Gene therapy via inducible nitric oxide synthase: a tool for the treatment of a diverse range of pathological conditions

Positron Emission Tomography of Nitric Oxide by a Specific Radical-Generating Dihydropyridine Tracer

Nitric oxide (NO) plays a pivotal role as a biological signaling molecule, presenting challenges in its specific detection and differentiation from other reactive nitrogen and oxygen species within living organisms. Herein, a 18F-labeled (fluorine-18, t1/2 = 109.7 min) small-molecule tracer dimethyl 4-(4-(4-[18F]fluorobutoxy)benzyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate ([18F]BDHP) is developed based on the dihydropyridine scaffold for positron emission tomography (PET) imaging of NO in vivo. [18F]BDHP exhibits a highly sensitive and efficient C-C cleavage reaction specifically triggered by NO under physiological conditions, leading to the production of a 18F-labeled radical that is readily retained within the cells. High uptakes of [18F]BDHP are found within and around NO-generating cells, such as macrophages treated with lipopolysaccharide or benzo(a)pyrene. MicroPET/CT imaging of arthritic animal model mice reveals distinct tracer accumulation in the arthritic legs, showcasing a higher distribution of NO compared with the control legs. In summary, a specific radical-generating dihydropyridine tracer with a unique radical retention strategy has been established for the marking of NO in real-time in vivo.

Measurement of Exhaled Nitric Oxide in 456 Lung Cancer Patients Using a Ringdown FENO Analyzer

The objective of this study was to investigate the clinical value of exhaled nitric oxide (NO) for diagnosing lung cancer patients by using a relatively large sample. An online and near-real-time ringdown exhaled NO analyzer calibrated by an electrochemical sensor at clinical was used for breath analysis. A total of 740 breath samples from 284 healthy control subjects (H) and 456 lung cancer patients (LC) were collected. The recorded data included exhaled NO, medications taken within the last half month, demographics, fasting status and smoking status. The LC had a significantly higher level of exhaled NO than the H (H: 21.0 ± 12.1 ppb vs. LC: 34.1 ± 17.2 ppb). The area under the receiver operating characteristic curve for exhaled NO predicting LC and H was 0.728 (sensitivity was 0.798; specificity was 0.55). There was no significant difference in exhaled NO level between groups divided by different types of LC, tumor node metastasis (TNM) stage, sex, smoking status, age, body mass index (BMI) or fasting status. Exhaled NO level alone is not a useful clinical tool for identifying lung cancer, but it should be considered when developing a diagnosis model of lung cancer by using breath analysis.

Progress in internal/external stimuli responsive fluorescent carbon nanoparticles for theranostic and sensing applications

In the past decade, fluorescent carbon nanoparticles (FNPs) prepared from natural resources and biomaterials have been attractive due to their various properties, such as unique optical properties, great biocompatibility, water dispersion, and facile surface functionalization. Depending on the properties of the carbon sources and the subsequent carbonization processes, internal/external stimuli responsive carbon nanoparticles have been generated that are useful for theranostic and sensing applications. In this review, we highlight the recent developments in the use of FNPs in nanomedicine in great detail, particularly for FNPs responding to internal stimuli, including redox, pH, and enzymes, and external stimuli, including temperature, light, and magnetic fields, for drug delivery and sensing applications. Furthermore, we hope to provide insight that could stimulate further research aiming for unparalleled useful applications. As a result, there are many possibilities that can be explored from this smart material.

Protein Nanocage-Based Photo-Controlled Nitric Oxide Releasing Platform

A photoactive NO releasing system was constructed by incorporation of NO-bound Fe-S clusters into horse spleen apoferritin cavities with high loading efficacy. The composites retained intact core-shell structure and indicated advantages such as enhanced stability, reduced cytotoxicity, efficient cellular uptake, and photocontrolled NO releasing property.

Eburicoic acid from Laetiporus sulphureus (Bull.:Fr.) Murrill attenuates inflammatory responses through inhibiting LPS-induced activation of PI3K/Akt/mTOR/NF-κB pathways in RAW264.7 cells

Excessive activation of macrophages has been implicated in various types of inflammatory injury. Suppression of macrophage activation would have therapeutic benefits, leading to the alleviation of the progression of inflammatory diseases. Eburicoic acid (EA) is one of main bioactive components isolated from Laetiporus sulphureus (Bull.:Fr.) Murrill. In our previous study, we found that EA possessed anti-inflammatory activities. However, the cellular and molecular mechanisms underlying its anti-inflammatory activities remain to be poorly understood. The present study aimed to further evaluate its effect on lipopolysaccharide (LPS)-induced inflammatory responses in RAW264.7 macrophage cells. We investigated the anti-inflammatory effect by modulating LPS-induced activation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/nuclear transcription factor-κB (NF-κB) pathway in RAW264.7 cells. The results showed that EA caused no obvious cytotoxicity, and its suitable concentrations on RAW264.7 cells were in the range from 0.02 to 0.08 μM. EA significantly inhibited the releases of inflammatory mediators, nitrite oxide (NO) and prostaglandin E2 (PGE₂); suppressed mRNA and protein expression levels of inducible nitrite oxide synthase (iNOS) and cyclooxygenase-2 COX-2 and pro-inflammatory cytokine TNF-α, IL-6, and IL-1β; and reduced levels of phosphorylated PI3K, Akt, mTOR, and NF-κBp65 in LPS-induced RAW264.7 cells in dose- and time-dependent manners. These aforementioned results indicated that EA executed anti-inflammatory effect on LPS-induced RAW264.7 cells, and this effect might be achieved via suppressing the PI3K/Akt/mTOR/NF-κB signaling pathway and inhibiting the LPS-induced productions of inflammatory mediators and pro-inflammatory cytokines.

NO Photoreleaser-Deoxyadenosine and -Bile Acid Derivative Bioconjugates as Novel Potential Photochemotherapeutics

This contribution reports the synthesis of some novel bioconjugates with anticancer activity and able to release nitric oxide (NO) under visible light excitation. The 4-nitro-2-(trifluoromethyl)aniline derivative, a suitable NO photodonor, was conjugated with 2'-deoxyadenosine and urso- and cheno-deoxycholic acid derivatives, through a thioalkylic chain or the 4-alkyl-1,2,3-triazole moiety. Photochemical experiments demonstrated the effective release of NO from 2'-deoxyadenosine and ursodeoxycholic acid conjugates under the exclusive control of visible light inputs. Studies for the in vitro antiproliferative activity against leukemic K562 and colon carcinoma HCT116 cell lines are reported for all the compounds as well as a case study of photocytotoxicity against HCT116.

Nitric oxide-mediated sensitization of resistant tumor cells to apoptosis by chemo-immunotherapeutics

The generation of NO by the various NO synthases in normal and malignant tissues is manifested by various biological effects that are involved in the regulation of cell survival, differentiation and cell death. The role of NO in the cytotoxic immune response was first revealed by demonstrating the induction of iNOS in target cells by immune cytokines (e.g. IFN-γ, IL-1, TNF-α, etc.) and resulting in the sensitization of resistant tumor cells to death ligands-induced apoptosis. Endogenous/exogenous NO mediated its immune sensitizing effect by inhibiting NF-κΒ activity and downstream, inactivating the repressor transcription factor YY1, which inhibited both Fas and DR5 expressions. In addition, NO-mediated inhibition of NF-κΒ activity and inhibition downstream of its anti-apoptotic gene targets sensitized the tumor cells to apoptosis by chemotherapeutic drugs. We have identified in tumor cells a dysregulated pro-survival/anti-apoptotic loop consisting of NF-κB/Snail/YY1/RKIP/PTEN and its modification by NO was responsible, in large, for the reversal of chemo and immune resistance and sensitization to apoptotic mechanisms by cytotoxic agents. Moreover, tumor cells treated with exogenous NO donors resulted in the inhibition of NF-κΒ activity via S-nitrosylation of p50 and p65, inhibition of Snail (NF-κΒ target gene), inhibition of transcription repression by S-nitrosylation of YY1 and subsequent inhibition of epithelial-mesenchymal transition (EMT), induction of RKIP (inhibition of the transcription repressor Snail), and induction of PTEN (inhibition of the repressors Snail and YY1). Further, each gene product modified by NO in the loop was involved in chemo-immunosensitization. These above findings demonstrated that NO donors interference in the regulatory circuitry result in chemo-immunosensitization and inhibition of EMT. Overall, these observations suggest the potential anti-tumor therapeutic effect of NO donors in combination with subtoxic chemo-immuno drugs. This combination acts on multiple facets including reversal of chemo-immune resistance, and inhibition of both EMT and metastasis.

Antitumoral gene-based strategy involving nitric oxide synthase type III overexpression in hepatocellular carcinoma

Hepatocellular carcinoma develops in cirrhotic liver. The nitric oxide (NO) synthase type III (NOS-3) overexpression induces cell death in hepatoblastoma cells. The study developed gene therapy designed to specifically overexpress NOS-3 in cultured hepatoma cells, and in tumors derived from orthotopically implanted tumor cells in fibrotic livers. Liver fibrosis was induced by CCl4 administration in mice. The first-generation adenoviruses were designed to overexpress NOS-3 or green fluorescent protein, and luciferase complementary DNA under the regulation of murine alpha-fetoprotein (AFP) and Rous Sarcoma Virus (RSV) promoters, respectively. Both adenovirus and Hepa 1-6 cells were used for in vitro and in vivo experiments. Adenoviruses were administered through the tail vein 2 weeks after orthotopic tumor cell implantation. AFP-NOS-3/RSV-luciferase increased oxidative-related DNA damage, p53, CD95/CD95L expression and caspase-8, -9 and -3 activities in cultured Hepa 1-6 cells. The increased expression of CD95/CD95L and caspase-8 activity was abolished by Nω-nitro-l-arginine methyl ester hydrochloride, p53 and CD95 small interfering RNA. AFP-NOS-3/RSV-luciferase adenovirus increased cell death markers, and reduced cell proliferation of established tumors in fibrotic livers. The increase of oxidative/nitrosative stress induced by NOS-3 overexpression induced DNA damage, p53, CD95/CD95L expression and cell death in hepatocellular carcinoma cells. The effectiveness of the gene therapy has been demonstrated in vitro and in vivo.

PnPP-19, a Synthetic and Nontoxic Peptide Designed from a Phoneutria nigriventer Toxin, Potentiates Erectile Function via NO/cGMP

PURPOSE

We designed a peptide, PnPP-19, comprising the potential active core of the Phoneutria nigriventer native toxin PnTx2-6. We investigated its role on erectile function, and its toxicity and immunogenicity.

MATERIALS AND METHODS

Erectile function was evaluated by the intracavernous pressure-to-mean arterial pressure ratio during electrical field stimulation on rat pelvic ganglia. Cavernous strips were contracted with phenylephrine and relaxation was induced by electrical field stimulation with or without PnPP-19 (10(-8) M). Activity on sodium channels was evaluated by electrophysiological screening of transfected channels on Xenopus oocytes and dorsal root ganglion cells. Antibodies were detected by indirect enzyme-linked immunosorbent assay in mice previously treated with the peptide. Histopathological studies were performed with mouse organs treated with different doses of PnPP-19.

RESULTS

PnPP-19 was able to potentiate erection at 4 and 8 Hz in vivo and ex vivo. It showed no toxicity and low immunogenicity in mice, and did not affect sodium channels or rat hearts. PnPP-19 increased cyclic guanosine monophosphate levels at 8 Hz. This effect was inhibited by L-NAME (10(-4) M). Erectile function was partially inhibited by 7-nitroindazole (10(-5) M), a selective inhibitor of neuronal nitric oxide synthase.

CONCLUSIONS

PnPP-19 potentiates erection in vivo and ex vivo via the nitric oxide/cyclic guanosine monophosphate pathway. It does not affect sodium channels or rat hearts and shows no toxicity and low immunogenicity. These findings make it a promising candidate as a novel drug in the therapy of erectile dysfunction.

A mitochondrial-targeting and NO-based anticancer nanosystem with enhanced photo-controllability and low dark-toxicity

Compared to the generation of singlet oxygen in photodynamic therapy, photo-generation of nitric oxide (NO) would not be limited by the concentration of molecular oxygen. However, therapeutic applications of exogenous nitric oxide are usually limited by its short half-life and its vulnerability to many biological substances, thus straightforward and precise control over NO delivery may be critical to its therapeutic effects. Herein, we demonstrate a mitochondrial-targeting and photoactive NO-releasing system as an anticancer drug. Fabricated by covalently incorporating a photo-responsive NO-donor and a mitochondrial targeting ligand onto carbon dots, this nanosystem exhibits a multi-functional nature which combines mitochondrial-targeting, photocontrollable NO-releasing and cell imaging. Upon cellular internalization, the nanosystem could target mitochondria effectively. Furthermore, the system displays little dark toxicity under physiological temperature; but upon light irradiation, it could release NO, efficiently damage mitochondria and consequently cause prominent apoptosis of cancer cells. Moreover, evaluated by using MTT assay, this nanosystem shows high cytotoxicity towards two cancer cell lines. These observations provide new insights for exploiting NO in disease therapy.

Preparation of a mitochondria-targeted and NO-releasing nanoplatform and its enhanced pro-apoptotic effect on cancer cells

The therapeutic applications of exogenous nitric oxide are usually limited by its short half-life and its vulnerability to many biological substances, thus straightforward and precise spatiotemporal control of NO delivery may be critical to its therapeutic effects. Herein, the mitochondria-targeted and photoresponsive NO-releasing nanosystem is demonstrated as a new approach for cancer treatment. The nanosystem is fabricated by covalently incorporating a NO photo-donor and a mitochondria targeting ligand onto carbon-dots; accordingly, multi-functionalities (mitochondria-targeting, light-enhanced efficient NO-releasing, and cell imaging) are achieved. The in vitro NO release profiles for the nanosystem show that the duration of NO release from the present C-dot-based nanosystem containing immobilized SNO can be extended up to 8 hours or more. Upon cellular internalization, the nanosystem can target mitochondria and release NO. The action of the nanosystem on three cancer cell lines is evaluated; it is found that the targeted NO-releasing system can cause high cytotoxicity towards the cancer cells by specifically damaging their mitochondria. Additionally, light irradiation can amplify the cell apoptosis by enhancing NO release. These observations demonstrate that incorporating mitochondria-targeting ligand onto a NO-releasing system can enhance its pro-apoptosis action, thereby providing new insights for exploiting NO in cancer therapy.

Inhibition of neointimal hyperplasia in a rabbit vein graft model following non-viral transfection with human iNOS cDNA

Vein graft failure caused by neointimal hyperplasia (IH) after coronary artery bypass grafting with saphenous veins is a major clinical problem. The lack of safe and efficient vectors for vascular gene transfer has significantly hindered progress in this field. We have developed a Receptor-Targeted Nanocomplex (RTN) vector system for this purpose and assessed its therapeutic efficacy in a rabbit vein graft model of bypass grafting. Adventitial delivery of β-Galactosidase showed widespread transfection throughout the vein wall on day 7, estimated at about 10% of cells in the adventitia and media. Vein grafts were then transfected with a plasmid encoding inducible nitric oxide synthase (iNOS) and engrafted into the carotid artery. Fluorescent immunohistochemistry analysis of samples from rabbits killed at 7 days after surgery showed that mostly endothelial cells and macrophages were transfected. Morphometric analysis of vein graft samples from the 28-day groups showed approximately a 50% reduction of neointimal thickness and 64% reduction of neointimal area in the iNOS-treated group compared with the surgery control groups. This study demonstrates efficacy of iNOS gene delivery by the RTN formulation in reducing IH in the rabbit model of vein graft disease.

saRNA guided iNOS up-regulation improves erectile function of diabetic rats

PURPOSE

Promoter targeted saRNAs mediate sequence specific up-regulation of gene expression. We explored the therapeutic effect of RNA activation mediated iNOS gene activation on improving erectile function in a rat model of diabetes mellitus.

MATERIALS AND METHODS

An optimal saRNA sequence specific for iNOS promoter was cloned into an adenoviral vector, resulting in AdU6/shiNOS and AdU6/shControl. The corresponding viruses were used to transduce cultured rat cavernous smooth muscle cells. Streptozotocin induced diabetes models were established in rats and used to test the effects of intracavernous delivery of iNOS saRNA viruses on erectile function. iNOS expression in the cavernous smooth muscle cells or penile tissue of treated rats was assessed by reverse transcriptase-polymerase chain reaction and Western blot. Cyclic guanosine monophosphate was analyzed by enzyme-linked immunosorbent assay. Intracavernous pressure in response to cavernous nerve stimulation was measured using a data acquisition system on post-injection days 1, 3, 5, 7, 10 and 14.

RESULTS

Adenovirus mediated expression of iNOS saRNA caused sustained up-regulation of iNOS in cavernous smooth muscle cells. Intracavernous injection of AdU6/shiNOS activated iNOS expression in vivo and significantly increased peak intracavernous pressure in streptozotocin induced diabetic rats via nitric oxide/intracellular cyclic guanosine monophosphate activation.

CONCLUSIONS

Results show that saRNA mediated iNOS over expression in the penis can restore erectile function in streptozocin diabetic rats via the nitric oxide-cyclic guanosine monophosphate pathway.

Feasibility and dosimetry studies for 18F-NOS as a potential PET radiopharmaceutical for inducible nitric oxide synthase in humans

Nitric oxide (NO), the end product of the inducible form of NO synthase (iNOS), is an important mediator of a variety of inflammatory diseases. Therefore, a radiolabeled iNOS radiopharmaceutical for assessing iNOS protein concentration as a marker for its activity would be of value to the study and treatment of NO-related diseases. We recently synthesized an (18)F-radiolabeled analog of the reversible NOS inhibitor, 2-amino-4-methylpyridine ((18)F-NOS), and confirmed its utility in a murine model of lung inflammation. To determine its potential for use in humans, we measured (18)F-NOS myocardial activity in patients after orthotopic heart transplantation (OHT) and correlated it with pathologic allograft rejection, tissue iNOS levels, and calculated human radiation dosimetry.

METHODS

Two groups were studied-a kinetic analysis group and a dosimetry group. In the kinetic analysis group, 10 OHT patients underwent dynamic myocardial (18)F-NOS PET/CT, followed by endomyocardial biopsy. Myocardial (18)F-NOS PET was assessed using volume of distribution; standardized uptake values at 10 min; area under the myocardial moment curve (AUMC); and mean resident time at 5, 10, and 30 min after tracer injection. Tissue iNOS levels were measured by immunohistochemistry. In the dosimetry group, the biodistribution and radiation dosimetry were calculated using whole-body PET/CT in 4 healthy volunteers and 12 OHT patients. The combined time-activity curves were used for residence time calculation, and organ doses were calculated with OLINDA.

RESULTS

Both AUMC at 10 min (P < 0.05) and tissue iNOS (P < 0.0001) were higher in patients exhibiting rejection than in those without rejection. Moreover, the (18)F-NOS AUMC at 10 min correlated positively with tissue iNOS at 10 min (R(2) = 0.42, P < 0.05). (18)F-NOS activity was cleared by the hepatobiliary system. The critical organ was the bladder wall, with a dose of 95.3 μGy/MBq, and an effective dose of 15.9 μSv/MBq was calculated.

CONCLUSION

Myocardial (18)F-NOS activity is increased in organ rejection (a condition associated with increased iNOS levels) and correlates with tissue iNOS measurements with acceptable radiation exposure. Although further modifications to improve the performance of (18)F-NOS are needed, these data show the feasibility of PET of iNOS in the heart and other tissues.

Nitric oxide release: part II. Therapeutic applications

A wide range of nitric oxide (NO)-releasing materials has emerged as potential therapeutics that exploit NO's vast biological roles. Macromolecular NO-releasing scaffolds are particularly promising due to their ability to store and deliver larger NO payloads in a more controlled and effective manner compared to low molecular weight NO donors. While a variety of scaffolds (e.g., particles, dendrimers, and polymers/films) have been cleverly designed, the ultimate clinical utility of most NO-releasing macromolecules remains unrealized. Although not wholly predictive of clinical success, in vitro and in vivo investigations have enabled a preliminary evaluation of the therapeutic potential of such materials. In this tutorial review, we review the application of macromolecular NO therapies for cardiovascular disease, cancer, bacterial infections, and wound healing.

Molecular and biochemical characterization of nitric oxide synthase isoforms and their intracellular distribution in human peripheral blood mononuclear cells

Nitric oxide synthase (NOS) expression and catalytic status in human peripheral blood mononuclear cells (PBMCs) is debatable, while its sub-cellular distribution remains unascertained. The present study characterizes NOS transcripts by real time PCR, NOS protein by immunoprecipitation (IP)/Western blot (WB), nitric oxide (NO) generation by DAF-2DA and NOS sub-cellular distribution by immunogold electron microscopy in resting PBMCs, monocytes and lymphocytes obtained from healthy donors. We observed constitutive expression of full length NOS isoforms (nNOS, iNOS and eNOS) in PBMCs: with the highest expression of iNOS in comparison to nNOS and eNOS. Isolated monocytes expressed more eNOS transcript and protein as compared to nNOS and iNOS. Lymphocytes however had more iNOS transcripts and protein than nNOS and eNOS. NOS was catalytically active in PBMCs, monocytes as well as in lymphocytes as evident by NO generation in the presence of substrate and cofactors, which was significantly reduced in the presence of NOS inhibitor. Immunogold electron microscopy and morphometric analysis revealed the distinct pattern of NOS distribution in monocytes and lymphocytes and also exhibited differences in the nuclear-cytoplasmic ratio. nNOS localization was much more in the cytosol than in the nucleus among both monocytes and lymphocytes. Interestingly, iNOS distribution was comparable in both cytosol and nucleus among monocytes, but in lymphocytes iNOS was predominantly localized to the cytosol. The present study exhibits constitutive presence of all the NOS isoforms in PBMCs and reports the distinct pattern of NOS distribution among monocytes and lymphocytes.

Anti-inflammatory and anticancer compounds isolated from Ventilago madraspatana Gaertn., Rubia cordifolia Linn. and Lantana camara Linn

OBJECTIVES

The aim was to search for anti-inflammatory and anticancer compounds from three medicinal plants, viz. Ventilago madraspatana Gaertn., Rubia cordifolia Linn. and Lantana camara Linn.

METHODS

The NO* scavenging potential of selected plant extracts was determined on LPS/IFN-gamma activated murine peritoneal macrophage cultures, and iNOS and COX-2 expression was evaluated by Western blot analysis. Bio-assay guided fractionation yielded four compounds: physcion and emodin from V. madraspatana, 1-hydroxytectoquinone from R. cordifolia, and oleanonic acid from L. camara. The anti-inflammatory activity of these compounds was tested through the carrageenan-induced rat-paw oedema model. They were then tested against a murine tumour (Ehrlich ascites carcinoma), and three human cancer cell lines, namely A375 (malignant skin melanoma), Hep2 (epidermoid laryngeal carcinoma) and U937 (lymphoma).

KEY FINDINGS

All four compounds dose dependently inhibited NO* through suppression of iNOS protein without affecting macrophage viability. Physcion and emodin caused 65-68% reduction of oedema volume at 40 mg/kg, which validated their in-vivo anti-inflammatory effect. 1-Hydroxytectoquinone and oleanonic acid exhibited promising cytotoxicity against A375 cells.

CONCLUSIONS

Ethnomedical reports on these traditional medicinal plants have been rationalised through an insight into the anti-inflammatory as well as anticancer potential of four constituents, characterised to be prospective candidates for designing novel therapeutic agents.

A prospective, single-blind, multicenter, dose escalation study of intracoronary iNOS lipoplex (CAR-MP583) gene therapy for the prevention of restenosis in patients with de novo or restenotic coronary artery lesion (REGENT I extension)

Neointimal hyperplasia causing recurrent stenosis is a limitation of the clinical utility of percutaneous transluminal coronary interventions (PCI). Nitric oxide (NO) inhibits smooth muscle cell proliferation, platelet activation, and inflammatory responses, all of which have been implicated in the pathogenesis of restenosis. In animals, neointimal proliferation after balloon injury has been shown to be effectively reduced by gene transfer of the inducible NO synthase (iNOS). The primary objective of this first multicenter, prospective, single-blind, dose escalation study was to obtain safety and tolerability information of the iNOS lipoplex (CAR-MP583) gene therapy for reducing restenosis following PCI. Local coronary intramural CAR-MP583 delivery was achieved using the Infiltrator balloon catheter. A total of 30 patients were treated in the study (six patients, 0.5 μg; six patients, 2.0 μg; six patients, 5.0 μg; and 12 patients, 10 μg). There were no complications related to local application of CAR-MP583. In one patient, PCI procedure-related transient vessel occlusion occurred with consecutive troponin elevation. There were no signs of inflammatory responses or hepatic or renal toxicity. No dose relationship was seen with regard to adverse events across the dose groups. Thus, coronary intramural lipoplex-enhanced iNOS gene therapy during PCI is feasible and appears to be safe. These initial clinical results are encouraging to support further clinical research, in particular in conjunction with new local drug delivery technologies.

Amyloid-β decreases nitric oxide production in cultured retinal neurons: a possible mechanism for synaptic dysfunction in Alzheimer's disease?

The neurotoxicity of the amyloid-β peptide (Aβ) appears to be, at least in part, related to pathological activation of glutamate receptors by Aβ aggregates. However, the downstream signaling pathways leading to neurodegeneration are still incompletely understood. Hyperactivation of nitric oxide synthase (NOS) and increased nitric oxide (NO) production have been implicated in excitotoxic neuronal damage caused by overactivation of glutamate receptors, and it has been suggested that increased NO levels might also play a role in neurotoxicity in Alzheimer's disease. We have examined the effect of blockade of NO production on the neurotoxicity instigated by Aβ₄₂ and by elevated concentrations of glutamate in chick embryo retinal neurons in culture. Results showed that L-nitroarginine methyl ester, a potent inhibitor of all NOS isoforms, had no protective effect against neuronal death induced by either Aβ₄₂ (20 μM) or glutamate (1 mM). Surprisingly, at short incubation times both Aβ and glutamate decreased NO production in retinal neuronal cultures in the absence of neuronal death. Thus, excitotoxic insults induced by Aβ and glutamate cause inhibition rather than activation of NO synthase in retinal neurons, suggesting that cell death induced by Aβ or glutamate is not related to increased NO production. On the other hand, considering the role of NO in long term potentiation and synaptic plasticity, the decrease in NO levels instigated by Aβ and glutamate suggests a possible mechanism leading to synaptic failure in AD.

Long space missions, gene therapy, and the vital role of magnesium: a three-pronged plan for the next 50 years

Since pharmaceuticals cannot be used in space until liver and kidney dysfunctions are corrected, and with invariable malabsorption, it appears there is no alternative other than to use subcutaneous magnesium (Mg) replacements in the presence of deficiencies and use of gene therapy. I suggest beginning with the correction of as many as four gene deficiencies: atrial natriuretic peptide (ANP), nitric oxide (NO), vascular endothelial growth factor (VEGF), and erythropoietin (EPO), all as well as Mg related to perfusion and angiogenesis. There is no evidence of significant lunar radiation levels in the absence of a solar storm. It could then be determined whether this has resulted in correction of liver and kidney dysfunction. If this persists, serial additions of gene therapy will be required determining the effect of each individual gene trial on organ function. Microgravity and endothelial gaps with leaks trigger reduced plasma volume. Partial correction by use of a plasma volume substitute and development of a delivery device may reduce complexity of gene therapy. Research would be conducted both on Earth and in microgravity, with the development of subcutaneous pharmaceuticals and Mg, and a space walk-reliable subcutaneous silicon device, given that no replenishable subcutaneous device is presently available. A three-pronged approach provides a plan for the next 50 years: A. complete correction of a Mg deficit; B. partial replacement with plasma volume substitutes, and C. multiple gene factor strategy.

Potential renovascular hypertension, space missions, and the role of magnesium

Space flight (SF) and dust inhalation in habitats cause hypertension whereas in SF (alone) there is no consistent hypertension but reduced diurnal blood pressure (BP) variation instead. Current pharmaceutical subcutaneous delivery systems are inadequate and there is impairment in the absorption, metabolism, excretion, and deterioration of some pharmaceuticals. Data obtained from the National Aeronautics and Space Administration through the Freedom of Information Act shows that Irwin returned from his 12-day Apollo 15 mission in 1971 and was administered a bicycle stress test. With just three minutes of exercise, his BP was >275/125 mm Hg (heart rate of only 130 beats per minute). There was no acute renal insult. Irwin’s apparent spontaneous remission is suggested to be related to the increase of a protective vasodilator, and his atrial natriuretic peptide (ANP) reduced with SF because of reduced plasma volume. With invariable malabsorption and loss of bone/muscle storage sites, there are significant (P < 0.0001) reductions of magnesium (Mg) required for ANP synthesis and release. Reductions of Mg and ANP can trigger pronounced angiotensin (200%), endothelin, and catecholamine elevations (clearly shown in recent years) and vicious cycles between the latter and Mg deficits. There is proteinuria, elevated creatinine, and reduced renal concentrating ability with the potential for progressive inflammatory and oxidative stress-induced renal disease and hypertension with vicious cycles. After SF, animals show myocardial endothelial injuries and increased vascular resistance of extremities in humans. Even without dust, hypertension might eventually develop from renovascular hypertension during very long missions. Without sufficient endothelial protection from pharmaceuticals, a comprehensive gene research program should begin now.

Bench-to-bedside review: Inhaled nitric oxide therapy in adults

Nitric oxide (NO) is an endogenous mediator of vascular tone and host defence. Inhaled nitric oxide (iNO) results in preferential pulmonary vasodilatation and lowers pulmonary vascular resistance. The route of administration delivers NO selectively to ventilated lung units so that its effect augments that of hypoxic pulmonary vasoconstriction and improves oxygenation. This 'Bench-to-bedside' review focuses on the mechanisms of action of iNO and its clinical applications, with emphasis on acute lung injury and the acute respiratory distress syndrome. Developments in our understanding of the cellular and molecular actions of NO may help to explain the hitherto disappointing results of randomised controlled trials of iNO.