Targeting nociceptors to modulate neutrophil mobilization and homing in sepsis

脓毒症是ICU中危及生命的并发症，死亡率高。脓毒症的定义是对病原体的过度免疫激活和微血管功能障碍，导致受损的器官功能障碍和衰竭。目前，临床医生在ICU护理脓毒症患者时，无论是过度的免疫反应还是血管功能障碍都无法治疗。在第一个资助期内，我们确定了降钙素原（一种与脓毒症不良结局相关的脓毒症生物标志物）通过与内皮上的降钙素受体样受体（CRLR）/受体活性修饰蛋白1（RAMP 1）结合来影响血管完整性。拮抗降钙素原的激活或其对CRLR/RAMP 1的作用可预防脓毒症诱导的血管屏障功能障碍，并改善术后全身炎症患者的毛细血管渗漏。CRLR/RAMP 1复合物也存在于免疫细胞上，最近已被证明在细菌感染期间参与骨髓中伤害感受器的信号传导。我们的初步数据表明，CRLR/RAMP 1主要表达在未成熟的中性粒细胞上，这些中性粒细胞与脓毒症患者有限的抗微生物活性、组织损伤特性和不良结局相关。此外，在伤害感受器瞬时受体电位香草酸1（TRPV 1）缺陷的脓毒症小鼠表现出减少扩张的中性粒细胞计数在脓毒症和有限的脓毒症诱导的组织损伤。在第二个资助期内，申请人现在将合作研究脓毒症诱导的骨髓传入神经上表达的TRPV 1激活如何通过触发CRLR/RAMP 1激动剂降钙素基因相关肽（CGRP）在骨髓小生境中的释放来调节CRLR/RAMP 1对免疫细胞的活性。在鼠和猪多微生物败血症模型中，我们将剖析TRPV 1信号轴如何调节中性粒细胞表型，进入循环并归巢至靶组织，以及拮抗CRLR/RAMP 1是否是败血症期间将循环中性粒细胞表型向组织保护表型转变的一种手段。我们还将描述脓毒症期间内源性高降钙素原血症如何影响脓毒症患者的TRPV 1-CRLR/RAMP 1信号传导，并评估降钙素原水平升高是否可以识别特别表现出中性粒细胞不成熟和功能受损的患者，这些患者与更差的临床结局相关。与我们在临床研究单位342的合作伙伴一起，我们的目标是将TRPV 1-CRLR/RAMP 1轴确定为靶点，以定制脓毒症诱导的免疫反应并保护血管系统，从而改善脓毒症患者的器官功能和结局。

Sepsis is a life-threatening complication on the ICU with high mortality rates. Sepsis is defined by an overshooting immune activation and microvascular dysfunction in response to pathogens leading to compromised organ dysfunction and failure. Neither the overshooting immune response nor the dysfunction of the vasculature can currently be therapeutically addressed by clinicians when caring for septic patients on the ICU. In the first funding period, we identified that procalcitonin, a sepsis biomarker associated with adverse sepsis outcome, affects vascular integrity by binding to its receptor on the endothelium, the calcitonin receptor-like receptor (CRLR)/receptor activity modifying protein 1 (RAMP1). Antagonizing procalcitonin’s activation or its action on the CRLR/RAMP1 prevented sepsis-induced vascular barrier dysfunction and ameliorated capillary leakage in patients with post-operative systemic inflammation. The CRLR/RAMP1 complex is also present on immune cells and has recently been shown to be involved in signaling of nociceptors in the bone marrow during bacterial infection. Our preliminary data suggests that CRLR/RAMP1 is primarily expressed on immature neutrophils that have been associated with limited anti-microbial activity, tissue-damaging properties and adverse outcome in septic patients. In addition, septic mice deficient in the nociceptor transient receptor potential vanilloid 1 (TRPV1) exhibited reduced expansion of neutrophil counts during sepsis and limited sepsis-induced tissue injury. In the second funding period, the applicants will now team up to dissect how sepsis-induced activation of TRPV1 expressed on afferent nerves in the bone marrow modulates CRLR/RAMP1 activity on immune cells by triggering the release of the CRLR/RAMP1 agonist calcitonin gene-related peptide (CGRP) in the bone marrow niche. In murine and porcine models of polymicrobial sepsis we will dissect how this TRPV1 signaling axis modulates neutrophil phenotype, egress into the circulation and their homing to target tissues and whether antagonizing CRLR/RAMP1 is a means to shift circulating neutrophil phenotypes towards a tissue-protective phenotype during sepsis. We will also characterize how endogenous hyperprocalcitonemia during sepsis affects TRPV1-CRLR/RAMP1 signaling in septic patients and evaluate whether elevated levels of procalcitonin can identify patients particularly exhibiting neutrophil immaturity and impaired function associated with worse clinical outcome. Together with our collaboration partners in the clinical research unit 342 our goal with this proposal is to identify the TRPV1-CRLR/RAMP1 axis as a target to tailor sepsis-induced immune responses and protect the vasculature translating into improved organ function and outcome of patients with sepsis.