Downregulation of CXCR-2 but not CXCR-1 expression by human keratinocytes by UVB

Abstract

Interleukin-8 (IL-8) belongs to the CXC chemokine family. IL-8 exerts its biological activities by binding to specific cell surface receptors, CXCR-1 and CXCR-2. Both receptors bind IL-8 with high affinity but they have different affinities for MGSA/Groalpha and NAP-2. It has been shown that the expression of epidermal CXCR-2 is increased in psoriasis, suggesting that activation of KC mediated by CXCR-2 contributes to the characteristic epidermal changes observed in psoriasis. In order to examine the mechanism(s) by which UVB therapy is effective for several dermatoses including psoriasis, we sought to examine if UVB would modulate the expression of CXCR-1 and CXCR-2 in human keratinocytes (KC). Constitutive expression of CXCR-1 and CXCR-2 mRNA was detected by RT-PCR in normal cultured human KC. After 100 or 300 J/m(2) irradiation, a decrease in CXCR-2 mRNA was detectable from 12 h after irradiation; this downregulation was observed until 48 h after irradiation. In contrast, the CXCR-1 mRNA level was unchanged. Immunohistochemical studies and flow cytometry analysis confirmed the suppressive effect of UVB on the expression of CXCR-2 protein in cultured human keratinocytes. Immunohistochemical studies on two minimal erythema doses (2MED)-exposed and 2MED-unexposed skin from healthy volunteers revealed that CXCR-2 staining occurred over the whole layer of the epidermis but at 24 h after 2MED irradiation, the positive staining of CXCR-2 was decreased. A faint CXCR-1 staining was observed in the lower part of the epidermis both in unexposed and exposed skins. Our results indicate that UVB-induced growth inhibition of KC in hyperproliferative skin disorders may, in part, be related to downregulation of CXCR-2.

Impact of endoscopically minimal involvement on IL-8 mRNA expression in esophageal mucosa of patients with non-erosive reflux disease

“…IL-8 also exerted mitogenic actions directly or by binding to its receptors on epithelial cells [20,21] . Taken together, it is possible that IL-8, together with other cytokines as well as growth factors [14,22] , could contribute to epithelial cell proliferation even in NERD, and could be eventually linked to carcinogenesis. Again, unlike CXCR-1, CXCR-2 is not specific for IL-8 and can bind to other chemokines such as growth related oncogene α, but it has 2-to 5-fold higher affinity for IL-8 than CXCR-1 [19] .…”

“…Based on the technique described previously [14] with slight modification, the target sequence of CXCR-1 mRNA was amplified through 35 cycles, each consisting of denaturation at 94 for 30 sec, annealing at 53 for 30 sec and extension at 72 for 30 min, followed by a final extension at 72 for 5 min with specific primers (forward, 5'-CAGATCCACAGA-TGTGGGAT-3' and reverse, 5'-TCCAGCCATTCACCTTG-GAG-3') using an RT-PCR kit (Takara Shuzo Co., Otsu, Japan). Similarly, CXCR-2 mRNA expression was detected under the following conditions: amplification through 35 cycles, each consisting of denaturation at 94 for30 sec, annealing at 60 for 30 sec and extension at 72 for 30 min, followed by a final extension at 72 for 5 min with specific primers (forward, 5'-AGCTGCTCTTCTGGAGGTGT-3' and reverse, 5'-TTAGAGAGTAGTGGAAGTGTGC-3') [14] .…”

“…Similarly, CXCR-2 mRNA expression was detected under the following conditions: amplification through 35 cycles, each consisting of denaturation at 94 for30 sec, annealing at 60 for 30 sec and extension at 72 for 30 min, followed by a final extension at 72 for 5 min with specific primers (forward, 5'-AGCTGCTCTTCTGGAGGTGT-3' and reverse, 5'-TTAGAGAGTAGTGGAAGTGTGC-3') [14] . A 10-µl aliquot of each PCR product was analyzed by electrophoresis on 2 % agarose gel containing ethidium bromide, and the bands were examined under ultraviolet light for the presence of amplified DNA.…”

Molecular Machinations: Chemokine Signals in Host-Pathogen Interactions

“…Subsequently, they have been found on endodermal, mesenchymal, ectodermal, and neuroectodermal cells. Thus, chemokines may participate in the growth and migration of epithelial cells of the skin (88,118), digestive (51,123) and reproductive (182) tracts, and neuronal and glial cells of the central nervous system (70). Analysis of chemokine receptor expression by leukocytes has revealed that receptor subtypes are expressed to differing degrees by different cell types, thereby dictating their responsiveness to the various chemokines.…”

ELR+-CXC Chemokines and Their Receptors in Early Metanephric Development

“…Accordingly, their receptors, CXCR1 and CXCR2, originally shown to be expressed in leukocytes, 24 now have been reported on nonhematopoietic cells (e.g., keratinocytes, neurons, neuroendocrine, and oligodendroglial cells). [25][26][27][28][29] More recently, receptors have been described in a variety of embryonic populations. CXCR2 is widely distributed in human tissues including brain (undifferentiated neurons), heart (myocardiocytes), lung (bronchial epithelial cells), liver (hepatocytes), and kidney (early glomeruli and collecting duct).…”