Interleukin-6 trans-signaling contributes to chronic hypoxia-inducedpulmonary hypertension

摘要

Interleukin-6 (IL-6) is a pleotropic cytokine that signals through the membrane-bound IL-6 receptor (mIL-6R) to induce anti-inflammatory (“classic-signaling”) responses. This cytokine also binds to the soluble IL-6R (sIL-6R) to promote inflammation (“trans-signaling”). mIL-6R expression is restricted to hepatocytes and immune cells. Activated T cells release sIL-6R into adjacent tissues to induce trans-signaling. These cellular actions require the ubiquitously expressed membrane receptor gp130. Reports show that IL-6 is produced by pulmonary arterial smooth muscle cells (PASMCs) exposed to hypoxia in culture as well as the medial layer of the pulmonary arteries in mice exposed to chronic hypoxia (CH), and IL-6 knockout mice are protected from CH-induced pulmonary hypertension (PH). IL-6 has the potential to contribute to a broad array of downstream effects, such as cell growth and migration. CH-induced PH is associated with increased proliferation and migration of PASMCs to previously non-muscularized vessels of the lung. We tested the hypothesis that IL-6 trans-signaling contributes to CH-induced PH and arterial remodeling. Plasma levels of sgp130 were significantly decreased in mice exposed to CH (380 mmHg) for five days compared to normoxic control mice (630 mmHg), while sIL-6R levelswere unchanged. Consistent with our hypothesis, mice that received the IL-6trans-signaling-specific inhibitor sgp130Fc, a fusion protein of the solubleextracellular portion of gp130 with the constant portion of the mouse IgG1antibody, showed attenuation of CH-induced increases in right ventricularsystolic pressure, right ventricular and pulmonary arterial remodeling ascompared to vehicle (saline)-treated control mice. In addition, PASMCs culturedin the presence of IL-6 and sIL-6R showed enhanced migration but notproliferation compared to those treated with IL-6 or sIL-6R alone or in thepresence of sgp130Fc. These results indicate that IL-6 trans-signalingcontributes to pulmonary arterial cell migration and CH-induced PH.