Reduced lung endothelial angiotensin-converting enzyme activity in Watanabe hyperlipidemic rabbits in vivo

Increased circulatory RAS activity can be inhibited by statins in patients with hypercholesterolemia

OBJECTIVE

The objective of this paper is to investigate a profile on circulatory renin-angiotensin system (RAS) activity in hypercholesterolemic (HC) patients treated with statins.

METHODS

Eighteen primary HC patients and 18 sex- and age-matched healthy adults were included in this study as controls. Total cholesterol (TC), triglyceride (TG), LDL-C, blood glucose, angiotensin-converting enzyme (ACE) activity, and angiotensin II (Ang II) levels were measured before and four and eight weeks after beginning statin treatment in the HC group. Similar measurements were taken in the control group at baseline.

RESULTS

At baseline, TC, TG and LDL-C levels, as well as ACE activity and Ang II concentrations, were significantly higher in the HC group than in the control group. Based on the baseline data collection of 36 participants, there were significant positive correlations between ACE activity and TC (r = 0.54) or LDL-C (r = 0.51), and between Ang II level and TC (r = 0.34) or LDL-C (r = 0.27). TC, LDL-C, Ang II (35.46 ± 14.49 vs 71.10 ± 20.47 pg/ml, p < 0.05) levels and ACE activity (108.9 ± 51.9 vs 180.1 ± 71.3 U/L, p < 0.05) were decreased in HC patients eight weeks after starting statin treatment. In HC patients, RAS activity correlated positively with TC and LDL-C levels before and after treatment.

CONCLUSIONS

In HC patients, lowering serum cholesterol with statins is associated with decreased circulatory RAS activity.

Angiotensin, bradykinin and the endothelium

Angiotensins and kinins are endogenous peptides with diverse biological actions; as such, they represent current and future targets of therapeutic intervention. The field of angiotensin biology has changed significantly over the last 50 years. Our original understanding of the crucial role of angiotensin II in the regulation of vascular tone and electrolyte homeostasis has been expanded to include the discovery of new angiotensins, their important role in cardiovascular inflammation and the development of clinically useful synthesis inhibitors and receptor antagonists. While less applied progress has been achieved in the kinin field, there are continuous discoveries in bradykinin physiology and in the complexity of kinin interactions with other proteins. The present review focuses on mechanisms and interactions of angiotensins and kinins that deal specifically with vascular endothelium.

Pulmonary capillary endothelial dysfunction in early systemic sclerosis

OBJECTIVE

Pulmonary capillary endothelium-bound angiotensin-converting enzyme (PCEB-ACE) activity is a sensitive and quantifiable index of endothelial function in vivo. Systemic sclerosis (SSc) is characterized by endothelial damage and excess collagen formation, causing mainly pulmonary hypertension (PH) in the limited cutaneous SSc (lcSSc) subset and interstitial lung disease with pulmonary interstitial fibrosis (PIF) in the diffuse cutaneous SSc (dcSSc) subset. This study was undertaken to investigate the hypothesis that PCEB-ACE activity is reduced early in SSc, in the absence of PH or PIF.

METHODS

Applying indicator-dilution techniques, we measured single-pass transpulmonary hydrolysis and percent metabolism (%M) of a synthetic ACE substrate and calculated functional capillary surface area (FCSA) in 25 SSc patients and 11 controls. Substrate hydrolysis and %M reflect ACE activity per capillary; FCSA reflects ACE activity per vascular bed.

RESULTS

PCEB-ACE activity was decreased in both SSc subsets. Among patients without PH, substrate hydrolysis and %M were decreased in patients with lcSSc and more profoundly in those with dcSSc; loss of FCSA normalized to body surface area (FCSA/BSA) was observed in dcSSc, but not in lcSSc. High-resolution computed tomography of the lung, performed in all SSc patients, revealed no correlation between substrate %M, hydrolysis, or FCSA/BSA and the degree of PIF; 5 dcSSc and 5 lcSSc patients with no detectable PIF exhibited decreases in hydrolysis and %M, while FCSA/BSA was decreased only in dcSSc.

CONCLUSION

Depression of PCEB-ACE activity, indicating pulmonary endothelial dysfunction, occurs early in SSc, in the absence of PH or PIF, and is more pronounced, at this early pulmonary disease stage, in dcSSc than in lcSSc.