Restraint stress alters neutrophil and macrophage phenotypes during wound healing

Systematic review of the significance of neutrophil to lymphocyte ratio in anastomotic leak after gastrointestinal surgeries

INTRODUCTION

The inflammatory response is thought to be a critical initiator of epigenetic alterations. The neutrophil to lymphocyte ratio (NLR), a biomarker of inflammation, is computed by dividing the number of neutrophils by the number of lymphocytes. The primary goal of this systematic review and meta-analysis was to evaluate the pre-operative NLR of gastrointestinal surgery patients who had an anastomotic leak (AL) in comparison to those who did not AL.

METHODS

We performed a comprehensive search for relevant papers published before May 4, 2022, using PubMed, Scopus, and Web of Science. Standardized mean difference (SMD) with a 95% confidence interval (CI) was pooled in meta-analysis to yield a summary estimate. We utilized the random-effects model to create pooled effects since we discovered a substantial heterogeneity level. For evaluating quality, the Newcastle-Ottawa scale (NOS) was implemented.

RESULTS

The research comprised 12 studies with a total of 2940 individuals who had GI operations, 353 of whom went on to develop AL. We discovered that patients who had GI surgeries and acquired AL had significantly higher NLR levels than those who did not (random-effects model: SMD = 0.75, 95% CI = 0.11-1.38, p = 0.02). Patients with AL showed significantly higher NLR levels than control group in retrospective studies (SMD = 0.93, 95% CI = 0.20-1.66, p=0.01) but not in prospective studies (SMD = - 0.11, 95% CI = - 0.65-0.43, p = 0.69), according to the subgroup analysis based on research design. Subgroup analysis based on ethnicity yielded that white patients with AL exhibited significantly higher NLR values than the control group (SMD = 1.35, 95% CI = 0.01-2.68, p = 0.04) but this result was not applied to East Asian patients (SMD = 0.14, 95% CI = -0.13-0.41, p = 0.29).

CONCLUSION

Our research suggests a potential association between preoperative NLR and postoperative AL. However, it is essential to acknowledge the variability in the findings, with significantly higher NLR levels observed in retrospective studies and among white patients, but not consistently replicated in prospective studies and among East Asian patients. Further investigations with larger and more diverse cohorts are warranted to validate these findings and explore potential factors contributing to the observed discrepancies.

Profiling of serum factors associated with Staphylococcus aureus skin and soft tissue infections as a foundation for biomarker identification

Background

People living in close quarters, such as military trainees, are at increased risk for skin and soft tissue infections (SSTI), especially those caused by methicillin-resistant Staphylococcus aureus (MRSA). The serum immune factors associated with the onset of SSTI are not well understood.

Methods

We conducted a longitudinal study of SSTIs, enrolling US Army trainees before starting military training and following up for 14 weeks. Samples were collected on Day 0, 56, and 90. Serum chemokines and cytokines among 16 SSTI cases and 51 healthy controls were evaluated using an electro-chemiluminescence based multiplex assay platform.

Results

Of 54 tested cytokines, 12 were significantly higher among SSTI cases as compared to controls. Among the cases, there were correlations between factors associated with vascular injury (i.e., VCAM-1, ICAM-1, and Flt1), the angiogenetic factor VEGF, and IL-10. Unsupervised machine learning (Principal Component Analysis) revealed that IL10, IL17A, C-reactive protein, ICAM1, VCAM1, SAA, Flt1, and VGEF were indicative of SSTI.

Conclusion

The study demonstrates the power of immunoprofiling for identifying factors predictive of pre-illness state of SSTI thereby identifying early stages of an infection and individuals susceptible to SSTI.

Repeated stress-induced crosstalk between the sympathetic nervous system and mast cells contributes to delayed cutaneous wound healing in mice

The study identifies a link between the neuroimmune interaction and the impairment of wound healing induced by repeated stress. Stress increased mast cell mobilization and degranulation, levels of IL-10, and sympathetic reinnervation in mouse wounds. In contrast to mast cells, macrophage infiltration into wounds was significantly delayed in stressed mice. Chemical sympathectomy and the blockade of mast cell degranulation reversed the effect of stress on skin wound healing in vivo. In vitro, high epinephrine levels stimulated mast cell degranulation and IL-10 release. In conclusion, catecholamines released by the sympathetic nervous system stimulate mast cells to secrete anti-inflammatory cytokines that impair inflammatory cell mobilization, leading to a delay in the resolution of wound healing under stress conditions.

Autonomic nervous system receptor-mediated regulation of mast cell degranulation modulates the inflammation after corneal epithelial abrasion

Mast cells (MCs) regulate wound healing and are influenced by the autonomic nervous system (ANS). However, the underlying mechanisms affecting wound healing outcomes remain elusive. Here, we explored the specific role of the ANS by regulating MC degranulation following corneal epithelium abrasion. A mouse model of corneal abrasion was established by mechanically removing a 2-mm central epithelium. Wound closure, neutrophil infiltration, and transcription of injured corneas were investigated using whole-mount immunostaining, flow cytometry, and RNA-sequencing analysis, respectively. Inhibition of MC degranulation by the MC stabilizers cromolyn sodium and lodoxamide tromethamine increased the infiltration of neutrophils and delayed healing of abraded corneas. Moreover, transcriptomic profiling analysis showed that purified MCs from the limbus expressed adrenergic and cholinergic receptors. Pharmacological manipulation and sympathectomy with 6-hydroxydopamine confirmed that sympathetic nervous system signaling inhibited MC degranulation after corneal abrasion, whereas parasympathetic nervous system signaling enhanced MC degranulation. We conclude that normal degranulation of MCs in the corneal limbus and crosstalk between the ANS and MCs are crucial for the appropriate control of inflammation and the repair progress of wounded corneas. This suggests a potential approach for improving defective corneal wound healing by the administration of clinically available autonomic activity-modulating agents.

The disbalance of LRP1 and SIRPα by psychological stress dampens the clearance of tumor cells by macrophages

The relationship between chronic psychological stress and tumorigenesis has been well defined in epidemiological studies; however, the underlying mechanism remains underexplored. In this study, we discovered that impaired macrophage phagocytosis contributed to the psychological stress-evoked tumor susceptibility, and the stress hormone glucocorticoid (GC) was identified as a principal detrimental factor. Mechanistically, GC disturbed the balance of the “eat me” signal receptor (low-density lipoprotein receptor-related protein-1, LRP1) and the “don't eat me” signal receptor (signal regulatory protein alpha, SIRPα). Further analysis revealed that GC led to a direct, glucocorticoid receptor (GR)-dependent trans-repression of LRP1 expression, and the repressed LRP1, in turn, resulted in the elevated gene level of SIRPα by down-regulating miRNA-4695-3p. These data collectively demonstrate that stress induces the imbalance of the LRP1/SIRPα axis and entails the disturbance of tumor cell clearance by macrophages. Our findings provide the mechanistic insight into psychological stress-evoked tumor susceptibility and indicate that the balance of LRP1/SIRPα axis may serve as a potential therapeutic strategy for tumor treatment.

Effect of Silver Nanoparticles on Healing of Third-Degree Burns Infected with Pseudomonas Aeruginosa in Laboratory Mice

The treatment of full-thickness skin burn using nanomaterials is promising as a medical application reducing the risk of infection and severe dermal scarring. Therefore, this study aims to evaluate the effectiveness of nanomaterials, particularly 3% silver nanoparticles containing ointment (3% SNO), on the full-thickness skin burn of laboratory mice. A total number of 36 male mice were used, equally divided into three groups: negative control (not burned and not treated); positive control (+ve) (burned and treated with castor oil and white petroleum jelly); and SNO-treated group (burned and treated with 3% SNO). The skin of the animals’ back was shaved. A 2x0.5 cm metal plate was heated on a burner to burn the skin of the animals of positive control and SNO-treated groups. Pseudomonas aeruginosa bacterial suspension was applied to the burnt area. The application of SNO, as well as the mixture of white petroleum jelly and castor oil, was started after 6 hours of inducing burns and continued for 14 days (three times daily) in the respected groups. The SNO-treated group showed accelerated healing within 14 days demonstrated by re-epithelialization of the epidermal layer and proliferation of the fibroblasts in the dermal layer. Less healing evidence was observed in the +ve control group in the same period. In conclusion, to our knowledge, this is the first study that uses a 3% SNO formula and has found that it has a promising impact on the treatment of infected skin burns.

Rational design and latest advances of polysaccharide-based hydrogels for wound healing

Acute and chronic wounds cause severe physical trauma to patients and also bring an immense socio-economic burden. Hydrogels are considered to be effective wound dressings. Polysaccharides possessing distinctive properties such as biocompatibility, biodegradability, and nontoxicity are promising candidates to structure hydrogels for wound healing. Polysaccharide-based hydrogels can provide suitable moisture for the wound and act as a shield against bacteria. Adequate mechanical properties, degradability, and therapeutic agent controlled release of polysaccharide-based hydrogels have been already characterized for effective utilization. This review presented several crucial design considerations about hydrogels for wound healing, and the current state of polysaccharide (chitosan, alginate, hyaluronic acid, cellulose, dextran, and starch)-based hydrogels as wound dressings was also summarized. The commonly used crosslinking techniques, including physical, chemical, and enzymatic crosslinking, are discussed in detail. Finally, we outline the challenges and perspectives about the improvement of polysaccharide-based hydrogels.

Neutrophil/Lymphocyte Ratio as Predictor of Anastomotic Leak after Gastric Cancer Surgery

INTRODUCTION

Neutrophil/lymphocyte ratio (NLR) is known as a prognostic for the outcome of the patients with gastric cancer. As no definite risk marker for anastomotic leakage after gastric resection was identified, we investigated the possible role of NLR.

METHODS

Peripheral blood count for neutrophils and lymphocytes was done at the patient's admission. We retrospectively evaluated 204 gastric cancer patients, who underwent gastric resection, comparing the values of NLR between the group of patients with anastomotic leakage and those without complications.

RESULTS

Using the ROC curve, we found the cutoff value of NLR, which permitted the comparison of the group with low NLR, presenting increased NLR. The cutoff value for NLR was 3.54. Between the two groups, we could observe statistically significant differences in developing fistula (p < 0.01) and complications leading to death (p < 0.025). The odds ratio for patients with NLR greater than 3.54 to develop anastomotic leak was 17.62, compared to those with lower NLR.

CONCLUSION

Peripheral blood NLR proved to be a predictor for anastomotic leakage.

Novel Biomedical Functions of Surfactin A from Bacillus subtilis in Wound Healing Promotion and Scar Inhibition

Surfactin produced by Bacillus subtilis is a powerful biosurfactant in food, cosmetics, and pesticide industries. However, its suitability in wound healing applications is uncertain. In this article, we determined the effects of surfactin A from B. subtilis on wound healing, angiogenesis, cell migration, inflammatory response, and scar formation. The results indicated that 80.65 ± 2.03% of surfactin A-treated wounds were closed, whereas 44.30 ± 4.26% of the vehicle-treated wound areas remained open on day 7 (P < 0.05). In mechanisms, it upregulated the expression of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF), accelerated keratinocyte migration through mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) signaling pathways, and regulated the secretion of proinflammatory cytokines and macrophage phenotypic switch. More attractive, surfactin A showed a seductive capability to inhibit scar tissue formation by affecting the expression of α-smooth muscle actin (α-SMA) and transforming growth factor (TGF-β). Overall, the study revealed a new function and potential of surfactin A as an affordable and efficient wound healing drug.

Potential Mechanism of Dermal Wound Treatment With Preparations From the Skin Gel of Arabian Gulf Catfish: A Unique Furan Fatty Acid (F6) and Cholesta-3,5-Diene (S5) Recruit Neutrophils and Fibroblasts to Promote Wound Healing

Preparations from Arabian Gulf catfish (Arius bilineatus, Val) epidermal gel secretion (PCEGS) effectively heal chronic wounds in diabetic patients. However, specific lipid components of PCEGS that are responsible for various aspects of wound healing are unknown. Here, we report for the first time that, i) a unique preparation containing only proteins and lipids (Fraction B, FB), derived from the PCEGS accelerated the healing of experimental dermal wounds in female rats (transdermal punch biopsy) in vivo. Histological analyses showed that topical treatment of these wounds with FB promoted the migration of fibroblasts, facilitated the production of extracellular matrix (collagen, fibronectin), induced capillary formation and recruitment of immune cells, and accelerated overall wound healing by day 4 (tested at 1, 2, 3, 4, and 10 days; n=15 for vehicle; n=15 for FB treatment), ii) the lipids responsible for different stages of wound healing were separated into a protein-free bioactive lipid fraction, Ft, which contained a few common long-chain fatty acids, a unique furan fatty acid (F6) and a cholesterol metabolite, cholesta-3,5-diene (S5). Ft (the partially purified lipid fraction of PCEGS), and F6 and S5 present in Ft, proved to be bioactive for wound healing in human dermal fibroblasts. Ft increased the production and extracellular deposition of collagen and fibronectin, ex vivo, iii) Ft and its subcomponents, pure F6 and S5, also promoted human dermal fibroblast migration into the scratch wound gaps, ex vivo, iv) Ft, F6, and S5 promoted the recruitment of neutrophils (Green fluorescence protein labeled) to the site of injury in the transected tailfins of transgenic zebrafish, in vivo, v) Ft, but not F6 or S5, promoted the regeneration of tissues at the wound site in the transgenic zebrafish tailfin, in vivo. Therefore, we conclude that lipid fraction Ft from PCEGS contains the components necessary to promote complete wound healing, and F6 and S5 are responsible for promoting fibroblast and neutrophil recruitment to the site of wounds.

Sympathetic Nerves Positively Regulate Eosinophil-Driven Allergic Conjunctivitis via α1-Adrenergic Receptor Signaling

Eosinophils are a major cause of tissue injury in allergic conjunctivitis. The biological nature of eosinophils in the conjunctiva and the mechanisms that control eosinophils' responses in allergic conjunctivitis are currently not completely understood. This study reports that conjunctival eosinophils comprise two populations-Siglec-F^int and Siglec-F^hi-in different life stages. Siglec-F^int eosinophils partly expressed CD34 and were in the immature (or steady) state. Siglec-F^hi eosinophils did not express CD34, sharply increased in number after short ragweed (SRW) pollen challenge, and were in the mature (or activated) state. Moreover, chemical sympathectomy by 6-hydroxydopamine reduced the recruitment and activation of eosinophils, whereas the activation of the sympathetic nerve system (SNS) with restraint stress accelerated the recruitment and activation of eosinophils in SRW-induced conjunctivitis. It was also found that two eosinophil populations expressed alpha-1a-adrenergic receptors (α1a-ARs); in SRW-induced conjunctivitis, treatment with an α1a-AR antagonist decreased eosinophil responses, whereas treatment with an α1a-AR agonist aggravated eosinophil responses. Thus, eosinophil responses in conjunctivitis are regulated by the SNS via α1a-AR signaling. SNS inputs or α1a-AR function may be potential targets for the treatment of allergic conjunctivitis.

Effects of stress and cortisol on the polarization of carp macrophages

In teleost fish, myelopoiesis is maintained both in the head (HK) and trunk kidney (TK), but only the HK holds the endocrine cells that produce the stress hormone cortisol. We now compared the effects of prolonged restraint stress (in vivo) and cortisol (in vitro) on the polarization of HK and TK-derived carp macrophages. Monocytes/macrophages from both sources were treated in vitro with cortisol, lipopolysaccharide or with both factors combined. In vivo, fish were challenged by a prolonged restraint stress. Gene expression of several markers typical for classical M1 and alternative M2 macrophage polarization, as well as glucocorticoid receptors, were measured. Cells from both sources did not differ in the constitutive gene expression of glucocorticoid receptors, whereas they significantly differed in their response to cortisol and stress. In the LPS-stimulated HK monocytes/macrophages, cortisol in vitro counteracted the action of LPS while the effects of cortisol on the activity of TK monocytes/macrophages were less explicit. In vivo, restraint stress up-regulated gene expression of M2 markers in freshly isolated HK monocytes/macrophages, while at the same time it did not affect TK monocytes/macrophages. Moreover, LPS-stimulated HK monocytes/macrophages from stressed animals showed only minor differences in the gene expression of M1 and M2 markers, compared to LPS-treated monocytes/macrophages from control fish. In contrast, stress-induced changes in TK-derived LPS-treated cells were more pronounced. However, these changes did not clearly indicate whether in TK monocytes/macrophages stress will stimulate classical or alternative polarization. Altogether, our results imply that cortisol in vitro and stress in vivo direct HK, but not TK, monocytes/macrophages to the path of alternative polarization. These findings reveal that like in mammals, also in fish the glucocorticoids form important stimulators of alternative macrophage polarization.

Paradoxical Effect of LTB4 on the Regulation of Stress-Induced Corticosterone Production

Depression is a mental illness with a complex and multifactorial etiology, which has been associated with stress and inflammation. Infections, autoimmune diseases, envenomation, and trauma induce an inflammatory response that is characterized by increasing levels of circulating cytokines (e.g., IL-1β) and lipid mediators [e.g., PGE₂ and leukotrienes B₄ (LTB₄)]. Recently, we showed that LTB₄ production by the 5-lipoxygenase (5-LO) pathway regulates IL-1β and PGE₂ release, reducing tissue damage in a model of sterile inflammation. Since IL-1β and PGE₂ increase in serum of stressed patients and potentially trigger depression, we used an animal model of chronic unpredictable stress (CUS) to investigate the potential impact of LTB₄ over depression-like symptoms. At basal conditions, 5-LO deficiency (Alox5^−/−) reduces the preference for sucrose, while inducing a higher immobilization time on the tail suspension test when compared 129sv. Moreover, Alox5^−/− mice present increased caspase-1 expression and elevated levels of IL-1β, IL-17 and PGE₂ in the spleen, with increasing corticosterone levels in the frontal cortex but reducing systemic levels. Compared to 129sv mice, CUS induced higher levels of systemic, frontal cortex and hippocampal corticosterone, and also reduced sucrose preference, increased levels of splenic IL-1β, IL-17 and PGE₂ and reduced levels of LTB₄. Interestingly, CUS exposure did not alter the reduced sucrose preference shown by Alox5^−/− mice but greatly enhanced splenic PGE₂ production. Compared to Alox5^−/− mice at basal conditions, CUS exposure also increased levels of systemic corticosterone, which remained lower than those of CUS-129sv animals. We also observed that treatment with LTB₄ decreased caspase-1 expression and systemic levels of corticosterone in CUS-Alox5^−/− mice but there was no significant impact on the reduced sucrose preference. Our results demonstrate that LTB₄ controls the hypothalamic-pituitary-adrenal (HPA) axis by regulating levels of systemic corticosterone associated with the repression of caspase-1 expression and production of inflammatory mediators. One limitation of our study is that 129sv and Alox5^−/− mice were not littermates, not sharing, therefore, the same intra-uterine and preweaning environment. Even so, taken together our results indicate that 5-LO activity is critical for the regulation of stress-induced symptoms, suggesting that the Alox5^−/− mouse could be a natural model of corticosterone-independent reduced reward sensitivity.

Cotinine Plus Krill Oil Decreased Depressive Behavior, and Increased Astrocytes Survival in the Hippocampus of Mice Subjected to Restraint Stress

Restraint stress (RS) is a condition affecting millions of people worldwide. The investigation of new therapies to alleviate the consequences of prolonged RS is much needed. Cotinine, a nicotine-derivative, has shown to prevent the decrease in cerebral synaptic density, working memory deficits, anxiety, and depressive-like behavior after prolonged restraint stress (RS) in mice. Furthermore, post-treatment with cotinine reduced the adverse effects of chronic RS on astrocyte survival and architecture. On the other hand, the nutritional supplement krill oil (KO), has shown to be beneficial in decreasing depressive-like behavior and oxidative stress. In this study, in the search for effective preventative treatments to be used in people subjected to reduced mobility, the effect of co-treatment with cotinine plus KO in mice subjected to prolonged RS was investigated. The results show that cotinine plus KO prevented the loss of astrocytes, the appearance of depressive-like behavior and cognitive impairment induced by RS. The use of the combination of cotinine plus KO was more effective than cotinine alone in preventing the depressive-like behavior in the restrained mice. The potential use of this combination to alleviate the psychological effects of reduced mobility is discussed.

The mouse autonomic nervous system modulates inflammation and epithelial renewal after corneal abrasion through the activation of distinct local macrophages

Inflammation and reepithelialization after corneal abrasion are critical for the rapid restoration of vision and the prevention of microbial infections. However, the endogenous regulatory mechanisms are not completely understood. Here we report that the manipulation of autonomic nervous system (ANS) regulates the inflammation and healing processes. The activation of sympathetic nerves inhibited reepithelialization after corneal abrasion but increased the influx of neutrophils and the release of inflammatory cytokines. Conversely, the activation of parasympathetic nerves promoted reepithelialization and inhibited the influx of neutrophils and the release of inflammatory cytokines. Furthermore, we observed that CD64⁺CCR2⁺ macrophages in the cornea preferentially expressed the β-2 adrenergic receptor (AR), whereas CD64⁺CCR2^- macrophages preferentially expressed the α-7 nicotinic acetylcholine receptor (α7nAChR). After abrasion, the topical administration of a β2AR agonist further enhanced the expression of the proinflammatory genes in the CD64⁺CCR2⁺ cell subset sorted from injured corneas. In contrast, the topical administration of an α7nAChR agonist further enhanced the expression of the anti-inflammatory genes in the CD64⁺CCR2^- subset. Thus crosstalk between the ANS and local macrophage populations is necessary for the progress of corneal wound repair. Manipulation of ANS inputs to the wounded cornea may represent an alternative approach to the treatment of impaired wound healing.

Stimulatory effect of desipramine on lung metastases of adenocarcinoma MADB 106 in stress highly-sensitive and stress non-reactive rats

The effect of antidepressant drugs on tumor progress is very poorly recognized. The aim of the present study was to examine the effect of individual reactivity to stress and 24-day desipramine (DES) administration on the metastatic colonization of adenocarcinoma MADB 106 cells in the lungs of Wistar rats. Wistar rats were subjected to stress procedure according to the chronic mild stress (CMS) model of depression for two weeks and stress highly-sensitive (SHS) and stress non-reactive (SNR) rats were selected. SHS rats were more prone to cancer metastasis than SNR ones and chronic DES treatment further increased the number of lung metastases by 59% and 50% in comparison to vehicle-treated appropriate control rats. The increase in lung metastases was connected with DES-induced skew macrophage activity towards M2 functional phenotype in SHS and SNR rats. Moreover, during 24h after DES injection in healthy rats, the decreased number of TCD8⁺ and B cells in SHS and SNR rats as well as NK cell cytotoxic activity in SNR rats could be attributed to the lowered capacity to defend against cancer metastasis observed in chronic DES treated and tumor injected rats.

From Inflammation to Current and Alternative Therapies Involved in Wound Healing

Wound healing is a complex event that develops in three overlapping phases: inflammatory, proliferative, and remodeling. These phases are distinct in function and histological characteristics. However, they depend on the interaction of cytokines, growth factors, chemokines, and chemical mediators from cells to perform regulatory events. In this article, we will review the pathway in the skin healing cascade, relating the major chemical inflammatory mediators, cellular and molecular, as well as demonstrating the local and systemic factors that interfere in healing and disorders associated with tissue repair deficiency. Finally, we will discuss the current therapeutic interventions in the wounds treatment, and the alternative therapies used as promising results in the development of new products with healing potential.

Exercise prior to, but not concomitant with, stress reverses stress-induced delayed skin wound healing

Stress-induced prolonged inflammation impairs cutaneous wound healing. Exercise may inhibit this effect via an anti-inflammatory mechanism. Our aim was to investigate the effect of moderate exercise on skin wound healing in chronically stressed mice. Mice were trained five times per week on a treadmill or received no training. Mice underwent daily rotational stress from the 6th week until euthanasia. During the 8th week, two wounds were created in the dorsum and collected 10 days later. A control group only received wounds. Exercise was performed prior to and simultaneous with stress for 2 weeks or only prior to stress. Stress increased normetanephrine levels 10 days after wounding, resulting in an increased amount of inflammatory cells and reduced expression of inflammatory cytokines as well as angiogenesis, myofibroblast differentiation and matrix deposition. Concomitant exercise and stress potentiated these effects, intensifying the delayed wound contraction. When exercise was performed only prior to stress, however, the mice showed reduced inflammatory cells in granulation tissue 10 days after wounding and improved wound healing compared with animals with exercise and concomitant stress. Moderate exercise in association with stress potentiates the stress effect; however, when exercise was performed prior to stress, wound healing was improved.

Effects of silver nanoparticles on Staphylococcus aureus contaminated open wounds healing in mice: An experimental study

The microorganisms have been noted as the main cause of delayed wound healing. The most common pathogen causing the wound infections is Staphylococcus aureus. Silver nanoparticles (AgNPs) show ample antibacterial activities. In the present study, the effect of AgNPs on mouse wounds inoculated with S. aureus was investigated. Sixty male mice (20 to 30 g) were anesthetized, full-thickness skin wounds were made on their back and then the bacterial suspension was added to each wound bed. Treatments were administered on wound bed topically including gentamicin (8 mg kg^-1), AgNPs (0.08 mg kg^-1, 0.04 mg kg^-1 and 0.02 mg kg^-1) and normal saline in the control group. Wound healing was monitored macroscopically by taking digital photographs on days 0, 7, 14 and 21 of the experiment. Topical application of gentamicin and AgNPs (0.08 and 0.04 mg kg^-1) significantly increased the rate of wound healing more than treatment with AgNPs at a dose of 0.02 mg kg^-1and normal saline. The presence of silver nanoparticles in AgNPs groups (especially 0.08 mg kg^-1) improved wound appearance better than other groups without silver nanoparticles (gentamicin and control groups) and led to lesser wound scars. According to data analysis, healing rate of treated mice with gentamicin and AgNPs (0.08 mg kg^-1) was significantly (p < 0.001) faster than treated mice with other AgNPs doses and normal saline. The results of current study introduced an in vivo nanosilver accelerating effects on the treatment of on S. aureus infected skin wounds.

Tumors Alter Inflammation and Impair Dermal Wound Healing in Female Mice

Tissue repair is an integral component of cancer treatment (e.g., due to surgery, chemotherapy, radiation). Previous work has emphasized the immunosuppressive effects of tumors on adaptive immunity and has shown that surgery incites cancer metastases. However, the extent to which and how tumors may alter the clinically-relevant innate immune process of wound healing remains an untapped potential area of improvement for treatment, quality of life, and ultimately, mortality of cancer patients. In this study, 3.5 mm full-thickness dermal excisional wounds were placed on the dorsum of immunocompetent female mice with and without non-malignant flank AT-84 murine oral squamous cell carcinomas. Wound closure rate, inflammatory cell number and inflammatory signaling in wounds, and circulating myeloid cell concentrations were compared between tumor-bearing and tumor-free mice. Tumors delayed wound closure, suppressed inflammatory signaling, and altered myeloid cell trafficking in wounds. An in vitro scratch “wounding” assay of adult dermal fibroblasts treated with tumor cell-conditioned media supported the in vivo findings. This study demonstrates that tumors are sufficient to disrupt fundamental and clinically-relevant innate immune functions. The understanding of these underlying mechanisms provides potential for therapeutic interventions capable of improving the treatment of cancer while reducing morbidities and mortality.

Blockade of glucocorticoid receptors improves cutaneous wound healing in stressed mice

Stress is an important condition of modern life. The successful wound healing requires the execution of three major overlapping phases: inflammation, proliferation, and remodeling, and stress can disturb this process. Chronic stress impairs wound healing through the activation of the hypothalamic-pituitary-adrenal axis, and the glucocorticoids (GCs) hormones have been shown to delay wound closure. Therefore, the aim of this study was to investigate the effects of a GC receptor antagonist (RU486) treatment on cutaneous healing in chronically stressed mice. Male mice were submitted to rotational stress, whereas control animals were not subjected to stress. Stressed and control animals were treated with RU486. A full-thickness excisional lesion was generated, and seven days later, lesions were recovered. The RU486 treatment improves wound healing since contraction takes place earlier in RU486-treated in comparison to non-treated mice, and the RU486 treatment also improves the angiogenesis in Stress+RU486 mice when compared to stressed animals. The Stress+RU486 group showed a decrease in inflammatory cell infiltration and in hypoxia-inducible factor-1α and inducible nitric oxide synthase expression; meanwhile, there was an increase in myofibroblasts quantity. In conclusion, blockade of GC receptors with RU486 partially ameliorates stress-impaired wound healing, suggesting that stress inhibits healing through more than one functional pathway.

Nano-porous nitrocellulose liquid bandage modulates cell and cytokine response and accelerates cutaneous wound healing in a mouse model

Nitrocellulose liquid bandage (L-Bandage) is extensively used in hard-to-cover cuts and wounds management, owing to its flexibility, softness, transparency, and conformability. However, evidence supporting their mechanisms of action as wound dressing is scanty. This study introduces a novel nano-porous L-Bandage, and provides results from a mouse full-thickness wound model investigating its mechanism of action on wound healing. Different characteristics, such as porosity, mechanical properties and water vapor transmission rate (WVTR) were determined. The L-Bandage formed film had a porous network structure with mean diameter of 18 nm that could effectively prevent the bacterial invasion, and favorable properties of tensile strength, elongation, and WVTR. The L-Bandage treated wound exhibited accelerated healing, with reduced inflammations, enhanced wound re-epithelialization, contraction, granulation tissue formation, and rapid angiogenesis. Our data suggested that L-Bandage could serve as a promising wound dressing, because of its desirable properties for wound healing.

Chronic restraint stress after injury and shock is associated with persistent anemia despite prolonged elevation in erythropoietin levels

BACKGROUND

Following severe traumatic injury, critically ill patients have a prolonged hypercatacholamine state that is associated with bone marrow (BM) dysfunction and persistent anemia. However, current animal models of injury and shock result in a transient anemia. Daily restraint stress (chronic stress [CS]) has been shown to increase catecholamines. We hypothesize that adding CS following injury or injury and shock in rats will prolong the hypercatecholaminemia and prolong the initial anemia, despite elevated erythropoietin (EPO) levels.

METHODS

Male Sprague-Dawley rats (n = 6-8 per group) underwent lung contusion (LC) or combined LC/hemorrhagic shock (LCHS) followed by 6 days of CS. CS consisted of a 2-hour restraint period interrupted with repositioning and alarms every 30 minutes. At 7 days, urine was assessed for norepinephrine (NE) levels, blood for EPO and hemoglobin (Hgb), and BM for erythroid progenitor growth.

RESULTS

Animals undergoing LC or combined LCHS predictably recovered by Day 7; urine NE, EPO, and Hgb levels were normal. The addition of CS to LC and LCHS models was associated with a significant elevation in NE on Day 6. The addition of CS to LC led to a persistent 20% to 25% decrease in the growth of BM hematopoietic progenitor cells. These findings were further exaggerated when CS was added following LCHS, resulting in a 20%q to 40% reduction in BM erythroid progenitor colony growth and a 20% decrease in Hgb when compared with LCHS alone.

CONCLUSION

Exposing injured animals to CS results in prolonged elevation of NE and EPO, which is associated with worsening BM erythroid function and persistent anemia. Chronic restraint stress following injury and shock provides a clinically relevant model to further evaluate persistent injury-associated anemia seen in critically ill trauma patients. Furthermore, alleviating CS after severe injury is a potential therapeutic target to improve BM dysfunction and anemia.

Contrasting mechanisms by which social isolation and restraint impair healing in male mice

Stress modulates vital aspects of immune functioning in both human and non-human animals, including tissue repair. For example, dermal wounds heal more slowly and are associated with prolonged inflammation and increased bacterial load in mice that experience chronic physical restraint. Social stressors also negatively affect healing; however, previous studies suggest that the affected healing mechanisms may be stress model-specific. Here, the effects of either social isolation or physical restraint on dermal wound healing (3.5 mm wounds on the dorsum) were compared in hairless male mice. Social isolation beginning 3 weeks prior to wounding delayed healing comparably to physical restraint (12 h/day for eight days), in spite of marked differences in metabolic and hormonal consequences (i.e. body mass) between the two stress models. Additionally, isolated mice exhibited reductions in wound bacterial load and inflammatory gene expression (interleukin-1beta [IL-1β], monocyte chemoattractant protein [MCP]), whereas restraint significantly increased both of these parameters relative to controls. Experimentally augmenting bacterial concentrations in wounds of isolated mice did not ameliorate healing, whereas this treatment accelerated healing in controls. This work indicates that social isolation and restraint stressors comparably impair healing, but do so through disparate mechanisms and at different phases of healing.

Gonadal hormones differently modulate cutaneous wound healing of chronically stressed mice

Gonadal hormones influence physiological responses to stress and cutaneous wound healing. The aim of this study was to investigate the role of gonadal hormones on cutaneous wound healing in chronically stressed mice. Male and female mice were gonadectomized, and after 25 days, they were spun daily at 115 rpm for 15 min every hour until euthanasia. Twenty-eight days after the gonadectomy, an excisional lesion was created. The animals were killed 7 or 14 days after wounding, and the lesions were collected. Myofibroblast density, macrophage number, catecholamine level, collagen deposition, and blood vessel number were evaluated. In the intact and gonadectomized groups, stress increased the plasma catecholamine levels in both genders. In intact groups, stress impaired wound contraction and re-epithelialization and increased the macrophage number in males but not in females. In addition, stress compromised myofibroblastic differentiation and blood vessel formation and decreased collagen deposition in males but not in females. In contrast to intact mice, wound healing in ovariectomized female mice was affected by stress, while wound healing in castrated male mice was not. In conclusion, gender differences contribute to the cutaneous wound healing of chronically stressed mice. In addition, androgens contribute to the stress-induced impairment of the healing of cutaneous wounds but estrogens inhibit it.

The effects of social isolation on wound healing mechanisms in female mice

Various stressors impair wound healing in humans and rodents. For example, social isolation delays wound closure in rodents, but the healing mechanisms that underlie this delay have yet to be identified. Here, the effects of three weeks of social isolation on hypothalamic-pituitary-adrenal axis responses and healing factors involved in the inflammatory and proliferative phases of wound healing were assessed in adult female hairless mice. Social isolation reduced basal circulating corticosterone concentrations and increased body and thymus weights compared with group-housed controls. Isolation impaired dermal wound closure by up to 30% and reduced initial total wound bacterial load relative to controls. Inflammatory gene expression in the wounds was not affected by the observed differences in wound bacterial load. However, isolation reduced wound gene expression of keratinocyte growth factor and vascular endothelial growth factor, which are involved in keratinocyte proliferation/migration and angiogenesis during the proliferative phase of healing. These data indicate that social isolation induces healing impairments that may be attributed to reductions in growth factors necessary for proper skin cell proliferation and blood vessel growth during healing. This healing impairment occurred in the absence of both high wound bacterial load and elevated circulating glucocorticoids, which have previously been hypothesized to be required for stress-impaired healing in mice.

Influence of a probiotic lactobacillus strain on the intestinal ecosystem in a stress model mouse

Daily exposure to stressful situations affects the health of humans and animals. It has been shown that psychological stress affects the immune system and can exacerbate diseases. Probiotics can act as biological immunomodulators in healthy people, increasing both intestinal and systemic immune responses. The use of probiotics in stress situations may aid in reinforcing the immune system. The aim of this study was to evaluate the effect of a probiotic bacterium on the gut immune system of mice that were exposed to an experimental model of stress induced by food and mobility restriction. The current study focused on immune cells associated with the lamina propria of the intestine, including CD4+ and CD8+ T lymphocytes, CD11b+ macrophages, CD11c+ dendritic cells, and IgA+ B lymphocytes, as well as the concentrations of secretory IgA (S-IgA) and cytokine interferon gamma (INF-γ in intestinal fluid. We also evaluated the probiotic's influence on the gut microbiota. Probiotic administration increased IgA producing cells, CD4+ cells in the lamina propria of the small intestine, and S-IgA in the lumen; it also reduced the levels of IFN-γ that had increased during stress and improved the intestinal microbiota as measured by an increase in the lactobacilli population. The results obtained from administration of the probiotic to stressed mice suggest that the use of food containing these microorganisms may work as a palliative to reinforce the immune system.

Catecholamine stress alters neutrophil trafficking and impairs wound healing by β2-adrenergic receptor-mediated upregulation of IL-6

Stress-induced hormones can alter the inflammatory response to tissue injury, however, the precise mechanism by which epinephrine influences inflammatory response and wound healing is not well defined. Here we demonstrate that epinephrine alters the neutrophil (PMN)-dependent inflammatory response to a cutaneous wound. Using non-invasive real-time imaging of genetically-tagged PMNs in a murine skin wound, chronic, epinephrine-mediated stress was modeled by sustained delivery of epinephrine. Prolonged systemic exposure of epinephrine resulted in persistent PMN trafficking to the wound site via an IL-6 mediated mechanism, and this in turn impaired wound repair. Further, we demonstrate that β₂ adrenergic receptor-dependent activation of pro-inflammatory macrophages is critical for epinephrine-mediated IL-6 production. This study expands our current understanding of stress hormone-mediated impairment of wound healing and provides an important mechanistic link to explain how epinephrine stress exacerbates inflammation via increased number and lifetime of PMNs.

Chronic psychological stress induces the accumulation of myeloid-derived suppressor cells in mice

Chronic psychological stress has been shown to adversely impact immune system functions and compromise host defenses against various infections. However, the underlying mechanisms remain elusive. Recent studies have demonstrated that myeloid-derived suppressor cells (MDSCs) play an important role in regulating immunity. It is of interest to explore whether or not chronic psychological stress plays immunosuppressive functions partially by inducing MDSCs accumulation. In this work, we report that chronic psychological stress led to the accumulation of CD11b+Gr1+ cells in the bone marrow of BALB/c mice. Repeated β-agonist infusion showed no such effect. However, β-adrenergic blockade, but not glucocorticoids blockade, partially reversed the accumulation of CD11b+Gr1+ cells under the condition of chronic psychological stress, suggesting catecholamines collaborate with other factors to induce the accumulation. Further exploration indicates that cyclooxygenase 2 (COX-2)-prostaglandin E2 (PGE2) loop might act downstream to induce the accumulation. A majority of the accumulated CD11b+Gr1+ cells were Ly6G+Ly6C(low) immature neutrophils, which inhibited cytokine release of macrophages as well as T cell responsiveness. Moreover, the accumulated CD11b+Gr1+ cells under the condition of chronic psychological stress expressed multiple inhibitory molecules. Taken together, our data demonstrate for the first time that chronic psychological stress induces MDSCs accumulation in mice, which can contribute to immunosuppression.

Exploiting human CD34+ stem cell-conditioned medium for tissue repair

Despite the progress in our understanding of genes essential for stem cell regulation and development, little is known about the factors secreted by stem cells and their effect on tissue regeneration. In particular, the factors secreted by human CD34+ cells remain to be elucidated. We have approached this challenge by performing a cytokine/growth factor microarray analysis of secreted soluble factors in medium conditioned by adherent human CD34+ cells. Thirty-two abundantly secreted factors have been identified, all of which are associated with cell proliferation, survival, tissue repair, and wound healing. The cultured CD34+ cells expressed known stem cell genes such as Nanog, Oct4, Sox2, c-kit, and HoxB4. The conditioned medium containing the secreted factors prevented cell death in liver cells exposed to liver toxin in vitro via inhibition of the caspase-3 signaling pathway. More importantly, in vivo studies using animal models of liver damage demonstrated that injection of the conditioned medium could repair damaged liver tissue (significant reduction in the necroinflammatory activity), as well as enable the animals to survive. Thus, we demonstrate that medium conditioned by human CD34+ cells has the potential for therapeutic repair of damaged tissue in vivo.

MicroRNA-99 family targets AKT/mTOR signaling pathway in dermal wound healing

Recent studies suggest that microRNAs play important roles in dermal wound healing and microRNA deregulation has been linked with impaired wound repair. Here, using a mouse experimental wound healing model, we identified a panel of 63 differentially expressed microRNAs during dermal wound healing, including members of miR-99 family (miR-99a, miR-99b, miR-100). We further demonstrated that miR-99 family members regulate cell proliferation, cell migration, and AKT/mTOR signaling. Combined experimental and bioinformatics analyses revealed that miR-99 family members regulate AKT/mTOR signaling by targeting multiple genes, including known target genes (e.g., IGF1R, mTOR) and a new target (AKT1). The effects of miR-99 family members on the expression of IGF1R, mTOR and AKT1 were validated at both the mRNA and protein levels. Two adjacent miR-99 family targeting sites were identified in the 3′-UTR of the AKT1 mRNA. The direct interaction of miR-100 with these targeting sites was confirmed using luciferase reporter assays. The microRNA-100-directed recruitment of AKT1 mRNA to the RNAi-induced silencing complex (RISC) was confirmed by a ribonucleoprotein-IP assay. In summary, we identified a panel of differentially expressed microRNAs which may play important roles in wound healing. We provide evidence that miR-99 family members contribute to wound healing by regulating the AKT/mTOR signaling.

MMP-8 overexpression and persistence of neutrophils relate to stress-impaired healing and poor collagen architecture in mice

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) are critical for tissue remodeling during wound repair. Psychological stress has been found to impair wound healing in humans and animals. The objective of this study was to assess MMP and TIMP gene expression during stress-impaired healing. Female SKH-1 mice (n=299) were divided into control and stress groups (13h restraint/day for 3days prior to and 5days post-wounding). Two 3.5mm cutaneous full-thickness wounds were placed on the dorsum of each mouse and wound measurements were performed daily. RT-PCR for gene expression of MMP-2, MMP-8, MMP-9, TIMP-1 and TIMP-2 was performed at days 1, 3 and 5. Immunohistochemical analyses of the healed wounds were performed at days 15 and 28. As expected, wounds healed more slowly in restraint-stressed mice compared to controls. Stressed mice exhibited MMP-8 overexpression and lower TIMP-1 levels during healing, and poorer collagen organization once healed. MMP-8 overexpression may have stemmed from a higher level of neutrophils, observed in wound tissue on days 3 and 5. These findings implicate higher neutrophil numbers, MMP-8 overexpression, and TIMP-1 under-expression, as mechanisms that may compromise wound outcomes such as scarring under conditions of stress.