Melatonin suppresses cisplatin-induced nephrotoxicity via activation of Nrf-2/HO-1 pathway

Tempol, a superoxide dismutase mimetic agent, ameliorates cisplatin-induced nephrotoxicity through alleviation of mitochondrial dysfunction in mice

Background

Mitochondrial dysfunction is a crucial mechanism by which cisplatin, a potent chemotherapeutic agent, causes nephrotoxicity where mitochondrial electron transport complexes are shifted mostly toward imbalanced reactive oxygen species versus energy production. In the present study, the protective role of tempol, a membrane-permeable superoxide dismutase mimetic agent, was evaluated on mitochondrial dysfunction and the subsequent damage induced by cisplatin nephrotoxicity in mice.

Methods and Findings

Nephrotoxicity was assessed 72 h after a single i.p. injection of cisplatin (25 mg/kg) with or without oral administration of tempol (100 mg/kg/day). Serum creatinine and urea as well as glucosuria and proteinuria were evaluated. Both kidneys were isolated for estimation of oxidative stress markers, adenosine triphosphate (ATP) content and caspase-3 activity. Moreover, mitochondrial oxidative phosphorylation capacity, complexes I–IV activities and mitochondrial nitric oxide synthase (mNOS) protein expression were measured along with histological examinations of renal tubular damage and mitochondrial ultrastructural changes. Tempol was effective against cisplatin-induced elevation of serum creatinine and urea as well as glucosuria and proteinuria. Moreover, pretreatment with tempol notably inhibited cisplatin-induced oxidative stress and disruption of mitochondrial function by restoring mitochondrial oxidative phosphorylation, complexes I and III activities, mNOS protein expression and ATP content. Tempol also provided significant protection against apoptosis, tubular damage and mitochondrial ultrastructural changes. Interestingly, tempol did not interfere with the cytotoxic effect of cisplatin against the growth of solid Ehrlich carcinoma.

Conclusion

This study highlights the potential role of tempol in inhibiting cisplatin-induced nephrotoxicity without affecting its antitumor activity via amelioration of oxidative stress and mitochondrial dysfunction.

Role of the Nrf2 signaling system in health and disease

A key component of cytoprotective gene regulation is the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), also known as nuclear factor erythroid 2-like 2, from the gene NFE2L2. Under normal conditions, Nrf2 in the cell is targeted for proteasomal degradation by its inhibitor Kelch-like ECH-associated inhibitor 1 (Keap1). When stimulated by oxidative stress, electrophiles, or kinase activation, conformational changes in the Nrf2-Keap1 complex inhibit proteasomal degradation of Nrf2, facilitating an increase in the amount of Nrf2 that binds to antioxidant response element sequences in the promoter regions of a variety of antioxidant, detoxification, and metabolic control genes. Nrf2 activation is mostly associated with beneficial cytoprotective gene regulation, but it can also have deleterious effects. For example, gene mutations in some types of cancers can lead to constitutive activation of Nrf2 and give the tumor cells growth advantages and increased drug resistance. Because cases exist where Nrf2/Keap1/ARE signaling is either too low or too high, there is great interest in the development of both Nrf2 activators and Nrf2 inhibitors as the basis of new therapies.

Melatonin modulates microsomal PGE synthase 1 and NF-E2-related factor-2-regulated antioxidant enzyme expression in LPS-induced murine peritoneal macrophages

BACKGROUND AND PURPOSE

Increasing evidence demonstrates that melatonin regulates inflammatory and immune processes acting as both an activator and inhibitor of these responses. Nevertheless, the molecular mechanisms of its anti-inflammatory action remain unclear. Here we have characterized the cellular mechanisms underlying the redox modulation of LPS-stimulated inflammatory responses in murine peritoneal macrophages by melatonin to provide insight into its anti-inflammatory effects.

EXPERIMENTAL APPROACH

Murine peritoneal macrophages were isolated and treated with melatonin in the presence or absence of LPS (5 μg·mL(-1) ) for 18 h. Cell viability was determined using sulforhodamine B assay and NO production was measured using the Griess reaction. Pro-inflammatory enzymes and transcription factors were detected by Western blotting.

KEY RESULTS

Without affecting cell viability, melatonin (12.5, 25, 50 and 100 μM) reduced the level of nitrites, inducible NOS (iNOS), COX-2 and microsomal PGE synthase-1 (mPGES1) protein, and p38 MAPK phosphorylation, and prevented NF-κB translocation. Furthermore, melatonin treatment significantly increased NF-E2-related factor 2 (Nrf2) and haem oxygenase 1 (HO1) protein levels in murine macrophages exposed to LPS.

CONCLUSIONS AND IMPLICATIONS

Melatonin reduced pro-inflammatory mediators and enhanced the expression of HO1 via NF-κB, p38 MAPK and Nrf2 cascade signalling pathways in murine macrophages. Thus, melatonin might be a promising target for diseases associated with overactivation of macrophages.

Role of Nrf2/ARE pathway in protective effect of electroacupuncture against endotoxic shock-induced acute lung injury in rabbits

NF-E2 related factor 2 (Nrf2) is a major transcription factor and acts as a key regulator of antioxidant genes to exogenous stimulations. The aim of current study was to determine whether Nrf2/ARE pathway is involved in the protective effect of electroacupuncture on the injured lung in a rabbit model of endotoxic shock. A dose of lipopolysaccharide (LPS) 5 mg/kg was administered intravenously to replicate the model of acute lung injury induced by endotoxic shock. Electroacupuncture pretreatment was handled bilaterally at Zusanli and Feishu acupoints for five consecutive days while sham electroacupuncture punctured at non-acupoints. Fourty anesthetized New England male rabbits were randomized into normal control group (group C), LPS group (group L), electroacupuncture + LPS group (group EL) and sham electroacupuncture + LPS (group SEL). At 6 h after LPS administration, the animals were sacrificed and the blood samples were collected for biochemical measurements. The lungs were removed for calculation of wet-to-dry weight ratios (W/D), histopathologic examination, determination of heme oxygenase (HO)-1 protein and mRNA, Nrf2 total and nucleoprotein, as well as Nrf2 mRNA expression, and evaluation of the intracellular distribution of Nrf2 nucleoprotein. LPS caused extensive morphologic lung damage, which was lessened by electroacupuncture treatment. Besides, lung W/D ratios were significantly decreased, the level of malondialdehyde was inhibited, plasma levels of TNF-α and interleukin-6 were decreased, while the activities of superoxide dismutase, glutathione peroxidase and catalase were enhanced in the electroacupucnture treated animals. In addition, electroacupuncture stimulation distinctly increased the expressions of HO-1 and Nrf2 protein including Nrf2 total protein and nucleoprotein as well as mRNA in lung tissue, while these effects were blunted in the sham electroacupuncture group. We concluded that electroacupuncture treatment at ST36 and BL13 effectively attenuates lung injury in a rabbit model of endotoxic shock through activation of Nrf2/ARE pathway and following up-regulation of HO-1 expression.

Nuclear heme oxygenase-1 (HO-1) modulates subcellular distribution and activation of Nrf2, impacting metabolic and anti-oxidant defenses

With oxidative injury as well as in some solid tumors and myeloid leukemia cells, heme oxygenase-1 (HO-1), the anti-oxidant, anti-inflammatory, and anti-apoptotic microsomal stress protein, migrates to the nucleus in a truncated and enzymatically inactive form. However, the function of HO-1 in the nucleus is not completely clear. Nuclear factor erythroid 2-related factor 2 (Nrf2), a transcription factor and master regulator of numerous antioxidants and anti-apoptotic proteins, including HO-1, also accumulates in the nucleus with oxidative injury and in various types of cancer. Here we demonstrate that in oxidative stress, nuclear HO-1 interacts with Nrf2 and stabilizes it from glycogen synthase kinase 3β (GSK3β)-mediated phosphorylation coupled with ubiquitin-proteasomal degradation, thereby prolonging its accumulation in the nucleus. This regulation of Nrf2 post-induction by nuclear HO-1 is important for the preferential transcription of phase II detoxification enzymes such as NQO1 as well as glucose-6-phosphate dehydrogenase (G6PDH), a regulator of the pentose phosphate pathway. Using Nrf2 knock-out cells, we further demonstrate that nuclear HO-1-associated cytoprotection against oxidative stress depends on an HO-1/Nrf2 interaction. Although it is well known that Nrf2 induces HO-1 leading to mitigation of oxidant stress, we propose a novel mechanism by which HO-1, by modulating the activation of Nrf2, sets an adaptive reprogramming that enhances antioxidant defenses.

Ameliorative effect of melatonin against contrast media induced renal tubular cell injury

BACKGROUND AND OBJECTIVE

Reactive oxygen species (ROS) is a mediator of renal damage. Melatonin is a potent-free radical scavenger. Our objective was to test whether melatonin would protect against the nephrotoxicity of contrast media.

METHODS

In an experimental study 40 adult male Wistar rats were randomly divided into four equal groups including: 1) Control group (No drug), 2) Contrast media group (10 ml/kg iodixanol i.v. single dose), 3) Contrast media and melatonin (first 10 ml/kg iodixanol then 10 ml/kg/day melatonin by i.p. injection on days 3, 4 and 5) and 4) Contrast media and melatonin pretreatment group (melatonin 10 ml/ kg/day by i.p. injection on 1, 2 and 3 days, then 10 ml/kg iodixanol by i.v. injection on third day. The blood creatinine and BUN as well as the histological changes were evaluated for severity of renal injury (degeneration, vacuolization of tubular renal cells, dilatation of tubular lumen and presence of debris in the lumens), by scoring from one to four.

RESULTS

Contrast media significantly increased the creatinine and BUN and renal injury (p<0.05). Melatonin prevented and reversed the injury induced by contrast media (P<0.05). Pretreatment with melatonin reduced the renal injury induced by contrast media (P<0.05).

CONCLUSION

Melatonin is an effective drug to prevent contrast-induced renal injury. Therefore its usage (especially pretreatment) might be beneficial in patients who are planning to use contrast media agents.

Nuclear erythroid 2-related factor 2: a novel potential therapeutic target for liver fibrosis

Hepatic stellate cells (HSC) are the key fibrogenic cells of the liver. HSC activation is a process of cellular transdifferentiation that occurs upon liver injury, but the mechanisms underlying liver fibrosis are unknown. Nuclear erythroid 2-related factor 2 (Nrf2) is an oxidative stress-mediated transcription factor with a variety of downstream targets aimed at cytoprotection. However, Nrf2 has recently been implicated as a new therapeutic target for the treatment of liver fibrosis. This review focuses on the transcriptional repressors that either control liver injury or regulate specific fibrogenic functions of liver fibrosis. We also show that Nrf2 may reveal significant gene expression changes, suggesting that Nrf2 activation may ameliorate liver fibrosis.

The effect of preoperative melatonin on nuclear erythroid 2-related factor 2 activation in patients undergoing coronary artery bypass grafting surgery

During and after coronary artery bypass grafting (CABG), oxidative stress occurs. Finding an effective way to improve antioxidant response is important in CABG surgery. It has been shown that patients with coronary heart disease have a low Melatonin production rate. The present study aimed to investigate the effects of Melatoninon nuclear erythroid 2-related factor 2(Nrf2) activity in patients undergoing CABG surgery. Thirty volunteers undergoing CABG were randomized to receive 10 mg oral Melatonin (Melatonin group, n = 15) or placebo (placebo group, n = 15) before sleeping for 1 month before surgery. The activated Nrf2 was measured twice by DNA-based ELISA method in the nuclear extract of peripheral blood mononuclear cells of patients before aortic clumps and 45 minutes after CABG operation. Melatonin administration was associated with a significant increase in both plasma levels of Melatonin and Nrf2 concentration in Melatonin group compared to placebo group, respectively (15.2 ± 4.6 pmol/L, 0.28 ± 0.01 versus 1.1 ± 0.59 pmol/L, 0.20 ± 0.07, P < 0.05). The findings of the present study provide preliminary data suggesting that Melatonin may play a significant role in the potentiation of the antioxidant defense and attenuate cellular damages resulting from CABG surgery via theNrf2 pathway.