310 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Effect of Product Base on IL-lo• Release Treatment IL-lot Release (pg/ml) Base A with sunscreen (SPF 8) Base A without sunscreen* Base B with sunscreen (SPF 8) Base B without sunscreen* o 29.79, 25.36 o 22.00, 26.87 * Note: The two bases are chemically different, and the sunscreens are of a chemical nature. Table III Time Course IL-lo• Release From Skin 2 Protected With Sunscreen Product Times (min) IL-ltx Release (pg/ml) SPF 4 8 0 SPF 4 10 5 SPF 4 16 12.7 DISCUSSION Exposure to UV radiation, especially UVB (290-320 nm), has been shown to induce both physical and biochemical changes within the skin. Ley et al. (10) have shown that exposure to UV radiation induces pyrimidine dimer formation in DNA, while Bissett et al. (11) demonstrated the effect of UVB on skin aging using a hairless mouse model. Exposure to ultraviolet radiation has also been shown to increase prostaglandin synthesis (12), suppress the immune response (13), increase both IL-lot and IL-lot mRNA (14), and cause damage to the antioxidant defense mechanisms of the cell (15,16). Full-thickness skin models permit the measurement of effects of UV irradiation on skin in vitro. Kupper (17) has suggested that keratinocytes grown in vitro do not produce IL-lot unless "activated" by a stimulus. Constitutive production of IL-lot in vivo in unchallenged cells is very low (18). The model evaluated in our studies supports Kup- per's findings as demonstrated by the absence of IL-lot release in skin protected by sunscreen and in unirradiated Skin •. The application of the Transpore TM tape to the quartz glass as described previously by Diffey (5) provides an irregular surface like that of skin and allows for easy application of the sunscreens. The application of sunscreen to the tape also ensures that any IL-lot released is due to exposure of the skin to UV light and not to interaction of sunscreen on the skin. The data in Table I show that this in vitro method is capable of confirming that a sunscreen product has a minimum SPF. Currently this method is not practical for routine determination of a precise SPF. This is because the method is limited to use of only one port of the multiport solar simulator rather than all six. The ability to simultaneously use all six ports would permit concurrent time-course studies, allowing for rapid determination of SPF similar to the method used in vivo. As evidence of this, Table III shows a time course UV exposure study with a marketed SPF 4 sunscreen product. Clearly, in this study, SPF 4 is the exact SPF for the product, since UV exposure times for SPF 5 or SPF 8 (10 minutes and 16 minutes, respectively) resulted

SCREENING SUNSCREEN FORMULATIONS 311 in IL-lo• release. For routine practical use of the method, ability to simultaneously use all six ports is important. From the results gathered it appears that this method may prove useful as a tool for screening the SPF of sunscreens. The model is simple to use, measures a biological endpoint, and results can be obtained within 24 hours. We regard this method as a significant development. A rapid in vitro screen for determining whether a prototype sunscreen formulation minimally possesses the desired SPF is a worthwhile objective. Reliable identification of formulations significantly lacking their intended SPF would permit removal of these formulas from either pilot or final human SPF testing. Secondly, this method represents a significant achievement in the area of non-animal test methods development. Prior to the elimination or suspension of animal testing by most manu- facturers of personal care products, prototype sunscreen products were screened for SPF values in guinea pigs. This procedure clearly allows screening for SPF without the use of animals. REFERENCES (1) Sunscreen drug products for over-the-counter human use: Proposed safety, effective and labeling conditions, Fed. Reg., 43, 1978:38259-28260. (2) B. M. Cumpelik, Analytical procedures and evaluation of sunscreens, J. Soc. Cosmet. ½hem., 23, 333-345 (1972). (3) D. F. Robertson and G. A. Groves. The selection and use of topical sunscreens, &led. J. Aust., 2, 1445-1451 (1972). (4) G. A. Groves, P. P. Agin, and R. M. Sayre, In vitro and in vivo methods to define sunscreen, Aust. J. Dermatol., 20, 112-119 (1979). (5) B. L. Diffey and J. Robson, A new substrate to measure sunscreen protection factors throughout the ultraviolet spectrum. J. Soc. Cosmet. Chem., 40, 127-133 (1989). (6) C. A. Cole and R. L. Van Fossen, In vitro models for UVB and UVA photoprotection, Sunscreen Development, Evaluation, and Regulatory Aspects, 10, 395-404 (1990). (7) R. M. Sayre, P. P. Agin, D. L. Desrochers, and E. Marlowe, Sunscreen testing methods: In vitro predictions of effectiveness, J. Soc. Cosine. Chem., 31, 133-143 (1980). (8) J. C. Ansel, T. A. Luger, and I. Green, The effect of in vitro and in vivo UV irradiation on the production of ETAF activity by human and murine keratinocytes, J. Invest. Dermatol., 81, 519-523 (1983). (9) K. Punnonen, T. Puustinen, and C. T. Jansen, UVB irradiation induces changes in the distribution and release of •4C-arachidonic acid in human keratinocytes in culture, Arch. Dermatol. Res., 278, 441-444 (1986). (10) R. D. Ley, M. J. Peak, and L. L. Lyon, Induction ofpyrimidine dimers in epidermal DNA of hairless mice by UVB: An action spectrum,.]. Invest. Dermatol., 80:188-191 (1983). (11) D. L. Bissett, D. P. Hannon, and T. V. An animal model of solar-aged skin: Histological, physical, and visible changes in UV-irradiated hairless mouse skin, Photochem. Photobiol., 46(3):367-378 (1987). (12) A. K. Black, M. W. Greaves, C. N. Hensby, and N. A. Plummer, Increased prostaglandins E2 and F2tx in human skin at 6 and 24 hours after ultraviolet B irradiation (290-320 nm), Br..]. Clin. Pharmacol., 5, 431-436 (1978). (13) K. D. Cooper, P. F. Fox, and S. I. Katy, Effects of ultraviolet radiation on human epidermal cell alloantigen presentation: Initial depression of Langerhans cell dependent function is followed by the appearance of T6-DR + cells which enhance epidermal alloantigen presentation. J. Immunol., 134, 129-137 (1984). (14) T. S. Kupper, A. O. Chua, P. Flood, J. McGuire, and U. Gubler, Interleukin 1 gene expression in cultured human keratinocytes is augmented by ultraviolet irradiation, J. Clin. Invest., 80, 430-436 (1987).