Aminoglycoside induced nephrotoxicity: molecular modeling studies of calreticulin-gentamicin complex

Ranacyclin-NF, a Novel Bowman-Birk Type Protease Inhibitor from the Skin Secretion of the East Asian Frog, Pelophylax nigromaculatus

Serine protease inhibitors are found in plants, animals and microorganisms, where they play important roles in many physiological and pathological processes. Inhibitor scaffolds based on natural proteins and peptides have gradually become the focus of current research as they tend to bind to their targets with greater specificity than small molecules. In this report, a novel Bowman–Birk type inhibitor, named ranacyclin-NF (RNF), is described and was identified in the skin secretion of the East Asian frog, Pelophylax nigromaculatus. A synthetic replicate of the peptide was subjected to a series of functional assays. It displayed trypsin inhibitory activity with an inhibitory constant, Ki, of 447 nM and had negligible direct cytotoxicity. No observable direct antimicrobial activity was found but RNF improved the therapeutic potency of Gentamicin against Methicillin-resistant Staphylococcus aureus (MRSA). RNF shared significant sequence similarity to previously reported and related inhibitors from Odorrana grahami (ORB) and Rana esculenta (ranacyclin-T), both of which were found to be multi-functional. Two analogues of RNF, named ranacyclin-NF1 (RNF1) and ranacyclin-NF3L (RNF3L), were designed based on some features of ORB and ranacyclin-T to study structure–activity relationships. Structure–activity studies demonstrated that residues outside of the trypsin inhibitory loop (TIL) may be related to the efficacy of trypsin inhibitory activity.

Protective effect of Polygonatum sibiricum polysaccharides on gentamicin-induced acute kidney injury in rats via inhibiting p38 MAPK/ATF2 pathway

The aim of this study was to investigate the protective effect of Polygonatum sibiricum polysaccharides (PSP) on acute kidney injury (AKI) in rats. The AKI model was established with 100 mg/kg of gentamicin (GM) intramuscularly. Six hours post-injection, rats were given intragastrically different dosages of PSP (0.25, 0.5, and 1 g/kg) for seven consecutive days. Results showed that compared with the model group, the kidney coefficient of rats decreased significantly (P < 0.05), and rat serum CRE and urea levels were significantly decreased (P < 0.05) in the PSP treatment group. The expression of NGAL, KIM-1, IL-1β, IL-6, TNF-α, and p38 MAPK mRNA in the kidney were significantly decreased (P < 0.05). The protein expression of p38 MAPK, p-p38 MAPK, and p-ATF2 were decreased to different degrees. Among the three-PSP treatment groups, the medium-dose group displayed the most protective effects. In conclusion, PSP had a powerful protective effect on GM-induced AKI in rats, it decreased the expression of NGAL or KIM-1 mRNA in kidney tissue and inhibited the p38 MAPK/ATF2 signaling pathway and the production of inflammatory factors TNF-α, IL-1β, and IL-6.

Evaluation of the clinical use of the ETN PROtect® in non-union therapy

INTRODUCTION

Non-union of a long bone fracture remains a challenge in orthopaedic and trauma surgery. In the current study, we sought to determine the clinical effectiveness of tibial non-union treatment utilizing an antibiotic-coated intramedullary nail (Expert Tibia Nail (ETN) PROtect®) regarding prevention and treatment of infection and the clinical outcome.

PATIENTS AND METHODS

36 patients suffering from tibial non-unions that were treated with the ETN PROtect® in the course of non-union treatment between February 2010 and March 2015 were included in this clinical observational study. Clinical and radiological examinations were performed preoperatively as well as 4, 6 and 12 weeks and 6 and 12 months postoperatively as part of a standardized follow-up program. Data regarding perioperative complications, weight-bearing capacity, radiological signs of consolidation and subjective health status were assessed at each time point. Laboratory parameters such as C-reactive protein (CRP) and leukocyte count were collected preoperatively in order to assess the patients' risk profile for infection.

RESULTS

Patients had an average of 6.2 previous surgeries and 22 patients (61.1%) had a positive bacterial culture from intraoperatively removed tissue during the first operative treatment. 29 patients (80.6%) achieved full weight-bearing after an average of 7.7 months, furthermore 80.6% of patients achieved osseous consolidation. 3 deep infections occurred, including one amputation. Subjective health status increase based on the SF-12 questionnaire during our follow-up program.

CONCLUSION

The results from the current study indicate that the use of the ETN PROtect® in the applied non-union therapy has a high clinical effectiveness regarding osseous consolidation and time to weight bearing. In addition, the use of gentamicin-coated nails in the treatment of tibial non-unions might contribute to both successful treatment of the underlying infection and prevention of perioperative infection. The gentamicin-coated nail may serve as a beneficial adjunct treatment in the applied non-union therapy in addition to all established techniques in the treatment of infected non-unions.

Sex Difference in Gentamicin-induced Nephrotoxicity: Influence of L-arginine in Rat Model

Background:

L-arginine is an important precursor for the formation of nitric oxide (NO). According to previous studies, NO function is related to gender. Likewise, chronic renal diseases have lower prevalence in female. Gentamicin (GM) is an aminoglycoside antibiotic. According to some studies, males are more sensitive to GM renal nephrotoxicity. This study attempts to find protective effects of L-arginine on GM nephrotoxicity in male and female rats.

Methods:

Male and female rats were divided into eight groups: Rats were randomly assigned to 8 groups each including both male and female rats. The first and second groups received vehicle (saline), the third and fourth groups received gentamicin (80 mg/kg), the fifth and sixth groups received L-arginine (150 mg/kg), and finally, seventh and eighth groups received gentamicin+ L- arginine. Next, 9 days after administering drugs, blood samples were collected from the heart. After making sacrifices, the level of blood urea, creatinine (Cr), nitrite, and malondialdehyde (MDA) was measured in serums. Likewise, nitrite and MDA were measured in the homogenized kidney tissue.

Results:

GM significantly increased serum level of urea and Cr in male and female rats (P < 0.05). However, co-administration of GM + L-arginine significantly did not decrease urea and Cr level in male rats, whereas, in female rats, they significantly reduced (P < 0.05). In response to GM, renal MDA level increased in male and female rats (P < 0.05), and in the presence of GM + L-arginine, the level of MDA significantly decreased in both genders (P < 0.05).

Conclusions:

L-arginine demonstrated some protective effects in female rats but did not protect against GM nephrotoxicity in male rats for unknown reasons, probably related to the effects of sex hormones which needs further studies to be confirmed.

Patients' safety: is there a systemic release of gentamicin by gentamicin-coated tibia nails in clinical use?

INTRODUCTION

Osteitis is one of the most serious complications in orthopedic surgery. Expert Tibia Nail (ETN) PROtect™ coated with a biodegradable layer of gentamicin-laden polymer was developed for prophylaxis of osteomyelitis. In systemic administration, gentamicin has only a small therapeutic index and serious side effects; it is potentially nephrotoxic as well as ototoxic. It is not yet known if relevant gentamicin concentrations are released into the systemic circulation after implantation of gentamicin-coated nails. In order to evaluate the patients' risks profiles and increase patient safety, we measured gentamicin levels in pre- and postoperative serum samples of patients undergoing implantation of ETN PROtect.

METHODS

Twenty-five patients who received ETN PROtect between March 2012 and August 2014 were included in this study. Collection of blood samples occurred before the operation, at weeks 1-4, 3 and 6 months, and up to 1 year after the implantation. Measurement of gentamicin levels in serum samples was performed at the central laboratory of Heidelberg University Hospital. Additionally, laboratory parameters, C-reactive protein, leukocyte number, urea and creatinine concentrations were analyzed in routine controls before and after operating and assessed for systemic side effects.

RESULTS

Over the course of this prospective observational study, we were able to determine that gentamicin-coated nails do not release gentamicin into the systemic circulation above the lowest detectable level of 0.2 mg/dL. There were slight increases in the mean inflammation and renal retention markers, but no gentamicin-associated side effects could be linked to implantation. Furthermore, no allergic reactions could be detected during our study.

CONCLUSION

Our findings suggest that there is no relevant release of gentamicin into the systemic circulation causing a systemic effect, and serious side effects due to gentamicin-coated tibia nails should not be feared. Postoperative monitoring of renal function does not seem necessary because of the implantation of ETN PROtect.

Establishment of Simple and Routine Methods in Early Diagnosis of Gentamicin-Induced Kidney Injury Based on a Rat Model

The changes in biomarkers of gentamycin- (GM-) induced kidney injury have been studied by using simple and routine methods and also assessed the efficacy and utility of these routine biomarkers in early diagnosis. Eighty Sprague-Dawley (SD) rats were randomly divided into 4 groups: three experimental groups treated with different GM dosages (4, 20, and 100 mg·kg(-1)) and a control group. The experimental groups were given intramuscular GM injections once daily for 14 days, and the control group was given intramuscular sterile water. Blood and urine samples were collected on treatment days 1, 3, 7, and 14 to test for total protein (TP), albumin (ALB), blood urea nitrogen (BUN), creatinine (CRE), uric acid (UA), pH, specific gravity (SG), proteins (PRO), and cells in urinary sediment. Histopathology and kidney coefficient were performed on excised kidney specimens. The result indicated that serum CRE, BUN, and TP, urine PRO, and urinary hyaline casts and low-transitional epithelium showed an immediate and highly sensitive response to kidney injury, and the combined diagnosis with the above methods could be used in early diagnosis. Particularly, the process of the test was simple and quick, no special equipment, so it is more suit for primary medical institution.

Protective effect of pomegranate flower extract against gentamicin-induced renal toxicity in male rats

Introduction: Gentamicin (GM) as an antibiotic is used in clinic. However, its administration is limited by side effects such as nephrotoxicity. Herbal extracts could be used in therapeutic approaches.

Objectives: The present study was planned to investigate whether pomegranate flower extract (PFE) could ameliorate GM-induced renal toxicity in male rats.

Materials and Methods: Twenty eight male Wistar rats were divided into 5 groups. Groups 1 and 2 respectively received PFE 25 and 50 mg/kg for 9 days. Groups 3, 4 and 5 received saline, PFE 25 mg/kg, and PFE 50 mg/kg for 9 days, respectively, and GM (100 mg/kg/day) was administered from day 3 on. Blood samples were obtained, and after sacrificing the animals, the kidneys were removed for histopathology investigations.

Results: GM alone increased the serum levels of creatinine (Cr) and blood urea nitrogen (BUN), and tissue damage and kidney weight (P < 0.05). However, administration of low dose of PFE accompanied with GM decreased these markers significantly (P < 0.05). Low dose of PFE also ameliorated weight loss induced by GM (P < 0.05).

Conclusion: It is concluded that PFE 25 mg/kg is the effective dose to ameliorate nephrotoxicity induced by GM.

KIM-1 and NGAL as biomarkers of nephrotoxicity induced by gentamicin in rats

Gentamicin is a member of aminoglycosides, which has represented highly effective antimicrobial agents especially in Gram-negative infections despite their toxic effects in the kidney. Rapid diagnosis is vital to preserve renal function and to slow down renal injury. Owing to the poor sensitivity and specificity of serum creatinine (SCr) and blood urea nitrogen (BUN), new biomarkers for earlier and more accurate detection are needed. The aim of our study was to determine whether kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) may be useful biomarkers in the assessment of gentamicin-induced nephrotoxicity in rats. In this study, the two biomarkers of renal toxicity were assessed via ELISA, quantitative real-time PCR, and immunohistochemistry in rats treated with gentamicin for up to 7 days. Repeated administration of gentamicin to male SD rats for 1, 3, or 7 days resulted in a dose- and time-dependent increase in the expression of KIM-1 and NGAL. Changes in gene and protein expressions were found to correlate with the progressive histopathological alterations and preceded effects on traditional clinical parameters indicative of impaired kidney function. Both of the biomarkers are supported to be used as sensitive indicators of acute kidney injury caused by gentamicin.

Gentamicin binds to the megalin receptor as a competitive inhibitor using the common ligand binding motif of complement type repeats: insight from the nmr structure of the 10th complement type repeat domain alone and in complex with gentamicin

Gentamicin is an aminoglycoside widely used in treatments of, in particular, enterococcal, mycobacterial, and severe Gram-negative bacterial infections. Large doses of gentamicin cause nephrotoxicity and ototoxicity, entering the cell via the receptor megalin. Until now, no structural information has been available to describe the interaction with gentamicin in atomic detail, and neither have any three-dimensional structures of domains from the human megalin receptor been solved. To address this gap in our knowledge, we have solved the NMR structure of the 10th complement type repeat of human megalin and investigated its interaction with gentamicin. Using NMR titration data in HADDOCK, we have generated a three-dimensional model describing the complex between megalin and gentamicin. Gentamicin binds to megalin with low affinity and exploits the common ligand binding motif previously described (Jensen, G. A., Andersen, O. M., Bonvin, A. M., Bjerrum-Bohr, I., Etzerodt, M., Thogersen, H. C., O'Shea, C., Poulsen, F. M., and Kragelund, B. B. (2006) J. Mol. Biol. 362, 700-716) utilizing the indole side chain of Trp-1126 and the negatively charged residues Asp-1129, Asp-1131, and Asp-1133. Binding to megalin is highly similar to gentamicin binding to calreticulin. We discuss the impact of this novel insight for the future structure-based design of gentamicin antagonists.

Erythropoietin ameliorates genetamicin-induced renal toxicity: A biochemical and histopathological study

BACKGROUND

Investigations have attempted to modify the outcome of tubular injury by either ameliorating renal tubular damage or promoting tubular regeneration in the case of acute tubular necrosis.

OBJECTIVES

We investigated the protective effect of Eprex an erythropoietin analogue on tubular injury induced by gentamicin (GM).

MATERIALS AND METHODS

Forty male Wistar rats were randomly divided into four groups. In group 1,rats were served as a sham group. In group 2, rats were injected intraperitoneally with 100 mg/kg of GM for 10 consecutive days (positive control group) and then were sacrificed. In group 3, rats received GM for 10 days then Eprex 100U/kg was injected intraperitoneally for the next 10 days and then they were sacrificed at the day 20th. In group 4 rats were injected a combination of GM (80 mg/kg) and Eprex 100U/kg intraperitoneally for 10 days and then were sacrificed.

RESULTS

The results indicated that, Eprex prevented the increase in serum creatinine (Cr) and blood urea nitrogen (BUN). The effect of Eprex on damage score, showed that co-administration of GM and Eprex (group 3 and 4) reduced the kidney tissue damage compared to positive control group (P<0.05). This result indicat that Eprex potentially can reduce or prevent the kidney tissue damage.

CONCLUSIONS

Ameliorative effect of Eprex when the drug was given in combination with GM and also when the drug was applied after GM-induced tubular damage, revealed the renoprotective potency of Eprex. Eprex is a promising drug to prevent or attenuate tubular damage induced by GM or other nephrotoxic agents which act through the same mechanisms as gentamicin.