NOSTRIN is involved in benign prostatic hyperplasia via inhibition of proliferation, oxidative stress, and inflammation in prostate epithelial cells

Background: Benign prostatic hyperplasia (BPH) is a common disease among older men characterized by non-malignant proliferation of epithelial cells and inflammation. Nitric oxide synthase traffic inducer (NOSTRIN) is a pleiotropic regulator of endothelial cell function and signaling and exerts antiinflammatory, anti-proliferation, and modulating nuclear factor-kappa B (NF-kappa B) signaling effects. Its expression and function in BPH tissues and prostate epithelial cells are unknown. The study aims to investigate the expression and functions of NOSTRIN in BPH, and its possible molecular mechanism. Methods: The BPH model was constructed in male Institute of Cancer Research (ICR) mice using 5 mg/kg/day testosterone propionate (TP) for 30 days, and the model was evaluated by detecting prostate index, prostate epithelial thickness, and prostate-specific antigen (PSA) expression. Dihydrotestosterone (DHT, 10 nM)-induced in vitro model of human prostate epithelial cells (RWPE-1) was established. We generated lentivirus-harboring human NOSTRIN. The mRNA expression was detected by real-time quantitative polymerase chain reaction (PCR) assay; the protein expression or localization was detected by western blot assay, immunohistochemistry, or immunofluorescence staining. Cell proliferation was assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and 5-ethynyl-2'-deoxyuridine (EdU) staining. Reactive oxygen species (ROS) production was observed by dihydroethidium staining. Nitric oxide (NO) and malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity were detected using commercial kits. Enzyme-linked immunosorbent assay (ELISA) was used to determine levels of interleukin 1 beta (IL1B), interleukin 6 (IL6), interferon gamma (IFNG), and tumor necrosis factor (TNF). Results: NOSTRIN expression was significantly inhibited in the TP-induced ICR mouse BPH model and DHT-induced model of RWPE-1 proliferation. Protein expression of the BPH-related and proliferation markers PSA and proliferating cell nuclear antigen (PCNA) was suppressed in NOSTRIN-overexpressing RWPE-1 cells exposed to DHT. NOSTRIN overexpression notably inhibited the RWPE-1 cell proliferation in vitro, as evidenced by MTT and EdU staining. NOSTRIN overexpression significantly decreased the expression of cell cycle-related proteins cyclin dependent kinase 4 (CDK4) and cyclin D1 (CCND 1) in vitro. The production of ROS, NO, and lipid peroxidation products MDA was inhibited by NOSTRIN overexpression in vitro, while the SOD activity was increased. NOSTRIN overexpression reduced the mRNA expression of inflammatory mediator nitric oxide synthase 2 (NOS2) and inhibited the mRNA expression and secretion of pro-inflammatory cytokines IL1B, IL6, IFNG, and TNF in vitro. The mechanistic studies revealed an increased phosphorylation of NF-kappa B p65 in vivo and in vitro. Remarkably, NOSTRIN overexpression notably inhibited the protein expression of phospho-NF-kappa B p65 in vitro. Conclusions: NOSTRIN is involved in BPH by inhibiting proliferation, oxidative stress, and inflammation in prostate epithelial cells. These functions may act through the inhibition of NF-kappa B signaling.