Circadian Rhythm and its effect on Parkinson's disease

The circadian rhythm is a biological 24-hour clock of the brain that is responsible for regulating behavioral and psychological processes, including the sleep-wake cycle. In the brain, the SCN in the hypothalamus maintains the rhythm and influences the other pathways in the body. The TTFL feedback loops is specifically responsible for this and ensures the synchronization of all the clocks in the body. Circadian rhythms are also closely associated with Parkinson’s disease. Parkinson’s disease is a neurodegenerative disease and a component of that is the decrease production of dopamine. Dopamine can be regulated by circadian rhythm genes and Tyrosine Hydroxylase, which is crucial for dopamine production, is regulated by the CLOCK gene. However, people with Parkinson’s disease have been studied to have a decrease in the clock gene, BMAL1 and that worsens the production of dopaminergic neurons. The dopamine neurons are also decreased in PAM and PPL1 clusters, which is important for the PER responsible for the periods in the circadian clock.  

Another component of Parkinson’s disease is the over-expression of a-synuclein which leads to neuroinflammation. The glial cells that are responsible for regulating the function of the immune response also possess a circadian clock and the microglia clock can have numerous effects on parkinsonism due to disruptions. There is also a correlation between the circadian gene REV-ERBa and neuroinflammation, where the absence of the gene intensifies the effects of the inflammation and the decline of dopamine neurons in parkinsonism. These patients can also experience various sleep disorders because of the excess a- synuclein expression, changing the sleeping pattern of an individual. Lastly, studies are also showing that the disruption in circadian rhythms can also be related to non-motor symptoms that are observed in parkinsonism. The future of this research is leaning towards exploring the impact of circadian rhythms on the biological processes of individuals with Parkinson’s diseases and how findings can help with preventing and treating the disease.  

In a study from 2020, researchers performed an experiment to test if bright light could improve sleep and restore a circadian rhythm in patients that have Parkinson’s disease. At the conclusion of the study, it was founded that bright light could improve sleep patterns, specifically in Japanese patients. The patients were given dopamine in the morning to increase melatonin secretion, and when exposed to bright light, their scores improved. This shows that bright light can be an efficient form of therapy in fixing sleep problems in Parkinson patients that also receive dopamine. Further research can help explore the effects of bright light in the SCN in the hypothalamus and the long-term effects of this therapy.  
 
 
 
 
References: 
Endo, T., Matsumura, R., Tokuda, I.T. et al. Bright light improves sleep in patients with Parkinson’s disease: possible role of circadian restoration. Sci Rep 10, 7982 (2020). https://doi.org/10.1038/s41598-020-64645-6 

Xu K, Zhang Y, Shi Y, Zhang Y, Zhang C, Wang T, Lv P, Bai Y, Wang S. Circadian rhythm

disruption: a potential trigger in Parkinson's disease pathogenesis. Front Cell
Neurosci. 2024 Oct 30;18:1464595. doi: 10.3389/fncel.2024.1464595. PMID:
39539340; PMCID:PMC11557417.