L-Carnitine has a liver-protective effect through inhibition of inducible nitric oxide synthase induction in primary cultured rat hepatocytes

Background: L-Carnitine has protective effects on various injured organs. However, it has not been reported whether L-carnitine influences the induction of inducible nitric oxide synthase (iNOS) expression during inflammation. Nitric oxide (NO) produced by iNOS is an inflammatory indicator in organs which become inflamed, including the liver.Objective: This study aimed to examine whether L-carnitine influences the induction of iNOS gene expression in inflammatory cytokine-stimulated hepatocytes and the mechanisms involved in the action. Methods: L-Carnitine was added into the primary cultures of rat hepatocytes stimulated by interleukin-1β (an in vitro liver injury model). The production of NO and induction of iNOS and its signaling pathway were analyzed.Results: Transfection experiments with iNOS promoter-luciferase constructs revealed how L-carnitine inhibited iNOS mRNA synthesis activity and reduced its stability. In support of this observation, L-carnitine reduced iNOS mRNA and iNOS protein expression levels, resulting in reduced NO production. L-Carnitine blocked two essential pathways for iNOS induction: IκB kinase (IκB degradation/NF-κB activation) and phosphatidylinositol 3-kinase/Akt (type I IL-1 receptor upregulation).Conclusions: L-Carnitine inhibited the induction of inflammatory mediator iNOS, partially through inhibition of NF-κB activation, which demonstrated L-carnitine has protective effects in an in vitro liver injury model. L-Carnitine may have therapeutic potential for organ injuries, including the liver.Keywords: L-carnitine, hepatic encephalopathy, inducible nitric oxide synthase, liver injury, primary cultured hepatocytes, nuclear factor-κB, type I interleukin-1 receptor

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Glutathione inhibits expression of the proinflammatory biomarker inducible nitric oxide synthase in hepatocytes

Functional Foods in Health and Disease ◽

10.31989/ffhd.v8i11.547 ◽

2018 ◽

Vol 8 (12) ◽

pp. 544

Author(s):

Richi Nakatake ◽

Masaya Kotsuka ◽

Yuki Hashimoto ◽

Masahiko Hatta ◽

Morihiko Ishizaki ◽

...

Keyword(s):

Nitric Oxide ◽

Nitric Oxide Synthase ◽

Liver Injury ◽

Inducible Nitric Oxide Synthase ◽

Type I ◽

Tnf Α ◽

Oxide Synthase ◽

Necrosis Factor ◽

Inducible Nitric Oxide ◽

Inos Induction

Background: Intracellular glutathione (GSH) plays an important regulatory role in the host response to liver injury. However, there have been few scientific reports on the anti-inflammatory effects of GSH. In the inflamed liver, proinflammatory cytokines stimulate liver cells, followed by expression of inducible nitric oxide synthase (iNOS). Excessive nitric oxide (NO) levels produced by iNOS are one of the factors involved in liver injury. Therefore, inhibiting iNOS induction is important for preventing liver injury. This study aimed to investigate the protective effects of GSH on the liver by examining interleukin (IL)-1β-stimulated hepatocytes.Methods: Primary cultured rat hepatocytes were treated with IL-1β in the presence or absence of GSH. Induction of iNOS and its signaling pathway were analyzed.Results: Addition of GSH decreased IL-1β-induced iNOS protein and mRNA expression levels, which resulted in inhibition of NO production. GSH also decreased tumor necrosis factor (TNF)-α and IL-6 mRNA expression. GSH blocked “type I IL-1 receptor upregulation”, one of the essential signaling pathways for iNOS induction, through inactivation of an upstream kinase, phosphatidylinositol 3-kinase/Akt. In contrast, GSH had no effects on degradation of IκB and activation of NF-ĸB (nuclear translocation and its DNA binding). Transfection experiments revealed that GSH reduced iNOS mRNA levels at the promoter transactivation and mRNA stabilization steps. Delayed administration of GSH after IL-1β addition also inhibited iNOS induction. Conclusions: Our study suggests that GSH affects induction of inflammatory mediators, including iNOS and TNF-α, indicating its therapeutic potential for organ injuries, especially for the liver.Keywords: glutathione, inducible nitric oxide synthase, liver injury, primary cultured hepatocytes, type I interleukin-1 receptor, tumor necrosis factor-α

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Expression of the inducible nitric oxide synthase gene in diaphragm and skeletal muscle

Journal of Applied Physiology ◽

10.1152/jappl.1996.81.6.2415 ◽

1996 ◽

Vol 81 (6) ◽

pp. 2415-2420 ◽

Cited By ~ 42

Author(s):

Marita Thompson ◽

Lisa Becker ◽

Debbie Bryant ◽

Gary Williams ◽

Daniel Levin ◽

...

Keyword(s):

Nitric Oxide ◽

Skeletal Muscle ◽

Nitric Oxide Synthase ◽

Inducible Nitric Oxide Synthase ◽

No Synthase ◽

Inos Mrna ◽

Pump Failure ◽

Oxide Synthase ◽

Inducible Nitric Oxide

Thompson, Marita, Lisa Becker, Debbie Bryant, Gary Williams, Daniel Levin, Linda Margraf, and Brett P. Giroir. Expression of the inducible nitric oxide synthase gene in diaphragm and skeletal muscle. J. Appl. Physiol. 81(6): 2415–2420, 1996.—Nitric oxide (NO) is a pluripotent molecule that can be secreted by skeletal muscle through the activity of the neuronal constitutive isoform of NO synthase. To determine whether skeletal muscle and diaphragm might also express the macrophage-inducible form of NO synthase (iNOS) during provocative states, we examined tissue from mice at serial times after intravenous administration of Escherichia coli endotoxin. In these studies, iNOS mRNA was strongly expressed in the diaphragm and skeletal muscle of mice 4 h after intravenous endotoxin and was significantly diminished by 8 h after challenge. Induction of iNOS mRNA was followed by expression of iNOS immunoreactive protein on Western immunoblots. Increased iNOS activity was demonstrated by conversion of arginine to citrulline. Immunochemical analysis of diaphragmatic explants exposed to endotoxin in vitro revealed specific iNOS staining in myocytes, in addition to macrophages and endothelium. These results may be important in understanding the pathogenesis of respiratory pump failure during septic shock, as well as skeletal muscle injury during inflammation or metabolic stress.

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