In a groundbreaking discovery, scientists have revealed that human skin is equipped with taste receptors previously thought to be exclusive to the tongue. These receptors, known as type-2 taste receptors (TAS2Rs), are found in skin cells and serve a critical role in protecting the body from harmful substances.
Research led by biologists at Okayama University of Science has expanded our understanding of these receptors, which are located in the skin’s keratinocytes, the cells that make up the outermost layer of the epidermis. The findings suggest that TAS2Rs function similarly to those on the tongue, detecting bitter substances and preventing them from causing damage to the skin.
While taste receptors were once believed to be confined to the tongue, earlier studies have shown that TAS2Rs are distributed across various parts of the body, including the colon, stomach, and upper airways. A pivotal study in 2015 revealed that these receptors are not only present but actively functioning in the keratinized epithelial cells of human skin. The latest research delves deeper into understanding their specific role.
In the study, lab-grown human keratinocytes were exposed to phenylthiocarbamide (PTC), a bitter compound commonly used in genetic research related to taste. Upon detecting PTC, the TAS2Rs on the skin cells triggered the production of ABC transporters, which are proteins responsible for transporting substances across cell membranes. The transporters helped expel the bitter compound from the cells.
To confirm the effectiveness of this process, researchers used a visible tracer dye to monitor the movement of the compound. When treated with verapamil, a substance known to block the transporters, the dye accumulated inside the cells, indicating that the transporters were crucial for expelling the compound. This experiment demonstrated how the TAS2Rs help protect skin cells from potentially harmful bitter compounds.
The research builds on the theory that bitterness in taste serves as a defense mechanism to avoid ingesting toxins. However, recent studies have questioned whether bitterness is a reliable indicator of toxicity, as many bitter foods are not harmful, and some toxic substances lack bitterness. Nonetheless, the study suggests that for skin cells, the activation of TAS2Rs may help mitigate the effects of toxic substances.
In another part of the experiment, skin cells exposed to high levels of antihistamine exhibited significantly better survival rates when their bitter receptors were activated prior to exposure. The researchers concluded that activation of TAS2Rs by bitter compounds like PTC and saccharin enhanced the production of ABC transporters, thus preventing cell death caused by toxic substances.
The study also found that blocking the transporters with verapamil reversed this protective effect, further supporting the idea that TAS2Rs play a vital role in the skin’s defense mechanism.
The researchers propose that activating TAS2Rs with harmless bitter compounds could offer a promising therapeutic approach to enhance the body’s ability to expel toxins from the skin. They suggest that this discovery opens up new possibilities for drug development aimed at protecting skin cells from harmful substances.
As scientists continue to uncover the diverse functions of taste receptors throughout the body, this research highlights the surprising ways in which our skin can taste and protect itself from harm.
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