The double-edged nature of nicotine: toxicities and therapeutic potentials

Nicotine is the primary addictive component of cigarette smoke and is associated with various smoking-related diseases. However, recent research has revealed its broader cognitive-enhancing and anti-inflammatory properties, suggesting its potential therapeutic applications in several conditions. This review aims to examine the double-edged nature of nicotine, encompassing its positive and negative effects. We provide a concise overview of the physiochemical properties and pharmacology of nicotine, including insights into nicotine receptors. Therefore, the article is divided into two main sections: toxicity and therapeutic potential. We comprehensively explored nicotine-related diseases, focusing on specific signaling pathways and the underlying mechanisms that contribute to its effects. Furthermore, we addressed the current research challenges and future development perspectives. This review aims to inspire future researchers to explore the full medical potential of nicotine, which holds significant promise for the clinical management of specific diseases.

Blood pressure reduction after renal denervation in patients with or without chronic kidney disease

Background

Renal denervation (RDN) has emerged as an adjacent option for the treatment of hypertension. This analysis of the Erlanger registry aimed to compare the blood pressure (BP)-lowering effects and safety of RDN in patients with and without chronic kidney disease (CKD).

Methods

In this single-center retrospective analysis, 47 patients with and 127 without CKD underwent radiofrequency-, ultrasound- or alcohol-infusion-based RDN. Office and 24-h ambulatory BP and estimated glomerular filtration rate (eGFR) were measured at baseline, and after 6 and 12 months.

Results

A total of 174 patients with a mean age of 59.0 ± 10 years were followed up for 12 months. At baseline, mean eGFR was 55.8 ± 21 mL/min/1.73 m2 in patients with CKD and 87.3 ± 13 mL/min/1.73 m2 in patients without CKD. There was no significant eGFR decline in either of the groups during 12 months of follow-up. In patients without CKD, office systolic and diastolic BP were reduced by -15.3 ± 17.5/-7.9 ± 10.8 mmHg 6 months after RDN and by -16.1 ± 18.2/-7.7 ± 9.6 mmHg 12 months after RDN. In patients with CKD, office systolic and diastolic BP were reduced by -10.7 ± 24.0/-5.8 ± 13.2 mmHg 6 months after RDN and by -15.1 ± 24.9/-5.9 ± 12.9 mmHg 12 months after RDN. Accordingly, in patients without CKD, 24-h ambulatory systolic and diastolic BP were reduced by -7.2 ± 15.8/-4.9 ± 8.8 mmHg 6 months after RDN and by -9.0 ± 17.0/-6.2 ± 9.8 mmHg 12 months after RDN. In patients with CKD, 24-h systolic and diastolic BP were reduced by -7.4 ± 12.9/-4.2 ± 9.9 mmHg 6 months after RDN and by -8.0 ± 14.0/-3.6 ± 9.6 mmHg 12 months after RDN. There was no difference in the reduction of office and 24-h ambulatory BP between the two groups at any time point (all P > .2). Similar results have been found for the 6 months data. With exception of rare local adverse events, we did not observe any safety signals.

Conclusion

According to our single-center experience, we observed a similar reduction in 24-h, day and night-time ambulatory BP as well as in-office BP in patients with and without CKD at any time point up to 12 months. We conclude that RDN is an effective and safe treatment option for patients with hypertension and CKD.

An integral perspective of canonical cigarette and e-cigarette-related cardiovascular toxicity based on the adverse outcome pathway framework

BACKGROUND

Nowadays, cigarette smoking remains the leading cause of chronic disease and premature death, especially cardiovascular disease. As an emerging tobacco product, e-cigarettes have been advocated as alternatives to canonical cigarettes, and thus may be an aid to promote smoking cessation. However, recent studies indicated that e-cigarettes should not be completely harmless to the cardiovascular system.

AIM OF REVIEW

This review aimed to build up an integral perspective of cigarettes and e-cigarettes-related cardiovascular toxicity.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review adopted the adverse outcome pathway (AOP) framework as a pivotal tool and aimed to elucidate the association between the molecular initiating events (MIEs) induced by cigarette and e-cigarette exposure to the cardiovascular adverse outcome. Since the excessive generation of reactive oxygen species (ROS) has been widely approved to play a critical role in cigarette smoke-related CVD and may also be involved in e-cigarette-induced toxic effects, the ROS overproduction and subsequent oxidative stress are regarded as essential parts of this framework. As far as we know, this should be the first AOP framework focusing on cigarette and e-cigarette-related cardiovascular toxicity, and we hope our work to be a guide in exploring the biomarkers and novel therapies for cardiovascular injury.

Acute administration of nicotine induces transient elevation of blood pressure and increases myocardial infarct size in rats

Aims

We investigated the acute effects of nicotine on myocardial infarct size, no reflow, hemodynamics and cardiac function in an acute myocardial ischemia and reperfusion infarction rat model.

Main methods

Female Sprague-Dawley rats (n = 23/group) received an intravenous loading dose of nicotine at 2.0 μg/kg/min or saline control for 30 min before starting coronary artery occlusion, then followed by a maintenance dose 0.35 μg/kg/min of nicotine to the end of 30 min occlusion and 3 h reperfusion.

Key findings

At baseline, there was no difference in systolic blood pressure (BP in mmHg) (nicotine, 69.0 ± 2.7; control, 69.3 ± 4.4; p = NS) or diastolic BP (nicotine, 45.7 ± 3.2; control, 48.2 ± 4.2; p = NS) between groups. Nicotine administration initially increased systolic BP (nicotine, 97.0 ± 8.6; control, 69.2 ± 3.3, p < 0.0001) and diastolic BP (nicotine, 65.6 ± 6.4; control, 47.4 ± 3.1, p = 0.0003) at 10 min after starting injection of the loading dose; BP dropped to control levels in both groups at 30 min. During occlusion and reperfusion, the BP and heart rate were not altered by nicotine. Nicotine significantly increased myocardial infarct size as a percentage of the ischemic risk zone compared to the controls (nicotine, 54.9 ± 1.9; control, 48.6 ± 2.7, p < 0.05), but nicotine did not affect the no-reflow size and heart function.

Significance

While acute nicotine only transiently elevated blood pressure, it did not affect hemodynamic parameters during coronary artery occlusion. Nicotine increased myocardial infarct size, suggesting that the increase in infarct size was not simply due to an increase in oxygen demand due to altered afterload, heart rate, or contractility, but may have been due to a more direct effect on the myocardium.

Acute effects of electronic cigarettes on arterial pressure and peripheral sympathetic activity in young nonsmokers

Electronic cigarettes (e-cigarettes) are marketed as an alternative to smoking for those who want to decrease the health risks of tobacco. Tobacco cigarettes increase heart rate (HR) and arterial pressure, while reducing muscle sympathetic nerve activity (MSNA) through sympathetic baroreflex inhibition. The acute effects of e-cigarettes on arterial pressure and MSNA have not been reported: our purpose was to clarify this issue. Using a randomized crossover design, participants inhaled on a JUUL e-cigarette containing nicotine (59 mg/mL) and a similar placebo e-cigarette (0 mg/mL). Experiments were separated by ∼1 mo. We recorded baseline ECG, finger arterial pressure (n = 15), and MSNA (n = 10). Subjects rested for 10 min (BASE) and then inhaled once every 30 s on an e-cigarette that contained nicotine or placebo (VAPE) for 10 min followed by a 10-min recovery (REC). Data were expressed as Δ means ± SE from BASE. Heart rate increased in the nicotine condition during VAPE and returned to BASE values in REC (5.0 ± 1.3 beats/min nicotine vs. 0.1 ± 0.8 beats/min placebo, during VAPE; P < 0.01). Mean arterial pressure increased in the nicotine condition during VAPE and remained elevated during REC (6.5 ± 1.6 mmHg nicotine vs. 2.6 ± 1 mmHg placebo, during VAPE and 4.6.0 ± 1.7 mmHg nicotine vs. 1.4 ± 1.4 mmHg placebo, during REC; P < 0.05). MSNA decreased from BASE to VAPE and did not restore during REC (-7.1 ± 1.6 bursts/min nicotine vs. 2.6 ± 2 bursts/min placebo, during VAPE and -5.8 ± 1.7 bursts/min nicotine vs. 0.5 ± 1.4 bursts/min placebo, during REC; P < 0.05). Our results show that acute e-cigarette usage increases mean arterial pressure leading to a baroreflex-mediated inhibition of MSNA.NEW & NOTEWORTHY The JUUL e-cigarette is the most popular e-cigarette in the market. In the present study, inhaling on a JUUL e-cigarette increased mean arterial pressure and heart rate, and decreased muscle sympathetic nerve activity (MSNA). In contrast, inhaling on a placebo e-cigarette without nicotine elicited no sympathomimetic effects. Although previous tobacco cigarette studies have demonstrated increased mean arterial pressure and MSNA inhibition, ours is the first study to report similar responses while inhaling on an e-cigarette. Listen to this article's corresponding podcast at @ https://ajpheart.podbean.com/e/aerosolized-nicotine-and-cardiovascular-control/.

Habitual cigarette smoking raises pressor responses to spontaneous bursts of muscle sympathetic nerve activity

Smoking is a risk factor for cardiovascular diseases. Prior reports showed a transient increase in blood pressure (BP) following a spontaneous burst of muscle sympathetic nerve activity (MSNA). We hypothesized that this pressor response would be accentuated in smokers. Using signal-averaging techniques, we examined the BP (Finometer) response to MSNA in 18 otherwise healthy smokers and 42 healthy nonsmokers during resting conditions. The sensitivities of baroreflex control of MSNA and heart rate were also assessed. The mean resting MSNA, heart rate, and mean arterial pressure (MAP) were higher in smokers than nonsmokers. The MAP increase following a burst of MSNA was significantly greater in smokers than nonsmokers (Δ3.4 ± 0.3 vs. Δ1.6 ± 0.1 mmHg, P < 0.001). The baroreflex sensitivity (BRS) of burst incidence, burst area, or total activity was not different between the two groups. However, cardiac BRS was lower in smokers than nonsmokers (14.6 ± 1.7 vs. 24.6 ± 1.5 ms/mmHg, P < 0.001). Moreover, the MAP increase following a burst was negatively correlated with the cardiac BRS. These observations suggest that habitual smoking in otherwise healthy individuals raises the MAP increase following spontaneous MSNA and that the attenuated cardiac BRS in the smokers was a contributing factor. We speculate that the accentuated pressor increase in response to spontaneous MSNA may contribute to the elevated resting BP in the smokers.

Cardiac autonomic neuropathy in type 1 and type 2 diabetes patients

Background

Cardiac autonomic neuropathy (CAN) in diabetes is among the strongest risk markers for future global and cardiovascular mortality. The aim of this study was to analyse CAN prevalence and to compare the associations between CAN, the glycaemic control, cardiovascular risk factors, peripheral neuropathy, retinopathy and macroangiopathy in patients with type 1 (T1DM) and type 2 diabetes mellitus (T2DM).

Methods

One hundred ninety-five diabetic patients were included in this study. All patients were evaluated for detection of CAN (with standardised cardiovascular reflex tests), diabetes-related microvascular complications (polyneuropathy, retinopathy), common carotid artery intima-media thickness (IMT) and ankle-brachial index (ABI).

Results

The prevalence of CAN was 39.1% in T2DM and 61.8% in T1DM patients. Multivariate logistic regression analysis demonstrated that in T2DM, the odds [OR (95% confidence intervals)] of CAN increased with diabetes duration [1.67(1.42–1.92)], HbA1c [1.74(1.34–2.27)], cholesterol [1.01(1.00–1.01)], triglycerides [1.01(0.99–1.00)], smoking [2.35(1.23–4.49)], systolic blood pressure [1.01(1.00–1.03)], BMI [1.16(1.08–1.24)], glomerular filtration rate [0.91(0.88–0.93)], peripheral neuropathy [25.94(11.04–44.25)], retinopathy [13.13(3.03–84.73)] and IMT [10.12 (7.21–15.32)]. In T1DM, the odds of CAN increased with diabetes duration [1.62(1.13–2.31)], HbA1c [4.49(1.27–15.9)], age of patients [1.14(1.03–1.27)], glomerular filtration rate [0.94(0.89–0.99)], peripheral neuropathy [31.6(4.5–45.8)] and IMT [5.5(2.3–8.3)].

Conclusion

This study indicated that CAN is a more frequent complication in T1DM. Apart from glycaemic control, the existence of CAN is associated with potentially modifiable cardiovascular risk only in T2DM patients. The presence of other micro- and macrovascular complications increases the probability of having CAN in both types of DM (but more pronounced in T2DM).

Influences of lifestyle factors on cardiac autonomic nervous system activity over time

Physical activity, alcohol use and smoking might affect cardiovascular disease through modifying autonomic nervous system (ANS) activity. We investigated: 1) whether there are consistent relationships between lifestyle factors and cardiac ANS activity over time, and 2) whether 2-year changes in lifestyle factors relate to 2-year changes in cardiac activity. Baseline (n=2618) and 2-year follow-up (n=2010) data of the Netherlands Study of Depression and Anxiety was combined. Baseline data was collected in the Netherlands from 2004-2007. Lifestyle factors were habitual physical activity, frequency of sport activities, alcohol use, and smoking. Indicators of cardiac activity were heart rate (HR), respiratory sinus arrhythmia (RSA) and pre-ejection period (PEP) (100min of registration). The results showed that high physical activity (-1.8beats/min compared to low activity), high frequency of sport activities ('couple of times/week': -2.5beats/min compared to 'almost never') and mild/moderate alcohol use (-1.2beats/min compared to non-drinking) were related to low HR. Heavy smoking was related to high HR (>30cigarettes/day: +5.1beats/min compared to non-smoking). High frequency of sport activities was associated with high RSA ('couple of times/week':+1.7ms compared to 'almost never') and moderate smoking with longer PEP (11-20cigarettes/day: +2.8ms compared to non-smoking). Associations were consistent across waves. Furthermore, 2-year change in frequency of sport activities and number of smoked cigarettes/day was accompanied by 2-year change in HR (β=-0.076 and β=0.101, respectively) and RSA (β=0.046 and β=-0.040, respectively). Our findings support consistent effects of lifestyle on HR and parasympathetic activity in the expected direction. Cardiac autonomic dysregulation may be partly mediating the relationship between lifestyle and subsequent cardiovascular health.

Blood Pressure Reactivity to the Cold Pressor Test Predicts Hypertension Among Chinese Adults: The GenSalt Study

BACKGROUND

Blood pressure (BP) hyper-reactivity to the cold pressor test (CPT) has been suggested as a predictor of hypertension. We examined whether BP reactivity to the CPT was associated with hypertension incidence among the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) study participants from China.

METHODS

A total of 1,961 GenSalt study participants without any antihypertensive treatment completed the CPT at the baseline examination. Hypertension status was assessed at baseline (2003-2005) and 2 follow-up visits (2008-2009 and 2011-2012).

RESULTS

After adjustment for multiple covariates, both systolic BP (SBP) and diastolic BP reactivity to the CPT were significantly associated with hypertension incidence. For example, the multivariable adjusted odds ratios (ORs, 95% CI) of developing hypertension were 0.92 (0.66, 1.29), 1.42 (1.03, 1.97), and 1.45 (1.05, 2.00) for participants with maximum SBP responses of 6.7-12.0, 12.1-19.2, and ≥19.3mm Hg, respectively, compared to those with responses of <6.7mm Hg (P for trend = 0.006). Likewise, the multivariable-adjusted ORs (95% CI) of hypertension were 1.12 (0.79, 1.57), 1.62 (1.15, 2.29), and 1.82 (1.30, 2.55) for participants with the area under the curve of SBP responses of 3.0-16.0, 16.1-29.9, and ≥ 30.0mm Hg·min, respectively, compared to those with responses of < 3.0mm Hg·min (P for trend = 0.0001). The associations between BP reactivity variables and the risk of hypertension were not different among subgroups of sex, age, and baseline BP levels.

CONCLUSIONS

BP hyperreactivity to the cold stimulus may predict the risk of hypertension among Chinese adults.

Sources of variation analysis and derivation of reference intervals for ALP, LDH, and amylase isozymes using sera from the Asian multicenter study on reference values

BACKGROUND

Sources of variation (SV) of ALP, LDH, and amylase isozymes were explored.

METHODS

We analyzed 3511 sera from well-defined healthy individuals recruited during the 2009 Asian project for derivation of common reference intervals (RIs). Up-to-date electrophoresis auto-analyzer and reagents were employed for high resolution and reproducibility. SVs including sex, age, body mass index (BMI), ABO blood groups, and levels of drinking, smoking, and exercise were analyzed by multiple regression analysis. RIs were determined by parametric methods after refining healthy individuals by use of latent reference values exclusion method.

RESULTS

Age-related changes in ALP2-3 were different in females: ALP2, linear increase from 20-64y; ALP3, lowering until 45 y and rising steeply thereafter. ALP2 increased with BMI especially in females. ALP5 was barely detectable except in blood-types O and B. Age-related increases in LDH1-LDH3 were noted in females, whereas BMI-related increases were found only for LDH2-LDH5 in both sexes. Pancreatic amylase showed age-related increase in females and was slightly higher in blood-type O. RIs for absolute and relative activities of each isozyme were derived in consideration of sex and age.

CONCLUSIONS

Investigation of these isozymes revealed various age-, BMI-, and blood-type-related changes that are all relevant in clinical interpretation of enzyme test results.

A blunted sympathetic and accentuated parasympathetic response to postural change in subjects with depressive disorders

BACKGROUND

In recent years, the bi-directional relationship between depression and ANS dysfunction has received considerable attention, but findings remain inconclusive. In this study, we aimed to examine the spectral HRV response to postural change in subjects with depressive disorders and in healthy controls, in order to gain insight into the characteristics of autonomic nervous system (ANS) response to postural change in subjects with depressive disorders.

METHODS

We compared HRV response to postural change between subjects with depressive disorders and healthy controls aged 20-37 years. Depression severity was assessed by the self-reported Beck Depression Inventory-II (BDI-II). Spectral HRV was analyzed at two moments: 10 min seated rest and 10 min at standing position, with spontaneous breathing.

RESULTS

No significant differences existed in the resting spectral HRV indices between subjects with depressive disorders and controls, however, following postural change, the increasing level of LF and LF/HF was lower and the decreasing level of HF power was higher, in the individuals with depression than that in healthy subjects. The differences in the LF power, HF power and the LF/HF ratio between seated rest before standing up and after postural change were found negatively correlated with depression severity.

CONCLUSION

We found a blunted sympathetic and accentuated parasympathetic response to postural change in subjects with depressive disorder, suggesting that the autonomic impairment and early ANS dysfunction may exist among depressed individuals. These findings indicated that spectral analysis of HRV associated with postural change may be a more sensitive method than resting HRV analysis for detecting ANS dysfunction in depressive disorders.

LIMITATIONS

Further studies are needed to expand the sample size and to clarify the mechanisms responsible for the autonomic dysfunction observed in individuals with depressive disorders.

Preliminary effects of progressive muscle relaxation on cigarette craving and withdrawal symptoms in experienced smokers in acute cigarette abstinence: a randomized controlled trial

BACKGROUND

Cigarette craving usually occurs in conjunction with unpleasant feelings, including stress, as part of a withdrawal syndrome. Progressive muscle relaxation (PMR), a behavioral technique used to reduce stress by concentrating on achieving muscle relaxation, may reduce levels of cigarette craving and other substance-related negative feelings and withdrawal symptoms.

METHODS

Demographic and cigarette use data were collected from 32 experienced smokers at the King Chulalongkorn Memorial Hospital, Bangkok, Thailand using the Semi-Structured Assessment for Drug Dependence and Alcoholism. Participants were asked to refrain from smoking for at least 3 hours before the visit (acute abstinence) and were randomly allocated to a 1-session PMR group (n =16) or a control activity group (e.g., reading newspaper, n =16). The intervention group was instructed to practice PMR individually in a quiet, private, air-conditioned room for about 20minutes. Craving, other substance-related feelings, and autonomic nervous responses (e.g., blood pressure and pulse rate) were assessed immediately before and after the 1-session intervention.

RESULTS

There were no differences in demographics, cigarette use/dependence, and baseline craving characteristics between the PMR and control groups. However, the control group had higher levels of high and paranoia feeling, and pulse rate than the PMR group at baseline. After practicing PMR, but not after a control activity, smokers undergoing acute abstinence had significantly lower levels of cigarette craving, withdrawal symptoms, and systolic blood pressure than at baseline. After controlling for baseline differences, abstaining smokers using PMR had lower levels of cigarette craving, withdrawal symptoms, and systolic blood pressure than smokers who undertook a control activity.

CONCLUSIONS

PMR significantly reduces cigarette craving, withdrawal symptoms, and blood pressure in smokers undergoing acute abstinence. PMR may be used as an adjunct to cigarette dependency treatments.

Adverse effects of cigarette and noncigarette smoke exposure on the autonomic nervous system: mechanisms and implications for cardiovascular risk

This review summarizes the detrimental effects of cigarette and noncigarette emission exposure on autonomic function, with particular emphasis on the mechanisms of acute and chronic modulation of the sympathetic nervous system. We propose that the nicotine and fine particulate matter in tobacco smoke lead to increased sympathetic nerve activity, which becomes persistent via a positive feedback loop between sympathetic nerve activity and reactive oxidative species. Furthermore, we propose that baroreflex suppression of sympathetic activation is attenuated in habitual smokers; that is, the baroreflex plays a permissive role, allowing sympathoexcitation to occur without restraint in the setting of increased pressor response. This model is also applicable to other nontobacco cigarette emission exposures (e.g., marijuana, waterpipes [hookahs], electronic cigarettes, and even air pollution). Fortunately, emerging data suggest that baroreflex sensitivity and autonomic function may be restored after smoking cessation, providing further evidence in support of the health benefits of smoking cessation.

Sidestream cigarette smoke and cardiac autonomic regulation

BACKGROUND

The literature has already demonstrated that cigarette influences the cardiovascular system. In this study, we performed a literature review in order to investigate the relationship between sidestream cigarette smoke (SSCS) and cardiac autonomic regulation.

METHODS

Searches were performed on Medline, SciELO, Lilacs and Cochrane databases using the crossing between the key-words: "cigarette smoking", "autonomic nervous system", "air pollution" and "heart rate variability".

RESULTS

The selected studies indicated that SSCS exposure affects the sympathetic and parasympathetic responses to changes in arterial blood pressure. Moreover, heart rate responses to environmental tobacco smoke are increased in smokers compared to non-smokers. The mechanism involved on this process suggest increased oxidative stress in brainstem areas that regulate the cardiovascular system.

CONCLUSION

Further studies are necessary to add new elements in the literature to improve new therapies to treat cardiovascular disorders in subjects exposed to sidestream cigarette smoke.

Effects of cigarette smoking, metabolic syndrome and dehydroepiandrosterone deficiency on intima-media thickness and endothelial function in hypertensive postmenopausal women

Background

Cigarette smoking is a major risk factor of atherosclerosis. The aim of this study was to assess the relationship between smoking and arterial hypertension as well as endothelial dysfunction in postmenopausal women without clinically manifested symptoms of atherosclerosis.

Material/Methods

The study groups consisted of 35 current smokers and 45 nonsmokers. The thickness of intima-media complex (IMT), a marker of atherosclerosis, was measured in carotid arteries. Plasma concentrations of fasting glucose, insulin, lipoproteins, inflammatory markers (tumor necrosis factor-alpha, intercellular adhesion molecule-1), matrix metalloproteinases (metalloproteinase-9, tissue inhibitor of metalloproteinase-1), insulin, and dehydroepiandrosterone sulfate (DHEA-S) were measured.

Results

Smokers compared with nonsmokers showed lower fasting glucose levels in blood (87.0±10.9 and 93.2±13.6 mg/dl, p<0.05), higher mean systolic (131.1±15.9 vs. 123.0±10.9 mm Hg, p<0.05) and diastolic (81.7±11.4 vs. 75.2±9.2 mm Hg, p<0.05) blood pressure during daytime, and higher average heart rate during the daytime (78.2±9.3/min vs. 71.5±9.5/min, p<0.01) and at night (67.2±10.6/min vs. 61.7±7.7/min, p<0.05), respectively. The IMT in the right carotid artery was significantly higher in smokers than in nonsmokers (0.96±0.16 mm vs. 0.82±0.21, p<0.05) and was positively correlated with smoking intensity (R=0.36) and habit duration (R=0.35). The comparison of inflammatory markers, metalloproteinases, and DHEA-S concentrations in plasma did not reveal significant differences between the 2 groups. A significant negative correlation between DHEA-S concentration in plasma and IMT in right carotid artery was found in smokers.

Conclusions

Smoking in hypertensive postmenopausal women is associated with lower fasting blood glucose and BMI values, but higher arterial pressure and heart rate, and increases in IMT in right carotid artery.

Modulation of tyrosine hydroxylase, neuropeptide y, glutamate, and substance p in Ganglia and brain areas involved in cardiovascular control after chronic exposure to nicotine

Considering that nicotine instantly interacts with central and peripheral nervous systems promoting cardiovascular effects after tobacco smoking, we evaluated the modulation of glutamate, tyrosine hydroxylase (TH), neuropeptide Y (NPY), and substance P (SP) in nodose/petrosal and superior cervical ganglia, as well as TH and NPY in nucleus tractus solitarii (NTS) and hypothalamic paraventricular nucleus (PVN) of normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) after 8 weeks of nicotine exposure. Immunohistochemical and in situ hybridization data demonstrated increased expression of TH in brain and ganglia related to blood pressure control, preferentially in SHR, after nicotine exposure. The alkaloid also increased NPY immunoreactivity in ganglia, NTS, and PVN of SHR, in spite of decreasing its receptor (NPY1R) binding in NTS of both strains. Nicotine increased SP and glutamate in ganglia. In summary, nicotine positively modulated the studied variables in ganglia while its central effects were mainly constrained to SHR.

The association between cardiac autonomic neuropathy with metabolic and other factors in subjects with type 1 and type 2 diabetes

BACKGROUND

Cardiac autonomic neuropathy (CAN) is a common diabetes complication associated with poor prognosis. This cross-sectional study aimed to examine for associations between CAN and metabolic and other parameters in patients with either type 1 (T1DM) or type 2 (T2DM) diabetes.

PATIENTS AND METHODS

A total of 600 patients (T1DM, n=200; T2DM, n=400) were recruited. Participants with overt nephropathy, macrovascular complications, and treated hypertension were excluded. CAN was diagnosed when two of the four classical autonomic function tests were abnormal.

RESULTS

CAN was diagnosed in 42.0% and in 44.3% of the participants with T1DM and T2DM, respectively. Multivariate logistic regression analysis demonstrated that, in T1DM, the odds [OR (95% confidence intervals)] of CAN increased with higher waist circumference [1.36 (1.01-2.02)], systolic blood pressure [1.16 (1.03-1.31)], hypertension [1.19 (1.03-2.67)], smoking [1.10 (1.12-1.40], fasting glucose [1.01 (1.00-1.01)], HbA(1c) [1.69 (1.07-2.76)], pubertal diabetes onset [1.08 (1.03-1.24)], LDL cholesterol [1.01(1.00-1.02)], triglycerides [1.58 (1.24-1.48)], retinopathy [1.13 (1.04-1.41)], peripheral neuropathy [2.53 (1.07-2.99)], glomerular filtration rate [0.93 (0.87-0.99)], and microalbuminuria [1.24 (1.12-1.36)]. The same analysis in T2DM demonstrated that the odds of CAN increased with higher waist circumference [1.08 (1.00-1.39)], systolic blood pressure [1.06 (1.02-1.12)], hypertension [1.50 (1.24-2.03)], smoking [1.22 (1.14-1.49)], diabetes duration [1.20 (1.09-1.34)], fasting glucose [1.21 (1.12-1.31)], HbA(1c) [1.25 (1.08-1.45)], LDL cholesterol [1.35 (1.04-1.75)], triglycerides [1.30 (1.00-1.68)], retinopathy [1.24 (1.16-1.35)], peripheral neuropathy [1.79 (1.07-2.01)], glomerular filtration rate [0.96 (0.95-0.97)], and microalbuminuria [1.20 (1.14-1.36)].

CONCLUSIONS

CAN is common in diabetes and is associated with modifiable factors including central fat distribution, hypertension, dyslipidemia, worse diabetes control, and smoking, and with the other microvascular complications of diabetes. Our findings emphasize the need for a multifactorial intervention for the prevention of CAN.

Role of adenosine A2A receptor signaling in the nicotine-evoked attenuation of reflex cardiac sympathetic control

Baroreflex dysfunction contributes to increased cardiovascular risk in cigarette smokers. Given the importance of adenosinergic pathways in baroreflex control, the hypothesis was tested that defective central adenosinergic modulation of cardiac autonomic activity mediates the nicotine-baroreflex interaction. Baroreflex curves relating changes in heart rate (HR) to increases or decreases in blood pressure (BP) evoked by i.v. doses (1-16μg/kg) of phenylephrine (PE) and sodium nitroprusside (SNP), respectively, were constructed in conscious rats; slopes of the curves were taken as measures of baroreflex sensitivity (BRS). Nicotine (25 and 100μg/kg i.v.) dose-dependently reduced BRS(SNP) in contrast to no effect on BRS(PE). BRS(SNP) was also attenuated after intracisternal (i.c.) administration of nicotine. Similar reductions in BRS(SNP) were observed in rats pretreated with atropine or propranolol. The combined treatment with nicotine and atropine produced additive inhibitory effects on BRS, an effect that was not demonstrated upon concurrent exposure to nicotine and propranolol. BRS(SNP) was reduced in preparations treated with i.c. 8-phenyltheophylline (8-PT, nonselective adenosine receptor antagonist), 8-(3-Chlorostyryl) caffeine (CSC, A(2A) antagonist), or VUF5574 (A(3) antagonist). In contrast, BRS(SNP) was preserved after blockade of A(1) (DPCPX) or A(2B) (alloxazine) receptors or inhibition of adenosine uptake by dipyridamole. CSC or 8-PT abrogated the BRS(SNP) depressant effect of nicotine whereas other adenosinergic antagonists were without effect. Together, nicotine preferentially impairs reflex tachycardia via disruption of adenosine A(2A) receptor-mediated facilitation of reflex cardiac sympathoexcitation. Clinically, the attenuation by nicotine of compensatory sympathoexcitation may be detrimental in conditions such as hypothalamic defense response, posture changes, and ventricular rhythms.

Effects of sidestream cigarette smoke exposure on baroreflex components in spontaneously hypertensive rats

We evaluated short-term effects of sidestream cigarette smoke (SSCS) exposure on baroreflex function in spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) normotensive rats. Rats were exposed to SSCS during three weeks, 180 min, five days per week, in a concentration of carbon monoxide (CO) between 100 and 300 ppm. We observed that SSCS exposure increased tachycardic peak and heart rate range while it attenuated bradycardic reflex in WKY. In respect to SHR, SSCS also increased tachycardic peak. Taken together, our data suggests that three weeks of exposure to SSCS affects the sympathetic and parasympathetic component of the baroreflex in normotensive WKY while it tended to affect the sympathetic component in SHR.

Passive smoking in never-smokers is associated with increased plasma homocysteine levels

Smoking is associated with increased plasma homocysteine levels, and both are associated with an increased risk of cardiovascular disease. However, little information is available on the effects of passive smoking on the level of homocysteine in nonsmokers. We analyzed the data of self-reported never-smokers (aged > or = 20 years, n = 3,232), who were from the Third National Health and Nutrition Examination Survey. We quantified the passive nicotine exposure by dividing the never-smokers into quartiles as based on the serum cotinine values. Multiple linear and logistic regression models were used to determine any independent relationships between serum cotinine concentration and levels of homocysteine, vitamin B12, and folate. An elevated homocysteine level was defined as a concentration greater than the 80th percentile. A reduced folate or vitamin B12 level was defined as a concentration less than the 20th percentile.After adjusting for age, gender, body mass index, race, folate and vitamin B12 levels, increased cotinine levels (quartile III and IV) were found to be associated with hyperhomocysteinemia. There was a strong nonlinear increase in the serum homocysteine levels across the quartiles of cotinine. Multivariate analysis showed that age, male gender, non-Caucasian, low levels of folate and vitamin B12, and increased serum cotinine (quartile II-IV) were independently associated with elevated homocysteine levels. In conclusion, these findings indicate that passive smoke exposure in never-smokers is positively and independently associated with plasma homocysteine levels in a dose-dependent manner. These findings may help further determine the link between passive smoking and cardiovascular events.

Variables influencing heart rate

In both physiologic and pathological conditions, instantaneous heart rate value is the result of a rather complex interplay. It constantly varies under the influence of a number of factors: nonmodifiable and modifiable ones. Pharmacologic blockade with beta-adrenergic antagonists and/or with parasympathetic antagonists such as atropine have permitted the identification of the mechanisms of autonomic nervous regulation of heart rate in a variety of physiologic and pathological conditions. The analysis of heart rate and blood pressure variability has yielded additional information on the autonomic control of the circulation, which has proven to have diagnostic and prognostic implications in a number of clinically relevant conditions such as hypertension, acute myocardial infarction, heart failure, and predisposition to sudden cardiac death. This article will summarize, based on available epidemiologic and clinical studies, the key variables influencing heart rate and heart rate variability in view of the known association between heart rate and cardiovascular disease.

Is nicotine a key player or spectator in the induction and progression of cardiovascular disorders?

Cigarette smoking is common in societies worldwide and a growing body of evidence suggests that chronic cigarette smoking may affect the structure and function of cardiovascular system. The chronic exposure to high levels of nicotine, a major component of cigarette smoking, has been observed to play a pathogenic role in the induction and progression of cardiovascular disorders including cardiomyopathy and peripheral vascular disease. Nicotine alters the function of vascular endothelium, initiates the adhesion cascade and stimulates the vascular inflammatory events to induce atherosclerosis and hypertension. Moreover, nicotine has been noted to induce direct coronary spasm and ischemia, which develop coronary artery disease and myocardial infarction. In addition, nicotine stimulates the excessive release of impulses from sinoatrial node that may account for the induction of cardiac arrhythmia. The present review critically discussed the possible detrimental role of chronic nicotine exposure in cardiac and vascular endothelial dysfunction. Moreover, the signaling mechanisms involved in the pathogenesis of nicotine exposure-induced cardiovascular dysfunction have been discussed. In addition, the pharmacological interventions to ameliorate chronic nicotine exposure-induced cardiovascular abnormalities have been delineated.

Determinants of salivary alpha-amylase in humans and methodological considerations

Salivary alpha-amylase (sAA) has been proposed as a marker for activity of the sympathetic nervous system (SNS). Recent studies in support of this hypothesis have led to an increased number of researchers integrating amylase measurements into their study designs. Salivary alpha-amylase is produced locally in the salivary glands, controlled by the autonomic nervous system. This entails some methodological consequences and potential pitfalls that might lead to increased error variance and thus prevent successful testing of hypotheses. The goal of this review is to summarize basic and recent findings on methodological issues and potential factors influencing sAA measurement, and to derive a set of recommendations enabling researchers to successfully using sAA in psychoneuroendocrinological experiments.