Pozo-Morales Macarena, Garteizgogeascoa Inés, Perazzolo Camille, So Juhoon, Shin Donghun, Singh Sumeet Pal
IRIBHM , Free University of Brussels, Université Libre de Bruxelles (ULB) , Brussels , Belgium.
Department of Developmental Biology , McGowan Institute for Regenerative Medicine , Pittsburgh Liver Research Center , University of Pittsburgh , Pittsburgh , Pennsylvania , USA.
Hepatology. 2023 Mar 1;77(3):789-801. doi: 10.1002/hep.32663. Epub 2023 Feb 17.
Hepatocytes were the first cell type for which oscillations of cytoplasmic calcium levels in response to hormones were described. Since then, investigation of calcium dynamics in liver explants and culture has greatly increased our understanding of calcium signaling. A bottleneck, however, exists in observing calcium dynamics in a noninvasive manner because of the optical inaccessibility of the mammalian liver. Here, we aimed to take advantage of the transparency of the zebrafish larvae to image hepatocyte calcium dynamics in vivo at cellular resolution.
We developed a transgenic model expressing a calcium sensor, GCaMP6s, specifically in zebrafish hepatocytes. Using this, we provide a quantitative assessment of intracellular calcium dynamics during multiple contexts, including growth, feeding, ethanol-induced stress, and cell ablation. Specifically, we show that synchronized calcium oscillations are present in vivo , which are lost upon starvation. Starvation induces lipid accumulation in the liver. Feeding recommences calcium waves in the liver, but in a spatially restricted manner, as well as resolves starvation-induced hepatic steatosis. By using a genetically encoded scavenger for calcium, we show that dampening of calcium signaling accelerates the accumulation of starvation-related lipid droplets in the liver. Furthermore, ethanol treatment, as well as cell ablation, induces calcium flux, but with different dynamics. The former causes asynchronous calcium oscillations, whereas the latter leads to a single calcium spike.
We demonstrate the presence of oscillations, waves, and spikes in vivo . Calcium waves are present in response to nutrition and negatively regulate starvation-induced accumulation of lipid droplets.
肝细胞是最早被描述为细胞质钙水平会因激素而发生振荡的细胞类型。从那时起，对肝外植体和培养物中钙动力学的研究极大地增进了我们对钙信号传导的理解。然而，由于哺乳动物肝脏在光学上难以接近，以非侵入性方式观察钙动力学存在一个瓶颈。在这里，我们旨在利用斑马鱼幼虫的透明度，以细胞分辨率在体内成像肝细胞钙动力学。
我们开发了一种转基因模型，该模型在斑马鱼肝细胞中特异性表达钙传感器GCaMP6s。利用这个模型，我们对包括生长、进食、乙醇诱导的应激和细胞消融在内的多种情况下的细胞内钙动力学进行了定量评估。具体而言，我们表明体内存在同步钙振荡，饥饿时这些振荡会消失。饥饿会导致肝脏中脂质积累。重新进食会在肝脏中引发钙波，但这种钙波在空间上受到限制，同时也能缓解饥饿诱导的肝脂肪变性。通过使用一种基因编码的钙清除剂，我们表明钙信号的减弱会加速肝脏中与饥饿相关的脂滴积累。此外，乙醇处理以及细胞消融都会诱导钙通量，但动力学不同。前者会导致异步钙振荡，而后者会导致单个钙峰。
我们证明了体内存在振荡、波和峰。钙波在对营养的反应中出现，并对饥饿诱导的脂滴积累起负调节作用。
