Association of C-reactive protein with blood pressure

Plasma Inflammatory Markers and the Risk of Developing Hypertension in Men

Background

Several cross-sectional, but few prospective, studies suggest that inflammation may be involved in the development of hypertension. We examined markers of inflammation—high-sensitivity C-reactive protein, interleukin-6, and soluble intercellular adhesion molecule-1—and a marker of fibrinolysis, D-dimer, for their associations with incident hypertension in the Physicians’ Health Study.

Methods and Results

Baseline blood values and information on hypertension-related risk factors were collected in 1982. Incident hypertension was defined as self-reported initiation of antihypertensive treatment, systolic blood pressure ≥140 mm Hg, or diastolic blood pressure ≥90 mm Hg during follow-up. With use of a nested case-control design, 396 cases of incident hypertension and controls free of hypertension were matched 1:1 on age (mean 47.4 years) and follow-up time. In crude matched-pair analyses, the conditional relative risks of hypertension in the second through fourth versus the lowest quartiles for plasma high-sensitivity C-reactive protein were 1.27, 1.73, and 1.81 (P_trend=0.01); for interleukin-6, 1.22, 1.02, and 1.51 (P_trend=0.06); for soluble intercellular adhesion molecule-1, 1.00, 0.80, and 1.26 (P_trend=0.37); and for D-dimer, 1.61, 1.81, and 1.52 (P_trend=0.46). Multivariable adjustment attenuated the estimates. The multivariable relative risks of hypertension in the second through fourth compared to the lowest quartiles of high-sensitivity C-reactive protein were 1.24, 1.60, and 1.47 (P_trend=0.20); for interleukin-6, 1.08, 0.92, and 1.36 (P_trend=0.16); for soluble intercellular adhesion molecule-1, 0.89, 0.79, and 1.18 (P_trend=0.55); and for D-dimer, 1.48, 1.68, and 1.38 (P_trend=0.63).

Conclusions

Elevated plasma inflammatory markers and D-dimer were nonsignificantly associated with a higher risk of hypertension among initially healthy men.

Toll-like receptor 4 contributes to blood pressure regulation and vascular contraction in spontaneously hypertensive rats

Activation of Toll-like receptors (TLR) induces gene expression of proteins involved in the immune system response. TLR4 has been implicated in the development and progression of cardiovascular diseases. Innate and adaptive immunity contribute to hypertension-associated end-organ damage, although the mechanism by which this occurs remains unclear. In the present study we hypothesize that inhibition of TLR4 decreases blood pressure and improves vascular contractility in resistance arteries from spontaneously hypertensive rats (SHR). TLR4 protein expression in mesenteric resistance arteries was higher in 15 weeks-old SHR than in same age Wistar controls or in 5 weeks-old SHR. In order to decrease activation of TLR4, 15 weeks-old SHR and Wistar rats were treated with anti-TLR4 antibody or non-specific IgG control antibody for 15 days (1µg per day, i.p.). Treatment with anti-TLR4 decreased mean arterial pressure as well as TLR4 protein expression in mesenteric resistance arteries and interleukin-6 (IL-6) serum levels from SHR when compared to SHR treated with IgG. No changes in these parameters were found in Wistar treated rats. Mesenteric resistance arteries from anti-TLR4-treated SHR exhibited decreased maximal contractile response to noradrenaline compared to IgG-treated-SHR. Inhibition of cyclooxygenase-1 (Cox) and Cox-2, enzymes related to inflammatory pathways, decreased noradrenaline responses only in mesenteric resistance arteries of SHR treated with IgG. Cox-2 expression and thromboxane A₂ release were decreased in SHR treated with anti-TLR4 compared with IgG-treated-SHR. Our results suggest that TLR4 activation contributes to increased blood pressure, low grade inflammation and plays a role in the augmented vascular contractility displayed by SHR.

A common genetic variant of FCN3/CD164L2 is associated with essential hypertension in a Chinese population

Ficolin-3, encoded by FCN3, is the predominant recognition molecule of lectin pathway for the activation of complement component 3 (C3), which is an important risk factor for the development of hypertension. In our previous study, we found the complement system including ficolin-3 was overrepresented in the serum of type 2 diabetic patients. Since type 2 diabetes shares some pathogenic components, including excessive serum C3, with hypertension, this study aims to test the hypothesis that common variants at FCN3 might be associated with essential hypertension in our Chinese population. A total of 1797 subjects were recruited. Of them, 573 were with essential hypertension. Based on HapMap data, three tagging single nucleotide polymorphisms (rs2504778, rs10794501, and rs3813800) in FCN3/CD164L2 region were selected for genotyping by using MassARRAY. Logistic regression analysis was performed to evaluate the genetic effects on the prevalence of hypertension after adjusting for covariates. rs2504778, which locates in the upstream of FCN3 and in the intron of CD164L2, was found to be significantly associated with hypertension after adjusting for covariates (OR = 1.28, 95% CI: 1.05, 1.55, P = .015). Correction for multiple testing did not remarkably attenuate the significance (empirical P = .042 with 10 000 permutations). rs2504778 also showed a nominal association with systolic blood pressure (P = .044) in the quantitative trait analysis. No evidence of correlation with hypertension and blood pressure was observed for rs10794501 and rs3813800. We found that a common variant of FCN3/CD164L2 is associated with hypertension in our Chinese population. More studies with larger sample size are needed to confirm this finding.

Comparison of interleukin-6 and C-reactive protein for the risk of developing hypertension in women

Although markers of systemic inflammation may have a role in the development of hypertension, supportive clinical data remain limited. We, therefore, examined interleukin (IL)-6 and C-reactive protein (CRP) in a nested case-control study of 400 women developing hypertension and an equal number of age-matched normotensive control subjects during 10 years of follow-up as part of the Women's Health Study. All of the women initially had nonhypertensive blood pressure values and no history of diagnosis or treatment. Subjects provided self-reported risk factors, and IL-6 and CRP were measured from baseline bloods. Case subjects reported elevated systolic (>or=140 mm Hg) or diastolic (>or=90 mm Hg) blood pressure, newly diagnosed hypertension, or initiating antihypertensive treatment during follow-up. In crude-matched models, IL-6 and CRP quartiles were each strongly associated with hypertension risk (both Ps for trend <0.0001). In multivariate models, the linear trends became nonsignificant, and the relative risks (95% CIs) of hypertension for IL-6 reduced to 1.00 (ref), 1.29 (0.76 to 2.19), 2.14 (1.23 to 3.73), and 1.70 (0.92 to 3.13) and for CRP were 1.00 (ref), 2.09 (1.16 to 3.76), 2.51 (1.42 to 4.44), and 2.44 (1.29 to 4.64), primarily because of confounding by body mass index. Simultaneous adjustment for IL-6 and CRP modestly attenuated both sets of relative risks, although more for IL-6. Finally, there was no effect modification by baseline blood pressure or other risk factors (all Ps for interaction >0.05). Therefore, after multivariate adjustment and strong confounding by body mass index, IL-6 was weakly associated and CRP strongly associated with hypertension risk. In models simultaneously examining IL-6 and CRP, only CRP remained strongly associated with an increased risk of hypertension.