Different responses of astrocytes and neurons to nitric oxide: The role of glycolytically generated ATP in astrocyte protection

Abstract

It was recently proposed that in Jurkat cells, after inhibition of respiration by NO, glycolytically generated ATP plays a critical role in preventing the collapse of mitochondrial membrane potential (⌬m) and thus apoptotic cell death. We have investigated this observation further in primary cultures of rat cortical neurons and astrocytes-cell types that differ greatly in their glycolytic capacity. Continuous and significant (Ϸ85%) inhibition of respiration by NO (1.4 M at 175 M O2) generated by [(z)-1-[2-aminoethyl]-N-[2-ammonioethyl]amino]diazen-1-ium-1,2 diolate (DETA-NO) initially (10 min) depleted ATP concentrations by Ϸ25% in both cell types and increased the rate of glycolysis in astrocytes but not in neurons. Activation of glycolysis in astrocytes, as judged by lactate production, prevented further ATP depletion, whereas in neurons, which do not invoke this mechanism, there was a progressive decrease in ATP concentrations over the next 60 min. During this time, there was a persistent mitochondrial hyperpolarization and absence of apoptotic cell death in astrocytes, whereas in the neurons there was a progressive fall in ⌬m and increased apoptosis. After glucose deprivation or treatment with inhibitors of the F1F0-ATPase and adenine nucleotide translocase, astrocytes responded to NO with a fall in ⌬m and apoptotic cell death similar to the response in neurons. Finally, although treatment of astrocytes with NO partially prevented staurosporin-induced collapse in ⌬m and cell death, NO and staurosporin synergized in decreasing ⌬m and inducing apoptosis in neurons. These results demonstrate that although inhibition of cellular respiration by NO leads to neurotoxicity, it may also result in initial neuroprotection, depending on the glycolytic capacity of the particular cell.glycolysis ͉ mitochondrial membrane potential ͉ apoptosis ͉ oxygen consumption ͉ neurodegeneration N itric oxide (NO) is a physiological messenger (1) that has been reported either to cause or prevent cellular apoptotic death (2, 3). The mitochondrion is now emerging as a key organelle playing a role in the NO-mediated apoptotic pathway. Disruption of the membrane potential across the mitochondrial inner membrane (⌬ m ) dissipates the electrochemical gradient necessary for ATP synthesis (4). Moreover, ⌬ m collapse is associated with mitochondrial swelling, disruption of the outer mitochondrial membrane, and the release of proapoptotic factors such as cytochrome c, apoptosis-inducing factor, and some procaspases (5, 6) from the intermembrane space. NO inhibits the activity of certain components of the mitochondrial respiratory chain, including cytochrome c oxidase (reviewed in ref. 7), and it has recently been shown that endogenous NO formation in primary neurons triggers a rapid and transient ATP depletion associated with ⌬ m collapse and apoptosis (8).Beltrán et al. (9), however, have shown in Jurkat cells that inhibition of mitochondrial respiration by NO induces mitochondrial hyperpolarization. They suggested that this phenomenon may be a...

Nitric oxide, mitochondrial hyperpolarization, and T cell activation☆

“…Transient MHP is an early event preceding caspase activation, phosphatidylserine (PS) externalization, and disruption of Δψ m in Fas- [6] and H 2 O 2 -induced apoptosis of Jurkat human leukemia T cells and normal human peripheral blood lymphocytes (PBL) [8]. These observations were widely confirmed and extended to other apoptosis pathways [9,10,11,12,13,14]. Transient MHP is also triggered by activation of T cells by Con A [6] and CD3/CD28 costimulation [15] via ROI-and Ca 2+ -dependent production of NO [16].…”

“…Ibiza and colleagues recently showed that within minutes of binding to antigen, T cells produce NO via endothelial NO synthase (eNOS) [39]. NO promoted mitochondrial hyperpolarization, ATP depletion and relative resistance to apoptotic stimuli in astrocytes, lymphocytes and Jurkat cells [13,40]. Although pretreatment of normal T cells with NO resulted in elevation of mitochondrial and cytoplasmic Ca 2+ levels, Ca 2+ by itself was insufficient to induce NO synthesis or mitochondrial hyperpolarization in lymphocytes [16,39].…”

The role of nitric oxide in abnormal T cell signal transduction in systemic lupus erythematosus

“…NO promoted mitochondrial hyperpolarization, ATP depletion, and relative resistance to apoptotic stimuli in astrocytes, lymphocytes, and Jurkat cells [46,47]. Moreover, pretreatment of normal T cells with NO resulted in elevation of mitochondrial and cytoplasmic Ca 2+ level [43].…”

3,4-Dihydroxyphenylacetic acid (DOPAC) modulates the toxicity induced by nitric oxide in PC-12 cells via mitochondrial dysfunctioning

“…Mitochondrial function is very sensitive to the presence of nitric oxide (Brown, 1995;Borutaite and Brown, 1996;Lizasoain et al, 1996;Giulivi, 1998;Brookes et al, 1999;Brown, 1999) and the mechanism by which NO induces apoptosis in several cell types appears to encompass changes in mitochondrial membrane potential (Dc m ) (Almeida et al, 2001;Bal-Price and Brown, 2000;Brorson et al, 1999;Solenski et al, 2003). To investigate the alteration of Dc m in PC-12 cells treated with DOPAC, SNAP or DOPAC plus SNAP, the fluorescent probe RH 123 was used as described in Section 2.…”