Evening Primrose Oil Found to Ease Inflammation in Parkinsonism Rats

Andrea Lobo for Parkinson’s News Today

Treatment with evening primrose oil or EPO—made from the seeds of the flowering plant—was found to reduce brain inflammation and improve motor function in a rat model of Parkinson’s disease-like features, referred to as parkinsonism.

A new study in Egypt found that the oil, which contains omega-6 fatty acids, improved nerve cell survival and appeared to have both neuroprotective and anti-inflammatory effects when used in the animal model.

“These data suggest EPO to be a good candidate for parkinsonian patients,” the researchers wrote, adding, “The present study provided evidence that EPO’s anti-inflammatory properties were beneficial in protecting against experimentally induced parkinsonism in rats.”

The study, “Protective effects of evening primrose oil on behavioral activities, nigral microglia and histopathological changes in a rat model of rotenone-induced parkinsonism,” was published in the Journal of Chemical Neuroanatomy.

Parkinson’s is characterized by the death of neurons that release dopamine, a chemical messenger involved in communication between these nerve cells, in a part of the brain called the substantia nigra. This brain region plays a key role in the control of movement.

There is increasing evidence showing that neuroinflammation, or inflammation in the brain, is involved in the initiation and development of Parkinson’s.

Such neuroinflammation is mediated by microglia, the brain’s resident immune cells. Microglia release pro-inflammatory factors and so-called reactive oxygen species that promote neuroinflammation and contribute to the loss of neurons.

According to the researchers, a growing number of studies have investigated “the effects of fatty acids and their prospective beneficial effect on neurodegenerative diseases.”

Evening primrose oil, derived from plant seeds, has reported antioxidant and anti-inflammatory effects. The researchers now sought to test it as a treatment for parkinsonism.

In this study, they used a rat model of parkinsonism induced by the administration of rotenone, a broad spectrum insecticide, every two days for 24 days by injections under the skin.

This model mimicked hallmarks of Parkinson’s, including impaired motor coordination, inflammation in the brain and a decrease in the brain’s dopamine levels, associated with death of dopaminergic neurons in the substantia nigra. To evaluate motor function, rats underwent an open field test and were also assessed on a rotating rod.

EPO was given daily during the 24 days of rotenone administration. Results showed better motor performance with EPO treatment, as reflected by increased inactive sitting duration, better ambulation, and extended latency on the rotating rod. This benefit was more pronounced with the higher dose (10 mg/kg/day).

The levels of the pro-inflammatory molecules interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha were significantly increased by rotenone in the brain, an effect that was suppressed by the administration of EPO.

EPO also inhibited the increase in the levels of a transcription factor, called NF-kB, which activates production and release of pro-inflammatory molecules called cytokines. Transcription factors are proteins that regulate gene activity.

Untreated animals given rotenone showed nearly 91% less dopaminergic neurons than control animals. EPO treatment eased this neuronal loss.

Also, rotenone induced an increase in the number and activation of microglia cells, which was significantly prevented by treatment with EPO. Besides releasing inflammatory factors, activated microglia can engulf dying neurons, contributing for the neuronal loss.

“Microglia activation results in the release of huge quantities of cytokines … which toxically interfere with the survival of neurons,” the researchers wrote. “Consequently, inflammatory reaction inhibition derived from stimulated microglia might be an encouraging approach to protect dopaminergic neurons damaged in Parkinson’s.”

“Prohibition of microglial stimulation might deliver therapeutic advantages for inflammation associated with neurodegenerative illnesses. Moreover, compounds carrying anti-neuro-inflammatory properties are hopeful candidates for Parkinson’s therapy,” the researchers concluded.

The potential advantages of evening primrose oil derive from its active components, such as gamma-linolenic acid, which is a precursor of inflammation suppressors. This neuroprotective agent “enhances the possibility of EPO being considered in the therapeutic protocol of parkinsonism,” the scientists added.