Estudo dos processos de mobilização, ativação e apoptose das células da medula óssea em modelo de morte encefálica em ratos / Study of bone marrow cells mobilization, activation and apoptosis in brain dead rats

Estudos experimentais suportam a evidência de leucopenia persistente desencadeada pela morte encefálica (ME). OBJETIVO: Esse estudo teve como objetivo investigar o comportamento leucocitário na medula óssea e no sangue após a morte encefálica em ratos. MÉTODOS: A morte encefálica foi induzida através da inserção e insuflação rápida de um cateter no espaço intracraniano. Ratos falso-operados (FO) foram apenas trepanados. Decorridas seis horas, as células da medula óssea, coletadas da cavidade femural, foram utilizadas para as contagens total e diferencial e analisadas por citometria de fluxo para a caracterização das subpopulações linfocitárias, a expressão de moléculas de adesão granulocíticas e apoptose/necrose (método de Anexina V/Iodeto de Propídio (PI)). RESULTADOS: Ratos com ME apresentaram uma redução de 30% no número de células da medula óssea devido à redução de linfócitos (40%) e células segmentadas (45%). As subpopulações de linfócitos na medula óssea foram semelhantes nos animais ME e FO (CD3, p=0,1; CD4, p=0,4; CD3/CD4, p=0,4; CD5, p=0,4, CD3/CD5, p=0,2; CD8, p=0,8). A expressão de L-selectina e beta2-Integrinas nos granulócitos também não diferiram entre os grupos (CD11a, p=0,9; CD11b/c, p=0,7; CD62L, p=0,1). Não existem diferenças nas porcentagens de apoptose e de necrose (Anexina V, p=0,73; PI, p=0,21; Anexina V/PI, p=0,29). CONCLUSÃO: Os dados sugerem que a redução na mobilização de células da medula óssea para o sangue, desencadeada pela morte encefálica, não se relaciona a alterações de subpopulações de linfócitos, expressão de moléculas de adesão granulocíticas, ou apoptose e necrose...

Experimental findings support the evidence of a persistent leucopenia triggered by brain death (BD). AIMS: This study aimed to investigate leukocyte behavior in bone marrow and blood after BD in rats. METHODS: BD was induced by quickly inflation of an intracranial balloon catheter. Sham operated (SH) rats were trepanned only. Six hours thereafter bone marrow cells harvested from the femoral cavity were used for total and differential counts, and analyzed by flow cytometry to characterize lymphocyte subsets, granulocyte adhesion molecules expression, and apoptosis/necrosis (annexin V/propidium iodide (PI) protocol). RESULTS: BD rats exhibited a 30% reduction in bone marrow cells due to a reduction in lymphocytes (40%) and segmented cells (45%). Bone marrow lymphocyte subsets were similar in BD and SH rats (CD3, p=0.1; CD4, p=0.4; CD3/CD4, p=0.4; CD5, p=0.4, CD3/CD5, p=0.2; CD8, p=0.8). Expression of L-selectin and ?2-integrins on granulocytes did not differ (CD11a, p=0.9; CD11b/c, p=0.7; CD62L, p=0.1). There were no differences in the percentage of apoptosis and necrosis (Annexin V, p=0.73; PI, p=0.21; Annexin V/PI, p=0.29). CONCLUSIONS: Data presented suggest that the down-regulation of the bone marrow triggered by BD is not related to changes in lymphocyte subsets, granulocyte adhesion molecules expression, or apoptosis and necrosis...

Mesenteric hypoperfusion and inflammation induced by brain death are not affected by inhibition of the autonomic storm in rats

OBJECTIVES: Brain death is typically followed by autonomic changes that lead to hemodynamic instability, which is likely associated with microcirculatory dysfunction and inflammation. We evaluated the role of the microcirculation in the hemodynamic and inflammatory events that occur after brain death and the effects of autonomic storm inhibition via thoracic epidural blockade on mesenteric microcirculatory changes and inflammatory responses. METHODS: Male Wistar rats were anesthetized and mechanically ventilated. Brain death was induced via intracranial balloon inflation. Bupivacaine (brain death-thoracic epidural blockade group) or saline (brain death group) infusion via an epidural catheter was initiated immediately before brain death induction. Sham-operated animals were used as controls (SH group). The mesenteric microcirculation was analyzed via intravital microscopy, and the expression of adhesion molecules was evaluated via immunohistochemistry 180 min after brain death induction. RESULTS: A significant difference in mean arterial pressure behavior was observed between the brain death-thoracic epidural blockade group and the other groups, indicating that the former group experienced autonomic storm inhibition. However, the proportion of perfused small vessels in the brain death-thoracic epidural blockade group was similar to or lower than that in the brain death and SH groups, respectively. The expression of intercellular adhesion molecule 1 was similar between the brain death-thoracic epidural blockade and brain death groups but was significantly lower in the SH group than in the other two groups. The number of migrating leukocytes in the perivascular tissue followed the same trend for all groups. CONCLUSIONS: Although thoracic epidural blockade effectively inhibited the autonomic storm, it did not affect mesenteric hypoperfusion or inflammation induced by brain death. .

Paradoxical effects of brain death and associated trauma on rat mesenteric microcirculation: an intravital microscopic study

OBJECTIVE: Experimental findings support clinical evidence that brain death impairs the viability of organs for transplantation, triggering hemodynamic, hormonal, and inflammatory responses. However, several of these events could be consequences of brain death-associated trauma. This study investigated microcirculatory alterations and systemic inflammatory markers in brain-dead rats and the influence of the associated trauma. METHOD: Brain death was induced using intracranial balloon inflation; sham-operated rats were trepanned only. After 30 or 180 min, the mesenteric microcirculation was observed using intravital microscopy. The expression of Pselectin and ICAM-1 on the endothelium was evaluated using immunohistochemistry. The serum cytokine, chemokine, and corticosterone levels were quantified using enzyme-linked immunosorbent assays. White blood cell counts were also determined. RESULTS: Brain death resulted in a decrease in the mesenteric perfusion to 30 percent, a 2.6-fold increase in the expression of ICAM-1 and leukocyte migration at the mesentery, a 70 percent reduction in the serum corticosterone level and pronounced leukopenia. Similar increases in the cytokine and chemokine levels were seen in the both the experimental and control animals. CONCLUSION: The data presented in this study suggest that brain death itself induces hypoperfusion in the mesenteric microcirculation that is associated with a pronounced reduction in the endogenous corticosterone level, thereby leading to increased local inflammation and organ dysfunction. These events are paradoxically associated with induced leukopenia after brain damage.