Researchers have found that a compound produced by a certain soil bacterium has unusual properties that may help address neurologic damage such as Alzheimer's disease.

The natural compound, called Rapamycin, was first discovered in the soil of Easter Island in the South Pacific Ocean. "It's possible this could provide a new therapeutic approach to neurologic disease," said Viviana Perez, Assistant Professor at Oregon State University in the US.  Scientists have now identified two mechanisms of action of rapamycin. One was already known. 

The newly discovered mechanism, detailed in the journal Aging Cell, is what researchers said might help prevent neurologic damage and some related diseases. "The value of rapamycin is clearly linked to the issue of cellular senescence, a stage cells reach where they get old, stop proliferating and begin to secrete damaging substances that lead to inflammation," Perez said.  "Rapamycin appears to help stop that process," Perez added.

This secretion of the damaging compounds, researchers said, creates a toxic environment called senescence-associated secretory phenotype, or SASP.  It is believed this disrupts the cellular microenvironment and alters the ability of adjacent cells to function properly, compromising their tissue structure and function. This broad process is ultimately linked to ageing. "The increase in cellular senescence associated with ageing, and the inflammation associated with that, can help set the stage for a wide variety of degenerative diseases, including cancer, heart disease, diabetes and neurologic diseases, such as dementia or Alzheimer's," Perez said.

"In laboratory animals when we clear out senescent cells, they live longer and have fewer diseases. And rapamycin can have similar effects," Perez added. The use of rapamycin in humans has so far been constrained by an important side effect, an increase in insulin resistance that may raise the risk of diabetes. That concern still exists, limiting the use of rapamycin to help address degenerative disease until ways can be found to address that problem.

Scientists are searching for rapamycin analogues that may have the similar biological impact but do not cause that unwanted side effect.