[Toward the complete understanding of the pathogenic mechanism of clioquinol-induced subacute myelo-optic neuropathy (SMON)].

Clioquinol was extensively used as an amebicide to treat indigestion and diarrhea in the mid-1900s. However, it was withdrawn from the market in Japan because its use was epidemiologically linked to an increase in the incidence of subacute myelo-optic neuropathy (SMON). SMON is characterized by the subacute onset of sensory and motor disturbances in the lower extremities with occasional visual impairments, which are preceded by abdominal symptoms. Although pathological studies demonstrated axonopathy of the spinal cord and optic nerves, the underlying mechanisms of clioquinol toxicity have not been elucidated in detail. We previously performed a global analysis of human neuroblastoma cells using DNA chips and demonstrated that clioquinol induced 1) DNA double-strand breaks and subsequent activation of ATM/p53 signaling; 2) the expression of VGF, the precursor of neuropeptides involved in pain reactions, by inducing c-Fos; 3) the expression of interleukin-8, which is reported to be involved in intestinal inflammation, optic neuropathy, and neuropathic pain, by down-regulating GATA-2 and GATA-3. We also demonstrated that clioquinol induced zinc influx and oxidation of the copper chaperone ATOX1, leading to the impairment of the functional maturation of a copper-dependent enzyme dopamine-ß-hydroxylase and the inhibition of noradrenaline biosynthesis. Thus, clioquinol-induced neurotoxicity in SMON seems to be mediated by multiple pathways.

The 8-hydroxyquinoline derivative, clioquinol, is an alpha-1 adrenoceptor antagonist.

Clioquinol (5-chloro-7-iodo-8-hydroxyquinoline) is an antimicrobial agent whose actions as a zinc or copper ionophore and an iron chelator revived the interest in similar compounds for the treatment of fungal and bacterial infections, neurodegeneration and cancer. Recently, we reported zinc ionophores, including clioquinol, cause vasorelaxation in isolated arteries through mechanisms that involve sensory nerves, endothelium and vascular smooth muscle. Here, we report that clioquinol also uniquely acts as a competitive alpha-1 (α1) adrenoceptor antagonist. We employed ex vivo functional vascular contraction and pharmacological techniques in rat isolated mesenteric arteries, receptor binding assays using stabilized solubilized α1 receptor variants, or wild-type human α1-adrenoceptors transfected in COS-7 cells (African green monkey kidney fibroblast-like cells), and molecular dynamics homology modelling based on the recently published α1A adrenoceptor cryo-EM and α1B crystal structures. At higher concentrations, all ionophores including clioquinol cause a non-competitive antagonism of agonist-mediated contraction due to intracellular zinc delivery, as reported previously. However, at lower concentration ranges, clioquinol has an additional mechanism of competitively inhibiting α1-adrenoceptors that contributes to decreasing vascular contractility. Molecular dynamic simulation showed that clioquinol binds stably to the orthosteric binding site (Asp106) of the receptor, confirming the structural basis for competitive α1-adrenoceptor antagonism by clioquinol.

Synergistic activity of clioquinol with voriconazole and amphotericin B against fungi of interest in eye infections.

Keratoplasty represents a risk factor for fungal eye infections, despites the antibacterial actives in the corneal tissue preservation means, it does not contain active substances with antifungal action. Among the most commonly associated fungal agents are the species belonging to the genera Fusarium and Candida. These agents can trigger an infectious process characterized by swift progression associated with high rates of morbidity, causing irreversible damage. Polyene and azole antifungals are the main agents of ocular therapy, however, they demonstrate some limitations, such as their toxicity and fungal resistance. In this context, drug repositioning and the combination of antifungals may be an alternative. Hence, the goal of this study was to investigate the potential activity of clioquinol (CLQ), a derivative of 8-hydroxyquinoline with previously described antifungal activity, along with its triple and quadruple combinations with antifungal agents commonly used in ophthalmic fungal therapy, natamycin (NAT), voriconazole (VRC), and amphotericin B (AMB), against main fungal pathogens in eye infections. The MICs for CLQ ranged from 0.25 to 2.0 µg/mL, for NAT from 4.0 to 32.0 µg/mL, for AMB it ranged from 0.25 to 16.0 µg/mL and for VRC from 0.03125 to 512.0 µg/mL. Among the tested combinations, the VRC-AMB-CLQ combination stands out, which showed a synergistic effect for more than 50 % of the tested strains and did not present antagonistic results against any of them. Toxicity data were similar to those antifungals already used, even with lower potential toxicity. Therefore, both clioquinol and the triple combination VCR-AMB-CLQ exhibited promising profiles for use as active components in corneal tissue preservation medium.

Discovery of Novel 8-Hydroxyquinoline Derivatives with Potent In Vitro and In Vivo Antifungal Activity.

Fungal pathogens can cause life-threatening infections, yet current antifungals are inadequate at treating many of these, highlighting the importance of novel drug discovery. Here, we report hit compound L14, a novel 8-hydroxyquinoline derivative with potent and broad-spectrum antifungal activity. In vitro experiments exhibited that L14 had better activity and lower cytotoxicity than that of clioquinol and showed synergy in combination with fluconazole (FLC). In a Candida albicans-infected murine model, L14 at 2 mg/kg showed better in vivo efficacy than clioquinol at reducing fungal burden and extending the survival of C. albicans-infected mice. In addition, L14 alone or in combination with FLC had significant inhibitory activity against hypha and biofilm formation. Overall, our data indicated that 8-hydroxyquinoline derivative L14 has favorable pharmacokinetics and acceptable safety profiles and could be further investigated as a promising antifungal hit compound.

Understanding Alzheimer's Disease and its Metal Chelation Therapeutics: A Narrative Review.

The neurodegenerative disorders are age-related illnesses that cause the morphology or activity of neurons to deteriorate over time. Alzheimer's disease is the most frequent neurodegenerative illness in the long run. The rate of advancement might vary, even though it is a progressive neurological illness. Various explanations have been proposed, however the true etiology of Alzheimer's disease remains unclear. Most pharmacological interventions are based on the cholinergic theory, that is earliest idea. In accordance with the amyloid hypothesis, the buildup of beta-amyloid in brain regions is the primitive cause of illness. There is no proof that any one strategy is useful in avoiding Alzheimer's disease, though some epidemiological studies have suggested links within various modifiable variables, such as cardiovascular risk, diet and so on. Different metals like zinc, iron, and copper are naturally present in our bodies. In metal chelation therapy drugs are used to jam the metal ions from combining with other molecules in the body. Clioquinol is one of the metal chelation drugs used by researchers. Research on metal chelation is still ongoing. In the present review, we go over the latest developments in prevalence, incidence, etiology, or pathophysiology of our understanding of Alzheimer's disease. Additionally, a brief discussion on the development of therapeutic chelating agents and their viability as Alzheimer's disease medication candidates is presented. We also assess the effect of clioquinol as a potential metal chelator.

In vitro evaluation of the efficacy of 8-hydroxyquinoline derivatives for the control of Phaeomoniella chlamydospora, the causative agent of Petri disease in grapevines.

AIM: This study evaluates the in vitro efficacy of 8-hydroxyquinoline (8HQ) derivatives in controlling the phytopathogenic fungus Phaeomoniella chlamydospora. METHODS AND RESULTS: The in vitro tests assessed the susceptibility to the minimum inhibitory concentration (MIC), checkerboard assay, mycelial growth (MG) inhibition, and EC50 determination. Among the seven agricultural fungicides tested, tebuconazole (TEB) displayed the lowest MIC, 1.01 µg mL-1, followed by captan (CAP), thiophanate methyl (TM), and mancozeb with MICs of 4.06, 5.46, and 10.62 µg mL-1, respectively. The 8HQ derivatives used in this study were clioquinol and PH 151 (PH) with MICs of 1.09 and 2.02 µg mL-1, respectively. PH associated with TEB and CAP showed synergism and inhibited 95.8% of MG at the highest dose. TEB inhibited 100% of MG at the three highest doses, while associated with PH exhibited the lowest EC50 (0.863 + 0.0381 µg mL-1). CONCLUSIONS: We concluded that the 8HQ derivatives tested controlled effectively the P. chlamydospora in vitro. PH associated with CAP and TEB exhibited a synergistic effect. The association between PH and TM was considered indifferent. IMPACT STATEMENT: This study expands the list of active ingredients tested against P. chlamydospora, with the PH 151 and clioquinol derivatives being tested for the first time. The in vitro efficacy and synergistic action with other fungicides suggest a potential use as a grapevine wound protectant. This association makes it possible to reduce doses and increase the potency of both drugs, reducing the risk of resistance development and harm to humans and the environment.

Broad susceptibility of Candida auris strains to 8-hydroxyquinolines and mechanisms of resistance.

The fungal pathogen Candida auris represents a severe threat to hospitalized patients. Its resistance to multiple classes of antifungal drugs and ability to spread and resist decontamination in healthcare settings make it especially dangerous. We screened 1,990 clinically approved and late-stage investigational compounds for the potential to be repurposed as antifungal drugs targeting C. auris and narrowed our focus to five Food and Drug Administration (FDA)-approved compounds with inhibitory concentrations under 10 µM for C. auris and significantly lower toxicity to three human cell lines. These compounds, some of which had been previously identified in independent screens, include three dihalogenated 8-hydroxyquinolines: broxyquinoline, chloroxine, and clioquinol. A subsequent structure-activity study of 32 quinoline derivatives found that 8-hydroxyquinolines, especially those dihalogenated at the C5 and C7 positions, were the most effective inhibitors of C. auris. To pursue these compounds further, we exposed C. auris to clioquinol in an extended experimental evolution study and found that C. auris developed only twofold to fivefold resistance to the compound. DNA sequencing of resistant strains and subsequent verification by directed mutation in naive strains revealed that resistance was due to mutations in the transcriptional regulator CAP1 (causing upregulation of the drug transporter MDR1) and in the drug transporter CDR1. These mutations had only modest effects on resistance to traditional antifungal agents, and the CDR1 mutation rendered C. auris more susceptible to posaconazole. This observation raises the possibility that a combination treatment involving an 8-hydroxyquinoline and posaconazole might prevent C. auris from developing resistance to this established antifungal agent. IMPORTANCE The rapidly emerging fungal pathogen Candida auris represents a growing threat to hospitalized patients, in part due to frequent resistance to multiple classes of antifungal drugs. We identify a class of compounds, the dihalogenated 8-hydroxyquinolines, with broad fungistatic ability against a diverse collection of 13 strains of C. auris. Although this compound has been identified in previous screens, we extended the analysis by showing that C. auris developed only modest twofold to fivefold increases in resistance to this class of compounds despite long-term exposure; a noticeable difference from the 30- to 500-fold increases in resistance reported for similar studies with commonly used antifungal drugs. We also identify the mutations underlying the resistance. These results suggest that the dihalogenated 8-hydroxyquinolines are working inside the fungal cell and should be developed further to combat C. auris and other fungal pathogens. Lohse and colleagues characterize a class of compounds that inhibit the fungal pathogen C. auris. Unlike many other antifungal drugs, C. auris does not readily develop resistance to this class of compounds.

Identification of small molecule inhibitors against MMP-14 via High-Throughput screening.

Matrix metalloproteinases (MMPs) are involved in various cellular events in physiology and pathophysiology through endopeptidases activity. The expression levels and activities of most MMPs remain minimal in the normal conditions, whereas some MMPs are significantly activated in pathological conditions such as cancer and neovascularization. Hence, MMPs are considered as both diagnostic markers and potential targets for therapeutic agents. Twenty-three known human MMPs share a similar active site structure with a zinc-binding motif, resulting in lack of specificity. Therefore, the enhancement of target specificity is a primary goal for the development of specific MMP inhibitors. MMP-14 regulates VEGFA/VEGFR2-system through cleavage of the non-functional VEGFR1 in vascular angiogenesis. In this study, we developed a fluorescence-based enzymatic assay using a specific MMP-14 substrate generated from VEGFR1 cleavage site. This well optimized assay was used as a primary screen method to identify MMP-14 specific inhibitors from 1,200 Prestwick FDA-approved drug library. Of ten initial hits, two compounds showed IC50 values below 30 µM, which were further validated by direct binding analysis using surface plasmon resonance (SPR). Clioquinol and chloroxine, both of which contain a quinoline structure, were identified as MMP-14 inhibitors. Five analogs were tested, four of which were found to be completely devoid of inhibitory activity. Clioquinol exhibited selectivity towards MMP-14, as it showed no inhibitory activity towards four other MMPs.

Development of Clioquinol Platinum(IV) Conjugates as Autophagy-Targeted Antimetastatic Agents.

A series of autophagy-targeted antimetastatic clioquinol (CLQ) platinum(IV) conjugates were designed and prepared by incorporating an autophagy activator CLQ into the platinum(IV) system. Complex 5 with the cisplatin core bearing dual CLQ ligands with potent antitumor properties was screened out as a candidate. More importantly, it displayed potent antimetastatic properties both in vitro and in vivo as expected. Mechanism investigation manifested that complex 5 induced serious DNA damage to increase γ-H2AX and P53 expression and caused mitochondria-mediated apoptosis through the Bcl-2/Bax/caspase3 pathway. Then, it promoted prodeath autophagy by suppressing PI3K/AKT/mTOR signaling and activating the HIF-1α/Beclin1 pathway. The T-cell immunity was elevated by restraining the PD-L1 expression and subsequently increasing CD3+ and CD8+ T cells. Ultimately, metastasis of tumor cells was suppressed by the synergistic effects of DNA damage, autophagy promotion, and immune activation aroused by CLQ platinum(IV) complexes. Key proteins VEGFA, MMP-9, and CD34 tightly associated with angiogenesis and metastasis were downregulated.

Inhibitory mechanism of clioquinol and its derivatives at the exopeptidase site of human angiotensin-converting enzyme-2 and receptor binding domain of SARS-CoV-2 viral spike.

The outbreak of SARS-CoV-2 infections around the world has prompted scientists to explore different approaches to develop therapeutics against COVID-19. This study focused on investigating the mechanism of inhibition of clioquinol (CLQ) and its derivatives (7-bromo-5-chloro-8-hydroxyquinoline (CLBQ), 5, 7-Dichloro-8-hydroxyquinoline (CLCQ)) against the viral glycoprotein, and human angiotensin-converting enzyme-2 (hACE-2) involved in SARS-CoV-2 entry. The drugs were docked at the exopeptidase site of hACE-2 and receptor binding domain (RBD) sites of SARS-CoV-2 Sgp to calculate the binding affinity of the drugs. To understand and establish the inhibitory characteristics of the drugs, molecular dynamic (MD) simulation of the best fit docking complex performed. Evaluation of the binding energies of the drugs to hACE-2 after 100 ns MD simulations revealed CLQ to have the highest binding energy value of -40.4 kcal/mol close to MLN-7640 (-45.4 kcal/mol), and higher than the exhibited values for its derivatives: CLBQ (-34.5 kcal/mol) and CLCQ (-24.8 kcal/mol). This suggests that CLQ and CLBQ bind more strongly at the exopeptidase site than CLCQ. Nevertheless, the evaluation of binding affinity of the drugs to SARS-CoV-2 Sgp showed the drugs are weakly bound at the RBD site, with CLBQ, CLCQ, CLQ exhibiting relatively low energy values of -16.8 kcal/mol, -16.34 kcal/mol, -12.5 kcal/mol, respectively compared to the reference drug, Bisoxatin (BSX), with a value of -25.8 kcal/mol. The structural analysis further suggests decrease in systems stability and explain the mechanism of inhibition of clioquinol against SARS-CoV-2 as reported in previous in vitro study.Communicated by Ramaswamy H. Sarma.

Clioquinol induces autophagy by down-regulation of calreticulin in human neurotypic SH-SY5Y cells.

Clioquinol (CQ) is considered as a promising drug of neurodegenerative diseases. However, the underlying mechanism is unclear. Our previous study has proved that CQ induces S-phase cell cycle arrest through the elevation of intracellular calcium concentration ([Ca2+]i) with high levels of SERCA2. Furthermore, it could induce autophagy in an intracellular calcium independent manner in human neurotypic SH-SY5Y cells. In this study, the involvement of calreticulin (CRT) in autophagy induced by CQ was investigated. Our results illustrated the endoplasmic reticulum (ER) stress induced by CQ and DTT led to the cell death in different manners. DTT, an ER stress positive control, induced UPR accompanied with up-regulation of CRT and apoptosis, while CQ inhibited UPR accompanied with down-regulation of CRT，resulting in autophagy. Then, overexpression of CRT was shown to cause UPR and decrease [Ca2+]i, leading to cell apoptosis and inhibition of S-phase arrest induced by CQ. While the UPR was alleviated and autophagy was further enhanced in CRT deficient cells by using targeted siRNA. Meanwhile, down-regulation of CRT resulted in [Ca2+]i overload and induction of S-phase arrest. Finally, we found that the effect of CQ on the HT22 cells was similar to that on the SH-SY5Y cells. Our data showed for the first time that CQ decreased expression of CRT, leading to autophagy, an increase of [Ca2+]i, and cell S-phase arrest in the neurotypic cells. The present study describes the cellular signal pathways regulating autophagy by CQ and highlights the potential therapeutic application of CQ in neurodegenerative disorders.

Discovery of novel hybrids containing clioquinol-1-benzyl-1,2,3,6-tetrahydropyridine as multi-target-directed ligands (MTDLs) against Alzheimer's disease.

Based on the multitarget strategy, a series of novel clioquinol-1-benzyl-1,2,3,6-tetrahydropyridine hybrids were identified for the potential treatment of Alzheimer's disease (AD). Biological evaluation in vitro revealed that these hybrids exhibited significant inhibitory activities toward acetylcholinesterase (AChE). The optimal compound, 19n, exhibited excellent AChE inhibitory potency (IC50 = 0.11 µM), appropriate metal chelating functions, modulation of AChE- and metal-induced Aß aggregation, neuroprotection against okadaic acid-induced mitochondrial dysfunction and ROS damage, and interesting properties that reduced p-Tau levels in addition to no toxicity on SH-SY5Y cells observed at a concentration up to 50 µM. Most importantly, compound 19n was more well tolerated (>1200 mg/kg) than donepezil (LD50 = 28.124 mg/kg) in vivo. Moreover, compound 19n demonstrated marked improvements in cognitive and spatial memory in two AD mice models (scopolamine-induced and Aß1-42-induced) and suppressed inflammation induced by Aß1-42 in the cortex. The multifunctional profiles of compound 19n demonstrate that it deserves further investigation as a promising lead in the development of innovatively multifunctional drugs for Alzheimer's disease.

Alzheimer's Drug PBT2 Interacts with the Amyloid ß 1-42 Peptide Differently than Other 8-Hydroxyquinoline Chelating Drugs.

Although Alzheimer's disease (AD) was first described over a century ago, it remains the leading cause of age-related dementia. Innumerable changes have been linked to the pathology of AD; however, there remains much discord regarding which might be the initial cause of the disease. The "amyloid cascade hypothesis" proposes that the amyloid ß (Aß) peptide is central to disease pathology, which is supported by elevated Aß levels in the brain before the development of symptoms and correlations of amyloid burden with cognitive impairment. The "metals hypothesis" proposes a role for metal ions such as iron, copper, and zinc in the pathology of AD, which is supported by the accumulation of these metals within amyloid plaques in the brain. Metals have been shown to induce aggregation of Aß, and metal ion chelators have been shown to reverse this reaction in vitro. 8-Hydroxyquinoline-based chelators showed early promise as anti-Alzheimer's drugs. Both 5-chloro-7-iodo-8-hydroxyquinoline (CQ) and 5,7-dichloro-2-[(dimethylamino)methyl]-8-hydroxyquinoline (PBT2) underwent unsuccessful clinical trials for the treatment of AD. To gain insight into the mechanism of action of 8HQs, we have investigated the potential interaction of CQ, PBT2, and 5,7-dibromo-8-hydroxyquinoline (B2Q) with Cu(II)-bound Aß(1-42) using X-ray absorption spectroscopy (XAS), high energy resolution fluorescence detected (HERFD) XAS, and electron paramagnetic resonance (EPR). By XAS, we found CQ and B2Q sequestered ∼83% of the Cu(II) from Aß(1-42), whereas PBT2 sequestered only ∼59% of the Cu(II) from Aß(1-42), suggesting that CQ and B2Q have a higher relative Cu(II) affinity than PBT2. From our EPR, it became clear that PBT2 sequestered Cu(II) from a heterogeneous mixture of Cu(II)Aß(1-42) species in solution, leaving a single Cu(II)Aß(1-42) species. It follows that the Cu(II) site in this Cu(II)Aß(1-42) species is inaccessible to PBT2 and may be less solvent-exposed than in other Cu(II)Aß(1-42) species. We found no evidence to suggest that these 8HQs form ternary complexes with Cu(II)Aß(1-42).

The Zinc Ionophore Clioquinol Reduces Parkinson's Disease Patient-Derived Brain Extracts-Induced Neurodegeneration.

Parkinson's disease (PD) is pathologically characterized by intracellular α-synuclein-rich protein aggregates, named Lewy bodies (LB), and by the progressive loss of dopaminergic neurons in the substantia nigra. Several heavy metals, including zinc (Zn), have been suggested to play a role in PD progression, although the exact role of Zn in neurodegeneration remains to be fully elucidated. To address this gap, we investigated the effects of Zn modulation on the progression of degeneration in mice injected with PD patient-derived LB-extracts carrying toxic α-synuclein aggregates. Zn modulation was achieved using either a clioquinol-enriched diet, a Zn ionophore that redistributes cellular Zn, or a Zn-enriched diet that increases Zn levels. Clioquinol treatment significantly prevented dopaminergic neurodegeneration and reduced α-synuclein-associated pathology in LB-injected mice, while no differences were observed with Zn supplementation. Biochemical analyses further demonstrate that the expression levels of vesicle-specific Zn transporter ZnT3 in the striatum of LB-injected mice treated with clioquinol were decreased, suggesting an intracellular redistribution of Zn. Additionally, we found that clioquinol modulates the autophagy-lysosomal pathway by enhancing lysosomal redistribution within the neuronal compartments. Collectively, we found that in vivo pharmacological chelation of Zn, by dampening Zn-mediated cytotoxicity, can result in an overall attenuation of PD-linked lysosomal alterations and dopaminergic neurodegeneration. The results support zinc chelation as a disease-modifying strategy for treating PD.

Antimicrobial activity of clioquinol and nitroxoline: a scoping review.

Clioquinol and nitroxoline, two drugs with numerous pharmacological properties fallen into disuse for many decades. The first was considered dangerous due to contraindications and the second mainly because was taken as ineffective, despite its known antibacterial activity. In the last decades, the advances in pharmaceutical chemistry, molecular biology, toxicology and genetics allowed to better understand the cellular action of these compounds, some toxicological issues and/or activity scopes. Thus, a new opportunity for these drugs to be considered as potential antimicrobial agents has arisen. This review contemplates the trajectory of clioquinol and nitroxoline from their emergence to the present day, emphasizing the new studies that indicate the possibility of reintroduction for specific cases.

Dysregulation of Streptococcus pneumoniae zinc homeostasis breaks ampicillin resistance in a pneumonia infection model.

Streptococcus pneumoniae is the primary cause of community-acquired bacterial pneumonia with rates of penicillin and multidrug-resistance exceeding 80% and 40%, respectively. The innate immune response generates a variety of antimicrobial agents to control infection, including zinc stress. Here, we characterize the impact of zinc intoxication on S. pneumoniae, observing disruptions in central carbon metabolism, lipid biogenesis, and peptidoglycan biosynthesis. Characterization of the pivotal peptidoglycan biosynthetic enzyme GlmU indicates a sensitivity to zinc inhibition. Disruption of the sole zinc efflux pathway, czcD, renders S. pneumoniae highly susceptible to ß-lactam antibiotics. To dysregulate zinc homeostasis in the wild-type strain, we investigated the safe-for-human-use ionophore 5,7-dichloro-2-[(dimethylamino)methyl]quinolin-8-ol (PBT2). PBT2 rendered wild-type S. pneumoniae strains sensitive to a range of antibiotics. Using an invasive ampicillin-resistant strain, we demonstrate in a murine pneumonia infection model the efficacy of PBT2 + ampicillin treatment. These findings present a therapeutic modality to break antibiotic resistance in multidrug-resistant S. pneumoniae.

Founder genetic variants of ABCC4 and ABCC11 in the Japanese population are not associated with the development of subacute myelo-optico-neuropathy (SMON).

BACKGROUND: Subacute myelo-optico-neuropathy (SMON) is a severe neurological disorder associated with clioquinol administration, which frequently occurred in Japan during the 1950s and 1960s. The unique genetic background of the Japanese population is considered to be strongly involved in the development of this neurological disease. Recently, genetic variants of ABCC4 (OMIM: 605250) and ABCC11 (OMIM: 607040), which are particularly common in the Japanese population, were suggested as possible genetic susceptibility factors for the development of SMON. METHODS: We analyzed 125 Japanese SMON patients who provided consent for this study. Patient DNA was collected from peripheral blood, and genetic analysis was performed for ABCC4 rs3765534 (c.2268G>A, p.Glu857Lys) and ABCC11 rs17822931 (c.538G>A, p.Gly180Arg) polymorphisms using the Sanger sequencing method and/or TaqMan PCR method. The frequency distribution of each polymorphism was compared with that in healthy Japanese people recorded in two genomic databases (Human Genomic Variation Database and Integrative Japanese Genome Variation Database), and each genotype was compared with the clinical features of patients. RESULTS: The frequencies of ABCC4 rs3765334 and ABCC11 rs17822931 polymorphisms in SMON patients and healthy Japanese people were not significantly different in the multifaceted analysis. CONCLUSION: We conclude that the ABCC4 rs3765334 and ABCC11 rs17822931 polymorphisms are not associated with the development of SMON.

Synthesis of new clioquinol derivatives as potent α-glucosidase inhibitors; molecular docking, kinetic and structure-activity relationship studies.

Diabetes mellitus is a chronic metabolic disorder with increasing prevalence and long-term complications. The aim of this study was to identify α-glucosidase inhibitory compounds with potential anti-hyperglycemic activity. For this purpose, a series of new clioquinol derivatives 2a-11a was synthesized, and characterized by various spectroscopic techniques. The enzyme inhibitory activities of the resulting derivatives were assessed using an in-vitro mechanism-based assay. All the tested compounds 2a-11a of the series showed a significant α-glucosidase inhibition with IC50 values 43.86-325.81 µM, as compared to the standard drug acarbose 1C50: 875.75 ± 2.08 µM. Among them, compounds 4a, 5a, 10a, and 11a showed IC50 values of 105.51 ± 2.41, 119.24 ± 2.37, 99.15 ± 2.06, and 43.86 ± 2.71 µM, respectively. Kinetic study of the active analogues showed competitive, non-competitive, and mixed-type inhibitions. Furthermore, the molecular docking study was performed to elucidate the binding interactions of most active analogues with the various sites of α-glucosidase enzyme. The results indicate that these compounds have the potential to be further studied as new anti-diabetic agents.

Clioquinol Decreases Levels of Phosphorylated, Truncated, and Oligomerized Tau Protein.

The neuropathological hallmarks of Alzheimer's disease (AD) are senile plaques (SPs), which are composed of amyloid ß protein (Aß), and neurofibrillary tangles (NFTs), which consist of highly phosphorylated tau protein. As bio-metal imbalance may be involved in the formation of NFT and SPs, metal regulation may be a direction for AD treatment. Clioquinol (CQ) is a metal-protein attenuating compound with mild chelating effects for Zn2+ and Cu2+, and CQ can not only detach metals from SPs, but also decrease amyloid aggregation in the brain. Previous studies suggested that Cu2+ induces the hyperphosphorylation of tau. However, the effects of CQ on tau were not fully explored. To examine the effects of CQ on tau metabolism, we used a human neuroblastoma cell line, M1C cells, which express wild-type tau protein (4R0N) via tetracycline-off (TetOff) induction. In a morphological study and ATP assay, up to 10 µM CQ had no effect on cell viability; however, 100 µM CQ had cytotoxic effects. CQ decreased accumulation of Cu+ in the M1C cells (39.4% of the control), and both total and phosphorylated tau protein. It also decreased the activity of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK) (37.3% and 60.7% levels of the control, respectively), which are tau kinases. Of note, activation of protein phosphatase 2A (PP2A), which is a tau phosphatase, was also observed after CQ treatment. Fractionation experiments demonstrated a reduction of oligomeric tau in the tris insoluble, sarkosyl soluble fraction by CQ treatment. CQ also decreased caspase-cleaved tau, which accelerated the aggregation of tau protein. CQ activated autophagy and proteasome pathways, which are considered important for the degradation of tau protein. Although further studies are needed to elucidate the mechanisms responsible for the effects of CQ on tau, CQ may shed light on possible AD therapeutics.

Amplified Peroxidase-like Activity of Co2+ Using 8-Hydroxyquinoline and Its Application for Ultrasensitive Colorimetric Detection of Clioquinol.

8-Hydroxyquinoline (8HQ) and its derivatives display diverse bioactivities and therapeutic potentials. In this study, we unveiled that 8HQ can boost the peroxidase-like activity of Co2+ in the presence of bicarbonate (HCO3 - ) in neutral pH at room temperature. With 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonate) (ABTS) as the substrate, the formed Co2+ /8HQ/HCO3 - complex shows robust catalytic activity with the turnover number (kcat ) tens to hundreds of times higher than that of Co3 O4 and other Co2+ complexes in terms of per cobalt ion. This system was used to design colorimetric sensors for ultrasensitive detection of 8HQ-based drugs by activating the activity of Co2+ . Take detecting clioquinol as an example, a detection limit of 2.4 nM clioquinol with a linear range from 0.01 to 0.2 µM was obtained. This work not only revealed a new kind of ligand that activated the activity of Co2+ , but also provided a facile, low-cost, ultrasensitive, easy-to-use, and universal strategy for sensing various 8HQ-based drugs. Further development of this catalytic system might be beneficial to overcome drug resistance by combined medication.