Oxidative damage to DNA has been associated with neurodegenerative diseases. Developmental exposure to lead (Pb) has been shown to elevate the Alzheimer's disease (AD) related beta-amyloid peptide (Abeta), which is known to generate reactive oxygen species in the aging brain. This study measures the lifetime cerebral 8-hydroxy-2'-deoxyguanosine (oxo8dG) levels and the activity of the DNA repair enzyme 8-oxoguanine DNA glycosylase (Ogg1) in rats developmentally exposed to Pb. Oxo8dG was transiently modulated early in life (Postnatal day 5), but was later elevated 20 months after exposure to Pb had ceased, while Ogg1 activity was not altered. Furthermore, an age-dependent loss in the inverse correlation between Ogg1 activity and oxo8dG accumulation was observed. The effect of Pb on oxo8dG levels did not occur if animals were exposed to Pb in old age. These increases in DNA damage occurred in the absence of any Pb-induced changes in copper/zinc-superoxide dismutase (SOD1), manganese-SOD (SOD2), and reduced-form glutathion (GSH). These data suggest that oxidative damage and neurodegeneration in the aging brain could be impacted by the developmental disturbances.

Oncostatin M (OSM) is an interleukin-6 (IL-6) family cytokine that has been implicated in a number of biological processes including inflammation, hematopoiesis, immune responses, development, and bone homeostasis. Recent evidence suggests that OSM may promote breast tumor invasion and metastasis. We investigated the role of OSM in the formation of bone metastases in vivo using the 4T1.2 mouse mammary tumor model in which OSM expression was knocked down using shRNA (4T1.2-OSM). 4T1.2-OSM cells were injected orthotopically into Balb/c mice, resulting in a greater than 97% decrease in spontaneous metastasis to bone compared to control cells. Intratibial injection of these same 4T1.2-OSM cells also dramatically reduced the osteolytic destruction of trabecular bone volume compared to control cells. Furthermore, in a tumor resection model, mice bearing 4T1.2-OSM tumors showed an increase in survival by a median of 10 days. To investigate the specific cellular mechanisms important for OSM-induced osteolytic metastasis to bone, an in vitro model was developed using the RAW 264.7 preosteoclast cell line co-cultured with 4T1.2 mouse mammary tumor cells. Treatment of co-cultures with OSM resulted in a 3-fold induction of osteoclastogenesis using the TRAP assay. We identified several tumor cell-induced factors including vascular endothelial growth factor, IL-6, and a previously uncharacterized OSM-regulated bone metastasis factor, amphiregulin (AREG), which increased osteoclast differentiation by 4.5-fold. In addition, pretreatment of co-cultures with an anti-AREG neutralizing antibody completely reversed OSM-induced osteoclastogenesis. Our results suggest that one mechanism for OSM-induced osteoclast differentiation is via an AREG autocrine loop, resulting in decreased osteoprotegerin secretion by the 4T1.2 cells. These data provide evidence that OSM might be an important therapeutic target for the prevention of breast cancer metastasis to bone.

The community members of Libby, MT, have experienced significant asbestos exposure and developed numerous asbestos-related diseases including fibrosis and lung cancer due to an asbestos-contaminated vermiculite mine near the community. The form of asbestos in the contaminated vermiculite has been characterized in the amphibole family of fibers. However, the pathogenic effects of these fibers have not been previously characterized. The purpose of this study is to determine the cellular consequences of Libby amphibole exposure in macrophages compared to another well-characterized amphibole fiber; crocidolite asbestos. Our results indicate that Libby asbestos fibers are internalized by macrophages and localize to the cytoplasm and cytoplasmic vacuoles similar to crocidolite fibers. Libby asbestos fiber internalization generates a significant increase in intracellular reactive oxygen species (ROS) as determined by dichlorofluorescein diacetate and dihydroethidine fluorescence indicating that the superoxide anion is the major contributing ROS generated by Libby asbestos. Elevated superoxide levels in macrophages exposed to Libby asbestos coincide with a significant suppression of total superoxide dismutase activity. Both Libby and crocidolite asbestos generate oxidative stress in exposed macrophages by decreasing intracellular glutathione levels. Interestingly crocidolite asbestos, but not Libby asbestos, induces significant DNA damage in macrophages. This study provides evidence that the difference in the level of DNA damage observed between Libby and crocidolite asbestos may be a combined consequence of the distinct chemical compositions of each fiber as well as the activation of separate cellular pathways during asbestos exposure.