Monocyte chemoattractant protein-1 (MCP-1) and macrophage infiltration into the skin after burn injury in aged mice

Regeneration in Mice of Injured Skin, Heart, and Spinal Cord by α-Gal Nanoparticles Recapitulates Regeneration in Amphibians

The healing of skin wounds, myocardial, and spinal cord injuries in salamander, newt, and axolotl amphibians, and in mouse neonates, results in scar-free regeneration, whereas injuries in adult mice heal by fibrosis and scar formation. Although both types of healing are mediated by macrophages, regeneration in these amphibians and in mouse neonates also involves innate activation of the complement system. These differences suggest that localized complement activation in adult mouse injuries might induce regeneration instead of the default fibrosis and scar formation. Localized complement activation is feasible by antigen/antibody interaction between biodegradable nanoparticles presenting α-gal epitopes (α-gal nanoparticles) and the natural anti-Gal antibody which is abundant in humans. Administration of α-gal nanoparticles into injuries of anti-Gal-producing adult mice results in localized complement activation which induces rapid and extensive macrophage recruitment. These macrophages bind anti-Gal-coated α-gal nanoparticles and polarize into M2 pro-regenerative macrophages that orchestrate accelerated scar-free regeneration of skin wounds and regeneration of myocardium injured by myocardial infarction (MI). Furthermore, injection of α-gal nanoparticles into spinal cord injuries of anti-Gal-producing adult mice induces recruitment of M2 macrophages, that mediate extensive angiogenesis and axonal sprouting, which reconnects between proximal and distal severed axons. Thus, α-gal nanoparticle treatment in adult mice mimics physiologic regeneration in amphibians. These studies further suggest that α-gal nanoparticles may be of significance in the treatment of human injuries.

Kinetics of Inflammatory Mediators in the Immune Response to Burn Injury: Systematic Review and Meta-Analysis of Animal Studies

Burns are often accompanied by a dysfunctional immune response, which can lead to systemic inflammation, shock, and excessive scarring. The objective of this study was to provide insight into inflammatory pathways associated with burn-related complications. Because detailed information on the various inflammatory mediators is scattered over individual studies, we systematically reviewed animal experimental data for all reported inflammatory mediators. Meta-analyses of 352 studies revealed a strong increase in cytokines, chemokines, and growth factors, particularly 19 mediators in blood and 12 in burn tissue. Temporal kinetics showed long-lasting surges of proinflammatory cytokines in blood and burn tissue. Significant time-dependent effects were seen for IL-1β, IL-6, TGF-β1, and CCL2. The response of anti-inflammatory mediators was limited. Burn technique had a profound impact on systemic response levels. Large burn size and scalds further increased systemic, but not local inflammation. Animal characteristics greatly affected inflammation, for example, IL-1β, IL-6, and TNF-α levels were highest in young, male rats. Time-dependent effects and dissimilarities in response demonstrate the importance of appropriate study design. Collectively, this review presents a general overview of the burn-induced immune response exposing inflammatory pathways that could be targeted through immunotherapy for burn patients and provides guidance for experimental set-ups to advance burn research.

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.

Burn-Induced Apoptosis in the Livers of Aged Mice Is Associated With Caspase Cleavage of Bcl-xL

INTRODUCTION

Older adult burn victims have poorer outcomes than younger burn victims. The liver is critical for the recovery of patients with burns. Postburn hepatic apoptosis in young individuals compromises liver integrity; however, this pathway has not yet been studied in older individuals. Because aged animals with burns suffer significant liver damage, we hypothesized that apoptosis is altered in these animals and may affect liver function. Understanding postburn hepatic apoptosis and its effects on liver function in aged animals may help improve outcomes in older patients.

METHODS

We compared the protein and gene expression levels in young and aged mice after a 15% total-body-surface-area burn. Liver and serum samples were collected at different time points after injury.

RESULTS

Caspase-9 expression in liver tissue was downregulated by 47% in young animals and upregulated by 62% in aged animals 9 h postburn (P < 0.05). The livers of aged mice showed a Bcl-extra-large (Bcl-xL) transcription increase only after 6 h; however, the livers of young mice exhibited 4.3-fold, 14.4-fold, and 7.8-fold Bcl-xL transcription increases at 3, 6, and 9 h postburn, respectively (P < 0.05). The livers of young mice showed no changes in Caspase-9, Caspase-3, or Bcl-xL protein levels during the early postburn period. In contrast, the livers of aged mice contained cleaved caspase-9, reduced full-length caspase-3, and an accumulation of ΔN-Bcl-x at 6 and 9 h postburn (P < 0.05). p21 expression decreased in aged mice; however, it was significantly increased in the liver tissue of young mice postburn (P < 0.05). Serum amyloid A1 and serum amyloid A2 serum protein levels were 5.2- and 3.1-fold higher in young mice than in aged mice, respectively, at 6 and 9 h postburn (P < 0.05).

CONCLUSIONS

Livers of aged mice exhibited different apoptotic processes compared to those of young mice early after burn injury. Collectively, burn-induced liver apoptosis in aged mice compromises hepatic serum protein production.

CC chemokines family in fibrosis and aging: From mechanisms to therapy

Fibrosis is a universal aging-related pathological process in the different organ, but is actually a self-repair excessive response. To date, it still remains a large unmet therapeutic need to restore injured tissue architecture without detrimental side effects, due to the limited clinical success in the treatment of fibrotic disease. Although specific organ fibrosis and the associated triggers have distinct pathophysiological and clinical manifestations, they often share involved cascades and common traits, including inflammatory stimuli, endothelial cell injury, and macrophage recruitment. These pathological processes can be widely controlled by a kind of cytokines, namely chemokines. Chemokines act as a potent chemoattractant to regulate cell trafficking, angiogenesis, and extracellular matrix (ECM). Based on the position and number of N-terminal cysteine residues, chemokines are divided into four groups: the CXC group, the CX3C group, the (X)C group, and the CC group. The CC chemokine classes (28 members) is the most numerous and diverse subfamily of the four chemokine groups. In this Review, we summarized the latest advances in the understanding of the importance of CC chemokine in the pathogenesis of fibrosis and aging and discussed potential clinical therapeutic strategies and perspectives aimed at resolving excessive scarring formation.

Cutaneous burn injury induces neuroinflammation and reactive astrocyte activation in the hippocampus of aged mice

BACKGROUND

By 2050, one in six people globally will be 65 or older. Confusion and delirium are significant complications after burn injury, especially in the elderly population. The etiology is still unknown, however complications may be driven by pro-inflammatory activation of astrocytes within the hippocampus (HPC) after burn injury. Reduced levels of phosphorylated cyclic-AMP response binding element (pCREB), caused by elevated systemic pro-inflammatory cytokines, could lead to cognitive decline and memory impairment.

METHODS

To examine the effects of remote injury on neuroinflammation in advanced age, young and aged mice were subjected to a 15 % total body surface area scald burn or sham injury, and euthanized after 24 h. Expression of ccl2 and tnfa were measured by qPCR in the whole brain and HPC. Astrocyte activation was measured by immunofluorescence within the HPC. pCREB was measured by immunohistochemistry in the dentate gyrus.

RESULTS

We saw an 80-fold increase in ccl2 and a 30-fold elevation in tnfa after injury in the whole brain of aged mice compared to young groups and aged sham mice (p < 0.05 and p < 0.05, respectively). Additionally, there was a 30-fold increase in ccl2 within isolated HPC of aged injured mice when compared to sham injured animals (p < 0.05). When investigating specific HPC regions, immunofluorescence staining showed a >20 % rise in glial fibrillary acidic protein (GFAP) positive astrocytes within the cornu ammonis 3 (CA3) of aged injured mice when compared to all other groups (p < 0.05). Lastly, we observed a >20 % decrease in pCREB staining by immunohistochemistry in the dentate gyrus of aged mice compared to young regardless of injury (p < 0.05).

CONCLUSIONS

These novel data suggest that remote injury in aged, but not young, mice is associated with neuroinflammation and astrocyte activation within the HPC. These factors, paired with an age related reduction in pCREB, could help explain the increased cognitive decline seen in burn patients of advanced age. To our knowledge, we are the first group to examine the impact of advanced age combined with burn injury on inflammation and astrocyte activation within the brain.

α-Gal Nanoparticles Mediated Homing of Endogenous Stem Cells for Repair and Regeneration of External and Internal Injuries by Localized Complement Activation and Macrophage Recruitment

This review discusses a novel experimental approach for the regeneration of original tissue structure by recruitment of endogenous stem-cells to injured sites following administration of α-gal nanoparticles, which harness the natural anti-Gal antibody. Anti-Gal is produced in large amounts in all humans, and it binds the multiple α-gal epitopes (Galα1-3Galβ1-4GlcNAc-R) presented on α-gal nanoparticles. In situ binding of anti-Gal to α-gal nanoparticles activates the complement system and generates complement cleavage chemotactic-peptides that rapidly recruit macrophages. Macrophages reaching anti-Gal coated α-gal nanoparticles bind them via Fc/Fc receptor interaction and polarize into M2 pro-reparative macrophages. These macrophages secrete various cytokines that orchestrate regeneration of the injured tissue, including VEGF inducing neo-vascularization and cytokines directing homing of stem-cells to injury sites. Homing of stem-cells is also directed by interaction of complement cleavage peptides with their corresponding receptors on the stem-cells. Application of α-gal nanoparticles to skin wounds of anti-Gal producing mice results in decrease in healing time by half. Furthermore, α-gal nanoparticles treated wounds restore the normal structure of the injured skin without fibrosis or scar formation. Similarly, in a mouse model of occlusion/reperfusion myocardial-infarction, near complete regeneration after intramyocardial injection of α-gal nanoparticles was demonstrated, whereas hearts injected with saline display ~20% fibrosis and scar formation of the left ventricular wall. It is suggested that recruitment of stem-cells following anti-Gal/α-gal nanoparticles interaction in injured tissues may result in induction of localized regeneration facilitated by conducive microenvironments generated by pro-reparative macrophage secretions and “cues” provided by the extracellular matrix in the injury site.

Cinnamaldehyde-Based Self-Nanoemulsion (CA-SNEDDS) Accelerates Wound Healing and Exerts Antimicrobial, Antioxidant, and Anti-Inflammatory Effects in Rats’ Skin Burn Model

Cinnamaldehyde, the main phytoconstituent of the cinnamon oil, has been reported for its potential wound healing activity, associated to its antimicrobial and anti-inflammatory effects. In this study, we are reporting on the cinnamaldehyde-based self-nanoemulsifying drug delivery system (CA-SNEDDS), which was prepared and evaluated for its antimicrobial, antioxidant, anti-inflammatory, and wound healing potential using the rat third-degree skin injury model. The parameters, i.e., skin healing, proinflammatory, and oxidative/antioxidant markers, were evaluated after 3 weeks of treatment regimens with CA-SNEDDS. Twenty rats were divided randomly into negative control (untreated), SNEDDS control, silver sulfadiazine cream positive control (SS), and CA-SNEDDS groups. An aluminum cylinder (120 °C, 10-s duration) was used to induce 3rd-degree skin burns (1-inch square diameter each) on the rat’s dorsum. At the end of the experiment, skin biopsies were collected for biochemical analysis. The significantly reduced wound size in CA-SNEDDS compared to the negative group was observed. CA-SNEDDS-treated and SS-treated groups demonstrated significantly increased antioxidant biomarkers, i.e., superoxide dismutase (SOD) and catalase (CAT), and a significant reduction in the inflammatory marker, i.e., NAP-3, compared to the negative group. Compared to SNEDDS, CA-SNEDDS exhibited a substantial antimicrobial activity against all the tested organisms at the given dosage of 20 µL/disc. Among all the tested microorganisms, MRSA and S. typhimurium were the most susceptible bacteria, with an inhibition zone diameter (IZD) of 17.0 ± 0.3 mm and 19.0 ± 0.9 mm, respectively. CA-SNEDDS also exhibited strong antifungal activity against C. albicans and A. niger, with IZD of 35.0 ± 0.5 mm and 34.0 ± 0.5 mm, respectively. MIC and MBC of CA-SNEDDS for the tested bacteria ranged from 3.125 to 6.25 µL/mL and 6.25 to 12.5 µL/mL, respectively, while the MIC and MBC for C. albicans and A. niger were 1.56 µL/mL and 3.125 µL/mL, respectively. The MBIC and MBEC of CA-SNEDDS were also very significant for the tested bacteria and ranged from 6.25 to 12.5 µL/mL and 12.5 to 25.0 µL/mL, respectively, while the MBIC and MBEC for C. albicans and A. niger were 3.125 µL/mL and 6.25 µL/mL, respectively. Thus, the results indicated that CA-SNEDDS exhibited significant wound healing properties, which appeared to be attributed to the formulation’s antimicrobial, antioxidant, and anti-inflammatory effects.

Burn-Induced Local and Systemic Immune Response: Systematic Review and Meta-Analysis of Animal Studies

As burn injuries are often followed by a derailed immune response and excessive inflammation, a thorough understanding of the occurring reactions is key to prevent secondary complications. This systematic review, that includes 247 animal studies, shows the post-burn response of 14 different immune cell types involved in immediate and long-term effects, in both wound tissue and circulation. Peripheral blood neutrophil and monocyte numbers increased directly after burns, whereas thrombocyte numbers increased near the end of the first week. Lymphocyte numbers, however, were decreased for at least two weeks. In burn wound tissue, neutrophil and macrophage numbers accumulated during the first three weeks. Burns also altered cellular functions as we found increased migratory potential of leukocytes, impaired antibacterial activity of neutrophils and enhanced inflammatory mediator production by macrophages. Neutrophil surges were positively associated with burn size and were highest in rats. Altogether, this comprehensive overview of the temporal immune cell dynamics shows that unlike normal wound healing, burn injury induces a long-lasting inflammatory response. It provides a fundamental research basis to improve experimental set-ups, burn care and outcome.

Advanced age exacerbates intestinal epithelial permeability after burn injury in mice

BACKGROUND

Advanced age is an independent risk factor for morbidity and mortality after burn injury. Following burn, the intestines can become permeable leading to the leakage of bacteria and their products from the lumen of the ileum to the portal and systemic circulation. Here, we sought to determine the effects of advanced age on intestinal permeability post burn injury and assess intestinal inflammatory biomarkers.

METHODS

Young (4-5 months) and aged (18-22 months) female BALB/cBy mice were subjected to a 12-15% total body surface area (TBSA) sham or burn injury. 24 h after injury, mice were euthanized, and organs collected. Colony-forming units (CFU) were counted from plated mesenteric lymph nodes (MLN). Gene expression of ileal tight junctional proteins, occludin and zonula occludens 1 (ZO-1), in addition to ileal damage associated molecular pattern (DAMP) proteins, S100A8 and S100A9, as well as ileal inflammatory markers IL-6 and TNF-α were measured by qPCR. Intestinal cell death was measured by ELISA. Intestinal permeability was determined by FITC fluorescence in serum; 4kD FITC-dextran was given by oral gavage 3 h before euthanasia.

RESULTS

Aged mice subjected to burn injury had increased intestinal permeability as evidenced by a 5.8-fold higher level of FITC-dextran in their serum when compared to all other groups (p < 0.05). In addition, aged burn-injured mice exhibited heightened bacterial accumulation in the MLN with a 15.5-fold increase over all other groups (p < 0.05). Histology of ileum failed to show differences in villus length among all groups. Analysis of ileal tight junctional proteins and inflammatory marker gene expression revealed no difference in Ocln, Tjp1, Il6, or Tnf expression among all groups, but 2.3 and 2.9-fold upregulation of S100a8 and S100a9, respectively, in aged burn-injured mice relative to both young groups and aged sham-injured mice (p < 0.05). Lastly, cell death in the ileum was elevated more than two-fold in aged burn-injured mice relative to young animals regardless of injury (p < 0.05).

CONCLUSIONS

These data demonstrate that advanced age exacerbates intestinal epithelial permeability after burn injury. Heightened apoptosis may be responsible for the elevated intestinal leakiness and accumulation of bacteria in mesenteric lymph nodes. In addition, S100a8/9 may serve as a biomarker of elevated inflammation within the intestine.

Severity of thermal burn injury is associated with systemic neutrophil activation

Burn injuries elicit a unique and dynamic stress response which can lead to burn injury progression. Though neutrophils represent crucial players in the burn-induced immunological events, the dynamic secretion pattern and systemic levels of neutrophil-derived factors have not been investigated in detail so far. Serum levels of neutrophil elastase (NE), myeloperoxidase (MPO), citrullinated histone H3 (CitH3), and complement factor C3a were quantified in burn victims over 4 weeks post injury. Furthermore, the potential association with mortality, degree of burn injury, and inhalation trauma was evaluated. In addition, leukocyte, platelet, neutrophil, and lymphocyte counts were assessed. Lastly, we analyzed the association of neutrophil-derived factors with clinical severity scoring systems. Serum levels of NE, MPO, CitH3, and C3a were remarkably elevated in burn victims compared to healthy controls. Leukocyte and neutrophil counts were significantly increased on admission day and day 1, while relative lymphocytes were decreased in the first 7 days post burn trauma. Though neutrophil-derived factors did not predict mortality, patients suffering from 3rd degree burn injuries displayed increased CitH3 and NE levels. Accordingly, CitH3 and NE were elevated in cases with higher abbreviated burn severity indices (ABSI). Taken together, our data suggest a role for neutrophil activation and NETosis in burn injuries and burn injury progression. Targeting exacerbated neutrophil activation might represent a new therapeutic option for severe cases of burn injury.

Advanced age heightens hepatic damage in a murine model of scald burn injury

BACKGROUND

Elderly burn patients exhibit a lower survival rate compared with younger counterparts. The liver is susceptible to damage after burn injury, which predisposes to poor outcomes. Lipid homeostasis and the antioxidant glutathione system play fundamental roles in preserving liver integrity. Herein, we explored changes in these major pathways associated with liver damage in the aging animals after burn injury.

METHODS

We compared liver enzymes, histology, lipid-peroxidation, and glutathione-metabolism profiles from young and aged female mice after a 15% total body surface area burn. Mice were euthanized at 24 hours after injury, and livers and serum were collected.

RESULTS

Aged burn animals exhibited elevated (p < 0.05) aspartate aminotransferase and alanine aminotransferase levels and increased inflammatory cell infiltration, edema, and necrosis compared with their younger counterparts. The percentage of adipophilin-stained area in livers from young sham, young burn, aged sham, and aged burn groups was 10%, 44%, 16%, and 78% (p < 0.05), respectively. Liver malondialdehyde levels were 1.4 ± 0.5 nmol/mg, 2.06 ± 0.2 nmol/mg, 1.81 ± 0.12 nmol/mg, and 3.45 ± 0.2 nmol/mg (p < 0.05) in young sham, young burn, aged sham, and aged burn mice, respectively. Oxidized glutathione (GSSG) content increased 50% in the young burn, and 88% in aged burn animals compared with the young sham group (p < 0.05). The reduced glutathione GSH/GSSG ratio was significantly reduced by 54% in aged burn mice compared with young sham animals (p < 0.05). Furthermore, glutathione peroxidase gene expression showed a 96% decrease in the aged burn group compared with young sham mice (p < 0.05).

CONCLUSION

Aged burn animals exhibit severe liver damage from heightened lipid peroxidation and inadequate antioxidative response. The increased peroxidation is associated with abundant lipid deposits in hepatic tissue postburn and a weak antioxidative response due to hepatic glutathione peroxidase downregulation. Further studies will focus on the functional significance of these findings concerning hepatic homeostasis.

The Effects of Human Bone Marrow-Derived Mesenchymal Stem Cell Conditioned Media Produced with Fetal Bovine Serum or Human Platelet Lysate on Skin Rejuvenation Characteristics

Background and Objectives

Human mesenchymal stem cell-conditioned medium (MSC-CM) is produced using mesenchymal stem cell culture technology and has various benefits for the skin, including wrinkle removal, skin regeneration, and increased antioxidant activity. Its popularity is thus increasing in the field of functional cosmetics.

Methods and Results

In this study, we analyzed the effects of fetal bovine serum-supplemented MSC-CM (FBS- MSC-CM) and human platelet lysate-supplemented MSC-CM (hPL-MSC-CM) on skin rejuvenation characteristics. We found that the concentrations of important growth factors (VEGF, TGF-β1, and HGF) and secretory proteins for skin regeneration were significantly higher in hPL-MSC-CM than in FBS-MSC-CM. Furthermore, the capacity for inducing proliferation of human dermal fibroblast (HDF) and keratinocytes, the migration ability of HDF, extracellular matrix (ECM) production such as collagen and elastin was higher in hPL-MSC-CM than that in FBS- MSC-CM.

Conclusions

These results support the usefulness and high economic value of hPL-MSC-CM as an alternative source of FBS-MSC-CM in the cosmetic industry for skin rejuvenation.

Current and Emerging Topical Scar Mitigation Therapies for Craniofacial Burn Wound Healing

Burn injury in the craniofacial region causes significant health and psychosocial consequences and presents unique reconstructive challenges. Healing of severely burned skin and underlying soft tissue is a dynamic process involving many pathophysiological factors, often leading to devastating outcomes such as the formation of hypertrophic scars and debilitating contractures. There are limited treatment options currently used for post-burn scar mitigation but recent advances in our knowledge of the cellular and molecular wound and scar pathophysiology have allowed for development of new treatment concepts. Clinical effectiveness of these experimental therapies is currently being evaluated. In this review, we discuss current topical therapies for craniofacial burn injuries and emerging new therapeutic concepts that are highly translational.

Intracellular ATP Delivery Causes Rapid Tissue Regeneration via Upregulation of Cytokines, Chemokines, and Stem Cells

We have reported accelerated wound healing induced by intracellular ATP delivery in rabbits, through early massive accumulation, in situ proliferation, and M2 polarization of macrophages. Granulation tissue started to grow within first 24 h of treatment and continued the growth till the wound cavity is completely covered. However, the mechanisms underlying this macrophage response are totally unclear because no one has ever reported this before. In this study, we performed a preliminary exploration of the possible mechanisms by focusing on the roles of cytokines, growth factors, and stem cells in this process. Among the 33 adult rabbits, 18 were used for cytokine measurements and the remaining were used for histological and immunohistochemical studies. Four wounds were created on the ventral side of each ear. Two wounds on one side were treated with ATP-vesicles (10 mM ATP), and the other two were treated with controls (normal saline or Regranex). Dressing changes were made daily and the rabbits were sacrificed at 5 h, 12 h, and 1, 2, 3, 4, 6, 9, 15, and 26 days after wounding. Tissue samples were analyzed for cytokines and growth factors using real-time PCR and immunohistochemical staining. The control wounds showed an immediate increase in proinflammatory cytokines after wound creation but no further increase after this initial spike. The growth factor levels in the control wounds remained unchanged throughout the study. Conversely, the wounds treated with ATP-vesicles showed significantly higher expression of MCP-1 and stem cell markers (CD44, CD106, CD146, and CD34) at day 1, significantly higher IL-1β and TNF-α expression from day 1–4, and significantly higher VEGF-A, VEGF-D, and VEGFR-2 expression from day 4–6 when compared to the controls. The significant upregulation of these factors corresponded to the very early and rapid macrophage accumulation, in situ proliferation, and M2 polarization, resulting in unprecedented rapid granulation tissue generation due to direct macrophage collagen production and neovascularization.

Centenarians: An excellent example of resilience for successful ageing

Centenarians are remarkable not only because of their prolonged life, but also because they compress morbidity until the very last moments of their lives, thus being proposed as a model of successful, extraordinary ageing. From the medical viewpoint, centenarians do not escape the physiological decline or the age-related diseases or syndromes (i.e. frailty), but the rate of such processes is slow enough to be counterbalanced by their increased intrinsic capacity to respond to minor stresses of daily life (i.e. resilience). These new concepts are reviewed in this paper. Allostatic stresses lead to a chronic low-grade inflammation that has led to the proposal of the "inflammaging" theory of ageing and frailty. The biology of centenarians, described in this review, provides us with clues for intervention to promote healthy ageing in the general population. One of the major reasons for this healthy ageing has to do with the genetic signature that is specific for centenarians and certainly different from octogenarians who do not enjoy the extraordinary qualities of centenarians.

The Role of Chemokines in Wound Healing

Wound healing is a multistep process with four overlapping but distinct stages: hemostasis, inflammation, proliferation, and remodeling. An alteration at any stage may lead to the development of chronic non-healing wounds or excessive scar formation. Impaired wound healing presents a significant health and economic burden to millions of individuals worldwide, with diabetes mellitus and aging being major risk factors. Ongoing understanding of the mechanisms that underly wound healing is required for the development of new and improved therapies that increase repair. Chemokines are key regulators of the wound healing process. They are involved in the promotion and inhibition of angiogenesis and the recruitment of inflammatory cells, which release growth factors and cytokines to facilitate the wound healing process. Preclinical research studies in mice show that the administration of CCL2, CCL21, CXCL12, and a CXCR4 antagonist as well as broad-spectrum inhibition of the CC-chemokine class improve the wound healing process. The focus of this review is to highlight the contributions of chemokines during each stage of wound healing and to discuss the related molecular pathologies in complex and chronic non-healing wounds. We explore the therapeutic potential of targeting chemokines as a novel approach to overcome the debilitating effects of impaired wound healing.

Modelling physical resilience in ageing mice

Geroprotectors, a class of drugs targeting multiple deficits occurring with age, necessitate the development of new animal models to test their efficacy. The COST Action MouseAGE is a European network whose aim is to reach consensus on the translational path required for geroprotectors, interventions targeting the biology of ageing. In our previous work we identified frailty and loss of resilience as a potential target for geroprotectors. Frailty is the result of an accumulation of deficits, which occurs with age and reduces the ability to respond to adverse events (physical resilience). Modelling frailty and physical resilience in mice is challenging for many reasons. There is no consensus on the precise definition of frailty and resilience in patients or on how best to measure it. This makes it difficult to evaluate available mouse models. In addition, the characterization of those models is poor. Here we review potential models of physical resilience, focusing on those where there is some evidence that the administration of acute stressors requires integrative responses involving multiple tissues and where aged mice showed a delayed recovery or a worse outcome then young mice in response to the stressor. These models include sepsis, trauma, drug- and radiation exposure, kidney and brain ischemia, exposure to noise, heat and cold shock.

Inflammation and Monocyte Recruitment due to Aging and Mechanical Stretch in Alveolar Epithelium are Inhibited by the Molecular Chaperone 4-phenylbutyrate

Introduction

Ventilator-Induced lung injury (VILI) is a form of acute lung injury that is initiated or exacerbated by mechanical ventilation. The aging lung is also more susceptible to injury. Harmful mechanical stretch of the alveolar epithelium is a recognized mechanism of VILI, yet little is known about how mechanical stretch affects aged epithelial cells. Disruption to Endoplasmic Reticulum (ER) homeostasis results in a condition known as ER stress that leads to disruption of cellular homeostasis, apoptosis, and inflammation. ER stress is increased with aging and other pathological stimuli. We hypothesized that age and mechanical stretch increase alveolar epithelial cells' proinflammatory responses that are mediated by ER stress. Furthermore, we believed that inhibition of this upstream mechanism with 4PBA, an ER stress reducer, alleviates subsequent inflammation and monocyte recruitment.

Methods

Type II alveolar epithelial cells (ATII) were harvested from C57Bl6/J mice 2 months (young) and 20 months (old) of age. The cells were cyclically stretched at 15% change in surface area for up to 24 hours. Prior to stretch, groups were administered 4PBA or vehicle as a control.

Results

Mechanical stretch and age upregulated ER stress and proinflammatory MCP-1/CCL2 and MIP-1β/CCL4 chemokine expression in ATIIs. Age-matched and mismatched monocyte recruitment by ATII conditioned media was also quantified.

Conclusions

Age increases susceptibility to stretch-induced ER stress and downstream inflammatory gene expression in a primary ATII epithelial cell model. Administration of 4PBA attenuated the increased ER stress and proinflammatory responses from stretch and/or age and significantly reduced monocyte migration to ATII conditioned media.

Burn wounds in the young versus the aged patient display differential immunological responses

BACKGROUND

Individuals in the geriatric age range are more prone than younger individuals to convert their partial thickness thermal burns into full thickness injuries. We hypothesized that this often observed clinical phenomenon is strongly related to differential local injury responses mediated by the immune system.

MATERIALS & METHODS

Skin samples from areas with partial thickness thermal burns were obtained during routine excision and grafting procedures between post burn days 2-6. Tissue samples were grouped by age ranges with young patients defined as <30 years of age or aged patients defined as >65. Formalin fixed samples were used to confirm depth of burn injury and companion sections were homogenized for multiplex analysis using a Luminex platform. Immunohistochemical staining was used to quantify total macrophage numbers as well as the M1 and M2 subpopulations.

RESULTS

Our analysis includes samples derived from 11 young subjects (mean age=23) and 3 aged subjects (mean age=79.2). Our initial survey of analytes examined 31 cytokines/chemokines. Twelve were excluded from consideration as they were present in concentrations either above or below the optimal detection range. Two analytes emerged as candidate molecules with significant differences between the young and the aged patient responses to burn injury. EGF levels were on average 21.69pg/ml in young vs 14.87pg/ml in aged (p=0.032). RANTES/CCL5 levels were on average 14.86pg/ml in young vs 4.26pg/ml in aged (p=0.026). Elevated macrophage numbers were present within wounds of younger patients compared to the old (p<0.01), with a higher concentration of the M1 type in the elderly (p>0.05).

CONCLUSION

Our study has identified at least 2 well known cytokines, CCL5 (RANTES) and EGF, which are differentially regulated in response to burn injury by young versus aged burn victims. Evidence suggests that a proinflammatory environment can explain the high conversion rate from partial to full thickness burns. Our data suggest the need for future studies at the point of injury (cutaneous targets) that may be modulated by post burn release of cytokines/chemokines.

Cell Autonomous and Non-Autonomous Effects of Senescent Cells in the Skin

Human and mouse skin accumulate senescent cells in both the epidermis and dermis during aging. When chronically present, senescent cells are thought to enhance the age-dependent deterioration of the skin during extrinsic and intrinsic aging. However, when transiently present, senescent cells promote optimal wound healing. Here, we review recent studies on how senescent cells and the senescence-associated secretory phenotype (SASP) contribute to different physiological and pathophysiological conditions in the skin with a focus on some of the cell autonomous and non-autonomous functions of senescent cells in the context of skin aging and wound healing.

Acceleration of wound healing by α-gal nanoparticles interacting with the natural anti-Gal antibody

Application of α-gal nanoparticles to wounds and burns induces accelerated healing by harnessing the natural anti-Gal antibody which constitutes ~1% of human immunoglobulins. α-gal nanoparticles present multiple α-gal epitopes (Galα1-3Galβ1-4GlcNAc-R), the carbohydrate ligand of anti-Gal. Studied α-gal nanoparticles were comprised of glycolipids with α-gal epitopes, phospholipids, and cholesterol. Binding of anti-Gal to α-gal nanoparticles in wounds activates the complement cascade, resulting in formation of chemotactic complement cleavage peptides that induce rapid recruitment of many macrophages. The Fc/Fcγ receptors interaction between anti-Gal coating α-gal nanoparticles and the recruited macrophages activates macrophages to produce cytokines/growth factors that promote wound healing and recruit stem cells. Studies of wound healing by α-gal nanoparticles were feasible in α1,3galactosyltransferase knockout mice and pigs. In contrast to other nonprimate mammals, these mice and pigs lack the α-gal epitope, and thus they are not immunotolerant to it and produce anti-Gal. Treatment of skin wounds and burns with α-gal nanoparticles resulted in 40-60% decrease in healing time in comparison with control wounds treated with saline. This accelerated healing is associated with increased recruitment of macrophages and extensive angiogenesis in wounds, faster regrowth of epidermis, and regeneration of the dermis. The accelerated healing further decreases and may completely eliminate fibrosis and scar formation in wounds. Since healing of internal injuries is mediated by mechanisms similar to those in external wound healing, it is suggested that α-gal nanoparticles treatment may also improve regeneration and restoration of biological function following internal injuries such as surgical incisions, myocardial ischemia following infarction, and nerve injuries.

Chronic wound repair and healing in older adults: current status and future research

Older adults are more likely to have chronic wounds than younger people, and the effect of chronic wounds on quality of life is particularly profound in this population. Wound healing slows with age, but the basic biology underlying chronic wounds and the influence of age-associated changes on wound healing are poorly understood. Most studies have used in vitro approaches and various animal models, but observed changes translate poorly to human healing conditions. The effect of age and accompanying multimorbidity on the effectiveness of existing and emerging treatment approaches for chronic wounds is also unknown, and older adults tend to be excluded from randomized clinical trials. Poorly defined outcomes and variables; lack of standardization in data collection; and variations in the definition, measurement, and treatment of wounds also hamper clinical studies. The Association of Specialty Professors, in conjunction with the National Institute on Aging and the Wound Healing Society, held a workshop, summarized in this article, to explore the current state of knowledge and research challenges, engage investigators across disciplines, and identify research questions to guide future study of age-associated changes in chronic wound healing.

Chronic wound repair and healing in older adults: current status and future research

The incidence of chronic wounds is increased among older adults, and the impact of chronic wounds on quality of life is particularly profound in this population. It is well established that wound healing slows with age. However, the basic biology underlying chronic wounds and the influence of age-associated changes on wound healing are poorly understood. Most studies have used in vitro approaches and various animal models, but observed changes translate poorly to human healing conditions. The impact of age and accompanying multi-morbidity on the effectiveness of existing and emerging treatment approaches for chronic wounds is also unknown, and older adults tend to be excluded from randomized clinical trials. Poorly defined outcomes and variables, lack of standardization in data collection, and variations in the definition, measurement, and treatment of wounds also hamper clinical studies. The Association of Specialty Professors, in conjunction with the National Institute on Aging and the Wound Healing Society, held a workshop, summarized in this paper, to explore the current state of knowledge and research challenges, engage investigators across disciplines, and identify key research questions to guide future study of age-associated changes in chronic wound healing.

In situ increased chemokine expression in human cervical intraepithelial neoplasia

Chemokines play a role in tumor-inflammation and angiogenesis that could be involved in tumor progression. Monocyte chemoattractant protein-1 (MCP-1), Interleukin-8 (IL-8) and macrophage inflammatory proteins (MIP) have been identified in tumor tissues of patients with different neoplasms. Therefore, the aim of the current study was to investigate the expressions of MCP-1, IL-8 and MIP-1α, mononuclear leukocyte infiltration and leukocyte/chemokine expressions in cervical tissues from patients with cervical intraepithelial neoplasia (CIN) and controls. MCP-1, IL-8 and MIP-1α expressions and leukocyte infiltration were determined by indirect immunofluorescence in cervix biopsies from CIN patients (n=65) and 7 normal controls. Increased expressions of MCP-1 and IL-8 in CIN were observed. Increment of lymphocyte infiltration and coexpression of CD3/MCP-1 and CD3/IL-8 were found in CIN. CD3/MCP-1 cell percentage was found decreased and CD3/IL-8 percentage increased according to the CIN evolution. MIP-1α remained similar to control values. The increased expression of MCP-1 and IL-8 in cervical neoplasia may lead to tumor progression.

Chemokines and Their Receptors Are Key Players in the Orchestra That Regulates Wound Healing

SIGNIFICANCE

Normal wound healing progresses through a series of overlapping phases, all of which are coordinated and regulated by a variety of molecules, including chemokines. Because these regulatory molecules play roles during the various stages of healing, alterations in their presence or function can lead to dysregulation of the wound-healing process, potentially leading to the development of chronic, nonhealing wounds.

RECENT ADVANCES

A discovery that chemokines participate in a variety of disease conditions has propelled the study of these proteins to a level that potentially could lead to new avenues to treat disease. Their small size, exposed termini, and the fact that their only modifications are two disulfide bonds make them excellent targets for manipulation. In addition, because they bind to G-protein-coupled receptors (GPCRs), they are highly amenable to pharmacological modulation.

CRITICAL ISSUES

Chemokines are multifunctional, and in many situations, their functions are highly dependent on the microenvironment. Moreover, each specific chemokine can bind to several GPCRs to stimulate the function, and both can function as monomers, homodimers, heterodimers, and even oligomers. Activation of one receptor by any single chemokine can lead to desensitization of other chemokine receptors, or even other GPCRs in the same cell, with implications for how these proteins or their receptors could be used to manipulate function.

FUTURE DIRECTIONS

Investment in better understanding of the functions of chemokines and their receptors in a local context can reveal new ways for therapeutic intervention. Understanding how different chemokines can activate the same receptor and vice versa could identify new possibilities for drug development based on their heterotypic interactions.

Lipopolysaccharide upregulates α7 acetylcholine receptors: stimulation with GTS-21 mitigates growth arrest of macrophages and improves survival in burned mice

Nicotinic stimulation of the α7 acetylcholine receptors (α7AChRs) mitigates the lipopolysaccharide (LPS)-induced tumor necrosis factor α (TNF-α) and other cytokines release in macrophages. This effect is blocked by α7AChR antagonist, α-bungarotoxin (BTX). We tested and confirmed the hypotheses that LPS upregulates α7AChRs, and the prototypical α7AChR antagonists, vecuronium and BTX, do not block the effects of GTS-21, a specific α7AChR agonist, on TNF-α release. With the knockdown of α7AChR expression by short interference RNA, GTS-21 effects on inhibition of TNF-α release were not demonstrable. In addition, GTS-21 mitigated the LPS-induced growth arrest of macrophages in vitro in J774A.1 cells and ex vivo in peritoneal macrophages obtained from mice at 3 days after burn. Moreover, GTS-21 reduced mortality after burn injury in mice. These results indicate that (i) LPS upregulates α7AChRs; (ii) the therapeutic beneficial effects of GTS-21 on cytokine release are specifically mediated via α7AChRs and are preserved even when cotreated with prototypical antagonist, BTX, or clinically used muscle nicotinic antagonist, vecuronium; (iii) activation of α7AChRs by GTS-21 partially reverses the LPS-induced proliferation arrest; and (iv) GTS-21 reduces mortality in mice with burn injury. The in vivo beneficial effects of GTS-21 in burn injury warrant further studies.

Effects of lipopolysaccharide and CpG-DNA on burn-induced skin injury

Destruction of the skin barrier by thermal injury induces microbial invasion, which can lead to the development of systemic infection and septic shock. Microbial pathogens possess pathogen-associated molecular patterns (PAMPs), which are recognized by conserved receptors. To understand the role of PAMPs in thermal injury-induced mice, LPS or CpG-DNA were topically applied to dorsal skin after thermal injury. We observed an increase in the number of inflammatory cell infiltrates as well as thickening in the dermis upon treatment with LPS or CpG-DNA. We also found that expression of IL-1β, MIP-2, and RANTES induced by thermal injury was enhanced by LPS or CpG-DNA. In addition, the proportions of CD4(+) and CD8(+) T cells in the spleen and lymph nodes were altered by LPS or CpG-DNA. These results provide important information concerning PAMPs-induced inflammation upon thermal injury and provide a basis for studying the role of PAMPs in thermal injury-induced complications.

Rapid recruitment and activation of macrophages by anti-Gal/α-Gal liposome interaction accelerates wound healing

Macrophages are pivotal in promoting wound healing. We hypothesized that topical application of liposomes with glycolipids that carry Galα1-3Galβ1-4GlcNAc-R epitopes (α-gal liposomes) on wounds may accelerate the healing process by rapid recruitment and activation of macrophages in wounds. Immune complexes of the natural anti-Gal Ab (constituting ∼1% of Ig in humans) bound to its ligand, the α-gal epitope on α-gal liposomes would induce local activation of complement and generation of complement chemotactic factors that rapidly recruit macrophages. Subsequent binding of the Fc portion of anti-Gal coating α-gal liposomes to FcγRs on recruited macrophages may activate macrophage genes encoding cytokines that mediate wound healing. We documented the efficacy of this treatment in α1,3galactosyltrasferase knockout mice. In contrast to wild-type mice, these knockout mice lack α-gal epitopes and can produce the anti-Gal Ab. The healing time of excisional skin wounds treated with α-gal liposomes in these mice is twice as fast as that of control wounds. Moreover, scar formation in α-gal liposome-treated wounds is much lower than in physiologic healing. Additional sonication of α-gal liposomes resulted in their conversion into submicroscopic α-gal nanoparticles. These α-gal nanoparticles diffused more efficiently in wounds and further increased the efficacy of the treatment, resulting in 95-100% regeneration of the epidermis in wounds within 6 d. The study suggests that α-gal liposome and α-gal nanoparticle treatment may enhance wound healing in the clinic because of the presence of high complement activity and high anti-Gal Ab titers in humans.

Protection of burn-induced skin injuries by the flavonoid kaempferol

Thermal burn injury induces inflammatory cell infiltrates in the dermis and thickening of the epidermis. Following a burn injury, various mediators, including reactive oxygen species (ROS), are produced in macrophages and neutrophils, exposing all tissues to oxidative injury. The anti-oxidant activities of flavonoids have been widely exploited to scavenge ROS. In this study, we observed that several flavonoids-kaempferol, quercetin, fisetin, and chrysin-inhibit LPS-induced IL-8 promoter activation in RAW 264.7 cells. In contrast with quercetin and fisetin, pretreatment of kaempferol and chrysin did not decrease cell viability. Inflammatory cell infiltrates in the dermis and thickening of the epidermis induced by burn injuries in mice was relieved by kaempferol treatment. However, the injury was worsened by fisetin, quercetin, and chrysin. Expression of TNF-a induced by burn injuries was decreased by kaempferol. These findings suggest the potential use of kaempferol as a therapeutic in thermal burn-induced skin injuries. [BMB reports 2010; 43(1): 46-51].

Reactive oxygen intermediate-induced pathomechanisms contribute to immunosenescence, chronic inflammation and autoimmunity

Deregulation of reactive oxygen intermediates (ROI) resulting in either too high or too low concentrations are commonly recognized to be at least in part responsible for many changes associated with aging. This article reviews ROI-dependent mechanisms critically contributing to the decline of immune function during physiologic - or premature - aging. While ROI serve important effector functions in cellular metabolism, signalling and host defence, their fine-tuned generation declines over time, and ROI-mediated damage to several cellular components and/or signalling deviations become increasingly prevalent. Although distinct ROI-associated pathomechanisms contribute to immunosenescence of the innate and adaptive immune system, mutual amplification of dysfunctions may often result in hyporesponsiveness and immunodeficiency, or in chronic inflammation with hyperresponsiveness/deregulation, or both. In this context, we point out how imbalanced ROI contribute ambiguously to driving immunosenescence, chronic inflammation and autoimmunity. Although ROI may offer a distinct potential for therapeutic targeting along with the charming opportunity to rescue from deleterious processes of aging and chronic inflammatory diseases, such modifications, owing to the complexity of metabolic interactions, may carry a marked risk of unforeseen side effects.

Lung injury after hemorrhage is age dependent: role of peroxisome proliferator-activated receptor gamma

OBJECTIVE

The incidence of multiple organ failure in pediatric trauma victims is lower than in the adult population. However, the molecular mechanisms are not yet defined. We investigated whether the pathophysiologic characteristics of hemorrhage-induced lung injury may be age dependent and may be regulated by the peroxisome proliferator-activated receptor gamma (PPARgamma).

DESIGN

Prospective, laboratory investigation that used an established rodent model of hemorrhagic shock.

SETTING

University hospital laboratory.

SUBJECTS

Young (n = 67; 3-5 months old) and mature (n = 66; 11-13 months old) male rats.

INTERVENTIONS

Hemorrhagic shock was induced in young and mature rats by withdrawing blood to a mean arterial blood pressure of 50 mm Hg. After 3 hours, rats were rapidly resuscitated by infusing the shed blood and killed 3 hours thereafter.

MEASUREMENTS AND MAIN RESULTS

In young rats, lung injury was characterized by accumulation of red cells and neutrophils at the end of the resuscitation period; on Western blot analysis, lung expression of intercellular adhesion molecule-1 was increased. In contrast, the severity of lung injury was more pronounced in mature rats. Lung myeloperoxidase activity and expression of constitutive and inducible intercellular adhesion molecule-1 was significantly higher in mature rats compared with young rats. Mature rats also had higher plasma levels of cytokines and chemokines compared with young rats. This heightened inflammation was associated with higher degree of activation of nuclear factor-kappaB and down-regulation of PPARgamma and heat shock factor-1 in the lung of mature rats compared with young rats. Treatment with the PPARgamma ligand, the cyclopentenone prostaglandin 15-deoxy-Delta-prostaglandin J2, ameliorated lung injury in young, but not in mature animals.

CONCLUSIONS

Lung injury after severe hemorrhage is age dependent and may be secondary to a diverse regulation of PPARgamma.

Accelerated healing of skin burns by anti-Gal/alpha-gal liposomes interaction

Topical application of alpha-gal liposomes on burns results in rapid local recruitment of neutrophils and macrophages. Recruited macrophages are pivotal for healing of burns because they secrete cytokines/growth factors that induce epidermis regeneration and tissue repair. alpha-Gal liposomes have glycolipids with alpha-gal epitopes (Galalpha1-3Galbeta1-4GlcNAc-R) which bind anti-Gal, the most abundant natural antibody in humans constituting approximately 1% of immunoglobulins. Interaction of alpha-gal liposomes with anti-Gal within the fluid film formed on burns, activates complement and generates chemotactic complement cleavage peptides which effectively recruit neutrophils and macrophages. Anti-Gal IgG coating alpha-gal liposomes further binds to Fcgamma receptors on macrophages and activates them to secrete cytokines/growth factors. Efficacy of alpha-gal liposomes treatment in accelerating burn healing is demonstrated in the experimental model of alpha1,3galactosyltransferase knockout mice. These mice are the only available nonprimate mammals that can produce anti-Gal in titers similar to those in humans. Pairs of burns in mice were covered either with a spot bandage coated with 10mg alpha-gal liposomes, or with a control spot bandage coated with saline. On Day 3 post-treatment, the alpha-gal liposomes treated burns contained approximately 5-fold as many neutrophils as control burns, whereas macrophages were found only in alpha-gal liposomes treated burns. On Day 6, 50-100% of the surface area of alpha-gal liposomes treated burns were covered with regenerating epidermis (re-epithelialization), whereas almost no epidermis was found in control burns. The extensive recruitment of macrophages by anti-Gal/alpha-gal liposomes interaction was further demonstrated in vivo with polyvinyl alcohol (PVA) sponge discs containing alpha-gal liposomes, implanted subcutaneously. Since anti-Gal is abundant in all humans, it is suggested that treatment with alpha-gal liposomes will be effective also in patients with burns and other skin wounds.

Burn injury reveals altered phenotype in mannan-binding lectin-deficient mice

Burn injury destroys skin, the second largest innate immune organ in the body, and triggers chaotic immune and inflammatory responses. The pattern recognition molecule, mannan-binding lectin (MBL), plays an important role in the first-line host defense against infectious agents. MBL initiates the lectin complement pathway and acts as an opsonin. Recent studies suggest that MBL also modulates inflammatory responses. We report that local responses after burn in MBL null mice differ from those found in wild-type (WT) mice in the following important biological markers: spontaneous eschar separation, thinned epidermis and dermis, upregulation of soluble factors including cytokines, chemokines, cell adhesion molecules, a growth factor-binding protein, and matrix metalloproteinases. Mice lacking C1q, C4, or C3 did not show the lack of eschar separation seen in MBL null-burn phenotype. These findings implicate MBL as an important molecule in the maintenance of the homeostatic balance.

Mechanisms of endothelial dysfunction in obesity

Obesity is a chronic disease, whose incidence is alarmingly growing, affecting not only adults but also children and adolescents. It is associated with severe metabolic abnormalities and increased cardiovascular morbidity and mortality. Adipose tissue secretes a great number of hormones and cytokines that not only regulate substrate metabolism but may deeply and negatively influence endothelial physiology, a condition which may lead to the formation of the atherosclerotic plaque. In this review, the physiology of the endothelium is summarised and the mechanisms by which obesity, through the secretory products of adipose tissue, influences endothelial function are explained. A short description of methodological approaches to diagnose endothelial dysfunction is presented. The possible pathogenetic links between obesity and cardiovascular disease, mediated by oxidative stress, inflammation and endothelial dysfunction are described as well.

Aging and innate immune cells

The innate immune system serves an important role in preventing microbial invasion. However, it experiences significant changes with advancing age. Among the age-associated changes are: Aged macrophages and neutrophils have impaired respiratory burst and reactive nitrogen intermediates as a result of altered intracellular signaling, rendering them less able to destroy bacteria. Aged neutrophils are also less able to respond to rescue from apoptosis. Aged dendritic cells (DC) are less able to stimulate T and B cells. The altered T cell stimulation is a result of changes in human leukocyte antigen expression and cytokine production, and lower B cell stimulation is a result of changes in DC immune complex binding. Natural killer (NK) cells from the elderly are less capable of destroying tumor cells. NK T cells increase in number and have greater interleukin-4 production with age. Levels of various complement components are also altered with advancing age.