published_or_final_version / Pharmacology / Doctoral / Doctor of Philosophy

This thesis studied the role of spinal nitric oxide (NO) in carrageenan-induced dermal hyperalgesia in the rat hindpaw by means of intrathecal (i.t.) administration of various NO synthase (NOS) inhibitors. A spinal role for NO in carrageenan-induced thermal hyperalgesia was confirmed by dose-dependently reducing the hyperalgesia with a non-selective NOS inhibitor. Next, it was determined that a relatively selective neuronal NOS (nNOS) inhibitor and two relatively selective inducible NOS (iNOS) inhibitors were able to reduce carrageenan-induced thermal hyperalgesia. Finally, early administration of either an nNOS or an iNOS inhibitor had no significant effect on carrageenan-induced thermal hyperalgesia. However, late administration of an iNOS, but not an nNOS inhibitor, significantly reduced the thermal hyperalgesia. We therefore suggest that iNOS contributes to only the late stages of carrageenan-induced thermal hyperalgesia, while nNOS likely plays a role throughout the entire time course of the injury.

No description available.

published_or_final_version / Medicine / Master / Master of Philosophy

一氧化氮（NO）和內皮源性超極化因子（EDHFs）是內皮衍生的血管舒張因子兩大類。 EETs是構成EDHFs的主要類型，這是由花生四烯酸通過細胞色素P450 （CYP）表氧化酶的催化活性得到。雖然這兩個EET和NO誘導血管舒張，從而降低血壓，許多報告表明，NO對EET引起的血管舒張起抑製作用。然而，不管它的重要性，有關一氧化氮對EETs的抑制作用的機理尚未完全了解。 / 在本研究中，我調查了一氧化氮對EET的負調控。通過膜電位和動脈張力測量，我們發現， 11,12-EET可引起內皮剝脫豬冠狀動脈平滑肌細胞膜超極化和血管舒張。該反應被S-亞硝基-N-乙酰青黴胺（SNAP）和8-Br-cGMP，一個NO的供體和cGMP的膜穿透物類似物，分別抑制。 SNAP和8-Br-cGMP對11,12-EET引起的細胞膜超極化和血管舒張的抑製作用被羥鈷胺，一氧化氮清除劑; ODQ ，鳥苷酸環化酶抑製劑;和KT5823 ，蛋白激酶G（PKG）抑製劑逆轉。 SNAP和8-Br-cGMP對EET反應的抑製作用也被過度供應外源性激酶底物， TAT-TRPC1S¹⁷²和TAT -TRPC1T³¹³廢除。羥鈷胺，ODQ， KT5823， TAT -TRPC1，和TAT -scrambled獨自使用不影響11,12-EET引起的細胞膜超極化和血管舒張作用。然而，獨自使用14，15-EEZE（EET的拮抗劑）抑制了11,12-EET的作用。 此外，磷酸化試驗表明， PKG可以直接在Ser172和Thr313位點磷酸化TRPC1 。此外，TRPV4 ， TRPC1 ，或KCa1.1被選擇性地抑制時，11,12-EET未能引起細胞膜超極化和血管舒張。免疫共沉澱研究表明， TRPV4 ， TRPC1和KCa1.1物理上彼此相關聯。 / 以上結果表明，NO-cGMP-PKG通路可通過TRPC1的磷酸化來抑制11,12- EETs在冠狀動脈血管平滑肌細胞上的作用。此外，TRPV4，TRPC1和KCa1.1參與11,12-EET誘導平滑肌超極化和血管舒張，他們可能互相關聯。從本研究的結果表明，NO和cGMP可通過PKG-介導的TRPC1的磷酸化，抑製EET誘導的平滑肌超極化和血管舒張。 / Nitric oxide (NO) and endothelium-derived hyperpolarizing factors (EDHFs) are two main classes of endothelium-derived vascular relaxant factors. EETs constitute a major type of EDHFs, which are derived from arachidonic acids via the catalytic activity of cytochrome P450 (CYP) epoxygenases. Although both EET and NO induce vascular relaxation, thus reduce blood pressure, numerous reports demonstrated that NO exerts an inhibitory action on EET-induced vascular relaxation. However, despite of its importance, the mechanisms related to the inhibitory effects of NO on EETs are incompletely understood. / In the present study, I investigated the scheme for negative regulation of NO on EET action. Through measurements of membrane potential and arterial tension, we showed that 11,12-EET could induce membrane hyperpolarization and vascular relaxation in endothelium-denuded porcine coronary arteries. The responses were suppressed by S-nitroso-N-acetylpenicillamine (SNAP) and 8-Br-cGMP, a NO donor and a membrane-permeant analogue of cGMP, respectively. The inhibitory actions of SNAP and 8-Br-cGMP on 11,12-EET-induced membrane hyperpolarization and vascular relaxation were reversed by hydroxocobalamin, a NO scavenger; ODQ, a guanylyl cyclase inhibitor; and KT5823, a protein kinase G (PKG) inhibitor. The inhibitory actions of SNAP and 8-Br-cGMP on EET responses were also abrogated by shielding TRPC1-PKG phosphorylation sites with excessive supply of exogenous PKG substrates, TAT-TRPC1S¹⁷² and TAT-TRPC1T³¹³. Hydroxocobalamin, ODQ, KT5823, TAT-TRPC1 and TAT-scrambled alone has no effect on 11,12-EET-induced membrane hyperpolarization and vascular relaxation. However, 14,15-EEZE (a selective EET antagonist) alone inhibits the action of 11,12-EET. Furthermore, phosphorylation assay was performed and it demonstrated that PKG could directly phosphorylate TRPC1 at Ser¹⁷² and Thr³¹³. In addition, 11,12-EET failed to induce membrane hyperpolarization and vascular relaxation when TRPV4, TRPC1, or KCa1.1 was selectively inhibited. Co-immunoprecipitation studies demonstrated that TRPV4, TRPC1 and KCa1.1 physically associated with each other in smooth muscle cells. / Taking together, our findings demonstrated that the NO-cGMP-PKG pathway may act through the phosphorylation of TRPC1 to inhibit the action of 11,12-EETs in coronary arterial smooth muscle cells. Furthermore, TRPV4, TRPC1 and KCa1.1 are critically involved in the 11,12-EET-induced smooth muscle hyperpolarization and relaxation and that they may physically associate with each other. The results from this study demonstrated that NO and cGMP could lead to PKG-mediated phosphorylation of TRPC1, resulting in an inhibition of EET-induced smooth muscle hyperpolarization and vascular relaxation. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Zhang, Peng. / "Ca" on title page is subscript. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 115-133). / Abstracts also in Chinese.

Male-typical copulatory behaviors such as mounting and intromission are dependent on testicular androgens in most vertebrates, being eliminated by castration and re-instated by administration of exogenous testosterone. Testosterone implants in the preoptic area (POA) can re-instate behavior as effectively as systemic testosterone replacement, implicating this area as a critical locus of hormonal gating. The cellular mechanisms underlying this gating phenomenon are not well understood, but according to one model, testosterone induces an up-regulation of nitric oxide synthase (NOS) in the POA, increasing nitric oxide synthesis following exposure to a sexual stimulus. Nitric oxide in turn, possibly through its effect on catecholamine turnover, influences the way the stimulus is processed and enables the appropriate copulatory behavioral response. The experiments described in this Dissertation were designed to test this model as it pertains to hormonal gating in Cnemidophorus lizards. Specifically, experiments were conducted to test the predictions that nitric oxide synthesis inhibition would suppress the expression of behavior; that preoptic nitric oxide synthesis would be greater in animals expressing copulatory behavior; and that preoptic NOS expression, at both the mRNA and the protein levels, would be greater in animals exposed to testosterone than in animals deprived of hormone. All three of these predictions were upheld, offering support to the model as described. / text

No description available.

Yip Kwok Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 231-260). / Abstracts in English and Chinese. / Abstract (English) --- p.i / Abstract (Chinese) --- p.iv / Acknowledgements --- p.vi / Publications --- p.vii / Abbreviations --- p.viii / Contents --- p.xi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Mast cells --- p.2 / Chapter 1.2. --- "Mast cell origin, growth and development" --- p.2 / Chapter 1.2.1. --- Stem cell factor --- p.4 / Chapter 1.2.2. --- Interleukins --- p.6 / Chapter 1.3. --- Mast ceII heterogeneity --- p.7 / Chapter 1.4. --- Mast ceII mediators --- p.9 / Chapter 1.4.1. --- Pre-Synthesized mediators --- p.9 / Chapter 1.4.1.1. --- Histamine --- p.10 / Chapter 1.4.1.2. --- Protease --- p.11 / Chapter 1.4.2. --- Newly synthesized mediators --- p.13 / Chapter 1.4.2.1. --- Prostanoid --- p.14 / Chapter 1.4.2.2. --- Cysteinyl Leukotriene --- p.15 / Chapter 1.4.3. --- Mast cell-derived cytokines and growth factors --- p.16 / Chapter 1.5. --- Mast cell activation --- p.17 / Chapter 1.5.1. --- FceRI-dependent mast cell activation --- p.18 / Chapter 1.5.1.1. --- FceRI and IgE aggregation --- p.19 / Chapter 1.5.1.2. --- Protein-tyrosine kinase activation --- p.21 / Chapter 1.5.1.3. --- Phospholipase activation and calcium ion mobilization --- p.22 / Chapter 1.5.1.4. --- GTPase and MAPK activation --- p.24 / Chapter 1.5.2. --- Non-immunogical mast cell activation --- p.26 / Chapter 1.6. --- Roles of mast cell in inflammatory disease --- p.27 / Chapter 1.7. --- Nitric oxide --- p.28 / Chapter 1.8. --- Nitric oxide synthase --- p.30 / Chapter 1.9. --- Nitric oxide signaling in cellular level --- p.31 / Chapter 1.9.1. --- Direct effects of NO --- p.32 / Chapter 1.9.2. --- Indirect effects of NO --- p.34 / Chapter 1.10. --- Mast cell and nitric oxide --- p.35 / Chapter 1.11. --- Aim of Study --- p.37 / Chapter 2. --- Materials and Methods --- p.43 / Chapter 2.1. --- Material --- p.44 / Chapter 2.1.1. --- Human buffy coat for mast cell culture --- p.44 / Chapter 2.1.2. --- Materials for cell isolation and cell counting --- p.44 / Chapter 2.1.3. --- Materials for mast cell culture --- p.45 / Chapter 2.1.4. --- Material for buffers --- p.45 / Chapter 2.1.5. --- Materials for cytospin and May-Griinwald-Giemsa staining --- p.46 / Chapter 2.1.6. --- Materials for immunocytochemical staining --- p.46 / Chapter 2.1.7. --- Mast cell secretagogues --- p.47 / Chapter 2.1.8. --- Nitric oxide donors --- p.47 / Chapter 2.1.9. --- Soluble Guanylyl Cyclase activators and cGMP analogues --- p.47 / Chapter 2.1.10. --- Drugs involved in NO-sGC-cGMP pathway --- p.48 / Chapter 2.1.11. --- Materials for histamine assay --- p.48 / Chapter 2.1.12. --- Materials for Enzyme Immunosorbent Assay (EIA) --- p.49 / Chapter 2.1.13. --- Pro-inflammatory cytokines --- p.49 / Chapter 2.1.14. --- Materials for RNA extraction and RT-PCR --- p.49 / Chapter 2.1.15. --- Materials for Immunofluorescence staining --- p.50 / Chapter 2.1.16. --- Anti-asthmatic compounds --- p.51 / Chapter 2.1.17. --- Buffer and stock solution --- p.51 / Chapter 2.1.17.1. --- Buffer ingredients --- p.51 / Chapter 2.1.17.2. --- Stock solution --- p.52 / Chapter 2.2. --- Methods --- p.52 / Chapter 2.2.1. --- CD34+ cell isolation from human buffy coat --- p.52 / Chapter 2.2.2. --- CD34+ cell culture --- p.53 / Chapter 2.2.3. --- Human mast cell line (HMC-1 cells) culture --- p.54 / Chapter 2.2.4. --- Mast cell heterogeneity identification --- p.54 / Chapter 2.2.4.1. --- Cell smear preparation --- p.54 / Chapter 2.2.4.2. --- May-Gruwald-Giemsa staining --- p.55 / Chapter 2.2.4.3. --- Immunocytochemical staining --- p.55 / Chapter 2.2.5. --- Histamine release and measurement --- p.56 / Chapter 2.2.5.1. --- Histamine release --- p.56 / Chapter 2.2.5.2. --- Spectroflurometric determination of histamine content --- p.57 / Chapter 2.2.5.3. --- Calculation of histamine level --- p.57 / Chapter 2.2.6. --- Prostaglandin D2 (PGD2) measurement --- p.58 / Chapter 2.2.6.1. --- PGD2 production --- p.58 / Chapter 2.2.6.2. --- EIA methods for PGD2 measurement --- p.58 / Chapter 2.2.6.3. --- Calculation of PGD2 concentration --- p.59 / Chapter 2.2.7. --- Cysteinyl Leukotrienes (Cys-LTs) measurement --- p.59 / Chapter 2.2.7.1. --- Cys-LTs production --- p.59 / Chapter 2.2.7.2. --- EIA methods for Cys-LTs measurement --- p.60 / Chapter 2.2.7.3. --- Calculation of Cys-LTs concentration --- p.60 / Chapter 2.2.8. --- Tumor necrosis factor-alpha (TNF-α) measurement --- p.61 / Chapter 2.2.8.1. --- TNF-α production --- p.61 / Chapter 2.2.8.2. --- EIA methods for TNF-α measurement --- p.61 / Chapter 2.2.8.3. --- Calculation of TNF-α concentration --- p.62 / Chapter 2.2.9. --- Interleukin-8 (IL-8) measurement --- p.62 / Chapter 2.2.9.1. --- IL-8 production --- p.62 / Chapter 2.2.9.2. --- ELISA for IL-8 measurement --- p.62 / Chapter 2.2.9.3. --- Calculation of IL-8 concentration --- p.63 / Chapter 2.2.10. --- Data presentation --- p.63 / Chapter 2.2.11. --- Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) --- p.64 / Chapter 2.2.11.1. --- RNA extraction --- p.64 / Chapter 2.2.11.2. --- Reverse Transcriptase reaction for cDNA synthesis --- p.65 / Chapter 2.2.11.3. --- Polymerase Chain Reaction --- p.66 / Chapter 2.2.11.4. --- Agarose Gel Electrophoresis --- p.67 / Chapter 2.2.11.5. --- Data representation in RT-PCR experiment --- p.67 / Chapter 2.2.12. --- Immunofluorescence staining --- p.67 / Chapter 2.2.12.1. --- Cell smear preparation --- p.68 / Chapter 2.2.12.2. --- Immunofluorescence staining --- p.68 / Chapter 2.3. --- Statistical analysis --- p.69 / Chapter 3. --- Effect of Nitric Oxide Donors on Mast Cell Activation --- p.70 / Chapter 3.1. --- Introduction --- p.71 / Chapter 3.1.1. --- Mechanisms of NO release from NO donors --- p.71 / Chapter 3.1.2. --- Experimental aims --- p.77 / Chapter 3.2. --- Materials and methods --- p.77 / Chapter 3.3. --- Results --- p.78 / Chapter 3.3.1. --- Development of mast cells from buffy coat --- p.78 / Chapter 3.3.2. --- Morphological features of cultured mast cells --- p.78 / Chapter 3.3.3. --- Phenotype of cultured mast cells --- p.79 / Chapter 3.3.4. --- Effects of NO donors on immunologically stimulated mediators release --- p.79 / Chapter 3.3.4.1. --- SIN-1 and NOR-3 --- p.80 / Chapter 3.3.4.2. --- SNP and SNAP --- p.80 / Chapter 3.3.4.3. --- Diazeniumdiolates (NONOates) --- p.80 / Chapter 3.3.5. --- Effects of NO scavenger on NO donors mediated inhibition of immunologically stimulated mediators release --- p.82 / Chapter 3.3.6. --- Discussion --- p.83 / Chapter 4. --- Interaction between NO donors and pharmacological agentsin modulating mast cell activation --- p.123 / Chapter 4.1. --- Introduction --- p.124 / Chapter 4.1.1. --- Modulators of NO-sGC-cGMP pathway --- p.125 / Chapter 4.1.2. --- Anti-asthmatic compounds --- p.128 / Chapter 4.1.3. --- Experimental aims --- p.130 / Chapter 4.2. --- Materials and methods --- p.131 / Chapter 4.3. --- Results --- p.132 / Chapter 4.3.1. --- Effect of sGC activators on immunologically stimulated histamine release and the inhibitory action of DEA/NO --- p.132 / Chapter 4.3.2. --- Effect of cGMP analog on immunologically stimulated histamine release --- p.133 / Chapter 4.3.3. --- "Effects of the sGC inhibitor, ODQ, on DEA/NO induced inhibition on immunologically stimulated mediators release" --- p.134 / Chapter 4.3.4. --- Effects of anti-oxidants on the actions of NO donors in modulating immunologically stimulated mediators release --- p.134 / Chapter 4.3.5. --- The effects of NO donors on salbutamol mediated inhibition of immunologically stimulated histamine release from human mast cells --- p.135 / Chapter 4.3.6. --- The effects of NO donors on theophylline mediated inhibition of immunologically stimulated histamine release from human mast cells --- p.136 / Chapter 4.3.7. --- The effects of NO donors and DSCG on immunologically stimulated histamine release from human mast cells --- p.137 / Chapter 4.4. --- Discussion --- p.137 / Chapter 4.5. --- Further studies --- p.150 / Chapter 5. --- Human mast cells as a source of nitric oxide --- p.178 / Chapter 5.1. --- Introduction --- p.179 / Chapter 5.1.1. --- Nitric oxide synthases expression in mast cell --- p.180 / Chapter 5.1.2. --- Modulation of NOS expression --- p.182 / Chapter 5.1.3. --- Experimental aims --- p.186 / Chapter 5.2. --- Materials and methods --- p.186 / Chapter 5.3. --- Results --- p.187 / Chapter 5.3.1. --- NOS expression in human mast cell-line HMC-1 --- p.187 / Chapter 5.3.1.1. --- Basal --- p.187 / Chapter 5.3.1.2. --- Effect of cytokines --- p.188 / Chapter 5.3.2. --- NOS expression in cultured CD34+ derived human mast cells --- p.189 / Chapter 5.3.2.1. --- Basal --- p.189 / Chapter 5.3.2.2. --- Effect of cytokines --- p.189 / Chapter 5.3.2.3. --- Effect ofIgE and anti-IgE --- p.190 / Chapter 5.4. --- Discussion --- p.191 / Chapter 5.5. --- Further studies --- p.200 / Chapter 6. --- Conclusion --- p.218 / Chapter 7. --- References --- p.230

In nature bacteria predominantly live on surfaces, in matrix-encased communities called biofilms. Biofilm formation displays dynamic developmental patterns resembling those of multicellular organisms. Using cooperative traits such as cell-cell signaling, bacteria in biofilms form complex architectures, known as microcolonies, in which cells become highly differentiated from their planktonic counterparts. Microcolonies are generally highly tolerant to bactericides, rendering biofilms extremely difficult to eradicate. The aim of this study was to investigate the last, and least understood stage of biofilm development, which involves the coordinated dispersal of single cells that revert to a free-swimming planktonic phenotype and escape from the biofilm. Strategies to induce biofilm dispersal are of interest due to their potential to prevent biofilms and biofilm-related infections. In the model organism Pseudomonas aeruginosa, reproducible patterns of cell death and dispersal can occur within biofilm structures, leaving behind empty or hollow microcolonies. These events were previously linked with the appearance of oxidative and/or nitrosative stress in mature microcolonies. Here, the involvement of reactive oxygen and nitrogen intermediates in biofilm development and dispersal processes was investigated in both mono- and mixed-species biofilms. By using specific fluorescent dyes and P. aeruginosa mutant strains, nitric oxide (NO), a by-product of anaerobic respiration and an important messenger molecule in biological systems, was found to play a major role in P. aeruginosa biofilm dispersal. Further, the results demonstrated that exposure to physiological, non-toxic concentrations of NO (in the low nanomolar range) causes biofilm dispersal in P. aeruginosa and restores its vulnerability to conventional antimicrobials. By using microarray techniques, NO was shown to induce global changes in genetic expression, including enhanced metabolic activity and motility and decreased adhesion and virulence in P. aeruginosa biofilms. The regulatory pathway implicated c-di-GMP, a newly discovered messenger molecule involved in the transition from sessility to motility in many bacterial species. NO-mediated dispersal was also observed in other single- and multi-species biofilms of clinically and industrially relevant organisms. Hence, the combined exposure to NO and bactericides was identified as a potential novel strategy for the removal of microbial communities, providing a low cost and environmentally safe solution to biofilm control.

The vascular endothelium is a single cell layer that lines the lumen of the entire vasculature. It is the site of synthesis of nitric oxide (NO), a vasodilatory compound synthesized by endothelial nitric oxide synthase (eNOS). NO causes intracellular calcium sequestration of the vascular smooth muscle cells, relaxing and dilating the arteries. Age profoundly affects endothelium-dependent vasodilation, leading to specific losses of NO. We sought to determine what causes the age-specific loss of endothelial NO. This was accomplished by investigating whether there are differences in markers of eNOS post-translational regulation elements in the aortic endothelium of young (2-4 months; corresponding to an adolescent human adult) and old (32-34 months; corresponding to a 65-75 year-old human). F 344 x Brown Norway hybrid rats. Results show that maximal eNOS activity significantly declines with age (n=4;p���0.05) though there was no change in eNOS protein levels in the aortic endothelium. Endothelial NOS exists in two distinct subcellular fractions. No alterations were detected in the soluble, inactive fraction while significantly less eNOS protein is detected in the active, plasma membrane fraction of the endothelium (n=4;p���0.02). Endothelial NOS activation is also controlled by its phosphorylation state. In this work we demonstrate that free ceramides and ceramide-activated phosphatase (PP2A) activity are significantly elevated with age in the endothelium and correlate with specific alterations in eNOS phosphorylation status consistent with its inactivation. These changes were concomittent with an age-associated decline in endothelial glutathione (GSH) and increased sphingomyelinase activity which liberates ceramides from membrane sphingolipids. In previously published reports we demonstrated that the dithiol compound R-��-lipoic acid (LA) increased maximal NO synthesis in cultured endothelial cells and that LA improved age-associated loss of eNOS stimulatory phosphorylation in rats. Therefore, we administered pharmacologic doses of LA (40 mg/kg, i.p. over 24 h) to old rats to determine whether it restored NO-dependent vasomotor function. Results show that LA significantly increased endothelial GSH (p���0.05 compared to saline controls), decreased sphingomyelinase activity and reversed the age-related increase in ceramide (p���0.01) in old animals. Finally, LA significantly improved endothelium-dependent vasodilation, suggesting that it might be a good therapeutic agent for age-related vascular endothelial dysfunction. / Graduation date: 2005