Anti-inflammatory Effect of α -Linolenic Acid and Its Mode of Action through the Inhibition of Nitric Oxide Production and Inducible Nitric Oxide Synthase Gene Expression via NF-қB and Mitogen-Activated Protein Kinase Pathways
Anti-inflammatory Effect of α -Linolenic Acid and Its Mode of Action through the Inhibition of Nitric Oxide Production and Inducible Nitric Oxide Synthase Gene Expression via NF-қB and Mitogen-Activated Protein Kinase Pathways
Year: 2007
Authors: Ren. J. Chung, S.H.
Publication Name: J. Agric. Food Chem.
Publication Details: Volume 55; Pages 5073 − 5080.
Abstract:
Alpha-linolenic acid (ALA) isolated from Actinidia polygama fruits exhibits potent anti-inflammatory activity with an unknown mechanism. To elucidate the molecular mechanisms of ALA on pharmacological and biochemical actions in inflammation, we examined the effect of ALA on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in the murine macrophages cell line, RAW 264.7. We found that ALA has a strong inhibitory effect on the production of NO. ALA also inhibited inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and tumor necrosis factor-R (TNF-R) gene expressions induced by LPS. To explore the mechanisms associated with the inhibition of iNOS gene expression by ALA, we investigated its effect on LPS-induced nuclear factor-kappaB (NF-kappaB) activation. Treatment with ALA reduced a translocation of NF-kappaB subunit and NF-kappaB-dependent transcriptional activity. The activation of NF-kappaB was inhibited by prevention of the degradation of inhibitory factor-kappaBR. We also found that ALA inhibited LPS-induced phosphorylation of mitogen-activated protein kinases (MAPKs). In addition, the antinociceptive effect of ALA was also assessed by means of the acetic acid-induced abdominal constriction test and Randall-Selitto assay. ALA (5 and 10 mg/kg) showed the potent antinociceptive effects in these animal models. Taken together, these results suggest that ALA downregulates inflammatory iNOS, COX-2, and TNF-R gene expressions through the blocking of NF-kappaB and MAPKs activations in LPS-stimulated RAW 264.7 cells, which may be the mechanistic basis for the anti-inflammatory effect of ALA. (Authors abstract)
Nitric oxide (NO) is produced by inducible NO synthase (iNOS) in activated macrophages and is one of the most important inflammatory mediators. It induces various harmful responses including tissue injury, septic shock, and apoptosis. Expression of cyclooxygenase-2 (COX-2) plays a major role in the inflammatory process by catalyzing the production of prostaglandins (PGs). The binding of the potentially relevant transcription factor, nuclear factor-kB (NF-kappaB), to the kB sites has been shown to be functionally important for iNOS induction by LPS. The NF-kB family of transcription factors regulates various inflammatory cytokines, such as IL-1, IL-2, IL-6, IL-8, and tumor necrosis factor-R (TNF-R), as well as genes encoding COX-2 and iNOS. In this study, ALA was fractionated from Actinidia polygama (AP) fruits and evaluated for its effects on LPS induced NO production and iNOS, COX-2, and TNF-R gene expressions as well as to clarify its mode of action in RAW 264.7 cells, a murine macrophage cell line. As well the in vivo antinociceptive (ability to reduce sensitivity to painful stimuli) effect of ALA was investigated. The in vivo anti-inflammatory activity of ALA has been reported in previous work. This study suggests that ALA exerts its anti-inflammatory effect by inhibiting iNOS, COX-2, and TNF-R mRNA transcription steps in a dose-dependent fashion. The results suggest that ALA inhibits the nuclear translocation of the p65 protein and the LPS-induced DNA activation of NF-kB. Inhibition of NF-kB activity by ALA may be the result of the inhibition of I-kBR degradation and phosphorylation, followed by decrease in the translocation of the NF-kB subunits. The Randall-Selitto assay was also carried out to determine if ALA has any specific analgesic effect. ALA elevated the pain threshold toward a mechanical force at doses of 5 and 10 mg/kg, which could contribute to its peripheral analgesic effects. This is the first investigation showing that ALA markedly inhibits LPS-induced NO production and iNOS, COX- 2, and TNF-R gene expressions by blocking NF-kB activation and inhibiting the phosphorylation of MAP kinases in RAW 264.7 macrophages. These anti-inflammatory and antinociceptive effects were also evident in vivo. Because NF-kB is one of the critical transcription factors that regulate the transcription of many genes associated with inflammation, the inhibition of this transcription factor by ALA presents a potential therapeutic approach for the treatment of various inflammatory diseases. (Editors comments)
Nitric oxide (NO) is produced by inducible NO synthase (iNOS) in activated macrophages and is one of the most important inflammatory mediators. It induces various harmful responses including tissue injury, septic shock, and apoptosis. Expression of cyclooxygenase-2 (COX-2) plays a major role in the inflammatory process by catalyzing the production of prostaglandins (PGs). The binding of the potentially relevant transcription factor, nuclear factor-kB (NF-kappaB), to the kB sites has been shown to be functionally important for iNOS induction by LPS. The NF-kB family of transcription factors regulates various inflammatory cytokines, such as IL-1, IL-2, IL-6, IL-8, and tumor necrosis factor-R (TNF-R), as well as genes encoding COX-2 and iNOS. In this study, ALA was fractionated from Actinidia polygama (AP) fruits and evaluated for its effects on LPS induced NO production and iNOS, COX-2, and TNF-R gene expressions as well as to clarify its mode of action in RAW 264.7 cells, a murine macrophage cell line. As well the in vivo antinociceptive (ability to reduce sensitivity to painful stimuli) effect of ALA was investigated. The in vivo anti-inflammatory activity of ALA has been reported in previous work. This study suggests that ALA exerts its anti-inflammatory effect by inhibiting iNOS, COX-2, and TNF-R mRNA transcription steps in a dose-dependent fashion. The results suggest that ALA inhibits the nuclear translocation of the p65 protein and the LPS-induced DNA activation of NF-kB. Inhibition of NF-kB activity by ALA may be the result of the inhibition of I-kBR degradation and phosphorylation, followed by decrease in the translocation of the NF-kB subunits. The Randall-Selitto assay was also carried out to determine if ALA has any specific analgesic effect. ALA elevated the pain threshold toward a mechanical force at doses of 5 and 10 mg/kg, which could contribute to its peripheral analgesic effects. This is the first investigation showing that ALA markedly inhibits LPS-induced NO production and iNOS, COX- 2, and TNF-R gene expressions by blocking NF-kB activation and inhibiting the phosphorylation of MAP kinases in RAW 264.7 macrophages. These anti-inflammatory and antinociceptive effects were also evident in vivo. Because NF-kB is one of the critical transcription factors that regulate the transcription of many genes associated with inflammation, the inhibition of this transcription factor by ALA presents a potential therapeutic approach for the treatment of various inflammatory diseases. (Editors comments)
