The period length of fibroblast circadian gene expression varies widely among human individuals.

Mammalian circadian behavior is governed by a central clock in the suprachiasmatic nucleus of the brain hypothalamus, and its intrinsic period length is believed to affect the phase of daily activities. Measurement of this period length, normally accomplished by prolonged subject observation, is difficult and costly in humans. Because a circadian clock similar to that of the suprachiasmatic nucleus is present in most cell types, we were able to engineer a lentiviral circadian reporter that permits characterization of circadian rhythms in single skin biopsies. Using it, we have determined the period lengths of 19 human individuals. The average value from all subjects, 24.5 h, closely matches average values for human circadian physiology obtained in studies in which circadian period was assessed in the absence of the confounding effects of light input and sleep-wake cycle feedback. Nevertheless, the distribution of period lengths measured from biopsies from different individuals was wider than those reported for circadian physiology. A similar trend was observed when comparing wheel-running behavior with fibroblast period length in mouse strains containing circadian gene disruptions. In mice, inter-individual differences in fibroblast period length correlated with the period of running-wheel activity; in humans, fibroblasts from different individuals showed widely variant circadian periods. Given its robustness, the presented procedure should permit quantitative trait mapping of human period length.

Glucocorticoids aggravate hyperoxia-induced lung injury through decreased nuclear factor-kappa B activity.

We previously reported that exposure of mice to hyperoxia is characterized by extensive lung cell necrosis and apoptosis, mild inflammatory response, and elevated circulating levels of corticosterone. Administration of hydroxycortisone acetate during hyperoxia aggravated lung injury. Using adrenalectomized (ADX) and sham-operated (sham) mice, we studied the role of the glucocorticoids in hyperoxia-induced lung injury. Lung damage was attenuated in ADX mice as measured by lung weight and protein and cell content in bronchoalveolar lavage and as seen by light microscopy. Mortality was delayed by 10 h. Nuclear factor-kappaB (NF-kappaB) activity was significantly decreased in lungs of sham mice exposed to hyperoxia but was preserved in ADX mice. There was a correlation between NF-kappaB activity in ADX mice and decreased levels of IkappaBalpha. In contrast, activator protein-1 activity increased similarly in both groups of mice. Levels of interleukin-6 (IL-6), a transcriptional target of NF-kappaB, were higher in bronchoalveolar lavage and serum of ADX than sham mice. However, the protective effect of ADX was not mediated by IL-6, because administration of recombinant human IL-6 to sham mice did not prevent lung damage. These results demonstrate that the adrenal response aggravates alveolar injury and is likely to be mediated by the decrease of NF-kappaB function involved in cell survival.