Disruptive effect of chloroquine on lysosomes in cultured rat hepatocytes

Lysosomal dysfunction induced cytosolic vacuolation and increased intracellular amyloid-beta 42 (Aβ42) in human brain endothelial cells (HBEC-5i)

Lysosome is a primary degradative organelle and is crucial in cellular homeostasis. A reduction in its function due to ageing has been associated with the development of Alzheimer's disease (AD), a common neurodegenerative disorder characterised by the deposition of neurotoxic amyloid plaque in the brain and cerebral vessel walls. The breakdown of the blood-brain barrier (BBB) plays a vital role in the pathogenesis of AD. However, the impact of lysosomal dysfunction on brain endothelial cells, the key component of the BBB, in the disease progression is yet to be fully understood. In this study, human brain endothelial cells (HBEC-5i) were exposed to a lysosomotropic compound, chloroquine (CQ) for 24 h. Cell viability was assessed with the 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT) assay to determine the inhibitory concentration (IC) at IC₁₀ (17.5 µM), IC₂₅ (70.5 µM), and IC₅₀ (125 µM). The morphological changes observed include vacuoles arrested in the cytosols and cell shrinkage that were more prominent at IC₂₅ and IC₅₀. Lysosomal dysfunction was evaluated by measuring the lysosomal-associated membrane protein-1 (LAMP-1) and microtubule-associated protein light chain 3-II (LC3-II) using the capillary-based immunoassay. LC3-II was significantly increased at IC₂₅ and IC₅₀ (p < 0.05 and p < 0.001_, respectively). The concentration of intracellular and extracellular Aβ42 was quantitated using the enzyme-linked immunosorbent assay, which demonstrated a significant increase (p < 0.05) in intracellular Aβ42 at IC₂₅. This study showed that perturbation of lysosomal function impairs autophagy that leads to intracellular increment of Aβ, indicating the important roles of lysosomes in endothelial cells homeostasis and disease progression.

CD107a+ (LAMP-1) Cytotoxic CD8+ T-Cells in Lupus Nephritis Patients

Cytotoxic CD8+ T-cells play a pivotal role in the pathogenesis of systemic lupus erythematosus (SLE). The aim of this study was to investigate the role of CD107a (LAMP-1) on cytotoxic CD8+ T-cells in SLE-patients in particular with lupus nephritis. Peripheral blood of SLE-patients (n = 31) and healthy controls (n = 21) was analyzed for the expression of CD314 and CD107a by flow cytometry. Kidney biopsies of lupus nephritis patients were investigated for the presence of CD8+ and C107a+ cells by immunohistochemistry and immunofluorescence staining. The percentages of CD107a+ on CD8+ T-cells were significantly decreased in SLE-patients as compared to healthy controls (40.2 ± 18.5% vs. 47.9 ± 15.0%, p = 0.02). This was even more significant in SLE-patients with inactive disease. There was a significant correlation between the percentages of CD107a+CD8+ T-cells and SLEDAI. The evaluation of lupus nephritis biopsies showed a significant number of CD107a+CD8+ T-cells mainly located in the peritubular infiltrates. The intrarenal expression of CD107a+ was significantly correlated with proteinuria. These results demonstrate that CD8+ T-cells of patients with systemic lupus erythematosus have an altered expression of CD107a which seems to be associated with disease activity. The proof of intrarenal CD107a+CD8+ suggests a role in the pathogenesis of lupus nephritis.

Silica dust exposure induces autophagy in alveolar macrophages through switching Beclin1 affinity from Bcl-2 to PIK3C3

Increased deposition of silica dust in pulmonary interstitial tissues leads to silicosis, in which autophagy plays a defensive role in silica dust-associated stress response and cell death. Our previous studies revealed that silica dust exposure contributed to autophagy in pulmonary macrophages in vivo, while the specific regulatory mechanism is still unclear. This study aimed to figure out the regulatory mechanism as well as the role of autophagy in the pathogenesis of experimental silicosis. We used 3-methyladenine (3-MA) and ABT-737 to suppress the expression of phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3) and B cell leukemia/lymphoma 2 (Bcl-2), two critical initiators of autophagy, and detected and evaluated the autophagy in NR8383 cells with or without silica dust exposure. We found that exposure of silica dust increased autophagy in NR8383 cells and elevated the expression of Beclin1 and PIK3C3, but it reduced the expression of Bcl-2. The relationship among Beclin1, PIK3C3, and Bcl-2 were then investigated using immunoprecipitation analysis, and we found that suppression of PIK3C3 and/or Bcl-2 using 3-MA and/or ABT-737 could alter the autophagy induced by silica dust in NR8383 cells, and the complexes of Beclin1/PIK3C3 and Beclin1/Bcl-2 were both downregulated, which may be that inhibition of PIK3C3 and Bcl-2 altered the affinity of Beclin1 with PIK3C3 and Bcl-2 and lead to the silence of PIK3C3 signaling. These findings indicate that silica dust exposure induces autophagy via changing the connectivity of Beclin1 from Bcl-2 to PIK3C3.

Genes expression profiling of alveolar macrophages exposed to non-functionalized, anionic and cationic multi-walled carbon nanotubes shows three different mechanisms of toxicity

Functionalized multi-walled carbon nanotubes (MWCNT) have become the focus of increased research interest, particularly in their application as tools in different areas, such as the biomedical field. Despite the benefits associated with functionalization of MWCNT, particularly in overcoming issues relating to solubility, several studies have demonstrated that these functionalized nanoparticles display different toxicity profiles. For this study, we aim to compare NR8383 cells responses to three well-characterized MWCNT with varying functional groups. This study employed cytotoxicity assays, transcriptomics and proteomics to assess their toxicity using NR8383 rat alveolar macrophages as an in vitro model. The study findings indicated that all MWCNT altered ribosomal protein translation, cytoskeleton arrangement and induced pro-inflammatory response. Only functionalized MWCNT alter mTOR signaling pathway in conjunction with increased Lamtor gene expression. Furthermore, the type of functionalization was also important, with cationic MWCNT activating the transcription factor EB and inducing autophagy while the anionic MWCNT altering eukaryotic translation initiation factor 4 (EIF4) and phosphoprotein 70 ribosomal protein S6 kinase (p70S6K) signaling pathway as well as upregulation Tlr2 gene expression. This study proposes that MWCNT toxicity mechanisms are functionalization dependent and provides evidence that inflammatory response is a key event of carbon nanotubes toxicity.

Intracellular distribution and internalization pathways of guanidinylated bioresponsive poly(amido amine)s in gene delivery

Guanidinylated bioresponsive poly(amido amine)s polymers, CAR-CBA and CHL-CBA, were synthesized by Michael-type addition reaction between guanidine hydrochloride (CAR) or chlorhexidine (CHL) and N,N'-cystaminebisacrylamide (CBA). Previous studies have shown that both polymers had high transfection efficiencies as gene delivery carriers. In this study, we investigated the nucleolus localization abilities and cellular internalization pathways of these two polymers in gene delivery. Each polymer condensed plasmid DNA (pDNA) and formed nanoparticle complexes, and then their transfection studies were performed in MCF-7 cells. Both complexes were found enriched in nucleolus after cellular transfection, and their transfection efficiencies were significantly improved when transfection was performed on MCF-7 cells arrested at M phase. The transfection efficiency of CAR-CBA-pDNA was inhibited by chlorpromazine, and cell endosomes were disrupted after being exposed to CAR-CBA-pDNA. In regards to CHL-CBA-pDNA, its transfection efficiency was not affected by three types of endocytosis inhibitors used in the study, and CHL-CBA-pDNA showed no effect on endosomes. Cellular lactate dehydrogenase release and membrane morphology were changed after cells were transfected by the two complexes. The results indicated that both CAR-CBA and CHL-CBA polymers demonstrated good nucleolus localization abilities. It was beneficial for transfection when cells were arrested at M phase. CAR-CBA-pDNA cellular internalization was involved with clathrin-mediated endocytosis pathway, and escaping from endosomal entrapment, while the cellular uptake of CHL-CBA-pDNA occurs via clathrin- and caveolae-independent mechanism.

Expression and purification of a rapidly degraded protein, TMEM8B-a, in mammalian cell line

TMEM8B-a protein is the longer, predominant isoform of the TMEM8B gene product, which is a tumor metastasis suppressor in nasopharyngeal carcinoma (NPC) and lung cancer. TMEM8B-a is rapidly degraded via the proteasome pathway mediated by ezrin in many NPC and lung cancer cell lines, but TMEM8B-a is not ubiquitinated. In this study, we report the recombinant production of full-length modified TMEM8B-a in mammalian cells. We used the PiggyBac transposon system to efficiently generate normal and lung cancer cell lines with stable TMEM8B-a protein expression. 293FT cells were the best host cell line to express TMEM8B-a protein. Then, we treated the stable 293FT cell lines with various small-molecule inhibitors and demonstrated that treatment with MG-132 and bortezomib, which target the proteasome and disrupt its function, could prevent TMEM8B-a degradation and induce protein expression in 293FT cells. Finally, we utilized the combination of Twin-Strep-tag and Strep-Tactin XT resin to successfully purify the TMEM8B-a protein. The final yield was estimated to be approximately 10-20 μg of the purified TMEM8B-a per 3.0 × 10⁸ 293FT cells.

p53-Dependent PUMA to DRAM antagonistic interplay as a key molecular switch in cell-fate decision in normal/high glucose conditions

Background

As an important cellular stress sensor phosphoprotein p53 can trigger cell cycle arrest and apoptosis and regulate autophagy. The p53 activity mainly depends on its transactivating function, however, how p53 can select one or another biological outcome is still a matter of profound studies. Our previous findings indicate that switching cancer cells in high glucose (HG) impairs p53 apoptotic function and the transcription of target gene PUMA.

Methods and results

Here we report that, in response to drug adriamycin (ADR) in HG, p53 efficiently induced the expression of DRAM (damage-regulated autophagy modulator), a p53 target gene and a stress-induced regulator of autophagy. We found that ADR treatment of cancer cells in HG increased autophagy, as displayed by greater LC3II accumulation and p62 degradation compared to ADR-treated cells in low glucose. The increased autophagy in HG was in part dependent on p53-induced DRAM; indeed DRAM knockdown with specific siRNA reversed the expression of the autophagic markers in HG. A similar outcome was achieved by inhibiting p53 transcriptional activity with pifithrin-α. DRAM knockdown restored the ADR-induced cell death in HG to the levels obtained in low glucose. A similar outcome was achieved by inhibition of autophagy with cloroquine (CQ) or with silencing of autophagy gene ATG5. DRAM knockdown or inhibition of autophagy were both able to re-induce PUMA transcription in response to ADR, underlining a reciprocal interplay between PUMA to DRAM to unbalance p53 apoptotic activity in HG. Xenograft tumors transplanted in normoglycemic mice displayed growth delay after ADR treatment compared to those transplanted in diabetics mice and such different in vivo response correlated with PUMA to DRAM gene expression.

Conclusions

Altogether, these findings suggest that in normal/high glucose condition a mutual unbalance between p53-dependent apoptosis (PUMA) and autophagy (DRAM) gene occurred, modifying the ADR-induced cancer cell death in HG both in vitro and in vivo.

Selective imaging of internalized proteopathic α-synuclein seeds in primary neurons reveals mechanistic insight into transmission of synucleinopathies

Direct cell-to-cell transmission of proteopathic α-synuclein (α-syn) aggregates is thought to underlie the progression of neurodegenerative synucleinopathies. However, the specific intracellular processes governing this transmission remain unclear because currently available model systems are limited. For example, in cell culture models of α-syn-seeded aggregation, it is difficult to discern intracellular from extracellular exogenously applied α-syn seed species. Herein, we employed fluorescently labeled α-syn preformed fibrils (pffs) in conjunction with the membrane-impermeable fluorescence quencher trypan blue to selectively image internalized α-syn seeds in cultured primary neurons and to quantitatively characterize the concentration dependence, time course, and inhibition of pff uptake. To study the long-term fates of exogenous α-syn pffs in neurons, we developed a pff species labeled at amino acid residue 114 with the environmentally insensitive fluorophore BODIPY or the pH-sensitive dye pHrodo red. We found that pffs are rapidly trafficked along the endolysosomal pathway, where most of the material remains for days. We also found that brief pharmacological perturbation of lysosomes shortly after the pff treatment causes aberrations in intracellular processing of pff seeds concomitant with an increased rate of inclusion formation via recruitment of endogenous α-syn to a relatively small number of exogenous seeds. Our results validate a quantitative assay for pff uptake in primary neurons, implicate lysosomal processing as the major fate of internalized proteopathic seeds, and suggest lysosomal integrity as a significant rate-determining step in the transmission of α-syn pathology. Further, lysosomal processing of transmitted seeds may represent a new therapeutic target to combat the spread of synucleinopathies.

Intracellular Distribution and Nuclear Activity of Antisense Oligonucleotides After Unassisted Uptake in Myoblasts and Differentiated Myotubes In Vitro

Clinical efficacy of antisense oligonucleotides (AONs) for the treatment of neuromuscular disorders depends on efficient cellular uptake and proper intracellular routing to the target. Selection of AONs with highest in vitro efficiencies is usually based on chemical or physical methods for forced cellular delivery. Since these methods largely bypass existing natural mechanisms for membrane passage and intracellular trafficking, spontaneous uptake and distribution of AONs in cells are still poorly understood. Here, we report on the unassisted uptake of naked AONs, so-called gymnosis, in muscle cells in culture. We found that gymnosis works similarly well for proliferating myoblasts as for terminally differentiated myotubes. Cell biological analyses combined with microscopy imaging showed that a phosphorothioate backbone promotes efficient gymnosis, that uptake is clathrin mediated and mainly results in endosomal-lysosomal accumulation. Nuclear localization occurred at a low level, but the gymnotically delivered AONs effectively modulated the expression of their nuclear RNA targets. Chloroquine treatment after gymnotic delivery helped increase nuclear AON levels. In sum, we demonstrate that gymnosis is feasible in proliferating and non-proliferating muscle cells and we confirm the relevance of AON chemistry for uptake and intracellular trafficking with this method, which provides a useful means for bio-activity screening of AONs in vitro.

Sphingosine and Sphingosine Kinase 1 Involvement in Endocytic Membrane Trafficking

The balance between cholesterol and sphingolipids within the plasma membrane has long been implicated in endocytic membrane trafficking. However, in contrast to cholesterol functions, little is still known about the roles of sphingolipids and their metabolites. Perturbing the cholesterol/sphingomyelin balance was shown to induce narrow tubular plasma membrane invaginations enriched with sphingosine kinase 1 (SphK1), the enzyme that converts the bioactive sphingolipid metabolite sphingosine to sphingosine-1-phosphate, and suggested a role for sphingosine phosphorylation in endocytic membrane trafficking. Here we show that sphingosine and sphingosine-like SphK1 inhibitors induced rapid and massive formation of vesicles in diverse cell types that accumulated as dilated late endosomes. However, much smaller vesicles were formed in SphK1-deficient cells. Moreover, inhibition or deletion of SphK1 prolonged the lifetime of sphingosine-induced vesicles. Perturbing the plasma membrane cholesterol/sphingomyelin balance abrogated vesicle formation. This massive endosomal influx was accompanied by dramatic recruitment of the intracellular SphK1 and Bin/Amphiphysin/Rvs domain-containing proteins endophilin-A2 and endophilin-B1 to enlarged endosomes and formation of highly dynamic filamentous networks containing endophilin-B1 and SphK1. Together, our results highlight the importance of sphingosine and its conversion to sphingosine-1-phosphate by SphK1 in endocytic membrane trafficking.

A Grand Challenge. 2. Phenotypic Profiling of a Natural Product Library on Parkinson's Patient-Derived Cells

Harnessing the inherent biological relevance of natural products requires a method for the recognition of biological effects that may subsequently lead to the discovery of particular targets. An unbiased multidimensional profiling method was used to examine the activities of natural products on primary cells derived from a Parkinson's disease patient. The biological signature of 482 natural products was examined using multiparametric analysis to investigate known cellular pathways and organelles implicated in Parkinson's disease such as mitochondria, lysosomes, endosomes, apoptosis, and autophagy. By targeting several cell components simultaneously the chance of finding a phenotype was increased. The phenotypes were then clustered using an uncentered correlation. The multidimensional phenotypic screening showed that all natural products, in our screening set, were biologically relevant compounds as determined by an observed phenotypic effect. Multidimensional phenotypic screening can predict the cellular function and subcellular site of activity of new compounds, while the cluster analysis provides correlation with compounds with known mechanisms of action. This study reinforces the value of natural products as biologically relevant compounds.

Neuronal Storage Disease in a Group of Captive Humboldt Penguins (Spheniscus humboldti)

A neuronal storage disease affecting 5 captive Humboldt penguins is described. One bird died after 3 days of lethargy and anorexia. The 4 remaining birds died after a slowly progressing course of disease with signs that included lethargy, weakness, and neurologic dysfunction. Neurologic signs included dysphagia and ataxia. Gross lesions in the first animal to die consisted of hepatosplenomegaly indicative of avian malaria, which was confirmed histologically. The 4 remaining animals were mildly to moderately emaciated. Moderate to marked vacuolation of the neuronal perikarya was observed in Purkinje cells, neurons of the brainstem nuclei, and motorneurons of the spinal cord in all birds. By electron microscopy the vacuoles represented multilayered concentric lamellar structures. These findings were indicative of sphingolipidosis. All animals had been prophylactically treated for avian malaria, aspergillosis, and possible bacterial infections with chloroquine, itraconazole, and enrofloxacin. circumstantial evidence implicates chloroquine therapy as the possible cause of the storage disease.

WO3/Pt nanoparticles are NADPH oxidase biomimetics that mimic effector cells in vitro and in vivo

To provide a means of delivering an artificial immune effector cell-like attack on tumor cells, we report the tumoricidal ability of inorganic WO3/Pt nanoparticles that mimic a leukocyte's functional abilities. These nanoparticles route electrons from organic structures and electron carriers to form hydroxyl radicals within tumor cells. During visible light exposure, WO3/Pt nanoparticles manufacture hydroxyl radicals, degrade organic compounds, use NADPH, trigger lipid peroxidation, promote lysosomal membrane disruption, promote the loss of reduced glutathione, and activate apoptosis. In a model of advanced breast cancer metastasis to the eye's anterior chamber, we show that WO3/Pt nanoparticles prolong the survival of 4T1 tumor-bearing Balb/c mice. This new generation of inorganic photosensitizers do not photobleach, and therefore should provide an important therapeutic advance in photodynamic therapy. As biomimetic nanoparticles destroy targeted cells, they may be useful in treating ocular and other forms of cancer.

Dynamin Regulates Autophagy by Modulating Lysosomal Function

Autophagy is a central lysosomal degradation pathway required for maintaining cellular homeostasis and its dysfunction is associated with numerous human diseases. To identify players in autophagy, we tested ∼1200 chemically induced mutations on the X chromosome in Drosophila fat body clones and discovered that shibire (shi) plays an essential role in starvation-induced autophagy. shi encodes a dynamin protein required for fission of clathrin-coated vesicles from the plasma membrane during endocytosis. We showed that Shi is dispensable for autophagy initiation and autophagosome-lysosome fusion, but required for lysosomal/autolysosomal acidification. We also showed that other endocytic core machinery components like clathrin and AP2 play similar but not identical roles in regulating autophagy and lysosomal function as dynamin. Previous studies suggested that dynamin directly regulates autophagosome formation and autophagic lysosome reformation (ALR) through its excision activity. Here, we provide evidence that dynamin also regulates autophagy indirectly by regulating lysosomal function.

Signaling of chloroquine-induced stress in the yeast Saccharomyces cerevisiae requires the Hog1 and Slt2 mitogen-activated protein kinase pathways

Chloroquine (CQ) has been under clinical use for several decades, and yet little is known about CQ sensing and signaling mechanisms or about their impact on various biological pathways. We employed the budding yeast Saccharomyces cerevisiae as a model organism to study the pathways targeted by CQ. Our screening with yeast mutants revealed that it targets histone proteins and histone deacetylases (HDACs). Here, we also describe the novel role of mitogen-activated protein kinases Hog1 and Slt2, which aid in survival in the presence of CQ. Cells deficient in Hog1 or Slt2 are found to be CQ hypersensitive, and both proteins were phosphorylated in response to CQ exposure. CQ-activated Hog1p is translocated to the nucleus and facilitates the expression of GPD1 (glycerol-3-phosphate dehydrogenase), which is required for the synthesis of glycerol (one of the major osmolytes). Moreover, cells treated with CQ exhibited an increase in intracellular reactive oxygen species (ROS) levels and the effects were rescued by addition of reduced glutathione to the medium. The deletion of SOD1, the superoxide dismutase in yeast, resulted in hypersensitivity to CQ. We have also observed P38 as well as P42/44 phosphorylation in HEK293T human cells upon exposure to CQ, indicating that the kinds of responses generated in yeast and human cells are similar. In summary, our findings define the multiple biological pathways targeted by CQ that might be useful for understanding the toxicity modulated by this pharmacologically important molecule.

Chloroquine has a cytotoxic effect on Acanthamoeba encystation through modulation of autophagy

Encystation of Acanthamoeba castellanii is associated with resistance to chemotherapeutic agents. Blocking the encystation process could potentiate the efficacy of chemotherapeutic agents and biocides. During encystation, autophagy is highly stimulated and required for proper encystation of Acanthamoeba. In this study, the cytotoxic effect of chloroquine, a well-known autophagy-inhibitory drug, was tested in A. castellanii. Chloroquine was able to selectively reduce cell survival during the encystation of A. castellanii. However, A. castellanii trophozoites and mature cysts were resistant to chloroquine. Chloroquine treatment led to an increase in the number and size of lysosomes in encysting cells. Moreover, chloroquine inhibited the degradation of long-lived proteins in the encysting cells. Decreased autophagic flux, indicated by an increased number of lysosomes and decreased degradation of long-lived proteins, may be the mechanism by which cell death is induced by chloroquine in encysting Acanthamoeba. These results suggest a potential novel therapeutic application of chloroquine as an anti-Acanthamoeba drug. Our findings also suggest that targeting autophagy could be a therapeutic strategy against Acanthamoeba infection.

Chemoprevention of prostate cancer by d,l-sulforaphane is augmented by pharmacological inhibition of autophagy

There is a preclinical evidence that the oral administration of d,l-sulforaphane (SFN) can decrease the incidence or burden of early-stage prostate cancer [prostatic intraepithelial neoplasia (PIN)] and well-differentiated cancer (WDC) but not late-stage poorly differentiated cancer (PDC). Because SFN treatment induces cytoprotective autophagy in cultured human prostate cancer cells, the present study tested the hypothesis that chemopreventive efficacy of SFN could be augmented by the pharmacologic inhibition of autophagy using chloroquine (CQ). Incidence of PDC characterized by prostate weight of more than 1 g was significantly lower in the SFN + CQ group than in control (P = 0.004), CQ group (P = 0.026), or SFN group (P = 0.002 by Fisher exact test). Average size of the metastatic lymph node was lower by about 42% in the SFN + CQ group than in control (P = 0.043 by Wilcoxon test). On the other hand, the SFN + CQ combination was not superior to SFN alone with respect to inhibition of incidence or burden of microscopic PIN or WDC. SFN treatment caused in vivo autophagy as evidenced by transmission electron microscopy. Mechanistic studies showed that prevention of prostate cancer and metastasis by the SFN + CQ combination was associated with decreased cell proliferation, increased apoptosis, alterations in protein levels of autophagy regulators Atg5 and phospho-mTOR, and suppression of biochemical features of epithelial-mesenchymal transition. Plasma proteomics identified protein expression signature that may serve as biomarker of SFN + CQ exposure/response. This study offers a novel combination regimen for future clinical investigations for prevention of prostate cancer in humans.

Glucose restriction induces cell death in parental but not in homeodomain-interacting protein kinase 2-depleted RKO colon cancer cells: molecular mechanisms and implications for tumor therapy

Tumor cell tolerance to nutrient deprivation can be an important factor for tumor progression, and may depend on deregulation of both oncogenes and oncosuppressor proteins. Homeodomain-interacting protein kinase 2 (HIPK2) is an oncosuppressor that, following its activation by several cellular stress, induces cancer cell death via p53-dependent or -independent pathways. Here, we used genetically matched human RKO colon cancer cells harboring wt-HIPK2 (HIPK2^+/+) or stable HIPK2 siRNA interference (siHIPK2) to investigate in vitro whether HIPK2 influenced cell death in glucose restriction. We found that glucose starvation induced cell death, mainly due to c-Jun NH2-terminal kinase activation, in HIPK2^+/+cells compared with siHIPK2 cells that did not die. ¹H-nuclear magnetic resonance quantitative metabolic analyses showed a marked glycolytic activation in siHIPK2 cells. However, treatment with glycolysis inhibitor 2-deoxy-𝒟-glucose induced cell death only in HIPK2^+/+ cells but not in siHIPK2 cells. Similarly, siGlut-1 interference did not re-establish siHIPK2 cell death under glucose restriction, whereas marked cell death was reached only after zinc supplementation, a condition known to reactivate misfolded p53 and inhibit the pseudohypoxic phenotype in this setting. Further siHIPK2 cell death was reached with zinc in combination with autophagy inhibitor. We propose that the metabolic changes acquired by cells after HIPK2 silencing may contribute to induce resistance to cell death in glucose restriction condition, and therefore be directly relevant for tumor progression. Moreover, elimination of such a tolerance might serve as a new strategy for cancer therapy.

Protective effects of sinapic acid on lysosomal dysfunction in isoproterenol induced myocardial infarcted rats

In the pathology of myocardial infarction, lysosomal lipid peroxidation and resulting enzyme release play an important role. We evaluated the protective effects of sinapic acid on lysosomal dysfunction in isoproterenol induced myocardial infarcted rats. Male Wistar rats were treated with sinapic acid (12 mg/kg body weight) orally daily for 10 days and isoproterenol (100 mg/kg body weight) was injected twice at an interval of 24 h (9th and 10th day). Then, lysosomal lipid peroxidation, lysosomal enzymes in serum, heart homogenate, lysosomal fraction and myocardial infarct size were measured. Isoproterenol induced myocardial infarcted rats showed a significant increase in serum creatine kinase-MB and lysosomal lipid peroxidation. The activities of β-glucuronidase, β-galactosidase, cathepsin-B and D were significantly increased in serum, heart and the activities of β-glucuronidase and cathepsin-D were significantly decreased in lysosomal fraction of myocardial infarcted rats. Pre-and-co-treatment with sinapic acid normalized all the biochemical parameters and reduced myocardial infarct size in myocardial infarcted rats. In vitro studies confirmed the free radical scavenging effects of sinapic acid. The possible mechanisms for the observed effects are attributed to sinapic acid's free radical scavenging and membrane stabilizing properties. Thus, sinapic acid has protective effects on lysosomal dysfunction in isoproterenol induced myocardial infarcted rats.

Chloroquine-mediated lysosomal dysfunction enhances the anticancer effect of nutrient deprivation

PURPOSE

To investigate the ability of chloroquine, a lysosomotropic autophagy inhibitor, to enhance the anticancer effect of nutrient deprivation.

METHODS

Serum-deprived U251 glioma, B16 melanoma and L929 fibrosarcoma cells were treated with chloroquine in vitro. Cell viability was measured by crystal violet and MTT assay. Oxidative stress, apoptosis/necrosis and intracellular acidification were analyzed by flow cytometry. Cell morphology was examined by light and electron microscopy. Activation of AMP-activated protein kinase (AMPK) and autophagy were monitored by immunoblotting. RNA interference was used for AMPK and LC3b knockdown. The anticancer efficiency of intraperitoneal chloroquine in calorie-restricted mice was assessed using a B16 mouse melanoma model.

RESULTS

Chloroquine rapidly killed serum-starved cancer cells in vitro. This effect was not mimicked by autophagy inhibitors or LC3b shRNA, indicating autophagy-independent mechanism. Chloroquine-induced lysosomal accumulation and oxidative stress, leading to mitochondrial depolarization, caspase activation and mixed apoptotic/necrotic cell death, were prevented by lysosomal acidification inhibitor bafilomycin. AMPK downregulation participated in chloroquine action, as AMPK activation reduced, and AMPK shRNA mimicked chloroquine toxicity. Chloroquine inhibited melanoma growth in calorie-restricted mice, causing lysosomal accumulation, mitochondrial disintegration and selective necrosis of tumor cells.

CONCLUSION

Combined treatment with chloroquine and calorie restriction might be useful in cancer therapy.

Glucuronidated quercetin lowers blood pressure in spontaneously hypertensive rats via deconjugation

Background

Chronic oral quercetin reduces blood pressure and restores endothelial dysfunction in hypertensive animals. However, quercetin (aglycone) is usually not present in plasma, because it is rapidly metabolized into conjugated, mostly inactive, metabolites. The aim of the study is to analyze whether deconjugation of these metabolites is involved in the blood pressure lowering effect of quercetin.

Methodology/Principal Findings

We have analyzed the effects on blood pressure and vascular function in vitro of the conjugated metabolites of quercetin (quercetin-3-glucuronide, Q3GA; isorhamnetin-3-glucuronide, I3GA; and quercetin-3′-sulfate, Q3'S) in spontaneously hypertensive rats (SHR). Q3GA and I3GA (1 mg/kg i.v.), but not Q3'S, progressively reduced mean blood pressure (MBP), measured in conscious SHR. The hypotensive effect of Q3GA was abolished in SHR treated with the specific inhibitor of β-glucuronidase, saccharic acid 1,4-lactone (SAL, 10 mg/ml). In mesenteric arteries, unlike quercetin, Q3GA had no inhibitory effect in the contractile response to phenylephrine after 30 min of incubation. However, after 1 hour of incubation Q3GA strongly reduced this contractile response and this effect was prevented by SAL. Oral administration of quercetin (10 mg/Kg) induced a progressive decrease in MBP, which was also suppressed by SAL.

Conclusions

Conjugated metabolites are involved in the in vivo antihypertensive effect of quercetin, acting as molecules for the plasmatic transport of quercetin to the target tissues. Quercetin released from its glucuronidated metabolites could be responsible for its vasorelaxant and hypotensive effect.

A novel role for α-tocopherol transfer protein (α-TTP) in protecting against chloroquine toxicity

Chloroquine (CQ) is a widely prescribed anti-malarial agent and is also prescribed to treat autoimmune diseases. Clinical treatment with CQ is often accompanied by serious side effects such as hepatitis and retinopathy. As a weak base, CQ accumulates in intracellular acidic organelles, raises the pH, and induces osmotic swelling and permeabilization of acidic organelles, which account for CQ-induced cytotoxicity. We reported previously that CQ treatment caused α-tocopherol transfer protein (α-TTP), a gene product of familial vitamin E deficiency, to change its location from the cytosol to the surface of acidic organelles. Here we show that α-TTP plays a novel role in protecting against CQ toxicity both in vitro and in vivo. In the presence of CQ, rat hepatoma McARH7777 cells, which do not express α-TTP endogenously, showed more severe cytotoxicity, such as larger vacuolation of acidic organelles and caspase activation, than α-TTP transfectant cells. Similarly, α-TTP knockout mice showed more severe CQ toxicity, such as hepatotoxicity and retinopathy, than wild-type mice. These effects were not ameliorated by vitamin E supplementation. In contrast to bafilomycin A1 treatment, which prevents CQ accumulation in cells by raising the pH of acidic organelles, α-TTP expression prevented CQ accumulation without affecting the pH of acidic organelles. Taken together, our data suggest that α-TTP protects against CQ toxicity by preventing CQ accumulation in acidic organelles through a mechanism distinct from vitamin E transport.

Uptake and intracellular traffic of siRNA dendriplexes in glioblastoma cells and macrophages

BACKGROUND

Gene silencing using small interfering RNA (siRNA) is a promising new therapeutic approach for glioblastoma. The endocytic uptake and delivery of siRNA to intracellular compartments could be enhanced by complexation with polyamidoamine dendrimers. In the present work, the uptake mechanisms and intracellular traffic of siRNA/generation 7 dendrimer complexes (siRNA dendriplexes) were screened in T98G glioblastoma and J774 macrophages.

METHODS

The effect of a set of chemical inhibitors of endocytosis on the uptake and silencing capacity of dendriplexes was determined by flow cytometry. Colocalization of fluorescent dendriplexes with endocytic markers and occurrence of intracellular dissociation were assessed by confocal laser scanning microscopy.

RESULTS

Uptake of siRNA dendriplexes by T98G cells was reduced by methyl-β-cyclodextrin, and genistein, and cytochalasine D, silencing activity was reduced by genistein; dendriplexes colocalized with cholera toxin subunit B. Therefore, caveolin-dependent endocytosis was involved both in the uptake and silencing activity of siRNA dendriplexes. On the other hand, uptake of siRNA dendriplexes by J774 cells was reduced by methyl-β-cyclodextrin, genistein, chlorpromazine, chloroquine, cytochalasine D, and nocodazole, the silencing activity was not affected by chlorpromazine, genistein or chloroquine, and dendriplexes colocalized with transferrin and cholera toxin subunit B. Thus, both clathrin-dependent and caveolin-dependent endocytosis mediated the uptake and silencing activity of the siRNA dendriplexes. SiRNA dendriplexes were internalized at higher rates by T98G but induced lower silencing than in J774 cells. SiRNA dendriplexes showed relatively slow dissociation kinetics, and their escape towards the cytosol was not mediated by acidification independently of the uptake pathway.

CONCLUSION

The extent of cellular uptake of siRNA dendriplexes was inversely related to their silencing activity. The higher silencing activity of siRNA dendriplexes in J774 cells could be ascribed to the contribution of clathrin-dependent and caveolin-dependent endocytosis vs only caveolin-dependent endocytosis in T98G cells.

Transient lysosomal activation is essential for p75 nerve growth factor receptor expression in myelinated Schwann cells during Wallerian degeneration

Myelinated Schwann cells in the peripheral nervous system express the p75 nerve growth factor receptor (p75NGFR) as a consequence of Schwann cell dedifferentiation during Wallerian degeneration. p75NGFR has been implicated in the remyelination of regenerating nerves. Although many studies have shown various mechanisms underlying Schwann cell dedifferentiation, the molecular mechanism contributing to the re-expression of p75NGFR in differentiated Schwann cells is largely unknown. In the present study, we found that lysosomes were transiently activated in Schwann cells after nerve injury and that the inhibition of lysosomal activation by chloroquine or lysosomal acidification inhibitors prevented p75NGFR expression at the mRNA transcriptional level in an ex vivo Wallerian degeneration model. Lysosomal acidification inhibitors suppressed demyelination, but not axonal degeneration, thereby suggesting that demyelination mediated by lysosomes may be an important signal for inducing p75NGFR expression. Tumor necrosis factor-α (TNF-α) has been suggested to be involved in regulating p75NGFR expression in Schwann cells. In this study, we found that removing TNF-α in vivo did not significantly suppress the induction of both lysosomes and p75NGFR. Thus, these findings suggest that lysosomal activation is tightly correlated with the induction of p75NGFR in demyelinating Schwann cells during Wallerian degeneration.

A novel interaction of CLN3 with nonmuscle myosin-IIB and defects in cell motility of Cln3(-/-) cells

Juvenile neuronal ceroid lipofuscinosis (JNCL) is a pediatric lysosomal storage disorder characterized by accumulation of autofluorescent storage material and neurodegeneration, which result from mutations in CLN3. The function of CLN3, a lysosomal membrane protein, is currently unknown. We report that CLN3 interacts with cytoskeleton-associated nonmuscle myosin-IIB. Both CLN3 and myosin-IIB are ubiquitously expressed, yet mutations in either produce dramatic consequences in the CNS such as neurodegeneration in JNCL patients and Cln3(-/-) mouse models, or developmental deficiencies in Myh10(-/-) mice, respectively. A scratch assay revealed a migration defect associated with Cln3(-/-) cells. Inhibition of nonmuscle myosin-II with blebbistatin in WT cells resulted in a phenotype that mimics the Cln3(-/-) migration defect. Moreover, inhibiting lysosome function by treating cells with chloroquine exacerbated the migration defect in Cln3(-/-). Cln3(-/-) cells traversing a transwell filter under gradient trophic factor conditions displayed altered migration, further linking lysosomal function and cell migration. The myosin-IIB distribution in Cln3(-/-) cells is elongated, indicating a cytoskeleton defect caused by the loss of CLN3. In summary, cells lacking CLN3 have defects that suggest altered myosin-IIB activity, supporting a functional and physical interaction between CLN3 and myosin-IIB. We propose that the migration defect in Cln3(-/-) results, in part, from the loss of the CLN3-myosin-IIB interaction.

Ectodomain shedding of interleukin-2 receptor beta and generation of an intracellular functional fragment

Interleukin-2 (IL-2) regulates different functions of various lymphoid cell subsets. These are mediated by its binding to the IL-2 receptor (IL-2R) composed of three subunits (IL2-Ralpha, -beta, and -gamma(c)). IL-2Rbeta is responsible for the activation of several signaling pathways. Ectodomain shedding of membrane receptors is thought to be an important mechanism for down-regulation of cell surface receptor abundance but is also emerging as a mechanism that cell membrane-associated molecules require for proper action in vivo. Here, we demonstrate that IL-2Rbeta is cleaved in cell lines of different origin, including T cells, generating an intracellular 37-kDa fragment (37beta ic) that comprises the full intracellular C-terminal and transmembrane domains. Ectodomain shedding of IL-2Rbeta decreases in a mutant deleted of the juxtamembrane region, where cleavage is predicted to occur, and is inhibited by tissue inhibitor of metalloproteases-3. 37Beta ic is tyrosine-phosphorylated and associates with STAT-5, a canonic signal transducer of IL-2R. Finally, lymphoid cell transfection with a truncated form of IL-2Rbeta mimicking 37beta ic increases their proliferation. These data indicate that IL-2Rbeta is subject to ectodomain shedding generating an intracellular fragment biologically functional, because (i) it is phosphorylated, (ii) it associates with STAT5A, and (iii) it increases cell proliferation.

Autophagy is a renoprotective mechanism during in vitro hypoxia and in vivo ischemia-reperfusion injury

Autophagy mediates bulk degradation and recycling of cytoplasmic constituents to maintain cellular homeostasis. In response to stress, autophagy is induced and may either contribute to cell death or serve as a cell survival mechanism. Very little is known about autophagy in renal pathophysiology. This study examined autophagy and its pathological role in renal cell injury using in vitro and in vivo models of ischemia-reperfusion. We found that hypoxia (1% O2) induced autophagy in cultured renal proximal tubular cells. Blockade of autophagy by 3-methyladenine or small-interfering RNA knockdown of Beclin-1 and ATG5 (two key autophagic genes) sensitized the tubular cells to hypoxia-induced apoptosis. In an in vitro model of ischemia-reperfusion, autophagy was not induced by anoxic (0% O2) incubation in glucose-free buffer, but was induced during subsequent recovery/reperfusion period. In this model, suppression of autophagy also enhanced apoptosis. In vivo, autophagy was induced in kidney tissues during renal ischemia-reperfusion in mice. Autophagy was not obvious during the ischemia period, but was significantly enhanced during reperfusion. Inhibition of autophagy by chloroquine and 3-methyladenine worsened renal ischemia/reperfusion injury, as indicated by renal function, histology, and tubular apoptosis. Together, the results demonstrated autophagy induction during hypoxic and ischemic renal injury. Under these pathological conditions, autophagy may provide a protective mechanism for cell survival.

Oxidative stress and autophagy in the regulation of lysosome-dependent neuron death

Lysosomes critically regulate the pH-dependent catabolism of extracellular and intracellular macromolecules delivered from the endocytic/heterophagy and autophagy pathways, respectively. The importance of lysosomes to cell survival is underscored not only by their unique ability effectively to degrade metalloproteins and oxidatively damaged macromolecules, but also by the distinct potential for induction of both caspase-dependent and -independent cell death with a compromise in the integrity of lysosome function. Oxidative stress and free radical damage play a principal role in cell death induced by lysosome dysfunction and may be linked to several upstream and downstream stimuli, including alterations in the autophagy degradation pathway, inhibition of lysosome enzyme function, and lysosome membrane damage. Neurons are sensitive to lysosome dysfunction, and the contribution of oxidative stress and free radical damage to lysosome dysfunction may contribute to the etiology of neurodegenerative disease. This review provides a broad overview of lysosome function and explores the contribution of oxidative stress and autophagy to lysosome dysfunction-induced neuron death. Putative signaling pathways that either induce lysosome dysfunction or result from lysosome dysfunction or both, and the role of oxidative stress, free radical damage, and lysosome dysfunction in pediatric lysosomal storage disorders (neuronal ceroid lipofuscinoses or NCL/Batten disease) and in Alzheimer's disease are emphasized.

Elevated serum β-glucuronidase reflects hepatic lysosomal fragility following toxic liver injury in rats

The level of serum β-glucuronidase increases in various pathological conditions, including liver disorders. The aim of this investigation was to study the changes in liver lysosomal membrane stability during experimentally induced hepatic fibrosis that may result in the elevation of serum β-glucuronidase. Liver injury was induced by intraperitoneal injections of N-nitrosodimethylamine (NDMA) in adult male albino rats over 3 weeks. The progression of fibrosis was evaluated histopathologically as well as by monitoring liver collagen content. Lipid peroxides and β-glucuronidase levels were measured in the liver homogenate and subcellular fractions on days 0, 7, 14, and 21 after the start of NDMA administration. Serum β-glucuronidase levels were also determined. A significant increase was observed in β-glucuronidase levels in the serum, liver homogenate, and subcellular fractions, but not in the nuclear fraction on days 7, 14, and 21 after the start of NDMA administration. Lipid peroxides also increased in the liver homogenate and the lysosomal fraction. The measurement of lysosomal membrane stability revealed a maximum lysosomal fragility on day 21 during NDMA-induced fibrosis. In vitro studies showed that NDMA has no significant effect on liver lysosomal membrane permeability. The results of this investigation demonstrated that lysosomal fragility increases during NDMA-induced hepatic fibrosis, which could be attributed to increased lipid peroxidation of lysosomal membrane. In this study, we also elucidated the mechanism of increased β-glucuronidase and other lysosomal glycohydrolases in the serum during hepatic fibrosis.

Autophagy inhibition enhances therapy-induced apoptosis in a Myc-induced model of lymphoma

Autophagy is a lysosome-dependent degradative pathway frequently activated in tumor cells treated with chemotherapy or radiation. Whether autophagy observed in treated cancer cells represents a mechanism that allows tumor cells to survive therapy or a mechanism for initiating a nonapoptotic form of programmed cell death remains controversial. To address this issue, the role of autophagy in a Myc-induced model of lymphoma generated from cells derived from p53ER(TAM)/p53ER(TAM) mice (with ER denoting estrogen receptor) was examined. Such tumors are resistant to apoptosis due to a lack of nuclear p53. Systemic administration of tamoxifen led to p53 activation and tumor regression followed by tumor recurrence. Activation of p53 was associated with the rapid appearance of apoptotic cells and the induction of autophagy in surviving cells. Inhibition of autophagy with either chloroquine or ATG5 short hairpin RNA (shRNA) enhanced the ability of either p53 activation or alkylating drug therapy to induce tumor cell death. These studies provide evidence that autophagy serves as a survival pathway in tumor cells treated with apoptosis activators and a rationale for the use of autophagy inhibitors such as chloroquine in combination with therapies designed to induce apoptosis in human cancers.

Selective enhancement of cellular oxidative stress by chloroquine: implications for the treatment of glioblastoma multiforme

Chloroquine is used in the treatment of malaria, a disease caused by infection with the parasite Plasmodium. Although chloroquine appears to possess diverse pharmacological activity, its plasmodicidal activity results from augmentation of parasite oxidative stress. Chloroquine also appears to augment oxidative stress in metabolically active mammalian cells, including human astroglial cells. The authors propose that chloroquine may augment oxidative stress induced by radiotherapy in the treatment of glioblastoma multiforme, enhancing therapeutic efficacy. Such an effect would be consistent with the known pharmacological effects of chloroquine observed in Plasmodium. Other selective redox agents, such as tempol and artemisinin, should be investigated clinically for therapeutic benefit when coadministered with combined radio- and chemotherapy for cancer.

Ecotoxicological evaluation of the antimalarial drug chloroquine

There is limited information available about the potential environmental effects of chloroquine (CQ), a widely used antimalarial agent and a promising inexpensive drug in the management of HIV disease. The acute effects of CQ were studied using four ecotoxicological model systems. The most sensitive bioindicator was the immobilization of the cladoceran Daphnia magna, with an EC50 of 12 microM CQ at 72 h and a non-observed adverse effect level of 2.5 microM CQ, followed very closely by the decrease of the uptake of neutral red and the reduction of the lysosomal function in the fish cell line PLHC-1 derived from the top minnow Poeciliopsis lucida, probably due to the selective accumulation of the drug into the lysosomes. There was significant cellular stress as indicated by the increases on metallothionein and glucose-6P dehydrogenase levels after 24 h of exposure and succinate dehydrogenase activity mainly after 48 h. No changes were observed for ethoxyresorufin-O-deethylase (EROD) activity. The least sensitive model was the inhibition of bioluminescence in the bacterium Vibrio fischeri. An increase of more than five-fold in the toxicity from 24 to 72 h of exposure was observed for the inhibition of the growth in the alga Chlorella vulgaris and the content of total protein and MTS tetrazolium salt metabolization in PLHC-1 cells. At the morphological level, the most evident alterations in PLHC-1 cultures were hydropic degeneration from 25 microM CQ after 24h of exposure and the presence of many cells with pyknotic nuclei, condensed cytoplasm and apoptosis with concentrations higher than 50 microM CQ after 48 h of exposure. In conclusion, CQ should be classified as harmful to aquatic organisms.