Cyclic Nucleotide Regulation in Traumatic Brain Injury

描述(申请人提供)：先前的研究强调，脑和脊髓损伤后，第二信使环腺苷一磷酸(CAMP)的水平急剧下降，cAMP是神经元和炎症细胞中的关键细胞内信号分子。在过去的资助期间，我们的实验室发现，在创伤性脑损伤(TBI)后，cAMP的减少参与了创伤后大脑对继发性损伤的脆弱性，如血流动力学改变、炎症和长期突触功能障碍。磷酸二酯酶4(PDE4)是脑内负责cAMP水解的主要酶，目前是治疗包括神经创伤在内的各种人类神经系统疾病的重要分子靶点。我们在前一个资助期间完成的研究强调了不同PDE4亚型对创伤反应的复杂性，因为它们的不同时间依赖的细胞反应。这些细胞和生化变化的特征对于开发和测试针对特定PDE4亚型的新抑制剂至关重要。在目前的提案中，我们将解决阻碍PDE4抑制剂治疗脑外伤临床开发的几个知识空白，包括鉴定特定炎症细胞群中的PDE4异构体，以及评估异构体选择性PDE4抑制剂对创伤后炎症的影响。另一项将被研究的令人兴奋的最新发现是PDE4B亚型特异性抑制剂显著减少慢性认知障碍的能力，从而为脑外伤患者提供了一种新的治疗策略。因此，基于我们以前和新的初步数据，我们提出了以下四个目标：1)研究PDE4B在脑损伤后急性炎症中的作用，2)确定脑损伤后急性抑制PDE4B是否改善了病理和行为结果，3)测试PDE4B亚型选择性抑制剂是否改善了慢性认知障碍，最后，4)直接确定PDE4B的丢失是否改善了脑损伤后的预后，以及PDE4D的丢失是否恶化了脑损伤后的预后。这些研究将确定在TBI后的不同治疗时间窗需要选择性地抑制哪些特定的PDE4亚型，以减少炎症和病理，并在急性、亚急性和慢性三个治疗时间窗促进恢复。总之，这些研究将提供有关异构体选择性PDE4抑制剂产生益处的确切细胞事件的关键信息，并提供循证机制数据支持PDE4抑制剂在脑外伤后的急性、亚急性和慢性治疗时间窗中的使用。这一建议得到了一个多学科、多机构的研究团队的支持，该团队在实验性脑损伤模型、PDE4B和PDE4D基因敲除小鼠方面具有经验，并得到了在中枢神经系统药物发现方面有既定记录的药理学合作伙伴的支持。这些研究将为这些治疗脑损伤的新药的临床转化提供必要的临床前数据。

DESCRIPTION (provided by applicant): Previous studies have emphasized that after brain and spinal cord injury there are dramatic reductions in levels of the second messenger cyclic adenosine monophosphate (cAMP), a critical intracellular signaling molecule in neurons and inflammatory cells. Over the last funding period, our laboratory has found that after traumatic brain injury (TBI) cAMP reductions participate in the vulnerability of the posttraumatic brain to secondary injuries such as hemodynamic alterations, inflammation, and long-term synaptic dysfunction. Phosphodiesterase 4 (PDE4) is the major enzyme responsible for cAMP hydrolysis in the brain and currently is an important molecular target for the treatment of various human neurological diseases including neurotrauma. Studies we have completed during the previous funding period have emphasized the complexity of the response to trauma of different PDE4 isoforms in terms of their various time-dependent cellular responses. The characterization of these cellular and biochemical changes are critical for the development and testing of new inhibitors against specific PDE4 isoforms. In the current proposal, we will address several knowledge gaps that hamper clinical development of PDE4 inhibitors for the treatment of TBI, including the identification of PDE4 isoforms in specific inflammatory cell populations as well as assessing the effects on isoform-selective PDE4 inhibitors on posttraumatic inflammation. Another exciting recent discovery that will be investigated is the ability of PDE4B isoform-specific inhibitors to significantly reduce chronic cognitive deficits, thereby providing a novel therapeutic strategy for people living with TBI. Based on our previous and new preliminary data, we therefore propose the following four aims: 1) To investigate the contribution of PDE4B to acute inflammation after TBI, 2) To determine if inhibition of PDE4B acutely after TBI improves pathology and behavioral outcome, 3) To test whether a PDE4B isoform-selective inhibitor improves chronic cognitive deficits, and finally, 4) To directly determine if loss of PDE4B improves outcome and loss of PDE4D worsens outcome after TBI. These studies will determine which specific PDE4 isoforms need to be selectively inhibited at different therapeutic time windows after TBI to reduce inflammation and pathology, and promote recovery in three therapeutic time windows, acute, subacute and chronic. Together, these studies will provide critical information regarding the precise cellular events by which isoform-selective PDE4 inhibitors produce their benefits, and provide evidence-based mechanistic data to support the use of PDE4 inhibitors in acute, subacute, and chronic therapeutic time windows after TBI. This proposal is supported by a multidisciplinary, multi-institutional research team with experience in experimental TBI models, PDE4B and PDE4D knockout mice, and a pharmacological partner with an established record in CNS drug discovery. These studies will provide the necessary preclinical data for the clinical translation of these novel agents for the treatment of TBI.