Vaginal estrogen therapy is associated with increased Lactobacillus in the urine of postmenopausal women with overactive bladder symptoms

BACKGROUND

Previous work has shown that the vaginal microbiome decreases in Lactobacillus predominance and becomes more diverse after menopause. It has also been shown that estrogen therapy restores Lactobacillus dominance in the vagina and that topical estrogen is associated with overactive bladder symptom improvement. We now know that the bladder contains a unique microbiome and that increased bladder microbiome diversity is associated with overactive bladder. However, there is no understanding of how quickly each pelvic floor microbiome responds to estrogen or if those changes are associated with symptom improvement.

OBJECTIVE

This study aimed to determine if estrogen treatment of postmenopausal women with overactive bladder decreases urobiome diversity.

STUDY DESIGN

We analyzed data from postmenopausal participants in 2 trials (NCT02524769 and NCT02835846) who chose vaginal estrogen as the primary overactive bladder treatment and used 0.5 g of conjugated estrogen (Premarin cream; Pfizer, New York City, NY) twice weekly for 12 weeks. Baseline and 12-week follow-up data included the Overactive Bladder questionnaire, and participants provided urine samples via catheter, vaginal swabs, perineal swabs, and voided urine samples. Microbes were detected by an enhanced culture protocol. Linear mixed models were used to estimate microbiome changes over time. Urinary antimicrobial peptide activity was assessed by a bacterial growth inhibition assay and correlated with relative abundance of members of the urobiome.

RESULTS

In this study, 12 weeks of estrogen treatment resulted in decreased microbial diversity within the vagina (Shannon, P=.047; Richness, P=.043) but not in the other niches. A significant increase in Lactobacillus was detected in the bladder (P=.037) but not in the vagina (P=.33), perineum (P=.56), or voided urine (P=.28). The change in Lactobacillus levels in the bladder was associated with modest changes in urgency incontinence symptoms (P=.02). The relative abundance of the genus Corynebacterium correlated positively with urinary antimicrobial peptide activity after estrogen treatment.

CONCLUSION

Estrogen therapy may change the microbiome of different pelvic floor niches. The vagina begins to decrease in diversity, and the bladder experiences a significant increase in Lactobacillus levels; the latter is correlated with a modest improvement in the symptom severity subscale of the Overactive Bladder questionnaire.

Topical nicotinic receptor activation improves wound bacterial infection outcomes and TLR2-mediated inflammation in diabetic mouse wounds

The cholinergic anti-inflammatory pathway can directly affect skin antibacterial responses via nicotinic acetylcholine receptors (nAChRs). In particular, α7 nAChR (CHRNA7) present in the epidermis modulates the host response to wounding and/or wound bacterial infection. While physiologic inflammation is required to initiate normal wound repair and can be triggered by Toll-like receptor (TLR) activation, chronic inflammation is frequently observed in diabetic wounds and can occur, in part, via excessive TLR2 activation or production. Consequently, this can delay physiologic wound healing responses and increase diabetic host susceptibility to bacterial infection. In this study, we demonstrate that topical nAChR activation diminishes bacterial survival and systemic dissemination in a mouse model of diabetic wound infection, while reducing wound TLR2 production, relative to control mice. We further determined that the antimicrobial peptide activity of diabetic mouse wounds is increased compared to control mice, but this effect is lost following topical nAChR activation. Finally, we observed that human diabetic wounds exhibit impaired α7 nAChR (CHRNA7) abundance and localization relative to human control (nondiabetic) skin. These findings suggest that topical administration of nAChR agonists may improve wound healing and infection outcomes in diabetic wounds by dampening TLR2-mediated inflammation and antimicrobial peptide response, and that the diabetic microenvironment may promote aberrant CHRNA7 production/activation that likely contributes to diabetic wound pathogenesis.

Hyperglycaemia inhibits REG3A expression to exacerbate TLR3-mediated skin inflammation in diabetes

Dysregulated inflammatory responses are known to impair wound healing in diabetes, but the underlying mechanisms are poorly understood. Here we show that the antimicrobial protein REG3A controls TLR3-mediated inflammation after skin injury. This control is mediated by REG3A-induced SHP-1 protein, and acts selectively on TLR3-activated JNK2. In diabetic mouse skin, hyperglycaemia inhibits the expression of IL-17-induced IL-33 via glucose glycation. The decrease in cutaneous IL-33 reduces REG3A expression in epidermal keratinocytes. The reduction in REG3A is associated with lower levels of SHP-1, which normally inhibits TLR3-induced JNK2 phosphorylation, thereby increasing inflammation in skin wounds. To our knowledge, these findings show for the first time that REG3A can modulate specific cutaneous inflammatory responses and that the decrease in cutaneous REG3A exacerbates inflammation in diabetic skin wounds.

Patients with diabetes often have delayed wound healing, associated with excessive inflammation. Here the authors report that REG3A inhibits TLR3-driven inflammation in skin wounds, and show that REG3A is reduced in models of diabetes, which exacerbates inflammation in diabetic wounds.

Keratinocyte nicotinic acetylcholine receptor activation modulates early TLR2-mediated wound healing responses

The cholinergic anti-inflammatory pathway spans several macro- and micro-environments to control inflammation via α7 nicotinic acetylcholine receptors (nAChRs). Physiologic inflammation is necessary for normal wound repair and is triggered, in part, via Toll-like receptors (TLRs). Here, we demonstrate that keratinocyte nAChR activation dampens TLR2-mediated migration and pro-inflammatory cytokine and antimicrobial peptide (AMP) production, which is restored by a α7-selective nAChR antagonist. The mechanism of this response occurs by blocking the NF-κB and Erk1/2 pathway during early and late wound healing. In a mouse model of Staphylococcus aureus wound infection, topical nAChR activation reduces wound AMP and TLR2 production to augment bacterial survival in wild-type mice. These findings suggest that aberrant α7 nAChR activation may impair normal wound healing responses, and that pharmacologic administration of topical nAChR antagonists may improve wound healing outcomes in wounds necessitating a more robust inflammatory response.

Dynamic Role of Host Stress Responses in Modulating the Cutaneous Microbiome: Implications for Wound Healing and Infection

Significance: Humans are under constant bombardment by various stressors, including psychological anxiety and physiologic injury. Understanding how these stress responses influence the innate immune system and the skin microbiome remains elusive due to the complexity of the neuroimmune and stress response pathways. Both animal and human studies have provided critical information upon which to further elucidate the mechanisms by which mammalian stressors impair normal wound healing and/or promote chronic wound progression. Recent Advances: Development of high-throughput genomic and bioinformatic approaches has led to the discovery of both an epidermal and dermal microbiome with distinct characteristics. This technology is now being used to identify statistical correlations between specific microbiota profiles and clinical outcomes related to cutaneous wound healing and the response to pathogenic infection. Studies have also identified more prominent roles for typical skin commensal organisms in maintaining homeostasis and modulating inflammatory responses. Critical Issues: It is well-established that stress-induced factors, including catecholamines, acetylcholine, and glucocorticoids, increase the risk of impaired wound healing and susceptibility to infection. Despite the characterization of the cutaneous microbiome, little is known regarding the impact of these stress-induced molecules on the development and evolution of the cutaneous microbiome during wound healing. Future Directions: Further characterization of the mechanisms by which stress-induced molecules influence microbial proliferation and metabolism in wounds is necessary to identify altered microbial phenotypes that differentially influence host innate immune responses required for optimal healing. These mechanisms may yield beneficial as targets for manipulation of the microbiome to further benefit the host after cutaneous injury.

Interplay between bladder microbiota and urinary antimicrobial peptides: mechanisms for human urinary tract infection risk and symptom severity

Resident bacterial communities (microbiota) and host antimicrobial peptides (AMPs) are both essential components of normal host innate immune responses that limit infection and pathogen induced inflammation. However, their interdependence has not been investigated in the context of urinary tract infection (UTI) susceptibility. Here, we explored the interrelationship between the urinary microbiota and host AMP responses as mechanisms for UTI risk. Using prospectively collected day of surgery (DOS) urine specimens from female pelvic floor surgery participants, we report that the relative abundance and/or frequency of specific urinary microbiota distinguished between participants who did or did not develop a post-operative UTI. Furthermore, UTI risk significantly correlated with both specific urinary microbiota and β-defensin AMP levels. Finally, urinary AMP hydrophobicity and protease activity were greater in participants who developed UTI, and correlated positively with both UTI risk and pelvic floor symptoms. These data demonstrate an interdependency between the urinary microbiota, AMP responses and symptoms, and identify a potential mechanism for UTI risk. Assessment of bacterial microbiota and host innate immune AMP responses in parallel may identify increased risk of UTI in certain populations.

Episodic binge ethanol exposure impairs murine macrophage infiltration and delays wound closure by promoting defects in early innate immune responses

BACKGROUND

Exacerbation of cutaneous wound infections and delayed wound closure are frequent complications seen in alcohol exposed subjects who sustain injuries. We previously reported that acute alcohol exposure alters the early dermal inflammatory phase of wound healing and also several parameters of the proliferative wound healing phase in wounds from ethanol (EtOH)-treated mice for several days or weeks after EtOH exposure. Hence, it is likely that the cumulative defects arising in the early phases of the wound healing process directly contribute to the increased complications observed in intoxicated patients at the time of injury.

METHODS

C57BL/6 mice were given intraperitoneal EtOH (2.2 g/kg body weight) or vehicle (saline) EtOH using our episodic binge EtOH exposure protocol (3 days EtOH, 4 days off, 3 days EtOH) to yield a blood alcohol concentration (BAC) of 300 mg/dl at the time of wounding. Mice were subjected to six 3 mm full-thickness dorsal wounds and immediately treated topically with 10 μl of sterile saline (control) or diluted Staphylococcus aureus corresponding to 1 × 10(4) CFU/wound. Wounds were harvested at 24 hours post injury to evaluate wound area, neutrophil and macrophage accumulation, and the protein levels of cytokines, interleukin-6 (IL-6), IL-1β, and IL-10, and chemokines, macrophage inflammatory protein-2 (MIP-2) and MIP-1α, monocyte chemotactic protein-1 (MCP-1), and keratinocyte-derived chemokine (KC). The abundance and localization of cathelicidin-related antimicrobial peptide (CRAMP) and the kallikrein epidermal proteases (KLK5 and KLK7) were also determined.

RESULTS

Compared to control mice, EtOH-treated mice exhibited delayed wound closure, decreased macrophage accumulation, and impaired production of MIP-1α. Furthermore, skin from EtOH-treated mice demonstrated a reduction in the abundance of epidermal CRAMP and KLK7.

CONCLUSIONS

These findings suggest that EtOH exposure hinders several distinct components of the innate immune response, including phagocyte recruitment and chemokine/cytokine and AMP production. Together, these effects likely contribute to delayed wound closure and enhanced infection severity observed in intoxicated patients.

Interleukin-33 increases antibacterial defense by activation of inducible nitric oxide synthase in skin

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

Chronic alcohol exposure renders epithelial cells vulnerable to bacterial infection

Despite two centuries of reports linking alcohol consumption with enhanced susceptibility to bacterial infections and in particular gut-derived bacteria, there have been no studies or model systems to assess the impact of long-term alcohol exposure on the ability of the epithelial barrier to withstand bacterial infection. It is well established that acute alcohol exposure leads to reduction in tight and adherens junctions, which in turn leads to increases in epithelial cellular permeability to bacterial products, leading to endotoxemia and a variety of deleterious effects in both rodents and human. We hypothesized that reduced fortification at junctional structures should also reduce the epithelial barrier’s capacity to maintain its integrity in the face of bacterial challenge thus rendering epithelial cells more vulnerable to infection. In this study, we established a cell-culture based model system for long-term alcohol exposure to assess the impact of chronic alcohol exposure on the ability of Caco-2 intestinal epithelial cells to withstand infection when facing pathogenic bacteria under the intact or wounded conditions. We report that daily treatment with 0.2% ethanol for two months rendered Caco-2 cells far more susceptible to wound damage and cytotoxicity caused by most but not all bacterial pathogens tested in our studies. Consistent with acute alcohol exposure, long-term ethanol exposure also adversely impacted tight junction structures, but in contrast, it did not affect the adherens junction. Finally, alcohol-treated cells partially regained their ability to withstand infection when ethanol treatment was ceased for two weeks, indicating that alcohol’s deleterious effects on cells may be reversible.

Nicotinic acetylcholine receptor stimulation impairs epidermal permeability barrier function and recovery and modulates cornified envelope proteins

AIM

To characterize how nicotinic acetylcholine receptors (nAChRs) influence epidermal barrier function and recovery following prolonged stress or direct nAChR activation or antagonism.

MAIN METHODS

Mice were subjected to psychological stress or treated topically with nAChR agonist or antagonist for 3 days. We assessed barrier permeability and recovery by measuring transepidermal water loss (TEWL) before and after barrier disruption. In parallel, we analyzed the production and localization of several epidermal cornified envelope proteins in mouse skin and in human EpiDerm™ organotypic constructs stimulated with a nAChR agonist (nicotine) and/or a nAChR selective antagonist (α-bungarotoxin).

KEY FINDINGS

We determined that psychological stress in mice impairs barrier permeability function and recovery, an effect that is reversed by application of the α7 selective nAChR antagonist, α-bungarotoxin (Bung). In the absence of stress, both topical nicotine or Bung treatment alone impaired barrier permeability. We further observed that stress, topical nicotine, or topical Bung treatment in mice influenced the abundance and/or localization of filaggrin, loricrin, and involucrin. Similar alterations in these three major cornified envelope proteins were observed in human EpiDerm™ cultures.

SIGNIFICANCE

Perceived psychological stress and nicotine usage can both initiate or exacerbate several dermatoses by altering the cutaneous permeability barrier. Modulation of nAChRs by topical agonists or antagonists may be used to improve epidermal barrier function in skin diseases associated with defects in epidermal barrier permeability.

The antimicrobial protein REG3A regulates keratinocyte proliferation and differentiation after skin injury

Epithelial keratinocyte proliferation is an essential element of wound repair, and abnormal epithelial proliferation is an intrinsic element in the skin disorder psoriasis. The factors that trigger epithelial proliferation in these inflammatory processes are incompletely understood. Here we have shown that regenerating islet-derived protein 3-alpha (REG3A) is highly expressed in keratinocytes during psoriasis and wound repair and in imiquimod-induced psoriatic skin lesions. The expression of REG3A by keratinocytes is induced by interleukin-17 (IL-17) via activation of keratinocyte-encoded IL-17 receptor A (IL-17RA) and feeds back on keratinocytes to inhibit terminal differentiation and increase cell proliferation by binding to exostosin-like 3 (EXTL3) followed by activation of phosphatidylinositol 3 kinase (PI3K) and the kinase AKT. These findings reveal that REG3A, a secreted intestinal antimicrobial protein, can promote skin keratinocyte proliferation and can be induced by IL-17. This observation suggests that REG3A may mediate the epidermal hyperproliferation observed in normal wound repair and in psoriasis.

Sugar-coating wound repair: a review of FGF-10 and dermatan sulfate in wound healing and their potential application in burn wounds

Thousands of patients suffer from burn injuries each year, yet few therapies have been developed to accelerate the wound healing process. Most fibroblast growth factors (FGFs) have been extensively evaluated but only a few have been found to participate in the wound healing process. In particular, FGF-10 is robustly increased in the wound microenvironment after injury and has demonstrated some ability to promote wound healing in vitro and in vivo. Glycosaminoglycans are linear carbohydrates that participate in wound repair by influencing cytokine/growth factor localization and interaction with cognate receptors. Dermatan sulfate (DS) is the most abundant glycosaminoglycan in human wound fluid and has been postulated to be directly involved in the healing process. Recently, the combination of FGF-10 and DS demonstrated the potential to accelerate wound healing via increased keratinocyte proliferation and migration. Based on these preliminary studies, DS may serve as a cofactor for FGF-10, and together they are likely to expedite the healing process by stimulating keratinocyte activity. As a specific subtype of wounds, the overall healing process of burn injuries does not significantly differ from other types of wounds, where optimal repair results in matrix regeneration and complete reepithelialization. At present, standard burn treatment primarily involves topical application of antimicrobial agents, while no routine therapies target acceleration of reepithelialization, the key to wound closure. Thus, this novel therapeutic combination could be used in conjunction with some of the current therapies, but it would have the unique ability to initiate wound healing by stimulating keratinocyte epithelialization.

Alcohol exposure and mechanisms of tissue injury and repair

Tissue injury owing to acute and chronic alcohol consumption has extensive medical consequences, with the level and duration of alcohol exposure affecting both the magnitude of injury and the time frame to recovery. While the understanding of many of the molecular processes disrupted by alcohol has advanced, mechanisms of alcohol-induced tissue injury remain a subject of intensive research. Alcohol has multiple targets, as it affects diverse cellular and molecular processes. Some mechanisms of tissue damage as a result of alcohol may be common to many tissue types, while others are likely to be tissue specific. Here, we present a discussion of the alcohol-induced molecular and cellular disruptions associated with injury or recovery from injury in bone, muscle, skin, and gastric mucosa. In every case, the goal of characterizing the sites of alcohol action is to devise potential measures for protection, prevention, or therapeutic intervention.

Neuroendocrine nicotinic receptor activation increases susceptibility to bacterial infections by suppressing antimicrobial peptide production

Stress mobilizes elements from the neuroendocrine system to modulate immune responses. Cholinergic stimulation via nicotinic receptor (nAchR) is a major neuroendocrine signaling axis associated with the stress response whose specific effects on the immune system are unknown. Here, we show that nAchR activation by topical agonist application or deletion of the nAChR antagonist catestatin (Chga(-/-)) reduced antimicrobial peptide (AMP) activity in skin extracts and increased susceptibility to methicillin-resistant Staphylococcus aureus and Group A Streptococcus infections. The adverse effects on AMP expression and infection were rescued by topical application of a nAChR antagonist. Stress-induced nAChR activation increased infection in wild-type, but not Chga(-/-) or cathelicidin-deficient, mice. These data identify a mechanism for the negative regulation of host-innate AMP response to infection through cholinergic activation and indicate nAChR-mediated cathelicidin dysregulation as a potential mechanism for increased susceptibility to infection following prolonged stress or nicotine use.

Activation of TLR2 by a small molecule produced by Staphylococcus epidermidis increases antimicrobial defense against bacterial skin infections

Production of antimicrobial peptides by epithelia is an essential defense against infectious pathogens. In this study we evaluated whether the commensal microorganism Staphylococcus epidermidis may enhance production of antimicrobial peptides by keratinocytes and thus augment skin defense against infection. Exposure of cultured undifferentiated human keratinocytes to a sterile nontoxic small molecule of <10 kDa from S. epidermidis conditioned culture medium (SECM), but not similar preparations from other bacteria, enhanced human beta-defensin 2 (hBD2) and hBD3 mRNA expression and increased the capacity of cell lysates to inhibit the growth of group A Streptococcus (GAS) and S. aureus. Partial gene silencing of hBD3 inhibited this antimicrobial action. This effect was relevant in vivo as administration of SECM to mice decreased susceptibility to infection by GAS. Toll-like receptor 2 (TLR2) was important to this process as a TLR2-neutralizing antibody blocked induction of hBDs 2 and 3, and Tlr2-deficient mice did not show induction of mBD4. Taken together, these findings reveal a potential use for normal commensal bacterium S. epidermidis to activate TLR2 signaling and induce antimicrobial peptide expression, thus enabling the skin to mount an enhanced response to pathogens.

Antimicrobial anxiety: the impact of stress on antimicrobial immunity

Leukocytes and epithelial cells are fundamental to antimicrobial immunity. Their antimicrobial responses are an evolutionarily conserved component of the innate immune system and are influenced by the host's response to external stimuli. The efficacy of host defense via antimicrobial responses derives from the ability of AMPs to rapidly identify and eradicate foreign microbes and activate proinflammatory pathways, and from the capacity of later innate and adaptive immune responses to amplify protection through distinct biochemical mechanisms. Recent advances in neuroimmunology have identified a direct link between the neuroendocrine and immune systems, where environmental stimuli are generally believed to promote a transient effect on the immune system in response to environmental challenges and are presumably brought back to baseline levels via neuroendocrine pathways. Stress is an environmental stimulus that flares from a variety of circumstances and has become engrained in human society. Small bouts of stress are believed to enhance the host's immune response; however, prolonged periods of stress can be detrimental through excess production of neuroendocrine-derived mediators that dampen immune responses to invasive pathogens. Elucidation of the mechanisms behind stress-induced immune modulation of antimicrobial responses will ultimately lead to the development of more effective therapeutic interventions for pathologic conditions. It is the intent of this review to broaden the existing paradigm of how stress-related molecules dampen immune responses through suppression of antimicrobial mechanisms, and to emphasize that bacteria can use these factors to enhance microbial pathogenesis during stress.

Commensal bacteria regulate Toll-like receptor 3-dependent inflammation after skin injury

The normal microflora of the skin includes staphylococcal species that will induce inflammation when present below the dermis but are tolerated on the epidermal surface without initiating inflammation. Here we reveal a previously unknown mechanism by which a product of staphylococci inhibits skin inflammation. This inhibition is mediated by staphylococcal lipoteichoic acid (LTA), and acts selectively on keratinocytes triggered through Toll-like receptor (TLR) 3. The significance of this is seen by observations that TLR3 activation is required for normal inflammation after injury, and that keratinocytes require TLR3 to respond to RNA from damaged cells with the release of inflammatory cytokines. Staphylococcal LTA inhibits both inflammatory cytokine release from keratinocytes and inflammation triggered by injury through a TLR2-dependent mechanism. These findings show for the first time that the skin epithelium requires TLR3 for normal inflammation after wounding and that the microflora can modulate specific cutaneous inflammatory responses.

Neutrophil antimicrobial defense against Staphylococcus aureus is mediated by phagolysosomal but not extracellular trap-associated cathelicidin

Neutrophils kill invading pathogens by AMPs, including cathelicidins, ROS, and NETs. The human pathogen Staphylococcus aureus exhibits enhanced resistance to neutrophil AMPs, including the murine cathelicidin CRAMP, in part, as a result of alanylation of teichoic acids by the dlt operon. In this study, we took advantage of the hypersusceptible phenotype of S. aureus DeltadltA against cationic AMPs to study the impact of the murine cathelicidin CRAMP on staphylococcal killing and to identify its key site of action in murine neutrophils. We demonstrate that CRAMP remained intracellular during PMN exudation from blood and was secreted upon PMA stimulation. We show first evidence that CRAMP was recruited to phagolysosomes in infected neutrophils and exhibited intracellular activity against S. aureus. Later in infection, neutrophils produced NETs, and immunofluorescence revealed association of CRAMP with S. aureus in NETs, which similarly killed S. aureus wt and DeltadltA, indicating that CRAMP activity was reduced when associated with NETs. Indeed, the presence of DNA reduced the antimicrobial activity of CRAMP, and CRAMP localization in response to S. aureus was independent of the NADPH oxidase, whereas killing was partially dependent on a functional NADPH oxidase. Our study indicates that neutrophils use CRAMP in a timed and locally coordinated manner in defense against S. aureus.

Brewing complications: the effect of acute ethanol exposure on wound healing

Ethanol consumption is linked to a higher incidence of traumatic wounds and increases the risk for morbidity and mortality following surgical or traumatic injury. One of the most profound effects of acute ethanol exposure on wound healing occurs during the inflammatory response, and altered cytokine production is a primary component. Acute ethanol exposure also impairs the proliferative response during healing, causing delays in epithelial coverage, collagen synthesis, and blood vessel regrowth. The accumulated data support the paradigm that acute ethanol intoxication prior to injury significantly diminishes a patient's ability to heal efficiently.

FGF-10 and specific structural elements of dermatan sulfate size and sulfation promote maximal keratinocyte migration and cellular proliferation

Fibroblast growth factor-10 (FGF-10) is essential for epithelial development, while other members of this family, such as FGF-7, are not. FGF-10 is abundantly released into wounds following injury, and likely an essential growth factor required for this process. To evaluate how activation of this growth factor is controlled, multiple glycosaminoglycans were combined with FGF-10 assayed by measurement of the proliferation of cell lines expressing FGF receptor-2-IIIb, or keratinocyte migration in an in vitro wound repair assay. Dermatan sulfate (DS) exhibited greater potency than heparan sulfate or other chondroitin sulfates found in wounds. Structural variants of DS between 10 and 20 disaccharides containing iduronic acid showed maximal capacity to enable FGF-10 receptor stimulation. Furthermore, FGF-10 and DS markedly enhanced migration of keratinocytes in an in vitro wound scratch assay, while FGF-7 or other glycosaminoglycans did not. These data strongly suggest that FGF-10 activity is uniquely important in wound repair and that specific DS structural properties are necessary to promote FGF-10 function. These observations identify a novel interplay between DS and FGF-10 in mediating wound repair.

Acute ethanol exposure disrupts VEGF receptor cell signaling in endothelial cells

Physiological angiogenesis is regulated by various factors, including signaling through vascular endothelial growth factor (VEGF) receptors. We previously reported that a single dose of ethanol (1.4 g/kg), yielding a blood alcohol concentration of 100 mg/dl, significantly impairs angiogenesis in murine wounds, despite adequate levels of VEGF, suggesting direct effects of ethanol on endothelial cell signaling (40). To examine the mechanism by which ethanol influences angiogenesis in wounds, we employed two different in vitro angiogenesis assays to determine whether acute ethanol exposure (100 mg/dl) would have long-lasting effects on VEGF-induced capillary network formation. Ethanol exposure resulted in reduced VEGF-induced cord formation on collagen and reduced capillary network structure on Matrigel in vitro. In addition, ethanol exposure decreased expression of endothelial VEGF receptor-2, as well as VEGF receptor-2 phosphorylation in vitro. Inhibition of ethanol metabolism by 4-methylpyrazole partially abrogated the effect of ethanol on endothelial cell cord formation. However, mice treated with t-butanol, an alcohol not metabolized by alcohol dehydrogenase, exhibited no change in wound vascularity. These results suggest that products of ethanol metabolism are important factors in the development of ethanol-induced changes in endothelial cell responsiveness to VEGF. In vivo, ethanol exposure caused both decreased angiogenesis and increased hypoxia in wounds. Moreover, in vitro experiments demonstrated a direct effect of ethanol on the response to hypoxia in endothelial cells, as ethanol diminished nuclear hypoxia-inducible factor-1alpha protein levels. Together, the data establish that acute ethanol exposure significantly impairs angiogenesis and suggest that this effect is mediated by changes in endothelial cell responsiveness to both VEGF and hypoxia.

Psychological stress downregulates epidermal antimicrobial peptide expression and increases severity of cutaneous infections in mice

The skin is the first line of defense against microbial infection, and psychological stress (PS) has been shown to have adverse effects on cutaneous barrier function. Here we show that PS increased the severity of group A Streptococcus pyogenes (GAS) cutaneous skin infection in mice; this was accompanied by increased production of endogenous glucocorticoids (GCs), which inhibited epidermal lipid synthesis and decreased lamellar body (LB) secretion. LBs encapsulate antimicrobial peptides (AMPs), and PS or systemic or topical GC administration downregulated epidermal expression of murine AMPs cathelin-related AMP and beta-defensin 3. Pharmacological blockade of the stress hormone corticotrophin-releasing factor or of peripheral GC action, as well as topical administration of physiologic lipids, normalized epidermal AMP levels and delivery to LBs and decreased the severity of GAS infection during PS. Our results show that PS decreases the levels of 2 key AMPs in the epidermis and their delivery into LBs and that this is attributable to increased endogenous GC production. These data suggest that GC blockade and/or topical lipid administration could normalize cutaneous antimicrobial defense during PS or GC increase. We believe this to be the first mechanistic link between PS and increased susceptibility to infection by microbial pathogens.

Mechanical unloading impairs keratinocyte migration and angiogenesis during cutaneous wound healing

Although initially thought to improve an individual's ability to heal, mechanical unloading promoted by extended periods of bed rest has emerged as a contributing factor to delayed or aberrant tissue repair. Using a rat hindlimb unloading (HLU) model of hypogravity, we mimicked some aspects of physical inactivity by removing weight-bearing loads from the hindlimbs and producing a systemic cephalic fluid shift. This model simulates bed rest in that the animal undergoes physiological adaptations, resulting in a reduction in exercise capability, increased frequency of orthostatic intolerance, and a reduction in plasma volume. To investigate whether changes associated with prior prolonged bed rest correlate with impaired cutaneous wound healing, we examined wound closure, angiogenesis, and collagen content in day 2 to day 21 wounds from rats exposed to HLU 2 wk before excisional wounding. Wound closure was delayed in day 2 wounds from HLU rats compared with ambulatory controls. Although the levels of proangiogenic growth factors, fibroblast growth factor-2 (FGF-2), and vascular endothelial growth factor (VEGF) were similar between the two groups, wound vascularity was significantly reduced in day 7 wounds from HLU animals. To further examine this disparity, total collagen content was assessed but found to be similar between the two groups. Taken together, these results suggest that keratinocyte and endothelial cell function may be impaired during the wound healing process under periods of prolonged inactivity or bed rest.

The neuroendocrine peptide catestatin is a cutaneous antimicrobial and induced in the skin after injury

Epithelia establish a microbial barrier against infection through the production of antimicrobial peptides (AMPs). In this study, we investigated whether catestatin (Cst), a peptide derived from the neuroendocrine protein chromogranin A (CHGA), is a functional AMP and is present in the epidermis. We show that Cst is antimicrobial against relevant skin microbes, including gram-positive and gram-negative bacteria, yeast, and fungi. The antimicrobial mechanism of Cst was found to be similar to other AMPs, as it was dependent on bacterial charge and growth conditions, and induced membrane disruption. The potential relevance of Cst against skin pathogens was supported by the observation that CHGA was expressed in keratinocytes. In human skin, CHGA was found to be proteolytically processed into the antimicrobial fragment Cst, thus enabling its AMP function. Furthermore, Cst expression in murine skin increased in response to injury and infection, providing potential for increased protection against infection. These data demonstrate that a neuroendocrine peptide has antimicrobial function against a wide assortment of skin pathogens and is upregulated upon injury, thus demonstrating a direct link between the neuroendocrine and cutaneous immune systems. JID JOURNAL CLUB ARTICLE: For questions, answers, and open discussion about this article please go to http://network.nature.com/group/jidclub.

Genetic alteration of endothelial heparan sulfate selectively inhibits tumor angiogenesis

To examine the role of endothelial heparan sulfate during angiogenesis, we generated mice bearing an endothelial-targeted deletion in the biosynthetic enzyme N-acetylglucosamine N-deacetylase/N-sulfotransferase 1 (Ndst1). Physiological angiogenesis during cutaneous wound repair was unaffected, as was growth and reproductive capacity of the mice. In contrast, pathological angiogenesis in experimental tumors was altered, resulting in smaller tumors and reduced microvascular density and branching. To simulate the angiogenic environment of the tumor, endothelial cells were isolated and propagated in vitro with proangiogenic growth factors. Binding of FGF-2 and VEGF(164) to cells and to purified heparan sulfate was dramatically reduced. Mutant endothelial cells also exhibited altered sprouting responses to FGF-2 and VEGF(164), reduced Erk phosphorylation, and an increase in apoptosis in branching assays. Corresponding changes in growth factor binding to tumor endothelium and apoptosis were also observed in vivo. These findings demonstrate a cell-autonomous effect of heparan sulfate on endothelial cell growth in the context of tumor angiogenesis.

Matrix proteolytic activity during wound healing: modulation by acute ethanol exposure

BACKGROUND

Clinical studies demonstrate that intoxicated patients exhibit an increased incidence of wound healing complications. Previous studies in a murine excisional wound model revealed that acute ethanol exposure impairs the wound healing response, causing decreased angiogenesis and a significant reduction in wound collagen content.

METHODS

Using the same murine model of excisional wounding, we examined the effect of a single dose of ethanol on the overall collagen content and collagen type I and type III mRNA expression, transforming growth factor-beta (TGF-beta) production, and levels of several components of the extracellular matrix proteolytic cascade.

RESULTS

Wounds from ethanol-treated mice exhibited a significant decrease in collagen and in the production of collagen type I mRNA compared with saline controls. Exposure to ethanol also caused significant increase in wound TGF-beta by day 2 after injury (1.69 +/- 0.29 vs 12.34 +/- 3.97 pg/microg protein, p<0.01). In addition, wounds from mice exposed to ethanol had significantly increased levels of active urokinase plasminogen activator at day 7, (205.10 +/- 48.79 vs 642.70 +/- 159.80 pg/microg protein, p<0.001). The level of matrix metalloproteinase-8, a collagen type I proteinase, was 2.2-fold higher in wounds of ethanol-treated mice compared with control at day 7 (p<0.05).

CONCLUSIONS

These studies demonstrate that a single dose of ethanol decreases collagen production, increases the production of TGF-beta and increases levels of matrix degrading enzymes. This alteration in protease balance may partially explain the impaired wound healing that follows acute alcohol intoxication.

Recognition of hyaluronan released in sterile injury involves a unique receptor complex dependent on Toll-like receptor 4, CD44, and MD-2

Inflammation under sterile conditions is not well understood despite its importance in trauma and autoimmune disease. To investigate this process we established mouse models of sterile injury and explored the role of hyaluronan in mediating inflammation following injury. The response of cultured monocytes to hyaluronan was different than the response to lipopolysaccharide (LPS) despite both being dependent on Toll-like receptor 4 (TLR4). Cultured cells exposed to hyaluronan showed a pattern of gene induction that mimics the response seen in mouse skin after sterile injury with an increase in molecules such as transforming growth factor-beta2 and matrix metalloproteinase-13. These factors were not induced by LPS despite the mutual dependence of both hyaluronan and LPS on TLR4. Explanation for the unique response to hyaluronan was provided by observations that a lack of TLR4 or CD44 in mice diminished the response to sterile injury, and together with MD-2, was required for responsiveness to hyaluronan in vitro. Thus, a unique complex of TLR4, MD-2, and CD44 recognizes hyaluronan. Immunoprecipitation experiments confirmed the physical association of TLR4 and CD44. Taken together, our results define a previously unknown mechanism for initiation of sterile inflammation that involves recognition of released hyaluronan fragments as an endogenous signal of tissue injury.

Effects of acute ethanol exposure on the early inflammatory response after excisional injury

BACKGROUND

Alcohol consumption is involved in over half of all trauma-related injuries. These patients are known to exhibit a higher incidence of mortality and morbidity following injury compared with patients not exposed to ethanol. As studies from our laboratory demonstrated that ethanol exposure impairs re-epithelialization and angiogenesis after dermal wounding and because the earlier inflammatory phase of wound healing is likely to influence later responses, we chose to examine neutrophil infiltration and chemokine and proinflammatory cytokine levels in the skin following administration of a dermal excisional wound.

METHODS

BALB/c mice were given ethanol at a dose designed to increase blood alcohol concentration to 100 to 120 mg/dL at 30 minutes after treatment. Mice were then subjected to a full-thickness excisional wound. Wounds from ethanol and saline-treated mice were collected within the first 24 hours postinjury to assess neutrophil infiltration and myeloperoxidase (MPO) activity, neutrophil chemoattractant macrophage inflammatory protein-2 (MIP-2) and KC levels, and proinflammatory cytokine interleukin-1 beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha) levels.

RESULTS

At 12 and 24 hours after injury, MPO in wounds from ethanol-exposed mice was significantly reduced compared with wounds from vehicle-treated animals. Despite this, histological examination of wounds did not reveal a difference in neutrophil infiltration between the 2 groups. Peak levels of MIP-2 and KC observed at 12 hours postinjury were decreased in wounds from ethanol-treated mice by 32 and 45%, respectively, relative to wounds from control mice. Levels of TNFalpha and IL-1beta (potent inducers of MIP-2 and KC, as well as neutrophil activation) were also assessed. Levels of TNFalpha were not elevated in either group after injury. However, IL-1beta demonstrated significantly lower peak levels at 6 hours postinjury in wounds from ethanol-treated mice, 58% less than wounds from controls.

CONCLUSION

These studies reveal that early dermal inflammatory responses including MPO activity, production of MIP-2, KC, and IL-1beta are impaired in mice given ethanol before injury, which may also have detrimental affects on later stages of wound healing.

Novel Function for Vascular Endothelial Growth Factor Receptor-1 on Epidermal Keratinocytes

Vascular endothelial growth factor (VEGF-A), a potent stimulus for angiogenesis, is up-regulated in the skin after wounding. Although studies have shown that VEGF is important for wound repair, it is unclear whether this is based solely on its ability to promote angiogenesis or if VEGF can also promote healing by acting directly on non-endothelial cell types. By immunohistochemistry and reverse transcriptase-polymerase chain reaction, expression of VEGF receptor-1 (VEGFR-1), but not VEGFR-2, was detected in murine keratinocytes during wound repair and in normal human epidermal keratinocytes (NHEKs). The presence of VEGF receptors on NHEKs was verified by binding studies with 125I-VEGF. In vitro, VEGF stimulated the proliferation of NHEKs, an effect that could be blocked by treatment with neutralizing VEGFR-1 antibodies. A role for VEGFR-1 in keratinocytes was also shown in vivo because treatment of excisional wounds with neutralizing VEGFR-1 antibodies delayed re-epithelialization. Treatment with anti-VEGFR-1 antibodies also reduced the number of proliferating keratinocytes at the leading edge of the wound, suggesting that VEGF sends a proliferative signal to these cells. Together, these data describe a novel role for VEGFR-1 in keratinocytes and suggest that VEGF may play several roles in cutaneous wound repair.

Acute ethanol exposure impairs angiogenesis and the proliferative phase of wound healing

Acute ethanol exposure represents an increased risk factor for morbidity and mortality associated with surgical or traumatic injury. Despite clinical observations suggesting that ethanol exposure before injury alters tissue repair processes, little direct evidence about the mechanism by which ethanol affects the wound healing process is available. In this study, excisional wounds from female BALB/c mice with or without circulating ethanol levels of 100 mg/dl were used to assess wound closure, angiogenesis, and collagen content. Ethanol exposure resulted in a significant but transient delay in wound closure at day 2 postwounding (28 +/- 4% vs. 17 +/- 1%). In addition, total collagen content was significantly reduced by up to 37% in wounds from ethanol-treated mice compared with controls. The most significant effect of ethanol exposure on wounds was on vascularity because angiogenesis was reduced by up to 61% in wounds from ethanol-treated mice. The reduction in vessel density occurred despite near-normal levels of proangiogenic factors VEGF and FGF-2, suggesting a direct effect of ethanol exposure on endothelial cell function. Further evidence for a direct effect was observed in an in vitro angiogenesis assay because the exposure of endothelial cells to ethanol reduced angiogenic responsiveness to just 8.33% of control in a cord-forming assay. These studies provide novel information regarding the effect of a single dose of ethanol on multiple parameters of the wound healing process in vivo and suggest a potential mechanism by which ethanol impairs healing after traumatic injury.