Researchers find way to block heroin, morphine addiction

Written by Loren Grush

Opiate drugs, such as morphine and hydrocodone, are frequently prescribed medications to aid patients in need of chronic pain relief – but they often come at a cost. Opioid addiction can develop for those habitually talking these pain relievers, leading to physical dependence and withdrawal symptoms after abrupt disuse.

Now, researchers from the University of Adelaide in Australia and the University of Colorado have found a way to block addiction to opioids like morphine and heroin, while increasing pain relief at the same time. Their results could potentially lead to a new drug that could not only help people with severe pain, but also help heroin users kick the habit.

The major breakthrough is part of a paradigm shift in the way to treat drug addiction, according to the researchers. Opioid dependence has become a widespread problem, with one in five children experimenting with prescription opioids before the age of 17. According to the National Institute of Health, approximately 9 percent of the U.S. population is believed to abuse opioids – both prescription and illegal – over the course of their lifetimes.

“We know that drugs like morphine drive a reward system that causes elevations of dopamine in the brain,” Dr. Mark Hutchinson, ARC Research Fellow at the University of Adelaide’s School of Medical Sciences and the study’s lead author, told FoxNews.com. “Our work suggested [nervous system] pathways are important, but 90 percent of the cells in the brain are glia, which are immune cells. So we hypothesized that the immune system was probably involved in drug rewards as well – and we showed it was.”

Current pharmacological treatments for opioid addiction focus mostly on treating the central nervous system. While Hutchinson and his team acknowledged both the nervous system and the immune system play key roles in addiction, they decided to focus solely on the immune system’s response. This led them to the immune receptor Toll-Like receptor 4 (TLR4).

“Our paper shows that opioids bind to this receptor TLR4,” Hutchinson said. “TLR4 is known as the receptor that causes anaphylactic shock. It’s designed to recognize E. coli, so it’s a bacteria receptor. It also recognizes morphine, and in the brain, this causes the immune cells to hijack the reward pathways and drive pathological rewards to morphine,” ultimately amplifying addiction.

“If we develop drugs to block TLR4, we can stop drug rewards from presenting themselves,” Hutchinson added.

Laboratory studies have shown the drug (+)-naloxone selectively blocks the immune response to morphine, shutting down the need to keep taking opioids. Once the TLR4 is blocked, the neurochemistry of the brain changes, Hutchinson said, and dopamine is no longer produced.

Through their research, the scientists discovered another beneficial side effect of blocking TLR4 – amplifying the pain relief provided by opioids.

“When you block TLR4, you also increase the pain relief you get from the morphine,” Hutchinson said. “We might have a treatment for people who are addicted to illicit pain meds, but we also have an opportunity to intervene before this addiction starts in people needing pain relief. Perhaps in the future we might have a coformulation – morphine providing pain relief and then a drug like ours to stop TLR4 activity, modifying pain but also stopping the addiction.”

Hutchinson hopes this fundamental shift in treating drug addiction – by focusing on the immune response – will help many people in need of pain relief, while avoiding addiction. According to him, this kind of dependence is continuing to grow at an alarming rate.

“People have typically thought about drug addiction (as) being a seedy kind of problem,” Hutchinson said. “We’ve really transitioned away from that because of the availability of prescription opioids. This isn’t a treatment just for drug addicts; this could really have implications for the population’s health, by making opioid medications – which are great for pain relief – a whole lot better.”