**4. Asthma**

Asthma is an airway disease originating from complex interactions between genetic factors and environmental agents. It affects over 300 million people around the world and is characterized by airflow limitation resulting in shortness of breath. Bronchial obstruction is extremely variable and often reversible in asthma. Being a global health problem, tools which allow its early diagnosis, monitoring, and follow-up would offer great advantages for a better insight into its physiopathology. The articles discussed in the following sections prove that the proteomic content of sputum/induced sputum and BALf may allow for the identification of specific biomarkers in asthma.

### **4.1. Sputum/induced sputum**

2-DE coupled to MALDI/TOF allowed Lee et al. [25] to compare the proteomic profiles of sputum from patients with neutrophilic-type uncontrolled asthma (UA) and from patients with neutrophilic controlled asthma (CA). It could be observed that, while a few proteins (including calgranulin S100A9) were overexpressed in sputum of UA patients, others, associated with inflammation, anti-inflammation, enzymatic activity, and immunity signaling, were downregulated. Differences in protein abundance and composition between asthma and rhinitis were revealed by the proteomic approach (2D-DIGE and MS) applied by Suojalehto et al. [26] to induced sputum (IS) and nasal lavage fluid (NLF) of patients. Their findings showed that (i) fatty acid-binding protein 5 (FABP5) was upregulated in IS of asthmatics, (ii) vascular endothelial growth factor (VEGF) was increased in NLF of asthmatics, and (iii) in NLF of these subjects, FABP5 and VEGF were positively correlated with cysteinyl leukotriene (CysLT). Based on their results, the authors hypothesized that, in asthma, FABP5 may contribute to the airway remodeling and inflammation by regulating the levels of CysLTs which, in turn, induce VEGF production.
