Studying Chronic Exposure of Mice to Ultraviolet B Radiation

Summary

The protocol describes a study of the systemic and local skin effects of Ultraviolet B exposure in mice.

Abstract

Ultraviolet B (UVB) radiation (280-320 nm) has been recognized as a carcinogen since 1928, leading to sun exposure minimization. However, epidemiological studies suggest that sun exposure correlates with increased life expectancy and reduced incidence of cardiovascular diseases and certain cancers such as colon and endometrial cancer. UVB exposure also influences liver metabolism, protects against hepatocellular lipotoxicity, and affects metabolic health. These effects are partly due to vitamin D synthesis, though some are independent of vitamin D. Moreover, phototherapy with UVB has immunomodulatory properties and is used to treat skin conditions such as vitiligo and psoriasis while also affecting the systemic immune system. Given UVB's broad physiological effects, there are gaps in understanding the mechanism behind most of these effects. We showed that daily low-level UVB exposure enhances food-seeking behavior in male mice but not in females due to increased ghrelin secretion from skin adipocytes. In females, estrogen inhibits adipocytes' p53 activity, blocking ghrelin elevation and demonstrating a sex-dependent response to UVB radiation. Additionally, UVB-induced p53 activation in epidermal keratinocytes activates the hypothalamus-pituitary-gonadal axis, inducing sexual behavior and ovarian pro-fertility. This paper outlines a protocol for studying local and systemic effects of low UVB radiation using a C57BL/6J mouse model. Key elements include precise calibration of UVB doses, housing conditions, and careful hair removal to ensure consistent exposure. Mice are subjected to a graded UVB exposure regime over several weeks, with monitoring for health and behavioral changes. Methods for validation of radiation efficiency through pigmentation measurements are also detailed. By emphasizing calibration of UVB doses, rigorous animal care, and methodological controls, this protocol will facilitate the study of the comprehensive effects of UVB exposure, contributing to a nuanced understanding of its therapeutic benefits and risks.

Introduction

The frequencies of solar radiation that reach the earth's surface include ultraviolet (UV), UVA radiation (320-400 nm), and UVB radiation (280-320 nm). UVB is a mutation inducer. UV was recognized as a carcinogen in 1928¹, and from the mid-1900s, reducing sun exposure was recommended as a precautionary measure to avoid skin cancer². Although UVB is clearly an environmental trigger for skin cancer, research in the past decade³ with recent studies from our group^4,5,6 has shown that UVB has broad effects....

Protocol

All the experimental procedures described were performed in accordance with the guidelines of the Tel Aviv University Institutional Animal Care and Use Committee (IACUC permit: 01-20-043).

1. Habituation of the mice for the experiment

1. Obtain 7- to 8-week-old C57BL/6J mice by either purchasing from a commercial vendor or rearing in-house, depending on the IACUC protocol of the experimenter. This protocol tests the 15-week-old mice in C57BL/6J background, but the protocol must be calibrated on other mice strains and for younger ages (< 7 weeks old).
   NOTE: The protocol to use the different age-grouped mi....

Results

This method paper mentions the detailed step-by-step procedure of generating the UVB-exposure mouse model. Figure 1 clearly demonstrates the shaved area of the representative C57BL/6J mouse on the dorsal side prior to UVB exposure, demonstrating that 50%-60% of the dorsal area was shaved. The shaving protocol shows no sign of skin erythema, which is of utmost importance for dermatological studies. Figure 2 shows the set-up of the UVB exposure for the mice using .......

Discussion

UVB has long been recognized as an environmental risk factor for skin cancers; however, recent studies have illuminated a broader spectrum of UVB effects³. There is a need for studies that provide a deeper understanding of the systemic effects of UVB. The different doses used in basic research compared to clinical settings complicate our understanding of UVB effects, underscoring the importance of research that bridges these gaps.

The protocol for UVB exposure of C57BL/.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Disinfectant	Amity international	Not applicable
Exposure chamber	Made in house	Not applicable
Hair removal cream	Veet	Not applicable
Hair shaver	Heiniger	707-303 120V US
Isoflurane	Piramal Critical Care	Not applicable
Isoflurane system	Kent Scientific	VetFlo-1210S
PBS	Sigma Aldrich	TMS-012
Plexi-glass chamber	Made in house	Not applicable
UVB lamp	Ultra-Violet Products	XX-Series - 15 Watt
UVX radiometer	Ultra-Violet Products	97-0015-02