Acyclovir-induced nephrotoxicity: the role of the acyclovir aldehyde metabolite

Development of Novel N-Acylhydrazone Derivatives with High Anti-obesity Activity and Improved Safety by Exploring the Pharmaceutical Properties of Aldehyde Group

The discovery of effective and safe antiobesity agents remains a challenging yet promising field. Our previous studies identified Bouchardatine derivatives as potential antiobesity agents. However, the 8a-aldehyde moiety rendered them unsuitable for drug development. In this study, we designed two series of novel derivatives to modify this structural feature. Through a structure-activity relationship study, we elucidated the role of the 8a-aldehyde group in toxicity induction. We identified compound 14d, featuring an 8a-N-acylhydrazone moiety, which exhibited significant lipid-lowering activity and reduced toxicity. Compound 14d shares a similar lipid-lowering mechanism with our lead compound 3, but demonstrates improved pharmacokinetic properties and safety profile. Both oral and injectable administration of 14d significantly reduced body weight gain and ameliorated metabolic syndrome in diet-induced obese mice. Our findings identify 14d as a promising antiobesity agent and highlight the potential of substituting the aldehyde group with an N-acylhydrazone to enhance drug-like properties.

Simultaneous analysis of acyclovir and its metabolite using hydrophilic interaction liquid chromatography-tandem mass spectrometry

The antiviral drug acyclovir (ACV) may induce drug-induced neuropsychiatric symptoms as side effects. The detailed pathogenic mechanism remains unclear; however, it is hypothesized that 9-carboxymethoxymethylguanine (CMMG), a metabolite of ACV, is the causative compound. Therefore, the blood concentrations of ACV and CMMG should be analyzed in ACV toxicity studies. However, it is rare to find methods that can sufficiently separate the ACV and CMMG peaks during simultaneous analysis of both compounds. Therefore, we intended to develop a liquid chromatography-tandem mass spectrometry method with improved peak separation of analytes. Samples were deproteinized using methanol/acetonitrile solution (6:4, v/v). Analytes were separated on an InertSustain® Amide column (3 μm, 2.1 mm × 150 mm). The mobile phase consisted of acetonitrile/10 mM ammonium formate (5:95, v/v) (A) and acetonitrile/10 mM ammonium formate (95:5, v/v, pH 5.0) (B) and samples were eluted in the gradient mode. The separation of analytes was satisfactory and the peak shapes were good. Linear regression models weighted 1/x2 were obtained in the range of 0.25-10 μg/mL. The range of quality control (QC) bias was between 3.6% and 19.8%, and the within-run and between-run precisions of QC were within 13.5%. Recovery ranged from 83.6% to 103.7%, but ion suppression was observed. Samples from a patient with ACV encephalopathy were analyzed using this method. The resulting blood ACV and CMMG concentrations were 8.2 and 8.5 μg/mL, respectively. This method, with sufficient separation of ACV and CMMG, proved useful for use in ACV toxicity studies.

Association between aldehyde exposure and sex steroid hormones among adults

Exogenous and endogenous exposure to aldehydes is seen worldwide. Aldehydes are closely associated with human diseases, especially reproductive toxicity. However, the effect of aldehyde exposure on sex steroid hormones among adults remains uninvestigated. A total of 851 participants aged over 18 years were included in this cross-sectional analysis based on data from National Health and Nutrition Examination Survey (NHANES) 2013-2014. Serum aldehyde concentrations were quantified following an automated analytical method. Sex steroid hormones including total testosterone, estradiol, and sex hormone binding globulin (SHBG) were detected. Multivariate linear regression models, forest plots, generalized additive model (GAM), and smooth curve fitting analysis were used to assess the associations between quartiles of aldehydes and sex steroid hormones levels after adjusting for potential confounders. Butyraldehyde and propanaldehyde were found to be negatively associated with estradiol and SHBG in females and males, respectively. β values with 95% confidence intervals (95% CIs) were - 20.59 (- 38.30 to - 2.88) for Q2 vs. Q1 of butyraldehyde and - 8.13 (- 14.92 to - 1.33) and - 7.79 (- 14.91 to - 0.67) for Q2 vs. Q1 and Q4 vs. Q1 of propanaldehyde. No significant associations were observed between other aldehydes and sex hormones. In premenopausal women, isopentanaldehyde was inversely associated with serum total testosterone levels (Q4 vs. Q1: OR =  - 7.95, 95% CI: - 15.62 to - 0.27), whereas propanaldehyde was positively associated with serum estradiol concentration (Q3 vs. Q1: β = 28.88, 95% CI: 0.83 to 56.94). Compared with Q1, Q3 of isopentanaldehyde was associated with 3.53 pg/mL higher concentration of estradiol in postmenopausal women (β = 3.53, 95% CI: 0.08 to 6.97). Moreover, in males under 40 years, butyraldehyde and heptanaldehyde were inversely proportional to total testosterone levels and heptanaldehyde and butyraldehyde were negatively associated with estradiol and SHBG. Decreased total testosterone, elevated estradiol, and decreased SHBG levels were found in higher quartiles of benzaldehyde, hexanaldehyde and isopentanaldehyde, and propanaldehyde, respectively, in males aged over 60 years. In male participants aged 40-60 years, only hexanaldehyde was observed to be correlated with higher serum estradiol levels. In conclusion, our current research presented the association between six serum aldehydes and sex hormones. Of note, stratification analyses were conducted in participants with different menopausal statuses and age among males and females. Sex- and age-specific effect of aldehyde exposure on alterations in sex hormone levels were observed. Further studies are warranted to confirm the causal relationship and explore the underlying mechanisms.

New data on efficacy of valacyclovir in secondary prevention of maternal-fetal transmission of cytomegalovirus

OBJECTIVE

Congenital cytomegalovirus (CMV) infection is the leading cause of non-genetic hearing and neurological deficits. The aim of our study was to evaluate the efficacy and safety of valacyclovir (VCV) treatment in preventing CMV transmission to the fetus after maternal primary infection.

METHODS

This was a retrospective, multicenter study evaluating the rate of maternal-fetal CMV transmission in pregnancies with maternal primary CMV infection treated with VCV at a dosage of 8 g per day (VCV group) compared with a control group of untreated women. Each case underwent virological testing to confirm maternal primary infection and to provide accurate dating of onset of infection. The primary outcome was the presence of congenital CMV infection at birth diagnosed based on polymerase chain reaction analysis of saliva, urine and/or blood samples. The efficacy of VCV treatment was assessed using logistic regression analysis adjusted for a propensity score.

RESULTS

In total, 143 patients were included in the final analysis, of whom 59 were in the VCV group and 84 were in the untreated control group. On propensity-score-adjusted analysis, VCV treatment was significantly associated with an overall reduction in the rate of maternal-fetal CMV transmission (odds ratio, 0.40 (95% CI, 0.18-0.90); P = 0.029). The rate of maternal-fetal CMV transmission, determined at birth, in the VCV vs control group was 7% (1/14) vs 10% (1/10) after periconceptional maternal primary infection (P = 1.00), 22% (8/36) vs 41% (19/46) after first-trimester maternal primary infection (P = 0.068) and 25% (2/8) vs 52% (14/27) after second-trimester maternal primary infection (P = 0.244). When analyzing the efficacy of VCV treatment according to maternal viremia at treatment initiation, there was a trend towards greater efficacy when patients were viremia-positive (21% vs 43%; P = 0.072) compared with when they were viremia-negative (22% vs 17%; P = 0.659). Maternal side effects associated with VCV were mild and non-specific in most cases.

CONCLUSION

Our findings indicate that VCV treatment of pregnant women with primary CMV infection reduces the risk of maternal-fetal transmission of CMV and may be effective in cases with primary infection in the first and second trimesters. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Kaempferol Interferes with Varicella-Zoster Virus Replication in Human Foreskin Fibroblasts

Kaempferol, a natural flavonoid abundantly found in plants, is known to have pharmacological properties, such as anti-inflammatory and anti-cancer effects. In this study, we investigated the antiviral effects of kaempferol against a varicella-zoster virus (VZV) clinical isolate in vitro. We found that kaempferol significantly inhibited VZV replication without exhibiting cytotoxicity. Kaempferol exerted its antiviral effect at a similar stage of the VZV life cycle as acyclovir, which inhibits VZV DNA replication. Taken together, our results suggest that kaempferol inhibits VZV infection by blocking the DNA replication stage in the viral life cycle.

[A Pharmacist's Query Avoiding Exacerbation of Adverse Effects in a Patient with Acyclovir Encephalopathy: A Case Report]

We report a haemodialysis patient with end-stage renal failure whom a pharmacist aided in the management of acyclovir (ACV) encephalopathy, which may have been related to valacyclovir hydrochloride (VACV) administered without sufficient dose reduction. The patient 78 years was admitted with a tentative diagnosis of varicella zoster viral meningitis. A pharmacist suspected ACV encephalopathy related to excessive VACV administration and raised a query with the attending physician. According to the pharmacist's proposal, ACV administration was discontinued and continuous hemodiafiltration (CHDF) was performed. On day 5 of hospitalisation, the consciousness disorder was improved. In this report, we showed the detailed CHDF conditions of the present case, and the contribution of a pharmacist to treating and avoiding ACV encephalopathy was discussed.

Predicting Pharmacokinetics of Multisource Acyclovir Oral Products Through Physiologically Based Biopharmaceutics Modeling

Highly variable disposition after oral ingestion of acyclovir has been reported, although little is known regarding the underlying mechanisms. Different studies using the same reference product (Zovirax ®) showed that C_max and AUC were respectively 44 and 35% lower in Saudi Arabians than Europeans, consistent with higher frequencies of reduced-activity polymorphs of the organic cation transporter (OCT1) in Europeans. In this study, the contribution of physiology (i.e., OCT1 activity) to the oral disposition of acyclovir immediate release (IR) tablets was hypothesized to be greater than dissolution. The potential role of OCT1 was studied in a validated physiologically-based biopharmaceutics model (PBBM), while dissolution of two Chilean generics (with demonstrated bioequivalence) and the reference product was assessed in vitro. The PBBM suggested that OCT1 activity could partially explain population-related pharmacokinetic differences. Further, dissolution of generics was slower than the regulatory criterion for BCS III IR products. Remarkably, virtual bioequivalence (incorporating in vitro dissolution into the PBBM) correctly and robustly predicted the bioequivalence of these products, showcasing its value in support of failed BCS biowaivers. These findings suggest that very-rapid dissolution for acyclovir IR products may not be critical for BCS biowaiver. They also endorse the relevance of cross-over designs in bioequivalence trials.

Non-cytochrome P450 enzymes involved in the oxidative metabolism of xenobiotics: Focus on the regulation of gene expression and enzyme activity

Oxidative metabolism is one of the major biotransformation reactions that regulates the exposure of xenobiotics and their metabolites in the circulatory system and local tissues and organs, and influences their efficacy and toxicity. Although cytochrome (CY)P450s play critical roles in the oxidative reaction, extensive CYP450-independent oxidative metabolism also occurs in some xenobiotics, such as aldehyde oxidase, xanthine oxidoreductase, flavin-containing monooxygenase, monoamine oxidase, alcohol dehydrogenase, or aldehyde dehydrogenase-dependent oxidative metabolism. Drugs form a large portion of xenobiotics and are the primary target of this review. The common reaction mechanisms and roles of non-CYP450 enzymes in metabolism, factors affecting the expression and activity of non-CYP450 enzymes in terms of inhibition, induction, regulation, and species differences in pharmaceutical research and development have been summarized. These non-CYP450 enzymes are detoxifying enzymes, although sometimes they mediate severe toxicity. Synthetic or natural chemicals serve as inhibitors for these non-CYP450 enzymes. However, pharmacokinetic-based drug interactions through these inhibitors have rarely been reported in vivo. Although multiple mechanisms participate in the basal expression and regulation of non-CYP450 enzymes, only a limited number of inducers upregulate their expression. Therefore, these enzymes are considered non-inducible or less inducible. Overall, this review focuses on the potential xenobiotic factors that contribute to variations in gene expression levels and the activities of non-CYP450 enzymes.

Acute kidney injury and acyclovir-associated encephalopathy after administration of valacyclovir in an elderly person with normal renal function: A case report and literature review

INTRODUCTION

Acyclovir (ACV)-associated encephalopathy is related to an increase in plasma levels of 9-carboxymethoxymethylguanine, an ACV metabolite, and is often reported in patients with renal dysfunction. We report a case of ACV-associated encephalopathy with rapid progression of renal dysfunction after oral administration of valacyclovir (VACV) and review literature of previous ACV-associated encephalopathy cases.

PATIENT CONCERNS

An 88-year-old man was diagnosed with herpes zoster. VACV (3000 mg/day) treatment was initiated. Serum creatinine (Cr) level was 0.80 mg/dL. However, irritability, memory impairment, and decreased responsiveness occurred after 3 days. The Cr level was 6.76 mg/dL on admission.

DIAGNOSIS

He was diagnosed with ACV-associated encephalopathy with acute kidney injury.

INTERVENTIONS

VACV was discontinued, hemodialysis was initiated on the day of admission, and then the signs and symptoms improved approximately 72 hours after the admission.

CONCLUSION

Worsening of renal function and encephalopathy should be a focus when using VACV or ACV, regardless of age and original renal function. Acute kidney injury and ACV-associated encephalopathy may particularly occur in the elderly even when renal function is normal. Therefore, regular monitoring of renal function and consciousness is necessary during VACV treatment.

Antiviral Activities of Quercetin and Isoquercitrin Against Human Herpesviruses

We previously reported that the ethyl acetate (EtOAc) fraction of a 70% ethanol extract of Elaeocarpus sylvestris (ESE) inhibits varicella-zoster virus (VZV) and human cytomegalovirus (HCMV) replication in vitro. PGG (1,2,3,4,6-penta-O-galloyl-ß-D-glucose) is a major chemical constituent of the EtOAc fraction of ESE that inhibits VZV but not HCMV replication. In this study, we comprehensively screened the chemical compounds identified in the EtOAc fraction of ESE for potential antiviral properties. Among the examined compounds, quercetin and isoquercitrin displayed potent antiviral activities against both VZV and HCMV with no significant cytotoxic effects. Both compounds strongly suppressed the expression of VZV and HCMV immediate–early (IE) genes. Our collective results indicated that, in addition to PGG, quercetin and isoquercitrin are bioactive compounds in the EtOAc fraction of ESE that effectively inhibit human herpesvirus replication.

Physiologically Based Pharmacokinetic Models to Predict Maternal Pharmacokinetics and Fetal Exposure to Emtricitabine and Acyclovir

Pregnancy is associated with physiological changes that may impact drug pharmacokinetics (PK). The goals of this study were to build maternal-fetal physiologically based pharmacokinetic (PBPK) models for acyclovir and emtricitabine, 2 anti(retro)viral drugs with active renal net secretion, and to (1) evaluate the predicted maternal PK at different stages of pregnancy; (2) predict the changes in PK target parameters following the current dosing regimen of these drugs throughout pregnancy; (3) evaluate the predicted concentrations of these drugs in the umbilical vein at delivery; (4) compare the model performance for predicting maternal PK of emtricitabine in the third trimester with that of previously published PBPK models; and (5) compare different previously published approaches for estimating the placental permeability of these 2 drugs. Results showed that the pregnancy PBPK model for acyclovir predicted all maternal concentrations within a 2-fold error range, whereas the model for emtricitabine predicted 79% of the maternal concentrations values within that range. Extrapolation of these models to earlier stages of pregnancy indicated that the change in the median PK target parameters remained well above the target threshold. Concentrations of acyclovir and emtricitabine in the umbilical vein were overall adequately predicted. The comparison of different emtricitabine PBPK models suggested an overall similar predictive performance in the third trimester, but the comparison of different approaches for estimating placental drug permeability revealed large differences. These models can enhance the understanding of the PK behavior of renally excreted drugs, which may ultimately inform pharmacotherapeutic decision making in pregnant women and their fetuses.

Mechanisms of antimicrobial-induced nephrotoxicity in children

Drug-induced nephrotoxicity is responsible for 20% to 60% of cases of acute kidney injury in hospitalized patients and is associated with increased morbidity and mortality in both children and adults. Antimicrobials are one of the most common classes of medications prescribed globally and also among the most common causes of nephrotoxicity. A broad range of antimicrobial agents have been associated with nephrotoxicity, but the features of kidney injury vary based on the agent, its mechanism of injury and the site of toxicity within the kidney. Distinguishing nephrotoxicity caused by an antimicrobial agent from other potential inciting factors is important to facilitate both early recognition of drug toxicity and prompt cessation of an offending drug, as well as to avoid unnecessary discontinuation of an innocuous therapy. This review will detail the different types of antimicrobial-induced nephrotoxicity: acute tubular necrosis, acute interstitial nephritis and obstructive nephropathy. It will also describe the mechanism of injury caused by specific antimicrobial agents and classes (vancomycin, aminoglycosides, polymyxins, antivirals, amphotericin B), highlight the toxicodynamics of these drugs and provide guidance on administration or monitoring practices that can mitigate toxicity, when known. Particular attention will be paid to paediatric patients, when applicable, in whom nephrotoxin exposure is an often-underappreciated cause of kidney injury.

The footprints of mitochondrial impairment and cellular energy crisis in the pathogenesis of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and Fanconi's syndrome: A comprehensive review

Fanconi's Syndrome (FS) is a disorder characterized by impaired renal proximal tubule function. FS is associated with a vast defect in the renal reabsorption of several chemicals. Inherited and/or acquired conditions seem to be connected with FS. Several xenobiotics including many pharmaceuticals are capable of inducing FS and nephrotoxicity. Although the pathological state of FS is well described, the exact underlying etiology and cellular mechanism(s) of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and FS are not elucidated. Constant and high dependence of the renal reabsorption process to energy (ATP) makes mitochondrial dysfunction as a pivotal mechanism which could be involved in the pathogenesis of FS. The current review focuses on the footprints of mitochondrial impairment in the etiology of xenobiotics-induced FS. Moreover, the importance of mitochondria protecting agents and their preventive/therapeutic capability against FS is highlighted. The information collected in this review may provide significant clues to new therapeutic interventions aimed at minimizing xenobiotics-induced renal injury, serum electrolytes imbalance, and FS.

Determination of acyclovir in renal microdialysis fluid and confirmation of renal function index

Acyclovir (ACV) is a nucleoside antivirus-free agent that was developed and marketed by Burroughs Well-come of the United States. Renal damage from ACV has been a major factor limiting its clinical application. Thus, the renal toxicity mechanism of ACV requires systematic study. In our previous study, we speculated that the nephrotoxicity of ACV may be associated with oxidative stress. In addition to the study of ACV's toxic effect in vivo, it is also necessary to explore the absorption and distribution of ACV in the body to further investigate the changes to ACV in the body. In this study, the toxicokinetics ACV in the kidney of the rat were explored using microdialysis, and the renal function of rats was measured. The results showed that high-dose ACV is associated with renal toxicity after a single intravenous injection or successive administration.

Epidemiology of common resistant bacterial pathogens in the countries of the Arab League

No uniformly organised collection of data regarding antimicrobial resistance has occurred in the countries of the Arab League. 19 countries of the Arab League have published data for antimicrobial susceptibility for the WHO priority organisms, and seven of 14 of these organisms are included in this Review (Escherichia coli, Klebsiella spp, Pseudomonas aeruginosa, Acinetobacter baumannii, Salmonella spp, Staphylococcus aureus, and Streptococcus pneumoniae). Although E coli and Klebsiella spp resistance to third-generation cephalosporins is common in all countries, with prevalence reaching more than 50% in Egypt and Syria, carbapenem resistance is emerging, albeit with a prevalence of less than 10%. Conversely, a large amount of carbapenem resistance has been reported for P aeruginosa and A baumannii across the Arab League, reaching 50% and 88% of isolates in some countries. As for Salmonella spp, the prevalence of fluoroquinolone resistance has exceeded 30% in several areas. With regards to the Gram-positive pathogens, the prevalence of meticillin resistance in S aureus is reported to be between 20% and 30% in most countries, but exceeds 60% in Egypt and Iraq. The prevalence of penicillin non-susceptibility among pneumococci has reached more than 20% in Algeria, Egypt, Morocco, Saudi Arabia, and Tunisia. These findings highlight the need for structured national plans in the region to target infection prevention and antimicrobial stewardship.

Incidence and predictors of intravenous acyclovir-induced nephrotoxicity

To assess the incidence, predictive factors, and prognosis of acyclovir-induced nephrotoxicity. We conducted a historical prospective cohort study of patients treated with intravenous acyclovir in North Denmark Region from 2009 to 2016. Information on baseline demographics, co-morbidities, plasma creatinine, and treatment was obtained from the medical records. The primary outcome was an increase of ≥ 40 μmol/L in plasma creatinine level from baseline. We included 276 patients treated with intravenous acyclovir of which 29 (10.5%) met the primary outcome. In 14 cases, the treating physician considered acyclovir the main reason for nephrotoxicity, whereas a potential competing cause of renal impairment was present among the 15 remaining patients. Hypertension was the only predictive factor associated with nephrotoxicity (risk ratio (RR), 2.77; 95% confidence interval (CI), 1.41-5.46), while having no co-morbidities was protective (RR, 0.32; CI, 0.16-0.63). In all cases, the nephrotoxicity was reversible following rehydration and dose reduction or discontinuation of the drug. However, the normalized plasma creatinine upon treatment was significantly higher between cases with acyclovir-induced nephrotoxicity than cases with a potential competing cause (median [interquartile range (IQR)], 93.5 μmol/L [85-108] vs 75 μmol/L [66.5-88]; p = 0.019). Acyclovir-induced, reversible nephrotoxicity was observed in 5.1-10.5% of patients. It is difficult to predict who will develop acyclovir-induced nephrotoxicity; it may occur late in treatment and hypertension was the only independent predictive factor, while the absence of co-morbidities was protective. Ensuring hydration, frequent evaluations of renal function, and corresponding dose adjustment of intravenous acyclovir treatment seem prudent.

Emerging Kidney Models to Investigate Metabolism, Transport, and Toxicity of Drugs and Xenobiotics

The kidney is a major clearance organ of the body and is responsible for the elimination of many xenobiotics and prescription drugs. With its multitude of uptake and efflux transporters and metabolizing enzymes, the proximal tubule cell (PTC) in the nephron plays a key role in the disposition of xenobiotics and is also a primary site for toxicity. In this minireview, we first provide an overview of the major transporters and metabolizing enzymes in the PTCs responsible for biotransformation and disposition of drugs. Next, we discuss different cell sources that have been used to model PTCs in vitro, their pros and cons, and their characterization. As current technology is inadequate to evaluate reliably drug disposition and toxicity in the kidney, we then discuss recent advancements in kidney microphysiological systems (MPS) and the need to develop robust in vitro platforms that could be routinely used by pharmaceutical companies to screen compounds. Finally, we discuss the new and exciting field of stem cell-derived kidney models as potential cell sources for future kidney MPS. Given the push from both regulatory agencies and pharmaceutical companies to use more predictive "human-like" in vitro systems in the early stages of drug development to reduce attrition, these emerging models have the potential to be a game changer and may revolutionize how renal disposition and kidney toxicity in drug discovery are evaluated in the future.

Anti-HSV-2 activity of Terminalia chebula Retz extract and its constituents, chebulagic and chebulinic acids

Background

Development of new and effective therapeutics for sexually transmitted herpes simplex virus-2 (HSV-2) infection is important from public health perspective. With an aim to identify natural products from medicinal plants, in the present study, the potential of Terminalia chebula Retz was investigated for its activity against HSV-2.

Methods

Fruits of Terminalia chebula Retz were used to prepare 50% ethanolic extract. In addition, chebulagic acid and chebulinic acid both purified from T. chebula were also used. The extract as well as purified compounds were first used to determine their in vitro cytotoxicity on Vero cells by MTT assay. T. chebula extract, chebulagic acid, chebulinic acid along with acyclovir were subsequently assessed for direct anti-viral activity, and their ability to inhibit attachment and penetration of HSV-2 to the Vero cells. In addition, their anti-HSV-2 activity was also determined by in vitro post-infection plaque reduction assay.

Results

Cytotoxicity assay using Vero cells revealed CC₅₀ = 409.71 ± 47.70 μg/ml for the extract whereas chebulagic acid and chebulinic acid showed more than 95% cell viability up to 200 μg/ml. The extract from T. chebula (IC₅₀ = 0.01 ± 0.0002 μg/ml), chebulagic (IC₅₀ = 1.41 ± 0.51 μg/ml) and chebulinic acids (IC₅₀ = 0.06 ± 0.002 μg/ml) showed dose dependent potent in vitro direct anti-viral activity against HSV-2. These also effectively prevented the attachment as well as penetration of the HSV-2 to Vero cells. In comparison, acyclovir showed poor direct anti-viral activity and failed to significantly (p > 0.05) prevent the attachment as well as penetration of HSV-2 to Vero cells when tested upto 50 μg/ml. However, in post-infection plaque reduction assay, T. chebula extract, chebulagic and chebulinic acids showed IC₅₀ values of 50.06 ± 6.12, 31.84 ± 2.64, and 8.69 ± 2.09 μg/ml, respectively, which were much lower than acyclovir (71.80 ± 19.95 ng/ml).

Conclusions

The results presented herein suggest that T. chebula extract, chebulagic and chebulinic acids have higher direct antiviral activity against HSV-2 and efficacy to inhibit virus attachment and penetration to the host cells as compared to acyclovir. However, acyclovir is more potent to inhibit post-infection virus replication. Hence, T. chebula may be a useful candidate for developing alternative therapy for prevention of sexually transmitted HSV-2 infection.

Graphical abstract

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Methanol adducts leading to the identification of a reactive aldehyde metabolite of CPAQOP in human liver microsomes by ultra-high-performance liquid chromatography/mass spectrometry

RATIONALE

The incubation of CPAQOP (1-[(2R)-2-[[4-[3-chloro-4-(2-pyridyloxy)anilino]quinazolin-5-yl]oxymethyl]-1-piperidyl]-2-hydroxy) with human liver microsomes generated several metabolites that highlighted the hydroxyacetamide side chain was a major site of metabolism for the molecule. The metabolites were derived predominantly from oxidative biotransformations; however, two unexpected products were detected by liquid chromatography/ultraviolet/mass spectrometry (LC/UV/MS) and identified as methanol adducts. This observation prompted further LC/MS investigations into their formation.

METHODS

Three separate incubations of CPAQOP were conducted in human liver microsomes; Naïve, fortified with methoxyamine and fortified with glutathione. Separation was achieved via ultra-high-performance liquid chromatography with either methanol or acetonitrile gradients containing formic acid. MS analysis was conducted by electrospray ionisation LTQ Orbitrap mass spectrometry acquiring accurate mass full scan, data-dependent MS² and all ion fragmentation.

RESULTS

No methanol adducts were detected by MS when acetonitrile was used in the mobile phase instead of methanol, verifying that a metabolite was reacting with methanol on column. Although this reactive metabolite could not be isolated or structurally characterised by LC/MS directly, product ion spectra of the methanol adducts confirmed addition of methanol on the hydroxyacetamide side chain. Additional experiments using methoxyamine showed the disappearance of the two methanol adducts and appearance of a methoxyamine adduct, confirming the presence of an aldhyde. Product ion spectra of the methoxyamine adduct confirmed addition of methoxyamine to the hydroxyacetamide side chain.

CONCLUSIONS

The proposed bioactivation of CPAQOP occurred via the reactive aldehyde intermediate, which readily reacted with methanol in the mobile phase to form a pair of isomeric hemiacetal methanol adducts. In acidified methanol the equilibrium favoured the methanol adduct and in acidified acetonitrile it favoured the hydrate; therefore, the reactive aldehyde metabolite was not detected and could not be structurally characterised directly. Copyright © 2016 John Wiley & Sons, Ltd.

Drug-induced acute kidney injury in neonates

PURPOSE OF REVIEW

Acute kidney injury (AKI) is an independent risk factor for morbidity and mortality in critically ill neonates. Nephrotoxic medication exposure is common in neonates. Nephrotoxicity represents the most potentially avoidable cause of AKI in this population.

RECENT FINDINGS

Recent studies in critically ill children revealed the importance of recognizing AKI and potentially modifiable risk factors for the development of AKI such as nephrotoxic medication exposures. Data from critically ill children who have AKI suggest that survivors are at risk for the development of chronic kidney disease. Premature infants are born with incomplete nephrogenesis and are at risk for chronic kidney disease. The use of nephrotoxic medications in the neonatal intensive care unit is very common; yet the effects of medication nephrotoxicity on the short and long-term outcomes remains highly understudied.

SUMMARY

The neonatal kidney is predisposed to nephrotoxic AKI. Our ability to improve outcomes for this vulnerable group depends on a heightened awareness of this issue. It is important for clinicians to develop methods to minimize and prevent nephrotoxic AKI in neonates through a multidisciplinary approach aiming at earlier recognition and close monitoring of nephrotoxin-induced AKI.

Valacyclovir-Induced Acute Kidney Injury in Japanese Patients Based on the PMDA Adverse Drug Reactions Reporting Database

BACKGROUND

More than 250,000 reports of adverse drug events were included in the database of the Pharmaceuticals and Medical Devices Agency (PMDA) in Japan. However, these data have not been utilized sufficiently for analysis. While valacyclovir is the antiviral agent used worldwide, it is reported to induce nephrotoxicity. The aim of this study was to clarify the profiles of valacyclovir-induced adverse events using the PMDA database.

METHODS

Case reports were screened in the PMDA adverse event database from 2004 to 2011. The profiles of patients with acute kidney injury (AKI) were analyzed by sex, age, diseases, concomitant suspected drugs, and outcomes.

RESULTS

A total of 514 kidney-related adverse events were detected, and 344 were cases that included AKI. Of the AKI cases, 246 patients (71.5%) were female. There were 145 patients who were 70 to 79 years of age, which was the most affected of all age groups. Of the 344 patients, 183 patients had hypertension, and 65 had diabetes. Valacyclovir was the only drug used among 257 patients (74.1%).

CONCLUSIONS

There were many reports of AKI involving valacyclovir and females, particularly in the 70- to 79-year age group in Japan. The results suggest that these patients were most likely to develop AKI after valacyclovir treatment.

Proteomic characterization of acyclovir-induced nephrotoxicity in a mouse model

Acyclovir (ACV) is an effective and widely used antiviral agent. However, its clinical application is limited by severe nephrotoxicity. We assessed ACV-induced nephrotoxicity and identified the differentially expressed proteins using mass spectrometry-based proteomic analysis. In total, 30 ICR mice were intraperitoneally administrated ACV (150 or 600 mg/kg per day) for 9 days. After administration of ACV, levels of serum creatinine and urea nitrogen increased significantly. In addition, mouse kidneys exhibited histopathological changes and reduced expression levels of vascular endothelial growth factor (VEGF) and its receptor VEGFR2. In the proteomic analysis, more than 1,000 proteins were separated by two-dimensional polyacrylamide gel electrophoresis, and a total of 20 proteins were up- or down-regulated in the ACV group compared with the saline group. Among these, six proteins (MHC class II antigen, glyoxalase 1, peroxiredoxin 1, αB-crystallin, fibroblast growth factor receptor 1-IIIb, and cytochrome c oxidase subunit Vb) were identified in association with ACV-induced nephrotoxicity. These findings were confirmed by Western blotting analysis. The differential expression levels of α-BC, Prx1, Glo I and CcO Vb suggest that oxidative damage and mitochondrial injury may be involved in ACV-induced nephrotoxicity. Furthermore, VEGF and FGF may play a role in tissue repair and the restoration process following ACV nephrotoxicity.

Comparison of renal function indicators according to hydration volume in patients receiving intravenous acyclovir with CNS infection

PURPOSE

We aimed to compare the changes in renal function indicators as a function of hydration volume in patients treated with acyclovir for suspected herpes simplex virus (HSV) infection.

METHOD

We obtained data from 216 acyclovir-treated patients hospitalized between 2007 and 2012 for suspected HSV infection. Intravenous hydration volume and renal function indicators (serum creatinine [sCr], blood urea nitrogen [BUN], glutamate oxaloacetate transferase, glutamate pyruvate transferase, and uric acid levels; estimated glomerular filtration rate [eGFR]; and urine pH) were compared among the patients. The indicators were assessed before acyclovir infusion and after 3 days of acyclovir infusion.

RESULTS

Before acyclovir infusion, all the indicators were within normal ranges in all groups (hydration volume lower than 2 L/day, higher than 2 L/day, and without hydration). After acyclovir infusion for 3 days, the groups without hydration and with a volume lower than 2 L/day showed increased sCr (2.22 ± 0.51 and 1.70 ± 0.35 mg/dl, respectively), BUN levels (28.33 ± 0.57 and 22.14 ± 7.95 mg/dl, respectively), and glutamate oxaloacetate transferase (48.00 ± 2.65 IU/L, without hydration) and eGFRs lower than the normal range (53.03 ± 3.05 and 59.66 ± 10.25 ml/min, respectively; p < .001 for all parameters). The renal function indicators were within normal limits in the group with a hydration volume higher than 2 L/day.

CONCLUSIONS

Renal function indicators in acyclovir-treated patients varied according to hydration volume. Health care providers should consider whether the hydration volume in each patient receiving intravenous acyclovir is sufficient for preventing nephropathy.

Herpes zoster encephalopathy or acyclovir neurotoxicity: a management dilemma

This is a case report of a 69-year-old morbidly obese woman who presented with mental status changes after she was treated with acyclovir for shingles. The predominant symptoms were word-finding difficulties and visual hallucinations. Complicating her presentation was acyclovir-induced acute renal injury causing her creatinine level to rise up to 7.4 mg/dL. Acyclovir was discontinued on the suspicion of acyclovir neurotoxicity. Even though PCR for varicella zoster virus in the cerebrospinal fluid was positive, acyclovir was not restarted and the patient continued to improve and returned to her baseline.

N-terminal valine adduct from the anti-HIV drug abacavir in rat haemoglobin as evidence for abacavir metabolism to a reactive aldehyde in vivo

BACKGROUND AND PURPOSE

The aim of this study was to obtain evidence for the activation of the nucleoside reverse transcriptase inhibitor abacavir to reactive aldehyde metabolites in vivo. Protein haptenation by these reactive metabolites may be a factor in abacavir-induced toxic events.

EXPERIMENTAL APPROACH

The formation of N-terminal valine adducts from the abacavir-derived aldehydes was investigated in the haemoglobin of Wistar rats treated with eight daily doses (120 mg·kg(-1)) of abacavir. The analyses were conducted by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry upon comparison with synthetic standards.

KEY RESULTS

An N-terminal valine haemoglobin adduct derived from an α,β-unsaturated aldehyde metabolite of abacavir was identified in vivo for the first time.

CONCLUSIONS AND IMPLICATIONS

This preliminary work on abacavir metabolism provides the first unequivocal evidence for the formation of an α,β-unsaturated aldehyde metabolite in vivo and of its ability to form haptens with proteins. The methodology described herein can be used to assess the formation of this metabolite in human samples and has the potential to become a valuable pharmacological tool for mechanistic studies of abacavir toxicity. In fact, the simplicity of the method suggests that the abacavir adduct with the N-terminal valine of haemoglobin could be used to investigate abacavir-induced toxicity for accurate risk/benefit estimations.

Role of reactive metabolites in the circulation in extrahepatic toxicity

INTRODUCTION

Reactive metabolite-mediated toxicity is frequently limited to the organ where the electrophilic metabolites are generated. Some reactive metabolites, however, might have the ability to translocate from their site of formation. This suggests that for these reactive metabolites, investigations into the role of organs other than the one directly affected could be relevant to understanding the mechanism of toxicity.

AREAS COVERED

The authors discuss the physiological and biochemical factors that can enable reactive metabolites to cause toxicity in an organ distal from the site of generation. Furthermore, the authors present a case study which describes studies that demonstrate that S-(1,2-dichlorovinyl)-L-cysteine sulfoxide (DCVCS) and N-acetyl-S-(1,2-dichlorovinyl-L-cysteine sulfoxide (N-AcDCVCS), reactive metabolites of the known trichloroethylene metabolites S-(1,2-dichlorovinyl)-L-cysteine (DCVC), and N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (N-AcDCVC), are generated in the liver and translocate through the circulation to the kidney to cause nephrotoxicity.

EXPERT OPINION

The ability of reactive metabolites to translocate could be important to consider when investigating mechanisms of toxicity. A mechanistic approach, similar to the one described for DCVCS and N-AcDCVCS, could be useful in determining the role of circulating reactive metabolites in extrahepatic toxicity of drugs and other chemicals. If this is the case, intervention strategies that would not otherwise be feasible might be effective for reducing extrahepatic toxicity.