EGFR/ERBB receptors differentially modulate sebaceous lipogenesis

Near-infrared radiation causes sebaceous gland enlargement along with an ROS-dependent augmentation of epidermal growth factor receptor expression in hamsters

As near-infrared radiation (NIR), which is a composition of sunlight with an 780-1400 nm wavelength, is associated with skin aging such as wrinkles and slacks, the biological actions of NIR with high dermal penetration remains unclear. In the present study, we found that NIR irradiation (40 J/cm2 ) at different levels of irradiance (95-190 mW/cm2 ) using a laboratory device with a xenon flash lamp (780-1700 nm) caused sebaceous gland enlargement concomitantly with skin thickening in the auricle skin of hamsters. The sebaceous gland enlargement resulted from the proliferation of sebocytes due to an increase in the number of proliferating cell nuclear antigen (PCNA)- and lamin B1-positive cells in vivo. In addition, NIR irradiation transcriptionally augmented the production of epidermal growth factor receptor (EGFR) accompanied with an increase in the reactive oxygen species (ROS) level in hamster sebocytes in vitro. Furthermore, the administration of hydrogen peroxide increased the level of EGFR mRNA in the sebocytes. Therefore, these results provide novel evidence that NIR irradiation causes the hyperplasia of sebaceous glands in hamsters by mechanisms in which EGFR production is transcriptionally augmented through ROS-dependent pathways in sebocytes.

Linoleic Acid Induced Changes in SZ95 Sebocytes-Comparison with Palmitic Acid and Arachidonic Acid

Linoleic acid (LA) is an essential omega-6 polyunsaturated fatty acid (PUFA) derived from the diet. Sebocytes, whose primary role is to moisturise the skin, process free fatty acids (FFAs) to produce the lipid-rich sebum. Importantly, like other sebum components such as palmitic acid (PA), LA and its derivative arachidonic acid (AA) are known to modulate sebocyte functions. Given the different roles of PA, LA and AA in skin biology, the aim of this study was to assess the specificity of sebocytes for LA and to dissect the different roles of LA and AA in regulating sebocyte functions. Using RNA sequencing, we confirmed that gene expression changes in LA-treated sebocytes were largely distinct from those induced by PA. LA, but not AA, regulated the expression of genes related to cholesterol biosynthesis, androgen and nuclear receptor signalling, keratinisation, lipid homeostasis and differentiation. In contrast, a set of mostly down-regulated genes involved in lipid metabolism and immune functions overlapped in LA- and AA-treated sebocytes. Lipidomic analyses revealed that the changes in the lipid profile of LA-treated sebocytes were more pronounced than those of AA-treated sebocytes, suggesting that LA may serve not only as a precursor of AA but also as a potent regulator of sebaceous lipogenesis, which may not only influence the gene expression profile but also have further specific biological relevance. In conclusion, we have shown that sebocytes are able to respond selectively to different lipid stimuli and that LA-induced effects can be both AA-dependent and independent. Our findings allow for the consideration of LA application in the therapy of sebaceous gland-associated inflammatory skin diseases such as acne, where lipid modulation and selective targeting of AA metabolism are potential treatment options.

Desaturation of sebaceous-type saturated fatty acids through the SCD1 and the FADS2 pathways impacts lipid neosynthesis and inflammatory response in sebocytes in culture

Sebum is a lipid-rich mixture secreted by the sebaceous gland (SG) onto the skin surface. By penetrating through the epidermis, sebum may be involved in the regulation of epidermal and dermal cells in both healthy and diseased skin conditions. Saturated and monounsaturated fatty acids (FAs), found as free FAs (FFAs) and in bound form in neutral lipids, are essential constituents of sebum and key players of the inflammatory processes occurring in the pilosebaceous unit in acne-prone skin. Little is known on the interplay among uptake of saturated FFAs, their biotransformation, and induction of proinflammatory cytokines in sebocytes. In the human SG, palmitate (C16:0) is the precursor of sapienate (C16:1n-10) formed by insertion of a double bond (DB) at the Δ6 position catalysed by the fatty acid desaturase 2 (FADS2) enzyme. Conversely, palmitoleate (C16:1n-7) is formed by insertion of a DB at the Δ9 position catalysed by the stearoyl coenzyme A desaturase 1 (SCD1) enzyme. Other FFAs processed in the SG, also undergo these main desaturation pathways. We investigated lipogenesis and release of IL-6 and IL-8 pro-inflammatory cytokines in SZ95 sebocytes in vitro after treatment with saturated FFAs, that is, C16:0, margarate (C17:0), and stearate (C18:0) with or without specific inhibitors of SCD1 and FADS2 desaturase enzymes, and a drug with mixed inhibitory effects on FADS1 and FADS2 activities. C16:0 underwent extended desaturation through both SCD1 and FADS2 catalysed pathways and displayed the strongest lipoinflammatory effects. Inhibition of desaturation pathways proved to enhance lipoinflammation induced by SFAs in SZ95 sebocytes. Palmitate (C16:0), margarate (C17:0), and stearate (C18:0) are saturated fatty acids that induce different arrays of neutral lipids (triglycerides) and dissimilar grades of inflammation in sebocytes.

Sapienic Acid Metabolism Influences Membrane Plasticity and Protein Signaling in Breast Cancer Cell Lines

The importance of sapienic acid (6c-16:1), a monounsaturated fatty acid of the n-10 family formed from palmitic acid by delta-6 desaturase, and of its metabolism to 8c-18:1 and sebaleic acid (5c,8c-18:2) has been recently assessed in cancer. Data are lacking on the association between signaling cascades and exposure to sapienic acid comparing cell lines of the same cancer type. We used 50 μM sapienic acid supplementation, a non-toxic concentration, to cultivate MCF-7 and 2 triple-negative breast cancer cells (TNBC), MDA-MB-231 and BT-20. We followed up for three hours regarding membrane fatty acid remodeling by fatty acid-based membrane lipidome analysis and expression/phosphorylation of EGFR (epithelial growth factor receptor), mTOR (mammalian target of rapamycin) and AKT (protein kinase B) by Western blotting as an oncogenic signaling cascade. Results evidenced consistent differences among the three cell lines in the metabolism of n-10 fatty acids and signaling. Here, a new scenario is proposed for the role of sapienic acid: one based on changes in membrane composition and properties, and the other based on changes in expression/activation of growth factors and signaling cascades. This knowledge can indicate additional players and synergies in breast cancer cell metabolism, inspiring translational applications of tailored membrane lipid strategies to assist pharmacological interventions.

Eruptive Necrotizing Infundibular Crystalline Folliculitis: An Expression of an Abortive Sebaceous Follicular Repair Pathway Linked to Committed Infundibular Stem Cells?

ABSTRACT

Necrotizing infundibular crystalline folliculitis is a rare entity, which is a distinctive clinical and histopathological entity. Eruptive yellow waxy umbilicated folliculocentric plugs clinically correspond to pale crystalline filaments embedded in an amorphous sebum-rich material. Remarkably, only the superficial infundibular ostia remain, and the distended cavity is devoid of a follicular or sebaceous gland remnant. The pathogenesis of this enigmatic event remains to be established. The emergence of necrotizing infundibular crystalline folliculitis (NICF) as a paradoxical side effect of antitumor inhibitors epidermal growth factor receptor vascular endothelial growth factor and more recently programmed death-1 represents the expression of altered molecular pathways that underpin the pathogenesis of NICF. To explore these pathways, it is necessary to explore the hierarchy of follicular stem cells, particularly the potential role of committed infundibular stem cells that play a key role in wound healing. Committed infundibular stem cells are closely linked to the sebaceous gland stem cell axis, and this has relevance in the process of homeostatic repair of sebaceous follicles in the wake of folliculitis. The unscheduled modulation of this infundibular homeostatic sebaceous repair axis by epidermal growth factor receptor vascular endothelial growth factor, and programmed death-1 may lead to an aberrant outcome with metaplasia of infundibular keratinocytes to sebocytes. In the absence of sebaceous gland differentiation, these metaplastic infundibular sebocyte cells would lead to the consumption and loss of the infundibulum as a result of holocrine sebum production. This conceptual pathogenic pathway for NICF is constructed by incorporating recent advances in the fields of follicular stem cells, wound repair, follicular homeostasis, regulatory T cells, and molecular pathways linked to the biologicals inducing NICF.

Epidermal Growth Factor Modulates Palmitic Acid-Induced Inflammatory and Lipid Signaling Pathways in SZ95 Sebocytes

Epidermal growth factor (EGF) acts as a paracrine and autocrine mediator of cell proliferation and differentiation in various types of epithelial cells, such as sebocytes, which produce the lipid-rich sebum to moisturize the skin. However, sebum lipids via direct contact and by penetrating through the epidermis may have regulatory roles on epidermal and dermal cells as well. As EGF receptor (EGFR) is expressed throughout the proliferating and the lipid-producing layers of sebaceous glands (SGs) in healthy and acne-involved skin, we investigated the effect of EGF on SZ95 sebocytes and how it may alter the changes induced by palmitic acid (PA), a major sebum component with bioactive roles. We found that EGF is not only a potent stimulator of sebocyte proliferation, but also induces the secretion of interleukin (IL)6 and down-regulates the expression of genes involved in steroid and retinoid metabolism. Importantly, when applied in combination with PA, the PA-induced lipid accumulation was decreased and the cells secreted increased IL6 levels. Functional clustering of the differentially regulated genes in SZ95 sebocytes treated with EGF, PA or co-treated with EGF+PA further confirmed that EGF may be a potent inducer of hyperproliferative/inflammatory pathways (IL1 signaling), an effect being more pronounced in the presence of PA. However, while a group of inflammatory genes was up-regulated significantly in EGF+PA co-treated sebocytes, PA treatment in the absence of EGF, regulated genes only related to cell homeostasis. Meta-analysis of the gene expression profiles of whole acne tissue samples and EGF- and EGF+PA -treated SZ95 sebocytes showed that the EGF+PA co-activation of sebocytes may also have implications in disease. Altogether, our results reveal that PA-induced lipid accumulation and inflammation can be modulated by EGF in sebocytes, which also highlights the need for system biological approaches to better understand sebaceous (immuno)biology.

Chronic stress and adipose tissue in the anorexic state: endocrine and epigenetic mechanisms

Although adipose tissue metabolism in obesity has been widely studied, there is limited research on the anorexic state, where the endocrine system is disrupted by reduced adipose tissue mass and there are depot-specific changes in adipocyte type and function. Stress exposure at different stages of life can alter the balance between energy intake and expenditure and thereby contribute to the pathogenesis of anorexia nervosa. This review integrates information from human clinical trials to describe endocrine, genetic and epigenetic aspects of adipose tissue physiology in the anorexic condition. Changes in the hypothalamus-pituitary-thyroid, -adrenal, and -gonadal axes and their relationships to appetite regulation and adipocyte function are discussed. Because of the role of stress in triggering or magnifying anorexia, and the dynamic but also persistent nature of environmentally-induced epigenetic modifications, epigenetics is likely the link between stress and long-term changes in the endocrine system that disrupt homoeostatic food intake and adipose tissue metabolism. Herein, we focus on the adipocyte and changes in its function, including alterations reinforced by endocrine disturbance and dysfunctional adipokine regulation. This information is critical because of the poor understanding of anorexic pathophysiology, due to the lack of suitable research models, and the complexity of genetic and environmental interactions.

LACTB promotes metastasis of nasopharyngeal carcinoma via activation of ERBB3/EGFR-ERK signaling resulting in unfavorable patient survival

Nasopharyngeal carcinoma (NPC) originates in the nasopharyngeal epithelium and has the highest metastatic rate among head and neck cancers. Distant metastasis is the main reason for treatment failure with the underlying mechanisms remaining unclear. By comparing the expression profiling of NPCs versus non-cancerous nasopharyngeal tissues, we found LACTB was highly expressed in the tumor tissues. We found that elevated expression of the LACTB protein in primary NPCs correlated with poorer patient survival. LACTB is known to be a serine protease and a ubiquitous mitochondrial protein localized in the intermembrane space. Its role in tumor biology remains controversial. We found that the different methylation pattern of LACTB promoter led to its differential expression in NPC cells. Overexpressing LACTB in NPC cells promoted their motility in vitro and metastasis in vivo. While knocking down LACTB reduced the metastasis capability of NPC cells. However, LACTB did not influence cellular proliferation. We further found the role of LACTB in promoting NPC metastasis depended on the activation of ERBB3/EGFR-ERK signaling, which in turn, affected the stability and the following acetylation of histone H3. These findings may shed light on unveiling the mechanisms of NPC metastasis.

Kaempferia parviflora Extract as a Potential Anti-Acne Agent with Anti-Inflammatory, Sebostatic and Anti-Propionibacterium acnes Activity

Kaempferia parviflora, referred to as black ginger, has traditionally been used as a health-promoting alternative medicine. In this study, we examined the anti-inflammatory, sebostatic, and anti-Propionibacterium acnes activities of K. parviflora extract. The extract significantly down-regulated the expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2), and pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α) level. Moreover, the phosphorylation of IĸBα and nuclear factor-kappa B (NF-κB), and the enhanced nuclear translocation of NF-κB p65 in lipopolysaccharide-stimulated murine macrophage-like cell line (RAW 264.7) cells were markedly decreased by the extract. Notably, the main component of K. parviflora, 5,7-dimethoxyflavone, also modulated the expression of iNOS and NF-κB signal molecules in P. acnes-stimulated human keratinocyte (HaCaT) cells. Additionally, K. parviflora extract inhibited the lipogenesis of sebocytes, as evidenced by a reduced level of triglyceride and lipid accumulation in the sebocytes. The sebostatic effect was also confirmed by a reduced expression of peroxisome proliferation-activating receptors (PPAR-γ) and oil-red O staining in sebocytes. Taken together, this study suggests for the first time that K. parviflora extract could be developed as a potential natural anti-acne agent with anti-inflammatory, sebostatic, and anti-P. acnes activity.

Abnormal Anionic Porphyrin Sensing Effect for HER2 Gene Related DNA Detection via Impedance Difference between MWCNTs and Single-Stranded DNA or Double-Stranded DNA

Human epidermal growth factor receptor 2 (HER2) is a key tumor marker for several common and deadly cancers. It is of great importance to develop efficient detection methods for its over-expression. In this work, an electrochemical impedance spectroscopy (EIS) method adjustable by anionic porphyrin for HER2 gene detection has been proposed, based on the impedance difference between multi-walled carbon nanotubes (MWCNTs) and DNA. The interesting finding herein is that with the addition of anionic porphyrin, i.e., meso-tetra(4-sulfophenyl)-porphyrin (TSPP), the impedance value obtained at a glass carbon electrode (GCE) modified with MWCNTs and a single stranded DNA (ssDNA), the probe DNA that might be assembled tightly onto MWCNTs through π-π stacking interaction, gets a slight decrease; however, the impedance value from a GCE modified with MWCNTs and a double stranded DNA (dsDNA), the hybrid of the probe DNA with a target DNA, which might be assembled loosely onto MWCNTs for the screening effect of phosphate backbones in dsDNA, gets an obvious decrease. The reason may be that on the one hand, being rich in negative sulfonate groups, TSPP will try to push DNA far away from CNTs surface due to its strong electrostatic repulsion towards DNA; on the other hand, rich in planar phenyl or pyrrole rings, TSPP will compete with DNA for the surface of CNTs since it can also be assembled onto CNTs through conjugative interactions. In this way, the “loosely assembled” dsDNA will be repelled by this anionic porphyrin and released off CNTs surface much more than the “tightly assembled” ssDNA, leading to a bigger difference in the impedance value between dsDNA and ssDNA. Thus, through the amplification effect of TSPP on the impedance difference, the perfectly matched target DNA could be easily determined by EIS without any label. Under the optimized experimental conditions, this electrochemical sensor shows an excellent linear response to target DNA in a concentration range of 2.0 × 10⁻¹¹–2.0 × 10⁻⁶ M with a limit of detection (LOD) of 6.34 × 10⁻¹¹ M (S/N = 3). This abnormally sensitive electrochemical sensing performance resulting from anionic porphyrin for DNA sequences specific to HER2 gene will offer considerable promise for tumor diagnosis and treatment.

[Dermatofibroma with sebaceous induction]

BACKGROUND

Histiocytoma or dermatofibroma (DF) is a common benign skin tumour with several clinical and histopathological variants. Sebaceous induction overlying a dermatofibroma is rare and infrequently reported. Using a detailed clinical case, herein the semiological and dermoscopic features of this lesion are described and illustrated, and the differential diagnoses presented.

PATIENTS AND METHODS

A 52-year-old man consulted for a physical examination, which revealed a firm papular lesion of the upper middle back. The upper part of the nodule was covered by a slightly hyperpigmented surface, with numerous small whitish lobules. Microscopic examination revealed a dermatofibroma with sebaceous induction.

DISCUSSION

Sebaceous induction overlying a dermatofibroma is not frequent, and it occurs in most cases on or near the shoulder. The typical dermoscopic pattern involves many whitish globules or clumps grouped into clusters. The aetiology is unknown but could stem from a conducive microenvironment in shoulder skin, associated with growth factors secreted by the DF.

Recent advances in the endocrinology of the sebaceous gland

The sebaceous gland, long considered an evolutionary relic with little-to-no physiological relevance in humans, has emerged in recent decades as a key orchestrator and contributor to many cutaneous functions. In addition to the classical physico-chemical barrier function of the skin against constant environmental challenges, a more novel, neuro-immune modulatory role has also emerged. As part of the complex intercellular communication network of the integumentary system, the sebaceous gland acts as a “relay station” in the skin for many endocrine factors. This review aims to offer a comprehensive overview of endocrine effects and subsequent interactions on this much maligned mini-organ.

Genetically modified laboratory mice with sebaceous glands abnormalities

Sebaceous glands (SG) are exocrine glands that release their product by holocrine secretion, meaning that the whole cell becomes a secretion following disruption of the membrane. SG may be found in association with a hair follicle, forming the pilosebaceous unit, or as modified SG at different body sites such as the eyelids (Meibomian glands) or the preputial glands. Depending on their location, SG fulfill a number of functions, including protection of the skin and fur, thermoregulation, formation of the tear lipid film, and pheromone-based communication. Accordingly, SG abnormalities are associated with several diseases such as acne, cicatricial alopecia, and dry eye disease. An increasing number of genetically modified laboratory mouse lines develop SG abnormalities, and their study may provide important clues regarding the molecular pathways regulating SG development, physiology, and pathology. Here, we summarize in tabulated form the available mouse lines with SG abnormalities and, focusing on selected examples, discuss the insights they provide into SG biology and pathology. We hope this survey will become a helpful information source for researchers with a primary interest in SG but also as for researchers from unrelated fields that are unexpectedly confronted with a SG phenotype in newly generated mouse lines.

Epidermal Growth Factor Receptor Cell Survival Signaling Requires Phosphatidylcholine Biosynthesis

Identification of pro-cell survival signaling pathways has implications for cancer, cardiovascular, and neurodegenerative disease. We show that the Caenorhabditis elegans epidermal growth factor receptor LET-23 (LET-23 EGFR) has a prosurvival function in counteracting excitotoxicity, and we identify novel molecular players required for this prosurvival signaling. uv1 sensory cells in the C. elegans uterus undergo excitotoxic death in response to activation of the OSM-9/OCR-4 TRPV channel by the endogenous agonist nicotinamide. Activation of LET-23 EGFR can effectively prevent this excitotoxic death. We investigate the roles of signaling pathways known to act downstream of LET-23 EGFR in C. elegans and find that the LET-60 Ras/MAPK pathway, but not the IP₃ receptor pathway, is required for efficient LET-23 EGFR activity in its prosurvival function. However, activation of LET-60 Ras/MAPK pathway does not appear to be sufficient to fully mimic LET-23 EGFR activity. We screen for genes that are required for EGFR prosurvival function and uncover a role for phosphatidylcholine biosynthetic enzymes in EGFR prosurvival function. Finally, we show that exogenous application of phosphatidylcholine is sufficient to prevent some deaths in this excitotoxicity model. Our work implicates regulation of lipid synthesis downstream of EGFR in cell survival and death decisions.