Asthma is a chronic inflammatory disease characterized by bronchial hyperresponsiveness, immune cell infiltration into the airways, airway remodeling and mucus overproduction. Platelets are small anucleated cells known for their role in hemostasis and thrombosis. However, they also exhibit immune and pro-inflammatory functions. Few studies suggest their involvement in the pathophysiology of asthma. The objective of our study was to analyze the transcriptomic profile of platelets from patients with severe asthma compared to non asthmatic subjects.
Blood samples were collected from 5 severe asthma patients and 5 non asthmatic controls. Platelets were purified using immunomagnetic separation (Miltenyi Biotec). Total RNA was extracted and analyzed using whole genome U133 Plus 2.0 GeneChip Affymetrix microarrays. Significance analysis of microarray was used to analyze the array data with 2-fold cut-off and false discovery rate (FDR <5%). Principal component analysis (PCA) was performed using R software. Cluster and Treeview software packages were used for the hierarchical clustering analysis. The gene ontology (GO) enrichment analysis, the biological processes and networks of differentially expressed genes were analyzed through the use of Ingenuity Pathway Analysis.
The molecular signature of platelets from severe asthmatics was significantly different from the healthy subjects. Specifically, platelets from severe asthma patients were characterized by over-expression of genes related to inflammatory response and infection including CD9, CD36, CD164, SERPINB1, PANX1 and IFITM3. In addition, mRNA transcripts of factors controlling metabolism and transport of molecules such as phospholipase A1 (PLAAT1) and leucine rich repeat (LRRC32) were up-regulated in platelets from severe asthma patients. Conversely, several genes, implicated in cell death and survival (EHMT1, ABCC1, HMOX1, GSTP1, EIF3), were down-regulated. Functional annotation of the differentially expressed genes revealed dysregulation of the Th1 and Th2 activation pathways (CD28, IL12, TSLPR, PI3K) that play a critical role in the adaptive immunity and therefore impact the pathophysiology of asthma.
Transcriptome profiling of platelets from severe asthma patients and non-asthmatic controls allowed us to unravel the molecular basis of their special features and to determine candidate genes differentially expressed in these studied groups. This study presents a comprehensive resource to constitute a base for future investigations on the role of platelets in patients with severe asthma.Le texte complet de cet article est disponible en PDF.
Keywords : Asthma-Allergy, Transcriptome, Platelets