Homocysteine potentiates beta-amyloid neurotoxicity: role of oxidative stress.

The cause of neuronal degeneration in Alzheimer's disease (AD) has not been completely clarified, but has been variously attributed to increases in cytosolic calcium and increased generation of reactive oxygen species (ROS). The beta-amyloid fragment (Abeta) of the amyloid precursor protein induces calcium influx, ROS and apoptosis. Homocysteine (HC), a neurotoxic amino acid that accumulates in neurological disorders including AD, also induces calcium influx and oxidative stress, which has been shown to enhance neuronal excitotoxicity, leading to apoptosis. We examined the possibility that HC may augment Abeta neurotoxicity. HC potentiated the Abeta-induced increase in cytosolic calcium and apoptosis in differentiated SH-SY-5Y human neuroblastoma cells. The antioxidant vitamin E and the glutathione precursor N-acetyl-L-cysteine blocked apoptosis following cotreatment with HC and Abeta, indicating that apoptosis is associated with oxidative stress. These findings underscore that moderate accumulation of excitotoxins at concentrations that alone do not appear to initiate adverse events may enhance the effects of other factors known to cause neurodegeneration such as Abeta.

A pilot study of low-dose erythromycin in bronchiectasis.

Patients with bronchiectasis suffer from sputum production, recurrent exacerbations, and progressive airway destruction. Erythromycin is effective in diffuse panbronchiolitis, another suppurative airway disorder, although its efficacy is unknown in idiopathic bronchiectasis. A double-blind placebo-controlled study was therefore conducted to evaluate the effects of 8-week administration of low dose erythromycin (500 mg b.i.d.) in steady-state idiopathic bronchiectasis. Patients in the erythromycin group (n=11, 8 female, mean age 50+/-15 yrs), but not the placebo group (n=10, 8 female, mean age 59+/-16 yrs) had significantly improved forced expiratory volume in one second, forced vital capacity and 24-h sputum volume after 8 weeks (p<0.05). There was no parallel improvement in sputum pathogens, leukocytes, interleukin (IL)-1alpha and IL-8, tumour necrosis factor-alpha, or leukotriene B4. The results of this pilot study show that low-dose erythromycin improves lung function and sputum volume in bronchiectasis. Further studies are indicated to evaluate the efficacy of long-term erythromycin therapy in bronchiectasis.