title: Andrographolide enhances nuclear factor-kappaB subunit p65 Ser536 dephosphorylation through activation of protein phosphatase 2A in vascular smooth muscle cells.
abstract: Recent studies have demonstrated that transcription factor nuclear factor (NF)-κB inhibition may contribute to the protective anti-inflammatory actions of andrographolide, an abundant component of plants of the genus Andrographis. However, the precise mechanism by which andrographolide inhibits NF-κB signaling remains unclear. We thus investigated the mechanism involved in andrographolide suppression of NF-κB signaling in rat vascular smooth muscle cells (VSMCs) exposed to proinflammatory stimuli, LPS, and IFN-γ. Andrographolide was shown to suppress LPS/IFN-γ-induced inducible nitric-oxide synthase and matrix metalloprotease 9 expression in rat VSMCs. Andrographolide also inhibited LPS/IFN-γ-induced p65 nuclear translocation, DNA binding activity, p65 Ser(536) phosphorylation, and NF-κB reporter activity. However, IKK phosphorylation and downstream inhibitory κBα phosphorylation and degradation were not altered by the presence of andrographolide in LPS/IFN-γ-stimulated VSMCs. These andrographolide inhibitory actions could be prevented by selective inhibition of neutral sphingomyelinase and protein phosphatase 2A (PP2A). Furthermore, andrographolide was demonstrated to increase ceramide formation and PP2A activity in VSMCs and to inhibit neointimal formation in rat carotid injury models. These results suggest that andrographolide caused neutral sphingomyelinase-mediated ceramide formation and PP2A activation to dephosphorylate p65 Ser(536), leading to NF-κB inactivation and subsequent inducible nitric-oxide synthase down-regulation in rat VSMCs stimulated by LPS and IFN-γ.
authors.affiliation: Graduate Institute of Medical Sciences, Department of Pharmacology, Taipei Medical University, Taipei 11031, Taiwan.
authors.forename: Cheng Y
authors.initials: CY
authors.lastname: Hsieh
authors.forename: Ming J
authors.initials: MJ
authors.lastname: Hsu
authors.forename: George
authors.initials: G
authors.lastname: Hsiao
authors.forename: Yi H
authors.initials: YH
authors.lastname: Wang
authors.forename: Chi W
authors.initials: CW
authors.lastname: Huang
authors.forename: Shiuan W
authors.initials: SW
authors.lastname: Chen
authors.forename: Thanasekaran
authors.initials: T
authors.lastname: Jayakumar
authors.forename: Pei T
authors.initials: PT
authors.lastname: Chiu
authors.forename: Yi H
authors.initials: YH
authors.lastname: Chiu
authors.forename: Joen R
authors.initials: JR
authors.lastname: Sheu
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D035685:Andrographis / Q000737:chemistry; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry / Q000494:pharmacology*; D002467:Cell Nucleus / Q000378:metabolism*; D002518:Ceramides / Q000378:metabolism; D004224:Diterpenes / Q000737:chemistry / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis; D010766:Phosphorylation / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000378:metabolism; D013108:Sphingomyelin Phosphodiesterase / Q000037:antagonists & inhibitors / Q000378:metabolism; D051996:Transcription Factor RelA / Q000378:metabolism*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D002518:Ceramides; D004224:Diterpenes; D008070:Lipopolysaccharides; C498145:Rela protein, rat; D051996:Transcription Factor RelA; C030419:andrographolide; D012694:Serine; D007371:Interferon-gamma; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D054648:Protein Phosphatase 2; D013108:Sphingomyelin Phosphodiesterase; D020780:Matrix Metalloproteinase 9