TNF-α mediates the neuroprotective effect of TWEAK. (A) Mean concentration of TNF-α in the culture media of Wt cerebral cortical neurons 0 to 60 minutes after 60 minutes of incubation with TWEAK 100 ng/mL. n = 8, * and ** P < 0.05 compared to untreated sister cultures. Lines denote SD. (B) Mean neuronal survival in Wt cerebral cortical neurons exposed to 55 minutes of OGD conditions 24 hours after 60 minutes of incubation with TWEAK 100 ng/mL alone or in the presence of anti-TNF-α 0.04 μg/mL or anti-TNFR1 100 μg/mL antibodies or an immunoglobulin G isotype control. n = 12, *P < 0.05 compared to neurons exposed to OGD conditions without preconditioning with TWEAK, **P < 0.05 compared to cells preconditioned with TWEAK in the presence of anti-TNF-α or anti-TNFR1 antibodies. Lines denote SD. (C) Mean neuronal survival in TNF-α-/- neurons incubated for 60 minutes with TWEAK 0 to 300 ng/mL 24 hours before exposure to 55 minutes of OGD conditions. n = 10 per group. (D) Volume of the ischemic lesion in Wt and TNF-α-/- mice treated with vehicle control (white bars) or TWEAK 0.2 mg by intraperitoneal injection (gray bars) 24 hours before tMCAO. *P < 0.05 compared to non-preconditioned Wt mice. n = 12 per experimental group. Lines denote SD. Ig G: immunoglobulin G; Ns: non-significant; OGD: oxygen-glucose deprivation; TNF: tumor necrosis factor; TNFR1: tumor necrosis factor receptor 1; TWEAK: tumor necrosis factor-like weak inducer of apoptosis; Wt: wild-type.