Simultaneous analysis of clivorine and its four microsomal metabolites by high-performance liquid chromatography

Hepatic sinusoidal obstruction syndrome associated with consumption of Gynura segetum

BACKGROUND & AIMS

One major cause of hepatic sinusoidal obstruction syndrome (HSOS) is the intake of pyrrolizidine alkaloid (PA)-containing products. Over 8000 PA-induced HSOS cases have been reported worldwide and at least 51 among them were suspected to be attributed to exposure to the Chinese medicine 'Tusanqi'. PA-induced hepatotoxicity involves cytochrome P450-mediated metabolic activation of PAs to electrophilic pyrrolic metabolites which react with macromolecules, such as proteins. However, no studies have found such protein adduction in HSOS patients. We report one HSOS case confirmed by liver biopsy, where the patient claimed taking 'Tusanqi' as self-medication.

METHODS

The herb was analyzed by HPLC-MS, and its induced hepatotoxicity in rats was assessed by monitoring the alteration of serum ALT level and liver morphology. Blood pyrrole-protein adducts were determined by UPLC-MS.

RESULTS

The herb the patient consumed was identified as Gynura segetum, an erroneous substitute of non-PA-containing Sedum aizoon, called 'Tusanqi'. Hepatotoxic PAs senecionine and seneciphylline were detected in G. segetum. In the PA-exposed patient, serum pyrrole-protein adducts were detected by a newly developed analytical approach. The animal study showed a good correlation of liver injury with the ingestion of G. segetum.

CONCLUSIONS

For the first time, serum pyrrole-protein adducts were unequivocally detected in a PA-induced HSOS patient, and such adducts show a potential to be developed as a biomarker for the assessment of PA-induced HSOS. Similar to the well-known case of aristolochic acid-poisoning, the observed HSOS was confirmed to arise from the consumption of PA-containing G. segetum, an erroneous substitute of non-PA-containing S. aizoon.

Protection of S-adenosyl methionine against the toxicity of clivorine on hepatocytes

In this study, we investigated the protective effects of S-adenosyl-l-methionine (SAM), which is a precursor of cellular reduced glutathione (GSH), against the hepatotoxicity of pyrrolizidine alkaloid clivorine. MTT assay showed that SAM (5μM) prevented the cytotoxicity of clivorine on human normal liver L-02 cells. DNA fragmentation assay showed that SAM (5μM) improved clivorine-induced L-02 cell apoptosis, and the results of Western blot showed that SAM (5μM) decreased clivorine-induced caspase-3 activation. Cellular GSH analysis showed that when L-02 cells were exposed to different concentrations (0, 3, 10, 30, 50 and 100μM) of clivorine for 48h, cellular GSH was decreased in a concentration-dependent manner, while SAM (5μM) enhanced 50μM clivorine decreased cellular GSH. Further MTT assay showed that 5mM GSH and 5mM N-acetyl-l-cysteine (NAC) both had protective effects against clivorine-induced hepatotoxicity. Our results suggest that SAM has protective effects against the hepatotoxicity of clivorine possibly by enhancing cellular GSH level and increasing cellular defensive ability against clivorine-induced cytotoxicity.

The toxic effect of pyrrolizidine alkaloid clivorine on the human embryonic kidney 293 cells and its primary mechanism

Clivorine is an otonecine-type pyrrolizidine alkaloid (PA) isolated from the Chinese medicinal plant Ligularia hodgsonii Hook., and our previous reports have shown its toxicity on human normal liver L-02 cells. It is generally believed that biotransformation of PAs to its metabolites is required for their toxicity; thus, there is nearly no report about the toxicity of clivorine on other non-hepatic cells in vitro. The aim of this study is to observe the toxicity of clivorine on the non-hepatic human embryonic kidney 293 (HEK293) cell that is of epithelial origin, and its primary mechanism. Our results showed that clivorine significantly reduced HEK293 cell viability, but there was no detectable apoptotic DNA ladder and cleaved fragments of caspase-3 and caspase-9 in clivorine-treated cells, which indicates the toxicity of clivorine is not due to inducing apoptosis. The results of western blot showed that clivorine induced sustained p38, c-Jun N-terminal kinase (JNK) and extracellular signal-related kinases (ERK1/2) phosphorylation in a concentration- and time-dependent manner, and the JNK inhibitor SP600125 significantly augmented the toxicity of clivorine. Our results suggest that clivorine itself has direct toxicity on HEK293 cells, and phosphorylated JNK may play some role in counteracting the toxicity of clivorine on HEK293 cells.

Identification of five hepatotoxic pyrrolizidine alkaloids in a commonly used traditional Chinese medicinal herb, Herba Senecionis scandentis (Qianliguang)

Senecio scandens Buch.-Ham is a plant source for a commonly used traditional Chinese medicinal (TCM) herb Qianliguang. A TCM herbal proprietary product containing Qianliguang as the major herb for the treatment of sinusitis has been used in China for several decades, and has also been exported to other regions and countries worldwide. In the present study, the aqueous extract of S. scandens collected in the Shanxi Province of China was determined, for the first time, to contain hepatotoxic and tumorigenic pyrrolizidine alkaloids (PAs) by using high-performance liquid chromatography/mass spectrometric (HPLC/MS) analysis in various scanning modes. A total of nine toxic and two non-toxic PAs were detected in the aqueous extract of S. scandens, of which six PAs, namely neoplatyphylline, senecionine, senecionine N-oxide, seneciphylline, seneciphylline N-oxide and senkirkine, were unequivocally characterized, while other PAs were tentatively assigned as jacobine, jacozine N-oxide (or erucifoline N-oxide), 7-tigloylplatynecine, usaramine and an isomer of yamataimine. The estimated total content of toxic PAs in S. scandens was 10.82 microg/g herb, which was significantly higher than that (> or =1 microg/g herb) recommended by Belgium and Germany not to be used clinically. Among the PAs definitively identified, senecionine, seneciphylline, and senkirkine are known tumorigens capable of inducing liver tumors in experimental animals, while seneciphylline N-oxide and senecionine N-oxide are probably tumorigenic due to their potential conversion into seneciphylline and senecionine via metabolic reduction in the body. Thus, the current finding of the presence of toxic/tumorigenic PAs in S. scandens challenges the safety of using this TCM herb and its proprietary products.

Deacetylclivorine: A Gender-Selective Metabolite of Clivorine Formed in Female Sprague-Dawley Rat Liver Microsomes

Clivorine, a naturally occurring pyrrolizidine alkaloid, causes liver toxicity via its metabolic activation to generate toxic metabolite (pyrrolic ester). Female Sprague-Dawley (SD) rats are reported to be less susceptible to clivorine intoxication than male SD rats. However, the biochemical mechanism causing such gender difference is largely unknown. The present study investigated hepatic microsomal metabolism of clivorine in female rats to delineate the mechanism of the gender difference. Two pathways, which directly metabolize clivorine, were observed. First, the metabolic activation to produce the toxic pyrrolic ester followed by formations of bound pyrroles, dehydroretronecine, 7-glutathionyldehydroretronecine, and clivoric acid were found in female rats, and CYP3A1/2 isozymes were identified to catalyze the metabolic activation. Compared with male rats ( approximately 21%), the metabolic activation in female rats was significantly lower ( approximately 4%) possibly because of significantly lower CYP3A1/2 levels expressed in female rats. Second, a direct hydrolysis to generate the novel female rat-specific metabolite deacetylclivorine was shown as the predominant pathway ( approximately 16% clivorine metabolism) in female rat liver microsomes and was determined to be mediated by microsomal hydrolase A. Furthermore, when the metabolic activation was completely inhibited by ketoconazole, the amount of deacetylclivorine formed in a 1-h incubation significantly increased from 19.44 +/- 3.00 to 54.87 +/- 9.30 nmol/mg protein, suggesting that the two pathways compete with each other. Therefore, the lower susceptibility of female SD rats to clivorine intoxication is suggested to be caused by the significantly higher extent of the direct hydrolysis and a lower degree of the metabolic activation.

Comparison of the miniaturised techniques capillary electrochromatography and capillary liquid chromatography for the chiral separation of chlorthalidone

The aim of this study was to compare the miniaturised techniques, capillary electrochromatography (CEC) and capillary liquid chromatography (CLC), for the chiral separation of chlorthalidone. In both cases, hydroxypropyl-beta-cyclodextrin was used as a chiral selector in the mobile phase, while an achiral stationary phase was used. Earlier, this separation was already optimised in CEC. Now, the separation was optimised in CLC. The influence of the organic modifier content and the cyclodextrin concentration on the separation was studied by means of a central composite design. Optimal separation conditions were determined, after response modelling, from the response surface contour plots. When these conditions were compared with those of the CEC optimisation, we can see the potential of using CLC as a chiral separation technique since less chiral selector was used, faster separations were obtained and better repeatability was observed in comparison with its electrical-driven counterpart.