Brain natriuretic peptide is released from human astrocytoma cell line U373MG under hypoxia: a possible role in anti-apoptosis

• Published in: Journal of endocrinology Vol. 208; no. 1; pp. 51 - 57
• Main Authors: Katoh, Chisato, Osanai, Tomohiro, Tomita, Hirofumi, Okumura, Ken
• Format: Journal Article
• Language: English
• Published: Bristol BioScientifica 01.01.2011
• Subjects: Analysis of Variance; Apoptosis - physiology; Astrocytes - metabolism; Astrocytes - secretion; Biological and medical sciences; Blotting, Western; Cell Line, Tumor; Fundamental and applied biological sciences. Psychology; Humans; Hypoxia - genetics; Hypoxia - metabolism; Immunoenzyme Techniques; Medical sciences; Natriuretic Peptide, Brain - genetics; Natriuretic Peptide, Brain - metabolism; Natriuretic Peptide, Brain - secretion; Neurology; Phosphorylation; Regular papers; Reverse Transcriptase Polymerase Chain Reaction; Tumor Cells, Cultured - metabolism; Tumor Cells, Cultured - secretion; Tumors of the nervous system. Phacomatoses; Vertebrates: endocrinology; Human; Brain natriuretic peptide; Nervous system diseases; Oxygen; Environmental factor; Cell line; Glioma; Cell death; Central nervous system disease; Tumor; Hypoxia; Astrocytoma; Apoptosis
• ISSN: 0022-0795; 1479-6805
• DOI: 10.1677/JOE-10-0230

We have recently shown that the plasma brain-type natriuretic peptide (BNP) level is elevated in acute ischemic stroke patients, but the origin and role of BNP remain unclear. We investigated whether human astrocytes secrete BNP under hypoxia, and if so, what signaling pathway is involved, and what is the role of BNP. Human astrocytoma cell line U373MG was exposed to hypoxia by Anaeropack. BNP gene expression was increased by 3.9±2.5- and 6.5±2.9-fold at 12 and 24 h after hypoxia respectively (n=6, both P<0.05) and was associated with twofold increase in BNP protein at 24 h. BNP release in the culture media (pg/mg protein) was elevated from 1.8±1.8 under normoxia to 13.5±7.8 after 24-h hypoxia (n=9, P<0.01 versus normoxia). Western blot revealed the tyrosine415 phosphorylation of tyrosine kinase c-Src under hypoxia. Treatment of the cells with tyrosine kinase inhibitor PP1 abolished hypoxia-induced increase in BNP expression and release. In the cells exposed to hypoxia, caspase activity and apoptosis, measured by annexin-V–propidium iodide kit, were increased at 24 h compared with the cells under normoxia (n=5, both P<0.05). It was further increased in the cells transfected with siRNA for natriuretic peptide precursor B (n=6, both P<0.05) and reversed by administration of exogenous BNP (P<0.01). In conclusion, hypoxia increased BNP expression and release in human astrocytoma cell line U373MG through c-Src activation. BNP may play a pivotal role in anti-apoptosis of astrocytes under hypoxia.