Coarse particulate matter (PM 2.5-10) in Los Angeles Basin air induces expression of inflammation and cancer biomarkers in rat brains

Sci Rep. 2018 Apr 9;8(1):5708. doi: 10.1038/s41598-018-23885-3.


Air pollution is linked to brain inflammation, which accelerates tumorigenesis and neurodegeneration. The molecular mechanisms that connect air pollution with brain pathology are largely unknown but seem to depend on the chemical composition of airborne particulate matter (PM). We sourced ambient PM from Riverside, California, and selectively exposed rats to coarse (PM2.5-10: 2.5-10 µm), fine (PM<2.5: <2.5 µm), or ultrafine particles (UFPM: <0.15 µm). We characterized each PM type via atomic emission spectroscopy and detected nickel, cobalt and zinc within them. We then exposed rats separately to each PM type for short (2 weeks), intermediate (1-3 months) and long durations (1 year). All three metals accumulated in rat brains during intermediate-length PM exposures. Via RNAseq analysis we then determined that intermediate-length PM2.5-10 exposures triggered the expression of the early growth response gene 2 (EGR2), genes encoding inflammatory cytokine pathways (IL13-Rα1 and IL-16) and the oncogene RAC1. Gene upregulation occurred only in brains of rats exposed to PM2.5-10 and correlated with cerebral nickel accumulation. We hypothesize that the expression of inflammation and oncogenesis-related genes is triggered by the combinatorial exposure to certain metals and toxins in Los Angeles Basin PM2.5-10.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Air Pollutants / adverse effects*
  • Air Pollutants / analysis
  • Animals
  • Biomarkers, Tumor / genetics*
  • Brain Chemistry
  • Brain Neoplasms / chemically induced
  • Brain Neoplasms / genetics
  • Brain Neoplasms / veterinary*
  • Encephalitis / chemically induced
  • Encephalitis / genetics
  • Encephalitis / metabolism
  • Encephalitis / veterinary*
  • Gene Expression Profiling / veterinary*
  • Gene Expression Regulation / drug effects
  • Los Angeles
  • Nickel / analysis
  • Organ Specificity
  • Particle Size
  • Particulate Matter / adverse effects*
  • Particulate Matter / analysis
  • Rats
  • Sequence Analysis, RNA
  • Spectrophotometry, Atomic
  • Time Factors


  • Air Pollutants
  • Biomarkers, Tumor
  • Particulate Matter
  • Nickel