Use this URL to cite or link to this record in EThOS:
Title: Factors regulating cell shedding in mouse and rat small intestine
Author: Elramli, Ahmed Hamed
ISNI:       0000 0004 7656 6158
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2018
Availability of Full Text:
Access from EThOS:
Access from Institution:
The gut barrier is composed of a single layer of intestinal epithelial cells which are connected together by junctional complexes and are covered by a layer of glycocalyx. Its function is to prevent the passage of harmful and toxic substances from the gut lumen into the blood circulation. Structural homeostasis in the small intestine is maintained by the shedding of intestinal epithelial cells at the villus tip and generation of new cells within the crypt compartment. Increased gut permeability can result when the rate of intestinal epithelial cell shedding is greater than the rate of generation of new crypt cells, and this phenomenon is associated with several gastrointestinal diseases including inflammatory bowel disease (IBD). Lipopolysaccharide (LPS) is an integral cell wall component of Gram negative bacteria and following intraperitoneal administration induces the pathological shedding of murine small intestinal epithelial cells (SIEC). This thesis characterises the pathological apoptosis and shedding of SIECs induced by systemic LPS administration in wild-type mouse strains of different genetic background including C57BL/6J, Balb/C, CD1, FVB/N and DBA/2. We have also determined whether murine age and LPS derived from different bacterial species are factors that modulate the severity of SIEC apoptosis and shedding in C57BL/6J mice. Comparative studies were also conducted in Ludwig Olac Wistar rats following to determine whether this phenomenon occurred to the same extent within another species. SIEC apoptosis and shedding was additionally induced by the administration of other systemic stimuli to C57BL/6J mice including anti-CD3 antibody (to activate T cells), polyinosinic:polycytidylic acid (to mimic viral infection) and the putative downstream effector tumour necrosis factor (TNF). The roles of NF?B transcription factor subunits in regulating SIEC apoptosis and shedding in villi and crypts induced by all stimuli at 1.5 and 24 hours were assessed and compared with the responses to LPS. SIEC apoptosis and shedding was assessed morphologically and quantified by immunohistochemistry for active caspase-3. Ultrastructural analysis of SIEC apoptosis and shedding following LPS administration was conducted using transmission electron microscopy to determine the action of LPS on the intracellular components and how they may contribute to the breakdown of barrier function associated with this stimulus by modulating NF?B signalling. A broad spectrum proteomic analysis was also conducted to determine how LPS alters the small intestinal mucosal proteome to modulate susceptibility to SIEC apoptosis and shedding. Conclusion: In conclusion, this study has described the SIEC apoptosis and shedding that are induced by different stimuli including LPS, anti-CD3, poly I:C and TNF. Particularly it has indicated that LPS from different bacterial sources induces SIEC apoptosis and shedding in different mouse strains, at different ages and in both mouse and rats, but with different degrees of effectiveness. It has also indicated the role of the NF?B signalling pathway in regulating this process.
Supervisor: Pritchard, D. Mark ; Campbell, Barry ; Duckworth, Carrie Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral