Effects of smoking on platelets and on plasma thromboxane-prostacyclin balance in man

Systemic and Coronary Hemodynamic Effects of Tobacco Products on the Cardiovascular System and Potential Pathophysiologic Mechanisms

Tobacco product usage is the single most preventable cause of death in the United States. Smoking promotes atherosclerosis, producing disease in the coronary arteries, the aorta, the carotid and cerebral arteries and the large arteries in the peripheral circulation. The cardiovascular consequences of tobacco products have been the subject of intensive study for several decades. Despite the overwhelming epidemiologic association between smoking and vascular disease, the pathophysiologic mechanisms by which smoking exerts its deleterious effects remain incompletely understood. This review addresses the acute and long-term systemic and coronary hemodynamic effects of tobacco, with an emphasis of the impact on coronary blood flow and pathophysiologic mechanisms.

Nicotine and vascular dysfunction

Cigarette smoking is the single most important risk factor for the development of cardiovascular diseases (CVDs). However, the role of nicotine, the addictive component of all tobacco products, in the development of CVD is incompletely understood. Although increased public awareness of the harms of cigarette smoking has successfully led to a decline in its prevalence, the use of electronic cigarettes (e-cig) or electronic nicotine delivery system has increased dramatically in recent years because of the perception that these products are safe. This review summarizes our current knowledge of the expression and function of the nicotinic acetylcholine receptors in the cardiovascular system and the impact of nicotine exposure on cardiovascular health, with a focus on nicotine-induced vascular dysfunction. Nicotine alters vasoreactivity through endothelium-dependent and/or endothelium-independent mechanisms, leading to clinical manifestations in both cigarette smokers and e-cig users. In addition, nicotine induces vascular remodelling through its effects on proliferation, migration and matrix production of both vascular endothelial and vascular smooth muscle cells. The purpose of this review is to identify critical knowledge gaps regarding the effects of nicotine on the vasculature and to stimulate continued nicotine research.

Impact of Scotland's comprehensive, smoke-free legislation on stroke

Background

Previous studies have reported a reduction in acute coronary events following smoke-free legislation. Evidence is lacking on whether stroke is also reduced. The aim was to determine whether the incidence of stroke, overall and by sub-type, fell following introduction of smoke-free legislation across Scotland on 26 March 2006.

Methods and Findings

A negative binomial regression model was used to determine whether the introduction of smoke-free legislation resulted in a step and/or slope change in stroke incidence. The model was adjusted for age-group, sex, socioeconomic deprivation quintile, urban/rural residence and month. Interaction tests were also performed. Routine hospital administrative data and death certificates were used to identify all hospital admissions and pre-hospital deaths due to stroke (ICD10 codes I61, I63 and I64) in Scotland between 2000 and 2010 inclusive. Prior to the legislation, rates of all stroke, intracerebral haemorrhage and unspecified stroke were decreasing, whilst cerebral infarction was increasing at 0.97% per annum. Following the legislation, there was a dramatic fall in cerebral infarctions that persisted for around 20 months. No visible effect was observed for other types of stroke. The model confirmed an 8.90% (95% CI 4.85, 12.77, p<0.001) stepwise reduction in cerebral infarction at the time the legislation was implemented, after adjustment for potential confounders.

Conclusions

Following introduction of national, comprehensive smoke-free legislation there was a selective reduction in cerebral infarction that was not apparent in other types of stroke.

Cigarette smoking, cyclooxygenase-2 pathway and cancer

Cigarette smoking is a major cause of mortality and morbidity worldwide. Cyclooxygenase (COX) and its derived prostanoids, mainly including prostaglandin E2 (PGE2), thromboxane A2 (TxA2) and prostacyclin (PGI2), have well-known roles in cardiovascular disease and cancer, both of which are associated with cigarette smoking. This article is focused on the role of COX-2 pathway in smoke-related pathologies and cancer. Cigarette smoke exposure can induce COX-2 expression and activity, increase PGE2 and TxA2 release, and lead to an imbalance in PGI2 and TxA2 production in favor of the latter. It exerts pro-inflammatory effects in a PGE2-dependent manner, which contributes to carcinogenesis and tumor progression. TxA2 mediates other diverse biologic effects of cigarette smoking, such as platelet activation, cell contraction and angiogenesis, which may facilitate tumor growth and metastasis in smokers. Among cigarette smoke components, nicotine and its derived nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are the most potent carcinogens. COX-2 and PGE2 have been shown to play a pivotal role in many cancers associated with cigarette smoking, including cancers of lung, gastric and bladder, while the information for the role of TxA2 and PGI2 in smoke-associated cancers is limited. Recent findings from our group have revealed how NNK influences the TxA2 to promote the tumor growth. Better understanding in the above areas may help to generate new therapeutic protocols or to optimize the existing treatment strategy.

Chronobiology of hemostasis and inferences for the chronotherapy of coagulation disorders and thrombosis prevention

The hemostatic system in its multiple components displays an intricate organization in time which is characterized by circadian (approximately 24-hour), circaseptan (approximately 7-day), menstrual (approximately monthly), and circannual (approximately yearly) bioperiodicities. The interaction of the rhythms of the variables participating in hemostasis determine transient risk states of thromboembolic events, including myocardial infarction and stroke, and of hemorrhage and hemorrhagic events, each with a unique timing. The circadian staging of the rhythms in vascular, cellular, and coagulation factors that favors blood coagulation and thrombosis coincides with the daily minimum in fibrinolytic activity; as a result there is elevated risk in the morning of acute myocardial infarction and stroke. Similar hemostatic rhythms may determine the epidemiology of thromboembolic and hemorrhagic events during the week, month and year. This article focuses on the large-amplitude circadian rhythms operative in the hemostatic system. Their implication for preventive and curative pharmacotherapy of hemostatic disorders is presented, with discussion of related problems.

Influence of smoking on predictors of vascular disease

Beyond the already well-established strong causative relationship with cancer, smoking increases the risk for vascular disease. Smoking may act directly or adversely influence risk factors contributing to the development of vascular disease. Smoking causes endothelial dysfunction, dyslipidemia (decreased high-density lipoprotein cholesterol levels, hypertriglyceridemia and increased oxidation of low-density lipoprotein cholesterol) and platelet activation leading to a prothrombotic state. Smoking increases emerging risk factors (eg, fibrinogen, homocysteine, and high-sensitivity C-reactive protein) and increases insulin resistance and the risk of developing type 2 diabetes mellitus. The beneficial effects of statins and antioxidants (eg, vitamins C and E, beta-carotene) are counteracted by smoking. Smoking-induced alterations in growth factors, adhesion molecules, and even in genes can accelerate the progression of atherosclerosis. The aim of this review is to consider the adverse consequences of smoking on the factors predisposing to vascular disease and to emphasize the beneficial effects of smoking cessation.

Platelet aggregation induced by ADP or epinephrine is enhanced in habitual smokers

A novel system has been developed to evaluate biochemically induced platelet aggregation by means of a particle-counting technique that uses laser light scattering. Using this system, we compared the differences in platelet aggregability between 90 smoking healthy males after 10 hours of smoking abstinence and 141 age-matched nonsmoking healthy males. Smokers had more small spontaneous platelet aggregates and more medium and large aggregates induced by 1 or 5 microM of epinephrine than nonsmokers. No large aggregates with 5-microM epinephrine-induced platelet aggregation were seen in 10% of smokers and 24% of nonsmokers; these subjects showed no small aggregates in spontaneous aggregation at all. Smokers had significantly more small, medium, and large aggregates induced by 1 microM of adenosine diphosphate (ADP) than nonsmokers. Smokers showed a positive correlation between age and 1-microM epinephrine-induced large platelet aggregates, percent reduction of optical density, and 1-microM ADP-induced medium and large aggregates. Smokers also showed a positive correlation between fibrinogen concentration in plasma and small spontaneous aggregates. On the other hand, nonsmokers showed a significant positive correlation between age and small spontaneous aggregates, and a positive correlation between fibrinogen and 1- or 5-microM epinephrine-induced large aggregates, and between 1 microM ADP-induced large aggregates and percent reduction of optical density. These results confirmed that platelet aggregability is enhanced in smokers, and we speculate that long-term smoking might enhance the sensitivity of platelets to epinephrine or ADP.

Risk factors for ischemic stroke in a Russian community: a population-based case-control study

BACKGROUND AND PURPOSE

This study was conducted to determine the risk factors for ischemic stroke in a defined Russian population.

METHODS

Our data are based on a population-based case-control study of 237 patients with first-ever ischemic stroke and 237 age- and sex-matched controls. Logistic regression methods for matched pairs were used to estimate the relative risk for the variables studied.

RESULTS

In a multivariate analysis, hypertension, left ventricular hypertrophy on electrocardiography, ischemic heart disease, mitral valve disease, current cigarette smoking, and high body mass index were significant and independent risk factors for ischemic stroke in this Russian community.

CONCLUSIONS

The significant risk factors for ischemic stroke in Novosibirsk are similar to those from other populations and cohorts. This study, the first of stroke risk factors in Russia, has implications for clinical practice and the planning of stroke prevention in the population.

Effects of benzo(a)pyrene and nicotine on prostaglandin synthesis in buccal pouch and submandibular glands of the Syrian hamster

Adult male Syrian hamsters were treated by swabbing the apex of the buccal pouch with corn oil (control, C), 1 mM benzo(a)pyrene (BP), nicotine (NC), or BP+NC in corn oil, twice daily, 5 days a week. After a 4-week treatment, the pouches and submandibular glands were dissected and used for the determination of endogenous prostaglandin (PG) production and studies on in vitro PG synthesis. Of the three PGs analysed (PGE2, PGF2 alpha and 6-keto-PGF1 alpha), PGE2 was predominant in the pouch and the glands. BP or NC alone had only a weak effect on PG synthesis in both tissues. However, the combination of BP and NC had a synergistic effect, causing diminished PG synthesis in both tissues. In buccal pouch, BP+NC significantly decreased the concentrations of endogenous PGE2 and PGF2 alpha (PGE2: 0.669 +/- 0.254 versus 1.698 +/- 0.460, PGF2 alpha: 0.273 +/- 0.090 versus 0.625 +/- 0.272 ng/g tissue; BP+NC versus C; mean +/- SD, n = 5, p < 0.05). Similarly significant results were also found for in vitro PG synthesis (PGE2: 0.541 +/- 0.249 versus 1.399 +/- 0.340, PGF2 alpha: 1.045 +/- 0.428 versus 2.133 +/- 0.510 ng/g tissue; BP+NC versus C; mean +/- SD, n = 5, p < 0.05). In submandibular glands, BP+NC significantly diminished the concentration of endogenous PGE2 (1.183 +/- 0.175 versus 2.379 +/- 0.488 ng/g tissue; BP+NC versus C; mean +/- SD, n = 5, p < 0.05). The synthesis of 6-keto-PGF1 alpha in both tissues, and the synthesis of PGF2 alpha in submandibular gland, were slightly decreased with all treatments.

Cigarette smoking reduces human salivary eicosanoids

The effect of cigarette smoking on salivary eicosanoid levels was investigated in 10 smoker and 10 non-smoker volunteers. The smokers consumed an average of 20 cigarettes/day for the past 5 years or longer. The smoking status was validated by salivary cotinine level. Eicosanoids were extracted from saliva with ethanol, and the radioimmunoassay was performed to determine the concentrations of four major eicosanoids, i.e. prostaglandin E2 (PGE2), PGF2 alpha, 6-sulphidopeptide-containing leukotrienes (LTs) and 12-hydroxyeicosatetraenoic acid (12-HETE). The levels of PGE2, PGF2 alpha, and LTs were significantly lower in the saliva of smokers as compared to that of the non-smokers (1.74 +/- 0.32 vs 2.41 +/- 0.64, p = 0.006; 0.36 +/- 0.12 vs 0.54 +/- 0.18, p = 0.04; 2.24 +/- 0.96 vs 4.92 +/- 1.29, p = 0.006; mean +/- SD, ng/ml saliva). No significant differences were found in the levels of 12-HETE between the two groups. The results suggest that cigarette smoking reduces the concentrations of both the cyclooxygenase and 5-lipoxygenase products in saliva.

Effects of acrolein on human platelet aggregation

Acrolein, a component of tobacco smoke, potentiated platelet aggregation and increased thromboxane A2 (TXA2) formation caused by thrombin and arachidonic acid (AA). Acrolein produced these effects at concentrations in the range 50-5000 microM. Acrolein had no effect on platelet responses to ADP, epinephrine, collagen or the ionophore A23187. Acrolein increased the mobilization of [3H]arachidonic acid from prelabelled platelets in response to thrombin and arachidonic acid. The increased availability of substrate could partly explain the enhanced production of TXA2 and increased aggregation observed in the presence of acrolein. These findings could provide an explanation for the increased incidence of vascular disease in cigarette smokers.

Alterations of arachidonate metabolism in cardiovascular system by cigarette smoking

Male rats were exposed to freshly generated cigarette smoke once daily for various lengths of time. Inhalation of smoke was verified by elevated levels of carboxyhemoglobin. Metabolism of arachidonate in the cardiovascular system to thromboxane and prostacyclin through the cyclooxygenase pathway and their further metabolism to 15-keto-derivatives, and to 12-hydroxyeicosatetraenoic acid (12-HETE) through lipoxygenase pathway was investigated. Synthesis of thromboxane and prostacyclin in platelets and aortas respectively was not changed within 8 weeks of smoke exposure. However, formation of 12-HETE in platelets was significantly increased after 4 weeks of smoke exposure. Catabolism of thromboxane and prostacyclin as determined by NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase activity was greatly decreased in lung but not in kidney and stomach following 4 weeks of smoke exposure. Increased 12-lipoxygenase activity in platelets may lead to stimulation of migration and proliferation of smooth muscle cells and to increased synthesis of leukotrienes in neutrophils. Decreased pulmonary prostaglandin catabolic activity may result in increase in circulating thromboxane/prostacyclin ratio and subsequently alteration of vascular homeostasis. The consequence of these biochemical changes may contribute to the development of atherosclerosis, thromboembolism and emphysema commonly found in smokers.

Smoking as a risk factor for cerebral ischaemia

To assess whether a rigorous clinical classification, based on computerised tomography, of patients with cerebral ischaemia would identify subgroups at higher or lower risk with respect to cigarette smoking habits, a case-control study was carried out on 422 cases of first-episode cerebral ischaemia matched for age and sex with 422 community-based neighbourhood controls. Patients with ischaemic stroke due to extracranial or intracranial vascular disease were at higher risk from smoking than has previously been reported for stroke (relative risk 5.7, 95% confidence interval 2.8, 12.0) whereas those with stroke due to cardiac emboli had no excess risk associated with smoking (relative risk 0.4 [0.1, 1.8]). After cessation of smoking, the relative risk declined gradually over 10 years, at the end of which time a significant risk was still evident. This finding may imply that the risk incurred by smoking is due mainly to atheroma formation, rather than transient haematological effects. Exposure to smoking by a spouse was an independent risk factor for the whole group of cerebral ischaemia patients (relative risk 1.7 [1.1, 2.6]), but this was not so for smoking by either parent (relative risk 1.2 [0.8, 1.8]). These findings suggest that smoking is a more potent risk factor for the most common form of ischaemic stroke than has previously been appreciated. The persistent nature of the risk even after cessation of smoking and the possible risk associated with passive exposure strengthens public health arguments against smoking.

Relative participation of the gas phase and total particulate matter in the imbalance in prostacyclin and thromboxane formation seen following chronic cigarette smoke exposure

Chronic exposure to cigarette smoke causes an imbalance in the ratio of PGI2 and TXA2 production and is believed to favor the development of atherosclerosis. Components of the particulate phase of smoke (especially nicotine) as well as the gas phase of smoke have been shown to adversely alter arachidonic acid metabolism. To determine the relative participation of nicotine, particulate and gas phases in eliciting an imbalance in TXA2 formation, male Sprague-Dawley rats were chronically exposed (7 days/wk/mo.) to freshly generated whole smoke or gas phase from University of Kentucky Reference cigarettes and allowed access to regular drinking water or to water supplemented with nicotine (10 micrograms/ml). COHb levels were monitored to confirm smoke or gas phase inhalation. All treatment groups had lower body weights than shams. No differences in body weights were observed between smoke (+/- oral nicotine) and gas phase (+/- oral nicotine) treatment groups but all were significantly lower than oral nicotine treated animals. Platelet TXA2 production was elevated in all treatment groups compared to shams. No differences in TXA2 production were observed between smoke (+/- oral nicotine), gas phase and oral nicotine treated animals. Animals receiving gas phase/oral nicotine exhibited significantly higher platelet TXA2 production compared to the other treatments. Constituents of the gas phase as well as the particulate phase of whole smoke were both shown to elevate platelet TXA2 formation. Components of the particulate matter appear to modulate the effects of nicotine and the gas phase in the perturbation of TXA2 production in the rat smoking model.

Prostacyclin and thromboxane formation following chronic exposure to cigarette smoke condensate administered via osmotic pumps in rats. A method for chronic administration of particulates of whole smoke

Chronic cigarette smoke exposure in vivo causes decreased conversion of [14C]arachidonic acid (AA) to prostacyclin (PGI2) by isolated aortic tissue and increased conversion to thromboxane (TXA2) by isolated platelets from rats. Alterations in the PGL2/TXA2 balance may be part of the mechanism by which smoking increases the risk of cardiovascular disease. In order to ascertain whether the particulate phase of whole smoke alone could cause these changes, rats were administered smoke condensate in propylene glycol for 56 days via two Alzet (2ML4) osmotic pumps. Pumps containing vehicle, low dose (150 micrograms/hr) or high dose (300 micrograms/hr) condensate were implanted s.c. dorsal to the thoracic vertebrae in male Sprague-Dawley rats. Three-quarters of the condensate-treated rats developed fibrin cysts encapsulating the pumps. Cysts were not seen in vehicle-treated rats. Residual pump contents were weighed and analyzed by GLC to ensure condensate delivery. No significant difference in weight gain patterns between sham-operated and treatment groups were observed. Vehicle had no effect on aortic PGI2 or platelet TXA2 formation compared to sham. Low-dose condensate was without effect on PGI2/TXA2 formation. In high-dose condensate-treated rats, PGI2 and TXA2 formation were 84% and 136%, respectively, of the vehicle control (n.s.). Pump encapsulation may be a limiting factor in the administration of complex particulate suspensions.

Plasma prostaglandins in lung cancer

Plasma levels of three stable prostaglandin (PG) metabolites were measured in 29 patients with lung cancer. The mean level of 6-keto-PGF1 alpha, the hydrolysis product of prostacyclin, was significantly elevated in cancer patients compared to a control group with non-malignant respiratory disorders, although an overlap in values between the groups was seen. Levels correlated inversely with survival and showed a significant fall in 14 patients with tumour regression. The mean level of 11-deoxy-3,14-dihydro-15-keto-11,16-cyclo-prostaglandin E2 was also significantly elevated in cancer patients, but did not correlate with tumour response. 13,14-Dihydro-15-keto prostaglandin F2 alpha levels did not differ in lung cancer patients and controls. Contrary to previous reports we could not support a role for the metabolites of PGE2 and PGF2 alpha as tumour markers in lung cancer but plasma 6-keto-PGF1 alpha should be further evaluated in this regard.

Acute cigarette smoke exposure alters lung eicosanoid and inflammatory cell concentrations in rabbits

We studied lung clearance of technetium-labeled diethylenetriamine pentaacetic acid [( 99mTc]DTPA), plasma and bronchoalveolar lavage fluid (BALF) concentrations of 6-keto-PGF1 alpha (stable metabolite of prostacyclin, prostaglandin I2, PGI2), TxB2 (stable metabolite of thromboxane A2, TxA2), and leukotriene B4 (LTB4), and inflammatory cells as indices of lung injury in rabbits exposed to cigarette smoke (CSE). Thirty-one rabbits were randomly assigned to four groups: control sham exposure (SS, n = 6), sham smoke ibuprofen-pretreated (SS-I, n = 7), CSE (n = 6), and CSE ibuprofen-pretreated (CSE-I, n = 12). Ibuprofen, a cyclooxygenase eicosanoid inhibitor, was administered as a single daily intramuscular injection (25 mg/kg) for 7 d before the experiment. Cigarette or sham smoke was delivered by syringe in a series of 5, 10, 20, and 30 tidal volume breaths with a 15-min counting period between each subset of breaths to determine [99mTc]DTPA biological half-life (T1/2). The CSE-I group was retrospectively divided into rabbits who survived the 30-breath subset (CSE-IL, n = 6) and those who died during the 30-breath CSE (CSE-ID, n = 6). In the CSE, CSE-IL, and CSE-ID groups, [99mTc]DTPA T1/2 as well as BALF LTB4 levels were significantly decreased. Plasma and BALF 6-keto-PGF1 alpha increased in CSE rabbits compared to the other groups. Alveolar macrophages were lower in the CSE-ID rabbits than in the CSE-IL group. CSE and CSE-IL BALF lymphocyte levels were decreased compared to SS values. Our data indicate that acute CSE is associated with significant increases in 6-keto-PGF1 alpha and decreases in LTB4 as well as a significant reduction in lymphocytes. Furthermore, pretreatment with ibuprofen before CSE was associated with severe lung injury in half of the rabbits. The severity of lung injury may be related to a combination of a lower number of alveolar macrophages and blockade of lung PGI2.

Evaluation of platelet function in pregnancy. Comparative studies in non-smokers and smokers

We have evaluated the possible role of platelet functional abnormalities as a contributory cause of thrombosis during pregnancy and to the increased fetal mortality and morbidity among women who smoke. Fifty-three pregnant women were enrolled and evaluated on two separate prenatal visits held between the 20th and 36th week of pregnancy and, when possible, post partum. Smoking status was evaluated by personal statement and alveolar carbon monoxide levels. Women in the smoking group deliberately avoided cigarettes for at least 20 minutes before sampling. Plasma levels of beta-thromboglobulin, thromboxane B2, and 6-Keto PGF1 alpha were evaluated. A significant increase in 6-Keto PGF1 alpha was noted among smoking women as pregnancy advanced. 6-Keto PGF1 alpha levels decreased among non-smoking women while beta-thromboglobulin increased significantly between the 20th and 33rd week of pregnancy in non-smokers. Platelet aggregation, both in platelet rich plasma and in whole blood (by impedance aggregometry), was evaluated by five different parameters and four different aggregating agents. Significant differences between the non-smoking and smoking pregnant women were noted for selected age cohorts and aggregating agents. An increase in platelet reactivity among smokers was observed in whole blood by impedance aggregometry with adenosine diphosphate and in two age cohorts using platelet rich plasma. In two groups in which aggregation was significantly accelerated among non-smokers, epinephrine was used as the aggregating agent.

Effects of chronic smoking on platelet function

Platelet function was investigated in 20 healthy cigarette smokers and 23 nonsmokers. Cigarette consumption was 1.4 +/- 0.5 packs/day (mean +/- SD) and the duration of smoking was 19 +/- 12 years. Platelet surface activation in vitro, aggregation in vivo and in vitro, as well as the release of platelet-specific proteins in vivo were evaluated. The mean number of platelet aggregates counted on an activating surface (Formvar film) was higher in smokers (80 +/- 59) than in nonsmokers (43 +/- 27) (P less than .01), indicating enhanced activity following exposure to an activating surface. Smokers who were 50 years of age or older showed an enhanced platelet aggregation following an in vitro stimulation in comparison to younger smokers (105 +/- 54 vs 54 +/- 55 aggregates) (P less than .05). Those who smoked 20 years or more also showed enhanced aggregation in comparison to those who smoked less than 20 years (112 +/- 60 vs 53 +/- 45 aggregates) (P = .02). Circulating platelets showed no significant difference among smokers and nonsmokers in the following tests: platelet aggregate ratio (0.67 +/- 0.30 vs 0.86 +/- 0.76), platelet count per mm3, (310,000 +/- 82,000 vs 278,000 +/- 78,000/mm3), levels of platelet factor 4 (9.8 +/- 5.2 vs 9.4 +/- 5.3 ng/ml), and plasma concentrations of beta-thromboglobulin (53.9 +/- 23.5 vs 49.1 +/- 25.5 ng/ml). The data suggest that chronic smoking primes platelets, causing them to aggregate more readily when exposed to an activating stimulus in vitro.

Acute cigarette smoke exposure causes lung injury in rabbits treated with ibuprofen

We studied lung clearance of aerosolized technetium-labeled diethylenetriamine pentaacetic acid (99mTcDTPA), plasma concentrations of 6-keto-PGF1 alpha and thromboxane B2, and pulmonary edema as indices of lung injury in rabbits exposed to cigarette smoke (CSE). Forty-six rabbits were randomly assigned to 4 groups: control sham smoke exposure (SS, N = 9), sham smoke exposure ibuprofen-pretreated (SS-I, N = 10), CSE (N = 9), sham smoke exposure ibuprofen-pretreated (SS-I, N = 10), CSE (N = 9), and CSE ibuprofen-pretreated (CSE-I, N = 19). Ibuprofen (cyclooxygenase eicosanoid inhibitor) was administered as a single daily intramuscular injection (25 mg/kg) for 7 days before the experiment. Cigarette or sham smoke was delivered by syringe in a series of 5, 10, 20, and 30 tidal volume breaths with a 15-min counting period between each subset of breaths to determine 99mTcDTPA biological half-life (T1/2). In the ibuprofen pretreated group, CSE caused significant decreases in 99mTcDTPA T1/2 and dynamic lung compliance. Furthermore, these changes in lung function were accompanied by severe injury to type I alveolar cell epithelium, pulmonary edema, and frequently death of the rabbits. These findings suggest that inhibition of the cyclooxygenase pathway before CSE exacerbates lung injury in rabbits.

Platelet reactivity, fibrinogen and smoking

40 young healthy male volunteers (20 habitual smokers and 20 non-smokers) were investigated with respect to platelet reactivity, plasma fibrinogen and coagulation factor VIII. Smokers had significantly lower systolic blood pressures and higher venous platelet counts. The results for ADP-induced platelet aggregation, plasma concentrations for the 2 alpha-granule proteins, beta-thromboglobulin and platelet factor 4, did not differ between the 2 study groups involved; nor was there any difference between serum thromboxane B2 formation or plasma factor VIII:C activity. However, as compared to non-smokers, plasma fibrinogen levels were significantly higher among the smokers.

Cigarette smoking and platelet function

To assess the influence of cigarette smoking on platelet activation, we studied the changes in intraplatelet and platelet-released serotonin (5-HT) and plasma levels and platelet-associated production of thromboxane B2 (TXB2), in 6 non smokers and 6 habitual smokers, before and after acute exposure to smoke. Before smoking, habitual smokers showed slightly higher, albeit not significantly, 5-HT platelet concentrations and TXB2 plasma levels, as well as lower TXB2 platelet production after collagen and even more after ADP stimulation (0.59 +/- 0.27 vs 1.35 +/- 0.46 and 0.99 +/- 0.47 vs 2.08 +/- 0.51 ng/10(8) platelets for habitual smokers vs controls, 4 and 10 min after ADP, p less than 0.02). No significant differences in platelet 5-HT release were observed. Acute smoking did not induce any significant change from baseline in either 5-HT or TXB2 for controls, while significantly reduced TXB2 production from ADP-challenged platelets from habitual smokers (0.30 +/- 0.15 vs 0.59 +/- 0.27 ng/10(8) platelets, immediately after smoking vs baseline, p less than 0.01). Ninety min after the completion of the smoking, the values had returned to baseline. Immediately after smoking, significant differences were found between habitual smokers and controls for TXB2 platelet production (2.76 +/- 1.78 vs 6.42 +/- 1.60, p less than 0.025 and 3.01 +/- 1.90 vs 6.44 +/- 2.26 ng/10(8) platelets, p less than 0.05, for habitual smokers vs controls, 4 and 10 min after the addition of collagen; 0.30 +/- 0.15 vs 1.20 +/- 0.84 and 0.79 +/- 0.50 vs 1.70 +/- 0.74 ng/10(8) platelets, p less than 0.05, after ADP stimulation). Differences were no longer significant 90 min after smoking. Our data indicate that cigarette smoking is associated with platelet dysfunction, which seems due to impairment of metabolic platelet capacity rather than increased platelet activation in vivo.

[Thromboxane concentrations in the arterial blood of cigarette smokers]

Thromboxane concentrations were investigated in the arterial plasma of 44 patients (25 smokers, 19 nonsmokers) with chronic obstructive arterial disease (COAD) of the lower extremities, documented by angiography. The thromboxane levels were measured by radioimmunoassay. The results indicate that smokers with COAD have significantly higher thromboxane levels than nonsmokers with COAD. The potential effect of nicotine on thromboxane is discussed.

Relationship of angiographically defined coronary artery disease to serum lipoproteins and apolipoproteins in young survivors of myocardial infarction

The relationship of serum lipoprotein and apolipoprotein concentrations to angiographically determined coronary artery disease was investigated in 105 consecutive male survivors of myocardial infarction under the age of 45. Concentrations and composition of lipoproteins, lipid indexes, and nonlipid risk factors (tobacco consumption, hypertension, reduced glucose tolerance, and obesity) were related to a recently developed scoring system for semiquantitative estimation of diffuse coronary atheromatosis, as well as to the number and severity of significant coronary artery stenoses. The concentrations of cholesterol in very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL), in combination with serum triglyceride or VLDL triglyceride level, comprised the best set of independent discriminatory lipid variables between patients and control subjects. In the patients, LDL cholesterol and apolipoprotein B levels showed strong relationships to the extent and severity of coronary atheromatosis but not to the number and severity of distinct coronary stenoses. HDL2 cholesterol concentration correlated inversely with the coronary atheromatosis score, whereas other variables reflecting HDL concentration and composition or VLDL lipids were not independently related to any of the coronary scores. The LDL triglyceride level, an index of intermediate-density lipoprotein (IDL) accumulation, was significantly correlated to the coronary atheromatosis score in univariate analysis. Nonlipid risk factors were correlated neither to coronary atheromatosis nor to severity of stenoses. Stepwise multiple regression analyses of data adjusted for age, cumulative tobacco consumption, and weight indicated that 18% of the variation in the coronary atheromatosis score could be accounted for by levels of apolipoprotein B. Addition of other lipoprotein variables or the nonlipid variables hypertension and glucose tolerance did not significantly increase the value of R2. When ratios of lipoprotein lipids and apolipoproteins were included in the regression model, the highest multiple correlation coefficient was obtained with the LDL/HDL cholesterol ratio alone (R2 = .22). The present data demonstrate the importance of elevated LDL cholesterol and apolipoprotein B concentrations for the development of coronary atheromatosis in young male survivors of myocardial infarction. The lack of correlations between the levels of lipoprotein lipids and serum apolipoproteins and the severity of coronary stenoses suggests that mechanisms other than disturbances of lipoprotein metabolism may be involved in the progression of more advanced coronary lesions.

Alterations in prostacyclin and thromboxane formation by chronic cigarette smoke exposure: temporal relationships and whole smoke vs. gas phase

Chronic cigarette smoke exposure in vivo causes decreased conversion of [14C]arachidonic acid (AA) to prostacyclin (PGI2) by isolated aortic tissue and increased conversion to thromboxane (TXA2) by isolated platelets from rats. Alterations in the PGI2/TXA2 balance may be part of the mechanism through which smoking increases the risk of cardiovascular disease. To study the influence of smoke exposure duration on this response, male rats were exposed daily to 10 puffs of freshly generated cigarette smoke. Animals were killed after 1, 4, 14, 28 and 57 days of smoke exposure and 3, 7, 14 and 28 days after cessation of the 57-day of smoke-exposure regimen. Elevated carboxyhemoglobin levels during the smoke-exposure sessions verified smoke (gas phase) inhalation. Statistically significant alterations in prostacyclin synthesis preceded those of thromboxane. A decrease of 20-25% (P less than 0.05) in PGI2 production from [14C]AA in isolated aortic tissue was found beginning 28 days after smoke was initiated and quickly rebounded when smoke exposure was terminated. Increased production of TXA2 from [14C]AA by isolated platelets became statistically significant (P less than 0.05) on the 57th day and returned to normal 7-14 days after cessation of smoke exposure. To determine the effect of gas phase constituents on the PGI2/TXA2 balance a second series of experiments divided male and female Sprague-Dawley rats into sham, whole smoke and gas phase groups. Gas phase was produced by passing whole smoke through a Cambridge filter to remove particulate matter. Per cent COHb averaged 1.4 for sham, 7.8 for whole smoke and 9.4 for gas phase groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of smoking and nicotine on human prostacyclin and thromboxane production in vivo and in vitro

We studied the effects of smoking and nicotine on the production of proaggregatory thromboxane A2 (TxA2), antiaggregatory prostacyclin (epoprostenol, PGI2), and on lipid peroxidation in vivo and in vitro. In the in vivo study, serum concentrations of thromboxane B2 (TxB2), a stable metabolite of TxA2, increased immediately after smoking three cigarettes but not after smoking the equivalent amount of tobacco in a pipe, whereas serum lipid peroxide values did not change in either group. In vitro, nicotine (2 X 10(-3) mol/liter) inhibited pulmonary TxB2 production by 70% and simultaneously stimulated the production of 6-keto-prostaglandin F1 alpha, a stable metabolite of PGI2, by 40%, which suggest that nicotine does not exert its effect at the cyclooxygenase level. During aggregation in platelet-rich plasma, TxB2 production was inhibited by 53% with 2 X 10(-3) mol/liter of nicotine, and during whole blood clotting the inhibition was 34% with 2 X 10(-4) mol/liter of nicotine. Thus the rise in cigarette smokers' serum TxB2 was probably caused by some constituent of cigarette smoke other than nicotine. The increased production of TxA2 following cigarette smoking may provide one explanation for the increased incidence of atherosclerosis and its complications in cigarette smokers.

Platelet half-life, plasma thromboxane B2 and circulating endothelial-cells in peripheral vascular disease

We studied platelet half-life (T/2), plasma thromboxane B2-levels (TXB2) and circulating endothelial cells in 107 patients with a mean age of 63 +/- 6.8 years and angiographically proven peripheral vascular disease (PVD). Patients were divided into 4 groups according to Fontaine but also according to additional clinical manifestations of atherosclerosis like coronary heart disease (CHD) and cerebrovascular disease (CVD). Furthermore, the influence of sex and smoking was investigated. Compared to patients without atherosclerotic manifestations we could detect an enhanced platelet consumption measured as shortened platelet half-life time (79.2 +/- 9.1 vs 100.9 +/- 5.6 hours, p less than 0.001 and an increased platelet activity measured as increased TXB2-plasma levels (51.6 +/- 20.9 vs 23.2 +/- 11.2 ng/ml, p less than 0.001). Correspondingly, the amount of circulating endothelial cells was increased 45.2 +/- 25.7 vs 20.3 +/- 23.4, p less than 0.001). Patients with PVD who smoked had the shortest actual platelet half-life, the highest TXB2 plasma levels and the greatest amount of circulating endothelial cells compared to non-smoking patients and controls. Patients with clinical stage IV according to Fontaine had the shortest platelet half-life, the highest TXB2 plasma levels and the greatest amount of circulating endothelial cells compared to the other clinical stages. Analyzing the influence of additional clinical manifestations of atherosclerosis we could detect only in patients with PVD and CHD significant differences compared to the other groups.

Cigarette smoking reduces human gastric luminal prostaglandin E2

The effect of smoking three cigarettes on the release of prostaglandin E2 (PGE2) by the gastric mucosa was studied in seven healthy smokers. Smoking caused the expected increases in pulse rate, blood pressure, plasma glucose, and carboxyhaemoglobin. In addition, smoking resulted in a significant (p less than 0.05) reduction in the volume of pentagastrin stimulated gastric juice from 76.1 +/- 4.4 to 54.1 +/- 4.6 ml/15 min and PGE2 output from 22.8 +/- 4.9 to 12.2 +/- 3.8 ng/15 min but did not alter acid output. It is concluded that smoking reduces the amount of PGE2 in the gastric lumen and that this may explain why it is a risk factor for peptic ulcer.

Elevated glucose in vivo and in vitro adversely alters prostaglandin generation in rat aortas and platelets

An imbalance in prostacyclin (PGI2) and thromboxane (TXA2) generation from arachidonic acid (AA) may contribute to the marked increase in susceptibility to cardiovascular disease seen in diabetics. Rats made diabetic with streptozocin, and subsequently treated with saline or insulin, yielded aortic rings that synthesized decreasing amounts of PGI2 and platelets that generated increasing amounts of TXA2 in proportion to the degree of hyperglycemia. These alterations in AA metabolism were mimicked by incubating aortic rings or platelets from normal rats in buffer containing elevated glucose concentrations. Platelets incubated in elevated glucose displayed shorter times to maximal aggregation and higher percent maximal aggregation. Incubation of tissue in a buffer made hyperosmotic with mannitol had no effect on PGI2 or TXA2 formation, or platelet aggregation. These data suggest that hyperglycemia is involved in the PGI2/TXA2 imbalance and platelet abnormalities seen in diabetes, and reinforces the importance of rigid control of blood glucose as an approach to minimizing the incidence of diabetic cardiovascular complications.

Aggregation of and thromboxane B2 synthesis in platelets from newborn infants of smoking and non-smoking mothers

Cord blood platelet aggregation and thromboxane B2 (TxB2) synthesis were investigated in 20 healthy infants of drug-free healthy mothers with an uncomplicated pregnancy ending at term in a normal vaginal delivery. Eight of the mothers were habitual smokers and the remaining 12 were non-smokers. The platelet count was slightly lower in infants of smoking mothers than in the control infants. There were no differences between the two groups in the qualitative or quantitative aggregation responses (maximal change in optical density) to stimulation by 0.55, 1.1, 3.3 and 6.6 microM adenosine diphosphate, 0.5 and 1.0 mM arachidonic acid (AA) or collagen 1.0 and 5.5 mg/l. Nor was there any difference between the groups in regard to TxB2 synthesis after stimulation by these substances. The amount of TxB2 synthesized merely reflected the occurrence of reversible or irreversible platelet aggregation. Stimulation of platelets by AA induced by far the highest synthesis of TxB2. The generally decreased aggregability of platelets of newborn infants, compared with that in adults, was confirmed in this study. No effect of maternal smoking during pregnancy on the prostaglandin-dependent pathway of aggregation of cord blood platelets was demonstrated.

The effects of chronic cigarette smoking on cerebrovascular responsiveness to 5 per cent CO2 and 100 per cent O2 inhalation

Effects of chronic cigarette smoking on cerebrovascular responsiveness of volunteers at risk for stroke and not at risk for stroke were evaluated by serial measurements of cerebral blood flow using the 133Xe inhalation method. Resting gray matter blood flow values (Fg) measured while breathing room air were compared with Fg values measured during inhalation of either 5 per cent CO2 in air or 100 per cent O2. Changes in Fg values during inhalation of 5 per cent CO2 were used to estimate cerebral vasodilator capacitance, and those during inhalation of 100 per cent O2 were used to estimate cerebral vasoconstrictor capacitance. Results indicated that chronic cigarette smokers have both reduced vasodilator (P less than 0.01) and reduced vasoconstrictor (P less than 0.02) capacitance when compared with nonsmokers of the same ages regardless of whether or not other risk factors for stroke were present. Vasodilator capacitance to 5 per cent CO2 inhalation was reduced among smokers compared with nonsmokers of the same age by 48 per cent in non-risk subjects and 56 per cent in risk-factored subjects, while vasoconstrictor capacitance to 100 per cent O2 inhalation among smokers was decreased by 24 per cent in non-risk subjects and 34 per cent in risk-factored subjects. In risk-factored subjects, combined effects of smoking and other risks appeared to be additive.

Pulmonary NAD+-linked 15-hydroxyprostaglandin dehydrogenase activity is decreased by cigarette smoking

Male rats were exposed to freshly generated cigarette smoke once daily for 4 to 13 weeks. Inhalation of smoke was verified by elevated level of carboxyhemoglobin. NAD+-dependent 15-hydroxyprostaglandin dehydrogenase activity, the key enzyme responsible for biological inactivation of prostaglandins, was found to decrease in lung but not in kidney or stomach following cigarette smoke exposure. The consequence of impaired pulmonary metabolism of prostaglandins and thromboxane may result in alteration of vascular homeostasis and subsequently lead to cardiovascular disorders commonly found in smokers.

Platelet aggregability in smoking and non-smoking subjects

The hypothesis was investigated that the arachidonic acid (AA) system has a different impact on platelet function in smoking compared to non-smoking subjects. Arterial blood was sampled from smokers and non-smokers, and platelet-rich plasma (PRP) was prepared. There were no differences in sex and age distribution between the groups. One portion of the PRP was used to determine the lowest amount of AA required to induce platelet aggregation. In other portions the endogenous anti-aggregatory (prostacyclin/PGI2/-like) activity in the blood was determined, after reinforcing it with theophylline. There was no difference between smokers and non-smokers regarding the amount of AA required to induce platelet aggregation. In fresh PRP prepared from blood from non-smoking subjects theophylline (10(-4) M) induced a 12-17% inhibition of the ADP-induced aggregation of platelets, indicating the presence of endogenous subthreshold concentrations of PGI2-like activity in their blood. The corresponding inhibition in fresh PRP prepared from blood from smokers was significantly lower (4-7%), suggesting lower endogenous concentrations of PGI2-like activity in their blood, or alternatively, decreased platelet sensitivity to the action of such activity. From these data we conclude that smokers differ from non-smokers with regard to their platelet function: platelet aggregability in response to AA is unaffected, while the endogenous anti-aggregatory power in the plasma is decreased. These observations may be of significance for the cardiovascular hazards connected with smoking.

Cigarette smoke ventilation decreases thromboxane B2 metabolism in isolated rat lungs

3H-TxB2 was infused into the pulmonary circulation of isolated perfused rat lungs. The metabolites were analysed from the nonrecirculating perfusion effluent. When the lungs were ventilated with cigarette smoke the amount of unmetabolized TxB2 in the effluent was increased by 50%. The amount of the main metabolite was, however, not changed. The efflux of radioactivity from the lungs after a bolus injection of 3H-TxB2 was slower during cigarette smoke ventilation than during air ventilation. This suggests that cigarette smoke inhibits the enzymes metabolizing TxB2 rather than the pulmonary thromboxane uptake system.

Cigarette smoking stimulates lipoxygenase but not cyclooxygenase pathway in platelets

Male rats were exposed to freshly generated cigarette smoke once daily for 4 to 8 weeks. Inhalation of smoke was verified by elevated level of carboxyhemoglobin. Arachidonate metabolism through lipoxygenase and cyclooxygenase pathways in platelets was determined. Cigarette smoking increased 12-lipoxygenase activity significantly without affecting the cyclooxygenase pathway. In view of platelet-leukocyte interactions and potent chemotactic activity of 12-HETE for aortic smooth muscle cell migration, increased 12-lipoxygenase activity may predispose individuals to atherosclerosis, thromboembolism and emphysema commonly found in smokers.

Chronic cigarette smoke exposure adversely alters 14C-arachidonic acid metabolism in rat lungs, aortas and platelets

Male rats were exposed to freshly generated cigarette smoke once daily, 5 times a week for 10 weeks. Inhalation of smoke was verified by elevated carboxyhemoglobin in blood sampled immediately after smoke exposure and by increased lung aryl hydrocarbon hydroxylase activity 24 hours after the last smoke exposure. Aortic rings isolated from smoke-exposed rats synthesized less prostacyclin (PGI2) from 14C-arachidonic acid than rings from sham rats. Platelets from smoke-exposed rats synthesized more thromboxane (TXA2) from 14C-arachidonic acid than platelets from room controls but not those from sham rats. Lung microsomes from smoke-exposed rats synthesized more TXA2 and had a lower PGI2/TXA2 ratio than lung microsomes from room controls and shams. It is concluded that chronic cigarette smoke exposure alters arachidonic acid metabolism in aortas, platelets and lungs in a manner resulting in decreased PGI2 and increased TXA2, thereby creating a condition favoring platelet aggregation and a variety of cardiovascular diseases.

Malignant hypertension in women aged 15 to 44 years and its relation to cigarette smoking and oral contraceptives

To study the factors associated with malignant hypertension in young women, we reviewed the medical records of all women aged 15 to 44 years who were hospitalized in any of 15 affiliated hospitals from 1971 to 1980 with malignant hypertension. There were 15 new patients in this period, an incidence of 0.5 per 100,000 women of these ages per year. Four women had underlying renal disease. All of the remaining 11 used oral contraceptives, smoked cigarettes, or both. Nine were white, and 6 women had normal blood pressure in the 24 months before hospitalization. These findings support a relation of oral contraceptive use and cigarette smoking to an increased risk of malignant hypertension in young women.