Researchers in Spain recently identified a receptor of the immune system that appears to play a pivotal role in the development of psoriasis, highlighting a possible new therapeutic avenue for the disease.
The study, “CD69 controls the uptake of L-tryptophan through LAT1-CD98 and AhR-dependent secretion of IL-22 in psoriasis,” was published in Nature Immunology.
Psoriasis is thought to be caused by genetic and environmental factors that set off the immune system, including genetic mutations, skin injury, infection, stress, smoking, hormonal changes, and some classes of medications. But the precise mechanisms that trigger the disease are still not fully understood.
In this study, the scientists looked into the link between a receptor in immune cells, CD29, and the synthesis of proteins in the cells, with particular focus on its impact on an amino acid (tryptophan), such acids being the building blocks of all proteins. Researchers also studied how the interplay of these mechanisms influenced inflammation.
“The leukocyte activation receptor CD69 is present in inflammatory cells in the skin,” Dr. Francisco Sánchez-Madrid, with the the Centro de Investigaciones Cardiovasculares Carlos III (CNIC) in Madrid, said in a press release. “These cells consume free essential amino acids like tryptophan by using specialized transport systems present in the cell membrane, such as LAT1 (SLc7a5). Consumption of aminoacids by inflammatory cells in the skin increases sharply during the inflammatory reaction, because it is important for their proliferation and activation and for the secretion of inflammatory molecules that amplify tissue damage, like interleukins 22 and 17 (IL-22 and IL-17).”
Researchers found that CD69 associated with LAT1 and regulated the uptake of amino acids such as tryptophan, whose metabolism, in turn, regulates the expression of pro-inflammatory IL-22. “Increases in the circulating levels of tryptophan favor the development of psoriasis by leading to increased levels of IL-22 in the skin,” said Dr. Danay Cibrián.
They concluded that these findings could have important future applications for the development of therapeutic agents suitable for the treatment of psoriasis.
Psoriasis, affecting around 2% to 3% of people worldwide, is a skin disorder characterized by abnormally fast-dividing skin cells, which leads to the appearance of red plaques covered with white scales. This induces both emotional and physical problems, as the skin plays many important biological functions in addition to the aesthetic role.