Using Rotenone to Model Parkinson's Disease in Mice: A Review of the Role of Pharmacokinetics

Rotenone is a naturally occurring toxin that inhibits complex I of the mitochondrial electron transport chain. Several epidemiological studies have shown an increased risk of Parkinson's disease (PD) in individuals exposed chronically to rotenone, and it has received great attention for its ability to reproduce many critical features of PD in animal models. Laboratory studies of rotenone have repeatedly shown that it induces in vivo substantia nigra dopaminergic cell loss, a hallmark of PD neuropathology. Additionally, rotenone induces in vivo aggregation of α-synuclein, the major component of Lewy bodies and Lewy neurites found in the brain of PD patients and another hallmark of PD neuropathology. Some in vivo rotenone models also reproduce peripheral signs of PD, such as reduced intestinal motility and peripheral α-synuclein aggregation, both of which are thought to precede classical signs of PD in humans, such as cogwheel rigidity, bradykinesia, and resting tremor. Nevertheless, variability has been noted in cohorts of animals exposed to the same rotenone exposure regimen and also between cohorts exposed to similar doses of rotenone. Low doses, administered chronically, may reproduce PD symptoms and neuropathology more faithfully than excessively high doses, but overlap between toxicity and parkinsonian motor phenotypes makes it difficult to separate if behavior is examined in isolation. Rotenone degrades when exposed to light or water, and choice of vehicle may affect outcome. Rotenone is metabolized extensively in vivo, and choice of route of exposure influences greatly the dose used. However, male rodents may be capable of greater metabolism of rotenone, which could therefore reduce their total body exposure when compared with female rodents. The pharmacokinetics of rotenone has been studied extensively, over many decades. Here, we review these pharmacokinetics and models of PD using this important piscicide.

Saskatchewan movement disorders program

We review the Saskatchewan Movement Disorders Program, which started in 1968 and has had the dual goals of patient care and research. The clinics are structured to collect research-worthy data including videos, longitudinal follow-up, and autopsy studies of patients seen in the clinics. At every clinic visit, the patient is evaluated by one or both authors. A total of 25% to 30% of the deceased come to autopsy. Frozen half-brain and formalin-fixed remnants from autopsy are preserved in our laboratories. Patients not seen in our clinic are not included in research, which makes it different from brain banks. So far, 515 cases have come to autopsy. So far, there have been 17 collaborating scientific teams from Canada, the United States, Europe, and Japan. The collaborators are not charged for access to our resources. This program offers a unique opportunity to study multiple aspects of movement disorder patients seen in clinical practice.

Mitochondrial complex I inhibitor rotenone-induced toxicity and its potential mechanisms in Parkinson's disease models

The etiology of Parkinson's disease (PD) is attributed to both environmental and genetic factors. The development of PD reportedly involves mitochondrial impairment, oxidative stress, α-synuclein aggregation, dysfunctional protein degradation, glutamate toxicity, calcium overloading, inflammation and loss of neurotrophic factors. Based on a link between mitochondrial dysfunction and pesticide exposure, many laboratories, including ours, have recently developed parkinsonian models by utilization of rotenone, a well-known mitochondrial complex I inhibitor. Rotenone models for PD appear to mimic most clinical features of idiopathic PD and recapitulate the slow and progressive loss of dopaminergic (DA) neurons and the Lewy body formation in the nigral-striatal system. Notably, potential human parkinsonian pathogenetic and pathophysiological mechanisms have been revealed through these models. In this review, we summarized various rotenone-based models for PD and discussed the implied etiology of and treatment for PD.

Vascular damage mediates neuronal and non-neuronal pathology following short and long-term rotenone administration in Sprague-Dawley rats

Even though rotenone has been used extensively in recent years to produce a model of Parkinson disease in rats, its systemic effects either on neurons apart from dopaminergic structures or non-neuronal tissues have not been elucidated well. In our present study, 30 adult Sprague-Dawley rats were divided into three even groups. A short-term rotenone-treated group received 10 mg/kg b.w. rotenone daily for 7 days. The long-term rotenone-treated group received 3 mg/kg b.w. rotenone daily for 30 days. The control group received vehicle only and were kept 5 rats each in parallel to both short- and long-term rotenone treated groups. It was found that short-term rotenone treatment produced marked vascular damages associated with ischemic neuronal degeneration particularly in the thalamus, cerebellum and nucleus dentatus. In long-term rotenone-treated group, vascular changes were less severe and neuronal degeneration was associated with mild microglial proliferation and astrocytosis. Non-neuronal pathology as the result of short-term rotenone exposure consisted of degeneration and necrosis of seminiferous tubular epithelia with formation of spermatide multinucleate giant cells. On the other hand, long-term rotenone treatment did not affect testicles and only caused sinusoidal dilatation in the liver, myocardial degeneration in the heart and interstitial hemorrhages in the kidneys and lungs. In conclusions, damage to blood vasculature by rotenone appeared mediating neuronal and non-neuronal pathology in Sprague-Dawley rats. This effect might provide new insights for ethiopathogenesis of neurodegenerative diseases and contributes to the understanding of hemorrhagic stroke.