Role of FGFR2-signaling in the pathogenesis of acne

Age, sex, and cell type-resolved hypothalamic gene expression across the pubertal transition in mice

BACKGROUND

The hypothalamus plays a central role in regulating puberty. However, our knowledge of the postnatal gene regulatory networks that control the pubertal transition in males and females is incomplete. Here, we investigate the age-, sex- and cell-type-specific gene regulation in the hypothalamus across the pubertal transition.

METHODS

We used RNA-seq to profile hypothalamic gene expression in male and female mice at five time points spanning the onset of puberty (postnatal days (PD) 12, 22, 27, 32, and 37). By combining this data with hypothalamic single nuclei RNA-seq data from pre- and postpubertal mice, we assigned gene expression changes to their most likely cell types of origin. In our colony, pubertal onset occurs earlier in male mice, allowing us to focus on genes whose expression is dynamic across ages and offset between sexes, and to explore the bases of sex effects.

RESULTS

Our age-by-sex pattern of expression enriched for biological pathways involved hormone production, neuronal activation, and glial maturation. Additionally, we inferred a robust expansion of oligodendrocytes precursor cells into mature oligodendrocytes spanning the prepubertal (PD12) to peri-pubertal (PD27) timepoints. Using spatial transcriptomic data from postpubertal mice, we observed the lateral hypothalamic area and zona incerta were the most oligodendrocyte-rich regions and that these cells expressed genes known to be involved in pubertal regulation.

CONCLUSION

Together, by incorporating multiple biological timepoints and using sex as a variable, we identified gene and cell-type changes that may participate in orchestrating the pubertal transition and provided a resource for future studies of postnatal hypothalamic gene regulation.

KGF-2 ameliorates UVB-triggered skin photodamage in mice by attenuating DNA damage and inflammatory response and mitochondrial dysfunction

BACKGROUND

Long-term exposure to UVB induces DNA damage, inflammatory response, mitochondrial dysfunction, and apoptosis in skin cells, thus causing skin photodamage. Research has demonstrated the noteworthy antioxidant, anti-inflammatory, DNA repair, and mitochondrial protective properties of keratinocyte growth factor-2 (KGF-2).

METHODS

To examine the impact of KGF-2 on UVB-triggered skin photodamage in mice, hair-removed mice were initially exposed under UVB radiation and subsequently treated with KGF-2 hydrogel and repeated for 6 days. On day 7, the assessment of histopathological alterations, inflammation, DNA damage, mitochondrial function, and apoptosis in mouse skin was assessed.

RESULTS

It was found that KGF-2 could effectively relieve cutaneous photodamage symptoms and inhibit epidermal proliferation in mice. Meanwhile, KGF-2 was found to significantly reduce DNA damage, attenuate the inflammatory response, and inhibit the mitochondria-mediated intrinsic apoptotic pathway in the UVB-exposed mouse skin photodamage model.

CONCLUSION

To summarize, our results indicated that KGF-2 reduces the severity of mouse skin photodamage caused by UVB rays by attenuating DNA damage and the inflammatory response, besides inhibiting the mitochondria-mediated intrinsic apoptosis pathway.

Acne Transcriptomics: Fundamentals of Acne Pathogenesis and Isotretinoin Treatment

This review on acne transcriptomics allows for deeper insights into the pathogenesis of acne and isotretinoin's mode of action. Puberty-induced insulin-like growth factor 1 (IGF-1), insulin and androgen signaling activate the kinase AKT and mechanistic target of rapamycin complex 1 (mTORC1). A Western diet (hyperglycemic carbohydrates and milk/dairy products) also co-stimulates AKT/mTORC1 signaling. The AKT-mediated phosphorylation of nuclear FoxO1 and FoxO3 results in their extrusion into the cytoplasm, a critical switch which enhances the transactivation of lipogenic and proinflammatory transcription factors, including androgen receptor (AR), sterol regulatory element-binding transcription factor 1 (SREBF1), peroxisome proliferator-activated receptor γ (PPARγ) and signal transducer and activator of transcription 3 (STAT3), but reduces the FoxO1-dependent expression of GATA binding protein 6 (GATA6), the key transcription factor for infundibular keratinocyte homeostasis. The AKT-mediated phosphorylation of the p53-binding protein MDM2 promotes the degradation of p53. In contrast, isotretinoin enhances the expression of p53, FoxO1 and FoxO3 in the sebaceous glands of acne patients. The overexpression of these proapoptotic transcription factors explains isotretinoin's desirable sebum-suppressive effect via the induction of sebocyte apoptosis and the depletion of BLIMP1(+) sebocyte progenitor cells; it also explains its adverse effects, including teratogenicity (neural crest cell apoptosis), a reduced ovarian reserve (granulosa cell apoptosis), the risk of depression (the apoptosis of hypothalamic neurons), VLDL hyperlipidemia, intracranial hypertension and dry skin.

Hyaluronic acid-FGF2-derived peptide bioconjugates for suppression of FGFR2 and AR simultaneously as an acne antagonist

Acne is a chronic skin condition that has serious consequences for mental and social well-being because it frequently occurs on the face. Several acne treatment approaches have commonly been used but have been hampered by side effects or weak activity. Thus, the investigation of the safety and efficacy of anti-acne compounds is of considerable medical importance. Herein, an endogenous peptide (P5) derived from fibroblast growth factors 2 (FGF2) was conjugated to the polysaccharide hyaluronic acid (HA) to generate the bioconjugate nanoparticle HA-P5, which suppresses fibroblast growth factor receptors (FGFRs) to significantly rehabilitate acne lesions and reduce sebum accumulation in vivo and in vitro. Moreover, our results show that HA-P5 inhibits both fibroblast growth factor receptor 2 (FGFR2) and androgen receptor (AR) signalling in SZ95 cells, reverses the acne-prone transcriptome, and decreases sebum secretion. Furthermore, the cosuppression mechanism revealed that HA-P5 blocks FGFR2 activation, as well as the YTH N6-methyladenosine RNA binding protein F3 (YTHDF3) downstream molecules, including an N6-methyladenosine (m6A) reader that facilitates AR translation. More importantly, a significant difference between HA-P5 and the commercial FGFR inhibitor AZD4547 is that HA-P5 does not trigger the overexpression of aldo-keto reductase family 1 member C3 (AKR1C3), which blocks acne treatment by catalyzing the synthesis of testosterone. Overall, we demonstrate that a polysaccharide-conjugated and naturally derived oligopeptide HA-P5 can alleviate acne and act as an optimal FGFR2 inhibitor and reveal that YTHDF3 plays a crucial role in signalling between FGFR2 and AR.

Botulinum Neurotoxin Type A Directly Affects Sebocytes and Modulates Oleic Acid-Induced Lipogenesis

Excess sebum (seborrhea) results in oily skin and is associated with large pore size and acne. Studies in healthy, seborrheic volunteers have reported that intradermal injection of commercial preparations of botulinum neurotoxin type A (BoNT/A) (onabotulinumtoxinA, abobotulinumtoxinA, and incobotulinumtoxinA) reduced sebum production, and thus, skin oiliness and pore size. The mechanism for these effects has not been fully elucidated; however, several theories involving direct or indirect effects of BoNT/A on neuronal and/or dermal cells (e.g., sebocytes) have been proposed. In the present study, we evaluated the direct effect of native research grade BoNT/A complex, a commercial preparation of BoNT/A (onabotA), and BoNT/A variants on sebocyte lipogenesis using an in vitro sebocyte cell model. We show that picomolar concentrations of BoNT/A (BoNT/A complex: half maximal effective concentration [EC₅₀] = 24 pM; BoNT/A 150 kDa: EC₅₀ = 34 pM) modulate sebocyte lipogenesis and reduce oleic acid-induced sebocyte differentiation, lipogenesis, and holocrine-like secretion. Comparative studies with the binding domain of BoNT/A, which lacks enzymatic activity, show that this effect is independent of the enzymatic activity of BoNT/A and likely occurs via sebocyte cell surface receptors (e.g., fibroblast growth factor receptors). Overall, these results shed light on the potential mechanism of action and rationale for use of BoNT/A for treatment of sebum-related conditions.

Hidradenitis Suppurativa: A Perspective on Genetic Factors Involved in the Disease

Hidradenitis Suppurativa (HS) is a chronic inflammatory skin disease of the pilosebaceous unit, clinically consisting of painful nodules, abscesses, and sinus tracts mostly in, but not limited to, intertriginous skin areas. HS can be defined as a complex skin disease with multifactorial etiologies, including-among others-genetic, immunologic, epigenetic, and environmental factors. Based on genetic heterogeneity and complexity, three different forms can be recognized and considered separately as sporadic, familial, and syndromic. To date, several genetic variants associated to disease susceptibility, disease-onset, and/or treatment response have been reported; some of these reside in genes encoding the gamma-secretase subunits whereas others involve autoinflammatory and/or keratinization genes. The aim of this perspective work is to provide an overview of the contribution of several genetic studies encompassing family linkage analyses, target candidate gene studies, and -omic studies in this field. In our viewpoint, we discuss the role of genetics in Hidradenitis suppurativa considering findings based on Sanger sequencing as well as the more recent Next Generation Sequencing (i.e., exome sequencing or RNA Sequencing) with the aim of better understanding the etio-pathogenesis of the disease as well as identifying novel therapeutic strategies.

Acne Syndromes and Mosaicism

Abnormal mosaicism is the coexistence of cells with at least two genotypes, by the time of birth, in an individual derived from a single zygote, which leads to a disease phenotype. Somatic mosaicism can be further categorized into segmental mosaicism and nonsegmental somatic mosaicism. Acne is a chronic illness characterized by inflammatory changes around and in the pilosebaceous units, commonly due to hormone- and inflammatory signaling-mediated factors. Several systemic disorders, such as congenital adrenal hyperplasia, polycystic ovarian syndrome, and seborrhoea-acne-hirsutism-androgenetic alopecia syndrome have classically been associated with acne. Autoinflammatory syndromes, including PAPA, PASH, PAPASH, PsAPASH, PsaPSASH, PASS, and SAPHO syndromes include acneiform lesions as a key manifestation. Mosaic germline mutations in the FGFR2 gene have been associated with Apert syndrome and nevus comedonicus, two illnesses that are accompanied by acneiform lesions. In this review, we summarize the concept of cutaneous mosaicism and elaborate on acne syndromes, as well as acneiform mosaicism.

2b or Not 2b: How Opposing FGF Receptor Splice Variants Are Blocking Progress in Precision Oncology

More than ten thousand peer-reviewed studies have assessed the role of fibroblast growth factors (FGFs) and their receptors (FGFRs) in cancer, but few patients have yet benefited from drugs targeting this molecular family. Strategizing how best to use FGFR-targeted drugs is complicated by multiple variables, including RNA splicing events that alter the affinity of ligands for FGFRs and hence change the outcomes of stromal-epithelial interactions. The effects of splicing are most relevant to FGFR2; expression of the FGFR2b splice isoform can restore apoptotic sensitivity to cancer cells, whereas switching to FGFR2c may drive tumor progression by triggering epithelial-mesenchymal transition. The differentiating and regulatory actions of wild-type FGFR2b contrast with the proliferative actions of FGFR1 and FGFR3, and may be converted to mitogenicity either by splice switching or by silencing of tumor suppressor genes such as CDH1 or PTEN. Exclusive use of small-molecule pan-FGFR inhibitors may thus cause nonselective blockade of FGFR2 isoforms with opposing actions, undermining the rationale of FGFR2 drug targeting. This splice-dependent ability of FGFR2 to switch between tumor-suppressing and -driving functions highlights an unmet oncologic need for isoform-specific drug targeting, e.g., by antibody inhibition of ligand-FGFR2c binding, as well as for more nuanced molecular pathology prediction of FGFR2 actions in different stromal-tumor contexts.

A strategic review on the involvement of receptors, transcription factors and hormones in acne pathogenesis

Acne vulgaris is a very common pilosebaceous inflammatory disease occurring primarily on the face and also rare on the upper arms, trunk, and back, which is caused by Propionibacterium, Staphylococcus, Corynebacterium, and other species. Pathophysiology of acne comprises of irregular keratinocyte proliferation, differentiation, increased sebum output, bacterial antigens and cytokines induced inflammatory response. Treatment of acne requires proper knowledge on the pathophysiology then only the clinician can come out with a proper therapeutic dosage regimen. Understanding the pathophysiology not only includes the mechanism but also involvement of receptors. Thus, this review is framed in such a way that the authors have focused on the disease acne vulgaris, pathophysiology, transcription factors viz. the Forkhead Box O1 (FoxO1) Transcription Factor, hormones like androgens and receptors such as Histamine receptors, Retinoic receptor, Fibroblast growth factor receptors, Toll like receptor, Androgen receptor, Liver X-receptor, Melanocortin receptor, Peroxisome proliferator-activated receptor and epidermal growth factor receptors involvement in the progression of acne vulgaris.

An Integrated Approach to Unravel Hidradenitis Suppurativa Etiopathogenesis

Hidradenitis suppurativa/acne inversa (HS) is a chronic inflammatory disease involving hair follicles that presents with painful nodules, abscesses, fistulae, and hypertrophic scars, typically occurring in apocrine gland bearing skin. Establishing a diagnosis of HS may take up to 7 years after disease onset. HS severely impairs the quality of life of patients and its high frequency causes significant costs for health care system. HS patients have an increased risk of developing associated diseases, such as inflammatory bowel diseases and spondyloarthropathies, thereby suggesting a common pathophysiological mechanism. Familial cases, which are around 35% of HS patients, have allowed the identification of susceptibility genes. HS is perceived as a complex disease where environmental factors trigger chronic inflammation in the skin of genetically predisposed individuals. Despite the efforts made to understand HS etiopathogenesis, the exact mechanisms at the basis of the disease need to be still unraveled. In this review, we considered all OMICs studies performed on HS and observed that OMICs contribution in the context of HS appeared as not clear enough and/or rich of useful clinical information. Indeed, most studies focused only on one aspect—genome, transcriptome, or proteome—of the disease, enrolling small numbers of patients. This is quite limiting for the genetic studies, from different geographical areas and looking at a few aspects of HS pathogenesis without any integration of the findings obtained or a comparison among different studies. A strong need for an integrated approach using OMICs tools is required to discover novel actors involved in HS etiopathogenesis. Moreover, we suggest the constitution of consortia to enroll a higher number of patients to be analyzed following common and consensus OMICs strategies. Comparison and integration with the findings present in the OMICs repositories are mandatory. In a theoretic pipeline, the Skin-OMICs profile obtained from each HS patient should be compared and integrated with repositories and literature data by using appropriate InterOMICs approach. The final goal is not only to improve the knowledge of HS etiopathogenesis but also to provide novel tools to the clinicians with the eventual aim of offering a tailored treatment for HS patients.

Androgens modulate keratinocyte differentiation indirectly through enhancing growth factor production from dermal fibroblasts

BACKGROUND

The main pathogenesis of acne vulgaris is increase in sebum production and abnormal keratinization of the hair infundibulum. The androgens are involved in acne pathogenesis by modulating sebaceous glands to enhance sebum production. However, the molecular mechanisms of abnormal keratinization of the hair infundibulum are not fully elucidated.

OBJECTIVE

We hypothesized that the androgens affect the dermal fibroblasts, another androgen receptor-positive cells in the skin, resulting in abnormal keratinization through keratinocyte-fibroblast interaction.

METHODS

We investigated effects of androgens and estrogens on growth factors expressions by RT-PCR and western blot analysis in human fibroblast (hFB), human keratinocyte (hKC), and fibroblast-keratinocyte co-culture. In vivo, we examined the growth factor expression in acne lesions compared to normal hair follicles by laser-assisted confocal microscope.

RESULTS

In vitro, androgens but not estrogens significantly increased amphiregulin (AREG), epiregulin (EREG), fibroblast growth factor (FGF) 10, and insulin-like growth factor binding protein (IGFBP) 5 mRNA and protein expressions in human fibroblasts but not in keratinocytes. In vivo, AREG, EREG, FGF10, and IGFBP5 were more abundant in acne lesion compared to normal facial skin. FGF10 suppressed cytokeratin 1 and cytokeratin 10 expression in hKC, which was along with the decreased ratio of cytokeratin 10 against cytokeratin 14 in acne lesions compared to normal facial skin. Also, DHT suppressed cytokeratin 1 and cytokeratin 10, in fibroblast-keratinocyte co-culture similarly to the effect of FGF10 to hKC.

CONCLUSION

These observations suggested that androgens enhance growth factors production from dermal fibroblasts, and growth factors from fibroblasts alter keratinocyte differentiation in acne lesion.

Acne and nutrition: hypotheses, myths and facts

Acne is an inflammatory and multifactorial skin disease. Different external and internal factors, including air pollution, aggressive skincare products, medication, mechanical, hormonal and familial factors and, more recently, lifestyle and stress, have been suggested as having an impact on acne. Moreover, for many years nutrition was believed to cause or worsen acne. Over the last decades, however, it has become a dermatological doctrine that there is no direct association between diet and acne. Even if recent research has allowed to identify certain nutritional elements and behaviour that may impact on acne, including the excessive intake of dairy products and hyperglycaemic food, modern lifestyle nutrition, obesity and eating disorders, knowledge about the role of nutrition in the physiopathology of acne still remains sparse and hypotheses and myths continue to dominate the debate. Thus, further clinical and translational research is necessary to investigate and confirm the association between nutrition and acne.

Genetic architecture of acne vulgaris

Acne vulgaris is a ubiquitary skin disease characterized by chronic inflammation of the pilosebaceous unit resulting from bacterial colonization of hair follicles by Propionibacterium acnes, androgen-induced increased sebum production, altered keratinization and inflammation. Here, we review our current understanding of the genetic architecture of this intriguing disease. We analysed genomewide association studies (GWAS) and candidate genes studies for acne vulgaris. Moreover, we included GWAS studies for the associated disease polycystic ovary syndrome (PCOS). Overall, the available data revealed sixteen genetic loci flagged by single nucleotide polymorphisms (SNPs), none of which has been confirmed yet by independent studies. Moreover, a GWAS for PCOS identified 21 susceptible loci. The genetic architecture is complex which has been revealed by GWAS. Further and larger studies in different populations are required to confirm or disprove results from candidate gene studies as well to identify signals that may overlap between different populations. Finally, studies on rare genetic variants in acne and associated diseases like PCOS may deepen our understanding of its pathogenesis.

Fibroblast Growth Factor Receptor 2 (FGFR2) Is Required for Meibomian Gland Homeostasis in the Adult Mouse

Purpose

Little is known about the signaling mechanisms controlling meibomian gland (MG) homeostasis and the pathogenic processes leading to MG atrophy and dysfunction in dry eye disease (DED). We investigated the role of fibroblast growth factor receptor 2 (FGFR2) in the MG homeostasis of adult mice.

Methods

A triple transgenic mouse strain (Krt14-rtTA; tetO-Cre; Fgfr2flox/flox), referred to as Fgfr2CKO mice, was generated in which the Fgfr2 gene is ablated by Cre recombinase in keratin 14 (Krt14)-expressing epithelial cells on doxycycline (Dox) induction. FGFR2 expression in normal human and mouse MGs was evaluated by immunohistochemistry. Pathologic MG changes in transgenic mice with conditional deletion of FGFR2 were examined by lipid staining, histology, and immunostaining.

Results

FGFR2 was highly expressed in normal human MGs and adult mouse MGs. Two-month-old Fgfr2CKO mice fed Dox-containing chow for 2 weeks developed severe MG atrophy. MG acinar atrophy in the Fgfr2CKO mice was associated with reduced lipid (meibum) production and the development of clinical findings similar to those in humans with evaporative DED related to MG dysfunction (MGD). Immunohistochemical analyses showed that FGFR2 deletion severely affected proliferation and differentiation of MG acinar cells but affected MG ductal cells to a lesser extent.

Conclusions

FGFR2 deletion results in significant MG acinar atrophy and clinical manifestations of MGD in Fgfr2CKO mice, suggesting that MG homeostasis is FGFR2 dependent. The Fgfr2CKO mice with inducible MG atrophy can serve as a valuable animal model for investigating the pathogenesis of MGD and developing novel therapeutic strategies for MGD-related DED.

Generalized Comedones, Acne, and Hidradenitis Suppurativa in a Patient with an FGFR2 Missense Mutation

Mutations in the fibroblast growth factor-receptor gene 2 (FGFR2) gene have been implicated in numerous diseases, including nevus comedonicus (NC) and naevoid acne that have somatic missense mutations in FGFR2 in the affected tissue. A patient presented in our department with unusual, innumerable large comedones throughout his back reminiscient of NC, as well as multifocal hidradenitis suppurativa and acne. Topical and systemic treatments were unsuccessful. Whole exome sequencing of blood-derived DNA detected a germline mutation in FGFR2 that was predicted to be damaging. This could explain the multifocal and severe nature of the disease. We suggest screening other, phenotypically similar patients for FGFR2 mutations. Our findings, once confirmed independently, could indicate that therapeutic modulation of FGFR signaling in the acne tetrad could be effective.

Beyond acne: Current aspects of sebaceous gland biology and function

The sebaceous gland is most commonly found in association with a hair follicle. Its traditional function is the holocrine production of sebum, a complex mixture of lipids, cell debris, and other rather poorly characterized substances. Due to the gland's central role in acne pathogenesis, early research had focused on its lipogenic activity. Less studied aspects of the sebaceous gland, such as stem cell biology, the regulation of cellular differentiation by transcription factors, the significance of specific lipid fractions, the endocrine and specially the neuroendocrine role of the sebaceous gland, and its contribution to the innate immunity, the detoxification of the skin, and skin aging have only recently attracted the attention of researchers from different disciplines. Here, we summarize recent multidisciplinary progress in sebaceous gland research and discuss how sebaceous gland research may stimulate the development of novel therapeutic strategies targeting specific molecular pathways of the pathogenesis of skin diseases.

Photodynamic therapy inhibit Fibroblast Growth Factor-10 induced keratinocyte differentiation and proliferation through ROS in Fibroblast Growth Factor Receptor-2b pathway

5-aminolevulinic acid-photodynamic therapy (ALA-PDT) is known to be effective in several skin diseases such as acne, actinic keratoses, condyloma acuminata. However, some detailed mechanisms of ALA-PDT to treat these skin diseases still remain elusive. In this study, we aimed to investigate mechanism of ALA-PDT in in-vitro and in-vivo models. For in vitro, we use human keratinocyte cell line (HaCaT) cells. CCK-8 was used to detect cell proliferation activity, immunofluorescence and western blotting method to detect the content of keratin (K)1, K6, K16, protein kinase C (PKC), fibroblast growth factor receptor-2b (FGFR2b) protein, ELISA and RT-PCR to detect expression of interleukin (IL) 1α in the cell supernatant, and detect reactive oxygen species (ROS). For in vivo, we use 20 rabbits to induce hyperkeratosis acne model in their ear. Dermatoscope was used to see follicle hyperkeratosis and skin biopsy to analyze histology and immunohistochemical of PKC, FGFR2b, K1, K6 and K16. Results from this study suggest that ROS stimulated by ALA-PDT lead to inhibition of FGFR2b pathway in PKC downstream to cause reduction of IL1α expression, and eventually, keratinocytes differentiation and proliferation. Our data thus reveal a treatment mechanism of ALA-PDT underlying hyperkeratosis related dermatoses.

Genetic research and structural dysplasia assessment of anorectal malformations in neonatal male rats induced by di(n-butyl) phthalate

This study was the first to investigate the genetic abnormalities and structural dysplasia of anorectal malformations (ARMs) in male rats induced by di(n-butyl) phthalate (DBP). DBP was administered to timed-pregnant rats to establish the ARM rat model. The incidence of ARMs in male offspring was 39.5%. In neonatal period, decreased body weight and anogenital distance were observed. The general image and histological analysis of male offspring confirmed the presence of ARMs. Anatomical examination of the ARM male rats revealed the dysplasia in solid organs (heart-lung, liver, spleen, and kidney). The decreases of serum testosterone concentration and androgen receptor expression in terminal rectum were indicative of the antiandrogenic effects of DBP. Moreover, significant decreased mRNA expressions of these androgen-related genes such as sonic hedgehog, Gli2, Gli3, bone morphogenetic protein 4, Wnt5a, Hoxa13, Hoxd13, fibroblast growth factor 10, and fibroblast growth factor receptor 2 were found in terminal rectum of the ARM male pubs. These results demonstrated that development of ARM rats was impaired by maternal exposure to DBP. The antiandrogenic effects of DBP disturbing the androgen-related signaling networks might play an important role in the occurrence of ARMs.

Linking diet to acne metabolomics, inflammation, and comedogenesis: an update

Acne vulgaris, an epidemic inflammatory skin disease of adolescence, is closely related to Western diet. Three major food classes that promote acne are: 1) hyperglycemic carbohydrates, 2) milk and dairy products, 3) saturated fats including trans-fats and deficient ω-3 polyunsaturated fatty acids (PUFAs). Diet-induced insulin/insulin-like growth factor (IGF-1)-signaling is superimposed on elevated IGF-1 levels during puberty, thereby unmasking the impact of aberrant nutrigenomics on sebaceous gland homeostasis. Western diet provides abundant branched-chain amino acids (BCAAs), glutamine, and palmitic acid. Insulin and IGF-1 suppress the activity of the metabolic transcription factor forkhead box O1 (FoxO1). Insulin, IGF-1, BCAAs, glutamine, and palmitate activate the nutrient-sensitive kinase mechanistic target of rapamycin complex 1 (mTORC1), the key regulator of anabolism and lipogenesis. FoxO1 is a negative coregulator of androgen receptor, peroxisome proliferator-activated receptor-γ (PPARγ), liver X receptor-α, and sterol response element binding protein-1c (SREBP-1c), crucial transcription factors of sebaceous lipogenesis. mTORC1 stimulates the expression of PPARγ and SREBP-1c, promoting sebum production. SREBP-1c upregulates stearoyl-CoA- and Δ6-desaturase, enhancing the proportion of monounsaturated fatty acids in sebum triglycerides. Diet-mediated aberrations in sebum quantity (hyperseborrhea) and composition (dysseborrhea) promote Propionibacterium acnes overgrowth and biofilm formation with overexpression of the virulence factor triglyceride lipase increasing follicular levels of free palmitate and oleate. Free palmitate functions as a "danger signal," stimulating toll-like receptor-2-mediated inflammasome activation with interleukin-1β release, Th17 differentiation, and interleukin-17-mediated keratinocyte proliferation. Oleate stimulates P. acnes adhesion, keratinocyte proliferation, and comedogenesis via interleukin-1α release. Thus, diet-induced metabolomic alterations promote the visible sebofollicular inflammasomopathy acne vulgaris. Nutrition therapy of acne has to increase FoxO1 and to attenuate mTORC1/SREBP-1c signaling. Patients should balance total calorie uptake and restrict refined carbohydrates, milk, dairy protein supplements, saturated fats, and trans-fats. A paleolithic-like diet enriched in vegetables and fish is recommended. Plant-derived mTORC1 inhibitors and ω-3-PUFAs are promising dietary supplements supporting nutrition therapy of acne vulgaris.

Epidermal nevus syndromes

The term epidermal nevus syndrome (ENS) has been used to describe the association of epidermal hamartomas and extracutaneous abnormalities. Although many continue to use the term "ENS," it is now understood that this is not one disease, but rather a heterogeneous group with distinct genetic profiles defined by a common cutaneous phenotype: the presence of epidermal and adnexal hamartomas that are associated with other organ system involvement. One commonality is that epidermal nevi often follow the lines of Blaschko and it appears the more widespread the cutaneous manifestations, the greater the risk for extracutaneous manifestations. The majority of the extracutaneous manifestations involve the brain, eye, and skeletal systems. The CNS involvement is wide ranging and involves both clinical manifestations such as intellectual disability and seizures, as well as structural anomalies. Several subsets of ENS with characteristic features have been delineated including the nevus sebaceus syndrome, Proteus syndrome, CHILD syndrome, Becker's nevus syndrome, nevus comedonicus syndrome, and phakomatosis pigmentokeratotica. Advances in molecular biology have revealed that the manifestations of ENS are due to genomic mosaicism. It is likely that the varied clinical manifestations of ENS are due in great part to the functional effects of specific genetic defects. Optimal management of the patient with ENS involves an interdisciplinary approach given the potential for multisystem involvement. Of note, epidermal nevi have been associated with both benign and malignant neoplasms, and thus ongoing clinical follow-up is required.

New perspectives on antiacne plant drugs: contribution to modern therapeutics

Acne is a common but serious skin disease, which affects approximately 80% adolescents and young adults in 11-30 age group. 42.5% of men and 50.9% of women continue to suffer from this disease into their twenties. Bacterial resistance is now at the alarming stage due to the irrational use of antibiotics. Hence, search for new lead molecule/bioactive and rational delivery of the existing drug (for better therapeutic effect) to the site of action is the need of the hour. Plants and plant-derived products have been an integral part of health care system since time immemorial. Therefore, plants that are currently used for the treatment of acne and those with a high potential are summarized in the present review. Most active plant extracts, namely, P. granatum, M. alba, A. anomala, and M. aquifolium exhibit minimum inhibitory concentration (MIC) in the range of 4-50 µg/mL against P. acnes, while aromatic oils of C. obovoides, C. natsudaidai, C. japonica, and C. nardus possess MICs 0.005-0.6 μL/mL and phytomolecules such as rhodomyrtone, pulsaquinone, hydropulsaquinone, honokiol, magnolol, xanthohumol lupulones, chebulagic acid and rhinacanthin-C show MIC in the range of 0.5-12.5 μg/mL. Novel drug delivery strategies of important plant leads in the treatment of acne have also been discussed.

Acne as a chronic systemic disease

Acne is the most common skin disorder. In the majority of cases, acne is a disease that changes its skin distribution and severity over time; moreover, it can be a physically (scar development) and psychologically damaging condition that lasts for years. According to its clinical characteristics, it can be defined as a chronic disease according to the World Health Organization criteria. Acne is also a cardinal component of many systemic diseases or syndromes, such as congenital adrenal hyperplasia, seborrhea-acne-hirsutism-androgenetic alopecia syndrome, polycystic ovarian syndrome, hyperandrogenism-insulin resistance-acanthosis nigricans syndrome, Apert syndrome, synovitis-acne-pustulosis-hyperostosis-osteitis syndrome, and pyogenic arthritis-pyoderma gangrenosum-acne syndrome. Recent studies on the Ache hunter gatherers of Paraguay detected the lack of acne in association with markedly lower rates of obesity, diabetes mellitus, hyperlipidemia, and cardiovascular diseases, a finding that indicates either a nutritional or a genetic background of this impressive concomitance.

[Uncommon acne-associated syndromes and their significance in understanding the pathogenesis of acne]

Acne is an intriguing model for the study of interactions between hormones, innate immunity, inflammation and wound healing (scarring). The manifestations and involvement of acne in different systemic diseases and some rare syndromes demonstrate its multifaceted nature. Synovitis-Acne-Pustulosis-Hyperostosis-Osteitis (SAPHO) and Pyogenic Arthritis-Pyoderma gangrenosum-Acne (PAPA) syndromes, both regarded as autoinflammatory diseases, highlight the attributes of inflammation in acne. While SAPHO syndrome can be used to explore the pathogenic role of Propionibacterium acnes in acne, PAPA syndrome and Apert syndrome can help understand the genetic influence on acne. The genetic defects in the gain-of-function of FGFR2 mutations in Apert syndrome and acne nevus of Munro lend further support to the hypothesis that the interaction of forkhead box class O (FoxOs)-mediated transcriptional regulation with androgen receptor transactivation and insulin/insulin like growth factor-1(IGF-1)-signaling is crucial in acne pathogenesis. Novel biologics, such as tumor necrosis factor (TNF) blockers and IL-1 inhibitors, appear promising in opposing the inflammation associated with SAPHO and PAPA syndromes, but it remains to seen if they can also improve severe acne particularly in the long term.

The molecular and cellular basis of Apert syndrome

Apert syndrome (AS) is a rare genetic and congenital disease characterized by craniosynostosis and syndactly of hands and feet. AS patients generally require lifelong management, however there are still no effective treatment methods except surgery. In recent years, research has made great progress in the pathogenesis of AS. FGFR2 mediates extracellular signals into cells and the mutations in the FGFR2 gene cause AS occurrence. Activated FGFs/FGFR2 signaling disrupt the balance of cell proliferation, differentiation and apoptosis via its downstream signal pathways. However, how the pathways transform the balance is not well understood and contradictions have occurred in different studies. In this review, we'll focus on these problems to get a better understanding of AS pathogenesis.

Mouse models of Apert syndrome

INTRODUCTION

Apert syndrome is one of the more clinically distinct craniosynostosis syndromes in man. It is caused by gain-of-function mutations in FGFR2, over 98% of which are the two amino acid substitution mutations S252W and P253R. FGFR2 is widely expressed throughout development, so that many tissues are adversely affected in Apert syndrome, particularly the calvarial bones, which begin to fuse during embryonic development, and the brain.

DISCUSSION

Mouse models of both of these two causative mutations and a third rare splice mutation have been created and display many of the phenotypes typical of Apert syndrome. The molecular and cellular mechanisms underlying Apert phenotypes have begun to be elucidated, and proof-of-principle treatment of these phenotypes by chemical inhibitor and gene-based therapies has been demonstrated.

The role of androgen and androgen receptor in skin-related disorders

Androgen and androgen receptor (AR) may play important roles in several skin-related diseases, such as androgenetic alopecia and acne vulgaris. Current treatments for these androgen/AR-involved diseases, which target the synthesis of androgens or prevent its binding to AR, can cause significant adverse side effects. Based on the recent studies using AR knockout mice, it has been suggested that AR and androgens play distinct roles in the skin pathogenesis, and AR seems to be a better target than androgens for the treatment of these skin diseases. Here, we review recent studies of androgen/AR roles in several skin-related disorders, including acne vulgaris, androgenetic alopecia and hirsutism, as well as cutaneous wound healing.

p38 Inhibition ameliorates skin and skull abnormalities in Fgfr2 Beare-Stevenson mice

Beare-Stevenson cutis gyrata syndrome (BSS) is a human genetic disorder characterized by skin and skull abnormalities. BSS is caused by mutations in the FGF receptor 2 (FGFR2), but the molecular mechanisms that induce skin and skull abnormalities are unclear. We developed a mouse model of BSS harboring a FGFR2 Y394C mutation and identified p38 MAPK as an important signaling pathway mediating these abnormalities. Fgfr2+/Y394C mice exhibited epidermal hyperplasia and premature closure of cranial sutures (craniosynostosis) due to abnormal cell proliferation and differentiation. We found ligand-independent phosphorylation of FGFR2 and activation of p38 signaling in mutant skin and calvarial tissues. Treating Fgfr2+/Y394C mice with a p38 kinase inhibitor attenuated skin abnormalities by reversing cell proliferation and differentiation to near normal levels. This study reveals the pleiotropic effects of the FGFR2 Y394C mutation evidenced by cutis gyrata, acanthosis nigricans, and craniosynostosis and provides a useful model for investigating the molecular mechanisms of skin and skull development. The demonstration of a pathogenic role for p38 activation may lead to the development of therapeutic strategies for BSS and related conditions, such as acanthosis nigricans or craniosynostosis.

Long-term effectiveness of dobesilate in the treatment of papulopustular rosacea

This case report is a representative example from a study directed to assess the long-term clinical benefit of dobesilate in rosacea in five enrolled papulopustular rosacea patients with several years of disease, treated topically with 5% potassium dobesilate cream for 3 weeks. The patient suffered papulopustular rosacea for more than 10 years, during which she received topical metronidazole and azelaic acid, and systemic doxycycline therapies without satisfactory improvement. Dobesilate treatment promoted improvement of rosacea symptoms and signs. Two years after treatment the patient still shows a good facial cosmesis.

Isotretinoin and FoxO1: A scientific hypothesis

Oral isotretinoin (13-cis retinoic acid) is the most effective drug in the treatment of acne and restores all major pathogenetic factors of acne vulgaris. isotretinoin is regarded as a prodrug which after isomerizisation to all-trans-retinoic acid (ATRA) induces apoptosis in cells cultured from human sebaceous glands, meibomian glands, neuroblastoma cells, hypothalamic cells, hippocampus cells, Dalton's lymphoma ascites cells, B16F-10 melanoma cells, and neuronal crest cells and others. By means of translational research this paper provides substantial indirect evidence for isotretinoin's mode of action by upregulation of forkhead box class O (FoxO) transcription factors. FoxOs play a pivotal role in the regulation of androgen receptor transactivation, insulin/insulin like growth factor-1 (IGF-1)-signaling, peroxisome proliferator-activated receptor-γ (PPArγ)- and liver X receptor-α (LXrα)-mediated lipogenesis, β-catenin signaling, cell proliferation, apoptosis, reactive oxygene homeostasis, innate and acquired immunity, stem cell homeostasis, as well as anti-cancer effects. An accumulating body of evidence suggests that the therapeutic, adverse, teratogenic and chemopreventive effecs of isotretinoin are all mediated by upregulation of FoxO-mediated gene transcription. These FoxO-driven transcriptional changes of the second response of retinoic acid receptor (RAR)-mediated signaling counterbalance gene expression of acne due to increased growth factor signaling with downregulated nuclear FoxO proteins. The proposed isotretinoin→ATRA→RAR→FoxO interaction offers intriguing new insights into the mode of isotretinoin action and explains most therapeutic, adverse and teratogenic effects of isotretinoin in the treatment of acne by a common mode of FoxO-mediated transcriptional regulation.

Studying the genetic predisposing factors in the pathogenesis of acne vulgaris

Acne is one of the most common dermatologic diseases in the developed regions of the world, affecting a large percentage of the population. Despite the great improvement in the number and quality of studies of the molecular etiology of this disease in the past 3 decades, the detailed molecular pathogenesis and the cause of the large individual variations in severity of skin symptoms remain unknown. The roles of genetic inheritance and special genetic susceptibility and protective factors have been suggested for over 100 years, but their identification and determination started only in the 1990s. To date, only a small number of genetic polymorphisms affecting the expression and/or function of a handful of genes have been investigated. This review surveys the major findings of the classic and molecular genetic studies that have been conducted in this field, draws conclusions, and indicates how the available data help our current understanding of the pathogenesis of this common skin disease.