HIF-2α and Post-Viral Endothelial Dysfunction

1 Ribeiro et al. 2026 — Spike S1 → Sustained HIF-2α → Endothelial Barrier Failure

Full Citation:: Ribeiro A, Wallraven T, Lech M, Adorjan K, Stubbe HC, Seifert M, Wöhnl A, Kesseler V, Negele J, Schmaderer C. SARS-CoV-2 spike S1-mediated HIF-2α activation in retinal endothelial cells suggests a mechanism contributing to post-COVID endothelial dysfunction. Frontiers in Immunology. 2026;17:1770758. DOI:: 10.3389/fimmu.2026.1770758 PMID:: 41878417 Study Design:: Human cohort + in vitro mechanistic study Sample Size:: 41 post-COVID syndrome patients, 24 pre-pandemic healthy controls Key Findings::

- Elevated EPO, VEGF, MCP-1 in PCS plasma vs controls
- Spike S1 protein → transient HIF-1α + sustained HIF-2α in human retinal endothelial cells
- HIF-2α activation → impaired endothelial barrier function
- Belzutifan (HIF-2α inhibitor) rescued barrier integrity

Conclusion:: SARS-CoV-2 spike S1 directly drives sustained HIF-2α-mediated endothelial dysfunction, providing a druggable mechanism for post-COVID vascular pathology. Limitations:: Single endothelial cell type (retinal); moderate sample size; in vitro S1 exposure may not fully recapitulate in vivo; no replication yet. Certainty:: 0.50/1.0 Research Stream:: hif2a-endothelial-postviral

2 Deng et al. 2026 — IRF3 Retains HIF-α in Cytoplasm

Full Citation:: Deng H, Jia S, Zhu C, Hua J, Wang Z, Sun X, Liu W, Shi L, Li W, Gui J, Liu X, Xiao W. IRF3 attenuates hypoxia signaling by retaining HIF-α in the cytoplasm. Cell Reports. 2026;45(1):116815. DOI:: 10.1016/j.celrep.2025.116815 PMID:: 41520336 Study Design:: Mechanistic cell biology study Key Findings::

- Resting cytoplasmic IRF3 directly interacts with HIF-1α and HIF-2α
- IRF3 retains HIF-α in cytoplasm under hypoxia, preventing nuclear signaling
- IRF3 depletion → increased HIF transcriptional activity
- Antiviral IRF3 and HIF pathways directly intersect at protein interaction level

Conclusion:: Antiviral signaling (IRF3) directly regulates HIF-α stability, providing mechanistic link between viral infection and sustained HIF-2α activation. Limitations:: In vitro only; no in vivo validation; cell-type specific effects unexplored. Certainty:: 0.65/1.0 Research Stream:: hif2a-endothelial-postviral

3 Couteaudier et al. 2025 — HCV Hijacks HIF-2α for Viral Morphogenesis

Full Citation:: Couteaudier M, Nivard M, Cochard J, Mammano F, Roingeard P, de Rocquigny H, Chouteau P. Hypoxia-inducible factor 2 triggers the production of highly infectious native-like hepatitis C virus particles. Cellular and Molecular Life Sciences. 2025;82(1):241. DOI:: 10.1007/s00018-025-05739-0 PMID:: 40533570 Study Design:: In vitro viral culture model at physiological oxygen Key Findings::

- HIF-2α knockdown abolished production of infectious HCV lipoviroparticles
- HIF-1α knockdown had minimal effect on viral particle production
- HCV specifically exploits HIF-2α for viral morphogenesis under physiological hypoxia

Conclusion:: Viruses can directly hijack HIF-2α for replication, suggesting a general mechanism applicable to other post-viral triggers (EBV, HHV-6). Limitations:: HCV-specific; in vitro only; endothelial cell context not tested. Certainty:: 0.55/1.0 Research Stream:: hif2a-endothelial-postviral

4 Reiterer et al. 2019 — Acute vs Chronic Hypoxia: HIF-1α vs HIF-2α in Endothelium

Full Citation:: Reiterer M, Colaço R, Emrouznejad P, Jensen A, Rundqvist H, Johnson R, Branco C. Acute and chronic hypoxia differentially predispose lungs for metastases. Scientific Reports. 2019;9(1):10246. DOI:: 10.1038/s41598-019-46763-y PMID:: 31308473 Study Design:: Pulmonary EC-specific HIF-1α or HIF-2α knockout mice Key Findings::

- Acute hypoxia → HIF-1α-dependent EC death + vascular permeability → metastasis
- Chronic hypoxia → HIF-2α-dependent EC protection + vascular integrity
- HIF-2α deletion in ECs rendered lungs vulnerable to tumor seeding
- Establishes opposing roles: HIF-1α = acute/barrier-disruptive, HIF-2α = chronic/barrier-protective

Conclusion:: HIF isoform-specific endothelial responses determine vascular fate; sustained HIF-2α activation (as in post-viral) may represent maladaptive chronic response. Limitations:: Murine model; metastasis context; acute hypoxia model may not reflect viral dynamics. Certainty:: 0.60/1.0 Research Stream:: hif2a-endothelial-postviral

5 Bishop & Ratcliffe 2025 — HIF-2α at the Interface of Oxygen Sensing

Full Citation:: Bishop T, Ratcliffe P. Hypoxia-inducible factor 2α: at the interface between oxygen sensing systems in physiology and pathology. Physiology (Bethesda). 2025;40(5):0. DOI:: 10.1152/physiol.00043.2024 PMID:: 39946558 Study Design:: Comprehensive review Key Findings::

- Reviews HIF-2α as master regulator of oxygen sensing
- Covers HIF-2α-selective pharmacology (belzutifan/PT2385/PT2977)
- Links HIF-2α to paraganglioma, chemosensation, and altitude adaptation

Conclusion:: HIF-2α is the dominant isoform in chronic oxygen-sensing disorders, providing rationale for targeting HIF-2α in post-viral conditions. Limitations:: Review — no primary data; limited coverage of endothelial-specific roles. Certainty:: 0.80/1.0 Research Stream:: hif2a-endothelial-postviral

6 Sandvik et al. 2023 — Endothelial Dysfunction in ME/CFS (RituxME Substudy)

Full Citation:: Sandvik M, Sørland K, Leirgul E, Rekeland I, Stavland C, Mella O, Fluge Ø. Endothelial dysfunction in ME/CFS patients. PLoS One. 2023;18(2):e0280942. DOI:: 10.1371/journal.pone.0280942 PMID:: 36730360 Study Design:: Cross-sectional substudy of RituxME RCT Sample Size:: N~60 ME/CFS patients Key Findings::

- Impaired flow-mediated dilation (FMD) in large vessels
- Impaired post-occlusive reactive hyperemia (PORH) in small vessels
- Endothelial dysfunction confirmed in well-characterized Norwegian ME/CFS cohort
- No autoantibody specificity assessed

Conclusion:: Endothelial dysfunction is a replicable feature of ME/CFS, independent of known autoantibody targets. Limitations:: Rituximab trial context may confound; no HIF measurements; cross-sectional. Certainty:: 0.65/1.0 Research Stream:: hif2a-endothelial-postviral

7 Stein et al. 2025 — Immunoadsorption in β2AR Autoantibody-Positive Post-COVID ME/CFS

Full Citation:: Stein E, Heindrich C, Wittke K, Kedor C, Rust R, Freitag H, Sotzny F, Krüger A, Tölle M, Grabowski P, Scheibenbogen C, Kim L. Efficacy of repeated immunoadsorption in patients with post-COVID myalgic encephalomyelitis/chronic fatigue syndrome and elevated β2-adrenergic receptor autoantibodies: a prospective cohort study. The Lancet Regional Health — Europe. 2025;49:101161. DOI:: 10.1016/j.lanepe.2024.101161 PMID:: 39759581 Study Design:: Prospective pre-post cohort study Sample Size:: 20 post-COVID ME/CFS patients Key Findings::

- Immunoadsorption reduced β2AR autoantibodies
- Symptom improvement correlated with autoantibody reduction
- Defines β2AR autoantibody-positive ME/CFS subgroup (~30% of post-COVID ME/CFS)

Conclusion:: Autoimmune mechanism in β2AR-positive subgroup; the remaining ~70% β2AR-negative patients require alternative mechanism — HIF-2α-driven ED is a candidate. Limitations:: Pre-post design, no sham control; small sample; β2AR-negative group not analyzed separately. Certainty:: 0.55/1.0 Research Stream:: hif2a-endothelial-postviral

8 Shen et al. 2024 — NRF2-HIF2α Attenuates Endothelial Senescence

Full Citation:: Shen J, Lai Y, Lu Y, Liu Y, Zhang J, Wu Y, Pan Y, Chen H, Gao Q, Wei Q, Chen Y, Ye J, Lin Y, Liu B, Jiang J, Nan J. NRF2-HIF2α signaling attenuates endothelial cell senescence and maintains intercellular junctions in diabetes. International Journal of Biological Sciences. 2024;20(10):4055–4073. DOI:: 10.7150/ijbs.96719 PMID:: 39113713 Study Design:: In vitro HUVEC model under glycemic stress Key Findings::

- NRF2-HIF2α axis protects against endothelial cell senescence
- Maintains intercellular junctions via tight junction protein regulation
- Bidirectional: protective under moderate stress but sustained activation may drive dysfunction

Conclusion:: HIF-2α directly intersects with endothelial senescence pathways, relevant to post-viral accelerated vascular aging. Limitations:: In vitro only; diabetes context; senescence markers limited. Certainty:: 0.55/1.0 Research Stream:: hif2a-endothelial-postviral

9 Sales et al. 2026 — Darunavir Inhibits HIF-2α to Preserve Barrier Function

Full Citation:: Sales T, Daniel A, Silva L, Franco A, Costa Filho H, Monteiro C, Ferreira A, Alicrim S, Lopes A, Clementino M, Oliveira A, Nicolau L, Havt A, Soares P, Spechler S, Souza R, Souza M. The protease inhibitor darunavir prevents esophagitis and impairments in esophageal barrier function in a mouse model of GERD. American Journal of Physiology — Gastrointestinal and Liver Physiology. 2026;330(6):G718–G726. DOI:: 10.1152/ajpgi.00058.2025 PMID:: 42013031 Study Design:: Mouse GERD model + in vitro mechanistic Key Findings::

- HIF-2α activation directly drives esophageal barrier disruption
- Darunavir (HIV protease inhibitor) inhibits pepsin activity → reduces HIF-2α levels
- Preserved tight junction proteins (ZO-1, occludin) and barrier integrity

Conclusion:: Independent confirmation that HIF-2α activation causes barrier dysfunction, with darunavir as potential repurposable HIF-2α inhibitor. Limitations:: Mouse model; GERD (non-viral) context; darunavir’s antipeptic mechanism may not apply to endothelial barrier. Certainty:: 0.55/1.0 Research Stream:: hif2a-endothelial-postviral

10 Zhang et al. 2026 — Oxidative Stress as HIF Axis Switch

Full Citation:: Zhang Y, Cao L, Zhang R, Pi W, Wee Yong V, Xue M. Oxidative stress as the orchestrator of the HIF axis switch in intracerebral hemorrhage. Free Radical Biology and Medicine. 2026;244:312–322. DOI:: 10.1016/j.freeradbiomed.2025.12.011 PMID:: 41389853 Study Design:: Intracerebral hemorrhage model + HIF axis analysis Key Findings::

- HIF-1α → protective in acute ICH
- HIF-2α → context-dependent, shifted by oxidative stress
- Oxidative stress determines HIF-1α vs HIF-2α dominance
- Proposes HIF isoform "switch" model

Conclusion:: Oxidative stress from viral infection may shift HIF balance toward sustained HIF-2α, providing unifying mechanism for post-viral endothelial dysfunction. Limitations:: ICH (non-viral) context; brain-specific; switch model requires validation in endothelial cells. Certainty:: 0.55/1.0 Research Stream:: hif2a-endothelial-postviral

11 Morris et al. 2025 — HIFs in RSV Infection

Full Citation:: Morris D, Qu Y, Haas de Mello A, Jones-Hall Y, Liu T, Weglarz M, Ivanciuc T, Garofalo R, Casola A. Role of hypoxia-inducible factors in respiratory syncytial virus infection-associated lung disease. International Journal of Molecular Sciences. 2025;26(7):3182. DOI:: 10.3390/ijms26073182 PMID:: 40244000 Study Design:: In vitro and murine RSV infection models Key Findings::

- RSV stabilizes HIFs under normoxic conditions
- HIF-1α inhibition reduces viral replication
- Viral infection actively manipulates HIF pathway independent of hypoxia

Conclusion:: Viruses can induce HIF stabilization as part of their replication strategy, providing precedent for HIF-2α persistence after viral trigger. Limitations:: RSV-specific; HIF-2α not specifically separated from HIF-1α; lung epithelium focus rather than endothelium. Certainty:: 0.50/1.0 Research Stream:: hif2a-endothelial-postviral

12 Sørland et al. 2021 — Reduced Endothelial Function in ME/CFS

Full Citation:: Sørland K, Sandvik M, Rekeland I, Ribu L, Småstuen M, Mella O, Fluge Ø. Reduced endothelial function in myalgic encephalomyelitis/chronic fatigue syndrome — results from open-label cyclophosphamide intervention study. Frontiers in Medicine. 2021;8:642710. DOI:: 10.3389/fmed.2021.642710 PMID:: 33829023 Study Design:: Open-label intervention study Sample Size:: ME/CFS patients Key Findings::

- Reduced flow-mediated dilation at baseline in ME/CFS vs controls
- Endothelial function improved post-cyclophosphamide in some patients
- Independent replication of endothelial dysfunction in ME/CFS

Conclusion:: Immune-driven endothelial impairment is a feature of ME/CFS, potentially targetable by immunomodulation. Limitations:: Open-label, no placebo control; small sample; cyclophosphamide not a specific endothelial therapy. Certainty:: 0.50/1.0 Research Stream:: hif2a-endothelial-postviral

13 Romanowska-Kocejko et al. 2025 — Microvascular Function in Long COVID

Full Citation:: Romanowska-Kocejko M, Braczko A, Jędrzejewska A, Żarczyńska-Buchowiecka M, Kocejko T, Kutryb-Zając B, Hellmann M. Follow-up assessment of the microvascular function in patients with long COVID. Microvascular Research. 2025;157:104748. DOI:: 10.1016/j.mvr.2024.104748 PMID:: 39293561 Study Design:: Longitudinal follow-up study Sample Size:: 33 long COVID patients, 30 healthy controls Key Findings::

- Impaired microvascular function at initial and follow-up assessment
- Persistence of endothelial dysfunction months after acute COVID-19
- FMSF technique validated for microvascular assessment

Conclusion:: Microvascular endothelial dysfunction is sustained in long COVID, supporting chronic HIF-2α mechanism. Limitations:: Moderate sample; single-center; no direct HIF measurements. Certainty:: 0.55/1.0 Research Stream:: hif2a-endothelial-postviral

14 Wirth & Löhn 2024 — Microvascular Disturbances in Post-COVID ME/CFS

Full Citation:: Wirth K, Löhn M. Microvascular capillary and precapillary cardiovascular disturbances strongly interact to severely affect tissue perfusion and mitochondrial function in myalgic encephalomyelitis/chronic fatigue syndrome evolving from the post-COVID-19 syndrome. Medicina (Kaunas). 2024;60(2):194. DOI:: 10.3390/medicina60020194 PMID:: 38399482 Study Design:: Narrative review / hypothesis paper Key Findings::

- Links microvascular pathology (microclots, deformed RBCs, endothelial swelling) to tissue perfusion
- Proposes microvascular → mitochondrial dysfunction cascade
- Integrates post-COVID and ME/CFS microvascular findings

Conclusion:: Microvascular dysfunction may be the proximal cause of tissue hypoxia and energy failure in post-COVID ME/CFS. Limitations:: Narrative review, no primary data; HIF axis mentioned implicitly rather than explicitly. Certainty:: 0.40/1.0 Research Stream:: hif2a-endothelial-postviral

15 Qiang et al. 2026 — Saracatinib Targets Src/HIF in Endothelial Cells

Full Citation:: Qiang H, Shan L, Yiming Z, Xue Z, Hongsong P, Jiajing Z, Wenyan Z, Bo J, Hafezi-Moghadam A, Dawei S. Divergent mechanisms, unified therapy: saracatinib targets Src/HIF signaling in endothelial and microglial cells to treat retinopathy. Biochemical Pharmacology. 2026;250(Pt 2):118028. DOI:: 10.1016/j.bcp.2026.118028 PMID:: 42070593 Study Design:: In vitro + animal model of retinopathy Key Findings::

- Saracatinib (Src inhibitor) targets HIF signaling in endothelial cells
- Demonstrates pharmacological HIF pathway modulation in ECs
- Combined endothelial and microglial targeting

Conclusion:: HIF pathway in endothelial cells is druggable, supporting viability of therapeutic approaches like belzutifan. Limitations:: Retinopathy context; in vitro + animal model; saracatinib not HIF-2α-specific. Certainty:: 0.55/1.0 Research Stream:: hif2a-endothelial-postviral

16 Pasupneti et al. 2020 — Endothelial HIF-2α Prevents Emphysema

Full Citation:: Pasupneti S, Tian W, Tu A, Dahms P, Granucci E, Gandjeva A, Xiang M, Butcher E, Semenza G, Tuder R, Jiang X, Nicolls M. Endothelial HIF-2α as a key endogenous mediator preventing emphysema. American Journal of Respiratory and Critical Care Medicine. 2020;202(7):983–995. DOI:: 10.1164/rccm.202001-0078OC PMID:: 32515984 Study Design:: EC-specific HIF-2α knockout mice Key Findings::

- Endothelial HIF-2α critical for maintaining pulmonary vascular integrity
- EC-specific HIF-2α deletion → spontaneous emphysema
- HIF-2α regulates VEGF and endothelial survival in pulmonary circulation

Conclusion:: Endothelial HIF-2α is essential for pulmonary vascular homeostasis; its dysregulation (either loss or sustained activation) has pathological consequences. Limitations:: Murine model; loss-of-function only; relevance to post-viral gain-of-function not directly tested. Certainty:: 0.70/1.0 Research Stream:: hif2a-endothelial-postviral