Additional file 7 of Biologic TNF-α inhibitors reduce microgliosis, neuronal loss, and tau phosphorylation in a transgenic mouse model of tauopathy

Additional file 7: Fig. S6. Levels of TNF-α in the plasma (A) and whole-brain homogenates (B) were not significantly different between PS19-Saline and PS19-TfRMAb-TNFR and PS19-Etanercept mice, respectively. We attribute the lack of change in plasma and brain TNF-α levels with biologic TNF-α inhibitors to the time of plasma and brain sample collection. There was a 10-day lag between the last treatment dose (8 weeks after treatment initiation) and sample collection due to time for open-field testing (during week 9; Figure 1A). The plasma elimination half-lives of TfRMAb-TNFR and etanercept are ~ 4 h and ~13 h, respectively (Figure 5). Since it takes 6 elimination half-lives (24 h and 78 h for TfRMAb-TNFR and etanercept, respectively) for a drug to be completely eliminated from the blood circulation, we do not expect any circulating biologic TNF-α inhibitor at the time of sacrifice. Another potential reason for the lack of difference in plasma and brain TNF-α is the use of immunoassays. Since both the TfRMAb-TNFR and etanercept bind to TNF-α, detection of TNF-α using immunoassays may be complicated if the TNF-α is still bound to the biologic TNF-α inhibitor in the brain at the time of mouse sacrifice. Though this is unlikely considering the elimination half-lives of the drugs, to rule out any such interference, we measured the protein levels of IĸBα, which is degraded following TNF-α stimulation and is therefore expected to increase following TNF-α inhibition, in whole-brain homogenates using Western blotting (C). The TfRMAb-TNFR-treated PS19 mice had significantly higher (p