Redox activation of DUSP4 by N-acetylcysteine protects endothelial cells from Cd²⁺-induced apoptosis

N-Acetylcysteine Alleviates D-Galactose-Induced Injury of Ovarian Granulosa Cells in Female Rabbits by Regulating the PI3K/Akt/mTOR Signaling Pathway

The ovary plays a crucial role in the reproductive system of female animals. Ovarian problems such as ovarian insufficiency, premature aging, polycystic ovary syndrome, and ovarian cysts may lead to ovulation disorders, abnormal hormone secretion, or luteal dysfunction, thereby increasing the risk of infertility and abortion. Only when the ovarian function and other organs in the reproductive system remain healthy and work normally can female animals be ensured to carry out reproductive activities regularly, improve the pregnancy rate and litter size, promote the healthy development of the fetus, and then improve their economic value. The follicle, as the functional unit of the ovary, is composed of theca cells, granulosa cells (GCs), and oocytes. GCs are the largest cell population and main functional unit in follicles and provide the necessary nutrients for the growth and development of follicles. N-acetylcysteine (NAC) is a prevalent and cell-permeable antioxidant molecule that effectively prevents apoptosis and promotes cellular survival. Over the past few years, its function in boosting reproductive performance in animals at the cellular level has been widely acknowledged. However, its specific role and mechanism in influencing GCs is yet to be fully understood. The objective of this study was to examine the effects of NAC on ovarian damage in female rabbits. For this purpose, D-galactose (D-gal) was first used to establish a model of damaged GCs, with exposure to 1.5 mg/mL of D-gal leading to substantial damage. Subsequently, varying concentrations of NAC were introduced to determine the precise mechanism through which it influences cell damage. Based on the results of the Cell Counting Kit-8 assay, flow cytometry, and Western blotting, it was found that 0.5 mg/mL of NAC could significantly suppress cell apoptosis and promote proliferation. In particular, it decreased the expression levels of Bax, p53, and Caspase-9 genes, while concurrently upregulating the expression of the BCL-2 gene. Moreover, NAC was found to alleviate intracellular oxidative stress, suppress the discharge of mitochondrial Cytochrome c, and boost the enzymatic activities of CAT (Catalase), GSH (Glutathione), and SOD (Superoxide dismutase). RNA sequencing analysis subsequently underscored the critical role of the PI3K/Akt/mTOR pathway in governing proliferation and apoptosis within GCs. These findings demonstrated that NAC could significantly influence gene expression within this pathway, thereby clarifying the exact relationship between the PI3K/Akt/mTOR signaling cascade and the underlying cellular processes controlling proliferation and apoptosis. In conclusion, NAC can reduce the expression of Bax, p53, and Caspase-9 genes, inhibit the apoptosis of GCs, improve cell viability, and resist D-gal-induced oxidative stress by increasing the activity of CAT, GSH, and SOD. The molecular mechanism of NAC in alleviating D-gal-induced ovarian GC injury in female rabbits by regulating the PI3K/Akt/mTOR signaling pathway provides experimental evidence for the effect of NAC on animal reproductive function at the cellular level.

Transcriptomics reveals the mechanism of selenium-enriched Lactobacillus plantarum alleviating brain oxidative stress under cadmium stress in Luciobarbus capito

Cadmium (Cd) is one of toxic metal in environment and is thought to affect nervous system. There were an increasing number of studies on selenium (Se)-enriched probiotics which were believed to produce bioactive nanoselenium. The antagonism of Se on heavy metals can significantly affect biological toxicity of heavy metals. This study aimed to elucidate possible mechanism of brain injury in Luciobarbus capito after Cd exposure and the mitigation of Se-enriched probiotics through transcriptome analysis. The results revealed 465 differentially expressed genes in the Cd and the control brains (Cd vs C), including 320 genes with upregulated expression and 145 genes with downregulated expression. In addition, we found that there were 4117 differentially expressed genes in the Se-enriched L. plantarum plus Cd and the control brains (S1L1-Cd vs C), including 2552 genes with upregulated expression and 1565 genes with downregulated expression. There were 147 differentially expressed genes in the Se-enriched L. plantarum plus Cd and the control brains (S1L1-Cd vs Cd), including 40 genes with upregulated expression and 107 genes with downregulated expression. Moreover, GO enrichment analysis indicated that the differentially expressed genes were involved in biological processes cellular component, and molecular function. KEGG enrichment analysis indicated that MAPK signaling pathway, calcium signaling pathway, and PI3K-Akt signaling pathway were significantly enriched. Subsequently, qRT-PCR was performed, and we selected 15 related differentially expressed genes for verification. The qRT-PCR results revealed the same trend as the RNA-Seq results. In conclusion, this study elucidated relieving effect of Se-enriched probiotics on Cd exposure-induced brain oxidative stress. This study provided a theoretical basis for further research on genes related to Cd poisoning and the amelioration of Se-enriched probiotics on Cd poisoning.

Endothelial Dysfunction Induced by Cadmium and Mercury and its Relationship to Hypertension

Hypertension is an important public health concern that affects millions globally, leading to a large number of morbidities and fatalities. The etiology of hypertension is complex and multifactorial, and it involves environmental factors, including heavy metals. Cadmium and mercury are toxic elements commonly found in the environment, contributing to hypertension. We aimed to assess the role of cadmium and mercury-induced endothelial dysfunction in the development of hypertension. A narrative review was carried out through database searches. In this review, we discussed the critical roles of cadmium and mercury in the etiology of hypertension and provided new insights into potential mechanisms of their effect, focusing primarily on endothelial dysfunction. Although the mechanisms by which cadmium and mercury induce hypertension have yet to be completely elucidated, evidence for both implicates impaired nitric oxide signaling in their hypertensive etiology.

Chronic oral depleted uranium leads to reproductive damage in male rats through the ROS-hnRNP A2/B1-COX-2 signaling pathway

Depleted uranium (DU) is widely used in civil and military activities. The testis is one of the target organs of DU chronic toxicity. In this study, male SD rats were chronically exposed to DU by 3, 30, 300 mg U/kg through oral intake. After 6 months and 12 months of exposure, it was found that DU could lead to increased oxidative stress levels, decreased glutathione S-transferases (GSTs) expression, resulting in testicular injury and decreased serum testosterone (T) level in rats. Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) expression increases with the increase of DU exposure dose. After upregulation of hnRNP A2/B1 expression, the GC-1 cell injury caused by DU is aggravated, suggesting that hnRNP A2/B1 may play an important role in the reproductive toxicity of DU. At the same time, 12 months after chronic oral exposure to DU, the expression level of cyclooxygenase-2 (COX-2) and proinflammatory factor prostaglandin E2 (PGE2) in testicular tissue were increased, and the level of hnRNP A2/B1 caused by DU was decreased by reactive oxygen scavenger N-acetylcysteine (NAC). As hnRNP A2/B1 is a COX-2 regulator, DU may lead to the upregulation of hnRNP A2/B1 expression through the increase of oxidative stress level in germ cells, which in turn leads to the increase of COX-2 and PGE2 level, and ultimately result in the reproductive toxicity. In this study, the regulation mechanism of the ROS-hnRNP A2/B1-COX-2 pathway on DU-induced reproductive damage in male rats was hypothesized, providing a new target for the prevention and treatment of chronic poisoning of DU.

Influence of N-acetylcysteine on steroidogenesis and gene expression in porcine placental trophoblast cells

N-acetylcysteine (NAC) is a widely used anti-inflammatory agent and antioxidant in vivo and in vitro. As a nutritional supplement, NAC can improve production and reproductive performances in animals through enhancing placental function and regulating hormone production. Trophoblast proliferation and steroid hormone production are two major functions in the placenta. We hypothesized that the effects of NAC on placental function is due to its direct and indirect effects on gene expression in placental trophoblast cells (pTr). To evaluate this hypothesis, we investigated the effects of NAC on steroidogenesis, gene expression, and cell proliferation in porcine pTr in vitro. pTr were treated with NAC in serum-free medium for 24 h with different concentrations (0, 0.1 μM, 1.0 μM, 10.0 μM, 0.1 mM, 1.0 mM, and 10.0 mM). Low-dose NAC (1 μM) stimulated pTr proliferation and decreased progesterone production, while increasing estradiol production (P < 0.05). High-dose NAC (10 mM) suppressed cell proliferation (P < 0.05), but had no effect on steroidogenesis. Low-dose NAC increased CCDN1 and decreased CASP3 and CASP8 mRNA levels (P < 0.05), whereas high-dose NAC decreased CDK4 and CCDN1 and increased CASP3 mRNA levels (P < 0.05). NAC had no effect on the mRNA abundance of StAR and HSD3B. Low-dose NAC upregulated CYP19A1 mRNA expression, and high-dose NAC downregulated CYP11A1 mRNA abundance (P < 0.05). Only low-dose NAC increased NOS3 mRNA abundance and tetrahydrobiopterin reduction (BH4/BH2 ratio). We conclude that NAC may act directly and indirectly on pTr with a dose-dependent manner and may regulate placental function by affecting pTr differentiation via regulating pTr steroid synthesis, cell proliferation, and apoptosis in sows.

Fine air pollution particles induce endothelial senescence via redox-sensitive activation of local angiotensin system

Fine dust (FD) is a form of air pollution and is responsible for a wide range of diseases. Specially, FD is associated with several cardiovascular diseases (CVDs); long-term exposure to FD was shown to decrease endothelial function, but the underlying mechanism remains unclear. We investigated whether exposure to FD causes premature senescence-associated endothelial dysfunction in endothelial cells (ECs) isolated from porcine coronary arteries. The cells were treated with different concentrations of FD and senescence associated-beta galactosidase (SA-β-gal) activity, cell cycle progression, expression of endothelial nitric oxide synthase (eNOS), oxidative stress level, and vascular function were evaluated. We found that FD increased SA-β-gal activity, caused cell cycle arrest, and increased oxidative stress, suggesting the premature induction of senescence; on the other hand, eNOS expression was downregulated and platelet aggregation was enhanced. FD exposure impaired vasorelaxation in response to bradykinin and activated the local angiotensin system (LAS), which was inhibited by treatment with the antioxidant N-acetyl cysteine (NAC) and angiotensin II receptor type 1 (AT₁) antagonist losartan (LOS). NAC and LOS also suppressed FD-induced SA-β-gal activity, increased EC proliferation and eNOS expression, and improved endothelial function. These results demonstrate that FD induces premature senescence of ECs and is associated with increased oxidative stress and activation of LAS. This study can serve as a pharmacological target for prevention and/or treatment of air pollution-associated CVD.

Regulation of Dual-Specificity Phosphatase (DUSP) Ubiquitination and Protein Stability

Mitogen-activated protein kinases (MAPKs) are key regulators of signal transduction and cell responses. Abnormalities in MAPKs are associated with multiple diseases. Dual-specificity phosphatases (DUSPs) dephosphorylate many key signaling molecules, including MAPKs, leading to the regulation of duration, magnitude, or spatiotemporal profiles of MAPK activities. Hence, DUSPs need to be properly controlled. Protein post-translational modifications, such as ubiquitination, phosphorylation, methylation, and acetylation, play important roles in the regulation of protein stability and activity. Ubiquitination is critical for controlling protein degradation, activation, and interaction. For DUSPs, ubiquitination induces degradation of eight DUSPs, namely, DUSP1, DUSP4, DUSP5, DUSP6, DUSP7, DUSP8, DUSP9, and DUSP16. In addition, protein stability of DUSP2 and DUSP10 is enhanced by phosphorylation. Methylation-induced ubiquitination of DUSP14 stimulates its phosphatase activity. In this review, we summarize the knowledge of the regulation of DUSP stability and ubiquitination through post-translational modifications.

Extracellular Vesicles Released by Human Induced-Pluripotent Stem Cell-Derived Cardiomyocytes Promote Angiogenesis

Although cell survival post-transplantation is very low, emerging evidence using stem cell therapy for myocardial repair points toward a primary role of paracrine signaling mechanisms as the basis for improved cardiac function, decreased fibrosis, and increased angiogenesis. Recent studies have demonstrated that extracellular vesicles (EVs) such as exosomes secreted by stem cells stimulate angiogenesis, provide cytoprotection, and modulate apoptosis. However, the angiogenic potential of EVs secreted from human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM), a terminally differentiated cell type, has not been elucidated yet. Therefore, the main objective of this study is to isolate, characterize, and evaluate the in vitro angiogenic potential of EVs collected from hiPSC-CM conditioned media. The hiPSC-CM were cultured for 2 weeks and EVs were isolated from cell culture medium. Isolated EVs were characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis, and immunoblotting. Furthermore, the angiogenic potential of these EVs was evaluated by tube formation, wound-healing, and cell-proliferation assays in bovine aortic endothelial cells (BAEC). In addition, gene expression levels of growth factors was evaluated in hiPSC-derived endothelial cells (hiPSC-EC) treated with hiPSC-CM-derived EV (CM-EVs) to assess their role in promoting angiogenesis. TEM imaging of CM-EVs showed a presence of a double-membrane bound structure, which is a characteristic of EV. Nanoparticle tracking analysis further confirmed the size and shape of the secreted particles to be consistent with EVs. Furthermore, EV-specific markers (CD63 and HSP70) were enriched in these particles as illustrated by immunoblotting. Most importantly, BAEC treated with 100 μg/ml of CM-EVs showed significant increases in tube formation, wound closure, and cell proliferation as compared to control (no-EVs). Finally, treatment of hiPSC-EC with CM-EVs induced increased expression of pro-angiogenic growth factors by the endothelial cells. Overall, our results demonstrated that EVs isolated from hiPSC-CM enhance angiogenesis in endothelial cells. This acellular/cell-free approach constitutes a potential translational therapeutic to induce angiogenesis in patients with myocardial infarction.

Low-Intensity Ultrasound Reduces High Glucose-Induced Nitric Oxide Generation in Retinal Pigment Epithelial Cells

Diabetic retinopathy (DR) is a severe micro-vascular complication of diabetes. High glucose (HG)-evoked nitric oxide (NO) production mediated by increased oxidative stress is a key factor in DR pathogenesis. In this study, we examined whether low-intensity ultrasound (LIUS) stimulation can reduce HG-induced NO generation. We determined that LIUS stimulation decreased the HG-induced NO generation possibly via inhibition of reactive oxygen species (ROS) and subsequently diminished the associated pro-inflammatory pathway involving the induced expression of inducible nitric oxide synthase, cyclooxygenase-2 and vascular endothelial growth factor. In addition, we determined that LIUS stimulation reduced the quantity of NO produced by N-acetylcysteine, which was not mediated by ROS. These results indicate that LIUS can inhibit both ROS-dependent and -independent NO generation processes in ARPE-19 cells. We envision LIUS as a potential therapeutic alternative to treat DR. Further studies are required to understand the underlying mechanism of the LIUS-induced reduction of NO generation for DR therapy.

Potential Role of Exosomes in Mending a Broken Heart: Nanoshuttles Propelling Future Clinical Therapeutics Forward

Stem cell transplantation therapy is a promising adjunct for regenerating damaged heart tissue; however, only modest improvements in cardiac function have been observed due to poor survival of transplanted cells in the ischemic heart. Therefore, there remains an unmet need for therapies that can aid in attenuating cardiac damage. Recent studies have demonstrated that exosomes released by stem cells could serve as a potential cell-free therapeutic for cardiac repair. These exosomes/nanoshuttles, once thought to be merely a method of waste disposal, have been shown to play a crucial role in physiological functions including short- and long-distance intercellular communication. In this review, we have summarized studies demonstrating the potential role of exosomes in improving cardiac function, attenuating cardiac fibrosis, stimulating angiogenesis, and modulating miRNA expression. Furthermore, exosomes carry an important cargo of miRNAs and proteins that could play an important role as a diagnostic marker for cardiovascular disease post-myocardial infarction. Although there is promising evidence from preclinical studies that exosomes released by stem cells could serve as a potential cell-free therapeutic for myocardial repair, there are several challenges that need to be addressed before exosomes could be fully utilized as off-the-shelf therapeutics for cardiac repair.

Dual-Specificity Phosphatase 4 Overexpression in Cells Prevents Hypoxia/Reoxygenation-Induced Apoptosis via the Upregulation of eNOS

Mitogen-activated protein kinases (MAPKs) signaling cascades regulate several cellular functions, including differentiation, proliferation, survival, and apoptosis. The duration and magnitude of phosphorylation of these MAPKs are decisive determinants of their physiological functions. Dual-specificity phosphatases exert kinetic control over these signaling cascades. Previously, we demonstrated that DUSP4^−/− hearts sustain a larger infarct and have poor functional recovery, when isolated hearts were subjected to ischemia/reperfusion. Uncontrolled p38 activation and upregulation of Nox4 expression are the main effectors for this functional alteration. Here, dual-specificity phosphatase 4 (DUSP4) overexpression in endothelial cells was used to investigate the role of DUSP4 on the modulation of reactive oxygen species (ROS) generation and vascular function, when cells were subjected to hypoxia/reoxygenation (H/R) insult. Immunostaining with cleaved caspase-3 revealed that DUSP4 overexpression prevents caspase-3 activation and apoptosis after H/R. The beneficial effects occur via modulating p38 activity, increased NO bioavailability, and reduced oxidative stress. More importantly, DUSP4 overexpression upregulates eNOS protein expression (1.62 ± 0.33 versus 0.65 ± 0.16) during H/R-induced stress. NO is a critical small molecule involved in regulating vascular tone, vascular growth, platelet aggregation, and modulation of inflammation. The level of NO generation determined using DAF-2 fluorescence demonstrated that DUSP4 overexpression augments NO production and thus improves vascular function. The level of superoxide generated from cells after being subjected to H/R was determined using dihydroethidium-HPLC method. The results suggested that DUSP4 overexpression in cells decreases H/R-induced superoxide generation (1.56 ± 0.14 versus 1.19 ± 0.05) and thus reduces oxidant stress. This also correlates with the reduction in the total protein S-glutathionylation, an indicator of protein oxidation. These results further support our hypothesis that DUSP4 is an antioxidant gene and a key phosphatase in modulating MAPKs, especially p38, during oxidative stress, which regulates ROS generation and eNOS expression and thus protects against oxidant-induced injury or apoptosis. Overall, DUSP4 may serve as an excellent molecular target for the treatment of ischemic heart disease.

Modulation of p38 kinase by DUSP4 is important in regulating cardiovascular function under oxidative stress

Over-activation of p38 is implicated in many cardiovascular diseases (CVDs), including myocardial infarction, hypertrophy, heart failure, and ischemic heart disease. Numerous therapeutic interventions for CVDs have been directed toward the inhibition of the p38 mitogen-activated protein kinase activation that contributes to the detrimental effect after ischemia/reperfusion (I/R) injuries. However, the efficacy of these treatments is far from ideal, as they lack specificity and are associated with high toxicity. Previously, we demonstrated that N-acetyl cysteine (NAC) pretreatment up-regulates DUSP4 expression in endothelial cells, regulating p38 and ERK1/2 activities, and thus providing a protective effect against oxidative stress. Here, endothelial cells under hypoxia/reoxygenation (H/R) insult and isolated heart I/R injury were used to investigate the role of DUSP4 in the modulation of the p38 pathway. In rat endothelial cells, DUSP4 is time-dependently degraded by H/R (0.25 ± 0.07-fold change of control after 2h H/R). Its degradation is closely associated with hyperphosphorylation of p38 (2.1 ± 0.36-fold change) and cell apoptosis, as indicated by the increase in cells immunopositive for cleaved caspase-3 (12.59 ± 3.38%) or TUNEL labeling (29.46 ± 3.75%). The inhibition of p38 kinase activity with 20 µM SB203580 during H/R prevents H/R-induced apoptosis, assessed via TUNEL (12.99 ± 1.89%). Conversely, DUSP4 gene silencing in endothelial cells augments their sensitivity to H/R-induced apoptosis (45.81 ± 5.23%). This sensitivity is diminished via the inhibition of p38 activity (total apoptotic cells drop to 17.47 ± 1.45%). Interestingly, DUSP4 gene silencing contributes to the increase in superoxide generation from cells. Isolated Langendorff-perfused mouse hearts were subjected to global I/R injury. DUSP4(-/-) hearts had significantly larger infarct size than WT. The increase in I/R-induced infarct in DUSP4(-/-) mice significantly correlates with reduced functional recovery (assessed by RPP%, LVDP%, HR%, and dP/dtmax) as well as lower CF% and a higher initial LVEDP. From immunoblotting analysis, it is evident that p38 is significantly overactivated in DUSP4(-/-) mice after I/R injury. The activation of cleaved caspase-3 is seen in both WT and DUSP4(-/-) I/R hearts. Infusion of a p38 inhibitor prior to ischemia and during the reperfusion improves both WT and DUSP4(-/-) cardiac function. Therefore, the identification of p38 kinase modulation by DUSP4 provides a novel therapeutic target for oxidant-induced diseases, especially myocardial infarction.

Ghrelin protects against depleted uranium-induced apoptosis of MC3T3-E1 cells through oxidative stress-mediated p38-mitogen-activated protein kinase pathway

Depleted uranium (DU) mainly accumulates in the bone over the long term. Osteoblast cells are responsible for the formation of bone, and they are sensitive to DU damage. However, studies investigating methods of reducing DU damage in osteoblasts are rarely reported. Ghrelin is a stomach hormone that stimulates growth hormones released from the hypothalamic-pituitary axis, and it is believed to play an important physiological role in bone metabolism. This study evaluates the impact of ghrelin on DU-induced apoptosis of the osteoblast MC3T3-E1 and investigates its underlying mechanisms. The results show that ghrelin relieved the intracellular oxidative stress induced by DU, eliminated reactive oxygen species (ROS) and reduced lipid peroxidation by increasing intracellular GSH levels; in addition, ghrelin effectively suppressed apoptosis, enhanced mitochondrial membrane potential, and inhibited cytochrome c release and caspase-3 activation after DU exposure. Moreover, ghrelin significantly reduced the expression of DU-induced phosphorylated p38-mitogen-activated protein kinase (MAPK). A specific inhibitor (SB203580) or specific siRNA of p38-MAPK could significantly suppress DU-induced apoptosis and related signals, whereas ROS production was not affected. In addition, ghrelin receptor inhibition could reduce the anti-apoptosis effect of ghrelin on DU and reverse the effect of ghrelin on intracellular ROS and p38-MAPK after DU exposure. These results suggest that ghrelin can suppress DU-induced apoptosis of MC3T3-E1 cells, reduce DU-induced oxidative stress by interacting with its receptor, and inhibit downstream p38-MAPK activation, thereby suppressing the mitochondrial-dependent apoptosis pathway.

Loss of multidrug resistance-associated protein 1 potentiates chronic doxorubicin-induced cardiac dysfunction in mice

Doxorubicin (DOX), an effective cancer chemotherapeutic agent, induces dose-dependent cardiotoxicity, in part due to its ability to cause oxidative stress. We investigated the role of multidrug resistance-associated protein 1 (Mrp1/Abcc1) in DOX-induced cardiotoxicity in C57BL wild-type (WT) mice and their Mrp1 null (Mrp1(-/-)) littermates. Male mice were administered intraperitoneal DOX (3 or 2 mg/kg body weight) or saline twice a week for 3 weeks and examined 2 weeks after the last dose (protocol A total dose: 18 mg/kg) or for 5 weeks, and mice were examined 48 hours and 2 weeks after the last dose (protocol B total dose: 20 mg/kg). Chronic DOX induced body weight loss and hemotoxicity, adverse effects significantly exacerbated in Mrp1(-/-) versus WT mice. In the heart, significantly higher basal levels of glutathione (1.41-fold ± 0.27-fold) and glutathione disulfide (1.35-fold ± 0.16-fold) were detected in Mrp1(-/-) versus WT mice, and there were comparable decreases in the glutathione/glutathione disulfide ratio in WT and Mrp1(-/-) mice after DOX administration. Surprisingly, DOX induced comparable increases in 4-hydroxynonenal glutathione conjugate concentration in hearts from WT and Mrp1(-/-) mice. However, more DOX-induced apoptosis was detected in Mrp1(-/-) versus WT hearts (P < 0.05) (protocol A), and cardiac function, assessed by measurement of fractional shortening and ejection fraction with echocardiography, was significantly decreased by DOX in Mrp1(-/-) versus WT mice (P < 0.05; 95% confidence intervals of 20.0%-24.3% versus 23.7%-29.5% for fractional shortening, and 41.5%-48.4% versus 47.7%-56.7% for ejection fraction; protocol B). Together, these data indicate that Mrp1 protects the mouse heart against chronic DOX-induced cardiotoxicity.

Elevated glutathione is not sufficient to protect against doxorubicin-induced nuclear damage in heart in multidrug resistance-associated protein 1 (Mrp1/Abcc1) null mice

Cardiotoxicity is a major dose-limiting adverse effect of doxorubicin (DOX), mediated in part by overproduction of reactive oxygen species and oxidative stress. Abcc1 (Mrp1) mediates the efflux of reduced and oxidized glutathione (GSH, GSSG) and is also a major transporter that effluxes the GSH conjugate of 4-hydroxy-2-nonenal (HNE; GS-HNE), a toxic product of lipid peroxidation formed during oxidative stress. To assess the role of Mrp1 in protecting the heart from DOX-induced cardiac injury, wild-type (WT) and Mrp1 null (Mrp1(-/-)) C57BL/6 littermate mice were administered DOX (15 mg/kg) or saline (7.5 ml/kg) i.v., and heart ventricles were examined at 72 hours. Morphometric analysis by electron microscopy revealed extensive injuries in cytosol, mitochondria, and nuclei of DOX-treated mice in both genotypes. Significantly more severely injured nuclei were observed in Mrp1(-/-) versus WT mice (P = 0.031). GSH and the GSH/GSSG ratio were significantly increased in treatment-naïve Mrp1(-/-) versus WT mice; GSH remained significantly higher in Mrp1(-/-) versus WT mice after saline and DOX treatment, with no changes in GSSG or GSH/GSSG. GS-HNE, measured by mass spectrometry, was lower in the hearts of treatment-naïve Mrp1(-/-) versus WT mice (P < 0.05). DOX treatment decreased GS-HNE in WT but not Mrp1(-/-) mice, so that GS-HNE was modestly but significantly higher in Mrp1(-/-) versus WT hearts after DOX. Expression of enzymes mediating GSH synthesis and antioxidant proteins did not differ between genotypes. Thus, despite elevated GSH levels in Mrp1(-/-) hearts, DOX induced significantly more injury in the nuclei of Mrp1(-/-) versus WT hearts.