Differential expression of heparin‐binding EGF‐like growth factor (HB‐EGF) mRNA in normal human keratinocytes induced by a variety of natural and synthetic retinoids

Abstract

It was recently revealed that epidermal growth following topical treatment with all-trans retinoic acid (atRA) was at least partly induced by heparin-binding epidermal growth factor-like growth factor (HB-EGF) released from suprabasal keratinocytes. Since proliferation of keratinocytes appears to be one of the critical roles of atRA in depigmentation treatment and promotion of wound healing, HB-EGF is considered suitable for assessing the therapeutic value of topical retinoids. In this study, HB-EGF mRNA expression in normal human keratinocytes after atRA treatment was examined, and the effects of a variety of natural and synthetic retinoids were compared. The results of reverse transcription polymerase chain reaction (RT-PCR) suggested that induction of differentiation increased HB-EGF mRNA expression in cultured keratinocytes. Real-time PCR analyses revealed that HB-EGF mRNA expression was elevated dose-dependently with atRA, peaking at 12 h. This elevation was more prominent in confluent keratinocytes than in subconfluent cells, suggesting that differentiated keratinocytes are more subject to stimulation of HB-EGF expression by atRA than proliferating keratinocytes. HB-EGF mRNA was upregulated in differentiation-induced keratinocytes by all retinoids used in this study at 1 micromol/l, and marked upregulation was seen when treated with three isotypes of retinoic acid (atRA, and 9-cis and 13-cis retinoic acid). RARalpha-selective agonists (Am80, Am580, ER-38925, and TAC-101) and a panagonist of RARs (Re80) caused relatively low elevation of HB-EGF transcripts, as did all-trans retinol (Rol) and all-trans retinal (Ral). Although another panagonist (Ch55) showed the highest elevation of HB-EGF mRNA, it was relatively cytotoxic at the concentration employed. Ral and Rol were found to upregulate HB-EGF when used at 100 micromol/l to 1 mmol/l, to a similar extent of atRA at 1-10 micromol/l. The capacity of retinoids to upregulate HB-EGF may be an important index for investigation and development of an ideal synthetic retinoid, which has maximum benefits and minimum side-effects

Clinical Trial of Bleaching Treatment With 10% All-Trans Retinol Gel

“…In bleaching treatment with tretinoin and hydroquinone, we believe that the role of tretinoin is to wash melanin granules out of epidermis, whereas that of hydroquinone is to suppress strongly new melanin production 11,12 . Tretinoin induces exfoliation, and thus, it appears to also act as a penetration enhancer of hydroquinone.…”

“…However, because binding affinity to specific nuclear receptors (retinoic acid receptors; RARs) of ROL or RAL is far less than that of tretinoin, beneficial effects are also expected to be very moderate compared with tretinoin. Our previous study revealed that heparin‐binding epidermal growth factor‐like growth factor (HB‐EGF) mRNA, which plays a critical role in epidermal growth after retinoid treatment, 9,10 was upregulated by ROL or RAL to a similar extent as tretinoin, but only when ROL or RAL was used at 40 to 100 times higher concentration than tretinoin 11 . Because proliferation of keratinocytes and acceleration of epidermal turnover appear to be the two main mechanisms of accelerated melanin discharge by retinoids, 11,12 we consider that promotion of HB‐EGF mRNA expression may be used as an important index to evaluate the depigmenting ability of topical retinoids.…”

Regulation of keratin expression by retinoids

“…62,63 However, the role of RARα agonists as potent modulators of gene transcription in keratinocytes is obviously not a general phenomenon, since Am580/CD336 was less effective than retinoic acid in increasing the expression of other retinoid-regulated genes in cultured keratinocytes. 64 …”

ALK1 Opposes ALK5/Smad3 Signaling and Expression of Extracellular Matrix Components in Human Chondrocytes

“…PCR was performed using oligonucleotide primers for human ALK1 (forward primer, 5Ј-ACAA-CATCCTAGGCTTCATCGCCT-3Ј; reverse primer, 5Ј-TGGTTTGCCCTGTGTACCGAAGAT-3Ј), human ALK5 (forward primer, 5Ј-GGGGCGACGGCGTTA-CAGTGTTTCTGCCAC-3Ј; reverse primer, 5Ј-TGAGA-TGCAGACGAAGCACACTGGTCCAGC-3Ј (33) ), and human GAPDH (forward primer, 5Ј-GAAGGTGAAG-GTCGGAGTC-3Ј; reverse primer, 5Ј-GAAGATGGT-GATGGGATTTC-3Ј. (34) PCR was performed using Taq polymerase (Invitrogen) with an initial denaturation step of 5 min at 94°C, followed by 30-35 cycles of denaturation at 94°C (30 s), annealing at 55°C (45 s), and extension at 72°C (60 s). PCR products were resolved by agarose gel electrophoresis and visualized by ethidium bromide staining.…”