ThinkTwice! Genetic Analysis Shows Gene Expression is Changed by Cocaine (Part II) JOURNAL ARTICLE TEI PLAIN LANGUAGE ANTHOLOGY C C

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1 JOURNAL ARTILE Transformed into part of a plain language anthology Genetic Analysis Shows Gene Expression is hanged by ocaine (Part II) Abstract/Summary: hanges in gene activity are responsible for long-lasting changes to the brain reward system (BRS) caused by drug addiction. As described in Part 1, hip is a test that allows researchers to study the activity of thousands of genes. This study used hip to compare BRS gene activity in mice given the illegal drug ocaine to gene activity in mice given salt water. Many BRS genes were affected in mice given cocaine. A new family of genes, SIRT, was among the genes identified. Part of the SIRT mouse study showed that cocaine increases SIRT gene activity. A separate experiment using rats indicates that SIRT blockers reduce the amount of cocaine taken by rats. This study links SIRT to cocaine use and provides clues to possible new treatments for cocaine users. Background: A gene is the basic unit of instruction for a trait. Each gene is located in a specific place on a DNA (Deoxyribonucleic acid) molecule. DNA is a large molecule that contains thousands of genes. These genes, in turn, contain genetic instructions needed for functioning and development of all living things. Genetic instructions are read when DNA is activated to make smaller molecules called mrna (messenger Ribonucleic acid). Each mrna has a code to make one type of protein (See Figure 1). DNA can make many types of mrna and therefore can direct the production of many kinds of proteins. Genes in DNA can be turned on or off and their activity level can be turned up or down. In this way, the amount of each type of protein made can be controlled. DNA DNA Molecule mrna Figure 1 From DNA to Protein (Modified from original mrna PROTEIN Amino Acids link to Make Protein A G U A U G U A A Ribosome trna This article was transformed for age level from the original article: William Renthal, et al., (2009). Genome-wide Analysis of hromatin Regulation by ocaine Reveals a Role for Sirtuins. Neuron, 62, AUTHORS of Original Article: William Renthal,1,6 Arvind Kumar,1,6 Guanghua Xiao,2,6 Matthew Wilkinson,4 Herbert E. ovington III,4 Ian Maze,4 Devanjan Sikder,3 Alfred J. Robison,4 Quincey LaPlant,1,4 David M. Dietz,4 Scott J. Russo,4 Vincent Vialou,4 Sumana hakravarty,1 Thomas J. Kodadek,3 Ashley Stack,5 Mohamed Kabbaj,5 and Eric J. Nestler,1,4* 1 Departments of Psychiatry and Neuroscience 2 Department of linical Sciences 3 Department of Internal Medicine The University of Texas Southwestern Medical enter at Dallas, Dallas, TX 75390, USA 4 Fishberg Department of Neuroscience, Mount Sinai School of Medicine, New York, NY 10029, USA 5 Department of Biomedical Sciences, Florida State University, Tallahassee, FL 32306, USA 6 These authors contributed equally to this work This transformed article is for K 12 educational use only and follows peer-reviewed format. * orresponding author 1

2 Inside cells, DNA molecules are organized into chromosomes. In chromosomes, parts of the DNA molecule wrap around proteins (like thread around a spool) called histones (Figure 2). Histones are associated with individual genes. Histones help control which genes in a chromosome are turned on or off at a given time. They also help control how active the genes are once they are turned on. Just as the volume of a television set can be turned up or down, gene activity can be turned up or down (regulated). Adding or removing A (acetyl) Groups and M (methyl) Groups to or from histones can regulate gene activity. In general, A (acetyl) Groups added to histones turn up gene activity. When A Groups are removed from histones, gene activity is turned down. In general, M (methyl) Groups added to histones turn down gene activity. When M Groups are removed, gene activity increases. (See Figure 2). There are exceptions to this, however. Also, genes can be regulated in many other ways. DNA A AA M M M Histone Tails Histone hromosome Gene Activity increases when decreases when A Groups Added M Groups Removed A Groups Removed M Groups Added Figure 2 Histones (Modified from original Many substances in our environment affect gene activity. This is of major importance and is called epigenetics. Epigenetics refers to changes in the phenotype of an organism but not to its genotype. This means there is a change in the way genes act, but no actual change to the genes themselves. These changes can be good if they help the organism function well, but they are bad when they disturb normal function. Scientists do not know how long epigenetic 2

3 changes can last, but some can be passed from one generation to another. ocaine (and other addictive drugs) changes gene activity. Unfortunately, cocaine-related changes in gene activity cause long-lasting changes in the brain that can lead to full blown addiction. Drug addiction is a disease. As described above, cocaine and other addictive drugs cause biological changes in the body. The disease progresses when drug use acts as a stimulus. The stimulus activates the BRS and a reward is produced in response. The reward is a good feeling that results from higher levels of certain brain chemicals, such as dopamine. The reward causes a person to want to repeat the behavior that caused it, so the person seeks more drugs. Over time, the natural ability to respond to the reward decreases. An addicted person has cravings and becomes obsessed with getting the drug. Eventually, the addict must have more and more of the drug to feel its effects. Addiction is truly a devastating disease. Introduction: Past research has shown that the use of drugs, like cocaine, causes long-term changes in the BRS. A major goal for new research has been to learn how drugs act upon this area of the brain to cause addiction. Existing research has also shown that drug use can cause epigenetic changes in genes (Hyman, et al., 2006; Freeman, et al., 2001; Mclung and Nestler, 2003). A powerful test called hip is able to examine thousands of genes at once and identify which are turned on and which are turned up or down. hip was used in this study to compare gene activity in the BRS between mice given cocaine and those given salt water. Thousands of genes in the BRS of mice were analyzed by hip. A new gene family, SIRT (Sirtuins), was linked to cocaine use. This part of the study was done with rats. Mice and rats were used because the research could not be done safely with human volunteers. To ensure that the animals were well cared for, the research was conducted according to guidelines set forth by the National Institutes of Health and the Animal are and Use ommittee of Florida State University. Procedure: From this study, researchers identified thousands of genes affected by cocaine use. One group, SIRT (sirtuin), was of special interest because it had not been identified in previous research on the epigenetic effects of cocaine. hip was performed on BRS samples from mice treated with cocaine or salt water. In order to link a change in SIRT activity to cocaine use (behavior), another experiment using rats was done. Rats were used because they are more easily trained to push a lever to give themselves shots of cocaine. Thirty rats were used. The rats all weighed between g at the beginning of the experiment. Temperatures in the rats environment were constant at 22 o. Rats had access to as much food and water as they wanted. They were kept in a 12 hour light/dark cycle. The rats were connected to a device that would give them cocaine when they pushed a lever. The rats were monitored as they learned to use the lever. Of the 30 rats, 12 met all training requirements set by researchers. The results from these 12 rats were used in the analysis. Of these 12 rats, 7 were given a SIRT blocking chemical and 5 were given a SIRT boosting chemical. See Figure 3. 3

4 30 Rats Were Trained to Push a Lever to Give Themselves ocaine 12 Met Training Requirements Set by Researchers 18 Did Not Meet Training Requirements and Were Dropped From Experiment 7 rats Were Given SIRTS Blocker 5 rats Were Given SIRTS Booster 4 Figure 3 Rat Experiment Study Design Discussion: Part 1 of this study revealed that many BRS genes in mice were affected by cocaine use. Many of these BRS genes have been linked to cocaine use in previous studies (Freeman et al., 2001; Mclung and Nestler, 2003; Yao et al., 2004). ocaine caused increases in histone changes (A Groups and M Groups added or removed) at many more genes than it caused decreases. Some of these genes were greatly affected by cocaine. One group, the SIRT (sirtuins), was of special interest to the researchers. Before this study, no one knew SIRT was involved in cocaine addiction. Humans make seven forms of SIRT. They are involved in many processes in the body, like cell growth, and aging (Michan & Sinclair, 2007). SIRT genes were more active in cocaine-treated mice than in salt water-treated mice. Figure 4 shows the activity of both forms of SIRT identified in this study. Results: 3 G E 2.5 N E 2 A 1.5 T I V I T Y (*fold change) Salt Water-Treated 0 ocaine-treated SIRT 1 SIRT 2 *fold change is the number of times greater than normal Figure 4 SIRT Gene Activity in BRS of Mice Treated with ocaine and Salt Water

5 Rats trained to give themselves cocaine by pressing a lever received injections of either SIRT boosting or SIRT blocking chemicals. hemicals that boost SIRT caused cocaine-using and seeking behavior. hemicals that block SIRT decreased cocaine use at certain doses of cocaine (Figure 5). This is an exciting finding, because chemicals that lower SIRT activity might be important treatments for people addicted to cocaine. N U M B E R O F I N J E T I O N S ( o f S I R T B o o s t e r o r B l o c k e r ) Amount of ocaine Per Dose (μg) SIRT Blocker SIRT Booster Figure 5 Effect of SIRT on ocaine Self-Administration in Rats onclusion: The main findings of this study were: one group of SIRT genes, when active, increases cocaine use in rats and blocking SIRT activity may reduce cocaine use. Thus, this study provides more evidence that cocaine makes epigenetic changes to genes. These changes are related to behaviors linked to cocaine addiction. These cocaine-induced biological changes, in turn, result in long-lasting changes to the brain. References: Bowers, M.S., and Kalivas, P.W. (2003). Forebrain astroglial plasticity is induced following withdrawal from repeated cocaine administration. Eur. J. Neurosci. 17, Freeman, W.M., Nader, M.A., Nader, S.H., Robertson, D.J., Gioia, L., Mitchell, S.M., Daunais, J.B., Porrino, L.J., Friedman, D.P., and Vrana, K.E. (2001). hronic cocaine-mediated changes in non-human primate nucleus accumbens gene expression. J. Neurochem. 77,

6 References continued: Hyman, S.E., Malenka, R.., and Nestler, E.J. (2006). Neural mechanisms of addiction: the role of reward-related learning and memory. Annu. Rev. Neurosci. 29, Mclung,.A., and Nestler, E.J. (2003). Regulation of gene expression and cocaine reward by REB and DeltaFosB. Nat. Neurosci. 6, Medline Plus Accessed August 27, 2009 Michan, S., and Sinclair, D. (2007). Sirtuins in mammals: insights into their biological function. Biochem. J. 404, Nestler, E.J. (2008). Transcriptional mechanisms of addiction: role of delta-fosb. Philos. Trans. R. Soc. Lond. B Biol. Sci. 363, Renthal, W. et al., (2009). Genome-wide Analysis of hromatin Regulation by ocaine Reveals a Role for Sirtuins. Neuron, 62, Yao, W.D., Gainetdinov, R.R., Arbuckle, M.I., Sotnikova, T.D., yr, M., Beaulieu, J.M., Torres, G.E., Grant, S.G., and aron, M.G. (2004). Identification of PSD-95 as a regulator of dopamine-mediated synaptic and behavioral plasticity. Neuron 41, National Institutes of Health, The New Genetics Accessed August 26, 2009 Study Disclosure: Funding support for the study was from Grants supplied by NIDA (National Institute on Drug Abuse). No member of the research team disclosed a conflict of interest. Measures of Readability for this Translation (text only): Flesch-Kincaid Grade Level 8.1 Flesch Reading Ease