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A team from the University of Wisconsin-Madison has found a new method to examine stress and inflammation in the heart, a discovery which could provide further insight into Parkinson’s disease, a disease which can cause serious damage to the heart’s connections to the sympathetic nervous system.
The researchers examined 10 rhesus macaque monkeys who received doses of a neurotoxin that causes damage to the nerves in the hearts, in a similar way that Parkinson’s affects human hearts. Each monkey underwent PET scans before the neurotoxin and twice in the weeks after the doses so that the researchers could track the chemical processes in their bodies using radioactive tracers.
The researchers used three different tracers called radioligands to map when the nerves extending in the heart muscle were damaged, where the heart tissue was experiencing the most inflammation and where they found the most oxidative stress, focusing specifically on the left ventricle.
“We know there is damage in the heart in Parkinson’s, but we haven’t been able to look at exactly what’s causing it,” graduate student Jeanette Metzger, lead author of the study, said in a statement. “Now we can visualize in detail where inflammation and oxidative stress are happening in the heart, and how that relates to how Parkinson’s patients lose those neuronal connections in the heart.”
By tracing the progression of nerve damage and the progression of potential causes of that damage, the radioligands can also be used to test the efficacy of new treatments to protect the neurons that regulate the activity of the patients’ hearts.
The researchers also gave half of the monkeys in the study pioglitazone, a drug that has shown promise in protecting the central nervous system cells from inflammation and oxidative stress.
“The recovery of nerve function is much greater in the pioglitazone-treated animals,” Marina Emborg, a University of Wisconsin-Madison professor of medical physics and Parkinson’s researcher at the Wisconsin National Primate Research Center, said in a statement. “And what’s interesting is this method allows us to identify very specifically the differences the treatment made — separately for inflammation and for oxidative stress — across the heart.”
The team believes that the study indicates that Parkinson’s patients would benefit from radioligand scans to help catch the disease before other symptoms progress.
“Much of the neural degeneration that occurs in the heart can happen very early in the course of the disease,” Metzger said. “A lot of patients have problems with their heart before they have motor problems. While these PET techniques potentially provide a way to test drugs, they may also be used as tools to understand the mechanisms underlying early heart nerve damage.”
Approximately 60 percent of Parkinson’s patients have serious damage to the heart’s connections to the sympathetic nervous system by the time they are diagnosed. The sympathetic nervous system spur the heart to accelerate its pumping to match quick changes in activity and blood pressure in healthy patients.
“This neural degeneration in the heart means patients’ bodies are less prepared to respond to stress and to simple changes like standing up,” Emborg said. “They have increased risk for fatigue, fainting and falling that can cause injury and complicate other symptoms of the disease.”
Other diseases and ailments may also be detected by the new imaging technique, including the risk of heart attack, diabetes and other disorders that cause similar damage to the nerves in the heart.
