There are a wide range of biological reactions to UV light. In both animals and microbes, biological reactions at the cellular level include responses to DNA damage. In humans, exposure to UV light can also initiate reactions on the organ system level. While biological responses to UV light are largely considered to be negative, it is important to note that recent studies have also highlighted positive biological reactions to UV light. When considering the effects of UV light on biological systems, it is important to examine multiple types of biological reactions.
First, exposure to UV light can damage nucleic acids. Some of the DNA lesions produced by UV exposure can lead to cyclobutane-pyrimidine dimers, 6-4 photoproducts, and the valence isomers of 6-4 photporducts (Sinha and Hader, 225). In addition, UV exposure can induce uracil dimers in double-stranded RNA (Holick, 1346). As a reaction to the DNA damage, the cell may initiate one of a variety of DNA repair mechanisms, including base excision repair, nucleotide excision repair, recombinational repair, mutagenic repair, or another alternative repair pathway (Sinha and Hader, 225). The cell may also respond by using dimer bypass for replication (Sinha and Hader, 225). If the DNA damage is irreparable, the apoptosis pathway may be induced and the cell will undergo programmed cell death (Clydesdale, Dandie, and Muller, 547).
Use your promo and get a custom paper on
"Biological Reactions to UV Light".
Exposure to UV light can also lead to immune suppression (Clydesdale, Dandie, and Muller, 549). For instance, an organism may respond to UV light by reducing lymphocyt function and/or recirculation (Cydesdale, Dandie, and Muller, 549). Another possible response is the production of suppressor T cells (Clydesdale, Dandie, and Muller, 547). In addition, exposure to UV light can suppress the immune system by interfering with delayed-type hypersensitivity reactions (Clydesdale, Dandie, and Muller, 549).
In humans, exposure to UV light can induce effects that specifically affect the skin. For instance, the superficial blood vessels in the dermis become dilated in response to UV light exposure (“Harmful Effects”). This enables increased blood flow in the skin, leading to a condition known as erythema – or, more commonly, sunburn (“Harmful Effects”). This vasodilation is further exacerbated by the fact that keratinocytes react to UV light exposure by increasing production of nitric oxide (NO) (Cydesdale, Dandie, and Muller, 548). In addition, melanocytes in the skin react to UV exposure by increasing the activity of tyrosinase, an enzyme that is responsible for the production of melanin (“Harmful Effects”). These melanin granules are then distributed throughout the epidermis, which leads to a darkening of the skin (“Harmful Effects”). It is important to note that this tanning is a delayed biological reaction to UV light exposure.
While many of the biological reactions to UV light have negative consequences, some recent studies suggest that UV light can induce biological reactions with positive effects. Specifically, one of the biological reactions of exposure to the absorption of UV-B radiation in 7-dehydrocholesterol molecules in the plasma membrane is the initiation of the process that ultimately results in the production of vitamin D (Holick, 1348). Vitamin D plays a wide range of important roles in the body, including enabling adequate calcium absorption (Holick, 1348). Also, keratinocyte cells react to UV-B light exposure by increasing expression of beta endorphin, which may boost mood (Holick, 1348).
In conclusion, there are a wide range of biological reactions to UV light exposure. When UV light damages DNA, the possible reactions range from the initiation of simple repair mechanisms to the initiation of programmed cell death. At the same time, UV light exposure can also induce system-wide responses that can lead to both positive and negative consequences for humans. Therefore, future studies examining biological reactions in greater depth will be valuable for understanding the specific consequences of UV light exposure.
- Clydesdale, Gavin J., Geoffrey W. Dandie, and H. Konrad Muller. “Ultraviolet Light Induced Injury: Immunological and Inflammatory Effects.” Immunology & Cell Biology, 2001, vol. 79, pp. 547-68.
- Holick, Michael F. “Biological Effects of Sunlight, Ultraviolet Radiation, Visible Light, Infrared Radiation and Vitamin D for Health.” Anticancer Research, 2016, vol. 36, no. 3, pp. 1345-56.
- Sinha, Rajeshwar P. and Donat P Hader. “UV-Induced DNA Damage and Repair: A Review.” Photochemical and Photobiological Science, 2002, vol. 1, 225-236.
- “Ultraviolet Radiation.” University of Minnesota, 2003, http://enhs.umn.edu/
