RAGE upregulation and nuclear factor-kappaB activation associated with ageing rat cardiomyocyte dysfunction

Evidence suggests that ageing is a major risk factor for cardiac dysfunction. Interactions between advanced glycation endproducts (AGEs) and the receptor for AGEs (RAGE) are known to cause chronic cellular activation, including activation of nuclear factor-kappaB (NF-kappaB), which has been implicated as a causal factor in the ageing process. To assess whether cardiomyocyte contractile function and the interaction of AGEs with RAGE in the heart are altered in ageing, 25- and 2-month-old male rats were compared. Mechanical properties were assessed in ventricular myocytes using an edge-detection system, including peak twitch amplitude (PTA), time-to-PTA (TPS), time-to-75% relengthening (TR75) and maximal velocity of shortening/relengthening (+/-dL/dt) in ventricular myocytes. AGEs were detected by using a fluorescence assay. The expression of RAGE and NF-kappaB was assessed through a Western blot analysis. Compared with young myocytes, aged myocytes displayed a prolonged TR75 at 1 Hz. With increasing stimulus frequency (from 2 to 4 Hz), aged myocytes' PTA was significantly reduced relative to young myocytes. Aged rat hearts displayed high level of AGEs, RAGE upregulation and NF-kappaB activation. These findings demonstrate impaired cardiomyocyte relaxation and reduced tolerance to increased stimulus frequency in aged rats, which might be associated with enhanced AGEs, RAGE expression, and NF-kappaB activation.