Effect of rMnSOD on Sodium Reabsorption in Renal Proximal Tubule in Ochratoxin A-Treated Rats

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium that represent toxic real threat for human beings and animal health. In this study we evaluated the effect of a new recombinant mitochondrial manganese containing superoxide dismutase (rMnSOD) on oxidative stress and on the alterations of fluid reabsorption in renal proximal tubule (PT) as possible causes of OTA nephrotoxicity. Finally, we have measured the concentration of O₂^- in the kidney through dihydroethidium assay (DHE) and nitric oxide (NO) concentration through nitrites and nitrates assay. Male Sprague Dawley rats weighing 120-150 g were treated for 14 days by gavage, as follows: Control group, 12 rats received a corresponding amount of saline solution (including 10% DMSO); rMnSOD group, 12 rats treated with rMnSOD (10 µg/kg bw); OTA group, 12 rats treated with OTA (0.5 mg/kg bw) dissolved in 10% DMSO and then scaled to required volume with corn oil; rMnSOD + OTA, 12 rats treated with rMnSOD (10 µg/kg bw) plus OTA (0.5 mg/kg bw). Our results have shown that rMnSOD restores the alteration of reabsorption in PT in rats treated with OTA plus rMnSOD, probably through the response to pressure natriuresis, where nitric oxide plays a key role. Moreover, rMnSOD prevents the nephrotoxicity induced by OTA probably restoring the balance between superoxide and NO that is most probably the cause of hypertension and renal functional alterations through the inhibition of NO synthase. In conclusion these data provide important information for understanding of mechanism of toxic action of OTA. J. Cell. Biochem. 119: 424-430, 2018. © 2017 Wiley Periodicals, Inc.

S-Nitrosylation of Bcl-2 Negatively Affects Autophagy in Lung Epithelial Cells

Autophagy is a catabolic cellular mechanism involving lysosomal degradation of unwanted cellular components. Interaction between Beclin-1 and Bcl-2 proteins is known to play a critical role in the initiation of autophagy. We report that malignantly transformed lung epithelial cells are resistant to autophagy and express lower basal levels of autophagic proteins, Beclin-1 and LC3-II as compared to non-tumorigenic cells. Additionally, increased levels of nitric oxide (NO) and Bcl-2 were observed in transformed cells. Nitric oxide was found to negatively regulate autophagy initiation and autophagic flux by nitrosylating Bcl-2 and stabilizing its interaction with Beclin-1, resulting in inhibition of Beclin-1 activity. An increase in the apoptotic initiator caspase-9 and the apoptosis and autophagy-associated kinase p38/MAPK in both cell types indicated possible autophagy-apoptosis crosstalk. Pre-treatments with ABT-737 (Bcl-2 inhibitor) and aminoguanidine (NO inhibitor), and transfection with a non-nitrosylable Bcl-2 cysteine double-mutant plasmid resulted in increased autophagic flux (LC3-II/p62 upregulation) corresponding with decreased S-nitrocysteine expression, thus corroborating the regulatory role of Bcl-2 S-nitrosylation in autophagy. In conclusion, our study reveals a novel mechanism of autophagy resistance via post-translational modification of Bcl-2 protein by NO, which may be critical in driving cellular tumorigenesis.

In oesophageal squamous cells, nitric oxide causes S-nitrosylation of Akt and blocks SOX2 (sex determining region Y-box 2) expression

OBJECTIVE

Barrett's metaplasia might develop if GORD causes oesophageal squamous cells to convert into columnar cells. Acid and bile exposures upregulate columnar differentiation genes like CDX2 in oesophageal squamous cells, but it is not known if such exposures downregulate squamous differentiation genes like SOX2. In addition to acid and bile, patients with GORD also have high oesophageal concentrations of nitric oxide (NO). This study aims to determine how acid, bile salts and NO affect genes that influence oesophageal cell phenotype.

DESIGN

Oesophageal squamous cells from patients with Barrett's oesophagus were exposed to acidic bile salts or NOC-9 (an NO donor). SOX2, p63 (squamous transcription factor) and CDX2 mRNAs were measured by quantitative RT-PCR. SOX2 and its regulatory Akt pathway proteins were evaluated by western blotting. S-nitrosylation by NO was blocked by dithiothreitol. Immunohistochemistry for SOX2 was performed on the oesophagus of rats with surgically induced GORD which were fed diets with and without nitrite supplementation.

RESULTS

In oesophageal squamous cells, NO profoundly decreased SOX2 protein and caused a significantly greater decrease in SOX2 mRNA than did acidic bile salts. NO also decreased p63 and increased CDX2 expression. NO caused S-nitrosylation of Akt, blocking its phosphorylation. Akt pathway inhibition by LY294002 or Akt siRNA reduced SOX2 mRNA. Rats fed with nitrite-supplemented diets exhibited weaker SOX2 oesophageal staining than rats fed with normal diets.

CONCLUSIONS

In oesophageal squamous cells, NO blocks SOX2 expression through Akt S-nitrosylation. NO also increases CDX2 and decreases p63 expression. By triggering molecular events preventing squamous differentiation while promoting intestinal differentiation, NO might contribute to Barrett's pathogenesis.

Nitric oxide mediates bleomycin-induced angiogenesis and pulmonary fibrosis via regulation of VEGF

Pulmonary fibrosis is a progressive lung disease hallmarked by increased fibroblast proliferation, amplified levels of extracellular matrix deposition and increased angiogenesis. Although dysregulation of angiogenic mediators has been implicated in pulmonary fibrosis, the specific rate-limiting angiogenic markers involved and their role in the progression of pulmonary fibrosis remains unclear. We demonstrate that bleomycin treatment induces angiogenesis, and inhibition of the central angiogenic mediator VEGF using anti-VEGF antibody CBO-P11 significantly attenuates bleomycin-induced pulmonary fibrosis in vivo. Bleomycin-induced nitric oxide (NO) was observed to be the key upstream regulator of VEGF via the PI3k/Akt pathway. VEGF regulated other important angiogenic proteins including PAI-1 and IL-8 in response to bleomycin exposure. Inhibition of NO and VEGF activity significantly mitigated bleomycin-induced angiogenic and fibrogenic responses. NO and VEGF are key mediators of bleomycin-induced pulmonary fibrosis, and could serve as important targets against this debilitating disease. Overall, our data suggests an important role for angiogenic mediators in the pathogenesis of bleomycin-induced pulmonary fibrosis.

Nitric Oxide Prevents Mouse Embryonic Stem Cell Differentiation Through Regulation of Gene Expression, Cell Signaling, and Control of Cell Proliferation

Nitric oxide (NO) delays mouse embryonic stem cell (mESC) differentiation by regulating genes linked to pluripotency and differentiation. Nevertheless, no profound study has been conducted on cell differentiation regulation by this molecule through signaling on essential biological functions. We sought to demonstrate that NO positively regulates the pluripotency transcriptional core, enforcing changes in the chromatin structure, in addition to regulating cell proliferation, and signaling pathways with key roles in stemness. Culturing mESCs with 2 μM of the NO donor diethylenetriamine/NO (DETA/NO) in the absence of leukemia inhibitory factor (LIF) induced significant changes in the expression of 16 genes of the pluripotency transcriptional core. Furthermore, treatment with DETA/NO resulted in a high occupancy of activating H3K4me3 at the Oct4 and Nanog promoters and repressive H3K9me3 and H3k27me3 at the Brachyury promoter. Additionally, the activation of signaling pathways involved in pluripotency, such as Gsk3-β/β-catenin, was observed, in addition to activation of PI3 K/Akt, which is consistent with the protection of mESCs from cell death. Finally, a decrease in cell proliferation coincides with cell cycle arrest in G2/M. Our results provide novel insights into NO-mediated gene regulation and cell proliferation and suggest that NO is necessary but not sufficient for the maintenance of pluripotency and the prevention of cell differentiation. J. Cell. Biochem. 117: 2078-2088, 2016. © 2016 Wiley Periodicals, Inc.

Cinnamaldehyde and nitric oxide attenuate advanced glycation end products-induced the Jak/STAT signaling in human renal tubular cells

Cinnamaldehyde is a major and a bioactive compound isolated from the leaves of Cinnamomum osmophloeum kaneh. It possesses anti-diabetic properties in vitro and in vivo and has anti-inflammatory and anti-cancer effects. To explore whether cinnamaldehyde was linked to altered advanced glycation end products (AGE)-mediated diabetic nephropathy, the molecular mechanisms of cinnamaldehyde responsible for inhibition of AGE-reduced nitric oxide (NO) bioactivity in human renal proximal tubular cells were examined. We found that raising the ambient AGE concentration causes a dose-dependent decrease in NO generation. Cinnamaldehyde significantly reverses AGE-inhibited NO generation and induces high levels of cGMP synthesis and PKG activation. Treatments with cinnamaldehyde, the NO donor S-nitroso-N-acetylpenicillamine, and the JAK2 inhibitor AG490 markedly attenuated AGE-inhibited NOS protein levels and NO generation. Moreover, AGE-induced the JAK2-STAT1/STAT3 activation, RAGE/p27(Kip1) /collagen IV protein levels, and cellular hypertrophy were reversed by cinnamaldehyde. The ability of cinnamaldehyde to suppress STAT activation was also verified by the observation that it significantly increased SCOS-3 protein level. These findings indicate for the first time that in the presence of cinnamaldehyde, the suppression of AGE-induced biological responses is probably mediated by inactivating the JAK2-STAT1/STAT3 cascade or activating the NO pathway.

Regulation of hypoxia-inducible factor-1a by reactive oxygen species: new developments in an old debate

Hypoxia-Inducible Factor-1 (HIF-1) has been largely studied for its role in cell survival in hypoxic conditions. The regulation of HIF-1 is a complex process and involves a number of molecules and pathways. Among these mechanisms a direct regulatory role of reactive oxygen species (ROS) on HIF-1 alpha subunit has received a great deal of attention and the existing body of literature includes many contradictory findings. Other intermediates such as nitric oxide (NO), specific microRNAs (miR), and transcriptional and post-translational modification have also been implicated as players in ROS mediated HIF-1a regulation. The focus of this review is to present the past conflicting evidence along with more recent findings in order to relate various aspects of this complex process. Aside from the direct role of ROS on HIF-1a regulation under hypoxia and normoxia, we analyzed the effect of different sources and concentrations of NO and the interplay between superoxide (SO) and NO in this process. We also present findings on transcriptional and translational regulation of HIF-1a via ROS and the interplay with microRNAs in this process. This review further provides insight on ERK and PI3K/AKT signaling as a common mechanism relating several pathways of ROS mediated HIF-1a regulation. Ultimately further research and discovery regarding HIF-1 regulation by oxidative stress is warranted for better understanding of disease development and potential therapeutics for pathologies such as cancer, inflammatory diseases, and ischemia-reperfusion injury.

Effects of an aglycone-rich biotransformed soybean extract in human endothelial cells

Estrogen replacement therapy is not thought to be a safe treatment for prevention of cardiovascular disease in menopausal women; isoflavones are a possible alternative. Estrogen produces beneficial effects on the cardiovascular system by enhancing production of nitric oxide, a vasoprotective and antiatherosclerotic agent. Estrogen-like compounds such as isoflavones are also suggested for increasing nitric oxide production. Isoflavones are present mainly in soy foods as glucosides, but soy isoflavone aglycones, the biologically active estrogen-like compounds, are absorbed faster and in higher amounts than their glucoside derivatives and show higher biological activity, implying that they may be more effective in preventing chronic diseases such as coronary heart disease. We evaluated an extract of soybeans fermented by Aspergillus awamori on which polyphenol glucosides were biotransformed to aglycone forms on production of nitric oxide, prostaglandin E2 and endothelin-1 in vitro in human endothelial cells, comparing it with a non-fermented extract. Bioconverted soybean extracts enhanced endothelin-1, nitric oxide and prostaglandin E2 production, while the unfermented extract only enhanced endothelin-1 production. Thus, only the aglycone-rich forms of soybean extracts were able to increase nitric oxide and prostaglandin E2 production, demonstrating that, in endothelial cells in vitro, they may be usable as therapeutic agents against the development of atherosclerosis.

Low molecular weight heparin mediated regulation of nitric oxide synthase during burn wound healing

Nitric oxide (NO) is an important signal molecule in many types of cells and tissues. Efficiently balanced NO production was noted to play an important role in the healing of burns. Inducible nitric oxygen synthase (iNOS) is responsible for the discontinuous synthesis of high amounts of NO. Dysregulation of nitric oxygen synthase (NOS) activity has been associated with multiple organ failure in burn patients and may therefore represent a novel therapeutic target in such circumstances. Heparin and low molecular weight heparin (LMWH) derivatives may offer therapeutic benefit for inflammatory diseases, whereas NO plays a protagonist role. Burn injury in humans has been associated with a significant increase in NO(2)/NO(3) (nitrite/nitrate) plasma levels. In this prospective study burn patients were treated with and without LMWH to provide evidence that LMWH has NOS-reducing activity. This was proved by colorimetric and immunohistological studies. There was a significantly different NOS activity between the treated and the control group and our results suggest that LMWH was more effective in the treatment of burn patients through iNOS inhibition. Treatment with LMWH was initiated within 6 h post-burn.

ESTIMATION OF THE NITRIC OXIDE FORMED FROM HYDROXYLAMINE BY NITROSOMONAS

1. Nitric oxide that was produced by reducing nitrite with an excess of acidified potassium iodide under nitrogen in Warburg respirometer flasks was rapidly absorbed by a solution of permanganate in sodium hydroxide held in the side arm. A small amount of nitrous oxide (or nitrogen) that was also produced was not absorbed. 2. By using a quantitative method for the recovery of nitrite from samples of the alkaline permanganate, it was found that the sum of the nitrite N formed and the residual nitrous oxide N was equivalent to the nitrite N used to generate the gases. These results showed that alkaline permanganate completely oxidized nitric oxide to nitrite. The method was suitable for determining 0.4-20 mumoles of nitric oxide. 3. The technique was used to determine the nitric oxide content of the nitrogenous gas that was produced anaerobically from hydroxylamine by an extract of the autotrophic nitrifying micro-organism Nitrosomonas in the presence of methylene blue as electron acceptor.