Arsenite Alters Lysosome-Mediated Degradation and the Autophagy Process Leading to Immunosuppression in Human B-Lymphoblastoid Cell Lines

Persistent Link:
http://hdl.handle.net/10150/222895
Title:
Arsenite Alters Lysosome-Mediated Degradation and the Autophagy Process Leading to Immunosuppression in Human B-Lymphoblastoid Cell Lines
Author:
Bolt, Alicia Marie
Issue Date:
2012
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The immune system is a target of arsenic toxicity. Epidemiological data have shown that arsenic exposure is associated with characteristics of immunosuppression. Human B-lymphoblastoid cell lines (LCL) were used as an in vitro model of immune cell targeting by arsenic to investigate the mechanism of arsenic-induced cytotoxicity, which could provided insight into the mechanism underlying arsenic-induced immunotoxicity leading to the immunosuppression observed in humans. In LCL arsenite-induced cytotoxicity was not associated with apoptosis, but associated with hallmarks of autophagy, a cell stress-responsive process that facilitates the removal of cellular components through lysosome-mediated degradation. At environmentally relevant concentrations, arsenite-induced toxicity resulted in a decrease in cell proliferation that was correlated with hallmarks of autophagy including expansion of acidic vesicles, global induction of lysosomal gene expression, increased flux of the autophagosome marker LC3-II, and increased enzymatic activity of the lysosomal hydrolase cathepsin D. Investigation of the upstream cellular damage leading to the induction of autophagy revealed that arsenite induces proteotoxic damage leading to an accumulation of protein aggregates that may be targeted to the lysosome for degradation. In addition, global gene expression data showed an enrichment of ER stress responsive genes after arsenite exposure. Further evaluation of global gene expression data indicated that the global induction of lysosomal genes occurs before the activation of ER stress genes, suggesting that the induction of autophagy may occur before the generation of ER stress. To investigate the effect of arsenite-induced proteotoxicity and autophagy on normal immune function, the ability of LCL to process and present exogenous antigens onto MHC class II molecules was evaluated. Arsenite decreased antigen presentation of the exogenous antigen HSA. This decrease was associated with decreased lysosomal degradation of the model substrate DQ-Ova, suggesting that arsenite is disrupting lysosome-mediated degradation. In addition, arsenite exposure was associated with an increase in MHC class II protein aggregates, which could render them unavailable to bind peptide fragments. Through the identification that arsenite induces proteotoxicity and autophagy in LCL, it provides novel insight into the mechanisms of arsenic-induced immunotoxicity that could lead to a better understanding of the mechanisms underlying arsenic-induced immunosuppression observed in humans.
Type:
text; Electronic Dissertation
Keywords:
Immunotoxicity; Lymphoblastoid; Proteotoxicity; Pharmacology & Toxicology; Arsenic; Autophagy
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Pharmacology & Toxicology
Degree Grantor:
University of Arizona
Advisor:
Klimecki, Walter T.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleArsenite Alters Lysosome-Mediated Degradation and the Autophagy Process Leading to Immunosuppression in Human B-Lymphoblastoid Cell Linesen_US
dc.creatorBolt, Alicia Marieen_US
dc.contributor.authorBolt, Alicia Marieen_US
dc.date.issued2012-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe immune system is a target of arsenic toxicity. Epidemiological data have shown that arsenic exposure is associated with characteristics of immunosuppression. Human B-lymphoblastoid cell lines (LCL) were used as an in vitro model of immune cell targeting by arsenic to investigate the mechanism of arsenic-induced cytotoxicity, which could provided insight into the mechanism underlying arsenic-induced immunotoxicity leading to the immunosuppression observed in humans. In LCL arsenite-induced cytotoxicity was not associated with apoptosis, but associated with hallmarks of autophagy, a cell stress-responsive process that facilitates the removal of cellular components through lysosome-mediated degradation. At environmentally relevant concentrations, arsenite-induced toxicity resulted in a decrease in cell proliferation that was correlated with hallmarks of autophagy including expansion of acidic vesicles, global induction of lysosomal gene expression, increased flux of the autophagosome marker LC3-II, and increased enzymatic activity of the lysosomal hydrolase cathepsin D. Investigation of the upstream cellular damage leading to the induction of autophagy revealed that arsenite induces proteotoxic damage leading to an accumulation of protein aggregates that may be targeted to the lysosome for degradation. In addition, global gene expression data showed an enrichment of ER stress responsive genes after arsenite exposure. Further evaluation of global gene expression data indicated that the global induction of lysosomal genes occurs before the activation of ER stress genes, suggesting that the induction of autophagy may occur before the generation of ER stress. To investigate the effect of arsenite-induced proteotoxicity and autophagy on normal immune function, the ability of LCL to process and present exogenous antigens onto MHC class II molecules was evaluated. Arsenite decreased antigen presentation of the exogenous antigen HSA. This decrease was associated with decreased lysosomal degradation of the model substrate DQ-Ova, suggesting that arsenite is disrupting lysosome-mediated degradation. In addition, arsenite exposure was associated with an increase in MHC class II protein aggregates, which could render them unavailable to bind peptide fragments. Through the identification that arsenite induces proteotoxicity and autophagy in LCL, it provides novel insight into the mechanisms of arsenic-induced immunotoxicity that could lead to a better understanding of the mechanisms underlying arsenic-induced immunosuppression observed in humans.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectImmunotoxicityen_US
dc.subjectLymphoblastoiden_US
dc.subjectProteotoxicityen_US
dc.subjectPharmacology & Toxicologyen_US
dc.subjectArsenicen_US
dc.subjectAutophagyen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePharmacology & Toxicologyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorKlimecki, Walter T.en_US
dc.contributor.committeememberGandolfi, A. Jayen_US
dc.contributor.committeememberFutscher, Bernarden_US
dc.contributor.committeememberZhang, Donnaen_US
dc.contributor.committeememberVaillancourt, Richard R.en_US
dc.contributor.committeememberKlimecki, Walter T.en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.