Decreased peroxisome proliferator-activated receptor γ level and signalling in sebaceous glands of patients with acne vulgaris

A review of skin immune processes in acne

Acne vulgaris is one of the most prevalent skin conditions, affecting almost all teenagers worldwide. Multiple factors, including the excessive production of sebum, dysbiosis of the skin microbiome, disruption of keratinization within hair follicles, and local inflammation, are believed to trigger or aggravate acne. Immune activity plays a crucial role in the pathogenesis of acne. Recent research has improved our understanding of the immunostimulatory functions of microorganisms, lipid mediators, and neuropeptides. Additionally, significant advances have been made in elucidating the intricate mechanisms through which cutaneous innate and adaptive immune cells perceive and transmit stimulatory signals and initiate immune responses. However, our understanding of precise temporal and spatial patterns of immune activity throughout various stages of acne development remains limited. This review provides a comprehensive overview of the current knowledge concerning the immune processes involved in the initiation and progression of acne. Furthermore, we highlight the significance of detailed spatiotemporal analyses, including analyses of temporal dynamics of immune cell populations as well as single-cell and spatial RNA sequencing, for the development of targeted therapeutic and prevention strategies.

Combination of Fractional Microneedling Radiofrequency and Ablative Fractional Laser versus Ablative Fractional Laser Alone for Acne and Acne Scars

PURPOSE

Fractional microneedle radiofrequency (FMR) systems are used to treat inflammatory acne and scarring. Nonetheless, few controlled studies have combined this treatment with the traditional ablative fractional laser (AFL). We aimed to assess the safety and efficacy of the combination of FMR and AFL versus AFL alone in treating acne and acne scars.

MATERIALS AND METHODS

In this 20-week, randomized, split-face study, 23 Korean patients with facial acne and acne scars underwent FMR and AFL treatments. One half of each patient's face was randomly assigned to receive FMR+AFL, whereas the other half received AFL alone. Treatments were administered in three consecutive sessions at 4-week intervals. This study investigated the severity of inflammatory acne, acne scars, individual lesion counts, depressed scar volumes, as well as patient and physician satisfaction. In addition, five patients underwent skin biopsy, and sebum output was measured.

RESULTS

The FMR+AFL treatment demonstrated superior efficacy compared to AFL alone in terms of inflammatory acne and acne scar grading, lesion counts, and subjective satisfaction. The side effects were minimal and well-tolerated in both groups. Immunohistochemical findings from skin biopsy samples revealed that the application of FMR+AFL could induce an inhibitory effect on sebum secretion at the molecular level.

CONCLUSION

FMR combined with AFL is a well-tolerated and effective treatment modality for inflammatory acne and acne scarring.

Sebaceous immunobiology - skin homeostasis, pathophysiology, coordination of innate immunity and inflammatory response and disease associations

This review presents several aspects of the innovative concept of sebaceous immunobiology, which summarizes the numerous activities of the sebaceous gland including its classical physiological and pathophysiological tasks, namely sebum production and the development of seborrhea and acne. Sebaceous lipids, which represent 90% of the skin surface lipids in adolescents and adults, are markedly involved in the skin barrier function and perifollicular and dermal innate immune processes, leading to inflammatory skin diseases. Innovative experimental techniques using stem cell and sebocyte models have clarified the roles of distinct stem cells in sebaceous gland physiology and sebocyte function control mechanisms. The sebaceous gland represents an integral part of the pilosebaceous unit and its status is connected to hair follicle morphogenesis. Interestingly, professional inflammatory cells contribute to sebocyte differentiation and homeostasis, whereas the regulation of sebaceous gland function by immune cells is antigen-independent. Inflammation is involved in the very earliest differentiation changes of the pilosebaceous unit in acne. Sebocytes behave as potent immune regulators, integrating into the innate immune responses of the skin. Expressing inflammatory mediators, sebocytes also contribute to the polarization of cutaneous T cells towards the Th17 phenotype. In addition, the immune response of the perifollicular infiltrate depends on factors produced by the sebaceous glands, mostly sebaceous lipids. Human sebocytes in vitro express functional pattern recognition receptors, which are likely to interact with bacteria in acne pathogenesis. Sex steroids, peroxisome proliferator-activated receptor ligands, neuropeptides, endocannabinoids and a selective apoptotic process contribute to a complex regulation of sebocyte-induced immunological reaction in numerous acquired and congenital skin diseases, including hair diseases and atopic dermatitis.

Efficacy and safety of N-acetyl-GED-0507-34-LEVO gel in patients with moderate-to severe facial acne vulgaris: a phase IIb randomized double-blind, vehicle-controlled trial

BACKGROUND

Preliminary in vitro and in vivo studies have supported the efficacy of the peroxisome proliferator-activated receptor-γ (PPARγ) modulator N-acetyl-GED-0507-34-LEVO (NAC-GED) for the treatment of acne-inducing sebocyte differentiation, improving sebum composition and controlling the inflammatory process.

OBJECTIVES

To evaluate the efficacy and safety of NAC-GED (5% and 2%) in patients with moderate-to-severe facial acne vulgaris.

METHODS

This double-blind phase II randomized controlled clinical trial was conducted at 36 sites in Germany, Italy and Poland. Patients aged 12-30 years with facial acne, an Investigator Global Assessment (IGA) score of 3-4, and an inflammatory and noninflammatory lesion count of 20-100 were randomized to topical application of the study drug (2% or 5%) or placebo (vehicle), once daily for 12 weeks. The co-primary efficacy endpoints were percentage change from baseline in total lesion count (TLC) and IGA success at week 12; the safety endpoints were adverse events (AEs) and serious AEs. This study was registered with EudraCT (2018-003307-19).

RESULTS

Between Q1 in 2019 and Q1 in 2020 450 patients [n = 418 (92·9%) IGA 3; n = 32 (7·1%) IGA 4] were randomly assigned to NAC-GED 5% (n = 150), NAC-GED 2% (n = 150) or vehicle (n = 150). The percentage change in TLC reduction was statistically significantly higher in both the NAC-GED 5% [-57·1%, 95% confidence interval (CI) -60·8 to -53·4; P < 0·001] and NAC-GED 2% (-44·7%, 95% CI -49·1 to -40·1; P < 0·001) groups compared with vehicle (-33·9%, 95% CI -37·6 to -30·2). A higher proportion of patients treated with NAC-GED 5% experienced IGA success (45%, 95% CI 38-53) vs. the vehicle group (24%, 95% CI 18-31; P < 0·001). The IGA success rate was 33% in the NAC-GED 2% group (P = not significant vs. vehicle). The percentage of patients who had one or more AEs was 19%, 16% and 19% in the NAC-GED 5%, NAC-GED 2% and vehicle groups, respectively.

CONCLUSIONS

The topical application of NAC-GED 5% reduced TLC, increased the IGA success rate and was safe for use in patients with acne vulgaris. Thus, NAC-GED, a new PPARγ modulator, showed an effective clinical response. What is already known about this topic? Acne vulgaris, one of the most common dermatological diseases, affects more than 85% of adolescents. There is a medical need for innovative and safe treatment of acne vulgaris. The peroxisome proliferator-activated receptor-γ (PPARγ) is involved in lipid metabolism and specifically in cell differentiation, sebum production and the inflammatory reaction. What does this study add? N-acetyl-GED-0507-34-LEVO (NAC-GED 5%), a PPARγ modulator, significantly improves acne manifestations in patients with moderate-to-severe acne and is safe and well tolerated. The results suggest that the PPARγ receptor is a novel therapeutic target for acne. The results provide a basis for a large phase III trial to assess the effectiveness and safety profile of NAC-GED in combating a disease that afflicts 80-90% of adolescents.

Ferredoxin reductase regulates proliferation, differentiation, cell cycle and lipogenesis but not apoptosis in SZ95 sebocytes

Ferredoxin reductase (FDXR), a mitochondrial membrane-associated flavoprotein, is essential for electron transfer and modulates p53-dependent apoptosis in cancer cells.FDXR may be implicated in epidermal and sebocytic differentiation, but its explicit function in sebocytes remains to be elucidated. In the present study, immunohistochemistry revealed that FDXR expression was increased in sebaceous cells of acne lesions. FDXR, PPARγ, LXRα/β, SREBP1 and Sox9 expression was incremental during sebocyte differentiation. FDXR overexpression induced by Ad-GFP-FDXR infection enhanced differentiation, reactive oxygen species (ROS), lipogenesis and PPARγ expression, and consequnently inhibited proliferation in SZ95 sebocytes. Flow cytometry showed that FDXR overexpression induced significant blockade of G2/M phase but had no effect on sub-G1 (apoptotic) sebocytes. Insulin-like growth factor-1 (IGF-1)-induced FDXR and PPARγ expression and lipogenesis were abolished by pretreatment with PI3K inhibitor LY294002. These results suggest that FDXR overexpression might promote differentiation and lipogenesis via ROS production and suppress proliferation via G2/S blockade in SZ95 sebocytes. IGF-1 could facilitate differentiation and lipogenesis through PI3K/Akt/FDXR pathway. FDXR could serve as a potential marker of advanced sebaceous differentiation, and its overexpression may be involved in the development of acne lesions.

Contribution of GATA6 to homeostasis of the human upper pilosebaceous unit and acne pathogenesis

Although acne is the most common human inflammatory skin disease, its pathogenic mechanisms remain incompletely understood. Here we show that GATA6, which is expressed in the upper pilosebaceous unit of normal human skin, is down-regulated in acne. GATA6 controls keratinocyte proliferation and differentiation to prevent hyperkeratinisation of the infundibulum, which is the primary pathological event in acne. When overexpressed in immortalised human sebocytes, GATA6 triggers a junctional zone and sebaceous differentiation program whilst limiting lipid production and cell proliferation. It modulates the immunological repertoire of sebocytes, notably by upregulating PD-L1 and IL10. GATA6 expression contributes to the therapeutic effect of retinoic acid, the main treatment for acne. In a human sebaceous organoid model GATA6-mediated down-regulation of the infundibular differentiation program is mediated by induction of TGFβ signalling. We conclude that GATA6 is involved in regulation of the upper pilosebaceous unit and may be an actionable target in the treatment of acne.

PPAR-γ signalling as a key mediator of human hair follicle physiology and pathology

Peroxisome proliferator-activated receptors (PPARs) are abundantly expressed in human skin, with PPAR-γ being the most intensively investigated isoform. In various ex vivo and in vivo models, PPAR-γ-mediated signalling has recently surfaced as an essential element of hair follicle (HF) development, growth and stem cell biology. Moreover, the availability of novel, topically applicable PPAR-γ modulators with a favourable toxicological profile has extended the range of potential applications in clinical dermatology. In this review, we synthesize where this field currently stands and sketch promising future research avenues, focussing on the role of PPAR-γ-mediated signalling in the biology and pathology of human scalp HFs, with special emphasis on scarring alopecias such as lichen planopilaris and frontal fibrosing alopecia as model human epithelial stem cell diseases. In particular, we discuss whether and how pharmacological modulation of PPAR-γ signalling may be employed for the management of hair growth disorders, for example, in scarring alopecia (by reducing HF inflammation as well as by promoting the survival and suppressing pathological epithelial-mesenchymal transition of keratin 15 + epithelial stem cells in the bulge) and in hirsutism/hypertrichosis (by promoting catagen development). Moreover, we explore the potential role of PPAR-γ in androgenetic alopecia, HF energy metabolism and HF ageing, and consider clinical perspectives that emanate from the limited data available on this so far. As this field of translational human hair research is still in its infancy, many open questions exist, for which we briefly delineate selected experimental approaches that promise to generate instructive answers in the near future.

Effects of Intradermal Radiofrequency Treatment and Intense Pulsed Light Therapy in an Acne-induced Rabbit Ear Model

Acne vulgaris is a common condition that can have psychologically deleterious effects. Since current treatments carry the risks of antibiotic resistance or teratogenicity, novel treatment modalities are under investigation. Our study investigated the efficacy of intradermal radiofrequency treatment (RF) and intense pulsed light (IPL) in the treatment of acne vulgaris in a rabbit ear model. We evaluated the effectiveness of IPL, RF, and a combination treatment on cultured Cuticobacterium acnes strains in an induced rabbit ear model, according to clinical outcomes as well as histological and immunological approaches. We found that RF treatment markedly decreases papule volume, while IPL appears to have an immunomodulatory effect. In combination, the two have an additive effect in treatment. These findings suggest that combination of RF and IPL may be an effective therapeutic option for the treatment of acne vulgaris.

Update in the management of acne in adolescence

PURPOSE OF REVIEW

This review will update the pediatric provider on recent data on the pathogenesis and treatment of acne in adolescent patients. A special focus was made to summarize recent guidelines and fill in several identified practice gaps.

RECENT FINDINGS

Our understanding of the pathogenesis of acne is greatly expanding and data is emerging to tie diet, particularly the role of IGF-1 with inflammation in acne. Additionally, stronger recommendations to limit antibiotic usage in acne are being made worldwide. Although retinoids are considered the base of most effective acne treatment strategies, data suggests that all providers need to emphasize their importance in maintenance of acne.

SUMMARY

An effective acne management strategy targets multiple pathogenic factors in acne, using a retinoid as the foundation. Systemic antibiotics for moderate-to-severe acne should be used for acute management, then discontinued at 3-4 months, while maintaining on topical treatments. If therapy is ineffective, alternate treatments, such as combined oral contraceptives in females or isotretinoin, should be promptly employed to prevent prolonged psychological impact and cutaneous scarring.

Reduced adiponectin expression after high-fat diet is associated with selective up-regulation of ALDH1A1 and further retinoic acid receptor signaling in adipose tissue

Adiponectin is an adipocyte-derived adipokine with potent antidiabetic, anti-inflammatory, and antiatherogenic activity. Long-term, high-fat diet results in gain of body weight, adiposity, further inflammatory-based cardiovascular diseases, and reduced adiponectin secretion. Vitamin A derivatives/retinoids are involved in several of these processes, which mainly take place in white adipose tissue (WAT). In this study, we examined adiponectin expression as a function of dietary high-fat and high–vitamin A conditions in mice. A decrease of adiponectin expression in addition to an up-regulation of aldehyde dehydrogenase A1 (ALDH1A1), retinoid signaling, and retinoic acid response element signaling was selectively observed in WAT of mice fed a normal–vitamin A, high-fat diet. Reduced adiponectin expression in WAT was also observed in mice fed a high–vitamin A diet. Adipocyte cell culture revealed that endogenous and synthetic retinoic acid receptor (RAR)α- and RARγ-selective agonists, as well as a synthetic retinoid X receptor agonist, efficiently reduced adiponectin expression, whereas ALDH1A1 expression only increased with RAR agonists. We conclude that reduced adiponectin expression under high-fat dietary conditions is dependent on 1) increased ALDH1A1 expression in adipocytes, which does not increase all-trans-retinoic acid levels; 2) further RAR ligand–induced, WAT-selective, increased retinoic acid response element–mediated signaling; and 3) RAR ligand–dependent reduction of adiponectin expression.—Landrier, J.-F., Kasiri, E., Karkeni, E., Mihály, J., Béke, G., Weiss, K., Lucas, R., Aydemir, G., Salles, J., Walrand, S., de Lera, A. R., Rühl, R. Reduced adiponectin expression after high-fat diet is associated with selective up-regulation of ALDH1A1 and further retinoic acid receptor signaling in adipose tissue.