Evaluation of Dose-Fractionated Polymyxin B on Acute Kidney Injury Using a Translational In Vivo Rat Model

The Effect of Different Colistin Dosing Regimens on Nephrotoxicity: A Cohort Study

(1) Background: It is not known whether different daily dosing schemes have different effects on colistin nephrotoxicity. We examined the effect of once- versus twice- or thrice-daily doses of colistin on renal function. (2) Methods: We performed a multicenter retrospective cohort study of hospitalized patients with a baseline glomerular filtration rate ≥ 50 mL/min who received intravenously the same colistin dose once (regimen A), twice (regimen B) or thrice daily (regimen C). The primary endpoint was acute kidney injury (AKI), defined as fulfilment of any of the RIFLE (Risk-Injury-Failure-Loss-End stage renal disease) criteria. (3) Results: We included 306 patients; 132 (43.1%) received regimen A, 151 (49.3%) regimen B, and 23 (7.5%) regimen C. Ninety-nine (32.4%) patients developed AKI; there was no difference between regimen A vs. B and C [45 (34.1%) vs. 54 (31.0%), p = 0.57]. In a propensity score−matched cohort, AKI was similar in patients receiving Regimen A, Regimen B, and Regimen C (31.6% vs. 33.3%, p = 0.78). On logistic regression analysis, diabetes was an independent predictor of AKI (OR = 4.59, 95% CI 2.03−10.39, p = 0.001) while eGFR > 80 mL/min (OR = 0.50, 95% CI 0.25−0.99, p = 0.048) was inversely associated with AKI. (4) Conclusions: Colistin once daily is not more nephrotoxic than the standard colistin regimens. The only independent predictor of nephrotoxicity was diabetes mellitus, while eGFR > 80 mL/min had a protective effect.

Urinary Metabolomics from a Dose-Fractionated Polymyxin B Rat Model of Acute Kidney Injury

BACKGROUND

Polymyxin B treatment is limited by kidney injury. We sought to identify Polymyxin B related urinary metabolomic profile modifications for early detection of polymyxin-associated nephrotoxicity.

METHODS

Samples were obtained from a previously conducted study. Male Sprague-Dawley rats received dose-fractionated polymyxin B (12mg/kg/day) once daily (QD), twice daily (BID), and thrice daily (TID) for three days with urinary biomarkers and kidney histopathology scores determined. Daily urine was analysed for metabolites via 1H NMR. Principal Components Analyses identified spectral data trends with orthogonal Partial Least Square Discriminant Analysis applied to classify metabolic differences. Metabolomes were compared across groups (i.e., those receiving QD, BID, TID, and control) using a mixed-effects models. Spearman correlation was performed for injury biomarkers and the metabolome.

RESULTS

A total of 25 rats were treated with Polymyxin B, and n=2 received saline, contributing 77 urinary samples. Pre-dosing samples clustered well, characterized by higher amounts of citrate, 2-oxoglutarate, and hippurate. Day 1 samples showed higher taurine; day 3 samples had higher lactate, acetate, and creatine. Taurine was the only metabolite significantly increased in both BID and TID compared to QD group. Day 1 taurine correlated with increasing histopathology scores (rho=0.4167, P=0.038) and KIM-1 (rho =0.4052, P=0.036); whereas KIM-1 on day one and day 3 did not reach significance with histopathology (rho=0.3248, P=0.11 and rho=0.3739, P=0.066).

CONCLUSIONS

Polymyxin B causes increased amounts of urinary taurine on day 1 which then normalizes to baseline concentrations. Taurine may provide one of the earlier signals of acute kidney damage caused by polymyxin B.

Nephrotoxic antisense oligonucleotide SPC5001 induces kidney injury biomarkers in a proximal tubule-on-a-chip

Antisense oligonucleotides (ASOs) are a promising therapeutic modality. However, failure to predict acute kidney injury induced by SPC5001 ASO observed in a clinical trial suggests the need for additional preclinical models to complement the preceding animal toxicity studies. To explore the utility of in vitro systems in this space, we evaluated the induction of nephrotoxicity and kidney injury biomarkers by SPC5001 in human renal proximal tubule epithelial cells (HRPTEC), cultured in 2D, and in a recently developed kidney proximal tubule-on-a-chip. 2D HRPTEC cultures were exposed to the nephrotoxic ASO SPC5001 or the safe control ASO 556089 (0.16-40 µM) for up to 72 h, targeting PCSK9 and MALAT1, respectively. Both ASOs induced a concentration-dependent downregulation of their respective mRNA targets but cytotoxicity (determined by LDH activity) was not observed at any concentration. Next, chip-cultured HRPTEC were exposed to SPC5001 (0.5 and 5 µM) and 556089 (1 and 10 µM) for 48 h to confirm downregulation of their respective target transcripts, with 74.1 ± 5.2% for SPC5001 (5 µM) and 79.4 ± 0.8% for 556089 (10 µM). During extended exposure for up to 20 consecutive days, only SPC5001 induced cytotoxicity (at the higher concentration; 5 µM), as evaluated by LDH in the perfusate medium. Moreover, perfusate levels of biomarkers KIM-1, NGAL, clusterin, osteopontin and VEGF increased 2.5 ± 0.2-fold, 3.9 ± 0.9-fold, 2.3 ± 0.6-fold, 3.9 ± 1.7-fold and 1.9 ± 0.4-fold respectively, in response to SPC5001, generating distinct time-dependent profiles. In conclusion, target downregulation, cytotoxicity and kidney injury biomarkers were induced by the clinically nephrotoxic ASO SPC5001, demonstrating the translational potential of this kidney on-a-chip.

Effect of Different Dosage Frequency of Polymyxin B on Rat Nephrotoxicity

Background

Polymyxin B, as the final treatment against multidrug-resistant Gram-negative bacilli, is widely used in clinical practice. However, little is known about the nephrotoxicity of polymyxin B. The purpose of this study was to elucidate the relationship between polymyxin B nephrotoxicity and daily administration frequency.

Methods

Sprague–Dawley rats were randomly divided into three groups: 18 mg/kg/q24 h group (Group A, once daily), 9 mg/kg/q12 h group (Group B, twice daily), and normal saline control group (Group C). The rats were injected subcutaneously for 5 consecutive days with the same daily total dose and different frequency of administration. The serum creatinine (SCr) and blood urea nitrogen (BUN) of each group before administration (0 h), and 8 and 24 h after administration, were measured by tail vein blood sampling. On the sixth day, the rats in each group were killed, the left kidney was taken for pathological section observation, and the results of each group were compared.

Results

After 96 h of administrated polymyxin B, the total average level of SCr in Group A was 56.98±12.42 μmol/L, that of Group B was 52.02±8.68 μmol/L, and that of Group C was 34.36±5.39 μmol/L. BUN was 9.86±4.58, 10.54±4.08, and 3.55±0.73 mmol/L in Groups A, B, and C, respectively. The daily urinary protein excretion was 5004.45±1333.84 μg in Group A, 4608.04±1444.42 μg in Group B, and 2096.33±215.28 μg in Group C. In addition, according to the observation of pathological slices, compared with Group A, the number of exfoliated and necrotic cells of renal tubules in Group B was higher, and the morphological changes were more serious.

Conclusion

The experimental results showed that the renal toxicity in rats treated with a twice-daily subcutaneous dose of polymyxin B was higher than that in rats treated with once-daily dose of polymyxin B.

Comparing the Population Pharmacokinetics of and Acute Kidney Injury Due to Polymyxin B in Chinese Patients with or without Renal Insufficiency

Despite excellent bactericidal effect, dosing adjustment of polymyxin B for patients with renal insufficiency and polymyxin B-related nephrotoxicity is still a major concern to clinicians. The aim of this study was to compare the population pharmacokinetics (PK) properties of polymyxin B in Chinese patients with different renal functions and to investigate the relationship between PK parameters and polymyxin B-related acute kidney injury (AKI). A total of 37 patients with normal renal function (creatinine clearance ≥ 80 ml/min) and 33 with renal insufficiency (creatinine clearance < 80 ml/min) were included. In the two-compartment population PK models, the central compartment clearance (CL) (2.19 liters/h versus 1.58 liters/h; P < 0.001) and intercompartmental clearance (Q) (13.83 liters/h versus 10.28 liters/h; P < 0.001) values were significantly different between the two groups. The simulated values for AUC across 24 h at steady state (AUC_ss,24h) for patients with normal renal function were higher than those for patients with renal insufficiency. However, renal dosing adjustment of polymyxin B seemed not to be necessary. In addition, during the treatment, AKI occurred in 23 (32.86%) patients. The polymyxin B AUC_ss,24h in patients with AKI was significantly higher than that in patients without AKI (108.66 ± 70.10 mg · h/liter versus 66.18 ± 34.79 mg · h/liter; P = 0.001). Both the receiver operating characteristic (ROC) curve and logistic regression analysis showed that an AUC_ss,24h of >100 mg · h/liter was a good predictor for the probability of nephrotoxicity.