Retinal ischemia induces α-SMA-mediated capillary pericyte contraction coincident with perivascular glycogen depletion
Retinal ischemia induces α-SMA-mediated capillary pericyte contraction coincident with perivascular glycogen depletion
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DOI：
10.1186/s40478-019-0761-z
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发表时间：
2019-08-20
影响因子：
7.1
通讯作者：
Dalkara, Turgay
中科院分区：
文献类型：
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作者：
Alarcon-Martinez, Luis;Yilmaz-Ozcan, Sinem;Dalkara, Turgay
越来越多的证据表明，周细胞是脆弱的细胞，在各种神经退行性过程中发挥病理生理作用。微血管周细胞在大脑和冠状动脉缺血时收缩，在闭塞动脉重新打开后不放松，导致再灌注不完全。然而，缺血诱导周细胞收缩的细胞机制、其延迟出现以及是否在药理学上可逆尚不清楚。在这里，我们研究i)缺血诱导的周细胞收缩是否由α -平滑肌肌动蛋白（α - sma）介导，ii)缺血周细胞钙升高的来源，以及iii)微血管周围糖原是否可以支持缺血时周细胞的代谢。因此，我们在体内使用自适应光学扫描光检检查了视网膜缺血时周细胞的收缩性，在体外使用无偏体视学方法检查了周细胞收缩性。通过基因编码的钙指示剂（NG2-GCaMP6）或荧光探针（Fluo-4）检测，我们发现微血管收缩与周细胞钙含量增加有关。用RNA干扰抑制α - sma表达或用phalloidin或钙拮抗剂氨氯地平固定F-actin可防止收缩，表明收缩是由钙和α - sma介导的周细胞收缩引起的。卡贝诺洛酮或一种cx43选择性肽阻滞剂也能减少钙的升高，这与除了电压门控制的钙通道外，还涉及间隙连接介导的机制相一致。缺血1 h后，周细胞钙含量升高，毛细血管收缩明显，且与微血管周围糖原消耗一致，提示糖原颗粒生成的葡萄糖可支持周细胞代谢，延缓缺血引起的微血管功能障碍。事实上，当糖原分解被药理学抑制时，毛细血管收缩出现得更早。尽管再通，收缩仍然存在，但在再通期间给予周细胞松弛剂腺苷是可逆的。我们的研究表明，视网膜缺血是一种常见的致盲原因，可诱导α - sma和钙介导的持续周细胞收缩，这种收缩可被微血管周围糖原驱动的葡萄糖延迟。这些发现阐明了毛细血管周细胞的收缩性质，并确定了周围微血管端足和周细胞之间的一种新的代谢协作。
Increasing evidence indicates that pericytes are vulnerable cells, playing pathophysiological roles in various neurodegenerative processes. Microvascular pericytes contract during cerebral and coronary ischemia and do not relax after re-opening of the occluded artery, causing incomplete reperfusion. However, the cellular mechanisms underlying ischemia-induced pericyte contraction, its delayed emergence, and whether it is pharmacologically reversible are unclear. Here, we investigate i) whether ischemia-induced pericyte contractions are mediated by alpha-smooth muscle actin (alpha-SMA), ii) the sources of calcium rise in ischemic pericytes, and iii) if peri-microvascular glycogen can support pericyte metabolism during ischemia. Thus, we examined pericyte contractility in response to retinal ischemia both in vivo, using adaptive optics scanning light ophthalmoscopy and, ex vivo, using an unbiased stereological approach. We found that microvascular constrictions were associated with increased calcium in pericytes as detected by a genetically encoded calcium indicator (NG2-GCaMP6) or a fluoroprobe (Fluo-4). Knocking down alpha-SMA expression with RNA interference or fixing F-actin with phalloidin or calcium antagonist amlodipine prevented constrictions, suggesting that constrictions resulted from calcium- and alpha-SMA-mediated pericyte contractions. Carbenoxolone or a Cx43-selective peptide blocker also reduced calcium rise, consistent with involvement of gap junction-mediated mechanisms in addition to voltage-gated calcium channels. Pericyte calcium increase and capillary constrictions became significant after 1 h of ischemia and were coincident with depletion of peri-microvascular glycogen, suggesting that glucose derived from glycogen granules could support pericyte metabolism and delay ischemia-induced microvascular dysfunction. Indeed, capillary constrictions emerged earlier when glycogen breakdown was pharmacologically inhibited. Constrictions persisted despite recanalization but were reversible with pericyte-relaxant adenosine administered during recanalization. Our study demonstrates that retinal ischemia, a common cause of blindness, induces alpha-SMA- and calcium-mediated persistent pericyte contraction, which can be delayed by glucose driven from peri-microvascular glycogen. These findings clarify the contractile nature of capillary pericytes and identify a novel metabolic collaboration between peri-microvascular end-feet and pericytes.