Antimicrobial Peptide Cathelicidin and Vitamin D Receptor Gene Polymorphism in Oral Health

Nireeksha^1*, Mithra NH² and Suchetha KN³

^*Correspondence: Nireeksha, Department of Conservative Dentistry and Endodontics, AB Shetty Memorial Institute of Dental Sciences,Nitte University,Deralakatte,Mangalore, India,

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Introduction

Organisms possess very strong defence system to combat the invading pathogens and microorganisms [1].One of the principal defence system which plays a major role against microorganism is innate immunity system. The anti-microbial functionality of innate immunity modulates the disruption of gram negative, gram positive, fungi and virus principally by disruption of bacterial cell membrane [2]. Anti-microbial peptides enhances the chemical and physical barrier in mucous membrane and skin. Various recognized anti- microbial peptides are highly conserved and expressed in organisms such as insects (drosophila) rabbits, mice, crabs. They are expressed in response to inflammatory conditions by phagocyte cells like monocytes,macrophages and granulocytes [3]. Oral cavity inspite of these numerous bacterial colonies and has high chances of invasion to the body through GIT, epithelium, gut, surgical procedure rarely leads to infection. Thus, indicates a strong and efficient host defensive mechanism that is in action [4].Production of antimicrobial peptides from neutrophils, salivary gland makes saliva rich in its anti-microbial, anti-fungal and anti-bacterial properties. They perform various functions like stimulation of epidermal growth factor thereby promotes wound healing, stimulates keratinocytes, che motaxis and immune activation. The binding ability of LL- 37 to lipopolysaccharides and neutralizing its activity facilitates a strong positive correlation between inhibition of liopolysaccharides induced cytokine secretion . LL-37 influence epidermal growth factor levels, migration of keritonoctyes and mediates angiogenesis. This quality of these AMP's make them an area of interest and they are also extensively studied [5].These anti-microbial peptides destroyed by attraction,attachement and insertion. Attraction is electrostatic attraction between cationic and anionic moieties on bacterial membrane, these antimicrobial peptides attach in parallel/ perpendicular manner to the membrane thereby stretching the bacterial membrane further thinning it down leads to pore formation, further insertion of these antimicrobial peptides takes place by three different model systems barrel stave model, carpet model leading to bacterial dissociation. Several types of anti-microbial peptide adverse in their sequence and structure are identified. Among them cathelicidins are peptides which are crucial in inflammatory conditions.

Cathelicidins are transcribed from a single gene CAMP with a N-terminal (30 amino acid residues) a highly conserved pro-sequence and mature anti-microbial peptide name LL-37 at the C-terminal domain. It has been observed that LL- 37 play a role in oral inflammatory conditions, few studies show their association of these peptides. The peptide has anti- microbial activity against gram positive and negative bacteria specifically on clinically relevant pathogens such as Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus,Salomonella typhimium at a mic of <10 μg/ml, also has an effect on lowering release of pro-inflammatory mediators. This peptide is located in azurophil granule, immature neutrophils, NK cells, monocytes, mast cells, squamous epithelium, airway, mouth, tongue, oesophagus, intestine, cervix and vagina. Widely produced in salivary glands, acinar cel of submandibular glands and minor glands [6]. This systemic review will focus on Cathelicidins (LL- 37) and its role in oral inflammatory conditions.

Systematic Search Strategy

Electronic search strategy consisted of two stages: Stage 1 included studies that specifies anti-microbial peptide levels [7,8] and vitamin D receptor gene polymorphism, Stage 2 included systemic search to identify various studies evaluating these levels in association with oral health and disease Dental caries and Periodontitis.

Focused Question

For identifying various studies the below mentioned focused questions [9] were adapted using PICO criteria (Miller and forest 2001)"What is the role of anti-microbial peptide LL-37 (Cathelicidins) in oral health and the association of vitamin D receptor gene polymorphism and dental caries"

Population

Younger adolescence and middle aged with dental caries and periodontitis.

Intervention/Exposure

Salivary anti-microbial peptide levels and its protective anti-inflammatory effect on oral health.

Comparison

Control group with Good oral hygiene (Low caries index and good periodontal health) Case group with poor oral health status (High caries index and poor periodontal health).

Outcome

Effect of LL-37 levels and vitamin D receptor gene polymorphism on caries prevalence and periodontal health.

Scope

Clinical studies which involved estimation of LL- 37 and vitamin D receptor gene polymorphism conducted in human subjects. Comparison done between healthy individuals and study subjects with dental caries and periodontitis. Animal studies, abstracts, letter to editors, narrative reviews and case reports were excluded.

Source

Electronic search was performed in Pubmed medline, ISI web of science [10] and medline database applying Mesh terms "Dental caries", "periodontal disease", "Cathelicidins", "LL- 37", "Vitamin D", "VDR receptor gene polymorphism", "saliva". The search system reviewed the article published between 2009 to 2019. Also a hand search of references and related articles were performed.

Study Selection

Controlled observational studies comparing and evaluating dental caries and periodontitis with LL-37 and vitamin D levels were selected. Studies concerning permanent dentition individuals with any other [11] systemic disease and under medication that effect the salivary composition were excluded. Case report, review articles were excluded. Studies which presented at least 8 of evaluating criteria were considered as low risk bias and 4 to 7 criteria were considered "moderate risk" less than 3 criteria it was considered as high [12,13] risk bias ad excluded from the study due to low evidence.

Result

Electronic search retrieved 102 no-duplicate records. However after checking the titles, abstract and full texts, 9 studies were selected for this systematic review. Two of them [7] were excluded because they were classified has " high risk bias " leaving a total of 7 for systematic review (Figure 1) from the selected studies [4]. classified as low risk,3 classified as moderate risk bias (Table 1). Shows quality assessment, gives description of study group. Simon Sara included 33 children's grouped based on caries at baseline and developing caries were further evaluated [8]. Turkaglu et al. conducted a study including 4 participants with gingivitis and healthy periodontal tissue was included and presence/absence of caries was not of concern [6]. Another study conducted by Davidopoulu included 49 systemically healthy individuals evaluated for Decay index, periodontal index and gingival index and were divided into 3 groups based on caries experience [7].

Figure 1: Stages of study selection process.

Table 1: Quality assessment of selected articles.

Takeuchi conducted a study among 69 patients, comparison between them was done based on probing depth, clinical attachment levels, Bleeding on probing, Plaque record (Table 2) No comparison with healthy individuals was done [9]. Turkoglu in 2009 evaluated IL-18 and LL-37 in 18 healthy 41 individuals with chronic periodontitis and comparison of these levels was done [10]. Bsml and Folk gene role in VDR receptor gene polymorphism was analyzed by [11] among 400 and 380 consequently.

Both the studies included caries free group for comparison [11,12]. Based on the results of selected studies 5 studies showed statistical difference between groups with/without caries and with/without periodontitis. Two of the studies showed association between Bsml and Folk gene polymorphism and dental caries.

Table 2: Description of selected studies.

Discussion

The selected studies were those which satisfied the minimum criteria that would be able to evaluate the role of LL-37, Vitamin D in caries and periodontal conditions. Rolf kotsmann in 1956 first reported condition called morbus kostmann syndrome (infantile genetic agranulocytosis) with a missing serum factor. These patients were highly susceptible to repetitive infections primarily gingivitis and periodontitis persisted even after antibiotic treatment. Later absence of LL-37 in saliva and load were reported. LLYu 37 is tested as an anti-bio film compound, due to its broad spectrum effect, rare resistance development by bacteria's, bacterial growth inhibition and bactericidal activity. These Antimicrobial peptides help in maintaining oral health by allowing more resistant nonpathogenic bacteria to dominate the colonization. The conducive factor for anti-microbial activity is the low ionic strength of saliva, Therefore evaluation of LL-37 plays a major role in caries risk assessment and development of treatment strategies.

Majority of studies showed relationship between salivary LL-37, periodontitis and dental caries. In a study microbial composition was compared with LL-37 levels in children significant increase in LL-37 levels in healthy individuals throughout the study. This longitudinal study concluded that both antimicrobial composition of saliva and bacterial composition predispose development of dental caries [8]. In another study LL-37 levels were evaluated in different age group in patients with gingivitis showed that inflammation of gingiva as an increasing effect on LL-37 levels, independent of individual age group [6].

Caries experience and LL-37 were evaluated in relation to age, gender, type of dentition i.e., primary, mixed and permanent in a study which showed that there is low peptide at early childhood and 100 fold increase in adolescence in ng/ml. Variation in gender was served based on differences in immuno-competency. Thus suggested that LL-37 may serve as prognostic tool for disease and efficient therapeutic agent [7]. A study compared LL-37 in chronic periodontitis shows increase in LL-37 which may be attributed to response of innate defence mechanism against perio-odontopathic bacteria.

In contrast LL-37 was elevated in chronic periodontitis compare to healthy individuals, suggesting an important role of LL-37 in pathogenesis of chronic periodontitis they concluded that LL-37 in gingival crevicular fluid was sufficient to decrease or prevent periodontal destruction. IL-18 was evaluate to whether both LL- 37 and IL-18 contribute to innate immunity in periodontal destruction. IL-18 is a proinflammatory cytokine stimulates mediators of inflammation and activate neutrophil's thus a part of host defence it was showed that LL-37 can stimulate production of IL-18. But in this study there was no correlation between the LL- 37 levels and IL-18 in chronic periodontitis [10].

These peptides being one of the important effector molecules of innate immunity is produced by the circulating cells, bone marrow progenitor cells, various epithelial surfaces, inflamed gingival tissues. Vitamin D is critical for regulation of CAMP gene and DEFB [4] gene which codes forcathelicidin and defensins in both normal and hematopoietic cells. Therefore vitamin D boosts innate immunity system and helps in wound healing and infection control. Presence of pathogen stimulates (TLR) Toll-Like Receptor's of macrophages inducing expression of CYP27B1 (25- hydroxyvitamin D-1α-hydroxylase) which, in turn, leads to the production of bioactive 1,25(OH)2D from circulating inactive 25(OH) D. Locally increase in 1,25(OH)2D activates CAMP gene which codes for cathelicidin. The releases of cytokines are also mediated through stimulation of toll-like receptors through vitamin D. Thus, Vitamin D levels play a major role in modulating immunity Kong YY and Yu m et al studied the possible correlation between genetic polymorphism of vitamin D receptor and occurrence of dental caries. Vitamin D regulates the calcium metabolism and promotes calcium depositing on enamel, also in a meta-analysis they mentioned that supplementation with vitamin D decreases he occurrence of caries by 40%. Both these studies showed correlation between vitamin D and caries pattern even though the specific mechanism is not understood. A single variable like LL-37 is difficult to establish as a marker because dental caries is multifactorial as a maker in nature. Understanding the complexity of peptide and their role in innate immunity makes it complex to understand the role of these LL-37 peptides in dental caries [13]. They target a broad spectrum of microbial activity, the ease of synthesis they are ideal for formulation of peptide based oral health care products along with routine maintenance of oral hygiene methods. Since they help to kill bacteria selectively in mixed culture, they can be used as an adjuvant to standard hygiene care in immune-compromised patients, control biofilms, progression of caries, biofilms on implants also prevention of plaque mediated dental diseases. These Anti-microbial peptides can be idealized has biomarkers for dental caries assessment, the up regulation and down regulation of these peptides may help in monitoring treatment outcome pre and post treatment. They are highly conserved and show relatively lower potential to resistance against microbes.

Conclusion

The selected studies showed a significant variation in LL-37 levels in dental caries, periodontitis, gingivitis and vitamin D polymorphism with dental caries. Still the complexity in mechanism of action of LL-37 and its relationship with Vitamin D levels makes it difficult to conclude. Only with more evidence and analysis we will be able to establish vitamin D and L-37 have a major role to play in occurrence and progression of dental caries.

Ethical Statement

Not relevant.

References

1. Zasloff M. Antimicrobial peptides of multicellular organisms. Nature 2002; 415:389–395.
2. Alves D, Olivia Pereira M. Mini-review: Antimicrobial peptides and enzymes as promising candidates to functionalize biomaterial surfaces. Biofouling 2014; 30:483–499.
3. Hancock RE, Sahl HG. Antimicrobial and host-defense peptides as new anti-infective therapeutic strategies. Nat Biotechnol 2006; 24:1551–1557.
4. Dale BA, Tao R, Kimball JR, et al. Oral antimicrobial peptides and biological control of caries. BMC Oral Health 2006; 6:S13.
5. Koczulla AR, Bals R. Antimicrobial peptides: currentstatus, and therapeutic potential. Drugs 2003; 63:389–406.
6. Turkoglu O, Emingul G, Eren G, et al. Levels of ll-37 antimicrobial peptide in the gingival crevicular fluid of young and middle-aged subjects with or without gingivitis. Journal of Istanbul University Faculty of Dentistry 2017; 51:15-21.
7. Davidopouloua S, Eudoxia Diza, Menexes GC, et al.(2014) Salivary concentration of the antimicrobial peptide LL-37 in children. Archives of oral Biology 57:865-869.
8. Simon-soro A, sheriff A, Sadique S, Ramage G, Macpherson G, Mira A, Culshaw S, Malcolm J . Combined analysis of the salivarymicrobiome and host defence peptides predicts dental disease. ScientificReports 2018; 8:1484.
9. Takeuchi Y, Nagasawa T, Katagiri S, et al. Salivary levels of antibacterial peptide (LL- 37/hCAP-18) and cotinine in patients with chronic periodontitis. J Periodontol 83:766-72.
10. TurkogluO, Emingil G, Kutukcxuler N, et al.Gingival crevicular fluid levels of cathelicidin LL-37 and interlukin-18 in patients with chronic periodontitis. Periodontol 2009; 80:969-976.
11. Yu M, Jiang QZ, Sun ZY, et al. Association between single nucleotide polymorphisms in vitamin d receptor gene polymorphisms and permanent tooth caries susceptibility to permanent tooth caries in chinese adolescent. BioMed Research International. Volume 2017; Article ID 4096316, 7.
12. Kong YY, Zheng JM, Zhang WJ, et al. The relationship between vitamin D receptor gene polymorphism and deciduous tooth decay in Chinese children. BMC Oral Health 2017; 17:111.
13. Helmerhorst EJ,   Oppenheim   FG.   Saliva: a dynamic proteome. Journal of Dental Research 2007; 86:680-93.