Sapropterin is safe and effective in patients less than 4-years-old with BH4-responsive phenylalanine hydrolase deficiency

OBJECTIVE

To assess the safety and efficacy of tetrahydrobiopterin therapy with sapropterin to treat tetrahydrobiopterin (BH4)-responsive phenylalanine hydroxylase (PAH) deficiency in children aged <4 years compared with those aged ≥4 years.

STUDY DESIGN

We analyzed a longitudinal follow-up study conducted in all patients with BH4-responsive PAH deficiency throughout Japan. At the end of 2011, 43 patients were receiving sapropterin, of whom 21 were aged <4 years at the initiation of treatment. The starting dose of sapropterin was ≥10 mg/kg/day in 11 of these 21 patients. The duration of follow-up was ≥4 years in 6 of those 11 patients; 3 of these 6 were followed for ≥10 years. Nine patients were receiving sapropterin monotherapy at the end of 2011.

RESULTS

Serum phenylalanine level was maintained within the recommended optimal control range in all 21 patients who started sapropterin treatment before age 4 years. Only 1 nonserious adverse drug reaction occurred, an elevated alanine aminotransferase level in 1 patient. No significant abnormal behavior related to nerve disorders was reported.

CONCLUSION

Sapropterin therapy initiated before age 4 years was effective in maintaining serum phenylalanine level within the favorable range and was safe in Japanese patients with BH4-responsive PAH deficiency.

L-N-iminoethyl-lysine after experimental brain trauma attenuates cellular proliferation and astrocyte differentiation

BACKGROUND

The effects, and thereby possible benefit, of inhibiting nitric oxide synthases (NOS) after brain injury are not fully understood. Nitric oxide (NO) has both neuroprotective and damaging features, and its effect on the cellular proliferation and differentiation that occurs in response to traumatic brain injury (TBI) is largely unknown. This study was undertaken to investigate the effects of the selective inducible NOS-inhibitor, L-N-iminoethyl-lysine (L-NIL), on proliferating cell populations in rat brain areas with self-renewing capacity.

METHODS

A brain contusion was produced using a weight-drop model in rats. Animals received treatment with L-NIL or saline, and were killed after 6 days. Brain sections were stained with a cell marker of proliferation, Ki67, to detect dividing cells in the hippocampus, perilesional zone and the subventricular zone (SVZ).

RESULTS

A significant decrease of proliferating cells was seen in the SVZ bilaterally in L-NIL-treated animals compared to controls. Hippocampal proliferation showed a tendency to decrease in L-NIL-treated animals that did not reach statistical significance. Perilesional proliferation was equal in the treatment group and controls. The percentage of proliferating GFAP expressing cells was, however, lower in L-NIL-treated animals. The proliferating cell populations were predominantly immunoreactive for GFAP, while a smaller population was immunoreactive for Nestin. The inhibition of inducible NOS with L-NIL attenuated the level of cellular proliferation and influenced the differentiation of astrocytes at 6 days after experimental brain contusion.

CONCLUSIONS

Our results confirmed that reactive glial cells dominated the proliferating cell population after TBI and suggested that NO-regulated mechanisms are relevant for post-traumatic cellular proliferation and differentiation, since NO inhibition decreased the number of proliferating cells in the SVZ and the proportion of proliferating cells expressing GFAP, a marker of glial proliferation.

Tetrahydrobiopterin in the prevention of hypertonia in hypoxic fetal brain

OBJECTIVE

Tetrahydrobiopterin (BH(4)) deficiency is a cause of dystonia at birth. We hypothesized that BH(4) is a developmental factor determining vulnerability of the immature fetal brain to hypoxic-ischemic injury and subsequent motor deficits in newborns.

METHODS

Pregnant rabbits were subjected to 40-minute uterine ischemia, and fetal brains were investigated for global and focal changes in BH(4). Newborn kits were assessed by neurobehavioral tests following vehicle and sepiapterin (BH(4) analog) treatment of dams.

RESULTS

Naive fetal brains at 70% gestation (E22) were severely deficient for BH(4) compared with maternal and other fetal tissues. BH(4) concentration rapidly increased normally in the perinatal period, with the highest concentrations found in the thalamus compared with basal ganglia, frontal, occipital, hippocampus, and parietal cortex. Global sustained 40-minute hypoxia-ischemia depleted BH(4) in E22 thalamus and to a lesser extent in basal ganglia, but not in the frontal, occipital, and parietal regions. Maternal supplementation prior to hypoxia-ischemia with sepiapterin increased BH(4) in all brain regions and especially in the thalamus, but did not increase the intermediary metabolite, 7,8-BH(2). Sepiapterin treatment also reduced incidence of severe motor deficits and perinatal death following E22 hypoxia-ischemia.

INTERPRETATION

We conclude that early developmental BH(4) deficiency plays a critical role in hypoxic-ischemic brain injury. Increasing brain BH(4) via maternal supplementation may be an effective strategy in preventing motor deficits from antenatal hypoxia-ischemia.

Liposome-mediated Gene Therapy in the Kidney

Gene therapy directed to the kidney has been attempted to improve renal disorders such as inherited kidney diseases and common renal diseases that cause interstitial fibrosis, tubular atrophy, and glomerulosclerosis. Viral and non-viral vectors have been tried and been modulated to obtain sufficient transgene expression. However, gene delivery to the kidney is usually difficult because of characteristics of renal cell biology. Among non-viral vectors, the liposome system is a promising procedure for kidney-targeted gene therapy. Using cationic liposome, tubular cells were effectively transduced by retrograde injection of liposome/cDNA complex. Although transgene expression was reportedly modest using cationic liposomes, this method improved renal disease models such as carbonic anhydrase II deficiency and unilateral ureteral obstruction. In contrast, HVJ-liposome system is an effective transfection method to glomerular cells using intra-renal arterial infusion and improved glomerular disease models such as glomerulonephritis and glomerulosclerosis. In addition, intra-renal pelvic injection of DNA by HVJ-liposome system showed transgene expression in interstitial fibroblasts. In kidney-targeted gene therapy, liposome-mediated gene transfer is an attractive method because of its simplicity and reduced toxicity. In spite of modest transgene expression, several renal disease models were successfully modulated by liposome system. Although one limitation of liposome-mediated gene delivery is the duration of transgene expression, the liposome/cDNA complex can be repeatedly administered due to the absence of an immune response.

Anti-oxidant strategies

Oxidative stress plays an important role in causing organ injury in the compromised fetus and neonate. Recent experimental research and clinical studies have clarified important pathways in the production of reactive oxygen and nitrogen species. Free radicals are involved in causing cerebral damage after perinatal hypoxia-ischemia affecting membrane lipids, proteins, and DNA. Anti-oxidant strategies can be used as add-on neuroprotective therapy after perinatal oxidative stress. Selective inhibitors of neuronal and inducible nitric oxide synthase, allopurinol, melatonin, and erythropoietin are among the first compounds that are ready for clinical trials.

Effects of supplementation of BH4 after prolonged ischemia in skeletal muscle

PURPOSE

To determine whether the supplementation of tetrahydrobiopterin (BH(4), an essential cofactor of nitric oxide synthase; NOS) could attenuate endothelial dysfunction and improve NOS activity and cell viability in skeletal muscle after ischemia/reperfusion (I/R).

METHODS

A vascular pedicle isolated rat cremaster muscle model was used. Cremaster muscles were subjected to 4 h of ischemia followed by 2 h of reperfusion. Rats were given either normal saline or BH(4) by intravenous injection at 1 min prior to reperfusion. After reperfusion, average arteriole diameter, capillary perfusion, endothelial-dependent/-independent vasodilatation, NOS activity, and muscle cell viability were evaluated.

RESULTS

Supplementation of BH(4) prior to reperfusion significantly attenuated reperfusion-induced vasoconstriction, poor capillary perfusion, and endothelial dysfunction and enhanced cNOS activity and slightly improved cell viability in the skeletal muscle after I/R.

CONCLUSION

Supplementation of BH(4) during reperfusion provided a significant protection against I/R injury in rat skeletal muscle.

Nitric oxide, a double edged sword in cancer biology: Searching for therapeutic opportunities

Nitric oxide (NO) is a pleiotropic molecule critical to a number of physiological and pathological processes. The last decade has witnessed major advances in dissecting NO biology and its role in cancer pathogenesis. However, the complexity of the interactions between different levels of NO and several aspects of tumor development/progression has led to apparently conflicting findings. Furthermore, both anti-NO and NO-based anticancer strategies appear effective in several preclinical models. This paradoxical dichotomy is leaving investigators with a double challenge: to determine the net impact of NO on cancer behavior and to define the therapeutic role of NO-centered anticancer strategies. Only a comprehensive and dynamic view of the cascade of molecular and cellular events underlying tumor biology and affected by NO will allow investigators to exploit the potential antitumor properties of drugs interfering with NO metabolism. Available data suggest that NO should be considered neither a universal target nor a magic bullet, but rather a signal transducer to be modulated according to the molecular makeup of each individual cancer and the interplay with conventional antineoplastic agents.

Endothelial nitric oxide synthase is essential for postpneumonectomy compensatory vasodilation

BACKGROUND

After pneumonectomy, the remaining lung vasculature must vasodilate to compensate for increased blood volume. We hypothesized that endothelial nitric oxide synthase (eNOS) is essential for compensatory vasodilation after pneumonectomy.

METHODS

Adult, wild-type C57BL6 (WT) and eNOS knockout (eNOS-/-) mice underwent left pneumonectomy and recovered under normoxic conditions. Animals were lightly anesthetized at 1, 3, 7, or 14 days after pneumonectomy, and closed chest, systolic right ventricular pressure (RVP) was recorded using fine-needle cannulation. The right ventricle to left ventricle plus septum weight ratios were measured as an index of right ventricular hypertrophy. Two additional groups of mice (WT and eNOS-/-) were recovered after pneumonectomy in inhaled nitric oxide (iNO, 10 ppm), and RVP was measured on day 7.

RESULTS

The eNOS-/- mice had significantly higher preoperative RVP than did WT (17.1 +/- 0.4 versus 14.2 +/- 0.2 cmH2O, p = 0.001). Both groups exhibited transient periods of pulmonary hypertension after pneumonectomy. On day 1, RVP was 80% above baseline in eNOS-/- mice (30.7 +/- 0.8 cmH2O) versus 42% in WT mice (20.2 +/- 0.7 cmH2O, p = 0.0001). The RVP returned to baseline in WT mice (16.3 +/- 0.2 cmH2O) but remained significantly elevated in eNOS-/- mice (28.6 +/- 0.9 cmH2O) at day 3 and at each time thereafter (p = 0.0001). The iNO significantly reduced RVP in eNOS-/- animals to 15.2 +/- 0.3 cmH2O (p = 0.0001) while having no effect in WT animals. Right ventricular hypertrophy was not observed in any group.

CONCLUSIONS

Pneumonectomy results in a transient increase in RVP. Under normal circumstances, these pressures return to baseline within 3 days. The eNOS-/- mice failed to display compensatory vasodilation yet could be rescued with iNO. These results suggest that eNOS is essential for postpneumonectomy compensatory vasodilation.

Gene therapy for erectile dysfunction

The past decade has seen an explosion of new information on the physiology of penile erection, pathophysiology of erectile dysfunction (ED), and development of new oral agents (e.g., three PDE5 inhibitors) to manage ED. Although all three selective PDE5 inhibitors are effective in the majority of ED cases, these oral medications have failed in certain disease states, such as diabetic ED, postprostatectomy ED, and severe veno-occlusive dysfunction. Only about 50% to 60% of these cases benefit from PDE5 inhibitor therapy, prompting the development of new approaches, including gene-based therapies for the treatment of ED. The penis is a convenient tissue target for gene therapy because of its external location and accessibility, the ubiquity of endothelial lined spaces, and low level of blood flow, especially in the flaccid state. Initially, gene therapy has been reserved for the treatment of life-threatening disorders including cancer, hereditary and acquired diseases. However, gene therapy is an attractive therapeutic possibility for the treatment of ED. Evolution of nitric oxide (NO), a small gaseous, lipophilic signaling molecule that is produced by nitric oxide synthase (NOS) activates guanylate cyclase (GC), resulting in increased cyclic guanosine monophosphate (cGMP) production, plays a significant role in our understanding of cavernosal smooth muscle physiology. Many gene therapy strategies have focused on the NO/GS/cGMP pathway. All three NOS isoforms, endothelial NOS (eNOS), neuronal NOS (nNOS), and iNOS have been used for gene therapy in order to modulate erectile response. Various viral and nonviral vectors have been used to date for the transfer of genetic material to the target cell or tissues with various degrees of success. Recently, second generation or "gutless" (helper-dependent) adenovirus vectors have been developed in order to reduce cellular toxicity and immune response, while increasing efficient gene therapy. Varieties of other gene therapy trials have also been undertaken for the treatment of ED and are the focus of this review.

Effects of nitric oxide synthase inhibitor on acid aspiration-induced lung injury in rats

The current study was designed to determine the effects of nitric oxide synthase (NOS) in the development of acid aspiration-induced lung injury in rats. Hydrochloric acid (HCl, 0.1 N; 2 ml/kg) or normal saline (NS, 2 ml/kg) was instilled into the lung of anesthetized, ventilated Sprague-Dawley rats. NG-monomethyl-L-arginine (L-NMMA, 20 mg kg(-1)) and a selective inducible nitric oxide synthase (iNOS) inhibitor, ONO-1714 (0.1 and 0.3 mg kg(-1)), were used to block NOS. Bronchoalveolar lavage fluid (BALF) and wet and dry measurements of lung (W/D) were obtained 5h after HCl or NS instillation. Unlike the control group, rats instilled with HCl showed significant increases in total nuclear cell counts (NCC), neutrophil counts, concentrations of albumin, tumor necrosis factor-alpha (TNF-alpha), interleukine-6 (IL-6) and nitrites/nitrates (NO(x)) in BALF. These parameters were associated with the significantly increased W/D in the HCl group compared with the NS group. ONO-1714 (0.1 mg kg(-1)) significantly prevented the increases in all these parameters. Its inhibitory effects were superior to those of L-NMMA and 0.3 mg kg(-1) of ONO-1714. NOS plays an important role in the pathogenesis of acid aspiration-induced lung injury. Furthermore, selective iNOS inhibition at the optimal dose was most effective in improving lung injury induced by acid aspiration in rats.

Targeting endothelial cells with adenovirus expressing nitric oxide synthase prevents elevation of blood pressure in stroke-prone spontaneously hypertensive rats

Local adenoviral (Ad)-mediated gene transfer to the carotid artery of the stroke-prone spontaneously hypertensive rat (SHRSP) is successful in improving endothelial function. Here we explored the potential of systemic delivery of Ad encoding endothelial nitric oxide synthase (AdeNOS) to prevent elevation of blood pressure in the SHRSP using both nontargeted and vector targeting approaches. Systemic administration of nontargeted AdeNOS failed to modify the rise in blood pressure in SHRSP when administered during the 12th week of age (n = 5, P = 0.088, F = 3.0), an effect likely to result from sequestration of Ad by the liver. Rerouting Ad transduction using a bispecific antibody (anti-ACE/anti-Ad capsid, Fab9B9) that blocks Ad binding to the coxsackie and adenovirus receptor and simultaneously retargets AdeNOS to the angiotensin-converting enzyme resulted in efficient eNOS overexpression in the lung vasculature and a sustained hypotensive effect (n = 5, P = 0.007, F = 7.9). This study highlights the importance of vector targeting to achieve therapeutic gain and represents the first such study in cardiovascular gene therapy.

Endothelial nitric oxide synthase protects the post-ischemic liver: potential interactions with superoxide

Hepatic ischemia and reperfusion (I/R) continues to represent a significant cause of post-transplant liver failure. The roles that certain free radicals including nitric oxide (NO) and superoxide (O(2)(-)) play in this process are not well understood. The present study was designed to assess the role of endothelial cell nitric oxide synthase (eNOS) in I/R-induced liver injury in a murine model of hepatic I/R. Forty five minutes of partial (70%) hepatic ischemia followed by 3 and 6 h of reperfusion resulted in a significant increase in liver injury which occurred in the absence of neutrophil infiltration. eNOS-deficient mice displayed enhanced liver injury when compared to their wild type controls again in the absence of neutrophil infiltration. Interestingly, basal liver blood flow was significantly decreased in these mice when compared to controls though their blood flow during reperfusion was not significantly reduced from their wild type controls. Treatment of eNOS(-/-) mice with gadolinium chloride, a potent inhibitor of Kupffer cell function, but not superoxide dismutase, significantly reduced post-ischemic hepatocellular injury while either treatment protected the wild type mouse livers. Taken together, these data suggest that NO derived from eNOS may act to protect the post-ischemic liver possibly by suppression of Kupffer cell function and not by modulation of tissue perfusion. Further the data presented here would indicate that the protective effects conferred by SOD are related to its ability to increase the bioavailability of NO rather than by attenuating superoxide-dependent reactions. Data generated from these studies may prove useful in developing new drug therapies to treat the post-ischemic liver.

Nitric oxide: a newly discovered function on wound healing

Wound healing impairment represents a particularly challenging clinical problem to which no efficacious treatment regimens currently exist. The factors ensuring appropriate intercellular communication during wound repair are not completely understood. Although protein-type mediators are well-established players in this process, emerging evidence from both animal and human studies indicates that nitric oxide (NO) plays a key role in wound repair. The beneficial effects of NO on wound repair may be attributed to its functional influences on angiogenesis, inflammation, cell proliferation, matrix deposition, and remodeling. Recent findings from in vitro and in vivo studies of NO on wound repair are summarized in this review. The unveiled novel mechanisms support the use of NO-containing agents and/or NO synthase gene therapy as new therapeutic regimens for impaired wound healing.

Topical application of a nitric oxide synthase inhibitor reduces intraocular pressure in rabbits with experimental glaucoma

The role of nitric oxide (NO) in neuronal degeneration of glaucoma is well established, and drugs to inhibit NO production have been introduced in preclinical studies. The present experiments were made to investigate the pharmacological efficacy of a topical formulation of the nonselective nitric oxide synthase (NOS) inhibitor, nitro-L-arginine methyl ester (L-NAME), in an experimental model of glaucoma in rabbits. L-NAME was dissolved in an isotonic, mucoadhesive, viscosized, buffered solution in concentrations of 0.1%, 0.5%, or 1% (w/v). Ocular hypertension (of at least 15 mmHg compared to basal values) was induced by intra-ocular injection of alpha-chymotrypsin. The instillation of L-NAME topical formulations lowered the IOP of hypertensive rabbits in a dose-related manner, with a maximum drop of 12.0 mmHg 60 minutes after administration of the highest concentration. The area under the curve (AUC) of the DeltaIOP (mmHg) versus time (minutes) was 1050.3 +/- 141.7 and 15.1 +/- 2.5 for the 1% L-NAME-treated group and vehicle-treated group, respectively. No change was found in IOP or pupil diameter after instillation of L-NAME eye drops in normotensive rabbits. This study provides the first evidence that topical L-NAME significantly reduces the IOP in a model of ocular hypertension.

Novel features of nitric oxide, endothelial nitric oxide synthase, and atherosclerosis

There is a complex pathophysiologic scenario involving nitric oxide (NO), endothelial nitric oxide synthase (eNOS), and the development of atherosclerosis and unstable atheroma. Endothelial damage induced by atherosclerosis leads to the reduction in bioactivity of ENOS with subsequent impaired release of NO. An important mechanism is local enhanced degradation of NO by increased generation of reactive oxygen species and other free radicals, with subsequent cascade of oxidation-sensitive mechanisms in the arterial wall. Novel molecular approaches have resulted in the development of new strains of mice lacking eNOS. These experimental models will help to understand how to implement NO-based therapies against atherosclerosis. L-arginine, the precursor of NO, has demonstrated beneficial effects in atherosclerosis and disturbed shear stress. The target or goal for new drugs should be the complete restoration of NO-mediated signaling pathways in atherosclerotic arteries.

Reactive nitrogen species scavenging, rather than nitric oxide inhibition, protects from articular cartilage damage in rat zymosan-induced arthritis

1. The contribution of nitric oxide (NO) and peroxynitrite (PN) to inflammation in a zymosan-induced (1 mg, intra-articular, i.art.) rat model of arthritis was assessed by histopathology and by measuring the glycosaminoglycan (GAG) content of the articular cartilage. 2. Progression of the chronic synovitis in zymosan-induced arthritis (ZYA) was associated with increased nitrite and nitrotyrosine (3-NT) levels in the joint exudates that paralleled a progressive loss of the GAG content. An increase in 3-NT was also observed after i.art. PN. 3. The nonselective nitric oxide synthase (NOS) inhibitor l-N(G)-nitroarginine methyl ester (25-75 mg x kg(-1)day(-1)) or the selective inducible NOS inhibitor aminoguanidine (50-100 mg x kg(-1)day(-1)) given 1 h before (prophylactic) or 3 days after (therapeutic) injection of the zymosan ameliorated the synovitis, but worsened the GAG loss, as measured at the end of the experiment (day 7). 4. The PN scavenger uric acid (100-250 mg x kg(-1) i.p. four times daily) given prophylactically until the end of the experiment (day 14), in a dose compatible with its PN scavenging activity, significantly decreased both the synovitis and the GAG loss. 5. In conclusion, PN formation is associated with cartilage damage in addition to proinflammatory activity in ZYA. NOS inhibitors and a PN scavenger were able to reduce the cellular infiltration, while displaying opposite effects on cartilage homeostasis either by enhancing or ameliorating the damage, respectively.

Gene delivery of endothelial nitric oxide synthase into nucleus tractus solitarii induces biphasic response in cardiovascular functions of hypertensive rats

BACKGROUND

Nitric oxide (NO) plays an important role in central control of blood pressure (BP). An intrinsic defect in NO availability in brain nucleus contributes to the elevated BP in the spontaneously hypertensive rats (SHR). This study was aimed to investigate the effect of endothelial NO synthase (eNOS) gene delivery in the nucleus tractus solitarii (NTS) on the cardiovascular functions of SHR.

METHODS

Adenovirus vectors encoding either eNOS (Ad-eNOS) or green fluorescent protein (Ad-GFP) were used for gene transfer study. The cardiovascular functions in SHR received NTS gene delivery that were monitored by an oscillometric device.

RESULTS

Infection of neuronal cells with Ad-eNOS increased the nitrite production but decreased the level of superoxide anion (O(2)(-)), indicating that eNOS gene delivery increased NO availability. After microinjection into NTS, adenovirus-mediated GFP or eNOS expression was confirmed by fluorescence microscopy and immunohistochemical analysis. On days 3 to 14 after injection, a significant decrease in mean BP (MBP and heart rate (HR) was observed in Ad-eNOS-treated SHR, but not in Ad-GFP- or saline-treated SHR. Within this period, microinjection of the soluble guanylate cyclase inhibitor significantly reversed the Ad-eNOS-mediated depressor effect. However, on days 24 to 40, the MBP of Ad-eNOS-treated animals escalated, then returned to the normal range after day 50. The mechanism underlying the rebound of BP in Ad-eNOS-injected SHR remains to be elucidated.

CONCLUSIONS

Intra-NTS eNOS gene delivery causes a depressor response in SHR, but a transient increase in MBP was observed after the Ad-eNOS-induced hypotension disappeared.

Adenoviral transfer of endothelial nitric oxide synthase attenuates lesion formation in a novel murine model of postangioplasty restenosis

OBJECTIVE

Restenosis remains a major late complication of percutaneous transluminal coronary angioplasty (PTCA), for which the development of prevention strategies has thus far been hampered by the lack of a representative and practical animal model. We have, therefore, developed a murine model of PTCA-induced restenosis.

METHODS AND RESULTS

Rigid probe angioplasty of pre-existing atherosclerotic lesions in the carotid arteries of ApoE-deficient mice was found to result in an increase in lesion size (0.14+/-0.04x10(5) microm2 to 0.42+/-0.09x10(5) microm2, P=0.007) with a smooth muscle cell-rich, fibrotic lesion morphology. In an additional experiment, lesions were incubated immediately after angioplasty with adenovirus bearing an endothelial nitric oxide synthase (eNOS) transgene (Ad.APT.eNOS), or an "empty" control virus (Ad.APT.empty) at a titer of 1.5x10(9) pfu/mL. Ad.APT.eNOS treatment was seen to lead to a 73.1% reduction in plaque size (0.27+/-0.04x10(5) microm2 versus 1.02+/-0.39x10(5) microm2, P=0.07), which translated to a significantly lowered average degree of stenosis (33.6+/-4.1% versus 74.6+/-14.0%, P=0.02). Ad.APT.eNOS also decreased lesional collagen content from 29.1% to 4.8% (P<0.001).

CONCLUSIONS

We believe that we have established a representative murine model of postangioplasty restenosis, which may serve to elucidate the mechanisms underlying restenosis and to evaluate potential antirestenotic therapies.

Nitric oxide treatment and acute pulmonary inflammatory response in very premature infants with intractable respiratory failure shortly after birth

AIM

Premature infants with respiratory failure and early-onset pneumonia have low inducible nitric oxide synthase (NOS2) and no evidence of nitric oxide (NO) toxicity. However, inhalation of NO may not be indicated in sepsis because excessive NO generation has been reported. This prospective study was designed to test the hypothesis that inhaled NO is effective in a select group of small premature infants and that the responsiveness to NO is associated with low NOS2 enzyme.

METHODS

246 very low birthweight infants (birthweight <1500 g, VLBW) were screened for severe, intractable respiratory failure (oxygenation index >40, arterial-alveolar ratio for oxygen tension <0.10) that does not respond to two doses of surfactant within 5 h from birth. Infants with severe cardiac failure or a bleeding disorder were excluded. Five of the nine eligible cases received inhaled NO. They all had prolonged rupture of foetal membranes, early-onset pneumonia and persistent pulmonary hypertension.

RESULTS

All five responded strikingly, survived and appeared normal in follow-up. Airway specimens during the first day of life revealed very low NOS2, interleukin-1beta and surfactant protein A, compared with VLBW infants who had no acute infection despite histological chorioamnionitis. In early-onset pneumonia, NOS2 and other inflammatory mediators increased first during the recovery 1-2 d after birth.

CONCLUSION

VLBW infants with progressive respiratory failure and infection at birth have deficient pulmonary NOS2 and cytokine response. After surfactant therapy, these infants responded strikingly to inhaled NO. An acute pulmonary inflammatory response may contribute to respiratory adaptation in early-onset pneumonia.

Nitric oxide and wound repair

NO produced by both iNOS and eNOS plays many important roles in wound healing, from the inflammatory phase through to scar remodeling. NO has cytostatic, chemotactic, and vasodilatory effects during early wound repair, regulates proliferation and differentiation of several cell types, modulates collagen deposition and angiogenesis, and affects wound contraction. The data accumulated thus far indicates that the timing, level, and site of NO production are highly coordinated in normal wound repair. Defining states resulting from either inadequate substrate or depressed enzyme expression appear to contribute to impaired wound repair; however, NO represents only one factor in the complex process of wound healing. Approaches to improve NO availability may be of therapeutic value.

The inducible nitric oxide synthase inhibitor BBS-2 prevents acute lung injury in sheep after burn and smoke inhalation injury

In this study we examined the role of inducible nitric oxide synthase (iNOS) in acute respiratory distress syndrome (ARDS) in sheep with severe combined burn and smoke inhalation injury. BBS-2, a potent and highly selective iNOS dimerization inhibitor, was used to exclude effects on the endothelial and neuronal NOS isoforms. Seven days after surgical recovery, sheep were given a burn (40% of total body surface, 3rd degree) and insufflated with cotton smoke (48 breaths, < 40 degrees C) under anesthesia. BBS-2 was provided by constant infusion at 100 microg/kg/hour, beginning 1 hour after injury. During 48 hours, control sheep developed multiple signs of ARDS. These included decreased pulmonary gas exchange, increased pulmonary edema, abnormal lung compliance, and extensive airway obstruction. These pathologies were associated with a large increase in tracheal blood flow and elevated plasma NO2-/NO3- (NOx) levels. These variables were all stable in sham animals. Treatment of injured sheep with BBS-2 attenuated the increases in tracheal blood flow and plasma NOx levels, and significantly attenuated all the pulmonary pathologies that were noted. The results provide definitive evidence that iNOS is a key mediator of pulmonary pathology in sheep with ARDS resulting from combined burn and smoke inhalation injury.

Nitric oxide synthase inhibition as therapy for sepsis: a decade of promise

BACKGROUND

Inhibition of nitric oxide synthase (NOS) has held promise as a novel and important therapeutic target for sepsis for over a decade. However, the question as to whether an inhibitor of NOS will prove to be efficacious in human septic shock remains unanswered.

METHODS

Review of the pertinent English-language medical literature.

RESULTS

Observations of the induction of NOS (iNOS, NOS2) by proinflammatory cytokines led to the hypothesis that nitric oxide (NO) relaxes vascular smooth muscle, thereby producing vasodilation and hypotension in sepsis. Other effects of NO in vascular tone may be manifested by refractoriness to vasopressors or myocardial dysfunction. However, such negative effects of NO are balanced by the role of NO in maintaining microvascular perfusion and host defenses against invading pathogens. Initial animal studies of septic shock modulated by the administration of competitive inhibitors of NOS demonstrated that NOS inhibition might be beneficial therapy for clinical septic shock. However, subsequent animal studies have produced variable results, and a phase III clinical trial of a nonselective NOS inhibitor has failed to show benefit for therapy of septic shock.

CONCLUSION

A better understanding of the effects of NOS and its inhibitors is needed as is an understanding of the underlying pathophysiology of sepsis. Moreover, a nontoxic, short-acting, titratable, specific inhibitor of NOS2 has yet to be identified and tested. Until then, efforts should be designed to describe more completely the role of NO in the pathophysiology of sepsis.

Nitric oxide synthase gene therapy for cardiovascular disease

Gene therapy refers to the transfer of specific genes to the host tissue to intervene in a disease process, with resultant alleviation of the symptoms of a particular disease. Cardiovascular gene transfer is not only a powerful technique for studying the function of specific genes in cardiovascular biology and pathobiology, but also a novel and promising strategy for treating cardiovascular diseases. Since the mid-1990s, nitric oxide synthase (NOS), the enzyme that catalyzes the formation of nitric oxide (NO) from L-arginine, has received considerable attention as a potential candidate for cardiovascular gene therapy, because NO exerts critical and diverse functions in the cardiovascular system, and abnormalities in NO biology are apparent in a number of cardiovascular disease processes including cerebral vasospasm, atherosclerosis, postangioplasty restenosis, transplant vasculopathy, hypertension, diabetes mellitus, impotence and delayed wound healing. There are three NOS isoforms, i.e., endothelial (eNOS), neuronal (nNOS) and inducible (iNOS). All three NOS isoforms have been used in cardiovascular gene transfer studies with encouraging results. This review will discuss the rationale of NOS gene therapy in different cardiovascular disease settings and summarize the results of experimental NOS gene therapy from various animal models of cardiovascular disease to date.

Just say NO to muscle degeneration?

The devastating muscle degeneration characteristic of Duchenne muscular dystrophy is caused by mutations in the gene encoding dystrophin. The dystrophin complex has two functions: a structural role in maintaining sarcolemmal integrity during contraction and a scaffolding function that recruits signaling proteins such as neuronal nitric oxide synthase to the membrane. New studies indicate that transgenic restoration of nitric oxide (NO) production in the mdx dystrophic mouse improves muscle pathology. Although NO-mediated killing of inflammatory cells might be involved, other mechanisms are also possible. These results point to the therapeutic potential of manipulating the signaling activity of the dystophin complex as a way to ameliorate the progression of muscle degeneration.

Genetic targeting for cardiovascular therapeutics: are we near the summit or just beginning the climb?

This article is based on an Experimental Biology symposium held in April 2001 and presents the current status of gene therapy for cardiovascular diseases in experimental studies and clinical trials. Evidence for the use of gene therapy to limit neointimal hyperplasia and confer myocardial protection was presented, and it was found that augmenting local nitric oxide (NO) production using gene transfer (GT) of NO synthase or interruption of cell cycle progression through a genetic transfer of cell cycle regulatory genes limited vascular smooth muscle hyperplasia in animal models and infra-inguinal bypass patients. The results of application of vascular endothelial growth factor (VEGF) GT strategies for therapeutic angiogenesis in critical limb and myocardial ischemia in pilot clinical trials was reviewed. In addition, experimental evidence was presented that genetic manipulation of peptide systems (i.e., the renin-angiotensin II system and the kallikrein-kinin system) was effective in the treatment of systemic cardiovascular diseases such as hypertension, heart failure, and renal failure. Although, as of yet, there are no well controlled human trials proving the clinical benefits of gene therapy for cardiovascular diseases, the data presented here in animal models and in human subjects show that genetic targeting is a promising and encouraging modality, not only for the treatment and long-term control of cardiovascular diseases, but for their prevention as well.

Nitric oxide synthase (nNOS) gene transfer modifies venous bypass graft remodeling: effects on vascular smooth muscle cell differentiation and superoxide production

BACKGROUND

Pathological vascular remodeling in venous bypass grafts (VGs) results in smooth muscle cell (SMC) intimal hyperplasia and provides the substrate for progressive atherosclerosis, the principal cause of late VG failure. Nitric oxide (NO) bioactivity is reduced in VGs, in association with increased vascular superoxide production, but how these features relate to pathological VG remodeling remains unclear. We used gene transfer of the neuronal isoform of nitric oxide synthase (nNOS) to investigate how increased NO production modulates vascular remodeling in VGs and determined the effects on late VG phenotype.

METHODS AND RESULTS

New Zealand White rabbits (n=60) underwent jugular-carotid interposition bypass graft surgery with intraoperative adenoviral gene transfer of nNOS or beta-galactosidase. Vessels were analyzed after 3 days (early, to investigate acute injury/inflammation) or 28 days (late, to investigate SMC intimal hyperplasia). In early VGs, nNOS gene transfer significantly increased NOS activity and substantially reduced adhesion molecule expression and inflammatory cell infiltration. In late VGs, recombinant nNOS protein was no longer evident, but there were sustained effects on VG remodeling, resulting in a striking reduction in SMC intimal hyperplasia, a more differentiated intimal SMC phenotype, and reduced vascular superoxide production.

CONCLUSIONS

Intraoperative nNOS gene transfer has sustained favorable effects on VG remodeling and on the vascular phenotype of mature VGs. These findings suggest that early, transient modification of the response to vascular injury is a powerful approach to modulate VG biology and highlight the potential utility of NOS gene transfer as a therapeutic strategy in VGs.

Hemodynamic and cardiovascular effects of nitric oxide modulation in the therapy of septic shock

Nitric oxide synthase (NOS) of the inducible subtype (iNOS) plays a pivotal role in vasodilation associated with sepsis. Various biochemical pathways are involved, revealing targets for inhibiting the consequence of iNOS activation. Interactions of transcription factors, inducers, cofactors, and regulators of iNOS are important in understanding the development of iNOS inhibitors. Inhibition through L-arginine analogs, depletion of arginine, inhibition of cofactors, modulating gene transcription, and scavenging nitric oxide have been studied. Human studies were conducted only with nonselective L-arginine analogs. Reduction of mortality from sepsis was not reported. It is anticipated that iNOS-specific compounds will be clinically useful. The focus of future human trials will be on these agents. Although ideal therapy for treating vasodilation from sepsis is not available, research into the pathophysiology of NOS in sepsis clarified the complexities surrounding this therapeutic dilemma.

Treatment of psoriasis with topical NG-monomethyl-L-arginine, an inhibitor of nitric oxide synthesis

A double blind left, right comparative study was carried out in 17 psoriatic subjects to examine the influence of a topically applied inhibitor of nitric oxide (NO) synthesis on the pathogenic events of psoriasis. The inhibitor NG-monomethyl-L-arginine (L-NMMA) in aqueous cream BP was applied to one plaque while aqueous cream BP alone served as control. Compared with the control, the L-NMMA-treated side showed significant (77%) inhibition of NO production and a reduction in blood flow, confirming its bioavailability. L-NMMA significantly reduced staining for endothelial cells and intercellular adhesion molecule 1, while CD1a-positive Langerhans cells and CD8-positive suppressor cytotoxic T cells increased. CD4-positive lymphocytes and epidermal proliferation, as indicated by Ki-67 staining, were unaffected by this degree of inhibition of NO synthesis, and correspondingly significant clinical improvement was not found.

Endothelial nitric oxide synthase protects aortic allografts from the development of transplant arteriosclerosis

BACKGROUND

Inducible nitric oxide synthase (iNOS) is up-regulated in rejecting allografts and is protective against allograft arteriosclerosis; it suppresses neointimal smooth muscle cell accumulation and inhibits adhesion of platelets and leukocytes to the endothelium. However, the functional importance of endothelial NOS (eNOS) in the rejecting allografts remains unclear.

METHODS

We examined the effects of selective eNOS deficiency in aortic allografts in a murine chronic rejection model using grafts from eNOS knockout (KO) mice (C57BL/6 background; H2b) and normal C3H (H2K) as recipients. Grafts from wild-type C57BL/6 mice served as controls. Grafts from iNOS KO mice served as a second group of controls where the contribution from iNOS was eliminated but eNOS was preserved. Aortic grafts were harvested and analyzed at days 10-14, 18-22, and 26-30 after transplantation.

RESULTS

Endothelial NOS-deficient grafts showed significantly increased intima/media ratios at days 26-30 compared to controls. Immunostaining demonstrated that in eNOS KO grafts, eNOS was not detectable whereas iNOS was expressed prominently in infiltrating recipient mononuclear cells. In control grafts, eNOS expression was preserved in the endothelium even by day 30, and associated with a decrease in intimal thickening. We further demonstrated that early overexpression of iNOS by ex vivo gene transfer completely prevented the development of arteriosclerosis associated with eNOS deficiency.

CONCLUSIONS

We found that eNOS plays a protective role in allografts, and that in eNOS-deficient allografts, early overexpression of iNOS is capable of preventing the development of allograft arteriosclerosis. In allografts with dysfunctional vascular endothelium and impaired eNOS activity as a result of ischemia or native arteriosclerotic disease, iNOS gene therapy may serve to improve their long-term survival and function.

Treatment of septic shock in rats with nitric oxide synthase inhibitors and inhaled nitric oxide

OBJECTIVE

To evaluate the effect of treatment with a combination of nitric oxide synthase inhibitors and inhaled nitric oxide on systemic hypotension during sepsis.

DESIGN

Prospective, randomized, controlled study on anesthetized animals.

SETTING

A cardiopulmonary research laboratory.

SUBJECTS

Forty-seven male adult Sprague-Dawley rats.

INTERVENTIONS

Animals were anesthetized, mechanically ventilated with room air, and randomized into six groups: a) the control group (C, n=6) received normal saline infusion; b) the endotoxin-treated group received 100 mg/kg i.v. of Escherichia coli lipopolysaccharide (LPS, n=9); c) the third group received LPS, and 1 hr later the animals were treated with 100 mg/kg i.v. Nw-nitro-L-arginine (LNA, n=9); d) the fourth group received LPS, and after 1 hr, the animals were treated with 100 mg/kg i.v. aminoguanidine (AG, n=9); e) the fifth group received LPS and 1 hr later was treated with LNA plus 1 ppm inhaled nitric oxide (LNA+NO, n=7); f) the sixth group received LPS and 1 hr later was treated with aminoguanidine plus inhaled NO (AG+NO, n=7). Inhaled NO was administered continuously until the end of the experiment.

MEASUREMENTS AND MAIN RESULTS

Systemic mean blood pressure (MAP) was monitored through a catheter in the carotid artery. Mean exhaled NO (ENO) was measured before LPS (T0) and every 30 mins thereafter for 5 hrs. Arterial blood gases and pH were measured every 30 mins for the first 2 hrs and then every hour. No attempt was made to regulate the animal body temperature. All the rats became equally hypothermic (28.9+/-1.2 degrees C [SEM]) at the end of the experiment. In the control group, blood pressure and pH remained stable for the duration of the experiment, however, ENO increased gradually from 1.3+/-0.7 to 17.6+/-3.1 ppb after 5 hrs (p< .05). In the LPS treated rats, MAP decreased in the first 30 mins and then remained stable for 5 hrs. The decrease in MAP was associated with a gradual increase in ENO, which was significant after 180 mins (58.9+/-16.6 ppb) and reached 95.3+/-27.5 ppb after 5 hrs (p< .05). LNA and AG prevented the increase in ENO after LPS to the level in the control group. AG caused a partial reversal of systemic hypotension, which lasted for the duration of the experiment. LNA reversed systemic hypotension almost completely but only transiently for 1 hr, and caused severe metabolic acidosis in all animals. The co-administration of NO with AG had no added benefits on MAP and pH. In contrast, NO inhalation increased the duration of the reversal in MAP after LNA, alleviated the degree of acidosis, and decreased the mortality rate (from 55% to 29%).

CONCLUSIONS

In this animal model, LPS-induced hypotension was alleviated slightly and durably after AG, but only transiently after LNA. Furthermore, co-administration of NO with AG had no added benefits but alleviated the severity of metabolic acidosis and mortality after LNA. We conclude that nitric oxide synthase (NOS) inhibitors, given as a single large bolus in the early phase of sepsis, can exhibit some beneficial effects. Administration of inhaled NO with NOS inhibitors provided more benefits in some conditions and therefore may be a useful therapeutic combination in sepsis. NO production in sepsis does not seem to be a primary cause of systemic hypotension. Other factors are likely to have a major role.

Nitric oxide in septic shock: directions for future therapy?

Septic shock is a major cause of death among patients in intensive care units. It has a mortality rate of 20% to 80%. The clinical syndrome of septic shock is characterised by hypotension, hyporesponsiveness to vasoconstrictors and volume depletion which will then lead to multiorgan dysfunction and death. Except for surgical and supportive care, no specific therapy is known. Recently interest has been focused on the role of nitric oxide (NO) in septic shock. Large amounts of NO released by the endothelium and vascular smooth muscle cells lead to profound vasodilation and hyporesponsiveness to vasoconstrictors. The cytotoxic effect of NO could also cause tissue injury and organ failure. Inhibition of NO synthase, the enzyme responsible for NO production, has been proposed as a new therapy for septic shock. However, experimental reports have provided conflicting results, demonstrating both beneficial and detrimental effects. A brief review of the role of NO in septic shock and the possible use of NO synthase inhibitors as potential therapeutic agents is presented here.

Prolonged reduction of high blood pressure with human nitric oxide synthase gene delivery

Endothelium-derived nitric oxide (NO) in peripheral vessels has been shown to modulate vascular resistance and blood pressure. We explored the effect of a continuous supply of human endothelial NO synthase (eNOS) on the blood pressure of spontaneously hypertensive rats (SHR) by somatic gene delivery. A DNA construct containing the human eNOS gene fused to the cytomegalovirus promoter/enhancer was injected into SHR through the tail vein. A single injection of the naked eNOS plasmid DNA caused a significant reduction of systemic blood pressure for 5 to 6 weeks in SHR, and the effect continued for up to 10 to 12 weeks after a second injection. The differences were significant from 2 to 12 weeks postinjections (n=6, P<.01). In a separate experiment, L-arginine, the substrate of eNOS, was supplied in drinking water at a concentration of 7.5 g/L for 11 weeks after eNOS gene delivery. A maximal blood pressure reduction of 21 mm Hg in SHR was observed with eNOS DNA compared with that of control SHR injected with vector DNA (181.9+/-1.46 versus 202.7+/-2.79 mm Hg, mean+/-SEM, n=6, P<.01). Human eNOS gene delivery induces significant increases in urinary and aortic cGMP levels and urinary and serum nitrite/nitrate content (P<.05), while no significant differences in body weight, heart rate, water intake, food consumption, or urine excretion were observed. These results indicate that somatic delivery of the human eNOS gene induces a prolonged reduction of high blood pressure and raises the potential of using eNOS gene therapy for hypertension and cardiovascular diseases.

Vascular gene transfer of the human inducible nitric oxide synthase: characterization of activity and effects on myointimal hyperplasia

BACKGROUND

Nitric oxide (NO) has been shown to decrease myointimal hyperplasia in injured blood vessels. We hypothesize inducible No synthase (iNOS) gene transfer even at low efficiency will provide adequate local no production to achieve this goal.

MATERIALS AND METHODS

A retroviral vector containing the human iNOS cDNA (DFGiNOS) was used to transfer the iNOS gene into vascular cells and isolated blood vessels to answer the following questions: can vascular endothelial and smooth muscle cells support iNOS activity and will low efficiency iNOS gene transfer suppress myointimal hyperplasia in injured porcine arteries?

RESULTS

DFGiNOS-infected sheep pulmonary artery endothelial cells (SPAEC) expressed significant iNOS mRNA and protein, releasing nitrite levels of 155.0 +/- 10.7 nmol/mg protein/24 h vs. 5.5 +/- 1.1 by control cells. Transduced rat smooth muscle cells (RSMC) also expressed abundant iNOS mRNA and protein, but, in contrast to SPAEC, NO synthesis was dependent on exogenous tetrahydrobiopterin (BH4) (291.8 +/- 10.4 nmol nitrite/mg protein/24 hr with BH4, 37.7 +/- 2.6 without BH4). Only porcine arteries infected with DFGiNOS following balloon injury exhibited a 3-fold increase in total NO synthesis and a 15-fold increase in cGMP levels over control vessels in a BH4 dependent fashion, despite only a 1% gene transfer efficiency. Transfer of iNOS completely prevented the 53% increase in myointimal thickness induced by balloon catheter injury; the administration of a NOS inhibitor reversed this effect.

CONCLUSIONS

These in vitro findings suggest that vascular iNOS gene transfer may be feasible. Furthermore, a low gene transfer efficiency may be sufficient to inhibit myointimal hyperplasia following arterial balloon injury, although a source of BH4 may be required.