DIFFERENT PATHWAYS OF APOPTOSIS REVEALED BY 2-CHLORO-ADENOSINE AND DEOXY-D-RIBOSE IN MAMMALIAN ASTROGLIAL CELLS

Both the adenosine analogue 2-chloro-adenosine (2-CA) and the reducing sugar deoxy-D-ribose (dRib) induce apoptosis of astroglial cells in r at brain primary cultures (Abbracchio et al.: Biochem Biophys Res Comm un 213:908-915, 1995), The present study was undertaken to elucidate b y both morphological and cytofluorimetric analyses the intracellular m echanism(s) involved in induction of apoptosis by these two agents, Th e poly(ADP-ribose)polymerase (PARP) inhibitor 3-aminobenzamide did not prevent either 2-CA- or dRib-induced cell death, suggesting that acti vation of PARP is not critically important for induction of apoptosis in astrocytes. The radical scavenger N-acetyl-cysteine (NAG) strongly inhibited dRib- but not 2-CA-induced cell death, suggesting a differen tial role for radical formation in apoptosis by these two agents, A ti me-dependent increase of cells with depolarized mitochondria was obser ved in dRib-, and to a lesser extent, in 2-CA-treated cultures, NAC al so prevented dRib- but not 2-CA-induced mitochondrial changes, We conc lude that, in mammalian astrocytes, apoptosis can proceed through dive rse and multiple pathways, depending upon the apoptotic stimulus, For dRib, apoptosis likely proceeds through generation of radicals and mit ochondrial involvement, An adenosine extracellular receptor linked to an as yet unidentified signaling pathway may instead mediate 2-CA-indu ced cell death, which may have intriguing implications for both nervou s system development and brain response to trauma and ischemia. (C) 19 97 Wiley-Liss, Inc.