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Stress-activated signalling is stimulated by hepatocyte isolation
Başlık:
Stress-activated signalling is stimulated by hepatocyte isolation
Yazar:
Armitage, Suzanne, author.
ISBN:
9780438043374
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (405 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Özet:
Within the body the liver plays many important roles. It is involved in many aspects of metabolism as well as producing vital protein products, such as vitamins and plasma proteins. Many of the liver-specific functions are performed by just one of liver cell types, namely the hepatocytes. For this reason, hepatocytes are widely used as an in vitro research tool. One drawback of this system, however, is that hepatocytes rapidly dedifferentiate during culture, whereby many of their liver-specific functions are lost. The mechanisms of this dedifferentiation process are little understood. Cellular signalling cascades, such as those of the mitogen-activated protein kinases (MAPK) and nuclear factor kappa B (NFkappaB), are crucial to the response of cells to their changing environment or in response to stimuli, such as cellular stresses. For this reason it is proposed that these same cascades may play important roles in the dedifferentiation of hepatocytes upon cell isolation. The aim of the work presented in this thesis was to identify the early signalling events within these signalling cascades triggered during hepatocyte isolation. With the use of both phospho-specific immunoblotting and radiochemical activity assays the activation status of the MAPK isoforms, Erk, INK and p38, was defined both in intact liver and in isolated hepatocytes during early culture. In addition to this, electromobility shift assays were employed to define the activation status of NFkappaB. Expression of downstream target genes of these signalling cascades was identified using both Northern and Western analysis techniques. Experimental results indicate that the isolation of hepatocytes initiates temporal signalling events within these cells. In particular, activation of the MAPK isoforms, Erk, JNK1, JTSIK2 and p38, occurs early in culture, together with activation of the NFkappaB signalling cascade. These profiles of activation are transient in nature with the activation status of these signalling events returning to basal (equivalent to that of the intact liver) within 24 hours of culture. In addition, hepatocyte isolation induces expression of the immediate early genes Mob-1 and IkappaB (the NFkappaB inhibitor molecule), together with increased expression of NFkappaB p65. These results are presented together in Figure 4.1. Areas of this work were published in the paper Varley et. al. (1999). After defining these early signalling events, chemical inhibitors of these signalling cascades were employed to define casual links between these events and the subsequent dedifferentiation of hepatocytes. It is postulated that activation of NFkappaB during hepatocyte isolation occurs via a pathway involving phosphorylation and degradation of IkappaB. This activation of NFkappaB is proposed to be regulated, in part, by both nitric oxide and p38. Definition of the early signalling events triggered by isolation of hepatocytes from their physiological environment provides an understanding of some of the factors involved in hepatocyte dedifferentiation. Information presented in this thesis provides a starting point for improving hepatocyte isolation techniques to enable the development of more physiological in vitro research tools for the study of liver-specific functions.
Notlar:
School code: 1543
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684274.1) | 684274-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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