Ivermectin and its target molecules: shared and unique modulation mechanisms of ion channels and receptors by ivermectin

The role of the methoxy group in approved drugs

The methoxy substituent is prevalent in natural products and, consequently, is present in many natural product-derived drugs. It has also been installed in modern drug molecules with no remnant of natural product features because medicinal chemists have been taking advantage of the benefits that this small functional group can bestow on ligand-target binding, physicochemical properties, and ADME parameters. Herein, over 230 methoxy-containing small-molecule drugs, as well as several fluoromethoxy-containing drugs, are presented from the vantage point of the methoxy group. Biochemical mechanisms of action, medicinal chemistry SAR studies, and numerous X-ray cocrystal structures are analyzed to identify the precise role of the methoxy group for many of the drugs and drug classes. Although the methoxy substituent can be considered as the hybridization of a hydroxy and a methyl group, the combination of these functionalities often results in unique effects that can amount to more than the sum of the individual parts.

Impact of Ae-GRD on Ivermectin Resistance and Its Regulation by miR-71-5p in Aedes aegypti

iGABAR, a member of the Cys-loop ligand-gated ion channel superfamily, is a significant target of the insecticide ivermectin (IVM). GRD is the potential subunit of the insect iGABAR. However, little information about GRD in Ae. aegypti has been reported. In this study, we involved cloning and characterizing the iGABAR subunit GRD of Ae. aegypti (Ae-GRD). Sequence analysis indicated that Ae-GRD, as part of the cysteine-loop ligand-gated ion channel family, is similar to other insect GRD. RNA interference (RNAi) was employed to explore IVM resistance in Ae. aegypti, resulting in a significant reduction in Ae-GRD expression (p < 0.05), and the mortality of Ae. aegypti adults with Ae-GRD knockdown was significantly decreased after exposure to ivermectin. Bioinformatics prediction identified miR-71-5p as a potential regulator of Ae-GRD. In vitro, dual-luciferase reporter assays confirmed that Ae-GRD expression was regulated by miR-71-5p. Microinjection of miR-71-5p mimics upregulated miR-71-5p expression and downregulated Ae-GRD gene expression, reducing mortality by 34.52% following IVM treatment. Conversely, microinjection of a miR-71-5p inhibitor decreased miR-71-5p expression but did not affect the susceptibility to IVM despite increased Ae-GRD expression (p < 0.05). In conclusion, Ae-GRD, as one of the iGABA receptor subunits, is a potential target of ivermectin. It may influence ivermectin resistance by modulating the GABA signaling pathway. The inhibition of Ae-GRD expression by miR-71-5p decreased ivermectin resistance and consequently lowered the mortality rate of Ae. aegypti mosquitoes. This finding provides empirical evidence of the relationship between Ae-GRD and its miRNA in modulating insecticide resistance, offering novel perspectives for mosquito control strategies.

Mosquitocidal effect of ivermectin-treated nettings and sprayed walls on Anopheles gambiae s.s

Ivermectin (IVM) has been proposed as a new tool for malaria control as it is toxic on vectors feeding on treated humans or cattle. Nevertheless, IVM may have a direct mosquitocidal effect when applied on bed nets or sprayed walls. The potential for IVM application as a new insecticide for long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) was tested in this proof-of-concept study in a laboratory and semi-field environment. Laboratory-reared, insecticide-susceptible Kisumu Anopheles gambiae were exposed to IVM on impregnated netting materials and sprayed plastered- and mud walls using cone bioassays. The results showed a direct mosquitocidal effect of IVM on this mosquito strain as all mosquitoes died by 24 h after exposure to IVM. The effect was slower on the IVM-sprayed walls compared to the treated nettings. Further work to evaluate possibility of IVM as a new insecticide formulation in LLINs and IRS will be required.

Development and in vitro antiviral activity of ivermectin liposomes as a potential drug carrier system

This study aimed to assess and compare diverse formulations of ivermectin-loaded liposomes, employing lipid film hydration and ethanol injection methods. Three lipids (DOPC, SPC, and DSPC) were used in predetermined molar ratios. A total of 18 formulations were created, and a factorial design determined the optimal formulation based on particle size, polydispersity index (PDI), zeta potential, and encapsulation efficiency. The average mean particle size, PDI and zeta potential of the selected formulations (F1, F2, F7, F9, and F11) was, respectively, 196.40 ± 44.60 nm, 0.39 ± 0.09, and -40.24 ± 9.17. The encapsulation efficiency exceeded 80%, with a mean loading capacity of 4.00 ± 1.70%. In vitro studies included transmission electron microscopy, Fourier transform infrared spectroscopy, drug release, and antiviral activity assessments against SARS-CoV-2. The liposomal formulations demonstrated superior antiviral activity compared to free ivermectin, as indicated by lower IC50 values. The results of this study emphasize the effectiveness of ivermectin-loaded liposomes in inhibiting viral activity, highlighting their potential as promising candidates for antiviral therapy. The findings suggest that the strategic use of liposomes as drug carriers can significantly modulate and improve the antiviral properties of ivermectin, offering a novel approach to harnessing its full therapeutic potential. Collectively, these results provide a robust foundation for further exploration of ivermectin as a viral protection tool and optimization of its delivery mechanisms.

Structural determinants of the direct inhibition of GIRK channels by Sigma-1 receptor antagonist

G-protein-gated inward rectifier K+ (GIRK) channels play a critical role in the regulation of the excitability of cardiomyocytes and neurons and include GIRK1, GIRK2, GIRK3 and GIRK4 subfamily members. BD1047 dihydrobromide (BD1047) is one of the representative antagonists of the multifunctional Sigma-1 receptor (S1R). In the analysis of the effect of BD1047 on the regulation of Gi-coupled receptors by S1R using GIRK channel as an effector, we observed that BD1047, as well as BD1063, directly inhibited GIRK currents even in the absence of S1R and in a voltage-independent manner. Thus, we aimed to clarify the effect of BD1047 on GIRK channels and identify the structural determinants. By electrophysiological recordings in Xenopus oocytes, we observed that BD1047 directly inhibited GIRK channel currents, producing a much stronger inhibition of GIRK4 compared to GIRK2. It also inhibited ACh-induced native GIRK current in isolated rat atrial myocytes. Chimeric and mutagenesis studies of GIRK2 and GIRK4 combined with molecular docking analysis demonstrated the importance of Leu77 and Leu84 within the cytoplasmic, proximal N-terminal region and Glu147 within the pore-forming region of GIRK4 for inhibition by BD1047. The activator of GIRK channels, ivermectin, competed with BD1047 at Leu77 on GIRK4. This study provides us with a novel inhibitor of GIRK channels and information for developing pharmacological treatments for GIRK4-associated diseases.

Considering ivermectin for treatment of schistosomiasis

Because of recent reports of praziquantel resistance in schistosome infections, there have been suggestions to employ ivermectin as a possible alternative, especially as its chemical composition is different from that of praziquantel, so cross-resistance is not expected. In order to ascertain possible damage and elimination of worms, we used ivermectin by oral gavage in infected mice, at a high dose (30.1 mg/kg, bordering toxicity). We also tested the efficacy of the drug at various times postinfection (PI), to check on possible effect on young and mature stages of the parasites. Thus, we treated mice on days 21 and 22 or on days 41 and 42 and even on days 21, 22, 41, and 42 PI. None of the treatment regimens resulted in cure rates or signs of lessened pathology in the mice. We also compared the effect of ivermectin to that of artemisone, an artemisinin derivative which had served us in the past as an effective anti-schistosome drug, and there was a stark difference in the artemisone's efficacy compared to that of ivermectin; while ivermectin was not effective, artemisone eliminated most of the worms, prevented egg production and granulomatous inflammatory response. We assume that the reported lack of activity of ivermectin, in comparison with praziquantel and artemisinins, originates from the difference in their mode of action. In wake of our results, we suggest that ivermectin is not a suitable drug for treatment of schistosomiasis.

The relationship between intraflagellar transport and upstream protein trafficking pathways and macrocyclic lactone resistance in Caenorhabditis elegans

Parasitic nematodes are globally important and place a heavy disease burden on infected humans, crops, and livestock, while commonly administered anthelmintics used for treatment are being rendered ineffective by increasing levels of resistance. It has recently been shown in the model nematode Caenorhabditis elegans that the sensory cilia of the amphid neurons play an important role in resistance toward macrocyclic lactones such as ivermectin (an avermectin) and moxidectin (a milbemycin) either through reduced uptake or intertissue signaling pathways. This study interrogated the extent to which ciliary defects relate to macrocyclic lactone resistance and dye-filling defects using a combination of forward genetics and targeted resistance screening approaches and confirmed the importance of intraflagellar transport in this process. This approach also identified the protein trafficking pathways used by the downstream effectors and the components of the ciliary basal body that are required for effector entry into these nonmotile structures. In total, 24 novel C. elegans anthelmintic survival-associated genes were identified in this study. When combined with previously known resistance genes, there are now 46 resistance-associated genes that are directly involved in amphid, cilia, and intraflagellar transport function.

Failure of scabies treatment: a systematic review and meta-analysis

BACKGROUND

Treatment failure is considered to be an important factor in relation to the increase in scabies incidence over the last decade. However, the regional and temporal differences, in addition to the predictors of therapy failure, are unclear.

OBJECTIVES

We aimed to conduct a systematic review of the prevalence of treatment failure in patients with scabies and investigation of associated factors.

METHODS

We searched MEDLINE, EMBASE, CINAHL, Web of Science, Scopus, Global Health and the Cochrane Central Register of Controlled Trials from inception to August 2021 for randomized and quasi-randomized trials, in addition to observational studies that enrolled children or adults diagnosed with confirmed or clinical scabies treated with permethrin, ivermectin, crotamiton, benzyl benzoate, malathion, sulfur or lindane, and measured treatment failure or factors associated with treatment failure. We performed a random effects meta-analysis for all outcomes reported by at least two studies.

RESULTS

A total of 147 studies were eligible for inclusion in the systematic review. The overall prevalence of treatment failure was 15.2% [95% confidence interval (CI) 12.9-17.6; I2 = 95.3%, moderate-certainty evidence] with regional differences between World Health Organization regions (P = 0.003) being highest in the Western Pacific region (26.9%, 95% CI 14.5-41.2). Oral ivermectin (11.8%, 95% CI 8.4-15.4), topical ivermectin (9.3%, 95% CI 5.1-14.3) and permethrin (10.8%, 95% CI 7.5-14.5) had relatively lower failure prevalence compared with the overall prevalence. Failure prevalence was lower in patients treated with two doses of oral ivermectin (7.1%, 95% CI 3.1-12.3) compared with those treated with one dose (15.2%, 95% CI 10.8-20.2; P = 0.021). Overall and permethrin treatment failure prevalence in the included studies (1983-2021) increased by 0.27% and 0.58% per year, respectively. Only three studies conducted a multivariable risk factor analysis; no studies assessed resistance.

CONCLUSIONS

A second dose of ivermectin showed lower failure prevalence than single-dose ivermectin, which should be considered in all guidelines. The increase in treatment failure over time hints at decreasing mite susceptibility for several drugs, but reasons for failure are rarely assessed. Ideally, scabicide susceptibility testing should be implemented in future studies.

Ivermectin affects Arabidopsis thaliana microtubules through predicted binding site of β-tubulin

The ivermectin is a potent nematocide and insecticide, which has low toxicity for humans and domestic animals, but due to low biotransformation, it can be dangerous for non-target organisms. The recent determination of ivermectin absorption and accumulation in tissues of higher plants and multiple shreds of evidence of its negative impact on plant physiology provide a basis for the search for ivermectin's molecular targets and mechanisms of action in plant cells. In this research, for the first time, the ivermectin effect on microtubules of Arabidopsis thaliana cells was studied. It was revealed that ivermectin (250 μg mL-1) disrupts the microtubule network, induces the loss of microtubule orientation, leads to microtubule curvature and shrinkage, and their longitudinal and cross-linked bundling in various cells of A. thaliana primary roots. Further, the previously proposed binding of ivermectin to the β1-tubulin taxane site was developed and confirmed using molecular dynamics simulations of ivermectin complexes with Haemonchus contortus and A. thaliana β1-tubulins. It was predicted that similar to other microtubule stabilizing agents ivermectin binding causes M-loop stabilization in both H. contortus and A. thaliana β-tubulin, which leads to the enhancement of lateral contacts between subunits of adjacent protofilaments preventing microtubule depolymerization.

Anthelmintic efficacy evaluation and mechanism of N-methylbenzo[d]oxazol-2-amine

Parasitic roundworms cause significant sickness and mortality in animals and humans. In livestock, these nematodes have severe economic impact and result in losses in food production on a global scale. None of the currently available drugs ideally suit all treatment circumstances, and the development of drug-resistant nematode strains has become a challenge to control the infection. There is an urgent need to develop novel anthelmintic compounds. According to our previous report, N-methylbenzo[d]oxazol-2-amine (1) showed anthelmintic activity and lowest cytotoxicity. In this study, in vivo anthelmintic properties were evaluated using Trichinella spiralis infected mice. Toxicity was evaluated using the rats and mode of action using molecular docking and metabolomics approaches. The in vivo results demonstrate that a dose of 250 mg/kg reduced the T. spiralis abundance in the digestive tract by 49%. The 250 mg/kg Albendazole was served as control. The relatively low acute toxicity was categorized into chemical category 5, with an LD50 greater than 2000 mg/kg body. Molecular docking analysis showed the T. spiralis tubulin beta chain and glutamate-gated channels might not be the main targets of compound 1. Metabolomics analysis was used to explain the effects of compound 1 on the T. spiralis adult worm. The results demonstrated that compound 1 significantly up-regulated the metabolism of purine, pyrimidine and down-regulated sphingolipid metabolism. In conclusion, compound 1 could be a potential molecule for anthelmintic development. The bioavailability, pharmacokinetics, and absorption of this compound should be studied further to provide information for its future efficacy improvement.

The effects of P-glycoprotein induction on ivermectin-induced behavioural alterations in zebrafish (Danio rerio) under varying diets

The neuroprotective effects of inducing the blood-brain barrier ATP-binding cassette protein transporter P-glycoprotein (P-gp) with clotrimazole (CTZ) in both fed and fasted zebrafish (Danio rerio) against the CNS-toxicant ivermectin (IVM, 22,23-dihydro avermectin B1a + 22,23-dihydro avermectin B1b) were examined. Zebrafish were administered 2 μmol/kg IVM intraperitoneally, and various behavioural assays (swimming performance, exploratory behaviour, olfactory responses, motor coordination, and escape responses) were used to measure neurological dysfunction. IVM administration alone caused a decrease in mean swim speed (91 % of controls), maximal speed (71 %), passage rate (81 %), 90° turns (81 %), and response to food stimulus (39 %). IVM exposure also increased the percent time that fish spent immobile (45 % increase over controls) and the percent of lethargic fish (40 % increase). Fish administered 30 μmol/kg of the P-gp inducer CTZ intraperitoneally 3 d prior to IVM exposure exhibited a change in only the % time spent immobile. These data indicate that P-gp induction may be limited in protecting the zebrafish CNS from IVM over baseline. Fasted fish did not differ from fed fish in the effects of IVM on behaviour, and no differences were seen following P-gp induction with CTZ. These results suggest that this chemical defence system is not downregulated when fish are challenged with limited energy availability.

Impact of Ivermectin on the Gut Microbial Ecosystem

Ivermectin is a an anti-helminthic that is critical globally for both human and veterinary care. To the best of our knowledge, information available regarding the influence of ivermectin (IVM) on the gut microbiota has only been collected from diseased donors, who were treated with IVM alone or in combination with other medicines. Results thus obtained were influenced by multiple elements beyond IVM, such as disease, and other medical treatments. The research presented here investigated the impact of IVM on the gut microbial structure established in a Triple-SHIME® (simulator of the human intestinal microbial ecosystem), using fecal material from three healthy adults. The microbial communities were grown using three different culture media: standard SHIME media and SHIME media with either soluble or insoluble fiber added (control, SF, ISF). IVM introduced minor and temporary changes to the gut microbial community in terms of composition and metabolite production, as revealed by 16S rRNA amplicon sequencing analysis, flow cytometry, and GC-MS. Thus, it was concluded that IVM is not expected to induce dysbiosis or yield adverse effects if administered to healthy adults. In addition, the donor's starting community influences the relationship between IVM and the gut microbiome, and the soluble fiber component in feed could protect the gut microbiota from IVM; an increase in short-chain fatty acid production was predicted by PICRUSt2 and detected with IVM treatment.

Knockdown of the glutamate-gated chloride channel gene decreases emamectin benzoate susceptibility in the fall armyworm, Spodoptera frugiperda

Emamectin benzoate (EB), a derivative of avermectin, is the primary insecticide used to control the fall armyworm (FAW) in China. However, the specific molecular targets of EB against FAW remain unclear. In this study, we cloned the glutamate-gated chloride channel (GluCl) gene, which is known to be a primary molecular target for avermectin. We first investigated the transcript levels of SfGluCl in FAW and found that the expression level of SfGluCl in the head and nerve cord was significantly higher than that in other tissues. Furthermore, we found that the expression level of SfGluCl was significantly higher in eggs than that in other developmental stages, including larvae, pupae, and adults. Additionally, we identified three variable splice forms of SfGluCl in exons 3 and 9 and found that their splice frequencies remained unaffected by treatment with the LC50 of EB. RNAi mediated knockdown of SfGluCl showed a significant reduction of 42% and 65% after 48 and 72 h of dsRNA feeding, respectively. Importantly, knockdown of SfGluCl sifgnificantly reduced LC50 and LC90 EB treatment induced mortality of FAW larvae by 15% and 44%, respectively, compared to the control group feeding by dsEGFP. In contrast, there were no significant changes in the mortality of FAW larvae treated with the control insecticides chlorantraniliprole and spinetoram. Finally, molecular docking simulations revealed that EB bound to the large amino-terminal extracellular domain of SfGluCl by forming five hydrogen bonds, two alkyl hydrophobic interactions and one salt bridge. These findings strongly suggest that GluCl may serve as one of the molecular targets of EB in FAW, shedding light on the mode of action of this important insecticide.

Nonspecific membrane bilayer perturbations by ivermectin underlie SARS-CoV-2 in vitro activity

Since it was proposed as a potential host-directed antiviral agent for SARS-CoV-2, the antiparasitic drug ivermectin has been investigated thoroughly in clinical trials, which have provided insufficient support for its clinical efficacy. To examine the potential for ivermectin to be repurposed as an antiviral agent, we therefore undertook a series of preclinical studies. Consistent with early reports, ivermectin decreased SARS-CoV-2 viral burden in in vitro models at low micromolar concentrations, five- to ten-fold higher than the reported toxic clinical concentration. At similar concentrations, ivermectin also decreased cell viability and increased biomarkers of cytotoxicity and apoptosis. Further mechanistic and profiling studies revealed that ivermectin nonspecifically perturbs membrane bilayers at the same concentrations where it decreases the SARS-CoV-2 viral burden, resulting in nonspecific modulation of membrane-based targets such as G-protein coupled receptors and ion channels. These results suggest that a primary molecular mechanism for the in vitro antiviral activity of ivermectin may be nonspecific membrane perturbation, indicating that ivermectin is unlikely to be translatable into a safe and effective antiviral agent. These results and experimental workflow provide a useful paradigm for performing preclinical studies on (pandemic-related) drug repurposing candidates.

Repurposing Selamectin as an Antimicrobial Drug against Hospital-Acquired Staphylococcus aureus Infections

The emergence of multidrug-resistant strains requires the urgent discovery of new antibacterial drugs. In this context, an antibacterial screening of a subset of anthelmintic avermectins against gram-positive and gram-negative strains was performed. Selamectin completely inhibited bacterial growth at 6.3 μg/mL concentrations against reference gram-positive strains, while no antibacterial activity was found against gram-negative strains up to the highest concentration tested of 50 μg/mL. Given its relevance as a community and hospital pathogen, further studies have been performed on selamectin activity against Staphylococcus aureus (S. aureus), using clinical isolates with different antibiotic resistance profiles and a reference biofilm-producing strain. Antibacterial studies have been extensive on clinical S. aureus isolates with different antibiotic resistance profiles. Mean MIC90 values of 6.2 μg/mL were reported for all tested S. aureus strains, except for the macrolide-resistant isolate with constitutive macrolide-lincosamide-streptogramin B resistance phenotype (MIC90 9.9 μg/mL). Scanning Electron Microscopy (SEM) showed that selamectin exposure caused relevant cell surface alterations. A synergistic effect was observed between ampicillin and selamectin, dictated by an FIC value of 0.5 against methicillin-resistant strain. Drug administration at MIC concentration reduced the intracellular bacterial load by 81.3%. The effect on preformed biofilm was investigated via crystal violet and confocal laser scanning microscopy. Selamectin reduced the biofilm biomass in a dose-dependent manner with minimal biofilm eradication concentrations inducing a 50% eradication (MBEC50) at 5.89 μg/mL. The cytotoxic tests indicated that selamectin exhibited no relevant hemolytic and cytotoxic activity at active concentrations. These data suggest that selamectin may represent a timely and promising macrocyclic lactone for the treatment of S. aureus infections.

Vitamins E and A increase the passing of the P-gp substrate ivermectin into the brain in mice

This study aimed to determine the effect of administration of oral vitamins A and E at different doses on plasma and brain concentrations of ivermectin in mice. The study was carried out on 174 Swiss Albino male mice aged 8-10 weeks. After leaving six mice for method validation, the remaining mice were randomly divided into seven groups with equal numbers of animals. Mice received ivermectin (0.2 mg/kg, subcutaneous) alone and in combination with low (vitamin A: 4000 IU/kg; vitamin E: 35 mg/kg) and high (vitamin A: 30 000 IU/kg; vitamin E: 500 mg/kg) oral doses of vitamins A and E. The plasma and brain concentrations of ivermectin were measured using high-performance liquid chromatography-fluorescence detector. We determined that high doses of vitamins A and E and their combinations increased the passing ratio of ivermectin into the brain significantly. The high-dose vitamin E and the combination of high-concentration vitamins E and A significantly increased the plasma concentration of ivermectin (P < 0.05). The high-dose vitamins E and A and their high-dose combination increased the brain concentration of ivermectin by 3, 2, and 2.7 times, respectively. This research is the first in vivo study to determine the interaction between P-gp substrates and vitamins E and A.

The diverse family of Cys-loop receptors in Caenorhabditis elegans: insights from electrophysiological studies

Cys-loop receptors integrate a large family of pentameric ligand-gated ion channels that mediate fast ionotropic responses in vertebrates and invertebrates. Their vital role in converting neurotransmitter recognition into an electrical impulse makes these receptors essential for a great variety of physiological processes. In vertebrates, the Cys-loop receptor family includes the cation-selective channels, nicotinic acetylcholine and 5-hydroxytryptamine type 3 receptors, and the anion-selective channels, GABAA and glycine receptors, whereas in invertebrates, the repertoire is significantly larger. The free-living nematode Caenorhabditis elegans has the largest known Cys-loop receptor family as well as unique receptors that are absent in vertebrates and constitute attractive targets for anthelmintic drugs. Given the large number and variety of Cys-loop receptor subunits and the multiple possible ways of subunit assembly, C. elegans offers a large diversity of receptors although only a limited number of them have been characterized to date. C. elegans has emerged as a powerful model for the study of the nervous system and human diseases as well as a model for antiparasitic drug discovery. This nematode has also shown promise in the pharmaceutical industry search for new therapeutic compounds. C. elegans is therefore a powerful model organism to explore the biology and pharmacology of Cys-loop receptors and their potential as targets for novel therapeutic interventions. In this review, we provide a comprehensive overview of what is known about the function of C. elegans Cys-loop receptors from an electrophysiological perspective.

Physical and pharmacokinetic characterization of Soluvec™, a novel, solvent-free aqueous ivermectin formulation

Purpose: To describe application of the Quicksol™ solvent-free approach to solubilize ivermectin (IVM). Methods: Lyophilized IVM complexed with hydroxypropyl-β-cyclodextrin (HP-β-CD) was resolubilized in aqueous polysorbate-80, generating Soluvec™. Lyophilizate was examined by Fourier-transform infrared spectroscopy and differential scanning calorimetry; Soluvec, by dynamic light scattering. Pharmacokinetics was evaluated in dogs allocated to subcutaneous (SC) or intramuscular (IM) Soluvec or oral IVM. Results: IVM in Soluvec was tightly bound by HPβCD, forming nearly monodisperse 28 nm particles with solubility ∼2500-times that of free IVM. SC and IM Soluvec increased IVM exposure, peak IVM and extended duration of IVM exposure, versus oral dosing. Conclusion: The Quicksol method generated Soluvec, a concentrated aqueous parenteral IVM formulation with pharmacokinetic properties suitable for veterinary or human use.

P2X4 receptor modulates gut inflammation and favours microbial homeostasis in colitis

BACKGROUND

Inflammatory bowel disease (IBD) is a non-specific chronic inflammatory disease of the intestine. In addition to genetic susceptibility, environmental factors and dysregulated host immunity, the gut microbiota is implicated in the pathogenesis of Crohn's disease (CD) or ulcerative colitis (UC), the two primary types of IBD. The P2X4 receptor has been demonstrated to have a crucial role in preventing infection, inflammation, and organ damage. However, it remains unclear whether the P2X4 receptor affects IBD and the underlying mechanisms.

METHODS

Colitis was induced in mice administrated with dextran sodium sulphate (DSS). 16S rDNA sequencing was used to analyze the gut microbiota in knockout and wild-type mice. Clinical and histopathological parameters were monitored throughout the disease progression.

RESULTS

Gene Expression Omnibus analysis showed the downregulation of P2RX4 (P2rx4) expression in colonic tissues from patients or mice with IBD. However, its expression at the protein levels was upregulated on day 4 or 6 and then downregulated on day 7 in C57BL/6 mice treated with DSS. Gene ablation of P2rx4 aggravated DSS-induced colitis accompanying gut microbiota dysbiosis in mice. Moreover, P2X4 receptor-positive modulator ivermectin alleviated colitis and corrected dysregulated microbiota in wild-type C57BL/6 mice. Further antibiotic-treated gut microbiota depletion, cohousing experiment, and fecal microbiota transplantation proved that gut microbiota dysbiosis was associated with the aggravation of colitis in the mouse model initiated by P2rx4.

CONCLUSIONS

Our findings elaborate on an unrevealed etiopathophysiological mechanism by which microbiota dysbiosis induced by the P2X4 receptor influences the development of colitis, indicating that the P2X4 receptor represents a promising target for treating patients with CD and UC.

Structural Elucidation of Ivermectin Binding to α7nAChR and the Induced Channel Desensitization

The α7 nicotinic acetylcholine receptor (α7nAChR) mediates signaling in the central nervous system and cholinergic anti-inflammatory pathways. Ivermectin is a positive allosteric modulator of a full-length α7nAChR and an agonist of the α7nAChR construct containing transmembrane (TMD) and intracellular (ICD) domains, but structural insights of the binding have not previously been determined. Here, combining nuclear magnetic resonance as a primary experimental tool with Rosetta comparative modeling and molecular dynamics simulations, we have revealed details of ivermectin binding to the α7nAChR TMD + ICD and corresponding structural changes in an ivermectin-induced desensitized state. Ivermectin binding was stabilized predominantly by hydrophobic interactions from interfacial residues between adjacent subunits near the extracellular end of the TMD, where the inter-subunit gap was substantially expanded in comparison to the apo structure. The ion-permeation pathway showed a profile distinctly different from the resting-state profile but similar to profiles of desensitized α7nAChR. The ICD also exhibited structural changes, including reorientation of the MX and h3 helices relative to the channel axis. The resulting structures of the α7nAChR TMD + ICD in complex with ivermectin provide opportunities for discovering new modulators of therapeutic potential and exploring the structural basis of cytoplasmic signaling under different α7nAChR functional states.

Pharmacokinetic and pharmacodynamic considerations for treating sarcoptic mange with cross-relevance to Australian wildlife

Sarcoptes scabiei is the microscopic burrowing mite responsible for sarcoptic mange, which is reported in approximately 150 mammalian species. In Australia, sarcoptic mange affects a number of native and introduced wildlife species, is particularly severe in bare-nosed wombats (Vombatus ursinus) and an emerging issue in koala and quenda. There are a variety of acaricides available for the treatment of sarcoptic mange which are generally effective in eliminating mites from humans and animals in captivity. In wild populations, effective treatment is challenging, and concerns exist regarding safety, efficacy and the potential emergence of acaricide resistance. There are risks where acaricides are used intensively or inadequately, which could adversely affect treatment success rates as well as animal welfare. While reviews on epidemiology, treatment strategies, and pathogenesis of sarcoptic mange in wildlife are available, there is currently no review evaluating the use of specific acaricides in the context of their pharmacokinetic and pharmacodynamic properties, and subsequent likelihood of emerging drug resistance, particularly for Australian wildlife. This review critically evaluates acaricides that have been utilised to treat sarcoptic mange in wildlife, including dosage forms and routes, pharmacokinetics, mode of action and efficacy. We also highlight the reports of resistance of S. scabiei to acaricides, including clinical and in vitro observations.

Possible Interaction of Opioidergic and Nitrergic Pathways in the Anticonvulsant Effect of Ivermectin on Pentylenetetrazole-Induced Clonic Seizures in Mice

Ivermectin (IVM) is an antiparasitic drug that primarily works by the activation of GABA_A receptors. The potential pharmacological pathways behind the anti-convulsant effect of IVM haven't yet been identified. In this study, intravenous injection of pentylenetetrazole (PTZ)-induced clonic seizure in mice was investigated in order to assess the possible influence of IVM on clonic seizure threshold (CST). We also look at the function of the Opioidergic and nitrergic pathways in IVM anticonvulsant action on clonic seizure threshold. IVM (0.5, 1, 5, and 10 mg/kg, i.p.) raised the PTZ-induced CST, according to our findings. Furthermore, the ineffective dose of nitric oxide synthase inhibitors (L-NAME 10 mg/kg, i.p.), and (7-NI 30 mg/kg, i.p.) or opioidergic system agonist (morphine 0.25 mg/kg, i.p.) were able to amplify the anticonvulsive action of IVM (0.2 mg/kg, i.p.). Moreover, the anticonvulsant effect of IVM was reversed by an opioid receptor antagonist (naltrexone 1 mg/kg, i.p.). Furthermore, the combination of the ineffective dose of morphine as an opioid receptor agonist with either L-NAME (2 mg/kg, i.p.) or 7-NI (10 mg/kg, i.p.) and with an ineffective dose of IVM (0.2 mg/kg, i.p.) had a significant anticonvulsant effect. Taken together, IVM has anticonvulsant activity against PTZ-induced clonic seizures in mice, which may be mediated at least in part through the interaction of the opioidergic system and the nitric oxide pathway.

Is the antiparasitic drug ivermectin a suitable candidate for the treatment of epilepsy?

There are only a few drugs that can seriously lay claim to the title of "wonder drug," and ivermectin, the world's first endectocide and forerunner of a completely new class of antiparasitic agents, is among them. Ivermectin, a mixture of two macrolytic lactone derivatives (avermectin B1a and B1b in a ratio of 80:20), exerts its highly potent antiparasitic effect by activating the glutamate-gated chloride channel, which is absent in vertebrate species. However, in mammals, ivermectin activates several other Cys-loop receptors, including the inhibitory γ-aminobutyric acid type A and glycine receptors and the excitatory nicotinic acetylcholine receptor of brain neurons. Based on these effects on vertebrate receptors, ivermectin has recently been proposed to constitute a multifaceted wonder drug for various novel neurological indications, including alcohol use disorders, motor neuron diseases, and epilepsy. This review critically discusses the preclinical and clinical evidence of antiseizure effects of ivermectin and provides several arguments supporting that ivermectin is not a suitable candidate drug for the treatment of epilepsy. First, ivermectin penetrates the mammalian brain poorly, so it does not exert any pharmacological effects via mammalian ligand-gated ion channels in the brain unless it is used at high, potentially toxic doses or the blood-brain barrier is functionally impaired. Second, ivermectin is not selective but activates numerous inhibitory and excitatory receptors. Third, the preclinical evidence for antiseizure effects of ivermectin is equivocal, and at least in part, median effective doses in seizure models are in the range of the median lethal dose. Fourth, the only robust clinical evidence of antiseizure effects stems from the treatment of patients with onchocerciasis, in which the reduction of seizures is due to a reduction in microfilaria densities but not a direct antiseizure effect of ivermectin. We hope that this critical analysis of available data will avert the unjustified hype associated with the recent use of ivermectin to control COVID-19 from recurring in neurological diseases such as epilepsy.

Phenotypic Profiling of Macrocyclic Lactones on Parasitic Schistosoma Flatworms

Macrocyclic lactones are front-line therapies for parasitic roundworm infections; however, there are no comprehensive studies on the activity of this drug class against parasitic flatworms. Ivermectin is well known to be inactive against flatworms. However, the structure-activity relationship of macrocyclic lactones may vary across phyla, and it is entirely possible other members of this drug class do in fact show antiparasitic activity on flatworms. For example, there are several reports hinting at the anti-schistosomal activity of doramectin and moxidectin. To explore this class further, we developed an automated imaging assay combined with measurement of lactate levels from worm media. This assay was applied to the screening of 21 macrocyclic lactones (avermectins, milbemycins, and others such as spinosyns) against adult schistosomes. These in vitro assays identified several macrocyclic lactones (emamectin, milbemycin oxime, and the moxidectin metabolite 23-ketonemadectin) that caused contractile paralysis and lack of lactate production. Several of these were also active against miracidia, which infect the snail intermediate host. Hits prioritized from these in vitro assays were administered to mice harboring patent schistosome infections. However, no reduction in worm burden was observed. Nevertheless, these data show the utility of a multiplexed in vitro screening platform to quantitatively assess drug action and exclude inactive compounds from a chemical series before proceeding to in vivo studies. While the prototypical macrocyclic lactone ivermectin displays minimal activity against adult Schistosoma mansoni, this family of compounds does contain schistocidal compounds which may serve as a starting point for development of new anti-flatworm chemotherapies.

Synthesis and evaluation of the effects of solid lipid nanoparticles of ivermectin and ivermectin on cuprizone-induced demyelination via targeting the TRPA1/NF-kB/GFAP signaling pathway

Objectives

Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS) and its cause is unknown. Several environmental and genetic factors may have roles in the pathogenesis of MS. The synthesis of solid lipid nanoparticles (SLNs) for ivermectin (IVM) loading was performed to increase its efficiency and bioavailability and evaluate its ability in improving the behavioral and histopathological changes induced by cuprizone (CPZ) in the male C57BL/6 mice.

Materials and Methods

Four groups of 7 adult C57BL/6 mice including control (normal diet), CPZ, IVM, and nano-IVM groups were chosen. After synthesis of nano-ivermectin, demyelination was induced by adding 0.2% CPZ to animal feed for 6 weeks. IVM and nano-IVM (1 mg/kg/day, IP) were given for the final 14 days of the study. At last, behavioral tests, histochemical assays, and immunohistochemistry of TRPA1, NF-kB p65, and GFAP were done.

Results

The time of immobility of mice in the IVM and nano-IVM groups was reduced compared to the CPZ group. Histopathological examination revealed demyelination in the CPZ group, which was ameliorated by IVM and nano-IVM administration. In IVM and nano-IVM groups corpus callosum levels of TRPA1, NF-kB p65, and GFAP were decreased compared to the CPZ group. In the IVM and nano-IVM groups, the levels of MBP were significantly higher than in the CPZ group.

Conclusion

The results evidenced that IVM and nano-IVM administration is capable of reducing demyelination in mice.

Separation and Detection of Abamectin, Ivermectin, Albendazole and Three Metabolites in Eggs Using Reversed-Phase HPLC Coupled with a Photo Diode Array Detector

An innovative and sensitive approach using high-performance liquid chromatography-photo diode array detection (HPLC-PDAD) was developed and optimized for the simultaneous determination of abamectin (ABM), ivermectin (IVM), albendazole (ABZ) and three metabolites in eggs. The samples were extracted with acetonitrile (MeCN)/water (90:10, v/v), and the extracts containing the targets were cleaned up and concentrated by a series of liquid-liquid extraction (LLE) steps. A reversed-phase C18 column and a mobile phase consisting of 0.1% trifluoroacetic acid (TFA) aqueous solution and methanol (MeOH) were utilized to perform optimal chromatographic separation. The developed method was validated on the basis of international guidelines. The limits of detection (LODs) and quantitation (LOQs) were 2.1-10.5 µg/kg and 7.8-28.4 µg/kg, respectively. Satisfactory linear relationships were observed for the targets in their corresponding concentration ranges. The mean recoveries ranged from 85.7% to 97.21% at 4 addition levels, with intraday and interday relative standard deviations (RSDs) in the ranges of 1.68-4.77% and 1.74-5.31%, respectively. The presented protocol was demonstrated to be applicable and reliable by being applied for the detection of target residues in locally sourced egg samples.

Anticonvulsant effects of ivermectin on pentylenetetrazole- and maximal electroshock-induced seizures in mice: the role of GABAergic system and KATP channels

Introduction

Ivermectin (IVM) is an antiparasitic medicine that exerts its function through glutamate-gated chloride channels and GABA_A receptors predominantly. There is paucity of information on anti-seizure activity of IVM. Moreover, the probable pharmacological mechanisms underlying this phenomenon have not been identified.

Materials and methods

In this study, pentylenetetrazole (PTZ)-induced clonic seizures and maximal electroshock (MES)-induced tonic-clonic seizure models, respectively in mice was utilized to inquire whether IVM could alter clonic seizure threshold (CST) and seizure susceptibility. To assess the underlying mechanism behind the anti-seizure activity of IVM, we used positive and negative allosteric modulators of GABA_A (diazepam and flumazenil, respectively) as well as K_ATP channel opener and closer (cromakalim and glibenclamide, respectively). Data are provided as mean ± S.E.M. After the performance of the variance homogeneity test, a one-way and two-way analysis of variance was used. Fisher's exact test was performed in case of MES. P-value less than 0.05 considered statistically significant.

Results

and Discussion: Our data showed that IVM (0.5, 1, 5, and 10 mg/kg, i.p.) increased CST. Furthermore, flumazenil 0.25 mg/kg, i.p. and glibenclamide 1 mg/kg, i.p., could inhibit the anticonvulsant effects of IVM. Supplementary, an ineffective dose of diazepam 0.02 mg/kg, i.p. or cromakalim 10 μg/kg, i.p. were able to enhance the anticonvulsant effects of IVM. Besides, we figure out that the IVM (1 and 5 mg/kg, i.p.) could delay the onset of first clonic seizure and also might decrease the frequency of clonic seizures induced by PTZ (85 mg/kg, i.p.). Finally, IVM could prevent the incidence and death in MES-induced tonic-clonic seizures.

Conclusion

Based on the obtained results, it can be concluded that IVM may exert anticonvulsant effects against PTZ- and MES-induced seizures in mice that might be mediated by GABA_A receptors and K_ATP channels.

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Ivermectin exerts anticonvulsant effects on PTZ-induced clonic seizures.

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Ivermectin prevents MES-induced tonic-clonic seizures in mice.

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Ivermectin has the most anticonvulsant effects in doses of 1 and 5 mg/kg in mice.

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These anticonvulsant effects may be mediated through the GABAergic system.

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ATP-sensitive potassium channels could play a role in these anti-seizure effects.

Central Effects of Ivermectin in Alleviation of Covid-19-induced Dysauto-nomia

Covid-19 may be associated with various neurological disorders, including dysautonomia, a dysfunction of the autonomic nervous system (ANS). In Covid-19, hypoxia, immunoinflammatory abnormality, and deregulation of the renin-angiotensin system (RAS) may increase sympathetic discharge with dysautonomia development. Direct SARS-CoV-2 cytopathic effects and associated inflammatory reaction may lead to neuroinflammation, affecting different parts of the central nervous system (CNS), including the autonomic center in the hypothalamus, causing dysautonomia. High circulating AngII, hypoxia, oxidative stress, high pro-inflammatory cytokines, and emotional stress can also provoke autonomic deregulation and high sympathetic outflow with the development of the sympathetic storm. During SARS-CoV-2 infection with neuro-invasion, GABA-ergic neurons and nicotinic acetylcholine receptor (nAChR) are inhibited in the hypothalamic pre-sympathetic neurons leading to sympathetic storm and dysautonomia. Different therapeutic modalities are applied to treat SARS-CoV-2 infection, like antiviral and anti-inflammatory drugs. Ivermectin (IVM) is a robust repurposed drug widely used to prevent and manage mild-moderate Covid-19. IVM activates both GABA-ergic neurons and nAChRs to mitigate SARS-CoV-2 infection- induced dysautonomia. Therefore, in this brief report, we try to identify the potential role of IVM in managing Covid-19-induced dysautonomia.

P-glycoprotein inhibition affects ivermectin-induced behavioural alterations in fed and fasted zebrafish (Danio rerio)

The role of the blood-brain barrier ATP-binding cassette protein transporter P-glycoprotein (P-gp) in protecting zebrafish (Danio rerio) from the central nervous system neurotoxicant ivermectin (IVM, 22,23-dihydroavermectin B1a + 22,23-dihydroavermectin B1b) was examined in the absence and presence of the competitive inhibitor cyclosporin A (CsA). Zebrafish injected intraperitoneally with 1, 2, 5, or 10 µmol/kg IVM exhibited mortality 30 min following administration at the highest dose. At sublethal doses > 1 µmol/kg, IVM altered the swimming performance, exploratory behaviour, motor coordination, escape response and olfactory response in exposed fish. When fish were exposed to IVM in the presence of CsA, alterations in swimming and behaviours increased significantly and at the highest IVM/CsA ratio resulted in a complete lack of exploratory and olfactory behaviours. In separate experiments, fish were either fed or fasted, and the effects of IVM and CsA administration were examined. The effects of IVM administration and the exacerbated effects seen with CsA co-administration were not affected by fasting. This study provides evidence that P-gp provides a protective role in the BBB of fish against environmental neurotoxicants. The results also show that P-gp activity is maintained even under conditions of food deprivation, suggesting that this chemical defence system is prioritized over other energy expenditures during diet limitation.

Ivermectin contributes to attenuating the severity of acute lung injury in mice

Ivermectin has been proposed as a potential anti-inflammatory drug in addition to its antiparasitic activity. Here we investigated the potential role of ivermectin in the pathogenesis of acute lung injury (ALI) using the lipopolysaccharide (LPS)- or bleomycin (BLM)-induced mice models. Male C57BL/6 mice were given ivermectin orally every day for the remainder of the experiment at doses of 1 or 2 mg/kg after 24 h of LPS or BLM treatment. Ivermectin reversed severe lung injury caused by LPS or BLM challenge, including mortality, changes in diffuse ground-glass and consolidation shadows on lung CT imaging, lung histopathological scores, lung wet/dry ratio, and protein content in the bronchoalveolar lavage fluid (BALF). Furthermore, ivermectin also reduced total lung BALF inflammatory cells, infiltrating neutrophils, myeloperoxidase activity, and plasma TNF-α and IL-6 levels in mice treated with LPS or BLM. Finally, the mechanism study showed that LPS or BLM administration increased JNK, Erk1/2, and p38 MAPK phosphorylation while decreasing IκBα expression, an inhibitor of NF-κB. However, ivermectin increased IκBα expression but blocked elevated phosphorylated JNK and p38 MAPK, not Erk1/2, in both ALI mice. These findings suggested that ivermectin may alleviate ALI caused by LPS or BLM in mice, partly via lowering the inflammatory response, which is mediated at least by the inhibition of MAPK and NF-κB signaling. Collectively, ivermectin might be used to treat acute lung injury/acute respiratory distress syndrome.

Efficacy and safety of ivermectin in the treatment of mild to moderate COVID-19 infection: a randomized, double-blind, placebo-controlled trial

Background

The emergent outbreak of coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has emphasized the requirement for therapeutic opportunities to overcome this pandemic. Ivermectin is an antiparasitic drug that has shown effectiveness against various agents, including SARS-CoV-2. This study aimed to assess the efficacy of ivermectin treatment compared with the standard of care (SOC) among people with mild to moderate COVID-19 symptoms.

Methods

In this randomized, double-blind, placebo-controlled, single-center, parallel-arm, superiority trial among adult hospitalized patients with mild to moderate COVID-19, 72 patients (mean age 48.57 ± 14.80 years) were randomly assigned to either the ivermectin (n=36) or placebo (n=36) group, along with receiving standard care. We aimed to compare the negativity of reverse transcription polymerase chain reaction (RT-PCR) result at days 7 and 14 of enrolment as the primary outcome. The secondary outcomes were duration of hospitalization, frequency of clinical worsening, survival on day 28, and adverse events.

Results

At days 7 and 14, no differences were observed in the proportion of PCR-positive patients (RR 0.97 at day 7 (p=0.759) and 0.95 at day 14 (p=0.813). No significant differences were found between the groups for any of the secondary endpoints, and no adverse events were reported.

Conclusion

No difference was found in the proportion of PCR-positive cases after treatment with ivermectin compared with standard care among patients with mild to moderate COVID-19 symptoms. However, early symptomatic recovery was observed without side effects.

Trial registration

ClinicalTrials.gov NCT05076253. Registered on 8 October 2021, prospectively.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06649-3.

The nematode serotonin-gated chloride channel MOD-1: A novel target for anthelmintic therapy

Anthelmintics are used to treat human and veterinary parasitic diseases, as well as to reduce crop and livestock production loss associated with parasitosis. The free-living nematode Caenorhabditis elegans, a model system for anthelmintic drug discovery, has a serotonin (5-HT)-gated chloride channel, MOD-1, which belongs to the Cys-loop receptor family and modulates locomotory and behavioral functions. Since MOD-1 is unique to nematodes, it is emerging as an attractive anthelmintic drug target, but details of MOD-1 function are unclear. Here, we revealed novel aspects of MOD-1 function from the molecular level to the organism level and identified compounds targeting this receptor, which may provide new directions for anthelmintic drug discovery. We used whole-cell current recordings from heterologously expressed MOD-1 to show that tryptamine, a weak partial agonist of vertebrate 5-HT₃ receptors, efficaciously activates MOD-1. A screen for modulators revealed that GABAergic ligands piperazine and muscimol reduce 5-HT-elicited currents, thus identifying novel MOD-1 allosteric inhibitors. Next, we performed locomotor activity assays, and we found 5-HT and tryptamine rapidly decrease worm motility, which is reversible only at low 5-HT concentrations. Mutants lacking MOD-1 are partially resistant to both drugs, demonstrating its key role in locomotion. Acting as an antagonist of MOD-1, we showed piperazine reduces the locomotor effects of exogenous 5-HT. Therefore, tryptamine- and piperazine-derived compounds, acting at MOD-1 through different molecular mechanisms, emerge as promising anthelmintic agents. This study enhances our knowledge of the function and drug selectivity of Cys-loop receptors and postulates MOD-1 as a potential target for anthelmintic therapy.

ADAP restraint of STAT1 signaling regulates macrophage phagocytosis in immune thrombocytopenia

Heightened platelet phagocytosis by macrophages accompanied by an increase in IFN-γ play key roles in the etiology of immune thrombocytopenia (ITP); however, it remains elusive how macrophage-mediated platelet clearance is regulated in ITP. Here, we report that adhesion and degranulation-protein adaptor protein (ADAP) restrains platelet phagocytosis by macrophages in ITP via modulation of signal transducer and activator of transcription 1 (STAT1)-FcγR signaling. We show that ITP was associated with the underexpression of ADAP in splenic macrophages. Furthermore, macrophages from Adap^−/− mice exhibited elevated platelet phagocytosis and upregulated proinflammatory signaling, and thrombocytopenia in Adap^−/− mice was mitigated by the depletion of macrophages. Mechanistically, ADAP interacted and competed with STAT1 binding to importin α5. ADAP deficiency potentiated STAT1 nuclear entry, leading to a selective enhancement of FcγRI/IV transcription in macrophages. Moreover, pharmacological inhibition of STAT1 or disruption of the STAT1-importin α5 interaction relieved thrombocytopenia in Adap^−/− mice. Thus, our findings not only reveal a critical role for ADAP as an intracellular immune checkpoint for shaping macrophage phagocytosis in ITP but also identify the ADAP-STAT1-importin α5 module as a promising therapeutic target in the treatment of ITP.

Broadening the spectrum of ivermectin: Its effect on Trypanosoma cruzi and related trypanosomatids

Chagas disease is an endemic American parasitosis, caused by Trypanosoma cruzi. The current therapies, benznidazole (BZN) and nifurtimox (NFX), show limited efficacy and multiple side effects. Thus, there is a need to develop new trypanocidal strategies. Ivermectin (IVM) is a broad-spectrum antiparasitic drug with low human and veterinary toxicity with effects against T. brucei and Leishmania spp. Considering this and its relatively low cost, we evaluate IVM as a potential repurposed trypanocidal drug on T. cruzi and other trypanosomatids. We found that IVM affected, in a dose-dependent manner, the proliferation of T. cruzi epimastigotes as well as the amastigotes and trypomastigotes survival. The Selectivity Index for the amastigote stage with respect to Vero cells was 12. The IVM effect was also observed in Phytomonas jma 066 and Leishmania mexicana proliferation but not in Crithidia fasciculata. On the epimastigote stage, the IVM effect was trypanostatic at 50 μM but trypanocidal at 100 μM. The assays of the drug combinations of IVM with BNZ or NFX showed mainly additive effects among combinations. In silico studies showed that classical structures belonging to glutamate-gated Cl channels, the most common IVM target, are absent in kinetoplastids. However, we found in the studied trypanosomatid genomes one copy for putative IMPα and IMPβ, potential targets for IVM. The putative IMPα genes (with 76% similarity) showed conserved Armadillo domains but lacked the canonical IMPβ binding sequence. These results allowed us to propose a novel molecular target in T. cruzi and suggest IVM as a good candidate for drug repurposing in the Chagas disease context.

Clinical-Epidemiology Aspect of Inpatients With Moderate or Severe COVID-19 in a Brazilian Macroregion: Disease and Countermeasures

COVID-19, also known as coronavirus disease 2019, is an infectious viral disease caused by SARS-CoV-2, a novel coronavirus. Since its emergence, its epidemiology has been explored; however, for some regions of the world, COVID-19’s behavior, incidence, and impact remain unclear. In continental nations like Brazil, this lack of knowledge results in nonuniform control, prevention, and treatment measures, which can be controversial in some locations. This study aimed to describe the epidemiological profile of patients with COVID-19 in the macroregion of Triângulo Sul in the state of Minas Gerais (MG), Brazil. Between March 25 and October 21, 2020, data were collected and statistically analyzed from 395 hospitalized patients in the city of Uberaba, MG, suspected to have moderate or severe forms of the disease. Of the 395 suspected cases, 82% were confirmed to be positive for COVID-19. The mean age of positive patients was 58.4 years, and 60.76% were male. Following these patients throughout their hospitalization, a mortality rate of 31.3% was observed. In the population positive for COVID-19, the risk of death increased by 4% for each year of the patient’s age. Likewise, the older the patient, the longer their hospitalization and the higher the risk of developing acute respiratory failure. Among the treatments tested in patients, heparin was associated with protection against mortality, and the absence of anticoagulant use was linked to a more than six times greater risk of death. Finally, comorbidities in patients with COVID-19 were positively correlated with increased hospitalization time. In summary, this study revealed that age, presence of comorbidities, length of hospitalization, and drug treatment considerably altered COVID-19’s lethality. To understand infection rates and the factors involved in COVID-19’s lethality, knowledge of the local epidemiology is necessary.

Kinase Inhibitors as Potential Therapeutic Agents in the Treatment of COVID-19

Corona virus is quickly spreading around the world. The goal of viral management is to disrupt the virus’s life cycle, minimize lung damage, and alleviate severe symptoms. Numerous strategies have been used, including repurposing existing antivirals or drugs used in previous viral outbreaks. One such strategy is to repurpose FDA-approved kinase inhibitors that are potential chemotherapeutic agents and have demonstrated antiviral activity against a variety of viruses, including MERS, SARS-CoV-1, and others, by inhibiting the viral life cycle and the inflammatory response associated with COVID-19. The purpose of this article is to identify licensed kinase inhibitors that have the ability to reduce the virus’s life cycle, from entrance through viral propagation from cell to cell. Several of these inhibitors, including imatinib, ruxolitinib, silmitasertib, and tofacitinib (alone and in conjunction with hydroxychloroquine), are now undergoing clinical studies to determine their efficacy as a possible treatment drug. The FDA approved baricitinib (a Janus kinase inhibitor) in combination with remdesivir for the treatment of COVID-19 patients receiving hospital care in November 2020. While in vitro trials with gilteritinib, fedratinib, and osimertinib are encouraging, further research is necessary before these inhibitors may be used to treat COVID-19 patients.

P2Y1 purinergic receptor identified as a diabetes target in a small-molecule screen to reverse circadian β-cell failure

The mammalian circadian clock drives daily oscillations in physiology and behavior through an autoregulatory transcription feedback loop present in central and peripheral cells. Ablation of the core clock within the endocrine pancreas of adult animals impairs the transcription and splicing of genes involved in hormone exocytosis and causes hypoinsulinemic diabetes. Here, we developed a genetically sensitized small-molecule screen to identify druggable proteins and mechanistic pathways involved in circadian β-cell failure. Our approach was to generate β-cells expressing a nanoluciferase reporter within the proinsulin polypeptide to screen 2640 pharmacologically active compounds and identify insulinotropic molecules that bypass the secretory defect in CRISPR-Cas9-targeted clock mutant β-cells. We validated hit compounds in primary mouse islets and identified known modulators of ligand-gated ion channels and G-protein-coupled receptors, including the antihelmintic ivermectin. Single-cell electrophysiology in circadian mutant mouse and human cadaveric islets revealed ivermectin as a glucose-dependent secretagogue. Genetic, genomic, and pharmacological analyses established the P2Y1 receptor as a clock-controlled mediator of the insulinotropic activity of ivermectin. These findings identify the P2Y1 purinergic receptor as a diabetes target based upon a genetically sensitized phenotypic screen.

Ivermectin Prophylaxis Used for COVID-19: A Citywide, Prospective, Observational Study of 223,128 Subjects Using Propensity Score Matching

Background: Ivermectin has demonstrated different mechanisms of action that potentially protect from both coronavirus disease 2019 (COVID-19) infection and COVID-19-related comorbidities. Based on the studies suggesting efficacy in prophylaxis combined with the known safety profile of ivermectin, a citywide prevention program using ivermectin for COVID-19 was implemented in Itajaí, a southern city in Brazil in the state of Santa Catarina. The objective of this study was to evaluate the impact of regular ivermectin use on subsequent COVID-19 infection and mortality rates.

Materials and methods: We analyzed data from a prospective, observational study of the citywide COVID-19 prevention with ivermectin program, which was conducted between July 2020 and December 2020 in Itajaí, Brazil. Study design, institutional review board approval, and analysis of registry data occurred after completion of the program. The program consisted of inviting the entire population of Itajaí to a medical visit to enroll in the program and to compile baseline, personal, demographic, and medical information. In the absence of contraindications, ivermectin was offered as an optional treatment to be taken for two consecutive days every 15 days at a dose of 0.2 mg/kg/day. In cases where a participating citizen of Itajaí became ill with COVID-19, they were recommended not to use ivermectin or any other medication in early outpatient treatment. Clinical outcomes of infection, hospitalization, and death were automatically reported and entered into the registry in real time. Study analysis consisted of comparing ivermectin users with non-users using cohorts of infected patients propensity score-matched by age, sex, and comorbidities. COVID-19 infection and mortality rates were analyzed with and without the use of propensity score matching (PSM).

Results: Of the 223,128 citizens of Itajaí considered for the study, a total of 159,561 subjects were included in the analysis: 113,845 (71.3%) regular ivermectin users and 45,716 (23.3%) non-users. Of these, 4,311 ivermectin users were infected, among which 4,197 were from the city of Itajaí (3.7% infection rate), and 3,034 non-users (from Itajaí) were infected (6.6% infection rate), with a 44% reduction in COVID-19 infection rate (risk ratio [RR], 0.56; 95% confidence interval (95% CI), 0.53-0.58; p < 0.0001). Using PSM, two cohorts of 3,034 subjects suffering from COVID-19 infection were compared. The regular use of ivermectin led to a 68% reduction in COVID-19 mortality (25 [0.8%] versus 79 [2.6%] among ivermectin non-users; RR, 0.32; 95% CI, 0.20-0.49; p < 0.0001). When adjusted for residual variables, reduction in mortality rate was 70% (RR, 0.30; 95% CI, 0.19-0.46; p < 0.0001). There was a 56% reduction in hospitalization rate (44 versus 99 hospitalizations among ivermectin users and non-users, respectively; RR, 0.44; 95% CI, 0.31-0.63; p < 0.0001). After adjustment for residual variables, reduction in hospitalization rate was 67% (RR, 0.33; 95% CI, 023-0.66; p < 0.0001).

Conclusion: In this large PSM study, regular use of ivermectin as a prophylactic agent was associated with significantly reduced COVID-19 infection, hospitalization, and mortality rates.

Identification and pharmacological characterization of histamine-gated chloride channels in the fall armyworm, Spodoptera frugiperda

Histamine-gated chloride channels (HACls) mediate fast inhibitory neurotransmission in invertebrate nervous systems and have important roles in light reception, color processing, temperature preference and light-dark cycle. The fall armyworm, Spodoptera frugiperda is a main destructive pest of grain and row crops. However, the pharmacological characterization of HACls in S. frugiperda remain unknown. In this study, we identified two cDNAs encoding SfHACl1 and SfHACl2 in S. frugiperda. They had similar expression patterns and were most abundantly expressed in the head of larvae and at the egg stage. Electrophysiological analysis with the two-electrode voltage clamp method showed that histamine (HA) and γ-aminobutyric acid (GABA) activated inward currents when SfHACls were singly or collectively expressed with different ratios in Xenopus laevis oocytes. These channels were ≥2000-fold more sensitive to HA than to GABA. They were anion-selective channels, which were highly dependent on changes in external chloride concentrations, but insensitive to changes in external sodium concentrations. The insecticides abamectin (ABM) and emamectin benzoate (EB) also activated these channels with the EC₅₀ to SfHACl1 lower than that to SfHACl2. And the EC_50s of ABM and EB to the co-expressed channels gradually increased with increase in the injection ratio of SfHACl2 cRNA. Homology models and docking simulations revealed that HA bound to the large amino-terminal extracellular domain of SfHACl1 and SfHACl2 by forming 4 and 2 hydrogen bonds, respectively. The docking simulations of ABM and EB had similar binding sites in the transmembrane regions. Overall, these findings indicated that HACls act as targets for macrolide, and this study provides theoretical guidance for further derivatization of abamectin insecticides.

COVID-19: A review of newly formed viral clades, pathophysiology, therapeutic strategies and current vaccination tasks

Today, the world population is facing an existential threat by an invisible enemy known as severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) or COVID-19. It is highly contagious and has infected a larger fraction of human population across the globe on various routes of transmission. The detailed knowledge of the SARS-CoV-2 structure and clinical aspects offers an important insight into the evolution of infection, disease progression and helps in executing the different therapies effectively. Herein, we have discussed in detail about the genome structure of SARS-CoV-2 and its role in the proteomic rational spread of different muted species and pathogenesis in infecting the host cells. The mechanisms behind the viral outbreak and its immune response, the availability of existing diagnostics techniques, the treatment efficacy of repurposed drugs and the emerging vaccine trials for the SARS-CoV-2 outbreak also have been highlighted. Furthermore, the possible antiviral effects of various herbal products and their extracted molecules in inhibiting SARS-CoV-2 replication and cellular entry are also reported. Finally, we conclude our opinion on current challenges involved in the drug development, bulk production of drug/vaccines and their storage requirements, logistical procedures and limitations related to dosage trials for larger population.

A novel ion conducting route besides the central pore in an inherited mutant of G-protein-gated inwardly rectifying K+ channel

G-protein-gated inwardly rectifying K⁺ (GIRK; Kir3.x) channels play important physiological roles in various organs. Some of the disease-associated mutations of GIRK channels are known to induce loss of K⁺ selectivity but their structural changes remain unclear. In this study, we investigated the mechanisms underlying the abnormal ion selectivity of inherited GIRK mutants. By the two-electrode voltage-clamp analysis of GIRK mutants heterologously expressed in Xenopus oocytes, we observed that Kir3.2 G156S permeates Li⁺ better than Rb⁺ , while T154del or L173R of Kir3.2 and T158A of Kir3.4 permeate Rb⁺ better than Li⁺ , suggesting a unique conformational change in the G156S mutant. Applications of blockers of the selectivity filter (SF) pathway, Ba²⁺ or Tertiapin-Q (TPN-Q), remarkably increased the Li⁺ -selectivity of Kir3.2 G156S but did not alter those of the other mutants. In single-channel recordings of Kir3.2 G156S expressed in mouse fibroblasts, two types of events were observed, one attributable to a TPN-Q-sensitive K⁺ current and the second a TPN-Q-resistant Li⁺ current. The results show that a novel Li⁺ -permeable and blocker-resistant pathway exists in G156S in addition to the SF pathway. Mutations in the pore helix, S148F and T151A also induced high Li⁺ permeation. Our results demonstrate that the mechanism underlying the loss of K⁺ selectivity of Kir3.2 G156S involves formation of a novel ion permeation pathway besides the SF pathway, which allows permeation of various species of cations. KEY POINTS: G-protein-gated inwardly rectifying K⁺ (GIRK; Kir3.x) channels play important roles in controlling excitation of cells in various organs, such as the brain and the heart. Some of the disease-associated mutations of GIRK channels are known to induce loss of K⁺ selectivity but their structural changes remain unclear. In this study, we investigated the mechanisms underlying the abnormal ion selectivity of inherited mutants of Kir3.2 and Kir3.4. Here we show that a novel Na⁺ , Li⁺ -permeable and blocker-resistant pathway exists in an inherited mutant, Kir3.2 G156S, in addition to the conventional ion conducting pathway formed by the selectivity filter (SF). Our results demonstrate that the mechanism underlying the loss of K⁺ selectivity of Kir3.2 G156S involves formation of a novel ion permeation pathway besides the SF pathway, which allows permeation of various species of cations.

Ligand-gated ion channels as targets of neuroactive insecticides

The Cys-loop superfamily of ligand-gated ion channels (Cys-loop receptors) is one of the most ubiquitous ion channel families in vertebrates and invertebrates. Despite their ubiquity, they are targeted by several classes of pesticides, including neonicotinoids, phenylpyrazols, and macrolides such as ivermectins. The current commercialized compounds have high target site selectivity, which contributes to the safety of insecticide use. Structural analyses have accelerated progress in this field; notably, the X-ray crystal structures of acetylcholine binding protein and glutamate-gated Cl channels revealed the details of the molecular interactions between insecticides and their targets. Recently, the functional expression of the insect nicotinic acetylcholine receptor (nAChR) has been described, and detailed evaluations using the insect nAChR have emerged. This review discusses the basic concepts and the current insights into the molecular mechanisms of neuroactive insecticides targeting the ligand-gated ion channels, particularly Cys-loop receptors, and presents insights into target-based selectivity, resistance, and future drug design.

Taspine is a natural product that suppresses P2X4 receptor activity via phosphoinositide 3-kinase inhibition

BACKGROUND & PURPOSE

P2X4 is a ligand-gated cation channel activated by extracellular ATP, involved in neuropathic pain, inflammation and arterial tone.

EXPERIMENTAL APPROACH

Natural products were screened against human or mouse P2X4 activity using fura-2 loaded 1321N1 cells for measurement of intracellular Ca²⁺ responses; whole-cell currents were measured by patch clamp electrophysiological. Human primary macrophage chemokine release was used to assess effect of taspine on inflammatory cell function. An enzymatic assay was performed to assess the effect of taspine on recombinant PI3-kinase.

KEY RESULTS

A natural product screen identified taspine as an inhibitor of human P2X4 activity. Taspine inhibits human and mouse P2X4-mediated Ca²⁺ influx in 1321N1 cells expressing receptors (IC₅₀ 1.6±0.4 μM and 1.6±0.3 μM, respectively), but lacked activity at human P2X2, P2X3, P2X2/3 and P2X7 receptors. Taspine inhibited the maximal response at human and mouse P2X4 but had no effect on ATP potency. Taspine has a slow onset rate (~15 mins for half-maximal inhibition), irreversible over 30 minutes of washout. Taspine inhibits P2X4-mediated Ca²⁺ signalling in mouse BV-2 microglia cells and human primary macrophage. Taspine inhibited P2X4-mediated CXCL5 secretion in human primary macrophage. Taspine reversed ivermectin-induced potentiation of P2X4 currents in 1321N1 stably expressing cells. The known PI3-kinase inhibitor LY294002 mimicked the properties of taspine on P2X4-mediated Ca²⁺ influx and whole-cell currents. Taspine directly inhibited the enzymatic activity of recombinant PI3-kinase in a competitive manner.

CONCLUSIONS AND IMPLICATIONS

Taspine is a novel natural product P2X4 inhibitor, mediating its effect through PI3-kinase inhibitor rather than receptor antagonism. Taspine can inhibit the pro-inflammatory signalling by P2X4 in human primary macrophage.

Elephants in the Dark: Insights and Incongruities in Pentameric Ligand-gated Ion Channel Models

The superfamily of pentameric ligand-gated ion channels (pLGICs) comprises key players in electrochemical signal transduction across evolution, including historic model systems for receptor allostery and targets for drug development. Accordingly, structural studies of these channels have steadily increased, and now approach 250 depositions in the protein data bank. This review contextualizes currently available structures in the pLGIC family, focusing on morphology, ligand binding, and gating in three model subfamilies: the prokaryotic channel GLIC, the cation-selective nicotinic acetylcholine receptor, and the anion-selective glycine receptor. Common themes include the challenging process of capturing and annotating channels in distinct functional states; partially conserved gating mechanisms, including remodeling at the extracellular/transmembrane-domain interface; and diversity beyond the protein level, arising from posttranslational modifications, ligands, lipids, and signaling partners. Interpreting pLGIC structures can be compared to describing an elephant in the dark, relying on touch alone to comprehend the many parts of a monumental beast: each structure represents a snapshot in time under specific experimental conditions, which must be integrated with further structure, function, and simulations data to build a comprehensive model, and understand how one channel may fundamentally differ from another.

Efficacy of Topical Ivermectin 1% in the Treatment of Demodex Blepharitis

The purpose of this study was to evaluate the efficacy of topical ivermectin 1% cream application on the eyelashes in combination with eyelid hygiene in the treatment of Demodex blepharitis.

Lack of detectable short-term effects of a single dose of ivermectin on the human immune system

Background

Ivermectin is widely used in human and animal medicine to treat and prevent parasite nematode infections. It has been suggested that its mode of action requires the host immune system, as it is difficult to reproduce its clinical efficacy in vitro. We therefore studied the effects of a single dose of ivermectin (Stromectol^®—0.15 mg/kg) on cytokine levels and immune cell gene expression in human volunteers. This dose reduces bloodstream microfilariae rapidly and for several months when given in mass drug administration programmes.

Methods

Healthy volunteers with no travel history to endemic regions were given 3–4 tablets, depending on their weight, of either ivermectin or a placebo. Blood samples were drawn immediately prior to administration, 4 h and 24 h afterwards, and complete blood counts performed. Serum levels of 41 cytokines and chemokines were measured using Luminex^® and expression levels of 770 myeloid-cell-related genes determined using the NanoString nCounter^®. Cytokine levels at 4 h and 24 h post-treatment were compared to the levels pre-treatment using simple t tests to determine if any individual results required further investigation, taking p =  < 0.05 as the level of significance. NanoString data were analysed on the proprietary software, nSolver™.

Results

No significant differences were observed in complete blood counts or cytokine levels at either time point between people given ivermectin versus placebo. Only three genes showed a significant change in expression in peripheral blood mononuclear cells 4 h after ivermectin was given; there were no significant changes 24 h after drug administration or in polymorphonuclear cells at either time point. Leukocytes isolated from those participants given ivermectin showed no difference in their ability to kill Brugia malayi microfilariae in vitro.

Conclusions

Overall, our data do not support a direct effect of ivermectin, when given at the dose used in current filarial elimination programmes, on the human immune system.

Trial registration ClinicalTrials.gov NCT03459794 Registered 9th March 2018, Retrospectively registered https://clinicaltrials.gov/ct2/show/NCT03459794?term=NCT03459794&draw=2&rank=1.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04810-6.

Macrolides: From Toxins to Therapeutics

Macrolides are a diverse class of hydrophobic compounds characterized by a macrocyclic lactone ring and distinguished by variable side chains/groups. Some of the most well characterized macrolides are toxins produced by marine bacteria, sea sponges, and other species. Many marine macrolide toxins act as biomimetic molecules to natural actin-binding proteins, affecting actin polymerization, while other toxins act on different cytoskeletal components. The disruption of natural cytoskeletal processes affects cell motility and cytokinesis, and can result in cellular death. While many macrolides are toxic in nature, others have been shown to display therapeutic properties. Indeed, some of the most well known antibiotic compounds, including erythromycin, are macrolides. In addition to antibiotic properties, macrolides have been shown to display antiviral, antiparasitic, antifungal, and immunosuppressive actions. Here, we review each functional class of macrolides for their common structures, mechanisms of action, pharmacology, and human cellular targets.