HMOX1 and multiple sclerosis: In the brain, the HMOX pathway is very important as a defensive mechanism for neurons exposed to oxidative stress, contributing to the degradation of heme to biliverdin, free iron, and carbon monoxide; and particularly HMOX1 expression has been found upregulated in the brains of patients with PD, Alzheimer disease, and multiple sclerosis.16,17 Moreover, upregulation of HMOX1 in astrocytes increases neuronal oxidative stress and sequestration of iron nonlinked to transferrin in the mitochondrial department.17