Chronic Porphyromonas gingivalis lipopolysaccharide induces adverse myocardial infarction wound healing through activation of CD8+ T cells

Sex as a biological variable for cardiovascular physiology

There have been ongoing efforts by federal agencies and scientific communities since the early 1990s to incorporate sex and/or gender in all aspects of cardiovascular research. Scientific journals provide a critical function as change agents to influence transformation by encouraging submissions for topic areas, and by setting standards and expectations for articles submitted to the journal. As part of ongoing efforts to advance sex and gender in cardiovascular physiology research, the American Journal of Physiology-Heart and Circulatory Physiology recently launched a call for papers on Considering Sex as a Biological Variable. This call was an overwhelming success, resulting in 78 articles published in this collection. This review summarizes the major themes of the collection, including Sex as a Biological Variable Within: Endothelial Cell and Vascular Physiology, Cardiovascular Immunity and Inflammation, Metabolism and Mitochondrial Energy, Extracellular Matrix Turnover and Fibrosis, Neurohormonal Signaling, and Cardiovascular Clinical and Epidemiology Assessments. Several articles also focused on establishing rigor and reproducibility of key physiological measurements involved in cardiovascular health and disease, as well as recommendations and considerations for study design. Combined, these articles summarize our current understanding of sex and gender influences on cardiovascular physiology and pathophysiology and provide insight into future directions needed to further expand our knowledge.

ERG mediates the inhibition of NK cell cytotoxicity through the HLX/STAT4/Perforin signaling pathway, thereby promoting the progression of myocardial infarction

This study aimed to investigate the role of ERG in the HLX/STAT4/Perforin signaling axis, impacting natural killer (NK) cell cytotoxicity and myocardial infarction (MI) progression. NK cell cytotoxicity was assessed via co-culture and 51Cr release assays. Datasets GSE34198 and GSE97320 identified common differentially expressed genes in MI. NK cell gene expression was analyzed in MI patients and healthy individuals using qRT-PCR and Western blotting. ERG's regulation of HLX and STAT4's regulation of perforin were studied through computational tools (MEM) and ChIP experiments. HLX's influence on STAT4 was explored with the MG132 proteasome inhibitor. Findings were validated in a mouse MI model.ERG, a commonly upregulated gene, was identified in NK cells from MI patients and mice. ERG upregulated HLX, leading to STAT4 proteasomal degradation and reduced Perforin expression. Consequently, NK cell cytotoxicity decreased, promoting MI progression. ERG mediates the HLX/STAT4/Perforin axis to inhibit NK cell cytotoxicity, fostering MI progression. These results provide vital insights into MI's molecular mechanisms.

An eNAMPT-neutralizing mAb reduces post-infarct myocardial fibrosis and left ventricular dysfunction

Myocardial infarction (MI) triggers adverse ventricular remodeling (VR), cardiac fibrosis, and subsequent heart failure. Extracellular nicotinamide phosphoribosyltransferase (eNAMPT) is postulated to play a significant role in VR processing via activation of the TLR4 inflammatory pathway. We hypothesized that an eNAMPT specific monoclonal antibody (mAb) could target and neutralize overexpressed eNAMPT post-MI and attenuate chronic cardiac inflammation and fibrosis. We investigated humanized ALT-100 and ALT-300 mAb with high eNAMPT-neutralizing capacity in an infarct rat model to test our hypothesis. ALT-300 was 99mTc-labeled to generate 99mTc-ALT-300 for imaging myocardial eNAMPT expression at 2 hours, 1 week, and 4 weeks post-IRI. The eNAMPT-neutralizing ALT-100 mAb (0.4 mg/kg) or saline was administered intraperitoneally at 1 hour and 24 hours post-reperfusion and twice a week for 4 weeks. Cardiac function changes were determined by echocardiography at 3 days and 4 weeks post-IRI. 99mTc-ALT-300 uptake was initially localized to the ischemic area at risk (IAR) of the left ventricle (LV) and subsequently extended to adjacent non-ischemic areas 2 hours to 4 weeks post-IRI. Radioactive uptake (%ID/g) of 99mTc-ALT-300 in the IAR increased from 1 week to 4 weeks (0.54 ± 0.16 vs. 0.78 ± 0.13, P < 0.01). Rats receiving ALT-100 mAb exhibited significantly improved myocardial histopathology and cardiac function at 4 weeks, with a significant reduction in the collagen volume fraction (%LV) compared to controls (21.5 ± 6.1% vs. 29.5 ± 9.9%, P < 0.05). Neutralization of the eNAMPT/TLR4 inflammatory cascade is a promising therapeutic strategy for MI by reducing chronic inflammation, fibrosis, and preserving cardiac function.

A review of the historical use of sex as a biological variable in the American Journal of Physiology-Heart and Circulatory Physiology

Despite National Institute of Health (NIH) mandates requiring sex as a biological variable (SABV), female underrepresentation persists in research, driving the American Journal of Physiology-Heart and Circulatory Physiology (Am J Physiol-Heart Circ) to publish SABV expectations in 2021. To determine progress within the Am J Physiol-Heart Circ, this mini-review evaluated SABV during the first 6 mo of each decade from 1980 to 2020, and 2019, to mitigate pandemic influence. Of the 1,205 articles published, 1,087 articles were included in this review (articles without original research subjects were excluded), of which 72.9% identified subjects. There were consistently fewer female human participants than males, except within 2019 (1980: females n = 3, males n = 5; 1990: females n = 70, males n = 199; 2000: females n = 305, males n = 355; 2010: females n = 186, males n = 472; 2019: females n = 1,695, males n = 1,550; 2020: females n = 1,157, males n = 1,222) and fewer female animals than males (1980: females n = 58, males n = 1,291; 1990: females n = 447, males n = 2,628; 2000: females n = 590, males n = 3,083; 2010: females n = 663, males n = 4,517; 2019: females n = 338, males n = 1,340; 2020: females n = 1,372, males n = 1,973). Only 16 (12.3%) articles including humans discussed SABV from 1980 to 2020. There are persistent SABV disparities within Am J Physiol-Heart Circ with some improvements in recent years. It is imperative that organizations such as the American Physiological Society and NIH foster an expectation of SABV as the norm, not the exception.

Regulation of cardiac fibroblasts by lymphocytes after a myocardial infarction: playing in the major league

Cardiac fibrosis is a pathological condition characterized by excessive accumulation of extracellular matrix components within the myocardium, which can lead to impaired cardiac function and heart failure. Studies have shown that lymphocytes including B and T cells play important roles in the development and progression of cardiac fibrosis after a myocardial infarction. In this review, we focus on the regulation of cardiac fibrosis by lymphocyte subsets, with a particular emphasis on CD4+ and CD8+ T cells and their effects on fibroblasts and cardiac remodeling. We also highlight areas for further exploration of the interactions between T cells and fibroblasts necessary for understanding and treating cardiac fibrosis and heart failure.

The cardiac wound healing response to myocardial infarction

Myocardial infarction (MI) is defined as evidence of myocardial necrosis consistent with prolonged ischemia. In response to MI, the myocardium undergoes a series of wound healing events that initiate inflammation and shift to anti-inflammation before transitioning to tissue repair that culminates in scar formation to replace the region of the necrotic myocardium. The overall response to MI is determined by two major steps, the first of which is the secretion of proteases by infiltrating leukocytes to breakdown extracellular matrix (ECM) components, a necessary step to remove necrotic cardiomyocytes. The second step is the generation of new ECM that comprises the scar; and this step is governed by the cardiac fibroblasts as the major source of new ECM synthesis. The leukocyte component resides in the middle of the two-step process, contributing to both sides as the leukocytes transition from pro-inflammatory to anti-inflammatory and reparative cell phenotypes. The balance between the two steps determines the final quantity and quality of scar formed, which in turn contributes to chronic outcomes following MI, including the progression to heart failure. This review will summarize our current knowledge regarding the cardiac wound healing response to MI, primarily focused on experimental models of MI in mice. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Immune System Diseases > Molecular and Cellular Physiology.

Riding the wave: a quantitative report of electrocardiogram utilization for myocardial infarction confirmation

The purpose of this study was to generate a quantitative profile of electrocardiograms (ECGs) for confirming surgical success of permanent coronary artery ligation. An ECG was recorded at baseline, and 0, 1, and 5 min after ligation and analyzed using iWorkx LabScribe software. Cohort 1 (C57Bl6/J, n = 8/sex) was enrolled to determine ECG characteristics that were confirmed in cohort 2 (C57Bl6/J, n = 6/sex; CD8-/-n = 6 males/4 females). Of the 16 mice in cohort 1, 12 (6/sex) had an infarct ≥35% and four mice (2/sex) had <35% based on 2,3,5-triphenyltetrazolium chloride staining. After ligation, the QRS complex and R-S amplitude were significantly different compared with baseline. No differences were observed in the R-S amplitude between mice with infarcts ≥35% versus <35% at any time point, whereas the QRS complex was significant 1 min after ligation. Receiver operating characteristic (ROC) curve linked changes in the QRS complex but not the R-S amplitude at 1 and 5 min with surgical success. Data were normalized to baseline values to calculate fold change. ROC analysis of the normalized QRS data indicated strong sensitivity and specificity for infarcts ≥35%; normalized R-S amplitude remained nonsignificant. With a cutoff generated by ROC analysis of cohort 1 (>80% sensitivity; >90% specificity), the non-normalized QRS complex of cohort 2 had an 86% success rate (2 false positives; 1 false negative). The normalized data had a 77% success rate (2 false positives; 3 false negatives). Neither sex nor genotype was associated with false predictions (P = 0.18). Our data indicate that the area under the QRS complex 1 min after ligation can improve reproducibility in MI surgeries.NEW & NOTEWORTHY Our study describes a quantitative method for using an electrocardiogram (ECG) to determine which animals have infarcts that reflect coronary artery ligation. Using a quantitative ECG, investigators will have the benefit of having real-time feedback during the procedure, which will ultimately decrease the amount of time investigators spend performing experiments. This overall increase in efficiency will help investigators decrease animal numbers used due to better surgical outcomes.

Innate immune stimulation prevents chronic stress-induced depressive and anxiogenic-like behaviors in female mice

It has been reported that pre-stimulation of the innate immune system can prevent depressive and anxiogenic-like behaviors in chronically stressed male mice. However, it is unclear whether similar effects can be observed in female animals. In the present study, we investigated this question in female mice. Our results showed that a single injection of lipopolysaccharide (LPS; 100 μg/kg) one day before stress exposure prevented increased immobility time in the tail suspension test and forced swimming test and decreased sucrose intake in the sucrose preference test in chronic unpredictable stress (CUS)-treated female mice. The single LPS pre-injection (100 μg/kg) prevented the CUS-induced decrease in (i) time spent in open arms and number of entries into open arms in the elevated plus maze test, (ii) time spent in lit side in the light-dark test, and (iii) time spent in the central region of the open field in the open field test, along with no changes in locomotor activity. It was also found that the single LPS pre-injection in female mice prevented the CUS-induced increase in the expression levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 mRNA in the hippocampus and medial prefrontal cortex. Inhibition of innate immune system stimulation by minocycline pretreatment abrogated the preventive effect of LPS on CUS-induced depressive and anxiogenic-like behaviors and neuroinflammatory responses in the hippocampus and medial prefrontal cortex in female mice. These results suggest that pre-stimulation of the innate immune system by LPS injection may prevent the development of behavioral abnormalities in female mice.

Immunomodulatory effects of icariin in a myocardial infarction mouse model

Myocardial infarction (MI) is a prevalent cardiovascular disease defined by myocardial ischemia and hypoxic damage caused by plaque rupture, thrombosis, lumen stenosis, or blockage in the coronary artery. However, the development of emergency percutaneous coronary interventional therapy has enabled the rapid restoration of blood perfusion to ischemic myocardium and the rescue of dying myocardium cells. Some dying myocardium cells have caused irreversible damage and impaired cardiac function recovery in recent years. Icariin has been utilized to treat various ailments as a natural chemical extract. In this study, we employed a variety of approaches to observe MI, including western blotting, quantitative RT–PCR, immunohistochemistry, and flow cytometric analysis using icariin. As demonstrated by the research findings, icariin may prevent MI-induced cell apoptosis. This is accomplished by inhibiting proinflammatory factors via the Nrf2/HO-1 signaling pathways. These data imply that icariin may be an effective treatment for MI.

A common oral pathogen Porphyromonas gingivalis induces myocarditis in rats

AIM

To evaluate whether Porphyromonas gingivalis (P. gingivalis) inoculation could induce cardiac remodelling in rats.

MATERIALS AND METHODS

The study was conducted on 33 Wistar rats, which were distributed in the following experimental groups: not inoculated; inoculated with 1 × 10⁸ CFU/ml of bacteria; inoculated with 3 × 10⁸ CFU/ml of bacteria. The animals were inoculated at baseline and on the 15th day of follow-up. Blood collection was performed at baseline and 60 min after each inoculation. At 29 days, the animals were subjected to echocardiography and at 30 days to haemodynamic studies before sacrificing them.

RESULTS

Impact of the bacteria was more evident in rats that received higher P. gingivalis concentration. Thus, 3 × 10⁸ CFU/ml of bacteria increased the rectal temperature and water content in the lung as well as myocardial necrosis and fibrosis. P. gingivalis induced the intensification of DNA fragmentation and increased the levels of malondialdehyde, oxidized proteins, and macrophage expression in the myocardium. These findings were associated with lower LV isovolumetric relaxation time, +dP/dt, -dP/dt, and higher end-diastolic pressure.

CONCLUSIONS

P. gingivalis bacteraemia is significantly associated with adverse cardiac remodelling and may play a biological role in the genesis of heart failure.

S100A9 is a functional effector of infarct wall thinning after myocardial infarction

Neutrophils infiltrate into the left ventricle (LV) early after myocardial infarction (MI) and launch a proinflammatory response. Along with neutrophil infiltration, LV wall thinning due to cardiomyocyte necrosis also peaks at day 1 in the mouse model of MI. To understand the correlation, we examined a previously published data set that included day 0 (n = 10) and MI day (D) 1 (n = 10) neutrophil proteome and echocardiography assessments. Out of 123 proteins, 4 proteins positively correlated with the infarct wall thinning index (1/wall thickness): histone 1.2 (r = 0.62, P = 0.004), S100A9 (r = 0.60, P = 0.005), histone 3.1 (r = 0.55, P = 0.01), and fibrinogen (r = 0.47, P = 0.04). As S100A9 was the highest ranked secreted protein, we hypothesized that S100A9 is a functional effector of infarct wall thinning. We exogenously administered S100A8/A9 at the time of MI to mice [C57BL/6J, male, 3-6 mo of age, n = 7 M (D1), and n = 5 M (D3)] and compared with saline vehicle control-treated mice [n = 6 M (D1) and n = 6 M (D3)] at MI days 1 and 3. At MI day 3, the S100A8/A9 group showed a 22% increase in the wall thinning index compared with saline (P = 0.02), along with higher dilation and lower ejection fraction. The decline in cardiac physiology occurred subsequent to increased neutrophil and macrophage infiltration at MI day 1 and increased macrophage infiltration at D3. Our results reveal that S100A9 is a functional effector of infarct wall thinning.NEW & NOTEWORTHY S100A9 is a functional marker of infarct wall thinning.

Organized Chaos: Deciphering Immune Cell Heterogeneity's Role in Inflammation in the Heart

During homeostasis, immune cells perform daily housekeeping functions to maintain heart health by acting as sentinels for tissue damage and foreign particles. Resident immune cells compose 5% of the cellular population in healthy human ventricular tissue. In response to injury, there is an increase in inflammation within the heart due to the influx of immune cells. Some of the most common immune cells recruited to the heart are macrophages, dendritic cells, neutrophils, and T-cells. In this review, we will discuss what is known about cardiac immune cell heterogeneity during homeostasis, how these cell populations change in response to a pathology such as myocardial infarction or pressure overload, and what stimuli are regulating these processes. In addition, we will summarize technologies used to evaluate cell heterogeneity in models of cardiovascular disease.

Guidelines for in vivo mouse models of myocardial infarction

Despite significant improvements in reperfusion strategies, acute coronary syndromes all too often culminate in a myocardial infarction (MI). The consequent MI can, in turn, lead to remodeling of the left ventricle (LV), the development of LV dysfunction, and ultimately progression to heart failure (HF). Accordingly, an improved understanding of the underlying mechanisms of MI remodeling and progression to HF is necessary. One common approach to examine MI pathology is with murine models that recapitulate components of the clinical context of acute coronary syndrome and subsequent MI. We evaluated the different approaches used to produce MI in mouse models and identified opportunities to consolidate methods, recognizing that reperfused and nonreperfused MI yield different responses. The overall goal in compiling this consensus statement is to unify best practices regarding mouse MI models to improve interpretation and allow comparative examination across studies and laboratories. These guidelines will help to establish rigor and reproducibility and provide increased potential for clinical translation.