Fungal melanin-induced metabolic reprogramming in macrophages is crucial for inflammation

Abstract

The overuse of antifungal and immunosuppressant drugs and the higher frequency of organ transplantation has resulted in mycosis being increasingly intractable, and there is a great need for the development of new therapies. Melanin is an important virulence factor that can inhibit the inflammatory response in the host and facilitate fungal survival by several methods. However, a recent study showed that the Akt/mTOR/HIF1α axis in macrophages was activated after melanin-binding proteins recognised the DHN melanin of Aspergillus fumigatus, with a resulting metabolic shift towards glycolysis (i.e., metabolic reprogramming). As a result, antimicrobial compounds (e.g., inflammatory mediators and reactive oxygen species) were increased to fight the fungal invasion. Actually, DHN melanin from other fungi and DOPA melanin can induce inflammation and stimulate the production of melanin-binding antibodies. In addition, DOPA melanin contains conserved repeating units that are similar to those of DHN melanin. Therefore, we evaluated the associated evidence to propose an interesting and reasonable hypothesis that melanin promotes inflammation by metabolic reprogramming, which could provide a research direction for antifungal therapy. It suggests that regulating the metabolism of immune cells can guide the inflammatory response against fungi, despite the presence of immunosuppressant melanin. Since the biochemical molecules of glycolysis are clearly described, regulating glycolysis in macrophages may be easier than inventing new antifungal drugs. Further clarification of our hypothesis may strengthen the candidacy of melanin for future antifungal vaccines.

Keywords: DHNmelanin; DOPA melanin; Glycolysis; Immunometabolism; Inflammation; Metabolic reprogramming.