Dietary beta-carotene and ultraviolet-induced immunosuppression.
Ultraviolet (UV)-induced immunosuppression is a critical step in UV carcinogenesis, permitting tumour outgrowth. We investigated the effect of dietary beta-carotene on UV suppression of contact hypersensitivity (CHS) to trinitrochlorobenzene (TNCB) in BALB/c mice. Mice were fed for 10-16 weeks chow alone or supplemented with 1% beta-carotene or placebo as beadlets. Serum beta-carotene was detectable by high performance liquid chromatography (HPLC) analysis only in beta-carotene-fed mice (2.06 +/- 0.15 micrograms/ml). Serum retinol was 0.22-0.27 micrograms/ml in all three groups. Mice (n = 41/dietary group) were irradiated with 0, 4.5, 9 or 18 kJ/m2 of UVB and the CHS response was measured. Decreased CHS responses were observed in all UV-irradiated groups compared with unirradiated controls. UV dose-responses for suppression of CHS derived by first-order regression analyses of plots of percentage suppression of CHS as a function of log10UV dose showed significant slopes (P < 0.02) for all three dietary groups and similar residual variances between groups, P > 0.05. The UV dose for 50% suppression of CHS was 6.3 kJ/m2 for control, 6.4 kJ/m2 for placebo, and 5.5 kJ/m2 for beta-carotene-fed mice. No significant differences in slopes or elevations between UV dose-responses were observed, P > 0.05. Skin levels of the initiator of UV-induced immunosuppression, cis urocanic acid, were determined by HPLC in mice given 0 or 9 kJ/m2 of UV (n = 28/dietary group). No significant differences were observed between dietary groups (range 35.2-41.1 ng/mg skin, P > 0.15) We conclude feeding beta-carotene to BALB/c mice does not alter susceptibility to UV immune suppression, in contrast to human studies.
Noonan
F P
FP
Department of Dermatology, George Washington University Medical Centre, Washington, DC 20037, USA.
Webber
L J
LJ
De Fabo
E C
EC
Hoffman
H A
HA
Bendich
A
A
Mathews-Roth
M
M
D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000097:blood / Q000276:immunology; D001835:Body Weight / Q000187:drug effects / Q000276:immunology; D002338:Carotenoids / Q000008:administration & dosage* / Q000097:blood / Q000276:immunology*; D003877:Dermatitis, Contact / Q000209:etiology / Q000276:immunology; D004032:Diet; D004307:Dose-Response Relationship, Radiation; D005260:Female; D007165:Immunosuppression Therapy; D051379:Mice; D008807:Mice, Inbred BALB C; D013237:Stereoisomerism; D014466:Ultraviolet Rays; D014560:Urocanic Acid / Q000737:chemistry / Q000528:radiation effects; D014801:Vitamin A / Q000097:blood; D019207:beta Carotene
D000970:Antineoplastic Agents; D019207:beta Carotene; D014801:Vitamin A; D002338:Carotenoids; D014560:Urocanic Acid