Impact of para -phenylenediamine on cyclooxygenases expression and prostaglandin formation in human immortalized keratinocytes (HaCaT)

• Published in: Toxicology (Amsterdam) 2008-07, Vol.249 (2), p.167-175
• Main Authors: Moeller, Ruth, Lichter, Jutta, Blömeke, Brunhilde
• Format: Article
• Language: English
• Subjects: Acetylation; Acetylcysteine - pharmacology; Arachidonic Acid - metabolism; Bandrowski's base (BB); Biological and medical sciences; Cell Line; COX-2; Cyclooxygenase (COX-1; Cyclooxygenase 1 - biosynthesis; Cyclooxygenase 2 - biosynthesis; Dinoprost - biosynthesis; Dinoprostone - biosynthesis; Emergency; Enzyme-Linked Immunosorbent Assay; Free Radical Scavengers - pharmacology; Gene Expression - drug effects; Human immortalized keratinocytes (HaCaT); Humans; Indicators and Reagents; Keratinocytes - metabolism; Medical sciences; para-Phenylenediamine (PPD); Phenylenediamines - pharmacology; Phospholipases A2 - biosynthesis; Phospholipases A2 - genetics; Prostaglandin-Endoperoxide Synthases - biosynthesis; Prostaglandins - biosynthesis; Reactive oxygen species (ROS); Reverse Transcriptase Polymerase Chain Reaction; RNA - biosynthesis; RNA - isolation & purification; Toxicology
• ISSN: 0300-483X; 1879-3185
• DOI: 10.1016/j.tox.2008.05.002

Abstract para -Phenylenediamine, a monocyclic arylamine, is a frequently used chemical and ingredient of oxidative hair coloring products. Thus exposure occurs predominantly via skin. Cyclooxygenases, the key enzymes in prostaglandin synthesis, exhibit manifold physiological and pathophysiologial functions in skin and skin cells such as keratinocytes. We studied if para -phenylenediamine impacts on the expression of enzymes in the cyclooxygenase pathway in human immortalized keratinocytes (HaCaT) as a model for keratinocytes. We analyzed COX-1 , COX-2 and cPLA2 steady state mRNA levels for 100–400 μM PPD after 2–24 h and found clear COX-2 induction for 400 μM PPD after 24 h, while cPLA2 and COX-1 levels were increased dose-dependently between 8 and 24 h. Increased expression was accompanied by enhanced prostaglandin E2 and F2α formation. Specific involvement of COX enzymes was confirmed by prostaglandin analysis in the presence of exogenous arachidonic acid and inhibition experiments using COX inhibitor NS-398. In addition, para -phenylenediamine-induced prostaglandin formation was completely inhibited in cells pre-stimulated with the anti-oxidant N -acetylcysteine. N -acetylation of PPD was observed in HaCaT yielding mono-acetyl-PPD (MAPPD) and di-acetyl-PPD (DAPPD). Further investigations of MAPPD and DAPPD and the generated auto-oxidation product Bandrowski's base (BB) found that these compounds were not able to impact on COX enzyme expression and activity. In sum, these results demonstrate that para -phenylenediamine, but not its generated acetylated derivatives or BB, induces COX expression and activity in human keratinocytes likely via oxidative processes.