Abstract
The aim of this study was to investigate the ability of sildenafil to regulate osteopontin (OPN) gene and protein in peripheral blood mononuclear cells (PBMCs) from healthy blood donors. OPN is expressed by a wide variety of cell types, including immune cells. OPN functions are linked to various physiological and pathological conditions. Sildenafil is a selective inhibitor of type 5 phosphodiesterase. Sildenafil has recently been found to have immunomodulatory effects in animal models and in studies performed in humans. PMA-stimulated and unstimulated PBMCs from 16 healthy blood donors (men) were cultured with sildenafil (at concentrations of 400 ng/ml and 4 µg/ml). OPN level in culture supernatants was measured by enzyme-linked immunosorbent assay. The analysis of OPN gene expression was performed by real-time PCR. Cell viability was assessed by trypan blue staining. PMA plus ionomycin stimulation of PBMCs resulted in a significant increase of OPN production and gene expression (p < 0.001). Sildenafil significantly decreased OPN secretion (p < 0.05) and gene expression (p < 0.05) in stimulated PBMCs; however, had no effect on OPN in unstimulated PBMCs. Sildenafil did not affect PBMCs viability. Sildenafil downregulates OPN in PBMCs from healthy men. Despite accumulating evidence for the immunomodulatory effects of sildenafil on human immune system cells, further studies are needed to determine if this drug affects the level of cGMP and NF-κB in PBMCs. In addition, it is needed to evaluate sildenafil’s activity in PBMCs from patients with elevated OPN levels.
Highlights
Osteopontin (OPN) is a member of the small integrin-binding ligand N-linked glycoprotein family proteins (Fisher et al 2001; Ramaiah and Rittling 2008; Rangaswami et al 2006)
OPN is expressed by a wide variety of cell types such as bone cells, neurons, epithelial cells, pericytes, fibroblasts, hepatocytes, tubular cells, vascular smooth muscle cells and immune system cells [T and B cells, natural killer (NK) cells, NK T cells, dendritic cells, macrophages, neutrophils] (Denhardt and Noda 1998; Ramaiah and Rittling 2008; Uede 2011)
To investigate the ability of sildenafil to regulate OPN expression in human peripheral blood mononuclear cells (PBMCs), non-stimulated or phorbol myristate acetate (PMA) + ionomycin-stimulated cells were cultured in the absence or presence of sildenafil at concentrations of 400 ng/ml and 4 μg/ml
Summary
Osteopontin (OPN) is a member of the small integrin-binding ligand N-linked glycoprotein family proteins (Fisher et al 2001; Ramaiah and Rittling 2008; Rangaswami et al 2006). OPN is expressed by a wide variety of cell types such as bone cells, neurons, epithelial cells, pericytes, fibroblasts, hepatocytes, tubular cells, vascular smooth muscle cells and immune system cells [T and B cells, natural killer (NK) cells, NK T cells, dendritic cells, macrophages, neutrophils] (Denhardt and Noda 1998; Ramaiah and Rittling 2008; Uede 2011). OPN stimulates antibodies production by B cells, regulates macrophages migration, activation, capacity for phagocytosis and nitric oxide production
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