Pharmacological insights into the role of P2X4 receptors in behavioural regulation: lessons from ivermectin

This is the publisher's version, also available electronically from http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8920271&fileId=S1461145712000909Purinergic ionotropic P2X receptors are a family of cation-permeable channels that bind extracellular adenosine 5′-triphosphate. In particular, convergent lines of evidence have recently highlighted P2X4 receptors as a potentially critical target in the regulation of multiple nervous and behavioural functions, including pain, neuroendocrine regulation and hippocampal plasticity. Nevertheless, the role of the P2X4 receptor in behavioural organization remains poorly investigated. To study the effects of P2X4 activation, we tested the acute effects of its potent positive allosteric modulator ivermectin (IVM, 2.5–10 mg/kg i.p.) on a broad set of paradigms capturing complementary aspects of perceptual, emotional and cognitive regulation in mice. In a novel open field, IVM did not induce significant changes in locomotor activity, but increased the time spent in the peripheral zone. In contrast, IVM produced anxiolytic-like effects in the elevated plus maze and marble burying tasks, as well as depression-like behaviours in the tail-suspension and forced swim tests. The agent induced no significant behavioural changes in the conditioned place preference test and in the novel object recognition task. Finally, the drug induced a dose-dependent decrease in sensorimotor gating, as assessed by pre-pulse inhibition (PPI) of the acoustic startle reflex. In P2X4 knockout mice, the effects of IVM in the open field and elevated plus maze were similar to those observed in wild type mice; conversely, the drug significantly increased startle amplitude and failed to reduce PPI. Taken together, these results suggest that P2X4 receptors may play a role in the regulation of sensorimotor gatin

Avermectins differentially affect ethanol intake and receptor function: implications for developing new therapeutics for alcohol use disorders

Abstract Our laboratory is investigating ivermectin (IVM) and other members of the avermectin family as new pharmacotherapeutics to prevent and/or treat alcohol use disorders (AUDs). Earlier work found that IVM significantly reduced ethanol intake in mice and that this effect likely reflects IVM's ability to modulate ligand-gated ion channels. We hypothesized that structural modifications that enhance IVM's effects on key receptors and/or increase its brain concentration should improve its anti-alcohol efficacy. We tested this hypothesis by comparing the abilities of IVM and two other avermectins, abamectin (ABM) and selamectin (SEL), to reduce ethanol intake in mice, to alter modulation of GABA A Rs and P2X 4 Rs expressed in Xenopus oocytes and to increase their ability to penetrate the brain. IVM and ABM significantly reduced ethanol intake and antagonized the inhibitory effects of ethanol on P2X 4 R function. In contrast, SEL did not affect either measure, despite achieving higher brain concentrations than IVM and ABM. All three potentiated GABA A R function. These findings suggest that chemical structure and effects on receptor function play key roles in the ability of avermectins to reduce ethanol intake and that these factors are more important than brain penetration alone. The direct relationship between the effect of these avermectins on P2X 4 R function and ethanol intake suggest that the ability to antagonize ethanol-mediated inhibition of P2X 4 R function may be a good predictor of the potential of an avermectin to reduce ethanol intake and support the use of avermectins as a platform for developing novel drugs to prevent and/or treat AUDs

Dihydromyricetin supplementation improves ethanol-induced lipid accumulation and inflammation

IntroductionExcessive alcohol consumption leads to a myriad of detrimental health effects, including alcohol-associated liver disease (ALD). Unfortunately, no available treatments exist to combat the progression of ALD beyond corticosteroid administration and/or liver transplants. Dihydromyricetin (DHM) is a bioactive polyphenol and flavonoid that has traditionally been used in Chinese herbal medicine for its robust antioxidant and anti-inflammatory properties. It is derived from many plants, including Hovenia dulcis and is found as the active ingredient in a variety of popular hangover remedies. Investigations utilizing DHM have demonstrated its ability to alleviate ethanol-induced disruptions in mitochondrial and lipid metabolism, while demonstrating hepatoprotective activity.MethodsFemale c57BL/6J mice (n = 12/group) were treated using the Lieber DeCarli forced-drinking and ethanol (EtOH) containing liquid diet, for 5 weeks. Mice were randomly divided into three groups: (1) No-EtOH, (2) EtOH [5% (v/v)], and (3) EtOH [5% (v/v)] + DHM (6 mg/mL). Mice were exposed to ethanol for 2 weeks to ensure the development of ALD pathology prior to receiving dihydromyricetin supplementation. Statistical analysis included one-way ANOVA along with Bonferroni multiple comparison tests, where p ≤ 0.05 was considered statistically significant.ResultsDihydromyricetin administration significantly improved aminotransferase levels (AST/ALT) and reduced levels of circulating lipids including LDL/VLDL, total cholesterol (free cholesterol), and triglycerides. DHM demonstrated enhanced lipid clearance by way of increased lipophagy activity, shown as the increased interaction and colocalization of p62/SQSTM-1, LC3B, and PLIN-1 proteins. DHM-fed mice had increased hepatocyte-to-hepatocyte lipid droplet (LD) heterogeneity, suggesting increased neutralization and sequestration of free lipids into LDs. DHM administration significantly reduced prominent pro-inflammatory cytokines commonly associated with ALD pathology such as TNF-α, IL-6, and IL-17.DiscussionDihydromyricetin is commercially available as a dietary supplement. The results of this proof-of-concept study demonstrate its potential utility and functionality as a cost-effective and safe candidate to combat inflammation and the progression of ALD pathology

Sodium Butyrate Supplementation Modulates Neuroinflammatory Response Aggravated by Antibiotic Treatment in a Mouse Model of Binge-like Ethanol Drinking

Growing evidence supports the pivotal role of the bidirectional interplay between the gut microbiota and the central nervous system during the progression of alcohol use disorder (AUD). In our previous study, supplementation with sodium butyrate (SB) in C57BL/6J mice prevented increased ethanol consumption in a binge-like drinking paradigm (DID) as a result of treatment with a non-absorbable antibiotic cocktail (ABX). In this study, we tested the hypothesis that SB protection against enhanced ABX-induced ethanol consumption in mice is partially due to modulation of neuroinflammatory responses. Pro- and anti-inflammatory cytokines, as well as changes in microglia and astrocytes were analyzed in hippocampus tissues from ABX-, SB-, ABX+SB-treated mice subjected to 4-week DID. We found that ethanol without or with ABX treatment increased mRNA levels of key brain cytokines (MCP-1, TNF-α, IL-1β, IL-6 and IL-10) while SB supplementation prevented these changes. Additionally, SB supplementation prevented changes in microglia, i.e., increase in Iba-1 positive cell number and morphology, and in astrocytes, i.e., decrease in GFAP-positive cell number, induced by combination of ethanol and ABX treatments. Our results suggest that gut microbiota metabolites can influence drinking behavior by modulation of neuroinflammation, highlighting the potential for microbiome-targeting strategies for treatment or prevention of AUD

Microbiome meets microglia in neuroinflammation and neurological disorders

One of the emerging hot topics in biosciences is the intriguing link between gut microbial communities and its influences outside the gastrointestinal tract, such as the central nervous system (CNS), including its cognitive activities and immune responses. Beyond its neuroprotective properties, microglia are also critical for neuronal synaptic pruning and neural remodeling during CNS development. Prolonged microglia activation and neuroinflammation are considered key contributors to neurological disorders. In this regard, it is becoming increasingly important to consider the potential influences underlying the crosstalk between the intestinal microbiota ecosystem and host when determining biomarkers of disease and treatment efficacy. The commensal microbiota is critical for immune development and continuous function through the recognition of bacteria-produced and regulated metabolites. In cases of microbial dysbiosis and microglial dysfunction, chronic neuroinflammation may persist, leading to the propagation of neurological disorders. To address potential mechanisms, this review focuses on the microbiota-gut-brain axis as it relates to communication pathways that have been linked to aberrant CNS immune activity and pathology. We also address anti-inflammatory and neuroprotective mediators which may counteract these detrimental activities. Finally, we explore the potential benefits of current and novel microbiome-targeted approaches to treat neuroinflammation and consequential neurological disease

Similarities in Blood Mononuclear Cell Membrane Phospholipid Profiles During Malignancy

Phospholipids (PLs), key elements of cellular membranes, are regulated reciprocally with membrane proteins and can act as sensors for alterations in physiological or pathological states of cells including initiation and development of cancer. On the other hand, peripheral blood mononuclear cells (MNCs) play an important role in antitumor immune response by reacting to cancerous modifications in distant organs. In the current study, we tested the hypothesis that tumor initiation and development are reflected in the alteration pattern of the MNC PL component. We analyzed MNC membrane PL fractions in samples from healthy individuals and from patients with diverse types of cancers to reveal possible alterations induced by malignancy. Compared to healthy controls, the cancer samples demonstrated shifts in several membrane PL profiles. In particular, when analyzing cancer data pooled together, there were significantly higher levels in lysophosphatidylcholine, phosphatidylcholine, and phosphatidylethanolamine fractions, and significantly lower quantities in phosphatidylinositol, phosphatidylserine, and phosphatidic acid fractions in cancer samples compared to controls. The levels of sphingomyelins and diphosphatidylglycerols were relatively unaffected. Most of the differences in PLs were sustained during the analysis of individual cancers such as breast cancer and chronic lymphocytic leukemia. Our findings suggest the presence of a common pattern of changes in MNC PLs during malignancy