Fig 2: Scheme showing the proposed mechanisms for the IL-1ß-induced alterations in membrane expression of GluA2 and GluA1 subunits of AMPA receptor in hippocampus of hyperammonemic rats. Hyperammonemia increases IL-1ß, enhancing activation of IL-1 receptor. This leads to activation of Src, reflected in increased phosphorylation of Tyr416. a Src in turn enhances phosphorylation at Tyr1472 and membrane expression of GluN2B, which leads to activation of p38. Activated p38 binds to and reduces phosphorylation at Thr560 and activity of PKC?, thus resulting in reduced phosphorylation at Ser880 and enhanced membrane expression of GluA2. b Src also activates PKCd which enhances phosphorylation of GluN2B at Ser1303, reducing membrane expression of CaMKII and phosphorylation at Ser831 and membrane expression of GluA1

Fig 3: IL-1 receptor, Src, and GluN2B-mediated activation of p38 leads to the alterations in membrane expression and phosphorylation of the GluA2 but not of the GluA1 subunit in hyperammonemic rats. IL-1Ra, PP2, SB239063, an inhibitor of p38 MAP-kinase, or ifenprodil, an antagonist of GluN2B-containing NMDA receptors, were added to hippocampal slices. Phosphorylation of p38 (a, b, c), GluA1 at Ser831 (g), and GluA2 at Ser880 (e) and membrane expression of GluA1 (f) and GluA2 (d) subunits were analyzed as described in the “Methods” section. Values are expressed as percentage of basal levels in control rats and are the mean ± SEM of 18, 16, 20, 30, 17, 22, and 29 rats per group in a, b, c, d, e, f, and g respectively. Data were analyzed by two-way ANOVA. In a, F (1, 66) = 0.004793 for effect of HA, p = 0.9450; F (1, 66) = 23.42 for effect of IL-1Ra, p < 0.0001; and F (1, 66) = 6.695 for interaction, p = 0.0119. In b, F (1, 59) = 0.02867 for effect of HA, p = 0.8661; F (1, 59) = 6.959 for effect of PP2, p = 0.0106; and F (1, 59) = 4.611 for interaction, p = 0.0359. In c, F (1, 76) = 2.894 for effect of HA, p = 0.0930; F (1, 76) = 7.961 for effect of ifenprodil, p = 0.0061; and F (1, 76) = 1.682 for interaction, p = 0.1985. In d, F (1, 116) = 4.486 for effect of HA, p = 0.0363; F (1, 116) = 7.577 for effect of SB239063, p = 0.0069; and F (1, 116) = 2.616 for interaction, p = 0.1085. In e, F (1, 64) = 0.2959 for effect of HA, p = 0.5883; F (1, 64) = 26.34 for effect of SB239063, p < 0.0001; and F (1, 64) = 10.08 for interaction, p = 0.0023. In f, F (1, 83) = 0.006480 for effect of HA, p = 0.9360; F (1, 83) = 0.1665 for effect of SB239063, p = 0.6843; and F (1, 83) = 2.228 for interaction, p = 0.1393. In g, F (1, 110) = 6.864 for effect of HA, p = 0.0100; F (1, 110) = 0.9431 for effect of SB239063, p = 0.3336; and F (1, 110) = 0.001793 for interaction, p = 0.9663. Values significantly different from control rats are indicated by asterisk and from hyperammonemic rats are indicated by “a”. Bonferroni post-test: *p < 0.05, ***p < 0.001, ap < 0.05, aap < 0.01, aaap < 0.001

Fig 4: Enhanced activation of IL-1 receptor and Src leads to increased phosphorylation of GluN2B subunit at Ser1303 and reduced membrane-associated CaMKII in hyperammonemic rats. IL-1Ra or PP2 were added to hippocampal slices. CaMKII membrane association (a, b) and phosphorylation of GluN2B subunit at Ser1303 (c, d) were analyzed as described in the “Methods” section. Values are expressed as percentage of basal levels in control rats and are the mean ± SEM of 12, 15, 17, and 17 rats per group in a, b, c, and d respectively. Data were analyzed by two-way ANOVA. In a, F (1, 45) = 0.2872 for effect of HA, p = 0.5947; F (1, 45) = 1.742 for effect of IL-1Ra, p = 0.1936; and F (1, 45) = 7.909 for interaction, p = 0.0073. In b, F (1, 54) = 0.4278 for effect of HA, p = 0.5159; F (1, 54) = 18.16 for effect of PP2, p < 0.0001; and F (1, 54) = 8.633 for interaction, p = 0.0048. In c, F (1, 63) = 1.059 for effect of HA, p = 0.3073; F (1, 63) = 1.244 for effect of IL-1Ra, p = 0.2689; and F (1, 63) = 9.532 for interaction, p = 0.0030. In d, F (1, 63) = 1.701 for effect of HA, p = 0.1969; F (1, 63) = 2.920 for effect of PP2, p = 0.0924; and F (1, 63) = 7.765 for interaction, p = 0.0070. Values significantly different from control rats are indicated by asterisk and from hyperammonemic rats are indicated by “a”. Bonferroni post-test: **p < 0.01, ap < 0.05, aap < 0.01, aaap < 0.001

Fig 5: (A) Diagram demonstrating the simplified view of glia secreted IL-1 and PGE2 promotes substance P and pain sensation, which provide a positive feedback to the glia, fuelling more IL-1 and PGE2. (B) Proposed mechanism of action of Andro and NSAIDS. For details, see Discussion section.