Downregulation of TGFbeta isoforms and their receptors contributes to keratinocyte hyperproliferation in psoriasis vulgaris.
BACKGROUND
Psoriasis vulgaris is a chronic inflammatory disorder characterized by epidermal hyperproliferation. Transforming growth factor beta (TGFbetas) have a major antiproliferative action in epidermis.


OBJECTIVE
We evaluated the distribution and levels of expression of TGFbeta isoforms and their receptors in psoriatic versus normal skin with the goal of discovering potential alterations in TGFbeta signal transduction associated with psoriasis.


METHODS
Expression of TGFbeta isoforms and their receptors was analyzed in normal and psoriatic skin using immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques. Furthermore, DNA synthesis was measured in normal keratinocytes transfected with a dominant-negative TGFbeta receptor II (TbetaRII) vector that eliminated most of the cytoplasmic TbetaRII domain.


RESULTS
Marked elevations in DNA synthesis, as assessed by BrdU incorporation and proliferating cell nuclear antigen (PCNA) immunoreactivity, were confirmed in psoriatic epithelial cells. Using immunohistochemistry and RT-PCR analysis, expression of TGFbeta2 and 3 was diminished in the psoriatic epidermis as compared with those observed in normal skin. With respect to TGFbeta receptors, expression of TbetaRI and II was markedly decreased in the psoriatic epidermis. In addition, levels of Smad2 mRNA were also decreased in psoriatic skin. Transfection of normal keratinocytes with the dominant-negative TbetaRII vector significantly elevated DNA synthesis as compared with keratincoytes transfected with control vector (under condition of TGFbeta addition), suggesting that the dominant-negative TbetaRII mutant inhibits the antiproliferative effects of TGFbeta.


CONCLUSIONS
The present investigation strongly suggest that the TGFbeta signaling pathway is downregulated in psoriatic skin and this situation leads to abnormal cell proliferation due to a functional decrease in growth regulation.
Doi
Hisao
H
Department of Dermatology, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki, Osaka 569-8686, Japan.
Shibata
Masa-Aki
MA
Kiyokane
Kimihiro
K
Otsuki
Yoshinori
Y
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002455:Cell Division; D015536:Down-Regulation; D005799:Genes, Dominant; D006801:Humans; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000473:pathology*; D008875:Middle Aged; D020033:Protein Isoforms / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011565:Psoriasis / Q000378:metabolism* / Q000473:pathology*; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012867:Skin / Q000378:metabolism; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D020033:Protein Isoforms; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II