Metabolome analysis of erythrocytes from patients with chronic hepatitis C reveals the etiology of ribavirin-induced hemolysis

Ribavirin for treating Lassa fever: A systematic review of pre-clinical studies and implications for human dosing

Ribavirin is currently the standard of care for treating Lassa fever. However, the human clinical trial data supporting its use suffer from several serious flaws that render the results and conclusions unreliable. We performed a systematic review of available pre-clinical data and human pharmacokinetic data on ribavirin in Lassa. In in-vitro studies, the EC50 of ribavirin ranged from 0.6 μg/ml to 21.72 μg/ml and the EC90 ranged from 1.5 μg/ml to 29 μg/ml. The mean EC50 was 7 μg/ml and the mean EC90 was 15 μg/ml. Human PK data in patients with Lassa fever was sparse and did not allow for estimation of concentration profiles or pharmacokinetic parameters. Pharmacokinetic modelling based on healthy human data suggests that the concentration profiles of current ribavirin regimes only exceed the mean EC50 for less than 20% of the time and the mean EC90 for less than 10% of the time, raising the possibility that the current ribavirin regimens in clinical use are unlikely to reliably achieve serum concentrations required to inhibit Lassa virus replication. The results of this review highlight serious issues with the evidence, which, by today standards, would be unlikely to support the transition of ribavirin from pre-clinical studies to human clinical trials. Additional pre-clinical studies are needed before embarking on expensive and challenging clinical trials of ribavirin in Lassa fever.

Novel variant in glycophorin c gene protects against ribavirin-induced anemia during chronic hepatitis C treatment

BACKGROUND

The current use of ribavirin in difficult-to-cure chronic hepatitis C patients (HCV) and patients with severe respiratory infections is constrained by the issue of ribavirin-induced hemolytic anemia that affects 30% of treated patients, requiring dosage modification or discontinuation. Though some genetic variants have been identified predicting this adverse effect, known clinical and genetic factors do not entirely explain the risk of ribavirin-induced anemia.

METHODS

We assessed the associations of previously identified variants in inosine triphosphatase (ITPA), solute carrier 28A2 (SLC28A2) and vitamin D receptor (VDR) genes with ribavirin-induced anemia defined as hemoglobin decline of ≥30 g/L on treatment, followed by a staged discovery (n = 114), replication (n = 74), and combined (n = 188) genome-wide association study to uncover potential new predictive variants.

RESULTS

We identified a novel association in the gene coding glycophorin C (rs6741425; OR:0.12, 95%CI:0.04-0.34, P = 2.94 × 10^-6) that predicts protection against ribavirin-induced anemia. We also replicated the associations of ITPA and VDR genetic variants with the development of ribavirin-induced anemia (rs1127354; OR:0.13, 95%CI:0.04-0.41, P = 8.66 ×10^-5; and rs1544410; OR:1.65, 95%CI:1.01-2.70, P = 0.0437).

CONCLUSIONS

GYPC variation affecting erythrocyte membrane strength is important in predicting risk for developing ribavirin-induced anemia. ITPA and VDR genetic variants are also important predictors of this adverse reaction.

Elevated pentose phosphate pathway is involved in the recovery of hypoxia‑induced erythrocytosis

As a typical model of hypoxia-induced excessive erythrocytosis, high altitude polycythemia (HAPC) results in microcirculation disturbance, aggravates tissue hypoxia and results in a severe clinical outcome, without any effective intervention methods except for returning to an oxygen-rich environment. The present study aimed to explore potential therapeutic targets which may participate in the recovery of HAPC by studying the mechanisms of reducing the hemoglobin (HB) concentration during re-oxygenation. A total of 14 and 13 subjects were recruited over a 5,300 m distance and 5,170 m area. The patients were classified into HAPC or control groups based on their HB value. Plasma samples were collected on the day when they finished their stay in plateau for a year, and on the 180th day following their reaching in plain. Metabolic profiling was conducted by UPLC-QTOF/MS. MetaboAnalyst platform was performed to explore the most perturbed metabolic pathways. A panel of differential metabolites were obtained in the recovery phase of HAPC and control groups. The present study identified the uniquely upregulated pentose phosphate pathway in HAPC subjects, along with a significantly decreased HB level. The findings were verified via a direct comparison between HAPC and control subjects at a high altitude. An increased pentose phosphate pathway was identified in control groups compared with HAPC subjects. An elevated pentose phosphate pathway may therefore participate in the recovery of HAPC, whereas a downregulated pentose phosphate pathway may contribute to hypoxia-induced erythrocytosis. The results of the present study provide potential therapeutic strategies and novel insights into the pathogenesis of hypoxia-induced polycythemia.

Effects of ribavirin/sofosbuvir treatment and ITPA phenotype on endogenous purines

Ribavirin (RBV), a purine analog, causes hemolytic anemia in some patients. In vitro, anemia appears to result from depletion of endogenous purines, but there are limited data in vivo. Single nucleotide polymorphisms in the gene encoding the inosine triphosphatase (ITPA) enzyme have been associated with protection against RBV-induced anemia and may mediate the effect of RBV treatment on endogenous purines. The purpose of this work was to determine the effect of RBV treatment on endogenous purine concentrations in individuals being treated for chronic hepatitis C virus (HCV) infection. Adenosine triphosphate (ATP), guanosine triphosphate (GTP), inosine triphosphate (ITP) and ribavirin triphosphate (RTP) were measured in whole blood obtained from 47 HCV-infected individuals at day zero (baseline), day three, day 28 and day 84 of RBV/sofosbuvir (SOF) treatment. ATP decreased -35.1% and -38.6% (p < 0.0001) at day 28 and day 84 of treatment, respectively compared to baseline. The decrease in ATP was greater in patients with ≤60% ITPA activity compared to those with 100% ITPA activity (-29.4% vs. -9.6%). GTP did not change during treatment but was 16.5% (p = 0.01) higher per 100 pmol/106 cells RTP in those with 100% ITPA activity. No significant change or effect of RTP or ITPA phenotype was noted for ITP. In summary, only ATP was reduced by RBV/SOF treatment and ITPA variants had larger reductions in ATP suggesting RBV-induced anemia is due to a different mechanism than predicted from in-vitro studies. These data emphasize the importance of characterizing the effect of nucleos(t)ide analog treatment on endogenous purines in-vivo.

Capillary electrophoresis mass spectrometry as a tool for untargeted metabolomics

Highly polar and ionic metabolites, such as sugars, most amino acids, organic acids or nucleotides are not retained by conventional reversed-phase LC columns and polar stationary phases and hydrophilic-interaction LC lacks of robustness, which is still limiting their applications for untargeted metabolomics where reproducibility is a must. Biological samples such as blood, urine or even tissues include many hydrophilic compounds secreted from cells, their analysis is essential for biomarker discovery, disease progression or treatment effects. This review focuses on CE coupled to MS as a mature technique for untargeted metabolomics including sample pretreatment, types of matrices, analytical methods, applications and data treatment strategies for polar compound analysis in biological matrices. The main applications and results of CE-MS in untargeted metabolomics are discussed and presented in a tabulated format.

Capillary Electrophoresis in Metabolomics

Metabolomics is an analytical toolbox to describe (all) low-molecular-weight compounds in a biological system, as cells, tissues, urine, and feces, as well as in serum and plasma. To analyze such complex biological samples, high requirements on the analytical technique are needed due to the high variation in compound physico-chemistry (cholesterol derivatives, amino acids, fatty acids as SCFA, MCFA, or LCFA, or pathway-related metabolites belonging to each individual organism) and concentration dynamic range. All main separation techniques (LC-MS, GC-MS) are applied in routine to metabolomics hyphenated or not to mass spectrometry, and capillary electrophoresis is a powerful high-resolving technique but still underused in this field of complex samples. Metabolomics can be performed in the non-targeted way to gain an overview on metabolite profiles in biological samples. Targeted metabolomics is applied to analyze quantitatively pre-selected metabolites. This chapter reviews the use of capillary electrophoresis in the field of metabolomics and exemplifies solutions in metabolite profiling and analysis in urine and plasma.

Non-immune Hemolysis: Diagnostic Considerations

Non-immune hemolytic anemia (NIHA) is characterized by positive routine hemolytic tests but negative anti-human immunoglobulin (Coombs) test. Hereditary non-immune hemolysis includes disorders of erythrocytic enzymes, membrane, hemoglobin (qualitative and quantitative disorders), as well as the rare hereditary forms of thrombotic microangiopathies. Acquired NIHA includes paroxysmal nocturnal hemolysis (PNH), infections, drug and metal intoxications with as a target red blood cells or endothelium of capillaries, the rare acquired forms of thalassemia or erythrocytic membrane disorders, and hemolysis secondary to a dysfunctioning artificial (prosthetic) cardiac valve. Identification of the specific cause of NIHA is sometimes difficult and requires not only a good knowledge of this entity but mainly a qualified specialized hematologic laboratory. An algorithm to be used in every new patient consulting for NIHA is proposed in the last part of this article.