Combined inhibition of P-selectin and ICAM-1 reduces myocardial injury following ischemia and reperfusion

A new method for the treatment of myocardial ischemia-reperfusion injury based on γδT cell-mediated immune response

Acute myocardial ischemia is a disease with high morbidity and mortality, and re-perfusion is currently the best intervention. However, re-perfusion may lead to further myocardial injury and increase the area of myocardial infarction. The mechanism of myocardial ischemia-re-perfusion injury is complex, but with more in-depth study, it has been proved that the immune system plays an important role in the process of MIRI. Among them, the γδT cell population has received increasing attention as the main early source of IL-17A in many immune response models. Because γδT cells have the characteristics of linking innate immunity and adaptive immunity,they can rapidly produce IL-17A and produce subsequent immune killing of cardiomyocytes. It can be seen that γδT cells play an important role in MIRI. Therefore, here we review the research progress of immune response in myocardial ischemia-re-perfusion injury, the key characteristics of γδT cells and the role of rapidly produced IL-17 in myocardial ischemia-re-perfusion injury, and propose relevant treatment strategies and prospects for myocardial repair, in order to provide new ideas and methods for clinical treatment of myocardial ischemia-re-perfusion injury.

Role of CC-chemokine receptor 5 on myocardial ischemia-reperfusion injury in rats

The expression level of CC-chemokine receptor 5 (CCR5) is enhanced post inflammatory stimulations and might play a crucial role on inflammatory cells infiltration post myocardial ischemia. The purpose of this study was to evaluate the role of CCR5 on myocardial ischemia-reperfusion (I/R) injury in rats. Adult male rats were randomized to sham group, I/R group (I/R, 30 min coronary artery occlusion followed by 2-h reperfusion), ischemic preconditioning (I/R + Pre), CCR5 antibody group [I/R + CCR5Ab (0.2 mg/kg)], and CCR5 agonist group [I/R + CCR5Ago, RNATES (0.1 mg/kg)], n = 12 each group. The serum level of creatine kinase (CK) and tumor necrosis factor α (TNF-α) were measured by ELISA. Myocardial infarction size and myeloperoxidase (MPO) activity were determined. Myocardial protein expression of CCR5 and intercellular adhesion molecule-1 (ICAM-1) were evaluated by Western blotting and immunohistochemistry staining, respectively. Myocardial nuclear factor-kappa B (NF-κB) activity was assayed by electrophoretic mobility shift assay. Myocardial CCR5 protein expression was significantly reduced in I/R + Pre group (P < 0.05 vs. I/R) and further reduced in I/R + CCR5Ab group (P < 0.05 vs. I/R + Pre). LVSP and ±dP/dt(max) were significantly lower while serum CK and TNF-α as well as myocardial MPO activity, ICAM-1 expression, and NF-κB activity were significantly higher in I/R group than in sham group (all P < 0.05), which were significantly reversed by I/R + Pre (all P < 0.05 vs. I/R) and I/R + CCR5Ab (all P < 0.05 vs. I/R + Pre) while aggravated by I/R + CCR5Ago (all P < 0.05 vs. I/R). Our results suggest that blocking CCR5 attenuates while enhancing CCR5 aggravates myocardial I/R injury through modulating inflammatory responses in rat heart.

Infiltration of polymorphonuclear cells into the post-ischaemic myocardium is dependent on beta2 and alpha4 integrins

Polymorphonuclear cells (PMN) are believed to be important effector cells responsible the myocardial damage seen following ischaemia. However, the exact kinetics of their migration remains controversial. Isolated PMN (10 x 10(6) cells) labelled with (51)Cr were injected into four groups of Lewis rats: 0 h (T0h; n = 13), 2 h (T2h; n = 7), 4 h (T4h; n = 7) or 6 h following ischaemia (T6h; n = 4). In all recipients, a left thoracotomy and ligation of the left anterior descending coronary was performed. Control animals underwent sham thoracotomy (n = 10). All animals were killed at 24 h and the radioactivity in the tissue measured to estimate labelled PMN migration. Monoclonal antibody blockade was also performed in experimental animals to assess the contribution of beta2 and alpha4 integrins to the PMN migration (n = 32). Labelled PMN migration to the myocardium was similar in all experimental groups, T0-T6h (7.2-11 x 10(5) labelled PMN) and significantly higher than sham controls (2.2 x 10(5) labelled PMN; P = 0.03). In contrast PMN migration to dermal inflammatory sites was highest in T0h group, and reached background level in the T4h and T6h groups. beta2 integrin blockade inhibited labelled PMN migration by 32%. Blockade of alpha4 integrin inhibited PMN migration by 30% while the combined beta2 + alpha4 blockade resulted in 63% inhibition of labelled PMN migration compared to treatment with isotype control antibody (P = 0.035). PMN migration following myocardial ischaemia persists over several hours after myocardial infarction and does not follow similar migration kinetics to dermal inflammation. Our findings also suggest that PMN migration is dependent equally on beta2 and alpha4 integrins.

Changes in P-selectin expression on cardiac microvessels in blood-perfused rat hearts subjected to ischemia-reperfusion

BACKGROUND

During cardiac surgery involving cardiopulmonary bypass, activation of polymorphonuclear cells is believed to contribute to ischemia-reperfusion injury and subsequent myocardial impairment of function. The early tethering of polymorphonuclear cells to blood vessel walls depends upon recognition of the adhesion molecule P-selectin on endothelium. The purpose of this study was to define the kinetic changes in expression of P-selectin on myocardial vessels in a model of global ischemia-reperfusion injury.

METHODS

In a novel recirculating blood-based perfusion system, rat hearts were subjected to 30 minutes of aerobic perfusion, 60 minutes of global ischemia, and 60 minutes of reperfusion, or to 120 minutes of continuous aerobic blood perfusion (with or without leukocyte/platelet depletion). Heart function (left ventricular developed pressure), heart rate, and perfusion pressure were monitored throughout. Hearts were sampled at defined periods for microvascular expression of P-selectin, identified by immunohistochemistry.

RESULTS

In control (nonperfused) hearts and in hearts subjected to perfusion and ischemia, few cardiac vessels (8% to 16%) expressed P-selectin. After 15 minutes of reperfusion, P-selectin was present on the majority of vessels (77%; p < 0.05) but expression decreased subsequently throughout the remaining duration of reperfusion. Interestingly, upregulation of P-selectin also occurred when hearts were subjected to continuous perfusion alone (no ischemia), but this upregulation was less rapid. Depletion of leukocytes/platelets from the blood perfusate did not modify P-selectin expression.

CONCLUSIONS

The augmented expression of P-selectin on myocardial vessels during reperfusion of ischemic hearts probably reflects changes induced during global ischemia and by the duration of perfusion through the nonbiological tubing of the circuit. That is likely to mimic the effects initiated during cardiopulmonary bypass.

Effect of ischemic preconditioning on P-selectin expression in hepatocytes of rats with cirrhotic ischemia-reperfusion injury

AIM: To investigate the effects and mechanisms of ischemic preconditioning (IPC) on the ischemia/reperfusion (I/R) injury of liver cirrhosis in rats and the effect of IPC on P-selectin expression in hepatocytes.

METHODS: Forty male SD rats with liver cirrhosis were randomly divided into sham operation group (SO group), ischemia/reperfusion group (I/R group), ischemic preconditioning group (IPC group), L-Arginine preconditioning group (APC group), L-NAME preconditioning group (NPC group), eight rats in each group. Hepatocellular viability was assessed by hepatic adenine nucleotide level and energy charge (EC) determined by HPLC, ALT, AST and LDH in serum measured by auto- biochemical analyzer and bile output. The expression of P-selectin in the liver tissue was analyzed by immunohistochemical technique. Leukocyte count in ischemic hepatic lobe was calculated.

RESULTS: At 120 min after reperfusion, the level of ATP and EC in IPC and APC groups was higher than that in I/R group significantly. The increases in AST, ALT and LDH were prevented in IPC and APC groups. The livers produced more bile in IPC group than in I/R group during 120 min after reperfusion (0.101 ± 0.027 vs 0.066 ± 0.027 mL/g liver, P = 0.002). There was a significant difference between APC and I/R groups, (P = 0.001). The leukocyte count in liver tissues significantly increased in I/R group as compared with SO group (P < 0.05). The increase in the leukocyte count was prevented in IPC group. Administration of L-arginine resulted in the same effects as in IPC group. However, inhibition of NO synthesis (NPC group) held back the beneficial effects of preconditioning. Significant promotion of P-selectin expression in hepatocytes in the I/R group was observed compared with the SO group (P < 0.01). IPC or L-arginine attenuated P-selectin expression remarkably (P < 0.01). However, inhibition of NO synthesis enhanced P-selectin expression (P < 0.01). The degree of P-selectin expression was positively correlated with the leukocyte counts infiltrating in liver (r = 0.602, P = 0.000).

CONCLUSION: IPC can attenuate the damage induced by I/R in cirrhotic liver and increase the ischemic tolerance of the rats with liver cirrhosis. IPC can abolish I/R induced leukocyte adhesion and infiltration by preventing post-ischemic P-selectin expression in the rats with liver cirrhosis via a NO-initiated pathway.

ICAM-1 and VCAM-1 mediate endotoxemic myocardial dysfunction independent of neutrophil accumulation

Both intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) have been implicated in neutrophil-mediated lung and liver injury during sepsis. However, the role of these adhesion molecules as well as the contribution of neutrophils in myocardial dysfunction during sepsis remains to be determined. The purpose of this study was to examine the role of ICAM-1, VCAM-1, and neutrophils in lipopolysaccharide (LPS)-induced myocardial dysfunction. Mice were subjected to LPS (0.5 mg/kg ip) or vehicle (normal saline), and left ventricular developed pressure (LVDP) was determined by the Langendorff technique. LVDP was depressed by nearly 40% at 6 h after LPS. Immunofluorescent staining revealed a temporal increase in myocardial ICAM-1/VCAM-1 expression and neutrophils after LPS. Antibody blockade of VCAM-1 reduced myocardial neutrophil accumulation and abrogated LPS-induced cardiac dysfunction. Antibody blockade or absence of ICAM-1 (gene knockout) also abrogated LPS-induced cardiac dysfunction but did not reduce neutrophil accumulation. Neutrophil depletion (vinblastine or antibody) did not protect from LPS-induced myocardial dysfunction. Our results suggest that although endotoxemic myocardial dysfunction requires both ICAM-1 and VCAM-1, it occurs independent of neutrophil accumulation.

alpha(4)-integrin mediates neutrophil-induced free radical injury to cardiac myocytes

Previous work has demonstrated that circulating neutrophils (polymorphonuclear leukocytes [PMNs]) adhere to cardiac myocytes via beta(2)-integrins and cause cellular injury via the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase enzyme system. Since PMNs induced to leave the vasculature (emigrated PMNs) express the alpha(4)-integrin, we asked whether (a) these PMNs also induce myocyte injury via NADPH oxidase; (b) beta(2)-integrins (CD18) still signal oxidant production, or if this process is now coupled to the alpha(4)-integrin; and (c) dysfunction is superoxide dependent within the myocyte or at the myocyte-PMN interface. Emigrated PMNs exposed to cardiac myocytes quickly induced significant changes in myocyte function. Myocyte shortening was decreased by 30-50% and rates of contraction and relaxation were reduced by 30% within the first 10 min. Both alpha(4)-integrin antibody (Ab)-treated PMNs and NADPH oxidase-deficient PMNs were unable to reduce myocyte shortening. An increased level of oxidative stress was detected in myocytes within 5 min of PMN adhesion. Addition of an anti-alpha(4)-integrin Ab, but not an anti-CD18 Ab, prevented oxidant production, suggesting that in emigrated PMNs the NADPH oxidase system is uncoupled from CD18 and can be activated via the alpha(4)-integrin. Addition of exogenous superoxide dismutase (SOD) inhibited all parameters of dysfunction measured, whereas overexpression of intracellular SOD within the myocytes did not inhibit the oxidative stress or the myocyte dysfunction caused by the emigrated PMNs. These findings demonstrate that profound molecular changes occur within PMNs as they emigrate, such that CD18 and associated intracellular signaling pathways leading to oxidant production are uncoupled and newly expressed alpha(4)-integrin functions as the ligand that signals oxidant production. The results also provide pathological relevance as the emigrated PMNs have the capacity to injure cardiac myocytes through the alpha(4)-integrin-coupled NADPH oxidase pathway that can be inhibited by extracellular, but not intracellular SOD.

Role of leukocytes in uterine hypoperfusion and fetal growth retardation induced by ischemia-reperfusion

We investigated leukocyte involvement in uterine hypoperfusion and intrauterine fetal growth retardation (IUGR) induced by ischemia-reperfusion (I/R) in Sprague-Dawley rats. On day 17 of gestation, leukocyte accumulation in the uterus and placenta subjected to 30 min of ischemia, followed by reperfusion, was assessed by measuring myeloperoxidase (MPO) activity. Uterine MPO activity was significantly higher after 1 h of reperfusion than it was before ischemia (P < 0.05), without any increase in placental MPO activity. Immunohistochemical staining showed leukocyte accumulation in the uterus subjected to I/R. The effects of treatment with monoclonal antibodies against CD11a (WT1) and CD18 (WT3) at a dose of 0.8 mg/kg on uterine blood flow and IUGR were investigated. Laser-Doppler flowmetry demonstrated that uterine hypoperfusion at 2 h after ischemia (blood flow, -51.7 +/- 1.2%; P < 0.01) was inhibited by WT1 and WT3 treatment. I/R-induced IUGR at full term (P < 0.05 vs. nonischemic horn) was prevented by WT1 and WT3 treatment on day 17. These results indicate that leukocyte accumulation may play an important role in the pathogenesis of uterine hypoperfusion and IUGR induced by I/R in pregnant rats.

Inhaled NO reduces leukocyte-endothelial cell interactions and myocardial dysfunction in endotoxemic rats

Inhaled nitric oxide (NO) has been shown to have some protective effect in the peripheral distal inflamed vasculature. The objective of the study was to determine whether inhaled NO would reduce endotoxin-induced leukocyte activation and myocardial contractile dysfunction. Rats were treated with either saline or endotoxin (10 mg/kg iv) and then allowed to breathe (4 h) either air or air plus NO (10 ppm). In endotoxemic rats, mesenteric venular endothelium leukocyte firm adhesion increased compared with control rats (1.15 +/- 0.32 vs. 4.08 +/- 0.96 leukocytes/100 microm; P < 0.05). Inhaled NO significantly attenuated endotoxin-induced venular endothelium leukocyte adhesion (4.08 +/- 0.96 vs. 1.86 +/- 0.76 leukocytes/100 microm; P < 0.05) and FITC-conjugated anti-intercellular adhesion molecule-1 fluorescence intensity. Endotoxin-induced myocardial dysfunction and leukocyte content increases were reduced in inhaled NO-treated rats. These observations suggest that inhaled NO reduces the degree of cardiovascular dysfunction and inflammation in endotoxemic rats.