Apoptotic cell death in rat lung following mustard gas inhalation.

To investigate apoptosis as a mechanism of sulfur mustard (SM) inhalation injury in animals, we studied different caspases (caspase-8, -9, -3, and -6) in the lungs from a ventilated rat SM aerosol inhalation model. SM activated all four caspases in cells obtained from bronchoalveolar lavage fluid (BALF) as early as 6 h after exposure. Caspase-8, which is known to initiate the extrinsic Fas-mediated pathway of apoptosis, was increased fivefold between 6 and 24 h, decreasing to the unexposed-control level at 48 h. The initiator, caspase-9, in the intrinsic mitochondrial pathway of apoptosis as well as the executioner caspases, caspase-3 and -6, all peaked (P < 0.01) at 24 h; caspase-3 and -6 remained elevated, but caspase-9 decreased to unexposed-control level at 48 h. To study further the Fas pathway, we examined soluble as well as membrane-bound Fas ligand (sFas-L and mFas-L, respectively) and Fas receptor (Fas-R) in both BALF cells and BALF. At 24 h after SM exposure, sFas-L increased significantly in both BALF cells (P < 0.01) and BALF (P < 0.05). However, mFas-L increased only in BALF cells between 24 and 48 h (P < 0.1 and P < 0.001, respectively). Fas-R increased only in BALF cells by 6 h (P < 0.01) after SM exposure. Apoptosis in SM-inhaled rat lung specimens was also confirmed by both immunohistochemical staining using cleaved caspase-3 and -9 antibodies and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining as early as 6 h in the proximal trachea and bronchi, but not before 48 h in distal airways. These findings suggest pathogenic mechanisms at the cellular and molecular levels and logical therapeutic target(s) for SM inhalation injury in animals.

Phosphine toxicity: a story of disrupted mitochondrial metabolism.

Rodenticides and pesticides pose a significant threat not only to the environment but also directly to humans by way of accidental and/or intentional exposure. Metal phosphides, such as aluminum, magnesium, and zinc phosphides, have gained popularity owing to ease of manufacture and application. These agents and their hydrolysis by-product phosphine gas (PH3 ) are more than adequate for eliminating pests, primarily in the grain storage industry. In addition to the potential for accidental exposures in the manufacture and use of these agents, intentional exposures must also be considered. As examples, ingestion of metal phosphides is a well-known suicide route, especially in Asia; and intentional release of PH3 in a populated area cannot be discounted. Metal phosphides cause a wide array of effects that include cellular poisoning, oxidative stress, cholinesterase inhibition, circulatory failure, cardiotoxicity, gastrointestinal and pulmonary toxicity, hepatic damage, neurological toxicity, electrolyte imbalance, and overall metabolic disturbances. Mortality rates often exceed 70%. There are no specific antidotes against metal phosphide poisoning. Current therapeutic intervention is limited to supportive care. The development of beneficial medical countermeasures will rely on investigative mechanistic toxicology; the ultimate goal will be to identify specific treatments and therapeutic windows for intervention.

The role of NAD+ depletion in the mechanism of sulfur mustard-induced metabolic injury.

Results of our previous studies on the chemical warfare agent sulfur mustard (2,2'-dichlorodiethyl sulfide) suggested that mustard-induced inhibition of glycolysis is not solely a function of NAD+ depletion. To define the role of NAD+ in mustard-induced metabolic injury, we examined the effects of mustard+/-niacinamide on energy metabolism in cultured human keratinocytes. Sulfur mustard caused concentration-dependent decreases in viable cell number and ATP content at 24 hours, but not earlier, and time- and concentration-dependent glycolytic inhibition and NAD+ depletion as early as 4 hours. Niacinamide partially protected NAD+ levels at all time points, but did not prevent adverse effects on glycolysis, intracellular ATP, or viable cell number. These results support our earlier conclusions and suggest that sulfur mustard may inhibit glycolysis directly.