The Self-Assembling Peptide P11-4 Prevents Collagen Proteolysis in Dentin.

The major goal in restorative dentistry is to develop a true regenerative approach that fully recovers hydroxyapatite crystals within the caries lesion. Recently, a rationally designed self-assembling peptide P11-4 (Ace-QQRFEWEFEQQ-NH2) has been developed to enhance remineralization on initial caries lesions, yet its applicability on dentin tissues remains unclear. Thus, the present study investigated the interaction of P11-4 with the organic dentin components as well as the effect of P11-4 on the proteolytic activity, mechanical properties of the bonding interface, and nanoleakage evaluation to artificial caries-affected dentin. Surface plasmon resonance and atomic force microscopy indicated that P11-4 binds to collagen type I fibers, increasing their width from 214 ± 4 nm to 308 ± 5 nm ( P < 0.0001). P11-4 also increased the resistance of collagen type I fibers against the proteolytic activity of collagenases. The immediate treatment of artificial caries-affected dentin with P11-4 enhanced the microtensile bonding strength of the bonding interface ( P < 0.0001), reaching values close to sound dentin and decreasing the proteolytic activity at the hybrid layer; however, such effects decreased after 6 mo of water storage ( P < 0.05). In conclusion, P11-4 interacts with collagen type I, increasing the resistance of collagen fibers to proteolysis, and improves stability of the hybrid layer formed by artificial caries-affected dentin.

PAR-1 and PAR-2 Expression Is Enhanced in Inflamed Odontoblast Cells.

Protease-activated receptors (PARs) are G protein-coupled receptors, which are activated by proteolytical cleavage of the amino-terminus and act as sensors for extracellular proteases. We hypothesized that PAR-1 and PAR-2 can be modulated by inflammatory stimulus in human dental pulp cells. PAR-1 and PAR-2 gene expression in human pulp tissue and MDPC-23 cells were analyzed by quantitative polymerase chain reaction. Monoclonal PAR-1 and PAR-2 antibodies were used to investigate the cellular expression of these receptors using Western blot, flow cytometry, and confocal microscopy in MDPC-23 cells. Immunofluorescence assays of human intact and carious teeth were performed to assess the presence of PAR-1 and PAR-2 in the dentin-pulp complex. The results show for the first time that human odontoblasts and MDPC-23 cells constitutively express PAR-1 and PAR-2. PAR-2 activation increased significantly the messenger RNA expression of matrix metalloproteinase (MMP)-2, MMP-9, MMP-13, and MMP-14 in MDPC-23 cells ( P < 0.05), while the expression of these enzymes decreased significantly in the PAR-1 agonist group ( P < 0.05). The high-performance liquid chromatography and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry analysis showed the presence of MMP-13 activity cleaving PAR-1 at specific, noncanonical site TLDPRS42↓F43LL in human dental pulp tissues. Also, we detected a presence of a trypsin-like activity cleaving PAR-2 at canonical site SKGR20↓S21LIGRL in pulp tissues. Confocal microscopy analysis of human dentin-pulp complex showed intense positive staining of PAR-1 and PAR-2 in the odontoblast processes in dentinal tubules of carious teeth compared to intact ones. The present results support the hypothesis of activation of the upregulated PAR-1 and PAR-2 by endogenous proteases abundant during the inflammatory response in dentin-pulp complex.

Coupling of vinculin to F-actin demands Syndecan-4 proteoglycan.

Syndecans are heparan sulfate proteoglycans characterized as transmembrane receptors that act cooperatively with the cell surface and extracellular matrix proteins. Syn4 knockdown was performed in order to address its role in endothelial cells (EC) behavior. Normal EC and shRNA-Syn4-EC cells were studied comparatively using complementary confocal, super-resolution and non-linear microscopic techniques. Confocal and super-resolution microscopy revealed that Syn4 knockdown alters the level and arrangement of essential proteins for focal adhesion, evidenced by the decoupling of vinculin from F-actin filaments. Furthermore, Syn4 knockdown alters the actin network leading to filopodial protrusions connected by VE-cadherin-rich junction. shRNA-Syn4-EC showed reduced adhesion and increased migration. Also, Syn4 silencing alters cell cycle as well as cell proliferation. Moreover, the ability of EC to form tube-like structures in matrigel is reduced when Syn4 is silenced. Together, the results suggest a mechanism in which Syndecan-4 acts as a central mediator that bridges fibronectin, integrin and intracellular components (actin and vinculin) and once silenced, the cytoskeleton protein network is disrupted. Ultimately, the results highlight Syn4 relevance for balanced cell behavior.

Abundance of MMPs and cysteine cathepsins in caries-affected dentin.

Degradation of dentin matrix components within caries dentin has been correlated with the activity of host-derived proteases, such as matrix metalloproteases (MMPs) and cysteine cathepsins (CTs). Since this relationship has not been fully established, we hypothesized that the abundance of MMPs and CTs in caries-affected dentin must be higher than in intact dentin. To test this premise, we obtained 5 slices (200 µm) from 5 intact teeth and from 5 caries-affected teeth (1 slice/tooth) and individually incubated them with primary antibodies for CT-B, CT-K, MMP-2, or MMP-9. Negative controls were incubated with pre-immune serum. Specimens were washed and re-incubated with the respective fluorescent secondary antibody. Collagen identification, attained by the autofluorescence capture technique, and protease localization were evaluated by multi-photon confocal microscopy. The images were analyzed with ZEN software, which also quantitatively measured the percentages of collagen and protease distribution in dentin compartments. The abundance of the test enzymes was markedly higher in caries-affected than in intact dentin. CT-B exhibited the highest percentage of co-localization with collagen, followed by MMP-9, MMP-2, and CT-K. The high expression of CTs and MMPs in caries-affected teeth indicates that those host-derived enzymes are intensely involved with caries progression.

Tooth bleaching increases dentinal protease activity.

Hydrogen peroxide is an oxidative agent commonly used for dental bleaching procedures. The structural and biochemical responses of enamel, dentin, and pulp tissues to the in vivo bleaching of human (n = 20) premolars were investigated in this study. Atomic force microscopy (AFM) was used to observe enamel nanostructure. The chemical composition of enamel and dentin was analyzed by infrared spectroscopy (FTIR). The enzymatic activities of dental cathepsin B and matrix metalloproteinases (MMPs) were monitored with fluorogenic substrates. The amount of collagen in dentin was measured by emission of collagen autofluorescence with confocal fluorescence microscopy. The presence of Reactive Oxygen Species (ROS) in the pulp was evaluated with a fluorogenic 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) probe. Vital bleaching of teeth significantly altered all tested parameters: AFM images revealed a corrosion of surface enamel nanostructure; FTIR analysis showed a loss of carbonate and proteins from enamel and dentin, along with an increase in the proteolytic activity of cathepsin-B and MMPs; and there was a reduction in the autofluorescence of collagen and an increase in both cathepsin-B activity and ROS in pulp tissues. Together, these results indicate that 35% hydrogen peroxide used in clinical bleaching protocols dramatically alters the structural and biochemical properties of dental hard and soft pulp tissue.

Chlorhexidine inhibits the activity of dental cysteine cathepsins.

The co-expression of MMPs and cysteine cathepsins in the human dentin-pulp complex indicates that both classes of enzymes can contribute to the endogenous proteolytic activity of dentin. Chlorhexidine (CHX) is an efficient inhibitor of MMP activity. This study investigated whether CHX could also inhibit cysteine cathepsins present in dentin. The inhibitory profile of CHX on the activity of dentin-extracted and recombinant cysteine cathepsins (B, K, and L) was monitored in fluorogenic substrates. The rate of substrate hydrolysis was spectrofluorimetrically measured, and inhibitory constants were calculated. Molecular docking was performed to predict the binding affinity between CHX and cysteine cathepsins. The results showed that CHX inhibited the proteolytic activity of dentin-extracted cysteine cathepsins in a dose-dependent manner. The proteolytic activity of human recombinant cathepsins was also inhibited by CHX. Molecular docking analysis suggested that CHX strongly interacts with the subsites S2 to S2' of cysteine cathepsins B, K, and L in a very similar manner. Taken together, these results clearly showed that CHX is a potent inhibitor of the cysteine cathepsins-proteolytic enzymes present in the dentin-pulp complex.

Cysteine cathepsins in human carious dentin.

Matrix metalloproteinases (MMPs) are important in dentinal caries, and analysis of recent data demonstrates the presence of other collagen-degrading enzymes, cysteine cathepsins, in human dentin. This study aimed to examine the presence, source, and activity of cysteine cathepsins in human caries. Cathepsin B was detected with immunostaining. Saliva and dentin cysteine cathepsin and MMP activities on caries lesions were analyzed spectrofluorometrically. Immunostaining demonstrated stronger cathepsins B in carious than in healthy dentin. In carious dentin, cysteine cathepsin activity increased with increasing depth and age in chronic lesions, but decreased with age in active lesions. MMP activity decreased with age in both active and chronic lesions. Salivary MMP activities were higher in patients with active than chronic lesions and with increasing lesion depth, while cysteine cathepsin activities showed no differences. The results indicate that, along with MMPs, cysteine cathepsins are important, especially in active and deep caries.

Role of purines on hepatic ischemia-reperfusion lesions in rabbit.

In this work, we evaluate the effects of adenosine 5' triphosphate (ATP) on hepatic lesions caused by ischemia/reperfusion (I/R) in liver rabbit. Rabbits were pretreated with ATP (15 mg/kg IV) or saline solution 0.9% (SS), before the hepatic I/R procedure. We evaluated the effects of ATP on hepatic injury before and after I/R. The warm hepatic I/R procedure caused profound acute liver injury, as indicated by elevated serum aspartate aminotransferase, alanine aminotransferase, and lactic dehydrogenase levels, as well as a high apoptotic cell count. All these changes were attenuate by ATP treatment before the hepatic I/R procedure. These results suggested that ATP exerted protective effects on hepatic I/R lesions in the rabbit. This ATP effect may be related to improved energy metabolism during reperfusion in ischemic livers protecting against functional damage of cellular and subcellular membranes during lipid peroxidation.

l-Arginine supplementation protects against hepatic ischemia-reperfusion lesions in rabbits.

We evaluated the effects of a substrate in the biosynthesis of nitric oxide (NO)-l-arginine (LARG)-on hepatic lesions caused by ischemia/reperfusion (I/R) injury in rabbit livers. Rabbits were pretreated with LARG (150 mg/kg IV) or saline solution 0.9% (SS) before the hepatic I/R procedure. The effects of LARG on hepatic injury were evaluated before and after I/R. The warm hepatic I/R procedure produced profound acute liver injury, as indicated by elevated values of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactic dehydrogenase (LDH), as well as a high apoptotic cell count. All changes were attenuated by treatment with LARG before the hepatic I/R procedure. These results suggested that LARG produced protective effects on hepatic I/R lesions. This protective effect of LARG was probably associated with blocking generation of superoxide anions during the hepatic I/R procedure.

Protective effects of heparin on hepatic ischemia and reperfusion lesions in rabbits.

Because the role of heparin (HEP) in hepatic ischemia/reperfusion (I/R) injury is still not fully understood, we investigated the effects of treatment with HEP on hepatic I/R injury in rabbits. For I/R procedures, the portal vein and hepatic artery were occluded by a metallic clamp to promote ischemia. The clamp was removed after 30 minutes to allow reperfusion. Rabbits undergoing the I/R procedure were treated with HEP (100 U/kg) or saline solution 0.9% (SS). When compared with levels before I/R, the serum aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase, levels were increased by the hepatic I/R procedure, among rabbits treated with SS or HEP. However, the increase in these enzymes was lower among rabbits treated with HEP. Histologic analysis of hepatic tissue of rabbits undergoing I/R and treated with SS showed marked lesions in the central lobule with significant inflammatory infiltration. In contrast, a significant reduction in lesions caused by I/R was observed in the livers of rabbits treated with HEP. After starting reperfusion, we visualized apoptotic cells with nuclear staining among rabbits submitted to I/R and treated with SS, but not those treated with HEP. These results suggested that HEP was able to attenuate hepatic lesions caused by I/R in the livers of rabbits.

Effects of allopurinol on ischemia and reperfusion in rabbit livers.

In this work, we evaluated the effects of allopurinol (ALO), an inhibitor of xanthine oxidase (XO), on hepatic lesions caused by ischemia/reperfusion (I/R) in the rabbit liver. Rabbits were pretreated with ALO (10 mg/kg IV) or saline solution 0.9% before the hepatic I/R procedure. The effects of ALO on hepatic injury were evaluated before and after I/R. A standard, warm hepatic I/R procedure caused profound acute liver injury, as indicated by elevated serum aspartate aminotransferase, alanine aminotransferase, and lactic dehydrogenase levels, as well as a high apoptotic cell count. All of these changes were reversed by the administration of ALO before the hepatic I/R procedure. In conclusion, ALO exerted protective effects on hepatic I/R lesions. This protective effect of ALO was probably associated with blocking the generation of superoxide anions during the hepatic I/R procedure by inhibiting XO activity.

The role of Tyr605 and Ala607 of thimet oligopeptidase and Tyr606 and Gly608 of neurolysin in substrate hydrolysis and inhibitor binding

The physicochemical properties of TOP (thimet oligopeptidase) and NEL (neurolysin) and their hydrolytic activities towards the FRET (fluorescence resonance energy transfer) peptide series Abz-GFSXFRQ-EDDnp [where Abz is o-aminobenzoyl; X = Ala, Ile, Leu, Phe, Tyr, Trp, Ser, Gln, Glu, His, Arg or Pro; and EDDnp is N-(2,4-dinitrophenyl)-ethylenediamine] were compared with those of site-mutated analogues. Mutations at Tyr605 and Ala 607 in TOP and at Tyr606 and Gly608 in NEL did not affect the overall folding of the two peptidases, as indicated by their thermal stability, CD analysis and the pH-dependence of the intrinsic fluorescence of the protein. The kinetic parameters for the hydrolysis of substrates with systematic variations at position P1 showed that Tyr605 and Tyr606 of TOP and NEL respectively, played a role in subsite S1. Ala607 of TOP and Gly608 of NEL contributed to the flexibility of the loops formed by residues 600-612 (GHLAGGYDGQYYG; one-letter amino acid codes used) in NEL and 599-611 (GHLAGGYDAQYYG; one-letter amino acid codes used) in TOP contributing to the distinct substrate specificities, particularly with an isoleucine residue at P1. TOP Y605A was inhibited less efficiently by JA-2 {N-[1-(R,S)-carboxy-3-phenylpropyl]Ala-Aib-Tyr-p-aminobenzoate}, which suggested that the aromatic ring of Tyr605 was an important anchor for its interaction with wild-type TOP. The hydroxy groups of Tyr605 and Tyr606 did not contribute to the pH-activity profiles, since the pKs obtained in the assays of mutants TOP Y605F and NEL Y606F were similar to those of wild-type peptidases. However, the pH-kcat/Km dependence curve of TOP Y605A differed from that of wild-type TOP and from TOP Y606F. These results provide insights into the residues involved in the substrate specificities of TOP and NEL and how they select cytosolic peptides for hydrolysis.

Enzyme and integrin expression by high and low metastatic melanoma cell lines.

Dissemination of a malignant tumour is the result of a cascade of events beginning with detachment of cells from primary tumour followed by extravasation and growth at secondary sites. The differences in metastatic ability could be attributed to properties intrinsic to the various tumour types. Thus the clonal selection of tumour cells from successive metastases apparently results in cells better equipped for survival and formation of colonies in secondary sites, indicating that survival is not a random phenomenon. Many studies of malignant cells have correlated the overexpression of adhesion receptors such as integrins and the production of cysteine proteases and glycosidases with the progression of malignancy. The interaction of cysteine proteases with basement membrane components has been implicated in tumour invasion, activation of hormones and growth factors. On the other hand, the expression of the heparanase gene and its protein has been associated with the metastatic potential of several human and mouse tumour cell lines. This study aimed to investigate the correlations between the metastatic properties of clones with high and low metastatic potential and their ability to adhere to the extracellular matrix and to degrade proteins and sulphated glycosaminoglycans present there. Clonal selection of the B16F10 cell line was performed, and the clones were examined for the expression of an integrin-type laminin receptor. A significantly higher level was detected in a high metastatic clone. Enzymatic assays showed higher activity for alpha-d-N-acetylglucosaminidase, beta-d-N-acetylgalactosaminidase and beta-d-glucuronidase in conditioned medium from low metastatic clones compared with that from high metastatic clones. However, higher endopeptidase activity was observed in conditioned medium from high metastatic clones. In summary, these results showed a positive correlation between high metastatic potential and endopeptidase secretion. Similarly, a positive correlation was observed between low metastatic cells and the secretion of glycosaminoglycan-degrading glycosidases.

Proteinase activity regulation by glycosaminoglycans.

There are few reports concerning the biological role and the mechanisms of interaction between proteinases and carbohydrates other than those involved in clotting. It has been shown that the interplay of enzymes and glycosaminoglycans is able to modulate the activity of different proteases and also to affect their structures. From the large number of proteases belonging to the well-known protease families and also the variety of carbohydrates described as widely distributed, only few events have been analyzed more deeply. The term "family" is used to describe a group of proteases in which every member shows an evolutionary relationship to at least one other protease. This relationship may be evident throughout the entire sequence, or at least in that part of the sequence responsible for catalytic activity. The majority of proteases belong to the serine, cysteine, aspartic or metalloprotease families. By considering the existing limited proteolysis process, in addition to the initial idea that the proteinases participate only in digestive processes, it is possible to conclude that the function of the enzymes is strictly limited to the cleavage of intended substrates since the destruction of functional proteins would result in normal tissue damage. In addition, the location as well as the eventual regulation of protease activity promoted by glycosaminoglycans can play an essential role in the development of several physiopathological conditions.

Proteinase activity regulation by glycosaminoglycans

There are few reports concerning the biological role and the mechanisms of interaction between proteinases and carbohydrates other than those involved in clotting. It has been shown that the interplay of enzymes and glycosaminoglycans is able to modulate the activity of different proteases and also to affect their structures. From the large number of proteases belonging to the well-known protease families and also the variety of carbohydrates described as widely distributed, only few events have been analyzed more deeply. The term "family" is used to describe a group of proteases in which every member shows an evolutionary relationship to at least one other protease. This relationship may be evident throughout the entire sequence, or at least in that part of the sequence responsible for catalytic activity. The majority of proteases belong to the serine, cysteine, aspartic or metalloprotease families. By considering the existing limited proteolysis process, in addition to the initial idea that the proteinases participate only in digestive processes, it is possible to conclude that the function of the enzymes is strictly limited to the cleavage of intended substrates since the destruction of functional proteins would result in normal tissue damage. In addition, the location as well as the eventual regulation of protease activity promoted by glycosaminoglycans can play an essential role in the development of several physiopathological conditions

Comparison of the specificity, stability and individual rate constants with respective activation parameters for the peptidase activity of cruzipain and its recombinant form, cruzain, from Trypanosoma cruzi.

The Trypanosoma cruzi cysteine protease cruzipain contains a 130-amino-acid C-terminal extension, in addition to the catalytic domain. Natural cruzipain is a complex of isoforms, because of the simultaneous expression of several genes, and the presence of either high mannose-type, hybrid monoantennary-type or complex biantenary-type oligosacharide chains at Asn255 of the C-terminal extension. Cruzipain and its recombinant form without this extension (cruzain) were studied comparatively in this work. S2 to S2' subsite specificities of these enzymes were examined using four series of substrates derived from the internally quenched fluorescent peptide Abz-KLRFSKQ-EDDnp (Abz, ortho-aminobenzoic acid; EDDnp, N-(2,4-dinitrophenyl)-ethylenediamine). Large differences in the kinetic parameters were not observed between the enzymes; however, Km values were consistently lower for the hydrolysis of most of the substrates by cruzain. No difference in the pH-activity profile between the two enzymes was found, but in 1 m NaCl cruzipain presented a kcat value significantly higher than that of cruzain. The activation energy of denaturation for the enzymes did not differ significantly; however, a negative entropy value was observed for cruzipain denaturation whereas the value for cruzain was positive. We determined the individual rate constants (k1, substrate diffusion; k-1, substrate dissociation; k2, acylation; k3, deacylation) and the respective activation energies and entropies for hydrolysis of Abz-KLRFSKQ-EDDnp determining the temperature dependence of the Michaelis-Menten parameters kcat/Km and kcat as previously described [Ayala, Y.M. & Di Cera, E. (2000) Protein Sci. 9, 1589-1593]. Differences between the two enzymes were clearly detected in the activation energies E1 and E-1, which are significantly higher for cruzipain. The corresponding DeltaS1 and DeltaS-1 were positive and significantly higher for cruzipain than for cruzain. These results indicate the presence of a larger energy barrier for cruzipain relating to substrate diffusion and dissociation, which could be related to the C-terminal extension and/or glycosylation state of cruzipain.

Development of new heparin-like compounds and other antithrombotic drugs and their interaction with vascular endothelial cells

The anticlotting and antithrombotic activities of heparin, heparan sulfate, low molecular weight heparins, heparin and heparin-like compounds from various sources used in clinical practice or under development are briefly reviewed. Heparin isolated from shrimp mimics the pharmacological activities of low molecular weight heparins. A heparan sulfate from Artemia franciscana and a dermatan sulfate from tuna fish show a potent heparin cofactor II activity. A heparan sulfate derived from bovine pancreas has a potent antithrombotic activity in an arterial and venous thrombosis model with a negligible activity upon the serine proteases of the coagulation cascade. It is suggested that the antithrombotic activity of heparin and other antithrombotic agents is due at least in part to their action on endothelial cells stimulating the synthesis of an antithrombotic heparan sulfate.

Development of new heparin-like compounds and other antithrombotic drugs and their interaction with vascular endothelial cells.

The anticlotting and antithrombotic activities of heparin, heparan sulfate, low molecular weight heparins, heparin and heparin-like compounds from various sources used in clinical practice or under development are briefly reviewed. Heparin isolated from shrimp mimics the pharmacological activities of low molecular weight heparins. A heparan sulfate from Artemia franciscana and a dermatan sulfate from tuna fish show a potent heparin cofactor II activity. A heparan sulfate derived from bovine pancreas has a potent antithrombotic activity in an arterial and venous thrombosis model with a negligible activity upon the serine proteases of the coagulation cascade. It is suggested that the antithrombotic activity of heparin and other antithrombotic agents is due at least in part to their action on endothelial cells stimulating the synthesis of an antithrombotic heparan sulfate.