Scientists from the Florida campus of The Scripps Research Institute have identified a protein that may act as the trigger controlling the addictive impact of cocaine in the brain. The findings may one day lead to new therapies to treat addiction.
The study was published on August 15, 2010, in the prestigious journal Nature Neuroscience.
The results from the new study strongly suggest that a protein known as methyl CpG binding protein 2 (MeCP2) interacts with a type of genetic material known as microRNA to control an individual's motivation to consume cocaine.
"The study shows that MeCP2 blunts the amount by which microRNA-212 is increased in response to cocaine," said Paul Kenny, an associate professor in the Department of Molecular Therapeutics at Scripps Florida who led the study. "We have previously shown that miR-212 is very protective against cocaine addiction. Therefore, the conclusion is that MeCP2 may regulate vulnerability to addiction in some people through its inhibitory influence on miR-212. Without this influence, the expression of miiR-212 would be far greater in response to cocaine use, and the risk of addiction would likely be far lower."
This is the first time that MeCP2 has been shown to play a role in regulating cocaine addiction. Previously, the protein was most linked to Rett syndrome, a progressive neurodevelopmental disorder and one of the most common causes of mental retardation in females.
Interactions Shape Vulnerability
These new findings come on the heels of another cocaine addiction study by Kenny and his Scripps Florida colleagues published in the journal Nature in early July. That study showed for the first time that miR-212 — a type of small non-protein coding RNA that can regulate the expression levels of hundreds or even thousands of genes —influenced response to the drug in rats. Animals with increased miR-212 expression were less motivated to consume cocaine, pointing to the protective effects of miR-212 against cocaine addiction.
"The new findings are a significant advance from this previous study," Kenny said, "because they clearly demonstrate why microRNA-212 is not always fully protective – because MeCP2 regulates by how much miR-212 levels will increase in response to cocaine. This suggests that our initial findings may be central to explaining the complex process of addiction, and understanding how miR-212 signaling is regulated will be important. This study adds another level of detail to the blueprint."
A major goal of drug abuse research is to understand why certain individuals make the switch from casual to compulsive drug use and develop into addicts. Periods of easy access to the drug, along with repeated overconsumption, can quickly trigger the emergence of addiction-like abnormalities in animal models.
In the new study, the scientists first looked at the expression of MeCP2 in the brain after exposure to cocaine. They found that expression was increased in those animals given extended access to the drug.
"At that point," Kenny said, "we wanted to know if this increase was behaviorally significant – did it influence the motivation to take the drug?"
Using a virus to disrupt expression of MeCP2, the scientists found that rats consumed less and less cocaine. Intriguingly, levels of miR-212 were also far higher in those animals. Because increases in miR-212 suppress attraction to cocaine, the disruption of MeCP2, in essence, put miR-212 in charge and reduced vulnerability to the drug.
"We concluded that MeCP2 may play an important role in addiction by regulating the magnitude by which miR-212 expression is increased in response to cocaine," said Kenny. "In other words, MeCP2 seems to control just how much you can protect yourself against the addictive properties of cocaine."
Intriguingly, that was not the end of the story. In addition to MeCP2 blunting miR-212 expression, the scientists also found that the opposite was also true – that miR-212 could in turn decrease levels of MeCP2. This suggests that both are locked together in a regulatory loop. Importantly, the two had opposite effects on the expression of a particular growth factor in the brain – called BDNF – that regulates just how rewarding cocaine is.
While the new study fills in an important piece of the puzzle, the Kenny lab is hard at work to further increase our understanding of addiction.
"We still don't know what exactly influences the activity levels of MeCP2 on miR-212 expression," Kenny said. "Now we plan to explore what drives it – whether it's environmentally driven, and if genetic and epigenetic influences are important."
The first author of the study, "MeCP2 Controls BDNF Expression and Cocaine Intake through Homeostatic Interactions with microRNA-212," is Heh-In Im of The Scripps Research Institute. Other authors include Jonathan A. Hollander and Purva Bali, also of Scripps Research.
The study was supported by the National Institutes of Health, Ruth L. Kirschstein National Research Service Awards, and The National Alliance for Research on Schizophrenia and Depression.
About The Scripps Research Institute
The Scripps Research Institute is one of the world's largest independent, non-profit biomedical research organizations, at the forefront of basic biomedical science that seeks to comprehend the most fundamental processes of life. Scripps Research is internationally recognized for its discoveries in immunology, molecular and cellular biology, chemistry, neurosciences, autoimmune, cardiovascular, and infectious diseases, and synthetic vaccine development. Established in its current configuration in 1961, it employs approximately 3,000 scientists, postdoctoral fellows, scientific and other technicians, doctoral degree graduate students, and administrative and technical support personnel. Scripps Research is headquartered in La Jolla, California. It also includes Scripps Florida, whose researchers focus on basic biomedical science, drug discovery, and technology development. Scripps Florida is located in Jupiter, Florida.
Mika Ono | EurekAlert!
How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH
A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Physics and Astronomy
23.06.2017 | Information Technology