Peptidoglycan is an important pathogenic factor of the inflammatory response in sepsis

PGN and LTA from Staphylococcus aureus Induced Inflammation and Decreased Lactation through Regulating DNA Methylation and Histone H3 Acetylation in Bovine Mammary Epithelial Cells

Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) are the most common pathogens of mastitis, and S. aureus generally causes subclinical mastitis which is more persistent and resistant to treatment. Peptidoglycan (PGN) and lipoteichoic acid (LTA) are cell wall components of S. aureus. Although the roles of PGN and LTA in causing inflammation are well studied, the epigenetic mechanisms of the effects of PGN and LTA on the inflammation and lactation remain poorly understood. This study characterized the gene expression profiling by RNA sequencing and investigated DNA methylation and histone acetylation in relation to inflammation and lactation in the immortalized bovine mammary epithelial cell line (MAC-T). The cells were cultured for 24 h with neither PGN nor LTA (CON), PGN (30 μg/mL), LTA (30 μg/mL), and PGN (30 μg/mL) + LTA (30 μg/mL), respectively. The number of differentially expressed genes (DEGs) and the expression of proinflammatory factors including interleukin (IL)-1β, IL-6, IL-8, chemokine (C-X-C motif) ligand (CXCL)1, and CXCL6 of the treatments increased in the following order: CON < PGN < LTA < PGN + LTA, and the DEGs mainly enriched on the cytokine-cytokine receptor interaction and chemokine signaling pathway. LTA and PGN + LTA induced hypomethylation of global DNA by suppressing DNA methyltransferase (DNMT) activity. PGN and LTA, alone or combined, decreased the mRNA expression of casein genes (CSN1S1, CSN2, and CSN3) and the expression of two caseins (CSN2 and CSN3), and reduced histone H3 acetylation by suppressing histone acetyltransferase (HAT) activity and promoting histone deacetylase (HDAC) activity. Collectively, this study revealed that PGN and LTA induced inflammation probably due to decreasing DNA methylation through regulating DNMT activity, and decreased lactation possibly through reducing histone H3 acetylation by regulating HAT and HDAC activity in bovine mammary epithelial cells.

Translocation of bacterial NOD2 agonist and its link with inflammation

INTRODUCTION

The gut is often considered as the motor of critical illness through bacterial translocation, which amplifies the inflammatory response and alters the immune status. However, systemic bacterial translocation was rarely proven and endotoxin measurement only reflects translocation of Gram-negative-derived products. The process could be more frequently identified if peptidoglycan, derived from both Gram-negative and Gram-positive bacteria, was measured.

METHODS

We developed a new tool to detect circulating peptidoglycan-like structure using a NOD2-transfected cell line. We also measured plasma and cell-associated endotoxin and different plasma markers of inflammation. We studied 21 patients undergoing abdominal aortic surgery (AAS), and 21 patients undergoing carotid artery surgery (CAS) were included as negative controls. Patients were sampled during surgery until two days post-surgery.

RESULTS

In 90.5% of the AAS patients, a NOD2 agonist peak was detected in plasma before aortic clamping, but after gut manipulation by the surgeon, and persisted after blood reperfusion. As expected, no peak was detected in plasma from CAS patients (P = 0.003). Leukocyte-bound endotoxin appeared after blood reperfusion in 71% of the AAS patients, and circulating endotoxin was detected for 57% of them. The levels of interleukin (IL)-6, IL-10 and of inflammatory markers (C-reactive protein, procalcitonin) were maximal at postoperative day 1 or 2 in AAS patients. The levels of circulating NOD2 agonist positively correlated with those of cortisol and IL-10.

CONCLUSIONS

The measurement of circulating NOD2 agonist gives a higher informative tool than that of circulating endotoxin for early and sensitive detection of the translocation of bacterial products. The data suggest that circulating NOD2 agonist contributes to further enhance the stress response following surgery.

GSK-3beta inhibitors attenuate the organ injury/dysfunction caused by endotoxemia in the rat

OBJECTIVE

Serine-threonine protein kinase glycogen synthase kinase (GSK)-3 is involved in regulation of many cell functions, but its role in regulation of inflammatory response is unknown. Here we investigate the effects of GSK-3beta inhibition on organ injury/dysfunction caused by lipopolysaccharide or coadministration of lipopolysaccharide and peptidoglycan in the rat.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Ninety-nine anesthetized male Wistar rats.

INTERVENTIONS

Study 1: Rats received either intravenous Escherichia coli lipopolysaccharide (6 mg/kg) or vehicle (1 mL/kg; saline). Study 2: Rats received either intravenous E. coli lipopolysaccharide (1 mg/kg) and Staphylococcus aureus peptidoglycan (0.3 mg/kg) or vehicle. The potent and selective GSK-3beta inhibitors TDZD-8 (1 mg/kg intravenously), SB216763 (0.6 mg/kg intravenously), and SB415286 (1 mg/kg intravenously) or vehicle (10% dimethyl sulfoxide) was administered 30 mins before lipopolysaccharide or lipopolysaccharide and peptidoglycan.

MEASUREMENTS AND MAIN RESULTS

Endotoxemia resulted in increases in the serum levels of creatinine (indicator of renal dysfunction), aspartate aminotransferase, alanine aminotransferase (markers for hepatocellular injury), lipase (indicator of pancreatic injury), and creatine kinase (indicator of neuromuscular injury). Coadministration of lipopolysaccharide and peptidoglycan resulted in hepatocellular injury and renal dysfunction. All GSK-3beta inhibitors attenuated the organ injury/dysfunction caused by lipopolysaccharide or lipopolysaccharide and peptidoglycan. GSK-3beta inhibition reduced the Ser536 phosphorylation of nuclear factor-kappaB subunit p65 and the messenger RNA expression of nuclear factor-kappaB-dependent proinflammatory mediators but had no effect on the nuclear factor-kappaB/DNA binding activity in the lung. GSK-3beta inhibition reduced the increase in nuclear factor-kappaB p65 activity caused by interleukin-1 in human embryonic kidney cells in vitro.

CONCLUSIONS

The potent and selective GSK-3beta inhibitors TDZD-8, SB216763, and SB415286 reduced the organ injury/dysfunction caused by lipopolysaccharide or lipopolysaccharide and peptidoglycan in the rat. We propose that GSK-3beta inhibition may be useful in the therapy of the organ injury/dysfunction associated with sepsis, shock, and other diseases associated with local or systemic inflammation.

Diagnostic and predictive value of the silkworm larvae plasma test for postoperative infection following gastrointestinal surgery

OBJECTIVE

To determine whether the silkworm larvae plasma (SLP) test is a reliable diagnostic marker of infection in patients with infectious complications following gastrointestinal surgery.

DESIGN

Prospective study.

SETTING

Department of Surgery, University Hospital, Shiga University of Medical Science.

PATIENTS

One hundred and twelve adult patients undergoing gastrointestinal surgery

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Thirty-nine of 112 patients developed infectious complications (infected group). Seven patients with sepsis (severely infected group) and 32 patients without sepsis (minor infected group) were observed. The operation time, blood loss, and age were significantly greater in both infected groups than in the noninfected group. The systemic inflammatory response syndrome score on postoperative day (POD) 1 and POD7 was highest in the severely infected group. The increase in C-reactive protein on POD3 and POD7 was significantly higher in both infected groups than in the noninfected group. White blood cell counts on POD7 were elevated significantly higher in the severely infected group than in the other groups. Immediately after surgery, SLP activity significantly increased compared with presurgery in all groups and was significantly higher in the minor and severely infected groups than in the noninfected group. The increased SLP activity returned to preoperative levels in the minor and noninfected groups; however, SLP activity in the severely infected groups remained high throughout the observational period. The most significant factor and time point that predicted infectious complications were the SLP test on POD1; sensitivity 66.7%, specificity 90.4%, positive and negative predictive values 78.8% and 83.5%. The area under the receiver operating characteristic curve for the SLP test was 0.813 +/- 0.046.

CONCLUSIONS

The SLP test appears to be a useful marker of diagnosis and prediction of infectious complications following gastrointestinal surgery. Moreover, the SLP test may be able to evaluate not only the existence but also the severity of infection in surgical patients.

Polymersome Encapsulated Hemoglobin: A Novel Type of Oxygen Carrier

Bovine hemoglobin (Hb) was encapsulated inside polymer vesicles (polymersomes) to form polymersome encapsulated Hb (PEH) dispersions. PEH particles are 100% surface PEGylated with longer PEG chains and possess thicker hydrophobic membranes as compared to conventional liposomes. Polymersomes were self-assembled from poly(butadiene)-poly(ethylene glycol) (PBD-PEO) amphiphilic diblock copolymers with PBD-PEO molecular weights of 22-12.6, 5-2.3, 2.5-1.3, and 1.8-0.9 kDa. The first two diblock copolymers possessed linear hydrophobic PBD blocks, while the later possessed branched PBD blocks. PEH dispersions were extruded through 100 and 200 nm pore radii membranes. The size distribution, Hb encapsulation efficiency, P(50), cooperativity coefficient, and methemoglobin (metHb) level of PEH dispersions were consistent with values required for efficient oxygen delivery in the systemic circulation. The influence of different molecular weight diblock copolymers on the physical properties of PEH dispersions was analyzed. PBD-PEO copolymers with molecular weights of 22-12.6 and 2.5-1.3 kDa completely dissolved in aqueous solution to form polymersomes, while the other two copolymers formed a mixture of solid copolymer precipitates and polymersomes. PEHs self-assembled from 22-12.6 and 2.5-1.3 kDa PBD-PEO copolymers possessed Hb loading capacities greater than PEG-LEHs, PEGylated actin-containing LEHs, and nonmodified LEHs, although their sizes were smaller and their hydrophobic membranes were thicker. The Hb loading capacities of these polymersomes were also higher than lipogel encapsulated hemoglobin particles and nanoscale hydrogel encapsulated hemoglobin particles. PEH dispersions exhibited average radii larger than 50 nm and exhibited oxygen affinities comparable to human erythrocytes. Polymersomes did not induce Hb oxidation. The interaction between Hb and the membrane of 2.5-1.3 kDa PBD-PEO polymersomes improved the monodispersity of these particular PEH dispersions. These results suggest that PEHs could serve as efficient oxygen therapeutics.