Selective inhibition of soluble tumor necrosis factor alters the neuroinflammatory response following moderate spinal cord injury in mice

Clinical and animal model studies have implicated inflammation and glial and peripheral im-mune cell responses in the pathophysiology of spinal cord injury (SCI). A key player in the in-flammatory response after SCI is the pleiotropic cytokine tumor necrosis factor (TNF), which ex-ists both in both transmembrane (tmTNF) and a soluble (solTNF) form. In the present study, we extend our previous findings of a therapeutic effect of topically blocking solTNF signaling after SCI for three consecutive days on lesion size and functional outcome to study the effect on spatio-temporal changes in the inflammatory response after SCI in mice treated with the selective solTNF inhibitor XPro1595 and compared to saline-treated mice. We found that despite compa-rable TNF and TNF receptor levels between XPro1595- and saline-treated mice, XPro1595 transi-ently decreased pro-inflammatory interleukin (IL)-1 and IL-6 levels and increased pro-regenerative IL-10 levels in the acute phase after SCI. This was complemented by a decrease in the number of infiltrated leukocytes (macrophages and neutrophils) in the lesioned area of the spinal cord and an increase in the number of microglia in the peri-lesion area 14 days after SCI, fol-lowed by a decrease in microglial activation in the peri-lesion area 21 days after SCI. This trans-lated into increased myelin preservation and improved functional outcomes in XPro1595-treated mice 35 days after SCI. Collectively, our data suggests that selective targeting of solTNF time-dependently modulates the neuroinflammatory response by favoring a pro-regenerative envi-ronment in the lesioned spinal cord, leading to improved functional outcomes.