Arwed Hostmann

Epratuzumab targeting of CD22 affects adhesion molecule expression and migration of B-cells in systemic lupus erythematosus

IntroductionEpratuzumab, a humanized anti-CD22 monoclonal antibody, is under investigation as a therapeutic antibody in non-Hodgkins lymphoma and systemic lupus erythematosus (SLE), but its mechanism of action on B-cells remains elusive. Treatment of SLE patients with epratuzumab leads to a reduction of circulating CD27negative B-cells, although epratuzumab is weakly cytotoxic to B-cells in vitro. Therefore, potential effects of epratuzumab on adhesion molecule expression and the migration of B-cells have been evaluated.MethodsEpratuzumab binding specificity and the surface expression of adhesion molecules (CD62L, β7 integrin and β1 integrin) after culture with epratuzumab was studied on B-cell subsets of SLE patients by flow cytometry. In addition, in vitro transwell migration assays were performed to analyze the effects of epratuzumab on migration towards different chemokines such as CXCL12, CXCL13 or to CXCR3 ligands, and to assess the functional consequences of altered adhesion molecule expression.ResultsEpratuzumab binding was considerably higher on B-cells relative to other cell types assessed. No binding of epratuzumab was observed on T-cells, while weak non-specific binding of epratuzumab on monocytes was noted. On B-cells, binding of epratuzumab was particularly enhanced on CD27negative B-cells compared to CD27positive B-cells, primarily related to a higher expression of CD22 on CD27negative B-cells. Moreover, epratuzumab binding led to a decrease in the cell surface expression of CD62L and β7 integrin, while the expression of β1 integrin was enhanced. The effects on the pattern of adhesion molecule expression observed with epratuzumab were principally confined to a fraction of the CD27negative B-cell subpopulation and were associated with enhanced spontaneous migration of B-cells. Furthermore, epratuzumab also enhanced the migration of CD27negative B-cells towards the chemokine CXCL12.ConclusionsThe current data suggest that epratuzumab has effects on the expression of the adhesion molecules CD62L, β7 integrin and β1 integrin as well as on migration towards CXCL12, primarily of CD27negative B-cells. Therefore, induced changes in migration appear to be part of the mechanism of action of epratuzumab and are consistent with the observation that CD27negative B-cells were found to be preferentially reduced in the peripheral blood under treatment.

Trauma induces apoptosis in human thoracolumbar intervertebral discs

BackgroundVertebral fractures resulting from high energy trauma often comprise the risk of posttraumatic degenerative changes in the affected intervertebral discs (IVD). Particularly in conservatively treated patients, or in cases after implant removal of an exclusively posterior stabilization, consecutive disc degeneration and the associated functional losing of the spinal segment clearly represent detrimental treatment results. In this regard, apoptosis of IVD cells has been suggested to be involved in the critical changes of the extracellular matrix.MethodsTo investigate whether fractures of the vertebrae induce apoptosis in the affected IVD, disc tissue from patients (n = 17) undergoing open reduction and internal fixation of thoracolumbar spine fractures were analysed in regards to caspase activity, apoptosis-receptor expression levels and gene expression of apoptosis-regulating proteins such as Bax and Bcl-2. Healthy IVD tissue (n = 3) obtained from patients undergoing surgical resection of adjacent vertebrae were used as control samples.ResultsIn contrast to healthy control IVD tissues, samples from traumatic thoracolumbar IVD showed positive TUNEL staining and a significant increase of caspase-3/7 activity. Interestingly, analyses of the initiator caspase-8 and -9 revealed significantly increased activation levels compared to control values, suggesting the coexistent activation of both the extrinsic (receptor-mediated) and intrinsic (mitochondria-mediated) apoptosis pathway. Accordingly, expression levels of the Fas receptor (FasR) mRNA were significantly increased. Although the TNF receptor I (TNFR I) was only slightly upregulated, corresponding TNFα from trauma IVD presented significantly increased mRNA expression values. Furthermore, traumatic IVD cells demonstrated significantly reduced expression of the mitochondria-bound anti-apoptotic Bcl-2, thereby maintaining baseline transcriptional levels of the pro-apoptotic Bax protein when compared to control IVD cells.ConclusionOur data suggest that thoracolumbar fractures induce early caspase-dependent apoptosis in IVD cells of the affected intervertebral disc, in part, by downregulation of the anti-apoptotic protein Bcl-2 (intrinsic apoptosis pathway), as well as signalling via the death receptor complex (TNFR I and FasR).

Apoptosis of human intervertebral discs after trauma compares to degenerated discs involving both receptor-mediated and mitochondrial-dependent pathways

Post‐traumatic disc degeneration with consecutive loss of reduction and kyphosis remains a debatable issue within both the operative and nonoperative treatment regimen of thoracolumbar spine fractures. Intervertebral disc (IVD) cell apoptosis has been suggested to play a vital role in promoting the degeneration process. To evaluate and compare apoptosis‐regulating signaling mechanisms, IVDs were obtained from patients with thoracolumbar spine fractures (n = 21), patients suffering from symptomatic IVD degeneration (n = 6), and from patients undergoing surgical resection of a primary vertebral tumor (n = 3 used as control samples). All tissues were prospectively analyzed in regards to caspase‐3/7, ‐8, and ‐9 activity, apoptosis‐receptor expression levels, and gene expression of the mitochondria‐bound apoptosis‐regulating proteins Bax and Bcl‐2. Morphologic changes characteristic for apoptotic cell death were confirmed by H&E staining. Statistical significance was designated at p < 0.05 using the Students t‐test. Both traumatic and degenerative IVD demonstrated a significant increase of caspase‐3/7 activity with evident apoptosis. Although caspase‐3/7 activation was significantly greater in degenerated discs, both showed equally significant activation of the initiator caspases 8 and 9. Traumatic IVD alone demonstrated a significant increase of the Fas receptor (FasR), whereas the TNF receptor I (TNFR I) was equally up‐regulated in both morbid IVD groups. Only traumatic IVD showed distinct changes in up‐regulated TNF expression, in addition to significantly down‐regulated antiapoptotic Bcl‐2 protein. Our results suggest that post‐traumatic disc changes may be promoted and amplified by both the intrinsic mitochondria‐mediated and extrinsic receptor‐mediated apoptosis signaling pathways, which could be, in part, one possible explanation for developing subsequent disc degeneration.

IL-10 overexpression differentially affects cartilage matrix gene expression in response to TNF-α in human articular chondrocytes in vitro

Cartilage-specific extracellular matrix synthesis is the prerequisite for chondrocyte survival and cartilage function, but is affected by the pro-inflammatory cytokine TNF-alpha in arthritis. The aim of the present study was to characterize whether the immunoregulatory cytokine IL-10 might modulate cartilage matrix and cytokine expression in response to TNF-alpha. Primary human articular chondrocytes were treated with either recombinant IL-10, TNF-alpha or a combination of both (at 10ng/mL each) or transduced with an adenoviral vector overexpressing human IL-10 and subsequently stimulated with 10ng/ml TNF-alpha for 6 or 24h. The effects of IL-10 on the cartilage-specific matrix proteins collagen type II, aggrecan, matrix-metalloproteinases (MMP)-3, -13 and pro-inflammatory cytokines were evaluated by real-time RT-PCR and immunohistochemistry. Transduced chondrocytes overexpressed high levels of IL-10 which significantly up-regulated collagen type II expression. TNF-alpha suppressed collagen type II and aggrecan, but increased MMP and cytokine expression in chondrocytes compared to the non-stimulated controls. The TNF-alpha mediated down-regulation of aggrecan expression was significantly antagonized by IL-10 overexpression, whereas the suppression of collagen type II was barely affected. The MMP-13 and IL-1beta expression by TNF-alpha was slightly reduced by IL-10. These results suggest that IL-10 overexpression modulates some catabolic features of TNF-alpha in chondrocytes.

Systemic Ubiquitin Release After Blunt Trauma and Burns: Association With Injury Severity, Posttraumatic Complications, and Survival

BACKGROUND Recent data suggest that ubiquitin (Ub) is systemically released after trauma, has pleiotropic effects on host defense mechanisms, and that Ub administration reduces fluid shifts into tissues during inflammation. Ub release after burns (B) has not been studied and its association with injury severity and outcome after blunt trauma (T) is unknown. Thus, we evaluated Ubs association with injury severity and outcomes after B and T. METHODS Injury severity was assessed with the Injury Severity Score (ISS) in T and burn size (% total body surface area, %TBSA) in B. A total of 129 T (ISS: 26 +/- 13) and 55 B (46% +/- 18% TBSA) were observed for sepsis/multiple organ failure (MOF) and survival. In B, sequential organ failure assessment scores were documented daily. Fifty volunteers served as controls (C) Ub serum levels were measured on day 0 (admission), 1, 3, 5, and 7 by enzyme-linked immunosorbent assay. Data were analyzed using bivariate or partial correlation analyses, t test, and analysis of variance with Tukey post-hoc test for multiple comparisons (two-tailed p < 0.05). RESULTS Ub was significantly elevated in patients. Peak levels (ng/mL) were detectable on day 0 (C: 118 +/- 76; T: 359 +/- 205; B: 573 +/- 331) and increased with increased ISS, %TBSA, and presence of inhalation injury. In T, Ub normalized by day 3, but remained elevated in B. In B, Ub correlated significantly negative with sequential organ failure assessment scores (r: -0.143; p = 0.0147), sepsis/MOF development (r: -0.363; p = 0.001), and survival (r: -0.231; p = 0.009). Compared with B who recovered uneventfully, Ub levels were significantly lower on days 1 to 7 and on days 5/7 in B who developed sepsis/MOF or died, respectively. CONCLUSION Ub concentrations reflect the extent of tissue damage. Along with Ubs previously described anti- inflammatory properties, this study suggests that its systemic release is protective, that burn patients who develop sepsis/MOF have a relative Ub deficiency and that Ub could play an important role during the physiologic response to burn injury.

Modulation of systemic antigen-specific immune responses by oral antigen in humans.

Oral antigen uptake can induce systemic immune responses ranging from tolerance to immunity. However, the underlying mechanisms are poorly understood, especially in humans. Here, keyhole limpet hemocyanin (KLH), a neoantigen which has been used in earlier studies of oral tolerance, was fed in a repeated low‐dose and a single high‐dose protocol to healthy volunteers. KLH‐specific CD4+ T‐cell proliferation and cytokine production, as well as KLH‐specific serum Ab and the effects of oral KLH on a subsequent parenterally induced systemic immune response, were analyzed. Repeated low‐dose oral KLH alone induced antigen‐specific CD4+ T cells positive predominantly for the gut‐homing receptor integrin β7 and the cytokines IL‐2 and TNF‐α; some CD4+ T cells also produced IL‐4. Oral feeding of KLH accelerated a subsequent parenterally induced systemic CD4+ T‐cell response. The cytokine pattern of KLH‐specific CD4+ T cells shifted toward more IL‐4‐ and IL‐10‐ and less IFN‐γ‐, IL‐2‐ and TNF‐α‐producing cells. The parenterally induced systemic KLH‐specific B‐cell response was accelerated and amplified by oral KLH. The impact of single high‐dose oral KLH on antigen‐specific immune responses was less pronounced compared with repeated low‐dose oral KLH. These findings suggest that oral antigen can effectively modulate subsequently induced systemic antigen‐specific immune responses. Immunomodulation by oral antigen may offer new therapeutic strategies for Th type1‐mediated inflammatory diseases and for the development of vaccination strategies.

Impaired erythropoiesis after haemorrhagic shock in mice is associated with erythroid progenitor apoptosis in vivo.

Objective: Multiply traumatised patients often suffer from blood loss and from subsequent therapy‐resistant anaemia, possibly mediated by apoptosis, necrosis, or humoral factors. Therefore, the underlying mechanisms were investigated in bone marrow (BM) and peripheral blood in a murine resuscitated haemorrhagic shock (HS) model.

Biphasic onset of splenic apoptosis following hemorrhagic shock : critical implications for Bax, Bcl-2, and Mcl-1 proteins

IntroductionThe innate immune response to trauma hemorrhage involves inflammatory mediators, thus promoting cellular dysfunction as well as cell death in diverse tissues. These effects ultimately bear the risk of post-traumatic complications such as organ dysfunction, multiple organ failure, or adult respiratory distress syndrome. In this study, a murine model of resuscitated hemorrhagic shock (HS) was used to determine the apoptosis in spleen as a marker of cellular injury and reduced immune functions.MethodsMale C57BL-6 mice were subjected to sham operation or resuscitated HS. At t = 0 hours, t = 24 hours, and t = 72 hours, mice were euthanized and the spleens were removed and evaluated for apoptotic changes via DNA fragmentation, caspase activities, and activation of both extrinsic and intrinsic apoptotic pathways. Spleens from untreated mice were used as control samples.ResultsHS was associated with distinct lymphocytopenia as early as t = 0 hours after hemorrhage without regaining baseline levels within the consecutive 72 hours when compared with sham and control groups. A rapid activation of splenic apoptosis in HS mice was observed at t = 0 hours and t = 72 hours after hemorrhage and predominantly confirmed by increased DNA fragmentation, elevated caspase-3/7, caspase-8, and caspase-9 activities, and enhanced expression of intrinsic mitochondrial proteins. Accordingly, mitochondrial pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins were inversely expressed within the 72-hour observation period, thereby supporting significant pro-apoptotic changes. Solely at t = 24 hours, expression of the anti-apoptotic Mcl-1 protein shows a significant increase when compared with sham-operated and control animals. Furthermore, expression of extrinsic death receptors were only slightly increased.ConclusionOur data suggest that HS induces apoptotic changes in spleen through a biphasic caspase-dependent mechanism and imply a detrimental imbalance of pro- and anti-apoptotic mitochondrial proteins Bax, Bcl-2, and Mcl-1, thereby promoting post-traumatic immunosuppression.

Dendritic cells from human mesenteric lymph nodes in inflammatory and non-inflammatory bowel diseases: subsets and function of plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDC) in mesenteric lymph nodes (MLN) may be important regulators of both inflammatory and non‐inflammatory mucosal immune responses but human studies are rare. Here we compare pDC from human MLN and peripheral blood (PB) by phenotype and function. MLN from patients with or without inflammatory bowel disease (IBD) undergoing colon surgery and PB from patients with IBD and from controls were used to isolate mononuclear cells. The pDC were analysed by flow cytometry for the expression of CD40, CD80, CD83, CD86, CCR6, CCR7, CX3CR1, CD103 and HLA‐DR. Purified pDC from MLN and PB were stimulated with staphylococcus enterotoxin B (SEB), CpG‐A, interleukin‐3 (IL‐3), SEB + IL‐3, CpG‐A + IL‐3 or left unstimulated, and cultured alone or with purified allogeneic CD4+ CD45RA+ HLA‐DR‐ T cells. Subsequently, concentrations of IL‐1β, IL‐2, IL‐4, IL‐6, IL‐8, IL‐10, IL‐12, IL‐17, interferon‐α (IFN‐α), IFN‐γ and tumour necrosis factor‐α (TNF‐α) in culture supernatants were determined by multiplex bead array. The PB pDC from IBD patients exhibited an activated and matured phenotype whereas MLN pDC and control PB pDC were less activated. CpG‐A and CpG‐A + IL‐3‐stimulated MLN pDC secreted less IL‐6 and TNF‐α compared with PB pDC from controls. Compared with co‐cultures of naive CD4 T cells with PB pDC, co‐cultures with MLN pDC contained more IL‐2, IL‐10 and IFN‐γ when stimulated with SEB and SEB + IL‐3, and less IFN‐α when stimulated with CpG‐A. MLN pDC differ phenotypically from PB pDC and their pattern of cytokine secretion and may contribute to specific outcomes of mucosal immune reactions.

Epratuzumab affects B cells trafficking in systemic lupus erythematosus

Background Epratuzumab, a humanised anti-CD22 monoclonal antibody, is under investigation as a therapeutic antibody in non-Hodgkins lymphoma and systemic lupus erythematosus (SLE), but its mechanism of action on B cells remains elusive. Treatment of SLE patients with epratuzumab leads to a reduction of circulating CD27negative B cells, although epratuzumab is weakly cytotoxic to B cells in vitro. Therefore, potential effects of epratuzumab on adhesion molecule expression and the migration of B cells have been evaluated. Methods Epratuzumab binding specificity and the surface expression of adhesion molecules (CD62L, β7 integrin and β1 integrin) after culture with epratuzumab was studied on B cell subsets of SLE patients by flow cytometry. In addition, in vitro transwell migration assays were performed to analyse the effects of epratuzumab on migration towards different chemokines such as CXCL12, CXCL13 or to CXCR3 ligands, and to assess the functional consequences of altered adhesion molecule expression. Results Epratuzumab binding was considerably higher on B cells relative to other cell types assessed. No binding of epratuzumab was observed on T cells, while weak non-specific binding of epratuzumab on monocytes was noted. On B cells, binding of epratuzumab was particularly enhanced on CD27negative B cells compared to CD27positive B cells, primarily related to a higher expression of CD22 on CD27negative B cells. Moreover, epratuzumab binding led to a decrease in the cell surface expression of CD62L and β7 integrin, while the expression of β1 integrin was enhanced. The effects on the pattern of adhesion molecule expression observed with epratuzumab were principally confined to a fraction of the CD27negative B cell subpopulation and were associated with enhanced spontaneous migration of B cells. Furthermore, epratuzumab also enhanced the migration of CD27negative B cells towards the chemokine CXCL12. Conclusions The current data suggest that epratuzumab has effects on the expression of the adhesion molecules CD62L, β7 integrin and β1 integrin as well as on migration towards CXCL12, primarily of CD27negative B cells. Therefore, induced changes in migration appear to be part of the mechanism of action of epratuzumab and are consistent with the observation that CD27negative B cells are preferentially removed from the peripheral blood under treatment.