CXCL10 gene deficiency prevents decrease in Hb levels

s overexpressing OmpC and OmpF. Similar to SM10-treatment, overexpression of porins in DrecA strain get 2883-98-9 decreased viability by 100 fold. In addition, strains overexpressing OmpC or OmpF, but not those overexpressing FolD or PurE, exhibited filamentation, DNA condensation and accumulation of FM4-64 dye in different areas of the bacterial membrane, and a larger fraction of anucleate cells. These results demonstrated that membrane cues themselves can induce DNA damage, and suggested that the effect of SM10 on DNA damage levels could be a response to membrane alteration rather than a consequence of interfering with DNA repair. Membrane stress induces the production of reactive oxygen species Since SM10 triggers both membrane alteration and DNA breaks, we tested whether reactive oxygen species, particularly hydroxyl radical production, plays a role in SM10induced damage. ROS can damage both DNA and membranes. Kohanski and colleagues have suggested that hydroxyl radical generation contributes to the mechanism of killing of bactericidal antibiotics. This was proposed as a common mechanism for all bactericidal drugs, whereby antibiotics cause a surge in the TCA cycle, leading to increased superoxide production. This in turn would damage iron-sulfur clusters, causing an increase in internal iron and Fenton reaction-mediated hydroxyl radical formation. We examined if the toxicity of SM10 was accompanied by hydroxyl radical production. Early exponential phase MG1655 cultures were incubated with SM10 and stained with hydroxyphenyl fluorescein. HPF was reported to be oxidized by hydroxyl radicals with high specificity, generating free fluorescein. Interestingly, attempting to inhibit the Fenton reaction and hydroxyl radical formation with the iron chelator 2,29-dipyridyl resulted in even higher hydroxyl radical formation and higher levels of DNA damage. This coincides with a 12 log decrease in viability after cotreatment with SM10 and dipyridyl compared to SM10 only. Hydroxyl radical formation was also induced by overexpression of porins in the absence of SM10 treatment. Early exponential-phase cultures of MG1655 carrying high copy number plasmids encoding the porins OmpC or OmpF, or PurE or FolD as negative controls, were incubated with 0.1 mM IPTG for 3 hr and analyzed using the HPF assay. While the magnitude of the positive signal was relatively low and did not change upon addition of IPTG in the control strains, the background level of HPF+ cells in the porin-overexpressing strains was higher and increased 8-fold with the addition of IPTG in the strains overexpressing OmpC or OmpF. Interestingly, in contrast to the effect of dipyridyl on SM10 treated cells, addition of dipyridyl reduced the hydroxyl radicals in cells overexpressing OmpC and the viability of the cells increased accordingly. This suggests that, although both SM10 and overexpression of porins induce envelope stress, DNA damage, hydroxyl radical formation and/or ROS, and eventual death, the involvement of iron and the mechanism that leads to the production of reactive oxygen species may differ between SM10 treatment and porin overexpression. The Collins group observed that aminoglycoside treatment affected genes regulated by the ArcAB two-component signal transduction system as well as genes associated with the response to mistranslation of proteins, an effect of aminoglycosides. They reported that cpxA and cpxR mutants did not generate a positive HPF or DiBAC signal, and that degP and