We have sequenced the genome of the intracellular symbiont Buchnera aphidicola from the aphid Baizongia pistacea. This strain diverged 80 -150 million years ago from the common ancestor of two previously sequenced Buchnera strains. Here, a field-collected, nonclonal sample of insects was used as source material for laboratory procedures. As a consequence, the genome assembly unveiled intrapopulational variation, consisting of Ϸ1,200 polymorphic sites. Comparison of the 618-kb (kbp) genome with the two other Buchnera genomes revealed a nearly perfect gene-order conservation, indicating that the onset of genomic stasis coincided closely with establishment of the symbiosis with aphids, Ϸ200 million years ago. Extensive genome reduction also predates the synchronous diversification of Buchnera and its host; but, at a slower rate, gene loss continues among the extant lineages. A computational study of protein folding predicts that proteins in Buchnera, as well as proteins of other intracellular bacteria, are generally characterized by smaller folding efficiency compared with proteins of free living bacteria. These and other degenerative genomic features are discussed in light of compensatory processes and theoretical predictions on the long-term evolutionary fate of symbionts like Buchnera.

This review considers the molecular toxicology of combustion-derived nanoparticles (CDNP) following inhalation exposure. CDNP originate from a number of sources and in this review we consider diesel soot, welding fume, carbon black and coal fly ash. A substantial literature demonstrates that these pose a hazard to the lungs through their potential to cause oxidative stress, inflammation and cancer; they also have the potential to redistribute to other organs following pulmonary deposition. These different CDNP show considerable heterogeneity in composition and solubility, meaning that oxidative stress may originate from different components depending on the particle under consideration. Key CDNP-associated properties of large surface area and the presence of metals and organics all have the potential to produce oxidative stress. CDNP may also exert genotoxic effects, depending on their composition. CDNP and their components also have the potential to translocate to the brain and also the blood, and thereby reach other targets such as the cardiovascular system, spleen and liver. CDNP therefore can be seen as a group of particulate toxins unified by a common mechanism of injury and properties of translocation which have the potential to mediate a range of adverse effects in the lungs and other organs and warrant further research.

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Oxidants and tumor necrosis factor-alpha (TNF-alpha) activate transcription factors such as nuclear factor-kappaB (NF-kappaB), which is involved in the transcription of proinflammatory mediators, including interleukin-8 (IL-8). Curcumin (diferuloylmethane) is a naturally occurring flavonoid present in the spice turmeric, which has a long traditional use as a chemotherapeutic agent for many diseases. We hypothesize that curcumin may possess both antioxidant and antiinflammatory properties by increasing the glutathione levels and inhibiting oxidant- and cytokine-induced NF-kappaB activation and IL-8 release from cultured alveolar epithelial cells (A549). Treatment of A549 cells with hydrogen peroxide (H2O2; 100 microM) and TNF-alpha (10 ng/ml) significantly increased NF-kappaB and activator protein-1 (AP-1) activation, as well as IL-8 release. Curcumin inhibited both H2O2- and TNF-alpha-mediated activation of NF-kappaB and AP-1, and IL-8 release. Furthermore, an increased level of GSH and glutamylcysteine ligase catalytic subunit mRNA expression was observed in curcumin-treated cells as compared with untreated cells. Curcumin interacted directly with superoxide anion (O2*-) and hydroxyl radical (*OH) as shown by electron paramagnetic resonance, quenching the interaction of the radicals with the spin trap, Tempone-H. This suggests that curcumin has multiple properties: as an oxygen radical scavenger, antioxidant through modulation of glutathione levels, and antiinflammatory agent through inhibition of IL-8 release in lung cells.

Ultrafine (Uf) particles are a component of particulate air pollution suggested to be responsible for the health effects associated with elevations of this pollutant. We have previously suggested that Uf particles, through the induction of oxidative stress, may induce inflammation in the lung, thus exacerbating preexisting illness in susceptible individuals. Alveolar macrophages are considered to play a key role in particlemediated inflammation and lung disease. The effect of Uf particles on rat alveolar macrophages and human blood monocytes was investigated with reference to the roles of calcium and reactive oxygen species (ROS). TNF-alpha protein release, intracellular calcium concentration, TNF-alpha mRNA expression, and transcription factor activation were studied as end points after treatment of rat alveolar macrophages or peripheral blood monocytes. The calcium channel blocker verapamil, the intracellular calcium chelator BAPTA-AM, the calmodulin inhibitor W-7, and the antioxidants Trolox and Nacystelin (NAL) were included in combination with Uf particles. Verapamil reduced intracellular calcium concentration in rat alveolar macrophages on stimulation with Uf particles. This effect was also apparent with transcription factor AP-1 activation. All antagonists and antioxidants reduced Uf-stimulated nuclear localization of the p50 and p65 subunits of NF-kappaB in human monocytes. Verapamil, BAPTA-AM, and NAL reduced Uf-stimulated TNF-alpha protein release, whereas only verapamil reduced Uf-stimulated mRNA expression in rat alveolar macrophages. In human monocytes, verapamil, Trolox, BAPTA-AM, and W-7 reduced Uf-stimulated TNF-alpha protein release. These findings suggest that Uf particles may exert proinflammatory effects by modulating intracellular calcium concentrations, activation of transcription factors, and cytokine production through a ROS-mediated mechanism.

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Changes in the ratio of intracellular reduced and disulfide forms of glutathione (GSH/GSSG) can affect signaling pathways that participate in various physiological responses from cell proliferation to gene expression and apoptosis. It is also now known that many proteins have a highly conserved cysteine (sulfhydryl) sequence in their active/regulatory sites, which are primary targets of oxidative modifications and thus important components of redox signaling. However, the mechanism by which oxidants and GSH/protein-cysteine-thiols actually participate in redox signaling still remains to be elucidated. Initial studies involving the role of cysteine in various proteins have revealed that cysteine-SH may mediate redox signaling via reversible or irreversible oxidative modification to Cys-sulfenate or Cys-sulfinate and Cys-sulfonate species, respectively. Oxidative stress possibly via the modification of cysteine residues activates multiple stress kinase pathways and transcription factors nuclear factor-kappaB and activator protein-1, which differentially regulate the genes for proinflammatory cytokines as well as the protective antioxidant genes. Understanding the redox signaling mechanisms for differential gene regulation may allow for the development of novel pharmacological approaches that preferentially up-regulate key antioxidants genes, which, in turn, reduce or resolve inflammation and injury. This forum article features the current knowledge on the role of GSH in redox signaling, particularly the regulation of transcription factors and downstream signaling in lung inflammation.

These data propose a role for modification of nucleosomal structure in inflammatory cytokine gene transcription in response to smoking. The imbalance between histone deacetylation and acetylation in favor of acetylation may contribute to the enhanced inflammation in smokers susceptible to the development of COPD.