Selective inhibition of NADPH oxidase reverses the over contraction of diabetic rat aorta.

Abnormal vascular responsiveness in diabetes has been attributed to a number of changes in contractile pathways, affected in part by the overproduction of reactive oxygen species (ROS). It has been reported that NADPH oxidase (NOX) is increased in diabetic (streptozotocin treated; STZ) rat arteries; however the pharmacological agents used to inhibit NOX activity are known to be unsuitable for in vitro studies and have a high level of non-selectivity. Here we have used the highly selective NOX inhibitor VAS2870 in diabetic rat aorta and compared its effects with apocynin, SOD, and allopurinol on phenylephrine and U46619 induced contraction. Male Wistar rats were injected intraperitoneally with 65mg/kg STZ and development of diabetes was confirmed by testing blood glucose levels. Rats were killed by CO2 asphyxiation, and the thoracic aorta removed and mounted in an organ bath under a tension of 1g. Diabetic rat aortas exhibit a greatly increased response to phenylephrine, which was reduced to a level consistent with control rat aorta by 10(-5)M VAS2870 and 150U/ml SOD. Incubation with VAS2870 led to an increase in normal rat aorta contraction, but led to a significant reduction in phenylephrine and U46619 induced tone in diabetic rat aorta, which indicates that ROS in diabetic rats directly contributes to these contractile responses. Apocynin and allopurinol had no effect on contraction in diabetic or normal rat aorta. This data is the first to show that selective inhibition of NOX reduces diabetic arterial contraction in direct comparison with inhibition of other known contributors of ROS.

A method for characterising cell death in vitro by combining propidium iodide staining with immunohistochemistry.

The fluorescent exclusion dye propidium iodide (PI) is widely used as a vital dye in tissue culture systems and labels the nucleus in dying cells which lack an intact plasma membrane. We have developed a method, which allows the preservation of the PI signal in paraformaldehyde-fixed tissue, enabling subsequent immunohistochemical characterisation of labelled cells. We have tested this method in a model of ischemia based on oxygen and glucose deprivation in organotypic hippocampal slice cultures, in combination with immunocytochemical detection of calpain-I mediated spectrin breakdown products (BDPs). Using confocal laser microscopy it was possible to correlate at the single cell level which cells were PI positive and which cells expressed BDPs. This method can also be used with other immunocytochemical markers to determine the phenotype of cells, which accumulate PI in vitro. By fixing tissue at different times after insults, it is possible to obtain a 'snapshot' of viability at any time during the experimental protocol and subsequently characterise those cells which had accumulated PI at the time of fixation. The technique may also prove useful in characterising cell death in other in vitro and in vivo systems.