Mechanism of lung injury caused by PM10 and ultrafine particles with special reference to COPD.

Particulate air pollution (particles with a 50% cut-off aerodynamic diameter of 10 microm (PM10)) has strong associations with the adverse health events detected by epidemiological studies in chronic obstructive pulmonary disease patients in diverse geographical locations. Transition metals may determine the toxic effects of PM10 through oxidative stress which may be injurious as shown by an increase in airspace epithelial permeability and may lead to inflammation through the activation of transcription factors for pro-inflammatory genes in both macrophages and epithelial cells. Recently, the present authors have shown that particulate air pollution may cause further molecular events that enhance transcription factor activation by causing acetylation of histones leading to unwinding of deoxyribonucleic acid (DNA) enhancing transcription factor DNA binding and increasing transcription for pro-inflammatory genes. Further, ultrafine particles (< 100 nm diameter), which have marked toxicity, may be responsible for some of the PM10 adverse effects. The current authors have demonstrated that ultrafine carbon black (ufCB) does not have its effects via transition metal-mediated mechanisms. However, ufCB and other ultrafines generate free radicals at their surface as measured by a number of chemical assays and are able to cause oxidative stress to cells and this is likely to be a factor in their ability to cause inflammation. Changes in calcium resulting from oxidative stress within cells may be an additional factor leading to transcription of pro-inflammatory genes. Understanding the mechanisms of the harmful effects of particulate air pollution in chronic obstructive pulmonary disease may help in risk strategy for individuals who are susceptible to the effects of air pollution.