FP034
MEMBRANE-BOUND ACE AND ACE MRNA TRANSCRIPTS IN MONOCYTE SUBSETS OF HD PATIENTS

Introduction and Aims: Recently membrane-bound ACE protein expression was reported to be elevated in monocytes of hemodialysis patients (HD) in comparison to healthy controls. Especially the CD14++CD16+ subset (Mo2) appeared to express large amounts of ACE. Elevated Mo2 numbers in combination with high ACE expression were associated with cardiovascular disease and mortality in these patients. The relationship of membrane-bound ACE protein expression and ACE mRNA expression in isolated monocyte subsets was not investigated up to now. In 10 Dialysis patients both data sets were available.

Methods: : Monocytes were isolated from 10 HD patients .The monocytes subset sorting protocol, performed on a ARIA II (BD) device, included separation of the three subsets (CD14++CD16-, Mo1; CD14++CD16+, Mo2; CD14(+)CD16++, Mo3) after staining with anti-CD14 and -CD16 specific antibodies. Membrane-bound ACE (CD143) was detected using the anti-CD143 specific clone 9B9. The antibody staining protocol included a FcR-blocking step to prevent unspecific staining results. Isotype controls were also part of the experimental setting. RNA expression data (x-fold expression compared to healthy controls) were calculated using the formula: 2 -(dCT (ACE target) - dCt(ß-actin))/2 -(dCT (ACE control ) - dCt(ß-actin)).

Results: As reported previously, membrane -bound ACE is primarily expressed in Mo2 cells of HD patients (%Mo2: 5.3±3.8 vs. %Mo1: 1.8±1.2 and %Mo3: 0.7±0.7, p<0.05, ANOVA). However, ACE mRNA expression was significantly elevated in both Mo2 and Mo3 compared to Mo1 (Mo2: 5.2±0.6, Mo3: 5.6±0.6 vs Mo1: 4.4±0.4, p<0.05, ANOVA).

Conclusions: Membrane-bound-ACE expression is a feature of inflammatory Mo2 monocytes contributing to local angiotensin II production (Ang II). The intracellular ACE machinery, especially part of Mo2 and Mo3 monocytes may a prerequisite for Ang II triggered differentiation effects towards macrophages on the one and dendritic cells on the other hand.