Cathelicidin impact on inflammatory cells

Inhalation Delivery of Host Defense Peptides (HDP) using Nano- Formulation Strategies: A Pragmatic Approach for Therapy of Pulmonary Ailments

Host defense peptides (HDP) are small cationic molecules released by the immune systems of the body, having multidimensional properties including anti-inflammatory, anticancer, antimicrobial and immune-modulatory activity. These molecules gained importance due to their broad-spectrum pharmacological activities, and hence being actively investigated. Presently, respiratory infections represent a major global health problem, and HDP has an enormous potential to be used as an alternative therapeutics against respiratory infections and related inflammatory ailments. Because of their short half-life, protease sensitivity, poor pharmacokinetics, and first-pass metabolism, it is challenging to deliver HDP as such inside the physiological system in a controlled way by conventional delivery systems. Many HDPs are efficacious only at practically high molar-concentrations, which is not convincing for the development of drug regimen due to their intrinsic detrimental effects. To avail the efficacy of HDP in pulmonary diseases, it is essential to deliver an appropriate payload into the targeted site of lungs. Inhalable HDP can be a potentially suitable alternative for various lung disorders including tuberculosis, Cystic fibrosis, Pneumonia, Lung cancer, and others as they are active against resistant microbes and cells and exhibit improved targeting with reduced adverse effects. In this review, we give an overview of the pharmacological efficacy of HDP and deliberate strategies for designing inhalable formulations for enhanced activity and issues related to their clinical implications.

The roles of vitamin D and cathelicidin in type 1 diabetes susceptibility

Type 1 diabetes has an increasingly greater incidence and prevalence with no cure available. Vitamin D supplementation is well documented to reduce the risk of developing type 1 diabetes. Being involved in the modulation of cathelicidin expression, the question whether cathelicidin may be one of the underlying cause arises. Cathelicidin has been implicated in both the development and the protection against type 1 diabetes by mediating the interplay between the gut microbiome, the immune system and β cell function. While its potential on type 1 diabetes treatment seems high, the understanding of its effects is still limited. This review aims to contribute to a more comprehensive understanding of the potential of vitamin D and cathelicidin as adjuvants in type 1 diabetes therapy.

[The role of vitamin D in seasonal acute respiratory viral infections and COVID-19]

A link between vitamin D deficiency and susceptibility to infectious diseases was suggested over a hundred years ago. Epidemiological studies show a strong association between seasonal fluctuations in vitamin D levels and the incidence of various infectious diseases, including septic shock, acute respiratory infections, and influenza. Our understanding of vitamin D metabolism and its extra-skeletal functions has improved significantly over the past three decades, and the discovery that the vitamin D receptor and 1a-hydroxylase, an enzyme needed to convert vitamin D to its active form, is present in the cells of the immune system, revolutionized in this area. Recent studies have shown that vitamin D regulates the expression of specific endogenous antimicrobial peptides in immune cells, modulates the immune response and the course of autoimmune processes; these actions indicate the potential role of vitamin D in modulating the immune response to various infectious diseases. This publication reviews the literature on the effects of vitamin D on immunity, its potential in the prevention and treatment of viral diseases, with a particular focus on COVID-19.

COVID-19 Disease and Vitamin D: A Mini-Review

Novel coronavirus disease (COVID-19) pandemic caused by SARS-CoV-2, for which there is no effective treatment except employing prevention strategies, has already instituted significant number of deaths. In this review, we provide a scientific view on the potential role of vitamin D in SARS-CoV-2 virus/COVID-19 disease. Vitamin D is well-known to play a significant role in maintaining the immune health of an individual. Moreover, it induces antimicrobial peptide expression that can decrease viral replication and regulate the levels of pro-inflammatory/anti-inflammatory cytokines. Therefore, supplementation of vitamin D has the potential to reduce the incidence, severity and the risk of death from pneumonia resulting from the cytokine storm of many viral infections including COVID-19. We suggest that supplementation of subjects at high risk of COVID-19 with vitamin D (1.000 to 3.000 IU) to maintain its optimum serum concentrations may be of significant benefit for both in the prevention and treatment of the COVID-19.

Synthetic Host Defense Peptides Inhibit Venezuelan Equine Encephalitis Virus Replication and the Associated Inflammatory Response

Venezuelan equine encephalitis virus (VEEV), a New World alphavirus of the Togaviridae family of viruses causes periodic outbreaks of disease in humans and equines. Disease following VEEV infection manifests as a febrile illness with flu-like symptoms, which can progress to encephalitis and cause permanent neurological sequelae in a small number of cases. VEEV is classified as a category B select agent due to ease of aerosolization and high retention of infectivity in the aerosol form. Currently, there are no FDA-approved vaccines or therapeutics available to combat VEEV infection. VEEV infection in vivo is characterized by extensive systemic inflammation that can exacerbate infection by potentially increasing the susceptibility of off-site cells to infection and dissemination of the virus. Hence, a therapeutic targeting both the infection and associated inflammation represents an unmet need. We have previously demonstrated that host defense peptides (HDPs), short peptides that are key components of the innate immune response, exhibit antiviral activity against a multitude of viruses including VEEV. In this study, we designed synthetic peptides derived from indolicidin, a naturally occurring HDP, and tested their efficacy against VEEV. Two candidate synthetic peptides inhibited VEEV replication by approximately 1000-fold and decreased the expression of inflammatory mediators such as IL1α, IL1β, IFNγ, and TNFα at both the gene and protein expression levels. Furthermore, an increase in expression levels of genes involved in chemotaxis of leukocytes and anti-inflammatory genes such as IL1RN was also observed. Overall, we conclude that our synthetic peptides inhibit VEEV replication and the inflammatory burden associated with VEEV infection.

Old Polyanionic Drug Suramin Suppresses Detrimental Cytotoxicity of the Host Defense Peptide LL-37

The host defense peptide LL-37 is the only human cathelicidin, characterized by pleiotropic activity ranging from immunological to anti-neoplastic functions. However, its overexpression has been associated with harmful inflammatory responses and apoptosis. Thus, for the latter cases, the development of strategies aiming to reduce LL-37 toxicity is highly desired as these have the potential to provide a viable solution. Here, we demonstrate that the reduction of LL-37 toxicity might be achieved by the impairment of its cell surface binding through interaction with small organic compounds that are able to alter the peptide conformation and minimize its cell penetration ability. In this regard, the performed cell viability and internalization studies showed a remarkable attenuation of LL-37 cytotoxicity toward colon and monocytic cells in the presence of the polysulfonated drug suramin. The mechanistic examinations of the molecular details indicated that this effect was coupled with the ability of suramin to alter LL-37 secondary structure via the formation of peptide-drug complexes. Moreover, a comparison with other therapeutic agents having common features unveiled the peculiar ability of suramin to optimize the binding to the peptide sequence. The newly discovered suramin action is hoped to inspire the elaboration of novel repurposing strategies aimed to reduce LL-37 cytotoxicity under pathological conditions.

"What Doesn't Kill You Makes You Stronger": Future Applications of Amyloid Aggregates in Biomedicine

Amyloid proteins are linked to the pathogenesis of several diseases including Alzheimer's disease, but at the same time a range of functional amyloids are physiologically important in humans. Although the disease pathogenies have been associated with protein aggregation, the mechanisms and factors that lead to protein aggregation are not completely understood. Paradoxically, unique characteristics of amyloids provide new opportunities for engineering innovative materials with biomedical applications. In this review, we discuss not only outstanding advances in biomedical applications of amyloid peptides, but also the mechanism of amyloid aggregation, factors affecting the process, and core sequences driving the aggregation. We aim with this review to provide a useful manual for those who engineer amyloids for innovative medicine solutions.

Cryptosporidium parvum Subverts Antimicrobial Activity of CRAMP by Reducing Its Expression in Neonatal Mice

Cryptosporidium parvum causes diarrhea in infants under 5 years, in immunosuppressed individuals or in young ruminants. This parasite infects the apical side of ileal epithelial cells where it develops itself and induces inflammation. Antimicrobial peptides (AMPs) are part of the innate immune response, playing a major role in the control of the acute phase of C. parvum infection in neonates. Intestinal AMP production in neonates is characterized by high expressions of Cathelicidin Related Antimicrobial Peptide (CRAMP), the unique cathelicidin in mice known to fight bacterial infections. In this study, we investigated the role of CRAMP during cryptosporidiosis in neonates. We demonstrated that sporozoites are sensitive to CRAMP antimicrobial activity. However, during C. parvum infection the intestinal expression of CRAMP was significantly and selectively reduced, while other AMPs were upregulated. Moreover, despite high CRAMP expression in the intestine of neonates at homeostasis, the depletion of CRAMP did not worsen C. parvum infection. This result might be explained by the rapid downregulation of CRAMP induced by infection. However, the exogenous administration of CRAMP dampened the parasite burden in neonates. Taken together these results suggest that C. parvum impairs the production of CRAMP to subvert the host response, and highlight exogenous cathelicidin supplements as a potential treatment strategy.

Antimicrobial peptides as an argument for the involvement of innate immunity in psoriasis (Review)

Antimicrobial peptides (AMPs) are a group of oligopeptides found in most multicellular organisms with a capacity for rapid and nonspecific destruction of pathogens. The action of destroying pathogens is associated with a strong proinflammatory activity, stimulating the secretion of cytokines, chemokines, growth factors but also chemotaxis, the activation of dendritic cells and involving adaptive immunity also. The action of AMPs fits perfectly into the characteristics of innate immunity which makes these peptides candidates to be considered as an important element of this type of immunity. It has been shown that AMPs are involved in a number of cellular processes such as: differentiation, proliferation, maturation, thus widening the degree of involvement of these peptides in the pathogenesis of chronic inflammatory diseases. In psoriasis, AMPs act both as a pro-inflammatory and chemotaxis factor and through the cathelicidin (LL-37)/dc DNA complex as a possible autoantigen for T cells, triggering an autoimmune response, activating the Th17/IL23 axis and maintaining the inflammatory process. Thus, many arguments are accumulated to consider that innate immunity through AMPs is an important link in the pathogenesis of psoriasis. Moreover, the action of antimicrobial peptides in psoriasis is almost entirely characteristic for the general mode of action of innate immunity.

Host genetics and tumor environment determine the functional impact of neutrophils in mouse tumor models

Background

Neutrophils have been reported to have protumor, antitumor or neutral effects in cancer progression. The underlying causes for this functional variability are not clear.

Methods

We studied the role of neutrophils in six different mouse tumor models by intratumoral injection of antimicrobial peptides or vaccination. Changes in systemic and intratumoral immune cells were analyzed by flow-cytometry and mass-cytometry. The role of neutrophils was studied by antibody-mediated neutrophil depletion. Neutrophils from different mouse strains were compared by RNA sequencing.

Results

The antimicrobial peptide Omiganan reduced the growth of TC-1 tumors in BL/6 mice and CT26 tumors in BALB/c mice. No significant effects were observed in B16F10, MC38 and 4T1 tumors. Growth delay was associated with increased abundance of neutrophils in TC-1 but not CT26 tumors. Systemic neutrophil depletion abrogated Omiganan efficacy in TC-1 but further reduced growth of CT26, indicating that neutrophils were required for the antitumor effect in TC-1 but suppressed tumor control in CT26. Neutrophils were also required for a therapeutic vaccine-induced T-cell mediated control of RMA tumors in BL/6 mice. Clearly, the circulating and intratumoral neutrophils differed in the expression of Ly6G and CD62L, between TC-1 and CT26 and between blood neutrophils of tumor-naïve BL/6 and BALB/c mice. RNA-sequencing revealed that neutrophils from BL/6 mice but not BALB/c mice displayed a robust profile of immune activation, matching their opposing roles in TC-1 and RMA versus CT26.

Conclusions

Neutrophil functionality differs strongly between mouse strains and tumor types, with consequences for tumor progression and therapy.

A New Era of Antibiotics: The Clinical Potential of Antimicrobial Peptides

Antimicrobial resistance is a multifaceted crisis, imposing a serious threat to global health. The traditional antibiotic pipeline has been exhausted, prompting research into alternate antimicrobial strategies. Inspired by nature, antimicrobial peptides are rapidly gaining attention for their clinical potential as they present distinct advantages over traditional antibiotics. Antimicrobial peptides are found in all forms of life and demonstrate a pivotal role in the innate immune system. Many antimicrobial peptides are evolutionarily conserved, with limited propensity for resistance. Additionally, chemical modifications to the peptide backbone can be used to improve biological activity and stability and reduce toxicity. This review details the therapeutic potential of peptide-based antimicrobials, as well as the challenges needed to overcome in order for clinical translation. We explore the proposed mechanisms of activity, design of synthetic biomimics, and how this novel class of antimicrobial compound may address the need for effective antibiotics. Finally, we discuss commercially available peptide-based antimicrobials and antimicrobial peptides in clinical trials.

Vitamin D in COVID - 19: Dousing the fire or averting the storm? - A perspective from the Asia-Pacific

COVID-19, the acute respiratory tract infection (RTI) caused by the Coronavirus, Sars-CoV-2, has swept around the world. No country has been spared from its onslaught. Treatments that can reduce the risk of infection and mortality from the disease are desperately needed. Though high quality randomized controlled trials are lacking, some observational and interventional studies that explore the link between vitamin D and RTIs exist. Vitamin D modulates both innate as well as adaptive immunity and may potentially prevent or mitigate the complications associated with RTIs. Evidence linking vitamin D to COVID-19 include that the outbreak occurred in winter in the northern hemisphere at a time when vitamin D levels are lowest in resident populations, that blacks and minority ethnic individuals who are known to have lower levels of vitamin D appear to be disproportionately affected and have more severe complications from the disease, that vitamin D deficiency has been shown to contribute to acute respiratory distress syndrome and that case fatality rates increase with age and in populations with comorbid conditions such as diabetes, hypertension, and cardiovascular disease, all of which are associated with lower vitamin D levels. This narrative review summarizes the current knowledge about the epidemiology and pathophysiology of COVID-19, the evidence linking vitamin D and RTIs, especially COVID-19, the mechanistic reasons behind the possible protective effect of vitamin D in COVID-19, and the evidence with regard to vitamin D supplementation in RTIs. It concludes with some recommendations regarding supplementation of vitamin D in patients with COVID-19.

Novel Anti-Inflammatory Approaches for Cystic Fibrosis Lung Disease: Identification of Molecular Targets and Design of Innovative Therapies

Cystic fibrosis (CF) is the most common genetic disorder among Caucasians, estimated to affect more than 70,000 people in the world. Severe and persistent bronchial inflammation and chronic bacterial infection, along with airway mucus obstruction, are hallmarks of CF lung disease and participate in its progression. Anti-inflammatory therapies are, therefore, of particular interest for CF lung disease. Furthermore, a better understanding of the molecular mechanisms involved in airway infection and inflammation in CF has led to the development of new therapeutic approaches that are currently under evaluation by clinical trials. These new strategies dedicated to CF inflammation are designed to treat different dysregulated aspects such as oxidative stress, cytokine secretion, and the targeting of dysregulated pathways. In this review, we summarize the current understanding of the cellular and molecular mechanisms that contribute to abnormal lung inflammation in CF, as well as the new anti-inflammatory strategies proposed to CF patients by exploring novel molecular targets and novel drug approaches.

Vitamin D deficiency as a factor for immunity stimulation and lower risk of acute respiratory infections and COVID-19

During the COVID-19 pandemic, the efforts of many researchers around the world are aimed at finding preventive and prophylactic measures as well as therapeutic agents against SARS-CoV-2. Recent studies have showed that vitamin D deficiency could be one of many factors associated with the development and severity of acute respiratory infections, and vitamin D could be used for prevention and treatment of these patients. This review summarizes data about the role of vitamin D in the pathogenesis and prevention of respiratory viral infections, including new coronavirus infection as well as mechanisms for reducing the risk of infection with vitamin D therapy. Probably, this review will be of interest for endocrinologists and other specialists.

Cathelicidin-related Antimicrobial Peptide Contributes to Host Immune Responses Against Pulmonary Infection with Acinetobacter baumannii in Mice

Acinetobacter baumannii is known for its multidrug antibiotic resistance. New approaches to treating drug-resistant bacterial infections are urgently required. Cathelicidin-related antimicrobial peptide (CRAMP) is a murine antimicrobial peptide that exerts diverse immune functions, including both direct bacterial cell killing and immunomodulatory effects. In this study, we sought to identify the role of CRAMP in the host immune response to multidrug-resistant Acinetobacter baumannii. Wild-type (WT) and CRAMP knockout mice were infected intranasally with the bacteria. CRAMP^−/− mice exhibited increased bacterial colony-forming units (CFUs) in bronchoalveolar lavage (BAL) fluid after A. baumannii infection compared to WT mice. The loss of CRAMP expression resulted in a significant decrease in the recruitment of immune cells, primarily neutrophils. The levels of IL-6 and CXCL1 were lower, whereas the levels of IL-10 were significantly higher in the BAL fluid of CRAMP^−/− mice compared to WT mice 1 day after infection. In an in vitro assay using thioglycollate-induced peritoneal neutrophils, the ability of bacterial phagocytosis and killing was impaired in CRAMP^−/− neutrophils compared to the WT cells. CRAMP was also essential for the production of cytokines and chemokines in response to A. baumannii in neutrophils. In addition, the A. baumannii-induced inhibitor of κB-α degradation and phosphorylation of p38 MAPK were impaired in CRAMP^−/− neutrophils, whereas ERK and JNK phosphorylation was upregulated. Our results indicate that CRAMP plays an important role in the host defense against pulmonary infection with A. baumannii by promoting the antibacterial activity of neutrophils and regulating the innate immune responses.

Significance of LL-37 on Immunomodulation and Disease Outcome

LL-37, also called cathelicidin, is an important part of the human immune system, which can resist various pathogens. A plethora of experiments have demonstrated that it has the multifunctional effects of immune regulation, in addition to antimicrobial activity. Recently, there have been increasing interest in its immune function. It was found that LL-37 can have two distinct functions in different tissues and different microenvironments. Thus, it is necessary to investigate LL-37 immune functions from the two sides of the same coin. On the one side, LL-37 promotes inflammation and immune response and exerts its anti-infective and antitumor effects; on the other side, it has the ability to inhibit inflammation and promote carcinogenesis. This review presents a brief summary of its expression, structure, and immunomodulatory effects as well as brief discussions on the role of this small peptide as a key factor in the development and treatment of various inflammation-related diseases and cancers.

β-Defensin Strengthens Antimicrobial Peritoneal Mast Cell Response

Mast cells (MCs) are engaged in the processes of host defense, primarily via the presence of receptors responsible for the detection of pathogen-associated molecular patterns (PAMPs). Since BDs are exclusively host defense molecules, and MCs can elicit the antimicrobial response, this study is aimed at determining whether BDs might be involved in MC pathogen defense. We found that defensin BD-2 significantly augments the mRNA and protein expression of Toll-like receptors (TLRs) and retinoic acid-inducible gene-I-like receptor (RLR) essential for the detection of viral molecules, i.e., TLR3, TLR7, TLR9, and RIG-I in mature tissue rat peritoneal MCs (PMCs). We established that BD-2 might stimulate PMCs to release proinflammatory and immunoregulatory mediators and to induce a migratory response. Presented data on IgE-coated PMC upon BD-2 treatment suggest that in the case of allergies, there is an enhanced MC immune response and cell influx to the site of the ongoing infection. In conclusion, our data highlight that BD-2 might strongly influence MC features and activity, mainly by strengthening their role in the inflammatory mechanisms and controlling the activity of cells participating in antimicrobial processes.

Host Cathelicidin Exacerbates Group B Streptococcus Urinary Tract Infection

Group B Streptococcus (GBS) causes frequent urinary tract infection (UTI) in susceptible populations, including individuals with type 2 diabetes and pregnant women; however, specific host factors responsible for increased GBS susceptibility in these populations are not well characterized. Here, we investigate cathelicidin, a cationic antimicrobial peptide, known to be critical for defense during UTI with uropathogenic Escherichia coli (UPEC). We observed a loss of antimicrobial activity of human and mouse cathelicidins against GBS and UPEC in synthetic urine and no evidence for increased cathelicidin resistance in GBS urinary isolates. Furthermore, we found that GBS degrades cathelicidin in a protease-dependent manner. Surprisingly, in a UTI model, cathelicidin-deficient (Camp-/-) mice showed decreased GBS burdens and mast cell recruitment in the bladder compared to levels in wild-type (WT) mice. Pharmacologic inhibition of mast cells reduced GBS burdens and histamine release in WT but not Camp-/- mice. Streptozotocin-induced diabetic mice had increased bladder cathelicidin production and mast cell recruitment at 24 h postinfection with GBS compared to levels in nondiabetic controls. We propose that cathelicidin is an important immune regulator but ineffective antimicrobial peptide against GBS in urine. Combined, our findings may in part explain the increased frequency of GBS UTI in diabetic and pregnant individuals.IMPORTANCE Certain populations such as diabetic individuals are at increased risk for developing urinary tract infections (UTI), although the underlying reasons for this susceptibility are not fully known. Additionally, diabetics are more likely to become infected with certain types of bacteria, such as group B Streptococcus (GBS). In this study, we find that an antimicrobial peptide called cathelicidin, which is thought to protect the bladder from infection, is ineffective in controlling GBS and alters the type of immune cells that migrate to the bladder during infection. Using a mouse model of diabetes, we observe that diabetic mice are more susceptible to GBS infection even though they also have more infiltrating immune cells and increased production of cathelicidin. Taken together, our findings identify this antimicrobial peptide as a potential contributor to increased susceptibility of diabetic individuals to GBS UTI.

Hitchhiking with Nature: Snake Venom Peptides to Fight Cancer and Superbugs

Abstract

For decades, natural products in general and snake venoms (SV) in particular have been a rich source of bioactive compounds for drug discovery, and they remain a promising substrate for therapeutic development. Currently, a handful of SV-based drugs for diagnosis and treatment of various cardiovascular disorders and blood abnormalities are on the market. Likewise, far more SV compounds and their mimetics are under investigation today for diverse therapeutic applications, including antibiotic-resistant bacteria and cancer. In this review, we analyze the state of the art regarding SV-derived compounds with therapeutic potential, focusing on the development of antimicrobial and anticancer drugs. Specifically, information about SV peptides experimentally validated or predicted to act as antimicrobial and anticancer peptides (AMPs and ACPs, respectively) has been collected and analyzed. Their principal activities both in vitro and in vivo, structures, mechanisms of action, and attempts at sequence optimization are discussed in order to highlight their potential as drug leads.

Key Contribution

This review describes the state of the art in snake venom-derived peptides and their therapeutic applications. This work reinforces the potential of snake venom components as therapeutic agents, particularly in the quest for new antimicrobial and anticancer drugs.

COVID-19: an updated review

COVID-19 is a zoonotic disease that showed higher levels of transmissibility in humans. Coronavirus has the largest recognized genome (28–33 kb) of a positive-sense single stranded RNA. The genome composed of 5′-end, the translationable mRNA sequences for the key proteins; replicase, spike, envelop membrane, and nucleocapsid and 3′-end (polyA tail). This highly contagious virus may impair the immune system in the early phase of the disease, hence the symptoms of the disease appear very rapidly. Importantly until now, there is no efficient strategy for containing the disease. So, all the world scientists today are in a race against time to find a vaccine or treatment to COVID-19, which requires a deeper understanding.

Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths

The world is in the grip of the COVID-19 pandemic. Public health measures that can reduce the risk of infection and death in addition to quarantines are desperately needed. This article reviews the roles of vitamin D in reducing the risk of respiratory tract infections, knowledge about the epidemiology of influenza and COVID-19, and how vitamin D supplementation might be a useful measure to reduce risk. Through several mechanisms, vitamin D can reduce risk of infections. Those mechanisms include inducing cathelicidins and defensins that can lower viral replication rates and reducing concentrations of pro-inflammatory cytokines that produce the inflammation that injures the lining of the lungs, leading to pneumonia, as well as increasing concentrations of anti-inflammatory cytokines. Several observational studies and clinical trials reported that vitamin D supplementation reduced the risk of influenza, whereas others did not. Evidence supporting the role of vitamin D in reducing risk of COVID-19 includes that the outbreak occurred in winter, a time when 25-hydroxyvitamin D (25(OH)D) concentrations are lowest; that the number of cases in the Southern Hemisphere near the end of summer are low; that vitamin D deficiency has been found to contribute to acute respiratory distress syndrome; and that case-fatality rates increase with age and with chronic disease comorbidity, both of which are associated with lower 25(OH)D concentration. To reduce the risk of infection, it is recommended that people at risk of influenza and/or COVID-19 consider taking 10,000 IU/d of vitamin D₃ for a few weeks to rapidly raise 25(OH)D concentrations, followed by 5000 IU/d. The goal should be to raise 25(OH)D concentrations above 40-60 ng/mL (100-150 nmol/L). For treatment of people who become infected with COVID-19, higher vitamin D₃ doses might be useful. Randomized controlled trials and large population studies should be conducted to evaluate these recommendations.

Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths

The world is in the grip of the COVID-19 pandemic. Public health measures that can reduce the risk of infection and death in addition to quarantines are desperately needed. This article reviews the roles of vitamin D in reducing the risk of respiratory tract infections, knowledge about the epidemiology of influenza and COVID-19, and how vitamin D supplementation might be a useful measure to reduce risk. Through several mechanisms, vitamin D can reduce risk of infections. Those mechanisms include inducing cathelicidins and defensins that can lower viral replication rates and reducing concentrations of pro-inflammatory cytokines that produce the inflammation that injures the lining of the lungs, leading to pneumonia, as well as increasing concentrations of anti-inflammatory cytokines. Several observational studies and clinical trials reported that vitamin D supplementation reduced the risk of influenza, whereas others did not. Evidence supporting the role of vitamin D in reducing risk of COVID-19 includes that the outbreak occurred in winter, a time when 25-hydroxyvitamin D (25(OH)D) concentrations are lowest; that the number of cases in the Southern Hemisphere near the end of summer are low; that vitamin D deficiency has been found to contribute to acute respiratory distress syndrome; and that case-fatality rates increase with age and with chronic disease comorbidity, both of which are associated with lower 25(OH)D concentration. To reduce the risk of infection, it is recommended that people at risk of influenza and/or COVID-19 consider taking 10,000 IU/d of vitamin D₃ for a few weeks to rapidly raise 25(OH)D concentrations, followed by 5000 IU/d. The goal should be to raise 25(OH)D concentrations above 40-60 ng/mL (100-150 nmol/L). For treatment of people who become infected with COVID-19, higher vitamin D₃ doses might be useful. Randomized controlled trials and large population studies should be conducted to evaluate these recommendations.

Differential Abilities of Mammalian Cathelicidins to Inhibit Bacterial Biofilm Formation and Promote Multifaceted Immune Functions of Neutrophils

Mammalian cathelicidins act as the potent microbicidal molecules for controlling bacterial infection, and are considered promising alternatives to traditional antibiotics. Their ability to modulate host immune responses, as well as their bactericidal activities, is essential for therapeutic interventions. In this study, we compared the bactericidal activities, antibiofilm activities and immune-modulatory properties of cathelicidins BMAP-27, BMAP-34, mCRAMP, and LL-37, and evaluated the therapeutic efficacy of the combination of BMAP-27 and LL-37 using a mouse pulmonary infection model. Our results showed that all of the four cathelicidins effectively killed bacteria via rapid induction of membrane permeabilization, and BMAP-27 exhibited the most excellent bactericidal activity against diverse bacterial pathogens. BMAP-27, mCRAMP, and LL-37 effectively inhibited biofilm formation, while BMAP-34, mCRAMP and LL-37 exerted immunomodulatory functions with varying degrees of efficacy by stimulating the chemotaxis of neutrophils, inducing the production of reactive oxygen species, and facilitating the formation of neutrophil extracellular traps. Of note, the combination of BMAP-27 and LL-37 effectively enhanced the clearance of Pseudomonas aeruginosa and reduced the organ injury in vivo. Together, these findings highlight that identifying the appropriate synergistic combination of mammalian cathelicidins with different beneficial properties may be an effective strategy against bacterial infection.

The Contribution of Chemoattractant GPCRs, Formylpeptide Receptors, to Inflammation and Cancer

A hallmark of inflammatory responses is leukocyte mobilization, which is mediated by pathogen and host released chemotactic factors that activate Gi-protein-coupled seven-transmembrane receptors (GPCRs) on host cell surface. Formylpeptide receptors (FPRs, Fprs in mice) are members of the chemoattractant GPCR family, shown to be critical in myeloid cell trafficking during infection, inflammation, immune responses, and cancer progression. Accumulating evidence demonstrates that both human FPRs and murine Fprs are involved in a number of patho-physiological processes because of their expression on a wide variety of cell types in addition to myeloid cells. The unique capacity of FPRs (Fprs) to interact with numerous structurally unrelated chemotactic ligands enables these receptors to participate in orchestrated disease initiation, progression, and resolution. One murine Fpr member, Fpr2, and its endogenous agonist peptide, Cathelicidin-related antimicrobial peptide (CRAMP), have been demonstrated as key mediators of colon mucosal homeostasis and protection from inflammation and associated tumorigenesis. Recent availability of genetically engineered mouse models greatly expanded the understanding of the role of FPRs (Fprs) in pathophysiology that places these molecules in the list of potential targets for therapeutic intervention of diseases.

The Role of Antimicrobial Neutrophil Extract in Modification of the Inflammatory Response During Osteochondral Autograft and Allograft Transplantation in Rabbits

Osteochondral autograft or allograft transplantation is one of the surgical options for the management of large cartilage defects; however, the mechanisms of cartilage healing after this procedure, especially the immunological mechanisms, are not fully understood. The present study examined whether a grafting procedure changed the in-vitro responses of neutrophils and monocyte-derived macrophages (MDMs). Additionally, antimicrobial neutrophil extract (ANE) was assessed for its ability to modulate excessive cellular responses during and after implantation. The neutrophil secretory response was tested by measuring enzyme release and free radical generation, while the MDM response was evaluated by assessing morphological and functional changes of the cells after polarization. Osteochondral implantation evoked a transient secretory response by circulating neutrophils, but MDMs were not activated postoperatively. ANE from rabbit blood may be considered as a modulator of the inflammatory response because of its influence on neutrophils and MDMs. Inhibition of the neutrophil secretory response prevents complications that may arise following excessive activity of these cells. Stimulation of MDMs with ANE induces formation of a partial anti-inflammatory phenotype with enhanced regenerative properties.

Expression and Function of Host Defense Peptides at Inflammation Sites

There is a growing interest in the complex role of host defense peptides (HDPs) in the pathophysiology of several immune-mediated inflammatory diseases. The physicochemical properties and selective interaction of HDPs with various receptors define their immunomodulatory effects. However, it is quite challenging to understand their function because some HDPs play opposing pro-inflammatory and anti-inflammatory roles, depending on their expression level within the site of inflammation. While it is known that HDPs maintain constitutive host protection against invading microorganisms, the inducible nature of HDPs in various cells and tissues is an important aspect of the molecular events of inflammation. This review outlines the biological functions and emerging roles of HDPs in different inflammatory conditions. We further discuss the current data on the clinical relevance of impaired HDPs expression in inflammation and selected diseases.

Personalized pharmacological therapy for ARDS: a light at the end of the tunnel

Introduction: Pharmacotherapy for the acute respiratory distress syndrome (ARDS) has been tested in preclinical and clinical studies. However, to date, no pharmacological interventions have proven effective. This may be attributed to lack of proper identification of different ARDS phenotypes.Areas covered: We designed inclusive search strings and searched four bibliographic databases (Cochrane Database of Systematic Reviews, PubMed, Web of Science, and clinicaltrials.gov) to identify relevant research. Search results were mainly restricted to papers published from 2009 through 2019. ARDS is a heterogeneous syndrome, and its different phenotypes - defined according to clinical, radiological, and biological parameters - may affect response to therapy. The most promising pharmacological approaches to date have been based on ARDS pathophysiology. They focus on reducing inflammation and pulmonary edema, promoting selective vasodilation, and repairing alveolar epithelial and endothelial cells.Expert opinion: Pharmacotherapeutic approaches targeting ARDS pathophysiology have failed to exert beneficial effects. Personalized medicine targeting the different ARDS phenotypes has emerged as an option to improve survival. Identification of specific ARDS patient phenotypes that respond to specific therapies seems to be the most important challenge for the next decade. Additional research is warranted before personalized medicine approaches can be applied at bedside for ARDS patients.

Snake Venom Cathelicidins as Natural Antimicrobial Peptides

Bioactive small molecules isolated from animals, plants, fungi and bacteria, including natural antimicrobial peptides, have shown great therapeutic potential worldwide. Among these peptides, snake venom cathelicidins are being widely exploited, because the variation in the composition of the venom reflects a range of biological activities that may be of biotechnological interest. Cathelicidins are short, cationic, and amphipathic molecules. They play an important role in host defense against microbial infections. We are currently facing a strong limitation on pharmacological interventions for infection control, which has become increasingly complex due to the lack of effective therapeutic options. In this review, we will focus on natural snake venom cathelicidins as promising candidates for the development of new antibacterial agents to fight antibiotic-resistant bacteria. We will highlight their antibacterial and antibiofilm activities, mechanism of action, and modulation of the innate immune response.

Cathelicidin Contributes to the Restriction of Leishmania in Human Host Macrophages

In cutaneous Leishmaniasis the parasitic control in human host macrophages is still poorly understood. We found an increased expression of the human cathelicidin CAMP in skin lesions of Ethiopian patients with cutaneous leishmaniasis. Vitamin D driven, Cathelicidin-type antimicrobial peptides (CAMP) play an important role in the elimination of invading microorganisms. Recombinant cathelicidin was able to induce cell-death characteristics in Leishmania in a dose dependent manner. Using human primary macrophages, we demonstrated pro-inflammatory macrophages (hMDM1) to express a higher level of human cathelicidin, both on gene and protein level, compared to anti-inflammatory macrophages (hMDM2). Activating the CAMP pathway using Vitamin D in hMDM1 resulted in a cathelicidin-mediated-Leishmania restriction. Finally, a reduction of cathelicidin in hMDM1, using a RNA interference (RNAi) approach, increased Leishmania parasite survival. In all, these data show the human cathelicidin to contribute to the innate immune response against Leishmaniasis in a human primary cell model.

Novel potential biomarkers for the diagnosis and monitoring of patients with ulcerative colitis

Unambiguously, great progress has been achieved in the unraveling of more pathological pathways implicated in the development and progression of ulcerative colitis during the last decades. Novel effective drugs that have augmented the management armamentarium have been developed alongside this growing comprehension of the disease, rendering mucosal healing not only a feasible but the optimal goal of every therapy. Clinical evaluation, colonoscopy and biomarkers are the tools used by practitioners for the diagnosis and assessment of the status of the disease in order to achieve clinical remission and mucosal healing for their patients. Among these tools, colonoscopy is the gold method for the cause but is still an invasive, high-cost procedure with possible adverse events such as perforation. While clinical evaluation entails much subjectivity, biomarkers are objective, easily reproducible, non-invasive, cheap and potent surrogate tools of mucosal inflammation. Unfortunately, the well-established, currently in use serum biomarkers, such as C-reactive protein, erythrocyte sedimentation rate and others, do not display sufficiently acceptable sensitivity and specificity rates for the diagnosis of ulcerative colitis and, most importantly, do not represent precisely the mucosal inflammation status of the disease. Therefore, the discovery of new serum biomarkers has been the cause of several studies attempting to discover an "optimal" serum biomarker during the recent years. After thorough research, collection and examination of current data, this review focuses on and selectively presents promising, potential, novel serum biomarkers of ulcerative colitis as they are indicated by studies on the patient over the last years.

Immunomodulatory Functions of the Human Cathelicidin LL-37 (aa 13-31)-Derived Peptides are Associated with Predicted α-Helical Propensity and Hydrophobic Index

The anti-endotoxin activity of the cationic peptide LL-37 and its derivative IG-19 is attributed to electrostatic interaction of the peptides’ positive charge with negatively charged bacterial lipopolysaccharides (LPS), and in part to the alteration of intracellular mechanisms independent of peptide binding to LPS. We examined the immunomodulatory responses induced by IG-19 and four IG-19-derived scrambled peptides (IG-19a–d), in the presence and absence of LPS, in macrophages and peripheral blood-derived mononuclear cells. All peptides had identical net charge (+5) and amino acid composition, but different hydrophobicity and α-helical propensity. Peptide IG-19 suppressed LPS-induced cytokine/chemokine production by >90%, IG-19a and IG-19b suppressed it by 40–50%, and IG-19c and IG-19d did not suppress cytokine/chemokine production at all. In silico prediction algorithms and the peptide retention time (RT) on a C18 RP HPLC column indicated a linear association between α-helical propensity and hydrophobicity with the ability of the peptides to inhibit LPS-induced responses. Peptide RT exhibited a significant correlation (>70%) between the suppression of LPS-induced cytokine/chemokine production and peptide-induced production of the anti-inflammatory cytokine IL-1RA. These results indicate that RT on a C18 column can be used as a predictor for the immunomodulatory functions of cationic peptides. Overall, we demonstrated that the immunomodulatory functions of LL-37-derived peptides with identical positive charge and amino acid composition are directly associated with the predicted α-helical propensity and hydrophobicity of the peptides.

A review on the role of M2 macrophages in bladder cancer; pathophysiology and targeting

Tumor-associated macrophages (TAMs) which are often referred to as immunosuppressive cells (M2 macrophage), constitute a subset of tumor microenvironment cells and affect tumor progression in solid tumors. Recently, these cells have gained remarkable importance as therapeutic candidates for solid tumors. In bladder cancer, major studies have focused on evaluating TAMs in response to Bacillus Calmette-Guerin (BCG) therapy. M2 macrophages may directly impact the BCG-induced immune responses against tumor in bladder cancer. They are the main inhibitors of the tumor microenvironment that promotes growth and metastasis of the tumor. However, the clinical significance of M2 macrophages in bladder cancer is controversial. In this review, we will discuss the clinical significance of M2 macrophages in prognosis of bladder cancer as well as worth of their potential targeting in bladder cancer treatment. In the following, we will introduce important factors resulting in M2 macrophage promotion and also experimental therapeutic agents that may cause the inhibition of bladder cancer tumor growth.

Human Antimicrobial Peptides as Therapeutics for Viral Infections

Successful in vivo infection following pathogen entry requires the evasion and subversion of multiple immunological barriers. Antimicrobial peptides (AMPs) are one of the first immune pathways upregulated during infection by multiple pathogens, in multiple organs in vivo. In humans, there are many classes of AMPs exhibiting broad antimicrobial activities, with defensins and the human cathelicidin LL-37 being the best studied examples. Whereas historically the efficacy and therapeutic potential of AMPs against bacterial infection has been the primary focus of research, recent studies have begun to elucidate the antiviral properties of AMPs as well as their role in regulation of inflammation and chemoattraction. AMPs as therapeutic tools seem especially promising against emerging infectious viral pathogens for which no approved vaccines or treatments are currently available, such as dengue virus (DENV) and Zika virus (ZIKV). In this review, we summarize recent studies elucidating the efficacy and diverse mechanisms of action of various classes of AMPs against multiple viral pathogens, as well as the potential use of human AMPs in novel antiviral therapeutic strategies.

Bacterial lipopolysaccharide and antimicrobial LL-37 enhance ICAM-1 expression and NF-κB p65 phosphorylation in senescent endothelial cells

Cellular senescence is associated with the induction of a proinflammatory phenotype. Notably, senescent endothelial cells are detected at the sites of atherosclerotic lesions, suggesting the involvement of senescent endothelial cells in atherogenesis. Moreover, bacterial infection has been speculated to contribute to the pathogenesis of atherosclerosis. The present study investigated the effects of Gram‑negative bacterial lipopolysaccharide (LPS) and LL‑37 (a human antimicrobial peptide of the cathelicidin family), on senescent endothelial cells, using serially passaged human endothelial cells. The results indicated that senescent endothelial cells exhibited the basal proinflammatory phenotype, as evidenced by higher intercellular adhesion molecule‑1 (ICAM‑1) expression and NF‑κB p65 phosphorylation, compared with non‑senescent cells. Additionally, exposure to LPS and LL‑37 further enhanced the expression of ICAM‑1 in senescent endothelial cells, compared with non‑senescent cells. Of note, the NF‑κB p65 pathway was more activated in senescent endothelial cells stimulated with LPS and LL‑37. Furthermore, the expression levels of the receptors for LPS and LL‑37 [toll‑like receptor 4 (TLR4) and purinergic receptor P2X 7 (P2X7), respectively] were upregulated in senescent endothelial cells. These observations indicated that LPS and LL‑37 enhanced the ICAM‑1 expression and NF‑κB p65 activation in senescent endothelial cells, potentially via the upregulated TLR4 and P2X7. Thus, senescent endothelial cells may contribute to the pathogenesis of atherosclerosis via the basal proinflammatory phenotype and the enhanced inflammatory responses against atherogenic factors, including LPS and LL‑37.

Characterization of host defense molecules in the human pancreas

The gut microbiota can play a role in pancreatitis and, likely, in the development of type 1 diabetes (T1D). Anti-microbial peptides and secretory proteins are important mediators of the innate immune response against bacteria but their expression in the human pancreas is not fully known. In this study, immunohistochemistry was used to analyze the expression of seven anti-microbial peptides (Defensin α1, α4, β1-4 and Cathelicidin) and two secretory proteins with known antimicrobial properties (REG3A and GP2) in pancreatic and duodenal biopsies from 10 non-diabetic organ donors and one organ donor that died at onset of T1D. Immunohistochemical data was compared with previously published whole-transcriptome data sets. Seven (Defensin α1, β2, β3, α4, GP2, Cathelicidin, and REG3A) host defense molecules showed positive staining patterns in most non-diabetic organ donors, whereas two (Defensin β1 and β4) were negative in all non-diabetic donors. Two molecules (Defensin α1 and GP2) were restricted to the exocrine pancreas whereas two (Defensin β3, α4) were only expressed in islet tissue. Cathelicidin, β2, and REG3A were expressed in both islets and exocrine tissue. The donor that died at onset of T1D had generally less positivity for the host defense molecules, but, notably, this pancreas was the only one where defensin β1 was found. Neither donor age, immune-cell infiltration, nor duodenal expression correlated to the pancreatic expression of host defense molecules. In conclusion, these findings could have important implications for the inflammatory processes in diabetes and pancreatitis as we find several host defense molecules expressed by the pancreatic tissue.

Changes in the Activity of Ovine Blood-derived Macrophages Stimulated with Antimicrobial Peptide Extract (AMP) or Platelet-rich Plasma (PRP)

Introduction

Antimicrobial peptides (AMP) are a large group of innate immune effectors, which apart from antimicrobial activity show immunomodulative properties. Platelet-rich plasma (PRP) is a source of autologous growth factors and is used for stimulation of bone and soft tissue healing. The purpose of this study was to assess the influence of PRP and AMP extract on ovine monocyte-derived macrophage cultures.

Material and Methods

The study was conducted on ovine macrophages (Mfs) previously stimulated with LPS or dexamethasone and then with preparations of PRP or AMP. Following activation of the Mfs their morphological and functional features were assessed.

Results

The study revealed pro-inflammatory influence of both examined preparations on Mfs cultures on the basis of morphology, ROS generation and arginase activity. Both preparations enhanced the pro-inflammatory response of cultured Mfs.

Conclusion

This activity may intensify the antimicrobial action of Mfs, however, in cases of excessive and prolonged inflammation the use of these preparations should be limited.

Human cathelicidin peptide LL-37 as a therapeutic antiviral targeting Venezuelan equine encephalitis virus infections

Venezuelan equine encephalitis virus (VEEV), a new world alphavirus belonging to the Togaviridae family, causes periodic disease outbreaks in humans and equines with high associated mortality and morbidity. VEEV is highly infectious via the aerosol route and so has been developed as a biological weapon (Hawley and Eitzen, 2001). Despite its current classification as a category B select agent, there are no FDA approved vaccines or therapeutics to counter VEEV infections. Here we utilize a naturally occurring host defense peptide, LL-37, as a therapeutic strategy to inhibit VEEV multiplication in infected cells. LL-37 has previously demonstrated activity against several viruses by directly interacting with viral particles and indirectly by establishing an antiviral state in the host cell. We show that LL-37 exhibited potent antiviral activity against VEEV by inhibiting viral replication. Genomic RNA copies of the TC-83 strain of VEEV and viral titers were significantly reduced compared to non-treated controls. LL-37 also inhibited the virulent Trinidad Donkey (TrD) strain of VEEV. Entry assays revealed a robust reduction of viral RNA copies at the early stages of TC-83 infection. Pre-incubation of cells with LL-37 and TC-83 resulted in a strong inhibitory response, indicating that LL-37 impacts early stages of the infectious process. Confocal and electron microscopy images confirmed the aggregation of viral particles, which potentially accounts for entry prevention and hence reduced viral infection. LL-37 treatment also modulated type I interferon (IFN) expression in infected cells. LL-37 treatment dramatically increased IFNβ1 expression in treated cells in a time-dependent manner. Our results establish LL-37 as a relevant and novel potential therapeutic strategy for the treatment of VEEV infections.

Structure and function of the Ts2631 endolysin of Thermus scotoductus phage vB_Tsc2631 with unique N-terminal extension used for peptidoglycan binding

To escape from hosts after completing their life cycle, bacteriophages often use endolysins, which degrade bacterial peptidoglycan. While mesophilic phages have been extensively studied, their thermophilic counterparts are not well characterized. Here, we present a detailed analysis of the structure and function of Ts2631 endolysin from thermophilic phage vB_Tsc2631, which is a zinc-dependent amidase. The active site of Ts2631 consists of His30, Tyr58, His131 and Cys139, which are involved in Zn²⁺ coordination and catalysis. We found that the active site residues are necessary for lysis yet not crucial for peptidoglycan binding. To elucidate residues involved in the enzyme interaction with peptidoglycan, we tested single-residue substitution variants and identified Tyr60 and Lys70 as essential residues. Moreover, substitution of Cys80, abrogating disulfide bridge formation, inactivates Ts2631, as do substitutions of His31, Thr32 and Asn85 residues. The endolysin contains a positively charged N-terminal extension of 20 residues that can protrude from the remainder of the enzyme and is crucial for peptidoglycan binding. We show that the deletion of 20 residues from the N-terminus abolished the bacteriolytic activity of the enzyme. Because Ts2631 exhibits intrinsic antibacterial activity and unusual thermal stability, it is perfectly suited as a scaffold for the development of antimicrobial agents.

Characterization of paucibacillary ileal lesions in sheep with subclinical active infection by Mycobacterium avium subsp. paratuberculosis

Paratuberculosis (PTB) or Johne's disease is a contagious enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Ovine PTB is less understood than bovine PTB, especially concerning paucibacillary infection and its evolution into clinical disease. We combined shotgun proteomics, histopathology and immunohistochemistry for the characterization of ileal tissues collected from seven asymptomatic sheep negative to serum ELISA, positive to feces and tissue MAP IS900 and F57 PCR, histologically classified as paucibacillary, actively infected, together with 3 MAP-free controls (K). Following shotgun proteomics with label-free quantitation and differential analysis, 96 proteins were significantly changed in PTB vs K, and were mostly involved in immune defense processes and in the macrophage-MAP interaction. Principal component analysis (PCA) of protein abundances highlighted two PTB sample clusters, PTB1 and PTB2, indicating a dichotomy in their proteomic profiles. This was in line with the PCA of histopathology data and was related to features of type 2 (PTB1) and type 3a (PTB2) lesions, respectively. PTB2 proteomes differed more than PTB1 proteomes from K: 43 proteins changed significantly only in PTB2 and 11 only in PTB1. The differential proteins cathelicidin, haptoglobin, S100A8 and S100A9 were evaluated by immunohistochemistry. K tissues were negative to cathelicidin and haptoglobin and sparsely positive to S100A8 and S100A9. PTB tissues were positive to all four proteins, with significantly more cells in PTB2 than in PTB1. In conclusion, we described several pathways altered in paucibacillary PTB, highlighted some proteomic differences among paucibacillary PTB cases, and identified potential markers for disease understanding, staging, and detection.

The endogenous antimicrobial cathelicidin LL37 induces platelet activation and augments thrombus formation

Platelet-associated complications including thrombosis, thrombocytopenia, and hemorrhage are commonly observed during various inflammatory diseases such as sepsis, inflammatory bowel disease, and psoriasis. Despite the reported evidence on numerous mechanisms/molecules that may contribute to the dysfunction of platelets, the primary mechanisms that underpin platelet-associated complications during inflammatory diseases are not fully established. Here, we report the discovery of formyl peptide receptor 2, FPR2/ALX, in platelets and its primary role in the development of platelet-associated complications via ligation with its ligand, LL37. LL37 acts as a powerful endogenous antimicrobial peptide, but it also regulates innate immune responses. We demonstrate the impact of LL37 in the modulation of platelet reactivity, hemostasis, and thrombosis. LL37 activates a range of platelet functions, enhances thrombus formation, and shortens the tail bleeding time in mice. By utilizing a pharmacological inhibitor and Fpr2/3 (an ortholog of human FPR2/ALX)-deficient mice, the functional dependence of LL37 on FPR2/ALX was determined. Because the level of LL37 is increased in numerous inflammatory diseases, these results point toward a critical role for LL37 and FPR2/ALX in the development of platelet-related complications in such diseases. Hence, a better understanding of the clinical relevance of LL37 and FPR2/ALX in diverse pathophysiological settings will pave the way for the development of improved therapeutic strategies for a range of thromboinflammatory diseases.

Galleria mellonella: A Novel Invertebrate Model to Distinguish Intestinal Symbionts From Pathobionts

Insects and mammals share evolutionary conserved innate immune responses to maintain intestinal homeostasis. We investigated whether the larvae of the greater wax moth Galleria mellonella may be used as an experimental organism to distinguish between symbiotic Bacteroides vulgatus and pathobiotic Escherichia coli, which are mammalian intestinal commensals. Oral application of the symbiont or pathobiont to G. mellonella resulted in clearly distinguishable innate immune responses that could be verified by analyzing similar innate immune components in mice in vivo and in vitro. The differential innate immune responses were initiated by the recognition of bacterial components via pattern recognition receptors. The pathobiont detection resulted in increased expression of reactive oxygen and nitrogen species related genes as well as antimicrobial peptide gene expression. In contrast, the treatment/application with symbiotic bacteria led to weakened immune responses in both mammalian and insect models. As symbionts and pathobionts play a crucial role in development of inflammatory bowel diseases, we hence suggest G. mellonella as a future replacement organism in inflammatory bowel disease research.

Cathelicidins: Immunomodulatory Antimicrobials

Cathelicidins are host defense peptides with antimicrobial and immunomodulatory functions. These effector molecules of the innate immune system of many vertebrates are diverse in their amino acid sequence but share physicochemical characteristics like positive charge and amphipathicity. Besides being antimicrobial, cathelicidins have a wide variety in immunomodulatory functions, both boosting and inhibiting inflammation, directing chemotaxis, and effecting cell differentiation, primarily towards type 1 immune responses. In this review, we will examine the biology and various functions of cathelicidins, focusing on putting in vitro results in the context of in vivo situations. The pro-inflammatory and anti-inflammatory functions are highlighted, as well both direct and indirect effects on chemotaxis and cell differentiation. Additionally, we will discuss the potential and limitations of using cathelicidins as immunomodulatory or antimicrobial drugs.

Anti-inflammatory activities of Aedes aegypti cecropins and their protection against murine endotoxin shock

BACKGROUND

Mosquitoes are armed with physiologically active compounds to suppress the host immunity including host inflammatory reaction. However, the specific anti-inflammatory components in mosquitoes remain unknown.

RESULTS

By searching for the immunomodulatory molecules from the mosquito Aedes aegypti (Diptera: Culicidae) at NCBI for anti-inflammatory function, five cecropins (for short in this study: AeaeCec1, 2, 3, 4 and 5) were selected. AeaeCec1-5 efficiently inhibited the expression of inducible nitric oxide synthase (iNOS), nitrite, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-stimulated mouse peritoneal macrophages and human peripheral blood mononuclear cells (PBMCs) with low toxicity to mammalian cells. Among the five analogues, AeaeCec5 had the strongest anti-inflammatory activity, and generated an additive effect with other AeaeCec peptides. In a mouse model of endotoxin shock, AeaeCec1-5 effectively reduced TNF-α, IL-1β and IL-6 expression in lungs, serum and peritoneal lavage and correspondingly reduced lung damage and edema, with AeaeCec5 showing the best protection. In mice infected with Escherichia coli or Pseudomonas aeruginosa, administration of AeaeCec5 reduced the production of TNF-α, IL-1β and IL-6 and correspondingly reduced lung tissue damage. These effects of Ae. aegypti AeaeCec1-5 were attributed to an efficient inhibition of the activation of mitogen-activated protein kinases (MAPKs) and transcriptional nuclear factor-κB (NF-κB) signaling pathways, as well as partial neutralization of LPS.

CONCLUSIONS

The current work characterized the specific anti-inflammatory agents in Ae. aegypti and provided AeaeCec5 as a potent anti-endotoxin peptide that could serve as the basis for the development of anti-inflammatory therapy.

Hoodwinking the Big-Eater to Prosper: The Salmonella-Macrophage Paradigm

Salmonella is a major cause of morbidity and mortality in the developing and underdeveloped nations. Being a foodborne disease, Salmonella infection is primarily contracted through the ingestion of contaminated food or water, or due to close contact with infected/carrier individuals. It is an intracellular pathogen, which can survive and replicate in various cells including macrophages, dendritic cells, epithelial cells, and other white blood cells. Once Salmonella crosses the intestinal barrier, it disseminates to various systemic sites by circulation via immune cells. One of the major cell types which are involved in Salmonella infection are host macrophages. They are the niche for intracellular survival and proliferation of Salmonella and a mode of dissemination to distal systemic sites. These cells are very crucial as they mediate the mounting of an appropriate innate and adaptive anti-Salmonella immune response. In this review, we have tried to concise the current knowledge of complex interactions that occur between Salmonella and macrophages.