Do leukocytes have a role in hypertension?

Joint Effect of Cigarette Smoking and Body Mass Index on White Blood Cell Count in Korean Adults

Background

White blood cell count is an independent risk factor for cardiovascular disease. Several lifestyle and metabolic factors such as cigarette smoking and obesity are known to be associated with an elevated white blood cell count. However, the joint effect of cigarette smoking and obesity on white blood cell count has not yet been fully described.

Methods

We explored the joint effect of cigarette smoking and obesity on white blood cell count using multiple logistic regression analyses after adjusting for confounding variables in a population-based, cross-sectional study of 416,065 Korean adults.

Results

Cigarette smoking and body mass index have a dose-response relationship with a higher white blood cell count, but no synergistic interaction is observed between them (men, P for interaction=0.797; women, P for interaction=0.311). Cigarette smoking and body mass index might have an additive combination effect on high white blood cell count. Obese male smokers were 2.36 times more likely and obese female smokers 2.35 times more likely to have a high white blood cell count when compared with normal body mass index non-smokers.

Conclusion

Cigarette smoking and body mass index are independently associated with an elevated white blood cell count in both men and women.

Effect of interval training program on white blood cell count in the management of hypertension: A randomized controlled study

OBJECTIVE

Elevated white blood cell (WBC) count is considered to be prospectively and positively associated with cardiovascular diseases, particularly hypertension. Also, the positive role of exercise in the management of hypertension has been well and long established. However the relationship between WBC count and hypertensive management particularly in the nonpharmacological technique is ambiguous and unclear. Therefore the purpose of the present study was to determine the effect of interval training program on WBC count and cardiovascular parameters in male hypertensive patients.

MATERIALS AND METHODS

A total of 245 male patients with mild to moderate (systolic blood pressure (SBP) between 140 mmHg and 179 mmHg and diastolic blood pressure (DBP) between 90 mmHg and 109 mmHg) essential hypertension were age matched and grouped into experimental and control groups. The experimental (n=140; 58.90±7.35 years) group involved in an 8-week interval training (60-79% HR max reserve) program of between 45 minutes to 60 minutes, while the age-matched controls hypertensive (n=105; 58.27±6.24 years) group remain sedentary during this period. Cardiovascular parameters (SBP, DBP, and VO(2) max) and WBC count were assessed. Student's t and Pearson correlation tests were used in data analysis.

RESULTS

Findings of the study revealed a significant effect of the interval training program on VO2max, SBP, and DBP and WBC count at P<0.05 and VO2max is negatively related to the WBC count (r=-0.339) at P<0.01.

CONCLUSIONS

It was concluded that the interval training program is an effective adjunct nonpharmacological management of hypertension and the therapeutic effect of exercise programs may be mediated through suppression of inflammatory (WBC count) reaction.

Association of white blood cell count with systolic blood pressure within the normotensive range

Hypertension and inflammation promote cardiovascular disease (CVD). Even high normal systolic blood pressure (SBP) is associated with increased CVD risk. We assessed the relationship of elevated SBP within the normotensive range and white blood cell (WBC) count. This is a cross-sectional study of 3484 white asymptomatic individuals (mean age: 43+/-8 years, 79% males) without hypertension with SBP<140 mm Hg. White blood cell count >or=75th percentile (8.35 x 10(9) cells/l) was considered cutoff for elevated WBC. Subjects were classified into three levels of SBP (first: <120 mm Hg, n=1,176, 34%; second: 120-129 mm Hg, n=1,654, 47%; third: 130-139 mm Hg, n=654, 19%). Mean WBC count increased linearly across SBP categories (first: 6.14+/-1.54, second: 6.20+/-1.52, third: 6.41+/-1.62, P=0.02 for trend). There was a linear increase in prevalence of elevated WBC across higher SBP categories (22, 24 and 28%, P=0.02). As compared to those with SBP<120 mm Hg, in multivariate linear regression analyses (adjusting for age, gender, smoking status, diabetes, body mass index, physical activity, cholesterol/high-density lipoprotein cholesterol ratio) WBC count was significantly higher among participants with SBP 130-139 mm Hg (regression coefficient: 2.64, 95% confidence interval: 1.04-4.24, P=0.001). Odds ratio for prevalence of elevated WBC with SBP<120 mm Hg as reference group was 1.14 (0.92-1.41) for SBP 120-129 mm Hg and 1.50 (1.15-1.92) for SBP 130-139 mm Hg. In conclusion, Higher SBP within the normotensive range is also associated with elevated WBC count. Further studies are needed to clarify the role of inflammation in high normal SBP and associated CVD risk.

White blood cell count as a risk factor for hypertension; a study of Japanese male office workers

OBJECTIVE

To investigate the association of white blood cell (WBC) count with risk of hypertension.

DESIGN

Cross-sectional and longitudinal studies.

SETTING

A work site in Japan.

PARTICIPANTS

A total of 3776 Japanese male office workers aged 23-49 years were enrolled in this study; 2900 hypertension-free [systolic blood pressure (SBP) < 140 mm Hg, diastolic blood pressure (DBP) < 90 mm Hg, no medication for hypertension, and no past history of hypertension] men were followed up over a 4-year period.

MAIN OUTCOME MEASURES

Blood pressure levels and the incidence of hypertension (SBP > or = 140 mm Hg and/or DBP > or = 90 mm Hg or medication for hypertension) according to WBC count at study entry.

RESULTS

After controlling for potential predictors of hypertension, SBP and DBP levels increased in a dose-dependent manner among both never-smokers and ex-smokers as WBC count increased. Among current smokers, only SBP level increased progressively with WBC count level. The multivariate-adjusted relative risk for development of hypertension compared with the first WBC count quintile was 1.29, 1.21, 1.67, and 1.92 among never-smokers (P for trend = 0.002): and 1.34, 1.46, 1.84, and 1.97 among ex-smokers (P for trend = 0.030) with the second, third, fourth, and fifth quintiles, respectively. Among current smokers, the respective multivariate-adjusted relative risks for hypertension relative to the first WBC count quintile were 0.91, 0.97, 1.08, and 0.84 (P for trend = 0.999).

CONCLUSIONS

WBC count is an important risk factor for hypertension, and the increased risk for hypertension associated with WBC count is more pronounced in non-smokers.

Polymorphonuclear integrins, membrane fluidity, and cytosolic Ca(2+) content after activation in essential hypertension

The purpose of this research was to obtain further information about the role of polymorphonuclear leukocytes in essential hypertension. These cells could be involved in the pathogenesis of organ injury. Thirty subjects (14 men and 16 women) with essential hypertension were enrolled. In these subjects we determined, at baseline and after in vitro activation with 4-phorbol 12-myristate 13-acetate and N:-formyl-methionyl-leucyl-phenylalanine, the polymorphonuclear leukocyte membrane fluidity, obtained by labeling the cells with 1-[4-(trimethylamino)phenyl]-6-phenyl-1,3, 5-hexatriene, cytosolic Ca(2+) concentration, obtained by marking the cells with Fura 2-AM, and integrin pattern (CD11a, CD11b, CD11c, and CD18), by using the indirect immunofluorescence with a flow cytometer. At baseline there was no difference in membrane fluidity between normal subjects and hypertensives, whereas hypertensives showed an increase in cytosolic Ca(2+) content and an increase of the phenotypical expression of CD11a, CD11b, and CD18. In normal subjects and in hypertensives, after activation, no variation was found in membrane fluidity and cytosolic Ca(2+) content. In normal subjects, after activation, we observed a significant increase of the expression of all adhesion molecules, whereas in hypertensives we found an increase of the expression of CD11b, CD11c, and CD18 but also a decrease of CD11a. The behavior of the polymorphonuclear leukocyte integrin profile may have several explanations, and in particular, the trend of CD11a after chemotactic activation may be related to its cleavage or to an altered integrin phosphorylation/dephosphorylation balance hypothetically present in this clinical condition.

Neutrophil arachidonic acid level and adhesive capability are increased in essential hypertension

BACKGROUND

We recently demonstrated that arachidonic:linoleic acid ratio of erythrocytes of essential hypertension patients is greater than normal.

OBJECTIVE

To investigate fatty acid composition, capability for adhesion to biological substrate and expression of beta2 integrins of leucocytes obtained from peripheral blood and skin window exudate of essential hypertension patients.

DESIGN

Neutrophil activation state was evaluated by reproducing the various conditions occurring in vivo during the life of the cell (i.e. under the 'resting' condition, such as in peripheral blood, and 'primed' condition, such as after transmigration through the endothelium and after administration of specific chemo-attractants). Because both peripheral blood and skin window leucocytes of the subjects were obtained on the same day, we could be sure that there had been no dietary influences on changes in levels of fatty acid. Thus, the observed changes should reliably reflect the metabolic rate of utilization of fatty acids coupled to the activation and migration of cells.

RESULTS

Leucocytes from essential hypertension patients were richer in arachidonic acid than were the corresponding cells from normotensive subjects; this difference was also evident for functionally activated skin window leucocytes, in spite of there having been a greater loss of poly-unsaturated fatty acids and arachidonic acid after migration. Moreover, a greater than normal arachidonic acid:linoleic acid ratio was shown for the first time to apply for leucocytes of essential hypertension patients, so extending our previous findings on the erythrocytes. Leucocytes from essential hypertension patients, collected both from peripheral blood and from skin window exudate, proved far more adhesive than the corresponding cells from age-matched and sex-matched controls, but this was not associated with a quantitative hyperexpression of beta2 integrins.

CONCLUSIONS

The results suggest that an increase in availability of arachidonic acid in leucocytes could be a further expression of the generalized disturbance of fatty acid levels associated with essential hypertension and that a condition of hyperadhesion of neutrophils could occur spontaneously in vivo during the course of hypertension.

Leukocyte activation in atherosclerosis: correlation with risk factors

Leukocytes have been implicated in the development of atherosclerotic vascular diseases, and numerous abnormalities of leukocytes in conjunction with atherosclerosis have been reported. The aim of this study of middle-aged asymptomatic subjects with early atherosclerosis was to determine whether a relationship exists between the levels of plasma markers of leukocyte activation, i.e. cytokines and proteases and risk factors for atherosclerosis or the degree of atherosclerotic disease. Using ELISAs we measured the plasma levels of neutrophil gelatinase-associated lipocalin (NGAL), neutrophil protease 4 (NP4) as markers for neutrophil activation, tumor necrosis factor alpha (TNF) and soluble TNF receptor-1 (sTNFR-1) as markers of monocyte/macrophage activation in 156 subjects with asymptomatic carotid artery plaque detected at ultrasound examination. Plasma TNF and sTNFR-1 levels were found to correlate with systolic blood pressure (r = 0.32, P < 0.04 and r = 0.22, P < 0.05, respectively). plasma NGAL level to correlate with diastolic blood pressure (r = 0.22; P < 0.005), the plasma levels of sTNFR-1 and NGAL to correlate with age (r = 0.28, P < 0.001 and r = 0.20, P < 0.05, respectively). As compared with non-smokers (n = 112), smokers (n = 43) had higher plasma levels of TNF (2.9 vs. 1.4 microg/l; P < 0.02) and of NP4 (27.5 vs. 23.4 microg/l; P < 0.05). The plasma NGAL level was higher in hypertensive women (n = 7) than in normotensive women (n = 85) (109 vs. 87 microg/l; P < 0.05). We thus demonstrated that, in subjects with asymptomatic early atherosclerosis, the plasma levels of markers of systemic leukocyte activation were correlated with age and blood pressure, and were higher in smokers and hypertensives. These results support the hypothesized relationship between the level of systemic leukocyte activation and risk factors for atherosclerotic vascular disease.

White blood cell count and hypertension incidence. The NHANES I Epidemiologic Follow-up Study

To test the hypothesis that elevated white blood cell count (WBC) is associated with increased incidence of essential hypertension, data from the NHANES I Epidemiologic Follow-up Study (NHEFS) were analyzed. Incidence of hypertension was determined in a cohort of 5782 white and 674 black persons with complete data who were normotensive at baseline. There was a statistically significant increase of about 50% in risk of hypertension over approximately 10 years' follow-up in white men aged 25-74 years with WBC > 8600 compared to men with WBC < 6200 cells/mm3. The association was independent of other risk variables. In white women, an association of high WBC with increased age-adjusted risk of hypertension was seen only at ages 45-64 and 65-74 years. The association was diminished and no longer significant after controlling for multiple risk variables. Data for black women suggested an increased risk among women with higher WBC compared to those with lower WBC at ages 65-74 after controlling other risk variables (p = 0.0001). No positive association was seen in black men. Thus, data from NHEFS confirm the previously reported association of higher WBC with increased incidence of hypertension in white men, and possibly older white and black women. Given the lack of a compelling biological explanation, further studies of this association are needed, especially in women and blacks.

Immune system of the spontaneously hypertensive rat: II. Morphology and function

The spontaneously hypertensive rat (SHR) is a stress-sensitive animal which exhibits moderate immune dysfunction that has been implicated in the onset of hypertension. In this study, we examined the morphology of SHR thymus and spleen and further characterized the immune deficiency using Wistar-Kyoto (WKY) and Fisher 344 (F-344) rats for comparison. The adult SHR thymus does not display the increase in medullary volume typically noted with aging and the volume density of the marginal zone is decreased in the spleen. In vivo tritiated-thymidine incorporation is also decreased in the spleen of unstimulated SHR. In mixed lymphocyte reactions (MLR), the proliferative response of SHR splenocytes is significantly decreased relative to controls, WKY and F-344. Addition of interleukin-1 (IL-1), interleukin-2 (IL-2), or indomethacin to the MLR cultures does not increase proliferation. The proliferative response to T cell receptor monoclonal antibody (mAb-TCR) or interleukin-2 (IL-2) are similarly impaired in the SHR. The depressed proliferative T cell response is reversed by prolactin. It is suggested that the SHR is a valuable model for the study of immune deficiency.

Relations of cardiovascular risk factors to aortic pulse wave velocity in asymptomatic middle-aged women

Cross-sectional associations between aortic elasticity assessed by carotid to femoral pulse wave velocity (PWV) and cardiovascular risk factors were examined in 429 apparently healthy middle-aged women. PWV was strongly and positively related to blood pressure and hypertension. Weak but significant positive associations were also found between PWV and age, heart rate, some lipids and lipoproteins, blood glucose (either as a continuous or dichotomous variable), body mass index, haematocrit, leucocyte count and family history of diabetes. No associations were observed between PWV and high density lipoprotein cholesterol, apolipoprotein A1, fibrinogen, cigarette smoking, menopausal status and a family history of hypertension or myocardial infarction. After adjustment for systolic blood pressure, PWV remained significantly related to heart rate, leucocyte count, blood glucose (as a dichotomous variable) and a family history of diabetes. Multiple regression analysis showed that systolic blood pressure and, to a lesser extent, heart rate, leucocyte count and a family history of diabetes were all independent determinants of PWV. This pattern of associations suggests that arterial stiffness measured by PWV reflects the sclerotic rather than the atherotic component of atherosclerosis. The potential influence of a family history of diabetes on the elastic properties of the aorta needs to be ascertained in further studies.

Leukocytes synthesize angiotensinogen

To determine whether leukocytes express the angiotensinogen gene, we subjected circulating rat leukocytes and murine bone marrow cells to Northern blot analysis and hybridization with homologous angiotensinogen complementary DNA. Angiotensinogen messenger RNA sequences were detected in circulating adult rat leukocytes, in murine-irradiated and nonirradiated bone marrow stromal cells, and in an adherent stromal cell line (preadipocyte). Western blot analysis of rat leukocyte homogenate showed that rat leukocytes contain two main angiotensinogen isoforms with approximate molecular weights of 46.5 and 53.9 kd. Synthesis and release of angiotensinogen protein by rat leukocytes was confirmed by immunoprecipitation of radiolabeled angiotensinogen from cell lysate and media of rat leukocytes that were metabolically labeled with 35S-L-methionine. In addition, the angiotensinogen protein present in media of rat leukocytes was enzymatically cleaved by hog renin, resulting in generation of angiotensin I (305 +/- 47 pg angiotensin I per milliliter of media per hour). We conclude that circulating rat leukocytes express the angiotensinogen gene and synthesize and release angiotensinogen with the capability to generate angiotensin. Expression of angiotensinogen by leukocytes may provide a mobile angiotensin-generating system of potential importance in the regulation of local inflammatory responses, tissue injury (i.e., myocardial infarction), and arterial hypertension.

Platelets, endothelium-dependent responses and atherosclerosis

Basal release of endothelium-derived relaxing factor (EDRF) and prostacyclin from intact vascular endothelium may inhibit continuously platelet aggregation. If local platelet aggregation occurs, platelet-derived adenine nucleotides stimulate the release of EDRF. Stimulated EDRF release may override the direct vasoconstrictor effects of other platelet products such as thromboxane and serotonin resulting in local vasodilatation. In addition, stimulation of EDRF release by adenine nucleotides may inhibit further platelet adhesion and aggregation by a feedback mechanism. Thus, intact vascular endothelium may play an important role in the defense against platelet deposition and vasospasm. In atherosclerosis, basal and stimulated release of EDRF is markedly reduced. Endothelial dysfunction will impair this protective mechanism and will favour vasoconstriction and further platelet disposition. Occurrence of occlusive thrombus formation in patients with coronary artery disease may be pathophysiologically related to this impairment of endothelial defense.