Dihydrotestosterone inhibits lectin-like oxidized-LDL receptor-1 expression in aortic endothelial cells via a NF-κB/AP-1-mediated mechanism

The role of N-cadherin/c-Jun/NDRG1 axis in the progression of prostate cancer

The dysregulation of androgen receptor (AR) signaling is a critical event in the progression of prostate cancer (PCa) and hormone therapy consisting of androgen deprivation (ADT) or AR inhibition is therefore used to treat advanced cases. It is known that N-cadherin becomes upregulated following ADT and can directly induce PCa transformation to the castration-resistant stage (CRPC). However, the relationship between AR and N-cadherin is unclear and may promote better understanding of CRPC pathogenesis and progression. Here, we demonstrate a new axis of N-cadherin/c-Jun/N-myc downstream regulated gene 1 (NDRG1) that N-cadherin promotes c-Jun expression and suppresses NDRG1 to promote invasion and migration of PCa cells through epithelial to mesenchymal transition (EMT). Targeting N-cadherin in combination with enzalutamide (ENZ) treatment synergistically suppressed PC3 cell proliferation in vivo and in vitro. Further studies showed that compared to lower Gleason score (GS) (GS < 7) cases, high GS (GS > 7) cases exhibited elevated N-cadherin expression and reduced NDRG1 expression, corroborating our in vitro observations. We further demonstrate that c-Jun, AR, and DNA methyltransferase-1 (DNMT1) form a complex in the 12-O-tetradecanoyl phorbol-13-acetate (TPA) response elements (TREs) region of the NDRG1 promoter, which suppresses NDRG1 transcription through DNA hypermethylation. In conclusion, we demonstrate an underlying mechanism for how N-cadherin collaborates with AR and NDRG1 to promote CRPC progression. Controlling N-cadherin/c-Jun/NDRG1 axis may help to overcome resistance to commonly used hormone therapy to improve long-term patient outcomes.

Sertad1 promotes prostate cancer progression through binding androgen receptor ligand binding domain

Androgen receptor (AR) signaling is involved in the initiation and progression of prostate cancer (PCa), which is the most frequently diagnosed nonskin cancer and remains a leading cause of cancer-related death in men. Further investigation of the involvement of AR signaling in PCa progression is urgently needed. In the present study, we performed a yeast two-hybrid screen and demonstrated that SERTA domain-containing protein 1 (Sertad1) is a novel AR-binding protein that binds to the AR ligand binding domain (LBD). The binding between AR-LBD and Sertad1 was confirmed by glutathione S-transferase (GST) pull-down assays and immunoprecipitation (IP) and confocal immunofluorescence co-localization experiments. Furthermore, we demonstrated that DHT inhibited Sertad1 protein degradation in prostate cancer cell lines and that Sertad1 knockdown inhibited the proliferation of prostate cancer cells in vitro. In human PCa tumor tissues, Sertad1 expression is positively correlated with AR expression and the Gleason score. Taken together, this report is the first to show that Sertad1 is a novel AR-LBD-binding protein, and DHT-liganded AR-LBD inhibits Sertad1 degradation. Thus, Sertad1 may represent a novel therapeutic target for the treatment of AR-positive PCa.

The role of androgen receptors in atherosclerosis

Male disadvantage in cardiovascular health is well recognised. However, the influence of androgens on atherosclerosis, one of the major causes of many life-threatening cardiovascular events, is not well understood. With the dramatic increase in clinical prescription of testosterone in the past decade, concerns about the cardiovascular side-effects of androgen supplementation or androgen deprivation therapy are increasing. Potential atheroprotective effects of testosterone could be secondary to (aromatase-mediated) conversion into oestradiol or, alternatively, to direct activation of androgen receptors (AR). Recent development of animal models with cell-specific AR knockout has indicated a complex role for androgen action in atherosclerosis. Most studies suggest androgens are atheroprotective but the precise role of AR remains unclear. Increased use of AR knockout models should clarify the role of AR in atherogenesis and, thus, lead to exploitation of this pathway as a therapeutic target.

Antioxidant response of osteoblasts to doxycycline in an inflammatory model induced by C-reactive protein and interleukin-6

Objectives: Investigation of osteoblastic responses to oxidative stress, induced by C-reactive protein (CRP) and IL-6 and ameliorating effects of doxycycline (Dox); using assays for 5-alpha dihydrotestosterone (DHT) as an antioxidant marker of healing. IL-6 and CRP are risk markers of periodontitis and prevalent comorbidities in periodontitis subjects. Methods: Confluent monolayer cultures of osteoblasts were incubated with radiolabelled testosterone (14C-T) as substrate, in the presence or absence (Control) of pre-determined optimal concentrations of CRP, IL-6, Dox; alone and in combination (n=8) for 24h in MEM. The eluent was solvent-extracted for steroid metabolites. They were separated using TLC in a benzene/ acetone solvent system 4:1 v/v; and quantified using radioisotope scanning. The identity of formed metabolites was confirmed using the mobility of cold standards added to the samples and disclosed in iodine. Further confirmation of the authenticity of DHT was carried out by combined gas chromatrography-mass spectrometry, after derivatization to pentafluorobenzyloxime trimethyl silyl ether. Results: The yields of DHT from 14C-testosterone showed 2-fold and 1.8-fold- inhibition in response to IL-6 and CRP respectively and 28% stimulation in response to Dox, via the 5-alpha reductase pathway. The combination of IL-6 + CRP showed a 2-fold reduction in the yields of DHT, elevated to control values when combined with Dox (n=8; p<0.001). Yields of 4-androstenedione showed an inverse relationship to those of DHT, in response to the agents tested, in keeping with the 17-beta hydroxysteroid dehydrogenase pathway. Conclusions: Inhibition of DHT synthesis in osteoblasts by IL-6 and CRP was overcome by doxycycline. Oxidative actions of IL-6 and CRP; and antioxidant actions of Dox are reinforced by the metabolic yields of DHT in response to agents tested. Using a novel metabolically active model allows closer extrapolation to in vivo conditions; in the context of adjunctive therapeutic applications for periodontitis and prevalent comorbidities.

Lipopolysaccharide induced LOX-1 expression via TLR4/MyD88/ROS activated p38MAPK-NF-κB pathway

Lectin-like receptor for oxidized low density lipoprotein (LOX-1) plays a key role in endothelial ox-LDL endocytosis, endothelial dysfunction and atherogenesis. In the present study, the effect of lipopolysaccharide (LPS) on LOX-1 expression and the underlying molecular pathways were investigated. Human umbilical vein endothelial cells (HUVECs) were treated with LPS and the protein expressions of LOX-1, TLR4, TLR2, MyD88, Nox4, Nox2, PI3K, p38MAPK, JNK, ERK, Nrf1, Nrf2 and p65 were examined by Western blotting. The intracellular reactive oxygen species (ROS) production was examined by flow cytometry with fluorescence probe DCFH2-DA. The role of TLR4, MyD88 and Nox4 were determined with specific siRNA. The endothelial ox-LDL uptake and the endothelial-monocyte adhesion were evaluated with DiI-ox-LDL and Hoechst 33342 respectively. The effect of LPS on LOX-1 expression in aorta tissue was also studied with male C57/BL6 mice by intraperitoneal injection of LPS. The results showed that LPS induced LOX-1 protein expression in a time- and concentration-dependent manner. The mRNA expression of LOX-1 was also upregulated. The protein expression of LOX-1 and phosphorylated p38MAPK, p65 was significantly enhanced by LPS both in vitro and in vivo. LPS induced LOX-1 expression was blocked by siRNA for TLR4, MyD88, and Nox4 and inhibitors for p38MAPK, NF-κB, cyclooxygenase-2, and NADPH oxidase. Both LPS induced ox-LDL uptake and endothelial-monocyte adhesion were significantly inhibited by anti-LOX-1 antibody. LPS dramatically induced LOX-1 protein expression in aorta tissues. In conclusion, our data suggested that LPS induces LOX-1 expression via TLR4/MyD88/ROS activated p38MAPK/NF-κB pathway in endothelial cells, which provides new regulatory mechanisms for LOX-1 expression.

Role of lectin-like oxidized low density lipoprotein-1 in fetoplacental vascular dysfunction in preeclampsia

The bioavailability of nitric oxide (NO) represents a key marker in vascular health. A decrease in NO induces a pathological condition denominated endothelial dysfunction, syndrome observed in different pathologies, such as obesity, diabetes, kidney disease, cardiovascular disease, and preeclampsia (PE). PE is one of the major risks for maternal death and fetal loss. Recent studies suggest that the placenta of pregnant women with PE express high levels of lectin-like oxidized LDL receptor-1 (LOX-1), which induces endothelial dysfunction by increasing reactive oxygen species (ROS) and decreasing intracellular NO. Besides LOX-1 activation induces changes in migration and apoptosis of syncytiotrophoblast cells. However, the role of this receptor in placental tissue is still unknown. In this review we will describes the physiological roles of LOX-1 in normal placenta development and the potential involvement of this receptor in the pathophysiology of PE.