Cross-linking interferes with assessing sulfur mustard-induced DNA damage in human peripheral blood lymphocytes using the comet assay.

Sulfur mustard (SM) is a blistering agent that produces DNA strand breaks. To detect SM-induced DNA single strand breaks in human peripheral blood lymphocytes (PBL), cells were exposed to various concentrations of SM (10 to 1000 muM), and the comet assay (single-cell gel electrophoresis) was performed. We observed a SM concentration- and time-dependent increase in detectable DNA damage. To test whether SM-induced DNA cross-linking inhibits DNA migration in the comet assay, PBL were exposed to a) SM alone (10 to 1000 muM), b) H(2)O(2) (0.001%), which produces DNA single strand breaks with no cross-links, or c) SM followed at 2, 4, or 6 h by H(2)O(2). With H(2)O(2) alone, a large amount of strand breakage was detected. With H(2)O(2) plus SM, detectable H(2)O(2)-induced strand breaks decreased as SM concentration increased up to 30 muM; at 30 muM and above, the response with H(2)O(2) plus SM was similar to that with SM alone. Interference with the detection of H(2)O(2)-induced DNA strand breaks appears to be SM concentration-dependent up to 30 muM, and independent of SM concentration at >/=30 muM. This is presumably due to SM-induced cross-linking. It follows that cross-linking in DNA of SM-exposed PBL also interferes with DNA migration and detection of DNA strand breaks when cells are exposed to SM alone.

Synaptic PDZ domain-mediated protein interactions are disrupted by inhalational anesthetics.

Anesthetics exert multiple effects on the central nervous system through altering synaptic transmission, but the mechanisms for this process are poorly understood. PDZ domain-mediated protein interactions play a central role in organizing signaling complexes around synaptic receptors for efficient signal transduction. We report here that clinically relevant concentrations of inhalational anesthetics dose-dependently and specifically inhibit the PDZ domain-mediated protein interaction between PSD-95 or PSD-93 and the N-methyl-d-aspartate receptor or neuronal nitric-oxide synthase. These inhibitory effects are immediate, potent, and reversible and occur at a hydrophobic peptide-binding groove on the surface of the second PDZ domain of PSD-95 in a manner relevant to anesthetic action. These findings reveal the PDZ domain as a new molecular target for inhalational anesthetics.