Recent Chinese research has found how cGAS (cyclic GMP-AMP synthase), an enzyme and DNA sensor dubbed as a cell's gatekeeper, activates immune responses when the body has a viral infection, providing new perspectives for treatments of some autoimmune diseases.

The recognition of microbial nucleic acids is a major mechanism by which the immune system detects pathogens. cGAS is a DNA sensor in the cytosol that activates innate immune responses. It not only plays a key role in mediating protective immune defense against infection by many DNA-containing pathogens but also detects tumor-derived DNA and generates intrinsic anti-tumor immunity.

However, aberrant activation of the cGAS pathway can also lead to autoimmune and inflammatory diseases.

In autoimmune diseases, the cell nucleus spits small DNA fragments into the cytoplasm or the cells have difficulty breaking down DNA from dead cells. DNA fragments, therefore, accumulate in the cytoplasm and the immune system cells start fighting themselves instead of pathogens from the outside.

In recent years, scientists have been trying to understand how cGAS activates immune responses and whether blocking or regulating the pathway may have an effect on autoimmune diseases.

In a paper published online in the U.S. journal Cell, researchers from China's Academy of Military Medical Sciences reported that acetylation inhibits cGAS activation. It is found that aspirin can directly acetylate cGAS and efficiently inhibit cGAS-mediated immune responses.

Acetylation is a chemical reaction that most of the proteins in the human body undergo. The process of acetylation is important for several main chemical reactions in the body like protein formation and drug bio-transformation.

In lab experiments, the researchers found that aspirin can effectively suppress self-DNA-induced autoimmunity in Aicardi-Goutieres syndrome (AGS) patient cells and in an AGS mouse model.

AGS is a rare inflammatory disorder most typically affecting the brain and the skin. The majority of affected individuals experience significant intellectual and physical problems.

The researchers said their study reveals that acetylation contributes to cGAS activity regulation and provides a potential therapy for treating DNA-mediated autoimmune diseases. (Xinhua)