Cisplatin decreases the abundance of aquaporin water channels in rat kidney

Is oral nano-curcumin formulation a safe and effective measure for preventing cisplatin-induced nephrotoxicity in cancer patients?

Nephrotoxicity is one of the most important complications in cancer patients under treatment with cisplatin-containing regimens. Curcumin, as the most important active component of Curcuma longa, is an antioxidant and anti-inflammatory compound. In this clinical trial, we assessed the preventive effect of nano-curcumin oral formulation against cisplatin-induced nephrotoxicity in cancer patients. In this triple-blind clinical trial 30 cancer patients on cisplatin were randomly included in the treatment group, receiving nano-curcumin 40 mg capsules ( n  = 15) or the placebo group ( n  = 15) twice a day during four chemotherapy courses. Kidney function was measured at the beginning of the study and then at the end of each course of chemotherapy. There was no significant difference in acute kidney injury occurrence rate and creatinine and blood urine nitrogen serum levels between the treatment and placebo groups at the end of each chemotherapy course ( P value >0.05). Just at the end of the first course, the difference was close to significant ( P  = 0.055). We also found no difference in mortality and recurrence rate in an average 30-month follow-up. Nano-curcumin in the prescribed dose and duration was not effective in preventing cisplatin-induced nephrotoxicity in cancer patients in comparison with the placebo. Further studies with larger sample size using different doses and duration of nano-curcumin are recommended.

Diagnostic challenges of superficial mucoceles: An update

A superficial mucocele is a unique variant of a mucocele of the oral cavity that was described by Eveson for the first time in 1988. It occurs due to subepithelial extravasation of sialomucin at the epithelial-connective tissue interface and is related to damage of the minor salivary gland ducts. Clinically, they appear as small, asymptomatic, clear, tense vesicles with a predilection for the soft palate, retromolar pads, and posterior buccal mucosa. They are reported to occur more frequently in women than in men. Before Eveson endeavoured to describe these rather peculiar lesions, they were often misdiagnosed as vesiculobullous lesions such as bullous lichen planus, mucous membrane pemphigoid, and the like. It is incumbent on the present-day pathologist to be cognizant of the presence of these entities as it could present a formidable diagnostic challenge otherwise. This review gives an updated account on the etiology, prevalence, clinical features, differential diagnosis, and management of superficial mucoceles.

Profound hyponatremia and dehydration: A case of cisplatin induced renal salt wasting syndrome

Cisplatin is a well-known chemotherapeutic agent that can be associated with hyponatremia. It is known to be associated with a multitude of renal disorders including acute kidney injury with reduced glomerular filtration, Fanconi syndrome, and renal tubular acidosis, nephrogenic diabetes insipidus and renal salt wasting syndrome. We report a case of an elderly male presenting with significant recurrent hyponatremia, and prerenal azotemia. With recent exposure to cisplatin along with significant hypovolemia and urinary loss of sodium, he was diagnosed to have cisplatin induced renal salt wasting syndrome.

Glucocorticoid Receptor Maintains Vasopressin Responses in Kidney Collecting Duct Cells

Water permeability of the kidney collecting ducts is regulated in part by the amount of the molecular water channel protein aquaporin-2 (AQP2), whose expression, in turn, is regulated by the pituitary peptide hormone vasopressin. We previously showed that stable glucocorticoid receptor knockdown diminished the vasopressin-induced Aqp2 gene expression in the collecting duct cell model mpkCCD. Here, we investigated the pathways regulated by the glucocorticoid receptor by comparing transcriptomes of the mpkCCD cells with or without stable glucocorticoid receptor knockdown. Glucocorticoid receptor knockdown downregulated 5,394 transcripts associated with 55 KEGG pathways including "vasopressin-regulated water reabsorption," indicative of positive regulatory roles of these pathways in the vasopressin-induced Aqp2 gene expression. Quantitative RT-PCR confirmed the downregulation of the vasopressin V2 receptor transcript upon glucocorticoid receptor knockdown. Glucocorticoid receptor knockdown upregulated 3,785 transcripts associated with 42 KEGG pathways including the "TNF signaling pathway" and "TGFβ signaling pathway," suggesting the negative regulatory roles of these pathways in the vasopressin-induced Aqp2 gene expression. Quantitative RT-PCR confirmed the upregulation of TNF and TGFβ receptor transcripts upon glucocorticoid receptor knockdown. TNF or TGFβ inhibitor alone, in the absence of vasopressin, did not induce Aqp2 gene transcription. However, TNF or TGFβ blunted the vasopressin-induced Aqp2 gene expression. In particular, TGFβ reduced vasopressin-induced increases in Akt phosphorylation without inducing epithelial-to-mesenchymal transition or interfering with vasopressin-induced apical AQP2 trafficking. In summary, our RNA-seq transcriptomic comparison revealed positive and negative regulatory pathways maintained by the glucocorticoid receptor for the vasopressin-induced Aqp2 gene expression.

Molecular Mechanisms and Biomarkers Associated with Chemotherapy-Induced AKI

Acute kidney injury (AKI) is a life-threatening condition characterized by a rapid and transient decrease in kidney function. AKI is part of an array of conditions collectively defined as acute kidney diseases (AKD). In AKD, persistent kidney damage and dysfunction lead to chronic kidney disease (CKD) over time. A variety of insults can trigger AKI; however, chemotherapy-associated nephrotoxicity is increasingly recognized as a significant side effect of chemotherapy. New biomarkers are urgently needed to identify patients at high risk of developing chemotherapy-associated nephrotoxicity and subsequent AKI. However, a lack of understanding of cellular mechanisms that trigger chemotherapy-related nephrotoxicity has hindered the identification of effective biomarkers to date. In this review, we aim to (1) describe the known and potential mechanisms related to chemotherapy-induced AKI; (2) summarize the available biomarkers for early AKI detection, and (3) raise awareness of chemotherapy-induced AKI.

The role of AQP3 and AQP4 channels in cisplatin-induced cardiovascular edema and the protective effect of melatonin

BACKGROUND

The present study evaluates the development of edema, the change in the AQP3, AQP4, p53 and Bax gene expressions, and the protective effects of melatonin in rat hearts administered with cisplatin.

METHODS AND RESULTS

A total of 28 Wistar albino rats were divided into four groups. The vehicle was administered intraperitoneally (i.p.) to the rats in the control group. The melatonin group (Mel) received melatonin at a dose of 10 mg/kg for 13 days. The cisplatin group (Cis) received cisplatin on days 1, 5, 9 and 13 at a dose of 4 mg/kg. The rats in the cisplatin + melatonin (Cis+Mel) group underwent the procedures both in the Mel and Cis groups. Blood and left ventricular samples were taken and analyzed on day 14 of the study. AQP3, p53 and Bax gene expressions were found to be significantly increased following cisplatin administration compared to the control, while melatonin administration significantly decreased the expression of these genes (p < 0.05). Melatonin administration also significantly decreased the level of AQP4 gene expression compared to the cis. On histological examination, congestion, hemorrhage, extracellular and intracellular edema, and degenerative changes were significantly more common in the Cis than in the control. Melatonin administration significantly decreased intracellular edema (p = 0.010) and degenerative changes (p = 0.010), and the improvement in extracellular edema was close to statistical significance (p = 0.051) in melatonin.

CONCLUSIONS

These results indicate that melatonin had an ameliorative effect on myocardial edema and AQP channels, and that it may be used as a protective molecule against myocardial edema secondary to cisplatin administration.

Gasdermin E deficiency attenuates acute kidney injury by inhibiting pyroptosis and inflammation

Pyroptosis, one kind of inflammatory regulated cell death, is involved in various inflammatory diseases, including acute kidney injury (AKI). Besides Gasdermin D (GSDMD), GSDME is a newly identified mediator of pyroptosis via the cleavage of caspase-3 generating pyroptotic GSDME-N. Here, we investigated the role of GSDME in renal cellular pyroptosis and AKI pathogenesis employing GSDME-deficient mice and human tubular epithelial cells (TECs) with the interventions of pharmacological and genetic approaches. After cisplatin treatment, GSDME-mediated pyroptosis was induced as shown by the characteristic pyroptotic morphology in TECs, upregulated GSDME-N expression and enhanced release of IL-1β and LDH, and decreased cell viability. Strikingly, silencing GSDME in mice attenuated acute kidney injury and inflammation. The pyroptotic role of GSDME was also verified in human TECs in vitro. Further investigation showed that inhibition of caspase-3 blocked GSDME-N cleavage and attenuated cisplatin-induced pyroptosis and kidney dysfunction. Moreover, deletion of GSDME also protected against kidney injury induced by ischemia-reperfusion. Taken together, the findings from current study demonstrated that caspase-3/GSDME-triggered pyroptosis and inflammation contributes to AKI, providing new insights into the understanding and treatment of this disease.

The protective efficacy of vitamin E and cod liver oil against cisplatin-induced acute kidney injury in rats

Cisplatin (CP) is a highly effective chemotherapeutic agent against neoplasms, but its clinical utility is limited due to the side effects of its dose-dependent nephrotoxicity. Vitamin E (Vit E) and cod liver oil (CLO) are natural substances with chemoprotective effects. The present study was conducted to evaluate the protective effects of Vit E and/or CLO for CP-induced acute kidney injury (AKI) in rats. This study involved 40 mature male Wistar albino rats that were equally allocated into eight groups: Veh, Vit E, CLO, Vit E + CLO, CP, Vit E + CP, CLO + CP, and Vit E + CLO + CP. The co-administration of Vit E and CLO significantly ameliorated CP-induced elevations in serum creatinine (Cr), blood urea nitrogen (BUN), interleukin 1 beta (IL-1β), and interleukin- 6 (IL-6). Further, rats that received Vit E and/or CLO showed significant decrease in malondialdehyde (MDA) and increases in superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels in renal tissues, compared to CP-intoxicated rats. Additionally, the treatment restored the normal histological architecture (except for few cast formations) and upregulated the immunostaining area% of aquaporin 3 (AQP3) and downregulated the immunostaining area% of Bcl2 associated X protein (BAX) and inducible nitric oxide synthase (iNOS). The observed effects were stronger in the combination treatment group. The obtained data revealed that Vit E and CLO co-administration protects against the CP-induced AKI more than monotherapy with Vit E or CLO.

Changes in hemodynamics, renal blood flow and urine output during continuous renal replacement therapies

Continuous renal replacement therapies (CRRT) affect hemodynamics and urine output. Some theories suggest a reduced renal blood flow as the cause of the decreased urine output, but the exact mechanisms remain unclear. A prospective experimental study was carried out in 32 piglets (2–3 months old) in order to compare the impact of CRRT on hemodynamics, renal perfusion, urine output and renal function in healthy animals and in those with non-oliguric acute kidney injury (AKI). CRRT was started according to our clinical protocol, with an initial blood flow of 20 ml/min, with 10 ml/min increases every minute until a goal flow of 5 ml/kg/min. Heart rate, blood pressure, central venous pressure, cardiac output, renal blood flow and urine output were registered at baseline and during the first 6 h of CRRT. Blood and urine samples were drawn at baseline and after 2 and 6 h of therapy. Blood pressure, cardiac index and urine output significantly decreased after starting CRRT in all piglets. Renal blood flow, however, steadily increased throughout the study. Cisplatin piglets had lower cardiac index, higher vascular resistance, lower renal blood flow and lower urine output than control piglets. Plasma levels of ADH and urine levels of aquaporin-2 were lower, whereas kidney injury biomarkers were higher in the cisplatin group of piglets. According to our findings, a reduced renal blood flow doesn’t seem to be the cause of the decrease in urine output after starting CRRT.

Tempol (4-hydroxy tempo) protects mice from cisplatin-induced acute kidney injury via modulation of expression of aquaporins and kidney injury molecule-1

Tempol (4-hydroxy tempo), a pleiotropic antioxidant is reported to afford protection against cisplatin (CP)-induced nephrotoxicity. However, molecular mechanisms of action of tempol in improving the renal function in CP-induced nephrotoxicity are not fully understood. We investigated the attenuating effect of tempol against CP-induced alterations in kidney injury molecule-1 (KIM-1) and aquaporins (AQPs) in mice. Tempol (100 mg/kg, po) pretreatment with CP (20 mg/kg ip) showed restoration in renal function markers including electrolytes. CP treatment upregulated mRNA expression of KIM-1 and downregulated AQP and arginine vasopressin (AVP) expression which was attenuated by tempol. Immunoblotting analysis revealed that CP-induced alterations in KIM-1 and AQP expression were restored by tempol. Immunofluorocense study also showed restorative effect of tempol on the expression of AQP2 in CP-treated mice. In conclusion, this study provides experimental evidence that tempol resolved urinary concentration defect by the restoration of AQP, AVP and KIM-1 levels indicating a potential use of tempol in ameliorating the AKI in cancer patients under the treatment with CP.

Cisplatin Decreases ENaC Activity Contributing to Renal Salt Wasting Syndrome

Cisplatin (CDDP) is an important anticancer drug. A common side effect of CDDP is renal salt and water-wasting syndrome (RSWS). The origin of RSWS is obscure. Emerging evidence, though, suggests that broad inhibition of sodium transport proteins by CDDP may result in decreases in tubular reabsorption, causing increases in sodium and water excretion. In this sense, CDDP would be acting like a diuretic. The effect of CDDP on the epithelial Na⁺ channel (ENaC), which is the final arbiter fine-tuning renal Na⁺ excretion, is unknown. We test here whether CDDP affects ENaC to promote renal salt and water excretion. The effects of CDDP and benzamil (BZM), a blocker of ENaC, on excretion of a sodium load were quantified. Similar to BZM, CDDP facilitated renal Na⁺ excretion. To directly quantify the effects on ENaC, principal cells in split-open tubules were patch clamped. CDDP, at doses comparable to those used for chemotherapy (1.5 µM), significantly decreased ENaC activity in native tubules. To further elaborate on this mechanism, the dose-dependent effects of CDDP on mouse ENaC (mENaC) heterologously expressed in Chinese Hamster Ovary (CHO) cells were tested using patch clamping. As in native tubules, CDDP significantly decreased the activity of mENaC expressed in CHO cells. Dose–response curves and competition with amiloride identified CDDP as a weak inhibitor of ENaC (apparent IC₅₀ = 1 µM) that competes with amiloride for inhibition of the channel, weakening the inhibitory actions of the latter. Such observations are consistent with CDDP being a partial modulator of ENaC, which possibly has a binding site that overlaps with that of amiloride. These findings are consistent with inhibition of ENaC by CDDP contributing to the RSWS caused by this important chemotherapy drug.

Protective effects of zingerone on cisplatin-induced nephrotoxicity in female rats

Zingerone (ZO), one of the active components of ginger (Zingiber officinale), is a phenolic alkanone with antioxidant, antiapoptotic, and anti-inflammatory properties. Cisplatin (CP) is a widely used chemotherapeutic drug for solid tumors, but its therapeutic use is limited due to dose-dependent nephrotoxicity. In the present study, we investigated the ameliorative effect of ZO against CP-induced nephrotoxicity. Intraperitoneal administration of single-dose CP (7 mg/kg body weight) on the first day enhanced kidney lipid peroxidation and reduced antioxidant enzyme activities such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione (GSH). CP increased serum urea and creatinine levels and disrupted histological integrity while causing a decrease aquaporin 1 (AQP1) level in the kidney tissues. CP induced inflammatory responses by elevating the levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-33 (IL-33) and nuclear factor kappa B (NF-κB), and activities of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Moreover, it also caused oxidative DNA damage and activation of apoptotic pathway by increasing of 8-hydroxy-2'-deoxyguanosine (8-OHdG), p53, cysteine aspartate-specific protease-3 (caspase-3), and Bcl-2-associated x protein (bax) while decreasing B cell lymphoma-2 (Bcl-2). However, treatment with ZO at a dose of 25 and 50 mg/kg b.wt. for 7 days significantly decreased oxidative stress, apoptosis, inflammation, and histopathological alterations while increased AQP1 levels in the kidney tissue. The results of the current study suggested that ZO as an effective natural product attenuates CP-induced nephrotoxicity.

An Early Decrease in Release of Aquaporin-2 in Urinary Extracellular Vesicles After Cisplatin Treatment in Rats

Aquaporin-1 (AQP1) and AQP2 are important proteins involved in the regulation of renal water handling. Both AQPs have been found in urinary extracellular vesicles (uEVs) (uEV-AQP1 and -AQP2). Cisplatin, an antineoplastic agent, is known to down-regulate renal AQP1 and AQP2. However, the effect of cisplatin on the release of uEV-AQP1 and -AQP2 is largely unknown. In this study, we examined whether treatment of rats with cisplatin affected the release of uEV-AQP1 and -AQP2. Blood tests indicated that renal function was little altered at 24 h after cisplatin treatment but thereafter decreased dramatically at all of the other time points examined. Release of uEV-AQP1 was slightly increased at 24 h and decreased at 168 h. On the other hand, release of uEV-AQP2 was decreased dramatically at 24 h, and the decrease was maintained during the experimental period. These data suggest that uEV-AQP2 can be used to detect early renal impairment due to cisplatin. Furthermore, a combination of uEV-AQP2 and -AQP1 may be useful for estimation of cisplatin-induced renal injury in a stage-dependent manner.

Integrin linked kinase regulates the transcription of AQP2 by NFATC3

Two processes are associated with progressive loss of renal function: 1) decreased aquaporin-2 (AQP2) expression and urinary concentrating capacity (Nephrogenic Diabetes Insipidus, NDI); and 2) changes in extracellular matrix (ECM) composition, e.g. increased collagen I (Col I) deposition, characteristic of tubule-interstitial fibrosis. AQP2 expression is regulated by both the ECM-to-intracellular scaffold protein integrin-linked kinase (ILK) by NFATc/AP1 and other transcription factors. In the present work, we used in vivo and in vitro approaches to examine ILK participation in NFATc3/AP-1-mediated increases in AQP2 gene expression. Both NFATc3 knock-out mice and ILK conditional-knockdown mice (cKD-ILK) display symptoms of NDI (polyuria and reduced AQP2 expression). NFATc3 is upregulated in the renal medulla tubular cells of cKD-ILK mice but with reduced nuclear localization. Inner medullary collecting duct mIMCD3 cells were subjected to ILK depletion and transfected with reporter plasmids. Pharmacological activators or inhibitors determined the effect of ILK activity on NFATc/AP-1-dependent increases in transcription of AQP2. Finally, mIMCD3 cultured on Col I showed reduced activity of the ILK/GSK3β/NFATc/AQP2 axis, suggesting this pathway is a potential target for therapeutic treatment of NDI.

Evaluation of The Protective Effect of Hydro-Alcoholic Extract of Raspberry Fruit on Aquaporin1 Expression in Rats Kidney Treated by Methotrexate

OBJECTIVE

Methotrexate (MTX) is an antimetabolite drug commonly prescribed for the various cancers and autoimmune diseases. Despite its considerable therapeutic effects, nephrotoxicity is the most important side-effect of treatment with MTX. Aquaporin1 (AQP1) is a water channel proteins which is present in mammalian kidney. Raspberry fruit with antioxidant properties is able to protect biological systems from the harmful effects of free radicals. The purpose of this study was to investigate the effect of raspberry extract on expression of AQP1 and the MTX-induced nephrotoxicity in rats.

MATERIALS AND METHODS

In this experimental study, 60 adult male Wistar rats were divided into nine groups including control, sham, MTX treated group [single dose of 20 mg/kg of body weight (BW) MTX at the third day], raspberry treated groups [intraperitoneal (I.P) injection of 100, 200, 400 mg/kg of BW raspberry extract for ten consecutive days], MTX and raspberry treated groups. At day 11, rats were sacrificed via chloroform inhalation and kidney tissues were fixed in formalin solution for histological and immunohistochemistry analysis. The serological assays for urea, creatinine, uric acid and interleukin-6 (IL-6) levels were also performed.

RESULTS

MTX elevated serum level of the urea, creatinine, uric acid, IL-6, renal tissue damage and decreased the AQP1 expression level. Raspberry fruit extract improved the kidney function and reduced side effects of MTX in treated rats. Expression of AQP1, in a dose dependent manner was also ameliorated, as compared to control group.

CONCLUSION

According to the findings of this study, it can be concluded that biological activity of compounds presented in raspberry fruit extract especially anthocyanins may have chemo-protective effect on kidney function and AQP1 expression in rats treated by MTX.

Sex-dependent expression of water channel AQP1 along the rat nephron

In the mammalian kidney, nonglycosylated and glycosylated forms of aquaporin protein 1 (AQP1) coexist in the luminal and basolateral plasma membranes of proximal tubule and descending thin limb. Factors that influence AQP1 expression in (patho)physiological conditions are poorly known. Thus far, only angiotensin II and hypertonicity were found to upregulate AQP1 expression in rat proximal tubule in vivo and in vitro (Bouley R, Palomino Z, Tang SS, Nunes P, Kobori H, Lu HA, Shum WW, Sabolic I, Brown D, Ingelfinger JR, Jung FF. Am J Physiol Renal Physiol 297: F1575-F1586, 2009), a phenomenon that may be relevant for higher blood pressure observed in men and male experimental animals. Here we investigated the sex-dependent AQP1 protein and mRNA expression in the rat kidney by immunochemical methods and qRT-PCR in tissue samples from prepubertal and intact gonadectomized animals and sex hormone-treated gonadectomized adult male and female animals. In adult rats, the overall renal AQP1 protein and mRNA expression was ∼80% and ∼40% higher, respectively, in males than in females, downregulated by gonadectomy in both sexes and upregulated strongly by testosterone and moderately by progesterone treatment; estradiol treatment had no effect. In prepubertal rats, the AQP1 protein expression was low compared with adults and slightly higher in females, whereas the AQP1 mRNA expression was low and similar in both sexes. The observed differences in AQP1 protein expression in various experiments mainly reflect changes in the glycosylated form. The male-dominant expression of renal AQP1 in rats, which develops after puberty largely in the glycosylated form of the protein, may contribute to enhanced fluid reabsorption following the androgen- or progesterone-stimulated activities of sodium-reabsorptive mechanisms in proximal tubules.

Time course of organic anion transporter 5 (Oat5) urinary excretion in rats treated with cisplatin: a novel urinary biomarker for early detection of drug-induced nephrotoxicity

Cisplatin is a widely used citostatic drug employed in the treatment of many solid tumors. Its principal side-effect is nephrotoxicity. The organic anion transporter 5 (Oat5) is exclusively expressed in the kidneys. The aim of this study was to evaluate the time course of Oat5 urinary excretion and changes in conventional biomarkers, such as creatinine and urea plasma levels (Urp and Crp), and protein and glucose urinary levels (Pu and Gluu), between others, and compared them to the onset and progression of histological changes after cisplatin treatment. Male Wistar rats were treated with cisplatin with 5 mg/kg b.w., i.p., and experiments were carried out after 2, 4, 7 and 14 days of treatment. Two days after cisplatin administration, only Oat5 urinary excretion was found markedly modified. On day 4, Urp, Crp, PU and GluU were increased. By the seventh day, a severe impairment in tubular architecture was observed, and from this point and thereon, Oat5 urinary excretion and PU showed a tendency to return to their basal values. Meanwhile, Urp, Crp and GluU tended to return to their basal values by the day 14 of treatment, when kidney morphology showed an important recovery. So Oat5 urinary abundance was elevated 2 days after cisplatin treatment, when no modifications of traditional markers of renal injury were still observed. Therefore, the results showed in this work, in addition to previous data obtained by our group, propose that Oat5 urinary excretion might potentially serve as a noninvasive early biomarker of cisplatin-induced nephrotoxicity.

Activation of G-protein-coupled receptor 40 attenuates the cisplatin-induced apoptosis of human renal proximal tubule epithelial cells

G-protein-coupled receptor 40 (GPR40) is known to play a role in the regulation of fatty acids, insulin secretion and inflammation. However, the pathophysiological roles of GPR40 in kidney disease have not yet been identified. In the present study, we investigated the expression of GPR40 during cisplatin-induced kidney injury using male Sprague-Dawley rats that were treated with 8 mg/kg cisplatin. Control rats were treated with saline. Following treatment with cisplatin, the protein expression of GPR40 in the kidneys was decreased in association with an increase in serum creatinine levels and the Bax/Bcl-2 expression ratio. To further investigate the function of GPR40, the human renal proximal tubule epithelial cell line (HK-2) was cultured with cisplatin in the absence or presence of GW9508, a selective GPR40 agonist. Pre-treatment of the HK-2 cells with GW9508 attenuated the decrease in cell viability induced by treatment with cisplatin. Treatment with cisplatin increased the number of cells with condensed nuclei, which was ameliorated by GW9508 pre-treatment. TUNEL assay also revealed that pre-treatment with GW9508 ameliorated cisplatin-induced apoptosis. Treatment with cisplatin increased the Bax/Bcl-2 expression ratio and cleaved caspase-3 expression, and promoted the activation of nuclear factor-κB (NF-κB). These changes were attenuated by pre-treatment with GW9508. The cisplatin-induced generation of reactive oxygen species (ROS) and the activation of the Src/epidermal growth factor receptor (EGFR)/extracellular signal-regulated kinase (ERK) pathway were also counteracted by pre-treatment with GW9508. Thus, the activation of GPR40 attenuates cisplatin-induced apoptosis by inhibiting the generation of ROS, the activation of the Src/EGFR/ERK signaling pathway and the nuclear activation of NF-κB and pro-apoptotic factors.

Alpha-lipoic acid attenuates lipopolysaccharide-induced kidney injury

BACKGROUND

Kidney is one of the major target organs in sepsis, while effective prevention of septic acute kidney injury has not yet been established. α-Lipoic acid (LA) has been known to exert beneficial effects against lipopolysaccharide (LPS)-induced damages in various organs such as heart, lung, and liver. We investigated the protective effect of LA on LPS-induced kidney injury.

METHODS

Two groups of rats were treated with LPS (20 mg/kg, i.p.), one of which being co-treated with LA (50 mg/kg), while the control group was treated with vehicle alone. Human renal proximal tubular epithelial cells (HK-2 cells) were cultured with or without LPS (10 μg/ml) in the presence or absence of LA (100 μg/ml) for 3 h prior to LPS treatment.

RESULTS

Serum creatinine level was increased in LPS-treated rats, which was attenuated by LA co-treatment. LPS treatment induced cleaved caspase-3 expression in the kidney, which was counteracted by LA. Terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive cells increased in the kidneys of LPS-treated rats compared with controls, which was counteracted by LA treatment. Protein expression of inducible nitric oxide synthase and cyclooxygenase-2 detected by immunoblotting and/or immunohistochemical staining, along with mRNA levels of pro-inflammatory cytokines detected by real-time polymerase chain reaction, was increased in the kidney with LPS administration, which was ameliorated with LA treatment. LA also protected LPS-induced tubular dysfunction, preserving type 3 Na(+)/H(+) exchanger and aquaporin 2 expressions in the kidney. Suppression of LPS-induced expression of cleaved caspase-3 by LA was also observed in HK-2 cells. Increased protein expression of phospho-extracellular signal-regulated kinases 1/2 and c-Jun N-terminal kinases by LPS treatment was attenuated by LA pretreatment, while p38 was not affected by either LPS or LA treatment. MitoTracker Red demonstrated LA prevented LPS-induced increment of mitochondrial oxidative stress, where concurrent 4',6-diamidino-2-phenylindole staining also revealed marked fragmentation and condensation of nuclei in HK-2 cells treated with LPS, which was prevented by LA.

CONCLUSION

LA treatment attenuates LPS-induced kidney injury, such as renal tubular dysfunction, by suppression of apoptosis, and inflammation.

Acute kidney injury in the cancer patient

Acute kidney injury (AKI) is a frequent and significant complication of cancer and cancer therapy. Cancer patients frequently encounter risk factors for AKI including older age, CKD, prerenal conditions, sepsis, exposure to nephrotoxins, and obstructive physiology. AKI can also be secondary to paraneoplastic conditions, including glomerulonephritis and microangiopathic processes. This complication can have significant consequences, including effects on patients' ability to continue to receive therapy for their malignancy. This review will serve to summarize potential etiologies of AKI that present in patients with cancer as well as to highlight specific patient populations, such as the critically ill cancer patient.

Effect of mesenchymal stem cells on renal injury in rats with severe acute pancreatitis

The aim of this study was to preliminarily investigate the effect of bone marrow mesenchymal stem cells (MSCs) on structural change of capillary endothelial barrier and expression variation of aquaporin 1 (AQP1) in kidney at the onset of renal injury caused by severe acute pancreatitis (SAP). Ninety male Sprague-Dawley (SD) rats were divided into the control group, the SAP group in which animals received induction of SAP and the MSCs-treated group in which SAP-induced animals were injected with MSCs. They were further subdivided according to the time point that the animals were killed; 6 h, 12 h and 24 h after the closure of the incision, serum, pancreatic and renal samples were collected, respectively. The level of serum amylase (AMY), creatinine (Cr) and blood urea nitrogen (BUN) were analysed, the change of pancreatic histology was assessed, the structural change of the renal interstitial capillaries was evaluated using the transmission electron microscope (TEM) and the location and expression of AQP1 in kidney were analysed using immunohistochemistry, quantitative polymerase chain reaction and Western blot. The outcomes showed that the level of serum AMY, Cr, BUN elevated, the damage of pancreatic tissue and renal capillary endothelial barrier was aggravated and the expression of AQP1 was reduced significantly after induced pancreatitis. But after treatments with MSCs, the elevation of AMY, Cr and BUN was inhibited, the damage of pancreatic tissue and renal interstitial capillary barrier was alleviated and the down-regulation of AQP1 was reversed. In summary, the MSCs therapy could alleviate renal injury in rats with SAP, the mechanism of which might be related to reduction of the damage to renal interstitial capillary endothelial barrier, and up-expression of AQP1 in kidney.

Protective effect of selenium on cisplatin induced nephrotoxicity: A double-blind controlled randomized clinical trial

BACKGROUND

Renal injury is common following cisplatin infusion. Some agents have been used to attenuate cisplatin nephrotoxicity. However, except hydration, none of them has been proved to be effective.

OBJECTIVE

In this study selenium as an antioxidant supplement was tested on cisplatin induced renal injury.

PATIENTS AND METHODS

122 cancerous patients (85 male and 37 female; age range of 14 to 82 years old) were enrolled to receive chemotherapy regimens consisting cisplatin. They were allocated into two groups using a random number list . Investigators, patients and analyzers all, were blinded in allocation by using sealed opaque envelopes. Intervention group received a single 400 mcg selenium tablet and patients in control group took a placebo tablet which was similar with selenium preparation in color, weight, shape and taste. Primary end points were an increase in plasma creatinine above 1.5 mg/dl in men and 1.4mg/dl in women, or increase of plasma creatinine more than 50% from baseline or urine flow rate less than 0.5 ml/kg/h. Creatinine level was measured initially and on the 5th day after cisplatin therapy.

RESULTS

There was no difference in cumulative dose of cisplatin between the groups (p=0.54). There were not evidences of acute renal failure (ARF) in cases. While, among placebo group, 7 patients had criteria of acute kidney injury. Conclusions :selenium could probably prevent cisplatin-induced acute kidney injury, when it is added to hydration therapy in cancerous patients.

Elemental bioimaging in kidney by LA-ICP-MS as a tool to study nephrotoxicity and renal protective strategies in cisplatin therapies

A laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)-based methodology is presented for Pt, Cu, and Zn bioimaging on whole kidney 3 μm sagittal sections from rats treated with pharmacological doses of cisplatin, which were sacrificed once renal damage had taken place. Pt turned out to accumulate in the kidney cortex and corticomedullary junction, corresponding to areas where the proximal tubule S3 segments (the most sensitive cells to cisplatin nephrotoxicity) are located. This demonstrates the connection between platinum accumulation and renal damage proved by histological examination of HE-stained sections and evaluation of serum and urine biochemical parameters. Cu and Zn distribution maps revealed a significant displacement in cells by Pt, as compared to control tissues. A dramatic decrease in the Pt accumulation in the cortex was observed when cilastatin was coadministered with cisplatin, which can be related to its nephroprotective effect. Excellent imaging reproducibility, sensitivity (LOD 50 fg), and resolution (down to 8 μm) were achieved, demonstrating that LA-ICP-MS can be applied as a microscopic metal detector at cellular level in certain tissues. A simple and quick approach for the estimation of Pt tissue levels was proposed, based on tissue spiking.

Recent advances in diagnosis and treatment of acute kidney injury in patients with cancer

Acute Kidney Injury (AKI) is a common complication in patients with cancer and even though there are many causes of renal failure in this population the classical classification of prerenal, renal, and postrenal is useful as a diagnostic guide. Important risk factors for AKI are dehydration, use of nephrotoxic drugs, preexisting renal impairment and large tumor burden. The development of AKI is associated with poor prognosis but early recognition and treatment initiation are associated with better outcomes in this population.

Cisplatin decreases renal cyclooxygenase-2 expression and activity in rats

AIM

Cisplatin (CP) induced acute renal failure (ARF) has previously been associated with decreased urinary prostaglandin E2 (PGE2) excretion and reduced aquaporin 2 (AQP2) expression in kidney collecting duct. In this study we examined the expression of cyclooxygenase (COX)-1 and -2 as well as AQP2 and the Na-K-2Cl cotransporter in kidneys from rats with CP induced ARF.

METHODS

Rats were treated with either CP or saline and followed for 5 days. Kidneys were dissected into three zones and prepared for immunoblotting, quantitative polymerase chain reaction (QPCR) and immunohistochemistry. Renal content and urinary PGE2 excretion was measured.

RESULTS

Cisplatin treatment was associated with polyuria and a significant decreased creatinine clearance. Inner medullary PGE2 content and urinary PGE2 excretion was decreased in CP-treated rats. QPCR and semiquatitative immunoblotting demonstrated that CP treatment reduced COX-2, AQP2 and Na-K-2Cl cotransporter abundance in the different kidney zones, whereas no change in COX-1 was observed. Results were confirmed by immunohistochemistry.

CONCLUSION

Cyclooxygenase-2 expression is decreased in inner medulla and cortex. Consistent with this urinary PGE2 levels were reduced. These data suggest that downregulation of COX-2 is responsible for impaired de novo generation of vasodilatory prostaglandins which may play an important role for the CP induced renal vasoconstriction and development of nephropathy.

Cisplatin-induced renal salt wasting syndrome

Cisplatin was the first platinum compound to be introduced as a chemotherapeutic agent with antineoplastic activity against a wide variety of solid tumors. Renal impairment with a decline in glomerular filtration has been the classical nephrotoxicity of cisplatin. Renal salt wasting syndrome is yet another, though it is not common. Previous studies were identified by searching the Pubmed database using the following keywords: cisplatin, cisplatin nephrotoxicity, renal salt wasting, and salt loosing nephropathy. Renal salt wasting syndrome has been described in 17 case reports since 1984. It is a rare side effect of cisplatin that manifests with polyuria, hypovolemia, and hyponatremia, and, because of similarities in clinical settings and laboratory values, it is frequently misdiagnosed as a syndrome of inappropriate antidiuretic hormone. Other causes of polyuria and hyponatremia should be excluded. Treatment aims at restoring the lost water and salt. Substituting cisplatin with carboplatin depends on individual clinical settings. Prognosis is excellent, as recovery was the rule in all the reported cases.

Aquaporins: The renal water channels

Water is the most abundant molecule in any cell. Specialized membrane channel, proteins called aquaporins, facilitate water transport across cell membranes. At least seven aquaporins (AQP): 1, 2, 3, 4, 6, 7, and 11 are expressed in the kidneys. Aquaporins play a role in both the short-term and long-term regulation of water balance as well as in the pathophysiology of water balance disorders. Aquaporin is composed of a single peptide chain consisting of approximately 270 amino acids. Inherited central and nephrogenic diabetes insipidus are primarily due to the decreased expression of AQP2 while mutation in the AQP2 molecule is responsible for inherited central diabetes insipidus. In acquired causes of nephrogenic diabetes insipidus, there is a downregulation of AQP2 expression in the inner medulla of the kidney. Nephrotic syndrome is characterized by excessive sodium and water reabsorption, although in spite of this, patients do not develop hyponatremia. There is a marked downregulation of both AQP2 and AQP3 expression, which could be a physiologic response to extracellular water reabsorption in patients with nephrotic syndrome. There are some conditions in which aquaporin expression has been found to increase such as experimentally induced heart failure, cirrhosis, and pregnancy. Some drugs such as cisplatin and cyclosporine, also alter the expression of aquaporins. The three-pore model of peritoneal transport depicts the importance of aquaporins. Thus, the understanding of renal water channels has solved the mystery behind many water balance disorders. Further insights into the molecular structure and biology of aquaporins will help to lay a foundation for the development of future drugs.

Organic cation transporter 2 mediates cisplatin-induced oto- and nephrotoxicity and is a target for protective interventions

The use of the effective antineoplastic agent cisplatin is limited by its serious side effects, such as oto- and nephrotoxicity. Ototoxicity is a problem of special importance in children, because deafness hampers their language and psychosocial development. Recently, organic cation transporters (OCTs) were identified in vitro as cellular uptake mechanisms for cisplatin. In the present study, we investigated in an in vivo model the role of OCTs in the development of cisplatin oto- and nephrotoxicity. The functional effects of cisplatin treatment on kidney (24 hours excretion of glucose, water, and protein) and hearing (auditory brainstem response) were studied in wild-type and OCT1/2 double-knockout (KO) mice. No sign of ototoxicity and only mild nephrotoxicity were observed after cisplatin treatment of knockout mice. Comedication of wild-type mice with cisplatin and the organic cation cimetidine protected from ototoxicity and partly from nephrotoxicity. For the first time we showed that OCT2 is expressed in hair cells of the cochlea. Furthermore, cisplatin-sensitive cell lines from pediatric tumors showed no expression of mRNA for OCTs, indicating the feasibility of therapeutic approaches aimed to reduce cisplatin toxicities by competing OCT2-mediated cisplatin uptake in renal proximal tubular and cochlear hair cells. These findings are very important to establish chemotherapeutical protocols aimed to maximize the antineoplastic effect of cisplatin while reducing the risk of toxicities.

Study of the Association of -667 Aquaporin-2 (AQP-2) A/G Promoter Polymorphism with the Incidence and Clinical Course of Chronic Kidney Disease in Korea

BACKGROUND

Impaired urinary concentration is uniformly present with advanced disease in chronic renal failure. Aquaporin-2 (AQP-2) is known to be expressed in the renal collecting duct cells and participates in urinary concentration in response to vasopressin. Recently, the study of AQP expression in various forms of chronic kidney disease (CKD) demonstrated a reduction in AQP-2 expression associated with a loss of nephrons and the presence of chronic interstitial fibrosis. No information on aquaporin genetic variations in CKD is available to date. The aim of our study was to evaluate the possible impact of aquaporin-2 genotype on the development and clinical course of CKD.

METHODS

Blood samples from 259 patients with CKD and 106 ethnicity-, age-, and sex-matched healthy controls were collected, and genomic DNA was extracted. AQP-2 -667 genotype was assessed by PCR, followed by restriction fragment length polymorphism analysis.

RESULTS

There were no significant differences in genotype and allele frequencies between the patients and healthy controls (p = 0.3936, p = 0.2941, respectively). In all, 79 (30.5%) patients had the AQP-2 -667 wild-type A/A, 123 (47.5%) were heterozygous for the G allele, and 57 (22.0%) patients showed homozygosity. After subclassification of CKD according to underlying disease, no significant differences were observed between those patients and controls (p = 0.72 for diabetic nephropathy, p = 0.52 for hypertensive nephropathy, p = 0.27 for chronic glomerulonephritis, and p = 0.80 for unknown etiology). Genotype and allele frequencies of the AQP-2 gene polymorphism (rs3759126) of hypertensive patients in pre-ESRD did not show a noticeable difference compared with normal blood pressure patients in pre-ESRD (p = 0.50). No correlation was found to exist between the AQP-2 gene polymorphism (rs3759126) and serum electrolyte levels in pre-ESRD patients (p = 0.38 for serum sodium level and p = 0.44 for serum potassium level).

CONCLUSION

Our data indicate that no association exists between the -667 AQP-2 A/G polymorphism and susceptibility to CKD or its clinical course.

Effect of Cisplatin on parotid gland function in concomitant radiochemotherapy

PURPOSE

To determine the influence of concomitant radiochemotherapy with cisplatin on parotid gland tissue complication probability.

METHODS AND MATERIALS

Patients treated with either radiotherapy (n = 61) or concomitant radiochemotherapy with cisplatin (n = 36) for head-and-neck cancer were prospectively evaluated. The dose and volume distributions of the parotid glands were noted in dose-volume histograms. Stimulated salivary flow rates were measured before, during the 2(nd) and 6(th) weeks and at 4 weeks and 6 months after the treatment. The data were fit using the normal tissue complication probability model of Lyman. Complication was defined as a reduction of the salivary flow rate to less than 25% of the pretreatment flow rate.

RESULTS

The normal tissue complication probability model parameter TD(50) (the dose leading to a complication probability of 50%) was found to be 32.2 Gy at 4 weeks and 32.1 Gy at 6 months for concomitant radiochemotherapy and 41.1 Gy at 4 weeks and 39.6 Gy at 6 months for radiotherapy. The tolerated dose for concomitant radiochemotherapy was at least 7 to 8 Gy lower than for radiotherapy alone at TD(50).

CONCLUSIONS

In this study, the concomitant radiochemotherapy tended to cause a higher probability of parotid gland tissue damage. Advanced radiotherapy planning approaches such as intensity-modulated radiotherapy may be particularly important for parotid sparing in radiochemotherapy because of cisplatin-related increased radiosensitivity of glands.

alpha-Lipoic acid prevents cisplatin-induced acute kidney injury in rats

BACKGROUND

Cisplatin-induced nephropathy has been related to increased lipid peroxide formation and decreased activity of antioxidant enzymes in the kidney. The present study aimed to examine whether treatment with alpha-lipoic acid (alpha-LA) prevents the cisplatin-induced nephrotoxicity.

METHODS

Two groups of rats were treated with cisplatin, one of which being cotreated with alpha-LA. The control group was treated with vehicle only. Four days later, the expression of aquaporins and sodium transporters was determined in the kidney by immunoblotting and immunohistochemistry. The arginine vasopressin-stimulated generation of cAMP was measured by radioimmunoassay. The expression of nitric oxide synthases (NOS) was determined by immunoblotting. The mRNA expression of endothelin-1 (ET-1) and tumour necrosis factor (TNF)-alpha was measured by real-time PCR. Apoptosis was examined by TUNEL staining.

RESULTS

Following the treatment with cisplatin, urinary volume and fractional excretion of sodium increased. Accordingly, the expression of aquaporins 1-3, Na,K-ATPase, NHE3 and NKCC2 was decreased. The expression of adenylyl cyclase VI and vasopressin-stimulated cAMP generation was decreased. The expression of inducible NOS was increased, while that of endothelial NOS decreased. The ET-1 expression was increased. TUNEL-positive cells were increased, in association with an increased expression of TNF-alpha. alpha-LA treatment prevented dysregulation of these parameters and resumed the renal function.

CONCLUSION

alpha-LA may prevent the cisplatin-induced nephrotoxicity, possibly through preserving the activities of NO and ET systems and inhibiting the development of apoptosis.

Effects of antioxidant drugs in rats with acute renal injury

Acute renal failure is mainly caused by ischemia/reperfusion (I/R) injury or nephrotoxic drugs, in which reactive oxygen species (ROS) may play an important role. Therefore, antioxidants are expected to decrease the vulnerability of renal injury associated with oxidative challenges. α-Lipoic acid (α-LA), potent antioxidant, could act as ROS scavengers, iron chelators and enzyme modulators. In rats with acute renal injury, dysregulation of aquaporin (AQP) water channels and sodium transporters has been noted. I/R injury or cisplatin induced marked down-regulation of AQP1, AQP2 and AQP3 water channels, and type-3 Na-H exchanger, Na,K-ATPase, and Na-K-2Cl cotransporters, in association with impairment of urinary concentration and tubular sodium reabsorption. Treatment with α-LA prevented the dysregulation of AQP channels and sodium transporters, along with improved urinary concentrating capability and renal sodium reabsorption.

Rosiglitazone ameliorates cisplatin-induced renal injury in mice

BACKGROUND

Inflammatory mechanisms may play an important role in the pathogenesis of cisplatin nephrotoxicity. Agonists of the peroxisome proliferator-activated receptor-gamma (PPARgamma), such as rosiglitazone, have been recently demonstrated to regulate inflammation by modulating the production of inflammatory mediators and adhesion molecules. The purpose of this study was to examine the protective effects of rosiglitazone on cisplatin nephrotoxicity and to explore the mechanism of its renoprotection.

METHODS

Mice were treated with cisplatin with or without pre-treatment with rosiglitazone. Renal functions, histological findings, aquaporin 2 (AQP2) and adhesion molecule expression, macrophage infiltration and tumour necrosis factor-alpha (TNF-alpha) levels were investigated. The effect of rosiglitazone on nuclear factor (NF)-kappaB activity and on viability was examined using cultured human kidney (HK-2) cells.

RESULTS

Rosiglitazone significantly decreased both the damage to renal function and histological pathology after cisplatin injection. Pre-treatment with rosiglitazone reduced the systemic levels of TNF-alpha and down-regulated adhesion molecule expression in addition to the infiltration of inflammatory cells after cisplatin administration. Rosiglitazone restored the decreased AQP2 expression after cisplatin treatment. Pre-treatment with rosiglitazone blocked the phosphorylation of the p65 subunit of NF-kappaB in cultured HK-2 cells. Rosiglitazone had a protective effect via a PPARgamma-dependent pathway in cisplatin-treated HK-2 cells.

CONCLUSION

These results showed that pre-treatment with rosiglitazone attenuates cisplatin-induced renal damage through the suppression of TNF-alpha overproduction and NF-kappaB activation.

Toxicité rénale des anticancéreux

Nephrotoxicity is an inherent adverse effect of certain anticancer drugs. Anti neoplasic drugs have a narrow therapeutic index and the amount of drug necessary to produce a significant reduction in tumour burden usually produces significant nephrotoxicity. The dosage used in clinical trials represents often the maximum tolerated doses determined during phase I drug evaluation. Greater toxicity is acceptable during curative therapy than during palliative therapy. But cancer patients often exhibit excretory reduced organ function. Modulation of pharmacokinetics and pharmacodynamics of these drugs in cancer patients is therefore necessary in order to improve tolerance. Patients with malignancies are particularly vulnerable to development of renal abnormalities. Conversely, patients with renal abnormalities who have undergone kidney transplantation are at high risk for malignancy. Clinical syndromes of renal involvement are diverse and sometimes insidious. Despite the recent advances in understanding the mechanism of anticancer drug nephrotoxicity, prevention still relies on drug dosage decrease and active screening for renal abnormalities as part of the usual biological work up in patients treated with anticancer drugs.

Butein Ameliorates Renal Concentrating Ability in Cisplatin-Induced Acute Renal Failure in Rats

The present study examined whether the cisplatin-induced nephropathy could be ameliorated by administration of butein isolated from the stems of Rhus verniciflua STOCKS. The present study showed that polyuric profile was revealed in cisplatin-induced acute renal failure (ARF) rats associated with decreases in urinary sodium, potassium, chloride, and creatinine excretion, and osmolality. Among these renal functional parameters, urinary volume and osmolality were partially restored by administration of butein (10 mg/kg, i.p.), but electrolytes and creatinine excretion were not restored. Both solute-free water reabsorption and creatinine clearance were also significantly decreased in rats subjected to cisplatin. When butein was administered in rats with cisplatin-induced ARF for 4 d, solute-free water reabsorption was improved by 91% compared with that of cisplatin-induced ARF rats, but creatinine clearance was not restored. The expression levels of aquaporin 2 (AQP 2) in the inner, outer medulla, and cortex were significantly decreased in the kidney of ARF, which were partially reverted by administration of butein. In histological examination of the kidney, butein treatment partially prevented the lesions at tubules of renal cortex in cisplatin-induced ARF rats, while the lesions at glomeruli were not ameliorated. Taken together, butein ameliorates renal concentrating ability via up-regulation of renal AQP 2 water channel in rats with cisplatin-induced ARF without ameliorating effect on renal filtration defect.

Protective effects of glycyrrhizin on gentamicin-induced acute renal failure in rats

The aim of this study was to investigate the effects of glycyrrhizin (200 mg/kg/day) on renal function in association with the regulation of aquaporin 2 water channel in rats with gentamicin (100 mg/kg/day)-induced acute renal failure. Polyuria in rats with gentamicin-induced acute renal failure was associated with down-regulation of renal aquaporin 2 in the inner and outer renal medulla, and cortex. Glycyrrhizin administration restored the expression of aquaporin 2 with paralleled changes in urine output. Changes in renal functional parameters, such as creatinine clearance, urinary osmolality, and solute-free reabsorption, accompanying acute renal failure were also partially restored after administration of glycyrrhizin. Histological changes in rats with gentamicin-induced acute renal failure were also abrogated by glycyrrhizin treatment. The above results suggest that glycyrrhizin treatment could ameliorate renal defects in rats with acute renal failure induced by gentamicin.

Expression of salt and urea transporters in rat kidney during cisplatin-induced polyuria

BACKGROUND

Cisplatin (CP) induced polyuria in rats is associated with a reduction in medullary hypertonicity, normally generated by the thick ascending limb (TAL) salt transporters, and the collecting duct urea transporters (UT). To investigate the molecular basis of this abnormality, we determined the protein abundance of major salt and UT isoforms in rat kidney during CP-induced polyuria.

METHODS

Male Sprague-Dawley rats received either a single injection of CP (5 mg/kg, N = 6) or saline (N = 6) intraperitoneally five days before sacrifice. Urine, blood, and kidneys were collected and analyzed.

RESULTS

CP-treated rats developed polyuric acute renal failure as assessed by increased blood urea nitrogen (BUN), urine volume and decreased urine osmolality. Western analysis of kidney homogenates revealed a marked reduction in band density of the bumetanide-sensitive Na-K-2Cl cotransporter in cortex (60% of control values, P < 0.05), but not in outer medulla (OM) (106% of control values). There were no differences in band densities for the renal outer medullary potassium channel (ROMK), the type III Na-H exchanger (NHE3), the alpha-subunit of Na,K-ATPase in the OM; or for UT-A1, UT-A2 or UT-A4 in outer or inner medulla. However, the band pattern of UT-A2 and UT-A4 proteins in the OM of CP-treated rats was different from the control rats, suggesting a qualitative modification of these proteins.

CONCLUSIONS

Changes in the abundance of outer or inner medullary salt or urea transporters are unlikely to play a role in the CP-induced reduction in medullary hypertonicity. However, qualitative changes in UT proteins may affect their functionality and thus may have a role.

Amphotericin B decreases adenylyl cyclase activity and aquaporin-2 expression in rat kidney

The present study was intended to examine whether the amphotericin-induced urinary concentration defect can be related to an altered regulation of aquaporin (AQP) water channels in the kidney. Male Sprague-Dawley rats were injected with amphotericin B (6 mg/kg/d, IP ) for 21 days. The protein expression of AQP1-3, Gsalpha, and adenylyl cyclase was determined in the kidney. To further specify the primary point of dysregulation of AQP channels that are activated by the arginine vasopressin/cyclic adenosine monophosphate (AVP/cAMP) pathway, different components of adenylyl cyclase complex were separately examined for their cAMP-generating activities. Amphotericin treatment resulted in kidney failure associated with decreased tubular water reabsorption and increased urinary flow rate. The expression of AQP2 proteins was significantly decreased in the outer medulla and inner medulla but not in the cortex. The expression of AQP2 proteins in the membrane fraction changed in parallel with that in the cytoplasmic fraction, suggesting a preserved targeting. Neither the expression of AQP1 nor that of AQP3 was significantly affected in the cortex, outer medulla, or inner medulla. The cAMP generation in response to AVP or sodium fluoride was decreased, whereas that to forskolin was not significantly altered. The expression of Gsalpha proteins was decreased in the inner medulla, whereas that of adenylyl cyclase VI remained unaltered. These findings indicate that the amphotericin-induced urinary concentration defect may in part be causally related to a reduced abundance of AQP2 channels in the kidney. It is also suggested that the primary impairment in the pathway leading to the activation of AQP channels that are regulated by the AVP/cAMP pathway lies at the level of G proteins.

Diminished renal expression of aquaporin water channels in rats with experimental bilateral ureteral obstruction

Whether postobstructive diuresis could be related to altered regulation of aquaporin (AQP) water channels in the kidney was investigated. Male Sprague-Dawley rats underwent bilateral obstruction of the proximal ureters for 48 h. The renal expression of AQP1 to AQP4 proteins was then determined by Western blot and immunohistochemical analyses. For elucidation of the primary impairment in the upstream pathway leading to the expression of cAMP-mediated AQP channels, the expression of G(salpha) and that of adenylyl cyclase were also determined. For some rats, the obstruction was released for collection of urine samples. After the ureteral obstruction, the urinary flow rate was increased and free water reabsorption was decreased. In the obstructed kidneys, the expression of AQP1 to AQP3 was decreased in the cortex, outer medulla, and inner medulla, whereas that of AQP4 was decreased in the inner medulla. Immunoreactivities for AQP1 to AQP4 were also decreased in the obstructed kidneys. The protein expression of G(salpha) was decreased in the cortex, outer medulla, and inner medulla, whereas that of adenylyl cyclase VI was decreased in the outer and inner medullae. cAMP generation stimulated by arginine vasopressin was decreased in the cortex, outer medulla, and inner medulla. cAMP generation in response to forskolin was decreased in the outer and inner medullae, whereas that in response to sodium fluoride was decreased in the cortex, outer medulla, and inner medulla. These results suggest that a reduced abundance of AQP water channels in the kidney accounts in part for postobstructive diuresis. The primary impairment of AQP channels that are regulated via the arginine vasopressin/cAMP pathway may lie at the level of G proteins and adenylyl cyclase itself.

Gentamicin decreases the abundance of aquaporin water channels in rat kidney

The present study was performed to examine whether the gentamicin-induced urinary concentration defect is related to an altered regulation of aquaporin (AQP) water channels in the kidney. Male Sprague-Dawley rats were subcutaneously injected with gentamicin (20, 50 or 100 mg/kg per day) for 6 days. The protein expression of AQP1-3 channels and the catalytic activity of adenylyl cyclase were determined in the kidney. Gentamicin treatment resulted in renal failure associated with decreased tubular free water reabsorption and increased urinary flow rate. The expression of AQP2 proteins was significantly decreased in the kidney, in which the cortex was most susceptible, followed by the outer medulla and inner medulla in order. Gentamicin treatment also decreased the shuttling of AQP2, as evidenced by a decrease of its expression in the membrane fraction in proportion to that in the cytoplasmic fraction. The protein expression of AQP1 as well as that of AQP3 was also decreased in the cortex by treatment with the highest dose of gentamicin. The cAMP generation in response to arginine vasopressin or sodium fluoride was decreased by gentamicin, while that to forskolin was not significantly altered. These findings suggest that the primary impairment in the pathway leading to the generation of cAMP lies at the level of G proteins, resulting in a decreased expression of cAMP-mediated AQP channels. The gentamicin-induced urinary concentration defect may in part be accounted for by a reduced abundance of AQP water channels in the kidney.