Dityrosine, a protein product of oxidative stress, as a possible marker of acute myocardial infarctions

Postmortem Immunohistochemical Findings in Early Acute Myocardial Infarction: A Systematic Review

The diagnosis of early acute myocardial infarction is of particular importance in forensic practice considering the frequency of sudden cardiac death and the difficulty of positively identifying it through classical histological methods if survival is less than 6 h. This article aims to analyze potential immunohistochemical markers that could be useful in diagnosing acute myocardial infarction within the first 6 h of its onset. We conducted an extensive evaluation of the literature according to the PRISMA guidelines for reporting systematic literature reviews. We searched the Web of Science and PubMed databases from their inception to 2023 using the following keywords: "myocardial infarction" and "immunohistochemistry". Fifteen studies met the inclusion criteria. Immunohistochemical markers as complement factors and CD59, myoglobin, fibrinogen, desmin, tumor necrosis factor alpha (TNF-α), P-38, JNK (Jun N Terminal Kinase), transforming growth factor β1 (TGF-β1), cardiac troponins, fibronectin, H-FABP (heart fatty acid binding protein), dityrosine, fibronectin, CD15, IL-1β, IL-6, IL-15, IL-8, MCP-1, ICAM-1, CD18, and tryptase can be used to identify the first six hours of acute myocardial infarction. These markers are mostly studied in experimental animal models. It is necessary to conduct extensive studies on human myocardial tissue fragments, which will involve the analysis of several immunohistochemical markers and careful analysis of the available data on perimortem events, resuscitation, and postmortem intervals in the context of a uniform laboratory methodology.

Effects of Dityrosine on Lactic Acid Metabolism in Mice Gastrocnemius Muscle During Endurance Exercise via the Oxidative Stress-Induced Mitochondria Damage

Dityrosine (Dityr) has been detected in commercial food as a product of protein oxidation and has been shown to pose a threat to human health. This study aims to investigate whether Dityr causes a decrease in lactic acid metabolism in the gastrocnemius muscle during endurance exercise. C57BL/6 mice were administered Dityr or saline by gavage for 13 weeks and underwent an endurance exercise test on a treadmill. Dityr caused a severe reduction in motion displacement and endurance time, along with a significant increase in lactic acid accumulation in the blood and gastrocnemius muscle in mice after exercise. Dityr induced significant mitochondrial defects in the gastrocnemius muscle of mice. Additionally, Dityr induced serious oxidative stress in the gastrocnemius muscle, accompanied by inflammation, which might be one of the causes of mitochondrial dysfunction. Moreover, significant apoptosis in the gastrocnemius muscle increased after exposure to Dityr. This study confirmed that Dityr induced oxidative stress in the gastrocnemius muscle, which further caused significant mitochondrial damage in the gastrocnemius muscle cell, resulting in decreased capacity of lactic acid metabolism and finally affected performance in endurance exercise. This may be one of the possible mechanisms by which highly oxidized foods cause a decreased muscle energy metabolism.

Chlorogenic Acid Attenuates Doxorubicin-Induced Oxidative Stress and Markers of Apoptosis in Cardiomyocytes via Nrf2/HO-1 and Dityrosine Signaling

(1) Background: Doxorubicin (DOX) is extensively used for cancer treatments; however, its clinical application is limited because of its cardiotoxic adverse effects. A combination of DOX and agents with cardioprotective properties is an effective strategy to ameliorate DOX-related cardiotoxicity. Polyphenolic compounds are ideal for the investigation of novel cardioprotective agents. Chlorogenic acid (CGA), an essential dietary polyphenol found in plants, has been previously reported to exert antioxidant, cardioprotective, and antiapoptotic properties. The current research evaluated CGA's in vivo cardioprotective properties in DOX-induced cardiotoxicity and the probable mechanisms underlying this protection. (2) Methods: CGA's cardioprotective properties were investigated in rats that were treated with CGA (100 mg/kg, p.o.) for fourteen days. The experimental model of cardiotoxicity was induced with a single intraperitoneal (15 mg/kg i.p.) injection of DOX on the 10th day. (3) Results: Treatment with CGA significantly improved the DOX-caused altered cardiac damage markers (LDH, CK-MB, and cTn-T), and a marked improvement in cardiac histopathological features accompanied this. DOX downregulated the expression of Nrf2/HO-1 signaling pathways, and the CGA reversed this effect. Consistently, caspase-3, an apoptotic-related marker, and dityrosine expression were suppressed, while Nrf2 and HO-1 expressions were elevated in the cardiac tissues of DOX-treated rats after treatment with the CGA. Furthermore, the recovery was confirmed by the downregulation of 8-OHdG and dityrosine (DT) expressions in immunohistochemical findings. (4) Conclusions: CGA demonstrated a considerable cardioprotective effect against DOX-induced cardiotoxicity. One of the possible mechanisms for these protective properties was the upregulation of the Nrf2/HO-1-dependent pathway and the downregulation of DT, which may ameliorate oxidative stress and cardiomyocyte apoptosis. These findings suggest that CGA may be cardioprotective, particularly in patients receiving DOX-based chemotherapy.

Dityrosine cross-linking and its potential roles in Alzheimer's disease

Oxidative stress is a significant source of damage that accumulates during aging and contributes to Alzheimer's disease (AD) pathogenesis. Oxidation of proteins can give rise to covalent links between adjacent tyrosines known as dityrosine (DiY) cross-linking, amongst other modifications, and this observation suggests that DiY could serve as a biomarker of accumulated oxidative stress over the lifespan. Many studies have focused on understanding the contribution of DiY to AD pathogenesis and have revealed that DiY crosslinks can be found in both Aβ and tau deposits - the two key proteins involved in the formation of amyloid plaques and tau tangles, respectively. However, there is no consensus yet in the field on the impact of DiY on Aβ and tau function, aggregation, and toxicity. Here we review the current understanding of the role of DiY on Aβ and tau gathered over the last 20 years since the first observation, and discuss the effect of this modification for Aβ and tau aggregation, and its potential as a biomarker for AD.

Dityrosine in food: A review of its occurrence, health effects, detection methods, and mitigation strategies

Protein and amino acid oxidation in food products produce many new compounds, of which the reactive and toxic compound dityrosine, derived from oxidized tyrosine, is the most widely studied. The high reactivity of dityrosine enables this compound to induce oxidative stress and disrupt thyroid hormone function, contributing to the pathological processes of several diseases, such as obesity, diabetes, cognitive dysfunction, aging, and age-related diseases. From the perspective of food safety and human health, protein-oxidation products in food are the main concern of consumers, health management departments, and the food industry. This review highlights the latest research on the formation pathways, toxicity, detection methods, occurrence in food, and mitigation strategies for dityrosine. Furthermore, the control of dityrosine in family cooking and food-processing industry has been discussed. Food-derived dityrosine primarily originates from high-protein foods, such as meat and dairy products. Considering its toxicity, combining rapid high sensitivity dityrosine detection techniques with feasible control methods could be an effective strategy to ensure food safety and maintain human health. However, the current dityrosine detection and mitigation strategies exhibit some inherent characteristics and limitations. Therefore, developing technologies for rapid and effective dityrosine detection and control at the industrial level is necessary.

Identification of Differentially Expressed Genes and Prediction of Expression Regulation Networks in Dysfunctional Endothelium

The detection of early coronary atherosclerosis (ECA) is still a challenge and the mechanism of endothelial dysfunction remains unclear. In the present study, we aimed to identify differentially expressed genes (DEGs) and the regulatory network of miRNAs as well as TFs in dysfunctional endothelium to elucidate the possible pathogenesis of ECA and find new potential markers. The GSE132651 data set of the GEO database was used for the bioinformatic analysis. Principal component analysis (PCA), the identification of DEGs, correlation analysis between significant DEGs, the prediction of regulatory networks of miRNA and transcription factors (TFs), the validation of the selected significant DEGs, and the receiver operating characteristic (ROC) curve analysis as well as area under the curve (AUC) values were performed. We identified ten genes with significantly upregulated signatures and thirteen genes with significantly downregulated signals. Following this, we found twenty-two miRNAs regulating two or more DEGs based on the miRNA–target gene regulatory network. TFs with targets ≥ 10 were E2F1, RBPJ, SSX3, MMS19, POU3F3, HOXB5, and KLF4. Finally, three significant DEGs (TOX, RasGRP3, TSPAN13) were selected to perform validation experiments. Our study identified TOX, RasGRP3, and TSPAN13 in dysfunctional endothelium and provided potential biomarkers as well as new insights into the possible molecular mechanisms of ECA.

Dityrosine Cross-links are Present in Alzheimer's Disease-derived Tau Oligomers and Paired Helical Filaments (PHF) which Promotes the Stability of the PHF-core Tau (297-391) In Vitro

A characteristic hallmark of Alzheimer's Disease (AD) is the pathological aggregation and deposition of tau into paired helical filaments (PHF) in neurofibrillary tangles (NFTs). Oxidative stress is an early event during AD pathogenesis and is associated with tau-mediated AD pathology. Oxidative environments can result in the formation of covalent dityrosine crosslinks that can increase protein stability and insolubility. Dityrosine cross-linking has been shown in Aβ plaques in AD and α-synuclein aggregates in Lewy bodies in ex vivo tissue sections, and this modification may increase the insolubility of these aggregates and their resistance to degradation. Using the PHF-core tau fragment (residues 297 - 391) as a model, we have previously demonstrated that dityrosine formation traps tau assemblies to reduce further elongation. However, it is unknown whether dityrosine crosslinks are found in tau deposits in vivo in AD and its relevance to disease mechanism is unclear. Here, using transmission electron microscope (TEM) double immunogold-labelling, we reveal that neurofibrillary NFTs in AD are heavily decorated with dityrosine crosslinks alongside tau. Single immunogold-labelling TEM and fluorescence spectroscopy revealed the presence of dityrosine on AD brain-derived tau oligomers and fibrils. Using the tau (297-391) PHF-core fragment as a model, we further showed that prefibrillar tau species are more amenable to dityrosine crosslinking than tau fibrils. Dityrosine formation results in heat and SDS stability of oxidised prefibrillar and fibrillar tau assemblies. This finding has implications for understanding the mechanism governing the insolubility and toxicity of tau assemblies in vivo.

Lycopene Regulates Dietary Dityrosine-Induced Mitochondrial-Lipid Homeostasis by Increasing Mitochondrial Complex Activity

SCOPE

Dityrosine (DT), a marker of protein oxidation, is widely found in many high-protein foods. Dietary intake of DT induces myocardial oxidative stress injury and impairs energy metabolism. Lycopene is a common dietary supplement with antioxidant and mitochondrial-lipid homeostasis modulating abilities. This study aimed to examine the effects of lycopene on DT-induced disturbances in myocardial function and energy metabolism.

METHODS AND RESULTS

Four-week-old C57BL/6J mice received intragastric administration of either tyrosine (420 µg kg^-1 BW), DT (420 µg kg^-1 BW), or lycopene at high (10 mg kg^-1 BW) and low (5 mg kg^-1 BW) doses for 35 days. Lycopene administration effectively reduced oxidative stress, cardiac fatty acid accumulation, and cardiac hypertrophy and improved mitochondrial performance in DT-induced mice. In vitro experiments in H9c2 cells showed that DT directly inhibited the activity of the respiratory chain complex, whereas oxidative phosphorylation and β-oxidation gene expression is upregulated. Lycopene enhanced the activity of the complexes and inhibited ROS production caused by compensatory regulation.

CONCLUSION

Lycopene improves DT-mediated myocardial energy homeostasis disorder by promoting the activity of respiratory chain complexes I and IV and alleviates the accumulation of cardiac fatty acids and myocardial hypertrophy.

Immunohistochemistry in the Detection of Early Myocardial Infarction: Systematic Review and Analysis of Limitations Because of Autolysis and Putrefaction

The postmortem diagnosis of acute myocardial infarction is one of the main problems in forensic practice, especially in cases in which death occurs soon after (from minutes to a few hours) the onset of the ischemic damage. Several authors have highlighted the possibility to overcome the limits of conventional histology in this diagnosis by utilizing immunohistochemistry. In the present research, we examined over 30 scientific studies and picked out over 20 main immunohistochemical antigens analyzed with a view to enabling the rapid diagnosis of early myocardial infarction. The aim of our review was to examine and summarize all the principal markers studied to date and also to consider their limitations, including protein alteration because of cadaveric autolysis and putrefaction.

Dietary Dityrosine Induces Mitochondrial Dysfunction by Diminished Thyroid Hormone Function in Mouse Myocardia

Oxidized tyrosine products (OTP) have been detected in commercial foods with high protein content, such as meat and milk products. OTP intake induces tissue oxidative stress and affects the normal activity of the hypothalamic-pituitary-thyroid axis (HPT). This study aims to investigate the effects of OTP and their main product, dityrosine (Dityr), on mouse myocardial function and myocardial energy metabolism. Mice received daily intragastric administration of either tyrosine (Tyr; 420 μg/kg body weight), Dityr (420 μg/kg body weight), or OTP (1909 μg/kg body weight) for 35 days. Additionally, H9c2 cells were incubated with various concentrations of Dityr for 72 h. We found that OTP and pure Dityr induced oxidative stress in growing mice and in H9c2 cells, resulting in a redox state imbalance, myocardial injury, mitochondrial dysfunction, and energy metabolism disorder. Dityr interferes with T3 regulation of the myocardium via the PI3K/AKT/GSK3β pathway, leading to myocardial mitochondrial damage and energy metabolism disorders. Food-borne OTP, especially Dityr, can disrupt thyroid hormone function in mouse myocardia leading to mitochondrial dysfunction, energy metabolism disorder, and oxidative stress.

The impact of sex and myocardial ischemic preconditioning on immunohistochemical markers of acute myocardial infarction

The immunohistochemical detection of dityrosine, troponins I (cTNI) and T (cTnT), and connexin 43 has been proposed as a tool for the diagnosis of myocardial infarction with short survival times. Results of clinical and experimental studies reveal that gender and/or ischemic preconditioning of the heart may have an influence on severity and magnitude of myocardial infarction. To clarify the question, if the above-mentioned markers are influenced by sex or ischemic preconditioning, experiments on isolated rat hearts using the Langendorff technique were performed. Using the hearts of 12 male and 12 female Wistar rats a local ischemia was induced through ligation of the left coronary artery. Furthermore, 12 male rat hearts underwent ischemic preconditioning of the heart by stopping the perfusion of the whole heart for 30 min and subsequently reperfusing the heart for another 60 min, before inducing local ischemia. The perfusion time after ligation varied from 10 to 60 min. A control group was comprised out of 6 male and 2 female rat hearts. These were placed in the Langendorff system for 60 min without further manipulation or received ischemic preconditioning without subsequent local ischemia or were excised without being mounted on the Langendorff system at all. All hearts were fixed in formalin and stained immunohistochemically. Depletion of the marker cTnT appeared to be less in females when compared to male hearts, for all other markers tested, no apparent difference in staining results were seen when comparing male and female rat hearts. Male rat hearts with ischemic preconditioning showed no difference compared to male rat hearts without ischemic preconditioning when stained fort dityrosine. Connexin 43 staining was less pronounced in hearts with ischemic preconditioning, whereas cTnI as well as cTnT depletion was more pronounced in preconditioned hearts. The presented findings indicate to some extent the vulnerability of the investigated markers for the influencing factors tested.

Antiremodeling Effect of Xanthine Oxidase Inhibition in a Canine Model of Atrial Fibrillation

In a canine rapid atrial stimulation model of atrial fibrillation (AF), we have demonstrated an increased production of reactive oxygen species (ROS) along with electrical and structural remodeling. In the present study, we hypothesized that antioxidants can suppress atrial remodeling canines with AF. We therefore evaluated the effect of febuxostat, a xanthine oxidase (XO) inhibitor and a pure antioxidant, on atrial remodeling.AF was produced by performing a 3-week rapid atrial pacing (400 bpm) in 13 dogs divided into three groups: pacing + febuxostat group (n = 5; atrial pacing with 50 mg/day of febuxostat (administration); pacing control group (n = 5; atrial pacing without any drug administration); and non-pacing group (n = 3). Electrophysiological studies were conducted in the first 2 groups every week. Atrial tissue fibrosis was evaluated by Azan and immunofluorescent staining of fibronectin. Oxidative stress was evaluated by DHE and FCF-DA staining.Shortening of the refractory period and increase in AF inducibility appeared gradually in the pacing control group, but such changes were suppressed in the pacing + febuxostat group (P = 0.05). The pacing control group showed increase in fibrosis, which was suppressed in the febuxostat group. In DHE and DCF-DA staining, the pacing control group showed an increase in oxidative stress, which was suppressed in the pacing + febuxostat group. The pacing control group exhibited fibronectin expression, which was suppressed in the pacing + febuxostat group.The antioxidant effect of febuxostat may achieve an inhibition of new-onset AF in canines.

Immunohistochemical study on dystrophin expression in CAD-related sudden cardiac death: a marker of early myocardial ischaemia

The aims of this study were to assess if dystrophin can be a tool for the forensic evaluation of sudden cardiac death due to coronary atherosclerotic disease (CAD) and particularly if it can be a marker of early myocardial ischaemia. Then in this investigation, the dystrophin was compared to C5b-9 and fibronectin to analyze if there are some differences in the expression of these proteins. Two groups of CAD-related sudden cardiac death, respectively the group 1 with gross and/or histological evidence and the group 2 with no specific histological signs of myocardial ischaemia were used. A third group formed by cases of acute mechanical asphyxiation was used as a control. The immunohistochemical staining by dystrophin, C5b-9 and fibronectin antibodies was performed. Loss of sarcolemmal dystrophin was observed in different degrees according to more or less significant histological evidence of myocardial ischaemia. Moreover, the comparison between loss of dystrophin expression and fibronectin positivity showed significant differences in group 2. The results suggested that dystrophin can be used in forensic diagnosis of CAD-related sudden cardiac death and as marker of early myocardial ischaemia.

Matrixmetalloproteinases and tissue inhibitors of metalloproteinases: Immunhistochemical markers in the diagnosis of lethal myocardial infarctions?

Matrixmetalloproteinases (MMP) 2 and 9 as well as tissue inhibitor of metalloproteinases (TIMP) 1 were tested as markers of myocardial early ischemia/infarctions. Experiments with an animal model, the isolated Langendorff heart, and analysis of human tissue samples drawn during autopsies were performed. Results of the experiments with the Langendorff model implied that the detectable amount of the markers might increase early after the onset of ischemia, in less than one hour, under ideal conditions. The results of the examined human cases showed that MMP-2 is constantly detectable in human myocardial tissue with an increased amount in case of an infarction with longer survival times. MMP-9 and TIMP-1 were negative in control cases, distinct positive staining results were obtained mainly in cases of infarctions with longer survival times and only rarely in those with a short survival time. According to these results MMPs and TIMPs do not qualify as first choice markers of myocardial infarctions. As an interesting side finding in the Langendorff experiments, positive staining results for all three markers were seen in myocardial areas that were mechanically traumatized by ECG-electrodes or ligation of blood vessels. These findings make the markers interesting for forensic wound age estimation.

Immunohistochemical detection of early myocardial infarction: a systematic review

The postmortem diagnosis of early myocardial infarction is a challenge for forensic pathologists because the routine histology is neither specific. Many authors have suggested the use of the immunohistochemistry to fill the gaps in the histological diagnosis of early myocardial infarction. This review aims to analyse advances of immunohistochemical detection of early cardiac damage due to ischaemia. To this purpose, we reviewed experimental studies that investigated immunohistochemical markers and their estimated timing of expression. The review was performed according to specific inclusion and exclusion criteria, and a total of 23 studies assessing the immunohistochemical markers for the diagnosis and timing of early myocardial infarction were identified. The literature review highlights that the analysed markers are complement components, others being inflammatory mediators, cardiac cell proteins, plasma proteins, stress or hypoxia-induced factors and proteins associated with heart failure. All studies demonstrate the effectiveness of the tested markers in the early detection of myocardial infarction in both animal and human samples.

Decreased mRNA levels of cardiac Cx43 and ZO1 in sudden cardiac death related to coronary atherosclerosis: a pilot study

Sudden cardiac death (SCD) is the most frequent cause of sudden unexplained death in forensic practice. The most common cause of SCD is coronary artery disease related to coronary atherosclerosis. Previous study suggested the possible application of connexin 43 (Cx43) and zonula occludens-1 (ZO1) immunostaining in the early diagnosis of myocardial ischemia. However, there appears to be insufficient data with regard to their mRNA levels. The present study investigated the cardiac mRNA levels of Cx43 and ZO1, using forensic autopsy materials consisting of 41 control cases without any disease or structural abnormality of the heart (group 1), 32 deaths due to acute ischemic heart disease related to coronary atherosclerosis without apparent myocardial necrosis (group 2), and 29 traumatic deaths with coronary atherosclerosis (group 3). Ten candidate reference genes were evaluated in the left ventricles of 10 forensic autopsy cases. EEF1A1, PPIA, TPT1, and RPL13A were identified as the most stable reference genes. Using these validated reference genes, mRNA levels of Cx43 and ZO1 were examined in the bilateral ventricles and atria of the heart. Relative mRNA quantification demonstrated decreased calibrated normalized relative quantity (CNRQ) values of Cx43 and ZO1 in bilateral ventricles of group 2. When using one conventional reference gene (GAPDH or ACTB) for normalization, nearly no difference was detected among the three groups. These findings indicate that ventricular gap junction remodeling may be a key contributor to rhythm disturbances. Analysis of cardiac Cx43 and ZO1 using real-time PCR is useful in diagnosis of SCD, and validation of reference genes is crucial.

Dityrosine as a marker of acute myocardial infarction? Experiments with the isolated Langendorff heart

The isolated Langendorff heart was used to evaluate dityrosine as a marker of acute myocardial infarctions. The animal model allowed the generation of local infarctions with defined survival times, as well as infarctions with and without reperfusion. The results showed that dityrosine, at least under the conditions of the animal model, occurs very shortly after early ischemia and infarctions, since positive staining results were already obtained after a survival time of only 5 min. Furthermore, it could be proved that the occurrence of dityrosine does not depend on a reperfusion of the ischemic muscle area and that there are no differences in the staining patterns of infarctions with and without reperfusion. Positive staining results for dityrosine in control hearts without infarctions had to be considered when evaluating the tissue samples of the study hearts. In part, the positive staining results of the control hearts seemed to be an artefact of the Langendorff system, easily identifiable by a distinctive staining pattern. Positive staining results in tissue samples of hearts that suffered from arrhythmia on the other hand implied that the occurrence of dityrosine is not specific for myocardial infarctions. Taking into account the results of previous works on human tissue samples, however, these findings did not question the use of dityrosine as a diagnostic tool; they simply showed that myocardial damage due to oxidative stress might occur under various pathologic conditions.