| Summary: | === Experimental autoimmune encephalomyelitis (EAE) models multiple sclerosis (MS) and is characterized by marked mononuclear cell influx in the brain.
Inflammation leads to demyelinating lesions and disease. Several studies have demonstrated a role for chemokines during EAE. It remains to be determined whether these mediators modulate EAE primarily by mediating leukocyte influx into the CNS or by modifying lymphocyte activation and/or trafficking into lymphoid organs. After induction of EAE with MOG35-55, leukocyte recruitment peaked on day 14 and correlated with symptom onset, TNF-á production and production of CCL2
and CCL5. Levels of CXCL-10 and CCL3 were not different from control animals.
We demonstrated that leukocyte rolling and adhesion also peaked at day 14. The treatment with anti-CCL2 or anti-CCL5 antibodies just prior to the intravital microscopy prevented leukocyte adhesion, but not rolling. To confirm the role of CCL2 on leukocyte recruitment, we performed different treatments with the mutant protein P8A, described as an inhibitor of CCL2 activity. P8A was able to decrease leukocyte adhesion and ameliorated the clinical course of disease. Our data suggest that induction of leukocyte adhesion to the brain microvasculature is an important mechanism by which CCL2 and CCL5 participate in the pathogenesis of
EAE. Next, we investigated the role of kinins in driving EAE and chemokine production in the brain. The kinins are relevant mediators of inflammation and act through stimulation of two receptor subtypes, B1 and B2. For the present study B1- deficient (B1-/-), B2-deficient (B2- /-) and wild type (WT) mice were used. The incidence of disease was similar in the groups, but the disease in B2-/- mice was less severe. At day 14 after EAE induction, there was a significant decrease in the
number of adherent leukocytes when compared with WT mice. EAE induced an increase of B1 mRNA in brain tissue and this was partially prevented in B2-/- mice. Expression of CCL5 was suppressed in both B1
-/- and B2 -/- mice, but CCL2 expression was only inhibited in B2-/- mice. Altogether, our results suggest that B2 receptors have two major effects in the control of EAE severity: B2 regulates the expression of chemokines, including CCL2 and CCL5, the expression of B1 receptors, and B1-dependent leukocyte influx. Blockade of chemokine action (eg.
by using P8A) or production (eg. by using bradykinin antagonists) may represent a valid strategy to prevent leukocyte influx into the brain and disease severity in patients with MS. === A Encefalomielite Autoimune Experimental (EAE), modelo animal da Esclerose Multipla (EM), e caracterizada como uma doenca inflamatoria cronica, com um intenso influxo de celulas mononucleares para o sistema nervoso central (SNC).
Varios estudos tem demonstrado uma participacao das quimiocinas durante a EAE, mas ainda nao foi esclarecido como esses mediadores regulam o recrutamento de leucocitos para o SNC. Apos a inducao da EAE com MOG35-55, o recrutamento de leucocitos foi marcante no dia 14 apos a inducao, com um aumento dos eventos de rolamento e adesao, correlacionando com o pico de manifestacao clinica e inflamacao, assim como um aumento da producao de TNF¿, CCL2 e CCL5. Nenhuma diferenca foi observada quanto aos niveis de
CCL3 e CXCL10. O tratamento com anticorpos anti-CCL2 e anti-CCL5 2h antes da microscopia intravital foi capaz de promover uma diminuicao no processo de adesao, sem alterar o rolamento. Para confirmar o papel da quimiocina CCL2 no recrutamento de leucocitos, foram realizados diferentes tratamentos com a proteina mutante P8A, descrita como inibidora da atividade da CCL2. A proteina P8A foi capaz de diminuir a adesao de leucocitos e exibir um quadro clinico menos grave. Esses dados sugerem que a inducao da adesao de leucocitos na microvasculatura cerebral e um evento importante na patogenia da EAE e que as quimiocinas CCL2 e CCL5 podem modular este processo. Depois foi investigado o papel das cininas no recrutamento de leucocitos para o SNC no mesmo modelo.
As cininas sao mediadores relevantes da inflamacao e atuam atraves de dois receptores especificos acoplados a proteina G, B1 e B2. Para este estudo foram utilizados animais WT, B1-/- e B2-/-. A incidencia da doenca foi similar entre os grupos, mas os animais B2
-/- exibiram menor gravidade da doenca. No dia 14o apos a inducao, houve uma diminuicao do numero de leucocitos aderidos nos
animais knockout quando comparados com animais WT. Alem disso, animais com EAE demonstraram um aumento da expressao de receptores B1 no extrato de cerebro, parcialmente diminuidos nos animais B2 -/-. A producao de CCL5 foi diminuida nos animais B1
-/- e B2 -/-, mas CCL2 apenas foi diminuida nos animais
B2 -/-. Contudo, esses resultados sugerem que receptores B2 possuem um importante papel no controle da doenca, via regulacao da expressao de B1, modulacao da quimiocina CCL2 e, consequente, controle da adesao de leucocitos.
Logo, o bloqueio da atividade da quimiocina CCL2 pelo uso da P8A ou por antagonistas de BK pode representar uma importante estrategia para suprimir o influxo de leucocitos para o SNC e, consequentemente, controlar a gravidade da doenca.
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