title: Metallothionein-null mice exhibit reduced tolerance to ultraviolet B injury in vivo.
abstract: Events that induce expression of the metallothionein (MT) gene, such as injection of cadmium chloride, cold stress or topical application of 1,25-dihydroxyvitamin D3, can deplete the number of ultraviolet (UV) B-induced sunburn cells (SBC) in mouse skin in vivo. MT-null mouse skin explants exhibit reduced tolerance to UVB injury in vitro. However, the in vivo response of MT-null mice to UVB injury has not been investigated. In the present study, we investigated the role of the MT gene on UVB injury in vivo. MT-null mice that are deficient in MT-I and MT-II genes were studied and compared with homozygous wild-type mice. Mouse dorsal skin was irradiated with 0.05, 0.70 and 1.40 J/cm2 UVB. The thickness of the dorsal skin was measured with a spring micrometer before and 24 h after UVB irradiation. In addition, SBC were counted 24 h after UVB irradiation. No significant difference was found in the change of skin thickness between MT-null mice and control mice irradiated with low-dose UVB (0.05 J/cm2) (Student's t-test, t = 1.519, P = 0.167). At higher doses (0.70 and 1.40 J/cm2), the skin of MT-null mice became much thicker than that of control mice (Student's t-test, t = 6.576, P < 0.01 and t = 3.142, P = 0.007, respectively). More SBC were detected in MT-null mice skin irradiated with the highest dose of UVB (1.40 J/cm2) (Student's t-test, t = 4.258, P < 0.01). These results suggest that the MT gene in mice has a photoprotective role in vivo.
authors.affiliation: Department of Dermatology, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100083, China.
authors.forename: W-H
authors.initials: WH
authors.lastname: Wang
authors.forename: L-F
authors.initials: LF
authors.lastname: Li
authors.forename: B-X
authors.initials: BX
authors.lastname: Zhang
authors.forename: X-Y
authors.initials: XY
authors.lastname: Lu
mesh_terms: D000818:Animals; D004307:Dose-Response Relationship, Radiation; D005260:Female; D008668:Metallothionein / Q000172:deficiency / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D012867:Skin / Q000473:pathology / Q000528:radiation effects*; D013471:Sunburn / Q000473:pathology; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D008668:Metallothionein