Altered processing of the amyloid precursor protein and decreased expression of ADAM 10 by chronic hypoxia in SH-SY5Y: no role for the stress-activated JNK and p38 signalling pathways.
Clinical studies suggest that the incidence of Alzheimer's disease (AD) is increased following an ischaemic or hypoxic episode, such as stroke. Furthermore, levels of the AD-associated amyloid beta-peptides (Abeta) and the amyloid precursor protein (APP) are enhanced in experimental ischaemia. In our previous study [Webster, N.J., Green, K.N., Peers, C., Vaughan, P.F., Altered processing of amyloid precursor protein in the human neuroblastoma SH-SY5Y by chronic hypoxia, J. Neurochem., 83 (2002) 1262-1271] we reported that exposing cells of neuronal origin to a period of chronic hypoxia (CH; 2.5% O(2), 24 h) led to a decrease in processing of the amyloid precursor protein (APP) by the alternative and neuroprotective alpha-secretase pathway. In SH-SY5Y cells, the most likely mechanism was that CH inhibits the protein level of ADAM 10, a disintegrin metalloprotease widely believed to be the alpha-secretase. One effect of CH is to alter the activity of the stress-activated protein kinases (SAPKs) c-Jun amino terminal kinase (JNK) and p38. Thus, the main aims of this study were to investigate the effect of CH on (1) the activity of these SAPKs in SH-SY5Y and (2) whether changes in the activity of these kinases may account for the CH-induced decreases in ADAM 10 expression and sAPPalpha secretion. We demonstrated that the phosphorylation (activity) of JNK was decreased approximately 50% following a period of CH. An inhibitor of JNK did not mimic the effects of CH on either ADAM 10 expression or sAPPalpha secretion under conditions in which the phosphorylation of c-Jun was inhibited by approximately 80%. Thus the loss of JNK activity does not appear to be linked to the decrease in expression of ADAM 10 and secretion of sAPPalpha. In contrast, phosphorylation (activity) of p38 was enhanced approximately 300% following a period of CH. However, inhibitors of p38 were unable to reverse the loss of sAPPalpha in CH cells, indicating that this increase in activity was not linked to the altered processing of APP.
Webster
Nicola J
NJ
Institute for Cardiovascular Research, Worsley Medical and Dental Building, University of Leeds, Leeds LS2 9JT, United Kingdom. mrpnjw@leeds.ac.uk
Green
Kim N
KN
Settle
Victoria J
VJ
Peers
Chris
C
Vaughan
Peter F T
PF
D051722:ADAM Proteins; D000072197:ADAM10 Protein; D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000873:Anthracenes / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D048670:MAP Kinase Kinase 4; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism*; D010080:Oxazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013312:Stress, Physiological / Q000378:metabolism; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
C105138:2-methyl-4-phenyl-(4-pyridyl)oxazole; D016564:Amyloid beta-Protein Precursor; D000873:Anthracenes; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D010080:Oxazoles; D011725:Pyridines; C432165:pyrazolanthrone; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D053829:Amyloid Precursor Protein Secretases; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000072197:ADAM10 Protein; C491236:ADAM10 protein, human