In situ localization and characterization of active proteases in chronically inflamed and healthy human gingival tissues

Zebrafish lipid metabolism: from mediating early patterning to the metabolism of dietary fat and cholesterol

Lipids serve essential functions in cells as signaling molecules, membrane components, and sources of energy. Defects in lipid metabolism are implicated in a number of pandemic human diseases, including diabetes, obesity, and hypercholesterolemia. Many aspects of how fatty acids and cholesterol are absorbed and processed by intestinal cells remain unclear and present a hurdle to developing approaches for disease prevention and treatment. Numerous studies have shown that the zebrafish is an excellent model for vertebrate lipid metabolism. In this chapter, we review studies that employ zebrafish to better understand lipid signaling and metabolism.

A new model system swims into focus: using the zebrafish to visualize intestinal metabolism in vivo

Many fundamental questions remain regarding the cellular and molecular mechanisms of digestive lipid metabolism. One major impediment to answering important questions in the field has been the lack of a tractable and sufficiently complex model system. Until recently, most studies of lipid metabolism have been performed in vitro or in mice, yet each approach possesses certain limitations. The zebrafish (Danio rerio) offers an excellent model system in which to study lipid metabolism in vivo, owing to its small size, genetic tractability and optical clarity. Fluorescent lipid dyes and optical reporters of lipid-modifying enzymes are now being used in live zebrafish to generate visible readouts of digestive physiology. Here we review recent advances in visualizing intestinal lipid metabolism in live larval zebrafish.

In vivo imaging of zebrafish digestive organ function using multiple quenched fluorescent reporters

Optical clarity of larvae makes the zebrafish ideal for real-time analyses of vertebrate organ function through the use of fluorescent reporters of enzymatic activities. A key function of digestive organs is to couple the generation of enzymes with mechanical processes that enable nutrient availability and absorption. However, it has been extremely difficult, and in many cases not possible, to directly observe digestive processes in a live vertebrate. Here we describe a new method to visualize intestinal protein and lipid processing simultaneously in live zebrafish larvae using a quenched fluorescent protein (EnzChek) and phospholipid (PED6). By employing these reagents, we found that wild-type larvae exhibit significant variation in intestinal phospholipase and protease activities within a group but display a strong correlation between the activities within individuals. Furthermore, we found that pancreas function is essential for larval digestive protease activity but not for larval intestinal phospholipase activity. Although fat-free (ffr) mutant larvae were previously described to exhibit impaired lipid processes, we found they also had significantly reduced protease activity. Finally, we selected and evaluated compounds that were previously suggested to have altered phospholipase activity and are known or suspected to have inflammatory effects in the intestinal tract including nonsteroidal anti-inflammatory drugs, and identified a compound that significantly increases intestinal phospholipid processing. Thus the multiple fluorescent reporter-based methodology facilitates the rapid analysis of digestive organ function in live zebrafish larvae.

Matrix metalloproteinase levels in children with aggressive periodontitis

BACKGROUND

Matrix metalloproteinases (MMPs) are a family of host-derived proteinases reported to mediate multiple functions associated with periodontal destruction and inflammation. Most of the existing data have been gathered from adults with chronic periodontitis. The purpose of this study was to determine the MMP levels in a cohort of African American children with and without aggressive periodontitis.

METHODS

Gingival crevicular fluid (GCF) was collected in a cohort of 44 African American children, 7 to 19 years of age, with and without aggressive periodontitis (AgP) and compared to healthy unrelated children and to adults with chronic periodontitis (CP). GCF volume was determined with a calibrated gingival fluid meter. The samples were assayed for MMP-1, -2, -3, -8, -9, -12, and -13 using fluorimetric substrates.

RESULTS

The MMP levels from diseased sites in the subjects with AgP were statistically higher (P <0.05) in almost all instances than those associated with the unrelated controls or with the subjects with CP. MMP-8 was significantly elevated in the diseased sites of the children with AgP relative to non-diseased sites in the same children (P = 0.002), as well as the siblings, non-diseased controls, and subjects with CP (P < or =0.0001). There was no positive correlation between probing depth and any MMP level.

CONCLUSIONS

MMP levels were elevated in AgP sites relative to non-diseased sites in the same subjects, in siblings, and in unrelated controls. MMPs associated with the AgP sites in children were generally elevated compared to an adult cohort with a history of CP.

The MMP activity in developing rat molar roots and incisors demonstrated by in situ zymography

Matrix metalloproteinases (MMPs) have been expressed during root development and periodontal tissue formation, whereas it is not known if these MMP molecules are enzymatically active to degrade the extracellular matrices (ECMs). The present study was designed to investigate the gelatinolytic and collagenolytic activity in rat molar root and incisor development. Three-week old rat mandibles were frozen and cut without fixation or decalcification and processed for in situ zymography using substrates gelatin and collagen. The enzymatic activity was assessed according to the intensity of fluorescence due to the lysis of the substrates. Odontoblasts, predentin, cementum, bone and the enamel matrix showed the high activity. The present study demonstrated MMP activity in calcified tissues using in situ zymography for the first time and the possible involvement of the MMP activity in molar root and incisor development and periodontal tissue formation.

Joint and bone disease in mucopolysaccharidoses VI and VII: identification of new therapeutic targets and biomarkers using animal models

The mucopolysaccharidoses (MPS) are inherited metabolic disorders resulting from the defective catabolism of glycosaminoglycans. In this report, we find that the stimulation of MPS connective tissue cells by the inflammatory cytokines causes enhanced secretion of several matrix-degrading metalloproteinases (MMPs). In addition, expression of tissue inhibitor of metalloproteinase-1 was elevated, consistent with the enhanced MMP activity. These findings were not restricted to one particular MPS disorder or species, and are consistent with previous observations in animal models with chemically induced arthritis. Bromodeoxyuridine incorporation studies also revealed that MPS chondrocytes proliferated up to 5-fold faster than normal chondrocytes, and released elevated levels of transforming growth factor-beta, presumably to counteract the marked chondrocyte apoptosis and matrix degradation associated with MMP expression. Despite this compensatory mechanism, studies of endochondral ossification revealed a reduction in chondro-differentiation in the growth plates. Thus, although MPS chondrocytes grew faster, most of the newly formed cells were immature and could not mineralize into bone. Our studies suggest that altered MMP expression, most likely stimulated by inflammatory cytokines and nitric oxide, is an important feature of the MPS disorders. These data also identify several proinflammatory cytokines, nitric oxide, and MMPs as novel therapeutic targets and/or biomarkers of MPS joint and bone disease. This information should aid in the evaluation of existing therapies for these disorders, such as enzyme replacement therapy and bone marrow transplantation, and may lead to the development of new therapeutic approaches.

Proteinase Activity in Human and Murine Saliva as a Biomarker for Proteinase Inhibitor Efficacy

As molecularly targeted agents reach the clinic, there is a need for assays to detect their presence and effectiveness against target molecules in vivo. Proteinase inhibitors are one example of a class of therapeutic agent for which satisfactory methods of identifying successful target modulation in vivo are lacking. This is of particular importance while these drugs are in clinical trials because standard maximum-tolerated dose-finding studies often are not suitable due to lack of toxicity. Saliva represents a readily accessible bodily fluid that can be repeatedly sampled and used for assaying in vivo effects of systemic drugs. Here we show the development of a simple assay that can be used to measure proteinase activity in saliva and proteinase inhibition after systemic treatment with three different proteinase inhibitors. A variety of gelatinolytic activities present in human and murine saliva have been assayed with a fluorescent dye-labeled substrate and assigned to different proteinase categories by inclusion of specific classes of inhibitors. Treatment of mice with either matrix metalloproteinase inhibitors or a urokinase inhibitor for a period as short as 48 hours results in levels of the drugs that can be detected in saliva by mass spectrometry and concomitant decreases in salivary proteinase activity, thus demonstrating that these inhibitors successfully modulate their targets in vivo.

Gelatinase activity in synovial fluid and synovium obtained from healthy and osteoarthritic joints of dogs

OBJECTIVE

To determine matrix metalloproteinase (MMP) activity in synovial fluid (SF) obtained from the joints of dogs with degenerative joint disease (DJD) secondary to various underlying conditions.

SAMPLE POPULATION

35 samples of SF obtained from 18 clinically normal (control) dogs and 34 samples of SF obtained from 17 dogs with DJD; dogs with DJD were from 2 populations (client-owned dogs and research dogs that had DJD secondary to the lysosomal storage disease mucopolysaccharidosis VII).

PROCEDURE

MMP activity in samples of SF was semiquantitatively examined by use of gelatin or casein zymography. Western blot analysis was performed by use of antibodies for MMP-2 and MMP-9. In addition, in situ MMP activity was observed in sections of synovial membrane obtained from healthy and osteoarthritic joints.

RESULTS

Samples of SF from osteoarthritic joints had higher MMP-2 activity and dramatically increased MMP-9 activity, compared with values for healthy joints. Substrate-overlay analyses indicated minimal gelatin-degrading activity in synoviocytes obtained from control dogs, whereas greater activity was seen in osteoarthritic synoviocytes, with additional activity in the underlying tissue.

CONCLUSIONS AND CLINICAL RELEVANCE

Higher MMP-2 activity and dramatic increases in MMP-9 activity were associated with the osteoarthritic state, even though MMP-2 activity was detected in healthy joints. This study expands information on MMP production in SF of osteoarthritic joints in other species and documents the similarity of MMP activity patterns regardless of the cause of DJD.

In vivo localization of gelatinases (MMP-2 and -9) by in situ zymography with a selective gelatinase inhibitor

In situ zymography provides a tool to localize proteolytic activity in tissues in vivo. However, it has been difficult to discriminate between the proteases responsible for the detected activity. We used a selective tissue-permeable gelatinase inhibitor, the CTTHWGFTLC-peptide (CTT) in inflamed human gingiva. The CTT-peptide was evidenced to home, target to, and selectively inhibit the areas of gelatinolytic activity in inflamed human gingiva expressing MMP-2 and -9. Gelatinolytic activity, MMP-9 immunoreactivity, and mRNA expression as well as CD-45-positive inflammatory cells colocalized well in the inflamed human gingival connective tissue. Gelatinolytic activity corresponding to MMP-2 colocalized with laminin-5 gamma2-chain immunoreactivity and was detected in the close vicinity of the sulcular basement membrane region. Furthermore, the CTT-peptide inhibited beta-caseinolysis by human MMP-2 and MMP-9 as well as laminin-5 gamma2-chain degradation by MMP-2 in vitro. Thus, the CTT-peptide may prove to be a useful tool (i) to discriminate between gelatinolytic proteases detected by in situ zymography and (ii) to preventMMP-2-dependent induction of epithelial cell migration and gelatinase-dependent tissue destruction in inflammatory and malignant diseases.