Pentoxifylline is as effective as leukocyte depletion for modulating pulmonary reperfusion injury

Pathogenesis of indirect (secondary) acute lung injury

At present, therapeutic interventions to treat acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) remain largely limited to lung-protective strategies, as no real molecular-pathophysiologic-driven therapeutic intervention has yet become available. This is in part the result of the heterogeneous nature of the etiological processes that contribute to the state of ALI/ARDS. This article sets out to understand the development of ALI resulting from indirect pulmonary insults, such as extrapulmonary sepsis and trauma, shock, burn injury or mass transfusion, as opposed to direct pulmonary challenges, such as pneumonia, aspiration or lung contusion. Here, we consider not only the experimental and clinical data concerning the roles of various immune (neutrophil, macrophage, lymphocyte and dendritic) as well as nonimmune (epithelial and endothelial) cells in orchestrating the development of ALI resulting from indirect pulmonary stimuli, but also how these cell populations might be targeted therapeutically.

Epithelial cell apoptosis and neutrophil recruitment in acute lung injury-a unifying hypothesis? What we have learned from small interfering RNAs

In spite of protective ventilatory strategies, Acute Lung Injury (ALI) remains associated with high morbidity and mortality. One reason for the lack of therapeutic options might be that ALI is a co-morbid event associated with a diverse family of diseases and, thus, may be the result of distinct pathological processes. Among them, activated neutrophil- (PMN-) induced tissue injury and epithelial cell apoptosis mediated lung damage represent two potentially important candidate pathomechanisms that have been put forward. Several approaches have been undertaken to test these hypotheses, with substantial success in the treatment of experimental forms of ALI. With this in mind, we will summarize these two current hypotheses of ALI briefly, emphasizing the role of apoptosis in regulating PMN and/or lung epithelial cell responses. In addition, the contribution that Fas-mediated inflammation may play as a potential biological link between lung cell apoptosis and PMN recruitment will be considered, as well as the in vivo application of small interfering RNA (siRNA) as a novel approach to the inhibition of ALI and its therapeutic implications.

Isquemia e reperfusão de músculo sóleo de ratos sob ação da pentoxifilina

CONTEXTO: A reperfusão de músculo esquelético piora as lesões já presentes no período de isquemia, pois a produção de espécies reativas de oxigênio, associadas à intensa participação de neutrófilos, amplia a reação inflamatória que induz alterações teciduais. OBJETIVO: Avaliar as alterações morfológicas e imuno-histoquímicas de músculo esquelético (sóleo) de ratos submetidos a isquemia e reperfusão com pentoxifilina. MÉTODOS: Sessenta ratos foram submetidos a isquemia do membro pélvico, por 6 horas, pelo clampeamento da artéria ilíaca comum esquerda. Após isquemia, os animais do grupo A (n = 30) foram observados por 4 horas, e os do grupo B (n = 30), por 24 horas. Seis animais constituíram o grupo simulado. Administrou-se pentoxifilina apenas no período de reperfusão em A2 (n = 10) e B2 (n = 10) e nos períodos de isquemia e reperfusão em A3 (n = 10) e B3 (n = 10). O músculo sóleo foi avaliado por análise histológica (dissociação de fibras, infiltrado leucocitário, necrose) e imuno-histoquímica (apoptose pela expressão da caspase-3). Foram aplicados os testes não-paramétricos de Kruskal-Wallis e Mann-Whitney (p < 0,05). RESULTADOS: As alterações foram mais intensas no grupo B1, com médias de escore da dissociação de fibras musculares de 2,16 ± 0,14, infiltrado neutrofílico de 2,05 ± 0,10 e expressão da caspase-3 na área perivascular de 4,30 ± 0,79; e menos intensas no grupo A3, com respectivas médias de 0,76 ± 0,16, 0,92 ± 0,10 e 0,67 ± 0,15 (p < 0,05). A caspase-3 mostrou-se mais expressiva no grupo B1 na área perivascular, com média de 4,30 ± 0,79, em comparação com o grupo B1 na área perinuclear, com média de 0,91 ± 0,32 (p < 0,05). CONCLUSÕES: As lesões são mais intensas quando o tempo de observação é maior após a reperfusão, e a pentoxifilina atenua essas lesões, sobretudo quando usada no início das fases de isquemia e de reperfusão.

In vivo observation of leukocyte-endothelium interaction in ischemia reperfusion injury with the dorsal window chamber and the effects of pentoxifylline on reperfusion injury

OBJECTIVE

Ischemia reperfusion injury can cause failure in microsurgical operations. Interaction between leukocytes and endothelium is recognized as an integral step in ischemia reperfusion injury. Pentoxifylline is a methylxanthine derivative that has pharmacological properties that can be beneficial in ischemia reperfusion injury. The aim of this study was to investigate the in vivo effect of pentoxifylline on leukocyte-endothelium interaction in ischemia reperfusion injury.

METHODS

Intravital fluorescent microscopy was used to observe leukocyte-endothelium interaction in a "dorsal window chamber" model. Twenty-eight postcapillary veins were analyzed in group 1, and twenty-two in group 2. Group 1 received 25 mg/kg pentoxifylline 20 min before reperfusion. Group 2 received an equivalent volume of 0.9% saline at the same time. The period of ischemia was 4 h.

RESULTS

Quantification of leukocyte 'sticking' and 'rolling' was done before ischemia and at 30, 60, and 120 min after reperfusion. Offline video analysis was used for evaluating the results. Statistical evaluation showed that pentoxifylline significantly attenuated leukocyte 'sticking' and 'rolling' in postcapillary venules. It was also effective in preventing 'no-reflow' when compared with the control group.

CONCLUSION

These results indicate pentoxifylline diminishes leukocyte-endothelium interaction, and may have a therapeutic role in preventing ischemia reperfusion injury in microsurgical operations.