Brain’s “helper” cells turn toxic in injury and disease

Brain’s “helper” cells turn toxic in injury and disease

Star-shaped cells called astrocytes—often characterized as “helper” cells—may contribute to damage caused by brain injury and disease by turning toxic and destroying neurons, according to study results published Wednesday in Nature.

Astrocytes are one of the three types of glial, or non-neuronal, cells, the most abundant kind found in the brain. They are widely regarded as support cells that nourish neurons and pack the spaces between them, but it is becoming increasingly clear that they play other important roles in normal, healthy brain function. They can synthesize neurotransmitters to send signals among glial cells, and form networks that regulate neuronal activity.

Astrocytes can also react to brain injury and disease in various ways. Following nerve damage, for example, they form scar tissue that can aid in the regeneration of severed fibers. But they are also implicated in a wide variety of neurological and psychiatric diseases.

The new findings show that under certain conditions astrocytes can transform into a highly toxic state and kill other types of brain cells. But by providing fresh insights into the process of neurodegeneration, they could eventually lead to novel treatments for a wide range of diseases.

The results of the new study build on earlier work from the laboratory of neurobiologist Ben Barres at Stanford University, which isolated reactive astrocytes from mice with experimentally induced stroke and brain inflammation, and used DNA chip technology to create genetic profiles of the cells. Those studies found that stroke and inflammation triggered the conversion of astrocytes into two reactive cell types: A1 cells, which ramp up their production of immune system molecules called complement proteins, and A2 cells, which express high levels of growth factor proteins that promote the survival of brain cells and formation of connections between them.

Complement proteins attach themselves to brain synapses, “tagging” them for destruction by microglia—the brain’s resident immune cells—leading the researchers to hypothesize that A1 astrocytes may be harmful… Read More>>

Source: Scientific American

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