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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.

Multiple studies indicate that post-traumatic stress disorder (PTSD) is a risk factor for cardiovascular disease (CVD), however the mechanisms behind this correlation is unknown. We hypothesize that PTSD stimulates recruitment of monocyte-derived macrophages to the heart, resulting in increased cardiac fibrosis and resetting cardiac homeostasis. To induce experimental PTSD, male C57BL/6 mice were given 5 different foot-shocks (IFS; 1.0 mA, 1 sec duration) in 6 min. Before each shock, a tone was played to act as the PTSD-associated trigger. Control mice were also placed in the IFS chambers for 6 min but did not receive foot shocks. Behavioral testing was performed to characterize mice into non-responders (NR; IFS mice that do not demonstrate PTSD-like behavioral characteristics) and PTSD-like mice. Terminal timepoints selected were 4-weeks (4.6±0.7 months old) and 13-weeks (8.2±0.0 months old) post-IFS. Doppler echocardiography was collected at the 4-week time point. Histological and immunoblot assessments were collected at 13-weeks post-IFS to determine chronic alterations in cardiac homeostasis. Doppler measurements revealed that 4-weeks post-IFS, PTSD-like mice had decreased aortic ejection time (p This work was supported by the National Institutes of Health T32GM123055; the American Heart Association Innovator Project IPA35260039; the Biomedical Laboratory Research and Development Service of the Veterans Affairs Office of Research and Development Award IK2BX003922; and South Carolina Translational Research Center UL1TR001450 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Post-myocardial infarction (MI) left ventricular scar formation and composition is one critical determinant of myocardial remodeling. CD8+ T-cells are adverse regulators of the post-MI remodeling process, leading to decreased cardiac function and survival. Based on our previous studies, we hypothesize that CD8+ T-cells impair cardiac function by altering scar composition, leading to poor tissue biomechanical properties.MI was induced by permanently ligating the left anterior descending coronary artery on C57BL6/J wildtype (WT; 3-7 months of age, n≥4/sex/Day post-MI) and CD8atm1mak (CD8-/-; 3-7 months of age, n≥4/sex/Day post-MI) mice. To test potential effects on the scar, CD8-/- mice were injected with either vehicle or naïve splenic CD8+ T-cells via tail vein, 4 hours post-coronary artery ligation. At day 7 post-MI, infarct tissue was collected and underwent passive stretch biomechanical analysis using an Aurora Scientific tension-length dual mode lever servosystem. To examine a possible mechanism of scar alteration, we tested the effects of recombinant granzymes (Gzm) B and K, which are highly expressed in CD8+ T-cells, on collagen cleavage using a fluorogenic collagen cleavage assay.Scar biomechanics of CD8-/- mice demonstrated increased regional stiffness compared to WT mice. Re-supplementation with splenic CD8+ T-cells decreased scar tissue stiffness by more than 2-fold compared to vehicle treated CD8-/- mice, mimicking the biomechanics of WT mice. Ex-vivo GzmK demonstrated the ability to cleave collagen in a concentration and temporal-dependent manner. Cleavage of the collagen substrate was detected within a 6-hour period at GzmK concentrations as low as 50 nanomolar (nM), and as early as 2-hours at 100 nM. GzmK at a concentration of 100 nM demonstrated a 10-fold greater collagen cleavage capacity compared to GzmB at the same concentration suggesting that GzmK actions may be distinctly separate from that of GzmB in the post-MI setting.In conclusion, our data demonstrates that CD8+ T-cells regulate cardiac fibrosis likely through release of granzymes, leading to alterations in the biomechanical capability of the left ventricle. This project was funded by the National Institutes of Health T32GM123055, GM113278; the American Heart Association Innovator Project IPA35260039; the Biomedical Laboratory Research and Development Service of the Veterans Affairs Office of Research and Development Award IK2BX003922; and South Carolina Translational Research Center UL1TR001450. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

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.

Although there is a well-documented link between periodontal disease and heart health, the mechanisms are unclear. Our study indicates that in response to circulating periodontal endotoxins, memory CD8+ T cells are activated, resulting in an acceleration of macrophage-mediated inflammation after MI. Blocking activation of effector CD8+ T cells had no effect on the macrophage numbers or wall thinning at post-MI day 1, indicating that this response was likely due in part to memory CD8+ T cells.

Oral and gum health have long been associated with incidence and outcomes of cardiovascular disease. Periodontal disease increases myocardial infarction (MI) mortality by sevenfold through mechanisms that are not fully understood. The goal of this study was to evaluate whether lipopolysaccharide (LPS) from a periodontal pathogen accelerates inflammation after MI through memory T-cell activation. We compared four groups [no MI, chronic LPS, day 1 after MI, and day 1 after MI with chronic LPS (LPS + MI); n = 68 mice] using the mouse heart attack research tool 1.0 database and tissue bank coupled with new analyses and experiments. LPS + MI increased total CD8(+) T cells in the left ventricle versus the other groups (P < 0.05 vs. all). Memory CD8(+) T cells (CD44( + )CD27(+)) were 10-fold greater in LPS + MI than in MI alone (P = 0.02). Interleukin (IL)-4 stimulated splenic CD8(+) T cells away from an effector phenotype and toward a memory phenotype, inducing secretion of factors associated with the Wnt/β-catenin signaling that promoted monocyte migration and decreased viability. To dissect the effect of CD8(+) T cells after MI, we administered a major histocompatibility complex-I-blocking antibody starting 7 days before MI, which prevented effector CD8(+) T-cell activation without affecting the memory response. The reduction in effector cells diminished infarct wall thinning but had no effect on macrophage numbers or MertK expression. LPS + MI + IgG attenuated macrophages within the infarct without effecting CD8(+) T cells, suggesting these two processes were independent. Overall, our data indicate that effector and memory CD8(+) T cells at post-MI day 1 are amplified by chronic LPS to potentially promote infarct wall thinning. NEW & NOTEWORTHY Although there is a well-documented link between periodontal disease and heart health, the mechanisms are unclear. Our study indicates that in response to circulating periodontal endotoxins, memory CD8(+) T cells are activated, resulting in an acceleration of macrophage-mediated inflammation after MI. Blocking activation of effector CD8(+) T cells had no effect on the macrophage numbers or wall thinning at post-MI day 1, indicating that this response was likely due in part to memory CD8(+) T cells.

Following a myocardial infarction (MI) monocytes and T-cells begin to infiltrate into the ischemic area in effort to remove necrotic debris and initiate formation of scar tissue. Interleukin (IL)-4 has been linked to improved cardiac wound healing via alterations in both the macrophage and T-cell populations. The goal of this study was determine if proteins secreted by IL-4 stimulated CD8+ T-cells would regulate monocyte physiology that would ultimately improve cardiac healing after an MI. Isolated splenic naïve CD8+ T-cells from day 0 (no MI) mice (n=5/sex/stimulation)were cultured in RPMI with either 0.1% FBS (unstimulated) or 0.1% FBS+ IL-4. After 24 hours of stimulation, the cells and media were collected and separated by centrifugation. The cell pellet was stained and analyzed for markers of activation (CD44) and memory (CD27) by flowcytometry. Conditioned media (secretome) was collected for stimulation of bone marrow monocytes (n=4; females only). After stimulation with the secretome, monocytes were analyzed for viability, phagocytosis, and macrophage phenotype by flow cytometry. Migration of the monocytes after stimulation was also measured using electric cell-substrate impedance sensing (ECIS). After IL-4 stimulation, there was a shift from effector (CD44+ CD27-) to the memory phenotype (CD44+ CD27+; p