Interferon-gamma-induced RANTES production by human keratinocytes is enhanced by IL-1beta, TNF-alpha, IL-4 and IL-13 and is inhibited by dexamethasone and tacrolimus

BACKGROUND AND METHODS: Recent studies have shown that RANTES plays a role in the pathogenesis of inflammatory skin diseases. We examined the production of RANTES by human keratinocytes (KCs) when cultured with various cytokines. RESULTS: IFN-gamma (100 ng/ml) or IL-1beta (100 ng/ml) significantly induced RANTES production by KCs in 48-hour culture. These cytokines synergistically increased RANTES production by KCs. TNF-alpha (100 ng/ml), IL-4 (100 ng/ml) or IL-13 (100 ng/ml) markedly enhanced the RANTES production by KCs induced by IFN-gamma (100 ng/ml) although none of those cytokines significantly enhanced that induced by IL-1beta (100 ng/ml) in 48-hour culture. Dexamethasone (10(-8) M) strongly inhibited RANTES production by KCs induced by the combination of IFN-gamma and IL-4, while tacrolimus (FK-506, 10(-8) and 10(-6) M) showed partial inhibition. CONCLUSIONS: These results revealed that RANTES production by KCs is regulated by inflammatory cytokines, such as IFN-gamma, IL-1beta, TNF-alpha, IL-4 and IL-13, and can be modulated by immunosuppressive drugs. Our data suggest that RANTES is involved in skin inflammation.     

Expression of lysosome-associated membrane protein 1 (Lamp-1) and galectins in human keratinocytes is regulated by differentiation

Lysosomes and their components are suspected to be involved in epidermal differentiation. In this study, lysosomal enzyme activities, expression of the lysosome-associated membrane protein 1 (Lamp-1) and expression of the epidermal galectins-1, -3 and -7 were investigated in human keratinocytes cultured at different cell densities (subconfluence, confluence and postconfluence) in order to induce differentiation. Detected by Western blot and immunofluorescence, Lamp-1 expression is transiently upregulated at culture confluence, but reduced at postconfluence. Northern blot analyses performed on subconfluent, confluent and post-confluent cultures of keratinocytes show that Lamp-1 mRNA expression is also upregulated at culture confluence, but downregulated at postconfluence. Measurements of lysosomal enzyme activities indicate a transient upregulation at culture confluence, whereas cathepsins B, C and L are particularly downregulated at postconfluence. Cell density and differentiation of epidermal cells also differentially regulates galectin expression in autocrine cultures. As the expression of galectin-1 mRNA is high in subconfluent cells, it is assumed to be associated with their proliferative state. On the other hand, as the mRNA levels for galectins-3 and -7 are notably upregulated at culture confluence (galectin-7) or at postconfluence (galectin-3), their expression is thought to be related to the differentiated state of keratinocytes. However, we collected evidence by confocal microscopy that galectin-3 and Lamp-1 do not colocalize in vitro in keratinocytes. Altogether, our results suggest that the upregulated Lamp-1 expression at confluence could be involved in keratinocyte differentiation, but apparently not through interaction with galectin-3.     

Carbonic anhydrases in human keratinocytes and their regulation by all‐trans retinoic acid and 1α,25‐dihydroxyvitamin D3

Carbonic anhydrases (CAs) are ubiquitously expressed enzymes and catalyse an important physiological reaction of interconverting the hydration of carbon dioxide to bicarbonates, which is crucial for maintaining acid/base equilibrium in certain tissues. While 15 different isoforms of CAs are present in various cell types in human tissues, their expression pattern in the epidermis remains to be investigated. Here, we report the expression of 5 CA isoforms (CAII, CAIX, CAXI, CAXII and CAXIII) in human primary keratinocytes. Further, we demonstrate that the expression of CAII and CAIX in these cells is significantly up‐regulated by the biologically active metabolites of vitamin A (all‐trans retinoic acid) and vitamin D (1α,25‐dihydroxyvitamin D₃), respectively. Taken together, apart from providing new information on the expression of CAs in the skin, our results highlight a previously undisclosed connection between vitamin A and CAII expression and vitamin D and CAIX expression.     

Erythroid differentiation regulator 1 (Erdr1) is a proapototic factor in human keratinocytes

Skin is constantly exposed to physical and chemical stressors. The exposure of keratinocytes to ultraviolet B (UVB) irradiation causes epidermal damage via induction of apoptosis. Erythroid differentiation regulator 1 (Erdr1) modulates growth and survival of cells under various stressful conditions, but the function of Erdr1 in human keratinocyte apoptosis has not been investigated so far. Here, we investigated the effect of Erdr1 on UVB-induced apoptosis in human keratinocytes and also examined the underlying regulatory mechanism. First, Erdr1 expression was detected in human primary keratinocytes and normal human skin tissues. Expression of Erdr1 was enhanced in human keratinocytes following UVB irradiation. Knock-down of Erdr1 led to resistance to UVB-induced apoptosis. Also, Erdr1 overexpression increased UVB-induced apoptosis and induced caspase-3 activation. Furthermore, the extracellular signal-regulated kinase (ERK) inhibitor PD98059 and the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 significantly reduced Erdr1 expression following UVB irradiation. These results indicate that UVB induces Erdr1 via a MAPK-dependent mechanism. Taken together, these findings suggest that Erdr1 has a role as a proapoptotic factor in human keratinocytes and acts via ERK and p38 MAPK pathways. Therefore, Erdr1 may be a potential therapeutic target to reduce apoptosis in keratinocytes in conditions such as psoriasis and skin cancer.     

tPA of human keratinocytes: contribution to cell surface-associated plasminogen activation and upregulation by retinoic acid

Abstract We tested distinct variants of a human kerationocytc line (HaCaT) for the expression of tissue-type plasminogen activator (tPA)-specific mRNA. as well as cell surface-associated and secreted tPA. Cells of early passages (passage no. 22) only expressed urokinase plasminogen activator (uPA)- bul not tPA-specific mRNA. Cells after prolonged culture (passage no. 44) expressed uPA- and tPA-specific mRNA, bul did not release tPA in the extracellular space and did nol display surface-associated IPA. HaCaT cells transformed with the c-Ha-ras oncogene (HaCaT^ras) showed both secreted and surface-associated tPA antigen. The secreted and the surface-associated plasminogen activator (PA)-activity of HaCaT^ras cells were in part inhibitable by anticatalytic anti-tPA antibodies, thus indicating thai tPA contributes to extracellular and surface-associated plasminogen activation. Finally, we demonstrate that tPA secretion of HaCaT 44 cells can be induced by retinoic acid, most likely via interaction of retinoic acid with nuclear-associated retinoic acid-receptor(s).     

TGF-beta is not involved in early phase growth inhibition of keratinocytes by 1alpha,25(OH)2vitamin D3

BACKGROUND: It has been proposed that transforming growth factor-beta (TGF-beta) is involved in the growth inhibition of normal human epidermal keratinocytes (NHEK) by 1alpha,25-dihydoxyvitamin D(3) (1alpha,25(OH)(2)D(3)), although this is still controversial because of the difficulty in blocking TGF-beta activity completely. OBJECTIVE: To determine whether TGF-beta is involved in early phase growth inhibition by 1alpha,25(OH)(2)D(3). METHODS: TGF-beta mRNA was detected by ribonuclease protection assay (RPA), and biological active TGF-beta was determined by a luciferase reporter assay. To block intrinsic TGF-beta activity completely, we constructed an adenovirus vector expressing a truncated TGF-beta type II receptor with a dominant negative effect (AdexTbetaTR) that blocks TGF-beta signal transduction. RESULTS: 1alpha,25(OH)(2)D(3) slightly upregulated TGF-beta1 and TGF-beta2 after 24 h according to an RPA and a luciferase reporter assay, however growth inhibition by 1alpha,25(OH)(2)D(3) occurred at 6 h. The addition of 10(-6) M of 1alpha,25(OH)(2)D(3) to NHEK infected with AdexTbetaTR or AdexLacZ (control vector) reduced DNA synthesis to 59.3 and 62.2% at 6 h, respectively. There was no significant difference in cell number after a 3-day incubation with AdexTbetaTR or AdexLacZ-infected cells treated with 1alpha,25(OH)(2)D(3). CONCLUSION: Since 1alpha,25(OH)(2)D(3) rapidly inhibits NHEK growth regardless of the prevention of TGF-beta signal transduction, TGF-beta is not involved in early phase growth inhibition by 1alpha,25(OH)(2)D(3).     

Effect of retinoic acid on apoptosis and DNA repair in human keratinocytes after UVB irradiation

BACKGROUND: Skin cancer is extremely common. Epidemiological studies indicated that ultraviolet radiation (UV) is the primary cause for skin cancers, and that retinoic acid (RA) is able to inhibit this UV-induced skin carcinogenesis; however, the molecular mechanism of the anti-UV action of RA is unclear. OBJECTIVE: The purpose of this study is to investigate if RA enhances the removal of UV-induced DNA damage. METHODS: The effect of RA on UV-induced apoptosis and DNA repair was investigated by ELISA apoptosis assay and CAT assay. RESULTS: Both all-trans-RA and 9-cis-RA did not promote UV-induced apoptosis nor the repair of UV-damaged DNA in human keratinocytes. Furthermore, RA did not induce the expression of p53. CONCLUSION: The inhibition of RA on skin carcinogenesis is not due to enhanced removal of UV-damaged DNA. Therefore, RA does not inhibit skin cancer development at the initiation stage, but possibly at the promotion and progression stages.     

Interleukin-17 is produced by both Th1 and Th2 lymphocytes, and modulates interferon-gamma- and interleukin-4-induced activation of human keratinocytes

Interleukin-17 is a T-cell-derived cytokine, detected in skin affected by allergic contact dermatitis and psoriasis, which regulates keratinocyte expression of adhesion molecules and chemokines. In this study, we have analyzed whether interleukin-17 production segregates with a particular T helper (Th) cell subset, and have examined the capacity of interleukin-17 to modulate the activation of keratinocytes induced by Th1 and Th2 cytokines. A panel of 80 nickel-specific CD4+ T cell clones (36 Th0, 30 Th1, and 14 Th2) was isolated from peripheral blood or lesional skin of allergic contact dermatitis patients. Significant amounts (> 50 pg per ml) of interleukin-17 were released by about 50% of activated Th0, Th1, and Th2 cells. Interleukin-17 alone and in cooperation with interleukin-4, or to a lesser extent with interferon-gamma, decreased the interleukin-1 receptor antagonist to interleukin-1alpha ratio in the supernatants as well as in cell lysates from keratinocytes. In addition, interleukin-17 stimulated the release of growth-regulated oncogene-alpha, granulocyte-macrophage colony stimulating factor, and interleukin-6, with synergistic or additive effects when used together with interferon-gamma or interleukin-4. Interleukin-17 and interleukin-4 also increased stem cell factor release, a function that was inhibited by interferon-gamma. Moreover, interleukin-17 and interleukin-4 enhanced interferon-gamma-induced expression of intercellular adhesion molecule 1, but not CD40, on keratinocytes. The constitutive expression of interleukin-17 and interferon-gamma receptors on keratinocytes was not modulated by interleukin-17, interferon-gamma, or interleukin-4, whereas the interleukin-4 receptor was significantly downregulated by interferon-gamma. As a whole, the results indicate that interleukin-17 can participate relevantly in T-cell-mediated skin immune responses by amplifying both interferon-gamma- and interleukin-4-induced activation of keratinocytes.     

Growth inhibition of human keratinocytes by MC903 (calcipotriol) is linked to dephosphorylation of retinoblastoma gene product

Aim This paper compares the effects of MC903 (calcipotriol) and 1,25-dihydroxyvitamin D₃[1,25(OH)₂D₃; calcitriol] on differentiation and proliferation of normal human keratinocytes cultured in serum-free medium. In order to understand the inhibitory mechanism of MC903, we examined its effect on cell cycle kinetics and the phosphorylation of retinoblastoma gene product (pRB), a tumor suppressor gene products, in normal human keratinocytes. Background The hormonally active form of vitamin D₃, 1,25-dihydroxy vitamin D₃ [1,25(OH)₂D₃], regulates the differentiation and proliferation of epidermal keratinocytes in vitro. MC903 is a novel vitamin D₃ analogue which is at least 100 times less potent than 1,25(OH)₂D₃ in its effects on calcium homeostasis. Methods We analyzed cell differentiation and cell cycle by flow cytometry using a FACScan, and pRB phosphorylation by Western blotting and densitometer. Results MC903 induced growth inhibition and differentiation of human keratinocytes. Cell cycle analysis demonstrated that 10^-6 M of MC903 induced cell cycle arrest in both G1/G0 (62.4 ± 0.7% versus 56.5 ± 1.7% in control, p < 0.01) and G2 + M (19.2 ± 0.3% versus 14.0 ± 0.9% in control, p < 0.01) phase. 10^-6 M of MC903 also increased the depnosphorylated pRB from 25% at 0 h to 84% at 48 h, as well as 1,25(OH)₂D₃. Conclusions Since pRB phosphorylation is supposed to be essential for the progression from G1 to S phase, the inhibition of pRB phosphorylation could be responsible for the G1/G0 growth arrest induced by MC903 in normal human keratinocytes.     

Cytochrome P450, CYP26AI, is expressed at low levels in human epidermal keratinocytes and is not retinoic acid-inducible

Retinoids, and their synthetic analogues, are well-established regulators of the squamous differentiation programme both in vivo and in vitro. Despite this, very few studies have focused on the mechanism by which retinoid action is terminated, e.g. metabolism. Recently, a new cytochrome P450 family member (CYP26AI) was cloned. CYP26AI was reported to have substrate specificity for retinoids and to be retinoid-inducible. In this study, we have examined the expression and retinoic acid (RA) inducibility of CYP26AI in human epidermis and cultured keratinocytes. We found very low levels of CYP26AI mRNA expression in both epidermis and keratinocytes. Furthermore, we found no evidence for RA inducibility of CYP26 mRNA expression. This lack of RA inducibility was not due to inactivity of the retinoids, as we show that transglutaminase was still repressed by RA in the same cultures. Despite the low levels of CYP26AI expression in the keratinocytes, the keratinocytes were still capable of significant RA metabolism. In conclusion, our study reports, for the first time, that CYP26AI is unlikely to contribute to RA metabolism in keratinocytes. These studies also indicate that as yet unknown isoforms of cytochrome P450 may be involved in RA metabolism in keratinocytes.