Effect of lipopolysaccharide on angiotensin II type 1 receptor expression and function in human pulmonary microvascular endothelial cells

Cell-Specific Protective Signaling Induced by the Novel AT2R-Agonist NP-6A4 on Human Endothelial and Smooth Muscle Cells

Cardiovascular disease incidence continues to rise and new treatment paradigms are warranted. We reported previously that activation of Angiotensin II receptor (encoded by the X-linked Agtr2 gene) by a new peptide agonist, NP-6A4, was more effective in protecting mouse cardiomyocyte HL-1 cells and human coronary artery vascular smooth muscle cells (hCAVSMCs) from acute nutrient deficiency than other drugs tested. To elucidate further the protective effects of NP-6A4 in human cells, we studied the effects of NP-6A4 treatment on functions of human coronary artery endothelial cells (hCAECs), and hCAVSMCs. In hCAVSMCs, NP-6A4 (1 μM) increased Agtr2 mRNA (sixfold, p < 0.05) after 12-h exposure, whereas in hCAECs, significant increase in Agtr2 mRNA (hCAECs: eightfold) was observed after prolonged exposure. Interestingly, NP-6A4 treatment (1 μM, 12 h) increased AT2R protein levels in all human cells tested. Pre-treatment with AT2R-antagonist PD123319 (20 μM) and anti-AT2R siRNA (1 μM) suppressed this effect. Thus, NP-6A4 activates a positive feedback loop for AT2R expression and signaling in hCAVSMCs and hCAECs. NP-6A4 (1–20 μM) increased cell index (CI) of hCAVSMCs as determined by real time cell analyzer (RTCA), indicating that high concentrations of NP-6A4 were not cytotoxic for hCAVSMCs, rather promoting better cell attachment and growth. Seahorse Extracellular Flux Assay revealed that NP-6A4 (1 μM) treatment for 7 days increased whole cell-based mitochondrial parameters of hCAVSMCs, specifically maximal respiration (p < 0.05), spare respiratory capacity (p < 0.05) and ATP production (p < 0.05). NP-6A4 (1 μM; 7 days) also suppressed Reactive Oxygen Species (ROS) in hCAVSMCs. Exposure to Doxorubicin (DOXO) (1 μM) increased ROS in hCAVSMCs and this effect was suppressed by NP-6A4 (1 μM). In hCAECs grown in complete medium, NP-6A4 (1 μM) and Ang II (1 μM) exerted similar changes in CI. Additionally, NP-6A4 (5 μM: 12 h) increased expression of eNOS (sixfold, p < 0.05) and generation of nitric oxide (1.3-fold, p < 0.05) in hCAECs and pre-treatment with PD123319 (20 μM) suppressed this effect partially (65%). Finally, NP-6A4 decreased phosphorylation of Jun-N-terminal kinase, implicated in apoptosis of ECs in atherosclerotic sites. Taken together, NP-6A4, through its ability to increase AT2R expression and signaling, exerts different cell-specific protective effects in human VSMCs and ECs.

Angiotensin II aggravates lipopolysaccharide induced human pulmonary microvascular endothelial cells permeability in high glucose status

Lung infection is one of the most common infections in diabetes mellitus and is characterized by increased pulmonary microvascular endothelial permeability. Local Angiotensin II (AngII) plays an important role in the pathogenesis of lung diseases. However, whether AngII can aggravate diabetic infectious lung injury is not clear. Therefore, we investigated the effects of AngII on the permeability of human pulmonary microvascular endothelial cells (HPMVECs) challenged by lipopolysaccharide (LPS) in high glucose states in vitro. HPMVECs were divided into five groups: a control group (CON), a high glucose group (HG), an LPS + high glucose group (LH), an LPS + high glucose + AngII group (LHA), and an LPS + high glucose + Losartan group (LHL). The HPMVECs permeability as well as the F-actin levels, cytoskeleton, apoptosis and TNF-α concentrations were evaluated. Compared to the CON group, the HG, LH and LHA groups had significantly higher cellular permeability, cellular apoptosis and TNF-α levels, with more extensive cytoskeletal damage and lower F-actin levels. Additionally, cells in the LHA group exhibited significantly elevated permeability, apoptosis and TNF-α concentrations, lower F-actin levels and more extensive cytoskeletal damage than either the LH or HG group. However, compared to the HG or LH group, the LHL group showed significantly lower cellular permeability, cell apoptosis, cytoskeletal damage and TNF-α concentrations and higher F-actin levels. This study suggests that in a diabetic infectious lung injury cellular model, AngII could aggravate the permeability of HPMVEC via F-actin dynamics and cell apoptosis. Furthermore, blocking the Angiotension II Type 1 Receptor could significantly alleviate the hyperpermeability of HPMVECs.