Depigmentation: What’s New (For Professionals)

Depigmentation: What’s New (For Professionals)

Introduction

• Hydroquinone in its monobenzyl form for is toxic.
• Triluma ® brings nothing new: it is so old that depigmentation creams are available as a generic and as a combinable prescription.
• What is new is ebselen ®.

Ebselen ®

• inhibition of transfer of melanocytes
• proven by cultures and HMB45 (melanin in melanosomes) on melanoderm.
• proven experimentally by treating guinea pigs for 12 days on the ears:
• quantity of melanin proven by quantitative spectrophotometry, immunohistochemistry (HMB45), fontana masson stain and electronic microscopy.
• 30% of quantititive decrease when compared with control groups.
• culture of melanocytes in a membrane of melanocytes and keratinocytes. In the membrane, contact between melanocytes and keratinocytes can be seen=result=inhibition from 200 to 135 in the content of melanosomes by ebselen (30%).
• with the help of kinesin, the melanosome fixes itself to actin=how does ebselen work?=melanosomes are normally attached to actin for their migration in the melanocyte:

1. By marking: HMB45 is distributed where the actin filaments are distributes (linear appearance).
2. Ebselen enables the melanosome to detach itself from actin.
3. the melanosome is therefore imprisonned within the melanocyte and cannot be transfered to the neighbouring keratinocytes.

The depigmenting effect of retinaldehyde (ystheal, diacneal, diroseal, eluage):

• study on B16 melanocytes: at an equal concentration, retinaldehyde is much more depigmenting than retinoic acid.
• also observed in the epidermis of the guinea pig.
• retinaldehyde is not melanotoxic (DOPA, TUNEL shows no increases apoptosis of melanocytes, nor on electronic microscopy)
• to summarize, retinaldehyde does not intervene in the synthesis or maturation of the melanosome in CD44 knockout mice, there is no thickening or depigmentation in CD44 knockout mice. Therefore, the effect of retinoids is through the action on Cd44: Role de CD44 dans la pigmentation.

Source of information: HMDP visiting expert Professor JH Saurat -Singapore – January 2010