Lactoferrin promotes collagen gel contractile activity of fibroblasts mediated by lipoprotein receptorsThis paper is one of a selection of papers published in this Special Issue, entitled 7th International Conference on Lactoferrin: Structure, Function, and Applications, and has undergone the Journal's usual peer review process

Longitudinal analysis of wound healing response post SMILE and LASIK surgery using proteomic profiling of tears

Different types of refractive surgeries often exhibit differences in wound healing responses. The current study investigated post-operative tear protein profiles in subjects who underwent LASIK and SMILE to elucidate global changes to the proteomic profile during the period the patient cornea undergoes healing. In this study, 10 patients underwent LASIK and SMILE surgery with a contralateral paired eye design. Tear samples were collected using Schirmer's strips preoperatively, at 1 month, 3 months and 6 months postoperatively. Quantitative ITRAQ labeled proteomics was performed and the tear protein ratios were normalized to pre-operative protein levels for each subject. Whole proteomics identified 1345 proteins in tears from LASIK and 1584 proteins in SMILE across time points. About 67 proteins were common in LASIK and SMILE tears across all the time points. Wound healing responses were differentially regulated between two refractive surgeries (SMILE and LASIK). The proteins Ceruloplasmin, Clusterin, Serotransferrin were upregulated at 1 month and 3 months and downregulated at 6 months post operatively in LASIK surgery where as in SMILE these were downregulated. Galectin 3 binding protein showed upregulation at 1 month and the levels decreased at 3 months and 6 months postop in LASIK tears whereas the levels increased at 3 months and 6 months post-op in SMILE tears. The levels of proteins that protect from oxidative stress were higher in SMILE as compared to LASIK postoperatively. The extracellular matrix proteins showed an increase in expression at 6 months in SMILE tears and was stabilized at 6 months in LASIK tears post operatively. Different refractive surgeries induce distinct wound healing responses as identified in tears. This study has implications in targeting key proteins for improving the clinical outcome postrefractive surgery.

Enhanced intracellular uptake of an albumin fusion protein in cancer cells by its forced cell surface recruitment

Albumin fusion or conjugation is a well-established technique for tumor delivery and is mainly mediated by albumin-induced caveolae-dependent endocytosis. We report that caveolae-dependent endocytic signaling activated by human serum albumin (HSA) is not sufficiently strong to induce cellular uptake, mainly due to its electrostatic repulsion from the negatively charged cell surface sulfated glycosaminoglycans (GAGs), and fusion of the cell-surface-retained protein with HSA is an effective strategy to activate the HSA-induced endocytic signal, thereby improving its intracellular uptake. In this study, human lactoferrin (hLF), a protein that accumulates on the cell surface along with GAGs, was selected for delivery into human lung adenocarcinoma PC-14 cells. When added exogenously, hLF-fused HSA (hLF-HSA) was successfully endocytosed, whereas the simultaneous addition of HSA and hLF did not result in endocytosis, indicating less efficient activation of endocytic signaling by HSA alone and the importance of its fusion. Importantly, the treatment of cells with chlorate, a known inhibitor of GAG sulfation, dramatically suppressed the endocytosis of hLF-HSA owing to the loss of the hLF-GAG interaction. Therefore, the cell-surface localization of HSA imposed by fusion with the cell-surface-retained protein enhances its binding to the relevant receptor, which improves intracellular delivery as an albumin-fusion platform.

Biomedical Applications of Lactoferrin on the Ocular Surface

Lactoferrin (LF) is a first-line defense protein with a pleiotropic functional pattern that includes anti-inflammatory, immunomodulatory, antiviral, antibacterial, and antitumoral properties. Remarkably, this iron-binding glycoprotein promotes iron retention, restricting free radical production and avoiding oxidative damage and inflammation. On the ocular surface, LF is released from corneal epithelial cells and lacrimal glands, representing a significant percentage of the total tear fluid proteins. Due to its multifunctionality, the availability of LF may be limited in several ocular disorders. Consequently, to reinforce the action of this highly beneficial glycoprotein on the ocular surface, LF has been proposed for the treatment of different conditions such as dry eye, keratoconus, conjunctivitis, and viral or bacterial ocular infections, among others. In this review, we outline the structure and the biological functions of LF, its relevant role at the ocular surface, its implication in LF-related ocular surface disorders, and its potential for biomedical applications.

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.

Targeting cancer with lactoferrin nanoparticles: recent advances

Lactoferrin, an iron storage protein, is known for its microbicidal activity and its ability to modulate the immune system, mediated through specific interactions with receptors on cell surfaces for internalization. These activities confer a significant versatility to lactoferrin, presenting it as a targeting ligand to disease-bearing cells. Early efforts in developing targeted delivery systems have focused on nano- and microcomposites comprised of metal and polymeric materials. These can be targeted through conjugation or adsorption of lactoferrin to achieve recognition to receptor-expressing cells. More recently, efforts are underway to utilize lactoferrin itself as a medium in loading the therapeutic agent. The functional efficiency of drug-loaded lactoferrin nanoparticles has been evaluated in different disease conditions such as cancer, HIV, Parkinson's disease, etc. This review will present the details of composition and performance of various delivery systems designed and developed using lactoferrin as targeting agent for the treatment of cancer.

In Situ Tissue Regeneration of Renal Tissue Induced by Collagen Hydrogel Injection

Host stem/progenitor cells can be mobilized and recruited to a target location using biomaterials, and these cells may be used for in situ tissue regeneration. The objective of this study was to investigate whether host biologic resources could be used to regenerate renal tissue in situ. Collagen hydrogel was injected into the kidneys of normal mice, and rat kidneys that had sustained ischemia/reperfusion injury. After injection, the kidneys of both animal models were examined up to 4 weeks for host tissue response. The infiltrating host cells present within the injection regions expressed renal stem/progenitor cell markers, PAX‐2, CD24, and CD133, as well as mesenchymal stem cell marker, CD44. The regenerated renal structures were identified by immunohistochemistry for renal cell specific markers, including synaptopodin and CD31 for glomeruli and cytokeratin and neprilysin for tubules. Quantitatively, the number of glomeruli found in the injected regions was significantly higher when compared to normal regions of renal cortex. This phenomenon occurred in normal and ischemic injured kidneys. Furthermore, the renal function after ischemia/reperfusion injury was recovered after collagen hydrogel injection. These results demonstrate that introduction of biomaterials into the kidney is able to facilitate the regeneration of glomerular and tubular structures in normal and injured kidneys. Such an approach has the potential to become a simple and effective treatment for patients with renal failure. Stem Cells Translational Medicine2018;7:241–250

Acute phase proteins as promising biomarkers: Perspectives and limitations for human and veterinary medicine

Acute phase proteins (APPs) are highly conserved plasma proteins that are increasingly secreted by the liver in response to a variety of injuries, independently of their location and cause. APPs favor the systemic regulation of defense, coagulation, proteolysis, and tissue repair. Various APPs have been applied as general diagnostic parameters for a long time. Through proteomic techniques, more and more APPs have been discovered to be differentially altered. Since they are not consistently explainable by a stereotypic hepatic expression of sets of APPs, most of these results have unfortunately been neglected or attributed to the nonspecificity of the acute phase reaction. Moreover, it appears that various extrahepatic tissues are also able to express APPs. These extrahepatic APPs show focally specific roles in tissue homeostasis and repair and are released primarily into interstitial and distal fluids. Since these focal proteins might leak into the circulatory system, mixtures of hepatic and extrahepatic APP species can be expected in blood. Hence, a selective alteration of parts of APPs might be expected. There are several hints on multiple molecular forms and fragments of tissue-derived APPs. These differences offer the chance for multiple selective determinations. Thus, specific proteoforms might indeed serve as tissue-specific disease indicators.

Oral administration of bovine lactoferrin attenuates ultraviolet B-induced skin photodamage in hairless mice

Lactoferrin (LF) is recognized as a host defensive glycoprotein, especially for newborn infants. The aim of this study was to investigate whether orally administered LF had protective activity against UV-induced skin damage in hairless mice. Transepidermal water loss and skin hydration were evaluated in nonirradiated mice, UVB-irradiated mice, and UVB-irradiated and LF-administered mice. Supplementation with LF (1,600 mg/kg per day) effectively suppressed the increase in transepidermal water loss, reduction in skin hydration, aberrant epidermal hyperplasia, and cell apoptosis induced by UV irradiation. Although no significant changes in superoxide dismutase-like activity or malondialdehyde levels were observed in the skin with both UV irradiation and LF administration, UV-stimulated IL-1β levels in the skin were significantly suppressed by the administration of LF. Oral supplementation with LF has the potential to reduce IL-1β levels and prevent UV-induced skin damage. Further studies are needed to elucidate the relationships between the antiinflammatory effects and skin protective function of LF.

Differential roles of JNK, ERK1/2, and p38 mitogen-activated protein kinases on endothelial cell tissue repair functions in response to tumor necrosis factor-α

Tumor necrosis factor (TNF)-α can alter tissue repair functions in a variety of cells including endothelial cells. However, the mechanism by which TNF-α mediates these functional changes has not fully been studied. We investigated the role of mitogen-activated protein kinases (MAPKs) on mediating the regulatory effect of TNF-α on the tissue repair functions of human pulmonary artery endothelial cells (HPAECs). TNF-α protected HPAECs from undergoing apoptosis induced by serum and growth factor deprivation, augmented collagen gel contraction, and stimulated wound closure. TNF-α activated c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinases 1 and 2 (ERK1/2), and p38. Inhibitors of JNK (SP600125, 5 µM) or ERK1/2 (PD98059, 5 µM) significantly inhibited TNF-α-stimulated cell survival, contraction of collagen gels, and wound closure. In contrast, the p38 inhibitor SB203580 (5 µM) further amplified all of the TNF-α effects on HPAECs. TNF-α specifically activated p38α but not other p38 isoforms and suppression of p38α by an siRNA resulted in further amplification of the TNF-α effect. These results suggest that TNF-α stimulates tissue repair functions of HPAECs, and this may be mediated, at least in part, positively via JNK and ERK1/2, and negatively through p38α. MAPKs may play a role in endothelial cell-mediated tissue repair, especially in an inflammatory milieu where TNF-α is present.

Lactoferrin: an alternative view of its role in human biological fluids

Lactoferrin is a major component of biologically important mucosal fluids and of the specific granules of neutrophils. Understanding its biological function is essential for understanding neutrophil- and mucosal-mediated immunity. In this review, we reevaluate the in vivo functions of human lactoferrin (hLF) emphasizing in vivo studies and in vitro studies performed in biologically relevant fluids. We discuss the evidence in the literature that supports (or does not support) proposed roles for hLF in mucosal immunity and in neutrophil function. We argue that the current literature supports a microbiostatic role, but not a microbicidal role, for hLF in vivo. The literature also supports a role for hLF in inhibiting colonization and infection of epithelial surfaces by microorganisms and in protecting tissues from neutrophil-mediated damage. Using this information, we briefly discuss hLF in the context of the complex biological fluids in which it is found.

The role of metal ions in biological oxidation - the past and the present

Two theories, one based on the metabolism of inorganic substances, the other on metabolism of organic substances, have played an important role in the explanation of the origin of life. They demonstrate that the original environment of life on Earth was seawater containing micronutrients with structural, metabolic and catalytic activity. It is assumed that the first primitive organisms lived around 3.8 billion years ago and it was also then that the first catalytic reaction involving metal ions occurred. Biological oxidation leading to oxidative stress and cell damage in animals represents one of these types of reactions which are responsible for many animal diseases. The role of prooxidative and antioxidative actions of transition metal ions as well as their neuropathological consequences have therefore been the topic for many research projects. There is hope that metal chelates and antioxidants might prove to be a modern mode of therapy for i.e. neurogenerative diseases. The aim of this review is to show the evolution of scientific knowledge on metal ions, their biological oxidation, and an overview of their role in physiology and in pathological processes.