Increased activation ability of monocytes from ALS patients.

Neuroinflammation is increasingly recognized as an important mediator of disease progression in patients with amyotrophic lateral sclerosis (ALS). Recent research suggests that pro-inflammatory microglia in ALS mice promote motoneuron cytotoxicity by secreting reactive oxygen species and pro-inflammatory cytokines. Gene expression analyses indicate that peripheral circulating monocytes from ALS patients are skewed towards a pro-inflammatory state that contributes to ALS disease progression. Better understanding of macrophage phenotypes of ALS patients is therefore warranted. In this study, we demonstrate that M1 macrophages differentiated from ALS circulating monocytes produced more pro-inflammatory cytokines, including IL-6 and TNFα, than M1 macrophages derived from healthy control monocytes. More importantly, IL-6 protein levels of ALS M1 macrophages positively correlated with disease burden, and TNFα protein levels of ALS M1 macrophages positively correlate with disease progression rates. Collectively, these data suggest that monocytes from ALS patients are more readily activated and differentiated to a pro-inflammatory M1 phenotype, and represent a potential target for immunomodulatory therapy.