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Evidence suggesting that Hsp72 is actively participating in cellular signalling as well interacting with immune system dynamics has been increasing. This is true in healthy, stressed and diseased cells but to different degrees. Modulation of the plasma membrane association and secretion in the extracellular environment by different types of stressors is the key event that leads to different degrees of immune system activation. Hence a better understanding of the mechanisms of Hsp72 secretion and association with plasma membrane is crucial. This thesis investigated the tissue source and mechanism of Hsp72 surface presentation to plasma membrane structures and release in relation with different cellular and physiological stressors. In vivo models confirmed that different tissue types determine specific Hsp72 responses following the same stress and increase serum Hsp72 dependant on intensity and duration of the stress. Diseases models confirm that Hsp72 responses in specific cell populations is related to disease progression, while in vitro models clearly showed that there are multiple mechanisms of secretion and surface presentation, dependent on the nature of the stressor as well as the intensity and duration. This observations clearly change the view of extracellular Hsp72 as a danger signal and lead to a revision of the original danger model. It also suggests that manipulation of Hsp72 translocation through the different pathways involved may prove effective therapeutically.

Oxidative stress has been associated with a wide range of diseases, including cardiovascular diseases, Alzheimer's disease, atherosclerosis, Parkinson's disease and cancer. It also plays a role in the ageing process. Hyperhomocysteimia is commonly found to be associated with these diseases. The hyperhomocysteimia is a result of a deficiency in both folate and cobalamin Folate is known to reduce Hey and protect cells from apoptosis, but there are no studies investigating the impact of cobalamin on apoptosis induced by oxidative stress or the mechanism(s) of the protection. The aims of the research are to investigate the protective role of cobalamin and the possible mechanism(s) for this protection. It also examines the protective role of novel cobalamin and investigates their superior protection. The methods used in this research for apoptosis detection we used caspase-3 and the annexin-V, while for necrosis we used PI staining, where cell viability were detected using MTS assay. We also measured the generation of superoxide by Lucigenin-enhanced chemiluminescence and reactive oxygene species by using the redox active prob DCFH-DA. Moreover, the intracellular proteins were measured via staining with specific fluorescent-conjugated antibodies were detected using flowcytometry. Our result demonstrated that 25|iM of cobalamin protects cells from apoptosis. The protection by cobalamin was associated with induction of iHsp72 and iHO-1, and these are shown to be essential for the protection. Furthermore, our research demonstrated a novel mechanism of cobalamin-apoptosis protection involving induction of NfkB, ERK1/2 and AKT signal transduction pathways. In order to protect cells from apoptosis induced by oxidative stress, cobalamin induces the pNfkB which in turn regulate the iNOS and HO-1 induction. Cobalamin also induces thepERK1/2 which regulates the induction of Hps72 and Nrf2. And finally, pAKT induced by cobalamin which regulate the Nrf2 and HO-1 induction. The inhibition of any of theses pathways leads to loss the protection. The GSCbl and NACCbl provide a superior protection against oxidative stress, this protection involved induction of the signal transduction pathways and Hsps. To conclude; cobalamin provides protection against cells death induced by oxidative stress. Cobalamin achieves this by multiple pathways which include direct antioxidant stimulation and induction of signal transduction pathways. Different cobalamin derivatives have superior protections. These finding are a useful pharmaceutical tool in the treatment of the oxidative stress related diseases.