Differential inflammatory responses in aging and disease: TNF-alpha and IL-6 as possible biomarkers. 
Oxidative stress has been reported to increase during aging and conditions of hypoxia.  Although low oxygen saturation has a key role in the development of several age-related diseases, the underlying mechanisms are still unknown.  We analyzed the relationship between aging and hypoxia by examining oxidative stress and inflammation-related cytokines.  We collected blood samples from three volunteer experimental groups, consisting of one group of normoxic middle-aged people and two groups of individuals older than 75 years, which comprised a subgroup of normoxic subjects and another with oxyhemoglobin saturation lower than 95% (hypoxic).  Our results showed a fall in antioxidant defenses in older people with hypoxia.  TNF-alpha, the first element in the cytokine cascade, was significantly increased in the aged population, implying that aging is accompanied by a gradual increase in this inflammatory biomarker.  IL-6 was not associated with aging, but it was highly elevated under hypoxia conditions in elderly subjects.  Thus, these parameters could be used as biological markers of different inflammatory processes triggered by oxidative stress induced by a decrease in antioxidant defenses in the elderly population, with TNF-alpha as an indicator of chronic processes, such as aging, and IL-6 as a marker for acute responses, such as hypoxia.