Substance P tachykininergic NK1 receptor emetic signal transduction pathways

急性（第1天）和延迟性（第3-7天）恶心和呕吐是顺铂等癌症治疗药物令人恐惧和虚弱的副作用。在没有预防性治疗的情况下，几乎所有患者都因服用类似顺铂的药物而呕吐。必须控制这些副作用，以维持患者的依从性和生活质量。然而，在美国，含有5-羟色胺5-HT3受体（5-HT3R）拮抗剂和P物质（SP）神经激肽NK1受体（NK1R）拮抗剂的最佳止吐方案（Akynzeo）的成本超过500美元/片，只能保护高达80%的患者。顺铂类药物释放5-羟色胺（5-HT）和SP，刺激肠道和脑干呕吐位点中相应的细胞膜结合细胞外呕吐受体，引起呕吐。对于这一应用至关重要的是，在呕吐领域存在着主要的空白，因为缺乏对以下方面的理解：(1)在所讨论的呕吐受体刺激后的呕吐细胞内信号机制的激活；ii)在不同的吐吐信号级联中是否存在信号收敛的潜在点（如Ca2+）。随着新的癌症治疗方法的发展，我们必须确定共同的基本细胞内信号分子，这些分子是诱导呕吐和抑制癌症的基础，这样我们才能开发出更安全的没有呕吐的癌症治疗方法，这将节省时间、精力和研究资金。尽管NK1R下游的呕吐信号级联尚不清楚，但我们最近已经确定了细胞内5-HT3R呕吐级联[17,18]。与窄谱5-HT3R阻滞剂不同，NK1R拮抗剂对多种呕吐原因表现出广谱止吐功效。因此，对NK1R催吐信号的充分理解可能使我们能够识别出独特的细胞内信号，其拮抗剂/抑制剂可以抑制癌症的形成而不会呕吐。事实上，通过NK1Rs的SP在中枢神经系统肿瘤的发展中起着核心作用，其相应的拮抗剂具有癌症化疗潜力[15,16]。此外，我们的初步数据强烈表明，磷脂酶C （PLC）级联及其与Akt/GSK-3aβ通路的相互作用是nk1r诱发呕吐的主要参与者。本申请的目的是采用广泛的方法，包括药理学，行为学，钙成像，免疫组织化学和Western blot技术，描绘nk1r介导的呕吐信号转导，包括磷脂酶C的激活和相应的下游信号，包括细胞外Ca2+内流和细胞内Ca2+释放在呕吐中的作用，以及诱发的呕吐是否可以通过Akt/GSK-3αβ途径调节。不仅关于细胞内呕吐机制的信息很少，而且迫切需要替代广谱止吐药来保护所有因细胞毒性化疗引起的呕吐的癌症患者。这项建议的发现不仅将介绍几种新的高效止吐药，而且还可能有助于揭示通用止吐药的潜力，这将降低预防癌症，艾滋病毒或胃肠道疾病患者群体恶心和呕吐的成本。

Acute (day 1) and delayed (days 3-7) nausea and vomiting are the feared and debilitating side-effects of cancer therapeutics such as cisplatin. In the absence of prophylactic therapy, nearly all patients vomit from cisplatin-like drugs. These side-effects must be controlled to maintain patient compliance and quality of life. However, the cost of the best antiemetic regimen (Akynzeo) containing a serotonin 5-HT3 receptor (5-HT3R) antagonist and a substance P (SP) neurokinin NK1 receptor (NK1R)-antagonist is over $500 per pill in the USA and can only protect up to 80% of patients. Cisplatin-like drugs release serotonin (5-HT) and SP which stimulate their corresponding cell membrane-bound extracellular emetic receptors in both the gut and brainstem emetic loci to evoke vomiting. Of critical importance to this application, major gaps exist in the emesis field in that there is a lack of understanding of i) activation of emetic intracellular signaling mechanisms following stimulation of discussed emetic receptors; and ii) whether potential point(s) of signal convergence (e.g. Ca2+) exist among diverse emetic signaling cascades. As new cancer therapeutics are being developed, it becomes vital that we define shared fundamental intracellular signaling molecules that underlie induction of emesis versus cancer suppression, so that we can develop safer cancer therapeutics without emesis, which will save time, effort and research dollars. Although the emetic signaling cascade(s) downstream of NK1R remain unknown, we recently have identified the intracellular 5-HT3R emetic cascade [17,18]. Unlike the narrow-spectrum 5-HT3R blockers, NK1R antagonists exhibit broad-spectrum antiemetic efficacy against diverse causes of vomiting. Thus, a full understanding of NK1R emetic signals may allow us to identify unique intracellular signal(s) whose antagonists/inhibitors would suppress cancer formation without vomiting. Indeed, SP via NK1Rs plays a central role in the development of CNS tumors and its corresponding antagonists possess cancer chemotherapeutic potential [15,16]. Furthermore, our preliminary data strongly suggest that the phospholipase C (PLC) cascade and its interaction with the Akt/GSK-3aβ pathway are major players in NK1R-evoked vomiting. The purpose of this application is to take a broad approach involving pharmacological, behavioral, calcium imaging, immunohistochemical and Western blot techniques, to delineate the NK1R-mediated emetic signal transduction involving activation of phospholipase C and corresponding downstream signals including the role of extracellular Ca2+ influx and intracellular Ca2+ release in vomiting, as well as whether the evoked emesis can be modulated by the Akt/GSK-3αβ pathway. Not only there is scant information regarding intracellular mechanisms of emesis, but also there is an urgent and unmet need for alternative broad-spectrum antiemetics for protection of all cancer patients suffering from vomiting caused by cytotoxic chemotherapeutics. The findings of this proposal will introduce not only several new highly potent classes of antiemetics, but may also help reveal the potential of universal antiemetics, which will lower the cost of prevention of nausea and vomiting in diverse patient communities suffering from cancer, HIV or gastrointestinal disorders.