METABOLIC AND CELLULAR CHARACTERIZATION OF IMMORTALIZED HUMAN MICROGLIAL CELLS UNDER HEAT-STRESS

Microglia are able to shift from a resting to an activated state durin g which they acquire functions typical of primitive forms of mononucle ar phagocytes, as well as highly differentiated forms of these cell ty pes. Activation of the microglia after a trauma involves functional re adjustments including both the resurrection of basic cell functions an d the development of functions implicated in cell-cell interactions. H ere, the behaviour of the human microglial cell line CHME-5 was observ ed after hyperthermia. The strong expression of the inducible form of the hsp70 proteins and their nuclear location, like the more nucleolar presence of the hsc70 proteins seemed to confer heat resistance to th e cells. Following minor morphological changes, the observation of the cytoskeleton network during stress recovery revealed a differential s ensitivity of actin and tubuline to heat shock. The energy metabolism of both the microglial cell line and the monocyte cell line U937 were compared, under basal conditions, using phosphorus-31 NMR, to discern those phosphorylated metabolites which could be specific of either the monocytic or the macrophagic phenotype. A very high content of phosph ocreatine was observed in the microglial clone whereas this compound w as absent in monocytes. The lower CHME-5 phosphomonoester content as c ompared to monocytes also suggested that the microglial cell line disp layed a more macrophagic metabolic pattern. After heat shock, the CHME -5 phosphorylated compounds showed large, transient, perturbations. Ce lls recovered their basal metabolic content 24 h after heat stress. Th is behaviour, in addition to the expression of inducible hsp70 protein s and the cytoskeleton rearrangement, are indicative of the particular adaptation of the microglial cell line to stress situations. (C) 1998 Elsevier Science Ltd. All rights reserved.