Neoechinulin A isolated from marine-derived Microsporum sp. suppresses insulin-like growth factor (IGF)-1-induced lipogenesis and P. acne mediated pathogenesis of acne in human sebocytes

Abstract

Acne vulgaris is one of the most common skin diseases and the pathogenesis of this disorder involved the increased production of sebum and inflammation induced by Propionibacterium acnes. The sebaceous gland is a holocrine gland located in the dermis of the skin, and sebocytes, the main cell type in sebaceous gland excrete sebum. Moreover, pro-inflammatory cytokines that are secreated by sebaceous gland have also been implicated in pathogenesis of acne. It has been reported that a varity of secondary metabolites derived from natural sources, including marine source, possess potential phamaceutial properties. This research focused on the development of natural agents for acne treatment from marine-derived fungus. Here, we isolated Tricycloalternarene 2b (8.7 mg) from a EtOAc extract of culture broth of marine-derived fungus identified as Alterneria sp.. Neoechinulin A (19.7 mg) a indole alkaloid was isolated from EtOAc extract (2.3 g) of Microsporum sp. a culture broth. The structures of two compounds were elucidated based on LREIMS, 1D (1H and 13C) and 2D (DEPT, HMQC, and HMBC) NMR spectroscopic results. In order to investigate the cytotoxic effect of the isolated compounds, human sebocytes were treated with different concentrations of the two compounds. The results showed that tricycloalternarene 2b decreased cell viability significantly, whereas neoechinulin A did not show any cytotoxicity towards the sebocytes under the condition tested. Excessive lipid is an important factor of the pathogenesis of acne of sebum. Here we demonstrated that neoechinulin A suppressed cell proliferation and sebum accumulation as lipid droplets in insulin like growth factor (IGF)-1- differentiated human sebocytes. Excess sebum production in sebocytes accompanied with the induction of sresponse element binding proteins (SREBPs) and PPAR. SREBP’s are a class of transcription factors capable of regulating lipid production. Studies have demonstrated that SREBPs are important in sebaceous gland lipid metabolism, and thus represent a potential drug target for the treatment of acne. PPAR ligands are required for induction of differentiation of and lipogenesis. Moreover, forkhead box O1 (FoxO1) transcription factors regulate the activity of important target genes involved in the pathogenesis of acne. The potent functions of FoxO1 protein are tightly controlled by phosphoinositide-3kinase (PI3K)/Akt signaling pathways under physiological conditions. The results indicated that neoechinulin A inhibited the expression of SREBP-1, PPAR and C/EBP induced by IGF-1 (20 ng/ml). Furthermore, phosphorylation of FoxO1 also decreased via blocking the PI3K/Akt signaling pathway. Major symptom of acne pathogenesis is abnormal colonization by anaerobic Gram-positive bacterium, Propionibacterium acnes which is closely related to the induction of inflammatory mediators. To determine the effect of neoechinulin A on innate immune response and its involvement on pathogenesis of acne, we investigated proinflammatory cytokine expression, and viability of human sebocytes in response to to P. acnes infection. In the skin, pattern recognition receptors such as toll-like receptors (TLRs) are involved in the immediate immunological response and nuclear translocation of (NF)κB related to production of inflammatory cytokines. We found that neoehinulin A decreased TLR-2,-4 and proinflammatory cytokines production induced by P. acne infection. The molecular pathway studies showed that neoehinulin A cells from P. acne infection by down-regulating the inflammatory signaling pathway NF-κB. Furthermore, we confirmed that the P. acne-induced transcriptions of AP-1 and phosphorylation of MAPK signaling cascade were regulated by neoehinulin A treatment. In conclusion, this study suggests that neoechinulin A isolated from marine-derived fungus Microsporum sp. can be developed as a natural topical applicaiotn with its potential ability to contro excess sebum production and inflammation.