The Role And Mechanism Of MEK/ERK/RSK Pathway In Chlamydia Trachomatis Infection

Globally,Chlamydia trachomatis(CT)infection is the most common sexually transmitted disease.CT genital infection can cause epididymitis,prostatitis,cervicitis,annexitis,infertility,and atopic pregnancy,which have been identified as the major public health problems.Recently,case reports of CT antibiotic-resistant are gradually increasing and serious.The antibiotic resistance was presenting significant difficulty in the clinical treatment of CT.In this study,a high prevalence(8.6%)of CT infection from urine specimens was observed among men attending STD clinics in the Guangdong province,China.The highest prevalence was among participants aged 21-30.The most prevalent genotypes were D,E,F,and J.The prevalence of CT infection appeared to be regionally distributed.The western and northern regions have a comparatively low prevalence,while the eastern region has a high prevalence rate.This study extended the existing literature by assessing CT prevalence and genotyping from urine samples of men attending STD clinics.In order to provide better insight into the mechanism involved in CT treatment failure of,we compared the infectivity of CT in four cells lines,McCoy,HeLa,Vero and HaCat,which are commonly used in the culturing of CT.We observed that McCoy and HeLa cells were more sensitive to CT infection than Vero and HaCat cells.Moreover,McCoy and HeLa are good cell lines for the culture of CT and therefore suitable for antibiotic susceptibility testing in vitro.In recent years,a meta-analysis of chlamydia treatment reported that the cure rate for azithromycin was reduced and hence persistence in treatment has become a central issue in chlamydial research.Under exposure to certain adverse conditions,such as those imposed by IFN-,y,antibiotics or deprivation of nutrients,C.trachomatis can change to a status of persistent infection.The accepted definition of chlamydial persistence is defined by a reduced or absent production of infectious progeny elementary bodies.Morphologically,this reversible state is characterized by aberrant bodies,specifically enlarged pleomorphic reticulate bodies.These aberrant bodies may remain within infected cells for lengthy periods and,upon removal of the persistence inducer,are reversible to yield infectious elementary bodies.IFN-y,azithromycin,penicillin,ofloxacin-induced persistence has been well characterized in this study.The cell culture models provide convenient vehicles allowing researchers to study the mechanisms involved in persistent C.trachomatis infections.We further compared the transcriptomic profiles of persistent and acute infections.We chose five inhibitors of host signaling pathways to observe their effect on Chlamydia infection.VX-11e,an ERK inhibitor,could inhibit chlamydial infection in Hela cells.We then focused on inhibitors of MEK/ERK signaling pathway,U0126,VX-11e and BVD-523(ulixertinib),to explore their role in Chlamydia infection.Percent infectivity analysis,measurement of the size of inclusion bodies,and EB titer assay were decreased upon exposure to VX-11e,BVD-523 and U0126.Aberrant bodies were captured by transmission electron microscopy.BVD-523,a Phase ? study of clinical trial,was used in the animal model experiment of Chlamydia infection.Results indicated that BVD-523 could inhibit Chlamydia infection in mice.VX-11e and BVD-523,the small molecule inhibitors of ERK signaling pathway,may serve as possible new targets for drug development in host-directed therapy of Chlamydia.Ribosomal S6 kinase(RSK)is an important downstream gene in the ERK signaling pathway,however,little is known about its role in the RSK signaling pathway in CT infection.In this study,we explored the role and mechanism of RSK signaling pathway in CT infection.Two RSK inhibitors,LJH685 and LJI308,can significantly inhibit CT infection.Percent infectivity analysis,inclusion size measurement,EB titer assay were decreased upon exposure to LJH685 and LJI308.Moreover,LJH685 and LJI308 have synergistic effects with azithromycin.RSK signaling pathway inhibitors were first applied to CT infection in our study.To the best of our knowledge,this is the first report of the involvement of the ERX/RSK signaling pathway in the regulation of Chlamydia infection.The effectors of the ERK/RSK signaling pathway may serve as possible new targets for drug development in the treatment of Chlamydia.In summary,this study demonstrated the epidemiological characteristics of CT infection in the Guangdong Province,established CT persistent infection models,and explored the role of ERK/RSK signaling pathway in CT infection.This study would provide the basis for future investigations into the discovery of new therapeutic target for Chlamydia treatment.