results①Emodin show effective against MRSA133630.②Growth suppression and changes of protein expression were observed with SA strains in the presence of emodin.③A total of349different proteins were identified between MRSA control group and MSSA control group,162were up-regulated and187were down-regulated. Among them,107proteins (such as rsbW, IcaB, atl) that involve in glucose metabolism/gluconeogenesis, pyruvate metabolism and ABC transport system were significant changed with a1.5fold change at least and a p-value<0.05.④A total of200different proteins were identified between MSSA treatment group and control group,69were up-regulated and131were down-regulated. Among them,49proteins (such as msrA, sdrD, sdrE) were significant changed with a p-value<0.05, most of whom are important enzymes involves pyruvate metabolism, some of the rest are implicated in oxidation and virulence.⑤A total of158changed proteins were indecnified between MRSA treatment group and MRSA control group,58were up-regulated and100were dowm-regulated.32sinificant changed proteins (such as sodA, pykA, tcaA) with a p-value<0.05involves in proteolysis, superoxide metabolic process and virulence were identified.ConclusionEmodin is effective against MSSA and MRSA isolates. Significant difference in glucose metabolism, transport system and virulence was observed between MSSA proteome profiles and that of MRSA. Some proteins of MRSA, such as lip, sspB, atl, capG and prsA, might be the candidate multi-drugs resistant targets; Two-component sensor histidine kinase might be the candidate target of emodin against Staphylococcus aureus, which should be confirmed by further studies.