Pheral immune cells [2,11] we established a technique that could target 
CNS TLR4 receptors. Accordingly, we developed interfering peptides coupled to a truncated Tat carrier sequence [15] in an attempt to block TLR4 signalling in brain slices, and subsequently examined their efficacy in preventing TLR4 activation in vivo. Specifically, the peptides were designed to block TLR4-MyD88 binding via the intracellular TIR domain induced by LPS activation of TLR4 (Figure 1A). We based our sequence on epta-peptides directed against the BB-loop within the TIR domains of TLR4 (Tat-MyD88) and MyD88 (Tat-TLR4) [16,17]. We first determined whether these interfering peptides entered cells in brain slices after bath application in vitro or crossed the BBB and entered CNS cells after i.p. injections in vivo. Dansylated TatMyD88 was injected intraperitoneally (i.p.; 6 mg/kg) into mice and 30 minutes later acute brain slices were prepared for immediate examination using two-photon laser scanning microscopy (TPLSM). Strong dansyl I-BRD9 web fluorescence was detected within cells in the hippocampus, in contrast to vehicle injected controls (Figure 1B,C), indicating that the Tat-fused peptides could cross the BBB and permeate CNS cells. Similarly fluorescence was observed within cells in brain slices when brain slices were incubated in ACSF with dansylated Tat-MyD88. These observations of labelled Tat-MyD88 peptides in CNS cells show that these peptides can enter cells where they potentially have access to the intracellular binding site of MyD88 and TLR4 receptors. We next tested whether Tat-MyD88 effectively blocked the interaction between TLR4 and MyD88 under conditions where we saw that the dansylated peptides entered cells. We tested their efficacy in the whole brain by assessing their ability to prevent protein-protein interactions via co-immunoprecipitation. Mice were injected (i.p. 6 mg/kg) with either vehicle (control), TatMyD88 peptide, or a scrambled version of the MyD88 sequence coupled to Tat (Tat-scram) and whole brain lysates were prepared 30 minutes later. Western blots of immunoprecipitated brain lysate prepared from mice injected with Tat-MyD88 showed a reduction in the 
intensity of the MyD88 band co-immunoprecipitated using anti-TLR4 antibody (62.0362.73 a.u.) compared to unMedChemExpress ASP015K treated control (100.00612.45 a.u., p = .041) and Tat-scram treated (103.9466.67 a.u., p = .004; Figure 1D,E). Likewise, the reverse co-immunoprecipitation of TLR4 using the MyD88 antibody was also 15755315 diminished in mice injected with Tat-MyD88 (50.6367.53 a.u.) compared to untreated control (100.0063.58 a.u., p = .004) and Tat-scram treated (98.9263.84 a.u., p = .005). No change was observed in the co-immunoprecipitation of either MyD88 with TLR4 (p = .794), or TLR4 with MyD88 (p = .847) when Tatscram treated animals were compared to untreated controls (Figure 1D,E). This data reveals that i.p. injections of the Tatconjugated interfering peptide Tat-MyD88 are capable of blocking interactions between MyD88 and TLR4 in the brain in vivo.The disruption of co-immunoprecipitation supports the possibility that Tat-interfering peptides cause functional disruption, which we tested by examining the efficacy of Tat-MyD88 and TatTLR4 to inhibit LPS activation of second messenger pathways and cytokine production in both brain slices and in vivo. We began by determining the time course of downstream kinase activation in acutely prepared brain slices treated with LPS. Lysates were prepared 0, 15, 3.Pheral immune cells [2,11] we established a technique that could target CNS TLR4 receptors. Accordingly, we developed interfering peptides coupled to a truncated Tat carrier sequence [15] in an attempt to block TLR4 signalling in brain slices, and subsequently examined their efficacy in preventing TLR4 activation in vivo. Specifically, the peptides were designed to block TLR4-MyD88 binding via the intracellular TIR domain induced by LPS activation of TLR4 (Figure 1A). We based our sequence on epta-peptides directed against the BB-loop within the TIR domains of TLR4 (Tat-MyD88) and MyD88 (Tat-TLR4) [16,17]. We first determined whether these interfering peptides entered cells in brain slices after bath application in vitro or crossed the BBB and entered CNS cells after i.p. injections in vivo. Dansylated TatMyD88 was injected intraperitoneally (i.p.; 6 mg/kg) into mice and 30 minutes later acute brain slices were prepared for immediate examination using two-photon laser scanning microscopy (TPLSM). Strong dansyl fluorescence was detected within cells in the hippocampus, in contrast to vehicle injected controls (Figure 1B,C), indicating that the Tat-fused peptides could cross the BBB and permeate CNS cells. Similarly fluorescence was observed within cells in brain slices when brain slices were incubated in ACSF with dansylated Tat-MyD88. These observations of labelled Tat-MyD88 peptides in CNS cells show that these peptides can enter cells where they potentially have access to the intracellular binding site of MyD88 and TLR4 receptors. We next tested whether Tat-MyD88 effectively blocked the interaction between TLR4 and MyD88 under conditions where we saw that the dansylated peptides entered cells. We tested their efficacy in the whole brain by assessing their ability to prevent protein-protein interactions via co-immunoprecipitation. Mice were injected (i.p. 6 mg/kg) with either vehicle (control), TatMyD88 peptide, or a scrambled version of the MyD88 sequence coupled to Tat (Tat-scram) and whole brain lysates were prepared 30 minutes later. Western blots of immunoprecipitated brain lysate prepared from mice injected with Tat-MyD88 showed a reduction in the intensity of the MyD88 band co-immunoprecipitated using anti-TLR4 antibody (62.0362.73 a.u.) compared to untreated control (100.00612.45 a.u., p = .041) and Tat-scram treated (103.9466.67 a.u., p = .004; Figure 1D,E). Likewise, the reverse co-immunoprecipitation of TLR4 using the MyD88 antibody was also 15755315 diminished in mice injected with Tat-MyD88 (50.6367.53 a.u.) compared to untreated control (100.0063.58 a.u., p = .004) and Tat-scram treated (98.9263.84 a.u., p = .005). No change was observed in the co-immunoprecipitation of either MyD88 with TLR4 (p = .794), or TLR4 with MyD88 (p = .847) when Tatscram treated animals were compared to untreated controls (Figure 1D,E). This data reveals that i.p. injections of the Tatconjugated interfering peptide Tat-MyD88 are capable of blocking interactions between MyD88 and TLR4 in the brain in vivo.The disruption of co-immunoprecipitation supports the possibility that Tat-interfering peptides cause functional disruption, which we tested by examining the efficacy of Tat-MyD88 and TatTLR4 to inhibit LPS activation of second messenger pathways and cytokine production in both brain slices and in vivo. We began by determining the time course of downstream kinase activation in acutely prepared brain slices treated with LPS. Lysates were prepared 0, 15, 3.
