Conformational change and GTPase activity of human tubulin: A comparative study on Alzheimer's disease and healthy brain.

In Alzheimer's disease (AD), the most common form of dementia, microtubules (MTs) play a pivotal role through their highly dynamic structure and instability. They mediate axonal transport that is crucial to synaptic viability. MT assembly, dynamic instability and stabilization are modulated by tau proteins, whose detachment initiates MT disintegration. Albeit extensive research, the role of GTPase activity in molecular mechanism of stability remains controversial. We hypothesized that GTPase activity is altered in AD leading to microtubule dynamic dysfunction and ultimately to neuronal death. In this paper, fresh tubulin was purified by chromatography from normal young adult, normal aged, and Alzheimer's brain tissues. Polymerization pattern, assembly kinetics and dynamics, critical concentration, GTPase activity, interaction with tau, intermolecular geometry, and conformational changes were explored via Förster Resonance Energy Transfer (FRET) and various spectroscopy methods. Results showed slower MT assembly process in samples from the brains of people with AD compared with normal young and aged brains. This observation was characterized by prolonged lag phase and increased critical and inactive concentration of tubulin. In addition, the GTPase activity in samples from AD brains was significantly higher than in both normal young and normal aged samples, concurrent with profound conformational changes and contracted intermolecular MT-tau distances as revealed by FRET. These alterations were partially restored in the presence of a microtubule stabilizer, paclitaxel. We proposed that alterations of both tubulin function and GTPase activity may be involved in the molecular neuropathogenesis of AD, thus providing new avenues for therapeutic approaches.

Plasma Cytokines Profile in Subjects with Alzheimer's Disease: Interleukin 1 Alpha as a Candidate for Target Therapy.

Background: Alzheimer's disease (AD) is the main cause of the neurodegenerative disorder, which is not detected unless the cognitive deficits are manifested. An early prediagnostic specific biomarker preferably detectable in plasma and hence non-invasive is highly sought-after. Various hypotheses refer to AD, with amyloid-beta (Aß) being the most studied hypothesis and inflammation being the most recent theory wherein pro-and anti-inflammatory cytokines are the main culprits. Materials and Methods: In this study, the cognitive performance of AD patients (n=39) was assessed using mini-mental state examination (MMSE), AD assessment scale-cognitive subscale (ADAS-cog), and clinical dementia rating (CDR). Their neuropsychiatric symptoms were evaluated through neuropsychiatric inventory-questionnaire (NPI-Q). Moreover, plasma levels of routine biochemical markers, pro-/anti-inflammatory cytokines such as tumor necrosis factor α (TNF-α), interleukin-1 α (IL-1α), IL-1ß, IL-2, IL-4, IL-6, IL-8, IL-12p70, IL-10, Interferon-gamma, chemokines, including prostaglandin E2 (PGE-2), monocyte chemoattractant protein-1, interferon gamma-induced protein 10, Aß peptide species (42, 40) and Transthyretin (TTR) were measured. Results: Our results revealed that Aß 42/40 ratio and TTR were correlated (r=0.367, P=0.037). IL-1α was directly correlated with ADAS-cog (r=0.386, P=0.017) and Aß 40 (r=0.379, P=0.019), but was inversely correlated with IL-4 (r=-0.406, P=0.011). Negative correlations were found between MMSE and PGE2 (r=-0.405, P=0.012) and TNF-α/ IL-10 ratio (r=-0.35, P=0.037). CDR was positively correlated with both PGE2 (r=0.358, P=0.027) and TNF-α (r=0.416, P=0.013). There was a positive correlation between NPI-caregiver distress with CDR (r=0.363, P=0.045) and ADAS-cog (r=0.449, P=0.019). Conclusion: Based on the observed correlation between IL-1α, as a clinical moiety, and ADAS-cog, as a clinical manifestation of AD, anti-IL-1α therapy in AD could be suggested.