O sistema NADPH oxidase de neutrófilos e a formação de AGES (produtos finais de glicação avançada) em ratos diabéticos

Abstract

Chronic hyperglycemia observed in diabetes disease leads to the advanced glycation end products (AGEs) formation, which are able to damage the patient organs, especially the kidney. Some AGEs formation reactions may also generate reactive oxygen species (ROS) and they are able to compete with oxidative stress and structural and functional macromolecules damages. Neutrophils are immune cells capable of expressing great amount of important ROS generator enzymes such as NADPH oxidase just after inflammatory stimuli. There are still questions about the relationship between the neutrophil NADPH oxidase system and AGEs despite the information that in vivo AGEs formation may involve neutrophils. The present study aims to contribute to the understanding of NADPH oxidase role and its ROS generation in AGEs formation and what is the impact of these products formation in renal function of rat model. Our experimental diabetes model was reached by alloxan i.p. injection in rats. These animals were divided in five groups: control, diabetic, diabetic treated with aminoguanidine (AG), diabetic treated with apocynin (AP) and diabetic treated with apocynin and aminoguanidine (AG + AP). AG is an AGEs formation inhibitor, and AP is a NADPH oxidase inhibitor. The inhibitors compounds or the vehicle (water) were administered by gavage for 50 days after DM confirmation. ROS formation reflects the NADPH oxidase activity and it was measured by chemiluminescence assay and by cytochrome C reduction in peritoneal neutrophils. The expression of NADPH oxidase p47phox and p67phox subunits was assessed by immunofluorescence. Circulating AGEs were analyzed by fluorescence and the renal function was evaluated by serum urea and creatinin concentration and by kidney histological sections. Our results showed that AP treatment decreased ROS generation in both control and diabetic groups, but did not affect the process of AGEs formation. This may indicate that in our experimental model there is no interrelation between the neutrophil NADPH oxidase system and the AGEs formation. It was also observed that the AP attenuated glomerulonephritis in diabetic mice. AG, at the administered dose and time, 100mg/Kg for 50 dias, improved glycemic control, prevented the AGEs formation and prevented glomerular damage. Furthermore, AG treatment increased the NADPH oxidase activity and its p47phox and p67phox cytosolic subunits expression. We are not able to confirm if the increased activity and expression of NADPH oxidase were caused by the AGEs decrease in our system or by an isolated effect of aminoguanidine not yet described. Understanding the NADPH oxidase role in experimental diabetes could improve the knowledge about the persistent inflammatory process that occurs due to these products accumulation during the disease complication, allowing a better clinical approach and treatment of these patients.