Variability in bioreactivity linked to changes in size and zeta potential of diesel exhaust particles in human immune cells

Acting as fuel combustion catalysts to increase fuel economy, cerium dioxide (ceria, CeO(2)) nanoparticles have been used in Europe as diesel fuel additives (Envirox™). We attempted to examine the effects of particles emitted from a diesel engine burning either diesel (diesel exhaust particles, DEP) or diesel doped with various concentrations of CeO(2) (DEP-Env) on innate immune responses in THP-1 and primary human peripheral blood mononuclear cells (PBMC). Batches of DEP and DEP-Env were obtained on three separate occasions using identical collection and extraction protocols with the aim of determining the reproducibility of particles generated at different times. However, we observed significant differences in size and surface charge (zeta potential) of the DEP and DEP-Env across the three batches. We also observed that exposure of THP-1 cells and PBMC to identical concentrations of DEP and DEP-Env from the three batches resulted in statistically significant differences in bioreactivity as determined by IL-1β, TNF-α, IL-6, IFN-γ, and IL-12p40 mRNA (by qRT-PCR) and protein expression (by ELISPOT assays). Importantly, bioreactivity was noted in very tight ranges of DEP size (60 to 120 nm) and zeta potential (−37 to −41 mV). Thus, these physical properties of DEP and DEP-Env were found to be the primary determinants of the bioreactivity measured in this study. Our findings also point to the potential risk of over- or under- estimation of expected bioreactivity effects (and by inference of public health risks) from bulk DEP use without taking into account potential batch-to-batch variations in physical (and possibly chemical) properties

Activation-Induced Cytidine Deaminase Deficiency Causes Organ-Specific Autoimmune Disease

Activation-induced cytidine deaminase (AID) expressed by germinal center B cells is a central regulator of somatic hypermutation (SHM) and class switch recombination (CSR). Humans with AID mutations develop not only the autosomal recessive form of hyper-IgM syndrome (HIGM2) associated with B cell hyperplasia, but also autoimmune disorders by unknown mechanisms. We report here that AID−/− mice spontaneously develop tertiary lymphoid organs (TLOs) in non-lymphoid tissues including the stomach at around 6 months of age. At a later stage, AID−/− mice develop a severe gastritis characterized by loss of gastric glands and epithelial hyperplasia. The disease development was not attenuated even under germ-free (GF) conditions. Gastric autoantigen -specific serum IgM was elevated in AID−/− mice, and the serum levels correlated with the gastritis pathological score. Adoptive transfer experiments suggest that autoimmune CD4+ T cells mediate gastritis development as terminal effector cells. These results suggest that abnormal B-cell expansion due to AID deficiency can drive B-cell autoimmunity, and in turn promote TLO formation, which ultimately leads to the propagation of organ-specific autoimmune effector CD4+ T cells. Thus, AID plays an important role in the containment of autoimmune diseases by negative regulation of autoreactive B cells

Farnesyl transferase inhibitor resistance probed by target mutagenesis

Mutation in the target oncoprotein is a common mechanism of resistance to tyrosine kinase inhibitors, as exemplified by the many BCR/ABL mutations that thwart imatinib activity in patients with chronic myelogenous leukemia. It remains unclear whether normal cellular protein targets of chemotherapeutics will evolve drug resistance via mutation to a similar extent. We conducted an in vitro screen for resistance to lonafarnib, a farnesyl protein transferase inhibitor that blocks prenylation of a number of proteins important in cell proliferation, and identified 9 mutations clustering around the lonafarnib binding site. In patients treated with a combination of imatinib and lonafarnib, we identified farnesyl protein transferase mutations in residues identified in our screen. Substitutions at Y361 were found in patients prior to treatment initiation, suggesting that these mutants might confer a proliferative advantage to leukemia cells, which we were able to confirm in cell culture. In vitro mutagenesis of normal cellular enzymes can be exploited to identify mutations that confer chemotherapy resistance to novel agents