Heat-killed BCG induces biphasic cyclooxygenase 2+ splenic macrophage formation—role of IL-10 and bone marrow precursors

Abstract

Previous studies have shown that prostaglandin E(2) (PGE(2)) release by splenic F4/80(+) cyclooxygenase (COX)-2(+) macrophages (MØ) isolated from mice, treated with mycobacterial components, plays a major role in the regulation of immune responses. However, splenic MØ, isolated from untreated mice and treated in vitro with lipopolysaccharide and interferon-gamma, express COX-1 and COX-2 within 1 day but release only minimal amounts of PGE(2) following elicitation with calcium ionophore A23187. For further characterization of in vivo requirements for development of PGE(2)-releasing MØ (PGE(2)-MØ), C57Bl/6 [wild-type (WT)], and interleukin (IL)-10-deficient (IL-10(-/-)) mice were treated intraperitoneally with heat-killed Mycobacterium bovis bacillus Calmette-Guerin (HK-BCG). One day following injection, COX-2 was induced in splenic MØ of both mouse strains. However, PGE(2) biosynthesis by these MØ was not increased. Thus, expression of COX-2 is not sufficient to induce PGE(2) production in vivo or in vitro. In sharp contrast, 14 days after HK-BCG treatment, PGE(2) release by COX-2(+) splenic MØ increased as much as sevenfold, and a greater increase was seen in IL-10(-/-) cells than in WT cells. To further determine whether the 14-day splenic PGE(2)-MØ could be derived from bone marrow precursors, we established a chimera in which bone marrow cells were transfused from green fluorescent protein (GFP)-transgenic donors to WT mice. Donors and recipients were treated with HK-BCG simultaneously, and marrow transfusion was performed on Days 1 and 2. On Day 14 after BCG treatment, a significant number of spleen cells coexpressed COX-2 and GFP, indicating that bone marrow-derived COX-2(+) MØ may be responsible for the increased PGE(2) production.

Persistent Inactivation of Macrophage Cyclooxygenase-2 in Mycobacterial Pulmonary Inflammation

“…The type of COX-2 expressed depended on the tissue type, phagocytosis of the mycobacteria in vivo, and the nature of MØ precursors (20,21,23). The data presented here indicate that alveolar MØ activated by in vivo phagocytosis of mycobacteria express COX-2 that is NE-dissociated and catalytically inactive, failing to increase release of PGE 2 .…”

“…In sharp contrast, within 24 hours after intraperitoneal administration, HK-BCG induces inactive COX-2 transiently in splenic and peritoneal MØ, followed by active COX-2 in splenic MØ at 7 to 14 days after administration (20,21). Splenic MØ with active COX-2 are derived from bone marrow (23). The formation of these COX-2 1 MØ subsets seems to be dependent on the microorganism and its phagocytosis, the tissue, and the presence of bone marrow-derived precursors which become mature MØ expressing active COX-2 at inflammatory sites (20,21,23,24).…”

“…Splenic MØ with active COX-2 are derived from bone marrow (23). The formation of these COX-2 1 MØ subsets seems to be dependent on the microorganism and its phagocytosis, the tissue, and the presence of bone marrow-derived precursors which become mature MØ expressing active COX-2 at inflammatory sites (20,21,23,24). Thus, COX-2 1 MØ could potentially either inhibit or promote PGE 2 -sensitive antimicrobial immunity (7,20,21).…”

Depletion of cellular cholesterol enhances macrophage MAPK activation by chitin microparticles but not by heat-killed Mycobacterium bovis BCG

“…Expression of F4/80, Mac-1, Fc␥R, SR-A, TLR4, or MR on MØ was determined cytometrically as indicated previously (28).…”

Cholera Toxin Induces a Shift from Inactive to Active Cyclooxygenase 2 in Alveolar Macrophages Activated by Mycobacterium bovis BCG

“…However, in these M1 M, both COX-1 and COX-2 are dissociated from the nuclear envelop (NE), accumulate in aggregates in the endoplasmic reticulum (ER), and are catalytically inactive. Although PGE synthase, which converts PGH 2 to PGE 2 , appears to be active (15), these COX-2 ϩ M release no PGE 2 (13). Furthermore, the impairment of PGE 2 release seems to be independent of degradation of PGE 2 driven by 15-hydroxyprostaglandin dehydrogenase (16).…”