Human salivary peptide histatin-1 stimulates epithelial and endothelial cell adhesion and barrier function

GPCR/endocytosis/ERK signaling/S2R is involved in the regulation of the internalization, mitochondria-targeting and -activating properties of human salivary histatin 1

Human salivary histatin 1 (Hst1) exhibits a series of cell-activating properties, such as promoting cell spreading, migration, and metabolic activity. We recently have shown that fluorescently labeled Hst1 (F-Hst1) targets and activates mitochondria, presenting an important molecular mechanism. However, its regulating signaling pathways remain to be elucidated. We investigated the influence of specific inhibitors of G protein-coupled receptors (GPCR), endocytosis pathways, extracellular signal-regulated kinases 1/2 (ERK1/2) signaling, p38 signaling, mitochondrial respiration and Na+/K+-ATPase activity on the uptake, mitochondria-targeting and -activating properties of F-Hst1. We performed a siRNA knockdown (KD) to assess the effect of Sigma-2 receptor (S2R) /Transmembrane Protein 97 (TMEM97)—a recently identified target protein of Hst1. We also adopted live cell imaging to monitor the whole intracellular trafficking process of F-Hst1. Our results showed that the inhibition of cellular respiration hindered the internalization of F-Hst1. The inhibitors of GPCR, ERK1/2, phagocytosis, and clathrin-mediated endocytosis (CME) as well as siRNA KD of S2R/TMEM97 significantly reduced the uptake, which was accompanied by the nullification of the promoting effect of F-Hst1 on cell metabolic activity. Only the inhibitor of CME and KD of S2R/TMEM97 significantly compromised the mitochondria-targeting of Hst1. We further showed the intracellular trafficking and targeting process of F-Hst1, in which early endosome plays an important role. Overall, phagocytosis, CME, GPCR, ERK signaling, and S2R/TMEM97 are involved in the internalization of Hst1, while only CME and S2R/TMEM97 are critical for its subcellular targeting. The inhibition of either internalization or mitochondria-targeting of Hst1 could significantly compromise its mitochondria-activating property.

Identification of VEGFR2 as the Histatin-1 receptor in endothelial cells

Histatin-1 is a salivary peptide with antimicrobial and wound healing promoting activities, which was previously shown to stimulate angiogenesis in vitro and in vivo via inducing endothelial cell migration. The mechanisms underlying the proangiogenic effects of Histatin-1 remain poorly understood and specifically, the endothelial receptor for this peptide, is unknown. Based on the similarities between Histatin-1-dependent responses and those induced by the prototypical angiogenic receptor, vascular endothelial growth factor receptor 2 (VEGFR2), we hypothesized that VEGFR2 is the Histatin-1 receptor in endothelial cells. First, we observed that VEGFR2 is necessary for Histatin-1-induced endothelial cell migration, as shown by both pharmacological inhibition studies and siRNA-mediated ablation of VEGFR2. Moreover, Histatin-1 co-immunoprecipitated and co-localized with VEGFR2, associating spatial proximity between these proteins with receptor activation. Indeed, pulldown assays with pure, tagged and non-tagged proteins showed that Histatin-1 and VEGFR2 directly interact in vitro. Optical tweezers experiments permitted estimating kinetic parameters and rupture forces, indicating that the Histatin-1-VEGFR2 interaction is transient, but specific and direct. Sequence alignment and molecular modeling identified residues Phe26, Tyr30 and Tyr34 within the C-terminal domain of Histatin-1 as relevant for VEGFR2 binding and activation. This was corroborated by mutation and molecular dynamics analyses, as well as in direct binding assays. Importantly, these residues were required for Histatin-1 to induce endothelial cell migration and angiogenesis in vitro. Taken together, our findings reveal that VEGFR2 is the endothelial cell receptor of Histatin-1 and provide insights to the mechanism by which this peptide promotes endothelial cell migration and angiogenesis.

Natural Peptides Inducing Cancer Cell Death: Mechanisms and Properties of Specific Candidates for Cancer Therapeutics

Nowadays, cancer has become the second highest leading cause of death, and it is expected to continue to affect the population in forthcoming years. Additionally, treatment options will become less accessible to the public as cases continue to grow and disease mechanisms expand. Hence, specific candidates with confirmed anticancer effects are required to develop new drugs. Among the novel therapeutic options, proteins are considered a relevant source, given that they have bioactive peptides encrypted within their sequences. These bioactive peptides, which are molecules consisting of 2–50 amino acids, have specific activities when administered, producing anticancer effects. Current databases report the effects of peptides. However, uncertainty is found when their molecular mechanisms are investigated. Furthermore, analyses addressing their interaction networks or their directly implicated mechanisms are needed to elucidate their effects on cancer cells entirely. Therefore, relevant peptides considered as candidates for cancer therapeutics with specific sequences and known anticancer mechanisms were accurately reviewed. Likewise, those features which turn certain peptides into candidates and the mechanisms by which peptides mediate tumor cell death were highlighted. This information will make robust the knowledge of these candidate peptides with recognized mechanisms and enhance their non-toxic capacity in relation to healthy cells and further avoid cell resistance.

Natural Peptides Inducing Cancer Cell Death: Mechanisms and Properties of Specific Candidates for Cancer Therapeutics

Nowadays, cancer has become the second highest leading cause of death, and it is expected to continue to affect the population in forthcoming years. Additionally, treatment options will become less accessible to the public as cases continue to grow and disease mechanisms expand. Hence, specific candidates with confirmed anticancer effects are required to develop new drugs. Among the novel therapeutic options, proteins are considered a relevant source, given that they have bioactive peptides encrypted within their sequences. These bioactive peptides, which are molecules consisting of 2–50 amino acids, have specific activities when administered, producing anticancer effects. Current databases report the effects of peptides. However, uncertainty is found when their molecular mechanisms are investigated. Furthermore, analyses addressing their interaction networks or their directly implicated mechanisms are needed to elucidate their effects on cancer cells entirely. Therefore, relevant peptides considered as candidates for cancer therapeutics with specific sequences and known anticancer mechanisms were accurately reviewed. Likewise, those features which turn certain peptides into candidates and the mechanisms by which peptides mediate tumor cell death were highlighted. This information will make robust the knowledge of these candidate peptides with recognized mechanisms and enhance their non-toxic capacity in relation to healthy cells and further avoid cell resistance.

Histatin 1 enhanced the speed and quality of wound healing through regulating the behaviour of fibroblast

Objectives

Histatin 1(Hst 1) has been proved to promote wound healing. However, there was no specific study on the regulation made by Hst 1 of fibroblasts in the process of wound healing. This research comprehensively studied the regulation of Hst 1 on the function of fibroblasts in the process of wound healing and preliminary mechanism about it.

Materials and methods

The full‐thickness skin wound model was made on the back of C57/BL6 mice. The wound healing, collagen deposition and fibroblast distribution were detected on days 3, 5 and 7 after injury. Fibroblast was cultured in vitro and stimulated with Hst 1, and then, their biological characteristics and functions were detected.

Results

Histatin 1 can effectively promote wound healing, improve collagen deposition during and after healing and increase the number and function of fibroblasts. After healing, the mechanical properties of the skin also improved. In vitro, the migration ability of fibroblasts stimulated by Hst 1 was significantly improved, and the fibroblasts transformed more into myofibroblasts, which improved the function of contraction and collagen secretion. In fibroblasts, mTOR signalling pathway can be activated by Hst 1.

Conclusions

Histatin 1 can accelerate wound healing and improve the mechanical properties of healed skin by promoting the function of fibroblasts. The intermolecular mechanisms need to be further studied, and this study provides a direction about mTOR signalling pathway.

Histatin-1 is an endogenous ligand of the sigma-2 receptor

The Sigma-2 receptor (S2R) (a.k.a TMEM97) is an important endoplasmic reticular protein involved in cancer, cholesterol processing, cell migration, and neurodegenerative diseases, including Niemann-Pick Type C. While several S2R pharmacologic agents have been discovered, its recent (2017) cloning has limited biological investigation, and no endogenous ligands of the S2R are known. Histatins are a family of endogenous antimicrobial peptides that have numerous important effects in multiple biological systems, including antifungal, antibacterial, cancer pathogenesis, immunomodulation, and wound healing. Histatin-1 (Hst1) has important roles in epithelial wound healing and cell migration, and is the primary wound healing agent in saliva. Little is understood about the downstream machinery that underpins the effects of histatins, and no mammalian receptor is known to date. In this study, we show, using biophysical methods and functional assays, that Hst1 is an endogenous ligand for S2R and that S2R is a mammalian receptor for Hst1.

Human Salivary Histatin-1-Functionalized Gelatin Methacrylate Hydrogels Promote the Regeneration of Cartilage and Subchondral Bone in Temporomandibular Joints

The avascular structure and lack of regenerative cells make the repair of osteochondral defects in the temporomandibular joint (TMJ) highly challenging in the clinic. To provide a viable treatment option, we developed a methacrylated gelatin (Gel-MA) hydrogel functionalized with human salivary histatin-1 (Hst1). Gel-MA is highly biocompatible, biodegradable, and cost-effective. Hst1 is capable of activating a series of cell activities, such as adhesion, migration, differentiation, and angiogenesis. To evaluate the efficacy of Hst1/Gel-MA, critical-size osteochondral defects (3 mm in diameter and 3 mm in depth) of TMJ in New Zealand white rabbits were surgically created and randomly assigned to one of the three treatment groups: (1) control (no filling material); (2) Gel-MA hydrogel; (3) Hst1/Gel-MA hydrogel. Samples were retrieved 1, 2, and 4 weeks post-surgery and subjected to gross examination and a series of histomorphometric and immunological analyses. In comparison with the control and Gel-MA alone groups, Hst1/Gel-MA hydrogel was associated with significantly higher International Cartilage Repair Society score, modified O’Driscoll score, area percentages of newly formed bone, cartilage, collagen fiber, and glycosaminoglycan, and expression of collagen II and aggrecan. In conclusion, Hst1/Gel-MA hydrogels significantly enhance bone and cartilage regeneration, thus bearing promising application potential for repairing osteochondral defects.

Extractable surface proteins of indigenous probiotic strains confer anti-adhesion knack and protect against methicillin-resistant Staphylococcus aureus induced epithelial hyperpermeability in HT-29 cell line

Probiotic intervention has been long believed to have beneficial effects on human health by curbing the intestinal colonization of pathogens. However, the application of live probiotics therapy may not be an ideal approach to circumvent the infections of superbug origin due to the risk of horizontal antibiotic resistance genes transfer. In this study, the anti-adhesion ability of extractable cell surface proteins from two indigenous potential probiotic strains (Lactiplantibacillus plantarum A5 and Limosilactobacillus fermentum Lf1) and two standard reference strains (Lactobacillus acidophilus NCFM and Lacticaseibacillus rhamnosus LGG) was evaluated against clinical isolates of Methicillin-Resistant Staphylococcus aureus (MRSA) on porcine gastric mucin and HT-29 cells. The surface proteins from the probiotic strains were extracted by treatment with 5 M lithium chloride. The surface protein quantification and SDS-PAGE profiling indicated that the yield and protein patterns were strain-specific. Surface proteins significantly hampered the mucoadhesion of MRSA isolates via protective, competitive, and displacement. Similarly, the treatment with surface proteins probiotic strains displayed anti-adhesion against MRSA isolates on HT-29 cells without affecting the viability of the cell line. Surface proteins treatment to the confluent monolayer of HT-29 cells maintained the epithelial integrity; however, MRSA isolates (10⁹ cells/mL) showed considerable alteration in the epithelial integrity by exacerbating the FITC-dextran transflux. Contrarily, the co-treatment with surface proteins with MRSA isolates significantly lowered the FITC-dextran transflux across the differentiated HT-29 monolayer. Overall, the findings of this study suggest that probiotic-derived surface proteins could be the novel biotherapeutics to combat the MRSA colonization and their concomitant intestinal infections.

LFchimera: a synthetic mimic of the two antimicrobial domains of bovine lactoferrin

Saliva is essential for the maintenance of oral health. When salivary flow is impaired, the risk of various oral diseases such as caries and candidiasis increases drastically. Under healthy conditions, saliva provides effective protection against microbial colonization by the collaborative action of numerous host-defense molecules. This review describes how saliva has been the guideline for the design and characterization of a heterodimeric antimicrobial construct called LFchimera. This construct mimics the helical parts of two antimicrobial domains in the crystal structure of bovine lactoferrin. It shows high antimicrobial activity against a broad spectrum of Gram-positive and Gram-negative bacteria, fungi, and parasites including biowarfare agents such as Bacillus anthracis, Burkholderia pseudomallei, and Yersinia pestis. Further, sublethal concentrations of LFchimera inhibited biofilm formation, the invasiveness of HeLa cells by Yersinia spp., and prevented haemolysis of enteropathogenic Escherichia coli, demonstrating the versatility of these peptides.

Histatin-1 is a novel osteogenic factor that promotes bone cell adhesion, migration, and differentiation

Histatin-1 is a salivary antimicrobial peptide involved in the maintenance of enamel and oral mucosal homeostasis. Moreover, Histatin-1 has been shown to promote re-epithelialization in soft tissues, by stimulating cell adhesion and migration in oral and dermal keratinocytes, gingival and skin fibroblasts, endothelial cells and corneal epithelial cells. The broad-spectrum activity of Histatin-1 suggests that it behaves as a universal wound healing promoter, although this is far from being clear yet. Here, we report that Histatin-1 is a novel osteogenic factor that promotes bone cell adhesion, migration, and differentiation. Specifically, Histatin-1 promoted cell adhesion, spreading, and migration of SAOS-2 cells and MC3T3-E1 preosteoblasts in vitro, when placed on a fibronectin matrix. Besides, Histatin-1 induced the expression of osteogenic genes, including osteocalcin, osteopontin, and Runx2, and increased both activity and protein levels of alkaline phosphatase. Furthermore, Histatin-1 promoted mineralization in vitro, as it augmented the formation of calcium deposits in both SAOS-2 and MC3T3-E1 cells. Mechanistically, although Histatin-1 failed to activate ERK1/2, FAK, and Akt, which are signaling proteins associated with osteogenic differentiation or cell migration, it triggered nuclear relocalization of β-catenin. Strikingly, the effects of Histatin-1 were recapitulated in cells that are nonosteogenically committed, since it promoted surface adhesion, migration, and the acquisition of osteogenic markers in primary mesenchymal cells derived from the apical papilla and dental pulp. Collectively, these observations indicate that Histatin-1 is a novel osteogenic factor that promotes bone cell differentiation, surface adhesion and migration, as crucial events required for bone tissue regeneration.

Effects and mechanisms of histatins as novel skin wound-healing agents

Wound healing is a complex and important physiological process that maintains the integrity of skin after various injuries. Abnormal wound healing, especially of chronic wounds, impairs normal physical function. Therefore, the search for effective and safe healing agents is one of the main concerns. Histatins are histidine-rich low molecular weight peptides that are expressed in the saliva of both humans and higher primates. Histatins have two main biological effects, cell stimulation and bacteria killing, with the former playing an important role in wound healing by promoting epithelial cell and fibroblast migration and angiogenesis and enhancing the re-epithelialization of the wounded area. Because of these biological effects, histatins have been shown to be promising agents of improved wound healing. Histatins are categorized into many subtypes, of which histatin 1 and its hydrolysates are the most effective in promoting wound healing. This review addresses the bioactivity of histatins in wound healing, such as their stimulatory effects on epithelial cells and fibroblasts, and elucidates the possible mechanisms by which histatin subtypes induce their biological effects.

In vitro Interactions between Streptococcus intermedius and Streptococcus salivarius K12 on a Titanium Cylindrical Surface

Peri-implantitis is a steadily rising disease and is caused by oral bacterial pathogens able to form biofilm on implant surfaces and peri-implant tissues, making antibiotics treatment less effective. The use of commercial probiotics against oral pathogens could serve as an alternative to prevent biofilm formation. Streptococcus intermedius is one of the early colonizers of biofilm formation in dental implants. The aim of this study was to model the interaction between S. intermedius and Streptococcus salivarius strain K12, a probiotic bacterium producing bacteriocins. S. intermedius was co-cultured with S. salivarius K12 in an in vitro model simulating the biofilm formation in a dental implant composed by a titanium cylinder system. Biofilm formation rate was assessed by Real-Time PCR quantification of bacterial count and expression levels of luxS gene, used in response to cell density in the biofilm. Biofilm formation, bacteriocin production, luxS expression patterns were found to be already expressed within the first 12 h. More importantly, S. salivarius K12 was able to counter the biofilm formation in a titanium cylinder under the tested condition. In conclusion, our dental implant model may be useful for exploring probiotic-pathogen interaction to find an alternative to antibiotics for peri-implantitis treatment.

Monosomy 3 Influences Epithelial-Mesenchymal Transition Gene Expression in Uveal Melanoma Patients; Consequences for Liquid Biopsy

Despite outstanding advances in diagnosis and the treatment of primary uveal melanoma (UM), nearly 50% of UM patients develop metastases via hematogenous dissemination, driven by the epithelial-mesenchymal transition (EMT). Despite the failure in UM to date, a liquid biopsy may offer a feasible non-invasive approach for monitoring metastatic disease progression and addressing protracted dormancy. To detect circulating tumor cells (CTCs) in UM patients, we evaluated the mRNA expression of EMT-associated transcription factors in CD45-depleted blood fraction, using qRT-PCR. ddPCR was employed to assess UM-specific GNA11, GNAQ, PLCβ4, and CYSLTR2 mutations in plasma DNA. Moreover, microarray analysis was performed on total RNA isolated from tumor tissues to estimate the prognostic value of EMT-associated gene expression. In total, 42 primary UM and 11 metastatic patients were enrolled. All CD45-depleted samples were negative for CTC when compared to the peripheral blood fraction of 60 healthy controls. Tumor-specific mutations were detected in the plasma of 21.4% patients, merely, in 9.4% of primary UM, while 54.5% in metastatic patients. Unsupervised hierarchical clustering of differentially expressed EMT genes showed significant differences between monosomy 3 and disomy 3 tumors. Newly identified genes can serve as non-invasive prognostic biomarkers that can support therapeutic decisions.

Human Salivary Histatin-1 Promotes Osteogenic Cell Spreading on Both Bio-Inert Substrates and Titanium SLA Surfaces

Promoting cell spreading is crucial to enhance bone healing and implant osteointegration. In this study, we investigated the stimulatory effect of human salivary histatin-1 (Hst-1) on the spreading of osteogenic cells in vitro as well as the potential signaling pathways involved. Osteogenic cells were seeded on bio-inert glass slides with or without the presence of Hst1 in dose-dependent or time-course assays. 1 scrambled and 6 truncated Hst1 variants were also evaluated. Cell spreading was analyzed using a well-established point-counting method. Fluorescent microscopy was adopted to examine the cellular uptake of fluorescently labeled Hst1 (F-Hst1) and also the cell spreading on sandblasted and acid etched titanium surfaces. Signaling inhibitors, such as U0126, SB203580, and pertussis toxin (PTx) were used to identify the potential role of extracellular-signal-regulated kinase, p38 and G protein-coupled receptor pathways, respectively. After 60 min incubation, Hst1 significantly promoted the spreading of osteogenic cells with an optimal concentration of 10 μM, while truncated and scrambled Hst1 did not. F-Hst1 was taken up and localized in the vicinity of the nuclei. U0126 and SB2030580, but not PTx, inhibited the effect of Hst1. 10 μM Hst1 significantly promoted the spreading of osteogenic cells on both bio-inert substrates and titanium SLA surfaces, which involved ERK and p38 signaling. Human salivary histatin-1 might be a promising peptide to enhance bone healing and implant osteointegration in clinic.

Harnessing biomolecules for bioinspired dental biomaterials

Dental clinicians have relied for centuries on traditional dental materials (polymers, ceramics, metals, and composites) to restore oral health and function to patients. Clinical outcomes for many crucial dental therapies remain poor despite many decades of intense research on these materials. Recent attention has been paid to biomolecules as a chassis for engineered preventive, restorative, and regenerative approaches in dentistry. Indeed, biomolecules represent a uniquely versatile and precise tool to enable the design and development of bioinspired multifunctional dental materials to spur advancements in dentistry. In this review, we survey the range of biomolecules that have been used across dental biomaterials. Our particular focus is on the key biological activity imparted by each biomolecule toward prevention of dental and oral diseases as well as restoration of oral health. Additional emphasis is placed on the structure-function relationships between biomolecules and their biological activity, the unique challenges of each clinical condition, limitations of conventional therapies, and the advantages of each class of biomolecule for said challenge. Biomaterials for bone regeneration are not reviewed as numerous existing reviews on the topic have been recently published. We conclude our narrative review with an outlook on the future of biomolecules in dental biomaterials and potential avenues of innovation for biomaterial-based patient oral care.

Endothelial Cells Derived From Patients With Diabetic Macular Edema Recapitulate Clinical Evaluations of Anti-VEGF Responsiveness Through the Neuronal Pentraxin 2 Pathway

Diabetic macular edema (DME) remains a leading cause of vision loss worldwide. DME is commonly treated with intravitreal injections of vascular endothelial growth factor (VEGF)-neutralizing antibodies. VEGF inhibitors (anti-VEGFs) are effective, but not all patients fully respond to them. Given the potential side effects, inconvenience, and high cost of anti-VEGFs, identifying who may not respond appropriately to them and why is essential. Herein we determine first the response to anti-VEGFs, using spectral-domain optical coherence tomography scans obtained from a cohort of patients with DME throughout the 1st year of treatment. We found that fluid fully cleared at some time during the 1st year in 28% of eyes ("full responders"); fluid cleared only partly in 66% ("partial responders"); and fluid remained unchanged in 6% ("nonresponders"). To understand this differential response, we generated induced pluripotent stem cells (iPSCs) from full responders and nonresponders, from subjects with diabetes but no DME, and from age-matched volunteers without diabetes. We differentiated these iPSCs into endothelial cells (iPSC-ECs). Monolayers of iPSC-ECs derived from patients with diabetes showed a marked and prolonged increase in permeability upon exposure to VEGF; the response was significantly exaggerated in iPSC-ECs from nonresponders. Moreover, phosphorylation of key cellular proteins in response to VEGF, including VEGFR2, and gene expression profiles, such as that of neuronal pentraxin 2, differed between full responders and nonresponders. In this study, iPSCs were used in order to predict patients' responses to anti-VEGFs and to identify key mechanisms that underpin the differential outcomes observed in the clinic. This approach identified NPTX2 as playing a significant role in patient-linked responses and as having potential as a new therapeutic target for DME.

Innate Inspiration: Antifungal Peptides and Other Immunotherapeutics From the Host Immune Response

The purpose of this review is to describe antifungal therapeutic candidates in preclinical and clinical development derived from, or directly influenced by, the immune system, with a specific focus on antimicrobial peptides (AMP). Although the focus of this review is AMP with direct antimicrobial effects on fungi, we will also discuss compounds with direct antifungal activity, including monoclonal antibodies (mAb), as well as immunomodulatory molecules that can enhance the immune response to fungal infection, including immunomodulatory AMP, vaccines, checkpoint inhibitors, interferon and colony stimulating factors as well as immune cell therapies. The focus of this manuscript will be a non-exhaustive review of antifungal compounds in preclinical and clinical development that are based on the principles of immunology and the authors acknowledge the incredible amount of in vitro and in vivo work that has been conducted to develop such therapeutic candidates.

Human Salivary Histatin-1 Is More Efficacious in Promoting Acute Skin Wound Healing Than Acellular Dermal Matrix Paste

A rapid wound healing is beneficial for not only recovering esthetics but also reducing pain, complications and healthcare burdens. For such a purpose, continuous efforts have been taken to develop viable dressing material. Acellular dermal matrix (ADM) paste has been used to repair burn wounds and is shown to promote angiogenesis as well as fibroblast attachment and migration. However, its efficacy still needs to be significantly improved to meet clinical demands for accelerating acute skin wound healing. To approach this problem, we studied the added value of a human salivary peptide - Histatin 1 (Hst1). Hst1 was chosen because of its potency to promote the adhesion, spreading, migration, metabolic activity and cell-cell junction of major skin cells and endothelial cells. In this study, we hypothesized that ADM paste and Hst1 showed a better effect on the healing of surgically created acute skin wounds in mice since ADM paste may act as a slow release system for Hst1. Our results showed that the healing efficacy of 10 μM topically administrated Hst1 was significantly higher compared to the control (no Hst1, no ADM) from day 3 to day 10 post-surgery. In contrast, ADM alone failed in our system at all time points. Also, the combination of ADM paste and Hst1 did not show a better effect on percentage of wound healing. Histological analysis showed that 10 μM Hst1 was associated with maximal thickness of newly formed epidermal layer on day 7 as well as the largest collagen area on day 14. In addition, immunohistochemical staining showed that the number of CD31-positive blood vessels in the group of 10 μM Hst1 was 2.3 times compared to the control. The vascular endothelial growth factor (VEGF) expression in the groups of 10 μM Hst1 group and ADM + 10 μM Hst1 group was significantly higher compared with the control group. Furthermore, 10 μM Hst1 group was associated with significantly lower levels of CD68-positive macrophage number, interleukin-1β (IL-1β) expression and C-reactive protein (CRP) expression than those of the other groups (control, ADM alone and ADM + 10 μM Hst1). In contrast, ADM was only associated with significantly lower CD68-positive macrophage number and IL-1β expression in comparison with the control. The co-administration of Hst1 and ADM paste did not yield more beneficial effects than Hst1 alone. In conclusion, the topically administrated of 10 μM Hst1 could be a promising alternative dressing in managing acute wound healing.

Salivary Histatin 1 and 2 Are Targeted to Mitochondria and Endoplasmic Reticulum in Human Cells

Human salivary histatin 1 (Hst1) and Hst2 exhibit a series of cell-activating properties (e.g., promoting adhesion, spreading, migration and metabolic activity of mammalian cells). In contrast, Hst5 shows an anti-fungal property but no cell-activating properties. Previous findings suggest that their uptake and association with subcellular targets may play a determinant role in their functions. In this study, we studied the uptake dynamics and subcellular targets of Hst1, Hst2 and Hst5 in epithelial cells (HO1N1 human buccal carcinoma epithelial cell line). Confocal laser scanning microscopy (CLSM) revealed that fluorescently labeled Hst1 (F-Hst1) was taken up into the intracellular space of epithelial cells. Then, 60 min post-incubation, the total fluorescence of cell-associated F-Hst1, as measured using flow cytometry, was significantly higher compared to those of F-Hst2 and F-Hst5. In contrast, virtually no association occurred using the negative control—scrambled F-Hst1 (F-Hst^scr). CLSM images revealed that F-Hst1, 2 and 5 co-localized with mitotracker^TM-labeled mitochondria. In addition, F-Hst1 and F-Hst2 but neither F-Hst5 nor F-Hst1^scr co-localized with the ER-tracker^TM-labeled endoplasmic reticulum. No co-localization of Hst1, 2 and 5 with lysosomes or the Golgi apparatus was observed. Furthermore, Hst1 and Hst2 but not Hst5 or Hst1^scr significantly promoted the metabolic activity of both human epithelial cell lines, HaCaT human keratinocytes and primary human gingival fibroblasts.

Presence of Histatin-1 in Human Tears and Association with Aqueous Deficient Dry Eye Diagnosis: A Preliminary Study

The aims of this study were to determine if histatin-1 (H1) is present in normal human tears and whether tear levels of H1 varied between normal patients and those with aqueous deficient dry eye disease (ADDE). Patient samples were obtained from 11 normal patients and 11 severe ADDE patients. Relevant patient characteristics, including age, sex, and dry eye disease (DED) diagnostic parameters were collected. Multiple qualitative and quantitative methods were used to compare the concentration of H1 between patient groups. Mixed linear modeling was used to compare H1 levels between groups, and diagnostic performance was assessed using the receiver-operator-characteristic (ROC). ADDE patients had significantly lower H1 concentrations (85.9 ± 63.7 ng/ml) than the normal group (891.6 ± 196.5 ng/ml) (p < 0.001), while controlling for age and sex. ROC analysis indicated that H1 concentration is potentially a biomarker for ADDE (area under curve = 0.96). Reclassification of patients by DED parameters including, Ocular Surface Disease Index (OSDI) (≤13, >13) and Schirmer I (without anesthesia) (<10 mm, ≥10 mm) showed significant differences in H1 level (OSDI, p = 0.004) and Schirmer I ((p = 0.010). In conclusion, this is the first preliminary report of the presence of H1 in human tears. H1 concentrations are lower in ADDE patients and H1 may have diagnostic potential in evaluation ADDE patients.

Salivary peptide histatin 1 mediated cell adhesion: a possible role in mesenchymal-epithelial transition and in pathologies

Histatins are histidine-rich peptides present in the saliva of humans and higher primates and have been implicated in the protection of the oral cavity. Histatin 1 is one of the most abundant histatins and recent reports show that it has a stimulating effect on cellular adherence, thereby suggesting a role in maintaining the quality of the epithelial barrier and stimulating mesenchymal-to-epithelial transition. Here we summarize these findings and discuss them in the context of previous reports. The recent findings also provide new insights in the physiological functions of histatin 1, which are discussed here. Furthermore, we put forward a possible role of histatin 1 in various pathologies and its potential function in clinical applications.

Potential Therapeutic Effects of Gut Hormones, Ghrelin and Obestatin in Oral Mucositis

Chemotherapy and/or head and neck radiotherapy are frequently associated with oral mucositis. Oral pain, odynophagia and dysphagia, opioid use, weight loss, dehydration, systemic infection, hospitalization and introduction of a feeding tube should be mentioned as the main determinated effect of oral mucositis. Oral mucositis leads to a decreased quality of life and an increase in treatment costs. Moreover, oral mucositis is a life-threatening disease. In addition to its own direct life-threatening consequences, it can also lead to a reduced survival due to the discontinuation or dose reduction of anti-neoplasm therapy. There are numerous strategies for the prevention or treatment of oral mucositis; however, their effectiveness is limited and does not correspond to expectations. This review is focused on the ghrelin and obestatin as potentially useful candidates for the prevention and treatment of chemo- or/and radiotherapy-induced oral mucositis.

Histatins, wound healing, and cell migration

Wounds in the oral mucosa heal faster and more efficiently than those in the skin, although the mechanisms underlying these differences are not completely clear. In the last 10 years, a group of salivary peptides, the histatins, has gained attention on behalf of their ability to improve several phases of the wound-healing process. In addition to their roles as anti-microbial agents and in enamel maintenance, histatins elicit other biological effects, namely by promoting the migration of different cell types contained in the oral mucosa and in non-oral tissues. Histatins, and specifically histatin-1, promote cell adhesion and migration in oral keratinocytes, gingival and dermal fibroblasts, non-oral epithelial cells, and endothelial cells. This is particularly relevant, as histatin-1 promotes the re-epithelialization phase and the angiogenic responses by increasing epithelial and endothelial cell migration. Although the molecular mechanisms associated with histatin-dependent cell migration remain poorly understood, recent studies have pointed to the control of signaling endosomes and the balance of small GTPases. This review aimed to update the literature on the effects of histatins in cell migration, with a focus on wound healing. We will also discuss the consequences that this increasing field will have in disease and therapy design.

The salivary peptide histatin-1 promotes endothelial cell adhesion, migration, and angiogenesis

Saliva is a key factor that contributes to the high efficiency of wound healing in the oral mucosa. This is not only attributed to physical cues but also to the presence of specific peptides in the saliva, such as histatins. Histatin-1 is a 38 aa antimicrobial peptide, highly enriched in human saliva, which has been previously reported to promote the migration of oral keratinocytes and fibroblasts in vitro However, the participation of histatin-1 in other crucial events required for wound healing, such as angiogenesis, is unknown. Here we demonstrate that histatin-1 promotes angiogenesis, as shown in vivo, using the chick chorioallantoic membrane model, and by an in vitro tube formation assay, using both human primary cultured endothelial cells (HUVECs) and the EA.hy926 cell line. Specifically, histatin-1 promoted endothelial cell adhesion and spreading onto fibronectin, as well as endothelial cell migration in the wound closure and Boyden chamber assays. These actions required the activation of the Ras and Rab interactor 2 (RIN2)/Rab5/Rac1 signaling axis, as histatin-1 increased the recruitment of RIN2, a Rab5-guanine nucleotide exchange factor (GEF) to early endosomes, leading to sequential Rab5/Rac1 activation. Accordingly, interfering with either Rab5 or Rac1 activities prevented histatin-1-dependent endothelial cell migration. Finally, by immunodepletion assays, we showed that salivary histatin-1 is required for the promigratory effects of saliva on endothelial cells. In conclusion, we report that salivary histatin-1 is a novel proangiogenic factor that may contribute to oral wound healing.-Torres, P., Díaz, J., Arce, M., Silva, P., Mendoza, P., Lois, P., Molina-Berríos, A., Owen, G. I., Palma, V., Torres, V. A. The salivary peptide histatin-1 promotes endothelial cell adhesion, migration, and angiogenesis.