Early Stages of Alzheimer\u27s Disease: Evolving the Care Team for Optimal Patient Management.

Alzheimer\u27s disease (AD) is a progressive, neurodegenerative disease that creates complex challenges and a significant burden for patients and caregivers. Although underlying pathological changes due to AD may be detected in research studies decades prior to symptom onset, many patients in the early stages of AD remain undiagnosed in clinical practice. Increasing evidence points to the importance of an early and accurate AD diagnosis to optimize outcomes for patients and their families, yet many barriers remain along the diagnostic journey. Through a series of international working group meetings, a diverse group of experts contributed their perspectives to create a blueprint for a patient-centered diagnostic journey for individuals in the early stages of AD and an evolving, transdisciplinary care team. Here, we discuss key learnings, implications, and recommendations

Resistance to MPTP-Neurotoxicity in α-Synuclein Knockout Mice Is Complemented by Human α-Synuclein and Associated with Increased β-Synuclein and Akt Activation

Genetic and biochemical abnormalities of α-synuclein are associated with the pathogenesis of Parkinson's disease. In the present study we investigated the in vivo interaction of mouse and human α-synuclein with the potent parkinsonian neurotoxin, MPTP. We find that while lack of mouse α-synuclein in mice is associated with reduced vulnerability to MPTP, increased levels of human α-synuclein expression is not associated with obvious changes in the vulnerability of dopaminergic neurons to MPTP. However, expressing human α-synuclein variants (human wild type or A53T) in the α-synuclein null mice completely restores the vulnerability of nigral dopaminergic neurons to MPTP. These results indicate that human α-synuclein can functionally replace mouse α-synuclein in regard to vulnerability of dopaminergic neurons to MPTP-toxicity. Significantly, α-synuclein null mice and wild type mice were equally sensitive to neurodegeneration induced by 2′NH2-MPTP, a MPTP analog that is selective for serotoninergic and noradrenergic neurons. These results suggest that effects of α-synuclein on MPTP like compounds are selective for nigral dopaminergic neurons. Immunoblot analysis of β-synuclein and Akt levels in the mice reveals selective increases in β-synuclein and phosphorylated Akt levels in ventral midbrain, but not in other brain regions, of α-synuclein null mice, implicating the α-synuclein-level dependent regulation of β-synuclein expression in modulation of MPTP-toxicity by α-synuclein. Together these findings provide new mechanistic insights on the role α-synuclein in modulating neurodegenerative phenotypes by regulation of Akt-mediated cell survival signaling in vivo

Levels of α-synuclein affects β-synuclein expression and basal <i>Akt</i> phosphorylation <i>in vivo</i>.

<p><b><i>A.</i></b> Total tissue extracts from cortex and ventral midbrain of wild type (WT), moSyn-null mice (KO), and HuSyn transgenic (line I2-2) on moSyn-KO background (KO+) were immunobloted for endogenous β-synuclein, <i>Akt</i> (pSer473 and total) and GAPDH. <b><i>B and C.</i></b> Semi-quantitative analysis of β-synuclein <b>(B)</b> and pSer473-<i>Akt</i> levels <b><i>(C)</i></b>. The values are mean ± SEM from 4 animals (<i>*p>0.05, **p>0.01</i>, ANOVA with Newman-Keuls post-test).</p

Nigrostriatal system in transgenic wild type and mutant human α-synuclein overexpressing mice do not show increased sensitivity to acute MPTP intoxication.

<p>Transgenic mice expressing moderate levels (∼3-fold over endogenous levels) of wild type (WT, line I2-2), A30P mutant (line T3), and A53T mutant (line N2-5) human α-synuclein were subjected to acute paradigm of MPTP (18 mg MPTP/kg free base X4, every 2h). <i>A.</i> Striatal levels of dopamine and major metabolite DOPAC in transgenic and non-transgenic littermate cohorts were analyzed 7 days after the last MPTP injection. No differences were seen among transgenic and non-transgenic mice receiving the same treatments (saline or MPTP). <i>B.</i> Stereologic neuronal counts of TH-immunopositive and total neurons in transgenic and non-transgenic littermate cohorts analyzed two weeks following the last MPTP injection. While MPTP treatments caused a significant reduction in TH-immunopositive and total neurons, no significant differences in neuronal counts are observed between transgenic and non transgenic mice receiving the same treatment (saline or MPTP). Data represent mean ± SEM. *<i>p<0.05</i>, statistical significance versus saline controls using two way ANOVA, n = 5-6 per group, n.s not significant.</p

Levels of striatal dopamine and its metabolites in wild type and α-synuclein knock out mice following 2′NH₂MPTP treatment.

<p>Striatal levels of dopamine and its metabolites measured after 2 weeks of acute 2′NH₂MPTP (15 mg/kg, i.p.) administered four times every two hours in wild type and α-synuclein knock out mice. Data are expressed as mean (n = 5) ± SEM. Statistical analysis was performed by ANOVA, revealing no significant differences among group means. DA, dopamine; DOPAC, 3,4-dihydroxy-phenylacetic acid; HVA, homovanillic acid, WT, wild type; KO, knock out.</p

Effects of sub acute MPTP regimen, aging, and transgene expression level on the MPTP sensitivity of nigral dopaminergic neurons in human A53T α-synuclein transgenic mice.

<p><i>A.</i> Stereologic cell counts of total and TH-immunopositive neurons of SNpc in non transgenic and human A53T transgenic mice (line N2-5, ∼3-fold) analyzed two weeks after a sub-acute paradigm of MPTP (30 mg MPTP/kg free base once a day for 5 days). Although sub acute MPTP caused significant reductions in total and TH-positive neurons no significant differences were seen among transgenic and non transgenic mice receiving the same treatments (saline or MPTP). <i>B</i>. TH-positive and total neuronal counts in SNpc of 12-14 month old non transgenic and human A53T transgenic mice (line N2-5) after acute MPTP (15 mg MPTP/kg free base X4, every 2 h) at 7 days. Acute MPTP in older mice caused significant reduction in total and TH-positive neurons no significant differences were seen among transgenic and non transgenic mice receiving the same treatments (saline or MPTP). <i>C</i>. Cell counts of TH-positive and total neurons in high expressing lines of human A53T transgenic mice (G2-3 line, ∼6-fold) 7 days after acute MPTP intoxication (18 mg MPTP/kg free base X4, every 2 h). MPTP-intoxication resulted in a significant reduction of total and TH-positive neuronal counts in non transgenic and high expressing lines of A53T transgenic mice compared to saline treatments. A moderate increase in the vulnerability was observed in A53T transgenic mice. Data represent mean ± SEM. *<i>p<0.05</i>, statistical significance versus saline controls using two way ANOVA, n = 5-6 per group, n.s., not significant. #, significant using Neuman-Keuls post-test (<i>p<0.05</i>) but not with the Tukey-Kramer post test.</p

Human α-synuclein complements MPTP resistant phenotype of mouse α-synuclein null mice.

<p><b><i>A.</i></b> Expression of mouse and human α-synuclein in wild type (WT), mouse α-synuclein nulls (KO) and mice expressing wild type human α-synuclein (line I2-2) on a mouse α-synuclein null background (hWT/KO), total proteins isolated from 9 month old striata were subjected to immunoblot analysis for total α-synuclein (Syn-1), human α-synuclein (HuSyn), and GAPDH. <b><i>B and C.</i></b> TH-immunostaining staining of striatum (B) and SNpc (C) 7 days following saline or acute MPTP (20 mg/kg free base four times every 2 hour) treatment in wild type (WT), mouse α-Syn nulls (KO) and human α-Syn transgenic [wild type (hWT, line I2-2) and A53T (line N2-5)] on the mouse α-Syn null background (hWT/KO; A53T/KO). Only the KO is protected from MPTP toxicity. <b><i>D and E</i></b>. MPTP intoxication results in significant reductions in striatal DA-levels <b><i>(D)</i></b> and TH-positive neuronal cells <b><i>(E)</i></b> in mice with either mouse or human α-Syn expression. The α-Syn KO mice were completely protected against MPTP. The reduced basal number of DAergic neurons in α-Syn KO mice was not complemented by the human α-Syn expression <b><i>(E)</i></b>. Data represent mean ± SEM. ^@,** <i>p<0.05</i>, versus saline and ^#<i>p<0.05</i>, versus wild type MPTP, Two way ANOVA, n = 5-6, n.s not significant, scale bar: 200 µm.</p