Excessive levels of iron, a mineral vital for healthy blood and brain function, may increase the risk of developing Parkinson's disease and dementia, according to a study by researchers at the Salk Institute in California.
Iron is crucial for producing hemoglobin, the protein in red blood cells that transports oxygen throughout the body. The body does not produce iron independently; it is obtained from dietary sources like lean red meat, clams, oysters, spinach, lentils, tofu, and white beans. While iron deficiency, which affects approximately one in seven Americans, is linked to developmental issues and cognitive decline due to its role in energy and neurotransmitter production, this new research highlights the potential dangers of iron overload.
The study found that excess iron can gradually accumulate within neurons. While this accumulation may have minimal impact in younger individuals, it can lead to nerve cell death in older adults by compromising cellular defenses and increasing vulnerability to stressors. Cell death in brain regions associated with memory and cognition, such as the hippocampus and cerebral cortex, can result in dementia, affecting an estimated 7 million Americans. Parkinson's disease, which impacts about 1 million Americans, is characterized by the loss of neurons that produce dopamine, a neurotransmitter essential for coordinating movement. The death of these specific neurons could contribute to the progression of Parkinson's.
Researchers propose that monitoring iron levels could be a key strategy in preventing neurodegenerative diseases. Dr. Pam Maher, senior study author and research professor at the Salk Institute, noted the growing focus on brain resilience in the context of Alzheimer's and other neurodegenerative disorders. "Our study reveals that cells lose resilience when iron hits a certain level, making neurons more susceptible to stressors that damage or even kill them," she stated.
Both dementia and Parkinson's disease are experiencing rising rates in the U.S. Experts predict that dementia diagnoses could double by 2050. The Parkinson's Foundation estimates that 1.2 million Americans will be diagnosed with Parkinson's by 2030, with approximately 90,000 new cases diagnosed annually, an increase from previous estimates. While environmental factors like pollution and pesticides, along with chronic conditions such as obesity and diabetes, are suspected contributors, the exact causes are still under investigation.
The study, published in the journal Cell Death Discovery, utilized human neural cells derived from neuroblastoma, a nervous system cancer. Researchers compared the effects of acute and chronic iron exposure, with acute exposure lasting six to eight hours and chronic exposure spanning approximately nine days to simulate slow accumulation over time. The researchers identified a new pathway termed "chronoferroptosis," a variation of ferroptosis, a known process of cell death triggered by lipid peroxidation. This occurs when free radicals damage cell membranes. However, in chronoferroptosis, the pathway does not immediately result in cell death. Instead, neurons subjected to chronic iron exposure exhibited long-term functional changes, becoming vulnerable to neurodegenerative conditions, whereas acutely exposed neurons could withstand the stress.
"We think these coordinated alterations in iron-handling and antioxidant defense proteins make chronically exposed neurons vulnerable to neurodegenerative pathology," said Dr. Nawab John Dar, co-corresponding study author and postdoctoral researcher at the Salk Institute. "Entering this state of chronoferroptosis may set neurons up for age-related failure."
Dar emphasized that it is not the absolute amount of iron but the duration of exposure to elevated levels that determines cellular fate. "It's one of the most important minerals in the body," he added. "So, it isn't the iron itself that is a problem with age. It is this accumulation of iron over time that is the problem."
The researchers demonstrated that iron toxicity in this context could be mitigated by Ferrostatin-1, a synthetic antioxidant that inhibits chronoferroptosis and prevents cell stress and death. The study acknowledges limitations, including the absence of a precise iron threshold for chronoferroptosis and the use of cell models rather than human subjects.