Updated November 11, 2014.
Written or reviewed by a board-certified physician. See About.com's Medical Review Board.
Mitochondria are organelles, meaning microscopic structures that exist within the cells of the body and help the cell to survive. Mitochondria have the job of metabolism, meaning providing the cell with energy.Â
As you likely know, oxygen is important for life. Mitochondria are the reason why. Mitochondria use oxygen as a required part of generating energy for cellular functioning.Â
While disorders of mitochondrial function were once thought to be relatively rare, there is a growing suspicion that they may be under-diagnosed.
 More importantly, mitochondria may play an important role in diseases known to be relatively common, such as Parkinson’s disease and Alzheimer’s.
About one percent of people over the age of 55 have Parkinson’s disease. Classically, cells within the substantia nigra, a dopamine containing region in the brainstem, begin to die.  Because these cells contain dopamine, giving dopamine can restore some of the functioning in Parkinson’s disease. Doing so is only a way to alleviate symptoms, though—so far, nothing has been found that can actually stop the disease itself from marching onwards.
The cause of Parkinson’s disease remains mysterious. Certainly some abnormal proteins are deposited, but it’s not clear if those proteins are the main problem or just a sign of trouble elsewhere.Â
There are several good reasons for believing that mitochondria are impacted in Parkinson’s disease, and may even be the first source of trouble. For example, in some rare inherited forms of Parkinson’s, such as PINK1 or Parkin, a genetic mutation is known to impact mitochondrial function.
Certain toxins that cause Parkinson-like symptoms (parkinsonism) primarily act on mitochondria. For example, in 1982 an additive called MPTP in street drugs caused parkinsonism in a group of people in Los Angeles. The drug is metabolized into something called MPP, the mechanism of action of which is inhibition of mitochondrial function at an area called complex one.Â
Complex one is also targeted by rotenone, an organic but nevertheless toxic substance commonly used as an insecticide. The drug has been used in reservoirs and lakes. Once in the body, it is easily absorbed into cell membranes. Exposure to rotenone has been tied to an increased risk of developing Parkinson’s disease, and the drug is commonly used to induce parkinsonism in animal studies.Â
Those kind of animal studies have shown that the substantia nigra decline just as in Parkinson’s disease, and that there is an increased  production of alpha-synuclein, one of the major proteins known to accumulate in Parkinson’s. In other words, mitochondrial toxicity in animals can lead to something that looks very much like Parkinson’s disease in people.
All of this is of more than just academic interest. The research above has suggested that reducing the interaction between alpha-synuclein and mitochondria may reduce neurodegeneration. Studies are underway as a result, with improvement of parkinsonian symptoms in animal models.Â
As mitochondria are found everywhere in the body, another interesting idea is that the mitochondria may be used as biomarkers of disease. These can be used both to measure disease severity and perhaps to show whether an experimental treatment is working. The question of whether mitochondrial DNA damage could be detectable in blood samples of people with Parkinson’s disease is also being actively explored. Early research suggests that complex one may be reduced by 16 to 55% in platelets of people with Parkinson’s disease. Â
In short, there's more to Parkinson's disease than meets the eye-- a great deal of it will need a microscope and more to really understand!
Sources:Â
R Bertarbet, TB Sherer, G MacKenzie et al. Chronic Systemic pesticide exposure reproduces features of Parkinson’s disease. Nat Neurosci. 2000 Dec;3(12):1301-6.
M Gu, JM Cooper, JW Taanman, AH Schapira. Mitochondrial DNA transmission of the itochondrial defect in Parkinson’s disease. Ann Neurol 1998 Aug 44(2): 177-86
Y Mizuno, S Ikeb, N Hattori et al. Role of mitochondria in the etiology and pathologenesis of Parkinson’s disease. Biochim Biophys Acta. 1995 May 24;1271(1):265-74. Review.
CM Tanner, F Kamel, GW Ross et al. Rotenone, Paraquat and Parkinson’s disease. Environmental Health Perspectives 2011 119(6)
Written or reviewed by a board-certified physician. See About.com's Medical Review Board.
Mitochondria are organelles, meaning microscopic structures that exist within the cells of the body and help the cell to survive. Mitochondria have the job of metabolism, meaning providing the cell with energy.Â
As you likely know, oxygen is important for life. Mitochondria are the reason why. Mitochondria use oxygen as a required part of generating energy for cellular functioning.Â
While disorders of mitochondrial function were once thought to be relatively rare, there is a growing suspicion that they may be under-diagnosed.
 More importantly, mitochondria may play an important role in diseases known to be relatively common, such as Parkinson’s disease and Alzheimer’s.
About one percent of people over the age of 55 have Parkinson’s disease. Classically, cells within the substantia nigra, a dopamine containing region in the brainstem, begin to die.  Because these cells contain dopamine, giving dopamine can restore some of the functioning in Parkinson’s disease. Doing so is only a way to alleviate symptoms, though—so far, nothing has been found that can actually stop the disease itself from marching onwards.
The cause of Parkinson’s disease remains mysterious. Certainly some abnormal proteins are deposited, but it’s not clear if those proteins are the main problem or just a sign of trouble elsewhere.Â
There are several good reasons for believing that mitochondria are impacted in Parkinson’s disease, and may even be the first source of trouble. For example, in some rare inherited forms of Parkinson’s, such as PINK1 or Parkin, a genetic mutation is known to impact mitochondrial function.
Certain toxins that cause Parkinson-like symptoms (parkinsonism) primarily act on mitochondria. For example, in 1982 an additive called MPTP in street drugs caused parkinsonism in a group of people in Los Angeles. The drug is metabolized into something called MPP, the mechanism of action of which is inhibition of mitochondrial function at an area called complex one.Â
Complex one is also targeted by rotenone, an organic but nevertheless toxic substance commonly used as an insecticide. The drug has been used in reservoirs and lakes. Once in the body, it is easily absorbed into cell membranes. Exposure to rotenone has been tied to an increased risk of developing Parkinson’s disease, and the drug is commonly used to induce parkinsonism in animal studies.Â
Those kind of animal studies have shown that the substantia nigra decline just as in Parkinson’s disease, and that there is an increased  production of alpha-synuclein, one of the major proteins known to accumulate in Parkinson’s. In other words, mitochondrial toxicity in animals can lead to something that looks very much like Parkinson’s disease in people.
All of this is of more than just academic interest. The research above has suggested that reducing the interaction between alpha-synuclein and mitochondria may reduce neurodegeneration. Studies are underway as a result, with improvement of parkinsonian symptoms in animal models.Â
As mitochondria are found everywhere in the body, another interesting idea is that the mitochondria may be used as biomarkers of disease. These can be used both to measure disease severity and perhaps to show whether an experimental treatment is working. The question of whether mitochondrial DNA damage could be detectable in blood samples of people with Parkinson’s disease is also being actively explored. Early research suggests that complex one may be reduced by 16 to 55% in platelets of people with Parkinson’s disease. Â
In short, there's more to Parkinson's disease than meets the eye-- a great deal of it will need a microscope and more to really understand!
Sources:Â
R Bertarbet, TB Sherer, G MacKenzie et al. Chronic Systemic pesticide exposure reproduces features of Parkinson’s disease. Nat Neurosci. 2000 Dec;3(12):1301-6.
M Gu, JM Cooper, JW Taanman, AH Schapira. Mitochondrial DNA transmission of the itochondrial defect in Parkinson’s disease. Ann Neurol 1998 Aug 44(2): 177-86
Y Mizuno, S Ikeb, N Hattori et al. Role of mitochondria in the etiology and pathologenesis of Parkinson’s disease. Biochim Biophys Acta. 1995 May 24;1271(1):265-74. Review.
CM Tanner, F Kamel, GW Ross et al. Rotenone, Paraquat and Parkinson’s disease. Environmental Health Perspectives 2011 119(6)