Phosphorylation of muramyl peptides by NAGK is required for NOD2 activation.

Bacterial cell wall components provide various unique molecular structures that are detected by pattern recognition receptors (PRRs) of the innate immune system as non-self. Most bacterial species form a cell wall that consists of peptidoglycan (PGN), a polymeric structure comprising alternating amino sugars that form strands cross-linked by short peptides. Muramyl dipeptide (MDP) has been well documented as a minimal immunogenic component of peptidoglycan1-3. MDP is sensed by the cytosolic nucleotide-binding oligomerization domain-containing protein 24 (NOD2). Upon engagement, it triggers pro-inflammatory gene expression, and this functionality is of critical importance in maintaining a healthy intestinal barrier function5. Here, using a forward genetic screen to identify factors required for MDP detection, we identified N-acetylglucosamine kinase (NAGK) as being essential for the immunostimulatory activity of MDP. NAGK is broadly expressed in immune cells and has previously been described to contribute to the hexosamine biosynthetic salvage pathway6. Mechanistically, NAGK functions upstream of NOD2 by directly phosphorylating the N-acetylmuramic acid moiety of MDP at the hydroxyl group of its C6 position, yielding 6-O-phospho-MDP. NAGK-phosphorylated MDP-but not unmodified MDP-constitutes an agonist for NOD2. Macrophages from mice deficient in NAGK are completely deficient in MDP sensing. These results reveal a link between amino sugar metabolism and innate immunity to bacterial cell walls

Alterações hemodinâmicas e intracranianas em cães com hemorragia aguda, anestesiados com isofluorano Hemodynamic and intracranial alterations in dogs with acute hemorrhage anesthetized with isoflurane

Estudaram-se possíveis alterações hemodinâmicas e intracranianas em cães submetidos à hemorragia aguda e anestesiados pelo isofluorano. Verificou-se também a influência do anestésico no mecanismo de auto-regulação cerebral. Utilizaram-se 20 cães adultos que foram induzidos à anestesia geral com isofluorano por máscara naso-oral a 3,5V% (volume %). Após a intubação orotraqueal, reajustou-se o vaporizador para 2,1V%. Induziu-se a hipovolemia retirando-se volume total de 35ml/kg de sangue. Avaliaram-se pressão intracraniana (PIC), temperaturas intracraniana (TIC) e corpórea (T), pressão de perfusão cerebral (PPC), pressões arteriais sistólica (PAS), diastólica (PAD) e média (PAM), freqüências cardíaca (FC) e respiratória (FR), índices cardíaco (IC) e sistólico (IS), pressão venosa central (PVC), pressão da artéria pulmonar (PAP), concentração de dióxido de carbono ao final da expiração (ETCO2) e saturação de oxihemoglobina (SpO2). Imediatamente após a hipovolemia, houve redução significativa da PIC, PPC, PAS, PAD, PAM, IC, IS e PAP. Após 10 minutos, houve aumento gradativo das médias, permanecendo neste patamar até o final do período experimental. Concluiu-se que a hemorragia aguda promoveu redução das variáveis hemodinâmicas, sendo possível verificar a ativação de mecanismos compensatórios. Além disso, houve redução da perfusão sangüínea e ativação do mecanismo de auto-regulação cerebral, conseqüentes à hipovolemia associada à anestesia com isofluorano.<br>Intracranial and hemodynamic alterations in 20 adult dogs anesthetized with isoflurane and submitted to acute hemorrhage were studied. Anesthetic influence on cerebral auto-regulation mechanism was also observed. General anesthesia was induced with at 3.5V% (volume %) isoflurane. Thereafter, orotracheal intubation was performed and vaporizer was calibrated to 2.1V%. To induce hypovolemia, a total amount of 35 ml/kg-1 of blood was taken from each dog. Intracranial pressure (ICP); intracranial (ICT) and body temperatures (BT); cerebral perfusion pressure (CPP); systolic (SAP), diastolic (DAP) and mean arterial pressures (MAP); heart (HR) and respiratory rates (RR); cardiac (CI) and stroke indexes (SI); central venous pressure (CVP); pulmonary arterial pressure (PAP); end tidal dioxide carbon (ETCO2); and oxyhemoglobin saturation (SpO2) were evaluated. Immediately after hypovolemia, there was significative reduction of ICP, CPP, SAP, DAP, MAP, CI, SI, and PAP. Ten minutes after, the values increased gradually until the end of the experimental period. Indeed, acute hemorrhage caused reduction of hemodynamic variables and activation of the compensatory mechanisms. Cerebral blood perfusion was reduced and cerebral auto-regulation mechanism was activated due to hypovolemia associated to isoflurane anesthesia