Contribution of Lung Macrophages to the Inflammatory Responses Induced by Exposure to Air Pollutants

Abstract

Large population cohort studies have indicated an association between exposure to particulate matter and cardiopulmonary morbidity and mortality. The inhalation of toxic environmental particles and gases impacts the innate and adaptive defense systems of the lung. Lung macrophages play a critically important role in the recognition and processing of any inhaled foreign material such as pathogens or particulate matter. Alveolar macrophages and lung epithelial cells are the predominant cells that process and remove inhaled particulate matter from the lung. Cooperatively, they produce proinflammatory mediators when exposed to atmospheric particles. These mediators produce integrated local (lung, controlled predominantly by epithelial cells) and systemic (bone marrow and vascular system, controlled predominantly by macrophages) inflammatory responses. The systemic response results in an increase in the release of leukocytes from the bone marrow and an increased production of acute phase proteins from the liver, with both factors impacting blood vessels and leading to destabilization of existing atherosclerotic plaques. This review focuses on lung macrophages and their role in orchestrating the inflammatory responses induced by exposure to air pollutants.

Monocyte and Macrophage Plasticity in Tissue Repair and Regeneration

“…53 Alveolar macrophages in the lungs phagocytose any potentially harmful pathogen that is taken in from the air during respiration. 55 Interestingly, the cervical region consists of both proinflammatory type I macrophage (M1) and anti-inflammatory or propreparative type II macrophage (M2) phenotypes (discussed later), which are possibly responsible for the maternal tissue repair after birth. Increased presence of M2 macrophages during labor and immediately after birth suggests a key role of M2 macrophages in maternal tissue repair after birth.…”

Inflammatory, anti-inflammatory and regulatory cytokines in relatively healthy lung tissue as an essential part of the local immune system

“…Alveolar macrophages unique to lung tissue play a pivotal role in maintaining local immunity. Moreover, alveolar macrophages elicit and further amplify the immune response 28,29 . Importantly, the amount of secreted anti-inflammatory cytokine IL-10 decreases, suggesting the inflammatory response predominance over the tissue anti-inflammatory response, if excited by an antigen.…”

“…Importantly, the amount of secreted anti-inflammatory cytokine IL-10 decreases, suggesting the inflammatory response predominance over the tissue anti-inflammatory response, if excited by an antigen. Although epithelial tissue is also a source of cytokines, alveolar macrophages are overall more potent producers of inflammatory mediators than is the epithelium 28 . Antigen exposure causes an increase in acute phase inflammatory cytokines IL-1β, IL-6 produced by alveolar macrophages 6,7 .…”

Tumor Necrosis Factor-Alpha as Biomarkers of Exposure to Indoor Pollutants Among Primary School Children in Klang Valley

“…Air Pollutants TNF-α act as an inflammatory mediator release when there are interaction of alveolar macrophages in the lung with atmospheric particles (Hiraiwa and Van Eeden, 2013). School children living in urban area which are exposed to high concentration of indoor air pollutants significantly have a high level of TNF-α.…”