Intravenous immunoglobulin fails to improve ARDS in patients undergoing ECMO therapy.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is associated with high mortality rates. ARDS patients suffer from severe hypoxemia, and extracorporeal membrane oxygenation (ECMO) therapy may be necessary to ensure oxygenation. ARDS has various etiologies, including trauma, ischemia-reperfusion injury or infections of various origins, and the associated immunological responses may vary. To support the immunological response in this patient collective, we used intravenous IgM immunoglobulin therapy to enhance the likelihood of pulmonary recovery. METHODS: ARDS patients admitted to the intensive care unit (ICU) who were placed on ECMO and treated with (IVIG group; n = 29) or without (control group; n = 28) intravenous IgM-enriched immunoglobulins for 3 days in the initial stages of ARDS were analyzed retrospectively. RESULTS: The baseline characteristics did not differ between the groups, although the IVIG group showed a significantly reduced oxygenation index compared to the control group. We found no differences in the length of ICU stay or ventilation parameters. We did not find a significant difference between the groups for the extent of inflammation or for overall survival. CONCLUSION: We conclude that administration of IgM-enriched immunoglobulins as an additional therapy did not have a beneficial effect in patients with severe ARDS requiring ECMO support. TRIAL REGISTRATION: Clinical Trials: NCT02961166; retrospectively registered.

ADAM15 exerts an antiapoptotic effect on osteoarthritic chondrocytes via up-regulation of the X-linked inhibitor of apoptosis.

OBJECTIVE: To investigate the capacity of ADAM15, a disintegrin metalloproteinase that is up-regulated in osteoarthritic (OA) cartilage, to protect chondrocytes against apoptosis induced by growth factor deprivation and genotoxic stress. METHODS: Caspase 3/7 activity was determined in primary OA and ADAM15-transfected T/C28a4 chondrocytes upon exposure to the DNA-damaging agent camptothecin or serum withdrawal. Camptothecin-induced cytotoxicity was determined by measuring cellular ATP content. (Anti-)apoptotic proteins were analyzed by immunoblotting, and levels of messenger RNA (mRNA) for X-linked inhibitor of apoptosis (XIAP) were determined using real-time polymerase chain reaction. RNA interference was applied for down-regulation of ADAM15 and XIAP expression. Immunohistochemistry analysis of normal and OA cartilage samples was performed using XIAP- and ADAM15-specific antibodies. RESULTS: ADAM15-transfected chondrocytes cultured on a collagen matrix displayed significantly reduced caspase 3/7 activity upon serum or intermittent matrix withdrawal, compared with vector-transfected control cells. Apoptosis induction by camptothecin exposure also led to significantly elevated caspase 3/7 activity and reduced cell viability of the vector-transfected compared with ADAM15-transfected chondrocytes. Increased levels of activated caspase 3 and cleaved poly(ADP-ribose) polymerase were detected in the vector controls. XIAP, an inhibitor of activated caspase 3, was significantly up-regulated ( approximately 3-fold) at the protein and mRNA levels in ADAM15-transfected chondrocytes upon camptothecin treatment. Specific down-regulation of either ADAM15 or XIAP in OA chondrocytes led to significant sensitization to camptothecin-induced caspase 3/7 activity. Immunohistochemical analysis revealed low to moderate XIAP expression in normal specimens and markedly increased XIAP staining, colocalizing with ADAM15, in OA cartilage. CONCLUSION: ADAM15 conveys antiapoptotic properties to OA chondrocytes that might sustain their potential to better resist the influence of death-inducing stimuli under pathophysiologic conditions.

ADAM15 modulates outside-in signalling in chondrocyte-matrix interactions.

ADAM15 belongs to a family of transmembrane multi-domain proteins implicated in proteolysis, cell-cell and cell-matrix interactions in various disease conditions. In osteoarthritis (OA), ADAM15 is up-regulated in the chondrocytes already at early stages of cartilage degeneration where it seems to exert homeostatic effects likely associated with its ability to enhance integrin-mediated chondrocyte adhesion to the surrounding collagen matrix. The aim of our present study was, therefore, to characterize functional domains of ADAM15 involved in collagen II (CII) interaction and to analyse associated outside-in signalling events. Accordingly, ADAM15 and respective deletion mutants were stably transfected into the chondrocyte cell line T/C28a4. Transfected cells were adhered to CII and phosphoproteins analysed by Western blotting. Co-immunoprecipitation served to identify protein binding to ADAM15. Our results elucidate the prodomain as critical for the capacity of ADAM15 to enhance CII adhesion, thereby identifying for the first time a cell-adhesive role of a metalloproteinase prodomain. Moreover, the cytoplasmic tail of ADAM15 confers a modulatory effect on the autophosphorylation site Y397 of the focal adhesion kinase (FAK) during chondrocyte-collagen interaction. In conclusion, the newly uncovered impact of ADAM15 on signalling events that arise from chondrocyte interactions with its collagen matrix might contribute to the elucidation of the mechanism underlying its proposed chondroprotective role in degenerative cartilage disease.