Accumulation Of Vesicles Research Articles

Caveolae internalization repairs wounded cells and muscle fibers

Rapid repair of plasma membrane wounds is critical for cellular survival. Muscle fibers are particularly susceptible to injury, and defective sarcolemma resealing causes muscular dystrophy. Caveolae accumulate in dystrophic muscle fibers and caveolin and cavin mutations cause muscle pathology, but the underlying mechanism is unknown. Here we show that muscle fibers and other cell types repair membrane wounds by a mechanism involving Ca(2+)-triggered exocytosis of lysosomes, release of acid sphingomyelinase, and rapid lesion removal by caveolar endocytosis. Wounding or exposure to sphingomyelinase triggered endocytosis and intracellular accumulation of caveolar vesicles, which gradually merged into larger compartments. The pore-forming toxin SLO was directly visualized entering cells within caveolar vesicles, and depletion of caveolin inhibited plasma membrane resealing. Our findings directly link lesion removal by caveolar endocytosis to the maintenance of plasma membrane and muscle fiber integrity, providing a mechanistic explanation for the muscle pathology associated with mutations in caveolae proteins. DOI:http://dx.doi.org/10.7554/eLife.00926.001.

Double-membraned Liposomes Sculpted by Poliovirus 3AB Protein

Infection with many positive-strand RNA viruses dramatically remodels cellular membranes, resulting in the accumulation of double-membraned vesicles that resemble cellular autophagosomes. In this study, a single protein encoded by poliovirus, 3AB, is shown to be sufficient to induce the formation of double-membraned liposomes via the invagination of single-membraned liposomes. Poliovirus 3AB is a 109-amino acid protein with a natively unstructured N-terminal domain. HeLa cells transduced with 3AB protein displayed intracellular membrane disruption; specifically, the formation of cytoplasmic invaginations. The ability of a single viral protein to produce structures of similar topology to cellular autophagosomes should facilitate the understanding of both cellular and viral mechanisms for membrane remodeling.

The effect of hydrostatic pressure on structural organization of maize root cells

We analyzed the effect of hydrostatic pressure at 24 MPa level on the growth and organization of corn seedlings cells. At pressure value of 2 MPa, we observed the clarification of the mitochondrial matrix, clusterization of endoplasmic reticulum elements with formation of ergastorplasm sites and the increasing number of small vacuoles in the cytoplasm. We detected the accumulation of vesicles with electron-dense content on the trans side of dictyosomes, which indicates a change in the endomembranous system traffic. The reduction of electronic density of tonoplast was accompanied by a reduction of osmiophilic inclusions in the vacuoles. Increasing the pressure up to 4 MPa showed the emergence of destructive alterations in the tonoplast. None of the variants showed any violation of plasmalemma integrity, as confirmed by coloring with Evans blue. When we reset the hydrostatic pressure to atmospheric pressure, the frequency of structural distortions of the tonoplast membrane was proportional to the pressure difference: the minimum was at reset from 2 to 0 MPa and the maximum was at reset from 4 to 0 MPa. Thus, it has been concluded, that the endomembraneous system is among the targets of pressure effect on the plant cells.

A ginseng metabolite, compound K, induces autophagy and apoptosis via generation of reactive oxygen species and activation of JNK in human colon cancer cells

Compound K (20-O-(β-D-glucopyranosyl)-20(S)-protopanaxadiol) is an active metabolite of ginsenosides and induces apoptosis in various types of cancer cells. This study investigated the role of autophagy in compound K-induced cell death of human HCT-116 colon cancer cells. Compound K activated an autophagy pathway characterized by the accumulation of vesicles, the increased positive acridine orange-stained cells, the accumulation of LC3-II, and the elevation of autophagic flux. Whereas blockade of compound K-induced autophagy by 3-methyladenein and bafilomycin A1 significantly increased cell viability. In addition, compound K augmented the time-dependent expression of the autophagy-related proteins Atg5, Atg6, and Atg7. However, knockdown of Atg5, Atg6, and Atg7 markedly inhibited the detrimental impact of compound K on LC3-II accumulation and cell vitality. Compound K-provoked autophagy was also linked to the generation of intracellular reactive oxygen species (ROS); both of these processes were mitigated by the pre-treatment of cells with the antioxidant N-acetylcysteine. Moreover, compound K activated the c-Jun NH2-terminal kinase (JNK) signaling pathway, whereas downregulation of JNK by its specific inhibitor SP600125 or by small interfering RNA against JNK attenuated autophagy-mediated cell death in response to compound K. Compound K also provoked apoptosis, as evidenced by an increased number of apoptotic bodies and sub-G1 hypodiploid cells, enhanced activation of caspase-3 and caspase-9, and modulation of Bcl-2 and Bcl-2-associated X protein expression. Notably, compound K-stimulated autophagy as well as apoptosis was induced by disrupting the interaction between Atg6 and Bcl-2. Taken together, these results indicate that the induction of autophagy and apoptosis by compound K is mediated through ROS generation and JNK activation in human colon cancer cells.

SCG10 promotes non-amyloidogenic processing of amyloid precursor protein by facilitating its trafficking to the cell surface

The processing of amyloid precursor protein (APP) is a key event in the pathogenesis of Alzheimer's disease. As certain cleavage pathways tend to occur in particular subcellular compartments, the processing of APP is greatly influenced by factors that regulate its trafficking. Here we report that SCG10 directly interacts with the KFFEQ motif of the APP intracellular domain and promotes the non-amyloidogenic processing of the APP. Knockdown of SCG10 led to decreases in α cleavage products, sAPPα and CTFα, while increases of both Aβ1-40 and Aβ1-42. Elevation of SCG10 induced APP accumulation in post-Golgi vesicles and on the cell surface by facilitating its secretory pathway. In addition, the APP processing was dependent on the palmitoylation-mediated membrane-anchoring of SCG10. Furthermore, elevation of SCG10 reduced Aβ accumulation and amyloid plaque formation in the hippocampus of APPswe/PS1dE9 mice. Taken together, these results show that SCG10 has a potential role in preventing and treating Alzheimer's disease.

The intermediate filament network protein, vimentin, is required for parvoviral infection

Intermediate filaments (IFs) have recently been shown to serve novel roles during infection by many viruses. Here we have begun to study the role of IFs during the early steps of infection by the parvovirus minute virus of mice (MVM). We found that during early infection with MVM, after endosomal escape, the vimentin IF network was considerably altered, yielding collapsed immunofluorescence staining near the nuclear periphery. Furthermore, we found that vimentin plays an important role in the life cycle of MVM. The number of cells, which successfully replicated MVM, was reduced in infected cells in which the vimentin network was genetically or pharmacologically modified; viral endocytosis, however, remained unaltered. Perinuclear accumulation of MVM-containing vesicles was reduced in cells lacking vimentin. Our data suggests that vimentin is required for the MVM life cycle, presenting possibly a dual role: (1) following MVM escape from endosomes and (2) during endosomal trafficking of MVM.

Anti-VEGF– and anti-VEGF receptor–induced vascular alteration in mouse healthy tissues

Systemic therapy with anti-VEGF drugs such as bevacizumab is widely used for treatment of human patients with various solid tumors. However, systemic impacts of such drugs in host healthy vasculatures remain poorly understood. Here, we show that, in mice, systemic delivery of an anti-VEGF or an anti-VEGF receptor (VEGFR)-2 neutralizing antibody caused global vascular regression. Among all examined tissues, vasculatures in endocrine glands, intestinal villi, and uterus are the most affected in response to VEGF or VEGFR-2 blockades. Thyroid vascular fenestrations were virtually completely blocked by VEGF blockade, leading to marked accumulation of intraendothelial caveolae vesicles. VEGF blockade markedly increased thyroid endothelial cell apoptosis, and withdrawal of anti-VEGF resulted in full recovery of vascular density and architecture after 14 d. Prolonged anti-VEGF treatment resulted in a significant decrease of the circulating level of the predominant thyroid hormone free thyroxine, but not the minimal isoform of triiodothyronine, suggesting that chronic anti-VEGF treatment impairs thyroid functions. Conversely, VEGFR-1-specific blockade produced virtually no obvious phenotypes. These findings provide structural and functional bases of anti-VEGF-specific drug-induced side effects in relation to vascular changes in healthy tissues. Understanding anti-VEGF drug-induced vascular alterations in healthy tissues is crucial to minimize and even to avoid adverse effects produced by currently used anti-VEGF-specific drugs.

Risedronate Positively Affects Osteogenic Differentiation of Human Mesenchymal Stromal Cells

Bisphosphonates are widely used for the treatment of bone pathologies, mainly due to their ability to inhibit osteoclastic activity and thus bone resorption. Yet, their potential effect on bone formation is unclear. Our aim was to determine whether risedronate can affect osteoblastic differentiation of mesenchymal stromal cells (MSC). We evaluated the effect of the risedronate, which is a bisphosphonate widely used in clinical settings, on the differentiation of precursor cells of osteoblasts and adipocytes. Thus, MSC from human bone marrow were induced to differentiate into osteoblasts or adipocytes in the presence or absence of two risedronate concentrations (10⁻⁸ M and 10⁻⁹ M). Risedronate increased the levels of osteogenic markers including the extracellular matrix mineralization on cells induced to osteoblasts. On the other hand, such bisphosphonates did not have significant effects on the pparγ2 and lpl adipogenic genes or the fat vesicle accumulation on the cells induced into adipocytes. In addition, it increased the expression of early osteogenic differentiation genes like runx2 on MSC not induced to differentiate. Risedronate concentrations used favor the osteogenic differentiation and the MSC commitment towards osteoblasts. This suggests the possibility of using this bisphosphonate in cyclic bone treatments with anabolic drugs, enhancing the effect of the latter via a previous MSC commitment to preosteoblasts.

Interaction of the Antimicrobial Peptide Gomesin with Model Membranes: A Calorimetric Study

Gomesin is a potent cationic antimicrobial peptide (z = +6) isolated from the Brazilian spider Acanthoscurria gomesiana . The interaction of gomesin with large unilamellar vesicles composed of a 1:1 mixture of zwitterionic (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and anionic (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) phospholipids is studied with isothermal titration calorimetry (ITC). In parallel, light scattering and optical microscopy are used to assess peptide-induced vesicle aggregation. The ability of gomesin to permeabilize the membrane is examined with fluorescence spectroscopy of the leakage of 5,6-carboxyfluorescein (CF). Vesicles coated with 3 mol % 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (PE-PEG) lipids are also investigated to assess the influence of peptide-induced vesicle aggregation in the activity of gomesin. The ITC and light scattering titrations are done in two ways: lipid into peptide and peptide into lipid injections. Although some differences arise between the two setups, the basic interaction of gomesin with anionic vesicles is preserved. A surface partition model combined with the Gouy-Chapman theory is put forward to fit the ITC results. The intrinsic binding constant of gomesin is found to be K ≈ 10(3) M(-1). The interaction of gomesin with anionic membranes is highly exothermic and enthalpy-driven. Binding of gomesin is virtually always accompanied by vesicle aggregation and changes in membrane permeability, leading to CF leakage. Addition of PE-PEG to the membrane strongly attenuates vesicle aggregation but does not significantly change the mode of action of gomesin. The results point to a strong interaction of gomesin with the membrane surface, causing membrane rupture without a deep penetration into the bilayer core.

Specialized sorting of GLUT4 and its recruitment to the cell surface are independently regulated by distinct Rabs

Adipocyte glucose uptake in response to insulin is essential for physiological glucose homeostasis: stimulation of adipocytes with insulin results in insertion of the glucose transporter GLUT4 into the plasma membrane and subsequent glucose uptake. Here we establish that RAB10 and RAB14 are key regulators of GLUT4 trafficking that function at independent, sequential steps of GLUT4 translocation. RAB14 functions upstream of RAB10 in the sorting of GLUT4 to the specialized transport vesicles that ferry GLUT4 to the plasma membrane. RAB10 and its GTPase-activating protein (GAP) AS160 comprise the principal signaling module downstream of insulin receptor activation that regulates the accumulation of GLUT4 transport vesicles at the plasma membrane. Although both RAB10 and RAB14 are regulated by the GAP activity of AS160 in vitro, only RAB10 is under the control of AS160 in vivo. Insulin regulation of the pool of RAB10 required for GLUT4 translocation occurs through regulation of AS160, since activation of RAB10 by DENND4C, its GTP exchange factor, does not require insulin stimulation.

Membrane cholesterol and sphingomyelin, and ostreolysin A are obligatory for pore-formation by a MACPF/CDC-like pore-forming protein, pleurotolysin B

The mushroom Pleurotus ostreatus has been reported to produce the hemolytic proteins ostreolysin (OlyA), pleurotolysin A (PlyA) and pleurotolysin B (PlyB). The present study of the native and recombinant proteins dissects out their lipid-binding characteristics and their roles in lipid binding and membrane permeabilization. Using lipid-binding studies, permeabilization of erythrocytes, large unilamellar vesicles of various lipid compositions, and electron microscopy, we show that OlyA, a PlyA homolog, preferentially binds to membranes rich in sterol and sphingomyelin, but it does not permeabilize them. The N-terminally truncated Δ48PlyB corresponds to the mature and active form of native PlyB, and it has a membrane attack complex-perforin (MACPF) domain. Δ48PlyB spontaneously oligomerizes in solution, and binds weakly to various lipid membranes but is not able to perforate them. However, binding of Δ48PlyB to the cholesterol and sphingomyelin membranes, and consequently, their permeabilization is dramatically promoted in the presence of OlyA. On these membranes, Δ48PlyB and OlyA form predominantly 13-meric oligomers. These are rosette-like structures with a thickness of ∼9 nm from the membrane surface, with 19.7 nm and 4.9 nm outer and inner diameters, respectively. When present on opposing vesicle membranes, these oligomers can dimerize and thus promote aggregation of vesicles. Based on the structural and functional characteristics of Δ48PlyB, we suggest that it shares some features with MACPF/cholesterol-dependent cytolysin (CDC) proteins. OlyA is obligatory for the Δ48PlyB permeabilization of membranes rich in cholesterol and sphingomyelin.

Hierarchical self-assembly of miktoarm star polymers containing a polycationic segment: A general concept

We recently introduced a concept for the counterion-mediated hierarchical self-assembly of an amphiphilic ABC miktoarm star terpolymer in aqueous media into micrometer-sized compartmentalized particles with a highly periodic lamellar fine structure (“woodlice”). Herein, we extend this concept to different miktoarm star polymer systems containing a polycationic segment. The presence of a poly(N-methyl-2-vinylpyridinium) (P2VPq) block and its interaction with iodide/triiodide counterions is crucial. In analogy to linear diblock copolymer systems the hydrophilic/hydrophobic balance of polybutadiene-arm-poly(N-methyl-2-vinylpyridinium iodide)-arm-polystyrene miktoarm star terpolymers determines the morphology of the primary building blocks (spherical micelles and cylindrical micelles/vesicles) and the obtained superstructures (stacked lamellar structures and multilamellar vesicles) during this hierarchical process. When an ABA' miktoarm star copolymer (polystyrene-arm-poly(N-methyl-2-vinylpyridinium iodide)-arm-polystyrene) without a dynamic core-forming block was investigated, a different mechanism into “woodlouse” structured aggregates via aggregation and deformation of intermediate vesicles was found. The individual steps of the different self-assembly processes were investigated by transmission electron microscopy and additionally supported by dynamic light scattering, differential scanning calorimetry, and small-angle X-ray scattering.

AB0064 Spontaneous adipogenesis in bone marrow derived mesenchymal stromal cells after chronic treatment with glucocorticoids

BackgroundMesenchymal stromal cells (MSCs) are a promising therapeutic tool for many inflammatory autoimmune diseases because of their immunosuppressive potential. MSCs autologous transplantation showed less therapeutic efficacy respect to the allogenic...

Specific cleavage of the lung surfactant protein A by human cathepsin S may impair its antibacterial properties

Human cysteine cathepsins (Cats) are implicated in lung injuries and tissue remodeling and have recently emerged as important players in pulmonary inflammations. The proteolytic activities of Cat B, L, K, S and H are dramatically increased in the sputum of patients with cystic fibrosis (CF), suggesting a possible involvement in the CF pathophysiology. We found that pulmonary surfactant protein A (SP-A) that participates to innate host defense is extensively degraded in CF expectorations. Breakdown of SP-A was markedly decreased in CF sputum by E-64 and Mu-Leu-Hph-VSPh, a Cat S inhibitor. Cat S cleaved efficiently and specifically SP-A within critical residues of the solvent-exposed loop of its carbohydrate recognition (C-type lectin) domain that allows binding to pathogens. Cat S decreased aggregation properties of SP-A (self-aggregation, aggregation of phospholipid vesicles and rough LPS). Moreover cleavage of SP-A by Cat S reduced binding to yeast mannan and impaired agglutination of Escherichia coli and Pseudomonas aeruginosa, a foremost detrimental pathogen colonizing the lungs of CF patients. Besides human neutrophil serine proteases and bacterial proteases, we propose that Cat S may participate in the pathophysiology of CF by weakening the antibacterial activity of SP-A. More broadly, present results provide further indication that Cat S, along with Cats B and L, could display immuno-modulatory functions by inactivating key proteins involved in the innate immunity defense.

Protocadherin 17 Regulates Presynaptic Assembly in Topographic Corticobasal Ganglia Circuits

Highly topographic organization of neural circuits exists for the regulation of various brain functions incorticobasal ganglia circuits. Although neural circuit-specific refinement during synapse development is essential for the execution of particular neural functions, the molecular and cellular mechanisms for synapse refinement are largely unknown. Here, we show that protocadherin 17 (PCDH17), one of the nonclustered δ2-protocadherin family members, is enriched along corticobasal ganglia synapses in a zone-specific manner during synaptogenesis and regulates presynaptic assembly in these synapses. PCDH17 deficiency in mice causes facilitated presynaptic vesicle accumulation and enhanced synaptic transmission efficacy in corticobasal ganglia circuits. Furthermore, PCDH17(-/-) mice exhibit antidepressant-like phenotypes that are known to be regulated by corticobasal ganglia circuits. Our findings demonstrate a critical role for PCDH17 in the synaptic development of specific corticobasal ganglia circuits and suggest the involvement of PCDH17 in such circuits in depressive behaviors.

Prions disturb post-Golgi trafficking of membrane proteins

Conformational conversion of normal cellular prion protein PrP(C) into pathogenic PrP(Sc) is central to the pathogenesis of prion diseases. However, the pathogenic mechanism remains unknown. Here we show that post-Golgi vesicular trafficking is significantly delayed in prion-infected N2a cells. Accordingly, cell surface expression of membrane proteins examined, including PrP(C), insulin receptor involved in neuroprotection, and attractin, whose mutation causes prion disease-like spongiform neurodegeneration, is reduced. Instead, they accumulate in the Golgi apparatus. PrP(Sc) is detected throughout endosomal compartments, being particularly abundant in recycling endosome. We also show reduced surface expression of PrP(C) and insulin receptor in prion-infected mouse brains well before the onset of disease. These results suggest that prion infection might impair post-Golgi trafficking of membrane proteins to the cell surface in neurons via PrP(Sc) accumulated in recycling endosome, and eventually induce neuronal dysfunctions associated with prion diseases.

Native α-synuclein induces clustering of synaptic-vesicle mimics via binding to phospholipids and synaptobrevin-2/VAMP2

α-Synuclein is a presynaptic protein that is implicated in Parkinson's and other neurodegenerative diseases. Physiologically, native α-synuclein promotes presynaptic SNARE-complex assembly, but its molecular mechanism of action remains unknown. Here, we found that native α-synuclein promotes clustering of synaptic-vesicle mimics, using a single-vesicle optical microscopy system. This vesicle-clustering activity was observed for both recombinant and native α-synuclein purified from mouse brain. Clustering was dependent on specific interactions of native α-synuclein with both synaptobrevin-2/VAMP2 and anionic lipids. Out of the three familial Parkinson's disease-related point mutants of α-synuclein, only the lipid-binding deficient mutation A30P disrupted clustering, hinting at a possible loss of function phenotype for this mutant. α-Synuclein had little effect on Ca(2+)-triggered fusion in our reconstituted single-vesicle system, consistent with in vivo data. α-Synuclein may therefore lead to accumulation of synaptic vesicles at the active zone, providing a 'buffer' of synaptic vesicles, without affecting neurotransmitter release itself. DOI:http://dx.doi.org/10.7554/eLife.00592.001.

Defects of Vps15 in skeletal muscles lead to autophagic vacuolar myopathy and lysosomal disease

The complex of Vacuolar Protein Sorting 34 and 15 (Vps34 and Vps15) has Class III phosphatidylinositol 3-kinase activity and putative roles in nutrient sensing, mammalian Target Of Rapamycin (mTOR) activation by amino acids, cell growth, vesicular trafficking and autophagy. Contrary to expectations, here we show that Vps15-deficient mouse tissues are competent for LC3-positive autophagosome formation and maintain mTOR activation. However, an impaired lysosomal function in mutant cells is traced by accumulation of adaptor protein p62, LC3 and Lamp2 positive vesicles, which can be reverted to normal levels after ectopic overexpression of Vps15. Mice lacking Vps15 in skeletal muscles, develop a severe myopathy. Distinct from the autophagy deficient Atg7−/− mutants, pathognomonic morphological hallmarks of autophagic vacuolar myopathy (AVM) are observed in Vps15−/− mutants, including elevated creatine kinase plasma levels, accumulation of autophagosomes, glycogen and sarcolemmal features within the fibres. Importantly, Vps34/Vps15 overexpression in myoblasts of Danon AVM disease patients alleviates the glycogen accumulation. Thus, the activity of the Vps34/Vps15 complex is critical in disease conditions such as AVMs, and possibly a variety of other lysosomal storage diseases.

Abstract 1686: A Phase 1 dose escalation study to establish the maximum tolerated dose (MTD), pharmacokinetic (PK) and pharmacodynamic (PD) parameters of hydroxychloroquine (HCQ) in combination with vorinostat (V) in patients with advanced solid tumors - final results.

Abstract Background: Autophagy is a cellular process that generates energy to assure cell survival in response to insults such as hypoxia, nutrient deprivation or cytotoxic mediators. Autophagy contributes to cancer cell survival as well as drug resistance. Several anticancer agents, including Vorinostat (V) are reported to induce autophagy as a cytoprotective mechanism. In preclinical models, the addition of Hydroxycholoquine (HCQ) to V inhibited autophagy and significantly increased the anticancer effects of V. The objectives of this trial were to determine the MTD of HCQ in combination with V both administered daily (QD) in patients (pts) with advanced solid tumors, to evaluate PK and PD parameters, and test anti-tumor activity. Biomarkers were evaluated in tumors and peripheral blood mononuclear cells (PBMC) to investigate synergistic antitumor activity of V in combination with HCQ. Methods: We used a 3+3 dose escalation design of V at 300-400 mg QD plus HCQ QD at 400-1000 mg in 21 day cycles. Patients with advanced solid tumors and no available treatment with ECOG PS 0-2 and adequate organ function were eligible. Results: 32 patients were enrolled with 27 evaluable for toxicity studies. No dose limiting toxicity (DLT) was observed in cohorts 1 or 2. In cohort 3 (400 mg V/600 mg HCQ), 1/6 pts had DLT of Gr 3 anemia and fatigue. In cohort 4 (400 mg V/800 mg HCQ), 4/8 pts had DLT with Gr 3 fatigue (3 pts) and Gr 2 seizure on C1D8 (1 pt). De-escalation to 400 mg V/600 mg HCQ resulted in no further DLTs, defining the MTD. 10 pts were treated at the MTD. Treatment-related toxicities were Gr 1-2: nausea (11 pts), diarrhea (8), fatigue (6), anorexia (4), weight loss (4), anemia (4), and elevated creatinine (4). Gr 3 toxicities were fatigue (3), anemia, thrombocytopenia and neutropenia (1 each). One pt (renal cell cancer) had a confirmed PR (cohort 2, completed 43 cycles), and 2 pts with colorectal cancer had prolonged SD (>4 cycles). HCQ trough and V plasma concentrations (preliminary) showed no drug interactions compared to previously published data. PD analyses of biomarkers of HCQ and V in PBMCs at baseline compared to weeks 1 and 6 confirmed the results from pre-clinical studies showing accumulation of autophagic vesicles and induction of LC3-II, p21 and cathepsin D. The results of biopsies from 3 patients at MTD demonstrated greater induction of these PD markers in tumor compared to PBMC. Conclusions: The MTD was established as HCQ 600 mg + V 400 mg. Dose-dependent fatigue represented DLT in several patients. Anti-tumor activity was seen in one patient with RCC and 2 patients with CRC had prolonged SD. Based on these data phase II studies are planned in patients with renal and colorectal cancer. Citation Format: Monica M. Mita, Devalingam Mahalingam, John Sarantopoulos, Ravi Amaravadi, Alain Mita, Tyler Curiel, Steffan Nawrocki, Frank Giles, Jennifer Carew. A Phase 1 dose escalation study to establish the maximum tolerated dose (MTD), pharmacokinetic (PK) and pharmacodynamic (PD) parameters of hydroxychloroquine (HCQ) in combination with vorinostat (V) in patients with advanced solid tumors - final results. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1686. doi:10.1158/1538-7445.AM2013-1686

Chloroquine causes similar electroretinogram modifications, neuronal phospholipidosis and marked impairment of synaptic vesicle transport in Albino and Pigmented Rats

Retinal toxicity of chloroquine has been known for several years, but the mechanism(s) of toxicity remain controversial; some author support the idea that the binding of chloroquine to melanin pigments in the retinal pigmented epithelium (RPE) play a major toxic role by concentrating the drug in the eye. In our study, 12 albinos Sprague-Dawley (SD) and 12 pigmented Brown Norway (BN) rats were treated orally for 3 months with chloroquine to compare functional and pathological findings. On Flash electroretinograms (ERG) performed in scotopic conditions, similar and progressive (time-dependent) delayed onset and decreased amplitudes of oscillatory potentials (from Day 71) and b-waves (on Day 92) were identified in both BN and SD rats. In both strains, identical morphological changes consisted of neuronal phospholipidosis associated with UV auto-fluorescence without evidence of retinal degeneration and gliosis; the RPE did not show any morphological lesions or autofluorescence. IHC analyses demonstrated a decrease in GABA expression in the inner nuclear layer. In addition, a marked accumulation of synaptic vesicles coupled with a marked disruption of neurofilaments in the optic nerve fibers was identified.In conclusion, ERG observations were very similar to those described in humans. Comparable ERG modifications, histopathology and immunohistochemistry findings were observed in the retina of both rat strains suggesting that melanin pigment is unlikely involved. chloroquine-induced impairment of synaptic vesicle transport, likely related to disruption of neurofilaments was identified and non-previously reported. This new mechanism of toxicity may also be responsible for the burry vision described in humans chronically treated with chloroquine.