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that are excreted to the skin surface and form sebum. The function of sebum is still a matter of investigation. It is only hypothesized that sebum may play a role in the protection of skin from dehydration, ultraviolet radiation (UVR), wrinkling, and infection ( 1, 2 ). The sebaceous lipid mixture is highly complex and consists of triacylglycerols (TAG), diacylglycerols (DAG), and free fatty acids (FFA), which together account for 50-60% of its composition. Sebum also contains 20-30% wax esters (WE), 10-16% squalene (SQ), and 2-4% cholesterol esters (CE) ( 1, 2 ). Initial analyses of the components of the sebaceous lipid mixture conducted by led to the identifi cation of several different types of acyl chains in esters with glycerol, cholesterol, and waxes. Fatty acids (FA) with an odd number of carbon atoms, branched side chains, and sites of unsaturation at unconventional positions were characterized. However, information on the intact lipids remained to be determined. A detailed characterization of the lipid repertoire in sebum in physiologic and diseased conditions is very limited due to the unavailability of methods for the comprehensive and simultaneous analysis of whole lipids. Prior investigations of the composition of sebum have been mostly concerned with acne, a multifactorial skin disorder that affects the pilosebaceous unit. Currently, only a few parameters are addressed when investigating alterations in sebum, such as SQ levels and the composition of FA obtained from the hydrolysis of TAG, DAG, WE, and CE. The methodology for the targeted analysis of SQ involves gas chromatography (GC) with Abstract Sebum is a complex lipid mixture that is synthesized in sebaceous glands and excreted on the skin surface. The purpose of this study was the comprehensive detection of the intact lipids that compose sebum. These lipids exist as a broad range of chemical structures and concentrations. Sebum was collected with SebuTape TM from the foreheads of healthy donors, and then separated by HPLC on a C8 stationary phase with sub 2 µm particle size. This HPLC method provided high resolution and excellent reproduc- Skin is a metabolically active tissue that contains sebaceous glands, which are specialized organelles equipped for the synthesis of a broad spectrum of lipid compounds

Vitiligo is characterized by the progressive disappearance of pigment cells from skin and hair follicle. Several in vitro and in vivo studies show evidence of an altered redox status, suggesting that loss of cellular redox equilibrium might be the pathogenic mechanism in vitiligo. However, despite the numerous data supporting a pathogenic role of oxidative stress, there is still no consensus explanation underlying the oxidative stress-driven disappear of melanocytes from the epidermis. In this study, in vitro characterization of melanocytes cultures from non-lesional vitiligo skin revealed at the cellular level aberrant function of signal transduction pathways common with neurodegenerative diseases including modification of lipid metabolism, hyperactivation of mitogen-activated protein kinase (MAPK) and cAMP response element-binding protein (CREB), constitutive p53-dependent stress signal transduction cascades, and enhanced sensibility to pro-apoptotic stimuli. Notably, these long-term effects of subcytotoxic oxidative stress are also biomarkers of pre-senescent cellular phenotype. Consistent with this, vitiligo cells showed a significant increase in p16 that did not correlate with the chronological age of the donor. Moreover, vitiligo melanocytes produced many biologically active proteins among the senescence-associated secretory phenotype (SAPS), such as interleukin-6 (IL-6), matrix metallo proteinase-3 (MMP3), cyclooxygenase-2 (Cox-2), insulin-like growth factor-binding protein-3 and 7 (IGFBP3, IGFBP7). Together, these data argue for a complicated pathophysiologic puzzle underlying melanocytes degeneration resembling, from the biological point of view, neurodegenerative diseases. Our results suggest new possible targets for intervention that in combination with current therapies could correct melanocytes intrinsic defects.

The data further support the involvement of lipid oxidation and particularly by-products of squalene oxidation in comedogenesis.

inflammatory responses (1-3). Quantitative and qualitative modifications of sebaceous lipids likely trigger inflammatory responses causative of acne lesions commonly called comedones (4-7). Juvenile acne, which affects approximately 80% of adolescents in industrialized countries, develops during puberty when androgens and other endocrine factors stimulate sebum secretion, thereby generating conditions for development of lesions (8). Studies aimed at the identification of lipid alterations involved in acne pathogenesis date back to the early 70s to late 80s (9-14); however, the complexity of the sebum composition has represented a major limitation to understanding lipid modifications involved with acne. The recent availability of methods with improved analytical performance and high-throughput opens new perspectives to understanding sebum alterations in acne.GC-MS has been widely employed to investigate sebum lipids. GC-MS conditions are suitable for analysis of FFAs, squalene, and cholesterol and also allow for detection of wax esters and sterol oxidation products (15). The latest advances in GC-MS analysis have provided structural information and detailed fingerprints of intact sebaceous lipids (16,17). Coupling the separation power of HPLC with high-resolution MS has also proved to meet the difficult task of analyzing intact structures of sebaceous mixture components (18). On the other hand, no separative spectroscopic methods based on NMR have been used for the quantitative analysis of sebum lipids independent of their fatty acid composition (19). Acne is a complex and multifactorial skin disorder targeting the pilosebaceous unit, wherein the sebaceous gland produces and secretes a lipid-rich mixture known as sebum. Increased sebogenesis is pivotal in the pathogenesis of acne and predisposes skin to deregulated Abstract

Oxylipins are fatty acid-derived signaling compounds produced by all eukaryotes so far investigated; in mycotoxigenic fungi, they modulate toxin production and interactions with the host plants. Among the many enzymes responsible for oxylipin generation, Linoleate Diol Synthase 1 (LDS1) produces mainly 8-hydroperoxyoctadecenoic acid and subsequently different di-hydroxyoctadecenoic acids. In this study, we inactivated a copy of the putative LDS1 ortholog (acc. N. FVEG_09294.3) of Fusarium verticillioides, with the aim to investigate its influence on the oxylipin profile of the fungus, on its development, secondary metabolism and virulence. LC-MS/MS oxylipin profiling carried out on the selected mutant strain revealed significant quali-quantitative differences for several oxylipins when compared to the WT strain. The Fvlds1-deleted mutant grew better, produced more conidia, synthesized more fumonisins and infected maize cobs faster than the WT strain. We hypothesize that oxylipins may act as regulators of gene expression in the toxigenic plant pathogen F. verticillioides, in turn causing notable changes in its phenotype. These changes could relate to the ability of oxylipins to re-shape the transcriptional profile of F. verticillioides by inducing chromatin modifications and exerting a direct control on the transcription of secondary metabolism in fungi.

In some filamentous fungi, the pathways related to the oxidative stress and oxylipins production are involved both in the process of host-recognition and in the pathogenic phase. In fact, recent studies have shown that the production of oxylipins in filamentous fungi, yeasts and chromists is also related to the development of the organism itself and to mechanisms of communication with the host at the cellular level. The oxylipins, also produced by the host during defense reactions, are able to induce sporulation and to regulate the biosynthesis of mycotoxins in several pathogenic fungi. In A. flavus, the oxylipins play a crucial role as signals for regulating the biosynthesis of aflatoxins, the conidiogenesis and the formation of sclerotia. To investigate the involvement of an oxylipins based cross-talk into Z. mays and A. flavus interaction, we analyzed the oxylipins profile of the wild type strain and of three mutants of A. flavus that are deleted at the Aflox1 gene level also during maize kernel invasion. A lipidomic approach has been addressed through the use of LC-ToF-MS, followed by a statistical analysis of the principal components (PCA). The results showed the existence of a difference between the oxylipins profile generated by the WT and the mutants onto challenged maize. In relation to this, aflatoxin synthesis which is largely hampered in vitro, is intriguingly restored. These results highlight the important role of maize oxylipin in driving secondary metabolism in A. flavus.

The skin surface lipids (SSL) result from the blending of sebaceous and epidermal lipids, which derive from the sebaceous gland (SG) secretion and the permeability barrier of the stratum corneum (SC), respectively. In humans, the composition of the SSL is distinctive of the anatomical distribution of the SG. Thus, the abundance of sebum biomarkers is consistent with the density of the SG. Limited evidence on the influence that the SG exerts on the SC lipidome is available. We explored the differential amounts of sebaceous and epidermal lipids in areas at different SG density with lipidomics approaches. SC was sampled with adhesive patches from forearm, chest, and forehead of 10 healthy adults (8F, 2M) after mechanical removal of sebum with absorbing paper. Lipid extracts of SC were analysed by HPLC/(-)ESI-TOF-MS. In the untargeted approach, the naïve molecular features extraction algorithm was used to extract meaningful entities. Aligned and normalized data were evaluated by univariate and multivariate statistics. Quantitative analysis of free fatty acids (FFA) and cholesterol sulfate (CHS) was performed by targeted HPLC/(-)ESI-TOF-MS, whereas cholesterol and squalene were quantified by GC-MS. Untargeted approaches demonstrated that the relative abundance of numerous lipid species was distinctive of SC depending upon the different SG density. The discriminating species included FFA, CHS, and ceramides. Targeted analyses confirmed that sebaceous FFA and epidermal FFA were increased and decreased, respectively, in areas at high SG density. CHS and squalene, which are biomarkers of epidermal and sebaceous lipid matrices, respectively, were both significantly higher in areas at elevated SG density. Overall, results indicated that the SG secretion intervenes in shaping the lipid composition of the epidermal permeability barrier.