628996284

IM M U N OB IOLOG Y

Heme oxygenase-l expression inhibits dendritic celi maturation and proinflammatory function but conserves IL-10expression

Christine Chauveau. Sśverine Remy. Pierre Joseph Royer. Marcelo Hill. Sśverine Tanguy-Royer. Franęois-Xavier Hubert. LaurentTesson. Regis Brion. Gaelle Beriou. Marc Gregoire. Regis Josien. Maria Cristina Cuturi. and ignacio Anegon

Heme oxygenase-1 (HO-1) is an intracellu-lar enzyme that degrades heme and inhibits immune responses and inflammation in vivo. In most celi types. HO-1 is induc-ible by inllammatory stimuli and oxidative stress. Here we demonstrate that human monocyte-derived immature dendritic cells (iDCs) and several but not all freshly isolated rat spienić DC subsets and rat bonę marrow-derived iDCs. spontane-ously express HO-1. HO-1 expression drastically decreases during human and rat DC maturation induced in vitro. In

Introduction _ human tissues. iDCs also express HO-1, whereas maturę DCs do not. Inductlon of HO-1 expression withcobalt protoporphy-rin (CoPP) in human and rat DCs inhibits lipopolysaccharide {LPSHnduced pheno-typic maturation and secretion of proin-flammatory cytokines. resulting in the inhibition of alloreactive T-cell prolifera-tion. CoPP-treated DCs. however, retain the ability to produce the anti-inflammatory cytokine interleukin 10 (IL-10). Reactive oxygen species induced by LPS in DCs were inhibited by induction of HO-1. In conclusion. we identify. for the first time, the capacity of HO-1 to błock maturation of DCs and to inhibit proinflammatory and allogeneic immune responses while preserving IL-10 production. This novel immune function for HO-1 may be of interest for the inhibition of immune responses in autoimmune diseases. trans-plantation. and other conditions involv-ing activation of the immune system. (Blood. 2005:106:1694-1702)

o 2005 by The American Society of Hematology

Heme oxygenases (HOs)are the rate-l i miting intracellular enzymes that degrade heme to biliverdin, free divalent iron. and CO (for a review. see Otterbein and Choi¹). Three distinct HO enzymes have been identified: HO-1, HO-2. and HO-3.¹ HO-1 is a stiess iesponsive gene whose expression is induced by a variety of stimuli including heme. heavy metals. inflammatory cytokines. and nitric oxide.‘ HO-1 is known for its cytoprotective effect against oxidative injuries and inflammation.¹ Induction of HO-1 expres-sion by pharmacologic activators or gene transfer has had therapeu-tic effects in a variety of conditions or disorders involving the immune system, including transplantation and inflammatory disorders.²'⁸ Biliverdin and its metabolite. bilirubin, are known for their antioxidant⁹ and immunosuppressive effects.¹⁰ HO-1 and CO have been shown to inhibit lipopolysaccharide (LPS)-induced expres-sion of proinflammatory cytokines and to increase LPS-induced expression of interleukin 10 (IL-10) in macrophages.¹¹-¹² More-over, IL-10 ind u ces HO-1 expression in macrophages.^LV15 We previously reported that overexpression of HO-1, obtained with an HO-l-encoding adenovirus in rats having heart transplants, results in long-tenn allograft survival associated with an inhibition of cellular allogeneic immune responses. which could be mediated by adenoviral transduction of dendritic cells (DCs).⁶

DCs play a central role in the induction of immunity and tolerance (for a review, see Steiliman et al¹⁶). In tire absence of inflammation. immature DCs (iDCs) located in peripheral tissues specialize in taking up innocuous and cell-associated self antigens.

They continuously capture antigens and migrate to draining lymph nodes where they can induce tolerance.¹⁶ In the piesence of danger signals. DCs undergo maturation. a process involving up-regulation of surface major histocompatibility complex (MMC) class II and costimulatory molecules, secretion of proinflammatory and anti-inflammatory cytokines. and the acquired ability to stimulate differentiation of naive Tcells into effector cells.

Our working hypotliesis was that DCs can expiess HO-1. which can regulate DC functions. In this study, we demonstrate that human and rat iDCs express HO-1 and that HO-1 expression is down-regulated by maturation stimuli. Our results also demonstrate that induction of HO-1 expression renders DCs refractory to LPS-induced maturation. but preserves IL-10 secretion. suggesting tliat HO-1 may be used to rogulate DC functions.

Materials and methods

Animals

Six- to 10-week-old I^wis.lA and Lewis.IW rats (Centrc Janvier, Le Genest Saint-Isles. France) were used.

Celi preparation. culture. and treatments

Hat DCs. Rat spienić OX62⁺ DCs were purified as prcviously described.¹⁷ Briefly, spleen fragments were digested with collagenase I) (Rochc.

From the Institut National de la Santó et de la Recherche Medicale (INSERM) Unit 643 and Institut de Transplantation et de Recherche en Transplantation (ITERT). Nantes. France: and INSERM U601. Nantes. France.

Submitted Febmary4.2005: accepted April 28. 2005. Prepublished online as Blood First Edition Paper. May 26. 2C05: DOI 10.11S2.blood-2005-02-0494.

Suppoited by the Fondation Progreffe. EU grant QLK3-CT-2C01-C0422 (I.A.) and Agence pour la Recherche contrę le Cancer (ARC. nationale: M.G.). S.R. and P.J.R. contributed egually to this work.

The online version of tlie aiticle contains a data supplement.

Reprints: Ignacio Anegon. INSERM U643. CHRU Nantes. 30 boulevard Jean Monnet. 44093 Nantes. France: e-mail: ianegonO-nantes.insemi.fr.

The publication costs of this article were defrayed in part by page charge payment. Therefore. and solely to indicate this fact. this article is hereby maiked "adv'ertisement" inaccordancewith 18 U.S.C. sedion 1734.

© 2005 by The American Society of Hematology

1694

BLOOD. 1 SEPTEMBER 2005 • VOLUME 106. NUMBER5