Heterozygosity in the glutathione synthesis gene Gclm increases sensitivity to diesel exhaust particulate induced lung inflammation in mice

Abstract

Context: Inhalation of ambient fine particulate matter (PM_2.5) is associated with adverse respiratory and cardiovascular effects. A major fraction of PM_2.5 in urban settings is diesel exhaust particulate (DEP), and DEP-induced lung inflammation is likely a critical event mediating many of its adverse health effects. Oxidative stress has been proposed to be an important factor in PM_2.5-induced lung inflammation, and the balance between pro- and antioxidants is an important regulator of this inflammation. An important intracellular antioxidant is the tripeptide thiol glutathione (GSH). Glutamate cysteine ligase (GCL) carries out the first step in GSH synthesis. In humans, relatively common genetic polymorphisms in both the catalytic (Gclc) and modifier (Gclm) subunits of GCL have been associated with increased risk for lung and cardiovascular diseases.

Objective: This study was aimed to determine the effects of Gclm expression on lung inflammation following DEP exposure in mice.

Materials and methods: We exposed Gclm wild type, heterozygous, and null mice to DEP via intranasal instillation and assessed lung inflammation as determined by neutrophils and inflammatory cytokines in lung lavage, inflammatory cytokine mRNA levels in lung tissue, as well as total lung GSH, Gclc, and Gclm protein levels.

Results: The Gclm heterozygosity was associated with a significant increase in DEP-induced lung inflammation when compared to that of wild type mice.

Discussion and conclusion: This finding indicates that GSH synthesis can mediate DEP-induced lung inflammation and suggests that polymorphisms in Gclm may be an important factor in determining adverse health outcomes in humans following inhalation of PM_2.5.

Keywords::

• Diesel exhaust particulate
• lung inflammation
• glutathione
• oxidative stress
• glutamate cysteine ligase