Effects of pneumoperitoneum and Trendelenburg position on intracranial pressure assessed using different non-invasive methods

BACKGROUND

The laparoscopic approach is becoming increasingly frequent for many different surgical procedures. However, the combination of pneumoperitoneum and Trendelenburg positioning associated with this approach may increase the patient's risk for elevated intracranial pressure (ICP). Given that the gold standard for the measurement of ICP is invasive, little is known about the effect of these common procedures on ICP.

METHODS

We prospectively studied 40 patients without any history of cerebral disease who were undergoing laparoscopic procedures. Three different methods were used for non-invasive estimation of ICP: ultrasonography of the optic nerve sheath diameter (ONSD); transcranial Doppler-based (TCD) pulsatility index (ICP_PI); and a method based on the diastolic component of the TCD cerebral blood flow velocity (ICP_FVd). The ONSD and TCD were measured immediately after induction of general anaesthesia, after pneumoperitoneum insufflation, after Trendelenburg positioning, and again at the end of the procedure.

RESULTS

The ONSD, ICP_FVd, and ICP_PI increased significantly after the combination of pneumoperitoneum insufflation and Trendelenburg positioning. The ICP_FVd showed an area under the curve of 0.80 [95% confidence interval (CI) 0.70-0.90] to distinguish the stage associated with the application of pneumoperitoneum and Trendelenburg position; ONSD and ICP_PI showed an area under the curve of 0.75 (95% CI 0.65-0.86) and 0.70 (95% CI 0.58-0.81), respectively.

CONCLUSIONS

The concomitance of pneumoperitoneum and the Trendelenburg position can increase ICP as estimated with non-invasive methods. In high-risk patients undergoing laparoscopic procedures, non-invasive ICP monitoring through a combination of ONSD ultrasonography and TCD-derived ICP_FVd could be a valid option to assess the risk of increased ICP.

Longitudinal assessment of hepatitis C fibrosis progression by collagen and smooth muscle actin morphometry in comparison to serum markers

BACKGROUND

Assessment of fibrosis progression in chronic liver disease relies upon non-invasive tools and changes in semi-quantitative histopathology scores that may not be reliable.

AIM

To assess the diagnostic performance of the FibroSURE (FS) index and collagen/alpha smooth muscle actin (α-SMA) morphometry in relation to longitudinal changes in fibrosis on paired biopsies.

METHODS

The study cohort included 201 chronic hepatitis C (CHC) nonresponders enrolled in a prior phase II anti-fibrotic study. Serum FS and paired biopsies, with both collagen and α-SMA morphometry, were evaluated at baseline and week 52.

RESULTS

Study patients were mostly male (67%) and Caucasian (77%), with Ishak stages 2 (n = 79), 3 (n = 88) and 4 (n = 30), excluded (n = 4 stage 1 or 5). Mean biopsy length was 22.9 mm. For baseline Ishak 2/3 vs. 4, there were no significant differences in AUROCs for collagen (0.71), SMA (0.66) or FS (0.70). At week 52, 62% of patients had no change in Ishak stage, but collagen/α-SMA increased by 34-51% (P < 0.0001), and FS decreased by 5% (P = 0.008). Among the 33% of patients with +/-1 Ishak stage change, FS changes were not significant, but α-SMA increased 29-72%, and collagen increased by 12-38% (P = 0.01 for +1 only).

CONCLUSIONS

Longitudinal changes in collagen and α-SMA morphometry are apparent prior to change in histological stage or FibroSURE in CHC nonresponders with intermediate fibrosis. This likely reflects quantitative morphological differences that are not detected by routine histological staging or serum markers such as FibroSURE.

Intraoperative non invasive intracranial pressure monitoring during pneumoperitoneum: a case report and a review of the published cases and case report series

Non-invasive measurement of ICP (nICP) can be warranted in patients at risk for developing increased ICP during pneumoperitoneum (PP). Our aim was to assess available data on the application of nICP monitoring during these procedures and to present a patient assessed with an innovative combination of noninvasive tools. Literature review of nICP assessment during PP did not find any studies comparing different methods intraprocedurally and only few studies of any nICP monitoring were available: transcranial Doppler (TCD) studies used the pulsatility index (PI) as an estimator of ICP and failed to detect a significant ICP increase during PP, whereas two out of three optic nerve sheath diameter (ONSD) studies detected a statistically significant ICP increase. In the case study, we describe a 52 year old man with a high grade thalamic glioma who underwent urgent laparoscopic cholecystectomy. Considering the high intraoperative risk of developing intracranial hypertension, he was monitored through parallel ONSD ultrasound measurement and TCD derived formulae (flow velocity diastolic formula, FVdnICP, and PI). ONSD and FVdnICP methods indicated a significant ICP increase during PP, whereas PI was not significantly increased. Our experience, combined with the literature review, seems to suggest that PI might not detect ICP changes in this context, however we indicate a possible interest of nICP monitoring during PP by means of ONSD and of TCD derived FVdNICP, especially for patients at risk for increased ICP.

Recipient IL-33 stimulates donor T cells to promote Type 1 alloimmunity and lethal acute GVHD (TRAN1P.931)

Graft-versus-host disease (GVHD) is a severe and often fatal complication of allogeneic (allo) hematopoietic cell transplantation (HCT). Total body irradiation (TBI) conditioning of the recipient and subsequent GVHD-associated alloimmune responses cause significant gut epithelial cell damage. As IL-33 is an epithelial cell-derived cytokine with pleiotropic functions, we investigated the impact of IL-33 on GVHD pathogenesis. Mice received TBI and alloHCT (allogeneic bone marrow (BM) +/- T cells). Where indicated, recipient mice, donor BM or T cells were deficient for IL-33 or its receptor, ST2. Survival, weight, and clinical score were monitored. Tissues and serum were harvested for IL-33 quantitation and analysis of alloimmune responses. We find that IL-33 expression is increased rapidly in CD45- cells of the gut after TBI, and sustained at least through day 14 in alloHCT recipients. Recipient, but not donor, IL-33 acting on ST2-expressing donor T cells fueled Type 1 responses and GVHD. The IL-33 antagonist ST2-Fc prevented GVHD and reduced Type 1 alloimmune responses, whereas IL-33 administration post-alloHCT (d+3 to d+7) accelerated GVHD lethality and Type 1 alloimmunity. These potent responses overcome regulatory functions of IL-33 to promote GVHD. In summary, our findings are the first to reveal a detrimental role for IL-33 underlying GVHD pathogenesis and establish the IL-33/ST2 axis as a targetable pathway to lessen the risk of GVHD following alloHCT.

The iron sequestering protein Lipocalin 2 is critical to IL-33-exposed dendritic cell stimulation of Th2 responses and allergic airway disease (IRC7P.424)

IL-33 is an IL-1 cytokine with emerging pleotropic functions, but ascribed a prominent role in Type 2-mediated responses to pathogens due to its capacity to generate and support T helper type 2 (Th2) cells. Likewise, IL-33 and Th2 cell are viewed as dominant drivers of inflammatory lung disorders, including asthma. Previous studies have revealed that IL-33 stimulates the capacity of dendritic cells (DC) to initiate Th2 responses and, thus instigate allergic airway disease (AAD) in mice. However, the precise mechanisms by which IL-33 promotes DC-mediated Th2 polarization was not known. To answer this question, we preformed microarray analysis on DC after exposure to IL-33. This analysis identified multiple genes involved in iron homeostasis and metabolism upregulated by IL-33. The most dramatically increase gene in DC by IL-33 was Lipocalin 2 (Lcn2), an iron sequestering protein that facilitates DC iron uptake. After IL-33-exposure, DC deficient in Lcn2 displayed a significantly reduced capacity to generate Th2 responses, however, LPS-exposed DC lacking Lcn2 were fully capable of Th1 polarization. Identical finding were observed when DC iron uptake was blocked through chelation during their exposure to IL-33. In a DC-induced model of AAD, blocking DC iron uptake resulted in significantly decreased disease severity. These data define a novel role for IL-33-stimulated iron uptake by Lcn2 in the generation of Th2 responses.

DAP12 deficiency in liver allografts results in enhanced donor DC migration, augmented effector T cell responses and abrogation of transplant tolerance (TRAN3P.883)

Liver interstitial dendritic cells (DC) have been implicated in immune regulation and tolerance induction. We found that the transmembrane immuno-adaptor DNAX-activating protein of 12kDa (DAP12) negatively regulated conventional liver DC maturation and their in vivo migratory and T cell allostimulatory ability. Livers were transplanted from B6 wild-type (wt) or DAP12-/- mice into wt C3H recipients. Donor DC (H2-Kb+CD11c+) were quantified in spleens by flow cytometry. Anti-donor T cell reactivity was evaluated by ex vivo CFSE-MLR and in vivo delayed-type hypersensitivity responses, while T effector and regulatory T cells were determined by flow analysis. A 3-4-fold increase in donor-derived DC was detected in the spleens of DAP12-/- liver recipients compared with those given wt grafts. Moreover, pro-inflammatory cytokine gene expression in the graft, IFNγ production by graft-infiltrating CD8+ T cells, and systemic levels of IFNγ were all elevated significantly in hosts of DAP12-/- liver recipients. DAP12-/- grafts also exhibited reduced incidences of CD4+Foxp3+ cells and enhanced CD8+ T cell IFNγ secretion in response to donor antigen challenge. Unlike wt grafts, DAP12-/- livers failed to induce tolerance and were rejected acutely. Thus, DAP12 expression in liver grafts regulates donor DC migration to host lymphoid tissue, alloreactive T cell responses and transplant tolerance.

Metabolic mechanisms underlying IL-33 mediated Th2 polarization and allergic airway disease (IRM7P.494)

IL-33 is a recent IL-1 cytokine with emerging pleotropic functions. Experimental studies have suggested that IL-33 supports Treg responses, drives CD8+ T cell IFN-γ production, and acts as a potent mediator of Th2 responses. The current study tests the hypothesis that IL-33 modulates mDC gene expression and pathway activities facilitating Th2 polarization. Using gene expression and efficiency analysis, we identified multiple genes involved in iron homeostasis and metabolism which were upregulated in mDC by IL-33. Desferrioxamine (DFO) was utilized to assess the impact of blocking mDC iron uptake during IL-33 stimulation on subsequent Th2 polarization and capacity to stimuli allergic airway disease (AAD). Generation of CD4+IL-5+ Th2 cells by IL-33-exposed DC was ablated by iron chelation, resulting in decreased IL-5 production and cellular proliferation. However, induced Th1 responses were unaffected in DFO-treated LPS-stimulated DC. Using an OVA/IL-33 mDC induced model of AAD, blocking DC iron uptake with DFO decreased several phenotypic hallmarks of the disease, including IgE (p&lt;0.05) and IL-33 production in the lungs of animals. In conclusion, iron uptake is necessary for IL-33 generation of pro-inflammatory DC supporting Th2 polarization. Blocking iron uptake in a model of mDC induced AAD alters disease phenotype when compared to control animals. These data suggest that regulation of iron uptake may be a potential mechanism behind IL-33 induction of Th2 responses.

IL-33 stimulates dendritic cell secretion of IL-2 that promotes selective expansion of ST2+Foxp3+ regulatory T cells (IRC5P.460)

IL-33 is a pleiotropic IL-1 family cytokine that signals via ST2 and expands ST2+Foxp3+ regulatory T cells (Treg) in vivo. As ST2+ Treg show poor expansion by direct IL-33 stimulation, we sought to define mechanisms mediating their expansion. IL-2 signaling promotes ST2 expression on CD4+ T cells, and dendritic cells (DC) express ST2 (able to respond to IL-33), and are a potential source of IL-2. Thus, we examined if IL-33 mediates ST2+ Treg expansion by stimulating DC IL-2 production. CD11c+ wild type (WT) or IL-2 knockout (KO) bone marrow DC were exposed to IL-33 or LPS. DC phenotype was evaluated by multi-color flow cytometric analysis. The influence of IL-33 DC on T cell function was evaluated in MLR with CD4+ T cells, and T cell proliferation and phenotype were determined by flow analysis. Cytokines were quantitated by ELISA. We found that unlike LPS, IL-33 does not influence DC surface phenotype or induce pro-inflammatory cytokine production compared to controls. However, IL-33 induces a 5-fold increase IL-2 production by DC. In MLR, IL-33 DC selectively expand an activated subset of ST2+Foxp3+ Treg that are CD44hiICOShi. IL-33 DC-derived IL-2 is critical since IL-33-exposed IL-2 KO DC fail to expand ST2+ Treg. In summary, IL-33 licenses DC to selectively expand a subset of activated Treg through production of IL-2, in the absence of classical DC activation. These findings may be harnessed to aid the development of novel therapeutics aimed at promoting immune tolerance.

Conditional STAT3-deficiency augments Flt3 ligand-driven myeloid-derived suppressor cell expansion but limits their suppressor function (IRM7P.487)

Fms-like tyrosine kinase 3 ligand (Flt3L) is a potent hematopoietic growth factor that profoundly expands immunostimulatory dendritic cells (DC). Despite this, the influence of Flt3L on immunoregulatory myeloid-derived suppressor cells (MDSC) has not been described. Since DC and MDSC arise from common myeloid progenitors, and Flt3L-driven DC expansion is STAT3-dependent, we sought to precisely define the role of STAT3 in MDSC downstream of Flt3L signaling. We bred myeloid cell-specific STAT3-deficient mice (LysMCre x STAT3loxP) and administered Flt3L (10 μg/d ip, 10d). Splenic DC (CD11c+) and MDSC (Gr-1+) were isolated by magnetic bead selection. Stimulation and suppression of CD3+ T cell responses was assayed in MLR. As expected, STAT3-deficiency prevented Flt3L-mediated CD11c+ DC expansion. However, we observed an increase in MDSC (CD11b+Gr1+) frequency and absolute numbers in STAT3-deficient mice administered Flt3L. Interestingly, Flt3L-expanded MDSC from STAT3-deficient mice exhibited reduced suppressive capacity against CD3+ T cells in MLR compared to controls. These data identify a previously unappreciated STAT3-independent pathway for MDSC expansion, but reinforce the need for STAT3 signaling for their full suppressive capacity. Likewise, we establish that STAT3 has reciprocal effects on suppressive MDSC and immunostimulatory DC expansion. Together, these findings enhance understanding of the immunomodulatory properties of Flt3L.

Rapamycin-resistant mTORC1 restrains dendritic cell B7-H1 expression that requires IL-1β to enhance regulatory T cell induction (P1349)

Introduction: The mammalian Target of Rapamycin (mTOR) is a central regulator of dendritic cell (DC) function that performs the catalytic activity of mTOR complex (mTORC)1 and 2. mTORC2 functions independently from mTORC1 and is resistant to inhibition by rapamycin (RAPA); however, mTORC1 has both RAPA-sensitive and -resistant outputs. Our goal was to ascertain the role of RAPA-resistant mTOR in DC. Methods: WT C57BL/6 or B7-H1-/- bone marrow-derived DC were generated with the addition of RAPA or ATP-competitive mTOR inhibitor, which blocks all mTOR signaling. DC lacking rictor, an mTORC2-specific subunit, were generated from conditional rictor KO mice. DC induction of regulatory T cells (Treg) was determined in MLR, using BALB/c CD4+CD25- T cell responders. Results and Conclusion: RAPA and mTORC2 deletion reduced DC B7-H1 expression, but ATP-competitive mTOR inhibitors enhanced B7-H1 expression. Augmented B7-H1 expression was blocked by STAT3 inhibition and correlated with reduced expression of the STAT3 negative regulator, SOCS3. DC exposed to ATP-competitive mTOR inhibitors increased Treg induction, which was dependent on DC B7-H1. IL-1β neutralization additionally reduced Treg induction by B7-H1-/- ATP-competitive mTOR inhibitor-exposed DC, suggesting that IL-1β and B7-H1 act additively to promote Treg induction by these DC. These findings establish a RAPA-resistant mTORC1 pathway that acts through SOCS3 and STAT3 to regulate DC B7-H1 expression and Treg induction.

Flt3 ligand expands and activates myeloid-derived suppressor cells in a STAT3-independent manner (P1074)

Introduction: Fms-like tyrosine kinase 3 ligand (Flt3L) promotes dendritic cell (DC) expansion; however, its influence on myeloid-derived suppressor cells (MDSC), an immature population of myeloid cells that suppresses T cell immunity, has not been studied. Methods: BALB/c mice were treated with Flt3L (10 μg/d i.p., 10 d) in the presence or absence of STAT3 inhibitor S31-201 (5 mg/kg/d). Splenic DC and MDSC were isolated by CD11c+ and Gr1+ magnetic bead selection, respectively. Stimulation and suppression of CD3+ T cell responses were assayed by MLR. Syngeneic MDSC were adoptively transferred (5x106) to BALB/c recipients 1 d before C57BL/6 heart transplantation and survival monitored. Results and Conclusions: Flt3L increased MDSC (CD11b+Gr1+) frequency and absolute numbers. MDSC from Flt3L-treated mice potently suppressed CD3+ T cell proliferation greater than control MDSC from naïve splenocytes. Conversely, Flt3L-expanded DC stimulated increased proliferation of allogeneic T cells compared to those from naïve control mice. While STAT3 is considered crucial for MDSC expansion and activation, STAT3 inhibition reduced Flt3L-mediated DC, but not MDSC, expansion. STAT3 inhibition augmented MDSC expansion by Flt3L, without affecting their suppressive capacity. Flt3L-expanded MDSC, but not control MDSC, demonstrated in vivo suppressive activity by prolonging fully MHC-mismatched heart transplant survival. Together, these data identify a novel immunomodulatory function of Flt3L.

CD11c+ dendritic cells are required for IL-33-mediated expansion of ST2+Foxp3+ regulatory T cells in vivo (P1075)

IL-33 is an IL-1 cytokine that signals via ST2, which is expressed on T cells and myeloid cells. Although IL-33 promotes Th2 responses, its administration potently expands CD4+Foxp3+ regulatory T cells (Treg). We examined if IL-33 expands murine Treg directly or indirectly through its impact on CD11c+ DC. The ability of IL-33 to facilitate CD3/CD28-stimulated proliferation of wild-type (WT) or ST2-/- Treg was compared to IL-2. The impact of IL-33 on the capacity of DC to expand Treg was defined in vitro on bone marrow (BM)-generated DC from WT or ST2-/- mice and in vivo using CD11c-DTR BM chimeras administered diphtheria toxin (DT) to deplete CD11c+ cells during IL-33 treatment. The capacity of IL-33-expanded Treg from Foxp3-RFP reporter mice to suppress effector T cells was assessed. We found that IL-33 directly expands Treg in vitro, including an ST2+ subset absent from IL-2-treated cultures. IL-33-exposed DC generate ST2+ Treg from naïve T cells, and is dependent on ST2 expressed by DC. IL-33 failed to expand Treg in vivo, especially ST2+ Treg, in the absence of CD11c+ cells. In conclusion, IL-33 promotes the expansion of suppressive Foxp3+ Treg, including an ST2+ subset in vitro and in vivo. This results from IL-33 activity directly on Treg, but more significantly, indirectly through its impact on CD11c+ cells. These findings have important implications for further characterization of ST2+ Treg and the development of novel therapeutics aimed at promoting immune tolerance.

IL-27 and B7-H1 mediate liver plasmacytoid DC ability to suppress delayed-type hypersensitivity responses (48.9)

IL-27 and B7-H1 are regulatory molecules that modulate immune responses. Plasmacytoid (p) dendritic cells (DC) can promote tolerance. We investigated the contribution of IL-27 and B7-H1 to the ability of murine pDC to regulate T cell responses and to suppress delayed-type hypersensitivity (DTH) reactions to ovalbumin (OVA). PDCA-1+ pDC were purified from livers and spleens of Flt3L-mobilized, C57BL/6J wild type (WT), Ebi3 knockout (KO), or B7-H1 KO mice. pDC phenotype was evaluated by flow cytometry. IL-27p28 was quantified by ELISA and flow cytometry. Ebi3 expression was evaluated by Western blot. T cell allostimulatory capacity of pDC was determined in CFSE MLR. For DTH, mice were immunized with OVA-pulsed bone marrow-derived conventional DC with or without pDC from mice fed OVA. Mice were challenged with heat-aggregated OVA and footpad swelling and T cell responses quantified. Liver pDC express high levels of IL-27p28 and Ebi3 (the components of IL-27) but low IL-12p35 (that forms IL-35 with Ebi3). They express high levels of B7-H1 compared to spleen pDC. Ebi3 KO and B7-H1 KO pDC show enhanced T cell allostimulatory capacity compared to WT pDC. Liver but not spleen pDC suppress DTH responses to OVA, a phenomenon dependent on IL-27 and B7-H1. In conclusion, liver pDC exhibit high expression of IL-27 and B7-H1 that mediate their regulatory ability in vitro and in vivo. Liver pDC, IL-27, and B7-H1 may be important therapeutic targets to promote tolerance or enhance immunity.

IL-27 promotes IL-10 production and B7-H1 expression by plasmacytoid DC and augments their expansion of allogeneic Foxp3+ CD4+ T cells (147.2)

IL-27 is an immunoregulatory cytokine that influences T cell responses and can promote Treg function. Plasmacytoid dendritic cells (pDC) possess immunoregulatory properties that can favor induction of immune tolerance. We investigated the influence of IL-27 on pDC phenotype, function, and interaction with allogeneic T cells. pDC (mPDCA-1+) were immunobead-purified from livers and spleens of Flt3L-treated C57BL/6 mice. Cells were cultured with CpG B, IL-27, or both, and their phenotype and cytokine production analyzed by flow cytometry. T cell allostimulatory capacity of pDC was determined in CFSE MLR, including analysis of Foxp3 expression. CpG B upregulated MHC class II and CD86 on pDC, however, liver pDC expressed greater levels of the coregulator B7-H1, IL-27p28, IL-10, and the IL-27 receptor (R)/WSX-1 compared to spleen pDC. Exposure to exogenous IL-27 augmented B7-H1 and IL-10 but decreased CD86 expression only on liver pDC. Inhibition of STAT3 blunted upregulation of B7-H1. Liver pDC exposed to exogenous IL-27 selectively expanded CD4+Foxp3+ T cells, despite no change in overall CD4+ T cell proliferation. In conclusion, IL-27 enhances the immunoregulatory potential of pDC through upregulation of B7-H1 and IL-10, but not CD86. IL-27-conditioned liver pDC exhibit enhanced ability to expand allogeneic CD4+Foxp3+ T cells compared to spleen pDC. IL-27 may facilitate immunoregulation through the modulation of pDC function and subsequent control of allogeneic T cell responses.

Liver DC modulate Foxp3 expression in allogeneic CD4+ T cells via IL-27 (145.3)

Liver dendritic cells (DC) possess immunoregulatory properties that influence the nature of T cell responses. We investigated the impact of IL-27 on CD4+ T cell responses by liver DC. Both plasmacytoid DC (mPDCA-1+) and myeloid DC (CD11c+ mPDCA-1-) were immunobead-purified from livers and spleens of Flt3L-treated C57BL/6 mice. DC phenotype was analyzed by flow cytometry and cytokine levels were quantified by ELISA. Ebi-3 (a component of the IL-27 molecule) protein expression was determined by Western blot. T cell allostimulatory capacity in MLR was quantified by CFSE dilution analysis, and Foxp3+ T cells quantified by intracellular flow cytometric analysis. Liver DC exhibited reduced expression of antigen (Ag)-presenting and costimulatory molecules and induced inferior T cell proliferation compared to splenic DC. They also produced elevated levels of IL-27p28, IL-10, and IL-6, but reduced IL-12p40 levels compared to splenic DC. Liver DC expressed higher levels of Ebi-3 protein compared to spleen DC. Blockade of IL-27 in allogeneic MLR resulted in greater levels of Foxp3+ T cells when liver but not spleen DC were used as stimulators. Thus, liver DC exhibit lower Ag-presenting and costimulatory molecule expression but produce greater levels of immunoregulatory cytokines than splenic DC, which may contribute to their poor CD4+ T cell allostimulatory capacity. Interestingly, IL-27 produced by liver DC may inhibit their ability to induce Foxp3+ regulatory T cells.

Dendritic cell immunobiology in relation to liver transplant outcome

The unique immunologic environment of the liver, together with its anatomic location downstream of the gut, influences the maturation and function of its interstitial dendritic cell (DC) populations. These well-equipped, antigen-presenting cells play critical roles in regulation of innate and adaptive immunity. New information is emerging about the molecular regulation of liver DC maturation and function, and their tolerogenic potential, while new insight is being gained regarding interactions between liver DC and other immune effector cell populations (NK, NKT cells) in addition to T cells. During transplantation, factors that affect liver DC biology include ischemia-reperfusion injury, liver regeneration, viral infection and the actions of anti-inflammatory and immunosuppressive drugs. Herein, we review the molecular and cell biology of hepatic DC populations in relation to the regulation of alloimmune responses and liver transplant outcome.

Combined mTOR inhibition and post-transplant infusion of alloantigen-specific Treg promotes long-term graft survival in otherwise unmanipulated hosts (141.42)

Protocols that achieve donor-specific tolerance of MHC-mismatched organ grafts remain an unmet clinical goal. We report a strategy that combines post-transplant administration of alloAg-specific Treg (AAsTreg) with inhibition of the mammalian target of rapamycin (Rapa) (mTOR) to promote long-term, donor-specific heart graft survival.

AAsTreg selection was achieved by co-culture of CD4+CD25+ Treg with immature dendritic cells (DC) in the presence of conditioned media. This rendered cells that potently inhibited T cell proliferation in an Ag-specific manner. However, AAsTreg remained unable to control T cell activation when stimulated by mature DC, - a phenomenon dependent on IL-6 release. Exploiting the in vivo inhibitory effects of Rapa on inflammatory cytokine (IL-6) production, T cell proliferation and graft infiltration, AAsTreg were administered post-transplant (d7) in combination with short-term Rapa. AAsTreg exerted a pro-tolerogenic effect: &gt;80% long-term graft survivors [LTS] (MST&gt;150d). Polyclonal Treg exerted an inferior protective effect: 40% LTS (MST=45d). Moreover, the pro-tolerogenic effect was Ag-specific as AAsTreg selected against third party DC failed to prolong graft survival. Significantly, LTS exhibited alloreactive T cell anergy. Thus, combination of mTOR inhibition with AAsTreg is an effective, clinically-applicable approach to promote long-term graft survival.

Attitudes of anaesthetists to awareness and depth of anaesthesia monitoring in the UK

BACKGROUND AND OBJECTIVE

Awareness with postoperative recall of intraoperative events is a rare but serious complication of general anaesthesia. This survey investigated the attitude of anaesthetists in the UK to awareness and depth of anaesthesia monitoring.

METHODS

Questionnaires were sent to 4927 consultant anaesthetists in 285 hospitals in the UK in September 2004. The responses were recorded in an electronic database, summarized and compared with the results of studies performed in Australia and the USA.

RESULTS

The response rate was 44%. When judged against published awareness rates, anaesthetists underestimated the incidence of awareness in their own practice (median 1: 5000). One-third of respondents have dealt with patients who have experienced intraoperative recall. The majority of anaesthetists perceived awareness as a minor problem on an 11-point scale (modal score 2, median score 3, IQR 2-5). Eighty-six percent of anaesthetists considered clinical signs unreliable but 91% felt that measurement of end-tidal anaesthetic agent concentration reduces the likelihood of awareness. The majority of anaesthetists would use a monitor at least some of the time if one was available to them. Overall, the attitudes of anaesthetists in the UK, USA and Australia are remarkably similar.

CONCLUSIONS

Anaesthetists tend not to view awareness as a serious problem. Although most accept that clinical signs are unreliable indicators of awareness, few believe that monitors of anaesthetic depth should be used for routine cases.

Interactions Between Fatty Acids and Arginine Metabolism: Implications for the Design of Immune‐Enhancing Diets

BACKGROUND

Trauma increases the enzyme arginase, thus depleting arginine necessary for producing nitric oxide. Arginine and omega-3 fatty acids are components in immune-enhancing diets. These diets decrease infections in surgical patients, perhaps by preventing arginine deficiency. This study examines whether omega-3 fatty acids alter the metabolic fate of arginine. Thus, we hypothesized there could be differential effects of varying prostaglandins on regulation of arginase.

METHODS

Prostaglandins PGE1, PGE2, and PGE3 were tested using RAW 264.7 cells cultured in the presence of these prostaglandins for 24 hours. IL-13 (10 ng/mL) was added 24 hours later to induce arginase I. NO production was induced by adding LPS (2 microg/mL) to the cultures after another 24 hours.

RESULTS

Arginase activity (nmol/min/mg) was induced by all prostaglandins but significantly more by PGE1 (466.05+/-30.25) and PGE2 (248.45+/-15.05) than PGE3 (139.87+/-19.88; p < .002) when co-cultured with IL-13. Western blots correlated the increase in arginase I expression. Nitrate levels (microM) were inversely proportional to activity with PGE3 having the highest production (3.89+/-0.19) and PGE2 and PGE1 with the lowest (2.75+/-0.49 and 1.54+/-0.19, respectively). Inhibition of arginase I using nor-hydroxyarginine increased and equalized nitrate levels.

CONCLUSIONS

Different prostaglandins significantly alter the metabolism of arginine. Prostaglandins from omega-6 fatty acids increases arginase I expression. By decreasing arginase I expression, prostaglandins from omega-3 fatty acids may increase available arginine. The specific combinations of dietary fatty acids and arginine should be considered when tailoring dietary regimens.

Association between outcome, cerebral pressure reactivity and slow ICP waves following head injury

OBJECTIVE

To investigate the relationships between slow vasogenic waves ('B waves') of intracranial pressure (ICP), pressure-reactivity and outcome after traumatic brain injury.

MATERIAL AND METHOD

193 head-injured patients (age 34 +/- 16.7 years; median GCS 6) were monitored from 1997 to 2002. ICP, arterial blood pressure (ABP) were continuously monitored. Pressure-reactivity index (PRx) and magnitude of ICP slow waves were evaluated using the bed-side computers.

RESULTS

Distribution of PRx in different outcome groups indicated that pressure-reactivity was significantly worse in patients with fatal outcome. A magnitude of spontaneous slow waves of ICP was gradually decreasing in poorer outcome grades. Mortality indicated threshold rise from 20% to 70% when averaged PRx increased above 0.3 (p < 0.01). There was no threshold for mortality observed along distribution of magnitude of ICP slow waves. Mortality gradually increased when the magnitude of slow waves decreased (R = -0.26; p < 0.0001).

CONCLUSION

Inadequate pressure-reactivity and low magnitude of slow vasogenic waves of ICP are associated with fatal outcome after head injury. Based on brain monitoring data, differentiation between favourable outcome and severe disability is more problematic than differentiation between survivors and non-survivors.

Intracranial hypertension: what additional information can be derived from ICP waveform after head injury?

OBJECTIVE

Although intracranial hypertension is one of the important prognostic factors after head injury, increased intracranial pressure (ICP) may also be observed in patients with favourable outcome. We have studied whether the value of ICP monitoring can be augmented by indices describing cerebrovascular pressure-reactivity and pressure-volume compensatory reserve derived from ICP and arterial blood pressure (ABP) waveforms.

METHOD

96 patients with intracranial hypertension were studied retrospectively: 57 with fatal outcome and 39 with favourable outcome. ABP and ICP waveforms were recorded. Indices of cerebrovascular reactivity (PRx) and cerebrospinal compensatory reserve (RAP) were calculated as moving correlation coefficients between slow waves of ABP and ICP, and between slow waves of ICP pulse amplitude and mean ICP, respectively. The magnitude of 'slow waves' was derived using ICP low-pass spectral filtration.

RESULTS

The most significant difference was found in the magnitude of slow waves that was persistently higher in patients with a favourable outcome (p<0.00004). In patients who died ICP was significantly higher (p<0.0001) and cerebrovascular pressure-reactivity (described by PRx) was compromised (p<0.024). In the same patients, pressure-volume compensatory reserve showed a gradual deterioration over time with a sudden drop of RAP when ICP started to rise, suggesting an overlapping disruption of the vasomotor response.

CONCLUSION

Indices derived from ICP waveform analysis can be helpful for the interpretation of progressive intracranial hypertension in patients after brain trauma.

Predictive value of Glasgow Coma Scale after brain trauma: change in trend over the past ten years

BACKGROUND

Age and the Glasgow Coma Scale (GCS) score on admission are considered important predictors of outcome after traumatic brain injury. We investigated the predictive value of the GCS in a large group of patients whose computerised multimodal bedside monitoring data had been collected over the previous 10 years.

METHODS

Data from 358 subjects with head injury, collected between 1992 and 2001, were analysed retrospectively. Patients were grouped according to year of admission. Glasgow Outcome Scores (GOS) were determined at six months. Spearman's correlation coefficients between GCS and GOS scores were calculated for each year.

RESULTS

On average 34 (SD: 7) patients were monitored every year. We found a significant correlation between the GCS and GOS for the first five years (overall 1992-1996: r = 0.41; p<0.00001; n = 183) and consistent lack of correlations from 1997 onwards (overall 1997-2001: r = 0.091; p = 0.226; n = 175). In contrast, correlations between age and GOS were in both time periods significant and similar (r = -0.24 v r = -0.24; p<0.002).

CONCLUSIONS

The admission GCS lost its predictive value for outcome in this group of patients from 1997 onwards. The predictive value of the GCS should be carefully reconsidered when building prognostic models incorporating multimodality monitoring after head injury.

Recent advances in neuroanaesthesia

In order to provide optimum intracranial operating conditions for neurosurgery, anaesthetists must have a thorough understanding of brain physiology and how this is affected by pathology and anaesthetic drugs and techniques. This article discusses the current understanding of cerebral vascular physiology and how novel neuroanaesthetic drugs and techniques affect it.

A DNA helicase from Pisum sativum is homologous to translation initiation factor and stimulates topoisomerase I activity

DNA helicases play an essential role in all aspects of nucleic acid metabolism, by providing a duplex-unwinding function. This is the first report of the isolation of a cDNA (1.6 kb) clone encoding functional DNA helicase from a plant (pea, Pisum sativum). The deduced amino-acid sequence has eight conserved helicase motifs of the DEAD-box protein family. It is a unique member of this family, containing DESD and SRT motifs instead of DEAD/H and SAT. The encoded 45.5 kDa protein has been overexpressed in bacteria and purified to homogeneity. The purified protein contains ATP-dependent DNA and RNA helicase, DNA-dependent ATPase, and ATP-binding activities. The protein sequence contains striking homology with eIF-4A, which has not so far been reported as DNA helicase. The antibodies against pea helicase inhibit in vitro translation. The gene is expressed as 1.6 kb mRNA in different organs of pea. The enzyme is localized in the nucleus and cytosol, and unwinds DNA in the 3' to 5' direction. The pea helicase interacts with pea topoisomerase I protein and stimulates its activity. These results suggest that pea DNA helicase could be an important multifunctional protein involved in protein synthesis, maintaining the basic activities of the cell, and in upregulation of topoisomerase I activity. The discovery of such a protein with intrinsic multiple activity should make an important contribution to our better understanding of DNA and RNA transactions in plants.

Intravenous buscopan for analgesia following laparoscopic sterilisation

Following reports that tubal smooth muscle spasm may contribute to pelvic pain following laparoscopic sterilisation, we studied the effect of buscopan (an anticholinergic agent used to relieve smooth muscle spasm) on 45 patients undergoing general anaesthesia for day-case laparoscopic sterilisation. Patients were randomly allocated to receive either buscopan 20 mg or saline placebo after induction of anaesthesia. There were no significant differences in pain scores or postoperative analgesic requirements between the two groups. We conclude that intravenous buscopan confers no benefit in day-case laparoscopic sterilisation.

Severe head injury in the United Kingdom and Ireland: a survey of practice and implications for management

OBJECTIVE

To study the current intensive care management of patients with severe head injury (defined as a Glasgow Coma Scale score of < or = 8) in neurosurgical referral centers in the United Kingdom (UK) and ireland.

DATA COLLECTION

A questionnaire was sent to the directors of the 44 neurosurgical referral units identified from the UK Medical Directory. After 4 wks, a copy of the questionnaire was sent to all nonresponders, with a cover letter urging them to respond. The aim was to collect data regarding the characteristics of the intensive care units (ICU), sedation, monitoring modalities used, the treatment of intracranial hypertension, and general care of severely head-injured patients.

DATA EXTRACTION

Forty completed questionnaires were returned. Only 35 (88%) centers provided care for the severely head-injured as defined in the questionnaire. Patients were managed in specialized neurosurgical ICUs in 66% of centers and in general ICUs in the remainder of the centers. The ICUs were coordinated by an anesthesiologist in 66% of instances and by a neurosurgeon in 23%. The mean number of beds per units was 7.9 (range 4 to 16), with 1:1 nurse/bed ratio and 5.5 nurses per bed (total number of nursing staff per bed) (range 2.75 to 8). Annual caseload varied between units with the majority of units (49%) receiving between 25 and 50 patients with severe head injury, 23% receiving between 50 and 100 patients with severe head injury, and 29% receiving > 100 patients with severe head injury. There was considerable variability in both the nature of monitoring and therapy between centers. Although blood and central venous pressures were invasively monitored in > 50% of the patients in 94% and 77% of the centers, respectively, intracranial pressure was only monitored routinely in 57% of the centers. Jugular venous bulb oximetry, transcranial Doppler ultrasonography, electroencephalography, and near-infrared spectroscopy were rarely used. Nearly all centers used propofol and midazolam for sedation, with morphine, fentanyl, and alfentanil as the main analgesics. Muscle relaxation was commonly used, with 40% of the centers employing it in 100% of their patients. Atracurium and vecuronium were the most commonly used agents. Only 68% of the centers had a protocol for the treatment of intracranial hypertension. Although hyperventilation to a Paco2 of 26 to 30 torr (3.5 to 4.0 kPa) was the norm in the majority of centers (56%), two centers aimed for Paco2 values < 26 torr (< 3.5 kPa). A quarter of the units did not aim for a cerebral perfusion pressure of > 60 mm Hg. Mild hypothermia was rarely used and 14% of the centers continued to use corticosteroids for the treatment of intracranial hypertension as a result of head trauma.

CONCLUSION

We conclude that there are wide variations in the management of the severely head-injured patient in the UK and Ireland. Some of the therapies employed are not supported by available research findings. Rationalization (using rational management, i.e., based on good evidence) of the intensive care management of severe head injury with the development of widely accepted guidelines may result in an improvement in the quality of care of the head-injured patient.

Dynamic and static cerebral autoregulation during isoflurane, desflurane, and propofol anesthesia

BACKGROUND

Although inhalation anesthetic agents are thought to impair cerebral autoregulation more than intravenous agents, there are few controlled studies in humans.

METHODS

In the first group (n = 24), dynamic autoregulation was assessed from the response of middle cerebral artery blood flow velocity (Vmca) to a transient step decrease in mean arterial blood pressure (MABP). The transient hypotension was induced by rapid deflation of thigh cuffs after inflation for 3 min. In the second group (n = 18), static autoregulation was studied by observing Vmca in response to a phenylephrine-induced increase in MABP. All patients were studied during fentanyl (3 micrograms.kg-1.h-1)/nitrous oxide (70%) anesthesia, followed by, in a randomized manner, isoflurane, desflurane, or propofol in a low dose (0.5 MAC or 100 micrograms.kg-1.min-1) and a high dose (1.5 MAC or 200 micrograms.kg-1.min-1). The dynamic rate of regulation (dROR) was assessed from the rate of change in cerebrovascular resistance (MABP/Vmca) with the blood pressure decreases using computer modeling, whereas the static rate of regulation (sROR) was assessed from the change in Vmca with the change in MABP.

RESULTS

Low-dose isoflurane delayed (dROR decreased) but did not reduce the autoregulatory response (sROR intact). Low-dose desflurane decreased both dROR and sROR. During 1.5 MAC isoflurane or desflurane, autoregulation was ablated (both dROR and sROR impaired). Neither dROR nor sROR changed with low- or high-dose propofol.

CONCLUSIONS

At 1.5 MAC, isoflurane and desflurane impaired autoregulation whereas propofol (200 micrograms.kg-1.min-1) preserved it.

Effect of the Valsalva maneuver on intracranial hypertension

We describe a case of intracranial hypertension in a previously healthy 25-year-old man who sustained a head injury in a motor vehicle accident, in whom a Valsalva maneuver resulted in parallel reductions in mean arterial blood pressure, cerebral blood flow velocity in the middle cerebral artery, and intracranial pressure. The effects of raising intrathoracic pressure in patients with intracranial hypertension are discussed.

Septicemia due to Yersinia enterocolitica in a hemodialyzed, iron-depleted patient receiving omeprazole and oral iron supplementation

Septicemia occurred in a long-term hemodialysis patient on oral iron supplementation who had been treated for esophageal ulcer by omeprazole, an ulcer-healing drug. Yersinia enterocolitica serotype 0:3 was recovered from blood cultures. A raised intraintestinal pH and an increased intraluminal iron load may have been contributing factors for the enhanced proliferation and generalized infection of Y enterocolitica.