The Effects of Overexpression of Histamine Releasing Factor (HRF) in a Transgenic Mouse Model Yueh-Chiao Yeh2, Liping Xie3, Jacqueline M. Langdon 1 , Allen C. Myers1, Sun-Young Oh 1 , Zhou Zhu 1 , Susan M. MacDonald4* 1 Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America, 2 Graduate Institute of Natural Healing Sciences, Nanhua University, Chiayi, Taiwan, 3 Aurora Sinai Medical Center, Milwaukee, Wisconsin, United States of America, 4 The Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland, United States of America Abstract Background: Asthma is a disease that affects all ages, races and ethnic groups. Its incidence is increasing both in Westernized countries and underdeveloped countries. It involves inflammation, genetics and environment and therefore, proteins that exacerbate the asthmatic, allergic phenotype are important. Our laboratory purified and cloned a histamine releasing factor (HRF) that was a complete stimulus for histamine and IL-4 secretion from a subpopulation of allergic donors’ basophils. Throughout the course of studying HRF, it was uncovered that HRF enhances or primes histamine release and IL- 13 production from all anti-IgE antibody stimulated basophils. In order to further delineate the biology of HRF, we generated a mouse model. Methodology/Principal Findings: We constructed an inducible transgenic mouse model with HRF targeted to lung epithelial cells, via the Clara cells. In antigen na¨ıve mice, overproduction of HRF yielded increases in BAL macrophages and statistical increases in mRNA levels for MCP-1 in the HRF transgenic mice compared to littermate controls. In addition to demonstrating intracellular HRF in the lung epithelial cells, we have also been able to document HRF’s presence extracellularly in the BAL fluid of these transgenic mice. Furthermore, in the OVA challenged model, we show that HRF exacerbates the allergic, asthmatic responses. We found statistically significant increases in serum and BAL IgE, IL-4 protein and eosinophils in transgenic mice compared to controls. Conclusions/Significance: This mouse model demonstrates that HRF expression enhances allergic, asthmatic inflammation and can now be used as a tool to further dissect the biology of HRF. Citation: Yeh Y-C, Xie L, Langdon JM, Myers AC, Oh S-Y, et al. (2010) The Effects of Overexpression of Histamine Releasing Factor (HRF) in a Transgenic Mouse Model. PLoS ONE 5(6): e11077. doi:10.1371/journal.pone.0011077 Editor: Dominik Hartl, Ludwig-Maximilians-Universita¨t M u¨nchen, Germany Received March 8, 2010; Accepted May 15, 2010; Published June 11, 2010 Copyright: 2010 Yeh et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Supported by National Institutes of Health Allergy, Immunology (AI) AI3265 and Heart Lung (HL) HL079349. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: smacdona@jhmi.edu Introduction We identified a histamine releasing activity that was found in late phase fluids from nasal lavages, bronchoalveolar lavage (BAL) fluids and skin blister fluids that directly induced histamine release from basophils isolated from a subpopulation of allergic donors [1]. After purification and cloning, this histamine releasing factor (HRF) was found to be identical to translationally controlled tumor protein (TCTP), which is also known as p23 [2–4]. This recombinant molecule was found to have the same properties as the originally described HRF derived from nasal secretions, namely, an ability to induce histamine release from selected donors, HRF-responders (HRF-R). This protein is ubiquitously expressed as an intracellular protein. HRF has no leader sequence, therefore, how it gets secreted was elusive until Amzallage et al documented that HRF or as it is alternatively known, TCTP, was secreted by an ER/Golgi-independent route [5]. Furthermore, they documented that secreted HRF/TCTP comes from a pre- existing intracellular pool and co-distributes with TSAP6, a member of a family of proteins that are involved in vesicular trafficking and secretory processes [6,7]. Homologs of HRF have been described in parasites including Plasmodium falciparum, Wucheria bancrofti, Brugiia malea and Schistosoma Mansinai, all of which possess mast cell/basophil histamine releasing activity [8–10]. HRF was initially described as a complete secretogogue for histamine and IL-4 secretion from basophils of allergic donors [11]. Initially, it was thought that these donors had a certain type of IgE that interacted with HRF to induce secretion [2]. However, it was subsequently demonstrated that HRF primed all basophils for histamine release as well as IL-4 and IL-13 secretion regardless of the type of IgE [12]. Additional studies demonstrated that HRF did not appear to directly interact with IgE [13,14]. HRF was also shown to stimulate eosinophils to produce IL-8 and induce an intracellular calcium response [15]. Moreover, HRF has been shown to inhibit cytokine production from stimulated primary T cells and the Jurkat T cell line [16] at the level of gene transcription [16]. Furthermore, Kang et al have identified this molecule as a B cell growth factor [17]. This group demonstrated that HRF bound PLoS ONE | www.plosone.org 1 June 2010 | Volume 5 | Issue 6 | e11077