Background: Professional soccer players are susceptible to amyotrophic lateral sclerosis. Strenuous physical activity has been associated with persistent inflammatory conditions and elevation of systemic cytokine levels, which could contribute to the vulnerability of these athletes. To investigate changes induced by playing soccer in the systemic profiles of growth factors and of the principal cytokines involved in the inflammatory response, we compared the serum concentrations of these factors in Italian professional soccer players and sedentary subjects. We also investigated the effects of the sera on primary cultured motor neurons in relation to their cytokine and growth factor content.
Methods: Serum concentrations of cytokines and growth factors were measured by a biochip array analyzer. Neurotoxicity of sera was assessed by immunocytochemical assays in primary motor neuron cultures from mouse embryos.
Results: Circulating levels of interleukin-8, tumor necrosis factor-alpha and interleukin-4 were lower in soccer players than controls. However, the viability of primary cultured mouse motor neurons treated with sera from the two groups did not differ significantly. Vascular endothelial growth factor (VEGF) independently emerged as a systemic protective factor for motor neurons.
Conclusions: We found significant alterations in circulating pro-inflammatory cytokines in Italian professional soccer players, showing an unbalanced inflammatory condition in these subjects. VEGF was a protective serum factor affecting motor neuron survival.