Inter-individual variability in heat-induced heat stress protein expression: a comparative analysis using biometabolic labelling, immuno blotting and flow cytometry

M.Sc.Heat shock proteins (HSP) are a group of highly conserved proteins induced in pro- and eukaryotes by a wide variety of environmental stresses such as heat shock (HS) and oxidative injury. HSP are classified into families according to their apparent molecular mass and respective inducers. Induction of HSP is primarily regulated on transcriptional level through multiple copies of a conserved cis-acting heat shock element (HSE) in the promoter region of all hsp genes to which the heat shock transcription factor (HSF) binds. Members of the HSP family function collectively as molecular chaperone systems, and fulfil essential roles under normal conditions and provide protection and adaptation during and following stress. The induction of HSP following stress and the subsequent protection confer HSP the potential application in stress therapy and in biomarking of stress. During a previous study in which the effect of Mycobacterium tuberculosis (M.tb) on the stress response of peripheral blood moncytes (PBM) from different donors was investigated, it was observed that different individuals from different South African populations showed differential a HSP synthesis in response to M.tb. This compelled us to investigate the following: Variation in HSP synthesis in peripheral blood monocytes (PBM) from different individuals in response to the classical HSP inducer, HS. The most appropriate technique to study HSP expression on protein level. HSP synthesis was studied in PBM from 36 individuals (European (E): n=22; non-Europeans (nE): n=14) using biometabolic labelling. Three techniques were compared in the determination of HSP expression in six donors in terms of HSP synthesis, which is measured by biometabolic labelling, and accumulation of hsp70 that were measured by Western blot analysis and flow cytometry. Results obtained are : European (E) and non-European (nE) populations differed significantly (p < 0.05) from each other in spite of a prominent variation in HSP synthesis within donors ; Flow cytometry is the technique of choice for the analysis of HSP levels, since it allows fast and safe measurement of HSP levels in single cel populations within a mixed population. Data from flow cytometry correlate with Western blot analysis, but not with biometabolic labelling. The means and ranges for different HSP synthesis in different populations reported in this study, set a standard for the use of HSP as biomarker of pa environmental stress for populations inhabiting southern Africa. Efficient measurement of HSP expression as biomarker of stress can therefore be implemented in routine analysis of environmental stress, as well as investigations concerning the implications of HSP in pathology