Sexually dimorphic proteinuria in Wistar rats: Relevance to clinical models

The role of Sirt3-induced autophagy in renal structural damage caused by periodontitis in rats

OBJECTIVE

This research aimed to explore the effect of periodontitis on renal tissues injury in rats and the role of Sirtuin3 (Sirt3) and its regulation of autophagy in this progression.

MATERIAL AND METHODS

Thirty Wistar rats were assigned into three groups: control, periodontitis (P), and periodontitis with gavage administration of Sirt3 activator resveratrol (P + RSV). To induce periodontitis, the wire ligature was placed around the cervical region of the rat maxillary first molar. After 8 weeks, micro-computed tomography (Micro-CT) and hematoxylin and eosin (HE) were used to evaluate the alveolar bone resorption and periodontal inflammation. Serum and urine biochemical indicators were measured to assess renal function. The pathological changes of the kidney were observed via HE and periodic acid Schiff (PAS) staining. Autophagosome was viewed by transmission electron microscopy (TEM). Real-time PCR and western blot were used to test expressions of Sirt3 and autophagy indicators in renal and periodontal tissues, including mammalian target of rapamycin (mTOR), phosphor-mTOR (p-mTOR), BECN1 (Beclin-1), and microtubule-associated protein 1 light chain 3 (LC3).

RESULTS

Alveolar bone destruction, resorption, and periodontal inflammation were observed in the P group (compared with the control group), and the above indexes were significantly improved after RSV intervention; the obvious changes in renal tissue structure in the P group were partially recovered after RSV intervention, while renal functional status was not affected (among the three groups); in addition, the levels of Sirt3 and autophagy in kidney and periodontal tissues of P group were inhibited, manifested as a decrease in the number of autophagosomes (renal tissue) and expressions of autophagy marker Beclin-1 and LC3 conversion rate and an increase in the expression of p-mTOR. After Sirt3 activation (RSV), the above indicators were significantly improved.

CONCLUSION

Periodontitis causes renal structural damage in rats, which may be connected to the effect of Sirt3-induced autophagy.

A Review of Specific Biomarkers of Chronic Renal Injury and Their Potential Application in Nonclinical Safety Assessment Studies

A host of novel renal biomarkers have been developed over the past few decades which have enhanced monitoring of renal disease and drug-induced kidney injury in both preclinical studies and in humans. Since chronic kidney disease (CKD) and acute kidney injury (AKI) share similar underlying mechanisms and the tubulointerstitial compartment has a functional role in the progression of CKD, urinary biomarkers of AKI may provide predictive information in chronic renal disease. Numerous studies have explored whether the recent AKI biomarkers could improve upon the standard clinical biomarkers, estimated glomerular filtration rate (eGFR), and urinary albumin to creatinine ratio, for predicting outcomes in CKD patients. This review is an introduction to alternative assays that can be utilized in chronic (>3 months duration) nonclinical safety studies to provide information on renal dysfunction and to demonstrate specific situations where these assays could be utilized in nonclinical drug development. Novel biomarkers such as symmetrical dimethyl arginine, dickkopf homolog 3, and cystatin C predict chronic renal injury in animals, act as surrogates for GFR, and may predict changes in GFR in patients over time, ultimately providing a bridge from preclinical to clinical renal monitoring.

Renal alterations caused by ligature-induced periodontitis persist after ligature removal in rats

BACKGROUND AND OBJECTIVE

Periodontitis may crosstalk with renal diseases, yet that remains unclear. We investigated whether the renal alterations caused by induced periodontitis are reversible after removal of the ligatures in experimental ligature-induced periodontitis.

MATERIAL AND METHODS

Twenty-four female rats were divided into three groups: control (without periodontitis), periodontitis (20 days of ligature-induced periodontitis), and P20-20 (20 days of ligature-induced periodontitis and 20 days after ligature removal). The following periodontal parameters were assessed: gingival bleeding index, probing pocket depth, myeloperoxidase activity, and alveolar bone height. For renal tissues, histopathology, malonaldehyde (MDA) levels, glutathione (GSH) content, and renal weight were evaluated. In the blood, creatinine, uric acid, albumin, total cholesterol, total protein, and glucose levels were assessed. Total protein and creatinine levels in urine were also investigated.

RESULTS

Rat renal tissues did not demonstrate reversal of periodontitis-related changes in the P20-20 group in terms of MDA, GSH, and histopathological evaluations when compared to the periodontitis group. Accordingly, only total cholesterol levels were reversible in the P20-20.

CONCLUSION

Renal alterations caused by ligature-induced periodontitis persisted even after removal of ligatures in rats.

Sulforaphane-conjugated selenium nanoparticles: towards a synergistic anticancer effect

Sulforaphane-modified selenium nanoparticles can be prepared in a simple aqueous-phase redox reaction through reduction of selenite with ascorbic acid. The sulforaphane molecules present in the reaction mixture adsorb on the nanoparticle surface, forming an adlayer. The resulting conjugate was examined with several physicochemical techniques, including microscopy, spectroscopy, x-ray diffraction, dynamic light scattering and zeta potential measurements. As shown in in vivo investigations on rats, the nanomaterial administered intraperitoneally is eliminated mainly in urine (and, to a lesser extent, in feces); however, it is also retained in the body. The modified nanoparticles mainly accumulate in the liver, but the basic parameters of blood and urine remain within normal limits. The sulforaphane-conjugated nanoparticles reveal considerable anticancer action, as demonstrated on several cancer cell cultures in vitro. This finding is due to the synergistic effect of elemental selenium and sulforaphane molecules assembled in one nanostructure (conjugate). On the other hand, the cytotoxic action on normal cells is relatively low. The high antitumor activity and selectivity of the conjugate with respect to diseased and healthy cells is extremely promising from the point of view of cancer treatment.

Traditional Renal Biomarkers and New Approaches to Diagnostics

Traditional biomarkers of renal disease have a number of limitations, whether evaluating veterinary patients or performing preclinical toxicity studies. Serum creatinine and urea nitrogen are affected by nonrenal influences that limit their usefulness for detecting small but significant decreases in glomerular filtration rate (GFR) in veterinary patients. These nonrenal influences can be more controlled in preclinical studies than in clinical patients; however, because of its high functional reserve, these estimates of GFR are insensitive for detecting kidney injury prior to loss of a substantial proportion of functioning nephrons. Urine biomarkers can be highly sensitive for tubular or glomerular injury that might lead to irreversible damage to the nephron. Several proteins are qualified by the Food and Drug Administration for nonclinical application as urinary biomarkers of drug-induced nephrotoxicity, and many of these also have preliminary data supporting their usefulness for kidney injury in dogs and cats. In addition to these relatively recently identified biomarkers, efforts are underway to discover new renal biomarkers using a variety of techniques including liquid chromatography-mass spectrometry and small RNA sequencing. Ultimately, the interplay between preclinical studies and clinical patients in discovery and validation of renal biomarkers is critical to their successful implementation.

Sub-acute administration of lower doses of nicotine caused sex-dependent improvement of renal function in Wistar rats

•

Exposure to nicotine is associated with sex-dependent variation in electrolyte disturbances.

•

Lower doses of sub-acute nicotine administration enhanced renal function.

•

Nicotine-enhanced renal function is more pronounced in female than in male Wistar rats.

•

Nicotine-enhanced renal function may be mediated through α7-nAchR.

The adverse and beneficial health effects of nicotine (NIC), the major alkaloid found in cigarettes and tobacco, are controversial. Most studies on NIC have focused on its effects on cardiovascular and nervous functions. This study aimed at determining dose- and sex-specific effects of sub-acute (28 days) NIC administration on some indices of kidney function in Wistar rats. Forty rats (20 males and 20 females), 8–9 weeks old (each housed in separate metabolic cage), were used for this study such that graded doses of NIC (1, 2 and 4 mg/kg i.p. for 28 days) were administered to both sexes while each control received distilled water at 0.2 mL/100 g i.p. Blood was collected under ketamine anesthesia (10 mg/kg i.m) for analyses and results obtained were compared at p < 0.05. The result showed beneficial alterations in plasma and urine level of creatinine, urea and uric acid (p < 0.05) as well as plasma and urine electrolyte level (Na⁺ and K⁺) in both sexes (p < 0.05). Also, there was significant improvement in creatinine clearance (p < 0.05) with no appreciable difference in their histological examination. Although these beneficial effects were more pronounced in the female than in the male (p < 0.05), administration at the highest dose showed potentially deleterious alterations from normal beneficial trend (p < 0.05) in both sexes. It was concluded that sub-acute administration of lower doses of NIC improves kidney function of Wistar rats; an effect that was more pronounced in the females than their male counterparts.

Ocimum gratissimum Ameliorates Gentamicin-Induced Kidney Injury but Decreases Creatinine Clearance Following Sub-Chronic Administration in Rats

The effects of aqueous extract of Ocimum gratissimum leaf (AOGL) on the renal function of rats with gentamicin-induced nephrotoxicity were investigated. This study involved the use of forty five (45) adult male Wistar rats (housed in separate metabolic cages) such that graded doses of OAGL were administered to the experimental groups (p.o.) for 28 days after exposure to gentamicin toxicity (100 mg/kg i.p.) for 1 week. At the end of the study, comparisons of some indices of renal function as well as antioxidant status (GSH and TBARS) were made between the control, toxic and AOGL-treated groups at P < 0.05. The result showed that gentamicin treatment caused significant increase (P < .05) in urine output, urea, creatinine, total protein, relative kidney weight, and TBARS, as well as significant decrease (P < .05) in urine creatinine and GSH levels. Post-treatment with graded doses of AOGL caused significant increase in food consumption, GSH, urine, and plasma creatinine, as well as significant decrease (P < .05) in relative kidney weight, TBARS, and urine total protein. There was an appreciable difference in the kidney histology of the AOGL-treated groups when compared with the toxic control. Hence, the extract has therapeutic potential in the management of gentamicin-induced kidney injury, although a risk profile of renal dysfunction is not unlikely from 28 days of administration as evident by the decrease in creatinine clearance.

Impact of gonadectomy on blood pressure regulation in ageing male and female rats

BACKGROUND

Sexual dimorphism in blood pressure has been associated with differential expression of the angiotensin II (AII) receptors and with activity of the nervous system. It is generally accepted that ageing affects kidney function as well as autonomic nervous system and hormonal balance. Given that hypertension is more prevalent in men than women until women reach their seventh decade, we hypothesised that females would be relatively protected from adverse effects of ageing compared to males and that this would be mediated by the protective effect of ovarian steroids.

METHODS

Intact and gonadectomised male and female normotensive Wistar rats aged 6, 12 and 18 months were used to study renal function, blood pressure, heart rate, and blood pressure variability.

RESULTS

We observed that intact females had lower levels of proteinuria and higher (12.5%) creatinine clearance compared to intact males and that this difference was abolished by castration but not by ovariectomy. Ovariectomy resulted in a change by 9% in heart rate, resulting in similar cardiovascular parameters to those observed in males or gonadectomised males. Spectral analysis of systolic blood pressure revealed that high-frequency power spectra were significantly elevated in the females vs. males and were reduced by ovariectomy.

CONCLUSIONS

Taken altogether, the results show that females are protected from age-related declining renal function and to a lesser extent from rising blood pressure in comparison to males. Whilst ovariectomy had some deleterious effects in females, the strongest effects were associated with gonadectomy in males, suggesting a damaging effect of male hormones.