Extracellular Actin Scavenger System Research Articles

Plasma gelsolin levels are associated with diabetes, sex, race, and poverty

BackgroundThe growing epidemic of the inflammation-related metabolic disease, type 2 diabetes mellitus, presents a challenge to improve our understanding of potential mechanisms or biomarkers to prevent or better control this age-associated disease. A gelsolin isoform is secreted into the plasma as part of the extracellular actin scavenger system which serves a protective role by digesting and removing actin filaments released from damaged cells. Recent data indicate a role for decreased plasma gelsolin (pGSN) levels as a biomarker of inflammatory conditions. Extracellular vesicles (EVs), a heterogeneous group of cell-derived membranous structures involved in intercellular signaling, have been implicated in metabolic and inflammatory diseases including type 2 diabetes mellitus. We examined whether pGSN levels were associated with EV concentration and inflammatory plasma proteins in individuals with or without diabetes.MethodsWe quantified pGSN longitudinally (n = 104) in a socioeconomically diverse cohort of middle-aged African American and White study participants with and without diabetes mellitus. Plasma gelsolin levels were assayed by ELISA. EV concentration (sub-cohort n = 40) was measured using nanoparticle tracking analysis. Inflammatory plasma proteins were assayed on the SomaScan® v4 proteomic platform.ResultspGSN levels were lower in men than women. White individuals with diabetes had significantly lower levels of pGSN compared to White individuals without diabetes and to African American individuals either with or without diabetes. For adults living below poverty, those with diabetes had lower pGSN levels than those without diabetes. Adults living above poverty had similar pGSN levels regardless of diabetes status. No correlation between EV concentrations and pGSN levels was identified (r = − 0.03; p = 0.85). Large-scale exploratory plasma protein proteomics revealed 47 proteins that significantly differed by diabetes status, 19 of which significantly correlated with pGSN levels, including adiponectin.ConclusionsIn this cohort of racially diverse individuals with and without diabetes, we found differences in pGSN levels with diabetes status, sex, race, and poverty. We also report significant associations of pGSN with the adipokine, adiponectin, and other inflammation- and diabetes-related proteins. These data provide mechanistic insights into the relationship of pGSN and diabetes.

Pathophysiological implications of actin-free Gc-globulin concentration changes in blood plasma and cerebrospinal fluid collected from patients with Alzheimer's disease and other neurological disorders.

The extracellular actin scavenging system (EASS) is composed of plasma Gc-globulin and gelsolin, and is responsible for the elimination of toxic actin from the bloodstream. In this study, we assessed the actin-free Gc-globulin concentrations in blood plasma and cerebrospinal fluid (CSF) obtained from subjects with neurodegenerative and inflammatory diseases of the central nervous system (CNS) as well as in a control group. Using an enzyme-linked immunosorbent assay (ELISA), we measured the actinfree Gc-globulin concentrations in blood plasma and CSF obtained from subjects diagnosed with Alzheimer's disease (AD) (n = 20), amyotrophic lateral sclerosis (ALS) (n = 12), multiple sclerosis (MS) (n = 42), tick-borne encephalitis (TBE) (n = 12), and from a control group (n = 20). The concentrations of free Gc-globulin in plasma collected from patients diagnosed with AD (509.6 ±87.6 mg/L) and ALS (455.5 ±99.8 mg/L) did not differ significantly between each other, but were significantly higher compared to the reference group (311.7 ±87.5 mg/L) (p < 0.001 and p < 0.006, respectively) as well as to MS (310.8 ±66.6 mg/L) (p < 0.001 and p < 0.001, respectively) and TBE (256.7 ±76 mg/L) (p < 0.001 and p < 0.003, respectively). In CSF collected from patients diagnosed with AD and ALS, the concentrations of free Gc-globulin were 2.6 ±1.1 mg/L and 2.7 ±1.9 mg/L, respectively. They did not differ significantly between each other and were significantly higher compared to the reference group (1.5 ±0.9 mg/L) (p < 0.005 and p < 0.041, respectively). Interestingly, in patients with AD, significantly higher values of Gcglobulin were detected compared to multiple sclerosis patients (1.7 ±0.9 mg/L) (p < 0.013). Higher concentrations of free Gc-globulin in blood plasma and CSF collected from patients suffering from neurodegenerative diseases may indicate a potential role of this protein in their pathogenesis, and represent a potential tool for the diagnosis of CNS diseases.

Persistent depletion of plasma gelsolin (pGSN) after exposure of mice to heavy silicon ions

Little is known about plasma proteins that can be used as biomarkers for early and late responses to radiation. The purpose of this study was to determine a link between depletion of plasma gelsolin (pGSN) and cell-death as well as inflammatory responses in the lung (one of the tissues known to be radiosensitive) of the same exposed CBA/CaJ mice after exposure to heavy silicon (28Si) ions. To prevent the development of multiple organ dysfunctions, pGSN (an important component of the extracellular actin-scavenging system) is responsible for the removal of actin that is released into the circulation during inflammation and from dying cells. We evaluated the levels of pGSN in plasma collected from groups of mice (5 mice in each) at 1 week (wk) and 1 month (1 mo) after exposure whole body to different doses of 28Si ions, i.e. 0, 0.1, 0.25, or 0.5 Gy (2 fractionated exposures, 15 days apart that totaled each selected dose). In the same mouse, the measurements of pGSN levels were coupled with the quantitation of injuries in the lung, determined by (a) the levels of cleaved poly (ADP-ribose) polymerase (cleaved-PARP), a marker of apoptotic cell-death, (b) the levels of activated nuclear factor-kappa B (NF-κB) and selected cytokines, i.e. tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and IL-6, from tissue-lysates of the lung. Further, the ratio of neutrophils and lymphocytes (N/L) was determined in the same mouse. Our data indicated: (i) the magnitude of pGSN depletion was dependent to radiation dose at both harvest times, (ii) a persistent depletion of pGSN up to 1 mo post-exposure to 0.25 or 0.5 Gy of 28Si ions, (iii) an inverse-correlation between pGSN depletion and increased levels of cleaved-PARP, including activated NF-κB/pro-inflammatory cytokines in the lung, and (iv) at both harvest times, statistically significant increases in the N/L ratio in groups of mice exposed to 0.5 Gy only. Our findings suggested that depletion in pGSN levels reflects not only the responses to 28Si-ion exposure at both harvest times but also early and late-occurring damage.

Plasma gelsolin improves lung host defense against pneumonia by enhancing macrophage NOS3 function.

Plasma gelsolin (pGSN) functions as part of the "extracellular actin-scavenging system," but its potential to improve host defense against infection has not been studied. In a mouse model of primary pneumococcal pneumonia, recombinant human pGSN (rhu-pGSN) caused enhanced bacterial clearance, reduced acute inflammation, and improved survival. In vitro, rhu-pGSN rapidly improved lung macrophage uptake and killing of bacteria (Streptococcus pneumoniae, Escherichia coli, and Francisella tularensis). pGSN triggers activating phosphorylation (Ser(1177)) of macrophage nitric oxide synthase type III (NOS3), an enzyme with important bactericidal functions in lung macrophages. rhu-pGSN failed to enhance bacterial killing by NOS3(-/-) macrophages in vitro or bacterial clearance in NOS3(-/-) mice in vivo. Prophylaxis with immunomodulators may be especially relevant for patients at risk for secondary bacterial pneumonia, e.g., after influenza. Treatment of mice with pGSN challenged with pneumococci on postinfluenza day 7 (the peak of enhanced susceptibility to secondary infection) caused a ∼15-fold improvement in bacterial clearance, reduced acute neutrophilic inflammation, and markedly improved survival, even without antibiotic therapy. pGSN is a potential immunomodulator for improving lung host defense against primary and secondary bacterial pneumonia.

The value of decreased plasma gelsolin levels in patients with systemic lupus erythematosus and rheumatoid arthritis in diagnosis and disease activity evaluation

Plasma gelsolin, the extracellular gelsolin isoform, circulates in the blood of healthy individuals at a concentration of 200 ± 50 mg/l and plays important roles in the extracellular actin-scavenging system during tissue damage. Decreased plasma gelsolin levels have been observed in many inflammatory diseases. In the present study, the variation and potential clinical application of plasma gelsolin levels in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) were analysed. Plasma samples and clinical data were collected from informed and consenting participants: 47 SLE patients, 60 RA patients and 50 age- and gender-matched healthy individuals. Semiquantitative western blotting was used for measuring plasma gelsolin levels. The plasma gelsolin levels in patients with SLE and RA were significantly decreased compared with healthy controls (145.3 ± 40.4 versus 182.7 ± 38.3 mg/l and 100.8 ± 36 versus 182.7 ± 38.3 mg/l, p < 0.001), and plasma gelsolin levels were especially lower in RA than in SLE patients (100.8 ± 36 versus 145.3 ± 40.4 mg/L, p < 0.001). An analysis of the clinical data showed a significant negative correlation between plasma gelsolin levels and SLE Disease Activity Index (SLEDAI) scores (r = 0.659, p < 0.001) but no correlation between plasma gelsolin levels and RA disease activity score 28 (DAS28) (r = 0.076, p = 0.569). Different clinical characteristics were also observed in SLE and RA patients with normal and decreased plasma gelsolin levels.This study found significantly lower plasma gelsolin levels in patients with SLE and RA compared with healthy controls and documented a significant negative correlation between plasma gelsolin levels and SLEDAI, which suggested the potential clinical application of plasma gelsolin in SLE diagnosis and disease activity evaluation. The different clinical characteristics in SLE and RA patients with normal and decreased plasma gelsolin levels indicate differences in the basis of the diseases.

Plasma gelsolin enhances lung macrophage host defense against bacterial pneumonia in mice

Plasma gelsolin (pGSN) functions as part of the ‘extracellular actin scavenging system’ but its potential to improve host defense against infection has not been studied. Mice (C57BL/6, male) were pre‐treated with recombinant human plasma gelsolin (rhu‐pGSN, 400 mg/kg, s.c.) or vehicle 2 h before infection with Strep. pneumoniae (serotype 3, 150K CFU, i.n.) and evaluated 24 h later. rhu‐pGSN caused enhanced bacterial clearance (% bacterial left alive in lungs, mean±SD: control, 88 ± 38 vs. rhu‐pGSN‐treated, 10 ± 5; n ≥ 13 mice/grp) and reduced acute inflammation (% BAL PMNs: control, 30 ± 11 vs. rhu‐pGSN‐treated, 8 ± 3). Similar results were seen with aerosolized rhu‐pGSN. In vitro, rhu‐pGSN rapidly improved lung macrophage uptake and killing of bacteria. rhu‐pGSN caused an activating phosphorylation (ser1177) of macrophage nitric oxide synthase type III (NOS3), which has important bactericidal functions in the AM. rhu‐pGSN failed to enhance bacterial killing in NOS3−/− macrophages. pGSN binds sphingosine‐1‐phosphate (S1P), and may enhance its delivery to the S1P1 receptor. Both S1P and the S1P mimic, FTY720P, enhanced macrophage uptake and killing of bacteria, and activated macrophage NOS3 as well. Plasma gelsolin enhances innate resistance to pneumococcal pneumonia via lung macrophage NOS3, and is a potential immunomodulator for improving lung host defense against bacterial pneumonia. Support: NIH ES00002 ES11008

Plasma gelsolin: A general prognostic marker of health

Plasma gelsolin (pGSN) is the only component of two member extracellular actin scavenger system capable of severing circulating actin microfilaments. Here, we put forth the hypothesis that pGSN level is an important and sensitive general prognostic biomarker for health and disease conditions in humans, urging the need for gelsolin replacement therapy to improve patient’s health status. Clinical significance and the therapeutic importance of this protein have been well illustrated in animal models as well as in patients with various diseases. Patients with decreased pGSN levels were observed to have higher mortality rate, longer hospital stay and longer ventilation time in intensive care units as compared to healthy controls. pGSN levels were found to be increasing in patients recovering from diseases; furthermore, it has been confirmed that repletion with exogenous recombinant pGSN increases the survival rate in animal models of different acute insults. To be used as a biomarker of health, however, establishing the accurate levels of gelsolin in human plasma and understanding its variance with age, race, gender and health status is a prerequisite. Upon establishing the accurate levels of pGSN in healthy individuals, this biomarker would predict the prognosis/disease progression in multiple health conditions and help in prioritizing the ones in-need of gelsolin replacement therapy.

Depletion of Plasma Gelsolin in Patients with Tick-Borne Encephalitis and Lyme Neuroborreliosis

Background/Aims: Cell damage during the course of inflammation results in cytoplasmic actin release, which if not eliminated by the extracellular actin scavenger system, composed of gelsolin and vitamin D binding protein, can cause dysfunction of hemostasis and toxicity towards surrounding cells. In this study, we test the hypothesis that an inflammatory reaction induced by central nervous system infections such as tick-borne encephalitis (TBE) or Lyme neuroborreliosis (LNB) will result in plasma gelsolin concentration changes in the blood and cerebrospinal fluid (CSF). Methods: Quantitative Western blot was used to determine gelsolin levels in 58 samples, which include: 29 patients without infection (diagnosed with conditions such as idiopathic cephalalgia, idiopathic Bell’s facial nerve palsy and ischialgia due to discopathy in which standard CSF diagnostic tests show no abnormalities), 12 patients diagnosed with TBE, and 17 patients diagnosed with LNB sub forma meningitis. Results and Conclusion: The gelsolin concentration in the blood of patients with TBE (163.2 ± 80.8 µg/ml) and LNB (113.6 ± 56.8 µg/ml) was significantly lower (p < 0.05 and p < 0.001, respectively) compared to the control group (226.3 ± 100.7 µg/ml). Furthermore, there was no statistically significant difference between the CSF gelsolin concentration in patients with TBE (3.9 ± 3.3 µg/ml), LNB (2.9 ± 1.2 µg/ml) and the control group (3.7 ± 3.3 µg/ml). An observed decrease in gelsolin concentration in the blood of TBE and LNB patients supports previous findings indicating the involvement of gelsolin in the pathophysiology of an inflammatory response. Therefore, evaluation of blood gelsolin concentration and administration of recombinant plasma gelsolin might provide a new tool to develop diagnostic and therapeutic strategies for TBE and LNB.

Hypogelsolinemia, a disorder of the extracellular actin scavenger system, in patients with multiple sclerosis

BackgroundExtracellular gelsolin (GSN) and GC-globulin/Vitamin D-binding protein (DBP) appear to play an important role in clearing the actin from extracellular fluids and in modulating cellular responses to anionic bioactive lipids. In this study we hypothesized that cellular actin release and/or increase in bioactive lipids associated with multiple sclerosis (MS) development will translate into alteration of the actin scavenger system protein concentrations in blood and cerebrospinal fluid (CSF) of patients with MS.MethodsWe measured GSN and DBP concentrations in blood and CSF obtained from patients diagnosed with MS (n = 56) in comparison to a control group (n = 20) that includes patients diagnosed with conditions such as idiopathic cephalgia (n = 11), idiopathic (Bell's) facial nerve palsy (n = 7) and ischialgia due to discopathy (n = 2). GSN and DBP levels were measured by Western blot and ELISA, respectively.ResultsWe found that the GSN concentration in the blood of the MS group (115 ± 78 μg/ml) was significantly lower (p < 0.001) compared to the control group (244 ± 96 μg/ml). In contrast, there was no statistically significant difference between blood DBP concentrations in patients with MS (310 ± 68 μg/ml) and the control group (314 ± 82 μg/ml). GSN and DBP concentrations in CSF also did not significantly differ between those two groups.ConclusionsThe decrease of GSN concentration in blood and CSF of MS subjects suggests that this protein may be involved in chronic inflammation associated with neurodegeneration. Additionally, the results presented here suggest the possible utility of GSN evaluation for diagnostic purposes. Reversing plasma GSN deficiency might represent a new strategy in MS treatment.

Evolution of vitamin D binding protein concentration in sera from cardiac surgery patients is determined by triglyceridemia

Multiple human and animal studies have reviewed the (non-)actin scavenger functions of vitamin D binding protein (DBP). Recently, we demonstrated the partially lipid bound character of DBP. The purpose of the present study was to explore the link between actin, lipids and DBP in a cohort of patients undergoing cardiac surgery. The interplay between DBP, actin and lipids was investigated in a cohort study of 35 Caucasian patients who underwent cardiac surgery. Total and actin-free DBP concentrations were assessed by immunonephelometry and ELISA. Total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, creatine kinase (-MB) and C-reactive protein (CRP) were measured using routine methods. Low-density lipoprotein cholesterol was calculated according to the Friedewald formula. The DBP phenotypes and the macromolecular bound DBP fractions were determined by polyacrylamide gel electrophoresis (PAGE) and confirmed by Western blotting. Using PAGE and Western blotting with an anti-human DBP polyclonal antibody, the actin-bound DBP complex was identified in serum. Following cardiac surgery, total serum DBP concentrations were characterized by a two phased course. This was paralleled by a similar pattern in serum total cholesterol, HDL-cholesterol and triglyceride concentrations. Good correlation was found between total and actin free serum DBP concentrations (r=0.69, p<0.0001). The serum actin free DBP/total DBP ratio remained stable throughout the study period. Although no significant correlation between cumulative CK-MB enzyme release and delta serum total DBP concentration was observed (p=NS), the latter value correlated significantly with delta serum triglyceride concentrations (r=0.37, p<0.05). The lipid bound character is an underestimated property of DBP in the extracellular actin-scavenger system.

Plasma Gelsolin: Function, Prognostic Value, and Potential Therapeutic Use

Gelsolin is a highly conserved, multifunctional actin-binding protein initially described in the cytosol of macrophages and subsequently identified in many vertebrate cells. A unique property of gelsolin is that in addition to its widely recognized function as a cytoplasmic regulator of actin organization, the same gene expresses a splice variant coding for a distinct isoform, plasma gelsolin, which is secreted into extracellular fluids. The secreted form of gelsolin has been implicated in a number of processes such as the extracellular actin scavenging system and the presentation of lysophosphatidic acid and other inflammatory mediators to their receptors, in addition to its function as a substrate for extracellular matrix-modulating enzymes. Consistent with these proposed functions, blood gelsolin levels decrease markedly in a variety of clinical conditions such as acute respiratory distress syndrome, sepsis, major trauma, prolonged hyperoxia, malaria, and liver injury. This correlation between blood gelsolin levels and critical clinical conditions suggests the potential utility of gelsolin as a prognostic marker as well as the possibility for therapeutic replenishment of gelsolin to alleviate the injurious cascades in these settings. This review summarizes current data supporting a role of plasma gelsolin in extracellular fluids and the potential for its use as a diagnostic marker or therapeutic treatment in several medical conditions.

Decreased levels of the gelsolin plasma isoform in patients with rheumatoid arthritis

IntroductionGelsolin is an intracellular actin-binding protein involved in cell shape changes, cell motility, and apoptosis. An extracellular gelsolin isoform, plasma gelsolin circulates in the blood of healthy individuals at a concentration of 200 ± 50 mg/L and has been suggested to be a key component of an extracellular actin-scavenging system during tissue damage. Levels of plasma gelsolin decrease during acute injury and inflammation, and administration of recombinant plasma gelsolin to animals improves outcomes following sepsis or burn injuries. In the present study, we investigated plasma gelsolin in patients with rheumatoid arthritis.MethodsCirculating and intra-articular levels of plasma gelsolin were measured in 78 patients with rheumatoid arthritis using a functional (pyrene-actin nucleation) assay and compared with 62 age- and gender-matched healthy controls.ResultsCirculating plasma gelsolin levels were significantly lower in patients with rheumatoid arthritis compared with healthy controls (141 ± 32 versus 196 ± 40 mg/L, P = 0.0002). The patients' intra-articular plasma gelsolin levels were significantly lower than in the paired plasma samples (94 ± 24 versus 141 ± 32 mg/L, P = 0.0001). Actin was detected in the synovial fluids of all but four of the patients, and immunoprecipitation experiments identified gelsolin-actin complexes.ConclusionsThe plasma isoform of gelsolin is decreased in the plasma of patients with rheumatoid arthritis compared with healthy controls. The reduced plasma concentrations in combination with the presence of actin and gelsolin-actin complexes in synovial fluids suggest a local consumption of this potentially anti-inflammatory protein in the inflamed joint.

Protein chemical characterization of Gc globulin (vitamin D-binding protein) isoforms; Gc-1f, Gc-1s and Gc-2

Gc globulin, also called vitamin D-binding protein, is a plasma protein involved in the extracellular actin-scavenger system, vitamin D transport and possibly also other biological activities. Low levels of Gc globulin have been found to correlate with multiple organ failure and non-survival of patients with fulminant hepatic failure and trauma. Here, we characterize the dominant isoforms of plasma-derived Gc globulin from Cohn fraction IV paste with respect to amino acid sequence and posttranslational modifications. Gc globulin was purified in large scale and the isoforms separated by ion exchange chromatography. The separated isoforms and several commercial preparations of individual isoforms were characterized by mass spectrometry. This revealed that the major isoforms were non-glycosylated. Compared to the Gc-1f isoform the other dominating isoforms represented an Asp/Glu substitution (Gc-1s) and a Thr/Lys substitution (Gc-2) in agreement with DNA sequencing studies. The commercial preparations were found to represent mainly one or two isoforms. An O-linked glycan with a mass of 656 Da and terminating with a sialic acid residue was detected on a minor proportion of Gc globulin molecules.

Comparison of rocket and crossed immuno‐electrophoresis assays for determination of the level of actin complexing of Gc globulin

Objective. Gc globulin (vitamin D‐binding protein) is a component of the extracellular actin scavenger system. The level of Gc globulin is reduced in patients with fulminant hepatic failure, septic shock and trauma. Furthermore, low levels of Gc globulin in patients with fulminant hepatic failure and multiple trauma have been found to correlate with the morbidity and mortality of patients. Owing to a large increase in the turnover of Gc globulin upon complex formation with actin, it may be important to determine both the total Gc globulin concentration and the degree of complexing with actin for estimating the clinical prognosis of a patient. For this reason, we have compared a crossed immuno‐electrophoresis method (CIE), suitable for visualizing the degree of complexing with actin, with a rocket immuno‐electrophoresis method (RIE), previously used for determination of the complex degree. Material and methods. Sera from healthy donors and from patients with acetaminophen‐induced liver disease or trauma were investigated using CIE, RIE and enzyme‐linked immunosorbent assay (ELISA). Results. Using the CIE, no Gc globulin‐actin complexes were detected among healthy donors. Complexes were present in 21 of 39 patients with liver disease and 3 of 37 trauma patients. High complex ratios (> 20 %) were found in 6 of 7 patients with hepatic encephalopathy. Using the RIE, complexes were detected in most samples. Conclusion. The results show that the CIE method may be used for determining the degree of actin complexing in conjunction with ELISA or RIE in determining the levels of total Gc globulin.

Actin-free Gc globulin: A rapidly assessed biomarker of organ dysfunction in acute liver failure and cirrhosis

Reductions in serum levels of Gc globulin, a hepatically synthesized component of the extracellular actin scavenger system responsible for complexing circulating actin and attenuating intravascular microthrombus formation, are associated with poor outcome in acute liver failure. Clinically applicable assays of the important actin-free fraction (Af-Gc) have not been available until now. We measured actin-free Gc globulin levels with a novel, rapid assay in 61 cases of acute liver failure (ALF) and in 91 patients with cirrhosis (40 of whom were clinically unstable with extrahepatic organ dysfunction), and studied associations with liver dysfunction, extrahepatic organ dysfunction, indices of disseminated coagulation, and outcome. Reductions in Af-Gc levels mirrored hepatic dysfunction and organ dysfunction in both groups, and discriminated patients with poor prognosis from those with good prognosis in the ALF cohort. Levels were lowest in patients with ALF (10% of control values), but levels were also markedly reduced in both unstable (28%) and stable (44%) patients with cirrhosis. Associations with markers of disseminated intravascular coagulation were seen in both groups, most notably in the cirrhosis cohort, supporting a pathophysiological role for reduced Af-Gc in the evolution of organ dysfunction. In acetaminophen-induced ALF, Af-Gc identified patients with poor prognosis as well as did the Acute Physiology and Chronic Health Evaluation (APACHE II) score (area under the receiver operating characteristic curve, 0.7), and in cirrhosis, Af-Gc was an independent predictor of mortality by multifactorial analysis. In conclusion, the importance of Af-Gc reductions in the development of multiple organ dysfunction in ALF and cirrhosis is highlighted, probably resulting from reduced hepatic production and peripheral exhaustion of this arm of the extracellular actin scavenger system.

Large‐scale purification and characterization of non‐glycosylated Gc globulin (vitamin D‐binding protein) from plasma fraction IV

Gc globulin, also called vitamin D-binding protein, is a plasma protein involved in the extracellular actin-scavenger system. Low levels of Gc globulin have been found to correlate with multiple organ failure and nonsurvival of patients with fulminant hepatic failure and trauma. Therefore substitution therapy with Gc globulin might be beneficial for such patients, increasing their chance of survival. In the present study, we describe a large-scale purification process for the production of a virus-safe human plasma-derived Gc globulin from Cohn fraction IV paste. The process includes three ion-exchange-chromatography steps, followed by a gel filtration, and two virus-reduction steps are implemented. The Gc globulin product was characterized with respect to purity, functional activity, glycosylation and, finally, with respect to content of endotoxin. From the results, it can be concluded that human Gc globulin purified from Cohn fraction IV is non-glycosylated. The purified Gc globulin is able to mask the presence of endotoxin by 20%.

Characterization of plasma gelsolin as a substrate for matrix metalloproteinases

We previously showed that plasma gelsolin, a major component of the extracellular actin scavenging system, is an matrix metalloproteinase (MMP)-14 substrate. Here we confirmed that plasma gelsolin is cleaved by MMP-14 at the plasma level, and found that it was most efficiently digested by MMP-3 followed by MMP-2, MMP-1, MMP-14, and MMP-9, in that order. Plasma gelsolin (90 kDa) was cut into several fragments of 43-48 kDa by MMP-3. The MMP-3 cleavage sites in plasma gelsolin were determined by labeling the C termini generated by in-gel digestion with 50% H2 18O combined with peptide mass mapping, and sequencing of the N-terminal amino acids. Plasma gelsolin was cleaved at Asn416-Val417, Ser51-Met52, and Ala435-Gln436. Proteolytic cleavage by MMP-3 resulted in considerable loss of its actin filament-depolymerizing activity. This suggests that MMPs weaken the extracellular actin-scavenging system by cleaving plasma gelsolin and may, therefore, be involved in pathological conditions induced by extracellular actin, such as endothelial injury, respiratory distress syndrome, hepatic necrosis, and septic shock.

The extracellular actin scavenger system in trauma and major surgery

In spite of a vast number of studies over the last three decades, the pathophysiological processes taking place after severe trauma are not yet fully understood. New knowledge about these processes...

Plasma concentration of Gc-globulin is associated with organ dysfunction and sepsis after injury.

Clinical and experimental studies suggest that the proteins of the extracellular actin scavenger system have a role in the pathophysiological processes taking place in critically ill and injured patients. Circulating levels of Gc-globulin and gelsolin are reduced shortly after severe trauma, and admission levels of Gc-globulin are associated with survival. Herein, we sought to measure the association between admission levels of Gc-globulin and postinjury organ dysfunction and infection. We also wanted to describe the serial changes in Gc-globulin in these severely injured patients. Prospective cohort. Intensive care unit at a county hospital that serves as a level one trauma center. Ninety-eight consecutive trauma victims admitted to the intensive care unit for >24 hrs during a 4-month period. Circulating levels of Gc-globulin were measured by using immunonephelometry. All patients were evaluated daily to obtain the necessary data for assessment of organ dysfunction and sepsis. The median Gc-globulin concentration at admission was 127 mg/L in patients who developed severe multiple organ dysfunction compared with 184 mg/L in patients who did not (p =.001). The admission level of Gc-globulin was comparable to known risk factors such as age and injury severity score, regarding development of organ dysfunction. Plasma concentrations of Gc-globulin remained significantly lower in patients who developed respiratory failure and sepsis, compared with patients who did not develop these complications (p =.02 and p=.015, respectively). Admission plasma concentration of Gc-globulin is lower in patients who develop organ dysfunction and sepsis after traumatic injury. These data, combined with the work of others, support the hypothesis that actin release and depletion of the extracellular actin scavenger system proteins are associated with, and may contribute in part to, the complications of sepsis and organ dysfunction, particularly respiratory failure and thrombocytopenia.

Gc-globulin is an acute phase reactant and an indicator of muscle injury after spinal surgery.

Actin is the dominating protein in mammalian cells, including muscle cells, and is released into the circulation after tissue injury. Gc-globulin, one of the proteins in the Extracellular Actin Scavenger System (EASS) is responsible for the clearance of actin from the circulation. Clinical studies show that plasma levels of Gc-globulin are reduced in situations with tissue death, and that the degree of reduction correlates with development of organ dysfunction and survival. The purpose of the present study was to describe the serial changes in Gc-globulin after a standardized surgical procedure resulting in major muscle injury, comparing changes in Gc-globulin with changes in other acute phase proteins. Twelve patients who underwent posterolateral lumbar fusion from L4 or L5 to sacrum were included in the study. Peripheral venous blood samples were obtained before surgery and on day 1, 3, 5, 12, 21, and 28 after surgery. Serum samples were analyzed for total Gc-globulin (Gc(total)), percentage of Gc-globulin complexed with actin (GC(complexed)), albumin, orosomucoid, haptoglobin, transferrin and creatin phosphokinase (CK). Gc(total) decreased to 87% of pre-operative values on day one. Thereafter the levels increased to a maximum of 135% of pre-operative values on day five, approaching baseline values towards the end of the observation period. Compared to this, changes in GC(complexed) displayed a mirror-like time-course, with levels of Gc(total) and GC(complexed) being significantly inversely correlated on day one (P < 0.05). Levels of albumin remained below pre-operative values the first three weeks post-operatively, reaching baseline at the end of the observation period (P < 0.05). The initial changes in Gc-globulin can be explained by increased release of actin from injured muscle tissue. Subsequently Gc-globulin displays characteristics of a so-called positive acute phase reactant, supporting previous in vitro studies, and clinical studies after minor surgery. In spite of genetic linkage and structural homology Gc-globulin and albumin are regulated differently after surgical trauma.