Tu-San-Qi (Gynura japonica): the culprit behind pyrrolizidine alkaloid-induced liver injury in China

Mass spectrometric analysis strategies for pyrrolizidine alkaloids

Pyrrolizidine alkaloids (PAs) in food and natural preparations have received widespread attention due to their hepatotoxicity, genotoxicity, and embryotoxicity. Mass spectrometry (MS), as a high resolution, high sensitive, and high throughput detection tool, has been the most commonly used technique for the determination of PAs. The continuous advancement of new technologies, methods, and strategies in the field of MS has contributed to the improvement of the analytical efficiency and methodological enhancement of PAs. This paper provides an overview of the structure, toxicity properties and commonly employed analytical methods, focusing on the concepts, advances, and novel techniques and applications of MS-based methods for the analysis of PAs. Additionally, the remaining challenges, future perspectives, and trends for PA detection are discussed. This review provides a reference for toxicological studies of PAs, content monitoring, and the establishment of quality control and safety standards for herbal and food products.

Insight into pyrrolizidine alkaloids degradation and the chemical structures of their degradation products using ultra high performance liquid chromatography and Q-Exactive Orbitrap mass spectrometry

Pyrrolizidine alkaloids (PAs), released into the environment by donor plants, are absorbed by crops or transported by animals, posing a global food safety concern. Photolysis is an effective way to eliminate harmful substances in the environment or food. Photolysis happens as PAs move among plants, environment and crops. In this study, we first investigated the photolysis and hydrolysis of 15 PAs and identified their degradation products via ultra-high performance liquid chromatography and Q-Exactive Orbitrap mass spectrometry. PAs were degraded under UV radiation but minimally affected by visible light from a xenon lamp, and solvent pH had little impact on their photolysis. PAs were stable in neutral and acidic solutions but degraded by 50% within 24 h in alkaline conditions. The degradation products of PAs were mainly PAs/PANOs isomers and some minor byproducts. Cytotoxicity and computational analysis revealed isomers had similar toxicity, with minor products being less toxic. This study is a precursor for revealing the potential PAs degradation dynamics in the environment and food products, providing a reference for systematic evaluations of potential health and ecological risks of their degradation products.

Functional metabolomics characterizes the contribution of farnesoid X receptor in pyrrolizidine alkaloid-induced hepatic sinusoidal obstruction syndrome

Consumption of herbal products containing pyrrolizidine alkaloids (PAs) is one of the major causes for hepatic sinusoidal obstruction syndrome (HSOS), a deadly liver disease. However, the crucial metabolic variation and biomarkers which can reflect these changes remain amphibious and thus to result in a lack of effective prevention, diagnosis and treatments against this disease. The aim of the study was to determine the impact of HSOS caused by PA exposure, and to translate metabolomics-derived biomarkers to the mechanism. In present study, cholic acid species (namely, cholic acid, taurine conjugated-cholic acid, and glycine conjugated-cholic acid) were identified as the candidate biomarkers (area under the ROC curve 0.968 [95% CI 0.908-0.994], sensitivity 83.87%, specificity 96.55%) for PA-HSOS using two independent cohorts of patients with PA-HSOS. The increased primary bile acid biosynthesis and decreased liver expression of farnesoid X receptor (FXR, which is known to inhibit bile acid biosynthesis in hepatocytes) were highlighted in PA-HSOS patients. Furtherly, a murine PA-HSOS model induced by senecionine (50 mg/kg, p.o.), a hepatotoxic PA, showed increased biosynthesis of cholic acid species via inhibition of hepatic FXR-SHP singling and treatment with the FXR agonist obeticholic acid restored the cholic acid species to the normal levels and protected mice from senecionine-induced HSOS. This work elucidates that increased levels of cholic acid species can serve as diagnostic biomarkers in PA-HSOS and targeting FXR may represent a therapeutic strategy for treating PA-HSOS in clinics.

Detoxification and underlying mechanisms towards toxic alkaloids by Traditional Chinese Medicine processing: A comprehensive review

BACKGROUND

Alkaloids have attracted enduring interest worldwide due to their remarkable therapeutic effects, including analgesic, anti-inflammatory, and anti-tumor properties, thus offering a rich source for lead compound design and new drug discovery. However, some of these alkaloids possess intrinsic toxicity. Processing (Paozhi) is a pre-treatment step before the application of herbal medicines in traditional Chinese medicine (TCM) clinics, which has been employed for centuries to mitigate the toxicity of alkaloid-rich TCMs.

PURPOSE

To explore the toxicity phenotypes, chemical basis, mode of action, detoxification processing methods, and underlying mechanisms, we can gain crucial insights into the safe and rational use of these toxic alkaloid-rich herbs. Such insights have the great potential to offer new strategies for drug discovery and development, ultimately improving the quality of life for millions of people.

METHODS

Literatures published or early accessed until December 31, 2023, were retrieved from databases including PubMed, Web of Science, and CNKI. The following keywords, such as "toxicity", "alkaloid", "detoxification", "processing", "traditional Chinese medicine", "medicinal plant", and "plant", were used in combination or separately for screening.

RESULTS

Toxicity of alkaloids in TCM includes hepatotoxicity, nephrotoxicity, neurotoxicity, cardiotoxicity, and other forms of toxicity, primarily induced by pyrrolizidines, quinolizidines, isoquinolines, indoles, pyridines, terpenoids, and amines. Factors such as whether the toxic-alkaloid enriched part is limited or heat-sensitive, and whether toxic alkaloids are also therapeutic components, are critical for choosing appropriate detoxification processing methods. Mechanisms of alkaloid detoxification includes physical removal, chemical decomposition or transformation, as well as biological modifications.

CONCLUSION

Through this exploration, we review toxic alkaloids and the mechanisms underlying their toxicity, discuss methods to reduce toxicity, and unravel the intricate mechanisms behind detoxification. These offers insights into the quality control of herbs containing toxic alkaloids, safe and rational use of alkaloid-rich TCMs in clinics, new strategies for drug discovery and development, and ultimately helping improve the quality of life for millions of people.

Gynura segetum induces hepatic sinusoidal obstruction syndrome in a child: A case report

RATIONALE

Hepatic sinusoidal obstruction syndrome (HSOS), which includes hepatic stasis and portal hypertension, is a rare vascular disorder of the liver. It is often associated with hematopoietic stem cell transplantation. It is also possible to treat this disease using Chinese herbal medicines that contain pyrrolizidine alkaloids (PAs). This disease is extremely rare in children and poses a serious threat to their health. To our knowledge, this is the first case of HSOS in a child with PAs.

PATIENT CONCERNS

We report a 4-year-old boy suffering from abdominal pain, hepatomegaly, massive ascites, elevated liver enzyme level, and severe portal hypertension as a result of the consumption of Gynura segetum (also known as Tusanqi in Chinese, a traditional herbal medicine containing PAs).

DIAGNOSES

The child was finally diagnosed with PA-HSOS based on pathological diagnosis and imaging examination.

INTERVENTION

With active symptomatic and supportive care and sequential anticoagulation therapy, the abdominal distension and liver function improved in the patient.

OUTCOMES

The patient was eventually recovered. The levels of liver enzymes, hemoglobin, and bilirubin were normal, and the international normalized ratio fluctuated between 2.0 and 3.0 during 1-year follow-up after discharge.

LESSONS

This case report emphasizes the prevention of Chinese herb-induced liver injury in children and the importance of active long-term sequential anticoagulant therapy to reduce the progressive damage of PA-HSOS in the liver.

The toxicokinetic and metabolism of structurally diverse pyrrolizidine alkaloids in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Pyrrolizidine alkaloids (PAs) are a group of phytotoxins present in about 3% of flowering plants worldwide. Ingestion of PA-containing herbal products may lead to hepatotoxicity. Notably, the toxicokinetic (TK) behaviors, especially pyrrole-protein adducts (PPAs) having the same structure but generated from metabolic activation of different PAs, significantly affect the toxicity of structurally diverse PAs, therefore studying them in their pure form is preferable to extracts to stratify toxic potency of different PAs co-existing in herbal extracts. However, previous studies mainly focus on the establishment of TK profiles of the intact PAs, revealing less or no kinetic information on the main PA metabolites (PA N-oxides) and PPAs which mediate PA-induced hepatotoxicity. In this study, PPA was measured as the biomarker of PA exposure and PA-induced toxicity.

AIM OF STUDY

This study aims to investigate the TK difference between structurally diverse PAs of retronecine-type PAs: retrorsine (RTS) and monocrotaline (MCT), and otonecine-type PA: clivorine (CLI), and their toxicity-related metabolite PPAs and PA N-oxides, the main metabolite of retronecine-type PAs, for the establishment of a more accurate risk assessment of PAs exposure.

MATERIALS AND METHODS

The TK studies were conducted using rats through intravenous (i.v.) or oral (p.o.) administration of PAs at 20 mg/kg. The main TK parameters of PAs and PA N-oxides were determined from plasma concentration-time profiles, and the kinetic profiles of PPAs were assessed from both plasma and erythrocyte concentration-time profiles.

RESULTS

MCT demonstrated the slowest but the highest extent of absorption among the three PAs, while RTS demonstrated a similar absorption rate with a lower extent than CLI. For elimination, MCT demonstrated a similar elimination rate as RTS but the lowest extent of elimination among the three PAs, and CLI exhibited significantly faster elimination than MCT and RTS. Moreover, the formation of PA N-oxide, which only occurs in retronecine-type PAs, was remarkably less in MCT-treated rats compared to RTS-treated ones. Of note, the retronecine-type RTS and MCT induced more PPAs via p.o. than i.v. administration route, whereas the otonecine-type CLI showed the opposite trend.

CONCLUSION

Dramatic TK differences, including not only PAs but also PA N-oxides and the derived protein adduct PPAs, were found among structurally diverse PAs in rats, laying the basis for varied hepatotoxic potencies induced by different PA-containing herbal products. Notably, our findings for the first time uncovered that oral administration of retronecine-type PAs might cause severer toxicity compared with the intravenous route, which warrants further in-depth exploration.

Anticoagulant therapy likely increases risk of bleeding in Gynura segetum-induced hepatic sinus obstruction syndrome

This study aimed to analyze the clinical characteristics of Gynura segetum (Tusanqi)-induced hepatic sinusoidal obstruction syndrome (HSOS) and the benefits and risks of anticoagulant therapy for Tusanqi-induced HSOS. This was a retrospective analysis of 49 patients with Tusanqi-induced HSOS who were treated with anticoagulation or standard therapy between July 2006 and December 2022. Clinical manifestations included abdominal pain (n = 47) and peritoneal or pleural effusion (n = 46); 2 patients died. Nineteen patients requested standard medical treatment, while 30 were treated with anticoagulants. HSOS resolved within 6 months in 22 patients but did not resolve in 27 patients. The resolution rate was higher in the anticoagulant than standard treatment group (P = .037). Logistic regression analysis revealed that a history of chronic liver disease or treatment increased the risk of poor outcomes. Bleeding complications occurred in 6 patients in the anticoagulant treatment group. Early diagnosis and anticoagulant treatment are beneficial for rapid recovery after Tusanqi-induced HSOS. However, anticoagulant treatment is associated with the risk of multisite bleeding.

Diagnosis, toxicological mechanism, and detoxification for hepatotoxicity induced by pyrrolizidine alkaloids from herbal medicines or other plants

Pyrrolizidine alkaloids (PAs) are one type of phytotoxins distributed in various plants, including many medicinal herbs. Many organs might suffer injuries from the intake of PAs, and the liver is the most susceptible one. The diagnosis, toxicological mechanism, and detoxification of PAs-induced hepatotoxicity have been studied for several decades, which is of great significance for its prevention, diagnosis, and therapy. When the liver was exposed to PAs, liver sinusoidal endothelial cells (LSECs) loss, hemorrhage, liver parenchymal cells death, nodular regeneration, Kupffer cells activation, and fibrogenesis occurred. These pathological changes classified the PAs-induced liver injury as acute, sub-acute, and chronic type. PAs metabolic activation, mitochondria injury, glutathione (GSH) depletion, inflammation, and LSECs damage-induced activation of the coagulation system were well recognized to play critical roles in the pathological process of PAs-induced hepatotoxicity. A lot of natural compounds like glycyrrhizic acid, (-)-epicatechin, quercetin, baicalein, chlorogenic acid, and so on were demonstrated to be effective in alleviating PAs-induced liver injury, which rendered them huge potential to be developed into therapeutic drugs for PAs poisoning in clinics. This review presents updated information about the diagnosis, toxicological mechanism, and detoxification studies on PAs-induced hepatotoxicity.

Histological evaluation of pyrrolizidine alkaloid-induced hepatic sinusoidal obstruction syndrome: Correlation with Drum Tower Severity Scoring

BACKGROUND

Hepatic sinusoidal obstruction syndrome induced by pyrrolizidine alkaloids (PA-HSOS) is a complication of drug-induced liver damage. Few studies have examined the relationship between pathological changes and clinical circumstances in PA-HSOS. The Drum Tower Severity Scoring System (DTSS) was developed using prognostic indicators from clinical treatment outcomes. We hypothesized that the severity of pathological damage is consistent with DTSS.

AIMS

We aimed to improve our understanding and assessment of vascular liver injury disease histopathology by studying larger sample sizes of human histopathological samples. We also wanted to confirm the link between histopathological findings and DTSS.

METHODS

The study included 62 patients with PA-HSOS who underwent transjugular liver biopsy. Their hepatic pathological tissues were evaluated. Analyses of linear regression and Spearman's correlation were employed to examine the relationship between DTSS and pathological characteristics.

RESULTS

Clinical performance and the DTSS score were used to determine histopathological severity. The sinusoidal congestion area (SCA), central venous endothelial injury (CVEI), and fibrinoid exudation in congestion foci (FECF) were significant indicators. SCA was linearly related to the DTSS score.

CONCLUSION

Our findings show that hepatic pathological characteristics correlate with DTSS scores in PA-HSOS. SCA, CVEI, and FECF may be helpful for determining PA-HSOS severity.

Melatonin attenuates monocrotaline-induced hepatic sinusoidal obstruction syndrome in rats via activation of Sirtuin-3

Melatonin possesses potent hepatoprotective properties, but it remains to be elucidated whether melatonin has a therapeutic effect on monocrotaline (MCT)-induced hepatic sinusoidal obstruction syndrome (HSOS). In this study, male Sprague Dawley rats were intraperitoneally injected with melatonin or the same volume of vehicle at 0 and 24 h after MCT intragastric administration. Next, hematoxylin-eosin staining and electron microscopy were performed to evaluate the hepatic sinusoidal injury of rats. Endothelial cell marker RECA-1 was observed by immunohistochemistry. Hepatic oxidative stress was analyzed by detecting malondialdehyde, glutathione S-transferase, and reactive oxygen species. Assessment of liver function was carried out by analysis of serum aspartate aminotransferase, alanine aminotransferase, total bilirubin, and albumin levels. Real-time polymerase chain reaction and Western blot analysis were used to identify liver Sirtuin-3 (SIRT3) and active matrix metallopeptidase 9 (MMP-9) expression. Besides, liver sinusoidal endothelial cells (LSECs) were used for the in vitro functional verification experiment. Specifically, liver histology of the melatonin-treated groups showed that the pathological damages caused by MCT were significantly attenuated, total HSOS scores were decreased, and the elevation of serum hyaluronic acid observed in the model group was also reduced. Moreover, melatonin treatment also improved the survival of rats after partial hepatectomy. Administration of melatonin ameliorated MCT-induced LSECs injury, hepatic oxidative stress, and hepatic dysfunction. Furthermore, melatonin treatment increased SIRT3 expression while attenuating MMP-9 activity in liver tissues. Cell experiment also demonstrated that SIRT3 might mediate the protective effect of melatonin on LSECs. Collectively, our study provided the potential rationale for the application of melatonin for the prevention of MCT-induced HSOS.

Prognostic risk factors for patients with hepatic sinusoidal obstruction syndrome caused by pyrrolizidine alkaloids

Pyrrolizidine alkaloids induced hepatic sinusoidal obstruction syndrome (PA-HSOS) often occurs after consuming herbs or a dietary supplement containing the plant Tu-San-Qi. Limited data exists to identify patients with fatal outcomes for early interventions. We aimed to analyze the predictors for 3-month survival. We retrospectively enrolled PA-HSOS patients in 5 hospitals and extracted data from the onset of PA-HSOS to 36 months. Outcome measurements were 3-month and 36-month survival rates, baseline prognostic predictors for survival, and the effects of anticoagulant therapy. Among 49 enrollees, the median age was 60 and 49% male. At the onset of PA-HSOS, patients with Child-Turcotte-Pugh (CTP) class of A, B, or C were 8.2% (4/49), 42.8% (21/49) and 49.0% (24/49), respectively. None of them received a transjugular intrahepatic portosystemic shunt or a liver transplant. The 3-month and 36-month survival rates were 86% and 76%, respectively. Compared to the CTP class A or B, class C at baseline independently predicted lower survival rates at both 3 and 36 months. However, anticoagulation therapy treatment within the first 3 months independently predicted significantly higher survival rates at both time points. CTP class C and anticoagulant therapy were the independent predictors for short-term and long-term survival. Anticoagulant therapy could decrease mortality rate of CTP class C patients. The greatest benefit of anticoagulant evaluated by 3-month survival rate was in patients with CTP class C compared with those without treatment (93% vs 40%, P = .009). There were no bleeding complications reported in patients treated with the anticoagulant.

Idiopathic hypereosinophilic syndrome with hepatic sinusoidal obstruction syndrome: A case report and literature review

BACKGROUND

Hypereosinophilic syndrome (HES) is classified as primary, secondary or idiopathic. Idiopathic HES (IHES) has a variable clinical presentation and may involve multiple organs causing severe damage. Hepatic sinusoidal obstruction syndrome (HSOS) is characterized by damage to the endothelial cells of the hepatic sinusoids of the hepatic venules, with occlusion of the hepatic venules, and hepatocyte necrosis. We report a case of IHES with HSOS of uncertain etiology.

CASE SUMMARY

A 70-year-old male patient was admitted to our hospital with pruritus and a rash on the extremities for > 5 mo. He had previously undergone antiallergic treatment and herbal therapy in the local hospital, but the symptoms recurred. Relevant examinations were completed after admission. Bone marrow aspiration biopsy showed a significantly higher percentage of eosinophils (23%) with approximately normal morphology. Ultrasound-guided hepatic aspiration biopsy indicated HSOS. Contrast-enhanced computed tomography (CT) of the upper abdomen showed hepatic venule congestion with hydrothorax and ascites. The patient was initially diagnosed with IHES and hepatic venule occlusion. Prednisone, low molecular weight heparin and ursodeoxycholic acid were given for treatment, followed by discontinuation of low molecular weight heparin due to ecchymosis. Routine blood tests, biochemical tests, and imaging such as enhanced CT of the upper abdomen and pelvis were reviewed regularly.

CONCLUSION

Hypereosinophilia may play a facilitating role in the occurrence and development of HSOS.

Clinicopathological characteristics and diagnosis of hepatic sinusoidal obstruction syndrome caused by Tusanqi - Case report and literature review

Tusanqi-induced hepatic sinusoidal obstruction syndrome (HSOS) is caused by exposure to pyrrolizidine alkaloids (PAs) and manifests as abdominal distension, liver pain, ascites, jaundice, and hepatomegaly. Pathologically, hepatic congestion and sinusoidal occlusion are observed in HSOS. We summarized the clinical characteristics of 124 patients with HSOS caused by Tusanqi in China between 1980 and 2019, along with those of 831 patients from seven English case series. The main clinical manifestations of PA-HSOS included abdominal pain, ascites, and jaundice. Common imaging features included characteristic heterogeneous density, slender hepatic veins, and other nonspecific changes. The acute stage is primarily manifested as hepatic sinus congestion and necrosis. Meanwhile, the persistence of hepatic sinus congestion and the onset of perisinusoidal fibrosis were observed during the repair stage. Finally, the persistence of hepatic sinusoidal fibrosis and resultant central hepatic vein occlusion were observed in the chronic stage. The new Nanjing standard for PA-HSOS incorporates the history of PA consumption and imaging features and eliminates weight gain and the serum total bilirubin value. Preliminary clinical validation of the Nanjing standard for PA-HSOS diagnosis revealed a sensitivity and specificity of 95.35 and 100%, respectively.

Transjugular Intrahepatic Portosystemic Shunt Benefits for Hepatic Sinusoidal Obstruction Syndrome Associated with Consumption of Gynura Segetum: a Propensity Score-Matched Analysis

PURPOSE

Pyrrolidine alkaloids-related hepatic sinusoidal obstruction syndrome (PA-HSOS) is associated with a high mortality rate without standardized therapy. The efficacy of transjugular intrahepatic portosystemic shunts (TIPS) remains controversial. The study aimed to explore the risk factors influencing the clinical response in patients with PA-HSOS related to Gynura segetum (GS) to assess the disease prognosis at an early stage and to evaluate the efficacy of TIPS in these patients.

METHODS

This study retrospectively enrolled patients diagnosed with PA-HSOS between January 2014 and June 2021 with a clear history of exposure to GS. Univariate and multivariate logistic regression analyses were used to evaluate the risk factors influencing the clinical response in patients with PA-HSOS. Propensity score matched (PSM) was performed to compensate for differences in baseline characteristics between patients with and without TIPS. The primary outcome was the clinical response defined as the disappearance of ascites with normal total bilirubin levels and/or a reduction of elevated transaminase levels < 50% within 2 weeks.

RESULTS

A total of 67 patients were identified in our cohort with a clinical response rate of 58.2%. Of these, thirteen patients were assigned to the TIPS group and 54 to the conservative treatment group. Logistic regression analysis revealed that TIPS treatment (P = 0.047), serum globulin levels (P = 0.043), and prothrombin time (P = 0.001) were independent factors influencing clinical response. After PSM, there was a higher long-term survival rate of patients (92.3% vs. 51.3%, P = 0.021) and a shorter hospital stay (P = 0.043), but a high trend in hospital costs (P = 0.070) in the TIPS group. The 6-month survival probability in patients undergoing TIPS therapy was more than ninefold higher than in patients without receiving that treatment [hazard ratio (95% CI) = 9.304 (4.250, 13.262), P < 0.05].

CONCLUSIONS

TIPS therapy may be an effective treatment option for patients with GS-related PA-HSOS.

Potential biomarkers screening of Polygonum multiflorum radix-induced liver injury based on metabonomics analysis of clinical samples

ETHNOPHARMACOLOGICAL RELEVANCE

Polygonum multiflorum Radix (PMR) is the dried root tuber of Polygonum multiflorum Thunb., which has been used in the clinic for a variety of pharmacological activities. However, Polygonum multiflorum Radix-induced liver injury (PMR-ILI) has been reported in recent years, which has limited its clinical use to some extent. The occurrence of PMR-ILI is not universal, so finding the different metabolic characteristics between PMR-ILI and Polygonum multiflorum Radix-tolerance group (PMR-T) is very important for the PMR rational clinical application and PMR-ILI early clinical diagnosis.

METHODS

In this study, 6 clinical plasma samples of PMR-ILI and 13 PMR-T were collected and analyzed by high-resolution liquid chromatography-mass spectrometry. Firstly, the differential metabolites of the two groups were screened by conventional screening methods such as multivariate statistical analysis. Secondly, the characteristic metabolites with greater contribution, correlation with liver injury and high sensitivity were screened by correlation analysis with clinical liver injury indicators, random forest analysis, and receiver operating characteristic curve (ROC).

RESULTS

After multivariate statistical analysis and screening analysis, 29 differential metabolites were identified. Compared with PMR-T group, the metabolism of glycerol and phospholipid, glutamine and glutamate, phenylalanine, sphingolipid and tryptophan in PMR-ILI group were disturbed. After correlation analysis with liver injury indexes and random forest screening, 8 potential biomarkers closely related to clinical liver injury were obtained. Finally, 3 potential biomarkers with high expression in PMR-ILI, hypoxanthine, LysoPC(P-16:0/0:0) and taurochenodesoxycholic acid, were screened out through the analysis of ROC, which can provide a basis for the early clinical diagnosis.

CONCLUSION

Based on the analysis of the PMR-ILI and PMR-T plasma samples by LC-MS, three biomarkers of clinical liver injury of Polygonum multiflorum Radix were selected: hypoxanthine, LysoPC(P-16:0/0:0) and taurochenodeoxycholic acid.

Comparative Pharmacokinetic Study of Two Pyrrolizidine Alkaloids Lasiocarpine and Heliotrine in Rats

Lasiocarpine (LAS) and heliotrine (HEL) are two different ester types of toxic pyrrolizidine alkaloids (PAs): open-chain diester and monoester. However, the pharmacokinetics of these two types of PAs in rats have not been reported. In the present study, two LC-MS/MS methods for determining LAS and HEL were established and validated. The methods exhibited good linearity, accuracy, and precision and were then applied to a comparative pharmacokinetic study. After intravenous administration to male rats at 1 mg/kg, the AUC_0-t values of LAS and HEL were 336 ± 26 ng/mL × h and 170 ± 5 ng/mL × h. After oral administration at 10 mg/kg, the AUC_0-t of LAS was much lower than that of HEL (18.2 ± 3.8 ng/mL × h vs. 396 ± 18 ng/mL × h), while the C_max of LAS was lower than that of HEL (51.7 ± 22.5 ng/mL × h vs. 320 ± 26 ng/mL × h). The absolute oral bioavailability of LAS was 0.5%, which was significantly lower than that of HEL (23.3%). The results revealed that the pharmacokinetic behaviors of LAS differed from that of HEL.

Targeting erythrocyte-mediated hypoxia to alleviate lung injury induced by pyrrolizidine alkaloids

Pyrrolizidine alkaloids (PAs) are widely distributed natural toxins and have been extensively studied for their hepatotoxicity. However, PA-induced pulmonary toxicity remains less studied regarding the initiating mechanism and treatment approaches. Our previous study demonstrated the formation of pyrrole-hemoglobin adducts after PA exposure in vivo, which is suspected to affect the oxygen-carrying capacity of erythrocytes [red blood cells (RBCs)] consequently. The present study aimed to investigate the effects of PAs on the oxygen-carrying capacity of RBCs and the potential of targeting RBC-mediated hypoxia to alleviate PA-induced lung injury. First, rats were treated with retrorsine (RTS) or monocrotaline (MCT) intravenously at 0.2 mmol/kg. The results of Raman spectrometry analysis on blood samples revealed both RTS and MCT significantly reduced the oxygen-carrying capacity of RBCs. Further, MCT (0.2 mmol/kg) was orally given to the rats with or without pretreatment with two doses of erythropoietin (Epo, 500 IU/kg/dose every other day), an RBC-stimulating agent. Biochemical and histological results showed pretreatment with Epo effectively reduced the cardiopulmonary toxicity induced by MCT. These findings provide the first evidence that adduction on hemoglobin, and the resulting RBC damage and impaired oxygen-carrying capacity, are the major initiating mechanism underlying PA-induced pulmonary arterial hypertension (PAH), while targeting the RBC damage is a potential therapeutic approach for PA-induced lung injury.

Formation of DHP-DNA Adducts from Rat Liver Microsomal Metabolism of 1,2-Unsaturated Pyrrolizidine Alkaloid-Containing Plant Extracts and Dietary Supplements

1,2-Unsaturated pyrrolizidine alkaloids (PAs) are carcinogenic phytochemicals. We previously determined that carcinogenic PAs and PA N-oxides commonly form a set of four (±)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP)-DNA adducts, namely, DHP-dG-3, DHP-dG-4, DHP-dA-3, and DHP-dA-4. This set of DHP-DNA adducts has been implicated as a potential biomarker of PA-induced liver tumor initiation from metabolism of individual carcinogenic PAs. To date, it is not known whether this generality occurs from metabolism of PA-containing plant extracts. In this study, we investigate the rat liver microsomal metabolism of nine PA-containing plant extracts and two PA-containing dietary supplements in the presence of calf thymus DNA. The presence of carcinogenic PAs and PA N-oxides in plant extracts was first confirmed by LC-MS/MS analysis with selected reaction monitoring mode. Upon rat liver microsomal metabolism of these PA-containing plant extracts and dietary supplements, the formation of this set of DHP-DNA adducts was confirmed. Thus, these results indicate that metabolism of PA-containing plant extracts and dietary supplements can generate DHP-dG-3, DHP-dG-4, DHP-dA-3, and DHP-dA-4 adducts, thereby potentially initiating liver tumor formation.

Inflammation Intensifies Monocrotaline-Induced Liver Injury

Pyrrolizidine alkaloids (PAs) are the most common toxins of plant origin, and it is evident that PAs pollute soil, water, nearby plants, and derived foods. Cases of human poisoning due to ingestion of PA-contaminated foods have been reported in several countries. Monocrotaline (MCT) is a pyrrolizidine alkaloid from the plants of Crotalaria genus that causes hepatic and cardiopulmonary toxicities, and the exhibition of the toxicities requires the metabolic activation by CYP3A4 to form electrophilic dehydro-monocrotaline (DHM). The present study demonstrated that myeloperoxidase (MPO) also participated in the bioactivation of MCT. N-Chloromonocrotaline was detected in both HClO/MCT incubations and MPO/H2O2/MgCl2/MCT incubations. DHM-derived N-acetylcysteine (NAC) conjugates were detected in the above incubations fortified with NAC. Lipopolysaccharide-induced inflammation in mice resulted in an elevated level of hepatic MPO activity, increased metabolic activation of MCT, and intensified elevation of serum ALT and AST activity induced by MCT. MPO inhibitor 4-aminobenzoic acid hydrazide was found to reverse these alterations. Mpo-KO mice were resistant to the observed potentiating effect of inflammation on MCT-induced liver injury. In conclusion, inflammation intensified MCT-induced liver injury. MPO participated in the observed potentiating effect of inflammation on the hepatotoxicity induced by MCT.

Agreement between Wedged Hepatic Venous Pressure and Portal Pressure in Hepatic Sinusoidal Obstruction Syndrome

Background: Wedge hepatic vein pressure (WHVP) accurately estimates the portal pressure (PP) in chronic sinusoidal portal hypertension patients. Whether this applies to patients with acute portal hypertension due to hepatic sinusoidal obstruction syndrome (HSOS) is unclear. Our aim was to assess the agreement between WHVP and PP in patients with HSOS by comparing them to decompensated cirrhosis patients. Methods: From December 2013 to December 2021, patients with pyrrolidine alkaloid-induced HSOS (PA-HSOS) receiving hepatic venous pressure gradient (HVPG) measurement and transjugular intrahepatic portosystem shunt (TIPS) were retrospectively collected and matched with those of patients with virus- or alcohol-related cirrhosis as a cirrhosis group. Pearson’s correlation (R), intraclass correlation coefficient (ICC), scatter plots, and the Bland−Altman method were performed for agreement evaluation. Results: A total of 64 patients were analyzed (30 PA-HSOS and 34 cirrhosis groups). The correlation between WHVP and PP was moderate in the PA-HSOS group (R: 0.58, p = 0.001; ICC: 0.68, p = 0.002) but good in the cirrhosis group (R: 0.81, p < 0.001; ICC: 0.90, p < 0.001). The percentage of patients with inconsistent WHVP and PP in the two groups was 13 (43.3%) and 15 (26.5%) (p = 0.156), respectively, and an overestimation of PP was more common in the PA-HSOS group (33.3% vs. 2.9%, p = 0.004). HVPG and portal pressure gradient (PPG) consistency was poor in both groups (R: 0.51 vs. 0.26; ICC: 0.65 vs. 0.41; p < 0.05). Conclusions: WHVP in patients with PA-HSOS did not estimate PP as accurately as in patients with virus- or alcohol-related cirrhosis, which was mainly due to PP overestimation.

Integrative Metabolomics and Proteomics Detected Hepatotoxicity in Mice Associated with Alkaloids from Eupatorium fortunei Turcz

The traditional Chinese herbal medicine Eupatorium fortunei Turcz. (E. fortunei) has been widely adopted to treat nausea, diabetes, siriasis, and poor appetite. However, E. fortunei contains multiple pyrrolizidine alkaloids (PAs). This study aimed to investigate the hepatotoxicity of total alkaloids in E. fortunei (EFTAs) and identify the toxic mechanisms of EFTAs on hepatocytes. Liquid chromatography with a tandem mass spectrometry assay with reference standards indicated that EFTAs mainly consisted of eight PAs whose content accounted for 92.38% of EFTAs. EFTAs markedly decreased mouse body and liver weights and increased the contents of AST and ALT. The histopathological assays demonstrated that, after exposition to EFTAs, the structures of hepatocytes were damaged and the fibrosis and apoptosis in hepatocytes were accelerated. Moreover, EFTAs increased the serum level of inflammatory cytokines and aggravated circulating oxidative stress. A combination of hepatic proteomics and metabolomics was used to investigate the toxic mechanisms of EFTAs. The study revealed that EFTAs seriously disrupted glycerophospholipid metabolism by upregulating the contents of lysophosphatidylglycerol acyltransferase 1 and phosphatidylinositol and downregulating the contents of choline/ethanolamine kinase beta, choline-ethanolamine phosphotransferase 1, phospholipase D4, 1-acylglycerophosphocholine, phosphatidylcholine, and dihydroxyacetone phosphate in the liver, resulting in detrimental inflammation, fibrosis, and apoptosis. This study revealed that EFTAs induced severe hepatotoxicity by disrupting glycerophospholipid metabolism.

Comparison of the prognostic models for mortality in idiosyncratic drug-induced liver injury

BACKGROUND

Several models have been proposed to predict acute liver failure/death in patients with drug-induced liver injury (DILI), but the predictive performances of them have not been systematically compared. We aim to compare the current models for their predictive potency of mortality at DILI onset.

METHODS

DILI patients hospitalized at both Beijing Friendship Hospital and the Fifth Medical Center of PLA General Hospital were categorized into death/liver transplantation (LT) or survival without LT group. Predictive potency of 28-day, 90-day, 6-month and 12-month death/LT outcomes of Hy's Law, nHy's Law, Robles-Diaz Model, drug-induced liver toxicity (DrILTox ALF) Score, Model for End-stage Liver Disease (MELD) Score, and Ghabril Model was compared by Delong method.

RESULTS

A total of 6.3% (83/1314) patients died or received LT within 12 months after DILI onset. The area under receiver operating characteristic of Hy's Law, nHy's Law, and Robles-Diaz Model was all lower than 0.750 for the prediction of within 12 months' mortality. DrILTox ALF Score, MELD Score and Ghabril Model showed better predictive potency of 28-day [0.896 (0.878-0.912), 0.934 (0.919-0.947), 0.935 (0.921-0.948), respectively], 90-day [0.883 (0.864-0.899), 0.951 (0.938-0.962), 0.952 (0.939-0.963), respectively], 6-month [0.820 (0.799-0.841), 0.905 (0.888-0.921) and 0.908 (0.891-0.923), respectively] and 12-month [0.801 (0.779-0.823), 0.882 (0.863-0.899) and 0.885 (0.866-0.902), respectively] mortality.

CONCLUSION

Despite the difference of clinical characteristics and implicated-drug categories between China and industrialized countries, we demonstrate that MELD Score and Ghabril Model have the best predictive performance in the prediction of mortality within 12 months after DILI onset.

Risk Assessment of (Herbal) Teas Containing Pyrrolizidine Alkaloids (PAs) Based on Margin of Exposure Approach and Relative Potency (REP) Factors

Pyrrolizidine alkaloids (PAs) present distinct toxicity potencies depending on their metabolites and in vivo toxicokinetics. To represent the potency differences of various PAs, the interim relative potency (REP) factors have been derived. However, little is known about the risk assessment for (herbal) teas when taking REP factors into account. In this study, a set of 68 individual 1,2-unsaturated PA in 21 types of (herbal) teas was analyzed using LC-MS/MS. The REP factors for these PAs were applied on the PA levels. The margin of exposure (MOE) approach was employed to assess the risks of the exposure to PAs due to consumption of (herbal) teas. The results show that the total PA levels ranged from 13.4 to 286,682.2 μg/kg d.m., which were decreased by REP correction in most of the teas. The MOE values for tephroseris, borage and lemon balm (melissa) tea based on REP-corrected PA levels were below 10,000, assuming daily consumption of one cup of tea during a lifetime, indicating that consuming these teas may raise a concern. Our study also indicates a priority for risk management for tephroseris tea, as having nephrosis tea for more than 11.2 weeks during a 75-year lifetime would result in an MOE of 10,000.

Investigation of Gynura segetum root extract (GSrE) induced hepatotoxicity based on metabolomic signatures and microbial community profiling in rats

In recent years, many reports focus on the hepatotoxicity of Gynura segetum root extract (GSrE), but the interaction between GSrE and the gut microbiota is still unclear. This study investigated the mechanism of GSrE-induced hepatotoxicity of different doses and exposure durations by combining metabolomics and gut microbiota analysis. SD rats were divided into 3 groups: blank, low-dose (7.5 g/kg), and high-dose (15 g/kg) groups. Urine and feces samples were collected on day 0, day 10, and day 21. Metabolomics based on gas chromatography-mass spectrometry (GC-MS) was carried out to identify metabolites and metabolic pathways. 16S rDNA gene sequencing was applied to investigate the composition of gut microbiota before and after GSrE-induced hepatotoxicity. Finally, a correlation analysis of metabolites and gut microbiota was performed. Differential metabolites in urine and feces involved amino acids, carbohydrates, lipids, organic acids, and short chain fatty acids. Among them, L-valine, L-proline, DL-arabinose, pentanoic acid, D-allose, and D-glucose in urine and D-lactic acid and glycerol in fecal metabolites depended on the exposure of time and dose. In addition, 16S rDNA sequencing analysis revealed that GSrE-induced hepatotoxicity significantly altered the composition of gut microbiota, namely, f_Muribaculaceae_Unclassified, Lactobacillus, Bacteroides, Lachnospiraceae_NK4A136_group, f_Ruminococcaceae_Unclassified, Prevotellaceae_Ga6A1_group, and Escherichia-Shigella. The correlation analysis between gut microbiota and differential metabolites showed the crosstalk between the gut microbiota and metabolism in host involving energy, lipid, and amino acid metabolisms. In summary, our findings revealed that peripheral metabolism and gut microbiota disorders were time- and dose-related and the correlation between gut microbiota and metabolites in GSrE-induced hepatotoxicity.

Nrf2-mediated liver protection by 18β-glycyrrhetinic acid against pyrrolizidine alkaloid-induced toxicity through PI3K/Akt/GSK3β pathway

BACKGROUND

Misusage of pyrrolizidine alkaloid (PA)-containing plants or unaware intake of PA-contaminated foodstuffs causes thousands of PA poisoning cases in humans. PA intoxication is accompanied by oxidative stress and subsequent extensive hepatocellular damage. Our previous study has demonstrated that 18β-glycyrrhetinic acid (GA), a bioactive constituent of liquorice, prevented PA-induced hepatotoxicity in rats, however the underlying mechanisms remain unclear.

OBJECTIVE

This study aims to explore the mechanisms underlying the hepato-protective effect of GA in combating retrorsine (RTS, a representative toxic PA)-induced liver injury.

METHODS

Histological and biochemical assessments were employed to evaluate the protective effect of GA on RTS-induced hepatotoxicity in rats. Sulforhodamine B assay, real-time PCR, western blotting, and immunostaining were used to explore the underlying mechanisms in human hepatocytes and rats.

RESULTS

Our findings demonstrated that GA alleviated RTS-induced elevation of serum ALT and bilirubin levels, as well as hepatocytes necrosis and sinusoidal endothelial cells (SECs) damage in rats. GA also enhanced the activities and expressions of several antioxidant enzymes through upregulating nuclear factor-erythroid 2-related factor2 (Nrf2). Moreover, inhibition of Nrf2 blocked the hepatoprotective effect of GA against RTS intoxication. Mechanistically, GA increased the phosphorylation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and enhanced glycogen synthase kinase 3 beta (GSK3β) inhibitory phosphorylation at serine 9, thus promoting the nuclear accumulation of Nrf2 and activating its downstream targets.

CONCLUSION

This study for the first time demonstrated that GA exerted protective effects against RTS-induced liver injury by potentiating the Nrf2-mediated antioxidant system through PI3K/Akt/GSK3β pathway. The findings indicated that GA may serve as a potential candidate drug for the treatment of PA intoxication.

Sorting out the plants responsible for a contamination with pyrrolizidine alkaloids in spice seeds by means of LC-MS/MS and DNA barcoding: Proof of principle with cumin and anise spice seeds

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Identification of contaminating plants in seed spice with DNA barcoding.

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The obtained data concurs the previously obtained results with DNA metabarcoding.

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Heliotropium sp. is the predominant source of phytotoxic PA/PANOs in those samples.

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The presence of only 2 Heliotropium seeds/jar can render a sample non-compliant.

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The benefit combining chemical and molecular approach to check for phytotoxins.

High value commodities such as spices suffer from occasional contaminations of both chemical and biological origin. Consequently, quality control and safety monitoring has become a pressing issue for the spice industry. Two recent independent studies showed that at least one third of the analyzed cumin and green anise spice seeds samples surpassed the by the European Union recently established threshold value for toxic pyrrolizidine alkaloids (PAs) and their corresponding N-oxides (PANOs). These heterocyclic secondary plant metabolites are produced by a large number of different plant families. In those spice seeds, it was found by means of DNA metabarcoding, that predominant contamination was due to the presence of herbal material from the Heliotropium genus (Boraginaceae). Unfortunately, the use of this specific type of DNA-based identification remains controversial for the majority of the official instances and preference is still given to the use of more tangible classical approaches, including microscopy and chemical analysis. However, these methodologies often suffer from inherent drawbacks. Here we demonstrate that at least for spice seeds, a combinatory approach of microscopy, chemical analysis and classical DNA barcoding of the isolated contaminants using the matK and trnH-psbA loci, provides qualitative and quantitative information on the amount of plant material responsible for the contaminations and the extent of the contamination. The generated data also demonstrates that the presence of a very limited number of Heliotropium sp. seeds in a standard commercially available canister is sufficient to surpass the allowed threshold value, illustrating once more the importance of weed control.

Development of a Drum Tower Severity Scoring (DTSS) system for pyrrolizidine alkaloid-induced hepatic sinusoidal obstruction syndrome

BACKGROUND AND AIMS

There has been no reliable severity system based on the prognosis to guide therapeutic strategies for patients with pyrrolizidine alkaloid (PA)-induced hepatic sinusoidal obstruction syndrome (HSOS). We aimed to create a novel Drum Tower Severity Scoring (DTSS) system for these patients to guide therapy.

METHODS

172 Patients with PA-HSOS who received supportive care and anticoagulation therapy in Nanjing Drum Tower Hospital from January 2008 to December 2020 were enrolled and analyzed retrospectively. These patients were randomized into a training or validation set in a 3:1 ratio. Next, we established and validated the newly developed DTSS system.

RESULTS

Analysis identified a predictive formula: logit (P) = 0.004 × aspartate aminotransferase (AST, U/L) + 0.019 × total bilirubin (TB, μmol/L) - 0.571 × fibrinogen (FIB, g/L) - 0.093 × peak portal vein velocity (PVV, cm/s) + 1.122. Next, we quantified the above variables to establish the DTSS system. For the training set, the area under the ROC curve (AUC) (n = 127) was 0.787 [95% confidence interval (CI) 0.706-0.868; p < 0.001]. With a lower cut-off value of 6.5, the sensitivity and negative predictive value for predicting no response to supportive care and anticoagulation therapy were 94.7% and 88.0%, respectively. When applying a high cut-off value of 10.5, the specificity was 92.9% and the positive predictive value was 78.3%. For the validation set, the system performed stable with an AUC of 0.808.

CONCLUSIONS

The DTSS system can predict the outcome of supportive care and anticoagulation in PA-HSOS patients with satisfactory accuracy by evaluating severity, and may have potential significance for guiding therapy.

Correlation Investigation between Pyrrole-DNA and Pyrrole-Protein Adducts in Male ICR Mice Exposed to Retrorsine, a Hepatotoxic Pyrrolizidine Alkaloid

Pyrrolizidine alkaloids (PAs) have been found in over 6000 plants worldwide and represent the most common hepatotoxic phytotoxins. Catalyzed by hepatic cytochrome P450 enzymes, PAs are metabolized into reactive pyrrolic metabolites, which can alkylate cellular proteins and DNA to form pyrrole-protein adducts and pyrrole-DNA adducts, leading to cytotoxicity, genotoxicity, and tumorigenicity. To date, the correlation between these PA-derived pyrrole-protein and pyrrole-DNA adducts has not been well investigated. Retrorsine is a representative hepatotoxic and carcinogenic PA. In the present study, the correlations among the PA-derived liver DNA adducts, liver protein adducts, and serum protein adducts in retrorsine-treated mice under different dosage regimens were studied. The results showed positive correlations among these adducts, in which serum pyrrole-protein adducts were more accessible and present in higher abundance, and thus could be used as a suitable surrogate biomarker for pyrrole-DNA adducts to indicate the genetic or carcinogenic risk posed by retrorsine.

Novel Functional Food from an invasive species Polygonum cuspidatum: Safety evaluation, Chemical Composition, and Hepatoprotective Effects

Accidentally, we found that the shoots of Polygonum cuspidatum (SPC) have been consumed for centuries as a traditional vegetable in the Shennongjia region of China. Local residents believe that SPC has biological effects such as antibacterial, anti-aging, and antioxidant. To provide scientific support for the use of SPC as a functional food, SPC was evaluated in terms of safety, chemical composition, antioxidant activity both in vivo and in vitro. In the first, SPC exhibited no adverse cytotoxic effects or acute toxicity in mice. Then the chemical composition of SPC was determined by UHPLC-ESI-QTOF-MS/MS. 22 compounds were identified from the SPC extracts, including phenolic, flavonoid, stilbene, and anthraquinone. Finally, an acute ethanol-induced oxidative stress model in mice showed hepatoprotective effects. In brief, our study indicated that SPC is a safe, multi-functional food with antioxidant and hepatoprotective activities. Importantly, the consumption of SPC as a functional food provides a novel strategy of efficient utilization of the invasive plant.

Liquorice Extract and 18β-Glycyrrhetinic Acid Protect Against Experimental Pyrrolizidine Alkaloid-Induced Hepatotoxicity in Rats Through Inhibiting Cytochrome P450-Mediated Metabolic Activation

Misuse of pyrrolizidine alkaloid (PA)-containing plants or consumption of PA-contaminated foodstuffs causes numerous poisoning cases in humans yearly, while effective therapeutic strategies are still limited. PA-induced liver injury was initiated by cytochrome P450 (CYP)-mediated metabolic activation and subsequent formation of adducts with cellular proteins. Liquorice, a hepato-protective herbal medicine, is commonly used concurrently with PA-containing herbs in many compound traditional Chinese medicine formulas, and no PA-poisoning cases have been reported with this combination. The present study aimed to investigate hepato-protective effects of liquorice aqueous extract (EX) and 18β-glycyrrhetinic acid (GA, the primary bioactive constituent of liquorice) against PA-induced hepatotoxicity and the underlying mechanism. Histopathological and biochemical analysis demonstrated that both single- and multiple-treatment of EX (500 mg/kg) or GA (50 mg/kg) significantly attenuated liver damage caused by retrorsine (RTS, a representative hepatotoxic PA). The formation of pyrrole-protein adducts was significantly reduced by single- (30.3% reduction in liver; 50.8% reduction in plasma) and multiple- (32.5% reduction in liver; 56.5% reduction in plasma) treatment of GA in rats. Single- and multiple-treatment of EX also decreased the formation of pyrrole-protein adducts, with 30.2 and 31.1% reduction in rat liver and 51.8 and 53.1% reduction in rat plasma, respectively. In addition, in vitro metabolism assay with rat liver microsomes demonstrated that GA reduced the formation of metabolic activation-derived pyrrole-glutathione conjugate in a dose-dependent manner with the estimated IC₅₀ value of 5.07 µM. Further mechanism study showed that GA inhibited activities of CYPs, especially CYP3A1, the major CYP isoform responsible for the metabolic activation of RTS in rats. Enzymatic kinetic study revealed a competitive inhibition of rat CYP3A1 by GA. In conclusion, our findings demonstrated that both EX and GA exhibited significant hepato-protective effects against RTS-induced hepatotoxicity, mainly through the competitive inhibition of CYP-mediated metabolic activation of RTS.

Dietary alcohol exacerbates the hepatotoxicity induced by pyrrolizidine alkaloids: Hazard from food contamination

Pyrrolizidine alkaloids (PAs) are the most common plant-derived toxins with emerging evidence to contaminate soil, water, nearby plants and derived food products. Outbreaks of human poisoning cases, due to the ingestion of PA-contaminated food, have been reported in various countries including Ethiopia. This study first investigated the contamination of PAs in retail honey in Ethiopia. A striking 77% of honey samples (27/30) were found to contain PAs with the content ranging over 1.5-323.4 μg/kg. Notably, these PAs were also found as contaminants in mead, an alcoholic beverage made from local honey, indicating the transfer of PAs from the primarily contaminated honey into mead. Further toxicological examinations revealed that long-term PA exposure caused vasculature damage, fibrosis, and steatosis in mouse livers, and co-exposure to dietary alcohol exacerbated the PA-induced chronic hepatotoxicity. Furthermore, the study revealed that moderate alcohol intake did not affect the initiation mechanism (hepatic cytochrome P450-mediated bioactivation) of PA-induced hepatotoxicity but significantly disturbed hepatic glutathione homeostasis, thereby increasing oxidative stress in mouse liver and enhancing PA-induced hepatotoxicity. Our findings exemplify the carry-over of PA contamination through the food chain. Precautionary interventions are warranted on the hazardous effects of dietary exposure to PAs, particularly with concomitant alcohol consumption.

The key role of gut-liver axis in pyrrolizidine alkaloid-induced hepatotoxicity and enterotoxicity

Pyrrolizidine alkaloids (PAs) are the most common phytotoxins with documented human hepatotoxicity. PAs require metabolic activation by cytochromes P450 to generate toxic intermediates which bind to proteins and form protein adducts, thereby causing cytotoxicity. This study investigated the role of the gut-liver axis in PA intoxication and the underlying mechanisms. We exposed mice to retrorsine (RTS), a representative PA, and for the first time found RTS-induced intestinal epithelium damage and disruption to intestinal barrier function. Using mice with tissue-selective ablation of P450 activity, we found that hepatic P450s, but not intestinal P450s, were essential for PA bioactivation. Besides, in RTS-exposed, bile duct-cannulated rats, we found the liver-derived reactive PA metabolites were transported by bile into the intestine to exert enterotoxicity. The impact of gut-derived pathogenic factors in RTS-induced hepatotoxicity was further studied in mice with dextran sulfate sodium (DSS)-induced chronic colitis. DSS treatment increased the hepatic endotoxin level and depleted hepatic reduced glutathione, thereby suppressing the PA detoxification pathway. Compared to RTS-exposed normal mice, the colitic mice displayed more severe RTS-induced hepatic vasculature damage, fibrosis, and steatosis. Overall, our findings provide the first mode-of-action evidence of PA-induced enterotoxicity and highlight the importance of gut barrier function in PA-induced liver injury.

Fasting augments pyrrolizidine alkaloid-induced hepatotoxicity

Pyrrolizidine alkaloids (PAs) are phytotoxins widely present in various natural products and foodstuffs. The present study aims to investigate the effects of fasting on PA-induced hepatotoxicity and the underlying biochemical mechanisms. The results of hepatotoxic study showed that 15-h overnight fasting significantly exacerbated the hepatotoxicity of retrorsine (RTS, a representative toxic PA) in fasted rats compared to fed rats, as indicated by remarkably elevated plasma ALT and bilirubin levels and obvious liver histological changes. Further toxicokinetic studies revealed that fasting significantly enhanced cytochromes P450 enzymes (CYPs)-mediated metabolic activation of RTS leading to increased formation of pyrrole-protein adducts and thus decreased the in vivo exposure and excretion of both parent RTS and its N-oxide metabolite. Metabolic studies demonstrated that fasting induced enzyme activities of CYP1A2, CYP2B6 and CYP2E1 that participated in catalyzing RTS to its reactive pyrrolic metabolites. Moreover, fasting also dramatically decreased hepatic glutathione (GSH) content, which restricted the detoxification of GSH by neutralizing the reactive pyrrolic metabolite of RTS, further contributing to the enhanced hepatotoxicity. The present findings may have an impact on future PA toxicity tests with different dietary styles and/or risk assessment of metabolite-mediated toxins by considering the profound effects of fasting.

Pyrrolizidine Alkaloid-Induced Hepatotoxicity Associated with the Formation of Reactive Metabolite-Derived Pyrrole-Protein Adducts

Pyrrolizidine alkaloids (PAs) with 1,2-unsaturated necine base are hepatotoxic phytotoxins. Acute PA intoxication is initiated by the formation of adducts between PA-derived reactive pyrrolic metabolites with cellular proteins. The present study aimed to investigate the correlation between the formation of hepatic pyrrole-protein adducts and occurrence of PA-induced liver injury (PA-ILI), and to further explore the use of such adducts for rapidly screening the hepatotoxic potency of natural products which contain PAs. Aqueous extracts of Crotalaria sessiliflora (containing one PA: monocrotaline) and Gynura japonica (containing two PAs: senecionine and seneciphylline) were orally administered to rats at different doses for 24 h to investigate PA-ILI. Serum alanine aminotransferase (ALT) activity, hepatic glutathione (GSH) level, and liver histological changes of the treated rats were evaluated to assess the severity of PA-ILI. The levels of pyrrole-protein adducts formed in the rats' livers were determined by a well-established spectrophotometric method. The biological and histological results showed a dose-dependent hepatotoxicity with significantly different toxic severity among groups of rats treated with herbal extracts containing different PAs. Both serum ALT activity and the amount of hepatic pyrrole-protein adducts increased in a dose-dependent manner. Moreover, the elevation of ALT activity correlated well with the formation of hepatic pyrrole-protein adducts, regardless of the structures of different PAs. The findings revealed that the formation of hepatic pyrrole-protein adducts-which directly correlated with the elevation of serum ALT activity-was a common insult leading to PA-ILI, suggesting a potential for using pyrrole-protein adducts to screen hepatotoxicity and rank PA-containing natural products, which generally contain multiple PAs with different structures.

Herbal and dietary supplement induced liver injury: Highlights from the recent literature

Herbal-induced liver injury (HILI) is an important and increasingly concerning cause of liver toxicity, and this study presents recent updates to the literature. An extensive literature review was conducted encompassing September 2019 through March 2021. Studies with clinically significant findings were analyzed and included in this review. We emphasized those studies that provided a causality assessment methodology, such as Roussel Uclaf Causality Assessment Method scores. Our review includes reports of individual herbals, including Garcinia cambogia, green tea extract, kratom as well as classes such as performance enhancing supplements, Traditional Chinese medicine, Ayurvedic medicine and herbal contamination. Newly described herbals include ashwagandha, boldo, skyfruit, and 'Thermo gun'. Several studies discussing data from national registries, including the United States Drug-Induced Liver Injury (DILI) Network, Spanish DILI Registry, and Latin American DILI Network were incorporated. There has also been a continued interest in hepatoprotection, with promising use of herbals to counter hepatotoxicity from anti-tubercular medications. We also elucidated the current legal conversation surrounding use of herbals by presenting updates from the Federal Drug Administration. The highlights of the literature over the past year indicate interest in HILI that will continue as the supplement industry in the United States grows.

Developing urinary pyrrole-amino acid adducts as non-invasive biomarkers for identifying pyrrolizidine alkaloids-induced liver injury in human

Pyrrolizidine alkaloids (PAs) have been found in over 6000 plants worldwide and represent the most common hepatotoxic phytotoxins. Currently, a definitive diagnostic method for PA-induced liver injury (PA-ILI) is lacking. In the present study, using a newly developed analytical method, we identified four pyrrole-amino acid adducts (PAAAs), namely pyrrole-7-cysteine, pyrrole-9-cysteine, pyrrole-9-histidine, and pyrrole-7-acetylcysteine, which are generated from reactive pyrrolic metabolites of PAs, in the urine of PA-treated male Sprague Dawley rats and PA-ILI patients. The elimination profiles, abundance, and persistence of PAAAs were systematically investigated first in PA-treated rat models via oral administration of retrorsine at a single dose of 40 mg/kg and multiple doses of 5 mg/kg/day for 14 consecutive days, confirming that these urinary excreted PAAAs were derived specifically from PA exposure. Moreover, we determined that these PAAAs were detected in ~ 82% (129/158) of urine samples collected from ~ 91% (58/64) of PA-ILI patients with pyrrole-7-cysteine and pyrrole-9-histidine detectable in urine samples collected at 3 months or longer times after hospital admission, indicating adequate persistence time for use as a clinical test. As direct evidence of PA exposure, we propose that PAAAs can be used as a biomarker of PA exposure and the measurement of urinary PAAAs could be used as a non-invasive test assisting the definitive diagnosis of PA-ILI in patients.

Metabolism-mediated cytotoxicity and genotoxicity of pyrrolizidine alkaloids

Pyrrolizidine alkaloids (PAs) and PA N-oxides are common phytotoxins produced by over 6000 plant species. Humans are frequently exposed to PAs via ingestion of PA-containing herbal products or PA-contaminated foods. PAs require metabolic activation to form pyrrole-protein adducts and pyrrole-DNA adducts which lead to cytotoxicity and genotoxicity. Individual PAs differ in their metabolic activation patterns, which may cause significant difference in toxic potency of different PAs. This review discusses the current knowledge and recent advances of metabolic pathways of different PAs, especially the metabolic activation and metabolism-mediated cytotoxicity and genotoxicity, and the risk evaluation methods of PA exposure. In addition, this review provides perspectives of precision toxicity assessment strategies and biomarker development for the risk control and translational investigations of human intoxication by PAs.

Clinical application of pyrrole-hemoglobin adducts as a biomarker of pyrrolizidine alkaloid exposure in humans

Pyrrolizidine alkaloids (PAs) are naturally occurring hepatotoxins widely present in hundreds of plant species and also known to contaminate many foodstuffs, such as grain, honey, and tea. The formation of pyrrole-protein adducts via metabolic activation of PAs has been suggested as a primary trigger initiating hepatotoxicity. The present study for the first time tested the suitability of pyrrole-hemoglobin adducts as a novel and specific biomarker of PA exposure in humans. The level and elimination kinetics of pyrrole-hemoglobin adducts were systematically investigated in the blood samples of 43 PA-induced liver injury (PA-ILI) patients. The results revealed significantly higher concentrations (84.50 ± 78.38 nM) and longer persistence (~ 4 months) of pyrrole-hemoglobin adducts than that (concentration: 9.53 ± 10.72 nM; persistence: ~ 2 months) of pyrrole-plasma protein adducts, our previously developed PA exposure biomarker. Our findings confirmed that pyrrole-hemoglobin adducts with higher level and longer persistence should serve as a more applicable PA exposure biomarker for future clinical diagnosis of PA-ILI in drug/herb-induced liver injury patients.