The Synthesis of Amphiphilic Glycolipids as Potential Inhibitors of Bacterial Adhesion

The synthesis of glycolipids as potential anti-bacterial agents and glycolipid mimetics is the main focus of the research presented in this thesis. A variety of glycolipids based around an aspartic acid, aliphatic or aromatic scaffold were investigated. Chapter 1 describes the biological importance of glycolipids and how they can be utilised as anti-adhesion agents and immunomodulators. The concept of multivalency is also discussed, with specific examples relating to the anti-adhesion approach. A variety of O-glycolipids based around an aspartic acid scaffold were constructed in chapter 2. Based on a modular approach, a diverse range of glycolipids were synthesised. They exhibited variations in hydrocarbon chain length, number of hydrocarbon chains, connectivity of carbohydrate moiety and the carbohydrate moiety used. Although originally designed to act as immunomodulators their ability to inhibit bacterial adhesion in immunocompromised individuals was also investigated. Furthermore the glycolipids were tested as low molecular weight organogelators (LWOG), and promising results were obtained. Chapter 3 deals with the synthesis of O- and N-glycolipids built around an aliphatic core. Initially the synthesis proved problematic but success was achieved utilising DMTMM as the coupling reagent. Similarly to the aspartic acid analogues, the glycolipids exhibited variation in the chemical nature of the spacer groups used to link the carbohydrate to the aliphatic core. The O- and N-glycolipids were synthesised with a view to examine their ability to inhibit bacterial adhesion in Cystic Fibrosis (CF) patients. The synthesis of a range of glycolipids based around an aromatic core is discussed in chapter 4. Again variation in the linker utilised to connect the carbohydrate moiety and the aromatic core is explored. This time the importance of the presence of the hydrocarbon chain was also investigated. Therefore variation in the connectivity of the lipidic chain is explored, and analogues of varying hydrocarbon chain length were synthesised. The O- and N-glycolipids were synthesised as potential anti-adhesion agents in order to determine a structural activity relationship. The biological evaluation of selected glycolipids is discussed in chapter 5. Selected aspartic acid, aliphatic and aromatic glycolipids are investigated as potential inhibitors of Burkholderia multivorans adhesion to a model of lung epithelial cells of CF patients. Promising preliminary results were obtained for both a mono- and di-valent aromatic-based glycolipid

A Concise Synthesis of Glycolipids Based on Aspartic Acid Building Blocks

L-Aspartic acid building blocks bearing galactosyl moieties were used to synthesise glycolipid mimetics of variable hydrocarbon chain length. The glycolipids were readily prepared through amide bond formation using the TBTU/HOBt coupling methodology. It was observed that, under these conditions, activation of the α-carboxylic acid of the intermediates led to near complete racemisation of the chiral centre if the reaction was carried out in the presence of a base such as triethylamine. The enantiomerically pure glycolipids were obtained after careful consideration of the synthetic sequence and by performing the coupling reactions in the absence of base

A Concise Synthesis of Glycolipids Based on Aspartic Acid Building Blocks

L-Aspartic acid building blocks bearing galactosyl moieties were used to synthesise glycolipid mimetics of variable hydrocarbon chain length. The glycolipids were readily prepared through amide bond formation using the TBTU/HOBt coupling methodology. It was observed that, under these conditions, activation of the α-carboxylic acid of the intermediates led to near complete racemisation of the chiral centre if the reaction was carried out in the presence of a base such as triethylamine. The enantiomerically pure glycolipids were obtained after careful consideration of the synthetic sequence and by performing the coupling reactions in the absence of base

Homologous and heterologous desensitization of guanylyl cyclase-B signaling in GH3 somatolactotropes

The guanylyl cyclases, GC-A and GC-B, are selective receptors for atrial and C-type natriuretic peptides (ANP and CNP, respectively). In the anterior pituitary, CNP and GC-B are major regulators of cGMP production in gonadotropes and yet mouse models of disrupted CNP and GC-B indicate a potential role in growth hormone secretion. In the current study, we investigate the molecular and pharmacological properties of the CNP/GC-B system in somatotrope lineage cells. Primary rat pituitary and GH3 somatolactotropes expressed functional GC-A and GC-B receptors that had similar EC50 properties in terms of cGMP production. Interestingly, GC-B signaling underwent rapid homologous desensitization in a protein phosphatase 2A (PP2A)-dependent manner. Chronic exposure to either CNP or ANP caused a significant down-regulation of both GC-A- and GC-B-dependent cGMP accumulation in a ligand-specific manner. However, this down-regulation was not accompanied by alterations in the sub-cellular localization of these receptors. Heterologous desensitization of GC-B signaling occurred in GH3 cells following exposure to either sphingosine-1-phosphate or thyrotrophin-releasing hormone (TRH). This heterologous desensitization was protein kinase C (PKC)-dependent, as pre-treatment with GF109203X prevented the effect of TRH on CNP/GC-B signaling. Collectively, these data indicate common and distinct properties of particulate guanylyl cyclase receptors in somatotropes and reveal that independent mechanisms of homologous and heterologous desensitization occur involving either PP2A or PKC. Guanylyl cyclase receptors thus represent potential novel therapeutic targets for treating growth-hormone-associated disorders

Patient Health Questionnaire-9 scores do not accurately estimate depression prevalence: individual participant data meta-analysis.

OBJECTIVES: Depression symptom questionnaires are not for diagnostic classification. Patient Health Questionnaire-9 (PHQ-9) scores ≥10 are nonetheless often used to estimate depression prevalence. We compared PHQ-9 ≥10 prevalence to Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (SCID) major depression prevalence and assessed whether an alternative PHQ-9 cutoff could more accurately estimate prevalence. STUDY DESIGN AND SETTING: Individual participant data meta-analysis of datasets comparing PHQ-9 scores to SCID major depression status. RESULTS: A total of 9,242 participants (1,389 SCID major depression cases) from 44 primary studies were included. Pooled PHQ-9 ≥10 prevalence was 24.6% (95% confidence interval [CI]: 20.8%, 28.9%); pooled SCID major depression prevalence was 12.1% (95% CI: 9.6%, 15.2%); and pooled difference was 11.9% (95% CI: 9.3%, 14.6%). The mean study-level PHQ-9 ≥10 to SCID-based prevalence ratio was 2.5 times. PHQ-9 ≥14 and the PHQ-9 diagnostic algorithm provided prevalence closest to SCID major depression prevalence, but study-level prevalence differed from SCID-based prevalence by an average absolute difference of 4.8% for PHQ-9 ≥14 (95% prediction interval: -13.6%, 14.5%) and 5.6% for the PHQ-9 diagnostic algorithm (95% prediction interval: -16.4%, 15.0%). CONCLUSION: PHQ-9 ≥10 substantially overestimates depression prevalence. There is too much heterogeneity to correct statistically in individual studies

The Synthesis of Amphiphilic Glycolipids as Potential Inhibitors of Bacterial Adhesion

The synthesis of glycolipids as potential anti-bacterial agents and glycolipid mimetics is the main focus of the research presented in this thesis. A variety of glycolipids based around an aspartic acid, aliphatic or aromatic scaffold were investigated. Chapter 1 describes the biological importance of glycolipids and how they can be utilised as anti-adhesion agents and immunomodulators. The concept of multivalency is also discussed, with specific examples relating to the anti-adhesion approach. A variety of O-glycolipids based around an aspartic acid scaffold were constructed in chapter 2. Based on a modular approach, a diverse range of glycolipids were synthesised. They exhibited variations in hydrocarbon chain length, number of hydrocarbon chains, connectivity of carbohydrate moiety and the carbohydrate moiety used. Although originally designed to act as immunomodulators their ability to inhibit bacterial adhesion in immunocompromised individuals was also investigated. Furthermore the glycolipids were tested as low molecular weight organogelators (LWOG), and promising results were obtained. Chapter 3 deals with the synthesis of O- and N-glycolipids built around an aliphatic core. Initially the synthesis proved problematic but success was achieved utilising DMTMM as the coupling reagent. Similarly to the aspartic acid analogues, the glycolipids exhibited variation in the chemical nature of the spacer groups used to link the carbohydrate to the aliphatic core. The O- and N-glycolipids were synthesised with a view to examine their ability to inhibit bacterial adhesion in Cystic Fibrosis (CF) patients. The synthesis of a range of glycolipids based around an aromatic core is discussed in chapter 4. Again variation in the linker utilised to connect the carbohydrate moiety and the aromatic core is explored. This time the importance of the presence of the hydrocarbon chain was also investigated. Therefore variation in the connectivity of the lipidic chain is explored, and analogues of varying hydrocarbon chain length were synthesised. The O- and N-glycolipids were synthesised as potential anti-adhesion agents in order to determine a structural activity relationship. The biological evaluation of selected glycolipids is discussed in chapter 5. Selected aspartic acid, aliphatic and aromatic glycolipids are investigated as potential inhibitors of Burkholderia multivorans adhesion to a model of lung epithelial cells of CF patients. Promising preliminary results were obtained for both a mono- and di-valent aromatic-based glycolipid

The Synthesis of Amphiphilic Glycolipids as Potential Inhibitors of Bacterial Adhesion

The synthesis of glycolipids as potential anti-bacterial agents and glycolipid mimetics is the main focus of the research presented in this thesis. A variety of glycolipids based around an aspartic acid, aliphatic or aromatic scaffold were investigated. Chapter 1 describes the biological importance of glycolipids and how they can be utilised as anti-adhesion agents and immunomodulators. The concept of multivalency is also discussed, with specific examples relating to the anti-adhesion approach. A variety of O-glycolipids based around an aspartic acid scaffold were constructed in chapter 2. Based on a modular approach, a diverse range of glycolipids were synthesised. They exhibited variations in hydrocarbon chain length, number of hydrocarbon chains, connectivity of carbohydrate moiety and the carbohydrate moiety used. Although originally designed to act as immunomodulators their ability to inhibit bacterial adhesion in immunocompromised individuals was also investigated. Furthermore the glycolipids were tested as low molecular weight organogelators (LWOG), and promising results were obtained. Chapter 3 deals with the synthesis of O- and N-glycolipids built around an aliphatic core. Initially the synthesis proved problematic but success was achieved utilising DMTMM as the coupling reagent. Similarly to the aspartic acid analogues, the glycolipids exhibited variation in the chemical nature of the spacer groups used to link the carbohydrate to the aliphatic core. The O- and N-glycolipids were synthesised with a view to examine their ability to inhibit bacterial adhesion in Cystic Fibrosis (CF) patients. The synthesis of a range of glycolipids based around an aromatic core is discussed in chapter 4. Again variation in the linker utilised to connect the carbohydrate moiety and the aromatic core is explored. This time the importance of the presence of the hydrocarbon chain was also investigated. Therefore variation in the connectivity of the lipidic chain is explored, and analogues of varying hydrocarbon chain length were synthesised. The O- and N-glycolipids were synthesised as potential anti-adhesion agents in order to determine a structural activity relationship. The biological evaluation of selected glycolipids is discussed in chapter 5. Selected aspartic acid, aliphatic and aromatic glycolipids are investigated as potential inhibitors of Burkholderia multivorans adhesion to a model of lung epithelial cells of CF patients. Promising preliminary results were obtained for both a mono- and di-valent aromatic-based glycolipid

The Synthesis of Amphiphilic Glycolipids as Potential Inhibitors of Bacterial Adhesion

The synthesis of glycolipids as potential anti-bacterial agents and glycolipid mimetics is the main focus of the research presented in this thesis. A variety of glycolipids based around an aspartic acid, aliphatic or aromatic scaffold were investigated. Chapter 1 describes the biological importance of glycolipids and how they can be utilised as anti-adhesion agents and immunomodulators. The concept of multivalency is also discussed, with specific examples relating to the anti-adhesion approach. A variety of O-glycolipids based around an aspartic acid scaffold were constructed in chapter 2. Based on a modular approach, a diverse range of glycolipids were synthesised. They exhibited variations in hydrocarbon chain length, number of hydrocarbon chains, connectivity of carbohydrate moiety and the carbohydrate moiety used. Although originally designed to act as immunomodulators their ability to inhibit bacterial adhesion in immunocompromised individuals was also investigated. Furthermore the glycolipids were tested as low molecular weight organogelators (LWOG), and promising results were obtained. Chapter 3 deals with the synthesis of O- and N-glycolipids built around an aliphatic core. Initially the synthesis proved problematic but success was achieved utilising DMTMM as the coupling reagent. Similarly to the aspartic acid analogues, the glycolipids exhibited variation in the chemical nature of the spacer groups used to link the carbohydrate to the aliphatic core. The O- and N-glycolipids were synthesised with a view to examine their ability to inhibit bacterial adhesion in Cystic Fibrosis (CF) patients. The synthesis of a range of glycolipids based around an aromatic core is discussed in chapter 4. Again variation in the linker utilised to connect the carbohydrate moiety and the aromatic core is explored. This time the importance of the presence of the hydrocarbon chain was also investigated. Therefore variation in the connectivity of the lipidic chain is explored, and analogues of varying hydrocarbon chain length were synthesised. The O- and N-glycolipids were synthesised as potential anti-adhesion agents in order to determine a structural activity relationship. The biological evaluation of selected glycolipids is discussed in chapter 5. Selected aspartic acid, aliphatic and aromatic glycolipids are investigated as potential inhibitors of Burkholderia multivorans adhesion to a model of lung epithelial cells of CF patients. Promising preliminary results were obtained for both a mono- and di-valent aromatic-based glycolipid

A Concise Synthesis of Glycolipids Based on Aspartic Acid Building Blocks

L-Aspartic acid building blocks bearing galactosyl moieties were used to synthesise glycolipid mimetics of variable hydrocarbon chain length. The glycolipids were readily prepared through amide bond formation using the TBTU/HOBt coupling methodology. It was observed that, under these conditions, activation of the α-carboxylic acid of the intermediates led to near complete racemisation of the chiral centre if the reaction was carried out in the presence of a base such as triethylamine. The enantiomerically pure glycolipids were obtained after careful consideration of the synthetic sequence and by performing the coupling reactions in the absence of base