Andrographolide inhibits hypoxia‐induced hypoxia‐inducible factor 1α and endothelin 1 expression through the heme oxygenase 1/CO/cGMP/MKP‐5 pathways in EA.hy926 cells

• Published in: Environmental toxicology 2018-03, Vol.33 (3), p.269-279
• Main Authors: Lin, Hung‐Chih, Su, Shih‐Li, Lin, Wan‐Chun, Lin, Ai‐Hsuan, Yang, Ya‐Chen, Lii, Chong‐Kuei, Chen, Haw‐Wen
• Format: Article
• Language: English
• Subjects: andrographolide; Anti-Inflammatory Agents - pharmacology; Carbon Monoxide - metabolism; Cell Hypoxia; Cell Line; Cyclic GMP - analogs & derivatives; Cyclic GMP - metabolism; Cyclic GMP - pharmacology; Diterpenes - pharmacology; Dual-Specificity Phosphatases - metabolism; endothelin 1; Endothelin-1 - metabolism; heme oxygenase 1; Heme Oxygenase-1 - metabolism; Humans; Hypoxia-Inducible Factor 1, alpha Subunit - metabolism; hypoxia‐inducible factor 1α; Mitogen-Activated Protein Kinase Phosphatases - metabolism; mitogen‐activated protein kinase phosphatase 5; p38 Mitogen-Activated Protein Kinases - metabolism; Thionucleotides - pharmacology
• ISSN: 1520-4081; 1522-7278
• DOI: 10.1002/tox.22514

Andrographolide is a potent anti‐inflammatory agent found in Andrographis paniculata. Endothelin 1 (ET‐1) is an endothelium‐derived vasoconstrictor with pro‐inflammatory properties secreted in response to hypoxia. Mitogen‐activated protein kinase phosphatase 5 (MKP‐5) is a dual‐specificity phosphatase that dephosphorylates threonine and tyrosine residues of MAPKs. We showed previously that hypoxia‐induced HIF‐1α expression and ET‐1 secretion are dependent on p38 MAPK in EA.hy926 cells. Here, we investigate what role MKP‐5 plays in andrographolide's inhibition of hypoxia‐induced expression of HIF‐1α and ET‐1. Hypoxic conditions were created using the hypoxia‐mimetic agent CoCl2. Andrographolide enhanced HO‐1 and MKP‐5 expression and cellular cGMP content in addition to inhibiting hypoxia‐induced ROS generation. Concomitantly, the HO‐1 byproduct CO and the cGMP analogue 8‐bromoguanosine 3′,5′‐cyclic monophosphate (8‐Br‐cGMP) increased MKP‐5 expression, and pretreatment with CO and 8‐Br‐cGMP inhibited hypoxia‐induced HIF‐1α and ET‐1 expression. Transfection of HO‐1 siRNA or pretreatment with the HO‐1 inhibitor ZnPP‐9 or 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one, a specific inhibitor of soluble guanylate cyclase, reduced andrographolide‐induced MKP‐5 expression. Moreover, silencing MKP‐5 or treatment with the phosphatase inhibitor vanadate abrogated andrographolide's suppressing hypoxia‐induced p38 MAPK activation and HIF‐1α expression. The inhibition of hypoxia‐induced HIF‐1α and ET‐1 expression by andrographolide is likely associated with HO‐1/CO/cGMP/MKP‐5 pathways, which is involved in inhibiting hypoxia‐induced p38 MAPK activation.