Signal transduction and metabolism in chondrocytes is modulated by lactoferrin

Identification of crucial salivary proteins/genes and pathways involved in pathogenesis of temporomandibular disorders

Temporomandibular disorder (TMD) is a collective term for a group of conditions that lead to impairment of the function of the temporomandibular joint. The proteins/genes and signaling pathways associated with TMD are still poorly understood. The aim of this study was to identify key differentially expressed salivary proteins/genes (DEGs) associated with TMD progression using LC-MS/MS coupled with a bioinformatics approach. The protein–protein interaction network was obtained from the STRING database and the hub genes were identified using Cytoscape including cytoHubba and MCODE plug-ins. In addition, enrichment of gene ontology functions and the Reactome signaling pathway was performed. A total of 140 proteins/genes were differentially expressed. From cluster analysis, a set of 20 hub genes were significantly modulated: ALB, APOA1, B2M, C3, CAT, CLU, CTSD, ENO1, GSN, HBB, HP, HSPA8, LTF, LYZ, MMP9, S100A9, SERPINA1, TF, TPI1, and TXN. Two enriched signaling pathways, glycolysis and gluconeogenesis, and tryptophan signaling pathway involving the hub genes CAT, ENO1, and TPI1 have been identified. The rest of the hub genes were mainly enriched in the innate immune system and antimicrobial peptides signaling pathways. In summary, hub DEGs and the signaling pathways identified here have elucidated the molecular mechanisms of TMD pathogenesis.

Albumin fusion with human lactoferrin shows enhanced inhibition of cancer cell migration

The fusion of human serum albumin (HSA) with human lactoferrin (hLF) (designated as hLF-HSA) has improved the pharmacokinetic properties and anti-proliferative activities of hLF against cancer cells. In this study, we evaluated the anti-migratory activities of hLF and hLF-HSA against the human lung adenocarcinoma PC-14 cell line using wound healing and Boyden chamber assays. Despite the unexpected hLF-induced migration, hLF-HSA clearly demonstrated the complete inhibition of PC-14 cell migration. To examine the mechanism underlying the enhanced PC-14 cell migration by hLF alone but suppressed migration by hLF-HSA, we focused on the matrix metalloproteinase (MMP) family of endopeptidases because MMPs are often reported to play important roles in facilitating the migration and metastasis of cancer cells. Furthermore, hLF is a transactivator of MMP1 transcription. As expected, treatment of cells with hLF and hLF-HSA led to the upregulation and downregulation of MMP1, respectively. In contrast, MMP9 expression levels, which are often associated with cancer migration, were unchanged in the presence of either protein. An MMP inhibitor attenuated hLF-induced migration of PC-14 cells. Therefore, specific enhancement and suppression of MMP1 expression by hLF and hLF-HSA have been implicated as causes of a marked increase and decrease in PC-14 cell migration, respectively. In conclusion, the fusion of HSA with hLF (hLF-HSA) promoted its anti-migratory effects against cancer cells. Therefore, hLF-HSA is a promising anti-cancer drug candidate based on its improved anti-migratory activity towards cancer cells.

Lactoferrin Induces Erythropoietin Synthesis and Rescues Cognitive Functions in the Offspring of Rats Subjected to Prenatal Hypoxia

The protective effects of recombinant human lactoferrin rhLF (branded “CAPRABEL™”) on the cognitive functions of rat offspring subjected to prenatal hypoxia (7% O₂, 3 h, 14th day of gestation) have been analyzed. About 90% of rhLF in CAPRABEL was iron-free (apo-LF). Rat dams received several injections of 10 mg of CAPRABEL during either gestation (before and after the hypoxic attack) or lactation. Western blotting revealed the appearance of erythropoietin (EPO) alongside the hypoxia-inducible factors (HIFs) in organ homogenates of apo-rhLF-treated pregnant females, their embryos (but not placentas), and in suckling pups from the dams treated with apo-rhLF during lactation. Apo-rhLF injected to rat dams either during pregnancy or nurturing the pups was able to rescue cognitive deficits caused by prenatal hypoxia and improve various types of memory both in young and adult offspring when tested in the radial maze and by the Novel Object Recognition (NOR) test. The data obtained suggested that the apo-form of human LF injected to female rats during gestation or lactation protects the cognitive functions of their offspring impaired by prenatal hypoxia.

Effect of single-dose locally applied lactoferrin on autograft healing in peri-implant bone in rat models

Immediate dental implant installation into fresh extraction sockets has become a common surgical technique and yields successful clinical results. In addition, complete contact may not be possible with this procedure cause of defects between the bone wall and the implant surface. Therefore, different graft materials have been used in the literature to increase the peri‑implant bone volume. The aim of the present study was to evaluate the effect of single-dose and locally applied lactoferrin on autograft healing in peri‑implant area and bone implant contact value. Twenty-four Sprague-Dawley rats were included in this study. Firstly, a trephine drill was used for creating a cylindrical bony defects (6.5 mm in diameter and 3 mm in depth) under sterile saline irrigation in the lateral side of the femur. Subsequently, implant beds -2.5 mm diameter and 6 mm depth - were prepared in the middle of each defect with special implant drills. All of the implants were installed and primary stability was achieved. Rats were randomly divided into 3 groups (n = 8 each): Group-1 had empty defects, Group-2 had defects filled with autograft, and Group-3 had defects filled with autograft and lactoferrin solution (100 μg/ml) combination. All of the rats were sacrificed at postoperative 4th week and samples were analyzed with micro-computed tomography, histomorphometry and immunohistochemistry respectively. It was found that Group 3 had the least area of fibrous tissue (6.75±0.83mm²) according to the other 2 groups (p<0.001). On the other hand, Group 3 had the highest osteoblast number (25.50±3.29), osteoclast number (21.25±1.03), newly formed bone area (20.50±1.30 mm²), total healing area (22.62±0.93 mm²), defect closure rate (80.37±1.40%), bone implant contact value (23.2%±0.6%), and percentage bone volume (18.2%±0.3%) (p<0.001). Matrix metalloproteinase-3 expression was found to be highest in Group 3 by immunohistochemistry analysis. In this study it was observed that the results of the different analysis techniques supported each other. According to these findings it can be stated that a single-dose and locally applied lactoferrin solution plays an important role in the autograft healing in peri‑implant area and increasing bone implant contact value. These findings will shed light on further clinical studies of implant osseointegration.

Effects of lactoferrin on osteogenic differentiation and related gene expressions of osteoblast precursor cells MC3T3-E1 under mechanical strain

We aimed to evaluate the effects of lactoferrin (LF) on the osteogenic differentiation and related gene expressions of mouse embryonic osteoblast precursor cells MC3T3-E1 under mechanical strain. MC3T3-E1 cells were randomly divided into control, strain loading, LF and strain loading + LF groups. Alkaline phosphatase (ALP) activity was measured. Cytoskeletal morphology was measured by rhodamine-phalloidin staining. Formation of mineralized nodules was observed by alizarin red staining. The expressions of differentiation-related genes type I collagen (COL-1), interleukin-6 (IL-6) and osteocalcin (OCN) were determined by RT-PCR, and those of p-Runx2 and p-ERK1/2 proteins were detected by Western blotting. The number of ALP positive cells and expressions of OCN, COL-1 and IL-6 were significantly elevated (P<0.05). The optical density of strain loading + LF group was higher than those in strain loading and LF groups after incubation for 4 and 7 days (P<0.05). The cell volume and extension range were elevated in strain loading + LF group compared with those in strain loading group. The amount of mineralized nodules in strain loading + LF group was significantly higher than those in strain loading and LF groups, while it was slightly higher in LF group than that in strain loading group. The expressions of p-ERK1/2 and p-Runx2 in strain loading + LF group exceeded those in strain loading and LF groups (P<0.05). The synergistic action of LF and mechanical strain can effectively promote the proliferation, differentiation and mineralization of osteoblasts, probably being associated with the ERK1/2 signaling pathway.

Lactoferrin may inhibit the development of cancer via its immunostimulatory and immunomodulatory activities (Review)

Lactoferrin (Lf) is secreted by ectodermal tissue and has a structure similar to that of transferrin. Although Lf seems to be multifunctional, its main function is related to the natural defense system of mammals. The present review aims to highlight the major actions of Lf, including the regulation of cell growth, the inhibition of toxic compound formation, the removal of harmful free radicals and its important role in immune response regulation. Moreover, Lf has antibacterial, antiviral, antioxidant, anticancer and anti‑inflammatory activities. In addition, the use of Lf for functionalization of drug nanocarriers, with emphasis on tumor‑targeted drug delivery, is illustrated. Such effects serve as an important theoretical basis for its future development and application. In neurodegenerative diseases and the brains of elderly people, Lf expression is markedly upregulated. Lf may exert an anti‑inflammatory effect by inhibiting the formation of hydroxyl free radicals. Through its antioxidant properties, Lf can prevent DNA damage, thereby preventing tumor formation in the central nervous system. In addition, Lf specifically activates the p53 tumor suppressor gene.

Proteomic Analysis Reveals Commonly Secreted Proteins of Mesenchymal Stem Cells Derived from Bone Marrow, Adipose Tissue, and Synovial Membrane to Show Potential for Cartilage Regeneration in Knee Osteoarthritis

Paracrine factors secreted by mesenchymal stem cells (MSCs) reportedly modulate inflammation and reparative processes in damaged tissues and have been explored for knee osteoarthritis (OA) therapy. Although various studies have reported the effects of paracrine factors in knee OA, it is not yet clear which paracrine factors directly affect the regeneration of damaged cartilage and which are secreted under various knee OA conditions. In this study, we cultured MSCs derived from three types of tissues and treated each type with IL-1β and TNF-α or not to obtain conditioned medium. Each conditioned medium was used to analyse the paracrine factors related to cartilage regeneration using liquid chromatography-tandem mass spectrometry. Bone marrow-, adipose tissue-, and synovial membrane-MSCs (all-MSCs) exhibited expression of 93 proteins under normal conditions and 105 proteins under inflammatory conditions. It was confirmed that the types of secreted proteins differed depending on the environmental conditions, and the proteins were validated using ELISA. The results of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis using a list of proteins secreted by all-MSCs under each condition confirmed that the secreted proteins were closely related to cartilage repair under inflammatory conditions. Protein-protein interaction networks were confirmed to change depending on environmental differences and were found to enhance the secretion of paracrine factors related to cartilage regeneration under inflammatory conditions. In conclusion, our results demonstrated that compared with knee OA conditions, the differential expression proteins may contribute to the regeneration of damaged cartilage. In addition, the detailed information on commonly secreted proteins by all-MSCs provides a comprehensive basis for understanding the potential of paracrine factors to influence tissue repair and regeneration in knee OA.

Lactoferrin as a regenerative agent: The old-new panacea?

Lactoferrin (Lf) possesses various biological properties and therapeutic potentials being a perspective anti-inflammatory, antibacterial, antiviral, antioxidant, antitumor, and immunomodulatory agent. A significant body of literature has also demonstrated that Lf modulates regenerative processes in different anatomical structures, such as bone, cartilage, skin, mucosa, cornea, tendon, vasculature, and adipose tissue. Hence, this review collected and analyzed the data on the regenerative effects of Lf, as well as paid specific attention to their molecular basis. Furthermore, tissue and condition-specific activities of different Lf types as well as problems of their delivery to the targeted organs were discussed. The authors strongly hope that this review will stimulate researchers to focus on the highlighted topics thus accelerating the progress of Lf's wider clinical application.

Binding of lactoferrin to the surface of low-density lipoproteins modified by myeloperoxidase prevents intracellular cholesterol accumulation by human blood monocytes

Myeloperoxidase (MPO) is a unique heme-containing peroxidase that can catalyze the formation of hypochlorous acid (HOCl). The strong interaction of MPO with low-density lipoproteins (LDL) promotes proatherogenic modification of LDL by HOCl. The MPO-modified LDL (Mox-LDL) accumulate in macrophages, resulting in the formation of foam cells, which is the pathognomonic symptom of atherosclerosis. A promising approach to prophylaxis and atherosclerosis therapy is searching for remedies that prevent the modification or accumulation of LDL in macrophages. Lactoferrin (LF) has several application points in obesity pathogenesis. We aimed to study LF binding to Mox-LDL and their accumulation in monocytes transformed into macrophages. Using surface plasmon resonance and ELISA techniques, we observed no LF interaction with intact LDL, whereas Mox-LDL strongly interacted with LF. The affinity of Mox-LDL to LF increased with the degree of oxidative modification of LDL. Moreover, an excess of MPO did not prevent interaction of Mox-LDL with LF. LF inhibits accumulation of cholesterol in macrophages exposed to Mox-LDL. The results obtained reinforce the notion of LF potency as a remedy against atherosclerosis.

Lactoferrin promotes osteogenesis of MC3T3-E1 cells induced by mechanical strain in an extracellular signal-regulated kinase 1/2-dependent manner

INTRODUCTION

This study aimed to investigate the role of lactoferrin (LF) in the mechanical strain-induced osteogenesis of nontransformed osteoblastic cells (MC3T3-E1 cells) and related mechanism.

METHODS

MC3T3-E1 cells were cultured in vitro and treated with 100 μg/mL LF, followed by a 2000 μ mechanical strain load. U0126 was used to determine the role of extracellular signal-regulated kinase 1/2 (Erk1/2). Alizarin red S staining was performed to observe the cell mineralization potential. The osteogenic results were analyzed by reverse transcription-polymerase chain reaction and western blotting.

RESULTS

The expression of Col1, Alp, Ocn, Bsp, and Opn mRNA and p-Erk1/2 proteins was significantly upregulated under mechanical strain load. In addition, mineralized nodule formation was increased. After adding LF, the expression of the biomarkers and the formation of mineralized nodules were further promoted. On treatment with the Erk1/2 inhibitor U0126, the expression of Col1, Alp, and p-Erk1/2 mRNA and protein was significantly downregulated.

CONCLUSIONS

These findings demonstrate that LF promotes osteogenic activity by activating osteogenesis-related biomarkers, corroborating that the effects of mechanical strain depend on Erk1/2 signaling pathway.

ITLN1 modulates invasive potential and metabolic reprogramming of ovarian cancer cells in omental microenvironment

Advanced ovarian cancer usually spreads to the omentum. However, the omental cell-derived molecular determinants modulating its progression have not been thoroughly characterized. Here, we show that circulating ITLN1 has prognostic significance in patients with advanced ovarian cancer. Further studies demonstrate that ITLN1 suppresses lactotransferrin’s effect on ovarian cancer cell invasion potential and proliferation by decreasing MMP1 expression and inducing a metabolic shift in metastatic ovarian cancer cells. Additionally, ovarian cancer-bearing mice treated with ITLN1 demonstrate marked decrease in tumor growth rates. These data suggest that downregulation of mesothelial cell-derived ITLN1 in the omental tumor microenvironment facilitates ovarian cancer progression.

Advanced ovarian cancer usually spreads to the omentum. Here, the authors show that circulating intelectin-1 (ITLN1) has prognostic significance in patients with advanced ovarian cancer, and that mesothelial cell-derived ITLN1 in the omental tumor microenvironment suppresses ovarian cancer progression.

The Chinese Medicinal Formulation Guzhi Zengsheng Zhitongwan Modulates Chondrocyte Structure, Dynamics, and Metabolism by Controlling Multiple Functional Proteins

Traditional Chinese medicine is one of the oldest medical systems in the world and has its unique principles and theories in the prevention and treatment of human diseases, which are achieved through the interactions of different types of materia medica in the form of Chinese medicinal formulations. GZZSZTW, a classical and effective Chinese medicinal formulation, was designed and created by professor Bailing Liu who is the only national medical master professor in the clinical research field of traditional Chinese medicine and skeletal diseases. GZZSZTW has been widely used in clinical settings for several decades for the treatment of joint diseases. However, the underlying molecular mechanisms are still largely unknown. In the present study, we performed quantitative proteomic analysis to investigate the effects of GZZSZTW on mouse primary chondrocytes using state-of-the-art iTRAQ technology. We demonstrated that the Chinese medicinal formulation GZZSZTW modulates chondrocyte structure, dynamics, and metabolism by controlling multiple functional proteins that are involved in the cellular processes of DNA replication and transcription, protein synthesis and degradation, cytoskeleton dynamics, and signal transduction. Thus, this study has expanded the current knowledge of the molecular mechanism of GZZSZTW treatment on chondrocytes. It has also shed new light on possible strategies to further prevent and treat cartilage-related diseases using traditional Chinese medicinal formulations.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

Lactoferrin Promotes Osteogenesis through TGF-β Receptor II Binding in Osteoblasts and Activation of Canonical TGF-β Signaling in MC3T3-E1 Cells and C57BL/6J Mice

Background

Lactoferrin (LF), as a major functional protein in dairy products, is known to modulate bone anabolic effects. However, the underlying molecular mechanisms remain unclear; the receptor of LF in osteoblast differentiation has not been identified.

Objective

The aims of the study were to 1) illuminate whether the receptor of LF in osteoblast differentiation is transforming growth factor-β (TGF-β) receptor (TβR) II and 2) determine whether the TGF-β signaling pathway is activated by LF in promoting osteogenesis in vitro and in vivo, in addition to P38 and extracellular signal-regulated kinase (ERK) pathways.

Methods

We utilized co-immunoprecipitation to detect any binding of LF to TβRII. Subsequently, the role of the TGF-β signaling pathway involved in LF-induced osteoblast proliferation and differentiation was determined by inhibition of TβRI activity by inhibition and knockout of TβRII expression by small guide RNA (sgRNAs) in MC3T3-E1 cells. In addition, 4-wk-old male C57BL/6J mice were orally administered 100 mg LF/kg body weight for 16 wk, after which any activation of the TGF-β signaling pathway in vivo was measured by Western blots.

Results

LF was shown to directly interact with the TβRII protein and to activate the TGF-β signaling pathway in MC3T3-E1 cells. Inhibition of TβRI activity and knockout TβRII expression both attenuated the stimulation of LF in osteoblast proliferation and differentiation by 30-50%. LF-induced activation of TGF-β canonical signaling resulted in upregulation of osteogenic factors. Moreover, the expression of phosphorylated-drosophila mothers against decapentaplegic protein 2 (SMAD2) was increased by 1-fold after LF treatment in the femoral tissue of mice.

Conclusions

This study provides evidence identifying TβRII as an LF receptor in LF-induced osteoblast differentiation. In addition, the TβRII-dependent TGF-β canonical signaling pathways were proven to play an important role in mediating LF-induced osteogenesis both in MC3T3-E1 cells and in C57BL/6J mice.

Lactoferrin promotes murine C2C12 myoblast proliferation and differentiation and myotube hypertrophy

Lactoferrin (Lf) is a multifunctional glycoprotein, which promotes the proliferation of murine C2C12 myoblasts. In the present study, it was investigated how Lf promotes myoblast proliferation and whether Lf promotes myoblast differentiation or induces myotube hypertrophy. Lf promoted the proliferation of myoblasts in a dose-dependent manner. Myoblast proliferation increased on day 3 when myoblasts were cultured in the presence of Lf for three days and also when myoblasts were cultured in the presence of Lf for the first day and in the absence of Lf for the subsequent two days. In addition, Lf induced the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 in myoblasts. The mitogen-activated protein kinase kinase 1/2 inhibitor U0126 inhibited Lf-induced ERK1/2 phosphorylation and repressed Lf-promoted myoblast proliferation. C2C12 myoblasts, myotubes and skeletal muscle expressed low-density lipoprotein receptor-related protein (LRP)1 mRNA and Lf-promoted myoblast proliferation was attenuated by an LRP1 antagonist or LRP1 gene silencing. The knockdown of LRP1 repressed Lf-induced phosphorylation of ERK1/2. Furthermore, when myoblasts were induced to differentiate, Lf increased the expression of the myotube-specific structural protein, myosin heavy chain (MyHC) and promoted myotube formation. Knockdown of LRP1 repressed Lf-induced MyHC expression. Lf also increased myotube size following differentiation. These results indicate that Lf promotes myoblast proliferation and differentiation, at least partially through LRP1 and also stimulates myotube hypertrophy.

Acid-sensing ion channel 1a mediates acid-induced inhibition of matrix metabolism of rat articular chondrocytes via the MAPK signaling pathway

The acid-sensing ion channel 1a (ASIC1a), which is activated by extracellular acid, contributes to the pathogenesis of rheumatoid arthritis. However, it remains unclear whether ASIC1a mediates acid-induced matrix metabolism in rat articular chondrocytes via activation of the MAPK signaling pathway. In the current study, we found that extracellular acidification (pH 6.0) inhibited proliferation and induced apoptosis of articular chondrocytes in a dose-dependent manner, while the expression of phosphorylated ERK1/2 and P38 MAPK increased, but, this effect was blocked by the Ca²⁺ chelator BAPTA-AM and the ASIC1a-specific blocker PcTx-1. In addition, extracellular acidification increased the expression of c-fos, GAG, HYP, and TIM1/2. These effects were inhibited by the Ca²⁺ chelator BAPTA-AM, ERK1/2 inhibitor PD98059, and ASIC1a-specific blocker PcTx-1, but not the P38 MAPK inhibitor SB203580. Finally, extracellular acidification increased the expression of c-jun and MMP-2/9, and these effects were blocked by the Ca²⁺ chelator BAPTA-AM, P38 MAPK inhibitor SB203580, and ASIC1a-specific blocker PcTx-1, but not the ERK1/2 inhibitor PD98059. In conclusion, ASIC1a inhibits the expression of MMP-2/9, GAG, HYP, and TIMP-1/2 by the Ca²⁺-dependent P38 MAPK/c-jun and ERK/c-fos signaling pathways.

Lactoferrin causes IgA and IgG2b isotype switching through betaglycan binding and activation of canonical TGF-β signaling

Lactoferrin (LF), a pleiotropic iron-binding glycoprotein, is known to modulate the humoral immune response. However, its exact role in Ig synthesis has yet to be elucidated. In this study, we investigated the effect of LF on Ig production by mouse B cells and its underlying mechanisms. LF, like transforming growth factor (TGF)-β1, stimulated B cells to produce IgA and IgG2b, while downregulating other isotypes. Using limiting dilution analysis, LF was shown to increase the frequency of IgA-secreting B-cell clones. This was paralleled by an increase in Ig germ-line α (GLα) transcripts, indicating that LF plays a role as an IgA switch factor. Interestingly, LF directly interacted with betaglycan (TGF-β receptor III, TβRIII) and in turn induced phosphorylation of TβRI and Smad3 through formation of the TβRIII/TβRII/TβRI complex, leading to IgA isotype switching. Peroral administration of LF increased intestinal/serum IgA production as well as number of IgA plasma cells in lamina propria. Finally, we found that LF has an adjuvant activity when nontoxigenic Salmonella typhimurium was inoculated perorally, conferring protection against intragastrical infection of toxigenic S. typhimurium. These results suggest that LF has an important effect on the mucosal/systemic IgA response and can contribute to protection against intestinal pathogens.

Lactoferrin inhibits dexamethasone-induced chondrocyte impairment from osteoarthritic cartilage through up-regulation of extracellular signal-regulated kinase 1/2 and suppression of FASL, FAS, and Caspase 3

Dexamethasone (Dex) is commonly used for osteoarthritis (OA) with excellent anti-inflammatory and analgesic effect. However, Dex also has many side effects following repeated use over prolonged periods mainly through increasing apoptosis and inhibiting proliferation. Lactoferrin (LF) exerts significantly anabolic effect on many cells and little is known about its effect on OA chondrocytes. Therefore, the aim of this study is to investigate whether LF can inhibit Dex-induced OA chondrocytes apoptosis and explore its possible molecular mechanism involved in. MTT assay was used to determine the optimal concentration of Dex and recombinant human LF (rhLF) on chondrocytes at different time and dose points. Chondrocytes were then stimulated with Dex in the absence or presence of optimal concentration of rhLF. Cell proliferation and viability were evaluated using MTT and LIVE/DEAD assay, respectively. Cell apoptosis was evaluated by multi-parameter apoptosis assay kit using both confocal microscopy and flow cytometry, respectively. The expression of extracellular signal-regulated kinase (ERK), FAS, FASL, and Caspase-3 (CASP3) at the mRNA and protein levels were examined by real-time polymerase chain reaction (PCR) and immunocytochemistry, respectively. The optimal concentration of Dex (25 μg/ml) and rhLF (200 μg/ml) were chosen for the following experiments. rhLF significantly reversed the detrimental effect of Dex on chondrocytes proliferation, viability, and apoptosis. In addition, rhLF significantly prevented Dex-induced down-regulation of ERK and up-regulation of FAS, FASL, and CASP3. These findings demonstrated that rhLF acts as an anabolic effect on chondrocytes through significantly reversing Dex-induced chondrocytes apoptosis. This study may contribute to further investigating the clinical application of LF on OA.

Genome-wide pathway analysis reveals different signaling pathways between secreted lactoferrin and intracellular delta-lactoferrin

Human lactoferrin (LF) is a multifunctional protein involved in immunomodulation, cellular growth, and differentiation. In addition to its secreted form (sLF), an alternative form (ΔLF) lacking the signal sequence has been found to be downregulated in cancer. Although the signaling pathways mediated by LF have been studied in a few cell models, there have been no relevant systemic approaches. Therefore, this study was carried out to identify and compare signaling networks provoked by the two LF isoforms. For this, the two forms were overexpressed in HEK293 cells using the Flp-In T-Rex system, after which genome-wide expression analysis of 18,367 genes was conducted. Pathway analysis of the genes showing altered expression identified pathways which are responsible for cell survival and apoptosis. In addition, the pathways mediated by the two LF forms were within distantly related networks. GPCR, PI3K complex, and POU5F1, which are involved in receptor-mediated pathways, were centered in the sLF network, whereas RIF1, NOS3, and RNPS1, which are involved in intracellular signaling, were centered in the ΔLF network. These results suggest that structural differences between the LF isoforms, mainly glycosylation, determine the fate of LF signaling. Furthermore, these findings provide information relating to the role of ΔLF which is downregulated during carcinogenesis.

Productive entry pathways of human rhinoviruses

Currently, complete or partial genome sequences of more than 150 human rhinovirus (HRV) isolates are known. Twelve species A use members of the low-density lipoprotein receptor family for cell entry, whereas the remaining HRV-A and all HRV-B bind ICAM-1. HRV-Cs exploit an unknown receptor. At least all A and B type viruses depend on receptor-mediated endocytosis for infection. In HeLa cells, they are internalized mainly by a clathrin- and dynamin-dependent mechanism. Upon uptake into acidic compartments, the icosahedral HRV capsid expands by ~4% and holes open at the 2-fold axes, close to the pseudo-3-fold axes and at the base of the star-shaped dome protruding at the vertices. RNA-protein interactions are broken and new ones are established, the small internal myristoylated capsid protein VP4 is expelled, and amphipathic N-terminal sequences of VP1 become exposed. The now hydrophobic subviral particle attaches to the inner surface of endosomes and transfers its genomic (+) ssRNA into the cytosol. The RNA leaves the virus starting with the poly(A) tail at its 3′-end and passes through a membrane pore contiguous with one of the holes in the capsid wall. Alternatively, the endosome is disrupted and the RNA freely diffuses into the cytoplasm.

Lactoferrin--50 years on

It is now some 50 years since iron-binding lactoferrin was first isolated and purified, an event that opened the way to subsequent extensive research on lactoferrin structure and function. The initial recognition that lactoferrin closely resembled the plasma iron-transport protein transferrin meant that lactoferrin was first thought to mediate intestinal iron absorption or to act as an antimicrobial agent. It was also suggested that it could mediate the hyposideraemia of inflammation. This paper will assess to what extent early proposals have stood the test of time and also suggest possible mechanisms by which lactoferrin can mediate the large number of potential functions that have subsequently been proposed. It will also review the ability of lactoferrin to resist digestion in the gastrointestinal tract and identify areas for future research.

Lactoferrin a multiple bioactive protein: an overview

BACKGROUND

Lactoferrin (Lf) is an 80kDa iron-binding glycoprotein of the transferrin family. It is abundant in milk and in most biological fluids and is a cell-secreted molecule that bridges innate and adaptive immune function in mammals. Its protective effects range from anticancer, anti-inflammatory and immune modulator activities to antimicrobial activities against a large number of microorganisms. This wide range of activities is made possible by mechanisms of action involving not only the capacity of Lf to bind iron but also interactions of Lf with molecular and cellular components of both hosts and pathogens.

SCOPE OF REVIEW

This review summarizes the activities of Lf, its regulation and potential applications.

MAJOR CONCLUSIONS

The extensive uses of Lf in the treatment of various infectious diseases in animals and humans has been the driving force in Lf research however, a lot of work is required to obtain a better understanding of its activity.

GENERAL SIGNIFICANCE

The large potential applications of Lf have led scientists to develop this nutraceutical protein for use in feed, food and pharmaceutical applications. This article is part of a Special Issue entitled Molecular Mechanisms of Iron Transport and Disorders.

Human lactoferrin suppresses TNF-α-induced intercellular adhesion molecule-1 expression via competition with NF-κB in endothelial cells

Lactoferrin (Lf) is known to have anti-inflammatory activity, but the mechanisms of action by Lf remain to be elucidated. Here, we demonstrated that TNF-α-induced expression of intercellular adhesion molecule-1 (ICAM-1) was down-regulated by Lf in a DNA-binding dependent manner at transcriptional level in endothelial cells. Our results showed that Lf bound to a DNA region in the ICAM-1 promoter in vitro as well as in chromatin context. Lf inhibited binding of NF-κB to a proximal NF-κB site in ICAM-1 promoter. This type of repression represents an additional mechanism for the action of Lf in regulation of gene expression.

Molecular evolution of the transferrin family and associated receptors

BACKGROUND

In vertebrates, serum transferrins are essential iron transporters that have bind and release Fe(III) in response to receptor binding and changes in pH. Some family members such as lactoferrin and melanotransferrin can also bind iron while others have lost this ability and have gained other functions, e.g., inhibitor of carbonic anhydrase (mammals), saxiphilin (frogs) and otolith matrix protein 1 (fish).

SCOPE OF REVIEW

This article provides an overview of the known transferrin family members and their associated receptors and interacting partners.

MAJOR CONCLUSIONS

The number of transferrin genes has proliferated as a result of multiple duplication events, and the resulting paralogs have developed a wide array of new functions. Some homologs in the most primitive metazoan groups resemble both serum and melanotransferrins, but the major yolk proteins show considerable divergence from the rest of the family. Among the transferrin receptors, the lack of TFR2 in birds and reptiles, and the lack of any TFR homologs among the insects draw attention to the differences in iron transport and regulation in those groups.

GENERAL SIGNIFICANCE

The transferrin family members are important because of their clinical significance, interesting biochemical properties, and evolutionary history. More work is needed to better understand the functions and evolution of the non-vertebrate family members. This article is part of a Special Issue entitled Molecular Mechanisms of Iron Transport and Disorders.

A novel polymorphism of the lactoferrin gene and its association with milk composition and body traits in dairy goats

Milk composition and body measurement traits, influenced by genes and environmental factors, play important roles in value assessments of efficiency and productivity in dairy goats. Lactoferrin (LF), involved in the efficient expression of protein in milk, is also an anabolic factor in skeletal tissue and a potent osteoblast survival factor. Therefore, it is an important candidate gene for milk composition and body measurement trait selection in marker-assisted selection. We employed PCR-SSCP and DNA sequencing to screen the genetic variations of the LF gene in 549 Chinese dairy goats. A novel single-nucleotide polymorphism (SNP) (G198A in exon II) of the LF gene was detected. The frequencies of the AA genotype were 0.0285 and 0.0261 in GZ and SN populations, respectively. Both populations were found to have low levels of polymorphism and were in Hardy-Weinberg disequilibrium (P < 0.05). We found significant (P < 0.05) associations of the SNP marker with milk protein and acidity in the total population; animals with the AA genotype had higher mean values for milk protein than those with the GA genotype. Animals with genotype AA had higher mean values for withers height than those with genotype GG (P < 0.05). We concluded that this SNP of the LF gene has potential as a genetic marker for milk composition and body traits in dairy goat breeding.