The role of gram-positive bacteria in pulp inflammation – NF-κB as a potential therapeutic target?

龋齿在世界范围内具有显著的患病率。它通过细菌将碳水化合物转化为有机酸来破坏牙齿。革兰氏阳性菌起着关键作用，变形链球菌特别是其合成大量细胞外基质的能力，这有利于生物膜的形成，以及其即使在低pH值下也能代谢各种碳水化合物的能力。在龋齿病变中，微生物及其产物通过牙本质小管扩散到牙髓腔，导致牙髓炎症。脂磷壁酸（LTA）锚定在革兰氏阳性菌（如S。在深龋洞中起着核心作用。通过与细胞膜上的TLR-2结合，它在牙髓-牙本质界面的成牙本质细胞以及中心的牙髓成纤维细胞中引发免疫应答。在细胞内，NF-κB信号级联被激活，导致各种趋化因子和细胞因子的分泌，以调节炎症和恢复组织稳态。此外，牙髓通过形成三级牙本质来保护自身免受微生物刺激物的影响。到目前为止，治疗无症状牙齿或可逆性牙髓炎的目标是去除大部分受感染的牙本质并修复牙齿。当临床症状表现为不可逆的牙髓炎时，活髓治疗不再适用，必须开始根管治疗。然而，在未来，免疫调节疗法可能会提供一种替代牙髓切除不可逆牙髓炎通过控制牙髓炎症，并允许再生。因此，拟定项目的目的是研究临床上确定的特异性作用于NF-κB信号通路的药理学药物是否适用于治疗牙髓炎症。为解决这一首要问题，将设立五个有具体目标的次级项目。第一个重点是一个新的共培养模型与S。研究LTA是否通过TLR-2激活牙髓-牙本质界面细胞和牙髓成纤维细胞诱导NF-κB核内易位。在下文中，一方面通过遗传分析研究细胞分化，另一方面研究免疫学特性，特别是炎性小体和促炎细胞因子的活化，研究两种细胞类型的防御反应。此外，由细胞释放的抗菌分子可以触发S.变异株，将通过RNA测序进行分析。最后，三个临床上建立的药物，乙酰水杨酸，氢化可的松，和他克莫司，将专门控制牙髓牙本质界面的细胞和牙髓成纤维细胞的炎症反应的潜力进行了研究。

Dental caries has a significant prevalence worldwide. It destroys teeth by bacteria that convert carbohydrates into organic acids. Gram-positive ones play a key role, with Streptococcus mutans in particular being distinguished by its ability to synthesize large amounts of extracellular matrix, which favors biofilm formation, and its ability to metabolize a variety of carbohydrates even at low pH. In a caries lesion, the microorganisms and their products diffuse to the pulp cavity through dentinal tubules, leading to inflammation of the dental pulp. Lipoteichoic acid (LTA), which is anchored in the cell membrane of gram-positive bacteria like S. mutans, plays a central role in deep cavities. By binding to TLR-2 on cell membranes, it triggers immune responses in the odontoblasts at the pulp-dentin-interface as well as pulp fibroblasts in the center. Intracellularly, the NF-κB signaling cascade is activated, leading to the secretion of various chemokines and cytokines to modulate the inflammation and restore tissue homeostasis. Furthermore, the dental pulp reacts by forming tertiary dentin to shield itself from the microbial irritants. Until now, the goal of caries treatment in asymptomatic teeth or those with reversible pulpitis has been to remove most of the infected dentin and to restore the tooth. When clinical symptoms demonstrate irreversible pulpitis, vital pulp therapy is no longer indicated and root canal treatment must be initiated. In the future, however, immunomodulatory therapeutics may provide an alternative to pulp removal for irreversible pulpitis by controlling pulp inflammation and allowing regeneration. Therefore, the aim of the proposed project is to investigate, whether clinically established pharmacological agents acting specifically on the NF-κB signaling pathway would be suitable for the treatment of inflammatory conditions of the dental pulp. To address the overarching question, five subprojects with specific objectives will be established. The first focuses on a novel coculture model with S. mutans and investigates whether LTA induces intranuclear translocation of NF-κB via TLR-2 activation in cells of the pulp-dentin-interface and in pulp fibroblasts, respectively. In the following, the defense responses of both cell types are studied on the one hand on cell differentiation by genetic profiling, and on the other hand on the immunological properties, especially the activation of inflammasomes and proinflammatory cytokines. In addition, antimicrobial molecules released by the cells could trigger an adaptive response in S. mutans, which will be analyzed by RNA sequencing. Finally, the potential of three clinically established drugs, acetylsalicylic acid, hydrocortisone, and tacrolimus, will be investigated to specifically control the inflammatory response in cells of the pulp-dentin interface and in dental pulp fibroblasts.