Macrophages and post-burn immune dysfunction

Microbial infections in burn patients

Polymicrobial infections are the leading causes of complications incurred from injuries that burn patients develop. Such patients admitted to the hospital have a high risk of developing hospital-acquired infections, with longer patient stays leading to increased chances of acquiring such drug-resistant infections. Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus mirabilis are the most common multidrug-resistant (MDR) Gram-negative bacteria identified in burn wound infections (BWIs). BWIs caused by viruses, like Herpes Simplex and Varicella Zoster, and fungi-like Candida spp. appear to occur occasionally. However, the preponderance of infection by opportunistic pathogens is very high in burn patients. Variations in the causative agents of BWIs are due to differences in geographic location and infection control measures. Overall, burn injuries are characterized by elevated serum cytokine levels, systemic immune response, and immunosuppression. Hence, early detection and treatment can accelerate the wound-healing process and reduce the risk of further infections at the site of injury. A multidisciplinary collaboration between burn surgeons and infectious disease specialists is also needed to properly monitor antibiotic resistance in BWI pathogens, help check the super-spread of MDR pathogens, and improve treatment outcomes as a result.

The mutual regulation between γδ T cells and macrophages during wound healing

Macrophages are the main cells shaping the local microenvironment during wound healing. As the prime T cells in the skin, γδ T cells participate in regulating microenvironment construction, determining their mutual regulation helps to understand the mechanisms of wound healing, and explore innovative therapeutic options for wound repair. This review introduced their respective role in wound healing firstly, and then summarized the regulatory effect of γδ T cells on macrophages, including chemotaxis, polarization, apoptosis, and pyroptosis. Last, the retrograde regulation on γδ T cells by macrophages was also discussed. The main purpose is to excavate novel interventions for treating wound and provide new thought for further research.

Spatiotemporal orchestration of macrophage activation trajectories by Vγ4 T cells during skin wound healing

Dysregulated macrophage polarization from pro-inflammatory M1 to anti-inflammatory M2 phenotypes underlies impaired cutaneous wound healing. This study reveals Vγ4+ γδ T cells spatiotemporally calibrate macrophage trajectories during skin repair via sophisticated interferon-γ (IFN-γ) conditioning across multiple interconnected tissues. Locally within wound beds, infiltrating Vγ4+ γδ T cells directly potentiate M1 activation and suppress M2 polarization thereby prolonging local inflammation. In draining lymph nodes, infiltrated Vγ4+ γδ T cells expand populations of IFN-γ-competent lymphocytes which disseminate systemically and infiltrate into wound tissues, further enforcing M1 macrophages programming. Moreover, Vγ4+γδ T cells flushed into bone marrow stimulate increased IFN-γ production, which elevates the output of pro-inflammatory Ly6C+monocytes. Mobilization of these monocytes continually replenishes the M1 macrophage pool in wounds, preventing phenotypic conversion to M2 activation. Thus, multi-axis coordination of macrophage activation trajectories by trafficking Vγ4+ γδ T cells provides a sophisticated immunological mechanism regulating inflammation timing and resolution during skin repair.

Accounting for the health risk of probiotics

Probiotics have long been associated with a myriad of health benefits, so much so that their adverse effects whether mild or severe, are often neglected or overshadowed by the enormous volume of articles describing their beneficial effects in the current literature. Recent evidence has demonstrated several health risks of probiotics that warrant serious reconsideration of their applications and further investigations. This review aims to highlight studies that report on how probiotics might cause opportunistic systemic and local infections, detrimental immunological effects, metabolic disturbance, allergic reactions, and facilitating the spread of antimicrobial resistance. To offer a recent account of the literature, articles within the last five years were prioritized. The narration of these evidence was based on the nature of the studies in the following order of preference: clinical studies or human samples, in vivo or animal models, in situ, in vitro and/or in silico. We hope that this review will inform consumers, food scientists, and medical practitioners, on the health risks, while also encouraging research that will focus on and clarify the adverse effects of probiotics.

Mesenchymal stem cell transplantation in burn wound healing: uncovering the mechanisms of local regeneration and tissue repair

Burn injuries pose a significant healthcare burden worldwide, often leading to long-term disabilities and reduced quality of life. To explore the impacts of the transplantation of mesenchymal stem cells (MSCs) on the healing of burns and the levels of serum cytokines, 60 fully grown Sprague-Dawley rats were randomly divided into three groups (n = 20 each): group I (control), group II (burn induction), and group III (burn induction + bone marrow (BM)-MSC transplantation). Groups II and III were further divided into four subgroups (n = 5 each) based on euthanasia duration (7, 14, 21, and 28 days post transplant). The experiment concluded with an anesthesia overdose for rat death. After 7, 14, 21, and 28 days, the rats were assessed by clinical, laboratory, and histopathology investigations. The results revealed significant improvements in burn healing potentiality in the group treated with MSC. Furthermore, cytokine levels were measured, with significant increases in interleukin (IL)-6 and interferon alpha (IFN) observed, while IL-10 and transforming growth factor beta (TGF-β) decreased at 7 days and increased until 28 days post burn. Also, the group that underwent the experiment exhibited increased levels of pro-inflammatory cytokines and the anti-inflammatory cytokine IL-10 when compared to the control group. Histological assessments showed better re-epithelialization, neovascularization, and collagen deposition in the experimental group, suggesting that MSC transplantation in burn wounds may promote burn healing by modulating the immune response and promoting tissue regeneration.

Fibrosis in burns: an overview of mechanisms and therapies

Scar development remains a common occurrence and a major healthcare challenge affecting the lives of millions of patients annually. Severe injuries to the skin, such as burns can lead to pathological wound healing patterns, often characterized by dermal fibrosis or excessive scarring, and chronic inflammation. The two most common forms of fibrotic diseases following burn trauma are hypertrophic scars (HSCs) and keloids, which severely impact the patient's quality of life. Although the cellular and molecular mechanisms are similar, HSC and keloids have several distinct differences. In this review, we discuss the different forms of fibrosis that occur postburn injury, emphasizing how the extent of burn influences scar development. Moreover, we highlight how a systemic response induced by a burn injury drives wound fibrosis, including both the role of the inflammatory response, as well as the fate of fibroblast during skin healing. Finally, we list potential therapeutics aimed at alleviating pathological scar formation. An understanding of the mechanisms of postburn fibrosis will allow us to effectively move studies from bench to bedside.

Tunable Sulfated Alginate-based Hydrogel Platform with enhanced anti-inflammatory and antioxidant capacity for promoting burn wound repair

Amidst progressive advancements in tissue engineering, there has been a significant enhancement in the efficacy of anti-inflammatory hydrogel dressings, addressing a myriad of clinical challenges on wound healing. A frequent complication during the initial stages of deep second-degree burn wound healing is the onset of an inflammatory storm, typically occurring without effective intervention. This event disrupts normal biological healing sequences, leading to undesirable regression. In response, we have customized a tunable, multidimensional anti-inflammatory hydrogel platform based on sulfated alginates (Algs), loaded with Prussian blue (PB) nanozymes. This platform competently eliminates surplus reactive oxygen species (ROS) present in the wound bed. Algs, functioning as a mimic of sulfated glycosaminoglycans (including heparin, heparan sulfate, and chondroitin sulfate) in the extracellular matrices (ECM), demonstrate a high affinity towards inflammatory chemokines such as interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1). This affinity effectively impedes the infiltration of inflammatory cells into the wound. Concurrently, Algs markedly modulate the macrophage phenotype transition from M1 to M2. Ultimately, our potent anti-inflammatory hydrogels, which strategically target inflammatory chemokines, M1 macrophages, and ROS, successfully attenuate dysregulated hyperinflammation in wound sites. Precise immunomodulation administered to deep second-degree burn wounds in mice has demonstrated promotion of neovascular maturation, granulation tissue formation, collagen deposition, and wound closure. Our biomimetic hydrogels, therefore, represent a significant expansion in the repertoire of anti-inflammatory strategies available for clinical practice.

Accelerated Burn Healing in a Mouse Experimental Model Using α-Gal Nanoparticles

Macrophages play a pivotal role in the process of healing burns. One of the major risks in the course of burn healing, in the absence of regenerating epidermis, is infections, which greatly contribute to morbidity and mortality in such patients. Therefore, it is widely agreed that accelerating the recruitment of macrophages into burns may contribute to faster regeneration of the epidermis, thus decreasing the risk of infections. This review describes a unique method for the rapid recruitment of macrophages into burns and the activation of these macrophages to mediate accelerated regrowth of the epidermis and healing of burns. The method is based on the application of bio-degradable "α-gal" nanoparticles to burns. These nanoparticles present multiple α-gal epitopes (Galα1-3Galβ1-4GlcNAc-R), which bind the abundant natural anti-Gal antibody that constitutes ~1% of immunoglobulins in humans. Anti-Gal/α-gal nanoparticle interaction activates the complement system, resulting in localized production of the complement cleavage peptides C5a and C3a, which are highly effective chemotactic factors for monocyte-derived macrophages. The macrophages recruited into the α-gal nanoparticle-treated burns are activated following interaction between the Fc portion of anti-Gal coating the nanoparticles and the multiple Fc receptors on macrophage cell membranes. The activated macrophages secrete a variety of cytokines/growth factors that accelerate the regrowth of the epidermis and regeneration of the injured skin, thereby cutting the healing time by half. Studies on the healing of thermal injuries in the skin of anti-Gal-producing mice demonstrated a much faster recruitment of macrophages into burns treated with α-gal nanoparticles than in control burns treated with saline and healing of the burns within 6 days, whereas healing of control burns took ~12 days. α-Gal nanoparticles are non-toxic and do not cause chronic granulomas. These findings suggest that α-gal nanoparticles treatment may harness anti-Gal for inducing similar accelerated burn healing effects also in humans.

Feasibility of using red cell distribution width for prediction of postoperative mortality in severe burn patients: an association with acute kidney injury after surgery

BACKGROUND

Severe burns cause pathophysiological processes that result in mortality. A laboratory biomarker, red cell distribution width (RDW), is known as a predictor of mortality in critically-ill patients. We examined the association between RDW and postoperative mortality in severe burn patients.

METHODS

We retrospectively analyzed medical data of 731 severely burned patients who underwent surgery under general anesthesia. We evaluated whether preoperative RDW value can predict 3-month mortality after burn surgery using receiver operating characteristic (ROC) curve analysis, logistic regression, and Cox proportional-hazards regression analysis. Mortality was also analyzed according to preoperative RDW values and incidence of postoperative acute kidney injury (AKI).

RESULTS

The 3-month mortality rate after burn surgery was 27.1% (198/731). The area under the ROC curve of preoperative RDW to predict mortality after burn surgery was 0.701 (95% confidence interval [CI], 0.667-0.734; P < 0.001) with a cut-off point of 12.9. The adjusted hazard ratio in patients with RDW > 12.9 was 1.238 (95% CI, 1.138-1.347; P < 0.001). Subgroup analysis showed that the survival rate was 88.8% for the non-AKI group with RDW ≤ 12.9 and 17.6% for the AKI group with RDW > 12.9. Preoperative RDW was considered an independent risk factor for mortality (odds ratio, 1.679; 95% CI, 1.378- 2.046; P < 0.001).

CONCLUSIONS

Preoperative RDW may predict 3-month postoperative mortality in patients with severe burns, while preoperative RDW > 12.9 and postoperative AKI may further increase mortality after burn surgery.

Revealing the biological mechanism of acupuncture in alleviating excessive inflammatory responses and organ damage in sepsis: a systematic review

Sepsis is a systemic inflammation caused by a maladjusted host response to infection. In severe cases, it can cause multiple organ dysfunction syndrome (MODS) and even endanger life. Acupuncture is widely accepted and applied in the treatment of sepsis, and breakthroughs have been made regarding its mechanism of action in recent years. In this review, we systematically discuss the current clinical applications of acupuncture in the treatment of sepsis and focus on the mechanisms of acupuncture in animal models of systemic inflammation. In clinical research, acupuncture can not only effectively inhibit excessive inflammatory reactions but also improve the immunosuppressive state of patients with sepsis, thus maintaining immune homeostasis. Mechanistically, a change in the acupoint microenvironment is the initial response link for acupuncture to take effect, whereas PROKR2 neurons, high-threshold thin nerve fibres, cannabinoid CB2 receptor (CB2R) activation, and Ca2+ influx are the key material bases. The cholinergic anti-inflammatory pathway of the vagus nervous system, the adrenal dopamine anti-inflammatory pathway, and the sympathetic nervous system are key to the transmission of acupuncture information and the inhibition of systemic inflammation. In MODS, acupuncture protects against septic organ damage by inhibiting excessive inflammatory reactions, resisting oxidative stress, protecting mitochondrial function, and reducing apoptosis and tissue or organ damage.

A burns and COVID-19 shared stress responding gene network deciphers CD1C-CD141- DCs as the key cellular components in septic prognosis

Differential body responses to various stresses, infectious or noninfectious, govern clinical outcomes ranging from asymptoma to death. However, the common molecular and cellular nature of the stress responsome across different stimuli is not described. In this study, we compared the expression behaviors between burns and COVID-19 infection by choosing the transcriptome of peripheral blood from related patients as the analytic target since the blood cells reflect the systemic landscape of immune status. To this end, we identified an immune co-stimulator (CD86)-centered network, named stress-response core (SRC), which was robustly co-expressed in burns and COVID-19. The enhancement of SRC genes (SRCs) expression indicated favorable prognosis and less severity in both conditions. An independent whole blood single-cell RNA sequencing of COVID-19 patients demonstrated that the monocyte-dendritic cell (Mono-DC) wing was the major cellular source of SRC, among which the higher expression of the SRCs in the monocyte was associated with the asymptomatic COVID-19 patients, while the quantity-restricted and function-defected CD1C-CD141-DCs were recognized as the key signature which linked to bad consequences. Specifically, the proportion of the CD1C-CD141-DCs and their SRCs expression were step-wise reduced along with worse clinic conditions while the subcluster of CD1C-CD141-DCs from the critical COVID-19 patients was characterized of IFN signaling quiescence, high mitochondrial metabolism and immune-communication inactivation. Thus, our study identified an expression-synchronized and function-focused gene network in Mono-DC population whose expression status was prognosis-related and might serve as a new target of diagnosis and therapy.

The effect of carvacrol on the proinflammatory cytokines, histology, and fertility outcome of cisplatin-related ovarian change in a rat model

OBJECTIVE

In women, agents used in chemotherapy treatment have side effects such as accelerating follicular depletion and early menopause. Thus, cytotoxic treatments may cause various effects ranging from partial damage to the ovary to premature ovarian failure (POI) and infertility. This study aimed to investigate the protective effect of carvacrol on cisplatin (CIS)-induced reproductive toxicity in female rats.

MATERIALS AND METHODS

The animals were divided to four groups; a healthy group (HG), administered only cisplatin 2.5 mg/kg (CIS); cisplatin 2.5 mg/kg + carvacrol mg/kg (CC-50), and cisplatin 2.5 mg/kg + carvacrol 100 mg/kg (CC-100). In this study, the CC-50 and CC-100 groups were injected with carvacrol at 50 and 100 mg/kg intraperitoneally (IP). The CIS and HG groupswere administered normal saline as a solvent in the same way. One hour afterwardthe CC-50 and CC-100 groups were injected with cisplatin at 2.5 mg/kg IP. This procedure was continued once a day for 14 days. At the end of this period, six rats from each group were euthanized with high-dose anaesthesia. Biochemical (oxidant-antioxidant and proinflammatory cytokines) and histopathological examinations were performed on the right ovarian tissue removed from the dead rats. The remaining (n = 6 in each group) animals were kept in the laboratory with mature male rats for two months for breeding. Rats that didn't give birth within two months were considered infertile. A one-way ANOVA test was used for the biochemical analysis, the a Kruskal Wallis test was used for the histopathological analysis.

RESULTS

It has been observed that cisplatine causes oxidative stress and inflammatory damage in the ovarian tissue of animals and ultimately causes infertility due to this oxidative stress. While carvacrol significantly suppressed cisplatin-related oxidative stress in ovarian tissue at the 50 and 100 mg/kg doses, it could suppress proinflammatory cytokine increase only at thecytokine increase only at the 100 mg/kg dose. In addition, carvacrol significantly reduced the development of cisplatin-related infertility (from 0 to 83.3%) at a dose of 100 mg/kg.

CONCLUSION

These findings suggest that carvacrol at high doses can reduce the harmful effects of cisplatin on the ovary and improve ovarian reserve in rats.

VARIABLES INFLUENCING THE DIFFERENTIAL HOST RESPONSE TO BURNS IN PEDIATRIC AND ADULT PATIENTS

ABSTRACT

Burn injury is a significant source of morbidity and mortality in the pediatric population. Although 40,000 pediatric patients in the United States are admitted to the hospital with burn wounds annually, significant differences exist in the management and treatment of these patients, even among highly specialized burn centers. Some aspects of pediatric burn research, such as metabolic changes and nutritional support after burn injury, have been studied extensively; however, in many aspects of burn care, pediatric research lags behind the study of adult populations. This review compares and contrasts a wide array of physiologic and immune responses between children and adults after burn injury. Such a review elucidates where robust research has been conducted, where adult research is applicable to pediatric patients, and where additional pediatric burn research needs to be conducted.

The Complexity of the Post-Burn Immune Response: An Overview of the Associated Local and Systemic Complications

Burn injury induces a complex inflammatory response, both locally and systemically, and is not yet completely unravelled and understood. In order to enable the development of accurate treatment options, it is of paramount importance to fully understand post-burn immunology. Research in the last decades describes insights into the prolonged and excessive inflammatory response that could exist after both severe and milder burn trauma and that this response differs from that of none-burn acute trauma. Persistent activity of complement, acute phase proteins and pro- and anti-inflammatory mediators, changes in lymphocyte activity, activation of the stress response and infiltration of immune cells have all been related to post-burn local and systemic pathology. This "narrative" review explores the current state of knowledge, focusing on both the local and systemic immunology post-burn, and further questions how it is linked to the clinical outcome. Moreover, it illustrates the complexity of post-burn immunology and the existing gaps in knowledge on underlying mechanisms of burn pathology.

Extracorporeal Blood Purification in Burns: For Whom, Why, and How?

Patients with serious thermal burn injuries require immediate and specialized care in order to minimize morbidity and mortality. Optimal fluid resuscitation, nutritional support, pulmonary care, burn wound care, and infection control practices represent key aspects of patient care in burn centers. When severely burned, the patient usually presents a systemic inflammatory response syndrome, soon balanced by a counter anti-inflammatory response syndrome. These may lead to immune dysregulation/exhaustion favoring infectious complications that dramatically impair the prognosis of burn patients. This narrative review provides an overview of the main concepts, current understanding, and potential applications of extracorporeal blood purification techniques for burn patient management. Current understanding of burn patients' immune responses is reported. Hypotheses and data on the potential value of immunoregulation are reviewed. Finally, how extracorporeal blood purification may be of interest in this specific population is discussed.

Genetic and immune crosstalk between severe burns and blunt trauma: A study of transcriptomic data

Background: Severe burns and blunt trauma can lead to multiple organ dysfunction syndrome, the leading cause of death in intensive care units. In addition to infection, the degree of immune inflammatory response also affects prognosis. However, the characteristics and clinical relevance of the common mechanisms of these major diseases are still underexplored.

Methods: In the present study, we performed microarray data analysis to identify immune-related differentially expressed genes (DEGs) involved in both disease progression in burns and blunt trauma. Six analyses were subsequently performed, including gene enrichment analysis, protein‐protein interaction (PPI) network construction, immune cell infiltration analysis, core gene identification, co-expression network analysis, and clinical correlation analysis.

Results: A total of 117 common immune-related DEGs was selected for subsequent analyses. Functional analysis emphasizes the important role of Th17 cell differentiation, Th1 and Th2 cell differentiation, Cytokine-cytokine receptor interaction and T cell receptor signaling pathway in these two diseases. Finally, eight core DEGs were identified using cytoHubba, including CD8A, IL10, CCL5, CD28, LCK, CCL4, IL2RB, and STAT1. The correlation analysis showed that the identified core DEGs were more or less significantly associated with simultaneous dysregulation of immune cells in blunt trauma and sepsis patients. Of these, the downregulation of CD8A and CD28 had a worse prognosis.

Conclusion: Our analysis lays the groundwork for future studies to elucidate molecular mechanisms shared in burns and blunt trauma. The functional roles of identified core immune-related DEGs and dysregulated immune cell subsets warrant further in-depth study.

Exendin-4 Exacerbates Burn-Induced Mortality in Mice by Switching to Th2 Response

INTRODUCTION

To determine if Exendin-4 could be a therapeutic agent for burn-induced hyperglycemia.

MATERIALS AND METHODS

Male Balb/c mice received a bolus of Exendin-4 intraperitoneally immediately after 15% total body surface area scald injury. Tail glucose levels were recorded and T-cell functions were analyzed at 4 h and 24 h postburn (pb). Pancreatic pathology was observed consecutively. The secretions of cytokines were detected in serum, spleen, and lung. Apoptosis of splenic CD3+ T-cells was examined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and flow cytometry.

RESULTS

Although Exendin-4 could attenuate burn-induced hyperglycemia in mice at 4 h pb, it accelerated their survival dose dependently with progressive depletion of splenocyte number. T-cell function underwent two-phasic changes following Exendin-4 treatment. Compared to placebo mice, T-cell from Exendin-4-treated mice was manifested with increased proliferation, while decreased IL-2 secretion and lower ratio of IL-4/IFN-γ at 4 h pb. However, at 24 h pb, it showed decreased proliferation, while increased IL-2 secretion and higher ratio of IL-4/IFN-γ. Exendin-4 could elicit higher circulating IL-6 and IL-10 levels at 4 h pb, which were pronounced in the lung at 24 h pb. In the meanwhile, severe inflammation could be found in the pancreas. At 24 h pb, the numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling or caspase-3 positive cells and the apoptosis of CD3+ T-cells were significantly increased in the spleens of Exendin-4 mice relative to placebo mice.

CONCLUSIONS

These data support a pathogenic role of Exendin-4 signaling during thermal injury, warning against its clinical application in acute insults.

Modern aspects of burn injury immunopathogenesis and immuno-biochemical markers of wound healing (review of literature)

Burns are one of the most common traumatic injuries in the world, representing a global public health problem. Major burns (severe burn injury or burn disease) are one of the most life-threatening injuries. There is a great need to identify and monitor the development of complications (sepsis and septic shock, coagulopathy and DIC) in burned patients. The basis of the pathogenesis of burn injury, as well as any general pathological process, is an inflammatory reaction, ultimately aimed at restoring the structure and function of the damaged tissue. A feature of the inflammatory reaction in burn injury is the scale of alteration of the skin and mucous membranes. The review presents the main aspects of the burn injuries immunopathogenesis and the features of post-burn immune dysfunction, manifested by disorders in the innate and adaptive immunity systems. Attention is focused on the role in the immunopathogenesis of developing systemic and local disorders in burn injury. Also the role are discussed of a minor subpopulations of lymphocytes (Treg-, Th-17-, γδT-cells) in the immunopathogenesis and in the bacterial infection protection. The characteristics of the main immuno-biochemical markers of burn injury (cytokines and growth factors, nitric oxide, matrix metalloproteases, bacteria concentration levels) are present. The prognostic role of these biomarkers in assessing of the severity degree of patients with burn injury and wound healing processes is shown. The review has been compiled using references from major databases such as RSCI, Web of Science, PubMed, Scopus and Google Scholar (up to march 2022). After obtaining all reports from database, the papers were carefully analyzed in order to find data related to the topic of this review (60 references).

Early detection of soluble CD27, BTLA, and TIM-3 predicts the development of nosocomial infection in pediatric burn patients

Thermal injury induces concurrent inflammatory and immune dysfunction, which is associated with adverse clinical outcomes. However, these effects in the pediatric population are less studied and there is no standard method to identify those at risk for developing infections. Our goal was to better understand immune dysfunction and identify soluble protein markers following pediatric thermal injury. Further we wanted to determine which early inflammatory, soluble, or immune function markers are most predictive of the development of nosocomial infections (NI) after burn injury. We performed a prospective observational study at a single American Burn Association-verified Pediatric Burn Center. A total of 94 pediatric burn subjects were enrolled and twenty-three of those subjects developed a NI with a median time to diagnosis of 8 days. Whole blood samples, collected within the first 72 hours after injury, were used to compare various markers of inflammation, immune function, and soluble proteins between those who recovered without developing an infection and those who developed a NI after burn injury. Within the first three days of burn injury, innate and adaptive immune function markers (ex vivo lipopolysaccharide-induced tumor necrosis factor alpha production capacity, and ex vivo phytohemagglutinin-induced interleukin-10 production capacity, respectively) were decreased for those subjects who developed a subsequent NI. Further analysis of soluble protein targets associated with these pathways displayed significant increases in soluble CD27, BTLA, and TIM-3 for those who developed a NI. Our findings indicate that suppression of both the innate and adaptive immune function occurs concurrently within the first 72 hours following pediatric thermal injury. At the same time, subjects who developed NI have increased soluble protein biomarkers. Soluble CD27, BTLA, and TIM-3 were highly predictive of the development of subsequent infectious complications. This study identifies early soluble protein makers that are predictive of infection in pediatric burn subjects. These findings should inform future immunomodulatory therapeutic studies.

Murine burn lesion model for studying acute and chronic wound infections

Acute wounds, such as thermal injury, and chronic wounds are challenging for patients and the healthcare system around the world. Thermal injury of considerable size induces immunosuppression, which renders the patient susceptible to wound infections, but also in other foci like the airways and urinary tract. Infected thermal lesions can progress to chronic wounds with biofilm making them more difficult to treat. While animal models have their limitations, murine wound models are still the best tool at the moment to identify strategies to overcome these challenges. Here, we present a murine burn model, which has been developed to study biofilm formation, the significance of wound healing, and for identifying novel treatment candidates. Investigating the effect of a thermal injury in mice, we observed that 48 h after introduction of the injury, the mice showed a reduction in polymorphonuclear neutrophil granulocytes (PMNs) and a reduced capacity for phagocytosis and oxidative burst. Regarding the chronic wound, Pseudomonas aeruginosa biofilm arrested wound healing and kept the wound in an inflammatory state, but suppressing PMN function by means of the PMN factor S100A8/A9, corresponding to observations in human venous leg ulcers. Monotherapy and dual treatment with S100A8/A9 and ciprofloxacin on P. aeruginosa biofilm-infected murine wounds have been investigated. In combination, S100A8/A9 and ciprofloxacin reduced the bacterial quantity, lowered the proinflammatory response, and increased anti-inflammatory cytokines after 4 days of treatment. When the treatment was prolonged, an additional prevention of resistance development was detected in all the dual-treated mice. In the present review, we provide data on using the murine model for research with the aim of better understanding pathophysiology of wounds and for identifying novel treatments for humans suffering from these lesions.

Hemostasis and Anti-Inflammatory Abilities of AuNPs-Coated Chitosan Dressing for Burn Wounds

Burn injuries are a common hazard in the military, as fire is likely to be weaponized. Thus, it is important to find an effective substance to accelerate burn wound healing. This study used chitosan and gold nanoparticles (AuNPs) as wound dressings and investigated their effectiveness in femoral artery hemorrhage swine and rat burn models. Chitosan dressing has significant hemostatic properties compared with gauze. Histological results showed that burn wounds treated with chitosan or AuNP-coated chitosan dressings exhibited more cells and a continuous structure of the epidermis and dermis than those of the control and untreated lesion groups. Furthermore, both chitosan dressings have been shown to positively regulate the expression of genes- and cytokines/chemokines-related to the wound healing process; AuNP-coated chitosan significantly lessened severe sepsis and inflammation, balanced the activities of pro-fibrotic and anti-fibrotic ligands for tissue homeostasis, regulated angiogenesis, and inhibited apoptosis activity, thereby being beneficial for the burn microenvironment. Hence, chitosan alone or in combination with AuNPs represents a prospective therapeutic substance as a burn dressing which might be helpful for burn wound care. This study provides a novel hemostasis dressing for modern warfare that is simple to use by most medical and paramedical personnel handling for burn treatment.

Regulation of Key Immune-Related Genes in the Heart Following Burn Injury

Immune cascade is one of major factors leading to cardiac dysfunction after burn injury. TLRs are a class of pattern-recognition receptors (PRRs) that initiate the innate immune response by sensing conserved molecular patterns for early immune recognition of a pathogen. The Rat Toll-Like Receptor (TLR) Signaling Pathway RT² Profiler PCR Array profiles the expression of 84 genes central to TLR-mediated signal transduction and innate immunity, and is a validated tool for identifying differentially expressed genes (DEGs). We employed the PCR array to identify burn-induced cardiac TLR-signaling-related DEGs. A total of 38 up-regulated DEGs and 19 down-regulated DEGs were identified. Network analysis determined that all DEGS had 10 clusters, while up-regulated DEGs had 6 clusters and down-regulated DEGs had 5 clusters. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEGs were involved in TLR signaling, the RIG-I-Like receptor signaling pathway, the IL-17 signaling pathway, and the NFkB signaling pathway. Function analysis indicated that DEGs were associated with Toll-like receptor 2 binding, Lipopeptide binding, Toll-like receptor binding, and NAD(P)+ nucleosidase activity. The validation of 18 up-regulated DEGs (≥10-fold change) and 6 down-regulated DEGs (≤5-fold change) demonstrated that the PCR array is a trusted method for identifying DEGs. The analysis of validated DEG-derived protein–protein interaction networks will guide our future investigations. In summary, this study not only identified the TLR-signaling-pathway-related DEGs after burn injury, but also confirmed that the burn-induced cardiac cytokine cascade plays an important role in burn-induced heart dysfunction. The results will provide the novel therapeutic targets to protect the heart after burn injury.

Modern Aspects of Burn Injury Immunopathogenesis and Prognostic Immunobiochemical Markers (Mini-Review)

Burn injuries are among the most common peacetime injuries, with mortality ranging from 2.3% to 3.6%. At the same time, 85–90% of patients with burns are people of working age and children. Burn injury leads to metabolic disorders and systemic inflammatory response, inefficient energy consumption, and other physiological changes that can lead to dysfunction of organs and systems. The most formidable complication of burn injuries is sepsis mediated by multiple organ failure, the most common cause of poor prognosis in patients and has specific differences in these injuries. The purpose of this article was to dwell in detail on the most promising immunobiochemical markers of sepsis in the format of a mini-review, based on the main aspects of the immunopathogenesis of this complication. The pathogenesis of a burn injury and any general pathological process is based on an inflammatory reaction and large-scale changes in the skin and mucous membranes. This review is devoted to the progress in understanding the main aspects of the immunopathogenesis of burn lesions and the features of post-burn immune dysfunction, manifested by disorders in the innate and adaptive immunity systems. Attention is focused on the role in the immunopathogenesis of the development of systemic and local disorders in burn injury. Characterization of primary immunobiochemical markers of burn injury (cytokines, growth factors, C-reactive protein, procalcitonin, presepsin, matrix metalloproteinases, reactive oxygen species, nitric oxide, hemostasis parameters) is presented. The problem of treating burn lesions is associated with constant monitoring of the condition of patients and regular monitoring of specific immunobiochemical markers predicting sepsis for the timely initiation of a specific therapy.

Measures of Adaptive Immune Function Predict the Risk of Nosocomial Infection in Pediatric Burn Patients

Thermal injury results in changes in the inflammatory and innate immune response of pediatric patients. Plasma cytokines, cellular profiles, and reduction in innate immune function following burn injury has also been correlated to adverse outcomes (e.g., mortality and infectious complications). Changes in adaptive immune function following thermal injury are not as well characterized. Our goal was to better understand if adaptive immune dysfunction occurs early after pediatric thermal injury and is a risk factor for nosocomial infections (NI). A prospective, longitudinal immune function observational study was performed at a single ABA-verified pediatric burn center. Eighty burn patients were enrolled with 20 developing a NI, defined using CDC criteria. We collected whole blood samples from pediatric burn patients within the first 72 hours from injury and between days 4-7, where applicable to analyze adaptive immune function. We compared immune function between burn patients who went on to develop NI and those that did not. Within the first 72 hours of injury, burn patients who developed NI had significantly lower absolute CD4+ lymphocyte counts and whole blood ex vivo phytohemagglutinin (PHA)-induced IFNγ and IL-10 production capacity compared to those that did not develop infection. Further analysis using receiver operating characteristic curve revealed that PHA-induced IL-10 production capacity had the highest area under the curve. Our data demonstrates early adaptive immune suppression occurs following pediatric thermal injury and PHA-induced IL-10 production capacity appears to be a predictor for the development of NI.

Identifying changes in immune cells and constructing prognostic models using immune-related genes in post-burn immunosuppression

BACKGROUND

Burn patients are prone to infection as well as immunosuppression, which is a significant cause of death. Currently, there is a lack of prognostic biomarkers for immunosuppression in burn patients. This study was conducted to identify immune-related genes that are prognosis biomarkers in post-burn immunosuppression and potential targets for immunotherapy.

METHODS

We downloaded the gene expression profiles and clinical data of 213 burn patients and 79 healthy samples from the Gene Expression Omnibus (GEO) database. Immune infiltration analysis was used to identify the proportion of circulating immune cells. Functional enrichment analyses were carried out to identify immune-related genes that were used to build miRNA-mRNA networks to screen key genes. Next, we carried out correlation analysis between immune cells and key genes that were then used to construct logistic regression models in GSE77791 and were validated in GSE19743. Finally, we determined the expression of key genes in burn patients using quantitative reverse transcription polymerase chain reaction (qRT-PCR).

RESULTS

A total of 745 differently expressed genes were screened out: 299 were up-regulated and 446 were down-regulated. The number of Th-cells (CD4+) decreased while neutrophils increased in burn patients. The enrichment analysis showed that down-regulated genes were enriched in the T-cell activation pathway, while up-regulated genes were enriched in neutrophil activation response in burn patients. We screened out key genes (NFATC2, RORA, and CAMK4) that could be regulated by miRNA. The expression of key genes was related to the proportion of Th-cells (CD4+) and survival, and was an excellent predictor of prognosis in burns with an area under the curve (AUC) value of 0.945. Finally, we determined that NFATC2, RORA, and CAMK4 were down-regulated in burn patients.

CONCLUSION

We found that NFATC2, RORA, and CAMK4 were likely prognostic biomarkers in post-burn immunosuppression and potential immunotherapeutic targets to convert Th-cell dysfunction.

Innate Immune System Response to Burn Damage-Focus on Cytokine Alteration

In the literature, burns are understood as traumatic events accompanied by increased morbidity and mortality among affected patients. Their characteristic feature is the formation of swelling and redness at the site of the burn, which indicates the development of inflammation. This reaction is not only important in the healing process of wounds but is also responsible for stimulating the patient’s innate immune system. As a result of the loss of the protective ability of the epidermis, microbes which include bacteria, fungi, and viruses have easier access to the system, which can result in infections. However, the patient is still able to overcome the infections that occur through a cascade of cytokines and growth factors stimulated by inflammation. Long-term inflammation also has negative consequences for the body, which may result in multi-organ failure or lead to fibrosis and scarring of the skin. The innate immune response to burns is not only immediate, but also severe and prolonged, and some people with burn shock may also experience immunosuppression accompanied by an increased susceptibility to fatal infections. This immunosuppression includes apoptosis-induced lymphopenia, decreased interleukin 2 (IL-2) secretion, neutrophil storm, impaired phagocytosis, and decreased monocyte human leukocyte antigen-DR. This is why it is important to understand how the immune system works in people with burns and during infections of wounds by microorganisms. The aim of this study was to characterize the molecular pathways of cell signaling of the immune system of people affected by burns, taking into account the role of microbial infections.

High-Voltage, Pulsed Electric Fields Eliminate Pseudomonas aeruginosa Stable Infection in a Mouse Burn Model

Objective: The incidence of severe infectious complications after burn injury increases mortality by 40%. However, traditional approaches for managing burn infections are not always effective. High-voltage, pulsed electric field (PEF) treatment shortly after a burn injury has demonstrated an antimicrobial effect in vivo; however, the working parameters and long-term effects of PEF treatment have not yet been investigated. Approach: Nine sets of PEF parameters were investigated to optimize the applied voltage, pulse duration, and frequency or pulse repetition for disinfection of Pseudomonas aeruginosa infection in a stable mouse burn wound model. The bacterial load after PEF administration was monitored for 3 days through bioluminescence imaging. Histological assessments and inflammation response analyses were performed at 1 and 24 h after the therapy. Results: Among all tested PEF parameters, the best disinfection efficacy of P. aeruginosa infection was achieved with a combination of 500 V, 100 μs, and 200 pulses delivered at 3 Hz through two plate electrodes positioned 1 mm apart for up to 3 days after the injury. Histological examinations revealed fewer inflammatory signs in PEF-treated wounds compared with untreated infected burns. Moreover, the expression levels of multiple inflammatory-related cytokines (interleukin [IL]-1α/β, IL-6, IL-10, leukemia inhibitory factor [LIF], and tumor necrosis factor-alpha [TNF-α]), chemokines (macrophage inflammatory protein [MIP]-1α/β and monocyte chemoattractant protein-1 [MCP-1]), and inflammation-related factors (vascular endothelial growth factor [VEGF], macrophage colony-stimulating factor [M-CSF], and granulocyte-macrophage colony-stimulating factor [G-CSF]) were significantly decreased in the infected burn wound after PEF treatment. Innovation: We showed that PEF treatment on infected wounds reduces the P. aeruginosa load and modulates inflammatory responses. Conclusion: The data presented in this study suggest that PEF treatment is a potent candidate for antimicrobial therapy for P. aeruginosa burn infections.

miRNAs as Regulators of the Early Local Response to Burn Injuries

In burn injuries, risk factors and limitations to treatment success are difficult to assess clinically. However, local cellular responses are characterized by specific gene-expression patterns. MicroRNAs (miRNAs) are single-stranded, non-coding RNAs that regulate mRNA expression on a posttranscriptional level. Secreted through exosome-like vesicles (ELV), miRNAs are intracellular signalers and epigenetic regulators. To date, their role in the regulation of the early burn response remains unclear. Here, we identified 43 miRNAs as potential regulators of the early burn response through the bioinformatics analysis of an existing dataset. We used an established human ex vivo skin model of a deep partial-thickness burn to characterize ELVs and miRNAs in dermal interstitial fluid (dISF). Moreover, we identified miR-497-5p as stably downregulated in tissue and dISF in the early phase after a burn injury. MiR-218-5p and miR-212-3p were downregulated in dISF, but not in tissue. Target genes of the miRNAs were mainly upregulated in tissue post-burn. The altered levels of miRNAs in dISF of thermally injured skin mark them as new biomarker candidates for burn injuries. To our knowledge, this is the first study to report miRNAs altered in the dISF in the early phase of deep partial-thickness burns.

Plasma extracellular vesicles released after severe burn injury modulate macrophage phenotype and function

Extracellular vesicles (EVs) have emerged as key regulators of immune function across multiple diseases. Severe burn injury is a devastating trauma with significant immune dysfunction that results in an ∼12% mortality rate due to sepsis-induced organ failure, pneumonia, and other infections. Severe burn causes a biphasic immune response: an early (0-72 h) hyper-inflammatory state, with release of damage-associated molecular pattern molecules, such as high-mobility group protein 1 (HMGB1), and proinflammatory cytokines (e.g., IL-1β), followed by an immunosuppressive state (1-2+ wk post injury), associated with increased susceptibility to life-threatening infections. We have reported that early after severe burn injury HMGB1 and IL-1β are enriched in plasma EVs. Here we tested the impact of EVs isolated after burn injury on phenotypic and functional consequences in vivo and in vitro using adoptive transfers of EV. EVs isolated early from mice that underwent a 20% total body surface area burn injury (burn EVs) caused similar hallmark cytokine responses in naïve mice to those seen in burned mice. Burn EVs transferred to RAW264.7 macrophages caused similar functional (i.e., cytokine secretion) and immune gene expression changes seen with their associated phase of post-burn immune dysfunction. Burn EVs isolated early (24 h) induced MCP-1, IL-12p70, and IFNγ, whereas EVs isolated later blunted RAW proinflammatory responses to bacterial endotoxin (LPS). We also describe significantly increased HMGB1 cargo in burn EVs purified days 1 to 7 after injury. Thus, burn EVs cause immune outcomes in naïve mice and macrophages similar to findings after severe burn injury, suggesting EVs promote post-burn immune dysfunction.

Efficacy of Acupuncture on Pain Mechanisms, Inflammatory Responses, and Wound Healing in the Acute Phase of Major Burns: An Experimental Study on Rats

OBJECTIVES

We investigated acupuncture, a potential contributor for burn-care, on physiological and pathological pain mechanisms and systemic and local inflammatory responses in a rat experimental burn model.

METHODS

Forty male Sprague-Dawley rats were divided into 2 groups. One-hour groups(5 rats/group) were observed for 1 hour and included Sh1(sham/observation), ShA1(sham+acupuncture/observation), Brn1(burn/observation), and BrnA1(burn+acupuncture/observation). Seven-day groups(5 rats/group) were observed for 7 days and included Sh7(sham/observation), ShA7(sham+acupuncture/observation), Brn7(burn/observation), and BrnA7(burn+acupuncture/observation). "Pain-distress scores" were noted daily, acupuncture was repeated within every wound-dressing change on alternate days. After observation periods, blood samples for interleukin-6 and beta-endorphin and skin biopsies for inflammatory-changes and immunohistochemical-staining of interleukin-6 were collected for analysis( P< .05 ).

RESULTS

In 1-hour groups, interleukin-6 accumulation in burn wounds of BrnA1 was less than Brn1, with Brn1 having the highest mean blood level(P< .05). Mean beta-endorphin levels were higher in ShA1, Brn1, and BrnA1 than in Sh1(P< .05). In all 7-day groups, the agonizing period was 48 to72 hours after burn, with Brn7 most affected(P< .05). Microvessels were multiplied in Brn7group, with significantly higher numbers in burn wounds of BrnA7(P˂ .05). Burn wounds of BrnA7 had less accumulation of interleukin-6 than Brn7 with Brn7-group having the highest mean blood level and Sh7, ShA7, and BrnA7 having similarly low levels(P˃ .05). Beta-endorphin levels in ShA7, Brn7, and BrnA7 were lower than in Sh7(P< .05).

CONCLUSIONS

Acupuncture contributed to management of physiological and pathological pain, modulation of inflammatory responses, and associated enhancement of angiogenesis in acute phase of burn injury in rats.

Factors Associated with Mortality Following Burns Complicated by Necrotizing Skin and Soft Tissue Infections: A Systematic Review and Meta-analysis of Individual Participant Data

We reviewed studies with individual participant data of patients who sustained burn injury and subsequently developed necrotizing skin and soft tissue infections (NSTI). Characteristics and managements were compared between patients who lived and patients who died to determine factors associated with mortality. Six databases (PubMed, EMBASE, Cochrane Library, Web of Science, Scopus and CINAHL) were searched. PRISMA-IPD guidelines were followed throughout the review. Eligible patients sustained a burn injury, treated in any setting, and diagnosed with a NSTI following burn injury. Comparisons were made between burned patients who lived "non-mortality" and burned patients who died "mortality" following NSTI using non-parametric univariate analyses. Fifty-eight studies with 78 patients were published from 1970 through 2019. Non-mortality resulted in 58 patients and mortality resulted in 20 patients. Patients with mortality had significantly greater median %TBSA burned (45%[IQR:44-64%] versus 35%[IQR:11-59%],p=0.033), more intubations (79% versus 43%,p=0.013), less debridements (83% versus 98%,p=0.039), less skin excisions (83% versus 98%,p=0.039), more complications (100% versus 50%,p<0.001), management at a burn center (100% versus 71%,p=0.008), underwent less flap surgeries (5% versus 35%,p=0.014), less graft survival (25% versus 86%,p<0.001), and less healed wounds (5% versus 95%,p<0.001), compared to patients with non-mortality, respectively. Non-mortality patients had more debridements, skin excised, systemic antimicrobials, skin graft survival, flaps, improvement following surgery and healed wounds compared to mortality patients. Mortality patients had greater %TBSA burned, intubations, management at a burn center and complications compared to non-mortality patients.

Trauma-induced lung injury is associated with infiltration of activated TLR expressing myeloid cells

INTRODUCTION

Traumatic injury with hemorrhage (TH) induces an inflammatory response in the lung resulting in lung injury involving activation of immune cells including myeloid cells (i.e., monocytes, granulocytes and macrophages), in part through TLRs. TLRs, via the recognition of damage associated molecular patterns (DAMPs), are a key link between tissue injury and inflammation. Nonetheless, the role of TLRs in myeloid cell activation and TH-induced lung injury remains ill defined.

METHODS

C57BL/6 male mice were subjected to TH or sham treatment (n = 4-6 /group). Lung tissues were collected two hrs. after injury. Single cells were isolated from the lungs by enzymatic digestion and myeloid cell TLR expression and activation (i.e., cytokine production) were assessed using flow cytometry techniques.

RESULTS

The injury was associated with a profound change in the lung myeloid cell population. TH markedly increased lung CD11b⁺ monocyte numbers and Gr1⁺ granulocyte numbers as compared to sham mice. The number of cells expressing TLR2, TLR4, and TLR9 were increased 4-7 fold in the TH mice. Activation for elevated cytokine (TNFα, IL-10) production was observed in the lung monocyte population of the TH mice.

CONCLUSIONS

Trauma-induced lung injury is associated with infiltration of the lungs with TLR expressing myeloid cells that are activated for elevated cytokine responses. This elevation in TLR expression may contribute to DAMP-mediated pulmonary complications of an inflammatory nature and warrants further investigation.

The pathogenesis and diagnosis of sepsis post burn injury

Burn is an under-appreciated trauma that is associated with unacceptably high morbidity and mortality. Although the survival rate after devastating burn injuries has continued to increase in previous decades due to medical advances in burn wound care, nutritional and fluid resuscitation and improved infection control practices, there are still large numbers of patients at a high risk of death. One of the most common complications of burn is sepsis, which is defined as “severe organ dysfunction attributed to host's disordered response to infection” and is the primary cause of death in burn patients. Indeed, burn injuries are accompanied by a series of events that lead to sepsis and multiple organ dysfunction syndrome, such as a hypovolaemic state, immune and inflammatory responses and metabolic changes. Therefore, clear diagnostic criteria and predictive biomarkers are especially important in the prevention and treatment of sepsis and septic shock. In this review, we focus on the pathogenesis of burn wound infection and the post-burn events leading to sepsis. Moreover, the clinical and promising biomarkers of burn sepsis will also be summarized.

Burn Injury Induces Intestinal Inflammatory Response Mediated by Th17 in Burn-Primed Endotoxemic Mice

Objective

This study aimed to elucidate the mechanism underlying the susceptibility to infection-related acute lung injury by focusing on the role of gut mucosal T-helper (Th) 17 cells that preferentially produce IL-17 with probiotics in a burn-primed endotoxemic mice model.

Methods

Mice were subjected to a 15% total body surface area third-degree burn. Survival from lethal lipopolysaccharide (LPS) administration (3 mg/kg) on 11th day post-burn was assessed in mice fed by chow with or without 1.2% Lactobacillus powder after burn injury. Lamina propria mononuclear cells were enzymatically isolated from the ileum removed on 11th day post-burn and incubated along with 1 μg/mL LPS or 10 μg/mL anti-CD3 antibody for 24 hours; subsequently, the following 7 cytokines were analyzed in the supernatant: IFN-γ, TNF-α, IL-2, IL-4, IL-6, IL-10, and IL-17.

Results

Lactobacillus treatment post-burn injury markedly improved survival after lethal endotoxemia in burn-primed mice (64.3% versus 21.4%, P = 0.03). The production of proinflammatory cytokines such as TNF-α, IL-6, and IL-17 by lamina propria mononuclear T-lymphocytes and macrophages including Th17 response was augmented by burn injury but decreased with Lactobacillus treatment after burn injury.

Conclusions

Th17- and Th17-mediated inflammatory responses in the gut mucosa may play a vital role, which could be attenuated by Lactobacillus treatment, in survival of lethal endotoxemia in burn-primed mice.

An Assessment of Research Priorities to Dampen the Pendulum Swing of Burn Resuscitation

On June 17 to 18, 2019, the American Burn Association, in conjunction with Underwriters Laboratories, convened a group of experts on burn resuscitation in Washington, DC. The goal of the meeting was to identify and discuss novel research and strategies to optimize the process of burn resuscitation. Patients who sustain a large thermal injury (involving >20% of the total body surface area [TBSA]) face a sequence of challenges, beginning with burn shock. Over the last century, research has helped elucidate much of the underlying pathophysiology of burn shock, which places multiple organ systems at risk of damage or dysfunction. These studies advanced the understanding of the need for fluids for resuscitation. The resultant practice of judicious and timely infusion of crystalloids has improved mortality after major thermal injury. However, much remains unclear about how to further improve and customize resuscitation practice to limit the morbidities associated with edema and volume overload. Herein, we review the history and pathophysiology of shock following thermal injury, and propose some of the priorities for resuscitation research. Recommendations include: studying the utility of alternative endpoints to resuscitation, reexamining plasma as a primary or adjunctive resuscitation fluid, and applying information about inflammation and endotheliopathy to target the underlying causes of burn shock. Undoubtedly, these future research efforts will require a concerted effort from the burn and research communities.

Viral Infections in Burn Patients: A State-Of-The-Art Review

Infections that are triggered by the accompanying immunosuppression in patients with burn wounds are very common regardless of age. Among burn patients, the most frequently diagnosed infections include the bacterial ones primarily caused by Pseudomonas aeruginosa or Klebsiella pneumonia, as well as fungal infections with the etiology of Candida spp. or Aspergillus spp. Besides, burn wounds are highly susceptible to viral infections mainly due to the impaired immune responses and defective functions of the immune cells within the wound microenvironment. The most prevalent viruses that invade burn wounds include herpes simplex virus (HSV), cytomegalovirus (CMV), human papilloma virus (HPV), and varicella zoster virus (VZV). Likewise, less prevalent infections such as those caused by the orf virus or Epstein-Barr Virus (EBV) might also occur in immunosuppressed burn patients. Viral infections result in increased morbidity and mortality rates in severely burned patients. Additionally, a positive correlation between the hospitalization duration and the severity of the viral infection has been demonstrated. Viral infections trigger the occurrence of various complications, ranging from mild symptoms to even fatal incidents. Accurate detection of viral infection is of great clinical importance because of the possibility for a quicker introduction of proper treatment therapy and shortening of hospitalization time. The aim of this paper is to provide a comprehensive review of the literature and summarize the findings regarding the most common viral infections in immunosuppressed burn patients.

Plasma TNFα and Unknown Factor/s Potentially Impede Erythroblast Enucleation Obstructing Terminal Maturation of Red Blood Cells in Burn Patients

INTRODUCTION

In this study, using burn patient's peripheral blood mononuclear cells (PBMCs), we have shown that the Epo independent stage of terminal enucleation to reticulocyte formation is impeded in the presence of autologous plasma (BP). Furthermore, substitution with allogeneic control plasma (CP) from the healthy individual in place of BP rectified this enucleation defect. The exclusive role of burn microenvironment in late-stage erythropoiesis defect was further demarcated through control healthy human bone marrow cells cultured in the presence of CP, BP, and cytokines.

METHODS

PBMCs and human bone marrow (huBM) were differentiated ex vivo to enucleated reticulocytes in the presence of required growth factors and 5% CP or BP. Effect of systemic mediators in burn microenvironment like IL-6, IL-15, and TNFα was also explored. Neutralization experiments were carried out by adding varying concentrations (25 ng-400 ng/mL) of Anti-TNFα Ab to either CP+TNFα or BP.

RESULTS

Reticulocyte proportion and maturation index were significantly improved upon substituting BP with CP during differentiation of burn PBMCs. In the huBM ex vivo culture, addition of IL-6 and IL-15 to CP inhibited the proliferation stages of erythropoiesis, whereas TNFα supplementation caused maximum diminution at erythroblast enucleation stage. Supplementation with anti-TNFα in the BP showed significant but partial restoration in the enucleation process, revealing the possibility of other crucial microenvironmental factors that could impact RBC production in burn patients.

CONCLUSION

Exogenous TNFα impairs late-stage erythropoiesis by blocking enucleation, but neutralization of TNFα in BP only partially restored terminal enucleation indicating additional plasma factor(s) impair(s) late-stage RBC maturation in burn patients.

Nutritional management of a kitten with thermal burns and septicaemia

Case summary

A 3-month-old entire female British Shorthair cat presented for further management of thermal burns after falling into a bath of scalding water. On presentation to the primary care clinician the kitten was obtunded, markedly painful and relatively bradycardic, consistent with a state of shock. The haircoat was wet, with erythematous skin and sloughing from the digital pads and anal mucosa. The primary care clinician administered opioid analgesia, sedation, antibiotics and started intravenous (IV) fluid therapy prior to referral. On arrival to the referral hospital the kitten was obtunded with respiratory and cardiovascular stability but was overtly painful and resistant to handling. The kitten required intensive management with IV and regional analgesia, IV broad-spectrum antibiosis, IV fluid therapy, enteral nutrition and wound management, including surgical debridement and topical antibiotic therapy. Septicaemia developed during the hospitalisation. Multidrug-resistant Escherichia coli and Pseudomonas aeruginosa were cultured, and antibiosis was escalated to IV imipenem. Acute respiratory distress syndrome was suspected following the development of dyspnoea. Early enteral nutrition within 24 h of admission was initiated using an oesophageal feeding tube and a veterinary therapeutic liquid diet. Over the ensuing 72 h the kitten started voluntary intake of food alongside oesophageal tube feeds. The kitten experienced continued weight loss despite the provision of nutritional support to meet, and then later exceed, the estimated resting energy requirements. Caloric intake was gradually increased to a total of 438% of the calculated resting energy requirement using the most recent daily body weight, eventually resulting in stabilisation of weight loss and weight gain.

Relevance and novel information

There is limited published information on the nutritional management of veterinary patients with thermal burn injury. Hypermetabolic states related to burn injuries are induced and maintained by complex interactions of catecholamines, stress hormones and inflammatory cytokines on proteolysis, lipolysis and glycogenolysis. Secondary infections are common following burn injury and the subsequent proinflammatory state perpetuates hypermetabolism and catabolism. These states present a challenge in both predicting and providing adequate nutrition, particularly in a paediatric septic patient. This subset of patients should be monitored closely during hospitalisation to ensure body weight and condition are maintained (while taking into consideration hydration status), and caloric intake is adjusted accordingly to meet nutritional support goals. Extensive research exists regarding the nutritional requirements and metabolic derangements of people with thermal burns. However, the importance of maintaining body weight and body condition in veterinary burn patients, and the association between nutritional support and reduced morbidity and mortality, has not been investigated and remains to be elucidated.

Immunological approaches and therapy in burns (Review)

Burns have become an important public health problem in the last two decades, with just over a quarter of a million deaths annually. Major burns are accompanied by a strong inflammatory response, which will most often lead to systemic response inflammatory syndrome, followed by sepsis and finally induce multiple organ failure. The main mechanism involved in wound healing after burns is the inflammatory process, characterized by the recruitment of myeloid and T cells and by the involvement of numerous cytokines, chemokines, complement fractions, as well as various growth factors. Inflammasomes, protein-based cytosolic complexes, activated during metabolic stress or infection, play a role in modulating and improving the defense capacity of the innate immune system. Nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome has been studied predominantly and several hypotheses have been issued. Restoring the balance between the pro-inflammatory response and the anti-inflammatory activity is the key element to effective therapy in burns. Severe burns require nutritional support and pharmacotherapy not only for burn area but for different pathological complications of burn injury. In-depth research is required to find new ways to modulate the defense capacity, to prevent the complications of abnormal immune response and to treat burn injuries efficiently.

Clinical Importance of a Cytokine Network in Major Burns

Major burns elicit an acute inflammatory response including various inflammatory cytokines. Cytokines play mutual interacting roles in inflammatory diseases. There is little evidence of the clinical significance of the cytokine network in patients with major burns. This study aimed to investigate the clinical significance of the cytokine network in patients with major burn. This prospective observational study comprising 38 patients with major burns (total body surface area (%TBSA) ≥ 20%) and 12 healthy controls was conducted from April 2014 to December 2016. Blood samples were collected from patients at six points: day 1, day 2, days 3-5, 1 week, 2 weeks, and 1 month after the burn injury. Inflammatory cytokines (interferon [IFN]-α, IFN-γ, interleukin [IL]-1β, IL-6, IL-8, IL-12/IL-23p40, IL-17A, monocyte chemotactic protein-1 [MCP-1], TNF-α), and anti-inflammatory cytokines (IL-4, IL-10) were measured. Twenty-eight-day mortality, %TBSA, prognostic burn index (PBI) and Sequential Organ Failure Assessment (SOFA), and Acute Physiology and Chronic Health Evaluation (APACHE) II scores were evaluated. Hierarchical clustering analysis and network visualization showed one cluster and network, respectively. Both were formed by four cytokines including IL-6, IL-8, IL-10, and MCP-1 on days 1 and 2, suggesting the presence of a cytokine network in the early hospital phase. Each cytokine showed significant associations with the SOFA score within 5 days and 1 month after burn injury. Cox regression analysis highlighting days 1 and 2 showed significant correlation of IL-6, IL-8, and IL-10 with 28-day mortality. We showed a cytokine network and its relation with prognosis and injury severity on days 1 and 2 and suggest that this cytokine network may play a role in major burns.

Severe Coagulopathy Secondary to Fulminant Herpes Simplex Virus Hepatitis in a Severely Burned Patient: A Case Report and Review of the Literature

Fulminant hepatic failure secondary to herpes simplex virus (HSV) is a rare complication that is associated with high mortality. Here, we describe the case of a critically ill patient with severe burns and inhalation injury who developed severe coagulopathy during her hospital stay, which was later found to be caused by HSV hepatitis. In addition, we review the current literature on HSV hepatitis. Only three prior reports document liver involvement of HSV in patients with burn. Clinical symptoms, diagnostic factors, and management of HSV hepatitis in patients with burn are presented. Because of severe immunosuppression and potentially fatal nature of this infection, clinicians should have a heightened suspicion for HSV hepatitis in burn patients with HSV mucocutaneous involvement, unexplained liver dysfunction, and severe coagulopathy, and it should prompt immediate initiation of intravenous acyclovir.

Severe Burn Injury Progression and Phasic Changes of Gene Expression in Mouse Model

Patients with severe burns are susceptible to infectious complications including burn-site infections and sepsis. The purpose of this study was to explore the pathologic development of burn injury in a mouse model and to screen genes dysregulated at different time points on the basis of gene expression microarrays. Differential expression analysis identified a total 223 genes that related to only time progression independent of burn injury and 214 genes with aberrant expression due to burn injury. Weighted gene co-expression network analysis (WGCNA) of the 214 genes obtained seven gene modules which named as red, blue, turquoise, green, brown, yellow, and gray module, and the blue module was found to be significantly associated with severe burn injury progression, and in which several genes were previously reported being associated with inflammation and immune response, such as interleukin IL-6, IL-8, and IL-1b. Functional enrichment analysis indicated significant enrichment of biological processes that related to metabolism and catabolism, and pathways of proteasome, notch signaling and cell cycle. This result supports a phase progression of severe burn with gene expression changes and interpretation of biological processes in mouse.

Topical Insulin Modulates Inflammatory and Proliferative Phases of Burn-Wound Healing in Diabetes-Induced Rats

The healing time of burn wounds depends on surface area and depth of the burn and associated comorbidities. Diabetes mellitus (DM) causes delays in the healing process by extending the inflammatory phase. Treatment with topical insulin can improve the inflammatory phase, restore metabolic dysregulation, and modulate impaired cellular signaling in burn wounds. The objective of this study was to evaluate markers of the inflammatory and proliferative phases of second-degree burns after topical insulin treatment in diabetic rats. Type I DM was induced with streptozotocin in male Wistar rats. The animals' backs were shaved and subjected to thermal burning. Rats were randomized into two groups: control diabetic (DC) and insulin diabetic (DI). At Days 7 and 14 postburn, rats were euthanized, and wound-tissue sections were evaluated by hematoxylin and eosin, Weigert, and Verhöeff staining, immunohistochemistry-paraffin, and enzyme-linked immunosorbent assay. A significant increase in reepithelialization was seen on Days 7 and 14 in DI versus DC rats. On Day 7, interleukin (IL)-1β, IL-6, monocyte chemotactic protein (MCP)-1, and F4/80 expression were increased in DI versus DC rats. On Day 14, MCP-1 expression was decreased and F4/80 increased in DI versus DC rats. On Days 7 and 14, Ki-67, transforming growth factor-β1, vascular endothelial growth factor expression, and formation of elastic fibers were increased in DI versus DC rats. Topical insulin modulates burn-wound healing in diabetic animals by balancing inflammation and promoting angiogenesis and formation of elastic fibers.

Effects of Myeloperoxidase on Methicillin-Resistant Staphylococcus aureus-Colonized Burn Wounds in Rats

Objective: To achieve better therapeutic results in burn wound infections and to examine alternatives to antibiotics, we designed this study to elaborate the role of myeloperoxidase (MPO) on infected burn wounds in rats. Approach: We compared chemical properties as well as bacteriostatic ability of MPO in different concentrations with NeutroPhase. Subsequently, we applied MPO (MPO group), NeutroPhase (NeutroPhase group), NaCl+H₂O₂ (NaCl+H₂O₂ group), or NaCl (control group) on rat dorsal burn wounds inoculated with methicillin-resistant Staphylococcus aureus (MRSA). Their effects on MRSA-colonized wounds were evaluated by microscopy, histologic section, and Western blot. Results: MPO produced more H⁺ and HClO^-, leading to a more acidic environment. Moreover, MPO inhibited the growth of MRSA more intensely after 6 h of inoculation ex vivo. In vivo the open wound rate in the MPO group was significantly lower, while the contraction rate and epithelialization rate of MPO group were higher than that of the control group, NaCl+H₂O₂ group, and NeutroPhase group on day 20. The hematoxylin and eosin staining of MPO group showed better wound healing than other groups. More vascular endothelial growth factor (VEGF) was expressed in wound tissue of MPO group by Western blot. Innovation: This is the first study to use MPO for MRSA-colonized burn wound therapy. Conclusion: MPO displayed more effective bacteriostatic ability, possibly beneficial for MRSA-colonized wound healing.

Burn injury is associated with an infiltration of the wound site with myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) have been identified in the burn wound, however their characterization is incomplete. To study this, mice were subjected to a major burn and skin cells were isolated 3 days thereafter for analysis. Significant infiltration of the burn wound with MDSCs was observed as compared with uninjured skin. The skin of naïve mice did not contain MDSCs. Characterization of the cells showed that 33% of MDSCs in the wound were monocytic (M)-MDSCs, which was significantly less than that found in uninjured skin (52%). In contrast, polymorphonuclear (PMN)-MDSCs were greater in the burn wound as compared with uninjured skin. Burn wound TLR expression by both MDSCs subsets was decreased as compared with uninjured skin. Wound MDSCs produced pro- and anti-inflammatory cytokines and iNOS was present in both MDSC subsets, whereas ARG1 was only present in M-MDSCs. In conclusion, both M- and PMN-MDSCs infiltrate burn wound with after injury, however, they displayed decreased TLR expression, suggesting receptor down-regulation.