Altered tumor growth and metastasis of a T-cell lymphoma in Timp-1 transgenic mice

The concept of tumor suppression by tissue inhibitor of metalloproteinases (TIMPs) has evolved primarily from studies of genetically modulated tumor cells. The next step is to focus on the host and assess the protective potential of host TIMP-1 on primary tumor growth and metastasis. We generated two transgenic mouse lines with altered Timp-1 expression in skin and liver: one overexpressed Timp-1 (Timp-1(high)), and the other had antisense RNA-mediated Timp-1 reduction (Timp-1(low)). ESbL-lacZ T-lymphoma cells provided the tumor challenge, as they form primary tumors upon intradermal injection with spontaneous metastasis to liver. Metastases were examined in X-Gal-stained whole-organ mounts. Timp-1 overexpression inhibited intradermal tumor growth and spontaneous metastasis, leading to prolonged survival of the mice. The opposite effects occurred in Timp-1(low) mice, leading to shorter host survival. Experimental metastasis assays showed that Timp-1-compromised livers in Timp-1(low) mice showed at least a doubling of metastatic foci and numerous additional micrometastases, indicative of increased host susceptibility. However, Timp-1(high) mouse livers showed an unaltered metastatic load in the experimental metastasis assay. In conclusion, these data demonstrate that Timp-1 levels within a tissue predetermine the development and progression of T-cell lymphoma.     

Production of tissue inhibitor of metalloproteinases-1 (TIMP-1) by human astrocytic tumors

Production of tissue inhibitor of metalloproteinases-1 (TIMP-1), a specific inhibitor of matrix metalloproteinases, was investigated in human astrocytic tumors (n = 15) and normal brain tissues (n = 3). Enzyme immunoassay indicated that TIMP-1 levels in the culture media of tumor explants were significantly higher in glioblastomas as compared with anaplastic astrocytomas, astrocytomas, and normal brain tissues. Immunohistochemistry using a monoclonal antibody against TIMP-1 demonstrated that TIMP-1 was detectable mainly in tumor cells, especially in glioblastoma. These results suggest that increased expression of TIMP-1 is associated with the malignant progression of astrocytic tumors.     

The natriuretic activity of the K+ channel blocker U-37883A displays an ADH-dependence

Tissue inhibitors of metalloproteinases (TIMPs) prevent uncontrolled connective tissue destruction by limiting the activity of matrix metalloproteinases (MMPs). That TIMPs should be susceptible to oxidative inactivation is suggested by their complex tertiary structure which is dependent upon 6 disulphide bonds. We examined the oxidative inactivation of human recombinant TIMP-1 (hr TIMP-1) by HOCl and the inhibition of this process by anti-rheumatic agents. TIMP-1 was exposed to HOCl in the presence of a variety of disease modifying anti-rheumatic drugs. TIMP-1 activity was measured by its ability to inhibit BC1 collagenase activity as measured by a fluorimetric assay using the synthetic peptide substrate (DNP-Pro-Leu-Ala-Leu-Trp-Ala-Arg), best cleaved by MMP-1. The neutrophil derived oxidant HOCl, but not the derived oxidant N-chlorotaurine, can inactivate TIMP-1 at concentrations achieved at sites of inflammation. Anti-rheumatic drugs have the ability to protect hrTIMP-1 from inactivation by HOCl. For D-penicillamine, this effect occurs at plasma levels achieved with patients taking the drug but for other anti-rheumatic drugs tested this occurs at relatively high concentrations that are unlikely to be achieved in vivo, except possibly in a microenvironment. These results are in keeping with the concept that biologically derived oxidants can potentiate tissue damage by inactivating key but susceptible protein inhibitors such as TIMP-1 which form the major local defence against MMP induced tissue breakdown.     

Differential expression of matrix metalloproteinase and tissue inhibitor of matrix metalloproteinase genes in the mouse central nervous system in normal and inflammatory states

Matrix metalloproteinases (MMPs) are implicated in the pathogenesis of inflammatory disorders of the central nervous system (CNS) whereas the contribution of the major endogenous counter-regulators of MMPs, the tissue inhibitors of the matrix metalloproteinases (TIMPs), is unclear. We investigated the temporal and spatial expression patterns in the CNS of nine MMP genes and three TIMP genes in normal mice, in mice with EAE, and in transgenic mice with astrocyte (glial fibrillary acidic protein)-targeted expression of the cytokines interleukin-3 (macrophage/microglial demyelinating disease), interleukin-6 (neurodegenerative disease), or tumor necrosis factor-alpha (lymphocytic encephalomyelitis). In normal mice, the MMPs MT1-MMP, stromelysin 3, and gelatinase B were expressed at low levels, whereas high expression of TIMP-2 and TIMP-3 was observed predominantly in neurons and in the choroid plexus, respectively. In EAE and the transgenic mice, significant induction or up-regulation of various MMP genes was observed, the pattern of which was somewhat specific for each of the models, and there was significant induction of TIMP-1. In situ localization experiments revealed a dichotomy between MMP expression that was restricted to leukocytes and possibly microglia within inflammatory lesions and TIMP-1 expression that was observed in activated astrocytes circumscribing the lesions. These findings demonstrate specific spatial and temporal regulation in the expression of individual MMP and TIMP genes in the CNS in normal and inflammatory states. The distinct localization of TIMP-1 and MMP expression during CNS inflammation suggests a dynamic state in which the interplay between these gene products may determine both the size and resolution of the destructive inflammatory focus.     

High levels of messenger RNAs for tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) in primary breast carcinomas are associated with development of distant metastases

Tissue inhibitors of metalloproteinases (TIMPs) are believed to possess several cellular functions, particularly the contrasting activities of inhibiting tissue-degrading enzymes and promoting cellular growth. In attempts to elucidate which of these functions may prevail in breast cancer, expression of mRNAs for TIMP-1 and TIMP-2 in the primary carcinomas from 34 breast cancer patients was related to known prognostic parameters and the clinical outcome. High levels of TIMP-1 mRNA showed significant correlation with the presence of lymph node metastases (P = 0.0067), development of distant metastases (P = 0.014), and early death of the disease (P = 0.020). Elevated expression of TIMP-2 mRNA was associated with development of distant metastases (P = 0.0055). No correlations, however, were observed between mRNA levels of TIMPs and prognostic factors such as patient age, tumor size, grade of anaplasia, or steroid receptor status; neither were any correlations found between these clinicopathological characteristics and the mRNA expression of the collagenolytic enzymes matrix metalloproteinase-2 and matrix metalloproteinase-9. The present data suggest that high levels of TIMP-1 and TIMP-2 mRNAs in the primary carcinomas are strongly associated with development of metastasis in breast cancer.     

Epithelial cells up-regulate matrix metalloproteinases in cells within the same mammary carcinoma that have undergone an epithelial-mesenchymal transition

A metastatic rat mammary carcinoma cell line, BC1, contains cells that have retained epithelial differentiation characteristics and metaplastic cells that have undergone an epithelial-mesenchymal transition. These two subpopulations cooperate to degrade collagen. We have used novel PCR assays to quantitate, for the first time, absolute levels of the mRNAs encoding matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in cell and tumor samples. BC1 tumors expressed high levels of the collagenase-3, TIMP-2, stromelysin-1, and gelatinase B genes and low levels of the stromelysin-2 and TIMP-1 genes. This pattern of expression was repeated in cultures of BC1 and cultures containing mixed clones of epithelial cells and metaplastic cells. In both BC1 and the biclonal cultures, metaplastic cells were the main source of collagenase-3, stromelysin-1 and stromelysin-2, whereas TIMPs were equally distributed and epithelial cells were the main source of gelatinase B. High levels of all four MMP mRNAs in metaplastic cells were dependent on coculture with epithelial cells, suggesting the production of an inducing factor by the epithelial cells. In contrast, gelatinase B mRNA was produced at a high level by epithelial cells in the absence of metaplastic cells. TIMP-2 mRNA was abundant in both subpopulations grown alone and did not change substantially upon coculture. Thus, the interclonal cooperativity to degrade collagen in BC1 cells required the induction of MMPs in metaplastic cells by epithelial cells. Interclonal cooperativity may be important to the progression of neoplastic tumors, a feature of which is phenotypic heterogeneity.     

Increased expression of matrix metalloproteinases in vivo in scleritis tissue and in vitro in cultured human scleral fibroblasts

Scleritis is a sight-threatening inflammatory disorder of the eye characterized by the degradation of scleral matrix. Matrix metalloproteinases (MMPs) are ubiquitous proteolytic enzymes important in physiological and pathological processes, the activity of which is stringently controlled by the action of a family of natural antagonists, the tissue inhibitors of matrix metalloproteinases (TIMPs). We hypothesized that enhanced expression of MMPs, without the negative regulatory influence of TIMPs, may be a key feature of tissue destruction in inflammatory eye diseases, such as scleritis. The aim of this study was to localize and characterize cells expressing MMPs and TIMPs in sclera affected by necrotizing scleritis and, in a parallel study, to establish whether cytokines modulate MMP expression in cultured human scleral fibroblasts. In situ hybridization and immunohistochemical analyses indicated that resident scleral fibroblasts as well as inflammatory cells such as macrophages and T lymphocytes express stromelysin, gelatinase B, and TIMP-1 in necrotizing scleritis tissue. In addition, cytoplasmic immunoreactivity for tumor necrosis factor-alpha, an inducer of MMPs, was detected in infiltrating inflammatory cells. Cultured scleral fibroblasts stimulated with the combination of interleukin-1 alpha plus tumor necrosis factor-alpha increased TIMP-1 mRNA twofold above constitutive levels. By contrast, these cytokines induced a sevenfold increase in the steady-state levels of stromelysin mRNA. Using Western blotting, stromelysin and TIMP-1 protein production paralleled mRNA induction in cytokine-stimulated human scleral fibroblasts. Culture supernatants harvested from cytokine-stimulated human scleral fibroblasts were subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis gelatin substrate zymography. Our results revealed a prominent 92-kd gelatinolytic band corresponding to gelatinase B, which was inducible with interleukin-1 alpha. These data provide evidence for our hypothesis, that an imbalance between enzyme/inhibitor ratios may be the underlying mechanism of the tissue destruction characteristic of scleritis. Our results demonstrate the potential involvement of MMPs and their modulation by cytokines produced by infiltrating inflammatory cells in destructive ocular inflammation.     

IL-10 inhibition of human prostate PC-3 ML cell metastases in SCID mice: IL-10 stimulation of TIMP-1 and inhibition of MMP-2/MMP-9 expression

The molecular mechanism by which IL-10 inhibits metastases was examined using a SCID mouse model. Human PC-3 ML subclones normally metastasize to the lumbar vertebrae (approximately 70% mice injected, n = 14/20) following intravenous injection in severe combined immunodeficient (SCID) mice. IL-10 treatment of the PC-3 ML cells (15 ng/ml for 36 h) and the SCID mice (0.03 mg/kg/day for 30 days) reduced the number of metastases to 5% of the mice (n = 1/20). More importantly, following discontinuation of IL-10 treatment on day 30, the mice remained tumor-free and mouse survival rates increased dramatically (from < 30% in untreated mice) to about 85% in IL-10-treated mice. IL-10 did not appear to alter the growth rates or colony-forming ability of the PC-3 ML cells in vitro. Likewise, the growth of subcutaneous tumors and established bone marrow metastases was not inhibited by IL-10 treatment of the SCID mice. However IL-10 may inhibit the production of matrix metalloproteases (MMP) and prevent the establishment of metastasis. We therefore examined the influence of IL-10 on PC-3 ML production of MMP-2/MMP-9 and the tissue inhibitors of metalloproteinases (TIMP-1/2). Enzyme-linked immunosandwich assays (ELISAs) revealed that IL-10 (15 ng/ml for 36 h) treatment of the PC-3 ML cells down-regulated MMP-2 and MMP-9 while up-regulating TIMP-1 (not TIMP-2) expression. Likewise, IL-10-treated mice exhibited similar changes in TIMP-1 and MMP-2/MMP-9 expression. The IL-10 effects were blocked by IL-10 receptor antibodies. In comparison to IL-10, IL-4 failed to influence metastasis or the expression of TIMP-1, TIMP-2, MMP-2 and MMP-9 by PC-3 ML cells. We suggest that IL-10-regulated increases in the molar ratio of TIMP-1/MMP-9 and TIMP-2/MMP-2 might inhibit processes critical to the establishment of bone marrow metastasis.     

Expression of the tissue metalloproteinase inhibitors TIMP-1 and TIMP-2 in malignant fibrous histiocytomas and dermatofibromas as studied by in situ hybridization and immunohistochemistry

The expression of tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) was studied in eight malignant fibrous histiocytomas (MFH) and in eight dermatofibromas (DF) using in situ hybridization methods (ISH). Immunohistochemical stainings were also performed using corresponding antibodies to TIMP-1 and TIMP-2. In ISH the neoplastic cells of MFHs showed a high level of expression for both TIMP-1 and TIMP-2 mRNAs. The cells usually expressed similarly both TIMPs, except for osteoclast-like giant cells, which showed a distinct signal for TIMP-2 but not for TIMP-1. A distinctly lower level of both TIMP-1 and TIMP-2 mRNAs was seen in DFs. Immunohistochemical stainings were concordant with the results obtained by ISH. The findings suggest that the behavior of MFHs and DFs is not directly or solely dependent on the quantity of type IV collagenase inhibitors. The increased TIMP synthesis in MFHs might represent a chaotic response of malignant cells to increased matrix degradation. Alternatively, it may reflect a deranged communication between type IV collagenases and TIMPs in malignant tissues.     

Immunohistochemistry of matrix metalloproteinases (MMP), their substrates, and their inhibitors (TIMP) during trophoblast invasion in the human placenta

The invasion of extravillous trophoblast cells into the maternal endometrium is one of the key events in human placentation. The ability of these cells to infiltrate the uterine wall and to anchor the placenta to it as well as their ability to infiltrate and to adjust utero-placental vessels to pregnancy depends, among other things, on their ability to secrete enzymes that degrade the extracellular matrix. Most of the latter enzymes belong to the family of matrix metalloproteinases. Their activity is regulated by the tissue inhibitors of matrix metalloproteinases. We have studied the distribution patterns of matrix metalloproteinases-1, -2, -3, and -9 and their inhibitors TIMP-1 and TIMP-2 as compared to the distribution of their substrates along the invasive pathway of extravillous trophoblast of 1st, 2nd, and 3rd trimester placentas by means of light microscopy on paraffin and cryostat sections as well as at the ultrastructural level (only 3rd trimester placenta). The comparison of different methods proved to be necessary, since the immunohistochemical distribution patterns of these soluble enzymes are considerably influenced by the pretreatment of tissues. All three methods revealed immunoreactivities of both, proteinases and their inhibitors, not only intracellularly in the extravillous trophoblast but also extracellularly in its surrounding matrix, the distribution patterns depending on the stage of pregnancy and on the degree of differentiation of trophoblast cells along their invasive pathway. Within the extracellular matrix, immunolocalization of matrix metalloproteinases as well as their inhibitors showed a specific relation to certain extracellular matrix molecules.     

Elevated tissue inhibitor of metalloproteinase 1 RNA in colorectal cancer stroma correlates with lymph node and distant metastases

Tissue inhibitor of metalloproteinase (TIMP) inhibits the proteolytic activity of several matrix metalloproteinases centrally involved in tumor invasion and metastases. The purpose of this study was to determine the origin of TIMP-1 mRNA production in both human colorectal cancer (CRC) and metastatic liver lesions as well as define the relationships between TIMP-1 RNA expression and standard clinicopathological variables of CRC. Total cellular RNA, extracted from 56 CRC and 10 liver metastases, were examined by Northern blot hybridization. The mean/normal mucosa fold increase of TIMP-1 RNA was significantly elevated in both CRC (12.1 +/- 1.7) and liver metastases (10.0 +/- 3.6). No relationship was noted between TIMP-1 expression and tumor size, location nor differentiation. Based on lymph node metastases status, significantly higher TIMP-1 RNA levels were found in CRC with metastases than in those without metastases (15.6 +/- 3.3 versus 7.9 +/- 1.3) (P = 0.04). Similarly, TIMP-1 RNA levels were higher in primary CRC with distant metastases than those without distant metastases (17.6 +/- 4.1 versus 9.3 +/- 1.9) (P = 0. 04). In situ hybridization localized TIMP-1 mRNA predominantly in tumor stroma within spindle fibroblast-like cells rather than in cancer cells themselves. The correlation between the increased TIMP-1 mRNA level and advanced CRC stage noted in this study reflects a possible growth-promoting function for TIMP-1 in human CRC.     

Sputum metalloproteinase-9/tissue inhibitor of metalloproteinase-1 ratio correlates with airflow obstruction in asthma and chronic bronchitis

Asthma and chronic bronchitis are inflammatory diseases with extracellular matrix (ECM) remodeling and collagen deposition. Collagen homeostasis is controlled by metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). We evaluated MMP and TIMP balance in induced sputum of 10 control, 31 untreated asthmatic, and 16 chronic bronchitic subjects. We first performed zymographic analysis to identify the profile of MMPs. Zymography revealed a similar MMPs profile in all populations studied and that MMP-9 was the major enzyme released. We then measured, using enzyme immunoassay, the concentrations of MMP-9 and of its inhibitor TIMP-1 and evaluated whether airflow limitation may be associated with an imbalance between these enzymes. MMP-9 and TIMP-1 concentrations were greater in sputum of patients with asthma and chronic bronchitis than in control subjects. The molar ratio between MMP-9 and TIMP-1 was lower in asthmatics and chronic bronchitics than in control subjects, and positively correlated with FEV1 values. In asthma, MMP-9 levels were significantly correlated with the number of macrophages and neutrophils. This study shows that airway inflammation in asthma and chronic bronchitis is associated with an imbalance between MMP-9 and TIMP-1 which may have a role in the pathogenesis of ECM remodeling and airflow obstruction.     

Autocrine regulation of matrix metalloproteinase-9 gene expression and secretion by tumor necrosis factor-alpha (TNF-alpha) in NB4 leukemic cells: specific involvement of TNF receptor type 1

Matrix metalloproteinases have been reported to be involved in tumor cell invasion and metastasis. Dissemination of malignant cells in acute myeloid leukemia (AML) may be mediated by similar mechanisms. Here, we report, that the t(15/17)+ acute promyelocytic leukemia (APL) cell line NB4 constitutively expresses and releases the proenzyme form of matrix metalloproteinase-9 (MMP-9, 92 kDa type IV collagenase/gelatinase, gelatinase B), as well as tissue inhibitor of metalloproteinases-1 (TIMP-1). Both proteins were identified by N-terminal amino acid sequence analysis after purification using gelatin Sepharose affinity chromatography. Whereas 12-O-tetradecanoylphorbol-13 acetate (TPA) increased both MMP-9 and TIMP-1 mRNA levels, tumor necrosis factor-alpha (TNF-alpha) stimulated only MMP-9 gene expression in a dose- and time-dependent manner. Neutralizing monoclonal antibodies (MoABs) to TNF-alpha (anti-TNF-alpha) decreased the constitutive and TPA-dependent expression of MMP-9 but did not influence TIMP-1 expression, either in unstimulated or in TPA-treated NB4 cells. FACS analyses showed that NB4 cells express both TNF receptor 1 (TNF-R1) and TNF-R2 to a similar extent. Blocking MoABs against TNF-R 1 (anti-TNF-R1) decreased the constitutive expression of MMP-9, whereas anti-TNF-R2 had almost no effect. Our results show, that in NB4 cells the expression of MMP-9 but not of TIMP-1 is maintained by autocrine stimulation with TNF-alpha. Thus, leukemic cells may be enabled to leave the bone marrow and infiltrate peripheral tissues by a dysfunction in the regulation of the MMP-9:TIMP-1 equilibrium, possibly triggered through autostimulation by TNF-alpha.     

Expression of gelatinase A and its activator MT1-MMP in the inflammatory periprosthetic response to polyethylene

Wear debris of polyethylene prosthetic components is known to induce a host granulomatous reaction which recruits numerous macrophages and multinucleated giant cells. By releasing cellular mediators of a nonspecific inflammatory reaction, activated phagocytic cells are thought to play a key role in osteolysis leading to aseptic loosening of the prosthesis. Matrix metalloproteinases (MMPs) have been implicated in this destructive process by their ability to degrade extracellular matrix components of bone and adjacent connective tissue. To investigate the roles of gelatinase A, its activator MT1-MMP, and the MMP inhibitors TIMP-1 and TIMP-2 in aseptic loosening of polyethylene prostheses, immunohistochemistry (IHC) and in situ hybridization (ISH) were performed on periprosthetic pseudosynovial interface tissues. Gelatinase A and MT1-MMP were strongly detected immunohistochemically in macrophages and multinucleated giant cells in contact with polyethylene wear debris. In contrast to MT1-MMP, gelatinase A mRNAs were not found in phagocytic cells but in surrounding fibroblasts, thereby suggesting cooperation between macrophages and fibroblasts in this process. While TIMP-1 was expressed essentially in hyperplastic pseudosynoviocytes as assessed by IHC and ISH, TIMP-2, MT1-MMP, and gelatinase A were colocalized in phagocytic cells. These data support the concept of progelatinase A activation involving a trimolecular complex (MT1-MMP-TIMP-2-gelatinase A) mechanism. Thus, this study demonstrated that gelatinase A and its activator might contribute to the aseptic loosening of polyethylene prostheses.     

Production of matrix metalloproteinases at the bone-implant interface in loose total hip replacements

BACKGROUND: Incidence of aseptic loosening of hip prostheses is increasing in recent years. Previous studies suggested involvement of proteinases and cytokines in the accelerated bone lysis associated with loosening. EXPERIMENTAL DESIGN: To investigate the role of matrix metalloproteinases (MMPs) in the loosening we immunolocalized MMP-1 (tissue collagenase), MMP-2 (gelatinase A), MMP-3 (stromelysin-1), MMP-9 (gelatinase B) and their common inhibitors, tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2), in the bone-prosthesis interface membranes. In situ hybridization was performed for the detection of MMP-9 mRNA in the membranes. The amounts of these MMPs and TIMPs in the tissue were measured by the sandwich enzyme immunoassays and enzyme activities assayed using radiolabeled collagen, gelatin, and carboxymethylated transferrin substrates. We also examined the ability of the cells from interface membranes to resorb mouse calvaria bone. RESULTS: The membranes obtained from the loose bone-implant interface were composed of fibrous granulation tissue containing numerous multinucleated giant cells with high density polyethylene debris. Immunohistochemical examination revealed that the giant cells were strongly positive for MMP-9 and weakly for MMP-1. Expression of MMP-9 mRNA in the cells was demonstrated by in situ hybridization. MMP-2 and TIMP-2 were immunolocalized mainly in the fibroblasts. TIMP-1 was localized in the endothelial cells of the blood vessels and weakly in fibroblasts. However, MMP-3 was almost negative in the membrane tissue. Sandwich enzyme immunoassays showed that MMP-9 levels are significantly higher in both homogenates and culture media of the cup and stem interface membranes than the control pseudocapsule. Gelatinolytic activity was also remarkably higher in the membrane samples than the control. The cells isolated from the membranes had no ability to resorb calvaria bone. CONCLUSIONS: These data demonstrate that MMP-9 is produced by the multinucleated giant cells appeared by the reaction to polyethylene debris in the interface membranes. This proteinase may play a role in degradation of the extracellular matrix macromolecules present around and on the surface of the bone trabeculae, facilitating the osteoclastic bone resorption.     

Matrix metalloproteinases and TIMPs are associated with blood-brain barrier opening after reperfusion in rat brain

BACKGROUND and PURPOSE: Reperfusion disrupts cerebral capillaries, causing cerebral edema and hemorrhage. Middle cerebral artery occlusion (MCAO) induces the matrix-degrading metalloproteinases, but their role in capillary injury after reperfusion is unknown. Matrix metalloproteinases (MMPs) and tissue inhibitors to metalloproteinases (TIMPs) modulate capillary permeability. Therefore, we measured blood-brain barrier (BBB) permeability, brain water and electrolytes, MMPs, and TIMPs at multiple times after reperfusion. METHODS: Adult rats underwent MCAO for 2 hours by the suture method. Brain uptake of 14C-sucrose was measured from 3 hours to 14 days after reperfusion. Levels of MMPs and TIMPs were measured by zymography and reverse zymography, respectively, in contiguous tissues. Other rats had water and electrolytes measured at 3, 24, or 48 hours after reperfusion. Treatment with a synthetic MMP inhibitor, BB-1101, on BBB permeability and cerebral edema was studied. RESULTS: Brain sucrose uptake increased after 3 and 48 hours of reperfusion, with maximal opening at 48 hours and return to normal by 14 days. There was a correlation between the levels of gelatinase A at 3 hours and the sucrose uptake (P<0.05). Gelatinase A (MMP-2) was maximally increased at 5 days, and TIMP-2 was highest at 5 days. Gelatinase B and TIMP-1 were maximally elevated at 48 hours. The inhibitor of gelatinase B, TIMP-1, was also increased at 48 hours. Treatment with BB-1101 reduced BBB opening at 3 hours and brain edema at 24 hours, but neither was affected at 48 hours. CONCLUSIONS: The initial opening at 3 hours correlated with gelatinase A levels and was blocked by a synthetic MMP inhibitor. The delayed opening, which was associated with elevated levels of gelatinase B, failed to respond to the MMP inhibitor, suggesting different mechanisms of injury for the biphasic BBB injury.