Temporal activity of plasminogen activators and matrix metalloproteinases during cutaneous wound repair

BACKGROUND

Response to tissue injury begins with the deposition of a fibrin-rich clot or the provisional matrix. The provisional matrix consists of plasma-borne matrix molecules that serve as scaffolding for the ensuing migration of cells. During wound repair multiple cell types must migrate through the clot-matrix scaffolding. The migration of these cells through the matrix is dependent on the activity of the fibrinolytic and proteolytic systems, which include the plasminogen activator (PA) system and matrix metalloproteinases (MMP). The aim of this study was to better understand the temporal activity of these enzymes during normal wound repair.

METHODS

We used the murine excisional wound model and extracted proteins under nonreducing conditions. With use of gelatin and casein zymography, we determined the activity of the MMPs during the course of wound repair. In addition, we quantified the activity of MMP-2 and MMP-9 by a standardized assay. Plasminogen zymograms were used to detect urokinase PA and tissue PA activity. Western blots were used to detect the natural inhibitor of PAs, plasminogen activator inhibitor type 1.

RESULTS

Our results demonstrate the temporal activity of MMP-2, MMP-3, MMP-7, and MMP-9 during the course of normal dermal repair. The activity of urokinase PA and tissue PA were also determined; it preceded the activity of the MMPs.

CONCLUSIONS

We demonstrate the temporal activity of the 2 protease families, MMPs and PAs, in the normal process of cutaneous wound healing.

Changes in matrix composition during the growth and regression of human hemangiomas

BACKGROUND

Hemangiomas offer an uncommon opportunity to study rapid vessel growth and spontaneous regression of a vascular human tumor. In contrast, venous malformations are another type of vascular tumor that grows slowly without spontaneous involution. Extracellular matrix (ECM) molecules modulate the responsiveness of endothelial cells to mitogenic stimuli such as basic fibroblast growth factor (bFGF), a well-recognized stimulant of angiogenesis. In this study we hypothesized that in hemangiomas, sites of angiogenesis may have a different ECM composition than sites of vascular regression.

MATERIALS AND METHODS

Using immunohistochemistry, we analyzed proliferating hemangiomas, regressing hemangiomas, venous malformations, and normal skin for the basement membrane ECM molecules collagen IV and laminin and plasma-borne ECM molecules fibronectin and vitronectin. We used metabolic labeling to determine whether primary human dermal microvascular endothelial cells regulated FGFR-1 or FGFR-2 when grown on these different matrices.

RESULTS

We found that proliferating hemangiomas showed extensive deposition of vitronectin in the subendothelial space. In contrast, regressing hemangiomas or venous malformations did not show vitronectin deposition. Venous malformations, which are composed of ectatic lakes of venous channels, also lacked laminin in their basement membranes. We also found that cultured microvascular endothelial cells grown on vitronectin increased synthesis of FGFR-1 and FGFR-2 protein.

CONCLUSIONS

Changes in the ECM environment occur in conjunction with the angiogenic state of a vascular human tumor. Furthermore, changes in the ECM environment alone can directly regulate synthesis of angiogenic growth factor receptors.

TIMP-1 contact sites and perturbations of stromelysin 1 mapped by NMR and a paramagnetic surface probe

Surfaces of the 173 residue catalytic domain of human matrix metalloproteinase 3 (MMP-3(DeltaC)) affected by binding of the N-terminal, 126 residue inhibitory domain of human TIMP-1 (N-TIMP-1) have been investigated using an amide-directed, NMR-based approach. The interface was mapped by a novel method that compares amide proton line broadening by paramagnetic Gd-EDTA in the presence and absence of the binding partner. The results are consistent with the X-ray model of the complex of MMP-3(DeltaC) with TIMP-1 (Gomis-Rüth et al. (1997) Nature 389, 77-81). Residues Tyr155, Asn162, Val163, Leu164, His166, Ala167, Ala169, and Phe210 of MMP-3(DeltaC) are protected from broadening by the Gd-EDTA probe by binding to N-TIMP-1. N-TIMP-1-induced exposure of backbone amides of Asp238, Asn240, Gly241, and Ser244 of helix C of MMP-3(DeltaC) to Gd-EDTA confirms that the displacement of the N-terminus of MMP-3(DeltaC) occurs not only in the crystal but also in solution. These results validate comparative paramagnetic surface probing as a means of mapping protein-protein interfaces. Novel N-TIMP-1-dependent changes in hydrogen bonding near the active site of MMP-3(DeltaC) are reported. N-TIMP-1 binding causes the amide of Tyr223 of MMP-3(DeltaC) bound by N-TIMP-1 to exchange with water rapidly, implying a lack of the hydrogen bond observed in the crystal structure. The backbone amide proton of Asn162 becomes protected from rapid exchange upon forming a complex with N-TIMP-1 and could form a hydrogen bond to N-TIMP-1. N-TIMP-1 binding dramatically increases the rate of amide hydrogen exchange of Asp177 of the fifth beta strand of MMP-3(DeltaC), disrupting its otherwise stable hydrogen bond.

Hydrogen exchange in the lipid bilayer-bound gramicidin channel

Hydrogen exchange experiments for a membrane-bound polypeptide could lead to interesting functional and structural insights. Here, hydrogen/deuterium exchange, saturation transfer and differential relaxation experiments have been performed on oriented lipid bilayer-bound polypeptide samples to measure the exchange lifetimes. The polypeptide, gramicidin A, forms a monovalent cation selective channel across membranes. The pH dependent results suggest that the indole N epsilon 1-H groups show base catalyzed hydrogen exchange, but that the backbone amide sites are not base catalyzed, consistent with the exclusion of anions from this channel. Furthermore, the recently described [1] orientational distribution of the individual peptide carbonyls (i.e. carbonyls either tipped slightly in toward or away from the channel axis) is consistent with the observed difference in odd- and even-numbered amide residue exchange lifetimes.

Conformational trapping in a membrane environment: a regulatory mechanism for protein activity?

Functional regulation of proteins is central to living organisms. Here it is shown that a nonfunctional conformational state of a polypeptide can be kinetically trapped in a lipid bilayer environment. This state is a metastable structure that is stable for weeks just above the phase transition temperature of the lipid. When the samples are incubated for several days at 68 degrees C, 50% of the trapped conformation converts to the minimum-energy functional state. This result suggests the possibility that another mechanism for functional regulation of protein activity may be available for membrane proteins: that cells may insert proteins into membranes in inactive states pending the biological demand for protein function.

Folding and characterization of the amino-terminal domain of human tissue inhibitor of metalloproteinases-1 (TIMP-1) expressed at high yield in E. coli

Methods are described for producing an active amino-terminal domain of tissue inhibitor of metalloproteinases-1 (N-TIMP-1) from inactive protein expressed as inclusion bodies in E. coli. Yields exceed 20 mg per litre of bacterial culture. Activity measurements, CD spectroscopy and NMR spectroscopy of the 15N-labeled protein show that it is fully active, homogeneous in conformation and suitable for high-resolution structural analysis. The affinity of N-TIMP-1 for matrix metalloproteinases 1, 2 and 3 is 6-8-fold less than that of the recombinant full-length protein, indicating that deletion of the C-terminal domain reduces the free energy of interaction by < 10%.

Solitary intracerebral plasmacytoma

Solitary extramedullary plasmacytomas are rare. Most of them are seen in the nasopharynx, upper respiratory tract, lamina propria of gastro-intestinal tract, lymph nodes, testicles and other soft tissues. So far only 20 such cases are reported in the literature. Here they arise from the dura, or from the periadventitial cells of intracranial vessels. Intracerebral plasmacytomas (ICPC) are extremely rare. Till 1982, Hensen and Urich could trace only 10 occurrences. Here the 11th case, probably the first Indian case report of the occurrence of a solitary plasmacytoma within the left temporal lobe of a 16 year old boy, is presented.

Surface charge effects upon membrane transport processes: the effects of surface charge on the monensin-mediated transport of lithium ions through phospholipid bilayers studied by 7Li-NMR spectroscopy

Addition of monensin to preparations of large unilamellar vesicles prepared from egg-yolk phosphatidylcholine (egg PC) or egg PC containing 5% phosphatidylserine (PS-) or cetylpyridinium (CP+) ions in lithium chloride solution allows the transport of Li+ ions to be monitored by an NMR magnetisation transfer technique. The kinetics of the transport are followed as a function of the metal ion and monensin concentrations and are compatible with a model in which one monensin molecule transports one Li+ ion. The data allow the extraction of the rate constants for the association and dissociation of the monensin-Li+ complex in the water/membrane interfaces and the evaluation of the stability constants for complex formation in the interfaces. Placing positive charge (CP+) on the membrane surface reduces the formation rate by a factor of about three but hardly alters the dissociation rate. Placing negative charge (PS-) on the membrane surface hardly alters the formation rate but speeds the dissociation rate by about a factor of three. Data from relaxation times of 7Li+ inside the vesicles and from the total enclosed volumes as the vesicles are formed, point to appreciable Li+ surface interactions that increase as the charge on the surface is made more negative. The size of the vesicles formed by the dialytic detergent removal technique increases with the surface charge. The results support a view that enzyme-phospholipid or substrate-phospholipid interactions could play an important role in determining the efficacity of action of membrane bound enzymes. The relevance of the results in the role of Li+ in the control of manic depression is also discussed.

The monensin-mediated transport of Na+ and K+ through phospholipid bilayers studied by 23Na- and 39K-NMR

Addition of monesin to preparations of large unilamellar vesicles made from egg yolk phosphatidylcholine (EPC) in sodium or potassium chloride solution and from dioleoylphosphatidylcholine (DOPC) in sodium chloride solutions gives rise to dynamic 23Na- and 39K-NMR spectra. The dynamic spectra arise from the monensin-mediated transport of the metal ions through the membrane. The kinetics of the transport are followed as a function of monensin and metal ion concentrations and are compatible with a model in which one monensin molecule transports one metal ion. Rate constants for the association and dissociation of the monensin-metal complex in the membrane/water interface are extracted and the stability constants for complex formation are evaluated. The rate constants in DOPC are similar to those in EPC, confirming that diffusion is not rate-limiting in the transport process and that dissociation of the complex is the rate-limiting step. Although potassium on its own is transported more rapidly, sodium forms the more stable complex and is therefore transported preferentially in competition with potassium.

Nuclear magnetic resonance spectra of oriented bicyclic systems containing heteroatom(s): the spectrum of 2-thiocoumarin

From the proton nmr studies of 2-thiocoumarin and coumarin, it is concluded that the relative interproton distances in the two oxygen heteroatom bicyclic systems are similar. The values for the phenyl ring protons do not deviate significantly from the regular hexagonal geometry, unlike bicyclic systems with nitrogens as the heteroatoms, such as diazanaphthalenes. Larger values of the indirect spin–spin couplings within the protons of the ring containing the oxygen heteroatom, compared to the values between the ortho protons in the phenyl rings in coumarin and 2-thiocoumarin, correspond to the olefinic nature of these protons. This is in contrast to results for the nitrogen heterocycles where both the rings are aromatic.

Streptomyces Somalinesiscausing Mycetomas in South India

Biopsy specimens from 102 patients with mycetoma were examined histologically; Streptomyces somaliensis was found in 5 cases. The clinical features, radiology and histology of actinomycotic mycetoma due to S. somaliensis ar ' e described. The geographic distribution of the organism, its incidence and prevalence in India and the importance of histological examination in the diagnosis of the infection are discussed.

Correlated clinical, histopathological, HBV and AFP studies of primary carcinoma liver

This paper presents the clinical and histopathological features of 221 Primary Carcinoma Liver studied over the last eight years. HBsAg studies were carried out in 93, AFP studies in 87 and both HBsAg and AFP in the same serum samples in 78. HBsAg positivity rate by CIEP was 29% and AFP positivity was 52%. There appears to be greater AFP posivity in HBsAg positive group compared to HBsAg negative group. Correlation of cell type with AFP positivity reveals significant greater positivity in clear type. The need for indepth studies to use morphological appearances of cancer cells as simple marker of altered function is suggested. Anti e was positive in 40% of HBsAg positive cases studied for e system, while e antigen was positive in 32%. A very unusual finding of e antigen and Anti e present at the same time in a patient with primary liver carcinoma is documented.

Nocardia species from bronchopulmonary infections and mycetomas

350 specimens comprising sputum, bronchial aspirate, pleural fluid, pus and biopsy material were investigated for the presence of Nocardia spp. by the paraffin bait technique. Nocardia spp. were isolated in 15 of them. The physiological and morphological characteristics of the organisms and the use of paraffin baiting, a selective technique for isolating Nocardia spp. from clinical specimens, are discussed.