Amplifiers co-translationally enhance CFTR biosynthesis via PCBP1-mediated regulation of CFTR mRNA.

BACKGROUND: Cystic fibrosis (CF) is a recessive disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. We previously described a first-in-class CFTR modulator that functions as an amplifier to selectively increase CFTR expression and function. The amplifier mechanism is distinct from and complementary to corrector and potentiator classes of CFTR modulators. Here we characterize the mechanism by which amplifiers increase CFTR mRNA, protein, and activity. METHODS: Biochemical studies elucidated the action of amplifiers on CFTR mRNA abundance and translation and defined the role of an amplifier-binding protein that was identified using chemical proteomics. RESULTS: Amplifiers stabilize CFTR mRNA through a process that requires only the translated sequence of CFTR and involves translational elongation. Amplifiers enrich ER-associated CFTR mRNA and increase its translational efficiency through increasing the fraction of CFTR mRNA associated with polysomes. Pulldowns identified the poly(rC)-binding protein 1 (PCBP1) as directly binding to amplifier. A PCBP1 consensus element was identified within the CFTR open reading frame that binds PCBP1. This sequence proved necessary for amplifier responsiveness. CONCLUSIONS: Small molecule amplifiers co-translationally increase CFTR mRNA stability. They enhance translation through addressing the inherently inefficient membrane targeting of CFTR mRNA. Amplifiers bind directly to PCBP1, show enhanced affinity in the presence of bound RNA, and require a PCBP1 consensus element within CFTR mRNA to elicit translational effects. These modulators represent a promising new and mechanistically novel class of CFTR therapeutic. They may be useful as a monotherapy or in combination with other CFTR modulators.

The Effect of Concomitant Sirolimus and Propofol Therapy on Triglyceride Concentrations in Critically Ill Patients.

BACKGROUND: Sirolimus and propofol are both independently associated with the development of hypertriglyceridemia (HTG) during therapy. To date, there are no published reports describing synergistic or additive drug interaction resulting in HTG with concomitant use of these medications. STUDY QUESTION: To identify the occurrence of HTG in patients receiving concomitant sirolimus and propofol infusion therapy. METHODS: Adult patients receiving sirolimus and a continuous propofol infusion for at least 12 hours from January 2005 to August 2009 were retrospectively evaluated. Data included Acute Physiology and Chronic Health Evaluation II score, weight, length of propofol therapy, and baseline triglyceride (TG) concentrations. The major outcome was incidence of HTG (TGs ≥500 mg/dL). Minor outcomes included the change in TG concentration from therapy initiation and manifestations of propofol-related infusion syndrome (PRIS). RESULTS: Sixteen patients were included in the analysis, with 8 (50%) of the patients developing HTG. The patients in this case series had the following mean values: Acute Physiology and Chronic Health Evaluation II score of 20.2 ± 5.3, weight of 76.3 ± 21.2 kg, and baseline TG concentrations of 181.3 ± 89.7 mg/dL. Indications for sirolimus therapy included hematopoietic stem-cell transplantation (n = 15) and heart transplantation (n = 1). Mean length of propofol infusion was 99.8 ± 88.5 hours. The mean TG concentration during infusion was 515.6 ± 468.1 mg/dL. Fourteen (87.5%) patients had an increase of ≥100 mg/dL, 12 (75%) patients had an increase of ≥200 mg/dL, and 6 (37.5%) patients had an increase of ≥300 mg/dL in TG concentrations during therapy. Eleven patients developed one manifestation of PRIS, excluding HTG, and one patient had more than 2 new onset PRIS manifestations during propofol therapy. CONCLUSIONS: Coadministration of propofol and sirolimus can potentially result in HTG, which may warrant more frequent monitoring. Further analysis is needed to examine the mechanism and clinical impact of this interaction.

Use of a High-Throughput Phenotypic Screening Strategy to Identify Amplifiers, a Novel Pharmacological Class of Small Molecules That Exhibit Functional Synergy with Potentiators and Correctors.

Cystic fibrosis (CF) is a lethal genetic disorder caused by mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Despite recent groundbreaking approval of genotype-specific small-molecule drugs, a significant portion of CF patients still lack effective therapeutic options that address the underlying cause of the disease. Through a phenotypic high-throughput screen of approximately 54,000 small molecules, we identified a novel class of CFTR modulators called amplifiers. The identified compound, the characteristics of which are represented here by PTI-CH, selectively increases the expression of immature CFTR protein across different CFTR mutations, including F508del-CFTR, by targeting the inefficiencies of early CFTR biosynthesis. PTI-CH also augments the activity of other CFTR modulators and was found to possess novel characteristics that distinguish it from CFTR potentiator and corrector moieties. The PTI-CH-mediated increase in F508del-CFTR did not elicit cytosolic or endoplasmic reticulum-associated cellular stress responses. Based on these data, amplifiers represent a promising new class of CFTR modulators for the treatment of CF that can be used synergistically with other CFTR modulators.

Orkambi® and amplifier co-therapy improves function from a rare CFTR mutation in gene-edited cells and patient tissue.

The combination therapy of lumacaftor and ivacaftor (Orkambi®) is approved for patients bearing the major cystic fibrosis (CF) mutation: ΔF508 It has been predicted that Orkambi® could treat patients with rarer mutations of similar "theratype"; however, a standardized approach confirming efficacy in these cohorts has not been reported. Here, we demonstrate that patients bearing the rare mutation: c.3700 A>G, causing protein misprocessing and altered channel function-similar to ΔF508-CFTR, are unlikely to yield a robust Orkambi® response. While in silico and biochemical studies confirmed that this mutation could be corrected and potentiated by lumacaftor and ivacaftor, respectively, this combination led to a minor in vitro response in patient-derived tissue. A CRISPR/Cas9-edited bronchial epithelial cell line bearing this mutation enabled studies showing that an "amplifier" compound, effective in increasing the levels of immature CFTR protein, augmented the Orkambi® response. Importantly, this "amplifier" effect was recapitulated in patient-derived nasal cultures-providing the first evidence for its efficacy in augmenting Orkambi® in tissues harboring a rare CF-causing mutation. We propose that this multi-disciplinary approach, including creation of CRISPR/Cas9-edited cells to profile modulators together with validation using primary tissue, will facilitate therapy development for patients with rare CF mutations.

Gelsolin and Progression of Aortic Arch Calcification in Chronic Hemodialysis Patients.

BACKGROUND: Vascular calcification (VC) is a key process associated with cardiovascular mortality in dialysis patients. Gelsolin is an actin-binding protein that can modulate inflammation, correlated inversely with hemodialysis (HD) mortality and involved in bone calcification homeostasis. In this report, we aim to characterize progression in aortic arch calcification (AAC) and investigate its association with gelsolin. METHODS: 184 HD patients were enrolled and their annual posterior-anterior chest X-ray films (CXR) in 2009 and 2013 were examined. The severity of AAC was classified as grade 0 to 3. Blood levels of gelsolin were measured by ELISA kits. Biographic and biochemical data at baseline were analyzed with status of AAC at baseline and changes after 4 years. RESULTS: At baseline, 60% of the patients had detectable AAC on CXR. After 4 years, 77% had AAC. Patients with grade 1 and 2 AAC had increased risk of progression (Odds ratio [OR] 2~3, P=0.001) compared to those with grade 0 at baseline. Compared to those with no AAC, patients with AAC progression had older age, lower gelsolin, higher waist circumference and prevalence of vascular disease. Regression analysis confirmed baseline gelsolin (odds ratio 0.845, 95% confidence interval [0.734-0.974]) and waist circumference as the independent factors associated with AAC progression. Gelsolin is positively correlated with serum albumin and negatively with tumor necrosis factor-alpha. CONCLUSION: Our study demonstrated that HD patients with grades 1 or 2 baseline AAC are at increased risk of further progression compared to those with grade 0. We also found lower blood levels of gelsolin associated with progressive AAC. Further investigation into the mechanistic roles of gelsolin in vascular calcification may provide new understanding of this key process.

Gelsolin decreases actin toxicity and inflammation in murine multiple sclerosis.

Gelsolin is the fourth most abundant protein in the body and its depletion in the blood has been found in multiple sclerosis (MS) patients. How gelsolin affects the MS brain has not been studied. We found that while the secreted form of gelsolin (pGSN) decreased in the blood of experimental autoimmune encephalomyelitis (EAE) mice, pGSN concentration increased in the EAE brain. Recombinant human pGSN (rhp-GSN) decreased extracellular actin and myeloperoxidase activity in the brain, resulting in reduced disease activity and less severe clinical disease, suggesting that gelsolin could be a potential therapeutic target for MS.

Gelsolin and adipokines are associated with protein-energy wasting in hemodialysis patients.

Protein-energy wasting (PEW) contributes to mortality in hemodialysis (HD) patients. Adipokines regulate energy homeostasis and body weight. Circulating gelsolin can modulate inflammation and is correlated with HD mortality. Whether adipokines and gelsolin play important roles in PEW remains unclear. Based on the criteria proposed by the International Society of Renal Nutrition and Metabolism, we examined the associations between PEW and biomarkers (gelsolin, leptin, adiponectin, interleukin-6, tumor necrosis factor alpha [TNF-α]) in 188 stable HD patients. Patients with PEW had significantly lower serum leptin levels, and tended to have higher adiponectin, TNF-α, and lower gelsolin levels. Logistic regression analysis revealed that gelsolin, leptin, adiponectin, and blood urea nitrogen were independently associated with PEW score. Serum creatinine, TNF-α, gender, renin-angiotensin system (RAS) blockade, and lipid-lowering agents were not associated with PEW score. Patients on lipid-lowering agents had lower PEW scores and those with RAS blockade had higher PEW scores. Our study confirms that gelsolin, adiponectin, and leptin are significant associates with PEW in HD patients. Further understanding of how these factors contribute to PEW may help design novel therapeutic strategies for PEW in chronic kidney disease.

Rapamycin-insensitive up-regulation of adipocyte phospholipase A2 in tuberous sclerosis and lymphangioleiomyomatosis.

Tuberous sclerosis syndrome (TSC) is an autosomal dominant tumor suppressor gene syndrome affecting multiple organs, including renal angiomyolipomas and pulmonary lymphangioleiomyomatosis (LAM). LAM is a female-predominant interstitial lung disease characterized by the progressive cyst formation and respiratory failure, which is also seen in sporadic patients without TSC. Mutations in TSC1 or TSC2 cause TSC, result in hyperactivation of mammalian target of rapamycin (mTOR), and are also seen in LAM cells in sporadic LAM. We recently reported that prostaglandin biosynthesis and cyclooxygenase-2 were deregulated in TSC and LAM. Phospholipase A2 (PLA2) is the rate-limiting enzyme that catalyzes the conversion of plasma membrane phospholipids into prostaglandins. In this study, we identified upregulation of adipocyte AdPLA2 (PLA2G16) in LAM nodule cells using publicly available expression data. We showed that the levels of AdPLA2 transcript and protein were higher in LAM lungs compared with control lungs. We then showed that TSC2 negatively regulates the expression of AdPLA2, and loss of TSC2 is associated with elevated production of prostaglandin E2 (PGE2) and prostacyclin (PGI2) in cell culture models. Mouse model studies also showed increased expression of AdPLA2 in xenograft tumors, estrogen-induced lung metastatic lesions of Tsc2 null leiomyoma-derived cells, and spontaneous renal cystadenomas from Tsc2+/- mice. Importantly, rapamycin treatment did not affect the expression of AdPLA2 and the production of PGE2 by TSC2-deficient mouse embryonic fibroblast (Tsc2-/-MEFs), rat uterine leiomyoma-derived ELT3 cells, and LAM patient-associated renal angiomyolipoma-derived "mesenchymal" cells. Furthermore, methyl arachidonyl fluorophosphate (MAFP), a potent irreversible PLA2 inhibitor, selectively suppressed the growth and induced apoptosis of TSC2-deficient LAM patient-derived cells relative to TSC2-addback cells. Our findings suggest that AdPLA2 plays an important role in promoting tumorigenesis and disease progression by modulating the production of prostaglandins and may serve as a potential therapeutic target in TSC and LAM.

Rapamycin-resistant poly (ADP-ribose) polymerase-1 overexpression is a potential therapeutic target in lymphangioleiomyomatosis.

Lymphangioleiomyomatosis (LAM) is a female-predominant cystic lung disease that can lead to respiratory failure. LAM cells typically have inactivating tuberous sclerosis complex 2 (TSC2) mutations and mammalian target of rapamycin (mTOR) complex (mTORC) 1 activation. Clinical response to the mTORC1 inhibitors has been limited, prompting a search for additional therapy for LAM. In this study, we investigated the impact of TSC2 on the expression of poly (ADP-ribose) polymerase (PARP)-1 that initiates the DNA repair pathway, and tested the efficacy of PARP1 inhibitors in the survival of TSC2-deficient (TSC2(-)) cells. We analyzed publicly available expression arrays of TSC2(-) cells and validated the findings using real-time RT-PCR, immunoblotting, and immunohistochemistry. We examined the impact of rapamycin and Torin 1 on PARP1 expression. We also tested the effect of PARP1 inhibitors, 8-hydroxy-2-methylquinazoline-4-one and 3,4-dihydro-5[4-(1-piperindinyl)butoxy]-1(2H)-isoquinoline, on the survival of TSC2(-) cells. We identified the up-regulation of PARP1 in TSC2(-) cells relative to cells in which wild-type TSC2 has been reintroduced (TSC2-addback [TSC2(+)] cells). The transcript levels of PARP1 in TSC2(-) cells were not affected by rapamycin. PARP1 levels were increased in TSC2(-) cells, xenograft tumors of rat-derived TSC2(-) cells, renal cystadenomas from Tsc2(+/-) mice, and human LAM nodules. RNA interference of mTOR failed to reduce PARP1 levels. Proliferation and survival of TSC2(-) cells was reduced in response to PARP1 inhibitor treatment, more so than TSC2(+) cells. TSC2(-) cells exhibit higher levels of PARP1 relative to TSC2(+) cells in an mTOR-insensitive manner. PARP1 inhibitors selectively suppress the growth and induce apoptosis of TSC2(-) cells from patients with LAM. Targeting PARP1 may be beneficial in the treatment of LAM and other neoplasm with mTORC1 activation.

Estradiol and mTORC2 cooperate to enhance prostaglandin biosynthesis and tumorigenesis in TSC2-deficient LAM cells.

Lymphangioleiomyomatosis (LAM) is a progressive neoplastic disorder that leads to lung destruction and respiratory failure primarily in women. LAM is typically caused by tuberous sclerosis complex 2 (TSC2) mutations resulting in mTORC1 activation in proliferative smooth muscle-like cells in the lung. The female predominance of LAM suggests that estradiol contributes to disease development. Metabolomic profiling identified an estradiol-enhanced prostaglandin biosynthesis signature in Tsc2-deficient (TSC(-)) cells, both in vitro and in vivo. Estradiol increased the expression of cyclooxygenase-2 (COX-2), a rate-limiting enzyme in prostaglandin biosynthesis, which was also increased at baseline in TSC-deficient cells and was not affected by rapamycin treatment. However, both Torin 1 treatment and Rictor knockdown led to reduced COX-2 expression and phospho-Akt-S473. Prostaglandin production was also increased in TSC-deficient cells. In preclinical models, both Celecoxib and aspirin reduced tumor development. LAM patients had significantly higher serum prostaglandin levels than healthy women. 15-epi-lipoxin-A4 was identified in exhaled breath condensate from LAM subjects and was increased by aspirin treatment, indicative of functional COX-2 expression in the LAM airway. In vitro, 15-epi-lipoxin-A4 reduced the proliferation of LAM patient-derived cells in a dose-dependent manner. Targeting COX-2 and prostaglandin pathways may have therapeutic value in LAM and TSC-related diseases, and possibly in other conditions associated with mTOR hyperactivation.

Assessment of clinical response to ivacaftor with lung clearance index in cystic fibrosis patients with a G551D-CFTR mutation and preserved spirometry: a randomised controlled trial.

BACKGROUND: Ivacaftor has shown a clinical benefit in patients with cystic fibrosis who have the G551D-CFTR mutation and reduced lung function. Lung clearance index (LCI) using multiple-breath washout might be an alternative to and more sensitive method than forced expiratory volume in 1 s (FEV1) to assess treatment response in the growing number of children and young adults with cystic fibrosis who have normal spirometry. The aim of the study was to assess the treatment effects of ivacaftor on LCI in patients with cystic fibrosis, a G551D-CFTR mutation, and an FEV1 >90% predicted. METHODS: This phase 2, multicentre, placebo-controlled, double-blind 2×2 crossover study of ivacaftor treatment was conducted in patients with cystic fibrosis, at least one G551D-CFTR allele, and an FEV1 >90% predicted. Patients also had to have an LCI higher than 7·4 at screening, age of 6 years or older, and a weight higher than or equal to 15 kg. Eligible patients were randomly allocated to receive one of two treatment sequences (placebo first followed by ivacaftor 150 mg twice daily [sequence 1] or ivacaftor 150 mg twice daily first followed by placebo [sequence 2]) of 28 days' treatment in each period, with a 28-day washout between the two treatment periods. Randomisation (ratio 1:1) was done with block sizes of 4, and all site personnel including the investigator, the study monitor, and the Vertex study team were masked to treatment assignment. The primary outcome measure was change from baseline in LCI. The study is registered at ClinicalTrials.gov, NCT01262352. FINDINGS: Between February and November, 2011, 21 patients were enrolled, of which 11 were assigned to the sequence 1 group, and 10 to the sequence 2 group. 20 of these patients received treatment and 17 completed the trial (eight in sequence 1 group and 9 in sequence 2 group). Treatment with ivacaftor led to significant improvements compared with placebo in LCI (difference between groups in the average of mean changes from baseline at days 15 and 29 was -2·16 [95% CI -2·88 to -1·44]; p<0·0001). Adverse events experienced by study participants were similar between treatment groups; at least one adverse event was reported by 15 (79%) of 19 patients who received placebo and 13 (72%) of 18 patients who received ivacaftor. No deaths occurred during study period. INTERPRETATION: In patients with cystic fibrosis aged 6 years or older who have at least one G551D-CFTR allele, ivacaftor led to improvements in LCI. LCI might be a more sensitive alternative to FEV1 in detecting response to intervention in these patients with mild lung disease. FUNDING: Vertex Pharmaceuticals Incorporated.

Plasma-type gelsolin is decreased in human blood and cerebrospinal fluid after subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Subarachnoid hemorrhage (SAH) pathophysiology involves neurovascular proteolysis and inflammation. How these 2 phenomena are related remains unclear. We hypothesize that matrix metalloproteinases (MMPs) mediate the depletion of anti-inflammatory plasma-type gelsolin (pGSN). METHODS: We enrolled 42 consecutive SAH subjects and sampled cerebrospinal fluid (CSF) and blood on post-SAH Days 2 to 3, 4 to 5, 6 to 7, and 10 to 14. Control subjects were 20 consecutive non-SAH hydrocephalus patients with lumbar drains. Enzyme-linked immunosorbent assay, Western blotting, and zymography were used to quantify pGSN and MMP-9. RESULTS: In CSF, pGSN was lower in SAH compared with control subjects on post-SAH Days 2 to 3 (P=0.0007), 4 to 5 (P=0.041), and 10 to 14 (P=0.007). In blood, pGSN decreased over time (P=0.001) and was lower in SAH compared with control subjects on post-SAH Days 4 to 5 (P=0.037), 6 to 7 (P=0.006), and 10 to 14 (P=0.006). Western blots demonstrated that SAH CSF had novel bands at 52 and 46 kDa, representing cleaved pGSN fragments. Gelatin zymography showed that CSF MMP-9 was elevated in SAH compared with control subjects. Higher CSF MMP-9 correlated with lower CSF pGSN on post-SAH Day 7 (r=-0.38; P=0.05). CONCLUSIONS: SAH is associated with decreased CSF and blood pGSN and elevated CSF MMP-9. Novel cleaved pGSN fragments are present in CSF of SAH subjects, consistent with pGSN cleavage by MMPs. Because pGSN is known to inhibit inflammatory mediators, these findings suggest that MMPs may reduce pGSN and exacerbate inflammation after SAH. Further studies are warranted to investigate the mechanisms underlying MMP-pGSN signaling in SAH.

Oxygen saturation/fraction of inspired oxygen ratio is a simple predictor of noninvasive positive pressure ventilation failure in critically ill patients.

PURPOSE: Noninvasive positive pressure ventilation (NPPV) can improve outcomes of critically ill patients. Early and simple predictors of NPPV outcome could improve clinical management of patients with respiratory failure. MATERIALS AND METHODS: A prospective observational study was conducted in a medical intensive care unit of a tertiary medical center. Patients requiring NPPV were included and followed. Clinical data including respiratory mechanics at the time of NPPV initiation, and clinical outcomes were recorded. Data were analyzed to identify variables that distinguished NPPV success or failure. RESULTS: A total of 133 patients were included in the study. Noninvasive positive pressure ventilation success rate was 41%. Patients diagnosed with malignancy had only 29% NPPV success rate. Among patients without malignancy, higher oxygen saturation, oxygen saturation/fraction of inspired oxygen (SF) ratios, and SF/minute ventilation ratios were associated with NPPV success. Receiver operating characteristic curve analyses identify SF ratio less than 98.5 to be a specific (89% specificity, P = .013) predictor of NPPV failure. Furthermore, for patients requiring at least 24 hours of NPPV support, tidal volume/predicted body weight ratio negatively correlated with respiratory improvement. CONCLUSIONS: For patients without malignancy, SF ratios at the time of NPPV initiation discriminated NPPV success and failure, and could be used to help guide the management of critically ill patients who require ventilatory support.

The potential role of plasma gelsolin in dialysis-related protein-energy wasting.

Protein-energy wasting (PEW) is increasingly recognized to be a prevalent and significant contributor to the clinical deterioration of patients with chronic kidney disease (CKD). While factors reflecting various aspects of PEW correlate with outcomes in CKD, the mechanism linking PEW and CKD outcomes is not completely understood. Plasma gelsolin (pGSN) is a highly abundant circulating protein that is depleted by inflammatory mediators and mainly produced by muscles. Recent data documenting the prognostic ability of low pGSN levels in hemodialysis patients suggests that circulating pGSN levels incorporate the degree of systemic inflammation and muscle wasting. Therefore, pGSN deficiency appears to be a powerful biomarker and a potential therapeutic target in CKD patients.

Rapamycin-insensitive up-regulation of MMP2 and other genes in tuberous sclerosis complex 2-deficient lymphangioleiomyomatosis-like cells.

Increased matrix metalloproteinase (MMP) activity has been implicated in the pathogenesis of lymphangioleiomyomatosis (LAM). The objective of this study was to investigate how tuberous sclerosis complex (TSC) 1 or TSC2 deficiency alters MMP expression and regulation. We studied immortalized cells that lack TSC2 derived from an angiomyolipoma of a patient with LAM, a TSC2 addback derivative, and murine embryonic fibroblast cells that lack Tsc1 or -2 and respective controls. Global gene expression analysis was performed in the angiomyolipoma and derivative cell lines. MMP levels in the conditioned media from these cells were analyzed by zymography and ELISA. We found increased MMP-2 expression in cells lacking TSC1/TSC2 compared with their respective controls by zymography. MMP-2 overproduction by these cells was not affected by rapamycin treatment. Gene expression analysis confirmed increased MMP-2 gene expression that was not affected by rapamycin. Furthermore, multiple other genes were found to be overexpressed in rapamycin-treated TSC2-deficient cells compared with TSC2(+) cells. We conclude that TSC1/TSC2 deficiency leads to MMP-2 overproduction that is rapamycin-insensitive, and that several genes exhibit similar patterns, suggesting that TSC1/TSC2-dependent, but mammalian target of rapamycin-independent, pathways may be involved in the pathogenesis of LAM.

mTORC1-S6K activation by endotoxin contributes to cytokine up-regulation and early lethality in animals.

BACKGROUND: mTORC1 (mammalian target of rapamycin complex 1) activation has been demonstrated in response to endotoxin challenge, but the mechanism and significance are unclear. We investigated the effect of mTORC1 suppression in an animal model of endotoxemia and in a cellular model of endotoxin signaling. METHODOLOGY/PRINCIPAL FINDINGS: Mice were treated with the mTORC1 inhibitor rapamycin or vehicle prior to lethal endotoxin challenge. Mortality and cytokine levels were assessed. Cultured macrophage-like cells were challenged with endotoxin with or without inhibitors of various pathways known to be upstream of mTORC1. Activated pathways, including downstream S6K pathway, were assessed by immunoblots. We found that mTORC1-S6K suppression by rapamycin delayed mortality of mice challenged with lethal endotoxin, and was associated with dampened circulating levels of VEGF, IL-1ß, IFN-γ and IL-5. Furthermore, in vitro cellular studies demonstrated that LPS (lipopolysaccharide) activation of mTORC1-S6K still occurs in the presence of PI3K-Akt inhibition alone, but can be suppressed by concurrent inhibition of PI3K-Akt and MEK-ERK pathways. CONCLUSIONS/SIGNIFICANCE: We conclude that cellular activation of mTORC1-S6K contributes to cytokine up-regulation and mortality in response to endotoxin, and may occur via multiple pathways.

Plasma gelsolin and circulating actin correlate with hemodialysis mortality.

Plasma gelsolin (pGSN) binds actin and bioactive mediators to localize inflammation. Low pGSN correlates with adverse outcomes in acute injury, whereas administration of recombinant pGSN reduces mortality in experimental sepsis. We found that mean pGSN levels of 150 patients randomly selected from 10,044 starting chronic hemodialysis were 140 +/- 42 mg/L, 30 to 50% lower than levels reported for healthy individuals. In a larger sample, we performed a case-control analysis to evaluate the relationship of pGSN and circulating actin with mortality; pGSN levels were significantly lower in 114 patients who died within 1 yr of dialysis initiation than in 109 survivors (117 +/- 38 mg/L versus 147 +/- 42 mg/L, P < 0.001). pGSN levels had a graded, inverse relationship with 1-yr mortality, such that patients with pGSN < 130 mg/L experienced a > 3-fold risk for mortality compared with those with pGSN > or = 150 mg/L. The 69% of patients with detectable circulating actin had lower pGSN levels than those without (127 +/- 45 mg/L versus 141 +/- 36 mg/L, P = 0.026). Compared with patients who had elevated pGSN and no detectable actin, those with low pGSN levels and detectable actin had markedly increased mortality (odds ratio 9.8, 95% confidence interval 2.9 to 33.5). Worsening renal function correlated with pGSN decline in 53 subjects with CKD not on dialysis. In summary, low pGSN and detectable circulating actin identify chronic hemodialysis patients at highest risk for 1-yr mortality.

Plasma gelsolin depletion and circulating actin in sepsis: a pilot study.

BACKGROUND: Depletion of the circulating actin-binding protein, plasma gelsolin (pGSN) has been described in septic patients and animals. We hypothesized that the extent of pGSN reduction correlates with outcomes of septic patients and that circulating actin is a manifestation of sepsis. METHODOLOGY/PRINCIPAL FINDINGS: We assayed pGSN in plasma samples from non-surgical septic patients identified from a pre-existing database which prospectively enrolled patients admitted to adult intensive care units at an academic hospital. We identified 21 non-surgical septic patients for the study. Actinemia was detected in 17 of the 21 patients, suggesting actin released into circulation from injured tissues is a manifestation of sepsis. Furthermore, we documented the depletion of pGSN in human clinical sepsis, and that the survivors had significantly higher pGSN levels than the non-survivors (163+/-47 mg/L vs. 89+/-48 mg/L, p = 0.01). pGSN levels were more strongly predictive of 28-day mortality than APACHE III scores. For every quartile reduction in pGSN, the odds of death increased 3.4-fold. CONCLUSION: We conclude that circulating actin and pGSN deficiency are associated with early sepsis. The degree of pGSN deficiency correlates with sepsis mortality. Reversing pGSN deficiency may be an effective treatment for sepsis.

Plasma gelsolin is a marker and therapeutic agent in animal sepsis.

OBJECTIVE: Plasma gelsolin is a circulating actin-binding protein that serves a protective role against tissue injuries. Depletion of plasma gelsolin in systemic inflammation may contribute to adverse outcomes. We examined the role of plasma gelsolin in animal models of sepsis. DESIGN: Animal and laboratory experiments. SETTING: Academic research laboratory. SUBJECTS: Adult male mice. INTERVENTIONS: Mice subjected to endotoxin or cecal ligation and puncture (CLP) were treated with exogenous plasma gelsolin or placebo. MEASUREMENTS AND MAIN RESULTS: We document the depletion of plasma gelsolin (25-50% of normal) in murine models of sepsis associated with the presence of circulating actin within 6 hrs of septic challenge. Repletion of plasma gelsolin leads to solubilization of circulating actin aggregates and significantly reduces mortality in endotoxemic mice (survival rates were 88% in the gelsolin group vs. 0% in the saline group, p < .001) and in CLP-challenged mice (survival rates were 30% in the gelsolin group vs. 0% in the saline group, p = .001). Plasma gelsolin repletion also shifted the cytokine profile of endotoxemic mice toward anti-inflammatory (plasma interleukin-10 levels were 205 +/- 108 pg/mL in the gelsolin group vs. 39 +/- 29 pg/mL in the saline group, p = .02). CONCLUSIONS: We propose that circulation of particulate actin is a marker for sepsis-induced cell injury, that plasma gelsolin has a crucial protective role in sepsis, and that gelsolin replacement represents a potential therapy for this common lethal condition.