Blockade of JAK2 by tyrphostin AG-490 inhibits antigen-induced eosinophil recruitment into the mouse airways

A multi-omics Mendelian randomization identifies putatively causal genes and DNA methylation sites for asthma

Background

Asthma is a global chronic respiratory disease with complex pathogenesis. While current therapies offer some relief, they often fall short in effectively managing symptoms and preventing exacerbations for numerous patients. Thus, understanding its mechanisms and discovering new drug targets remains a pressing need for better treatment.

Methods

Using the GEO dataset, we screened differentially expressed genes (DEGs) in asthma patients' blood. Employing Summary Data-based Mendelian Randomization (SMR) and Two-Sample Mendelian Randomization (TSMR), we pinpointed asthma causal genes, causal DNA methylation sites, and methylation sites affecting gene expression, cross validated with at least 2 large-scale GWAS from each source. We utilized colocalization for genetic associations, meta-analysis for data integration, two-step MR for methylation-gene-asthma mediation mechanism. Druggability was evaluated using Open Target, virtual screening, and docking.

Results

Among the 954 DEGs found in asthma patients' blood, increased expression of CEP95 (discovery, OR_SMR = 0.94, 95% CI: 0.91-0.97), RBM6 (discovery, OR_SMR = 0.97, 95% CI: 0.95-0.99), and ITPKB (discovery, OR_SMR = 0.82, 95% CI: 0.74-0.92) in the blood decreased the risk of asthma, higher levels of HOXB-AS1 (discovery, OR_SMR = 1.05, 95% CI: 1.03-1.07), ETS1 (discovery, OR_SMR = 1.62, 95% CI: 1.29-2.04), and JAK2 (discovery, OR_SMR = 1.13, 95% CI: 1.06-1.21) in the blood increased the risk of asthma. Additionally, a total of 8 methylation sites on ITPKB, ETS1, and JAK2 were identified to influence asthma. An increase in methylation at site cg16265553 raised the risk of asthma partially by suppressing ITPKB expression. Similarly, increased methylation at cg13661497 reduced the asthma risk totally by suppressing JAK2 expression. The impact of CEP95, HOXB-AS1, and RBM6 expressions on asthma was further confirmed in lung tissues. Except for HOXB-AS1, all the other genes were potential druggable targets.

Conclusion

Our study highlighted that specific gene expressions and methylation sites significantly influence asthma risk and revealed a potential methylation-to-gene-to-asthma mechanism. This provided pivotal evidence for future targeted functional studies and the development of preventive and treatment strategies.

Icariin attenuates asthmatic airway inflammation via modulating alveolar macrophage activation based on network pharmacology and in vivo experiments

BACKGROUND

Icariin (ICA) inhibits inflammatory response in various diseases, but the mechanism underlying ICA treating airway inflammation in asthma needs further understood. We aimed to predict and validate the potential targets of ICA against asthma-associated airway inflammation using network pharmacology and experiments.

METHODS

The ovalbumin-induced asthma-associated airway inflammation mice model was established. The effects of ICA were evaluated by behavioral, airway hyperresponsiveness, lung pathological changes, inflammatory cell and cytokines counts. Next, the corresponding targets of ICA were mined via the SEA, CTD, HERB, PharmMapper, Symmap database and the literature. Pubmed-Gene and GeneCards databases were used to screen asthma and airway inflammation-related targets. The overlapping targets were used to build an interaction network, analyze gene ontology and enrich pathways. Subsequently, flow cytometry, quantitative real-time PCR and western blotting were employed for validation.

RESULTS

ICA alleviated the airway inflammation of asthma; 402 targets of ICA, 5136 targets of asthma and 4531 targets of airway inflammation were screened; 216 overlapping targets were matched and predicted ICA possesses the potential to modulate asthmatic airway inflammation by macrophage activation/polarization. Additionally, ICA decreased M1 but elevated M2. Potential targets that were disrupted by asthma inflammation were restored by ICA treatment.

CONCLUSIONS

ICA alleviates airway inflammation in asthma by inhibiting the M1 polarization of alveolar macrophages, which is related to metabolic reprogramming. Jun, Jak2, Syk, Tnf, Aldh2, Aldh9a1, Nos1, Nos2 and Nos3 represent potential targets of therapeutic intervention. The present study enhances understanding of the anti-airway inflammation effects of ICA, especially in asthma.

Weighted Breaths: Exploring Biologic and Non-Biologic Therapies for Co-Existing Asthma and Obesity

PURPOSE OF REVIEW

To discuss the effectiveness of biologics, some of which comprise the newest class of asthma controller medications, and non-biologics in the treatment of asthma co-existing with obesity.

RECENT FINDINGS

Our review of recent preliminary and published data from clinical trials revealed that obese asthmatics respond favorably to dupilumab, mepolizumab, omalizumab, and tezepelumab, which are biologics currently indicated as add-on maintenance therapy for severe asthma. Furthermore, clinical trials are ongoing to assess the efficacy of non-biologics in the treatment of obese asthma, including a glucagon-like peptide-1 receptor agonist, a Janus kinase inhibitor, and probiotics. Although many biologics presently indicated as add-on maintenance therapy for severe asthma exhibit efficacy in obese asthmatics, other phenotypes of asthma co-existing with obesity may be refractory to these medications. Thus, to improve quality of life and asthma control, it is imperative to identify therapeutic options for all existing phenotypes of obese asthma.

Blockade of JAK2 signaling produces immunomodulatory effect to preserve pancreatic homeostasis in severe acute pancreatitis

JAK/STAT plays an important role in cytokine signal transduction and it is potentially involved in the proinflammatory response during the early phase of severe acute pancreatitis (SAP). However, whether JAK2 activity is upregulated and whether JAK2 inhibition plays a role in the maintenance of pancreatic homeostasis during SAP is incompletely understood. Here we show that JAK2/STAT3 activity is highly elevated in SAP and blockade of JAK2 by AG-490 protects against SAP-induced pancreatic inflammation and injury. Gene expression and ELISA studies showed that JAK2 inhibition altered the cytokine profiles in both the circulation and pancreases. Further analysis revealed that JAK2 inhibition restored the level of cytokines critical for macrophage polarization towards M2 macrophage. Our findings suggest that pharmacological targeting at JAK2/STAT signalling may be an effective choice of therapeutic interventions against SAP.

LncRNA analysis of lung tissues after hUC-MSCs and FTY720 treatment of lipopolysaccharide-induced acute lung injury in mouse models

Acute lung injury (ALI), a persistent lung inflammatory response syndrome, may evolve into acute respiratory distress syndrome (ARDS). Characterized by rapid onset, critical features, and a complex etiology, ALI remains a challenging critical respiratory disease. Recently, mesenchymal stem cells (MSCs) have provided a new solution for the treatment of ALI. We built a lipopolysaccharide (LPS)-induced ALI model in mice. After treatment with human umbilical cord mesenchymal stem cells (hUC-MSCs), FTY720, or a combination of hUC-MSCs and FTY207, the lung inflammatory response was apparently attenuated. To understand the mechanism underlying MSCs treatment of ALI at the genetic level, significant differentially expressed long non-coding RNAs (lncRNAs) between the treatment and model groups were analyzed using microarray technology. Moreover, genetic gene prediction, gene ontology (GO) analysis, pathway analysis, and transcription factor (TF) prediction were carried out. The results showed that a total of 66 lncRNAs were differentially expressed in all three treatment groups, including 8 up-regulated and 58 down-regulated lncRNAs. LncRNA A_30_P01029806 and A_30_P01029194, which were down-regulated, were involved in the signaling pathways closely related to ALI. Through further TF analysis, we identified several significant TFs which lay a foundation for revealing the mechanism underlying lncRNAs treatment of ALI. LncRNA A_30_P01029806 and A_30_P01029194 may serve as candidate biomarkers in the diagnosis and treatment of ALI.

Association analyses of the JAK/STAT signaling pathway with the progression and prognosis of colon cancer

The present study investigated the association between the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway with tumor progression and prognosis of colon cancer. A total of 62 patients with colon cancer were selected as the colon cancer group, and 40 patients with colon lesions were selected as the benign colon lesion group. Immunohistochemistry was used to detect the expression levels of JAK-1 and STAT-3 proteins in colon tissues. The association of JAK-1 and STAT-3 proteins with the pathological parameters and prognosis of colon cancer were analyzed. The total positive rates of JAK-1 and STAT-3 proteins in lesions of patients in the colon cancer group were significantly higher compared with those in the benign colon lesion group (P<0.05). The positive expression of JAK-1 and STAT-3 proteins in patients with colon cancer were not significantly associated with sex, age, tumor differentiation degree and neurovascular invasion (P>0.05), but significantly associated with the clinical stage of colon cancer, tumor infiltration depth and lymph node metastasis (P<0.05). The survival time of patients with colon cancer with positively-expressed JAK-1 and STAT-3 proteins was significantly shorter compared with that of patients with negatively-expressed JAK-1 and STAT-3 proteins (P<0.05). tumor-node-metastasis (TNM) stage, lymph node metastasis and the expression of JAK-1 and STAT-3 proteins in the tumor were associated with the prognosis of patients with colon cancer (P<0.05). TNM stage and the expression levels of JAK-1 and STAT-3 proteins were independent risk factors influencing the prognosis of colon cancer (P<0.05). The JAK/STAT signal may be used as a novel tumor marker and prognostic factor for the diagnosis, assessment and prognosis of colon cancer.

Overexpression of microRNA-375 impedes platelet-derived growth factor-induced proliferation and migration of human fetal airway smooth muscle cells by targeting Janus kinase 2

The abnormal proliferation and migration of airway smooth muscle (ASM) cells play a critical role in airway remodeling during the development of asthma. MicroRNAs (miRNAs) have emerged as critical regulators of ASM cell proliferation and migration in airway remodeling. In this study, we aimed to investigate the potential role of miR-375 in the regulation of platelet-derived growth factor (PDGF)-induced fetal ASM cell proliferation and migration. Our results showed that miR-375 expression was significantly decreased in fetal ASM cells that were treated with PDGF. Functional data showed that overexpression of miR-375 inhibited the proliferation and migration of fetal ASM cells, whereas inhibition of miR-375 enhanced the proliferation and migration of fetal ASM cells. The results of bioinformatics analysis and a dual-luciferase reporter assay showed that miR-375 binds directly to the 3'-untranslated region of Janus kinase 2 (JAK2). Further data confirmed that miR-375 negatively regulates the expression of JAK2 in fetal ASM cells. Moreover, miR-375 also impeded the PDGF-induced activation of signal transducer and activator of transcription 3 (STAT3) in fetal ASM cells. However, restoration of JAK2 expression partially reversed the inhibitory effect of miR-375 on fetal ASM cell proliferation and migration. Overall, our results demonstrate that miR-375 inhibits fetal ASM cell proliferation and migration by targeting JAK2/STAT3 signaling. Our study provides a potential therapeutic target for the development of novel treatment strategies for pediatric asthma.

Recombinant human brain natriuretic peptide ameliorates trauma-induced acute lung injury via inhibiting JAK/STAT signaling pathway in rats

BACKGROUND

JAK/STAT signal pathway plays an important role in the inflammation process of acute lung injury (ALI). This study aimed to investigate the correlation between recombinant human brain natriuretic peptide (rhBNP) and the JAK/STAT signaling pathway and to explore the protective mechanism of rhBNP against trauma-induced ALI.

METHODS

The arterial partial pressure in oxygen, lung wet-dry weight ratios, protein content in bronchoalveolar lavage fluid, the histopathologic of the lung, as well as the protein expressions of STAT1, JAK2, and STAT3 were detected.

RESULTS

Sprague-Dawley rats were randomly divided into five groups: a control group, a sham-operated group, an ALI group, an ALI + rhBNP group, and an ALI + AG490 group. At 4 hours, 12 hours, 1 day, 3 days, and 7 days after injury, injured lung specimens were harvested. rhBNP pretreatment significantly ameliorated hypoxemia and histopathologic changes and alleviated pulmonary edema in trauma-induced ALI rats. rhBNP pretreatment reduced the phosphorylated protein and total protein level of STAT1. Similarly to JAK-specific inhibitor AG490, rhBNP was shown to significantly inhibit the phosphorylation of JAK2 and STAT3 in rats with trauma-induced ALI.

CONCLUSION

Our experimental findings indicated that rhBNP can protect rats against trauma-induced ALI and that its underlying mechanism may be related to the inhibition of JAK/STAT signaling pathway activation.

Genetics of hypersensitivity to aspirin and nonsteroidal anti-inflammatory drugs

Various hypersensitivity reactions have been reported with aspirin and nonsteroidal anti-inflammatory drugs. Hypersensitivity can occur regardless of a chemical drug structure or its therapeutic potency. Allergic conditions include aspirin-exacerbated respiratory disease (AERD or aspirin-induced asthma), aspirin-induced urticaria/angioedema (AIU), and anaphylaxis. Several genetic studies on aspirin hypersensitivity have been performed to discover the genetic predisposition to aspirin hypersensitivity and to gain insight into the phenotypic diversity. This article updates data on the genetic mechanisms that govern AERD and AIU and summarizes recent findings on the molecular genetic mechanism of aspirin hypersensitivity.

Hypereosinophilia, JAK2V617F, and Budd-Chiari syndrome: who is responsible for what?

Budd-Chiari syndrome (BCS) is characterized by hepatic venous outflow obstruction, which sometimes may be life threatening, with the development of fulminant hepatic failure. In cases of this kind, the most frequent underlying cause of BCS, myeloproliferative neoplasms (MPN), should always be excluded first, and molecular analysis of the Janus Kinase 2 (JAK2) mutation must always be performed [1]. While the association of BCS with polycythemia vera, essential thrombocythemia, and idiopathic myelofibrosis is well documented, hypereosinophilia has only been described in sporadic cases [2–7]. Furthermore, Jak2 mutation in association with hypereosinophilia has been reported very rarely and its prevalence in this disorder still requires further investigation [8,9]. To the best of our knowledge, cases with the above association occurring together with BCS have not been reported until now. Here, we describe a young woman presenting with idiopathic eosinophilia, JAK2 mutation, and BCS. We also elaborate briefly on the biological mechanism and clinical features of this rare entity. In our opinion, this case supports the formal inclusion of hypereosinophilic syndrome (HES) in the WHO MPN category and also raises the possible pathogenetic contribution of eosinophils, or their products, in MPN-associated splanchnic vein thrombosis.

The role of protein tyrosine phosphatases in the regulation of allergic asthma: implication of TC-PTP and PTP-1B in the modulation of disease development

Protein tyrosine phosphorylation is an important early event in the signal transduction of numerous cell receptors involved in the immune response. The implication of protein tyrosine kinases in allergic asthma is well recognized, but the role of protein tyrosine phosphatases (PTPs) remains poorly understood. However, we recently reported that global inhibition of PTPs during either the allergen-sensitization phase or the allergen-challenge phase reduced the development of asthma and that this correlated with an increased T helper 1 (Th1) response in both lung and spleen tissues. Therefore, in this study we investigated individual roles of PTPs involved in regulating the immune response. We observed that genetic deficiency for PTP-1B resulted in increased recruitment of lung inflammatory cells, while protein tyrosine phosphatase-phosphatase and tensin homologue deleted (PTP-PEST)-deficient mice exhibited a phenotype similar to that of wild-type mice. Importantly, we found that a heterozygous mutation of T cell PTP (TC-PTP) dramatically abrogates immunoglobulin E production and reduces the recruitment of inflammatory cells to the lung, conferring an important role for TC-PTP in the development of allergic asthma. As opposed to other studies on Src homology phosphatase-1 (SHP-1) deficiency, specific acute SHP-1 inhibition during allergen challenge did not affect disease outcome. Collectively, our results underscore the importance of PTPs in the development of allergic asthma.

The JAK-3 inhibitor CP-690550 is a potent anti-inflammatory agent in a murine model of pulmonary eosinophilia

Janus kinase 3 (JAK-3) is a tyrosine kinase that has been shown to participate in the signaling of several cytokines that are believed to play a role in allergic airway disease, e.g. IL-2, 4 and 9. The current study describes the immunosuppressive effects of CP-690550, a novel, small molecule inhibitor of JAK-3, in a murine model of allergic pulmonary inflammation. In vitro, CP-690550 potently inhibited IL-4 induced upregulation of CD23 (IC(50)=57 nM) and class II major histocompatibility complex (MHCII) expression (IC(50)=71 nM) on murine B cells. Repeat aerosol exposure to ovalbumin in wild-type mice sensitized to the antigen resulted in preferential recruitment of Th2-like cells (IL-4+ and IL-5+) into bronchoalveolar lavage fluid (BAL). The importance of IL-4 in the development of pulmonary eosinophilia was supported by a marked (90%) reduction in the influx of these cells in IL-4KO mice similarly sensitized and ovalbumin exposed. Animals dosed with CP-690550 (15 mg/kg/d) during the period of antigen sensitization and boost demonstrated marked reductions in BAL eosinophils and levels of IL-13 and eotaxin following ovalbumin aerosol exposure. The JAK-3 inhibitor (1.5-15 mg/kg/d) also effectively reduced the same parameters when administered during the period of antigen challenge. In contrast, the calcineurin inhibitor tacrolimus (10 mg/kg) was effective only when administered during the period of ovalbumin aerosol exposure. These data support the participation of JAK-3 in processes that contribute to pulmonary eosinophilia in the allergic mouse model. CP-690550 represents an intriguing novel therapy for treatment of allergic conditions associated with airway eosinophilia including asthma and rhinitis.

Suppression of IL-1beta expression by the Jak 2 inhibitor AG490 in cerulein-stimulated pancreatic acinar cells

Cerulein pancreatitis is similar to human edematous pancreatitis with dysregulation of the digestive enzyme production and cytoplasmic vacuolization, the death of acinar cells, edema formation, and an infiltration of inflammatory cells into the pancreas. Cytokines are up-regulated in pancreatic acinar cells stimulated with cerulein. In various cells and tissues, Janus kinase (Jak)/signal transducer and activator of transcription (Stat) pathway mediates inflammatory process. In the present study, we investigated whether the activation of Jak/Stat signaling mediates IL-1beta expression in pancreatic acinar AR42J cells stimulated with cerulein in vitro as well as the rats with cerulein pancreatitis in vivo using AG490, the Jak2 inhibitor. Activation of Jak2 and Stat3 were monitored by Western blot analysis for phosphorylated Jak2 and phosphorylated Stat3. mRNA expression and protein level of IL-1beta were determined by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbant assay (ELISA). Histological examination of pancreatic tissues were performed and serum IL-1beta levels of the rats were determined by ELISA. As a result, cerulein induced the activation of Jak2 and Stat3 as well as IL-1beta expression, which was inhibited by the treatment of AG490 in AR42J cells. In cerulein pancreatitis of the rats, edematous and inflammatory changes of the pancreas and increased serum levels of IL-1beta were suppressed by AG490 treatment. In conclusion, Jak2/Stat3 pathway may be the underlying mechanism in the pathogenesis of pancreatitis by inducing cytokines such as IL-1beta.

Biallelic mutation of SOCS-1 impairs JAK2 degradation and sustains phospho-JAK2 action in the MedB-1 mediastinal lymphoma line

Primary mediastinal B-cell lymphoma (PMBL) is a well-defined subtype of diffuse large B-cell lymphoma. Molecular cytogenetics revealed frequent gains of 9p24. JAK2, mapping in this region, is presently regarded as a candidate oncogene because expression profiling showed high Janus kinase-2 (JAK2) transcript levels and JAK2 was found to be constitutively phosphorylated in mediastinal B-cell lymphomas. We confirm that in the MedB-1 mediastinal B-cell line, harboring a trisomy 9, JAK2 transcription is elevated and the product is highly phosphorylated. However, JAK2 is not overexpressed at the protein level. On top, JAK2 protein turnover is even delayed. This unexpected finding coincides with a biallelic mutation of the suppressor of cytokine signaling-1 (SOCS-1) gene in this cell, which abrogates SOCS box function of the protein. Ectopic expression of wild-type (wt) SOCS-1 in MedB-1 leads to growth arrest and dramatic reduction of phospho-JAK2 and its downstream partner phospho-signal transducer and activator of transcription-5 (phospho-STAT5). Ultimately, the target gene cyclin D1 is repressed in transfectants while RB1, which is silenced in MedB-1, is induced. We conclude that, in MedB-1, action of phospho-JAK2 is sustained due to defective SOCS-1. Hence, SOCS-1 qualifies as a novel tumor suppressor. Of note, SOCS-1 mutations are also present in the parental tumor of MedB-1 and were detected in 9 of 20 PMBLs.

Biochemical assessment of intracellular signal transduction pathways in eosinophils: implications for pharmacotherapy

Allergic asthma and allergic rhinitis are inflammatory diseases of the airway. Cytokines and chemokines produced by T helper (Th) type 2 cells (GM-CSF, IL-4, IL-5, IL-6, IL-9, IL-10 and IL-13), eotaxin, transforming growth factor-beta, and IL-11 orchestrate most pathophysiological processes of the late-phase allergic reaction, including the recruitment, activation, and delayed apoptosis of eosinophils, as well as eosinophilic degranulation to release eosinophilic cationic protein, major basic protein, and eosinophil-derived neurotoxin. These processes are regulated through an extensive network of interactive intracellular signal transduction pathways that have been intensively investigated recently. Our present review updates the cytokine and chemokine-mediated signal transduction mechanisms including the RAS-RAF-mitogen-activated protein kinases, Janus kinases (signal transducers and activators of transcription), phosphatidylinositol 3-kinase, nuclear factor-kappa B, activator protein-1, GATA, and cyclic AMP-dependent pathways, and describes the roles of different signaling pathways in the regulation of eosinophil differentiation, recruitment, degranulation, and expression of adhesion molecules. We shall also discuss different biochemical methods for the assessment of various intracellular signal transduction molecules, and various antagonists of receptors, modulators, and inhibitors of intracellular signaling molecules, many of which are potential therapeutic agents for treating allergic diseases.

Jak2 and Ca2+/calmodulin are key intermediates for bradykinin B2 receptor-mediated activation of Na+/H+ exchange in KNRK and CHO cells

Na(+)/H(+) exchangers are ubiquitous in mammalian cells, carrying out key functions, such as cell volume defense, acid-base homeostasis, and regulation of the cytoskeleton. We used two screening technologies (FLIPR and microphysiometry) to characterize the signal transduction pathway used by the bradykinin B(2) receptor to activate Na(+)/H(+) exchange in two cell lines, KNRK and CHO. In both cell types, B(2) receptor activation resulted in rapid increases in the rate of proton extrusion that were sodium-dependent and could be blocked by the Na(+)/H(+) exchange inhibitors EIPA and MIA or by replacing extracellular sodium with TMA. Activation of Na(+)/H(+) exchange by bradykinin was concentration-dependent and could be blocked by the selective B(2) receptor antagonist HOE140, but not by the B(1) receptor antagonist des-Arg10-HOE140. Inhibitors of Jak2 tyrosine kinase (genistein and AG490) and of CAM (W-7 and calmidazolium) attenuated bradykinin-induced activation of Na(+)/H(+) exchange. Bradykinin induced formation of a complex between CAM and Jak2, supporting a regulatory role for Jak2 and CAM in the activation of Na(+)/H(+) exchange in KNRK and CHO cells. We propose that this pathway (B(2) receptor --> Jak2 --> CAM --> Na(+)/H(+) exchanger) is a fundamental regulator of Na(+)/H(+) exchange activity.

Tyrosine kinase inhibitors: a new approach for asthma

The pathogenesis of allergic asthma involves the interplay of inflammatory cells and airway-resident cells, and of their secreted mediators including cytokines, chemokines, growth factors and inflammatory mediators. Receptor tyrosine kinases are important for the pathogenesis of airway remodeling. Activation of epidermal growth factor (EGF) receptor kinase and platelet-derived growth factor (PDGF) receptor kinase leads to hyperplasia of airway smooth muscle cells, epithelial cells and goblet cells. Stimulation of non-receptor tyrosine kinases (e.g. Lyn, Lck, Syk, ZAP-70, Fyn, Btk, Itk) is the earliest detectable signaling response upon antigen-induced immunoreceptor activation in inflammatory cells. Cytokine receptor dimerization upon ligand stimulation induces activation of Janus tyrosine kinases (JAKs), leading to recruitment and phosphorylation of signal transducer and activator of transcription (STAT) for selective gene expression regulation. Activation of chemokine receptors can trigger JAK-STAT pathway, Lck, Fyn, Lyn, Fgr, and Syk/Zap-70 to induce chemotaxis of inflammatory cells. Inhibitors of tyrosine kinases have been shown in vitro to block growth factor-induced hyperplasia of airway-resident cells; antigen-induced inflammatory cell activation and cytokine synthesis; cytokine-mediated pro-inflammatory gene expression in inflammatory and airway cells; and chemokine-induced chemotaxis of inflammatory cells. Recently, anti-inflammatory effects of tyrosine kinase inhibitors (e.g. genistein, tyrphostin AG213, piceatannol, tyrphostin AG490, WHI-P97, WHI-P131, Syk antisense) in animal models of allergic asthma have been reported. Therefore, development of inhibitors of tyrosine kinases can be a very attractive strategy for the treatment of asthma.

Signaling molecules as therapeutic targets in allergic diseases

A molecular understanding of physiologic and pathologic processes requires complete knowledge about the signal transduction mechanism of involved cells. Signal transduction research is a rapidly growing field in basic science. Unlike intercellular inflammatory mediators, signaling molecules show less functional redundancy. This allows inhibition of multiple cytokines/mediators by blocking one common signaling molecule. Interference with signaling pathways has shown significant potential for inhibition of fundamental processes as well as clinical phenotype of allergic diseases. The purpose of this review was to provide a theoretical classification of signaling molecules based on their function and to analyze various strategies for developing effective signaling inhibitors for allergic diseases.

Janus Kinase 2, an Early Target of α7 Nicotinic Acetylcholine Receptor-mediated Neuroprotection against Aβ-(1–42) Amyloid

The molecular mechanisms of alpha7 nicotinic acetylcholine receptor (nAChR)-mediated neuroprotection remain unclear. In this study we provide evidence that nicotine stimulation of alpha7 nAChR transduces signals to phosphatidylinositol 3-kinase and Akt via Janus kinase 2 (JAK2) in a cascade, which results in neuroprotection. Exposure to beta-amyloid results in the activation of the apoptotic enzyme caspase-3 and cleavage of the DNA-repairing enzyme poly-(ADP-ribose) polymerase. This cascade is inhibited by nicotine through JAK2 activation, and these effects are blocked by preincubation with the JAK2-specific inhibitor AG-490. We also found that pretreatment of cells with angiotensin II blocks the nicotine-induced activation of JAK2 via the AT(2) receptor and completely prevents alpha7 nAChR-mediated neuroprotective effects further suggesting a pivotal role for JAK2. These findings identify novel mechanisms of receptor interactions relevant to neuronal viability and suggest novel therapeutic strategies to optimize neuroprotection.

Fgr deficiency results in defective eosinophil recruitment to the lung during allergic airway inflammation

Using a mouse model of allergic lung inflammation, we found that mice deficient of Fgr, a Src family tyrosine kinase highly expressed in myelomonocytic cells, fail to develop lung eosinophilia in response to repeated challenge with aerosolized OVA. Both tissue and airway eosinophilia were markedly reduced in fgr(-/-) mice, whereas mice with the sole deficiency of Hck, another Src family member, responded normally. Release of allergic mediators, such as histamine, IL-4, RANTES/CCL5, and eotaxin/CCL11, in the airways of OVA-treated animals was equal in wild-type and fgr(-/-) mice. However, lung eosinophilia in Fgr-deficient mice correlated with a defective accumulation of GM-CSF and IL-5 in the airways, whereas secretion of these cytokines by spleen cells in response to OVA was normal. Examination of mRNA expression in whole lung tissue allowed us to detect comparable expression of transcripts for eotaxin/CCL11, macrophage-inflammatory protein-1 alpha/CCL3, macrophage-inflammatory protein-1 beta/CCL4, monocyte chemoattractant protein-1/CCL2, TCA-3/CCL1, IL-4, IL-10, IL-2, IL-3, IL-9, IL-15, and IFN-gamma in OVA-sensitized wild-type and fgr(-/-) mice. In contrast, the increase in IL-5 and IL-13 mRNA expression was lower in fgr(-/-) compared with wild-type mice. These findings suggest that deficiency of Fgr results in a marked reduction of lung eosinophilia and the establishment of a positive feedback loop based on autocrine secretion of eosinophil-active cytokines. These results identify Fgr as a novel pharmacological target to control allergic inflammation.

Intracellular signal transduction in eosinophils and its clinical significance

The incidence and prevalence of allergic diseases such as asthma and allergic rhinitis have recently been increasing worldwide. Eosinophils are the principal effector cells for the pathogenesis of allergic inflammation via the secretion of highly cytotoxic granular proteins including eosinophil cationic protein, major basic protein and eosinophil protein X. Blood and tissue eosinophilia is a common manifestation of late-phase allergic inflammation causing tissue damage. The development of eosinophilia correlates with the production of haematopoietic cytokines including interleukin (IL)-3. IL-5 and granulocyte macrophage colony stimulating factor (GM-CSF), and eosinophil-specific chemoattractant, eotaxin, from T-lymphocytes and the epithelium respectively. Elucidation of intracellular mechanisms that control the activation, apoptosis and recruitment of eosinophils to tissues is therefore fundamental in understanding these disease processes and provides targets for novel drug therapy. Over the past decade, there has been intensive investigation for the intracellular signal transduction regulating various biological functions of eosinophils and their roles in the pathogenesis of eosinophil-related diseases. This review will emphasize on the cytokine and chemokine-mediated signal transductions including the RAS-RAF-mitogen-activated protein kinases (MAPK), Janus kinases (JAK)-signal transducers and activators of transcription (STAT), phosphatidylinositol 3-kinase (PI3K) and nuclear factor-kappa B (NF-kappaB), and various antagonists of receptors and inhibitors of intracellular signaling molecules as potential therapeutic agents of allergic diseases.

Interleukin-5: a novel target for asthma therapy

Eosinophilic airway inflammation is the main histologic correlate of airway hyper-responsiveness (AHR) and tissue injury in the pathogenesis of bronchial asthma. There is strong evidence for a central role of CD4+ T-cells secreting pro-allergic Th2-cytokines, such as IL-4 and IL-5, in the induction of airway eosinophilia and AHR. IL-5 appears to be one of the main pro-inflammatory mediators among a growing number of cytokines and chemokines that induce, regulate and sustain eosinophilic airway inflammation. Animal studies provide confirmatory evidence for the important role of IL-5 in the induction and maintenance of eosinophilic airway infiltration leading to altered airway function. Interfering with the action of IL-5 represents one of the new immunomodulatory therapeutic strategies in the treatment of bronchial asthma. Compared to established immunosuppressive agents like steroids, a major advantage of this strategy is the specificity of reducing eosinophilic inflammation, thus possibly acting nearly without side effects. There are several possible ways to inhibit the effects of IL-5 including alteration of the signalling pathway in the IL-5 producing cell by inhibition or modification of transcription factors or the use of antisense oligonucleotides and blocking of the IL-5 protein itself by monoclonal antibodies, soluble IL-5 receptor or antagonists of the IL-5 receptor expressed on the surface of eosinophils. Although preliminary data from the first clinical trials gave rise to skepticism about the efficacy of anti-IL-5 treatment regarding the improvement of lung function of asthmatic patients, further studies with a better defined profile of the target population may provide encouraging results, allowing the introduction of this truly new therapeutic concept.

Role of receptor for advanced glycation end-product (RAGE) and the JAK/STAT-signaling pathway in AGE-induced collagen production in NRK-49F cells

Advanced glycation end-product (AGE) is important in the pathogenesis of diabetic nephropathy (DN), and captopril (an angiotensin converting enzyme inhibitor) is effective in treating this disorder. We have shown that the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) cascade is responsible for AGE-induced mitogenesis in NRK-49F (normal rat kidney fibroblast) cells, but its role in renal fibrosis in DN remains unknown. Therefore, we have sought to determine whether JAK/STAT is involved in AGE-regulated collagen production in NRK-49F cells. We found that AGE time (1-7 days) and dose (10-200 microg/ml)-dependently increased collagen production in these cells. Additionally, AGE increased RAGE (receptor for AGE) protein expression. AGE-induced RAGE expression was dose-dependently inhibited by antisense RAGE oligodeoxynucleotide (ODN) and captopril. AGE-induced type I collagen production and JAK2-STAT1/STAT3 activation were decreased by AG-490 (a specific JAK2 inhibitor), antisense RAGE ODN and captopril. Meanwhile, STAT1 and STAT3 decoy ODNs also suppressed the induction of collagen by AGE. We concluded that RAGE and the JAK2-STAT1/STAT3 pathway were involved in AGE-induced collagen production in NRK-49F cells. Furthermore, captopril was found to reverse AGE-induced collagen production, probably by attenuating RAGE expression and JAK2-STAT1/STAT3 activities.