Angiotensin-converting Enzyme Overexpression in Mouse Myelomonocytic Cells Augments Resistance to Listeria and Methicillin-resistant Staphylococcus aureus

Derick Okwan-Duodu,Vivekanand Datta,Xiao Z Shen,Helen S Goodridge,Ellen A Bernstein,Sebastien Fuchs,George Y Liu,Kenneth E Bernstein

doi:10.1074/jbc.m110.163782

Derick Okwan-Duodu, Vivekanand Datta + Show 6 more

Open Access

https://doi.org/10.1074/jbc.m110.163782

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Abstract

Gene targeting in ES cells was used to substitute control of angiotensin converting enzyme (ACE) expression from the endogenous promoter to the mouse c-fms promoter. The result is an animal model called ACE 10/10 in which ACE is overexpressed by monocytes, macrophages, and other myelomonocytic lineage cells. To study the immune response of these mice to bacterial infection, we challenged them with Listeria monocytogenes or methicillin-resistant Staphylococcus aureus (MRSA). ACE 10/10 mice have a significantly enhanced immune response to both bacteria in vivo and in vitro. For example, 5 days after Listeria infection, the spleen and liver of ACE 10/10 mice had 8.0- and 5.2-fold less bacteria than wild type mice (WT). In a model of MRSA skin infection, ACE 10/10 mice had 50-fold less bacteria than WT mice. Histologic examination showed a prominent infiltrate of ACE-positive mononuclear cells in the skin lesions from ACE 10/10. Increased bacterial resistance in ACE 10/10 is directly due to overexpression of ACE, as it is eliminated by an ACE inhibitor. Critical to increased immunity in ACE 10/10 is the overexpression of iNOS and reactive nitrogen intermediates, as inhibition of iNOS by the inhibitor 1400W eliminated all in vitro and in vivo differences in innate bacterial resistance between ACE 10/10 and WT mice. Increased resistance to MRSA was transferable by bone marrow transplantation. The overexpression of ACE and iNOS by myelomonocytic cells substantially boosts innate immunity and may represent a new means to address serious bacterial infections.

Highlights

Growth models in mice are somewhat artificial. This led us to ask whether the enhanced immune response observed in angiotensin converting enzyme (ACE) 10/10 mice would be present when these animals were exposed to two models of bacterial infection: Listeria monocytogenes (Listeria), a Gram-positive rod-shaped bacterium that is a much studied intracellular pathogen, and methicillin-resistant Staphylococcus aureus (MRSA), an aggressive extracellular micro-organism that is increasing in prevalence and incidence [14, 15]
Increased Resistance to L. monocytogenes Infection in ACE 10/10 Mice—We tested the response of ACE 10/10 mice to Listeria infection in vivo and in vitro
The result is that tissues that normally express c-fms, such as monocytes, macrophages, and other myelomonocytic cells overexpress ACE

Summary

Introduction

TPM from ACE 10/10 consistently showed a 2.2- to 2.9-fold increased production of nitrite, as compared with identically treated cells from WT mice. Given both the increased production of iNOS and nitrites by ACE 10/10 cells, we directly investigated the role of iNOS in the killing of Listeria by performing an in vitro killing assay (Fig. 4A).

Results

Conclusion