Human host defense peptide LL-37 facilitates double-stranded RNA pro-inflammatory signaling through up-regulation of TLR3 expression in vascular smooth muscle cells.

OBJECTIVE: The importance of human host defense peptide LL-37 in vascular innate immunity is not understood. Here, we assess the impact of LL-37 on double-stranded RNA (dsRNA) signaling in human vascular smooth muscle cells. MATERIALS AND METHODS: Cellular import of LL-37 and synthetic dsRNA (poly I:C) were investigated by immunocytochemistry and fluorescence imaging. Transcript and protein expression were determined by qPCR, ELISA and Western blot. Knockdown of TLR3 was performed by siRNA. RESULTS: LL-37 was rapidly internalized, suggesting that it has intracellular actions. Co-stimulation with poly I:C and LL-37 enhanced pro-inflammatory IL-6 and MCP-1 transcripts several fold compared to treatment with poly I:C or LL-37 alone. Poly I:C increased IL-6 and MCP-1 protein production, and this effect was potentiated by LL-37. LL-37-induced stimulation of poly I:C signaling was not associated with enhanced import of poly I:C. Treatment with poly I:C and LL-37 in combination increased expression of dsRNA receptor TLR3 compared to stimulation with poly I:C or LL-37 alone. In TLR3 knockdown cells, treatment with poly I:C and LL-37 in combination had no effect on IL-6 and MCP-1 expression, showing loss of function. CONCLUSIONS: LL-37 potentiates dsRNA-induced cytokine production through up-regulation of TLR3 expression representing a novel pro-inflammatory mechanism.

Antimicrobial peptide LL-37 and its pro-form, hCAP18, in desquamated epithelial cells of human whole saliva.

The antimicrobial peptide LL-37 is active against oral bacteria and has been demonstrated to be present in human saliva, but its distribution in different fractions of saliva is not known. LL-37 is formed from its intracellular pro-form, hCAP18, in an extracellular enzymatic reaction catalyzed by proteinase 3 and kallikrein 5. Here, we prepared cell-containing and cell-free fractions of unstimulated human whole saliva by centrifugation after depolymerization of mucins with dithiothreitol, and measured the levels of hCAP18/LL-37 in these fractions using ELISA. Cellular expression of hCAP18/LL-37 was determined by western blotting and immunocytochemistry. The ELISA analyses demonstrated that both cells and cell-free saliva contained hCAP18/LL-37. Western blot analysis of cell-pellet homogenates showed a strong band corresponding to hCAP18 at the correct molecular weight and a weak band corresponding to LL-37. Phase-contrast and light microscopy revealed that the cells consisted of desquamated epithelial cells. These cells expressed cytoplasmic immunoreactivity for hCAP18/LL-37. The peripheral part of the cytoplasm, corresponding to the plasma membrane, was particularly rich in hCAP18/LL-37 immunoreactivity. No immunoreactivity was observed after omission of the primary antibody. We conclude that desquamated epithelial cells of human whole saliva contain antimicrobial hCAP18/LL-37, suggesting that these cells may take part in the innate immune system by harboring and releasing these peptides.

Odontoblast-like MDPC-23 cells produce pro-inflammatory IL-6 in response to lipoteichoic acid and express the antimicrobial peptide CRAMP.

Objective: Odontoblasts are thought to be involved in innate immunity but their precise role in this process is not fully understood. Here, we assess effects of lipopolysaccharide (LPS) and lipoteichoic acid (LTA), produced by Gram-negative and Gram-positive bacteria, respectively, on matrix metalloproteinase-8 (MMP-8), interleukin-6 (IL-6) and cathelin-related antimicrobial peptide (CRAMP) expression in odontoblast-like MDPC-23 cells.Material and methods: Gene activity and protein production was determined by quantitative real-time RT-PCR and ELISA, respectively. Cellular expression of CRAMP was determined by immunocytochemistry.Results: Stimulation with LTA (5 and 25 µg/ml) but not LPS (1 and 5 µg/ml) for 24 h enhanced IL-6 mRNA expression. The LTA-induced up-regulation of IL-6 mRNA levels was associated with increased IL-6 protein levels. Stimulation with either LPS or LTA for 24 h lacked effect on both MMP-8 transcript and protein expression. Immunocytochemistry disclosed that MDPC-23 cells expressed immunoreactivity for CRAMP. MDPC-23 cells showed mRNA expression for CRAMP, but stimulation with either LPS or LTA did not modulate CRAMP transcript expression.Conclusions: We show that MDPC-23 cells possess immune-like cell properties such as LTA-induced IL-6 production and expression of the antimicrobial peptide CRAMP, suggesting that odontoblasts may modulate innate immunity via these mechanisms.

The host defense peptide LL-37 is internalized by human periodontal ligament cells and prevents LPS-induced MCP-1 production.

OBJECTIVE: The human host defense peptide LL-37 both shows antimicrobial effects and modulates host cell properties. Here, we assess the effects of synthesized LL-37 on lipopolysaccharide (LPS)-induced inflammation in human periodontal ligament (PDL) cells and investigates underlying mechanisms. BACKGROUND: LL-37 has been detected in the periodontal tissues, but its functional importance for PDL cell innate immune responses is not known. METHODS: Human PDL cells were obtained from premolars extracted on orthodontic indications. Cellular pro-inflammatory monocyte chemoattractant protein-1 (MCP-1) mRNA expression was determined using quantitative real-time RT-PCR. MCP-1 protein production was assessed by western blot and ELISA. Internalization of LL-37 by PDL cells was visualized by immunocytochemistry. Nuclear factor kappa-light-chain-enhancer of activated B-cell (NF-κB) activity was assessed by western blot of phosphorylated p65, phosphorylated p105, and IκBα proteins. Binding of LL-37 to PDL cell DNA was determined by isolation and purification of DNA and dot blot for LL-37 immunoreactivity. RESULTS: Treatment with LL-37 (1 µmol/L) for 24 hours prevented LPS-induced stimulation of MCP-1 expression analyzed both on transcript and on protein levels. Stimulation with LL-37 (1 µmol/L) for 24 hours had no effect on toll-like receptor (TLR)2 and TLR4 transcript expression, suggesting that LL-37 acts downstream of the TLRs. Preincubation with LL-37 for 60 minutes followed by stimulation with LPS for 24 hours in the absence of LL-37 completely prevented LPS-evoked MCP-1 transcript expression, implying that LL-37 acts intracellularly and not via binding and neutralization of LPS. In PDL cells stimulated with LL-37 for 60 minutes, the peptide was internalized as demonstrated by immunocytochemistry, suggesting an intracellular mechanism of action. LL-37 immunoreactivity was observed both in the cytosol and in the nucleus. Downregulation of LPS-induced MCP-1 by LL-37 was not mediated by reduction in NF-κB activity as shown by unaltered expression of phosphorylated p65, phosphorylated p105, and IκBα NF-κB proteins in the presence of LL-37. Immunoreactivity for LL-37 was observed in PDL cell DNA treated with but not without 0.1 and 1 µmol/L LL-37 for 60 minutes in vitro. CONCLUSION: LL-37 abolishes LPS-induced MCP-1 production in human PDL cells through an intracellular, NF-κB-independent mechanism which probably involves direct interaction between LL-37 and DNA.

High prevalence of pituitary hormone deficiency in both unilateral and bilateral optic nerve hypoplasia.

AIM: This study examined the prevalence of neurological impairment and pituitary hormone deficiency (PHD) in patients with unilateral and bilateral optic nerve hypoplasia (ONH). METHODS: A population-based cross-sectional cohort study of 65 patients (51% female) with ONH was conducted in Stockholm. Of these were 35 bilateral and 30 unilateral. The patients were below 20 years of age, living in Stockholm in December 2009 and found through database searching. The median age at the analysis of the results in January 2018 was 16.1 years (range 8.1-27.5 years). Neurological assessments and blood sampling were conducted, neuroradiology was reviewed and growth curves were analysed. Diagnoses of PHDs were based on clinical and biochemical evidence of hormone deficiency. RESULTS: Neurological impairments were identified in 47% of the patients and impairments in gross and fine motor function were more prevalent in bilateral ONH (p < 0.001). In addition, 9% had cerebral palsy and 14% had epilepsy. The prevalence of PHD was 29 and 19% had multiple PHD. CONCLUSION: Children with ONH had a high risk of neurological impairment, especially in bilateral disease. Both unilateral and bilateral ONH signified an increased prevalence of PHD and all these children should be endocrinologically followed up until completed puberty.

LL-37-induced human osteoblast cytotoxicity and permeability occurs independently of cellular LL-37 uptake through clathrin-mediated endocytosis.

The host defense peptide LL-37 is cytotoxic for bacteria but it has also been reported to reduce host cell viability through an intracellular mechanism. LL-37-evoked cytotoxicity may be involved in the loss of bone tissue in periodontitis which is an inflammatory disease characterized by high concentrations of LL-37 observed locally in the periodontal tissue at the inflammation process. Here, we showed that LL-37 reduced human osteoblast-like MG63 cell viability assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and increased plasma membrane permeability determined by measuring intracellular Ca2+ levels and lactate dehydrogenase (LDH) release. Treatment with chlorpromazine, a well-recognized inhibitor of clathrin-mediated endocytosis, reduced cellular uptake of synthesized LL-37 b y about 30% assessed by Western blotting and ELISA, while filipin, an inhibitor of caveolin-mediated endocytosis, had no effect. The chlorpromazine-induced attenuation of LL-37 uptake was not associated with modulation of LL-37-induced cytotoxicity and LL-37-evoked plasma membrane permeability. Clathrin heavy chain 2 is a major protein of the polyhedral coat of coated pits and vesicles encoded by clathrin heavy chain like 1 gene. Down-regulation of clathrin heavy chain like 1 gene activity by siRNA reduced uptake of LL-37 but did not affect LL-37-induced cytotoxicity and permeability. Thus, we show, using both a pharmacological approach and knockdown of clathrin heavy chain like 1 expression, that LL-37-induced MG63 cell cytotoxicity and permeability occurs independently of LL-37 uptake via clathrin-mediated endocytosis.

Children with optic nerve hypoplasia face a high risk of neurodevelopmental disorders.

AIM: Optic nerve hypoplasia (ONH) is a congenital ocular malformation that has been associated with neurodevelopmental disorders, but the prevalence in unilateral disease and less severe visual impairment is unknown. We studied intellectual disability and autism spectrum disorders (ASDs) in patients with ONH. METHODS: This was a population-based cross-sectional cohort study of 65 patients (33 female) with ONH below 20 years of age, living in Stockholm in December 2009, with data analysed in January 2016. Of these 35 were bilateral and 30 were unilateral. Neurodevelopmental disorders were diagnosed or confirmed by neurological assessments, the Five to Fifteen parent questionnaire and reviewing previous neuropsychological investigations or conducting neuropsychological tests. RESULTS: Bilateral ONH patients had lower mean full scale intelligence quotient scores than unilateral patients (84.4 and 99.4, respectively, p = 0.049). We assessed intellectual disability in 55 eligible patients, and it was more common in patients with bilateral ONH (18 of 32, 56%) than unilateral ONH (two of 23, 9%, p < 0.001). ASDs were diagnosed in seven of 42 (17%) patients. CONCLUSION: Children with bilateral ONH had a high risk of neurodevelopmental disorders, especially intellectual disability. The risk was lower in unilateral ONH, but the levels of neurodevelopmental disorders warrant screening of both groups.

Activation of glial cells induces proinflammatory properties in brain capillary endothelial cells in vitro.

Neurodegenerative diseases are often accompanied by neuroinflammation and impairment of the blood-brain barrier (BBB) mediated by activated glial cells through their release of proinflammatory molecules. To study the effects of glial cells on mouse brain endothelial cells (mBECs), we developed an in vitro BBB model with inflammation by preactivating mixed glial cells (MGCs) with lipopolysaccharide (LPS) before co-culturing with mBECs to study the influence of molecules released by activated MGCs. The response of the mBECs to activated MGCs was compared to direct stimulation with LPS. The cytokine profile of activated MGCs was analyzed together with their effects on the mBEC's integrity, expression of tight junction proteins, adhesion molecules, and BBB-specific transport proteins. Stimulation of MGCs significantly upregulated mRNA expression and secretion of several pro-inflammatory cytokines. Co-culturing mBECs with pre-stimulated MGCs significantly affected the barrier integrity of mBECs similar to direct stimulation with LPS. The gene expression levels of tight junction proteins were unaltered, but tight junction proteins revealed rearrangements with respect to subcellular distribution. Compared to direct stimulation with LPS, the expression of cell-adhesion molecules was significantly increased when mBECs were co-cultured with prestimulated MGCs and thus pre-activating MGCs transforms mBECs into a proinflammatory phenotype.

LL-37-induced caspase-independent apoptosis is associated with plasma membrane permeabilization in human osteoblast-like cells.

The host defense peptide LL-37 is active against both gram-positive and gram-negative bacteria, but it has also been shown to reduce human host cell viability. However, the mechanisms behind LL-37-induced human host cell cytotoxicity are not yet fully understood. Here, we assess if LL-37-evoked attenuation of human osteoblast-like MG63 cell viability is associated with apoptosis, and if the underlying mechanism may involve LL-37-induced plasma membrane permeabilization. MG63 cell viability and plasma membrane permeabilization were investigated by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method and by measuring lactate dehydrogenase (LDH) release, respectively. Apoptosis was assessed by the terminal deoxynucleotidyl dUTP nick end labeling (TUNEL) assay and Annexin V flow cytometry, and caspase-3 and poly (ADP-ribose) polymerase (PARP) cleavage were determined by Western blot. LL-37 (4 and 10 µM) reduced both cell number and cell viability, and these effects were associated with a pro-apoptotic effect demonstrated by positive TUNEL staining and Annexin V flow cytometry. LL-37-induced apoptosis was not coupled to either caspase-3 or PARP cleavage, suggesting that LL-37 causes caspase-independent apoptosis in MG63 cells. Both LL-37 and the well-known plasma membrane permeabilizer Triton X-100 reduced cell viability and stimulated LDH release. Triton X-100-treated cells showed positive TUNEL staining, and the detergent accumulated cells in late apoptosis/necrosis. Similar to LL-37, Triton X-100 caused no PARP cleavage. We conclude that LL-37 promotes caspase-independent apoptosis, and that this effect seems coupled to plasma membrane permeabilization in human MG63 cells.

[Important to evaluate children with visual impairment]. / Viktigt att överväga utredning av barn med optikusmissbildningar.

Congenital optic disc malformations can cause visual impairment. Diagnostics can be challenging during early infancy and childhood and visual prognosis difficult to predict; optical coherence tomography may be of value. The children often have coexisting comorbidities like pituitary hormone deficiency, neurodevelopmental disorders, and neurological impairments, and evaluation by a pediatrician should be performed. Also, genetic analyses should be considered. Co-operation in multidisciplinary teams is of value for correct diagnosis, visual habilitation and treatment of hormonal and neurological dysfunctions.

Whole genome sequencing unveils genetic heterogeneity in optic nerve hypoplasia.

Optic nerve hypoplasia (ONH) is a congenital malformation with a reduced number of retinal ganglion cell axons in a thin optic nerve. It is a common cause of visual impairment in children and ONH is associated with neurodevelopmental disorders, pituitary hormone deficiencies, and brain malformations. In most cases, the aetiology is unknown, but both environmental factors and genetic causes have been described. This study aimed to identify genetic variants underlying ONH in a well-characterised cohort of individuals with ONH. We performed array comparative genomic hybridization and whole genome sequencing in 29 individuals with ONH. Rare variants were verified by Sanger sequencing and inheritance was assessed in parental samples. We identified 11 rare single nucleotide variants (SNVs) in ten individuals, including a homozygous variant in KIF7 (previously associated with Joubert syndrome), a heterozygous de novo variant in COL4A1 (previously described in an individual with porencephaly), and a homozygous variant in COL4A2. In addition, one individual harboured a heterozygous variant in OPA1 and a heterozygous variant in COL4A1, both were inherited and assessed as variants of unknown clinical significance. Finally, a heterozygous deletion of 341 kb involving exons 7-18 of SOX5 (associated with Lamb-Schaffer syndrome) was identified in one individual. The overall diagnostic yield of pathogenic or likely pathogenic variants in individuals with ONH using whole genome sequencing was 4/29 (14%). Our results show that there is a genetic heterogeneity in ONH and indicate that genetic causes of ONH are not rare. We conclude that genetic testing is valuable in a substantial proportion of the individuals with ONH, especially in cases with non-isolated ONH.

The host defense peptide LL-37 triggers release of nucleic acids from human mast cells.

The human host defense peptide LL-37 possesses antimicrobial activity but also affects host cell function and viability. Mast cells are involved in innate immunity but no data have been presented on effects of LL-37 on human mast cell viability and export of nucleic acids. Here, we demonstrated by immunofluorescence microscopy that synthesized LL-37 was internalized by human LAD2 mast cells and detected both in cytoplasm and nucleus. Treatment with high (4 and 10 µM) but not low (1 µM) concentrations of LL-37 for 4 h reduced cell viability assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Stimulation with 10 µM LL-37 for 4 h enhanced export of nucleic acids, total protein and lactate dehydrogenase (LDH), suggesting that both nuclear and plasma membranes are permeabilized by LL-37. Although LL-37 triggered release of nucleic acids, no extracellular trap-like structures were observed by laser scanning confocal microscopy of cells incubated with the plasma membrane impermeable nucleic acid fluorophore SYTOX-Green, indicating that LL-37 promotes export of nucleic acids but not formation of extracellular traps. On the other hand, phorbol-12-myristate-13-acetate (PMA), which is a well-known inducer of extracellular traps, stimulated export of nucleic acids and also formation of extracellular trap-like structures. However, PMA had no effect on export of either total protein or LDH. Hence, LL-37 and PMA seem to stimulate export of nucleic acids from LAD2 mast cells through different pathways. In conclusion, we demonstrate that LL-37 triggers release of nucleic acids from human mast cells but not the formation of extracellular trap-like structures.

Lipocalin-2 Functions as Inhibitor of Innate Resistance to Mycobacterium tuberculosis.

Lipocalin-2 is a constituent of the neutrophil secondary granules and is expressed de novo by macrophages and epithelium in response to inflammation. Lipocalin-2 acts in a bacteriostatic fashion by binding iron-loaded siderophores required for bacterial growth. Mycobacterium tuberculosis (M.tb) produces siderophores that can be bound by lipocalin-2. The impact of lipocalin-2 in the innate immune response toward extracellular bacteria has been established whereas the effect on intracellular bacteria, such as M.tb, is less well-described. Here we show that lipocalin-2 surprisingly confers a growth advantage on M.tb in the early stages of infection (3 weeks post-challenge). Using mixed bone marrow chimeras, we demonstrate that lipocalin-2 derived from granulocytes, but not from epithelia and macrophages, leads to increased susceptibility to M.tb infection. In contrast, lipocalin-2 is not observed to promote mycobacterial growth at later stages of M.tb infection. We demonstrate co-localization of granulocytes and mycobacteria within the nascent granulomas at week 3 post-challenge, but not in the consolidated granulomas at week 5. We hypothesize that neutrophil-derived lipocalin-2 acts to supply a source of iron to M.tb in infected macrophages within the immature granuloma, thereby facilitating mycobacterial growth.

Optic nerve hypoplasia in children and adolescents; prevalence, ocular characteristics and behavioural problems.

PURPOSE: To report prevalence, ocular characteristics and coexisting behavioural problems in children and adolescents with optic nerve hypoplasia (ONH), which is a common cause of visual impairment in children in western countries, often associated with neurological or endocrinological problems and where autism has been reported in severe cases with blindness. METHODS: This is a population-based cross-sectional study of patients <20 years of age who had been diagnosed with ONH and lived in the county of Stockholm in December 2009. Ophthalmological assessments including fundus photographs with optic disc analyses were made. A questionnaire was used to screen for behaviour and development. RESULTS: The prevalence of ONH in all living children <18 years of age in Stockholm was 17.3/100 000 with a prevalence of visual impairment (<0.3) of 3.9/100 000. In total, 66 patients, median age 9.3 years (0.6-19.4), 36 with bilateral and 30 with unilateral ONH, were included in the current study; 53 were re-examined clinically, group A, and 13 agreed to retrospective analyses of existing medical records, group B. Analyses of the optic discs were made in fundus photographs from 53 patients comparing a semi-automated (Retinal Size Tool) and a manual method (Zeki). There was a strong curvilinear correlation (r(S)  = -0.91 p < 0.0001 for both eyes). Behavioural problems were more common (p < 0.05) in bilateral ONH. CONCLUSION: Optic nerve hypoplasia is a common ocular malformation with a prevalence of 17.3/100 000 children and adolescents <18 years of age in Stockholm. Unilateral ONH seems as common as bilateral.

Human α-defensin expression is not dependent on CCAAT/enhancer binding protein-ε in a murine model.

Specific granule deficiency (SGD) is a rare congenital disorder characterized by recurrent infections. The disease is caused by inactivating mutations of the CCAAT/enhancer binding protein-ε (C/EBP-ε) gene. As a consequence, specific and gelatinase granules lack most matrix proteins. Furthermore, azurophil granules contain diminished amounts of their most abundant proteins, α-defensins, also known as human neutrophil peptides (HNPs). In accordance with this, in vitro models have demonstrated induction of HNPs by C/EBP-ε. Since mice do not express myeloid defensins, they cannot per se be used to characterize the role of C/EBP-ε in controlling HNP expression in vivo. We therefore crossed a transgenic HNP-1-expressing mouse with the Cebpe-/- mouse to study the in vivo significance of C/EBP-ε for HNP-1 transcription and expression. Surprisingly, neither expression nor processing of HNP-1 was affected by lack of C/EBP-ε in these mice. Transduction of C/EBP-ε into primary bone marrow cells from HNP-1 mice induced some HNP-1 expression, but not to levels comparable to expression human cells. Taken together, our data infer that the HNP-1 of the transgenic mouse does not show an expression pattern equivalent to endogenous secondary granule proteins. This limits the use of these transgenic mice as a model for human conditions.

Papillon-Lefèvre syndrome patient reveals species-dependent requirements for neutrophil defenses.

Papillon-Lefèvre syndrome (PLS) results from mutations that inactivate cysteine protease cathepsin C (CTSC), which processes a variety of serine proteases considered essential for antimicrobial defense. Despite serine protease-deficient immune cell populations, PLS patients do not exhibit marked immunodeficiency. Here, we characterized a 24-year-old woman who had suffered from severe juvenile periodontal disease, but was otherwise healthy, and identified a homozygous missense mutation in CTSC indicative of PLS. Proteome analysis of patient neutrophil granules revealed that several proteins that normally localize to azurophil granules, including the major serine proteases, elastase, cathepsin G, and proteinase 3, were absent. Accordingly, neutrophils from this patient were incapable of producing neutrophil extracellular traps (NETs) in response to ROS and were unable to process endogenous cathelicidin hCAP-18 into the antibacterial peptide LL-37 in response to ionomycin. In immature myeloid cells from patient bone marrow, biosynthesis of CTSC and neutrophil serine proteases appeared normal along with initial processing and sorting to cellular storage. In contrast, these proteins were completely absent in mature neutrophils, indicating that CTSC mutation promotes protease degradation in more mature hematopoietic subsets, but does not affect protease production in progenitor cells. Together, these data indicate CTSC protects serine proteases from degradation in mature immune cells and suggest that neutrophil serine proteases are dispensable for human immunoprotection.