Nedocromil sodium prevents the release of 15-hydroxyeicosatetraenoic acid from human bronchial epithelial cells exposed to toluene diisocyanate in vitro

The Anti-allergic Cromones: Past, Present, and Future

The anti-allergic cromones were originally synthesized in the 1960s by Fisons Plc, and the first drug to emerge from this program, disodium cromoglycate was subsequently marketed for the treatment of asthma and other allergic conditions. Whilst early studies demonstrated that the ability of the cromones to prevent allergic reactions was due to their 'mast cell stabilizing' properties, the exact pharmacological mechanism by which this occurred, remained a mystery. Here, we briefly review the history of these drugs, recount some aspects of their pharmacology, and discuss two new explanations for their unique actions. We further suggest how these findings could be used to predict further uses for the cromones.

Anti-allergic cromones inhibit histamine and eicosanoid release from activated human and murine mast cells by releasing Annexin A1

Background and Purpose

Although the ‘cromones’ (di-sodium cromoglycate and sodium nedocromil) are used to treat allergy and asthma, their ‘mast cell stabilising’ mechanism of pharmacological action has never been convincingly explained. Here, we investigate the hypothesis that these drugs act by stimulating the release of the anti-inflammatory protein Annexin-A1 (Anx-A1) from mast cells.

Experimental approach

We used biochemical and immuno-neutralisation techniques to investigate the mechanism by which cromones suppress histamine and eicosanoid release from cord-derived human mast cells (CDMCs) or murine bone marrow-derived mast cells (BMDMCs) from wild type and Anx-A1 null mice.

Key results

CDMCs activated by IgE-FcRε1 crosslinking, released histamine and prostaglandin (PG) D₂, which were inhibited (30–65%) by 5 min pre-treatment with cromoglycate (10 nM) or nedocromil (10 nM), as well as dexamethasone (2 nM) and human recombinant Anx-A1 (1–10 nM). In CDMCs cromones potentiated (2–5 fold) protein kinase C (PKC) phosphorylation and Anx-A1 phosphorylation and secretion (3–5 fold). Incubation of CDMCs with a neutralising anti-Anx-A1 monoclonal antibody reversed the cromone inhibitory effect.

Nedocromil (10 nM) also inhibited (40–60%) the release of mediators from murine bone marrow derived-mast cells from wild type mice activated by compound 48/80 and IgE-FcRε1 cross-linking, but were inactive in such cells when these were prepared from Anx-A1 null mice or when the neutralising anti-Anx-A1 antibody was present.

Conclusions and Implications

We conclude that stimulation of phosphorylation and secretion of Anx-A1 is an important component of inhibitory cromone actions on mast cells, which could explain their acute pharmacological actions in allergy. These findings also highlight a new pathway for reducing mediator release from these cells.

Antiallergic cromones inhibit neutrophil recruitment onto vascular endothelium via annexin-A1 mobilization

OBJECTIVE

To determine whether the inhibitory action of the antiallergic cromone "mast cell stabilizing" drugs on polymorphonuclear leukocyte (PMN) trafficking is mediated through an annexin-A1 (Anx-A1) dependent mechanism.

METHODS AND RESULTS

Intravital microscopy was used to monitor the actions of cromones in the inflamed microcirculation. Reperfusion injury provoked a dramatic increase in adherent and emigrated leukocytes in the mesenteric vascular bed, associated with augmented tissue levels of myeloperoxidase. Nedocromil, 2 to 20 mg/kg, significantly (P<0.05) inhibited cell adhesion and emigration, as well as myeloperoxidase release, in wild-type but not Anx-A1(-/-) mice. Short pretreatment of human PMNs with nedocromil, 10 nmol/L, inhibited cell adhesion (P<0.05) in the flow chamber assay, and this effect was reversed by specific anti-AnxA1 or a combination of antiformyl peptide receptors 1 and 2, but not irrelevant control, antibodies. Western blotting experiments revealed that cromones stimulate protein kinase C-dependent phosphorylation and release Anx-A1 in human PMNs.

CONCLUSIONS

We propose a novel mechanism to explain the antiinflammatory actions of cromones on PMN trafficking, an effect that has long puzzled investigators.

Cromoglycate drugs suppress eicosanoid generation in U937 cells by promoting the release of Anx-A1

Using biochemical, epifluorescence and electron microscopic techniques in a U937 model system, we investigated the effect of anti-allergic drugs di-sodium cromoglycate and sodium nedocromil on the trafficking and release of the anti-inflammatory protein Annexin-A1 (Anx-A1) when this was triggered by glucocorticoid (GC) treatment. GCs alone produced a rapid (within 5 min) concentration-dependent activation of PKCα/β (Protein Kinase C; EC 2.7.11.13) and phosphorylation of Anx-A1 on Ser²⁷. Both phosphoproteins accumulated at the plasma membrane and Anx-A1 was subsequently externalised thereby inhibiting thromboxane (Tx) B₂ generation. When administered alone, cromoglycate or nedocromil had little effect on this pathway however, in the presence of a fixed sub-maximal concentration of GCs, increasing amounts of the cromoglycate-like drugs caused a striking concentration-dependent enhancement of Anx-A1 and PKCα/β phosphorylation, membrane recruitment and Anx-A1 release from cells resulting in greatly enhanced inhibition of TxB₂ generation. GCs also stimulated phosphatase accumulation at the plasma membrane of U937 cells. Both cromoglycate and nedocromil inhibited this enzymatic activity as well as that of a highly purified PP2A phosphatase preparation. We conclude that stimulation by the cromoglycate-like drugs of intracellular Anx-A1 trafficking and release (hence inhibition of eicosanoid release) is secondary to inhibition of a phosphatase PP2A (phosphoprotein phosphatase; EC 3.1.3.16), which probably forms part of a control loop to limit Anx-A1 release. These experiments provide a basis for a novel mechanism of action for the cromolyns, a group of drugs that have long puzzled investigators.

Inverse relationship between 15-lipoxygenase-2 and PPAR-gamma gene expression in normal epithelia compared with tumor epithelia

15-Lipoxygenase-2 (15-LOX-2) synthesizes 15-S-hydroxyeicosatetraenoic acid (15-S-HETE), an endogenous ligand for the nuclear receptor, peroxisome proliferator-activated receptor-gamma (PPAR-gamma). Several studies have described an inverse relationship between 15-LOX-2 and PPAR-gamma expression in normal versus tumor samples. To systematically determine if this is a ubiquitous phenomenon, we used a variety of epithelial and nonepithelial cells and some tissues to further evaluate the extent of this inverse relationship. The levels of mRNA or protein were measured by reverse transcriptase polymerase chain reaction or Western gray level intensity, whereas distribution was determined by in situ hybridization or immunofluorescence. 15-S-HETE was measured by liquid chromatography/tandem mass spectrometry. Normal epithelial cells/samples generally expressed high levels of 15-LOX-2 along with the enzyme product 15-S-HETE, but both levels were reduced in cancer cells/samples. In contrast, most cancer cells expressed high levels of PPAR-gamma mRNA and protein, which were absent from normal epithelial cells. Overall, the inverse relationship between these two genes was primarily restricted to epithelial samples. Forced expression of PPAR-gamma reduced 15-LOX-2 protein levels in normal cells, whereas forced expression of 15-LOX-2 in tumor cells suppressed PPAR-gamma protein levels. These results suggest that feedback mechanisms may contribute to the loss of 15-LOX-2 pathway components, which coincide with an increase in PPAR-gamma in many epithelial cancers.

Effect of nedocromil sodium on allergen-induced airway responses and changes in the quantity of airway smooth muscle in rats

BACKGROUND

Allergen exposures induce growth of airway smooth muscle in the Brown Norway rat.

OBJECTIVE

The purpose of the study was to examine the role of mediators associated with the early and late responses in the induction of airway smooth muscle growth.

METHODS

Nedocromil sodium was administered to block early and late responses in ovalbumin-sensitized and ovalbumin-challenged rats undergoing single or multiple challenges (5 times at 5-day intervals) with ovalbumin. Airway smooth muscle was quantitated by morphometry on lungs removed 2 days after the final challenge.

RESULTS

Nedocromil sodium administered before ovalbumin challenge blocked both the early and late responses. When administered 2 hours after ovalbumin challenge, it also blocked the late response. Rats undergoing challenge with aerosolized ovalbumin five times at 5-day intervals were also treated with nedocromil before (n = 10) or 2 hours after (n = 10) each ovalbumin inhalation, respectively. The quantity of airway smooth muscle standardized for size was greater after ovalbumin challenge (0.069 +/- 0.005) compared with saline controls (0.033 +/- 0.003, p < 0.005). Nedocromil significantly reduced the airway smooth muscle (0.036 +/- 0.003, p < 0.005) when administered before ovalbumin. However, the airway smooth muscle in rats that received nedocromil 2 hours after ovalbumin challenge (0.046 +/- 0.003), although lower than in ovalbumin-challenged rats (p < 0.01), was still significantly higher than in saline-treated rats (p < 0.05).

CONCLUSIONS

Allergen-induced early responses, late responses, and airway inflammation are antagonized by nedocromil. The mediators of both the early and late responses contribute to allergen-induced airway smooth muscle growth, a process that can be prevented by administration of nedocromil.

The effect of human eosinophils on cultured human nasal epithelial cell activity and the influence of nedocromil sodium in vitro

Although there is increasing evidence of a pathogenic role for eosinophils in the airway epithelium, there is little direct evidence which demonstrates that eosinophils influence epithelial cell activity in humans. We have cultured human nasal epithelial cells in vitro and studied the effect of isolated human eosinophils on the ciliary beat frequency (CBF) and cell membrane integrity of these cells after incubation in the absence or presence of 0.1 microM phorbol 12-myristate 13-acetate (PMA) or 0.1 mg/ml opsonized latex beads and the absence or presence of 10(-5) M nedocromil sodium. CBF was monitored by an analogue contrast-enhancement technique, and cell damage was assessed by release of 51Cr from the cells. Cell cultures were also assessed for the percentage of eosinophil cationic protein (ECP) released into the medium at the end of incubation. Neither 0.1 microM PMA, 0.1 mg/ml opsonized latex beads, 10(-5) M nedocromil sodium, nor eosinophils alone altered the CBF of the epithelial cells. PMA-stimulated eosinophils, however, attenuated the CBF significantly, from 10.2 +/- 0.3 to 8.8 +/- 0.4 Hz (P less than 0.05) after 15 h of incubation. Similarly, opsonized latex bead-stimulated eosinophils led to a significant attenuation of CBF from 9.2 +/- 0.3 to 8.4 +/- 0.3 Hz (P less than 0.05), 6.9 +/- 0.5 Hz (P less than 0.001), and 7.5 +/- 0.3 Hz (P less than 0.001) after 2, 15, and 24 h of incubation, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Protective effect of nedocromil sodium on the IL1-induced release of GM-CSF from cultured human bronchial epithelial cells

Cultured human bronchial epithelial cells constitutively produce granulocyte-macrophage colony-stimulating factor (GM-CSF). The synthesis and release of GM-CSF is upregulated in bronchial epithelium of patients with symptomatic asthma and this may contribute to the local activation of inflammatory cells in their bronchial mucosa. The cause of this upregulation of GM-CSF expression is unknown, but an increased release of interleukin-1 (IL1) from other airway resident cells might be involved, as an increase in GM-CSF production can be induced in vitro in normal bronchial epithelial cells by IL1 and the airway secretions of asthmatics contain high amounts of this cytokine. In the present study, we have evaluated the effect of the anti-inflammatory and antiasthmatic drug, nedocromil sodium, on the spontaneous and IL1-induced expression of GM-CSF in cultured bronchial epithelial cells. This compound, at the concentration of 10(-5) M, reduced the IL1-induced increase in GM-CSF release from epithelial cells by more than 40%, but it did not affect the constitutive production of GM-CSF.