Loss Of Myofibrils Research Articles

Oxytocin protects cardiomyocytes from apoptosis induced by ischemia–reperfusion in rat heart: Role of mitochondrial ATP-dependent potassium channel and permeability transition pore

The current study examines the protective effect of oxytocin (OT) on cardiomyocyte apoptosis modulated by mitochondrial ATP-dependent potassium (mitoKATP) channel and permeability transition pore (mPTP) in the preconditioned myocardium of anesthetized rats. Eighty rats were equally divided into eight groups. The hearts of all animals except for the sham group were subjected to 25min ischemia and 120min reperfusion. Oxytocin, 5-hydroxydeconoate (5-HD), a specific inhibitor of the mitoKATP channel, and atractyloside (ATRC), an mPTP opener, were used prior to ischemia. Hemodynamic parameters were recorded throughout the experiment. Evaluations were made by infarct size, plasma lactate dehydrogenase level (LDH), transmission electron microscopy (TEM) and immunohistochemistry studies. OT prevented mean arterial pressure drop during early phase of ischemia and reperfusion. Treatment with OT before IR induction normalizes cardiomyocytes both in light microscopy and TEM observations. In addition, OT significantly reduced TUNEL- and increased Bcl-2-labeled positive cell number relative to IR (p<0.05). However, 5HD or ATRC inhibited the protective effects of OT on cardiomyocytes damaged by IR (p<0.05). Ultrastructural changes including extensive myofibril loss, sarcolemmal disruption and mitochondrial swelling due to amorphous dens bodies indicate necrosis induction in 5HD and ATRC as well as in IR groups. Restoration of immunohistochemistry parameters and protection against IR-induced ultrastructural changes confirm OT cardioprotective effects via mitoKATP channel and mPTP modulation in apoptosis induced by ischemia–reperfusion.

Transforming growth factor-β and oxidative stress mediate tachycardia-induced cellular remodelling in cultured atrial-derived myocytes

Atrial fibrillation (AF), a common tachyarrhythmia in clinical practice, is associated with increased oxidative stress. Structural remodelling in atrial myocytes, including myofibril degradation, is an important characteristic of AF. However, the mechanism underlying AF-induced cellular structural remodelling remains unclear. The aim of this study was to investigate the role of oxidative stress and related factors in tachycardia-induced atrial structural remodelling. Cultured atrial-derived myocytes (HL-1 cell line) were subjected to electrical stimulation. Immunofluorescence and immunoblotting were used to evaluate oxidative stress, myofibril degradation, and transforming growth factor-β (TGF-β) expression. Tachypacing in HL-1 cells induced TGF-β expression, pronounced oxidative stress including up-regulation of NADPH oxidases (Nox2/4), and myofibril degradation. Oxidative stress scavenger, NADPH oxidase inhibitors, and small-interfering RNAs for Nox2/4 blocked tachypacing-induced myofibril degradation, suggesting that Nox-derived oxidative stress may lead to tachycardia-induced myofibril degradation. Blockade of TGF-β signalling by neutralizing TGF-β antibodies attenuated myofibril loss in response to tachypacing, implicating autocrine and/or paracrine roles for TGF-β in such effects. Tachypacing also induced the activation of p-Smad3 (an effective mediator of TGF-β) and small-interfering RNAs for Nox2/4 attenuated its activation, supporting a crosstalk between both signalling pathways. Furthermore, TGF-β expression, oxidative stress, and myofibril loss were greater in the atria of patients with AF than those with sinus rhythm. Rapid activation in atrial myocytes promotes myofibril degradation through autocrine/paracrine TGF-β signalling and increased oxidative stress. These findings provide an important mechanistic insight into AF-related structural remodelling.

Rosiglitazone and pioglitazone aggravate doxorubicin-induced cardiomyopathy in Wistar rats

Recently the cardiovascular safety of thiazolidinediones (TZDs) has been questioned. This study was designed to assess the effect of rosiglitazone (ROSI 5 mg/kg p.o.) and pioglitazone (PIO 10 mg/kg p.o.) on doxorubicin (DOX 15 mg/kg i.p. single dose) induced cardiomyopathy in Wistar rats. DOX (15 mg/kg i.p. single dose) induced cardiomyopathy was evidenced by a significant ( p < 0.001) increase in serum lactate dehydrogenase (LDH), cholesterol profile, thiobarbituric acid reactive substance (TBARS), catalase (CAT) levels and a significant ( p < 0.001) decrease in glutathione and superoxide dismutase levels followed by histopathological and transmission electron microscopic changes. Rosiglitazone (5 mg/kg p.o.) and pioglitazone (10 mg/kg p.o.) were administered for 14 days and doxorubicin (15 mg/kg i.p. single dose) was injected on the 10th day of drug treatment. The biochemical estimations revealed that treatment with both these drugs significantly ( p < 0.001) increased the serum LDH, cardiac TBARS and catalase levels, while the antioxidant enzyme levels of glutathione and superoxide dismutase were reduced. The administration of rosiglitazone significantly ( p < 0.001) reduced the level of serum high density lipoprotein (HDL) and raised the level of low density lipoprotein (LDL) while pioglitazone treatment had shown entirely opposite trend; significantly ( p < 0.001) increased HDL level and lowered the LDL level. The transmission electron microscopy and histopathology of rat's cardiac tissue, however, revealed that treatment with both these drugs caused extensive damage to the myocardium as evidenced by condensed chromatin marginates, loss of myofibrils and vacuolization and aggravated doxorubicin-induced cardiomyopathy.

Rosiglitazone and pioglitazone aggravate doxorubicin-induced cardiomyopathy in Wistar rats

Recently the cardiovascular safety of thiazolidinediones (TZDs) has been questioned. This study was designed to assess the effect of rosiglitazone (ROSI 5 mg/kg p.o.) and pioglitazone (PIO 10 mg/kg p.o.) on doxorubicin (DOX 15 mg/kg i.p. single dose) induced cardiomyopathy in Wistar rats. DOX (15 mg/kg i.p. single dose) induced cardiomyopathy was evidenced by a significant ( p < 0.001) increase in serum lactate dehydrogenase (LDH), cholesterol profile, thiobarbituric acid reactive substance (TBARS), catalase (CAT) levels and a significant ( p < 0.001) decrease in glutathione and superoxide dismutase levels followed by histopathological and transmission electron microscopic changes. Rosiglitazone (5 mg/kg p.o.) and pioglitazone (10 mg/kg p.o.) were administered for 14 days and doxorubicin (15 mg/kg i.p. single dose) was injected on the 10th day of drug treatment. The biochemical estimations revealed that treatment with both these drugs significantly ( p < 0.001) increased the serum LDH, cardiac TBARS and catalase levels, while the antioxidant enzyme levels of glutathione and superoxide dismutase were reduced. The administration of rosiglitazone significantly ( p < 0.001) reduced the level of serum high density lipoprotein (HDL) and raised the level of low density lipoprotein (LDL) while pioglitazone treatment had shown entirely opposite trend; significantly ( p < 0.001) increased HDL level and lowered the LDL level. The transmission electron microscopy and histopathology of rat's cardiac tissue, however, revealed that treatment with both these drugs caused extensive damage to the myocardium as evidenced by condensed chromatin marginates, loss of myofibrils and vacuolization and aggravated doxorubicin-induced cardiomyopathy.

Arg/Abl‐binding protein, a Z‐body and Z‐band protein, binds sarcomeric, costameric, and signaling molecules

ArgBP2 (Arg/Abl-Binding Protein) is expressed at high levels in the heart and is localized in the Z-bands of mature myofibrils. ArgBP2 is a member of a small family of proteins that also includes vinexin and CAP (c-Cbl-associated protein), all characterized by having one sorbin homology (SOHO) domain and three C-terminal SH3 domains. Antibodies directed against ArgBP2 also react with the Z-bodies of myofibril precursors: premyofibrils and nascent myofibrils. Expression in cardiomyocytes of plasmids encoding Yellow Fluorescent Protein (YFP) fused to either full length ArgBP2, the SOHO, mid-ArgBP or the SH3 domains of ArgBP2 led to Z-band targeting of the fusion proteins, whereas an N-terminal fragment lacking these domains did not target to Z-bands. Although ArgBP2 is not found in skeletal muscle cells, YFP-ArgBP2 did target to Z-bodies and Z-bands in cultured myotubes. GST-ArgBP2-SH3 bound actin, α-actinin and vinculin proteins in blot overlays, cosedimentation assays, and EM negative staining techniques. Over-expression of ArgBP2 and ArgBP2-SH3 domains, but not YFP alone, led to loss of myofibrils in cardiomyocytes. Fluorescence recovery after photobleaching was used to measure the rapid dynamics of both the full length and some truncated versions of ArgBP2. Our results indicate that ArgBP2 may play an important role in the assembly and maintenance of myofibrils in cardiomyocytes.

Sudden Death in a Dog After Doxorubicin Chemotherapy

A case is reported of fatal cardiomyopathy in an 8-year-old female German Shepherd after standard chemotherapy with doxorubicin for splenic hemangiosarcoma. The main gross lesion was a moderate bilateral cardiac ventricular dilation with diffusely pale myocardium. Histological analysis revealed severe multifocal vacuolar degeneration of cardiomyocytes, myocytolysis, myofibril loss, myocardial fibrosis, and edema. Myocardial fiber vacuolization and myocytolysis were highly suggestive of doxorubicin cardiotoxicity.

Influence of Ionizing Radiation on Echis pyramidium Snake Venom: Biochemical and Immunological Aspects

The effect of a single LD50 dose of native Echis pyramidum venom (27.69μg/mouse) on the activities of certain serum enzymes levels: aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), urea, creatinine, lactate dehydrogenase (LDH), creatine phosphokinase (CPK), creatine kinase isoenzyme (CK-MB) were studied. Samples from the serum were collected 4hr following LD50 venom dose intraperitonealy injected in male Swiss albino mice. The activities of these enzymes showed significant elevation compared to the non-envenomated group. In contrast, an equivalent dose of 1.5 kGy γ irradiated Echis pyramidum venom (27.69g/mouse) did not cause any significant increase compared to non-envenomated group. The effect of a dose that is equivalent to 1⁄2 LD50 (13.8 μg/50 μl) of native Echis pyramidum venom on plasma creatine phosphokinase (CPK) induced a significant increase of creatine phosphokinase (CPK) level compared to normal control (P<0.01). In contrast, an equivalent dose of 1.5 kGy γ irradiated Echis pyramidum venom showed non significant difference in creatine phosphokinase activity when compared to the normal control. Light microscopic examinations of gastrocenemius muscles of mice injected with native Echis pyramidum venom (1⁄2 LD50; 13.8μg/50μl) showed fragmentation, disorganization, loss of myofibrils in some of the muscle fibers, hemorrhage in-between the muscle fibers and mononuclear cellular infiltration. While light microscopic examinations of gastrocenemius muscles of mice injected with 1.5 kGy γ irradiated Echis pyramidum venom (13.8μg/50μl; a dose identical to that used from native venom) showed that most muscle fibers were of normal appearance except for small area of fragmentation and disorganized myofibrils and oedema of the intercellular connective tissue. Double immunodiffusion test revealed a similar reactivity for native, 1 kGy, 1.5 kGy and 3 kGy γ irradiated Echis pyramidum venoms against a commercial polyvalent Egyptian antivenin. The visible lines obtained in the immunodiffusion reactions were identical and joined smoothly at the corners, indicating that there was no change in their antigenic reactivity. These results demonstrate that the ability of the venom antigens to react with its corresponding antibodies was maintained in spite of being exposed to radiation doses of 1 kGy, 1.5 kGy and 3 kGy. Both antivenins raised against native or 1.5 kGy γ irradiated venoms recognized Echis pyramidum venom when submitted to protein blotting, but the anti 1.5 kGy γ irradiated venom show a higher intensity bands than the antivenin raised against native Echis pyramidum venom, in spite of having less neutralizing activity (native neutralize 50 LD50, 1.5 kGy γ irradiated neutralize 40 LD50), this indicates that antibodies were formed not only for toxic fraction but also for non toxic fraction. Irradiation of the whole Echis Pyramidium Venom with 1.5KGy reduced its lethality 12.5 times though keeping its immunogenicity. The 1.5KGy dose was shown to be the best radiation dose to promote detoxification without significantly affecting its immunogenicity. Thus results of this study confirm the conclusion that γ radiation is a suitable way to detoxify Echis Pyramidium Venom without affecting its immunogenicity provided that proper dose is used.

Biopsy-proven myocardial sequels in Kawasaki disease with giant coronary aneurysms

Although most Kawasaki disease with giant coronary aneurysms is asymptomatic, conventional investigations might not identify previous lesions, or all Kawasaki disease with giant aneurysms at risk of future myocardial lesions. We evaluated the long-term histopathology of the myocardium, especially of intramural small vessels in asymptomatic Kawasaki disease with giant aneurysms. The initial study comprised 16 consecutive Kawasaki patients - male-to-female ratio was 12:4 - aged from 2 to 12 years, and in the subsequent study, the same patients were aged from 4.9 to 16 years. Endomyocardial biopsies were histopathologically evaluated. Microangiopathies, mitochondrial abnormalities, and loss or disarray of myofibrils were compared by electron microscopy. The incidence of histopathological abnormalities such as degeneration, hypertrophy, and inflammatory cell infiltration was quite high in the initial study, and inflammatory cell infiltration, interstitial fibrosis, and disarray were very noticeable at follow-up biopsies. The area of fibrous tissue was significantly higher in patients administered with intravenous immunoglobulin at follow-up biopsies. Electron microscopy showed microangiopathies including microthrombi within intramural small vessels in some patients at follow-up biopsies. The sites of the coronary aneurysms did not seem to have an impact on the biopsy findings, suggesting that the underlying pathophysiology is related to the original disease process. Whether the abnormalities were due to direct myocardial injury, chronic ischaemia, repeated small-vessel thrombosis, or other problems associated only with biopsies, is difficult to determine. However, this subgroup had residual abnormal lesions in the myocardium. Follow-up should be more aggressive in this group of patients to identify myocardial damage that could be asymptomatic.

Upstream therapy in atrial fibrillation: Traveling up the river to find the source

Like other arrhythmias, atrial fibrillation (AF) is most often treated with direct ion channel blockers or catheter ablation. In many patients, however, a “structural substrate” of AF predominates a “pure electrical substrate.” The structural substrate of AF is due to preexistent underlying heart disease, aging, or the arrhythmia itself. Biopsies in patients with AF revealed that structural changes consist of extracellular matrix changes (fibrosis, inflammation, amyloidosis) and cellular changes (hypertrophy, loss of myofibrils and replacement with glycogen, changes in size and shape of mitochondria). 1 Ausma J. van der Velden H.M. Lenders M.H. et al. Reverse structural and gap-junctional remodeling after prolonged atrial fibrillation in the goat. Circulation. 2003; 107: 2051-2058 Crossref PubMed Scopus (189) Google Scholar , 2 Li D. Shinagawa K. Pang L. et al. Effects of angiotensin-converting enzyme inhibition on the development of the atrial fibrillation substrate in dogs with ventricular tachypacing-induced congestive heart failure. Circulation. 2001; 104: 2608-2614 Crossref PubMed Scopus (604) Google Scholar The above changes may lead to heterogeneity in electrical properties such as areas of conduction slowing, zones of conduction block, and zones of (electrical) scarring, making the atria prone to the development of AF. 2 Li D. Shinagawa K. Pang L. et al. Effects of angiotensin-converting enzyme inhibition on the development of the atrial fibrillation substrate in dogs with ventricular tachypacing-induced congestive heart failure. Circulation. 2001; 104: 2608-2614 Crossref PubMed Scopus (604) Google Scholar The development of the structural substrate for AF may take years and even decades. These findings suggest that there is a considerable window of opportunity for preventing the onset or modifying the natural course of AF. Possible candidate drugs that interfere with structural remodeling are those interacting with fibrogenesis and inflammation: blockers of the renin-angiotensin pathway, statins, and polyunsaturated fatty-acids (PUFA), as described in the present paper. 3 Ramadeen A. Laurent G. dos Santos C. et al. n-3 Polyunsaturated fatty acids alter expression of fibrotic and hypertrophic genes in a dog model of atrial cardiomyopathy. Heart Rhythm. 2010; 7: 520-528 Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar

Heat Stress in Rat Adriamycin Cardiomyopathy: Heat Shock Protein 25 and Myosin Accumulation

In order to evaluate the effects of hyperthermia on adriamycin cardiomyopathy and its relationship with heat shock protein induction and myosin accumulation, female Sprague-Dawley rats (21–24 days) were randomized into four groups: the control, adriamycin, temperature and temperature-adriamycin groups. Adriamycin was injected i.v. at a dose of 27 mg/Kg (0.1 ml). The rats were exposed to a temperature of 45ºC for 35 min, followed by a recovery (1 h) at room temperature prior to adriamycin treatment. Body weight was recorded weekly. The thickness of the ventricular wall and percentage of cellular damage were biometrically and ultrastructurally evaluated, respectively. Heat shock protein 25 and myosin accumulation were determined through Western blot analysis. The determinations were carried out monthly until the third month after treatment. At eight and twelve weeks after treatment, the thickness of the ventricular wall seemed to decrease in the adriamycin-treated rats in relation to the other groups. An electron microscopic analysis of the adriamycin group’s left ventricular wall samples, showed more sarcomeric changes and loss of myofibrils than the control, temperature and temperature-adriamycin groups. At 24 hours after treatment with adriamycin, higher levels of heat shock protein 25 and myosin were observed (week 0) in the temperature-adriamycin group than in the control and adriamycin groups (4, 8 and 12 weeks). Hyperthermia was confirmed by a multivariate approach to induce heat shock protein 25 and myosin, which would strengthen cardiac-sarcomeric myosin arrangement.

Role of Sarcomere Disruption in Stretch-Induced Force Loss of Myofibrils

Stretching of activated skeletal muscle results in loss of force. In the absence of direct evidence, it is often assumed that sarcomere disruption is the cause of stretch-induced force loss. We stretched mechanically isolated rabbits psoas myofibrils on the descending limb of the length-tension relationship and asked the specific questions: does sarcomere disruption occur and does it affect the magnitude of stretch-induced force loss? Myofibrils were mounted on an inverted microscope with one end attached to a glass micro needle and the other to a silicon nitrate force lever. Myofibrils (n=11) were maximally activated at an average resting sarcomere length of 2.8 ± 0.2 μm. At peak isometric stress (234 ± 92 kN m−2), myofibrils were stretched by 34.3 ± 5.2 % at a speed of 3.3 % s−1 and immediately returned to the reference lengths at the same speed. Myofibrils were subsequently relaxed and re-activated after 3-5 minutes of rest to reassess post-stretch stress. Post-stretch isometric stress was reduced by 34 ± 9.6 % compared with pre-stretch stress. Eight out of 11 myofibrils had no sarcomere disruption after stretching while the remaining 3 myofibrils had a small percentage of sarcomeres pulled beyond filament overlap suggesting sarcomere disruption. The average stress reduction in the disrupted and non-disrupted myofibrils was the same (27 ± 13 % vs 36 ± 8%; p = 0.83). We conclude from these results that stretch-induced loss of force in myofibrils can occur in the absence of sarcomere disruption, and that sarcomere disruption does not increase force loss following myofibril stretch.

A comparative study of myocardial function and morphology during fasting/refeeding and food restriction in rats

This study compared the influence of fasting/refeeding cycles and food restriction on rat myocardial performance and morphology. Sixty-day-old male Wistar rats were submitted to food ad libitum (C), 50% food restriction (R50), and fasting/refeeding cycles (RF) for 12 weeks. Myocardial function was evaluated under baseline conditions and after progressive increase in calcium and isoproterenol. Myocardium ultrastructure was examined in the papillary muscle. Fasting/refeeding cycles maintained rat body weight and left ventricle weight between control and food-restricted rats. Under baseline conditions, the time to peak tension (TPT) was more prolonged in R50 than in RF and C rats. Furthermore, the maximum tension decline rate (-dT/dt) increased less in R50 than in RF with calcium elevation. While the R50 group showed focal changes in many muscle fibers, such as the disorganization or loss of myofilaments, polymorphic mitochondria with disrupted cristae, and irregular appearance or infolding of the plasma membrane, the RF rats displayed few alterations such as loss or disorganization of myofibrils. Food restriction promotes myocardial dysfunction, not observed in RF rats, and higher morphological damage than with fasting/refeeding. The increase in TPT may be attributed possibly to the disorganization and loss of myofibrils; however, the mechanisms responsible for the alteration in -dT/dt in R50 needs to be further clarified.

Dose-dependent antioxidant responses and pathological changes in tenca ( Tinca tinca) after acute oral exposure to Microcystis under laboratory conditions

The effects of cyanobacterial cells containing microcystins (MCs), toxins from cyanobacteria, on oxidative stress biomarkers from liver and kidney of Tenca fish ( Tinca tinca) were investigated under laboratory conditions. Moreover, a histopathological study of liver, kidney, heart and intestine tissues was performed. Fish were orally exposed to cyanobacterial cells dosing 0, 5, 11, 25 and 55 μg MC-LR/fish mixed with the food. Results showed a dose-dependent decrease of superoxide dismutase (SOD) activity, and also of catalase (CAT) in the liver. Glutathione levels and protein oxidation, however, were not altered by the exposure to the cyanobacterial material. The microscopic study revealed tissue alterations even at the lower cyanobacterial cells doses. Onion-like hepatocytes in the liver, glomerulopathy in the kidney, loss of myofibrils in the heart and vacuolated enterocytes in the gastrointestinal tract were the main changes observed. These findings suggest that this fresh water fish can be adversely affected by cyanobacterial blooms in their natural habitats.

Detection and imaging of non-contractile inclusions and sarcomeric anomalies in skeletal muscle by second harmonic generation combined with two-photon excited fluorescence

The large size of the multinucleated muscle fibers of skeletal muscle makes their examination for structural and pathological defects a challenge. Sections and single fibers are accessible to antibodies and other markers but imaging of such samples does not provide a three-dimensional view of the muscle. Regrettably, bundles of fibers cannot be stained or imaged easily. Two-photon microscopy techniques overcome these obstacles. Second harmonic generation (SHG) by myosin filaments and two-photon excited fluorescence (2PEF) of mitochondrial and lysosomal components provides detailed structural information on unstained tissue. Furthermore, the infrared exciting light can penetrate several layers of muscle fibers and the minimal processing is particularly valuable for fragile biopsies. Here we demonstrate the usefulness of SHG, combined with 2PEF, to reveal enlarged lysosomes and accumulations of non-contractile material in muscles from the mouse model for the lysosomal storage disorder Pompe disease (PD), and in biopsies from adult and infant PD patients. SHG and 2PEF also detect sarcomeric defects that may presage the loss of myofibrils in atrophying muscle and signify loss of elasticity. The combination of SHG and 2PEF should be useful in the analysis and diagnosis of a wide range of skeletal muscle pathologies.

Diffuse-regressive alterations and apoptosis of myocytes: Possible causes of myocardial dysfunction in HIV-related cardiomyopathy

ObjectiveTo determine the frequency of cardiac alterations in necropsies of AIDS patients in pre-HAART era and better understand the pathogenesis of HIV-related cardiomyopathy. DesignRetrospective study of 94 complete necropsies. MethodMacroscopic, histopathologic (histochemical, immunohistochemical and in situ hybridization techniques) and ultra structural myocardial evaluation (23 cases). ResultsCardiac alterations were observed in 94.4%; 74% showed variable degrees of cardiac dilation not related to known cardiovascular diseases. Eighty-two percent (81.8%) of patients with biventricular dilation showed diffuse-regressive alterations (thinning and waving cardiomyocytes with increase of lipofuscin pigment granules). Myocarditis was diagnosed in 27 cases (28.7%), 16 (59.3%) of known etiology. The ultra structural study has revealed cardiomyocytes alterations (mitochondriosis, loss of myofibrils, increase in the amount of perinuclear-lipofuscin pigment granules) associated to activation signals of capillary-endothelial cells (enhancement of pseudopodia and transcellular channels). Cardiomyocytes' apoptosis was demonstrated at structural level in 10 (43.5%) patients; tumor necrosis factor α (TNF α) was detected in 17/18 cases. ConclusionsThis pioneer study described the association of histopathological and ultra structural findings (thinning and waving cardiomyocytes with increase of lipofuscin pigment granules, mitochondriosis and loss of myofibrils) with different degrees of cardiac-chamber dilation probably representing a spectrum of alterations that would lead to myocardial dysfunction and development of HIV-related cardiomyopathy. Cardiomyocytes' apoptosis observed at ultra structural level and demonstration of TNF α associated to described alterations suggest that this cytokine plays an important role in both negative-inotropic effect and capacity to induce apoptosis through death receptor-controlled pathway.

Intracardiac lipid accumulation, lipoatrophy of muscle cells and expansion of myocardial infarction in type 2 diabetic patients

The overall mortality of diabetic patients after myocardial infarction is 3–4 times higher than non-diabetics. The cellular mechanisms underlying such a poor clinical prognosis remain incompletely understood. Recent reports suggest that lipotoxicity associated with impaired liporegulation is among the leading factors in the pathogenesis of type 2 diabetes. The goal of this study was to investigate whether excess lipid accumulation specifically in heart muscle cells contributes to the expansion of myocardial infarction in type 2 diabetic patients. Comparative structural analysis of cardiac tissue was performed on autopsy samples from the infracted hearts of diabetic and non-diabetic individuals with special reference to the expansion of the infarction, degenerative changes, lipoatrophy, cell death, and replacement fibrosis. We found that progressive accumulation of lipids in cardiac myocytes was accompanied by considerable loss of myofibrils and was frequently observed in the heart tissue of type 2 diabetic patients. This indicates that disassembly of the contractile apparatus in the cells infiltrated with lipids weakens their capability for functional activity. Analysis of degenerative changes in the diabetic tissue has shown that lipid-laden cardiac myocytes were more susceptible to necrotic and apoptotic cells death leading to expansion of the infarction and the development of progressive focal replacement fibrosis both in the perinecrotic zone and in the areas located far from the site of injury. Our data show that lipoatrophy and loss of muscle cells during the post-infarction period aggravate the functional impairment in the diabetic heart and limits its adaptive capacity for compensatory remodeling. This suggests that lipotoxic myocardial injury associated with defects of lipid metabolism in type 2 diabetes predisposes its evolution toward congestive heart failure and is an important factor contributing to a high mortality following infarction.

Angelica sinensis: A Novel Adjunct to Prevent Doxorubicin‐Induced Chronic Cardiotoxicity

Doxorubicin is an anthracycline antibiotic agent used in the treatment of a variety of solid and haematopoietic tumours, but its use is limited by formation of metabolites that induce acute and chronic cardiac toxicities. Angelica sinensis has been widely used to treat cardiovascular and cerebrovascular diseases in China. In the present study, we used an in vivo mouse model to explore whether A. sinensis could protect against doxorubicin-induced chronic cardiotoxicity. Male ICR mice were treated with distilled water or water extraction of A. sinensis (15 g/kg, orally) daily for 4 weeks, followed by saline or doxorubicin (15 mg/kg, intravenously) treatments weekly. Cardiotoxicity was assessed by electrocardiograph, antioxidant activity in cardiac tissues, serum levels of creatine kinase, aspartate aminotransferase (AST) and histopathological change in cardiac tissues. A cumulative dose of doxorubicin (60 mg/kg) caused animal death and myocardial injury characterized by increased QT interval and decreased heart rate in electrocardiograph, decrease of heart antioxidant activity, increase of serum AST, as well as myocardial lesions. Pre-treatment with A. sinensis significantly reduced mortality and improved heart performance of the doxorubicin-treated mice as evidenced from normalization of antioxidative activity and serum AST, preventing loss of myofibrils as well as improving arrhythmias and conduction abnormalities. Furthermore, the in vitro cytotoxic study showed that A. sinensis did not compromise the antitumour activity of doxorubicin. These results suggested that A. sinensis elicited a typical cardioprotective effect on doxorubicin-related oxidative stress, and could be a novel adjunct in the combination with doxorubicin chemotherapy.

Early nifurtimox-induced biochemical and ultrastructural alterations in rat heart

Nifurtimox (Nfx) and Benznidazole (Bz) are being used for the treatment of the acute phase of Chagas' disease. Recently, they were also considered for use in the indeterminate phase. Both the nitroheterocyclic drugs have serious toxic side effects. The mechanism of Nfx toxicity is associated with the formation of reactive oxygen species (ROS) generated during nitroreduction. Potential effects on cardiac function have not been established yet, despite the well-known cardiopathy often produced by the disease itself. We describe experiments testing some acute effects of Nfx on the male Sprague Dawley rat heart. Nifurtimox was present in the heart at 1, 3 and 6 h after intragastric (i.g) treatment. In vitro studies on Nfx microsomal and cytosolic nitroreductase activities showed that only the microsomal fraction had the ability to nitroreduce it. Cytochrome P450 and cytochrome P450 reductase would be involved in the process as suggested by their response to specific inhibitors. Nifurtimox increased the cardiac protein carbonyl content at 1 and 3 h and decreased the protein sulfhydryl content at 3 h. In addition, 24 h after treatment ultrastructural alterations such as marked cytoplasmic vacuolization, separation and loss of myofibrils and mitochondrial swelling were observed. Results suggest that Nfx administration might aggravate pre-existing adverse cardiac conditions. Human & Experimental Toxicology (2007) 26, 781 -788.

Protective effect of Lycium barbarum on doxorubicin‐induced cardiotoxicity

The objective of this work was to explore the hypothesis that Lycium barbarum (LB) may be protective against doxorubicin (DOX)-induced cardiotoxicity through antioxidant-mediated mechanisms. Male SD rats were treated with distilled water or a water extract of LB (25 mg/kg, p.o.) daily and saline or DOX (5 mg/kg, i.v.) weekly for 3 weeks. Mortality, general condition and body weight were observed during the experiment. DOX-induced cardiotoxicity was assessed by electrocardiograph, heart antioxidant activity, serum levels of creatine kinase (CK) and aspartate aminotransferase (AST) and histopathological change. The DOX group showed higher mortality (38%) and worse physical characterization. Moreover, DOX caused myocardial injury manifested by arrhythmias and conduction abnormalities in ECG (increased QT and ST intervals and ST elevation), a decrease of heart antioxidant activity, an increase of serum CK and AST, as well as myocardial lesions. Pretreatment with LB significantly prevented the loss of myofibrils and improved the heart function of the DOX-treated rats as evidenced from lower mortality (13%), normalization of antioxidative activity and serum AST and CK, as well as improving arrhythmias and conduction abnormalities. These results suggested that LB elicited a typical cardioprotective effect on DOX-related oxidative stress. Furthermore, in vitro cytotoxic study showed the antitumor activity of DOX was not compromised by LB. It is possible that LB could be used as a useful adjunct in combination with DOX chemotherapy.

Cardioprotective response to chronic administration of vitamin E in isoproterenol induced myocardial necrosis: Hemodynamic, biochemical and ultrastructural studies

The present study evaluated the cardioprotective potential of vitamin-E by studying its effect on hemodynamic parameters, lipid peroxidation, myocyte injury marker and ultrastructural changes in model of isoproterenol-induced myocardial necrosis in rats. Wistar albino male rats (150-200 g) were randomly divided into saline, ISP control, and vit E groups. Vitamin E group was administered vitamin E at a dose of 100mg/kg/day while saline and ISP control groups received saline orally for one month. On 29(th) and 30(th) day, ISP (85 mg/kg, sc) was administered at an interval of 24 h to vit E and ISP control rats. On 31(st) day, rats of all groups were anesthetized and hemodynamic parameters were recorded. At the end of experimentation, animals were sacrificed; hearts were excised and processed for biochemical and ultrastructural studies. ISP administration produced marked cardiac necrosis as evidenced by significant decrease in my ocardial creatine kinase-MB as well as increase in malonaldialdehyde levels. ISP-induced myocardial necrosis resulted in myocardial dysfunction as evidenced by significant depression in heart rate and mean arterial pressure in the ISP control group as compared to saline control. Salient ultrastructural changes including extensive loss of myofibrils, muscle necrosis, loss of mitochondria, and formation of several intracytoplasmic vacuoles and lipid droplets further confirmed the ISP-induced myocardial damage. However, subsequent to ISP challenge, vit E treatment significantly preserved the myocardium by restoring myocardial CK-MB activity, inhibiting the ISP-induced lipid peroxidation and ultrastructural changes. Additionally, pre-and co-treatment of vit E prevented the deleterious ultrastructural changes caused by ISP. These beneficial effects of chronic vit E treatment also translated into significant restoration of the altered hemodynamic parameters. The present study clearly demonstrated the cardioprotective potential of vit E at dose of 100 mg/kg in ISP-induced model of myocardial necrosis in rats. The significant restoration of altered hemodynamic parameters, myocardial CK-MB activity, prevention of ISP-induced rise in lipid peroxidation and ultrastructural changes may confirm its cardioprotective effect.