Modulation of the pro-inflammatory cytokines and matrix metalloproteinases production in co-cultivated human keratinocytes and melanocytes

Dangerous liaisons: Loss of keratinocyte control over melanocytes in melanomagenesis

Melanomas arise from transformed melanocytes, positioned at the dermal-epidermal junction in the basal layer of the epidermis. Melanocytes are completely surrounded by keratinocyte neighbors, with which they communicate through direct contact and paracrine signaling to maintain normal growth control and homeostasis. UV radiation from sunlight reshapes this communication network to drive a protective tanning response. However, repeated rounds of sun exposure result in accumulation of mutations in melanocytes that have been considered as primary drivers of melanoma initiation and progression. It is now clear that mutations in melanocytes are not sufficient to drive tumor formation-the tumor environment plays a critical role. This review focuses on changes in melanocyte-keratinocyte communication that contribute to melanoma initiation and progression, with a particular focus on recent mechanistic insights that lay a foundation for developing new ways to intercept melanoma development.

[Penetration capacity and local anti-inflammatory effect of a methyl salicylate gel with turpentine essence, camphor, and menthol for the symptomatic local treatment of muscular and joint pains]

Introduction

Oral non-steroidal anti-inflammatory drugs (NSAIDs) are effective in managing musculoskeletal pain, but often are associated with side effects. Therefore, topical anti-inflammatory drugs are considered a suitable alternative for certain patients.

Objective

To determine the skin penetration capacity and anti-inflammatory efficacy of a methyl salicylate gel (MS) with turpentine essence, camphor and menthol (GelSMETAM).

Methods

Human skin explants were used (three biological replicates with 3 technical replicates each were performed). To assess penetration capacity, methyl salicylate (MS) levels were quantified at different intervals using liquid chromatography with tandem mass spectrometry (LC-MS/MS). For the anti-inflammatory effect, the gene expression of major pro-inflammatory factors was quantified 30 minutes, 8 hours, and 12 hours after an impact; comparing GelSMETAM application with untreated controls.

Results

The results showed that approximately 0.8% of the total applied methyl salicylate penetrated the skin with a time-dependent concentration increase. The anti-inflammatory effect demonstrated a significant reduction in the gene expression of TNFα, IL1α, IL6, IL8, and NFKβ at 30 minutes (between -39% and -53.6% compared to control), which was maintained at 8 hours except for TNFα (between -59% and -92.6%) and persisted even at 12 hours (-69.4%) for IL1α.

Conclusion

The results support the hypothesis that GelSMETAM provides an effective and prolonged anti-inflammatory response, positioning it as a suitable option for the management of musculoskeletal pain.

Human cutaneous interfollicular melanocytes differentiate temporarily under genotoxic stress

DNA-damage response of cutaneous interfollicular melanocytes to fractionated radiotherapy was investigated by immunostaining of tissue sections from punch biopsies collected before, during, and after the treatment of patients for breast cancer. Our clinical assay with sterilized hair follicles, excluded the migration of immature melanocytes from the bulge, and highlighted interfollicular melanocytes as an autonomous self-renewing population. About thirty percent are immature. Surrounding keratinocytes induced and maintained melanocyte differentiation as long as treatment was ongoing. Concomitant with differentiation, melanocytes were protected from apoptosis by transient upregulation of Bcl-2 and CXCR2. CXCR2 upregulation also indicated the instigation of premature senescence, preventing proliferation. The stem cell factor BMI1 was constitutively expressed exclusively in interfollicular melanocytes and further upregulated upon irradiation. BMI1 prevents apoptosis, terminal differentiation, and premature senescence, allowing dedifferentiation post-treatment, by suppressing the p53/p21-and p16-mediated response and upregulating CXCR2 to genotoxic damage. The pre-treatment immature subset of interfollicular melanocytes was restored after the exposure ended.

Alpha-Synuclein and Its Role in Melanocytes

Pigmentation is an important process in skin physiology and skin diseases and presumably also plays a role in Parkinson’s disease (PD). In PD, alpha-Synuclein (aSyn) has been shown to be involved in the pigmentation of neurons. The presynaptic protein is intensively investigated for its pathological role in PD, but its physiological function remains unknown. We hypothesized that aSyn is both involved in melanocytic differentiation and melanosome trafficking processes. We detected a strong expression of aSyn in human epidermal melanocytes (NHEMs) and observed its regulation in melanocytic differentiation via the microphthalmia-associated transcription factor (MITF), a central regulator of differentiation. Moreover, we investigated its role in pigmentation by performing siRNA experiments but found no effect on the total melanin content. We discovered a localization of aSyn to melanosomes, and further analysis of aSyn knockdown revealed an important role in melanocytic morphology and a reduction in melanosome release. Additionally, we found a reduction of transferred melanosomes in co-culture experiments of melanocytes and keratinocytes but no complete inhibition of melanosome transmission. In summary, this study highlights a novel physiological role of aSyn in melanocytic morphology and its so far unknown function in the pigment secretion in melanocytes.

Advanced glycation end products alter the m6A-modified RNA profiles in human dermal fibroblasts

Background: To explore advanced glycation end products (AGEs)-induced m⁶A modification in fibroblasts and its potential role in photoaging. Methods: We studied m⁶A modification in AGEs-bovine serum albumin-treated fibroblasts with m⁶A-mRNA & lncRNA epitranscriptomic microarray and bioinformatics analysis. The m⁶A modification level was also investigated in skin samples. Results: m⁶A methylation microarray analysis revealed m⁶A modification profiles in AGEs-treated fibroblasts. Gene ontology, Kyoto Encyclopedia of Genes and Genomes, protein-protein interaction and competing endogenous RNA network analysis indicated that the genes of differentially methylated mRNAs and lncRNAs were mainly related to inflammation processes. We also found that AGEs-bovine serum albumin dose-dependently increased the m⁶A level and METTL14 expression in both fibroblasts and sun-exposed skin. Conclusion: Our study provided novel information regarding alterations of m⁶A modifications in AGEs-induced dermal fibroblasts and potential targets for treatment of photoaging.

Increased expression of Toll-like receptor 7 and 9 in vitiligo melanocytes: a pilot study

BACKGROUND

Toll-like receptors (TLRs) are expressed on human melanocytes, and play an important role in innate and acquired immunity. The role of TLRs in the pathogenesis of vitiligo has not been fully described.

AIM

To investigate the expression of TLRs in melanocytes from patients with vitiligo and healthy controls (HCs).

METHODS

Primary cultured vitiligo and control melanocytes were obtained from perilesional normal skin of patients with generalized vitiligo and HCs. TLRs mRNA expression in melanocytes were determined by real-time reverse transcription PCR and protein expression by western blotting. Apoptosis was analysed using an annexin V-fluorescein isothiocyanate apoptosis detection kit, and tyrosinase activity and melanin content were measured by a modified dopachrome and colorimetric method. Interleukin (IL)-6, IL-8 and soluble cell adhesion molecule (sICAM)-1 expression were measured by ELISA.

RESULTS

In vitiligo melanocytes, compared with control melanocytes, apoptosis rate, expression of TLR7 and TLR9 mRNA and protein, and production of IL-8, IL-6 and sICAM-1 were significantly increased, whereas tyrosinase activity and melanin content were significantly decreased.

CONCLUSIONS

Our results suggest that the increased expression of TLR7 and TLR9 might correlate with melanocyte dysfunction in vitiligo.

Low-dose radiations derived from cone-beam CT induce transient DNA damage and persistent inflammatory reactions in stem cells from deciduous teeth

OBJECTIVES

Cone-beam CT (CBCT), a radiographic tool for diagnosis, treatment, and follow-up in dental practice, was introduced also in pediatric radiology, especially orthodontics. Such patients subjected to repetitive X-rays examinations may receive substantial levels of radiation doses. Ionizing radiation (IR), a recognized carcinogenic factor causing DNA double-strand breaks (DSBs) could be harmful to undifferentiated cells such as dental pulp stem cells (DPSCs) since inaccurately repaired or unrepaired DSBs may lead to malignant transformation. The H2AX and MRE11 proteins generated following DSBs formation and pro-inflammatory cytokines (CKs) secreted after irradiation are relevant candidates to monitor the cellular responses induced by CBCT.

METHODS

DPSCs were extracted from human exfoliated deciduous teeth and their phenotype was assessed by immunocytochemistry and flow-cytometry. Cells were exposed to IR doses: 5.4-107.7 mGy, corresponding to 0.5-8 consecutive skull exposures, respectively. H2AX and MRE11 were detected in whole cells, while IL-1α, IL-6, IL-8, TNFα in supernatants, using enzyme-linked immunosorbent assay (ELISA) at different time points after exposure.

RESULTS

The phosphorylation level of H2AX in DPSCs increased considerably at 0.5 h after exposure (p < 0.001 for 3, 5, 8 skull exposures and p < 0.05 for 1 skull exposure, respectively). MRE11 response could only be detected for the highest IR dose (p < 0.001) in the same interval. CKs secretion increased upon CBCT exposure according to doses and time.

CONCLUSIONS

The DPSCs exposure to CBCT induces transient DNA damage and persistent inflammatory reaction in DPSCs drawing the attention on the potential risks of IR exposures and on the importance of dose monitoring in pediatric population.

Paracrine regulation of melanogenesis

Melanocytes are generally characterized by the basic ability of melanin synthesis and transfer to adjacent keratinocytes. This constitutes an individual skin phenotype and provides epidermal protection from various stimuli, such as ultraviolet irradiation, through a complex process called melanogenesis, which can be regulated by autocrine or paracrine factors. Recent evidence has revealed the paracrine effects of keratinocytes on melanogenesis by secreting cytokines, including α-melanocyte stimulating hormone and endothelin-1. In addition to keratinocytes, there are other types of cells in the skin, such as fibroblasts and immune cells, which are also actively involved in the regulation of melanocyte behaviour through the production of paracrine factors. In addition, extracellular matrix proteins, which are secreted mainly by skin-resident cells, not only play direct roles in regulating melanocyte morphology and functions but also provide structural support between the epidermis and dermis to control the distribution of various secreted cytokines from keratinocytes and/or fibroblasts, which are potentially involved in the regulation of melanogenesis. Moreover, understanding the origin of melanocytes (neural crest cells) and the presence of nerve endings in the epidermis can reveal the intimate contact between melanocytes and cutaneous specific nervous system proteins. Melanocytes are associated with all these networks with corresponding receptors expressed on the cell surface. In this review, we provide an overview of recent advances in determining the intimate relationships between melanocytes and their surrounding elements, which provide insights into the complex nature of the regulation of melanogenesis.