AhR promotes phosphorylation of ARNT isoform 1 in human T cell malignancies as a switch for optimal AhR activity.

The aryl hydrocarbon receptor nuclear translocator (ARNT) is a transcription factor present in immune cells as a long and short isoform, referred to as isoforms 1 and 3, respectively. However, investigation into potential ARNT isoform­specific immune functions is lacking despite the well-established heterodimerization requirement of ARNT with, and for the activity of, the aryl hydrocarbon receptor (AhR), a critical mediator of immune homeostasis. Here, using global and targeted transcriptomics analyses, we show that the relative ARNT isoform 1:3 ratio in human T cell lymphoma cells dictates the amplitude and direction of AhR target gene regulation. Specifically, shifting the ARNT isoform 1:3 ratio lower by suppressing isoform 1 enhances, or higher by suppressing isoform 3 abrogates, AhR responsiveness to ligand activation through preprograming a cellular genetic background that directs explicit gene expression patterns. Moreover, the fluctuations in gene expression patterns that accompany a decrease or increase in the ARNT isoform 1:3 ratio are associated with inflammation or immunosuppression, respectively. Molecular studies identified the unique casein kinase 2 (CK2) phosphorylation site within isoform 1 as an essential parameter to the mechanism of ARNT isoform­specific regulation of AhR signaling. Notably, CK2-mediated phosphorylation of ARNT isoform 1 is dependent on ligand-induced AhR nuclear translocation and is required for optimal AhR target gene regulation. These observations reveal ARNT as a central modulator of AhR activity predicated on the status of the ARNT isoform ratio and suggest that ARNT-based therapies are a viable option for tuning the immune system to target immune disorders.

Attenuation of intestinal inflammation in interleukin-10-deficient mice infected with Citrobacter rodentium.

Interleukin-10 (IL-10) curtails immune responses to microbial infection and autoantigens and contributes to intestinal immune homeostasis, yet administration of IL-10 has not been effective at attenuating chronic intestinal inflammatory conditions, suggesting that its immune functions may be context dependent. To gain a broader understanding of the importance of IL-10 in controlling mucosal immune responses to infectious challenges, we employed the murine attaching and effacing pathogen Citrobacter rodentium, which colonizes primarily the surfaces of the cecum and colon and causes transient mucosal inflammation driven by Th17 and Th1 T helper cells. Infection induced macrophage and dendritic cell production of IL-10, which diminished antibacterial host defenses, because IL-10-deficient mice cleared infection faster than wild-type controls. In parallel, the mice had less acute infection-associated colitis and resolved it more rapidly than controls. Importantly, transient C. rodentium infection protected IL-10-deficient mice against the later development of spontaneous colitis that normally occurs with aging in these mice. Genome-wide expression studies revealed that IL-10 deficiency was associated with downregulation of proinflammatory pathways but increased expression of the anti-inflammatory cytokine IL-27 in response to infection. IL-27 was found to suppress in vitro Th17 and, to a lesser degree, Th1 differentiation independent of IL-10. Furthermore, neutralization of IL-27 resulted in more severe colitis in infected IL-10-deficient mice. Together, these findings indicate that IL-10 is dispensable for resolving C. rodentium-associated colitis and further suggest that IL-27 may be a critical factor for controlling intestinal inflammation and Th17 and Th1 development by IL-10-independent mechanisms.

ROS generated by pollen NADPH oxidase provide a signal that augments antigen-induced allergic airway inflammation.

Pollen exposure induces allergic airway inflammation in sensitized subjects. The role of antigenic pollen proteins in the induction of allergic airway inflammation is well characterized, but the contribution of other constituents in pollen grains to this process is unknown. Here we show that pollen grains and their extracts contain intrinsic NADPH oxidases. The pollen NADPH oxidases rapidly increased the levels of ROS in lung epithelium as well as the amount of oxidized glutathione (GSSG) and 4-hydroxynonenal (4-HNE) in airway-lining fluid. These oxidases, as well as products of oxidative stress (such as GSSG and 4-HNE) generated by these enzymes, induced neutrophil recruitment to the airways independent of the adaptive immune response. Removal of pollen NADPH oxidase activity from the challenge material reduced antigen-induced allergic airway inflammation, the number of mucin-containing cells in airway epithelium, and antigen-specific IgE levels in sensitized mice. Furthermore, challenge with Amb a 1, the major antigen in ragweed pollen extract that does not possess NADPH oxidase activity, induced low-grade allergic airway inflammation. Addition of GSSG or 4-HNE to Amb a 1 challenge material boosted allergic airway inflammation. We propose that oxidative stress generated by pollen NADPH oxidases (signal 1) augments allergic airway inflammation induced by pollen antigen (signal 2).

Colostrinin decreases hypersensitivity and allergic responses to common allergens.

BACKGROUND: Colostrinin (CLN), isolated from mothers' pre-milk fluid (colostrum), is a uniform mixture of low-molecular-weight, proline-rich polypeptides. CLN induces neurite outgrowth of pheochromocytoma cells, extends the lifespan of diploid fibroblast cells, inhibits beta-amyloid-induced apoptosis and improves cognitive functions when administered to Alzheimer's disease patients. OBJECTIVE: The aim of this study was to investigate potential allergic responses to CLN and its impact on allergic sensitization and inflammation caused by common allergens. METHODS: We used a well-characterized mouse model of allergic airway inflammation. Changes in IgE/IgG1 and mucin levels, airway eosinophilia and hyperreactivity to methacholine were determined by ELISA, differential cell counting and whole-body plethysmography, respectively. RESULTS: CLN did not increase IgE/IgG1 levels or induce cutaneous hypersensitivity reaction, airway inflammation and mucin production. Importantly, CLN significantly (p < 0.001) decreased IgE/IgG1 production, airway eosinophilia, mucin production and hypersensitivity induced by allergenic extracts from ragweed pollen grains and house dust mites. CONCLUSION: CLN itself is non-allergenic; however, it is effective in preventing allergic responses to known indoor and outdoor allergens. These data support the safe application of CLN and its potential use in the prevention of allergic inflammation in humans.

Gene plasticity in colonic circular smooth muscle cells underlies motility dysfunction in a model of postinfective IBS.

The cellular mechanisms of motility dysfunction in postinfectious irritable bowel syndrome (PI-IBS) are not known. We used a rat model of neonatal inflammation to test the hypothesis that gene plasticity in colonic circular smooth muscle cells underlies motility dysfunction in PI-IBS. Mild/moderate or severe inflammation was induced in neonatal and adult rats. Experiments were performed in tissues obtained at 7 days (short term) and 6-8 wk (long term) after the induction of inflammation. Severe inflammation in neonatal rats induced persistent long-term smooth muscle hyperreactivity to acetylcholine (ACh), whereas that in adult rat caused smooth muscle hyporeactivity that showed partial recovery in the long term. Mild/moderate inflammation had no effect in neonatal rats, but it induced smooth muscle hyporeactivity to ACh in adult rats, which recovered fully in the long term. Smooth muscle hyperreactivity to ACh resulted in accelerated colonic transit and increase in defecation rate, whereas hyporeactivity had opposite effects. Smooth muscle hyperreactivity to ACh was associated with increase in transcription rate of key cell-signaling proteins of the excitation-contraction coupling alpha1C subunit of Cav1.2 (L-type) calcium channels, Galphaq, and 20-kDa myosin light chain (MLC20), whereas hyporeactivity was associated with their suppression. Inflammation in adult rats induced classical inflammatory response, which was absent in neonatal rats. Severe neonatal inflammation enhanced plasma norepinephrine and muscularis propria vasoactive intestinal polypeptide in the long term. We conclude that severe, but not mild/moderate, inflammation in a state of immature or impaired stress and immune response systems alters the transcription rate of key cell-signaling proteins of excitation-contraction coupling in colonic circular smooth muscle cells to enhance their contractility and accelerate colonic transit and defecation rate.

Norepinephrine mediates the transcriptional effects of heterotypic chronic stress on colonic motor function.

Chronic stress precipitates or exacerbates the symptoms of functional bowel disorders, including motility dysfunction. The cellular mechanisms of these effects are not understood. We tested the hypothesis that heterotypic chronic stress (HeCS) elevates the release of norepinephrine from the adrenal medulla, which enhances transcription of the gene-regulating expression of Ca(v)1.2 (L-type) channels in colonic circular smooth muscle cells, resulting in enhanced colonic motor function. The experiments were performed in rats using a 9-day heterotypic chronic stress (HeCS) protocol. We found that HeCS, but not acute stress, time dependently enhances the contractile response to ACh in colonic circular smooth muscle strips and in single dissociated smooth muscle cells, the plasma levels of norepinephrine and the mRNA and protein expressions of the alpha(1C) subunit of Ca(v)1.2 channels. These effects result in faster colonic transit and increase in defecation rate. The effects of HeCS are blocked by adrenalectomy but not by depletion of norepinephrine in sympathetic neurons. The inhibition of receptors for glucocortocoids, corticotropin-releasing hormone or nicotine also does not block the effects of heterotypic chronic stress. Norepinephrine acts on alpha- and beta(3)-adrenergic receptors to induce the transcription of alpha(1C) subunit. We conclude that HeCS alters colonic motor function by elevating the plasma levels of norepinephrine. Colonic motor dysfunction is associated with enhanced gene transcription of Ca(v)1.2 channels in circular smooth muscle cells. These findings suggest the potential cellular mechanisms by which heterotypic chronic stress may exacerbate motility dysfunction in patients with irritable bowel syndrome.

Inhibiting pollen reduced nicotinamide adenine dinucleotide phosphate oxidase-induced signal by intrapulmonary administration of antioxidants blocks allergic airway inflammation.

BACKGROUND: Ragweed extract (RWE) contains NADPH oxidases that induce oxidative stress in the airways independent of adaptive immunity (signal 1) and augment antigen (signal 2)-induced allergic airway inflammation. OBJECTIVE: To test whether inhibiting signal 1 by administering antioxidants inhibits allergic airway inflammation in mice. METHODS: The ability of ascorbic acid (AA), N-acetyl cystenine (NAC), and tocopherol to scavenge pollen NADPH oxidase-generated reactive oxygen species (ROS) was measured. These antioxidants were administered locally to inhibit signal 1 in the airways of RWE-sensitized mice. Recruitment of inflammatory cells, mucin production, calcium-activated chloride channel 3, IL-4, and IL-13 mRNA expression was quantified in the lungs. RESULTS: Antioxidants inhibited ROS generation by pollen NADPH oxidases and intracellular ROS generation in cultured epithelial cells. AA in combination with NAC or Tocopherol decreased RWE-induced ROS levels in cultured bronchial epithelial cells. Coadministration of antioxidants with RWE challenge inhibited 4-hydroxynonenal adduct formation, upregulation of Clca3 and IL-4 in lungs, mucin production, recruitment of eosinophils, and total inflammatory cells into the airways. Administration of antioxidants with a second RWE challenge also inhibited airway inflammation. However, administration of AA+NAC 4 or 24 hours after RWE challenge failed to inhibit allergic inflammation. CONCLUSION: Signal 1 plays a proinflammatory role during repeated exposure to pollen extract. We propose that inhibiting signal 1 by increasing antioxidant potential in the airways may be a novel therapeutic strategy to attenuate pollen-induced allergic airway inflammation. CLINICAL IMPLICATIONS: Administration of antioxidants in the airways may constitute a novel therapeutic strategy to prevent pollen induced allergic airway inflammation.

A novel role of VIP in colonic motility function: induction of excitation-transcription coupling in smooth muscle cells.

BACKGROUND & AIMS: Vasoactive intestinal polypeptide (VIP) relaxes smooth muscle by generation of cAMP and activation of protein kinase A (PKA). However, PKA activation also phosphorylates the transcription factor CREB. The aim of this study was to investigate whether the phosphorylation of CREB induces gene expression of the pore-forming alpha(1C) subunit of Ca(v)1.2 channels (L-type calcium channels), whose promoter has 2 binding sites for CREB. METHODS: The experiments were performed on primary cultures of human colonic circular smooth muscle cells and freshly obtained human and rat colonic circular muscle strips. RESULTS: The incubation of human colonic circular smooth muscle cells or muscle strips with VIP for 24 hours enhanced the expression of alpha(1C) protein and mRNA as well as the contractile response to acetylcholine and KCl. On the contrary, incubation of the muscle strips with VIP antagonist for 24 hours suppressed cell contractility. The incubation of the cells with VIP caused sustained generation of cAMP for 24 hours, but PKA activation and CREB phosphorylation were transient. The inhibition of PKA by H-89 or silencing of CREB gene with targeted RNAi blocked the transcription of alpha(1C). Progressive 5' deletions of halpha(1C)1b promoter and site-directed mutations of the 2 CREB binding cis-elements indicated that most of alpha(1C) transcription was mediated by the 5' cAMP response element. CONCLUSIONS: The excitation-transcription coupling stimulated by VIP induces expression of the Ca(v)1.2 channels. The influx of calcium through these channels is a critical step in excitation-contraction coupling in smooth muscle cells.

Subpollen particles: carriers of allergenic proteins and oxidases.

BACKGROUND: Pollen is known to induce allergic asthma in atopic individuals, although only a few inhaled pollen grains penetrate into the lower respiratory tract. OBJECTIVE: We sought to provide evidence that subpollen particles (SPPs) of respirable size, possessing both antigenic and redox properties, are released from weed pollen grains and to test their role in allergic airway inflammation. METHODS: The release of SPPs was analyzed by means of microscopic imaging and flow cytometry. The redox properties of SPPs and the SPP-mediated oxidative effect on epithelial cells were determined by using redox-sensitive probes and specific inhibitors. Western blotting and amino acid sequence analysis were used to examine the protein components of the SPP. The allergenic properties of the SPP were determined in a murine model of experimental asthma. RESULTS: Ragweed pollen grains released 0.5 to 4.5 microm of SPPs on hydration. These contained Amb a 1, along with other allergenic proteins of ragweed pollen, and possessed nicotinamide adenine dinucleotide (reduced) or nicotinamide adenine dinucleotide phosphate (reduced) [NAD(P)H] oxidase activity. The SPPs significantly increased the levels of reactive oxygen species (ROS) in cultured cells and induced allergic airway inflammation in the experimental animals. Pretreatment of the SPPs with NAD(P)H oxidase inhibitors attenuated their capacity to increase ROS levels in the airway epithelial cells and subsequent airway inflammation. CONCLUSIONS: The allergenic potency of SPPs released from ragweed pollen grains is mediated in tandem by ROS generated by intrinsic NAD(P)H oxidases and antigenic proteins. CLINICAL IMPLICATIONS: Severe clinical symptoms associated with seasonal asthma might be explained by immune responses to inhaled SPPs carrying allergenic proteins and ROS-producing NAD(P)H oxidases.

Effect of pollen-mediated oxidative stress on immediate hypersensitivity reactions and late-phase inflammation in allergic conjunctivitis.

BACKGROUND: Allergic eye diseases are complex inflammatory conditions of the conjunctiva that are becoming increasingly prevalent and present an increasing economic burden because of direct and indirect health expenditures. OBJECTIVE: We sought to identify factors that may synergize with antigen-induced allergic inflammation and lead to allergic conjunctivitis. We used a murine model of allergic conjunctivitis to test the effect of oxidative stress generated by pollen oxidases using nicotinamide adenine dinucleotide (reduced) or nicotinamide adenine dinucleotide phosphate (reduced) (NAD[P]H) as an electron donor present in pollen grains. METHODS: Reactive oxygen species (ROS) generation by hydrated Ambrosia artemisiifolia pollen (short ragweed pollen; RWP) grains was determined by using 2'-7'-dihydro-dichlorofluorescein diacetate, nitroblue tetrazolium reduction, and Amplex Red assay. The RWP-induced changes in intracellular ROS levels were examined in A549 cells, human primary bronchial epithelial cells, and murine conjunctiva. RESULTS: Ragweed pollen grains contain NAD(P)H oxidase activity, which is diphenyleneiodonium-sensitive and quinacrine-sensitive and sodium azide-resistant. These NAD(P)H oxidases generate a superoxide anion that can be converted to H2O2 by pollen grain-associated superoxide dismutase. These diffusible oxygen radicals from pollen grains increase intracellular ROS levels in cultured epithelial cells and murine conjunctiva. Similar phenomena were observed in sensitized and naive mice, indicating that the RWP-induced oxidative stress in conjunctival epithelium is independent of adaptive immunity. Inactivation of NAD(P)H oxidase activity in RWP decreases the immediate-type hypersensitivity and inflammatory cell infiltration into the conjunctiva. CONCLUSION: Our data suggest that ROS generated by NAD(P)H oxidases in pollen grains intensify immediate allergic reactions and recruitment of inflammatory cells in murine conjunctiva.

CCL7 and CXCL10 orchestrate oxidative stress-induced neutrophilic lung inflammation.

Oxidative stress from ozone (O(3)) exposure augments airway neutrophil recruitment and chemokine production. We and others have shown that severe and sudden asthma is associated with airway neutrophilia, and that O(3) oxidative stress is likely to augment neutrophilic airway inflammation in severe asthma. However, very little is known about chemokines that orchestrate oxidative stress-induced neutrophilic airway inflammation in vivo. To identify these chemokines, three groups of BALB/c mice were exposed to sham air, 0.2 ppm O(3), or 0.8 ppm O(3) for 6 h. Compared with sham air, 0.8 ppm O(3), but not 0.2 ppm O(3), induced pronounced neutrophilic airway inflammation that peaked at 18 h postexposure. The 0.8 ppm O(3) up-regulated lung mRNA of CXCL1,2,3 (mouse growth-related oncogene-alpha and macrophage-inflammatory protein-2), CXCL10 (IFN-gamma-inducible protein-10), CCL3 (macrophage-inflammatory protein-1alpha), CCL7 (monocyte chemoattractant protein-3), and CCL11 (eotaxin) at 0 h postexposure, and expression of CXCL10, CCL3, and CCL7 mRNA was sustained 18 h postexposure. O(3) increased lung protein levels of CXCL10, CCL7, and CCR3 (CCL7R). The airway epithelium was identified as a source of CCL7. The role of up-regulated chemokines was determined by administering control IgG or IgG Abs against six murine chemokines before O(3) exposure. As expected, anti-mouse growth-related oncogene-alpha inhibited neutrophil recruitment. Surprisingly, Abs to CCL7 and CXCL10 also decreased neutrophil recruitment by 63 and 72%, respectively. These findings indicate that CCL7 and CXCL10, two chemokines not previously reported to orchestrate neutrophilic inflammation, play a critical role in mediating oxidative stress-induced neutrophilic airway inflammation. These observations may have relevance in induction of neutrophilia in severe asthma.

In vivo role of p38 mitogen-activated protein kinase in mediating the anti-inflammatory effects of CpG oligodeoxynucleotide in murine asthma.

DNA containing unmethylated CpG motifs is intrinsically immunostimulatory, inducing the production of a variety of cytokines and chemokines by immune cells. The strong Th1 response triggered by CpG oligodeoxynucleotide (ODN) inhibits the development of Th2-mediated allergic asthma in mice. This work documents that CpG ODN-induced IL-12 production plays a critical role in this process, because intrapulmonary CpG ODN inhibits allergic inflammation in wild-type but not IL-12(-/-) mice. CpG ODN rapidly localized to alveolar macrophages (AM), thereby triggering the phosphorylation of p38 mitogen-activated protein kinase (MAP kinase). AM cultured with CpG but not control ODN up-regulated IL-12 p40 expression and release, and these effects were blocked by the highly specific p38 MAP kinase inhibitor SB202190. Intrapulmonary administration of this inhibitor blocked the ability of CpG ODN to produce IL-12 in the lungs and reversed the anti-inflammatory effects of CpG ODN on allergic lung inflammation. These findings indicate that IL-12 production by AM is stimulated by intrapulmonary CpG ODN administration through a p38 MAP kinase-dependent process, and IL-12 is a key cytokine that mediates CpG ODN-induced protection against allergic lung inflammation.