High affinity receptor for IgE stimulation activates protein kinase D augmenting activator protein-1 activity for cytokine producing in mast cells

Loss of Protein Kinase D2 Activity Protects Against Bleomycin-Induced Dermal Fibrosis in Mice

Protein kinase D (PKD) has been linked to inflammatory responses in various pathologic conditions; however, its role in inflammation-induced dermal fibrosis has not been evaluated. In this study, we aimed to investigate the roles and mechanisms of protein kinase D2 (PKD2) in inflammation-induced dermal fibrosis and evaluate the therapeutic potential of PKD inhibitors in this disease. Using homozygous kinase-dead PKD2 knock-in (KI) mice, we examined whether genetic ablation or pharmacologic inhibition of PKD2 activity affected dermal inflammation and fibrosis in a bleomycin (BLM)-induced skin fibrosis model. Our data showed that dermal thickness and collagen fibers were significantly reduced in BLM-treated PKD2 KI mice compared with that in wild-type mice, and so was the expression of α-smooth muscle actin and collagens and the mRNA levels of transforming growth factor-β1 and interleukin-6 in the KI mice. Corroboratively, pharmacologic inhibition of PKD by CRT0066101 also significantly blocked BLM-induced dermal fibrosis and reduced α-smooth muscle actin, collagen, and interleukin-6 expression. Further analyses indicated that loss of PKD2 activity significantly blocked BLM-induced infiltration of monocytes/macrophages and neutrophils in the dermis. Moreover, using bone marrow-derived macrophages, we demonstrated that PKD activity was required for cytokine production and migration of macrophages. We have further identified Akt as a major downstream target of PKD2 in the early inflammatory phase of the fibrotic process. Taken together, our findings indicate that PKD2 promotes dermal fibrosis via regulating immune cell infiltration, cytokine production, and downstream activation of Akt in lesional skin, and targeted inhibition of PKD2 may benefit the treatment of this condition.

Multifaceted Functions of Protein Kinase D in Pathological Processes and Human Diseases

Protein kinase D (PKD) is a family of serine/threonine protein kinases operating in the signaling network of the second messenger diacylglycerol. The three family members, PKD1, PKD2, and PKD3, are activated by a variety of extracellular stimuli and transduce cell signals affecting many aspects of basic cell functions including secretion, migration, proliferation, survival, angiogenesis, and immune response. Dysregulation of PKD in expression and activity has been detected in many human diseases. Further loss- or gain-of-function studies at cellular levels and in animal models provide strong support for crucial roles of PKD in many pathological conditions, including cancer, metabolic disorders, cardiac diseases, central nervous system disorders, inflammatory diseases, and immune dysregulation. Complexity in enzymatic regulation and function is evident as PKD isoforms may act differently in different biological systems and disease models, and understanding the molecular mechanisms underlying these differences and their biological significance in vivo is essential for the development of safer and more effective PKD-targeted therapies. In this review, to provide a global understanding of PKD function, we present an overview of the PKD family in several major human diseases with more focus on cancer-associated biological processes.

Regulation of Osteoclast Differentiation at Multiple Stages by Protein Kinase D Family Kinases

Balanced osteoclast and osteoblast activity is necessary for skeletal health, whereas unbalanced osteoclast activity causes bone loss in many skeletal conditions. A better understanding of pathways that regulate osteoclast differentiation and activity is necessary for the development of new therapies to better manage bone resorption. The roles of Protein Kinase D (PKD) family of serine/threonine kinases in osteoclasts have not been well characterized. In this study we use immunofluorescence analysis to reveal that PKD2 and PKD3, the isoforms expressed in osteoclasts, are found in the nucleus and cytoplasm, the mitotic spindle and midbody, and in association with the actin belt. We show that PKD inhibitors CRT0066101 and CID755673 inhibit several distinct aspects of osteoclast formation. Treating bone marrow macrophages with lower doses of the PKD inhibitors had little effect on M-CSF + RANKL-dependent induction into committed osteoclast precursors, but inhibited their motility and subsequent differentiation into multinucleated mature osteoclasts, whereas higher doses of the PKD inhibitors induced apoptosis of the preosteoclasts. Treating post-fusion multinucleated osteoclasts with the inhibitors disrupted the osteoclast actin belts and impaired their resorptive activity. In conclusion, these data implicate PKD kinases as positive regulators of osteoclasts, which are essential for multiple distinct processes throughout their formation and function.

Lysophosphatidic acid via LPA-receptor 5/protein kinase D-dependent pathways induces a motile and pro-inflammatory microglial phenotype

BACKGROUND

Extracellular lysophosphatidic acid (LPA) species transmit signals via six different G protein-coupled receptors (LPAR1-6) and are indispensible for brain development and function of the nervous system. However, under neuroinflammatory conditions or brain damage, LPA levels increase, thereby inducing signaling cascades that counteract brain function. We describe a critical role for 1-oleyl-2-hydroxy-sn-glycero-3-phosphate (termed "LPA" throughout our study) in mediating a motile and pro-inflammatory microglial phenotype via LPAR5 that couples to protein kinase D (PKD)-mediated pathways.

METHODS

Using the xCELLigence system and time-lapse microscopy, we investigated the migrational response of microglial cells. Different M1 and M2 markers were analyzed by confocal microscopy, flow cytometry, and immunoblotting. Using qPCR and ELISA, we studied the expression of migratory genes and quantitated the secretion of pro-inflammatory cytokines and chemokines, respectively. Different transcription factors that promote the regulation of pro-inflammatory genes were analyzed by western blot. Reactive oxygen species (ROS) and nitric oxide (NO) production, phagocytosis, and microglial cytotoxicity were determined using commercially available assay kits.

RESULTS

LPA induces MAPK family and AKT activation and pro-inflammatory transcription factors' phosphorylation (NF-κB, c-Jun, STAT1, and STAT3) that were inhibited by both LPAR5 and PKD family antagonists. LPA increases migratory capacity, induces secretion of pro-inflammatory cytokines and chemokines and expression of M1 markers, enhances production of ROS and NO by microglia, and augments cytotoxicity of microglial cell-conditioned medium towards neurons. The PKD family inhibitor blunted all of these effects. We propose that interference with this signaling axis could aid in the development of new therapeutic approaches to control neuroinflammation under conditions of overshooting LPA production.

CONCLUSIONS

In the present study, we show that inflammatory LPA levels increased the migratory response of microglia and promoted a pro-inflammatory phenotype via the LPAR5/PKD axis. Interference with this signaling axis reduced microglial migration, blunted microglial cytotoxicity, and abrogated the expression and secretion of pro-inflammatory mediators.

Severe Nausea and Vomiting in the Evaluation of Nitrous Oxide in the Gas Mixture for Anesthesia II Trial

Background

The Evaluation of Nitrous oxide in the Gas Mixture for Anesthesia II trial randomly assigned 7,112 noncardiac surgery patients to a nitrous oxide or nitrous oxide–free anesthetic; severe postoperative nausea and vomiting (PONV) was a prespecified secondary end point. Thus, the authors evaluated the association between nitrous oxide, severe PONV, and effectiveness of PONV prophylaxis in this setting.

Methods

Univariate and multivariate analyses of patient, surgical, and other perioperative characteristics were used to identify the risk factors for severe PONV and to measure the impact of severe PONV on patient outcomes.

Results

Avoiding nitrous oxide reduced the risk of severe PONV (11 vs. 15%; risk ratio [RR], 0.74 [95% CI, 0.63 to 0.84]; P < 0.001), with a stronger effect in Asian patients (RR, 0.55 [95% CI, 0.43 to 0.69]; interaction P = 0.004) but lower effect in those who received PONV prophylaxis (RR, 0.89 [95% CI, 0.76 to 1.05]; P = 0.18). Gastrointestinal surgery was associated with an increased risk of severe PONV when compared with most other types of surgery (P < 0.001). Patients with severe PONV had lower quality of recovery scores (10.4 [95% CI, 10.2 to 10.7] vs. 13.1 [95% CI, 13.0 to 13.2], P < 0.0005); severe PONV was associated with postoperative fever (15 vs. 20%, P = 0.001). Patients with severe PONV had a longer hospital stay (adjusted hazard ratio, 1.14 [95% CI, 1.05 to 1.23], P = 0.002).

Conclusions

The increased risk of PONV with nitrous oxide is near eliminated by antiemetic prophylaxis. Severe PONV, which is seen in more than 10% of patients, is associated with postoperative fever, poor quality of recovery, and prolonged hospitalization.

Targeting vascular endothelial growth factor receptor 2 and protein kinase D1 related pathways by a multiple kinase inhibitor in angiogenesis and inflammation related processes in vitro

Emerging evidence suggests that the vascular endothelial growth factor receptor 2 (VEGFR2) and protein kinase D1 (PKD1) signaling axis plays a critical role in normal and pathological angiogenesis and inflammation related processes. Despite all efforts, the currently available therapeutic interventions are limited. Prior studies have also proved that a multiple target inhibitor can be more efficient compared to a single target one. Therefore, development of novel inflammatory pathway-specific inhibitors would be of great value. To test this possibility, we screened our molecular library using recombinant kinase assays and identified the previously described compound VCC251801 with strong inhibitory effect on both VEGFR2 and PKD1. We further analyzed the effect of VCC251801 in the endothelium-derived EA.hy926 cell line and in different inflammatory cell types. In EA.hy926 cells, VCC251801 potently inhibited the intracellular activation and signaling of VEGFR2 and PKD1 which inhibition eventually resulted in diminished cell proliferation. In this model, our compound was also an efficient inhibitor of in vitro angiogenesis by interfering with endothelial cell migration and tube formation processes. Our results from functional assays in inflammatory cellular models such as neutrophils and mast cells suggested an anti-inflammatory effect of VCC251801. The neutrophil study showed that VCC251801 specifically blocked the immobilized immune-complex and the adhesion dependent TNF-α -fibrinogen stimulated neutrophil activation. Furthermore, similar results were found in mast cell degranulation assay where VCC251801 caused significant reduction of mast cell response. In summary, we described a novel function of a multiple kinase inhibitor which strongly inhibits the VEGFR2-PKD1 signaling and might be a novel inhibitor of pathological inflammatory pathways.

Eicosapentaenoic acid and docosahexaenoic acid suppress Th2 cytokine expression in RBL-2H3 basophilic leukemia cells

It is known that the intake of omega-3 fatty acids, such as eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), is beneficial for preventing and/or treating allergic diseases. The pathogenesis of allergic diseases is associated with overactivation of Th2-skewed immunity. Basophils generate large amounts of Th2 cytokines such as interleukin (IL)-4 and IL-13, which are critically involved in allergic inflammation. We investigated how EPA and DHA affect Th2 cytokine expression in phorbol 12-myristate 13-acetate- and ionomycin (PI)-activated RBL-2H3 basophilic leukemia cells. EPA and DHA induced a dramatic decrease in the production of IL-4 and IL-13 and their transcription in a dose-dependent manner. Luciferase assays of RBL-2H3 cells stably expressing Il4 and Il13 promoter-reporter plasmids demonstrated a significant suppression of PI-induced promoter activation. Analysis of certain transcription factors revealed that nuclear expression of c-Fos and the mRNA expression were suppressed by EPA and DHA. Furthermore, they significantly inhibited the nuclear expression and translocation of nuclear factor of activated T cells (NF-AT)1. In contrast, the expression levels of nuclear factor kappa-B (NF-κB), GATA-binding proteins (GATAs), and CCAAT/enhancer binding protein alpha (C/EBPα) were not significantly affected by EPA and DHA. Phosphorylation of extracellular signal-related kinase was inhibited by EPA and DHA, and phosphorylation of p38 mitogen-activated protein kinase was decreased by DHA, but not by EPA. Taken together, our data suggest that EPA and DHA may suppress Th2-skewed allergic immune responses by inhibiting the expression of basophilic IL-4 and IL-13.

A targeted library screen reveals a new inhibitor scaffold for protein kinase D

Protein kinase D (PKD) has emerged as a potential therapeutic target in multiple pathological conditions, including cancer and heart diseases. Potent and selective small molecule inhibitors of PKD are valuable for dissecting PKD-mediated cellular signaling pathways and for therapeutic application. In this study, we evaluated a targeted library of 235 small organic kinase inhibitors for PKD1 inhibitory activity at a single concentration. Twenty-eight PKD inhibitory chemotypes were identified and six exhibited excellent PKD1 selectivity. Five of the six lead structures share a common scaffold, with compound 139 being the most potent and selective for PKD vs PKC and CAMK. Compound 139 was an ATP-competitive PKD1 inhibitor with a low double-digit nanomolar potency and was also cell-active. Kinase profiling analysis identified this class of small molecules as pan-PKD inhibitors, confirmed their selectivity again PKC and CAMK, and demonstrated an overall favorable selectivity profile that could be further enhanced through structural modification. Furthermore, using a PKD homology model based on similar protein kinase structures, docking modes for compound 139 were explored and compared to literature examples of PKD inhibition. Modeling of these compounds at the ATP-binding site of PKD was used to rationalize its high potency and provide the foundation for future further optimization. Accordingly, using biochemical screening of a small number of privileged scaffolds and computational modeling, we have identified a new core structure for highly potent PKD inhibition with promising selectivity against closely related kinases. These lead structures represent an excellent starting point for the further optimization and the design of selective and therapeutically effective small molecule inhibitors of PKD.

Polydatin (PD) inhibits IgE-mediated passive cutaneous anaphylaxis in mice by stabilizing mast cells through modulating Ca²⁺ mobilization

Mast cells play a key role in the pathogenesis of asthma and are a promising target for therapeutic intervention in asthma. This study investigated the effects of polydatin (PD), a resveratrol glucoside, on mast cell degranulation upon cross-linking of the high-affinity IgE receptors (FcεRI), as well as the anti-allergic activity of PD in vivo. Herein, we demonstrated that PD treatment for 30 min suppressed FcεRI-mediated mast cell degranulation in a dose-dependent manner. Concomitantly, PD significantly decreased FcεRI-mediated Ca²⁺ increase in mast cells. The suppressive effects of PD on FcεRI-mediated Ca²⁺ increase were largely inhibited by using LaCl₃ to block the Ca²⁺ release-activated Ca²⁺ channels (CRACs). Furthermore, PD significantly inhibited Ca²⁺ entry through CRACs evoked by thapsigargin (TG). Knocking down protein expression of Orai1, the pore-forming subunit of CRACs, significantly decreased PD suppression of FcεRI-induced intracellular Ca²⁺ influx and mast cell degranulation. In a mouse model of mast cell-dependent passive cutaneous anaphylaxis (PCA), in vivo PD administration suppressed mast cell degranulation and inhibited anaphylaxis. Taken together, our data indicate that PD stabilizes mast cells by suppressing FcεRI-induced Ca²⁺ mobilization mainly through inhibiting Ca²⁺ entry via CRACs, thus exerting a protective effect against PCA.

Saikosaponin-d inhibits β-conglycinin induced activation of rat basophilic leukemia-2H3 cells

β-Conglycinin is one of the major storage proteins in soybean and has been identified as a potential diagnostic marker for severe allergic reactions to soybean. Unfortunately, there is a lack of information on the signal transduction pathways of β-conglycinin induced mast cell activation and how to alleviate these allergic reactions. Bupleurum falcatum, a traditional oriental medicine, has been widely utilized in the treatment of influenza, fever, malaria and menstrual disorders. Furthermore, it has been reported that saikosaponins, the important principle of B. falcatum, possesses anti-allergic activities. Therefore, the present study investigated whether or not saikosaponin-d, an extract of B. falcatum, was effective in the treatment of allergic reactions cased by β-conglycinin, using a rat basophilic leukemia-2H3 cell line. There were multiple signaling pathways contributing to the development of β-conglycinin-mediated rat basophilic leukemia-2H3 cell activation. The intracellular calcium mobilization and tyrosine phosphorylation were early events, which in turn elicited reactive oxygen species production, gene activation of Cdc42 and c-Fos, and ultimately led to β-hexosaminidase release. Saikosaponin-d inhibited rat basophilic leukemia-2H3 cell degranulation by suppressing these critical incidents in the signal transduction pathway. These results suggest that saikosaponin-d exhibited anti-allergic activity and could become an effective herbal therapy for alleviating soybean allergy.

Lipopolysaccharide enhances FcεRI-mediated mast cell degranulation by increasing Ca2+ entry through store-operated Ca2+ channels: implications for lipopolysaccharide exacerbating allergic asthma

Lipopolysaccharide (LPS) can exacerbate asthma; however, the mechanisms are not fully understood. This study investigated the effect of LPS on antigen-stimulated mast cell degranulation and the underlying mechanisms. We found that LPS enhanced degranulation in RBL-2H3 cells and mouse peritoneal mast cells upon FcεRI activation, in a dose- and time-dependent manner. Parallel to the alteration of degranulation, LPS increased FcεRI-activated Ca(2+) mobilization, as well as Ca(2+) entry through store-operated calcium channels (SOCs) evoked by thapsigargin. Blocking Ca(2+) entry through SOCs completely abolished LPS enhancement of mast cell degranulation. Consistent with functional alteration of SOCs, LPS increased mRNA and protein levels of Orai1 and STIM1, two major subunits of SOCs, in a time-dependent manner. In addition, LPS increased the mRNA level of Toll-like receptor 4 (TLR4) in a time-dependent manner. Blocking TLR4 with Cli-095 inhibited LPS, increasing transcription and expression of SOC subunits. Concomitantly, the effect of LPS enhancement of Ca(2+) mobilization and mast cell degranulation was largely reduced by Cli-095. Administration of LPS (1 μg) in vivo aggravated airway hyperreactivity and inflammatory reactions in allergic asthmatic mice. Histamine levels in serum and bronchoalveolar lavage fluid were increased by LPS treatment. In addition, Ca(2+) mobilization was enhanced in peritoneal mast cells isolated from LPS-treated asthmatic mice. Taken together, these results imply that LPS enhances mast cell degranulation, which potentially contributes to LPS exacerbating allergic asthma. Lipopolysaccharide increases Ca(2+) entry through SOCs by upregulating transcription and expression of SOC subunits, mainly through interacting with TLR4 in mast cells, resulting in enhancement of mast cell degranulation upon antigen stimulation.