Tsang, Siu Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 107-121). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.v / Table of Contents --- p.vi / List of Abbreviations --- p.x / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Renin-angiotensin system (RAS) --- p.1 / Chapter 1.1.1 --- Circulating RAS --- p.2 / Chapter 1.1.2 --- Tissue-specific RAS --- p.5 / Chapter 1.2 --- RAS inhibitors --- p.7 / Chapter 1.2.1 --- Angiotensin converting enzyme inhibitor --- p.8 / Chapter 1.2.2 --- Non-specific angiotensin II receptor blocker --- p.9 / Chapter 1.2.3 --- Specific AT1 receptor antagonist --- p.10 / Chapter 1.2.4 --- Specific AT2 receptor antagonist --- p.11 / Chapter 1.3 --- Pancreas and functions of exocrine pancreas --- p.14 / Chapter 1.3.1 --- Structure of pancreas --- p.14 / Chapter 1.3.2 --- Exocrine secretions and pancreatic enzymes --- p.16 / Chapter 1.3.3 --- Regulation of exocrine secretions --- p.17 / Chapter 1.4 --- Pancreatic RAS --- p.18 / Chapter 1.4.1 --- Expression and localization --- p.18 / Chapter 1.4.2 --- Regulation --- p.19 / Chapter 1.4.3 --- Clinical relevance to the pancreas --- p.20 / Chapter 1.5 --- Acute pancreatitis --- p.21 / Chapter 1.5.1 --- Pathogenesis --- p.21 / Chapter 1.5.2 --- Experimental models of acute pancreatitis --- p.22 / Chapter 1.5.3 --- Criteria of acute pancreatitis --- p.23 / Chapter 1.5.4 --- Oxidative stress in acute pancreatitis --- p.24 / Chapter 1.6 --- RAS and acute pancreatitis in exocrine pancreas --- p.26 / Chapter 1.6.1 --- RAS and acute pancreatitis --- p.26 / Chapter 1.6.2 --- RAS and pancreatic microcirculation --- p.26 / Chapter 1.6.3 --- RAS and tissue injury --- p.27 / Chapter 1.6.4 --- Exocrine pancreatic RAS and acute pancreatitis-induced injury --- p.28 / Chapter 1.7 --- Aims of study --- p.29 / Chapter Chapter 2 --- Materials and Methods / Chapter 2.1 --- Animal models and RAS inhibitors --- p.30 / Chapter 2.1.1 --- Cerulein-induced acute pancreatitis --- p.30 / Chapter 2.1.2 --- Prophylactic treatment with RAS inhibitors --- p.31 / Chapter 2.1.3 --- Therapeutic treatment with RAS inhibitors --- p.32 / Chapter 2.2 --- Evaluation of pancreatic injury --- p.32 / Chapter 2.2.1 --- Assessment of pancreatic water content --- p.33 / Chapter 2.2.2 --- Measurement of α-amylase activity in plasma --- p.33 / Chapter 2.2.3 --- Measurement of lipase activity in plasma --- p.34 / Chapter 2.3 --- Histopathological examinations --- p.34 / Chapter 2.3.1 --- Preparation of paraffin blocks --- p.35 / Chapter 2.3.2 --- Hematoxylin and eosin staining --- p.35 / Chapter 2.4 --- Biochemical assay of pancreatic oxidative status --- p.37 / Chapter 2.4.1 --- Sample preparation --- p.37 / Chapter 2.4.2 --- Quantification of protein content --- p.37 / Chapter 2.4.3 --- Measurement of glutathione levels --- p.38 / Chapter 2.4.4 --- Assessment of protein oxidation --- p.38 / Chapter 2.4.5 --- Assessment of lipid peroxidation --- p.39 / Chapter 2.4.6 --- Measurement of NADPH oxidase activity --- p.40 / Chapter 2.5 --- Studies of pancreatic digestive enzyme secretions from isolated acini --- p.40 / Chapter 2.5.1 --- Dissociation of acini from pancreatic tissue --- p.40 / Chapter 2.5.2 --- Treatment with peptides and RAS inhibitors --- p.42 / Chapter 2.5.3 --- Quantification of protein and DNA contents --- p.43 / Chapter 2.5.4 --- Measurement of a-amylase and lipase secretions --- p.44 / Chapter 2.5.5 --- RT-PCR analysis of RAS components in acinar cells --- p.44 / Chapter 2.6 --- Studies of RAS inhibitors on acute pancreatitis-induced systemic inflammation --- p.45 / Chapter 2.6.1 --- Systemic inflammation treatment --- p.45 / Chapter 2.6.2 --- Measurement of myeloperoxidase activity in lung and liver --- p.46 / Chapter 2.7 --- Statistical analysis --- p.47 / Chapter Chapter 3 --- Results / Chapter 3.1 --- Time-course experiment of acute pancreatitis model --- p.48 / Chapter 3.1.1 --- Effect of acute pancreatitis on tissue injury --- p.48 / Chapter 3.1.2 --- Effects of acute pancreatitis on oxidative status --- p.48 / Chapter 3.2 --- Evaluation of ramiprilat and saralasin on changes of acute pancreatitis- induced pancreatic injury --- p.50 / Chapter 3.2.1 --- Changes in tissue injury and histopathology --- p.50 / Chapter 3.2.2 --- Changes in oxidative status --- p.57 / Chapter 3.3 --- Evaluation of losartan and PD123319 on changes of acute pancreatitis- induced pancreatic injury --- p.61 / Chapter 3.3.1 --- Changes in tissue injury and histopathology --- p.61 / Chapter 3.3.2 --- Changes in oxidative status --- p.68 / Chapter 3.4 --- Evaluation of acinar secretions of digestive enzymes --- p.71 / Chapter 3.4.1 --- Cholecystokinin octapeptide-induced acinar secretions --- p.71 / Chapter 3.4.2 --- Angiotensin II-induced acinar secretions --- p.71 / Chapter 3.4.3 --- Effects of losartan and PD 123319 on α-amylase secretion --- p.74 / Chapter 3.5 --- Existence and regulation of acinar RAS by acute pancreatitis --- p.75 / Chapter 3.5.1 --- Expression of angiotensinogen and its regulation by acute pancreatitis in acini --- p.76 / Chapter 3.5.2 --- Expression of AT1 receptor and its regulation by acute pancreatitis in acini --- p.76 / Chapter 3.5.3 --- Expression of AT2 receptor and its regulation by acute pancreatitis in acini --- p.76 / Chapter 3.5.4 --- Evaluation of RAS inhibitors in acute pancreatitis-induced acinar cells --- p.80 / Chapter 3.6 --- Preliminary data on acute pancreatitis-induced systemic inflammation --- p.81 / Chapter 3.6.1 --- Time-course experiment on lung injury --- p.81 / Chapter 3.6.2 --- Time-course experiment on liver injury --- p.83 / Chapter 3.6.3 --- Evaluation of losartan on systemic inflammation --- p.85 / Chapter Chapter 4 --- Discussion / Chapter 4.1 --- "Actions of RAS inhibitors on the changes of tissue injury, oxidative status and histopathology in acute pancreatitis-induced pancreas" --- p.87 / Chapter 4.1.1 --- Differential effects of ramiprilat and saralasin --- p.88 / Chapter 4.1.2 --- Differential effects of losartan and PD123319 --- p.92 / Chapter 4.2 --- Potential functions of RAS in pancreatic acinar secretions --- p.95 / Chapter 4.2.1 --- Potential role of AT1 receptor --- p.96 / Chapter 4.2.2 --- Potential role of AT2 receptor --- p.98 / Chapter 4.3 --- Regulation of RAS in acute pancreatitis-induced acini --- p.98 / Chapter 4.3.1 --- Regulation of RAS components in acinar cells --- p.99 / Chapter 4.3.2 --- Differential actions of losartan and PD123319 --- p.100 / Chapter 4.4 --- Potential role of RAS in acute pancreatitis --- p.102 / Chapter 4.4.1 --- Regulation of RAS components by acute pancreatitis --- p.102 / Chapter 4.4.2 --- Differential functions of AT1 and AT2 receptors in acute pancreatitis --- p.103 / Chapter 4.5 --- Conclusion --- p.104 / Chapter 4.6 --- Further studies --- p.105 / Chapter Chapter 5 --- Bibliography --- p.107

Conclusion. These data provide a clue that AT1 receptor blocker could effectively attenuate severe form of pancreatitis and its-associated systemic inflammation in experimental models of AP. The underlying mechanisms may be involved in Ang II-induced NADPH oxidase derived oxidative stress, particularly NFkappaB and ERK1/2-dependent CREB activation. The pro-inflammatory pathways would commonly converge to transcribe an array of genes such as IL-6, thus regulating the severity of pancreatitis and the onset of its complications. All these in vivo and in vitro data provide substantial evidence that Ang II is involved in AT1 receptor-mediated signaling cascade in regulating the pathogenesis of AP. The findings provide a new insight on potential application of AT 1 receptor blockade for a therapeutic approach in the management of AP. (Abstract shortened by UMI.) / Recent advance in basic research has revealed that the renin-angiotensin system (RAS) plays an important role in the pathogenesis of AP. In this regard, the present study aimed at investigating the effectiveness of RAS blockade in clinically relevant AP animal model and AP-associated systemic inflammation. More importantly, the underlying mechanistic pathways involved in angiotensin II (Ang II)-induced pro-inflammatory actions were elucidated using both in vivo and in vitro systems. / Results. Major components of RAS were up-regulated in obstructive pancreatitis model. Blockade of AT1 receptor attenuated pancreatic injury induced by the two models. Moreover, losartan could significantly ameliorate AP-associated systemic inflammation. Analysis of protein expression levels revealed that losartan treatment improved AP-associated elevation of NADPH oxidase p67 and p22 subunits. Double-immunostaining confirmed that expression of NADPH oxidase was localized to pancreatic acinar cells. AT1 receptor antagonism not only reduced oxidative stress but also suppressed nuclear factor kappaB (NFkappaB) activation, as evidenced by reversal effects on IkappaBbeta depletion, augmentation of phosphor NFkappaB p65, and enhanced nuclear kappaB binding activity. Blockade of AT1 receptor could also suppress the levels of kappaB-related protein expression, including intercellular adhesion molecule-1, cyclooxygenase-2, and IL-1. On the other hand, pancreatic mRNA and protein levels of IL-6 were enhanced by obstructive AP, which were antagonized by AT1 receptor blocker. Losartan treatment could reverse extracellular-regulated kinase (ERK) 1/2 and cAMP-responsive element binding protein (CREB) phosphorylation brought by obstructive AP. In vitro studies, exogenous application of Ang II induced ERK1/2 and CREB activation in AR42J cells. Concomitantly, IL-6 expression was augmented dose- and time-dependently in response to Ang II, which was reversed by treatment of AT1 receptor blocker (losartan) and ERK1/2 inhibitor (PD98059). Ang II induced NFkappaB activation was reversed by pre-treatment of AT1 receptor blocker and NADPH oxidase inhibitor but not ERK1/2 inhibitor in vitro. Moreover, Ang II-induced superoxide generation was detected. Treatment of antioxidant prevented Ang II-induced ERK1/2 activation. On top of these, in vitro experiments revealed that Ang II could sustain the activation of caerulein-induced NFkappaB and ERK1/2 in an AT1 receptor-mediated manner, but not secretagogue-induced hypersecretion. / Chan, Yuk Cheung. / Adviser: Po Siny Lzung. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3246. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 228-262). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.