Activation of NF-kappaB pathway in Duchenne muscular dystrophy: relation to age

Muscle degeneration in Duchenne muscular dystrophy (DMD) is exacerbated by increased oxidative stress and the endogenous inflammatory response, with a key role played by nuclear factor kappa-B (NF-kappaB) and other related factors such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-6. However the time course of expression of these molecules and the relation with the amount of necrosis and regeneration have never been investigated. The expression of NF-kappaB, the cytokines TNF-alpha and IL-6 and the antioxidant enzyme glutathione peroxidase (GPx) was studied in muscle samples from 14 patients with DMD aged between 2 and 9 years. Moreover a quantitative morphological evaluation was performed to evaluate necrotic and regenerative areas. The highest percentage of necrosis was revealed within 4 years of age, with a significant negative correlation with age (p < 0.003), which paralleled to a significant decrement of regenerating area (p < 0.0004). We reported the novel observation that the number of NF-kappaB positive fibers and the NF-kappaB DNA-binding activity, revealed by EMSA, are high at two years of life and significantly decline with age (p < 0.0005 and p < 0.0001). The expression of TNF-alpha, IL-6 and GPx was upregulated in DMD muscles compared to controls and significantly increased with age on real-time PCR analysis (p < 0.0002; p < 0.0005; p < 0.03 respectively) and ELISA (p < 0.002; p < 0.02; p < 0.0001 respectively). Since anti-inflammatory and anti-oxidant drugs are nowadays being translated to clinical studies in DMD, the reported insights on these therapeutic targets appear relevant. Further studies on the interactions among these pathways in different DMD phases and on the response of these cascades to treatments currently under investigation are needed to better elucidate their relevance as therapeutic targets.