Distribution and expression of soluble epoxide hydrolase in human brain - PubMed (original) (raw)

Distribution and expression of soluble epoxide hydrolase in human brain

Priyanka Sura et al. J Histochem Cytochem. 2008 Jun.

Abstract

Epoxyeicosatrienoic acids (EETs) are cytochrome P450 metabolites of arachidonic acid, which function in the brain to regulate cerebral blood flow and protect against ischemic brain injury. EETs are converted by soluble epoxide hydrolase (sEH) to the corresponding inactive diol metabolites. Previous animal studies have indicated that sEH gene deletion or treatment with sEH inhibitors results in increased levels of EETs and protection against stroke-induced brain damage. To begin elucidating the underlying mechanism for these effects, we sought to determine the distribution, expression, and activity of sEH in human brain samples obtained from patients with no neurological changes/pathologies. Immunohistochemical analyses showed the distribution of sEH mainly in the neuronal cell bodies, oligodendrocytes, and scattered astrocytes. Surprisingly, in the choroid plexus, sEH was found to be highly expressed in ependymal cells. Vascular localization of sEH was evident in several regions, where it was highly expressed in the smooth muscles of the arterioles. Western blot analysis and enzyme assays confirmed the presence of sEH in the normal brain. Our results indicate differential localization of sEH in the human brain, thus suggestive of an essential role for this enzyme in the central nervous system. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.

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Figures

Figure 1

Figure 1

Soluble epoxide hydrolase (sEH) immunoreactivity (brown) in sections of human brain. (A) Occipital lobe, negative control with no primary antibody. No immunoreactivity was present in the neurons (arrows). (B) Occipital lobe. There is diffuse sEH immunoreactivity of the neuronal cell bodies (arrows). (C) Parietal lobe. sEH immunoreactivity was observed in scattered glial cells (arrows). (D) Parietal lobe, double immunolabeling for sEH (brown) and GFAP (blue). Note there is colocalization of blue over brown (arrows) and some glial cells with sEH immunoreactivity alone (arrowheads). (E) White matter, immunoreactivity of sEH in the white matter, neuropil (arrowhead), and occasional staining of glial cells (arrows). (F) Substantia nigra. sEH immunoreactivity was observed in glial cells (arrows). Note the presence of dark brown granular neuromelanin in the cytoplasm of neurons (arrowheads). (G) Pituitary. There is marked sEH immunoreactivity in acidophils and chromophobes (arrows). However, there is no staining in basophils (arrowheads). (H) Cerebellum. There is scattered sEH immunoreactivity in the granular cell layer and molecular cell layer glia (arrows). Bar = 120 μm.

Figure 2

Figure 2

sEH immunoreactivity (brown) in medulla, spinal cord, meningeal blood vessels, and choroid plexus. (A) Medulla oblongata, immunoreactivity of sEH in the neuronal cell bodies of medulla (arrows). (B) Spinal cord. sEH immunoreactivity was observed in neuronal cell bodies of spinal cord (arrows). (C) Meningeal blood vessels. There is intense immunoreactivity of the endothelial cells and the smooth muscles of arteries and arterioles (arrows). (D) Choroid plexus. The ependymal cells (arrows) lining the choroid plexus are immunoreactive. Bar = 120 μm.

Figure 3

Figure 3

Western blot analysis of sEH expression in the human brain. There is sEH expression in the human frontal lobe, occipital lobe, parietal lobe, temporal lobe, and thalamus. His-tagged purified human sEH (hsEH) and human liver are used as positive controls. β-actin was used as a loading control for brain tissue samples.

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