Evaluation of the efficacy of antihistamines using human monocyte-derived dendritic cells stimulated with histamine

Mast cell stabilizer ketotifen fumarate reverses inflammatory but not neuropathic-induced mechanical pain in mice

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Our preclinical findings indicate that ketotifen fumarate's analgesic effects are MC-dependent, and the case series report presented supports its use for the treatment of chronic pain.

Introduction:

Mast cell (MC) activation could establish a positive feedback loop that perpetuates inflammation and maintains pain. Stabilizing MCs with ketotifen fumarate (KF) may disrupt this loop and relieve pain.

Objective:

We aimed to test the effect of treatment with KF in pain assays in mice and in a case series of patients with chronic widespread pain.

Methods:

The analgesic effect of KF was tested in CD-1 mice injected with formalin, complete Freund's adjuvant, or subjected to spared nerve injury. In addition, wild-type (C57BL/6) and MC-deficient (C57BL/6-Kit^W-sh/W-sh) mice were injected with formalin or complete Freund's adjuvant and treated with KF. Patients with chronic widespread pain (n = 5; age: 13–16 years) who failed to respond to standard of care participated in a 16-week treatment trial with KF (6 mg/d). Ketotifen fumarate's therapeutic effect was evaluated using the patient global impression of change.

Results:

In the mouse experiments, KF produced dose- and MC-dependent analgesic effects against mechanical allodynia in the acute and chronic inflammatory pain but not neuropathic pain assays. In the patient case series, 4 patients reported that activity limitations, symptoms, emotions, and overall quality of life related to their pain condition were “better” or “a great deal better” since beginning treatment with KF. This was accompanied by improvements in pain comorbid symptoms.

Conclusion:

Treatment with KF is capable of reducing established inflammatory-induced mechanical nociception in an MC-dependent manner in mice, and it may be beneficial for the treatment of chronic pain conditions.

Histamine regulates murine primary dendritic cell functions

OBJECTIVE AND DESIGN

The modulation of antigen uptake and activation of dendritic cells (DCs) by histamine may function as a regulator of inflammation. Therefore, we sought to determine the impact of histamine on antigen uptake by and activation of murine DCs.

MATERIAL AND METHODS

DCs from spleen and lung were either identified by flow cytometry or were immunomagnetically enriched. Cells were stimulated with histamine, and the regulation of MHC-II and co-stimulatory molecule expression (CD80, CD86, and ICOS-L) and antigen uptake were quantified by flow cytometry. Individual contributions of the histamine receptor subtypes were determined by using the antagonists mepyramine (histamine H1-receptor: H1R), famotidine (H2R), and JNJ 7777120 (H4R).

RESULTS

Histamine accelerated the uptake of soluble antigen via the H1R, H2R, and H4R in splenic DCs. Co-stimulatory molecule expression was enhanced already by enrichment procedures, thus, the analyses were performed in unseparated cell populations. Histamine enhanced the expression of CD86 and ICOS-L while expression of CD80 was unaffected. Antagonism at H1R, H2R, and H4R and at H1R and H4R reduced the histamine-induced enhanced expression of CD86 and ICOS-L, respectively.

CONCLUSIONS

Histamine contributes to the regulation of the immunological synapse by stimulation of antigen uptake and activation of DCs via H1R, H2R, and H4R.

Mast Cell Stabilizer (Ketotifen) in Fibromyalgia: Phase 1 Randomized Controlled Clinical Trial

OBJECTIVES

Compared with pain-free controls, patients with fibromyalgia (FM) have more mast cells in the skin. Whether mast cells are involved in the pathogenesis of FM is unclear. We sought to determine the effects of a mast cell stabilizer (ketotifen) on FM symptoms.

MATERIALS AND METHODS

Fifty-one FM patients were randomized to daily oral ketotifen 2 mg bid (n=24) for 8 weeks or placebo (N=27). Mean age of patients was 51.2 years (SD=8.4); 88% were female and 88% were white; 22% were taking concomitant opiates; and mean pressure pain sensitivity (range, 0 to 20) was 10.0 (0.4). At study entry, the weekly average pain intensity was 6.4 (1.1) and the mean score on the Revised Fibromyalgia Impact Questionnaire-Revised was 66.8 (14.0).

RESULTS

We found no statistically significant treatment group differences from baseline in either group for the 2 primary measures: weekly average pain intensity (ketotifen -1.3 [1.9] vs. placebo -1.5 [1.9], P=0.7); and Fibromyalgia Impact Questionnaire-Revised score (-12.1 [19.5] vs. -12.2 [18.1], P=0.9). No secondary outcome measures (Brief Pain Inventory pain intensity and pressure pain sensitivity) reached statistical significance; results did not differ in the intent-to-treat and completer analyses. Other than transient sedation (6 [28.6%] vs. 1 [4.0%]), ketotifen was well tolerated.

DISCUSSION

The study results question whether skin mast cells play a major role in the pathogenesis of FM. However, given the role of mast cells in peripheral and central nociception, and the minimal side effects of ketotifen, a randomized clinical trial using increasing doses of ketotifen may be warranted.

Unique immunomodulatory effects of azelastine on dendritic cells in vitro

Allergic contact dermatitis and atopic dermatitis are among the most common inflammatory skin diseases in western countries, and antigen-presenting cells like dendritic cells (DC) are key players in their pathophysiology. Histamine, an important mediator of allergic reactions, influences DC maturation and cytokine secretion, which led us to investigate the immunomodulatory potential of the well-known histamine H1 receptor antagonists: azelastine, olopatadine, cetirizine, and pyrilamine. Unlike other H1 antihistamines, azelastine decreased lipopolysaccharide-induced tumor necrosis factor α and interleukin-12 secretion from murine bone marrow-derived DC. This effect was independent of histamine receptors H1, H2, or H4 and may be linked to inhibition of the nuclear factor kappa B pathway. Moreover, only azelastine reduced proliferation of allogenic T cells in a mixed leukocyte reaction. We then tested topical application of the H1 antihistamines on mice sensitized against toluene-2,4-diisocyanate, a model of Th2-mediated allergic contact dermatitis. In contrast to the in vitro results, all investigated substances were efficacious in reducing allergic ear swelling. Azelastine has unique effects on dendritic cells and T cell interaction in vitro. However, this did not translate into superior in vivo efficacy for Th2-mediated allergic dermatitis, possibly due to the effects of the antihistamines on other cell types involved in skin inflammation. Future research will have to clarify whether these properties are relevant to in vivo models of allergic inflammation with a different T cell polarization.

Second-Generation Antihistamines

Antihistamines are useful medications for the treatment of a variety of allergic disorders. Second-generation antihistamines avidly and selectively bind to peripheral histamine H1 receptors and, consequently, provide gratifying relief of histamine-mediated symptoms in a majority of atopic patients. This tight receptor specificity additionally leads to few effects on other neuronal or hormonal systems, with the result that adverse effects associated with these medications, with the exception of noticeable sedation in about 10% of cetirizine-treated patients, resemble those of placebo overall. Similarly, serious adverse drug reactions and interactions are uncommon with these medicines. Therapeutic interchange to one of the available second-generation antihistamines is a reasonable approach to limiting an institutional formulary, and adoption of such a policy has proven capable of creating substantial cost savings. Differences in overall efficacy and safety between available second-generation antihistamines, when administered in equivalent dosages, are not large. However, among the antihistamines presently available, fexofenadine may offer the best overall balance of effectiveness and safety, and this agent is an appropriate selection for initial or switch therapy for most patients with mild or moderate allergic symptoms. Cetirizine is the most potent antihistamine available and has been subjected to more clinical study than any other. This agent is appropriate for patients proven unresponsive to other antihistamines and for those with the most severe symptoms who might benefit from antihistamine treatment of the highest potency that can be dose-titrated up to maximal intensity.

[Recent development of new drugs for the treatment of allergic diseases]

Due to the prevalence of allergic diseases such as bronchial asthma, allergic rhinoconjunctivitis and dermallergosis, efforts at the discovery of novel and effective medications for prevention and treatment of these conditions have been reinforced. Recently, it has been recognized that these allergic diseases are a chronic inflammatory disorder of the lower and upper airways and skin. In this article, we reviewed the recent development of the following new antiallergic therapies: anti-Th2 cytokine antibodies, decoy receptors, receptor antibodies, anti-IgE antibodies, anti-cell adhesion molecules antibodies, antisense oligonucleotides, keratinocyte modulators, inhibitors of phosphodiesterase 4, tachykinin receptor antagonists, and anti-histaminic drugs. Most of these new agents are aimed to inhibit various components of allergic inflammation. The future use of allergic disease therapies hold great promise and excitement.

H1 and H2 histamine receptors are absent on Langerhans cells and present on dermal dendritic cells

Human monocyte-derived dendritic cells (MoDC) have both histamine H1 and H2 receptors and can induce CD86 expression by histamine. Nevertheless, it has not been reported whether human epidermal Langerhans cells (LC) have histamine receptors or not. In this study, using RT-PCR, we investigated the expression of H1 and H2 receptor mRNA on DC with the features of LC (LC-like DC) that were generated in vitro from peripheral blood monocytes, LC derived from CD34+ hematopoietic progenitor cells, and LC obtained from human epidermis. We compared the histamine-induced CD86 expression among these cells. In contrast to MoDC, LC and LC-like DC did not express H1 or H2 receptors. In addition, they could not augment the CD86 expression by histamine. Interestingly, when transforming growth factor-beta1 (TGF-beta1) was added to the culture of MoDC, the expression of H1 and H2 receptors and the histamine-induced CD86 expression were abrogated in a concentration-dependent fashion. Finally, in the assessment of the cell surface expression of histamine receptors using fluorescence-labeled histamine, histamine could bind to MoDC and dermal dendritic cells obtained from the skin, whereas there was no specific binding of histamine to LC-like DC or LC obtained from the skin. These data suggest that LC do not express either H1 or H2 receptors, mainly because of the effect of TGF-beta1. This made a striking contrast with the expression of the functional H1 and H2 receptors on MoDC and dermal dendritic cells.