Early Ascorbic Acid Administration Prevents Vascular Endothelial Cell Damage In Septic Mice

Ascorbic acid (AsA) therapy for sepsis is thought to have a protective effect on vascular endothelial cells, but the effect of AsA therapy on endothelial cell dysfunction over time and the appropriate timing for AsA administration to demonstrate efficacy is unclear. Septic mice, induced by cecal ligation and puncture (CLP), were examined for the effect of AsA administration (200 mg/kg) on vascular endothelial cell dysfunction at two administration timings: early group (AsA was administered immediately after CLP) and late group (AsA was administered 12 h after CLP). Survival rates were compared between the early and late administration groups, and vascular endothelial cell damage, indicated by the dihydrobiopterin/tetrahydrobiopterin ratio, serum syndecan-1, and endothelial nitric oxide synthase, as well as liver damage, were examined. The early group showed significantly improved survival compared to the non-treatment group (p < 0.05), while the late group showed no improved survival compared to the non-treatment group. Early AsA administration suppressed damage to the vascular endothelial system and liver compared to the non-treatment group. In septic mice, early AsA administration immediately after CLP may have protective effects on vascular endothelial cells, resulting in reduced organ dysfunction and improved survival.

New insights into the development of radiation-induced cardiac damage using a mouse model

Background The improvement of anticancer-therapy results in a greater amount of long-term survivors after radiotherapy. Therefore, the understanding of cardiotoxicity after irradiation is of increasing importance. Long-term adverse cardiovascular events may become evident years or decades after radiotherapy. The relative contribution of irradiation in relation to other cancer treatments can often only be estimated. Recent experimental and clinical evidence suggests that cardiovascular symptoms, including exertional dyspnoea, may be caused by heart failure with preserved ejection fraction (HFpEF), which remains incompletely understood in patients after radiation therapy. Purpose We aim to characterize the development of radiation-induced cardiomyopathy and elucidate underlying patho-mechanisms. Methods Mice received a single dose of whole thorax irradiation (12.5 Gy) and were sacrificed at 1 and 3 days or 3, 6, 12, 16, 20 and 25–30 weeks. Endothelial cells and immune cells at different time points were quantified using flow cytometry (FACS). Structural changes and localization of endothelial cell damage was imaged using light-sheet fluorescence microscopy (LSFM) with CD31 staining. Development of fibrosis was determined using qRT-PCR (fibronectin and TGFβ), western blot (collagen-1,α-smooth muscle) and (immune-)histological analyses. Functional analyses were conducted using echocardiography and pressure-volume-(PV-)catheterization. Results Endothelial damage was determined by significant reduction of CD31 expression in mouse hearts 6 weeks after irradiation compared to sham-treated control mice using FACS analyses. LSFM showed structural changes especially in the edge zone of left ventricle presented as less densely CD31 stained regions. Additionally, we investigated cardiac immune cell response regarding innate and adaptive immunity, showing specific response to tissue damage at different time points. Invasion of monocytes started 6 weeks after irradiation and highest level of monocytes and macrophages was measured at 12 weeks. Regarding cardiac long-term damage, myocardial fibrosis was detected on RNA- and protein-level as well as in histological analyses with significant changes 20 weeks after chest irradiation. This could be correlated with echocardiographic parameters for diastolic dysfunction (elevated isovolumic relaxation time/mitral valve deceleration time). Also functional reserve of irradiated mice was reduced, investigated by measurement of cardiac output and stroke volume after dobutamine injection in PV-catheterization. Conclusion We described a novel time-dependent endothelial cell damage and immune cell response after thoracic irradiation in mice, which could also be imaged using LSFM. Characterization of long-term damage showed cardiac fibrosis correlating with diastolic dysfunction and reduced contractile reserve. Furthermore, therapeutic approaches will be investigated using the established mouse model. FUNDunding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Dr. S.M. Mrotzek acknowledges the following funding source: IFORES research grant from the Medical Faculty, University Duisburg-Essen, Germany.

Early Ascorbic Acid Administration Prevents Vascular Endothelial Cell Damage in Septic Mice

Background: Ascorbic acid (AsA) therapy for sepsis is thought to have a protective effect on vascular endothelial cells. However, the effect of AsA therapy on endothelial cell dysfunction over time and the appropriate timing for AsA administration to demonstrate efficacy is unclear.Methods: Septic mice were induced by cecal ligation and puncture (CLP). The effect of AsA administration (200 mg/kg) on vascular endothelial cell dysfunction in sepsis was examined using septic mice at two administration timings: early group (AsA was administered immediately after CLP) and late group (AsA was administered 12 h after CLP). First, survival rates were compared between the early and late administration groups. Next, the dihydrobiopterin/tetrahydrobiopterin (BH2/BH4) ratio, serum syndecan-1, and endothelial nitric oxide synthase (eNOS) were measured as indicators of vascular endothelial cell damage, and liver tissue was examined for organ damage to verify the effect of early AsA administration in septic mice.Results: In survival experiments, the early group showed significantly improved survival compared to the non-treatment group (p < 0.05), while the late group showed no improved survival compared to the non-treatment group. The BH2/BH4 ratio increased after 6 hours following CLP, and the increase was suppressed by early AsA administration (0.12 ± 0.02 vs. 0.07 ± 0.016, p < 0.05). Serum syndecan-1 levels were significantly elevated at 12 h after CLP, and early AsA administration prevented the increase (25.4 ± 12.1 vs. 9.9 ± 2.7 mg/ml, p < 0.05). The expression of eNOS at 12 h after CLP was decreased in the non-treatment group, but the expression was protected by early AsA administration. Moreover, hematoxylin and eosin staining of hepatocytes showed reduced liver damage in the early group compared to the non-treatment group.Conclusions: In septic mice, early AsA administration immediately after CLP may have protective effects on vascular endothelial cells by decreasing the BH2/BH4 ratio, resulting in reduced organ dysfunction and improved survival. To achieve this effect, early administration of AsA is required before BH4 is oxidized.