Chemoattraction of macrophages by secretory molecules derived from cells expressing the signal peptide of eosinophil cationic protein.
BACKGROUND
Eosinophil cationic protein is a clinical asthma biomarker that would be released into blood, especially gathered in bronchia. The signal peptide of eosinophil cationic protein (ECPsp) plays an important role in translocating ECP to the extracellular space. We previously reported that ECPsp inhibits microbial growth and regulates the expression of mammalian genes encoding tumor growth factor-α (TGF-α) and epidermal growth factor receptor (EGFR).


RESULTS
In the present study, we first generated a DNA microarray dataset, which showed that ECPsp upregulated proinflammatory molecules, including chemokines, interferon-induced molecules, and Toll-like receptors. The levels of mRNAs encoding CCL5, CXCL10, CXCL11, CXCL16, STAT1, and STAT2 were increased in the presence of ECPsp by 2.07-, 4.21-, 7.52-, 2.6-, 3.58-, and 1.67-fold, respectively. We then constructed a functional linkage network by integrating the microarray dataset with the pathway database of Kyoto Encyclopedia of Genes and Genomes (KEGG). Follow-up analysis revealed that STAT1 and STAT2, important transcriptional factors that regulate cytokine expression and release, served as hubs to connect the pathways of cytokine stimulation (TGF-α and EGFR pathways) and inflammatory responses. Furthermore, integrating TGF-α and EGFR with the functional linkage network indicated that STAT1 and STAT2 served as hubs that connect two functional clusters, including (1) cell proliferation and survival, and (2) inflammation. Finally, we found that conditioned medium in which cells that express ECPsp had been cultured could chemoattract macrophages. Experimentally, we also demonstrated that the migration of macrophage could be inhibited by the individual treatment of siRNAs of STAT1 or STAT2. Therefore, we hypothesize that ECPsp may function as a regulator for enhancing the migration of macrophages through the upregulation of the transcriptional factors STAT1 and STAT2.


CONCLUSIONS
The increased expression and release of various cytokines triggered by ECPsp may attract macrophages to bronchia to purge damaged cells. Our approach, involving experimental and computational systems biology, predicts pathways and potential biological functions for further characterization of this novel function of ECPsp under inflammatory conditions.
College of Medicine, China Medical University, Taichung, Taiwan.
Yu-Shu
YS
Liu
Pei-Wen
PW
Tsai
Yong
Y
Wang
Tan-Chi
TC
Fan
Chia-Hung
CH
Hsieh
Margaret Dah-Tsyr
MD
Chang
Tun-Wen
TW
Pai
Chien-Fu
CF
Huang
Chung-Yu
CY
Lan
Hao-Teng
HT
Chang
D000818:Animals; D002460:Cell Line; D002465:Cell Movement; D018925:Chemokines / Q000378:metabolism; D002630:Chemotactic Factors / Q000737:chemistry* / Q000378:metabolism*; D016000:Cluster Analysis; D017077:Culture Media, Conditioned / Q000378:metabolism; D047150:Eosinophil Cationic Protein / Q000737:chemistry* / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D021382:Protein Sorting Signals; D050794:STAT1 Transcription Factor / Q000235:genetics; D050795:STAT2 Transcription Factor / Q000235:genetics; D015398:Signal Transduction; D049490:Systems Biology; D016211:Transforming Growth Factor alpha / Q000378:metabolism; D015854:Up-Regulation
D018925:Chemokines; D002630:Chemotactic Factors; D017077:Culture Media, Conditioned; D021382:Protein Sorting Signals; D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D016211:Transforming Growth Factor alpha; D066246:ErbB Receptors; D047150:Eosinophil Cationic Protein