UVB Activates Hypothalamic-Pituitary-Adrenal Axis in C57BL/6 Mice

Area of Science:

• Endocrinology
• Dermatology
• Neuroscience

Background:

• The hypothalamic-pituitary-adrenal (HPA) axis is a key regulator of the stress response.
• The effects of ultraviolet B (UVB) radiation on the HPA axis are not fully understood.

Purpose of the Study:

• To investigate whether UVB exposure activates the HPA axis.
• To identify the mechanisms and pathways involved in UVB-induced HPA axis activation.

Main Methods:

• C57BL/6 mice were exposed to UVB or sham irradiation.
• Plasma, skin, brain, and adrenal tissues were collected at 12 and 24 hours post-exposure.
• Levels of CRH, Ucn, β-END, ACTH, and CORT were measured using molecular and immunohistochemical techniques.
• Hypophysectomy was performed to assess the role of the pituitary gland.

Main Results:

• UVB exposure significantly increased plasma levels of CRH, Ucn, β-END, ACTH, and CORT.
• UVB increased Ucn, β-END, and CORT expression in the skin at both gene and protein levels.
• UVB stimulated CRH expression in the hypothalamus and increased adrenal mRNAs for MC2R, StAR, and CYP11B1.
• Hypophysectomy abolished systemic but not skin CORT responses to UVB, confirming pituitary dependence for systemic effects.

Conclusions:

• UVB radiation activates the HPA axis, initiating responses in the skin.
• The HPA axis activation by UVB involves CRH, Ucn, β-END, ACTH, and CORT.
• Systemic effects of UVB on the HPA axis are pituitary-dependent, while local skin responses are not.