Histamine content and secretion in basophils and mast cells

Involvement of TRPV4 in Serotonin-Evoked Scratching

Several thermo-sensitive TRP channels (TRPV1, -3; TRPA1) have been implicated in itch. In contrast, the role of transient receptor potential vanilloid type-4 (TRPV4) in itch is unknown. Therefore, we investigated if TRPV4, a temperature-sensitive cation channel, plays an important role in acute itch in mice. Four different pruritogens including serotonin (5-hydroxytrytamine, 5-HT), histamine, SLIGRL (PAR2/MrgprC11 agonist) and chloroquine (MrgprA3 agonist) were intradermally injected and itch-related scratching behavior was assessed. TRPV4 knockout (TRPV4KO) mice exhibited significantly fewer 5-HT-evoked scratching bouts compared to wild-type (WT) mice. Notably, no differences between TRPV4KO and WT mice were observed in the number of scratch bouts elicited by SLIGRL and histamine. Pretreatment with a TRPV4 antagonist significantly attenuated 5-HT-evoked scratching in vivo. Using calcium imaging in cultured primary murine dorsal root ganglion (DRG) neurons, the response of neurons after 5-HT application, but not other pruritogens, was significantly lower in TRPV4KO compared to WT mice. A TRPV4 antagonist significantly suppressed 5-HT-evoked responses in DRG cells from WT mice. Approximately 90% of 5-HT-sensitive DRG neurons were immunoreactive for an antibody to TRPV4, as assessed by calcium imaging. These results indicate that serotonin-induced itch is linked to TRPV4.

Regulation of secretory granule size by the precise generation and fusion of unit granules

Morphometric evidence derived from studies of mast cells, pancreatic acinar cells and other cell types supports a model in which the post-Golgi processes that generate mature secretory granules can be resolved into three steps: (1) fusion of small, Golgi-derived progranules to produce immature secretory granules which have a highly constrained volume; (2) transformation of such immature granules into mature secretory granules, a process often associated with a reduction in the maturing granule's volume, as well as changes in the appearance of its content and (3) fusion of secretory granules of the smallest size, termed 'unit granules', forming granules whose volumes are multiples of the unit granule's volume. Mutations which perturb this process can cause significant pathology. For example, Chediak-Higashi syndrome / lysosomal trafficking regulator (CHS)/(Lyst) mutations result in giant secretory granules in a number of cell types in human beings with the Chediak-Higashi syndrome and in 'beige' (Lyst(bg)/Lyst(bg)) mice. Analysis of the secretory granules of mast cells and pancreatic acinar cells in Lyst-deficient beige mice suggests that beige mouse secretory granules retain the ability to fuse randomly with other secretory granules no matter what the size of the fusion partners. By contrast, in normal mice, the pattern of granule-granule fusion occurs exclusively by the addition of unit granules, either to each other or to larger granules. The normal pattern of fusion is termed unit addition and the fusion evident in cells with CHS/Lyst mutations is called random addition. The proposed model of secretory granule formation has several implications. For example, in neurosecretory cells, the secretion of small amounts of cargo in granules constrained to a very narrow size increases the precision of the information conveyed by secretion. By contrast, in pancreatic acinar cells and mast cells, large granules composed of multiple unit granules permit the cells to store large amounts of material without requiring the amount of membrane necessary to package the same amount of cargo into small granules. In addition, the formation of mature secretory granules that are multimers of unit granules provides a mechanism for mixing in large granules the contents of unit granules which differ in their content of cargo.

Lower respiratory tract complications during nasal provocation: nonspecific stimulant or specific allergen?

BACKGROUND

Allergic rhinitis (AR) is an allergic inflammatory disease in which allergen exposure leads to the appearance of symptoms in sensitized individuals because of histamine liberation from nasal mucosal mast cells. Comorbidity of this disease with allergic asthma is common. Therefore, the one airway one disease theory has been put forward. Lower respiratory tract provocation tests with both nonspecific (methacholine) and specific stimulants (allergen) have yielded positive results in nonasthmatic patients with AR. However, not enough research is available to demonstrate whether there is a response in the lower respiratory tract during nasal provocation tests (NPTs) performed to evaluate only nasal airway in these patients.

OBJECTIVES

To determine if the lower respiratory tract was affected as a result of NPTs with nonspecific and specific stimulants in nonasthmatic patients with AR and to determine the frequency of lower respiratory tract obstruction due to NPT with nonspecific and specific stimulants.

METHODS

Thirty-six participants were enrolled in the study between November 2005 and January 2006 (18 AR patients and 18 healthy control subjects). Patients underwent 2 sessions of NPT. The first session was performed with nasal methacholine as a nonspecific stimulant, and the second session was performed with nasal Olea europaea extract as a specific stimulant. The control group underwent only nonspecific nasal provocation with methacholine. Basal nasal opening and nasal pressures were evaluated spirometrically by rhinomanometric measurements and basal respiratory function tests in both groups before methacholine nasal provocation. Whether or not nasal provocation was achieved, spirometric measurements were performed in all patients and controls after NPTs.

RESULTS

NPTs with methacholine resulted in a similar frequency of nasal provocation in the patient and control groups (P = .63). However, the mean methacholine dose was lower in patients with AR (P = .049). There was a decrease in parameters of asthma, including the ratio of forced expiratory volume in 1 second to forced vital capacity (P = .04), peak expiratory flow (P = .01), and forced expiratory flow between 25% and 75% (P = .004), as a result of NPTs with methacholine in the patient group. However, NPTs with allergen did not cause a change in lower respiratory tract obstruction criteria.

CONCLUSIONS

Lower respiratory tract obstruction can occur after NPTs with nonspecific stimulants; therefore, tests performed with specific allergens can be regarded as safer.

Enumeration and immunohistochemical characterisation of bone marrow basophils in myeloproliferative disorders using the basophil specific monoclonal antibody 2D7

BACKGROUND

Basophils are highly specialised granulocytes that express a unique profile of antigens and increase in myeloproliferative disorders (MPD). In chronic myeloid leukaemia (CML), basophilia is a diagnostic and prognostic determinant. So far, however, no reliable approach for routine detection and enumeration of bone marrow basophils has become available.

OBJECTIVE

To detect and enumerate basophils in bone marrow sections in patients with CML and other MPD.

METHODS

The anti-basophil antibody 2D7 was applied to paraffin embedded bone marrow sections from normal/reactive subjects (n = 31), patients with CML (chronic phase, n = 37; accelerated phase, n = 9), and other MPD (chronic idiopathic myelofibrosis (CIMF), n = 20; polycythaemia vera (PV), n = 20; essential thrombocythaemia (ET), n = 20; indolent systemic mastocytosis (ISM), n = 7).

RESULTS

As assessed by serial section staining, 2D7(+) cells were found to co-express myeloperoxidase, histidine decarboxylase, CD9, and CD43, but did not express B cell or T cell restricted antigens. 2D7(+) bone marrow cells were found to increase in CML compared with normal/reactive bone marrow and other MPD (median numbers of 2D7(+) cells/mm(2): CML, 33; normal/reactive bone marrow, 6; CIMF, 10; PV, 6; ET, 5; ISM, 3; p<0.05). The highest basophil counts were recorded in accelerated phase CML (115/mm(2)).

CONCLUSIONS

A novel immunohistochemical procedure has been established for basophil detection in normal bone marrow and MPD. This approach should help in the quantification of bone marrow basophils at diagnosis and during anti-leukaemic treatment.

Ultrastructural studies of human basophils and mast cells

Ultrastructural studies of human mast cells (HMCs) and basophils (HBs) are reviewed. Sources of HMCs include biopsies of tissue sites and in situ study of excised diseased organs; isolated, partially purified samples from excised organs; and growth-factor-stimulated mast cells that develop de novo in cultures of cord blood cells. Sources of HBs for study include partially purified peripheral blood basophils, basophils in tissue biopsies, and specific growth factor-stimulated basophils arising de novo from cord blood cells. The ultrastructural studies reviewed deal with identity, secretion, vesicles, recovery, and synthesis issues related to the biology of these similar cells.

The increased histamine release in ischaemic heart disease patients undergoing coronaroangiography is not mediated by specific IgE

BACKGROUND

The release of histamine by iodinated contrast media (ICM) is higher in coronary artery disease patients than in noncoronary patients during coronary angiogram.

METHODS

Eighty-eight patients who underwent a coronary angiography were classified either as having coronary artery disease or as noncoronary patients. Histamine concentration was higher than the 6.8 nM upper limit in 7 cases (group 1), of whom six were coronary artery disease patients. We compared the IgE and complement fractions in plasma of these patients to two control groups with normal histamine blood level, one (group 2) with and the other (group 3) without coronary artery disease.

RESULTS

No difference of total IgE and C(3c) and C(4) complement fractions was found among the three groups. Anti-ioxaglate IgE-RIA was positive in only one patient from group 1. The affinity of drug-IgE binding in the serum of this patient was very low (Kd: 18.7 mM). The level of anti-ICM IgE detected by ioxitalamate- and iomeprol-Sepharose RIA was significantly higher in groups 2 and 3 than in group 1.

CONCLUSIONS

The higher histamine release in ischaemic heart disease patients undergoing coronaroangiography is not mediated by IgE or complement activation. Further studies are needed to investigate the implication of histamine release factors.

Comparison of effects of ioxaglate versus iomeprol on histamine and tryptase release in patients with ischemic cardiomyopathy

We observed a release of histamine, but not of tryptase, in arterial blood from 64 patients with ischemic heart disease and 24 patients without coronary disease, which was provoked by ioxaglate, a ionic compound, but was not provoked by iomeprol, a non-ionic radiocontrast compound. The release of histamine in arterial blood after ionic contrast medium injection was higher in patients with ischemic heart disease compared with patients without coronary disease, suggesting that an increased release from heart mast cells previously observed exists also for systemic blood basophils.