Department of Biochemistry, University College of Science, Osmania University, Hyderabad-500 007, Telangana State, India.
Department of Biochemistry, University College of Science, Osmania University, Hyderabad-500 007, Telangana State, India.
Peptides. 2019 May;115:15-26. doi: 10.1016/j.peptides.2019.02.006. Epub 2019 Feb 15.
Aflatoxins are potent carcinogenic mycotoxins produced as secondary metabolites mainly by the fungi Aspergillus flavus and Aspergillus parasiticus. Control measures to curtail the contamination of aflatoxin in food products is still a challenge. Although there are several reports on the antifungal peptides, there is no specific study on the action of antifungal peptides on aflatoxin synthesis. This work details the effect of four antimicrobial peptides (AMPs) - PPD1 (FRLHF), 66-10 (FRLKFH), 77-3 (FRLKFHF) and D4E1 (FKLRAKIKVRLRAKIKL) on the aflatoxin production by A. flavus and A. parasiticus. Results of the investigations suggests that AMPs at near minimum inhibitory concentrations (MIC) were effectively inhibiting aflatoxins, without hindering the growth of the fungi. These AMPs, at concentrations near MIC, induced membrane permeabilisation, without inducing cellular leakage. The involvement of oxidative stress for the aflatoxin synthesis was reversed by the antioxidant nature of the peptides as evidenced by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assay, reactive oxygen species production, malondialdehyde and antioxidant enzymes analysis. Quantitative real time polymerase chain reaction (RT-qPCR) analysis of the aflatoxin gene cluster showed that 'aflR' and its downstream genes expressions were significantly down regulated. Conidiation of the fungi were negatively influenced by the peptides as evidenced by scanning electron microscopy analysis and RT-qPCR. mRNA levels of Manganese-superoxide dismutase (Mn-SOD) showed a decrease in the expression in RT-qPCR. The effect of these peptides on aflatoxin inhibition provides insight into their use as novel antiaflatoxigenic molecules.
黄曲霉毒素是一种强效的致癌真菌毒素，主要作为次级代谢物由真菌黄曲霉和寄生曲霉产生。控制黄曲霉毒素污染食品的措施仍然是一个挑战。虽然有一些关于抗菌肽的报道，但没有关于抗菌肽对黄曲霉毒素合成作用的专门研究。这项工作详细说明了四种抗菌肽（AMPs）-PPD1（FRLHF）、66-10（FRLKFH）、77-3（FRLKFHF）和 D4E1（FKLRAKIKVRLRAKIKL）对黄曲霉和寄生曲霉产黄曲霉毒素的影响。研究结果表明，接近最小抑菌浓度（MIC）的 AMPs 有效地抑制了黄曲霉毒素的产生，而不会抑制真菌的生长。这些 AMPs 在接近 MIC 的浓度下诱导了膜通透性，而不会引起细胞渗漏。如 2,2-二苯基-1-苦基肼（DPPH）和 2,2'-联氮-双（3-乙基苯并噻唑啉-6-磺酸（ABTS）测定、活性氧产生、丙二醛和抗氧化酶分析所证明的，肽的抗氧化性质逆转了黄曲霉毒素合成的氧化应激。实时定量聚合酶链反应（RT-qPCR）分析黄曲霉毒素基因簇表明，'aflR'及其下游基因的表达显著下调。肽对真菌的产孢有负面影响，这可以通过扫描电子显微镜分析和 RT-qPCR 得到证明。锰超氧化物歧化酶（Mn-SOD）的 mRNA 水平在 RT-qPCR 中表达下降。这些肽对黄曲霉毒素抑制的影响为它们作为新型抗黄曲霉毒素分子的应用提供了启示。
