Discovery of 7-aminophenanthridin-6-one as a new scaffold for matrix metalloproteinase inhibitors with multitarget neuroprotective activity

Impaired angiogenesis in ageing: the central role of the extracellular matrix

Each step in angiogenesis is regulated by the extracellular matrix (ECM). Accumulating evidence indicates that ageing-related changes in the ECM driven by cellular senescence lead to a reduction in neovascularisation, reduced microvascular density, and an increased risk of tissue ischaemic injury. These changes can lead to health events that have major negative impacts on quality of life and place a significant financial burden on the healthcare system. Elucidating interactions between the ECM and cells during angiogenesis in the context of ageing is neceary to clarify the mechanisms underlying reduced angiogenesis in older adults. In this review, we summarize ageing-related changes in the composition, structure, and function of the ECM and their relevance for angiogenesis. Then, we explore in detail the mechanisms of interaction between the aged ECM and cells during impaired angiogenesis in the older population for the first time, discussing diseases caused by restricted angiogenesis. We also outline several novel pro-angiogenic therapeutic strategies targeting the ECM that can provide new insights into the choice of appropriate treatments for a variety of age-related diseases. Based on the knowledge gathered from recent reports and journal articles, we provide a better understanding of the mechanisms underlying impaired angiogenesis with age and contribute to the development of effective treatments that will enhance quality of life.

Advances in the discovery of heterocyclic-based drugs against Alzheimer's disease

INTRODUCTION

Alzheimer's disease is a multifactorial neurodegenerative disorder characterized by beta-amyloid accumulation and tau protein hyperphosphorylation. The disease involves interconnected mechanisms, which can be clustered into two target-packs based on the affected proteins. Pack-1 focuses on beta-amyloid accumulation, oxidative stress, and metal homeostasis dysfunction, and Pack-2 involves tau protein, calcium homeostasis, and neuroinflammation. Against this background heterocyclic system, there is a powerful source of pharmacophores to develop effective small drugs to treat multifactorial diseases like Alzheimer's.

AREAS COVERED

This review highlights the most promising heterocyclic systems as potential hit candidates with multi-target capacity for the development of new drugs targeting Alzheimer's disease. The selection of these heterocyclic systems was based on two crucial factors: their synthetic versatility and their well-documented biological properties of therapeutic potential in neurodegenerative diseases.

EXPERT OPINION

The synthesis of small drugs against Alzheimer's disease requires a multifactorial approach that targets the key pathological proteins. In this context, the utilization of heterocyclic systems, with well-established synthetic processes and facile functionalization, becomes a crucial element in the design phases. Furthermore, the selection of hit heterocyclic should be guided by a full understanding of their biological activities. Thus, the identification of promising heterocyclic scaffolds with known biological effects increases the potential to develop effective molecules against Alzheimer's disease.

Neuroprotective activity of selenium nanoparticles against the effect of amino acid enantiomers in Alzheimer's disease

Alzheimer's disease (AD), the most prevalent neurodegenerative disease, is characterized by extracellular accumulation of amyloid-beta protein (Aβ), which is believed to be the very starting event of AD neurodegeneration. In this work, D-Phe, D-Ala, and D-Glu amino acids, which are the non-occurring enantiomeric form in the human body, and also D-Asp and DL-SeMet, have proved to be amyloidogenic regarding Aβ₄₂ aggregation in TEM studies. These amyloidogenic amino acid enantiomers also widened Aβ₄₂ fibrils up to 437% regarding Aβ₄₂ alone, suggesting that Aβ₄₂ aggregation is enantiomerically dependent. To inhibit enantiomeric-induced amyloid aggregation, selenium nanoparticles stabilized with chitosan (Ch-SeNPs) were successfully synthesized and employed. Thus, Ch-SeNPs reduced and even completely inhibited Aβ₄₂ aggregation produced in the presence of some amino acid enantiomers. In addition, through UV-Vis spectroscopy and fluorescence studies, it was deduced that Ch-SeNPs were able to interact differently with amino acids depending on their enantiomeric form. On the other hand, antioxidant properties of amino acid enantiomers were evaluated by DPPH and TBARS assays, with Tyr enantiomers being the only ones showing antioxidant effect. All spectroscopic data were statistically analysed through experimental design and response surface analysis, showing that the interaction between the Ch-SeNPs and the amino acids studied was enantioselective and allowing, in some cases, to establish the concentration ratios in which this interaction is maximum.

Neuroprotective mechanisms of multitarget 7-aminophenanthridin-6(5H)-one derivatives against metal-induced amyloid proteins generation and aggregation

Brain's metals accumulation is associated with toxic proteins, like amyloid-proteins (Aβ), formation, accumulation, and aggregation, leading to neurodegeneration. Metals downregulate the correct folding, disaggregation, or degradation mechanisms of toxic proteins, as heat shock proteins (HSPs) and proteasome. The 7-amino-phenanthridin-6(5H)-one derivatives (APH) showed neuroprotective effects against metal-induced cell death through their antioxidant effect, independently of their chelating activity. However, additional neuroprotective mechanisms seem to be involved. We tested the most promising APH compounds (APH1-5, 10-100 μM) chemical ability to prevent metal-induced Aβ proteins aggregation; the APH1-5 effect on HSP70 and proteasome 20S (P20S) expression, the metals effect on Aβ formation and the involvement of HSP70 and P20S in the process, and the APH1-5 neuroprotective effects against Aβ proteins (1 μM) and metals in SN56 cells. Our results show that APH1-5 compounds chemically avoid metal-induced Aβ proteins aggregation and induce HSP70 and P20S expression. Additionally, iron and cadmium induced Aβ proteins formation through downregulation of HSP70 and P20S. Finally, APH1-5 compounds protected against Aβ proteins-induced neuronal cell death, reversing partially or completely this effect. These data may help to provide a new therapeutic approach against the neurotoxic effect induced by metals and other environmental pollutants, especially when mediated by toxic proteins.

Neuroprotective Action of Multitarget 7-Aminophenanthridin-6(5H)-one Derivatives against Metal-Induced Cell Death and Oxidative Stress in SN56 Cells

Neurodegenerative diseases have been associated with brain metal accumulation, which produces oxidative stress (OS), matrix metalloproteinases (MMPs) induction, and neuronal cell death. Several metals have been reported to downregulate both the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway and the antioxidant enzymes regulated by it, mediating OS induction and neurodegeneration. Among a recently discovered family of multitarget 7-amino-phenanthridin-6-one derivatives (APH) the most promising compounds were tested against metal-induced cell death and OS in SN56 cells. These compounds, designed to have chelating activity, are known to inhibit some MMPs and to present antioxidant and neuroprotective effects against hydrogen peroxide treatment to SN56 neuronal cells. However, the mechanisms that mediate this protective effect are not fully understood. The obtained results show that compounds APH1, APH2, APH3, APH4, and APH5 were only able to chelate iron and copper ions among all metals studied and that APH3, APH4, and APH5 were also able to chelate mercury ion. However, none of them was able to chelate zinc, cadmium, and aluminum, thus exhibiting selective chelating activity that can be partly responsible for their neuroprotective action. Otherwise, our results indicate that their antioxidant effect is mediated through induction of the Nrf2 pathway that leads to overexpression of antioxidant enzymes. Finally, these compounds exhibited neuroprotective effects, reversing partially or completely the cytotoxic effects induced by the metals studied depending on the compound used. APH4 was the most effective and safe compound.