Cigarette smoke activates guanylate cyclase and increases guanosine 3',5'-monophosphate in tissues

Cross-Regulation of the Cellular Redox System, Oxygen, and Sphingolipid Signalling

Redox-active mediators are now appreciated as powerful molecules to regulate cellular dynamics such as viability, proliferation, migration, cell contraction, and relaxation, as well as gene expression under physiological and pathophysiological conditions. These molecules include the various reactive oxygen species (ROS), and the gasotransmitters nitric oxide (NO∙), carbon monoxide (CO), and hydrogen sulfide (H2S). For each of these molecules, direct targets have been identified which transmit the signal from the cellular redox state to a cellular response. Besides these redox mediators, various sphingolipid species have turned out as highly bioactive with strong signalling potential. Recent data suggest that there is a cross-regulation existing between the redox mediators and sphingolipid molecules that have a fundamental impact on a cell’s fate and organ function. This review will summarize the effects of the different redox-active mediators on sphingolipid signalling and metabolism, and the impact of this cross-talk on pathophysiological processes. The relevance of therapeutic approaches will be highlighted.

ACTH-Modulated Membrane Guanylate Cyclase Signaling System: Origin and Creation

The membrane guanylate cyclase (MGC) cellular signaling pathway consists of seven signaling pathways and is critical for the survival of prokaryotes eukaryotes, and highly complex vertebrate organisms. A sequel to the author's earlier comprehensive reviews, covering the field of MGC from its origin to its establishment to the year 2014, this article exclusively deals with the history of its development from the year 1963 to 1987. It narrates the efforts involved in building on small projects, brick by brick, and its emergence from the chasm of disbelief, through steady, continuous work. To make the presentation simple and chronologically continuous, the subject matters of the earlier reviews and publication of these authors have been freely borrowed with appropriate citations.

Vascular Responses to Extractable Fractions of Ilex paraguariensis in Rats Fed Standard and High-Cholesterol Diets

The authors investigated the vasorelaxant properties of the aqueous (Aq-EF) and acid n-butanolic (acn-BuOH) extractable fractions from Ilex paraguariensis leaves. Perfusion pressure was evaluated using isolated and perfused mesenteric arterial beds (MABs) from rats fed hypercholesterolemic and standard diets. Extract-induced vasorelaxation in the presence and absence of various inhibitors was examined following precontraction of the MABs with methoxamine (30 μM) solution. In hypercholesterolemic-diet rats, relaxation in intact MABs was significantly decreased with ac-n-BuOH-EF bolus (300, 600, 900 μg) in comparison to those in standard-diet rats. After the endothelium was stripped from the MABs, the vascular responses to ac-n-BuOH-EF and 900 μg bolus of Aq-EF were significantly changed. Treatment of the MABs with an inhibitor of nitric oxide synthase, NG -nitro-L-arginine methylester hydrochloride (L-NAME, 10 mM), did not change either ac-n-BuOH-EF- or Aq-EF-induced vasodilation except for the 900 g bolus of Aq-EF. The guanilate cyclase inhibitor methylene blue (100 μM) did not affect vasodilation for either fraction in the MABs from the hypercholesterolemic-diet rats. The chronic oral administration of I. paraguariensis extract in hypercholesterolemic-diet rats resulted in a significant reduction in serum levels of cholesterol and triglycerides. These results suggest that I. paraguariensis ac-n-BuOH-EF and Aq-EF induce vasodilation in standard-diet rats in a dose-dependent manner and that the hypercholesterolemic diet substantially reduced the effect of ac-n-BuOH-EF on precontracted MABs.

Regulation of gene expression by tobacco product preparations in cultured human dermal fibroblasts

Skin fibroblasts comprise the first barrier of defense against wounds, and tobacco products directly contact the oral cavity. Cultured human dermal fibroblasts were exposed to smokeless tobacco extract (STE), total particulate matter (TPM) from tobacco smoke, or nicotine at concentrations comparable to those found in these extracts for 1h or 5h. Differences were identified in pathway-specific genes between treatments and vehicle using qRT-PCR. At 1h, IL1α was suppressed significantly by TPM and less significantly by STE. Neither FOS nor JUN was suppressed at 1h by tobacco products. IL8, TNFα, VCAM1, and NFκB1 were suppressed after 5h with STE, whereas only TNFα and NFκB1 were suppressed by TPM. At 1h with TPM, secreted levels of IL10 and TNFα were increased. Potentially confounding effects of nicotine were exemplified by genes such as ATF3 (5h), which was increased by nicotine but suppressed by other components of STE. Within 2h, TPM stimulated nitric oxide production, and both STE and TPM increased reactive oxygen species. The biological significance of these findings and utilization of the gene expression changes reported herein regarding effects of the tobacco product preparations on dermal fibroblasts will require additional research.

Cell-specific expression and immunolocalization of nitric oxide synthase isoforms and soluble guanylyl cyclase α1 and β1 subunits in the ovary of fetal, neonatal and immature pigs

The present study is designed to investigate the cellular expression and immunolocalization of three different nitric oxide synthase (NOS) isoforms and soluble guanylyl cyclase (sGC) subunits in the porcine ovary. Our results showed that in the fetal and neonatal pigs, all three isoforms of NOS were mainly localized in the oocyte and showed the expression of gradual increase in the granulosa cell and theca cell with the growing follicle. In addition, subunits of the sGC, sGC α1 and β1 were mainly expressed in the granulosa cell in precious studies. The bioactivity of total NOS, eNOS, iNOS and nNOS was detected in the ovary and were higher at prenatal stages compared to postnatal stages. However, the activities of nNOS were no different between prenatal stages and postnatal stages. Taken together, our findings suggested that the NOS/sGC pathway may be involved in the follicular formation and development in the porcine ovary.

Cell-specific expression and immunolocalization of nitric oxide synthase isoforms and the related nitric oxide/cyclic GMP signaling pathway in the ovaries of neonatal and immature rats

OBJECTIVE

The present study is designed to investigate the cellular expressions and immunolocalizations of three different nitric oxide synthase (NOS) isoforms and the related nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling pathway in the ovaries of neonatal and immature rats.

METHODS

The ovaries were obtained from ICR (Institute for Cancer Research) female Sprague-Dawley rats at postnatal days 1, 5, 7, 10, and 19. Then we carried out the histologic examination, immunohistochemistry, measurement of NOS activity, and modifications within the NO/cGMP pathway.

RESULTS

During postnatal days 1, 5, 7, 10, and 19, all three isoforms of NOS were mainly localized to the oocytes and expressed as a gradual increase in granulosa cells and theca cells within the growing follicle. The ovarian total NOS activities and NO levels were increased at postnatal days 7 and 10 compared with other days.

CONCLUSIONS

Our findings suggest that the locally produced NO and the NO/NOS signaling systems are involved in the follicular development to puberty.

Membrane guanylate cyclase is a beautiful signal transduction machine: overview

This article is a sequel to the four earlier comprehensive reviews which covered the field of membrane guanylate cyclase from its origin to the year 2002 (Sharma in Mol Cell Biochem 230:3-30, 2002) and then to the year 2004 (Duda et al. in Peptides 26:969-984, 2005); and of the Ca(2+)-modulated membrane guanylate cyclase to the year 1997 (Pugh et al. in Biosci Rep 17:429-473, 1997) and then to 2004 (Sharma et al. in Curr Top Biochem Res 6:111-144, 2004). This article contains three parts. The first part is "Historical"; it is brief, general, and freely borrowed from the earlier reviews, covering the field from its origin to the year 2004 (Sharma in Mol Cell Biochem, 230:3-30, 2002; Duda et al. in Peptides 26:969-984, 2005). The second part focuses on the "Ca(2+)-modulated ROS-GC membrane guanylate cyclase subfamily". It is divided into two sections. Section "Historical" and covers the area from its inception to the year 2004. It is also freely borrowed from an earlier review (Sharma et al. in Curr Top Biochem Res 6:111-144, 2004). Section "Ca(2+)-modulated ROS-GC membrane guanylate cyclase subfamily" covers the area from the year 2004 to May 2009. The objective is to focus on the chronological development, recognize major contributions of the original investigators, correct misplaced facts, and project on the future trend of the field of mammalian membrane guanylate cyclase. The third portion covers the present status and concludes with future directions in the field.

Novel techniques for real-time monitoring of cGMP in living cells

Recent developments of biophysical and electrophysiological techniques have enabled researchers to monitor levels of free intracellular cGMP in real-time and in intact living cells. These techniques are based on the use of cGMP sensors, which respond to cGMP with changes in transmembrane ion current or changes in fluorescence. Here, we describe the principles of these techniques, compare them in terms of sensitivity and discuss possible application for current cell biology and physiology.

Smoking-gene interaction and disease development: relevance to pancreatic cancer and atherosclerosis

There is little doubt that cigarette smoking remains a major environmental health risk that humans are facing in the twenty-first century. Cigarette smokers are more likely to develop many forms of diseases than nonsmokers, including cancers and vascular diseases. With the availability of the human genome sequence, we become more aware of the genetic contributions to these common diseases, especially the interactive relations between environmental factors (e.g., smoking) and genes on disease susceptibility, development, and prognosis. Although smoking is responsible for up to 30% of pancreatic cancers and about 10% of cases are ascribed to genetic reasons, some genetic variants do not predispose carriers to disease development unless they are exposed to a specific adverse environment such as smoking. This smoke-gene interaction could potentially be responsible for most of the cases. Certain polymorphisms in genes such as CYP1A1 have been shown particularly sensitive to smoking-induced pathogenesis, including pancreatic cancer and atherosclerosis. We found that individuals with CYP1A1 CC genotype had a more than three fold increase in risk for severe coronary atherosclerosis when they smoked. Patients with endothelial nitric oxide synthase (eNOS) intron 4 27 repeat homozygotes were more likely to develop severe coronary stenosis when they smoked. On the other hand, DNA variants at the eNOS gene also dictate how smoking affects the expression of eNOS. We showed that GSTM1 deficiency was not involved in smoking-induced vascular diseases, but p53 polymorphisms tended to modify the disease severity in smokers. We are still at an early stage of defining the pairs and mechanisms of smoke-gene interaction, and this etiologic mechanism may hold great potential for risk assessment, treatment strategy, and prognostic predictions.

Physiologie und Pathophysiologie der erektilen Dysfunktion

Notions and hypotheses of the pathophysiologic process in erectile dysfunction--its errors and embarrassment--are focused on beginning with Aristotle and continued in the Renaissance and the Enlightenment. Only in the middle of the nineteenth century was there recognition of the central role of relaxation of the trabecular muscles. It took another 100 years until we had a useful treatment option at hand.

Cell-specific expression and regulation of soluble guanylyl cyclase alpha 1 and beta 1 subunits in the rat ovary

Soluble guanylyl cyclase (sGC) is activated by nitric oxide (NO) and carbon monoxide, resulting in cGMP production. Recent studies indicate that NO and cGMP influence ovarian functions. However, little information is available regarding the ovarian expression of sGC. The present study examined sGC alpha(1) and beta(1) subunit protein levels in the ovary during postnatal development, gonadotropin-induced follicle growth, ovulation, and luteinization as well as in cultured rat granulosa cells. In postnatal rats, sGC alpha(1) subunit immunoreactivity was high in granulosa cells of primordial and primary follicles on Day 5 but low in granulosa cells of larger follicles on Days 10 and 19. Theca cells of developing follicles, but not stromal cells, also demonstrated moderate sGC alpha(1) immunoreactivity. In gonadotropin- treated immature rats, intense sGC alpha(1) subunit staining was similarly observed in granulosa cells of primordial and primary follicles, but such staining was low in granulosa cells of small antral follicles and undetectable in granulosa cells of large antral and preovulatory follicles. Following ovulation, corpora lutea expressed moderate sGC alpha(1) immunoreactivity. Similar ovarian localization and expression patterns were seen for sGC beta(1), indicating regulated coexpression of sGC subunits. Immunoblot analysis revealed no change in total ovarian sGC alpha(1) and beta(1) subunit protein levels during gonadotropin treatment. Similarly, no effect of FSH on sGC subunit protein levels was apparent in cultured granulosa cells. These findings indicate regulated, cell- specific patterns of sGC expression in the ovary and are consistent with roles for cGMP in modulating ovarian functions.

Genetic influence on cigarette-induced cardiovascular disease

Cigarette smoking as an addictive habit has accompanied human beings for more than 4 centuries. It is also one of the most potent and prevalent environmental health risks human beings are exposed to, and it is responsible for more than 1000 deaths each day in the United States. With recent research progress, it becomes clear that cigarette smoking can cause almost all major diseases prevalent today, such as cancer or heart disease. These detrimental effects are not only present in active smokers who choose the risk, but also to innocent bystanders, as passive smokers, who are exposed to cigarettes not-by-choice. While the cigarette-induced harm to human health is indiscriminate and severe, the degree of damage also varies from individual to individual. This intersubject variability in cigarette-induced pathologies is partly mediated by genetic variants of genes that may participate in detoxification process, eg, cytochrome P450 (CYP), cellular susceptibility to toxins, such as p53, or disease development. Through population studies, we have learned that certain CYP1A1 variants, such as Mspl polymorphism, may render the carriers more susceptible to cigarette-induced lung cancer or severe coronary atherosclerosis. The endothelial nitric oxide synthase intron 4 rare allele homozygotes are more likely to have myocardial infarction if they also smoke. In vitro experimental approach has further demonstrated that cigarettes may specifically regulate these genes in genotype-dependent fashion. While we still know little about genetic basis and molecular pathways for cigarette-induced pathological changes, understanding these mechanisms will be of great value in designing strategies to further reduce smoking in targeted populations, and to implement more effective measures in prevention and treatment of cigarette-induced diseases.

Ophidian envenomation strategies and the role of purines

Snake envenomation employs three well integrated strategies: prey immobilization via hypotension, prey immobilization via paralysis, and prey digestion. Purines (adenosine, guanosine and inosine) evidently play a central role in the envenomation strategies of most advanced snakes. Purines constitute the perfect multifunctional toxins, participating simultaneously in all three envenomation strategies. Because they are endogenous regulatory compounds in all vertebrates, it is impossible for any prey organism to develop resistance to them. Purine generation from endogenous precursors in the prey explains the presence of many hitherto unexplained enzyme activities in snake venoms: 5'-nucleotidase, endonucleases (including ribonuclease), phosphodiesterase, ATPase, ADPase, phosphomonoesterase, and NADase. Phospholipases A(2), cytotoxins, myotoxins, and heparinase also participate in purine liberation, in addition to their better known functions. Adenosine contributes to prey immobilization by activation of neuronal adenosine A(1) receptors, suppressing acetylcholine release from motor neurons and excitatory neurotransmitters from central sites. It also exacerbates venom-induced hypotension by activating A(2) receptors in the vasculature. Adenosine and inosine both activate mast cell A(3) receptors, liberating vasoactive substances and increasing vascular permeability. Guanosine probably contributes to hypotension, by augmenting vascular endothelial cGMP levels via an unknown mechanism. Novel functions are suggested for toxins that act upon blood coagulation factors, including nitric oxide production, using the prey's carboxypeptidases. Leucine aminopeptidase may link venom hemorrhagic metalloproteases and endogenous chymotrypsin-like proteases with venom L-amino acid oxidase (LAO), accelerating the latter. The primary function of LAO is probably to promote prey hypotension by activating soluble guanylate cyclase in the presence of superoxide dismutase. LAO's apoptotic activity, too slow to be relevant to prey capture, is undoubtedly secondary and probably serves principally a digestive function. It is concluded that the principal function of L-type Ca(2+) channel antagonists and muscarinic toxins, in Dendroaspis venoms, and acetylcholinesterase in other elapid venoms, is to promote hypotension. Venom dipeptidyl peptidase IV-like enzymes probably also contribute to hypotension by destroying vasoconstrictive peptides such as Peptide YY, neuropeptide Y and substance P. Purines apparently bind to other toxins which then serve as molecular chaperones to deposit the bound purines at specific subsets of purine receptors. The assignment of pharmacological activities such as transient neurotransmitter suppression, histamine release and antinociception, to a variety of proteinaceous toxins, is probably erroneous. Such effects are probably due instead to purines bound to these toxins, and/or to free venom purines.

Nitric oxide generation in aqueous solutions of cigarette smoke and approaches to its origin

By using the ESR spin trapping technique with the N-methyl-D-glucamine dithiocarbamate (MGD)2-Fe(II) complex, the generation of nitric oxide (NO), a gaseous free radical, was observed in NO spin trapping solution bubbled with the filtered main-stream of cigarette smoke. The ESR signal with a three-line spectrum characteristic of an NO radical, which was not observed immediately after bubbling of smoke, started rapidly increasing with time up to around 25 min after the last addition of ferrous ions Fe(II), and then slowly approached a peak value dependent on the burned cigarette mass and on the smoking speed. The production of NO was, however, much affected by air oxidation and enhanced by the addition of ascorbic acid. A certain concentration of sodium nitrite (NaNO2) solution, in which nitrite NO2- is assumed as the main origin of the NO, mimicked closely the time course of NO generation resulting from the smoke of one cigarette. The cigarette smoke that was passed through alkaline pyrogallol solution as a deoxidizer; however, it exhibited an unchanged intensity of NO signal throughout the measurement. These results strongly suggest that NO would be gradually reproduced from NO2- in the reductive aqueous solution containing excess Fe(II) through NO2, which is initially formed and is concomitantly oxidized from NO in cigarette smoke.

Nitric oxide inhalation transiently elevates pulmonary levels of cGMP, iNOS mRNA, and TNF-alpha

The initial pulmonary vasodilation that occurs during nitric oxide (. NO) inhalation does not appear to be maintained chronically in many cases. . NO may acutely relax vascular smooth muscle by increasing levels of guanosine 3',5'-cyclic monophosphate (cGMP), tumor necrosis factor (TNF)-alpha, and inducible nitric oxide synthase (iNOS) while decreasing levels of lipid peroxidation. It was hypothesized that the acute . NO-induced changes in cGMP, TNF-alpha, iNOS, and lipid peroxidation, all of which may mediate vasodilation, are transient rather than sustained. Lungs from rats kept in chambers containing 6 parts/million . NO for 1 h, 1 day, or 1 wk were analyzed for levels of . NO-induced vasodilatory mediators. Pulmonary cGMP, iNOS mRNA, and TNF-alpha were increased 1 h after . NO exposure but decreased to control values at later times. Levels of malonyl dialdehyde, an indicator of lipid peroxidation, were decreased at all times during . NO inhalation. As a whole, the data suggest that in lungs the vasodilatory mediators cGMP, iNOS, and TNF-alpha are only acutely and transiently elevated during inhalation of . NO, consistent with the initially positive clinical response to inhaled . NO that deteriorates over time.

The nitric oxide/cyclic GMP pathway: a potential major regulator of cochlear physiology

The nitric oxide (NO)/cyclic guanosine monophosphate (GMP) pathway is now recognized as a major regulatory system in cell physiology and tissue homeostasis. This pathway may control processes as diverse as muscle relaxation, gut peristalsis, neurotransmission and hormonal secretion. It is also involved in the development and function of sensory systems such as vision and olfaction. This review will detail the NO/cyclic GMP pathway, evaluate studies in the auditory system and discuss its potential participation in cochlear blood flow, supporting cell physiology and excitotoxicity.

Activation of human neutrophil procollagenase by nitrogen dioxide and peroxynitrite: a novel mechanism for procollagenase activation involving nitric oxide

The involvement of nitric oxide (NO) and its reactive intermediates such as nitrogen dioxide (NO2) and peroxynitrite (ONOO-) in the activation of matrix metallo-proteinase was investigated. The human neutrophil procollagenase (matrix metalloproteinase-8) (M(r), 85 kDa) was purified to homogeneity from human neutrophils by using column chromatography. After incubation of human neutrophil procollagenase with various nitrogen oxide-generating systems, collagenolytic activity in each reaction system was measured. In addition, neutrophil collagenase activity was determined by assessment of proteolysis of human alpha 1-protease inhibitor. NO was formed by the propylamine NONOate, and NO2 was generated by oxidation of NO with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (carboxy-PTIO). NO2, formed by NONOate and carboxy-PTIO, and the synthetic ONOO- exhibited strong activation of the procollagenase at 1-20 microM. Significant activation of the procollagenase was observed with use of authentic NO2 gas as well. Constant flux infusion of ONOO- into the procollagenase solution resulted in stronger procollagenase activation than did a bolus addition of ONOO- to the reaction mixture. However, NO showed only weak activating potential under the aerobic (ambient) condition; an NO concentration of more than 10 mM was needed for appreciable activation of the procollagenase. Of considerable importance was the fact that NO participates in activation of the neutrophil collagenase through its conversion to NO2 or ONOO- in human neutrophils. These results suggest that NO2 and ONOO- may be potent activators of human neutrophil procollagenase.

Smoke-derived nitric oxide and vascular prostacyclin are unable to counteract the platelet effect of increased thromboxane formation in healthy female smokers

The incidence of cigarette smoking tends to be higher in women, justifying directed studies on smoke-related mechanisms of cardiovascular disorder in females. Platelet activity plays an important etiological role in several settings of cardiovascular disease. Cigarette smoking facilitates platelet formation of proaggregatory thromboxane A2. However, cigarette smoke contains nitric oxide (NO), which has antiplatelet activity. Furthermore, the formation of anti-aggregatory prostacyclin (PGI2) may be higher in smokers than in non-smokers. Hence, the concerted action of NO and PGI2 on platelet activity in smoking females is important to elucidate. The metabolites of TxA2, NO, and PGI2, as well as cyclic guanosine 3':5'-monophosphate (cGMP; second messenger for NO in the platelets) and cyclic adenosine 3':5'-monophosphate (cAMP; second messenger for PGI2 in the platelets), were analysed in 23 healthy female smokers (daily consumption 11-20 cigarettes per day) and in 26 matched non-smokers. The urinary excretion of 2,3-dinor TxB2 (metabolite of TxA2) was considerably higher in smokers than in non-smokers (177 vs. 72 pg/mg creatinine, respectively; P<0.001). Plasma and urinary levels of nitrate (metabolite of inhaled NO) did not differ between the groups. Plasma and urinary cGMP were slightly increased (252 vs. 193 nmol/L; P<0.05 and 0.63 vs. 0.51 micromol/24 h; P<0.05, respectively) in smokers compared to non-smokers, while platelet cGMP was lower in smokers than in non-smokers (81 vs. 10.3 pmol/10(6) platelets, respectively; P<0.05). The urinary excretion of 2,3-dinor-6-keto-PGF1a (metabolite of PGI2) did not differ between the groups. Platelet or urinary cAMP did not differ between the groups either, while plasma cAMP was lower in smokers than in non-smokers (19.2 vs. 26.2 nmol/l, respectively; P<0.001). In healthy female smokers NO is not absorbed from the inhaled smoke, and endothelial PGI2 formation is not enhanced to counterbalance the increased platelet formation of proaggregatory TxA2.

Inhaled cigarette smoke selectively reverses human hypoxic vasoconstriction

The acute effects of the inhaled gas phase of cigarette smoke on pulmonary (PAP) and systemic (SAP) arterial pressures and on plasma arterial cGMP content were compared with those of inhaling 10, 20 and 80 ppm nitric oxide (NO) in one healthy adult volunteer spontaneously breathing a hypoxic gas mixture. Hypoxia (FIO2 0.12) induced a sustained, stable pulmonary vasoconstriction. Inhaled NO induced a dose-dependent fall in PAP; plasma cGMP rose from 39.4 (hypoxia) to 164 pmol/ml (hypoxia plus 80 ppm NO). Exposure to cigarette smoke induced a rapid, consistent and reversible fall in PAP; plasma cGMP rose from 45.5 (hypoxia) to 138 pmol/ml (hypoxia plus cigarette smoke). Neither NO nor cigarette smoke inhalation induced any change in SAP. These data suggest that exposure to cigarette smoke is able selectively to reverse acute hypoxic vasoconstriction in humans without causing systemic vasodilation, an effect likely mediated through the NO-cGMP pathway.

The role of nitric oxide (formerly endothelium-derived relaxing factor-EDRF) in vasodilatation and vasodilator therapy

Nitric oxide is widely distributed in the body. It has an important role in the regulation of the circulation and as yet, ill-defined roles in nervous and immune systems. It is derived from L-arginine from a reaction catalysed by a constitutive intracellular enzyme, nitric oxide synthase. It is recognised as the endogenous nitrovasodilator whose action is mimicked by all exogenous nitrovasodilators. After production in the vascular endothelial cell, it diffuses to the smooth muscle cell where it activates the enzyme guanylate cyclase which leads to an increase in cyclic GMP and thence to muscle relaxation. The duration of its action is brief, a few seconds. Disorders of NO metabolism underlie many disease states including endotoxic shock in which prolonged production of nitric oxide may be induced by cytokines. Deficiencies in endogenous production may account for hypertension in various disease states including atherosclerosis and chronic renal failure. NO therapy been used experimentally to successfully treat idiopathic pulmonary hypertension and pulmonary hypertension associated with cardiac and respiratory diseases. However, the long-term benefits have yet to be studied. Administration of NO requires the use of a device to monitor the concentrations of both NO and of NO2. The latter is a noxious agent and a time-related product of the reaction between NO and O2 and is a possible contaminant of preparations of NO. Precautions must be taken to prevent contamination of the work-place atmosphere with NO and NO2. These include gas scavenging and the use of a leak-free system for spontaneous and mechanical ventilation. Using NO in its gaseous form, clinicians have at long last been provided with the means to treat pulmonary hypertension without adversely causing systemic hypotension. The therapy is most suited to short-term use in mechanically ventilated patients. Safe practical long-term NO therapy must await the development of agents which release NO from aerosol preparations.

Pulmonary effects of endogenous and exogenous nitric oxide in the pig: relation to cigarette smoke inhalation

1. Pentobarbitone-anaesthetized pigs were challenged with cigarette smoke (unfiltered or filtered through a Cambridge glass fibre filter to remove the particulate phase including nicotine), as well as nicotine aerosol and the gas phase components nitric oxide (NO) and carbon monoxide (CO); the effects on the bronchial and pulmonary circulations, and pulmonary airway mechanics, were examined. The relative importance of endogenous NO mechanisms in the pig lung was also studied by giving the NO synthesis inhibitor NG-nitro-L-arginine (L-NOARG; 50 mg kg-1) intravenously. Mean arterial pressure and blood flow in the bronchial, pulmonary and femoral circulations were measured, the latter with ultrasonic flow probes around the supplying arteries, and vascular resistance (VR) was calculated. Changes in pulmonary airways resistance (Rpulm) and lung dynamic compliance (Cdyn) were also determined. Finally, the concentration of NO in inhaled air during cigarette smoke and NO gas challenges was continuously monitored by a chemiluminescence method and the relative contribution of NO in cigarette smoke-induced vascular effects in the pig lung was calculated. 2. Cigarette smoke challenge, with or without a Cambridge filter, caused a rapid vasodilator response in the bronchial circulation and the major part (75%) of this response was probably caused by NO present in smoke. NO challenge caused profound bronchial vasodilation with dose-response characteristics between 10 and 100 p.p.m. The small part of the cigarette smoke-induced response not explained by the NO content may be caused by CO, showing weak vasodilator effect in the bronchial circulation. The L-NOARG-induced relative increase in bronchial VR was 2-3 times higher than the changes in pulmonary, femoral and systemic VR, suggesting a strong influence of endothelial NO mechanisms on basal tone in the bronchial circulation.3. Challenge with unfiltered cigarette smoke induced variable responses in the pulmonary circulation,whereas inhalation of filtered smoke caused consistent pulmonary vasodilatation. The major part of this vasodilator response was probably caused by NO, which was a potent dilator of the pulmonary circulation with maximal effect achieved with as little as 10 p.p.m. The effect of NO may be opposed in unfiltered smoke by the particulate phase (but not nicotine), presumably by inducing sympathetic reflexes. L-NOARG caused similar relative increases in pulmonary, femoral and systemic VR.4. Cigarette smoke inhalation induced bronchodilatation in the pentobarbitone-anaesthetized pig as revealed by changes in Rpulm and Cdyn. Both NO and nicotine may contribute to this response. NO inhalation reduced Rpulm in the basal state with maximal effect at 30 p.p.m. The mechanism for NO-induced bronchodilatation may be indirect in the pig, since pretreatment with L-NOARG blocked the response. L-NOARG did not affect basal Rpulm.5. In conclusion, bronchial vasodilatation caused by continuous cigarette smoke inhalation in the pig,seems to be largely mediated (approximately 75%) by NO. The remaining part could be mediated by CO. Cigarette smoke particles, but not nicotine, may counteract NO-induced relaxation in the pulmonary circulation, thus resulting in variable effects in the pulmonary circulation during challenge with unfiltered cigarette smoke. NO also acts as a bronchodilator in the pig, but the mechanism may be indirect. Finally, endogenous NO mechanisms appear to be strongly involved in the control of basal tone in the bronchial circulation, less so in the pulmonary circulation and not at all in bronchial smooth muscle.

Inhaled nitric oxide reverses pulmonary vasoconstriction in the hypoxic and acidotic newborn lamb

We determined whether inhaling low levels of nitric oxide (NO) gas could selectively reverse hypoxic pulmonary vasoconstriction in the near-term newborn lamb and whether vasodilation would be attenuated by respiratory acidosis. To examine the mechanism of air and NO-induced pulmonary vasodilation soon after birth, we measured plasma and lung cGMP levels in the newly ventilated fetal lamb. Breathing at FIO2 0.10 nearly doubled the pulmonary vascular resistance index in newborn lambs and decreased pulmonary blood flow primarily by reducing left-to-right blood flow through the ductus arteriosus. Inhaling 20 ppm NO at FIO2 0.10 completely reversed hypoxic pulmonary vasoconstriction within minutes. Maximum pulmonary vasodilation occurred during inhalation of > or = 80 ppm NO. Breathing 8% CO2 at FIO2 0.10 elevated the pulmonary vascular resistance index to a level similar to breathing at FIO2 0.10 without added CO2. Respiratory acidosis did not attenuate pulmonary vasodilation by inhaled NO. In none of our studies did inhaling NO produce systemic hypotension or elevate methemoglobin levels. Four minutes after initiating ventilation with air in the fetal lamb lung, cGMP concentration nearly doubled without changing preductal plasma cGMP concentration. Ventilation with 80 ppm NO at FIO2 0.21 increased both lung and preductal plasma cGMP concentration threefold. Our data suggest that inhaled NO gas is a rapid and potent selective vasodilator of the newborn pulmonary circulation with an elevated vascular tone due to hypoxia and respiratory acidosis that acts by increasing lung cGMP concentration.

Bronchodilator action of inhaled nitric oxide in guinea pigs

The effects of inhaling nitric oxide (NO) on airway mechanics were studied in anesthetized and mechanically ventilated guinea pigs. In animals without induced bronchoconstriction, breathing 300 ppm NO decreased baseline pulmonary resistance (RL) from 0.138 +/- 0.004 (mean +/- SE) to 0.125 +/- 0.002 cmH2O/ml.s (P less than 0.05). When an intravenous infusion of methacholine (3.5-12 micrograms/kg.min) was used to increase RL from 0.143 +/- 0.008 to 0.474 +/- 0.041 cmH2O/ml.s (P less than 0.05), inhalation of 5-300 ppm NO-containing gas mixtures produced a dose-related, rapid, consistent, and reversible reduction of RL and an increase of dynamic lung compliance. The onset of bronchodilation was rapid, beginning within 30 s after commencing inhalation. An inhaled NO concentration of 15.0 +/- 2.1 ppm was required to reduce RL by 50% of the induced bronchoconstriction. Inhalation of 100 ppm NO for 1 h did not produce tolerance to its bronchodilator effect nor did it induce substantial methemoglobinemia (less than 2%). The bronchodilating effects of NO were additive with the effects of inhaled terbutaline, irrespective of the sequence of NO and terbutaline administration. Inhaling aerosol generated from S-nitroso-N-acetylpenicillamine also induced a rapid and profound decrease of RL from 0.453 +/- 0.022 to 0.287 +/- 0.022 cmH2O/ml.s, which lasted for over 15 min in guinea pigs broncho-constricted with methacholine. Our results indicate that low levels of inhaled gaseous NO, or an aerosolized NO-releasing compound are potent bronchodilators in guinea pigs.

Recent progress in testing the longevity determinant and dysdifferentiation hypotheses of aging

An overview of the longevity determinant and dysdifferentiation hypotheses is presented, highlighting some of the major postulates and predictions. Results of recent experiments testing these hypotheses are discussed, including the search for specific longevity determinant genes and evidence that cancer and aging may have common causative mechanisms of action and control. Regulation of oxidative stress is considered a potential longevity determinant mechanism and methods and results testing this prediction are reviewed. Possibility of enhancing protective mechanisms against oxidative stress is discussed by way of intervention of central regulatory mechanisms of antioxidants using the cyclase-arachidonic acidcyclooxygenase (GAC model).

Evidence for cigarette smoke-induced calcitonin secretion from lungs of man and hamster

In hamsters, acute cigarette smoke inhalation increased serum levels of the hormone calcitonin; and, in humans, smoking of two high-nicotine content cigarettes increased serum and urine levels of this hormone. The source of this immunoreactive calcitonin (iCT) does not appear to be the thyroid gland, since previously thyroidectomized patients demonstrated a similar response. In the hamster, the increased serum iCT levels were accompanied by a decreased lung tissue iCT content and hypocalcemia. It is suggested that the source of the cigarette smoke-induced hypercalcitonemia is the lung, possibly from the iCT-containing pulmonary neuroendocrine (PNE) cells. Moreover, this response appears to be dependent on the nicotine content of the cigarettes.

Negative regulation of cyclic-AMP levels by carbamylcholine in dog thyroid is not mediated by cyclic-GMP

Carbamylcholine, through calcium, enhances cyclic-GMP accumulation and depresses cyclic-AMP accumulation in TSH stimulated dog thyroid. The results presented show that compounds which can be transformed to nitric oxide increase cyclic-GMP accumulation in the dog thyroid. These compounds do not require extracellular calcium for their action. In thyroid stimulated by TSH, these compounds do not depress AMP accumulation. Cyclic-GMP is not the main intracellular signal involved in the negative regulation of cyclic-AMP levels in dog thyroid.

Dietary vitamin E and pulmonary biochemical responses of rats to cigarette smoking

The effect of dietary vitamin E on cellular susceptibility to cigarette smoking was studied in rats. Young male rats maintained on a basal vitamin E-deficient diet with or without 100 ppm vitamin E supplementation for 4 or 5 weeks were exposed to either sham or cigarette smoke for up to 7 days. Higher animal mortality rate was observed in the animals fed the vitamin E-deficient diet than in the supplemented group when they were subjected to acute levels of cigarette smoking. Relative to the respective sham groups, a greater alteration of biochemical parameters, such as reduced glutathione (GSH) and related enzymes, was found in the lungs of smoked rats fed the deficient diet than in the supplemented group. Animal lungs exhibited a greater biochemical response to whole smoke than the gaseous phase of smoke. The results suggest that the nutritional status of vitamin E may influence the cellular susceptibility of rats to cigarette smoking.

Effect of diesel particulate exposure on adenylate and guanylate cyclase of rat and guinea pig liver and lung

An examination of the effects of 250 or 1500 micrograms m-3 concentrations of diesel particulate from diesel exhaust on the activity of adenylate or guanylate cyclase was undertaken using liver and lung tissue of rats and guinea pigs. These membrane and cytosolic enzymes were selected to screen for functional or regulatory alterations in these tissues. The studies for adenylate cyclase used the microsomal membrane fraction of each tissue; for guanylate cyclase, the microsomal membrane and supernate fractions were used. Basal and fluoride-stimulated adenylate cyclase activity were measured. Basal and sodium azide-stimulated guanylate cyclase activity were also determined. The basal activity of rat liver adenylate cyclase is generally unchanged throughout 52 weeks of diesel exposure. Stimulated adenylate cyclase shows an age-related decrease for all animal treatments throughout the study. Changes in enzyme activity occurred at 12 weeks and 52 weeks after 1500 micrograms m-3 exposure. Soluble stimulated guinea pig lung guanylate cyclase was first increased (6 weeks) and then decreased (24 weeks) by diesel exposure. At 52 weeks, there was no change. The data suggest the following trends: (1) an increased basal adenylate cyclase in the rat lung; (2) an age-related decrease in adenylate cyclase activity in rat liver, and (3) a biphasic exposure-related response of soluble guanylate cyclase for the guinea pig lung during the first 24 weeks, but no change at 52 weeks. In general, however, these studies suggest that diesel exposure does not substantially alter either of these intracellular regulating enzymes.

Cigarette smoke exposure in vivo increases cyclic GMP in rat lung

The enzyme guanylate cyclase is stimulated to produce cycle guanosine 3',5'-monophosphate (GMP) when lung tissue is exposed to cigarette smoke in vitro. These experiments tested whether in vivo exposure in rats to cigarette smoke produces a similar response. Adult rats were anaesthetized with pentobarbital and ventilation with mixtures of air and cigarette smoke at 10 cm H2O inspiratory pressure was achieved after a tracheotomy was performed. Lung tissue samples were taken at intervals during 20 min exposure period and analyzed for levels of cyclic adenosine 3', 5'-monophosphate (AMP) and cycle GMP. Blood carboxyhemoglobin (COHb) levels at 5 min and 15 min of exposure showed high, but sublethal levels of COHb. lung tissue cAMP was unchanged with this exposure, but cGMP levels rose dramatically. Rat lungs showed no changes related to ventilation under similar conditions in the absence of smoke. This observed response of cGMP to cigarette smoke may represent an important pulmonary defense mechanism.

Synthesis of adenosine 3',5'-monophosphate by guanylate cyclase, a new pathway for its formation

The 105 000 X g gupernatant fractions from homogenates of various rat tissues catalyzed the formation of both cyclic GMP and cyclic AMP from GTP and ATP, respectively. Generally cyclic AMP formation with crude or purified preparations of soluble guanylate cyclase was only observed when enzyme activity was increased with sodium azide, sodium nitroprusside, N-methyl-N'-nitro-N-nitrosoguanidine, sodium nitrite, nitric oxide gas, hydroxyl radical and sodium arachidonate. Sodium fluoride did not alter the formation of either cyclic nucleotide. After chromatography of supernatant preparations on Sephadex G-200 columns or polyacrylamide gel electrophoresis, the formation of cyclic AMP and cyclic GMP was catalyzed by similar fractions. These studies indicate that the properties of guanylate cyclase are altered with activation. Since the synthesis of cyclic AMP and cyclic GMP reported in this study appears to be catalyzed by the same protein, one of the properties of activated guanylate cyclase is its ability to catalyze the formation of cyclic AMP from ATP. The properties of this newly described pathway for cyclic AMP formation are quite different from those previously described for adenylate cyclase preparations. The physiological significance of this pathway for cyclic AMP formation is not known. However, these studies suggest that the effects of some agents and processes to increase cyclic AMP accumulation in tissue could result from the activation of either adenylate cyclase or guanylate cyclase.