Abstract 1275: Novel Anti-Inflammatory Mechanisms of Ac-SDKP in High Blood Pressure-Induced Target Organ Damage
Background: High blood pressure (HBP) is an important risk factor for cardiac, renal and vascular dysfunction. Excess inflammation is the major pathogenic mechanism for HBP-induced target organ damage (TOD). Ac-SDKP, a tetrapeptide specifically degraded by angiotensin converting enzyme, reduces inflammation, fibrosis and TOD induced by high blood pressure.
Hypothesis: In this study, we hypothesize that Ac-SDKP exerts its anti-inflammatory effects by inhibiting 1) differentiation of bone marrow stem (BMS) cells to macrophages, 2) activation and migration of macrophages and 3) release of pro-inflammatory cytokine, TNF-α by activated macrophages.
Methods: BMS cells were freshly isolated from mouse tibia and femurs. The differentiation of murine BMS cells to macrophages was analyzed by FACS using F4/80 as a marker of macrophage maturation. Myocardial macrophage activation in DOCA salt-treated hypertensive mice was detected by Western blotting of Mac-2 protein. Macrophage migration was measured in a modified Boyden chamber. TNF-α release by activated macrophages was measured by enzyme-linked immunossays (ELISA).
Results: Ac-SDKP (10 nM) reduced the differentiation of cultured BMS cells to mature macrophages by 24.5% (Geometric mean of F4/80 positivity: vehicle, 14.09±1.06; Ac-SDKP, 10.63±0.35; P<0.05). Ac-SDKP also decreased macrophage colony stimulating factor (M-CSF)-dependent macrophage migration in a dose-dependent manner [Absorbance: vehicle, 1.87±0.29; Ac-SDKP (10nm), 0.65±0.04; Ac-SDKP (1000 nM), 0.60±0.02]. This inhibitory effect was blocked by anti-AC-SDKP monoclocal blocking antibody. In vivo, Ac-SDKP reduced the infiltration of activated macrophages into the myocardium of DOCA salt-treated hypertensive mice (Mac-2, densitometric units: DOCA, 1.3±0.62; DOCA+Ac-SDKP, 0.64±0.28, P<0.05). In addition, Ac-SDKP significantly decreased the secretion of TNF-α by peritoneal macrophages stimulated with bacterial LPS (pg/ng of cell protein: LPS, 704±8.8; LPS+Ac-SDKP, 635±12, P<0.05).
Conclusion: This study reveals a novel and previously unknown mechanisms of the anti-inflammatory property of Ac-SDKP. Ac-SDKP can be a new therapeutic option for the treatment of high blood pressure-induced inflammation and TOD.