Synergistic induction of human cathelicidin antimicrobial peptide gene expression by vitamin D and stilbenoids

Gut distress and intervention via communications of SARS-CoV-2 with mucosal exposome

Acute coronavirus disease 2019 (COVID-19) has been associated with prevalent gastrointestinal distress, characterized by fecal shedding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA or persistent antigen presence in the gut. Using a meta-analysis, the present review addressed gastrointestinal symptoms, such as nausea, vomiting, abdominal pain, and diarrhea. Despite limited data on the gut-lung axis, viral transmission to the gut and its influence on gut mucosa and microbial community were found to be associated by means of various biochemical mechanisms. Notably, the prolonged presence of viral antigens and disrupted mucosal immunity may increase gut microbial and inflammatory risks, leading to acute pathological outcomes or post-acute COVID-19 symptoms. Patients with COVID-19 exhibit lower bacterial diversity and a higher relative abundance of opportunistic pathogens in their gut microbiota than healthy controls. Considering the dysbiotic changes during infection, remodeling or supplementation with beneficial microbial communities may counteract adverse outcomes in the gut and other organs in patients with COVID-19. Moreover, nutritional status, such as vitamin D deficiency, has been associated with disease severity in patients with COVID-19 via the regulation of the gut microbial community and host immunity. The nutritional and microbiological interventions improve the gut exposome including the host immunity, gut microbiota, and nutritional status, contributing to defense against acute or post-acute COVID-19 in the gut-lung axis.

Regulation of Host Defense Peptide Synthesis by Polyphenols

The rise of antimicrobial resistance has created an urgent need for antibiotic-alternative strategies for disease control and prevention. Host defense peptides (HDPs), which have both antimicrobial and immunomodulatory properties, are an important component of the innate immune system. A host-directed approach to stimulate the synthesis of endogenous HDPs has emerged as a promising solution to treat infections with a minimum risk for developing antimicrobial resistance. Among a diverse group of compounds that have been identified as inducers of HDP synthesis are polyphenols, which are naturally occurring secondary metabolites of plants characterized by the presence of multiple phenol units. In addition to their well-known antioxidant and anti-inflammatory activities, a variety of polyphenols have been shown to stimulate HDP synthesis across animal species. This review summarizes both the in vitro and in vivo evidence of polyphenols regulating HDP synthesis. The mechanisms by which polyphenols induce HDP gene expression are also discussed. Natural polyphenols warrant further investigation as potential antibiotic alternatives for the control and prevention of infectious diseases.

Interplay of Vitamin D and SIRT1 in Tissue-Specific Metabolism-Potential Roles in Prevention and Treatment of Non-Communicable Diseases Including Cancer

The importance of the prevention and control of non-communicable diseases, including obesity, metabolic syndrome, type 2 diabetes, cardiovascular diseases, and cancer, is increasing as a requirement of the aging population in developed countries and the sustainability of healthcare. Similarly, the 2013-2030 action plan of the WHO for the prevention and control of non-communicable diseases seeks these achievements. Adequate lifestyle changes, alone or with the necessary treatments, could reduce the risk of mortality or the deterioration of quality of life. In our recent work, we summarized the role of two central factors, i.e., appropriate levels of vitamin D and SIRT1, which are connected to adequate lifestyles with beneficial effects on the prevention and control of non-communicable diseases. Both of these factors have received increased attention in relation to the COVID-19 pandemic as they both take part in regulation of the main metabolic processes, i.e., lipid/glucose/energy homeostasis, oxidative stress, redox balance, and cell fate, as well as in the healthy regulation of the immune system. Vitamin D and SIRT1 have direct and indirect influence of the regulation of transcription and epigenetic changes and are related to cytoplasmic signaling pathways such as PLC/DAG/IP3/PKC/MAPK, MEK/Erk, insulin/mTOR/cell growth, proliferation; leptin/PI3K-Akt-mTORC1, Akt/NFĸB/COX-2, NFĸB/TNFα, IL-6, IL-8, IL-1β, and AMPK/PGC-1α/GLUT4, among others. Through their proper regulation, they maintain normal body weight, lipid profile, insulin secretion and sensitivity, balance between the pro- and anti-inflammatory processes under normal conditions and infections, maintain endothelial health; balance cell differentiation, proliferation, and fate; and balance the circadian rhythm of the cellular metabolism. The role of these two molecules is interconnected in the molecular network, and they regulate each other in several layers of the homeostasis of energy and the cellular metabolism. Both have a central role in the maintenance of healthy and balanced immune regulation and redox reactions; therefore, they could constitute promising targets either for prevention or as complementary therapies to achieve a better quality of life, at any age, for healthy people and patients under chronic conditions.

High-Throughput Screening for Epigenetic Compounds That Induce Human β-Defensin 1 Synthesis

Antimicrobial host defense peptides (HDPs) are critically important for innate immunity. Small-molecule compounds with the ability to induce HDP synthesis are being actively explored for antimicrobial therapy. To facilitate the discovery of the compounds that specifically activate human β-defensin 1 (DEFB1) gene transcription, we established a cell-based high-throughput screening assay that employs HT-29/DEFB1-luc, a stable reporter cell line expressing the luciferase gene driven by a 3-Kb DEFB1 gene promoter. A screening of a library of 148 small-molecule epigenetic compounds led to the identification of 28 hits, with a minimum strictly standardized mean difference of 3.0. Fourteen compounds were further selected and confirmed to be capable of inducing DEFB1 mRNA expression in human HT-29 colonic epithelial cells. Desirably, the human cathelicidin antimicrobial peptide (CAMP) gene was also induced by these epigenetic compounds. Benzamide-containing histone deacetylase inhibitors (HDACi) were among the most potent HDP inducers identified in this study. Additionally, several major genes involved in intestinal barrier function, such as claudin-1, claudin-2, tight junction protein 1, and mucin 2, were differentially regulated by HDP inducers. These findings suggest the potential for the development of benzamide-based HDACi as host-directed antimicrobials for infectious disease control and prevention.

The Nexus of Diet, Gut Microbiota and Inflammatory Bowel Diseases in Dogs

Canine inflammatory bowel diseases (IBD) are of increasing interest in veterinary medicine. They refer to complex and debilitating conditions of dogs' gastrointestinal tract. Although little evidence for causal inferences is currently available, it is believed that IBD pathophysiology entails intricate interactions between environmental factors, the intestinal immune system, and the microbial communities that colonize the gut. To better understand the mechanisms underlying these disorders, leveraging factors associated with the development of these diseases is imperative. Of these factors, emerging evidence supports the role of dietary patterns as key players influencing the composition and function of gut microbes, with subsequent effects on health and disease. In this review, we particularly focus on addressing IBD in dogs and discuss how specific nutrients may elicit or relieve gut inflammation. Gaining mechanistic insights into such interplay and the underpinning mechanisms is key to inferring dietary recommendations, and setting up new and promising therapeutics.

Vitamin D supplementation for irritable bowel syndrome: A systematic review and meta-analysis

BACKGROUND AND AIM

Irritable bowel syndrome (IBS) is a prevalent and complex gastrointestinal disorder characterized by chronic abdominal pain and altered bowel habits. Observational studies have suggested a relationship between serum vitamin D levels and IBS symptoms. This systematic review and meta-analysis aimed to investigate the clinical effects of vitamin D supplementation on IBS symptom severity and quality of life (QoL) measures.

METHODS

Medline, Embase, Scopus, Web of Science, and The Cochrane Library databases were systematically searched. Data abstraction and quality assessment were conducted by four authors independently, and discrepancies were resolved through consensus from the senior author. Continuous data were pooled with standardized mean difference (SMD) using the DerSimonian and Laird's random-effects model. Sensitivity analysis by risk of bias and potentially "predatory" publication were performed as well.

RESULTS

A total of 685 patients across eight studies were included in the meta-analysis. Vitamin D supplementation significantly improved IBS symptom severity scale scores, with a SMD of -0.77 (95% confidence interval [CI] -1.47 to -0.07, P = 0.04, I²  = 91%). Improvements in IBS-QoL scores were also observed, albeit not statistically significant (SMD 0.54; 95% CI -0.34 to 1.41, P = 0.15, I²  = 87%). However, small sample sizes, a relatively young study population, limited ethnicities, and varied vitamin D dosing strategies across the studies were notable limitations.

CONCLUSIONS

Vitamin D supplementation could be part of our clinical armamentarium when managing IBS patients due to the potential efficacy and good safety profile. Further randomized, controlled trials are required to confirm the therapeutic effects.

Upregulating Human Cathelicidin Antimicrobial Peptide LL-37 Expression May Prevent Severe COVID-19 Inflammatory Responses and Reduce Microthrombosis

COVID-19 is characterized by hyperactivation by inflammatory cytokines and recruitment of macrophages, neutrophils, and other immune cells, all hallmarks of a strong inflammatory response that can lead to severe complications and multi-organ damage. Mortality in COVID-19 patients is associated with a high prevalence of neutrophil extracellular trap (NET) formation and microthrombosis that are exacerbated by hyperglycemia, diabetes, and old age. SARS-CoV-2 infection in humans and non-human primates have revealed long-term neurological consequences of COVID-19, possibly concomitant with the formation of Lewy bodies in the brain and invasion of the nervous system via the olfactory bulb. In this paper, we review the relevance of the human cathelicidin LL-37 in SARS-CoV-2 infections. LL-37 is an immunomodulatory, host defense peptide with direct anti-SARS-CoV-2 activity, and pleiotropic effects on the inflammatory response, neovascularization, Lewy body formation, and pancreatic islet cell function. The bioactive form of vitamin D and a number of other compounds induce LL-37 expression and one might predict its upregulation, could reduce the prevalence of severe COVID-19. We hypothesize upregulation of LL-37 will act therapeutically, facilitating efficient NET clearance by macrophages, speeding endothelial repair after inflammatory tissue damage, preventing α-synuclein aggregation, and supporting blood-glucose level stabilization by facilitating insulin release and islet β-cell neogenesis. In addition, it has been postulated that LL-37 can directly bind the S1 domain of SARS-CoV-2, mask angiotensin converting enzyme 2 (ACE2) receptors, and limit SARS-CoV-2 infection. Purposeful upregulation of LL-37 could also serve as a preventative and therapeutic strategy for SARS-CoV-2 infections.

Vitamin D and colorectal cancer: Chemopreventive perspectives through the gut microbiota and the immune system

Vitamin D and its receptor are involved in health and diseases through multiple mechanisms including the immune system and gut microbiota modulations. Gut microbiota variations have huge implications in intestinal and extra-intestinal disorders such as colorectal cancer (CRC). This review highlights the preventive role of vitamin D in colorectal tumorigenesis through the effects on the immune system and gut microbiota modulation. The different associations between vitamin D, gut microbial homeostasis, immune system, and CRC, are dissected. Vitamin D is supposed to exert several chemopreventive effects on CRC including direct antineoplastic mechanisms, the effects on the immune system, and gut microbiota modulation. Large clinical studies with a randomized design, are required to confirm the role of vitamin D in CRC, confirming its key role in the complex interplay between the gut immune system and microbiota.

Resveratrol, EGCG and Vitamins Modulate Activated T Lymphocytes

Vitamins and bioactives, which are constituents of the food chain, modulate T lymphocyte proliferation and differentiation, antibody production, and prevent inflammation and autoimmunity. We investigated the effects of vitamins (vitamin A (VA), D (VD), E (VE)) and bioactives (i.e., resveratrol (Res), epigallocatechin-3-gallate (EGCG)) on the adaptive immune response, as well as their synergistic or antagonistic interactions. Freshly isolated T lymphocytes from healthy individuals were activated with anti-CD3/CD28 antibodies for 4–5 days in the presence of bioactives and were analyzed by cytofluorometry. Interleukins, cytokines, and chemokines were measured by multiple ELISA. Gene expression was measured by quantitative RT-PCR. Res and EGCG increased CD4 surface intensity. EGCG led to an increased proportion of CD8⁺ lymphocytes. Anti-CD3/CD28 activation induced exuberant secretion of interleukins and cytokines by T lymphocyte subsets. VD strongly enhanced T_h2 cytokines (e.g., IL-5, IL-13), whereas Res and EGCG favored secretion of T_h1 cytokines (e.g., IL-2, INF-γ). Res and VD mutually influenced cytokine production, but VD dominated the cytokine secretion pattern. The substances changed gene expression of interleukins and cytokines in a similar way as they did secretion. Collectively, VD strongly modulated cytokine and interleukin production and favored T_h2 functions. Resveratrol and EGCG promoted the T_h1 response. VA and VE had only a marginal effect, but they altered both T_h1 and T_h2 response. In vivo, bioactives might therefore interact with vitamins and support the outcome and extent of the adaptive immune response.

Factors Affecting Gut Microbiome in Daily Diet

There is a growing recognition that a good diet can help people maintain mental and physical health, while a bad one will cause the disorder of body function, and even lead to several diseases. A lot of attentions have been devoted to analyze every possible health-related factor in the daily diet, including food ingredients, additives, and cooking process. With the support of high-throughput sequencing technology, there is accumulating evidence gradually clarifying that most of these factors are mainly through the interactions with gut microbiome to trigger downstream effects. The gut microbiome may be able to act as a very sensitive mirror in response to human daily diet. A complex network of interactions among diet, gut microbiome, and health has been gradually depicted, but it is rarely discussed from a more comprehensive perspective. To this end, this review summarized the latest updates in diet-gut microbiome interactions, analyzed most identified factors involved in this process, showed the possibility of maintaining health or alleviating diseases by diet intervention, aiming to help people choose a suitable recipe more accurately.

Association of Gut Microbiome and Vitamin D Deficiency in Knee Osteoarthritis Patients: A Pilot Study

BACKGROUND

Few preclinical studies have shown that Knee osteoarthritis (KOA) is linked to gut microbiome dysbiosis and chronic inflammation. This pilot study was designed to look at the gut microbiome composition in KOA patients and normal individuals with or without vitamin D deficiency (VDD, serum vitamin D <30 ng/mL).

METHODS

This pilot study was conducted prospectively in 24 participants. The faecal samples of all the participants were taken for DNA extraction. The V3-V4 region of 16s rRNA was amplified, and the library was prepared and sequenced on the Illumina Miseq platform.

RESULTS

The mean (±SD) age was 45.5 (±10.2) years with no defined comorbidities. Of 447 total Operational Taxonomic Units (OTUs), a differential abundance of 16 nominally significant OTUs between the groups was observed. Linear discriminate analysis (LEfSe) revealed a significant difference in bacteria among the study groups. Pseudobutyrivibrio and Odoribacter were specific for VDD, while Parabacteroides, Butyricimonas and Gordonibacter were abundant in the KOA_VDD group, and Peptococcus, Intestimonas, Delftia and Oribacterium were abundant in the KOA group. About 80% of bacterial species were common among different groups and hence labelled as core bacterial species. However, the core microbiome of KOA and VDD groups were not seen in the KOA_VDD group, suggesting that these bacterial groups were affected by the interaction of the KOA and VDD factors.

CONCLUSION

Parabacteroides, Butyricimonas, Pseudobutyrivibrio, Odoribacter and Gordonibacter are the predominant bacteria in vitamin D deficient patients with or without KOA. Together these results indicate an association between the gut microbiome, vitamin D and knee osteoarthritis.

Modulation of Innate Immune Toxicity by Silver Nanoparticle Exposure and the Preventive Effects of Pterostilbene

Silver nanoparticles pose a potential risk to ecosystems and living organisms due to their widespread use in various fields and subsequent gradual release into the environment. Only a few studies have investigated the effects of silver nanoparticles (AgNPs) toxicity on immunological functions. Furthermore, these toxic effects have not been fully explored. Recent studies have indicated that zebrafish are considered a good alternative model for testing toxicity and for evaluating immunological toxicity. Therefore, the purpose of this study was to investigate the toxicity effects of AgNPs on innate immunity using a zebrafish model and to investigate whether the natural compound pterostilbene (PTE) could provide protection against AgNPs-induced immunotoxicity. Wild type and neutrophil- and macrophage-transgenic zebrafish lines were used in the experiments. The results indicated that the exposure to AgNPs induced toxic effects including death, malformation and the innate immune toxicity of zebrafish. In addition, AgNPs affect the number and function of neutrophils and macrophages. The expression of immune-related cytokines and chemokines was also affected. Notably, the addition of PTE could activate immune cells and promote their accumulation in injured areas in zebrafish, thereby reducing the damage caused by AgNPs. In conclusion, AgNPs may induce innate immune toxicity and PTE could ameliorate this toxicity.

Discovery of natural products capable of inducing porcine host defense peptide gene expression using cell-based high throughput screening

Background

In-feed antibiotics are being phased out in livestock production worldwide. Alternatives to antibiotics are urgently needed to maintain animal health and production performance. Host defense peptides (HDPs) are known for their broad-spectrum antimicrobial and immunomodulatory capabilities. Enhancing the synthesis of endogenous HDPs represents a promising antibiotic alternative strategy to disease control and prevention.

Methods

To identify natural products with an ability to stimulate the synthesis of endogenous HDPs, we performed a high-throughput screening of 1261 natural products using a newly-established stable luciferase reporter cell line known as IPEC-J2/pBD3-luc. The ability of the hit compounds to induce HDP genes in porcine IPEC-J2 intestinal epithelial cells, 3D4/31 macrophages, and jejunal explants were verified using RT-qPCR. Augmentation of the antibacterial activity of porcine 3D4/31 macrophages against a Gram-negative bacterium (enterotoxigenic E. coli) and a Gram-positive bacterium (Staphylococcus aureus) were further confirmed with four selected HDP-inducing compounds.

Results

A total of 48 natural products with a minimum Z-score of 2.0 were identified after high-throughput screening, with 21 compounds giving at least 2-fold increase in luciferase activity in a follow-up dose-response experiment. Xanthohumol and deoxyshikonin were further found to be the most potent in inducing pBD3 mRNA expression, showing a minimum 10-fold increase in IPEC-J2, 3D4/31 cells, and jejunal explants. Other compounds such as isorhapontigenin and calycosin also enhanced pBD3 mRNA expression by at least 10-fold in both IPEC-J2 cells and jejunal explants, but not 3D4/31 cells. In addition to pBD3, other porcine HDP genes such as pBD2, PG1-5, and pEP2C were induced to different magnitudes by xanthohumol, deoxyshikonin, isorhapontigenin, and calycosin, although clear gene- and cell type-specific patterns of regulation were observed. Desirably, these four compounds had a minimum effect on the expression of several representative inflammatory cytokine genes. Furthermore, when used at HDP-inducing concentrations, these compounds showed no obvious direct antibacterial activity, but significantly augmented the antibacterial activity of 3D4/31 macrophages (P < 0.05) against both Gram-negative and Gram-positive bacteria.

Conclusions

Our results indicate that these newly-identified natural HDP-inducing compounds have the potential to be developed as novel alternatives to antibiotics for prophylactic and therapeutic treatment of infectious diseases in livestock production.

Regular Supplementation With Resveratrol Improves Bone Mineral Density in Postmenopausal Women: A Randomized, Placebo-Controlled Trial

Resveratrol, a naturally occurring polyphenol in red grapes and berries, can act as a phytoestrogen. It has been shown to improve both systemic and cerebral circulatory functions, possibly through activation of endothelial estrogen receptors. in vitro and in vivo studies in rodent models also indicate a bone-protective role for resveratrol, particularly in ovariectomized rat models that mimic postmenopausal osteoporosis caused by estrogen deficiency. Hypothesizing a circulatory benefit of resveratrol in bone tissue, we investigated whether resveratrol supplementation could improve bone health in postmenopausal women. The Resveratrol for Healthy Aging in Women (RESHAW) trial was a 24-month randomized, double-blind, placebo-controlled, two-period crossover intervention conducted to evaluate the effects of resveratrol (75 mg twice daily) on cognition, cerebrovascular function, bone health, cardiometabolic markers, and well-being in postmenopausal women. After 12 months of supplementation with resveratrol versus placebo, there were positive effects on bone density in the lumbar spine (+0.016 ± 0.003 g/cm² ) and neck of femur (+0.005 ± 0.002 g/cm² ), which were accompanied by a 7.24% reduction in C-terminal telopeptide type-1 collagen levels, a bone resorption marker, compared with placebo. The increase in bone mineral density in the femoral neck resulted in an improvement in T-score (+0.070 ± 0.018) and a reduction in the 10-year probability of major and hip fracture risk. The magnitude of improvement was higher in women with poor bone health biomarker status. Importantly, the improvement in femoral neck T-score with resveratrol correlated with improvement in perfusion. Our subanalysis also revealed that the bone-protective benefit of resveratrol was greater in participants who supplemented with vitamin D plus calcium. Regular supplementation with 75 mg of resveratrol twice daily has the potential to slow bone loss in the lumbar spine and femoral neck, common fracture sites in postmenopausal women without overt osteoporosis. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Relationship Between Vitamin D Deficiency and Disease Activity in Patients with Inflammatory Bowel Disease in Ahvaz, Iran

Background and Aims

Previous studies have shown that vitamin D plays an important role in inflammatory bowel disease (IBD). This study was designed to investigate the relationship between vitamin D levels and disease activity in IBD patients in Ahvaz, Iran.

Methods

This cross-sectional study was conducted on adult IBD patients referring to the outpatient clinic of gastroenterology at Imam Khomeini Hospital in Ahvaz city, in the southwest of Iran. Each patient’s disease activity defined according to Crohn’s disease activity index (CDAI) in Crohn’s disease (CD) and Truelove score in ulcerative colitis (UC) patients, serum 25[OH]D was measured using the radioimmunoassay method. Vitamin D deficiency was defined as concentration of <20 nmol/L.

Results

Studied subjects were 130 UC and 23 CD patients (62.1% females) with a mean age of 37.5 ± 12.35 years. Vitamin D deficiency was present in 99 (64.7%) IBD patients. Fifty-three patients (34.6%) had active disease who, compared with patients in remission, had more frequent low vitamin D levels (80 vs 56.7%, P = 0.017). In UC patients, disease activity was significantly associated with vitamin D deficiency (P = 0.035), but no such relationship was observed in CD patients (P = 0.74).

Conclusion

Vitamin D deficiency was significantly associated with disease activity in IBD, especially in UC patients. Therefore, careful monitoring of vitamin D deficiency in these patients is highly recommended. Prospective cohort studies are also needed to determine the role of vitamin D deficiency and its treatment in the clinical course of IBD.

The value of antimicrobial peptides in the age of resistance

Accelerating growth and global expansion of antimicrobial resistance has deepened the need for discovery of novel antimicrobial agents. Antimicrobial peptides have clear advantages over conventional antibiotics which include slower emergence of resistance, broad-spectrum antibiofilm activity, and the ability to favourably modulate the host immune response. Broad bacterial susceptibility to antimicrobial peptides offers an additional tool to expand knowledge about the evolution of antimicrobial resistance. Structural and functional limitations, combined with a stricter regulatory environment, have hampered the clinical translation of antimicrobial peptides as potential therapeutic agents. Existing computational and experimental tools attempt to ease the preclinical and clinical development of antimicrobial peptides as novel therapeutics. This Review identifies the benefits, challenges, and opportunities of using antimicrobial peptides against multidrug-resistant pathogens, highlights advances in the deployment of novel promising antimicrobial peptides, and underlines the needs and priorities in designing focused development strategies taking into account the most advanced tools available.

Vitamin D and the Host-Gut Microbiome: A Brief Overview

There is a growing body of evidence for the effects of vitamin D on intestinal host-microbiome interactions related to gut dysbiosis and bowel inflammation. This brief review highlights the potential links between vitamin D and gut health, emphasizing the role of vitamin D in microbiological and immunological mechanisms of inflammatory bowel diseases. A comprehensive literature search was carried out in PubMed and Google Scholar using combinations of keywords "vitamin D," "intestines," "gut microflora," "bowel inflammation". Only articles published in English and related to the study topic are included in the review. We discuss how vitamin D (a) modulates intestinal microbiome function, (b) controls antimicrobial peptide expression, and (c) has a protective effect on epithelial barriers in the gut mucosa. Vitamin D and its nuclear receptor (VDR) regulate intestinal barrier integrity, and control innate and adaptive immunity in the gut. Metabolites from the gut microbiota may also regulate expression of VDR, while vitamin D may influence the gut microbiota and exert anti-inflammatory and immune-modulating effects. The underlying mechanism of vitamin D in the pathogenesis of bowel diseases is not fully understood, but maintaining an optimal vitamin D status appears to be beneficial for gut health. Future studies will shed light on the molecular mechanisms through which vitamin D and VDR interactions affect intestinal mucosal immunity, pathogen invasion, symbiont colonization, and antimicrobial peptide expression.

Stilbenoids: A Natural Arsenal against Bacterial Pathogens

The escalating emergence of resistant bacterial strains is one of the most important threats to human health. With the increasing incidence of multi-drugs infections, there is an urgent need to restock our antibiotic arsenal. Natural products are an invaluable source of inspiration in drug design and development. One of the most widely distributed groups of natural products in the plant kingdom is represented by stilbenoids. Stilbenoids are synthesised by plants as means of protection against pathogens, whereby the potential antimicrobial activity of this class of natural compounds has attracted great interest in the last years. The purpose of this review is to provide an overview of recent achievements in the study of stilbenoids as antimicrobial agents, with particular emphasis on the sources, chemical structures, and the mechanism of action of the most promising natural compounds. Attention has been paid to the main structure modifications on the stilbenoid core that have expanded the antimicrobial activity with respect to the parent natural compounds, opening the possibility of their further development. The collected results highlight the therapeutic versatility of natural and synthetic resveratrol derivatives and provide a prospective insight into their potential development as antimicrobial agents.

A mouse model for vitamin D-induced human cathelicidin antimicrobial peptide gene expression

In humans and other primates, 1,25(OH)₂vitamin D₃ regulates the expression of the cathelicidin antimicrobial peptide (CAMP) gene via toll-like receptor (TLR) signaling that activates the vitamin D pathway. Mice and other mammals lack the vitamin D response element (VDRE) in their CAMP promoters. To elucidate the biological importance of this pathway, we generated transgenic mice that carry a genomic DNA fragment encompassing the entire human CAMP gene and crossed them with Camp knockout (KO) mice. We observed expression of the human transgene in various tissues and innate immune cells. However, in mouse CAMP transgenic macrophages, TLR activation in the presence of 25(OH)D₃ did not induce expression of either CAMP or CYP27B1 as would normally occur in human macrophages, reinforcing important species differences in the actions of vitamin D. Transgenic mice did show increased resistance to colonization by Salmonella typhimurium in the gut. Furthermore, the human CAMP gene restored wound healing in the skin of Camp KO mice. Topical application of 1,25(OH)₂vitamin D₃ to the skin of CAMP transgenic mice induced CAMP expression and increased killing of Staphylococcus aureus in a wound infection model. Our model can help elucidate the biological importance of the vitamin D-cathelicidin pathway in both pathogenic and non-pathogenic states.

The Interplay between Immune System and Microbiota in Osteoporosis

Osteoporosis is a disease characterized by low bone mass and alterations of bone microarchitecture, with an increased risk of fractures. It is a multifactorial disorder that is more frequent in postmenopausal women but can be associated to other diseases (inflammatory and metabolic diseases). At present, several options are available to treat osteoporosis trying to block bone reabsorption and reduce the risk of fracture. Anyway, these drugs have safety and tolerance problems in long-term treatment. Recently, gut microbiota has been highlighted to have strong influence on bone metabolism, becoming a potential new target to modify bone mineral density. Such evidences are mainly based on mouse models, showing an involvement in modulating the interaction between the immune system and bone cells. Germ-free mice represent a basic model to understand the interaction between microbiota, immune system, and bone cells, even though data are controversial. Anyway, such models have unequivocally demonstrated a connection between such systems, even if the mechanism is unclear. Gut microbiota is a complex system that influences calcium and vitamin D absorption and modulates gut permeability, hormonal secretion, and immune response. A key role is played by the T helper 17 lymphocytes, TNF, interleukin 17, and RANK ligand system. Other important pathways include NOD1, NOD2, and Toll-like receptor 5. Prebiotics and probiotics are a wide range of substances and germs that can influence and modify microbiota. Several studies demonstrated actions by different prebiotics and probiotics in different animals, differing according to sex, age, and hormonal status. Data on the effects on humans are poor and controversial. Gut microbiota manipulation appears a possible strategy to prevent and treat osteopenia and/or osteoporosis as well as other possible bone alterations, even though further clinical studies are necessary to identify correct procedures in humans.

Dietary Nutrients Mediate Intestinal Host Defense Peptide Expression

The intestinal tract is the shared locus of intestinal epithelial cells, immune cells, nutrient digestion and absorption, and microbial survival. The gut in animals faces continuous challenges in communicating with the external environment. Threats from endogenous imbalance and exogenous feeds, especially pathogens, could trigger a disorder of homeostasis, leading to intestinal disease and even systematic disease risk. As a part of the intestinal protective barrier, endogenous host defense peptides (HDPs) play multiple beneficial physiological roles in the gut mucosa. Moreover, enhancing endogenous HDPs is being developed as a new strategy for resisting pathogens and commensal microbes, and to maintain intestinal health and reduce antibiotic use. In recent years, multiple nutrients such as branched-chain amino acids, SCFAs, lactose, zinc, and cholecalciferol (vitamin D3) have been reported to significantly increase HDP expression. Nutritional intervention has received more attention and is viewed as a promising means to defend against pathogenic infections and intestinal inflammation. The present review focuses on current discoveries surrounding HDP expression and nutritional regulation of mechanisms in the gut. Our aim is to provide a comprehensive overview, referable tactics, and novel opinions.

Inducible expression of defensins and cathelicidins by nutrients and associated regulatory mechanisms

Host defense peptides (HDPs) are crucial components of the body's first line of defense that protect organisms from infections and mediate immune responses. Defensins and cathelicidins are the two most important families of HDPs in mammals. In this review, we summarize the nutrients that are involved in inducible expression of endogenous defensins and cathelicidins. In addition, the mitogen-activated protein kinases (MAPK), nuclear factor kappa B (NF-κB) and histone deacetylase (HDAC) signaling pathways that play vital roles in the induction of defensin and cathelicidin expression are highlighted. Endogenous defensins and cathelicidins induced by nutrients may be potential alternatives to antibiotic treatments against infection and diseases. This review mainly focuses on the inducible expression and regulatory mechanisms of defensins and cathelicidins in multiple species by different nutrients and the potential applications of defensin- and cathelicidin-inducing nutrients.

Irritable bowel syndrome: a review of the general aspects and the potential role of vitamin D

Irritable Bowel Syndrome (IBS) is a bowel disorder leading to symptoms such as abdominal pain, modifications in the motility and bowel habits, distention, bloating, and gas. Vitamin D (VD) may interfere in a plethora of cellular mechanisms, and act directly or indirectly in the regulation of the microbiome, the release of anti-microbial peptides, modulation of the immune system and inflammation processes; which in turn, may positively interfere with the altered gut function. The main purpose of this review was to survey studies involving the impacts of VD on IBS. Area covered: Eligible studies including the term VD and IBS were searched in the MEDLINE-PubMed and EMBASE (2009-2018). VD may act direct or indirectly in the regulation of the gut microbiome, immune response, and psychosocial factors that may be included in the list of IBS triggering factors. Expert opinion: Once VD plays an essential role in many processes associated with IBS, its deficiency may be associated with IBS, and the supplementation could help in the therapeutic approach for this condition. For these reasons, the understanding of the association of VD in IBS is indispensable for the development of new strategies that could improve the quality of life of the patient.

Vitamin D, the gut microbiome and inflammatory bowel disease

Vitamin D has an important role in bone metabolism but recently has been recognized as an immunoregulator, and this has led to investigations on the effect of Vitamin D supplementation in various autoimmune diseases and its anti-inflammatory effects. There is some evidence that Vitamin D can regulate gastrointestinal inflammation. In addition, previous studies have shown that Vitamin D can affect the gut microbiome. The aim of this review is to evaluate the effect of Vitamin D on inflammatory processes, especially its relation to the inflammatory bowel disease (IBD) and gut microbiome. There is some evidence that Vitamin D can regulate gastrointestinal inflammation, with epidemiological studies showing that individuals with higher serum Vitamin D have a lower incidence of IBD, particularly Crohn's disease. Vitamin D changes transcription of cathelicidin and DEFB4 (defensin, beta 4) that can affect the gut microbiome. Several cell types of the immune system express Vitamin D receptor, and hence the use of Vitamin D in immune regulation has some potential. Furthermore, Vitamin D deficiency leads to dysbiosis of gut microbiome and reported to cause severe colitis. Vitamin D supplementation is low cost and available and can be a therapeutic option.

Astragalus polysaccharides exerts anti-infective activity by inducing human cathelicidin antimicrobial peptide LL-37 in respiratory epithelial cells

Astragalus polysaccharides (APS), one of the major active components in Astragalus membranaceus, is an effective immunomodulator used in the treatment of immunological diseases in China. However, the anti-infective action and mechanism of APS is not fully known. In the present study, we found that APS induced the expression of human cathelicidin antimicrobial peptide LL-37, a key host anti-infective molecule, in both mRNA and protein levels in respiratory epithelial cells HBE16 and A549. Furthermore, the lysate and supernatant from APS-treated HBE16 cells both exhibited an obvious antibacterial action, which was partially neutralizated by LL-37 monoclonal antibody. In addition, APS also significantly elevated the phosphorylation of p38 MAPK and JNK and caused the degradation of IκBα. Specific inhibitors of p38 MAPK, JNK, or NF-κB obviously abolished APS-induced LL-37 synthesis and antibacterial activity, respectively. Taken together, our results confirmed the enhancement of APS on LL-37 induction and antibacterial action in respiratory epithelial cells, which may be attributed to activation of p38 MAPK/JNK and NF-κB pathways. Furthermore, these results also supported the clinical application of APS in the treatment of infectious diseases.

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.

Nanofiber-based sutures induce endogenous antimicrobial peptide

AIM

The aim of this study was to develop nanofiber-based sutures capable of inducing endogenous antimicrobial peptide production.

METHODS

We used co-axial electrospinning deposition and rolling to fabricate sutures containing pam3CSK4 peptide and 25-hydroxyvitamin D₃ (25D₃).

RESULTS

The diameters and mechanical properties of the sutures were adjustable to meet the criteria of United States Pharmacopeia designation. 25D₃ exhibited a sustained release from nanofiber sutures over 4 weeks. Pam3CSK4 peptide also showed an initial burst followed by a sustained release over 4 weeks. The co-delivery of 25D₃ and pam3CSK4 peptide enhanced cathelicidin antimicrobial peptide production from U937 cells and keratinocytes compared with 25D₃ delivery alone. In addition, the 25D₃/pam3CSK4 peptide co-loaded nanofiber sutures did not significantly influence proliferation of keratinocytes, fibroblasts, or the monocytic cell lines U937 and HL-60.

CONCLUSION

The use of 25D₃/pam3CSK4 peptide co-loaded nanofiber sutures could potentially induce endogenous antimicrobial peptide production and reduce surgical site infections.

Biological effects of combined resveratrol and vitamin D3 on ovarian tissue

BACKGROUND

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a natural antioxidant polyphenol able to exert a wide range of biological effect on several tissues. Despite its important beneficial properties, it has a low water solubility, which limits its therapeutic applications in humans. Resveratrol also acts as a phytoestrogen that modulates estrogen receptor (ER)-mediated transcription. In addition, it has been shown that ovarian tissues benefit greatly from vitamin D3, which exerts its beneficial effects through VDR receptors. The aim was to evaluate the cooperative effects of resveratrol combined with vitamin D3 on ovarian cells and tissues and some other organs as well. Moreover, the modulation of specific intracellular pathways involving ER and VDR receptors has been studied.

METHODS

The experiments were performed both in vitro and in vivo, to analyze cell viability, radical oxygen species production, signal transductions through Western Blot, and resveratrol quantification by HPLC.

RESULTS

Cell viability, radical oxygen species production, and intracellular pathways have been studied on CHO-K1 cells. Also, the relative mechanism activated following oral intake in female Wistar rats as animal model was investigated, evaluating bioavailability, biodistribution and signal transduction in heart, kidney, liver and ovarian tissues. Both in in vitro and in vivo experiments, resveratrol exerts more evident effects when administered in combination with vitD in ovarian cells, showing a common biphasic cooperative effect: The role of vitamin D3 in maintaining and supporting the biological activity of resveratrol has been clearly observed. Moreover, resveratrol plus vitamin D3 blood concentrations showed a biphasic absorption rate.

CONCLUSIONS

Such results could be used as a fundamental data for the development of new therapies for gynecological conditions, such as hot-flashes.

SIRT1 enzymatically potentiates 1,25-dihydroxyvitamin D3 signaling via vitamin D receptor deacetylation

The hormonal metabolite of vitamin D, 1,25-dihydroxyvitamin D₃ (1,25D), binds to the vitamin D receptor (VDR) and promotes heterodimerization of VDR with a retinoid-X-receptor (RXR) to genomically regulate diverse cellular processes. Herein, it is revealed for the first time that VDR is post-translationally acetylated, and that VDR immunoprecipitated from human embryonic kidney (HEK293) cells displays a dramatic decrease in acetylated receptor in the presence of 1,25D-ligand, sirtuin-1 (SIRT1) deacetylase, or the resveratrol activator of SIRT1. To elucidate the functional significance of VDR deacetylation, vitamin-d-responsive-element (VDRE)-based transcriptional assays were performed to determine if deacetylase overexpression affects VDR/VDRE-driven transcription. In HEK293 kidney and TE85 bone cells, co-transfection of low amounts (1-5ng) of a SIRT1-expression vector elicits a reproducible and statistically significant enhancement (1.3- to 2.6-fold) in transcription mediated by VDREs from the CYP3A4 and cyp24a1 genes, where the magnitude of response to 1,25D-ligand is 6- to 30-fold. Inhibition of SIRT1 via EX-527, or utilization of a SIRT1 loss-of-function mutant (H363Y), resulted in abrogation of SIRT1-mediated VDR potentiation. Studies with a novel, non-acetylatable VDR mutant (K413R) showed that the mutant VDR possesses enhanced responsiveness to 1,25D, in conjunction with reduced, but still significant, sensitivity to exogenous SIRT1, indicating that acetylation of lysine 413 is relevant, but that other acetylated residues in VDR contribute to modulation of its activity. We conclude that the acetylation of VDR comprises a negative feedback loop that attenuates 1,25D-VDR signaling. This regulatory loop is reversed by SIRT1-catalyzed deacetylation of VDR to amplify VDR signaling and 1,25D actions.

Oral spray wintertime vitamin D3 supplementation has no impact on inflammation in Gaelic footballers

Vitamin D inadequacy [total 25(OH)D <50 nmol/L] is widespread in athletes. The biologically active metabolite, 1,25-dihydroxyvitamin D, may be involved in regulating inflammation although in vitro findings have not been consistently replicated in human intervention trials. This study, conducted at a latitude of 55°N, aimed to assess inflammatory biomarkers in Gaelic footballers before and after a wintertime vitamin D₃ intervention. Samples from a 12-week double-blind, randomized, placebo-controlled trial, in which 42 Gaelic footballers received 3000 IU (75 μg) vitamin D₃ daily or placebo via oral spray solutions, were analysed for a range of inflammatory biomarkers. Cytokines (interleukin-8 and tumor necrosis factor-α), cathelicidin and high sensitivity C-reactive protein were quantified by multiplex assay, enzyme-linked immunosorbent assay and clinical biochemistry, respectively. White blood cell, lymphocyte, and neutrophil concentrations were determined by full blood profile. Data on total 25-hydroxyvitamin D, measured by LC-MS/MS, were available from the previous study. Vitamin D₃ supplementation significantly increased mean total 25-hydroxyvitamin D concentrations from 47 to 84 nmol/L (P = 0.006); yet this had no effect on white blood cell count (P = 0.699), lymphocyte (P = 0.694), neutrophil (P = 0.594), interleukin-8 (P = 0.334), tumor necrosis factor-α (P = 0.587), cathelicidin (P = 0.745) or high sensitivity C-reactive protein concentration (P = 0.621) compared to placebo. 12-weeks vitamin D₃ supplementation did not impact the immune profile of Gaelic footballers. This is likely because biomarkers were within their respective normal range or at a concentration similar to that of the general population at baseline. Future studies are encouraged to use inflammation as their primary outcome measure and recruit athletes at risk of compromised immunity.

Immune Cell Regulatory Pathways Unexplored as Host-Directed Therapeutic Targets for Mycobacterium tuberculosis: An Opportunity to Apply Precision Medicine Innovations to Infectious Diseases

The lack of novel antimicrobial drugs in development for tuberculosis treatment has provided an impetus for the discovery of adjunctive host-directed therapies (HDTs). Several promising HDT candidates are being evaluated, but major advancement of tuberculosis HDTs will require understanding of the master or "core" cell signaling pathways that control intersecting immunologic and metabolic regulatory mechanisms, collectively described as "immunometabolism." Core regulatory pathways conserved in all eukaryotic cells include poly (ADP-ribose) polymerases (PARPs), sirtuins, AMP-activated protein kinase (AMPK), and mechanistic target of rapamycin (mTOR) signaling. Critical interactions of these signaling pathways with each other and their roles as master regulators of immunometabolic functions will be addressed, as well as how Mycobacterium tuberculosis is already known to influence various other cell signaling pathways interacting with them. Knowledge of these essential mechanisms of cell function regulation has led to breakthrough targeted treatment advances for many diseases, most prominently in oncology. Leveraging these exciting advances in precision medicine for the development of innovative next-generation HDTs may lead to entirely new paradigms for treatment and prevention of tuberculosis and other infectious diseases.

Resveratrol potentiates vitamin D and nuclear receptor signaling

The 1,25-dihydroxyvitamin D3 (1,25D) hormone is derived from vitamin D generated in skin or obtained from the diet, and binds to and activates the vitamin D receptor (VDR) in target tissues including kidney, colon/small intestine, and bone/muscle. We tested resveratrol for its ability to modulate VDR signaling, using vitamin D responsive element (VDRE) and mammalian 2-hybrid (M2H) transcriptional system technology. Via VDRE-based assays in kidney, colon and myoblast cells, VDR-mediated transcription was activated by resveratrol, and a cooperative effect on transactivation was observed with resveratrol plus 1,25D. The M2H assay revealed a modest, resveratrol-induced dimerization of VDR with its retinoid X receptor (RXR) heteropartner. Cells treated with both resveratrol and 1,25D displayed synergistic stimulation of VDR-RXR heterodimerization, while resveratrol antagonized rexinoid-mediated RXR-RXR homodimerization. Increased transactivation in response to resveratrol was also observed with a subset of other nuclear receptors and their respective cognate responsive elements. Evaluation of wild-type versus a ligand-binding domain mutant VDR revealed that hormone-responsiveness to 1,25D was severely depressed, while the response to resveratrol was only moderately attenuated. Moreover, radiolabeled 1,25D-displacement assays demonstrated an increase in VDR-bound 1,25D in the presence of resveratrol. Thus, resveratrol may affect VDR and other nuclear receptors indirectly, likely via the ability of resveratrol to: (1) potentiate 1,25D binding to VDR; (2) activate RXR; and/or (3) stimulate SIRT1, an enzyme known to deacetylate nuclear receptors. The results of this study elucidate a possible pathway for crosstalk between two nutritionally derived lipids, vitamin D and resveratrol, both of which converge on VDR signaling.

Calcitriol-modulated human antibiotics: New pathophysiological aspects of vitamin D

Traditionally, calcitriol has been considered a calcium and phosphate regulating hormone, but has recently been shown to play a pivotal role in innate immunity. Many barrier and immune cells have membrane and intracellular receptors that recognize different microbial antigens. Activation of these receptors induces synthesis of 1α-hydroxylase, which acts on 25 hydroxyvitamin D to generate intracellular calcitriol. Calcitriol activates its receptor and enhances the synthesis of important human antibiotics like cathelicidin and β2-defensin while inhibiting hepcidin. These pluripotent peptides have an important role in innate immunity, and their regulation is abnormal in hypovitaminosis D. The literature on their secretion mechanisms, levels in different organic fluids, mechanism of action, and relationship with vitamin D is reviewed here.

Virtual screening of a milk peptide database for the identification of food-derived antimicrobial peptides

SCOPE

Milk provides a wide range of bioactive substances, such as antimicrobial peptides and proteins. Our study aimed to identify novel antimicrobial peptides naturally present in milk.

METHODS AND RESULTS

The components of an endogenous bovine milk peptide database were virtually screened for charge, amphipathy, and predicted secondary structure. Thus, 23 of 248 screened peptides were identified as candidates for antimicrobial effects. After commercial synthesis, their antimicrobial activities were determined against Escherichia coli NEB5α, E. coli ATCC25922, and Bacillus subtilis ATCC6051. In the tested concentration range (<2 mM), bacteriostatic activity of 14 peptides was detected including nine peptides inhibiting both Gram-positive and Gram-negative bacteria. The most effective fragment was TKLTEEEKNRLNFLKKISQRYQKFΑLPQYLK corresponding to αS2 -casein151-181 , with minimum inhibitory concentration (MIC) of 4.0 μM against B. subtilis ATCC6051, and minimum inhibitory concentrations of 16.2 μM against both E. coli strains. Circular dichroism spectroscopy revealed conformational changes of most active peptides in a membrane-mimic environment, transitioning from an unordered to α-helical structure.

CONCLUSION

Screening of food peptide databases by prediction tools is an efficient method to identify novel antimicrobial food-derived peptides. Milk-derived antimicrobial peptides may have potential use as functional food ingredients and help to understand the molecular mechanisms of anti-infective milk effects.

Increasing ultraviolet light exposure is associated with reduced mortality from Clostridium difficile infection

BACKGROUND

Clostridium difficile infection (CDI) is an increasingly common cause of inpatient mortality. Vitamin D deficiency is associated with more aggressive CDI. We aimed to determine if average annual ultraviolet light (UV) exposure was associated with mortality in patients with CDI.

METHODS

We used the US National Inpatient Sample (NIS) from 2004-2011 to assess the mortality risk in patients with a diagnosis of CDI (as per ICD-9CM 008.45). Annual average state UV exposure was assigned to each hospitalization. Logistic regression was used to determine the effects of UV exposure on mortality, controlling for age, gender, race and other comorbidities.

RESULTS

During the study period, there were 2.61 million hospitalizations with a diagnosis of CDI. The mortality rate was 9.0%. In univariate analysis, the odds ratio (OR) of inpatient mortality for the UV index was 0.97 (95% CI 0.95-0.99; p = 0.008) per unit of UV exposure. In a multivariable model adjusting for age, gender, race, Charlson-Deyo index, season and coexisting inflammatory bowel disease, the UV index remained a protective predictor, with an OR of 0.94 (95% CI 0.92-0.96; p < 0.001). In the multivariate model, a seasonal effect was also present, with the highest risk of inpatient mortality in the period from January to March (OR 1.11; 95% CI 1.08-1.14) and the lowest risk, from July to September (OR 0.95; 95% CI 0.92-0.98).

CONCLUSIONS

An increase in UV exposure index is associated with a reduced risk of inpatient mortality in patients with CDI. A seasonal effect is also present, with the highest risk of death during winter months. Further studies exploring the role of UV light in CDI are necessary.

Augmentation of Cationic Antimicrobial Peptide Production with Histone Deacetylase Inhibitors as a Novel Epigenetic Therapy for Bacterial Infections

The emergence of antibiotic resistance seriously threatens our ability to treat many common and medically important bacterial infections. Novel therapeutics are needed that can be used alone or in conjunction with antibiotics. Cationic antimicrobial peptides (CAMPs) are important effectors of the host innate defense that exhibit broad-spectrum activity against a wide range of microorganisms. CAMPs are carried within phagocytic granules and are constitutively or inducibly expressed by multiple cell types, including epithelial cells. The role of histone modification enzymes, specifically the histone deacetylases (HDAC), in down-regulating the transcription of CAMP-encoding genes is increasingly appreciated as is the capacity of HDAC inhibitors (HDACi) to block the action of HDACs to increase CAMP expression. The use of synthetic and natural HDACi molecules to increase CAMPs on mucosal surfaces, therefore, has potential therapeutic applications. Here, we review host and pathogen regulation of CAMP expression through the induction of HDACs and assess the therapeutic potential of natural and synthetic HDACi based on evidence from tissue culture systems, animal models, and clinical trials.