Pyrrolidine Dithiocarbamate Attenuates Endotoxin-induced Acute Lung Injury

Lung injury in the acute respiratory distress syndrome (ARDS) is in part due to polymorphonuclear leukocyte (PMN)-mediated oxidative tissue damage. By means of nuclear factor-κB (NF-κB) activation, oxidants may also induce several genes implicated in the inflammatory response. The dithiocarbamates are antioxidants with potent inhibitory effects on NF-κB. We postulated that the pyrrolidine derivative pyrrolidine dithiocarbamate (PDTC) would attenuate lung injury following intratracheal challenge with endotoxin (lipopolysaccharide; LPS) through its effect as an antioxidant and inhibitor of gene activation. Rats were given PDTC (1 mmole/kg) by intraperitoneal injection, followed by intratracheal administration of LPS. The transpulmonary flux of [¹²⁵I] albumin (permeability index; PI) was used as a measure of lung injury. Northern blot analysis of total lung RNA was performed to assess induction of tumor necrosis factor-α (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) messenger RNA (mRNA) as markers of NF-κB activation. The effect of in vivo treatment with PDTC on LPS-induced NF-κB DNA binding activity in macrophage nuclear extracts was evaluated with the electrophoretic mobility shift assay (EMSA). PDTC administration attenuated LPS-induced increases in lung permeability (PI = 0.16 ± 0.02 for LPS versus 0.06 ± 0.01 for LPS + PDTC; P < 0.05). TNF-α levels and PMN counts in bronchoalveolar lavage fluid (BALF) were unaffected, as were whole-lung TNF-α and ICAM-1 mRNA expression. PDTC had no effect on NF-κB activation as evaluated with EMSA. PDTC reduced lung lipid peroxidation as assessed by levels of malondialdehyde, without reducing neutrophil oxidant production. We conclude that PDTC attenuates LPS-induced acute lung injury. This effect occurs independently of any effect on NF-κB. PDTC reduces oxidant-mediated cellular injury, as demonstrated by a reduction in the accumulation of malondialdehyde. Administration of PDTC may represent a novel approach to limiting neutrophil-mediated oxidant injury.