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

Live to die another day: novel insights may explain the pathophysiology behind smoker's paradox in SARS-CoV-2 infection

The severe acute respiratory coronavirus 2 (SARS-CoV-2) infection demonstrates a highly variable and unpredictable course. Several reports have claimed a smoker's paradox in coronavirus disease 2019 (COVID-19), in line with previous suggestions that smoking is associated with better survival after acute myocardial infarction and appears protective in preeclampsia. Several plausible physiological explanations exist accounting for the paradoxical observation of smoking engendering protection against SARS-CoV-2 infection. In this review, we delineate novel mechanisms whereby smoking habits and smokers' genetic polymorphism status affecting various nitric oxide (NO) pathways (endothelial NO synthase, cytochrome P450 (CYP450), erythropoietin receptor (EPOR); β-common receptor (βcR)), along with tobacco smoke modulation of microRNA-155 and aryl-hydrocarbon receptor (AHR) effects, may be important determinators of SARS-CoV-2 infection and COVID-19 course. While transient NO bioavailability increase and beneficial immunoregulatory modulations through the above-mentioned pathways using exogenous, endogenous, genetic and/or therapeutic modalities may have direct and specific, viricidal SARS-CoV-2 effects, employing tobacco smoke inhalation to achieve protection equals self-harm. Tobacco smoking remains the leading cause of death, illness, and impoverishment.

Review of biomarkers to assess the effects of switching from cigarettes to modified risk tobacco products

Context: One approach to reducing the harm caused by cigarette smoking, at both individual and population level, is to develop, assess and commercialize modified risk alternatives that adult smokers can switch to. Studies to demonstrate the exposure and risk reduction potential of such products generally involve the measuring of biomarkers, of both exposure and effect, sampled in various biological matrices.Objective: In this review, we detail the pros and cons for using several biomarkers as indicators of effects of changing from conventional cigarettes to modified risk products.Materials and methods: English language publications between 2008 and 2017 were retrieved from PubMed using the same search criteria for each of the 25 assessed biomarkers. Nine exclusion criteria were applied to exclude non-relevant publications.Results: A total of 8876 articles were retrieved (of which 7476 were excluded according to the exclusion criteria). The literature indicates that not all assessed biomarkers return to baseline levels following smoking cessation during the study periods but that nine had potential for use in medium to long-term studies.Discussion and conclusion: In clinical studies, it is important to choose biomarkers that show the biological effect of cessation within the duration of the study.

Inhaled nitric oxide increases urinary nitric oxide metabolites and cyclic guanosine monophosphate in premature infants: relationship to pulmonary outcome

OBJECTIVE

Inhaled nitric oxide (iNO) has been tested to prevent bronchopulmonary dysplasia (BPD) in premature infants, however, the role of cyclic guanosine monophosphate (cGMP) is not known. We hypothesized that levels of NO metabolites (NOx) and cGMP in urine, as a noninvasive source for biospecimen collection, would reflect the dose of iNO and relate to pulmonary outcome.

STUDY DESIGN

Studies were performed on 125 infants who required mechanical ventilation at 7 to 14 days and received 24 days of iNO at 20-2 ppm. A control group of 19 infants did not receive iNO.

RESULTS

In NO-treated infants there was a dose-dependent increase of both NOx and cGMP per creatinine (maximal 3.1- and 2-fold, respectively, at 10-20 ppm iNO) compared with off iNO. NOx and cGMP concentrations at both 2 ppm and off iNO were inversely related to severity of lung disease during the 1st month, and the NOx levels were lower in infants who died or developed BPD at term. NOx was higher in Caucasian compared with other infants at all iNO doses.

CONCLUSION

Urinary NOx and cGMP are biomarkers of endogenous NO production and lung uptake of iNO, and some levels reflect the severity of lung disease. These results support a role of the NO-cGMP pathway in lung development.

Lack of evidence for contribution of Glu298Asp (G894T) polymorphism of endothelial nitric oxide synthase gene to plasma nitric oxide levels

INTRODUCTION

Both positive and negative associations between a rare allele of 27-bp repeat polymorphism in intron 4 of endothelial nitric oxide synthase and plasma nitric oxide (NO) levels were previously reported, and further, these conflicting results were suggested to be partly accounted for smoking status of subjects. However, the genetic contribution of Glu298Asp (G894T) polymorphism to plasma NO levels with respect to smoking status has not been published.

METHODS

In a group of 411 healthy Korean subjects aged 19-81 years, the end product of NO (NO(x): nitrite plus nitrate) as an index of plasma NO levels was measured by the Griess method. The genotypes of G894T polymorphism were determined by the banding patterns on gel electrophoresis after restriction enzyme digestion.

RESULTS

Comparison of plasma NO(x) levels revealed no significant differences across the genotypes and alleles of G894T polymorphism, which is independently of smoking status. However, significant differences in plasma NO(x) levels between nonsmokers and smokers were observed (P = 0.0040). Furthermore, only the common G allele was found to be responsible for these differences. Multiple regression analysis showed that the most independent contributing factor for plasma NO(x) levels was smoking (P = 0.0119) and followed by triglycerides (P = 0.0384).

CONCLUSIONS

Our results indicate no substantial effect of G894T polymorphism on the variance of plasma NO(x) levels in healthy Korean population.

Dysfunctional endothelial nitric oxide biosynthesis in healthy smokers with impaired endothelium-dependent vasodilatation

BACKGROUND

The mechanisms involved in the dysfunction of both endothelium-dependent vasodilatation (EDV) and NO biosynthesis related to smoking are unclear. In this study, EDV was assessed in healthy smokers and nonsmokers in vivo and, using serum from the same individuals, was related to the NO biosynthetic pathway in vitro.

METHODS AND RESULTS

Flow-mediated EDV of the brachial artery was measured in 23 male patients (8 nonsmokers and 15 smokers). Serum was collected, added to confluent ( approximately 85%) monolayers of human umbilical vein endothelial cells (HUVECs), and incubated for 12 hours. Basal and substance P-stimulated NO production was measured. The HUVECs used for measuring basal NO production were lysed, and both endothelial NO synthase (eNOS) protein expression and eNOS activity were determined. EDV was lower in smokers compared with nonsmokers (P<0.001). HUVECs treated with serum from smokers compared with nonsmokers showed significantly lower basal (P<0.0001) and stimulated (P<0.02) NO production, higher eNOS expression (P<0.0001), but lower eNOS activity (P<0.004). There was a significant positive correlation between in vivo EDV and in vitro substance P-stimulated NO production (rho=0.57, P<0.01) and between basal NO production and eNOS activity (r=0.54, P<0.008) and a negative correlation between basal NO production and eNOS protein expression (r=-0.60, P<0.003). CONCLUIONS: This is the first study to combine an in vivo model with a near-physiological in vitro model to demonstrate an association between decreased NO production and reduced EDV. Cigarette smoking was associated with reduced EDV, NO generation, and eNOS activity in the presence of increased eNOS protein expression.

Risk factors and clinical manifestations of pre-eclampsia

OBJECTIVE

To study associations between established risk factors for pre-eclampsia and different clinical manifestations of the disease.

DESIGN

A population-based, nested case-control study.

SETTING

Information from 12,804 consecutive deliveries that took place over three years at a birth clinic, which alone serves a population of nearly 240,000 in Rogaland county, Norway.

SUBJECTS

Cases of pre-eclampsia (n = 323) and healthy controls (n = 650) were selected. Pre-eclampsia was defined as increase in diastolic blood pressure (> or = 25 mmHg to > or = 90 mmHg) and proteinuria (> or = 1+ by dipstick testing) after 20 weeks of pregnancy.

MAIN STUDY MEASURES

Parity, previous pre-eclampsia, blood pressure, maternal weight, and maternal smoking were included as study variables. Women with pre-eclampsia were grouped according to clinical manifestations of the disease (i.e. severity [mild, moderate or severe]) and time of onset (early or late gestation). Associations with the study factors were estimated as relative risks (odds ratio, OR).

RESULTS

Both nulliparity and hypertension increased pre-eclampsia risk, with no clear preference for any clinical subtype. High maternal weight was related to a higher risk of mild and moderate, but not severe, pre-eclampsia. Previous pre-eclampsia strongly increased the risk for pre-eclampsia in the current pregnancy, and the risk of early onset disease was especially high (OR 42.4; 95% CI 11.9-151.6). Overall, smoking was associated with a reduced risk for pre-eclampsia (OR 0.6; 95% CI 0.4-0.9). However, no effect of smoking was observed in the early onset disease group and among women with repeated pre-eclampsia.

CONCLUSION

Nulliparity and hypertension increased the risk for each subgroup of pre-eclampsia, but high maternal weight, previous pre-eclampsia and smoking were not consistently associated with each clinical subtype. This observation may suggest that heterogeneous clinical manifestations of pre-eclampsia may be preceded by different pathological mechanisms.

Cigarette smoking, endothelial injury and cardiovascular disease

Despite the fact that the epidemiological evidence linking cigarette smoking with cardiovascular disease is overwhelming, the precise components of cigarette smoke responsible for this relationship and the mechanisms by which they exert their effect have not yet been elucidated. There are however, some promising pointers as a result of recent developments and this review concentrates on new evidence since earlier reviews of this topic. It is now known that the endothelium has a vastly more important role than was ever thought to be the case a decade ago. Its role in health and disease is increasingly understood, as is the relationship between endothelial injury and the development of atherosclerosis. There is considerable evidence that cigarette smoking can result in both morphological and biochemical disturbances to the endothelium both in vivo and in cell culture systems. Cigarette smoke is a complex mixture and only a few components have been extensively studied. Nicotine and carbon monoxide are much less damaging than is whole smoke. However the free radical components of cigarette smoke have been shown to cause damage in model systems. Further work will be necessary to consolidate the evidence base but the data reported in this review suggest that the free radical components of cigarette smoke may be responsible for the morphological and functional damage to endothelium that has been observed in model systems.

Plasma nitric oxide before and after smoking cessation with nicotine nasal spray

Nicotine may affect cardiovascular function through release of neurotransmitters from autonomic nerves or release of vasoactive substances from the vascular endothelium. Nitric oxide is a neurotransmitter and endothelium-derived factor that reduces tone of vascular smooth muscle. Experiments were designed to determine whether or not use of nicotine nasal spray for smoking cessation affects plasma levels of nitric oxide. Forty smokers self-administered nicotine by nasal spray (one 0.5 mg spray to each nostril). Blood samples were taken before the use of the nasal spray and at treatment day 7 for the measurement of cotinine by high pressure liquid chromatography and nitric oxide (NOx) by chemiluminescence. Age-comparable controls were never-smokers nonnicotine users recruited from laboratory personnel. Mean plasma concentrations of NOx from smokers before treatment were significantly greater compared with nonsmokers (23 +/- 10, n = 40 and 15 +/- 6, n = 13 nmoles/mL [mean +/- SD], respectively, P < 0.01). Plasma NOx in smokers was not significantly correlated with the average daily number of cigarettes smoked (r2 = 0.02, P > 0.05) but was positively and linearly correlated with plasma cotinine (r2 = 0.13, P < 0.02). In 32 self-reported abstinent smokers (confirmed by expired carbon monoxide < 9 ppm) using nicotine nasal spray, cotinine decreased by 64% from pretreatment levels of 284 +/- 103 to posttreatment levels of 90 +/- 58 ng/mL. Plasma NOx was unchanged and went from 23.0 +/- 10.1 at pretreatment to 21 +/- 12 nmoles/mL with nicotine treatment. These results suggest that nicotine-use, independent of cigarette smoking, affects plasma NOx.

Relationship of diastolic blood pressure with cyclic GMP excretion among young adults (the CARDIA Study): influence of a family history of hypertension. Coronary Artery Risk Development in Young Adults

BACKGROUND

Guanosine 3':5'-cyclic monophosphate (cGMP) is the second messenger of nitric oxide and atrial natriuretic factor, and mediates local vasodilatation. These vasodilatory factors are important in blood pressure regulation and possibly in the etiology of hypertension. Urinary cGMP levels among normotensive young adults have not previously been studied.

SUBJECTS

A subset of normotensive participants from the CARDIA study (n = 563), aged 23-35 years, was studied. The sample was approximately balanced for sex and race (black/white).

METHODS

Twenty-four-hour urinary cGMP levels were measured using an enzyme immunoassay; levels were adjusted for creatinine excretion. The blood pressure, smoking status, and risk factors for hypertension [including a family history of hypertension (FHH), the body mass index, education, alcohol intake, and sodium excretion] were also measured.

RESULTS

Women excreted more cGMP than did men, and blacks excreted more cGMP than did whites (both P < 0.0001). Excretion of cGMP was also greater among smokers (P < 0.001) and those with an FHH (P = 0.05), and was related directly and independently to sodium excretion (P < 0.02). The diastolic blood pressure (DBP) was related inversely to the excretion of cGMP among individuals without an FHH (r = -0.36, P < 0.001), but not among individuals with an FHH. In multiple regression analysis, the excretion of cGMP remained related significantly to the DBP and accounted for more variance in DBP than did any other variable among those without an FHH (delta R2 = 0.08, P < 0.001).

CONCLUSIONS

Urinary cGMP excretion is related inversely and independently to the DBP among those without an FHH but not among those with an FHH, suggesting that cGMP-related vasodilatation is impaired in those with an FHH. Sex differences in urinary excretion of cGMP are consistent with results from studies showing that estrogen increases the endothelial production of nitric oxide.

Transformation of subcutaneous nitric oxide into nitrate in the rat

Following its addition to arterialized blood in vitro, nitric oxide (NO) is transformed into nitrate in the erythrocytes. Inhaled NO is similarly transformed into nitrate in the blood in vivo. These observations suggest that nitrate is a universal end-metabolite of NO, i.e. of endogenously formed NO as well. However, endogenous NO may also be inactivated in tissues, i.e. outside the vascular lumen. To study the fate of NO metabolized with delayed access to the blood, rats were given subcutaneous injections of 15NO or K15NO3, and the plasma concentrations of 15NO3(-) were followed for 450 min after injection. The values for the distribution volume and plasma decay (t12) of 15NO3(-) did not differ between rats given 15N-labelled NO and NO3(-). The area under the plasma decay curve for rats given 15NO amounted to 89% of the corresponding area for animals given K15NO3. This demonstrates that 15NO, when given extravascularly in millimolar concentrations, is mainly transformed into 15N-labelled nitrate. Other rats were kept in an atmosphere containing a mixture of 16O2 and 18O2. Nitrate residues containing either one or two 18O atoms were isolated from the blood, indicating that inhaled oxygen was incorporated during both the formation of NO and the subsequent transformation of NO into nitrate. The fraction of nitrate residues containing two 18O atoms was larger than that containing one 18O atom. We propose that nitrate is a major stable metabolite of endogenous NO that does not primarily diffuse into the vascular lumen following formation. Hence nitrate seems to be the quantitatively most important end-product of the metabolism of endogenous NO. The transformation of endogenous NO into nitrate involves the incorporation of inhaled oxygen.