Vitamin C promotes wound healing through novel pleiotropic mechanisms.

Vitamin C (VitC) or ascorbic acid (AscA), a cofactor for collagen synthesis and a primary antioxidant, is rapidly consumed post-wounding. Parenteral VitC administration suppresses pro-inflammatory responses while promoting anti-inflammatory and pro-resolution effects in human/murine sepsis. We hypothesised that VitC could promote wound healing by altering the inflammatory, proliferative and remodelling phases of wound healing. Mice unable to synthesise VitC (Gulo(-/-) ) were used in this study. VitC was provided in the water (sufficient), withheld from another group (deficient) and supplemented by daily intra-peritoneal infusion (200 mg/kg, deficient + AscA) in a third group. Full thickness excisional wounds (6 mm) were created and tissue collected on days 7 and 14 for histology, quantitative polymerase chain reaction (qPCR) and Western blotting. Human neonatal dermal fibroblasts (HnDFs) were used to assess effects of In conclusion, VitC favorably on proliferation. Histological analysis showed improved wound matrix deposition and organisation in sufficient and deficient +AscA mice. Wounds from VitC sufficient and deficient + AscA mice had reduced expression of pro-inflammatory mediators and higher expression of wound healing mediators. Supplementation of HnDF with AscA induced the expression of self-renewal genes and promoted fibroblast proliferation. VitC favourably impacts the spatiotemporal expression of transcripts associated with early resolution of inflammation and tissue remodelling.

Phase I safety trial of intravenous ascorbic acid in patients with severe sepsis.

BACKGROUND: Parenterally administered ascorbic acid modulates sepsis-induced inflammation and coagulation in experimental animal models. The objective of this randomized, double-blind, placebo-controlled, phase I trial was to determine the safety of intravenously infused ascorbic acid in patients with severe sepsis. METHODS: Twenty-four patients with severe sepsis in the medical intensive care unit were randomized 1:1:1 to receive intravenous infusions every six hours for four days of ascorbic acid: Lo-AscA (50 mg/kg/24 h, n = 8), or Hi-AscA (200 mg/kg/24 h, n = 8), or Placebo (5% dextrose/water, n = 8). The primary end points were ascorbic acid safety and tolerability, assessed as treatment-related adverse-event frequency and severity. Patients were monitored for worsened arterial hypotension, tachycardia, hypernatremia, and nausea or vomiting. In addition Sequential Organ Failure Assessment (SOFA) scores and plasma levels of ascorbic acid, C-reactive protein, procalcitonin, and thrombomodulin were monitored. RESULTS: Mean plasma ascorbic acid levels at entry for the entire cohort were 17.9 ± 2.4 µM (normal range 50-70 µM). Ascorbic acid infusion rapidly and significantly increased plasma ascorbic acid levels. No adverse safety events were observed in ascorbic acid-infused patients. Patients receiving ascorbic acid exhibited prompt reductions in SOFA scores while placebo patients exhibited no such reduction. Ascorbic acid significantly reduced the proinflammatory biomarkers C-reactive protein and procalcitonin. Unlike placebo patients, thrombomodulin in ascorbic acid infused patients exhibited no significant rise, suggesting attenuation of vascular endothelial injury. CONCLUSIONS: Intravenous ascorbic acid infusion was safe and well tolerated in this study and may positively impact the extent of multiple organ failure and biomarkers of inflammation and endothelial injury. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT01434121.

Resolution of sterile inflammation: role for vitamin C.

INTRODUCTION: Macrophage reprogramming is vital for resolution of acute inflammation. Parenteral vitamin C (VitC) attenuates proinflammatory states in murine and human sepsis. However information about the mechanism by which VitC regulates resolution of inflammation is limited. METHODS: To examine whether physiological levels of VitC modulate resolution of inflammation, we used transgenic mice lacking L-gulono-γ-lactone oxidase. VitC sufficient/deficient mice were subjected to a thioglycollate-elicited peritonitis model of sterile inflammation. Some VitC deficient mice received daily parenteral VitC (200 mg/kg) for 3 or 5 days following thioglycollate infusion. Peritoneal macrophages harvested on day 3 or day 5 were examined for intracellular VitC levels, pro- and anti-inflammatory protein and lipid mediators, mitochondrial function, and response to lipopolysaccharide (LPS). The THP-1 cell line was used to determine the modulatory activities of VitC in activated human macrophages. RESULTS: VitC deficiency significantly delayed resolution of inflammation and generated an exaggerated proinflammatory response to in vitro LPS stimulation. VitC sufficiency and in vivo VitC supplementation restored macrophage phenotype and function in VitC deficient mice. VitC loading of THP-1 macrophages attenuated LPS-induced proinflammatory responses. CONCLUSION: VitC sufficiency favorably modulates macrophage function. In vivo or in vitro VitC supplementation restores macrophage phenotype and function leading to timely resolution of inflammation.

Mechanisms of attenuation of abdominal sepsis induced acute lung injury by ascorbic acid.

Bacterial infections of the lungs and abdomen are among the most common causes of sepsis. Abdominal peritonitis often results in acute lung injury (ALI). Recent reports demonstrate a potential benefit of parenteral vitamin C [ascorbic acid (AscA)] in the pathogenesis of sepsis. Therefore we examined the mechanisms of vitamin C supplementation in the setting of abdominal peritonitis-mediated ALI. We hypothesized that vitamin C supplementation would protect lungs by restoring alveolar epithelial barrier integrity and preventing sepsis-associated coagulopathy. Male C57BL/6 mice were intraperitoneally injected with a fecal stem solution to induce abdominal peritonitis (FIP) 30 min prior to receiving either AscA (200 mg/kg) or dehydroascorbic acid (200 mg/kg). Variables examined included survival, extent of ALI, pulmonary inflammatory markers (myeloperoxidase, chemokines), bronchoalveolar epithelial permeability, alveolar fluid clearance, epithelial ion channel, and pump expression (aquaporin 5, cystic fibrosis transmembrane conductance regulator, epithelial sodium channel, and Na(+)-K(+)-ATPase), tight junction protein expression (claudins, occludins, zona occludens), cytoskeletal rearrangements (F-actin polymerization), and coagulation parameters (thromboelastography, pro- and anticoagulants, fibrinolysis mediators) of septic blood. FIP-mediated ALI was characterized by compromised lung epithelial permeability, reduced alveolar fluid clearance, pulmonary inflammation and neutrophil sequestration, coagulation abnormalities, and increased mortality. Parenteral vitamin C infusion protected mice from the deleterious consequences of sepsis by multiple mechanisms, including attenuation of the proinflammatory response, enhancement of epithelial barrier function, increasing alveolar fluid clearance, and prevention of sepsis-associated coagulation abnormalities. Parenteral vitamin C may potentially have a role in the management of sepsis and ALI associated with sepsis.

Biological Effects of Intravenous Vitamin C on Neutrophil Extracellular Traps and the Endothelial Glycocalyx in Patients with Sepsis-Induced ARDS.

(1) Background: The disease-modifying mechanisms of high-dose intravenous vitamin C (HDIVC) in sepsis induced acute respiratory distress syndrome (ARDS) is unclear. (2) Methods: We performed a post hoc study of plasma biomarkers from subjects enrolled in the randomized placebo-controlled trial CITRIS-ALI. We explored the effects of HDIVC on cell-free DNA (cfDNA) and syndecan-1, surrogates for neutrophil extracellular trap (NET) formation and degradation of the endothelial glycocalyx, respectively. (3) Results: In 167 study subjects, baseline cfDNA levels in HDIVC (84 subjects) and placebo (83 subjects) were 2.18 ng/µL (SD 4.20 ng/µL) and 2.65 ng/µL (SD 3.87 ng/µL), respectively, p = 0.45. At 48-h, the cfDNA reduction was 1.02 ng/µL greater in HDIVC than placebo, p = 0.05. Mean baseline syndecan-1 levels in HDIVC and placebo were 9.49 ng/mL (SD 5.57 ng/mL) and 10.83 ng/mL (SD 5.95 ng/mL), respectively, p = 0.14. At 48 h, placebo subjects exhibited a 1.53 ng/mL (95% CI, 0.96 to 2.11) increase in syndecan-1 vs. 0.75 ng/mL (95% CI, 0.21 to 1.29, p = 0.05), in HDIVC subjects. (4) Conclusions: HDIVC infusion attenuated cell-free DNA and syndecan-1, biomarkers associated with sepsis-induced ARDS. Improvement of these biomarkers suggests amelioration of NETosis and shedding of the vascular endothelial glycocalyx, respectively.

Ascorbic acid attenuates lipopolysaccharide-induced acute lung injury.

OBJECTIVE: Sepsis-induced lung injury is a persisting clinical problem with no direct therapy. Recent work suggests that intravenously infused ascorbic acid improves the circulatory dysfunction of sepsis. We used a model of endotoxin-induced acute lung injury to determine whether parenteral ascorbic acid modulates the dysregulated proinflammatory, procoagulant state that leads to lung injury. DESIGN: C57BL/6 mice were exposed to lethal lipopolysaccharide doses (10 µg/g of body weight) to induce acute lung injury. SETTING: Laboratory investigation. SUBJECTS: Wild-type C57BL/6 mice. INTERVENTIONS: Ascorbic acid or its oxidized form (dehydroascorbic acid) was administered intraperitoneally at 200 mg/kg 30 mins after the lethal lipopolysaccharide dose. MEASUREMENTS AND MAIN RESULTS: We quantified survival, lung capillary leak, proinflammatory chemokine expression, and lung microvascular thrombosis. Lipopolysaccharide induced 100% lethality in mice within 28 hrs of exposure and in lung we observed intense neutrophil sequestration, loss of capillary barrier function, exuberant pulmonary inflammation, and extensive microthrombus formation. A time-delayed infusion protocol of both ascorbic acid and dehydroascorbic acid significantly prolonged survival. Both ascorbic acid and dehydroascorbic acid preserved lung architecture and barrier function while attenuating proinflammatory chemokine expression and microvascular thrombosis. Ascorbic acid and dehydroascorbic acid attenuated nuclear factor kappa B activation and normalized coagulation parameters. CONCLUSIONS: Ascorbic acid administered in an interventional manner following lipopolysaccharide infusion attenuates proinflammatory, procoagulant states that induce lung vascular injury in an animal model of sepsis.

The Emerging Role of Vitamin C as a Treatment for Sepsis.

Sepsis, a life-threatening organ dysfunction due to a dysregulated host response to infection, is a leading cause of morbidity and mortality worldwide. Decades of research have failed to identify any specific therapeutic targets outside of antibiotics, infectious source elimination, and supportive care. More recently, vitamin C has emerged as a potential therapeutic agent to treat sepsis. Vitamin C has been shown to be deficient in septic patients and the administration of high dose intravenous as opposed to oral vitamin C leads to markedly improved and elevated serum levels. Its physiologic role in sepsis includes attenuating oxidative stress and inflammation, improving vasopressor synthesis, enhancing immune cell function, improving endovascular function, and epigenetic immunologic modifications. Multiple clinical trials have demonstrated the safety of vitamin C and two recent studies have shown promising data on mortality improvement. Currently, larger randomized controlled studies are underway to validate these findings. With further study, vitamin C may become standard of care for the treatment of sepsis, but given its safety profile, current treatment can be justified with compassionate use.

A Preliminary Investigation towards the Risk Stratification of Allogeneic Stem Cell Recipients with Respect to the Potential for Development of GVHD via Their Pre-Transplant Plasma Lipid and Metabolic Signature.

The clinical outcome of allogeneic hematopoietic stem cell transplantation (SCT) may be influenced by the metabolic status of the recipient following conditioning, which in turn may enable risk stratification with respect to the development of transplant-associated complications such as graft vs. host disease (GVHD). To better understand the impact of the metabolic profile of transplant recipients on post-transplant alloreactivity, we investigated the metabolic signature of 14 patients undergoing myeloablative conditioning followed by either human leukocyte antigen (HLA)-matched related or unrelated donor SCT, or autologous SCT. Blood samples were taken following conditioning and prior to transplant on day 0 and the plasma was comprehensively characterized with respect to its lipidome and metabolome via liquid chromatography/mass spectrometry (LCMS) and gas chromatography/mass spectrometry (GCMS). A pro-inflammatory metabolic profile was observed in patients who eventually developed GVHD. Five potential pre-transplant biomarkers, 2-aminobutyric acid, 1-monopalmitin, diacylglycerols (DG 38:5, DG 38:6), and fatty acid FA 20:1 demonstrated high sensitivity and specificity towards predicting post-transplant GVHD. The resulting predictive model demonstrated an estimated predictive accuracy of risk stratification of 100%, with area under the curve of the ROC of 0.995. The likelihood ratio of 1-monopalmitin (infinity), DG 38:5 (6.0), and DG 38:6 (6.0) also demonstrated that a patient with a positive test result for these biomarkers following conditioning and prior to transplant will be at risk of developing GVHD. Collectively, the data suggest the possibility that pre-transplant metabolic signature may be used for risk stratification of SCT recipients with respect to development of alloreactivity.

Temporal map of the pig polytrauma plasma proteome with fluid resuscitation and intravenous vitamin C treatment.

BACKGROUND: Fluid resuscitation plays a prominent role in stabilizing trauma patients with hemorrhagic shock yet there remains uncertainty with regard to optimal administration time, volume, and fluid composition (e.g., whole blood, component, colloids) leading to complications such as trauma-induced coagulopathies (TIC), acidosis, and poor oxygen transport. Synthetic fluids in combination with antioxidants (e.g., vitamin C) may resolve some of these problems. OBJECTIVES: We applied quantitative mass spectrometry-based proteomics [liquid chromatography-mass spectrometry (LC-MS/MS)] to map the effects of fluid resuscitation and intravenous vitamin C (VitC) in a pig model of polytrauma (hemorrhagic shock, tissue injury, liver reperfusion, hypothermia, and comminuted bone fracture). The goal was to determine the effects of VitC on plasma protein expression, with respect to changes associated with coagulation and trauma-induced coagulopathy (TIC). METHODS: Longitudinal blood samples were drawn from nine male Sinclair pigs at baseline, 2 h post trauma, and 0.25, 2, and 4 h post fluid resuscitation with 500 mL hydroxyethyl starch. Pigs were treated intravenously (N = 3/treatment group) with saline, 50 mg VitC/kg (Lo-VitC), or 200 mg VitC/kg (Hi-VitC) during fluid resuscitation. RESULTS: A total of 436 plasma proteins were quantified of which 136 changed following trauma and resuscitation; 34 were associated with coagulation, complement cascade, and glycolysis. Unexpectedly, Lo-VitC and Hi-VitC treatments stabilized ADAMTS13 levels by ~4-fold (P = .056) relative to saline and enhanced ADAMTS13/von Willebrand factor (VWF) cleavage efficiency based on LC-MS/MS evidence for the semitryptic VWF cleavage product (VWF1275-1286 ). CONCLUSIONS: This study provides the first comprehensive map of trauma-induced changes to the plasma proteome, especially with respect to proteins driving the development of TIC.

Hypoxia inducible factor-1 activation by prolyl 4-hydroxylase-2 gene silencing attenuates myocardial ischemia reperfusion injury.

Hypoxia inducible factor-1 (HIF-1) regulates changes in transcription of key genes such as inducible NO synthase (iNOS) in hypoxic/ischemic environments. In normoxia, HIF-1 activation is controlled by HIF-1alpha-prolyl 4-hydroxylases, which target HIF-1alpha for ubiquitination and proteasomal degradation. We hypothesized that normoxic HIF-1 preservation could attenuate cardiac ischemia/reperfusion injury via a preconditioning effect. HIF-1 preservation was achieved by using small interfering RNA (siRNA) to silence murine HIF-1alpha-prolyl-4 hydroxylase-2 (PHD2). PHD2 siRNA reduced PHD2 mRNA expression 89+/-1.5% (P<0.001) in a time- and concentration-dependent manner in normoxic murine microvascular endothelial cells (EC). PHD2 silencing in normoxic EC stabilized HIF-1alpha protein levels while significantly increasing HIF-1 transcriptional activity and iNOS mRNA expression. Wild-type mice infused with PHD2 siRNA (1.5 microg/g body weight) showed a 61+/-2.4% (P<0.05) reduction in cardiac PHD2 mRNA within 24 hours. In addition HIF-1alpha protein levels and HIF-1-dependent iNOS mRNA levels were increased. PHD2 siRNA-transfected hearts from wild-type mice (n=6) subjected to 30 minutes ischemia followed by 60 minutes reperfusion exhibited reduced infarct size when compared with saline-treated controls (9.7+/-1.9% versus 31.6+/-1.8%, respectively, P<0.0001, n=6) and to control mice transfected with a nontargeting siRNA control (28.4+/-3.0%, P<0.0001, n=6). Hearts from iNOS knockout mice receiving PHD2 siRNA by identical injection protocol (n=6) exhibited infarct size indistinguishable from saline controls (28.7+/-1.3%). These results show that in vitro and in vivo, PHD2 silencing using a siRNA strategy produces transcriptionally active HIF-1. Normoxic activation of HIF-1 in hearts following in vivo PHD2 siRNA administration attenuates reperfusion injury via an iNOS-dependent pathway.

Interventional vitamin C: A strategy for attenuation of coagulopathy and inflammation in a swine multiple injuries model.

BACKGROUND: Coagulopathy and inflammation induced by hemorrhagic shock and traumatic injury are associated with increased mortality and morbidity. Vitamin C (VitC) is an antioxidant with potential protective effects on the proinflammatory and procoagulant pathways. We hypothesized that high-dose VitC administered as a supplement to fluid resuscitation would attenuate inflammation, coagulation dysfunction, and end-organ tissue damage in a swine model of multiple injuries and hemorrhage. METHODS: Male Sinclair swine (n = 24; mean body weight, 27 kg) were anesthetized, intubated, mechanically ventilated, and instrumented for physiologic monitoring. Following stabilization, swine were subjected to shock/traumatic injury (hypothermia, liver ischemia and reperfusion, comminuted femur fracture, hemorrhagic hypotension), resuscitated with 500 mL of hydroxyethyl starch, and randomized to receive either intravenous normal saline (NS), low-dose VitC (50 mg/kg; LO), or high-dose VitC (200 mg/kg; HI). Hemodynamics, blood chemistry, hematology, and coagulation function (ROTEM) were monitored to 4 hours postresuscitation. Histological and molecular analyses were obtained for liver, kidney, and lung. RESULTS: Compared with VitC animals, NS swine showed significant histological end-organ damage, elevated acute lung injury scores, and increased mRNA expression of tissue proinflammatory mediators (IL-1ß, IL-8, TNFα), plasminogen activation inhibitor-1 and tissue factor. There were no statistically significant differences between treatment groups on mean arterial pressure or univariate measures of coagulation function; however, NS showed impaired multivariate clotting function at 4 hours. CONCLUSION: Although correction of coagulation dysfunction was modest, intravenous high-dose VitC may mitigate the proinflammatory/procoagulant response that contributes to multiple organ failure following acute severe multiple injuries. LEVEL OF EVIDENCE: Prospective randomized controlled blinded trial study, Preclinical (animal-based).

Redox Potential Measurements in Red Blood Cell Packets Using Nanoporous Gold Electrodes.

The redox potential of packed red blood cells (RBCs) was measured over a 56-day storage period using a newly developed potentiometric methodology consisting of a nanoporous gold electrode and a silver chloride coated silver reference electrode. Both milliliter- and microliter-sized volumes were separately evaluated. The addition of Vitamin C (VitC) in differing doses to the packed RBCs was also assessed as a means to improve redox stability and prolong storage duration. For RBCs containing only saline, the open-circuit potential (OCP) was ∼ -80 mV vs Ag/AgCl and drifted slightly with time; greater differences were also noted between different electrodes. The addition of exogenous VitC to the RBC shifts the OCP to more negative values, stabilizes the redox potential, and improves reproducibly between different electrodes due to the poising of blood. Over the 56-day storage period, the redox potential of the RBCs increased slightly, which can be attributed to change in pH and/or increasing oxidative stress during storage. Cyclic voltammograms acquired after open-circuit potential measurements showed a characteristic peak attributed to the oxidation of VitC. This peak decreased during storage with a time constant of 20.8 days. Likewise, the intercellular concentration of VitC increased with a time constant of 20.2 days as measured using a fluorescence assay. Collectively, these results demonstrate the usefulness of electrochemical measurements in the study of stored blood products.

Attenuation of Red Blood Cell Storage Lesions with Vitamin C.

Stored red blood cells (RBCs) undergo oxidative stress that induces deleterious metabolic, structural, biochemical, and molecular changes collectively referred to as "storage lesions". We hypothesized that vitamin C (VitC, reduced or oxidized) would reduce red cell storage lesions, thus prolonging their storage duration. Whole-blood-derived, leuko-reduced, SAGM (saline-adenine-glucose-mannitol)-preserved RBC concentrates were equally divided into four pediatric storage bags and the following additions made: (1) saline (saline); (2) 0.3 mmol/L reduced VitC (Lo VitC); (3) 3 mmol/L reduced VitC (Hi VitC); or (4) 0.3 mmol/L oxidized VitC (dehydroascorbic acid, DHA) as final concentrations. Biochemical and rheological parameters were serially assessed at baseline (prior to supplementation) and Days 7, 21, 42, and 56 for RBC VitC concentration, pH, osmotic fragility by mechanical fragility index, and percent hemolysis, LDH release, glutathione depletion, RBC membrane integrity by scanning electron microscopy, and Western blot for ß-spectrin. VitC exposure (reduced and oxidized) significantly increased RBC antioxidant status with varying dynamics and produced trends in reduction in osmotic fragility and increases in membrane integrity. CONCLUSION: VitC partially protects RBC from oxidative changes during storage. Combining VitC with other antioxidants has the potential to improve long-term storage of RBC.

Intravenous vitamin C as adjunctive therapy for enterovirus/rhinovirus induced acute respiratory distress syndrome.

We report a case of virus-induced acute respiratory distress syndrome (ARDS) treated with parenteral vitamin C in a patient testing positive for enterovirus/rhinovirus on viral screening. This report outlines the first use of high dose intravenous vitamin C as an interventional therapy for ARDS, resulting from enterovirus/rhinovirus respiratory infection. From very significant preclinical research performed at Virginia Commonwealth University with vitamin C and with the very positive results of a previously performed phase I safety trial infusing high dose vitamin C intravenously into patients with severe sepsis, we reasoned that infusing identical dosing to a patient with ARDS from viral infection would be therapeutic. We report here the case of a 20-year-old, previously healthy, female who contracted respiratory enterovirus/rhinovirus infection that led to acute lung injury and rapidly to ARDS. She contracted the infection in central Italy while on an 8-d spring break from college. During a return flight to the United States, she developed increasing dyspnea and hypoxemia that rapidly developed into acute lung injury that led to ARDS. When support with mechanical ventilation failed, extracorporeal membrane oxygenation (ECMO) was initiated. Twelve hours following ECMO initiation, high dose intravenous vitamin C was begun. The patient's recovery was rapid. ECMO and mechanical ventilation were discontinued by day-7 and the patient recovered with no long-term ARDS sequelae. Infusing high dose intravenous vitamin C into this patient with virus-induced ARDS was associated with rapid resolution of lung injury with no evidence of post-ARDS fibroproliferative sequelae. Intravenous vitamin C as a treatment for ARDS may open a new era of therapy for ARDS from many causes.

Impact of high dose vitamin C on platelet function.

AIM: To examine the effect of high doses of vitamin C (VitC) on ex vivo human platelets (PLTs). METHODS: Platelet concentrates collected for therapeutic or prophylactic transfusions were exposed to: (1) normal saline (control); (2) 0.3 mmol/L VitC (Lo VitC); or (3) 3 mmol/L VitC (Hi VitC, final concentrations) and stored appropriately. The VitC additive was preservative-free buffered ascorbic acid in water, pH 5.5 to 7.0, adjusted with sodium bicarbonate and sodium hydroxide. The doses of VitC used here correspond to plasma VitC levels reported in recently completed clinical trials. Prior to supplementation, a baseline sample was collected for analysis. PLTs were sampled again on days 2, 5 and 8 and assayed for changes in PLT function by: Thromboelastography (TEG), for changes in viscoelastic properties; aggregometry, for PLT aggregation and adenosine triphosphate (ATP) secretion in response to collagen or adenosine diphosphate (ADP); and flow cytometry, for changes in expression of CD-31, CD41a, CD62p and CD63. In addition, PLT intracellular VitC content was measured using a fluorimetric assay for ascorbic acid and PLT poor plasma was used for plasma coagulation tests [prothrombin time (PT), partial thrombplastin time (PTT), functional fibrinogen] and Lipidomics analysis (UPLC ESI-MS/MS). RESULTS: VitC supplementation significantly increased PLTs intracellular ascorbic acid levels from 1.2 mmol/L at baseline to 3.2 mmol/L (Lo VitC) and 15.7 mmol/L (Hi VitC, P < 0.05). VitC supplementation did not significantly change PT and PTT values, or functional fibrinogen levels over the 8 d exposure period (P > 0.05). PLT function assayed by TEG, aggregometry and flow cytometry was not significantly altered by Lo or Hi VitC for up to 5 d. However, PLTs exposed to 3 mmol/L VitC for 8 d demonstrated significantly increased R and K times by TEG and a decrease in the α-angle (P < 0.05). There was also a fall of 20 mm in maximum amplitude associated with the Hi VitC compared to both baseline and day 8 saline controls. Platelet aggregation studies, showed uniform declines in collagen and ADP-induced platelet aggregations over the 8-d study period in all three groups (P > 0.05). Collagen and ADP-induced ATP secretion was also not different between the three groups (P > 0.05). Finally, VitC at the higher dose (3 mmol/L) also induced the release of several eicosanoids including thromboxane B2 and prostaglandin E2, as well as products of arachidonic acid metabolism via the lipoxygenases pathway such as 11-/12-/15-hydroxyicosatetraenoic acid (P < 0.05). CONCLUSION: Alterations in PLT function by exposure to 3 mmol/L VitC for 8 d suggest that caution should be exerted with prolonged use of intravenous high dose VitC.

Regulation of hypoxia inducible factor-1 by nitric oxide in contrast to hypoxia in microvascular endothelium.

Hypoxia activates the transcription factor, hypoxia inducible factor-1 (HIF-1). Besides hypoxia, HIF-1 can be activated under normoxic conditions by nitric oxide. The signal transduction pathways involved in HIF-1alpha stabilization, HIF-1 DNA binding and transactivation by NO and hypoxia in microvascular endothelium remains unknown. We report that protein phosphorylation is involved in HIF-1 activation during hypoxia and NO. The phosphatidylinositol 3-kinase (PI-3K)/Akt pathway has differential effects on HIF-1 activation by hypoxia and NO. Our data indicate that the PI-3K/Akt pathway is insufficient for HIF-1alpha induction by hypoxia. The lipid and protein phosphatase activities of PTEN also appear to be involved in regulation of HIF-1alpha by NO.

Atypical mechanism of NF-kappaB activation during reoxygenation stress in microvascular endothelium: a role for tyrosine kinases.

The transcription factor nuclear factor kappaB (NF-kappaB) regulates genes that contribute to acute inflammatory reactions in cytokine-activated endothelium. Tumor necrosis factor activates NF-kappaB through serine phosphorylation, induced by inhibitor kappaB kinases (IKK), and subsequent degradation of inhibitor kappaB (IkappaB). In contrast to cytokine stress, our studies show that oxidative stress, generated by exposure to hypoxia followed by reoxygenation (H/R), failed to activate IKK in human microvascular endothelial cells (HMEC-1). We report an alternative mechanism for NF-kappaB activation during H/R stress without IkappaBalpha degradation. This mechanism involves activation of protein tyrosine kinases (PTK) that phosphorylate IkappaBalpha with peak phosphorylation occurring after 30 min of reoxygenation. Involvement of PTK was reinforced by the demonstration that the PTK inhibitor, herbimycin A, prevented H/R-mediated NF-kappaB activation. Tyrosine phosphorylation alters the association between IkappaBalpha and NF-kappaB with sufficient intensity to allow transient NF-kappaB translocation to the cell nuclei within 45 min of onset of reoxygenation stress. Immunofluorescence imaging of NF-kappaB protein reveals it to be shuttled between the nucleus and cytoplasm within 90 min of reoxygenation. Furthermore, IkappaBalpha appears to be associated with NF-kappaB during the nucleo-cytoplasmic shuttling and is thus protected from degradation. Overall, these studies suggest that tyrosine phosphorylation of IkappaBalpha represents a proteolysis-independent mechanism of NF-kappaB activation that can be targeted for preventing H/R-mediated injury without affecting normal inflammatory responses.

Reoxygenating microvascular endothelium exhibits temporal dissociation of NF-kappaB and AP-1 activation.

Alterations of cellular redox balance in microvascular endothelium results in changes of essential cell functions. These alterations may arise, in part, due to modifications in the pattern of gene expression produced by transcription factor activation. Endothelium subjected to hypoxia/reoxygenation becomes redox imbalanced, thereby leading to activation and perhaps production of a proinflammatory state. A human dermal microvascular endothelial cell line (HMEC-1) was exposed to 6 h of hypoxia (3% O(2)) followed by return to normoxia atmospheric conditions. Reactive oxygen species (ROS) generation (dichlorofluoroscein epifluorescence) was immediate and significant following reoxygenation. Electrophoretic mobility shift assays revealed activation of the oxidant sensitive transcription factors NFkappaB and AP-1, though importantly, peak activation of each factor was separated temporally by greater than 60 min. NFkappaB activation occurred without degradation of the inhibitory protein IkappaBalpha. Reoxygenating HMEC-1 exhibited a greater than 500-fold increase in polymorphonuclear neutrophil (PMN) adhesion when compared to normoxic controls. Exposure of reoxygenating HMEC-1 to the antioxidant pyrrolidine dithiocarbamate produced complete abrogation of NFkappaB activation and the intensive PMN adhesion observed in untreated, posthypoxic HMEC-1. Though rexoygenation stress induced significant upregulation of PMN adhesion, no upregulation of interleukin-8 production was observed. Our results suggest that ROS generation occurring in endothelium following onset of reoxygenation stress signals activation of key transcription factors and that their activation takes place in a temporal fashion. The temporal feature of transcription factor activation may be key to production of a postischemic proinflammatory state.

Attenuation of sepsis-induced organ injury in mice by vitamin C.

BACKGROUND: Multiple organ dysfunction syndrome (MODS) is the principal cause of death in patients with sepsis. Recent work supports the notion that parenteral vitamin C (VitC) is protective in sepsis through pleiotropic mechanisms. Whether suboptimal levels of circulating VitC increase susceptibility to sepsis-induced MODS is unknown. MATERIALS AND METHODS: Unlike mice, humans lack the ability to synthesize VitC because of loss of L-gulono-γ-lactone oxidase (Gulo), the final enzyme in the biosynthesis of VitC. To examine whether physiological levels of VitC are required for defense against a catastrophic infection, we induced sepsis in VitC sufficient and VitC deficient Gulo(-/-) mice by intraperitoneal infusion of a fecal stem solution (FIP). Some VitC deficient Gulo(-/-) mice received a parenteral infusion of ascorbic acid (AscA, 200 mg/kg) 30 minutes after induction of FIP. We used molecular, histological, and biochemical analyses to assess for MODS as well as abnormalities in the coagulation system and circulating blood cells. RESULTS: FIP produced injury to lungs, kidneys and liver (MODS) in VitC deficient Gulo(-/-) mice. MODS was not evident in FIP-exposed VitC sufficient Gulo(-/-) mice and attenuated in VitC deficient Gulo(-/-) mice infused with AscA. Septic VitC deficient Gulo(-/-) mice developed significant abnormalities in the coagulation system and circulating blood cells. These were attenuated by VitC sufficiency/infusion in septic Gulo(-/-) mice. CONCLUSIONS: VitC deficient Gulo(-/-) mice were more susceptible to sepsis-induced MODS. VitC sufficiency or parenteral infusion of VitC, following induction of sepsis, normalized physiological functions that attenuated the development of MODS in sepsis.