Human β-defensin 3 induces STAT1 phosphorylation, tyrosine phosphatase activity, and cytokine synthesis in T cells

ERK1/2-CEBPB Axis-Regulated hBD1 Enhances Anti-Tuberculosis Capacity in Alveolar Type II Epithelial Cells

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), remains a global health crisis with substantial morbidity and mortality rates. Type II alveolar epithelial cells (AEC-II) play a critical role in the pulmonary immune response against Mtb infection by secreting effector molecules such as antimicrobial peptides (AMPs). Here, human β-defensin 1 (hBD1), an important AMP produced by AEC-II, has been demonstrated to exert potent anti-tuberculosis activity. HBD1 overexpression effectively inhibited Mtb proliferation in AEC-II, while mice lacking hBD1 exhibited susceptibility to Mtb and increased lung tissue inflammation. Mechanistically, in A549 cells infected with Mtb, STAT1 negatively regulated hBD1 transcription, while CEBPB was the primary transcription factor upregulating hBD1 expression. Furthermore, we revealed that the ERK1/2 signaling pathway activated by Mtb infection led to CEBPB phosphorylation and nuclear translocation, which subsequently promoted hBD1 expression. Our findings suggest that the ERK1/2-CEBPB-hBD1 regulatory axis can be a potential therapeutic target for anti-tuberculosis therapy aimed at enhancing the immune response of AEC-II cells.

The Contribution of Antimicrobial Peptides to Immune Cell Function: A Review of Recent Advances

The development of novel antimicrobial agents to replace antibiotics has become urgent due to the emergence of multidrug-resistant microorganisms. Antimicrobial peptides (AMPs), widely distributed in all kingdoms of life, present strong antimicrobial activity against a variety of bacteria, fungi, parasites, and viruses. The potential of AMPs as new alternatives to antibiotics has gradually attracted considerable interest. In addition, AMPs exhibit strong anticancer potential as well as anti-inflammatory and immunomodulatory activity. Many studies have provided evidence that AMPs can recruit and activate immune cells, controlling inflammation. This review highlights the scientific literature focusing on evidence for the anti-inflammatory mechanisms of different AMPs in immune cells, including macrophages, monocytes, lymphocytes, mast cells, dendritic cells, neutrophils, and eosinophils. A variety of immunomodulatory characteristics, including the abilities to activate and differentiate immune cells, change the content and expression of inflammatory mediators, and regulate specific cellular functions and inflammation-related signaling pathways, are summarized and discussed in detail. This comprehensive review contributes to a better understanding of the role of AMPs in the regulation of the immune system and provides a reference for the use of AMPs as novel anti-inflammatory drugs for the treatment of various inflammatory diseases.

Immunomodulatory and Allergenic Properties of Antimicrobial Peptides

With the growing problem of the emergence of antibiotic-resistant bacteria, the search for alternative ways to combat bacterial infections is extremely urgent. While analyzing the effect of antimicrobial peptides (AMPs) on immunocompetent cells, their effect on all parts of the immune system, and on humoral and cellular immunity, is revealed. AMPs have direct effects on neutrophils, monocytes, dendritic cells, T-lymphocytes, and mast cells, participating in innate immunity. They act on B-lymphocytes indirectly, enhancing the induction of antigen-specific immunity, which ultimately leads to the activation of adaptive immunity. The adjuvant activity of AMPs in relation to bacterial and viral antigens was the reason for their inclusion in vaccines and made it possible to formulate the concept of a “defensin vaccine” as an innovative basis for constructing vaccines. The immunomodulatory function of AMPs involves their influence on cells in the nearest microenvironment, recruitment and activation of other cells, supporting the response to pathogenic microorganisms and completing the inflammatory process, thus exhibiting a systemic effect. For the successful use of AMPs in medical practice, it is necessary to study their immunomodulatory activity in detail, taking into account their pleiotropy. The degree of maturity of the immune system and microenvironment can contribute to the prevention of complications and increase the effectiveness of therapy, since AMPs can suppress inflammation in some circumstances, but aggravate the response and damage of organism in others. It should also be taken into account that the real functions of one or another AMP depend on the types of total regulatory effects on the target cell, and not only on properties of an individual peptide. A wide spectrum of biological activity, including direct effects on pathogens, inactivation of bacterial toxins and influence on immunocompetent cells, has attracted the attention of researchers, however, the cytostatic activity of AMPs against normal cells, as well as their allergenic properties and low stability to host proteases, are serious limitations for the medical use of AMPs. In this connection, the tasks of searching for compounds that selectively affect the target and development of an appropriate method of application become critically important. The scope of this review is to summarize the current concepts and newest advances in research of the immunomodulatory activity of natural and synthetic AMPs, and to examine the prospects and limitations of their medical use.

Copy number gain of pro-inflammatory genes in patients with HBV-related acute-on-chronic liver failure

Background

Host genetic factors such as single nucleotide variations may play a crucial role in the onset and progression of HBV-related acute-on-chronic liver failure (ACLF). However, the underlying genomic copy number variations (CNVs) involved in the pathology are currently unclear.

Methods

We genotyped two cohorts with 389 HBV-related ACLF patients and 391 asymptomatic HBV carriers (AsCs), and then carried out CNV-based global burden analysis and a genome-wide association study (GWAS).

Results

For 1874 rare CNVs, HBV-related ACLF patients exhibited a high burden of deletion segments with a size of 100–200 kb (P value = 0.04), and the related genes were significantly enriched in leukocyte transendothelial migration pathway (P value = 4.68 × 10^–3). For 352 common CNVs, GWAS predicted 17 significant association signals, and the peak one was a duplication segment located on 1p36.13 (~ 38 Kb, P value = 1.99 × 10^–4, OR = 2.66). The associated CNVs resulted in more copy number of pro-inflammatory genes (MST1L, DEFB, and HCG4B) in HBV-related ACLF patients than in AsC controls.

Conclusions

Our results suggested that the impact of host CNV on HBV-related ACLF may be through decreasing natural immunity and enhancing host inflammatory response during HBV infection. The findings highlighted the potential importance of gene dosage on excessive hepatic inflammation of this disease.

Human defensins and Th-1 cytokines in hepatitis C viral infection

INTRODUCTION

active or chronic exacerbated forms of hepatitis C virus (HCV) infection subsequently progress to liver disease and human defensins has been determined to have some level of anti-viral properties invitro whilst the expression of T helper-1 cytokines is known to promote complete recovery from acute HCV infection. The study sought to determine relationship between these immune responses.

METHODS

a cross sectional descriptive study design was employed. Hundred and thirty-two individuals were assessed were assessed for to anti-HCV, HCV RNA, serum levels of human alpha defensins 1 (HAD-1) and human beta defensins 1 (HBD-1). T helper 1 cytokines (IL-2, IFN gamma, TNF alpha) secreted in serum were also analyzed using commercial ELISA assay. The study was conducted in Kumasi, Obuasi and Daboya in Ghana.

RESULTS

the serum mean concentrations of HAD-1, HBD-1, IL-2, IFN gamma and TNF alpha showed no significant difference in concentrations among participants with chronic, spontaneously recovered or negative to HCV infection (p>0.05). Persons with hepatitis B co-infection were more likely to develop chronic HCV infection (p=0.039). HAD-1 and HBD-1 showed significant positive association with IL-2 (p=0.000) whilst only HAD-1 positively correlated with IL-2 (p<0.000).

CONCLUSION

the immunological markers determined had no association with the status of HCV infection. HAD-1 increased with increasing levels of IL-2. These findings suggest that during HCV infection, inflammatory response through the production of cytokines by IL-2 cells may affect the release of HAD-1 and HBD-1.

Human β-defensin-3 reduces excessive autophagy in intestinal epithelial cells and in experimental necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of mortality in preterm newborns. Intestinal barrier dysfunction is one key event in NEC pathogenesis. Human β-defensin-3 (hBD3), one member of cationic host defence peptides, was reported to reduce the development of necrotizing enterocolitis in a neonatal rat model. And autophagy was induced in the intestine of human and animals with NEC. We hypothesized that regulation of autophagy might play a critical role in hBD3-mediated protection against NEC injury. Autophagy activity was evaluated both in intestinal epithelial cells and in NEC models. Newborn Sprague-Dawley rats were divided randomly into four groups: Control + NS, Control + rapamycin, NEC + NS, and NEC + hBD3. Body weight, histological score, survival time, enterocyte migration and mucosal barrier were recorded. Our results showed that hBD3 pretreatment could effectively inhibit autophagy activity in cultured IEC-6 and Caco2 enterocytes, and CXCR4 might be involved in hBD3-mediated autophagy suppression. Moreover, hBD3-induced inhibition of autophagy significantly promoted the intestinal epithelial cell migration by wound healing assay and transwell migration assay. In the rat model of NEC, hBD3 could noticeably reduce the expression of autophagy-activated proteins, down-regulate the expression of inflammatory mediators, and promote the mucosal integrity. Our data suggest an additional role of hBD3-mediated protection against intestinal mucosal injury: inhibition of over-activated autophagy in enterocytes.

Reciprocal role of hBD2 and hBD3 on the adaptive immune response by measuring T lymphocyte proliferation in terms of CD4 and CCR6 expression

Background Human β-defensins (hBD2 and hBD3) are small cationic antimicrobial peptides of innate immune system which can act as a barrier against the majority of pathogens, contributing to the host immune defence. Objective The aim of study is to determine whether hBD2 and hBD3 play a role in development and proliferation of human effector CD4 T cells or not. Furthermore, if enhanced proliferation is observed in the presence of hBD2 and hBD3, these data will demonstrate whether chemokine receptor type 6 (CCR6) is required to be present for this activity to occur. Methods In this study, we examined the effect of hBD2 and hBD3 on CD4+ T cell proliferation in CCR6+ and CCR6- T cells through co-culture of peripheral blood mononuclear cells with anti-CD3 and anti-CD28 stimulation in the presence or absence of hBD2 and hBD3. Proliferation was assessed using flow cytometry. Results It was demonstrated that, co-culture with hBD2 and hBD3 led to up-regulation of CD4+ T cell proliferation after 72 h whereas, CD4+ T cell proliferation was suppressed after 96 h. On the other hand, CCR6- and CCR6+ T cell proliferation was up-regulated after 72 h. But, CCR6+ only was down-regulated in the second cycle in the presence of hBD3. In contrast, after 96 h CCR6+ and CCR6- T cell proliferation was decreased. Conclusion Collectively, our data indicated that hBD2 and hBD3 play a positive and negative regulatory role in development and proliferation of human effector CD4+ T cells which is essential for optimal adaptive immune responses and the control of immunopathology.

Multifaceted immune functions of human defensins and underlying mechanisms

Defensins have been long recognized as natural antimicrobial peptides, but they also possess diverse and versatile immune functions. Defensins can both induce inflammation and suppress inflammatory responses by acting on specific cells through distinct mechanisms. Defensins can also modulate the immune response by forming a complex with cellular molecules including proteins, nucleic acids, and carbohydrates. The mechanisms of defensin-mediated immune modulation appear to be cell-type and context specific. Because the levels of human defensins are often altered in response to infection or disease states, suggesting their clinical relevance, this review summarizes the complex immune functions of human defensins and their underlying mechanisms of action, which have implications for the development of new therapeutics.

Importance of phosphoinositide binding by human β-defensin 3 for Akt-dependent cytokine induction

Host defense peptides (HDPs) are well-characterized for their antimicrobial activities but also variously display potent immunomodulatory effects. Human β-defensin 3 (HBD-3) belongs to a well-known HDP family known as defensins and is able to induce leukocyte chemotactic recruitment, leukocyte activation/maturation, proinflammatory cytokine release, and co-stimulatory marker expression. HBD-3-stimulated cytokine induction is NF-κB-dependent and was initially suggested to act via G protein-coupled C-C chemokine receptor phospholipase C (PLC) and/or Toll-like receptor signaling. Subsequent pharmacological inhibition, however, revealed that NF-κB activation by HBD-3 is receptor-independent and instead involves the phosphoinositide 3-kinase (PI3K)-protein kinase B (Akt) pathway, the mechanism of which remains undetermined. Recently, we have shown that HBD-3 can enter mammalian cells and bind to inner membrane phosphoinositide 4,5-bisphosphate [PI(4,5)P₂], an important second lipid messenger of PLC and PI3K-Akt pathways. In this study, we report that the interaction of HBD-3 with PI(4,5)P₂ is important for PI3K-Akt-NF-κΒ-mediated induction of tumor necrosis factor and interleukin-6. These data provide insights into the mechanism of immunomodulation by HBD-3, and more generally, highlight the complex multifaceted signaling roles of HDPs in innate defense. Furthermore, it is suggested that the proposed mode of action may be conserved in other HDPs.

Defensins in Viral Infection and Pathogenesis

α, β, and θ defensins are effectors of the innate immune system with potent antibacterial, antiviral, and antifungal activity. Defensins have direct antiviral activity in cell culture, with varied mechanisms for individual viruses, although some common themes have emerged. In addition, defensins have potent immunomodulatory activity that can alter innate and adaptive immune responses to viral infection. In some cases, there is evidence for paradoxical escape from defensin neutralization or enhancement of viral infection. The direct and indirect activities of defensins have led to their development as therapeutics and vaccine components. The major area of investigation that continues to lag is the connection between the effects of defensins in cell culture models and viral pathogenesis in vivo. Model systems to study defensin biology, including more physiologic models designed to bridge this gap, are also discussed.

Localization and developmental expression of two chicken host defense peptides: cathelicidin-2 and avian β-defensin 9

In the first weeks of life young chickens are highly susceptible to infectious diseases due to immaturity of the immune system. Little is known about the expression of host defense peptides (HDPs) during this period. In this study we examined the expression pattern of two chicken HDPs, the cathelicidin CATH-2 and the β-defensin AvBD9 by immunohistochemistry in a set of organs from embryonic day 12 until four weeks posthatch. AvBD9 was predominantly found in enteroendocrine cells throughout the intestine, the first report of in vivo HDP expression in this cell type, and showed stable expression levels during development. CATH-2 was exclusively found in heterophils which decreased after hatch in most of the examined organs including spleen, bursa and small intestine. In the lung CATH-2 expression was biphasic and peaked at the first day posthatch. In short, CATH-2 and AvBD9 appear to be expressed in cell types strategically located to respond to infectious stimuli, suggesting these peptides play a role in embryonic and early posthatch defense.

Cytotoxicity of HBD3 for dendritic cells, normal human epidermal keratinocytes, hTERT keratinocytes, and primary oral gingival epithelial keratinocytes in cell culture conditions

Human β-defensin 3 (HBD3) is a prominent host defense peptide. In our recent work, we observed that HBD3 modulates pro-inflammatory agonist-induced chemokine and cytokine responses in human myeloid dendritic cells (DCs), often at 20.0 μM concentrations. Since HBD3 can be cytotoxic in some circumstances, it is necessary to assess its cytotoxicity for DCs, normal human epidermal keratinocytes (NHEKs), human telomerase reverse transcriptase (hTERT) keratinocytes, and primary oral gingival epithelial (GE) keratinocytes in different cell culture conditions. Cells, in serum free media with resazurin and in complete media with 10% fetal bovine serum and resazurin, were incubated with 5, 10, 20, and 40 μM HBD3. Cytotoxicity was determined by measuring metabolic conversion of resazurin to resorufin. The lethal dose 50 (LD50, mean μM±Std Err) values were determined from the median fluorescent intensities of test concentrations compared to live and killed cell controls. The LD50 value range of HBD3 was 18.2-35.9 μM in serum-free media for DCs, NHEKs, hTERT keratinocytes, and GE keratinocytes, and >40.0 μM in complete media. Thus, HBD3 was cytotoxic at higher concentrations, which must be considered in future studies of HBD3-modulated chemokine and cytokine responses in vitro.

Human β-defensin-3 promotes intestinal epithelial cell migration and reduces the development of necrotizing enterocolitis in a neonatal rat model

BACKGROUND

The aim of this study was to investigate the effects of human β-defensin-3 (hBD3) on intestinal wound healing and in a neonatal rat model of necrotizing enterocolitis (NEC).

METHODS

Enterocyte migration and proliferation were detected in vitro and in vivo. The role of chemokine receptor CCR6 and its downstream signaling pathway was assessed. Newborn Sprague-Dawley rats were randomly divided into four groups: Control+NS, Control+hBD3, NEC+NS, and NEC+hBD3. Body weight, histological score, survival time, cytokines expression, and mucosal integrity were evaluated.

RESULTS

hBD3 could stimulate enterocyte migration, but not proliferation, both in cultured enterocytes and in the NEC model. Neutralizing antibody and small interfering RNA confirmed this stimulatory effect was mediated by CCR6. Furthermore, hBD3 induced Rho activation, myosin light chain 2 phosphorylation, and F-actin accumulation. The bactericidal activity of hBD3 was maintained throughout a broad pH range. Strikingly, hBD3 administration decreased the incidence of NEC, increased the survival rate, and reduced the severity of NEC. Moreover, hBD3 reduced the proinflammatory cytokines expression in ileum and serum and preserved the intestinal barrier integrity.

CONCLUSION

This study provided evidence that the antimicrobial peptide hBD3 might participate in intestinal wound healing by promoting enterocyte migration and show beneficial effects on newborn rats with NEC.