[Frontiers in Bioscience E3, 81-88, January 1, 2011]

Inhibiting the Na+/H+ exchanger reduces reperfusion injury: a small animal MRI study

Peter Ferrazzano1, 5, Yejie Shi2, 4, 5, Namratta Manhas2, 5, Yanping Wang2, Beth Hutchinson3, 4, Xinzhi Chen2, 4, Vishal Chanana5, Josiah Gerdts2, Mary Elizabeth Meyerand3, 4, Dandan Sun2, 4, 5

1Department of Pediatrics, University of Wisconsin, Madison, WI 53792, 2 Department of Neurological Surgery, University of Wisconsin, Madison, WI 53792, 3Department of Medical Physics, University of Wisconsin, Madison, WI 53792, 4Neuroscience Training Program, University of Wisconsin, Madison, WI 53792, 5Waisman Center, University of Wisconsin, Madison, WI 53792

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Materials and methods
3.1. Animal preparation
3.2. Focal ischemic model
3.3. Magnetic resonance imaging (MRI)
3.4. Calculation of infarct volume
3.5. Pure cortical neuron cultures
3.6. Oxygen and glucose deprivation (OGD) treatment
3.7. Neuronal mortality measurement
3.8. Statistics
4. Results
4.1. Correlation of T2 images with TTC staining
4.2. NHE-1+/- mice demonstrate smaller infarct on MRI
4.3. Inhibition of NHE-1 with HOE642 (Cariporide) is protective when administered prior to reperfusion
4.4. Inhibition of NHE-1 with HOE642 remains protective when administered during early reperfusion
5. Discussion
5.1. Quantification of ischemic brain lesion with MRI
5.2. Neuroprotection mediated by HOE642
6. Acknowledgements
7. References

1. ABSTRACT

We used magnetic resonance imaging (MRI) to assess the efficacy of Na+/H+ exchanger isoform 1 (NHE-1) inhibition following cerebral ischemia. Transient focal cerebral ischemia was induced in wild-type controls (NHE-1+/+), NHE-1 genetic knockdown mice (NHE-1+/-), and NHE-1+/+ mice treated with the selective NHE-1 inhibitor HOE642. Diffusion weighted imaging (DWI) revealed a brain lesion as early as 1 hour following reperfusion and illustrated significant protection in NHE-1+/- mice (16.2 +/- 7.9 mm3 in NHE-1+/- mice vs. 47.5 +/- 16.6 mm3 in NHE-1+/+ mice). Knockdown of NHE-1 showed significantly smaller infarct at 72 hours on T2 imaging (21.2 +/- 12.6 mm3 in NHE-1+/- mice vs. 64.6 +/- 2.5 mm3 in NHE-1+/+ mice). Administration of HOE642 prior to reperfusion or during early reperfusion reduced ischemic damage. Thus, high resolution T2 images can be used for consistent and precise calculation of lesion volumes, while changes of DWI are a sensitive early marker of ischemic injury. The results of this study demonstrate the therapeutic potential for inhibition of NHE-1 in treating cerebral ischemia.