Hepcidin is an antibacterial, stress-inducible peptide of the biliary system

Novel Antibacterial Properties of the Human Dental Pulp Multipotent Mesenchymal Stromal Cell Secretome

It is well recognized that clearance of bacterial infection within the dental pulp precedes pulpal regeneration. However, although the regenerative potential of the human dental pulp has been investigated extensively, its antimicrobial potential remains to be examined in detail. In the current study bactericidal assays were used to demonstrate that the secretome of dental pulp multipotent mesenchymal stromal cells (MSCs) has direct antibacterial activity against the archetypal Gram-positive and Gram-negative bacteria, Staphylococcus aureus and Escherichia coli, respectively, as well as the oral pathogens Streptococcus mutans, Lactobacillus acidophilus, and Fusobacterium nucleatum. Furthermore, a cytokine/growth factor array, enzyme-linked immunosorbent assays, and antibody blocking were used to show that cytokines and growth factors present in the dental pulp MSC secretome, including hepatocyte growth factor, angiopoietin-1, IL-6, and IL-8, contribute to this novel antibacterial activity. This study elucidated a novel and diverse antimicrobial secretome from human dental pulp MSCs, suggesting that these cells contribute to the antibacterial properties of the dental pulp. With this improved understanding of the secretome of dental pulp MSCs and its novel antibacterial activity, new evidence for the ability of the dental pulp to fight infection and restore functional competence is emerging, providing further support for the biological basis of pulpal repair and regeneration.

β-Defensin 1 Is Prominent in the Liver and Induced During Cholestasis by Bilirubin and Bile Acids via Farnesoid X Receptor and Constitutive Androstane Receptor

Background & aims

Knowledge about innate antimicrobial defense of the liver is limited. We investigated hepatic expression and regulation of antimicrobial peptides with focus on the human beta defensin-1 (hBD-1).

Methods

Radial diffusion assay was used to analyze antimicrobial activity of liver tissue. Different defensins including hBD-1 and its activator thioredoxin-1 (TXN) were analyzed in healthy and cholestatic liver samples by qPCR and immunostaining. Regulation of hBD-1 expression was studied in vitro and in vivo using bile duct-ligated mice. Regulation of hBD-1 via bilirubin and bile acids (BAs) was studied using siRNA.

Results

We found strong antimicrobial activity of liver tissue against Escherichia coli. As a potential mediator of this antimicrobial activity we detected high expression of hBD-1 and TXN in hepatocytes, whereas other defensins were minimally expressed. Using a specific antibody for the reduced, antimicrobially active form of hBD-1 we found hBD-1 in co-localization with TXN within hepatocytes. hBD-1 was upregulated in cholestasis in a graded fashion. In cholestatic mice hepatic AMP expression (Defb-1 and Hamp) was enhanced. Bilirubin and BAs were able to induce hBD-1 in hepatic cell cultures in vitro. Treatment with siRNA and/or agonists demonstrated that the farnesoid X receptor (FXR) mediates basal expression of hBD-1, whereas both constitutive androstane receptor (CAR) and FXR seem to be responsible for the induction of hBD-1 by bilirubin.

Conclusion

hBD-1 is prominently expressed in hepatocytes. It is induced during cholestasis through bilirubin and BAs, mediated by CAR and especially FXR. Reduction by TXN activates hBD-1 to a potential key player in innate antimicrobial defense of the liver.

Balance of cardiac and systemic hepcidin and its role in heart physiology and pathology

Hepcidin is the main regulator of iron metabolism in tissues. Its serum levels are mostly correlated with the levels of hepcidin expression from the liver, but local hepcidin can be important for the physiology of other organs as well. There is an increasing evidence that this is the case with cardiac hepcidin. This has been confirmed by studies with models of ischemic heart disease and other heart pathologies. In this review the discussion dissects the role of cardiac hepcidin in cellular homeostasis. This review is complemented with examination of the role of systemic hepcidin in heart disease and its use as a biochemical marker. The relationship between systemic vs local hepcidin in the heart is important because it can help us understand how the fine balance between the actions of two hepcidins affects heart function. Manipulating the axis systemic/cardiac hepcidin could serve as a new therapeutic strategy in heart diseases.

Management of anemia in patients with diabetic kidney disease: A consensus statement

This consensus statement focuses on the window of opportunity, which exists while treating patients with diabetic kidney disease and anemia.

Antimicrobial proteins and peptides in human lung diseases: A friend and foe partnership with host proteases

Lung antimicrobial proteins and peptides (AMPs) are major sentinels of innate immunity by preventing microbial colonization and infection. Nevertheless bactericidal activity of AMPs against Gram-positive and Gram-negative bacteria is compromised in patients with chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF) and asthma. Evidence is accumulating that expression of harmful human serine proteases, matrix metalloproteases and cysteine cathepsins is markedely increased in these chronic lung diseases. The local imbalance between proteases and protease inhibitors compromises lung tissue integrity and function, by not only degrading extracellular matrix components, but also non-matrix proteins. Despite the fact that AMPs are somewhat resistant to proteolytic degradation, some human proteases cleave them efficiently and impair their antimicrobial potency. By contrast, certain AMPs may be effective as antiproteases. Host proteases participate in concert with bacterial proteases in the degradation of key innate immunity peptides/proteins and thus may play immunomodulatory activities during chronic lung diseases. In this context, the present review highlights the current knowledge and recent discoveries on the ability of host enzymes to interact with AMPs, providing a better understanding of the role of human proteases in innate host defense.

Heat shock 70-kDa protein 5 (Hspa5) is essential for pronephros formation by mediating retinoic acid signaling

Heat shock 70-kDa protein 5 (Hspa5), also known as binding immunoglobulin protein (Bip) or glucose-regulated protein 78 (Grp78), belongs to the heat shock protein 70 kDa family. As a multifunctional protein, it participates in protein folding and calcium homeostasis and serves as an essential regulator of the endoplasmic reticulum (ER) stress response. It has also been implicated in signal transduction by acting as a receptor or co-receptor residing at the plasma membrane. Its function during embryonic development, however, remains largely elusive. In this study, we used morpholino antisense oligonucleotides (MOs) to knock down Hspa5 activity in Xenopus embryos. In Hspa5 morphants, pronephros formation was strongly inhibited with the reduction of pronephric marker genes Lim homeobox protein 1 (lhx1), pax2, and β1 subunit of Na/K-ATPase (atp1b1). Pronephros tissue was induced in vitro by treating animal caps with all-trans-retinoic acid and activin. Depletion of Hspa5 in animal caps, however, blocked the induction of pronephros as well as reduced the expression of retinoic acid (RA)-responsive genes, suggesting that knockdown of Hspa5 attenuated RA signaling. Knockdown of Hspa5 in animal caps resulted in decreased expression of lhx1, a transcription factor directly regulated by RA signaling and essential for pronephros specification. Co-injection of Hspa5MO with lhx1 mRNA partially rescued the phenotype induced by Hspa5MO. These results suggest that the RA-Lhx1 signaling cascade is involved in Hspa5MO-induced pronephros malformation. This study shows that Hspa5, a key regulator of the unfolded protein response, plays an essential role in pronephros formation, which is mediated in part through RA signaling during early embryonic development.

Concentrations of preptin, salusins and hepcidins in plasma and milk of lactating women with or without gestational diabetes mellitus

This study was undertaken to ascertain whether human milk contains preptin, salusin-alpha (salusin-α) and -beta (salusin-β) and pro-hepcidin and hepcidin-25, and whether there are relationships between plasma and milk preptin, salusin-α and -β and pro-hepcidin and hepcidin-25 concentrations in lactating mothers with and without gestational diabetes mellitus (GDM). Blood was obtained from non-lactating women (n = 12), non-diabetic lactating women (n = 12), and GDM lactating women (n = 12). Colostrum, transitional milk, and mature milk samples were collected just before suckling from healthy and GDM lactating women. Peptides concentrations were determined by ELISA and EIA. Mammary gland tissues were screened immunohistochemically for these peptides. Women with GDM had significantly higher plasma and colostum preptin concentrations than healthy lactating women during the colostral and transitional milk period. Salusin-alpha and -beta levels in milk and plasma were lower in women with GDM. Salusin-α and -β were significantly lower in both plasma and colostrums of GDM than of healthy lactating women. Women with GDM had significantly higher colostum prohepcidin and hepcidin-25 concentrations than healthy lactating women during the colostral period. Plasma prohepcidin was also higher in women with GDM than in healthy lactating women during the colostral period, but plasma prohepcidin and hepcidin-25 levels decreased during mature milk period. Transitional milk pro-hepcidin and hepcidin-25 levels in women with GDM were higher than in healthy lactating women. All these results revealed that the mammary gland produces those peptides, which were present in milk at levels correlating with plasma concentrations.

Serum hepcidin: indication of its role as an "acute phase" marker in febrile children

Background

Hepcidin is classified as a type II acute phase protein; its production is a component of the innate immune response to infections.

Objective

To evaluate the alterations of serum hepcidin in children during and following an acute febrile infection.

Materials and methods

22 children with fever of acute onset (< 6 hours) admitted to the 2^nd Department of Pediatrics-University of Athens. Based on clinical and laboratory findings our sample formed two groups: the viral infection group (13 children) and the bacterial infection group (9 children). Hepcidin, ferritin and serum iron measurements were performed in all subjects.

Results

Serum hepcidin values did not differ notably between children with viral and bacterial infection, but a significant reduction of hepcidin was noted in both groups post-infection.

Conclusion

Our study provides clinical pediatric data on the role of hepcidin in the face of an acute infection. In our sample of children, hepcidin was found to rise during the acute infection and fall post-infection.

Hepcidin protects against lipopolysaccharide-induced liver injury in a mouse model of obstructive jaundice

Obstructive jaundice (OJ) increases the risk of liver injury and sepsis, leading to increased mortality. Cholestatic liver injury is associated with a downregulation of hepcidin expression levels. In fact, hepcidin has an important antimicrobial effect, especially against Escherichia coli. It is unknown whether supplementing recombinant hepcidin is effective in alleviating cholestasis-induced liver injury and mortality in mice with superimposed sepsis. A mouse model of cholestasis was developed using extrahepatic bile duct ligation for 3 days. In addition, sepsis due to E. coli 0111:B4 lipopolysaccharide (LPS) was induced in the model. The serum levels of total bilirubin, AST, ALT, and LDH and the mRNA levels of IL-1β, TNF-α, and MCP-1 in the liver were significantly higher in the OJ mice receiving LPS than in the sham-operated mice receiving LPS. Compared to the OJ mice receiving LPS, the hepcidin-pretreated OJ mice receiving LPS showed a significant decrease in the above mentioned parameters, as well as a reversal in the downregulation of LC3B-II and upregulation of cleaved caspase-3; this, in turn, led to significantly decreased lethality in 24h. In conclusion, these results indicate that hepcidin pretreatment significantly reduced hepatic proinflammatory cytokine expression and liver injury, leading to reduced early lethality in OJ mice receiving LPS. Enhanced autophagy and reduced apoptosis may account for the protective effects of hepcidin.

The role of airway epithelial cells in response to mycobacteria infection

Airway epithelial cells (AECs) are part of the frontline defense against infection of pathogens by providing both a physical barrier and immunological function. The role of AECs in the innate and adaptive immune responses, through the production of antimicrobial molecules and proinflammatory factors against a variety of pathogens, has been well established. Tuberculosis (TB), a contagious disease primarily affecting the lungs, is caused by the infection of various strains of mycobacteria. In response to mycobacteria infection, epithelial expression of Toll-like receptors and surfactant proteins plays the most prominent roles in the recognition and binding of the pathogen, as well as the initiation of the immune response. Moreover, the antimicrobial substances, proinflammatory factors secreted by AECs, composed a major part of the innate immune response and mediation of adaptive immunity against the pathogen. Thus, a better understanding of the role and mechanism of AECs in response to mycobacteria will provide insight into the relationship of epithelial cells and lung immunocytes against TB, which may facilitate our understanding of the pathogenesis and immunological mechanism of pulmonary tuberculosis disease.

Identification of new altered genes in rat cochleae with noise-induced hearing loss

Because genes that are highly expressed in the cochlea after noise stress may have crucial regulatory roles in hearing, the identification of these genes may be useful for restoring normal auditory function. This study assessed altered gene expression at 1h following the cessation of noise exposure by using microarrays and real-time polymerase chain reaction (qPCR) in rats. In addition, the auditory threshold shifts and morphological changes of hair cells were observed. This study indicated that applied noise induced outer hair cell loss and a 40-50 dB hearing loss. Totally 239 altered genes were involved in the immune system process, response to stress, or response to stimulus. The expression of five up-regulated genes (Reg3b, Lcn2, Serpina3n, Nob1 and Hamp) was confirmed by qPCR. Future experiments will focus on several of these new candidate genes and may provide insight into the underlying auditory pathophysiology.