Innate defense regulator IDR-1018 activates human mast cells through G protein-, phospholipase C-, MAPK- and NF-ĸB-sensitive pathways

Candida albicans and Antifungal Peptides

Candida albicans, a ubiquitous opportunistic fungal pathogen, plays a pivotal role in human health and disease. As a commensal organism, it normally resides harmlessly within the human microbiota. However, under certain conditions, C. albicans can transition into a pathogenic state, leading to various infections collectively known as candidiasis. With the increasing prevalence of immunocompromised individuals and the widespread use of invasive medical procedures, candidiasis has become a significant public health concern. The emergence of drug-resistant strains further complicates treatment options, highlighting the urgent need for alternative therapeutic strategies. Antifungal peptides (AFPs) have gained considerable attention as potential candidates for combating Candida spp. infections. These naturally occurring peptides possess broad-spectrum antimicrobial activity, including specific efficacy against C. albicans. AFPs exhibit several advantageous properties, such as rapid killing kinetics, low propensity for resistance development, and diverse mechanisms of action, making them promising alternatives to conventional antifungal agents. In recent years, extensive research has focused on discovering and developing novel AFPs with improved efficacy and selectivity against Candida species. Advances in biotechnology and synthetic peptide design have enabled the modification and optimization of natural peptides, enhancing their stability, bioavailability, and therapeutic potential. Nevertheless, several challenges must be addressed before AFPs can be widely implemented in clinical practice. These include optimizing peptide stability, enhancing delivery methods, overcoming potential toxicity concerns, and conducting comprehensive preclinical and clinical studies. This commentary presents a short overview of candidemia and AFP; articles and reviews published in the last 10 years were searched on The National Library of Medicine (National Center for Biotechnology Information-NIH-PubMed). The terms used were C. albicans infections, antimicrobial peptides, antifungal peptides, antifungal peptides mechanisms of action, candidemia treatments and guidelines, synthetic peptides and their challenges, and antimicrobial peptides in clinical trials as the main ones. Older publications were cited if they brought some relevant concept or helped to bring a perspective into our narrative. Articles older than 20 years and those that appeared in PubMed but did not match our goal to bring updated information about using antifungal peptides as an alternative to C. albicans infections were not considered.

Modulation of the immune response by the host defense peptide IDR-1002 in chicken hepatic cell culture

IDR-1002, a synthetic host defense peptide (HDP), appears to be a potential candidate for the treatment of bacterial infections and the consequent inflammatory response due to its potent immunomodulatory activity. This is of relevance to the emerging issue of antimicrobial resistance in the farming sector. In this study, the effects of IDR-1002 were investigated on a chicken hepatocyte‒non-parenchymal cell co-culture, and the results revealed that IDR-1002 had complex effects on the regulation of the hepatic innate immunity. IDR-1002 increased the levels of both RANTES (Regulated on Activation, Normal T cell Expressed and Secreted) and Macrophage colony stimulating factor (M-CSF), suggesting the peptide plays a role in the modulation of macrophage differentiation, also reflected by the reduced concentrations of interleukin (IL)-6 and IL-10. The pro-inflammatory cytokine release triggered by the bacterial cell wall component lipoteichoic acid (LTA) was ameliorated by the concomitantly applied IDR-1002 based on the levels of IL-6, chicken chemotactic and angiogenic factor (CXCLi2) and interferon (IFN)-γ. Moreover, the production of nuclear factor erythroid 2-related factor 2 (Nrf2), an essential transcription factor in the antioxidant defense pathway, was increased after IDR-1002 exposure, while protein carbonyl (PC) levels were also elevated. These findings suggest that IDR-1002 affects the interplay of the cellular immune response and redox homeostasis, thus the peptide represents a promising tool in the treatment of bacterially induced inflammation in chickens.

The Combination of Synoeca-MP Antimicrobial Peptide with IDR-1018 Stimulates Proliferation, Migration, and the Expression of Pro-Regenerative Genes in Both Human Skin Cell Cultures and 3D Skin Equivalents

In skin lesions, the development of microbial infection affects the healing process, increasing morbidity and mortality rates in patients with severe burns, diabetic foot, and other types of skin injuries. Synoeca-MP is an antimicrobial peptide (AMP) that exhibits activity against several bacteria of clinical importance, but its cytotoxicity can represent a problem for its positioning as an effective antimicrobial compound. In contrast, the immunomodulatory peptide IDR-1018 presents low toxicity and a wide regenerative potential due to its ability to reduce apoptotic mRNA expression and promote skin cell proliferation. In the present study, we used human skin cells and a 3D skin equivalent models to analyze the potential of the IDR-1018 peptide to attenuate the cytotoxicity of synoeca-MP, as well as the influence of synoeca-MP/IDR-1018 combination on cell proliferation, regenerative processes, and wound repair. We found that the addition of IDR-1018 significantly improved the biological properties of synoeca-MP on skin cells without modifying its antibacterial activity against S. aureus. Likewise, in both melanocytes and keratinocytes, the treatment with synoeca-MP/IDR-1018 combination induces cell proliferation and migration, while in a 3D human skin equivalent model, it can accelerate wound reepithelization. Furthermore, treatment with this peptide combination generates an up-regulation in the expression of pro-regenerative genes in both monolayer cell cultures and in 3D skin equivalents. This data suggests that the synoeca-MP/IDR-1018 combination possesses a good profile of antimicrobial and pro-regenerative activity, opening the door to the development of new strategies for the treatment of skin lesions.

The dual antimicrobial and immunomodulatory roles of host defense peptides and their applications in animal production

Host defense peptides (HDPs) are small molecules with broad-spectrum antimicrobial activities against infectious bacteria, viruses, and fungi. Increasing evidence suggests that HDPs can also indirectly protect hosts by modulating their immune responses. Due to these dual roles, HDPs have been considered one of the most promising antibiotic substitutes to improve growth performance, intestinal health, and immunity in farm animals. This review describes the antimicrobial and immunomodulatory roles of host defense peptides and their recent applications in animal production.

Biodistribution and Toxicity of Innate Defense Regulator 1018 (IDR-1018)

Innate defense regulators (IDRs) are synthetic host-defense peptides (HDPs) with broad-spectrum anti-infective properties, including immunomodulatory, anti-biofilm and direct antimicrobial activities. A lack of pharmacokinetic data about these peptides hinders their development and makes it challenging to fully understand how they work in vivo since their mechanism of action is dependent on tissue concentrations of the peptide. Here, we set out to define in detail the pharmacokinetics of a well-characterized IDR molecule, IDR-1018. To make the peptide traceable, it was radiolabeled with the long-lived gamma-emitting isotope gallium-67. After a series of bench-top characterizations, the radiotracer was administered to healthy mice intravenously (IV) or subcutaneously (SQ) at various dose levels (2.5-13 mg/kg). Nuclear imaging and ex-vivo biodistributions were used to quantify organ and tissue uptake of the radiotracer over time. When administered as an IV bolus, the distribution profile of the radiotracer changed as the dose was escalated. At 2.5 mg/kg, the peptide was well-tolerated, poorly circulated in the blood and was cleared predominately by the reticuloendothelial system. Higher doses (7 and 13 mg/kg) as an IV bolus were almost immediately lethal due to respiratory arrest; significant lung uptake of the radiotracer was observed from nuclear scans of these animals, and histological examination found extensive damage to the pulmonary vasculature and alveoli. When administered SQ at a dose of 3 mg/kg, radiolabeled IDR-1018 was rapidly absorbed from the site of injection and predominately cleared renally. Apart from the SQ injection site, no other tissue had a concentration above the minimum inhibitory concentration that would enable this peptide to exert direct antimicrobial effects against most pathogenic bacteria. Tissue concentrations were sufficient however to disrupt microbial biofilms and alter the host immune response. Overall, this study demonstrated that the administration of synthetic IDR peptide in vivo is best suited to local administration which avoids some of the issues associated with peptide toxicity that are observed when administered systemically by IV injection, an issue that will have to be addressed through formulation.

The Antimicrobial Peptides Human β-Defensins Induce the Secretion of Angiogenin in Human Dermal Fibroblasts

The skin produces a plethora of antimicrobial peptides that not only show antimicrobial activities against pathogens but also exhibit various immunomodulatory functions. Human β-defensins (hBDs) are the most well-characterized skin-derived antimicrobial peptides and contribute to diverse biological processes, including cytokine production and the migration, proliferation, and differentiation of host cells. Additionally, hBD-3 was recently reported to promote wound healing and angiogenesis, by inducing the expression of various angiogenic factors and the migration and proliferation of fibroblasts. Angiogenin is one of the most potent angiogenic factors; however, the effects of hBDs on angiogenin production in fibroblasts remain unclear. Here, we investigated the effects of hBDs on the secretion of angiogenin by human dermal fibroblasts. Both in vitro and ex vivo studies demonstrated that hBD-1, hBD-2, hBD-3, and hBD-4 dose-dependently increased angiogenin production by fibroblasts. hBD-mediated angiogenin secretion involved the epidermal growth factor receptor (EGFR), Src family kinase, c-Jun N-terminal kinase (JNK), p38, and nuclear factor-kappa B (NF-κB) pathways, as evidenced by the inhibitory effects of specific inhibitors for these pathways. Indeed, we confirmed that hBDs induced the activation of the EGFR, Src, JNK, p38, and NF-κB pathways. This study identified a novel role of hBDs in angiogenesis, through the production of angiogenin, in addition to their antimicrobial activities and other immunomodulatory properties.

Transplantation and immunosuppression: a review of novel transplant-related immunosuppressant drugs

Immunosuppressive drugs used in the transplantation period are generally defined as induction and maintenance therapy. The use of immunosuppressants, which are particularly useful and have fewer side effects, decreased both mortality and morbidity. Many drugs such as steroids, calcineurin inhibitors (cyclosporine-A, tacrolimus), antimetabolites (mycophenolate mofetil, azathioprine), and mTOR inhibitors (sirolimus, everolimus) are used as immunosuppressive agents. Although immunosuppressant drugs cause many side effects such as hypertension, infection, and hyperlipidemia, they are the agents that should be used to prevent organ rejection. This shows the importance of individualized drug use. The optimal immunosuppressive therapy post-transplant is not established. Therefore, discovering less toxic but more potent new agents is of great importance, and new experimental and clinical studies are needed in this regard.Our review discussed the mechanism of immunosuppressants, new agents' discovery, and current therapeutic protocols in the transplantation.

Enhancement of Mast Cell Degranulation Mediated by Purinergic Receptors' Activation and PI3K Type δ

Mast cells express multiple metabotropic purinergic P2Y receptor (P2YR) subtypes. Few studies have evaluated their role in human mast cell (HMC) allergic response as quantified by degranulation induced by cross-linking the high-affinity IgE receptor (FcεRI). We have previously shown that extracellular nucleotides modify the FcεRI activation-dependent degranulation in HMCs derived from human lungs, but the mechanism of this action has not been fully delineated. This study was undertaken to determine the mechanism of activation of P2YRs on the degranulation of HMCs and elucidate the specific postreceptor pathways involved. Sensitized LAD2 cells, a human-derived mast cell line, were subjected to a weak allergic stimulation (WAS) using a low concentration of Ag in the absence and presence of P2YR agonists. Only the metabotropic purinergic P2Y11 receptor (P2Y11R) agonist, adenosine 5'-(3-thio)triphosphate (ATPγS), enhanced WAS-induced degranulation resulting in a net 7-fold increase in release (n = 4; p < 0.01). None of the P2YR agonists tested, including high concentrations of ATPγS (1000 μM), enhanced WAS-induced intracellular Ca²⁺ mobilization, an essential component of activated FcεRI-induced degranulation. Both a PI3K inhibitor and the relevant gene knockout decreased the ATPγS-induced enhancement. The effect of ATPγS was associated with enhanced phosphorylation of PI3K type δ and protein kinase B, but not the phosphoinositide-dependent kinase-1. The effects of ATPγS were dose dependently inhibited by NF157, a P2Y11R antagonist. To our knowledge, these data indicate for the first time that P2YR is linked to enhancement of allergic degranulation in HMC via the PI3K/protein kinase B pathway.

Two Sides of the Coin: Mast Cells as a Key Regulator of Allergy and Acute/Chronic Inflammation

It is well known that mast cells (MCs) initiate type I allergic reactions and inflammation in a quick response to the various stimulants, including—but not limited to—allergens, pathogen-associated molecular patterns (PAMPs), and damage-associated molecular patterns (DAMPs). MCs highly express receptors of these ligands and proteases (e.g., tryptase, chymase) and cytokines (TNF), and other granular components (e.g., histamine and serotonin) and aggravate the allergic reaction and inflammation. On the other hand, accumulated evidence has revealed that MCs also possess immune-regulatory functions, suppressing chronic inflammation and allergic reactions on some occasions. IL-2 and IL-10 released from MCs inhibit excessive immune responses. Recently, it has been revealed that allergen immunotherapy modulates the function of MCs from their allergic function to their regulatory function to suppress allergic reactions. This evidence suggests the possibility that manipulation of MCs functions will result in a novel approach to the treatment of various MCs-mediated diseases.

Mannose receptor (CD206) activation in tumor-associated macrophages enhances adaptive and innate antitumor immune responses

Solid tumors elicit a detectable immune response including the infiltration of tumor-associated macrophages (TAMs). Unfortunately, this immune response is co-opted into contributing toward tumor growth instead of preventing its progression. We seek to reestablish an antitumor immune response by selectively targeting surface receptors and endogenous signaling processes of the macrophage subtypes driving cancer progression. RP-182 is a synthetic 10-mer amphipathic analog of host defense peptides that selectively induces a conformational switch of the mannose receptor CD206 expressed on TAMs displaying an M2-like phenotype. RP-182-mediated activation of this receptor in human and murine M2-like macrophages elicits a program of endocytosis, phagosome-lysosome formation, and autophagy and reprograms M2-like TAMs to an antitumor M1-like phenotype. In syngeneic and autochthonous murine cancer models, RP-182 suppressed tumor growth, extended survival, and was an effective combination partner with chemo- or immune checkpoint therapy. Antitumor activity of RP-182 was also observed in CD206^high patient-derived xenotransplantation models. Mechanistically, via selective reduction of immunosuppressive M2-like TAMs, RP-182 improved adaptive and innate antitumor immune responses, including increased cancer cell phagocytosis by reprogrammed TAMs.

Topical Gynura procumbens as a Novel Therapeutic Improves Wound Healing in Diabetic Mice

Nonhealing wounds are major socioeconomic challenges to healthcare systems worldwide. Therefore, there is a substantially unmet need to develop new drugs for wound healing. Gynura procumbens, a herb found in Southeast Asia, may be an effective therapeutic for nonhealing diabetic wounds. The aim of this study was to evaluate the efficacy of G. procumbens on wound healing in the diabetic milieu. G. procumbens extract was obtained using 95% ethanol and its components were determined by thin layer chromatography. Diabetes was induced in mice using streptozotocin. We found that G. procumbens extract contained stigmasterol, kaempferol and quercetin compounds. Topical application of G. procumbens on the wounded skin of diabetic mice accelerated wound healing and induced the expression of angiogenin, epidermal growth factor, fibroblast growth factor, transforming growth factor and vascular endothelial growth factor. Furthermore, G. procumbens promoted in vitro wound healing and enhanced the migration and/or proliferation of human endothelial cells, fibroblasts, keratinocytes and mast cells cultured in diabetic conditions. Finally, G. procumbens promoted vascular formation in the diabetic mice. To the best of our knowledge, this is the first study that evaluates in vivo wound healing activities of G. procumbens and activation of cells involved in wound healing process in diabetic conditions. The findings that G. procumbens accelerates wound healing and activates cells involved in the wound healing process suggest that G. procumbens might be an effective alternative therapeutic option for nonhealing diabetic wounds.

Chemocentric Informatics Analysis: Dexamethasone Versus Combination Therapy for COVID-19

COVID-19 is a biphasic infectious disease with no approved vaccine or pharmacotherapy. The first drug that has shown promise in reducing COVID-19 mortality in severely-ill patients is dexamethasone, a cheap, well-known anti-inflammatory glucocorticoid, approved for the treatment of inflammatory conditions including respiratory diseases such as asthma and tuberculosis. However, about 80% of COVID-19 patients requiring oxygenation, and about 67% of patients on ventilators, are not responsive to dexamethasone therapy mainly. Additionally, using higher doses of dexamethasone for prolonged periods of time can lead to severe side effects and some patients may develop corticosteroid resistance leading to treatment failure. In order to increase the therapeutic efficacy of dexamethasone in COVID-19 patients, while minimizing dexamethasone-related complications that could result from using higher doses of the drug, we applied a chemocentric informatics approach to identify combination therapies. Our results indicated that combining dexamethasone with fast long-acting beta-2 adrenergic agonists (LABAs), such as formoterol and salmeterol, can ease respiratory symptoms hastily, until dexamethasone's anti-inflammatory and immunosuppressant effects kick in. Our studies demonstrated that LABAs and dexamethasone (or other glucocorticoids) exert synergistic effects that will augment both anti-inflammatory and fibronectin-mediated anticoagulant effects. We also propose other alternatives to LABAs that are supported by sound systems biology evidence, such as nitric oxide. Other drugs such as sevoflurane and treprostinil interact with the SARS-CoV-2 interactome and deserve further exploration. Moreover, our chemocentric informatics approach provides systems biology evidence that combination therapies for COVID-19 will have higher chances of perturbing the SARS-CoV-2 human interactome, which may negatively impact COVID-19 disease pathways.

Anti-inflammatory effect of bee venom in phthalic anhydride-induced atopic dermatitis animal model

Globally, many people have been affected with atopic dermatitis (AD), a chronic inflammatory skin disease. AD is associated with multiple factors such as genetic, inflammatory, and immune factors. Bee venom (BV) is now widely used for the treatment of several inflammatory diseases. However, its effect on 5% phthalic anhydride (PA)-induced AD has not been reported yet. We investigated the anti-inflammatory and anti-AD effects of BV in a PA-induced animal model of AD. Balb/c mice were treated with topical application of 5% PA to the dorsal skin and ears for induction of AD. After 24 h, BV was applied on the back and ear skin of the mice three times a week for 4 weeks. BV treatment significantly reduced the PA-induced AD clinical score, back and ear epidermal thickness, as well as IgE level and infiltration of immune cells in the skin tissues compared to those of control mice. The levels of inflammatory cytokines in the serum were significantly decreased in BV-treated group compared to PA-treated group. In addition, BV inhibited the expression of iNOS and COX-2 as well as the activation of mitogen-activated protein kinase (MAPK) and NF-ҡB induced by PA in the skin tissues. We also found that BV abrogated the lipopolysaccharide or TNF-α/IFN-γ-induced NO production, expression of iNOS and COX-2, as well as MAPK and NF-ҡB signaling pathway in RAW 264.7 and HaCaT cells. These results suggest that BV may be a potential therapeutic macromolecule for the treatment of AD.

Activation of PLCγ/AKT/IκBα/p65 signaling increases inflammation in mast cells to promote growth of cutaneous neurofibroma

AIM

Cutaneous neurofibroma (cNF), a hallmark feature of neurofibromatosis type 1 (NF1), results in psychological and physical damage to patients. Considering the important role of mast cells in neurofibroma development, the aim of this study was to elucidate the underlying mechanism of the interaction between cNF cells and mast cells.

MAIN METHODS

SW10 cells with Nf1 knocked down were used as a cNF cell model. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and colony formation assays, as well as a mouse xenograft tumor model, were used to assess the cNF tumor growth in vivo and in vitro. ELISAs and IHC were used to examine the inflammatory activity of mast cells.

KEY FINDINGS

We demonstrated that cNF cells activated mast cells, which in turn promoted the cNF cell growth, while suppression of the inflammatory activity of cNF-associated mast cells reversed their stimulating effect on the growth of cNF cells. Mechanistic studies revealed that SW10 cells upregulated PLCγ/AKT/IκBα/p65 signaling in mast cells, thereby increasing inflammation. Moreover, PLCγ modulated the AKT/IκBα/p65 signaling activity and played a critical role in the interaction of mast cells and cNF cells. Knockdown of PLCγ in mast cells diminished their cNF cell-induced inflammatory activity and subsequently reduced the cNF cell growth in vivo and in vitro.

SIGNIFICANCE

This study revealed a novel interaction between mast cells and cNF cells, suggesting a potential strategy for treating cNF by targeting the newly recognized signaling pathway.

IDR-1018 induces cell proliferation, migration, and reparative gene expression in 2D culture and 3D human skin equivalents

Skin lesions are associated with functional/cosmetic problems for those afflicted. Scarless regeneration is a challenge, not limited to the skin, and focus of active investigation. Recently, the host defense peptide innate defense regulatory peptide 1018 (IDR-1018) has shown exciting regenerative properties. Nevertheless, literature regarding IDR-1018 regenerative potential is scarce and limited to animal models. Here, we evaluated the regenerative potential of IDR-1018 using human 2D and 3D human skin equivalents. First, we investigated IDR-1018 using human cells found in skin-primary fibroblasts, primary keratinocytes, and the MeWo melanocytes cell line. IDR-1018 promoted cell proliferation and expression of marker of proliferation Ki-67, matrix metalloproteinase 1, and hyaluronan synthase 2 by fibroblasts. In keratinocytes, a drastic increase in expression was observed for Ki-67, matrix metalloproteinase 1, C-X-C motif chemokine receptor type 4, C-X-C motif chemokine receptor type 7, fibroblast growth factor 2, hyaluronan synthase 2, vascular endothelial growth factor, and elastin, reflecting an intense stimulation of these cells. In melanocytes, increased migration and proliferation were observed following IDR-1018 treatment. The capacity of IDR-1018 to promote dermal contraction was verified using a dermal model. Finally, using a 3D human skin equivalent lesion model, we revealed that the regenerative potential of IDR1018, previously tested in mice and pigs, is valid for human skin tissue. Lesions closed faster in IDR-1018-treated samples, and the gene expression signature observed in 2D was reproduced in the 3D human skin equivalents. Overall, the present data show the regenerative potential of IDR-1018 in an experimental system comprising human cells, underscoring the potential application for clinical investigation.

Berberine suppresses IL-33-induced inflammatory responses in mast cells by inactivating NF-κB and p38 signaling

Berberine (BBR) possesses many pharmacological characteristics including anti-inflammation, anti-allergy, anti-angiogenesis and anti-tumor. However, the effects and mechanisms of BBR on IL-33-induced mast cell inflammatory responses are kept unknown. To investigate these, rat peritoneal mast cells (RPMCs) were isolated from the peritoneal cavity and cultured with BBR treatment in combination IL-33 stimulation. Firstly, cytotoxic effect of BBR on RPMCs was detected by MTT assay. Then, IL-33-induced cytokine production and the expression of ST2 receptor, were evaluated by ELISA and real-time PCR, respectively. In addition, NF-κB and MAPK signaling involved in IL-33-mediated mast cell activation were assessed by Western blot, which also was confirmed using the signal transduction inhibitors. Simultaneously, the effect of BBR on IL-33-activated enhancement of IgE-mediated mast cell responses was analyzed. Lastly, SD rats were used to explore the effect of BBR on IL-33-induced inflammation in vivo. BBR treatment significantly reduced IL-33-stimulated cytokine production in RPMCs, such as IL-6, TNF-α, IL-13 and MCP-1, but had little effect in ST2 expression. BBR modulated IL-33 signaling via suppressing IL-33-induced NF-ΚB transcription and p38 phosphorylation, but not ERK and JNK. Additionally, BBR also hampered the combined effects of IL-33 and IgE-mediated mast cell activation. Decreased cytokine production followed BBR treatment in vitro was consistent with that in vivo, where BBR injection i.p. into rats obviously inhibited IL-33-induced plasma cytokine levels. These findings demonstrated that BBR suppressed IL-33-mediated inflammation in mast cells by inactivating NF-κB and p38 signaling, suggesting its potential application for the treatment of allergic inflammation.