ImmunoStroke: From Immune cells to stroke recovery.Plasma-kallikrein mediated modulation of T cells and microglia responses during long-term stroke recovery.

血浆激肽释放酶（PK）是激肽释放酶-激肽系统（KKS）的关键组分，由于其促炎和促血栓形成的双重作用，代表了用于中风治疗的最有前途的新治疗靶点之一。事实上，我们已经证明，急性缺血性中风触发PK激活，而药物抑制和PK基因删除显着减少脑内血栓形成和血脑屏障损伤。引人注目的是，我们的初步数据表明，直接阻断PK还可以改善功能的长期恢复，同时减少中风后脑浸润T细胞。然而，仍然难以理解PK（一种在血浆中起作用的可溶性分子）如何干扰免疫环境。因此，我们将使用最先进的转录组学、免疫组学和蛋白质组学分析，对PK抑制后T细胞和小胶质细胞的功能状态进行深入的免疫表型分析。然而，从临床角度来看，卒中中PK抑制的概念仍处于临床转化的最早阶段，因为目前还没有人定制的PK抑制剂。因此，与PK机制相关的新靶点可能导致已经验证的治疗选择或甚至上市，即，药物再利用具体而言，最近在遗传学和生物信息学方面的突破与系统医学相结合，彻底改变了医学的概念，也为确定新的治疗靶点提供了新的策略。因此，通过实施新的系统医学方法，我们的目标是确定与PK和KKS机制相关的从头治疗靶点，这可以最大限度地减少成功临床实施所需的时间。最后，我们的目标是阐明缺血条件下PK-T细胞和PK-小胶质细胞之间的分子相互作用，这仍然没有完全理解。事实上，PK直接激活蛋白酶激活受体（PAR），广泛表达于各种细胞类型，包括T细胞和小胶质细胞。重要的是，我们的初步数据表明中风小鼠脑浸润T细胞中PAR的表达上调。确切地说，来自缺血脑的T细胞直接上调PAR 1 -4表达，而抗PK治疗似乎特异性下调T细胞中的PAR表达。因此，我们打算分析PAR，T细胞和小胶质细胞之间的功能性相互作用后，从抗PK治疗中风小鼠或纯化的PK血清治疗，以进一步关联这些结果与我们的转录组学和蛋白质组学数据。因此，我们在这里的目的是最终阐明参与长期中风恢复的PK-T细胞和PK-小胶质细胞相互作用的最相关的潜在机制，同时确定新的潜在机制相关的PK靶点，以促进快速的临床转化。

Plasma kallikrein (PK), a key component of the kallikrein-kinin system (KKS), represents one of the most promising novel therapeutic targets for stroke therapy due to its proinflammatory and prothrombotic dual role. Indeed, we have demonstrated that acute ischemic stroke triggers PK activation, while both pharmacological inhibition and genetic deletion of PK significantly reduce intracerebral thrombus formation and blood-brain barrier damage. Strikingly, our preliminary data indicate that direct blocking of PK also improves functional long-term recovery together with a reduction in brain-infiltrating T cells upon stroke. However, it still remains elusive how PK, a soluble molecule acting in the blood plasma, interferes with the immune environment. Thus, we will deeply immunophenotype the functional state of T cells and microglia after PK inhibition using cutting-edge transcriptomics, immunomics, and proteomics analysis. However, from the clinical perspective, the concept of PK inhibition in stroke is still at the earliest stage of clinical translation since human-tailored PK inhibitors are currently not available. Therefore, novel targets mechanistically related to PK could lead to already validated therapeutic options or even marketed, i.e., drug repurposing. Specifically, recent breakthroughs in genetics and bioinformatics united in systems medicine have revolutionized the concept of medicine also providing new strategies to identify novel therapeutic targets. Therefore, through implementing a novel systems medicine approach, we aim to identify de novo therapeutic targets mechanistically related to PK and the KKS, which could maximally reduce the time required for successful clinical implementation. Finally, we aim to elucidate the molecular interactions between PK-T cells and PK-microglia under ischemic conditions, which are still not completely understood. In fact, PK directly activates the protease-activated receptors (PARs), broadly expressed by various cell types including T cells and microglia. Importantly, our preliminary data indicate an upregulated expression of PARs in brain-infiltrating T cells from stroked mice. Precisely, T cells from ischemic brains directly upregulate PAR1-4 expression, whereas anti-PK treatment seems to downregulate PAR expression specifically in T cells. Thus, we intend to analyse the functional interaction between PAR, T cells, and microglia upon treatment with serum from anti-PK treated stroked mice or purified PK to further correlate these results with our transcriptomics and proteomics data. Hence, we here aim to ultimately elucidate the most relevant underlying mechanisms of PK-T cell and PK-microglia interaction involved in long-term stroke recovery while identifying new potential mechanistic-related PK targets to promote rapid clinical translation.