Clinical significance of cardiac contractile proteins for the diagnosis of myocardial injury

The nonlinear motion of cells subject to external forces

To develop a minimal model for a cell moving in a crowded environment such as in tissue, we investigate the response of a liquid drop of active matter moving on a flat rigid substrate to forces applied at its boundaries. We consider two different self-propulsion mechanisms, active stresses and treadmilling polymerisation, and we investigate how the active drop motion is altered by these surface forces. We find a highly non-linear response to forces that we characterise using drop velocity, drop shape, and the traction between the drop and the substrate. Each self-propulsion mechanism gives rise to two main modes of motion: a long thin drop with zero traction in the bulk, mostly occurring under strong stretching forces, and a parabolic drop with finite traction in the bulk, mostly occurring under strong squeezing forces. In each case there is a sharp transition between parabolic, and long thin drops as a function of the applied forces and indications of drop break-up where large forces stretch the drop.

Porcine Circovirus type 2 infected myocardial tissue transcriptome signature

The goal of this study was to compare the global gene expression profile in cardiac tissues of pig infected with porcine circovirus 2 (PCV2) to that of healthy cells. Since PCV2 infection causes severe cardiovascular lesions, the myocardial tissue model was chosen for this study. In High-throughput transcriptome analysis, DESeq2 and CLC genomics workbench analyses revealed a total of 196 significantly differentially expressed genes (DEGs) (p-value < 0.05). Furthermore, 194 transcripts were upregulated, while only two were downregulated (HSPA6 and DNAJA1), with fold changes ranging from 16.293 to -10.002. Among the KEGG canonical pathways targeted by the DEGs in the functional analysis, adrenergic signalling in cardiomyocytes, Cardiac Muscle Contraction, Hypertrophic Cardiomyopathy (HCM), and Dilated Cardiomyopathy (DCM) tends to be enriched. The differentially expressed highly connected (DEHC) biomarker genes in pathogenicity of PCV2 infection, such as LDB3, MYOZ2, CASQ2, TNNT2, MLC2V, MYBPC3, ACTC1, TCAP, TNNI3, TRDN, CSRP3, MYL3, RYR2, LMOD2, MYH7, etc., were identified using protein-protein interaction (PPI) network analysis. The study might provide detailed information on the dysregulated genes and biological pathways in infected myocardial tissues that may be essential for PCV2-related heart pathology.

Efficacy and safety of Chinese herbal medicine Wen Xin granules for the treatment of unstable angina pectoris with Yang deficiency and blood stasis syndrome: study protocol for a randomized controlled trial

INTRODUCTION

Unstable angina pectoris (UAP) is the common type of coronary heart disease with the risk of developing into acute myocardial infarction (AMI). Currently, there are still numerous patients suffering from recurrent angina after revascularization or conventional medication due to the microvascular lesions, endothelial dysfunction, chronic inflammation, in-stent restenosis, and other factors. As an important part of China's medical and health care system, traditional Chinese medicine (TCM) has rich clinical experience in the treatment of UAP. According to the theory of TCM, Yang deficiency and blood stasis syndrome is a common type of UAP. Wen Xin decoction, as a type of Chinese herbal medicine, has been used in the clinic for years and shown great efficacy in the treatment of UAP with Yang deficiency and blood stasis syndrome. This study aims to evaluate the efficacy and safety of Wen Xin granular in patients with UAP.

METHODS AND ANALYSIS

This is a double-blinded, randomized, placebo-controlled clinical trial. A total of 502 participants will be randomly allocated to the intervention group and the placebo group. Based on conventional medication, the intervention group will be treated with Wen Xin granular and the placebo group will be treated with Wen Xin granular placebo. The primary outcomes are major adverse cardiovascular events (MACE). Assessments will be performed 1 year after the treatment. The secondary outcomes include TCM symptom scale score, Seattle angina questionnaire, and thromboelastography. Assessments will be performed at baseline (before randomization) and 4 and 8 weeks after randomization.

DISCUSSION

This trial will provide high-quality data on the benefits and risks of Wen Xin granular in patients with UAP.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04661709 . Registered on 30 November 2020.

Exogenous cathepsin V protein protects human cardiomyocytes HCM from angiotensin Ⅱ-Induced hypertrophy

Angiotensin (Ang) Ⅱ-induced cardiac hypertrophy can deteriorate to heart failure, a leading cause of mortality. Endogenous Cathepsin V (CTSV) has been reported to be cardioprotective against hypertrophy. However, little is known about the effect of exogenous CTSV on cardiac hypertrophy. We used the human cardiomyocytes HCM as a cell model to investigate the effects of exogenous CTSV on Ang Ⅱ-induced cardiac cell hypertrophy. Cell surface area and expression of classical markers of hypertrophy were analyzed. We further explored the mechanism of CTSV cardioprotective by assessing the levels and activities of PI3K/Akt/mTOR and MAPK signaling pathway proteins. We found that pre-treating cardiomyocytes with CTSV could significantly inhibit Ang Ⅱ-induced hypertrophy. The mRNA expression of hypertrophy markers ANP, BNP and β-MHC was obviously elevated in Ang Ⅱ-treated cardiac cells. Whereas, exogenous CTSV effectively halted this elevation. Further study revealed that the protective effects of exogenous CTSV might be mediated by repressing the phosphorylation of proteins in the PI3K/Akt/mTOR and MAPK pathways. Based on our results, we concluded that exogenous CTSV inhibited Ang Ⅱ-induced hypertrophy in HCM cells by inhibiting PI3K/Akt/mTOR. This study provides experimental evidence for the application of CTSV protein for the treatment of cardiac hypertrophy.

Insight into the role of DL-α-lipoic acid against cyclophosphamide induced alterations in calcium sensitivity of cardiac myofilaments

Cyclophosphamide (CP), a potent antitumor drug, is known to cause severe cardiotoxicity. The present study is aimed at evaluating the role of DL-alpha-Lipoic acid (LA) on the calcium responsiveness of cardiac myofilaments isolated from CP treated rats. Adult male Wistar rats were divided into four treatment groups. Two groups received single intraperitoneal injection of CP (200 mg/kg b.wt.) to induce cardiotoxicity, one of these groups received LA treatment (25 mg/kg b.wt. for 10 days). A vehicle treated control group and a LA drug control were also included. Cardiotoxicity was evident from increased levels of cardiac Troponin I in serum of CP treated rats. The pCa-actomyosin ATPase relationship of myofilaments demonstrated a rightward shift indicating diminished responsiveness in CP treated rats. The hill coefficient was reduced and the myofibrillar myosin Ca(2+)-ATPase and K(+)-(EDTA) activities were also significantly (P < 0.05) reduced. Ultrastructural observations were also in agreement with the above abnormal changes, wherein loss of myofilaments occurred. LA effectively normalized these abnormalities and restored the cardiac function in CP administered rats.

Cardiac troponin and beta-type myosin heavy chain concentrations in patients with polymyositis or dermatomyositis

Cardiac troponin T (cTnT), cardiac troponin I (cTnI), myosin heavy chains (MHC), myoglobin, creatine kinase (CK), and creatine kinase isoenzyme MB (CKMB), were measured in blood samples from 39 polymyositis (PM) or dermatomyositis (DM) patients without clinical evidence for cardiac involvement to evaluate their clinical usefulness in this patient population. MHC, myoglobin, and CKMB were frequently elevated and correlated with each other and with disease severity. Undetectable cTnI in all but one patient indicated that MHC was released from skeletal muscle, thereby providing the first laboratory evidence of frequent slow-twitch muscle fibre-necrosis in patients with PM or DM. CKMB was elevated in 51%, cTnT in 41%, and cTnI in only 2.5% of patients. cTnI did not correlate with other markers or with disease severity scores. The close correlations found between cTnT and skeletal muscle damage markers and the relationship between cTnT with disease severity without clinical evidence for myocardial damage suggest a release of cTnT from skeletal muscle. The relationship of cTnT with disease severity indicates a possible role of the marker for risk stratification. However, the prognostic values of cardiac troponins and other muscle damage markers in PM/DM patients remain to be compared in prospective outcome trials.

Attenuation of isoproterenol-mediated myocardial injury in rat by an inhibitor of polyamine synthesis

OBJECTIVE

Ornithine decarboxylase (ODC) is an initial rate-limiting enzyme in the synthesis of polyamines (putrescine, spermidine, and spermine) that play a role in cell growth and differentiation. Recent studies have shown that spermidine and spermine cause injury to a variety of cells including myocytes in vitro. In this investigation, we used alpha-difluoromethylornithine (DFMO), a specific and irreversible inhibitor of ODC activity and polyamine synthesis to test the hypothesis that polyamines contribute to myocardial injury in rat.

METHODS

Male Sprague Dawley rats were treated with (i) saline (0.2 ml/day, s.c.), (ii) isoproterenol (ISO) (5 mg/kg/day for 8 days, s.c.) to produce necrotizing myocardial injury, or with (iii) DFMO + ISO. DFMO was started 2 days before the initiation of ISO and both ISO and DFMO were continued until the end of the experimental period. Myocardial injury was assessed by determining the increased release of creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) into the plasma, and by morphometric analysis of the lesion area in heart sections stained with Gomori trichrome.

RESULTS

ISO induced the release of CPK and LDH by 6 hr and 24 hr, respectively, and produced subendocardial necrosis, which was both acute and resolving following 8 days of ISO. DFMO treatment inhibited ISO-induced increases in (i) ODC activity and putrescine and spermidine levels in heart, (ii) CPK and LDH activity in plasma, and (iii) the area of subendocardial lesions.

CONCLUSIONS

These observations suggest that polyamines are one of the intracellular factors that contribute to ISO-mediated cardiac injury in the rat.

Cardiac troponin T alterations in myocardium and serum of rats after stressful, prolonged intense exercise

The goal of this study was to determine whether the stress of forced exercise would result in injury to the myocardium. Male rats with 8% of body weight attached to the tail were forced to swim 3.5 h (3.5S), forced to swim 5 h (5S), or pretrained for 8 days and then forced to swim 5 h (T5S). Rats were killed immediately after they swam (0 h PS) and at 3 h (3 h PS), 24 h (24 h PS), and 48 h after they swam (48 h PS). Tissue homogenates of the left ventricle were analyzed by Western blot analysis for cardiac troponin T (cTnT). Serum cTnT was quantified by immunoassay. Results indicated that, in the 3.5S, 5S, and T5S groups, serum cTnT was significantly (P < 0.01) increased at 0 and 3 h PS. The 5S group demonstrated a greater increase in serum cTnT than the 3.5S group (P < 0.01) and the T5S group (P < 0.01) at 0 h PS. Western blot analysis indicated significant decreases (P < 0. 01) in myocardial cTnT in the 5S group only at 0 h PS (P < 0.01) and 3 h PS (P < 0.05). Histological evidence of localized myocyte damage demonstrated by interstitial inflammatory infiltrates consisting of neutrophils, lymphocytes, and histiocytes, as well as vesicular nuclei-enlarged chromatin patterns, was observed in left ventricle specimens from the 5S group at 24 and 48 h PS. Our findings demonstrate that stressful, forced exercise induces alterations in myocardial cTnT and that training before exercise attenuates the exercise-induced heart damage.

Different intracellular compartmentations of cardiac troponins and myosin heavy chains: a causal connection to their different early release after myocardial damage

We investigated the net myocardial release of creatine kinase isoenzyme MB (CKMB), myoglobin, cardiac troponin T (cTnT), cardiac troponin I (cTnI), and cardiac β-type myosin heavy chain (β-MHC) into the coronary circulation after cardioplegic cardiac arrest in humans. Cardiac markers were measured in paired arterial, central venous, and coronary sinus blood in 19 patients undergoing elective coronary artery bypass grafting (CABG) before aortic cross-clamping and 1, 5, 10, and 20 min after aortic declamping. cTnT and cTnI were released into the coronary sinus in parallel to each other and almost simultaneously to myoglobin and CKMB within 20 min of reperfusion. In contrast, no β-MHC was released in the same patients during the study period. The average soluble cTnT and cTnI pools in right atrial appendages of 11 patients with right atrial and right ventricular pressures within reference values were comparable and were ∼8% of total myocardial troponin content. The soluble β-MHC pool was &lt;0.1% in all patients. Our results demonstrate the impact of the different intracellular compartmention of regulatory and contractile proteins on their early release from damaged myocardium.

Early laboratory indicators of acute myocardial infarction

Biochemical markers of myocardial injury have evolved so that the diagnosis or exclusion of acute myocardial infarction can be determined within a short time with a high degree of sensitivity and specificity. The use of these markers in patients complaining of chest pain allows for medically appropriate and cost-effective triage decision making in the emergency department.

Cardiac troponin I to diagnose percutaneous transluminal coronary angioplasty-related myocardial injury

The purposes of the present study were to evaluate cardiac troponin 1 (cTnl) in the diagnosis of percutaneous transluminal coronary angioplasty (PTCA)-related myocardial injury in comparison with cardiac troponin T (cTnT) and creatine kinase (CK) MB mass concentration, and to investigate the frequency of myocardial injury, as indicated by myocardial protein release, after clinically symptomless side-branch occlusion (SBO) which may occur in the proximity of the attempted stenosis. The final study population comprised 80 patients undergoing elective, single vessel PTCA. Blood samples were drawn before, 6, 24 and 48 h after PTCA. cTnI, cTnT and CKMB mass baseline values were within the reference intervals in all patients (cTnI < 0.1 microgram/l, cTnT < 0.2 microgram/l, CKMB < 5 micrograms/l). Two patients presented with primary failure of PTCA, and visually successful PTCA was performed in all remaining patients. Seven patients (four with SBO) subsequently developed acute myocardial infarction (AMI). Symptomless SBO occurred in 16 patients. In controls (n = 55) there were no significant increases in cTnI, cTnT, or CKMB concentrations compared with baseline values, and all markers stayed within their reference intervals. In half the patients with symptomless SBO (n = 8) all markers were slightly to moderately increased, in two additional patients only CKMB was elevated (cTnI: 0.1-1.0 microgram/l; cTnT: 0.25-0.81 microgram/l and CKMB: 7.9-25.6 micrograms/l). In the majority of patients with primary failure or AMI we found pronounced increases in all tested markers (cTnI: 0.2-12.0 micrograms/l; cTnT: 0.44-12.10 micrograms/l; CKMB: 19.2-423.0 micrograms/l). The results of this study indicate that cTnI is comparably useful to cTnT or CKMB mass for diagnosing myocardial injury in PTCA patients. From our results a preference for one of the tested parameters cannot be clearly derived. Post-procedural cTnI, cTnT, and CKMB mass values are not higher than baseline values in uncomplicated cases, whereas AMI after PTCA leads to pronounced marker increases. SBO, even when symptomless, leads frequently (in about half the patients) to slight marker increases.

Cumulative troponin T release after acute myocardial infarction. Influence of reperfusion

For troponin T a characteristic biphasic change in the plasma time-concentration curve has been described, especially in patients with early reperfusion after thrombolytic therapy. As troponin T is bound to myofibrillar structures, treatment strategy or treatment outcome could influence the cumulative plasma release of this protein in a different way compared to the cumulative release of free cytoplasmic cardiac enzymes. The present study is the first study comparing the total quantity of troponin T released by the heart during the first 168 hours after acute myocardial infarction, both in patients treated with thrombolytic therapy (n = 16) and in patients not treated with thrombolytic therapy (n = 7). On the basis of clinical symptoms and coronary arteriogram within 24 hours, the patients treated with thrombolytic therapy were divided into two groups, reperfused (n = 9) and non-reperfused (n = 7). In the patients not treated with thrombolytic therapy, absence of spontaneous early reperfusion was judged only from clinical symptoms. Cumulative troponin T release into plasma was compared to the cumulative release of the cytoplasmic cardiac enzymes creatine kinase (EC 2.7.3.2) and hydroxybutyrate dehydrogenase (EC 1.1.1.27). Cumulative release, i. e., infarct size, was calculated using a two-compartment model for circulating proteins. Mean tissue contents, per gram wet weight, of 156 U/g for hydroxybutyrate dehydrogenase, 2.163 U/g for creatine kinase and 234 microg/g for troponin T, were used to express infarct size in gram-equivalents of healthy myocardium per litre plasma (g-eq/l). Release rates were represented by the ratio of cumulative quantities released in 10 hours and 72 hours for creatine kinase and hydroxybutyrate dehydrogenase and in 10 hours and 168 hours for troponin T.

CONCLUSIONS

- Plasma time-concentration curves and release rates of troponin T in patients treated with thrombolytic therapy showing reperfusion differ significantly from those of patients not treated with thrombolytic therapy, showing no reperfusion. - Creatine kinase and hydroxybutyrate dehydrogenase release is completed within 72-100 hours in all patients, whereas troponin T release still continues after 168 hours. - Cumulative troponin T release at 168 hours is only a fraction (around 8%) of cumulative cytoplasmic enzyme release and the percentage released is not influenced by the treatment strategy or outcome, i. e., vessel patency. - Although troponin T release is only a fraction of the cumulative enzyme release (infarct size) there is a highly significant correlation between both, independent of the treatment strategy or treatment outcome.

Cardiac troponin I and troponin T: are enzymes still relevant as cardiac markers?

Creatine kinase (CK) MB and lactate dehydrogenase (LDH) isoenzyme 1 are not heart-specific. By contrast, the regulatory proteins troponin I and troponin T are expressed in three different isoforms, one for slow-twitch skeletal muscle fibers, one for fast-twitch skeletal muscle fibers, and one for cardiac muscle (cTnI, cTnT). cTnI and cTnT are usually not detectable in patients without myocardial damage, which is a prerequisite for high diagnostic performance. After acute myocardial infarction (AMI) cTnI, cTnT, and CKMB mass have a comparable early sensitivity. cTnI and cTnT usually peak in parallel except for patients without reperfusion in whom cTnI peaks about 1 day and cTnT approximately 3-4 days after onset of AMI. Both stay increased for at least 4-5 days. cTnT tends to stay increased longer than cTnI. Because the sensitivities of cTnI and cTnT for myocardial injury are comparable, their specificities are the main topic of current debate. Recent reports on mismatches of cTnI and cTnT in patients with renal failure and myopathy without other evidence for myocardial injury suggest that cTnT could be reexpressed similar to CKMB and LDH-1 in chronically damaged human skeletal muscle. In contrast to cTnT, CKMB, and LDH-1, cTnI is not expressed in skeletal muscle during fetal development. So far, an increase in cTnI has been reported only after myocardial damage. Because of currently higher costs, troponin measurement should be restricted at present to clinical settings that really require their high specificity. Based on its distinct functional association with the metabolism of acute ischemic myocardium and according to initial clinical results, glycogen phosphorylase isoenzyme BB is a promising enzyme for the early detection of ischemic myocardial damage.

Progress in myocardial damage detection: new biochemical markers for clinicians

New clinical requirements for triaging chest pain patients challenge the abilities of the current cardiac markers. Serial measurements of myoglobin, creatine kinase (CK) isoenzyme MB (CKMB) mass, or CK isoforms in emergency rooms help to rapidly rule out acute myocardial infarction (AMI). However, within the first 3 to 4 h from chest pain onset, their sensitivities are too low to contribute significantly to AMI diagnosis during this period. CKMB and lactate dehydrogenase (LDH) isoenzyme 1 are not heart-specific, which hampers reliable diagnosis in patients with concomitant skeletal muscle damage. By contrast, the regulatory proteins troponin I and troponin T are expressed in three different isoforms: one for slow-twitch skeletal muscle fibers, one for fast-twitch skeletal muscle fibers, and one for cardiac muscle (cTnI, cTnT); cardiac-specific cTnI and cTnT assays are already available for routine use. cTnT and cTnI are the most promising markers for risk stratification in patients with unstable angina pectoris. Recent reports on increased cTnT in patients with renal failure or myopathy without evidence of myocardial injury and undetectable cTnI suggest that cTnT could be reexpressed similar to CKMB and LDH-1 in chronically damaged human skeletal muscle. Therefore, cTnI is probably the most heart-specific marker. Among the recently proposed new markers for early AMI diagnosis: glycogen phosphorylase isoenzyme BB (GPBB), fatty acid binding protein, phosphoglyceric acid mutase isoenzyme MB, enolase isoenzyme alpha beta, S100a0, and annexin V, GPBB is the most promising because it increases as early as 1 to 4 h from chest pain onset and its early release appears to be essentially dependent on ischemic myocardial injury.

Cardiac troponin I in the diagnosis of myocardial injury and infarction

We used a cardiospecific enzymoimmunometric assay to measure cardiac troponin I (cTnI) in samples serially drawn from 78 patients with acute myocardial infarction (AMI), 7 patients with unstable angina (Braunwald class III), 22 multi-traumatized patients, and in 30 athletes after eccentric exercise, as well as in 101 non-traumatic chest pain patients on admission to the emergency department. cTnI assay crossreactivity with crude human skeletal muscle homogenates was < 0.1%. cTnI could not be detected in athletes or multi-traumatized patients except for 2 trauma patients with myocardial damage. Increased cTnI concentrations were found in 6 of 7 patients with unstable angina at rest and in all AMI patients. After AMI, cTnI increased about 3.5 h (median) after the onset of chest pain, reached peak values parallel to CKMB, and stayed increased for at least 4 days. Cardiac troponin T (cTnT) increased and mostly peaked parallel to cTnI. cTnT sensitivity on the 7th day after AMI was significantly higher than that of cTnI. In contrast to cTnI, cTnT mostly showed a second, usually smaller, peak about day 4 after AMI. During the first 4 h after the onset of chest pain and before thrombolytic therapy the sensitivities of myoglobin (0.43) and CKMB mass (0.56) were significantly higher than those of both troponins (cTnI, 0.29; cTnT, 0.25). Areas under receiver operator characteristic curves indicated only moderate diagnostic accuracies of bio-chemical markers for early AMI diagnosis in non-traumatic chest pain patients that cTnI is a highly sensitive and specific marker for myocardial damage which is suitable for early and late diagnosis.