Transforming growth factor-β and psoriasis: a new link

Genome-wide DNA methylation of Munro's microabscess reveals the epigenetic regulation in the pathogenesis of psoriasis

Introduction

Munro's microabscess is a typical pathological feature in the early psoriatic lesion, mainly characterized by the accumulation of neutrophils in the epidermis. DNA methylation microenvironment of Munro's microabscess and the crosstalk with transcription and its effect on neutrophils have not yet been revealed.

Methods

Performed genome-wide DNA methylation analysis and further differential methylation analysis of psoriatic skin lesions with and without Munro's microabscess from two batch samples consisting of 114 former samples in the discovery stage and 21 newly-collected samples in the validation stage. Utilized GO, MEME, and other tools to conduct downstream analysis on differentially methylated sites (DMSs). Correlation analysis of methylation level and transcriptome data was also conducted.

Results

We observed 647 overlapping DMSs associated with Munro's microabscess. Subsequently, GO pathway analysis revealed that DNA methylation might affect the physical properties associated with skin cells through focal adhesion and cellsubstrate junction and was likely to recruit neutrophils in the epidermis. Via the MEME tool, used to investigate the possible binding transcription factors (TFs) of 20 motifs around the 647 DMSs, it was found that DNA methylation regulated the binding of AP1 family members and the recruitment of neutrophils in the epidermis through the TGF-beta pathway and the TH17 pathway. Meanwhile, combined with our earlier transcriptome data, we found DNA methylation would regulate the expressions of CFDP, SIRT6, SMG6, TRAPPC9, HSD17B7, and KIAA0415, indicating these genes would potentially promote the process of Munro's microabscess.

Discussion

In conclusion, DNA methylation may affect the course of psoriasis by regulating the progression of Munro's microabscess in psoriatic skin lesions.

Apremilast interferes with the TGFβ1-induced transition of human skin fibroblasts into profibrotic myofibroblasts: in vitro study

OBJECTIVES

Fibroblast-to-myofibroblast transition and extracellular matrix overproduction represent progressive events in chronic inflammatory and fibrotic diseases, in which TGFβ1 is one of the key mediators. Phosphodiesterase 4 (PDE4) acts as a proinflammatory enzyme through the degradation of cyclic adenosine monophosphate and it is overexpressed in skin fibroblasts. The study investigated how apremilast (a PDE4 inhibitor) interferes with the intracellular signalling pathways responsible for the TGFβ1-induced fibroblast-to-myofibroblast transition and profibrotic extracellular matrix protein synthesis.

METHODS

Cultured human skin fibroblasts were stimulated with TGFβ1 (10 ng/ml) alone or combined with apremilast (1 and 10 μM) for 4, 16 and 24 h. Other aliquots of the same cells were previously stimulated with TGFβ1 and then treated with apremilast (1 and 10 μM) for 4, 16 and 24 h, always under stimulation with TGFβ1. Gene and protein expression of αSMA, type I collagen (COL1) and fibronectin were evaluated, together with the activation of small mothers against decapentaplegic 2 and 3 (Smad2/3) and extracellular signal-regulated kinase (Erk1/2) proteins.

RESULTS

Apremilast reduced the TGFβ1-induced increase in αSMA, COL1 and fibronectin gene expression at 4 and 16 h, and protein synthesis at 24 h of treatment in cultured fibroblasts, even for cells already differentiated into myofibroblasts by way of a previous stimulation with TGFβ1. Apremilast inhibited the TGFβ1-induced Smad2/3 and Erk1/2 phosphorylation at 15 and 30 min.

CONCLUSION

Apremilast seems to inhibit in vitro the fibroblast-to-myofibroblast transition and the profibrotic activity induced by TGFβ1 in cultured human skin fibroblasts by downregulating Smad2/3 and Erk1/2 intracellular signalling pathways.