Marit Synnøve Hellum

• Tøsdal, Margunn Bye; Lunde, Turid Helen Felli; Hervig, Tor Audun; Sun, Chen; Sandberg, Sverre & Hellum, Marit Synnøve [Vis alle 8 forfattere av denne artikkelen] (2026). Decreasing Platelet Aggregation Despite Increasing Soluble P-selectin during Pregnancy in Women with and without Heterozygous Factor v Leiden Mutation. Thrombosis and Haemostasis. ISSN 0340-6245. doi: 10.1055/a-2791-6450. Fulltekst i vitenarkiv Vis sammendrag

  Background: Risk of venous thromboembolism (VTE) is increased in pregnancy and postpartum, and 40% of VTEs in pregnancy (Caucasians) are associated with heterozygous factor V Leiden mutation (FVL). Thrombin generation is increased in individuals with FVL and in pregnant women, and thrombin amplifies both platelet and coagulation activation. Although both contribute to VTE pathophysiology, the mechanisms of platelet activation in pregnant women, particularly with heterozygous FVL, remain poorly understood. Objectives: To describe the physiological course of the platelet activation marker plasma soluble P-selectin (sP-selectin), whole blood platelet aggregation, and thromboelastography (TEG) parameters throughout pregnancy and postpartum, and assess differences between women with and without heterozygous FVL. Patients/Methods: A total of 22 pregnant women with heterozygous FVL and 22 without were enrolled. Blood samples were collected at multiple time points during and after pregnancy. Platelet activation and aggregation were evaluated using sP-selectin, multiple electrode aggregometry (MEA) with adenosine diphosphate, arachidonic acid, thrombin receptor-activating peptide-6 as agonists, and TEG. Results: sP-selectin levels increased significantly during pregnancy, while platelet aggregation decreased in response to all agonists (P < 0.005). TEG maximum amplitude (MA) increased throughout pregnancy. No significant differences were observed between women with and without FVL. Conclusion: In late pregnancy, decreased platelet aggregation responses were observed alongside increased sP-selectin levels, with no differences in levels between women with and without heterozygous FVL. These findings indicate that the presence of heterozygous FVL does not significantly influence platelet function during pregnancy. The cause of the unexpected, reduced platelet aggregation remains unclear and warrants further investigation.

• Hellum, Marit Synnøve; Sletten, Marit; Skogstad, Marie Jeanette; Stavseth, Vidar; Glosli, Heidi & Backe, Paul Hoff [Vis alle 8 forfattere av denne artikkelen] (2025). Characterization of a novel factor X variant, p.F139L, associated with bleedings in heterozygous and compound heterozygous form. Thrombosis Research. ISSN 0049-3848. 253. doi: 10.1016/j.thromres.2025.109412. Fulltekst i vitenarkiv Vis sammendrag

  Introduction Congenital factor X (FX) deficiency is a rare bleeding disorder. Heterozygous patients may experience bleedings like epistaxis or bleeding complications after dental extraction and surgery, whereas homozygous individuals often experience more severe bleedings. Aim To characterize a new FX variant found in two unrelated probands with mild to moderate bleeding tendencies. Methods Prothrombin time (PT) Quick, APTT, FX activity, FX antigen, thrombin generation and DNA sequencing were performed for probands and their families. F10 variants were explored in programs for in silico predictions and structural analyses, and in vitro expression was used for further characterization. Results A novel missense variant (c.415T>C, p.F139L) was found in heterozygous form in proband 1 and in compound heterozygous form in proband 2, in combination with a previously known missense variant (c.424G>A, p.E142K). All individuals carrying the p.F139L variant had borderline/prolonged PT Quick (11.9–15.9 s) and APTT (36–43 s) and reduced thrombin generation. Both FX antigen (30–51 %) and activity (37–63 IU/dL) were reduced, indicating a type I deficiency. Structural analysis indicated that interactions between the EGF-2 and the protease domain of FX could be disrupted in the p.F139L variant, causing destabilization of the protein. The p.E142K variant was predicted to have less impact on FX structure. In vitro expression results further supported plasma findings. Conclusion We report a new FX variant, p.F139L, causing a type I FX deficiency associated with mild to moderate bleedings in heterozygous and compound heterozygous form. The variant causes structural changes which likely affect intracellular processing of FX.

• Harjen, Hannah Jayne; Hellum, Marit Synnøve; Rørtveit, Runa; Oscarson, Malin; Anfinsen, Kristin Paaske & Moldal, Elena Regine [Vis alle 9 forfattere av denne artikkelen] (2022). Persistent hypercoagulability in dogs envenomated by the European adder (Vipera berus berus). PLOS ONE. 17(2). doi: 10.1371/journal.pone.0263238. Fulltekst i vitenarkiv Vis sammendrag

  Background Envenomation by the European adder, Vipera berus berus (Vbb), is a medical emergency. The overall in vivo haemostatic effects of pro- and anticoagulant components in Vbb venom, and the downstream effects of cellular injury and systemic inflammation, are unclear. Objectives To longitudinally describe the global coagulation status of dogs after Vbb envenomation and compare to healthy controls. A secondary aim was to investigate differences between dogs treated with and without antivenom. Methods Citrated plasma was collected at presentation, 12 hours (h), 24 h, 36 h and 15 days after bite from 28 dogs envenomated by Vbb, and from 28 healthy controls at a single timepoint. Thrombin generation (initiated with and without exogenous phospholipids and tissue factor), thrombin-antithrombin (TAT)-complexes and the procoagulant activity of phosphatidylserine (PS)-expressing extracellular vesicles (EVs), expressed as PS-equivalents, were measured. Results At presentation the envenomated dogs were hypercoagulable compared to controls, measured as increased thrombin generation, TAT-complexes and PS-equivalents. The hypercoagulability decreased gradually but compared to controls thrombin generation and PS-equivalents were still increased at day 15. The discrepancy in peak thrombin between envenomated dogs and controls was greater when the measurement was phospholipid-dependent, indicating that PS-positive EVs contribute to hypercoagulability. Lag time was shorter in non-antivenom treated dogs, compared to antivenom treated dogs <24 h after envenomation. Conclusions Hypercoagulability was measured in dogs up to 15 days after Vbb envenomation. Dogs treated with antivenom may be less hypercoagulable than their non-antivenom treated counterparts. Thrombin generation is a promising diagnostic and monitoring tool for Vbb envenomation.

• Rognes, Ingrid Nygren; Hellum, Marit; Ottestad, William; Bache, Kristi Grønvold; Eken, Torsten & Henriksson, Carola Elisabeth (2021). Extracellular vesicle-associated procoagulant activity is highest the first 3 hours after trauma and thereafter declines substantially: A prospective observational pilot study. Journal of Trauma and Acute Care Surgery. ISSN 2163-0755. 91(4), s. 681–691. doi: 10.1097/TA.0000000000003333. Fulltekst i vitenarkiv Vis sammendrag

  Background: Trauma patients have high concentrations of circulating extracellular vesicles (EVs) following injury, but the functional role of EVs in this setting is only partly deciphered. We aimed to describe in detail EV-associated procoagulant activity in individual trauma patients during the first 12 hours after injury to explore their putative function and relate findings to relevant trauma characteristics and outcome. Methods: In a prospective observational study of 33 convenience recruited trauma patients, citrated plasma samples were obtained at trauma center admission and 2, 4, 6, and 8 hours thereafter. We measured thrombin generation from isolated EVs and the procoagulant activity of phosphatidylserine (PS)-exposing EVs. Correlation and multivariable linear regression analyses were used to explore associations between EV-associated procoagulant activity and trauma characteristics as well as outcome measures. Results: EV-associated procoagulant activity was highest in the first 3 hours after injury. EV-associated thrombin generation normalized within 7 to 12 hours of injury, whereas the procoagulant activity of PS-exposing EVs declined to a level right above that of healthy volunteers. Increased EV-associated procoagulant activity at admission was associated with higher New Injury Severity Score, lower admission base excess, higher admission international normalized ratio, prolonged admission activated partial thromboplastin time, higher Sequential Organ Failure Assessment score at day 0, and fewer ventilator-free days. Conclusion: Our data suggest that EVs have a transient hypercoagulable function and may play a role in the early phase of hemostasis after injury. The role of EVs in trauma-induced coagulopathy and posttraumatic thrombosis should be studied bearing in mind this novel temporal pattern. Level of evidence: Prognostic/epidemiologic, level V.

• Garabet, Lamya Samir Noori; Ghanima, Waleed Khalid; Hellum, Marit Synnøve; Sandset, Per Morten; Bussel, James B. & Tran, Hoa Thi Tuyet [Vis alle 7 forfattere av denne artikkelen] (2019). Increased microvesicle-associated thrombin generation in patients with immune thrombocytopenia after initiation of thrombopoietin receptor agonists. Platelets. ISSN 0953-7104. doi: 10.1080/09537104.2019.1639655. Fulltekst i vitenarkiv
• Aass, Hans Christian Dalsbotten; Hellum, Marit Synnøve; Siebke, Anne-Marie; Brandtzæg, Petter; Berg, Jens Petter & Øvstebø, Reidun [Vis alle 7 forfattere av denne artikkelen] (2018). Whole-blood incubation with the Neisseria meningitidis lpxL1 mutant induces less pro-inflammatory cytokines than the wild type, and IL-10 reduces the MyD88-dependent cytokines. Innate Immunity. ISSN 1753-4259. 24(2), s. 101–111. doi: 10.1177/1753425917749299. Fulltekst i vitenarkiv Vis sammendrag

  Levels of bacterial LPS, pro-inflammatory cytokines and IL-10 are related to the severity of meningococcal septicaemia. Patients infected with a Neisseria meninigitidis lpxL1 mutant (Nm-mutant) with penta-acylated lipid A present with a milder meningococcal disease than those infected with hexa-acylated Nm wild type (Nm-wt). The aim was to compare the pro-inflammatory responses after ex vivo incubation with the heat-inactivated Nm-wt or the Nm-mutant in citrated whole blood, and the modulating effects of IL-10. Concomitantly, we measured intracellular IL-6, IL-8 and TNF-α to elucidate which cell types were responsible for the pro-inflammatory responses. Incubation with Nm-wt (106/ml;107/ml;108/ml) resulted in a dose-dependent increase of the MyD88-dependent pro-inflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α), which were mainly derived from monocytes. In comparison, only 108/ml of the Nm-mutant significantly increased the concentration of these cytokines. The MyD88-independent cytokines (IP-10, RANTES) were evidently increased after incubation with the Nm-wt but were unaffected by the Nm-mutant. Co-incubation with IL-10 significantly reduced the concentrations of the MyD88-dependent cytokines induced by both the Nm-wt and the Nm-mutant, whereas the MyD88-independent cytokines were almost unaffected. In summary, the Nm-mutant is a weaker inducer of the MyD88-dependent/independent cytokines than the Nm-wt in whole blood, and IL-10 attenuates the Nm-stimulated increase in MyD88-dependent pro-inflammatory cytokines.

• Hellum, Marit Synnøve; Siebke, Anne-Marie; Berg, Jens Petter; Brandtzæg, Petter; Øvstebø, Reidun & Henriksson, Carola (2017). The Neisseria meningitidis lpxL1 mutant induces less tissue factor expression and activity in primary human monocytes and monocyte-derived microvesicles than the wild type meningococcus. Innate Immunity. ISSN 1753-4259. 23(2), s. 196–205. doi: 10.1177/1753425916684201. Fulltekst i vitenarkiv
• Hellum, Marit Synnøve; Lie, Maria Isabel Lopes Romao Franc; Øvstebø, Reidun; Hauge, Truls & Henriksson, Carola (2017). The effect of corn trypsin inhibitor, anti-tissue factor pathway inhibitor antibodies and phospholipids on microvesicle-associated thrombin generation in patients with pancreatic cancer and healthy controls. PLOS ONE. 12(9). doi: 10.1371/journal.pone.0184579. Fulltekst i vitenarkiv Vis sammendrag

  Circulating microvesicles (MVs) are suggested to be important contributors to cancer-associated thrombosis due to the presence of surface-bound procoagulant molecules like tissue factor (TF) and phosphatidylserine (PS). Pancreatic cancer is considered to be one of the most prothrombotic malignancies. The aim of this study was to describe the impact of analytical variables on MV-associated thrombin generation in patients with pancreatic cancer and in healthy controls. MVs were isolated from citrated plasma and added to pooled normal plasma (PNP). Thrombin generation was measured by the calibrated automated thrombogram. The impact of corn trypsin inhibitor (CTI), anti-tissue factor pathway inhibitor (TFPI) antibodies and phospholipids was described. Antibodies against TF were used to assess TF-dependency, and MV-bound PS activity was measured with the Zymuphen MP-activity kit. MVs from the pancreatic cancer patients displayed higher thrombin generation and higher PS-activity than MVs from the healthy control group, while TF-dependency was observed in only 1 out of 13 patient samples. Adequate thrombin generation-curves were only achieved when CTI was omitted and anti-TFPI antibodies were added to PNP prepared in low contact-activating tubes. Addition of phospholipids reduced the significant differences between the two groups, and should be omitted. This modified thrombin generation assay could be useful for measurement of procoagulant circulating MVs, allowing the contribution from MVs affecting both the intrinsic and the extrinsic pathway to be measured.

• Hellum, Marit Synnøve; Øvstebø, Reidun; Brusletto, Berit Sletbakk; Berg, Jens Petter; Brandtzæg, Petter & Henriksson, Carola (2014). Microparticle-associated tissue factor activity correlates with plasma levels of bacterial lipopolysaccharides in meningocoocal septic shock. Thrombosis Research. ISSN 0049-3848. 133(3), s. 507–514. doi: 10.1016/j.thromres.2013.12.031. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Iversen, Nina; Sletten, Marit; Hellum, Marit Synnøve; Skogstad, Marie Jeanette; Chollet, Maria Eugenia & Skarpen, Ellen [Vis alle 11 forfattere av denne artikkelen] (2019). Functional characterization of FV deficiency in Norway: Effects of F5 mutations on secretion, endoplasmic reticulum stress, apoptosis, and activated protein C sensitivity. Fulltekst i vitenarkiv

Se alle arbeider i NVA