Neuroscience

Articles and news from the latest research reports.

Posts tagged opioids

162 notes

Missing Enzyme Linked to Drug Addiction

A missing brain enzyme increases concentrations of a protein related to pain-killer addiction, according to an animal study. The results were presented at The Endocrine Society’s 95th Annual Meeting in San Francisco.

image

Opioids are pain-killing drugs, derived from the opium plant, which block signals of pain between nerves in the body. They are manufactured in prescription medications like morphine and codeine, and also are found in some illegal drugs, like heroin. Both legal and illegal opioids can be highly addictive.

In addition to the synthetic opioids, natural opioids are produced by the body. Most people have heard of the so-called feel-good endorphins, which are opioid-like proteins produced by various organs in the body in response to certain activities, like exercise.

Drug addiction occurs, in part, because opioid-containing drugs alter the brain’s biochemical balance of naturally produced opioids. Nationwide, drug abuse of opioid-containing prescription drugs is skyrocketing, and researchers are trying to identify the risk factors that differentiate people who get addicted from those who do not.

In this particular animal model, researchers eliminated an enzyme called prohormone convertase 2, or PC2, which normally converts pre-hormonal substances into active hormones in certain parts of the brain. Previous research by this team demonstrated that PC2 levels increase after long-term morphine treatment, according to study lead author Theodore C. Friedman, MD, PhD, chairman of the internal medicine department at Charles R. Drew University of Medicine and Science in Los Angeles.

“This raises the possibility that PC2-derived peptides may be involved in some of the addiction parameters related to morphine,” Friedman said.

For this study, Friedman and his co-researchers analyzed the effects of morphine on the brain after knocking out the PC2 enzyme in mice. Morphine normally binds to a protein on cells known as the mu opioid receptor, or MOR. They found that MOR concentrations were higher in mice lacking PC2, compared to other mice.

To analyze the effects of PC2 elimination, the researchers examined MOR levels in specific parts of the brain that are related to pain relief, as well as to behaviors associated with reward and addiction. They measured these levels using a scientific test called immunohistochemistry, which uses specific antibodies to identify the cells in which proteins are expressed.

“In this study, we found that PC2 knockout mice have higher levels of MOR in brain regions related to drug addiction,” Friedman said. “We conclude that PC2 regulates endogenous opioids involved in the addiction response and in its absence, up-regulation of MOR expression occurs in key brain areas related to drug addiction.”

(Source: newswise.com)

Filed under drug addiction opioids brain prohormone convertase 2 enzymes animal model neuroscience science

120 notes

Researchers Design Variant of Main Painkiller Receptor Opioids, such as morphine, are still the most effective class of painkillers, but they come with unwanted side effects and can also be addictive and deadly at high doses. Designing new pain-killing drugs of this type involves testing them on their corresponding receptors, but access to meaningful quantities of these receptors that can work in experimental conditions has always been a limiting factor.  Now, an interdisciplinary collaboration between researchers at the University of Pennsylvania has developed a variant of the mu opioid receptor that has several advantages when it comes to experimentation. This variant can be grown in large quantities in bacteria and is also water-soluble, enabling experiments and applications that had previously been very challenging or impossible.   The study was led by Renyu Liu, an assistant professor in the Department of Anesthesiology and Critical Care at Penn’s Perelman School of Medicine, and Jeffery Saven, an associate professor in the Department of Chemistry in the School of Arts and Sciences. Jose Manuel Perez-Aguilar, then a graduate student in the Department of Chemistry, and Jin Xi, Felipe Matsunaga and Xu Cui, lab members in the Department of Anesthesiology and Critical Care, along with Bernard Selling of Impact Biologicals Inc., contributed significantly to this study. Their research was published in the Journal PLOS ONE. The mu opioid receptor belongs to a class of cellular membrane proteins called G protein-coupled receptors, or GPCRs. Involved in wide range of biological processes, these receptors bind to molecules in the environment, initiating cellular signaling pathways. In the case of this receptor, binding to opioid molecules leads to a profound reduction of pain but also to a variety of unpleasant and potentially fatal side-effects, a problem that researchers from multiple disciplines are attempting to address. “There are two directions for solving this problem in basic science, either working on the opioid molecule or working on the receptor,” Liu said. “We’re doing the latter.” Experimenting on the mu opioid receptor has been challenging for several reasons. The human receptor itself is relatively scarce, appearing in small quantities on only a few types of cells, making harvesting appreciable amounts impractical. Researchers have also been unable to grow it recombinantly — genetically engineering bacteria to express the protein en masse — as some parts of the protein are toxic to E.coli. Hydrophobic, or water-hating, amino acid groups on the exterior of the receptor that help it sit in the cell’s membrane also make it insoluble in water when isolated. The researchers set out to address these challenges by computationally designing variants of the mu opioid receptor. This task had challenges of its own; their research was conducted long before the crystal structure of receptor was known.          “The problem with this receptor is that the native structure has only very recently been solved and only a significant re-engineered mouse model at that,” Liu said. “When we started this project, we were blind.” Starting with only the gene sequence for the human version of the receptor, the researchers knew the order of the protein’s amino acids but not how they were folded together. The structures for other GPCRs, such as rhodopsin and the beta-2 adrenergic receptor, were known at the time, however. “Based on the comparison of our sequence to the sequences of those GPCRs, we built a computer model of the protein,” Saven said. “When the structure of the mouse version of this receptor appeared, we were able to compare our model to that structure, and they matched up really well.” From that comparison, the researchers were able to identify the hydrophobic amino acids on the exterior of the structure, as well as some of those that were potentially toxic to E. coli. “The objective then was to redesign those exterior amino acids,” Saven said. “Based on the physical and chemical interactions these amino acids have with each other and with water, we were able to identify sequence combinations that are consistent with the model — where atoms don’t overlap in space — and preferentially occupy the exterior surface with ones that are water soluble.” Replacing 53 of the protein’s 288 amino acids, the research team introduced the new gene sequence into E. coli, which were able to produce large quantities of the variant. Beyond looking like the now-available mouse mu opioid receptor, the researchers were able to show its value to future studies by performing functional tests.   “We showed that this water-soluble form of the protein can compete with the native, membrane-based form when binding with antagonists that are fluorescently labeled,” Saven said. “You can watch the fluorescence shift as more of these water-soluble variants are floating around in the solution.”    The team’s computational approach enables further iterations of the variant to be more easily designed, meaning it can be tweaked alongside experimental conditions.  “This is a great product that can do a lot of things,” Liu said. “You can use this variant to look at the structure-function relationship for the receptor, or even potentially use it as a screening tool.”

Researchers Design Variant of Main Painkiller Receptor

Opioids, such as morphine, are still the most effective class of painkillers, but they come with unwanted side effects and can also be addictive and deadly at high doses. Designing new pain-killing drugs of this type involves testing them on their corresponding receptors, but access to meaningful quantities of these receptors that can work in experimental conditions has always been a limiting factor. 

Now, an interdisciplinary collaboration between researchers at the University of Pennsylvania has developed a variant of the mu opioid receptor that has several advantages when it comes to experimentation. This variant can be grown in large quantities in bacteria and is also water-soluble, enabling experiments and applications that had previously been very challenging or impossible.  

The study was led by Renyu Liu, an assistant professor in the Department of Anesthesiology and Critical Care at Penn’s Perelman School of Medicine, and Jeffery Saven, an associate professor in the Department of Chemistry in the School of Arts and Sciences. Jose Manuel Perez-Aguilar, then a graduate student in the Department of Chemistry, and Jin Xi, Felipe Matsunaga and Xu Cui, lab members in the Department of Anesthesiology and Critical Care, along with Bernard Selling of Impact Biologicals Inc., contributed significantly to this study.

Their research was published in the Journal PLOS ONE.

The mu opioid receptor belongs to a class of cellular membrane proteins called G protein-coupled receptors, or GPCRs. Involved in wide range of biological processes, these receptors bind to molecules in the environment, initiating cellular signaling pathways. In the case of this receptor, binding to opioid molecules leads to a profound reduction of pain but also to a variety of unpleasant and potentially fatal side-effects, a problem that researchers from multiple disciplines are attempting to address.

“There are two directions for solving this problem in basic science, either working on the opioid molecule or working on the receptor,” Liu said. “We’re doing the latter.”

Experimenting on the mu opioid receptor has been challenging for several reasons. The human receptor itself is relatively scarce, appearing in small quantities on only a few types of cells, making harvesting appreciable amounts impractical. Researchers have also been unable to grow it recombinantly — genetically engineering bacteria to express the protein en masse — as some parts of the protein are toxic to E.coli. Hydrophobic, or water-hating, amino acid groups on the exterior of the receptor that help it sit in the cell’s membrane also make it insoluble in water when isolated.

The researchers set out to address these challenges by computationally designing variants of the mu opioid receptor. This task had challenges of its own; their research was conducted long before the crystal structure of receptor was known.         

“The problem with this receptor is that the native structure has only very recently been solved and only a significant re-engineered mouse model at that,” Liu said. “When we started this project, we were blind.”

Starting with only the gene sequence for the human version of the receptor, the researchers knew the order of the protein’s amino acids but not how they were folded together. The structures for other GPCRs, such as rhodopsin and the beta-2 adrenergic receptor, were known at the time, however.

“Based on the comparison of our sequence to the sequences of those GPCRs, we built a computer model of the protein,” Saven said. “When the structure of the mouse version of this receptor appeared, we were able to compare our model to that structure, and they matched up really well.”

From that comparison, the researchers were able to identify the hydrophobic amino acids on the exterior of the structure, as well as some of those that were potentially toxic to E. coli.

“The objective then was to redesign those exterior amino acids,” Saven said. “Based on the physical and chemical interactions these amino acids have with each other and with water, we were able to identify sequence combinations that are consistent with the model — where atoms don’t overlap in space — and preferentially occupy the exterior surface with ones that are water soluble.”

Replacing 53 of the protein’s 288 amino acids, the research team introduced the new gene sequence into E. coli, which were able to produce large quantities of the variant. Beyond looking like the now-available mouse mu opioid receptor, the researchers were able to show its value to future studies by performing functional tests.  

“We showed that this water-soluble form of the protein can compete with the native, membrane-based form when binding with antagonists that are fluorescently labeled,” Saven said. “You can watch the fluorescence shift as more of these water-soluble variants are floating around in the solution.”   

The team’s computational approach enables further iterations of the variant to be more easily designed, meaning it can be tweaked alongside experimental conditions. 

“This is a great product that can do a lot of things,” Liu said. “You can use this variant to look at the structure-function relationship for the receptor, or even potentially use it as a screening tool.”

Filed under opioids opioid receptors G protein-coupled receptors E.coli rhodopsin amino acids neuroscience science

78 notes

Neurostimulation Lowers Need for Opioids in Chronic Pain

Expert Panel of Physicians and Neuroscientists Announce International Guidance on Using Neurostimulation to Significantly Reduce the Need for Opioids in Chronic Pain

Recognizing that treatment of chronic pain can be confounding, the Neuromodulation Appropriateness Consensus Committee (NACC), an international group of more than 60 leading pain specialists, has created the first consensus guidelines for the use of neurostimulation in chronic pain.

Neurostimulation is an established and growing area of pain therapy that treats nerves with electrical stimulation rather than drugs. The NACC findings, announced at the International Neuromodulation Society (INS) 11th World Congress, address provider training, patient screening, and treatment recommendations.

While the extent and suffering of chronic pain is becoming better recognized, the danger of opioids for addiction, diversion or misuse is well known. Long-term opioid use can lead to the need for escalating doses to bring relief, and raises the risk of physical dependence, overdose, weight gain, depression, and immune and hormone system dysfunction.

“Many studies contain insufficient evidence to prove the safety or effectiveness of any long-term opioid regimen for chronic pain,” said study lead author Dr. Timothy Deer, INS president-elect and director of the Center for Pain Relief in Charleston, W. Va. “Indeed, many patients discontinue long-term opioid therapy due to insufficient pain relief or adverse events.”

Neurostimulation has been shown in clinical studies to be safe and effective for properly selected patients, and is approved by the FDA to treat chronic pain of the trunk and limbs. It belongs to a family of therapies known as neuromodulation because they modulate, or alter, the function of nerves, such as nerves that may have become hypersensitized or damaged, or are otherwise sending pain signals long past the initial injury. Since the components of neurostimulators bear some resemblance to heart pacemakers, they are sometimes called pain pacemakers.

The NACC recommends neurostimulation be used earlier in the treatment of some kinds of chronic pain, such as failed back surgery syndrome and complex regional pain syndrome. A study being presented at the world congress shows neurostimulation effectiveness correlates with early use in those conditions, with the added benefit of shortening the time patients spend trying other methods and containing long-term costs of managing chronic pain.

The most common form of neurostimulation, spinal cord stimulation (SCS), was introduced in 1967 and is now implanted in some 4,000 patients annually in the United States. With SCS, appropriately selected patients who have had back and/or leg pain longer than six months often find their symptoms relieved by 50 percent or more. The therapy uses slender electrical leads placed beneath the skin along the spinal cord and connected to a compact pulse generator, about the size of a pocket watch, that sends mild current along the leads to elicit a natural biological response and limit pain messages sent to the brain. Patients try the minimally invasive technique to see if it works for them before receiving a permanent implant.

“The lessons learned over the last few decades of clinical practice have influenced neurostimulator design, placement, and programming – and added new insights into spinal anatomy and pain physiology,” said INS President Dr. Simon Thomson, consultant in in pain medicine and neuromodulation at Basildon and Thurrock University NHS Trust in the United Kingdom.

Although neurostimulation devices may seem novel at first, using electrical current to limit pain dates back to antiquity, when standing on an electric fish was one remedy. Use of modern neurostimulation devices is likely to expand as the aging populace lives longer with chronic conditions, while technological refinements and clinical evidence continue to accumulate.

“A reduction in opioid use among patients treated with spinal cord stimulation was shown in a several studies, notably a 2005 randomized controlled clinical trial led by Dr. Richard North under the auspices of the Johns Hopkins University School of Medicine,” commented INS Secretary and study co-author Dr. Marc Russo, director of the Hunter Pain Clinic in New South Wales, Australia. “Broad-based studies show that within two years, using spinal cord stimulation rather than repeat back surgery is not only a more cost-effective use of health resources, it also is correlated with higher rates of return to work.”

Consensus committee authors believe that when appropriately applied, neurostimulation to target treatment directly to nerves can improve productivity and quality of life for chronic pain patients, offering a potentially less costly and risky option than repeat surgery or long-term painkiller use. They recommend:

  • Neuromodulation providers receive at least 12 hours of continuing medical education per year directly related to improving outcomes with neuromodulation, with additional mentoring by a credentialed provider at a hospital officially accredited by the Joint Commission on Accreditation of Healthcare Organizations or its equivalent.
  • Spinal cord stimulation should be used early in the treatment of failed back surgery syndrome as long as there is no progression of a neurological condition requiring semi-urgent intervention.
  • Patient selection decisions should be made with any clinicians who are treating co-existing conditions, who may include the patient’s primary care provider, cardiologist, or neurologist.
  • Due to the emotional impact of the experience of pain, an assessment of a psychologist or psychiatrist is recommended within the first year of implant.
  • Spinal cord stimulation and peripheral nerve stimulation should be considered earlier, when possible, and are recommended to be trialed in the first two years of chronic pain.
  • Peripheral nerve stimulation (beyond the spine) should be reserved for patients in whom the pain distribution is primarily in a named nerve that is known to connect the area of pain. Temporary relief of the patients’ pain by an injection of local anesthetic in the nerve distribution should be seen as an encouraging sign for the use of this therapy.
  • To cover an area that is not located in the distribution of a named peripheral nerve, stimulation of a peripheral nerve field with electrodes placed in the subcutaneous area just beneath the skin may give relief if stimulation from SCS does not reach this area. In many cases a hybrid of two or more of these methods may present the best chance of an acceptable outcome.
  • SCS should be used as an early intervention in patients with Raynaud’s syndrome and other painful ischemic vascular disorders, which involve insufficient blood supply to part of the body. If ischemic symptoms persist despite initial surgical or reasonable medical treatment, SCS should be trialed.
  • In the use of spinal cord stimulation to treat painful diabetic peripheral neuropathy, decision-making should be performed on an individualized basis, considering current diagnoses and other factors. A type of SCS that stimulates a structure at the edge of the spinal column, the dorsal root ganglion, may be most suited for this disorder.

(Source: newswise.com)

Filed under chronic pain neurostimulation pain therapy spinal cord opioids neuroscience science

free counters