Aims:The aim of this study was to evaluate the physicochemical properties of the pleural mesothelial barrier and of the biological markers that facilitate or eliminate the passage of molecules through the pleura.Methods and Material:Pleural fluid samples from sixty-five patients with heart failure were analyzed. The biological markers studied were lactate dehydrogenase (LDH), adenosine deaminase (ADA), interleukin-6 (IL-6), C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), carcinoembryonic antigen (CEA), copper/zinc superoxide dismutase (CuZnSOD), matrix metalloproteinase-2 (MMP-2), -3 (MMP-3), -7(MMP-7), -8 (MMP-8) and -9 (MMP-9). Based on the pleural fluid/serum ratio, these molecules were divided into three groups: a) the LDH-like group with a pleural fluid/serum ratio between 0,4 and 0,8 (LDH, CEA, CuZnSOD, ADA, CRP, MMP-8), b) molecules with a pleural fluid/serum ratio less than 0,4 (MMP-7 and MMP-9) and c) molecules with a pleural fluid/serum ratio equal or above 1 (TNF-α, IL-6, MMP-2 and MMP-3).Results:No correlation between the molecular radius and the pleural fluid to serum ratio of the above biological markers was found.Conclusions:The molecular size is not a major determinant for the passage of molecules through the mesothelial barrier. Several other factors may influence the transport of the above molecules to pleural cavity, such as their charge and shape.

Numerous studies have revealed the significant action of airway epithelium as a nonspecific defence mechanism in airways. In addition, epithelial cells release biologically active agents, which modulate airway tone. Importantly, airway epithelium function is influenced by physiological parameters, including the release of endogenous factors, age, gender, load, and bronchi size. The primary goal of this review is to summarize knowledge concerning the effect of the aforementioned parameters on the modulatory role of airway epithelium on airway smooth muscle responsiveness. These effects may be implicated in the pathophysiology of airway diseases like asthma and Chronic Obstructive Pulmonary Disease (COPD).