Inhibition of nitric oxide aggravates pancreatic mitocondrial dysfunction during endotoxemia

Abstract

Pancreas has been described to be early affected in endotoxemia. As mitochondria are the main source of ATP, it is essential to maintain mitochondrial bioenergetics during recovery from pancreatic cellular, tissue and organic damage in this syndrome. Moreover, high systemic NO levels observed during endotoxemia could be involved in pancreatic tissue damage, as well as initiating cellular recovery processes such as autophagy. The aim of this project was to analyze the relationship between the severity of the systemic inflammatory insult and pancreatic mitochondrial dysfunction during endotoxemia, focusing on NO as a possible damage modulator. Female Sprague Dawley rats (45 days) were i.p. injected with: vehicle (control); LPS 0.5 mg/kg (LPS 0.5) and LPS 8 mg/kg (LPS 8). Co-treatment with i.p. L-NAME 20 mg/kg was performed in all experimental groups. Blood NO levels (by EPR), as well as plasma nitrate/nitrite content increased 4-fold (LPS 0.5) and 7-fold (LPS 8) compared to control group (p<0.05). Plasma TNF-α and IL-6 levels increase was related to the severity of endotoxemia. Pancreatic mitochondrial function was evaluated by mitochondrial oxygen consumption, ATP production and mitochondrial complex activities. ATP production was found significantly decreased (30%) in both LPS-treatments (control value: 70.4 ± 5 nmol ATP/min mg protein, p <0.05). L-NAME co-treatment showed decreased NO markers without influencing the levels of TNF-α and IL-6. However, L-NAME co-treatment significantly worsened mitochondrial function in all parameters studied. Our results show that the severity of the endotoxemic process is correlated to both blood NO levels and pancreatic mitochondrial dysfunction. In addition, they also suggest that NO is necessary to partially preserve pancreatic mitochondrial function in these pathologies.