Environmental factors may trigger onset of multiple sclerosis

A new study finds that certain environmental conditions may precipitate structural changes that take place in myelin sheaths in the onset of multiple sclerosis (MS). Myelin sheaths are the "insulating tape" surrounding axons; axons carry electrical impulses in neurons.

The research demonstrates that myelin sheaths undergo structural transitions when triggered by changes in local environmental conditions, such as salt concentration (salinity) and temperature. These transitions, according to the study published in the Proceedings of the National Academy of Sciences of the USA (PNAS), render the body vulnerable to autoimmune attacks that can lead to MS.

Physiological conditions are regulated in the body itself, but temperature and salinity are subject to localized external changes. The results presented in the study suggest that even minor changes in these conditions may trigger multiple sclerosis.

"The myelin sheaths undergo structural transitions at the molecular level when affected by different environmental conditions. These small modifications create structural instabilities that allow the immune system to attack neurons," says the lead author.

The researchers used X-ray scattering and cryogenic transmission electron microscopy (cryo-TEM) to track and measure the myelin sheaths in healthy and diseased animal models. They found that healthy lamellar membranes spontaneously morphed into different pathological structures of nano-scale tubes called inverted hexagonal shapes.

These phase transitions have different transition points, which depend on the lipid’s compositions, and are ion specific. In extreme environmental conditions, authors find an additional dense lamellar phase and that the native lipid composition results in similar pathology as the diseased composition. These findings demonstrate that several local environmental changes can trigger pathological structural changes.

"These results highlight that local environmental conditions are critical for myelin function. These conditions should be considered as alternative possibilities for early diagnosis and as a means of avoiding the onset of demyelination," says the author. "Since we believe that these structural modifications result in myelin membrane vulnerability to the immune system attacks, it can help explain the causes of MS and perhaps pave the way for a treatment or a cure.

"Since we now have a new biophysical understanding to investigate the degradation of myelin sheaths, we are following up on other candidates that can induce such structural transition. There are several molecular candidates, including specific proteins and other alterations in the myelin's fatty acids, that are relevant, which may unravel further insights to fight multiple sclerosis and related disorders," the author concludes.

https://www.aftau.org/weblog-medicine--health?&storyid4704=2410&ncs4704=3