Using the Patch-Clamp technique to shed light on ion channels structure, function and pharmacology

Ion channels are membrane proteins that selectively allow ions to flow down their electrochemical gradient across the cellular membrane. They localize in both plasma and intracellular membranes and regulate a variety of functions such as neuronal excitability, heartbeat, muscle contraction and hormones release. Thus, understanding the molecular mechanism of ion channels function and regulation is one of the key goals of modern Biophysics. During my PhD thesis, by combining patch-clamp measurements with site-direct mutagenesis, fluorophore labeling experiments and pharmacological assays, I explored some functional and structural properties of different ion transporters: the Na+/Ca2+ exchanger (NCX); the large conductance Ca2+-voltage activated K+ channel (BK) channel; the human Transient receptor potential, member A1 (TRPA1) channel

The chemistry and pharmacology of citrus limonoids

Citrus limonoids (CLs) are a group of highly oxygenated terpenoid secondary metabolites found mostly in the seeds, fruits and peel tissues of citrus fruits such as lemons, limes, oranges, pumellos, grapefruits, bergamots, and mandarins. Represented by limonin, the aglycones and glycosides of CLs have shown to display numerous pharmacological activities including anticancer, antimicrobial, antioxidant, antidiabetic and insecticidal among others. In this review, the chemistry and pharmacology of CLs are systematically scrutinised through the use of medicinal chemistry tools and structure-activity relationship approach. Synthetic derivatives and other structurally-related limonoids from other sources are include in the analysis. With the focus on literature in the past decade, the chemical classification of CLs, their physico-chemical properties as drugs, their biosynthesis and enzymatic modifications, possible ways of enhancing their biological activities through structural modifications, their ligand efficiency metrics and systematic graphical radar plot analysis to assess their developability as drugs are among those discussed in detai

Hunting for lubeluzole analogues as antimyotonic agents with reduced cardiac liability

Lubeluzole is a neuroprotective agent displaying antimyotonic activity. Lubeluzole clinical development as an antiischemic drug was discontinued due to a lack of efficacy in human trials and possible cardiac toxicity. Since lubeluzole is a potent inhibitor of the hERG channel, involved in long QT syndromes and the potentially fatal cardiac arrhythmia Torsade de Pointes, a series of lubeluzole analogues were prepared to investigate the structural requirements to reduce the affinity for hERG channels to possibly obtain safe antimyotonic drugs. Compound 16o was identified as the less potent hERG blocker possibly endowed with lower cardiac liability in comparison with the parent compound. Antimyotonic activity of 16o was also investigated in vitro on hNav1.4 and higher use-dependence was observed in comparison to lubeluzole, thus suggesting greater selectivity toward highly excited tissues, such as the myotonic muscle. To further verify the cardiac safety of 16o, patch-clamp experiments on hNav1.5 were also carried out and a 3-fold reduction of potency in comparison with hNav1.4 in phasic block was observed. In vivo evaluation of the antimyotonic activity showed unintended effects on rat motor performance. Ex vivo studies suggested calcium channel blocking activity as a possible off-target source of the 16o unintended effects, also reinforced by possible interaction with β2 receptors, as indicated by in vitro binding assays and in silico studies. In conclusion, we think our results may support the rational design of lubeluzole analogues endowed with both antimyotonic activity and lower hERG liability