SEB-1 Sebocytes Research Articles

Salicylic acid treats acne vulgaris by suppressing AMPK/SREBP1 pathway in sebocytes.

Acne vulgaris is a prevalent cutaneous disease characterized by a multifactorial pathogenic process including hyperseborrhea, inflammation, over-keratinization of follicular keratinocytes and Propionibacterium acnes (Pacnes) overgrowth. Salicylic acid (SA), a beta-hydroxy acid, is frequently used in the treatment of acne. SA has been found to decrease skin lipids and to possess anti-inflammatory properties. However, few studies have elucidated the mechanisms and pathways involved in such treatment of acne. In this study, we initially investigated the anti-acne properties of SA in human SEB-1 sebocytes. Treatment with SA decreased sebocyte lipogenesis by downregulating the adenosine monophosphate-activated protein kinase (AMPK)/sterol response element-binding protein-1 (SREBP-1) pathway and reduced inflammation by suppressing the NF-κB pathway in these cells. Salicylic acid also decreased the cell viability of SEB-1 by increasing apoptosis via the death signal receptor pathway. Subsequently, histopathological analysis of a rabbit ear acne model after application of SA for three weeks confirmed that SA suppressed the levels of cytokines and major pathogenic proteins around acne lesions, which supports the mechanisms suggested by our in vitro experiments. These results initially clarified that therapeutic activities of SA in acne vulgaris treatment could be associated with the regulation of SREBP-1 pathway and NF-κB pathway in human SEB-1 sebocytes.

472 Differential inflammatory responses induced by Cutibacterium acnes are not dependent on strain-types but are associated with the presence of a linear plasmid

Cutibacterium acnes (C. acnes, formerly Propionibacterium acnes), is normally well tolerated by human skin. Different strain-types of C. acnes are enriched in acne, and it has been hypothesized that strain-types may promote disease. To study the host immune response against strain-types and the genetic basis for such differences, we generated a library of >1000 C. acnes isolates from swabs of lesional and non-lesional sites of acne patients and healthy volunteers. C. acnes strain-level identity was determined by high resolution sequence typing and the inflammatory potential of each isolate was assessed by high-throughput screening of IL-8 secretion from SEB-1 sebocytes and normal human keratinocytes (NHEK) exposed to sterile bacterial supernatants. Consistent with prior findings, a higher frequency of C. acnes phylotype IA1 strains were recovered from acne lesional sites (specifically C1 and C2 sequence types (ST)). However, non-lesional sites from acne patients were found to have K1 and K2 STs, similar to healthy skin. Furthermore, and contrary to predictions, many of the K1/K2 STs from healthy skin and non-lesional acne promoted greater IL-8 production compared to lesional C1/C2 STs (p=0.012). Moreover, clonal isolates from the same ST promoted different cytokine responses, with high and low cytokine-inducing strains identified within K1, C1, C2 and H1 STs. The capacity of identical STs to promote different inflammatory responses was validated by intradermal injection of sterile supernatants into mice and subsequent qRT-PCR for IL-8, CXCL1 and IL-1β. The functional differences within these strains could not be attributed to protease or lipase activity, short chain fatty acid or porphyrin production. Instead, whole genome sequencing revealed the presence of a linear plasmid only in the pro-inflammatory strains. Several putative virulence genes are present in this plasmid. We conclude that a virulence plasmid is most highly associated with the proinflammatory activity of C. acnes.

MG-132 treatment promotes TRAIL-mediated apoptosis in SEB-1 sebocytes

AimsThis study aimed to identify the mechanism of how MG-132 stimulates cell death in SEB-1 sebocytes. Materials and methodsTUNEL staining and annexin-FITC/PI flow cytometry were utilized to examine the apoptotic cell number of SEB-1 sebocytes and HaCaT keratinocytes upon MG-132 and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) treatment. MTT assay and CCK-8 assay monitored the proliferative rate and viability of both cell lines with different treatment. Western blotting (WB) and qPCR were performed to detect the expression of TRAIL and members of Bcl-2 family at protein and gene level. Additionally, RNA interfering was used to knockdown the mRNA transcription of TRAIL and BIK gene. Key findingsMG-132 treatment enhanced cell death in SEB-1 sebocytes but not in HaCaT keratinocytes. Meanwhile, TRAIL concentrations in SEB-1 sebocytes treated with MG-132 were markedly elevated. Furthermore, treatment with TRAIL or the TRAIL receptor-specific monoclonal antibody AY4 at various doses stimulated cell death in SEB-1 sebocytes in a time- and dose-dependent manner. Silencing of TRAIL restored the cell viability of SEB-1 cells to a normal level after MG-132 treatment. Combined treatment of SEB-1 sebocytes with TRAIL and MG-132 synergistically triggered cell death, suppressed cell proliferation and survival, and promoted BIK expression. Furthermore, BCL2 Interacting Killer (BIK) knockdown via RNA interference participated in the recovery of cell survival reduced by treatment with TRAIL and MG-132. SignificanceThese findings suggest that treatment with the selective proteasome suppressor MG-132 and TRAIL induces cell death in sebocytes through upregulation of BIK, a member of the Bcl-2 family.

Platycodin D May Improve Acne and Prevent Scarring by Downregulating SREBP-1 Expression Via Inhibition of IGF-1R/PI3K/Akt Pathway and Modulating Inflammation with an Increase in Collagen.

BackgroundAlthough many therapeutic agents have been developed, only a few drugs are known to target multiple pathogenic factors in the treatment of acne.ObjectiveThe purpose of this study was to identify a new drug candidate, platycodin D, which is a substance extracted from the root of Platycodon grandiflorum.MethodsUsing western blotting and Cell Counting Kit-8 assay, we studied the effects of platycodin D on SEB-1 sebocytes, fibroblasts, and keratinocytes. We investigated its effects in view of lipogenesis, collagen production, anti-inflammatory activity, and dyskeratinization.ResultsIn SEB-1 sebocytes, platycodin D showed a sebosuppressive effect by downregulating ERK and insulin- like growth factor-1R/PI3K/Akt/sterol-regulatory element binding protein-1 signaling pathways. In addition, adiponectin, one of the adipokines responsible for sebum production, was decreased in platycodin D-treated SEB-1 sebocytes. In fibroblasts, platycodin D increased collagen production and reduced inflammation by inhibiting nuclear factor kappa B and matrix metalloproteinases. Platycodin D also showed anti-inflammatory effects on keratinocytes. It also suppressed keratin 16 expression induced by lipopolysaccharide. Furthermore, platycodin D showed no cytotoxicity on both SEB-1 sebocytes and fibroblasts.ConclusionOur data demonstrate the clinical feasibility of platycodin D for acne treatment and the prevention of acne scarring by sebosuppressive and anti-inflammatory effects, as well as through an increase in collagen levels.

Activity-Guided Purification Identifies Lupeol, a Pentacyclic Triterpene, As a Therapeutic Agent Multiple Pathogenic Factors of Acne

Acne vulgaris is a nearly universal cutaneous disease characterized by multifactorial pathogenic processes. Because current acne medications have various side effects, investigating new pharmacologically active molecules is important for treating acne. As natural products generally provide various classes of relatively safe compounds with medicinal potentials, we performed activity-guided purification after a series of screenings from the extracts of five medicinal plants to explore alternative acne medications. Lupeol, a pentacyclic triterpene, from the hexane extract of Solanum melongena L. (SM) was identified after instrumental analysis. Lupeol targeted most of the major pathogenic features of acne with desired physicochemical traits. It strongly suppressed lipogenesis by modulating the IGF-1R/phosphatidylinositide 3 kinase (PI3K)/Akt/sterol response element-binding protein-1 (SREBP-1) signaling pathway in SEB-1 sebocytes, and reduced inflammation by suppressing the NF-κB pathway in SEB-1 sebocytes and HaCaT keratinocytes. Lupeol exhibited a marginal effect on cell viability and may have modulated dyskeratosis of the epidermis. Subsequently, histopathological analysis of human patients' acne tissues after applying lupeol for 4 weeks demonstrated that lupeol markedly attenuated the levels of both the number of infiltrated cells and major pathogenic proteins examined in vitro around comedones or sebaceous glands, providing solid evidence for suggested therapeutic mechanisms. These results demonstrate the clinical feasibility of applying lupeol for the treatment of acne.

Epigallocatechin-3-Gallate Improves Acne in Humans by Modulating Intracellular Molecular Targets and Inhibiting P. acnes

Acne vulgaris is a highly prevalent skin disorder characterized by hyperseborrhea, inflammation, and Propionibacterium acnes overgrowth. Only isotretinoin and hormonal therapy reduce sebum production. To identify a new drug candidate that modulates sebum, we examined the effects of EGCG, the major polyphenol in green tea, on human SEB-1 sebocytes and in patients with acne. In SEB-1 sebocytes, we found that EGCG reduced sebum by modulating the AMPK-SREBP-1 signaling pathway. EGCG also reduces inflammation by suppressing the NF-κB and AP-1 pathways. EGCG also induces cytotoxicity of SEB-1 sebocytes via apoptosis and decreases the viability of P. acnes, thus targeting almost all the pathogenic features of acne. Finally, and most importantly, EGCG significantly improved acne in an 8-week randomized, split-face, clinical trial, and was well tolerated. Our data provide a therapeutic rationale for the use of EGCG in acne.

Isotretinoin increases skin-surface levels of neutrophil gelatinase-associated lipocalin in patients treated for severe acne

A clear-cut need exists for safe and effective alternatives to the use of isotretinoin in severe acne. Lack of data regarding the specifics of isotretinoin's mechanism of action has hampered progress in this area. Recently, the protein neutrophil gelatinase-associated lipocalin (NGAL) has been identified as a mediator of the apoptotic effect of isotretinoin on sebocytes. To establish further the clinical relevance of NGAL and to elucidate the factors that induce NGAL expression in sebocytes. Methods were developed to isolate and quantify skin-surface levels of NGAL from normal subjects and patients with acne undergoing treatment with isotretinoin. Patients with acne were found to have higher skin levels of NGAL compared with normal subjects. Studies in SEB-1 sebocytes indicate that NGAL expression is increased in response to Propionibacterium acnes and interleukin (IL)-1β. In patients, isotretinoin increases NGAL levels by 2·4-fold on the skin surface and this increase precedes decreases in sebum and P. acnes counts. These data support the hypothesis that NGAL is an important mediator of the early effects of isotretinoin on the sebaceous glands and provide insights into the mechanisms that regulate NGAL expression in the skin.

Metabolic Changes in Skin Caused by Scd1 Deficiency: A Focus on Retinol Metabolism

We previously reported that mice with skin-specific deletion of stearoyl-CoA desaturase-1 (Scd1) recapitulated the skin phenotype and hypermetabolism observed in mice with a whole-body deletion of Scd1. In this study, we first performed a diet-induced obesity experiment at thermoneutral temperature (33°C) and found that skin-specific Scd1 knockout (SKO) mice still remain resistant to obesity. To elucidate the metabolic changes in the skin that contribute to the obesity resistance and skin phenotype, we performed microarray analysis of skin gene expression in male SKO and control mice fed a standard rodent diet. We identified an extraordinary number of differentially expressed genes that support the previously documented histological observations of sebaceous gland hypoplasia, inflammation and epidermal hyperplasia in SKO mice. Additionally, transcript levels were reduced in skin of SKO mice for genes involved in fatty acid synthesis, elongation and desaturation, which may be attributed to decreased abundance of key transcription factors including SREBP1c, ChREBP and LXRα. Conversely, genes involved in cholesterol synthesis were increased, suggesting an imbalance between skin fatty acid and cholesterol synthesis. Unexpectedly, we observed a robust elevation in skin retinol, retinoic acid and retinoic acid-induced genes in SKO mice. Furthermore, SEB-1 sebocytes treated with retinol and SCD inhibitor also display an elevation in retinoic acid-induced genes. These results highlight the importance of monounsaturated fatty acid synthesis for maintaining retinol homeostasis and point to disturbed retinol metabolism as a novel contributor to the Scd1 deficiency-induced skin phenotype.

Histone H4 Is a Major Component of the Antimicrobial Action of Human Sebocytes

Antimicrobial peptides, such as cathelicidin and beta defensins, directly kill microbes and have been detected in human sebaceous glands and cell lines. Despite the presence of several such peptides, the apparent abundance of these is insufficient for direct killing of most skin pathogens. In this study, we sought to determine which molecules provide the majority of antimicrobial peptide activity in human sebocytes. Acid-soluble protein extracts of SEB-1 sebocytes were separated by reverse-phase high-performance liquid chromatography and were assayed for their capacity to inhibit the growth of Staphylococcus aureus. Antimicrobial activity was isolated in a single major fraction and identified to be histone H4 by mass spectrometry and western blot analysis. The importance of histone H4 in the antimicrobial activity of sebocytes was confirmed by a specific neutralizing antibody and by direct demonstration that recombinant histone H4 had antimicrobial activity against S. aureus and Propionibacterium acnes. In addition, histone H4 enhanced the antimicrobial action of free fatty acids in human sebum. Taken together, these results indicate that the release of histone H4 by holocrine secretion from the sebaceous gland may play an important role in innate immunity.

IGF-1 Induces SREBP-1 Expression and Lipogenesis in SEB-1 Sebocytes via Activation of the Phosphoinositide 3-Kinase/Akt Pathway

Understanding the factors that regulate sebum production is important in identifying therapeutic targets for acne therapy. Insulin and IGF-1 stimulate sebaceous gland lipogenesis. IGF-1 increases expression of sterol response element-binding protein-1 (SREBP-1), a transcription factor that regulates numerous genes involved in lipid biosynthesis. SREBP-1 expression, in turn, stimulates lipogenesis in sebocytes. The goal of this study was to identify the intracellular signaling pathway(s) that transduces the lipogenic signal initiated by IGF-1. Sebocytes were treated with IGF-1 and assayed for activation of the phosphoinositide 3-kinase (PI3-K) pathway and of the three major arms of the mitogen-activated protein kinase (MAPK) pathway (MAPK/extracellular signal-regulated kinase (ERK), p38 MAPK, and stress-activated protein kinase/c-Jun-N terminal kinase). IGF-1 activated the MAPK/ERK and PI-3K pathways. Using specific inhibitors of each pathway, we found that the increase in expression of SREBP-1 induced by IGF-1 was blocked in the presence of the PI3-K inhibitor but not in the presence of the MAPK/ERK inhibitor. Furthermore, inhibition of the PI3-K pathway also blocked the IGF-1-induced transcription of SREBP target genes and sebocyte lipogenesis. These data indicate that IGF-1 transmits its lipogenic signal in sebocytes through activation of Akt. Specific targeted interruption of this pathway in the sebaceous gland could be a desirable approach to reducing sebum production and improving acne.

Neutrophil gelatinase–associated lipocalin mediates 13-cis retinoic acid–induced apoptosis of human sebaceous gland cells

13-cis retinoic acid (13-cis RA; also known as isotretinoin) is the most potent agent available for treatment of acne. It is known that the drug induces apoptosis in cells cultured from human sebaceous glands, but its mechanism of action has not been determined. In this study, skin biopsies were taken from 7 patients with acne prior to and at 1 week of treatment with 13-cis RA. TUNEL staining confirmed that 13-cis RA induced apoptosis in sebaceous glands. Transcriptional profiling of patient skin and cultured human sebaceous gland cells (SEB-1 sebocytes) indicated that lipocalin 2 was among the genes most highly upregulated by 13-cis RA. Lipocalin 2 encodes neutrophil gelatinase-associated lipocalin (NGAL), which functions in innate immune defense and induces apoptosis of murine B lymphocytes. Increased immunolocalization of NGAL was noted in patients' sebaceous glands following treatment with 13-cis RA, and recombinant NGAL induced apoptosis in SEB-1 sebocytes. Furthermore, apoptosis in response to 13-cis RA was inhibited in the presence of siRNA to lipocalin 2. These data indicate that NGAL mediates the apoptotic effect of 13-cis RA and suggest that agents that selectively induce NGAL expression in sebaceous glands might represent therapeutic alternatives to the use of 13-cis RA to treat individuals with acne.

Thematic review series: Skin Lipids. Sebaceous gland lipids: friend or foe?

Sebaceous glands are intriguing glands that are found throughout the human body except on the palms of the hands and soles of the feet. The true function of these glands has yet to be determined, but there are several theories, including antioxidant effects, antibacterial effects, and transport of pheromones. Sebaceous glands produce lipids that are involved in the pathogenesis of one of the most prevalent diseases of adolescence, acne. Although the majority of lipids produced by the sebaceous gland are also produced in other areas of the body, there are two that are characteristic of the sebaceous gland, wax esters and squalene. This review seeks to present an update on the physiology of the sebaceous glands, with particular emphasis on the production of sebaceous lipids.

13-cis Retinoic Acid Induces Apoptosis and Cell Cycle Arrest in Human SEB-1 Sebocytes

Isotretinoin (13-cis retinoic acid (13-cis RA)) is the most potent inhibitor of sebum production, a key component in the pathophysiology of acne, yet its mechanism of action remains largely unknown. The effects of 13-cis RA, 9-cis retinoic acid (9-cis RA), and all-trans retinoic acid (ATRA) on cell proliferation, apoptosis, and cell cycle proteins were examined in SEB-1 sebocytes and keratinocytes. 13-cis RA causes significant dose-dependent and time-dependent decreases in viable SEB-1 sebocytes. A portion of this decrease can be attributed to cell cycle arrest as evidenced by decreased DNA synthesis, increased p21 protein expression, and decreased cyclin D1. Although not previously demonstrated in sebocytes, we report that 13-cis RA induces apoptosis in SEB-1 sebocytes as shown by increased Annexin V-FITC staining, increased TUNEL staining, and increased cleaved caspase 3 protein. Furthermore, the ability of 13-cis RA to induce apoptosis cannot be recapitulated by 9-cis RA or ATRA, and it is not inhibited by the presence of a retinoid acid receptor (RAR) pan-antagonist AGN 193109. Taken together these data indicate that 13-cis RA causes cell cycle arrest and induces apoptosis in SEB-1 sebocytes by a RAR-independent mechanism, which contributes to its sebosuppressive effect and the resolution of acne.

Peroxisome Proliferator-Activated Receptors Increase Human Sebum Production

Sebum production is key in the pathophysiology of acne, an extremely common condition, which when severe, may require treatment with isotretinoin, a known teratogen. Apart from isotretinoin and hormonal therapy, no agents are available to reduce sebum. Increasing our understanding of the regulation of sebum production is a milestone in identifying alternative therapeutic targets. Studies in sebocytes and human sebaceous glands indicate that agonists of peroxisome proliferator-activated receptors (PPARs) alter sebaceous lipid production. The goal of this study is to verify the expression and activity of PPARs in human skin and SEB-1 sebocytes and to assess the effects of PPAR ligands on sebum production in patients. To investigate the contribution of each receptor subtype to sebum production, lipogenesis assays were performed in SEB-1 sebocytes that were treated with PPAR ligands and isotretinoin. Isotretinoin significantly decreased lipogenesis, while the PPARalpha agonist-GW7647, PPARdelta agonist-GW0742, PPARalpha/delta agonist-GW2433, PPARgamma agonist rosiglitazone, and the pan-agonist-GW4148, increased lipogenesis. Patients treated with thiazolidinediones or fibrates had significant increases in sebum production (37 and 77%, respectively) when compared to age-, disease-, and sex-matched controls. These data indicate that PPARs play a role in regulating sebum production and that selective modulation of their activity may represent a novel therapeutic strategy for the treatment of acne.

Human Skin is a Steroidogenic Tissue: Steroidogenic Enzymes and Cofactors Are Expressed in Epidermis, Normal Sebocytes, and an Immortalized Sebocyte Cell Line (SEB-1)

Although the human sebaceous gland can synthesize cholesterol from acetate and can further metabolize steroids such as dehydroepiandrosterone into potent androgens, the de novo production of steroids from cholesterol has not been demonstrated in human skin. The goal of this study was to delineate the steroidogenic pathway upstream from dehydroepiandrosterone by documenting the presence of members of the P450 side chain cleavage system (P450scc). This system catalyzes the initial step in steroid hormone synthesis following translocation of cholesterol to the inner mitochondrial membrane. In concert with its cofactors, adrenodoxin and adrenodoxin reductase, and the transcription factor steroidogenic factor 1, P450scc converts cholesterol to pregnenolone. An SV40 immortalized human sebaceous gland cell line (SEB-1) was established in order to facilitate investigation of the P450scc system. The sebaceous phenotype of SEB-1 sebocytes was confirmed using immunohistochemistry, Oil Red O staining, and gene array expression analysis. Presence of P450scc, adrenodoxin reductase, cytochrome P450 17-hydroxylase (P450c17), and steroidogenic factor 1 was documented in human facial skin, human sebocytes, and SEB-1 sebocytes. Using immunohistochemistry, antibodies to the above proteins localized to epidermis, hair follicles, sebaceous ducts, and sebaceous glands in sections of facial skin. Results of immunohistochemistry were confirmed with Western blotting. Biochemical activity of cytochrome P450scc and P450c17 was demonstrated in SEB-1 sebocytes using radioimmunoassay. The relative abundance of mRNA for P450scc, P450c17, and steroidogenic factor 1 in SEB-1 sebocytes and sebaceous glands was compared to mRNA levels in ovarian theca and granulosa cells using real-time quantitative polymerase chain reaction. Gene array expression analysis and quantitative polymerase chain reaction indicated that mRNA for P450scc is more abundant than mRNA for both P450c17 and steroidogenic factor 1 in sebaceous glands and SEB-1 cells. These data demonstrate that the skin is in fact a steroidogenic tissue. The clinical significance of this finding in mediating androgenic skin disorders such as acne, hirsutism, or androgenetic alopecia remains to be established.