Composite prostheses for the repair of abdominal wall defects: effect of the structure of the adhesion barrier component

The component of a composite prosthesis, which makes contact with the visceral peritoneum, can be reabsorbable or non-reabsorbable, and laminar or reticular. This study was designed to determine whether the composition of this second, barrier component could improve its behavior at this interface. Abdominal wall defects in rabbits were repaired using a polypropylene prosthesis (PP), or the composites Sepramesh (PP+h) or Vicryl (PP+v). Fourteen days after surgery, the implants were evaluated by light and scanning electron microscopy, and immunohistochemistry. Prosthetic areas occupied by adhesions (PP: 71.08±5.09, PP+h: 18.55±4.96, P+v: 69.69±16.81%), neoperitoneal thickness (PP: 256.17±21.68, PP+h: 83.11±19.63, PP+v:213.72±35.90 μm) and macrophage counts (PP: 8.73±1.16, PP+h: 27.33±4.13, PP+v: 31.24±3.08%) showed significant differences (P<0.05). The tested biomaterials induced an optimal recipient tissue infiltration. Least adhesion formation was observed on the PP+h implants. This suggests that the second component, although reabsorbable, should be smooth in structure.     

Dorsal root ganglia cocultured with macrophages: an in vitro model to study experimental demyelination

The present investigation introduces an in vitro model to study macrophage properties during demyelination. Rat dorsal root ganglia (DRG) were cultured for obtaining myelinated peripheral nerve fibers. These cultures were exposed to non-resident macrophages. In untreated control cultures, there was no indication of myelin removal by the added macrophages. DRG were exposed to enzymatically generated oxygen radicals using the xanthin/xanthin oxidase or the glucose/glucose oxidase system. Assessment of Schwann cell viability and ultrastructural morphology revealed different patterns of cell cytotoxicity and morphological changes in different experiments. High concentrations caused complete tissue necrosis of the DRG, while low concentrations did not affect either cell viability or ultrastructural morphology. Under intermediate experimental conditions, oxygen radicals caused non-lethal Schwann cell damage leading to Schwann cell retraction and myelin sheath rejection. Myelin lamellae were disrupted and decompacted. These changes were followed by a selective macrophage attack on myelin sheats, resulting in demyelination. Axons, Schwann cells and sensory ganglion cells survived this attack. The specificity of the oxygen radical effects was tested in experiments using the oxygen radical scavengers catalase and superoxide dismutase. Catalase prevented the described effects on cell morphology and subsequently blocked demyelination by non-resident macrophages.Supported by a grant from the Deutsche Forschungsgemeinschaft (DFG) (Br 1274/1-1)     

CD154-CD40-induced reactivation of latent HIV-1 infection

Reservoirs of latent HIV-1 in T cells and macrophages pose one of the major obstacles that hamper final eradication of HIV-1 from infected patients. Targeting costimulatory molecules expressed on cell types harboring latent HIV-1 to achieve reactivation may provide a new approach to overcome this problem. One such molecule is CD40, a member of the tumor necrosis factor (TNF)-receptor family. Using THP89GFP cells as a model for latently infected macrophages, we demonstrate that trimeric forms of recombinant CD154 allow for the direct reactivation of latent HIV-1 infection. Reactivation is augmented by the release of TNF-alpha. The presence of TNF-alpha is also crucial for the expression of late structural genes such as p24 Gag. In addition, levels of secreted TNF-alpha are sufficiently high to reactivate latent HIV-1 in a latently HIV-1-infected T-cell line (J89GFP). Taken together, our results demonstrate that costimulatory molecules may be attractive targets to reactivate latent HIV-1 in infected patients.     

The innate immune response under the control of the LXR pathway

Macrophages play essential roles in infection and resolution of inflammation. This review summarizes recent findings that suggest a relevant role for the nuclear receptor liver X receptor (LXR) in the evolution of immune responses. By exerting both positive and negative regulation of specific macrophage gene expression networks, LXRs display anti-inflammatory activities and promote macrophage survival in bacterial infection settings. Agonists that activate the LXR pathway may be used to enhance innate immunity to highly virulent pathogens that otherwise induce macrophage apoptosis as a means to subvert host immune defense.     

Human immunodeficiency virus 1 favors the persistence of infection by activating macrophages through TNF

Macrophages play a major role in HIV-1 persistence. In the present paper, we demonstrate that the absence of apoptosis in HIV-1-infected primary human monocyte-differentiated macrophages (MDM) correlates with an increase in anti-apoptotic (Bcl-2 and Bcl-x(L)) and a decrease in pro-apoptotic (Bax and Bad) proteins. This is associated with macrophage activation as shown by tumor necrosis factor (TNF) production and NF-kappaB activation upon infection. TNF production was shown to be involved in the upregulation of Bcl-2 and Bcl-x(L) because this increase was abolished by an anti-TNF anti-serum or an inhibitor of TNF synthesis. In parallel, inhibition of TNF production induced an increase in the number of apoptotic cells. Furthermore, using an inhibitor of NF-kappaB activation, we demonstrated that TNF-induced upregulation of Bcl-x(L) and Bcl-2 occurs, respectively, through a NF-kappaB-dependent and an NF-kappaB-independent pathway.     

Interleukin-1 dysregulation is an intrinsic defect in macrophages from MRL autoimmune-prone mice

Macrophages (M?) from pre-diseased autoimmune-prone MRL mice (both MRL/+ and MRL/1pr) dramatically underproduce the cytokine interleukin-1 (IL-1) in comparison to M? from a number of normal strains. In this study we show that IL-1 dysregulation by MRL M? is fully expressed at birth, and that this defect does not change with time or the development of disease. We also constructed adult irradiation chimeras (consisting of A/J → MRL and MRL → A/J mice), and show that M? isolated from these chimeras display a pattern of IL-1 production indistinguishable from that of the donor strain controls. Moreover, when we constructed a mixed chimera (A/J + MRL → A/J), the A/J and MRL M? coexisting within the same animal retained their individual patterns of IL-1 production when isolated by negative selection. Taken together, these results provide the first substantive evidence for an intrinsic defect (IL-1 dysregulation) in M? from MRL autoimmune-prone mice.     

Is there a role of taurine bromamine in inflammation? Interactive effects with nitrite and hydrogen peroxide

Objective and Design: The myeloperoxidase system of neutrophils generates chlorinating and brominating oxidants in vivo. The major haloamines of the system are taurine chloramine (TauCl) and taurine bromamine (TauBr). It has been demonstrated in vitro that TauCl exerts both antiinflammatory and anti-bacterial properties. Much less is known about TauBr. The present study was conducted to compare bactericidal and immunoregulatory capacity of TauBr with that of the major chlorinating oxidants: HOCl and TauCl. Moreover, the effect of nitrites and H₂O₂ on TauBr activity was investigated.Materials: TauBr was prepared by reaction of HOBr with taurine. The reaction was monitored by UV absorption spectra.Methods: Bactericidal activity of TauBr, TauCl and HOCl was tested by incubation of E. coli with the compounds and determined by the pour-plate method. To test the anti-inflammatory activity the compounds were incubated with LPS and IFN- stimulated murine peritoneal macrophages. The production of following mediators was measured: nitrites by Griess reaction; TNF-, IL-6, IL-10, IL-12p40 using capture ELISA. In some experiments the compounds were incubated with either nitrites or H₂O₂.Results: In our experimental set-up TauBr and HOCl exerted strong bactericidal effects on E. coli (MBC = 110 M and 8 M, respectively), while TauCl (< 1000 M) did not kill test bacteria. However, both, TauBr and TauCl, at noncytotoxic concentrations (< 300 M) inhibited the cytokine and nitric oxide production by macrophages. H₂O₂ completely abolished the biological activities of TauBr but not those of TauCl. Nitrites did not affect any activity of TauBr or TauCl while they diminished the HOCl^– mediated bacterial killing.Conclusion: TauBr, despite very low concentration of Br^– in body fluids, may support TauCl and HOCl in the regulation of inflammatory response and in killing of bacteria by neutrophils. However, TauBr activity in vivo will depend on the presence of H₂O₂ and possible other mediators of inflammation which can compete with target molecules for TauBr.Received 16 August 2004; returned for revision 16 September 2004; accepted by A. Falus 13 October 2004     

Cellular localization of inflammatory cytokines in human glomerulonephritis

We evaluated the expression of inflammatory cytokines in renal tissues obtained from 45 patients with several types of glomerulonephritis. Immunofluorescence studies with specific antibodies to interleukin (IL)-1, IL-1, IL-6, tumour necrosis factor (TNF)-, and TNF- showed intense cytoplasmic staining in the glomeruli and interstitium. Cells positive for these cytokines were found frequently in tissue from patients with lupus nephritis (WHO Class IV) and membranoproliferative glomerulonephritis, and, to a lesser extent, in tissue from patients with mesangial proliferative glomerulonephritis, Henoch-Schönlein purpura nephritis, and minimal change nephrotic syndrome. Most of these cells were dual-stained with a monoclonal antibody to monocytes-macrophages. In situ hybridization for cytokine mRNA, combined with immunoperoxidase staining for monocytes-macrophages, detected IL-1, IL-6, and TNF- mRNA in monocytes-macrophages infiltrating the glomeruli and interstitium. Occasionally, there was weak or moderate immunostaining for IL-1, IL-6, and TNF- in the glomerular mesangial and epithelial cells, but in situ hybridization signals were rarely found in these loci. These findings suggest that infiltrating monocytes-macrophages, rather than resident glomerular cells, are the major source of inflammatory cytokines in human glomerulonephritis.     

Macrophage colony-stimulating factor gene transfer into tumor cells induces macrophage infiltration but not tumor suppression

In order to analyze the effect of a high local concentration of macrophage colony-stimulating factor (M-CSF; CSF-1) on tumor growth, the plasmacytoma cell line J558L was transfected with the human M-CSF gene and injected into syngeneic BALB/c mice. In contrast to the parental tumors, M-CSF transfectants were heavily infiltrated by macrophages as evidenced by immunohistochemistry with antibodies to Mac-1 and Mac-3 and by isolation of the macrophages from the tumor. Nevertheless, tumor growth was only slightly affected by M-CSF and M-CSF-producing cells grew as tumor in all cases. The growth retardation of M-CSF-producing cells varied depending on the experiment and seemed to be due to an indirect effect because the growth rate of the cells in vitro had not changed upon gene transfer. Attempts to activate the tumor-infiltrating macrophages for tumor suppression by systemic application of interferon-γ and/or lipopolysaccharide were not successful. Altogether, our results suggest that M-CSF is a potent chemoattractant for macrophages in vivo but alone is not sufficient to activate these macrophages for tumoricidal activity.