Plasma Inflammatory Cytokines Are Elevated in ALS

Abstract

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease which leads to death in a median time of 2-3 years. Inflammation has been claimed important to the ALS pathogenesis, but its role is still not well-characterized. In the present study, a panel of five cytokines (IL-2, IL-6, IL-10, IFN-gamma, and TNF-alpha) measured in plasma has been investigated in ALS. These biomarkers of inflammation were measured in a population-based cohort of 79 patients with ALS and 79 age- and sex-matched healthy controls using the Bio-Plex technology (Bio-Rad). All the five cytokines were significantly increased in plasma samples of patients compared with controls (p < 0.0001), with IL-6 having the highest median concentration (10.11 pg/ml) in the ALS group. Furthermore, IL-6 was the plasma cytokine with the highest discrimination ability between patients and controls according to the receiver operating characteristic analysis (area under the curve = 0.93). At a cut-off point of 5.71 pg/ml, it was able to classify patients and controls with 91% of sensitivity and 87% of specificity. In the ALS group, plasma IL-6 concentration correlated with demographic (age: rs = 0.25, p = 0.025) and clinical (revised ALS Functional Rating Scale at evaluation: rs = -0.32, p = 0.007; Manual Muscle Testing: rs = -0.33, p = 0.004; progression: rs = 0.29, p = 0.0395) parameters. In line with previous studies, our results confirm that inflammatory cytokines are elevated in ALS, supporting a possible role of inflammation in disease mechanism and progression. However, the precise role of inflammation in ALS needs to be further investigated on larger samples and with more mechanistic studies.

Keywords: ALS; biomarker; cytokines; inflammation; plasma.

Figure 1

Biomarker levels in ALS patients and controls. The figure shows the plasma levels (pg/ml) of the five cytokines under investigation in the study groups, ALS (blue) and controls (red). The horizontal lines represent the median of the distribution. The y-axes are truncated to 620 pg/ml to facilitate the visualization.

Figure 2

Area under the curve (AUC). The figure shows the receiver operating characteristic (ROC) curves for the five cytokines under investigation.