Acute effects of nicotine infusion on platelets in nicotine users with normal and impaired renal function

Smokeless tobacco, snus, at admission for percutaneous coronary intervention and future risk for cardiac events

Objective

To assess the risk of future death and cardiac events following percutaneous coronary intervention (PCI) in patients using smokeless tobacco, snus, compared with patients not using snus at admission for a first PCI.

Methods

The Swedish Coronary Angiography and Angioplasty Registry is a prospective registry on coronary diagnostic procedures and interventions. A total of 74 958 patients admitted for a first PCI were enrolled between 2009 and 2018, 6790 snus users and 68 168 not using snus. We used Cox proportional hazards regression for statistical modelling on imputed datasets as well as complete-case datasets.

Results

Patients using snus were younger (mean (SD) age 61.0 (±10.2) years) than patients not using snus (67.6 (±11.1), p<0.001) and more often male (95.4% vs 67.4%, p<0.001). After multivariable adjustment, snus use was not associated with the primary composite outcome of all-cause mortality, new coronary revascularisation or new hospitalisation for heart failure at 1 year (HR 0.98, 95% CI 0.91 to 1.05). In patients using snus at baseline who underwent a second PCI (n=1443), the duration from the index intervention was shorter for subjects who continued using snus (n=921, 63.8%) compared with subjects who had stopped (mean number of days 285 vs 406, p value=0.001).

Conclusions

Snus use at admission for a first PCI was not associated with a higher occurrence of all-cause mortality, new revascularisation or heart failure hospitalisation. Discontinuing snus after a first PCI was associated with a significantly longer duration to a subsequent PCI.

Effects of nicotine, its metabolites and tobacco extracts on human platelet function in vitro

Cigarette smoking is a leading cause of cardiovascular disease. The cardiovascular effects of smoking are probably multifactorial, including effects on platelets. Previous reports investigating the effects of nicotine and tobacco on platelet function are inconsistent. The present study investigated in vitro effects of nicotine, its major metabolites, tobacco extracts and extract of tobacco-free snuff on human platelets. None of the metabolites cotinine, cotinine-N-oxide, nicotine-1'-N-oxide or trans-3'-hydroxycotinine (0.1-10 μM) affected platelet aggregation or P-selectin expression. Nicotine (10 μM) weakly increased platelet aggregation, whereas trans-3'-hydroxycotinine (0.1 μM) and nicotine-1'-N-oxide (1-10 μM) weakly inhibited adhesion to fibrinogen. To elucidate the influence of other tobacco compounds, we investigated the impact of moist tobacco and smoke extracts on platelet function. Filtered extracts of oral snuff, cigarette smoke and tobacco free snuff inhibited platelet adhesion concentration-dependently. The inhibitory effects of tobacco extracts on platelet adhesion were independent of nicotine content and the nitric-oxide-pathway and not mediated through a platelet-nicotine-receptor. Taken together, tobacco extracts inhibit platelet activation during short-term in vitro challenge. As only limited effects of nicotine and nicotine metabolites were seen, the tobacco-induced platelet inhibition are likely induced by other compounds present in tobacco and tobacco free snuff.

Activity of ectonucleotidases and adenosine deaminase in rats exposed to cigarette smoke

Cigarette smoke is a complex mixture of various toxic substances that are capable of initiating oxidative damage and promoting blood platelet alterations. In this study, we investigated the activities of the ectoenzymes NTPDase (ectonucleoside triphosphate diphosphohydrolase, CD39) and 5'-nucleotidase (CD73) in platelets as well as adenosine deaminase (ADA) in the plasma of rats exposed to aged and diluted sidestream smoke during 4 weeks. The rats were divided into two groups: I (control) and II (exposed to smoke). After the exposure period, blood was collected and the platelets and plasma were separated for enzymatic assay. The results demonstrated that NTPDase (with ATP as substrate) and 5'-nucleotidase (AMP as substrate) activities were significantly higher in group II (p < 0.05) as compared to group I, while no significant difference was observed for NTPDase with ADP as substrate. The ADA activity was significantly reduced in group II (p < 0.05) as compared with group I. Platelet aggregation was significantly increased in group II (p < 0.05) as compared with group I. We suggest that these alterations in the activity of enzymes from the purinergic system are associated with an increase in platelet aggregation. However, our study has demonstrated that the organism tries to compensate for this enhanced aggregation by increasing hydrolysis of AMP and reducing hydrolysis of adenosine, a potent inhibitor of aggregation and an important modulator of vascular tone.

Nicotine upregulates the expression of P2Y12 on vascular cells and megakaryoblasts

BACKGROUND

P2Y12 is the major platelet receptor that mediates ADP-induced aggregation. P2Y12 is also expressed by vascular cells. The factors that regulate P2Y12 expression have not been determined. Since nicotine (NIC) has effects on platelet activation and vascular function, and because nicotinic and purinerigic receptors may interact, we determined whether nicotine altered P2Y12 expression.

METHODS

Four cell lines (human coronary artery endothelial cells, HCAEC; human umbilical vein endothelial cells, HUVEC; human aortic smooth muscle cells, HASMC; and human megakaryoblastic cells, MEG-01) were cultured in the absence or presence of nicotine. Immunoblotting for P2Y12, P2Y2, and actin was performed.

RESULTS

Nicotine, at concentrations of 0.1-1.0 microM, induced P2Y12 (but not P2Y2) expression in all the four cell lines. HASMC exhibited the greatest induction with a sixfold mean increase in P2Y12 expression in response to 0.25 microM nicotine. The induction was inhibited by nicotinic acetylcholine receptor antagonists. Healthy smokers were observed to have higher P2Y12 expression in platelet lysates compared to non-smokers.

CONCLUSION

Nicotine induces the expression of P2Y12 in vascular cells and megakaryoblasts, and is mediated by nicotinic acetylcholine receptors. Smokers exhibit higher platelet P2Y12, possibly mediated via nicotine. These results may contribute to a better understanding of the effects of cigarette smoking on platelet activation and the vessel wall.

CONDENSED ABSTRACT

The factors that regulate the expression of P2Y12, the platelet ADP receptor, have not been determined. Four cell lines (human coronary artery endothelial cells, HCAEC; human umbilical vein endothelial cells, HUVEC; human aortic smooth muscle cells, HASMC; and human megakaryoblastic cells, MEG-01) were cultured in the absence or presence of nicotine. Nicotine, at concentrations of 0.1-1.0 microM, induced P2Y12 expression in all the four cell lines. HASMC exhibited the greatest induction with a sixfold mean increase in P2Y12 expression in response to 0.25 microM nicotine. The induction was inhibited by nicotinic acetylcholine receptor antagonists. Healthy smokers were observed to have higher P2Y12 expression in platelet lysates compared to non-smokers. These results may contribute to a better understanding of the effects of cigarette smoking on platelet activation and the vessel wall.

Secondhand smoke as an acute threat for the cardiovascular system: a change in paradigm

The evidence that active smoking is a risk factor for cardiovascular disease (CVD) and the leading cause of preventable death is overwhelming. However, numerous epidemiological findings indicate that even passive exposure to cigarette smoke may exert detrimental effects on vascular homoeostasis. Recent experimental data provide a deeper insight into the pathophysiological mechanisms linking secondhand smoke (SHS) to CVD. Importantly, most of these effects appear to be characterized by a rapid onset. For example, the relatively low doses of toxins inhaled by passive smoking are sufficient to elicit acute endothelial dysfunction, and these effects may be related, at least in part, to the inactivation of nitric oxide. Moreover, passive smoking may directly impair the viability of endothelial cells and reduce the number and functional activity of circulating endothelial progenitor cells. In addition, platelets of non-smokers appear to be susceptible to pro-aggregatory changes with every passive smoke exposure. Overall, SHS induces oxidative stress and promotes vascular inflammation. Apart from vasoconstriction and thrombus formation, however, the myocardial oxygen balance is further impaired by SHS-induced adrenergic stimulation and autonomic dysfunction. These data strongly suggest that passive smoking is capable of precipitating acute manifestations of CVD (atherothrombosis) and may also have a negative impact on the outcome of patients who suffer acute coronary syndromes.

Relationships between fibrinogen, plasminogen activator inhibitor-1, and their gene polymorphisms in current smokers with essential hypertension

BACKGROUND

To elucidate the role of some haemostatic gene polymorphisms and environmental factors, we studied fibrinogen (Fb), plasminogen activator inhibitor-1 (PAI-1), and tissue plasminogen activator (t-PA) levels with respect to Fb G455A and PAI-1 4G/5G gene polymorphisms in smokers and nonsmokers with essential hypertension.

MATERIAL AND METHODS

The study was done in 90 patients (including 30 smokers) with essential hypertension (HT) and 40 controls (including 8 smokers). Fb and PAI-1 genotypes were PCR identified. The groups did not differ significantly as to genotype frequencies.

RESULTS

When allele A455 carriers were compared, HT patients had significantly higher Fb (p=0.015) and t-PA levels (p=0.013). Comparison of 4G allele carriers (4G/4G homozygotes) revealed significantly higher Fb (p=0.045), PAI-1 (p=0.009), and t-PA levels (p=0.007) in HT patients than controls. Interactions of Fb and PAI-1 gene polymorphisms with smoking were disclosed in HT patients only. Allele A455-carrying HT smokers compared with nonsmokers had significantly higher t-PA (12.1 +/- 5.8 vs. 7.4 +/- 3.1 ng/ml; p=0.002) and tendency to higher Fb (3.36 +/- 0.74 vs. 2.95 +/- 0.70 g/l; p=0.075) levels. Higher Fb levels were disclosed in 4G/4G smokers than nonsmokers (3.31 +/- 0.81 vs. 2.84 +/- 0.85 g/l; p=0.064). Finally, in smokers, significantly higher levels of PAI-1 were found in 4G/4G (42.1 +/- 29.4 ng/ml) as compared with 4G/5G (18.6 +/- 13.7 ng/ml; p=0.025) and 5G/5G (14.4 +/- 10.8 ng/ml; p=0.044) genotypes.

CONCLUSIONS

Smoking potentiates the prothrombotic effect of allele A455 and PAI-1 4G/4G genotype in untreated essential hypertension, reflected by increased levels of haemostatic risk factors and accelerated progression of cardiovascular diseases.

Comparison of plasma levels of cytokines and in vitro generation of reactive oxygen species after nicotine infusion in nicotine users with normal and impaired renal function

Several in vitro and animal studies suggest effects of nicotine on the immune system, but little evidence exists regarding the in vivo immunomodulation of nicotine in humans. The increased use of nicotine replacement therapy to aid smoking cessation claims further understanding of how nicotine affects blood leukocytes. This is of particular importance when nicotine therapy is used in diseases associated with alterations of the immune system, such as chronic renal failure. The present study evaluates the acute effects of nicotine infusion (NI) on some immunoregulatory functions in seven healthy subjects and seven patients with renal failure. All subjects were nicotine users and had refrained from using nicotine for 36 h before NI. Blood was collected before, immediately after, and 2 h after NI. Plasma concentrations of intercellular adhesion molecule-1 (ICAM-1) and the cytokines interleukin-2 (IL-2), IL-4, IL-10, interferon-gamma and RANTES were measured using specific immunoassays. The generation of reactive oxygen species (ROS) induced by formyl-methionyl-leucyl-phenylalanine (fMLP), Ristocetin, adenosine 5'-diphosphate, or collagen was registered in whole blood as luminol-dependent chemiluminescence. Except for fMLP, these compounds induce leukocyte ROS generation by platelet mediated mechanisms. NI did not significantly affect the levels of the cytokines and ICAM-1 in any group. The peak and the persistent ROS production, induced by collagen and Ristocetin, was lower at some time points in patients with renal failure as compared to healthy subjects. Also in patients with renal failure, both peak height and persistent ROS generation induced by Ristocetin were reduced immediately after NI. Thus, nicotine inhibits some of the platelet-mediated activation of leukocyte ROS generation, and may be associated with platelet defects in renal failure.