Chronic hypoxia of endothelial cells boosts HIF-1α-NLRP1 circuit in Alzheimer’s disease

• Published in: Free radical biology & medicine 2023-08, Vol.204, p.385-393
• Main Authors: Jung, Eunyoung, Kim, Ye Eun, Jeon, Hui Su, Yoo, Myeongjong, Kim, Minsu, Kim, Young-Myeong, Koh, Seong-Ho, Choi, Yoon Kyung
• Format: Article
• Language: English
• Subjects: Alzheimer Disease - genetics; Alzheimer Disease - metabolism; Alzheimer's disease; Animals; Caspase 1 - metabolism; Endothelial Cells - metabolism; HIF-1α; Humans; Hypoxia - metabolism; Hypoxia-Inducible Factor 1, alpha Subunit - genetics; Hypoxia-Inducible Factor 1, alpha Subunit - metabolism; Ischemic vessels; Mice; Mice, Transgenic; NADPH Oxidases - metabolism; NLR Proteins - metabolism; NLRP1 inflammasome; Oxygen - metabolism
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2023.05.011

Cerebral microvasculature of patients with Alzheimer's disease (AD) exhibits reduced capillary diameter and impaired blood flow. Molecular mechanisms of ischemic vessels affecting AD progressions have not been well established yet. In the present study, we found that in vivo triple (PS1M146V, APPswe, tauP301L) transgenic AD mouse model (3x-Tg AD) brains and retinas showed hypoxic vessels expressing hypoxyprobe and hypoxia inducible factor-1α (HIF-1α). To mimic in vivo hypoxic vessels, we used in vitro oxygen-glucose deprivation (OGD)-treated endothelial cells. HIF-1α protein was increased through reactive oxygen species (ROS) producing NADPH oxidases (NOX) (i.e., Nox2, Nox4). OGD-induced HIF-1α upregulated Nox2 and Nox4, demonstrating crosstalk between HIF-1α and NOX (i.e., Nox2, Nox4). Interestingly, NLR family pyrin domain containing 1 (NLRP1) protein was promoted by OGD, and such effect was blocked by downregulation of Nox4 and HIF-1α. Knockdown of NLRP1 also diminished OGD-mediated protein levels of Nox2, Nox4, and HIF-1α in human brain microvascular endothelial cells. These results showed interplay among HIF-1α, Nox4 and NLRP1 in OGD-treated endothelial cells. Expression of NLRP3 was not detected well in hypoxic endothelial cells of 3x-Tg AD retinas or OGD-treated endothelial cells. Instead, hypoxic endothelial cells of 3x-Tg AD brains and retinas markedly expressed NLRP1, the adaptor molecule apoptosis-associated speck-like protein containing a CARD (ASC), caspase-1, and interleukin-1β (IL-1β). Taken together, our results suggest that AD brains and retinas can trigger chronic hypoxia especially in microvascular endothelial cells, consequently leading to NLRP1 inflammasome formation and upregulation of ASC-caspase-1-IL-1β cascades. In addition, NLRP1 can stimulate HIF-1α expression and form HIF-1α-NLRP1 circuit. These consequences might further destroy vascular system in AD. [Display omitted] •In vivo triple transgenic AD mouse model brains and retinas showed hypoxic vessels expressing hypoxyprobe and HIF-1α.•In in vitro OGD-treated endothelial cells, HIF-1α upregulated NADPH oxidase (NOX) (i.e., Nox2, Nox4).•NLRP1 protein was promoted by OGD, and such effect was blocked by downregulation of Nox4 and HIF-1α.•Hypoxic endothelial cells of AD brains and retinas markedly expressed NLRP1, ASC, caspase-1, and interleukin-1β (IL-1β).•Chronic hypoxia in microvascular endothelial cells leads to HIF-1α-NLRP1 circuit in AD.