Antioxidant properties of mesenchymal stem cells against oxidative stress in a murine model of colitis

Objective

To investigate the effects of oxidative stress injury in dextran sulfate sodium (DSS)-induced colitis in mice treated with mesenchymal stem cells (MSC).

Results

Mice exposed to oral administration of 2% DSS over 7 days presented a high disease activity index and an intense colonic inflammation. Systemic infusion of MSC protected from severe colitis, reducing weight loss and diarrhea while lowering the infiltration of inflammatory cells. Moreover, toxic colitis injury increased oxidative stress. Administration of DSS decreased reduced glutathione (GSH) and superoxide dismutase (SOD) activity, and increased thiobarbituric acid-reactive substances levels in the colon. No alteration was found in catalase (CAT) and glutathione peroxidase (GPx) activity. Otherwise, MSC transplantation was able to prevent the decrease of GSH levels and SOD activity suggestive of an antioxidant property of MSC.

Conclusion

The oxidative stress is a pathomechanism underlying the pathophysiology of colitis and MSC play an important role in preventing the impairment of antioxidants defenses in inflamed colon.

     

Absence of autoantibodies against correctly folded recombinant fibrillin-1 protein in systemic sclerosis patients

Autoantibodies against short recombinant fragments of fibrillin-1 produced in bacterial expression systems have been found in tight-skin mouse, systemic sclerosis, mixed connective tissue disease, and primary pulmonary hypertension syndrome. In patients with scleroderma, the frequency of anti-fibrillin-1 antibodies was 42% in Caucasians. Until now it has been unclear whether this immune response has a primary function in disease pathogenesis or is a secondary phenomenon. In the present study we analyzed the frequency of autoantibodies against two overlapping recombinant polypeptides spanning the N-terminal and C-terminal halves of human fibrillin-1, which were produced in human embryonic kidney (HEK-293) cells. Correct three-dimensional structures of the recombinant fibrillin-1 polypeptides were shown by electron microscopy and immunoreactivity with antibodies. Screening of fibrillin-1 antibodies was performed in 41 sera from systemic sclerosis patients and in 44 healthy controls with a Caucasian background. Microtiter plates were coated with the recombinant polypeptides of fibrillin-1 and incubated with 1:100 diluted sera. Positive binding was defined as being more than 2 SD above the mean of the control group. ELISAs showed that none of the sera of patients with systemic sclerosis contained autoantibodies against the N-terminal or C-terminal recombinant fibrillin-1 polypeptide. The data show the absence of autoantibodies against recombinant fibrillin-1 protein in Caucasian systemic sclerosis patients. Because the correct three-dimensional folding of the recombinant proteins has been substantiated by several independent methods, we conclude that autoantibodies against correctly folded fibrillin are not a primary phenomenon in the pathogenesis of systemic sclerosis.     

Simvastatin prevents vascular complications in the chronic reactive oxygen species murine model of systemic sclerosis

Aims Systemic sclerosis (SSc) is characterized by vasculopathy and organ fibrosis. Although microvascular alterations are very well characterized, structural and functional abnormalities of large vessels are not well defined. Therefore, we evaluated the effect of simvastatin administration on aortic and small renal arteries thickening, and on myofibroblasts differentiation in a murine model of SSc. Methods and results SSc was induced in BALB/c mice by daily subcutaneous injections of hypochlorous acid (HOCl, 100?μl) for 6 weeks. Mice (n?=?23) were randomized to receive: HOCl (n?=?10); HOCl plus simvastatin (40?mg/kg; n?=?8); or vehicle (n?=?5). Simvastatin administration started 30?min after HOCl injection, and up to week 6. Aortic and small renal arteries intima–media thickness was evaluated by histological analysis. Immunostaining for α-smooth muscle actin (SMA), vascular endothelial growth factor receptor 2 (VEGFR2), and CD31 in aortic tissues was performed to evaluate myofibroblast differentiation and endothelial markers.In HOCl-treated mice, intima–media thickening with reduced lumen diameter was observed in the aorta and in small renal arteries and simvastatin administration prevented this increase. Aortic and renal myofibroblasts count, as expressed by α-SMA?+?density, was lower in the group of mice treated with simvastatin compared to HOCl-treated mice. Simvastatin prevented the reduction in VEGFR2 and CD31 expression induced by HOCl. Conclusions The administration of simvastatin regulates collagen deposition in the aortic tissues and in the small renal arteries by modulating myofibroblasts differentiation and vascular markers. Further studies are needed to better address the effect of statins in the macrovascular component of SSc.     

E-Selectin expression in a murine model of chronic colitis

The objective of this study was to quantify E-selectin surface expression in the colon as well as other tissues in a CD4(+) T-cell model of chronic colitis in mice using the newly developed dual radiolabel monoclonal antibody technique. Male SCID mice were reconstituted with either 5 x 10(5) CD4(+) CD45RB(low) or CD45RB(high) T-cells isolated from normal CB-17 donor mouse spleens and subsequently monitored for clinical signs of colitis. We found that animals injected with CD45RB(high) but not CD45RB(low) T-cells nor PBS developed colitis at 6-8 weeks following reconstitution as assessed by loss of body weight, development of loose stools and/or diarrhea, and histopathology. Concurrent with the onset of distal bowel inflammation was enhanced expression of E-selectin compared to SCID mice injected with PBS or reconstituted with CD45RB(low) T-cells, both of which did not develop colitis. We also observed significant increases in E-selectin expression in cecum, small intestine, mesentery, and liver of colitic mice. Our data confirm that reconstitution of SCID mice with CD45RB(high) but not CD45RB(low) T-cells induces chronic colitis and demonstrate that this chronic colitis is associated with enhanced expression of an endothelial cell-specific adhesion molecule. Furthermore, our studies demonstrate that reconstitution of SCID mice with CD45RB(high) T-cells enhances E-selectin expression in a variety of tissues distant from the site of active inflammation.     

Nifedipine decreases sVCAM-1 concentrations and oxidative stress in systemic sclerosis but does not affect the concentrations of vascular endothelial growth factor or its soluble receptor 1

Microvascular injury, oxidative stress, and impaired angiogenesis are prominent features of systemic sclerosis (SSc). We compared serum markers of these phenomena at baseline and after treatment with nifedipine in SSc patients. Forty successive SSc patients were compared with 20 matched healthy subjects. All SSc patients stopped taking calcium-channel blockers 72 hours before measurements. Twenty SSc patients were also examined after 14 days of treatment with nifedipine (60 mg/day). Quantitative ELISA was used to measure the serum concentrations of vascular endothelial growth factor (VEGF), soluble VEGF receptor 1 (sVEGFR-1), soluble vascular cell adhesion molecule 1 (sVCAM-1), carbonyl residues, and advanced oxidation protein products (AOPP). The median concentrations of VEGF, sVEGFR-1, sVCAM-1, carbonyl residues, and AOPP were significantly higher in SSc patients than in healthy subjects at baseline. A correlation was found between VEGF concentration and carbonyl residue concentration (r = 0.43; P = 0.007). Nifedipine treatment led to a significant decrease in concentrations of sVCAM-1, carbonyl residues, and AOPP but did not affect concentrations of VEGF and sVEGFR-1. Nifedipine treatment ameliorated endothelium injury in patients with SSc, as shown by the concentrations of adhesion molecules and oxidative damage markers. The fact that VEGF and sVEGFR-1 concentrations were not changed whereas oxidative stress was ameliorated by nifedipine is consistent with the hypothesis that VEGF signalling is impaired in SSc. However, more experimental evidence is needed to determine whether the VEGF pathway is intrinsically defective in SSc.     

Leukocyte and endothelial cell adhesion molecules in a chronic murine model of myocardial reperfusion injury

Expression of endothelial and leukocyte cell adhesion molecules is a principal determinant of polymorphonuclear neutrophil (PMN) recruitment during inflammation. It has been demonstrated that pharmacological inhibition of these molecules can attenuate PMN influx and subsequent tissue injury. We determined the temporal expression of alpha-granule membrane protein-40 (P-selectin), endothelial leukocyte adhesion molecule 1 (E-selectin), and intercellular cell adhesion molecule 1 (ICAM-1) after coronary artery occlusion and up to 3 days of reperfusion. The expression of all of these cell adhesion molecules peaked around 24 h of reperfusion. We determined the extent to which these molecules contribute to PMN infiltration by utilizing mice deficient (-/-) in P-selectin, E-selectin, ICAM-1, and CD18. Each group underwent 30 min of in vivo, regional, left anterior descending (LAD) coronary artery ischemia and 24 h of reperfusion. PMN accumulation in the ischemic-reperfused (I/R) zone was assessed using histological techniques. Deficiencies of P-selectin, E-selectin, ICAM-1, or CD18 resulted in significant (P < 0.05) attenuation of PMN infiltration into the I/R myocardium (MI/R). In addition, P-selectin, E-selectin, ICAM-1, and CD18 -/- mice exhibited significantly (P < 0.05) smaller areas of necrosis after MI/R compared with wild-type mice. These data demonstrate that MI/R induces coronary vascular expression of P-selectin, E-selectin, and ICAM-1 in mice. Furthermore, genetic deficiency of P-selectin, E-selectin, ICAM-1, or CD18 attenuates PMN sequestration and myocardial injury after in vivo MI/R. We conclude that P-selectin, E-selectin, ICAM-1, and CD18 are involved in the pathogenesis of MI/R injury in mice.     

Study of the oxidative stress in a rat model of chronic brain hypoperfusion

A multiple analysis of the cerebral oxidative stress was performed on a physiological model of dementia accomplished by three-vessel occlusion in aged rats. The forward rate constant of creatine kinase, k_for, was studied by saturation transfer ³¹P magnetic resonance spectroscopy in adult and aged rat brain during chronic hypoperfusion. In addition, free radicals in aging rat brain homogenates before and/or after occlusion were investigated by spin-trapping electron paramagnetic resonance spectroscopy (EPR). Finally, biochemical measurements of oxidative phosphorylation parameters in the above physiological model were performed. The significant reduction of k_for in rat brain compared to controls 2 and 10 weeks after occlusion indicates a disorder in brain energy metabolism. This result is consistent with the decrease of the coefficient of oxidative phosphorylation (ADP:O), and the oxidative phosphorylation rate measured in vitro on brain mitochondria. The EPR study showed a significant increase of the ascorbyl free radical concentration in this animal model. Application of -phenyl-N-tert-butylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin traps revealed formation of highly reactive hydroxyl radical (OH) trapped in DMSO as the CH₃ adduct. It was concluded that the ascorbate as a major antioxidant in brain seems to be useful in monitoring chronic cerebral hypoperfusion.     

Systemic sclerosis sera affect fibrillin-1 deposition by dermal blood microvascular endothelial cells: therapeutic implications of cyclophosphamide

Introduction

Systemic sclerosis (SSc) is a connective tissue disorder characterized by endothelial cell injury, autoimmunity and fibrosis. The following three fibrillin-1 alterations have been reported in SSc. (1) Fibrillin-1 microfibrils are disorganized in SSc dermis. (2) Fibrillin-1 microfibrils produced by SSc fibroblasts are unstable. (3) Mutations in the FBN1 gene and anti-fibrillin-1 autoantibodies have been reported in SSc. Fibrillin-1 microfibrils, which are abundantly produced by blood and lymphatic microvascular endothelial cells (B-MVECs and Ly-MVECs, respectively), sequester in the extracellular matrix the latent form of the potent profibrotic cytokine transforming growth factor β (TGF-β). In the present study, we evaluated the effects of SSc sera on the deposition of fibrillin-1 and microfibril-associated glycoprotein 1 (MAGP-1) and the expression of focal adhesion molecules by dermal B-MVECs and Ly-MVECs.

Methods

Dermal B-MVECs and Ly-MVECs were challenged with sera from SSc patients who were treatment-naïve or under cyclophosphamide (CYC) treatment and with sera from healthy controls. Fibrillin-1/MAGP-1 synthesis and deposition and the expression of α_vβ₃ integrin/phosphorylated focal adhesion kinase and vinculin/actin were evaluated by immunofluorescence and quantified by morphometric analysis.

Results

Fibrillin-1 and MAGP-1 colocalized in all experimental conditions, forming a honeycomb pattern in B-MVECs and a dense mesh of short segments in Ly-MVECs. In B-MVECs, fibrillin-1/MAGP-1 production and α_vβ₃ integrin expression significantly decreased upon challenge with sera from naïve SSc patients compared with healthy controls. Upon challenge of B-MVECs with sera from CYC-treated SSc patients, fibrillin-1/MAGP-1 and α_vβ₃ integrin levels were comparable to those of cells treated with healthy sera. Ly-MVECs challenged with SSc sera did not differ from those treated with healthy control sera in the expression of any of the molecules assayed.

Conclusions

Because of the critical role of fibrillin-1 in sequestering the latent form of TGF-β in the extracellular matrix, its decreased deposition by B-MVECs challenged with SSc sera might contribute to dermal fibrosis. In SSc, CYC treatment might limit fibrosis through the maintenance of physiologic fibrillin-1 synthesis and deposition by B-MVECs.     

Calcium and oxidative stress mediate perillaldehyde-induced apoptosis in Candida albicans

New anti-Candida albicans drugs are needed due to the emergence of resistant cases in recent years. Perillaldehyde (PAE) is a natural monoterpenoid compound derived from Perilla frutescens. The minimum inhibitory concentration of PAE against C. albicans was 0.4 μL/mL. We aimed to elucidate the antifungal mode of action of PAE against C. albicans. The antifungal activity of PAE against C. albicans was found to correlate with an elevation in intracellular Ca²⁺ and accumulation of ROS. Several downstream apoptosis events such as the disruption of mitochondrial membrane potential, phosphatidylserine externalization, cytochrome c release, and metacaspase activation were observed in PAE-treated cells. DNA damage and nuclear fragmentation assays also revealed apoptosis of C. albicans cells. In summary, by means of fluorescent microscopy, flow cytometer analysis, and Western blot, our data uncovered that PAE exerts its antifungal activity through Ca²⁺ and oxidative stress-mediated apoptosis mechanisms. This study deciphered the mode of action of PAE, which will be useful in the design of improved antifungal therapies.

     

The various aggregation states of beta-amyloid 1-42 mediate different effects on oxidative stress, neurodegeneration, and BACE-1 expression

The amyloid cascade hypothesis suggests that the insoluble and fibrillar form of beta-amyloid (A beta) may play a primary pathogenic role in Alzheimer disease at the molecular level. However, neither the rate of dementia nor the extent of neuronal change seems to correlate with the levels of amyloidotic plaques (i.e., aggregated/fibrillar A beta). Recent evidence suggests, however, that neurotoxicity may be exerted also by rather small soluble aggregates of A beta, including oligomers. To characterize the mechanisms underlying toxicity mediated by the various aggregation states of A beta peptides is then a major goal of research. In this work we investigated the effects of fibrillar, prefibrillar, and oligomeric A beta(1-42) on the induction of oxidative stress, cell death, and BACE-1 expression in NT2 neuronal cells. We found that prefibrillar and oligomeric A beta(1-42) resulted in a more dramatic increase in the oxidative stress markers 4-hydroxynonenal and hydrogen peroxide compared to fibrillar A beta(1-42). Moreover, increased oxidative stress levels also resulted in a more rapid and significant induction of both apoptotic and necrotic neuronal cell death. Accordingly, fibrillar A beta(1-42), but not the soluble nonfibrillar forms, was the only condition able to up-regulate BACE-1 expression and activity.     

Effects of chronic immobilization stress on biokinetics and dosimetry of 67 Ga in a murine model

The aim of this work is to determine the effect of chronic immobilization stress on kinetics and dosimetry of 67Ga in a mouse model. A control group (CG) and a stress group (SG), each with 15 mice, were included in the study, and the latter group was subjected to a chronic immobilization stress model 2 h daily for 14 consecutive days. At day 13, 67Ga-citrate was administered intraperitoneally (11.24 ± 0.44 MBq) to each mouse. Then, sets of three mice were obtained sequentially at 24, 36, 48, 60 and 72 h, in which the radionuclide activity was measured with an activity counter. The 67Ga biokinetic data showed a fast blood clearance in the SG, with a mean residence time of 0.06 h. The calculated mean radiation absorbed doses were: liver (2.45 × 10−03 Gy), heart (3.17 × 10−04 Gy) and kidney (1.88 × 10−04 Gy) in the SG. The results show that stress reduced weight gain by approximately 13% and also increased adrenal gland weight by 26%. On the other hand, chronic stress accelerates 67Ga clearance after 24 h compared to normal conditions. It is concluded that murine organisms under chronic immobilization stress have higher gallium-67 clearance rates, decreasing the cumulated activity and absorbed dose in all organs.     

Evidence against oxidative stress as mechanism of endothelial dysfunction in methionine loading model

Endothelial dysfunction reflects reduced nitric oxide (NO) bioavailability due to either reduced production, inactivation of NO, or reduced smooth muscle responsiveness. Oral methionine loading causes acute endothelial dysfunction in healthy subjects and provides a model in which to study mechanisms. Endothelial function was assessed using flow-mediated dilatation (FMD) of the brachial artery in humans. Three markers of oxidative stress were measured ex vivo in venous blood. NO responsiveness was assessed in vascular smooth muscle and platelets. Oral methionine loading induced endothelial dysfunction (FMD decreased from 2.8 +/- 0.8 to 0.3 +/- 0.3% with methionine and from 2.8 +/- 0.8 to 1.3 +/- 0.3% with placebo; P < 0.05). No significant changes in measures of plasma oxidative stress or in vascular or platelet sensitivity to submaximal doses of NO donors were detected. These data suggest that oxidative stress is not the mechanism of endothelial dysfunction after oral methionine loading. Furthermore, the preservation of vascular and platelet NO sensitivity makes a signal transduction abnormality unlikely.     

Activin,a grape seed-derived proanthocyanidin extract,reduces plasma levels of oxidative stress and adhesion molecules (ICAM-1, VCAM-1 and E-selectin) in systemic sclerosis

This study evaluated whether a new generation antioxidant Activin derived from the grape seed proanthocyanidins, could reduce the induction of the adhesion molecules as a result of inflammatory response in the plasma of systemic sclerosis (SSc) patients. SSc patients were divided into two groups: one group was treated with Activin, a grape seed-derived proanthocyanidins, while the other group served as control. Patients were given Activin 100 mg/day orally for one month after which the blood samples were withdrawn from both groups of the patients. Blood was also taken from normal human volunteers. Plasma was obtained in fasting state between 8 to 9 A.M. from two groups of SSc patients and controls. Soluble adhesion molecules including ICAM-1, VCAM-1, E-selectin and P-selectin as well as malonaldehyde, a marker for oxidative stress, were measured. The results of our study demonstrated up-regulation of these soluble adhesion molecules except for P-selectin, in the plasma of the SSc patients compared to those obtained from human volunteers. Activin significantly attenuated the increased expression of these adhesion molecules. In addition, there was a significant increase in the amount of malondialdehyde formation in the plasma of the SSc patients, which was also attenuated by Activin. The results of this study demonstrated that Activin could reduce the inflammatory response and the oxidative stress developed in SSc patients.     

离体大鼠主动脉内皮细胞氧化应激损伤模型的建立及评价

目的：建立离体大鼠主动脉内皮细胞氧化应激损伤模型,为细胞损伤及细胞凋亡的调控研究提供基础。方法：大鼠断头处死在无菌条件下开胸取主动脉,经组织块培养法后传代培养得到充足主动脉内皮细胞,接种于96孔板或爬片培养,每组设6个复孔,用于之后的各项试验检测。以不加H₂O₂的组作为对照组,以不同浓度的H₂O₂（100、200、300、400、500 μmol/L）作用于内皮细胞相同时间12 h,来筛选最佳作用浓度;依据结果以相同浓度的H₂O₂（100和200 μmol/L）分别作用不同时间（3、6、9、12及24 h）,来筛选最佳作用时间。通过免疫荧光法鉴定、细胞存活率检测、生化指标（LDH-L、NO、MDA、SOD）检测及内皮细胞凋亡指数等变化,评价及验证模型的建立。结果：对细胞内Ⅷ型胶原抗原进行免疫荧光染色后鉴定血管内皮细胞培养成功;在12 h的相同作用时间下,随着H₂O₂浓度的加大,细胞存活率呈显著下降（77.63%±5.20%~40.90%±2.10%）;相同浓度（100 μmol/L组和200 μmol/L组）随着作用时间的增加,细胞存活率呈显著递减（100 μmol/L组为86.83%±12.11%~44.26%±5.70%,200 μmol/L组为78.28%±11.98%~34.45%±5.87%）;以H₂O₂浓度为100 μmol/L作用3、6、9、12及24 h,培养液中生化指标在9 h后LDH-L与MDA呈显著递增,NO与SOD呈显著递减;在H₂O₂浓度为100 μmol/L与作用时间12 h的条件下,流式检测结果显示内皮细胞凋亡率为16.92%±2.37%,显著高于对照组2.68%±0.47%（P<0.01）; TUNEL检测内皮细胞凋亡指数为17.65%±2.36%,显著高于对照组的3.23%±0.57%（P<0.01）。结论：该方法成功建立了体外血管内皮细胞氧化应激损伤模型,探索了轻重适度的诱导细胞损伤和细胞凋亡的造模方法,可以成为开展多种血管内皮细胞损伤及凋亡调控机制研究的基础。     

Role of oxidative stress in multiparity-induced endothelial dysfunction

Multiparity is associated with increased risk of cardiovascular disease. We tested whether multiparity induces oxidative stress in rat vascular tissue. Coronary arteries and thoracic aorta were isolated from multiparous and age-matched virgin rats. Relaxation to ACh and sodium nitroprusside (SNP) was measured by wire myography. We also tested the effect of the superoxide dismutase mimetic MnTE2PyP (30 microM), the NADPH oxidase inhibitor apocynin (10 microM), and the peroxynitrite scavenger FeTPPs (10 microM) on ACh-mediated relaxation in coronary arteries. Vascular superoxide anion was measured using the luminol derivative L-012 and nitric oxide (NO) generation by the Griess reaction. Multiparity reduced maximal response and sensitivity to ACh in coronary arteries [maximal relaxation (E(max)): multiparous 49+/-3% vs. virgins 95%+/-3%; EC(50): multiparous 135+/-1 nM vs. virgins 60+/-1 nM], and in aortic rings (E(max): multiparous 38+/-3% vs. virgins 79+/-4%; EC(50): multiparous 160+/-2 nM vs. virgins 90+/-3 nM). Coronary arteries from the two groups relaxed similarly to SNP. Superoxide anions formation was significantly higher in both coronary arteries (2.8-fold increase) and aorta (4.1-fold increase) from multiparous rats compared with virgins. In multiparous rats, incubation with MnTE2PyP, apocynin, and FeTPPs improved maximal relaxation to ACh (MnTE2PyP: 74+/-5%; vehicle: 41+/-5%; apocynin: 73+/-3% vs. vehicle: 41+/-3%; FeTPPs: 72+/-3% vs. vehicle: 46+/-3%) and increased sensitivity (EC(50): MnTE2PyP: 61+/-0.5 nM vs. vehicle: 91+/-1 nM; apocynin: 45+/-3 nM vs. vehicle: 91+/-6 nM; FeTPP: 131 +/- 2 nM vs. vehicle: 185+/-1 nM). Multiparity also reduced total nitrate/nitrite levels (multiparous: 2.5+/-2 micromol/mg protein vs. virgins: 7+/-1 micromol/mg protein) and endothelial nitric oxide synthase protein levels (multiparous: 0.53+/-0.1 protein/actin vs. virgins: 1.0+/-0.14 protein/actin). These data suggest that multiparity induces endothelial dysfunction through decreased NO bioavailability and increased reactive oxygen species formation.     

Regulation of Bcl-2 protein expression during oxidative stress in neuronal and in endothelial cells.

The relationship between oxidative stress and Bcl-2 expression was investigated in two different experimental models of oxidative stress. Acute oxidative stress was assessed by measuring, with fluorescence microscopy and cytofluorimetry, the increase in fluorescence of the oxidation-sensitive probe dihydrorhodamine 123, both in retinal rod receptor cells exposed to bright light (0.32 mW/cm(2) for 15 minutes) and in human endothelial cells treated with the immunosuppressant cyclosporin A (200 microM for 21 h). In both cell types, acute oxidative stress reduced Bcl-2 expression and also caused a significant increase in the level of nucleosomes. Interestingly, chronic treatment with clinical concentrations of cyclosporin A (0.5-2.5 microM for 8 days) led to a significant increase in Bcl-2 expression, while nucleosomes were similar to control level. This suggests that up-regulation of Bcl-2 protein by low levels of oxidants may represent a critical factor in cellular adaptation to drug toxicity.     

Atrial fibrosis in a chronic murine model of obstructive sleep apnea: mechanisms and prevention by mesenchymal stem cells

Background

OSA increases atrial fibrillation (AF) risk and is associated with poor AF treatment outcomes. However, a causal association is not firmly established and the mechanisms involved are poorly understood. The aims of this work were to determine whether chronic obstructive sleep apnea (OSA) induces an atrial pro-arrhythmogenic substrate and to explore whether mesenchymal stem cells (MSC) are able to prevent it in a rat model of OSA.

Methods

A custom-made setup was used to mimic recurrent OSA-like airway obstructions in rats. OSA-rats (n = 16) were subjected to 15-second obstructions, 60 apneas/hour, 6 hours/day during 21 consecutive days. Sham rats (n = 14) were placed in the setup but no obstructions were applied. In a second series of rats, MSC were administered to OSA-rats and saline to Sham-rats. Myocardial collagen deposit was evaluated in Picrosirius-red stained samples. mRNA expression of genes involved in collagen turnover, inflammation and oxidative stress were quantified by real time PCR. MMP-2 protein levels were quantified by Western Blot.

Results

A 43% greater interstitial collagen fraction was observed in the atria, but not in the ventricles, of OSA-rats compared to Sham-rats (Sham 8.32 ± 0.46% vs OSA 11.90 ± 0.59%, P < 0.01). Angiotensin-I Converting Enzyme (ACE) and Interleukin 6 (IL-6) expression were significantly increased in both atria, while Matrix Metalloproteinase-2 (MMP-2) expression was decreased. MSC administration blunted OSA-induced atrial fibrosis (Sham + Saline 8.39 ± 0.56% vs OSA + MSC 9.57 ± 0.31%, P = 0.11), as well as changes in MMP-2 and IL-6 expression. Interleukin 1-β (IL-1β) plasma concentration correlated to atrial but not ventricular fibrosis. Notably, a 2.5-fold increase in IL-1β plasma levels was observed in the OSA group, which was prevented in rats receiving MSC.

Conclusions

OSA induces selective atrial fibrosis in a chronic murine model, which can be mediated in part by the systemic and local inflammation and by decreased collagen-degradation. MSCs transplantation prevents atrial fibrosis, suggesting that these stem cells could counterbalance inflammation in OSA.     

Erythropoietin induces heme oxygenase-1 expression and attenuates oxidative stress

Recent studies have established that erythropoietin (EPO) is a pleiotropic cytokine. In this study we investigated whether pleiotropic effects of EPO may involve regulation of heme oxygenase (HO)-1, an anti-oxidative stress protein. A stimulatory effect of EPO on HO-1 expression was demonstrated in cultured renal endothelial cells, in which EPO decreased intracellular oxidative stress and provided cytoprotection against H(2)O(2). These beneficial effects were partially reversed by a HO-1 inhibitor. We then evaluated whether EPO induces HO-1 and ameliorates renal injury in vivo. Administration of EPO to Dahl salt-sensitive (DS) rats with low salt diet, a model of chronic tubulointerstitial injury, reduced proteinuria, and renal injury including peritubular capillaries rarefaction as compared to vehicle-treated DS rats. This renoprotection was associated with up-regulation of HO-1 in the kidney. In conclusion, EPO-induced HO-1 expression is likely to provide cytoprotection against oxidative stress.     

Zonal expression of StARD1 and oxidative stress in alcoholic-related liver disease

Alcoholic-related liver disease (ALD) is one of the leading causes of chronic liver disease and morbidity. Unfortunately, the pathogenesis of ALD is still incompletely understood. StARD1 has emerged as a key player in other etiologies of chronic liver disease, and alcohol-induced liver injury exhibits zonal distribution. Here, we report that StARD1 is predominantly expressed in perivenous (PV) zone of liver sections from mice-fed chronic and acute-on-chronic ALD models compared to periportal (PP) area and is observed as early as 10 days of alcohol feeding. Ethanol and chemical hypoxia induced the expression of StARD1 in isolated primary mouse hepatocytes. The zonal-dependent expression of StARD1 resulted in the accumulation of cholesterol in mitochondria and increased lipid peroxidation in PV hepatocytes compared to PP hepatocytes, effects that were abrogated in PV hepatocytes upon hepatocyte-specific Stard1 KO mice. Transmission electron microscopy indicated differential glycogen and lipid droplets content between PP and PV areas, and alcohol feeding decreased glycogen content in both areas while increased lipid droplets content preferentially in PV zone. Moreover, transmission electron microscopy revealed that mitochondria from PV zone exhibited reduced length with respect to PP area, and alcohol feeding increased mitochondrial number, particularly, in PV zone. Extracellular flux analysis indicated lower maximal respiration and spared respiratory capacity in control PV hepatocytes that were reversed upon alcohol feeding. These findings reveal a differential morphology and functional activity of mitochondria between PP and PV hepatocytes following alcohol feeding and that StARD1 may play a key role in the zonal-dependent liver injury characteristic of ALD.     

BRG1 interacts with Nrf2 to selectively mediate HO-1 induction in response to oxidative stress

NF-E2-related factor 2 (Nrf2) regulates antioxidant-responsive element-mediated induction of cytoprotective genes in response to oxidative stress. The purpose of this study was to determine the role of BRG1, a catalytic subunit of SWI2/SNF2-like chromatin-remodeling complexes, in Nrf2-mediated gene expression. Small interfering RNA knockdown of BRG1 in SW480 cells selectively decreased inducible expression of the heme oxygenase 1 (HO-1) gene after diethylmaleate treatment but did not affect other Nrf2 target genes, such as the gene encoding NADPH:quinone oxidoreductase 1 (NQO1). Chromatin immunoprecipitation analysis revealed that Nrf2 recruits BRG1 to both HO-1 and NQO1 regulatory regions. However, BRG1 knockdown selectively decreased the recruitment of RNA polymerase II to the HO-1 promoter but not to the NQO1 promoter. HO-1, but not other Nrf2-regulated genes, harbors a sequence of TG repeats capable of forming Z-DNA with BRG1 assistance. Similarly, replacement of the TG repeats with an alternative Z-DNA-forming sequence led to BRG1-mediated activation of HO-1. These results thus demonstrate that BRG1, through the facilitation of Z-DNA formation and subsequent recruitment of RNA polymerase II, is critical in Nrf2-mediated inducible expression of HO-1.