PROTECTIVE EFFECT OF FR183998, A Na+/H+ EXCHANGER INHIBITOR, AND ITS INHIBITION OF iNOS INDUCTION IN HEPATIC ISCHEMIA-REPERFUSION INJURY IN RATS

Targeting Calcium Homeostasis in Myocardial Ischemia/Reperfusion Injury: An Overview of Regulatory Mechanisms and Therapeutic Reagents

Calcium homeostasis plays an essential role in maintaining excitation–contraction coupling (ECC) in cardiomyocytes, including calcium release, recapture, and storage. Disruption of calcium homeostasis may affect heart function, leading to the development of various heart diseases. Myocardial ischemia/reperfusion (MI/R) injury may occur after revascularization, which is a treatment used in coronary heart disease. MI/R injury is a complex pathological process, and the main cause of increased mortality and disability after treatment of coronary heart disease. However, current methods and drugs for treating MI/R injury are very scarce, not ideal, and have limitations. Studies have shown that MI/R injury can cause calcium overload that can further aggravate MI/R injury. Therefore, we reviewed the effects of critical calcium pathway regulators on MI/R injury and drew an intuitive diagram of the calcium homeostasis pathway. We also summarized and analyzed calcium pathway-related or MI/R drugs under research or marketing by searching Therapeutic Target and PubMed Databases. The data analysis showed that six drugs and corresponding targets are used to treat MI/R injury and involved in calcium signaling pathways. We emphasize the relevance of further detailed investigation of MI/R injury and calcium homeostasis and the therapeutic role of calcium homeostasis in MI/R injury, which bridges basic research and clinical applications of MI/R injury.

The Proton Pump Inhibitor Lansoprazole Has Hepatoprotective Effects in In Vitro and In Vivo Rat Models of Acute Liver Injury

BACKGROUND/AIMS

The proton pump inhibitor lansoprazole (LPZ) is clinically used to reduce gastric acid secretion, but little is known about its possible hepatoprotective effects. This study aimed to investigate the hepatoprotective effects of LPZ and its potential mechanisms using in vitro and in vivo rat models of liver injury.

METHODS

For the in vitro model of liver injury, primary cultured rat hepatocytes were treated with interleukin-1β in the presence or absence of LPZ. The influence of LPZ on inducible nitric oxide synthase (iNOS) induction and nitric oxide (NO) production and on the associated signaling pathways was analyzed. For the in vivo model, rats were treated with D-galactosamine (GalN) and lipopolysaccharide (LPS). The effects of LPZ on survival and proinflammatory mediator expression (including iNOS and tumor necrosis factor-α) in these rats were examined.

RESULTS

LPZ inhibited iNOS induction partially through suppression of the nuclear factor-kappa B signaling pathway in hepatocytes, thereby reducing potential liver injury from excessive NO levels. Additionally, LPZ increased survival by 50% and decreased iNOS, tumor necrosis factor-α, and cytokine-induced neutrophil chemoattractant-1 mRNA expression in the livers of GalN/LPS-treated rats. LPZ also inhibited nuclear factor-kappa B activation by GalN/LPS.

CONCLUSIONS

LPZ inhibits the induction of several inflammatory mediators (including cytokines, chemokines, and NO) partially through suppression of nuclear factor-kappa B, resulting in the prevention of fulminant liver failure. The therapeutic potential of LPZ for liver injuries warrants further investigation.

Elental® amino acid component has protective effects on primary cultured hepatocytes and a rat model of acute liver injury

Amino acids can exert protective effects on the liver either when administered as a medication or following an operation. In this study, we examined the protective effects of amino acids on the liver using in vitro and in vivo models by studying their influence on the induction of inducible nitric oxide synthase (iNOS) and nitric oxide production as a liver injury marker in cultured hepatocytes and liver-protective effects in d-galactosamine and lipopolysaccharide (GalN/LPS)-treated rats, respectively. Primary cultured rat hepatocytes were treated with interleukin (IL)-1β in the presence or absence of Elental® amino acid component (EleAA; 17 amino acids). Rats were pretreated with either EleAA or a diet containing selected amino acids followed by GalN/LPS injection. Survival rate and mRNA expression were analyzed. EleAA inhibited iNOS induction through reduction of mRNA synthesis and stability in cultured hepatocytes, indicating prevention of liver injury, but did not show a liver-protective effect in GalN/LPS rats. Among EleAA, Lys, Trp, His, and Arg (4AA) markedly decreased nitric oxide production and inhibited nuclear factor-κB (NF-κB) activation. In GalN/LPS rats, 4AA (3% of each amino acid in diet) increased survival rate by 50% and decreased mRNA expression of iNOS, tumor necrosis factor-α, and cytokine-induced neutrophil chemoattractant-1 in the liver. 4AA reduced NF-κB activation induced by GalN/LPS. 4AA inhibited the expression of inflammatory mediators, in part through inhibition of NF-κB activation in cultured hepatocytes and GalN/LPS-treated rats. The results suggest that EleAA has therapeutic potential for organ injuries including liver.

Pyropia yezoensis glycoprotein regulates antioxidant status and prevents hepatotoxicity in a rat model of D-galactosamine/lipopolysaccharide-induced acute liver failure

The present study aimed to investigate the effects of Pyropia yezoensis glycoprotein (PYGP) on hepatic antioxidative enzyme activity and mitogen-activated protein kinase (MAPK) phosphorylation in a rat model of D-galactosamine/lipopolysaccharide (D-GalN/LPS)-induced hepatotoxicity. Glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) were measured to determine the severity of hepatotoxicity. Treatment with D‑GalN/LPS significantly increased the GOT, GPT and lipid peroxidation levels, and decreased the antioxidant capacity of the rats. Treatment with PYGP (150 and 300 mg/kg/body weight) decreased the levels of GOT, GPT and lipid peroxidation levels. The activities of antioxidative enzymes, including catalase, glutathione S‑transferase and glutathione were upregulated following PYGP treatment. Furthermore, D‑GalN/LPS‑induced MAPK phosphorylation, and inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expression were downregulated by PYGP. These results indicated that PYGP may exert hepatoprotective effects via the upregulation of antioxidative enzymes, and the downregulation of the MAPK signaling pathway and iNOS and COX-2 expression.

pyroGlu-Leu inhibits the induction of inducible nitric oxide synthase in interleukin-1β-stimulated primary cultured rat hepatocytes

Pyroglutamyl leucine (pyroGlu-Leu), which is a peptide isolated from wheat gluten hydrolysate, has been reported to be a hepatoprotective compound in acute liver failure. In inflamed liver, proinflammatory cytokines including interleukin (IL)-1β and tumor necrosis factor (TNF)-α stimulate the induction of inducible nitric oxide synthase (iNOS). Excess production of nitric oxide (NO) by iNOS is an inflammatory biomarker in liver injury. We examined proinflammatory cytokine-stimulated hepatocytes as a simple "in vitro inflammation model" to determine liver protective effects of pyroGlu-Leu and its mechanisms of action. We hypothesized that pyroGlu-Leu inhibits the induction of iNOS gene expression, resulting in the attenuation of hepatic inflammation. Hepatocytes were isolated from rats by collagenase perfusion and cultured. Primary cultured cells were treated with IL-1β in the presence or absence of pyroGlu-Leu. The induction of iNOS and its signaling pathway were analyzed. IL-1β stimulated the enhancement of NO production in hepatocytes and this effect was inhibited by pyroGlu-Leu. pyroGlu-Leu decreased the expression of iNOS protein and its mRNA. Transfection experiments with iNOS-luciferase constructs revealed that pyroGlu-Leu inhibited both of iNOS promoter transactivation and its mRNA stabilization. pyroGlu-Leu also decreased the expression of an iNOS gene antisense transcript, which is involved in iNOS mRNA stability. However, pyroGlu-Leu had no effects on IκB degradation and NF-κB activation. Results demonstrate that pyroGlu-Leu inhibited the induction of iNOS gene expression at transcriptional and post-transcriptional steps through IκB/NF-κB-independent pathway, leading to the prevention of NO production. pyroGlu-Leu may have therapeutic potential for liver injury through the suppression of iNOS.

Temporal and spatial dependence of inflammatory biomarkers and suppression by fluvastatin in dextran sodium sulfate-induced rat colitis model

BACKGROUND

Dextran sodium sulfate (DSS)-induced colitis in rats is widely used as an experimental model for elucidating the etiology of ulcerative colitis (UC) and developing its novel remedy. We investigated the temporal and spatial changes in inflammatory mediators such as tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) in the regions of rectum and distal colon and examined whether statins, which were designed to lower plasma cholesterol levels, influenced those mediators.

METHODS

Colitis was induced in rats by oral administration of 5 % DSS for 5 days, followed by 2 % DSS for 10 days. 5 % DSS rats were treated with fluvastatin (20 mg/kg) concomitantly for 5 days. The expression of inflammatory mediators of a sequence of four regions in rectum (R) and distal colon (D0, D1, and D2) was determined by quantitative RT-PCR.

RESULTS

The peak of colitic damage, which was confirmed clinically and histopathologically, was found on days 4-6. The expression of TNF-α, iNOS, cytokine-induced neutrophil chemoattractant-1, interleukin (IL)-1β, and IL-6 mRNA increased in R time dependently, showing the peak on days 4-6, and then decreased thereafter. The levels of mRNAs reduced from R to D0, D1, and D2 region dependently. Fluvastatin decreased the expression of these markers in addition to the prevention of DSS-induced damage.

CONCLUSIONS

Results demonstrated that the expression of inflammatory biomarkers had time and region specificity and was markedly inhibited by fluvastatin. To obtain a precise drug effect for UC, it is important to elucidate the temporal and spatial dependence of inflammatory biomarkers in DSS colitis model.

Fluvastatin inhibits the induction of inducible nitric oxide synthase, an inflammatory biomarker, in hepatocytes

AIM

Statins (3-hydroxy-3-methylglutaryl coenzyme A [HMG-CoA] reductase inhibitors), which were originally designed to lower plasma cholesterol levels, are increasingly recognized as anti-inflammatory agents. In the inflamed liver, pro-inflammatory cytokines stimulate the induction of inducible nitric oxide synthase (iNOS). Overproduction of NO by iNOS has been implicated as a factor in liver injury. We examined pro-inflammatory cytokine-stimulated hepatocytes as a simple in vitro injury model to determine liver-protective effects of statins. We hypothesized that statins are involved in the downregulation of iNOS, resulting in decreased hepatic inflammation.

METHODS

Hepatocytes were isolated from rats by collagenase perfusion and centrifugation. Primary cultured hepatocytes were treated with interleukin (IL)-1β in the presence or absence of fluvastatin. The induction of iNOS and its signaling pathway were analyzed.

RESULTS

IL-1β produced increased levels of NO. This effect was inhibited by fluvastatin, which exerted its maximal effects at 100 μM. Fluvastatin decreased the levels of iNOS protein and its mRNA expression. Fluvastatin had no effects on IκB degradation and nuclear factor-κB activation. However, fluvastatin inhibited the upregulation of type I IL-1 receptor mRNA and protein expression. Transfection experiments demonstrated that fluvastatin suppressed iNOS induction by the inhibition of promoter transactivation and mRNA stabilization. Fluvastatin reduced the expression of an iNOS gene antisense-transcript, which is involved in iNOS mRNA stability.

CONCLUSION

Results indicate that fluvastatin inhibits the induction of iNOS at both transcriptional and post-transcriptional steps, leading to the prevention of NO production. Fluvastatin may provide therapeutic potential in iNOS induction involved in various liver injuries.

alpha-lipoic acid prevents the induction of iNOS gene expression through destabilization of its mRNA in proinflammatory cytokine-stimulated hepatocytes

BACKGROUND/AIMS

α-Lipoic acid (α-LA) has been reported to reduce ischemia-reperfusion injury (IRI). Proinflammatory cytokines stimulate the induction of inducible nitric oxide synthase (iNOS) gene expression, leading to excess production of NO and resulting in liver injury including IRI. We hypothesized that inhibition of iNOS induction underlies the protective effects of α-LA on the liver. The objective was to investigate whether α-LA directly influences iNOS induction in cultured hepatocytes, which is used as a simple in vitro injury model, and the mechanism involved.

METHODS

Primary cultured rat hepatocytes were treated with interleukin (IL)-1β in the presence or absence of α-LA. The induction of iNOS and NO production and its signal were analyzed.

RESULTS

α-LA inhibited the expression of iNOS mRNA and protein dose- and time-dependently, resulting in decreases in NO production. α-LA had no effects on the degradation of IκB proteins and activation of NF-κB. In contrast, α-LA inhibited the upregulation of type I IL-1 receptor stimulated by IL-1β, although α-LA had no effect on Akt activation. Transfection experiments with iNOS promoter-luciferase constructs revealed that α-LA had no effect on the transactivation of the iNOS promoter, but decreased the stabilization of iNOS mRNA. Further, α-LA inhibited the expression of an iNOS gene antisense-transcript, which is involved in iNOS mRNA stability.

CONCLUSIONS

Results indicate that α-LA inhibits the induction of iNOS gene expression at a posttranscriptional step via iNOS mRNA stabilization, rather than promoter activation. It may provide useful therapeutic effects through the suppression of iNOS induction involved in liver injury.

Japanese herbal medicine, inchinkoto, inhibits inducible nitric oxide synthase induction in interleukin-1β-stimulated hepatocytes

AIM

  A herbal medicine, kampo inchinkoto (TJ-135), is used to treat jaundice and liver fibrosis in patients with cirrhosis. In the inflamed liver, proinflammatory cytokines stimulate the induction of inducible nitric oxide synthase (iNOS) gene expression. Over-production of nitric oxide (NO) by iNOS has been implicated as a factor in liver injury. We examined interleukin (IL)-1β-stimulated hepatocytes as a simple in vitro injury model to determine liver-protective effects of TJ-135. The objective was to investigate whether TJ-135 influences iNOS induction and to determine its mechanism.

METHODS

  Primary cultured rat hepatocytes were treated with IL-1β in the presence or absence of TJ-135. The induction of iNOS and its signaling pathway were analyzed.

RESULTS

  IL-1β produced increased levels of NO. This effect was inhibited by TJ-135, which exerted its maximal effects at 3 mg/mL. TJ-135 decreased the levels of iNOS protein and its mRNA expression. Experiments with nuclear extracts revealed that TJ-135 inhibited the translocation of nuclear factor-κB (NF-κB) to the nucleus and its DNA binding. TJ-135 also inhibited the activation of Akt, resulting in the reduction of type I IL-1 receptor mRNA and protein expression. Transfection experiments with iNOS promoter-luciferase constructs demonstrated that TJ-135 suppressed iNOS induction by inhibition of promoter transactivation and mRNA stabilization. TJ-135 reduced the expression of an iNOS gene antisense-transcript. Delayed administration or withdrawal of TJ-135 after IL-1β addition also inhibited iNOS induction.

CONCLUSIONS

  RESULTS indicate that TJ-135 inhibits the induction of iNOS at both transcriptional and post-transcriptional steps, leading to the prevention of NO production. TJ-135 may have therapeutic potential for various liver injuries through the suppression of iNOS induction.

Active hexose correlated compound inhibits the expression of proinflammatory biomarker iNOS in hepatocytes

BACKGROUND/AIMS

Excess production of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) has been implicated as proinflammatory biomarker in liver injury. The application of active hexose correlated compound (AHCC) as a functional food in complementary and alternative medicine has increased. The possibility that AHCC might inhibit iNOS induction was investigated as a potential liver-protective effect.

METHODS

Hepatocytes were isolated from rats by collagenase perfusion and cultured. Primary cultured hepatocytes were treated with interleukin-1β in the presence or absence of AHCC-sugar fraction (AHCC-SF).

RESULTS AND CONCLUSION

AHCC-SF inhibited the production of NO and reduced expressions of iNOS mRNA and its protein. AHCC-SF had no effects on either IκB degradation or nuclear factor-κB (NF-κB) activation. In contrast, AHCC-SF inhibited the upregulation of type I interleukin-1 receptor (IL-1RI) through the inhibition of Akt phosphorylation. Transfection experiments with iNOS promoter-luciferase constructs revealed that AHCC-SF reduced the levels of iNOS mRNA at both promoter transactivation and mRNA stabilization steps. AHCC-SF inhibited the expression of iNOS gene antisense transcript, which is involved in iNOS mRNA stabilization. These findings demonstrate that AHCC-SF suppresses iNOS gene expression through a IκB/NF-κB-independent but Akt/IL-1RI-dependent pathway, resulting in the reduction of NO production. AHCC-SF may have therapeutic potential for various liver injuries.

Remote or conventional ischemic preconditioning--local liver metabolism in rats studied with microdialysis

BACKGROUND

Ischemic preconditioning (IPC) of the liver decreases liver injury secondary to ischemia and reperfusion. An attractive alternative to IPC is remote ischemic preconditioning (R-IPC), but these two methods have not previously been compared.

MATERIAL AND METHODS

Eighty-seven rats were randomized into four groups: sham operated (n = 15), 1 h segmental ischemia (IRI, n = 24), preceded by IPC (n = 24), or R-IPC (n = 24) (to the left hindleg). IPC and R-IPC were performed with 10 min ischemia and 10 min of reperfusion. Analyses of liver microdialysate (MD), serum transaminase levels, and liver histology were made.

RESULTS

Rats treated with IPC and R-IPC had significantly lower AST, 71.5 (19.6) IU/L respective 96.6 (12.4) at 4 h reperfusion than those subjected to IRI alone, 155 (20.9), P = 0.0004 and P = 0.04 respectively. IPC also had lower ALT levels, 41.6 (11.3) IU/L than had IRI 107.4 (15.5), P = 0.003. The MD glycerol was significantly higher during ischemia in the R-IPC [759 (84) μM] and the IRI [732 (67)] groups than in the IPC 514 (70) group, P = 0.022 and P = 0.046 respectively. The MD glucose after ischemia was lower in the IPC group 7.1 (1.2) than in the IRI group 12.7 (1.6), P = 0.005. Preconditioning to the liver caused an direct increase in lactate, glucose and glycerol in the ischemic segment compared with the control segment an effect not seen in the R-IPC and IRI groups.

CONCLUSIONS

IPC affects glucose metabolism in the rat liver, observed with MD. IPC reduces liver cell injury during ischemic and reperfusion in rats. R-IPC performed over the same length of time as IPC does not have the same effect as the latter on ALT levels and MD glycerol; this may suggest that R-IPC does not offer the same protection as IPC in this setting of rat liver IRI.

Peroxidation of n-3 Polyunsaturated Fatty Acids Inhibits the Induction of iNOS Gene Expression in Proinflammatory Cytokine-Stimulated Hepatocytes

Eicosapentaenoic acid and docosahexaenoic acid (EPA/DHA), n-3 polyunsaturated fatty acids (PUFAs), have a variety of biological activities including anti-inflammatory and anticancer effects. We hypothesized that their peroxidized products contributed in part to anti-inflammatory effects. In the liver, the production of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) has been implicated as one of the factors in hepatic inflammation and injury. We examined whether the peroxidation of EPA/DHA influences the induction of iNOS and NO production in proinflammatory cytokine-stimulated cultured hepatocytes, which is in vitro liver inflammation model. Peroxidized EPA/DHA inhibited the induction of iNOS and NO production in parallel with the increased levels of their peroxidation, whereas unoxidized EPA/DHA had no effects at all. Peroxidized EPA/DHA reduced the activation of transcription factor, NF-κB, and the expression of the iNOS antisense transcript, which are involved in iNOS promoter transactivation (mRNA synthesis) and its mRNA stabilization, respectively. These findings demonstrated that peroxidized products of EPA/DHA suppressed the induction of iNOS gene expression through both of the transcriptional and posttranscriptional steps, leading to the prevention of hepatic inflammation.

Sivelestat suppresses iNOS gene expression in proinflammatory cytokine-stimulated hepatocytes

BACKGROUND

Recent evidence has indicated that sivelestat, a neutrophil elastase inhibitor, has liver-protective effects in a variety of liver injuries. Proinflammatory cytokines including interleukin (IL)-1β stimulate the induction of inducible nitric oxide synthase (iNOS) gene expression, leading to excess production of NO and resulting in liver damage. We hypothesized that inhibition of iNOS induction underlies the protective effects of sivelestat on the liver. The objective of this study was to investigate whether sivelestat directly influences iNOS induction in cultured hepatocytes, which is used as a simple in vitro injury model, and to determine the mechanism involved.

METHODS

Primary cultured rat hepatocytes were treated with IL-1β in the presence or absence of sivelestat. The induction of iNOS and its signaling pathway were analyzed.

RESULTS

Sivelestat inhibited the induction of iNOS mRNA and its protein, followed by decreased production of NO. Transfection and iNOS gene antisense-transcript experiments revealed that sivelestat reduced the levels of iNOS mRNA at both the promoter activation and mRNA stabilization steps. However, sivelestat had no effects on the degradation of IκB and nuclear translocation of NF-κB subunit p65, although it moderately blocked the activation of NF-κB. In contrast, sivelestat blocked the upregulation of IL-1 receptor I through the inactivation of phosphatidylinositol 3-kinase/Akt.

CONCLUSIONS

Delayed sivelestat addition experiments demonstrated that the destabilization of the iNOS mRNA contributed more significantly to the inhibitory effects of sivelestat than the reduction in iNOS mRNA synthesis. Sivelestat may provide useful therapeutic effects through the suppression of iNOS induction involved in liver injury.

A role for complement in the enhanced susceptibility of steatotic livers to ischemia and reperfusion injury

Hepatic steatosis typically renders the donor organ unusable, as donor organs with >30% steatosis are more likely to develop graft failure. The mechanisms leading to failure are not well defined, but steatosis enhances hepatic susceptibility to ischemia reperfusion injury (IRI). We investigated the role of complement in hepatic IRI in lean and steatotic (diet-induced) mice. Steatotic mice were significantly more susceptible to total warm hepatic IRI than lean mice as determined by serum alanine aminotransferase, histopathologically assessed damage, and 24-h survival. C3 deficiency protected both lean and steatotic mice from IRI, as determined by all measured outcomes. Furthermore, treatment of wild-type mice with the complement inhibitor CR2-Crry provided protection equivalent to that seen in C3-deficient mice. Importantly, although steatotic livers were much more susceptible to IRI than lean livers, by most measures there was no statistical difference between the level of IRI to steatotic or lean livers when complement was inhibited. To investigate the clinical relevance of these findings in the context of transplantation, we treated recipients of lean or steatotic liver grafts with saline or CR2-Crry. There was a marked reduction in graft inflammation and injury and significantly improved 7-day survival in CR2-Crry-treated recipients of either lean or steatotic grafts. These data indicate that complement plays a key role in the enhanced susceptibility of steatotic livers to IRI and suggest that complement inhibition represents a potential strategy to reduce the donor shortage by allowing the more routine use of marginal steatotic donor livers.