Iron plays a potential role in oxidative stress-mediated injuries and pathologies e.g. rheumatoid arthritis (RA). Four decades ago it was suggested that iron may have a crucial role in the progression of inflammation in RA. Indeed, free radicals generated by iron can cause damage to lipids, proteins, carbohydrates, and DNA. It is this destructive process that is believed to occur in rheumatoid joints. However, none had differentiated between the role of iron in both acute and chronic phases of the disease and the origin of this 'labile' iron. Since RA cells are chronically exposed to oxidative stress, we have therefore chosen Jurkat cells to be our cell model. We used the parental (J16) cell line was used to mimic the acute phase of oxidative stress and the H2O2-resistant (HJ16) cells to mimic the chronic phase. By using hydrogen peroxide (H2O2) as the oxidising agent, we aim to study the role of iron in acute and chronic phase of oxidative stress and to know its origin. In the present study, we found that both antioxidants and H2O2-induced labile iron are modulated when cells are chronically exposed to H2O2. HJ16 cells contain higher total intracellular glutathione levels and glutathione peroxidase activity than J16 cells while the superoxide dismutase and catalase activity are similar. Haem oxygenase-1 (HO-1) was not detectable nor was it induced in these cell lines; HO-2 on the other hand was expressed but not induced. Although they had the same ‘basal’ LIP and L-Ft levels, J16 cells contain more than 7-fold higher H-Ft levels than in HJ16 cells. It was also found that H2O2-induced labile iron is directly correlated with necrotic cell death. These results are consistent with the conclusion that both antioxidant defence mechanism and labile iron status are modulated in cells chronically exposed to H2O2. We have also shown that the ‘basal’ and ‘H2O2-induced’ NFκB activation was higher in the HJ16 cells. We have also provided a link between labile iron release, lysosomal membrane damage and the ensuing necrotic cell death following H2O2 treatment.
|Date of Award||1 Aug 2008|
|Supervisor||Charareh Pourzand (Supervisor) & Nicolas Hall (Supervisor)|
- haem oxygenase
- rheumatoid arthritis
- oxidative stress