Inhibition of caspases rescues brown adipocytes from apoptosis downregulating BCL-XS and upregulating BCL-2 gene expression

Serum deprivation of the immortalized brown adipocyte cell line resulted in growth arrest in G(0)/G(1) phases of the cell cycle and apoptosis, as dete cted by DNA laddering, nuclei condensation and fragmentation, and an increa se in the percentage of hypodiploid cells. In addition, apoptosis in these cells is accompanied by an induction of the expression of the apoptotic for m of the Bcl-x gene, the isoform Bcl-xS, and by a decrease of Bcl-2 express ion, Bcl-xL remaining almost undetectable. The loss of mitochondrial membra ne potential was associated with apoptosis. Z-VAD, a cell-permeable inhibit or of caspases, but not cycloheximide, precludes DNA laddering under serum deprivation. Moreover, Z-VAD rescues serum-deprived brown adipocytes from a poptosis, decreasing the percentage of hypodiploid cells, the percentage of apoptotic cells under Tunnel assay, and the external display of phosphatid ylserine. More importantly, Z-VAD survival effects on immortalized brown ad ipocytes concur with a downregulation of Bcl-xS mRNA/protein and an upregul ation of Bcl-2 protein content. Ultimately, Z-VAD prevents the loss of mito chondrial membrane potential. (C) 1999 Academic Press.