Mechanism of DNA Intercalation by Chloroquine Provides Insights into Toxicity.

Chloroquine has been used as a potent antimalarial, anticancer drug, and prophylactic. While chloroquine is known to interact with DNA, the details of DNA-ligand interactions have remained unclear. Here we characterize chloroquine-double-stranded DNA binding with four complementary approaches, including optical tweezers, atomic force microscopy, duplex DNA melting measurements, and isothermal titration calorimetry. We show that chloroquine intercalates into double stranded DNA (dsDNA) with a KD ~ 200 µM, and this binding is entropically driven. We propose that chloroquine-induced dsDNA intercalation, which happens in the same concentration range as its observed toxic effects on cells, is responsible for the drug's cytotoxicity.

Evaluation of weak genotoxicity of hydroxychloroquine in human TK6 cells.

Hydroxychloroquine (HCQ), a derivative of chloroquine (CQ), is an antimalarial and antirheumatic drug. Since there is limited data available on the genotoxicity of HCQ, in the current study, we used a battery of in vitro assays to systematically examine the genotoxicity of HCQ in human lymphoblastoid TK6 cells. We first showed that HCQ is not mutagenic in TK6 cells up to 80 µM with or without exogenous metabolic activation. Subsequently, we found that short-term (3-4 h) HCQ treatment did not cause DNA strand breakage as measured by the comet assay and the phosphorylation of histone H2A.X (γH2A.X), and did not induce chromosomal damage as determined by the micronucleus (MN) assay. However, after 24-h treatment, both CQ and HCQ induced comparable and weak DNA damage and MN formation in TK6 cells; upregulated p53 and p53-mediated DNA damage responsive genes; and triggered apoptosis and mitochondrial damage that may partially contribute to the observed MN formation. Using a benchmark dose (BMD) modeling analysis, the lower 95% confidence limit of BMD50 values (BMDL50) for MN induction in TK6 cells were about 19.7 µM for CQ and 16.3 µM for HCQ. These results provide additional information for quantitative genotoxic risk assessment of these drugs.

Antioxidants and mitochondrial/lysosomal protective agents reverse toxicity induced by titanium dioxide nanoparticles on human lymphocytes.

Most of the literature has focused on titanium dioxide (TiO2) nanoparticles (NPs) toxicity, showing the importance of oxidative stress, mitochondrial dysfunction, and cell death in TiO2-induced toxicity. For this purpose, in the current study, we investigated the protective role of antioxidant and mitochondrial/lysosomal protective agents to minimize TiO2 NPs-induced toxicity in human lymphocytes. Human lymphocytes were obtained from heathy individuals and treated with different concentrations (80, 160, and 320 µg/mL) of TiO2 NPs, and then human lymphocytes preincubated with butylated hydroxytoluene (BHT), cyclosporin A (CsA), and chloroquine separately were exposed to TiO2 NPs for 6 h. In all the above-mentioned treated groups, adverse parameters such as cytotoxicity, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), lysosomal membrane destabilization, the levels of malondialdehyde (MDA), and glutathione (GSH) were measured. The results showed that TiO2 nanoparticles induced cytotoxicity through ROS formation, MMP collapse, lysosomal damages, depletion of GSH, and lipid peroxidation. However, BHT as an antioxidant, CsA as a mitochondrial permeability transition (MPT) pore sealing agent, and chloroquine as a lysosomotropic agent, significantly inhibited all the TiO2 NPs-induced cellular and organelle toxicities. Thus, it seems that antioxidant and mitochondrial/lysosomal protective agents are promising preventive strategies against TiO2 NPs-induced toxicity.

Impaired Lysosome Reformation in Chloroquine-Treated Retinal Pigment Epithelial Cells.

Purpose: To model the in vivo effects of chloroquine on the retinal pigment epithelium in experimentally tractable cell culture systems and determine the effects of mild chloroquine treatment on lysosome function and turnover. Methods: Effects of low-dose chloroquine treatment on lysosomal function and accessibility to newly endocytosed cargo were investigated in primary and embryonic stem cell-derived RPE cells and ARPE19 cells using fluorescence and electron microscopy of fluorescent and gold-labeled probes. Lysosomal protein expression and accumulation were measured by quantitative PCR and Western blotting. Results: Initial chloroquine-induced lysosome neutralization was followed by partial recovery, lysosomal expansion, and accumulation of undegraded endocytic, phagocytic, and autophagic cargo and inhibition of cathepsin D processing. Accumulation of enlarged lysosomes was accompanied by a gradual loss of accessibility of these structures to the endocytic pathway, implying impaired lysosome reformation. Chloroquine-induced accumulation of pro-cathepsin D, as well as the lysosomal membrane protein, LAMP1, was reproduced by treatment with protease inhibitors and preceded changes in lysosomal gene expression. Conclusions: Low-dose chloroquine treatment inhibits lysosome reformation, causing a gradual depletion of lysosomes able to interact with cargo-carrying vacuoles and degrade their content. The resulting accumulation of newly synthesized pro-cathepsin D and LAMP1 reflects inhibition of normal turnover of lysosomal constituents and possibly lysosomes themselves. A better understanding of the mechanisms underlying lysosome reformation may reveal new targets for the treatment of chloroquine-induced retinopathy.

Chloroquine Intervenes Nephrotoxicity of Nilotinib through Deubiquitinase USP13-Mediated Stabilization of Bcl-XL.

Nephrotoxicity has become prominent due to the increase in the clinical use of nilotinib, a second-generation BCR-ABL1 inhibitor in the first-line treatment of Philadelphia chromosome-positive chronic myeloid leukemia. To date, the mechanism of nilotinib nephrotoxicity is still unknown, leading to a lack of clinical intervention strategies. Here, it is found that nilotinib could induce glomerular atrophy, renal tubular degeneration, and kidney fibrosis in an animal model. Mechanistically, nilotinib induces intrinsic apoptosis by specifically reducing the level of BCL2 like 1 (Bcl-XL) in both vascular endothelial cells and renal tubular epithelial cells, as well as in vivo. It is confirmed that chloroquine (CQ) intervenes with nilotinib-induced apoptosis and improves mitochondrial integrity, reactive oxygen species accumulation, and DNA damage by reversing the decreased Bcl-XL. The intervention effect is dependent on the alleviation of the nilotinib-induced reduction in ubiquitin specific peptidase 13 (USP13) and does not rely on autophagy inhibition. Additionally, it is found that USP13 abrogates cell apoptosis by preventing excessive ubiquitin-proteasome degradation of Bcl-XL. In conclusion, the research reveals the molecular mechanism of nilotinib's nephrotoxicity, highlighting USP13 as an important regulator of Bcl-XL stability in determining cell fate, and provides CQ analogs as a clinical intervention strategy for nilotinib's nephrotoxicity.

New sight into interaction between endoplasmic reticulum stress and autophagy induced by vanadium in duck renal tubule epithelial cells.

Vanadium (V) is a common environmental and industrial pollutant that can cause nephrotoxicity in animals in excess. The purpose of this research was to explore the interaction between endoplasmic reticulum (ER) stress and autophagy induced by V in the kidney of ducks. Duck renal tubule epithelial cells were exposed to different concentrations of sodium metavanadate (NaVO3) (0, 100 and 200 µM) and PERK inhibitor (GSK, 1 µM), or autophagy inhibitor (chloroquine, 50 µM) alone for 24 h (chloroquine for the last 4 h). The results showed that exposure to V caused the dilatation and swelling of the ER and intracellular calcium overload, and upregulated PERK, eIF2α, ATF4 and CHOP mRNA levels and p-PERK and CHOP protein levels associated with ER stress in cells. Additionally, V markedly increased the number of autophagosomes, acidic vesicular organelles (AVOs) and LC3 puncta, as well as the mRNA levels of Beclin1, Atg5, Atg12, LC3A and LC3B and protein levels of Beclin1, Atg5 and LC3B-II/LC3B-I, but decreased the imRNA and protein levels of p62. Moreover, treatment with the PERK inhibitor ameliorated the changed factors above induced by V, but the V-induced variation of ER-stress related factors were aggravated after treatment with the autophagy inhibitor. Together, our data suggested that excessive V could induce ER stress and autophagy in duck renal tubular epithelial cells. ER stress might promote V-induced autophagy via the PERK/ATF4/CHOP signaling pathway, and autophagy may play a role in alleviating ER stress induced by V.

Casein kinase I inhibitor D4476 influences autophagy and apoptosis in chloroquine-induced adult retinal pigment epithelial-19 cells.

The antimalarial drug chloroquine (CQ) induces retinopathy, a disorder characterized by lysosomotropic alteration. In this study, we examined whether D4476 (4-(4-(2,3-dihydrobenzo [1,4] dioxin-6-yl)-5-pyridin-2-yl-1H-imidazole-2-yl) benzamide), a specific casein kinase 1 inhibitor, alleviate CQ-induced retinopathy in adult retinal pigment epithelial (ARPE-19) cells. Cultured ARPE-19 cells were exposed to CQ with or without D4476 and cell death was quantified using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. To examine autophagy flux, ARPE-19 cells were transfected with green fluorescence protein light chain 3 (GFP-LC3)-red fluorescence protein (RFP)-LC3ΔG plasmid DNA and co-stained with the lysosomal-associated membrane protein (LAMP)-1 antibody. Western blotting and fluorescence-activated cell sorting (FACS) showed apoptosis, whereas the fluorescence intensity of 2'-7'-dichlorofluorescein diacetate revealed levels of cellular oxidative stress. We then confirmed the effect of D4476 on the interaction between Beclin 1 and B-cell lymphoma-2 (Bcl-2) through immunoprecipitation with an anti-Bcl-2 antibody. Following CQ exposure, ARPE-19 cells accumulated autophagosomes because of defective lysosomal degradation. Furthermore, CQ trapped Beclin 1 with Bcl-2, disturbing autophagy initiation and autolysosome formation. However, D4476 alleviated CQ-induced effects by rescuing ARPE-19 cells from CQ-induced toxicity by modulating the association between Beclin 1 and Bcl-2. Therefore, D4476 controls autophagy and apoptosis simultaneously by upregulating autophagy flux, decreasing ROS formation, and triggering the expression of anti-apoptotic proteins through inhibition of mTOR, JNK, and p38 MAPK signals. We conclude that D4476 is a promising treatment strategy for CQ-mediated retinopathy.

Effects of Chloroquine and Hydroxychloroquine on the Cardiovascular System - Limitations for Use in the Treatment of COVID-19

Abstract Chloroquine (CQ) and Hydroxychloroquine (HCQ) are antimalarial drugs, with anti-inflammatory properties that justify their use in the treatment of systemic lupus erythematosus and rheumatic diseases. A pandemic caused by the new coronavirus led the entire world's scientific community to look for drugs already available on the market, capable of exercising beneficial actions in the fight against the disease. Preliminary studies in patients, as well as in vitro studies, suggested possible therapeutic effects associated with the use of HCQ and CQ in the treatment of COVID-19. Despite controversies over the effects of these drugs in combating the "cytokine storm" associated with COVID and the dismal of results in different clinical trials in Brazil, their use has been encouraged and several ongoing investigative studies are underway. In addition to the possible beneficial effects on the prognosis of patients with SARS-CoV-2, such drugs include varied effects on the cardiovascular system, ranging from positive developments related to their vasodilator properties to potential negative effects, such as cardiotoxicity. This work presents the main effects exerted by these drugs on the cardiovascular system, in order to contribute to a scientific discussion about the repurposing of these drugs in the context of COVID-19.

Afectaciones oftalmológicas causadas por la infección del SARS-CoV-2 / Ophthalmologic conditions caused by SARS-Cov-2 infections

La epidemia de la enfermedad por coronavirus del año 2019 (COVID-19) comenzó en Wuhan, en la provincia de Hubei, China, y en poco tiempo se extendió a otros continentes.1 El primer médico en alertar sobre esta nueva enfermedad en China fue Li Wenliang, especialista en oftalmología que enfermó y falleció a causa de la enfermedad.2 La transmisión de mayor rapidez se reporta por vía respiratoria, aunque existen estudios que describen la existencia de transmisibilidad del síndrome respiratorio agudo grave 2 (SARS-CoV-2 por sus siglas en inglés) mediante la lágrima y la conjuntiva de los pacientes infectados por COVID-19.3 La primera evidencia sobre esta vía de contagio se relata desde el 22 de enero, cuando Guangfa Wang, miembro del panel nacional de expertos en neumonía, informó que fue infectado por el SARS-CoV-2 durante la inspección en Wuhan. Llevaba una máscara N95 pero no usaba equipamiento para proteger sus ojos. Varios días antes del inicio de la neumonía, Wang se quejó de enrojecimiento ocular.4 Varios autores plantean que particularmente el conducto lagrimal funciona como un canal para recoger y transportar el fluido lagrimal desde la superficie ocular hasta el meato nasal inferior. Esto es conveniente para el drenaje del virus desde los tejidos del tracto ocular hasta el tracto respiratorio. Otra teoría propuesta para la afección oftalmológica es la diseminación del virus por vía hematógena a la glándula lagrimal.4,5 Algunos protocolos presentaron casos de aislamiento de cultivos en uno de cada tres pacientes, procedentes de muestras lagrimales, sin precisarse el mecanismo exacto al momento de cómo es que su diseminación culmina a ese nivel. Algunas de las propiedades de afinidad del el SARS-CoV-2 se debe a la alta adherencia de las células diana de la enzima convertidora de angiotensinógeno II (ACE2). De este modo, participan a nivel sistémico en los diferentes ejes, como el sistema renina-angiotensina-aldosterona, para así ejercer su virulencia.3 Sobre su cuadro clínico se describe como característica la presencia de conjuntivitis viral inespecífica. Además se reportan alteraciones atípicas como anosmia, hiposmia y disgeusia. Estas últimas corresponden al cuadro del protocolo inicial del interrogatorio por parte de la Sociedad de Oftalmología de México, España e Italia.3 Lu Chen, Meizhou Liu y otros6 del Hospital Chinchen, en China, reportaron en marzo de 2020 manera específica las manifestaciones oculares en relación con el SARS-CoV-2. Se trata de un paciente positivo mediante la prueba de reacción en cadena de la polimerasa con transcriptasa inversa (RT-PCR), con conjuntivitis folicular viral bilateral, con 19 días de evolución, donde se destaca la aparición de manifestaciones oculares como: ojo rojo, sensación de cuerpo extraño, epífora y visión borrosa, todo esto de manera bilateral. A la exploración por biomicroscopia se pueden definir hallazgos como: inyección conjuntival moderada; secreciones acuosas; nodulaciones foliculares conjuntivales en párpado inferior sin presentarse hemorragia; y manifestaciones en córnea, segmento anterior o posterior.3 Científicos brasileños han descrito en The Lancet algunas alteraciones en la retina de pacientes de COVID-19 utilizando la Tomografía de Coherencia Óptica (OCT), y han encontrado microhemorragias y lesiones a nivel de la capa de células ganglionares y de la plexiforme interna.1,2 La presencia de COVID-19 ha determinado la posible progresión de enfermedades tales como: el glaucoma crónico, la retinopatía diabética, la degeneración macular asociada a la edad, enfermedades corneales e inflamatorias, entre otras.5 Se ha descrito la presencia del SARS-CoV-2 en las lágrimas de pacientes con COVID-19.3 Algunos estudios confirman que los pacientes con síntomas oculares tenían más probabilidades de tener recuentos más altos de glóbulos blancos y neutrófilos y mayores niveles de procalcitonina, proteína C reactiva y lactato deshidrogenasa que los pacientes sin síntomas oculares, lo cual evidencia mayor gravedad del cuadro.4 En el Tratamiento de la COVID-19 se han estudiado determinados fármacos que pudieran producir alteraciones oftalmológicas.1 La cloroquina y la hidroxicloroquina, con efecto antiviral, causarían toxicidad ocular con altas dosis y tratamientos prolongados la expresión de dicha toxicidad se manifiesta por la aparición de depósitos corneales, catarata subcapsular posterior, disfunción del cuerpo ciliar y retinopatía. Por otra parte se ha confirmado que el Lopinavir/ritonavir (Kaletra) tiene entre sus efectos adversos sistémicos la hepatopatía, que puede provocar un tinte ictérico conjuntival.5 Consideramos que, al tratarse de un virus con tan fácil diseminación, el contagio por vía ocular es una posibilidad real e inminente, por ello se precisan de manera intencionada las medidas de protección ocular, sobre todo para el personal de salud. Dentro de ellos el personal que brinda atención oftalmológica es especialmente vulnerable por su proximidad a las vías respiratorias y ojos de pacientes. Los sistemas de salud deberán garantizar recursos de desinfección y control necesarios para evitar la propagación de la enfermedad(AU)

TNFα enhances trovafloxacin-induced in vitro hepatotoxicity by inhibiting protective autophagy.

Trovafloxacin (TVX) is associated with idiosyncratic drug-induced liver injury (iDILI) and inflammation-mediated hepatotoxicity. However, the inflammatory stress-regulated mechanisms in iDILI remain unclear. Herein, we elucidated the novel role of tumor-necrosis factor alpha (TNFα), an inflammatory stress factor, in TVX-induced in vitro hepatotoxicity and synergistic toxicity. TVX specifically induced synergistic toxicity in HepG2 cells with TNFα, which inhibits autophagy. TVX-treated HepG2 cells induced protective autophagy by inhibiting the expression of mTOR signaling proteins, while ATG5 knockdown in HepG2 cells, responsible for the impairment of autophagy, enhanced TVX-induced toxicity due to the increase in cytochrome C release and JNK pathway activation. Interestingly, the expression of mTOR signal proteins, which were suppressed by TVX, disrupted the negative feedback of the PI3K/AKT pathway and TNFα rebounded p70S6K phosphorylation. Co-treatment with TVX and TNFα inhibited protective autophagy by maintaining p70S6K activity, which enhanced TVX-induced cytotoxicity. Phosphorylation of p70S6K was inhibited by siRNA knockdown and rapamycin to restore TNFα-inhibited autophagy, which prevented the synergistic effect on TVX-induced cytotoxicity. These results indicate that TVX activates protective autophagy in HepG2 cells exposed to toxicity and an imbalance in negative feedback regulation of autophagy by TNFα synergistically enhanced the toxicity. The finding from this study may contribute to a better understanding of the mechanisms underlying iDILI associated with inflammatory stress.

Ototoxicity prevention during the SARS-CoV-2 (COVID-19) emergency.

Aim of this paper is to remind the risk of ototoxicity when using chloroquine and hydroxychloroquine, in particular as prophylactic agents against SARS-CoV-2, during the pandemic. Healthy subjects taking chloroquine and hydroxychloroquine as prophylactic agents against SARS-CoV-2, during the pandemic, should be screened periodically, at least by Otoacoustic Emissions (OAEs) in order to detect early manifestations of possible cochlear ototoxic damages.

Medical treatment options for COVID-19.

Therapeutic options for coronavirus disease 2019 are desperately needed to respond to the ongoing severe acute respiratory syndrome coronavirus 2 pandemic. Both antiviral drugs and immunomodulators might have their place in the management of coronavirus disease 2019. Unfortunately, no drugs have been approved yet to treat infections with human coronaviruses. As it will take years to develop new therapies for severe acute respiratory syndrome coronavirus 2, the current focus is on the repurposing of drugs that have been approved or are in development for other conditions. Several clinical trials have already been conducted or are currently ongoing to evaluate the efficacy of such drugs. Here, we discuss the potential of these therapies for the treatment of coronavirus disease 2019.

Efetividade e toxicidade da cloroquina e da hidroxicloroquina associada (ou não) à azitromicina para tratamento da COVID-19. O que sabemos até o momento? / Effectiveness and toxicity of chloroquine and hydroxychloroquine associated (or not) with azithromycin for the treatment of COVID-19. What do we know so far?

Objetivos: identificar as evidências científicas existentes até o presente momento sobre a efetividade do uso da cloroquina, da hidroxicloroquina associada (ou não) à azitromicina para tratamento da afecção pelo coronavírus e seus possíveis efeitos adversos e tóxicos aos seres humanos. Métodos: a revisão narrativa utilizou-se das bases de dados PubMed, LILACS, SciElo e Google Acadêmico. Nessas, buscaram-se estudos, utilizando-se dos descritores "covid", "coronavirus", "SARS-CoV-2", "chloroquine", "hydroxychloroquine", "azithromycin" e "adverse effects" junto com os operadores booleanos "AND" e "OR". Resultados: sete artigos, das trinta publicações encontradas, atenderam aos critérios de inclusão, sendo utilizados para compor a presente revisão. Dos sete ensaios clínicos analisados, cinco apresentaram resultados de cura e/ou remissão dos sintomas e/ou redução da carga viral dos pacientes, no entanto apresentaram muitas limitações. Conclusão: a literatura científica é escassa e divergente quanto à efetividade dos medicamentos cloroquina e hidroxicloroquina associada (ou não) à azitromicina no tratamento da COVID-19, pela rápida disseminação e instalação da pandemia na esfera global. É necessário a realização de ensaios clínicos pragmáticos, envolvendo um número maior de pacientes, para que seja possível analisar a efetividade no combate ao coronavírus, bem como a segurança do uso desses fármacos.(AU)

Objective: to identify the scientific evidence existing to date on the effectiveness of the use of chloroquine, hydroxychloroquine associated (or not) to azithromycin for the treatment of COVID-19 disease and its possible adverse drug events and toxicity to human health. Methods: the narrative review was performed using the PubMed, LILACS, SciElo and Google Academic databases. In these, studies were sought, using the descriptors "covid", "coronavirus", "SARS-CoV-2", "chloroquine", "hydroxychloroquine", "azithromycin", "adverse effects" and "toxicity", together with the Boolean operator "AND" and "OR". Results: seven studies of thirty publications met the inclusion criteria and were used in the present review. Of the seven clinical trials analyzed, five showed results of cure and/or remission of symptoms and/or reduction of patients' viral load, however these studies had many limitations. Conclusion: scientific literature is scarce and divergent as to the effectiveness of the drugs chloroquine and hydroxychloroquine associated (or not) with azithromycin in the treatment of COVID-19, due to the rapid spread and installation of the pandemic in the global sphere. It is necessary to carry out pragmatic clinical trials, involving a larger number of patients, so that it is possible to analyze the effectiveness in combating the coronavirus, as well as the safety of the use of these drugs.(AU)

The Chronic Adverse Effect of Chloroquine on Kidney in Rats through an Autophagy Dependent and Independent Pathways.

BACKGROUND: Chloroquine (CQ), a classic autophagy inhibitor, is used clinically for malaria prophylaxis and pulmonary hypertension treatment. The adverse effects of CQ on morphological and functional changes in the kidney were investigated in the current study due to CQ accumulation in the kidney. METHODS: Twelve male Sprague-Dawley rats were randomly divided into 2 groups for 4 weeks: group 1, control (n = 6); and group 2, CQ administration group (50 mg-1·kg per day ip; n = 6). Serum aldosterone and vasopressin were measured by radioimmunoassay. Immunofluorescence was used to colocalize Tunel with aquaporin 1, aquaporin 2 (AQP2), and Tamm-Horsfall protein. Expression of AQP2 and mineralocorticoid (MR) was detected by western blot and immunohistochemistry. RESULTS: In the present study, 4 weeks of CQ administration were shown to induce severe kidney injury, including glomerular sclerosis and tubular cells apoptosis, especially distal tubular cells. Decreased expression of LC3II/I and p-AKT was demonstrated in CQ-treated rats. Glomerular and proximal tubule injury were associated with impaired autophagy flux, and distal tubule injury may be associated with downregulated cyclic adenosine monophosphate (cAMP)/PKA/AKT signaling. Both MR and AQP2, which are mainly located in the distal tubule and collecting duct, were significantly reduced in CQ-treated rats, thus leading to increased exosomal secretion of AQP2 in urine. Additionally, chronic CQ administration increased aldosterone and vasopressin levels in serum, but lowered the blood pressure, glomerular filtration rate, and urine concentration. CONCLUSIONS: CQ administration damages glomerular, proximal tubule autophagy, and severe distal tubular cells apoptosis by inhibiting cAMP/PKA/AKT signaling.

Spinal somatostatin-positive interneurons transmit chemical itch.

Recent studies have made significant progress in identifying distinct populations of peripheral neurons involved in itch transmission, whereas the cellular identity of spinal interneurons that contribute to itch processing is still a debate. Combining genetic and pharmacological ablation of spinal excitatory neuronal subtypes and behavioral assays, we demonstrate that spinal somatostatin-positive (SOM) excitatory interneurons transmit pruritic sensation. We found that the ablation of spinal SOM/Lbx1 (SOM) neurons caused significant attenuation of scratching responses evoked by various chemical pruritogens (chemical itch). In an attempt to identify substrates of spinal itch neural circuit, we observed that spinal SOM neurons partially overlapped with neurons expressing natriuretic peptide receptor A (Npra), the receptor of peripheral itch transmitter B-type natriuretic peptide. Spinal SOM neurons, however, did not show any overlap with itch transmission neurons expressing gastrin-releasing peptide receptor in the dorsal spinal cord, and the gastrin-releasing peptide-triggered scratching responses were intact after ablating spinal SOM neurons. Dual ablation of SOM and Npra neurons in the spinal cord reduced chemical itch responses to a greater extent than ablation of SOM or Npra neurons alone, suggesting the existence of parallel spinal pathways transmitting chemical itch. Furthermore, we showed that SOM peptide modulated itch processing through disinhibition of somatostatin receptor 2A-positive inhibitory interneuron. Together, our findings reveal a novel spinal mechanism for sensory encoding of itch perception.

Polyhexamethylene biguanide and chloroquine induce programmed cell death in Acanthamoeba castellanii.

Several chemotherapeutic drugs have been described as amoebicidal agents acting against Acanthamoeba trophozoites and cysts. However, the underlying mechanism of action is poorly characterized. Here, we describe programmed cell death (PCD) in A. castellanii induced by polyhexamethylene biguanide (PHMB) and chloroquine. We used four types of amoebicidal agents including 0.02% PHMB, 0.02% chlorhexidine digluconate, 100 µM chloroquine, and 100 µM 2,6-dichlorobenzonitrile to kill Acanthamoeba trophozoites and cysts. Exposure to PHMB and chloroquine induced cell shrinkage and membrane blebbing in Acanthamoeba, observed microscopically. Externalization of phosphatidyl serine on the membranes of Acanthamoeba was detected by annexin V staining. Apoptotic cell death of Acanthamoeba by PHMB and chloroquine was confirmed by FACS analysis. Nuclear fragmentation of Acanthamoeba was demonstrated by DAPI staining. PHMB induced PCD in trophozoites and cysts, and chloroquine induced PCD in cysts. These findings are discussed to establish the most effective treatment for Acanthamoeba-induced keratitis.

Chloroquine as a possible disinfection adjunct of disinfection solutions against Acanthamoeba.

Acanthamoeba keratitis is commonly encountered by contact lens wearers. Contact lens solution plays an important role in the safe use of contact lenses. The most popular products for disinfecting lenses are multipurpose disinfecting solutions (MPDS). However, almost all MPDS retailed in Korea are ineffective in killing Acanthamoeba. The objective of this study was to determine the possibility of using autophagy inhibitor chloroquine as a disinfecting agent to improve the amoebicidal activity of MPDS against Acanthamoeba, especially the cyst. Amoebicidal effects of eight different MPDSs combined with chloroquine (CQ), an autophagy inhibitor, and their cytotoxicities to human corneal epithelium cells were determined. Almost all MPDS showed strong amoebicidal effect on trophozoites after 8 h of exposure. However, they showed inadequate amoebicidal effect on cysts even after 24 h of exposure. MPDSs combined with 100 µM CQ increased their amoebicidal effects on immature cyst by inhibiting formation of mature cysts. Incubation with 100 µM CQ for 30 min did not have cytotoxicity to human corneal epithelial cells.

GPCR Kinase (GRK)-2 Is a Key Negative Regulator of Itch: l-Glutamine Attenuates Itch via a Rapid Induction of GRK2 in an ERK-Dependent Way.

Many itch mediators activate GPCR and trigger itch via activation of GPCR-mediated signaling pathways. GPCRs are desensitized by GPCR kinases (GRKs). The aim of this study is to explore the role of GRKs in itch response and the link between GRKs and glutamine, an amino acid previously shown to be an itch reliever. Itch responses were evoked by histamine, chloroquine, and dinitrochlorobenzene-induced contact dermatitis (CD). Phosphorylation and protein expression were detected by immunofluorescent staining and Western blotting. GRK2 knockdown using small interfering RNA enhanced itch responses evoked by histamine, chloroquine, and dinitrochlorobenzene-induced CD, whereas GRK2 overexpression using GRK2-expressing adenovirus reduced the itch responses. Glutamine reduced all itch evoked by histamine, chloroquine, and dinitrochlorobenzene-induced CD. Glutamine-mediated inhibition of itch was abolished by GRK2 knockdown. Glutamine application resulted in a rapid and strong expression of GRK2 in not only dinitrochlorobenzene-induced CD (within 10 minutes) but also cultured rat dorsal root ganglion cells, F11 (within 1 minute). ERK inhibitor abrogates glutamine-mediated GRK2 expression and inhibition of itch in dinitrochlorobenzene-induced CD. Our data indicate that GRK2 is a key negative regulator of itch and that glutamine attenuates itch via a rapid induction of GRK2 in an ERK-dependent way.

TNF-α/TNFR1 Signaling is Required for the Full Expression of Acute and Chronic Itch in Mice via Peripheral and Central Mechanisms.

Increasing evidence suggests that cytokines and chemokines play crucial roles in chronic itch. In the present study, we evaluated the roles of tumor necrosis factor-alpha (TNF-α) and its receptors TNF receptor subtype-1 (TNFR1) and TNFR2 in acute and chronic itch in mice. Compared to wild-type (WT) mice, TNFR1-knockout (TNFR1-KO) and TNFR1/R2 double-KO (DKO), but not TNFR2-KO mice, exhibited reduced acute itch induced by compound 48/80 and chloroquine (CQ). Application of the TNF-synthesis inhibitor thalidomide and the TNF-α antagonist etanercept dose-dependently suppressed acute itch. Intradermal injection of TNF-α was not sufficient to evoke scratching, but potentiated itch induced by compound 48/80, but not CQ. In addition, compound 48/80 induced TNF-α mRNA expression in the skin, while CQ induced its expression in the dorsal root ganglia (DRG) and spinal cord. Furthermore, chronic itch induced by dry skin was reduced by administration of thalidomide and etanercept and in TNFR1/R2 DKO mice. Dry skin induced TNF-α expression in the skin, DRG, and spinal cord and TNFR1 expression only in the spinal cord. Thus, our findings suggest that TNF-α/TNFR1 signaling is required for the full expression of acute and chronic itch via peripheral and central mechanisms, and targeting TNFR1 may be beneficial for chronic itch treatment.

Pharmacological evidence for the involvement of adenosine triphosphate sensitive potassium channels in chloroquine-induced itch in mice.

BACKGROUND: Chloroquine (CQ) evokes itch in human and scratching behavior in rodents through a histamine-independent pathway. Chloroquine directly excites peripheral sensory neurons which convey itch signals to the central nervous system. It has been revealed that ATP-sensitive potassium channels (KATP channels) are important in regulating neuronal excitability. Thus, we aimed to investigate the involvement of KATP channels in CQ-induced itch which may also reveal a linkage between metabolic state of cells and itch. METHODS: Intradermal (id) injection of CQ at dose of 400µg/site induces the scratching behavior. KATP channel openers, diazoxide (DZX) and minoxidil (MIN), and a KATP channel blocker, glibenclamide (GLI), were administered intraperitoneally (ip) before CQ. Then the behavior was recorded for 30min, in an unmanned condition, and the scratching bouts were counted by an expert observer who was blinded to the experiments. Furthermore, quantitative reverse transcription-PCR (qRT-PCR) was used to investigate the possible changes in dermal expression of Kcnj8 and Kcnj11, the genes encoding the KATP channels. RESULTS: Our results show that either DZX (10mg/kg, ip) or MIN (10mg/kg, ip) significantly attenuated CQ-induced scratching behavior in mice. Moreover, pretreatment with GLI (3mg/kg, ip) significantly reversed the anti-pruritic effects of DZX and MIN. Our finding of qRT-PCR analysis also show that the expression of Kcnj8 is decreased after CQ injection. CONCLUSIONS: We suggest that KATP channels are possibly involved in CQ-induced itch. While, further studies will be significant to better elucidate the association of metabolic state of cells and itch.