Hepatotoxicity and drug interactions in liver transplant candidates and recipients

A novel epigenetic mechanism unravels hsa-miR-148a-3p-mediated CYP2B6 downregulation in alcoholic hepatitis disease

Cytochrome P450 (CYP) enzymes play critical roles in drug transformation, and the total CYPs are markedly decreased in alcoholic hepatitis (AH), a fatal alcoholic liver disease. miRNAs are endogenous small noncoding RNAs that regulate many essential biological processes. Knowledge concerning miRNA regulation of CYPs in AH disease is limited. Here we presented the changes of key CYPs in liver samples of AH patients retrieved from GEO database, performed in silico prediction of miRNAs potentially targeting the dysregulated CYP transcripts, and deciphered a novel mechanism underlying miRNA mediated CYPs expression in liver cells. Nine miRNAs were predicted to regulate CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C19, CYP2J2, and CYP3A4, among which hsa-miR-148a-3p was selected as a case study. Biochemical and molecular evidences demonstrated that miR-148a promoted CYP2B6 expression by increasing mRNA stability via directly binding to the 3'UTR sequence, and that this positive posttranscriptional regulation was AGO1/2-dependent. Further, luciferase reporter gene assay and RNA secondary structure analysis illustrated that the seedless target site, not the seed target site, controlled miR-148a-mediated CYP2B6 upregulation. Moreover, we identified HNF4A as a liver-specific transcription factor of MIR-148A through EMSA and chromatin immunoprecipitation experiments. In conclusion, ethanol downregulated miR-148a in hepatocytes through HNF4A regulation, which eventually decreased CYP2B6 expression. Our finding will benefit the understanding of dysregulated drug metabolism in AH patients and highlight an unconventional mechanism for epigenetic regulation of CYP gene expression.

Drug Metabolism in the Liver

Metabolism is a biotransformation process, where endogenous and exogenous compounds are converted to more polar products to facilitate their elimination from the body. The process of metabolism is divided into 3 phases. Phase I metabolism involves functionalization reactions. Phase II drug metabolism is a conjugation reaction. Phase III refers to transporter-mediated elimination of drug and/or metabolites from body normally via liver, gut, kidney, or lung. This review presents basic information on drug-metabolizing enzymes and potential factors that might affect the metabolic capacities of the enzyme or alter drug response or drug-mediated toxicities.

Drug Metabolism, Drug Interactions, and Drug-Induced Liver Injury in Living Donor Liver Transplant Patients

Living donor liver transplant (LDLT) fills a critically needed gap in the number of livers available for transplant. However, little is known about the functional recovery of the liver in the donor and in the recipient after surgery. Given that both donor and recipients are treated with several drugs, it is important to characterize the time course of recovery of hepatic synthetic, metabolic, and excretory function in these patients. In the absence of data from LDLT, information on the effect of liver disease on the pharmacokinetics of medications can be used as guidance for drug dosing in LDLT patients.

Management of the Liver Transplant Recipient: Approach to Allograft Dysfunction

Liver transplant (LT) recipients are living longer than ever today and many will experience some form of allograft dysfunction. The common causes of allograft dysfunction vary significantly depending on the timing since LT. Most allograft abnormalities are manageable with minimally invasive procedures, medications, and lifestyle modification. The most common differential diagnoses by time period after LT, and diagnostic and management considerations, are highlighted. Collaboration and comanagement of LT recipients between primary care and the transplant hepatologist is essential for optimizing recipient and allograft outcomes.

A Cross-Sectional Study Comparing the Frequency of Drug Interactions After Adding Simeprevir- or Sofosbuvir-Containing Therapy to Medication Profiles of Hepatitis C Monoinfected Patients

INTRODUCTION

This study compares the expected occurrence of contraindicated drug-drug interactions (XDDIs) when simeprevir (SIM)- or sofosbuvir (SOF)-containing therapy is added to medication profiles of patients with hepatitis C (HCV) monoinfection to quantify, in relative terms, the population-based risk of XDDIs. Second, this study identified the predictors of XDDIs when HCV therapies are added to medication profiles.

METHODS

A cross-sectional study was performed among Veterans' Affairs patients. Inclusion criteria were: (1) age ≥18 years, (2) HCV infection, and (3) availability of a medication list. Patients with human immunodeficiency virus were excluded. Demographics, comorbidities, year of HCV diagnosis, and most recent medication list were collected from medical records. The primary outcome was the presence of XDDIs involving HCV therapy and the medications in the patient's home medication list after the addition of either SIM- or SOF-containing regimens. To define XDDIs, Lexi-Interact drug interaction software was used.

RESULTS

4,251 patients were included. The prevalence of XDDIs involving SIM- or SOF-containing therapy were 12.6% and 4.7% (p < 0.001), respectively. In multivariable analyses examining the predictors of XDDIs involving SIM-containing therapy, the only medication-related predictor was use of ≥6 home medications (odds ratio OR 4.58, 95% confidence interval CI 3.54-5.20, p < 0.001). Similarly, use of ≥6 home medications was also the only variable associated with an increased probability of XDDI involving SOF-containing therapy (OR 3.83, 95% CI 2.57-5.70, p < 0.001).

CONCLUSIONS

Sofosbuvir-containing therapy had a lower frequency of XDDIs than SIM-containing therapy. Polypharmacy with various classes of home medications predicted XDDIs involving SIM- or SOF-containing therapy.

Infections after orthotopic liver transplantation

Opportunistic infections are a leading cause of morbidity and mortality after orthotopic liver transplantation. Systemic immunosuppression renders the liver recipient susceptible to de novo infection with bacteria, viruses and fungi post-transplantation as well to reactivation of pre-existing, latent disease. Pathogens are also transmissible via the donor organ. The time from transplantation and degree of immunosuppression may guide the differential diagnosis of potential infectious agents. However, typical systemic signs and symptoms of infection are often absent or blunted after transplant and a high index of suspicion is needed. Invasive procedures are often required to procure tissue for culture and guide antimicrobial therapy. Antimicrobial prophylaxis reduces the incidence of opportunistic infections and is routinely employed in the care of patients after liver transplant. In this review, we survey common bacterial, fungal, and viral infections after orthotopic liver transplantation and highlight recent developments in their diagnosis and management.