title: Activation of VEGFR-2 signaling in response to moderate dose of ultraviolet B promotes survival of normal human keratinocytes.
abstract: Mounting evidence indicates that signaling via VEGF receptors (VEGFRs) extends beyond blood vessel formation. Recently, VEGFRs are also found to be constitutively expressed in keratinocytes and epidermal appendages. Here, we show that the expression of VEGFRs (including VEGFR-1, VEGFR-2, and NRP-1) was significantly enhanced by moderate dose of ultraviolet B (UVB) in normal human keratinocytes and epidermis. The elevated expression of VEGFRs by UVB was independent of autocrine stimulation by their natural ligand, VEGF, but mainly mediated through hypoxia and oxidative stress. Moderate dose UVB also promoted tyrosine phosphorylation of VEGFR-1 and VEGFR-2, this effect was again VEGF independent. Both α and δ isoforms of protein kinase C (PKC) were required for UVB-induced phosphorylation of VEGFR-1, but only the δ isoform was required for VEGFR-2 phosphorylation. The phosphorylation of VEGFRs or isoforms of PKC was completely inhibited by PP2, a specific inhibitor for Src family kinases (SFKs), indicating that SFKs are upstream of PKC and VEGFRs. Moderate dose UVB-induced VEGF exerted an anti-apoptotic effect for keratinocytes, whereas high dose UVB-induced VEGF played as an inflammatory factor. Of note, neutralization of VEGFR-2 but not VEGFR-1 exacerbated UVB-induced cell death and reduced survival of keratinocytes. Furthermore, VEGFR-2 neutralization inhibited the activation of ERK1/2 and Akt by UVB, suggesting that VEGFR-2 signaling was involved in the pro-survival mechanism via ERK1/2 and PI3-K/Akt pathway. Taken together, we demonstrate for the first time that VEGFR-2 signaling is activated and promotes survival of keratinocytes under moderate dose of UVB irradiation.
authors: Department of Dermatology, The Second Affiliated Hospital, Zhejiang University, School of Medicine, Hangzhou, Zhejiang Province, PR China.
authors: Jian-Wei
authors: JW
authors: Zhu
authors: Xian-Jie
authors: XJ
authors: Wu
authors: Dan
authors: D
authors: Luo
authors: Zhong-Fa
authors: ZF
authors: Lu
authors: Sui-Qing
authors: SQ
authors: Cai
authors: Min
authors: M
authors: Zheng
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000528:radiation effects; D002470:Cell Survival; D002478:Cells, Cultured; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D015603:Keratinocytes / Q000166:cytology* / Q000378:metabolism / Q000528:radiation effects*; D008297:Male; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000528:radiation effects; D015398:Signal Transduction / Q000187:drug effects; D014466:Ultraviolet Rays; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism* / Q000528:radiation effects*; D055815:Young Adult
chemical_list: D040301:Vascular Endothelial Growth Factor Receptor-2