Gentamicin caused renal injury deeply related to methylglyoxal and Nɛ-(carboxyethyl)lysine (CEL)

Circulating Concentrations of advanced Glycation end Products, Carboxymethyl Lysine and Methylglyoxal are Associated With Renal Function in Individuals With Diabetes

OBJECTIVE

Diabetic kidney disease (DKD) is one of the most severe chronic complications of diabetes and is associated with higher level of advanced glycation end products (AGEs). The aim of this study was to investigate the diagnostic potential of combined detection of multiple serum AGEs in diagnosing DKD.

METHODS

Serum AGEs, Nε-(carboxymethyl) lysine (CML), Nε-(carboxyethyl) lysine, and methylglyoxal (MGO) levels were measured by enzyme-linked immunosorbent assay in 176 individuals with type 2 diabetes. Participants were classified into normoalbuminuria, microalbuminuria, and macroalbuminuria group according to their urinary albumin to creatinine ratio (UACR).

RESULTS

Higher serum AGEs levels were found to be positively correlated with U-Alb, UACR, and blood urea nitrogen in the study of 176 individuals with type 2 diabetes. CML and MGO levels were positively correlated with U-Alb, UACR, blood urea nitrogen, Scr, and uric acid, and negatively correlated with estimated glomerular filtration rate (P < .05). Multivariate logistic regression analysis showed that elevated levels of AGEs, CML, and MGO were independent risk factors for the progression of DKD (odds ratio = 1.861, 1.016, 7.607, P < .01). The sensitivity, specificity, and area under receiver operating characteristic curve of combined detection of AGEs, MGO, and CML were higher than those of three individual detections (area under the curve = 0.952, 0.772, 0.868, 0905, respectively, P < .05).

CONCLUSION

The combined detection of AGEs, CML, and MGO may improve the reliability of early diagnosis of DKD.

Evaluation of the nephrotoxicity and safety of low-dose aristolochic acid, extending to the use of Xixin (Asurum), by determination of methylglyoxal and d-lactate

ETHNOPHARMACOLOGICAL RELEVANCE

Most Aristolochiaceae plants are prohibited due to aristolochic acid nephropathy (AAN), except Xixin (Asarum spp.). Xixin contains trace amounts of aristolochic acid (AA) and is widely used in Traditional Chinese Medicine. Methylglyoxal and d-lactate are regarded as biomarkers for nephrotoxicity.

AIM OF THE STUDY

The use of Xixin (Asarum spp.) is essential and controversial. This study aimed to evaluate tubulointerstitial injury and interstitial renal fibrosis by determining urinary methylglyoxal and d-lactate after withdrawal of low-dose AA in a chronic mouse model.

MATERIALS AND METHODS

C3H/He mice in the AA group (n = 24/group) were given ad libitum access to distilled water containing 3 μg/mL AA (0.5 mg/kg/day) for 56 days and drinking water from days 57 to 84. The severity of tubulointerstitial injury and fibrosis were evaluated using the tubulointerstitial histological score (TIHS) and Masson's trichrome staining. Urinary and serum methylglyoxal were determined by high-performance liquid chromatography (HPLC); urinary d-lactate were determined by column-switching HPLC.

RESULTS

After AA withdrawal, serum methylglyoxal in the AA group increased from day 56 (429.4 ± 48.3 μg/L) to 84 (600.2 ± 99.9 μg/L), and peaked on day 70 (878.3 ± 171.8 μg/L; p < 0.05); TIHS and fibrosis exhibited similar patterns. Urinary methylglyoxal was high on day 56 (3.522 ± 1.061 μg), declined by day 70 (1.583 ± 0.437 μg) and increased by day 84 (2.390 ± 0.130 μg). Moreover, urinary d-lactate was elevated on day 56 (82.10 ± 18.80 μg) and higher from day 70 (201.10 ± 90.82 μg) to 84 (193.28 ± 61.32 μg).

CONCLUSIONS

Methylglyoxal is induced after AA-induced tubulointerstitial injury, so methylglyoxal excretion and metabolism may be a detoxification and repair strategy. A low cumulative AA dose is the key factor that limits tubulointerstitial injury and helps to repair. Thus, AA-containing herbs, especially Xixin, should be used at low doses for short durations (less than one month).

Utilizing methylglyoxal and D-lactate in urine to evaluate saikosaponin C treatment in mice with accelerated nephrotoxic serum nephritis

The relationship between methylglyoxal (MGO) and D-lactate during saikosaponin C (SSC) treatment of mice with accelerated nephrotoxic serum (NTS) nephritis was investigated. NTS nephritis was induced by administration of anti-basement membrane antibodies to C57BL/6 mice and three dosages of SSC were administered for 14 days. Proteinuria, blood urea nitrogen, serum creatinine, renal histology, urinary MGO and d-lactate changes were examined. Compared to the NTS control group, the middle dosage (10 mg/kg/day) of SSC significantly alleviated the development of nephritis based on urine protein measurements (34.40 ± 6.85 vs. 17.33 ± 4.79 mg/day, p<0.05). Pathological observation of the glomerular basement membrane (GBM) revealed monocyte infiltration, hypertrophy, and crescents were alleviated, and injury scoring also showed improved efficacy for the middle dose of SSC during nephritis (7.92 ± 1.37 vs. 3.50 ± 1.14, p<0.05). Moreover, the significant decreases in urinary levels of MGO (24.71 ± 3.46 vs. 16.72 ± 2.36 μg/mg, p<0.05) and D-lactate (0.31 ± 0.04 vs. 0.23 ± 0.02 μmol/mg, p<0.05) were consistent with the biochemical and pathological examinations. This study demonstrates that MGO and D-lactate may reflect the extent of damage and the efficacy of SSC in NTS nephritis; further studies are required to enable clinical application.

Methylglyoxal and D-lactate in cisplatin-induced acute kidney injury: Investigation of the potential mechanism via fluorogenic derivatization liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS) proteomic analysis

Nephrotoxicity severely limits the chemotherapeutic efficacy of cisplatin (CDDP). Oxidative stress is associated with CDDP-induced acute kidney injury (AKI). Methylglyoxal (MG) forms advanced glycation end products that elevate oxidative stress. We aimed to explore the role of MG and its metabolite D-lactate and identify the proteins involved in CDDP-induced AKI. Six-week-old female BALB/c mice were intraperitoneally administered CDDP (5 mg/kg/day) for 3 or 5 days. Blood urea nitrogen (42.6 ± 7.4 vs. 18.3 ± 2.5; p < 0.05) and urinary N-acetyl-β-D-glucosaminide (NAG; 4.89 ± 0.61 vs. 2.43 ± 0.31 U/L; p < 0.05) were significantly elevated in the CDDP 5-day group compared to control mice. Histological analysis confirmed AKI was successfully induced. Confocal microscopy revealed TNF-α was significantly increased in the CDDP 5-day group. Fluorogenic derivatized liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS) showed the kidney MG (36.25 ± 1.68 vs. 18.95 ± 2.24 mg/g protein, p < 0.05) and D-lactate (1.78 ± 0.29 vs. 1.12 ± 0.06 mol/g protein, p < 0.05) contents were significantly higher in the CDDP 5-day group than control group. FD-LC-MS/MS proteomics identified 33 and nine altered peaks in the CDDP 3-day group and CDDP 5-day group (vs. control group); of the 35 proteins identified using the MOSCOT database, 11 were antioxidant-related. Western blotting confirmed that superoxide dismutase 1 (SOD-1) and parkinson disease protein 7 (DJ-1) are upregulated and may participate with MG in CDDP-induced AKI. This study demonstrates TNF-α, MG, SOD-1 and DJ-1 play crucial roles in CDDP-induced AKI.

Lipid composition and cell surface hydrophobicity of Candida albicans influence the efficacy of fluconazole-gentamicin treatment

Adherence of the fungus, Candida albicans, to biotic (e.g. human tissues) and abiotic (e.g. catheters) surfaces can lead to emergence of opportunistic infections in humans. The process of adhesion and further biofilm development depends, in part, on cell surface hydrophobicity (CSH). In this study, we compared the resistance of C. albicans strains with different CSH to the most commonly prescribed antifungal drug, fluconazole, and the newly described synergistic combination, fluconazole and gentamicin. The hydrophobic strain was more resistant to fluconazole due to, among others, overexpression of the ERG11 gene encoding the fluconazole target protein (CYP51A1, Erg11p), which leads to overproduction of ergosterol in this strain. Additionally, the hydrophobic strain displayed high efflux activity of the multidrug resistance Cdr1 pump due to high expression of the CDR1 gene. On the other hand, the hydrophobic C. albicans strain was more susceptible to fluconazole-gentamicin combination because of its different effect on lipid content in the two strains. The combination resulted in ergosterol depletion with subsequent Cdr1p mislocalization and loss of activity in the hydrophobic strain. We propose that C. albicans strains with different CSH may possess altered lipid metabolism and consequently may differ in their response to treatment.

A novel preventive mechanism of gentamicin-induced nephrotoxicity by atorvastatin

Atorvastatin (ATO) inhibits the synthesis of nonsteroidal isoprenoid compounds and possesses a pleiotropic effect. However, the detailed mechanism of ATO in preventing gentamicin (GM)-induced renal injury remains obscure. Although underlying multifaceted mechanisms involving GM-induced nephrotoxicity were well known, further work on elucidating the essential mechanism was needed. Using a fluorogenic derivatization-liquid chromatography tandem mass spectrometry proteomic method (FD-LC-MS/MS method), we investigated the effects and mechanisms of ATO treatment on GM-induced nephrotoxicity in rats. Consequently, 49 differentially expressed proteins were identified. The most significant mechanisms of nephrotoxicity caused by GM were mitochondrial dysfunction, fatty acid metabolism and oxidative stress. Their upstream regulator was found to be PPARα. The proteins involved in GM nephrotoxicity were sodium-hydrogen exchanger regulatory factor (SLC9A3R1), cathepsin V (CTSV), macrophage migration inhibitory factor (MIF) and RhoGDP dissociation inhibitor alpha (ARHGDIA). After ATO intervention, we observed a reversed enrichment pattern of their expression, especially in CTSV and SLC9A3R1 (P-value<0.05). We predicted that ATO may improve abnormal phospholipid metabolism and phospholipidosis caused by GM and also alleviate cell volume homeostasis and reverse the interference of GM with the transporter. Furthermore, proteomic results also provided clues as to GM-induced nephrotoxicity biomarkers such as CTSV and transthyretin.

Metabolic profiling of metformin treatment for low-level Pb-induced nephrotoxicity in rat urine

Chronic kidney disease is a worldwide problem, and Pb contamination is a potential risk factor. Since current biomarkers are not sensitive for the diagnosis of Pb-induced nephrotoxicity, novel biomarkers are needed. Metformin has both hypoglycaemic effects and reno-protection ability. However, its mechanism of action is unknown. We aimed to discover the early biomarkers for the diagnosis of low-level Pb-induced nephrotoxicity and understand the mechanism of reno-protection of metformin. Male Wistar rats were randomly divided into control, Pb, Pb + ML, Pb + MH and MH groups. Pb (250 ppm) was given daily via drinking water. Metformin (50 or 100 mg/kg/d) was orally administered. Urine was analysed by nuclear magnetic resonance (NMR)-based metabolomics coupled with multivariate statistical analysis, and potential biomarkers were subsequently quantified. The results showed that Pb-induced nephrotoxicity was closely correlated with the elevation of 5-aminolevulinic acid, D-lactate and guanidinoacetic acid in urine. After co-treatment with metformin, 5-aminolevulinic acid and D-lactate were decreased. This is the first demonstration that urinary 5-aminolevulinic acid, D-lactate and guanidinoacetic acid could be early biomarkers of low-level Pb-induced nephrotoxicity in rats. The reno-protection of metformin might be attributable to the reduction of D-lactate excretion.

Phosphocreatine protects endothelial cells from Methylglyoxal induced oxidative stress and apoptosis via the regulation of PI3K/Akt/eNOS and NF-κB pathway

Methylglyoxal (MGO), an active metabolite of glucose, can cause cellular injury which has an affinity for the progression of diabetes-associated atherosclerosis. Phosphocreatine (PCr) is a well-known high-energy phosphate compound. However, its protective effects and mechanism in the formation of a diabetes-associated atherosclerosis have not been clarified. In the present study, we investigated whether PCr could prevent MGO-induced apoptosis in human umbilical vascular endothelial cells (HUVECs) and explored the possible mechanisms. Cells were pre-treated with PCr and then stimulated with MGO. Cell morphology, cytotoxicity and apoptosis were assessed by light microscopy, MTT assay, and Annexin V-FITC respectively. Apoptotic-related proteins were evaluated by Western blotting. Reactive oxygen species (ROS) generation, intracellular calcium and mitochondrial membrane potential (MMP) were measured with fluorescent probes. Our results showed that PCr dose-dependently prevented MGO associated HUVEC cytotoxicity and suppressed MGO activated ROS generation as well as apoptotic biochemical changes such as lactate dehydrogenase, malondialdehyde leakage, loss of MMP, decreased Bcl-2/Bax protein ratio, levels of caspase-3 and 9. In addition, the antiapoptotic effect of PCr enhanced p-Akt/Akt protein ratio, NO synthase (eNOS) activation, NO production and cGMP levels and also was partially suppressed by a PI3K inhibitor (LY294002). Furthermore, PCr also inhibited MGO-induced transcriptional activity of Nuclear factor kappa B (NFκB). In conclusion, our data described that PCr exerts an antiapoptotic effect in HUVECs exposed to oxidative stress by MGO through the mitochondrial pathway and the modulation of PI3K/Akt/eNOS and NF-κB signaling pathway. Thus, it might be a candidate therapeutic agent for diabetic-associated cardiovascular diseases.

Low-molecular-weight chitosan scavenges methylglyoxal and N (ε)-(carboxyethyl)lysine, the major factors contributing to the pathogenesis of nephropathy

Methylglyoxal (MG) can cause protein glycation, resulting in cell damage and dysfunction. Accumulation of MG and its downstream metabolite N^ε-(carboxyethyl)lysine (CEL) has been identified in several variations of nephropathy, including diabetic, hypertensive, and gentamicin-induced nephropathies. In this study, we investigated the effects of low-molecular-weight chitosan (lmw-chitosan) on MG-induced carbonyl stress in aristolochic acid-induced nephropathy. We used a buffer to investigate whether MG could be scavenged by lmw-chitosan in vitro. In addition, we also used a mouse model of aristolochic acid-induced nephropathy, which exhibits 12-fold greater accumulation of MG in the kidneys than that found in control animals, to examine whether lmw-chitosan could decrease MG levels in vivo. Examination of the binding of lmw-chitosan with MG in vitro demonstrated that the concentration of lmw-chitosan necessary to achieve 50% inhibition was 4.60 µg mL⁻¹. Treatment with lmw-chitosan (500 mg kg⁻¹ day⁻¹ orally) for 14 days significantly decreased renal MG accumulation from 212.86 ± 24.34 to 86.15 ± 33.79 µg g⁻¹ protein (p < 0.05) and CEL levels from 4.60 ± 0.27 to 2.84 ± 0.28 µmol µg⁻¹ protein (p < 0.05) in the aristolochic acid-induced nephropathy model. These data suggest that lmw-chitosan might represent a novel treatment modality for MG-related diseases such as nephropathy.

Chitosan Prevents Gentamicin-Induced Nephrotoxicity via a Carbonyl Stress-Dependent Pathway

Aminoglycosides are widely used to treat infections; however, their applications are limited by nephrotoxicity. With the increase of antibiotic resistance, the use of aminoglycosides is inevitable. Low-molecular-weight chitosan (LMWC) has shown renal protective effects in dialysis patients. However, no study has evaluated LMWC for preventing aminoglycoside-induced nephrotoxicity or determined the mechanisms underlying the renal protective effects. In this study, LMWC (165 or 825 mg/kg/day) or metformin (100 mg/kg/day) was orally administered for 13 days to rats with nephropathy induced by gentamicin (GM), a kind of aminoglycoside (150 mg/kg/day i.p. for 6 days). Both LMCW doses improved renal function. Serum creatinine levels improved in rats treated with 165 and 825 mg/kg/day LMWC (from 2.14 ± 0.74 mg/dL to 1.26 ± 0.46 mg/dL and 0.69 ± 0.12 mg/dL, resp., P < 0.05). Blood urea nitrogen levels were also improved in these rats (from 73.73 ± 21.13 mg/dL to 58.70 ± 22.71 mg/dL and 28.82 ± 3.84 mg/dL, resp., P < 0.05). Additionally, renal tissue morphology improved after LMWC treatment, and accumulation of renal methylglyoxal, a damage factor associated with carbonyl stress, was reversed. These results show that LMWC prevents GM-induced renal toxicity via a carbonyl stress-dependent pathway.