Franchini Marco, Zini Eric, Osto Melania, Jablonski Katarina, Kaufmann Karin, Lutz Thomas A, Reusch Claudia E, Ackermann Mathias
Institute of Virology, Vetsuisse Faculty, University of Zürich, Winterthurerstrasse 266a, 8057 Zürich, Switzerland.
Vet Immunol Immunopathol. 2010 Nov 15;138(1-2):70-8. doi: 10.1016/j.vetimm.2010.07.001. Epub 2010 Aug 1.
Toll-like receptors (TLRs) are cellular receptors that recognize molecules derived from pathogens, endogenous molecules generated after cellular stress, and free fatty acids. TLR activation leads to a proinflammatory reaction that is fundamental in the initiation of an innate immune response and subsequent adaptive responses but also can damage tissues. TLRs are not only expressed within the immune system, but also in most other organ systems including the pancreas. TLR4 is expressed in pancreatic β-cells of rodents and humans and its stimulation affects insulin secretion in response to glucose. A low-grade inflammation is often associated with disturbed performance of β-cells and insulin resistance, the cardinal metabolic event of type-2 diabetes. Feline diabetes mellitus shares many similarities with type-2 diabetes in humans. Our objective was to elucidate the role of TLRs in feline pancreatic islets and islet-like clusters (ILC) that consist of islets with their adjacent tissue. We tested whether TLRs are triggered by their agonists and lead to the expression of inflammatory cytokines. We confirmed the expression of all known feline TLRs in pancreas and ILC. Furthermore, stimulation with TLR agonists increased IL-6 mRNA and protein content and the expression of other proinflammatory cytokines indicating a clear proinflammatory response. The reactivity to TLR ligands was stronger in β-cell enriched populations obtained after sorting by FACS indicating that inflammatory stimuli can also be generated within β-cells. We conclude that the microenvironment of feline β-cells harbor the potential for inflammatory reactions, that can be initiated by molecules released from bacteria or viruses or other molecules recognized by TLRs. Therefore infections associated with bacteriemia and viremia can induce inflammation in islets and damage the endocrine pancreatic tissue.
Toll样受体(TLRs)是一类细胞受体,可识别源自病原体的分子、细胞应激后产生的内源性分子以及游离脂肪酸。TLR激活会引发促炎反应,这在先天免疫反应的启动及随后的适应性反应中至关重要,但也可能损害组织。TLRs不仅在免疫系统中表达,还在包括胰腺在内的大多数其他器官系统中表达。TLR4在啮齿动物和人类的胰腺β细胞中表达,其刺激会影响葡萄糖刺激下的胰岛素分泌。低度炎症通常与β细胞功能紊乱和胰岛素抵抗相关,而胰岛素抵抗是2型糖尿病的主要代谢事件。猫糖尿病与人类2型糖尿病有许多相似之处。我们的目的是阐明TLRs在猫胰岛和胰岛样簇(ILC,由胰岛及其相邻组织组成)中的作用。我们测试了TLRs是否会被其激动剂触发并导致炎性细胞因子的表达。我们证实了所有已知的猫TLRs在胰腺和ILC中的表达。此外,用TLR激动剂刺激会增加IL-6的mRNA和蛋白质含量以及其他促炎细胞因子的表达,表明有明显的促炎反应。通过荧光激活细胞分选(FACS)分选后获得的富含β细胞的群体对TLR配体的反应更强,这表明β细胞内也可产生炎症刺激。我们得出结论,猫β细胞的微环境具有引发炎症反应的潜力,这种反应可由细菌或病毒释放的分子或TLRs识别的其他分子引发。因此,与菌血症和病毒血症相关的感染可诱导胰岛炎症并损害胰腺内分泌组织。