Ceramide-Mediated Apoptosis in Lung Epithelial Cells Is Regulated by Glutathione

Abstract

Reactive oxygen species (ROS) are mediators of lung injury, and glutathione (GSH) is the major nonprotein antioxidant that protects the cell from oxidative stress. We have recently shown that H(2)O(2) induces ceramide-mediated apoptosis in human lung epithelial cells. We hypothesized that ROS-mediated depletion of GSH plays a regulatory role in ceramide generation, and thus in the induction of apoptosis. Our present studies demonstrate that GSH at physiologic concentrations (1 to 10 mM) inhibits ceramide production in a time- and dose-dependent manner in A549 human alveolar epithelial cells. On the other hand, buthionine-sulfoximine-mediated depletion of intracellular GSH induces elevation of ceramide levels and apoptosis. In addition, GSH blocks H(2)O(2)-mediated induction of intracellular ceramide generation and apoptosis. These effects were not mimicked by oxidized GSH (GSSG) or other thiol antioxidants, such as dithiothreitol and 2-mercaptoethanol. Moreover, increase of intracellular H(2)O(2), mediated by inhibition of catalase by aminotriazole, also induces ceramide generation and apoptosis. These effects were blocked by N-acetylcysteine. Our results suggest that GSH depletion may be the link between oxidative stress and ceramide-mediated apoptosis in the lung.

Overcoming resistance to γ-rays in squamous carcinoma cells by poly-drug elevation of ceramide levels

“…A significant decrease in glutathione has also been measured. Lavrentiadou et al (2001) recently reported that the ROS-mediated depletion of glutathione plays a key role in ceramide generation by removing its inhibitory effect on neutral sphingomyelinase (Liu and Hannun, 1997;Liu et al, 1998). Therefore, we propose an amplification loop in which glutathione depletion is triggered by the induction of ROS and this drop in glutathione activates ceramide formation by the activation of neutral sphingomyelinase.…”

Pulmonary Epithelial Neuropilin-1 Deletion Enhances Development of Cigarette Smoke–induced Emphysema

“…Results were normalized to cells undergoing mock transfection and vehicle treatment (fetal bovine serum-free medium for CSE, or 0.1% ethanol for ceramide) for the same duration and compared with cells transfected with nontargeting siRNA. Both CSE and ceramide were previously reported to produce endothelial and alveolar septal cell apoptosis and airspace enlargement in rodent models (44,46) as well as endothelial and epithelial cell death in vitro (47)(48)(49)(50). Apoptosis was quantified using the Apopercentage kit (Biocolor Ltd., Accurate Chemical and Scientific Corporation, Westbury, NY) following the manufacturer's instructions.…”

Vitamin E Regulates SMase Activity, GSH levels, and Inhibits Neuronal Death in Stroke-Prone Spontaneously Hypertensive Rats during Hypoxia and Reoxygenation

“…Cellular GSH levels are closely correlated with cell survival under adverse conditions (Bridges et al, 1991). Lavrentiadou et al (2001) demonstrated the role of GSH in preventing epithelial cell apoptosis. GSH depressed both early before ceramide production and it after events leading to apoptosis.…”

“…The activity of N-SMase was higher in the SHRSP/IZM than in the WKY/IZM neurons. A previous report demonstrated that the expression of N-SMase via the initial production of ceramide was induced by the depletion of GSH (Lavrentiadou et al, 2001). Verheij et al, (1996) reported that ceramide induces the stress-activated protein kinase/c-jun kinase (SAPK/JNK) signaling that precedes apoptosis.…”

“…On the other hand, neuronal cell death may involve the activation of magnesium-dependent neutral sphingomyelinase (N-SMase) caused by a drop in GSH levels, followed by a rapid rise in cellular ceramide levels (Liu et al, 1998). The expression of N-SMase closely linked to the initial production of ceramide was induced by the depletion of GSH (Lavrentiadou et al, 2001). …”