Dual stimuli-responsive polyphosphazene-based molecular gates for controlled drug delivery in lung cancer cells

A switchable silane derived stimuli-responsive bottle-brush polyphosphazene (PPz) was prepared and attached to the surface of mesoporous silica nanoparticles (MSNs). The hybrid polymer with PEG-like Jeffamine® M-2005 side-arms undergo conformational changes in response to both pH and temperature due to its amphiphilic substituents and protonatable main-chain, hence were investigated as a gatekeeper. Safranin O as control fluorophore or the anticancer drug camptothecin (CPT) were encapsulated in the PPz-coated MSNs. At temperatures below the lower critical solution temperature (LCST), the swollen conformation of PPz efficiently blocked the cargo within the pores. However, above the LCST, the PPz collapsed, allowing release of the payload. Additionally, protonation of the polymer backbone at lower pH values was observed to enhance opening of the pores from the surface of the MSNs and therefore the release of the dye. In vitro studies demonstrated the ability of these nanoparticles loaded with the drug camptothecin to be endocytosed in both models of tumor (A549) and healthy epithelial (BEAS-2B) lung cells. Their accumulation and the release of the chemotherapeutic drug, co-localized within lysosomes, was faster and higher for tumor than for healthy cells, further, the biocompatibility of PPz-gated nanosystem without drug was demonstrated. Tailored dual responsive polyphosphazenes thus represent novel and promising candidates in the construction of future gated mesoporous silica nanocarriers designs for lung cancer-directed treatment.

Mesoporous Silica Micromotors with a Reversible Temperature Regulated On-Off Polyphosphazene Switch

The incorporation of an extraneous on-off braking system is necessary for the effective motion control of the next generation of micrometer-sized motors. Here, the design and synthesis of micromotors is reported based on mesoporous silica particles containing bipyridine groups, introduced by cocondensation, for entrapping catalytic cobalt(II) ions within the mesochannels, and functionalized on the surface with silane-derived temperature responsive bottle-brush polyphosphazene. Switching the polymers in a narrow temperature window of 25-30 °C between the swollen and collapsed state, allows the access for the fuel H₂ O₂ contained in the dispersion medium to cobalt(II) bipyridinato catalyst sites. The decomposition of hydrogen peroxide is monitored by optical microscopy, and effectively operated by reversibly closing or opening the pores by the grafted gate-like polyphosphazene, to control on demand the oxygen bubble generation. This design represents one of the few examples using temperature as a trigger for the reversible on-off external switching of mesoporous silica micromotors.

Development of a highly sensitive gas chromatography-mass spectrometry method preceded by solid-phase microextraction for the analysis of propofol in low-volume cerebral microdialysate samples

To date, the commonly used intravenous anesthetic propofol has been widely studied, and fundamental pharmacodynamic and pharmacokinetic characteristics of the drug are known. However, propofol has not yet been quantified in vivo in the target organ, the human brain. Here, cerebral microdialysis offers the unique opportunity to sample propofol in the living human organism. Therefore, a highly sensitive analytical method for propofol quantitation in small sample volumes of 30 μL, based on direct immersion solid‐phase microextraction was developed. Preconcentration was followed by gas chromatographic separation and mass spectrometric detection of the compound. This optimized method provided a linear range between the lower limit of detection (50 ng/L) and 200 μg/L. Matrix‐matched calibration was used to compensate recovery issues. A precision of 2.7% relative standard deviation between five consecutive measurements and an interday precision of 6.4% relative standard deviation could be achieved. Furthermore, the permeability of propofol through a cerebral microdialysate system was tested. In summary, the developed method to analyze cerebral microdialysate samples, allows the in vivo quantitation of propofol in the living human brain. Additionally the calculation of extracellular fluid levels is enabled since the recovery of the cerebral microdialysis regarding propofol was determined.

Identification of Der p 23, a peritrophin-like protein, as a new major Dermatophagoides pteronyssinus allergen associated with the peritrophic matrix of mite fecal pellets

The house dust mite (HDM) Dermatophagoides pteronyssinus is one of most important allergen sources and a major elicitor of allergic asthma. We screened a D. pteronyssinus expression cDNA library with IgE Abs from HDM allergic patients. A cDNA coding for a new major allergen was isolated, which showed sequence homology to peritrophins, which contain chitin-binding domains and are part of the peritrophic matrix lining the gut of arthropods. The mature Der p 23 allergen was expressed in Escherichia coli as an 8-kDa protein without its hydrophobic leader sequence and purified to homogeneity. It reacted with IgE Abs from 74% of D. pteronyssinus allergic patients (n = 347) at levels comparable to the two major HDM allergens, Der p 1 and Der p 2. Thus, Der p 23 represents a new major D. pteronyssinus allergen. Furthermore, rDer p 23 exhibited high allergenic activity as demonstrated by upregulation of CD203c expression on basophils from D. pteronyssinus allergic patients. Immunogold electron microscopy localized the allergen in the peritrophic matrix lining the midgut of D. pteronyssinus as well as on the surface of the fecal pellets. Thus, we identified a new major D. pteronyssinus allergen as peritrophin-like protein. The high allergenic activity of Der p 23 and its frequent recognition as respiratory allergen may be explained by the fact that it becomes airborne and respirable through its association with mite feces. Der p 23 may be an essential component for diagnosis and specific immunotherapy of HDM allergy.

Carrier-bound nonallergenic Der p 2 peptides induce IgG antibodies blocking allergen-induced basophil activation in allergic patients

BACKGROUND

More than 90% of house dust mite-allergic patients are sensitized to the major Dermatophagoides pteronyssinus allergen, Der p 2. The aim of this study was to develop and characterize an allergy vaccine based on carrier-bound Der p 2 peptides, which should allow reducing IgE- and T-cell-mediated side-effects during specific immunotherapy (SIT).

METHODS

Five Der p 2 peptides (P1-P5) were synthesized and analyzed regarding IgE reactivity and allergenic activity. Lymphoproliferative and cytokine responses induced with Der p 2 and Der p 2 peptides were determined in peripheral blood mononuclear cells from mite-allergic patients. Der p 2-specific IgG antibodies induced with carrier-bound Der p 2 peptides in mice and rabbits were tested for their capacity to inhibit IgE binding and basophil activation in allergic patients.

RESULTS

Of five overlapping peptides (P1-P5) covering the Der p 2 sequence, two peptides (P2 and P4) were identified, which showed no relevant IgE reactivity, allergenic activity, and induced lower Der p 2-specific T-cell activation than Der p 2. However, when coupled to a carrier, P2 and P4 induced Der p 2-specific IgG antibodies in animals, which inhibited allergic patients' IgE binding to the allergen and allergen-induced basophil activation similar as antibodies induced with Der p 2.

CONCLUSIONS

Carrier-bound Der p 2 peptides should allow avoiding IgE-mediated side-effects, and because of their low potential to activate allergen-specific T cells, they may reduce late-phase side-effects during SIT. Further, these peptides may be also useful for prophylactic vaccination.

Glucocorticosteroids rescue basophils from dasatinib-augmented immunoglobulin E-mediated histamine release

BACKGROUND

Dasatinib is a multikinase inhibitor active against several tyrosine kinases including ABL, KIT, Lyn and Btk. Apart from its known antileukemic activity, the drug produces several side effects including edemas and pleural effusions, which are supposedly triggered by activated immune cells. Effusion formation can be treated effectively by glucocorticosteroids. We have recently shown that low concentrations of dasatinib (<0.1 µM) promote IgE-dependent secretion of histamine in basophils, especially in allergic individuals. In the current study, we asked whether glucocorticosteroids inhibit dasatinib-induced activation of basophils.

METHODS

Basophils were preincubated with dexamethasone, prednisolone and hydrocortisone for 24 h, and were then exposed to an anti-IgE antibody (normal basophils) or the allergens Bet v 1 and Phl p 5 (allergic patients) with or without low concentrations of dasatinib (0.025 µM). After incubation, basophils were examined for histamine release and expression of CD63 and CD203c.

RESULTS

All three glucocorticosteroids were found to counteract IgE-dependent and dasatinib-enhanced histamine release in basophils in nonallergic and allergic individuals. In addition, glucocorticosteroids were found to inhibit anti-IgE-induced upregulation of CD63 and CD203c in the presence or absence of dasatinib. The inhibitory effects of glucocorticosteroids were dose-dependent (effective range: 1-10 µM) and seen in all donors examined.

CONCLUSIONS

Glucocorticosteroids rescue IgE receptor cross-linked basophils from additional costimulatory effects of low-dose dasatinib which may have clinical implications in dasatinib-treated patients.

The protein tyrosine kinase Tec regulates mast cell function

Mast cells play crucial roles in a variety of normal and pathophysiological processes and their activation has to be tightly controlled. Here, we demonstrate that the protein tyrosine kinase Tec is a crucial regulator of murine mast cell function. Tec was activated upon Fc epsilon RI stimulation of BM-derived mast cells (BMMC). The release of histamine in the absence of Tec was normal in vitro and in vivo; however, leukotriene C(4) levels were reduced in Tec(-) (/) (-) BMMC. Furthermore, the production of IL-4 was severely impaired, and GM-CSF, TNF-alpha and IL-13 levels were also diminished. Finally, a comparison of WT, Tec(-) (/) (-), Btk(-) (/) (-) and Tec(-) (/) (-)Btk(-) (/) (-) BMMC revealed a negative role for Btk in the regulation of IL-4 production, while for the efficient production of TNF-alpha, IL-13 and GM-CSF, both Tec and Btk were required. Our results demonstrate a crucial role for Tec in mast cells, which is partially different to the function of the well-characterized family member Btk.

Midostaurin (PKC412) inhibits immunoglobulin E-dependent activation and mediator release in human blood basophils and mast cells

BACKGROUND

KIT tyrosine kinase inhibitors (TKI), such as nilotinib or midostaurin (PKC412), are increasingly used in clinical trials to counteract neoplastic cell growth in patients with aggressive mast cell (MC) disorders. However, these patients suffer not only from MC infiltration and consecutive organ damage but also from MC mediator-related symptoms.

METHODS

We examined the effects of three KIT TKI, imatinib, nilotinib, and midostaurin, on IgE-dependent mediator release in normal human blood basophils and cultured cord blood cell-derived MC, and on spontaneous histamine secretion in the MC leukaemia cell line HMC-1 and the basophil cell line KU812.

RESULTS

The multi-kinase inhibitor midostaurin that interacts with KIT and protein kinase C was found to counteract anti-IgE-induced mediator release in blood basophils and cultured cord blood cell-derived MC in all samples examined. By contrast, no effects of imatinib or nilotinib on histamine secretion in basophils or MC were found. The effects of midostaurin on histamine release were dose-dependent and occurred at pharmacologic concentrations (IC(50) 10-100 nm). Midostaurin was also found to inhibit the IgE-dependent up-regulation of CD63 on cultured cord blood cell-derived human MC, but did not inhibit IgE-dependent up-regulation of CD63 or CD203c in human blood basophils.

CONCLUSION

Midostaurin may be a beneficial drug in aggressive systemic mastocytosis not only because of its growth-inhibitory effects but also because of its additional effects on activation and mediator release in MC and basophils.

CD203c is overexpressed on neoplastic mast cells in systemic mastocytosis and is upregulated upon IgE receptor cross-linking

The ectoenzyme E-NPP3 (CD203c) has recently been identified as a novel activation-linked cell surface antigen on basophils. In the present study, we examined expression of CD203c on normal mast cells (MC)and bone marrow (bm) MC derived from 85 patients with systemic mastocytosis (SM), including cases with indolent SM (ISM, n=72), SM with associated clonal hematologic non-MC-lineage disease (SM-AHNMD, n=6), aggressive SM (ASM, n=3), and mast cell leukemia (MCL, n=4). Surface expression of CD203c was analyzed by multicolor flow cytometry. In patients with SM, bm MC expressed significantly higher amounts of CD203c compared to normal bm MC (median MFI in controls: 260 versus median MFI in SM: 516, p<0.05). Slightly lower amounts of CD203c were detected on MC in SM-AHNMD and ASM compared to ISM. To demonstrate CD203c expression in MC at the mRNA level, neoplastic MC were highly enriched by cell sorting, and were found to express CD203c mRNA in RT-PCR analysis. Cross-linking of the IgE receptor on MC resulted in a substantial upregulation of CD203c, whereas the KIT-ligand stem cell factor (SCF) showed no significant effects. In conclusion, CD203c is a novel activation-linked surface antigen on MC that is upregulated in response to IgE receptor cross-linking and is overexpressed on neoplastic MC in patients with SM.

Cigarette smoke facilitates allergen penetration across respiratory epithelium

BACKGROUND

The association between cigarette smoke exposure and allergic airway disease is a matter for debate. We sought to investigate in an in vitro system whether active smoking reduces the integrity and barrier function of the respiratory epithelium and thus facilitates allergen penetration.

METHODS

We cultured the human bronchial epithelial cell line 16HBE14o- in a transwell culture system as a surrogate for the intact respiratory epithelium. The cell monolayer was exposed to standardized cigarette smoke extract (CSE). The extent and effects of trans-epithelial allergen penetration were measured using 125I-labelled purified major respiratory allergens (rBet v 1, rPhl p 5 and rDer p 2) and histamine release experiments.

RESULTS

Exposure of cells to concentrations of CSE similar to those found in smokers induced the development of para-cellular gaps and a decrease in trans-epithelial resistance. CSE exposure induced a more than threefold increase in allergen penetration. Increased subepithelial allergen concentrations provoked a substantial augmentation of histamine release from sensitized basophils.

CONCLUSIONS

Our results indicate that cigarette smoke is a potent factor capable of reducing the barrier function of the respiratory epithelium for allergens and may contribute to increased allergic inflammation, exacerbation of allergic disease and boosting of IgE memory.

A hypoallergenic hybrid molecule with increased immunogenicity consisting of derivatives of the major grass pollen allergens, Phl p 2 and Phl p 6

Allergen-specific immunotherapy is currently based on the administration of allergen extracts containing natural allergens. However, its broad application is limited by the poor quality of these extracts. Based on recombinant allergens, well-defined allergy vaccines for allergen-specific immunotherapy can be produced. Furthermore, they can be modified to reduce their allergenic activity and to avoid IgE-mediated side effects. Here, we demonstrate that the immunogenicity of two grass pollen-derived hypoallergenic allergen derivatives could be increased by engineering them as a single hybrid molecule. We used a hypoallergenic Phl p 2 mosaic, generated by fragmentation of the Phl p 2 sequence and reassembly of the resulting peptides in an altered order, and a truncated Phl p 6 allergen, to produce a hybrid protein. The hybrid retained the reduction of IgE reactivity and allergenic activity of its components as shown by ELISA and basophil activation assays. Immunization with the hybrid molecule demonstrated the increased immunogenicity of this molecule, leading to higher levels of allergen-specific IgG antibodies compared to the single components. These antibodies could inhibit patients' IgE binding to the wild-type allergens. Thus, the described strategy allows the development of safer and more efficacious vaccines for the treatment of grass pollen allergy.

Targeting of heat-shock protein 32/heme oxygenase-1 in canine mastocytoma cells is associated with reduced growth and induction of apoptosis

OBJECTIVE

Advanced mast cell (MC) neoplasms are usually resistant to conventional therapy. Therefore, current research focuses on new targets in neoplastic MC and development of respective targeted drugs. Mastocytomas in dogs often behave as aggressive tumors. We report that heat-shock protein 32 (Hsp32), also known as heme oxygenase-1, is a survival-enhancing molecule and new target in canine mastocytoma cells.

MATERIALS AND METHODS

As assessed by reverse transcriptase polymerase chain reaction, Northern blotting, immunocytochemistry, and Western blotting, primary neoplastic dog MC, and the canine mastocytoma-derived cell line C2 expressed Hsp32 mRNA and the Hsp32 protein in a constitutive manner.

RESULTS

The KIT-targeting drug midostaurin inhibited expression of Hsp32, as well as survival in C2 cells. Confirming the functional role of Hsp32, the inhibitory effect of midostaurin on C2 cells was markedly reduced by the Hsp32-inductor hemin. Two pharmacologic Hsp32-inhibitors, styrene maleic-acid micelle-encapsulated ZnPP (SMA-ZnPP) and pegylated zinc-protoporphyrin (PEG-ZnPP) were applied. Both drugs were found to inhibit proliferation of C2 cells as well as growth of primary neoplastic canine MC. The growth-inhibitory effects of SMA-ZnPP and PEG-ZnPP were dose- and time-dependent (IC(50): 1-10 muM) and found to be associated with induction of apoptosis.

CONCLUSIONS

Hsp32 is an important survival factor and interesting new target in neoplastic canine MC. Trials with Hsp32-targeted drugs are now warranted to define the clinical efficacy of these drugs.

Characterization of Der p 21, a new important allergen derived from the gut of house dust mites

BACKGROUND

The house dust mite (HDM) Dermatophagoides pteronyssinus is a major allergen source eliciting allergic asthma. The aim of the study was to identify new important HDM allergens associated with allergic asthma.

METHODS

A cDNA coding for a new mite allergen, designated Der p 21, was isolated using immunoglobulin E (IgE) antibodies from patients with allergic asthma out of a D. pteronyssinus expression cDNA library and expressed in Escherichia coli.

RESULTS

Circular dichroism analysis of the purified allergen showed that rDer p 21 (14 726 Da) is one of the few mite allergens with an alpha-helical secondary structure. The protein exhibited high thermal stability and refolding capacity, and, as determined by small angle X-ray scattering, formed a dimer consisting of two flat triangles. rDer p 21 bound high levels of patients' IgE antibodies and showed high allergenic activity in basophil activation experiments. Rabbit anti-Der p 21 IgG antibodies inhibited mite-allergic patients' IgE binding and allowed the ultrastructural localization of the allergen in the midgut (epithelium, lumen and faeces) of D. pteronyssinus by immunogold electron microscopy. Der p 21 revealed sequence homology with group 5 mite allergens, but IgE and IgG reactivity data and cross-inhibition studies identified it as a new mite allergen.

CONCLUSIONS

Der p 21 is a new important mite allergen which is liberated into the environment via faecal particles and hence may be associated with allergic asthma.

A high-affinity monoclonal anti-IgE antibody for depletion of IgE and IgE-bearing cells

BACKGROUND

We have identified a monoclonal anti-human immunoglobulin E (IgE) antibody, which recognizes FcepsilonRI-bound IgE and prevents binding of IgE to FcepsilonRI. In this study, we assessed the binding kinetics and affinity of monoclonal antibody 12 (mAb12) for IgE and investigated whether mAb12 can be used for depletion of IgE and isolation of IgE-bearing cells from peripheral blood.

METHODS

Binding kinetics and affinity for IgE were studied using Biacore surface plasmon resonance technique experiments. IgE antibodies were depleted from serum using sepharose-coupled mAb12 and IgE-bearing cells were enriched from heparinized blood samples with mAb12. The extent and biological relevance of IgE depletion were studied by quantitative IgE measurements and basophil histamine release experiments. Specific binding of mAb12 to IgE-bearing cells (basophils, mast cells, IgE-secreting plasma cells) was demonstrated by FACS.

RESULTS

Monoclonal antibody 12 shows rapid association (k(a) = 5.46e5/Ms) with IgE, almost no dissociation (k(d) = 8.8e-5/s) and an affinity for IgE (K(D) = 1.61e-10 M), which is as high as that of FcepsilonRI. Immobilized mAb12 could be used to deplete IgE antibodies and isolate IgE-bearing cells from peripheral blood in a single-step procedure.

CONCLUSIONS

Monoclonal antibody 12 is a high affinity anti-human IgE antibody, which efficiently removes IgE and IgE-bearing cells from peripheral blood and may thus be used for extracorporeal depletion of IgE and IgE-bearing cells.

Immunohistochemical assessment of CD25 is equally sensitive and diagnostic in mastocytosis compared to flow cytometry

BACKGROUND

Systemic mastocytosis (SM) is a clonal myeloid disorder characterized by abnormal accumulation and growth of mast cells (MC) in internal organs. In most cases, the bone marrow is involved. Expression of CD25 in bone marrow MC, with or without coexpression of CD2, is an important minor SM criterion. So far, most studies have examined CD25-expression on MC by flow cytometry.

MATERIALS AND METHODS

We examined the expression of CD25 in MC in patients with SM (n = 25) by immunohistochemistry (IHC) and compared these data with results obtained by flow cytometric assessment of CD25-expression. In addition, we compared CD25-staining results with that obtained with an antibody against CD2.

RESULTS

In a majority of all patients (> 80%), CD25 was detectable by both staining techniques. However, in one patient, CD25 was only detectable on MC by IHC, but not by flow cytometry, and in two patients in whom IHC could not be applied because of lack of compact MC infiltrates, flow cytometry revealed aberrant expression of CD25. The antibody against CD2 produced diagnostic staining results in a smaller group of patients (flow cytometry: 65%; IHC: 28% of SM cases) compared to CD25 (> 80%).

CONCLUSIONS

CD25-IHC is equally diagnostic and sensitive in SM compared to flow cytometry and thus can be recommended as a diagnostic test. Our data also suggest that the diagnostic value of CD25 exceeds that of CD2, and that optimal assessment of CD25-expression in neoplastic MC in all patients requires the application of both techniques, flow cytometry and IHC.

Synergistic antiproliferative effects of KIT tyrosine kinase inhibitors on neoplastic canine mast cells

Aggressive mast cell (MC) tumors are hematopoietic neoplasms characterized by uncontrolled growth of MC and resistance to conventional drugs. In most cases, the tyrosine kinase (TK) receptor KIT is involved in malignant cell growth. Therefore, several KIT TK-targeting drugs are currently being tested for their ability to block growth of neoplastic MC. We examined the effects of four TK inhibitors (imatinib, midostaurin, nilotinib, and dasatinib) on C2 canine mastocytoma cells, as well as primary neoplastic canine MC. As assessed by (3)H-thymidine incorporation experiments, all TK inhibitors produced dose-dependent inhibition of proliferation in C2 cells with the following IC(50) values: imatinib: 269 +/- 180 nM, midostaurin: 157 +/- 35 nM, nilotinib: 55 +/- 24 nM, dasatinib: 12 +/- 3 nM. Growth-inhibitory effects of TK inhibitors were also observed in primary neoplastic mast cells, although IC(50) values for each drug varied from patient to patient, with midostaurin being the most potent agent in all samples tested. In consecutive experiments, we were able to show that TK inhibitors cooperate with each other in producing growth inhibition in C2 cells with synergistic effects observed with most drug combinations. In flow cytometry and TUNEL assay experiments, growth-inhibitory effects of TK inhibitors were found to be associated with cell-cycle arrest and apoptosis. Together, these data show that several TK-targeting drugs induce apoptosis and inhibit proliferation in canine mastocytoma cells in vitro, and that synergistic drug interactions can be obtained. Clinical trials are now warranted to explore whether these TK inhibitors also counteract growth of neoplastic cells in vivo in patients with aggressive MC tumors.

The Btk tyrosine kinase is a major target of the Bcr-Abl inhibitor dasatinib

Dasatinib is a small-molecule kinase inhibitor used for the treatment of imatinib-resistant chronic myelogenous leukemia (CML). We have analyzed the kinases targeted by dasatinib by using an unbiased chemical proteomics approach to detect binding proteins directly from lysates of CML cells. Besides Abl and Src kinases, we have identified the Tec kinases Btk and Tec, but not Itk, as major binders of dasatinib. The kinase activity of Btk and Tec, but not of Itk, was inhibited by nanomolar concentrations of dasatinib in vitro and in cultured cells. We identified the gatekeeper residue as the critical determinant of dasatinib susceptibility. Mutation of Thr-474 in Btk to Ile and Thr-442 in Tec to Ile conferred resistance to dasatinib, whereas mutation of the corresponding residue in Itk (Phe-435) to Thr sensitized the otherwise insensitive Itk to dasatinib. The configuration of this residue may be a predictor for dasatinib sensitivity across the kinome. Analysis of mast cells derived from Btk-deficient mice suggested that inhibition of Btk by dasatinib may be responsible for the observed reduction in histamine release upon dasatinib treatment. Furthermore, dasatinib inhibited histamine release in primary human basophils and secretion of proinflammatory cytokines in immune cells. The observed inhibition of Tec kinases by dasatinib predicts immunosuppressive (side) effects of this drug and may offer therapeutic opportunities for inflammatory and immunological disorders.