RESUMEN
OBJECTIVES: Through the hexosamine biosynthetic pathway (HBP) proteins are modified by O-linked-ß-N-acetylglucosamine (O-GlcNAc), which acts as a stress sensor. Augmentation of O-GlcNAc confers cardioprotection against ischemia- reperfusion injury, but its role in ischemic preconditioning (IPC) is unknown. Azaserine and alloxan are unspecific blockers of the HBP and have been used to block the cardioprotective effects of O-GlcNAc. We hypothesized that IPC reduces infarct size and increases O-GlcNAc levels in hearts subjected to ischemia-reperfusion injury, and that these effects could be blocked by azaserine and alloxan. DESIGN: Isolated rat hearts subjected to 40 min global ischemia and 120 min reperfusion were randomized to control, IPC, IPC + azaserine or alloxan, or control + azaserine or alloxan. The effects on infarct size, hemodynamic recovery, myocardial O-GlcNAc levels, and HBP enzyme activities were determined. RESULTS: IPC reduced infarct size, increased O-GlcNAc levels, O-GlcNAc-transferase levels, and O-GlcNAc-transferase activity. Azaserine and alloxan did not block the effect of IPC on O-GlcNAc levels and O-GlcNAc-transferase activity. CONCLUSIONS: IPC increased O-GlcNAc levels though increased O-GlcNAc-transferase expression and activity. Azaserine and alloxan failed to block these effects presumably due to poor specificity and sensitivity of the blockers, and IPC-mediated cardioprotection may therefore still be dependent on O-GlcNAc.
Asunto(s)
Acetilglucosamina/metabolismo , Precondicionamiento Isquémico Miocárdico , Infarto del Miocardio/prevención & control , Daño por Reperfusión Miocárdica/prevención & control , Miocardio/metabolismo , Aloxano/farmacología , Animales , Azaserina/farmacología , Modelos Animales de Enfermedad , Glicosilación , Hemodinámica , Masculino , Infarto del Miocardio/metabolismo , Infarto del Miocardio/patología , Infarto del Miocardio/fisiopatología , Daño por Reperfusión Miocárdica/metabolismo , Daño por Reperfusión Miocárdica/patología , Daño por Reperfusión Miocárdica/fisiopatología , Miocardio/patología , N-Acetilglucosaminiltransferasas/metabolismo , Ratas , Ratas Wistar , Recuperación de la Función , Factores de Tiempo , Regulación hacia ArribaRESUMEN
beta-O-linked N-acetylglucosamine (O-GlcNAc) is posttranslationally added to serine and threonine residues of many nuclear and cytoplasmic proteins found in metazoans. This modification is dynamic and responsive to numerous stimuli and conditions, suggesting an important role in many regulatory pathways. Moreover, the O-GlcNAc modification seems to compete with phosphorylation for sites of attachment, indicating a reciprocal relationship with phosphorylation. This chapter includes protocols for: (1) identifying the O-GlcNAc modification on proteins through immunoblotting, lectin affinity chromatography, and galactosyltransferase labeling; and (2) identifying and enriching for the sites of attachment using the mass spectrometry-based beta-elimination followed by Michael addition with dithiothreitol (BEMAD) technique.