Eva Sticova

Complete OATP1B1 and OATP1B3 deficiency causes human Rotor syndrome by interrupting conjugated bilirubin reuptake into the liver

Bilirubin, a breakdown product of heme, is normally glucuronidated and excreted by the liver into bile. Failure of this system can lead to a buildup of conjugated bilirubin in the blood, resulting in jaundice. The mechanistic basis of bilirubin excretion and hyperbilirubinemia syndromes is largely understood, but that of Rotor syndrome, an autosomal recessive disorder characterized by conjugated hyperbilirubinemia, coproporphyrinuria, and near-absent hepatic uptake of anionic diagnostics, has remained enigmatic. Here, we analyzed 8 Rotor-syndrome families and found that Rotor syndrome was linked to mutations predicted to cause complete and simultaneous deficiencies of the organic anion transporting polypeptides OATP1B1 and OATP1B3. These important detoxification-limiting proteins mediate uptake and clearance of countless drugs and drug conjugates across the sinusoidal hepatocyte membrane. OATP1B1 polymorphisms have previously been linked to drug hypersensitivities. Using mice deficient in Oatp1a/1b and in the multispecific sinusoidal export pump Abcc3, we found that Abcc3 secretes bilirubin conjugates into the blood, while Oatp1a/1b transporters mediate their hepatic reuptake. Transgenic expression of human OATP1B1 or OATP1B3 restored the function of this detoxification-enhancing liver-blood shuttle in Oatp1a/1b-deficient mice. Within liver lobules, this shuttle may allow flexible transfer of bilirubin conjugates (and probably also drug conjugates) formed in upstream hepatocytes to downstream hepatocytes, thereby preventing local saturation of further detoxification processes and hepatocyte toxic injury. Thus, disruption of hepatic reuptake of bilirubin glucuronide due to coexisting OATP1B1 and OATP1B3 deficiencies explains Rotor-type hyperbilirubinemia. Moreover, OATP1B1 and OATP1B3 null mutations may confer substantial drug toxicity risks.

New insights in bilirubin metabolism and their clinical implications

Bilirubin, a major end product of heme breakdown, is an important constituent of bile, responsible for its characteristic colour. Over recent decades, our understanding of bilirubin metabolism has expanded along with the processes of elimination of other endogenous and exogenous anionic substrates, mediated by the action of multiple transport systems at the sinusoidal and canalicular membrane of hepatocytes. Several inherited disorders characterised by impaired bilirubin conjugation (Crigler-Najjar syndrome type I and type II, Gilbert syndrome) or transport (Dubin-Johnson and Rotor syndrome) result in various degrees of hyperbilirubinemia of either the predominantly unconjugated or predominantly conjugated type. Moreover, disrupted regulation of hepatobiliary transport systems can explain jaundice in many acquired liver disorders. In this review, we discuss the recent data on liver bilirubin handling based on the discovery of the molecular basis of Rotor syndrome. The data show that a substantial fraction of bilirubin conjugates is primarily secreted by MRP3 at the sinusoidal membrane into the blood, from where they are subsequently reuptaken by sinusoidal membrane-bound organic anion transporting polypeptides OATP1B1 and OATP1B3. OATP1B proteins are also responsible for liver clearance of bilirubin conjugated in splanchnic organs, such as the intestine and kidney, and for a number of endogenous compounds, xenobiotics and drugs. Absence of one or both OATP1B proteins thus may have serious impact on toxicity of commonly used drugs cleared by this system such as statins, sartans, methotrexate or rifampicin. The liver-blood cycling of conjugated bilirubin is impaired in cholestatic and parenchymal liver diseases and this impairment most likely contributes to jaundice accompanying these disorders.

Metformin prevents ischemia reperfusion-induced oxidative stress in the fatty liver by attenuation of reactive oxygen species formation

Nonalcoholic fatty liver disease is associated with chronic oxidative stress. In our study, we explored the antioxidant effect of antidiabetic metformin on chronic [high-fat diet (HFD)-induced] and acute oxidative stress induced by short-term warm partial ischemia-reperfusion (I/R) or on a combination of both in the liver. Wistar rats were fed a standard diet (SD) or HFD for 10 wk, half of them being administered metformin (150 mg·kg body wt(-1)·day(-1)). Metformin treatment prevented acute stress-induced necroinflammatory reaction, reduced alanine aminotransferase and aspartate aminotransferase serum activity, and diminished lipoperoxidation. The effect was more pronounced in the HFD than in the SD group. The metformin-treated groups exhibited less severe mitochondrial damage (markers: cytochrome c release, citrate synthase activity, mtDNA copy number, mitochondrial respiration) and apoptosis (caspase 9 and caspase 3 activation). Metformin-treated HFD-fed rats subjected to I/R exhibited increased antioxidant enzyme activity as well as attenuated mitochondrial respiratory capacity and ATP resynthesis. The exposure to I/R significantly increased NADH- and succinate-related reactive oxygen species (ROS) mitochondrial production in vitro. The effect of I/R was significantly alleviated by previous metformin treatment. Metformin downregulated the I/R-induced expression of proinflammatory (TNF-α, TLR4, IL-1β, Ccr2) and infiltrating monocyte (Ly6c) and macrophage (CD11b) markers. Our data indicate that metformin reduces mitochondrial performance but concomitantly protects the liver from I/R-induced injury. We propose that the beneficial effect of metformin action is based on a combination of three contributory mechanisms: increased antioxidant enzyme activity, lower mitochondrial ROS production, and reduction of postischemic inflammation.

Prevalence and risk factors of steatosis after liver transplantation and patient outcomes

Steatosis occurs frequently after liver transplantation (LT). We aimed to determine the prevalence of steatosis in adult LT recipients, to determine the effects of significant (>33%; grades 2‐3) steatosis on patient survival, and to identify risk factors for the development of significant steatosis and its effect on fibrosis progression. We retrospectively examined 2360 posttransplant biopsies of 548 LT recipients. Survival was compared between patients with significant steatosis and those with grades 0‐1 steatosis. Patients with significant steatosis were compared to controls without steatosis (grade 0) for clinical and laboratory factors and fibrosis progression. Steatosis was found in 309 (56.4%) patients, including 93 (17.0%) patients with significant steatosis. Steatohepatitis (nonalcoholic fatty liver disease activity score ≥ 5) was diagnosed in 57 (10.4%) patients. The prevalence of steatosis increased from 30.3% at 1 year to 47.6% at 10 years after LT (P < 0.001). Survival times did not differ between groups (P = 0.29). On multivariate analysis of pretransplant factors and initial immunosuppression (IS), alcohol‐induced cirrhosis (P < 0.001) and high body mass index (BMI; P = 0.002) were associated with the development of significant steatosis, whereas increased levels of alkaline phosphatase (P = 0.01) and mycophenolate mofetil given initially (P = 0.009) appeared to protect against significant steatosis. On multivariate analysis of posttransplant factors, high BMI (P < 0.001), serum triglycerides (P < 0.001), alcohol consumption (P = 0.005), and type 2 diabetes mellitus (P = 0.048) were associated with significant steatosis, whereas high creatinine (P = 0.02) appeared to protect against significant steatosis. Significant steatosis was not associated with a higher fibrosis stage (P = 0.62). Posttransplant steatosis affects 56.4% of LT recipients, and the prevalence increases with time after LT. Recipient factors and types of IS affect the risk for significant steatosis, which is not associated with a higher fibrosis stage or worse patient survival. Liver Transplantation 22 644‐655 2016 AASLD.

Dubin-Johnson syndrome coinciding with colon cancer and atherosclerosis

Hyperbilirubinemia has been presumed to prevent the process of atherogenesis and cancerogenesis mainly by decreasing oxidative stress. Dubin-Johnson syndrome is a rare, autosomal recessive, inherited disorder characterized by biphasic, predominantly conjugated hyperbilirubinemia with no progression to end-stage liver disease. The molecular basis in Dubin-Johnson syndrome is absence or deficiency of human canalicular multispecific organic anion transporter MRP2/cMOAT caused by homozygous or compound heterozygous mutation(s) in ABCC2 located on chromosome 10q24. Clinical onset of the syndrome is most often seen in the late teens or early adulthood. In this report, we describe a case of previously unrecognized Dubin-Johnson syndrome caused by two novel pathogenic mutations (c.2360_2366delCCCTGTC and c.3258+1G>A), coinciding with cholestatic liver disease in an 82-year-old male patient. The patient, suffering from advanced atherosclerosis with serious involvement of coronary arteries, developed colorectal cancer with nodal metastases. The subsequent findings do not support the protective role of Dubin-Johnson type hyperbilirubinemia.

The Increased Activity of Liver Lysosomal Lipase in Nonalcoholic Fatty Liver Disease Contributes to the Development of Hepatic Insulin Resistance

We tested the hypothesis that TAG accumulation in the liver induced by short-term high-fat diet (HFD) in rats leads to the dysregulation of endogenous TAG degradation by lysosomal lipase (LIPA) via lysosomal pathway and is causally linked with the onset of hepatic insulin resistance. We found that LIPA could be translocated between qualitatively different depots (light and dense lysosomes). In contrast to dense lysosomal fraction, LIPA associated with light lysosomes exhibits high activity on both intracellular TAG and exogenous substrate and prandial- or diet-dependent regulation. On standard diet, LIPA activity was upregulated in fasted and downregulated in fed animals. In the HFD group, we demonstrated an increased TAG content, elevated LIPA activity, enhanced production of diacylglycerol, and the abolishment of prandial-dependent LIPA regulation in light lysosomal fraction. The impairment of insulin signalling and increased activation of PKCε was found in liver of HFD-fed animals. Lipolysis of intracellular TAG, mediated by LIPA, is increased in steatosis probably due to the enhanced formation of phagolysosomes. Consequent overproduction of diacylglycerol may represent the causal link between HFD-induced hepatic TAG accumulation and hepatic insulin resistance via PKCε activation.

A case of acute generalized pustular psoriasis of von Zumbusch treated with adalimumab

Editor Generalized pustular psoriasis of von Zumbusch (GPP-VZ) is an acute rare variant of psoriasis often associated with systemic symptoms such as fever, chills, malaise, infections and dehydration. The clinical picture consists of extensive sterile pustules on widespread erythema. Abnormal laboratory values are typical such as leucocytosis, neutrophilia, elevated C-reactive protein (CRP) and erythrocyte sedimentation rate. An 80-year-old female with a history of plaque type psoriasis with exacerbations of localized pustular psoriasis for the last 35 years was referred to our clinic. Past treatments included topical steroids, UVB phototherapy and acitretin (with intolerance experience). One week before admission, according to the patient,she received intravenous infusion for back pain. Unfortunately we were not able to track what was the content of infusion since it was in another city. A couple of days later she developed pustular erythematous lesions which started to extend very fast. At the day of admission 30% of the body surface area involvement and unilateral swelling of the right upper extremity was observed (Fig. 1a). Deep venous thrombosis was excluded. Laboratory evaluation revealed leucocytosis (21 K/mm), neutrophilia and elevated CRP 78 mg/dL. No signs of infection were present. Punch biopsy confirmed the diagnosis of GPP (Fig. 2). We initiated oral methotrexate 10 mg but progression of the disease was very fast (Fig. 1c). We decided for biologic therapy. Quantiferon TB Gold gave us uncertain results twice. A chest X-ray and CT scan could not rule out past tuberculotic changes and the pneumologist decided to perform bronchoscopy in order to obtain bronchoalveolar lavage for Mycobacterium tuberculosis PCR and for bacteriological examination. PCR was negative but cultivation was positive for Klebsiella pneumoniae and Enterococcus faecalis. Immediate intravenous therapy with amoxicillin/clavulanate was started and the patient was transferred to the medical intensive care unit. Because of the continuing dissemination of the skin lesions we decided to emergently start treatment with adalimumab 80 mg subcutaneously. After 4 days we saw a dramatically clinical and laboratory improve-

Silymarin prevents acetaminophen-induced hepatotoxicity in mice

Acetaminophen or paracetamol (APAP) overdose is a common cause of liver injury. Silymarin (SLM) is a hepatoprotective agent widely used for treating liver injury of different origin. In order to evaluate the possible beneficial effects of SLM, Balb/c mice were pretreated with SLM (100 mg/kg b.wt. per os) once daily for three days. Two hours after the last SLM dose, the mice were administered APAP (300 mg/kg b.wt. i.p.) and killed 6 (T6), 12 (T12) and 24 (T24) hours later. SLM-treated mice exhibited a significant reduction in APAP-induced liver injury, assessed according to AST and ALT release and histological examination. SLM treatment significantly reduced superoxide production, as indicated by lower GSSG content, lower HO-1 induction, alleviated nitrosative stress, decreased p-JNK activation and direct measurement of mitochondrial superoxide production in vitro. SLM did not affect the APAP-induced decrease in CYP2E1 activity and expression during the first 12 hrs. Neutrophil infiltration and enhanced expression of inflammatory markers were first detected at T12 in both groups. Inflammation progressed in the APAP group at T24 but became attenuated in SLM-treated animals. Histological examination suggests that necrosis the dominant cell death pathway in APAP intoxication, which is partially preventable by SLM pretreatment. We demonstrate that SLM significantly protects against APAP-induced liver damage through the scavenger activity of SLM and the reduction of superoxide and peroxynitrite content. Neutrophil-induced damage is probably secondary to necrosis development.

Toxic epidermal necrolysis induced by vemurafenib after nivolumab failure

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The Optimal Timing for Pancreatic Islet Transplantation into Subcutaneous Scaffolds Assessed by Multimodal Imaging

Subcutaneously implanted polymeric scaffolds represent an alternative transplantation site for pancreatic islets (PIs) with the option of vascularisation enhancement by mesenchymal stem cells (MSC). Nevertheless, a proper timing of the transplantation steps is crucial. In this study, scaffolds supplemented with plastic rods were implanted into diabetic rats and two timing schemes for subsequent transplantation of bioluminescent PIs (4 or 7 days after rod removal) were examined by multimodal imaging. The cavities were left to heal spontaneously or with 10 million injected MSCs. Morphological and vascularisation changes were examined by MRI, while the localisation and viability of transplanted islets were monitored by bioluminescence imaging. The results show that PIs transplanted 4 days after rod removal showed the higher optical signal and vascularisation compared to transplantation after 7 days. MSCs slightly improved vascularisation of the graft but hindered therapeutic efficiency of PIs. Long-term glycaemia normalisation (4 months) was attained in 80% of animals. In summary, multimodal imaging confirmed the long-term survival and function of transplanted PIs in the devices. The best outcome was reached with PIs transplanted on day 4 after rod removal and therefore the suggested protocol holds a potential for further applications.