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RationaleAsthma and obesity often co-occur. It has been hypothesized that asthma may contribute to childhood obesity onset.ObjectivesTo determine if childhood asthma is associated with incident obesity and examine the role of asthma medication in this association.MethodsWe studied 8,716 children between ages 6 and 18.5 years who were nonobese at study entry participating in 18 US cohorts of the Environmental influences on Child Health Outcomes program (among 7,299 children with complete covariate data mean [SD] study entry age = 7.2 [1.6] years and follow up = 5.3 [3.1] years).Measurements and main resultsWe defined asthma based on caregiver report of provider diagnosis. Incident obesity was defined as the first documented body mass index ≥95th percentile for age and sex following asthma status ascertainment. Over the study period, 26% of children had an asthma diagnosis and 11% developed obesity. Cox proportional hazards models with sex-specific baseline hazards were fitted to assess the association of asthma diagnosis with obesity incidence. Children with asthma had a 23% (95% confidence intervals [CI] = 4, 44) higher risk for subsequently developing obesity compared with those without asthma. A novel mediation analysis was also conducted to decompose the total asthma effect on obesity into pathways mediated and not mediated by asthma medication use. Use of asthma medication attenuated the total estimated effect of asthma on obesity by 64% (excess hazard ratios = 0.64; 95% CI = -1.05, -0.23).ConclusionsThis nationwide study supports the hypothesis that childhood asthma is associated with later risk of obesity. Asthma medication may reduce this association and merits further investigation as a potential strategy for obesity prevention among children with asthma.

Cytoprotective heat shock proteins (Hsps) are critical for intestinal homeostasis and are known to be decreased in inflammatory bowel diseases. Signals responsible for maintenance of Hsp expression are incompletely understood. In this study, we find that Hsp25/27 and Hsp70 protein expressions are differentially regulated along the longitudinal length of the large intestine, being highest in the proximal colon and decreasing to the distal colon. This longitudinal gradient was similar in both conventionally colonized mouse colon as well as biopsies of human proximal and distal colon but was abolished in the colon of germ-free mice, suggesting a role of intestinal microbiota in the Hsp regional expression. Correspondingly, analysis of 16S ribosomal RNA genes of bacteria from each colonic segment indicated increased bacterial richness and diversity in the proximal colon. The mechanism of regulation is transcriptional, as Hsp70 mRNA followed a similar pattern to Hsp70 protein expression. Lysates of mucosa-associated bacteria from the proximal colon stimulated greater Hsp25 and Hsp70 mRNA transcription and subsequent protein expression in intestinal epithelial cells than did lysates from distal colon. In addition, transrectal administration of cecal contents stimulated Hsp25 and Hsp70 expression in the distal colon. Thus host-microbial interactions resulting in differential Hsp expression may have significant implications for the maintenance of intestinal homeostasis and possibly for development of inflammatory diseases of the bowel. 16S ribosomal RNA gene; colonic bacteria; heat shock protein 25; heat shock protein 70 doi: 10.1152/ajpgi.00357.2010.

The ability of Salmonella typhimurium to enter intestinal epithelial cells constitutes a crucial step in pathogenesis. Salmonella invasion of the intestinal epithelium requires bacterial type three secretion system. Type three secretion system is a transport device that injects virulence proteins, called effectors, to paralyze or reprogram the eukaryotic cells. A virulence factor for Salmonella (AvrA) is a Salmonella effector that inhibits the host's inflammatory responses. The mechanism by which AvrA modulates host cell signaling is not entirely clear, p53 is situated at the crossroads of a network of signaling pathways that are essential for genotoxic and nongenotoxic stress responses. We hypothesized that Salmonella infection activates the p53 pathway. We demonstrated that Salmonella infection increased p53 acetylation. Cells infected with AvrA-sufficient Salmonella have increased p53 acetylation, whereas cells infected with AvrA-deficient Salmonella have less p53 acetylation. In a cell-free system, AvrA possessed acetyltransferase activity and used p53 as a substrate. AvrA expression increased p53 transcriptional activity and induced cell cycle arrest. HCT116 p53-/- cells had less inflammatory responses. In a mouse model of Salmonella infection, intestinal epithelial p53 acetylation was increased by AvrA expression. Our studies provide novel mechanistic evidence that Salmonella modulates the p53 pathway during intestinal inflammation and infection. bacteria; TTSS; effector; inflammation; acetylation; ubiquitination doi: 10.1152/ajpgi.00526.2009.

Mucosal inflammation, through cytokines such as interferon-[gamma] (IFN-[gamma]) and tumor necrosis factor-[alpha]] (TNF-[alpha]), has many effects on the intestinal epithelium, including selective translational inhibition of the cytoprotective protein heat shock protein 70 (HspT0). To further elucidate the mechanisms underlying this effect, we examined the role of stress granules in mediating the actions of these proinflammatory cytokines. Using conditionally immortalized young adult mouse colonic epithelial cells, we demonstrate that IFN-[gamma] and TNF-[alpha], which upregulate eukaryotic initiation factor-[alpha] (elF-2[alpha] phosphorylation and reduce Hsp70 translation, significantly enhance stress granule formation in heat-shocked intestinal epithelial cells. The IFN-[gamma] and TNF-[alpha] effects in upregulation of stress granule formation and downregulation of Hsp70 were elF-2[alpha] dependent, and the effect could be negated by blocking elF-2[alpha] phosphorylation with use of an RNA-dependent protein kinase inhibitor. Correspondingly, IFN-[gamma] and TNF-[alpha] increased binding of cytoplasmic proteins to the 3'-untranslated region of Hsp70 mRNA, suggesting specific recruitment of Hsp70 to stress granules as the mechanism of IFN-[gamma] and TNF-[alpha] inhibition of Hsp70 translation. We thus report a novel linkage between inflammatory cytokine production, stress granule formation, and Hsp70 translation inhibition, providing additional insights into the response of intestinal epithelial cells to inflammatory stress. inflammatory bowel disease; IFN-[gamma] doi: 10.1152/ajpgi.00234.2009.

Platelet-activating factor (PAF) is a phospholipid inter- and intracellular mediator implicated in intestinal injury primarily via induction of an inflammatory cascade. We find that PAF also has direct pathological effects on intestinal epithelial cells (IEC). PAF induces [Cl.sup.-] channel activation, which is associated with intracellular acidosis and apoptosis. Using the rat small IEC line IEC-6, electrophysiological experiments demonstrated that PAF induces [Cl.sup.-] channel activation. This PAF-activated [Cl.sup.-] current was inhibited by [Ca.sup.2+] chelation and a calcium calmodulin kinase II inhibitor, suggesting PAF activation of a [Ca.sup.2+]-activated [Cl.sup.-] channel. To determine the pathological consequences of [Cl.sup.-] channel activation, microfluorimetry experiments were performed, which revealed PAF-induced intracellular acidosis, which is also inhibited by the [Cl.sup.-] channel inhibitor 4,4'diisothiocyanostilbene-2,2'disulfonic acid and [Ca.sup.2+] chelation. PAF-induced intracellular acidosis is associated with caspase 3 activation and DNA fragmentation. PAF-induced caspase activation was abolished in cells transfected with a pH compensatory Na/H exchanger construct to enhance [H.sup.+] extruding ability and prevent intracellular acidosis. As C1C-3 is a known intestinal [Cl.sup.-] channel dependent on both [Ca.sup.2+] and calcium calmodulin kinase II phosphorylation, we generated ClC-3 knockdown cells using short hairpin RNA. PAF induced [Cl.sup.-] current; acidosis and apoptosis were all significantly decreased in ClC-3 knockdown cells. Our data suggest a novel mechanism of PAF-induced injury by which PAF induces intracellular acidosis via activation of the [Ca.sup.2+]-dependent [Cl.sup.-] channel ClC-3, resulting in apoptosis of IEC. intestinal injury; intestinal barrier; ion transport; [C.sup.a2+]-activated [Cl.sup.-] channel

Flagellin is a bacterial protein responsible for activation of Toll-like receptor 5 (TLR5), which we hypothesize is involved in Salmonella's induction of cytoprotective heat shock proteins in intestinal epithelial cells. Flagellin induces the cytoprotective heat shock protein Hsp25 in different intestinal epithelial cell lines and in mouse intestine. Flagellin induces Hsp25 expression in a time-dependent manner in vitro. This effect is transcriptional, as confirmed by luciferase reporter assays and actinomycin D treatment. In addition, Hsp25 induction requires p38 MAPK activation and is only observed when flagellin is added to the basolateral side of polarized intestinal epithelial cells, consistent with the known location of TLR5. Flagellin-mediated Hsp25 induction is associated with increased protective effects against oxidant stress, an effect that is at least partially mediated by p38 MAPK. Use of small interfering RNA against Hsp25 demonstrates that flagellin-mediated protection against oxidant stress is to some degree mediated through Hsp25 induction. This suggests that, by protecting against oxidant injury, the induction of Hsp25 expression by flagellin may contribute to intestinal homeostasis. In a coculture cell model and in a mouse model of Salmonella enterica Serovar Typhimurium infection, not only does infection with wild-type and a flagellin-deletion mutant strain of Salmonella show that flagellin induces Hsp25 in vivo, but it also demonstrates that in the case of live Salmonella infection, flagellin serves as a major stimulus for the induction of Hsp25 expression. These data provide evidence that flagellin is required for Salmonella-mediated induction of Hsp25 expression in intestinal epithelium. intestinal epithelial cells; oxidant stress; innate immunity; Toll-like receptors