Mechanism of crosstalk inhibition of IL-6 signaling in response to LPS and TNFα

Negative regulation of cytokine signaling is critical for the generation of the appropriate cellular outcome in response to signals, and can be modulated by other concomitant extracellular stimuli (“crosstalk”). Using both genetic and pharmacological manipulations we have investigated the mechanisms by which the pro-inflammatory stimuli, lipopolysaccharide (LPS) and Tumor necrosis factor α (TNFα), negatively regulate interleukin-6 (IL-6) signaling in primary mouse macrophages. Analysis of suppressor of cytokine signalling 3 (SOCS3)-deficient macrophages reveal that SOCS3 is necessary but surprisingly, not sufficient for the complete crosstalk inhibition of IL-6 signaling induced by LPS and TNFα. Analysis of macrophages from gp130 (Y757F) mutant mice suggest that SH2 domain-containing tyrosine phosphatase (SHP2) activity does not explain the residual inhibitory effect of these pro-inflammatory stimuli. In addition, p38 mitogen-activated protein kinase (p38) activation also negatively regulates IL-6 signaling independent of its parallel and necessary action to induce SOCS3 expression. Finally, we have identified an additional, novel mechanism of crosstalk inhibition: a reduction in total cellular levels of gp130 following stimulation with LPS and TNFα.     

Inhaled β2 -agonists and airway responses to allergen

A series of investigations show that the regular use of inhaled β₂ -agonists will increase all aspects of the airway response to allergen. The mechanism of this effect is uncertain; however, it appears to be different from the mechanism that produces tolerance to β₂ -agonist effects. One possibility is that the regular use of β₂ -agonists might induce a mast cell β-receptor dysfunction that might make mast cells more prone to release mediators. As a result β₂ -agonist use plus allergen exposure might cause more mediator release than does allergen exposure alone. The corollary of this is that β₂ -agonist use plus allergen exposure might cause more airway inflammation than does allergen exposure alone. These hypotheses are both testable. I believe that this is a clinically important phenomenon and may well be a major reason for β₂ -agonist–induced worsened asthma control. Further investigations are indicated to identify the mechanism and the clinical relevance of the phenomenon. (J Allergy Clin Immunol 1998;102:S96-9)     

Expression and function of a novel variant of estrogen receptor-α36 in murine airways

Evidence suggests that estrogen signaling is involved in sex differences in the prevalence rates and control of asthma, but the expression patterns of estrogen receptor variants and estrogen function in the lung are not well established. We investigated the expression of major estrogen receptor variants occurring naturally and after the development of allergen-induced airway hyperreactivity in a murine model of allergic asthma, along with the role of estrogen signaling in small-airway ciliary motion and smooth muscle contraction. Female BALB/c mice were sensitized with ovalbumin, and estrogen receptor expression patterns were examined by immunofluorescence and Western blot analysis. Time-lapse video and photodiode-based displacement measurement systems were used to assess the effects of estrogen signaling on airway ciliary beat frequency and smooth muscle contraction. We found that a novel variant of estrogen receptor (ER)-α, ER-α36, is expressed in airway epithelial and smooth muscle cells. ER-α36 was predominately localized on the plasma membranes of airway cells. After sensitization to allergen, the expression levels of ER-α36 increased significantly (P < 0.01), whereas the expression of ER-β and ER-α66 did not significantly change. Estrogen treatment in vitro resulted in a rapid increase in airway cilia motion in a dose-dependent fashion, but did not exert any effect on airway smooth muscle contraction. We speculate that the up-regulation of estrogen receptor expression associated with allergen-induced airway hyperresponsiveness may constitute a protective mechanism to facilitate the clearance of mucus. The identification and localization of specific estrogen receptor subtypes in the lung could lead to newer therapeutic avenues aimed at addressing sex differences of asthma susceptibility.     

The role of γδ T cells in the airways

Based on their T cell receptor expression two distinct T cell populations have been identified and designated as alphabeta and gammadelta T cells. While the specific role of alphabeta T cells is well understood, the specific function of gammabeta T cells remains elusive. Despite the limited knowledge on what gammadelta T cells exactly recognize as their antigen or antigens, several studies have clearly demonstrated that gammadelta T cells are important regulators of immune responses. Studies on gammadelta T cells in the lung have shown that gammadelta T cells influence B and T cell responses. For instance, gammadelta T cells modulate CD4+alphabeta T cells in tuberculosis, and in allergic inflammation they support IgE production. Furthermore, a recent study on their role as part of the innate immune response has demonstrated that gammadelta T cells regulate airway function independently of alphabeta T cells. This novel finding provides an opportunity to review previous studies on gammadelta T cells in the lung of mice and humans. The examination of these data demonstrates that understanding the role of the various subsets of gammadelta T cells will be critical in elucidating their function as "immunosurveillance cells" of the lung.     

Molecular biology of the nasal airways: how do we assess cellular and molecular responses in the nose?

We summarize studies herein that relate to use of molecular techniques to assess mechanism of toxicant and carcinogen action on the nasal mucosa. Specifically, we present the results of an in vivo mutagenesis assay with the herbicide alachlor, which causes olfactory mucosal tumors in rats following dietary administration. A positive response was found in olfactory mucosa after 3 mo of treatment. There was no increase in mutant frequency in the adjacent nasal respiratory mucosa or in liver, which are both non-target tissues for alachlor carcinogenesis. We also summarize previous findings of gene expression studies. One on these was a GeneChip experiment aimed at elucidating the mechanism of alachlor olfactory carcinogenesis, wherein we found that oxidative stress and gelatinase genes were upregulated early in the carcinogenic process, while genes consistent with activation of Wnt signaling were activated later in the carcinogenic process. The final example presented summarizes the results of a microarray experiment designed to identify novel olfactory genes involved in the plasticity of the olfactory mucosa. Those studies identified novel olfactory mucosal genes including Sgpl1 and Pon1. In each instance, precise sampling is emphasized and proper controls are discussed, and examples of independent means of validation of genomics experiments are presented.     

Adipokine expression and secretion by canine adipocytes: stimulation of inflammatory adipokine production by LPS and TNFα

Adiposity and obesity are increasing in dogs. We have examined here the endocrine function of canine adipose tissue and the regulation of production of inflammation-related adipokines by dog adipocytes. Adiponectin, leptin, IL-6, MCP-1 and TNFα genes were expressed in the main adipose depots of dogs, but there were no major depot differences in mRNA levels. Each adipokine was expressed in canine adipocytes differentiated in culture and secreted into the medium (leptin undetected). IL-6, MCP-1 and TNFα were also expressed and secreted by preadipocytes; adiponectin and leptin were only expressed after adipocyte differentiation. The inflammatory mediators LPS and TNFα had major stimulatory effects on the expression and secretion of IL-6, MCP-1 and TNFα; there was a >5,000-fold increase in IL-6 mRNA level with LPS. IL-6 release into the medium was increased >50-fold over 24 h with LPS and TNFα, while MCP-1 release was increased 23- and 40-fold by TNFα and LPS, respectively. However, there was no effect, or small reductions, in adiponectin and leptin mRNA levels with the inflammatory mediators. Dexamethasone-stimulated leptin gene expression, had no effect on adiponectin expression, but decreased the expression and secretion of IL-6 and MCP-1. The PPARγ agonist rosiglitazone stimulated both adiponectin and leptin expression and inhibited the expression of IL-6, MCP-1 and TNFα; MCP-1 secretion was reduced. These results demonstrate that canine adipocytes express and secrete key adipokines and show that adipocytes of this species are highly responsive to inflammatory mediators with the induction of major increases in the production of inflammation-related adipokines.     

Anthropogenic climate change and allergen exposure: The role of plant biology

Accumulation of anthropogenic gases, particularly CO(2), is likely to have 2 fundamental effects on plant biology. The first is an indirect effect through Earth's increasing average surface temperatures, with subsequent effects on other aspects of climate, such as rainfall and extreme weather events. The second is a direct effect caused by CO(2)-induced stimulation of photosynthesis and plant growth. Both effects are likely to alter a number of fundamental aspects of plant biology and human health, including aerobiology and allergic diseases, respectively. This review highlights the current and projected effect of increasing CO(2) and climate change in the context of plants and allergen exposure, emphasizing direct effects on plant physiologic parameters (eg, pollen production) and indirect effects (eg, fungal sporulation) related to diverse biotic and abiotic interactions. Overall, the review assumes that future global mitigation efforts will be limited and suggests a number of key research areas that will assist in adapting to the ongoing challenges to public health associated with increased allergen exposure.     

Molecular and functional characterization of carp TNF: a link between TNF polymorphism and trypanotolerance?

Two carp tumor necrosis factor alpha (TNFalpha) genes have been cloned and sequenced. Both TNF1 and TNF2 sequences have several polymorphisms in the 3' UTR and TNF2 has a polymorphism in the coding sequence. Lipopolysaccharide and the protozoan blood flagellate Trypanoplasma borreli induced expression of TNFalpha in carp head kidney phagocytes when added in vitro. Differential expression was observed, with TNF2 being higher expressed than TNF1. We used the TNFalpha-specific inhibitor pentoxifylline to demonstrate the involvement of carp TNFalpha in the induction of nitric oxide and in the stimulation of cell proliferation. In addition, two carp lines differing in their resistance to T. borreli were typed for the TNF2 polymorphism and association between one isoform and resistance was found.     

The role of small airways in monitoring the response to asthma treatment: what is beyond FEV1?

The definition of asthma has evolved from that of an episodic disease characterized by reversible airways constriction to a chronic inflammatory disease of the airways, with at least partially reversible airway constriction. Increasing evidence supports the notion that small and large airways play a central role in asthma pathophysiology with regard to inflammation, remodeling and symptoms. The contribution of the distal airways to the asthma phenotype carries implications for the delivery of inhaled medications to the appropriate areas of the lung and for the monitoring of the response to asthma treatment. Asthma control is evaluated on the basis of symptoms, lung function and exacerbations. However, evidence suggests that dissociation between lung function and respiratory symptoms, quality of life and airway inflammation exists. In this study, common spirometric parameters offer limited information with regard to the peripheral airways, and it is therefore necessary to move beyond FEV₁. Several functional parameters and inflammatory markers, which are discussed in the present study, can be employed to evaluate distal lung function. In this study, extrafine formulations deliver inhaled drugs throughout the bronchial tree (both large and small airways) and are effective on parameters that directly or indirectly measure air trapping/airway closure.     

Gelatin promotes murine fibrosarcoma L929 cell detachment and protects the cells from TNFα-induced cytotoxicity

Purpose: Gelatin has been considered to exist as intermediate substance of collagen catabolism in tissue remodeling or under inflammatory conditions. We have initiated the study on possible biological functions of gelatin that can exist temporally and locally under the conditions of remodeling and inflammation Materials and methods: To this purpose, we investigated cell proliferation and survival on gelatin-coated dishes and the response to tumor necrosis factor α (TNFα)–induced cytotoxicity in L929 cells. Autophagy level, ATP level, and ROS generation are examined. Results: L929 cells detached from the gelatin-coated dishes and formed multicellular aggregates. TNFα-induced cytotoxicity in L929 cells was inhibited by gelatin-coating culture. The cells on gelatin-coated dishes showed reduced cellular ATP levels and increased adenosine 5′-monophosphate (AMP)–activated protein kinase (AMPK) phosphorylation, leading to increased ROS generation and autophagy. Conclusion: This study showed that gelatin-coated culture protected L929 cells from TNFα-induced cytotoxicity and suggested for a possible pathophysiological function of gelatin in regulating cellular functions.     

Binding of LPS and LPS—LDL Complexes to Rat Hepatocytes

We studied binding of ³H-LPS toxin and LPS complexes with serum ¹²⁵I-LDL to primary culture of rat hepatocytes. Receptor binding of LPS and LDL—LPS complex was ∼50 and 77% of the total, respectively. Scatchard plot was linear in both cases. LDL and LDL—LPS complexes were inessential for LPS binding, while LDL—LPS binding was appreciably suppressed by LPS (−30%) and LDL (−65%).__________Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 139, No. 4, pp. 436–438, April, 2005     

Crucial role of TNFα-induced adipose-related protein (TIARP) in the pathogenesis of autoimmune arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disorder with a variable disease outcome, and is characterized by inflammation of multiple joints. Proinflammtory cytokines, such as tumor necrosis factor alpha (TNFα), interleukin-6 (IL-6) are thought to play crucial roles in the pathology of RA. The prognosis of patients with RA has improved significantly with the recent availability of biologics targeting TNFα and IL-6. Immunization of DBA/1 mice with glucose-6-phosphate isomerase (GPI) induces severe acute arthritis. This arthritis can be controlled by TNFα antagonists, suggesting similar etiology to RA. We performed GeneChip analysis using splenocytes of mice with GPI-induced arthritis. Among the arrayed TNFα-related genes, the expression of TNFα-induced adipose-related protein (TIARP) mRNA was the highest. TIARP was detected specifically in joints and spleens of arthritic mice. Among the splenocytes, CD11b(+) cells were the main source of TIARP mRNA. STEAP4 (the human ortholog of TIARP) was highly upregulated in joints of patients with RA and especially co-localized with CD68(+) macrophages. In this study, we discuss the role of TIARP in the generation of experimental autoimmune arthritis and the possible clinical application of for the treatment of RA.     

Expression of a metastatic phenotype in IFNs-primed/TNFα-activated B16 murine melanoma cells: role of JAK1/PKCδ signal transduction factors

In previous studies, we found that IFNγ and TNFα generated by activated macrophages stimulate the metastatic potential in F10-M3 cells, a clone isolated from B16-F10 murine melanoma line. In this phenomenon, TNFα promoted the expression of a metastatic phenotype in tumor cells previously primed with IFNγ. Here, we demonstrate that IFNα or IFNβ may replace IFNγ in priming tumor cells. We also noticed that an enhancement of the expression of p55TNFα receptor was associated with the preconditioning of tumor cells with IFNγ and IFNβ. By the use of an appropriate inhibitor, we observed that JAK1 signal transduction pathway was involved in the expression of a metastatic phenotype and of p55TNFα receptor shown in IFNγ- and IFNβ-primed melanoma cells stimulated with TNFα. Furthermore, the activity of the protein kinase C (PKC) was required for IFNγ-primed melanoma cells to express a metastatic phenotype after stimulation with TNFα. In conclusion, our study shows that a metastatic phenotype was expressed in B16 murine melanoma cells stimulated with TNFα regardless of whether the cells were primed with IFNγ IFNα or IFNβ. The molecular events leading to the expression of a metastatic phenotype in F10-M3 melanoma cells are represented by: (a) an enhanced expression of p55TNFα receptor in IFNs-primed tumor cells dependent on JAK1 signal transduction pathway; and (b) an intact PKC activity during TNFα stimulation.     

Synergism of basic fibroblast growth factor and interleukin-1β to induce articular cartilage-degradation in the rabbit

Interleukin-1 (IL-1) and basic fibroblast growth factor (bFGF) synergistically induce proteasesin vitro. To investigate this synergyin vivo, we injected IL-1 and bFGF alone and in combination into the lapine knee. Three days later, we compared the glycosaminoglcan (GAG) content of tibial cartilage of cytokinetreated and contralateral control-knees. IL-1 caused significant increases of granulocytes and GAG in the synovial fluid but minor cartilage-GAG losses of 11, 11 & 16% at 5kU, 10 kU and 100 kU IL-1/knee, respectively. bFGF at 2 and 10 g/knee caused no changes. 10 g bFGF in combination with 10 kU IL-1 induced a 33% GAG loss (p<0.01) that lasted 21 days. IL-1/bFGF induced cartilage degradation may be useful to 1) evaluate agents which modulated proteoglycan catabolism and 2) assess factors that accelerate cartilage-repair.     

The role of Th17 cells: explanation of relationship between periodontitis and COPD?

Periodontitis and chronic obstructive pulmonary disease (COPD) are chronic inflammatory diseases with common risk factors, such as long-term smoking, age, and social deprivation. Many observational studies have shown that periodontitis and COPD are correlated. Moreover, they share a common pathophysiological process involving local accumulation of inflammatory cells and cytokines and damage of soft tissues. The T helper 17 (Th17) cells and the related cytokines, interleukin (IL)-17, IL-22, IL-1β, IL-6, IL-23, and transforming growth factor (TGF)-β, play a crucial regulatory role during the pathophysiological process. This paper reviewed the essential roles of Th17 lineage in the occurrence of periodontitis and COPD. The gaps in the study of their common pathological mechanism were also evaluated to explore future research directions. Therefore, this review can provide study direction for the association between periodontitis and COPD and new ideas for the clinical diagnosis and treatment of the two diseases.