| Ischemic stroke has been the top three disease burden of the world, and tumor has also been an important threat for human life. Previous reports have shown cancer patients are vulnerable to ischemic stroke, and could reach the incident peak within 3 months. These indicate that patients with tumor and stroke comorbidity are more common in clinical, and the main reasons may be the following: 1) cancer induced coagulation disorders, and side effects of radiotherapy, chemotherapy and surgical treatment; 2) with the progress of cancer therapy and the improvement of treatment strategies, especially advocating disease-free survival, cancer patients are prone to have a prolonged survival period. Therefore, the possibility of the cancer patients complicated by ischemic stroke has been dramatically increased. 3) Cancer occurs more frequently in people over 69 years of age, which is similar with ischemic stroke. This provide a fundament for cancer and ischemic stroke comorbidity.Previous clinical studies have focused on the causes and the risk of ischemic stroke in cancer patients. But how is the injury of ischemic stroke in cancer patients compared with the ischemic stroke patients, and its mechanisms remain unclear. Only a few retrospective clinical studies indicated that cancer patients undergone ischemic stroke were prone to be with high mortality and poor prognosis. The main aim of our study is to explore the exacerbated effect of tumor on ischemic stroke and its mechanism. Regulatory T cells (Treg)play a very importantly protective role in ischemic stroke, however, mediate the immune escape of the tumor. Therefore,we focus on the role of Treg cells in tumor-induced ischemic brain injury in order to provide mew treatment strategies for ischemic brain injury.The main methods of this subject are as follows: 1) Retrospective analysis of clinical data, ischemic stroke patients were divided into two groups: the patients with tumor complicated by ischemic stroke and the ischemic stroke patients. And the volume of cerebral infarction, NIHSS score, hospital death and other indicators were analyzed. 2) The animal model of tumor complicated with ischemic stroke was established by subcutaneous tumor combined with distal middle cerebral artery coagulation. The infarct volume and long-term movement and sensory function were examined. 3) Treg cells were detected in peripheral blood, brain tissue and tumor by using flow cytometry in wild-type C57 mice and T, B lymphocyte-deficient Ragl-/- mice (requiring immunological reconstitution), in order to prove the redistribution of Treg cells after ischemic stroke in tumor mice. 4) The endogenous Treg cells were ablated with CD25 neutralizing antibody, whether the exacerbated effects of tumor on ischemic stroke injury vanished or not was observed, which could prove that Treg cells redistribution mediate exacerbated effects of tumor on ischemic brain injury. 5) Treg cells (incubated with neuropilin 1 neutralizing antibody or control antibody) and CD4+CD25-T cell were transferred to Ragl-/- mice after establishment of tumor companied with ischemic stroke. Whether Nrp1 neutralizing antibodies can block Treg cell redistribution and reverse the exacerbated effects of tumor on ischemic stroke injury were observed. 6) Nrpl neutralizing antibody was intraperitoneally injected to tumor mice combined with ischemic stroke, to further verify the correctness of our theory. Finally, the brain tissue was subjected to mRNA sequencing.The main results of our study are as follows: 1) Infarct volume of cancer patients with ischemic stroke is significantly greater than that of patients only with ischemic stroke, and NIHSS score is also significantly higher than that of matched patients. The mortality and infection rate of cancer patients with ischemic stroke also significantly increased compared with those of matched patients. This suggests that ischemic brain damage in cancer patients is heavier than that in ischemic stroke patients. 2) The infarct volume of the brain slices and the sensory motor function within 21 days of the cancer patients with ischemic stroke were significantly increased (worse) than those of the ischemic stroke alone, and it further confirmed the exacerbated effects of tumor on ischemic stroke. 3) In the wild type C57 mice,Treg cells in peripheral blood were significantly down-regulated and the infused Treg in the brain tissue also significantly decreased, while the Treg cells raised in the tumor tissue significantly increased. Similar results were found in immune deficiency Ragl-/- mice(Immune function reconstituting with Treg cells and CD4+CD25-T cells transferred to peripheral blood). This part shows that the occurrence of ischemic stroke promotes Treg cells to migrate from peripheral blood to tumor in MC38 mice. The redistribution of Treg cells do exist. 4) After endogenous Treg cells ablation, the exacerbated effect of tumor on ischemic stroke vanished. It suggests that re-distribution of Treg cells in tumor mice occurred after ischemic brain damage plays a pivotal role in the exacerbated effect of tumor on ischemic stroke. 5) The immune function of Ragl-/- mice were reconstructed as described above,however, before transferred to peripheral blood, Treg cells were incubated by Nrpl blocking antibody. We observe that the aggravated effect of tumor on ischemic stroke is reversed by Nrpl receptor blockade, and the redistribution of Treg cells also disappears. It suggests that Nrp1 mediates the redistribution of Treg cells and plays a decisive role in tumor-led aggravated ischemic brain damage. 6) After intraperitoneal injection of Nrpl neutralizing antibody, the infarct volume of tumor mice with ischemic stroke is significantly reduced,and the number of misplaced errors in staggered experiment was also decreased, and also the redistribution of Treg cells was reversed (the proportion Treg cells raised in tumor tissue significantly decreased, while significantly increased in the peripheral blood). mRNA-sequencing shows that the inflammation-related genes in the tumor mice with ischemic stroke are significantly higher than that in ischemic stroke alone, while the Nrp1 antibody down-regulates the inflammation-related genes.In summary, the results of our study show that the damage of ischemic stroke in the mice preserved tumor is more severe than that of mice with ischemic brain injury alone. The main mechanism is that the occurrence of ischemic stroke in tumor mice promotes Treg cells to migration from the peripheral blood to the tumor tissue (redistribution),so that the proportion of Treg cell in peripheral blood and brain tissue significantly decreased, thereby it will weaken protective effects of the Treg cells on the stroke. At the same time, we also demonstrated that redistribution of Treg cells is mainly mediated by the Nrp1 receptor,thus blocking the Nrp1 receptor on Treg cells can block the redistribution of Treg cells and further exert therapeutic effects on ischemic stroke in tumor mice. |
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