Harnessing ionic mechanisms to achieve disease modification in neurodegenerative disorders

Progressive neuronal death is the key pathogenic event leading to clinical symptoms in neurodegenerative disorders (NDDs). Neuroprotective treatments are virtually unavailable, partly because of the marked internal heterogeneity of the mechanisms underlying pathology. Targeted neuroprotection would require deep mechanistic knowledge across the entire aetiological spectrum of each NDD and the development of tailored treatments. Although ideal, this strategy appears challenging, as it would require a degree of characterization of both the disease and the patient that is currently unavailable. The alternate strategy is to search for commonalities across molecularly distinct NDD forms and exploit these for the development of drugs with broad-spectrum efficacy. In this view, mounting evidence points to ionic mechanisms (IMs) as targets with potential therapeutic efficacy across distinct NDD subtypes. The scope of this review is to present clinical and preclinical evidence supporting the link between disruption of IMs and neuronal death in specific NDDs and to critically revise past and ongoing attempts of harnessing IMs for the development of neuroprotective treatments.

Bilirubin and brain: A pharmacological approach

For many decades, the world scientific literature has accounted for a number of works on the biological effects of bilirubin-IXalpha (BR). The first studies focused on the neurotoxic effects of the excessive production of BR, in particular regarding both physiological neonatal jaundice and the more severe ones, typically as consequences of severe hemolysis or other underlying diseases. Only since 1987, has significant evidence, however, underlined the neuroprotective role of BR linked to the scavenging effect of free radicals as reactive oxygen species and nitric oxide and its congeners. Despite the presence in the literature of many excellent papers dealing with the multiple roles played by BR in health and disease, there were very few and somewhat dated reviews that summarize the key findings related to the neuroprotective and neurotoxic effects of the bile pigment and underlying mechanisms. In light of the previous statements, the aim of this review is to provide a summary of the main discoveries in the last years on the effects of BR on the central nervous system. An analytical description about the synthesis of BR, its distribution in the systemic circulation, liver metabolism and elimination through feces and urine will be provided, together with the main mechanisms claimed to describe the neurotoxicity and neuroprotection by the bile pigment. Finally, the possible translational aspects of pharmacological modulation in the production of BR in order to prevent or counteract toxic effects or enhance the protective actions, will be discussed.

Two cellular hypotheses explaining the initiation of ketamine's antidepressant actions: Direct inhibition and disinhibition

A single, low dose of ketamine evokes antidepressant actions in depressed patients and in patients with treatment-resistant depression (TRD). Unlike classic antidepressants, which regulate monoamine neurotransmitter systems, ketamine is an antagonist of the N-methyl-D-aspartate (NMDA) family of glutamate receptors. The effectiveness of NMDAR antagonists in TRD unveils a new set of targets for therapeutic intervention in major depressive disorder (MDD) and TRD. However, a better understanding of the cellular mechanisms underlying these effects is required for guiding future therapeutic strategies, in order to minimize side effects and prolong duration of efficacy. Here we review the evidence for and against two hypotheses that have been proposed to explain how NMDAR antagonism initiates protein synthesis and increases excitatory synaptic drive in corticolimbic brain regions, either through selective antagonism of inhibitory interneurons and cortical disinhibition, or by direct inhibition of cortical pyramidal neurons. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.

Characterization and evaluation of synthetic riluzole with β-cyclodextrin and 2,6-di-O-methyl-β-cyclodextrin inclusion complexes

β-Cyclodextrin (β-CD) and 2,6-di-O-methyl-β-cyclodextrin (DM-β-CD) inclusion complexes with riluzole (RLZ) were prepared to improve water solubility and broaden potential pharmaceutical applications. CDs/RLZ inclusion complexes were confirmed via phase solubility studies, FT-IR spectroscopy, PXRD, DSC, (1)H NMR, and SEM. Phase solubility studies indicated that β-CD and DM-β-CD can form 1:1 inclusion complexes with RLZ, and the stability constants were 663.17 and 1609.07M(-1), respectively. Water solubility and dissolution rate of RLZ were significantly improved in complex forms, implying that the inclusion complexes may develop pharmaceutical applications. Preliminary in vitro cytotoxicity assay also showed that RLZ hepatotoxicity was not increased in the inclusion complexes.

Isobolographic analysis of the mechanisms of action of anticonvulsants from a combination effect

The nature of the pharmacodynamic interactions of drugs is influenced by the drugs׳ mechanisms of action. It has been hypothesized that drugs with different mechanisms are likely to interact synergistically, whereas those with similar mechanisms seem to produce additive interactions. In this review, we describe an extensive investigation of the published literature on drug combinations of anticonvulsants, the nature of the interaction of which has been evaluated by type I and II isobolographic analyses and the subthreshold method. The molecular targets of antiepileptic drugs (AEDs) include Na(+) and Ca(2+) channels, GABA type-A receptor, and glutamate receptors such as NMDA and AMPA/kainate receptors. The results of this review indicate that the nature of interactions evaluated by type I isobolographic analyses but not by the two other methods seems to be consistent with the above hypothesis. Type I isobolographic analyses may be used not only for evaluating drug combinations but also for predicting the targets of new drugs.