New therapeutic strategies in neurodegenerative diseases: focus on glaucoma and Alzheimer's disease

Traditionally, aging has been viewed as a natural course of life that leads to an increased risk of disease and death. Among the different age-related disorders neurodegenerative conditions are common. This thesis will focus on neurodegenerative phenomena and, in particular, on glaucoma and Alzheimer’s disease. Elevated intraocular pressure (IOP) is a major risk factor for glaucoma and the only target of current therapies. In eyes not responding to IOP-lowering drugs, IOP can be reduced by surgery. However, conjunctival and subconjunctival scarring limits the long-term success of several glaucoma surgical procedures. Anti-metabolites treatment during surgery or follow-up can help physicians to keep the surgery functioning, but with some ocular side-effects. This study aimed to identify a pharmacological treatment capable of inhibiting the proliferation of the Tenon’s capsule fibroblasts that cause episcleral fibrosis, potentially improving the surgical outcome. Primary human Tenon’s fibroblasts (HTFs) were isolated from tissue explants and characterized by immunofluorescence. The cytotoxic potential of the tested drugs was analysed with the MTT test, while the migration and proliferation of HTFs were assessed by the wound-healing assay. Taken all together, the results obtained indicate that: 1) at least in our experimental conditions, HTFs proliferation, rather than migration, is responsible for wound healing; and 2) among the antiproliferative drugs tested, Pg48 and Sb46 significantly slow the rate of wound closure. Pg48 and Sb46, two drugs already approved for cancer treatment, could represent a new therapeutic approach for improving the outcome of glaucoma surgery. Ongoing experiments in animal models will help determine their actual efficacy and safety in vivo. The second part of the thesis concerns Alzheimer’s disease (AD), which is the leading cause of dementia worldwide. Among the hypotheses formulated over time to explain its pathogenesis, that of the “amyloid cascade” has dominated the field of research for the past 25 years, despite inconsistencies suggesting that different mechanisms are probably involved. Attractive is the more recent alternative hypothesis of the "loss-of-function", according to which the pathogenic mechanism is linked to a reduction of the pool of soluble Aβ, rather than its accumulation in the polymerized state. Consistent with this view, high levels of soluble Aβ42 peptides in the CSF are associated with normal cognition and regular hippocampal volume, despite increasing brain amyloidosis in human. Starting from these premises, the aim of my study was to test in vivo the therapeutic potential of an Aβ42 analogue, called pep-3695, which carries a mutation that makes the peptide less prone to aggregation. To this end, biodistribution analyses and behavioural tests were performed on pep-3695-treated 5XFAD mice. Although preliminary, our results indicate that 5XFAD mice treated with pep-3695 perform better in the nesting behavioural test than control animals treated with a scrambled peptide. Biodistribution analyses revealed that different brain regions are targeted by the peptide, consistent with the areas involved in higher cerebral functions such as memory formation and consolidation, emotion processing, and social interactions. Taken together, these data support the Aβ loss-of-function hypothesis and suggest future experimental efforts to develop therapeutic strategies that increase rather than decrease soluble Aβ levels.