Pilot-Scale Study Of Human Plasma Proteomics Identifies ApoE And IL33 As Markers In Atopic Asthma

Abstract

Background

The pathobiology of atopic asthma is complex and the symptoms similar to other respiratory diseases. As such, identification of biomarkers of atopic asthma is of prime importance for better diagnosis and control of the disease.

Objectives

We sought to study the changes in plasma proteome and cytokine-expression profile across healthy and atopic asthmatics for identifying biomarkers and exploring aberrant pathways for atopic asthma.

Methods

A pilot-scale study in humans was performed to identify differentially expressed proteins in blood plasma of healthy controls (n=5) and treatment-naïve atopic asthma patients (n=5) using quantitative label-free liquid chromatography–tandem mass spectrometry proteomics and ELISA.

Results

Mass spectrometry–based proteomic analysis revealed ApoE to be significantly downregulated in atopic asthmatics compared to healthy volunteers. Decreased expression of ApoE in atopic asthmatics was validated by immunoblotting (50.74% decrease). Comparison with atopic asthmatics and COPD patients showed that ApoE was decreased (36.33%) in atopic asthma compared to COPD. IL33 was significantly upregulated in atopic asthmatics compared to healthy subjects (3.84-fold).

Conclusion

ApoE was downregulated and IL33 upregulated in atopic asthma patients compared to healthy volunteers. These two proteins' profiles were distinct in atopic asthma from healthy and COPD plasma samples. Differential expression of these proteins could serve as a probable candidate for a two-protein classifier–based prognostic biomarker of atopic asthma.

Keywords:

• atopic asthma
• LC-MS/MS
• apolipoprotein E
• ApoE
• interleukin 33
• IL33
• biomarkers

Acknowledgments

The authors are grateful to the Centre for Cellular and Molecular Platforms (C-CAMP) for performing the LC-MS/MS run. The authors are also thankful to Dr Parthasarathi Bhattacharyya for critically reviewing the manuscript.

Abbreviations

COPD, chronic obstructive pulmonary disorder; FEV1, forced expiratory volume in 1 second; ApoE, apolipoprotein E; IL33, interleukin 33; LC-MS/MS, liquid chromatography–tandem mass spectrometry; NSAF, normalized spectral abundance factor; IPA, ingenuity pathway analysis.

Ethics Approval And Informed Consent

Human Ethics Committee clearance (BIHEC/2014-15/4) from Bose Institute, Kolkata was obtained to work with human blood samples. All human blood samples were collected with written informed consent from patients and healthy subjects. The methods used were in accordance with relevant guidelines and regulations. All the experimental protocols were approved by the aforementioned committee.

Availability Of Data And Materials

Supporting figures and tables are included in the Supplementary file and Table S2.

Funding

This work was supported by a grant from the Indian Council of Medical Research ICMR (BIC/12[28]/2012). Author Moumita Bhowmik is grateful to the CSIR, Government of India for the CSIR-SRF Fellowship. Author Sreyashi Majumdar is grateful to the Department of Science and Technology, Government of India for the DST-Inspire Fellowship.

Author Contributions

SS, SGB, and AD conceptualized and designed the study. MB, SM, and AD were involved in acquisition of data. SM, MB, SGB, and SS were involved in data analysis. All authors contributed toward drafting and critically revising the paper, gave final approval of the version to be published, and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.