tetano
Editor, Senior Moderator
Acta Neuropathol
. 2026 Aug 29;152(1):26.
doi: 10.1007/s00401-026-03074-7.
María Payá 1 2 3 , Cristian Alcahut-Rodríguez 2 , Rosa A Barbella-Aponte 4 , Francisco Hernández-Fernández 2 3 5 , Juan D Molina-Nuevo 3 5 , Gemma Barroso-García 6 , Beatriz Castro-Robles 1 3 , Susana López-López 1 3 7 , Lourdes Arias-Salazar 1 3 , Óscar Ayo-Martín 2 3 , Jorge García-García 2 3 , Blanca Yélamos-Sanz 1 3 , Natalia García-Flores 1 3 , Alba G Arandilla 6 , Rafael Moreno-Luna 8 9 , Alicia Aliena-Valero 10 , Isabel Vielba-Gómez 10 11 , José I Tembl 10 11 , Juan B Salom 10 12 , Gemma Serrano-Heras # 13 14 , Tomás Segura # 15 16 17
Affiliations
The pathophysiological mechanisms underlying the hypercoagulable state and thrombotic events associated with COVID-19 remain incompletely understood. To investigate prothrombotic alterations during SARS-CoV-2 infection, we performed an exploratory and integrated analysis of cerebral thrombi retrieved, during the first wave of the pandemic, by mechanical thrombectomy from stroke patients with (n=6) and without (n=6) COVID-19. We combined histological and ultrastructural assessment with quantitative proteomics and elemental profiling to identify differences in cellular organization and in protein and metal composition. Immunohistochemical quantification revealed a trend toward increased macrophage abundance, a more diffuse CD68⁺ staining pattern, and reduced platelet content in COVID-19 thrombi. In contrast, neutrophil extracellular traps (NETs) burden, neutrophil number, and erythrocyte content did not differ significantly between groups. Transmission electron microscopy showed a disorganized ultrastructural fibrillar network in thrombi from COVID-19 stroke patients, consistent with the irregular and less densely packed extracellular matrix observed by Masson's trichrome staining. Furthermore, quantitative proteomics by liquid chromatography-tandem mass spectrometry (LC-MS/MS) identified 48 differentially expressed proteins among 720 shared proteins, with marked upregulation of hemoglobin subunits (α, β, γ, and δ), haptoglobin, biliverdin reductase and redox-regulating proteins, alongside downregulation of platelet-related proteins in COVID-19 thrombi. Total reflection X-ray fluorescence (TXRF) confirmed increased iron levels in COVID-19-associated thrombi. Notably, glycophorin A immunostaining did not indicate increased erythrocyte abundance, and erythrocyte structural proteins were not differentially expressed in proteomic analysis, suggesting that hemoglobin and iron were largely present in a cell-free form within the retrieved thrombi of COVID-19 stroke patients. In addition, acute-phase reactants, classical complement components, and immunoglobulins were detected exclusively in COVID-19 samples, consistent with a distinctive immune-inflammatory and oxidative signature. Overall, these findings support a novel pathophysiological mechanism underlying COVID-19-associated hypercoagulability and thrombosis, involving elevated circulating cell-free hemoglobin and increased iron content. Furthermore, this study highlights the potential contribution of hemoglobin/iron-related processes to the COVID-19 prothrombotic state and may provide molecular targets for future therapeutic strategies.
Keywords: COVID-19; Hemoglobin; Hypercoagulability; Iron; Prothrombotic state; Quantitative proteomics; Stroke.
. 2026 Aug 29;152(1):26.
doi: 10.1007/s00401-026-03074-7.
High levels of cell-free hemoglobin and iron in cerebral thrombi of pre-Omicron COVID-19 stroke patients: novel drivers of SARS-CoV-2-induced prothrombotic state
María Payá 1 2 3 , Cristian Alcahut-Rodríguez 2 , Rosa A Barbella-Aponte 4 , Francisco Hernández-Fernández 2 3 5 , Juan D Molina-Nuevo 3 5 , Gemma Barroso-García 6 , Beatriz Castro-Robles 1 3 , Susana López-López 1 3 7 , Lourdes Arias-Salazar 1 3 , Óscar Ayo-Martín 2 3 , Jorge García-García 2 3 , Blanca Yélamos-Sanz 1 3 , Natalia García-Flores 1 3 , Alba G Arandilla 6 , Rafael Moreno-Luna 8 9 , Alicia Aliena-Valero 10 , Isabel Vielba-Gómez 10 11 , José I Tembl 10 11 , Juan B Salom 10 12 , Gemma Serrano-Heras # 13 14 , Tomás Segura # 15 16 17
Affiliations
- PMID: 42667425
- PMCID: PMC13525952
- DOI: 10.1007/s00401-026-03074-7
Abstract
The pathophysiological mechanisms underlying the hypercoagulable state and thrombotic events associated with COVID-19 remain incompletely understood. To investigate prothrombotic alterations during SARS-CoV-2 infection, we performed an exploratory and integrated analysis of cerebral thrombi retrieved, during the first wave of the pandemic, by mechanical thrombectomy from stroke patients with (n=6) and without (n=6) COVID-19. We combined histological and ultrastructural assessment with quantitative proteomics and elemental profiling to identify differences in cellular organization and in protein and metal composition. Immunohistochemical quantification revealed a trend toward increased macrophage abundance, a more diffuse CD68⁺ staining pattern, and reduced platelet content in COVID-19 thrombi. In contrast, neutrophil extracellular traps (NETs) burden, neutrophil number, and erythrocyte content did not differ significantly between groups. Transmission electron microscopy showed a disorganized ultrastructural fibrillar network in thrombi from COVID-19 stroke patients, consistent with the irregular and less densely packed extracellular matrix observed by Masson's trichrome staining. Furthermore, quantitative proteomics by liquid chromatography-tandem mass spectrometry (LC-MS/MS) identified 48 differentially expressed proteins among 720 shared proteins, with marked upregulation of hemoglobin subunits (α, β, γ, and δ), haptoglobin, biliverdin reductase and redox-regulating proteins, alongside downregulation of platelet-related proteins in COVID-19 thrombi. Total reflection X-ray fluorescence (TXRF) confirmed increased iron levels in COVID-19-associated thrombi. Notably, glycophorin A immunostaining did not indicate increased erythrocyte abundance, and erythrocyte structural proteins were not differentially expressed in proteomic analysis, suggesting that hemoglobin and iron were largely present in a cell-free form within the retrieved thrombi of COVID-19 stroke patients. In addition, acute-phase reactants, classical complement components, and immunoglobulins were detected exclusively in COVID-19 samples, consistent with a distinctive immune-inflammatory and oxidative signature. Overall, these findings support a novel pathophysiological mechanism underlying COVID-19-associated hypercoagulability and thrombosis, involving elevated circulating cell-free hemoglobin and increased iron content. Furthermore, this study highlights the potential contribution of hemoglobin/iron-related processes to the COVID-19 prothrombotic state and may provide molecular targets for future therapeutic strategies.
Keywords: COVID-19; Hemoglobin; Hypercoagulability; Iron; Prothrombotic state; Quantitative proteomics; Stroke.