Dissertations / Theses on the topic 'Gut toxicity'

Environmental contamination is a public health concern. In particular persistent organic pollutants like Polychlorinated Biphenyls (PCBs) have been associated with multiple chronic inflammatory diseases, including non-alcoholic fatty liver disease (NAFLD). NAFLD prevalence has steadily increased and is expected to continue to rise with an estimated 25% of the world’s population and 80-100 million people affected in the United States alone. Importantly, the liver is the primary site for endobiotic and xenobiotic metabolism, hence its proper function is critical for the body’s response to innate and extrinsic molecules. One way to combat the deleterious effects of PCB toxicity and fatty liver disease is by increasing consumption of beverages and foods that contain beneficial bioactive nutrients, like dietary polyphenols. However, the biological properties of these dietary compounds are subject to their bioavailability which is directly dependent on the activity of the liver. The first aim of this dissertation was to test the hypothesis that in the presence of a compromised liver, PCB-126 toxicity is altered. Indeed, hepatic and systemic PCB-126 toxicity was exacerbated in this severe liver injury mouse model with an observed increase in hepatic inflammation, systemic inflammation, and early markers of endothelial cell dysfunction. Interestingly, we also observed an increase in the novel gut-liver axis derived cardiovascular disease (CVD) marker trimethylamine-N-oxide (TMAO). Taken altogether, aim 1 proved that a compromised liver can alter PCB toxicity, with implications of the gut microbiota in disease pathology. In aim 2 we investigated whether GTE can protect against MCD-induced hepatic toxicity and development of NAFLD. Results indicated that MCD mice exhibited severe liver injury and gut dysbiosis and unexpectedly, GTE had no protective effects. Interestingly MCD mice displayed differential epigallocatechin-3-gallate (EGCG) metabolism at the hepatic and gut microbiota level, which may alter polyphenol bioavailability and therapeutic potential. Overall, the results provide insight into how a dysfunctional liver and gut dysbiosis can alter polyphenol metabolism, possibly reducing its therapeutic efficiency. In aim 3 we sought to determine potential protective effects of a prebiotic in this mouse model. MCD-fed mice were exposed to PCB-126 with or without inulin supplementation. Although findings from this study are preliminary, our evidence indicates that inulin restores body weight and body composition in this MCD+PCB mouse model and alters the expression of Cyp1a1 in PCB exposed mice, suggesting that inulin’s protective effects may be a result of its ability to interact with the AhR pathway. However further analysis will need to be done to examine the effects of inulin on hepatic, systemic, and gut microbiota endpoints. Overall the data contained in this dissertation suggests that in the presence of a compromised liver both pollutant toxicity and nutrient metabolism are altered, with implications of the gut-microbiota in disease risk. These findings suggest that individuals with end stage liver injury may be more susceptible to pollutant-induced toxicity and nutritional intervention may be unsuccessful at mitigating disease risk.

Gut microbial composition and activity exert a strong influence on the metabolic phenotype of the host, and variation in the metabolic phenotype is a major factor underlying inter-individual variation in drug responses. In this thesis, the role of gut microflora on the mammalian metabolic system was explored with specific focus on the influence on xenobiotic metabolism and toxicity. Systems biology approaches were utilised to examine microfloral-mammalian interactions and mechanisms of drug toxicity. Multi-omic techniques, namely transcriptomics and metabonomics, were employed to characterise animal models used for investigating microfloral-mammalian interactions. These included germ-free, antibiotic-treated, and 'conve-ntional' rats. The utility of applying systems biology approaches to elucidate mechanisms of toxicity was demonstrated in conventional animals administered methapyrilene using metabonomic and protein-analysis techniques. Finally, the influence of the gut microbiota on the metabolism and toxicity of hydrazine was explored using an integrated transcriptomic and metabonomic approach. Microfloral absence modulated host metabolism directly and indirectly at the transcriptome and metabonome level, specifically drug, lipid and energy metabolism. Temporary suppression of the microbiota through antibiotic treatment did not disrupt the biological system greatly but minor disruption was observed upon re-colonisation. Methapyrilene dosing modified the structure and activity of a urea cycle enzyme and by integrating metabonomics and focused assays the potential for these protein modifications to be a mechanism of toxicity were investigated. In germ-free anitn~ls the effect of hrdrazine was variable, \A{ith toxicity enhanced in two of the three members compared to conventional animals. This highlights the potential for microbiota to influence host susceptibility towards drug toxicity and shows that toxic responses can be diverse in the absence of a functional microbiome. These studies demonstrate the use of applying systems biology approaches to investigate complex biological systems and indicate that gut microorganisms can modulate host metabolism and potentially be a factor in idiosyncratic drug responses.

The small intestine and the liver regulate several physiological functions together including the absorption and bioavailability of drugs and bile and nitrogen homeostasis. It is important to study these two organs together to gain a holistic understanding of their communication with each other. However, there is a lack of culture models that investigate the use of primary cells/tissues from the liver and the intestine to study their interaction and importance in manifestation of drug toxicity. The studies described in this dissertation were conducted using inverted rat intestinal explants obtained from three regions of the jejunum, named as the proximal, medial and distal jejunum. Markers of enterocyte, goblet cell and Paneth cell function in the jejunum followed in vivo – like spatial trends reported for the entire small intestine. Jejunum explants were integrated with hepatocytes to model the intestine-liver axis. Integration of jejunum explants from the proximal region with hepatocytes had a beneficial effect on both hepatocyte urea secretion and jejunum mucin secretion, hinting at communication between these organs in culture. Integrated cultures of the rat jejunum and hepatocytes were used to investigate ethanol toxicity in vitro. Trends in activities of enzymes involved in ethanol metabolism and mucus secretion in integrated cultures with proximal jejunum explants corroborated with in vivo reports on ethanol toxicity. Various metabolites secreted and metabolized in vitro were also identified using mass spectrometry. Spatial trends in concentrations of several lipids including bile acids, lysophosphatidylcholines and fatty acids corroborated with in vivo reports of lipid metabolism. The integrated intestine-liver cultures can be used as a platform for future investigations of drug toxicity, lipid metabolism and inter-organ communication.
Doctor of Philosophy

Variations in drug metabolism may alter drug efficacy and cause toxicity; better understanding of the mechanisms and risks shall help to practice precision medicine. At the 21st International Symposium on Microsomes and Drug Oxidations held in Davis, California, USA, in October 2-6, 2016, a number of speakers reported some new findings and ongoing studies on the regulation mechanisms behind variable drug metabolism and toxicity, and discussed potential implications to personalized medications. A considerably insightful overview was provided on genetic and epigenetic regulation of gene expression involved in drug absorption, distribution, metabolism, and excretion (ADME) and drug response. Altered drug metabolism and disposition as well as molecular mechanisms among diseased and special populations were presented. In addition, the roles of gut microbiota in drug metabolism and toxicology as well as long non-coding RNAs in liver functions and diseases were discussed. These findings may offer new insights into improved understanding of ADME regulatory mechanisms and advance drug metabolism research. (C) 2017 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.

Tetrodotoxin (TTX) is a lethal neurotoxin isolated mainly from the organs of wild puffer fishes. Although the neurotoxicity mechanisms of TTX are well known, the TTX origin and the biosynthetic mechanisms inside its hosts remain unresolved. In recent decades, the numerous reports of TTX-producing bacteria strongly suggested its bacterial origin. However, this origin is currently being challenged by the low and inconsistent TTX productions in vitro by the previously reported TTX-producing bacteria. Culturable TTX-producing bacteria were frequently isolated and reported from the guts of TTX-bearing animals including puffer fishes, however, these bacteria were estimated to account for 0.1% of the total gut bacteria. Moreover, the identification and functions of the non-culturable gut bacteria participating in TTX biosynthesis have never been reported. I hypothesize that the puffer fish gut bacteria and the entire gut environment serve as a functional integrality responsible for TTX biosynthesis. In this study, 16S rRNA amplicon metagenomics pipeline was established to profile the entire gut bacterial structures of both toxic and non-toxic puffer fishes respectively. UniFrac based principal coordinate analysis showed that bacterial diversities were significantly different (P-value < 0.001) between the gut environments of toxic puffer fishes and the non-toxics. Vibrio and Cyanobacteria were identified as centralities of gut bacteria co-occurrence network in toxic puffer fishes, implying their key roles in TTX biosynthesis. The results of metagenome prediction and gene set enrichment indicated that arginine biosynthesis was significant enriched (P-value < 0.05) in the toxic group. To further investigate the roles of key bacteria and arginine biosynthesis in producing TTX, metabolomics pipeline was established along with 16S rRNA amplicon metagenomics to monitor the dynamics of metabolites and bacterial compositions in guts of toxic puffer fishes during their detoxification process. The average TTX concentrations in the liver after a 60-day culture (6.41 ± 3.00 µg/g) was found significantly lower (P-value < 0.01) than that of the same species from the wild (31.86 ± 22.20 µg/g). The relative abundance of Vibrio was found positively correlated with the liver TTX concentrations. With the increase of culture periods, the relative abundance of Vibrio and Cyanobacteria decreased. In addition, both the metabolites and functional genes in arginine biosynthesis metabolic pathway were found significantly down-regulated (P-value < 0.05). These results indicated that both Vibrio and Cyanobacteria bacterial symbionts participated in TTX biosynthesis using arginine as a potential precursor in the gut environment of toxic puffer fishes.

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-06-04T14:42:13Z No. of bitstreams: 1 DISSERTA??O FINAL - ANGELO ABEL.pdf: 2908441 bytes, checksum: 7b4f57513c25b05da3fbcc36003b7939 (MD5)
Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-06-11T14:34:47Z (GMT) No. of bitstreams: 1 DISSERTA??O FINAL - ANGELO ABEL.pdf: 2908441 bytes, checksum: 7b4f57513c25b05da3fbcc36003b7939 (MD5)
Made available in DSpace on 2018-06-11T14:46:48Z (GMT). No. of bitstreams: 1 DISSERTA??O FINAL - ANGELO ABEL.pdf: 2908441 bytes, checksum: 7b4f57513c25b05da3fbcc36003b7939 (MD5) Previous issue date: 2017-09-29
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
In this work, the sample-flame propagation indexes were simulated in laboratory, in detriment and in comparison to the generalized burning during the fires in internal environments. The respective chemical and physical properties of the paints, the emanated gases, were compared; evidencing its toxicities, toxicological thresholds and using the tests of horizontal burning and vertical burning. In the experimental part, the paint films were produced for later burning in a quartz chamber with the use of the electric furnace, from which the gases were collected, according to each thermal degradation orientation obtained by the TGA pallet, in order to analyze the toxicities in gas chromatography. In the results the different firing behaviors for each paint can be compared by virtue of its physico-chemical composition, together with its gas release rates in each temperature range.
Neste trabalho produziu-se a partir das tintas acr?licas ? base d??gua, os ?ndices de propaga??o de chama amostral e simulada em laborat?rio, em detrimento e em comparativo ? queima generalizada durante os inc?ndios em ambientes internos. Foram comparadas as respectivas propriedades qu?micas e f?sicas das tintas, dos gases emanados; evidenciando as suas toxicidades, limiares toxicol?gicos e empregando os testes de queima horizontal e queima vertical. Na parte experimental foram produzidos os filmes de tintas, para posterior queima em c?mara de quartzo com o uso do forno el?trico, onde a partir deste, coletou-se os gases, segundo cada orienta??o de degrada??o t?rmica obtida pala TGA, para ent?o serem analisadas as toxicidades em cromatografia gasosa. Nos resultados podem ser comparados os diferentes comportamentos de queima para cada tinta em virtude de sua composi??o f?sico-qu?mica, juntamente com suas taxas de libera??es de gases em cada faixa de temperatura.

Made available in DSpace on 2014-12-17T15:41:49Z (GMT). No. of bitstreams: 1 MariaSBL_DISSERT.pdf: 2808268 bytes, checksum: 81a073dbeea9c81ef1ced46ef6336e4c (MD5) Previous issue date: 2010-07-08
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The problems of water supply in Northeast Brazil are severe and require more focused studies. This work was intended to assess water quality in the watershed Pirangi, located in the Northeastern state of the newborn using the Water Quality Index, AQI associated with the Index of Toxicity-IT. The data presented in this study were collected in November 2008, June 2009 and March 2010 at eight sampling stations distributed throughout the basin. The study covered nine parameters, based on guidelines established by CETESB, and seven members of Metal Toxicity index-IT. These waters are framed in the classification between GOOD and BAD showing AQI 41.34 minimum and a maximum of 76.23. Virtually all seven metals analyzed were below the detection limits of ICP-OES giving IT a water equal to one when they are absent and 0 when there are levels of trace metals
Os problemas de abastecimento de ?gua no Nordeste do Brasil s?o graves e necessitam de estudos mais direcionados. O presente trabalho foi desenvolvido com o prop?sito de monitorar a qualidade da ?gua na Bacia Hidrogr?fica Pirangi, localizada na regi?o Nordeste do Estado do RN usando o ?ndice de Qualidade da ?gua-IQA associado com o ?ndice de Toxidez-IT. Os dados apresentados nesta pesquisa foram coletados em novembro de 2008, junho de 2009 e mar?o de 2010 em oito esta??es amostrais distribu?das ao longo da bacia. O estudo abrangeu nove par?metros, baseado nas diretrizes estabelecidas pela CETESB, al?m de sete metais integrantes do ?ndice de Toxidez-IT. Estas ?guas enquadraram-se na classifica??o entre BOA e RUIM apresentando IQA m?nimo de 41,34 e m?ximo de 76,23. Praticamente os sete metais analisados estavam abaixo dos limites de detec??o do ICP-OES dando ? ?gua um IT igual a 1 quando estes est?o ausentes e 0 quando se encontram teores de metais tra?os

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Hyptis pectinata L. Poit. (Lamiaceae), widely known as Sambacaitá, is an example of a plant commonly used in folk Medicine; various biological effects are associated with its extracts, such as: analgesic, anti-inflammatory, and anti-microbial. Many studies in vivo and in vitro has assessed the effects promoted by the aqueous extract and essential oil of the leaves of the plant, whose chemical composition constitute their water soluble compounds and their volatile compounds, respectively. This study aimed at keeping on these studies, determining the chemical constituents and the acute toxicity of the sample of the aqueous extract and essential oil used to study the analgesic effect of these extracts in an acute articular inflammatory condition, similar to an episode of acute arthritis as in Gout. The phyto-chemical studies of aqueous extract identified the presence of alkaloid, tannin and flavonoid. The analysis of the constituents of the essential oil was made by gas chromatography and mass spectrometer, showing as main constituents: β- cariofilene and Germacrene-D. The evaluation of acute toxicity was represented by the establishment of DL50 in Swiss mice, obtained by the probits method, it was not possible to measure the DL50 of the aqueous extract due to its low toxicity, as for the essential oil, it was obtained a 1.1 g/kg DL50. The analgesic effect was studied using the sodium urate crystals induced arthritis model, in Wistar mice, as proposed by Coderre and Wall; the aqueous extract presented expressive analgesic effect with the 50 mg/kg doses, which was reverted by the opioid antagonist, naloxone (5 mg/kg). The essential oil did not present analgesic effect with the tested doses. The results showed that the aqueous extract has low toxicity and it presents analgesic effect in a rheumatic condition, similar to Gout arthritis, while the essential oil presents medium toxicity and it does not show analgesic effect in the proposed rheumatic condition.
A Hyptis pectinata L. Poit. (Lamiaceae), vulgarmente conhecida como sambacaitá, é um exemplo de planta comumente utilizada na medicina popular; diversos efeitos biológicos estão associados aos seus extratos, tais como analgésico, antiinflamatório e antimicrobiano. Vários estudos in vivo e in vitro têm avaliado estes efeitos promovidos pelo extrato aquoso e óleo essencial das folhas da planta, cujas composições químicas, constituem os seus compostos solúveis em água e os seus compostos voláteis respectivamente. Este trabalho objetivou dar continuidade a esses estudos, determinando os constituintes químicos e a toxicidade aguda da amostra de extrato aquoso e óleo essencial utilizados, para estudar o efeito antinociceptivo (analgésico) dos extratos citados, em uma condição inflamatória articular aguda, similar a um ataque de artrite aguda como o ocorrido na gota. Os estudos fitoquímicos do extrato aquoso identificaram a presença de alcalóides, taninos e flavonóides. A análise dos constituintes do óleo essencial se deu por cromatografia gasosa e espectrômetro de massa, revelando como principais constituintes: β-cariofileno e germacreno-D. A avaliação da toxicidade aguda foi representada pela determinação da DL50, em camundongos swiss, obtida pelo método dos probitos; não foi possível mensurar a DL50 do extrato aquoso, devido a sua baixa toxicidade, já o óleo essencial, obteve uma DL50 de 1,1 g/kg. O efeito antinociceptivo foi estudado usando o modelo de artrite induzida por cristais de urato de sódio, em ratos wistar, proposto por Coderre e Wall. O extrato aquoso apresentou efeito antinociceptivo significativo na dose de 50 mg/Kg, o qual foi revertido pelo antagonista opióide, naloxona (5mg/kg). O óleo essencial não apresentou efeito antinociceptivo nas doses testadas. Os resultados mostraram que o extrato aquoso possui baixa toxicidade e apresenta atividade antinociceptiva numa condição reumática, semelhante à artrite gotosa; enquanto o óleo essencial apresenta toxicidade média e não apresenta atividade antinociceptiva na condição reumática proposta.

Made available in DSpace on 2014-12-17T14:02:02Z (GMT). No. of bitstreams: 1 JuskaMSM.pdf: 940466 bytes, checksum: 95c63af4ea67b2fb9341e2034e0242a4 (MD5) Previous issue date: 2006-07-30
The incidence of toxic cyanobacterial blooms is one of the important consequences of eutrophication in aquatic ecosystems. It is a very common phenomenon in reservoirs and shrimp ponds in the State of Rio Grande do Norte (RN), Brazil. Cyanobacterias produce toxins which can affect aquatic organisms and men trough the food chain. Aiming to contribute to the studies of cyanobacterias in RN, we propose: a) to evaluate the toxicity of isolated cyanobacterias in important fresh-water environments; and b) to verify the effects of both natural and cultured blooms occurred in reservoirs for human supply and in the cladoceran Ceriodaphnia silvestrii. This study was carried out using samples of natural blooms occurred between March and October of 2004 in Gargalheiras Dam (08? L e 39? W), in July of 2004 in Armando Ribeiro Gon?alves Dam (06o S e 37o W) and in commercial shrimp ponds (Litopenaeus vannamei) located in fresh-water environments. The samples were collected with plankton net (20?m.) for identification, isolation and obtaining of phytoplanktonic biomass for liophilization and later toxicity bioassays. The toxicity of cultured samples and natural blooms was investigated through bioassays in Swiss mice. Quantification of cyanobacteria in samples was conducted following the ?termol method, with 300mL samples fixed with lugol. The toxicity test with Ceriodaphnia silvestrii followed ABNT, 2001 recommendations, and were accomplished with natural hepatotoxic bloom s samples and cultured samples of both non-toxic and neurotoxic C. raciborskii. In this test, five newborns, aged between 6 and 24 hours, were exposed to different concentrations (0 a 800 mg.L-1) of crude cyanobacterial extracts during 24 and 48 hours. Three replicates were used per treatment. The pH, temperature and dissolved oxygen at the beginning and after 24 and 48hours from the test were measured. We estimated the CL50 through the Trimmed Spearman-Karber method. The blooms were constituted by Microcystis panniformis, M. aeruginosa, Anabaena circinalis, Cylindrospermopsis raciborskii and Planktothrix agardhii, producers of mycrocistin-LR confirmed with HPLC analysis. Samples of hepatotoxic blooms registered toxinogenic potential for C. silvestrii, with CL50-24h value of 47.48 mg.L-1 and CL5048h of 38.15 mg.L-1 for GARG samples in march/2005; CL50-24h of 113,13 mg.L-1 and CL5048h of 88,24 mg.L-1 for ARG July/2004; CL50-24h of 300.39 mg.L-1 and CL50-48h of 149.89 mg.L-1 for GARG October/2005. For cultured samples, values of CL50-24h and CL50-48h for C. raciborskii toxic strains were 228.05 and 120.28 mg.L-1, respectively. There was no mortality of C. silvestrii during the tests with non-toxic C. raciborskii strain. The toxicity test with C. silvestrii presented good sensitivity degree to cyanotoxins. The toxicity of natural hepatotoxic blooms samples (microcystins) and cultured neurotoxic saxitoxins producer samples analyzed in this study give us strong indications of that toxin s influence on the zooplanktonic community structure in tropical aquatic environments. Eleven cyanobacteria strains were isolated, representing 6 species: Anabaenopsis sp., Cylindrospermopsis raciborskii, Chroococcus sp., Microcystis panniformis, Geitlerinema unigranulatum e Planktothrix agardhii. None presented toxicity in Swiss mice. The strains were catalogued and deposited in the Laborat?rio de Ecologia e Toxicologia de Organismos Aqu?ticos (LETMA), in UFRN, and will be utilized in ecotoxicol?gical and ecophysiological studies, aiming to clarify the causes and control of cyanobacterial blooms in aquatic environments in RN. This state s reservoirs must receive broader attention from the authorities, considering the constant blooms occurring in waters used for human consumption
Incid?ncia de flora??es t?xicas de cianobact?rias ? uma das conseq??ncias da eutrofiza??o nos ecossistemas aqu?ticos, sendo comum a sua ocorr?ncia em reservat?rios e viveiros de cultivo de camar?o no Estado Rio Grande do Norte. Cianobact?rias podem produzir toxinas que podem afetar organismos aqu?ticos e o homem atrav?s da cadeia alimentar. Visando contribuir com o desenvolvimento de estudos ecotoxicol?gicos de cianobact?rias no RN, nos propomos avaliar a toxicidade de cianobact?rias isoladas de ambientes de ?guas doces e verificar o efeito de cultura e flora??es naturais ocorridas em reservat?rios para abastecimento humano, no crust?ceo clad?cero Ceriodaphnia silvestrii. O estudo foi conduzido com amostras de flora??es naturais ocorridas em mar?o e outubro de 2004 na Barragem Gargalheiras (08? L e 39? W), em julho de 2004 na Barragem Armando Ribeiro Gon?alves (06o S e 37o W) e em fazendas comerciais de cultivo de camar?o (Litopenaeus vannamei), localizadas em ambientes de ?gua doce do RN (6o 58 S e 38o 36 W). As amostras de flora??es foram coletadas com rede de pl?ncton (20?m) para identifica??o, isolamento e obten??o de biomassa fitoplanct?nica para liofiliza??o e posterior determina??o da toxicidade por bioensaios. A toxicidade das amostras de culturas e flora??es naturais foi investigada atrav?s de bioensaios em camundongos Swiss. A quantifica??o das cianobact?rias foi realizada pelo m?todo de ?termol, utlizando-se amostras (300mL) fixadas com lugol. O teste de toxicidade com Ceriodaphnia silvestrii seguiu as recomenda??es da ABNT (2001) e foram realizadas com amostras de flora??es naturais hepatot?xicas e culturas de C. raciborskii neurot?xica e n?o t?xica. No teste, cinco neonatos com idade entre 6 e 24 horas foram expostos a diferentes concentra??es (0 a 800 mg.L-1) de extrato bruto de cianobact?rias durante 24 e 48 horas. Tr?s replicatas por tratamentos foram usadas. Foram medidos o pH, a temperatura e o oxig?nio dissolvido no in?cio, com 24 e com 48 horas do teste. Atrav?s do m?todo Trimmed Spearman-Karber foi estimado a CL50. As flora??es eram mistas e compostas por Microcystis panniformis, M. aeruginosa, Anabaena circinalis, Cylindrospermopsis raciborskii e Planktothrix agardhii, produtoras de microcistina- LR, confirmada atrav?s de an?lise por HPLC. Amostras de flora??es hepatot?xicas registraram potencial toxinog?nico para o C. silvestrii, com valores de CL50-24h de 47.48 mg.L-1 e CL50-48h de 38.15 mg.L-1 para a amostra de GARG mar/05; CL50-24h de 113,13 mg.L-1 e CL50-48h de 88,24 mg.L-1 para ARG jul/04; CL50-24h de 300.39 mg.L-1 e CL50-48h de 149.89 mg.L-1 para GARG 10/05. Para as amostras de cultura valores de CL50-24h e CL50-48h para a cepa t?xica de C. raciborskii foram de 228.05 e 120.28 mg.L-1, respectivamente. N?o houve mortalidade dos C. silvestrii nos testes com a cepa de C. raciborskii n?o-t?xica. O teste de toxicidade com C. silvestrii apresentou um bom grau de sensibilidade ?s cianotoxinas. A toxicidade das amostras de flora??es naturais hepatot?xicas (microcistinas) e culturas neurot?xicas produtoras de saxitoxinas verificadas neste estudo fornece forte indicativos da influ?ncia dessas toxinas sobre a estrutura da comunidade zooplanct?nica em ambientes aqu?ticos tropicais. Foram isoladas 11 cepas de cianobact?rias de reservat?rios e viveiros do Estado, representadas por 6 esp?cies: Anabaenopsis sp., Cylindrospermopsis raciborskii, Chroococcus sp., Microcystis panniformis, Geitlerinema unigranulatum e Planktothrix agardhii. Nenhuma cepa apresentou toxicidade em camundongos Swiss. As cepas foram catalogadas e depositadas no Laborat?rio de Ecologia e Toxicologia de Organismos Aqu?ticos (LETMA) da UFRN e ser?o utilizadas em estudos ecotoxicol?gicos e ecofisiol?gicos visando esclarecer as causas e controle de flora??es de cianobact?rias nos ambientes aqu?ticos do Estado. Os reservat?rios do Rio Grande do Norte devem merecer maior aten??o perante os ?rg?os respons?veis, tendo em vista os constantes florescimentos t?xicos de cianobact?rias em ?guas utilizadas para consumo humano

Gastrointestinal toxicity is a significant side effect of many cancer treatments. Characterised by diarrhoea, abdominal pain and bleeding, this toxicity can affect up to 80% of patients, depending on treatment regimen. Currently, there are no highly effective intervention strategies for the vast majority of people affected, thus more evidence is required to improve future management. This thesis focussed primarily on gastrointestinal toxicity stemming from two major types of cancer treatment. These are chemotherapy, the most common form of cancer treatment, and small molecule tyrosine kinase inhibitors (SM-TKIs), a class of targeted therapies, often used in combination with chemotherapy. There is a clear gap in knowledge in understanding how these different cancer treatments cause gastrointestinal toxicity, and how the population of microorganisms in the intestine, the gut microbiome, links to these responses. This thesis therefore aimed to investigate the role of the gut microbiome in influencing the development and exacerbation of gastrointestinal toxicity stemming from cancer treatment. This was investigated in three main sections. Firstly, I aimed to examine the interaction between the gut microbiome and the innate immune system (chiefly the innate immune receptor Toll-like receptor 4 (TLR4)), and determine how this interaction could be involved in the development of gastrointestinal toxicity following chemotherapy. In order to achieve this aim, I characterised the microbial composition of a TLR4 conditional knockout mouse model and assessed changes due to chemotherapy treatment. There were no clear differences in the microbiome of wild type and TLR4 conditional knockout mice. Secondly, I aimed to characterise the role of the gut microbiome in diarrhoea stemming from the SM-TKI treatment neratinib, which causes high levels of diarrhoea. I found that, in a pre-clinical model, neratinib treatment does cause changes to microbial composition, however it was unclear if these changes were a key driver of diarrhoea development or simply a side effect of this diarrhoea. Therefore I analysed diarrhoea development following an initial, antibiotic-induced perturbation, showing that addition of narrow-spectrum antibiotics caused a significant decrease in diarrhoea severity and timespan. Finally, I clinically appraised the use of the gut microbiome in predicting risk of cancer treatment-induced gastrointestinal toxicity in two defined patient cohorts. A retrospective cohort showed that participants who went on to develop diarrhoea had significantly lower amounts of the bacterial genera Blautia and significantly higher amounts of the genera Collinsella. A longitudinal study was then developed. Pilot results did not show clear microbial clustering based on diarrhoea status. The results of my thesis demonstrate the emerging role gut microbiome composition has on the development of diarrhoea following cancer treatment. However I was unable to definitively identify any particular bacterial type that is a key mediator of this effect. The results presented here however provide strong rationale for further research in this area using specific machine learning and metabolomic techniques to identify compositional features that may be important in accurately predicting diarrhoea development following cancer treatment.
Thesis (Ph.D.) -- University of Adelaide, School of Biomedicine, 2021

The format of my thesis is as follows: a general introduction, a literature review, two research chapters, a second literature reviews, three research chapters, a general discussion and references. During my candidature, I made significant effort to publish my research findings. Each research chapter is presented in its original publication format. This may result in slight repetition between chapters arising from the same study. My thesis has three distinct themes relating to the pathobiology of chemotherapy-induced gut toxicity. The first aims to characterise the extent of tight junction disruption in the alimentary tract following chemotherapy treatment (clinically and preclinically), giving rise to the first two research chapters (Chapter 2 and 3). The first publication (Chapter 2) was completed early in my candidature (2013). The second publication (Chapter 3) arose from independent research funding I obtained from the Australian Dental Research Foundation. Together, these chapters formed the scope and theme for my PhD, and are therefore followed by two literature reviews and the remaining four research chapters. The second theme relates to involvement of innate immune regulation in the development of chemotherapy-induced gut toxicity and barrier dysfunction, giving rise to an additional two primary research chapters (Chapter 6 and 7). The third aim of this thesis was to develop a high throughput in vitro model for the study of chemotherapy-induced mucosal injury and targeted therapeutic approaches. This is summarised in Chapters 8 and 9. During my candidature, I had the opportunity to work with Professor Stephen Sonis from Dana- Farber Harvard Cancer Centre, Harvard University, Boston. After presenting my work at the Multinational Association for Supportive Care in Cancer in 2014 (Miami, USA), Professor Sonis and I developed the hypothesis that gut-derived inflammation affects central neurological functions. This formed the basis for my secondary literature review (Chapter 5) as well as an additional literature review on cytokine-mediated blood brain barrier permeability and its involvement in chemotherapy-induced cognitive decline. The latter literature review is not included as a chapter in this thesis, but as an appendix in its original publication format (PDF).
Thesis (Ph.D.) -- University of Adelaide, School of Medicine, 2016.

Radiotherapy is a mainstay treatment modality used for the treatment of more than 80% of patients with head and neck cancer (HNC). Despite the technological advances in radiotherapy delivery, two key limitations remain a challenge for HNC radiotherapy. First, HNC radiotherapy is associated with unacceptable levels of normal tissue toxicities. One of the most frequent and troublesome toxicities is oral mucositis (OM). Radiotherapy-induced OM refers to the inflammation and/or ulceration of the oral mucosa following radiotherapy. It can affect more than 90% of patients with HNC, with varying degrees of severity. The major challenges related to OM are the lack of effective interventions to prevent or treat OM and the lack of a robust predictive marker to predict OM risk. The second limitation of HNC radiotherapy is heterogeneity in patients' response in terms of tumour control and recurrence. Currently, there are no biomarkers to identify patients with a favourable response and those at risk for primary tumour failure or tumour recurrence. Therefore, finding new targets for OM interventions and predictive biomarkers to predict radiotherapy outcomes will help address these limitations of HNC radiotherapy and improve treatment success. Recent years have witnessed a growing interest in the role of the gut microbiome in cancer treatment efficacy and toxicity, including radiotherapy. The gut microbiome, a collection of microorganisms residing in the gastrointestinal tract, plays a central role in the modulation of systemic immune and inflammatory responses. Given that OM is an inflammatory condition and radiotherapy-induced immunogenic cell death is a key pathway by which radiotherapy kills tumour cells, we hypothesised that the gut microbiome may influence both the pathogenesis of OM and radiotherapy response through modulation of immune and inflammatory signalling. As such, this thesis aimed to investigate the impact of the gut microbiome on the development of radiotherapy-induced OM and radiotherapy outcomes in preclinical and clinical settings. Firstly, I investigated this in preclinical studies described in chapters 3-5. In chapter 3, I successfully developed an antibiotic-induced gut microbiota depletion (AIMD) method that allows for studying the development of OM in the absence of major bacterial taxa. In chapter 4, I established a radiation-induced OM model in rats using a single radiation dose of 20 Gy. These two models were used to conduct the main animal study (chapter 5), which demonstrated that the gut microbiome is involved in the pathogenesis of OM, particularly the healing stage, through the modulation of inflammatory cytokines. Lastly, to translate my preclinical findings to the clinical settings, I investigated whether patient pre-treatment gut microbiome is associated with the severity of OM and radiotherapy response in patients with HNC (chapter 6). The results from this clinical study showed that certain microbes in the baseline gut microbiome are associated with OM severity and tumour recurrence. Together, the results from this thesis suggest that the gut microbiome is involved in the pathogenesis of OM and is associated with radiotherapy response offering a potential target to treat or prevent OM and predict treatment outcomes.
Thesis (Ph.D.) -- University of Adelaide, School of Biomedicine, 2021

博士
國立中興大學
生物科技學研究所
107
Gut bacterial β-D-glucuronidases (GUSs) catalyze the removal of glucuronic acid from liver-produced β-D-glucuronides. These reactions can have deleterious consequences when they reverse xenobiotic metabolism. The human gut contains hundreds of GUSs of variable sequences and structures. To understand how any particular bacterial GUS(s) contributes to global GUS activity and affects human health, the substrate preference(s) of individual enzymes must be known. Herein, we report that representative GUSs vary in their ability to produce various xenobiotics from their respective glucuronides. In an attempt to explain the distinct substrate preference, we solved the structure of a bacterial GUS complexed with coumarin-3-D-glucuronide. Comparisons of this structure with other GUS structures identified differences in TIM barrel loop 3 (or the 2-helix loop) and loop 5 at the aglycone-binding site, where differences in their conformations, hydrophobicities and flexibilities appear to underlie the distinct substrate preference(s) of the GUSs. Additional sequence, structural and functional analysis indicated that several groups of functionally related gut bacterial GUSs exist. Our results pinpoint opportunistic gut bacterial GUSs as those that cause xenobiotic-induced toxicity. We propose a structure-activity relationship that should allow both the prediction of the functional roles of GUSs and the design of selective inhibitors. Furthermore, we demonstrated how charge, conformation, and substituents of several uronic iminocyclitols and analogues contribute to the inhibitory potency and selectivity for gut bacterial GUSs by using crystallographic and biochemical methods. Uronic isofagomine was a potent inhibitor (Ki up to 4 nM) unlike uronic deoxynojirimycin that showed a less potent inhibition (Ki up to 930 nM), indicating that the positive charge at the anomeric position, but not endocyclic oxygen position, was favorable to form electrostatic interactions with the two catalytic glutamates of GUSs. Moreover, D-glucaro-δ-lactam displayed good inhibitions (up to 280 nM) for bacterial GUSs owing to the half-chair conformation that favored several polar contacts and a charge-dipole interaction. Additionally, C6-alkylated uronic isofagomine displayed selective inhibition for opportunistic bacterial GUSs, which was attributed to the hydrophobic interactions between the propyl group and the loop 5 residues of the GUSs.In contrast, N1-alkylated analogue was a non-selective and moderate inhibitor for GUSs, which was explained by a steric hindrance between the alkyl group of the inhibitor and the catalytic acid/base glutamate of GUSs. In summary, we identified the responsible group of GUSs for the xenobiotic-induced toxicity, and developed a selective inhibitor targeting these GUSs.