Professor Stephan Rosenkranz

Organisation / Institute
Department III of Internal Medicine
Cologne University Heart Center


Prof. Stephan Rosenkranz
Department III of Internal Medicine,
Cologne University Heart Center
Kerpener Str. 62
50937 Köln, Germany






F. Role of IL-6 signaling and macrophage polarization in pulmonary hypertension

Professor Stephan Rosenkranz

Rationale and aims

Pulmonary hypertension (PH) is a devastating vascular disease characterized by a high mortality and limited treatment options. In addition to adverse regulation of vascular tone and remodeling, inflammation is increasingly recognized as a key pathogenic factor. However, the precise inflammatory mechanisms and their specific contribution to the pathobiology of PH remain elusive. In this project, we aim to evaluate the pathogenic relevance of interleukin (IL)-dependent macrophage and T-cell activation for vascular dysfunction in PH.

Current state of research and own preliminary work

Figure 1 (A) Inhibition of the catalytic class IA PI3K isoform p110 by PIK75 reversed pulmonary vascular remodeling and PH in the Sugen/Hypoxia model of PH. (B) Role of IL-6 and IL4-R for macrophage M2-polarization and its expected role in PH (modified from Mauer et al. Nat Immunol 2014). Loss of the protective six-transmembrane protein STAMP-2 in macrophages was associated with increased IL-6 expression (C) and perivascular accumulation of CD68-positive cells (D) in the pulmonary vasculature under hypoxic conditions.

Preliminary work has shown that selective interference with specific targets such as the catalytic PI3K isoform p110a is capable of preventing or even reversing PH and pulmonary vascular remodeling in rodent models (Figure 1 A). Among the inflammatory cytokines found in PH is IL-6, but its role in regulating immune responses remains a matter of scientific debate. Recently, critical roles in the regulation of macrophage polarization as well as T-lymphocyte function with respect to the manifestation of innate and adaptive immune responses have been defined. More specifically, abrogation of IL-6 signaling in myeloid lineage cells resulted in increased expression of proinflammatory M1-macrophage marker genes, while activation of alternative M2-polarization was reduced. Furthermore, IL-6 was shown to upregulate IL-4 receptor expression in macrophages, and loss of macrophage IL-6 signaling prevented IL-4-mediated M2-polarization and its beneficial metabolic effects (Figure 1 B). With regards to inflammatory resolution, loss of the protective six-transmembrane protein STAMP-2 in macrophages, which is downregulated in human PH, was associated with pulmonary upregulation of IL-6 and perivascular accumulation of CD68-positive cells under hypoxic conditions (Figure 1 C,D). Collectively, these findings assign IL-6 signaling a critical role in alternative macrophage polarization, thus impacting inflammation, and potentially vascular remodeling and PH.

Experimental approach and work program

The aim of this project is to define the role of macrophage- (and T cell-, 2nd term) intrinsic IL-6 signaling and to assess their impact on IL-4-mediated signals and macrophage polarization in pulmonary vascular remodeling and PH. To this end, we will use already available genetic mouse models to selectively prevent IL-6 signaling in macrophages (IL6Ra-Δmyel) (Mauer et al. Nat Immunol 2014) or T cells (IL-6RaT-KO) (Xu et al. Nat Commun 2017). Furthermore, we will explore the role of IL-4 by utilizing IL-4Ra knockout mice. In the first term, we will focus on myeloid cells, whereas T-cell function will be investigated in the second term. To systematically define the role of myeloid IL-6 and IL-4 in the context of PH, we will (1) compare macrophage polarization and PH phenotypes in WT vs. IL6Ra-Δmyel mice; (2) analyze the function of IL-4R signaling in PH by comparing WT vs. IL-4Ra-/- mice; (3) characterize the role of IL-4R in IL-6-induced PH by comparing WT vs. transgenic IL6-Tg(+) vs.  IL6-Tg(+)//IL-4Ra-/- mice; (4) analyze the effects of an anti-IL6R mAb as a treatment approach on macrophage polarization in Su/Hx-induced PH. Phenotypical characterization will include monitoring of body weight, body composition, energy expenditure, and glucose homeostasis. PH in mice will be induced by the established hypoxia model, and the degree of pulmonary vascular remodeling (aSMA and vWF double staining, morphometric analysis), PH (RV pressure as assessed by Millar® right heart catheter), and right ventricular hypertrophy (RV/LV+Septum ratio) will be compared among the genotypes. For the mAb treatment approach, the Sugen/Hypoxia (Su/Hx) model in the rat will be used. Mechanistically, we will assess the composition of remodeled vessels and the infiltration of inflammatory cells and macrophage polarization into pulmonary vascular lesions and hypertrophied RV via histology as well as gene expression analyses, cytokine / chemokine profiles (e.g., IL-1β, IL-4, IL-6, TNF-α, TGF-β, IL-10, IL-12, IL-4R, Arg1, iNOS, FGF, PDGF, CCL3, CCL5, CX3CL1), both in situ and in purified cells from pulmonary arteries in vitro. These studies will be complemented by analysis of ligand-stimulated signal relay in relevant cell types, such as ECs, vascular smooth muscle cells, and perivascular fibroblasts. Finally, alterations of IL-6/IL-4 signaling and the contribution of inflammatory cells will be monitored in other mammalian species including Sugen/hypoxia-induced PH in rat models and in PH patients. Collectively, these experiments will provide novel mechanistic insights into the inflammation-related pathobiology of pulmonary vascular disease and will allow us to define the cell-type-specific role of IL-6 signaling in the onset and progression of PH in vivo.

Potential future therapeutic implications

We anticipate that this study may potentially provide the molecular basis for novel, disease-modifying pharmacological interventions. Immune-modulatory therapies represent an exciting opportunity to further improve the treatment options of this deadly disease.

Added value through collaborations within the CCRC

This project will ideally integrate research expertise in metabolism and inflammatory IL signaling (Brüning) into the clinical context of PH (Rosenkranz). Since the project also aims to unravel the key steps involved in immune response regulation leading to pulmonary vascular pathology, close collaborations with S. Baldus (hemodynamics), A. Trifunovic (mitochondrial function), and M. Pasparakis (macrophage biology, ER stress, cell death) will enable us to better define specific aspects of inflammation-triggered stress-responses in PH. This project will also benefit from the core facilities for histopathology (A. Quaas/R. Büttner), mass spectrometry based proteomics (C. Freese / M. Krüger), and potentially from molecular imaging (B. Neumaier).

General Research Interest:

Prof. Stephan Rosenkranz

Prof. Stephan Rosenkranz attended the Medical School of the University of Giessen and graduated from there in 1994. His residency at the Department of Cardiology at the University of Cologne from 1995 to 1997 was followed by a post doctoral research fellowship in the laboratory of Prof. Andrius Kazlauskas at Harvard Medical School, Boston, USA, from 1997 to 1999. Thereafter, he continued his medical training at the University Heart Center Cologne and became an independent group leader supervising clinical and experimental research. In 2005 he received the board approval for Internal Medicine, and in 2006 he became an assistant professor at the University Heart Center Cologne receiving the board approvals for Cardiology and Intensive Care Medicine in 2006 and 2011. In 2012 he obtained a position as associate professor at the Department of Cardiology at the University Heart Center Cologne, and furthermore serves as coordinator of the research track “Cardiovascular Disease” at the Medical Faculty of the University of Cologne.

His work has been acknowledged amongst others by the Research Award of the German Heart Foundation in 2000, the Research Award of the German Society for Internal Medicine in 2002, and the Andreas Grüntzig Award of the German Society of Cardiology in 2011.