Regulation of extracellular matrix production by chemically synthesized subfragments of type I collagen carboxy propeptide

Liposome Encapsulation of the Palmitoyl-KTTKS Peptide: Structural and Functional Characterization

In this study, the amphiphilic N-palmitoyl-KTTKS peptide was integrated in the bilayer of egg-derived phosphatidylcholine (PC) vesicles using two different preparation methods, namely thin-film evaporation (TLE) and reverse-phase evaporation (REV). Both the REV and TLE methods allowed for the formation of homogeneous liposome dispersions (PdI < 0.20) with mean hydrodynamic diameters of <100 nm and <200 nm, respectively, a net negative surface charge and a percentage of structured phospholipids higher than 90%. The inclusion of the amphiphilic N-palmitoyl-KTTKS peptide within phospholipid-based vesicles could improve peptide stability and skin delivery. Therefore, the obtained liposomes were evaluated via experiments assessing the synthesis of collagen and the ECM in 3T3-NIH fibroblasts. The obtained results showed that, when delivered with PC liposomes, pal-KTTKS stimulated collagen production more than free pentapeptide and 1 mM ascorbic acid, used as a positive control.

Bioactive Peptides: Synthesis, Sources, Applications, and Proposed Mechanisms of Action

Bioactive peptides are a group of biological molecules that are normally buried in the structure of parent proteins and become active after the cleavage of the proteins. Another group of peptides is actively produced and found in many microorganisms and the body of organisms. Today, many groups of bioactive peptides have been marketed chemically or recombinantly. This article reviews the various production methods and sources of these important/ubiquitous and useful biomolecules. Their applications, such as antimicrobial, antihypertensive, antioxidant activities, blood-lipid-lowering effect, opioid role, antiobesity, ability to bind minerals, antidiabetic, and antiaging effects, will be explored. The types of pathways proposed for bioactive applications will be in the next part of the article, and at the end, the future perspectives of bioactive peptides will be reviewed. Reading this article is recommended for researchers interested in various fields of physiology, microbiology, biochemistry, and nanotechnology and food industry professionals.

Bioactivities, Applications, Safety, and Health Benefits of Bioactive Peptides From Food and By-Products: A Review

Bioactive peptides generated from food proteins have great potential as functional foods and nutraceuticals. Bioactive peptides possess several significant functions, such as antioxidative, anti-inflammatory, anticancer, antimicrobial, immunomodulatory, and antihypertensive effects in the living body. In recent years, numerous reports have been published describing bioactive peptides/hydrolysates produced from various food sources. Herein, we reviewed the bioactive peptides or protein hydrolysates found in the plant, animal, marine, and dairy products, as well as their by-products. This review also emphasizes the health benefits, bioactivities, and utilization of active peptides obtained from the mentioned sources. Their possible application in functional product development, feed, wound healing, pharmaceutical and cosmetic industries, and their use as food additives have all been investigated alongside considerations on their safety.

Transcriptomic analysis of human skin wound healing and rejuvenation following ablative fractional laser treatment

Ablative fractional laser treatment is considered the gold standard for skin rejuvenation. In order to understand how fractional laser works to rejuvenate skin, we performed microarray profiling on skin biopsies to identify temporal and dose-response changes in gene expression following fractional laser treatment. The backs of 14 women were treated with ablative fractional laser (Fraxel®) and 4 mm punch biopsies were collected from an untreated site and at the treated sites 1, 3, 7, 14, 21 and 28 days after the single treatment. In addition, in order to understand the effect that multiple fractional laser treatments have on skin rejuvenation, several sites were treated sequentially with either 1, 2, 3, or 4 treatments (with 28 days between treatments) followed by the collection of 4 mm punch biopsies. RNA was extracted from the biopsies, analyzed using Affymetrix U219 chips and gene expression was compared between untreated and treated sites. We observed dramatic changes in gene expression as early as 1 day after fractional laser treatment with changes remaining elevated even after 1 month. Analysis of individual genes demonstrated significant and time related changes in inflammatory, epidermal, and dermal genes, with dermal genes linked to extracellular matrix formation changing at later time points following fractional laser treatment. When comparing the age-related changes in skin gene expression to those induced by fractional laser, it was observed that fractional laser treatment reverses many of the changes in the aging gene expression. Finally, multiple fractional laser treatments, which cover different regions of a treatment area, resulted in a sustained or increased dermal remodeling response, with many genes either differentially regulated or continuously upregulated, supporting previous observations that maximal skin rejuvenation requires multiple fractional laser treatments. In conclusion, fractional laser treatment of human skin activates a number of biological processes involved in wound healing and tissue regeneration.

Collagen's enigmatic, highly conserved N-glycan has an essential proteostatic function

Intracellular procollagen folding begins at the protein's C-terminal propeptide (C-Pro) domain, which initiates triple-helix assembly and defines the composition and chain register of fibrillar collagen trimers. The C-Pro domain is later proteolytically cleaved and excreted from the body, while the mature triple helix is incorporated into the extracellular matrix. The procollagen C-Pro domain possesses a single N-glycosylation site that is widely conserved in all the fibrillar procollagens across humans and diverse other species. Given that the C-Pro domain is removed once procollagen folding is complete, the N-glycan might be presumed to be important for folding. Surprisingly, however, there is no difference in the folding and secretion of N-glycosylated versus non-N-glycosylated collagen type-I, leaving the function of the N-glycan unclear. We hypothesized that the collagen N-glycan might have a context-dependent function, specifically, that it could be required to promote procollagen folding only when proteostasis is challenged. We show that removal of the N-glycan from misfolding-prone C-Pro domain variants does indeed cause serious procollagen and ER proteostasis defects. The N-glycan promotes folding and secretion of destabilized C-Pro variants by providing access to the ER's lectin-based chaperone machinery. Finally, we show that the C-Pro N-glycan is actually critical for the folding and secretion of even wild-type procollagen under ER stress conditions. Such stress is commonly incurred during development, wound healing, and other processes in which collagen production plays a key role. Collectively, these results establish an essential, context-dependent function for procollagen's previously enigmatic N-glycan, wherein the carbohydrate moiety buffers procollagen folding against proteostatic challenge.

Combinations of peptides synergistically activate the regenerative capacity of skin cells in vitro

Objective

To explore synergistic effects related to skin regeneration, peptides with distinct biological mechanisms of action were evaluated in combination with different skin cell lines in the presence or absence of niacinamide (Nam). Furthermore, the synergistic responses of peptide combinations on global gene expression were compared with the changes that occur with fractional laser resurfacing treatment, a gold standard approach for skin rejuvenation, to further define optimal peptide combinations.

Methods

Microarray profiling was used to characterize the biological responses of peptide combinations (+/− Nam) relative to the individual components in epidermal keratinocyte and dermal fibroblast cell lines. Cellular functional assays were utilized to confirm the synergistic effects of peptide combinations. Bioinformatics approaches were used to link the synergistic effects of peptide combinations on gene expression to the transcriptomics of the skin rejuvenation response from fractional laser treatment.

Results

Microarray analysis of skin cells treated with peptide combinations revealed synergistic changes in gene expression compared with individual peptide controls. Bioinformatic analysis of synergy genes in keratinocytes revealed the activation of NRF2‐mediated oxidative stress responses by a combination of Ac‐PPYL, Pal‐KTTKS and Nam. Additional analysis revealed direct downstream transcriptional targets of NRF2/ARE exhibiting synergistic regulation by this combination of materials, which was corroborated by a cellular reporter assay. NRF2‐mediated oxidative stress response pathways were also found to be activated in the transcriptomics of the early skin rejuvenation response to fractional laser treatment, suggesting the importance of this biology in the early stages of tissue repair. Additionally, the second combination of peptides (pal‐KT and Ac‐PPYL) was found to synergistically restore cellular ATP levels that had been depleted due to the presence of ROS, indicating an additional mechanism, whereby peptide synergies may accelerate skin repair.

Conclusion

Through combinatorial synergy studies, we have identified additional in vitro skin repair mechanisms beyond the previously described functions of individual peptides and correlated these to the transcriptomics of the skin rejuvenation response of fractional laser treatment. These findings suggest that specific peptides can act together, via complementary and synergistic mechanisms, to holistically enhance the regenerative capacity of in vitro skin cells.

Peptides as Active Ingredients: A Challenge for Cosmeceutical Industry

Cosmeceutical field, which merges cosmetics and pharmaceuticals, is nowadays a highly investigated research area, because a scientific demonstration of the claimed bioactivity of new cosmeceutical ingredients is increasingly requested. In fact, an aspect differentiating traditional cosmetics from cosmeceuticals is the identification and characterization of the active ingredients and demonstrating its efficacy in the claimed activity. An interesting group of bioactive cosmeceutical ingredients are peptides, which due to their particular properties, meets most of the requirements presented by the cosmeceutical industry when composing new formulas. In this context, beside bioactivity, two additional aspects have been recently considered, when dealing with peptides as cosmeceutical ingredients: bioavailability and stability. We describe herein novel methods applied in order to enhance peptides skin-penetration and stability, reviewing both scientific articles and patents, issued in the cosmeceutical arena.

COLLAGEN: STRUCTURE, METABOLISM, PRODUCTION AND INDUSTRIAL APPLICATION

This review presents the current scientific literature data about structure, properties, and functions of collagen, which is known as one of the most abundant human and animal proteins. The building of collagen molecule from the primary structure to submolecular formations, the main stages of its synthesis and biodegradation are briefly described. The information about collagen diversity, its features and metabolic ways in various tissues, including skin, tendons, bones, etc. is presented. The problems of pathologies caused by collagen synthesis and breakdown disorders as well as age-related changes in collagen properties and their causes are discussed. A comparative analysis of the advantages and disadvantages of collagen and its derivatives obtaining from various sources (animals, marine, and recombinant) is given. The most productive methods for collagen extraction from various tissues are shown. The concept of collagen hydrolysis conditions influence on the physicochemical properties and biological activity of the obtained products is described. The applications of collagen and its products in various fields of industrial activity, such as pharmaceutical, cosmetic industry and medicine, are discussed. Further prospective directions of fundamental and applied investigations in this area of research are outlined.

Molecular Mechanisms of Dermal Aging and Antiaging Approaches

The dermis is primarily composed of the extracellular matrix (ECM) and fibroblasts. During the aging process, the dermis undergoes significant changes. Collagen, which is a major component of ECM, becomes fragmented and coarsely distributed, and its total amount decreases. This is mainly due to increased activity of matrix metalloproteinases, and impaired transforming growth factor-β signaling induced by reactive oxygen species generated during aging. The reduction in the amount of collagen hinders the mechanical interaction between fibroblasts and the ECM, and consequently leads to the deterioration of fibroblast function and further decrease in the amount of dermal collagen. Other ECM components, including elastic fibers, glycosaminglycans (GAGs), and proteoglycans (PGs), also change during aging, ultimately leading to a reduction in the amount of functional components. Elastic fibers decrease in intrinsically aged skin, but accumulate abnormally in photoaged skin. The changes in the levels of GAGs and PGs are highly diverse, and previous studies have reported conflicting results. A reduction in the levels of functional dermal components results in the emergence of clinical aging features, such as wrinkles and reduced elasticity. Various antiaging approaches, including topicals, energy-based procedures, and dermal fillers, can restore the molecular features of dermal aging with clinical efficacy. This review summarizes the current understanding of skin aging at the molecular level, and associated treatments, to put some of the new antiaging technology that has emerged in this rapidly expanding field into molecular context.

Serpin A1 C-Terminal Peptides as Collagen Turnover Modulators

The modulation of collagen turnover can be a relevant pharmacological target in the context of treating either pathological or pathophysiological conditions, such as collagen-related diseases and skin aging. Our recent work has focused on the search for short-chain peptides as lead compounds for further development of compounds that enhance the production of type I collagen. In this study we selected and synthesized overlapping peptides of the C-terminal portion of serpin A1 (residues 393-418), the impact of which on collagen production has been reported previously, in order to identify shorter and still active fragments and to provide insight on the mechanisms involved. The biological activity of each fragment was evaluated with cultured normal human dermal fibroblasts, and changes in the amounts of collagen were monitored in collected culture media by a sandwich ELISA technique developed in house. Interestingly, we identified a decapeptide, termed SA1-III (Ac-MGKVVNPTQK-NH2 ), as a promising candidate for our purposes; it is able to induce a significant increase in type I collagen levels in the culture medium of treated cells at micromolar concentrations.

Hexapeptide-11 is a novel modulator of the proteostasis network in human diploid fibroblasts

Despite the fact that several natural products (e.g. crude extracts or purified compounds) have been found to activate cell antioxidant responses and/or delay cellular senescence the effect(s) of small peptides on cell viability and/or modulation of protective mechanisms (e.g. the proteostasis network) remain largely elusive. We have thus studied a hexapeptide (Hexapeptide-11) of structure Phe-Val-Ala-Pro-Phe-Pro (FVAPFP) originally isolated from yeast extracts and later synthesized by solid state synthesis to high purity. We show herein that Hexapeptide-11 exhibits no significant toxicity in normal human diploid lung or skin fibroblasts. Exposure of fibroblasts to Hexapeptide-11 promoted dose and time-dependent activation of proteasome, autophagy, chaperones and antioxidant responses related genes. Moreover, it promoted increased nuclear accumulation of Nrf2; higher expression levels of proteasomal protein subunits and increased proteasome peptidase activities. In line with these findings we noted that Hexapeptide-11 conferred significant protection in fibroblasts against oxidative-stress-mediated premature cellular senescence, while at in vivo skin deformation assays in human subjects it improved skin elasticity. Finally, Hexapeptide-11 was found to induce the activity of extracellular MMPs and it also suppressed cell migration. Our presented findings indicate that Hexapeptide-11 is a promising anti-ageing agent.

Dermal Stability and In Vitro Skin Permeation of Collagen Pentapeptides (KTTKS and palmitoyl-KTTKS)

Collagen pentapeptide (Lys-Thr-Thr-Lys-Ser, KTTKS) and its palmitoylated derivative (pal-KTTKS) have received a great deal of attention as cosmeceutical ingredients for their anti-wrinkle effects. The objective of this study was to evaluate stability and permeability of KTTKS and pal-KTTKS in hairless mouse skin. In this study, a liquid chromatography-tandem mass spectrometric method was developed for the quantification of pal-KTTKS, and used for stability and permeability studies. Stability studies were performed using skin extracts and homogenates. Both KTTKS and pal-KTTKS were rapidly degraded, but pal-KTTKS was more stable than KTTKS. When protease inhibitors were added, the stability of both compounds (KTTKS and pal-KTTKS) improved significantly. In the skin permeation study, neither KTTKS nor pal-KTTKS was detected in the receptor solution, which indicates that neither compound could permeate through the full-thickness hairless mouse skin in the experimental conditions of this study. While KTTKS was not detected in any of the skin layers (the stratum corneum, epidermis, and dermis), pal-KTTKS was observed in all skin layers: 4.2 ± 0.7 μg/cm(2) in the stratum corneum, 2.8 ± 0.5 μg/cm(2) in the epidermis, and 0.3 ± 0.1 μg/cm(2) in the dermis. In conclusion, this study indicated that pal-KTTKS had greater stability and permeability than that of un-modified KTTKS, and may be a useful anti-wrinkle and anti-aging cosmeceutical agent.

The anti wrinkle efficacy of synthetic hexapeptide (Argireline) in Chinese Subjects

Abstract Background: This is the first multicenter clinical and experimental study of the anti wrinkle efficacy of Argireline in Chinese subjects. Objective: To evaluate the safety and efficacy of Argireline in the treatment of periorbital lines in Chinese subjects, and to observe the effect of Argireline on microstructural changes of the skin in the aged mice induced by D-galactose. Methods: The study was comprised of two parts: i) Clinical study: A total of 60 subjects received a single treatment in a 3:1 randomization ratio of Argireline: placebo. Argireline or placebo was applied to their periorbital wrinkles twice daily for 4 weeks, evaluations were made for the improvements in wrinkles. ii) Animal study: Argireline was applied to the aged mice twice daily for 6 weeks and the histopathological changes of skin tissue were evaluated. Results: In humans, the total anti wrinkle efficiency in the Argireline group was 48.9%, the depth of the wrinkles was notably reduced(P<0.01). In the aged mice, there was improvements in the morphology of skin tissue, the amount of typeⅠcollagen fibers increased(P<0.01) while type Ⅲ collagen fibers decreased (P<0.05). Conclusions: The studies revealed that Argireline had significant anti wrinkle effects in Chinese subjects.

The anti-wrinkle efficacy of Argireline

BACKGROUND

Argireline, a synthetic peptide, which is patterned from the N-terminal end of the protein SNAP-25, can both reduce the degree of existing facial wrinkles and demonstrate effectively against their development. In our past studies, we found out that Argireline had a significant anti-wrinkle effect in Chinese subjects and that it was safe and well tolerated.

OBJECTIVE

To observe the effect of Argireline on histological changes in the skin in the aged mice induced by D-galactose.

METHODS

Argireline was applied to the aged mice twice daily for 6 weeks. The histological changes in skin tissue were evaluated using hematoxylin-eosin (HE) and picrosirius-polarization (PSP) stains. The amount of type I and of type III collagen fibers were also semi-quantitatively compared using software Image-ProPlus.

RESULTS

There was an improvement in the histological structure of skin tissue in the aged mice; the amount of type I collagen fibers increased (P < 0.01), while that of type III collagen fibers decreased (P < 0.05).

CONCLUSIONS

This study revealed that Argireline could improve the histological structure of skin tissue and rejuvenate the aging skin.

Topically applied KTTKS: a review

Skin ageing is an irreversible process that is caused by both intrinsic and extrinsic factors. The possibility of arresting or delaying skin ageing represents a large research area and has a big potential in the cosmetics sector. Recently, the polypeptide lysine-threonine-threonine-lysine-serine (KTTKS) has attracted a lot of attention and it features in numerous up-market cosmetic products where it has become erroneously associated with the term 'pentapeptide'. In this study, we review in detail KTTKS and its major derivatives, in terms of the limited information in the literature and an appraisal of its physicochemical and theoretical skin permeation properties. There appears to be a sound in vitro basis for its action on fibroblasts due to its stimulatory effect on extracellular matrix synthesis, where the stimulatory effect of KTTKS is specific to collagen types I and III and fibronectin expression. However, there is a surprising absence of in vitro skin penetration data in the literature, and there are relatively few clinical studies using these materials.

CHIP-dependent p53 regulation occurs specifically during cellular senescence

p53 regulates several biological processes, including senescence. Its protein stability is regulated by ubiquitination and proteasomal degradation, mainly mediated by Mdm2. However, other E3 ligases have been identified, such as the chaperone-associated ligase CHIP, although their precise function regarding p53 degradation remains elusive. Interestingly, CHIP deficiency has been recently shown to result in accelerated aging in mice, although the molecular basis of this phenotype was not completely understood. In this study, we explore the role of CHIP in regulating p53 in senescence. We demonstrate that in senescent human fibroblasts, CHIP is up-regulated concomitant with a significant down-regulation of p53. Moreover, CHIP partially translocates to the nucleus and acquires higher ubiquitination levels in senescent cells. Notably, CHIP overexpression in young cells, to levels similar to those recorded during senescence, leads to p53 degradation to below its basal levels. In addition, whereas CHIP silencing has no effect on p53 stability in young cells, a considerable p53 accumulation occurs in their senescent counterparts. Finally, we have observed an attenuation of the CHIP-associated molecular folding-refolding machinery during senescence, and supportively, inhibition of Hsp90 activity leads to rapid p53 degradation only in senescent cells. Taking these results together, we conclude that CHIP-dependent p53 regulation occurs specifically during senescence.

Cosmeceuticals and peptides

In nature, the majority of chemical reactions, biological responses, and regulatory processes are modulated in some part by specific amino acid sequences. The transfer of these interactive sequences and the biological activities they induce to short, stable, and readily synthesized peptides has created a diverse new field of modulating molecules applicable to dermatology and skin care industries. Areas such as inflammation, pigmentation, cell proliferation and migration, angiogenesis, innate immunity, and extracellular matrix synthesis have yielded peptide candidates for application to this area.

Bioactive peptides: signaling the future

Natural processes within the body are modulated almost exclusively by the interaction of specific amino acid sequences, either as peptides or as subsections of proteins. With respect to skin, proteins and peptides are involved in the modulation of cell proliferation, cell migration, inflammation, angiogenesis, melanogenesis, and protein synthesis and regulation. The creation of therapeutic or bioactive peptide analogs of specific interactive sequences has opened the door to a diverse new field of pharmaceutical and active cosmetic ingredients for the skincare industry. Here, we describe the origin of such sequences, their role in nature, their application to dermatology, as well as the advantages and challenges posed by this new technology.

The pentapeptide KTTKS promoting the expressions of type I collagen and transforming growth factor-beta of tendon cells

Pentapeptide KTTKS, a subfragment of type I collagen propeptide, has been demonstrated to promote the extracellular release of collagen in fibroblasts. The present study was designed to investigate the effect and molecular mechanism of KTTKS on type I collagen expression of rat Achilles tendon cells. Genes related to the upregulation of collagen expression such as transforming growth factor-beta (TGF-beta), and mRNA-binding proteins (mRBP) E1 and K were also examined. MTT assay revealed cell viability was not affected by KTTKS treatment. Protein expression of type I collagen was determined by immunocytochemistry and Western blot analysis. Results showed that KTTKS induced type I collagen expression of tendon cells. The mRNA expressions of alpha1(I) procollagen, TGF-beta, mRBP K, as determined by reverse transcription-polymerase chain reaction (RT-PCR), were also enhanced after KTTKS treatment. The stability of preexisting alpha1(I) procollagen mRNA after the addition of alpha-amanitin was analyzed by RT-PCR at 24 and 48 h. Results showed that KTTKS slowed down the degradation of alpha1(I) procollagen mRNA (p = 0.021). Furthermore, the concentration of TGF-beta in conditioned medium, as determined by enzyme-linked immunosorbent assay, increased dose dependently in cells treated with KTTKS (p = 0.001). In conclusion, KTTKS promotes the expression of type I collagen and maintains its mRNA stability in a process associated with the upregulation of TGF-beta.

Cosmeceutical Peptides

BACKGROUND

Cosmeceuticals are skin care products that lie in a gray area between cosmetics and drugs. The desire for the improvement of aging skin has resulted in a plethora of products designed to improve the appearance beyond the simple camouflage of cosmetics. Many ingredients have been added to these products based on theoretical benefits discovered from in vitro studies on wound healing and other metabolic processes.

OBJECTIVE

To help the practicing dermatologist who is often the source of information for patients regarding the benefits of available cosmeceuticals.

METHODS AND MATERIALS

This article is a compilation of published studies on the effects and the practical applications of peptides as topical agents for skin improvement.

RESULTS

There does seem to be science that shows that these peptide cosmeceuticals have the potential to improve the appearance of aging skin. It is important to remember, however, that for benefit to be realized, the final product must be stable in formula, absorbed into the skin, and biologically active at the target for clinical benefit.

CONCLUSION

This article will provide dermatologists with more background to answer pressing questions from patients on this subject.

Stimulation of type II collagen biosynthesis and secretion in bovine chondrocytes cultured with degraded collagen

The functional integrity of articular cartilage is dependent on the maintenance of the extracellular matrix (ECM), a process which is controlled by chondrocytes. The regulation of ECM biosynthesis is complex and a variety of substances have been found to influence chondrocyte metabolism. In the present study we have investigated the effect of degraded collagen on the formation of type II collagen by mature bovine chondrocytes in a cell culture model. The culture medium was supplemented with collagen hydrolysate (CH) and biosynthesis of type II collagen by chondrocytes was compared to control cells treated with native type I and type II collagen and a collagen-free protein hydrolysate. The quantification of type II collagen by means of an ELISA technique was confirmed by immunocytochemical detection as well as by the incorporation of (14)C-proline in the ECM after a 48 h incubation. Chondrocytes in the control group were maintained in the basal medium for 11 days. The presence of extracellular CH led to a dose-dependent increase in type II collagen secretion. However, native collagens as well as a collagen-free hydrolysate of wheat proteins failed to stimulate the production of type II collagen in chondrocytes. These results clearly indicate a stimulatory effect of degraded collagen on the type II collagen biosynthesis of chondrocytes and suggest a possible feedback mechanism for the regulation of collagen turnover in cartilage tissue.

The effects of collagen fragments on the extracellular matrix metabolism of bovine and human chondrocytes

Cartilage matrix degradation generates collagen type II fragments. The objective of this study is to explore the possibility that these collagen fragments may be part of an endogenous metabolic feedback. Initially, collagen fragments were extracted from normal or osteoarthritic cartilage, as part of a matrix fragment preparation. Later, collagen fragments were generated by digestion of bovine collagen type II with bacterial collagenase (col2f). These fragments were added to cultures of isolated chondrocytes (bovine and human) and cartilage explants (human). In a dose-dependent manner, col2f caused inhibition of cell attachment to collagen, inhibition of collagen synthesis, and induction of matrix degradation. In addition, when col2f were added to human cartilage explants, an induction of gelatinase activity was detected in the media. These data sets present first evidence that degradation products of collagen may be directly involved in the regulation of cartilage homeostasis.

The globular domain of the proalpha 1(I) N-propeptide is not required for secretion, processing by procollagen N-proteinase, or fibrillogenesis of type I collagen in mice

The globular domain in the NH(2)-terminal propeptide (N-propeptide) of the proalpha1(I) chain is largely encoded by exon 2 of the Col1a1 gene and has been implicated in a number of processes that are involved in the biogenesis, maturation, and function of type I collagen. These include intracellular chain association, transcellular transport and secretion, proteolytic processing of the precursor, feedback regulation of synthesis, and control of fibrillogenesis. However, none of these proposed functions has been firmly established. To evaluate the function of this procollagen domain we have used a targeted mutagenesis approach to generate mice that lack exon 2 in the Col1a1 gene. Mouse lines were established on both a mixed 129 OlaHsd/Sv and C57BL/6 background and a pure 129 OlaHsd/Sv background. Adult mice on the mixed background are normal in appearance and are fertile. To the extent that they have been studied, procollagen synthesis, secretion, and proteolytic processing are normal in these mice, and collagen fibrillogenesis is only slightly altered. However, breeding of heterozygous mutant mice on the 129 background generated homozygous mutants at only 64% of the expected frequency. These findings suggest that although the N-propeptide is not essential for collagen biogenesis in mice it may play some essential role during embryonic development.

Biophysical characterization of the C-propeptide trimer from human procollagen III reveals a tri-lobed structure

Procollagen C-propeptide domains direct chain association during intracellular assembly of procollagen molecules. In addition, they control collagen solubility during extracellular proteolytic processing and fibril formation and interact with cell surface receptors and extracellular matrix components involved in feedback inhibition, mineralization, cell growth arrest, and chemotaxis. At present, three-dimensional structural information for the C-propeptides, which would help to understand the underlying molecular mechanisms, is lacking. Here we have carried out a biophysical study of the recombinant C-propeptide trimer from human procollagen III using laser light scattering, analytical ultracentrifugation, and small angle x-ray scattering. The results show that the trimer is an elongated molecule, which by modeling of the x-ray scattering data appears to be cruciform in shape with three large lobes and one minor lobe. We speculate that each of the major lobes corresponds to one of the three component polypeptide chains, which come together in a junction region to connect to the rest of the procollagen molecule.

Erythromycin modulates eosinophil chemotactic cytokine production by human lung fibroblasts in vitro

Recent studies suggest that erythromycin can suppress the production of some cytokines and may be an effective treatment for asthma. Eosinophil chemotactic cytokines have been suggested to contribute to the pathogenesis of asthma by the recruitment of eosinophils. We hypothesized that erythromycin modulates eosinophil chemotactic cytokine production. To test the hypothesis, we evaluated the potential of erythromycin to modulate the release of eosinophil chemoattractants from the human lung fibroblast cell line HFL-1. HFL-1 released eotaxin, granulocyte-macrophage colony-stimulating factor, and regulated and normal T-cell expressed and presumably secreted (RANTES) in response to interleukin-1beta or tumor necrosis factor alpha. Erythromycin attenuated the release of these cytokines and eosinophil chemotactic activity by the HFL-1. The suppressive effect on eotaxin was the most marked of these cytokines. Erythromycin therapy also suppressed eotaxin mRNA significantly. These results suggest a mechanism that may account for the apparent beneficial action of macrolide antibiotics in the treatment of allergic airway disorders.

Bradykinin stimulates eotaxin production by a human lung fibroblast cell line

BACKGROUND

Bradykinin, a potent inflammatory peptide, is increased in the airways of allergic patients. Accompanying the elevated bradykinin levels are increases in both eosinophils and fibroblasts. Eotaxin, a potent eosinophil-specific chemotactic factor, is released by fibroblasts and increased in the lower respiratory tract of allergic patients.

OBJECTIVE

We sought to test the hypothesis that lung fibro-blasts release eotaxin in response to bradykinin.

METHODS

The potential of bradykinin to induce the release of eotaxin from the human lung fibroblast cell line HFL-1 was tested by cell culture and evaluation of the culture supernatant fluids and RNA for immunoreactive eotaxin and eotaxin messenger RNA.

RESULTS

HFL-1 cells released eotaxin constitutively without stimulation, but bradykinin stimulated eotaxin release in a dose- and time-dependent manner and resulted in augmented expression of eotaxin messenger RNA. The release of eotaxin was sensitive to the action of glucocorticoids. Eosinophil chemotactic activity by HFL-1 supernatant fluids was inhibited by anti-human eotaxin-neutralizing antibody. Consistent with these results, inhibitors of bradykinin B2 receptors, but not bradykinin B1 receptors, inhibited bradykinin-induced eotaxin release.

CONCLUSION

These data demonstrate that bradykinin may stimulate lung fibroblasts to release eotaxin and suggest the potential for this mechanism to be important in modulation of lung inflammation.

Alpha2beta1 integrin recognition of the carboxyl-terminal propeptide of type I procollagen: integrin recognition and feed-back regulation of matrix biosynthesis are mediated by distinct sequences

It has recently been established that the carboxyl-terminal propeptide of type I collagen exert a feedback regulatory effect on extracellular matrix biosynthesis and that the propeptide bind to the alpha2beta1 integrin. This raises the intriguing hypothesis that the regulatory propeptide sequences exert their effects as a consequence of binding to the integrin. We show that recombinant alpha1(I) collagen chain C-terminal propeptide contains a binding site for the intact alpha2beta1 integrin and for a recombinant alpha2 integrin I domain, but not for the alpha1beta1 integrin, a structurally and functionally related collagen/laminin receptor. Additional studies employing a series of recombinant N-terminal and C-terminal deletion mutants, internal fragments of the propeptide, synthetic peptides, recombinant alpha2 integrin I domain and inhibitory monoclonal antibodies established that the previously identified sequences within the alpha1(I) C-terminal propeptide that mediate regulation of matrix biosynthesis are neither necessary nor sufficient for alpha2beta1 integrin binding. In contrast, the integrin recognition site is composed of a conformationally complex determinant located within a structurally distinct 115 amino acid region of the propeptide.

Synthesis and conformational properties of a recombinant C-propeptide of human type III procollagen

A cDNA was prepared that coded for the signal peptide of type III procollagen linked to the complete C-propeptide of the protein. The cDNA was then used to express the protein in a baculovirus recombinant system. Recombinant protein was recovered as a trimer from the medium of transfected cells in a yield of 1 to 2.5 mg per liter. Mapping of peptide fragments with and without reduction indicated that the protein contained the expected interchain disulfide bonds. Analysis by circular dichroism suggested that the conformation of the protein corresponded to the native conformation. Therefore, the protein should be appropriate for further tests of its biological function and analysis of structure by X-ray diffraction.

Molecular characterisation of integrin-procollagen C-propeptide interactions

The carboxyl-terminal propeptide of type I procollagen (CPP-I) plays a key role in regulation of collagen fibrillogenesis, and may exert feedback control of collagen biosynthesis. We have previously shown that CPP-I is a ligand for the integrin alpha2beta1 [Weston, S. A., Hulmes, D. J. S., Mould, A. P., Watson, R. B. & Humphries, M. J. (1994) Identification of the integrin alpha2beta1 as a cell surface receptor for the C-propeptide of type I procollagen, J. Biol. Chem. 269, 20982-20986] suggesting that some of the phenotypic effects of C-propeptides may be mediated by adhesion receptors. Here we have extended this work to study the molecular basis of this interaction. We have broadened the ligand range by demonstrating that the C-terminal propeptide of type II procollagen supports alpha2beta1-mediated binding of NHS human fibroblasts in cell attachment assays. Also, we have used function-blocking antibodies in cell attachment and solid-phase binding assays with purified integrin to expand the CPP-I receptor family, showing that integrin alpha1beta1 is also a receptor for CPP-I. Integrin alpha-subunit A-domains are known to be major ligand-binding sites and recombinant alpha1 and alpha2 subunit A-domains were able to bind CPP-I. Finally we have shown that peptides corresponding to potential integrin-binding sequences in CPP-I do not mediate integrin-CPP-I adhesion. Taken together, these studies indicate that the interactions between C-propeptides and integrins are more numerous than previously reported, that C-propeptides are a new class of molecule which bind to A-domains, and that the integrin-C-propeptide interaction does not utilise established peptide motifs.

Cleavage of type I procollagen by human mast cell chymase initiates collagen fibril formation and generates a unique carboxyl-terminal propeptide

The ability of human mast cell chymase and tryptase to process procollagen was examined. Purified human intestinal smooth muscle cell procollagen was incubated with human mast cell tryptase or human mast cell chymase. Purified chymase, but not tryptase, exhibited procollagen proteinase activity in the presence of EDTA. Addition of purified porcine heparin over a range of 0.1-100 microg/ml did not affect either the rate or the products of procollagen chymase cleavage. The cleavage site of chymase on the pro-alpha1(I) collagen carboxyl terminus was found to be in the propeptide region at Leu-1248-Ser-1249. Cleavage at this site suggested that the collagen products would form fibrils and confirmed the production of a unique carboxyl-terminal propeptide. Turbidometric fibril formation assay demonstrated de novo formation of chymase-generated collagen fibrils with characteristic lag, growth, and plateau phases. When observed by dark field microscopy, these fibrils were similar to fibrils formed by the action of procollagen proteinases. Thus, mast cell chymase, but not tryptase, exhibits procollagen peptidase-like activity as evidenced by its ability to process procollagen to fibril-forming collagen with concurrent formation of a unique carboxyl-terminal propeptide. These data demonstrate that mast cell chymase has a potential role in the regulation of collagen biosynthesis and in the pathogenesis of fibrosis.

Pathogenesis of scleroderma. Collagen

It is now evident that persistent overproduction of collagen and other connective tissue macromolecules results in excessive tissue deposition, and is responsible for the progressive nature of fibrosis in SSc. Up-regulation of collagen gene expression in SSc fibroblasts appears to be a critical event in the development of tissue fibrosis. The coordinate transcriptional activation of a number of extracellular matrix genes suggests a fundamental alteration in the regulatory control of gene expression in SSc fibroblasts. Trans-acting nuclear factors that bind to cis-acting elements in enhancer and promoter regions of the genes modulate the basal and inducible transcriptional activity of the collagen genes. The identity of the nuclear transcriptional factors that regulate normal collagen gene expression remains to be firmly established, and to date, no alterations in the level or in the activity of such DNA binding factors has been demonstrated in SSc fibroblasts. In addition to important interactions between fibroblasts and the extracellular matrix, cytokines and other cellular mediators can positively and negatively influence fibroblast collagen synthesis. Some of these signaling molecules may have physiologic roles, and their aberrant expression, or altered responsiveness of SSc fibroblasts to them, may result in the acquisition of the activated phenotype. The rapid expansion of knowledge regarding the effects of cytokines on extracellular matrix synthesis has led to an appreciation of the enormous complexity of regulatory networks that operate in the physiologic maintenance of connective tissue and which may be responsible for the occurrence of pathologic fibrosis. The ubiquitous growth factor TGF beta is the most potent inducer of collagen gene expression and connective tissue accumulation yet discovered. The expression of TGF beta in activated infiltrating mononuclear cells suggests a role for this cytokine as a mediator of fibroblast activation in SSc. Furthermore, the recognition that TGF beta is capable of inducing its own expression in a variety of cell types, coupled with the demonstration that a subpopulation of SSc dermal fibroblasts produces TGF beta, indicates the existence of a possible autocrine loop whereby lymphocyte-derived TGF beta in early SSc not only signals biosynthetic activation of fibroblasts in a paracrine manner, but autoinduces endogenous TGF beta production by the target fibroblasts themselves. Such an autocrine loop involving TGF beta may explain the persistent activation of collagen gene expression in SSc fibroblasts, and could be responsible for the progressive nature of fibrosis in SSc. Numerous other cytokines, as well as cell-matrix interactions, also modify collagen gene expression and can significantly influence the effects of TGF beta. Although their physiologic function in tissue remodeling or their involvement in abnormal fibrogenesis has not yet been conclusively demonstrated, the study of the biologic effects of these cytokines may provide important clues to understanding the pathogenesis of SSc, and to the development of rational drug therapy aimed at interrupting the abnormal fibrogenic process in this disease.

Differential expression of integrin alpha subunits supports distinct roles during lung branching morphogenesis

Epithelial branching morphogenesis is a process by which a continuous epithelium, embedded in mesenchyme, forms tubules that extend and branch into the surrounding mesenchyme. The morphogenetic process is responsible for the architecture of many organs including the lung. Proper expression and function of extracellular matrix (ECM) molecules, such as collagens and laminins, are necessary for branching to occur normally. However, little is known about the role of epithelial cell surface molecules that mediate epithelial-matrix interactions during this process. We have studied the expression patterns of cell surface collagen and laminin integrin receptor alpha subunits, alpha 1, alpha 2, alpha 3, and alpha 6, in relation to that of collagen and laminin during lung branching morphogenesis. The alpha 1 integrin subunit was present on endothelia and smooth muscles around airways and large blood vessels. The mesenchyme expressed high levels of alpha 2 and alpha 6 but not alpha 3, whereas the epithelium expressed all three integrin subunits. In contrast to the widespread epithelial expression of alpha 3 and alpha 6, the epithelial expression of alpha 2 was restricted to branch tips. By performing in situ hybridization and immunofluorescence on serial sections, we found that alpha 2 protein expression on the epithelium correlated spatially and temporally with high level expression of collagen IV and laminin-1 mRNAs, suggesting that the alpha 2-expressing epithelial cells were in the process of producing and assembling their collagen and laminin matrices. While the expression of alpha 3 and alpha 6 on all lung epithelia suggests that these integrins may be important to lung epithelial development, the unique expression pattern of the alpha 2 subunit suggests that the alpha 2 beta 1 integrin may be important at branch tips either in the process of collagen/laminin synthesis and assembly or extension of the epithelial tubules into the mesenchyme.

Characterization of the osteogenic stromal cell line MN7: identification of secreted MN7 proteins using two-dimensional polyacrylamide gel electrophoresis, western blotting, and microsequencing

Proteins secreted by the osteogenic stromal cell line MN7 were analyzed using two-dimensional polyacrylamide gel electrophoresis (PAGE), western blotting, immunodetection, and microsequencing. Trichloroacetic acid-precipitated proteins from the conditioned medium of MN7 cell cultures, harvested at different times of growth, were dissolved in denaturing and reducing sample buffer and separated in the first dimension according to isoelectric point and in the second dimension according to molecular weight. Protein patterns were visualized using silver staining. Among the 350 separated protein spots, we identified type I collagen, bone sialoprotein, osteonectin, and cathepsin B by western blotting and immunodetection using polyclonal antibodies. Osteocalcin could not be detected in the conditioned medium of MN7 cells. Furthermore, 15 MN7-specific protein spots were localized after comparison with two-dimensional PAGE patterns from the conditioned medium of the nonosteogenic stromal cell lines MM1 and MV1. Microsequencing of the internal peptides of five selected spots revealed three known proteins, namely the carboxyl-terminal propeptide of the alpha 2 chain of collagen type I, cathepsin L, and the tissue inhibitor of metalloproteinases-2, an 18 kilodalton peptide fragment from osteopontin that has not previously been described, and a novel glycosylated 85 kD protein with an average isoelectric point of 5.7. All identified proteins did not vary in presence between the different time points analyzed by two-dimensional PAGE. The use of two-dimensional PAGE to investigate the secreted proteins of MN7 cells will enable us to establish a complete protein data base of extracellular osteoblast-specific proteins. Furthermore, two-dimensional PAGE in combination with other techniques is a fast and accurate method for the identification of novel proteins that could function as markers in osteoblast differentiation and/or bone formation.

Collagen breakdown products and lung collagen metabolism: an in vitro study on fibroblast cultures

BACKGROUND

In fibrotic diseases such as pulmonary fibrosis there is evidence suggesting enhanced synthesis and degradation of lung connective tissue components, including collagen. It has therefore been hypothesised that products of collagen degradation may have a role in the promotion of collagen deposition. In support of this hypothesis, it has recently been shown that intravenous injection of lung collagen degradation products in experimental animals stimulated collagen synthesis leading to increased collagen deposition and diffuse interstitial lung disease.

METHODS

Rabbit and human fibroblast cultures from lung and skin were used as an in vitro model to study the responses of these cells to rabbit collagen degradation products. The effects of an acute exposure to collagen degradation products on synthesis of collagen and noncollagenous protein have been studied in confluent cultures by [3H]-proline incorporation. The effects of collagen degradation products on fibroblast proliferation and production of genetic types of collagen have also been investigated.

RESULTS

The acute exposure of rabbit lung fibroblast cultures to collagen degradation products significantly increased collagen synthesis without affecting non-collagenous protein synthesis. This effect was dose related, specific for lung fibroblasts, and species specific. Collagen degradation products altered the rate of synthesis of genetic types of collagen with a consequent decrease of type III/I+III collagen ratio (0.26 (0.04) treated with collagen degradation products; 0.45 (0.02) controls). These effects occurred without the intervention of serum factors. In addition, collagen degradation products neither affected fibroblast proliferation nor selected specific clones emphasising one type of collagen.

CONCLUSIONS

These results suggest that collagen degradation products can influence lung collagen metabolism by stimulating collagen synthesis. The regulation of collagen mass by collagen degradation products may be of importance in lung collagen homeostasis in vivo.

Collagen synthesis by fibroblasts cultured within a collagen sponge

We prepared a collagen sponge made of type I and III bovine collagen, glycosaminoglycans (GAG) and chitosan. Fibroblasts grown within the collagen sponge express a sixfold increase of their collagen synthesis, compared with fibroblasts embedded in a collagen gel. Moreover, collagen synthesis is twice as high in the collagen sponge than in a monolayer culture. The collagen sponge culture system promotes a dynamic model for us to perform studies on the regulations of collagen synthesis. Increased collagen production within the collagen sponge leads fibroblasts to reconstitute their own extracellular matrix, which should be more physiological than a bovine collagen gel.

Enhanced type III collagen gene expression during bleomycin induced lung fibrosis

BACKGROUND

Intratracheal instillation of bleomycin into mice leads to deposition of collagen in the lung and fibrosis, but the mechanism for this is poorly understood. Enhanced collagen gene expression, increased collagen synthesis, decreased collagen degradation, and proliferation of fibroblasts have all been proposed as possible contributors. To obtain information on the activity of collagen producing cells at an early stage in the development of pulmonary fibrosis in situ hybridisation was used to detect and localise products of the type III procollagen gene. In addition, assay of type III procollagen gene expression was performed using dot-blot analysis of lung RNA extracts.

METHODS

Lung fibrosis was induced in mice by intratracheal instillation of bleomycin sulphate (6 mg/kg body weight) and tissues were examined after three, 10, 21 and 35 days. RNA-RNA hybridisation was accomplished with riboprobes labelled with sulphur-35 which were generated from a 1.7 kb mouse procollagen a1(III) cDNA. In situ hybridisation was performed on sections fixed in paraformaldehyde and embedded in paraffin wax and steady state values of type III procollagen mRNA were assayed by dot-blot analysis of total lung RNA extracted by guanidium isothiocyanate.

RESULTS

Data obtained using both techniques suggest that type III procollagen gene expression was enhanced in bleomycin induced fibrosis and that expression was maximal between 10 and 35 days after a single dose of bleomycin. The most active cells were located in interstitial areas around the conducting airways, although these cells were usually seen in areas with no histological evidence of fibrosis. Regions with the most advanced fibrosis, as assessed by histological methods, rarely contained cells with activity above the threshold detectable by this technique.

CONCLUSIONS

These results suggest that activation of interstitial fibroblasts, with enhanced type III collagen gene expression, forms at least part of the mechanism leading to increased collagen deposition in bleomycin induced fibrosis and that this occurs before fibrosis is detected by conventional histological staining.

Domains of type X collagen: alteration of cartilage matrix by fibril association and proteoglycan accumulation

During endochondral bone formation, hypertrophic cartilage is replaced by bone or by a marrow cavity. The matrix of hypertrophic cartilage contains at least one tissue-specific component, type X collagen. Structurally type X collagen contains both a collagenous domain and a COOH-terminal non-collagenous one. However, the function(s) of this molecule have remained largely speculative. To examine the behavior and functions of type X collagen within hypertrophic cartilage, we (Chen, Q., E. Gibney, J. M. Fitch, C. Linsenmayer, T. M. Schmid, and T. F. Linsenmayer. 1990. Proc. Natl. Acad. Sci. USA. 87:8046-8050) recently devised an in vitro system in which exogenous type X collagen rapidly (15 min to several hours) moves into non-hypertrophic cartilage. There the molecule becomes associated with preexisting cartilage collagen fibrils. In the present investigation, we find that the isolated collagenous domain of type X collagen is sufficient for its association with fibrils. Furthermore, when non-hypertrophic cartilage is incubated for a longer time (overnight) with "intact" type X collagen, the molecule is found both in the matrix and inside of the chondrocytes. The properties of the matrix of such type X collagen-infiltrated cartilage become altered. Such changes include: (a) antigenic masking of type X collagen by proteoglycans; (b) loss of the permissiveness for further infiltration by type X collagen; and (c) enhanced accumulation of proteoglycans. Some of these changes are dependent on the presence of the COOH-terminal non-collagenous domain of the molecule. In fact, the isolated collagenous domain of type X collagen appears to exert an opposite effect on proteoglycan accumulation, producing a net decrease in their accumulation, particularly of the light form(s) of proteoglycans. Certain of these matrix alterations are similar to ones that have been observed to occur in vivo. This suggests that within hypertrophic cartilage type X collagen has regulatory as well as structural functions, and that these functions are achieved specifically by its two different domains.

Fibrogenesis in cirrhosis. Potential for therapeutic intervention

Liver cirrhosis is an end stage of several diseases that affect the liver chronically. It is characterized, among other things, by excess collagen deposition, distortion of liver architecture, tissue malfunction and hemodynamic alterations. Many of the complications of cirrhosis may result from excess matrix-deposition. Therefore, prevention of collagen accumulation or removal of collagen deposits could ameliorate the disease. In this article we discuss the pathophysiology of liver fibrosis and we describe various compounds with antiinflammatory and antifibrogenic activity. We discuss their possible mechanism of action and we describe animal and clinical studies in which these compounds have been utilized.