Differential cytostatic effects of NO donors and NO producing cells

Superparamagnetic Iron Oxide Nanoparticles Reprogram the Tumor Microenvironment and Reduce Lung Cancer Regrowth after Crizotinib Treatment

ALK-positive NSCLC patients demonstrate initial responses to ALK tyrosine kinase inhibitor (TKI) treatments, but eventually develop resistance, causing rapid tumor relapse and poor survival rates. Growing evidence suggests that the combination of drug and immune therapies greatly improves patient survival; however, due to the low immunogenicity of the tumors, ALK-positive patients do not respond to currently available immunotherapies. Tumor-associated macrophages (TAMs) play a crucial role in facilitating lung cancer growth by suppressing tumoricidal immune activation and absorbing chemotherapeutics. However, they can also be programmed toward a pro-inflammatory tumor suppressive phenotype, which represents a highly active area of therapy development. Iron loading of TAMs can achieve such reprogramming correlating with an improved prognosis in lung cancer patients. We previously showed that superparamagnetic iron oxide nanoparticles containing core-cross-linked polymer micelles (SPION-CCPMs) target macrophages and stimulate pro-inflammatory activation. Here, we show that SPION-CCPMs stimulate TAMs to secrete reactive nitrogen species and cytokines that exert tumoricidal activity. We further show that SPION-CCPMs reshape the immunosuppressive Eml4-Alk lung tumor microenvironment (TME) toward a cytotoxic profile hallmarked by the recruitment of CD8+ T cells, suggesting a multifactorial benefit of SPION-CCPM application. When intratracheally instilled into lung cancer-bearing mice, SPION-CCPMs delay tumor growth and, after first line therapy with a TKI, halt the regrowth of relapsing tumors. These findings identify SPIONs-CCPMs as an adjuvant therapy, which remodels the TME, resulting in a delay in the appearance of resistant tumors.

Molluscicidal and antioxidant activities of silver nanoparticles on the multi-species of snail intermediate hosts of schistosomiasis

BACKGROUND

Schistosomiasis, also known as bilharzia, is the second important parasitic disease after malaria. The present study aimed to evaluate the molluscicidal effects of silver nanoparticles on Biomphalaria alexandrina, B. glabrata, Oncomelania hupensis, snail intermediate hosts of intestinal schistosomes (i.e. Schistosoma mansoni and S. japonicum), along with the changes their antioxidant enzymes.

METHODS

Silver (Ag) nano powder (Ag-NPs) was selected to test the molluscicidal effects on three species of freshwater snails. Exposure to Ag-NPs induced snail mortality and the LC50 and LC90 values of Ag-NPs for each snail species were calculated by probit analysis. Control snails were maintained under the same experimental conditions in dechlorinated water. Snail hemolymph was collected to measure the levels of antioxidant enzymes, such as total antioxidants capacity (TCA), glutathione (GSH), catalase (CAT) and nitric oxide (NO). In addition, the non-target organism, Daphnia magna, was exposed to a series of Ag-NPs concentration, similar to the group of experimental snails, in order to evaluate the LC50 and LC90 and compare these values to those obtained for the targeted snails.

RESULTS

The results indicated that Ag-NPs had a molluscicidal effect on tested snails with the variation in lethal concentration. The LC50 values of Ag-NPs for B. alexandrina snails exposed for 24, 48, 72 hrs and 7 days were 7.91, 5.69, 3.83 and 1.91 parts per million (ppm), respectively. The LC50 values for B. glabrata snails exposed for 24, 48, 72 hrs and 7 days were 16.55, 10.44, 6.91 and 4.13 ppm, respectively, while the LC50 values for O. hupensis snails exposed for 24, 48, 72 hrs and 7 days were 46.5, 29.85, 24.49 and 9.62 ppm, respectively. Moreover, there is no mortality detected on D. magna when exposed to more than double and half concentration (50 ppm) of Ag-NPs during a continuous period of 3 hrs, whereas the LC90 value for B. alexandrina snails was 18 ppm. The molluscicidal effect of the synthesized Ag-NPs seems to be linked to a potential reduction of the antioxidant activity in the snail's hemolymph.

CONCLUSIONS

Synthesized Ag-NPs have a clear molluscicidal effect against various snail intermediate hosts of intestinal schistosome parasites and could potentially serve as next generation molluscicides.

Nitric Oxide Synthase Dependency in Hydroxyurea Inhibition of Erythroid Progenitor Growth

Hydroxyurea (HU) causes nitric oxide (NO) bioactivation, acting as both a NO donor and a stimulator of NO synthase (NOS). To examine whether HU effects are NO mediated by chemical degradation or enzymatic induction, we studied human and mouse erythroid cells during proliferation, apoptosis, and differentiation. The HU and NO donor demonstrated persisted versus temporary inhibition of erythroid cell growth during differentiation, as observed by γ- and β-globin gene expression. HU decreased the percentage of erythroleukemic K562 cells in the G2/M phase that was reversed by N-nitro l-arginine methyl ester hydrochloride (L-NAME). Besides activation of endothelial NOS, HU significantly increased apoptosis of K562 cells, again demonstrating NOS dependence. Administration of HU to mice significantly inhibited colony-forming unit-erythroid (CFU-E), mediated by NOS. Moreover, burst-forming-units-erythroid (BFU-E) and CFU-E ex vivo growth was inhibited by the administration of nitrate or nitrite to mice. Chronic in vivo NOS inhibition with L-NAME protected the bone marrow cellularity despite HU treatment of mice. NO metabolites and HU reduced the frequency of NOS-positive cells from CFU-E and BFU-E colonies that was reverted by NOS inhibition. HU regulation of the G2/M phase, apoptosis, differentiation, cellularity, and NOS immunoreactive cells was NOS dependent. Inhalation of NO therapy as well as strategies to increase endogenous NO production could replace or enhance HU activity.

Use of a solid mixture containing diethylenetriamine/nitric oxide (DETANO) to liberate nitric oxide gas in the presence of horticultural produce to extend postharvest life

Postharvest treatment of fruit and vegetables with a low concentration of nitric oxide gas can extend postharvest life but application of nitric oxide by release from a gas cylinder is not feasible for many horticultural situations. This paper reports on development of a solid mixture to generate nitric oxide gas in the presence of horticultural produce. The solid NO-donor compound, diethylenetriamine/nitric oxide (DETANO) was found to quantitatively liberate nitric oxide in the presence of a range of acidic substances including citric acid. A solid mixture of DETANO and citric acid with wheat starch added as a filler and moisture absorbent in the ratio of 1:10:20 was found to be stable for at least six months when stored in dry air. However, in humid air, absorption of moisture from the atmosphere led to reaction of DETANO with citric acid and the evolution of nitric oxide gas. When the dry mixture was placed in a container with strawberry and mushroom, the moisture given off by produce activated the mixture and resulted in a similar extension in postharvest life as achieved by direct fumigation with nitric oxide gas. Commercial use of such a solid mixture could be through tablets or sachets which are more manageable in a farm or packing house than gas fumigation.

Nitric oxide stimulates PC12 cell proliferation via cGMP and inhibits at higher concentrations mainly via energy depletion

We investigated the mechanisms by which nitric oxide (NO) from an NO donor (DETA/NO) regulates proliferation of pheochromocytoma PC12 cells. The NO donor stimulated proliferation at low concentrations, but reversibly and completely inhibited proliferation at higher concentrations. The stimulation (but not the inhibition) of proliferation was apparently due to NO stimulation of soluble guanylate cyclase to produce cGMP, as it was prevented by a specific cyclase inhibitor (ODQ), and replicated by a cell-permeable form of cGMP. The NO-induced cytostasis was not reversed by inhibitors of MEK kinase or poly(ADP-ribose)polymerase, or by treatments that bypass inhibition of ribonucleotide reductase or ornithine decarboxylase. Cytostatic concentrations of DETA/NO strongly inhibited respiration of PC12 cells, and specific respiratory inhibitors (rotenone, myxothiazol, or azide) caused complete cytostasis. Uridine and pyruvate reversed the cytostasis induced by the specific respiratory inhibitors, but not that induced by DETA/NO. However, the combination of uridine, pyruvate, and N-acetyl-cysteine did reverse DETA/NO-induced cytostasis. DETA/NO strongly and progressively inhibited glycolysis measured by glucose consumption, lactate production, and ATP level, and a specific glycolytic inhibitor (5 mM 2-deoxy-d-glucose) caused complete cytostasis. Our results indicate that NO at low concentrations increases cell proliferation via cGMP, while high concentrations of NO block proliferation via inhibition of both glycolysis and respiration, causing energy depletion.

Modification of endoplasmic reticulum Ca2+ stores by select oxidants produces changes reminiscent of those in cells from patients with Alzheimer disease

Abnormalities in calcium homeostasis and oxidative processes occur in fibroblasts from patients with Alzheimer disease (AD) and in fibroblasts and neurons from transgenic mice bearing a presenilin-1 (PS-1) mutation. Bombesin-releasable endoplasmic reticulum Ca2+ stores (BRCS) are exaggerated in all of these cells. Our previous studies show that H2O2 exaggerates BRCS. The goal of the present study was to determine whether select reactive species exaggerate BRCS in cultured human fibroblasts and to determine if the ability of fibroblasts to handle these specific oxidant species is altered in cells from AD patients. Two fluorescent indicators were used to distinguish different reactive oxygen species (ROS): 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethyl ester) (c-DCF) and 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM). ROS were produced by a variety of oxidants, including tert-butyl-hydroxyperoxide (t-BHP), hypoxanthine/xanthine oxidase, S-nitroso-N-acetylpenicillamine, 3-morpholinosydnonimine, and sodium nitroprusside. Different oxidants selectively induced various ROS in distinct patterns. These oxidants also induced selective modification in [Ca2+]i and/or BRCS. Of the several oxidants tested, t-BHP was most specific for exaggerating BRCS without affecting basal [Ca2+]i and inducing only c-DCF-detectable ROS. On the other hand, the results show that NO that reacted with DAF-FM was not responsible for alterations in BRCS. Furthermore, the c-DCF-detectable ROS production induced by t-BHP was higher in fibroblasts from AD patients bearing a PS-1 mutation (n = 7) than in those from aged controls (n = 8). The higher production of c-DCF-detectable ROS may underlie the exaggeration of BRCS in fibroblasts from AD patients. Thus, these results are consistent with the hypothesis that abnormalities in selective cellular ROS cause AD-related changes in intracellular calcium regulation.

Nitric oxide in control of luminescence from hatchetfish(Argyropelecus hemigymnus) photophores

Nitric oxide synthase-like immunoreactivity (NOS-LI IR) was detected by immunohistochemistry in ventral light organs of the mesopelagic fish, Argyropelecus hemigymnus. Strong NOS-LI IR was present in nerve fibres and in other cells central for production or modulation of light:immunoreactive fibres surrounded the photophores, and were also present in the filter area. Filter cells, particularly in the outer layers, showed strong IR throughout the cytoplasm. Pharmacological studies suggested that nitric oxide(NO) modulates adrenaline-stimulated light emission, and that the modulation is correlated to the ability of the light organ to respond to adrenaline. Adrenaline is known to produce two different types of light response in isolated photophores from Argyropelecus: a slow, long-lasting, high intensity response, or a fast and weak response of short duration. Incubation of photophores in the NO donors sodium nitroprusside or S-nitroso-N-acetylpenicillamine prior to adrenaline stimulation reduced the intensity of the strong and long-lasting type of response, but had little or even a potentiating effect on the weakly responding photophores. Hydroxylamine, which is converted to NO if catalase activity is present in the tissue, reduced the duration and the intensity of the adrenaline response in all tested organs. The NOS-inhibitor l-thiocitrulline potentiated the adrenaline response in the weakly responding organs; the weaker the adrenaline effect, the stronger the potentiation caused by l-thiocitrulline. The strongly responding organs were instead inhibited by l-thiocitrulline. The results suggest that NO has an important role in the control of light emission from Argyropelecus hemigymnus photophores. The cGMP analogue dibutyryl cGMP, the guanylate cyclase inhibitor ODQ and the phosphodiesterase inhibitor pentoxiphylline had no effect, indicating that the NO effect does not involve cGMP.

Free radical scavengers in susceptible/resistant Biomphalaria alexandrina snails before and after infection

The activities of catalase (Cat), superoxide dismutase (SOD), glutathione peroxidase (GSHPx), glutathione transferase (GST), glucose-6-phosphate dehydrogenase (G6PD) and glyceraldehyde3-phosphate dehydrogenase (G3PD) were studied in tissue and hemolymph of susceptible (S) (EgBS(2)) and resistant (R) (EgBR(2)) Biomphalaria alexandrina snails. The results showed that CAT and GST were higher in the hemolymph of snails susceptible to Schistosoma mansoni than in that of snails resistant to infestation, while SOD and G3PD were lower in the susceptible snails. The role of these enzymes as free radical scavengers was traced 1 and 24 h after infection of the two snail lines with S. mansoni. Moreover, the activities of SOD and G3PD were also measured 2 and 4 weeks post infection. The results revealed that the overall enzymatic activities were higher in susceptible than in resistant snail tissues. After 1 h of infection, all enzymes were increased in R and S snails except GST and G6PD which decreased in S snails. After 24 h of infection, GST increased in S snails and G3PD decreased in both S and R snails while other enzymes reached normal levels.

Depletion of deoxyribonucleoside triphosphate pools in tumor cells by nitric oxide

Nitric oxide displays pro- and anti-tumor activities, prompting further studies to better understand its precise role. Nitric oxide inhibits ribonucleotide reductase (RnR), the limiting enzyme for de novo dNTP synthesis. We report here the first detailed analysis of dNTP variations induced in tumor cells by NO. NO prodrugs induced a depletion in dNTP pools and an activation of the pyrimidine salvage pathway, as did hydroxyurea, the prototypic RnR inhibitor. In the presence of dipyridamole, which blocked salvaged dNTP synthesis, depletion of dNTP pools was also observed in tumor cells cocultured with macrophages expressing the high-output iNOS activity. This effect was rapid, reversible, blocked by NO scavengers, and cGMP independent. It was quantitatively correlated to iNOS activity. In the absence of dipyridamole, NO still induced a decrease in dATP concentration in tumor cells cocultured with macrophages, whereas surprisingly, concentrations of dCTP and dTTP expanded considerably, resulting in a strong imbalance in dNTP pools. NO prodrugs did not cause such an increase in pyrimidine dNTP, suggesting that pyrimidine nucleosides were released by NO-injured macrophages. Altered dNTP levels have been reported to promote mutagenesis and apoptosis. It is suggested that abnormal changes in dNTP pools in tumors might contribute to NO-dependent toxicity.

Different capacities of carp leukocytes to encounter nitric oxide-mediated stress: a role for the intracellular reduced glutathione pool

Carp head kidney (HK) phagocytes can be stimulated by lipopolysaccharide (LPS) to produce nitric oxide (NO). High production of NO can suppress the carp immune system. Carp peripheral blood leukocytes (PBL) are highly susceptible but HK phagocytes are relatively resistant to the immunosuppressive effects of NO. This study demonstrates that the antioxidant glutathione plays an important role in the protection against nitrosative stress. Carp HK phagocytes, especially the neutrophilic granulocytes, contain higher levels of glutathione than PBL. Moreover, freshly isolated carp neutrophilic granulocytes have higher mRNA levels than PBL of glucose-6-phosphate dehydrogenase (G6PD), manganese superoxide dismutase (MnSOD) and gamma-glutamylcysteine synthetase (gamma-GCS). Since these molecules are part of the glutathione redox cycle, neutrophilic granulocytes have a higher capacity than PBL to maintain glutathione in a reduced state following nitrosative stress. When stimulated with LPS, neutrophilic granulocytes upregulate the expression of G6PD, MnSOD and gamma-GCS.

Metabolic control of resistance of human epithelial cells to H2O2 and NO stresses

The carbon flux through the oxidative branch of the pentose phosphate pathway (PPP) can be viewed as an integrator of the antioxidant mechanisms via the generation of NADPH. It could therefore be used as a control point of the cellular response to an oxidative stress. Replacement of glucose by galactose sensitized the human epithelial cell line HGT-1 to H2O2 stress. Here we demonstrate that, due to the restricted galactose flux into the PPP, the H2O2 stress led to early cellular blebbing followed by cell necrosis, these changes being associated with a fall in the NADPH/NADP+ ratio and GSH depletion. H2O2 cytotoxicity was prevented by adding 2-deoxyglucose (2dGlc). This protection was associated with an increased flow of 2-deoxyglucose 6-phosphate into the oxidative branch of the PPP together with the prevention of the NADPH/NADP+ fall and the maintenance of intracellular GSH redox homoeostasis. Inhibitors of enzyme pathways connecting the PPP to GSH recycling abolished the 2dGlc protection. In carbohydrate-free culture conditions, 2dGlc dose-dependent protective effect was paralleled by a dose-dependent influx of 2dGlc into the PPP leading to the maintenance of the intracellular redox status. By contrast, in Glc-fed cells, the PPP was not a control point of the cellular resistance to H2O2 stress as they maintained a high NADPH/NADP+ ratio. Both 2dGlc and Glc inhibited, through the maintenance of GSH redox status, NO cytotoxicity on galactose-containing Dulbecco's modified Eagle's medium (Gal-DMEM)-fed cells. 2dGlc did not prevent the fall of ATP content in NO-treated Gal-DMEM-fed cells, indicating that NO cytotoxicity was essentially due to the disruption of GSH redox homoeostasis and not to the alteration of ATP production by the mitochondrial respiratory chain. The maintenance of ATP content in NO-treated glucose-fed cells was due to their ability to derive their energy from anaerobic glycolysis. In conclusion, Gal-DMEM and 2dGlc-supplemented Gal-DMEM provide a useful system to decipher and organize into a hierarchy the targets of several stresses at the level of intact barrier epithelial cells.

Rethinking cystic fibrosis pathology: the critical role of abnormal reduced glutathione (GSH) transport caused by CFTR mutation

Though the cause of cystic fibrosis (CF) pathology is understood to be the mutation of the CFTR protein, it has been difficult to trace the exact mechanisms by which the pathology arises and progresses from the mutation. Recent research findings have noted that the CFTR channel is not only permeant to chloride anions, but other, larger organic anions, including reduced glutathione (GSH). This explains the longstanding finding of extracellular GSH deficit and dramatically reduced extracellular GSH:GSSG (glutathione disulfide) ratio found to be chronic and progressive in CF patients. Given the vital role of GSH as an antioxidant, a mucolytic, and a regulator of inflammation, immune response, and cell viability via its redox status in the human body, it is reasonable to hypothesize that this condition plays some role in the pathogenesis of CF. This hypothesis is advanced by comparing the literature on pathological phenomena associated with GSH deficiency to the literature documenting CF pathology, with striking similarities noted. Several puzzling hallmarks of CF pathology, including reduced exhaled NO, exaggerated inflammation with decreased immunocompetence, increased mucus viscoelasticity, and lack of appropriate apoptosis by infected epithelial cells, are better understood when abnormal GSH transport from epithelia (those without anion channels redundant to the CFTR at the apical surface) is added as an additional explanatory factor. Such epithelia should have normal levels of total glutathione (though perhaps with diminished GSH:GSSG ratio in the cytosol), but impaired GSH transport due to CFTR mutation should lead to progressive extracellular deficit of both total glutathione and GSH, and, hypothetically, GSH:GSSG ratio alteration or even total glutathione deficit in cells with redundant anion channels, such as leukocytes, lymphocytes, erythrocytes, and hepatocytes. Therapeutic implications, including alternative methods of GSH augmentation, are discussed.