Increased nitric oxide levels in exhaled air of rat lung allografts

Methylene blue attenuates ischemia--reperfusion injury in lung transplantation

BACKGROUND

Ischemia-reperfusion injury (IRI) is one of the principal obstacles for the lung transplantation (LTx) success. Several strategies have been adopted to minimize the effects of IRI in lungs, including ex vivo conditioning of the grafts and the use of antioxidant drugs, such as methylene blue (MB). We hypothesized that MB could minimize the effects of IRI in a LTx rodent model.

METHODS

Forty rats were divided into four groups (n = 10) according to treatment (saline solution or MB) and graft cold ischemic time (3 or 6 h). All animals underwent unilateral LTx. Recipients received 2 mL of saline or MB intraperitoneally before transplantation. After 2 h of reperfusion, arterial blood and exhaled nitric oxide samples were collected and bronchoalveolar lavage performed. Then animals were euthanized, and histopathology analysis as well as cell counts and cytokine levels measurements in bronchoalveolar lavage fluid were performed.

RESULTS

There was a significant decrease in exhaled nitric oxide, neutrophils, interleukin-6, and tumor necrosis factor-α in MB-treated animals. PaO2 and uric acid levels were higher in MB group.

CONCLUSIONS

MB was able in attenuating IRI in this LTx model.

Measuring exhaled nitric oxide in animal models: methods and clinical implications

Animal models such as rats and mice are useful for studying the multiple roles of nitric oxide (NO) in various respiratory disorders. The production of NO is catalyzed by the three isoforms of the enzymes (NO synthases; NOS). Indirect assessment of NOS gene or protein expression only provides partial information on the role of NO in health and lung disease. NO can also be measured in exhaled air by invasive or non-invasive approaches as a direct and quantitative marker of NO production in animal models. Whilst addressing the different methods of exhaled NO analysis in small animals (rats and mice), this review also focuses on the possible clinical implications, and discusses the advantages and limitations of these methods.

Inducible nitric oxide production is an adaptation to cardiopulmonary bypass-induced inflammatory response

BACKGROUND

Cardiopulmonary bypass (CPB) increases nitric oxide (NO) production by the activation of NO synthases (NOS). However, the role of NO from inducible NOS (iNOS) in CPB-induced inflammatory response remains unclear. We examined the effect of a selective iNOS inhibitor, aminoguanidine, on CPB-induced inflammatory response in a rat-CPB model.

METHODS

Adult Sprague-Dawley rats underwent 60 minutes of CPB (100 mL x kg(-1) x min(-1), 34 degrees C). Group A (n = 10) received 100 mg/kg of aminoguanidine intraperitoneally 30 minutes before the initiation of CPB, and group B (n = 10) served as controls.

RESULTS

There were significant time-dependent changes in plasma interleukin (IL)-6, IL-8, nitrate + nitrite, the percentage ratio of nitrotyrosine to tyrosine (%NO2-Tyr, an indicator of peroxynitrite formation), and respiratory index (RI). Three hours after CPB termination, IL-6, IL-8, and RI were significantly higher in group A (IL-6, 397.5+/-80.6 pg/mL; IL-8, 26.99+/-6.57 ng/mL; RI, 1.87+/-0.31) than in group B (IL-6, 316.5+/-73.9 pg/mL, p <0.05; IL-8, 17.21+/-3.12 ng/mL, p < 0.01; RI, 1.57+/-0.24, p < 0.05) although nitrate + nitrite (31.8+/-4.1 micromol/L) and %NO2-Tyr (1.15%+/-0.20%) were significantly lower in group A than in group B (nitrate + nitrite, 50.2+/-5.0 micromol/L, p < 0.01; %NO2-Tyr, 1.46%+/-0.21%, p < 0.01). Western immunoblot analysis from lung tissue of group A identified marked iNOS inhibition without inhibiting endothelial-constitutive NOS, and neutrophil accumulation in the lung specimens was significantly greater in group A (6.5+/-0.7/alveoli) than in group B (4.4+/-0.4/alveoli, p < 0.01).

CONCLUSIONS

These results suggest that NO production from iNOS may be an adaptive response for attenuating the CPB-induced inflammatory response.

Endobronchial transfection of naked viral interleukin-10 gene in rat lung allotransplantation

BACKGROUND

Recent studies suggest that viral interleukin-10 (vIL-10) suppresses alloimmune response in transplantation. Tissue mRNA expression of inducible nitric oxide synthase (iNOS) and exhaled nitric oxide (NO) levels have been observed to increase in lung allograft rejection. The aims of this study were to examine the feasibility of vIL-10 gene transfer into rat lung allografts and to investigate its effect on subsequent allograft rejection.

METHODS

Male Lewis rats (RT1l) underwent left lung transplantation with allografts from Brown Norway rats (RT1n). The donor rats were endobronchially transfected 2 minutes before harvest with 400 microg (group I, n = 5), 600 microg (group II, n = 5), or 800 microg (group III, n = 5) of naked pCMVievIL-10. Group IV (n = 5) animals, serving as control, received 400 microg of naked pCF1-CAT. All recipients were sacrificed on postoperative day 5. Transgene expression of vIL-10 was assessed by both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Allograft gas exchange, exhaled NO level, histologic rejection score, and mRNA expression of graft cyokines were also assessed.

RESULTS

Transgene expression of lung graft vIL-10 was detected by both reverse transcriptase-polymerase chain reaction and immunohistochemistry. The iNOS mRNA expression in groups I, II, and III was significantly lower than that of group IV (p < 0.05, analysis of variance). Exhaled NO levels in groups I, II, and III were significantly lower than in group IV (p < 0.01, analysis of variance). There was no significant difference between groups with respect to gas exchange, peak airway pressure, or histologic rejection score.

CONCLUSIONS

It appears that endobronchial transfection of naked vIL-10 plasmid in a rat lung allotransplant model is feasible and suppresses lung iNOS mRNA expression and exhaled NO levels. An association between iNOS upregulation and high exhaled NO levels in lung allograft resection was also noted.

P-selectin participates in cardiopulmonary bypass-induced inflammatory response in association with nitric oxide and peroxynitrite production

OBJECTIVES

P-selectin participates in the development of inflammatory disorders. Cardiopulmonary bypass is thought to induce inflammatory response and increase nitric oxide production. To evaluate the role of P-selectin in bypass-induced inflammatory response and its association with nitric oxide production, we examined the effect of P-selectin monoclonal antibody in a rat model of cardiopulmonary bypass.

METHODS

Twenty adult Sprague-Dawley rats undergoing cardiopulmonary bypass for 60 minutes were divided into 2 groups. A 3-mg/kg dose of anti-rat specific P-selectin monoclonal antibody (ARP2-4; Sumitomo Pharmaceuticals, Osaka, Japan) was administered into the priming solution before bypass in group P (n = 10) and a 3-mg/kg dose of PNB1.6 (nonblocking monoclonal antibody) was added in group C for control (n = 10).

RESULTS

At the termination of bypass and 3 hours after the termination of bypass, plasma levels of interleukins 6 and 8, nitrate/nitrite, the percentage ratio of nitrotyrosine to tyrosine (an indicator of peroxynitrite formation), and the respiratory index were significantly higher than before bypass in both groups, and they were significantly lower in group P than in group C. Plasma P-selectin level in group C and exhaled nitric oxide concentration in both groups at termination of bypass were significantly lower than those before bypass, and they were significantly higher 3 hours after termination of bypass than before bypass in both groups. Plasma P-selectin level and exhaled nitric oxide concentration in group P were significantly higher than those in group C at the end of bypass, but they were significantly lower 3 hours after the termination of bypass.

CONCLUSIONS

These results demonstrate that P-selectin may participate in the augmentation of bypass-induced inflammatory response in association with nitric oxide and peroxynitrite production.

Exhaled nitric oxide correlates with experimental lung transplant rejection

BACKGROUND

Increased nitric oxide production accompanies acute lung allograft rejection. Transforming growth factor-beta1 is an immunosuppressive cytokine capable of ameliorating acute rejection. The purpose of this study was to determine whether exhaled nitric oxide (eNO) concentrations correlated with the degree of acute rejection.

METHODS

A model of acute lung transplant rejection in the rat was developed, and concentrations of eNO were measured at the time of animal sacrifice. In group 1 (partial immunosuppression), donor lungs were pretreated with transforming growth factor-beta1 before implantation. In group 2 (fulminant acute rejection), no immunosuppression was used. In group 3 (full immunosuppression), recipients received cyclosporine. Group 4 were normal rats.

RESULTS

When measured from both lungs, eNO concentrations were 4.97+/-0.68 versus 6.73+/-2.90 ppb for groups 1 and 2, respectively (p = 0.58). When measured selectively from transplanted left lungs, eNO concentrations were 8.61+/-0.97 versus 42.14+/-7.27 ppb, respectively (p<0.001). In groups 3 and 4, eNO concentrations were 1.02+/-0.21 and 1.51+/-0.74 ppb, respectively.

CONCLUSIONS

Exhaled nitric oxide is elevated in fulminant acute rejection, is reduced after partial immunosuppression using transforming growth factor-beta1 gene therapy, and is in the normal range in cyclosporine-treated animals. The measurement of eNO correlates with the degree of acute lung allograft rejection and may serve as a noninvasive measure of acute lung transplant rejection in the clinical setting.

Surveillance transbronchial lung biopsies: implication for survival after lung transplantation

OBJECTIVES

We wished to determine whether early rejection after lung transplantation as assessed by surveillance transbronchial biopsy predicts for survival.

METHODS

Between 1990 and 1997, 96 consecutive patients had lung transplantation: 89 had a minimum 1-month follow-up. For 71 consecutive patients we have 1-year follow-up and for 69 patients we have the results of the first 3 biopsies. Cytomegalovirus status, bronchiolitis obliterans prevalence, and use of total lymphoid irradiation are noted. Biopsies were done at 1 week and 1, 3, and 6 months. Standard immunosuppression consisted of induction antilymphocyte globulin and high-dose methylprednisolone induction for 1 week and standard maintenance triple therapy. Acute rejection treatment was with pulse methylprednisolone. Bronchiolitis obliterans syndrome was treated with total lymphoid irradiation and a change to tacrolimus and mycophenolate. Blinded grading using International Society for Heart and Lung Transplantation classification was done retrospectively.

RESULTS

Survival at 1 month and 1, 2, and 3 years for the 96-patient cohort with 1-year follow-up was 93%, 74%, 62%, and 56%. Survival was not significantly different for subsets with rejection on any combination of the first 3 biopsies (1/3, 2/3, 3/3) or absence of rejection on the first 3 biopsies. Ninety-one positive biopsy results were graded. Eighteen of 71 patients had one or more moderate or severe rejection episodes without survival difference relative to the others. There was no statistically significant association between acute rejection on the first 3 surveillance biopsy results and bronchiolitis obliterans.

CONCLUSIONS

Intensive induction and maintenance immunotherapy with surveillance transbronchial biopsies and aggressive treatment of acute rejection is associated with a survival similar to that of patients without early acute rejection. This regimen appears to uncouple the association between early acute rejection and bronchiolitis obliterans. Further study may elucidate this mechanism.

Nitric oxide production by bronchoalveolar cells during allograft rejection in the rat

BACKGROUND

We reported the increased nitric oxide (NO) level in exhaled air of rat lung transplant recipients during acute rejection (AR). The aim of this study was to determine the site and level of NO production in the rejected graft.

METHODS

Rat lung transplantation was performed in isografts and allografts.

RESULTS

In isografts, no AR and no significant increase in NO production was identified. In allografts, grades I-II of AR was seen on postoperative day (POD) 3 and grade III on POD 5. NO produced by BAL cells increased on both POD 3 (11.8+/-2.0 parts per billion [ppb]) and POD 5 (115.3+/-66.9 ppb). There was a highly significant correlation between the level of NO and the severity of AR (p=0.862, P<0.005). BAL cells from allografts expressed iNOS mRNA. Among them, macrophages, lymphocytes and neutrophils were immunostained for iNOS.

CONCLUSION

NO produced by BAL cells was detected in the early stages of rejection. Therefore, it may serve as a sensitive indicator of AR in lung transplantation.