Bibliographic updates

Claude MOLINA* and Jacques GAYRAUD**

1. New life for an old drug : Theophylline… against cough
2. Vernal keratoconjunctivitis (VKC) and tear peptide profile
3. Molecular phenotyping in sputum of allergic asthma
4. Link between atopic (AD) and contact (CD) dermatitis
5. In utero sensitization to tobacco smoke and development of childhood asthma

1. New life for an old drug : Theophylline… against cough

Theme: Asthma
Key words: Theophylline – Cough – Capsaicin – C Fibre – Vagus nerve

Theophylline has been used in the treatment of respiratory disorders for 80 years, particularly for chronic lung diseases and occasionally for asthma, but its side effects, mostly digestive, have restricted its prescription and it has become a backup treatment.

In fact, cough is one of the most frequent causes of consultation and also of self-medication. In the USA over-the-counter sales amount to billions of dollars.

The work presented by Eric Dupuis et al. (JACI 2014 7Janvier in press) of the London Pharmacological Laboratory is original in that it demonstrates, via a series of ingenious experimental and electro-physiological investigations, that apart from its bronchodilatory effects, Theophylline inhibits the cough reflex through a hitherto unknown  mechanism.

In the conscious guinea pig model, inhaling citric acid and capsaicin (a chilli pepper derivative) is inhibited by Theohylline; similarly in vivo activation of airway afferent C-Fibres and in vitro depolarisation of human and guinea pig vagus are considerably reduced.

Then, through a sequence of pharmaco-dynamic experiments, the authors show that Theophylliine lessens the sensorial excitability of airways through greater opening of calcium activated potassium canals. Finally, there is a demonstration of the antitussive activity of Theophylline in a cigarette smoke exposure model,

From a clinical point of view the product efficacy is well known in the treating of cough induced by some anti-hypertensive drugs  such as angiotensin converting enzyme inhibitors like Captopril. But these interesting experiments offer undeniable arguments in favour of a hitherto unknown beneficial property of Theophylline.

This will encourage the development of new antitussive derivatives, which in limiting secondary effects will mean that the use of opioids can be avoided. Finally, we should remember that Theophylline is a harmless and low-cost medicine, the use of which is already justified in all forms of cough, acute and above all chronic, often a problem for pneumo-allergists.

2. Vernal keratoconjunctivitis (VKC) and tear peptide profile

Theme: Ocular allergy
Key words: Vernal keratoconjunctivitis – Tear peptide profile – Serum albumin – Transferrin – Hemopexin – Mammaglobin B – Secretoglobin ID

It is known that VKC is a severe form of conjunctivitis affecting -young patients (aged 5-20) which reappears regularly in the spring and is characterized by the sensation of a foreign body in the eye with itching, photophobia, secretion, and corneal ulcers. An allergic origin is usually discovered, although often disputed, all the more since antiallergic therapy is generally unsuccessful.

The aim of the study presented (A. Leonardi et coll. Allergy décembre 2013 early view) was to analyse the peptide profiles in the tears of VKC subjects by means of sophisticated isotopic technology, in conjunction with mass spectrometry in order to elucidate compositional differences between healthy subjects and patients affected.

Tears were collected from 10 VKC patients and 10 healthy subjects (plus 8 others suffering from VKC which was more or less controlled by anti-inflammatory medication).

The peptidic separation of these samples was carried out by qualitative and qualitative isobaric analyses together with high performance liquid chromatography.

A significant number of peptides were examined and 78 proteins were identified.

The findings were as follows:
- In all VKC samples, serum albumin, Transferrin, and Hemopexin levels were 100 times higher than in control tears, and the presence of these proteins correlated significantly with the severity of the disorder and the degradation of the corneal surface.
- These bio-markers, as well as mammaglobin B and secretoglobin ID, were over expressed in VKC tears compared to controls.
- Lastly, tear samples from VKC patients treated with corticosteroids or topical cyclosporine showed a dramatic reduction in these protein levels.

All these peptides are therefore serum proteins like albumin, transferring and apolipoprotein, but other proteins were revealed like certain metabolic enzymes, immunoglobins, lipophilin, complement proteins, cytokins, growth factors, most of these having anti-inflammatory properties.

Finally these techniques have defined a particular VKC tear peptide profile, both qualitative and quantitative, and although they are not available to all laboratories they could be useful in diagnosing and treating the disorder, and possibly for other ocular inflammatory lesions.

PS : a general review of VKC has been published in Pediatric Allergy et Immunol Janaryr 2014 early view P.Vichyanond et al).

3. Molecular phenotyping in sputum of allergic asthma

Theme: Asthma
Key words: Molecular phenotyping of sputum – Allergic asthma – Th2 expression – Periostin – Chloral channel accessory – Serpin – Interleukin 4, IL 5, IL 13 – Hyper eosinophilia

The San Francisco team of pneumologists and geneticians has recently published a pilot study on this subject (MC Peters et al : JACI 2013  in press).

It is known that allergic asthma is the translation of a Th2 inflammation for which the authors have identified 2 phenotypes: one high and one low Th2 expression, these two sub-types having different symptomatology, sensitivity to treatment, and evolution.

The same team had already demonstrated a high genetic expression of IL5, IL4 and IL13 cytokins in airway epithelial cell samples examined by bronchial biopsy; they also showed that the IL13-activated gene signature of periostin (P), chloride channel accessory (CLCA 1) and Serpin (S) could be revealed by brushings and led to a clearer classification of allergic asthma.

In fact little is known about gene profiling in sputum. The authors therefore sought to use this non-invasive method in order to measure gene expression of these allergic asthmas.

37 asthmatics averaging 35 years of age and 15 controls were enrolled for the study: provoked sputum was analysed by PCR, with RNA extraction and examination of 14 genes indicating airway inflammation, in order to measure the gene expression in epithelial cells of IL13 activation (P, CLCA 1, S) at the same time as Th2 cytokin genes (IL4, 5, 13).

The findings were as follows:
- gene expression levels are significantly higher than normal for CLCA1 and P, but not for S, in asthmatic sufferers’ sputum cells
- IL 4, 5 and 13 expression levels are also significantly higher among asthmatics but with individual variations
- 26 of them, i.e. 70%, correspond to a high Th2 gene expression asthma and present increased blood and sputum eosinophilia, bronchial obstruction with decreased FEV1 and FENO, and lesser sensitivity to corticosteroids, that is to say a more severe form of asthma.

In conclusion, gene transcripts for IL4, IL5, and IL13 cytokines are easily detected in sputum cells from asthmatic patients, and offer a non-invasive and reliable means of identifying the different aspects of asthma. They lead to the differentiation of high and low Th2 gene expression asthmas, the first corresponding to a severe form, the second more reactive to corticosteroids.

4. Link between atopic (AD) and contact (CD) dermatitis

Theme: Skin allergy
Key words: Atopic dermatitis – Contact dermatitis – Interleukins 13, 17 – Interferon 

D.Simon’s Swiss team in Bern (Allergy 2014 69 1 125-131) point out in an original paper that AD, and CD whether allergic (ACD, due to Nickel for instance) or irritant (ICD), are characterized by the same clinical signs, although due to different causes.

From a pathologic point of view, Th17 cells are known to be present in the 3 types, albeit with different immune mechanism.

The authors were seeking to investigate IL17 expression in acute forms of the three types of D, its significance, and its correlation with lesion remodeling markers.

To this end, 9 patients underwent patch-tests followed by biopsies, concerning aero-allergens (house dust and pollen), contact allergens and irritants (lauryl-sulfate), on days 2, 3 and 4. Inflammatory cells, as well as the expression of different cytokines and extra-cellular matrix proteins, were evaluated by immunoflorescence with the help of corresponding antibodies. 27 specimens were examined and statistically analysed.
- Findings showed that IL17, but also IL21 and IL22, were expressed in the three D types, something new for ICD
- As expected, ACD and ICD were characterized by IFN γ expression, whereas in AD IL13 expression and high numbers of eosinophils were prominent
- The number of IL22 + T cells correlated with the number of eosinophils
- Markers of remodelling such as pro-collagen 3, MMP-9 and tenascin C, were observed in the three acute lesion types, and the last 2 mediators correlated with Th17 cells.

In all, the expression of IL17 and related cyokines such as IL22 was found in all acute eczematous legions whatever their origin, allergic or irritant. IL17 is therefore the common denominator, in relation to host defence mechanism and also intervene in skin remodeling.

On the same subject and in the same journal J. Thyssen et al. (2014 69 1 29-38), based on clinical investigations, mention the risks for AD sufferers treated by anti-inflammatory or emollient drugs of becoming sensitive to “metal” allergens or irritants. For other authors, the AD Th2-response may reduce this risk. Whatever the case, according to the state of the skin barrier (low hydration, high pH, presence of bacteria) and to environmental exposure (emollient ingredients, occupational exposure to chemicals such as DNCB, piercing), several factors are likely to complicate AD into contact eczema. It is therefore up to the clinician to adapt AD treatment to skin fragility.

5. In utero sensitisation to tobacco smoke and development of childhood asthma

Theme: Asthma – Pediatric allergy - Prevention
Key words: Tobacco smoke – In utero sensitization – Childhood asthma – PArkin CoRegulated Gene

An extensive European and Canadian survey, involving 57 researchers and 45 pneumo-allergy and genetics centres (including three French teams), is focused on the interaction between genetic and environmental factors in the development of early onset childhood asthma.

It is well known that the Genomewide study has identified multiple asthma development genes, yet they only explain a limited proportion of asthma heritability. The assumption of interaction between genetic predisposition and in utero or early life exposure to a well known environmental factor, tobacco smoke, is a possible explanation (S .Scholtens et al JACI décembre 2013 in press).

To test this, a first meta-analysis of this interaction was carried out using 9 studies participating in the GABRIEL consortium, including 6000 subjects of European descent. The findings were replicated in 4 independent studies enrolling 13000 subjects. Childhood asthma was defined as diagnosed by a doctor before the age of 16, tobacco smoke exposure as in utero if during pregnancy (2654 cases and 3073 controls in 7 studies) and as childhood exposure if from birth to age 16 (3048 cases and 3509 controls in 9 studies). The results of each of these investigations were analysed separately and then subjected to logistic regression statistics.

It appears that, overall, in utero tobacco smoke exposure increases the risk of childhood asthma. 536 705 SNPs (Single Nucleotide Polymorphism) were included in the analysis: 27 were identified, but only 4 on chromosome 10 were significant (linkage disequilibrium) and the most important marker was located on chromosome 18 close to gene EPB41L3.

This gene belongs to the membrane protein family and is an essential part of biological processes such as intercellular junction and apoptosis; it influences lung development in children in general. This in utero tobacco smoke exposure effect, which affects gene expression, could be explained by a series of mechanisms involving this marker.

As for childhood exposure to tobacco smoke, the Genome meta-analysis reveals that it also increases the risk of asthma development. 7 SNP on chromosome 5 had a certain significance (linkage disequilibrium). The chief marker was located on chromosome 6 in the PACRG (PArkin CoRegulated Gene), a gene associated with leprosy and Parkinson’s disease and playing an important role in the ciliary function in general and in airway mucus clearance.

In conclusion, this is the first discovery of SNP interaction between tobacco smoke exposure and asthma development, different from those reported so far and which could explain the absence of asthma heritability in general.
Comments and questions welcome:

Pr. Claude Molina

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Dr Jacques Gayraud

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Last updated 31 October 2014