Apoptosis of cardiac myocytes during cardiac allograft rejection. Relation to induction of nitric oxide synthase

Identification of cell-free DNA methylation patterns unique to the human left ventricle as a potential indicator of acute cellular rejection

Increased levels of donor-derived cell-free DNA (dd-cfDNA) in recipient plasma have been associated with rejection after transplantation. DNA sequence differences have been used to distinguish between donor and recipient, but epigenetic differences could also potentially identify dd-cfDNA. This pilot study aimed to identify ventricle-specific differentially methylated regions of DNA (DMRs) that could be detected in cfDNA. We identified 24 ventricle-specific DMRs and chose two for further study, one on chromosome 9 and one on chromosome 12. The specificity of both DMRs for the left ventricle was confirmed using genomic DNA from multiple human tissues. Serial matched samples of myocardium (n = 33) and plasma (n = 24) were collected from stable adult heart transplant recipients undergoing routine endomyocardial biopsy for rejection surveillance. Plasma DMR levels increased with biopsy-proven rejection grade for individual patients. Mean cellular apoptosis in biopsy samples increased significantly with rejection severity (2.4%, 4.4% and 10.0% for ACR 0R, 1R, and 2R, respectively) but did not show a consistent relationship with DMR levels. We identified multiple DNA methylation patterns unique to the human ventricle and conclude that epigenetic differences in cfDNA populations represent a promising alternative strategy for the non-invasive detection of rejection.

Minocycline reverses IL-17A/TRAF3IP2-mediated p38 MAPK/NF-κB/iNOS/NO-dependent cardiomyocyte contractile depression and death

Minocycline, an FDA-approved second-generation semisynthetic tetracycline, exerts antioxidant, anti-apoptotic and anti-inflammatory effects, independent of its antimicrobial properties. Interleukin (IL)-17A is an immune and inflammatory mediator, and its sustained induction is associated with various cardiovascular diseases. Here we investigated (i) whether IL-17A induces cardiomyocyte contractile depression and death, (ii) whether minocycline reverses IL-17A's negative inotropic effects and (iii) investigated the underlying molecular mechanisms. Indeed, treatment with recombinant mouse IL-17A impaired adult cardiomyocyte contractility as evidenced by a 34% inhibition in maximal velocity of shortening and relengthening after 4 h (P < .01). Contractile depression followed iNOS induction at 2 h (2.13-fold, P < .01) and NO generation at 3 h (3.71-fold, P <.01). Further mechanistic investigations revealed that IL-17A-dependent induction of iNOS occurred via TRAF3IP2, TRAF6, TAK1, NF-κB, and p38MAPK signaling. 1400 W, a highly specific iNOS inhibitor, suppressed IL-17A-induced NO generation and contractile depression, where as the NO donors SNAP and PAPA-NONOate both suppressed cardiomyocyte contractility. IL-17A also stimulated cardiomyocyte IL-1β and TNF-α secretion, however, their neutralization failed to modulate IL-17A-mediated contractile depression or viability. Further increases of IL-17A concentration and the duration of exposure enhanced IL-1β and TNF-α secreted levels, buthad no impact on adult cardiomyocyte viability. However, when combined with pathophysiological concentrations of IL-1β or TNF-α, IL-17A promoted adult cardiomyocyte death. Importantly, minocycline blunted IL-17A-mediated deleterious effects, indicating its therapeutic potential in inflammatory cardiac diseases.

Systemic Expression of Oxidative DNA Damage and Apoptosis Markers in Acute Renal Graft Dysfunction

Background: Acute renal graft dysfunction (AGD) is one of the primary complications after kidney transplantation. The aim of this study was to identify the systemic oxidative DNA damage and apoptosis markers in patients with AGD, which will aid the understanding of the underlying processes of the complication. Methods: A cross-sectional analytical study was conducted in renal transplant (RT) recipients with and without AGD. The follow-up time of patients was <1 year. Using the ELISA technique, the markers of oxidative DNA damage (8-hydroxy-2-deoxyguanosine and 8-oxoguanine-DNA-N-glycosylase-1) and apoptosis (caspase-3, caspase-8, soluble TNF receptor 1, and cytochrome C) were determined. Results: Donor age was significantly higher in patients with AGD versus those without AGD (43±11 years versus 34.1±10.6 years, respectively; p<0.001). Levels of 8-hydroxy-2-deoxyguanosine were also significantly higher in AGD patients than those without AGD (624.1±15.3 ng/mL and 563.02± 17.4 ng/mL, respectively; p=0.039) and the DNA repair enzyme 8-oxoguanine-DNA-N-glycosylase-1 was significantly diminished in AGD patients versus non-AGD patients (7.60±1.8 ng/mL versus 8.13±1.70 ng/mL, respectively; p=0.031). A significant elevation of soluble TNF receptor levels in AGD patients was also found versus those without AGD (1178.6±25.2 ng/mL versus 142.6±39 ng/mL, respectively; p=0.03). Caspase-3 levels were higher in patients with AGD (1.19±0.21 ng/mL) versus those without AGD (0.79±0.11 ng/mL; p=0.121) and was also significantly augmented in AGD versus healthy control subjects (0.24±0.1 ng/mL; p=0.036). Cytochrome c in AGD patients was 0.32±0.09 ng/mL and 0.16±0.03 ng/mL in those without AGD versus 0.08±0.01 ng/mL in healthy controls (p=0.130 and p=0.184, respectively). Conclusion: These findings suggest that oxidative DNA damage with insufficient DNA repair and higher levels of caspase-3 compared to controls are markers of apoptosis protein dysregulation in AGD patients.

Expression Pattern of Tumor Necrosis Factor-α-Induced Protein 8-Like 2 in Acute Rejection of Cardiac Allograft

BACKGROUND

Tumor necrosis factor-α-induced protein-8 like-2 (TIPE2) is a negative regulator of innate immunity and cellular immunity, yet the expression pattern of TIPE2 in acute rejection of cardiac allograft remain enigmatic.

METHODS

We developed cardiac transplantation models and divided into 3 groups: a naive group, a syngeneic group, and an allogeneic group. Then, we detected the messenger RNA and protein of TIPE2 in cardiac allografts. Real-time polymerase chain reaction showed expression of CD4 and CD8 in the donor heart, and immunofluorescence assay revealed the association between T cells and TIPE2.

RESULTS

In our study, we first found that the expression of TIPE2 in cardiac allografts is upregulated compared with the syngeneic control, and increases in a time-dependent manner. The immunocytochemistry of heart grafts revealed a strong expression of TIPE2 in the inflammatory cells, but not in the cardiomyocytes. Finally, we proved that CD4⁺ and CD8⁺ T cells infiltrated cardiac allografts abundantly, which express ample TIPE2.

CONCLUSIONS

The upregulated expression of TIPE2 in cardiac allografts, mainly came from T cells, which infiltrated the donor heart. This finding indicates that there may be an association between TIPE2 and acute cardiac allograft rejection.

Propolis Protects Endotoxin Induced Acute Lung and Liver Inflammation Through Attenuating Inflammatory Responses and Oxidative Stress

Propolis is a natural bee product, and it has many effects, including antioxidant, anti-inflammatory, antihepatotoxic, and anticancer activity. In this study, we aimed to explore the potential in vivo anti-inflammatory, antioxidant, and antiapoptotic properties of propolis extract on lipopolysaccharide (LPS)-induced inflammation in rats. Forty-two, 3- to 4-month-old male Sprague Dawley rats were used in six groups. LPS (1 mg/kg) was administered intraperitoneally to rats in inflammation, inflammation + propolis30, and inflammation+propolis90 groups. Thirty milligram/kilogram and 90 mg/kg of propolis were given orally 24 h after LPS injection. After the determination of the inflammation in lung and liver tissues by ¹⁸F-fluoro-deoxy-d-glucose-positron emission tomography (¹⁸FDG-PET), samples were collected. The levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), nitric oxide (NO), and DNA fragmentation were determined. The decrease of MDA levels in inflammation + propolis30 and inflammation + propolis90 groups was determined compared to the inflammation group in lung and liver tissues. The increase of SOD% inhibition in inflammation + propolis90 group was determined in liver, lung, and hemolysate compared to the inflammation group. Increased CAT activities in inflammation + propolis30 and inflammation + propolis90 groups were observed in liver tissue and hemolysate compared to inflammation group. In lung tissue, NO levels were lower in inflammation group compared to the control group, but DNA fragmentation levels were higher. ¹⁸F-FDG uptake of tissues in inflammation + propolis30 and inflammation + propolis90 groups was decreased compared to the inflammation group. In conclusion, the data of this study indicate that the propolis application may serve as a potential approach for treating inflammatory diseases through the effect of reducing inflammation and free oxygen radical production.

Graft Expression of p38 and Tumor Necrosis Factor-α in Heart Transplantation in Rats

Objectives

To investigate the expression of p38 mitogen-activated protein kinase and its relationship with myocardial apoptosis and tumor necrosis factor-α during acute cardiac allograft rejection and to study the effects of tacrolimus on the expression of the kinase.

Methods

Rats were divided into 3 groups: isograft (Lewis heart to Lewis rat; control group), allograft (Brown Norway heart to Lewis rat), and tacrolimus-treated allograft (Brown Norway heart to tacrolimus-treated Lewis rat). Grafts were collected 1, 3, 5, and 7 days after transplantation for determination of histopathological features, apoptosis of cardiac cells (by terminal deoxynucleotidyl transferase–mediated dUTP-biotin nick labeling), number of cells positive for both p38 and CD8 (by laser scanning confocal imaging), and expression of the kinase (by Western immunoblotting) and tumor necrosis factor-α (by reverse-transcriptase polymerase chain reaction).

Results

Compared with isografts from the control group, grafts from the untreated allograft group had significantly more apoptotic cells, greater expression of tumor necrosis factor-α and p38 mitogen-activated protein kinase, and more CD8-p38 double-positive cells at 5 and 7 days ( P<.05). The increases were prevented by treatment with tacrolimus.

Conclusions

The findings that the number of apoptotic cells, the number of CD8-p38 double-positive cells, the expression of tumor necrosis factor-α and p38 mitogen-activated protein kinase all increased during the same period in the allografts in nonimmunosuppressed recipients suggests that intragraft expression of p38 would be associated with the rejection in acute cardiac allograft rejection. Tacrolimus may alleviate rejection partly by inhibiting p38 mitogen-activated protein kinase.

The Inflammatory Response to Cardiopulmonary Bypass— Should It Be Treated?

Proinflammatory cytokines, including tumor necrosis factor (TNF) α and the interieukins, are important in the metabolic response to injury or infection. Although the importance of cytokine release during cardiopulmonary bypass (CPB) is not fully appreciated, increasing num bers of publications present evidence that cytokine release during CPB is detrimental. In addition, endoge nous inhibitors of cytokine function, including TNF-sol uble receptor and interleukin 1 receptor antagonist, are released in response to elevated proinflammatory cyto kine levels during and after CPB. The involvement of these endogenous inhibitors in the pathophysiology of proinflammatory cytokine-induced solid organ injury after CPB remains to be defined.

Therapeutic lymphangiogenesis ameliorates established acute lung allograft rejection

Lung transplantation is the only viable option for patients suffering from otherwise incurable end-stage pulmonary diseases such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis. Despite aggressive immunosuppression, acute rejection of the lung allograft occurs in over half of transplant recipients, and the factors that promote lung acceptance are poorly understood. The contribution of lymphatic vessels to transplant pathophysiology remains controversial, and data that directly address the exact roles of lymphatic vessels in lung allograft function and survival are limited. Here, we have shown that there is a marked decline in the density of lymphatic vessels, accompanied by accumulation of low-MW hyaluronan (HA) in mouse orthotopic allografts undergoing rejection. We found that stimulation of lymphangiogenesis with VEGF-C156S, a mutant form of VEGF-C with selective VEGFR-3 binding, alleviates an established rejection response and improves clearance of HA from the lung allograft. Longitudinal analysis of transbronchial biopsies from human lung transplant recipients demonstrated an association between resolution of acute lung rejection and decreased HA in the graft tissue. Taken together, these results indicate that lymphatic vessel formation after lung transplantation mediates HA drainage and suggest that treatments to stimulate lymphangiogenesis have promise for improving graft outcomes.

p-Hydroxybenzyl alcohol-containing biodegradable nanoparticle improves functional blood flow through angiogenesis in a mouse model of hindlimb ischemia

Therapeutic angiogenesis has achieved promising results for ischemic diseases or peripheral artery disease in preclinical and early-phase clinical studies. We examined the therapeutic angiogenic effects of HPOX, which is biodegradable polymer composing the antioxidant p-hydroxybenzyl alcohol (HBA), in a mouse model of hindlimb ischemia. HPOX effectively stimulated blood flow recovery, compared with its degraded compounds HBA and 1,4-cyclohexendimethanol, via promotion of capillary vessel density in the ischemic hindlimb. These effects were highly correlated with levels of angiogenic inducers, vascular endothelial cell growth factor (VEGF), heme oxygenase-1 (HO-1), and Akt/AMPK/endothelial nitric oxide synthase (eNOS) in ischemic mouse hindlimb muscle. Blood perfusion and neovascularization induced by HPOX were reduced in eNOS(-/-) and HO-1(+/-) mice. HPOX also elevated the endothelial cell markers VEGF receptor-2, CD31, and eNOS mRNAs in the ischemic hindlimb, indicating that HPOX increases endothelial cell population and angiogenesis in the ischemic muscle. However, this nanoparticle suppressed expression levels of several inflammatory genes in ischemic tissues. These results suggest that HPOX significantly promotes angiogenesis and blood flow perfusion in the ischemic mouse hindlimb via increased angiogenic inducers, along with suppression of inflammatory gene expression. Thus, HPOX can be used potentially as a noninvasive drug intervention to facilitate therapeutic angiogenesis.

Melatonin synergized with cyclosporine A improves cardiac allograft survival by suppressing inflammation and apoptosis

Melatonin, a widespread physiological mediator, has been demonstrated to exhibit a dose‑dependent immunoregulatory effect in vitro and in vivo, including mediating physiological circadian rhythms, neutralizing free radicals and exerting antisenescence actions. In the present study, the efficacy and mechanism of melatonin alone or in combination with cyclosporine (CsA) in prolonging heart transplantation survival was examined. Daily treatment with melatonin (200 mg/kg/day) through a gavage, significantly prolonged the survival of cardiac grafts (mean survival time, 13.4±2.4 days; n=7; P<0.0001) compared with the untreated controls (5.8±1.2 days; n=7). When CsA (5 mg/kg/day) was co‑administered with melatonin (50 mg/kg/day), the survival rate improved (31.6±2.4 days; n=7; P<0.001), compared with that achieved by only 20 mg/kg/day CsA (22±2.8 days; n=7). As expected, melatonin significantly alleviated the inflammatory response and apoptosis as determined by TdT‑mediated dUTP‑biotin nick end labeling assay (P<0.05). Further analysis demonstrated that melatonin significantly reduced p65 activation and the release of inflammatory factors. Therefore, these findings indicate that melatonin in combination with CsA protected the cardiac allograft by inhibiting inflammation‑induced apoptosis. These results provide evidence for a novel therapeutic approach for future immunosuppressive agents in organ transplantation.

Absence of FcγRIII results in increased proinflammatory response in FcγRIII-KO cardiac recipients

BACKGROUND

Alloantibody can contribute significantly to rejection of heart transplants by activation of complement and interactions with a variety of effector cells, including macrophages and monocytes through activating FcγRI, FcγRIII, FcγRIV, the inhibitory FcγRIIB and complement receptors. These receptors link cellular and humoral immunity by bridging the antibody specificity to effector cells. Activating FcγRs are also involved in serum amyloid P component (SAP)-mediated clearance of apoptotic bodies.

METHODS

B10.A (H-2a) hearts were transplanted into wild-type (WT) or FcγRIII-knockout (KO) C57BL/6 (H-2b) mouse recipients. Levels of alloantibodies and SAP in the circulation were determined by flow cytometry and enzyme-linked immunosorbent assay, respectively. Intragraft cytokine mRNA expression was measured by real-time polymerase chain reaction. Intragraft deposition of C4d, von Willebrand factor, SAP, and activated caspase 3 was visualized by immunochemistry.

RESULTS

B10.A hearts in C57BL/6 FcγRIII-KO recipients were rejected acutely within 6 to 8 days compared with 10 to 14 days in WT. The rejection in FcγRIII-KO was accompanied by higher levels of circulating IgM/IgG alloantibodies and SAP than in WT recipients. Histology in FcγRIII-KO cardiac allograft recipients indicated perivascular margination of monocytes and neutrophils, vascular endothelial cell injury, and intense vasculocentric infiltrates with extensive apoptosis. Higher numbers of apoptotic cells, stronger C4d and SAP deposition, and extensive activated caspase 3 were found in areas of dense pockets of apoptotic blebs in FcγRIII-KO.

CONCLUSIONS

We propose that absence of FcγRIII is associated with the lack of efficient SAP-mediated clearance of apoptotic cells through FcγRs. Apoptotic cells become immunogenic and induce enhanced inflammation, alloantibody production, and complement activation leading to accelerated cardiac allograft rejection.

Nitric oxide-mediated protein modification in cardiovascular physiology and pathology

Nitric oxide (NO) is a key regulator of cardiovascular functions including the control of vascular tone, anti-inflammatory properties of the endothelium, cardiac contractility, and thrombocyte activation and aggregation. Numerous experimental data support the view that NO not only acts via cyclic guanosine monophosphate (cGMP)-dependent mechanisms but also modulates protein function by nitrosation, nitrosylation, glutathiolation, and nitration, respectively. To understand how NO regulates all of these diverse biological processes on the molecular level a comprehensive assessment of NO-mediated cGMP-dependent and independent targets is required. Novel proteomic approaches allow the simultaneous identification of large quantities of proteins modified in an NO-dependent manner and thereby will considerably deepen our understanding of the role NO plays in cardiovascular physiology and pathophysiology.

Serum markers of apoptosis in the early period of heart transplantation

CONTEXT AND OBJECTIVE

To assess the relationship between levels of serum markers of apoptosis and rejection grades in heart transplant (HTx).

MATERIALS AND METHODS

A prospective study was conducted in 91 HTx. We correlated apoptosis markers and biopsy samples. The apoptosis markers were: TRAIL, TRAIL-R1, TRAIL-R2, TRAIL-R3, TRAIL-R4, sFas, sTNF-R1 and sTNF-R2.

RESULTS

The only significant correlation with rejection grade was sFas (r=0.329; p=0.005). Cyclosporine showed a proapoptotic effect (sTNF-R1 0.02 and sTNF-R2 0.02) and everolimus an antiapoptotic effect (sTNF-R1 r= -0.523; p=0.0001 and sTNF-R2 r= -0.405; p=0.0001).

CONCLUSIONS

The utility of specific apoptosis markers in peripheral blood for diagnosis of acute cellular rejection is low. Everolimus may have an anti-apoptotic effect.

Catalytic peroxynitrite decomposition improves reperfusion injury after heart transplantation

OBJECTIVE

Peroxynitrite, a reactive nitrogen species, has been implicated in the development of ischemia-reperfusion injury. The present study investigated the effects of the potent peroxynitrite decomposition catalyst FP15 on myocardial and endothelial function after hypothermic ischemia-reperfusion in a heterotopic rat heart transplantation model.

METHODS

After a 1-hour ischemic preservation and implantation of donor hearts, reperfusion was started after application of vehicle (5% glucose solution) or FP15 (0.3 mg/kg). The assessment of left ventricular pressure-volume relations, total coronary blood flow, endothelial function, immunohistochemical markers of nitro-oxidative stress, and myocardial high-energy phosphates was performed at 1 and 24 hours of reperfusion.

RESULTS

After 1 hour of reperfusion, myocardial contractility (maximal slope of systolic pressure increment at 140 μL left ventricular volume: 5435 ± 508 mm Hg/s vs 2346 ± 263 mm Hg/s), coronary blood flow (3.98 ± 0.33 mL/min/g vs 2.74 ± 0.29 mL/min/g), and endothelial function were significantly improved, nitro-oxidative stress was reduced, and myocardial high-energy phosphate content was preserved in the FP15-treated animals compared with controls.

CONCLUSIONS

Pharmacologic peroxynitrite decomposition reduces reperfusion injury after heart transplantation as the result of reduction of nitro-oxidative stress and prevention of energy depletion and exerts a beneficial effect against reperfusion-induced graft cardiac and coronary endothelial dysfunction.

Apoptosis and acute cellular rejection in human heart transplants

INTRODUCTION AND OBJECTIVES

Apoptosis has been implicated in the pathophysiology of various forms of heart disease. Acute cellular rejection leads to morbidity after heart transplantation and invasive techniques are needed for its diagnosis. We investigated the presence of cardiomyocyte apoptosis in transplanted hearts, its progression, its relationship with rejection, and the possibility that serological markers of apoptosis can be used to detect rejection noninvasively.

METHODS

Overall, 130 endomyocardial biopsies obtained sequentially from 14 consecutive patients during the first 6 months following heart transplantation underwent histochemical analysis. The degree of acute rejection was determined, myocyte apoptosis was assessed using the TUNEL method, and caspase-3 activity was measured. In the first 10 patients, soluble Fas, tumor necrosis factor-alpha (TNFα) and interleukin 6 levels were determined in serum collected at biopsy.

RESULTS

Apoptotic cells were detected in 81.5% of biopsies. No significant correlation was found between the apoptotic index and either the degree of rejection or the time from transplantation; there was only a trend to higher values during prolonged episodes of rejection, which did not reach statistical significance. An inverse correlation was observed between the degree of rejection and the TNFα level (rs=-0.33; P=.003). There was no correlation with any other variable.

CONCLUSIONS

Cardiomyocyte loss due to apoptosis was observed in transplanted hearts, but no correlation was observed with either acute rejection or the time from transplantation. Our findings suggest there could be an inverse correlation between rejection and the serum TNFα level. No serum parameter evaluated was regarded as suitable for the noninvasive diagnosis of acute rejection.

Cyclic AMP prolongs graft survival by suppressing apoptosis and inflammatory gene expression in acute cardiac allograft rejection

This study was designed to investigate the effects of cAMP on immune regulation and apoptosis during acute rat cardiac allograft rejection. We found that the production of immune markers such as inflammatory cytokines (IL-1beta, IL-6, and TNF-alpha), iNOS expression, and nitric oxide (NO) production, was significantly increased in the blood and transplanted hearts of allograft recipients, but not of isograft controls. These increases were effectively suppressed by the administration of the membrane permeable cAMP analog dibutyryl cAMP (db-cAMP). Administration of db-cAMP reduced allograft-induced elevation of several biochemical markers, such as adhesion molecule expression, iron-nitrosyl complex formation, caspase-3 activation, and apoptotic DNA fragmentation in an animal model. Furthermore, treatment of allograft recipients with db-cAMP prolonged median graft survival to 11 days compared with a median graft survival time of 8 days in saline-treated allograft recipients. These results suggest that db-cAMP exerts a beneficial effect on murine cardiac allograft survival by modulating allogeneic immune response and cytotoxicity.

Apoptotic cell death during accelerated rejection in sensitized rat recipients of cardiac allografts

Accelerated rejection due to host sensitization to major histocompatibility complex antigens is a critical problem in clinical organ transplantation in patients who have previously received an organ transplant, experienced acute rejection episodes, received blood transfusions, or been pregnant. The precise pathologic mechanisms underlying accelerated rejection have not been characterized. Herein, we describe apoptosis during T- and B-cell-driven accelerated rejection of cardiac allografts in presensitized recipients. In an established accelerated rejection model, Lewis rats were sensitized to skin grafts from Wistar-Furth rats; after 7 days, they received Wistar-Furth hearts. These grafts were rejected within 24 hours posttransplantation compared with 10 days in nonsensitized recipients (acute rejection, n = 5). Apoptosis was observed during accelerated rejection of cardiac allografts but not in naïve recipients of hearts, as demonstrated at DNA laddering and TUNEL (terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate nick-end labeling) assay. Apoptosis was discovered as a thus far unknown effector mechanism in accelerated cardiac transplant rejection that accompanies combined cellular and humoral immune alloreactivity. Apoptotic cell death in accelerated rejection and the cascade of upstream and downstream events leading to or resulting from this process should be considered critical steps in the pathogenesis of accelerated rejection.

Has the 2004 revision of the International Society of Heart and Lung Transplantation grading system improved the reproducibility of the diagnosis and grading of cardiac transplant rejection?

We compared the interobserver reproducibility of the 1990 and 2004 International Society for Heart and Lung Transplantation (ISHLT) grading system for cardiac rejection. The 2004 ISHLT grading system for cardiac allograft rejection did not improve reproducibility partly due to pathologists' disagreement in diagnosing Grades 1B/1R and 3A/2R rejection. To achieve better reproducibility, better criteria for defining 1B/1R vs. 3A/2R rejection and markers of myocyte injury are needed.

Reactive oxygen and reactive nitrogen as signaling molecules for caspase 3 activation in acute cardiac transplant rejection

Apoptosis is a significant factor in cardiac dysfunction and graft failure in cardiac rejection. In this study, we examined potential signaling molecules responsible for caspase 3 activation in a model of acute cardiac allograft rejection. The roles of reactive oxygen species (ROS) and nitric oxide (NO) were determined in untreated allografts and allograft recipients treated with either cyclosporine (CsA), alpha-phenyl-t-butylnitrone (PBN, a spin-trapping agent), vitamin C (VitC), Mn(III)tetrakis (1-methyl-4-pyridyl)porphyrin); MnTmPyP, a superoxide dismutase (SOD) mimetic), or L-(1-iminoethyl)lysine) (L-NIL), an inhibitor of inducible NO synthase (iNOS) enzyme activity. Graft tissue was taken for measuring superoxide radical production, Western blotting, and direct measurement of caspase 3 activity. Activation of caspase 3 in untreated allografts was revealed by the appearance of cleaved caspase 3 from pro-caspase 3 by Western blotting and functional caspase 3 catalytic activity. CsA or PBN inhibited iNOS expression and caspase 3 activity. VitC and MnTmPyP did not alter iNOS expression or decrease NO levels but did inhibit caspase 3 activity. In contrast, L-NIL completely inhibited the increase in NO production without altering iNOS expression and inhibited caspase 3 activity. The prevention of TUNEL staining by MnTmPyP and L-NIL confirmed downstream effects of superoxide and NO on apoptosis. These studies indicate that both superoxide and NO (precursors of peroxynitrite formation) play a significant role in caspase 3 activation in cardiac allograft rejection.

Overexpressed exogenous IL-4 And IL-10 paradoxically regulate allogenic T-cell and cardiac myocytes apoptosis through FAS/FASL pathway

BACKGROUND

The authors' previous study has shown that liposome-mediated ex vivo intracoronary interleukin (IL)-4 and IL-10 combined gene therapy suppressed the allo-immune responses and prolonged the cardiac allograft survival by 15 folds. However, the mechanism for promoting long-term allograft survival remains unknown.

METHODS

This study tested the hypothesis that this combined cytokine gene targeting may promote alloreactive T-cell apoptosis or prevent apoptosis of cardiac allograft myocytes through Fas/Fas ligand (FasL) pathway. A rabbit functional cervical heterotopic heart transplantation model was used, and plasmid human recombinant IL-4 and IL-10 gene complexed with cationic liposome (GAP/DLRIE) was delivered into cardiac allografts by intracoronary infusion ex vivo.

RESULTS

This liposome-mediated IL-4 and IL-10 combined gene therapy significantly increased apoptotic T cells detected by TUNEL staining. The caspase-8 or caspase-3 expressing T cells were also significantly increased. The Fas+ apoptotic T cells dominated in the population of apoptotic CD4+ T cells, but FasL+ CD4+ T-cell population was less effected in the combined gene therapy group. The effect of combined gene therapy on the infiltrative Fas+ CD8+ T-cell population is much less than that on Fas+ CD4+ cells, and there was almost no effect on the FasL+ CD8+ T-cell population. Furthermore, localized IL-4 and IL-10 combined gene therapy protected cardiac allograft myocytes by down-regulating its FasL expression, but not Fas.

CONCLUSIONS

These results suggest that this combined gene targeting strategy which induced localized overexpression of exogenous IL-4 and IL-10 may promote alloreactive T-cell apoptosis and prevent myocytes apoptosis through Fas/FasL cell surface interaction, therefore inducing cardiac allograft tolerance.

Apoptosis and cardiopulmonary bypass

AIM

The aim of this study was to ascertain the percentage of apoptotic myocytes in patients who underwent coronary artery bypass surgery. Apoptotic index (AI) obtained with in situ terminal deoxynucleotidyl transferase-labeled dUTP nick end labeling (TUNEL) method and Bak protein expression were compared.

PATIENTS AND METHODS

Twenty consecutive patients who underwent coronary artery bypass surgery, myocardial samples from the right atrium were taken in three stages: before cannulation (the first sample group), after declamping (the second sample group), and 20 minutes after reperfusion (the third sample group). The percentage of apoptotic cells was determined by TUNEL method. Expression of Bak protein was immunohistochemically analyzed. Intermittent ischemia and moderate hypothermia were used as methods of myocardial management during surgery. A statistical analysis was performed by using the Friedman ANOVA analysis of variances, the Kendall coefficient of concordance and the Wilcoxon matched pair test.

RESULTS

In the first sample group mean value of Bak expression was 2.61 +/- 2.18, compared with AI 5.38 +/- 3.58, after declamping (the second sample group) the mean value of Bak expression was 4.31 +/- 2.68 while AI was 7.63 +/- 4.38 and after 20 minutes of reperfusion in the third sample group mean value of Bak expression was 8.89 +/- 4.45, while AI was 15.6 +/- 8.45. When compared by using Wilcoxon matched pair test two methods significantly correlated, p > 0.0001.

CONCLUSION

The positive correlation between AI obtained by TUNEL method and expression of Bak protein may suggest that apoptosis is activated mainly through mitochondrial activation pathway in ischemic reperfusion injury. The results suggest that ischemic reperfusion injury increases the AI in the right atrial tissue. If so, immunohistochemical expression of Bak protein could be used as a marker of myocardial ischemia induced injury.

Bilirubin oxidation provoked by nitric oxide radicals predicts the progression of acute cardiac allograft rejection

Bilirubin, a strong intrinsic antioxidant, quenches free radicals produced under inflammatory conditions. The oxidized bilirubin metabolites, i.e. biopyrrins, are immediately excreted into urine and can indicate the intensity of oxidation in vivo. Our preliminary studies suggested the involvement of reactive nitrogen species (RNS) in generation of biopyrrins. However, little is known about biological significance of bilirubin oxidation by RNS. Here, we analyzed the correlation between bilirubin oxidation and nitric oxide (NO) radicals during rat acute cardiac allograft rejection. In allograft recipients, urinary biopyrrins steeply increased on day 3 prior to the increase in myocardial tissue damage marker, serum troponin-T. In contrast, no significant changes in urinary biopyrrins were evident in recipients of isografts or cyclosporine-A treated allografts. Urinary nitrotyrosine, a marker of oxidation by NO radicals also increased on day 3, while administration of a NO synthase inhibitor, N(G)-monomethyl-L-arginine apparently diminished the elevation of urinary biopyrrins as well as nitrotyrosine. Immunohistochemistry revealed enhanced local expression of heme oxygenase-1, biopyrrins and nitrotyrosine in allografts in accordance with the cellular infiltrates, suggesting that changes in urinary biopyrrins reflect the bilirubin oxidation in grafts undergoing rejection. These results indicate that locally evoked bilirubin oxidation by NO radicals can predict the progression of rejection.

Increased iNOS-expressing macrophage in long-term surviving rat small-bowel grafts

BACKGROUND

Inducible nitric oxide synthase (iNOS) produces nitric oxide and modulates many biologic processes critical in the development of rejection; however, its role in chronic rejection (CR) in small-bowel transplantation (SBT) is largely unknown.

METHODS

FK506 prevented acute rejection (AR); however, recipients eventually lost their bowel grafts to CR. Combined FK506 and rapamycin treatment prevented CR, thus leading to long-term graft survival. We investigated iNOS expression in our rat orthotopic SBT CR model.

RESULTS

Histologically, mesentery vascular occlusion and fibrosis, which are hallmarks of CR, were apparent in bowel grafts in an FK506 single-treatment group. In contrast, patients with long-term surviving grafts receiving FK506 and rapamycin developed mild vascular occlusion and fibrosis. Unlike in AR, low iNOS expression, which is associated with decreased macrophage infiltration, was observed in CR grafts. However, iNOS expression and macrophage infiltration was higher in long-term-surviving grafts than CR grafts. Immunofluorescence staining revealed that the majority of macrophages expressed iNOS in long-term surviving grafts.

COMMENTS

Sequential treatment combining FK506 and rapamycin prolonged survival of SBT animals with decreased vasculopathy and collagen deposition of the intestinal grafts. iNOS may play opposing roles in AR and CR in SBT.

IL-13 prolongs allograft survival: Association with inhibition of macrophage cytokine activation

Th2 cytokines, especially IL-4 and IL-10, may facilitate transplant tolerance induction but the role of IL-13, another Th2 cytokine, is not known. This study examined the effects of rat recombinant IL-13 (rIL-13) on alloimmune responses. In vitro effects of rIL-13 were compared in mixed lymphocyte cultures (MLC) on rat lymphocytes cultured with PVG stimulator cells. DA rats grafted with fully allogeneic PVG neonatal heart grafts were treated with 40,000 units of rIL-13 for 10 days and graft survival monitored by ECG. Cytokine mRNA expression in the graft and lymphoid tissues was studied by RT-PCR and alloantibody levels assayed. rIL-13 had no effect on MLC, unlike rIL-4 which enhanced proliferation and induced Th2 and inhibited Th1 cytokines in MLC. rIL-13 inhibited IL-12p35, IL-12p40 and TNF-alpha mRNA induction in dendritic cell cultures. Treatment with rIL-13 prolonged fully allogeneic PVG neonatal heart graft survival to 18-21 (13-27) days (median (range)); compared to 12 (9-15) days in untreated normal rejection (p<0.05) and 14 (10-24) days in sham treated controls (p<0.05). RT-PCR studies on graft tissue identified reduced mRNA expression for the dendritic cell/macrophage molecules iNOS, TNF-alpha and IL-12 compared to normal rejection. rIL-13 treatment did not increase Th2 cytokines as compared to normal rejection, or the Th2 dependent IgG1 alloantibody response, while IL-4 did. These studies demonstrated that rIL-13 can prolong allograft survival associated with inhibition of IL-12, TNF-alpha and iNOS mRNA induction, and suggest IL-13 could modify graft rejection by inhibition of dendritic cell and/or macrophage function.

Nitric oxide and peroxynitrite in health and disease

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

Comparison of FK 506, mycophenolate mofetil, and aminoguanidine effects on delay of corneal allograft rejection in an experimental model of low-risk and high-risk keratoplasty

The purpose of our study was to compare the effectiveness of immunosuppressive drugs on the prevention of allograft rejection in a murine model of low-risk and high-risk keratoplasty. The therapy included FK 506 (tacrolimus; 0.2 mg/kg), mycophenolate mofetil (30 mg/kg), aminoguanidine (0.1 g/kg), and combination of FK506 + mycophenolate mofetil or FK506 + aminoguanidine. The results obtained from the Gray's survival model stratified according to the type of subjects suggest that a major rejection risk reduction was achieved using FK506; good results also were obtained for mycophenolate mofetil. Although the point estimates of both the survival and relative risk of rejection suggest a deferred effect of the combination FK506 + mycophenolate mofetil, this finding did not prove statistically significant.

Cardiac failure in C5-deficient A/J mice after Candida albicans infection

The effect of a deficiency in the C5 component of complement on the pathophyisology of infection with the fungal pathogen Candida albicans was studied by using the A/J inbred mouse strain and the BcA17 congenic mouse strain. Acute infection caused by intravenous injection of C. albicans blastospores is associated with rapid fungal replication in the heart, brain, and, in particular, kidneys of C5-deficient mice. Histological studies and analysis of markers for tissue damage indicated that the heart is the organ that is most affected and that it ultimately fails in C5-deficient mice. In A/J and BcA17 mice, tissue damage is associated with (i) cellular infiltration in the heart, which is not seen in the kidney despite the higher fungal load in the latter organ, and (ii) a very strong inflammatory response, including elevated levels of many cytokines and chemokines. This results in cardiomyopathy, which is associated with elevated levels of creatine kinase and cardiac troponin I in the circulation. Damage to the cardiac muscle is associated with metabolic changes, including hypoglycemia, decreased lipid utilization resulting in elevated levels of cardiac triglycerides, and unproductive glucose utilization linked to a dramatic increase in the level of pyruvate dehydrogenase kinase 4 (Pdk4), a negative regulator of the pyruvate dehydrogenase complex.

Nitric oxide signaling in stretch‐induced apoptosis of neonatal rat cardiomyocytes

Pressure overload associated with hypertension is an important pathological factor leading to heart remodeling and ultimately heart failure partially due to cardiomyocyte apoptosis. Here we show that endogenous NO signaling plays a critical role in mechanical stretch-induced cardiomyocyte apoptosis. Mechanical stretch induced elevated expression of both eNOS and inducible NO synthase (iNOS) and increased synthesis of NO. A sustained increase in iNOS expression was also found in hearts of hypertensive rats in vivo. Blockade of NO signaling by inhibitors of NOS (L-NAME and AMT) or downstream guanylyl cyclase (ODQ) strongly inhibited stretch-induced apoptosis, mitochondria depolarization, and cytochrome c release, suggesting that NO is required in stretch-induced cardiomyocyte apoptosis. The expression of iNOS, but not eNOS, was blocked by L-NAME and ODQ, indicating that the iNOS induction is NO dependent. The initial elevation of NO is likely due to Ca(2+)-dependent activation of eNOS because elimination of intracellular calcium by EGTA-AM inhibited both iNOS induction and NO elevation. Other calcium signaling inhibitors (nifedipine, ryanodine, thapsigargin, and ionic gadolinium) also attenuated the initial NO elevation. These data indicate that mechanical signals initiate Ca(2+)-dependent NO synthesis, which is further amplified by activation of NO-induced iNOS expression, to regulate cardiomyocyte apoptosis.

Differential Rates of Apoptosis in Bronchoalveolar Lavage and Blood of Lung Transplant Patients

BACKGROUND

Lung transplant tolerance depends on effective control of T-cell proliferation and activation. Commonly used immunosuppressive agents promote peripheral blood-derived lymphocyte apoptosis and inhibit production of cytokines involved in lymphocyte proliferation and survival. However, there have been no studies of the effectiveness of immunosuppressive treatments on apoptosis of T cells derived from the airways of lung transplant recipients. Our main aim was to compare apoptosis of T cells derived from peripheral blood and bronchoalveolar lavage (BAL) from lung transplant recipients, with no evidence of chronic or acute cellular rejection, and healthy volunteers. Lung transplantation may also be associated with increased apoptosis of airway epithelial cells. To investigate this possibility, we also examined apoptosis of epithelial cells derived from bronchial brushing.

METHODS

BAL, blood, and bronchial brushings were obtained from lung transplant recipients (n = 9) and age-matched controls (n = 15). T cell and epithelial cell apoptosis, Fas, Bax, Bcl-2, and p53 were evaluated by flow cytometry.

RESULTS

Increased apoptosis of peripheral blood T cells and decreased Bcl-2 were observed in the transplant patients. In contrast, there was no significant change in apoptosis of airway T cells or apoptosis-related proteins. Increased apoptosis and increased p53 were observed in the airway epithelial cells from the transplant recipients, possibly as a result of ineffective control of infiltrating cytotoxic T cells.

CONCLUSIONS

Immunosuppressive agents may not be as effective in inducing apoptosis of airway-derived T cells as peripheral blood-derived T cells after lung transplantation. These findings may have implications on the outcome of the immune response in the airways after immunosuppressive therapy and may be particularly relevant to lung allograft rejection.

Apoptosis: pathophysiology and therapeutic implications for the cardiac surgeon

Cardiomyocyte apoptosis has been associated with the pathogenesis of heart failure as well as ischemic and inflammatory myocardial conditions. The aim of this study is to give a critical synopsis of cardiomyocyte apoptosis and identify methods to prevent or attenuate apoptosis in patients undergoing cardiac surgery. Clinical conditions and agents associated with decreased apoptotic index are early repair or replacement of valvular pathology before deterioration of ventricular function, afterload reduction with medication or intraaortic balloon pulsation in patients with acute increase in afterload or in hemodynamically compromised patients, decreasing catecholamine-induced cardiotoxicity by using beta-blockers, phosphodiesterase inhibitors, or early insertion of intraaortic balloon pulsation or ventricular assist device. Prompt coronary revascularization, which reduces myocardial ischemia time, is the most effective antiapoptotic therapy. Reduction of myocardial apoptosis associated with cardiopulmonary bypass and aortic cross-clamping are other therapeutic targets. Some investigational therapies include ischemic preconditioning and use of antiapoptotic medication such as the caspase inhibitors, antioxidants, calcium-channel blockers, the insulin-like growth factor-1, and the poly-adenosine diphosphate-ribose-synthetase inhibitors. Most of the therapeutic implications in reducing cardiomyocyte apoptosis are still in the experimental phase. Some options are already incorporated in the clinical practice of the cardiovascular surgeon. New therapeutic considerations include avoiding sustained and long-term use of catecholamines and reducing or avoiding cardiopulmonary bypass-when clinically feasible. Noncatecholamine inotropes should be preferred for patients undergoing heart failure surgery and for patients with low output syndrome after open-heart surgery. The lessons learned from apoptosis research reinforce more liberal and early insertion of intraaortic balloon pulsation or ventricular assist device in clinical low output states.

Apoptosis and oncosis in acute coronary syndromes: assessment and implications

The rational design of therapeutic interventions for protection of ischemic myocardium from ultimate death requires an understanding of the mechanistic basis of cardiomyocyte (CM) cell death, its timing and the tools for its quantification. Until recently, CM cell death following ischemia and/or reperfusion was considered to involve necrosis or 'accidental cell death' from very early on. Collective evidence over the past decade indicates that early CM cell death after myocardial ischemia and post-ischemic reperfusion involves apoptosis with cell shrinkage and drop-out, and/or oncosis with cell swelling followed by necrosis. This paradigm shift suggests that different approaches for cardioprotection are required. Oncologists, pathologists, anatomists and basic scientists who have studied apoptosis over the last three decades separated physiological apoptosis from inappropriate apoptosis in pathological states. Until recently, cardiologists resisted the concepts of CM apoptosis and regeneration. Cumulative evidence indicating that apoptosis in the heart may occur in different cell types, spread from one cell type to another, and occur in bursts, may have profound implications for therapies aimed at protection of ischemic myocardium by targeting CM apoptosis in acute coronary syndromes. This review focuses on a critique of the methods used for the assessment of CM apoptosis and the implications of CM apoptosis in acute coronary syndromes.

Early Inhibition of Caspase-3 Activity Lessens the Development of Graft Coronary Artery Disease

BACKGROUND

The role of apoptosis in the development of graft coronary artery disease (GCAD) is poorly understood. We have previously shown that early overexpression of the anti-apoptotic protein Bcl-2 lessens the development of GCAD. We hypothesized that early inhibition of apoptosis with a caspase-3 inhibitor would also lessen the development of GCAD.

METHODS

Heterotopic heart transplantation was performed in 4 groups of rats. Donor hearts were pretreated with 50 microg DEVD-CHO, a cell-permeable caspase-3 inhibitor, or vehicle. Recipient animals were pretreated with 1.7 mg/kg intraperitoneal DEVD-CHO or vehicle. Animals were treated with 7.5 mg/kg/d cyclosporine for 10 days to prevent acute rejection. On post-operative day 90, the animals were sacrificed and the transplanted hearts were assessed morphometrically for evidence of GCAD.

RESULTS

At 90 days, intimal proliferation was significantly higher in vehicle treated animals than in inhibitor treated animals. Moreover, the percentage of vessels with high-grade occlusion (>50%) was also lower in inhibitor treated animals.

CONCLUSIONS

Early inhibition of caspase-3 activity with cell-permeable DEVD-CHO lessens the development of GCAD. Caspase-3 inhibition may be a useful strategy for prevention of GCAD in clinical transplantation.

Cardiac transplantation and resistance artery myogenic tone

Transplantation is an effective treatment for end-stage heart disease; however, most grafts eventually fail by progressive cardiac failure. Primarily, failure is ischemic due to the occlusive nature of transplant vascular disease (TVD). Early after transplantation and preceding TVD, alterations in coronary physiology such as reduced vascular myogenic tone occur. Resistance arteries possess an inherent ability to constrict in response to transmural pressure; this constrictive response (myogenic tone) is important in fluid homeostasis. Recent evidence suggests that a decline in myogenic tone leads to deficits in cardiac contractility. Factors that reduce myogenic tone in transplantation include constitutive nitric oxide synthase and inducible nitric oxide synthase catalyzed, NO-mediated vasodilation as well as deficits in arterial contractile function. Reduced myogenic tone in allograft resistance arteries increases coronary blood flow such that hydrostatic pressure surpasses oncotic pressure, causing cardiac interstitial edema. This generalized edema decreases ventricular compliance leading to heart failure during the course of acute immune rejection of the graft. Cyclosporine A treatment reduces immune mediated dysregulation of myogenic tone, resulting in reduced interstitial edema and improved cardiac function. In this review, we discuss aspects of TVD and myogenic tone signaling mechanisms and how aberrations in myogenic regulation of arterial tone contribute to functional changes observed in cardiac transplant.

Protective mechanisms of a metalloporphyrinic peroxynitrite decomposition catalyst, WW85, in rat cardiac transplants

Nitric oxide (NO) derived from inducible NO synthase has been implicated in cardiac rejection. However, little is known about the role of the reactive nitrogen species peroxynitrite. We examined the protective actions of a peroxynitrite decomposition catalyst, WW85, in an experimental model of acute cardiac rejection. Heterotopic, abdominal transplantation of rat donor hearts was performed. Groups included isografts, allografts, or allografts treated with WW85, cyclosporine, or cyclosporine + WW85. We determined graft survival, histological rejection, and graft function (by in situ sonomicrometry). Intragraft biochemical analysis of cytokines and proapoptotic and antiapoptotic gene expression using reverse transcriptase-polymerase chain reaction were determined. Treatment with WW85 or cyclosporine alone prolonged graft survival, improved graft function, and decreased histological rejection. Graft survival was further significantly (P < 0.001) enhanced by combination treatment. A decrease was also shown in nitrotyrosine, poly(ADP-ribose) polymerase (PARP) activation, and lipid peroxide formation by WW85 that was potentiated when given in combination with cyclosporine. Benefits could not be ascribed to changes in intragraft myeloperoxidase activity. Only combination therapy produced significant decreases in inflammatory cytokine gene expression, suggesting that WW85 acted primarily downstream of these stimuli. In general, WW85 had no direct action on expression of the proapoptotic gene, Fas ligand; however, WW85 given alone or with cyclosporine enhanced expression of antiapoptotic genes Bcl-2 and Bcl-xL. Collectively, these findings suggest a protective action of the peroxynitrite decomposition catalyst WW85 on graft rejection that is independent of any action on leukocyte sequestration and cytokine gene expression. Rather, effects seem to be downstream on decreased protein nitration, decreased lipid peroxidation, and decreased PARP activation.

Cyclic adenosine monophosphate inhibits nitric oxide-induced apoptosis of cardiac muscle cells in a c-Jun N-terminal kinase-dependent manner

Cyclic adenosine monophosphate (cAMP) modulates various agent-induced apoptosis. In this study, we observed that cAMP had a significantly protective effect on nitric oxide (NO)-induced cytotoxicity in H9c2 cardiac muscle cells. Pretreatment with DBcAMP (cAMP analogue) or forskolin (adenylyl cyclase activator) also significantly prevented the SNP-induced apoptosis in H9c2 cells. In contrast, H-89 or KT5720 (PKA inhibitor) reversed the protective effects of DBcAMP. In this study, DBcAMP or forskolin reduced SNP-induced JNK/SAPK activation to the basal level, but KT5720 reversed the inhibitory effects of these two agents. In contrast to JNK/SAPK activation, DBcAMP and forskolin significantly enhanced SNP-activated p38 MAPK phosphorylation and did not affect SNP-mediated ERK activation. KT5720 reversed the effects of DBcAMP and forskolin on p38 MAPK phosphorylation. The inhibition of the JNK pathway by transfection of a dominant negative mutant of JNK/SAPK markedly reduced the extent of SNP-induced cell death. Taken together, we suggest that JNK/SAPK is related to cAMP-protective effect in SNP-induced apoptosis. In addition, c-AMP relating agents protected SNP-induced cell death in neonatal rat ventricular cardiomyocytes. The cAMP-relating agent-induced protective effect is not restricted in H9c2 cardiac muscle cells.

Effects of inhibition of poly(adenosine diphosphate-ribose) synthase on acute cardiac allograft rejection

BACKGROUND

Nitric oxide synthase (NOS)-2 is expressed during acute cardiac allograft rejection in association with death of heart muscle cells. The nuclear enzyme poly(adenosine diphosphate [ADP]-ribose) synthase (PARS) is activated by agonists such as NO and peroxynitrite, which cause single-strand DNA breaks; PARS, in turn can promote both necrosis and apoptosis. To investigate the hypothesis that NO produced by NOS-2 in cardiomyocytes activates PARS and contributes to heart muscle cell death by apoptosis, experiments were performed using a heterotopic rat abdominal heart transplant model and cytokine-stimulated heart muscle cells in tissue culture.

METHODS

Cardiac allografts were treated after transplantation with either the PARS inhibitor 5-aminoisoquinolinone at 3 mg/kg subcutaneously daily or with vehicle. Isolated purified adult rat cardiomyocytes incubated with cytokines to induce NOS-2 were treated in vitro with another PARS inhibitor, 3-aminobenzamide (3AB).

RESULTS

PARS inhibition increased cardiac-allograft survival from 6 +/- 2 to 10 +/- 3 days (n=6, n=6, P<0.05). The inflammatory infiltrate, NOS-2-positive macrophages, myocyte apoptosis, and myocyte content of nitrotyrosine and poly(ADP-ribose) were significantly decreased in PARS inhibited allografts at day 5 posttransplantation. Similarly, apoptosis and PARS activity were diminished in cytokine-stimulated adult rat cardiomyocytes when either 3AB or L-NMMA were applied.

CONCLUSIONS

The data indicate that PARS activation occurs during acute cardiac-allograft rejection and contributes significantly to the inflammatory response and to the death of cardiac muscle cells by apoptosis. They suggest that PARS inhibition combined with immunosuppression might enhance salvage of heart-muscle cells during acute cardiac-allograft rejection.

Effect of erythropoietin on bcl-2 gene expression in rat cardiac myocytes after traumatic brain injury

The purpose of this study was to investigate whether erythropoietin (EPO) has an effect on the expression of bcl-2 in rat cardiac myocytes following experimental isolated traumatic brain injury (TBI). Forty-eight Wistar-Albino female rats were randomly allocated into eight groups. Groups AC and BC were controls; groups AS and BS were sham-operated animals. Groups A1 and B1 underwent head trauma without treatment. Groups A2 and B2, head traumas plus EPO intraperitoneally (1000 IU/kg); groups A3 and B3, the vehicle groups, head traumas and intraperitoneal albumin (0.4 ml/rat). The method of weight drop was used to produce impact trauma at 24 hours after injury. Samples obtained from the left ventricle were assayed for lipid peroxidation and bcl-2 gene expression using real-time quantitative polymerase chain reactions. Lipid peroxidation in the heart tissue was determined by the concentration of thiobarbituric acid reactive substances (TBARs). The results showed that administration of EPO significantly reduced the increase in lipid peroxidation by-products after moderate or severe trauma. The bcl-2 expression was significantly higher in EPO (A2 and B2) compared to trauma groups (A1 and B1) suggesting a protective effect. These findings suggest that EPO may play an important role in the expression of bcl-2 and decrease in TBARs-the end product of lipid peroxidation in myocytes-after moderate or severe TBI.

3-Deazaadenosine prevents leukocyte invasion by suppression of adhesion molecule expression during acute cardiac allograft rejection: Involvement of apoptotic cell death

BACKGROUND

In the initial phase after cardiac transplantation, mononuclear cells infiltrate the graft, initiating a relevant impulse for rejection. 3-Deazaadenosine (c3Ado), an analog of adenosine, has proven anti-inflammatory properties both in vitro and in vivo. We hypothesized that c3Ado can serve as a therapeutic tool to reduce cellular infiltration in cardiac allograft transplantation.

METHODS

Using the Wistar-Furth-to-Lewis rat cardiac allograft model, animals were treated with 5 mg c3Ado subcutaneously twice per day. Allografts of untreated animals served as controls. Grafts were harvested on Days 1, 3 and 6 after transplantation for further examination (n = 4 per group and timepoint).

RESULTS

Immunohistochemical examination of c3Ado-treated grafts revealed up to 80% reduction of infiltrating major histocompatability complex (MHC) II-positive cells and T-cell-receptor-positive cells (R73) as well as ED1-positive monocytes and macrophages at Days 3 and 6 after transplantation. Adhesion molecule (ICAM-1 and VCAM-1) expression at Days 1 and 3 was almost completely abolished in c3Ado-treated grafts. However, c3Ado treatment did not prevent apoptotic cell death (TUNEL assay, DNA laddering) at Day 6, nor did it prolong allograft survival. As in controls, grafts were rejected at Day 7.

CONCLUSION

c3Ado significantly reduces graft infiltration by preventing leukocyte invasion, most likely through suppression of adhesion molecule expression. Although graft survival was not prolonged, treatment with c3Ado may still serve as a strategy to protect hearts from early damage after transplantation. Further studies will show whether peri-operative use of c3Ado can bridge the critical phase after transplantation when standard immunosuppression is not yet completely efficacious.

Cornea Graft Endothelial Cells Undergo Apoptosis by Way of an Alternate (Caspase-Independent) Pathway

PURPOSE

To look for apoptosis pathways involved in corneal endothelial cell death during acute graft rejection and to evaluate the potential role of nitric oxide in this process.

MATERIALS AND METHODS

Corneal buttons from Brown-Norway rats were transplanted into Lewis rat corneas. At different time intervals after transplantation, apoptosis was assessed by diamino-2-phenylindol staining and annexin-V binding on flat-mount corneas, and by terminal transferase dUTP nick end labeling (TUNEL), caspase-3 dependent and leukocyte elastase inhibitor (LEI)/LDNase II caspase-independent pathways on sections. Inducible nitric oxide synthase (NOS-II) expression and the presence of nitrotyrosine were assayed by immunohistochemistry.

RESULTS

Graft endothelial cells demonstrated nuclear fragmentation and LEI nuclear translocation, annexin-V binding, and membranes bleb formation. Apoptosis associated with caspase-3 activity or TUNEL-positive reaction was not observed at any time either in the graft or in the recipient corneal endothelial cells. During 14 days posttransplantation, the recipient corneal endothelial cells remained unaltered and their number unchanged in all studied corneas. NOS-II was expressed in infiltrating cells present within the graft. This expression was closely associated with the presence of nitrotyrosine in endothelial and infiltrating cells.

CONCLUSION

During the time course of corneal graft rejection, graft endothelial cells undergo apoptosis. Apoptosis is caspase 3 independent and TUNEL negative and is, probably, carried out by an alternative pathway driven by an LEI/L-Dnase II. Peroxynitrite formation may be an additional mechanism for cell toxicity and programmed cell death of the graft endothelial cells during the rejection process in this model.

FK 506 and aminoguanidine suppress iNOS induction in orthotopic corneal allografts and prolong graft survival in mice

The aim of this study was to compare the effectiveness of immunosuppressant FK 506 and the specific inhibitor of inducible nitric oxide synthase (iNOS) aminoguanidine (AG) in prevention of corneal graft rejection and to investigate the iNOS expression in the rejection process. Orthotopic corneal allografting in mice was performed (C57BL/10; H-2(b) to BALB/c; H-2(d)). FK 506 (0.3 mg/kg per day) or AG (100 mg/kg per day) was injected intraperitoneally for 4 weeks. Grafted mice without therapy served as controls. Immunohistological evaluation of iNOS-positive cells and macrophage infiltration in grafts 27th day after grafting was performed. Within 4 weeks FK 506 prevented graft rejection in 71% and AG in 57% of animals compared to 29% of clear grafts in controls. A significant proportion of iNOS-positive cells was detected in the rejected grafts of the control and AG-treated groups. The treatment with FK 506 resulted in the inhibition of iNOS expression to a high degree in the rejected corneas. Non-rejected corneas of all groups and non-transplanted corneas exhibited no iNOS-positive cells. A massive infiltration of macrophages was detected in the rejected grafts, whereas non-rejected grafts exhibited only slight infiltration of macrophages. The presented data suggest that overexpression of iNOS and/or activation of iNOS is one of the several influential factors that contribute to the rejection process and that iNOS suppression delays corneal allograft rejection. FK 506 and AG are effective drugs in preventing corneal allograft rejection. Higher beneficial effect of FK 506 on graft survival could be explained by its well-known selective T-cell immunosuppression.

Mitochondrial permeability transition in cardiomyocyte apoptosis during acute graft rejection

Evidence indicates that acute cardiac graft rejection is associated with cardiomyocyte apoptosis. Mitochondrial permeability transition (MPT) induces apoptotic cell death. We sought to determine whether MPT might play a role in cardiomyocyte apoptosis in the rat model of heterotopic cardiac transplantation. Syngenic and allogenic transplantations were performed, and both native and grafted hearts were harvested 3 or 5 d after transplantation for detection of acute rejection, assessment of Ca(2+)-induced MPT, and myocardial apoptosis by TUNEL staining and caspase 3 activity. Allogenic grafts developed severe acute rejection at day 5 with concomitant cardiomyocyte apoptosis (apoptotic index: 7.1 +/- 1.0% vs. 1.0 +/- 0.2% in syngenic hearts, and caspase 3 activity: 38 +/- 25 vs. 5 +/- 9 nmol/mg, in allogenic vs. syngenic grafts, respectively). At day 5, Ca(2+)-induced MPT was dramatically altered in allogenic when compared with syngenic grafts (mean Ca(2+) overload averaged 0 +/- 20 vs. 280 +/- 30 microM in allogenic and syngenic grafts, respectively). NIM811, a nonimmunosuppressive derivative of cyclosporin A (CsA), that specifically inhibits the MPT pore, did not alter acute rejection, but significantly delayed Ca(2+)-induced MPT pore opening, attenuated caspase 3 activity and cardiomyocyte apoptosis in allogenic grafts. This suggests that mitochondrial permeability transition pore opening may play an important role in cardiomyocyte apoptosis associated with acute cardiac graft rejection.

Cyclosporine treatment preserves coronary resistance artery function in rat cardiac allografts

BACKGROUND

A marked decline in vascular myogenic response occurs during the course of rat cardiac allograft rejection. Two important contributory features are an inducible nitrous oxide synthase (iNOS)-catalyzed, NO-mediated vasodilation and a loss of smooth muscle function. In this study, we examine the effect of cyclosporine immunosuppressive therapy on the alleviation of arterial dysfunction of coronary resistance arteries in allografts using pressure myography.

METHODS

Rats receiving heterotopic abdominal cardiac transplantation were treated with cyclosporine (5 mg/kg), Cremophore or distilled water. Coronary septal arteries (internal diameter 200 microm) were dissected from isograft (Lewis to Lewis) and allograft (Fisher to Lewis) rat hearts at Day 21 post-transplantation and mounted on a pressure myograph. Pressure-induced vasoconstriction was measured before and after iNOS inhibition with aminoguanidine (AG; 100 micromol/liter). Both endothelium-based (ACh-induced) and endothelium-independent (sodium nitroprusside-induced) vasorelaxation were also recorded in each group.

RESULTS

Pressure-induced myogenic contraction was reduced in allograft coronary arteries at Day 21 post-transplantation compared with matched isografts (p < 0.05). AG potentiated myogenic tone in allograft arteries, but had no effect on untreated Day 21 isograft vessels, indicating the presence of iNOS-based relaxation only in allograft vessels. Depolarization-induced vasoconstriction was lower in allograft compared with isograft arteries (p < 0.05). Cyclosporine therapy also improved depolarization-induced constriction in allograft vessels compared with untreated groups (p < 0.05). Furthermore, cyclosporine therapy preserved endothelium-based and endothelium-independent vasorelaxation in allograft arteries at Day 21 post-transplantation.

CONCLUSIONS

Cyclosporine immunosuppressive therapy has a significant effect on the alleviation of early endothelial and smooth muscle dysfunction in coronary allograft arteries.

Immunosuppression and transplant vascular disease: benefits and adverse effects

Cardiac allograft vasculopathy (CAV) occurs within 5 years of transplantation surgery and represents the main cause of death in long-term heart transplant survivors. The detailed pathogenesis of CAV is unknown, but there are strong indications that immunologic mechanisms, which are regulated by nonimmunologic factors, are the major cause of this phenomenon. Cyclosporine A (CsA) is a frequently used immunosuppressive agent in transplant medicine to prevent rejection. The mechanism of action of CsA involves initial binding to cyclophilin to form a complex that then inhibits calcineurin (CN), leading to reduced interleukin (IL)-2 production as part of the signal transduction pathway for the activation of B-lymphocytes and T-lymphocytes. Based on this proposed mechanism, it was expected that CsA should be an effective strategy in attenuating the host immune response against transplanted allograft tissue; however, CsA has not changed the outcome of CAV. Several mechanisms have been suggested for the ineffectiveness of CsA in long-term prevention of CAV. For example, routine therapeutic doses of CsA may block CN incompletely (50%), whereas complete blockade requires doses that are not clinically tolerable. Another explanation is the possible activation of T-cell receptors directly (CN independent) by the immune response, which induces protein kinase C theta (PKCtheta) and leads to IL-2 production and immune rejection. Moreover, there may be a role for nonimmunologic mechanisms, such as complement, which cannot be controlled by CsA, or CsA may cause hypercholesterolemia or induce overexpression of transforming growth factor-beta (TGF-beta). This review also compares the effect of CsA with other immunosuppressants in allograft artery preservation and their clinical efficacy.

Bcl-2-mediated inhibition of apoptosis in rat cardiac allografts worsens development of graft coronary artery disease

BACKGROUND

We hypothesized that adenovirally mediated Bcl-2 transfection of donor hearts would reduce the apoptosis that occurs during acute rejection while worsening the development of chronic graft coronary artery disease (GCAD).

METHODS

PVG donor hearts were treated with either AdvBcl-2 or AdvNull virus before heterotopic transplantation into ACI rats. Bcl-2 expression was assessed on post-operative day 4 (POD) 4 by western blot. Apoptosis was measured using (99m)Technetium-bound-annexin V imaging and caspase 3 activity assay. Allograft survival was determined in a separate cohort of animals. Long-term-treated animals were then assessed for measures of GCAD on POD 90.

RESULTS

Western blot analysis showed upregulation of Bcl-2 expression in AdvBcl-2-treated hearts. (99m)Tc-annexin V images demonstrated decreased uptake in the AdvBcl-2 group (1.41 +/- 0.33% vs 1.94 +/- 0.37%, p = 0.026). Caspase 3 activity was also significantly lower in this treatment group (0.112 +/- 0.032 vs 0.204 +/- 0.096, p = 0.049). Allograft survival was similar in both groups, respectively (7.7 +/- 1.2 vs 6.8 +/- 1.5 days, p = 0.340). GCAD, as determined by percent luminal narrowing (5.9 +/- 6.1% vs 1.6 +/- 1.5%, p = 0.039), intima-to-media ratio (5.1 +/- 5.1% vs 1.5 +/- 1.7%, p = 0.040) and percent of affected vessels (15.1 +/- 9.9% vs 5.3 +/- 4.4%, p = 0.009), was higher for the AdvBcl-2 group.

CONCLUSION

Treatment of cardiac allografts with AdvBcl-2 resulted in a reduction of apoptosis that did not significantly improve short-term graft survival, but worsened chronic GCAD.