Dantrolene Attenuates Cardiotoxicity of Doxorubicin Without Reducing its Antitumor Efficacy in a Breast Cancer Model

Dysregulation of calcium homeostasis is a major mechanism of doxorubicin (DOX)-induced cardiotoxicity. Treatment with DOX causes activation of sarcoplasmic reticulum (SR) ryanodine receptor (RYR) and rapid release of Ca²⁺ in the cytoplasm resulting in depression of myocardial function. The aim of this study was to examine the effect of dantrolene (DNT) a RYR blocker on both the cardiotoxicity and antitumor activity of DOX in a rat model of breast cancer. Female F344 rats with implanted MAT B III breast cancer cells were randomized to receive intraperitoneal DOX twice per week (12 mg/kg total dose), 5 mg/kg/day oral DNT or a combination of DOX + DNT for 3 weeks. Echocardiography and blood troponin I levels were used to measure myocardial injury. Hearts and tumors were evaluated for histopathological alterations. Blood glutathione was assessed as a measure of oxidative stress. The results showed that DNT improved DOX-induced alterations in the echocardiographic parameters by 50%. Histopathologic analysis of hearts showed reduced DOX induced cardiotoxicity in the group treated with DOX + DNT as shown by reduced interstitial edema, cytoplasmic vacuolization, and myofibrillar disruption, compared with DOX-only–treated hearts. Rats treated with DNT lost less body weight, had higher blood GSH levels and lower troponin I levels than DOX-treated rats. These data indicate that DNT is able to provide protection against DOX cardiotoxicity without reducing its antitumor activity. Further studies are needed to determine the optimal dosing of DNT and DOX in a tumor-bearing host.     

Caveolin-2-deficient mice show increased sensitivity to endotoxemia

Caveolin proteins are structural components of caveolae and are involved in the regulation of many biological processes. Recent studies have shown that caveolin-1 modulates inflammatory responses and is important for sepsis development. In the present study, we show that caveolin-1 and caveolin-2 have opposite roles in lipopolysaccharide (LPS)-induced sepsis using caveolin-deficient (Cav-1^-/- and Cav-2^-/-) mice for each of these proteins. While Cav-1^-/- mice displayed delayed mortality following challenge with LPS, Cav-2^-/- mice were more sensitive to LPS compared to wild-type (WT). With Cav-2^-/- mice, this effect was associated with increased intestinal injury and increased intestinal permeability. This negative outcome was also correlated with enhanced expression of iNOS in epithelial intestinal cells, and enhanced production of nitric oxide (NO). By contrast, Cav-1^-/- mice demonstrated a decrease in iNOS expression with decreased NO production, but no alteration in intestinal permeability. The differential expression of iNOS was associated with a significant increase of STAT-1 activation in these mice. Intestinal cells of Cav-2^-/- mice showed increased phosphorylation of STAT-1 at tyrosine 701 compared to wild-type. However, Cav-1^-/- mice-derived intestinal cells showed decreased levels of phosphorylation of STAT-1 at tyrosine 701. Since caveolin-2 is almost completely absent in Cav-1^-/- mice, we conclude that it is not just the absence of caveolin-2 that is responsible for the observed effects, but that the balance between caveolin-1 and caveolin-2 is important for iNOS expression and ultimately for sepsis outcome.     

松果菊苷对多柔比星心脏毒性保护作用及机制研究

目的:观察松果菊苷(ECH)能否减轻多柔比星(DOX)心脏毒性并初步阐明其作用机制。方法:通过单次腹腔注射大剂量多柔比星(15 mg/kg)建立急性心脏毒性小鼠模型,DOX处理后每日通过腹腔注射ECH(50 mg/kg/day)。实验分组如下:正常组(Control组);单纯松果菊苷处理组(ECH组);多柔比星处理组(DOX组);多柔比星+松果菊苷处理组(DOX+ECH组)。给药5天后检测左心室功能、心肌组织病理改变、氧化应激和心肌凋亡情况。结果:与Control组相比,DOX组小鼠心脏收缩和舒张功能明显减弱,心肌细胞出现空泡变性,心肌MDA含量、凋亡率以及促凋亡蛋白Bax和cleaved Caspase-3表达明显增加,而抑制凋亡蛋白Bcl-2表达量、SOD与GSH-Px活性明显下降。与DOX组相比,松果菊苷能明显改善心脏功能,缓解心肌空泡变性,降低MDA含量、凋亡率以及Bax和cleaved Caspase-3表达量,而提高Bcl-2表达量、SOD与GSH-Px活性(均P 0.05)。结论:松果菊苷可以通过抑制心肌组织氧化应激损伤和凋亡缓解多柔比星诱导的急性心脏毒性。     

Caveolin-2-deficient mice show increased sensitivity to endotoxemia

Caveolin proteins are structural components of caveolae and are involved in the regulation of many biological processes. Recent studies have shown that caveolin-1 modulates inflammatory responses and is important for sepsis development. In the present study, we show that caveolin-1 and caveolin-2 have opposite roles in lipopolysaccharide (LPS)-induced sepsis using caveolin-deficient (Cav-1^-/- and Cav-2^-/-) mice for each of these proteins. While Cav-1^-/- mice displayed delayed mortality following challenge with LPS, Cav-2^-/- mice were more sensitive to LPS compared to wild-type (WT). With Cav-2^-/- mice, this effect was associated with increased intestinal injury and increased intestinal permeability. This negative outcome was also correlated with enhanced expression of iNOS in intestinal epithelial cells, and enhanced production of nitric oxide (NO). By contrast, Cav-1^-/- mice demonstrated a decrease in iNOS expression with decreased NO production, but no alteration in intestinal permeability. The differential expression of iNOS was associated with a significant increase in STAT-1 activation in these mice. Intestinal cells of Cav-2^-/- mice showed increased phosphorylation of STAT-1 at tyrosine 701 compared to wild-type. However, Cav-1^-/- mice-derived intestinal cells showed decreased levels of phosphorylation of STAT-1 at tyrosine 701. Since caveolin-2 is almost completely absent in Cav-1^-/- mice, we conclude that it is not just the absence of caveolin-2 that is responsible for the observed effects, but that the balance between caveolin-1 and caveolin-2 is important for iNOS expression and ultimately for sepsis outcome.Key words: caveolin, sepsis, nitric oxide, lipopolysaccharide, permeability, endotoxemia, inflammation     

Antioxidant and antiapoptotic effects of proanthocyanidin and ginkgo biloba extract against doxorubicin‐induced cardiac injury in rats

Grape seed proanthocyanidins (GSPE) and ginkgo biloba extract (EGb761) are considered to have protective effects against several diseases. The cardiotoxicity of doxorubicin (DOX) has been reported to be associated with oxidative damage. This study was conducted to evaluate the cardioprotective effects of GSPE and EGb761 against DOX‐induced heart injury in rats. DOX was administered as a single i.p. dose (20 mg kg^–1) to adult male rats. DOX‐intoxicated rats were orally administered GSPE (200 mg kg^–1 day^–1) or EGb761 (100 mg kg^–1 day^–1) for 15 consecutive days, starting 10 days prior DOX injection. DOX‐induced cardiotoxicity was evidenced by a significant increase in serum aspartate transaminase (AST), creatine phosphokinase isoenzyme (CK‐MB), lactate dehydrogenase (LDH), total cholesterol (TC) and triglyceride (TG) activities and levels. Increased oxidative damage was expressed by the depletion of cardiac reduced glutathione (GSH), elevation of cardiac total antioxidant (TAO) level and accumulation of the lipid peroxidation product, malondialdehyde (MDA). Significant rises in cardiac tumour necrosis factor‐alpha (TNF‐α) and caspase‐3 levels were noticed in DOX‐intoxicated rats. These changes were ameliorated in the GSPE and EGb761‐treated groups. Histopathological analysis confirmed the cardioprotective effects of GSPE and EGb761. In conclusion, GSPE and EGb761 mediate their protective effect against DOX‐induced cardiac injury through antioxidant, anti‐inflammatory and antiapoptotic mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.     

Mitochondrial ROS‐induced ERK1/2 activation and HSF2‐mediated AT1R upregulation are required for doxorubicin‐induced cardiotoxicity

Doxorubicin (DOX), one useful chemotherapeutic agent, is limited in clinical use because of its serious cardiotoxicity. Growing evidence suggests that angiotensin receptor blockers (ARBs) have cardioprotective effects in DOX‐induced cardiomyopathy. However, the detailed mechanisms underlying the action of ARBs on the prevention of DOX‐induced cardiomyocyte cell death have yet to be investigated. Our results showed that angiotensin II receptor type I (AT₁R) plays a critical role in DOX‐induced cardiomyocyte apoptosis. We found that MAPK signaling pathways, especially ERK1/2, participated in modulating AT₁R gene expression through DOX‐induced mitochondrial ROS release. These results showed that several potential heat shock binding elements (HSE), which can be recognized by heat shock factors (HSFs), located at the AT₁R promoter region. HSF2 markedly translocated from the cytoplasm to the nucleus when cardiomyocytes were damaged by DOX. Furthermore, the DNA binding activity of HSF2 was enhanced by DOX via deSUMOylation. Overexpression of HSF2 enhanced DOX‐induced cardiomyocyte cell death as well. Taken together, we found that DOX induced mitochondrial ROS release to activate ERK‐mediated HSF2 nuclear translocation and AT₁R upregulation causing DOX‐damaged heart failure in vitro and in vivo.     

Supplementation of endogenous Ahr ligands reverses insulin resistance and associated inflammation in an insulin-dependent diabetic mouse model

Aryl-hydrocarbon receptor (Ahr) plays an important role in the regulation of intestinal homeostasis.Diabetes is characterized by vascular complications and intestinal dysfunction. We aimed at understanding the relationship between intestinal defense impairment and inflammation in diabetes and effects of Ahr ligands on diabetes-induced insulin resistance, endovascular inflammation, and intercellular adhesion molecule (ICAM) and flavin mono-oxygenase (FMO3) expression. Effects of Ahr ligands, such as tryptophan (Trp) and indole-3-carbinol (I3C) on intestinal barrier and inflammation of Ins2^Akita mice were examined. Myeloid differentiation primary response 88 (MYD88) is the adaptor for inflammatory signaling pathways. Ins2^Akita-MyD88^-/- mice were used to study the role of MyD88. Ins2^Akita mice demonstrated decreased Ahr and regenerating islet-derived 3-β (Reg3β) expression, and increased Klebsiella pneumoniae translocation. Ins2^Akita mice demonstrated increased inducible nitric oxide synthase (iNOS) expression of intestine; ICAM, iNOS, interleukin 1 beta (IL-1β), and FMO3 expression of liver; and ICAM, iNOS, and FMO3 expression in aorta. Trp and I3C decreased diabetes-induced translocation and increased Ahr and Reg3β expression of intestine. Ahr ligands reduced diabetes-induced ICAM and FMO3 expression in liver and aorta; IL-6, tumor necrosis factor alpha (TNF-α), and iNOS expression in Kupffer cells; plasma IL-6 and TNF-α levels; dipeptidyl peptidase (DPP4) activity; and insulin insensitivity. Ins2^Akita-MyD88^-/- mice demonstrated decreased expression of p-NF-κB of liver and ICAM of aorta compared with Ins2^Akita mice. Altogether, our data suggest that diabetes induces ICAM and FMO3 expression through the decrease in intestinal defense and MyD88. Ahr ligands reverse diabetes-induced intestinal defense impairment, insulin insensitivity, FMO3/ICAM expression, and systemic inflammation.     

Cannabidiol Protects against Doxorubicin-Induced Cardiomyopathy by Modulating Mitochondrial Function and Biogenesis

Doxorubicin (DOX) is a widely used, potent chemotherapeutic agent; however, its clinical application is limited because of its dose-dependent cardiotoxicity. DOX’s cardiotoxicity involves increased oxidative/nitrative stress, impaired mitochondrial function in cardiomyocytes/endothelial cells and cell death. Cannabidiol (CBD) is a nonpsychotropic constituent of marijuana, which is well tolerated in humans, with antioxidant, antiinflammatory and recently discovered antitumor properties. We aimed to explore the effects of CBD in a well-established mouse model of DOX-induced cardiomyopathy. DOX-induced cardiomyopathy was characterized by increased myocardial injury (elevated serum creatine kinase and lactate dehydrogenase levels), myocardial oxidative and nitrative stress (decreased total glutathione content and glutathione peroxidase 1 activity, increased lipid peroxidation, 3-nitrotyrosine formation and expression of inducible nitric oxide synthase mRNA), myocardial cell death (apoptotic and poly[ADP]-ribose polymerase 1 [PARP]-dependent) and cardiac dysfunction (decline in ejection fraction and left ventricular fractional shortening). DOX also impaired myocardial mitochondrial biogenesis (decreased mitochondrial copy number, mRNA expression of peroxisome proliferator-activated receptor γ coactivator 1-alpha, peroxisome proliferator-activated receptor alpha, estrogen-related receptor alpha), reduced mitochondrial function (attenuated complex I and II activities) and decreased myocardial expression of uncoupling protein 2 and 3 and medium-chain acyl-CoA dehydrogenase mRNA. Treatment with CBD markedly improved DOX-induced cardiac dysfunction, oxidative/nitrative stress and cell death. CBD also enhanced the DOX-induced impaired cardiac mitochondrial function and biogenesis. These data suggest that CBD may represent a novel cardioprotective strategy against DOX-induced cardiotoxicity, and the above-described effects on mitochondrial function and biogenesis may contribute to its beneficial properties described in numerous other models of tissue injury.     

Anti‐interleukin‐5‐neutralizing antibody attenuates caradiac injury and cadiac dysfunction by aggravating the inflammatory response in doxorubicin‐treated mice

Previous studies have demonstrated that interleukins (ILs) are closely associated with doxorubicin (DOX)‐induced cardiac injury. IL‐5 is an important member of the IL family, and this study was performed to investigate whether IL‐5 affects DOX‐induced cardiac injury and its underlying mechanisms. The cardiac IL‐5 expression was first detected and the results showed that cardiac IL‐5 levels were significantly lower in DOX‐treated mice, and IL‐5 was mainly derived from cardiac macrophage (Mø). In addition, some DOX‐treated mice received an injection of anti‐IL‐5‐neutralizing antibody (nAb), and we found that treatment with a mouse anti‐IL‐5 nAb significantly upregulated the levels of myocardial injury markers, aggravated cardiac dysfunction, increased M1 macrophage (Mø1) and decreased M2 macrophage (Mø2) differentiation, and promoted apoptotic marker expression. Furthermore, the effect of mouse IL‐5 nAb on DOX‐induced Mø differentiation and its role on mouse cardiomyocyte (MCM) cells apoptosis were detected in vitro, and the results exhibited that mouse IL‐5 nAb promoted Mø1 differentiation but inhibited Mø2 differentiation in vitro and alleviated apoptosis in MCM cells. Our results found a mouse anti‐IL‐5 nAb‐aggravated DOX‐induced cardiac injury and dysfunction by alleviating the inflammatory response and myocardial cell apoptosis.     

TNF-α inhibitor protects against myocardial ischemia/reperfusion injury via Notch1-mediated suppression of oxidative/nitrative stress

TNF-α inhibitor reportedly protects against myocardial ischemia/reperfusion (MI/R) injury. It can also increase Notch1 expression in inflammatory bowel disease, revealing the regulation of Notch1 signaling by TNF-α inhibitor. However, the interaction between TNF-α inhibitor and Notch1 signaling in MI/R remains unclear. This study aimed to determine the involvement of TNF-α inhibitor with Notch1 in MI/R and delineate the related mechanism. Notch1-specific small interfering RNA (20 μg) or Jagged1 (a Notch ligand, 12 μg) was delivered through intramyocardial injection. Forty-eight hours after injection, mice received 30 min of myocardial ischemia followed by 3 h (for cell apoptosis and oxidative/nitrative stress) or 24 h (for infarct size and cardiac function) of reperfusion. Ten minutes before reperfusion, mice randomly received an intraperitoneal injection of vehicle, etanercept, diphenyleneiodonium, 1400W, or EUK134. Finally, downregulation of Notch1 significantly reversed the alleviation of MI/R injury induced by etanercept, as evidenced by enlarged myocardial infarct size, suppressed cardiac function, and increased myocardial apoptosis. Moreover, Notch1 blockade increased the expression of inducible NO synthase (iNOS) and gp^91phox, enhanced NO and superoxide production, and accelerated their cytotoxic reaction product, peroxynitrite. Furthermore, NADPH inhibition with diphenyleneiodonium or iNOS suppression with 1400W mitigated the aggravation of MI/R injury induced by Notch1 downregulation in mice treated with etanercept. Additionally, either Notch1 activation with Jagged1 or peroxynitrite decomposition with EUK134 reduced nitrotyrosine content and attenuated MI/R injury. These data indicate that MI/R injury can be attenuated by TNF-α inhibitor, partly via Notch1 signaling-mediated suppression of oxidative/nitrative stress.     

Fatty acid amide hydrolase is a key regulator of endocannabinoid-induced myocardial tissue injury

Previous studies have suggested that increased levels of endocannabinoids in various cardiovascular disorders (e.g., various forms of shock, cardiomyopathies, atherosclerosis) through the activation of CB(1) cannabinoid receptors may promote cardiovascular dysfunction and tissue injury. We have investigated the role of the main endocannabinoid anandamide-metabolizing enzyme (fatty acid amide hydrolase; FAAH) in myocardial injury induced by an important chemotherapeutic drug, doxorubicin (DOX; known for its cardiotoxicity mediated by increased reactive oxygen and nitrogen species generation), using well-established acute and chronic cardiomyopathy models in mice. The DOX-induced myocardial oxidative/nitrative stress (increased 4-hydroxynonenal, protein carbonyl, and nitrotyrosine levels and decreased glutathione content) correlated with multiple cell death markers, which were enhanced in FAAH knockout mice exhibiting significantly increased DOX-induced mortality and cardiac dysfunction compared to their wild type. The effects of DOX in FAAH knockouts were attenuated by CB(1) receptor antagonists. Furthermore, anandamide induced enhanced cell death in human cardiomyocytes pretreated with FAAH inhibitor and enhanced sensitivity to ROS generation in inflammatory cells of FAAH knockouts. These results suggest that in pathological conditions associated with acute oxidative/nitrative stress FAAH plays a key role in controlling the tissue injury that is, at least in part, mediated by the activation of CB(1) receptors by endocannabinoids.     

MicroRNA-532-3p regulates mitochondrial fission through targeting apoptosis repressor with caspase recruitment domain in doxorubicin cardiotoxicity

Doxorubicin (DOX) is a wide-spectrum antitumor drug, but its clinical application is limited by its cardiotoxicity. However, the mechanisms underlying DOX-induced cardiomyopathy remain mostly unclear. Here we observed that apoptosis repressor with caspase recruitment domain (ARC) was downregulated in mouse heart and cardiomyocytes upon DOX treatment. Furthermore, enforced expression of ARC attenuated DOX-induced cardiomyocyte mitochondrial fission and apoptosis. ARC transgenic mice demonstrated reduced cardiotoxicity upon DOX administration. DOX-induced mitochondrial fission required the activity of dynamin-related protein 1 (Drp1). In elucidating the molecular mechanism by which ARC was downregulated upon DOX treatment, miR-532-3p was found to directly target ARC and participated in DOX-induced mitochondrial fission and apoptosis. MiR-532-3p was not involved in DOX-induced apoptosis in cancer cells. Taken together, these findings provide novel evidence that miR-532-3p and ARC constitute an antiapoptotic pathway that regulates DOX cardiotoxicity. Therefore, the development of new therapeutic strategies based on ARC and miR-532-3p is promising for overcoming the cardiotoxicity of chemotherapy for cancer therapy.Doxorubicin (DOX) is one of the most widely used anticancer drugs. A large number of patients treated with DOX develop carditoxicity, which can lead to congestive heart failure.^{1, 2} The exact mechanisms of DOX cardiotoxicity remain unclear. Multiple mechanisms by which DOX-induced irreversible myocaridial injures have been proposed, including reactive oxygen species (ROS) production, lipid peroxidation, mitochondrial impairment, intracellular calcium dysregulation and direct suppression of heart-special gene expression.^{3, 4, 5} Most of these mechanisms ultimately result in the activation of apoptotic signaling, leading to progressive loss of cardiac myocytes.² Considering the limited capacity for proliferation, it is essential to understand the molecular signaling underlying DOX-induced cardiomyocyte death in order to establish interventions that can effectively prevent cardiac cell loss and, thereby, preserve cardiac function.The heart has evolutionarily developed a highly expressed antiapoptotic protein, apoptosis repressor with caspase recruitment domain (ARC).⁶ ARC was initially discovered as an endogenous apoptosis inhibitor in postmitotic cells, such as cardiomyocytes, skeletal muscle cells and neurons. It can antagonize both intrinsic and extrinsic apoptosis signaling pathways.^{6, 7, 8} ARC has a role in maintaining physiological cardiac function. Under pathological conditions, ARC is downregulated, which may contribute to the occurrence of many heart diseases, such as hypertrophy, heart failure and cardiac infraction.^{9, 10} ARC-deficient mice exerted significantly accelerated cardiomyopathy under conditions of cardiac ischemia or pressure overload.¹¹ Our previous work showed heart of cardiac-special ARC transgenic mice were more resistant to ischemia injury and hypertrophic stimuli.¹² As for DOX cardiotoxicity, it was reported that ARC was downregulated in cardiomyocytes exposed to DOX and led to a significant induction of apoptosis.⁵ Enforced expression of ARC dramatically increased the resistance of cardiomyocytes to undergo apoptotic cell death following DOX administration.⁵ But the mechanism by which ARC was downregulated during this process is largely unknown. Our previous work has also proved that highly expressed ARC contributed to cancer cell resistance to chemotherapy by targeting the mitochondrial fission machinery.¹³ However, whether ARC inhibits mitochondrial fission in cardiomyocytes upon DOX treatment remains to be investigated.MicroRNAs (miRNAs) are a class of small non-coding RNAs and negative regulators of target genes by altering mRNA translation or stability.¹⁴ MiRNAs functionally participated in a wide variety of physiological or pathological processes.¹⁵ MiRNAs can regulate cardiac function such as the conductance of electrical signal, heart muscle contraction, heart growth and morphogenesis.¹⁶ Manipulation of miRNA can be developed to therapeutic approaches. However, it is not yet clear whether miRNAs are involved in the regulation of DOX cardiotoxicity. In our previous study, we have demonstrated that miR-185 negatively regulated ARC in gastric cancer cells.¹⁷ However, whether miRNAs can regulate ARC in DOX cardiotoxicity is unknown.In this study, we focused on the function of ARC in DOX cardiotoxicity both in cardiomyocytes and mice hearts. We found that ARC was downregulated in cardiomyocytes administered DOX. Enforced expression of ARC inhibited DOX-induced mitochondrial fission and apoptosis in cardiomyocytes. Heart-special ARC transgenic mice exhibited reduced cardiotoxicity. Besides, miR-532-3p could sensitize cardiomyocytes to DOX-induced mitochondrial fission and apoptosis through negatively regulating ARC expression. Our results identified a novel regulatory pathway for apoptosis involving miR-532-3p–ARC and possibly provide a valuable insight to protect against DOX cardiotoxicity during cancer chemical therapy.     

Toll-like receptor 3 plays a role in myocardial infarction and ischemia/reperfusion injury

Innate immune and inflammatory responses mediated by Toll like receptors (TLRs) have been implicated in myocardial ischemia/reperfusion (I/R) injury. This study examined the role of TLR3 in myocardial injury induced by two models, namely, myocardial infarction (MI) and I/R. First, we examined the role of TLR3 in MI. TLR3 deficient (TLR3^−/−) and wild type (WT) mice were subjected to MI induced by permanent ligation of the left anterior descending (LAD) coronary artery for 21 days. Cardiac function was measured by echocardiography. Next, we examined whether TLR3 contributes to myocardial I/R injury. TLR3^−/− and WT mice were subjected to myocardial ischemia (45 min) followed by reperfusion for up to 3 days. Cardiac function and myocardial infarct size were examined. We also examined the effect of TLR3 deficiency on I/R-induced myocardial apoptosis and inflammatory cytokine production. TLR3^−/− mice showed significant attenuation of cardiac dysfunction after MI or I/R. Myocardial infarct size and myocardial apoptosis induced by I/R injury were significantly attenuated in TLR3^−/− mice. TLR3 deficiency increases B-cell lymphoma 2 (BCL2) levels and attenuates I/R-increased Fas, Fas ligand or CD95L (FasL), Fas-Associated protein with Death Domain (FADD), Bax and Bak levels in the myocardium. TLR3 deficiency also attenuates I/R-induced myocardial nuclear factor KappaB (NF-κB) binding activity, Tumor necrosis factor alpha (TNF-α) and Interleukin-1 beta (IL-1β) production as well as I/R-induced infiltration of neutrophils and macrophages into the myocardium. TLR3 plays an important role in myocardial injury induced by MI or I/R. The mechanisms involve activation of apoptotic signaling and NF-κB binding activity. Modulation of TLR3 may be an effective approach for ameliorating heart injury in heart attack patients.     

Knockdown of Mtfp1 can minimize doxorubicin cardiotoxicity by inhibiting Dnm1l‐mediated mitochondrial fission

The long‐term usage of doxorubicin (DOX) is largely limited due to the development of severe cardiomyopathy. Many studies indicate that DOX‐induced cardiac injury is related to reactive oxygen species generation and ultimate activation of apoptosis. The role of novel mitochondrial fission protein 1 (Mtfp1) in DOX‐induced cardiotoxicity remains elusive. Here, we report the pro‐mitochondrial fission and pro‐apoptotic roles of Mtfp1 in DOX‐induced cardiotoxicity. DOX up‐regulates the Mtfp1 expression in HL‐1 cardiac myocytes. Knockdown of Mtfp1 prevents cardiac myocyte from undergoing mitochondrial fission, and subsequently reduces the DOX‐induced apoptosis by preventing dynamin 1‐like (Dnm1l) accumulation in mitochondria. In contrast, when Mtfp1 is overexpressed, a suboptimal dose of DOX can induce a significant percentage of cells to undergo mitochondrial fission and apoptosis. These data suggest that knocking down of Mtfp1 can minimize the cardiomyocytes loss in DOX‐induced cardiotoxicity. Thus, the regulation of Mtfp1 expression could be a novel therapeutic approach in chemotherapy‐induced cardiotoxicity.     

MHC Class II–Alpha Chain Knockout Mice Support Increased Viral Replication That Is Independent of Their Lack of MHC Class II Cell Surface Expression and Associated Immune Function Deficiencies

MHCII molecules are heterodimeric cell surface proteins composed of an α and β chain. These molecules are almost exclusively expressed on thymic epithelium and antigen presenting cells (APCs) and play a central role in the development and function of CD4 T cells. Various MHC-II knockout mice have been generated including MHC-IIAα^-/- (I-Aα^-/-), MHC-IIAβ^-/- (I-β^-/-) and the double knockout (I-Aαxβ^-/-). Here we report a very striking observation, namely that alphaviruses including the avirulent strain of Semliki Forest virus (aSFV), which causes asymptomatic infection in wild-type C57BL6/J (B6) mice, causes a very acute and lethal infection in I-Aα^-/-, but not in I-β^-/- or I-Aαxβ^-/-, mice. This susceptibility to aSFV is associated with high virus titres in muscle, spleen, liver, and brain compared to B6 mice. In addition, I-Aα^-/- mice show intact IFN-I responses in terms of IFN-I serum levels and IFN-I receptor expression and function. Radiation bone marrow chimeras of B6 mice reconstituted with I-Aα^-/- bone marrow expressed B6 phenotype, whereas radiation chimeras of I-Aα^-/- mice reconstituted with B6 bone marrow expressed the phenotype of high viral susceptibility. Virus replication experiments both in vivo and in vitro showed enhanced virus growth in tissues and cell cultures derived form I-Aα^-/- compared to B6 mice. This enhanced virus replication is evident for other alpha-, flavi- and poxviruses and may be of great benefit to producers of viral vaccines. In conclusion, I-Aα^-/- mice exhibit a striking susceptibility to virus infections independent of their defective MHC-II expression. Detailed genetic analysis will be carried out to characterise the underlining genetic defects responsible for the observed phenomenon.     

Creatine Kinase-Overexpression Improves Myocardial Energetics,Contractile Dysfunction and Survival in Murine Doxorubicin Cardiotoxicity

Doxorubicin (DOX) is a commonly used life-saving antineoplastic agent that also causes dose-dependent cardiotoxicity. Because ATP is absolutely required to sustain normal cardiac contractile function and because impaired ATP synthesis through creatine kinase (CK), the primary myocardial energy reserve reaction, may contribute to contractile dysfunction in heart failure, we hypothesized that impaired CK energy metabolism contributes to DOX-induced cardiotoxicity. We therefore overexpressed the myofibrillar isoform of CK (CK-M) in the heart and determined the energetic, contractile and survival effects of CK-M following weekly DOX (5mg/kg) administration using in vivo ³¹P MRS and ¹H MRI. In control animals, in vivo cardiac energetics were reduced at 7 weeks of DOX protocol and this was followed by a mild but significant reduction in left ventricular ejection fraction (EF) at 8 weeks of DOX, as compared to baseline. At baseline, CK-M overexpression (CK-M-OE) increased rates of ATP synthesis through cardiac CK (CK flux) but did not affect contractile function. Following DOX however, CK-M-OE hearts had better preservation of creatine phosphate and higher CK flux and higher EF as compared to control DOX hearts. Survival after DOX administration was significantly better in CK-M-OE than in control animals (p<0.02). Thus CK-M-OE attenuates the early decline in myocardial high-energy phosphates and contractile function caused by chronic DOX administration and increases survival. These findings suggest that CK impairment plays an energetic and functional role in this DOX-cardiotoxicity model and suggests that metabolic strategies, particularly those targeting CK, offer an appealing new strategy for limiting DOX-associated cardiotoxicity.     

Alteration of serum and cardiac tissue adropin,copeptin, irisin and TRPM2 expressions in DOX treated male rats

Abstract

Doxorubicin (DOX) cardiotoxicity is a significant side effect in cancer survivors. DOX and its metabolites alter cardiac gene expression and affect metabolic energy-related peptides. Adropin, copeptin, irisin and TRPM2 are produced locally in the heart and play a role in energy homeostasis. We investigated the fates of adropin, copeptin, irisin and TRPM2 in serum and cardiac tissues of DOX treated rats. Animals were divided into three groups of six: 1) untreated controls, 2) DOX treated and 3) saline treated. The rats were fed a standard diet ad libitum for 14 days then were sacrificed and heart and serum samples were taken. Adropin, copeptin, irisin levels in tissue homogenates and serum were measured using ELISA. Immunoreactivity of heart tissue adropin, copeptin, irisin and TRPM2 also were investigated. The peptides increased in both serum and cardiac tissue homogenates in animals treated with DOX compared to the other groups. DOX increased adropin in endocardial and myocardial cells, but it decreased expression of copeptin. DOX did not affect endocardial irisin and TRPM2 expressions, but myocardial irisin and TRPM2 expressions were increased. Serum adropin, irisin and copeptin were increased in DOX treated rats. Cardiac adropin, copeptin, irisin and TRPM2 are affected by DOX and may play a role in DOX cardiotoxicity.     

VEGFR1-Positive Macrophages Facilitate Liver Repair and Sinusoidal Reconstruction after Hepatic Ischemia/Reperfusion Injury

Liver repair after acute liver injury is characterized by hepatocyte proliferation, removal of necrotic tissue, and restoration of hepatocellular and hepatic microvascular architecture. Macrophage recruitment is essential for liver tissue repair and recovery from injury; however, the underlying mechanisms are unclear. Signaling through vascular endothelial growth factor receptor 1 (VEGFR1) is suggested to play a role in macrophage migration and angiogenesis. The aim of the present study was to examine the role of VEGFR1 in liver repair and sinusoidal reconstruction after hepatic ischemia/reperfusion (I/R). VEGFR1 tyrosine kinase knockout mice (VEGFR1 TK^-/- mice) and wild-type (WT) mice were subjected to hepatic warm I/R, and the processes of liver repair and sinusoidal reconstruction were examined. Compared with WT mice, VEGFR1 TK^-/- mice exhibited delayed liver repair after hepatic I/R. VEGFR1-expressing macrophages recruited to the injured liver showed reduced expression of epidermal growth factor (EGF). VEGFR1 TK^-/- mice also showed evidence of sustained sinusoidal functional and structural damage, and reduced expression of pro-angiogenic factors. Treatment of VEGFR1 TK^-/- mice with EGF attenuated hepatoceullar and sinusoidal injury during hepatic I/R. VEGFR1 TK^-/- bone marrow (BM) chimeric mice showed impaired liver repair and sinusoidal reconstruction, and reduced recruitment of VEGFR1-expressing macrophages to the injured liver. VEGFR1-macrophages recruited to the liver during hepatic I/R contribute to liver repair and sinusoidal reconstruction. VEGFR1 activation is a potential therapeutic strategy for promoting liver repair and sinusoidal restoration after acute liver injury.