Identification and Interpretation of Longitudinal Gene Expression Changes in Trauma

The relationship between leukocyte gene expression and recovery of respiratory function after injury may provide information on the etiology of multiple organ dysfunction.To find a list of genes for which expression after injury predicts respiratory recovery, and to identify which networks and pathways characterize these genes.Blood was sampled at 12 hours and at 1, 4, 7, 21 and 28 days from 147 patients who had been admitted to the hospital after blunt trauma. Leukocyte gene expression was measured using Affymetrix oligonucleotide arrays. A linear model, fit to each probe-set expression value, was used to impute the gene expression trajectory over the entire follow-up period. The proportional hazards model score test was used to calculate the statistical significance of each probe-set trajectory in predicting respiratory recovery. A list of genes was determined such that the expected proportion of false positive results was less than 10%. These genes were compared to the Gene Ontology for 'response to stimulus' and, using Ingenuity software, were mapped into networks and pathways.The median time to respiratory recovery was 6 days. There were 170 probe-sets representing 135 genes that were found to be related to respiratory recovery. These genes could be mapped to nine networks. Two known pathways that were activated were antigen processing and presentation and JAK-signaling.The examination of the relationship of gene expression over time with a patient's clinical course can provide information which may be useful in determining the mechanism of recovery or lack of recovery after severe injury

Induction and regulation of monocyte procoagulant activity

Monocyte (MO) procoagulant activity (PCA) is induced by various stimuli including allogeneic stimulation, immunocomplexes, and bacterial products. Antigen-antibody complex stimulation therefore represents a pathway for MO PCA induction. Activation of MO PCA has been demonstrated in immunocomplex disease and could represent a major pathology in transplanted immunocomplex disease patients. Stimulation of monocytes via their FcRI receptor has been demonstrated to induce TNF and PGE2. This report demonstrates that stimulation of the high-density FcRI receptor-bearing (FcRI+) MO by resetting with anti-Rh coated erythrocytes also induces significant PCA levels (P less than 0.001). Muramyl dipeptide (MDP), a Gram-positive bacterial cell wall analogue, further increased PCA levels in the FcRI stimulated MO subpopulation (P less than 0.003). Although increased PCA levels were also induced in the FcRI- MO subpopulation by MDP (P less than 0.003), the FcRI+ MO responded with much greater levels of PCA and PGE2 (P less than 0.001). Greater PCA levels in the FcRI-positive MO subpopulation may indicate that stimulation of MO through their FcRI represents a different pathway from allogenic PCA activation, which can be augmented by subsequent bacterial challenge. A novel inhibitory effect of IL-4 on MO PCA induction is also demonstrated. IL-4 downregulated MO PCA levels either after isolation stimulation (55 +/- 19%), FcRI stimulation (57 +/- 12%), or FcRI plus MDP stimulation (60 +/- 13%). PCA and PGE2 levels were concomitantly downregulated by IL-4 both in the FcRI-stimulated, FcRI+ and in the MDP-stimulated FcRI- MO subpopulations. Since indomethacin blocked MDP induced MO PGE2 production without affecting MO PCA levels, PGE2 production is not required for FcRI-stimulated PCA induction

Elevated monocyte interleukin-6 (IL-6) production in immunosppressed trauma patients. II. Downregulation by IL-4

Aberrant monocyte mediator production is pivotal in the development of posttrauma immunosuppression. We have previously shown that immunodepressed trauma patients\u27 monocytes produce elevated interleukin-6, suggesting their in vivo preactivation. This study confirms that preactivated patients\u27 Mo produce greater levels of IL-6 than normals\u27 Mo to the same in the in vitro Fc gamma RI stimulation. We also demonstrate the capacity of interleukin-4 to downregulate the elevated interleukin-6 production of trauma patients\u27 in vivo preactivated monocytes. Monocyte interleukin-6 downregulation by interleukin-4 is dose dependent and occurs whether Fc gamma RI cross-linking, muramyl dipeptide, indomethacin plus muramyl dipeptide, or interferon-gamma plus muramyl dipeptide is the interleukin-6 inducing stimulus. Furthermore, interleukin-4-dependent downregulation of monocyte interleukin-6 expression is confirmed at both the supernatant and the mRNA levels. Simultaneous downregulation of posttrauma elevated monokines implies a possible therapeutic benefit of interleukin-4 for trauma patients

Dibutyryl-cAMP modulation of receptor expression and antigen presentation capacity in monocyte subpopulations

Monocyte phenotype heterogeneity is often associated with functional differences between the distinguished Mphi subpopulations. We have previously demonstrated that the Mphi subpopulation separated and stimulated by rosetting Mphi via the Type I Fc gamma R (CD64) are poor antigen presenting cells but can be induced to greater production of TNF alpha, IL-6 and PGE2 than the Fc gamma RI- Mphi population. Here we demonstrate that the Fc gamma RI- Mphi represent the major antigen presenting Mphi population and that APC capacity of the FcRI- Mphi can be further increased by elevating intracellular cAMP levels. Treatment of the Fc gamma RI+ Mphi with db cAMP decreases both their expression of CD64 and their capacity to produce TNF alpha to the levels typical of Fc gamma RI- Mphi. Db cAMP treatment of the Fc gamma RI+ Mphi subpopulation, however, cannot augment the antigen presenting capacity of this low APC Mphi subpopulation to the level of that of the Fc gamma RI- Mphi. Basal expression of the Mo3 activation marker was comparable in the FcRI+/FcRI- Mphi subpopulations, but the FcRI+ Mphi were induced by db cAMP treatment to increase their Mo3 expression to higher levels than the FcRI- Mphi. These results suggest that although elevated intracellular cAMP levels can modulate some Fc gamma RI+ Mphi functions to more closely parallel those of the Fc gamma RI- Mphi, this treatment cannot increase the efficiency of the Fc gamma RI+ Mphi subpopulation as an antigen presenting cell

Antigen presentation by the CD4 positive monocyte subset

Although CD4 antigen is expressed on monocytes (MO), its functional role is uncharacterized. In this study, isolated human MO were separated into CD4+ and CD4- MO subsets and assessed for presentation of tetanus toxoid. The CD4- MO subset had decreased antigen presenting cell (APC) capacity as well as increased PGE2 production when compared to the CD4+ MO subset. Addition of a cyclo-oxygenase inhibitor (Indomethacin) did not restore the CD4- MO subset\u27s APC capacity to that of the similarly treated CD4+ MO subset, eliminating differential PGE2 production as the primary cause of differential APC capacity. Production of monokines such as IL-1 and plasminogen activator, which affect APC capacity, was similar in the CD4 MO subsets. However, tumor necrosis factor (TNF) production (IFN gamma plus MDP-induced) of the CD4+ MO subset was slightly greater than that of the CD4- MO. CD4- MO\u27s lower APC capacity is not totally explained by their differential IL-1, TNF, or PGE2 production

Elevated monocyte interleukin-6 (IL-6) production in immunosuppressed trauma patients. I. Role of Fc gamma RI cross-linking stimulation

This study demonstrates that immunodepressed trauma patients\u27 monocytes produce elevated interleukin-6 to adherence, bacterial, and cytokine stimulation compared to immunocompetent trauma patients\u27 or normals\u27 monocytes, suggesting their in vivo preactivation possibly mediated by the hyperimmunoglobulinemia which characterizes these patients. Furthermore, stimulation of monocytes through cross-linking their Fc gamma RI induces and augments interleukin-6 (IL-6) production to subsequent stimulation both in trauma patients\u27 (P less than 0.001) and in normals\u27 (P less than 0.001) monocytes. As we reported earlier, immunodepressed trauma patients have an increased proportion of Fc gamma RI-bearing monocytes in their total monocyte population and here we show that those Fc gamma RI+ monocytes produce significantly elevated interleukin-6, suggesting a relationship between elevated monocyte interleukin-6 production and Fc gamma RI triggering. Interleukin-6 induction by FcRI stimulation is not mediated solely by FcRI-induced M phi tumor necrosis factor alpha, IL-1 alpha, or IL-1 beta production and is independent of M phi prostaglandin E2 levels. Therefore, FcRI stimulation-induced elevated M phi IL-6 might contribute to the increased immunoglobulin levels posttrauma

Elevated tumor necrosis factor alpha production concomitant to elevated prostaglandin E2 production by trauma patients\u27 monocytes

The level of tumor necrosis factor alpha (TNF alpha), a monokine implicated in mediating septic shock, is elevated in the blood of some patients with sepsis. Monocytes from 11 trauma patients and 11 burn patients were suboptimally stimulated with interferon gamma and muramyl dipeptide, an analogue of bacterial wall products. The patients with sepsis showed significantly greater total TNF alpha levels (secreted in combination with cell-associated) 3 days before septic episodes, as compared with normal controls (32.38 to 2231.76 ng/10(6) monocytes per milliliter, median = 121.03 ng/10(6) monocytes per milliliter; normal control: 0.00 to 18.20 ng/10(6) monocytes per milliliter, median = 5.93 ng/10(6) monocytes per milliliter). Increases in patients\u27 total monocyte TNF alpha levels greater than 30 ng/10(6) monocytes per milliliter correlated with septic episodes. In patients with sepsis, the total monocyte TNF alpha levels were increased despite a concomitant increase in their prostaglandin E2 levels in both stimulated (interferon gamma plus muramyl dipeptide) and unstimulated in vitro assays (9 patients: stimulated prostaglandin E2 range, 30.1 to 123.6 ng/10(6) monocytes per milliliter). Massively elevated monocyte TNF alpha and prostaglandin E2 production occurred simultaneously in patients with sepsis

Aberrations in post-trauma monocyte (MO) subpopulation: role in septic shock syndrome

Appearance of increased proportions of monocytes bearing the 72kd(FcRI) receptor for IgG correlated to aberrant monocyte (MO) functions, depressed immune functions, and poor clinical outcome. The trauma patients\u27 FcRI+ MO subpopulation produced the majority of their elevated IL-6, TNF alpha, TGF beta, and PGE2. IgG stimulation of patients\u27 MO through FcRI not only stimulated TNF alpha, IL-6, and PGE2 levels, but also greatly augmented the levels of these monokines produced after subsequent bacterial challenge. Post-trauma increased IL-6 levels can lead to polyclonal B-cell activation and high levels of circulating, nonspecific IgG as seen in trauma patients. This nonspecific IgG triggers the FcRI on the increased numbers of FcRI+ MO leading to ever-increasing monokine levels. IL-4 was found to downregulate patients\u27 FcRI+ MO production of mediators. The cycle of altered cytokine levels, increased FcRI+ MO numbers, elevated IgG, and augmented triggering of FcRI+ MO may be broken by addition of IL-4