CYP2E1 and miRNA‐378a‐3p contribute to acetaminophen‐ or tripterygium glycosides‐induced hepatotoxicity

Increased expression of CYP2E1 may represent the main factor contributing to oxidative stress‐mediated liver damage in drug‐induced liver injury (DILI). However, the regulation mechanism of CYP2E1 expression is poorly described. The present study was aimed to investigate the role of CYP2E1 in acetaminophen (APAP)‐ or tripterygium glycosides (TG)‐induced hepatotoxicity as well as the regulation of CYP2E1 and miR‐378a‐3p expression by APAP or TG. Rats were randomly divided and treated with APAP, TG, chlormethiazole (CMZ), APAP + CMZ and TG + CMZ, respectively, for 4 weeks. Then, blood and liver samples were collected. Serum and hepatic biochemical parameters were measured using commercial kits. Liver histopathology was tested by H&E staining. Expression levels of CYP2E1 mRNA and miR‐378a‐3p were detected by qRT‐PCR. CYP2E1 protein expression was determined by Western blot. Our results showed that CMZ effectively restored the hepatic histopathological changes, oxidative stress biomarkers and TNF‐α levels induced by APAP or TG. CYP2E1 mRNA and/or protein expression levels were dramatically increased after chronic APAP or TG treatment, while this induction was significantly reversed by CMZ co‐treatment. Of note, miR‐378a‐3p expression levels were significantly suppressed after APAP, TG and/or CMZ treatment. These results suggested that CYP2E1 were highly induced after chronic APAP or TG treatment, which in turn play an important role in APAP‐ or TG‐induced hepatotoxicity. These inductions of CYP2E1 expression were probably carried out by inhibition of miR‐378a‐3p. Our findings might provide a new molecular basis for DILI.     

The peroxisome proliferator‐activated receptor‐γ agonist pioglitazone protects against cisplatin‐induced renal damage in mice

Peroxisome proliferator‐activated receptor‐γ (PPAR‐γ) agonists not only improve metabolic abnormalities of diabetes and consequent diabetic nephropathy, but they also protect against non‐diabetic kidney disease in experimental models. Here, we investigated the effect of PPAR‐γ agonist pioglitazone against acute renal injury on a cisplatin model in mice. Nephrotoxicity was induced by a single intraperitoneal (i.p.) injection of cisplatin (10 mg kg^–1). Pioglitazone was administered for six consecutive days in doses of 15 or 30 mg kg^–1 day^–1, per os (p.o.), starting 3 days before cisplatin injection. Cisplatin treatment to mice induced a marked renal failure, characterized by a significant increase in serum urea and creatinine levels and alterations in renal tissue architecture. Cisplatin exposure induced oxidative stress as indicated by decreased levels of non‐enzymatic antioxidant defenses [glutathione (GSH) and ascorbic acid levels] and components of the enzymatic antioxidant defenses [superoxide dismutase (SOD), catalase (CAT) glutathione peroxidase (GPx), glutathione reductase (GR) and and glutathione S‐transferase(GST) activities)] in renal tissue. Administration of pioglitazone markedly protected against the increase in urea and creatinine levels and histological alterations in kidney induced by cisplatin treatment. Pioglitazone administration ameliorated GSH and ascorbic acid levels decreased by cisplatin exposure in mice. Pioglitazone protected against the inhibition of CAT, SOD, GPx, GR and GST activities induced by cisplatin in the kidneys of mice. These results indicated that pioglitazone has a protective effect against cisplatin‐induced renal damage in mice. The protection is mediated by preventing the decline of antioxidant status. The results have implications in use of PPAR‐γ agonists in human application for protecting against drugs‐induced nephrotoxicity. Copyright © 2012 John Wiley & Sons, Ltd.     

Nano‐selenium attenuates nickel‐induced testosterone synthesis disturbance through inhibition of MAPK pathways in Sprague‐Dawley rats

The aim of this study was to investigate the protective effects of Nano‐Se against Ni‐induced testosterone synthesis disorder in rats and determine the underlying protective mechanism. Sprague‐Dawley rats were co‐treated with Ni (5.0 mg/kg, i.p.) and Nano‐Se (0.5, 1.0, and 2.0 mg/kg, oral gavage) for 14 days after which various endpoints were evaluated. The Ni‐induced abnormal pathological changes and elevated 8‐OHdG levels in the testes were attenuated by Nano‐Se administration. Importantly, decreased serum testosterone levels in the Ni‐treated rats were significantly restored by Nano‐Se treatment, particularly at 1.0 and 2.0 mg/kg. Furthermore, the mRNA and protein levels of testosterone synthetase were increased by Nano‐Se compared to the Ni group, whereas phosphorylated protein expression levels of mitogen‐activated protein kinase (MAPK) pathways were suppressed by Nano‐Se administration in the Ni‐treated rats. Overall, the results suggest that Nano‐Se may ameliorate the Ni‐induced testosterone synthesis disturbance via the inhibition of ERK1/2, p38, and JNK MAPK pathways.     

Nebivolol Ameliorates Cisplatin‐Induced Nephrotoxicity in Rats

Treatment with cisplatin is associated with dose‐limiting side effects, mainly nephrotoxicity. On the other hand, nebivolol, a β₁‐adrenoceptor antagonist, exhibits vasodilatory and antioxidative properties. This study aimed to determine whether nebivolol possesses a protective effect against cisplatin nephrotoxicity and explore many mechanisms underlying this potential effect. Nephrotoxicity was induced in Wistar rats by a single intraperitoneal injection of cisplatin (6 mg/kg) on day 2. Nebivolol (10 mg/kg) was administered orally for 7 consecutive days. Nebivolol showed a nephroprotective effect as demonstrated by the significant reduction in the elevated levels of serum creatinine and urea as well as renal levels of malondialdehyde, nitric oxide products (nitrite/nitrate), inducible nitric oxide synthase, tumour necrosis factor‐alpha, caspase‐3, angiotensin II and endothelin‐1 with a concurrent increase in renal levels of reduced glutathione and endothelial nitric oxide synthase compared to untreated rats. Histopathological examination confirmed the nephroprotective effect of nebivolol. Pre‐treatment with N_ω‐nitro‐L‐arginine methyl ester, the non‐specific nitric oxide synthase inhibitor, partially altered the protection afforded by nebivolol. In conclusion, nebivolol protects rats against cisplatin‐induced nephrotoxicity that is most likely through its antioxidant, anti‐inflammatory and antiapoptotic effects as well as by abrogation of the augmented angiotensin II and endothelin‐1 levels.     

β‐asarone and levodopa co‐administration protects against 6‐hydroxydopamine‐induced damage in parkinsonian rat mesencephalon by regulating autophagy: down‐expression Beclin‐1 and light chain 3B and up‐expression P62

In this study, we investigated Beclin‐1, light chain (LC)3B, and p62 expression in 6‐hydroxydopamine (6‐OHDA)‐induced parkinsonian rats after β‐asarone and levodopa (l ‐dopa) co‐administration. Unilateral 6‐OHDA injection into the medial forebrain bundle was used to create the models, except in sham‐operated rats. Rats were divided into eight groups: sham‐operated group; 6‐OHDA model group; madopar group (75 mg/kg, per os (p.o.)); l ‐dopa group (60 mg/kg, p.o.); β‐asarone group (15 mg/kg, p.o.); β‐asarone + l ‐dopa co‐administered group (15 mg/kg + 60 mg/kg, p.o.); 3‐methyladenine group (500 nmol, intraperitoneal injection); and rapamycin group (1 mg/kg, intraperitoneal injection). Then, Beclin‐1, LC3B, and p62 expression in the mesencephalon were detected. The mesencephalon was also observed by transmission electron microscope. The results showed that Beclin‐1 and LC3B expression decreased and that p62 expression increased significantly in the madopar, l ‐dopa, β‐asarone, and co‐administered groups when compared with the 6‐OHDA model. Beclin‐1 and LC3B expression in the β‐asarone and co‐administered groups were less than in the madopar or l ‐dopa groups, whereas p62 expression in the β‐asarone and co‐administered groups was higher than in the madopar or l ‐dopa groups. In addition, a significant decrease in autophagosome was exhibited in the β‐asarone and co‐administered groups when compared with the 6‐OHDA group. Our findings indicate that Beclin‐1 and LC3B expression decreased, whereas p62 expression increased after co‐administration treatment. In sum, all data suggest that the co‐administration of β‐asarone and l ‐dopa may contribute to the treatment of 6‐OHDA‐induced damage in rats by inhibiting autophagy activity.     

Wuzhi capsule regulates chloroacetaldehyde pharmacokinetics behaviour and alleviates high‐dose cyclophosphamide‐induced nephrotoxicity and neurotoxicity in rats

High‐dose cyclophosphamide (HD‐CTX) treatment often leads to severe nephrotoxicity and neurotoxicity, which are mainly caused by one of its metabolites, chloroacetaldehyde (CAA). However, there are no effective antidotes to prevent these side effects. The objective of this study was to evaluate the effect of Wuzhi Capsule (WZC) on the pharmacokinetics of CTX and its metabolites in rats, and the attenuation of CAA induced kidney and brain injuries, which was produced at equimolar with 2‐dechloroethylcyclophosphamide. Rats were treated with single‐ or multiple‐dose of WZC when giving HD‐CTX, and the plasma concentration of CTX and its metabolites were quantitated by UHPLC‐MS/MS Single‐dose, not multiple‐dose of WZC co‐administration (300 mg/kg) significantly reduced C_max and AUC_0→24 h of DC‐CTX by 33.10% and 35.51%, respectively. Biochemical assay suggested oxidative stress was involved in kidney and brain injuries by HD‐CTX, which were attenuated by single‐dose WZC (300 mg/kg) pre‐treatment, with increased glutathione, glutathione peroxidase and superoxide dismutase contents/or activities in both tissues and plasma (P < 0.05). Meanwhile, WZC pre‐treatment could also significantly decrease the plasma levels of creatinine, blood urea nitrogen and malondialdehyde (P < 0.05). Additionally, WZC treatment improved the morphology and pathology condition of the kidneys and brains in rats. In conclusion, single‐dose WZC co‐administration decreased CAA production and exerted protective effect on CTX‐induced oxidative stress in kidney and brain, whereas repetitive WZC co‐administration with CTX was probably not recommended.     

Novel synthetic protective compound,KR‐22335, against cisplatin‐induced auditory cell death

Cisplatin [cis‐diammine‐dichloroplatinum (II)] is a widely used chemotherapeutic agent, and one of its most severe side effects is ototoxicity. In the course of developing a new protective agent against cisplatin‐induced ototoxicity, we have been interested in a novel synthetic compound, 3‐Amino‐3‐(4‐fluoro‐phenyl)‐1H‐quinoline‐2,4‐dione (KR‐22335). We evaluated the effectiveness of KR‐22335 as an otoprotective agent against cisplatin‐induced toxicity. The otoprotective effect of KR‐22335 against cisplatin was tested in vitro in cochlear organs of Corti‐derived cell lines, HEI‐OC1, and in vivo in a zebrafish (Danio rerio) model. Cisplatin‐induced apoptosis, cell cycle arrest and an increase in intracellular reactive oxygen species (ROS) generation were demonstrated in HEI‐OC1 cells. KR‐22335 inhibited cisplatin‐induced apoptosis and mitochondrial injury in HEI‐OC1 cells. KR‐22335 inhibited cisplatin‐induced activation of JNK, p‐38, caspase‐3 and PARP in HEI‐OC1 cells. Scanning and transmission electron micrographs showed that KR‐22335 prevented cisplatin‐induced destruction of kinocilium and stereocilia in zebrafish neuromasts. Tissue TUNEL of neuromasts in zebrafish demonstrated that KR‐22335 blocked cisplatin‐induced TUNEL positive hair cells in neuromasts. The results of this study suggest that KR‐22335 may prevent ototoxicity caused by the administration of cisplatin through the inhibition of mitochondrial dysfunction and suppression of ROS generation. KR‐22335 may be considered as a potential candidate for protective agents against cisplatin‐induced ototoxicity. Copyright © 2013 John Wiley & Sons, Ltd.     

S‐allylcysteine attenuates renal injury by altering the expressions of iNOS and matrix metallo proteinase‐2 during cyclosporine‐induced nephrotoxicity in Wistar rats

Cyclosporine A (CsA) is the first choice immunosuppressant used for the prevention of allograft rejection in solid organ transplantation and immune‐mediated diseases. Reactive oxygen species‐induced oxidative stress and lipid peroxidation are implicated in the pathophysiology of CsA‐induced renal injury. In this work, we have studied the effect of a garlic‐derived compound, S‐allylcysteine (SAC) on CsA‐induced nephrotoxicity. CsA‐induced nephrotoxicity was assessed in terms of increased activities of serum marker enzymes and levels of kidney markers. CsA administration induced significant elevation in lipid peroxidation along with abnormal levels of enzymic and non‐enzymic antioxidants in the kidneys of the rats. SAC administration improved renal function by bringing about a significant decrease in peroxidative levels and increase in antioxidant status. Elevated expressions of inducible nitric oxide synthase (iNOS) and nuclear factor kappa B (NF‐κB) due to CsA administration were reduced by SAC treatment. An increase in the expression of matrix metalloproteinase‐2 (MMP‐2) was evident in CsA‐induced groups of rats, which was moderately reduced in SAC treated rats. An increase in the levels of serum constituent's urea, uric acid and creatinine was observed in the CsA‐induced rats, which was reduced upon treatment with SAC. These results indicate that SAC has a protective action against CsA‐induced nephrotoxicity which is also supported by histopathological studies. A comparative study of the antioxidant vitamin C and SAC is more valuable to assess the efficacy of the drug that can be used for the treatment of nephrotoxicity. Copyright © 2009 John Wiley & Sons, Ltd.     

Organic anion transporter 5 (Oat5) renal expression and urinary excretion in rats treated with cisplatin: a potential biomarker of cisplatin-induced nephrotoxicity

Cisplatin is one of the most potent chemotherapeutic antitumor drugs used in the treatment of a wide range of solid tumors. Its primary dose-limiting side effect is nephrotoxicity. The organic anion transporter 5 (Oat5) is exclusively localized in the kidney. Oat5 urinary excretion was recently proposed as a potential early biomarker of acute kidney injury (AKI). The aim of this study was to evaluate Oat5 renal expression and its urinary excretion in rats exposed to different doses of cisplatin, in comparison with traditional markers of renal injury, like renal histology, creatinine and urea plasma levels, creatinine clearance, protein and glucose urinary levels and urinary alkaline phosphatase (AP) activity. Male Wistar rats were treated with a single injection of cisplatin at different doses of 1, 2, 5 and 10 mg/kg b.w., i.p. (Cis1, Cis2, Cis5 and Cis10, n = 4, respectively) and experiments were carried out 48 h after cisplatin administration. The renal expression of Oat5 was evaluated by immunohistochemistry and Western blotting. Oat5 abundance, AP activity, creatinine, glucose and proteins were assayed in urine. Creatinine clearance and creatinine and urea plasma levels were also evaluated. In this experimental model, plasma urea and creatinine levels, creatinine clearance, AP urinary activity and protein and glucose urinary levels were significantly modified only at the highest cisplatin dose of 10 mg/kg b.w., i.p., as compared to control rats. In contrast, Oat5 urinary abundance was increased in a dose-related manner after the administration of cisplatin. Oat5 urinary abundance was elevated at a dose as low as 1 mg/kg b.w., i.p., implying renal perturbation, when no modifications of traditional markers of renal injury are yet observed. Oat5 renal expression was decreased in a dose-related manner, both in homogenates and apical membranes from cisplatin-treated kidneys. The increase in urinary Oat5 excretion might explain the decrease in the amount of Oat5 molecules in the renal tubule cells. Hence, the preclinical animal results showed in this work propose that Oat5 urinary excretion might potentially serve as a non-invasive early biomarker of cisplatin-induced AKI.     

Pitavastatin suppresses hyperglycaemia‐induced podocyte injury via bone morphogenetic protein‐7 preservation

Podocytes form the essential components of the glomerular filtration barrier and play a critical role in diabetic nephropathy. Recent evidence suggests that HMG‐CoA reductase inhibitors (statins) exert renoprotective effects. We investigated whether pitavastatin directly suppresses hyperglycaemia‐induced podocyte injury using cultured podocytes and, if so, the mechanism of the beneficial effects. Cultured podocytes were exposed to media containing normal (NG; 5 mmol/L) or high (HG; 25 mmol/L) glucose for 1 week. HG increased the lethal injury of podocytes and disruption of F‐actin fibers, and reduced the mRNA expression of novel podocyte markers, synaptopodin and Wilms tumor‐1 (WT‐1), in association with decreased bone morphogenetic protein‐7 (BMP‐7) expression. Pitavastatin (100 nmol/L) reduced podocyte injury and restored the mRNA expression of synaptopodin and WT1; however, these protective effects were abolished by BMP‐7 siRNA. Additionally, pitavastatin suppressed HG‐induced Rho kinase activation, as assessed by the phosphorylation level of myosin phosphatase targeting subunit 1 (MYTP1), and C3 exotoxin, a Rho inhibitor, mimicked the effect of pitavastatin on BMP‐7 preservation. Pitavastatin attenuates hyperglycaemia‐induced podocyte injury via Rho‐Rho kinase‐dependent BMP‐7 preservation.     

Amlodipine alleviates cisplatin-induced nephrotoxicity in rats through gamma-glutamyl transpeptidase (GGT) enzyme inhibition,associated with regulation of Nrf2/HO-1, MAPK/NF-κB,and Bax/Bcl-2 signaling

BackgroundThe therapeutic utility of the effective chemotherapeutic agent cisplatin is hampered by its nephrotoxic effect. We aimed from the current study to examine the possible protective effects of amlodipine through gamma-glutamyl transpeptidase (GGT) enzyme inhibition against cisplatin nephrotoxicity.MethodsAmlodipine (5 mg/kg, po) was administered to rats for 14 successive days. On the 10^th day, nephrotoxicity was induced by a single dose of cisplatin (6.5 mg/kg, ip). On the last day, blood samples were collected for estimation of kidney function, while kidney samples were used for determination of GGT activity, oxidative stress, inflammatory, and apoptotic markers, along with histopathological evaluation.ResultsAmlodipine alleviated renal injury that was manifested by significantly diminished serum creatinine and blood urea nitrogen levels, compared to cisplatin group. Amlodipine inhibited GGT enzyme, which participates in the metabolism of extracellular glutathione (GSH) and platinum-GSH-conjugates to a reactive toxic thiol. Besides, amlodipine diminished mRNA expression of NADPH oxidase in the kidney, while enhanced the anti-oxidant defense by activating Nrf2/HO-1 signaling. Additionally, it showed marked anti-inflammatory response by reducing expressions of p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor-kappa B (NF-κB), with subsequent down-regulation of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and vascular cell adhesion molecule-1 (VCAM-1). Moreover, amlodipine reduced Bax/Bcl-2 ratio and elevated hepatocyte growth factor (HGF), thus favoring renal cell survival.ConclusionsEffective GGT inhibition by amlodipine associated with enhancement of anti-oxidant defense and suppression of inflammatory signaling and apoptosis support our suggestion that amlodipine could replace toxic GGT inhibitors in protection against cisplatin nephrotoxicity.     

Protect effect of bicyclol on cisplatin-induced nephrotoxicity in mice

This study investigated the protective effects of bicyclol against cisplatin-induced nephrotoxicity and the possible mechanisms in mice. Bicyclol (250 mg/kg, p.o., 5 days) showed significant protection as evidenced by the decrease of elevated serum creatine and blood urea nitrogen, and improvement of histopathological injury induced by cisplatin. The formation of kidney malondialdehyde with a concomitant reduction of reduced glutathione were also inhibited by bicyclol, while the activities of kidney superoxide dismutase, catalase and glutathione peroxidase were all increased, respectively. Bicyclol also inhibited the increase of kidney and serum nitric oxide induced by cisplatin. In addition, induction of induced nitric oxide synthase and nitrotyrosine were suppressed by bicyclol. Bicyclol suppressed cisplatin-induced extracelluar signal regulated kinases 1/2 and p38 mitogen-activated protein kinase activation in the kidney of mice. Results obtained demonstrate that bicyclol pre-administration can prevent the nephrotoxicity induced by cisplatin.     

N‐acetylcysteine improves renal hemodynamics in rats with cisplatin‐induced nephrotoxicity

This work investigated the effect of N‐acetylcysteine (NAC), on renal hemodynamics in cisplatin (CP)‐induced nephrotoxicity in Wistar–Kyoto (WKY) rats. The animals were divided into four groups (n = 5 or 6). The first and second groups received normal saline (control) and intraperitoneal (i.p.) N‐acetylcysteine (500 mg kg^?1 per day for 9 days), respectively. The third and fourth groups were given a single intraperitoneal (i.p.) injection of CP (5 mg kg^?1) and an i.p. injection of CP (5 mg kg^?1) together with i.p. NAC (500 mg kg^?1 per day for 9 days), respectively. At the end of the experiment, rats were anesthetized and blood pressure and renal blood flow were monitored, followed by intravenous (i.v.) injection of norepinephrine (NE) for measurement of renal vasoconstrictor responses. CP caused a significant reduction in renal blood flow but did not affect NE‐induced renal vasoconstriction. In addition, CP significantly increased plasma concentrations of urea and creatinine and urinary N‐acetyl‐β‐D ‐glucosaminidase (NAG) activity and kidney relative weight. CP decreased body weight and creatinine clearance. Histopathologically, CP caused remarkable renal damage compared with control. NAC alone did not produce any significant change in any of the variables measured. However, NAC significantly ameliorated CP‐induced hemodynamic, biochemical and histopathological changes. The concentration of platinum in the kidneys of CP ? NAC treated rats was less than in CP‐treated rats by 37%. The results show that administration of i.p. NAC (500 mg kg^?1 per day for 9 days) reversed the renal hemodynamic changes as well as the biochemical and histopathological indices of CP‐induced nephrotoxicity in WKY rats. Copyright © 2009 John Wiley & Sons, Ltd.     

Dose‐Dependent Protection by Lipoic Acid against Cisplatin‐Induced Nephrotoxicity in Rats: Antioxidant Defense System

This study was designed to investigate the role of graded doses of lipoic acid pretreatment against cisplatin‐induced nephrotoxicity. Male Wistar rats were divided into six groups and treated as follows: 1) vehicle (saline) control; 2) cisplatin (16 mg/kg, intraperitoneally); 3) lipoic acid (100 mg/kg, intraperitoneally); 4) cisplatin plus lipoic acid (25 mg/kg); 5) cisplatin plus lipoic acid (50 mg/kg) and 6) cisplatin plus lipoic acid (100 mg/kg). Rats were sacrificed three days after treatment, and plasma as well as kidneys were isolated and analyzed. Plasma creatinine increased (677% of control) following cisplatin administration alone which was decreased by lipoic acid in a dose‐dependent manner. Cisplatin‐treated rats showed a depletion of renal glutathione (GSH), increased oxidized GSH and decreased GSH/GSH oxidized ratio (62%, 166% and 62% of control), respectively which were restored with lipoic acid pretreatment. Renal superoxide dismutase, catalase, glutathione peroxidase (GSH peroxidase) and glutathione reductase activities decreased (62%, 75%, 62% and 80% of control), respectively, and malondialdehyde content increased (204% of control) following cisplatin administration, which were restored with increasing doses of lipoic acid. The renal platinum concentration increased following cisplatin administration, which was possibly decreased by chelation with lipoic acid. The data suggest that the graded doses of lipoic acid effectively prevented a decrease in renal antioxidant defense system and prevented an increase in lipid peroxidation, platinum content and plasma creatinine concentrations in a dose‐dependent manner.     

Protective effects of emodin against cisplatin‐induced oxidative stress in cultured human kidney (HEK 293) cells

Emodin (a rhubarb anthraquinone) has strong antioxidant and anticancer actions, and recent studies indicated that it reduces cellular oxidative stress induced by various insults and drugs. Cisplatin is an anticancer drug that is associated with nephrotoxicity and induces oxidative stress in cultured human kidney (HEK 293) cells. This study aimed to assess the in‐vitro antioxidant properties of the emodin against cisplatin‐induced oxidative stress in HEK 293 cells. Our study revealed that emodin acted as a potent free radical scavenger and provided nephroprotection against cisplatin‐induced oxidative stress. Emodin as low as 0.5 µm did not decrease cell viability and restored the cisplatin‐induced glutathione depletion and total antioxidant capacity in a dose‐dependent manner. Emodin augmented the cisplatin‐induced inhibition of antioxidant enzymes (catalase, glutathione peroxidase, glutathione S‐transferase, glutathione reductase and superoxide dismutase). These results suggest that emodin has the potential to be used as an adjunct therapeutic agent in patients receiving cisplatin treatment. Copyright © 2012 John Wiley & Sons, Ltd.     

Sub‐chronic exposure to fluoride impacts the response to a subsequent nephrotoxic treatment with gentamicin

Fluoride is an important groundwater contaminant, and more than 200 million people are exposed to high fluoride levels in drinking water, the major source of fluoride exposure. Exposure above 2 ppm of fluoride is associated with renal impairment in humans. In rats, moderate levels of fluoride induce kidney injury at early stages in which the glomerular filtration rate (GFR) is not altered. In the present study, we investigated if sub‐nephrotoxic stimulus induced by fluoride might impact the response to a subsequent nephrotoxic treatment with gentamicin. Male Wistar rats (~21 days) were exposed to 0, 15 or 50 ppm of fluoride through drinking water during 40 days. Afer that, rats were co‐exposed to gentamicin (40 mg kg^–1 day^–1, 7 days). Gentamicin induced a marked decrease in the GFR and an increase in urinary levels as well as the protein and mRNA expression of biomarkers of early kidney injury, such as Kim‐1. Interestingly, gentamicin nephrotoxicity was less pronounced in groups previously exposed to fluoride than in the group only treated with gentamicin. Fluoride induced Hsp72, a cytoprotective molecule, which might have improved the response against gentamicin. Moreover, fluoride decreased the expression of megalin, a molecule necessary for internalization of gentamicin into the proximal tubule, potentially reducing gentamicin accumulation. The present results suggest that fluoride reduced gentamicin‐induced nephrotoxicity by inducing a compensatory response carried out by Hsp72 and by decreasing gentamicin accumulation. These findings should not be interpreted to suggest that fluoride is a protective agent as megalin deficiency could lead to serious adverse effects on the kidney physiology. Copyright © 2015 John Wiley & Sons, Ltd.     

Dexamethasone exacerbates cisplatin‐induced muscle atrophy

Dexamethasone for antiemetic therapy is typically administered with anticancer drugs such as cisplatin. We previously reported that cisplatin upregulates the muscle‐specific E3 ubiquitin ligase genes, namely muscle ring‐finger protein 1 (MuRF1) and atrophy gene‐1 (atrogin‐1), and promotes muscle atrophy in mice. It is well known that dexamethasone causes upregulation of MuRF1 and Atrogin‐1 expression in skeletal muscles. Although it is speculated that a combination of dexamethasone and cisplatin worsens muscle atrophy, there are no reports based on research. We thereby investigated the effects of cisplatin and dexamethasone, alone or in combination, on the expression of MuRF1 and Atrogin‐1 in murine skeletal muscles and C2C12 myotubes. Mice were intraperitoneally injected with cisplatin or the vehicle control once daily for 4 days. Dexamethasone or the vehicle control was subcutaneously administered 30 minutes prior to the administration of cisplatin. Dexamethasone enhanced MuRF1 and Atrogin‐1 gene expression upregulated by cisplatin in murine quadriceps muscles and C2C12 myotubes. Cisplatin‐caused upregulation of myostatin and downregulation of IGF‐1 gene expression were also enhanced by co‐administration of dexamethasone in murine quadriceps muscles and C2C12 myotubes. This study shows that the combination treatment of cisplatin and dexamethasone exacerbated muscle atrophy in mice. Therefore, this treatment regimen might exacerbate muscle atrophy in cancer patients.     

β‐LAPachone ameliorates doxorubicin‐induced cardiotoxicity via regulating autophagy and Nrf2 signalling pathways in mice

β‐LAPachone (B‐LAP) is a naphthoquinone that possesses antioxidant properties. In the present investigation, the protective effect of B‐LAP against doxorubicin (DOX)‐induced cardiotoxicity was examined in mice. Thirty‐five mice were divided into 5 groups: control group, B‐LAP (5 mg/kg) group, DOX (15 mg/kg) group, DOX+B‐LAP (2.5 mg/kg) group and DOX+B‐LAP (5 mg/kg) group. B‐LAP was administered orally for 14 days of experimental period. A single dose of DOX (15 mg/kg) was injected intraperitoneally on day 3. Cardiac function, histoarchitecture, indices of oxidative stress and circulating markers of cardiac injury were examined. B‐LAP (5 mg/kg) decreased serum levels of lactate dehydrogenase (LDH), creatine kinase MB (CK‐MB) and cardiac troponin I (cTnI), and ameliorated cardiac histopathological alterations. In addition to increasing cellular NAD⁺/NADH ratio, B‐LAP up‐regulated the cardiac levels of SIRT1, beclin‐1, p‐LKB1 and p‐AMPK, and reduced the cardiac levels of p‐mTOR, interleukin (IL)‐1β, TNF (tumour necrosis factor)‐α and caspase‐3. B‐LAP also elevated the nuclear accumulation of Nrf2 and simultaneously up‐regulated the protein levels of haem oxygenase (HO‐1) and glutathione S‐transferase (GST) in the hearts of DOX mice. While B‐LAP reduced malondialdehyde concentrations in heart of DOX‐treated mice, it further promoted the activities of cardiac superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT).In accordance with increased cell survival, B‐LAP significantly improved the cardiac function of DOX mice. Collectively, these findings underline the protective potential of B‐LAP against DOX‐induced cardiotoxicity by regulating autophagy and AMPK/Nrf2 signalling pathway in mice.     

Actein alleviates 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin‐mediated cellular dysfunction in osteoblastic MC3T3‐E1 cells

The environmental pollutant 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) is known to affect bone metabolism. We evaluated the protective effects of the triterpene glycoside actein from the herb black cohosh against TCDD‐induced toxicity in MC3T3‐E1 osteoblastic cells. We found that TCDD significantly reduced cell viability and increased apoptosis and autophagy in MC3T3‐E1 osteoblastic cells (P < .05). In addition, TCDD treatment resulted in a significant increase in intracellular calcium concentration, mitochondrial membrane potential collapse, reactive oxygen species (ROS) production, and cardiolipin peroxidation, whereas pretreatment with actein significantly mitigated these effects (P < .05). The effects of TCDD on extracellular signal‐related kinase (ERK), aryl hydrocarbon receptor, aryl hydrocarbon receptor repressor, and cytochrome P450 1A1 levels in MC3T3‐E1 cells were significantly inhibited by actein. The levels of superoxide dismutase, ERK1, and nuclear factor kappa B mRNA were also effectively restored by pretreatment with actein. Furthermore, actein treatment resulted in a significant increase in alkaline phosphatase (ALP) activity and collagen content, as well as in the expression of genes associated with osteoblastic differentiation (ALP, type I collagen, osteoprotegerin, bone sialoprotein, and osterix). This study demonstrates the underlying molecular mechanisms of cytoprotection exerted by actein against TCDD‐induced oxidative stress and osteoblast damage.