Bear bile powder attenuates senecionine-induced hepatic sinusoidal obstruction syndrome in mice.

Hepatic sinusoidal obstruction syndrome (HSOS) via exposure to pyrrolizidine alkaloids (PAs) is with high mortality and there is no effective treatment in clinics. Bear bile powder (BBP) is a famous traditional animal drug for curing a variety of hepatobiliary diseases such as cholestasis, inflammation, and fibrosis. Here, we aim to evaluate the protective effect of BBP against HSOS induced by senecionine, a highly hepatotoxic PA compound. Our results showed that BBP treatment protected mice from senecionine-induced HSOS dose-dependently, which was evident by improved liver histology including reduced infiltration of inflammatory cells and collagen positive cells, alleviated intrahepatic hemorrhage and hepatic sinusoidal endothelial cells, as well as decreased conventional serum liver function indicators. In addition, BBP treatment lowered matrix metalloproteinase 9 and pyrrole-protein adducts, two well-known markers positively associated with the severity of PA-induced HSOS. Further investigation showed that BBP treatment prevents the development of liver fibrosis by decreasing transforming growth factor beta and downstream fibrotic molecules. BBP treatment also alleviated senecionine-induced liver inflammation and lowered the pro-inflammatory cytokines, in which tauroursodeoxycholic acid played an important role. What's more, BBP treatment also decreased the accumulation of hydrophobic bile acids, such as cholic acid, taurocholic acid, glycocholic acid, as well. We concluded that BBP attenuates senecionine-induced HSOS in mice by repairing the bile acids homeostasis, preventing liver fibrosis, and alleviating liver inflammation. Our present study helps to pave the way to therapeutic approaches of the treatment of PA-induced liver injury in clinics.

Gynura segetum induces hepatic sinusoidal obstruction syndrome in mice by impairing autophagy.

PURPOSE: To investigate the underlying mechanism of hepatic sinusoidal obstruction syndrome (HSOS) induced by Gynura segetum by measuring autophagy in mouse models. METHODS: The model group was administered G. segetum (30 g/kg/d) by gavage, while the normal control group was administered an equal volume of saline daily for five weeks. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), hepatic histopathological examinations, and Masson staining were performed to evaluate liver injury. Liver intercellular adhesion molecule-1 (ICAM-1) and P-selectin were evaluated by immunohistochemistry. Hepatocellular apoptosis was assessed using the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Protein expression levels of autophagy markers were measured using Western blot analysis. RESULTS: Gynura segetum was found to significantly induce liver injury compared with control mice, as evidenced by the increase of serum transaminases, a decrease in triglyceride levels, and histopathological changes in mice. Gynura segetum remarkably induced hepatocellular apoptosis and upregulated the expressions of ICAM-1 and P-selectin and also downregulated the protein expression levels of LC3, Atg12 and cytoplasmic polyadenylation element binding protein. CONCLUSIONS: Our results suggested that G. segetum induced liver injury with HSOS, and it was partly due to its ability to impair the autophagy pathway.

Characterization of liver injury induced by a pyrrolizidine alkaloid in rats.

BACKGROUND: Pyrrolizidine alkaloids (PAs) are common phytotoxins. PA intoxication is reported to cause severe acute liver damage, typically known as hepatic sinusoidal obstruction syndrome (HSOS), but it remains obscure whether the acute liver damage may progress into chronic liver disease characterized by hepatic fibrosis. PURPOSE: This study aims to characterize the biochemical markers of liver injury and histological features of regressive and progressive liver fibrosis, and to examine changes in hepatic gene expression that may underpin mechanisms of fibrogenesis in rats induced by retrorsine (RTS), a representative toxic PA. STUDY DESIGN/METHODS: Rats were gavaged with RTS via two dosing regimens, i.e. a single dose of 40 mg/kg (Group 1) and two doses of 40 mg/kg and 20 mg/kg on day 0 and day 7 (Group 2), respectively. Rats receiving one (Group 3) or two (Group 4) doses of vehicle served as negative controls. The animals were followed for up to 16 weeks by serum biochemical analyses and histological examination, and gene expression assays of liver tissues. RESULTS: Acute liver injury on day 2 manifested as HSOS, characterized by sinusoidal dilation, endothelial cell damage, and elevated serum alanine aminotransferase activity and bilirubin levels. In Group 1, mild liver fibrosis developed at sinusoids and perisinusoidal space surrounding the central veins at week 1 and 2, and thereafter, all liver injury resolved gradually. In Group 2, liver fibrosis progressed within the 16-week observation period. No apparent liver injury was observed in Groups 3 and 4. Compared with negative control groups, RTS induced myofibroblastic activation, TGF-ß1 signaling, and changes in expression of matrix metalloproteinase 9 (MMP-9) and tissue inhibitor of metalloproteinase 1 (TIMP-1). These dynamic changes differed in Groups 1 and 2, corresponding with the regression and progression of liver fibrosis, respectively, in these groups. CONCLUSION: This study has provided in-vivo proof of concept that "one hit" and "two hits" of RTS lead to acute resolving liver injury and chronic progressive liver fibrosis, respectively. These animal models may serve as powerful tools for studying RTS toxicology and related preventive and therapeutic strategies and as positive controls for studying other PA- and non-PA-induced liver injury.

Gynura segetum induces hepatic sinusoidal obstruction syndrome in mice by impairing autophagy

ABSTRACT Purpose: To investigate the underlying mechanism of hepatic sinusoidal obstruction syndrome (HSOS) induced by Gynura segetum by measuring autophagy in mouse models. Methods: The model group was administered G. segetum (30 g/kg/d) by gavage, while the normal control group was administered an equal volume of saline daily for five weeks. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), hepatic histopathological examinations, and Masson staining were performed to evaluate liver injury. Liver intercellular adhesion molecule-1 (ICAM-1) and P-selectin were evaluated by immunohistochemistry. Hepatocellular apoptosis was assessed using the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Protein expression levels of autophagy markers were measured using Western blot analysis. Results: Gynura segetum was found to significantly induce liver injury compared with control mice, as evidenced by the increase of serum transaminases, a decrease in triglyceride levels, and histopathological changes in mice. Gynura segetum remarkably induced hepatocellular apoptosis and upregulated the expressions of ICAM-1 and P-selectin and also downregulated the protein expression levels of LC3, Atg12 and cytoplasmic polyadenylation element binding protein. Conclusions: Our results suggested that G. segetum induced liver injury with HSOS, and it was partly due to its ability to impair the autophagy pathway.

Gynura Rhizoma containing pyrrolizidine alkaloids induces the hepatic sinusoidal obstruction syndrome in mice via upregulating fibrosis-related factors.

Recently, hepatic sinusoidal obstruction syndrome (HSOS) caused by herbal preparations containing pyrrolizidine alkaloids (PAs), such as Gynura Rhizoma (Tusanqi), has gained global attention. However, the lack of a reliable and reproducible animal model has greatly hampered mechanistic studies. Therefore, we aimed to establish a reproducible HSOS mouse model and investigate the hepatotoxic mechanism. The model was established by intragastrical administration of Gynura Rhizoma extract, i.e., 1.0 g extract/kg per day (equal to 16.7 g crude drug/kg per day based on extraction rate and 49.1 mg PA/kg per day based on the total PA content in the extract determined) for 40 successive days. Then, the mice were sacrificed, and their blood samples and livers were collected for analyses. Using hematoxylin-eosin (HE) and Masson staining, scanning electron microscopy imaging, clinical biomarkers, and other assays, we showed that the HSOS was successfully induced in our mouse model. Furthermore, we detected the key factors involved in liver fibrosis in the mice, revealing significantly increased hydroxyproline concentration; elevated expression of α-smooth muscle actin (α-SMA) and fibrosis-related genes such as Collagen-1, Collagen-3, Mmp2, Mmp13, Timp1, Timp3, and Activin, upregulated Smad3 phosphorylation, and increased serum TGF-ß levels. Moreover, pro-inflammatory cytokines, including Tnf-α, Il-1ß, and Il-6, were also increased in the model. All these results demonstrate the key roles of the TGF-ß-Smad3 and inflammatory signaling pathways in this Gynura Rhizoma-induced HSOS mouse model, suggesting that blockade of fibrosis and/or inflammation should be an effective treatment for HSOS.

Hepatic veno-occlusive disease induced by Chinese medicinal herbs.

The potential hepatotoxic effects of products containing medicinal herbs, which are increasingly used without adequate control by health authorities, is well known. We report a case of toxic hepatic veno-occlusive disease (HVOD) presumably associated with the use of such herbal remedies.

Computed tomography findings of hepatic veno-occlusive disease caused by Sedum aizoon with histopathological correlation

This study investigated the value of computed tomography (CT) in the diagnosis and treatment of hepatic veno-occlusive disease (HVOD) caused by Sedum aizoon (SA). The clinical manifestations, treatment results, imaging findings, and histological findings of the liver were analyzed in 39 patients with HVOD caused by SA. Hepatomegaly, liver dysfunction, abdominal effusion, and geographic density changes on liver CT scans were found in all 39 patients. The pathological findings of histological liver examination included swelling and point-like necrosis of liver cells, significant expansion and congestion of the sinuses, endothelial swelling, and wall thickening with incomplete lumen occlusion of small liver vessels. CT geographic density changes were confirmed by histological examination of the liver in 18 patients. Sixteen patients with small amounts of ascites that started within 4 weeks of treatment recovered completely or significantly improved after symptomatic and supportive treatment. However, only 43.75% of the patients with larger amounts of ascites improved following symptomatic and supportive treatment. In conclusion, liver CT examination is a valuable, safe, and noninvasive tool for the diagnosis of HVOD caused by SA. In selected cases, liver CT examination may replace liver biopsy and histological analysis.

Computed tomography findings of hepatic veno-occlusive disease caused by Sedum aizoon with histopathological correlation.

This study investigated the value of computed tomography (CT) in the diagnosis and treatment of hepatic veno-occlusive disease (HVOD) caused by Sedum aizoon (SA). The clinical manifestations, treatment results, imaging findings, and histological findings of the liver were analyzed in 39 patients with HVOD caused by SA. Hepatomegaly, liver dysfunction, abdominal effusion, and geographic density changes on liver CT scans were found in all 39 patients. The pathological findings of histological liver examination included swelling and point-like necrosis of liver cells, significant expansion and congestion of the sinuses, endothelial swelling, and wall thickening with incomplete lumen occlusion of small liver vessels. CT geographic density changes were confirmed by histological examination of the liver in 18 patients. Sixteen patients with small amounts of ascites that started within 4 weeks of treatment recovered completely or significantly improved after symptomatic and supportive treatment. However, only 43.75% of the patients with larger amounts of ascites improved following symptomatic and supportive treatment. In conclusion, liver CT examination is a valuable, safe, and noninvasive tool for the diagnosis of HVOD caused by SA. In selected cases, liver CT examination may replace liver biopsy and histological analysis.

Regorafenib suppresses sinusoidal obstruction syndrome in rats.

BACKGROUND: Sinusoidal obstruction syndrome (SOS), a form of drug-induced liver injury related to oxaliplatin treatment, is associated with postoperative morbidity after hepatectomy. This study aimed to examine the impact of regorafenib, the first small-molecule kinase inhibitor to show efficacy against metastatic colorectal cancer, on a rat model of SOS. METHODS: Rats with monocrotaline (MCT)-induced SOS were divided into two groups according to treatment with either regorafenib (6 mg/kg) or vehicle alone, which were administered at 12 and 36 h, respectively, before MCT administration. Histopathologic examination and serum biochemistry tests were performed 48 h after MCT administration. Sinusoidal endothelial cells were evaluated by immunohistochemistry and electron microscopy. To examine whether regorafenib preserved remnant liver function, a 30% hepatectomy was performed in each group. RESULTS: The rats in the vehicle group displayed typical SOS features, whereas these features were suppressed in the regorafenib group. The total SOS scores were significantly lower in the regorafenib group than in the vehicle group. Immunohistochemistry and electron microscopy showed that regorafenib had a protective effect on sinusoidal endothelial cells. The postoperative survival rate after 7 d was significantly better in the regorafenib group than that in the vehicle group (26.7% versus 6.7%, P < 0.05). Regorafenib reduced the phosphorylation of extracellular signal-regulated kinase, which induced matrix metalloproteinase-9 (MMP-9) activation and decreased the activity of MMP-9, one of the crucial mediators of SOS development. CONCLUSIONS: Regorafenib suppressed MCT-induced SOS, concomitant with attenuating extracellular signal-regulated kinase phosphorylation, and MMP-9 activation, suggesting that regorafenib may be a favorable agent for use in combination with oxaliplatin-based chemotherapy.

Veno-occlusive disease of the liver in the absence of elevation in bilirubin in pediatric patients after hematopoietic stem cell transplantation.

Veno-occlusive disease (VOD) of the liver is a well-described and significant complication of hematopoietic stem cell transplantation (HSCT), with limited successful therapeutic options in severe cases. Prompt diagnosis and initiation of treatment is crucial to restrict the extent of disease. However, a subset of patients may not meet all current diagnostic criteria at presentation, and waiting for these to be met may delay therapy. We retrospectively reviewed 794 HSCT patients treated at our institution between 2003 and 2013, identifying 17 (2.1%) who developed VOD. Of these, 5 (29%) were noted to have an absence of elevated bilirubin at the time of VOD diagnosis and reversal of portal venous flow on ultrasound. Median total and conjugated bilirubin at VOD diagnosis were 1.0 and 0.2 mg/dL, respectively. All 5 patients were subsequently diagnosed with multiorgan failure associated with VOD, including 1 with encephalopathy. Four were treated with intravenous high-dose methylprednisolone (500 mg/m(2) per dose every 12 hours for 6 doses). One patient received defibrotide therapy in addition to steroids and another supportive care alone. VOD resolved in 4 of 5 patients, with median time to resolution of VOD, defined as recovery of all organ function and normalization of bilirubin and portal venous flow, of 8 days. Two patients died later from progressive primary disease and chronic graft-versus-host disease, respectively. We conclude that a high index of suspicion for VOD should be maintained in patients despite lack of bilirubin elevation in the presence of other diagnostic criteria such as hepatomegaly, abdominal pain, ascites, or weight gain. Early ultrasound evaluation in these patients may lead to more timely diagnosis and therapeutic interventions.

Pathogenesis of FOLFOX induced sinusoidal obstruction syndrome in a murine chemotherapy model.

BACKGROUND & AIMS: Sinusoidal obstruction syndrome (SOS) following oxaliplatin based chemotherapy can have a significant impact on post-operative outcome following resection of colorectal liver metastases. To date no relevant experimental models of oxaliplatin induced SOS have been described. The aim of this project was to establish a rodent model which could be utilised to investigate mechanisms underlying SOS to aid the development of therapeutic strategies. METHODS: C57Bl/6 mice, maintained on a purified diet, were treated with intra-peritoneal FOLFOX (n=10), or vehicle (n=10), weekly for five weeks and culled one week following final treatment. Sections of the liver and spleen were fixed in formalin and paraffin embedded for histological analysis. The role of oxidative stress on experimental-induced SOS was determined by dietary supplementation with butylated hydroxyanisole and N-acetylcysteine. RESULTS: FOLFOX treatment was associated with the development of sinusoidal dilatation and hepatocyte atrophy on H&E stained sections of the liver in keeping with SOS. Immunohistochemistry for p21 demonstrated the presence of replicative senescence within the sinusoidal endothelium. FOLFOX induced endothelial damage leads to a pro-thrombotic state within the liver associated with upregulation of PAI-1 (p<0.001), vWF (p<0.01) and Factor X (p<0.001), which may contribute to the propagation of liver injury. Dietary supplementation with the antioxidant BHA prevented the development of significant SOS. CONCLUSIONS: We have developed the first reproducible model of chemotherapy induced SOS that reflects the pathogenesis of this disease in patients. It appears that the use of antioxidants alongside oxaliplatin based chemotherapy may be of value in preventing the development of SOS in patients with colorectal liver metastases.

Expression of MMP-9 in hepatic sinusoidal obstruction syndrome induced by Gynura segetum.

BACKGROUND AND OBJECTIVE: Hepatic sinusoidal obstruction syndrome (HSOS) is characterized by painful hepatomegaly, ascites, increased body weight, and jaundice. Gynura segetum (Compositae), a plant widely used in Chinese traditional medicine, often leads to the development of HSOS. However, the mechanism is unclear. The aim was to study the role of matrix metalloproteinase-9 (MMP-9) in the onset of HSOS induced by Gynura segetum. METHODS: Twenty-five male Sprague-Dawley rats were randomly divided into two groups. Twenty were exposed to 600 mg/kg daily Gynura segetum extract solution for three weeks; five control rats were exposed to tap water alone. Liver sections were evaluated by light microscopy with a modified scoring system. Routine transmission electron microscopy (TEM) methods were used to evaluate the ultrastructual features of fixed liver tissue, and blood samples were collected to determine liver enzyme concentrations. MMP-9 expression was assessed by both immunohistochemical staining and enzyme-linked immunosorbent assay (ELISA) methods. RESULTS: A stable and reproducible rat model of HSOS was achieved by long-term exposure to Gynura segetum extract. The treated rats presented clinical symptoms and the histopathological manifestation of HSOS, including abnormal liver enzyme concentrations (alanine aminotransferase (ALT): (84.8±13.62) vs. (167.0±72.63) U/L, P<0.05; aspartate aminotransferase (AST): (27.6±6.31) vs. (232.8±108.58) U/L, P<0.05). Hematoxylin and eosin (H&E) staining and TEM together revealed deposition of red blood cells, the damage and destruction of hepatic sinusoidal endothelial cells, collapse of hepatic sinusoids, hemorrhage of subendothelial cells, atrophy and destruction of hepatocytes, etc. Compared with controls, the expression of MMP-9 in the blood sample, the lung and liver tissues of HSOS rats was increased. CONCLUSIONS: MMP-9 may have an important role in early pathological changes of HSOS, and thus the onset of the disease.

Prophylactic sesame oil attenuates sinusoidal obstruction syndrome by inhibiting matrix metalloproteinase-9 and oxidative stress.

BACKGROUND: Sinusoidal obstruction syndrome (SOS) occurs in patients undergoing hematopoietic cell transplantation and chemotherapy. The chemotherapeutic drugs oxaliplatin and cyclophosphamide cause SOS. Sesame oil is a nutrient-rich antioxidant popular in alternative medicine. It contains sesamin, sesamol, and sesamolin, all of which contribute to its antioxidant property. The authors investigated the protective effect of prophylactic sesame oil against monocrotaline-induced SOS in rats. METHODS: Male Sprague-Dawley rats were gavaged with a single dose of sesame oil (0.5, 1, 2, or 4 mL/kg). One hour later, those rats were gavaged with monocrotaline (90 mg/kg) to induce SOS. Control rats were treated with saline only. Aspartate transaminase, alanine transaminase, laminin, collagen, myeloperoxidase, nitrate content, lipid peroxidation, glutathione levels, matrix metalloproteinase (MMP)-9, and tissue inhibitor of matrix metalloproteinases (TIMP)-1 were assessed 48 hours after the monocrotaline gavage. RESULTS: All tested parameters except TIMP-1, laminin, collagen, and glutathione were higher in monocrotaline-treated rats than in saline-only-treated control rats. In sesame oil-treated rats, all tested parameters except TIMP-1, laminin, collagen, and glutathione were significantly attenuated compared with monocrotaline-only-treated rats. Sesame oil downregulated MMP-9 expression but upregulated TIMP-1 expression in monocrotaline-only-treated rats. In addition, a histological analysis of liver tissue samples showed that sesame oil showed significant protection. CONCLUSION: A single prophylactic dose of sesame oil protects against SOS by downregulating MMP-9 expression, upregulating TIMP-1 expression, and inhibiting oxidative stress.

Successful treatment with danhong injection for hepatic veno-occlusive disease.

Hepatic veno-occlusive disease (HVOD) is a clinical syndrome characterized as hepatomegaly, ascites, jaundice and elevation of hepatic enzymes as an outcome from fibrous obliteration of small centrilobular hepatic venules. It is recognized as a rare but life-threatening complication of organ transplantation, tumor eradication chemotherapy and is associated with haematopoietic stem cell transplantation (SCT). Recent researches report that ingestion of plants which contain pyrrolizidine alkaloids (PAs) is associated with the onset of HVOD with unclear pathogenesis. Nowadays, there is no effective therapeutic strategy for HVOD besides supportive care using diuretics or albumin. In our case, a 42-year-old woman administered a concoction of Chinese traditional medicine supposed to contain PAs, was found to develop HVOD confirmed by liver biopsy. A therapeutic strategy was developed using Danhong injection, accompanied with supportive care, and obtained a favorable response manifesting as regression of symptoms and decline of hepatic enzymes. Danhong injection, a Chinese medical product exerting a milder anticoagulation and antithrombotic effect, is beneficial to HVOD probably by promoting microcirculation, ameliorating liver function and inhibiting hepatic fibrosis.

Effect of ligustrazine on mice model of hepatic veno-occlusive disease induced by Gynura segetum.

BACKGROUND AND AIM: To investigate the therapeutic effect of ligustrazine on hepatic veno-occlusive disease (HVOD) induced by Gynura segetum and the possible mechanism of it. METHODS: Female Kunming mice (115) were randomly divided into four groups, gavaged with 30 g/kg per day Gynura segetum (group A), 30 g/kg per day Gynura segetum + 100 mg/kg per day ligustrazine (group B), 30 g/kg per day Gynura segetum + 200 mg/kg per day ligustrazine (group C) or 30 mL/kg per day phosphate-buffered saline (PBS) (group D). Thirty days later, all of the mice were killed. Blood samples and livers were harvested. Histological changes were evaluated by light microscopy. Liver function was measured, and the expression of tissue factor (TF), early growth response factor-1 (Egr-1) and nuclear factor-KBp65 (NF-KBp65) were determined by reverse transcription-polymerase chain reaction and Western blot. RESULTS: A total of 24 mice in group A developed HVOD. Compared with the controls, they had increased liver ratio, serum total bilirubin (TBIL), direct bilirubin (DBIL), transaminase and decreased albumin (ALB) (P < 0.05). Administration of ligustrazine improved the clinical signs and biochemistry parameters in a dose-dependent manner. Compared with group A, the expression of TF, Egr-1 and NF-KB p65 decreased in groups B and C (P < 0.05). CONCLUSION: Ligustrazine has a therapeutic effect on HVOD, improving clinical manifestations and liver function. The possible mechanism may be that ligustrazine could reduce the expression of TF by downregulating the expression of transcription factors: Egr-1 and NF-KB p65.

[Clinical analysis of hepatic veno-occlusive disease induced by Sedum aizoon].

OBJECTIVE: To discuss the clinical characteristics and precautionary measures of hepatic veno-occlusive disease (VOD) caused by Sedum aizoon. METHOD: The VOD induced by Sedum aizoon were reports in 41 patients comimg from national medical journals from 1998 to 2007 and their use and dose were analyzed. RESULT: The results shows that ADR of Sedum aizoon was serious. VOD has relationship with it, s dose use time the age of the patients and individual difference. CONCLUSION: To avoid of VOD induced by Sedum aizoon, it should be done through strengthening study on pharmacology and toxicology of Sedum aizoon. Enhancing patients of safety awareness, standardizing usage and dosage to guide the clinically rational use of drugs.

A case report of hepatic veno-occlusive disease after ingesting dainties.

Hepatic veno-occlusive disease (HVOD) is rarely encountered and easily misjudged as Budd-Chiari syndrome. It is often related to stem cell transplantation in recent years. We report a case of HVOD that is related to ingestion of some palatable local dishes. The diagnosis was confirmed by liver biopsy pathology with specific observation of inflammatory changes and fibrosis of venules intima, dilated sinusoids and central veins. Chronic diarrhea is unique for this case as a result of ingesting harmful stuffs. This case demonstrated that supervision and instruction of food recipe and traditional medicine are crucial, and prompt diagnosis, supportive care and specific treatment are essential to decreasing the morbidity and mortality of HVOD.

The efficacy and safety of comfrey.

Herbal medication has gathered increasing recognition in recent years with regard to both treatment options and health hazards. Pyrrolizidine alkaloids have been associated with substantial toxicity after their ingestion as tea and in the setting of contaminated cereals have led to endemic outbreaks in Jamaica, India and Afghanistan. In Western Europe, comfrey has been applied for inflammatory disorders such as arthritis, thrombophlebitis and gout and as a treatment for diarrhoea. Only recently was the use of comfrey leaves recognized as a substantial health hazard with hepatic toxicity in humans and carcinogenic potential in rodents. These effects are most likely due to various hepatotoxic pyrrolizidine alkaloids such as lasiocarpine and symphytine, and their related N-oxides. The mechanisms by which toxicity and mutagenicity are conveyed are still not fully understood, but seem to be mediated through a toxic mechanism related to the biotransformation of alkaloids by hepatic microsomal enzymes. This produces highly reactive pyrroles which act as powerful alkylating agents. The main liver injury caused by comfrey (Symphytum officinale) is veno-occlusive disease, a non-thrombotic obliteration of small hepatic veins leading to cirrhosis and eventually liver failure. Patients may present with either acute or chronic clinical signs with portal hypertension, hepatomegaly and abdominal pain as the main features. Therapeutic approaches include avoiding intake and, if hepatic failure is imminent, liver transplantation. In view of the known serious hazards and the ban on distributing comfrey in Germany and Canada, it is difficult to understand why comfrey is still freely available in the United States.