Monocyte 1α‐hydroxylase regulation: induction by inflammatory cytokines and suppression by dexamethasone and uremia toxin

Abstract: Alveolar macrophages acquire lα‐hydroxylase activity in inflammation, and thereby metabolize 25 hydroxyvitamin D3 (25 D3) to the active metabolite, la,25‐dihydroxyvitamin D3 (1,25 D3, calcitriol). Cal‐ citriol is a potent differentiation agent that modulates mononuclear phagocyte activation and effector functions. The mediators that induce macrophage lα‐hydroxylase activity are not well delineated. Furthermore, it is unclear whether calcitriol is a product only of terminally differentiated macrophages or whether less mature mononuclear phagocytes can produce it as well. The ability of newly recruited monocytes to produce calcitriol as an autocrine differentiation agent is particularly important in inflammation, as it may substantially expand the functional repertoire of these cells. To assess the effects of cytokines on lα‐hydroxylase activity, blood monocytes were cultured in the presence and absence of human recombinant tumor necrosis factor a (TNF‐α), interferon‐7 (IFN‐γ), and interleukins 1 and 2 and then incubated with 25 D3 substrate. The conditioned media were assayed for calcitriol by high‐performance liquid chromatography and competitive receptor binding assay. No detectable calcitriol was produced by unstimulated monocytes. However, all the cytokines markedly increased monocyte calcitriol production (range 133‐151 pg/mg protein; in all cases P < .001). We then determined whether calcitriol production was suppressed by preincubation with either dexamethasone or the putative uremia toxin guanidinosuccinic acid (GSA). Dexamethasone pretreatment significantly inhibited subsequent cytokine‐induced calcitriol production by monocytes, as did GSA (average 69 and 63% of control, respectively).Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141704/1/jlb0017.pd

Activation of Urokinase Plasminogen Activator and Its Receptor Axis Is Essential for Macrophage Infiltration in a Prostate Cancer Mouse Model1

Macrophages within the tumor microenvironment promote angiogenesis, extracellular matrix breakdown, and tumor cell migration, invasion, and metastasis. Activation of the urokinase plasminogen activator (uPA) and its receptor (uPAR) axis promotes prostate cancer tumorigenicity, invasion, metastasis, and survival within the tumor microenvironment. The link between macrophage infiltration and the uPA/uPAR axis in prostate cancer development has not been established, although it has been reported that uPA plays a critical role inmonocyte and macrophage chemotaxis. In this study, murine prostate cancer RM-1 cells were subcutaneously inoculated into wild-type (WT), uPA-/-, and uPAR-/- mice. Tumor volume was significantly diminished in both uPA-/- and uPAR-/- mice compared with WT controls. Greater inhibition of tumor volume was also observed in uPA-/- mice compared with uPAR-/- mice, suggesting the important contribution of stromal-derived uPA to sustain the tumor growth. Immunohistochemical staining revealed that tumors in uPA-/- and uPAR-/- mice displayed significantly lower proliferative indices, higher apoptotic indices, and less neovascularity compared with the tumors in WT mice. Tumors in uPA-/- and uPAR-/- mice displayed significantly less macrophage infiltration as demonstrated by F4/80 staining and MAC3+ cell numbers by flow cytometry compared with the tumors from WT mice. These findings suggest that the uPA/uPAR axis acts in both autocrine and paracrine manners in the tumor microenvironment, and activation of uPA/uPAR axis is essential for macrophage infiltration into prostate tumors