Potential role of pentosidine on susceptibility to small airway closure in elderly and smoking asthma

Evaluation of the severity of small airways obstruction and alveolar destruction in chronic obstructive pulmonary disease

BACKGROUND

Airflow limitation in COPD is caused by a mixture of small airways obstruction and alveolar destruction.

OBJECTIVE

To evaluate the contributions of these factors to airflow limitation through measurement of two biomarkers, pentosidine and vascular endothelial growth factor (VEGF), which reflect pathology or function of the lower respiratory tract of COPD.

METHODS

We measured pentosidine and VEGF levels in induced sputum from 23 non-smokers, 26 smokers without COPD, and 43 smokers with COPD. We evaluated the correlations of two biomarkers levels with the grade of low attenuation area (LAA) in high-resolution computed tomographic scans and the Δ N₂ from the nitrogen washout curve.

RESULTS

Pentosidine levels were significantly higher in smokers with COPD than in non-smokers and smokers without COPD. In contrast, VEGF levels were significantly lower in smokers without COPD than in non-smokers, and further decreased in smokers with COPD. In the four-stage classification of LAA grading, pentosidine levels steeply increased from grade I to Ⅳ, while VEGF levels decreased with increasing severity of LAA grade. Pentosidine levels were positively correlated with Δ N₂ in COPD patients with mild emphysema. In contrast, VEGF levels were inversely correlated with Δ N₂ in COPD patients with severe emphysema.

CONCLUSION

Pentosidine level is responsible for the severity of small airways obstruction, while VEGF level reflects the magnitude of alveolar destruction. Thus, simultaneous measurement of pentosidine and VEGF levels may be a promising approach to discriminate the severity of small airways obstruction and alveolar destruction in the lower respiratory tract of COPD.

Increased AGE-RAGE ratio in idiopathic pulmonary fibrosis

BACKGROUND

The abnormal epithelial-mesenchymal restorative capacity in idiopathic pulmonary fibrosis (IPF) has been recently associated with an accelerated aging process as a key point for the altered wound healing. The advanced glycation end-products (AGEs) are the consequence of non-enzymatic reactions between lipid and protein with several oxidants in the aging process. The receptor for AGEs (RAGEs) has been implicated in the lung fibrotic process and the alveolar homeostasis. However, this AGE-RAGE aging pathway has been under-explored in IPF.

METHODS

Lung samples from 16 IPF and 9 control patients were obtained through surgical lung biopsy. Differences in AGEs and RAGE expression between both groups were evaluated by RT-PCR, Western blot and immunohistochemistry. The effect of AGEs on cell viability of primary lung fibrotic fibroblasts and alveolar epithelial cells was assessed. Cell transformation of fibrotic fibroblasts cultured into glycated matrices was evaluated in different experimental conditions.

RESULTS

Our study demonstrates an increase of AGEs together with a decrease of RAGEs in IPF lungs, compared with control samples. Two specific AGEs involved in aging, pentosidine and Nε-Carboxymethyl lysine, were significantly increased in IPF samples. The immunohistochemistry identified higher staining of AGEs related to extracellular matrix (ECM) proteins and the apical surface of the alveolar epithelial cells (AECs) surrounding fibroblast foci in fibrotic lungs. On the other hand, RAGE location was present at the cell membrane of AECs in control lungs, while it was almost missing in pulmonary fibrotic tissue. In addition, in vitro cultures showed that the effect of AGEs on cell viability was different for AECs and fibrotic fibroblasts. AGEs decreased cell viability in AECs, even at low concentration, while fibroblast viability was less affected. Furthermore, fibroblast to myofibroblast transformation could be enhanced by ECM glycation.

CONCLUSIONS

All of these findings suggest a possible role of the increased ratio AGEs-RAGEs in IPF, which could be a relevant accelerating aging tissue reaction in the abnormal wound healing of the lung fibrotic process.