Dihydrotestosterone protects human vascular endothelial cells from H(2)O(2)-induced apoptosis through inhibition of caspase-3, caspase-9 and p38 MAPK

Androgenic Anabolic Steroids Cause Thiol Imbalance in the Vascular Endothelial Cells

BACKGROUND

Androgenic anabolic steroids (AASs) are synthetic drugs structurally related to testosterone, with the ability to bind to androgen receptors. Their uncontrolled use by professional and recreational sportspeople is a widespread problem. AAS abuse is correlated with severe damage to the cardiovascular system, including changes in homeostasis and coagulation disorders. AASs alter vascular function by blocking nitric oxide (NO)-mediated dilation, impairing endothelial growth and by potentiating vasoconstrictor signals.

METHODS

This paper demonstrated that long-term use of AASs (nandrolone and boldenone), negatively affects the basic cell functions of vascular endothelial cells. The susceptibility of endothelial cells to AASs depends on the expression of androgen receptors, although cells without androgen receptors can also be affected by high doses of AASs to a limited extent. Seven-day incubation with AASs diminishes endothelial cell proliferation and migration (determined by transwell and scratch migration assay) and monolayer formation (using transendothelial electrical resistance assay).

RESULTS

Disturbances in cell function were accompanied by downregulation of peroxiredoxins (PRDX1 and PRDX2), involved in maintaining the thiol-disulphide balance. In addition, AASs increased oxidation of the non-enzymatic thiol buffer, glutathione (GSH), reduced secretion of thiol oxidoreductase protein disulphide isomerase (PDI) from endothelial cells and affected the thiol pattern of PDI.

CONCLUSIONS

These changes may be related to a thiol-disulfide imbalance and vascular endothelium dysfunction, that are often correlated with abnormal platelet aggregation, inflammation, increased vascular permeability, and vascular smooth muscle cell proliferation-all of which are observed in athletes who abuse AASs.

Testosterone Protects Pancreatic β-cells from Apoptosis and Stress-Induced Accelerated Senescence

Purpose

Androgens are steroid hormones that are very important in the sexual development and the maintenance of male reproductive system, and also have diverse actions in non-reproductive tissues, including potent antioxidant capacity. Type 2 diabetes mellitus is caused by tissue insulin resistance and insufficient insulin secretion from the pancreatic β-cells. The progressive decline of pancreatic β-cells in diabetes is closely related with the severity of disease. We wanted to know whether dihydrotestosterone (DHT) can protect insulin secreting pancreatic β-cells from apoptosis and accelerated senescence induced by oxidative stress.

Materials and Methods

Cultured INS-1 cells were used. Various concentrations of H₂O₂ were applied to exert oxidative stresses. The degrees of apoptosis, accelerated senescence, and the changes of the expressions of related signaling molecules after the application of DHT were analyzed by CCK-8, p16 expression, SA-β-Gal staining, reverse transcription polymerase chain reactions and Western blots.

Results

The application of H₂O₂ significantly increased (p<0.05) the degree of senescence and apoptosis of cultured INS-1 β-cells. DHT not only showed anti-oxidant protective capacity, but also significantly reduced (p<0.05) the degree of accelerated senescence.

Conclusions

DHT effectively protects pancreatic islet INS-1 β-cells from H₂O₂ induced oxidative stress.

Evaluation of natural plant extracts as antioxidants in a bovine in vitro model of oxidative stress

Oxidative stress contributes to many inflammatory-based diseases of dairy cattle especially during periods of increased metabolic activity such as around calving. Endothelial cells play a key role in maintaining normal inflammatory responses, but they are especially susceptible to macromolecule damage during times of oxidative stress. Therefore, bovine aortic endothelial cells (BAEC) were used to study the effect of natural tannin-based extracts on oxidative stress that may improve health and well-being of cattle. Tannins are secondary metabolites in plants with potent antioxidant activity that have been used as natural feed additives for food-producing animals. However, there is little information on how tannin-rich plant extracts may affect oxidative stress in dairy cattle. The objective of this study was to evaluate the antioxidant effect of pomegranate (Punica granatum; PMG), tara (Caesalpinia spinosa; TA), chestnut (Castanea sativa; CH), and gambier (Uncaria gambir; GM) natural extracts using an in vitro BAEC model of oxidative stress. Natural extracts were tested at a concentration of 80 μg/mL. Viability, apoptosis, intracellular reactive oxygen species, and isoprostanes were determined on cultured BAEC treated with different plant natural extracts. No changes in cell viability was detected following PMG and GM treatments. In contrast, there was a 30% reduction of BAEC viability following treatment with CH or TA extracts. Intracellular reactive oxygen species production was significantly less abundant in cells treated with natural extracts than with the lipopolysaccharide control. Moreover, antioxidant activity varied according to the tested extract, showing a reduction of 63, 45, 51, and 27% in PMG, GM, CH, and TA, respectively. The formation of isoprostanes as a consequence of lipid peroxidation after induction of oxidative stress also were significantly decreased in PMG-treated cells when compared with the untreated cells. Theses findings suggest that PMG extract has the potential to mitigate oxidative stress without detrimental effects on cell viability. Further in vitro and in vivo research is warranted to explore the antioxidant potential of PMG extract as a dietary supplement to control oxidative stress in dairy cattle.

Perfusion change in benign prostatic hyperplasia before and after castration in a canine model: Contrast enhanced ultrasonography and CT perfusion study

Hormonal and vascular changes affecting the canine prostate after castration were investigated to identify the effects of hormones and perfusion on the development of benign prostatic hyperplasia (BPH). Concentrations of serum testosterone and estrogen and intraprostatic dihydrotestosterone (DHT) were compared between 5 normal dogs, 6 dogs with mild BPH, and 6 dogs with marked BPH. In addition, prostatic perfusion using contrast-enhanced ultrasonography (CEUS) and CT perfusion (CTP), as well as CT volumes of the prostates were compared. The changes in these values following castration were assessed in 6 dogs with marked BPH. CEUS revealed significantly slower prostatic arterial inflow and relatively faster venous outflow in BPH versus normal prostate. Permeability and blood volume were not significantly different between the groups via CTP. Intraprostatic DHT level was higher in BPH than in normal prostate and decreased significantly following castration, which was accompanied by a rapid decrease in prostatic volume. On CEUS, arterial inflow to the prostate significantly decreased following castration. Blood volume within the prostate decreased significantly by day 60 following castration. Permeability increased significantly during the early phase after castration; however, by day 60 post-castration, all perfusion parameters decreased significantly. Perfusion changes including venous parameters measured by CEUS and blood volume changes measured by CTP, however, did not support the backflow theory postulating that BPH is induced by vascular changes from congested testes. The major etiology for the development of BPH is attributed to be increased levels of DHT rather than vascular changes.

Androgens' effects on cerebrovascular function in health and disease

Androgens affect the cerebral vasculature and may contribute to sex differences in cerebrovascular diseases. Men are at a greater risk for stroke and vascular contributions to cognitive impairment and dementia (VCID) compared to women throughout much of the lifespan. The cerebral vasculature is a target for direct androgen actions, as it expresses several sex steroid receptors and metabolizing enzymes. Androgens’ actions on the cerebral vasculature are complex, as they have been shown to have both protective and detrimental effects, depending on factors such as age, dose, and disease state. When administered chronically, androgens are shown to be pro-angiogenic, promote vasoconstriction, and influence blood-brain barrier permeability. In addition to these direct effects of androgens on the cerebral vasculature, androgens also influence other vascular risk factors that may contribute to sex differences in cerebrovascular diseases. In men, low androgen levels have been linked to metabolic and cardiovascular diseases including hypertension, diabetes, hyperlipidemia, and obesity, which greatly increase the risk of stroke and VCID. Thus, a better understanding of androgens’ interactions with the cerebral vasculature under physiological and pathological conditions is of key importance.

Protective effects of Platycodon grandiflorus polysaccharides against apoptosis induced by carbonyl cyanide 3-chlorophenylhydrazone in 3D4/21 cells

This study aimed to investigate the potential protective effects of Platycodon grandiflorus polysaccharide (PGPS) on carbonyl cyanide 3-chlorophenylhydrazone (CCCP)-induced mitochondrial apoptosis in 3D4/21 cells. Apoptosis-related indicators such as cell viability, apoptosis rate, mitochondrial membrane potential (MMP), and apoptosis-related protein were examined. Results indicated that PGPSt can inhibit CCCP-induced cell damage, with cell-survival rate reaching 81% and apoptotic rate decreasing to 23%. Nuclear deformation was also significantly reduced in the PGPSt group, and changes in MMP were inhibited by PGPSt. Further analyses showed that the protein expression of Caspase-9 and Bcl-2 increased and the expression of cleaved Caspase-3 decreased, indicating that PGPSt significantly inhibited the CCCP-induced change in apoptotic protein expression. All these results suggested that PGPSt can antagonize 3D4/21 cell apoptosis by restoring MMP, protecting the integrity of nuclear morphology, and increasing Bcl-2 expression.

Helicobacter pylori infection combined with non-alcoholic fatty liver disease increase the risk of atherosclerosis: Focus in carotid artery plaque

Atherosclerosis has severe consequences on human health. Carotid artery plaques are a condition typically caused by atherosclerosis. Previous studies showed that nonalcoholic fatty liver disease (NAFLD) and Helicobacter pylori (H pylori) are risks factors for carotid artery plaque formation. We hypothesize that the combination of NAFLD with H pylori infection increases the risk of carotid artery plaque formation.A total of 4669 subjects aged > 40 years who underwent routine health checkups between January 2006 and December 2015 were retrospectively reviewed. A serial examination, including abdominal ultrasound, carotid artery ultrasound and esophago-gastroduodenoscopy (EGD), and biopsy urease testing, was conducted.In total, 2402 subjects were enrolled. There were no differences in H pylori infection status among patients with or without NAFLD. There was a trend of more participants with both NAFLD and H pylori infection (number [N]=583) presenting carotid artery plaque (N = 187,32.08%) than participants without NAFLD and H pylori infection (N = 589) who presented plaque formation (N = 106, 18.00%). Participants who had both H pylori infection and NAFLD had the highest risk of any carotid artery plaque (odds ratio [OR], 1.93; 95% confidence interval [CI], 1.413-2.636) based on a multivariate logistic regression analysis. This analysis also showed that age >60 years, male sex, low-density lipoprotein (LDL) >130 mg/dL, and H pylori infection were independent risk factors for concomitant NAFLD and carotid artery plaque formation.The combination of H pylori infection and NAFLD increases carotid artery plaque formation. H pylori eradication and NAFLD control may be warranted to prevent carotid artery plaque formation.

Contributions of sex to cerebrovascular function and pathology

Sex differences exist in how cerebral blood vessels function under both physiological and pathological conditions, contributing to observed sex differences in risk and outcomes of cerebrovascular diseases (CBVDs), such as vascular contributions to cognitive impairment and dementia (VCID) and stroke. Throughout most of the lifespan, women are protected from CBVDs; however, risk increases following menopause, suggesting sex hormones may play a significant role in this protection. The cerebrovasculature is a target for sex hormones, including estrogens, progestins, and androgens, where they can influence numerous vascular functions and pathologies. While there is a plethora of information on estrogen, the effects of progestins and androgens on the cerebrovasculature are less well-defined. Estrogen decreases cerebral tone and increases cerebral blood flow, while androgens increase tone. Both estrogens and androgens enhance angiogenesis/cerebrovascular remodeling. While both estrogens and androgens attenuate cerebrovascular inflammation, pro-inflammatory effects of androgens under physiological conditions have also been demonstrated. Sex hormones exert additional neuroprotective effects by attenuating oxidative stress and maintaining integrity and function of the blood brain barrier. Most animal studies utilize young, healthy, gonadectomized animals, which do not mimic the clinical conditions of aging individuals likely to get CBVDs. This is also concerning, as sex hormones appear to mediate cerebrovascular function differently based on age and disease state (e.g. metabolic syndrome). Through this review, we hope to inspire others to consider sex as a key biological variable in cerebrovascular research, as greater understanding of sex differences in cerebrovascular function will assist in developing personalized approaches to prevent and treat CBVDs.

Role of androgens in cardiovascular pathology

Cardiovascular effects of android hormones in normal and pathological conditions can lead to either positive or negative effects. The reason for this variation is unknown, but may be influenced by gender-specific effects of androids, heterogeneity of the vascular endothelium, differential expression of the androgen receptor in endothelial cells (ECs) and route of androgen administration. Generally, androgenic hormones are beneficial for ECs because these hormones induce nitric oxide production, proliferation, motility, and growth of ECs and inhibit inflammatory activation and induction of procoagulant, and adhesive properties in ECs. This indeed prevents endothelial dysfunction, an essential initial step in the development of vascular pathologies, including atherosclerosis. However, androgens can also activate endothelial production of some vasoconstrictors, which can have detrimental effects on the vascular endothelium. Androgens also activate proliferation, migration, and recruitment of endothelial progenitor cells (EPCs), thereby contributing to vascular repair and restoration of the endothelial layer. In this paper, we consider effects of androgen hormones on EC and EPC function in physiological and pathological conditions.

Dose dependent effects of cadmium on tumor angiogenesis

Angiogenesis is crucial for tumor growth and metastasis. Cadmium (Cd) exposure is associated with elevated cancer risk and mortality. Such association is, at least in part, attributable to Cd-induced tumor angiogenesis. Nevertheless, the reported effects of Cd on tumor angiogenesis appear to be either stimulatory or inhibitory, depending on the concentrations. Ultra-low concentrations of Cd (<0.5 μM) inhibit endothelial nitric oxide synthase activation, leading to reduced endothelial nitric oxide production and attenuated tumor angiogenesis. In contrast, low-lose Cd (1-10 μM) up-regulates vascular endothelial growth factor (VEGF)-mediated tumor angiogenesis by exerting sub-apoptotic levels of oxidative stress on both tumor cells and endothelial cells (ECs). The consequent activation of protein kinase B/Akt, nuclear factor-κB, and mitogen-activated protein kinase signaling cascades mediate the increased secretion of VEGF by tumor cells and the up-regulated VEGF receptor-2 expression in ECs. Furthermore, Cd in high concentrations (>10 μM) induces EC apoptosis via the activation of caspase-3, resulting in destruction of tumor vasculature. In this review, we summarize the current knowledge concerning the roles of Cd in tumor angiogenesis, with a focus on molecular mechanisms underlying the dose dependent effects of Cd on various EC phenotypes.

Salinomycin efficiency assessment in non-tumor (HB4a) and tumor (MCF-7) human breast cells

The search for anticancer drugs has led researchers to study salinomycin, an ionophore antibiotic that selectively destroys cancer stem cells. In this study, salinomycin was assessed in two human cell lines, a breast adenocarcinoma (MCF-7) and a non-tumor breast cell line (HB4a), to verify its selective action against tumor cells. Real-time assessment of cell proliferation showed that HB4a cells are more resistant to salinomycin than MCF-7 tumor cell line, and these data were confirmed in a cytotoxicity assay. The half maximal inhibitory concentration (IC50) values show the increased sensitivity of MCF-7 cells to salinomycin. In the comet assay, only MCF-7 cells showed the induction of DNA damage. Flow cytometric analysis showed that cell death by apoptosis/necrosis was only induced in the MCF-7 cells. The increased expression of GADD45A and CDKN1A genes was observed in all cell lines. Decreased expression of CCNA2 and CCNB1 genes occurred only in tumor cells, suggesting G2/M cell cycle arrest. Consequently, cell death was activated in tumor cells through strong inhibition of the antiapoptotic genes BCL-2, BCL-XL, and BIRC5 genes in MCF-7 cells. These data demonstrate the selectivity of salinomycin in killing human mammary tumor cells. The cell death observed only in MCF-7 tumor cells was confirmed by gene expression analysis, where there was downregulation of antiapoptotic genes. These data contribute to clarifying the mechanism of action of salinomycin as a promising antitumor drug and, for the first time, we observed the higher resistance of HB4a non-tumor breast cells to salinomycin.

Androgen actions on endothelium functions and cardiovascular diseases

The roles of androgens on cardiovascular physiology and pathophysiology are controversial as both beneficial and detrimental effects have been reported. Although the reasons for this discrepancy are unclear, multiple factors such as genetic and epigenetic variation, sex-specificity, hormone interactions, drug preparation and route of administration may contribute. Recently, growing evidence suggests that androgens exhibit beneficial effects on cardiovascular function though the mechanism remains to be elucidated. Endothelial cells (ECs) which line the interior surface of blood vessels are distributed throughout the circulatory system, and play a crucial role in cardiovascular function. Endothelial progenitor cells (EPCs) are considered an indispensable element for the reconstitution and maintenance of an intact endothelial layer. Endothelial dysfunction is regarded as an initiating step in development of atherosclerosis and cardiovascular diseases. The modulation of endothelial functions by androgens through either genomic or nongenomic signal pathways is one possible mechanism by which androgens act on the cardiovascular system. Obtaining insight into the mechanisms by which androgens affect EC and EPC functions will allow us to determine whether androgens possess beneficial effects on the cardiovascular system. This in turn may be critical in the prevention and therapy of cardiovascular diseases. This article seeks to review recent progress in androgen regulation of endothelial function, the sex-specificity of androgen actions, and its clinical applications in the cardiovascular system.

Research advances in the relationship between nonalcoholic fatty liver disease and atherosclerosis

Nonalcoholic fatty liver disease (NAFLD) is a metabolic stress-induced liver disease that is closely related not only to genetic susceptibility but also to insulin resistance and highly linked with metabolic syndrome. In recent years, the prevalence of NAFLD has increased rapidly, paralleling the epidemic of type 2 diabetes mellitus and obesity leading to cardiovascular disease. It has been demonstrated that NAFLD is highly associated with atherosclerosis. With recently gained knowledge, it appears that NAFLD may induce insulin resistance, dyslipidemia, oxidative stress, inflammation, and fluctuation of adipokines associated with atherosclerosis. In this review, we aimed to summarize recent discoveries related to both NAFLD and atherosclerosis, and to identify possible mechanisms linking them.

Herpes simplex virus 2 infects human endothelial ECV304 cells and induces cell apoptosis synergistically with ox-LDL

Virus infection has been shown to accelerate atherosclerosis. Serological studies indicate a link between the Herpes simplex virus (HSV) infection and atherosclerosis, which is initiated and progression of which is promoted by such factors as oxidized low-density lipoprotein (ox-LDL)-induced endothelial dysfunction. In order to recognize the direct role of HSV-2 in endothelial dysfunction, the present study investigated the infection of HSV-2 in endothelial ECV304 cells and the induction of cell apoptosis in the presence of ox-LDL. We firstly examined the HSV-2 infection by immunohistochemical assay for viral gB protein, quantitative PCR for viral ICP4 mRNA, or via virus growth determination. Then we investigated the regulation of HSV-2 infection on the cell viability and apoptosis, in the absence or presence of ox-LDL. In addition, we analyzed the apoptosis-associated molecules in the HSV-2-infected ECV304 cells. The results demonstrated that HSV-2 infected endothelial ECV304 cells and replicated efficiently, and the virus infection significantly reduced the cell viability and significantly induced cell apoptosis; particularly, cell viability reduction and cell apoptosis induction were aggravated by the ox-LDL presence. Moreover, the western blot assay confirmed the apoptosis induction; there was a significantly high level of released cytochrome c, activated caspase 3 and lyzed Poly (ADP-ribose) polymerase (PARP) by the activated caspase 3 in the HSV-2-infected ECV304 cells, particularly the cells subject to ox-LDL. Thus, we confirmed that HSV-2 infected endothelial ECV304 cells, induced cell apoptosis, which was aggravated by ox-LDL.

Influenza virus aggravates the ox-LDL-induced apoptosis of human endothelial cells via promoting p53 signaling

Oxidized low-density lipoprotein (ox-LDL) is well recognized to play a key role in the development of atherosclerosis. And influenza virus infection has been also recognized to promote the atherosclerosis onset and progressing. However, little is known about the mechanism into it. In present study, we investigated the infection of A/Porto Rico/8/1934 (H1N1) (PR8) influenza virus in human endothelial Eahy926 cells, and determined the induction of apoptosis by the virus infection in the cell. Then we investigated the apoptosis induced by ox-LDL in Eahy926 cells, determined the influence of influenza virus infection on the ox-LDL-induced apoptosis in Eahy926 cells. Results demonstrated that PR8 virus infected human endothelial Eahy926 cells, forming plaques and replicated efficiently in the cell. And the virus infection promoted apoptosis in the cell, upregulated cytchrome c release, activated caspase 3. And what's more, we found that combined PR8 virus infection and ox-LDL treatment promoted higher level of apoptosis and higher level of the activation of apoptosis-associated molecules. Further examination indicated that the p53 signaling was more significantly promoted by both treatments. Therefore, present study confirmed that influenza virus aggravated the ox-LDL-induced apoptosis of human endothelial Eahy926 cells via promoting p53 signaling.

Effects of dihydrotestosterone on adhesion and proliferation via PI3-K/Akt signaling in endothelial progenitor cells

The protective effects of male hormones on the cardiovascular system are still in dispute. There is now ample evidence that testosterone level is negatively correlated to the incidence and mortality of cardiovascular disease in men. Endothelial progenitor cells (EPCs) play a vital role in endothelial healing and vascular integrity, which are useful for promoting cardiovascular health. In this study, we investigated the effects of dihydrotestosterone (DHT), a non-aromatizable androgen, on human EPC function and the activation of the phosphatidylinositol-3-kinase (PI3-K)/Akt pathway in vitro. EPCs were incubated with a series of concentrations (1, 10, or 100 nmol/L in DMSO) of DHT for 24 h or with 10 nmol/L DHT for different time (6, 12, 24, 48 h). EPC adhesion and proliferation and the activation of Akt were assayed by cell counting, 5-ethynyl-2'-deoxyuridine incorporation assay, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and Western blot analysis. Our data demonstrated that DHT significantly increased the proliferative activity and adhesive ability of EPCs in a dose- and time-dependent manner, maximum at 10 nmol/L, 24 h (p < 0.05). Western blot analysis revealed that DHT promoted the phosphorylation of Akt, and the effects of different concentrations of DHT on Akt phosphorylation were consistent with those on EPC proliferation and adhesion (p < 0.05). However, the enhancing effects of DHT on EPCs decreased with administration of the pharmacological PI3-K blocker LY294002 (p < 0.05). In conclusion, DHT can modulate EPC proliferation and adhesion and the PI3-K/Akt pathway plays an important role in this process.

Endocrine disruptors differently influence estrogen receptor β and androgen receptor in male and female rat VSMC

Sex steroid hormones differently control the major physiological processes in male and female organisms. In particular, their effects on vascular smooth muscle cells (VSMCs) migration are at the root of sex/gender-related differences reported in the cardiovascular system. Several exogenous substances, defined endocrine disruptor chemicals (EDCs), could interfere with these androgen and estrogen effects; however, the sex/gender-related susceptibility of VSMC motility to EDCs is completely unknown. Here, the effect of naturally occurring (naringenin, Nar) and synthetic (bisphenol A, BPA) EDCs on male and female VSMC motility has been evaluated. 17β-estradiol (E2, 0.1 nM-1 µM) induced a dose-dependent inhibition of motility in female-derived VSMC. In contrast, neither dihydrotestosterone (DHT, 0.01-100 nM) nor the common precursor of sex steroid hormones, testosterone (Tes, 0.01-100 nM) modified male-derived VSMC motility. Estrogen receptor (ER) β subtype-dependent activation of p38 was necessary for the E2 effect on cell motility. High BPA concentration prevented E2 effects in female-derived cells being without any effect in male-derived cells. Nar mimicked E2 effects on female-derived cells even in the presence of E2 or BPA. Intriguingly, Nar also inhibited the male-derived VSMC mobility. This latter effect was prevented by ERβ inhibitor, but not by the androgen receptor (AR) inhibitor. As a whole, ERβ-dependent signals in VSMC results more susceptible to the impact of EDCs than AR signals suggesting a possible high and overall susceptibility of female to EDCs. However, several male-derived cells, including VSMC, express ERβ, which could also serve as target of EDC disruption in male organisms.

Oxidative actions of hydrogen peroxide in human gingival and oral periosteal fibroblasts: responses to glutathione and nicotine, relevant to healing in a redox environment

Background

This study aims to validate pro-oxidant actions of nicotine (N), using hydrogen peroxide (H₂O₂) and the antioxidant glutathione (G) in an in vitro model of human gingival fibroblasts (HGF) and human oral periosteal fibroblasts (HPF); radiolabelled androgens are used as biomarkers of redox status. Oxidative stress is an important mediator of inflammatory repair. The androgen metabolite 5α-dihydrotestosterone (DHT) is an effective biomarker of oxidative stress and healing.

Methods

6 Cell-lines of HGF and HPF established in confluent monolayer culture were incubated in Eagle's MEM using 14C-testosterone and 14C-4-androstendione as substrate; in conjunction with effective concentrations of N, G and H₂O₂ established at N250, G3 μg/ml and 3%H₂O₂ w/w, 0.5 μl/ml. Combinations of H₂O₂G and H₂O₂GN were used in order to compare the oxidative effects of N/H₂O₂ and their responses to glutathione. At 24 h, the medium was solvent extracted, evaporated to dryness and subjected to TLC in a benzene/acetone solvent system 4:1 v/v for the separation of metabolites. The separated metabolites were quantified using a radioisotope scanner.

Results

The mean trends of 6 cell-lines for both substrates and each cell type demonstrated that the yield of the main metabolite DHT was significantly reduced by N and H₂O₂ alone (2-fold, n=6; p<0.01). The inhibition caused by H₂O₂ was overcome by the antioxidant glutathione in the combination H₂O₂G, to values similar to those of controls (n=6; p<0.01). It is relevant that when N was added to this neutralized combination, the decrease in yields of DHT triggered by N were comparable to those induced by H₂O₂; and retaining the positive effect of G.

Conclusion

Oxidative stress mediated by H₂O₂ was overcome by glutathione and recurred when nicotine was added, suggestive of a pro- oxidant role for nicotine. Androgen biomarkers are a sensitive index of oxidative stress which affects wound healing.

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DHT is an effective redox marker in HGF and oral periosteal fibroblasts in vitro.

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Both nicotine and H₂O₂ reduced yields of DHT, indicative of induced oxidative stress.

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Nicotine has oxidative effects that are comparable to those of H₂O₂ mediated by AR.

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Effects of nicotine and H₂O₂ were reduced by glutathione in HGF and HPF cultures.

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Redox status is relevant to androgen receptor-mediated inflammatory wound healing.

Effects of different sources and levels of zinc on H2O2-induced apoptosis in IEC-6 cells

Zinc has been shown to be an inhibitor of apoptosis for many years. The present study was designed to investigate effects of three zinc chemical forms on H2O2-induced cell apoptosis in IEC-6 cells via analysis of cell vitality, LDH activity, apoptosis percentage, caspase-3 activity, and Bcl-2, Bax, and caspase-3, -8, and -9 gene expression. Cells were divided into H2O2 and zinc sources+H2O2 groups, and there are three different zinc sources [zinc oxide nanoparticle (nano-ZnO), zinc oxide (ZnO), and zinc sulfate (ZnSO4)] and three concentrations (normal = 25 μM, medium = 50 μM, and high = 100 μM) used in this article. In the present study, we found the striking cytotoxicity of H2O2 higher than 200 μM on cell vitality, LDH activity, and apoptosis percentage in the cells using five different concentrations (50, 100, 200, 400, and 800 μM) of H2O2 for 4 h. Moreover, we observed that cell vitality was increased, LDH activity and apoptotic percentage were decreased, and gene expression level of Bax and caspase-3 and -9 was markedly reduced, while gene expression level of Bcl-2 and ratio of Bcl-2/Bax were increased in normal concentration groups of nano-ZnO and ZnSO4 compared with H2O2 group, but no significant difference was observed in caspase-8 gene expression. Furthermore, medium or, more intensely, high concentrations of nano-ZnO and ZnSO4 enhanced H2O2-induced cell apoptosis. Compared with nano-ZnO and ZnSO4, ZnO showed weakest protective effect on H2O2-induced apoptosis at normal concentration and was less toxic to cells at high level. Taken together, we proposed that preventive and protective effects of zinc on H2O2-induced cell apoptosis varied in IEC-6 cells with its chemical forms and concentrations, and maybe for the first time, we suggested that nano-ZnO have a protective effect on H2O2-induced cell apoptosis in IEC-6 cells.

Reduced estradiol-induced vasodilation and poly-(ADP-ribose) polymerase (PARP) activity in the aortas of rats with experimental polycystic ovary syndrome (PCOS)

Polycystic ovary syndrome (PCOS) is a complex endocrine disorder characterized by hyperandrogenism and insulin resistance, both of which have been connected to atherosclerosis. Indeed, an increased risk of clinical manifestations of arterial vascular diseases has been described in PCOS. On the other hand endothelial dysfunction can be detected early on, before atherosclerosis develops. Thus we assumed that vascular dysfunction is also related directly to the hormonal imbalance rather than to its metabolic consequences. To detect early functional changes, we applied a novel rodent model of PCOS: rats were either sham operated or hyperandrogenism was achieved by implanting subcutaneous pellets of dihydrotestosterone (DHT). After ten weeks, myograph measurements were performed on isolated aortic rings. Previously we described an increased contractility to norepinephrine (NE). Here we found a reduced immediate relaxation to estradiol treatment in pre-contracted aortic rings from hyperandrogenic rats. Although the administration of vitamin D3 along with DHT reduced responsiveness to NE, it did not restore relaxation to estradiol. Poly-(ADP-ribose) polymerase (PARP) activity was assessed by poly-ADP-ribose immunostaining. Increased PAR staining in ovaries and circulating leukocytes from DHT rats showed enhanced DNA damage, which was reduced by concomitant vitamin D3 treatment. Surprisingly, PAR staining was reduced in both the endothelium and vascular smooth muscle cells of the aorta rings from hyperandrogenic rats. Thus in the early phase of PCOS, vascular tone is already shifted towards vasoconstriction, characterized by reduced vasorelaxation and vascular dysfunction is concomitant with altered PARP activity. Based on our findings, PARP inhibitors might have a future perspective in restoring metabolic disorders in PCOS.

Effects of Low-Dose versus High-Dose γ-Tocotrienol on the Bone Cells Exposed to the Hydrogen Peroxide-Induced Oxidative Stress and Apoptosis

Oxidative stress and apoptosis can disrupt the bone formation activity of osteoblasts which can lead to osteoporosis. This study was conducted to investigate the effects of γ-tocotrienol on lipid peroxidation, antioxidant enzymes activities, and apoptosis of osteoblast exposed to hydrogen peroxide (H₂O₂). Osteoblasts were treated with 1, 10, and 100 μM of γ-tocotrienol for 24 hours before being exposed to 490 μM (IC₅₀) H₂O₂ for 2 hours. Results showed that γ-tocotrienol prevented the malondialdehyde (MDA) elevation induced by H₂O₂ in a dose-dependent manner. As for the antioxidant enzymes assays, all doses of γ-tocotrienol were able to prevent the reduction in SOD and CAT activities, but only the dose of 1 μM of GTT was able to prevent the reduction in GPx. As for the apoptosis assays, γ-tocotrienol was able to reduce apoptosis at the dose of 1 and 10 μM. However, the dose of 100 μM of γ-tocotrienol induced an even higher apoptosis than H₂O₂. In conclusion, low doses of γ-tocotrienol offered protection for osteoblasts against H₂O₂ toxicity, but itself caused toxicity at the high doses.

Mechanisms for redox actions of nicotine and glutathione in cell culture, relevant to periodontitis

The oxidative effect of nicotine was investigated using androgen biomarkers of redox status and wound healing in fibroblasts; using the antioxidant glutathione for confirmation of responses. Cultures of human gingival (HGF) and periosteal fibroblasts (HPF) were incubated with substrates 14C-testosterone/14C-4-androstenedione in the presence or absence of serial concentrations of nicotine (N_100-500), glutathione (G_1–5) and their combinations, in medium. At 24 h the medium was solvent extracted for metabolites, separated by TLC and quantified using radioisotope scanning. Nicotine caused significant inhibition in yields of the physiologically active metabolite 5α-dihydrotestosterone (DHT) in HGF and HPF, overcome to varying degrees by the anti-oxidant glutathione (n = 6; p<0.01, one way ANOVA); this is suggestive of moderation of an oxidative mechanism induced by nicotine. Down-regulation of 5α-reductase activity by nicotine resulting in reduced yields of DHT was overcome by glutathione. Overcoming oxidative stress in a redox environment is applicable to treatment outcome.

TGF-β1 induces endothelial cell apoptosis by shifting VEGF activation of p38(MAPK) from the prosurvival p38β to proapoptotic p38α

TGF-β1 and VEGF, both angiogenesis inducers, have opposing effects on vascular endothelial cells. TGF-β1 induces apoptosis; VEGF induces survival. We have previously shown that TGF-β1 induces endothelial cell expression of VEGF, which mediates TGF-β1 induction of apoptosis through activation of p38 mitogen-activated protein kinase (MAPK). Because VEGF activates p38(MAPK) but protects the cells from apoptosis, this finding suggested that TGF-β1 converts p38(MAPK) signaling from prosurvival to proapoptotic. Four isoforms of p38(MAPK) -α, β, γ, and δ-have been identified. Therefore, we hypothesized that different p38(MAPK) isoforms control endothelial cell apoptosis or survival, and that TGF-β1 directs VEGF activation of p38(MAPK) from a prosurvival to a proapoptotic isoform. Here, we report that cultured endothelial cells express p38α, β, and γ. VEGF activates p38β, whereas TGF-β1 activates p38α. TGF-β1 treatment rapidly induces p38α activation and apoptosis. Subsequently, p38α activation is downregulated, p38β is activated, and the surviving cells become refractory to TGF-β1 induction of apoptosis and proliferate. Gene silencing of p38α blocks TGF-β1 induction of apoptosis, whereas downregulation of p38β or p38γ expression results in massive apoptosis. Thus, in endothelial cells p38α mediates apoptotic signaling, whereas p38β and p38γ transduce survival signaling. TGF-β1 activation of p38α is mediated by VEGF, which in the absence of TGF-β1 activates p38β. Therefore, these results show that TGF-β1 induces endothelial cell apoptosis by shifting VEGF signaling from the prosurvival p38β to the proapoptotic p38α.

Role of VPO1, a newly identified heme-containing peroxidase, in ox-LDL induced endothelial cell apoptosis

Myeloperoxidase (MPO) is an important enzyme involved in the genesis and development of atherosclerosis. Vascular peroxidase 1 (VPO1) is a newly discovered member of the peroxidase family that is mainly expressed in vascular endothelial cells and smooth muscle cells and has structural characteristics and biological activity similar to those of MPO. Our specific aims were to explore the effects of VPO1 on endothelial cell apoptosis induced by oxidized low-density lipoprotein (ox-LDL) and the underlying mechanisms. The results showed that ox-LDL induced endothelial cell apoptosis and the expression of VPO1 in endothelial cells in a concentration- and time-dependent manner concomitant with increased intracellular reactive oxygen species (ROS) and hypochlorous acid (HOCl) generation, and up-regulated protein expression of the NADPH oxidase gp91(phox) subunit and phosphorylation of p38 MAPK. All these effects of ox-LDL were inhibited by VPO1 gene silencing and NADPH oxidase gp91(phox) subunit gene silencing or by pretreatment with the NADPH oxidase inhibitor apocynin or diphenyliodonium. The p38 MAPK inhibitor SB203580 or the caspase-3 inhibitor DEVD-CHO significantly inhibited ox-LDL-induced endothelial cell apoptosis, but had no effect on intracellular ROS and HOCl generation or the expression of NADPH oxidase gp91(phox) subunit or VPO1. Collectively, these findings suggest for the first time that VPO1 plays a critical role in ox-LDL-induced endothelial cell apoptosis and that there is a positive feedback loop between VPO1/HOCl and the now-accepted dogma that the NADPH oxidase/ROS/p38 MAPK/caspase-3 pathway is involved in ox-LDL-induced endothelial cell apoptosis.