Protective role of glucose‐6‐phosphate dehydrogenase activity in the metabolic response of C6 rat glioma cells to polyunsaturated fatty acid exposure

Abstract

Polyunsaturated fatty acids (PUFAs) can influence tumor growth and migration, both in vitro and in vivo. The PUFA gamma-linolenic acid (GLA) has been reported to improve the poor prognosis associated with human gliomas, although its effects at sublethal concentrations on residual cells postsurgery are poorly understood. The study investigated the effects sublethal PUFA doses (90 or 150 microM) may have on rat C6 glioma cell energy metabolism, since an adequate energy supply is essential for cell proliferation, migration, and apoptosis. Of note was the identification of mitochondrial heterogeneity in relation to the mitochondrial membrane potential (MMP), which has been suggested but unproven in previous studies. GLA and eicosapentaenoic acid (EPA) caused significant changes in cellular fatty acid composition and increased the percentage of cells with a low MMP after a 96-h exposure period. The presence of PUFAs inhibited C6 cell proliferation and migration, although apoptosis was not induced. The protein expression and activity of glucose-6-phosphate dehydrogenase was increased after 96-h incubation with 90 microM GLA and EPA and would allow redox regulation through increased NADPH production, permitting the maintenance of adequate intracellular reduced glutathione concentrations and limiting rates of lipid peroxidation and reactive oxygen species generation. Neither NADP(+)-isocitrate dehydrogenase nor NADP(+)-malate dehydrogenase activity responded to PUFAs, suggesting it is glucose-6-phosphate dehydrogenase that is the principal source of NADPH in C6 cells. These data compliment studies showing that higher concentrations of GLA induced glioma cell death and tumor regression and suggest that GLA treatment could be useful for the inhibition of residual cell proliferation and migration after surgical removal of the tumor mass.

The novel ruthenium—γ‐linolenic complex [Ru2(aGLA)4Cl] inhibits C6 rat glioma cell proliferation and induces changes in mitochondrial membrane potential, increased reactive oxygen species generation and apoptosis in vitro

“…[10][11][12][13][14][15] The mechanisms of action of GLA include altered energy and lipid metabolism, reactive oxygen species production and caspase activation, cytochrome c liberation and apoptosis. [16][17][18][19] In addition, GLA's effects are selective to tumour cells sparing normal astrocytes and improving the radiotherapeutic response of tumours. [20][21] GLA has recently been shown to cause DNA damage and micronucleus formation in the C6 rat glioma cell in vitro.…”

Análise da expressão de proteínas envolvidas no controle do ciclo celular, apoptose, angiogênese, invasão e migração de células C6 in vitro e in vivo, após o tratamento com o ácido g-linolênico (GLA) e com um novo complexo dirutênico contendo Ibuprofeno (Ru-Ibp).

“…Considering that this cell line does not express COX2 under normal culture conditions (Fig. 3) or produce PGE 2 [48] these effects must be through a COX2-independent mechanism.…”

Análise comparativa das distribuições espaciais de moléculas envolvidas na migração e invasão de um tumor cerebral de rato in vivo.

“…Este evento levaria à degradação e remodelagem da MEC que são indispensáveis ao fenótipo invasivo dos tumores gliais (WEI et al, 1996;BELLAIL et al, 2004 (LOKESHWAR et al, 1994). Essa glicoproteína também pode ligar-se a FN, LN, VN, colágeno e condroitin sulfato (RANUNCOLO et al, 2002). O CD44 pode ser encontrado na sua forma padrão (CD44s) ou na forma variante (CD44v), cuja expressão está relacionada com a progressão neoplásica.…”

“…A figura 14 mostra as principais vias de sinalização mediadas por CD44. (RANUNCOLO et al 2002;ARIZA et al, 1995;LI et al, 1993a). Knüpfer et al (1999) (NAGY et al, 1995;TURLEY et al,1994;TURLEY et al,1993;AKIYAMA et al, 2001 A super-expressão de MMPs foi relatada em diversas neoplasias e o papel dessas enzimas no metabolismo tumoral já é um consenso na literatura.…”

“…Em vasos do hemisfério contralateral (hemisfério cerebral que não recebeu a injeção de células C6) não se observou a expressão de RHAMM em células associadas a vasos, o que indica que aquelas observadas nos vasos peritumorais poderiam ser células C6 infiltrativas. RANUNCOLO et al, 2002;ARIZA et al, 1995;LI et al, 1993A).…”