Smoking induces increased apoptosis in osteoblasts: changes in bone matrix organic components.

Clinical studies demonstrate the impact of smoking on bone tissue fragility and higher incidence of fractures. However, it is not totally understood which physiological mechanisms could be involved in these events. Previously, we showed important changes in bone tissue components in experimental model of cigarette smoke (CS) exposure. CS exposure induces worsening in bone mineralization and a decrease in collagen type I deposition, leading to bone fragility. Considering that the majority of clinical studies described bone structural changes by radiographic images, in this study we performed analyses "in situ" using tissue samples from smokers, former smokers and non-smokers to better understand how the increase in inflammatory mediators induced by smoking exposure could interfere in bone cells activity leading bone structural changes. We observed increased levels of IL-1ß, IL-6 and TNF-α in bone tissue homogenates with a concomitant increase in osteoblast apoptosis in smokers and former smokers compared with non-smokers. Histological changes in both smokers and former smokers were characterized by reduction in collagen type I. Only in smokers, it was observed decrease in trabecular area, suggesting increased bone resorption and increase in collagen type V. These results showed that osteoblasts apoptosis in association with increased bone resorption leads bone structural changes in smokers.

Chronic exposure to diesel particles worsened emphysema and increased M2-like phenotype macrophages in a PPE-induced model.

Chronic exposure to ambient levels of air pollution induces respiratory illness exacerbation by increasing inflammatory responses and apoptotic cells in pulmonary tissues. The ineffective phagocytosis of these apoptotic cells (efferocytosis) by macrophages has been considered an important factor in these pathological mechanisms. Depending on microenvironmental stimuli, macrophages can assume different phenotypes with different functional actions. M1 macrophages are recognized by their proinflammatory activity, whereas M2 macrophages play pivotal roles in responding to microorganisms and in efferocytosis to avoid the progression of inflammatory conditions. To verify how exposure to air pollutants interferes with macrophage polarization in emphysema development, we evaluated the different macrophage phenotypes in a PPE- induced model with the exposure to diesel exhaust particles. C57BL/6 mice received intranasal instillation of porcine pancreatic elastase (PPE) to induce emphysema, and the control groups received saline. Both groups were exposed to diesel exhaust particles or filtered air for 60 days according to the groups. We observed that both the diesel and PPE groups had an increase in alveolar enlargement, collagen and elastic fibers in the parenchyma and the number of macrophages, lymphocytes and epithelial cells in BAL, and these responses were exacerbated in animals that received PPE instillation prior to exposure to diesel exhaust particles. The same response pattern was found inCaspase-3 positive cell analysis, attesting to an increase in cell apoptosis, which is in agreement with the increase in M2 phenotype markers, measured by RT-PCR and flow cytometry analysis. We did not verify differences among the groups for the M1 phenotype. In conclusion, our results showed that both chronic exposure to diesel exhaust particles and PPE instillation induced inflammatory conditions, cell apoptosis and emphysema development, as well as an increase in M2 phenotype macrophages, and the combination of these two factors exacerbated these responses. The predominance of the M2-like phenotype likely occurred due to the increased demand for efferocytosis. However, M2 macrophage activity was ineffective, resulting in emphysema development and worsening of symptoms.