Autophagy inhibitors as a potential antiamoebic treatment for Acanthamoeba keratitis

Role of autophagy in stress and drug-responsive cell death in Entamoeba histolytica and its cross-talk with apoptosis-inducing factor

Cell death in unicellular protozoan parasite Entamoeba histolytica is not yet reported though it displays several features of autophagic cell death. Autophagic cell death was reported to take place in ancient protozoans under several stresses. Here we report the occurrence of autophagic cell death in the Entamoeba histolytica trophozoites under oxidative stress as well as by the treatment with metronidazole, the most-widely-used drug for amoebiasis treatment and was shown to generate oxidative stress in the trophozoites. The autophagic flux increases during nutrient deprivation and metronidazole treatment and decreases upon oxidative stress. During oxidative stress the autophagy leads to nucleophagy that is ultimately destined to be digested within the lysosomal chamber. The formation of nucleophagosome depends on the apoptosis-inducing factor (AIF) that translocates to the nucleus from cytoplasm upon oxidative stress. It was experimentally proved that ATG8 (Autophagy-related protein 8) binds with the AIF in the nucleus of the trophozoites and helps in ATG8 recruitment and autophagy initiation overall suggesting that oxidative stress-driven AIF translocation to nucleus results in binding with ATG8 and initiates nucleophagy leading to cell death.

Systems Biology and Cytokines Potential Role in Lung Cancer Immunotherapy Targeting Autophagic Axis

Lung cancer accounts for the highest number of deaths among men and women worldwide. Although extensive therapies, either alone or in conjunction with some specific drugs, continue to be the principal regimen for evolving lung cancer, significant improvements are still needed to understand the inherent biology behind progressive inflammation and its detection. Unfortunately, despite every advancement in its treatment, lung cancer patients display different growth mechanisms and continue to die at significant rates. Autophagy, which is a physiological defense mechanism, serves to meet the energy demands of nutrient-deprived cancer cells and sustain the tumor cells under stressed conditions. In contrast, autophagy is believed to play a dual role during different stages of tumorigenesis. During early stages, it acts as a tumor suppressor, degrading oncogenic proteins; however, during later stages, autophagy supports tumor cell survival by minimizing stress in the tumor microenvironment. The pivotal role of the IL6-IL17-IL23 signaling axis has been observed to trigger autophagic events in lung cancer patients. Since the obvious roles of autophagy are a result of different immune signaling cascades, systems biology can be an effective tool to understand these interconnections and enhance cancer treatment and immunotherapy. In this review, we focus on how systems biology can be exploited to target autophagic processes that resolve inflammatory responses and contribute to better treatment in carcinogenesis.

The roles of autophagy and mitophagy in corneal pathology: current knowledge and future perspectives

The cornea is the clear dome that covers the front portion of the globe. The primary functions of the cornea are to promote the refraction of light and to protect the eye from invading pathogens, both of which are essential for the preservation of vision. Homeostasis of each cellular layer of the cornea requires the orchestration of multiple processes, including the ability to respond to stress. One mechanism whereby cells respond to stress is autophagy, or the process of "self-eating." Autophagy functions to clear damaged proteins and organelles. During nutrient deprivation, amino acids released from protein breakdown via autophagy are used as a fuel source. Mitophagy, a selective form of autophagy, functions to clear damaged mitochondria. Thus, autophagy and mitophagy are important intracellular degradative processes that sustain tissue homeostasis. Importantly, the inhibition or excessive activation of these processes result in deleterious effects on the cell. In the eye, impairment or inhibition of these mechanisms have been associated with corneal disease, degenerations, and dystrophies. This review summarizes the current body of knowledge on autophagy and mitophagy at all layers in the cornea in both non-infectious and infectious corneal disease, dystrophies, and degenerations. It further highlights the critical gaps in our understanding of mitochondrial dysfunction, with implications for novel therapeutics in clinical practice.

Phragmites australis (Cav.) Trin. ex Steud. Extract Induces Apoptosis-like Programmed Cell Death in Acanthamoeba castellanii Trophozoites

Acanthamoeba keratitis (AK) is an infectious ocular disease which is difficult to diagnose correctly and cure. Development of an effective and safe therapeutic drug for AK is needed. Our preliminary screening of more than 200 extracts from wild plants collected in Korea suggested the potential amoebicidal activity of Phragmites australis (Cav.) Trin. ex Steud. extract (PAE) against Acanthamoeba species. Here, we aimed to analyze the amoebicidal activity of PAE on Acanthamoeba and its underlying amoebicidal mechanism. PAE induced amoebicidal activity against both A. castellanii and A. polyphaga trophozoites, while it showed low cytotoxicity in human corneal epithelial cells (HCE-2) and human retinal pigment epithelial cells (ARPE-19). Transmission electron microscopy analysis showed subcellular morphological changes, such as increased granules, abnormal mitochondria, and atypical cyst wall formation, in the PAE-treated A. castellanii. Fluorometric apoptosis assay and TUNEL assay revealed apoptosis-like programmed cell death (PCD) in the PAE-treated A. castellanii. The PAE treatment increased reactive oxygen species production and reduced mitochondrial membrane potential in the amoeba. The enhanced expression of autophagy-associated genes was also detected. These results suggested that PAE exerted a promising amoebicidal effect on A. castellanii trophozoites via the PCD pathway. PAE could be a potential candidate for developing a therapeutic drug for AK.

Autophagy in the normal and diseased cornea

The cornea and covering tear film are together the 'objective lens' of the eye through which 80% of light is refracted. Despite exposure to a physically harsh and at times infectious or toxic environment, transparency essential for sight is in most cases maintained. Such resiliency makes the avascular cornea a superb model for the exploration of autophagy in the regulation of homeostasis with relevancy to all organs. Nonetheless, missense mutations and inflammation respectively clog or apparently overwhelm autophagic flux to create dystrophies much like in neurodegenerative diseases or further exacerbate inflammation. Here there is opportunity to generate novel topical therapies towards the restoration of homeostasis with potential broad application.

Autophagy and lipid droplets are a defense mechanism against toxic copper oxide nanotubes in the eukaryotic microbial model Tetrahymena thermophila

The widespread use of inorganic nanomaterials of anthropogenic origin has significantly increased in the last decade, being now considered as emerging pollutants. This makes it necessary to carry out studies to further understand their toxicity and interactions with cells. In the present work we analyzed the toxicity of CuO nanotubes (CuONT) in the ciliate Tetrahymena thermophila, a eukaryotic unicellular model with animal biology. CuONT exposure rapidly induced ROS generation in the cell leading to oxidative stress and upregulation of genes encoding antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase), metal-chelating metallothioneins and cytochrome P450 monooxygenases. Comet assays and overexpression of genes involved in DNA repair confirmed oxidative DNA damage in CuONT-treated cells. Remarkably, both electron and fluorescent microscopy revealed numerous lipid droplets and autophagosomes containing CuONT aggregates and damaged mitochondria, indicating activation of macroautophagy, which was further confirmed by a dramatic upregulation of ATG (AuTophaGy related) genes. Treatment with autophagy inhibitors significantly increased CuONT toxicity, evidencing the protective role of autophagy towards CuONT-induced damage. Moreover, increased formation of lipid droplets appears as an additional mechanism of CuONT detoxification. Based on these results, we present a hypothetical scenario summarizing how T. thermophila responds to CuONT toxicity. This study corroborates the use of this ciliate as an excellent eukaryotic microbial model for analyzing the cellular response to stress caused by toxic metal nanoparticles.

Potential role of Acanthamoeba Rab7

Acanthamoeba castellanii is a free-living protozoan that causes several severe human parasitic diseases such as Acanthamoeba keratitis and granulomatous encephalitis. A. castellanii feeds on bacteria, yeasts, and other organic particles as food sources, but the mechanisms of digestion in acanthamoebal cells are unclear. Rab GTPases participate in endosomal delivery in eukaryotes after phagocytosis. This study aimed to determine the potential functions of A. castellanii Rab7 (AcRab7), which is involved in phagocytosis, and the relationship between AcRab7 and further cellular physiological phenomena. In this study, the inhibitor CID1067700 (CID) was used to specifically inhibit the binding of nucleotides to confirm the potential functions of AcRab7. Cellular proliferation and ATP assays were also used to detect underlying cellular physiological functions after blocking the phagocytosis pathway. We found that AcRab7 expression increased as the co-culture time with Escherichia coli increased. Immunofluorescence staining showed that AcRab7 colocalized with lysosomes in its GTP-activating form. In addition, AcRab7 inhibition resulted in a reduction in cell proliferation and ATP levels. Our results suggest that AcRab7 participates in endosomal delivery and dominates energy production and cell growth.

Evaluation of Nanoparticles with 5-Fluorouracil and Chloroquine on Acanthamoeba castellanii activity

Acanthamoeba is opportunistic pathogens that cause vision-threatening Acanthamoeba keratitis (AK). Previous studies proposed the use of chloroquine (CQ) and 5-fluorouracil (5FU) as anti-Acanthamoeba agents. The objective of this study was to determine the benefit of using 5FU and CQ nanoparticles (NP) formulations against A. castellanii that belonging to the T4 genotype and evaluate their anti-Acanthamoebic characteristic. Triplicate batches of 5FU nanoparticles (5FU-NP) were synthesized by using a modified nanoprecipitation method, while CQ anoparticles (CQ-NP) synthesized using a modified double emulsion method. The synthesized nanoparticles were subjected to biological assays to investigate their amoebicidal, amoebistatic, anti-encystation, and anti-excystation effects against A. castellanii, as well as cell cytotoxicity. Cytotoxicity assays were performed using human keratinocyte cells (HaCat) to determine the effect of CQ and 5FU nanoformulations on host cells. 5FU-NP with a concentration of 60µM showed significant inhibition to amoeba binding into human cell lines and remarkable prevention mainly during the encystation stage. Moreover, 5FU-NP resulted in less cytotoxicity and pathogenicity when compared with the free 5FU. On the other hand, CQ and CQ-NP, at the same concentration, showed poor inhibition to amoeba binding into human cells and insignificant prevention to encystation stage. Moderate human cells damage was resulted following their treatment with CQ and CQ-NP. In conclusion, 5FU may have the potential as an antiamoebic agent against Acanthamoeba spp. preferably as a nanoformulation to enhance its activity and reduce its cytoxicity.

Recent Advances of Autophagy in Non-Small Cell Lung Cancer: From Basic Mechanisms to Clinical Application

Lung cancer is characterized by the most common oncological disease and leading cause of cancer death worldwide, of which a group of subtypes known as non-small cell lung cancer (NSCLC) accounts for approximately 85%. In the past few decades, important progression in the therapies of NSCLC has enhanced our understanding of the biology and progression mechanisms of tumor. The application of immunotherapy and small molecule tyrosine kinase inhibitors has brought significant clinical benefits in certain patients. However, early metastasis and the emergence of resistance to antitumor therapy have resulted in the relatively low overall cure and survival rates for NSCLC. Autophagy is a conserved process that allows cells to recycle unused or damaged organelles and cellular components. It has been reported to be related to the progression of NSCLC and resistance to targeted therapy and cytotoxic chemotherapy. Therefore, autophagy is considered as a potential therapeutic target for NSCLC. Mounting results have been reported about the combination of tyrosine kinase inhibitors and inhibitors of autophagy in models of NSCLC. This review aims to provide a comprehensive review on the roles of autophagy in NSCLC, focusing on related clinical data of agents that regulate autophagy in NSCLC. Furthermore, this study will provide a theoretical basis for further improvement of autophagy-based cancer therapy.

Antiproliferation and Antiencystation Effect of Class II Histone Deacetylase Inhibitors on Acanthamoeba castellanii

Acanthamoeba is a ubiquitous and free-living protozoan pathogen responsible for causing Acanthamoeba keratitis (AK), a severe corneal infection inflicting immense pain that can result in permanent blindness. A drug-based treatment of AK has remained arduous because Acanthamoeba trophozoites undergo encystment to become highly drug-resistant cysts upon exposure to harsh environmental conditions such as amoebicidal agents (e.g., polyhexanide, chloroquine, and chlorohexidine). As such, drugs that block the Acanthamoeba encystation process could result in a successful AK treatment. Histone deacetylase inhibitors (HDACi) have recently emerged as novel therapeutic options for treating various protozoan and parasitic diseases. Here, we investigated whether novel HDACi suppress the proliferation and encystation of Acanthamoeba. Synthetic class II HDACi FFK29 (IIa selective) and MPK576 (IIb selective) dose-dependently decreased the viability of Acanthamoeba trophozoites. While these HDACi demonstrated a negligible effect on the viability of mature cysts, Acanthamoeba encystation was significantly inhibited by these HDACi. Apoptosis was slightly increased in trophozoites after a treatment with these HDACi, whereas cysts were unaffected by the HDACi exposure. The viability of human corneal cells was not affected by HDACi concentrations up to 10 μmol/L. In conclusion, these synthetic HDACi demonstrated potent amoebicidal effects and inhibited the growth and encystation of Acanthamoeba, thus highlighting their enormous potential for further development.

Amoebicidal activity of Cassia angustifolia extract and its effect on Acanthamoeba triangularis autophagy-related gene expression at the transcriptional level

Cassia angustifolia Vahl. plant is used for many therapeutic purposes, for example, in people with constipation, skin diseases, including helminthic and parasitic infections. In our study, we demonstrated an amoebicidal activity of C. angustifolia extract against Acanthamoeba triangularis trophozoite at a micromolar level. Scanning electron microscopy (SEM) images displayed morphological changes in the Acanthamoeba trophozoite, which included the formation of pores in cell membrane and the membrane rupture. In addition to the amoebicidal activity, effects of the extract on surviving trophozoites were observed, which included cyst formation and vacuolization by a microscope and transcriptional expression of Acanthamoeba autophagy in response to the stress by quantitative polymerase chain reaction. Our data showed that the surviving trophozoites were not transformed into cysts and the trophozoite number with enlarged vacuole was not significantly different from that of untreated control. Molecular analysis data demonstrated that the mRNA expression of AcATG genes was slightly changed. Interestingly, AcATG16 decreased significantly at 12 h post treatment, which may indicate a transcriptional regulation by the extract or a balance of intracellular signalling pathways in response to the stress, whereas AcATG3 and AcATG8b remained unchanged. Altogether, these data reveal the anti-Acanthamoeba activity of C. angustifolia extract and the autophagic response in the surviving trophozoites under the plant extract pressure, along with data on the formation of cysts. These represent a promising plant for future drug development. However, further isolation and purification of an active compound and cytotoxicity against human cells are needed, including a study on the autophagic response at the protein level.

Application of Histone Deacetylase Inhibitors MPK472 and KSK64 as a Potential Treatment Option for Acanthamoeba Keratitis

Treatment of Acanthamoeba keratitis (AK) is difficult because Acanthamoeba cysts are resistant to drugs, and as such, successful treatment requires an effective approach that inhibits cyst formation. Histone deacetylase inhibitors (HDACis) are involved in cell proliferation, differentiation, and apoptotic cell death. In this study, the effects of HDACis such as MPK472 and KSK64 on Acanthamoeba castellanii trophozoites and cysts were observed. MPK472 and KSK64 showed at least 60% amoebicidal activity against Acanthamoeba trophozoites at a concentration of 10 μM upon 8 h of treatment. Neither of the two HDACis affected mature cysts, but significant amoebicidal activities (36.4 and 33.9%) were observed against encysting Acanthamoeba following treatment with 5 and 10 μM HDACis for 24 h. Light microscopy and transmission electron microscopy results confirmed that the encystation of Acanthamoeba was inhibited by the two HDACis. In addition to this, low cytopathic effects on human corneal epithelial (HCE) cells were observed following treatment with MPK472 and KSK64 for 24 h. Our results indicate that the HDACis MPK472 and KSK64 could be used as new candidates for the development of an optimal therapeutic option for AK.

Histone Deacetylase Inhibitors Enhance the Amoebicidal Effect of Low Concentration of Polyhexamethylene Biguanide by Inducing Apoptosis

PURPOSE

The aim of this study was to reduce the cytotoxicity and improve the amoebicidal effect of polyhexamethylene biguanide (PHMB) at low concentrations by combining it with histone deacetylase (HDAC) inhibitors.

METHODS

To reduce the cytotoxic effect on human corneal epithelial (HCE) cells, the concentration of PHMB was reduced to 0.0002%. To enhance the amoebicidal effect of PHMB, HDAC inhibitors such as suberoylanilide hydroxamic acid, MS275, or MC1568 were combined with it. Acanthamoeba and HCE cells were treated with 3 combinations to evaluate the amoebicidal and cytotoxic effects. Microscopy and fluorescence-activated cell sorting analysis were performed to investigate the apoptotic cell death of Acanthamoeba by these combinatorial treatments.

RESULTS

The low concentration of PHMB (0.0002%) alone demonstrated no cytopathic effects (CPEs) on HCE cells. Three combinatorial treatments using 0.0002% PHMB with 10 μM suberoylanilide hydroxamic acid, 10 μM MS275, or 10 μM MC1568 showed higher amoebicidal effects on A. castellanii trophozoites than PHMB alone. Fluorescence-activated cell sorting analysis confirmed that HDAC inhibitors increased the apoptotic cell death of Acanthamoeba. Mild CPEs were observed from HCE cells cotreated with PHMB and the HDAC inhibitors after 24 hours of exposure.

CONCLUSIONS

Combinatorial treatments showed high amoebicidal effects on Acanthamoeba and low CPEs on HCE cells, which suggests their potential application for Acanthamoeba keratitis treatment.

Ferulic acid delayed amyloid β-induced pathological symptoms by autophagy pathway via a fasting-like effect in Caenorhabditis elegans

The amyloid β (Aβ) generation or aggregation plays a crucial role in Alzheimer's disease (AD). Autophagy agonists, which function as the clearance of Aβ, could be the potential drug candidates against AD. In staple food crops, ferulic acid (FA) is an enormously copious and almost ubiquitous phenolic antioxidant. In the present study, FA significantly inhibited Aβ-induced pathological symptoms of paralysis and hypersensitivity to exogenous serotonin, meanwhile restrained Aβ monomers, oligomers, and deposits in AD C. elegans. FA increased the expression of autophagy reporter LGG-1 and enhanced autophagy flux. However, the autophagy inhibitors abolished the restrictive action of FA on the worm paralysis phenotype. According to these results, FA triggered autophagy and ameliorated Aβ-induced pathological symptoms by the autophagy pathway. Moreover, FA activated the HLH-30 transcription factor to nuclear localization, which acts upstream of autophagy in fasted animals, reduced the level of lipids, but affected nor the growth of E. coli OP50, neither animal food intake behavior. These suggest that FA induced a fasting-like effect to activate the autophagy pathway. Additionally, FA ameliorated poly Q aggregations in Huntington's disease worm. Thus, FA could not only affect AD, broadly but also neurodegenerative diseases characterized by misfolded or aggregated proteins.

Alkyl-carbon chain length of two distinct compounds and derivatives are key determinants of their anti-Acanthamoeba activities

The opportunistic pathogen, Acanthamoeba castellanii is the causative agent for the sight threatening infection Acanthamoeba keratitis (AK). It is commonly associated with contact lens wearers, and prevalence is increasing at an alarming rate due to an inadequate preventive strategy to protect the lens from this protist. This problem is compounded by the lack of an effective acanthamoebocide, particularly with cysticidal activity in the contact lens solutions. We have used cytotoxicity assays and a variety of biophysical approaches to show that two molecules with tails made of alkyl carbon, alkylphosphocholines (APCs) and quaternary ammonium compounds (QACs) had significant chain-length dependent efficacy against A. castellanii trophozoites, the latter producing death via permeabilization, and DNA complexing. QACs were more effective than APCs and had activity against cysts. Conversely, the QAC with 12 alkyl carbon chain, was non toxic, its presence increased A. castellanii trophozoites biomass and delayed encystation by 96 h. Interestingly, it was unable to induce excystation and increased trophozoite sensitivity to APC16. These results present a mono- and multi-inhibitor management strategy effective against trophozoites and cysts that may be useful for formulating into contact lense cleaning solutions and reducing AK incidence.

Blocking drug-induced autophagy with chloroquine in HCT-116 colon cancer cells enhances DC maturation and T cell responses induced by tumor cell lysate

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Autophagy helps tumor cells to face drug-induced damages, stimulating tolerance.

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Autophagy inhibition improves the efficiency of antineoplastic agents.

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Blockage of autophagy with Chloroquine increases synthesis of tumor antigens.

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Blockage of autophagy changes the expression of ATG and tumor suppressor genes.

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Lysate of drug-treated cells enhances maturation/activation of human dendritic cells.

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Lysate of drug-treated cells induce Th1 alloresponse, and generation of tumor-specific CTL.

Autophagy is an important mechanism for tumor escape, allowing tumor cells to recover from the damage induced by chemotherapy, radiation therapy, and immunotherapy and contributing to the development of resistance. The pharmacological inhibition of autophagy contributes to increase the efficacy of antineoplastic agents. Exposing tumor cells to low concentrations of select autophagy-inducing antineoplastic agents increases their immunogenicity and enhances their ability to stimulate dendritic cell (DC) maturation. We tested whether the application of an autophagy-inhibiting agent, chloroquine (CQ), in combination with low concentrations of 5-fluorouracil (5-FU) increases the ability of tumor cells to induce DC maturation. DCs sensitized with the lysate of HCT-116 cells previously exposed to such a combination enhanced the DC maturation/activation ability. These matured DCs also increased the allogeneic responsiveness of both CD4+ and CD8+ T cells, which showed a greater proliferative response than those from DCs sensitized with control lysates. The T cells expanded in such cocultures were CD69+ and PD-1- and produced higher levels of IFN-γ and lower levels of IL-10, consistent with the preferential activation of Th1 cells. Cocultures of autologous DCs and lymphocytes improved the generation of cytotoxic T lymphocytes, as assessed by the expression of CD107a, perforin, and granzyme B. The drug combination increased the expression of genes related to the CEACAM family (BECN1, ATGs, MAPLC3B, ULK1, SQSTM1) and tumor suppressors (PCBP1). Furthermore, the decreased expression of genes related to metastasis and tumor progression (BNIP3, BNIP3L, FOSL2, HES1, LAMB3, LOXL2, NDRG1, P4HA1, PIK3R2) was noted. The combination of 5-FU and CQ increases the ability of tumor cells to drive DC maturation and enhances the ability of DCs to stimulate T cell responses.

Biologically active pigment and ShlA cytolysin of Serratia marcescens induce autophagy in a human ocular surface cell line

BACKGROUND

The cellular process of autophagy is essential for maintaining the health of ocular tissue. Dysregulation of autophagy is associated with several ocular diseases including keratoconus and macular degeneration. It is known that autophagy can be used to respond to microbial infections and that certain microbes can exploit the autophagic process to their benefit. In this study, a genetic approach was used to identify surface-associated and secreted products generated by the opportunistic pathogen Serratia marcescens involved in activation of autophagy.

METHODS

A recombinant human corneal limbal epithelial cell line expressing a LC3-GFP fusion protein was challenged with normalized secretomes from wild-type and mutant S. marcescens derivatives. LC3-GFP fluorescence patterns were used to assess the ability of wild-type and mutant bacteria to influence autophagy. Purified prodigiosin was obtained from stationary phase bacteria and used to challenge ocular cells.

RESULTS

Mutations in the global regulators eepR and gumB genes highly reduced the ability of the bacteria to activate autophagy in corneal cells. This effect was further narrowed down to the secreted cytolysin ShlA and the biologically active pigment prodigiosin. Purified prodigiosin and ShlA from Escherichia coli further supported the role of these factors in activating autophagy in human corneal cells. Additional genetic data indicate a role for flagellin and type I pili, but not the nuclease, S-layer protein, or serratamolide biosurfactant in activation of autophagy.

CONCLUSIONS

This work identifies specific bacterial components that activate autophagy and give insight into potential host-pathogen interactions or compounds that can be used to therapeutically manipulate autophagy.

Safety of intrastromal injection of polyhexamethylene biguanide and propamidine isethionate in a rabbit model

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Intrastromal Injection can be considered in deep Acanthamoeba keratitis (AK).

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Intrastromal injection of 0.01% PHMB or 0.05% propamidine isethionate is safe.

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This model system could help to determine the toxic effect of other agents.

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Further experiments may determine the toxicity of multiple intrastromal injection.

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AK animal model is required to evaluate the true effect of intrastromal injection.

Acanthamoeba keratitis (AK) is difficult to treat, especially when the corneal deep stroma is involved. Intrastromal injection of antimicrobial agents is an effective adjuvant therapy for deep recalcitrant microbial keratitis; however, it has not been used to treat AK due to suspected drug toxicity. The purpose of this study was to evaluate the toxicity of corneal intrastromal injection of polyhexamethylene biguanide (PHMB) and propamidine isethionate (Brolene®, Sanofi) in New Zealand white rabbits. We performed intrastromal injections of PHMB (0.02 or 0.01%) and propamidine isethionate (0.1 or 0.05%) into the rabbits’ right corneas. The left corneas were injected with phosphate-buffered saline as controls. The rabbits were sacrificed on the 7th day after injection, and the corneal buttons were harvested for further evaluation by slit lamp microscopy, specular microscopy, hematoxylin and eosin staining, scanning electron microscopy, terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling assays, and WST-1 assays. We found that intrastromal injection of 0.02% PHMB or 0.1% propamidine isethionate resulted in corneal epithelial erosion, corneal edema, and severe neovascularization. However, 0.01% PHMB or 0.05% propamidine isethionate did not induce obvious cornea toxicity. In conclusion, intrastromal injection of 0.01% PHMB or 0.05% propamidine isethionate may be promising adjunctive treatments for deep stromal AK.

Glycyrrhizic acid ameliorates LPS-induced acute lung injury by regulating autophagy through the PI3K/AKT/mTOR pathway

Acute lung injury (ALI) is a major pathological issue characterized by serious inflammatory response, and a major clinically critical illness with high morbidity and mortality. Glycyrrhizic acid (GA) is a major bioactive constituent isolated from traditional Chinese herb licorice, which has been reported to have positive effects on inflammation. Nevertheless, the effects of GA on lipopolysaccharide (LPS)-treated ALI in mice have not been reported. The purpose of our study is to investigate the inhibitory effects of GA on ALI treated by LPS and to elucidate its possible mechanisms. We found that GA significantly attenuated lung injury and decreased the production of inflammatory factors TNF-α, IL-1β, and HMGB1 with LPS treatment. GA induced autophagy which was showed by enhanced number of autophagosomes through upregulating the protein levels of LC3-II/I and Beclin-1 and downregulating SQSTM1/P62. Moreover, pre-treatment of 3-Methyladenine (3-MA), an autophagy inhibitor, reversed the inhibiting effects of GA on the secretion of inflammatory factors in ALI. The PI3K/AKT/mTOR pathway was associated with GA-induced autophagy under ALI induced by LPS. In conclusion, this study indicated that GA inhibited the production of inflammatory factors in LPS-induced ALI by regulating the PI3K/AKT/mTOR pathway related autophagy, which may provide a novel therapeutic perspective of GA in ameliorating ALI.

The Complex Nature of Tupanviruses

The discovery of giant viruses revealed a new level of complexity in the virosphere, raising important questions about the diversity, ecology, and evolution of these viruses. The family Mimiviridae was the first group of amoebal giant viruses to be discovered (by Bernard La Scola and Didier Raoult team), containing viruses with structural and genetic features that challenged many concepts of classic virology. The tupanviruses are among the newest members of this family and exhibit structural, biological, and genetic features never previously observed in other giant viruses. The complexity of these viruses has put us one step forward toward the comprehension of giant virus biology and evolution, but also has raised important questions that still need to be addressed. In this chapter, we tell the history behind the discovery of one of the most complex viruses isolated to date, highlighting the unique features exhibited by tupanviruses, and discuss how these giant viruses have contributed to redefining limits for the virosphere.

Effect of 2, 6-Dichlorobenzonitrile on Amoebicidal Activity of Multipurpose Contact Lens Disinfecting Solutions

Multipurpose contact lens disinfecting solutions (MPDS) are widely used to cleanse and disinfect microorganisms. However, disinfection efficacy of these MPDS against Acanthamoeba cyst remain insufficient. 2, 6-dichlorobenzonitrile (DCB), a cellulose synthesis inhibitor, is capable of increasing the amoebical effect against Acanthamoeba by inhibiting its encystation. In this study, we investigated the possibility of DCB as a disinfecting agent to improve the amoebicidal activity of MPDS against Acanthamoeba cyst. Eight commercial MPDS (from a to h) were assessed, all of which displayed insufficient amoebicidal activity against the mature cysts. Solution e, f, and h showed strong amoebicidal effect on the immature cysts. Amoebicidal efficacy against mature cysts remained inadequate even when the 8 MPDS were combined with 100 μM DCB. However, 4 kinds of MPDS (solution d, e, f, and h) including 100 μM DCB demonstrated strong amoebicidal activity against the immature cysts. The amoebicidal activity of solution d was increased by addition of DCB. Cytotoxicity was absent in human corneal epithelial cells treated with either DCB or mixture of DCB with MPDS. These results suggested that DCB can enhance the amoebicical activity of MPDS against Acanthamoeba immature cyst in vitro.

Functional importance for developmental regulation of sterol biosynthesis in Acanthamoeba castellanii

The sterol metabolome of Acanthamoeba castellanii (Ac) yielded 25 sterols. Substrate screening of cloned AcCYP51 revealed obtusifoliol as the natural substrate which converts to ∆8,14-sterol (<95%). The combination of [2H3-methyl]methionine incubation to intact cultures showing C28-ergosterol incorporates 2-2H atoms and C29-7-dehydroporiferasterol incorporates 5 2H-atoms, the natural distribution of sterols, CYP51 and previously published sterol methyltransferase (SMT) data indicate separate ∆24(28)- and ∆25(27)-olefin pathways to C28- and C29-sterol products from the protosterol cycloartenol. In cell-based culture, we observed a marked change in sterol compositions during the growth and encystment phases monitored microscopically and by trypan blue staining; trophozoites possess C28/C29-∆5,7-sterols, viable encysted cells (mature cyst) possess mostly C29-∆5-sterol and non-viable encysted cells possess C28/C29-∆5,7-sterols that turnover variably from stress to 6-methyl aromatic sterols associated with changed membrane fluidity affording lysis. An incompatible fit of steroidal aromatics in membranes was confirmed using the yeast sterol auxotroph GL7. Only viable cysts, including those treated with inhibitor, can excyst into trophozoites. 25-Azacycloartanol or voriconazole that target SMT and CYP51, respectively, are potent enzyme inhibitors in the nanomolar range against the cloned enzymes and amoeba cells. At minimum amoebicidal concentration of inhibitor amoeboid cells rapidly convert to encysted cells unable to excyst. The correlation between stage-specific sterol compositions and the physiological effects of ergosterol biosynthesis inhibitors suggests that amoeba fitness is controlled mainly by developmentally-regulated changes in the phytosterol B-ring; paired interference in the ∆5,7-sterol biosynthesis (to ∆5,7) - metabolism (to ∆5 or 6-methyl aromatic) congruence during cell proliferation and encystment could be a source of therapeutic intervention for Acanthamoeba infections.

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.

Toxic effects of selected proprietary dry eye drops on Acanthamoeba

Amoebae of the genus Acanthamoeba are ubiquitous protists that have been isolated from many sources such as soils, water and the air. They are responsible for infections including fatal encephalitis and a severe keratitis in humans. To date, there is no satisfactorily effective therapeutic agent against this pathogen and the infections it causes are exacerbated by the existence of a resistant cyst stage produced by this amoeba. As dry eye syndrome is a risk factor for Acanthamoeba keratitis, we aimed to evaluate the anti-Acanthamoeba activity of a variety of proprietary eye drops intended to treat dry eye syndrome. From the nine eye drop formulations tested, "Systane Ultra" was determined to be the most active against all tested Acanthamoeba strains. During our investigations into the mode of action of Systane Ultra, we discovered that it decreases mitochondrial membrane potential and ATP levels, induces chromatin condensation, and increases the permeability of the plasma-membrane.

Encystation: the most prevalent and underinvestigated differentiation pathway of eukaryotes

Not long ago, protists were considered one of four eukaryote kingdoms, but recent gene-based phylogenies show that they contribute to all nine eukaryote subdomains. The former kingdoms of animals, plants and fungi are now relegated to lower ranks within subdomains. Most unicellular protists respond to adverse conditions by differentiating into dormant walled cysts. As cysts, they survive long periods of starvation, drought and other environmental threats, only to re-emerge when conditions improve. For protists pathogens, the resilience of their cysts can prevent successful treatment or eradication of the disease. In this context, effort has been directed towards understanding the molecular mechanisms that control encystation. We here firstly summarize the prevalence of encystation across protists and next focus on Amoebozoa, where most of the health-related issues occur. We review current data on processes and genes involved in encystation of the obligate parasite Entamoeba histolytica and the opportunistic pathogen Acanthamoeba. We show how the cAMP-mediated signalling pathway that controls spore and stalk cell encapsulation in Dictyostelium fruiting bodies could be retraced to a stress-induced pathway controlling encystation in solitary Amoebozoa. We highlight the conservation and prevalence of cAMP signalling genes in Amoebozoan genomes and the suprisingly large and varied repertoire of proteins for sensing and processing environmental signals in individual species.

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.

Cedratvirus getuliensis replication cycle: an in-depth morphological analysis

The giant viruses are the largest and most complex viruses in the virosphere. In the last decade, new members have constantly been added to this group. Here, we provide an in-depth descriptive analysis of the replication cycle of Cedratvirus getuliensis, one of the largest viruses known to date. We tracked the virion entry, the early steps of virus factory and particles morphogenesis, and during this phase, we observed a complex and unique sequential organization of immature particle elements, including horseshoe and rectangular compartments, revealed by transverse and longitudinal sections, respectively, until the formation of the final ovoid-shaped striped virion. The genome and virion proteins are incorporated through a longitudinal opening in the immature virion, followed by the incorporation of the second cork and thickening of the capsid well. Moreover, many cell modifications occur during viral infection, including intense membrane trafficking important to viral morphogenesis and release, as evidenced by treatment using brefeldin A. Finally, we observed that Cedratvirus getuliensis particles are released after cellular lysis, although we obtained microscopic evidence that some particles are released by exocytosis. The present study provides new information on the unexplored steps in the life cycle of cedratviruses.

Activation of a c-Jun N-terminal kinase-mediated autophagy pathway attenuates the anticancer activity of gemcitabine in human bladder cancer cells

The role of autophagy in the anticancer activity of gemcitabine (GEM) in bladder cancer is unclear. The aim of this study is to determine whether GEM activates autophagy, the role of autophagy in the anticancer activity of GEM, and the underlying mechanism by which GEM induces autophagy. Human bladder cancer cell lines T24 and BIU87 were treated with GEM in vitro. Cell viability was measured using the Cell Counting Kit-8 assay. Apoptosis was detected by annexin V assay and western blot. Autophagy was measured by western blot and transmission electron microscopy. c-Jun N-terminal kinase (JNK) activation was detected by western blot. Chemical inhibitors were used for intervention of JNK and autophagy. GEM killed bladder cancer cells, which was associated with apoptosis induction. Autophagy was effectively activated by GEM. Suppressing autophagy in GEM-treated cells significantly decreased cell viability, which was associated with increased apoptosis. GEM-induced JNK activation and suppressed B-cell lymphoma 2 expression. The JNK inhibitor SP600125 inhibited GEM-induced autophagy activation and increased GEM's cytotoxicity. GEM kills bladder cancer cells through apoptosis. Meanwhile, JNK-mediated autophagy was activated, which protects the cells against apoptosis. Therefore, inhibition of autophagy could be exploited to enhance the anticancer efficacy of GEM for treating bladder cancer.

Efficacy of Korean Multipurpose Contact Lens Disinfecting Solutions against Acanthamoeba castellanii

Acanthamoeba keratitis has been increasing in recent years. Main risk factors are contact lens wear and their cleaning solutions. Most contact lens wearers use multipurpose disinfecting solutions (MPDS) for cleansing and disinfecting microorganisms because of its convenience. We determined amoebicidal effects of MPDS made in Korea and their cytotoxicity on human corneal epithelium cells. Fifteen commercial MPDS (A to O) were tested for their amoebicidal effects on Acanthamoeba castellanii trophozoites and cysts by using a most probable number (MPN) technique. Among them, 7 kinds of MPDS showed little or no amoebicidal effects for 24 hr exposure. Solutions A, B, G, H, L, and O showed positive amoebicidal effects, and solutions M and N killed almost all trophozoites and cysts after 24 hr exposure. However, 50%-N solution showed 56% cytotoxicity on human corneal epithelial cells within 4 hr exposure, and 50%-O solution also showed 62% cytotoxicity on human cells within 4 hr exposure. Solution A did not show any cytotoxicity on human cells. These results revealed that most MPDS made in Korea were ineffective to kill Acanthamoeba. The solutions having amoebicidal activity also showed high levels of cytotoxicity on human corneal epithelial cells. New formulations for improved MPDS that are amoebicidal but safe for host cells are needed to prevent Acanthamoeba keratitis.