Saliva-Derived Host Defense Peptides Histatin1 and LL-37 Increase Secretion of Antimicrobial Skin and Oral Mucosa Chemokine CCL20 in an IL-1α-Independent Manner

Abstract

Even though skin and oral mucosae are continuously in contact with commensal and opportunistic microorganisms, they generally remain healthy and uninflamed. Host defense peptides (HDPs) make up the body's first line of defense against many invading pathogens and are involved in the orchestration of innate immunity and the inflammatory response. In this study, we investigated the effect of two salivary HDPs, LL-37 and Hst1, on the inflammatory and antimicrobial response by skin and oral mucosa (gingiva) keratinocytes and fibroblasts. The potent antimicrobial chemokine CCL20 was investigated and compared with chemokines CCL2, CXCL1, CXCL8, and CCL27 and proinflammatory cytokines IL-1α and IL-6. Keratinocyte-fibroblast cocultures showed a synergistic increase in CCL20 secretion upon Hst1 and LL-37 exposure compared to monocultures. These cocultures also showed increased IL-6, CXCL1, CXCL8, and CCL2 secretion, which was IL-1α dependent. Secretion of the antimicrobial chemokine CCL20 was clearly IL-1α independent. These results indicate that salivary peptides can stimulate skin as well as gingiva cells to secrete antimicrobial chemokines as part of the hosts' defense to counteract infection.

Differential influence ofStreptococcus mitison host response to metals in reconstructed human skin and oral mucosa

“…58 Previously we have described intrinsic differences between skin and gingiva with regard to innate immunology, wound healing, and the response to contact sensitizers. 48,[59][60][61] In current study, under unexposed conditions, we show that RHS secretes higher baseline levels of cytokines involved in LC migration (IL-18 and CXCL12) than RHG, which is in line with our previous study, 25,48 and we also show that S. mitis increased the cytokine release of IL-6, CXCL8, CCL5, and CCL20 in RHS but not in RHG. Such relative inertness of RHG to S. mitis is supported by findings of others describing the regulatory role of S. mitis as an oral commensal on immune balance, where it inhibits CD 4+ T cell proliferation, promotes Th17 responses, and induces the secretion of IL-10 in human monocytes.…”

Human saliva stimulates skin and oral wound healing in vitro

“…This finding was surprising considering the large number of molecules present in saliva, including salivary leptins, CCL5 (RANTES), IL‐1α, and KGF, which are described as mitogens (Dawes et al, ; Groschl et al, ; Kroeze et al, ). However, it must also be considered that cytotoxic proteins such as LL37, as mentioned above, are also present in saliva, indicating that a delicate balance exists between mitogens and antimicrobial proteins (Boink et al, ). It has been shown that a prolonged acidic wound environment can prevent wound closure and re‐epithelialization (Kruse et al, ).…”

“…Previously, we have shown that histatin 1 and LL37 (both salivary peptides) stimulate inflammatory cytokine release from keratinocytes, the latter via an IL-1α-dependent pathway (Boink et al, 2017). Since IL-1α is pre-stored in the stratum corneum and is also readily synthesized by keratinocytes, it is most probable that saliva stimulates pro-inflammatory cytokine release from keratinocytes, which in turn stimulates an inflammatory cytokine cascade via the fibroblasts (Boink et al, 2017;Dawes et al, 2015;Spiekstra, Breetveld, Rustemeyer, Scheper, & Gibbs, 2007). Such an effect would be even more pronounced in the presence of a wound.…”

“…In this study, we show that migration reached a maximum in cultures supplemented with 20% saliva and decreased when 50% saliva was used. The reason for this is currently unknown, but it needs to be considered that saliva contains many peptides, for example, LL37, which have also been shown to be cytotoxic to cultured cells at high concentrations (>10 μM; Boink et al, ) and that in vivo saliva rarely has direct contact with fibroblasts because it first needs to penetrate granulation tissue forming in a wound bed or the epithelium in intact gingiva. Using a model to investigate epithelial expansion, we were indeed able to show that 50% saliva was not cytotoxic but resulted in maximum migration of differentiating skin keratinocytes growing out from a confluent circle over a cell culture surface.…”

“…In addition to its lubricating function, saliva contains a vast cocktail of proteins (>1,000 proteins) which function in synergy so that saliva is mitogenic, enhances cell migration, and also acts in an anti-microbial manner resulting in a healthy oral microflora (Denny et al, 2008;Mohanty et al, 2017). For example, defensins, LL37, histatins, and mucins protect against the formation of a pathogenic microbiome; whereas cytokines (Boink et al, 2017), chemokines, and growth factors directly enhance wound closure (Behm, Babilas, Landthaler, & Schreml, 2012). Saliva also stimulates the innate immune system, and therefore, the inflammatory phase of wound healing by stimulating fibroblasts to produce, for example, IL-6 and CXCL8 (Cvikl, Lussi, Moritz, Sculean, & Gruber, 2015).…”