A small linear association was suggested. The slope of the regression line was significantly greater than zero, suggesting that as microglial cell body number increased, DG volume increased (slope = 0.000019 mm3; 95% C.L. 0.00000564–0.00003169 mm3; t28 = 6.12; p < 0.01; Y = 0.22 mm3 + (0.00019 mm3 × X); adj r2 = 0.20). Previous research suggested

that via diverse mechanisms Pb exposure promotes neuroimmune disruption, and perhaps chronic microglial activation and microglial proliferation (Kraft and Harry, 2011). Neuroimmune system changes following early chronic exposure to Pb and blood levels between 2 μg/dL and 20 μg/dL have rarely been examined. Hippocampus/DG regions have been implicated

in animal models (Azzaoui Navitoclax in vitro et al., check details 2009, Kasten-Jolly et al., 2012 and Leasure et al., 2008) and clinical studies of asymptomatic Pb exposed children (Canfield et al., 2003, Chiodo et al., 2004 and Lanphear et al., 2005). Thus, we compared neuroinflammatory markers in anterior (without hippocampus) and posterior (with hippocampus) brain sections; and we compared the volume and number of neuroimmune cells in the DG. We predicted dose-dependent changes in gene expression of neuroinflammatory biomarkers consistent with heightened microglial activation, and increased microglial mean cell body volume and number. Understanding whether dose–response relationships exist between Pb and outcome variables can be critical for

understanding the nature of possible mechanisms of action, and also for comparison in subsequent studies that aim to replicate and refine the current findings. We also measured DG volume to examine evidence of neurodegeneration. The range of blood Pb levels achieved in the 30 ppm exposure groups (study 1 = 2.86–6.78 μg/dL; study 2 = 2.48–4.65 μg/dL) replicated the blood Pb levels of approximately 65% of low-income children tested in our child Pb exposure studies (unpublished data). Significant differences between exposure groups on outcome variables were found, but were not suggestive of heightened microglial activation. Increased neuroinflammatory response in Pb exposed animals was discounted by the absence of group effects for five of six neuroinflammatory markers examined, check including TNF-α, IFN-γ, IL10, iNOS and HO-1. Only IL6 differed in Pb exposed animals, and a dose-dependent reduction was observed. Astrocytes absorb free-floating brain Pb; within astrocytes 78 kDa glucose-regulated protein (GRP78) sequesters Pb, a process which inactivates this chaperone protein (Lindahl et al., 1999) and results in decreased release of IL6 (White et al., 2007). IL6 serves neuroprotective and neuroadaptive functions (Gruol et al., 2011 and Inomata et al., 2003) thus reduced IL6 may suggest one source of increased neurotoxic vulnerability in Pb exposed animals.