Effect Of Loureirin A Against Candida Albicans Biofilms And The Study Of Caenorhabditis Elegans Infection Models

Candida albicans(C.albicans)is an opportunistic fungal pathogen of humans that resides on mucosal surfaces and in the gastrointestinal and genitourinary tracts.However,it can cause life-threatening infections in immunosuppressed patients.Many C.albicans infections are due to the organism's ability to form a biofilm on implanted medical devices,such as heart stent,uethral cannula.C.albicans biofilm can cause repeated infection and drug resistance.Anti-biofilm drugs and suitable animal models are needed urgently.However,mice infection models have many disadvantages in large-scale screening of C.albicans pathogenic traits and anti-infective compounds.Therefore,antifungal studies require high-throughput,low-cost infection models.In this study,we investigated the effect of loureirin A against C.albicans biofilms and expored Caenorhabditis elegans(C.elegans)-C.albicans infection models in evaluating the pathogenicity of C.albicans and screening anti-infective drugs.Loureirin A(Lou A)is a phenylpropanoid compound isolated from dragon's blood,a resin obtained from trees of Dracaena spp.In this study,we evaluated the activity of Lou A against C.albicans biofilms.In 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide(XTT)reduction assays and scanning electron microscopy,we found that ? 5 ?g/ml Lou A had a significant effect against C.albicans biofilms,while 5-40 ?g/ml Lou A did not exhibit fungicidal effect against C.albicans.At 5 ?g/ml or more,Lou A significantly decreased cellular surface hydrophobicity(CSH).At 20 ?g/ml or more,Lou A suppressed hyphal formation in both liquid and solid hypha-inducing media.Consistently,real-time RT-PCR results indicated that Lou A down-regulated the expression of some adhesion-related genes and hypha/biofilm-related genes.Moreover,Lou A showed in vivo antifungal effect in both Galleria mellonella–C.albicans infection model and C.elegans-C.albicans infection model,and exhibited low toxicity.Collectively,Lou A exhibits an antibiofilm effect,and this effect may be associated with the suppression of pathogenic traits,adhesion and hyphal formation.We also investigated the C.elegans-C.albicans infection models and compared their advantages and disadvantages in evaluating the pathogenicity of C.albicans and screening anti-infective drugs.First,we successfully applied the C.elegans glp-4;sek-1 to liquid medium pathogenesis assay.And in the C.albicans-C.elegans glp-4;sek-1 liquid medium pathogenesis assay,C.albicans mutant strains(hog1?/?,pbs2?/? and hst7?/?)were less vir?lent than C.albicans wild type SC5314,antifungal drug fluconazole and anti-biofilm drug Lou A prolonged the life of C.elegans glp-4;sek-1 infected with C.albicans SC5314;Astragalus membranaceus extracts(AM extracts)did not prolong the life of C.elegans.Thus,the C.albicans-C.elegans glp-4;sek-1 liquid medium pathogenesis model can evaluate the pathogenicity of C.albicans and the effect of antifungal drugs,but not the effect of immunoprotective drugs.C.elegans glp-4;sek-1 are immunosuppressive and failed to screening immunoprotective drugs.So,we tried to establish a liquid medium pathogenesis model with C.elegans wild-type N2 Bristol,but did bot success because of the matricidal killing of the larvae.It was suggested that the C.elegans wild type N2 Bristol could be used for the solid medium pathogenesis model to understand the intricate balance between the virulence of C.albicans and the host's innate immune system.We successfully applied the C.elegans N2 Bristol to solid medium pathogenesis assay.And in the C.albicans-C.elegans N2 Bristol solid medium pathogenesis assay,C.albicans mutant strains(hog1?/?,pbs2?/? and hst7?/?)showed the same vir?lence as C.albicans wild type SC5314,antifungal drug fluconazole and anti-biofilm drug Lou A did not prolong the life of C.elegans N2 Bristol infected with C.albicans SC5314;AM extracts prolonged the life of C.elegans.Thus,the C.albicans-C.elegans N2 Bristol solid medium pathogenesis model cannot evaluate the pathogenicity of C.albicans and the effect of antifungal agents,but can evaluate the effect of immunoprotective drugs.In short,Lou A exhibited the effect against C.albicans biofilms,the C.albicans-C.elegans glp-4;sek-1 liquid medium pathogenesis model can evaluate the pathogenicity of C.albicans and the effect of antifungal agents,the C.albicans-C.elegans N2 Bristol solid medium pathogenesis model can evaluate the effect of immunoprotective drugs.