Nitroglycerin and Iloprost Improve Mitochondrial Function in Colon Homogenate Without Altering the Barrier Integrity of Caco-2 Monolayers

Abstract

Locally applied nitroglycerin [nitric oxide (NO) donor] and iloprost (analog of prostacyclin PGI2) improve regional gastric oxygenation and nitroglycerin preserves gastric mucosal barrier integrity. This suggests direct effects of these substances on oxygenation and barrier function. The aim of this study was to analyze the effect of iloprost and nitroglycerin on intestinal mitochondrial function and on mucosal barrier function in vitro. Mitochondrial oxygen consumption (respirometry) was determined in colon homogenates from 16 healthy rats before (baseline) and 15 min after incubation with nitroglycerin (25 and 250 μg/ml) and iloprost (0.1 and 1 μg/ml). State 2 (substrate-dependent oxygen consumption) and state 3 respiration (ADP-dependent oxygen consumption) were assessed and ADP/O ratio (ADP added/oxygen consumed) for complex I and II were calculated. For permeability measurement we used the Caco-2 monolayer. Fluorescein sulfonic acid (FS) (200 μg/ml) and the drugs were administered into the apical compartment of the transwell chamber. After 48 h, FS translocation was assessed as basolateral/apical FS. Both concentrations of nitroglycerin and iloprost reduced state 3 by stimulation via both complexes. Iloprost increased ADP/O ratio after stimulation via both complexes at both concentrations. Nitroglycerin increased ADP/O ratio at the higher concentration (250 μg/ml) after stimulation via complex I and at the lower concentration (25 μg/ml) via complex II. Neither nitroglycerin nor iloprost influenced FS translocation. Iloprost and nitroglycerin reduce the maximal mitochondrial respiration and improve the efficacy of oxidative phosphorylation in colon homogenates. Both drugs have no direct influence on mucosal barrier integrity of Caco-2 monolayers.

Nitroglycerin as a radiosensitizer in non-small cell lung cancer: Results of a prospective imaging-based phase II trial

“…Blood pressure measurements at the time of scanning could have offered more information, but were not obtained. According to several investigators an alternative mechanism of action of nitroglycerin could be NO-mediated inhibition of mitochondrial oxygen consumption [23][24][25][26]. In a separate in vitro experiment (see supplements) we also didn't observe a reduced oxygen consumption rate upon exposure to human plasma levels of nitroglycerin or even 100,000 fold higher (Fig.…”

Topical Melatonin Improves Gastric Microcirculatory Oxygenation During Hemorrhagic Shock in Dogs but Does Not Alter Barrier Integrity of Caco-2 Monolayers

“…To separate potential direct effects of melatonin on barrier function from those mediated by improvement of microcirculation, we performed the analysis of the intestinal barrier function in vitro . We used Caco-2 cells grown on porous membranes as a model system of intact intestinal epithelium ( 16 ). These cells exert functional and anatomic similarities to absorptive intestinal enterocytes and hence this a well-established model to study intestinal permeability ( 17 ).…”

Pravastatin and Gemfibrozil Modulate Differently Hepatic and Colonic Mitochondrial Respiration in Tissue Homogenates from Healthy Rats

“…Liver and colon homogenates were prepared as described previously [23,24,25]. Briefly, liver tissue was placed in 4 °C cold isolation buffer, minced into 2–3-mm 3 pieces, rinsed twice in isolation buffer to remove traces of blood, and homogenized (Potter-Elvehjem, Pro Scientific, Swedesboro, NJ, USA, 5 strokes, 2000 rpm).…”

“…Mitochondrial oxygen consumption was measured as described previously [23,24,25]. Briefly, the measurement was performed at 30 °C using a Clark-type electrode (model 782, Strathkelvin instruments, Glasgow, Scotland).…”