Light-microscopic immunocytochemistry for gentamicin and its use for studying uptake of the drug in kidney

Investigation the effects of 2-aminoethoxydiphenyl borate (2-APB) on aminoglycoside nephrotoxicity

Investigation the protective effect of transient receptor potential channel modulator 2-Aminoethoxydiphenyl Borate (2-APB) on aminoglycoside nephrotoxicity caused by reactive oxygen species, calcium-induced apoptosis and inflammation was aimed. Forty Wistar rats were divided (n=8) as follows: Control group; DMSO group; 2-APB group; Gentamicin group (injected 100 mg/kg gentamicin intramuscularly for 10 days); Gentamicin+ 2-APB group (injected 2 mg/kg 2-APB intraperitoneally, then after 30 minutes 100 mg/kg gentamicin was injected intramuscularly for 10 days). Blood samples were collected for biochemical analyses, kidney tissue samples were collected for light, electron microscopic and immunohistochemical investigations. In gentamicin group glomerular degeneration, tubular dilatation, vacuolization, desquamation of tubular cells and hyaline cast formation in luminal space and leukocyte infiltration were seen. Disorganization of microvilli of tubular cells, apical cytoplasmic blebbing, lipid accumulation, myelin figure like structure formation, increased lysosomes, mitochondrial swelling and disorganization of cristae structures, apoptotic changes and widening of intercellular space were found. TNF-α, IL-6 and caspase 3 expressions were increased. BUN and creatinine concentrations were increased. Increase in MDA levels and decrease in SOD activities were determined. Even though degeneration still continues in gentamicin+2-APB treatment group, severity and the area it occupied were decreased and the glomerular and tubule structures were generally preserved. TNF-α, IL-6, caspase 3 immunoreactivities and BUN, creatinine, MDA concentrations were reduced and SOD activities were increased markedly compared to gentamicin group. In conclusion, it has been considered that 2-APB can prevent gentamicin mediated nephrotoxicity with its anti-oxidant, anti-apoptotic and anti-inflammatory effects.

Dihydromyricetin protects against gentamicin-induced nephrotoxicity via upregulation of renal SIRT3 and PAX2

AIM

Gentamicin-induced nephrotoxicity limits its widespread use as an effective antibacterial agent. Oxidative stress, inflammatory cytokines and apoptotic cell death are major participants in gentamicin-induced nephrotoxicity. We therefore, investigated whether dihydromyricetin (DHM), the antioxidant and anti-inflammatory flavonoid, could protect against the nephrotoxic effects of gentamicin.

METHODS

Male Wistar rats administrated gentamicin (100 mg/kg/day, i.p.) for 8 days. DHM (400 mg/kg, p.o.) was concurrently given with gentamicin for 8 days. Control group received the vehicle of DHM and gentamicin. Histopathological examinations, biochemical measurements and immunohistochemical analyses were done at the end of the study.

KEY FINDINGS

Treatment with DHM improved the gentamicin induced deterioration of renal functions; serum levels of urea, creatinine and cystatin-C as well as urinary levels of Kim-1 and NGAL, the sensitive indicators for early renal damage, were declined. Additionally, DHM abrogated gentamicin-induced changes in kidney morphology. These nephroprotective effects were possibly mediated via decreasing renal gentamicin buildup, activating the antioxidant enzymes GSH, SOD and CAT and decreasing lipid peroxidation and nitric oxide levels. Further, DHM suppressed renal inflammation and apoptotic cell death by decreasing the expression of nuclear factor-kappa B (NF-κB), TNF-alpha and caspase-3. These effects were correlated to the upregulation of renal SIRT3 expression. Also, DHM activated the regeneration and replacement of injured tubular cells with new ones via enhancing PAX2 expression.

SIGNIFICANCE

DHM is a promising therapeutic target that could prevent acute renal injury induced by gentamicin and help renal tubular cells to recover through its antioxidant, anti-inflammatory and antiapoptotic properties.

Cinnamic acid ameliorate gentamicin-induced liver dysfunctions and nephrotoxicity in rats through induction of antioxidant activities

This study was the first to evaluate the possible protective effects of cinnamic acid (CA) against Gentamicin (GM) induced liver and kidney dysfunctions in rats. Adult male Wistar rats were randomly assigned to 4 equal groups (n = 8): Control group (saline, 0.5 ml/day), CA group (CA, 50 mg/kg/day), GM group (GM, 100 mg/kg/day), and GM + CA group (100 & 50 mg/kg/day). Following 12 days of treatments, blood and 24 h urine samples were collected and kidneys were taken out for biochemical, histopathological, and molecular studies. Following CA treatment, renal function markers and transaminases activities including serum urea (59.92%) and creatinine (50.41%), protein excretion rate (43.67%), and serum activities of aspartate aminotransferase (AST) (54.34%) and alanine aminotransferase (ALT) (47.26%) significantly reduced in the treated group as compared with the GM group (P < 0.05). Also, CA could significantly ameliorate the levels of triglyceride (29.70%), cholesterol (13.02%), very low-density lipoprotein (29.69%) and high-density lipoprotein-cholesterol (7.28%). CA could also attenuate oxidative stress through a decrease of serum malondialdehyde (MDA) (50.86%) and nitric oxide (NO) (0.85%) and an increase of renal catalase (CAT) (196.14%) and glutathione peroxidase (GPX) activities (45.88%) as well as GPX mRNA expression (44.42-fold) as compared with the GM group (P < 0.05). Moreover, histopathological evaluations revealed attenuated tubular damages and reduced inflammatory cellular infiltration in CA treated animals. Overall, CA alleviates GM-induced nephrotoxicity and alterations in transaminases activities in rats through its antioxidant activities.

Immortalized canine adipose-derived mesenchymal stem cells alleviate gentamicin-induced acute kidney injury by inhibiting endoplasmic reticulum stress in mice and dogs

Adipose-derived mesenchymal stem cells have been used to treat acute kidney injury (AKI). The role of endoplasmic reticulum (ER) stress in AKI treatment with canine adipose-derived mesenchymal stem cells (cADSCs) remains unknown. This study intended to investigate the therapeutic effects of cADSCs cultured in different media on AKI in mice and dogs and reveal the role of ER stress in this process. The mice were divided into two branches: a control group and a gentamicin induced group (this group treated with low-serum ADSC or high-serum ADSC or 4-phenylbutyric acid (4-PBA)). The dogs were divided into control, model, and cell-injected groups. To suppress ER stress, mice were simultaneously treated with 4-PBA. The results showed there were improvements in renal function and tissue damage and a corresponding decrease in ER stress in the kidneys of the mice that received cell injection. However, the cells cultured with 2% FBS showed a better growth state and resulted in lower ER stress levels in treated kidneys. In the 4-PBA-treated group, ER stress was suppressed, and there was corresponding kidney injury recovery. Similarly, both kidney damage and ER stress were alleviated after AKI dogs were injected with the cells. Our findings reveal that both allogeneic and xenogeneic cADSCs were effective treatments for AKI by inhibiting ER stress. These results also provide evidence for a new clinical therapy for acute renal disease in pets.

Chronotoxicity of Streptomycin-Induced Renal Injury in Mice

The aim of the present study was to investigate the "chronotoxicity" of streptomycin (SM) in relation to its circadian periodicity. Male ICR mice were injected intraperitoneally with SM (780 mg/kg, one shot) one of six time points throughout the day. Mortality was monitored until 14 d after the injection and clearly differed depending on the timing of the injection (i.e., mice were more sensitive to injection during the dark phase). Moreover, when mice were administered with non-lethal doses of SM (550 mg/kg, every 24 h for 3 d, in the light phase or dark phase), the levels of nephrotoxicity indicators (blood urea nitrogen and renal levels of malondialdehyde and cyclooxygenase-2) were significantly increased by the injection in the dark phase, but not in the light phase. These results suggested that SM showed clear chronotoxicity. Our current data indicated that chronotoxicology may provide valuable information on the importance of injection timings for evaluations of toxicity and undesirable side effects.

Gentamicin-Induced Acute Kidney Injury in an Animal Model Involves Programmed Necrosis of the Collecting Duct

BACKGROUND

Gentamicin is a potent aminoglycoside antibiotic that targets gram-negative bacteria, but nephrotoxicity limits its clinical application. The cause of gentamicin-induced AKI has been attributed mainly to apoptosis of the proximal tubule cells. However, blocking apoptosis only partially attenuates gentamicin-induced AKI in animals.

METHODS

Mice treated with gentamicin for 7 days developed AKI, and programmed cell death pathways were examined using pharmacologic inhibitors and in RIPK3-deficient mice. Effects in porcine and murine kidney cell lines were also examined.

RESULTS

Gentamicin caused a low level of apoptosis in the proximal tubules and significant ultrastructural alterations consistent with necroptosis, occurring predominantly in the collecting ducts (CDs), including cell and organelle swelling and rupture of the cell membrane. Upregulation of the key necroptotic signaling molecules, mixed lineage kinase domain-like pseudokinase (MLKL) and receptor-interacting serine/threonine-protein kinase 3 (RIPK3), was detected in gentamicin-treated mice and in cultured renal tubule cells. In addition, gentamicin induced apical accumulation of total and phosphorylated MLKL (pMLKL) in CDs in mouse kidney. Inhibiting a necroptotic protein, RIPK1, with necrostatin-1 (Nec-1), attenuated gentamicin-induced necrosis and upregulation of MLKL and RIPK3 in mice and cultured cells. Nec-1 also alleviated kidney inflammation and fibrosis, and significantly improved gentamicin-induced renal dysfunction in mice. Furthermore, deletion of RIPK3 in the Ripk3 ^-/- mice significantly attenuated gentamicin-induced AKI.

CONCLUSIONS

A previously unrecognized role of programmed necrosis in collecting ducts in gentamicin-induced kidney injury presents a potential new therapeutic strategy to alleviate gentamicin-induced AKI through inhibiting necroptosis.

Metabolism and disposition of oseltamivir (OS) in rats, determined by immunohistochemistry with monospecific antibody for OS or its active metabolite oseltamivir carboxylate (OC): A possibility of transporters dividing the drugs' excretion into the bile and kidney

Among any drugs, no comparative pharmacological study on how prodrug and its active metabolite behave in animal bodies is available. Immunohistochemistry (IHCs) using newly prepared two monoclonal antibodies, AOS‐96 and AOC‐160, monospecific for oseltamivir (OS) and its metabolite oseltamivir carboxylate (OC) were developed, simultaneously detecting the uptake or excretion of OS and OC in the intestine, liver, and kidney of rats to which OS was orally administered. In the intestine, IHC for OS revealed OS highly distributed to the absorptive epithelia with heavily stained cytoplasmic small granules (CSGs). IHC for OC showed that OC also distributed highly in the epithelia, but without CSGs, suggesting that OS was partly converted to OC in the cells. In the liver, OS distributed in the hepatocytes and on their bile capillaries, as well as on the lumina from the bile capillaries to the interlobular bile ducts. OC distributed in the whole cell of the hepatocytes, but without CSGs nor on any lumina through the interlobular bile ducts. In the kidney, a few levels of OS distributed in the cytoplasm of almost all the renal tubule cells, but they contained numerous CSGs. In contrast, OC distributed highly in the proximal tubules, but very slightly in the lower renal tubules of the nephrons. Thus, it was concluded that the two drugs behave in completely different ways in rat bodies. This paper also discusses a possibility of the correlation of OS or OC levels in tissue cells with their known transporters.

Immunohistochemistry for Anti-diabetes Drug, Alogliptin Using a Newly Prepared Monoclonal Antibody: Its Precise Localization in Rat Small Intestine

Knowledge of time sequence of localization of drugs in cells and tissues of animals may help in developing a better understanding of the actual overall pharmacokinetics of the drugs. We produced monoclonal antibody (mAb) against alogliptin (AG), a dipeptidyl peptidase-4 (DPP-4) inhibitor, conjugated to BSA with N-(γ-maleimidobutyryloxy)-succinimide. The mAb was specific for AG and did not cross-react with sitagliptin, vancomycin or amoxicillin. The mAb enabled us to develop an immunohistochemical method for detecting the localization of AG in the rat small intestine. One hour after a single oral administration of AG, immunohistochemistry revealed that the immunoreactivity of AG was observed in almost all of cells and tissues of the duodenum. The microvilli of the absorptive epithelial cells were moderately stained. The staining pattern of AG at jejunum and ilium was almost the same as that of duodenum, but the staining intensity, especially at absorptive epithelial cells and intestinal gland epithelial cells, became stronger towards the distal part of the small intestine. These results suggested that AG may be more actively absorbed from the lower part of the small intestine than in the upper part. It may affect the function of cells with membrane-bound DPP-4 because it was reported that membrane-bound form of DPP-4 exists in the microvilli of the absorptive epithelial cells.

Hyperbaric oxygen treatment and nephrotoxicity induced by gentamicin in rats

Background

Nephrotoxicity is a significant adverse side effect of gentamicin. Previous preclinical studies showed that hyperbaric oxygen treatment (HBOT) may have beneficial effects by attenuating renal damage in rats subjected to renal injury. We evaluated the effect of HBOT on acute renal failure caused by gentamicin.

Methods

Thirty-six rats were divided into four groups. Gentamicin (150 mg/kg for 5 consecutive days) was administered in 30 rats, 10 rats received only gentamicin, 10 rats received 100% oxygen therapy on days 1-5 of the experiment, 10 received daily HBOT on days 1-5 of the experiment, and the remaining six served as a control group. On day 6, renal function tests and renal pathological examinations were performed.

Results

Body weight and biochemical parameters were similar in all groups except for higher plasma levels of calcium in the 100% oxygen group (P = 0.03). All the rats in the experimental group showed biochemical parameters compatible with renal failure (high serum levels of urea and creatinine). All the rats in the control group had normal renal function tests. Two rats from the HBOT group died on the fifth day of the experiment. All rats in the control group demonstrated normal renal morphology. All 28 intoxicated rats showed moderate to severe histopathological changes without significant differences between the groups.

Conclusions

Treatment of gentamicin-induced nephrotoxicity with either HBOT or 100% oxygen for 5 days had no beneficial renal effect. Mortality was observed only in the HBOT group.

Gentamicin nephrotoxicity in animals: Current knowledge and future perspectives

Due to high relative blood flow the kidney is prone to drug-induced damage. Aminoglycoside type antibiotic gentamicin is one of the leading cause of drug-induced nephrotoxicity. In recent years gentamicin nephrotoxicity is significantly reduced by shifting to once daily dosage as well as by eliminating known risk factors. Application of gentamicin is still related to serious side effects which are reported more often compared to other antibiotics. Because gentamicin is still heavily used and is highly efficient in treating infections, it is important to find mechanisms to reduce its nephrotoxicity. This aim can only be achieved through better understanding of kidney metabolism of gentamicin. This problem has been extensively researched in the last 20 years. The experimental results have provided evidence for almost complete understanding of mechanisms responsible for gentamicin nephrotoxicity. We now have well described morphological, biochemical and functional changes in kidney due to gentamicin application. During the years, this model has become so popular that now it is used as an experimental model for nephrotoxicity per se. This situation can mislead an ordinary reader of scientific literature that we know everything about it and there is nothing new to discover here. But quite opposite is true. The precise and complete mechanism of gentamicin nephrotoxicity is still point of speculation and an unfinished story. With emerge of new and versatile technics in biomedicine we have an opportunity to reexamine old beliefs and discover new facts. This review focuses on current knowledge in this area and gives some future perspectives.

Drug-induced impairment of renal function

Pharmaceutical agents provide diagnostic and therapeutic utility that are central to patient care. However, all agents also carry adverse drug effect profiles. While most of these are clinically insignificant, some drugs may cause unacceptable toxicity that impacts negatively on patient morbidity and mortality. Recognizing adverse effects is important for administering appropriate drug doses, instituting preventive strategies, and withdrawing the offending agent due to toxicity. In the present article, we will review those drugs that are associated with impaired renal function. By focusing on pharmaceutical agents that are currently in clinical practice, we will provide an overview of nephrotoxic drugs that a treating physician is most likely to encounter. In doing so, we will summarize risk factors for nephrotoxicity, describe clinical manifestations, and address preventive and treatment strategies.

Urinary excretion pattern of exosomal aquaporin-2 in rats that received gentamicin

Urinary exosomes are nano-sized vesicles secreted into urine from all types of renal epithelial cells and are known to contain possible biomarker proteins for renal diseases. Gentamicin has been reported to decrease the level of renal aquaporin (AQP)2, which is known to be mainly expressed in renal collecting ducts and excreted into the urine via exosomes. In the present study, we investigated whether urinary exosomal AQP2 could serve as a potential biomarker for gentamicin-induced nephrotoxicity, especially collecting duct cell dysfunction. Gentamicin was given to rats intraperitoneally once every day starting on day 0. Gentamicin significantly increased the plasma creatinine concentration from day 5 and beyond. Also, gentamicin induced polyuria and a defective urine concentration mechanism on day 7, suggesting gentamicin-induced collecting duct cell dysfunction. Immunoblot analysis showed that gentamicin significantly increased urinary exosomal AQP2 excretion on day 1 but decreased it on day 7 compared with the control group. Similarly, increased excretion of exosomal tumor susceptibility gene 101 protein, frequently used as an exosome marker protein, was observed on day 1. However, gentamicin did not significantly affect the urinary excretion of exosomal tumor susceptibility gene 101 on day 7. Gentamicin slightly decreased renal AQP2 expression on day 2 and markedly decreased it on day 8. These data strongly suggest that the use of urinary exosomal AQP2 as a biomarker may allow detection of gentamicin-induced collecting duct cell dysfunction. Furthermore, urinary exosomal AQP2 might also be useful for the early detection of gentamicin-induced renal injury in addition to collecting duct injury.

In vivo multiphoton imaging of mitochondrial structure and function during acute kidney injury

Mitochondrial dysfunction has been implicated in the pathogenesis of acute kidney injury due to ischemia and toxic drugs. Methods for imaging mitochondrial function in cells using confocal microscopy are well established; more recently, it was shown that these techniques can be utilized in ex vivo kidney tissue using multiphoton microscopy. We extended this approach in vivo and found that kidney mitochondrial structure and function can be imaged in anesthetized rodents using multiphoton excitation of endogenous and exogenous fluorophores. Mitochondrial nicotinamide adenine dinucleotide increased markedly in rat kidneys in response to ischemia. Following intravenous injection, the mitochondrial membrane potential-dependent dye TMRM was taken up by proximal tubules; in response to ischemia, the membrane potential dissipated rapidly and mitochondria became shortened and fragmented in proximal tubules. In contrast, the mitochondrial membrane potential and structure were better maintained in distal tubules. Changes in mitochondrial structure, nicotinamide adenine dinucleotide, and membrane potential were found in the proximal, but not distal, tubules after gentamicin exposure. These changes were sporadic, highly variable among animals, and were preceded by changes in non-mitochondrial structures. Thus, real-time changes in mitochondrial structure and function can be imaged in rodent kidneys in vivo using multiphoton excitation of endogenous and exogenous fluorophores in response to ischemia-reperfusion injury or drug toxicity.

Immunocytochemistry for vancomycin using a monoclonal antibody that reveals accumulation of the drug in rat kidney and liver

We prepared monoclonal antibodies against N-(γ-maleimidobutyryloxy)succinimide-conjugated vancomycin (VM). The monoclonal antibody was specific for conjugated or free VM. The monoclonal antibody enabled us to develop an immunocytochemical method for detecting the uptake of VM in the rat kidney and liver. Three hours after a single intravenous (i.v.) injection of VM at the therapeutic dose, the immunocytochemistry revealed that VM accumulated in large amounts in both the S1 and S2 segments and in much smaller amounts in the S3 segment of the proximal tubules as well as in the distal tubules and collecting ducts. The drug was detected in the cytoplasm, cytoplasmic irregular granules, nuclei, and microvilli of the proximal tubule cells. The distal tubules and collecting ducts contained scattered swollen cells in which both the nuclei and cytoplasm were heavily immunostained. Twenty-four hours after injection, most of the swollen cells returned back to normal size and had somewhat decreased immunostaining. Also, significant amounts of VM remained accumulated for as long as 8 days postadministration. In the liver, similar drug accumulation was observed in the Kupffer cells and the endothelial cells of the hepatic sinusoids but not in the hepatocytes, suggesting that vancomycin cannot be eliminated via the liver. Immunoelectron microscopic studies demonstrated that in the collecting ducts, uptake of VM occurred exclusively in the lysosomes and cytoplasm of the principal cells and scarcely in the intercalated cells. Furthermore, double fluorescence staining using rats simultaneously administered with VM and gentamicin strongly suggests that both drugs colocalized in lysosomes in the proximal tubule cells of kidneys.

Distribution study of peplomycin in rat kidney revealed by immunocytochemistry using monoclonal antibodies

Peplomycin (PEP), an anti-tumor antibiotic related structurally to bleomycin, is widely used, especially for squamous cell carcinoma but shows renal toxicity. We prepared monoclonal antibodies (mAbs) against N-(γ-maleimidobutyryloxy)succinimide-conjugated PEP. The mAbs were monospecific for PEP, but did not react with bleomycin and other anticancer antibiotics. The mAbs enabled us to develop an immunocytochemical (ICC) method for detecting the uptake of PEP in the rat kidney. Two hours after a single i.v. administration of PEP, ICC revealed immunostaining for PEP in irregularly shaped cytoplasmic granules of the proximal tubules in which the microvilli were also stained. Also, staining occurred in the distal tubules and collecting ducts, in both of which we observed scattered swollen cells, reminiscent of necrotic cells, in which both the nuclei and cytoplasm reacted strongly with the antibody. Twenty-four hours after injection, PEP in the proximal tubules completely vanished, but yet significant amounts of PEP remained in both the distal tubules and collecting ducts. Distribution patterns of PEP in cells of the kidneys resembled, in some ways, those of our recent ICC studies for an organic cation aminoglycoside antibiotic gentamicin. This ICC suggests that PEP taken up in the proximal tubule cells is localized in the lysosomes, and organic cation transporters and bleomycin hydrolase might be involved in entrance and/or disappearance of PEP in this cell type. Furthermore, the distal tubules and collecting ducts may be the sites readily affected by some chemotherapeutic agents.

Immunocytochemistry for amoxicillin and its use for studying uptake of the drug in the intestine, liver, and kidney of rats

Specific transport systems for penicillins have been recognized, but their in vivo role in the context of other transporters remains unclear. We produced a serum against amoxicillin (anti-AMPC) conjugated to albumin with glutaraldehyde. The antiserum was specific for AMPC and ampicillin (ABPC) but cross-reacted weakly with cephalexin. This enabled us to develop an immunocytochemical (ICC) method for detecting the uptake of AMPC in the rat intestine, liver, and kidney. Three hours after a single oral administration of AMPC, the ICC method revealed that AMPC distributed to a high degree in the microvilli, nuclei, and cytoplasm of the absorptive epithelial cells of the intestine. AMPC distributed in the cytoplasm and nuclei of the hepatocytes in a characteristic granular morphology on the bile capillaries, and in addition, AMPC adsorption was observed on the luminal surface of the capillaries, intercalated portions, and interlobular bile ducts on the bile flow. Almost no AMPC could be detected 6 h postadministration in either the intestine or the liver. Meanwhile, in the kidney, AMPC persisted until 12 h postadministration to a high degree in the proximal tubules, especially in the S3 segment cells in the tubular lumen, in which numerous small bodies that strongly reacted with the antibody were observed. All these sites of AMPC accumulation correspond well to specific sites where certain transporter systems for penicillins occur, suggesting that AMPC is actually and actively absorbed, eliminated, or excreted at these sites, possibly through such certain penicillin transporters.

New insights into the mechanism of aminoglycoside nephrotoxicity: an integrative point of view

Nephrotoxicity is one of the most important side effects and therapeutical limitations of aminoglycoside antibiotics, especially gentamicin. Despite rigorous patient monitoring, nephrotoxicity appears in 10-25% of therapeutic courses. Traditionally, aminoglycoside nephrotoxicity has been considered to result mainly from tubular damage. Both lethal and sub-lethal alterations in tubular cells handicap reabsorption and, in severe cases, may lead to a significant tubular obstruction. However, a reduced glomerular filtration is necessary to explain the symptoms of the disease. Reduced filtration is not solely the result of tubular obstruction and tubular malfunction, resulting in tubuloglomerular feedback activation; renal vasoconstriction and mesangial contraction are also crucial to fully explain aminoglycoside nephrotoxicity. This review critically presents an integrative view on the interactions of tubular, glomerular, and vascular effects of gentamicin, in the context of the most recent information available. Moreover, it discusses therapeutic perspectives for prevention of aminoglycoside nephrotoxicity derived from the pathophysiological knowledge.