Characterization of urinary metabolites as biomarkers of colistin-induced nephrotoxicity in rats by a liquid chromatography/mass spectrometry-based metabolomics approach

Metabolomics highlights biochemical perturbations occurring in the kidney and liver of mice administered a human dose of colistin

Introduction: Colistin (CMS) is used for the curation of infections caused by multidrug-resistant bacteria. CMS is constrained by toxicity, particularly in kidney and neuronal cells. The recommended human doses are 2.5-5 mg/kg/day, and the toxicity is linked to higher doses. So far, the in vivo toxicity studies have used doses even 10-fold higher than human doses. It is essential to investigate the impact of metabolic response of doses, that are comparable to human doses, to identify biomarkers of latent toxicity. The innovation of the current study is the in vivo stimulation of CMS's impact using a range of CMS doses that have never been investigated before, i.e., 1 and 1.5 mg/kg. The 1 and 1.5 mg/kg, administered in mice, correspond to the therapeutic and toxic human doses, based on previous expertise of our team, regarding the human exposure. The study mainly focused on the biochemical impact of CMS on the metabolome, and on the alterations provoked by 50%-fold of dose increase. The main objectives were i) the comprehension of the biochemical changes resulting after CMS administration and ii) from its dose increase; and iii) the determination of dose-related metabolites that could be considered as toxicity monitoring biomarkers. Methods: The in vivo experiment employed two doses of CMS versus a control group treated with normal saline, and samples of plasma, kidney, and liver were analysed with a UPLC-MS-based metabolomics protocol. Both univariate and multivariate statistical approaches (PCA, OPLS-DA, PLS regression, ROC) and pathway analysis were combined for the data interpretation. Results: The results pointed out six dose-responding metabolites (PAA, DA4S, 2,8-DHA, etc.), dysregulation of renal dopamine, and extended perturbations in renal purine metabolism. Also, the study determined altered levels of liver suberylglycine, a metabolite linked to hepatic steatosis. One of the most intriguing findings was the detection of elevated levels of renal xanthine and uric acid, that act as AChE activators, leading to the rapid degradation of acetylcholine. This evidence provides a naïve hypothesis, for the potential association between the CMS induced nephrotoxicity and CMS induced 39 neurotoxicity, that should be further investigated.

Cyclosporine A-induced systemic metabolic perturbations in rats: A comprehensive metabolome analysis

A better understanding of cyclosporine A (CsA)-induced nephro- and hepatotoxicity at the molecular level is necessary for safe and effective use. Utilizing a sophisticated study design, this study explored metabolic alterations after long-term CsA treatment in vivo. Rats were exposed to CsA with 4, 10, and 25 mg/kg for 4 weeks and then sacrificed to obtain liver, kidney, urine, and serum for untargeted metabolomics analysis. Differential network analysis was conducted to explore the biological relevance of metabolites significantly altered by toxicity-induced disturbance. Dose-dependent toxicity was observed in all biospecimens. The toxic effects were characterized by alterations of metabolites related to energy metabolism and cellular membrane composition, which could lead to the cholestasis-induced accumulation of bile acids in the tissues. The unfavorable impacts were also demonstrated in the serum and urine. Intriguingly, phenylacetylglycine was increased in the kidney, urine, and serum treated with high doses versus controls. Differential correlation network analysis revealed the strong correlations of deoxycytidine and guanosine with other metabolites in the network, which highlighted the influence of repeated CsA exposure on DNA synthesis. Overall, prolonged CsA administration had system-level dose-dependent effects on the metabolome in treated rats, suggesting the need for careful usage and dose adjustment.

Pathway-level multi-omics analysis of the molecular mechanisms underlying the toxicity of long-term tacrolimus exposure

Tacrolimus (TAC)-based treatment is associated with nephrotoxicity and hepatotoxicity; however, the underlying molecular mechanisms responsible for this toxicity have not been fully explored. This study elucidated the molecular processes underlying the toxic effects of TAC using an integrative omics approach. Rats were sacrificed after 4 weeks of daily oral TAC administration at a dose of 5 mg/kg. The liver and kidney underwent genome-wide gene expression profiling and untargeted metabolomics assays. Molecular alterations were identified using individual data profiling modalities and further characterized by pathway-level transcriptomics-metabolomics integration analysis. Metabolic disturbances were mainly related to an imbalance in oxidant-antioxidant status, as well as in lipid and amino acid metabolism in the liver and kidney. Gene expression profiles also indicated profound molecular alterations, including in genes associated with a dysregulated immune response, proinflammatory signals, and programmed cell death in the liver and kidney. Joint-pathway analysis indicated that the toxicity of TAC was associated with DNA synthesis disruption, oxidative stress, and cell membrane permeabilization, as well as lipid and glucose metabolism. In conclusion, our pathway-level integration of transcriptome and metabolome and conventional analyses of individual omics profiles, provided a more comprehensive picture of the molecular changes resulting from TAC toxicity. This study also serves as a valuable resource for subsequent investigations aiming to understand the mechanism underlying the molecular toxicology of TAC.

Systems-level multi-omics characterization provides novel molecular insights into indomethacin toxicity

The mechanism of indomethacin toxicity at the systemic level is largely unknown. In this study, multi-specimen molecular characterization was conducted in rats treated with three doses of indomethacin (2.5, 5, and 10 mg/kg) for 1 week. Kidney, liver, urine, and serum samples were collected and analyzed using untargeted metabolomics. The kidney and liver transcriptomics data (10 mg indomethacin/kg and control) were subjected to a comprehensive omics-based analysis. Indomethacin exposure at 2.5 and 5 mg/kg doses did not cause significant metabolome changes, whereas considerable alterations in the metabolic profile compared to the control were induced by a dose of 10 mg/kg. Decreased levels of metabolites and an increased creatine level in the urine metabolome indicated injury to the kidney. The integrated omics analysis in both liver and kidney revealed an oxidant-antioxidant imbalance due to an excess of reactive oxygen species, likely originating from dysfunctional mitochondria. Specifically, indomethacin exposure induced changes in metabolites related to the citrate cycle, cell membrane composition, and DNA synthesis in the kidney. The dysregulation of genes related to ferroptosis and suppression of amino acid and fatty acid metabolism were evidence of indomethacin-induced nephrotoxicity. In conclusion, a multi-specimen omics investigation provided important insights into the mechanism of indomethacin toxicity. The identification of targets that ameliorate indomethacin toxicity will enhance the therapeutic utility of this drug.

Adverse Events and Drug Resistance in Critically Ill Patients Treated with Colistimethate Sodium: A Review of the Literature

The adverse events related to sodium colistimethate have had variability regarding the prevalence of nephrotoxicity, neurotoxicity, and less frequent respiratory depression. In recent years, its use has been relevant due to the increase of multidrug-resistant bacteria since it is considered the last-line drug, being its main adverse event and reason for discrepancies between authors' nephrotoxicity. The indiscriminate use of antibiotic therapy has generated multiple mechanisms of resistance, the most common being related to Colistin, the bactericidal escape effect. Based on the search criteria, no randomized clinical trials were identified showing safety and efficacy with the use of Colistin, inferring that the application of the appropriate dose is governed by expert opinion and retrospective and prospective observational studies, which confounding factors such as the severity of the patient and the predisposition to develop acute renal failure are constant. In this review, we focus on identifying the mechanism of nephrotoxicity and bacterial resistance, where much remains to be known.

Genome-wide gene expression analysis reveals molecular insights into the drug-induced toxicity of nephrotoxic agents

Drug-induced nephrotoxicity is frequently reported. However, the mechanisms underlying nephrotoxic medications and their overlapping molecular events, which might have therapeutic value, are unclear. We performed a genome-wide analysis of gene expression and a gene set enrichment analysis to identify common and unique pathways associated with the toxicity of colistin, ifosfamide, indomethacin, and puromycin. Rats were randomly allocated into the treatment or control group. The treatment group received a toxic dose once daily of each investigated drug for 1 week. Differentially expressed genes were found in the drug-treated kidney and liver compared to the control, except for colistin in the liver. Upregulated pathways were mainly related to cell death, cell cycle, protein synthesis, and immune response modulation in the kidney. Cell cycle was upregulated by all drugs. Downregulated pathways were associated with carbon metabolism, amino acid metabolism, and fatty acid metabolism. Indomethacin, colistin, and puromycin shared the most altered pathways in the kidney. Ifosfamide and indomethacin affected molecular processes greatly in the liver. Our findings provide insight into the mechanisms underlying the renal and hepatic adverse effects of the four drugs. Further investigation should explore the combinatory drug therapies that attenuate the toxic effects and maximize the effectiveness of nephrotoxic drugs.

Omeprazole Prevents Colistin-Induced Nephrotoxicity in Rats: Emphasis on Oxidative Stress, Inflammation, Apoptosis and Colistin Accumulation in Kidneys

The clinical value of colistin, a polymyxin antibiotic, is limited by its nephrotoxicity. Omeprazole is a commonly prescribed proton pump inhibitor. The current study aimed to evaluate the effects of the concomitant administration of omeprazole on colistin-induced nephrotoxicity in rats. Omeprazole significantly ameliorated colistin nephrotoxicity as evidenced by prevention in the rise in the serum level of creatinine, urea and cystactin C as well as urinary N-acetylglucosamine activity. This was confirmed by histological studies that indicated a decreased incidence of interstitial nephritis, degenerative cortical changes and collagen deposition. This was accompanied by the prevention of oxidative stress as omeprazole significantly inhibited the lipid peroxidation, glutathione depletion and enzymatic exhaustion of superoxide dismutase as well as catalase. Additionally, omeprazole inhibited the expression of interleukin-6 and tumor necrosis factor-α. Further, omeprazole inhibited the colistin-induced rise in Bax and the down-regulation of Bcl2 mRNA expression. An assessment of the serum levels of colistin revealed that omeprazole had no significant impact. However, it was observed that omeprazole significantly inhibited the accumulation of colistin in kidney tissues. In conclusion, omeprazole protects against colistin-induced nephrotoxicity. This can be attributed to, at least partly, omeprazole's anti-oxidant, anti-inflammatory and anti-apoptotic activities in addition to its ability to prevent the toxic accumulation of colistin in kidneys.

Organic Cation Transporters in Human Physiology, Pharmacology, and Toxicology

Individual cells and epithelia control the chemical exchange with the surrounding environment by the fine-tuned expression, localization, and function of an array of transmembrane proteins that dictate the selective permeability of the lipid bilayer to small molecules, as actual gatekeepers to the interface with the extracellular space. Among the variety of channels, transporters, and pumps that localize to cell membrane, organic cation transporters (OCTs) are considered to be extremely relevant in the transport across the plasma membrane of the majority of the endogenous substances and drugs that are positively charged near or at physiological pH. In humans, the following six organic cation transporters have been characterized in regards to their respective substrates, all belonging to the solute carrier 22 (SLC22) family: the organic cation transporters 1, 2, and 3 (OCT1–3); the organic cation/carnitine transporter novel 1 and 2 (OCTN1 and N2); and the organic cation transporter 6 (OCT6). OCTs are highly expressed on the plasma membrane of polarized epithelia, thus, playing a key role in intestinal absorption and renal reabsorption of nutrients (e.g., choline and carnitine), in the elimination of waste products (e.g., trimethylamine and trimethylamine N-oxide), and in the kinetic profile and therapeutic index of several drugs (e.g., metformin and platinum derivatives). As part of the Special Issue Physiology, Biochemistry, and Pharmacology of Transporters for Organic Cations, this article critically presents the physio-pathological, pharmacological, and toxicological roles of OCTs in the tissues in which they are primarily expressed.

Identification of serum metabolites associating with chronic kidney disease progression and anti-fibrotic effect of 5-methoxytryptophan

Early detection and accurate monitoring of chronic kidney disease (CKD) could improve care and retard progression to end-stage renal disease. Here, using untargeted metabolomics in 2155 participants including patients with stage 1–5 CKD and healthy controls, we identify five metabolites, including 5-methoxytryptophan (5-MTP), whose levels strongly correlate with clinical markers of kidney disease. 5-MTP levels decrease with progression of CKD, and in mouse kidneys after unilateral ureteral obstruction (UUO). Treatment with 5-MTP ameliorates renal interstitial fibrosis, inhibits IκB/NF-κB signaling, and enhances Keap1/Nrf2 signaling in mice with UUO or ischemia/reperfusion injury, as well as in cultured human kidney cells. Overexpression of tryptophan hydroxylase-1 (TPH-1), an enzyme involved in 5-MTP synthesis, reduces renal injury by attenuating renal inflammation and fibrosis, whereas TPH-1 deficiency exacerbates renal injury and fibrosis by activating NF-κB and inhibiting Nrf2 pathways. Together, our results suggest that TPH-1 may serve as a target in the treatment of CKD.

Accurate monitoring of chronic kidney disease (CKD) progression is essential for efficient disease management. Here Chen et al. identify five serum metabolites in patients with stage 1–5 CKD whose levels associate with disease progression, and find that 5-methoxytryptophan and its regulatory enzyme TPH-1 exert anti-fibrotic effects in mouse models of kidney injury.

Molecular Mechanisms of Colistin-Induced Nephrotoxicity

The emergence of multidrug resistant (MDR) infections and the shortage of new therapeutic options have made colistin, a polymyxin antibiotic, the main option for the treatment of MDR Gram-negative bacterial infections in the last decade. However, the rapid onset of renal damage often prevents the achievement of optimal therapeutic doses and/or forces the physicians to interrupt the therapy, increasing the risk of drug resistance. The proper management of colistin-induced nephrotoxicity remains challenging, mostly because the investigation of the cellular and molecular pharmacology of this drug, off the market for decades, has been largely neglected. For years, the renal damage induced by colistin was considered a mere consequence of the detergent activity of this drug on the cell membrane of proximal tubule cells. Lately, it has been proposed that the intracellular accumulation is a precondition for colistin-mediated renal damage, and that mitochondria might be a primary site of damage. Antioxidant approaches (e.g., ascorbic acid) have shown promising results in protecting the kidney of rodents exposed to colistin, yet none of these strategies have yet reached the bedside. Here we provide a critical overview of the possible mechanisms that may contribute to colistin-induced renal damage and the potential protective strategies under investigation.

Characterization of urinary biomarkers and their relevant mechanisms of zoledronate-induced nephrotoxicity using rats and HK-2 cells

The aim of this study was to identify biomarkers of zoledronate-induced nephrotoxicity and to further characterize the mechanisms underlying this process by analyzing urinary metabolites. Twenty-four rats were randomly divided into four groups containing four (two control groups) or eight rats (two zoledronate groups) per group. The rats were injected intravenously with saline or zoledronate (3 mg/kg) singly (single, 3 weeks) or repeatedly eight times (3 weeks/time, 24 weeks). Serum blood urea nitrogen, serum creatinine, creatinine clearance, and kidney injury observed by hematoxylin and eosin and immunohistochemical staining were changed only in the repeated zoledronate group (3 mg/kg, 3 weeks/time, 24 weeks). Urinary levels of S-adenosylmethionine, S-adenosylhomocysteine, l-cystathionine, l-γ-glutamylcysteine, and glutathione related to glutathione metabolism and fumaric acid and succinic acid related to the tricarboxylic acid cycle in the zoledronate-treated group (3 mg/kg, 3 weeks/time, 24 weeks) were significantly lower than those in the control group, suggesting that zoledronate may cause cellular oxidative stress. Besides, urinary levels of uracil and uridine related to pyrimidine metabolism also decreased after zoledronate treatment (3 mg/kg, 3 weeks/time, 24 weeks), while the levels of hypoxanthine related to purine metabolism, histamine related to histamine metabolism, and several amino acids were significantly increased. Moreover, zoledronate-induced enhanced oxidative stress and histamine overproduction were confirmed by reactive oxygen species (ROS) and histamine measurement in a human proximal tubular cell line. Taken together, zoledronate-induced nephrotoxicity may be attributed to it inducing perturbations in glutathione biosynthesis and the tricarboxylic acid cycle, further causing ROS overproduction, oxidative stress, and cellular inflammation, thereby leading to nephrotoxicity.