DNA-release by Streptococcus pneumoniae autolysin LytA induced Krueppel-like factor 4 expression in macrophages.

The recruitment of myeloid cells to the lung is of utmost importance for the elimination of invading pathogens. We investigated the Streptococcus pneumoniae-dependent induction mechanism of KLF4 in macrophages as a potential regulator of the macrophage immune response. We demonstrated that only viable pneumococci, which have direct contact to the host cells and release LytA-dependent DNA, induced KLF4. Exogenous supplementation of pneumococcal, other bacterial, eukaryotic foreign (human) or self (mouse) DNA to autolysis-deficient pneumococci restored (at least in part) pneumococci-related KLF4 induction. Experiments using TLR9, TRIF and MyD88 knockout macrophages revealed that TLR9, TRIF and MyD88 were partly involved in the S. pneumoniae-induced KLF4 expression. BMMs missing important DNA receptor related molecules (ASC-/-, STING-/-) showed no differences in pneumococci-related KLF4 expression. Similar results were observed with IFNAR-/- BMMs and Type I IFN stimulated cells. LyzMcre mediated knockdown of KLF4 in BMMs resulted in a decreased secretion of proinflammatory cytokines and enhanced IL-10 release. In summary, we showed that pneumococci-related KLF4 induction in macrophages is mediated via a PAMP-DAMP induction mechanism involving a hitherto unknown host cell DNA sensor leading to a more proinflammatory macrophage phenotype.

Adrenomedullin attenuates ventilator-induced lung injury in mice.

BACKGROUND: Mechanical ventilation (MV) is a life-saving intervention in acute respiratory failure without any alternative. However, even protective ventilation strategies applying minimal mechanical stress may evoke ventilator-induced lung injury (VILI). Adjuvant pharmacological strategies in addition to lung-protective ventilation to attenuate VILI are lacking. Adrenomedullin exhibited endothelial barrier-stabilising properties in vitro and in vivo. METHODS: In untreated mice (female C57/Bl6 mice, 11-15 weeks old) and animals treated with adrenomedullin, lung permeability, local and systemic inflammation and markers of distal organ function were assessed following 2 or 6 h of mechanical ventilation with 100% oxygen and protective or moderately injurious ventilator settings, respectively. RESULTS: Adrenomedullin dramatically reduced lung permeability in VILI in mice, leading to improved oxygenation. Adrenomedullin treatment reduced myosin light chain phosphorylation, attenuated the accumulation of leucocytes in the lung and prevented the increase in lactate and creatinine levels in mice ventilated with high tidal volumes. Moreover, adrenomedullin protected against VILI even when treatment was initiated 2 h after the beginning of mechanical ventilation in a 6 h VILI mouse model. CONCLUSION: Adjuvant treatment with adrenomedullin may be a promising new pharmacological approach to attenuate VILI.

A new strategy for the prevention of IgA anaphylactic transfusion reactions.

BACKGROUND: Management of patients with clinically significant anti-IgA is difficult and unsatisfactory in many aspects. PATIENTS AND METHOD: A 40-year-old man with common variable immunodeficiency had a previous history of anaphylaxis after an intramuscular immunoglobulin administration. His serum contained anti-IgA, and he required immunoglobulins for recurrent infections. RESULTS: The administration of intravenous immunoglobulins (IVIgG) containing less than 0.1 mg per mL IgA led to an anaphylactic reaction after the transfusion of only 2 to 3 mL. The same IVIgG charge was subsequently pretreated with freshly separated autologous plasma and given to the patient on three consecutive days without any reaction (1.25, 10, and 10 g each in 400 mL plasma). Anti-IgA activity did not increase, and the patient was treated again without complications. DISCUSSION: Ex vivo pretreatment of IVIgG preparations with autologous plasma appears to be safe and useful in the management of patients with clinically significant anti-IgA. To achieve a significant IgA blockage, the preparation to be used should not contain large amounts of IgA. CONCLUSION: The strategy described here appears to be safe and may help prevent anaphylaxis in many instances.