{
  "abstract": "Background. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with endothelial dysfunction. Multiple pathophysiological mechanisms have been proposed, including direct endothelial infection and indirect injury mediated by systemic inflammation. However, alternative receptors involved in SARS-CoV-2–induced endothelial damage remain to be fully elucidated. We hypothesized that the SARS-CoV-2 Spike protein contributes to endothelial dysfunction via Toll-like receptor 4 (TLR4)-mediated oxidative stress. Methods. We studied 20 patients with SARS-CoV-2 infection. Endothelial function was assessed by flow-mediated dilation (FMD). Serum levels of Spike protein and TNF-α were measured. In vitro, human umbilical vein endothelial cells (HUVECs) were incubated with recombinant Spike protein, TNF-α, or both, in the presence or absence of specific inhibitors of TLR4, NOX2, p47phox, PKC, and ACE2. Markers of endothelial activation (NO bioavailability, endothelin-1) and oxidative stress (H₂O₂, sNOX2-dp, p47phox phosphorylation) were evaluated. Results. Compared with controls, COVID-19 patients exhibited significantly reduced FMD. Linear regression analysis in the overall population showed that FMD inversely correlated with serum Spike protein and TNF-α levels. A significant positive correlation between TNF-α and Spike protein was also observed. In vitro, S protein (250 and 500 ng/mL) reduced nitric oxide (NO) bioavailability and significantly increased endothelin-1 levels compared with unstimulated HUVECs. These effects were attenuated by TLR4 or p47phox inhibition, whereas ACE2 inhibition (DX600) had no impact. Mechanistically, S protein increased H₂O₂ production, sNOX2-dp levels, p47phox, and PKC phosphorylation in a dose-dependent manner. NOX2 activation and p47phox phosphorylation were reduced by TLR4 or p47phox inhibitors, while ACE2 inhibition did not affect S protein–induced oxidative stress. Exposure of HUVECs to TNF-α alone, at concentrations comparable to those observed in patients, or to S protein alone induced endothelial activation and oxidative stress. Co-incubation with TNF-α and S protein further amplified these effects, which were significantly reduced by inhibition of TLR4, S protein, TNF-α, or p47phox. Conclusions. The Spike protein directly induces endothelial oxidative stress and dysfunction through a TLR4–NOX2–p47phox signaling pathway, independently of ACE2. TNF-α synergistically enhances these effects. These findings identify TLR4-mediated signaling as a key mechanism underlying COVID-19–related vascular damage and suggest potential therapeutic targets to prevent thrombotic complications.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 1,
  "authors": [
    {
      "name": "Cristina Nocella"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ebnbsfyzka2p5.bib",
  "cited_by": 0,
  "doi": null,
  "fulltext_url": "https://www.btvb.org/btvb/article/view/832",
  "id": "ebnbsfyzka2p5",
  "issns": [
    "2785-5309"
  ],
  "landing_url": "https://www.btvb.org/btvb/article/view/832",
  "language": "en",
  "licence": "CC-BY-NC",
  "licence_label": "CC BY-NC",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by-nc/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "lcc",
      "RC666-701"
    ]
  ],
  "openalex": null,
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-26",
  "publisher": "PAGEPress Publications",
  "ris": "https://research.draconitic.com/paper/ebnbsfyzka2p5.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T13:47:31Z",
      "native_id": "82821212647c40b8bf2d410fc95792b9",
      "source": "doaj",
      "url": "https://www.btvb.org/btvb/article/view/832"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "lcc:RC666-701",
      "subfield": "cardiovascular"
    }
  ],
  "title": "PO016 | TOLL-LIKE RECEPTOR 4-MEDIATED ENDOTHELIAL DYSFUNCTION VIA NOX2 ACTIVATION IN COVID-19",
  "title_text": "PO016 | TOLL-LIKE RECEPTOR 4-MEDIATED ENDOTHELIAL DYSFUNCTION VIA NOX2 ACTIVATION IN COVID-19",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T13:47:31Z",
  "url": "https://research.draconitic.com/paper/ebnbsfyzka2p5",
  "venue": "Bleeding, Thrombosis and Vascular Biology",
  "versions": []
}