Role of nitric oxide in experimental obliterative bronchiolitis (chronic rejection) in the rat

Sialoadhesin - a macrophage-restricted marker of immunoregulation and inflammation

Sialoadhesin (Sn, also known as Siglec-1 and CD169) is a macrophage-restricted cell surface receptor that is conserved across mammals. Sn is a member of the sialic acid-binding IgG-like lectin (Siglec) family of proteins characterized by affinity to specifically sialylated ligands, and under normal conditions is expressed on subsets of macrophages in secondary lymphoid tissues, such as lymph node and spleen. However, Sn-positive macrophages can also be found in a variety of pathological conditions, including (autoimmune) inflammatory infiltrates and tumours. Sn has been shown to contribute to sialylated pathogen uptake, antigen presentation and lymphocyte proliferation, and to influence both immunity and tolerance. This review presents Sn as a macrophage-specific marker of inflammation and immunoregulation with the potential to becoming an important biomarker for immunologically active macrophages and a target for therapy.

Rattus model utilizing selective pulmonary ischemia induces bronchiolitis obliterans organizing pneumonia

Bronchiolitis obliterans organizing pneumonia (BOOP), a morbid condition when associated with lung transplant and chronic lung disease, is believed to be a complication of ischemia. Our goal was to develop a simple and reliable model of lung ischemia in the Sprague-Dawley rat that would produce BOOP. Unilateral ischemia without airway occlusion was produced by an occlusive slipknot placed around the left main pulmonary artery. Studies were performed 7 days later. Relative pulmonary and systemic flow to each lung was measured by injection of technetium Tc 99m macroaggregated albumin. Histological sections were examined for structure and necrosis and scored for BOOP. Apoptosis was detected by immunohistochemistry with an antibody against cleaved caspase 3. Pulmonary artery blood flow to left lungs was less than 0.1% of the cardiac output, and bronchial artery circulation was ∼2% of aortic artery flow. Histological sections from ischemic left lungs consistently showed Masson bodies, inflammation, and young fibroblasts filling the distal airways and alveoli, consistent with BOOP. In quantitative evaluation of BOOP using epithelial changes, inflammation and fibrosis were higher in ischemic left lungs than right or sham-operated left lungs. Apoptosis was increased in areas exhibiting histological BOOP, but there was no histological evidence of necrosis. Toll-like receptor 4 expression was increased in ischemic left lungs over right. An occlusive slipknot around the main left pulmonary artery in rats produces BOOP, providing direct evidence that ischemia without immunomodulation or coinfection is sufficient to initiate this injury. It also affords an excellent model to study signaling and genetic mechanisms underlying BOOP.

Effect of simvastatin on development of obliterative airway disease: an experimental study

BACKGROUND

Obliterative bronchiolitis after lung transplantation is characterized by airway inflammation leading to obliteration of small airways. Statins are known to have lipid-independent immunomodulatory properties. We investigated the effect of simvastatin treatment on innate and adaptive immune responses and the development of obliterative airway disease (OAD).

METHODS

In fully MHC-mismatched rat tracheal allograft recipients, we used simvastatin at different doses (0.1 to 20 mg/kg/day orally) to assess its effect on OAD development. No immunosuppressive treatment was administered. Histologic, immunohistochemical and real-time RT-PCR analyses were performed 3, 10 and 30 days after transplantation.

RESULTS

Simvastatin treatment with doses ranging from 0.5 to 20 mg/kg/day significantly enhanced early epithelial recovery and reduced the development of OAD. No dose response was observed. Simvastatin treatment markedly reduced IL-23 mRNA and lymphocyte chemokine CCL20 production, and the infiltration of CD4(+) and CD8(+) T cells into allografts already at 3 days. At 10 days, simvastatin significantly attenuated the production of pro-inflammatory cytokines, IL-1β, TNF-α, MCP-1 and IP-10, and Th17-polarizing cytokines, IL-6 and IL-17e, and inhibited allograft infiltration by inflammatory cells. The protective effects of simvastatin on inflammation and OAD were partially mediated through nitric oxide synthase.

CONCLUSIONS

Simvastatin treatment inhibited adaptive T-cell alloimmune activation as depicted by reduced expression of lymphocyte chemokine and pro-inflammatory cytokine mRNA and reduced allograft infiltration by inflammatory cells. Importantly, simvastatin inhibits the development of OAD and this effect is partially mediated by increased nitric oxide activity. These results suggest a role for simvastatin in the prevention of obliterative bronchiolitis.

Animal models of chronic allograft injury: contributions and limitations to understanding the mechanism of long-term graft dysfunction

Advances in immunosuppression have reduced the incidence of acute graft loss after transplantation, but long-term allograft survival is still hindered by the development of chronic allograft injury, a multifactorial process that involves both immunologic and nonimmunologic components. Because these components become defined in the clinical setting, development of animal models enables exploration into underlying mechanisms leading to long-term graft dysfunction. This review presents animal models that have enabled investigation into chronic allograft injury and discusses pivotal models currently being used. The mechanisms uncovered by these models will ultimately lead to development of new therapeutic options to prevent long-term graft dysfunction.

Nitric oxide synthase in critically ischaemic muscle and alterations in isoform expression during revascularization surgery

BACKGROUND

Dysfunction of the nitric oxide pathway is implicated in peripheral arterial disease. Nitric oxide synthase (NOS) isoforms and NOS activity were studied in muscle from patients with critical leg ischaemia (CLI). Alterations in NOS during revascularization surgery were also assessed.

METHODS

Muscle biopsies were taken from patients with CLI undergoing amputation and also from patients undergoing femorodistal bypass at the start of surgery, after arterial clamping and following reperfusion. The presence of NOS within muscle sections was confirmed using reduced nicotinamide adenine dinucleotide phosphate diaphorase histochemistry. NOS isoform distribution was studied by immunohistochemistry. NOS mRNA and protein levels were measured using real-time reverse transcriptase-polymerase chain reaction and western blotting. NOS activity was assessed with the citrulline assay.

RESULTS

All three NOS isoforms were found in muscle, associated with muscle fibres and microvessels. NOS I and III protein expression was increased in CLI (P = 0.041). During revascularization, further ischaemia and reperfusion led to a rise in NOS III protein levels (P = 0.008). NOS activity was unchanged.

CONCLUSION

Alterations in NOS I and III occurred in muscle from patients with CLI and further changes occurred during bypass surgery.

Alterations in nitric oxide and cytokine production with airway inflammation in the absence of IL-10

IL-10 is an anti-inflammatory cytokine that suppresses NO synthase (NOS) and production of NO; its lack may promote NO production and alterations in cytokines modulated by NO with allergic airway inflammation (AI), such as IL-18 and IL-4. Therefore, we induced AI in IL-10 knockout ((-/-)) and IL-10-sufficient C57BL/6 (C57) mice with inhaled OVA and measured airway NO production, as exhaled NO (E(NO)) and bronchoalveolar lavage fluid nitrite levels. E(NO) and nitrite levels were elevated significantly in naive IL-10(-/-) mice as compared with C57 mice. With AI, E(NO) and nitrite levels increased in C57 mice and decreased in IL-10(-/-) mice. IL-18 production fell with both AI and addition of S-nitroso-N-acetyl-d,l-penicillamine (a NO donor) but was not significantly increased by chemical NOS inhibition by l-N(5)-(1-iminoethyl)-ornithine. IL-4 AI was increased significantly (up to 10-fold greater) in the absence of IL-10 but was reduced significantly with chemical inhibition of NOS. Airway responsiveness was lower in IL-10(-/-) mice and was associated with alteration in production of NO and IL-4. Thus, IL-4 production was increased, and likely decreased NO production, in a way not predicted by the absence of IL-10. Inhibition of IL-4 production, with inhibition of NOS in the absence of IL-10, demonstrated the importance of a NO and IL-4 feedback mechanism regulating this interaction.

Dual Role of Vascular Endothelial Growth Factor in Experimental Obliterative Bronchiolitis

Obliterative bronchiolitis (OB) is the major limitation for long-term survival of lung allograft recipients. We investigated the role of vascular endothelial growth factor (VEGF) in the development of OB in rat tracheal allografts. In nonimmunosuppressed allografts, VEGF mRNA and protein expression vanished in the epithelium and increased in smooth muscle cells and mononuclear inflammatory cells with progressive loss of epithelium and airway occlusion compared with syngeneic grafts. Intragraft VEGF overexpression by adenoviral transfer of a mouse VEGF(164) gene increased early epithelial cell proliferation and regeneration but increased microvascular remodeling and lymphangiogenesis and luminal occlusion by more than 50% compared with AdlacZ-treated allografts. Although VEGF receptor inhibition decreased early epithelial regeneration in noninfected allografts, it reduced microvascular remodeling, lymphangiogenesis, intragraft traffic of CD4(+) and CD8(+) T cells, and the degree of luminal occlusion. Simultaneous VEGF gene transfer and platelet-derived growth factor receptor inhibition with imatinib preserved respiratory epithelium and totally prevented luminal occlusion. In conclusion, our findings indicate that VEGF has a dual role in transplant OB. Our results suggest that VEGF may protect epithelial integrity. On the other hand, VEGF may enhance luminal occlusion by increasing the recruitment of mononuclear inflammatory cells with platelet-derived growth factor acting as a final effector molecule in this process.

Antiproliferative effects of NKH477, a forskolin derivative, on cytokine profile in rat lung allografts

OBJECTIVE

NKH477 was recently identified as a water-soluble forskolin derivative and was reported to prolong survival of murine cardiac allografts. However, the mechanism of the efficacy is not clear in vivo. The aim of this study was to investigate the immunosuppressive effects of NKH477 on acute lung allograft rejection in the rat model and its mechanism of action in vivo.

METHODS

Left lungs were transplanted orthotopically from Brown-Norway donors to Lewis recipients. Recipient rats were untreated or treated daily with different doses of NKH477. Grafts were excised on Day 3 or Day 5 to determine histopathological rejection and expressions of interleukin (IL)-2, IL-4, IL-10, and interferon (IFN)-gamma by enzyme-linked immunosorbent assay. The cytokine expression at Day 3 or Day 5 was also evaluated in recipient spleens by immunohistochemistry. Furthermore, mesenteric lymph node cells from recipients at Day 5 were cultured alone or stimulated with donor antigens for 72 hours to determine cell proliferation by means of thymidine incorporation.

RESULTS

NKH477 significantly extended allograft survival time in a dose-dependent manner and reduced histopathological rejection. Treatment with NKH477 inhibited IFN-gamma and IL-10 expression, whereas expression of these cytokines were markedly upregulated in the untreated allografts. Expression of IL-2 and IL-10 also increased in the spleen of untreated allorecipients. NKH477 suppressed expression of both cytokines in the spleen. In addition, lymphocyte proliferation was inhibited in NKH477-treated recipients as compared with untreated recipients.

CONCLUSION

These results suggest that NKH477 exerts an antiproliferative effect on lymphocytes in vivo with an altered cytokine profile in rat recipients of lung allografts.

Expression of endothelial nitric oxide synthase and vascular endothelial growth factor in oral squamous cell carcinoma: its correlation with angiogenesis and disease progression

BACKGROUND

Angiogenesis is a crucial step in the successful growth, invasion, and metastasis of a tumor. It has been popularly accepted that vascular endothelial growth factor (VEGF) is the most potent angiogenic factor in tumor angiogenesis. As another possible star molecule responsible for tumor angiogenesis, the role of nitric oxide (NO) in tumor biology has gained much attention in recent years. The aim of this study was to investigate whether the expression of endothelial nitric oxide synthase (eNOS) and VEGF in oral squamous cell carcinoma (OSCC) is associated with angiogenesis. The present study also made a preliminary exploration of the possible cross-talking existing between eNOS and VEGF during tumor angiogenesis.

METHODS

In this study, expression of eNOS and VEGF were studied immunohistochemically in tissue sections from 40 patients with OSCC and 20 normal controls. To exclude eNOS antibody cross-reactivity with inducible or neuronal nitric oxide (iNOS or nNOS), eNOS expression was confirmed by using an eNOS mRNA in situ hybridization kit. The intratumoral microvessels were highlighted by immunostaining with anti-factor VIII-related antigen monoclonal antibody and counted as well-established methods. Then, chi-square test or Student's t-test was performed to study the correlations between the expression of eNOS and VEGF, microvessel density (MVD), and various clinicopathologic factors.

RESULTS

Both eNOS and VEGF expression significantly increased in OSCC tissues, with a positive rate of 47.5% and 50%, respectively. The average MVD in OSCC tissues was 23.45 per high-power field (HPF), showing an obvious association with lymph node metastasis and clinical stages of patients with OSCC. Either eNOS or VEGF positivity was correlated with vessel involvement and OSCC progression. The mean MVD was significantly higher in eNOS- or VEGF-positive tumors than in eNOS- or VEGF-negative tumors. An obvious, correlation was also seen between eNOS and VEGF expression in OSCC tissues in this study.

CONCLUSIONS

Overexpression of eNOS and VEGF might make an important contribution to the tumor angiogenesis in OSCC. NO generation by eNOS might be implicated in the VEGF-associated angiogenic process. Further investigation of the possible cross-talking between eNOS and VEGF with respect to tumor angiogenesis is necessary.

Role of endogenous endothelin-1 in transplant obliterative airway disease in the rat

Endothelin-1 (ET-1) expression is increased after lung transplantation in association with ischemia reperfusion injury and acute rejection. However, little is known of the role of ET-1 during the development of obliterative bronchiolitis. In this study, we investigated the biological significance of ET-1 in obliterative airway disease development using a rat tracheal allograft model. Immunoreactivity of ET-1 and its receptors ET-RA and ET-RB was increased four-fold in allografts compared with syngrafts and localized to mononuclear cells and smooth muscle cells of the myofibroproliferative lesion and airway wall, indicating that ET-1 may mediate its effects in both a paracrine and autocrine manner in smooth muscle cells. Inhibition of ET-1 action by a nonselective ET-1 receptor antagonist, bosentan, significantly decreased tracheal occlusion, which was linked to delayed epithelial necrosis, suppressed smooth muscle cell proliferation, and a marked reduction in the number of interleukin-1beta and interleukin-2 immunoreactive cells. Our findings show that endogenous ET-1 activation is associated with obliteration of the airway wall, and blocking signaling downstream of ET-1 receptors leads to attenuation of obliterative airway disease. The results suggest that ET-1 has a proproliferative and proinflammatory role in the development of obliterative bronchiolitis.

Enhanced peroxynitrite decomposition protects against experimental obliterative bronchiolitis

Obliterative bronchiolitis (OB) affects over half of all survivors following lung or heart-lung transplantation. Respiratory epithelial cell injury, peribronchial inflammation, and proliferation of fibrovascular tissue causing airway occlusion characterize the lesion. While peroxynitrite is known to participate in other models of acute lung injury, its role in the evolution of OB is unclear. Using a rat model of experimental OB, tracheas from Brown-Norway or Lewis rats were transplanted into Lewis recipients. Treated animals received FP-15, a peroxynitrite decomposition catalyst, at 1 mg/kg/day intraperitoneal for 14 days. Luminal obstruction, epithelial loss, and inflammatory infiltrate were examined, as was nitrotyrosine staining by immunohistochemistry in explanted tracheas. By postoperative day 14, control allografts demonstrated marked peribronchial inflammation, near complete loss of respiratory epithelium and extensive intraluminal proliferation of fibrovascular connective tissue, with a mean 83% reduction in airway cross-sectional area. Allograft recipients treated with FP-15 showed reduced nitrotyrosine formation, preservation of respiratory epithelium, limited peribronchial inflammation, and only 14% (P <.001) reduction in airway cross-sectional area. Peroxynitrite therefore appears to play a role in the development of obliterative bronchiolitis in rats. The peroxynitrite decomposition catalyst, FP-15, is protective when administered daily and warrants investigation into its potential clinical utility.

Effects of brief ischemia and reperfusion on the myocardium and the role of nitric oxide

Brief myocardial ischemia/reperfusion has complex effects on the myocardium. In the short term the myocardium may be stunned with temporarily reduced contractile function, though this may also be accompanied by the modification and de novo synthesis of proteins that protect the heart against subsequent early or delayed insults. Repeated episodes of non-lethal ischemia, which are common in the clinical setting, combine all of these phenomena and may ultimately result in chronic contractile dysfunction. Nitric oxide is intimately linked to many of these alterations in cellular function and defense. This article examines data predominantly from in vivo large animal studies that relate to these ischemia-induced changes, the evidence for the proposed mechanisms behind both myocardial stunning and preconditioning while concentrating on the role of nitric oxide in these conditions.

Recipient iNOS but not eNOS deficiency reduces luminal narrowing in tracheal allografts

Chronic airway rejection is characterized by prolonged inflammation, epithelial damage, and eventual luminal obliterative bronchiolitis (OB). In cardiac allografts, the inducible nitric oxide synthase (iNOS) promotes acute rejection but paradoxically reduces neointimal formation, the hallmark of chronic rejection. The specific roles of NOS isoforms in modulating lymphocyte traffic and airway rejection are not known. Using a double lumen mouse tracheal transplant model, tracheal grafts from B10.A (allo) or C57BL/6J (iso) mice were transplanted into cyclosporine-treated wild-type (WT) iNOS(-/-) or endothelial NOS (eNOS)(-/-) recipients. OB was observed in WT tracheal allografts at 3 weeks (53 +/- 2% luminal occlusion vs. 17 +/- 1% for isografts, P < 0.05) with sites of obstructive lesion formation coinciding with areas of CD3(+) CD8(+) T cell-rich lymphocytic bronchitis. In contrast, allografts in iNOS(-/-) recipients exhibited reductions in local expression of proinflammatory chemokines and cytokines, graft T cell recruitment and apoptosis, and luminal obliteration (29 +/- 2%, P < 0.05 vs. WT allografts). Recipient eNOS deficiency, however, suppressed neither chemokine expression, lymphocyte infiltration, nor airway occlusion (54 +/- 2%). These data demonstrate that iNOS exacerbates luminal obliteration of airway allografts in contrast with the known suppression by iNOS of cardiac allograft vasculopathy. Because iNOS(-/-) airways transplanted into WT allograft hosts are not protected from rejection, these data suggest that iNOS expressed by graft-infiltrating leukocytes exerts the dominant influence on airway rejection.

Obliterative airway disease progresses in heterotopic airway allografts without persistent alloimmune stimulus

BACKGROUND

Up to 50% of human lung allografts develop chronic rejection manifested as obliterative bronchiolitis (OB). This complication frequently progresses despite maximal immunosuppression, suggesting that, once initiated, factors other than alloimmunity play a role in its progression. In animals, heterotopically transplanted allograft airways develop obliterative airway disease (OAD), an immunologically mediated lesion that is used as a preclinical model of OB. We sought to determine whether OAD would progress even after removal from the alloimmune environment.

METHODS

Tracheas from Lewis rats were transplanted subcutaneously into Brown Norway recipients to create allografts. After 7 or 14 days of alloimmune stimulus, these allografts were removed and retransplanted into an isogeneic environment for an additional 21 days. Histology was assessed at each time point, with quantitation of the airway epithelium and intraluminal fibroproliferation.

RESULTS

Allografts exposed to 14 days of alloimmune stimulus had a significant loss of airway epithelium compared with grafts exposed to only 7 days ( <0.001). There was little fibroproliferation seen in either of these groups. After retransplantation, the grafts initially exposed to 7 days of alloimmune stimulus had few abnormalities. In contrast, the group exposed initially to 14 days of alloimmunity and retransplanted had near complete obliteration of the lumen with fibroproliferation (96.9% occlusion, =0.001) and absent airway epithelium.

CONCLUSIONS

OAD progresses despite removal of alloimmunity if the initial period of alloimmune injury is sufficient. Airway epithelial loss correlated with progression to fibroproliferation, suggesting that the epithelium plays a significant role in the pathogenesis of OB.

Nitric oxide in the development of obliterative bronchiolitis in a heterotopic pig model

BACKGROUND

Inflammation, epithelial cell injury, and development of fibrosis and airway obliteration are the major histological features of posttransplant obliterative bronchiolitis (OB). The expression of inducible nitric oxide synthase (iNOS) in the damaged epithelium, accompanied by peroxynitrite, suggests that endogenous nitric oxide (NO) mediates the epithelial destruction preceding obliteration. To elucidate the role of NO in this cascade, heterotopic bronchial allografts were studied in pigs.

METHODS

Allografts or autografts were harvested serially 3-90 days after transplantation and processed for histology and immunocytochemistry for iNOS, nitrotyrosine, a marker of peroxynitrite formation, and superoxide dismutase (SOD).

RESULTS

During initial ischemic damage to the epithelium, iNOS, nitrotyrosine, and SOD were found to be strongly expressed in the epithelium of all implants as well as later, after partial recovery, parallel to onset of epithelial destruction and subsequent airway obliteration in allografts. The levels of expression of iNOS in fibroblasts during the early phase of obliteration paralleled the onset of fibrosis. Constant expression of iNOS and SOD, but not nitrotyrosine, occurred in autografts and allografts with blocked alloimmune response.

CONCLUSIONS

These findings suggest that an excessive amount of NO promotes posttransplant obliterative bronchiolitis by destroying airway epithelium and stimulating fibroblast activity. SOD may provide protection by binding reactive molecules and preventing peroxynitrite formation.

A comparison of rat tracheal transplant models: implantation verses anastomotic techniques for the study of airway rejection

BACKGROUND

In rodent models, investigators have transplanted donor tracheas into a recipient rat's abdomen or s.c. tissue to study airway rejection. We describe a modification of this model, which provides improved histology to study the airway injury related to obliterative bronchiolitis.

METHODS

The standard technique of implanting the donor trachea was compared to a model in which a tracheal Y graft was created by anastomosis of the donor trachea to the recipient airway. Syngeneic and allogeneic tracheal grafts (Lewis and Brown Norway rats) were harvested at 2 and 4 weeks using each model (eight groups).

RESULTS

Gross patency at the tracheal anastomosis grafts was 100%. All donor tracheas, which were implanted without an anastomosis, were occluded with mucus (syngeneic) or granulation tissue (allogeneic). Syngeneic implant grafts demonstrated significantly less lumenal granulation tissue 35.3%+/-32 than the allograft implant group (95.3%+/-9.2, P=0.0005 at 4 weeks). The anastomotic allograft group demonstrated significantly less lumenal granulation tissue 48.3%+/-23.7 when compared with the implanted allograft group (P=0.003). The implanted allograft demonstrated a severe loss of epithelial integrity by 2 weeks (16.7%+/-38), which progressed to complete loss by 4 weeks (P=0.0001 and P=0.0001 vs. native). This loss was significantly more than that of the anastomotic group at 2 weeks (89.5%+/-13, P=0.004) and 4 weeks (88.3+/-29, P=0.005).

CONCLUSIONS

The rat tracheal allograft anastomosed to the recipient airway demonstrated less lumenal granulation tissue obstruction and better preservation of epithelial integrity than an implant allograft, suggesting that an open airway improves assessment of transplant-related changes associated with rejection.

Blockade of CD28/B7-2 costimulation inhibits experimental obliterative bronchiolitis in rat tracheal allografts: suppression of helper T cell type1-dominated immune response

T cell activation is a proximal event in the initiation of chronic rejection that may ultimately lead to obliterative bronchiolitis (OB) after lung transplantation. In addition to primary signals generated by the T cell receptor, T cell activation relies on costimulatory signals, of which the most important are mediated via interaction between CD28 and its ligands B7-1 and B7-2. In nontreated rat tracheal allografts, B7-2, but not B7-1, expression peaked 10 d after transplantation, unlike in syngeneic grafts, where no B7-2 upregulation was observed. Selective blockade of the CD28/B7-1 T cell costimulatory pathway by a mutant form of CTLA4Ig (cytotoxic T lymphocyte antigen 4 immunoglobulin), CTLA4IgY100F, did not affect epithelial injury or degree of luminal occlusion in rat tracheal allografts. Treatment with CTLA4Ig fusion protein, which blocks both CD28/B7-1 and CD28/B7-2 interaction, significantly delayed the development of epithelial injury and airway occlusion. Immunohistochemical analyses of allografts showed that selective inhibition of the CD28/B7-1 pathway did not affect cytokine expression. In contrast, treatment with CTLA4Ig was associated with a significant decrease in the intragraft production of tumor necrosis factor alpha, interleukin 2, and interferon gamma, as well as slightly increased intragraft expression of interleukin 10. In conclusion, CTLA4Ig-mediated costimulatory blockade delays epithelial injury and attenuates obliterative changes and is associated with marked suppression of helper T cell type 1 (Th1)-dominated cytokine response. These observations emphasize the role of the CD28/B7-2 costimulatory pathway in regulating proinflammatory and Th1 cytokine responses and thereby in the development of epithelial and graft injury gradually leading to obliteration of the airway lumen.

Interleukin-1 receptor antagonist as a biomarker for bronchiolitis obliterans syndrome in lung transplant recipients

BACKGROUND

The major limitation to survival after lung transplantation is bronchiolitis obliterative syndrome (BOS). BOS is a chronic inflammatory/immunologic process characterized by fibroproliferation, matrix deposition, and obliteration of the airways. The mechanism(s) that lead to fibro-obliteration of allograft airways have not been fully elucidated. Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring antagonist of the pro-inflammatory cytokine IL-1 and has been associated with a number of fibroproliferative diseases.

METHODS

We determined whether IL-1Ra, as compared to IL-1beta, IL-10, transforming growth factor (TGF)-beta, and tumor necrosis factor (TNF)-alpha, in the bronchoalveolar lavage fluid (BALF) from lung transplant recipients was associated with BOS. BALF was collected from three groups of patients: BOS (n=22), acute rejection (n=33), and healthy transplant recipients (n=30).

RESULTS

IL-1Ra levels were significantly elevated in patients with BOS compared to healthy lung transplant recipients and patients with acute rejection (P<0.001 and P<0.05, respectively). Furthermore, when patients with BOS had their BALF analyzed from their last bronchoscopy before the development of BOS (Future BOS [FBOS] group) (n=20), their levels of IL-1Ra were also significantly elevated compared to healthy lung transplant recipients and patients with acute rejection (P<0.001 and P<0.05, respectively). Importantly, the elevated levels of IL-1Ra in the BOS and FBOS groups were not accompanied by any significant increases in IL-1beta, IL-10, TGF-beta, or TNF-alpha.

CONCLUSION

These findings suggest that elevated levels of IL-1Ra may be attenuating IL-1 bioactivity during the pathogenesis of BOS and creating a local environment that favors fibroproliferation and matrix deposition.

Prevention of bronchiolitis obliterans in rat lung allografts by type V collagen-induced oral tolerance

BACKGROUND

We have reported that feeding type V collagen (col(V)) to lung allograft recipients induces immune tolerance that prevents acute lung allograft rejection. Repeated acute rejection is a risk factor for or associated with chronic rejection, known as bronchiolitis obliterans (BO), the leading cause of death in lung allograft recipients. The current study examines if col(V)-induced oral tolerance prevents BO.

METHODS

WKY rats (RT1l) were fed either col(V) or diluent before orthotopic transplantation of F344 (RT1lvl) lung allografts. No rats received any immunosuppression. At 10 weeks posttransplantation the time to onset of BO, delayed type hypersensitivity (DTH) responses to donor antigens, and col(V) were examined. In addition, proliferative responses of recipient T lymphocytes to donor antigens, and ability of recipient antigen presenting cells to present alloantigens in lung allografts were evaluated.

RESULTS

The data show that recipient rats have sustained DTH responses to donor antigens and col(V). T lymphocytes from col(V)-fed lung allograft recipients were unable to proliferate in response to donor antigens, but feeding col(V) had no effect on the presentation of donor alloantigens by recipient antigen presenting cells. All diluent fed rats developed BO, but only mild acute rejection (grade 2) was present in all rats fed col(V). Transforming growth factor (TGF)-beta production was up-regulated systemically in col(V)-fed, but not diluent fed, lung allograft recipients, and neutralizing TGF-beta [corrected] recovered the DTH response to donor antigens in col(V)-fed rats.

CONCLUSIONS

Collectively these data show that col(V)-induces oral tolerance that prevents BO, and that tolerance may be mediated by systemic production of TGF-beta [corrected].

Crosstalk of endothelin-1 and platelet-derived growth factor in cardiac allograft arteriosclerosis

OBJECTIVES

In this study, we investigated the crosstalk of endothelin-1 (ET-1) and platelet-derived growth factor (PDGF) in coronary artery smooth muscle cell (SMC) proliferation in the rat cardiac allograft model.

BACKGROUND

Previous studies have suggested an independent role of ET-1 and PDGF in the development of cardiac allograft arteriosclerosis (i.e., chronic rejection).

METHODS

Heterotopic heart transplantations were performed from Dark Agouti to Wistar Furth rats. Grafts were harvested after five days in an acute rejection model and after 60 days in a chronic rejection model. In the in vitro part of the study, SMC proliferation and migration were quantitated, as well as messenger ribonucleic acid (mRNA) levels of ET-1 and PDGF ligands and receptors after growth factor stimulation.

RESULTS

Acute rejection induced both ET-1 receptors in the arterial wall. On linear regression analysis of chronically rejecting cardiac allografts, a strong correlation between intimal thickening and immunoreactivity of ET-1 and ET receptors A and B (ET(A) and ET(B)) in the arterial walls was observed. Treatment with Bosentan, a mixed ET-1 receptor antagonist, significantly reduced the incidence and intensity of arteriosclerotic lesions in rat cardiac allografts, as well as total intragraft ET(A) and ET(B) mRNA expression and intimal cell ET-1 and receptor immunoreactivity. This was associated with significantly reduced intragraft PDGF beta-receptor (PDGF-Rbeta) mRNA expression. In contrast, CGP 53716, a protein tyrosine kinase inhibitor selective for the PDGF receptor, did not reduce intragraft ET-1, ET(A) or ET(B) mRNA expression. In rat coronary artery SMC cultures, ET-1 stimulation significantly upregulated PDGF-Ralpha and -Rbeta mRNA expression and augmented PDGF-BB-mediated SMC proliferation as well as PDGF-AB- and PDGF-BB-mediated SMC migration.

CONCLUSIONS

Our results suggest that the ET-1/PDGF-Rbeta/PDGF-BB axis may operate in SMC migration and proliferation in cardiac allograft arteriosclerosis, thus explaining the marked beneficial effects of blocking the signaling downstream of ET-1 receptors.

Prevention of cytomegalovirus infection-enhanced experimental obliterative bronchiolitis by antiviral prophylaxis or immunosuppression in rat tracheal allografts

In this study, the prevention of rat cytomegalovirus (RCMV) infection-enhanced experimental obliterative bronchiolitis in rat tracheal allografts was investigated. RCMV infection markedly enhanced cell proliferation and histological changes of obliterative bronchiolitis, a form of chronic rejection after lung transplantation. These alterations were linked to increased interleukin (IL)-2 and tumor necrosis factor-alpha (TNF-alpha) immunoreactivity, and reduction of IL-10 expression. In recipient rats with acute RCMV infection, prophylaxis with either ganciclovir (DHPG) or hyperimmune serum (HIS) totally prevented RCMV infection-enhanced tracheal occlusion. DHPG treatment initiated during acute RCMV infection also reduced lesion development but markedly less than DHPG prophylaxis. Treatment of acute RCMV infection with HIS alone or in combination with DHPG had no significant effect on tracheal occlusion. Inhibition of the transcription of cytokines by high doses of cyclosporine A significantly reduced RCMV infection-enhanced tracheal obliteration. In rats with chronic RCMV infection, obliterative alterations were prevented by DHPG prophylaxis initiated at the time of transplantation. Prophylaxis either with DHPG or HIS did not affect the amount of infectious RCMV recovered from host salivary glands, nor were there differences seen in RCMV major immediate early DNA expression in tracheal allografts between different antiviral drug regimens. Immunohistochemical analysis of allografts revealed that inhibition of tracheal occlusion by antiviral prophylaxis was associated with a reduction in the number of ED1(+) macrophages and cells staining for Th1 cytokines and TNF-alpha, while immune modulation by cyclosporine A up-regulated IL-10 production. In conclusion, the results of the present study suggest that the CMV infection-enhanced chronic rejection develops independently of viral load but requires both immune activation and simultaneous CMV gene expression beyond immediate early genes.

Transfer of heme oxygenase 1 cDNA by a replication-deficient adenovirus enhances interleukin 10 production from alveolar macrophages that attenuates lipopolysaccharide-induced acute lung injury in mice

By using a direct, intratracheal inoculation of an adenovirus encoding heme oxygenase 1 (Ad.HO-1), model gene therapy for acute lung injury induced by inhaled pathogen was performed. Data demonstrated that Ad.HO-1 administration is as effective as the pharmacologic upregulation of the endogenous HO-1 gene expression by hemin to attenuate neutrophilic inflammations of the lung after aerosolized lipopolysaccharide (LPS) exposure. Interestingly, immunohistochemical analysis revealed that the HO-1 gene was transferred not only to the airway epithelium, but to the alveolar macrophages (AMs). Moreover, overexpression of exogenous HO-1 in the macrophages provided a high level of endogenous interleukin 10 (IL-10) production from the macrophages, and additional experiments using IL-10 knockout mice demonstrated that the increase in IL-10 in the macrophages was critical for the resolution of neutrophilic migration in the lung after LPS exposure. These results suggest that AMs not only are barriers for efficient gene transfer to the respiratory epithelium, but also represent logical targets for Ad-mediated, direct, in vivo gene therapy strategies for inflammatory disorders in humans.

Association of reactive nitrogen species metabolites, myeloperoxidase, and airway inflammation in lung transplants

BACKGROUND

We have previously reported that patients who had single or double lung transplants had higher concentrations than controls of nitrite and nitrate, which are metabolites of reactive nitrogen species (RNS), in bronchoalveolar lavage fluid (BALF) and serum.

METHODS

This study investigates implications of RNS metabolites as markers of airway inflammation in a distinct group of lung transplant patients (n = 40). All patients underwent spirometry, routine surveillance transbronchial lung biopsies, and bronchoalveolar lavage as required by clinical protocol. Four normal controls also had bronchoscopy for measurement of BALF nitrite (NO2-) and nitrate (NO3-). BALF NO2- and NO3-, myeloperoxidase (MPO), protein, and urea were assayed. Total nitrite (NO2- plus enzymatically reduced NO3-) and urea were measured in serum.

RESULTS

BALF RNS metabolites were mainly NO3-. Forced expiratory volume in 1 s (FEV1) obtained near bronchoscopy was compared with best postoperative FEV1. Total nitrite in transplant patients' BALF and serum were 3.8 +/- 0.2 and 49 +/- 5 microM, respectively. Total nitrite in controls' BALF and serum were 2.2 +/- 0.7 and 19 +/- 2 microM, respectively (P < 0.05 compared with transplant values). Serum total nitrite correlated (Pearson product moment) with percentage of neutrophils in BALF (R = 0.650, P < 0.0001), MPO (R = 0.431, P = 0.0055), change in FEV1 from baseline (deltaFEV1) (R = -0348, P = 0.0298), and days after transplantation (R = 0.345, P = 0.0294). None of the associated variables, airway inflanmmation (quantified as a score, "B"), deltaFEV1, serum, or BALF total nitrite, were explained by infection. Univariate analysis of airway inflammation in patients showed that it was associated with BALF neutrophils, deltaFEV1, and serum total nitrite.

CONCLUSIONS

Serum nitrite appears to reflect the degree of airway inflammation in this lung-transplant study group.

The heterotopic tracheal allograft as an animal model of obliterative bronchiolitis

Heterotopic tracheal allografts in small rodents have been shown to share many characteristics with the development of obliterative bronchiolitis (OB) in the clinic and therefore provide a suitable animal model for the study of OB. The model facilitates the examination of the pathogenesis of the disease and the elucidation of the cellular and molecular mechanisms involved in its development. The model provides a less technically demanding alternative to whole lung transplantation in small rodents and should lead to a speedier identification of new treatments that might prevent the development of post-transplantation OB in the clinic.

Increased alveolar macrophage nuclear factor-kappa B activation and macrophage inhibitory protein-1alpha levels in lung transplant patients

BACKGROUND

Lung transplantation is increasingly used as the treatment for many end-stage pulmonary diseases. A major cause of morbidity and mortality in patients who undergo lung transplantation is rejection of the allograft. Proinflammatory macrophage-derived cytokines may sustain and/or enhance the immunological response to lung allograft antigens. Nuclear factor-kappa B (NF-kappaB) is a transcription factor that regulates the production of many of these cytokines and growth factors in alveolar macrophages (AMs). The aim of our study was to evaluate the activation of NF-kappaB in AMs and the levels of one of the proinflammatory cytokines whose production it controls, macrophage inhibitory protein-1alpha (MIP-1alpha), in AMs from transplanted lungs compared to those from healthy controls.

METHODS

Twenty-eight (28) transplant recipients were included in the study. NFkappaB activation was evaluated by electrophoretic mobility shift assay of whole cell extracts and by immunohistochemical analysis on cytospin preparations. Concentrated bronchoalveolar lavage fluid was analyzed by enzyme-linked immunosorbent assay for MIP-1alpha levels.

RESULTS

NF-kappaB was activated in alveolar macrophages from transplant patients as compared to healthy controls. MIP-1alpha levels in epithelial-lining fluid were elevated in transplant patients as compared to healthy controls. Increased MIP-1alpha levels correlated with viral infections in the transplant patients. Neither finding was found to correlate with acute rejection by transbronchial biopsy.

CONCLUSIONS

These results demonstrate that NF-kappaB activation and MIP-1alpha levels are increased in transplanted lungs and may play a role in the inflammatory cytokine cascade that leads to the long-term tissue damage and allograft rejection in these patients.

Inducible nitric oxide synthase in the rat testis: evidence for potential roles in both normal function and inflammation-mediated infertility

In vitro data have indicated that nitric oxide (NO) inhibits Leydig cell testosterone production, suggesting that NO may play a role in the suppression of steroidogenesis and spermatogenic function during inflammation. Consequently, we investigated expression of the inflammation-inducible isoform of NO synthase (iNOS) in the inflamed adult rat testis and the ability of a broad-spectrum inhibitor of NO production, L-nitro-L-arginine methyl ester, to prevent Leydig cell dysfunction during inflammation. Unexpectedly, immunohistochemical and mRNA data established that iNOS is expressed constitutively in Leydig cells and in a stage-specific manner in Sertoli, peritubular, and spermatogenic cells in the normal testis. Expression was increased in a dose-dependent manner in all these cell types during lipopolysaccharide (LPS)-induced inflammation. In noninflamed testes, treatment with the NO synthase inhibitor reduced testicular interstitial fluid formation and testosterone production without any effect on serum LH levels. Administration of the inhibitor did not prevent the suppression of testicular interstitial fluid and testosterone production that occurs within 6 h after LPS treatment. Collectively, these data indicate a novel role for iNOS in autocrine or paracrine regulation of the testicular vasculature, Leydig cell steroidogenesis, and spermatogenesis in the normal testis. The data suggest that increased NO is not the major cause of acute Leydig cell dysfunction in the LPS-treated inflammation model, although a role for NO in this process cannot be excluded, particularly at other time points. Moreover, up-regulation of iNOS may contribute to the seminiferous epithelium damage caused by LPS-induced inflammation.

Epithelial re-growth is associated with inhibition of obliterative airway disease in orthotopic tracheal allografts in non-immunosuppressed rats

BACKGROUND

Because epithelial cells are targets of alloimmune injury leading ultimately to airway obliteration, we tested whether epithelial re-growth could prevent obliterative airway disease (OAD) in orthotopic tracheal allografts.

METHODS

Brown Norway tracheal segments were orthotopically transplanted into nonimmunosuppressed Lewis rats. Allografts were removed on days 2-10 (n=13), 30 (n=4), and 60 (n=5) for histology, computerized morphometry (obliteration), and immunohistochemical detection of mononuclear cells, smooth muscle alpha-actin, and tissue phenotype. Normal tracheas, host tracheas, and heterotopically transplanted allografts served as controls.

RESULTS

Orthotopic allografts removed on days 2-10 exhibited epithelial damage and re-growth and mononuclear cell infiltration. On days 30 and 60, partially ciliated cuboidal or attenuated epithelium completely covered the lumen. Although mononuclear cells declined, numerous T cells with a high CD4/CD8 ratio were found in the epithelium till day 60. Orthotopic allograft epithelium expressed donor phenotype on day 7, but recipient phenotype on days 30 and 60. Despite subepithelial alpha-actin positive myofibroblast proliferation, obliteration did not progress from day 7 to 30 and 60 (35, 30, and 33%, respectively). Although more than in normal or host tracheas, the obliteration in orthotopic allografts on days 30 and 60 was significantly less (P<0.001) than in heterotopic allografts.

CONCLUSIONS

We describe, for the first time, longterm patency of fully histoincompatible orthotopic tracheal allografts in nonimmunosuppressed rats. Despite acute alloimmune injury and induction of myofibroblast proliferation, epithelial re-growth from the host limited the progression of OAD, thus emphasizing the role of epithelium in the control of airway obliteration.

Immunosuppressive therapies for the prevention and treatment of obliterative airway disease in heterotopic rat trachea allografts

BACKGROUND

Obliterative bronchiolitis remains a major long-term complication after lung transplantation. Using a reproducible model of heterotopically transplanted rat tracheas, this study examined the role of several novel immunosuppresive compounds to prevent and reverse obliterative airway disease in these animals.

METHODS

Brown Norway rat trachea were transplanted into the greater omentum of Lewis (allografts) or Brown Norway (isografts) animals. Recipient animals were treated with rapamycin, cyclosporine, 15-deoxyspergulin, mycophenolate mofetil, or leflunomide from day 0, 7, or 14 until day of graft removal, either day 28 or 50. Trachea segments were evaluated for degree of lumenal occlusion, as well as percent and type of lumen epithelial cell coverage.

RESULTS

All untreated allografted tracheas obliterated completely, although isografts appeared patent with normal respiratory epithelium when they were removed. Leflunomide, rapamycin, and cyclosporine effectively prevented obliteration when treatment was initiated at day 0, with rapamycin showing continued efficacy when initiated as late as day 7. 15-deoxyspergulin and mycophenolate mofetil failed to consistently inhibit obliteration with any treatment schedule. An inverse correlation was found between epithelial coverage and degree of obliteration, and was especially pronounced in grafts from cyclosporine-treated animals.

CONCLUSIONS

Immunosuppressive drug therapy will inhibit airway obliteration, but efficacy sharply diminishes if initiation of treatment is delayed. Efficacy also varies among immunosuppressive compounds, and results indicate those drugs that enable epithelial regrowth most effectively inhibit airway graft obliteration.

Protein nitration, metabolites of reactive nitrogen species, and inflammation in lung allografts

This study investigated nitration and chlorination of epithelial lining fluid (ELF) proteins in patients (n = 29) who had undergone lung allotransplantation. We assayed lung lavage nitrotyrosine (NT) and chlorotyrosine (CT) by HPLC. We measured NT, nitrate (NO(3)(-)), and nitrate (NO(2)(-)) in bronchoalveolar lavage fluid (BALF) and total nitrite (NO(2)(-) + NO(3)(-)) in serum of another group of lung transplant patients (n = 82). In the first group (n = 29), percent nitration of tyrosines (Tyr) (NT/total Tyr x 100) in BALF proteins was: patients, 0.01 (0.00-0.12)%; median (25th-75th% confidence interval), and control subjects 0.01 (0.00-0.02)%. CT (CT/ total Tyr x 100) occurred only in the patients' BALF: 0.01 (0. 00- 0.02)%. In the second group (n = 82), nitrotyrosine (NT) was detected by ELISA in the BALF of patients: 9 (0-41) pmol/mg pro and control subjects: 28 (26-33). Total nitrite (NO(2)(-) + NO(3)(-)) in BALF of the patients: 3.3 (1.9-5.1) microM significantly exceeded that in control subjects: 1.3 (0.8-1.3) microM; p = 0.0133. Serum nitrite also was significantly higher in patients: 37 (26-55) microM than control subjects: 19 (17-20) microM; p = 0.0037. Airway inflammation in transbronchial biopsies (B score) correlated with NT in BALF (p = 0.0369). Lung transplants have increased airway concentrations of reactive nitrogen species (RNS) metabolites. NT, a marker of peroxynitrite (ONOO(-)), is related to the degree of airway inflammation in lung transplants.

Blockade of complement inhibits obliterative bronchiolitis in rat tracheal allografts

The role of complement activation in the development of obliterative bronchiolitis, a manifestation of chronic lung allograft rejection, was investigated in the heterotopic rat tracheal allograft model. An increase in intragraft complement components C3 and C5b-9 (membrane attack complex) as well as IgM and IgG deposits were demonstrated during the progressive loss of respiratory epithelium and airway occlusion in nontreated allografts compared with syngeneic grafts. A 7-d treatment with recombinant human soluble complement receptor type 1 (sCR1; 20 mg/kg/d, intraperitoneal), an inhibitor of both the classic and alternative complement pathways, significantly decreased epithelial necrosis and intragraft neutrophil infiltration, and reduced obliterative changes by 40%. Immunohistochemical analysis of the grafts showed that sCR1 treatment significantly decreased early C5b-9 and IgG deposits, neutrophil chemoattractant IL-8 immunoreactivity, and ICAM-1 expression. Treatment with sCR1 was associated with increased staining for Th2 cytokines, in particular IL-10, with concomitant downregulation of IL-2 and TNF-alpha immunoreactivity. In contrast, sCR1 treatment did not affect the number of graft-infiltrating CD4(+) and CD8(+) T cells, CD45(+) B cells, ED1(+) and ED3(+) macrophages, or immune activation with expression of IL-2Ralpha or MHC class II. In conclusion, this is the first study to demonstrate that blockade of complement activation attenuates the development of OB and suggests that in addition to T cell-driven responses, humoral and antigen-independent immune responses also operate in the disease process. A blockade of complement activation renders the chemokine milieu unattractive to neutrophils and also modulates the alloimmune response toward Th2 cytokines, which may have an antiproliferative role in fibroproliferative disorders.

Constitutive expressions of type I NOS in human airway smooth muscle cells: evidence for an antiproliferative role

In airway diseases, smooth muscle cells can proliferate at exaggerated rates; thus, the identification of endogenous pathways that limit proliferative responses is important. Here we show that human airway smooth muscle express type I nitric oxide synthase (NOS), which results in inhibition of DNA synthesis and cell proliferation. In addition, superoxide dismutase (SOD), a cell-permeable mimetic that increases the biological half-life and therefore enhances the biological activity of endogenously released nitric oxide (NO), or NO-releasing drugs also greatly reduce DNA synthesis and cell proliferation. Observations in this study have important clinical implications: 1) NOS inhibition may exacerbate airway disease and 2) inhaled SOD/mimetics or NO/nitrovasodilators may be therapies for the treatment of asthma or chronic obliterative pulmonary disease.

Role of platelet-derived growth factor in obliterative bronchiolitis (chronic rejection) in the rat

The role of platelet-derived growth factor (PDGF) in the development of obliterative bronchiolitis (OB) as a manifestation of chronic rejection was investigated in the heterotopic rat tracheal allograft model. An increase in intragraft PDGF-Ralpha and -Rbeta mRNA expression, and in PDGF-AA and -Ralpha immunoreactivity, was demonstrated during the progressive loss of respiratory epithelium and airway occlusion in nontreated allografts compared with syngeneic grafts. Treatment with CGP 53716, a protein-tyrosine kinase inhibitor selective for PDGF receptor, alone and in combination with suboptimal doses of cyclosporin A, significantly reduced myofibroproliferation and the degree of OB by more than 50%. CGP 53716 did not affect airway wall inflammatory cell proliferation, the number of graft-infiltrating CD4(+) or CD8(+) T cells, ED3(+) macrophages, or the level of immune activation determined as IL-2R and MHC class II expression. This study suggests a regulatory role for PDGF, especially for PDGF-AA and -Ralpha, in the development of obliterative bronchiolitis in this model, and demonstrates that inhibition of PDGF receptor protein-tyrosine kinase activation prevents these obliterative changes. Thus, receptor protein-tyrosine kinase inhibitors may provide a novel therapeutic strategy for the prevention of chronic rejection.

Asbestos exposure upregulates the adhesion of pleural leukocytes to pleural mesothelial cells via VCAM-1

This study was designed to assess the effects of in vitro and in vivo asbestos exposure on the adhesion of rat pleural leukocytes (RPLs) labeled with the fluorochrome calcein AM to rat pleural mesothelial cells (RPMCs). Exposure of RPMCs for 24 h to either crocidolite or chrysotile fibers (1.25-10 microgram/cm(2)) increased the adhesion of RPLs to RPMCs in a dose-dependent fashion, an effect that was potentiated by interleukin-1beta. These findings were not observed with nonfibrogenic carbonyl iron particles. Crocidolite and chrysotile plus interleukin-1beta also upregulated vascular cell adhesion molecule-1 mRNA and protein expression in RPMCs, and the binding of RPL to asbestos-treated RPMCs was abrogated by anti-vascular cell adhesion molecule-1 antibody. PRLs exposed by intermittent inhalation to crocidolite for 2 wk manifested significantly greater binding to RPMCs than did RPLs from sham-exposed animals. The ability of asbestos fibers to upregulate RPL adhesion to RPMCs may play a role in the induction and/or potentiation of asbestos-induced pleural injury.

Apoptosis in acute pulmonary allograft rejection and cytomegalovirus infection

Apoptosis is a form of programmed cell death, characterized by activation of endonucleases that cleave DNA into oligonucleosomal fragments, which can be identified by in situ terminal deoxyribonucleotide transferase-mediated dUTP nick-end labeling (TUNEL). This process has recently been implicated in cardiac and hepatic allograft rejection, and we investigated its contribution to acute pulmonary allograft rejection and cytomegalovirus (CMV) pneumonitis by in situ TUNEL of transbronchial biopsy specimens. In situ TUNEL was performed on 70 transbronchial biopsy samples collected from 25 pulmonary allograft recipients for diagnosis of acute rejection or CMV pneumonitis, and the number of apoptotic nuclei/mm2 was correlated with the rejection grade (International Society of Heart and Lung Transplantation classification). During acute pulmonary allograft rejection, apoptotic nuclei were demonstrated in pulmonary parenchymal cells and mononuclear infiltrating cells, and the number of apoptotic cells was positively correlated with the rejection grade. In addition, a marked increase in the density of apoptotic cells was found in pulmonary allografts with CMV pneumonitis. We conclude that apoptosis contributes to cell death during acute pulmonary allograft rejection and CMV infection.

Influence of aminoguanidine on parameters of liver injury and regeneration induced in rats by a necrogenic dose of thioacetamide

1. When aminoguanidine, a nucleophilic hydrazine compound, was administered to rats (50 mg kg(-1) body wt) 30 min before a necrogenic dose of thioacetamide (500 mg kg(-1) body wt), significant changes related to liver injury and hepatocellular regeneration were observed. 2. The extent of necrosis was noticeably less pronounced, as detected by the peak of serum aspartate aminotransferase activity. Depletion of hepatic glutathione (GSH) and the increase in malondialdehyde concentration as markers of oxidative stress, produced by thioacetamide metabolism, were significantly diminished. However, the activity of microsomal FAD monooxygenase, the system responsible for thioacetamide oxidation, did not show significant alterations. Antioxidant enzyme systems involved in the glutathione redox cycle, such as glutathione reductase and glutathione peroxidase activities, slightly decreased following aminoguanidine pretreatment. 3. Primary cultures of peritoneal macrophages from control rats, when incubated in the presence of serum collected following thioacetamide intoxication, showed a significant decrease in nitric oxide (NO) release at 24 h, that was more pronounced in the group pretreated with aminoguanidine. However, the sharp and progressive increase in macrophage NO release, when incubated in the presence of serum obtained at 48, 72 and 96 h, were increased by aminoguanidine-pretreatment. 4. The cell population involved in DNA synthesis sharply increased in both groups at 48 h of intoxication, although the values at 0, 24, 72 and 96 h were markedly higher in the group pre-treated with aminoguanidine. Polyploidy at 72 and 96 h of intoxication was delayed by the effect of aminoguanidine and a progressive increase in the hypodiploid hepatocyte population, which reached 16% of the total at 96 h, was observed. 5. These results indicate that a single dose of aminoguanidine before thioacetamide administration, markedly diminished the severity of the liver injury by decreasing oxidative stress and lipoperoxidation, but hepatocellular regeneration was apparently unaffected probably due to an enhanced mitogenic activity.

Aminoguanidine reduces glomerular inducible nitric oxide synthase (iNOS) and transforming growth factor-beta 1 (TGF-beta1) mRNA expression and diminishes glomerulosclerosis in NZB/W F1 mice

Over-expression of iNOS is implicated in the pathogenesis of glomerulonephritis in animal models of systemic lupus erythematosus. The aim of this study was to evaluate the effect of aminoguanidine, a selective inhibitor of iNOS, for the protection from glomerulosclerosis in NZB/W F1 mice. Female NZB/W F1 mice (n = 8) were treated with aminoguanidine (1 g/l) in drinking water for 4 months starting at age 2 months before the onset of glomerulonephritis. Controls were age- and sex-matched mice (n = 10) without aminoguanidine treatment. By glomerular microdissection and reverse-transcription competitive polymerase chain reaction, we found that glomerular iNOS/beta-actin and TGF-beta1/beta-actin mRNA ratios were reduced 15.1% (P<0.05) and 61.3% (P<0.01), respectively, in aminoguanidine-treated mice. Aminoguanidine significantly reduced the glomerular iNOS staining, urinary nitrite production and degree of glomerulosclerosis. In addition, the glomerular volume and mean glomerular cell number were reduced 33.2% (P<0.01) and 32.8% (P<0.01), respectively. Likewise, the urinary proteinuria was also significantly reduced by aminoguanidine. These results indicate that administration of aminoguanidine may reduce the progression of glomerulosclerosis in NZB/W F1 mice, possibly through inhibition of glomerular nitric oxide production.