A new molecule has a key role in the development of Alzheimer’s disease, as well as the higher susceptibility of women to the disease. This was shown by a study conducted by the Massachusetts Institute of Technology and Scripps Research. Scientists have analyzed the action of a chemically modified form of an inflammatory immune protein – part of the complement system, namely – C3. Levels of this protein were found to be higher in the brains of female patients who died of Alzheimer’s. Also, observations have shown that estrogen, which normally falls during menopause, has a protective effect against the formation of this form of the C3 fragment by the complement system. It is this chemical modification that is thought to lead to the progression of Alzheimer’s disease and is associated with an increased susceptibility in women. The complement system is part of the immune system that protects the body from infections and destroys disease-causing microorganisms. This system consists of about 50 plasma proteins that are transported to the liver and reach every cell. When encountering infectious agents, they are activated step by step – the complement cascade and provide effective immune protection. The main modifications that are associated with neurodegenerative diseases are related to a change in the C3 component of the complement system through a process of S-nitrosylation. In previous studies, scientists have found that this chemical reaction occurs in different cells when the activation of the action of a certain herb is necessary. The researchers used new methods to assess altered proteins in samples from 40 patients who had died of Alzheimer’s. Half of them had been diagnosed with the disease, and the rest had no cognitive impairment. In these samples, the scientists found 1,449 different types of modified proteins. Some of these have been linked to the development of Alzheimer’s – such as the C3 fragment of the complement system. The levels of these altered proteins were found to be up to 6 times higher in women who were affected by Alzheimer’s than in men. The disease is associated with elevated levels of these proteins and other inflammatory markers. Altered proteins can lead to the destruction of connections between neurons – synapses from microglial cells in the brain. Destruction of synapses is considered one of the leading causes of cognitive decline in Alzheimer’s. Estrogen has long been known to have protective functions for brain health and protection against changes in complement proteins. However, this protection is impaired with a drop in estrogen during menopause. The study confirmed the link between decreased estrogen and increased levels of altered C3 proteins. It is this that leads to significant destruction of synapses in the brain. References: https://dx.doi.org/10.1126/sciadv.ade0764 https://www.science.org/doi/10.1126/sciadv.ade0764