Dopamine, a neurotransmitter, is manufactured in the brain and other parts of the nervous system from the amino acid l-tyrosine. Among dopamine's many functions, it serves important roles in controlling voluntary movement, cognition and motivational behavior. Dopamine can also be converted into norepinephrine, a neurotransmitter and stress hormone. Dopamine deficiency is associated with conditions such as Parkinson's disease and attention deficit disorder. Recent research has uncovered significant influences of dopamine on the immune system with particular effects on a variety of degenerative neurological and inflammatory diseases.
Rheumatoid Arthritis
Dopamine may activate the immune system and aggravate symptoms of rheumatoid arthritis, according to a study published in the February 2011 "Journal of Immunology." Certain immune cells respond to dopamine by increasing production of inflammatory interleukin molecules, say the researchers. In the study, scientists also found dopamine in the joint tissue and synovial fluid of rheumatoid arthritis patients. The researchers say this study is the first of its kind to show the immune system effects of dopamine in rheumatoid arthritis.
Lymphocytes
A study published in the 2010 issue of the journal "Neuroendocrinology Letters" found that T lymphocytes -- a type of white blood cell -- contain five different receptors for dopamine. The researchers identified two that show the most immune-modulating ability. When the researchers added a dopamine-blocking agent for the most active receptor, production of the inflammatory molecule interferon decreased. However, heightened production of lymphocytes and other markers for increased immune system activity continued. The study results may be useful in the development of highly-targeted immune-modulating drugs.
Leukemia
There may be a dopamine-related causative factor behind leukemia in some people, say researchers of a study published in the August 2010 "Journal of Biological Chemistry." In the tissue culture study of T-lymphocyte cells affected with leukemia, researchers found an error in the mechanism that shuts off immune system activation after the T-lymphocyte cells have responded to dopamine, leading to a runaway immune response that may result in the eventual development of the disease.
Parkinson's Disease
Parkinson's disease, characterized by dopamine deficiency, may also have an immune system component, according to a study published in the January 2008 journal "PLoS One." Inflammation in the nerves, one of the processes of Parkinson's disease, may stem from oxidized proteins that have a toxic effect. An immune response ensues that leads to damage to the dopamine-producing cells in the brain, say the researchers. These study results shed new light on the causes and potential treatments for Parkinson's disease.
References
- "Journal of Immunology"; Dopamine Induces IL-6-Dependent IL-17 Production via D1-Like Receptor on CD4 Naive T Cells and D1-Like Receptor Antagonist SCH-23390 Inhibits Cartilage Destruction in a Human Rheumatoid Arthritis/SCID Mouse Chimera Model. Nakano K, et al.; 2011
- "Neuroendocrinology Letters"; Roles of dopamine receptor subtypes in mediating modulation of T lymphocyte function. Huang Y, et al.; 2010
- "Journal of Biological Chemistry"; D1 and D2 dopamine receptor-mediated inhibition of activated normal T cell proliferation is lost in jurkat T leukemic cells. Basu B, et al.; 2011
- PLoS One"; Nitrated alpha-synuclein immunity accelerates degeneration of nigral dopaminergic neurons. Benner EJ, et al.; 2008
