[Show abstract][Hide abstract] ABSTRACT: To investigate the role of matrix metalloproteinases (MMPs) in the responses of rats to a prolonged doxorubicin (DOX) treatment.
Male Wistar rats were used. DOX was administered by intraperitoneal injections of seven doses (cumulative dose was 15 mg/kg). Control animals were treated with saline. Tissue or plasma samples were collected at four and eight weeks after the application of the last dose. Protein levels were determined by immunoblot assay, and MMP activities were measured by gelatin zymography. Superoxide content was analyzed using a lucigenin chemiluminescence assay and superoxide dismutase (SOD) activities with a SOD assay kit. Qualitative structural alterations of the heart were characterized by transmission electron microscopy.
Systolic blood pressure was higher in DOX-treated rats as compared with the control rats at 8 weeks after treatment. In contrast, there were no differences in the heart rate between the control and DOX-treated rats. DOX treatment caused marked heterogeneous subcellular alterations of cardiomyocytes and structural disorganizations of the cardiac extracellular space. The effects of DOX were linked to a stimulation of plasma MMP-2 and MMP-9 activities that had already increased by 4 weeks after the end of the treatment. In the left ventricle, however, DOX only led to increased MMP-2 activation at 8 weeks after the end of treatment. These changes in tissue MMP-2 were connected with stimulation of Akt kinase activation, inhibition of SOD, an increase in superoxide levels, induction of iNOS protein expression and caspase-3 activation.
Our results show that MMPs are involved in the chronic cardiotoxicity of DOX in rats. The data also suggest that reactive oxygen species (superoxide), NO production (iNOS) and the Akt kinase pathway can modulate MMP-2 activities in rat hearts influenced by DOX.
Full-text · Article · Mar 2012 · Acta Pharmacologica Sinica
[Show abstract][Hide abstract] ABSTRACT: High-fat or high-carbohydrate food consumption contributes to changes in myocardial tolerance to ischemia. However, with respect to experimental models, most studies used diets with very high doses of cholesterol, saturated fatty acids, or fructose. In our study, we fed rats a high-fat diet based on lard in combination with administration of a sweet beverage (30% sucrose solution) (high-fat sucrose diet [HFS]). This diet was used to simulate the unhealthy dietary habit typical for developed countries. We hypothesized that the application of HFS diet for 48 days might initiate progression of pathologic changes in the heart associated with myocardial remodeling and activation of adaptive mechanisms. We investigated the influence of HFS diet on cardiac function and vulnerability to ischemia-reperfusion (I/R) injury in Langendorff-perfused rat hearts subjected to 30-minute global ischemia and 120-minute reperfusion as well as on Akt kinase and matrix metalloproteinases. We found lower food consumption in HFS group compared with controls, but a significant increase in visceral fat mass and concentrations of triacylglycerol, low-density lipoprotein, and very low-density lipoprotein cholesterol. Baseline heart functional parameters and their postischemic recovery were not affected by HFS diet. On the other hand, hearts of HFS group were more resistant to lethal I/R injury manifested by significantly smaller infarct size. In addition, there was lower content of collagen I and III in the left ventricle associated with Akt kinase activation and matrix metalloproteinase 9 up-regulation. In conclusion, feeding rats with HFS diet resulted in heart remodeling associated with activation of some adaptive mechanisms, which can contribute to modulation of myocardial resistance to I/R injury.
No preview · Article · Aug 2011 · Nutrition research
[Show abstract][Hide abstract] ABSTRACT: The study has been designed to characterize protein systems involved in the responses of rat hearts to chronic doxorubicin (DOX) treatment. We investigated the influence of DOX on cardiac function, mitogen-activated protein kinases (MAPKs) and heat stress proteins (HSPs). Doxorubicin was administered to rats by intraperitoneal injections over a period of 6 weeks. In control and DOX-treated hearts exposed to 20 min global ischemia and 40 min reperfusion the recovery of contractile function after ischemia/reperfusion (I/R) was determined. The levels and phosphorylation state of proteins in tissue samples were analyzed using specific antibodies. We found an activation of extracellular signal-regulated kinases (ERKs) in rat hearts exposed to DOX treatment and better recovery of contractile function after I/R. Analysis of HSPs showed that DOX induced up-regulation of the levels of HSP60 and down-regulation of HSP70 levels. The levels and/or specific phosphorylation of other studied proteins (p38-MAPK, HSP27, HSP90) were not influenced by DOX. The results point to the possible role of ERKs and some HSPs in mechanisms underlying the response of rat hearts to chronic DOX treatment.
Preview · Article · Apr 2008 · Physiological research / Academia Scientiarum Bohemoslovaca
[Show abstract][Hide abstract] ABSTRACT: Pretreatment with diazoxide, mitochondrial K(ATP) channel opener, was found to protect the rat heart against ischemia/reperfusion injury. Our aim was also to characterize the effects of diazoxide on the alterations of regulatory myocardial proteins, on mitochondrial ultrastructure, integrity and induction of apoptotic responses. Isolated rat hearts were Langendorff perfused and subjected to index ischemia (II) induced by 25 min global ischemia and 35 min reperfusion. In diazoxide- treated hearts, diazoxide (50 micromol/l) was applied 15 min before II. The levels and activation of specific proteins were determined using specific antibodies, activities of matrix metalloproteinases by zymography using gelatin as a substrate. The ultrastructure of mitochondria was investigated by electron microscopy of ultrathin sections of mitochondrial fractions embedded in Epon812. In rat hearts pretreated with diazoxide we found better recovery of contractile function after II. Electron microscopy studies revealed that application of diazoxide was connected with better preservation of mitochondrial integrity at basal conditions and after II in comparison to control hearts. Ischemia induced activation of caspase-3 as well as decrease of mitochondria-associated Bcl-2 levels but diazoxide treatment did not significantly influence these changes. On the other hand, diazoxide pretreatment reduced the cytosolic levels of pro-apoptotic Bax protein. Western blot analysis revealed that application of diazoxide increased activation of both ERK-1 and ERK-2 as compared with control hearts. ERK-2 activities were also higher in diazoxide-treated hearts after II when compared to control hearts. Moreover, application of diazoxide inhibited the activities of tissue matrix metalloproteinases (MMP-2). The results suggest that the cardioprotection mediated by diazoxide in rats is associated with preservation of mitochondrial integrity and function. The effect of diazoxide on ERK pathway points to the involvement of this signaling cascade in diazoxide-mediated adaptive responses of myocardium to ischemia.
No preview · Article · Jul 2007 · General Physiology and Biophysics