PMC:1283364 / 27523-30308 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/1283364","sourcedb":"PMC","sourceid":"1283364","source_url":"http://www.ncbi.nlm.nih.gov/pmc/1283364","text":"Aβ Levels Are Dramatically Reduced by Transgene Suppression\nCortical homogenates from young, predeposit tTA/APP mice used for Western blot in Figure 1 (line 107) were fractionated by sequential multi-step extraction with PBS, 2% SDS, and 70% FA followed by human-specific Aβ ELISA to measure transgene-derived peptide in each fraction. Aβ40 is shown in white, Aβ42 in black.\n(A) PBS-soluble Aβ levels are substantially reduced by both acute and chronic dox treatment (ANOVA, effect of treatment group F 4,24 = 137.10 and 386.01, p \u003c 0.001, for Aβ40 and Aβ42, respectively). Aβ levels in treated animals are indistinguishable from nontransgenic (NTg) animals (p \u003e 0.3, Tukey post-hoc test).\n(B) In the young animals tested here prior to the formation of visible amyloid deposits, most Aβ is extracted into the SDS fraction (84% and 76% of all transgene-derived Aβ40 and Aβ42, respectively). As in the PBS-soluble fraction, Aβ levels in the SDS fraction are significantly lowered by dox treatment compared to untreated animals (ANOVA effect of group F 4,24 = 197.57 and 163.48, p \u003c 0.001, for Aβ40 and Aβ42, respectively). Acutely treated animals retained a small (although significant) amount of residual peptide (p \u003c 0.001 compared to nontransgeinc, Tukey post-hoc test), whereas Aβ levels in mice born and raised on dox were reduced to levels indistinguishable from nontransgenic (p \u003e 0.8, Tukey post-hoc test).\n(C) The FA-soluble fraction already contains a small but significant pool of aggregated Aβ42 in untreated animals by 4 wk of age (p \u003c 0.05 versus nontransgenic; Tukey post-hoc test applied to significant effect of group ANOVA F 4,24 = 17.11, p \u003c 0.001). By 6 wk of age, the amount of Aβ in the FA fraction is increased significantly preceding the appearance of visible deposits 2 wk later. The FA pool is the only peptide fraction not lowered by acute dox treatment (4 wk untreated = 4 wk + 2 wk dox, p \u003e 0.9, Tukey post-hoc test), consistent with poor turnover of aggregated Aβ species.\n(D) Measurements of total Aβ, including both endogenous and transgene-derived peptides, show that animals born and raised on dox harbor Aβ levels identical to nontransgenic animals (p \u003e 0.9, Tukey post-hoc test, effect of group ANOVA F 4,24 = 39.13 and 35.29, p \u003c 0.001, for Aβ40 and Aβ42, respectively). Whereas chronic transgene suppression fully prevents synthesis of both peptides, acute dox treatment fully suppresses Aβ40 levels (p \u003e 0.8, Tukey post-hoc test), but leaves a small amount of nonsuppressed Aβ42. The residual Aβ42 observed in acutely treated young animals derives from uncleared aggregates extracted in the SDS and FA fractions. *, p \u003c 0.05; **, p \u003c 0.005; ***, p \u003c 0.001 versus 4-wk-old untreated mice, Tukey post-hoc applied to significant effect of group ANOVA.","divisions":[{"label":"title","span":{"begin":0,"end":59}},{"label":"p","span":{"begin":60,"end":374}},{"label":"p","span":{"begin":375,"end":689}},{"label":"p","span":{"begin":690,"end":1412}},{"label":"p","span":{"begin":1413,"end":2000}}],"tracks":[]}