Biomedical subjects

S M Shandelya

Publications and source records attributed to S M Shandelya.

3 recordsLinked to original sources

PubMed1993

Evaluation of the role of polymorphonuclear leukocytes on contractile function in myocardial reperfusion injury. Evidence for plasma-mediated leukocyte activation.

BACKGROUND: It has been hypothesized that chemotaxis and activation of polymorphonuclear leukocytes (PMNs) occur upon reperfusion of ischemic myocardium. Questions remain, however, regarding the mechanisms by which PMNs are chemotaxed and activated and how this process causes contractile failure. METHODS AND RESULTS: Studies were performed in an isolated rat heart model in which the effects of isolated cellular or humoral factors could be studied. Isolated rat hearts were perfused by the method of Langendorff, subjected to 20 minutes of global ischemia, and reperfused with perfusate alone or with perfusate containing PMNs, plasma, PMNs plus plasma, or PMNs plus inactivated plasma (preheated to 56 degrees C for 30 minutes to denature complement) (n = 10 in each group). Left ventricular developed pressure (LVDP) was measured during 1 minute of preischemic control infusion and on reflow after a 20-minute period of global ischemia. Additional measurements of free-radical generation were also performed on the coronary effluent by electron paramagnetic resonance spectroscopy (EPR) with the spin trap 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO). During control infusion, no significant alterations in LVDP were observed, and there was no measurable free-radical generation. Reperfusion with plasma or PMNs alone did not alter postischemic LVDP, whereas plasma and PMNs together caused marked injury. LVDP after 45 minutes of reflow with PMNs plus plasma was 31.9 +/- 6.1% of control compared with 60.6 +/- 9.9% with plasma, 64.5 +/- 8.8% with PMNs, and 63.6 +/- 7.2% with perfusate alone (p < 0.01). With plasma, which was preheated to deplete complement, this injury was not seen; LVDP was 70.8 +/- 10.9%. EPR measurements with the spin trap DMPO in the absence of PMNs demonstrated that oxygen free-radical generation is observed only during the first 1-2 minutes of reflow. Upon reperfusion with PMNs and plasma, however, radical generation persisted for more than 10 minutes. Increased neutrophil accumulation was observed in the postischemic heart in the absence of plasma; however, plasma factors were required for neutrophil-mediated contractile failure. C5a alone did not cause significant injury, but in the presence of PMNs it effectively substituted for plasma, causing marked injury. CONCLUSIONS: Thus, plasma factors, most likely complement, are required for neutrophil activation with oxygen free-radical generation and secondary contractile dysfunction.

Animals↗

PubMed1993

Cardioprotective actions of a monoclonal antibody against CD-18 in myocardial ischemia-reperfusion injury.

BACKGROUND: Previous studies have demonstrated that polymorphonuclear leukocytes (PMNs) are locally activated in reperfused myocardium and contribute to the myocardial cell injury associated with reperfusion. It has been suggested that the adhesion of activated PMNs in reperfused myocardium is mediated by the PMN adhesion molecule CD-18. In the present study, we performed experiments to determine if the specific anti-CD-18 monoclonal antibody (MAb) R15.7 can prevent PMN adhesion and PMN-mediated reperfusion injury in the heart. METHODS AND RESULTS: Studies were performed with isolated, Langendorff-perfused rat hearts (nine per group) in which the hearts were subjected to 20 minutes of global ischemia followed by 45 minutes of reperfusion. Human PMNs (50 million) and rat plasma (HNRP) were infused directly into the coronary circulation of nonischemic and postischemic hearts. When HNRP was administered to nonischemic hearts, no significant alterations in coronary flow, left ventricular developed pressure, or left ventricular end-diastolic pressure were observed. When hearts were reperfused in the presence of HNRP, however, marked impairment of contractile function was observed with more than 90% reduction in coronary flow throughout the reperfusion period (P < .001 versus baseline). In addition, left ventricular developed pressure was significantly depressed (P < .001 versus baseline) throughout the reperfusion period in the HNRP group and recovered to only 13.0 +/- 3.0% at 45 minutes of reperfusion. Moreover, left ventricular end-diastolic pressure was significantly elevated (P < .001) in the HNRP group throughout the reperfusion period. Treatment with the anti-CD-18 monoclonal antibody MAb R15.7 (20 micrograms/mL) at the time of reperfusion resulted in a 92.9 +/- 4.9% recovery of coronary flow (P < .001 versus HNRP) as well as a 71.0 +/- 10.1% recovery of left ventricular developed pressure (P < .001 versus HNRP). Administration of MAb R15.7 also very significantly attenuated the elevation in left ventricular end-diastolic pressure that was observed in the untreated HNRP (30.2 +/- 7.8 versus 110.3 +/- 10.3 mm Hg, P < .001) at 45 minutes of reperfusion. Cardiac myeloperoxidase activity, an index of PMN accumulation, was markedly reduced in the MAb R15.7 group at 45 minutes of reperfusion compared with the HNRP group (0.03 +/- 0.01 versus 0.3 +/- 0.05, P < .001). To determine that the protective effect of MAb R15.7 was based on functional blocking of CD-18, additional experiments were performed with identical concentrations of MAb 3.1, which binds to the alpha-subunit of LFA-1. This PMN-binding but non-CD-18-blocking antibody had little effect on the recovery of postischemic function or coronary flow and did not reduce tissue myeloperoxidase activity. CONCLUSIONS: The administration of a specific anti-CD-18 monoclonal antibody, MAb R15.7, attenuates much of the PMN-mediated contractile dysfunction associated with this in vitro model of myocardial ischemia-reperfusion injury by limiting PMN accumulation. We conclude that CD-18-mediated adhesion may play a critical role in the pathogenesis of PMN-induced myocardial injury.

Animals↗

PubMed1993

Soluble complement receptor type 1 inhibits the complement pathway and prevents contractile failure in the postischemic heart. Evidence that complement activation is required for neutrophil-mediated reperfusion injury.

BACKGROUND: Complement-mediated neutrophil activation has been hypothesized to be an important mechanism of reperfusion injury. It has been proposed that soluble complement receptor 1 (sCR1), a potent inhibitor of both classical and alternative complement pathways, may prevent the complement-dependent activation of polymorphonuclear leukocytes (PMNs) that occurs within postischemic myocardium and thereby inhibit PMN-derived free radical generation and prevent postischemic contractile failure. Therefore, we performed studies to determine the effects of sCR1 on contractile function, PMN adhesion, complement deposition, and PMN-derived free radical generation in the postischemic heart. METHODS AND RESULTS: Studies were performed in an isolated rat heart model in which the isolated effects of given cellular or humoral factors could be determined. Plasma and PMNs were present to study the effects of sCR1 on contractile function, coronary flow, leukocyte adhesion, complement deposition, and PMN-derived free radical generation. Isolated rat hearts were perfused by the method of Langendorff (n = 10 in each group) and subjected to 20 minutes of global ischemia and reperfusion with PMNs and plasma in the presence or absence of sCR1. Left ventricular developed pressure (LVDP), coronary flow (CF), left ventricular end-diastolic pressure (LVEDP), and rate-pressure product (RPP) were measured during the preischemic period, during 1-minute control infusion of PMNs and plasma, and on reflow following 20 minutes of global ischemia. During the preischemic control infusion, no significant alterations in the physiologic parameters were observed, and there was no measurable free radical generation. Reperfusion with sCR1 markedly improved the recovery of postischemic contractile function. LVDP after 45 minutes of reperfusion was 76 +/- 9.8% compared with 32 +/- 6.2% (P < .001). In addition, significant improvements in LVEDP, RPP, and CF were observed in hearts treated with sCR1. Additional experiments were also performed to determine the effect of sCR1 on complement-mediated PMN activation. Measurements of PMN-derived free radical generation were performed in both isolated PMNs and the coronary effluent of hearts using electron paramagnetic resonance spectroscopy (EPR) with the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). EPR measurements in both isolated PMNs and coronary effluent demonstrated that sCR1 blocked complement-mediated free radical generation from the PMNs. Increased accumulation of PMNs was observed both in hearts treated with sCR1 and in those not treated with sCR1. Immunohistochemical staining of the postischemic myocardial tissue demonstrated marked complement deposition on the endothelial surface of small arterioles and capillaries, which was prevented by sCR1 treatment. Thus, sCR1 did not prevent PMN adhesion but did prevent complement deposition with activation of the PMN oxidative burst. CONCLUSIONS: The potent complement inhibitor sCR1 was found to be effective at preventing postischemic myocardial contractile dysfunction and enhancing the recovery of coronary flow. This study demonstrated that complement activation occurs in postischemic myocardium and is necessary for activation of the neutrophil oxidative burst with the generation of reactive oxygen free radicals. The process of neutrophil adhesion, however, was not affected by sCR1 and was independent of complement factors. These findings demonstrate the sCR1 is a highly potent agent at preventing complement-mediated PMN activation and secondary free radical generation in the postischemic heart. This genetically engineered protein appears to be a promising therapeutic agent in the prevention of myocardial reperfusion injury.

Animals↗