The role of PPAR-gamma receptor in pruritus

Pruritogenic molecules in the skin of patients with dermatomyositis

Introduction

Pruritus is a common excruciating symptom in systemic autoimmune diseases such as dermatomyositis (DM) but the pathogenesis is not fully understood. We intended to investigate the targeted expression analysis of candidate molecules involved in the development of pruritus in lesional vs. non-lesional skin samples of patients affected with active DM. We looked for correlations between the investigated pruriceptive signaling molecules, disease activity, and itching sensation of DM patients.

Methods

Interleukins (IL-33 and IL-6), tumor necrosis factor α (TNF-α), peroxisome proliferator-activated receptor γ (PPAR-γ), and ion channels belonging to the transient receptor potential (TRP) family were analyzed. The expression of TNF-α, PPAR-γ, IL-33, IL-6, and TRP channels in lesional DM skin was evaluated by RT-qPCR and immunohistochemistry and was compared with non-lesional DM skin samples. Pruritus, disease activity, and damage of DM were evaluated by the 5-D itch scale and Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI), respectively. Statistical analysis was performed with IBM SPSS 28 software.

Results

A total of 17 active DM patients participated in the study. We could show that the itching score was positively correlated with the CDASI activity score (Kendall's tau-b = 0.571; p = 0.003). TNF-α gene expression was significantly higher in lesional DM skin than in non-lesional DM skin (p = 0.009) and differed in the subgroups of patients with different itch intensities (p = 0.038). The mRNA expression of lesional IL-6 correlated positively with 5-D itch and CDASI activity score (Kendall's tau-b = 0.585; p = 0.008 and 0.45; p = 0.013, respectively). TRPV4 expressions were positively correlated with CDASI damage score (Kendall's tau-b = 0.626; p < 0.001), but the mRNA expressions of the TRP family, PPAR-γ, IL-6, and IL-33 were not different in lesional and non-lesional samples. Immunohistochemistry analysis did not find significant alterations in the expressions of TNF-α, PPAR-γ, IL-6, and IL-33 in lesional and non-lesional regions.

Discussion

Our results argue that cutaneous disease activity, TNF-α, and IL-6 might play a central role in DM-associated itch, while TRPV4 plays a central role in tissue regeneration.

The mRNA Expression Profile of Psoriatic Lesion Distinct from Non-Lesion

Purpose

Psoriasis is a chronic recurring autoimmune skin disease with a complex etiology and chronic progression; however, its molecular mechanisms remain unclear.

Patients and Methods

We performed transcriptomic analysis to profile the mRNA expression of psoriatic lesions (PL) and non-lesion (NL) tissues from psoriasis patients along with normal skin from healthy donors. RT-qPCR was used to validate the mRNA expression profiles.

Results

A total of 237 differentially expressed genes were screened and identified by RNA sequencing. GO and KEGG analysis indicated that these DEGs were enriched in the PPAR signaling pathway and intermediate filament cytoskeleton. For PPAR signaling pathway, the expression of five genes, including ADIPOQ, AQP7, PLIN1, FABP4 and LPL, were all significantly decreased in psoriatic lesions compared to normal skin by RT-qPCR. There is a clear difference between psoriatic lesions and non-lesion in the expression of ADIPOQ, AQP7 and LPL. For intermediate filament cytoskeleton, including KRT27, KRT25, KRT71, KRT86 and KRT85 were significantly decreased in the psoriasis lesions, showing agreement with the RNA-seq data.

Conclusion

This study revealed a significant difference between the mRNA expression profiles of PL, NL tissue and normal skin.

Efficacy of a Topical Product Containing Purified Omental Lipids and Three Anti-Itching Compounds in the Treatment of Chronic Pruritus/Prurigo Nodularis in Elderly Subjects: A Prospective, Assessor-Blinded, 4-Week Trial with Transepidermal Water Loss and Optical Coherence Tomography Assessments

PURPOSE

To investigate the efficacy of a cream containing purified omental lipids 10% and three anti-itching substances (polidocanol/stimutex/palmitoylethanolamine) in elderly subjects with chronic pruritus/prurigo nodularis (CP/CPN).

PATIENTS AND METHODS

Thirty-five subjects (6 men; mean age 67±4 years) with CP/CPN were enrolled in a prospective, assessor-blinded, 4-week study. The cream was applied twice daily in the most affected body area. The primary endpoints were the evolution of the 10-cm visual analogue itch severity scale (VAS) and the 4-point verbal itching rating scale (VRS) (from 0 to 3). Secondary endpoints were the evolution of optical coherence tomography (OTC) of four skin parameters (acanthosis/hyperkeratosis/scale/dermal vascular pattern), assessed in a target lesioned area, and the transepidermal water loss (TEWL). Study endpoints were evaluated at baseline and after 2 and 4 weeks by an investigator unaware of the type of treatment.

RESULTS

All the enrolled subjects concluded the trial. At baseline, the mean±SD scores for VAS and VRS were 4.9±2.2 and 1.7±0.7, respectively. The treatment was associated with a significant reduction (p=0.0001) of VAS score of 60% at week 2 and of 86% at week 4. VRS score was significantly reduced by 49% after 2 weeks and by 81% after 4 weeks, in comparison with baseline. TEWL (expressed as g/m2/h) mean values were 18±5.4 at baseline and 12.7±4.4 at week 2 and 9.8±4.7 at week 4 (P=0.0001 vs baseline). All the OCT parameters evaluated improved during active treatment; acanthosis grade was 0.22 mm at baseline, 0.19 mm at week 2 and 0.17 mm at week 4 (p=0.0005), representing a 23% reduction in comparison with baseline. The product was very well tolerated.

CONCLUSION

This purified omental lipid with three anti-itching components cream reduces significantly itch intensity in subjects with chronic pruritus/prurigo nodularis, improving the skin barrier function and skin structure.

TRIAL NUMBER

ISRCTN869561669.