[A possible role of anti-endothelial cell antibody in the sera of MCTD patients on pulmonary vascular damage relating to pulmonary hypertension].

Abstract

Objectives: Pulmonary hypertension (PH) is one of the major fatal causes in patients with mixed connective tissue disease(MCTD), which showed remarkable angiopathy from large to small vessels in the lungs. However, the etiology of PH in MCTD is still unknown. Even the lung tissues of MCTD patients without overt clinical PH represent minor vascular damages such as microthrombus or slight intimal thickening. These findings suggest some serum factors cause endothelial cell damage especially to pulmonary micro vessels, which leads to PH in MCTD. To elucidate the mechanisms of PH in MCTD we studied the anti-endothelial cell antibodies (AECA) in the sera of MCTD patients, which are considered to correlate with activity in some collagen diseases, and compared the three kinds of endothelial cells, especially the effects on pulmonary endothelial cells.

Materials and methods: Sera from 14 MCTD patients who satisfied the Kasukawa's criteria in Japan including 4 cases of PH, 8 cases of non-PH and 3 untreated cases, and 5 healthy controls were analyzed as follows: (1) AECA to human pulmonary arterial endothelial cells (HPAEC), pulmonary microvascular endothelial cells (HMVE-L) and human aortic endothelial cells(HAEC) were analyzed by an indirect immunofluorescence method using flow cytometry. (2) Effects of MCTD patients' and healthy controls' sera on cell proliferation and induction of apoptosis on cultured HPAEC were investigated by methods of MTS and TUNEL. (3) A cytotoxic effect of patients' sera in combination with activated NK cells on HPAEC were studied by a method of LDH concentration.

Results: (1) Patients' sera from MCTD have IgG type AECA, and sera from MCTD patients with PH showed a higher intensity of AECA compared with non-PH and control cases (P < 0.01). (2) Only patient's sera revealed no potency of cell proliferation and induction of apoptosis in every kinds of endothelial cells compared with controls. (3) Sera from MCTD patients with PH, and from untreatment patients were high intensity of AECA, which shows cytotoxicity by addition of activated NK cells.

Conclusions: Apoptosis of pulmonary arterial endothelial cells induced by AECA in combination with activated NK cells may be the fist step of vascular damage associated with pulmonary hypertension in patients with MCTD.