Shichu Xiao

Interleukin-33 Increases Antibacterial Defense by Activation of Inducible Nitric Oxide Synthase in Skin

Interleukin-33 (IL-33) is associated with multiple diseases, including asthma, rheumatoid arthritis, tissue injuries and infections. Although IL-33 has been indicated to be involved in Staphylococcus aureus (S. aureus) wound infection, little is known about how IL-33 is regulated as a mechanism to increase host defense against skin bacterial infections. To explore the underlying intricate mechanism we first evaluated the expression of IL-33 in skin from S. aureus-infected human patients. Compared to normal controls, IL-33 was abundantly increased in skin of S. aureus-infected patients. We next developed a S. aureus cutaneous infection mouse model and found that IL-33 was significantly increased in dermal macrophages of infected mouse skin. The expression of IL-33 by macrophages was induced by staphylococcal peptidoglycan (PGN) and lipoteichoic acid (LTA) via activation of toll-like receptor 2(TLR2) –mitogen-activated protein kinase (MAPK)-AKT-signal transducer and activator of transcription 3(STAT3) signaling pathway as PGN and LTA failed to induce IL-33 in Tlr2-deficient peritoneal macrophages, and MAPK,AKT, STAT3 inhibitors significantly decreased PGN- or LTA-induced IL-33. IL-33, in turn, acted on macrophages to induce microbicidal nitric oxygen (NO) release. This induction was dependent on inducible nitric oxide synthase (iNOS) activation, as treatment of macrophages with an inhibitor of iNOS, aminoguanidine, significantly decreased IL-33-induced NO release. Moreover, aminoguanidine significantly blocked the capacity of IL-33 to inhibit the growth of S. aureus, and IL-33 silencing in macrophages significantly increased the survival of S. aureus in macrophages. Furthermore, the administration of IL-33-neutralizing antibody into mouse skin decreased iNOS production but increased the survival of S. aureus in skin. These findings reveal that IL-33 can promote antimicrobial capacity of dermal macrophages, thus enhancing antimicrobial defense against skin bacterial infections.

Evaluation of long term health-related quality of life in extensive burns: A 12-year experience in a burn center

OBJECTIVES We sought to evaluate the long term health-related quality of life (HRQOL) in patients survived severely extensive burn and identify their clinical predicting factors correlated with HRQOL. METHODS A cross-sectional study was conducted in 20 patients survived more than 2 years with extensive burn involving ≥70% total body surface area (TBSA) between 1997 and 2009 in a burn center in Shanghai. Short Form-36 Medical Outcomes Survey (SF-36), Brief Version of Burn Specific Health Scale (BSHS-B) and Michigan Hand Outcome Questionnaire (MHQ) were used for the present evaluation. SF-36 scores were compared with a healthy Chinese population, and linear correlation analysis was performed to screen the clinical relating factors predicting physical and mental component summary (PCS and MCS) scores from SF-36. RESULTS HRQOL scores from SF-36 were significantly lower in the domains of physical functioning, role limitations due to physical problems, pain, social functioning and role limitations due to emotional problems compared with population norms. Multiple linear regression analysis demonstrated that only return to work (RTW) predicted improved PCS. While age at injury, facial burns, skin grafting and length of hospital stay were correlated with MCS. Work, body image and heat sensitivity obtained the lowest BSHS-B scores in all 9 domains. Improvements of HRQOL could still be seen in BSHS-B scores in domains of simple abilities, hand function, work and affect even after a quite long interval between burns and testing. Hand function of extensive burn patients obtained relatively poor MHQ scores, especially in those without RTW. CONCLUSIONS Patients with extensive burns have a poorer quality of life compared with that of general population. Relatively poor physical and psychological problems still exist even after a long period. Meanwhile, a trend of gradual improvements was noted. This information will aid clinicians in decision-making of comprehensive systematic regimens for long term rehabilitation and psychosocial treatment.

Accelerated Expansion of Epidermal Keratinocyte and Improved Dermal Reconstruction Achieved by Engineered Amniotic Membrane

In this study, we used human amniotic membrane (AM) to prepare a dermal scaffold with intact basement membrane (BM) and good biostability for quick expansion and transplantation of epidermal keratinocytes (EKs). Fresh AM was treated by repeated freeze–thaw cycles and DNase digestion. This new method was able to cleanse the cell components effectively and retain the BM structure with continuous distributions of laminin, collagen IV, VI, and VII. Subsequently, the acellular amniotic membrane (AAM) was cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) for 5 min, 30 min, and 6 h. With the time of cross-linking prolonging, the mechanical strength and biostability of AAM increased gradually, while its cytotoxicity to EKs also increased. The 5-min cross-linked AAM (5min-AAM) had no significant cytotoxicity with good histocompatibility. The relative cell viability of EKs seeded on the 5min-AAM surface was 367 ± 33% and 631 ± 43% at 7 and 14 days of culture, respectively, both higher than 294 ± 30% and 503 ± 41% of the conventional cell culture dish (CCD) group, and the proportion of P63-positive cells was significantly higher than that of the CCD group on day 7 (54.32 ± 4.27% vs. 33.32 ± 3.18%, p < 0.05). When the 5min-AAM loaded with EKs (EK-AAM) was grafted onto full-thickness skin defects in nude mice, the cells survived well and formed an epidermis similar to normal skin. The new epidermis was thicker, and reconstruction of the dermal structure was good with an intact BM. Four weeks after transplantation, the wound contraction rate in the EK-AAM group was 43.09 ± 7.05%, significantly lower than that in the EK sheet group (57.49 ± 5.93%) and control group (69.94 ± 9.47%) (p < 0.05). In conclusion, repeated freeze–thaw treatment with appropriate EDC cross-linking offers AAM an intact BM structure with good operability and biostability. It may prove to be an ideal dermal scaffold to promote expansion of EKs in vitro and be transplanted for reconstruction of the dermal structure.

Cardiac apoptosis in burned rats with delayed fluid resuscitation

Clinical and experimental studies have shown that delayed fluid resuscitation postburn decreases heart function. We hypothesized that apoptosis occurs in the cardiomyocyte in this condition. To investigate this hypothesis, rats were burned, fluid resuscitation was delayed, and the integrity of cardiac genomic DNA in the burned rats was determined with an LM-PCR Ladder Assay kit. DNA fragmentation shown as DNA ladders on gels, the hallmark of apoptosis, was found in the heart tissue of these rats. In the early phase of delayed fluid resuscitation, the nuclear factor kappa B (NF-kappa B) was examined using an electrophoretic mobility shift assay and was found to be activated. In comparison with burned rats with immediate fluid resuscitation, nitric oxide levels in hearts from burned rats with delayed fluid resuscitation were significantly lower (P<0.01). These results suggest that apoptosis may be an important pathway for cardiac injury, which may result from the activation of NF-kappa B and decreased nitric oxide levels.

Role of inhibition of p38 mitogen-activated protein kinase in liver dysfunction after hemorrhagic shock and resuscitation

BACKGROUND The liver is one of the organs most frequently affected by trauma and hemorrhagic shock; the exact role of p38 mitogen-activated protein kinase (MAPK) activation in response to hepatic hemorrhagic shock/resuscitation (HS/R) remains unclear. MATERIALS AND METHODS C57Bl/6 mice were divided into four groups: sham-operated group, SB-only group, control group, and SB + HS/R group. Hepatocellular injury (aspartate aminotransferase [AST] and alanine aminotransferase [ALT]) and tumor necrosis factor (TNF-α) and interleukin (IL-1β) messenger ribonucleic acid (mRNA) expression in the liver were assessed 6 h after resuscitation, p38 MAPK activation in the liver was assessed at 30 min after resuscitation. RESULTS p38 MAPK activation was higher in the control group than other groups 30 min after resuscitation. p38 MAPK activation level in the SB + HS/R group did not change significantly compared with that of sham and SB-only groups, but was significantly lower than that in the control group. The TNF-α mRNA expression in the control group was significantly higher than that in the sham group. The TNF-α mRNA levels after HS/R in the SB + HS/R group were significantly lower than those in the control group and were roughly the same as those in the sham and SB-only groups. IL-1β mRNA expression showed similar changes in the four groups. Serum ALT and AST levels in the control group were significantly higher than those in the sham group. The increase in serum ALT and AST levels after HS/R in the SB + HS/R group was significantly less pronounced than that in the control group and markedly higher than that in the sham group. CONCLUSIONS p38 MAPK was phosphorylated during the HS/R process. Inhibiting the activation of p38 MAPK may attenuate HS/R injury to the liver.

Pathogenic alteration in severe burn wounds

The present study aims to define the trend of time related changes with local bacterial alteration of bacterial resistance in severe burns in our burn center during a 12-year period. Retrospective analysis of microbiological results on severely burned wounds between 1998 and 2009 was carried out. A study of 3615 microbial isolates was performed. Staphylococcus aureus was the most commonly isolated pathogen (38.2%) followed by A. baumannii (16.2%), Streptococcus viridans (11.4%), Pseudomonas aeruginosa (10.4%), coagulase-negative staphylococci (CNS, 9.2%). The species ratios of S. aureus and A. baumannii increased significantly from 1st to 8th week of hospitalization, while those of Streptococcus viridans, P. aeruginosa and coagulase-negative staphylococci decreased during the same period. Bacterial resistance rates were compared between the periods 1998-2003 and 2004-2009. Vancomycin remained as the most sensitive antibiotic in S. aureus including methicillin-resistant S. aureus (MRSA). It was very likely that the majority of infections caused by Streptococcus viridans, P. aeruginosa and coagulase-negative staphylococci occurred in the early stage of burn course and the majority of infections caused by A. baumannii occurred 4 weeks after admission. The use of different antibiotics was probably the major contributor to these trends.

A new method of wound treatment: targeted therapy of skin wounds with reactive oxygen species-responsive nanoparticles containing SDF-1α.

Objective To accelerate wound healing through promoting vascularization by using reactive oxygen species (ROS)-responsive nanoparticles loaded with stromal cell-derived factor-1α(SDF-1α). Methods The ROS-reactive nanomaterial poly-(1,4-phenyleneacetone dimethylene thioketal) was synthesized, and its physical and chemical properties were characterized. ROS-responsive nanoparticles containing SDF-1α were prepared through a multiple emulsion solvent evaporation method. The loading capacity, stability, activity of the encapsulated protein, toxicity, and in vivo distribution of these nanoparticles were determined. These nanoparticles were administered by intravenous infusion to mice with full-thickness skin defects to study their effects on the directed chemotaxis of bone marrow mesenchymal stem cells, wound vascularization, and wound healing. Results The synthesized ROS-reactive organic polymer poly-(1,4-phenyleneacetone dimethylene thioketal) possessed a molecular weight of approximately 11.5 kDa with a dispersity of 1.97. ROS-responsive nanoparticles containing SDF-1α were prepared with an average diameter of 110 nm and a drug loading capacity of 1.8%. The encapsulation process showed minimal effects on the activity of SDF-1α, and it could be effectively released from the nanoparticles in the presence of ROS. Encapsulated SDF-1α could exist for a long time in blood. In mice with full-thickness skin defects, SDF-1α was effectively released and targeted to the wounds, thus promoting the chemotaxis of bone marrow mesenchymal stem cells toward the wound and its periphery, inducing wound vascularization, and accelerating wound healing.

Epidemiology and Outcome Analysis of Severe Extensive Burns: A 12-Year Summary of 103 Cases in a Burn Center in China

The purpose of this article is to improve the treatment of severe extensive burns (SEB) patients by summarizing treatment experience in recent 12 years in China and analyzing the follow-up quality of life (QOL) in these patients. Clinical data and rescue measures of 103 SEB patients (≥70% TBSA) admitted in a burn center in Shanghai between 1997 and 2009 were reviewed, and QOL and hand function of those who survived more than 2 years were assessed by Brief Version of Burn Specific Health scale-B and Michigan Hand Outcome Questionnaire. Of these, 76.7% were caused by flames and 15.5% caused by scald. The median burn area was 87.5% (interquartile range, 77.0–95.0%) TBSA, of which third-degree burns accounted for 56.5% (interquartile range, 25.8–80.0%) TBSA; 71.8% were complicated by inhalation injury. The occurrence of in-hospital complications was 75.7%, with the respiratory system complications predominating (49.5%). The fatality rate was 28.2%, mainly due to sepsis and multiple organ dysfunction syndrome. Work, body image, and heat sensitivity got the lowest Brief Version of Burn Specific Health scale-B scores in all nine domains, and Michigan Hand Outcome Questionnaire scores were also relatively poor. Flame burns remain to be the main cause of SEB in China in recent 12 years. Treatment is still challenged because of the depth and extensive burn area and high occurrence of multiple system complications. How to ameliorate QOL of SEB patients, intensify the functional rehabilitation, and improve their physical appearance in particular remain to be a crux.

Reduction of CD47 on monocytes correlates with MODS in burn patients

Alternation of surface markers on monocytes is associated with the development of inflammation. The goals of the present study were to detect CD47 expression on monocytes by flow cytometry and explore its relationship with disease severity and MODS in burned patients. The results show CD47 expression on monocytes from all burned patients (n = 21) was lower than that from the healthy population (n = 21) for 24 days after burn. There was a significant difference in CD47 expression on monocytes between the patients with differing burn severity in the first 7 days after injury (P < 0.05). Considering the relationship between CD47 expression and MODS, we found the CD47 expression on monocytes from patients with MODS was lower (P < 0.05) in the first 3 days after injury than that from patients without MODS. In conclusion, diminished CD47 expression on monocytes is associated with burn severity and the occurrence of MODS in burn patients.

Deficiency of Smad3 results in enhanced inducible nitric oxide synthase–mediated hypotension in lipopolysaccharide-induced endotoxemia

BACKGROUND Smad3 is a principal intracellular mediator of signaling for transforming growth factor β, a cytokine involved in pleiotropic pathophysiological processes including inflammation and immunity. The function of Smad3 in regulating inducible nitric oxide synthase (iNOS) expression and septic shock has not been characterized. METHODS Smad3(-/-) (referred hereafter as KO) and wild-type (WT) mice were injected intraperitoneally with lipopolysaccharide (LPS) to induce the septic hypotension. Mortality, blood pressure, and plasma levels of nitrite were measured. The iNOS messenger RNA and protein levels in lung, kidney, and spleen were also analyzed. RESULTS Mice lacking functional Smad3 respond to LPS with greater mortality than their WT littermates. The high mortality of KO mice is accompanied by enhanced hypotension after intraperitoneal injection of LPS. Both KO and WT mice displayed an increase in plasma nitrite during the experimental period; however, LPS administration caused more dramatic changes in KO mice than WT mice. Likewise, the iNOS messenger RNA and protein levels in lung, kidney, and spleen were more strongly increased in KO mice than in WT mice after LPS administration. CONCLUSIONS Defects in the Smad3 gene may increase susceptibility to the development of septic hypotension because of enhanced iNOS production.