Protective role of NAD(P)H:quinone oxidoreductase 1 (NQO1) in cisplatin-induced nephrotoxicity

Beta-lapachone ameliorates the progression of primary sclerosing cholangitis pathogenesis in rodent models

AIMS

Primary sclerosing cholangitis (PSC) is a rare cholestatic liver disease characterized by chronic inflammation and severe fibrosis for which effective treatment options are currently lacking. In this study, we explored the potential of beta-lapachone (βL) as a drug candidate for PSC therapy.

MATERIALS AND METHODS

We employed an animal model fed a diet containing 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) to assess the preventive and therapeutic effects of βL. The beneficial effects of βL on PSC pathogenic characteristics, including blood biomarkers, inflammation, and fibrosis, were determined by assessing relevant parameters. Differential gene expression between each group was analyzed by RNA sequencing of liver tissues. Mdr2-/- mice were utilized to explore the involvement of Abcb4 in the βL-induced improvement of PSC pathogenesis.

KEY FINDINGS

βL effectively inhibited key features of PSC pathogenesis, as demonstrated by reduced blood biomarkers and improved pathogenic characteristics. Treatment with βL significantly mitigated DDC-induced apoptosis, cell proliferation, inflammation, and fibrosis. Analysis of differential gene expression confirmed a new insight that βL could stimulate the expression of genes related to NAD synthesis and Abcb4. Indeed, βL-induced NAD exhibited effective functioning, as evidenced by enhanced sirt1/3 and acetyl-lysine levels, leading to improved mitochondrial stability. The role of Abcb4 in response to βL was confirmed in Mdr2/Abcb4 KO mice, where the beneficial effects of βL were abolished.

SIGNIFICANCE

This study provided a new concept for PSC treatment, suggesting that pharmacological stimulation of the NAD synthetic pathway and Abcb4 via βL ameliorates PSC pathogenesis.

Oxidative stress and inflammation caused by 1-tetradecyl-3-methylimidazolium tetrafluoroborate in rat livers

The purpose of this study was to elucidate the mechanism underlying toxicity in the livers of male and female rats after treatment with 1-tetradecyl-3-methylimidazolium tetrafluoroborate ([C₁₄mim]BF₄, 0 [control], 12.5, 25, or 50 mg/kg) for 90 days. The results showed that [C₁₄mim]BF₄ exposure led to a high level of ROS and MDA in rat livers and the lower expression of Nrf2 and its downstream related antioxidant proteins. In addition, the expression of NF-κB p65 and the levels of inflammatory cytokines were upregulated in exposure groups rats' liver. After 30 days of cessation of exposure, the liver injury of rats in the 50 mg/kg exposure group was alleviated, and the above indicators were improved to varying degrees. The paper shows that [C₁₄mim]BF₄ could damage rat liver through oxidative stress and inflammatory pathway.

Cisplatin-Induced Kidney Toxicity: Potential Roles of Major NAD+-Dependent Enzymes and Plant-Derived Natural Products

Cisplatin is an FDA approved anti-cancer drug that is widely used for the treatment of a variety of solid tumors. However, the severe adverse effects of cisplatin, particularly kidney toxicity, restrict its clinical and medication applications. The major mechanisms of cisplatin-induced renal toxicity involve oxidative stress, inflammation, and renal fibrosis, which are covered in this short review. In particular, we review the underlying mechanisms of cisplatin kidney injury in the context of NAD⁺-dependent redox enzymes including mitochondrial complex I, NAD kinase, CD38, sirtuins, poly-ADP ribosylase polymerase, and nicotinamide nucleotide transhydrogenase (NNT) and their potential contributing roles in the amelioration of cisplatin-induced kidney injury conferred by natural products derived from plants. We also cover general procedures used to create animal models of cisplatin-induced kidney injury involving mice and rats. We highlight the fact that more studies will be needed to dissect the role of each NAD⁺-dependent redox enzyme and its involvement in modulating cisplatin-induced kidney injury, in conjunction with intensive research in NAD⁺ redox biology and the protective effects of natural products against cisplatin-induced kidney injury.

Iron deficiency aggravates DMNQ-induced cytotoxicity via redox cycling in kidney-derived cells

Iron, an essential element for most of living organisms, participates in many biological functions. Since iron is redox-active transition metal, it is known that excessive levels stimulate the formation of reactive oxygen species (ROS) and exacerbate cytotoxicity. An iron deficiency is the most common nutritional deficiency disorder in the world (about 30% of the population) and is more common than cases of iron overload. However, the effects of iron deficiency on ROS-induced cytotoxicity and the maintenance of intracellular redox homeostasis are not fully understood. The present study reports on an evaluation of the effects of iron deficiency on cytotoxicity induced by several ROS generators. In contrast to hydrogen peroxide and erastin, the cytotoxicity of 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), a redox cycling agent that induces intracellular superoxide anion formation, was exacerbated by iron deficiency. Cytochrome b₅ reductase was identified as a candidate enzyme responsible for the redox cycling of DMNQ under conditions of iron depletion. Moreover, the DMNQ-induced intracellular accumulation of ROS and a decrease in NADH/NAD⁺ ratios were enhanced by an iron deficiency. These negative changes were found to be ameliorated by overexpressing NAD(P)H:quinone oxidoreductase 1 (NQO1) in kidney-derived cells that originally showed a very low expression of NQO1. These results indicate that NQO1 plays a protective role against redox cycling quinone-mediated cytotoxicity under iron-depleted conditions. This is because NQO1 generates less-toxic hydroquinones via the two-electron reduction of quinones. The collective findings reported herein demonstrate that not only an iron overload but also an iron deficiency exacerbates ROS-mediated cytotoxicity.

NAD(P)H: quinone oxidoreductase 1 attenuates oxidative stress and apoptosis by regulating Sirt1 in diabetic nephropathy

Background

Diabetic nephropathy (DN) is one of the main complications of diabetes, and oxidative stress plays an important role in its progression. NAD(P)H: quinone oxidoreductase 1 (NQO1) protects cells from oxidative stress and toxic quinone damage. In the present study, we aimed to investigate the protective effects and underlying mechanisms of NQO1 on diabetes-induced renal tubular epithelial cell oxidative stress and apoptosis.

Methods

In vivo, the kidneys of db/db mice, which are a type 2 diabetes model, were infected with adeno-associated virus to induce NQO1 overexpression. In vitro, human renal tubular epithelial cells (HK-2 cells) were transfected with NQO1 pcDNA3.1(+) and cultured in high glucose (HG). Gene and protein expression was assessed by quantitative real-time PCR, western blotting, immunofluorescence analysis, and immunohistochemical staining. Reactive oxygen species (ROS) were examined by MitoSox red and flow cytometry. TUNEL assays were used to measure apoptosis.

Result

In vivo, NQO1 overexpression reduced the urinary albumin/creatinine ratio (UACR) and blood urea nitrogen (BUN) level in db/db mice. Our results revealed that NQO1 overexpression could significantly increase the ratio of NAD+/NADH and silencing information regulator 1 (Sirt1) expression and block tubular oxidative stress and apoptosis in diabetic kidneys. In vitro, NQO1 overexpression reduced the generation of ROS, NADPH oxidase 1 (Nox1) and Nox4, the Bax/Bcl-2 ratio and the expression of Cleaved Caspase-3 and increased NAD+/NADH levels and Sirt1 expression in HK-2 cells under HG conditions. However, these effects were reversed by the Sirt1 inhibitor EX527.

Conclusions

All these data suggest that NQO1 has a protective effect against oxidative stress and apoptosis in DN, which may be mediated by the regulation of Sirt1 through increasing intracellular NAD+/NADH levels. Therefore, NQO1 may be a new therapeutic target for DN.

Cytoglobin protects cancer cells from apoptosis by regulation of mitochondrial cardiolipin

Cytoglobin is important in the progression of oral squamous cell carcinoma but the molecular and cellular basis remain to be elucidated. In the current study, we develop a new cell model to study the function of cytoglobin in oral squamous carcinoma and response to cisplatin. Transcriptomic profiling showed cytoglobin mediated changes in expression of genes related to stress response, redox metabolism, mitochondrial function, cell adhesion, and fatty acid metabolism. Cellular and biochemical studies show that cytoglobin expression results in changes to phenotype associated with cancer progression including: increased cellular proliferation, motility and cell cycle progression. Cytoglobin also protects cells from cisplatin-induced apoptosis and oxidative stress with levels of the antioxidant glutathione increased and total and mitochondrial reactive oxygen species levels reduced. The mechanism of cisplatin resistance involved inhibition of caspase 9 activation and cytoglobin protected mitochondria from oxidative stress-induced fission. To understand the mechanism behind these phenotypic changes we employed lipidomic analysis and demonstrate that levels of the redox sensitive and apoptosis regulating cardiolipin are significantly up-regulated in cells expressing cytoglobin. In conclusion, our data shows that cytoglobin expression results in important phenotypic changes that could be exploited by cancer cells in vivo to facilitate disease progression.

Formononetin protects against cisplatin‑induced acute kidney injury through activation of the PPARα/Nrf2/HO‑1/NQO1 pathway

Acute kidney injury (AKI) is characterized by an abrupt deterioration of renal function. Formononetin (FOR) protects against cisplatin (CIS)‑induced AKI, and it has various potential pharmacological and biological effects, including anti‑inflammatory, antioxidative and anti‑apoptotic effects. The current study investigated the role of FOR in CIS‑induced AKI. Rats were treated with CIS to establish an AKI model, followed by treatment with FOR. HK‑2 cells were treated with CIS, FOR, GW6471 [a peroxisome proliferator‑activated receptor α (PPARα) antagonist], eupatilin (a PPARα agonist) and nuclear factor erythroid 2‑related factor 2 (Nrf2) small interfering RNA (siNrf2), and cell proliferation and apoptosis were determined by MTT and flow cytometry assays. The mRNA and proteins levels of PPARα, Nrf2, heme oxygenase‑1 (HO‑1) and NAD(P)H quinone dehydrogenase 1 (NQO1) were measured by reverse transcription‑quantitative PCR and western blotting. The results demonstrated that FOR attenuated the histopathological changes, the levels of blood urea nitrogen, creatinine, TNF‑α and IL‑1β, and the MDA content and MPO activity, whereas it enhanced CAT activity in the AKI rat model. Furthermore, FOR and eupatilin promoted cell viability and CAT activity, and increased the levels of PPARα, Nrf2 and HO‑1 and NQO1, but suppressed apoptosis and MPO activity, and reduced the levels of MDA, TNF‑α and IL‑1β in CIS‑treated HK‑2 cells. Notably, the aforementioned effects were reversed by GW6471 treatment or siNrf2 transfection. In conclusion, FOR protects against CIS‑induced AKI via activation of the PPARα/Nrf2/HO‑1/NQO1 pathway.

The potential roles of NAD(P)H:quinone oxidoreductase 1 in the development of diabetic nephropathy and actin polymerization

Diabetic nephropathy (DN) is a major complication of diabetes mellitus. NAD(P)H:quinone oxidoreductase 1 (NQO1) is an antioxidant enzyme that has been involved in the progression of several kidney injuries. However, the roles of NQO1 in DN are still unclear. We investigated the effects of NQO1 deficiency in streptozotocin (STZ)-induced DN mice. NQO1 was upregulated in the glomerulus and podocytes under hyperglycemic conditions. NQO1 knockout (NKO) mice showed more severe changes in blood glucose and body weight than WT mice after STZ treatment. Furthermore, STZ-mediated pathological parameters including glomerular injury, blood urea nitrogen levels, and foot process width were more severe in NKO mice than WT mice. Importantly, urine albumin-to-creatinine ratio (ACR) was higher in healthy, non-treated NKO mice than WT mice. ACR response to STZ or LPS was dramatically increased in the urine of NKO mice compared to vehicle controls, while it maintained a normal range following treatment of WT mice. More importantly, we found that NQO1 can stimulate actin polymerization in an in vitro biochemical assay without directly the accumulation on F-actin. In summary, NQO1 has an important role against the development of DN pathogenesis and is a novel contributor in actin reorganization via stimulating actin polymerization.

Cisplatin-resistant triple-negative breast cancer subtypes: multiple mechanisms of resistance

BACKGROUND

Understanding mechanisms underlying specific chemotherapeutic responses in subtypes of cancer may improve identification of treatment strategies most likely to benefit particular patients. For example, triple-negative breast cancer (TNBC) patients have variable response to the chemotherapeutic agent cisplatin. Understanding the basis of treatment response in cancer subtypes will lead to more informed decisions about selection of treatment strategies.

METHODS

In this study we used an integrative functional genomics approach to investigate the molecular mechanisms underlying known cisplatin-response differences among subtypes of TNBC. To identify changes in gene expression that could explain mechanisms of resistance, we examined 102 evolutionarily conserved cisplatin-associated genes, evaluating their differential expression in the cisplatin-sensitive, basal-like 1 (BL1) and basal-like 2 (BL2) subtypes, and the two cisplatin-resistant, luminal androgen receptor (LAR) and mesenchymal (M) subtypes of TNBC.

RESULTS

We found 20 genes that were differentially expressed in at least one subtype. Fifteen of the 20 genes are associated with cell death and are distributed among all TNBC subtypes. The less cisplatin-responsive LAR and M TNBC subtypes show different regulation of 13 genes compared to the more sensitive BL1 and BL2 subtypes. These 13 genes identify a variety of cisplatin-resistance mechanisms including increased transport and detoxification of cisplatin, and mis-regulation of the epithelial to mesenchymal transition.

CONCLUSIONS

We identified gene signatures in resistant TNBC subtypes indicative of mechanisms of cisplatin. Our results indicate that response to cisplatin in TNBC has a complex foundation based on impact of treatment on distinct cellular pathways. We find that examination of expression data in the context of heterogeneous data such as drug-gene interactions leads to a better understanding of mechanisms at work in cancer therapy response.

Dimethyl fumarate ameliorates cisplatin-induced renal tubulointerstitial lesions

Dimethyl fumarate (DMF) has an antioxidant effect by activating the nuclear factor erythroid 2-related transcription factor 2 (Nrf2). Cisplatin (CIS) has nephrotoxicity as a frequently associated side effect that is mainly mediated by oxidative stress. In this study, we investigated whether the DMF-mediated antioxidative mechanism activated by Nrf2 can ameliorate CIS-induced renal tubulointerstitial lesions in rats. In Experiments 1 and 2, 25 five-week-old male Wistar rats were divided into five groups: control, CIS, and 3 CIS+DMF groups (300, 1,500, and 7,500 ppm in Experiment 1; 2,000, 4,000, and 6,000 ppm in Experiment 2). Rats were fed their respective DMF-containing diet for 5 weeks. CIS was injected 1 week after starting DMF administration, and the same volume of saline was injected into the control group. CIS-induced severe tubular injury, such as necrosis and degeneration in the outer segment of the outer medulla, was inhibited in the 7,500 ppm DMF group and ameliorated in all DMF groups in Experiment 2. Increased interstitial mononuclear cell infiltration and increased Sirius red-positive areas were also observed in CIS-administered groups, and these increases tended to be dose-dependently inhibited by DMF co-administration in Experiments 1 and 2. The numbers of α-smooth muscle actin (SMA)-positive myofibroblasts, CD68-positive macrophages, and CD3-positive lymphocytes observed in the peritubular area also increased with CIS administration, and these increases were dose-dependently inhibited by DMF co-administration. Moreover, renal cortical mRNA expression of Nrf2-related genes such as NQO1 increased in DMF groups. This investigation showed that DMF ameliorates CIS-induced renal tubular injury via NQO1-mediated antioxidant mechanisms and reduces the consequent tubulointerstitial fibrosis.

Protective Effects of Gemigliptin, a Dipeptidyl Peptidase-4 Inhibitor, against Cisplatin-Induced Nephrotoxicity in Mice

Dipeptidyl peptidase-4 (DPP-4) inhibitors are widely used antihyperglycemic agents for the treatment of type 2 diabetes mellitus. Recently, the pleiotropic actions of DPP-4 inhibitors have drawn much attention. In the present study, we aimed to examine whether gemigliptin, a recently developed DPP-4 inhibitor, could protect against cisplatin-induced nephrotoxicity. We showed that pretreatment with gemigliptin attenuated cisplatin-induced renal dysfunction, as shown by analysis of plasma creatinine levels and blood urea nitrogen and histological damage. Elevated plasma levels of active glucagon-like peptide-1 were observed in gemigliptin-pretreated mice after cisplatin treatment, compared to that in cisplatin alone-treated mice. Gemigliptin attenuated cisplatin-induced apoptotic cell death, as assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and Western blot analysis in the kidneys. Gemigliptin also decreased the plasma levels of tumor necrosis factor-α and monocyte chemoattractant protein-1 and attenuated nuclear staining of nuclear factor kappa-B p65 in the kidneys. In addition, gemigliptin increased the protein expression of heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO1) in the kidneys of cisplatin-treated mice. Taken together, these results suggest that pretreatment with gemigliptin protects against cisplatin-induced nephrotoxicity in mice, possibly via inhibition of apoptotic cell death and inflammatory responses through induction of HO-1 and NQO1 expression.

Functions of NQO1 in Cellular Protection and CoQ10 Metabolism and its Potential Role as a Redox Sensitive Molecular Switch

NQO1 is one of the two major quinone reductases in mammalian systems. It is highly inducible and plays multiple roles in cellular adaptation to stress. A prevalent polymorphic form of NQO1 results in an absence of NQO1 protein and activity so it is important to elucidate the specific cellular functions of NQO1. Established roles of NQO1 include its ability to prevent certain quinones from one electron redox cycling but its role in quinone detoxification is dependent on the redox stability of the hydroquinone generated by two-electron reduction. Other documented roles of NQO1 include its ability to function as a component of the plasma membrane redox system generating antioxidant forms of ubiquinone and vitamin E and at high levels, as a direct superoxide reductase. Emerging roles of NQO1 include its function as an efficient intracellular generator of NAD⁺ for enzymes including PARP and sirtuins which has gained particular attention with respect to metabolic syndrome. NQO1 interacts with a growing list of proteins, including intrinsically disordered proteins, protecting them from 20S proteasomal degradation. The interactions of NQO1 also extend to mRNA. Recent identification of NQO1 as a mRNA binding protein have been investigated in more detail using SERPIN1A1 (which encodes the serine protease inhibitor α-1-antitrypsin) as a target mRNA and indicate a role of NQO1 in control of translation of α-1-antitrypsin, an important modulator of COPD and obesity related metabolic syndrome. NQO1 undergoes structural changes and alterations in its ability to bind other proteins as a result of the cellular reduced/oxidized pyridine nucleotide ratio. This suggests NQO1 may act as a cellular redox switch potentially altering its interactions with other proteins and mRNA as a result of the prevailing redox environment.

NAD+ augmentation ameliorates acute pancreatitis through regulation of inflammasome signalling

Acute pancreatitis (AP) is a complicated disease without specific drug therapy. The cofactor nicotinamide adenine dinucleotide (NAD⁺) is an important regulator of cellular metabolism and homeostasis. However, it remains unclear whether modulation of NAD⁺ levels has an impact on caerulein-induced AP. Therefore, in this study, we investigated the effect of increased cellular NAD⁺ levels on caerulein-induced AP. We demonstrated for the first time that the activities and expression of SIRT1 were suppressed by reduction of intracellular NAD⁺ levels and the p53-microRNA-34a pathway in caerulein-induced AP. Moreover, we confirmed that the increase of cellular NAD⁺ by NQO1 enzymatic action using the substrate β-Lapachone suppressed caerulein-induced AP with down-regulating TLR4-mediated inflammasome signalling, and thereby reducing the inflammatory responses and pancreatic cell death. These results suggest that pharmacological stimulation of NQO1 could be a promising therapeutic strategy to protect against pathological tissue damage in AP.

Catalytic competence, structure and stability of the cancer-associated R139W variant of the human NAD(P)H:quinone oxidoreductase 1 (NQO1)

The human NAD(P)H:quinone oxidoreductase 1 (NQO1; EC1.6.99.2) is an essential enzyme in the antioxidant defence system. Furthermore, NQO1 protects tumour suppressors like p53, p33^ING1b and p73 from proteasomal degradation. The activity of NQO1 is also exploited in chemotherapy for the activation of quinone-based treatments. Various single nucleotide polymorphisms are known, such as NQO1*2 and NQO1*3 yielding protein variants of NQO1 with single amino acid replacements, i.e. P187S and R139W, respectively. While the former NOQ1 variant is linked to a higher risk for specific kinds of cancer, the role, if any, of the arginine 139 to tryptophan exchange in disease development remains obscure. On the other hand, mitomycin C-resistant human colon cancer cells were shown to harbour the NQO1*3 variant resulting in substantially reduced enzymatic activity. However, the molecular cause for this decrease remains unclear. In order to resolve this issue, recombinant NQO1 R139W has been characterized biochemically and structurally. In this report, we show by X-ray crystallography and 2D-NMR spectroscopy that this variant adopts the same structure both in the crystal as well as in solution. Furthermore, the kinetic parameters obtained for the variant are similar to those reported for the wild-type protein. Similarly, thermostability of the variant was only slightly affected by the amino acid replacement. Therefore, we conclude that the previously reported effects in human cancer cells cannot be attributed to protein stability or enzyme activity. Instead, it appears that loss of exon 4 during maturation of a large fraction of pre-mRNA is the major reason of the observed lack of enzyme activity and hence reduced activation of quinone-based chemotherapeutics.

Protective effects of Tat-NQO1 against oxidative stress-induced HT-22 cell damage, and ischemic injury in animals

Oxidative stress is closely associated with various diseases and is considered to be a major factor in ischemia. NAD(P)H:quinone oxidoreductase 1 (NQO1) protein is a known antioxidant protein that plays a protective role in various cells against oxidative stress. We therefore investigated the effects of cell permeable Tat-NQO1 protein on hippocampal HT-22 cells, and in an animal ischemia model. The Tat-NQO1 protein transduced into HT-22 cells, and significantly inhibited against hydrogen peroxide (H₂O₂)-induced cell death and cellular toxicities. Tat-NQO1 protein inhibited the Akt and mitogen activated protein kinases (MAPK) activation as well as caspase-3 expression levels, in H₂O₂ exposed HT-22 cells. Moreover, Tat-NQO1 protein transduced into the CA1 region of the hippocampus of the animal brain and drastically protected against ischemic injury. Our results indicate that Tat-NQO1 protein exerts protection against neuronal cell death induced by oxidative stress, suggesting that Tat-NQO1 protein may potentially provide a therapeutic agent for neuronal diseases. [BMB Reports 2016; 49(11): 617-622].

NQO1 Deficiency Leads Enhanced Autophagy in Cisplatin-Induced Acute Kidney Injury Through the AMPK/TSC2/mTOR Signaling Pathway

AIMS

Recent studies have revealed that autophagy is induced under various disease conditions; however, the role of autophagy in pathological states is controversial.

NAD(P)H

quinone oxidoreductase 1 (NQO1) is a highly inducible cytoprotective gene that regulates reactive oxygen species (ROS) generation. In this study, we examined whether NQO1 deficiency affects the autophagy process in response to cisplatin-induced nephrotoxicity.

RESULTS

In vitro, NQO1 and autophagy-associated proteins were induced after cisplatin treatment and the autophagosomes markedly increased in the cisplatin-treated NQO1-knockdown ACHN cells together with increased ROS production. In vivo, NQO1-KO mice displayed a significant increase in cisplatin-induced acute kidney injury (AKI), as indicated by elevated tubular damage and apoptosis as well as by suppressed cytoprotective signals. In agreement with the in vitro findings, NQO1-KO cisplatin-treated mice displayed a notable increase in autophagy-associated protein expression compared with their wild-type counterparts. Meanwhile, the expression of Ras-related protein 7, which participates in autophagosome maturation and lysosome fusion, markedly decreased in NQO1-KO mice, indicating hampered progress in late autophagy, and was accompanied by increased p62 protein expression. Moreover, NQO1 deletion enhanced the effect of the mammalian target of the rapamycin inhibitor, rapamycin, and led to enhanced tuberous sclerosis complex 2 phosphorylation through AMP-activated protein kinase activation.

INNOVATION AND CONCLUSION

These results indicate that autophagy may be enhanced to counter the increased stress due to NQO1 deficiency, an oxidative stress barrier. The present results demonstrate the significant influence of NQO1 on the autophagy process and support the hypothesis that autophagy plays a protective role under oxidative stress conditions. Antioxid. Redox Signal. 24, 867-883.

Deletion of NAD(P)H:quinone oxidoreductase 1 represses Mre11-Rad50-Nbs1 complex protein expression in cisplatin-induced nephrotoxicity

The Mre11, Rad50, and Nbs1 (MRN) complex is a DNA double-strand break sensor involved in DNA damage repair. Herein, we explored whether deletion of

NAD(P)H

quinone oxidoreductase 1 (NQO1), a cytoprotective gene, affected MRN complex expression in the kidney after cisplatin-induced acute kidney injury (AKI). In vitro, cisplatin increased the expression of MRN complex proteins and NQO1 in NQO1-expressing ACHN cells in a time- and concentration-dependent manner. The expression of MRN complex proteins was relatively inhibited in NQO1-knockdown cells. In vivo, increased expression of renal MRN complex proteins was accompanied by upregulation of γ-H2A histone member X, a DNA damage marker, in cisplatin-treated wild-type mice. Although the NQO1-knockout (NQO1(-/-)) mice showed more severe cisplatin-induced renal damage, the renal expression of MRN complex proteins was lower than in NQO1-expressing mice; expression of poly[ADP-ribose] polymerase 1, which promotes MRN complex accumulation, was also lower in these animals. In addition, cisplatin-induced expression of DNA damage repair-related proteins, ataxia telangiectasia mutated and sirtuin1, markedly decreased in the NQO1(-/-) group, relative to the NQO1-expressing mice. These findings suggest that NQO1 deletion might be associated with decreased MRN complex expression, which might be partially responsible for the exacerbation of cisplatin-induced AKI in the absence of NQO1.

Integrated transcriptomic and proteomic analyses uncover regulatory roles of Nrf2 in the kidney

The transcription factor Nrf2 exerts protective effects in numerous experimental models of acute kidney injury, and is a promising therapeutic target in chronic kidney disease. To provide a detailed insight into the regulatory roles of Nrf2 in the kidney, we performed integrated transcriptomic and proteomic analyses of kidney tissue from wild-type and Nrf2 knockout mice treated with the Nrf2 inducer methyl-2-cyano-3,12-dioxooleano-1,9-dien-28-oate (CDDO-Me, also known as bardoxolone methyl). After 24 hours, analyses identified 2561 transcripts and 240 proteins that were differentially expressed in the kidneys of Nrf2 knockout mice, compared to wild-type counterparts, and 3122 transcripts and 68 proteins that were differentially expressed in wild-type mice treated with CDDO-Me, compared to vehicle control. In light of their sensitivity to genetic and pharmacological modulation of renal Nrf2 activity, genes/proteins that regulate xenobiotic disposition, redox balance, the intra/extracellular transport of small molecules, and the supply of NADPH and other cellular fuels were found to be positively regulated by Nrf2 in the kidney. This was verified by qPCR, immunoblotting, pathway analysis and immunohistochemistry. In addition, the levels of NADPH and glutathione were found to be significantly decreased in the kidneys of Nrf2 knockout mice. Thus, Nrf2 regulates genes that coordinate homeostatic processes in the kidney, highlighting its potential as a novel therapeutic target.

β-Lapachone enhances Mre11-Rad50-Nbs1 complex expression in cisplatin-induced nephrotoxicity

BACKGROUND

Recent studies suggest a potential involvement of the Mre11-Rad50-Nbs1 (MRN) complex, a DNA double-strand breaks (DSBs) sensor, in the development of nephrotoxicity following cisplatin administration. β-Lapachone is a topoisomerase I inhibitor known to reduce cisplatin-induced nephrotoxicity. In this study, by assessing MRN complex expression, we explored whether β-lapachone was involved in DNA damage response in the context of cisplatin-induced nephrotoxicity.

METHODS

Male Balb/c mice were randomly allocated to 4 groups: control, β-lapachone alone, cisplatin alone, and β-lapachone+cisplatin. β-Lapachone was administered with the diet (0.066%) for 2 weeks prior to cisplatin injection (18mg/kg). All mice were sacrificed 3 days after cisplatin treatment.

RESULTS

In the cisplatin-alone group, renal function was disrupted and MRN complex expression increased. As expected, β-lapachone co-treatment attenuated cisplatin-induced pathologic alterations. Notably, although β-lapachone markedly decreased cisplatin-induced renal cell apoptosis and DSBs formation, the β-lapachone+cisplatin group showed the highest MRN complex expression. Moreover, β-lapachone treatment increased the basal expression level of the MRN complex, which was accompanied by enhanced basal expression of SIRTuin1, which is known to regulate Nbs1 acetylation.

CONCLUSION

Although, it remains unclear how β-lapachone induces MRN complex expression, our findings suggest that β-lapachone might affect MRN complex expression and participate in DNA damage recovery in cisplatin-induced nephrotoxicity.

NAD(P)H:quinone oxidoreductase 1 activation reduces blood pressure through regulation of endothelial nitric oxide synthase acetylation in spontaneously hypertensive rats

BACKGROUND

Endothelial nitric oxide synthase (eNOS) is involved in blood pressure (BP) regulation through the production of nitric oxide. Sirtuin I (SIRT1), an NAD-dependent protein deacetylase, promotes vascular relaxation through deacetylation and activation of eNOS. β-Lapachone (βL) increases the cellular NAD(+)/NADH ratio by activating

NAD(P)H

quinone oxidoreductase 1 (NQO1). In this study, we verified whether activation of NQO1 by βL modulates BP through regulation of eNOS acetylation in a hypertensive animal model.

METHODS

Spontaneously hypertensive rats (SHRs) and an endothelial cell line (bEnd.3 cells) were used to investigate the hypotensive effect of βL and its mechanism of action.

RESULTS

βL treatment significantly lowered the BP in SHRs, but this hypotensive effect was completely blocked by eNOS inhibition with ω-nitro-l-arginine methyl ester. In vitro studies revealed that βL activated eNOS, which was accompanied by an increased NAD(+)/NADH ratio. Moreover, βL significantly decreased acetylation of eNOS; however, this reduced eNOS acetylation was completely precluded by inhibition of SIRT1 in the bEnd.3 cells and in the aorta of the SHRs. Consistent with these effects, βL-induced reduction in BP was also abolished by SIRT1 inhibition in the SHRs.

CONCLUSIONS

To the best of our knowledge, this is the first study to demonstrate that eNOS acetylation can be regulated by NQO1 activation in an SIRT1-dependent manner, which is correlated with the relief of hypertension. These findings provide strong evidence that NQO1 might be a new therapeutic target for hypertension.

Superoxide anion production and expression of gp91(phox) and p47(phox) are increased in glomeruli and proximal tubules of cisplatin-treated rats

The chemotherapeutic drug cisplatin has some side effects including nephrotoxicity that has been associated with reactive oxygen species production, particularly superoxide anion. The major source of superoxide anion is nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase. However, the specific segment of the nephron in which superoxide anion is produced has not been identified. Rats were sacrificed 72 h after cisplatin injection (7.5 mg/kg), and kidneys were obtained to isolate glomeruli and proximal and distal tubules. Cisplatin induced superoxide anion production in glomeruli and proximal tubules but not in distal tubules. This enhanced superoxide anion production was prevented by diphenylene iodonium, an inhibitor of NADPH oxidase. Consistently, this effect was associated with the increased expression of gp91(phox) and p47(phox), subunits of NADPH oxidase. The enhanced superoxide anion production in glomeruli and proximal tubules, associated with the increased expression of gp91(phox) and p47(phox), is involved in the oxidative stress in cisplatin-induced nephrotoxicity.

Augmentation of NAD(+) by NQO1 attenuates cisplatin-mediated hearing impairment

Cisplatin (cis-diaminedichloroplatinum-II) is an extensively used chemotherapeutic agent, and one of its most adverse effects is ototoxicity. A number of studies have demonstrated that these effects are related to oxidative stress and DNA damage. However, the precise mechanism underlying cisplatin-associated ototoxicity is still unclear. The cofactor nicotinamide adenine dinucleotide (NAD(+)) has emerged as a key regulator of cellular energy metabolism and homeostasis. Here, we demonstrate for the first time that, in cisplatin-mediated ototoxicity, the levels and activities of SIRT1 are suppressed by the reduction of intracellular NAD(+) levels. We provide evidence that the decrease in SIRT1 activity and expression facilitated by increasing poly(ADP-ribose) transferase (PARP)-1 activation and microRNA-34a through p53 activation aggravates cisplatin-mediated ototoxicity. Moreover, we show that the induction of cellular NAD(+) levels using β-lapachone (β-Lap), whose intracellular target is NQO1, prevents the toxic effects of cisplatin through the regulation of PARP-1 and SIRT1 activity. These results suggest that direct modulation of cellular NAD(+) levels by pharmacological agents could be a promising therapeutic approach for protection from cisplatin-induced ototoxicity.

S-allylcysteine prevents cisplatin-induced nephrotoxicity and oxidative stress

Objectives

Cisplatin (CP) is an antineoplastic agent that induces nephrotoxicity and oxidative stress. S-allylcysteine (SAC) is a garlic-derived antioxidant. This study aims to explore whether SAC protects against CP-induced nephrotoxicity in rats.

Methods

In the first stage, the SAC protective dose was determined by measuring renal damage and the oxidative stress markers malondialdehyde, oxidized proteins and glutathione in rats injected with CP. In the second stage, the effect of a single dose of SAC on the expression of nuclear factor-erythroid 2-related factor-2 (Nrf2), protein kinase C beta 2 (PKCβ2) and nicotinamide adenine dinucleotide phosphate oxidase subunits (p47phox and gp91phox) was studied. In addition, the effect of SAC on oxidative stress markers and on the activity of catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) in isolated proximal and distal tubules were evaluated.

Key findings

SAC (25 mg/kg) prevented the CP-induced renal damage and attenuated CP-induced decrease in Nrf2 levels and increase in PKCβ2, p47phox and gp91phox expression in renal cortex and oxidative stress and decrease in the activity of CAT, GPx and GR in proximal and distal tubules.

Conclusions

These data suggest that SAC provides renoprotection by attenuating CP-induced oxidative stress and decrease in the activity of CAT, GPx and GR.

Protection of NAD(P)H:quinone oxidoreductase 1 against renal ischemia/reperfusion injury in mice

Ischemia/reperfusion (I/R) is the most common cause of acute renal injury. I/R-induced reactive oxygen species (ROS) are thought to be a major factor in the development of acute renal injury by promoting the initial tubular damage.

NAD(P)H

quinone oxidoreductase 1 (NQO1) is a well-known antioxidant protein that regulates ROS generation. The purpose of this study was to investigate whether NQO1 modulates the renal I/R injury (IRI) associated with NADPH oxidase (NOX)-derived ROS production in an animal model. We analyzed renal function, oxidative stress, and tubular apoptosis after IRI. NQO1(-/-) mice showed increased blood urea nitrogen and creatinine levels, tubular damage, oxidative stress, and apoptosis. In the kidneys of NQO1(-/-) mice, the cellular NADPH/NADP(+) ratio was significantly higher and NOX activity was markedly higher than in those of NQO1(+/+) mice. The activation of NQO1 by β-lapachone (βL) significantly improved renal dysfunction and reduced tubular cell damage, oxidative stress, and apoptosis by renal I/R. Moreover, the βL treatment significantly lowered the cellular NADPH/NADP(+) ratio and dramatically reduced NOX activity in the kidneys after IRI. From these results, it was concluded that NQO1 has a protective role against renal injury induced by I/R and that this effect appears to be mediated by decreased NOX activity via cellular NADPH/NADP(+) modulation. These results provide convincing evidence that NQO1 activation might be beneficial for ameliorating renal injury induced by I/R.