Effect of the branched-chain alpha-keto acids accumulating in maple syrup urine disease on S100B release from glial cells.
Accumulation of the branched-chain alpha-keto acids (BCKA), alpha-ketoisocaproic acid (KIC), alpha-keto-beta-methylvaleric acid (KMV) and alpha-ketoisovaleric acid (KIV) and their respective branched-chain alpha-amino acids (BCAA) occurs in tissues and biological fluids of patients affected by the neurometabolic disorder maple syrup urine disease (MSUD). The objective of this study was to verify the effect of the BCKA on S100B release from C6 glioma cells. The cells were exposed to 1, 5 or 10 mM BCKA for different periods and the S100B release was measured afterwards. The results indicated that KIC and KIV, but not KMV, significantly enhanced S100B liberation after 6 h of exposure. Furthermore, the stimulatory effect of the BCKA on S100B release was prevented by coincubation with the energetic substrate creatine and with the N-nitro-l-arginine methyl ester (l-NAME), a nitric oxide synthase inhibitor, indicating that energy deficit and nitric oxide (NO) were probably involved in this effect. Furthermore, the increase of S100B release was prevented by preincubation with the protein kinase inhibitors KN-93 and H-89, indicating that KIC and KIV altered Ca2+/calmodulin (PKCaMII)- and cAMP (PKA)-dependent protein kinases activities, respectively. In contrast, other antioxidants such as glutathione (GSH) and trolox (soluble vitamin E) were not able to prevent KIC- and KIV-induced increase of S100B liberation, suggesting that the alteration of S100B release caused by the BCKA is not mediated by oxidation of sulfydryl or other essential groups of the enzyme as well as by lipid peroxyl radicals. Considering the importance of S100B for brain regulation, it is conceivable that enhanced liberation of this protein by increased levels of BCKA may contribute to the neurodegeneration characteristic of MSUD patients.
Funchal
Cláudia
C
Universidade Federal do Rio Grande do Sul, Instituto de Ciências Básicas da Saúde, Departamento de Bioquímica, Rua Ramiro Barcelos 2600 anexo, 90035-003 Porto Alegre, RS, Brazil. csfunchal@yahoo.com.br
Tramontina
Francine
F
Quincozes dos Santos
André
A
Fraga de Souza
Daniela
D
Gonçalves
Carlos Alberto
CA
Pessoa-Pureur
Regina
R
Wajner
Moacir
M
D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D003401:Creatine / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007651:Keto Acids / Q000378:metabolism* / Q000494:pharmacology; D008375:Maple Syrup Urine Disease / Q000150:complications* / Q000378:metabolism* / Q000503:physiopathology; D009410:Nerve Degeneration / Q000209:etiology* / Q000378:metabolism* / Q000503:physiopathology; D009414:Nerve Growth Factors / Q000378:metabolism*; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D011494:Protein Kinases / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000378:metabolism*
D004791:Enzyme Inhibitors; D007651:Keto Acids; D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579158:S100b protein, rat; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D011494:Protein Kinases; D003401:Creatine