The SARS-CoV-2 virus, which causes Covid-19, could increase the risk of ⛄brain degeneration seen in Parkinson's disease, according to a study perfౠormed in mice.
The study, published in the journal Movement Disorders, used mice that were genetically engineered to express the human ACE-2 receptor, which the SARS-CoV-2 virus uses to gain access to the cells in our ai🌼rway.
These mice were 𒁏infected with SARS-CoV-2 and allowed to recover.
The dose chosen in the study corresponds to moderate Covid-19 infection in human🐲s, with around 80 per cent of the infected mice surviving.
Thirty-eight days after the surviving animals recovered, one group was injected with a low dose of MPTP -- a chemical which causes permanent🤡 symptoms of Parkinson's disease -- that would not normally cause🐬 any loss of neurons. The control group was given saline.
Two weeks later, the animals were sacrificed and their brains e🅰xamined.
The researchers found that📖 Covid-19 i🥂nfection alone had no effect on the neurons in the basal ganglia, a region in the brains of vertebrates.
Hoওwever, mice that were given the low dose of MPTP after recovering from infection exhibited the classic pattern of neuron los🍷s seen in Parkinson’s disease, the researchers found.
This increased sensitivity after Covid-19 infection was similar🥂 to what was seen in the influenza study, suggesting that both vཧiruses could induce an equivalent increase in risk for developing Parkinson's.
";We thin👍k about a 'multi-hit’ hypothesis for Parkinson’s -- the virus itself does not kill the neuronsꩲ, but it does makes them more susceptible to a 'second hit', such as a toxin or bacteria or even an underlying genetic mutation," said Richard Smeyne, from the Thomas Jefferson University, US, and first author of the study.
Both influenza and SARS-CoV-2 have been found to cause a “cytokine storm” or an overproduction of pro-inflammatory chemica🧸ls, which can cross the blood-brain barrier and activate the brain's immune cells -- microglia.
The researchers found increased 𒆙numbers of activated microglia in the basal ganglia of mice that recovered from SARS-CoV2 and receive💖d MPTP.
While the mechanism is not fully understood,🧜 the researchers believe the increased microglia inflame the basal ganglia and cause cellular stress.
Thi💯s then lowers the neurons’ threshold to withstand subsequent stress, they said.
"We were concerned𒁃 about the long-term consequences of viral infection," said Peter Schmidt, a neuroscientist from New York University, US, who co-led the study.
The researchers are planning to determine whether vaccines can mitigate the experimental increase in Parkinson's pathology linked to prior SA🌠RS-CoV-2 ꦗinfection.
They are also testing other variants of the virus, as well as doses that correspond 🐲to milder cases in human🔴s.
"Parkinson's is a rare disease that affects 2 per cent of the population above 55 yea🤪rs, so the increase in risk is not necessarily a cause for panic," said Smeyne.
"🎉But understanding how ﷽coronavirus impacts the brain can help us prepare for the long-term consequences of this pandemic," he added.
(With PTI inputs)
