CCL20 and Beta-Defensin 2 Production by Human Lung Epithelial Cells and Macrophages in Response to Brucella abortus Infection

CCL20 Expression via AKT-ERK1/2-AP1 Pathway in Mycoplasma Pneumoniae Infection: Implications for EMT and Cell Migration

Purpose

Mycoplasma pneumoniae, a clinically significant respiratory pathogen, primarily causes community-acquired pneumonia and contributes to asthma development, with its persistent infection frequently resulting in fibrotic pulmonary changes and structural airway abnormalities. This study investigates the signaling pathways regulating CCL20 expression in THP-1 cells following M. pneumoniae infection and its impact on cell migration and epithelial-mesenchymal transition (EMT).

Methods

THP-1 cells were infected with M. pneumoniae, and the expression of CCL20 was measured over time and at various doses. In addition, co-culture experiments were performed using M. pneumoniae-infected THP-1 cells and bronchial epithelial cells to assess EMT and cell migration.

Results

M. pneumoniae infection significantly upregulated CCL20 production in THP-1 cells via the AKT-ERK1/2-AP1 pathway, a process that was both time- and dose-dependent. Furthermore, co-culturing M. pneumoniae-infected THP-1 cells with 16HBE cells promoted EMT and increased cell migration, a process that is believed to be associated with CCL20.

Conclusion

This study provides insights into the molecular mechanisms linking CCL20 to cell migration, highlighting potential therapeutic targets for M. pneumoniae-related lung diseases.

MIP-3-Alpha and MIP-3-Beta as Early Predictors of Pneumonia in Polytraumatized Patients

INTRODUCTION

Pneumonia is one of the most common complications in patients suffering multiple traumas and is associated with an exceptionally high mortality rate. MIP-3-alpha and MIP-3-beta are pro-inflammatory chemokines expressed in the pulmonary mucosa and are reported to play a crucial role in inflammation. Thus, the present study aimed to investigate whether there is an association between MIP-3-alpha- and MIP-3-beta expression and manifestation of pneumonia in patients suffering polytrauma.

MATERIAL AND METHODS

This prospective outcome study was conducted at our level I trauma center, and 110 polytraumatized patients (Injury Severity Score ≥ 16, ≥ 2 body regions) were prospectively enrolled (median age, 39 years; median Injury Severity Score (ISS), 33; 70.9% male) over four years. Protein levels were assessed at admission (day 0) and subsequently on days 1, 3, 5, 7, and 10 during routine blood draws, utilizing one separation gel tube for each measurement. Furthermore, the correlation between MIP-3-alpha- and MIP-3-beta expression and the manifestation of pneumonia was calculated.

RESULTS

We observed significantly higher levels of MIP-3-beta expression over the entire time course in the pneumonia cohort. MIP-3-alpha levels were elevated on days 3, 5, 7, and 10 post-trauma in patients suffering from pneumonia. In contrast, no comparable pattern was observed for other pro- and anti-inflammatory cytokines (e.g., IL-6 or TNF-alpha). A peak of serum level expression was documented on day 5 in both biomarkers (MIP-3-alpha 51.8 pg/mL; MIP-3-beta 328.0 pg/mL). ROC analysis provided a cut-off value of 19.3 pg/mL (sensitivity 0.87, specificity 0.33; AUC 0.757) for MIP-3-alpha, whereas a cut-off value of 209.5 pg/mL (sensitivity 0.78, specificity 0.34; AUC 0.757) was determined for MIP-3-beta on day 5.

CONCLUSION

The present study demonstrated elevated MIP-3-alpha and MIP-3-beta levels as sensitive pneumonia predictors in patients with multiple traumas. These biomarkers allow for identifying patients at high risk of developing pneumonia at an early stage.

The Importance of Lung Innate Immunity During Health and Disease

The lung is a vital organ for the body as the main source of oxygen input. Importantly, it is also an internal organ that has direct contact with the outside world. Innate immunity is a vital protective system in various organs, whereas, in the case of the lung, it helps maintain a healthy, functioning cellular and molecular environment and prevents any overt damage caused by pathogens or other inflammatory processes. Disturbances in lung innate immunity properties and processes, whether over-responsiveness of the process triggered by innate immunity or lack of responses due to dysfunctions in the immune cells that make up the innate immunity system of the lung, could be correlated to various pathological conditions. In this review, we discuss globally how the components of lung innate immunity are important not only for maintaining lung homeostasis but also during the pathophysiology of notable lung diseases beyond acute pulmonary infections, including chronic obstructive pulmonary disease (COPD), asthma, and pulmonary fibrosis.

Progress of CCL20-CCR6 in the airways: a promising new therapeutic target

The chemokine CCL20, a small cytokine that belongs to the C-C chemokine family, interacts with its homologous receptor CCR6, which is expressed on wide range of cell types. According to current research, the CCL20-CCR6 has been established as acritical player in a diverse range of inflammatory, oncogenic, and autoimmune diseases. Within the respiratory system, CCL20-CCR6 demonstrates heightened expression in conditions such as allergic asthma, chronic airway inflammation, non-small cell lung cancer (NSCLC), chronic obstructive pulmonary disease (COPD), and other respiratory diseases, which is conducive to the inflammatory mediators recruitment and tumor microenvironment remodeling. Numerous studies have demonstrated that therapeutic interventions targeting CCL20 and CCR6, including antibodies and antagonists, have the potential to mitigate disease progression. Despite the promising research prospects surrounding the CCL20-CCR6 chemokine axis, the precise mechanisms underlying its action in respiratory diseases remain largely elusive. In this review, we delve into the potential roles of the CCL20-CCR6 axis within the respiratory system by synthesizing and analyzing current research findings. Our objective is to provide a comprehensive understanding of the CCL20-CCR6 axis and its implications for respiratory health and disease. And we aspire to propel research endeavors in this domain and furnish valuable insights for the development of future therapeutic strategies.

Correlation and Clinical Significance of HBD-2 and CXCL-1/2 Levels at Skin Lesions with Psoriasis Vulgaris Severity

OBJECTIVE

This study was performed to explore the clinical significance of the expression of human beta-defensin 2 (HBD-2) and chemokine ligand 1/2 (CXCL-1/2) in psoriasis vulgaris.

METHODS

This study retrospectively included the study group (n = 160) and control group (n = 100) for analysis. The levels of inflammatory indicators, blood biochemical indicators, and immune indicators using ELISA. The psoriasis area and severity index (PASI) was used to evaluate disease severity. Levels of HBD-2, CXCL-1, CXCL-2 and CCL20 were determined by RT-PCR. The correlations of HBD-2, CXCL-1 and CXCL-2 levels with CCL20 and PASI scores were analyzed. The diagnostic value of HBD-2, CXCL-1 and CXCL-2 in psoriasis vulgaris was analyzed by ROC curve.

RESULTS

HBD-2, CXCL-1 and CXCL-2 were highly expressed in the lesions of psoriasis vulgaris patients, and were positively correlated with CCL20 and PASI score. HBD-2, CXCL-1 and CXCL-2 alone or in combination had high diagnostic value for psoriasis vulgaris and severe psoriasis, and the combined diagnostic value of the three was higher than that of a single indicator.

CONCLUSION

HBD-2, CXCL-1, and CXCL-2 levels are closely related to the severity of psoriasis vulgaris and can effectively diagnose the occurrence and progression of psoriasis vulgaris.

The underappreciated role of resident epithelial cell populations in metastatic progression: contributions of the lung alveolar epithelium

Metastatic cancer is difficult to treat and is responsible for the majority of cancer-related deaths. After cancer cells initiate metastasis and successfully seed a distant site, resident cells in the tissue play a key role in determining how metastatic progression develops. The lung is the second most frequent site of metastatic spread, and the primary site of metastasis within the lung is alveoli. The most abundant cell type in the alveolar niche is the epithelium. This review will examine the potential contributions of the alveolar epithelium to metastatic progression. It will also provide insight into other ways in which alveolar epithelial cells, acting as immune sentinels within the lung, may influence metastatic progression through their various interactions with cells in the surrounding microenvironment.

Human β-Defensin 2 and Its Postulated Role in Modulation of the Immune Response

Studies described so far suggest that human β-defensin 2 is an important protein of innate immune response which provides protection for the human organism against invading pathogens of bacterial, viral, fungal, as well as parasitical origin. Its pivotal role in enhancing immunity was proved in infants. It may also be considered a marker of inflammation. Its therapeutic administration has been suggested for maintenance of the balance of systemic homeostasis based on the appropriate composition of the microbiota. It has been suggested that it may be an important therapeutic tool for modulating the response of the immune system in many inflammatory diseases, offering new treatment modalities. For this reason, its properties and role in the human body discussed in this review should be studied in more detail.

Uncovering the Hidden Credentials of Brucella Virulence

Bacteria in the genus Brucella are important human and veterinary pathogens. The abortion and infertility they cause in food animals produce economic hardships in areas where the disease has not been controlled, and human brucellosis is one of the world's most common zoonoses. Brucella strains have also been isolated from wildlife, but we know much less about the pathobiology and epidemiology of these infections than we do about brucellosis in domestic animals. The brucellae maintain predominantly an intracellular lifestyle in their mammalian hosts, and their ability to subvert the host immune response and survive and replicate in macrophages and placental trophoblasts underlies their success as pathogens. We are just beginning to understand how these bacteria evolved from a progenitor alphaproteobacterium with an environmental niche and diverged to become highly host-adapted and host-specific pathogens. Two important virulence determinants played critical roles in this evolution: (i) a type IV secretion system that secretes effector molecules into the host cell cytoplasm that direct the intracellular trafficking of the brucellae and modulate host immune responses and (ii) a lipopolysaccharide moiety which poorly stimulates host inflammatory responses. This review highlights what we presently know about how these and other virulence determinants contribute to Brucella pathogenesis. Gaining a better understanding of how the brucellae produce disease will provide us with information that can be used to design better strategies for preventing brucellosis in animals and for preventing and treating this disease in humans.

Immunological pathways of macrophage response to Brucella ovis infection

As the molecular mechanisms of Brucella ovis pathogenicity are not completely clear, we have applied a transcriptome approach to identify the differentially expressed genes (DEGs) in RAW264.7 macrophage infected with B. ovis. The DEGs related to immune pathway were identified by Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) functional enrichment analysis. Quantitative real-time PCR (qRT-PCR) was performed to validate the transcriptome sequencing data. In total, we identified 337 up-regulated and 264 down-regulated DEGs in B. ovis-infected group versus mock group. Top 20 pathways were enriched by KEGG analysis and 20 GO by functional enrichment analysis in DEGs involved in the molecular function, cellular component, and biological process and so on, which revealed multiple immunological pathways in RAW264.7 macrophage cells in response to B. ovis infection, including inflammatory response, immune system process, immune response, cytokine activity, chemotaxis, chemokine-mediated signaling pathway, chemokine activity, and CCR chemokine receptor binding. qRT-PCR results showed Ccl2 (ENSMUST00000000193), Ccl2 (ENSMUST00000124479), Ccl3 (ENSMUST00000001008), Hmox1 (ENSMUST00000005548), Hmox1 (ENSMUST00000159631), Cxcl2 (ENSMUST00000075433), Cxcl2 (ENSMUST00000200681), Cxcl2 (ENSMUST00000200919), and Cxcl2 (ENSMUST00000202317). Our findings firstly elucidate the pathways involved in B. ovis-induced host immune response, which may lay the foundation for revealing the bacteria–host interaction and demonstrating the pathogenic mechanism of B. ovis.

Host and Pathogen Communication in the Respiratory Tract: Mechanisms and Models of a Complex Signaling Microenvironment

Chronic lung diseases are a leading cause of morbidity and mortality across the globe, encompassing a diverse range of conditions from infections with pathogenic microorganisms to underlying genetic disorders. The respiratory tract represents an active interface with the external environment having the primary immune function of resisting pathogen intrusion and maintaining homeostasis in response to the myriad of stimuli encountered within its microenvironment. To perform these vital functions and prevent lung disorders, a chemical and biological cross-talk occurs in the complex milieu of the lung that mediates and regulates the numerous cellular processes contributing to lung health. In this review, we will focus on the role of cross-talk in chronic lung infections, and discuss how different cell types and signaling pathways contribute to the chronicity of infection(s) and prevent effective immune clearance of pathogens. In the lung microenvironment, pathogens have developed the capacity to evade mucosal immunity using different mechanisms or virulence factors, leading to colonization and infection of the host; such mechanisms include the release of soluble and volatile factors, as well as contact dependent (juxtracrine) interactions. We explore the diverse modes of communication between the host and pathogen in the lung tissue milieu in the context of chronic lung infections. Lastly, we review current methods and approaches used to model and study these host-pathogen interactions in vitro, and the role of these technological platforms in advancing our knowledge about chronic lung diseases.

Brucella abortus Proliferates in Decidualized and Non-Decidualized Human Endometrial Cells Inducing a Proinflammatory Response

Brucella spp. have been associated with abortion in humans and animals. Although the mechanisms involved are not well established, it is known that placental Brucella infection is accompanied by inflammatory phenomena. The ability of Brucella abortus to infect and survive in human endometrial stromal cells (T-HESC cell line) and the cytokine response elicited were evaluated. B. abortus was able to infect and proliferate in both non-decidualized and decidualized T-HESC cells. Intracellular proliferation depended on the expression of a functional virB operon in the pathogen. B. abortus internalization was inhibited by cytochalasin D and to a lower extent by colchicine, but was not affected by monodansylcadaverine. The infection did not induce cytotoxicity and did not alter the decidualization status of cells. B. abortus infection elicited the secretion of IL-8 and MCP-1 in either decidualized or non-decidualized T-HESC, a response also induced by heat-killed B. abortus and outer membrane vesicles derived from this bacterium. The stimulation of T-HESC with conditioned media from Brucella-infected macrophages induced the production of IL-6, MCP-1 and IL-8 in a dose-dependent manner, and this effect was shown to depend on IL-1β and TNF-α. The proinflammatory responses of T-HESC to B. abortus and to factors produced by infected macrophages may contribute to the gestational complications of brucellosis.

Caspase-4 Mediates Restriction of Burkholderia pseudomallei in Human Alveolar Epithelial Cells

Melioidosis is an infectious disease with a high mortality rate responsible for community-acquired sepsis in Southeast Asia and Northern Australia. The causative agent of this disease is Burkholderia pseudomallei, a Gram-negative bacterium that resides in soil and contaminated natural water. After entering into host cells, the bacteria escape into the cytoplasm, which has numerous cytosolic sensors, including the noncanonical inflammatory caspases. Although the noncanonical inflammasome (caspase-11) has been investigated in a murine model of B. pseudomallei infection, its role in humans, particularly in lung epithelial cells, remains unknown. We, therefore, investigated the function of caspase-4 (ortholog of murine caspase-11) in intracellular killing of B. pseudomallei The results showed that B. pseudomallei induced caspase-4 activation at 12 h postinfection in human alveolar epithelial A549 cells. The number of intracellular B. pseudomallei bacteria was increased in the absence of caspase-4, suggesting its function in intracellular bacterial restriction. In contrast, a high level of caspase-4 processing was observed when cells were infected with lipopolysaccharide (LPS) mutant B. pseudomallei The enhanced bacterial clearance in LPS-mutant-infected cells is also correlated with a higher degree of caspase-4 activation. These results highlight the susceptibility of the LPS mutant to caspase-4-mediated intracellular bacterial killing.

The role of the innate immune system on pulmonary infections

Inhalation is required for respiration and life in all vertebrates. This process is not without risk, as it potentially exposes the host to environmental pathogens with every breath. This makes the upper respiratory tract one of the most common routes of infection and one of the leading causes of morbidity and mortality in the world. To combat this, the lung relies on the innate immune defenses. In contrast to the adaptive immune system, the innate immune system does not require sensitization, previous exposure or priming to attack foreign particles. In the lung, the innate immune response starts with the epithelial barrier and mucus production and is reinforced by phagocytic cells and T cells. These cells are vital for the production of cytokines, chemokines and anti-microbial peptides that are critical for clearance of infectious agents. In this review, we discuss all aspects of the innate immune response, with a special emphasis on ways to target aspects of the immune response to combat antibiotic resistant bacteria.

Immune Response to Mucosal Brucella Infection

Brucellosis is one of the most prevalent bacterial zoonosis of worldwide distribution. The disease is caused by Brucella spp., facultative intracellular pathogens. Brucellosis in animals results in abortion of fetuses, while in humans, it frequently manifests flu-like symptoms and a typical undulant fever, being osteoarthritis a common complication of the chronic infection. The two most common ways to acquire the infection in humans are through the ingestion of contaminated dairy products or by inhalation of contaminated aerosols. Brucella spp. enter the body mainly through the gastrointestinal and respiratory mucosa; however, most studies of immune response to Brucella spp. are performed analyzing models of systemic immunity. It is necessary to better understand the mucosal immune response induced by Brucella infection since this is the main entry site for the bacterium. In this review, some virulence factors and the mechanisms needed for pathogen invasion and persistence are discussed. Furthermore, some aspects of local immune responses induced during Brucella infection will be reviewed. With this knowledge, better vaccines can be designed focused on inducing protective mucosal immune response.

Histological and Comparative Transcriptome Analyses Provide Insights into Small Intestine Health in Diarrheal Piglets after Infection with Clostridium Perfringens Type C

C. perfringens type C can induce enteritis accompanied by diarrhea and annually causes significant economic losses to the global pig industry. The pathogenic mechanisms of C. perfringens type C in pigs are still largely unknown. To investigate this, we challenged seven-day-old piglets with C. perfringens type C to cause diarrhea. We performed hematoxylin & eosin (H&E) staining of the small intestine (including duodenum, jejunum, and ileum) and assessed gene expression in the ileal tissue. H&E staining of the duodenum, jejunum, and ileum demonstrated inflammation and edema of the lamina propria and submucosa. A total of 2181 differentially expressed genes (DEGs) were obtained in ileal tissues. Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis of DEGs indicated that the main pathways were enriched in the T cell receptor signaling pathway, NF-kappa B signaling pathway, and (tumor necrosis factor) TNF signaling pathway. These results provide insights into the pathogenicity of C. perfringens type C and improve our understanding of host-bacteria interactions.

SIRT1/FoxO3 axis alteration leads to aberrant immune responses in bronchial epithelial cells

Inflammation and ageing are intertwined in chronic obstructive pulmonary disease (COPD). The histone deacetylase SIRT1 and the related activation of FoxO3 protect from ageing and regulate inflammation. The role of SIRT1/FoxO3 in COPD is largely unknown. This study evaluated whether cigarette smoke, by modulating the SIRT1/FoxO3 axis, affects airway epithelial pro-inflammatory responses. Human bronchial epithelial cells (16HBE) and primary bronchial epithelial cells (PBECs) from COPD patients and controls were treated with/without cigarette smoke extract (CSE), Sirtinol or FoxO3 siRNA. SIRT1, FoxO3 and NF-κB nuclear accumulation, SIRT1 deacetylase activity, IL-8 and CCL20 expression/release and the release of 12 cytokines, neutrophil and lymphocyte chemotaxis were assessed. In PBECs, the constitutive FoxO3 expression was lower in patients with COPD than in controls. Furthermore, CSE reduced FoxO3 expression only in PBECs from controls. In 16HBE, CSE decreased SIRT1 activity and nuclear expression, enhanced NF-κB binding to the IL-8 gene promoter thus increasing IL-8 expression, decreased CCL20 expression, increased the neutrophil chemotaxis and decreased lymphocyte chemotaxis. Similarly, SIRT1 inhibition reduced FoxO3 expression and increased nuclear NF-κB. FoxO3 siRNA treatment increased IL-8 and decreased CCL20 expression in 16HBE. In conclusion, CSE impairs the function of SIRT1/FoxO3 axis in bronchial epithelium, dysregulating NF-κB activity and inducing pro-inflammatory responses.

Targeting and inactivation of bacterial toxins by human defensins

Defensins, as a prominent family of antimicrobial peptides (AMP), are major effectors of the innate immunity with a broad range of immune modulatory and antimicrobial activities. In particular, defensins are the only recognized fast-response molecules that can neutralize a broad range of bacterial toxins, many of which are among the deadliest compounds on the planet. For a decade, the mystery of how a small and structurally conserved group of peptides can neutralize a heterogeneous group of toxins with little to no sequential and structural similarity remained unresolved. Recently, it was found that defensins recognize and target structural plasticity/thermodynamic instability, fundamental physicochemical properties that unite many bacterial toxins and distinguish them from the majority of host proteins. Binding of human defensins promotes local unfolding of the affected toxins, destabilizes their secondary and tertiary structures, increases susceptibility to proteolysis, and leads to their precipitation. While the details of toxin destabilization by defensins remain obscure, here we briefly review properties and activities of bacterial toxins known to be affected by or resilient to defensins, and discuss how recognized features of defensins correlate with the observed inactivation.

The innate immune response to lower respiratory tract E. Coli infection and the role of the CCL2-CCR2 axis in neonatal mice

Neonates have greater morbidity/mortality from lower respiratory tract infections (LRTI) compared to older children. Lack of conditioning of the pulmonary immune system due to limited environmental exposures and/or infectious challenges likely contributes to the increase susceptibility in the neonate. In this study, we sought to gain insights into the nature and dynamics of the neonatal pulmonary immune response to LRTI using a murine model.

METHODS

Wildtype (WT) and Ccr2^-/- C57BL/6 neonatal and juvenile mice received E. coli or PBS by direct pharyngeal aspiration. Flow cytometry was used to measure immune cell dynamics and identify cytokine-producing cells. Real-time PCR and ELISA were used to measure cytokine/chemokine expression.

RESULTS

Innate immune cell recruitment in response to E. coli-induced LRTI was delayed in the neonatal lung compared to juvenile lung. Lung clearance of bacteria was also significantly delayed in the neonate. Ccr2^-/- neonates, which lack an intact CCL2-CCR2 axis, had higher mortality after E. coli challenged than Ccr2^+/+ neonates. A greater percentage of CD8⁺ T cells and monocytes from WT neonates challenged with E. coli produced TNF compared to controls.

CONCLUSION

The pulmonary immune response to E. coli-induced LRTI differed significantly between neonatal and juvenile mice. Neonates were more susceptible to increasing doses of E. coli and exhibited greater mortality than juveniles. In the absence of an intact CCL2-CCR2 axis, susceptibility to LRTI-induced mortality was further increased in neonatal mice. Taken together these findings underscore the importance of age-related differences in the innate immune response to LRTI during early stages of postnatal life.

Antimicrobial efficacy against Pseudomonas aeruginosa biofilm formation in a three-dimensional lung epithelial model and the influence of fetal bovine serum

In vitro models that mimic in vivo host-pathogen interactions are needed to evaluate candidate drugs that inhibit bacterial virulence traits. We established a new approach to study Pseudomonas aeruginosa biofilm susceptibility on biotic surfaces, using a three-dimensional (3-D) lung epithelial cell model. P. aeruginosa formed antibiotic resistant biofilms on 3-D cells without affecting cell viability. The biofilm-inhibitory activity of antibiotics and/or the anti-biofilm peptide DJK-5 were evaluated on 3-D cells compared to a plastic surface, in medium with and without fetal bovine serum (FBS). In both media, aminoglycosides were more efficacious in the 3-D cell model. In serum-free medium, most antibiotics (except polymyxins) showed enhanced efficacy when 3-D cells were present. In medium with FBS, colistin was less efficacious in the 3-D cell model. DJK-5 exerted potent inhibition of P. aeruginosa association with both substrates, only in serum-free medium. DJK-5 showed stronger inhibitory activity against P. aeruginosa associated with plastic compared to 3-D cells. The combined addition of tobramycin and DJK-5 exhibited more potent ability to inhibit P. aeruginosa association with both substrates. In conclusion, lung epithelial cells influence the efficacy of most antimicrobials against P. aeruginosa biofilm formation, which in turn depends on the presence or absence of FBS.

Impact of high-dose vitamin D3 on plasma free 25-hydroxyvitamin D concentrations and antimicrobial peptides in critically ill mechanically ventilated adults

OBJECTIVES

High-dose vitamin D₃ increases plasma total 25-hydroxyvitamin D [25(OH)D] in critically ill, ventilated patients; however, to our knowledge, the effect on plasma levels of free (nonprotein-bound) 25(OH)D has not been investigated in critical illness. Moreover, the relationship of free 25(OH)D and the regulation of endogenous antimicrobial peptides (AMPs) remains unknown. The aims of this study were to determine in critically ill adults with respiratory failure the effect of previous high-dose regimens of vitamin D₃ on free 25(OH)D concentrations, the relationship of free 25(OH)D with circulating cathelicidin (LL-37) and human beta-defensin-2 (hBD-2), and the associations between plasma levels of free 25(OH)D and these AMPs to alveolar macrophage phagocytosis function.

METHODS

In a double blind, randomized controlled trial, critically ill ventilator-dependent adults (N = 30) received enteral vitamin D₃ (250,000 or 500,000 IU total over 5 d) or placebo. Plasma was obtained serially for concentrations of free 25(OH)D, LL-37, hBD-2, and expression of peripheral blood mononuclear cell human cationic antimicrobial protein (hCAP18) mRNA. Total 25(OH)D and LL-37 concentrations and alveolar macrophage phagocytosis were determined in bronchoalveolar lavage fluid.

RESULTS

Plasma concentrations of free 25(OH)D over time were correlated with total 25(OH)D levels (r= 0.82; P < 0.001). The increase in free 25(OH)D was greater with the 500 000 IU vitamin D₃ dose than with the lower dose. The percent change in mRNA expression of hCAP18 was positively associated with percent change in free 25(OH)D at days 7 and 14 (ρ = 0.48; P = 0.04 and ρ = 0.59; P = 0.03, respectively). Additionally, plasma LL-37 levels correlated with the percentage of alveolar macrophages exhibiting phagocytosis (ρ = 0.51; P = 0.04).

CONCLUSIONS

The present study found a dose-related increase in plasma free-25(OH)D levels, which was associated with increasing circulating mRNA expression of hCAP18 over time. There were no correlations between changes in total and free 25(OH)D against plasma LL-37 and hBD-2 concentrations. Larger studies appear warranted to determine the impact of high-dose vitamin D₃ administration on endogenous AMPs.