Normal human primary CD4+ T lymphocytes synthesize and release functional osteoprotegerin in vitro

Abstract

Osteoprotegerin (OPG) acts as a decoy receptor for receptor activator of nuclear factor-kB ligand (RANKL) and TNF-related apoptosis-inducing ligand (TRAIL). OPG regulates bone remodeling and the immune response. The primary objective was to decipher, among human peripheral blood mononuclear leukocytes (PBML) that produce OPG, the subset(s) responsible for this synthesis and its regulation. To this end, normal human PBML and CD4-, 8-, 19-, 14-enriched subpopulations were studied in vitro for OPG synthesis. PBML were subjected to adherence and immunomagnetic separation, and OPG expression was analyzed by PCR, northern and western blotting, and ELISA. The antiapoptotic effects of OPG were studied on TRAIL-stimulated RPMI 8226 myeloma cells. OPG was time-dependently produced by primary CD4 þ T lymphocytes exclusively. OPG secretion was upregulated by anti-CD3 antibody stimulation or incubation with interleukin (IL)-4, IL-1b, TNF-a, GM-CSF, and vitamin D 3 . In contrast, IL-10 inhibited the basal and IL-4-induced production of OPG by T cells. Conditioned media from activated T lymphocytes decreased TRAIL-induced apoptosis of RPMI 8226 cells. This effect was reversed by addition of RANKL to the T-cell conditioned media. As human immunodeficiency virus-1 (HIV-1) targets CD4 þ T cells, we evaluated the effects of recombinant HIV-1 gp120 proteins on OPG synthesis. The gp120 from three different HIV-1 strains significantly reduced the basal output of OPG from T cells. Furthermore, all four protease inhibitors (PIs) used in highly active antiretroviral therapy decreased OPG synthesis by human blood T cells, nelfinavir being the most efficient PI. The simultaneous presence of an HIV-1 gp120 and a PI abrogated the basal output of OPG. In conclusion, these results highlight a new role for T lymphocytes involved in pathologies. Activated CD4 þ T cells could, through OPG release, have a paracrine effect on adjacent cells and contribute to reduce the local process of bone remodeling and cellular apoptosis.

Porphyromonas gingivalis Induces RANKL in T-cells

“…However, OPG expression was not detected in these cells and P. gingivalis challenge was not able to induce its expression. The lack of capacity by Jurkat T-cells to express OPG even in response bacterial challenge has previously been demonstrated [28], although it has also been reported that normal CD4+ T-cells can produce OPG [29]. This is an interesting point, as T-cell infiltrates in active periodontal lesions could stimulate bone resportion via RANKL, but it is not clear if they would be able to restore the physiological balance by compensatory OPG production that would inhibit osteoclastogenesis.…”

Pathological crosstalk in vitro between T lymphocytes and lesional keratinocytes in psoriasis: necessity of direct cell-to-cell contact

“…Anticoagulated blood was layered over Ficoll-Paque cushions and centrifuged at 400 g for 20 min, according to our previous report. 28 The mononuclear leukocyte fraction was collected at the interface, and was washed and resuspended in a-MEM þ 10% FBS. Mononuclear leukocytes (5 Â 10 6 cells per ml) were then subjected to adherence on plastic Petri dishes.…”

Osteoprotegerin Is Associated With Aneurysm Diameter and Proteolysis in Abdominal Aortic Aneurysm Disease

“…[7][8][9] OPG is a key regulator of bone remodeling 5,10 but has also been implicated in tumorigenesis, immunologic pathways, and vascular diseases. 6,7,[11][12][13][14][15] The precise role of OPG in vascular disease is currently controversial.…”