Calpain与PARP- - NF-κB炎症通路的交互调制在局灶性脑缺血引起的神经血管单元损伤中的作用

Neurovascular unit (NVU) is a dynamic structure consisting of brain microvessels, and closely juxtaposed astrocytes and neurons, which is the basis for the maintenance of normal functions of brain. Inflammatory reaction is reported to play a key role in NVU damage during focal cerebral ischemia. Nuclear factor-κB (NF-κB), a pivotal transcription factor, stimulates transcriptional activation of deleterious pro-inflammatory genes, such as tumor necrosis factor-α (TNF-α), interleukin-1β, intracellular adhesion molecule-1(ICAM-1), reducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). Poly(ADP-ribose) polymerase (PARP) is a nuclear enzyme which catalyzes the formation of poly(ADP-ribose) through transferring ADP-ribose units from NAD+ to a variety of nuclear proteins under genotoxicity. PARP is reported to participate in the regulation of gene expression through affecting transcription factors, particularly, increasing evidences highlight the central role of PARP in the regulation of NF-κB-driven gene expression. Recently, PARP - NF-κB inflammatory pathway is reported to involve in the NVU damage due to cerebral ischemia. Calpains, a calcium-dependent neutral protease family, are activated by calcium and autolytic processing, and regulated reversibly by calcium and calpastatin, an endogenous calpain inhibitor. Under pathological conditions, some factors in PARP - NF-κB inflammatory pathway, including PARP, TNF-α, iNOS, and COX-2, are contributed to calpain activation through disrupting intracellular calcium homeostasis. On the other hand, calpain degrades some factors in PARP - NF-κB inflammatory pathway, such as PARP, IκB (an endogenous NF-κB inhibitory protein), iNOS, and COX-2. In previous study, we have reported that calpain may be involved in the activation of PARP - NF-κB inflammatory pathway triggered by focal cerebral ischemia. Moreover, iNOS is contributed to the activaiton of calpain during focal cerebral ischemia. Therefore, we raise a hypothesis that the cross-talk between calpain signal and PARP - NF-κB inflammatory pathway is contributed to the NVU damage induced by focal cerebral iswchemia. Since the brain lesion due to focal cerebral ischemia encompasses an irreversibly injured core and a peripheral zone (penumbra), this project first investigates the effects of calpain inhibitor on PARP - NF-κB inflammatory pathway and the NVU damage in penumbra and core, and then, explores the effects of the inhibitors of PARP, iNOS and COX-2, and the neutralizing antibodies to TNF-α on calpain/calpastatin system and the NVU damage in penumbra and core in a rat model of focal cerebral ischemia, by which, demonstrating our hypothesis. This work will elucidate a new mechanism of penumbral evolution and reversion, by which, providing a theoretical basis for the protection of NVU and the combination of neuroprotective agents against focal cerebral ischemia.

多聚(ADP-核糖)聚合酶(PARP)-核因子-κB(NF-κB)炎症通路参与局灶性脑缺血(FCI)引起的神经血管单元(NVU)损伤。在病理条件下，PARP-NF-κB通路的一些因子，如PARP、iNOS，参与蛋白酶Calpain的活化，而Calpain也能水解PARP、NF-κB的抑制性蛋白IκB等。我们前期研究提示,在FCI时,Calpain可能上调PARP-NF-κB通路，而iNOS也参与Calpain的激活。据此，我们推测Calpain与PARP-NF-κB通路之间可能存在交互调制作用，共同参与FCI引起的NVU损伤。本项目拟利用大鼠FCI模型，研究Calpain抑制剂对半暗带和核心区PARP-NF-κB通路和NVU损伤以及PARP-NF-κB通路阻断剂对半暗带和核心区Calpain和NVU损伤的影响，以证实这一假设，阐述半暗带衍变和逆转的新机制，为NVU保护提供理论依据。