RESUMO
Type II pneumocytes (T II pneumocytes) produce hydrogen peroxide (H(2)O(2)), which may be potentially dangerous for the lung. These cells in culture differentiate to type I-like pneumocytes and it may reflect the differentiation which follows the injury of alveolar epithelium. This work was undertaken to estimate the H(2)O(2) release by T II pneumocytes, freshly isolated and cultured up to 8 days. The light and electron microscopy evaluation confirmed the differentiation of T II pneumocytes to type I-like cells. The release of H(2)O(2), estimated spectrofluorimetrically as homovanillic acid oxidation product obtained in the presence of horseradish peroxidase, was significantly higher at day 4 (0.63+/-0. 68nmol/mg protein/min, P=0.02) and 6 (0.46+/-0.31, P=0.001) compared to fresh cells (0.15+/-0.08). Phorbol esters increased H(2)O(2) release at day 2 (0.39+/-0.22 vs 0.16+/-0.08, P=0.02) and the inhibition of protein kinase C resulted in the decrease at day 2 (0.14+/-0.06 vs 0.07+/-0.02, P=0.025), day 6, (0.49+/-0.25 vs 0. 15+/-0.08, P=0.005) and 8 (0.76+/-0.63 vs 0.23+/-0.29, P=0.02). Inhibition of intracellular catalase resulted in a significant increase only at day 2 (0.23+/-0.1 vs 0.15+/-0.09, P=0.05). Inhibition of mitochondrial respiratory chain decreased H(2)O(2) release at day 2 (0.13+/-0.11 vs 0.07+/-0.07, P=0.002) and 4 (0. 75+/-0.88 vs 0.61+/-0.85, P=0.002). These results indicate that alveolar epithelium may be a source of potentially dangerous ROS and that the cell differentiation is accompanied by the increase of H(2)O(2) production. Both mitochondrial respiratory chain and membrane-bound NADPH-oxidase may be responsible for the production of H(2)O(2) by T II pneumocytes.
Assuntos
Peróxido de Hidrogênio/metabolismo , Pulmão/metabolismo , Animais , Catalase/metabolismo , Contagem de Células , Separação Celular , Células Cultivadas , Pulmão/citologia , Pulmão/ultraestrutura , Masculino , Microscopia Eletrônica , Cianeto de Potássio/farmacologia , Proteína Quinase C/metabolismo , Ratos , Ratos Wistar , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
UNLABELLED: We have investigated whether pretreatment with N-acetylcysteine (NAC) and/or ambroxol (Amb), drugs known as reactive oxygen species (ROS) scavengers, would minimize lipopolysaccharide (LPS)-induced leucocyte accumulation in rat lung microvasculature and protect lungs from damage and the effect of these drugs on chemotactic peptide (fMLP)-induced chemiluminescence of human polymorphonuclear leukocytes (PMNs). Animals were injected ip with NAC (27.6 mg/kg, n=8), ambroxol (70 mg/kg, n=8), combination NAC+ambroxol (n=8), or 1 ml buffer alone (n=8), once a day for 3 consecutive days. Then animals were injected with LPS (17 mg/kg), and killed 3 h later. In each of another four groups eight rats were used as a control, and received the same drug treatment but LPS was replaced with 0.9% NaCl. PMNs and macrophages (Ms) were counted in histologic slides of lung tissue. Using computer image analysis we measured the area of alveolar profiles. Luminol-enhanced chemiluminescence was measured in PMNs suspensions obtained from healthy volunteers. Chemiluminescence intensity was measured in resting and fMLP-stimulated cells, and compared between cells incubated with Amb, NAC or distilled water. We observed significant differences in the number of PMNs and Ms, alveolar profile area between control and LPS-treated animals (P<0.01). PMNs and Ms were numerous in lungs of LPS-administered animals (PMNs: Median (M)=137.5 per 6 high power fields range (r)=54.0; Ms: M=123.0 r=11.0), less numerous in ambroxol-treated group (PMNs: M=101.5 r=32.0 and Ms:53.5 r=36.0), not abundant in NAC (PMNs:M=56.0 r=28.0 and Ms:M=20.5 r=13.0) and in NAC+ambroxol treated rats (PMNs:M=53.5 r=21.0 and Ms:M=29.0 r=9.0), and rare in LPS+drugs-untreated control group (PMNs:M=40.5 r=19.0 and Ms:M=18.5 r=15.0). Chemiluminescence assay revealed that 100 micro;M ambroxol stimulated fMLP-induced PMNs chemiluminescence and NAC of the same concentration had no significant effect. CONCLUSION: In our experiment we showed that pretreatment with NAC and ambroxol may inhibit phagocyte influx to rat lung and may protect it from damage. We also revealed that NAC at dose 27.6 mg/kg has stronger protective properties than ambroxol at dose 70 mg/kg and this may result from enhancing effect of ambroxol on fMLP-provoked PMNs chemiluminescence.