Computational and experimental analysis reveals a requirement for eosinophil-derived IL-13 for the development of allergic airway responses in C57BL/6 mice

Eosinophils are found in the lungs of humans with allergic asthma, as well as in the lungs of animals in models of this disease. Increasing evidence suggests that these cells are integral to the development of allergic asthma in C57BL/6 mice. However, the specific function of eosinophils that is required for this event is not known. In this study, we experimentally validate a dynamic computational model and perform follow-up experimental observations to determine the mechanism of eosinophil modulation of T cell recruitment to the lung during development of allergic asthma. We find that eosinophils deficient in IL-13 were unable to rescue airway hyperresponsiveness, T cell recruitment to the lungs, and Th2 cytokine/chemokine production in ΔdblGATA eosinophil-deficient mice, even if Th2 cells were present. However, eosinophil-derived IL-13 alone was unable to rescue allergic asthma responses in the absence of competence of other IL-13-producing cells. We further computationally investigate the role of other cell types in the production of IL-13, which led to the various predictions including early and late pulses of IL-13 during airway hyperresponsiveness. These experiments suggest that eosinophils and T cells have an interdependent relationship, centered on IL-13, which regulates T cell recruitment to the lung and development of allergic asthma.     

The effective opening of nicotinic acetylcholine receptors with single agonist binding sites

We have identified a means by which agonist-evoked responses of nicotinic receptors can be conditionally eliminated. Modification of α7L119C mutants by the sulfhydryl reagent 2-aminoethyl methanethiosulfonate (MTSEA) reduces responses to acetylcholine (ACh) by more than 97%, whereas corresponding mutations in muscle-type receptors produce effects that depend on the specific subunits mutated and ACh concentration. We coexpressed α7L119C subunits with pseudo wild-type α7C116S subunits, as well as ACh-insensitive α7Y188F subunits with wild-type α7 subunits in Xenopus laevis oocytes using varying ratios of cRNA. When mutant α7 cRNA was coinjected at a 5:1 ratio with wild-type cRNA, net charge responses to 300 μM ACh were retained by α7L119C-containing mutants after MTSEA modification and by the ACh-insensitive Y188F-containing mutants, even though the expected number of ACh-sensitive wild-type binding sites would on average be fewer than two per receptor. Responses of muscle-type receptors with one MTSEA-sensitive subunit were reduced at low ACh concentrations, but much less of an effect was observed when ACh concentrations were high (1 mM), indicating that saturation of a single binding site with agonist can evoke strong activation of nicotinic ACh receptors. Single-channel patch clamp analysis revealed that the burst durations of fetal wild-type and α1β1γδL121C receptors were equivalent until the α1β1γδL121C mutants were exposed to MTSEA, after which the majority (81%) of bursts were brief (≤2 ms). The longest duration events of the receptors modified at only one binding site were similar to the long bursts of native receptors traditionally associated with the activation of receptors with two sites containing bound agonists.     

Substratum/bacterial interactions and larval attachment: Films and exopolysaccharides of Halomonas marina (ATCC 25374) and their effect on barnacle cyprid larvae,Balanus amphitrite Darwin

Laboratory experiments were conducted to study the interaction between adhesion of the bacterium Halomonas marina to substrata of different wettabilities, the combination of which has been demonstrated to influence the attachment response of cyprid larvae of the barnacle Balanus amphitrite. Cyprid attachment in the presence of bacterial films was shown to be inhibited when films were on polystyrene but not on tissue‐culture polystyrene or glass. Using an enzyme‐linked lectin assay, bacteria on polystyrene showed an increase in binding of the lectin concanavalin A compared to bacteria on tissue‐culture treated polystyrene, indicating a difference in surface polymers associated with H. marina when attached to different substrata. Although bacterial growth supernatants when adsorbed to polystyrene were inhibitory to barnacle attachment, exopolysaccharides, to which the lectins may be binding, were not inhibitory. The data indicate that adhesion of films of bacteria to polystyrene alters the exopolymer production by H. marina and it is suggested that this change may be involved in the inhibition of cyprid attachment. However, the inhibition of cyprid larvae does not appear to be associated with the exopolysaccharides of the bacterium.     

Protein tyrosine phosphorylation in Mycobacterium tuberculosis

Abstract Crude cell extracts from three strains of Mycobacterium tuberculosis were analyzed for the presence of proteins possessing phosphorylated tyrosine residues. A protein migrating at approximately 55 kDa was detected using an antiphosphotyrosine monoclonal antibody. In addition, less predominant bands were observed between 50 kDa and 60 kDa. That M. tuberculosis contains specific tyrosine phosphorylated proteins implies that M. tuberculosis has tyrosine kinase activity. Examination of other, non-pathogenic mycobacterium species yielded no major antiphosphotyrosine reactive proteins. This suggests that the antiphosphotyrosine reactive protein is specific to M. tuberculosis strains. These results provide evidence that M. tuberculosis contains an antiphosphotyrosine reactive protein.     

Phosphoinositide-3 Kinase Inhibition Modulates Responses to Rhinovirus by Mechanisms that Are Predominantly Independent of Autophagy

Human rhinoviruses (HRV) are a major cause of exacerbations of airways disease. Aspects of cell signalling responses to HRV infection remain unclear, particularly with regard to signalling via PI3K, and the PI3K-dependent pathway, autophagy. We investigated the roles of PI3K and autophagy in the responses of epithelial cells to major and minor group HRV infection. The PI3K inhibitor 3-MA, commonly used to inhibit autophagy, markedly reduced HRV-induced cytokine induction. Further investigation of potential targets of 3-MA and comparison of results using this inhibitor to a panel of general and class I-selective PI3K inhibitors showed that several PI3Ks cooperatively regulate responses to HRV. Targeting by siRNA of the autophagy proteins Beclin-1, Atg7, LC3, alone or in combination, or targeting of the autophagy-specific class III PI3K had at most only modest effects on HRV-induced cell signalling as judged by induction of proinflammatory cytokine production. Our data indicate that PI3K and mTOR are involved in induction of proinflammatory cytokines after HRV infection, and that autophagy has little role in the cytokine response to HRV or control of HRV replication.