Our previous studies have shown that 14,15‐epoxyeicosatrienoic acid (14,15‐EET) is a major product of arachidonic acid metabolism in astrocytes. The purpose of this study was to investigate cellular regulation of 14,15‐EET incorporation, distribution, and metabolism in primary cultures of rat brain cortical astrocytes. Incorporation of 14,15‐EET into astrocytes was lower (93,390 ± 11,121 dpm/5 × 106 cells) than incorporation of 8,9‐EET (226,500 ± 5,567 dpm/5 × 106 cells) and arachidonic acid (321,600 ± 1,200 dpm/5 × 106 cells). 14,15‐EET was distributed in the order neutral lipids and free fatty acids (solvent front) ≫ phosphatidylcholine (PC) > phosphatidylinositol (PI) > phosphatidylethanolamine. In contrast, 8,9‐EET and arachidonic acid were exclusively incorporated into PC. During incubation, astroglial epoxide hydrolase selectively metabolized 14,15‐EET, but not 8,9‐EET, to its vic‐diol. Although 4‐phenylchalcone oxide, a potent inhibitor of epoxide hydrolase, completely inhibited 14,15‐EET metabolism, a large amount of cell‐incorporated radioactivity remained as free 14,15‐EET. Long‐term exposure of astrocytes to 4β‐phorbol 12‐myristate 13‐acetate (4β‐PMA) resulted in a time‐dependent incorporation of 14,15‐EET into PI but not in control cells exposed to 4α‐phorbol 12,13‐didecanoate. PKC down‐regulation completely inhibited epoxide hydrolase metabolism of 14,15‐EET. Following recovery of down‐regulated PKC, 1 week after treatment with 4β‐PMA, astrocytes regained their normal pattern of low incorporation of 14,15‐EET. Protein kinase C (PKC) inhibition by staurosporine enhanced 14,15‐EET incorporation without affecting its metabolism to 14,15‐dihydroxyeicosatrienoic acid. Incorporation of 14,15‐EET by PKC‐down‐regulated cells was inhibited by thimerosal, a known inhibitor of fatty acyl‐CoA synthase. Our results suggest that the lower incorporation of 14,15‐EET into astroglial cells may be due to modulation of PKC‐mediated cellular mechanism(s).

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Glioblastoma multiforme (GBM), a standout among the most dangerous class of central nervous system (CNS) cancer, is most common and is an aggressive malignant brain tumor in adults. In spite of developments in modality therapy, it remains mostly incurable. Consequently, the need for novel systems, strategies, or therapeutic approaches for enhancing the assortment of active agents meant for GBM becomes an important criterion. Currently, cancer research focuses mainly on improving the treatment of GBM via diverse novel drug delivery systems. The treatment options at diagnosis are multimodal and include radiation therapy. Moreover, significant advances in understanding the molecular pathology of GBM and associated cell signaling pathways have opened opportunities for new therapies. Innovative treatment such as immunotherapy also gives hope for enhanced survival. The objective of this work was to collect and report the recent research findings to manage GBM. The present review includes existing novel drug delivery systems and therapies intended for managing GBM. Reported novel drug delivery systems and diverse therapies seem to be precise, secure, and relatively effective, which could lead to a new track for the obliteration of GBM.

No abstract

The microsomal epoxide hydrolase (mEH) and soluble epoxide hydrolase (sEH) enzymes exist in a variety of cells and tissues, including liver, kidney and testis. However, very little is known about brain epoxide hydrolases. Here we report the expression, localization and subcellular distribution of mEH and sEH in cultured neonatal rat cortical astrocytes by immunocytochemistry, subcellular fractionation, western blotting and radiometric enzyme assays. Our results showed a diffused immunofluorescence pattern for mEH, which co-localized with the astroglial cytoskeletal marker, glial fibrillary acidic protein (GFAP). The GFAP-positive cells also expressed sEH which was mainly localized in the cytoplasm especially in and around the nucleus. Western blot analyses, revealed a distinct protein band with a molecular mass of ~50 kDa, the signal intensity of which increased about 1.5-fold in the microsomal fraction over the whole cell lysate and other subcellular fractions. The polyclonal anti-human sEH rabbit serum recognized a protein band with a molecular mass similar to that of purified sEH protein (~62 kDa), and the signal intensity increased 1.7-fold in the 105,000×g supernatant fraction over the cell lysate. Although the corresponding mEH enzyme activities generally corroborated with the immunocytochemical and western blotting data a low sEH enzyme activity was detected especially in the total cell lysate and in the soluble fractions. These results suggest that rat brain cortical astrocytes differentially co-express mEH and sEH enzymes. The differential subcellular localization of mEH and sEH may play a role in the cerebrovascular functions that are known to be affected by brain-derived vasoactive epoxides.