Effect of Chronic Kidney Disease on Hepatic Clearance of Drugs in Rats

The pharmacokinetics of some hepatically cleared drugs have been reported to fluctuate in patients with renal impairment, but the definitive factors have not been clarified. We compared the pharmacokinetics of some drugs with different hepatic elimination processes in a chronic kidney disease (CKD) rat model, to optimize their administration during kidney injury. We chose indocyanine green (ICG), midazolam (MDZ), and acetaminophen (APAP) as reference drugs to determine changes in hepatic clearance pathways in presence of CKD. Drugs were intravenously administered via the jugular vein to the CKD model rats, previously established by adenine administration, and then, blood, bile, and urine samples were collected. The plasma concentration of ICG, which is eliminated into the bile without biotransformation, increased; and its total body clearance (CL_tot) significantly decreased in the CKD group compared to the control group. Moreover, the plasma concentrations of MDZ and APAP, metabolized in the liver by CYP3A and Ugt1a6 enzymes, respectively, were higher in the CKD group than in the control group. The biliary clearances of APAP and its derivative APAP-glucuronide increased in the CKD group, whereas their renal clearances were markedly decreased with respect to those in the control group. Altogether, plasma concentrations of some hepatically eliminated drugs increased in the CKD rat model, but depending on their pharmacokinetic characteristics. This study provides useful information for optimizing the administration of some hepatically cleared drugs in CKD patients.

Toxicology of paraquat and pharmacology of the protective effect of 5-hydroxy-1-methylhydantoin on lung injury caused by paraquat based on metabolomics

Paraquat (PQ) is a non-selective herbicide and is exceedingly toxic to humans. The mechanism of PQ toxicity is very complex and has not been clearly defined. There is no specific antidote for PQ poisoning. 5-hydroxy-1-methylhydantoin (HMH) is an intrinsic antioxidant and can protect against renal damage caused by PQ. The mechanism of PQ toxicology and the possible effects of HMH on PQ-induced lung injury were determined in this study. It was found that PQ decreased superoxide dismutase (SOD) activity and elevated the level of malondialdehyde (MDA), while HMH elevated SOD activity and decreased the level of MDA. Based on metabolomics, the citrate cycle, glutathione metabolism, taurine and hypotaurine metabolism, regulation of lipolysis in adipocytes, inflammatory mediator regulation of TRP channels, purine and pyrimidine metabolism, aldosterone synthesis and secretion, and phenylalanine metabolism were changed in the PQ group. Compared with the PQ group, the levels of N-acetyl-l-aspartic acid, L-glutamic acid, L-aspartic acid, mesaconic acid, adenosine 5′ monophosphate, methylmalonic acid, cytidine, phosphonoacetic acid, hypotaurine, glutathione (reduced) and cysteinylglycine increased, while the levels of corticosterone, xanthine, citric acid, prostaglandin G2, 4-pyridoxic acid and succinyl proline decreased in the HMH group. These metabolites revealed that HMH can alleviate inflammation caused by PQ and elevate the activity of intrinsic antioxidants. In conclusion, our results revealed PQ toxicology and the pharmacology underlying the protective effect of HMH on lung injury due to PQ. Toxicity caused by PQ results in lipid peroxidation and an increase in reactive oxygen species (ROS), nitric oxide (NO), damage to the biliary system, gastrointestinal system and nervous system, in addition to lungs, kidneys, and the liver. HMH is a good antioxidant and protects against lung injury caused by PQ. In summary, HMH efficiently reduced PQ-induced lung injury in mice.

The Radical Scavenger NZ-419 Suppresses Intestinal Polyp Development in Apc-Mutant Mice

Colorectal cancer is the fourth leading cause of cancer death worldwide, and it is important to establish effective methods for preventing colorectal cancer. One effective prevention strategy could be the use of antioxidants. However, the role of the direct antioxidative function of antioxidants against carcinogenesis has not been clarified. Thus, we aimed to determine whether the direct removal of reactive oxygen species by a hydroxyl radical scavenger, NZ-419, could inhibit colorectal carcinogenesis. NZ-419 is a creatinine metabolite that has been shown to be safe and to inhibit the progression of chronic kidney disease in rats, and it is now under clinical development. In the present study, we demonstrated that NZ-419 eliminated reactive oxygen species production in HCT116 cells after H₂O₂ stimulation and suppressed H₂O₂-induced Nrf2 promoter transcriptional activity. The administration of 500 ppm NZ-419 to Apc-mutant Min mice for 8 weeks resulted in a decrease in the number of polyps in the middle segment of the small intestine to 62.4% of the value in the untreated control (p < 0.05 vs. control group). As expected, NZ-419 treatment affected the levels of reactive carbonyl species, which are oxidative stress markers in the serum of Min mice. Suppression of the mRNA levels of the proliferation-associated factor c-Myc was observed in intestinal polyps of Min mice after NZ-419 treatment, with a weak suppression of epithelial cell proliferation assessed by proliferation cell nuclear antigen (PCNA) staining in the intestinal polyps. This study demonstrated that NZ-419 suppress the development of intestinal polyps in Min mice, suggesting the utility of radical scavenger/antioxidants as a cancer chemopreventive agent.

Oxidative stress contributes to vascular calcification in patients with chronic kidney disease

Vascular calcification (VC) is a major cause of mortality in patients with chronic kidney disease (CKD). While elevations in serum phosphorus contribute to VC, we provide evidence here for a major role of oxidative stress (OS) in VC pathogenesis without an apparent increase in serum phosphorus in early CKD. In a rat model for stage 5 CKD (CKD5), we observed 1) robust increases of VC and OS, 2) significant reductions of smooth muscle 22 alpha (SM22α) and calponin, and 3) upregulations in Runt-related transcription factor 2 (RUNX2) and collagen I in vascular smooth muscle cells (VSMCs). Inhibition of OS using MnTMPyP dramatically reduced these events without normalization of hyperphosphatemia. In CKD5 patients with VC (n = 11) but not in those without VC (n = 13), OS was significantly elevated. While the serum levels of calcium and phosphate were not altered in the animal model for early stage CKD (ECKD), OS, VC, SM22α, calponin, RUNX2, collagen I and NADPH oxidase 1 (NOX1) in VSMCs were all significantly changed. More importantly, serum (5%) derived from patients with ECKD (n = 30) or CKD5 (n = 30) induced SM22α and calponin downregulation, and RUNX2, collagen I, NOX1 upregulation along with a robust elevation of OS and calcium deposition in primary rat VSMCs. These alterations were all reduced by MnTMPyP, ML171 (a NOX1 inhibitor), and U0126 (an inhibitor of Erk signaling). Collectively, we provide a comprehensive set of evidence supporting an important role of OS in promoting VC development in CKD patients (particularly in those with ECKD); this was at least in part through induction of osteoblastic transition in VSMCs which may involve the Erk singling. Our research thus suggests that reductions in OS may prevent VC in CKD patients.

Protective mechanism of 1-methylhydantoin against lung injury induced by paraquat poisoning

Paraquat (PQ), one of the most widely used herbicides worldwide, causes severe toxic effects in humans and animals. 1-methylhydantoin (MH) is an active ingredient of Ranae Oviductus, which has broad pharmacological activities, e.g., eliminating reactive oxygen species and inhibiting inflammation. This study investigated the effects of MH on lung injury induced by PQ. A PQ poisoning model was established by intragastric infusion of PQ (25 mg/kg), and the control group was simultaneously gavaged with the same dose of saline. The MH group was intraperitoneally injected with 100 mg/kg once per day after intragastric infusion of PQ (25 mg/kg) for five consecutive days. All animals were sacrificed on the sixth day, and the lung tissues were dissected for metabolomics analysis. The lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity, TNF-α and malondialdehyde (MDA) content were determined according to the instructions of the detection kit. Compared with that in the control group, the content of LDH, TNF-α and MDA in the lung tissue of the PQ group was significantly higher, and the activity of SOD in the lung tissue was significantly lower (all p<0.05). Compared with that in the control group, the content of LDH, TNF-α and MDA in the MH group was significantly higher, and the activity of SOD was significantly lower (all p<0.05). However, the differences in SOD activity, LDH activity between the PQ and MH groups were not statistically significant (all p > 0.05). There were significant differences in MDA and TNF-α content between the PQ group and MH group (all p<0.05). MH decreased the production of malondialdehyde and TNF-α to protect against the lung injury caused by PQ poisoning, but it had no significant effect on the activity of LDH and SOD. There were significant differences in metabolomics between the MH group and the PQ poisoning group, primarily in bile acid biosynthesis and metabolism of cholesterol, nicotinate, nicotinamide, alanine, aspartate, glutamate, glycine, threonine, serine, phenylalanine and histidine. Therefore, this study highlights that MH has non-invasive mechanisms and may be a promising tool to treat lung injury induced by PQ poisoning.

Crystal structure of 3-(2-(4-isobutylphenyl)propanoyl)-1-methylimidazolidine-2,4-dione, C17H22N2O3

C17H22N2O3, monoclinic, P21/c, (no. 14) a = 18.419(4) Å, b = 5.7524(12) Å, c = 17.575(4) Å, β = 117.267(3)°, V =1655.2(6) Å3, Z = 4, R gt(F) = 0.0724, wR ref(F 2) = 0.1899, T = 187(2) K.

High-NaCl diet impairs dynamic renal blood flow autoregulation in rats with adenine-induced chronic renal failure

This study examined the effects of 2 wk of high-NaCl diet on kidney function and dynamic renal blood flow autoregulation (RBFA) in rats with adenine-induced chronic renal failure (ACRF). Male Sprague-Dawley rats received either chow containing adenine or were pair-fed an identical diet without adenine (controls). After 10 wk, rats were randomized to either remain on the same diet (0.6% NaCl) or to be switched to high 4% NaCl chow. Two weeks after randomization, renal clearance experiments were performed under isoflurane anesthesia and dynamic RBFA, baroreflex sensitivity (BRS), systolic arterial pressure variability (SAPV), and heart rate variability were assessed by spectral analytical techniques. Rats with ACRF showed marked reductions in glomerular filtration rate and renal blood flow (RBF), whereas mean arterial pressure and SAPV were significantly elevated. In addition, spontaneous BRS was reduced by ∼50% in ACRF animals. High-NaCl diet significantly increased transfer function fractional gain values between arterial pressure and RBF in the frequency range of the myogenic response (0.06–0.09 Hz) only in ACRF animals (0.3 ± 4.0 vs. −4.4 ± 3.8 dB; P < 0.05). Similarly, a high-NaCl diet significantly increased SAPV in the low-frequency range only in ACRF animals. To conclude, a 2-wk period of a high-NaCl diet in ACRF rats significantly impaired dynamic RBFA in the frequency range of the myogenic response and increased SAPV in the low-frequency range. These abnormalities may increase the susceptibility to hypertensive end-organ injury and progressive renal failure by facilitating pressure transmission to the microvasculature.

Creatinine and HMH (5-hydroxy-1-methylhydantoin, NZ-419) as intrinsic hydroxyl radical scavengers

Creatinine (Crn) is one of the main intrinsic hydroxyl radical (•OH) scavengers and an ideal one for healthy or normal mammals, although this fact has not yet become widely accepted. Our results from urinary data estimated that ca. 0.4-0.6% of Crn is used daily to scavenge •OH in normal mammals [ca. 50 μmole and ca. 400 pmole of •OH in healthy subjects and normal rats, respectively]. In human subjects, Crn reacts non-enzymatically with •OH to form creatol (CTL: 5-hydroxycreatinine) and demethylcreatinine (DMC) in a one to one ratio, and CTL partially decomposes to methylguanidine (MG). And so, the scavenged mole of •OH by Crn is nearly equal to their molar total sum (CTL + MG + DMC) or 2 × (CTL + MG). The molar ratio of (scavenged •OH)/Crn in healthy subjects and normal rats are 4.4 and 6.0 mmole/mole, respectively, i.e. almost similar, but in patients with chronic kidney disease (CKD) the ratio increases up to ca. 60 mmole/mole in proportion to the severity of CKD. Since the level of Crn might not be enough to scavenge all •OH, and MG starts accumulating as a uremic toxin, Crn is not really the ideal scavenger. 5-Hydroxy-1-methylhydantoin (HMH, NZ-419), a Crn metabolite, is another antioxidant, having •OH scavenging ability, and has been shown to inhibit the progression of CKD in rats in stead of Crn, if sufficient amounts are given orally.

Protective effect of an intrinsic antioxidant, HMH (5-hydroxy-1-methylhydantoin; NZ-419), against cellular damage of kidney tubules

HMH (5-hydroxy-1-methylhydantoin; NZ-419) is a mammalian creatinine metabolite and an intrinsic antioxidant. HMH prevents the progression of chronic kidney disease in rats when a sufficient amount is taken orally. We assessed whether intrinsic and higher levels of HMH could protect tubular epithelial cells, LLC-PK(1) cells, against known cellular damage caused by xenobiotics, such as cisplatin and cephaloridine, or by hypoxia/reoxygenation treatment. Both cell damage and peroxidation, monitored as the leakage of lactate dehydrogenase (LDH) and malondialdehyde (MDA), respectively, from cells into the media, were inhibited by HMH in a concentration-dependent manner. The minimum effective concentration of HMH (2.5 μM) seemed to be too low for HMH to only be a direct hydroxyl radical scavenger. Additional antioxidant effect(s) inhibiting reactive oxygen species generation and/or modulating signal transduction pathways were suggested. The possibility that intrinsic HMH could be a protectant for the kidney was indicated. At the same time, for sufficient inhibition, higher concentrations than intrinsic HMH concentrations may be necessary. Patterns of efficacies of HMH on LDH and MDA against different kinds of cellular damage were compared with our reported data on those of corresponding, naturally occurring antioxidants. A common and specific inhibitory mechanism as well as common target(s) in kidney injuries were indicated.