Researchers discover how the brain turns chronic stress into pathological anxiety

February 13, 2017

Science Daily/Scripps Research Institute

n a new study, researchers at The Scripps Research Institute (TSRI) have described how two important molecules in the brain work together to trigger intense anxiety.

The new findings in animal models point to a novel interaction in the regulation of the brain's stress response that may underlie the pathological anxiety related to symptoms of post-traumatic stress disorder (PTSD).

"Anxiety and stress disorders affect millions of people worldwide," explained study leader Marisa Roberto, a professor at TSRI. "Understanding the mechanisms underlying these disorders is important for identifying potential new targets for therapeutic use."

The researchers focused on the endogenous cannabinoid (endocannabinoid or eCB) system, which include natural lipid signaling molecules that bind to cannabinoid receptors in the brain. Cannabinoid (type 1) receptors control stress-mediating circuits by inhibiting neurotransmitter release -- a sort of gating mechanism to keep anxiety in check.

In contrast to the stress-reducing properties of endocannabinoids, a peptide molecule called corticotropin-releasing factor (CRF) activates the stress response and promotes increased sensitivity to stress and anxiety when activated over and over again.

In the new study, published in the journal Biological Psychiatry, the researchers investigated the interaction between the stress-promoting (CRF) and stress-constraining (eCBs) mechanisms in the central nucleus of the amygdala, a critical brain region involved in mediating emotional reactions. The findings suggest that overactive CRF signaling in this region produces a wide range of effects that override the stress-reducing capabilities of a major eCB called N-arachidonoylethanolamine (anandamide), turning chronic stress into unchecked, or pathological, anxiety.

"Anxiety is something that everyone experiences on a day-to-day basis," said study first author Luis A. Natividad, a research associate in the Roberto lab. "But it is unclear what changes this otherwise natural process into something debilitating."

To answer this question, Roberto's lab teamed up with Roberto Ciccocioppo's lab at the University of Camerino, Italy, and the lab of TSRI Professor Loren ("Larry") Parsons, a leader in the fields of endocannabinoid signaling, stress and drug addiction who passed away in 2016.

The researchers studied rats that were genetically selected for higher alcohol drinking and also display an anxiety-like phenotype. These rats exhibit a mutation in a gene called Crhr1 that increases CRF (type 1) receptor signaling.

Using behavioral, neurochemical and electrophysiological approaches, the researchers found that increased CRF signaling led to elevated activity of the anandamide clearance enzyme fatty acid amide hydrolase (FAAH). Increased CRF was also associated with drops in anandamide levels in the central nucleus of the amygdala. Together, increased FAAH activity and decreased anandamide signaling reduce inhibitory control of excitatory neurotransmission in this critical region, and lower the brain's ability to regulate stress and anxiety.

The researchers concluded that long-term dysregulation of CRF-FAAH mechanisms in the amygdala keeps anandamide from doing its job. Without anandamide to balance out the system, the brain is primed to react to stress.

Follow-up experiments showed that inhibiting FAAH could blunt CRF's effects and reduce signs of anxiety in the rats.

Roberto said the next step will be to further study this rat model to better understand relationships between high anxiety and alcoholism. She added that the rat model could also be useful for studying PTSD, where high anxiety is connected to a higher risk of developing alcoholism.

"The results of our study may be useful, not only in understanding the neurobiological basis of alcoholism, anxiety and possibly PTSD, but also in developing more efficacious pharmacotherapies to treat these disorders," added Ciccocioppo.

The researchers dedicated this study to Parsons. Natividad added a note on Parson's influence on the research and on the TSRI campus:

"Larry's guidance throughout the study was critical in bringing together a cohesive story exploring the relevance of endocannabinoid signaling with downstream neural processing in a way that is unique to the field and has translational relevance to the human condition. He serves as a role model for me not only as a scientist, but also in terms of being a good colleague, mentor and friend to those around him. I feel privileged to have been part of his lab, his teachings and mentorship. He will be dearly missed."

https://www.sciencedaily.com/releases/2017/02/170213131201.htm

Compound boosts marijuana-like chemical in the body to relieve pain at injury site

September 21, 2010

Science Daily/University of California -- Irvine

American and Italian researchers have found that a novel drug allows anandamide -- a marijuana-like chemical in the body -- to effectively control pain at the site of an injury.

Led by Daniele Piomelli, the Louise Turner Arnold Chair in Neurosciences and director of the Center for Drug Discovery at UC Irvine, the study suggests that such compounds could form the basis of pain medications that don't produce sedation, addiction or other central nervous system side effects common with existing painkillers, such as opiates.

"These findings raise hope that the analgesic properties of marijuana can be harnessed to curb pain," Piomelli said. "Marijuana itself is sometimes used in clinical settings for pain relief but causes many unwanted effects. However, specific drugs that amplify the actions of natural, marijuana-like chemicals are showing great promise."

For the study, which appears in the Sept. 19 online version of Nature Neuroscience, rats and mice were given a drug created by Piomelli and colleagues at the Italian universities of Urbino and Parma. The researchers discovered that the compound, URB937, did not enter the central nervous system but simply boosted the levels of anandamide in peripheral tissues. Still, it produced a profound analgesic effect for both acute and chronic pain. This was surprising, since anandamide had been thought to only work in the brain.

The synthetic drug inhibits FAAH, an enzyme in the body that breaks down anandamide, dubbed "the bliss molecule" for its similarities to the active ingredient in marijuana. A neurotransmitter that's part of the endocannabinoid system, anandamide has been shown in studies by Piomelli and others to play analgesic, antianxiety and antidepressant roles. It's also important in regulating food consumption. Blocking FAAH activity enhances the effects of anandamide without generating the "high" seen with marijuana.

Piomelli and his team are now collaborating with drug discovery specialists at the Italian Institute of Technology, in Genoa, to develop the new compound -- which is protected by a patent application -- into a clinically useful medication.

Researchers from UCI, the University of Georgia, the University of Naples, the University of Parma, the University of Urbino and the Italian Institute of Technology participated in the study, which was supported by the National Institute on Drug Abuse and the Italian Ministry of Public Education.

https://www.sciencedaily.com/releases/2010/09/100920131140.htm

Enzyme Builds Neurotransmitters Via Newly Discovered Pathway

September 22, 2006

Science Daily/Scripps Research Institute

Scientists at the Scripps Research Institute have uncovered a previously unknown function of an enzyme that appears to play a primary role in the biosynthesis of a large class of lipids that help modulate diverse physiological processes, including anxiety, inflammation, learning and memory and appetite.

The study, which was directed by Scripps Research Professor Benjamin Cravatt, Ph.D., is being published in the September 8 issue of The Journal of Biological Chemistry.

The new study describes a pathway-different than the one previously suggested-for the biosynthesis of neurotransmitter lipids, N-acyl ethanolamines (NAEs), which include the endogenous cannabinoid ("endocannabinoid") anandamide. The high activity of the enzyme a/b hydrolase4 (Abh4) in areas such as the central nervous system suggests that the pathway makes a "potentially major contribution" to endocannabinoid signaling.

Endocannabinoids are naturally produced substances similar to the active ingredient D9-tetrahydrocannabinol (THC) in marijuana. Cannabinoid receptors were first discovered in 1988; the first endocannabinoid, anandamide, which shares some of the pharmacologic properties of THC, was identified in 1992.

Other research has shown that the endogenous cannabinoid system helps control food intake, among other critical processes, by acting on cannabinoid receptors in the central nervous system. The system drives consumption of fat and calorie-rich foods and the amount of fat stored or expended and plays a significant role in energy homeostasis.

"At least one cannabinoid receptor antagonist is on the verge of approval for the treatment of obesity-metabolic disorders," said Cravatt. "Enzymes involved in endocannabinoid biosynthesis, such as the one highlighted in our study, can be viewed as complementary drug targets. One potential advantage of this approach is that it may prove more selective than a receptor antagonist. By inhibiting enzymes such as Abh4, we may be able to disrupt the activity of a single class of endocannabinoids, rather than all of them."

In the new study, the researchers provide biochemical evidence of an alternative pathway for NAE biosynthesis in vivo and demonstrate that these new routes are especially important for the creation of a number of NAEs, including anandamide. The researchers also isolated and identified the enzyme Abh4 by combining traditional protein purification and functional proteomic technologies, concluding that Abh4 "displayed multiple properties" that would be expected of an enzyme involved in NAE biosynthesis.

However, the authors of the study noted, the unique contribution that this Abh4-mediated route makes to the production of NAEs in vivo is yet to be determined and will require "the generation of genetic or pharmacological tools that selectively [interrupt] this pathway."

"The continued pursuit of additional enzymes involved in NAE biosynthesis should further enrich our understanding of the complex metabolic network that supports the endocannabinoid/NAE system in vivo," Cravatt said. "From a therapeutic perspective, any of these enzymes could represent an attractive drug target for a range of human disorders in which disruption of endocannabinoid signaling by cannabinoid receptor antagonists has proven beneficial."

Gabriel Simon of Scripps Research was the other author of the study, titled "Endocannabinoid biosynthesis proceeding through Glycerophospho-N-Acyl ethanolamine and a role for a/b hydrolase 4 in this pathway."

The research was supported by the National Institutes of Health, the Skaggs Institute for Chemical Biology, and the Helen L. Dorris Institute for the Study of Neurological and Psychiatric Disorders of Children and Adolescents.

https://www.sciencedaily.com/releases/2006/09/060915203730.htm

UC Irvine Researchers Demonstrate How Marijuana-Like Chemicals Work in the Brain

March 23, 1999

Science Daily/University of California, Irvine

Findings Could Lead to New Treatments for Schizophrenia, Parkinson's, Other Diseases

Researchers at UC Irvine's College of Medicine have discovered how chemicals in the brain that are related to the active ingredient of marijuana help regulate body movements and other motor activity in rats.

In the April issue of the journal Nature Neuroscience, the researchers also report finding a network of these chemicals within the brain that prevents the overactive motor behavior found in schizophrenia, Parkinson's disease and Tourette's syndrome. The discoveries ultimately could result in new treatments for these and other neurological diseases.

Daniele Piomelli, associate professor of pharmacology, and Andrea Giuffrida, a post-doctoral researcher, found that a marijuana-like chemical called anandamide (the Sanskrit word for "bliss") inhibits the effects of nerve cells that transmit dopamine, which is largely responsible for stimulating movement and other motor behavior in the brain. For years, scientists have linked the uncontrolled production of dopamine to schizophrenia, Tourette's syndrome (which causes severe "nervous tics") and Parkinson's disease.

"This shows for the first time how anandamides work in the brain to produce normal motor activity," Piomelli said. "Patients with schizophrenia and other diseases have reported that marijuana appears to relieve some of their symptoms, but scientists have never found a physiological reason why. By understanding how the anandamide system works similarly to marijuana, we can explore new ways to treat these diseases more effectively."

But Piomelli said his research group will not consider marijuana in future research aimed at developing new treatments, because its chemical activity doesn't produce the effects on dopamine that are useful for treating these diseases. "Marijuana doesn't provide the regulatory effects on dopamine in the brain that we're looking for," he said.

The researchers found that anandamide is part of a network of nerve cells in an area of the brain called the striatum, which coordinates all body movements and other motor behavior. In the striatum, the anandamide network inhibited dopamine's attempts to stimulate the body's motor nerves. Normally, nerve cells regulate this behavior by releasing anandamides at the same time they release dopamine. In order to temper the effects of dopamine, the anandamides bind to nerve cell sites called cannabinoid receptors, so-named because they are targets of tetrahydrocannabinol (marijuana's active ingredient) as well as related chemicals like anandamides. When anandamides were bound to these receptors, body movement in the rats decreased.

But when the researchers prevented the cannabinoid receptors from binding to anandamides, the blocked nerve cells could no longer inhibit dopamine's effects. In such a state, the rats experienced severe nervous tics and other uncontrolled motor activity. In humans, such exaggerated activity brought on by unregulated dopamine production can result in diseases such as schizophrenia, Tourette's and Parkinson's.

By enhancing the nerve cells' sensitivity to anandamide, new medicines could treat these diseases without the side effects of current medicines, Piomelli said. "Current drugs certainly halt the actions of dopamine, but the side effects, including sedation and dizziness, are very severe," he said. "Drugs that exploit the anandamide system can provide a gentler way of reducing the hyperactivity in the brain caused by too much dopamine."

But Piomelli said it will be many years before any drugs will be available on the market. "We're just beginning to map out where this system works in rats' brains. We still are a long way from knowing how anandamides work in humans, and any potential drugs would have to be tested rigorously for their effectiveness and safety."

Piomelli's research group discovered the existence of anandamides in the brain and has spent several years exploring how these chemicals and their nerve-cell receptors work in the central nervous system. Piomelli and Giuffrida were assisted in their research by Loren H. Parsons and Toni Kerr at the Scripps Research Institute, La Jolla, Calif., and Fernando Rodriguez de Fonseca and Miguel Navarro of the Universidad Complutense, Madrid.

https://www.sciencedaily.com/releases/1999/03/990323050735.htm