This thesis set out to investigate how heat stress may affect the oxidative balance and influence the activity patterns of animals. The use of wild animals has been scarce in testing the effects of heat stress on the oxidative balance of animals, especially under a simulated heat wave condition. Animals are expected to differ in their oxidative stress in response to heat stress, depending on their thermotolerance and the life history trait of activity is tested here as an indirect measure of thermotolerance. Therefore, two rodent species within the same family were used for experiments, one with a nocturnal activity rhythm and the other with a crepuscular/diurnal activity rhythm. Animals were tested firstly in a laboratory whole-body hyperthermia experiment, followed by a 3-day heat stress test with extreme temperatures. Following these experiments, animals were subjected to a simulated heat wave to determine how ecologically relevant temperatures may influence not just the oxidative balance of individuals, but also their activity patterns and water drinking in the absence of a microclimate. In order to determine the oxidative balance of individuals under control and heat treatment conditions, markers of oxidative damage and antioxidant defense were used. Markers for lipid and protein oxidation and a marker of enzymatic antioxidant activity and total non-enzymatic antioxidant activity were investigated in the liver, kidney, brain and heart. During the simulated heat wave, activity was measured with video recordings, with the videos analysed for water drinking behaviour as counts and time spent drinking water. During the whole-body hyperthermia experiment without the extreme temperatures, both species demonstrated no significant changes in liver oxidative markers except for high oxidative damage in the kidney for R. dilectus and high oxidative damage in the brain for M. namaquensis. During the 3-day acclimation experiment with extreme temperatures, both species were oxidatively stressed in the heart, with significant oxidative damage in the kidney for R. dilectus and significant oxidative damage in the liver for M. namaquensis. During the simulated heat wave, both species showed no significant changes in liver oxidative balance. The kidney was oxidatively stressed for M. namaquensis, with both species exhibiting signs of oxidative stress in the brain. Animals did not shift their activity during the heat wave, but rhythms demonstrated signs of disruption during the simulated heat wave. Activity increased during the day for both species during the heat wave. This was due to animals being uncomfortable and drinking more water. For the nocturnal species, the frequency of drinking water increased during the day and during the night during the simulated heat wave. The crepuscular species only increased in the amount of time spent drinking water during the day during the simulated heat wave. Overall, the nocturnal species was more susceptible to heat stress inducing either increased oxidative damage or reduced antioxidant defense compared to the crepuscular species, but this was tissue specific and also dependant on the experimental condition. It is recommended that future studies directly measure the reduced: oxidised state of individuals in addition to markers of defense and damage. / Thesis (PhD (Zoology))--University of Pretoria, 2019. / Zoology and Entomology / PhD (Zoology) / Unrestricted

Due to rapid urbanisation, people in metropolises spend the majority of their time indoors. Indoor mould contamination, as one of the most pungent biohazards in built environments, can ubiquitously present in humid areas and potentially compromise the health of occupants. Governmental institutions like the World Health Organisation and United States Environmental Protection Agency have put forward guidelines for indoor mould prevention. However, these guidelines normally require occupants to maintain a low indoor humidity (<75% or even 40%), and thus, in tropical and subtropical areas, one of the most widely used approaches to prevent indoor mould contamination is to continuously operate air-conditioners or dehumidifiers (AC/D). The 24 h operation of AC/D, however, conflicts with the requirement of energy sustainability, and hence posits a trade-off between sustainability and indoor mould hygiene. The aim of this study was to facilitate the development of sustainable and effective mould prevention strategies for indoor environments. The literature on currently adopted mould prevention strategies including that target moisture (24 h AC/D), temperature (air-conditioning system and cool wall paint) and nutrient (dust removal) elements as well as new nanoparticles technology (Ag, TiO 2 and MgO nanoparticles), was reviewed and the main limitations of these strategies were discussed. It was found that none of these current mould prevention measures has addressed both sustainability and mould hygiene on balance, urging further investigations. Therefore, the objective of the first phase investigation was to develop sustainable cause-specific mould control measures in built environments. A case study of a mould contaminated site was conducted to illustrate the micro-environments that contribute to mould contamination in buildings. The currently used 24-h AC/D approach was compared with and ranked against other sustainable alternatives. The results of this case study suggest that determining an effective non-24 h AC/D management regime tends to be a sustainable and user-friendly solution. To develop such a regime, understanding the critical mechanisms regulating indoor mould responses to water dynamics is essential. Thus, the objective of the second phase was to characterise the critical mechanism regulating the growth of common indoor moulds under water dynamics. It was hypothesised that oxidative stress is associated with the growth of indoor moulds under water dynamics. Using Cladosporium cladosporioides as a model, both its pre-germination and germinated spores were exposed to daily wet-dry cycles. Afterwards, the growth was assessed and cellular H 2 O 2 concentration and catalase activity were measured. It was found that under water dynamics, the longer growth delay in C. cladosporioides was associated with a higher encountered oxidative stress, with 12-12 wet-dry cycle (12 h wet, 12 h dry) showing the longest delay and highest oxidative stress. Pearson correlation and linear regression analysis suggest a positive correlation between growth delay and oxidative stress under water dynamics (R 2 =0.85, P<0.0001). Moreover, pre- germination spores generally exhibited shorter growth delay, lower cellular H 2 O 2 concentration and higher catalase activity. Collectively, these results suggest that the growth of C. cladosporioides is associated with oxidative stress under water dynamics. After revealing the association between the growth of C. cladosporioides and oxidative stress under water dynamics, at the third phase, this finding was extrapolated to different mould species (C. cladosporioides, Aspergillus niger and Aspergillus penicillioides), water activity (a w ) (0.4 a w , 0.6 a w and 0.8 a w ) and temperature levels (19 °C and 28 °C). In addition, the antioxidant responses of treated moulds, including antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase) were monitored. The results showed that lower water activity levels imposed higher oxidative stress to moulds, and A. penicillioides exhibited the highest tolerance which displayed the highest antioxidant activities and encountered lowest oxidative damage under water dynamics. Moreover, no significant difference was measured in terms of the survival, oxidative stress and antioxidant responses between these two temperature levels. The third phase of the study, for the first time discovered the reason contributing to the different resistance towards water dynamics among common indoor moulds, and further confirmed the important role of oxidative stress adaptation in withstanding transient water supply. In conclusion, this study reveals the critical role of oxidative stress adaptation in helping moulds to cope with changing water conditions, which may shed light on a new perspective for the future development of indoor mould prevention strategies. It also indicates that longer operation time of AC/D each day may not necessarily lead to better prevention of mould contamination, suggesting that in order to sustainably prevent mould contamination, one should operate reasonable non-24 h AC/D each day (12 h/day according to the examined species in this study) to yield a more stressful wet-dry cycle to moulds. The outcomes of this study foster the development of novel and sustainable indoor mould prevention strategies

Due to rapid urbanisation, people in metropolises spend the majority of their time indoors. Indoor mould contamination, as one of the most pungent biohazards in built environments, can ubiquitously present in humid areas and potentially compromise the health of occupants. Governmental institutions like the World Health Organisation and United States Environmental Protection Agency have put forward guidelines for indoor mould prevention. However, these guidelines normally require occupants to maintain a low indoor humidity (<75% or even 40%), and thus, in tropical and subtropical areas, one of the most widely used approaches to prevent indoor mould contamination is to continuously operate air-conditioners or dehumidifiers (AC/D). The 24 h operation of AC/D, however, conflicts with the requirement of energy sustainability, and hence posits a trade-off between sustainability and indoor mould hygiene. The aim of this study was to facilitate the development of sustainable and effective mould prevention strategies for indoor environments. The literature on currently adopted mould prevention strategies including that target moisture (24 h AC/D), temperature (air-conditioning system and cool wall paint) and nutrient (dust removal) elements as well as new nanoparticles technology (Ag, TiO 2 and MgO nanoparticles), was reviewed and the main limitations of these strategies were discussed. It was found that none of these current mould prevention measures has addressed both sustainability and mould hygiene on balance, urging further investigations. Therefore, the objective of the first phase investigation was to develop sustainable cause-specific mould control measures in built environments. A case study of a mould contaminated site was conducted to illustrate the micro-environments that contribute to mould contamination in buildings. The currently used 24-h AC/D approach was compared with and ranked against other sustainable alternatives. The results of this case study suggest that determining an effective non-24 h AC/D management regime tends to be a sustainable and user-friendly solution. To develop such a regime, understanding the critical mechanisms regulating indoor mould responses to water dynamics is essential. Thus, the objective of the second phase was to characterise the critical mechanism regulating the growth of common indoor moulds under water dynamics. It was hypothesised that oxidative stress is associated with the growth of indoor moulds under water dynamics. Using Cladosporium cladosporioides as a model, both its pre-germination and germinated spores were exposed to daily wet-dry cycles. Afterwards, the growth was assessed and cellular H 2 O 2 concentration and catalase activity were measured. It was found that under water dynamics, the longer growth delay in C. cladosporioides was associated with a higher encountered oxidative stress, with 12-12 wet-dry cycle (12 h wet, 12 h dry) showing the longest delay and highest oxidative stress. Pearson correlation and linear regression analysis suggest a positive correlation between growth delay and oxidative stress under water dynamics (R 2 =0.85, P<0.0001). Moreover, pre- germination spores generally exhibited shorter growth delay, lower cellular H 2 O 2 concentration and higher catalase activity. Collectively, these results suggest that the growth of C. cladosporioides is associated with oxidative stress under water dynamics. After revealing the association between the growth of C. cladosporioides and oxidative stress under water dynamics, at the third phase, this finding was extrapolated to different mould species (C. cladosporioides, Aspergillus niger and Aspergillus penicillioides), water activity (a w ) (0.4 a w , 0.6 a w and 0.8 a w ) and temperature levels (19 °C and 28 °C). In addition, the antioxidant responses of treated moulds, including antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase) were monitored. The results showed that lower water activity levels imposed higher oxidative stress to moulds, and A. penicillioides exhibited the highest tolerance which displayed the highest antioxidant activities and encountered lowest oxidative damage under water dynamics. Moreover, no significant difference was measured in terms of the survival, oxidative stress and antioxidant responses between these two temperature levels. The third phase of the study, for the first time discovered the reason contributing to the different resistance towards water dynamics among common indoor moulds, and further confirmed the important role of oxidative stress adaptation in withstanding transient water supply. In conclusion, this study reveals the critical role of oxidative stress adaptation in helping moulds to cope with changing water conditions, which may shed light on a new perspective for the future development of indoor mould prevention strategies. It also indicates that longer operation time of AC/D each day may not necessarily lead to better prevention of mould contamination, suggesting that in order to sustainably prevent mould contamination, one should operate reasonable non-24 h AC/D each day (12 h/day according to the examined species in this study) to yield a more stressful wet-dry cycle to moulds. The outcomes of this study foster the development of novel and sustainable indoor mould prevention strategies

Indiana University-Purdue University Indianapolis (IUPUI) / Type 1 and Type 2 diabetes (T1D/T2D) share a common etiology that involves an increase in oxidative stress that leads to dysfunction and subsequent β cell death. Lipoxygenases are enzymes that catalyze the oxygenation of polyunsaturated fatty acids to form lipid metabolites involved in a variety of biological functions including cellular oxidative stress response. On the other hand, Interleukin 6 (IL-6) signaling has been demonstrated to be protective in islets. In this study, we explored the effect of lipoxygenase enzymes 12-Lipoxygenase, 12/15 Lipoxygenase and IL-6 on β cell function and survival in mice using both STZ and high-fat diet (HFD) models of diabetes. Alox12-/- mice showed greater impairment in glucose tolerance following STZ and HFD compared to wild-type mice (WT), whereas Alox15-/- were protected against dysglycemia. These findings were accompanied by evidence of islet oxidative stress in Alox12-/- mice and reduced oxidative stress in Alox15-/- mice, consistent with alterations in the expression of antioxidant response enzymes in islets from these mice. Additionally, islets from Alox12-/- mice showed a compensatory increase in Alox15 gene expression and treatment of these mice with the 12/15-lipoxygenase inhibitor ML-351 rescued the dysglycemic phenotype. IL-6 was able to significantly attenuate the generation of reactive oxygen species by proinflammatory cytokines in human pancreatic islets. Furthermore, we find that IL-6 regulates the master antioxidant response protein NRF2. Collectively these results show that loss of Alox12 activates a compensatory increase in Alox15 that sensitizes β cells to oxidative stress and signaling by IL-6 is required for maximal antioxidant response under conditions of increased ROS formation, such as obesity.

No description available.

Listeria monocytogenes response to oxidative stress by sublethal sodium hypochlorite was investigated in this study. Continuous exposure of sublethal chlorine influenced biofilm formation and stress adaptation (homologous and heterologous) in L. monocytogenes. The biofilm forming ability of oxidative stress adapted and control cells were investigated on polystyrene surface at 22°C and 37°C. The oxidative stress adapted cells were found to form less biofilm in the presence of chlorine (p < 0.10) when compared to non-treated control cells at both the temperatures. In addition, the biofilm forming ability of L. monocytogenes was reduced significantly at higher sublethal chlorine concentrations (p < 0.10). In conclusion, oxidative stress adapted L. monocytogenes has developed tolerance to chlorine and some of the antibiotics. However, oxidative stress those cells did demonstrate an antibiofilm effect. This demonstrates that oxidative stress reduces L. monocytogenes biofilm formation but can also increase antibiotic resistance.

Little research has focused on the involvement of oxidative stress as it relates to the pathophysiology of osteoarthritis (OA); while inflammation has been extensively studied. The present study evaluates the ability to modulate the response of canine chondrocytes to both inflammation and oxidative stress in an in-vitro model. Chondrocytes were incubated and then stimulated to under-go oxidative stress by using hydrogen peroxide or inflammation using interleukin-1 beta and tumor necrosis factor alpha. For inhibition of oxidative stress an antioxidant, N-acetyl-cysteine, was used prior to induction with hydrogen peroxide in a subset of chondrocytes. Measures of oxidative stress were superoxide dismutase and reduced glutathione. Prostaglandin E2 was used as a measurement of inflammation. Chondrocytes responded appropriately to both oxidative stress and inflammation. The antioxidant N-acetyl-cysteine provided adequate protection against oxidative stress. Oxidative stress and inflammation should be considered to play a role in the pathophysiology of canine OA.

The purpose of this study was to induce an oxidative-stress adaptation in Listeria monocytogenes Bug600 (serotype 1/2a) and F1057 (serotype 4b) by pre-exposing to sublethal H2O2 and alkali-stress either singly or sequentially. Our findings show that the sequential pre-exposure of cells to pH 9 for 30 min treatment followed by 50 ppm H2O2 for 30 min at 37°C yielded the highest oxidative-stress resistant phenotypes of L. monocytogenes Bug600 and F1057. The sublethal H2O2 and sublethal alkali-stress induced oxidative-stress adaptations were completely reversible within 60 min at 37°C in the absence of such sublethal stress. However, the oxidative-stress adaptation induced at 37°C was stable at 4°C over a 24 h test period in both L. monocytogenes Bug600 and F1057. Future studies will focus on the potential cross-resistance of oxidative-stress adapted L. monocytogenes serotypes 1/2a and 4b to commonly used disinfectants and GRAS antimicrobials.

Background: The objective of this thesis was to measure oxidative stress (OS) in women with Bipolar Disorder (BD) who used combined oral contraceptives (OCU). Based on our literature review, it was predicted that OCU would increase OS levels relative to non-contraceptive users (NCU) in women. Methods: Thirty-five participants (BD n=25; Control n=10) were recruited from an ongoing study based in British Columbia ‘The Systematic Treatment Optimization Program in Early Mania.’ Participants were administered psychological screening tools (Young Mania Rating Scale (YMRS), Montgomery-Åsberg Depression Rating Scale, Mini International Neuropsychiatric Interview and Hamilton Depression Rating Scale) and provided a blood sample for the assays (Lipid Hydroperoxide (LPH), Protein Carbonylation, 4-Hydroxynonenal, 3-Nitrotyrosine (3-NT) and 17-Beta Estradiol). Results: In our primary analysis we did not find differences in OS between BD and controls relative to OCU. Within our remaining analyses, only BD women (n=17) and who gave smoking status were included. We found 3-NT to be increased in OCU compared to NCU (F (1, 12) = 5.639, p = 0.035). With respect to mood stabilizer use, 3-NT was increased in OCU relative to NCU (F (1, 10) = 6.33, p=0.031). As for atypical antipsychotics, 3-NT was heightened in OCU adjunctive users compared to NCU who did not use atypical antipsychotics (F (3, 10) = 4.822, p = 0.025). As for our correlation analyses, YRMS correlated with 3-NT and LPH in OCU BD women (r(11)= 0.711, p=0.014 and r(11) = 0.676, p=0.022, respectively) and 17-Beta Estradiol correlated with LPH (r(17) = 0.598, p = 0.001). Our results are preliminary and are limited by our small sample size and various other factors (i.e. controls). Conclusion: The association between hormones and oxidative stress still remains controversial. Here we showed, after controlling for smoking, BMI and age the use of a COC significantly increased 3-NT in women with BD. Moreover, hormones may influence the relationship between OS and mood episodes. / Thesis / Master of Science (MSc)

Omi/HtrA2 is a mitochondrial serine protease with a dual and opposite function depending on its subcellular localization. Most of the previous studies focused on Omi/HtrA2’s pro-apoptotic function when the protein is released to the cytoplasm. It is becoming apparent that the main function of Omi/HtrA2 is within the mitochondria, where it has a pro-survival role. However, its mechanism is still poorly understood. To this end, we used the yeast two-hybrid system to dissect the Omi/HtrA2 pathway by identifying novel interactors and substrates. Our studies revealed a novel function of Omi/HtrA2 in the regulation of a deubiquitinating (DUB) complex. In addition we found that Omi/HtrA2 participates in mitophagy by regulating Mulan E3 ubiquitin ligase, which recruits GABARAP (gamma-amino-butyric acid receptor-associated protein) to the mitochondria. Abro1 is the scaffold protein of the DUB complex known as BRISC (BRCC36 isopeptidase complex) that is specific for Lys-63 deubiquitination. This complex is similar to the BRCA-1 complex, a known and important player in DNA damage response. Using the yeast two-hybrid screen and a bait consisting of the unique carboxy-terminus of the Abro1 protein, we identified three transcription factors which are members of the activating protein 1 (AP-1) family, namely ATF4, ATF5 and JunD. The AP-1 family member ATF4 is ubiquitously expressed, like Abro1, and important in cell cycle regulation and survival, thus we further analyzed this interaction. Abro1’s interaction with ATF4 was specific and present only when cells are under cellular stress. When Abro1 protein level is increased it provides protection against stress-induced cell iv death, but interaction between Abro1 and ATF4 is necessary to achieve this protection. The significance of this interaction was the translocation of Abro1 from the cytoplasm to the nucleus. These results establish a new cytoprotective function of cytoplasmic Omi/HtrA2 as a regulator of the BRISC DUB complex. Under normal conditions Omi/HtrA2 is localized in the intermembrane space (IMS) of the mitochondria. We have recently identified that the mitochondrial Mulan E3 ubiquitin ligase is a substrate of Omi/HtrA2 protease. Mulan, along with MARCH5/MITOL and RNF185, are the only three mitochondrial E3 ubiquitin ligases identified thus far. The function of Mulan has been linked to cell growth, cell death and autophagy/mitophagy. In addition, we showed that Omi/HtrA2, through regulation of the Mulan protein level, controls mitophagy, especially during mitochondrial stress. To understand Mulan’s function and its control by Omi/HtrA2, we set out to identify E2 conjugating enzymes that form a complex with Mulan E3 ligase. We isolated four specific interacting E2’s, namely Ube2E2, Ube2E3, Ube2G2 and Ube2L3. To identify substrates for each unique Mulan-E2 complex we used fusion baits in a second yeast two-hybrid screening. One of the interactors isolated against the Mulan-Ube2E3 bait was the GABARAP protein, a member of the Atg8 (autophagy) family. The mammalian Atg8 family is composed of seven members that have been linked to important roles in autophagy/mitophagy. We characterized this interaction both in vitro and in vivo and its role in mitophagy. Our results suggest that Mulan participates in various pathways, depending on the nature of its partner E2 conjugating enzyme. In addition, we identified the pathway by which Mulan participates in mitophagy by recruiting GABARAP to the mitochondria. v I want to dedicate this hard work to the people who mean the most to me, the people who have been more than supportive in these past five years; they are my very small, but very loud and loving, family. My brother Raffaello has always been proud of me and always told his friends how his sister was a "doctor." My father, Alvaro, always told me I had to be better than him, a man who has a master’s degree in chemistry. Finally, but most importantly to me, I want to dedicate this work and degree to my mother, Maria Aparecida Troncon, a woman who is like no other. She has always supported me, and with small gestures like having snacks ready when I came to visit after work or coming with me to lab on the weekends so I would not be alone, she told me every day that she was proud of me. Every time she met someone she told them I was her doctor and she said it with the biggest smile on her face. Unfortunately she passed away on December 17th, 2012, just months shy of the completion of my degree. I remember how proud she was when I received my bachelor’s and I can only imagine the size of her smile when I walk across the stage this time as a Ph.D. I love you mom, you are my rock and my strength; without your constant support and dedication I would have not reached this point. I know you are smiling at me from above. Last but not least I want to dedicate this to the man who is my better-half. Thank you for all your love and support, Guillermo. I love you.