| Abstract |
Alzheimer is a neurodegenerative disease characterized by progressive loss of structure and
function of neurons in central nervous system, leading to cognitive decline, dementia and
eventually death. Neurotrophins and their receptors have been highly correlated with
Alzheimer’s disease as either their expression decreases during the progress of the disease or
their pathological isoforms appear.
Neurotrophins are growth factors with neurogenic and neuroprotective properties. They act by
binding either to their high – affinity receptors Trks or to p75NTR receptor. Despite their multiple
beneficial effects, their therapeutic potential is limited due to their polypeptidic nature, as well
as, their inability to cross blood – brain barrier (BBB).
Recent studies of our laboratory have demonstrated the ability of endogenous neurosteroid
dehydroepiandrosterone (DHEA) to inhibit neuronal apoptosis by selectively binding to
neurotrophin receptors, TrkA and p75NTR. However, DHEA is metabolized in vivo to androgenic
and estrogenic steroids, thus may increase the risk of developing hormone - depented cancer. To
overcome these problems, our chemists collaborators synthesized DHEA analogues, which
sustain the neuroprotective actions of the parental molecule while are deprived of the endocrine
effects.
The aim of this master thesis is firstly to screen such synthetic and natural molecules in vitro
and subsequently to estimate their biological effects. More specifically, we aim to test their
ability to activate the TrkA receptor (Tropomyosin related kinase A), which is the highly –
affinity endogenous neurotrophin receptor for Nerve Growth Factor (NGF). The neuroprotective
properties of these molecules and the activation of downstream pathways of the receptor were
tested in PC12 cell line and primary hippocampal neurons isolated from mice. On this diploma
thesis 46 synthetic compounds and natural extracts isolated from marine bacteria were screened.
Compounds ENTA-005, ENTA-010, ENTA-013, ENTA-013E, ENTA-013Z and ENTA-040, in
the concentration of 500 nM and 30 minutes after treatment, were able to induce TrkA
phosphorylation and provoke downstream signaling, as well as, protect cells from apoptosis after
serum deprivation. Furthermore, the ability of the compounds to act selectively though TrkA and
TrkB receptor, was tested and confirmed. The efficiency of the compounds to reverse the
apoptotic effects indiced by the toxic Aβ oligomers was tested. Finally, we examined the role of
the transmembrane domain of Trk receptors, showing that it has an important and necessary role
in neurotrophins’ and compounds’ signaling.
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In vitro study of the activity of new synthetic and natural neurotrophin analogues on TrkA receptor and in Alzheimer’s disease
