Research articleDown-regulation of purinergic P2X7 receptor expression and intracellular calcium dysregulation in peripheral blood mononuclear cells of patients with amyotrophic lateral sclerosis

•Expression of purineric receptors (P2X4 and P2X7) and intracellular Ca2+ changes were analyzed in PBMCs of ALS patients.•We observed a downregulation of P2X7 receptors in PBMCs of ALS patients compared to controls.•Intracellular Ca2+ dysregulation as a main characteristic of motor neurons in ALS is detectable in PBMCs.•Stimulation of PBMCs with different concentrations of ATP revealed decreased intracellular Ca2+ levels in ALS patients.

BackgroundAmyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder associated with intracellular Ca2+ dysregulation. The P2X receptor family is comprised of ligand-gated ion channels that respond to extracellular adenosine triphosphate (ATP) and increases permeability of calcium into the cell. The underlying mechanisms of purinergic signalling on peripheral blood mononuclear cells (PBMCs) in ALS remain unclear. Herein, we studied the expression of P2X4/P2X7 receptors and calcium homeostasis in blood cells of ALS patients.MethodsWe used PBMCs from 42 ALS patients and 19 controls. Purinergic receptors P2X4 (P2X4R) and P2X7 (P2X7R) were examined using western blot analysis. The effect of exogenous ATP on intracellular Ca2+ homeostasis in monocytes was measured using fluorimetry by Fura-2 on a single-cell level.ResultsWestern blot analysis revealed stable P2X4R expression in patients and controls. P2X7R expression was significantly reduced (p = 0.012) in ALS patients. Repetitive long-term ATP stimulation caused a sustained decrease in Ca2+ levels in the ALS group as measured by the area under the curve, peak amplitude and peak height.ConclusionThese results confirm our hypothesis that Ca2+ abnormalities in ALS are measurable in immune cells. These findings suggest that the reduction of P2X7 receptor expression on PBMCs leads to intracellular calcium dysregulation. Our study improves the understanding of ALS pathophysiology and proposes PBMCs as a non-invasive source to study ALS.