Macrophage inflammatory protein-1α (MIP-1α) enhances a receptor activator of nuclear factor κB ligand (RANKL) expression in mouse bone marrow stromal cells and osteoblasts through MAPK and PI3K/Akt pathways

Abstract

Osteolytic lesions are rapidly progressive during the terminal stages of myeloma, and the bone pain or bone fracture that occurs at these lesions decreases the patients' quality of life to a notable degree. In relation to the etiology of this bone destruction, it has been reported recently that MIP-1alpha, produced in large amounts in myeloma patients, acts indirectly on osteoclastic precursor cells, and activates osteoclasts by way of bone-marrow stromal cells or osteoblasts, although the details of this process remain obscure. In the present study, our group investigated the mechanism by which RANKL expression is induced by MIP-1alpha and the effects of MIP-1alpha on the activation of osteoclasts. RANKL mRNA and RANKL protein expressions increased in both ST2 cells and MC3T3-E1 cells in a MIP-1alpha concentration-dependent manner. RANKL mRNA expression began to increase at 1 h after the addition of MIP-1alpha; the increase became remarkable at 2 h, and continuous expression was observed subsequently. Both ST2 and MC3T3-E1 cells showed similar levels of increased RANKL protein expression at 1, 2, and 3 days after the addition of MIP-1alpha. After the addition of MIP-1alpha, the amount of phosphorylated ERK1/2 and Akt protein expressions showed an increase, as compared to the corresponding amount in the control group. On the other hand, the amount of phosphorylated p38MAPK protein expression showed a decrease from the amount in the control group after the addition of MIP-1alpha. U0126 (a MEK1/2 inhibitor) or LY294002 (a PI3K inhibitor) was added to ST2 and MC3T3-E1 cells, and was found to inhibit RANKL mRNA and RANKL protein expression in these cells. When SB203580, a p38MAPK inhibitor, was added, RANKL mRNA and RANKL protein expression were increased in these cells. MIP-1alpha was found to promote osteoclastic differentiation of C7 cells, an osteoclastic precursor cell line, in a MIP-1alpha concentration-dependent manner. MIP-1alpha promoted differentiation into osteoclasts more extensively in C7 cells incubated together with ST2 and MC3T3-E1 cells than in C7 cells incubated alone. These results suggested that MIP-1alpha directly acts on the osteoclastic precursor cells and induces osteoclastic differentiation. This substance also indirectly induces osteoclastic differentiation through the promotion of RANKL expression in bone-marrow stromal cells and osteoblasts. The findings of this investigation suggested that activation of the MEK/ERK and the PI3K/Akt pathways and inhibition of p38MAPK pathway were involved in RANKL expression induced by MIP-1alpha in bone-marrow stromal cells and osteoblasts. This finding may be useful in the development of an osteoclastic inhibitor that targets intracellular signaling factors.

Bone Anabolic Agents for the Treatment of Multiple Myeloma

“…It strongly correlates with osteolytic burden in MM [57][58][59]. Indeed, CCL3 by binding two receptors, CCR1 and CCR5, potently stimulates OC differentiation mediating the fusion of precursor cells into active mature OCs and upregulating RANKL expression by OBs [60][61][62]. CCL3 is also responsible for increased angiogenesis, tumor cell migration to the BM and tumor cell growth [7,63].…”

Modulation of tumor necrosis factor related apoptosis-inducing ligand (TRAIL) receptors in a human osteoclast model in vitro

“…This chemokine may also directly act on mature osteoclasts, and in a murine model, MlP-lahas been shown to increase osteoclast motility, although it did not alter osteoclast bone resorbing activity, adhesion, or survival (Yu et al, 2004). MlP-la may also act indirectly on these cells by stimulating RANKL production (Tsubaki et al, 2007).…”

“…MIP-la is produced by myeloma cells, and is known to stimulate osteoclast formation and bone resorption (Choi et al, 2000). Interestingly, it has been shown that MIP-la directly affects cell signaling pathways like activation of AKT/protein kinase B, and the MAPK pathway in myeloma cells through CCR5; mediating growth, survival and migration of myeloma cells (Tsubaki et al, 2007). However, it has not yet been shown if MIP-la is capable of inducing the same survival effects in human osteoclasts.…”

Mechanisms of Humoral Hypercalcemia of Malignancy in Leukemia/Lymphoma

“…MIP-1 binds to several chemokine (c-c motif) G-protein-coupled receptors including CCR1, CCR5 and CCR9, which are expressed in lymphocytes and monocytes/macrophages. It activates several signaling pathways, including PI3K, PLC, PKC, MAP kinase and JAK/STAT pathways (Tsubaki et al, 2007). MIP-1 can potently inhibit the binding of HIV to CCR5 on macrophages (Baba et al, 1999;Maurer & von, 2004).…”

“…The mechanisms by which MIP-1 induces osteoclastic bone resorption are controversial. One study demonstrated that a RANKL-dependent pathway was responsible for activation of osteoclasts (Tsubaki et al, 2007). MIP-1 enhances RANKL expression in mouse bone marrow stromal cells and osteoblasts through the MAPK and PI3K/Akt signaling pathways.…”