**8. Other pulmonary disorders**

### **8.1. Idiopathic pulmonary arterial hypertension**

Idiopathic pulmonary arterial hypertension (IPAH) is a rare, life-threatening disorder clinically characterized by sustained elevations of pulmonary artery pressure (PAP). Together with intimal proliferation, in situ thrombi, deposition of extracellular matrix, and inflammation, the remodeling of the pulmonary arterial vasculature with medial and adventitial thickening of the arteries and arterioles is the main feature of IPAH. This leads to increased pulmonary vascular resistance, right heart failure, and death. The latest proteomic studies aimed at providing insights into the molecular mechanisms underlying IPAH are presented in this section. All recent proteomic studies based on the use of an electrokinetic approach have been performed on serum/plasma.

The first proteomic approach aimed at identifying protein changes in serum from IPAH patients was performed by Yu et al. [48] by using a combination of 2-DE and MS. The attention of the authors was focused on α-1 antitrypsin and vitronectin that, being downregulated in IPAH patients, were indicated as proteins involved in the development of the disorder. In fact, while the decrease of plasma vitronectin might favor platelet aggregation and thrombus formation, the decrease of α-1 antitrypsin might induce apoptosis of endothelial cells resulting in proliferation of apoptosis-resistant endothelial cell arteriolar occlusion. 2-DE and immunoblotting were the combination applied by Terrier et al. [49] to identify the target antigens of antifibroblast antibodies (AFAs) in patients affected by IPAH. Among the 21 protein spots specifically recognized by serum IgG antibodies from IPAH patients, 16 proteins involved in (i) regulation of cytoskeletal function, (ii) cell contraction, (iii) oxidative stress, (iv) cell energy metabolism, and (v) other key cellular pathways were identified.

The comparative proteomic analysis based on 2-DE and MALDI-TOF performed by Zhang et al. [50] on serum of IPAH patients and controls identified, among other proteins showing significant changes, leucine-rich α-2-glycoprotein (LRG) as a possible specific prognostic biomarker of IPAH. 2D-DIGE coupled to MALDI-TOF-MS was used by Yeager et al. [51] to investigate the plasma proteome of IPAH children with good and poor outcome to long-term vasodilator therapy. Before and after therapy, serum amyloid A (SAA-4) was found to be fourfold lower in patients with good outcome compared to those with poor outcome, while serum amyloid P (SAP) was 1.3-fold lower prior to therapy in patients with good outcome. Since these proteins regulate circulating mononuclear phagocytes, they may contribute to the differential response to chronic vasodilator therapy.

### **8.2. Pulmonary embolism**

Pulmonary emboli usually arise from thrombi originating in the deep venous system of the lower extremities that travel to the lung and can lodge at the bifurcation of the main pulmonary artery or the lobar causing hemodynamic compromise. Mortality rates in patients with acute pulmonary embolism (PE) vary from 1.4 to 17.4% during the first 3 months of treatment. The causes of most early deaths are complications such as acute pulmonary arterial hypertension and right heart failure, whereas medical problems underlying PE are responsible for most late deaths. The subsections reported below describe the recent advances in PE proteomics.

#### *8.2.1. Plasma*

The authors observed that, although protein components were variably expressed in individuals, inflammatory and redox proteins were unambiguously upregulated in smokers com-

To elucidate putative molecular mechanisms underlying gender-based differences in the pathophysiology of COPD, Kohler et al. [45] applied 2D-DIGE coupled to nano-LC-MS to investigate the proteome of non-symptomatic smokers and smokers with COPD. The authors observed significant gender differences with a subset of 19 proteins providing a highly predictive model for classification of female non-symptomatic smokers from female smokers with COPD. Subsequent pathway analyses correlated the observed alterations to downregulation of the lysosomal pathway and upregulation of the oxidative phosphorylation pathway.

An interesting research (based on 2-DE and MALDI-TOF/TOF) by Pastor et al. [46, 47] evidenced a distinct proteomic reactive oxygen species (ROS) protein signature in BALf from COPD and lung cancer patients. Their findings highlight the role of ROS proteins in the pathogenic pathways of both diseases and provide new candidate biomarkers and predictive

Idiopathic pulmonary arterial hypertension (IPAH) is a rare, life-threatening disorder clinically characterized by sustained elevations of pulmonary artery pressure (PAP). Together with intimal proliferation, in situ thrombi, deposition of extracellular matrix, and inflammation, the remodeling of the pulmonary arterial vasculature with medial and adventitial thickening of the arteries and arterioles is the main feature of IPAH. This leads to increased pulmonary vascular resistance, right heart failure, and death. The latest proteomic studies aimed at providing insights into the molecular mechanisms underlying IPAH are presented in this section. All recent proteomic studies based on the use of an electrokinetic approach

The first proteomic approach aimed at identifying protein changes in serum from IPAH patients was performed by Yu et al. [48] by using a combination of 2-DE and MS. The attention of the authors was focused on α-1 antitrypsin and vitronectin that, being downregulated in IPAH patients, were indicated as proteins involved in the development of the disorder. In fact, while the decrease of plasma vitronectin might favor platelet aggregation and thrombus formation, the decrease of α-1 antitrypsin might induce apoptosis of endothelial cells resulting in proliferation of apoptosis-resistant endothelial cell arteriolar occlusion. 2-DE and immunoblotting were the combination applied by Terrier et al. [49] to identify the target antigens of antifibroblast antibodies (AFAs) in patients affected by IPAH. Among the 21 protein spots specifically recognized by serum IgG antibodies from IPAH patients, 16 proteins involved in (i) regulation of cytoskeletal function, (ii) cell contraction, (iii) oxidative stress, (iv) cell energy metabolism, and

No altered proteins were found in the corresponding male classification model.

pared to never-smokers.

32 Electrophoresis - Life Sciences Practical Applications

tools for lung cancer and COPD diagnosis.

**8.1. Idiopathic pulmonary arterial hypertension**

**8. Other pulmonary disorders**

have been performed on serum/plasma.

(v) other key cellular pathways were identified.

To identify biomarkers useful for the risk stratification in patients with acute symptomatic PE, Insenser et al. [52] studied the plasma proteome of PE patients with low, intermediate, and high risk. 2D-DIGE was used to compare the abundance of plasma proteins in the three cohorts, and candidate protein markers were identified by MALDI-TOF. Differences among patients with different PE severities were observed in a panel of four biomarkers (haptoglobin, hemopexin, α2-macroglobulin, and Ig α-1-chain C region) involved in iron metabolism pathways and acute-phase response. Among them, the reduced concentrations of haptoglobin could be considered an accurate signal for the biochemical detection of high-risk PE.
