Furthermore, we noted a modest increase in basal expression of BACE1 in the hippocampal CA1 region of
non-ischemic LTED sham animals, but similar to changes observed in basal ADAM 17 expression, this trend did not reach statistical significance (Fig. 5A: d and B). These results agree with the aforementioned α-secretase results, suggesting that non-amyloidogenic processing of APP is significantly impaired and that amyloidogenic processing of APP is significantly enhanced following long-term ovariectomy (LTED), particularly in the event of GCI. In light of the evidence suggesting a post-ischemic switch to amyloidogenic APP processing following surgical menopause, we next GDC-0068 research buy decided to more PLX-4720 solubility dmso closely examine the proteolytic processing of APP. As discussed previously, APP processing can be categorized as either non-amyloidogenic or amyloidogenic. Non-amyloidogenic processing of APP occurs through sequential cleavage by α- and γ-secretases and produces three non-toxic fragments: p3, sAPPα, and C83.7 In contrast, amyloidogenic APP processing occurs through sequential cleavage by β- and γ-secretases and produces the neurotoxic Aβ protein, as well as two other fragments: sAPPβ and C99.7 To investigate changes in APP processing in the current study, we performed Western
blotting analysis for the two APP C-Terminal fragments C99 and C83, which are representative of amyloidogenic and non-amyloidogenic APP processing, respectively, and we compared the C99/C83 ratio in the hippocampal CA1 region among the different treatment groups. As expected, the C99/C83 ratio was less than 1 in STED sham animals, suggesting that non-amyloidogenic APP processing predominates in the hippocampus under basal conditions (Fig. 6). This ratio was modestly elevated (1.0) 24 h following GCI in STED animals and returned to baseline if E2 therapy was administered immediately following ovariectomy
(Fig. 6), indicating that GCI promotes amyloidogenic and E2 promotes non-amyloidogenic processing of APP. While the C99/C83 ratio remained less than 1 in LTED sham animals, ifoxetine this ratio was significantly elevated (>1) in both LTED placebo- and LTED E2-treated females (Fig. 6). This observation corroborates our α- and β-secretase data, suggesting that following surgical menopause, GCI induces a major switch to amyloidogenic APP processing in the hippocampal CA1 and that delayed E2 therapy is unable to mitigate this event. The purpose of the current study was to test the hypothesis that surgical menopause leads to enhanced amyloidogenesis in the hippocampal CA1 region after ischemic injury and to decreased sensitivity of the APP processing pathway to E2 regulation.