Disassociation Between Left Ventricular Mechanical and Electrical Properties in Ischemic Rat Heart After G-CSF Treatment

Granulocyte colony-stimulating factor attenuates myocardial remodeling and ventricular arrhythmia susceptibility via the JAK2-STAT3 pathway in a rabbit model of coronary microembolization

Background

Coronary microembolization (CME) has a poor prognosis, with ventricular arrhythmia being the most serious consequence. Understanding the underlying mechanisms could improve its management. We investigated the effects of granulocyte colony-stimulating factor (G-CSF) on connexin-43 (Cx43) expression and ventricular arrhythmia susceptibility after CME.

Methods

Forty male rabbits were randomized into four groups (n = 10 each): Sham, CME, G-CSF, and AG490 (a JAK2 selective inhibitor). Rabbits in the CME, G-CSF, and AG490 groups underwent left anterior descending (LAD) artery catheterization and CME. Animals in the G-CSF and AG490 groups received intraperitoneal injection of G-CSF and G-CSF + AG490, respectively. The ventricular structure was assessed by echocardiography. Ventricular electrical properties were analyzed using cardiac electrophysiology. The myocardial interstitial collagen content and morphologic characteristics were evaluated using Masson and hematoxylin-eosin staining, respectively.

Results

Western blot and immunohistochemistry were employed to analyze the expressions of Cx43, G-CSF receptor (G-CSFR), JAK2, and STAT3. The ventricular effective refractory period (VERP), VERP dispersion, and inducibility and lethality of ventricular tachycardia/fibrillation were lower in the G-CSF than in the CME group (P < 0.01), indicating less severe myocardial damage and arrhythmias. The G-CSF group showed higher phosphorylated-Cx43 expression (P < 0.01 vs. CME). Those G-CSF-induced changes were reversed by A490, indicating the involvement of JAK2. G-CSFR, phosphorylated-JAK2, and phosphorylated-STAT3 protein levels were higher in the G-CSF group than in the AG490 (P < 0.01) and Sham (P < 0.05) groups.

Conclusion

G-CSF might attenuate myocardial remodeling via JAK2-STAT3 signaling and thereby reduce ventricular arrhythmia susceptibility after CME.

Neutrophil extracellular traps in ischemia-reperfusion injury-induced myocardial no-reflow: therapeutic potential of DNase-based reperfusion strategy

Emerging evidence suggests a potential role of neutrophil extracellular traps (NETs) in linking sterile inflammation and thrombosis. We hypothesized that NETs would be induced during myocardial ischemia-reperfusion (I/R), and NET-mediated microthrombosis may contribute to myocardial "no-reflow". Male Wistar rats were randomly divided into I/R control, DNase (DNase I, 20 μg/rat), recombinant tissue-type plasminogen activator (rt-PA, 420 μg/rat), DNase + rt-PA, and sham control groups after 45-min myocardial ischemia. In situ NET formation, the anatomic "no re-flow" area, and infarct size were evaluated immediately after 3 h of reperfusion. Long-term left ventricular (LV) functional and histological analyses were performed 45 days after operation. Compared with the I/R controls, the DNase + rt-PA group exhibited reduced NET density [8.38 ± 1.98 vs. 26.86 ± 3.07 (per 200 × field), P < 0.001] and "no-flow" area (15.22 ± 0.06 vs. 34.6 ± 0.05%, P < 0.05) in the ischemic region, as well as reduced infarct size (38.39 ± 0.05 vs. 71.00 ± 0.03%, P < 0.001). Additionally, compared with the I/R controls, DNase + rt-PA treatment significantly ameliorated I/R injury-induced LV remodeling (LV ejection fraction: 64.22 ± 3.37 vs. 33.81 ± 2.98%, P < 0.05; LV maximal slope of the LV systolic pressure increment: 3,785 ± 216 vs. 2,596 ± 299 mmHg/s, P < 0.05). The beneficial effect was not observed in rats treated with DNase I or rt-PA alone. Our study provides evidence for the existence of NETs in I/R-challenged myocardium and confirms the long-term benefit of a novel DNase-based reperfusion strategy (DNase I + rt-PA), which might be a promising option for the treatment of myocardial I/R injury and coronary no-reflow.

Modulation of mononuclear phagocyte inflammatory response by liposome-encapsulated voltage gated sodium channel inhibitor ameliorates myocardial ischemia/reperfusion injury in rats

BACKGROUND

Emerging evidence shows that anti-inflammatory strategies targeting inflammatory monocyte subset could reduce excessive inflammation and improve cardiovascular outcomes. Functional expression of voltage-gated sodium channels (VGSCs) have been demonstrated in monocytes and macrophages. We hypothesized that mononuclear phagocyte VGSCs are a target for monocyte/macrophage phenotypic switch, and liposome mediated inhibition of mononuclear phagocyte VGSC may attenuate myocardial ischemia/reperfusion (I/R) injury and improve post-infarction left ventricular remodeling.

METHODOLOGY/PRINCIPAL FINDINGS

Thin film dispersion method was used to prepare phenytoin (PHT, a non-selective VGSC inhibitor) entrapped liposomes. Pharmacokinetic study revealed that the distribution and elimination half-life of PHT entrapped liposomes were shorter than those of free PHT, indicating a rapid uptake by mononuclear phagocytes after intravenous injection. In rat peritoneal macrophages, several VGSC α subunits (NaV1.1, NaV1.3, NaV1.4, NaV1.5, NaV1.6, NaV1.7, NaVX, Scn1b, Scn3b and Scn4b) and β subunits were expressed at mRNA level, and PHT could suppress lipopolysaccharide induced M1 polarization (decreased TNF-α and CCL5 expression) and facilitate interleukin-4 induced M2 polarization (increased Arg1 and TGF-β1 expression). In vivo study using rat model of myocardial I/R injury, demonstrated that PHT entrapped liposome could partially suppress I/R injury induced CD43+ inflammatory monocyte expansion, along with decreased infarct size and left ventricular fibrosis. Transthoracic echocardiography and invasive hemodynamic analysis revealed that PHT entrapped liposome treatment could attenuate left ventricular structural and functional remodeling, as shown by increased ejection fraction, reduced end-systolic and end-diastolic volume, as well as an amelioration of left ventricular systolic (+dP/dt max) and diastolic (-dP/dt min) functions.

CONCLUSIONS/SIGNIFICANCE

Our work for the first time demonstrates the therapeutic potential of VGSC antagonism via liposome mediated monocyte/macrophage targeting in acute phase after myocardial I/R injury. These results suggest that VGSCs in mononuclear phagocyte system might be a novel target for immunomodulation and treatment of myocardial I/R injury.

Short-term intermittent administration of CXCR4 antagonist AMD3100 facilitates myocardial repair in experimental myocardial infarction

The binding of the stromal cell-derived factor-1α (SDF-1α) to the cysteine (C)-X-C motif chemokine receptor 4 (CXCR4) has emerged as a key signal for stem and progenitor cells trafficking to the circulation from the bone marrow. Our aim was to investigate the role of daily intermittent administration of AMD3100 (a specific reversible CXCR4 receptor antagonist) during the healing process after myocardial infarction (MI). Wistar rats were subjected to MI and AMD3100 was injected intraperitoneally after surgery. SDF-1α mRNA expression was measured by real-time polymerase chain reaction. Histology changes were analyzed with immunofluorescence, Masson's trichrome staining, and wheat germ agglutinin. The number of leukocytes in peripheral blood was measured by complete blood cell count analysis. The activities of matrix metalloproteinase-2/9 (MMP-2/9) were determined by gelatin zymography. The expression level of SDF-1α mRNA in the infarcted tissue was enhanced rapidly (6 h), peaked at 24 h, and then declined to the normal level at 7 days post-MI. AMD3100 further enhanced the increase of SDF-1α in infarct area. Increased leukocytes were observed in AMD3100-treated groups. The mobilization of c-kit(+) stem/progenitor cells and enhanced neovascularization were augmented by AMD3100. Additionally, AMD3100 improved ventricular remodeling, which was revealed by the decrease of infarct size, viable cardiomyocyte cross-sectional area and left ventricle (LV) expansion index, and the increase of LV free wall thickness. The activities of MMP-2/9 were up-regulated by AMD3100. In conclusion, short-term intermittent administration of AMD3100 could accelerate the wound healing process in experimental MI and be a potential therapy for the treatment of MI.

Acute effects of granulocyte colony-stimulating factor on early ventricular arrhythmias after coronary occlusion in rats

Objectives:

To evaluate the acute effects of colony-stimulating factor (G-CSF) on ventricular arrhythmias after coronary occlusion in rats.

Materials and Methods:

Male Wistar rats (10 weeks) received G-CSF (100 μg.kg^-1) or vehicle. Thirty minutes later, animals were infarcted by coronary occlusion under artificial respiration. Electrocardiogram was monitored for 30 min to evaluate ventricular arrhythmias.

Results:

G-CSF treatment reduced the number of premature ventricular beats and the number and duration of ventricular tachycardia. The incidence of ventricular fibrillation was significantly reduced by G-CSF (MI-Cont: 11.2 ± 2.4 vs. MI-GCSF: 5.4 ± 1 events; P < 0.05). However, total duration of ventricular fibrillation was not altered (MI-Cont: 84 ± 16 vs. MI-GCSF: 76 ± 13 sec).

Conclusions:

Acute administration of G-CSF before coronary ligature in rats reduces the incidence of ventricular premature beats and ventricular tachycardia, suggesting a possible direct electrophysiological effect of this cytokine independently of its genomic effects. However, the data suggest that G-CSF treatment may affect the spontaneous recovery from ventricular fibrillation. Acute G-CSF administration acts directly on cardiac electrophysiology, different from chronic treatment.