Depressed responsiveness of phospholipase C isoenzymes to phosphatidic acid in congestive heart failure

Multimodal MALDI Imaging Mass Spectrometry Reveals Spatially Correlated Lipid and Protein Changes in Mouse Heart with Acute Myocardial Infarction

Acute myocardial infarction (MI) is a cardiovascular disease that remains a major cause of morbidity and mortality worldwide despite advances in its prevention and treatment. During acute myocardial ischemia, the lack of oxygen switches the cell metabolism to anaerobic respiration, with lactate accumulation, ATP depletion, Na⁺ and Ca²⁺ overload, and inhibition of myocardial contractile function, which drastically modifies the lipid, protein, and small metabolite profile in the myocardium. Imaging mass spectrometry (IMS) is a powerful technique to comprehensively elucidate the spatial distribution patterns of lipids, peptides, and proteins in biological tissue sections. In this work, we demonstrate an application of multimodal chemical imaging using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), which provided comprehensive molecular information in situ within the same mouse heart tissue sections with myocardial infarction. MALDI-IMS (at 30 μm per pixel) revealed infarct-associated spatial alterations of several lipid species of sphingolipids, glycerophospholipids, lysophospholipids, and cardiolipins along with the acyl carnitines. Further, we performed multimodal MALDI-IMS (IMS3) where dual polarity lipid imaging was combined with subsequent protein MALDI-IMS analysis (at 30 μm per pixel) within the same tissue sections, which revealed accumulations of core histone proteins H4, H2A, and H2B along with post-translational modification products, acetylated H4 and H2A, on the borders of the infarcted region. This methodology allowed us to interpret the lipid and protein molecular pathology of the very same infarcted region in a mouse model of myocardial infarction. Therefore, the presented data highlight the potential of multimodal MALDI imaging mass spectrometry of the same tissue sections as a powerful approach for simultaneous investigation of spatial infarct-associated lipid and protein changes of myocardial infarction.

A high-throughput and untargeted lipidomics approach reveals new mechanistic insight and the effects of salvianolic acid B on the metabolic profiles in coronary heart disease rats using ultra-performance liquid chromatography with mass spectrometry

High-throughput lipidomics provides the possibility for the development of new therapeutic drugs. Accordingly, herein, we reveal the protective role of salvianolic acid B (Sal B) in rats with coronary heart disease (CHD) and propose a new mechanism for its action through a high-throughput and non-targeted lipidomics strategy. A CHD animal model was induced by consecutive high-fat diet feeding with vitamin D3 injection. At the end of the 8th week, the serum sample was analyzed to explore the metabolic biomarker and pathway changes using untargeted lipidomics based on ultra-performance liquid chromatography with mass spectrometry (UPLC/MS). In addition, blood and heart tissue samples were collected and processed for the detection of biochemical indicators and liver histological observation. After salvianolic acid B treatment, the levels of LDH, CK, CK-MB, MYO, CTn1, TG, TC, LDL-c, and Apo(b) were significantly lower than that in the model group, while the levels of HDL-c and Apo(a1) were significantly higher than that in the model group. Furthermore, the histological features of fibrosis and steatosis were also evidently relieved in the model group. A total of twenty-six potential biomarkers were identified to express the lipid metabolic turbulence in the CHD animal models, of which twenty-two were regulated by salvianolic acid B trending to the normal state, including TG(20:0/20:4/o-18:0), PC(20:4/18:1(9Z)), PC(18:3/20:2), PA(18:0/18:2), LysoPE(18:2/0:0), SM(d18:0/22:1), PE(22:6/0:0), LysoPE (20:4/0:0), sphinganine, Cer(d18:0/18:0), PS(14:0/14:1), PC (18:0/16:0), LysoPC(17:0), PE(22:2/20:1), PC(20:3/20:4), PE(20:4/P-16:0), PS(20:3/18:0), cholesterol sulfate, TG(15:0/22:6/18:1), prostaglandin E2, arachidonic acid and sphingosine-1-phosphate. According to the metabolite enrichment and pathway analyses, the pharmacological activity of salvianolic acid B on CHD is mainly involved in three vital metabolic pathways including glycerophospholipid metabolism, sphingolipid metabolism and arachidonic acid metabolism. Thus, based on the lipidomics-guided biochemical analysis of the lipid biomarkers and pathways, Sal B protects against CHD with good therapeutic effect by regulating glycerophospholipid metabolism, sphingolipid metabolism and arachidonic acid metabolism, inhibiting oxidative stress damage and lipid peroxidation.

High-throughput lipidomics provides the possibility for the development of new therapeutic drugs.

Pharmacodynamic Evaluation of Shenfu Injection in Rats With Ischemic Heart Failure and Its Effect on Small Molecules Using Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging

Objectives: We aimed to evaluate the effect of Shenfu injection in a rat model of ischemic heart failure and explore its mechanism.

Methods: A rat model of ischemic heart failure after myocardial infarction was established by ligating the left anterior descending coronary artery. Forty-eight hours after surgery, the rats were intraperitoneally administered Shenfu injection for 7 weeks. Then, left ventricular fractional shortening and left ventricular ejection fraction were measured using transthoracic echocardiography, whereas heart rate and left ventricular end-diastolic pressure were measured using a MD3000 biosignal acquisition and processing system. The hearts and lungs of the rats were excised and weighed to measure the heart and lung weight indexes. In addition, cardiac histopathological changes were observed via hematoxylin–eosin and Masson’s trichrome staining, and serum cardiac troponin content was detected using a cardiac troponin ELISA kit. Furthermore, matrix-assisted laser desorption/ionization–mass spectrometry imaging was used to detect the levels and distribution of small molecules in the hearts of rats with ischemic heart failure.

Results: We found that Shenfu injection can significantly increase left ventricular fractional shortening and left ventricular ejection fraction in rats with ischemic heart failure and significantly reduce the left ventricular end-diastolic pressure, heart and lung weight indexes, and cardiac troponin content; improve cardiac tissue morphology; and reduce infarct size. In addition, the matrix-assisted laser desorption/ionization–mass spectrometry imaging results demonstrated that 22:6 phospholipids were predominately distributed in the non-infarct zone, whereas 20:4 phospholipids tended to concentrate in the infarct zone. Shenfu injection significantly reduced taurine, glutathione, and phospholipids levels in the hearts of rats with ischemic heart failure and primarily changed the distribution of these molecules in the non-infarct zone.

Conclusion: Shenfu injection induced obvious myocardial protective effects in rats with ischemic heart failure by stimulating antioxidation and changing the phospholipid levels and distribution.

Anti-Myocardial Infarction Effects of Radix Aconiti Lateralis Preparata Extracts and Their Influence on Small Molecules in the Heart Using Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging

Radix Aconiti Lateralis Preparata (fuzi) is the processed product of Aconitum carmichaelii Debeaux tuber, and has great potential anti-myocardial infarction effects, including improving myocardial damage and energy metabolism in rats. However, the effects of Radix Aconiti Lateralis Preparata extracts in a rat model of myocardial infarction have not yet been fully illustrated. Herein, Radix Aconiti Lateral Preparata was used to prepare Radix Aconiti Lateralis Preparata extract (RAE), fuzi polysaccharides (FPS), and fuzi total alkaloid (FTA). Then, we aimed to compare the effects of RAE, FPS, and FTA in MI rats and further explore their influence on small molecules in the heart. We reported that Radix Aconiti Lateralis Preparata extract (RAE) and fuzi total alkaloid (FTA) significantly improved left ventricular function and structure, and reduced myocardial damage and infarct size in rats with myocardial infarction by the left anterior descending artery ligation. In contrast, fuzi polysaccharides (FPS) was less effective than RAE and FTA, indicating that alkaloids might play a major role in the treatment of myocardial infarction. Moreover, via matrix-assisted laser desorption/ionization–mass spectrometry imaging (MALDI–MSI), we further showed that RAE and FTA containing alkaloids as the main common components regulated myocardial energy metabolism-related molecules and phospholipids levels and distribution patterns against myocardial infarction. In particular, it was FTA, not RAE, that could also regulate potassium ions and glutamine to play a cardioprotective role in myocardial infarction, which revealed that an appropriate dose of alkaloids generated more obvious cardiotonic effects. These findings together suggested that Radix Aconiti Lateralis Preparata extracts containing an appropriate dose of alkaloids as its main pharmacological active components exerted protective effects against myocardial infarction by improving myocardial energy metabolism abnormalities and changing phospholipids levels and distribution patterns to stabilize the cardiomyocyte membrane structure. Thus, RAE and FTA extracted from Radix Aconiti Lateralis Preparata are potential candidates for the treatment of myocardial infarction.

Phospholipid-mediated signaling and heart disease

Cardiac hypertrophy, congestive heart failure, diabetic cardiomyopathy and myocardial ischemia-reperfusion injury are associated with a disturbance in cardiac sarcolemmal membrane phospholipid homeostasis. The contribution of the different phospholipases and their related signaling mechanisms to altered function of the diseased myocardium is not completely understood. Resolution of this issue is essential for both the understanding of the pathophysiology of heart disease and for determining if components of the phospholipid signaling pathways could serve as appropriate therapeutic targets. This review provides an outline of the role of phospholipase A2, C and D and subsequent signal transduction mechanisms in different cardiac pathologies with a discussion of their potential as targets for drug development for the prevention/treatment of heart disease.

Phospholipid-mediated signaling systems as novel targets for treatment of heart disease

The phospholipases associated with the cardiac sarcolemmal (SL) membrane hydrolyze specific membrane phospholipids to generate important lipid signaling molecules, which are known to influence normal cardiac function. However, impairment of the phospholipases and their related signaling events may be contributory factors in altering cardiac function of the diseased myocardium. The identification of the changes in such signaling systems as well as understanding the contribution of phospholipid-signaling pathways to the pathophysiology of heart disease are rapidly emerging areas of research in this field. In this paper, I provide an overview of the role of phospholipid-mediated signal transduction processes in cardiac hypertrophy and congestive heart failure, diabetic cardiomyopathy, as well as in ischemia-reperfusion. From the cumulative evidence presented, it is suggested that phospholipid-mediated signal transduction processes could serve as novel targets for the treatment of the different types of heart disease.

Subcellular remodeling as a viable target for the treatment of congestive heart failure

It is now well known that congestive heart failure (CHF) is invariably associated with cardiac hypertrophy, and changes in the shape and size of cardiomyocytes (cardiac remodeling) are considered to explain cardiac dysfunction in CHF. However, the mechanisms responsible for the transition of cardiac hypertrophy to heart failure are poorly understood. Several lines of evidence both from various experimental models of CHF and from patients with different types of CHF have indicated that the functions of different subcellular organelles such as extracellular matrix, sarcolemma, sarcoplasmic reticulum, myofibrils, mitochondria, and nucleus are defective. Subcellular abnormalities for protein contents, gene expression, and enzyme activities in the failing heart become evident as a consequence of prolonged hormonal imbalance, metabolic derangements, and cation maldistribution. In particular, the occurrence of oxidative stress, development of intracellular Ca2+ overload, activation of proteases and phospholipases, and alterations in cardiac gene expression result in changes in the biochemical composition, molecular structure, and function of different subcellular organelles (subcellular remodeling). Not only does subcellular remodeling appear to be intimately involved in the transition of cardiac hypertrophy to heart failure, the mismatching of the function of different subcellular organelles leads to the development of cardiac dysfunction. Although blockade of the renin-angiotensin system, sympathetic nervous system, and various other hormonal actions have been reported to produce beneficial effects on cardiac remodeling and heart dysfunction in CHF, the actions of various cardiac drugs on subcellular remodeling have not been examined extensively. Some recent studies have indicated that both the angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists attenuate changes in sarcolemma, sarcoplasmic reticulum, and myofibril enzyme activities, protein contents, and gene expression, and partly improve cardiac function in the failing hearts. It is suggested that subcellular remodeling is an excellent target for the development of improved drug therapy for CHF. Furthermore, extensive studies should investigate the effects of different agents individually or in combination on reverse subcellular remodeling, cardiac remodeling, and cardiac dysfunction in various experimental models of CHF.

Differential changes in phospholipase D and phosphatidate phosphohydrolase activities in ischemia–reperfusion of rat heart

Phospholipase D (PLD2) produces phosphatidic acid (PA), which is converted to 1,2 diacylglycerol (DAG) by phosphatidate phosphohydrolase (PAP2). Since PA and DAG regulate Ca(2+) movements, we examined PLD2 and PAP2 in the sarcolemma (SL) and sarcoplasmic reticular (SR) membranes from hearts subjected to ischemia and reperfusion (I-R). Although SL and SR PLD2 activities were unaltered after 30 min ischemia, 5 min reperfusion resulted in a 36% increase in SL PLD2 activity, whereas 30 min reperfusion resulted in a 30% decrease in SL PLD2 activity, as compared to the control value. SR PLD2 activity was decreased (39%) after 5 min reperfusion, but returned to control levels after 30 min reperfusion. Ischemia for 60 min resulted in depressed SL and SR PLD2 activities, characterized with reduced V(max) and increased K(m) values, which were not reversed during reperfusion. Although the SL PAP2 activity was decreased (31%) during ischemia and at 30 min reperfusion (28%), the SR PAP2 activity was unchanged after 30 min ischemia, but was decreased after 5 min reperfusion (25%) and almost completely recovered after 30 min reperfusion. A 60 min period of ischemia followed by reperfusion caused an irreversible depression of SL and SR PAP2 activities. Our results indicate that I-R induced cardiac dysfunction is associated with subcellular changes in PLD2 and PAP2 activities.

Expression of phospholipase D isozymes in scar and viable tissue in congestive heart failure due to myocardial infarction

The phospholipase D (PLD) associated with the cardiac sarcolemmal (SL) membrane hydrolyses phosphatidylcholine to produce phosphatidic acid, an important phospholipid signaling molecule known to influence cardiac function. The present study was undertaken to examine PLD isozyme mRNA expression, protein contents and activities in congestive heart failure (CHF) subsequent to myocardial infarction (MI). MI was induced in rats by occlusion of the left anterior descending coronary artery. At 8 weeks after the surgical procedure, hemodynamic assessment revealed that these experimental rats were at a moderate stage of CHF. Semi-quantitative reverse transcriptase-polymerase chain reaction revealed that PLD1 and PLD2 mRNA amounts were unchanged in viable left ventricular (LV) tissue of the failing heart. Furthermore, this technique demonstrated the presence of PLD1 and PLD2 mRNA in the scar tissue. While SL PLD1 and PLD2 protein contents were elevated in the viable LV tissue of the failing heart, SL PLD1 activity was significantly decreased, whereas SL PLD2 activity was significantly increased. On the other hand, although PLD1 protein was undetectable, PLD2 protein and activity were detected in the scar tissue. Our findings suggest that differential changes in PLD isozymes may contribute to the pathophysiology of CHF and may also be involved in the processes of scar remodeling.

Phospholipase C may be involved in norepinephrine-induced cardiac hypertrophy

Cardiac hypertrophy is characterized by increased cardiomyocyte size, mRNA levels for atrial natriuretic factor (ANF), and protein synthesis. Although activation of the phosphoinositide-specific phospholipase C (PLC) leads to the generation of diacylglycerol (DAG) and inositol 1,4,5-trisphosphate, the involvement of PLC in hypertrophic response remains to be fully understood. The present study was therefore undertaken to examine if the inhibition of PLC activity is associated with a decrease in ANF expression and protein synthesis in cardiomyocytes, due to norepinephrine (NE), a known hypertrophic agent. NE resulted in an increase in ANF gene expression and protein synthesis in adult rat cardiomyocytes, these effects of NE were attenuated by a PLC inhibitor, U73122. The NE-induced increase in ANF gene expression and protein synthesis was also inhibited by an alpha-adrenoceptor blocker, prazosin. Both U73122 and prazosin depressed the NE-induced increase in DAG production in cardiomyocytes. These results indicate that the alpha-adrenoceptor mediated PLC activation may be involved in the process of NE-induced cardiac hypertrophy.

Defective phosphatidic acid–phospholipase C signaling in diabetic cardiomyopathy

The effects of exogenous phosphatidic acid (PA) on Ca2+ transients and contractile activity were studied in cardiomyocytes isolated from chronic streptozotocin-induced diabetic rats. In control cells, 25 microM PA induced a significant increase in active cell shortening and Ca2+ transients. PA increased IP3 generation in the control cardiomyocytes and its inotropic effects were blocked by a phospholipase C inhibitor. In cardiomyocytes from diabetic rats, PA induced a 25% decrease in active cell shortening and no significant effect on Ca2+ transients. Basal and PA-induced IP3 generation in diabetic rat cardiomyocytes was 3-fold lower as compared to control cells. Sarcolemmal membrane PLC activity was impaired. Insulin treatment of the diabetic animals resulted in a partial recovery of PA responses. Our results, therefore, identify an important defect in the PA-PLC signaling pathway in diabetic rat cardiomyocytes, which may have significant implications for heart dysfunction during diabetes.

Depressed phosphatidic acid-induced contractile activity of failing cardiomyocytes

The effects of phosphatidic acid (PA), a known inotropic agent, on Ca(2+) transients and contractile activity of cardiomyocytes in congestive heart failure (CHF) due to myocardial infarction were examined. In control cells, PA induced a significant increase (25%) in active cell shortening and Ca(2+) transients. The phospholipase C (PLC) inhibitor, 2-nitro-4-carboxyphenyl N,N-diphenylcarbonate, blocked the positive inotropic action induced by PA, indicating that PA induces an increase in contractile activity and Ca(2+) transients through stimulation of PLC. Conversely, in failing cardiomyocytes there was a loss of PA-induced increase in active cell shortening and Ca(2+) transients. PA did not alter resting cell length. Both diastolic and systolic [Ca(2+)] were significantly elevated in the failing cardiomyocytes. In vitro assessment of the cardiac sarcolemmal (SL) PLC activity revealed that the impaired failing cardiomyocyte response to PA was associated with a diminished stimulation of SL PLC activity by PA. Our results identify an important defect in the PA-PLC signaling pathway in failing cardiomyocytes, which may have significant implications for the depressed contractile function during CHF.

Alterations of sarcolemmal phospholipase D and phosphatidate phosphohydrolase in congestive heart failure

Phospholipase D 2 (PLD2) is the major PLD isozyme associated with the cardiac sarcolemmal (SL) membrane. Hydrolysis of SL phosphatidylcholine (PC) by PLD2 produces phosphatidic acid (PA), which is then converted to 1,2 diacylglycerol (DAG) by the action of phosphatidate phosphohydrolase type 2 (PAP2). In view of the role of both PA and DAG in the regulation of Ca(2+) movements and the association of abnormal Ca(2+) homeostasis with congestive heart failure (CHF), we examined the status of both PLD2 and PAP2 in SL membranes in the infarcted heart upon occluding the left coronary artery in rats for 1, 2, 4, 8 and 16 weeks. A time-dependent increase in both SL PLD2 and PAP2 activities was observed in the non-infarcted left ventricular tissue following myocardial infarction (MI); however, the increase in PAP2 activity was greater than that in PLD2 activity. Furthermore, the contents of both PA and PC were reduced, whereas that of DAG was increased in the failing heart SL membrane. Treatment of the CHF animals with imidapril, an angiotensin-converting enzyme (ACE) inhibitor, attenuated the observed changes in heart function, SL PLD2 and PAP2 activities, as well as SL PA, PC and DAG contents. The results suggest that heart failure is associated with increased activities of both PLD2 and PAP2 in the SL membrane and the beneficial effect of imidapril on heart function may be due to its ability to prevent these changes in the phospholipid signaling molecules in the cardiac SL membrane.