Superfund Research Program
Pathogenesis of Toxicity of Vanadium Compounds
Project Leader: John Godleski
Grant Number: P42ES005947
Funding Period: 1995 - 2000
Work in Project 6 has continued to define mechanisms of toxicity of transition metals. In the past year several important studies were carried out toward this goal. These studies are described below under two main headings.
The differential ability of transition metals to induce pulmonary inflammation
Transition metals are potentially toxic agents that are found at numerous Superfund sites and have been implicated as causing adverse health effects. The relative toxicity and inflammatory potential of these metals are usually inferred from separate studies because little directly comparable data are available. The objective of this study was to compare the pulmonary effects of intratracheally-instilled, equimolar, soluble forms of six metal sulfates. Rats received either phosphate-buffered saline, 0.1 mol/kg, or 1.0 mol/kg of vanadium, nickel, iron (II), copper, manganese, or zinc. Bronchoalveolar lavage was performed at 0, 4, 16, or 48 h post-instillation. At the 0.1 mol/kg dose, only Cu induced significant neutrophil influx at 16 and 48 h (P< 0.05). For the 1.0 mol/kg dose at 4 h, Cu and Fe (II)-exposed animals had a significant increase in percent neutrophils compared to saline controls, and Cu had a significantly higher percentage than all other metals. After 16 h, each metal tested induced significant neutrophilia compared to controls, and Cu and Mn induced significantly higher neutrophilia than the other metals. At 48 h, neutrophilia was still increased in all metal exposures except Fe (II). Interestingly, significantly higher levels of eosinophils were only observed following instillation of Fe (II) (4 and 16 h) and Mn (16 h). Additionally, Cu and Ni-exposed rats had significantly higher levels of lactate dehydrogenase in lavage supernatant compared to the other metals and controls. These results indicate that transition metals differ in their ability to induce pulmonary inflammation and toxicity. Cu appears to be the most pro-inflammatory metal, followed by Mn and Ni, while V, Fe (II), and Zn induced similar levels of neutrophilia. Researchers concluded that the extent and cellular nature of metal-induced pulmonary inflammation depends on the individual metal.
The genetic response of alveolar macrophages to residual oil fly ash particles
Exposure to residual oil fly ash (ROFA) results in highly variable levels of respiratory tract inflammation. Alveolar macrophages (AMs) are primarily responsible for uptake of these particles and for the initiation of inflammation. The objectives of this study were to use microarrays to: 1) determine the overall in vitro response, at the level of gene expression, of human AMs to ROFA exposure and 2) to compare individual genetic responses to ROFA exposure. AMs from two individuals were collected from human volunteers (87-93% viability, >95% AMs), cultured separately for 2 h in RPMI-1640/0.5% serum on low-adherence plates. Cells received characterized ROFA or vehicle for 3 h and total RNA was isolated. Prior to screening, RNA was characterized by agarose-gel electrophoresis and ribonuclease-protection assays for nine proinflammatory mRNAs. Microarrays (NEN, 2400 genes) were hybridized with reverse-transcribed, differentially-labeled mRNA from AMs + ROFA exposure. The overall genetic response to ROFA was very different for the two individuals. AMs from one individual demonstrated substantially increased levels of mRNA transcripts for 29 genes with only 1 mRNA level decreased. In contrast, AMs from a second individual had increased levels of mRNA for 2 genes, and decreased mRNA concentrations for 21 others. Pre-existing, low-grade inflammation in one individual may explain these differences. The mRNA level changes are confirmed by Northern analysis. Differential responses by AMs to ROFA may, at least partially, explain variability in human responses to air pollution particles.