Vitamin D3 modulates the innate immune response through regulation of the hCAP-18/LL-37 gene expression and cytokine production

Vitamin D triggers hCAP18/LL-37 production: Implications for LL-37-induced human osteoblast cytotoxicity

The human cathelicidin LL-37 shows activity against microorganisms, but it is also cytotoxic to host cells. The CAMP gene codes for the LL-37 precursor hCAP18 which is processed extracellularly to active LL-37. It has previously been shown that vitamin D stimulates CAMP gene activity, but less information is available demonstrating that vitamin D also can increase hCAP18/LL-37 protein production. Here, we show with RT-qPCR that a physiological concentration of vitamin D (50 nM) enhances CAMP mRNA levels by about 170 times in human THP-1 monocyte cells. Stimulation with 50 nM vitamin D increases hCAP18/LL-37 protein contents 3-4 times in THP-1 cell lysates demonstrated by both dot blot analysis and ELISA applying two different hCAP18/LL-37 antibodies. Treatment with the proteasome inhibitor MG132 enhances hCAP18/LL-37 levels, suggesting that turnover of hCAP18/LL-37 protein is regulated by the proteasome. The hCAP18/LL-37 concentration in vitamin D-stimulated THP-1 cells corresponds to 1.04 μM LL-37. Interestingly, synthetic LL-37, at this concentration, reduces viability of human osteoblast-like MG63 cells, whereas the THP-1 cells are less sensitive as demonstrated by the MTT assay. In summary, we show that vitamin D enhances hCAP18/LL-37 production, and that this effect can be of physiological/pathophysiological relevance for LL-37-induced human osteoblast toxicity.

Associations of Serum Vitamin D With Dental Caries and Periodontitis: The HUNT Study

OBJECTIVE

To study the relationships of serum 25-hydroxyvitamin D [25(OH)D] with dental caries and periodontitis in a general Norwegian adult population.

METHODS

We analysed a subsample of 1605 participants from the Trøndelag Health Study (HUNT) in Norway that had serum 25(OH)D levels measured in HUNT3 (2006-08) and oral health assessed in the HUNT4 Oral Health Study (2017-19). Negative binomial and Poisson regression models were used to estimate the ratios of means (RMs; for count oral outcomes) and prevalence ratios (PRs; for dichotomous oral outcomes).

RESULTS

Serum 25(OH)D was inversely associated with the number of decayed teeth in a dose-response gradient (<30.0 nmol/L: RM 1.41, 95% CI 1.07-1.85; 30.0-49.9 nmol/L: 1.14, 0.98-1.32 and ≥75.0 nmol/L: 0.84, 0.67-1.04, as compared to the 50.0-74.9 nmol/L group, P for trend <.001). Each 25 nmol/L decrease in 25(OH)D level was associated with a 15% (RM 1.15, 95% CI 1.05-1.26) increase in the mean number of decayed teeth. Serum 25(OH)D <30.0 nmol/L was associated with a 35% higher prevalence of severe periodontitis (PR 1.35, 95% CI 1.00-1.83). No association was observed between 25(OH)D and the number of natural teeth.

CONCLUSION

The present study suggested that serum 25(OH)D level had an inverse and dose-response association with the number of decayed teeth, and serum 25(OH)D <30 nmol/L was associated with a higher prevalence of severe periodontitis in this Norwegian adult population.

Correlation between vitamin D levels in serum and the risk of dental caries in children: a systematic review and meta-analysis

BACKGROUND

Vitamin D plays a crucial role in oral health, and its deficiency is associated to significant changes in oral health diseases. We aimed to explore the relationship between levels of 25-hydroxyvitamin D (25(OH) D) and dental caries in children.

METHODS

Four electronic databases were searched by two investigators including PubMed, Embase, Web of Science, and Cochrane Library. Dental caries results were presented as either prevalence or based on the index of primary and permanent teeth/surfaces with decaying, missing, and filled areas, while vitamin D levels were determined through laboratory testing. Two researchers independently selected studies, collected information, assessed risk of bias, and evaluated the study quality. Any disagreements were resolved through discussion.

RESULTS

A total of 13 studies were included, comprising 5 cross-sectional studies, 5 cohort studies, 3 case-control studies, all of which had high methodological quality. Our meta-analysis showed that children with vitamin D deficiency had a 22% higher risk of dental caries than those with normal vitamin D levels, with a relative risk (RR) of 1.22 and a 95% confidence interval (CI) of 1.18 to 1. 25. Further subgroup analysis according to the three types of studies showed that the risk of dental caries in children with vitamin D deficiency was higher than that in normal vitamin D level group (cohort studies: 62%; cross-sectional studies, 19%; and case-control studies, 5%). Additionally, according to age, subgroup analysis also showed that the risk of dental caries in children with vitamin D deficiency was higher than that in normal vitamin D level group (permanent teeth studies, 28%; deciduous teeth studies, 68%; and mixed dentition studies 8%).

CONCLUSIONS

Levels of 25 (OH) D have been found negatively associated with dental caries in children, indicating that low vitamin D levels may be considered a potential risk factor to this dental disease.

Osteoporosis and dermatoporosis: a review on the role of vitamin D

Osteoporosis (OP) and Dermatoporosis (DP) are expressions of the aging process at the skin and bone levels, respectively. Both conditions are associated with increased morbidity for elderly people, and this requires necessary interventions. They share many common risk factors; among these, vitamin D (VD) deficiency appears to have a role. VD is involved in either disease with many mechanisms, among which immunomodulation. VD deficiency has been linked to OP because it inhibits the body's capacity to absorb calcium and maintain optimal bone health. Available evidence suggests that proper vitaminosis D also appears to be vital in preventing skin age-related issues. DP is often seen in elderly individuals, particularly those with long-term sun exposure and a history of chronic sun damage. VD deficiency can be linked to DP, since its involvement in collagen production, epidermal barrier function, inflammation regulation, wound healing, and sun protection. Aim of this review is to summarize the most updated existing evidence on the role of VD in the development of fragility syndromes such as DP and OP and the possible benefits of VD supplementation as a simple and harmful weapon against aging.

A certain protective effect of vitamin D against dental caries in US children and youth: A cross-sectional study

OBJECTIVES

Recent studies reported that evidence of the association between caries and vitamin D was inconclusive. We investigated the relationship between dental caries and serum vitamin D levels in US children and youth aged 5-19 years through the National Health and Nutrition Examination Survey (NHANES). The purpose of this study was to analyze the relations between serum 25-hydroxyvitamin-D [25(OH)D] level and dental caries in children and youth.

METHODS

Data were collected from the NHANES dataset performed in 2011-2018. A total of 8896 subjects completed the examination was enrolled. Serum 25(OH)D was determined by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). All teeth examined and caries assessment was conducted by licensed dentists. Statistical analyses included complex samples Chi-square tests, analysis of variance, logistic regression analyses, and restricted cubic splines conducted by R software.

RESULTS

There was a nonlinear relation between dental caries and age in youth. Vitamin D showed a relatively stable protective effect when the concentration exceeded 60 nmol/L. There was a dose-effect relation that a 10 nmol/L increase in serum 25(OH)D concentrations was associated with a decreased caries odd by 10%.

CONCLUSIONS

Our findings suggested that vitamin D sufficiency may be a protective factor for dental caries.

Vitamin D and Microbiome: Molecular Interaction in Inflammatory Bowel Disease Pathogenesis

Studies of systemic autoimmune diseases point to characteristic microbial patterns in various diseases, including inflammatory bowel disease (IBD). Autoimmune diseases, and IBD in particular, show a predisposition to vitamin D deficiency, leading to alterations in the microbiome and disruption of intestinal epithelial barrier integrity. In this review, we examine the role of the gut microbiome in IBD and discuss how vitamin D-vitamin D receptor (VDR)-associated molecular signaling pathways contribute to the development and progression of IBD through their effects on gut barrier function, the microbial community, and immune system function. The present data demonstrate that vitamin D promotes the proper function of the innate immune system by acting as an immunomodulator, exerting anti-inflammatory effects, and critically contributing to the maintenance of gut barrier integrity and modulation of the gut microbiota, mechanisms that may influence the IBD development and progression. VDR regulates the biological effects of vitamin D and is related to environmental, genetic, immunologic, and microbial aspects of IBD. Vitamin D influences the distribution of the fecal microbiota, with high vitamin D levels associated with increased levels of beneficial bacterial species and lower levels of pathogenic bacteria. Understanding the cellular functions of vitamin D-VDR signaling in intestinal epithelial cells may pave the way for the development of new treatment strategies for the therapeutic armamentarium of IBD in the near future.

Polymorphisms in vitamin D receptor genes and its relation with susceptibility to brucellosis: a case-control study

OBJECTIVE

One of the systemic infections is Brucellosis which is caused by facultative intracellular bacteria of the genus Brucella. Vitamin D is a fat-soluble prohormone, that metabolizes enzymes and its intracellular receptor creates the active hormone and also mediate in responses of immune system.

METHODS

Current research consists of 102 patients with brucellosis who were selected based on culture, PCR results serology, and clinical symptoms. The control group composed of 102 healthy people. The polymorphism of genes (Bsm I, Fok I, Taq I, Apa I) encoding Vitamin D receptor (VDR) were assessed by the PCR-RFLP method.

RESULTS

The results showed that ff, tt, aa, and bb genotypes in Fok I, ApaI, TaqI, and BsmI were significant in case/control groups (P-value ≤ 0.0001). The genotype frequency AA in the control group is higher than that of the study group, while genotype frequency aa in the study group is more than the control. The odds ratio for brucellosis in individuals with ff genotype is 37 times higher than that of Ff genotype. Also, the odds ratio of brucellosis in individuals with genotype tt, aa, and bb was 12, 53, and 6 times higher than those of the Aa, Bb, and Tt genotypes.

CONCLUSION

The genotypes aa and ff in the positions of the ApaI and FokI are of higher importance. The brucellosis risk in individuals accompanied aa genotype at Apa I is 53 times higher than that of the genotype AA, in other words, AA and BB, TT and FF genotypes are protective against the disease.

Antimicrobial Peptide Expression at the Ocular Surface and Their Therapeutic Use in the Treatment of Microbial Keratitis

Microbial keratitis is a common cause of ocular pain and visual impairment worldwide. The ocular surface has a relatively paucicellular microbial community, mostly found in the conjunctiva, while the cornea would be considered relatively sterile. However, in patients with microbial keratitis, the cornea can be infected with multiple pathogens including Staphylococcus aureus, Pseudomonas aeruginosa, and Fusarium sp. Treatment with topical antimicrobials serves as the standard of care for microbial keratitis, however, due to high rates of pathogen resistance to current antimicrobial medications, alternative therapeutic strategies must be developed. Multiple studies have characterized the expression and activity of antimicrobial peptides (AMPs), endogenous peptides with key antimicrobial and wound healing properties, on the ocular surface. Recent studies and clinical trials provide promise for the use of AMPs as therapeutic agents. This article reviews the repertoire of AMPs expressed at the ocular surface, how expression of these AMPs can be modulated, and the potential for harnessing the AMPs as potential therapeutics for patients with microbial keratitis.

Vitamin D3 Protects Mice from Diquat-Induced Oxidative Stress through the NF-κB/Nrf2/HO-1 Signaling Pathway

Vitamin D₃, as an indispensable and fat-soluble micronutrient, plays an important role in the health of humans and animals. At present, studies are focusing on the calcium absorption and immunoregulation function of vitamin D₃; this study was aimed at exploring the antioxidative stress ability of vitamin D₃ on diquat-induced intestinal dysfunction of ICR mice and the underlying mechanism. The results showed that oral gavage of vitamin D₃ daily significantly improved the body weight gain and immune organ index and significantly reverted the abnormal changes of ALT, AST, SOD, GSH-Px, T-AOC, and MDA in the serum and jejunum induced by diquat. The addition of vitamin D₃ also significantly reduced the concentration of DAO, D-LA, and certain proinflammatory cytokines in serum. Moreover, vitamin D₃ improved the pathological morphology of the duodenum, jejunum, colon, liver, and kidney tissues, and it also largely attenuated the degree of inflammatory infiltration of macrophages and cell apoptotic index of jejunal epithelial tissue induced by diquat. The results demonstrated that vitamin D₃ significantly recovered the intestinal barrier injury by enhancing the expression of mucins and tight junction proteins in the jejunum. In addition, the results indicated that vitamin D₃ could significantly reduce the phosphorylation level of NF-κB (p65) and enhance the expression of Nrf2 and HO-1 in the jejunum compared with the diquat-induced group. This study suggested that oral administration of vitamin D₃ can protect mice against oxidative damage by inhibiting the phosphorylation level of NF-κB (p65) and activating Nrf2-related signaling pathways.

Vitamin D3 protects turbot (Scophthalmus maximus L.) from bacterial infection

Accumulating evidence supports that vitamin D₃ (VD₃) possesses immunomodulatory properties besides its classical actions in calcium and bone homeostasis. In this study, juvenile turbots were fed with the diets containing 0 IU/kg VD₃ or the optimum dose of 400 IU/kg VD₃ for 8 weeks. To investigate the effects of VD₃ on anti-infectious immunity in fish, 10⁷ CFU Edwardsiella tarda was injected intraperitoneally to each juvenile turbot after the feeding trial. Our results showed that the mortality of infected turbots with dietary VD₃ was much lower than that in VD₃ deficient group, and the supplementation of dietary VD₃ significantly reduced the bacterial load in the spleen of infected turbots. Further analysis demonstrated that the production of reactive oxygen species (ROS) in haemocytes and lysozyme activity in serum was elevated, and the responses of T cells and B cells were modulated in VD₃-supplemented turbots. Moreover, the inflammation was significantly exacerbated in the infected turbots fed with 0 IU/kg VD₃ compared to the fish fed with 400 IU/kg VD₃. In addition, the head kidney macrophages (HKMs) in turbots were isolated and incubated with VD₃in vitro, the results showed that VD₃ significantly promoted the bactericidal activity in HKMs. In conclusion, our study has shown clear evidence that VD₃ positively regulates the innate and adaptive immunity in fish, which is beneficial to the defense in fish against pathogen infection.

Mechanisms for control of skin immune function by the microbiome

The skin represents the largest area for direct contact between microbes and host immunocytes and is a site for constant communication between the host and this diverse and essential microbial community. Coagulase-negative staphylococci are an abundant bacterial genus on the human skin and are regulated through various mechanisms that include the epidermal barrier environment and innate and adaptive immune systems within the epidermis and dermis. In turn, some species and strains of these bacteria produce beneficial products that augment host immunity by exerting specifically targeted antimicrobial, anti-inflammatory, or anti-neoplastic activity while also promoting broad innate and adaptive immune responses. The use of selected skin commensals as a therapeutic has shown promise in recent human clinical trials. This emerging concept of bacteriotherapy is defining mechanisms of action and validating the dependence on the microbiome for maintenance of immune homeostasis.

The Impact of Vitamin D on Skin Aging

The active metabolites of vitamin D₃ (D₃) and lumisterol (L₃) exert a variety of antiaging and photoprotective effects on the skin. These are achieved through immunomodulation and include anti-inflammatory actions, regulation of keratinocytes proliferation, and differentiation programs to build the epidermal barrier necessary for maintaining skin homeostasis. In addition, they induce antioxidative responses, inhibit DNA damage and induce DNA repair mechanisms to attenuate premature skin aging and cancerogenesis. The mechanism of action would involve interaction with multiple nuclear receptors including VDR, AhR, LXR, reverse agonism on RORα and -γ, and nongenomic actions through 1,25D₃-MARRS receptor and interaction with the nongenomic binding site of the VDR. Therefore, active forms of vitamin D₃ including its canonical (1,25(OH)₂D₃) and noncanonical (CYP11A1-intitated) D₃ derivatives as well as L₃ derivatives are promising agents for the prevention, attenuation, or treatment of premature skin aging. They could be administrated orally and/or topically. Other forms of parenteral application of vitamin D₃ precursor should be considered to avoid its predominant metabolism to 25(OH)D₃ that is not recognized by CYP11A1 enzyme. The efficacy of topically applied vitamin D₃ and L₃ derivatives needs further clinical evaluation in future trials.

An in silico scientific basis for LL-37 as a therapeutic for Covid-19

A multi‐pronged approach with help in all forms possible is essential to completely overcome the Covid‐19 pandemic. There is a requirement to research as many new and different types of approaches as possible to cater to the entire world population, complementing the vaccines with promising results. The need is also because SARS‐CoV‐2 has several unknown or variable facets which get revealed from time to time. In this work, in silico scientific findings are presented, which are indicative of the potential for the use of the LL‐37 human anti‐microbial peptide as a therapeutic against SARS‐CoV‐2. This indication is based on the high structural similarity of LL‐37 to the N‐terminal helix, with which the virus interacts, of the receptor for SARS‐CoV‐2, Angiotensin Converting Enzyme 2. Moreover, there is positive prediction of binding of LL‐37 to the receptor‐binding domain of SARS‐CoV‐2; this is the first study to have described this interaction. In silico data on the safety of LL‐37 are also reported. As Vitamin D is known to upregulate the expression of LL‐37, the vitamin is a candidate preventive molecule. This work provides the possible basis for an inverse correlation between Vitamin D levels in the body and the severity of or susceptibility to Covid‐19, as widely reported in literature. With the scientific link put forth herein, Vitamin D could be used at an effective, medically prescribed, safe dose as a preventive. The information in this report would be valuable in bolstering the worldwide efforts to eliminate the pandemic as early as possible.

Antimicrobial peptides and proteins: Interaction with the skin microbiota

The cutaneous microbiota comprises all living skin microorganisms. There is increasing evidence that the microbiota plays a crucial role in skin homeostasis. Accordingly, a dysbiosis of the microbiota may trigger cutaneous inflammation. The need for a balanced microbiota requires specific regulatory mechanisms that control and shape the microbiota. In this review, we highlight the present knowledge suggesting that antimicrobial peptides (AMPs) may exert a substantial influence on the microbiota by controlling their growth. This is supported by own data showing the differential influence of principal skin-derived AMPs on commensal staphylococci. Vice versa, we also illuminate how the cutaneous microbiota interacts with skin-derived AMPs by modulating AMP expression and how microbiota members protect themselves from the antimicrobial activity of AMPs. Taken together, the current picture suggests that a fine-tuned and well-balanced AMP-microbiota interplay on the skin surface may be crucial for skin health.

Cathelicidin levels in nasal secretions are associated with the severity of acute bronchiolitis

OBJECTIVE

To investigate the association of serum vitamin D and nasal secretion antimicrobial peptides (AMPs) levels with the severity of acute bronchiolitis.

STUDY DESIGN

We conducted a prospective single pediatric tertiary care center cohort study of inpatients aged 0-18 months with a first episode of acute bronchiolitis from November 1st 2014 to April 30th 2017. Disease severity was determined by the length of hospitalization and supplemental hospital data. Qualitative measurements included serum 25(OH)D and nasal secretion LL-37 and β-defensin-2 levels. Correlations were examined with the Mann-Whitney and Kruskal-Wallis criteria for qualitative and the correlation coefficient Spearman's rho for quantitative factors. Multiple linear and logarithmic regression were performed to adjust for confounding factors.

RESULTS

The study population consisted of 153 infants and toddlers with median age 3.1 months (interquartile range:1.6-4.9). No association was found between serum 25(OH)D and AMPs nasal secretions levels. Serum 25(OH)D and nasal secretion β-defensin-2 levels were not associated with the severity of bronchiolitis. In contrast, LL-37 levels were inversely associated with the length of hospitalization (rho = -0.340, p = .001), the need for medication use (p = .001), as well as the duration of oxygen supplementation (rho = -0.339, p = .001), and intravenous fluid administration (rho = -0.323, p = .001). This association remained significant after adjustment for potential confounders.

CONCLUSION

A significant association between LL-37 nasal secretions levels with the severity of acute bronchiolitis was found in hospitalized infants and toddlers. The role of LL-37 in the pathogenesis of bronchiolitis merits further investigation.

Periodontal health and disease: The contribution of genetics

Periodontitis is an infectious, inflammatory disease that is associated with a complex interplay between specific bacteria, host response, and environmental factors. Because of its high degree of familial aggregation, specifically for the more aggressive forms of the disease, genetics factors have been implicated in disease pathogenesis for several decades. This review provides an overview of what we currently know regarding the genetic and epigenetic contributions to periodontal disease and discusses future opportunities in the field.

Extending the vitamin D pathway to vitamin D3 and CYP27A1 in periodontal ligament cells

BACKGROUND

In periodontal connective tissue cells, the vitamin D pathway has been elucidated, and vitamin D₃ in the main storage form, 25-hydroxy vitamin D₃ (25[OH]D₃ ), and the functional form, 1,25-dihydroxy vitamin D₃ (1,25[OH]₂ D₃ ), have been found to induce the expression of human cationic antimicrobial protein (hCAP-18)/LL-37. Moreover, synergistic effects between Toll-like receptor agonists and 25(OH)D₃ have been reported. This research aimed at extending the vitamin D pathway to vitamin D₃ and CYP27A1 in human periodontal ligament cells (hPDLCs) to further explore its function in periodontal inflammatory reaction.

METHODS

Vitamin D₃ was used to stimulate hPDLCs in the presence or absence of Porphyromonas gingivalis lipopolysaccharide (Pg-LPS). Conversely, CYP27A1 RNA interference was performed to further validate the findings. The mRNA expression of hCAP-18 was determined with real-time polymerase chain reaction. Monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) were also detected. The cell supernatant levels of LL-37 were detected with enzyme-linked immunosorbent assay.

RESULTS

Vitamin D₃ significantly enhanced the generation of hCAP-18/LL-37. A combination of Pg-LPS and vitamin D₃ significantly promoted hCAP-18/LL-37 expression. When the expression of CYP27A1 was knocked down with RNA interference, the induction of hCAP-18/LL-37 expression was significantly inhibited. Therefore, the mRNA levels of MCP-1 and IL-8 in hPDLCs were significantly decreased through the vitamin D pathway.

CONCLUSION

The vitamin D pathway from vitamin D₃ to hCAP-18/LL-37 exists in hPDLCs, and CYP27A1 might be involved in periodontal immune defense.

Vitamin D and microbiota: Two sides of the same coin in the immunomodulatory aspects

The gut microbiota is crucial for host immune response, vitamin synthesis, short chain fatty acids (SCFAs) production, intestinal permeability, nutrient digestion energy metabolism and protection from pathogens. Therefore, gut microbiota guarantees the host's predisposition to gastrointestinal diseases. Intestinal microbiota may be damaged by environmental components with negative health conditions. Dysbiosis consisting in alteration in the gut microbiota has been involved in several disorders including inflammation, allergic reactions, autoimmune diseases, heart diseases, obesity, and metabolic syndrome and even in the state of malignant carcinogenesis existing in humans. Several epidemiological studies have shown that inadequate solar exposure results in vitamin D insufficiency/deficiency which has a strong impact on different immune responses and the occurrence of a wide range of pathological conditions. Additionally, new evidence indicates that the vitamin D pathway plays a key role in gut homeostasis. Due to the strong connection between vitamin D and microbiota, herein we focus on the new findings about intestinal bacteria-immune crosstalk and the impact of vitamin D in gut microbiota regulation, in order to offer new clarifications on their interaction. Understanding the mechanism by which vitamin D can affect the gut microbiota composition and its dynamic activities, as well as the innate and adaptive state of the immune system, is not only a fundamental research but also an opportunity to improve health status.

Chlorpyrifos stimulates expression of vitamin D3 receptor in skin cells irradiated with UVB

Skin, the organ responsible for vitamin D synthesis, is fully exposed to many xenobiotics, e.g. polycyclic aromatic hydrocarbons and pesticides. A broad spectrum organophosphorus insecticides (OP's), such as chlorpyrifos (CPS), are commonly used in agriculture and to control domestic insects. Thus, the aim of this study was to investigate the effect of chlorpyrifos, on the expression of vitamin D₃ receptor (VDR) in human keratinocytes cell line HaCaT and fibroblasts cell line BJ. The impact of CPS and UVB radiation on cell viability were examined by Neutral Red assay. The effect of CPS on VDR expression was evaluated by RT-qPCR and flow cytometry (FC). The presented study demonstrated that exposure to CPS and UVB significantly affects the viability of HaCaT and BJ cells lines. Results also revealed that exposure to CPS induced the expression at mRNA and protein level of VDR nuclear receptor in both cell lines exposed to UVB. In HaCaT incubated with 250 μM CPS and 15 mJ/cm² UVB, the relative VDR expression was ∼2-fold higher; whereas in BJ incubated with 250 μM CPS and 20 mJ/cm², UVB was∼3-fold higher. Results from FC confirmed this result, as VDR expression increased by ~250% in HaCaT incubated with 250 μM CPS and 20 mJ/cm² UVB, and in BJ incubated with 250 μM CPS, and 20 mJ/cm² UVB cells VDR expression increased by ~190%, compared with control. It can therefore be concluded that OPs pesticide might interfere with vitamin D₃ metabolism in skin cells.

25-Hydroxyvitamin D3 Alleviates Experimental Periodontitis via Promoting Expression of Cathelicidin in Mice with Type 2 Diabetic Mellitus

Type 2 diabetic mellitus is manifested by metabolic impairments with high prevalence worldwide, of which periodontitis represents a typical oral complication (also called diabetic periodontitis). Oral epithelia bear the brunt of periodontal damage from microscopic intruders; thus the defense function of epithelial cells is of vital significance. We have previously proved that 25-hydroxyvitamin D₃ (25-OHD₃) altered the expression of cathelicidin antimicrobial peptide in oral epithelial cells in vitro. Herein, we discovered that 25-OHD₃ intraperitoneal injection attenuated periodontal inflammation by promoting cathelicidin production in gingival epithelia and reducing fasting glucose of diabetic mice. Dotblotting of serum showed cathelicidin secretion was consistent with 25-OHD₃ treatment. Immunochemistry exhibited enhanced expression of cathelicidin and vitamin D receptors along with reduced expression of TLR4 in diabetic mice. Stereomicroscope showed less alveolar bone loss when injected with 25-OHD₃.These results showed 25-OHD₃ can promote cathelicidin and ameliorate the severity of diabetic periodontitis. Our study complemented the mechanism of cathelicidin and extended knowledge of 25-OHD₃'s role in diabetic periodontitis.

LL-37 treatment on human peripheral blood mononuclear cells modulates immune response and promotes regulatory T-cells generation

LL-37 is a host-defense peptide (HDP) and exerts a broad spectrum of microbicidal activity against bacteria, fungi, and viral pathogens. This peptide also interacts with human cells and influences their behavior, promoting angiogenesis, wound healing, immunomodulation, and affecting apoptosis. Lately, significant advances have been achieved regarding the elucidation of underlying mechanisms related to LL-37 effects over neutrophil and monocytes. However, how T-cells respond to LL-37 stimulation is still largely unknown. Here, we used flow cytometry to evaluate the effects of LL-37 over peripheral blood mononuclear cells (PBMCs) viability, T-cell proliferation, T-cell activation, as well as the generation of regulatory T-cells (Tregs). Those aspects were assessed both in immune homeostatic and inflammatory milieu. Furthermore, we investigated the transcript levels of the inflammatory factors INF-γ, TNF-ɑ, and TGF-β in these conditions. Interestingly, our data revealed that the treatment of PBMCs with LL-37 enhanced the viability of these cells and exerted wide effects over T cell response. Upon activation, LL-37 treated T-cells presented lower proliferation and also increased generation of Tregs. Finally, while non-stimulated cells increased the expression of inflammatory factors when treated with LL-37, activated cells treated with LL-37 presented a decreased production of the same inflammatory mediators. These results are important for the immunotherapy field, and indicate that the use of LL-37 must be carefully evaluated in both homeostatic and inflammatory scenarios, since the microenvironment clearly plays a crucial role in determining how T-cells respond to LL-37.

DNA methylation directly downregulates human cathelicidin antimicrobial peptide gene (CAMP) promoter activity

LL-37, the active product of human cathelicidin antimicrobial peptide (CAMP) has a broad spectrum of antibacterial activity. LL-37 also has important physiological functions in immune regulation, angiogenesis and in modulating apoptosis. The roles of LL-37 in oral squamous cell carcinoma (OSCC) are still not clear. The correlation between DNA methylation and human CAMP expression is also unknown. Here human CAMP/LL-37 expression was assessed by immunohistochemistry in normal and OSCC tissues. The results indicated that low expression of CAMP/LL-37 correlated with histological differentiation and lymph node metastasis and also promoted tumor progression. A cell-specific methylation pattern in the promoter region of human CAMP was detected. Treatment with 5-aza-2'-deoxycytidine, a DNA demethylation reagent can increase human CAMP expression in epithelial cancer cells. The reporter assay showed that unmethylated human CAMP promoter activity was significantly higher than methylated promoter activity. Taken together, these results suggested that human CAMP/LL-37 might act as a tumor-suppressor in OSCC and DNA methylation might play roles during carcinogenesis via directly downregulating human CAMP promoter activity.

The host defense peptide LL-37 is detected in human parotid and submandibular/sublingual saliva and expressed in glandular neutrophils

The human host defense peptide, LL-37, is an important player in the first line of defense against invading microorganisms. LL-37 and its precursor, hCAP18, have been detected in unstimulated whole saliva but no reports showing hCAP18/LL-37 in isolated, parotid, and/or submandibular/sublingual saliva have been presented. Here, we measured the levels of hCAP18/LL-37 in human parotid and submandibular/sublingual saliva and investigated the expression of hCAP18/LL-37 in parotid and submandibular gland tissue. Parotid and submandibular/sublingual saliva was collected from healthy volunteers, and the levels of hCAP18/LL-37 in saliva were analyzed by dot blot, ELISA, and western blotting. Cellular expression of hCAP18/LL-37 in human parotid and submandibular glands was investigated by immunohistochemistry. Immunoreactivity for hCAP18/LL-37 was detected in both parotid and submandibular/sublingual saliva of all individuals. The concentration of hCAP18/LL-37 was similar in parotid and submandibular/sublingual saliva, and was determined by densitometric scanning of each dot and normalization to the total protein concentration of each sample, and by ELISA. Double immunohistochemistry revealed that intravascular neutrophils of both parotid and submandibular glands express hCAP18/LL-37. For the first time, we demonstrate hCAP18/LL-37 in isolated human parotid and submandibular/sublingual saliva and expression of hCAP18/LL-37 in glandular intravascular neutrophils, indicating that neutrophils of the major salivary glands contribute to the LL-37 content of whole saliva.

Dietary modulation of endogenous host defense peptide synthesis as an alternative approach to in-feed antibiotics

Traditionally, antibiotics are included in animal feed at subtherapeutic levels for growth promotion and disease prevention. However, recent links between in-feed antibiotics and a rise in antibiotic-resistant pathogens have led to a ban of all antibiotics in livestock production by the European Union in January 2006 and a removal of medically important antibiotics in animal feeds in the United States in January 2017. An urgent need arises for antibiotic alternatives capable of maintaining animal health and productivity without triggering antimicrobial resistance. Host defense peptides (HDP) are a critical component of the animal innate immune system with direct antimicrobial and immunomodulatory activities. While in-feed supplementation of recombinant or synthetic HDP appears to be effective in maintaining animal performance and alleviating clinical symptoms in the context of disease, dietary modulation of the synthesis of endogenous host defense peptides has emerged as a cost-effective, antibiotic-alternative approach to disease control and prevention. Several different classes of small-molecule compounds have been found capable of promoting HDP synthesis. Among the most efficacious compounds are butyrate and vitamin D. Moreover, butyrate and vitamin D synergize with each other in enhancing HDP synthesis. This review will focus on the regulation of HDP synthesis by butyrate and vitamin D in humans, chickens, pigs, and cattle and argue for potential application of HDP-inducing compounds in antibiotic-free livestock production.

The Decline in Vitamin Research Funding: A Missed Opportunity?

Background: The National Nutrition Research Roadmap has called for support of greater collaborative, interdisciplinary research for multiple areas of nutrition research. However, a substantial reduction in federal funding makes responding to these calls challenging. Objectives: The objectives of this study were to examine temporal trends in research funding and to discuss the potential consequences of these trends. Methods: We searched the NIH RePORTER database to identify NIH research grants and USASpending to identify National Science Foundation and USDA research grants awarded from 1992 to 2015. We focused on those that pertained to vitamin research. For the years 2000 to 2015, we examined funding trends for different vitamins, including vitamins A, B (one-carbon B-vitamins were considered separately from other B-vitamins), C, D, E, and K. Results: From 1992 to 2015, total federal research spending increased from ∼$14 to $45 billion (2016 US dollars). Although vitamin research spending increased from ∼$89 to $95 million, the proportion of grants awarded for vitamin research declined by more than two-thirds, from 0.65% in 1992 to 0.2% in 2015. Federal agencies awarded 6035 vitamin research grants over the time period, with vitamin A associated with the most research projects per year on average (n = 115) and vitamin K the fewest (n = 8). Vitamin D research projects were associated with the greatest average yearly project value ($34.8 million). Conclusions: Vitamin research has faced a disproportionate decline in research funding from 1992 to 2015. Insufficient federal research funding streams risk stalling progress in vitamin research and leaving important advancements unrealized.

Vitamin D-induced up-regulation of human keratinocyte cathelicidin anti-microbial peptide expression involves retinoid X receptor α

The biologically active form of vitamin D, 1α,25-dihydroxyvitamin D3 (1,25D3), has been reported to positively regulate the human cathelicidin anti-microbial peptide (CAMP) gene coding for LL-37, but the mechanisms are not completely understood. We have determined the expression of CAMP, vitamin D receptor (VDR), and the retinoid X receptor (RXR) isoforms in human skin and gingival tissue biopsies and investigated the signaling pathways involved in 1,25D3-induced upregulation of CAMP. Human skin and gingival biopsies exhibited few VDR-immunoreactive cells within the stratum basale, whereas rat colon enterocytes (positive control) possessed abundant VDR immunoreactivity. Nuclear VDR immunoreactivity was demonstrated in human skin keratinocytes (HaCaT cells). Gene analysis revealed that human skin biopsies expressed higher levels of both CAMP and RXRα mRNA than human gingival biopsies, whereas VDR and RXRβ transcript levels were similar in skin and gingiva. In HaCaT cells, treatment with 1,25D3 (5 nM and 1 μM) for 4 and 24 h up-regulated CAMP mRNA several fold, and treatment with 1,25D3 for 24 h increased protein expression of the pro-form of LL-37 (hCAP-18) by about 13 times. The 1,25D3-evoked stimulation of HaCaT CAMP expression was associated with attenuated VDR mRNA and protein expression. Treatment with RXRα short interfering RNA reversed the 1,25D3-induced CAMP expression in HaCaT cells, showing that RXRα is involved in the up-regulation of CAMP by 1,25D3. We conclude that the 1,25D3-evoked stimulation of CAMP expression in human skin keratinocytes is dependent on RXRα but is not associated with the up-regulation of VDR expression.