Utilizing Nicorandil in the Protection of Neuronal Cells from Hypoxic Injury. A Basic Science Model.
Cenea Kemp, Linling Cheng, Christian Ghincea, Zihan Feng, Joseph Cleveland, David Fullerton, Muhammad Aftab, Thomas B. Reece
University of Colorado, Denver, Colorado, United States
Objective: Spinal cord ischemia during repair of aortic pathology remains at the forefront of the aortic surgeon’s mind given the risk of permanent paraplegia. Many surgical adjuncts have been developed to reduce this risk; various pharmacologic adjuncts have been suggested to do the same but there is not consistent use of a single agent. Nicorandil is a mitochondrial potassium ATP channel activator leading to its arterial vasodilator properties but also functions in venodilation via donation of the nitrate group contained within its chemical structure. Nicorandil has previously been shown to provide cardiac and neuronal protection. The aim of this study is to evaluate the effectiveness of nicorandil in protecting neuronal cells from a hypoxic injury meant to mimic the ischemic insult to the spinal cord during aortic surgery.
Methods: This study utilized a mouse neuronal cell line, known as HT-22 cells. The HT-22 cells were exposed to hypoxic conditions via a chamber set to 1% oxygen and 5% CO2; during the exposure, the cells were maintained in an oxygen-glucose deprivation (OGD) medium, initially without the addition of nicorandil, to further simulate spinal cord ischemia. The HT-22 cells were kept in the hypoxia chamber for various periods of time until an ideal timepoint was selected. Once the timepoint was selected, nicorandil was added to the OGD medium to assess for neuronal cell protection. The nicorandil was added at various concentrations to find the most effective dose. To ensure the mechanism of action of nicorandil on the K-ATP channel, 5-HD which functions to block mitochondrial ATP channels, was added to assess whether the neuroprotection of nicorandil would be maintained. Following cell treatment, the HT-22 cells were re-perfused and cell viability was assessed utilizing an MTS assay.
Results: An optimal time point of 24 hours in the hypoxia chamber was selected after multiple time points were evaluated. The 24-hour time point was selected as it achieved an adequate level of neuronal cell death of ~30% without overkill that might prevent cell recovery. The ideal concentration for nicorandil was determined to be 500uM. At this concentration, recovery of the HT-22 cell viability was consistently near 60% when compared to the control. At much higher concentrations, nicorandil was noted to be cytotoxic. With the introduction of the ATP channel blocker, 5-HD, the neuronal protective effects of nicorandil were lost.
Conclusions: Our study demonstrates a promising role for nicorandil in the use of neuroprotection during extensive aortic operations; these findings remain in line with our previous mouse model.
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