Get reliable laboratory findings - how to recognize the deceptive effects of angiotensin-converting enzyme inhibitor therapy in the laboratory diagnostics of sarcoidosis?

OBJECTIVES

Serum angiotensin-converting enzyme (ACE) is the only biomarker routinely used in the laboratory diagnostics of sarcoidosis, and ACE inhibitor (ACEi) drugs are among the most prescribed drugs worldwide. Taking ACEi can mislead medical teams by lowering ACE activity, delaying diagnosis and giving a false impression of disease activity of sarcoidosis. We aimed to develop a simple method to detect the presence of ACEi drugs in samples, to investigate the ACEi medication-caused interference and consequences in a retrospective study.

METHODS

ACE activity and the level of ACE inhibition were determined for 1823 patients with suspected sarcoidosis. These values were compared with the therapeutic information at the first and follow-up visits.

RESULTS

A total of 302 patients had biochemical evidence of an ACEi drug effect during diagnostic ACE activity testing. In their case, ACE activity was significantly lower (median(IQR): 4.41 U/L(2.93-6.72)) than in patients not taking ACEi (11.32 U/L(8.79-13.92), p<0.01). In 62 sarcoidosis patients, the ACEi reduced ACE activity to the reference range or below. Only in 40 % of the cases was the medication list recorded in the outpatient chart and only in 3 cases was low ACE activity associated with ACEi use. 67 % of the repeated ACE activity measurements were also performed during ACEi therapy.

CONCLUSIONS

Our study revealed that the use of ACEi is common in patients with suspected sarcoidosis. The ACE activity lowering effect of ACEi drugs may escape the attention of medical teams which can lead to diagnostic errors and unnecessary tests. Nevertheless, these pitfalls can be avoided by using a method suggested by our team.

Combined application of angiotensin converting enzyme and chitotriosidase analysis improves the laboratory diagnosis of sarcoidosis

Establishing the diagnosis of sarcoidosis most often requires biopsy and histopathologic evaluation, since there is no single marker with sufficient specificity and sensitivity for the disease. Our aims were to determine and compare the diagnostic accuracies of several potential biomarkers and to develop a combined biomarker analysis tool for the diagnosis of sarcoidosis. 133 healthy individuals and 104 patients with suspected sarcoidosis and diagnostic thoracic surgery were enrolled into this study. Histopathologic results were contrasted to biomarker levels of chitotriosidase (CTO), serum amyloid-A (SAA), soluble interleukin-2 receptor (sIL-2R), lysozyme (LZM) or angiotensin converting enzyme (ACE). Sarcoidosis was confirmed by histopathology in 69 patients. CTO activity, sIL-2R concentration and ACE activity could discriminate between sarcoidosis and control patients, while SAA and LZM concentrations could not. A new combined parameter, which was derived from the multiplication of ACE by CTO activities (double product) showed the best diagnostic accuracy in this clinical study: (AUC = 0.898, sensitivity: 90.5%, specificity: 79.3%, positive and negative predictive values: 90.5% and 79.3%, respectively). Sarcoidosis can be diagnosed with the combined analysis of ACE and CTO activities more accurately than with single serum biomarkers in the absence of invasive biopsy in the majority of cases with pulmonary manifestation of sarcoidosis.

Osteogenic differentiation of human lens epithelial cells might contribute to lens calcification

Calcification of the human lens has been described in senile cataracts and in young patients with congenital cataract or chronic uveitis. Lens calcification is also a major complication of cataract surgery and plays a role in the opacification of intraocular lenses. A cell-mediated process has been suggested in the background of lens calcification, but so far the exact mechanism remained unexplored. Lens calcification shares remarkable similarities with vascular calcification; in both pathological processes hydroxyapatite accumulates in the soft tissue. Vascular calcification is a regulated, cell-mediated process in which vascular cells undergo osteogenic differentiation. Our objective was to investigate whether human lens epithelial cells (HuLECs) can undergo osteogenic transition in vitro, and whether this process contributes to lens calcification. We used inorganic phosphate (Pi) and Ca to stimulate osteogenic differentiation of HuLECs. Osteogenic stimuli (2.5mmol/L Pi and 1.2mmol/L Ca) induced extracellular matrix mineralization and Ca deposition in HuLECs with the critical involvement of active Pi uptake. Osteogenic stimuli almost doubled mRNA expressions of osteo-/chondrogenic transcription factors Runx2 and Sox9, which was accompanied by a 1.9-fold increase in Runx2 and a 5.5-fold increase in Sox9 protein expressions. Osteogenic stimuli induced mRNA and protein expressions of alkaline phosphatase and osteocalcin in HuLEC. Ca content was higher in human cataractous lenses, compared to non-cataractous controls (n=10). Osteocalcin, an osteoblast-specific protein, was expressed in 2 out of 10 cataractous lenses. We conclude that osteogenic stimuli induce osteogenic differentiation of HuLECs and propose that this mechanism might play a role in lens calcification.

Pharmacological induction of ferritin prevents osteoblastic transformation of smooth muscle cells

Vascular calcification is a frequent complication of atherosclerosis, diabetes and chronic kidney disease. In the latter group of patients, calcification is commonly seen in tunica media where smooth muscle cells (SMC) undergo osteoblastic transformation. Risk factors such as elevated phosphorus levels and vitamin D3 analogues have been identified. In the light of earlier observations by our group and others, we sought to inhibit SMC calcification via induction of ferritin. Human aortic SMC were cultured using β-glycerophosphate with activated vitamin D3 , or inorganic phosphate with calcium, and induction of alkaline phosphatase (ALP) and osteocalcin as well as accumulation of calcium were used to monitor osteoblastic transformation. In addition, to examine the role of vitamin D3 analogues, plasma samples from patients on haemodialysis who had received calcitriol or paricalcitol were tested for their tendency to induce calcification of SMC. Addition of exogenous ferritin mitigates the transformation of SMC into osteoblast-like cells. Importantly, pharmacological induction of heavy chain ferritin by 3H-1,2-Dithiole-3-thione was able to inhibit the SMC transition into osteoblast-like cells and calcification of extracellular matrix. Plasma samples collected from patients after the administration of activated vitamin D3 caused significantly increased ALP activity in SMC compared to the samples drawn prior to activated vitamin D3 and here, again induction of ferritin diminished the osteoblastic transformation. Our data suggests that pharmacological induction of ferritin prevents osteoblastic transformation of SMC. Hence, utilization of such agents that will cause enhanced ferritin synthesis may have important clinical applications in prevention of vascular calcification.

New perspectives in the renin-angiotensin-aldosterone system (RAAS) III: endogenous inhibition of angiotensin converting enzyme (ACE) provides protection against cardiovascular diseases

ACE inhibitor drugs decrease mortality by up to one-fifth in cardiovascular patients. Surprisingly, there are reports dating back to 1979 suggesting the existence of endogenous ACE inhibitors. Here we investigated the clinical significance of this potential endogenous ACE inhibition.

ACE concentration and activity was measured in patient's serum samples (n = 151). ACE concentration was found to be in a wide range (47–288 ng/mL). ACE activity decreased with the increasing concentration of the serum albumin (HSA): ACE activity was 56±1 U/L in the presence of 2.4±0.3 mg/mL HSA, compared to 39±1 U/L in the presence of 12±1 mg/mL HSA (values are mean±SEM). Effects of the differences in ACE concentration were suppressed in human sera: patients with ACE DD genotype exhibited a 64% higher serum ACE concentration (range, 74–288 ng/mL, median, 155.2 ng/mL, n = 52) compared to patients with II genotype (range, 47–194 ng/mL, median, 94.5 ng/mL, n = 28) while the difference in ACE activities was only 32% (range, 27.3–59.8 U/L, median, 43.11 U/L, and range 15.6–55.4 U/L, median, 32.74 U/L, respectively) in the presence of 12±1 mg/mL HSA. No correlations were found between serum ACE concentration (or genotype) and cardiovascular diseases, in accordance with the proposed suppressed physiological ACE activities by HSA (concentration in the sera of these patients: 48.5±0.5 mg/mL) or other endogenous inhibitors.

Main implications are that (1) physiological ACE activity can be stabilized at a low level by endogenous ACE inhibitors, such as HSA; (2) angiotensin II elimination may have a significant role in angiotensin II related pathologies.

In vitro analysis of the properties of Beiqishen tea

OBJECTIVE

Chinese Beiqishen tea was studied in an in vitro test system.

METHODS

Phytochemical screening, trace element analysis, and the analysis of antioxidant properties were carried out. Characteristic constituents were determined by chromatographic (capillary gas chromatography and GCQ Ion Trap mass spectrometry) and spectrometric (ultraviolet and UV-VIS) methods. Element concentrations were determined by inductively coupled plasma optical emission spectrometry. Antioxidant capacity was studied by spectrophotometric and luminometric techniques using a Berthold Lumat 9501 luminometer. Hydrogen-donating activity, reducing power, and total scavenger capacity were measured.

RESULTS

Total polyphenol content was 20.77 +/- 0.52 g/100 g of drug; total flavonoid content was 0.485 +/- 0.036 g/100 g of drug; and tannin content was 9.063 +/- 0.782 g/100 g of drug. Caffeine content was 1.08 mg/100 g of drug. Essential oils were identified by gas chromatography: (+)-limonene (21%), p-cymene (1.7%), estragol (3.2%), beta-ocimene (1.4%), and thymol (2.6%). Metallic ion analysis showed significantly high concentrations of Al, As, Ba, Cr, Cu, Fe, Mn, Ni, and Ti in the drug. Antioxidant and scavenger properties were identified as a function of concentration.

CONCLUSIONS

The tea infusion contained some non-desirable trace elements and caffeine in addition to polyphenols and tannins in high concentrations. Therefore, the consumption of this tea may involve risks.