Regulation of reactive oxygen species by p53: implications for nitric oxide-mediated apoptosis

p53 Regulates Mitochondrial Dynamics in Vascular Smooth Muscle Cell Calcification

Arterial calcification is an important characteristic of cardiovascular disease. It has key parallels with skeletal mineralization; however, the underlying cellular mechanisms responsible are not fully understood. Mitochondrial dynamics regulate both bone and vascular function. In this study, we therefore examined mitochondrial function in vascular smooth muscle cell (VSMC) calcification. Phosphate (Pi)-induced VSMC calcification was associated with elongated mitochondria (1.6-fold increase, p < 0.001), increased mitochondrial reactive oxygen species (ROS) production (1.83-fold increase, p < 0.001) and reduced mitophagy (9.6-fold decrease, p < 0.01). An increase in protein expression of optic atrophy protein 1 (OPA1; 2.1-fold increase, p < 0.05) and a converse decrease in expression of dynamin-related protein 1 (DRP1; 1.5-fold decrease, p < 0.05), two crucial proteins required for the mitochondrial fusion and fission process, respectively, were noted. Furthermore, the phosphorylation of DRP1 Ser637 was increased in the cytoplasm of calcified VSMCs (5.50-fold increase), suppressing mitochondrial translocation of DRP1. Additionally, calcified VSMCs showed enhanced expression of p53 (2.5-fold increase, p < 0.05) and β-galactosidase activity (1.8-fold increase, p < 0.001), the cellular senescence markers. siRNA-mediated p53 knockdown reduced calcium deposition (8.1-fold decrease, p < 0.01), mitochondrial length (3.0-fold decrease, p < 0.001) and β-galactosidase activity (2.6-fold decrease, p < 0.001), with concomitant mitophagy induction (3.1-fold increase, p < 0.05). Reduced OPA1 (4.1-fold decrease, p < 0.05) and increased DRP1 protein expression (2.6-fold increase, p < 0.05) with decreased phosphorylation of DRP1 Ser637 (3.20-fold decrease, p < 0.001) was also observed upon p53 knockdown in calcifying VSMCs. In summary, we demonstrate that VSMC calcification promotes notable mitochondrial elongation and cellular senescence via DRP1 phosphorylation. Furthermore, our work indicates that p53-induced mitochondrial fusion underpins cellular senescence by reducing mitochondrial function.

Reactive Oxygen Species: Modulators of Phenotypic Switch of Vascular Smooth Muscle Cells

Reactive oxygen species (ROS) are natural byproducts of oxygen metabolism in the cell. At physiological levels, they play a vital role in cell signaling. However, high ROS levels cause oxidative stress, which is implicated in cardiovascular diseases (CVD) such as atherosclerosis, hypertension, and restenosis after angioplasty. Despite the great amount of research conducted to identify the role of ROS in CVD, the image is still far from being complete. A common event in CVD pathophysiology is the switch of vascular smooth muscle cells (VSMCs) from a contractile to a synthetic phenotype. Interestingly, oxidative stress is a major contributor to this phenotypic switch. In this review, we focus on the effect of ROS on the hallmarks of VSMC phenotypic switch, particularly proliferation and migration. In addition, we speculate on the underlying molecular mechanisms of these cellular events. Along these lines, the impact of ROS on the expression of contractile markers of VSMCs is discussed in depth. We conclude by commenting on the efficiency of antioxidants as CVD therapies.

Vascular calcification: New insights into endothelial cells

Vascular calcification, a common pathological basis of vascular disease, is caused by various diseases and is an independent risk factor for cardiovascular events. Therefore, elucidating the pathogenesis of vascular calcification has significant clinical benefits. It is generally believed that vascular calcification is similar to the processes of bone development and cartilage formation. The transformation of vascular smooth muscle cells into osteoblast- and chondrocyte-like cells is a key event. However, recent studies have found that under certain conditions, endothelial cells participate in vascular calcification via endothelial-mesenchymal transition, cytokine secretion, extracellular vesicle synthesis, angiogenesis regulation and hemodynamics. This review aims to explore the relationship between endothelial cells and vascular calcification and to provide a theoretical basis and new ideas for the active prevention and treatment of vascular calcification in the clinic.

The Role of Caspase-2 in Regulating Cell Fate

Caspase-2 is the most evolutionarily conserved member of the mammalian caspase family and has been implicated in both apoptotic and non-apoptotic signaling pathways, including tumor suppression, cell cycle regulation, and DNA repair. A myriad of signaling molecules is associated with the tight regulation of caspase-2 to mediate multiple cellular processes far beyond apoptotic cell death. This review provides a comprehensive overview of the literature pertaining to possible sophisticated molecular mechanisms underlying the multifaceted process of caspase-2 activation and to highlight its interplay between factors that promote or suppress apoptosis in a complicated regulatory network that determines the fate of a cell from its birth and throughout its life.

Functional Role of p53 in the Regulation of Chemical-Induced Oxidative Stress

The nuclear transcription factor p53, discovered in 1979, has a broad range of biological functions, primarily the regulation of apoptosis, the cell cycle, and DNA repair. In addition to these canonical functions, a growing body of evidence suggests that p53 plays an important role in regulating intracellular redox homeostasis through transcriptional and nontranscriptional mechanisms. Oxidative stress induction and p53 activation are common responses to chemical exposure and are suggested to play critical roles in chemical-induced toxicity. The activation of p53 can exert either prooxidant or antioxidant activity, depending on the context. In this review, we discuss the functional role of p53 in regulating chemical-induced oxidative stress, summarize the potential signaling pathways involved in p53's regulation of chemically mediated oxidative stress, and propose issues that should be addressed in future studies to improve understanding of the relationship between p53 and chemical-induced oxidative stress.

Loss of p53 Sensitizes Cells to Palmitic Acid-Induced Apoptosis by Reactive Oxygen Species Accumulation

Palmitic acid, the most common saturated free fatty acid, can lead to lipotoxicity and apoptosis when overloaded in non-fat cells. Palmitic acid accumulation can induce pancreatic β-cell dysfunction and cardiac myocyte apoptosis. Under various cellular stresses, the activation of p53 signaling can lead to cell cycle arrest, DNA repair, senescence, or apoptosis, depending on the severity/type of stress. Nonetheless, the precise role of p53 in lipotoxicity induced by palmitic acid is not clear. Here, our results show that palmitic acid induces p53 activation in a dose- and time-dependent manner. Furthermore, loss of p53 makes cells sensitive to palmitic acid-induced apoptosis. These results were demonstrated in human colon carcinoma cells (HCT116) and primary mouse embryo fibroblasts (MEF) through analysis of DNA fragmentation, flow cytometry, colony formation, and Western blots. In the HCT116 p53^−/− cell line, palmitic acid induced greater reactive oxygen species formation compared to the p53^+/+ cell line. The reactive oxygen species (ROS) scavengers N-acetyl cysteine (NAC) and reduced glutathione (GSH) partially attenuated apoptosis in the HCT116 p53^−/− cell line but had no obvious effect on the p53^+/+ cell line. Furthermore, p53 induced the expression of its downstream target genes, p21 and Sesn2, in response to ROS induced by palmitic acid. Loss of p21 also leads to more palmitic acid-induced cell apoptosis in the HCT116 cell line compared with HCT116 p53^+/+ and HCT116 p53^−/−. In a mouse model of obesity, glucose tolerance test assays showed higher glucose levels in p53^−/− mice that received a high fat diet compared to wild type mice that received the same diet. There were no obvious differences between p53^−/− and p53^+/+ mice that received a regular diet. We conclude that p53 may provide some protection against palmitic acid- induced apoptosis in cells by targeting its downstream genes in response to this stress.

Benzo[a]pyrene alters vascular function in rat aortas ex vivo and in vivo

Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon found in tobacco smoke and air pollution products. BaP exposure has been recently suggested to be a risk factor for hypertension in coke oven workers. The mechanisms of BaP on vascular smooth muscle function remain unclear. Here, we examined the influence and possible mechanism of BaP on vasoconstriction in rat thoracic aortas ex vivo and in vivo. In vivo exposure of rats to BaP (20 mg/kg) for 8 weeks caused a significant enhancement in the systolic blood pressure and enhanced aortic hyperreactivity to α1-adrenoceptor selective agonist phenylephrine in aortas. BaP (1 and 10 μM) treatment for 18 h induced an enhancement of phenylephrine-induced vasoconstriction in the organ cultures of aortas. Aryl hydrocarbon receptor antagonist α-naphthoflavone, protein kinase C (PKC) inhibitor chelerythrine, mitogen-activated protein kinases (MAPK) inhibitor PD98059, myosin light chain kinase (MLCK) inhibitor ML-9, and Rho-kinase inhibitor Y-27632 significantly suppressed BaP-enhanced vasoconstriction. BaP time-dependently triggered reactive oxygen species (ROS) production in primary vascular smooth muscle cells. Both antioxidant N-acetylcysteine and NAD(P)H oxidase inhibitor diphenyleneiodonium significantly inhibited BaP-triggered ROS production and vasoconstriction. These results suggest that BaP enhances aortic vasoconstriction via the activation of ROS and muscular signaling molecules PKC, MAPK, MLCK, and Rho-kinase.

Association between expression of TNF-α, P53 and HIF1α with asthenozoospermia

Reduced sperm motility (asthenozoospermia) accounts for a significant percentage of male infertility and numerous factors have been suggested to explain this phenomenon among which hypoxic and inflammatory markers are the least studied. Therefore, the aim of this study was to assess the main molecular markers involved in hypoxia (P53 and HIF-1α) and inflammation (TNF-α) pathways in infertile men with asthenozoospermia. Expression of these markers were assessed by qRT-PCR, and analysis of data show that mean of hypoxia markers (P53, HIF-1α) and also TNF- α were significantly higher in infertile men with asthenozoospermia compared to fertile men (p < 0.05). Unlike TNF-α, significant negative correlations were observed between expression of P53 (r = -0.568; p = 0.002) and HIF-1α (r = -0.403; p = 0.046) with sperm motility. In addition, a significant negative correlation was observed between expression of P53 with sperm concentration (r = -0.576; p < 0.001). In addition, a significant positive correlation was observed between hypoxia markers (P53, HIF-1α) and TNF-α (p < 0.01). However, no significant relation was observed between TNF-α and semen parameters. Taken together, the results of this study suggest the involvement of hypoxia pathway is more pronounced than the inflammatory pathway in asthenozoospermia.

Evaluation of the p53 and Thioredoxin reductase in sperm from asthenozoospermic males in comparison to normozoospermic males

Thioredoxin (Trx) system has a defensive role against the harmful effect of oxidative stress in sperm. p53 is an important regulator of apoptosis and normal process of spermatogenesis. Regulation of p53 by redox state of the cell and Thioredoxin system has been reported. The aim of this study was to evaluate the ROS level, Thioredoxin reductase (TrxR) activity and p53 protein levels in sperm of asthenozoospermic and normozoospermic males. Semen samples from 80 donors were divided into asthenozoospermic (n = 40) and normozoospermic (n = 40) groups using the WHO criteria. DNA fragmentation (TUNEL assay) of spermatozoa was identified·H₂O₂ and O₂•- were determined by flow cytometry. p53 protein levels and TrxR activity were measured in sperm cell lysate by appropriate kit. Total antioxidant capacity (TAC) and thiol groups in seminal plasma were measured spectrophotometery. MDA content in seminal plasma was determined fluorometrically.

RESULTS

The percentage of cells with H₂O₂, O₂•- and DNA fragmentation was higher in asthenozoospermic compared to normozoospermic groups (p < 0.05). The p53 protein level was significantly higher in asthenozoospermic group (P < 0.001). TrxR activity in normozoospermic was significantly higher than asthenozoospermic group (P < 0.001). Total thiol groups and TAC levels were significantly higher in normozoospermic samples (P < 0.05). A significantly high negative correlation was seen between p53 protein levels with TrxR activity (r = - 0.49, P < 0.001), total motility (r = - 0.65, P < 0.001). p53 and ROS levels were increased in asthenozoospermic males while the TrxR activity was decreased. These changes lead to an increase in apoptotic, immotile and immature spermatozoa in the ejaculatory semen.

Benzo[a]pyrene activates interleukin-6 induction and suppresses nitric oxide-induced apoptosis in rat vascular smooth muscle cells

Benzo[a]pyrene, a ubiquitous environmental pollutant, has been suggested to be capable of initiating and/or accelerating atherosclerosis. Accumulation of vascular smooth muscle cells (VSMCs) in vessel intima is a hallmark of atherosclerosis. Nitric oxide (NO) can suppress VSMCs proliferation and induce VSMCs apoptosis. NO plays a compensatory role in the vascular lesions to reduce proliferation and/or accelerate apoptosis of VSMCs. The aim of this study was to investigate whether benzo[a]pyrene can affect VSMCs growth and apoptosis induced by NO. Benzo[a]pyrene (1–30 μmol/L) did not affect the cell number and cell cycle distribution in VSMCs under serum deprivation condition. Sodium nitroprusside (SNP), a NO donor, decreased cell viability and induced apoptosis in VSMCs. Benzo[a]pyrene significantly suppressed SNP-induced cell viability reduction and apoptosis. VSMCs cultured in conditioned medium from cells treated with benzo[a]pyrene could also prevent SNP-induced apoptosis. Benzo[a]pyrene was capable of inducing the activation of nuclear factor (NF)-κB and phosphorylation of p38 mitogen-activated protein kinase (MAPK) in VSMCs. Both NF-κB inhibitor and p38 MAPK inhibitor significantly reversed the anti-apoptotic effect of benzo[a]pyrene on SNP-treated VSMCs. Incubation of VSMCs with benzo[a]pyrene significantly and dose-dependently increased interleukin (IL)-6 production. A neutralizing antibody to IL-6 effectively reversed the anti-apoptotic effect of benzo[a]pyrene on SNP-treated VSMCs. Taken together, these results demonstrate for the first time that benzo[a]pyrene activates IL-6 induction and protects VSMCs from NO-induced apoptosis. These findings propose a new mechanism for the atherogenic effect of benzo[a]pyrene.

Targeted Nitric Oxide Delivery by Supramolecular Nanofibers for the Prevention of Restenosis After Arterial Injury

AIMS

Cardiovascular interventions continue to fail as a result of arterial restenosis secondary to neointimal hyperplasia. We sought to develop and evaluate a systemically delivered nanostructure targeted to the site of arterial injury to prevent neointimal hyperplasia. Nanostructures were based on self-assembling biodegradable molecules known as peptide amphiphiles. The targeting motif was a collagen-binding peptide, and the therapeutic moiety was added by S-nitrosylation of cysteine residues.

RESULTS

Structure of the nanofibers was characterized by transmission electron microscopy and small-angle X-ray scattering. S-nitrosylation was confirmed by mass spectrometry, and nitric oxide (NO) release was assessed electrochemically and by chemiluminescent detection. The balloon carotid artery injury model was performed on 10-week-old male Sprague-Dawley rats. Immediately after injury, nanofibers were administered systemically via tail vein injection. S-nitrosylated (S-nitrosyl [SNO])-targeted nanofibers significantly reduced neointimal hyperplasia 2 weeks and 7 months following balloon angioplasty, with no change in inflammation.

INNOVATION

This is the first time that an S-nitrosothiol (RSNO)-based therapeutic was shown to have targeted local effects after systemic administration. This approach, combining supramolecular nanostructures with a therapeutic NO-based payload and a targeting moiety, overcomes the limitations of delivering NO to a site of interest, avoiding undesirable systemic side effects.

CONCLUSION

We successfully synthesized and characterized an RSNO-based therapy that when administered systemically, targets directly to the site of vascular injury. By integrating therapeutic and targeting chemistries, these targeted SNO nanofibers provided durable inhibition of neointimal hyperplasia in vivo and show great potential as a platform to treat cardiovascular diseases.

Ambient and household air pollution: complex triggers of disease

Concentrations of outdoor air pollution are on the rise, particularly due to rapid urbanization worldwide. Alternatively, poor ventilation, cigarette smoke, and other toxic chemicals contribute to rising concentrations of indoor air pollution. The World Health Organization recently reported that deaths attributable to indoor and outdoor air pollutant exposure are more than double what was originally documented. Epidemiological, clinical, and animal data have demonstrated a clear connection between rising concentrations of air pollution (both indoor and outdoor) and a host of adverse health effects. During the past five years, animal, clinical, and epidemiological studies have explored the adverse health effects associated with exposure to both indoor and outdoor air pollutants throughout the various stages of life. This review provides a summary of the detrimental effects of air pollution through examination of current animal, clinical, and epidemiological studies and exposure during three different periods: maternal (in utero), early life, and adulthood. Additionally, we recommend future lines of research while suggesting conceivable strategies to curb exposure to indoor and outdoor air pollutants.

Inhibiting protein arginine deiminases has antioxidant consequences

Ulcerative colitis is a dynamic, idiopathic, chronic inflammatory condition that carries a high colon cancer risk. We previously showed that Cl-amidine, a small-molecule inhibitor of the protein arginine deiminases, suppresses colitis in mice. Because colitis is defined as inflammation of the colon associated with infiltration of white blood cells that release free radicals and citrullination is an inflammation-dependent process, we asked whether Cl-amidine has antioxidant properties. Here we show that colitis induced with azoxymethane via intraperitoneal injection + 2% dextran sulfate sodium in the drinking water is suppressed by Cl-amidine (also given in the drinking water). Inducible nitric oxide synthase, an inflammatory marker, was also downregulated in macrophages by Cl-amidine. Because epithelial cell DNA damage associated with colitis is at least in part a result of an oxidative burst from overactive leukocytes, we tested the hypothesis that Cl-amidine can inhibit leukocyte activation, as well as subsequent target epithelial cell DNA damage in vitro and in vivo. Results are consistent with this hypothesis, and because DNA damage is a procancerous mechanism, our data predict that Cl-amidine will not only suppress colitis, but we hypothesize that it may prevent colon cancer associated with colitis.

Chlorogenic acid prevents isoproterenol-induced hypertrophy in neonatal rat myocytes

Cardiac hypertrophy is an independent risk factor for cardiovascular disease and its subsequent progression to heart failure represents a major cause of morbidity and mortality in the world. CGA is an important component of Chinese herbal medicine, acting as an antioxidant, scavenging free radicals and preventing inflammation. This study found that with the pre-treatment of chlorogenic acid in Iso-induced neonatal rat myocytes, the levels of the hypertrophic markers, ANP, BNP and β-MHC decreased. The nuclear translocation of NF-κB was blocked, whereas NF-κBIA, an inhibitor of NF-κB, was upregulated accordingly. And the level of the intracellular ROS was also reduced. These data reveal that chlorogenic acid may inhibit Iso-induced cardiac hypertrophy by attenuating NF-κB signaling pathway and suppressing ROS.

Quantitative proteomics analysis highlights the role of redox hemostasis and energy metabolism in human embryonic stem cell differentiation to neural cells

Neural differentiation of human embryonic stem cells (hESCs) is a unique opportunity for in vitro analyses of neurogenesis in humans. Extrinsic cues through neural plate formation are well described in the hESCs although intracellular mechanisms underlying neural development are largely unknown. Proteome analysis of hESC differentiation to neural cells will help to further define molecular mechanisms involved in neurogenesis in humans. Using a two-dimensional differential gel electrophoresis (2D-DIGE) system, we analyzed the proteome of hESC differentiation to neurons at three stages, early neural differentiation, neural ectoderm and mature neurons. Out of 137 differentially accumulated protein spots, 118 spots were identified using MALDI-TOF/TOF and LC MS/MS. We observed that proteins involved in redox hemostasis, vitamin and energy metabolism and ubiquitin dependent proteolysis were more abundant in differentiated cells, whereas the abundance of proteins associated with RNA processing and protein folding was higher in hESCs. Higher abundance of proteins involved in maintaining cellular redox state suggests the importance of redox hemostasis in neural differentiation. Furthermore, our results support the concept of a coupling mechanism between neuronal activity and glucose utilization. The protein network analysis showed that the majority of the interacting proteins were associated with the cell cycle and cellular proliferation. These results enhanced our understanding of the molecular dynamics that underlie neural commitment and differentiation.

BIOLOGICAL SIGNIFICANCE

In highlighting the role of redox and unique metabolic properties of neuronal cells, the present findings add insight to our understanding of hESC differentiation to neurons. The abundance of fourteen proteins involved in maintaining cellular redox state, including 10 members of peroxiredoxin (Prdx) family, mainly increased during differentiation, thus highlighting a link of neural differentiation to redox. Our results revealed markedly higher expression of genes encoding enzymes involved in the glycolysis and amino acid synthesis during differentiation. Protein network analysis predicted a number of critical mediators in hESC differentiation. These proteins included TP53, CTNNB1, SMARCA4, TNF, TERT, E2F1, MYC, RB1, and AR.

Janus-like role of fibroblast growth factor 2 in arteriosclerotic coronary artery disease: atherogenesis and angiogenesis

Angiogenic stimulation is a promising new strategy for treating patients with arteriosclerotic coronary artery disease. This strategy aims to ameliorate cardiac function by improving myocardial perfusion and lowering the risk of myocardial infarction. However, angiogenesis may contribute to the growth of atherosclerotic lesions. Atherogenesis is also a potential side effect of angiogenic therapy. Early clinical trials were performed using fibroblast growth factor 2 (FGF2) protein, which enhances the formation of new collateral vessels to reduce ischaemic symptoms. Conversely, angiogenic stimulation by FGF2 is a dilemma because it could cause negative angiogenic effects, such as atherosclerosis. Thus far, clinical trials in patients with recombinant FGF2 protein therapy have not yet yielded undisputable beneficial effects. Future trials should determine whether an improvement can be obtained in patients with coronary artery disease using a combination of FGF2 and other growth factors or a combination of the FGF2 gene and stem cell therapy. This review summarises the multiple roles of FGF2 in the progression of atherosclerosis, its effect on pro-angiogenesis and improvement of cardiac function in coronary artery disease, and the potentially unfavourable effect of angiogenesis on the prevention and treatment of atherogenesis.

Ionizing radiation potentiates dihydroartemisinin-induced apoptosis of A549 cells via a caspase-8-dependent pathway

This report is designed to explore the molecular mechanism by which dihydroartemisinin (DHA) and ionizing radiation (IR) induce apoptosis in human lung adenocarcinoma A549 cells. DHA treatment induced a concentration- and time-dependent reactive oxygen species (ROS)-mediated cell death with typical apoptotic characteristics such as breakdown of mitochondrial membrane potential (Δψm), caspases activation, DNA fragmentation and phosphatidylserine (PS) externalization. Inhibition of caspase-8 or -9 significantly blocked DHA-induced decrease of cell viability and activation of caspase-3, suggesting the dominant roles of caspase-8 and -9 in DHA-induced apoptosis. Silencing of proapoptotic protein Bax but not Bak significantly inhibited DHA-induced apoptosis in which Bax but not Bak was activated. In contrast to DHA treatment, low-dose (2 or 4 Gy) IR induced a long-playing generation of ROS. Interestingly, IR treatment for 24 h induced G2/M cell cycle arrest that disappeared at 36 h after treatment. More importantly, IR synergistically potentiated DHA-induced generation of ROS, activation of caspase-8 and -3, irreparable G2/M arrest and apoptosis, but did not enhance DHA-induced loss of Δψm and activation of caspase-9. Taken together, our results strongly demonstrate the remarkable synergistic efficacy of combination treatment with DHA and low-dose IR for A549 cells in which IR potentiates DHA-induced apoptosis largely by enhancing the caspase-8-mediated extrinsic pathway.

Cell stress proteins in atherothrombosis

Cell stress proteins (CSPs) are a large and heterogenous family of proteins, sharing two main characteristics: their levels and/or location are modified under stress and most of them can exert a chaperon function inside the cells. Nonetheless, they are also involved in the modulation of several mechanisms, both at the intracellular and the extracellular compartments. There are more than 100 proteins belonging to the CSPs family, among them the thioredoxin (TRX) system, which is the focus of the present paper. TRX system is composed of several proteins such as TRX and peroxiredoxin (PRDX), two thiol-containing enzymes that are key players in redox homeostasis due to their ability to scavenge potential harmful reactive oxygen species. In addition to their main role as antioxidants, recent data highlights their function in several processes such as cell signalling, immune inflammatory responses, or apoptosis, all of them key mechanisms involved in atherothrombosis. Moreover, since TRX and PRDX are present in the pathological vascular wall and can be secreted under prooxidative conditions to the circulation, several studies have addressed their role as diagnostic, prognostic, and therapeutic biomarkers of cardiovascular diseases (CVDs).

Cardiomyocyte specific ablation of p53 is not sufficient to block doxorubicin induced cardiac fibrosis and associated cytoskeletal changes

Doxorubicin (Dox) is an anthracycline used to effectively treat several forms of cancer. Unfortunately, the use of Dox is limited due to its association with cardiovascular complications which are manifested as acute and chronic cardiotoxicity. The pathophysiological mechanism of Dox induced cardiotoxicity appears to involve increased expression of the tumor suppressor protein p53 in cardiomyocytes, followed by cellular apoptosis. It is not known whether downregulation of p53 expression in cardiomyocytes would result in decreased rates of myocardial fibrosis which occurs in response to cardiomyocyte loss. Further, it is not known whether Dox can induce perivascular necrosis and associated fibrosis in the heart. In this study we measured the effects of acute Dox treatment on myocardial and perivascular apoptosis and fibrosis in a conditional knockout (CKO) mouse model system which harbours inactive p53 alleles specifically in cardiomyocytes. CKO mice treated with a single dose of Dox (20 mg/kg), did not display lower levels of myocardial apoptosis or reactive oxygen and nitrogen species (ROS/RNS) compared to control mice with intact p53 alleles. Interestingly, CKO mice also displayed higher levels of interstitial and perivascular fibrosis compared to controls 3 or 7 days after Dox treatment. Additionally, the decrease in levels of the microtubule protein α-tubulin, which occurs in response to Dox treatment, was not prevented in CKO mice. Overall, these results indicate that selective loss of p53 in cardiomyocytes is not sufficient to prevent Dox induced myocardial ROS/RNS generation, apoptosis, interstitial fibrosis and perivascular fibrosis. Further, these results support a role for p53 independent apoptotic pathways leading to Dox induced myocardial damage and highlight the importance of vascular lesions in Dox induced cardiotoxicity.