Chronic exposure to solar UVA plays a causative role in skin photoaging and photocarcinogenesis. Guided by exploratory difference-in-gel-electrophoresis (DIGE)-proteomics, we identified the thiol-dependent cysteine-proteases cathepsin B and cathepsin L as novel UVA-targets undergoing photo-oxidative inactivation upstream of autophagic-lysosomal dysfunction. In human skin fibroblasts, exposure to noncytotoxic doses of chronic UVA (9.9 J/cm ², twice a week, 3 weeks) caused pronounced photooxidative impairment of cathepsin B and L enzymatic activity suppressed by antioxidant intervention. Western blot analysis revealed extensive 4-hydroxy-2-trans-nonenal (4-HNE) modification of cathepsin B in UVA-exposed fibroblasts. Consistent with lysosomal impairment, accumulation of cellular autofluorescent material colocalizing with lysosomes was observed by confocal fluorescence microscopy, and extensive deposition of lipofuscin was detectable by transmission electron microscopy (TEM). Lysosomal expansion was further evidenced by increased immunodetection of lysosomal associated membrane protein-1 (Lamp-1) and Lysotracker-based flow cytometric analysis. While lysosomal membrane integrity remained intact, autophagic blockade was suggested by accumulation of cellular protein levels of LC3-II and p62 (sequestosome 1) in UVA-exposed fibroblasts. Furthermore, UVA-exposure modulated transcriptional levels of p62 (sequestosome 1, SQSTM1), α-synuclein (SNCA), and transglutaminase-2 (TGM2). Strikingly, pharmacological cathepsin B/L inhibition using CA074Me mimicked UVA-induced accumulation of lipofuscin and autophagic-lysosomal proteins (Lamp-1, LC3-II, and p62), as well as changes at the transcriptional levels. In order to determine if UVA-induced lysosomal impairment requires single or dual inactivation of cathepsin B and/or L, we used a genetic approach (siRNA) to selectively downregulate enzymatic activity of these target cathepsins. Monitoring protein levels of Lamp-1, LC3-II, and p62, we observed that only dual genetic antagonism (targeting both CTSB and CTSL expression) could mimic UVA-induced autophagic-lysosomal alterations, whereas single knockdown (targeting CTSB or CTSL only) did not reproduce the UVA-induced phenotype. Similarly, TEM revealed massive accumulation of lipofuscin-containing lysosomal vesicles in fibroblasts only after CTSB/CTSL-double knockdown. Taken together, our data indicate for the first time that UVA impairs lysosomal function causing autophagic-lysosomal alterations downstream of cathepsin B/L enzymatic inactivation. This work provides evidence for a heretofore unrecognized 'double-hit' mechanism of UVA skin photodamage where primary photo-oxidative insult occurs simultaneously with impaired clearance of damaged molecules and organelles downstream of dual inactivation of cathepsin B and L.

NF-E2-related factor 2 (Nrf2) is a transcription factor that is responsible for maintaining cellular homeostasis by controlling the fate of cells through transcriptional upregulation of antioxidant response element-bearing genes critical for eliminating toxicants and carcinogens. Under quiescent conditions, basal levels of Nrf2 are relatively low due to tight regulation by Keap1, a substrate adaptor protein for a Cullin 3 (Cul3)-E3 ubiquitin ligase complex that facilitates the ubiquitination and degradation of Nrf2. It is thought that when cells are exposed to oxidative stress, naturally-occurring compounds, or synthetic chemicals, cysteine residues in Keap1, particularly cysteine 151 (C151), are modified causing a conformational change that compromises the ability of the Keap1-Cul3-E3 ubiquitin ligase complex to properly ubiquitinate Nrf2. It is then stabilized and allowed to translocate into the nucleus to transcriptionally activate downstream genes. Interestingly, recent emerging data has revealed the "dark side" of Nrf2. Epigentic alterations and somatic mutations in either Nrf2 or Keap1 disrupting the Nrf2-Keap1 axis and causing constitutive activation of Nrf2 have been found in many human cancer cell lines and tumors. Thus, Nrf2 provides mutated cells a protective advantage against cytotoxic chemotherapeutics, allowing for further cell survival and growth. It is well known that arsenic is a human carcinogen and can activate the Nrf2 pathway through a Keap1-C151 independent mechanism. It has also been shown that arsenic can activate autophagy, a bulk-lysosomal degradation pathway. In this dissertation, we establish the cross-talk between the Nrf2-Keap1 pathway and autophagy by elucidating a novel non-canonical mechanism of Nrf2 activation. We found that deregulation of autophagy causes accumulation of p62, a substrate adaptor protein, which sequesters Keap1 into autophagosomes and activates the Nrf2 pathway. Moreover, we also demonstrate how arsenic blocks autophagic flux and prolongs Nrf2 activation through this novel mechanism. Additionally, activation of the Nrf2 pathway has been shown to confer protection against arsenic-induced toxicity and carcinogenicity. We demonstrate that co-treatment with sulforaphane alleviates arsenic-mediated autophagy. These studies suggest that the Keap1-C151 dependent mechanism triggers the chemopreventive role of Nrf2 while activation through p62 elicits the dark side. Therefore, the use of Keap1-C151-dependent compounds to counteract environmental insults continuous to be a promising strategy for cancer prevention.

Assisted reproductive technologies developed in domestic cattle serve as a starting point in similar studies on nondomestic bovids. The common eland is a useful model species for studies on rare tragelaphine antelopes. In Chapter 3 of the present study, effects of components/attributes of protein-free embryo culture media on the in vitro development of in vitro-derived bovine embryos were evaluated. A 2 x 2 factorial study comparing effects of groups of amino acids (20aa or 11aa) in two base media (modified KSOM or BM-3) demonstrated that amino acids and base medium affected embryonic development. A subsequent 7 x 2 factorial experiment to evaluate effects of osmotic pressure and supplement type in BM-3-20aa showed that embryonic development was largely affected by supplements and identified glucose (0.2 mM) as a crucial supplement. In Chapter 4, the use of behavioral training and handling of elands in a hydraulic chute to perform transvaginal ultrasound-guided oocyte retrieval without inducing general anesthesia were evaluated. Nine of 10 females associated specific sound cues with food treats. Females varied in their response interval to audio cues and to training for voluntary entry into the chute. Handling elands for oocyte retrieval required sedation and increased blood glucose levels. In Chapter 5, type of estrous synchronization or ovarian stimulation protocol did not affect ovarian response. Animals, but not month of the year, affected ovarian response. In 37 oocyte retrieval procedures using seven females, an average of 12.8 follicles yielded 9.8 oocytes, of which up to 73% matured to metaphase II. In vitro fertilization, intracytoplasmic sperm injection and nuclear transfer resulted in embryonic development. In conclusion, the bovine embryo culture study suggests that the beneficial effects of amino acids are influenced by the base medium and glucose plays more important roles in non-ATP producing pathways. Behavioral training and handling of sedated females in a hydraulic chute is a reliable method for collecting eland oocytes, which can undergo in vitro maturation and some in vitro embryonic development.

Low to moderate level of chronic arsenic exposure contributes to cardiovascular ailments including heart disease and aneurysms. Current research on the etiology and progression of cardiovascular disease focuses mainly on adult which fails to capture the developmental origins of cardiovascular disease. Thus, disruption in morphogenetic events during early development may initiate and pattern the molecular programming of cardiovascular ailments in adulthood. A major contributor to ischemic heart pathologies is coronary artery disease, however the influences by environmental arsenic in this disease process are not known. Similarly, the impact of toxicants on blood vessel formation and function during development has not been studied. Coronary vessel development is initiated by precursor cells that are derived from the epicardium. Epicardial derived cells undergo proliferate, migrate, and differentiate into several cardiac cell types which are the cellular components of the coronary vessels. The key cellular event occurs in this process is the epithelial to mesenchymal transition (EMT), which can also be utilized by endocardial cushion cells to form aortic and pulmonary valves. The TGFβ family of ligands and receptors are essential for developmental cardiac EMT and coronary smooth muscle cell differentiation. Whether arsenic has any impact on TGFβ mediated cardiovasculogenesis is not known. Monomethylarsonous acid [MMA(III)] is the most potent metabolite of inorganic arsenic and has been shown to partly account for arsenic induced toxicity. The fetus is exposed to relatively higher levels of MMA (III) as compared to adults probably due to deficiency in methylation of transferred inorganic arsenic from the placenta. However, the developmental toxicity of MMA (III) has not yet been studied. In this study, we exploit a novel cardiac progenitor cell line to recapitulate epicardial EMT in vitro and to study developmental toxicity caused by arsenicals. We show that chronic exposure to low level of arsenite and MMA (III) disrupts developmental EMT programming in epicardial cells causing deficits in cardiac mesenchyme production. The expression of EMT program genes is also decreased in a dose-dependent manner following exposure to arsenite and MMA (III). Smad-dependent TGFβ2 canonical signaling and the non-canonical Erk signaling pathways are abrogated as detected by decreases in phosphorylated Smad2/3, Erk1/2 and Erk5 proteins. There is also loss of nuclear accumulation of p-Smad and p-Erk5 due to arsenical exposure. These observations coincide with a decrease in vimentin positive mesenchymal cells invading three-dimensional collagen gels. However, arsenicals do not block TGFβ2 stimulated p38 activation. Additionally, smooth muscle cell differentiation, which is proven to be governed by p38 signaling in epicardial cells, also remains intact with arsenical exposure. Overall these results show that arsenite and MMA (III) are strong and selective cardiac silencers. The molecular mechanisms of arsenical toxicity on TGFβ-Smad signaling in epicardial cells is further explored. A relatively high level of acute arsenical exposure rapidly depletes phosphorylated nuclear Smad2/3. Restoration of the nuclear accumulation of Smads can be achieved by inhibiting the expression or activation of Smad specific exportins suggesting that arsenicals augment Smad nuclear exportation. Abrogated Smad signaling caused by arsenicals is associated with severe deficits in EMT during mouse epicardium and chick endocardial cushion development. Thus progenitor cell outgrowth, migration, invasion and vimentin filament reorganization are significantly inhibited in response to arsenical exposure. Disrupted Smad nuclear shuffling is probably caused by zinc displacement on the MH-1 DNA binding domain of Smad2/3. Thus zinc supplementation restores both nuclear content and transcriptional activities of Smad2/3. Rescued TGFβ-Smad signaling by zinc also contributes to cellular transformation and mesenchyme production in embryonic heart explants. LINE1 (L1) retrotransposons are a group of mobile DNA elements that shape the genome via novel epigenetic controls. Although expression of L1 is required for early embryo implantation and development, abnormally elevated L1 is shown to inhibit embryonic cells from transforming and differentiating during organogenesis. Cellular redox signaling, which is regulated by antioxidant responsive elements (AREs), has been shown to play a key role in L1 activation and retrotransposition. However, whether L1 can be induced by the cellular oxidative stress caused by arsenic is not known. We provide evidence showing that L1 ORF-1 and ORF-2 mRNA levels are both up-regulated by arsenic. Nuclear accumulation of L1 ORF-2 is observed in response to 30 min arsenic exposure, which may lead to active retrotransposition events in the genome. Transcriptional activity of L1 is regulated by Nrf2 as mutations in ARE regions within the L1 promoter and Nrf2 silencing using siRNA both significantly inhibit L1 transcriptional activity. Nrf2 overexpression together with arsenic exposure creates synergic induction in L1 promoter activity suggesting that arsenic mediated L1 activation is partially Nrf2 dependent. Taken together, these findings reveal a molecular mechanism responsible for arsenic cardiac toxicity and define a novel genetic toxic effect of arsenic during embryonic heart development.

3,4-(±)-Methylenedioxymethamphetamine (MDMA, ecstasy) is a widely abused amphetamine derivative. The metabolism of MDMA is thought to be a necessary component of MDMA-induced neurotoxicity, as direct administration of MDMA into the central nervous system of rats failed to reproduce the hallmark serotonin deficits seen following systemic administration of MDMA. Mechanistic questions remain regarding how MDMA elicits this neurotoxicity. Work of this thesis was undertaken to examine how MDMA-induced neurotoxicity is affected by the activity of two polymorphic enzymes involved in the metabolism of MDMA, namely cytochrome P450 family member 2D6 (CYP2D6) and catechol-O-methyltransferase (COMT), as well as the potential role microglia play in the facilitation of this neurotoxicity. Inhibition of CYP2D1, the homolog of human CYP2D6 in the rat, resulted in an attenuation of serotonergic neurotoxicity following MDMA-administration. In both a pharmacological model and a genetic model of CYP2D1 inhibition, serotonin deficits were alleviated when compared to normal-activity CYP2D1 counterparts. Inhibition of COMT, the primary detoxication enzyme in the MDMA pathway, resulted in potentiation of MDMA-induced neurotoxicity. In a pharmacological model of COMT inhibition, rats displayed greater long-term serotonin deficits after COMT inhibition. Mice devoid of COMT proved sensitive to the lethal hyperthermic effects of MDMA, illustrating the importance of this enzyme in preventing the acute toxicity of MDMA. Brain lesions often elicit a microglial response. Microglia have the potential of both beneficial and deleterious actions in the brain. Whether microglia are activated by nerve terminal degeneration produced by MDMA is an area of ongoing debate. Systemically delivered MDMA produces a modest increase in the amount of microglial cells present in the parietal cortex of rats over a one-week period. MDMA also increased the phagocytic activity of microglia in the cortex. The studies described herein support the hypothesis that metabolism is critical in MDMA-induced neurotoxicity. Furthermore, as both CYP2D6 and COMT are polymorphic in the human population, certain individuals are more at risk for severe serotonergic toxicity following MDMA administration. Finally, while microglia are likely not the cause of MDMA-induced neurotoxicity, contributions of these cells cannot be dismissed.

The modification of proteins by xenobiotic and endogenous electrophilic species produced in cells undergoing oxidative stress contributes to cellular toxicity and disease processes. Many xenobiotics are themselves reactive electrophiles; however non-reactive compounds may become reactive towards proteins and DNA following metabolism. Identifying actual sites of adduction on target proteins is critical for determining the structural and functional consequences associated with the modification. 1,4-benzoquinone (BQ) is a reactive quinone and environmental toxicant, formed from oxidative metabolism of benzene, an aromatic hydrocarbon found in gasoline and other fuels. Although environmental and occupational exposure to benzene is associated with the development of aplastic anemia and leukemia, the mechanism of toxicity remains elusive. Due to the electrophilic nature of BQ, it reacts with glutathione to form quinol-thioether (QT) conjugates that retain the ability to redox cycle between the reduced (HQ) and oxidized (BQ) forms. BQ and its QT metabolites are reactive, and can produce cellular necrosis through oxidative stress and protein modification. One further consequence of oxidative stress is the elevation of cellular membrane lipid peroxidation, resulting in the formation of reactive lipid-aldehydes such as 4-hydroxynonenal (4HNE). Adduction of critical amino acid residues in target bone marrow proteins by 4HNE and QTs following exposure to benzene could contribute to its hematotoxic effects. This dissertation builds upon the foundation of proteins targeted by electrophilic adduction by outlining techniques to pinpoint the specific amino acids targeted and furthermore predict the functional releavance of adduction. For the first time, protein targets of reactive endogenous lipid aldehydes are reported in the bone marrow of chemically treated rats. Furthermore, novel sites of adduction by aldehydes and benzene-glutathione conjugates are reported within functional regions of topoisomerase II. Inhibition of bone marrow DNA topoisomerase II by benzene metabolites is implicated as a potential mechanism of benzene-induced hematotoxicity and acute-myeloid leukemia. The strong inhibitory effect of these compounds on topoisomerase II activity suggests that their presence in the bone marrow may play a role in benzene-induced myelotoxicity.

3,4-(±)-Methylenedioxymethamphetamine (MDMA, Ecstasy) is a widely abused amphetamine derivative with potent stimulant properties. The neuropharmacological effects of MDMA are biphasic in nature. MDMA initially causes synaptic monoamine release, primarily of serotonin (5-HT), producing hyperthermia and hyperactivity (5-HT syndrome). Conversely, the long-term effects of MDMA manifest as a prolonged depletion in 5-HT, and structural damage to serotonergic nerve terminals. Monoamine transporter systems at the plasma membrane and storage vesicles of 5-HT neurons have been implicated in MDMA toxicity. Nonetheless, many mechanistic questions remain regarding the precise role of uptake transporters in MDMA neurotoxicity. The present study was designed to address the importance of the serotonin reuptake transporter (SERT) and the vesicular monoamine transporter 2 (VMAT2) to the physiological, behavioral and neurotoxic responses to MDMA. SERT functions as a primary regulator of 5-HT homeostasis, mediating the reuptake of 5-HT from the synaptic space following its release during neurotransmission. SERT is a molecular target site for MDMA and many antidepressant agents such as the selective serotonin reuptake inhibitor (SSRI) class. Pharmacological inhibition of SERT protects against MDMA-induced serotonergic neurotoxicity. Thus, the effects of MDMA are in part mediated by an ability to interact with and inhibit SERT. Using a SERT-knockout (SERT-KO) rat model, we determined that SERT deficiency modulated the acute toxicities of MDMA, such as hyperthermia and hyperactivity, whilst completely preventing long-term depletions in tissue 5-HT levels, indicating the abolishment of neurotoxicity. Disruption of vesicular monoamine storage via interaction with VMAT2 has also been implicated in MDMA neurotoxicity. VMAT2 participates in the transport of monoamine neurotransmitters, in particular 5-HT and dopamine (DA), into intra-neuronal storage vesicles. As such, VMAT2 is critical in maintaining neuronal health by preventing neurotransmitter oxidation within the cytosol. Pharmacological inhibition of VMAT2 with Ro4-1284 reduced MDMA-induced hyperactivity and averted hyperthermia along with persistent serotonergic deficits. Overall, our results corroborate the hypothesis that SERT and VMAT2 are critical to the in vivo effects of MDMA. Furthermore, given that VMAT2 inhibition diminished the behavioral response to MDMA in rats, pharmacological manipulation of this transporter could be used in the treatment of MDMA abuse and overdose.

Many pathological conditions, including renal disease, are associated with oxidative stress. 2,3,5-tris(Glutathion-S-yl)hydroquinone (TGHQ), a potent nephrotoxic and nephrocarcinogenic metabolite of benzene and hydroquinone, generates reactive oxygen species (ROS), can cause DNA strand breaks, and the subsequent activation of DNA repair proteins, including poly(ADP-ribose) polymerase (PARP)-1. Under robust oxidative damage, PARP-1 is hyper-activated, which causes elevations in intracellular calcium concentrations (iCa²⁺), NAD⁺ and ATP depletion, and ultimately necrotic cell death. The role of Ca²⁺ in PARP-dependent necrotic cell death remains unclear. We therefore sought to determine the relationship between Ca²⁺ and PARP-1 during TGHQ-induced necrotic cell death in human renal proximal tubule epithelial cells (HK-2). Extracellular Ca²⁺ is responsible for coupling PARP-1 activation to increases in iCa²⁺ during TGHQ-induced cell death. Moreover, organelles such as the endoplasmic reticulum and the mitochondria, which contain intracellular Ca²⁺ stores play no role in increases of iCa²⁺. PARP-1 inhibition attenuates increases in iCa²⁺ induced by TGHQ, and treatment with 2-aminoethoxydiphenyl borate (2-APB), a store-operated Ca²⁺ channel (SOC) inhibitor, restored cell viability, levels of NAD⁺, and attenuated PAR protein-ribosylation (PARylation). Concurrent with SOC activation having a direct effect on PARP-1 activity, and PARP-1 inhibition attenuating increases in iCa²⁺, the results suggest that PARP-1 and SOCs are coupled during TGHQ-induced cell death. We also explored the relationship between SOC activation and PARP-1 downstream of PARP-1 activity. Poly(ADP-ribose)glycohydrolase (PARG), which catalyzes the degradation of PARs to yield free ADP-ribose (ADPR), is known to activate SOCs. Interestingly, siRNA knockdown of PARG modestly increased PAR ribosylation, but did not restore cell viability in the presence of TGHQ, indicating that free ADPR is not responsible for SOC activation in HK-2 cells. Overall, our results suggest that PARP-1 and Ca²⁺ are coupled through SOC entry, and that this relationship may involve alternative PAR-mediated signaling that leads to necrotic cell death. To further elucidate the role of PAR polymers in response to TGHQ, we determined the cellular co-localization of PAR by immunofluorescent staining. PAR polymers originally co-localized in the nucleus, and in the cytosol at later time points. Immunoprecipitation with a pADPr antibody and further analysis via mass spectrometry revealed PARylation of many stress-related proteins and Ca²⁺-related proteins upon TGHQ treatment. We therefore speculate that cytosolic PAR may cause downstream signaling, PARylating proteins that activate store-operated Ca²⁺ entry either directly through Ca²⁺-related proteins or PARylation of stress-related proteins. Thus, PARylation of proteins may contribute to increases in iCa²⁺ concentrations, leading to PARP-1-dependent necrotic cell death. Our studies provide new insight into PARP-mediated necrotic cell death. Ca²⁺ is coupled to PARP-1 hyperactivation through SOCs, where iCa²⁺ increases are independent of PARG activity, demonstrating a novel signaling pathway for PARP-dependent necrotic cell death.

Introduktion: Läkemedelsbiverkningar delas in i två grupper; typ A och typ B. Typ A-biverkningar är dosberoende medan typ B-biverkningar är idiosynkrasiska och beroende av immunsystemet. Levern är kroppens huvudsakliga metabola organ, och drabbas ofta av läkemedelinducerad toxicitet. Ibland inducerar läkemedelsmetaboliter levertoxicitet, vilket kan medieras av immunsystemet. Karbamazepin är ett antiepileptikum och orsakar levertoxicitet, men den exakta mekanismen är inte klarlagd. Syfte: Syftet med detta arbete är att undersöka om karbamazepins levertoxicitet är beroende av metabolismen av karbamazepin och/eller immunsystemet. Material och metoder: En strukturerad litteraturundersökning utfördes med hjälp av databasen PubMed. 7 artiklar inkluderades i sammanställningen. Resultat: Resultat från in vivo-studier identifierade metaboliter producerade av cytokrom P450-monooxygenaser (CYP450) hos de individer som utvecklade levertoxicitet inducerad av karbamazepin. Samtidigt noterades en ökad nivå CYP3A. Expressionen av en rad immunsystemsmarkörer ökade också vid karbamazepin-inducerad levertoxicitet, exempelvis TNF-α, som leder till apoptos. Slutsats: Utifrån inkluderade studier kan slutsatsen dras att karbamazepins levertoxicitet induceras av dess metaboliter via immunsystemet. Undersökningarna var huvudsakligen associationsstudier, vilket försvårar slutsatser kring kausalitet. Därför behöver ytterligare studier göras så att mekanismen helt kan klargöras.

Neuroblastoma, a neuroendocrine tumor, is the most common cancer in infancy. 75 % of those affected are under the age of 5. The disease is heterogeneous and survival rate is low.   Current treatment of neuroblastoma consists of surgery, radiation and chemotherapy, where the targets for the treatment are the malign cells. Due to the cancer cells instable genome there is a risk for resistance development. This negatively impacts the treatments goal of hindering tumor growth and spread.  Tumor growth is not only determined by malign cells but also the interactions of those tumor cells with tumor vessels and different types of cells in the tumor stroma.   The aim of this paper is to develop a relevant histological method to study the properties of tumor stroma in tumor sections retrieved from human NB tumor xenografts in mice treated with angiogenesis inhibitors SU11657 and Zoledronic acid. The study is a continuation of previous studies with the inhibitors which have shown good effect on tumor growth and angiogenesis on neuroblastoma.   In the short term treatment with SU11657 and Zoledron acid showed that tumor growth declined. In the longer treatment with SU11657 the growth didn’t decline with the same rate compared to the short term treatment. Angiogenesis on the other hand decreased in all the treatments independent of treatment duration. The histological staining with Sirius red revealed that treated tumors had an increased amount of stroma compared to the untreated tumors.   In conclusion the relative increase of tumor volume, decreased number of vessels and expansion of tumor stroma in the longer treatment with SU11657 indicated that tumors might survive the angiogenesis inhibitor treatment through expansion/activation of its stroma. The histological staining with Sirius red in saturated picric acid marked the collagen, i.e. stroma, well and enabled quantification of the stroma.