Palmitolealdehyde targeting conidial pigmentation and surface morphology in Aspergillus fumigatus

Author:

araghavanS Hoda, L Gupta, P Vijay

Author address:

1Amity Institute of Biotechnology, Amity University Uttar Pradesh, NOIDA, India

Full conference title:

9th Advances Against Aspergillosis

Date: 26 February 2020

Abstract:

Purpose: Aspergillus fumigatus is a major fungal pathogen associated with varied invasive fungal infections all over the globe. The rapid emergence of antifungal drug resistance in A. fumigatus since past few years, has led to increased morbidity and mortality mainly among immunocompromised patients. Conidial pigment DHN-melanin is a major virulence factor that is well associated with other cell surface virulence determinants. It protects the fungus during unfavourable conditions and enhances their survival in-vitro and in-vivo. Therefore, the present study aims to investigate the antifungal efficacyof the phytocompound palmitolealdehyde (C9H) targeting conidial pigmentation and surface morphology in A. fumigatus. C9H is a naturally occurring fatty aldehydic compound that is present in various medicinal plants but its melanin inhibiting property against A. fumigatus is still unexplored.

Methods: Minimum effective concentration (MEC) of the phytocompound leading to formation of white demelanised A. fumigatus colonywas determined by broth micro-dilution assay. Reduction in conidial pigmentation and other surface virulence traits such as hydrophobins, polysaccharide and glycoproteins were estimated via biochemical assays. The transcript analysis of polyketide synthase gene pksP/alb1 (the 1st gene activated during conidial pigment biosynthesis)was done using RT-qPCR. Total proteome profiling was performed using LC-MS/MS. MTT assay was performed for cytotoxicity determination. Fractional inhibitory concentration (FIC) was determined using checkerboard assay.

Results: A. fumigatus formed white demelanised colony at 0.07 mg/mL concentration of C9H. There was 96% inhibition of melanin content in C9H treated A. fumigatus. The melanin reduction resulted in altered conidial surface with reduced surface hydrophobicity (55%) and cell wall polysaccharides such as glucans (53%), chitin (46%) and glycoproteins (40%). The phytocompound treatment enhanced the expression of pksP/alb1 gene (3.5 fold) in comparison to wild type A. fumigatus. The total proteome analysis showed that from a total of 1809 proteins, 309 proteins were differentially expressed. The gene ontology study, further revealed 36% membrane proteins and 7% extracellular proteins, were differentially expressed. On the basis of biological function, it was found that 3% cell wall integrity proteins, 9% secondary metabolites and 5% cell stress proteins were differentially expressed between the total protein isolated from C9H treated and WT A. fumigatus. Polyketide synthase protein (PKS) was up-regulated; however no further down-stream proteins formed during DHN-melanin biosynthesis were observed. The phytocompound C9H has been found to be non-cytotoxic for human lung epithelial normal cell line L-132 up to 0.625 mg/mL. FIC indexing revealed that C9H had an additive effect when used in combination with antifungal drug Amphotericin B (AmpB) and the therapeutic efficacy of both AmpB (4-fold) and C9H (2-fold) was enhanced.

Conclusion: The outcome of in vitro studies indicated that the phytocompound C9H has potential role ininhibition of conidial pigmentation leading to reduction in surface proteins and polysaccharides responsible for adherence and spreading infection in host body. The combinatorial approach may also help in overcoming the severe side-effects due the high dosage of the available antifungal drugs. Hence, it can be explored further as a lead for future therapeutic agent.

Abstract Number: 43

Link to conference website:

Link Conference abstract: 

AAAM 2020

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