Expression of bleomycin hydrolase in keratinization disorders

Area of Science:

• Dermatology
• Biochemistry
• Molecular Biology

Background:

• Bleomycin hydrolase (BH) is a neutral cysteine protease abundant in skin.
• BH expression is regulated by differentiation and cytokines.
• Its role in keratinization disorders remains unclear.

Purpose of the Study:

• Investigate the role of BH in human skin keratinization disorders.
• Compare BH expression with other serine and cysteine proteases in normal and lesional skin.
• Elucidate BH's potential involvement in epidermal differentiation.

Main Methods:

• Immunohistochemical analysis of BH, caspase-14, calpain I, kallikrein 5, and kallikrein 7.
• Study of normal human skin and lesional skin from various keratinization disorders.
• Semi-quantification of protease-positive staining intensity.

Main Results:

• BH-positive cells were found in granular layers of orthokeratotic/hyperkeratotic skin diseases.
• BH staining decreased in parakeratotic skin diseases (porokeratosis, pityriasis rubra pilaris, psoriasis).
• Similar patterns observed for caspase-14 and calpain I; kallikreins 5 and 7 increased in parakeratotic/inflammatory conditions.

Conclusions:

• BH expression is altered in keratinization disorders, particularly decreased in parakeratotic types.
• BH, a major citrulline aminopeptidase, may significantly impact epidermal terminal differentiation.
• BH likely plays a crucial role in the late stages of epidermal differentiation.