Tumor necrosis factor-induced lethal hepatitis: pharmacological intervention with verapamil, tannic acid, picotamide and K76COOH

Antimicrobial properties and phenolic contents of medicinal plants used by the Venda people for conditions related to venereal diseases

ETHNOPHARMACOLOGY RELEVANCE

Many people are infected by venereal diseases and the human immunodeficiency virus (HIV) in rural areas. Sexual transmitted diseases are considered a disgrace in the community because of the stigmas attached to them. Indigenous people tend to use several medicinal plants to treat these infectious diseases rather than western medicines.

AIM OF THE STUDY

This study was aimed to evaluate the antibacterial, antifungal, antigonococcal, HIV-type 1 reverse transcriptase (RT) and to determine phenolic content of twelve medicinal plants used by the Venda people to treat venereal diseases.

MATERIALS AND METHODS

The dried plant materials of twelve medicinal plants were extracted with petroleum ether (PE), dichloromethane (DCM), 80% ethanol (EtOH) and water. The extracts were evaluated for their antimicrobial properties against two Gram-positive (Bacillus subtilis and Staphylococcus aureus), three Gram-negative (Neisseria gonorrhoeae, Escherichia coli and Klebsiella pneumoniae) bacteria and a fungus Candida albicans. The phenolic contents including total phenolics, flavonoids, gallotannins and condensed tannins of the methanolic extracts of the same plants were also determined.

RESULTS

DCM and EtOH extracts of Bolusanthus speciosus bark and stems exhibited good activity (<0.1mg/ml) against Escherichia coli and Staphylococcus aureus with MIC values ranging from 0.098 to 0.012 mg/ml. The DCM extracts of Bolusanthus speciosus bark showed the best activity against Candida albicans with MIC and MFC values of 0.012 mg/ml. Water and 50% methanol extracts of Acacia karroo bark, Bolusanthus speciosus stems and Ximenia caffra roots and leaves showed good RT inhibition percentages (>70%) at 1mg/ml. All tested extracts exhibited dose dependent IC(50) values ranging from (0.1 to 0.6 mg/ml). Almost all plant species investigated contained phenolic compounds, which were greater than 5mg/g with the exception of Adansonia digitata bark and Aloe chabaudii roots. The highest level of flavonoids (11.9 μg/g) were detected in Ximenia caffra leaves. Whereas the highest amount of gallotannins were detected in Ekebergia capensis bark (69 μg/g). Condensed tannins were higher in Ekebergia capensis bark and Ximenia caffra roots (0.47 and 0.48% respectively). Adansonia digitata bark and Aloe chabaudii roots exhibited low levels of phenolic compounds as well as antimicrobial activities.

CONCLUSION

The presented results offer supporting evidence for effective use of selected plant extracts. More in vitro confirmatory tests using other assays and/or in vivo tests are required. Toxicity studies are urgently needed to support the safe usage of these plants.

Differential effects of tannic acid on cisplatin induced nephrotoxicity in rats

Cisplatin is a widely used antineoplastic drug. Major drawback of cisplatin therapy is its nephrotoxicity. The objective of this study was to check the effect of tannic acid on cisplatin induced nephrotoxicity. Post-treatment of tannic acid prevents cisplatin (5mg/kg) induced nephrotoxicity and decreases poly(ADP-ribose) polymerase cleavage, phosphorylation of p38 and hypoacetylation of histone H4. In contrast, co-treatment of tannic acid potentiates the nephrotoxicity. Comparative nephrotoxicity studies show that co-treatment of tannic acid with reduced dose of cisplatin (1.5mg/kg) developed almost similar nephrotoxicity. MALDI protein profiling of plasma samples provides indirect evidence that tannic acid co-treatment increases bioavailability of cisplatin.

Molecular mechanisms of the chemopreventive effect on hepatocellular carcinoma development in Mdr2 knockout mice

Dietary antioxidants and selenium compounds were shown to have a therapeutic effect against hepatocellular carcinoma in several mouse models. We tested the effects of tannic acid and selenomethionine on hepatocellular carcinoma development in Mdr2 knockout (Mdr2-KO) mice. Mdr2-KO and age-matched Mdr2 heterozygous control mice were fed with tannic acid or selenomethionine during the first 3 months of life. Then, several mice from each group were sacrificed, and liver tissue samples were removed for analysis. The remaining mice were fed a regular diet until the age of 16 months, at which time the number and size of liver tumors were determined. Liver tissue samples of 3-month-old mice were subjected to gene expression profiling analysis using cDNA macroarrays containing probes for 240 genes that regulate responses to oxidative stress and inflammation or lipid metabolism. Both tannic acid and selenomethionine had partial chemopreventive effect on development of hepatocellular carcinoma in Mdr2-KO mice: they reduced the incidence of large tumor nodules (diameter >1 cm) at age 16 months. Both agents inhibited gene expression and reversed up-regulation of many genes that control inflammation or response to oxidative stress in Mdr2-KO livers at age 3 months. This inhibitory effect on gene expression correlated with the ability of agents to reduce incidence of large tumors: selenomethionine was more active than tannic acid in both aspects. Understanding the molecular mechanism of chemoprevention effect could improve our therapeutic modalities while using these agents.

Studies on hepatoprotective, antispasmodic and calcium antagonist activities of the aqueous-methanol extract of Achillea millefolium

The crude extract of Achillea millefolium (Am.Cr) was studied for its possible hepatoprotective effect against d-galactosamine (d-GalN) and lipopolysaccharide (LPS) induced hepatitis in mice and antispasmodic effect in isolated gut preparations to rationalize some of the folklore uses. Co-administration of d-GalN (700 mg/kg) and LPS (25 microg/kg) produced 100% mortality in mice. Pre-treatment of animals with Am.Cr (300 mg/kg) reduced the mortality to 40%. Co-administration of d-GalN (700 mg/kg) and LPS (1 microg/kg) significantly raised the plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels compared with values in the control group (p < 0.05). Pre-treatment of mice with Am.Cr (150-600 mg/kg) significantly prevented the toxins induced rise in plasma ALT and AST (p < 0.05). The hepatoprotective effect of Am.Cr was further verified by histopathology of the liver, which showed improved architecture, absence of parenchymal congestion, decreased cellular swelling and apoptotic cells, compared with the toxin group of animals. In isolated rabbit jejunum preparations, Am.Cr caused a concentration-dependent (0.3-10 mg/mL) relaxation of both spontaneous and K(+)-induced contractions as well as shifting the Ca(++) concentration-response curves (CRCs) to the right, similar to that caused by verapamil. These results indicate that the crude extract of Achillea millefolium exhibits a hepatoprotective effect, which may be partly attributed to its observed calcium channel blocking activity.

Gallotannin inhibits the expression of chemokines and inflammatory cytokines in A549 cells

Tannins are plant-derived water-soluble polyphenols with wide-ranging biological activities. The mechanisms underlying the anti-inflammatory effect of tannins are not fully understood and may be the result of inhibition of poly(ADP-ribose) (PAR) glycohydrolase (PARG), the main catabolic enzyme of PAR metabolism. Therefore, we set out to investigate the mechanism of the anti-inflammatory effect of gallotannin (GT) in A549 cells with special regard to the role of poly(ADP-ribosyl)ation. Using an inflammation-focused low-density array and reverse transcription-polymerase chain reaction, we found that GT suppressed the expression of most cytokines and chemokines in cytokine-stimulated A549 cells, whereas the PARP inhibitor PJ-34 only inhibited few transcripts. Activation of the transcription factors, nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1), was blocked by GT, whereas PJ-34 only suppressed NF-kappaB activation but not AP-1 activation. GT also inhibited IkappaB phosphorylation and nuclear translocation of NF-kappaB, but PJ-34 had no effect on these upstream events. In the AP-1 pathway, GT treatment, even in the absence of cytokines, caused maximal phosphorylation of c-Jun N-terminal kinase and c-Jun. GT also caused a low-level phosphorylation of p38, extracellular signal-regulated kinases 1 and 2, activating transcription factor2, and cAMP-response element-binding protein but inhibited cytokine-induced phosphorylation of these kinases and transcription factors. GT inhibited protein phosphatases 1 and 2A, which may explain the increased phosphorylation of mitogen-activated protein kinase and their substrates. GT exerted potent antioxidant effect but failed to cause PAR accumulation. In summary, the potent inhibitory effects of GT on the transcription of cytokine and chemokine genes are probably not related to PARG inhibition. Inhibition of AP-1 activation and upstream signaling events may be responsible for the effects of GT.

Inhibitory effect of picroside II on hepatocyte apoptosis

AIM

To investigate the influence of picroside II on hepatocyte apoptosis and its mechanism.

METHODS

Morphological changes and quantification of apoptotic cells were determined under transmission electron microscopy and flow cytometry respectively. DNA fragmentation was visualized by agarose gel electrophoresis. Semi-quantitative reverse transcription-PCR (RT-PCR) was used to analyze the expression of bcl-2 and bax genes. The content of manganese-superoxide dismutase (SOD) in liver mitochondria was detected by the Marland method. The content of malonic aldehyde (MDA) and the protein level in liver tissue were determined by thiobarbituric acid colorimetry and Lowry method.

RESULTS

Picroside II decreased the levels of alanine aminotransferase and aspartate aminotransferase in the serum resulting from acute-liver injured mice induced with D-GalN and LPS; it also reduced the content of MDA, and thus, enhanced the activity of SOD. Picroside II 10 mg/kg was found to protect hepatocytes against apoptosis in a dose-dependent manner; it up-regulated the expression of bcl-2 genes, thus increased the bcl-2/bax ratio.

CONCLUSION

Picroside II can protect hepatocytes against injury and prevent hepatocytes from apoptosis. It might by upregulating the bcl-2 gene expression and antioxidation.

Cytoprotective effect of gallotannin in oxidatively stressed HaCaT keratinocytes: the role of poly(ADP-ribose) metabolism

Oxidative stress-induced cytotoxicity is mediated in part by accelerated poly-ADP ribosylation. Peroxynitrite and hydrogen peroxide cause DNA breakage triggering the activation of the DNA nick sensor enzyme poly(ADP-ribose) polymerase-1 (PARP-1). Overactivation of PARP-1 leads to cell dysfunction and cell death mainly due to depletion of NAD(+) (the substrate of PARP-1) and ATP. PARP-1 attaches most ADP-ribose residues onto itself, leading to downregulation of enzyme activity. Here, we have investigated the role of poly(ADP-ribose) glycohydrolase (PARG), the poly(ADP-ribose)-catabolyzing enzyme in oxidative stress-induced cytotoxicity in HaCaT cells. We have found that inhibition of PARG by gallotannin (GT) (50 microM) provided significant cytoprotection to peroxynitrite- or hydrogen peroxide-treated HaCaT cells, as assessed by lactate dehydrogenase release and propidium iodide uptake (parameters of necrotic cell death) as well as caspase activation (apoptotic parameter). GT pretreatment has also inhibited the depletion of cellular NAD(+) pools in hydrogen peroxide- or peroxynitrite-treated HaCaT cells. GT caused the accumulation of poly(ADP-ribose) and concomitant inhibition in cellular PARP activity in oxidatively stressed cells. Therefore, PARG is likely to contribute to maintaining the active state of PARP-1 by continuously removing inhibitory ADP-ribose residues from PARP-1.

Calcium and Its Role in the Nuclear Translocation and Activation of Cytosolic Phospholipase A2in Cells Rendered Sensitive to TNF-Induced Apoptosis by Cycloheximide

In these experiments, we investigated the role of calcium as a second messenger in the apoptotic activation of cytosolic phospholipase A(2) (cPLA(2)). As our model, we used a murine fibroblast cell line (C3HA) that was induced to undergo apoptosis by a combination of TNF and cycloheximide. Using fura 2 Ca(2+) imaging, we found strong evidence for an intracellular calcium response after 1 h of treatment, which correlated with the onset of phosphatidylserine externalization, but preceded effector procaspase processing by several hours. The response was strongest in the perinuclear region, where mean levels rose 83% (144 +/- 14 nM in untreated cells vs 264 +/- 39 nM in treated), while cells displaying morphological evidence of apoptosis had the highest levels of calcium (250-1000 nM). Verapamil blocked this response, indicating an extracellular source for the calcium. Fluorescence microscopy revealed a pattern of nuclear translocation of cPLA(2) during apoptosis, which was also blocked by verapamil, indicating an important role for calcium in this process. In addition, we found that verapamil prevented the release of [(3)H]arachidonic acid from C3HA cells induced to undergo apoptosis by the chemotherapeutic agents vinblastine, melphalan, and cis-platinum. Together, these data suggest that calcium is important for cPLA(2) activation by diverse apoptotic stimuli.

Role of thromboxane derived from COX-1 and -2 in hepatic microcirculatory dysfunction during endotoxemia in mice

Although thromboxanes (TXs), whose synthesis is regulated by cyclooxygenase (COX), have been suggested to promote inflammation in the liver, little is known about the role of TXA(2) in leukocyte endothelial interaction during endotoxemia. The present study was conducted to investigate the role of TXA(2) as well as that of COX in lipopolysaccharide (LPS)-induced hepatic microcirculatory dysfunction in male C57Bl/6 mice. We observed during in vivo fluorescence microscopic study that LPS caused significant accumulation of leukocytes adhering to the hepatic microvessels and non-perfused sinusoids. Levels of serum alanine transaminase (ALT) and tumor necrosis factor alpha (TNF alpha) also increased. LPS raised the TXB(2) level in the perfusate from isolated perfused liver. A TXA(2) synthase inhibitor, OKY-046, and a TXA(2) receptor antagonist, S-1452, reduced LPS-induced hepatic microcirculatory dysfunction by inhibiting TNF alpha production. OKY-046 suppressed the expression of an intercellular adhesion molecule (ICAM)-1 in an LPS-treated liver. In thromboxane prostanoid receptor-knockout mice, hepatic responses to LPS were minimized in comparison with those in their wild-type counterparts. In addition, a selective COX-1 inhibitor, SC-560, a selective COX-2 inhibitor, NS-398, and indomethacin significantly attenuated hepatic responses to LPS including microcirculatory dysfunction and release of ALT and TNF alpha. The effects of the COX inhibitors on hepatic responses to LPS exhibited results similar to those obtained with TXA(2) synthase inhibitor, and TXA(2) receptor antagonist. In conclusion, these results suggest that TXA(2) is involved in LPS-induced hepatic microcirculatory dysfunction partly through the release of TNF alpha, and that TXA(2) derived from COX-1 and COX-2 could be responsible for the microcirculatory dysfunction during endotoxemia.

Bilirubin release induced by tumor necrosis factor in combination with galactosamine is toxic to mice

Application of tumor necrosis factor (TNF) in combination with galactosamine (GalN) in mice causes severe apoptosis of hepatocytes, resulting in complete destruction of the liver. Administration of high levels of unconjugated bilirubin and abnormally high production of unconjugated bilirubin have been reported to cause liver damage and are associated with several human pathologies. Serum alanine aminotransferase as well as total and direct bilirubin levels in mice were determined. Bilirubin levels are shown to significantly increase after a challenge with TNF/GalN in mice. Pretreatment with a heme oxygenase-1 inhibitor significantly prevents this release in bilirubin and offers significant protection against TNF/GalN-induced lethality. A correlation between the release of unconjugated bilirubin and the toxicity accompanied with this release is provided.

Involvement of a serine protease, but not of neutrophil elastase, in tumor necrosis factor-induced lethal hepatitis and induction of platelet-activating factor

BACKGROUND/AIMS

Tumor necrosis factor (TNF) plays an essential role in several types of acute and chronic hepatitis. Our aims in the present study were to elucidate the mechanism by which TNF leads to acute lethal hepatitis, thereby focusing on the role of serine proteases and platelet-activating factor (PAF).

METHODS

All experiments were performed in a model of acute hepatitis, induced by TNF in combination with D-(+)-galactosamine (GalN). Neutrophil elastase (NE)-deficient mice, generated by gene targeting were used in the studies.

RESULTS

We found that a serine protease plays an essential mediating role in the in vivo TNF effect as alpha1-antitrypsin (alpha1-AT), soybean trypsin inhibitor (STI) and turkey trypsin inhibitor (TTI), confer complete protection. alpha1-AT and TTI, but not STI, reduce PAF blood levels, induced by TNF/GalN, which is compatible with an elastase-like serine protease involvement in PAF synthesis. In our search for relevant serine proteases we believed that NE was an excellent candidate protease. However, we found that TNF/GalN-induced lethality is not attenuated in mice deficient in NE.

CONCLUSIONS

The data suggest that TNF-induced lethal hepatitis is accompanied by increases in circulating PAF and plasma clotting time, and mediated by a serine protease, but not by NE.