Interferon-stimulated gene 15 as a general marker for acute and chronic neuronal injuries.

Activation of interferon (IFN) signaling in the central nervous system (CNS) is usually associated with inflammation. However, a robust activation of type I IFN-stimulated genes (ISGs) at pre-symptomatic stages occurs in the spinal cord of SOD1(G93A) mice, an amyotrophic lateral sclerosis (ALS) animal model, without obvious signs of inflammation. To determine if the same signaling pathway is elevated in other types of neuronal injuries, we examined the protein expression levels of an IFN-stimulated gene, ISG15, in mouse models of acute and chronic neuronal injuries. We found that ISG15 protein was dramatically increased in the brains of mice subjected to global ischemia and traumatic brain injury, and in transgenic mice overexpressing HIV gp120 protein. These results suggest that activation of ISGs is a shared feature of neuronal injuries and that ISG15 may be a suitable biomarker for detecting neuronal injuries in the CNS.