AOPPs induces EMT and fibrosis by activating oxidative stress through ERK/p38 MAPK signaling pathway in endometriosis.

Epithelial-mesenchymal transition (EMT) is known to play a crucial role in the development of endometriosis (EMs). However, the exact mechanisms involved in EMT regulation in EMs are not well understood. In this study, we performed comprehensive research using clinical samples, single-cell sequencing, and in vivo/in vitro models to investigate the effects of advanced oxidation protein products (AOPPs) on EMT and the underlying mechanisms in EMs. Combining bioinformatics analysis with experimental validation, our results show that AOPPs accumulate in EMs tissues, and their levels positively correlate with the expression of EMT markers in fibrotic lesions of EMs patients. Stimulation with AOPPs leads to a concentration- and time-dependent alteration of EMT markers expression in both in vitro and in vivo models. These effects are mainly mediated by the generation of reactive oxygen species and nitrite, along with the activation of the ERK and P38 signaling pathways. In chronic administration studies using normal rats, AOPPs induce EMT and enhance collagen deposition. These findings significantly contribute to our understanding of the molecular mechanisms of EMs and provide a foundation for future research and therapeutic development in this field.

CYP2E1 mediated advanced oxidation protein products exacerbate acetaminophen induced drug-derived liver injury in vitro and in vivo.

Drug-induced liver injury (DILI) is prevalent in the treatment of chronic kidney disease (CKD). Advanced oxidation protein products (AOPPs) are markers of CKD progression and participate in the occurrence and development of liver diseases. However, the mechanisms underlying the regulation of DILI in CKD have not been established. Herein, we demonstrate the involvement of Cytochrome p450 2E1 (CYP2E1) in DILI induced by AOPPs is exacerbated by exposure to acetaminophen (APAP). We used a adenine-induced CKD model, a model of DILI induced by APAP, and the AOPPs model was generated by intraperitoneal injection. The decline in renal function was associated with a significantly increased concentration of Scr, BUN and AOPPs, and renal tissue fibrosis. The ALT, AST, and AOPPs levels and liver tissue necrosis increased significantly in CKD model group compared with the sodium carboxymethyl cellulose (CMCNa) group. In the AOPPs model, compared to the PBS controls, ALT, AST, and AOPP levels, and liver tissue necrosis increased significantly. In HepG2 or L0-2 cell lines, cell survival was significantly reduced in the AOPP + APAP treatment and CYP2E1 protein expression was increased. FPS-ZM1 or NAC attenuated the hepatocyte toxicity induced by AOPP + APAP and suppression of CYP2E1 expression. AOPPs exacerbated APAP-induced DILI through CYP2E1 signaling pathways. Protein uremic toxins, such as AOPPs, can modify drug toxicity in patients with CKD. This study provides new a rationale to reduce the generation of DILIs in clinical treatment in patients with CKD. AOPPs targeting may present a novel approach to reduce the occurrence of DILI.

Human protozoa infection and dysplasia in ulcerative colitis: a neglected aspect in a prominent disease.

The chance of getting colorectal cancer (CRC) is higher in people with chronic ulcerative colitis (UC). The impact of parasitic infections on UC is underappreciated. The purpose of this study was to look into the effect of intestinal protozoal infections on the dysplastic changes generated by UC. The research included 152 adult patients with histologically confirmed UC and 152 healthy controls. Fecal samples were examined for the presence of parasites and fecal calprotectin (FC). The enzyme-linked immunosorbent assay measured serum anti-p53 antibodies (p53Abs) and metallothioneins (MTs). The advanced oxidation protein products (AOPPs) and reduced glutathione (GSH) levels were measured by a spectrophotometric method in all subjects. Serum C-reactive protein (CRP) and IL-6 were also measured. In addition, histopathological and immunohistochemical investigations of intestinal tissue were done. Our results exhibited significant increases in FC and CRP, IL-6, AOPPs, MTs, and p53Abs in ulcerative colitis patients with parasitic infections compared to those without parasites. In contrast, GSH levels showed a significant decrease in the same group compared with other groups. Histopathological and immunohistochemical assessments of intestinal tissue signified severe inflammation and strong expression of PD-L1 in patients with parasitic infections compared to others without parasitic infections. Our research indicated a greater frequency of intestinal protozoa in UC patients with elevated inflammatory and dysplastic biomarker levels. This suggests that these parasites may be involved in the etiology of chronic UC and the associated carcinogenetic process. This is the first report of a link between parasitic infections and dysplastic alterations in UC patients.

Effect of Advanced Oxidation Protein Products (AOPPs) and aging on the osteoclast differentiation of Myeloid-Derived Suppressor Cells (MDSCs) and its preliminary mechanism.

To verify the osteoclast differentiation ability of MDSCs from mice of different ages and explore the effect of AOPPs on the osteoclast differentiation of bone marrow MDSCs. Bone marrow cells from C57BL/6 (a.k.a C57) mice of different ages were subjected to flow cytometry, and CD11b+Ly6C+Ly6G+ MDSCs were sorted out. After induction of osteoclast differentiation, these cells were subjected to tartrate-resistant acid phosphatase (TRAP) and F-actin. MDSCs from bone marrows of old mice were injected into the tibial medullary cavity of young mice. One week later, the bone marrows were subjected to histological examination, TRAP, and cell count. MDSCs from bone marrows of old mice were sorted for induction of osteoclast differentiation, intervened with reactive oxygen species (ROS) scavenger, inducible nitric oxide synthase (iNOS) inhibitor, and nitric oxide (NO) scavenger, and then subjected to TRAP. 8-weeks-old C57 mice were injected with the same concentrations of either AOPPs or mouse serum albumin (MSA). Four weeks later, MDSCs from bone marrows were sorted and subjected to induction of osteoclast differentiation, followed by IHC staining and TRAP. MDSCs of 8-weeks-old C57 mice were extracted and subjected to in vitro induction of osteoclast differentiation with different concentrations of AOPPs, followed by TRAP training. The number of MDSCs in the bone marrows of old mice was significantly higher than that in young mice. MDSCs from bone marrows of old mice differentiated into large multinucleated TRAP+ osteoclasts, which were significantly different from those in the middle-aged and young mice in terms of cell quantity and morphology. The actin rings formed in the differentiated osteoclasts from MDSCs of bone marrows were densely distributed in the whole field of view, which were significantly denser than those in the middle-aged and young mice. After injection of MDSCs of old mice, the number of TRAP + osteoclasts in the tibial medullary cavity of young mice was significantly increased. NO inhibitor can significantly inhibit the osteoclast differentiation capacity of MDSCs from bone marrows of old mice. In vivo treatment with AOPPs significantly increased the proportion of MDSCs in the bone marrow, which is up to 55.2%. After injection of AOPPs in 8-week-old mice and induction of osteoclast differentiation from the MDSCs, the ratios of CD11b+ and Gr1+ cells were significantly higher than that in the control and MSA groups but was not significantly different from that in the 15-month-old mice. Upon in vitro treatment with different concentrations of AOPPs, the MDSCs did not show any sign of osteoclast differentiation. MDSCs can directly undergo osteoclast differentiation, the capacity of which is stronger in MDSCs of bone marrows of old mice; the NO pathway is a potential mechanism underlying this phenomenon. In vivo but not in vitro AOPPs treatment can induce osteoclast differentiation of MDSCs, indicating there might be other factors in the body that can interact with AOPPs to induce osteoclast differentiation of MDSCs.

Increased Expression of Circulating Stress Markers, Inflammatory Cytokines and Decreased Antioxidant Level in Diabetic Nephropathy.

Background and Objectives: The main objective of the present study was to determine the role of oxidative markers (glutathione (GSH), advanced oxidation protein products (AOPP), advanced glycation end products (AGEs), and malondialdehyde (MDA)) and inflammatory biomarkers (interleukin-6 IL-6, tumor necrosis factor α (TNF-α), myeloperoxide (MPO)) in the development of diabetic nephropathy along with routinely used biochemical parameters. Materials and Method: This was a case control study. All the selected patients were screened and enrolled by convenient non-probability sampling technique at the Jinnah hospital in Lahore. Informed consent was obtained before enrollment of the study subjects. A total of 450 patients enrolled in the study, and they were divided into three groups, 150 subjects with type 2 diabetes and 150 diagnosed diabetic nephropathy (DN) vs. 150 healthy individuals as a control group. Five mL of venous blood sample was taken from the antecubital vein of each participant. Statistical analysis was performed by SPSS. The results of all variables were evaluated by using one way ANOVA. Results: The mean value of biochemical parameters (WBCs, platelets, prothrombin time, HbA1c, glucose, urinary albumin-to creatinine ratio (UACR), triglycerides, LDL, HDL, serum creatinine, urinary albumin (creatinine)) were increased and Hb (g/dL), red blood cells (RBCs), hematocrit (Hct), free serum insulin levels, and estimated glomerular filtration rate (eGFR) were decreased in the nephropathy group compared to the control and type 2 diabetes groups. The mean values of MDA, AGE, and AOPPs in type 2 diabetes and diabetic nephropathy were significantly increased compared to the control group. GSH level was decreased in type 2 diabetics and DN patients as compared to the control group. In addition, IL-6, TNFα, and MPO levels were also increased in case of diabetes nephropathy compared to controls. Conclusions: ROS mediated injuries can be prevented by the restoration of an antioxidant defense system, through the administration of antioxidant agents. Moreover, increased levels of inflammatory mediators are responsible for enhancing inflammation in patients with diabetic nephropathy.

Assessment of Mancozeb Exposure, Absorbed Dose, and Oxidative Damage in Greenhouse Farmers.

Mancozeb (MNZ) is a fungicide commonly employed in many countries worldwide. This study assesses MNZ absorption dynamics in 19 greenhouse farmers, specifically following dermal exposure, aiming to verify the efficacy of both preventive actions and protective equipment. For data collection, a multi-assessment approach was used, which included a survey to record study population features. MNZ exposure was assessed through the indirect measurement of ethylene thiourea (ETU), widely employed as an MNZ biomarker. The ETU concentration was measured with the patch method, detecting environmental ETU trapped in filter paper pads, applied both on skin and working clothes, during the 8 h work shift. Urine and serum end-of-shift samples were also collected to measure ETU concentrations and well-known oxidative stress biomarkers, respectively, namely reactive oxygen metabolites (ROMs), advanced oxidation protein products (AOPPs), and biological antioxidant potential (BAP). It was observed that levels of ETU absorbed and ETU excreted were positively correlated. Additionally, working clothes effectively protected workers from MNZ exposure. Moreover, following stratification of the samples based on the specific working duty (i.e., preparation and spreading of MNZ and manipulation of MNZ-treated seedlings), it was found that the spreading group had higher ETU-related risk, despite lower chronic exposure levels. AOPP and ROM serum levels were higher in MNZ-exposed subjects compared with non-exposed controls, whereas BAP levels were significantly lower. Such results support an increase in the oxidative stress upon 8 h MNZ exposure at work. In particular, AOPP levels demonstrated a potential predictive role, as suggested by the contingency analysis results. Overall, this study, although conducted in a small group, confirms that ETU detection in pads, as well as in urine, might enable assessment of the risk associated with MNZ exposure in greenhouse workers. Additionally, the measurement of circulating oxidative stress biomarkers might help to stratify exposed workers based on their sensitivity to MNZ. Pivotally, the combination of both ETU measurement and biological monitoring might represent a novel valuable combined approach for risk assessment in farmhouse workers exposed to pesticides. In the future, these observations will help to implement effective preventive strategies in the workplace for workers at higher risk, including greenhouse farmers who are exposed to pesticides daily, as well as to clarify the occupational exposure levels to ETU.

Accumulation of advanced oxidation protein products contributes to age-related impairment of gap junction intercellular communication in osteocytes of male mice.

AIMS: Gap junction intercellular communication (GJIC) in osteocytes is impaired by oxidative stress, which is associated with age-related bone loss. Ageing is accompanied by the accumulation of advanced oxidation protein products (AOPPs). However, it is still unknown whether AOPP accumulation is involved in the impairment of osteocytes' GJIC. This study aims to investigate the effect of AOPP accumulation on osteocytes' GJIC in aged male mice and its mechanism. METHODS: Changes in AOPP levels, expression of connexin43 (Cx43), osteocyte network, and bone mass were detected in 18-month-old and three-month-old male mice. Cx43 expression, GJIC function, mitochondria membrane potential, reactive oxygen species (ROS) levels, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation were detected in murine osteocyte-like cells (MLOY4 cells) treated with AOPPs. The Cx43 expression, osteocyte network, bone mass, and mechanical properties were detected in three-month-old mice treated with AOPPs for 12 weeks. RESULTS: The AOPP levels were increased in aged mice and correlated with degeneration of osteocyte network, loss of bone mass, and decreased Cx43 expression. AOPP intervention induced NADPH oxidase activation and mitochondrial dysfunction, triggered ROS generation, reduced Cx43 expression, and ultimately impaired osteocytes' GJIC, which were ameliorated by NADPH oxidase inhibitor apocynin, mitochondria-targeted superoxide dismutase mimetic (mito-TEMPO), and ROS scavenger N-acetyl cysteine. Chronic AOPP loading accelerated the degradation of osteocyte networks and decreased Cx43 expression, resulting in deterioration of bone mass and mechanical properties in vivo. CONCLUSION: Our study suggests that AOPP accumulation contributes to age-related impairment of GJIC in osteocytes of male mice, which may be part of the pathogenic mechanism responsible for bone loss during ageing. Cite this article: Bone Joint Res 2022;11(7):413-425.

Salivary Markers of Oxidative Stress in Patients Undergoing Orthodontic Treatment with Clear Aligners versus Self-Ligating Brackets: A Non-Randomized Clinical Trial.

The aim of this work was to determine advanced the oxidative protein products (AOPPs), total antioxidant capacity (TAC), and myeloperoxidase activity (MPO) in the saliva of patients undergoing orthodontic treatment with clear removable aligners in comparison with another group in treatment with fixed passive self-ligating brackets applying light forces, before treatment, after 30 days, and after 90 days of treatment. This non-randomized clinical trial recruited patients consecutively, all of which were over 18 years of age and due to undergo orthodontic treatment. They were divided into two groups according to treatment type: Group A, 48 patients treated with clear aligners (Invisalign®); and Group B, 19 patients treated with Damon System® 0.22″ self-ligating brackets applying light forces. Saliva samples were collected by a single clinician following the same protocol and underwent three analyses-AOPPs, TAC, and MPO levels-at baseline before placing the apparatus, after 30 days, and after 90 days treatment. Orthodontic treatment, whether with clear aligners or fixed self-ligating brackets and light forces, increased AOPPs after the first 30 days of treatment. During the initial phases of orthodontic treatment, neither clear aligners nor fixed self-ligating brackets applying light forces showed changes in TAC and MPO. Orthodontic treatment with both clear aligners and fixed apparatus self-ligating brackets applying light forces increases oxidative stress (AOPPs) after the first 30 days of treatment. There are no differences in AOPP levels between treatment with clear aligners and self-ligating brackets during the first 90 days of treatment. The antioxidative capacity of saliva during the initial phases of orthodontic treatment, whether with self-ligating brackets or clear aligners, does not undergo significant changes. With either orthodontic technique, the patients' salivary antioxidant capacity is similar.

Advanced oxidation protein products upregulate ABCB1 expression and activity via HDAC2-Foxo3α-mediated signaling in vitro and in vivo.

The unpredictable pharmacokinetics of non-renal cleared drugs in chronic kidney disease (CKD) patients is associated with the activity of drug transporters. However, the mechanisms underlying regulation of drug transporters are yet to be established. In this study, we demonstrated the involvement of a HDAC2-Foxo3α pathway in advanced oxidation protein products (AOPPs)-induced ATP-binding cassette subfamily B member 1 (ABCB1) expression and activity. The correlation of AOPPs accumulation with concentration of cyclosporine in plasma was evaluated in 194 patients with transplantation. Molecular changes in acetylation of various histones and related regulatory molecules were examined in HepG2 cell cultures treated with AOPPs. Accumulation of AOPPs in serum in relation to molecular changes in HDAC2-Foxo3α in vivo were evaluated in 5/6 nephrectomy (5/6 nx) and oral adenine (Adenine) CKD rat models. Interestingly, the cyclosporine level was negatively correlated with AOPPs in plasma. In addition, AOPPs markedly suppressed the expression of histone deacetylase 2 (HDAC2), inducing ABCB1 expression and activity in vitro and in vivo. Importantly, AOPPs modulated phosphorylation of Foxo3α and the upstream Akt protein. Our findings indicate that AOPPs regulate the expression and activity of ABCB1 via reducing HDAC2 expression and activating Foxo3α-dependent signaling. The collective results support the utility of AOPPs as a potential target for drug and/or dosage adjustment in CKD patients. Targeting of AOPPs presents a novel approach to regulate non-renal clearance.

Targeting Scavenger Receptors in Inflammatory Disorders and Oxidative Stress.

Oxidative stress and inflammation cannot be considered as diseases themselves; however, they are major risk factors for the development and progression of the pathogenesis underlying many illnesses, such as cancer, neurological disorders (including Alzheimer's disease and Parkinson's disease), autoimmune and metabolic disorders, etc. According to the results obtained from extensive studies, oxidative stress-induced biomolecules, such as advanced oxidation protein products, advanced glycation end products, and advanced lipoxidation end products, are critical for an accelerated level of inflammation and oxidative stress-induced cellular damage, as reflected in their strong affinity to a wide range of scavenger receptors. Based on the limitations of antioxidative and anti-inflammatory molecules in practical applications, targeting such interactions between harmful molecules and their cellular receptors/signaling with advances in gene engineering technology, such as CRISPR or TALEN, may prove to be a safe and effective alternative. In this review, we summarize the findings of recent studies focused on the deletion of scavenger receptors under oxidative stress as a development in the therapeutic approaches against the diseases linked to inflammation and the contribution of advanced glycation end products (AGEs), advanced lipid peroxidation products (ALEs), and advanced oxidation protein products (AOPPs).

Advanced Oxidative Protein Products Drive Trophoblast Cells Into Senescence by Inhibiting the Autophagy: The Potential Implication of Preeclampsia.

Introduction: Advanced oxidation protein products (AOPPs), the novel marker of oxidative stress, have been found to be elevated in preeclampsia (PE). To date, the effect of AOPPs on the senescence of trophoblast cells is still unclear. In this study, we investigated whether AOPPs promoted the senescence of trophoblast cells and explored the underlying mechanisms of AOPPs-induced aging process which may facilitate the progression of PE. Methods: The trophoblast cell line HTR-8/SV neo cells were cultured in the presence of PBS, AOPPs, AOPPs plus an anti-oxidant N-acetyl-L-cysteine (NAC). In some experiments, cells were pre-treated with rapamycin (an activator of autophagy), 3-MA (an inhibitor of autophagy), or cyclic pifithrin-α (PFT-α, an antagonist of p53), and then treated with AOPPs. Cellular senescence was analyzed by measuring the levels of senescence-associated ß-galactosidase (SA ß-Gal), senescence-associated heterochromatin foci (SAHF), mitochondrial membrane potential (ΔΨm), and cell cycle. Cell autophagic flux was analyzed by measuring tandem fluorescence-tagged LC3 reporter (mCherry-EGFP-LC3). Levels of p53, phosphorylated p53 (p-p53), p21, BECN1, p62, p-mTOR and p-p70S6K were measured by western blot. Results: Treatment with AOPPs significantly increased the levels of SA ß-Gal and SAHF, the percentage of cells in the G0/G1 phase, and decreased cell ΔΨm compared with the control group. Co-treatment with NAC and AOPPs significantly reversed AOPPs-induced senescence. Pre-treatment with rapamycin or 3-MA significantly inhibited or promoted AOPPs-induced senescence, respectively. In addition, administration of AOPPs significantly decreased the numbers of mCherry+EGFP+ autophagosomes and mCherry+EGFP- autolysosomes in cells compared with cells treated with PBS. Furthermore, AOPPs significantly increased the levels of proteins p-p53, p21, p-mTOR and p-p70S6K compared with the control group. Pre-treatment with rapamycin or PFT-α significantly down-regulated the levels of SA ß-Gal, SAHF, p-p53, p21, autophagy related protein p62, the percentage of cells in the G0/G1 phase, and significantly up-regulated ΔΨm, autophagy related protein BECN1, autophagosomes and autolysosomes compared with cells only treated with AOPPs. Conclusion: AOPPs may induce trophoblast cell senescence by inhibiting the autophagy process in a p53/mTOR/p70S6K-dependent pathway.

Advanced oxidation protein products change biological behaviors of rat endometrial epithelial cells by activating ERK/P38 signaling pathways.

Advanced oxidation protein products (AOPPs) are a family of oxidized protein compounds and could induce oxidative stress and inflammatory lesion in various cells. The accumulation of AOPPs was associated with female reproductive diseases such as polycystic ovary syndrome (PCOS), leiomyoma and endometriosis. However, the relationship between AOPPs and endometrial cells is unclear. To explore the effects of accumulated AOPPs on endometrial cells, we treated normal rat endometrial epithelial cells (rEECs) and endometriosis model rats with AOPPs. Primary rEECs were collected from 8-week-old female Wistar rats. Increasing the amount of AOPPs in the media of rEECs enhanced rEEC proliferation and migration, and inhibited apoptosis. Moreover, AOPPs triggered the production of reactive oxygen species and nitrite along with activated ERK and P38 signal and this, in turn, led to an upregulation of proliferation and migration. With the treatment of antioxidants or the inhibitors of ERK and P38, the above effects of AOPPs on rEECs were attenuated. Additionally, in an endometriosis rat model, a similar phenomenon was observed in that the growth of endometriotic implants were promoted by AOPPs and EECs were significantly increased. This study indicated that the accumulation of AOPPs could promote rEEC proliferation and migration through ERK and P38 signal both in vivo and in vitroThis article has an associated First Person interview with the first author of the paper.

Advanced oxidation protein products upregulate efflux transporter expression and activity through activation of the Nrf-2-mediated signaling pathway in vitro and in vivo.

Clinical and benchtop studies suggest that chronic kidney disease (CKD) alters both renal and nonrenal clearance of drugs. Although studies have documented that the accumulating uremic toxins in the body under CKD conditions are humoral factors that alter the expression and/or activity of drug transporters, the specific process is poorly understood. In this study, we found that advanced oxidation protein products (AOPPs), which are a modified protein uremic toxin, could upregulate efflux transporters, including P-glycoprotein (ABCB1), multi-drug resistance-associated protein 2 (ABCC2) and breast cancer resistance protein (ABCG2) expression in CKD rat models and in HepG2 cells. Our research shows that renal function decline was associated with the accumulation of AOPPs in serum and the upregulation of efflux transporters in the liver in two rat models of CKD. In HepG2 cells, AOPPs significantly increased the expression of efflux transporters in a dose- and time-dependent manner and upregulated the mRNA expression, protein expression and activity of efflux transporters, but bovine serum albumin (BSA), a synthetic precursor of AOPPs, had no effect. This effect correlated with AOPPs activation of the nuclear factor E2-related factor 2 (Nrf-2)-mediated signaling pathway. Further investigation of the regulation of Nrf-2 by AOPPs revealed that ML385 and siNrf-2 abolished the upregulatory effects of AOPPs. These findings suggest that AOPPs upregulate ABCB1, ABCG2 and ABCC2 through Nrf-2 signaling pathways. Protein uremic toxins, such as AOPPs, may modify the nonrenal clearance of drugs in patients with CKD through effects on drug transporters.

The role of circulating soluble fms-like tyrosine kinase-1 in patients with diabetic foot ulcer: A possible mechanism of pathogenesis via a novel link between oxidative stress, inflammation and angiogenesis.

BACKGROUND: Diabetic foot ulcer (DFU) is one of the most devastating diabetic consequences leading to amputations. Oxidative stress, inflammation, vascular insufficiency and neuropathy have been linked to DFU development. Since soluble fms-like tyrosine kinase-1 (sFlt-1) is one of the anti-angiogenic factors regulating vascular endothelial growth factor (VEGF) biological activity. So, we aimed to evaluate its role in pathogenesis of DFU and its correlation with oxidative stress and inflammatory markers. METHODS: 60 type 2 diabetic patients: 30 without DFU and 30 with DFU in addition to 20 healthy controls were enrolled in the study. sFlt-1 and VEGF mRNA relative gene expressions and levels and sFlt-1/VEGF ratio were assessed. Also, Advanced oxidation protein products (AOPPs), malondialdhyde (MDA), Total thiol and, tumor necrosis factor alpha (TNF-α) levels were measured. RESULTS: sFlt-1 expression and level, AOPPs, MDA and TNF-α were significantly higher in diabetic patients as compared with the control group with highest levels in DFU patients. However, there were significant decrease in total thiol level and VEGF expression and level in diabetic patients with DFU. CONCLUSION: This study revealed that sFlt-1 is a major player in DFU pathogenesis and may be considered as a novel diagnostic biomarker for early detection of DFU.

Potential effect of carnosine encapsulated niosomes in bovine serum albumin modifications.

Protein modification and alteration are important factors in many age-related diseases such as diabetes and Alzheimer's disease. Modifications like the formation of advanced glycation end-products (AGE) and advanced oxidation protein products (AOPP) can cause harm to the organism and may contribute to protein aggregation and amyloid fibrils formation. Carnosine was used as a potential solution for protein modification complications. Furthermore, some organs like the brain are difficult to reach due to the blood-brain barrier. As such, new nano-engineered formulations were sought to bypass unwanted interactions and degradation. Thus, we propose the encapsulation of carnosine in niosomes as a potential solution. Initially, carnosine niosomes were synthesized and characterized. Then, modifications of bovine serum albumin (glycation, oxidation, and aggregation) were induced in vitro where carnosine and carnosine niosomes were added at different concentrations (2.5, 5, and 10 mM) to the reactions. In addition, biocomputational and docking studies were performed to elucidate the potential interactions. Data showed a dose-dependent inhibition of AGE, AOPP, and aggregation for both carnosine and niosome carnosine. Furthermore, the results suggest that carnosine interacts with specific amino acids implicated in the protein modification process. Carnosine nano-formulation shows promising potential in age-related protein modification and needs further exploration of its mechanisms.

The Antiglycoxidative Ability of Selected Phenolic Compounds-An In Vitro Study.

Hyperglycemia and oxidative stress may be observed in different diseases as important factors connected with their development. They often occur simultaneously and are considered together as one process: Glycoxidation. This can influence the function or structure of many macromolecules, for example albumin, by changing their physiological properties. This disturbs the homeostasis of the organism, so the search for natural compounds able to inhibit the glycoxidation process is a current and important issue. The aim of this study was the examination of the antiglycoxidative capacity of 16 selected phenolic compounds, belonging to three phenolic groups, as potential therapeutic agents. Their antiglycoxidative ability, in two concentrations (2 and 20 µM), were examined by in vitro study. The inhibition of the formation of both glycoxidative products (advanced glycation end products (AGEs) and advanced oxidation protein products (AOPPs)) were assayed. Stronger antiglycoxidative action toward the formation of both AOPPs and AGEs was observed for homoprotocatechuic and ferulic acids in lower concentrations, as well as catechin, quercetin, and 8-O-methylurolithin A in higher concentrations. Homoprotocatechuic acid demonstrated the highest antiglycoxidative capacity in both examined concentrations and amongst all of them. A strong, significant correlation between the percentage of AOPPs and AGEs inhibition by compounds from all phenolic groups, in both examined concentrations, was observed. The obtained results give an insight into the antiglycoxidative potential of phenolic compounds and indicate homoprotocatechuic acid to be the most promising antiglycoxidative agent, but further biological and pharmacological studies are needed.

Serum level of advanced oxidation protein products (AOPPs) in patients with Henoch-Schonlein purpura and its relationship with aberrant glycosylation of IgA1 and Cosmc mRNA expression.

BACKGROUND: Henoch-Schonlein purpura (HSP) is a systemic small vessel vasculitis that is mainly caused by IgA1-type immune complex deposition. Advanced oxidation protein products (AOPPs) are specific markers of protein oxidation. OBJECTIVE: To explore the role of AOPPs in the pathogenesis of HSP. METHODS: There are 51 HSP patients who were divided into four subgroups: (i) skin type - 20 cases; (ii) joint type - 8 cases; (iii) abdominal type - 12 cases; (iv) renal type - 11 cases; and 18 healthy volunteers were enrolled as controls. The serum levels of AOPPs and Gd-IgA1 were quantified by an HAA-lectin-based ELISA. The Cosmc mRNA expression in peripheral B lymphocytes was measured by RT-PCR. RESULTS: 1. Advanced oxidation protein products in different subgroups of HSP patients are all higher than the controls, while the renal-type subgroup is the highest and the skin-type subgroup is the lowest. 2. Spearman correlation analysis shows that: (i) AOPPs and Gd-IgA1 in HSP patients are positively correlated; both of them are positively correlated with the disease severity scores; (ii) AOPPs are negatively correlated with the relative expression value (RQ) of Cosmc mRNA. CONCLUSION: Advanced oxidation protein products play an important role in the pathogenesis of HSP, especially in renal-type patients.

Wnt/ß-catenin links oxidative stress to podocyte injury and proteinuria.

Podocyte injury is the major cause of proteinuria in primary glomerular diseases. Oxidative stress has long been thought to play a role in triggering podocyte damage; however, the underlying mechanism remains poorly understood. Here we show that the Wnt/ß-catenin pathway is involved in mediating oxidative stress-induced podocyte dysfunction. Advanced oxidation protein products, a marker and trigger of oxidative stress, were increased in the serum of patients with chronic kidney disease and correlated with impaired glomerular filtration, proteinuria, and circulating level of Wnt1. Both serum from patients with chronic kidney disease and exogenous advanced oxidation protein products induced Wnt1 and Wnt7a expression, activated ß-catenin, and reduced expression of podocyte-specific markers in vitro and in vivo. Blockade of Wnt signaling by Klotho or knockdown of ß-catenin by shRNA in podocytes abolished ß-catenin activation and the upregulation of fibronectin, desmin, matrix metalloproteinase-9, and Snail1 triggered by advanced oxidation protein products. Furthermore, conditional knockout mice with podocyte-specific ablation of ß-catenin were protected against podocyte injury and albuminuria after treatment with advanced oxidation protein products. The action of Wnt/ß-catenin was dependent on the receptor of advanced glycation end products (RAGE)-mediated NADPH oxidase induction, reactive oxygen species generation, and nuclear factor-κB activation. These studies uncover a novel mechanistic linkage of oxidative stress, Wnt/ß-catenin activation, and podocyte dysfunction.

A new model of diabetic nephropathy in C57BL/6 mice challenged with advanced oxidation protein products.

There remains a lack of robust mouse models with key features of advanced human diabetic nephropathy (DN). Few options of murine models of DN require mutations to be superimposed to obtain desired phenotypic characteristics. Most genetically modified mice are on the C57BL/6 background; however, they are notorious for resistance to develop DN. To overcome these conundrums, this study reports a novel DN model by challenging with advanced oxidation protein products (AOPPs) in streptozotocin-induced diabetic C57BL/6 mice. AOPPs-challenged diabetic C57BL/6 mice were more sensitive to develop progressive proteinuria, causing a 5.59-fold increase in urine albumin to creatinine ratio as compared to diabetic controls by 24 weeks. Typical lesions were present as demonstrated by significant diffuse mesangial expansion, diffuse podocyte foot process effacement, increased glomerular basement membrane thickness, focal arteriolar hyalinosis, mesangiolysis, and mild interstitial fibrosis. These changes were alleviated by losartan treatment. Collectively, these results suggest that AOPPs can accelerate the progression of DN in the resistant C57BL/6 mouse strain. Our studies offer a novel model for studying the pathogenesis of DN that resembles human diabetic kidney disease. It also makes it possible to interrogate the role of specific genetic modifications and to evaluate novel therapeutics to treat DN in preclinical setting.

Protective effects of Paeoniflorin against AOPP-induced oxidative injury in HUVECs by blocking the ROS-HIF-1α/VEGF pathway.

BACKGROUND: Paeoniflorin, a monoterpene glycoside, exerts protective vascular effects, showing good antioxidant properties. However, whether Paeoniflorin has protective effect against the oxidative damage induced by advanced oxidation protein products (AOPPs) in Human umbilical vein endothelial cells (HUVECs) is unknown, as is the underlying mechanism. PURPOSE: The present study was designed to investigate the effect of Paeoniflorin on oxidative damage of HUVECs and elucidate its underlying molecular mechanisms. METHODS: The fluorescence intensity of 2', 7'-dichlorofluorescein-diacetate (DCFH-DA) staining was detected for intracellular reactive oxygen species (ROS) production. The increases mitochondrial membrane potential (MMP) was measured via flow cytometry and confocal microscopy using MitoTracker® Deep Red/ MitoTracker® Green staining. The intracellular adenosine triphosphate (ATP) was measured by ATP Determination Kit according to the manufacturer's protocol. Nox2, Nox4, hypoxia inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and nuclear factor-κB (NF-κB) p65 expressions were detected by western blot. RESULTS: Our results showed that Paeoniflorin increases MMP and ATP levels of HUVECs induced by AOPPs, and attenuates NF-κB p65 expression on HUVECs might mainly result from its antioxidant capability by suppressing ROS production. Moreover, we also found that Paeoniflorin can suppress HIF-1α and VEGF protein expression through a decrease of ROS production via down-regulation of Nox2/Nox4 expression in HUVECs. AOPP-induced RAGE mRNA up-regulation was blocked by Paeoniflorin treatment in HUVECs. CONCLUSION: Our results provided the first experimental that Paeoniflorin protects against AOPP-induced oxidative damage in HUVECs, mainly through a mechanism involving a decrease in ROS production by the inhibition of Nox2/Nox4 and RAGE expression; restored ATP depletion and mitochondria dysfunction via ROS suppression; and down-regulated HIF-1α/VEGF, possibly via the ROS-NF-κB axis.