Impacts of engineered iron nanoparticles on oxidative stress, fatty acid composition, and histo-architecture of the smooth scallop Flexopecten glaber.

Engineered iron nanoparticles are widely used in environmental remediation, yet their potential toxic effects on marine biota remain poorly elucidated. This study aimed to gain insight into the nanoscale zero-valent iron (NZVI) toxicity mechanisms for marine invertebrates. Aside from the effect on oxidative status and histopathology, the effect of NZVI on lipid metabolism in bivalves was studied for the first time. To this end, specimens of Flexopecten glaber were exposed to ascending concentrations (0.5, 1, and 1.5 mg/L) of NZVI for 96 h. Results illustrate differential patterns of iron accumulation in the gills and the digestive gland. By increasing NZVI concentrations, the total iron level tended to markedly increase in the gills and decrease in the digestive gland, reaching 132 and 37.6 µg/g DW, respectively, in the specimens exposed to 1.5 mg/L. Biochemical and cellular biomarkers highlighted that NZVI caused oxidative stress (measured as hydrogen peroxide, malondialdehyde, and advanced oxidation protein product levels) and alterations of antioxidant defense systems, including reduced glutathione, non-protein thiol, glutathione peroxidase, superoxide dismutase, and catalase. Modulation of lipid metabolism with changed fatty acid compositions (mainly an increase in the saturation and a decrease in unsaturation levels) was also observed in both gills and digestive gland. Moreover, several histological damages, including lipofuscin accumulation, infiltrative inflammations, and digestive tubule alterations, were observed in the two studied organs, providing supplementary evidence regarding the toxic effect of NZVI. This study adds to the growing body of evidence pointing to the hazardous impacts of iron NPs on aquatic ecosystems.

The Comparative Effects of Inulin and Bacillus clausii on LPS-Induced Endotoxemic Rat Liver.

BACKGROUND: This paper sought to investigate the modifies of inulin and Bacillus clausii on the lipopolysaccharides (LPS) inducing oxidative stress signaling pathway in the endotoxemic rat model. METHODS: Wistar albino male rats (n = 36), divided into six groups, were formed randomly in the following stages: the control group; the prebiotic group (Inulin; 500 mg/kg); the probiotic group (Bacillus clausii; 1x109 CFU); the LPS group (1.5 mg/kg) as the endotoxemic model; the prebiotic group + LPS; and the probiotic group + LPS as treatment groups. RESULTS: The reactive oxygen species (ROS), advanced oxidation products of protein (AOPP), thiobarbituric acid reactive substances (TBARS), total oxidant status (TOS), oxidative stress index (OSI), and myeloperoxidase activity (MPO) levels increased in LPS-induced toxicity. Prebiotic treatment decreased LPS-induced hepatotoxicity on rat liver as observed in the decrease in the levels of oxidative stress parameters, such as ROS, TBARS, TOS, and OSI. The effect of the probiotic treatment on the ROS, AOPP, TOS, OSI levels was not statistically significant. However, it was determined that probiotic application was effective in the TBARS, TAS, and GSH levels. When the biochemical results of the prebiotic and probiotic treatment applications were compared, it was found that the prebiotic treatment was more effective on oxidative stress parameters (ROS, TBARS, TOS, and OSI). In addition, the histological damage score and MPO-staining results of the prebiotic treatment group were found to be more effective than the probiotic group. CONCLUSION: In this first study, where inulin and Bacillus clausii spores are used against liver damage caused by LPS, inulin provides much more effective protection than Bacillus clausii spores.

Examination of the effect of curcumin in experimental liver damage created by diethylnitrosamine in Swiss albino mice to superoxide dismutase and catalase activities and glutathione, malondialdehyde, and advanced oxidation protein products levels.

In this study, the effects of curcumin, glutathione (GSH), malondialdehyde (MDA) levels, advanced protein oxidation products (AOPP), superoxide dismutase (SOD), and catalase (CAT) activities in experimental liver damage with diethylnitrosamine (DEN) in Swiss albino mice were investigated. The subjects (n = 9) used in the study were divided into 5 groups as tumor control 1, tumor control 2, curcumin protective, curcumin treatment and healthy control groups Curcumin oral gavage (in 150 mg/kg of ethylalcohol) was given to the protecting group for 19 days, 5 days before the administration of DEN, and 24 h after the administration of DEN. Hundred microliters of ethylalcohol oral gavage was given to the healthy group for 19 days. While MDA levels decreased significantly in the curcumin preservative group (p < 0.05), (p = 0.002), the decrease was not significant in the treatment groups (p > 0.05), (p = 0.128). AOPP levels decreased significantly in the curcumin protective group (p < 0.05), (p = 0.009) but the decrease in the treatment group was not found significant (p > 0.05), (p = 0.073). SOD activities increased significantly in both groups. It was found as (p < 0.05), (p = 0.001) and (p < 0.05), (p = 0.002), respectively. GSH levels decreased but these reductions were not found statistically significant. CAT activities increased significantly in both groups. It was determined as (p < 0.05), (p = 0.001) for both groups.

Age-related accumulation of advanced oxidation protein products promotes osteoclastogenesis through disruption of redox homeostasis.

Enhanced osteoclastogenesis is one of the major causes of age-related bone loss. Aging is accompanied by accumulation of advanced oxidation protein products (AOPPs). However, whether AOPPs accumulation contributing to the osteoclastogenesis with aging remains unclear. Here, we showed that AOPPs accumulation was associated with the enhanced osteoclastogenesis and deterioration of bone microstructure in aged mice. In vitro, AOPPs directly induced osteoclastogenesis by interaction with receptor activator of nuclear factor κ B (RANK) and the receptor for advanced glycation end products (RAGE) in the primary bone marrow monocytes. Bindings of AOPPs to RANK and RAGE were able to activate nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, trigger generation of reactive oxygen species, then induce phosphorylation of mitogen-activated protein kinases and c-fos, upregulation of the nuclear factor of activated T cell c1, eventually induce bone marrow monocytes to differentiate into mature osteoclasts. Chronic exposure to AOPPs enhanced osteoclastogenesis and bone loss in mice, which could be alleviated by NADPH oxidase inhibitor apocynin. Local injection of AOPPs into subperiosteal area induced bone resorption at the site of administration, which was similar to the effect of RANK ligand. Together, these results suggested that AOPPs could serve as a novel regulator of osteoclastogenesis and AOPPs accumulation might play an important role in the development of age-related bone loss.

Advanced oxidation protein products downregulate CYP1A2 and CYP3A4 expression and activity via the NF-κB-mediated signaling pathway in vitro and in vivo.

Uremic toxin accumulation is one possible reason for alterations in hepatic drug metabolism in patients with chronic kidney disease (CKD). However, the types of uremic toxins and underlying mechanisms are poorly understood. In this study, we report the role of advanced oxidation protein products (AOPPs), a modified protein uremic toxin, in the downregulation of cytochromes P450 1A2 (CYP1A2) and P450 3A4 (CYP3A4) expression levels and activities. We found that AOPP accumulation in plasma in a rat CKD model was associated with decreased protein levels of CYP1A2 and CYP3A4. CYP1A2 and CYP3A4 metabolites (acetaminophen and 6ß-hydroxytestosterone, respectively,) in liver microsomes were also significantly decreased. In human hepatocytes, AOPPs significantly decreased CYP1A2 and CYP3A4 protein levels in a dose- and time-dependent manner and downregulated their activities; however, bovine serum albumin (BSA), a synthetic precursor of AOPPs, had no effect on these parameters. The effect of AOPPs was associated with upregulation of p-IKKα/ß, p-IκBα, p-NF-κB, and inflammatory cytokines protein levels and increases in p-IKKα/ß/IKKα, p-IκBα/IκBα, and p-NF-κB/NF-κB phosphorylation ratios. Further, NF-kB pathway inhibitors BAY-117082 and PDTC abolished the downregulatory effects of AOPPs. These findings suggest that AOPPs downregulate CYP1A2 and CYP3A4 expression and activities by increasing inflammatory cytokine production and stimulating NF-κB-mediated signaling. Protein uremic toxins, such as AOPPs, may modify the nonrenal clearance of drugs in patients with CKD by influencing metabolic enzymes.

Hydroxytyrosol promotes autophagy by regulating SIRT1 against advanced oxidation protein product­induced NADPH oxidase and inflammatory response.

Advanced oxidation protein products (AOPPs) can trigger NADPH oxidase (NOX) and lead to the production of reactive oxygen species (ROS) in the pathophysiology of rheumatoid arthritis (RA). Hydroxytyrosol (HT) is a phenolic composite in olive oil that has antioxidant and anti­inflammatory effects and enhances autophagy. Early research has revealed that HT can activate the silent information regulator 1 (SIRT1) pathway to induce autophagy and alleviate the cartilage inflammatory response caused by H2O2. However, whether HT can attenuate AOPP­induced NOX and inflammatory responses remains to be elucidated. The present study aimed to investigate how HT can alleviate the damage caused by AOPPs. In cell experiments, chondrocytes were pre­stimulated with HT and then exposed to AOPPs. First, it was found that HT promoted autophagy through the SIRT1 pathway, increased the expression of autophagy­related proteins including microtubule­associated protein 1 light chain 3, autophagy related (ATG)5 and ATG7, and decreased the expression of P62. Furthermore, HT reduced the expression of NOX, which was affected by AOPPs in chondrocytes through the SIRT1 pathway. Finally, the expression of inflammatory cytokines caused by AOPPs was downregulated following HT treatment. In conclusion, it was found that HT reduced the expression of NOX and inhibited the inflammatory response caused by AOPPs in chondrocytes through the SIRT1 pathway.

Advanced Oxidation Protein Products-Modified Albumin Induces Differentiation of RAW264.7 Macrophages into Dendritic-Like Cells Which Is Modulated by Cell Surface Thiols.

Local accumulation of Advanced Oxidation Protein Products (AOPP) induces pro-inflammatory and pro-fibrotic processes in kidneys and is an independent predictor of renal fibrosis and of rapid decline of eGFR in patients with chronic kidney disease (CKD). In addition to kidney damage, circulating AOPP may be regarded as mediators of systemic oxidative stress and, in this capacity, they might play a role in the progression of atherosclerotic damage of arterial walls. Atherosclerosis is a chronic inflammatory disease that involves activation of innate and adaptive immunity. Dendritic cells (DCs) are key cells in this process, due to their role in antigen presentation, inflammation resolution and T cell activation. AOPP consist in oxidative modifications of proteins (such as albumin and fibrinogen) that mainly occur through myeloperoxidase (MPO)-derived hypochlorite (HOCl). HOCl modified proteins have been found in atherosclerotic lesions. The oxidizing environment and the shifts in cellular redox equilibrium trigger inflammation, activate immune cells and induce immune responses. Thus, surface thiol groups contribute to the regulation of immune functions. The aims of this work are: (1) to evaluate whether AOPP-proteins induce activation and differentiation of mature macrophages into dendritic cells in vitro; and (2) to define the role of cell surface thiol groups and of free radicals in this process. AOPP-proteins were prepared by in vitro incubation of human serum albumin (HSA) with HOCl. Mouse macrophage-like RAW264.7 were treated with various concentrations of AOPP-HSA with or without the antioxidant N-acetyl cysteine (NAC). Following 48 h of HSA-AOPP treatment, RAW264.7 morphological changes were evaluated by microscopic observation, while markers of dendritic lineage and activation (CD40, CD86, and MHC class II) and allogeneic T cell proliferation were evaluated by flow cytometry. Cell surface thiols were measured by AlexaFluor-maleimide binding, and ROS production was assessed as DCF fluorescence by flow cytometry. HSA-AOPP induced the differentiation of RAW264.7 cells into a dendritic-like phenotype, as shown by morphological changes, by increased CD40, CD86 and MHC class II surface expression and by induction of T cell proliferation. The cell surface thiols dose dependently decreased following HSA-AOPP treatment, while ROS production increased. NAC pre-treatment enhanced the amount of cell surface thiols and prevented their reduction due to treatment with AOPP. Both ROS production and RAW264.7 differentiation into DC-like cells induced by HSA-AOPP were reduced by NAC. Our results highlight that oxidized plasma proteins modulate specific immune responses of macrophages through a process involving changes in the thiol redox equilibrium. We suggest that this mechanism may play a role in determining the rapid progression of the atherosclerotic process observed in CKD patients.

Advanced Oxidation Protein Products Induce Epithelial-Mesenchymal Transition of Intestinal Epithelial Cells via a PKC δ-Mediated, Redox-Dependent Signaling Pathway.

AIMS: Epithelial-mesenchymal transition (EMT) has been considered a fundamental mechanism in complications of Crohn's disease (CD), especially intestinal fibrosis. However, the mechanism underlying EMT regulation in intestinal fibrosis remains unclear. This study aimed to investigate the role of advanced oxidation protein products (AOPPs) in the occurrence of intestinal EMT. RESULTS: AOPPs accumulated in CD tissues and were associated with EMT marker expression in fibrotic lesions from CD patients. Challenge with AOPPs induced intestinal epithelial cell (IEC) phenotype transdifferentiation, fibroblast-like phenotype acquisition, and production of extracellular matrix, both in vitro and in vivo. The effect of AOPPs was mainly mediated by a protein kinase C (PKC) δ-mediated redox-dependent pathway, including phosphorylation of PKC δ, recruitment of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, production of reactive oxygen species, and NF-κB p65 activation. Inhibition of AOPP-redox signaling activation effectively blocked AOPP-induced EMT in vitro. Studies performed in normal rats showed that chronic administration of AOPPs triggered the occurrence of EMT in rat intestinal epithelia, accompanied by disruption of intestinal integrity, and by promotion of collagen deposition. These effects could be reversed by inhibition of NADPH oxidase. Innovation and Conclusion: This is the first study to demonstrate that AOPPs triggered the occurrence of EMT in IECs in vitro and in vivo through PKC δ-mediated redox-dependent signaling. Our study identifies the role of AOPPs and, in turn, EMT in intestinal fibrosis and provides novel potential targets for the treatment of intestinal fibrotic diseases. Antioxid. Redox Signal. 27, 37-56.

Fenton Reaction-Generated Advanced Oxidation Protein Products Induces Inflammation in Human Embryonic Kidney Cells.

Fenton reaction is a new mechanism able to generate advanced oxidation protein products (AOPPs) by exposing the human serum albumin to the Fenton system. Here, we characterized the effects of Fenton reaction-generated advanced oxidation protein products (AOPP-FR) on the gene transcription of the nuclear factor-κB (NF-κB), cyclooxygenase-2 (COX-2), and interleukin-6 (IL-6) in human embryonic kidney cells (HEK 293). To investigate the effects of AOPP-FR and AOPP-HOCl on transcription of inflammatory genes, the NF-κB, COX-2, and IL-6 luciferase promoter activities were analyzed. AOPP-FR and AOPP-HOCl were able to induce the activation of the gene transcription of NF-κB, COX-2, and IL-6 in HEK 293 cells. However, the effects of AOPP-FR were significantly higher than the effects of AOPP-HOCl in relation to COX-2 and IL-6. AOPP-FR induces the activation of the gene transcription of NF-κB, COX-2, and IL-6 and may represent a novel pathogenic mediator of inflammation in kidney.

Oxidized plasma albumin promotes platelet-endothelial crosstalk and endothelial tissue factor expression.

Plasma advanced oxidation protein products (AOPPs), a class of pro-inflammatory pathogenic mediators, accumulate in subjects with chronic kidney disease. Whether AOPPs contribute to coagulation abnormalities, which are frequently seen in uremic patients, is unknown. Here we report that AOPPs activate platelets via a CD36-mediated signaling pathway. Activation of signaling pathways by AOPP-platelet interaction resulted in the expression of several platelet activation markers and rapidly induced the expression of CD40 ligand, triggering platelet adhesion to endothelial cells and promoting endothelial tissue factor expression. AOPPs and serum tissue factor levels were considerably increased in end stage renal disease patients on hemodialysis and a significant correlation of AOPPs and serum tissue factor was found. Interestingly, serum levels of AOPPs and tissue factor were substantially lower in stable kidney transplant patients when compared with hemodialysis patients. Given that CD36 is known to transduce the effects of oxidized lipids into platelet hyperactivity, our findings reveal previously unknown pro-thrombotic activities of oxidized plasma albumin via a CD36 dependent pathway.

The Differences in the Cellular and Plasma Antioxidative Capacity Between Transient and Defined Focal Brain Ischemia: Does it Suggest Supporting Time-Dependent Neuroprotection Therapy?

There are many opened questions about the precocious role of oxidative stress in the physiopathology of the early stage of transitory ischemic attack (TIA) and defined focal brain ischemia, as well as about its correlation with clinical severity, short-lasting and clinical outcome prediction in these conditions. The study evaluates the values of glutathione (GSH), glutathione peroxidase, and superoxide dismutase (SOD) in hemolysates and total thiol content (-SH), advanced oxidation protein products (AOPP), SOD, and malondialdehyde (MDA) in plasma, in TIA and stroke patients in the early stage of their neurological onset. The results are interpreted in view of the potential relationship between tested parameters and clinical severity and clinical outcome prediction. Better hemolysates' and total antioxidant profile with higher values of AOPP were observed in TIA compared to stroke patients (p < 0.05). The stroke patients with initially better clinical presentation showed better antioxidant profile with lower values of AOPP (p < 0.05). In TIA patients, this was observed for GSH, -SH content, and AOPP (p < 0.05), which correlated with a short risk for stroke occurrence in this group (p < 0.01). Beyond MDA values, all tested parameters showed correlation with clinical outcome in stroke patients (p < 0.05). The measurement of oxidative stress in TIA and stroke patients would be important for identifying patients' subgroups which might receive supporting therapy providing better neurological recovery and clinical outcome. That approach might give us an additional view of a short-lasting risk of stroke occurrence after TIA, and its clinical outcome and prognosis.

AOPPs (advanced oxidation protein products) promote apoptosis in trophoblastic cells through interference with NADPH oxidase signaling: implications for preeclampsia.

PURPOSE: To investigate the role of placental advanced oxidation protein products (AOPPs) in the pathogenesis of preeclampsia (PE). METHODS: Expression of AOPPs in human placental tissues collected from women with or without PE was examined by immunohistochemistry. The effect of AOPPs on in vitro trophoblast cell function was also examined. Specifically, we exposed trophoblastic cells to AOPPs and measured the production of human chorionic gonadotropin (hCG) as well as their invasion capacity using an in vitro Transwell invasion assay. We also investigated the effect of AOPPs on trophoblastic apoptosis and whether this effect could be mediated through interference in NADPH oxidase signaling. RESULTS: AOPPs were expressed in placental tissues, and were significantly increased in placentas from women with PE versus normotensive controls. AOPPs also affected trophoblast cell function in vitro by significantly reducing ß-HCG production and inhibiting trophoblas cell invasive capacity. Exposure to AOPPs significantly increased apoptosis in trophoblastic cells, which was mediated through the NADPH oxidase pathway. CONCLUSIONS: AOPPs expression is increased in PE placentas and exposure to AOPPs adversely affects trophoblast cell function, which may contribute to the shallow trophoblast invasion that characterizes this disorder. Additional studies are needed to investigate further to determine whether AOPPs can be used as a biomarker for PE.

[Shenkang pill down-regulates AOPP-induced expression of inflammatory factor MCP-1 via a p38MAPK/NF-κB-dependent mechanism].

OBJECTIVE: To investigate the effect of the serum of rats fed with Shenkang pill in regulating monocyte chemoattractant protein 1 (MCP-1) expression induced by advanced oxidation protein products (AOPP) in mouse podocyte clone 5 (MPC5) and explore the underlying mechanism. METHODS: MPC5 cultured in vitro were incubated for different time lengths in the presence of different concentrations of serum of rats medicated with Shenkang pill, and the cell proliferation was assessed using MTT assay. In MPC5 treated with AOPP prior to exposure to the rat serum, the changes in the protein expressions of p38MAPK and IκBα were examined with Western blotting, NF-κB p65 nuclear translocation was analyzed with immunofluorescence assay, and MCP-1 expression in the supernatant was determined using ELISA kits. RESULTS: The medicated rat serum time- and concentration-dependently promoted the proliferation of MPC5, with the optimal serum concentration of 5% and incubation time of 24 h. AOPP significantly increased MCP-1 expression in the cell supernatant in a time-and concentration-dependent manner; pretreatment with SB203580 (a p38 inhibitor) or parthenolide (a NF-κB inhibitor) significantly decreased MCP-1 expression, and treatment with the medicated serum significantly decreased AOPP-induced MCP-1 expression. AOPP concentration-dependently increased the protein expression of P-p38 but decreased that of IκBα. Both the medicated serum and SB203580 increased IκBα protein in AOPP-induced cells, but the effect was more obvious with the medicated serum. The medicated serum also decreased NF-κB p65 nuclear translocation in AOPP-induced MPC5. CONCLUSION: Shenkang pill-medicated serum can decrease AOPP-induced expression of MPC-1 in MPC5 by regulating p38MAPK/NF-κB to mediate its anti-inflammatory effect. This finding provides a new theoretical basis for the application of Shenkang pill to treat diabetic nephropathy.

Advanced oxidation protein products induce inflammatory response in fibroblast-like synoviocytes through NADPH oxidase -dependent activation of NF-κB.

BACKGROUND: Advanced oxidation protein products (AOPPs), a marker of oxidative stress, are prevalent in many kinds of disorders. Rheumatoid arthritis (RA), mainly resulting from the dysfunction of fibroblast-like synoviocytes (FLSs), is related to oxidative stress. Although the increased levels of AOPPs in RA patients were reported, the effect of AOPPs on FLSs function still remains unclear. Therefore, our study aims to investigate whether AOPPs have an effect on the inflammatory response of FLSs in vitro. METHODS: FLSs obtained from both knees of rats were treated with or without AOPPs-modified rat serum albumin (AOPPs-RSA) in vitro. The mRNA and protein expression of tumor necrosis factor (TNF)-α, interleukin(IL)-1ß, matrix metalloproteinases(MMP)-3, MMP-13 and vascular endothelial growth factor (VEGF) were measured by real-time quantitative polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA), respectively. Reactive oxygen species (ROS) generation was detected by fluorescent microscope and fluorescence microplate reader. Immunoprecipitation, Co-Immunoprecipitation and western blot were performed to examine the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and nuclear factor kappa B (NF-κB). RESULTS: Exposure of FLSs to AOPPs upregulated the mRNA and protein expression of TNF-α, IL-1ß, MMP-3, MMP-13 and VEGF in a concentration dependent manner. AOPPs treatment triggered ROS production in FLSs, which was significantly abolished by ROS scavenger N-acetyl-L-cysteine (NAC), superoxide dismutase (SOD), NADPH oxidase inhibitors diphenyleneiodonium (DPI) and apocynin. Challenged AOPPs induced phosphorylation of p47(phox), triggered an interaction between p47(phox), p22(phox) and gp91(phox), and significantly upregulated expression of NADPH oxidase subunits p47(phox), p22(phox) and gp91(phox). IκB degradation and nuclear translocation of NF-κB p65 induced by AOPPs were significantly blocked by SOD, NAC, DPI and apocynin. CONCLUSIONS: These data indicate that AOPPs induce inflammatory response in FLSs is medicated through NADPH oxidase-dependent activation of NF-κB.

Advanced oxidation protein products enhances soluble Fms-like tyrosine kinase 1 expression in trophoblasts: a possible link between oxidative stress and preeclampsia.

Accumulation of advanced oxidation protein products (AOPPs) is prevalent in obesity, advanced maternal age, diabetes mellitus, and polycystic ovary syndrome. Alterations in the regulation and signaling of angiogenic pathways have been recognized as a link between these conditions and pre-eclampsia. To investigate the possible impact of AOPPs on soluble Fms-like tyrosine kinase 1 (sFlt-1) expression in trophoblasts. A trophoblast cell line (HRT-8/SVneo) was treated with various concentrations of AOPPs. The mRNA expression of sFlt-1, vascular endothelial growth factor (VEGF), and placental growth factor (PlGF) in trophoblasts were measured with the use of real-time polymerase chain reaction; and the secretion of sFlt-1, VEGF, and PlGF protein from trophoblasts were detected with the use of ELISA. Exposure of HRT-8/SVneo cells to AOPPs induced overexpression of sFlt-1 at mRNA and protein levels in a dose dependent manner. These effects could be inhibited by apocynin, an inhibitors of NADPH oxidase. Our data identified AOPPs as a class of important mediator in the regulation and signaling of angiogenic pathways of trophoblasts. Accumulation of AOPPs might contributes to the pathogenesis of preeclampsia by promoting sFlt-1 production in trophoblasts.

Effect of advanced oxidation protein products on the proliferation and osteogenic differentiation of rat mesenchymal stem cells.

Advanced oxidation protein products (AOPPs) as a novel marker of oxidative stress, are involved in a variety of diseases, including osteoporosis. Although a number of studies have shown the possible functions of AOPPs in biological processes, little is known about the role of AOPPs in the pathogenesis of osteoporosis. In this study, we aimed to investigate the effect of AOPPs on the proliferation and osteogenic differentiation of rat mesenchymal stem cells (MSCs). MSCs, isolated from bone marrow, were cultured in the absence or presence of AOPPs (50, 100, 200 and 400 mg/ml). MTT assay was used to determine the proliferative ability of the cells. Alkaline phosphatase (ALP) activity, the mRNA expression of ALP and collagen I and bone nodule formation were detected to assess osteogenic differentiation. Reactive oxygen species (ROS) generation was analyzed with the probe 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). The expression of receptor of advanced glycation end-products (RAGE) at the mRNA and protein level was detected by real-time PCR and western blot analysis, respectively. Compared with the control group, AOPPs inhibited MSC proliferation in a dose- and time-dependent manner. Moreover, AOPPs induced a significant reduction in ALP activity, as well as a decrease in ALP and collagen I mRNA levels in the MSCs; bone nodule formation was also inhibited. Furthermore, AOPPs increased ROS generation in the MSCs, and upregulated the expression of RAGE at the mRNA and protein level. These results suggest that AOPPs inhibit the proliferation and osteogenic differentiation of MSCs, possibly through the AOPPs-RAGE-ROS pathway; this may be an important mechanism in the development of osteoporosis.