Amitriptyline Usage Exacerbates the Immune Suppression Following Burn Injury

Resolving a paradox: antidepressants, neuroinflammation, and neurodegeneration

Depression is a known risk factor for dementia. Antidepressants are the most commonly used treatment for this condition, and are effective in at least half to two-thirds of cases. Extensive evidence from in vitro and animal models suggests that antidepressants have anti-inflammatory and neuroprotective properties. These effects have been shown to reduce the oxidative damage, amyloid aggregation, and expression of pro-inflammatory genes associated with animal models of neurodegenerative disorders. However, longitudinal research in humans has shown that antidepressants do not protect against dementia, and may even be associated with a risk of cognitive deterioration over time in older adults. The contrast between two sets of findings represents a paradox of significant clinical and public health significance, particularly when treating depression in late life. This review paper attempts to resolve this paradox by critically reviewing the medium- and long-term effects of antidepressants on peripheral immune-inflammatory responses, infection risk, gut microbiota, and neuroendocrine responses to stress, and how these effects may influence the risk of neurodegeneration. Briefly stated, it is possible that the peripheral actions of antidepressant medications may antagonize their beneficial effects against neuroinflammation. The implications of these findings are then explored with a particular focus on the development and testing of multimodal neuroprotective and anti-inflammatory treatments that could reduce the risk of Alzheimer’s and related dementias in patients suffering from depression.

Impact of chemical mixtures from wastewater treatment plant effluents on human immune cell activation: An effect-based analysis

BACKGROUND

Humans are exposed to many different chemicals on a daily basis, mostly as chemical mixtures, usually from food, consumer products and the environment. Wastewater treatment plant effluent contains mixtures of chemicals that have been discarded or excreted by humans and not removed by water treatment. These effluents contribute directly to water pollution, they are used in agriculture and may affect human health. The possible effect of such chemical mixtures on the immune system has not been characterized.

OBJECTIVE

The aim of this study was to investigate the effect of extracts obtained from four European wastewater treatment plant effluents on human primary immune cell activation.

METHODS

Immune cells were exposed to the effluent extracts and modulation of cell activation was performed by multi-parameter flow cytometry. Messenger-RNA (mRNA) expression of genes related to immune system and hormone receptors was measured by RT-PCR.

RESULTS

The exposure of immune cells to these extracts, containing 339 detected chemicals, significantly reduced the activation of human lymphocytes, mainly affecting T helper and mucosal-associated invariant T cells. In addition, basophil activation was also altered upon mixture exposure. Concerning mRNA expression, we observed that 12 transcripts were down-regulated by at least one extract while 11 were up-regulated. Correlation analyses between the analyzed immune parameters and the concentration of chemicals in the WWTP extracts, highlighted the most immunomodulatory chemicals.

DISCUSSION

Our results suggest that the mixture of chemicals present in the effluents of wastewater treatment plants could be considered as immunosuppressive, due to their ability to interfere with the activation of immune cells, a process of utmost importance for the functionality of the immune system. The combined approach of immune effect-based analysis and chemical content analysis used in our study provides a useful tool for investigating the effect of environmental mixtures on the human immune response.

Inhibition of DDX3X alleviates persistent inflammation, immune suppression and catabolism syndrome in a septic mice model

OBJECTIVE

DDX3X is involved in various pathological processes such as infection, immunity and cell death. This study aimed to investigate the effect of RK-33, a specific inhibitor of DDX3X, on the progression of sepsis to persistent inflammation, immune suppression and catabolism syndrome(PICS).

METHODS

The septic mice model was established using caecal ligation and perforation (CLP). The mice were randomly divided into four groups: sham group, sham + RK-33 group (20 mg/kg, intraperitoneal injection, once a day), CLP group and CLP + RK-33 group (20 mg/kg, intraperitoneal injection, once a day). The number of inflammatory cells in the peripheral blood, spleen and bone marrow was calculated, and inflammatory cytokines were detected using an enzyme-linked immunosorbent assay. The septic mice's body weight and skeletal muscle mass were measured, and skeletal muscle tissues were examined using eosin staining. Western blotting was performed to detect the expression levels of MuRF1, atrogin1 and NLRP3 in the skeletal muscle of septic mice. Additionally, reactive oxidative species, superoxide dismutase and malondialdehyde were measured using commercial kits.

RESULTS

RK-33 reduced inflammatory cell counts and cytokine levels in CLP mice, ameliorated the decline in CD4 and CD8 T cells and prevented the loss of body weight and skeletal muscle mass in septic mice. Additionally, RX-33 reduced oxidative stress in the skeletal muscle of septic mice.

CONCLUSION

In the established sepsis mouse model, RK-33 alleviated inflammation and oxidative stress, ameliorated CLP-induced immunosuppression and skeletal muscle atrophy and improved survival. These findings suggest that RK-33 could be a novel potential therapeutic agent for preventing the progression of sepsis to PICS.

Luteolin is an Effective Component of Platycodon grandiflorus in Promoting Wound Healing in Rats with Cutaneous Scald Injury

Background

Platycodon grandiflorus could significantly improve the pathological results of cutaneous scald injury, reduce the release of inflammatory factors and promote angiogenesis. This study investigated the wound healing effect of luteolin, an active component of P. grandiflorus, on induced cutaneous scald injury in Sprague-Dawley (SD) rats.

Methods

The protein expression levels of TNF-α and IL-6 were detected by ELISA. QRT-PCR was adopted to detect the expression of TGF-β1 and VEGF. Histopathological changes of scald wounds were analyzed by hematoxylin-eosin staining. Cell viability and migration ability were detected by CCK-8 assay and scratch assay.

Results

Both in vivo and in vitro experiments showed that luteolin promoted wound healing of cutaneous scald injury. Gene Oncology (GO) functional analysis and rescue experiments showed that endothelial nitric oxide synthase 3 (NOS3) was the critical target of luteolin in treating cutaneous scald.

Conclusion

This study demonstrated that luteolin is an effective component of P. grandiflorus and is effective in the treatment of cutaneous scald injury.

Plasma Neutrophil-to-Lymphocyte Ratio on the Third Day Postburn is Associated with 90-Day Mortality Among Patients with Burns Over 30% of Total Body Surface Area in Two Chinese Burns Centers

INTRODUCTION

Neutrophil-to-lymphocyte ratio (NLR) is a marker of inflammation. This study aimed to evaluate the potential role of NLR to predict 90-day mortality.

METHODS

Data of 577 patients with burns over 30% of total body surface area were collected and retrospectively analyzed. The risk factors for 90-day mortality were evaluated using logistic regression analyses. Receiver operating characteristic (ROC) curve analysis of the 3rd day NLR was performed and the optimal cut-off value was calculated. The 90-day mortality rates were compared between high and low NLR groups using Kaplan-Meier analysis.

RESULTS

Age, mechanical ventilation, burn index, 3rd day NLR, and 7th day red blood cell and platelet (PLT) counts were found to be independent predictive values for 90-day mortality. In contrast, percentage of total body surface area burned, inhalation injury, 1st day white blood cell and neutrophil counts, the 3rd day lymphocytes and PLT counts, and 7th day hemoglobin level were not independently associated with 90-day mortality. The area under the ROC curve of the 3rd day NLR for severe burn-delayed death prediction was 0.665 (95% confidence interval, 0.591-0.739), and the optimal cut-off value of the 3rd day NLR was 10.50. The 90-day mortality rates differed significantly between the NLR >10.5 group and the NLR ≤ 10.5 group (17.03% vs 5.92%, respectively; P < 0.01).

CONCLUSION

These results suggested that the 3rd day NLR was associated with an increased risk of death in severely burned patients; thus, it can provide useful information to predict 90-day mortality.

Amitriptyline Downregulates Chronic Inflammatory Response to Biomaterial in Mice

Recent data has signaled that in addition to its therapeutic indications as antidepressant and analgesic, amitriptyline (AM) exerts anti-inflammatory effects in humans and experimental animal models of acute inflammation. We tested the hypothesis that this compound could also modulate the chronic inflammatory process induced by synthetic matrix in mice. Polyether-polyurethane sponge disks were implanted subcutaneously in 9-week-old male C57BL/6 mice. The animals received by oral gavage 5.0 mg/kg of amitriptyline for seven consecutive days in two treatment regimens. In the first series, the treatment was initiated on the day of surgery and the implants removed at day 7 post-implantation. For the assessment of the effect of amitriptyline on chronic inflammation, the treatment was initiated 7 days post-implantation and the sponge discs removed 14 after implantation. The inflammatory markers evaluated, myeloperoxidase - MPO, nitrite content, IL-6, IFN-γ, TNF-α, CXCL1 and CCL2 levels, and NF-κB transcription factor activation were reduced in implants when the treatment began 7 days post-implantation (chronic inflammation). In contrast, only mast cell number, MPO activity and activation of NF-κB pathway decreased when the treatment began soon after implantation (sub-acute inflammation) in 7-day old implants. The anti-inflammatory effects of amitriptyline described here, extend its range of actions as a potential agent able to attenuate long-term inflammatory processes.

Effect of amitriptyline on orthodontic tooth movement in rats: an experimental study

Background. Orthodontic tooth movement (OTM) occurs in the alveolar bone; therefore, any condition affecting bone quality can alter OTM. This study aimed to evaluate the effect of amitriptyline on OTM in rats. Methods. Forty-five male Wistar rats were randomly divided into three groups: (I) no injection, (II) injection with saline solution, and (III) injection of amitriptyline. Next, a 60-gr force was applied to the maxillary left first molar tooth of all the rats, using a nickel‒titanium closed-coil spring ligated between the maxillary incisors and the left first molar tooth. The rats were sacrificed after 21 days to measure OTM and perform histological analysis to determine the number, width, and depth of resorptive lacunae, osteoclast counts, and periodontal ligament (PDL) width. Results. The highest and the lowest OTM rates were found in the control and amitriptyline groups, respectively; however, there was no significant difference between the study groups in this regard. Histological analysis showed a significantly lower number of resorption lacunae in the amitriptyline group than the saline group. Conclusion. Although no significant difference was noted in OTM after amitriptyline administration, a reduction in the number of resorptive lacunae in rats injected with amitriptyline suggests that amitriptyline affects the bone tissue at the cellular level.

Downregulation of miR-27b promotes skin wound healing in a rat model of scald burn by promoting fibroblast proliferation

The aim of the present study was to investigate the effect and mechanism of action of microRNA (miR)-27b on skin wound healing in rats with deep second-degree scald burns and in BJ human skin fibroblast cells. Rat models with deep second-degree scald burns were constructed and injected with miR-27b mimics and inhibitors at the wound site daily for 21 days. Healing of burned skin tissues was observed at 0, 3, 7, 14 and 21 days following modeling. H&E and Masson staining were used to observe the pathological structure and degree of collagen fibers in the burned skin tissues. The effects of miR-27b on BJ cell proliferation and migration were determined by MTT and scratch assays. Matrix metalloproteinase-1 (MMP-1), α-smooth muscle actin (α-SMA), collagen I and collagen III expression in rat skin tissues and BJ cells were measured via reverse transcription-quantitative PCR and western blot analysis. The results of the in vivo experiments demonstrated that miR-27b inhibition accelerated scalded skin healing and induced fibroblast growth. Furthermore, the in vitro experiments revealed that miR-27b inhibition increased BJ cell proliferation and migration. Furthermore, miR-27b inhibition upregulated MMP-1, α-SMA, collagen I and collagen III expression in the skin tissues and cells, while the overexpression of miR-27b demonstrated the opposite effect. In conclusion, the results of the present study revealed that miR-27b inhibition increased fibroblast proliferation, thereby accelerating scald wound healing in rats.

Novel Therapeutics for the Treatment of Burn Infection

Background: Burn injury continues to be a significant cause of morbidity and death, with infectious complications being the primary cause of death. Patients are susceptible to overwhelming infection secondary to both the physical breakdown of the skin and mucosal barrier and the immune dysfunction that accompanies the inflammatory response to a major burn. With resistance to traditional antibiosis looming as a serious threat to patient outcome, advancement in the treatment of burn infections is imperative. Methods: Between February 15 and March 15, 2020, a search of Pubmed and clinicaltrials.gov was performed using search terms such as "burn immunotherapy," "therapeutic microorganisms in burn," "burn infection clinical trials," and applicable variations. Results: Topical antimicrobial drugs continue to be standard of care for burn wound injuries, but personalized and molecular treatments that rely on immune manipulation of the host show great promise. We discuss novel therapeutics for the treatment of burn infection: Probiotics and therapeutic microorganisms, immune modulators, tailored monoclonal antibodies, and extracellular vesicles and proteins. Conclusions: The treatment strategies discussed employ manipulation of structure and function in host immune cells and pathogen virulence for improved outcomes in burn infection.

Acid Sphingomyelinase Inhibition Mitigates Histopathological and Behavioral Changes in a Murine Model of Traumatic Brain Injury

Traumatic brain injury (TBI) can lead to the development of chronic traumatic encephalopathy as a result of neuronal phosphorylated tau (p-tau) protein aggregation and neuroinflammation. Acid sphingomyelinase (Asm) may also contribute to post-TBI neurodegenerative disorders. We hypothesized that Asm inhibition would ameliorate p-tau aggregation, neuroinflammation, and behavioral changes after TBI in a murine model. TBI was generated using a weight-drop method. Asm inhibition in wild-type mice was achieved with a single injection of amitriptyline 1 h after TBI. Genetic Asm ablation was achieved using Asm-deficient mice (Asm^-/-). Thirty days after TBI, mice underwent behavioral testing with the forced swim test for symptoms of depression or were euthanized for neurohistological analysis. Neuroinflammation was quantified using the microglial markers, ionized calcium-binding adaptor molecule 1 and transmembrane protein 119. Compared to sham mice, TBI mice demonstrated increased hippocampal p-tau. Mice that received amitriptyline after TBI demonstrated decreased p-tau compared to mice that received a saline control. Further, post-TBI Asm^-/- mice demonstrated lower levels of p-tau compared to wild-type mice. Though a decrease in neuroinflammation was observed at 1 month post-TBI, no change was demonstrated with mice treated with amitriptyline. Similarly, TBI mice were more likely to show depression compared to mice that received amitriptyline after TBI. Utilizing a weight-drop method to induce moderate TBI, we have shown that genetic deficiency or pharmacological inhibition of Asm prevented hippocampal p-tau aggregation 1 month after injury as well as decreased symptoms of depression. These findings highlight an opportunity to potentially reduce the long-term consequences of TBI.

Amitriptyline Treatment Mitigates Sepsis-Induced Tumor Necrosis Factor Expression and Coagulopathy

During sepsis, the early innate response and inflammatory cytokine cascade are associated with activation of the coagulation cascade. Acute hypercoagulability can contribute to lethal sequela of vascular thrombosis, tissue ischemia, and organ failure. We investigated if amitriptyline (AMIT), an antidepressant drug with a number of anti-inflammatory effects, could ameliorate sepsis in a murine model of sepsis-cecal ligation and puncture (CLP). We hypothesized that AMIT treatment would reduce inflammation and mitigate sepsis-induced coagulopathy. Coagulation was measured using thromboelastometry and ferric chloride-induced carotid artery thrombosis. Our findings demonstrate a dynamic early hypercoagulability, followed by delayed hypocoagulability in septic mice. However, septic mice treated with AMIT were unaffected by these coagulation changes and exhibited a coagulation profile similar to sham mice. TNFα was markedly elevated in septic mice, but decreased in AMIT-treated mice. Exogenous administration of recombinant TNFα in naive mice recapitulated the acute sepsis-induced hypercoagulability profile. After sepsis and endotoxemia, peritoneal macrophages were the predominant source of TNFα expression. AMIT treatment significantly decreased macrophage TNFα expression and blunted M1 polarization. Altogether, during polymicrobial sepsis, AMIT treatment suppressed macrophage TNFα expression and the M1 phenotype, mitigating an initial hypercoagulable state, and protecting septic mice from delayed hypocoagulability. We propose that AMIT treatment is a promising therapeutic approach in the treatment of sepsis-associated coagulopathy and prevention of acute thromboembolic events or delayed bleeding complications.

The Role of Chemoprophylactic Agents in Modulating Platelet Aggregability After Traumatic Brain Injury

BACKGROUND

The pathophysiology behind the subacute but persistent hypercoagulable state after traumatic brain injury (TBI) is poorly understood but contributes to morbidity induced by venous thromboembolism. Because platelets and their microvesicles have been hypothesized to play a role in post-traumatic hypercoagulability, administration of commonly used agents may ameliorate this coagulability. We hypothesized that utilization of aspirin, ketorolac, amitriptyline, unfractionated heparin, or enoxaparin would modulate the platelet aggregation response after TBI.

METHODS

Concussive TBI was induced by weight drop. Mice were then randomized to receive aspirin, ketorolac, amitriptyline, heparin, enoxaparin, or saline control at 2 and 8 h after TBI. Mice were sacrificed at 6 or 24 h after injury to determine coagulability by rotational thromboelastometry (ROTEM), platelet function testing with impedance aggregometry, and microvesicle enumeration. Platelet sphingolipid metabolites were analyzed by mass spectrometry.

RESULTS

ROTEM demonstrated increased platelet contribution to maximum clot firmness at 6 h after TBI in mice that received aspirin or amitriptyline, but this did not persist at 24 h. By contrast, adenosine diphosphate- and arachidonic acid-induced platelet aggregation at 6 h was significantly lower in mice receiving ketorolac, aspirin, and amitriptyline compared with mice receiving saline at 6 h after injury and only arachidonic acid-initiated platelet aggregation was decreased by aspirin at 24 h. There were no differences in microvesicle production at either time point. Platelet sphingosine-1-phosphate levels were decreased at 6 h in the group receiving amitriptyline and increased at 24 h along with platelet ceramide levels at 24 h in the amitriptyline group.

CONCLUSION

After TBI, amitriptyline decreased platelet aggregability and increased contribution to clot in a manner similar to aspirin. The amitriptyline effects on platelet function and sphingolipid metabolites may represent a possible role of the acid sphingomyelinase in the hypercoagulability observed after injury. In addition, inhibition of platelet reactivity may be an underappreciated benefit of low molecular weight heparins, such as enoxaparin.

Intestinal Acid Sphingomyelinase Protects From Severe Pathogen-Driven Colitis

Inflammatory diseases of the gastrointestinal tract are emerging as a global problem with increased evidence and prevalence in numerous countries. A dysregulated sphingolipid metabolism occurs in patients with ulcerative colitis and is discussed to contribute to its pathogenesis. In the present study, we determined the impact of acid sphingomyelinase (Asm), which catalyzes the hydrolysis of sphingomyelin to ceramide, on the course of Citrobacter (C.) rodentium-driven colitis. C. rodentium is an enteric pathogen and induces colonic inflammation very similar to the pathology in patients with ulcerative colitis. We found that mice with Asm deficiency or Asm inhibition were strongly susceptible to C. rodentium infection. These mice showed increased levels of C. rodentium in the feces and were prone to bacterial spreading to the systemic organs. In addition, mice lacking Asm activity showed an uncontrolled inflammatory T_h1 and T_h17 response, which was accompanied by a stronger colonic pathology compared to infected wild type mice. These findings identified Asm as an essential regulator of mucosal immunity to the enteric pathogen C. rodentium.

Nortriptyline-induced oral ulceration: A case report

Drug-induced oral ulcers are lesions of the oral mucosa accompanied by painful symptoms, such as burning mouth, metallic taste, dysgeusia, or ageusia. This report demonstrates the first documented case of drug-induced oral ulcers with the tricyclic antidepressant nortriptyline. In this case, a 49-year-old female initiated treatment for refractory neuropathy with nortriptyline. Within 2 weeks of therapy, painful, oral, bubble-like ulcers developed. Complete symptom resolution occurred approximately 1 month after discontinuation of nortriptyline. Clinicians should be cognizant of nortriptyline's ability to potentially induce oral ulcers; however, the exact mechanism for this adverse event is unknown.

Acid Sphingomyelinase Inhibition Stabilizes Hepatic Ceramide Content and Improves Hepatic Biotransformation Capacity in a Murine Model of Polymicrobial Sepsis

Liver dysfunction during sepsis is an independent risk factor leading to increased mortality rates. Specifically, dysregulation of hepatic biotransformation capacity, especially of the cytochrome P450 (CYP) system, represents an important distress factor during host response. The activity of the conserved stress enzyme sphingomyelin phosphodiesterase 1 (SMPD1) has been shown to be elevated in sepsis patients, allowing for risk stratification. Therefore, the aim of the present study was to investigate whether SMPD1 activity has an impact on expression and activity of different hepatic CYP enzymes using an animal model of polymicrobial sepsis. Polymicrobial sepsis was induced in SMPD1 wild-type and heterozygous mice and hepatic ceramide content as well as CYP mRNA, protein expression and enzyme activities were assessed at two different time points, at 24 h, representing the acute phase, and at 28 days, representing the post-acute phase of host response. In the acute phase of sepsis, SMPD1^+/+ mice showed an increased hepatic C16- as well as C18-ceramide content. In addition, a downregulation of CYP expression and activities was detected. In SMPD1^+/- mice, however, no noticeable changes of ceramide content and CYP expression and activities during sepsis could be observed. After 28 days, CYP expression and activities were normalized again in all study groups, whereas mRNA expression remained downregulated in SMPD^+/+ animals. In conclusion, partial genetic inhibition of SMPD1 stabilizes hepatic ceramide content and improves hepatic monooxygenase function in the acute phase of polymicrobial sepsis. Since we were also able to show that the functional inhibitor of SMPD1, desipramine, ameliorates downregulation of CYP mRNA expression and activities in the acute phase of sepsis in wild-type mice, SMPD1 might be an interesting pharmacological target, which should be further investigated.

Acid Sphingomyelinase Inhibition Prevents Development of Sepsis Sequelae in the Murine Liver

The molecular mechanisms of maladaptive response in liver tissue with respect to the acute and post-acute phase of sepsis are not yet fully understood. Long-term sepsis survivors might develop hepatocellular/hepatobiliary injury and fibrosis. Here, we demonstrate that acid sphingomyelinase, an important regulator of hepatocyte apoptosis and hepatic stellate cell (HSC) activation, is linked to the promotion of liver dysfunction in the acute phase of sepsis as well as to fibrogenesis in the long-term. In both phases, we observed a beneficial effect of partial genetic sphingomyelinase deficiency in heterozygous animals (smpd1^+/−) on oxidative stress levels, hepatobiliary function, macrophage infiltration and on HSC activation. Strikingly, similar to heterozygote expression of SMPD1, either preventative (p-smpd1^+/+) or therapeutic (t-smpd1^+/+) pharmacological treatment strategies with desipramine – a functional inhibitor of acid sphingomyelinase (FIASMA) – significantly improved liver function and survival. The inhibition of sphingomyelinase exhibited a protective effect on liver function in the acute-phase, and the reduction of HSC activation diminished development of sepsis-associated liver fibrosis in the post-acute phase of sepsis. In summary, targeting sphingomyelinase with FDA-approved drugs is a novel promising strategy to overcome sepsis-induced liver dysfunction.

A Murine Model of Persistent Inflammation, Immune Suppression, and Catabolism Syndrome

Critically ill patients that survive sepsis can develop a Persistent Inflammation, Immunosuppression, and Catabolism Syndrome (PICS), which often leads to extended recovery periods and multiple complications. Here, we utilized a cecal ligation and puncture (CLP) method in mice with the goal of creating a model that concurrently displays all the characteristics of PICS. We observed that, after eight days, mice that survive the CLP develop persistent inflammation with significant myelopoiesis in the bone marrow and spleen. These mice also demonstrate ongoing immune suppression, as evidenced by the decreased total and naïve splenic CD4 and CD8 T cells with a concomitant increase in immature myeloid cells. The mice further display significant weight loss and decreased muscle mass, indicating a state of ongoing catabolism. When PICS mice are challenged with intranasal Pseudomonas aeruginosa, mortality is significantly elevated compared to sham mice. This mortality difference is associated with increased bacterial loads in the lung, as well as impaired neutrophil migration and neutrophil dysfunction in the PICS mice. Altogether, we have created a sepsis model that concurrently exhibits PICS characteristics. We postulate that this will help determine the mechanisms underlying PICS and identify potential therapeutic targets to improve outcomes for this patient population.

Bronchoalveolar Lavage Microvesicles Protect Burn-Injured Mice from Pulmonary Infection

BACKGROUND

Pseudomonas aeruginosa is a major cause of morbidity and mortality among burn patients, despite antibiotic therapy. There is a need to identify innate immune defenses that prevent P aeruginosa infection in injured adults in an effort to find therapeutic alternatives to antibiotics. Here, we tested our hypothesis that microvesicles (MVs) in bronchoalveolar (BAL) fluid have a role in the immunity of the lung in response to pathogens.

STUDY DESIGN

Microvesicles were isolated from murine BAL fluid, quantified using Nanoparticle Tracking Analysis, and injected into burn-injured mice before P aeruginosa infection. Survival was assessed and BAL bacterial loads enumerated. Neutrophil number and interleukin 6 activity were determined. Lungs were harvested and sphingosine (SPH) content analyzed via immunohistochemistry. Antimicrobial effects of MVs and SPH-enriched MVs were assessed in an in vitro assay.

RESULTS

Burn-injured mice have reduced BAL MV number and SPH content compared with sham. When BAL MVs from healthy mice are administered to injured mice, survival and bacterial clearance are improved robustly. We also observed that intranasal administration of MVs restores SPH levels after burn injury, MVs kill bacteria directly, and this bacterial killing is increased when the MVs are supplemented with SPH.

CONCLUSIONS

Using a preclinical model, BAL MVs are reduced after scald injury and BAL MV restoration to injured mice improves survival and bacterial clearance. The antimicrobial mechanisms leading to improved survival include the quantity and SPH content of BAL MVs.

Impact of tranexamic acid on coagulation and inflammation in murine models of traumatic brain injury and hemorrhage

BACKGROUND

Posttraumatic coagulopathy and inflammation can exacerbate secondary cerebral damage after traumatic brain injury (TBI). Tranexamic acid (TXA) has been shown clinically to reduce mortality in hemorrhaging and head-injured trauma patients and has the potential to mitigate secondary brain injury with its reported antifibrinolytic and antiinflammatory properties. We hypothesized that TXA would improve posttraumatic coagulation and inflammation in a murine model of TBI alone and in a combined injury model of TBI and hemorrhage (TBI/H).

METHODS

An established murine weight drop model was used to induce a moderate TBI. Mice were administered intraperitoneal injections of 10 mg/kg TXA or equivalent volume of saline 10 min after injury. An additional group of mice was subjected to TBI followed by hemorrhagic shock using a pressure-controlled model. TBI/H mice were given intraperitoneal injections of TXA or saline during resuscitation. Blood was collected at intervals after injury to assess coagulation by rotational thromboelastometry (ROTEM) and inflammation by Multiplex cytokine analysis. Soluble P-selectin, a biomarker of platelet activation, and serum neuron-specific enolase, a biomarker of cerebral injury, were measured at intervals. Brain homogenates were analyzed for inflammatory changes by Multiplex enzyme-linked immunosorbent assay, and splenic tissue was collected for splenic cell population assessment by flow cytometry.

RESULTS

There were no coagulation, serum or cerebral cytokine, P-selectin, or neuron-specific enolase differences between mice treated with TXA or saline after TBI. After the addition of hemorrhagic shock and resuscitation to TBI, TXA administration still did not affect coagulation parameters, systemic or cerebral inflammation, or platelet activation, as compared with saline alone. At 24 hours after TBI, mice given TXA demonstrated lower splenic total cell counts central memory CD8, effector CD8, B cell, and increased naive CD4 cell populations. By contrast, TXA did not affect splenic leukocyte populations after combined TBI/H.

CONCLUSIONS

Despite clinical data suggesting a mortality benefit, TXA did not modulate coagulation, inflammation, or biomarker generation in either the TBI or TBI/H murine models. Administration of TXA after TBI altered splenic leukocyte populations, which may contribute to a change in posttraumatic immune status. Future studies should be done to investigate the role of TXA in the development of posttraumatic immunosuppression and risk of nosocomial infections.