Interleukin 1 alpha mediates collagenase synthesis stimulated by phorbol 12-myristate 13-acetate

Molecular mechanisms regulating wound repair: Evidence for paracrine signaling from corneal epithelial cells to fibroblasts and immune cells following transient epithelial cell treatment with Mitomycin C

In this paper, we use RNAseq to identify senescence and phagocytosis as key factors to understanding how mitomyin C (MMC) stimulates regenerative wound repair. We use conditioned media (CM) from untreated (CMC) and MMC treated (CMM) human and mouse corneal epithelial cells to show that corneal epithelial cells indirectly exposed to MMC secrete elevated levels of immunomodulatory proteins including IL-1α and TGFβ1 compared to cells exposed to CMC. These factors increase epithelial and macrophage phagocytosis and promote ECM turnover. IL-1α supplementation can increase phagocytosis in control epithelial cells and attenuate TGFβ1 induced αSMA expression by corneal fibroblasts. Yet, we show that epithelial cell CM contains factors besides IL-1α that regulate phagocytosis and αSMA expression by fibroblasts. Exposure to CMM also impacts the activation of bone marrow derived dendritic cells and their ability to present antigen. These in vitro studies show how a brief exposure to MMC induces corneal epithelial cells to release proteins and other factors that function in a paracrine way to enhance debris removal and enlist resident epithelial and immune cells as well as stromal fibroblasts to support regenerative and not fibrotic wound healing.

Pivotal Role of Corneal Fibroblasts in Progression to Corneal Ulcer in Bacterial Keratitis

The shape and transparency of the cornea are essential for clear vision. However, its location at the ocular surface renders the cornea vulnerable to pathogenic microorganisms in the external environment. Pseudomonas aeruginosa and Staphylococcus aureus are two such microorganisms and are responsible for most cases of bacterial keratitis. The development of antimicrobial agents has allowed the successful treatment of bacterial keratitis if the infection is diagnosed promptly. However, no effective medical treatment is available after progression to corneal ulcer, which is characterized by excessive degradation of collagen in the corneal stroma and can lead to corneal perforation and corneal blindness. This collagen degradation is mediated by both infecting bacteria and corneal fibroblasts themselves, with a urokinase-type plasminogen activator (uPA)-plasmin-matrix metalloproteinase (MMP) cascade playing a central role in collagen destruction by the host cells. Bacterial factors stimulate the production by corneal fibroblasts of both uPA and pro-MMPs, released uPA mediates the conversion of plasminogen in the extracellular environment to plasmin, and plasmin mediates the conversion of secreted pro-MMPs to the active form of these enzymes, which then degrade stromal collagen. Bacterial factors also stimulate expression by corneal fibroblasts of the chemokine interleukin-8 and the adhesion molecule ICAM-1, both of which contribute to recruitment and activation of polymorphonuclear neutrophils, and these cells then further stimulate corneal fibroblasts via the secretion of interleukin-1. At this stage of the disease, bacteria are no longer necessary for collagen degradation. In this review, we discuss the pivotal role of corneal fibroblasts in corneal ulcer associated with infection by P. aeruginosa or S. aureus as well as the development of potential new modes of treatment for this condition.

IL-1 and TGF-β Modulation of Epithelial Basement Membrane Components Perlecan and Nidogen Production by Corneal Stromal Cells

Purpose

To determine whether (1) the in vitro expression of epithelial basement membrane components nidogen-1, nidogen-2, and perlecan by keratocytes, corneal fibroblasts, and myofibroblasts is modulated by cytokines/growth factors, and (2) perlecan protein is produced by stromal cells after photorefractive keratectomy.

Methods

Marker-verified rabbit keratocytes, corneal fibroblasts, myofibroblasts were stimulated with TGF-β1, IL-1α, IL-1β, TGF-β3, platelet-derived growth factor (PDGF)-AA, or PDGF-AB. Real-time quantitative RT-PCR was used to detect expression of nidogen-1, nidogen-2, and perlecan mRNAs. Western blotting evaluated changes in protein expression. Immunohistochemistry was performed on rabbit corneas for perlecan, alpha-smooth muscle actin, keratocan, vimentin, and CD45 at time points from 1 day to 1 month after photorefractive keratectomy (PRK).

Results

IL-1α or -1β significantly upregulated perlecan mRNA expression in keratocytes. TGF-β1 or -β3 markedly downregulated nidogen-1 or -2 mRNA expression in keratocytes. None of these cytokines had significant effects on nidogen-1, -2, or perlecan mRNA expression in corneal fibroblasts or myofibroblasts. IL-1α significantly upregulated, while TGF-β1 significantly downregulated, perlecan protein expression in keratocytes. Perlecan protein expression was upregulated in anterior stromal cells at 1 and 2 days after −4.5 or −9 diopters (D) PRK, but the subepithelial localization of perlecan became disrupted at 7 days and later time points in −9-D PRK corneas when myofibroblasts populated the anterior stroma.

Conclusions

IL-1 and TGF-β1 have opposing effects on perlecan and nidogen expression by keratocytes in vitro. Proximate participation of keratocytes is likely needed to regenerate normal epithelial basement membrane after corneal injury.

Autocrine IL-1β mediates the promotion of corneal neovascularization by senescent fibroblasts

Our previous study has confirmed that senescent fibroblasts promote corneal neovascularization (CNV) partially via the enhanced secretion of matrix metalloproteases (MMPs). However, the regulation of MMP expression in senescent fibroblasts remained unclear. In this study, we identified that the expression and secretion levels of interleukin-1β (IL-1β) were significantly upregulated in senescent human corneal fibroblasts than that in normal fibroblasts. Moreover, compared with vehicle-pretreated senescent fibroblasts, IL-1β pretreatment enhanced the expression of angiogenic factors but reduced the expression of angiostatic factors in senescent fibroblasts. When cocultured with human umbilical vein endothelial cells, IL-1β-pretreated senescent fibroblasts more strongly promoted their proliferation, migration, and tube-formation capacities than the vehicle-controlled senescent fibroblasts. In addition, either interleukin-1 receptor antagonist or anti-IL-1β neutralization completely inhibited the promotion of senescent fibroblasts in vascular tube formation in vitro and CNV in vivo. Therefore, we concluded that autocrine IL-1β mediated the promotion of senescent fibroblasts on corneal neovascularization.

Scopoletin downregulates MMP‑1 expression in human fibroblasts via inhibition of p38 phosphorylation

Irradiation of keratinocytes by ultraviolet B induces cytokine production, which in turn activates fibroblasts to produce cytokines and increase matrix metallopeptidase (MMP)‑1 protein expression. The present study investigated the effect and potential mechanisms of scopoletin on the regulation of MMP‑1 expression in fibroblasts. Scopoletin was isolated from Artemisia capillaris crude extract. Treatment of fibroblasts with scopoletin resulted in a decrease in the protein expression of MMP‑1 following stimulation with human keratinocyte (HaCaT) conditioned medium. To further explore the mechanism underlying this effect, the expression levels of proteins in the mitogen‑activated protein kinase (MAPK) and nuclear factor‑κB (NF‑κB) signaling pathways were evaluated via western blot analysis. The mRNA expression levels of interleukin (IL)‑1α and tumor necrosis factor (TNF) α were evaluated via reverse transcription‑quantitative polymerase chain reaction. The effect of scopoletin on cell viability was assessed with the MTT assay. The results demonstrated that scopoletin treatment markedly decreased MMP‑1, IL‑1α and TNFα mRNA expression in fibroblasts stimulated with HaCaT conditioned medium (40 mJ/cm2), without any apparent cell cytotoxicity, and in a dose‑dependent manner. In addition, western blot analysis demonstrated that scopoletin reduced the phosphorylation of p38 MAPK in fibroblasts. In summary, the present study demonstrated that scopoletin inhibited MMP‑1 and proinflammatory cytokine expression by inhibiting p38 MAPK phosphorylation. These findings suggest that scopoletin may have potential as a therapeutic agent to prevent and treat photoaging of the skin.

Keratoconus: an inflammatory disorder?

Keratoconus has been classically defined as a progressive, non-inflammatory condition, which produces a thinning and steepening of the cornea. Its pathophysiological mechanisms have been investigated for a long time. Both genetic and environmental factors have been associated with the disease. Recent studies have shown a significant role of proteolytic enzymes, cytokines, and free radicals; therefore, although keratoconus does not meet all the classic criteria for an inflammatory disease, the lack of inflammation has been questioned. The majority of studies in the tears of patients with keratoconus have found increased levels of interleukin-6 (IL-6), tumor necrosis factor-α(TNF-α), and matrix metalloproteinase (MMP)-9. Eye rubbing, a proven risk factor for keratoconus, has been also shown recently to increase the tear levels of MMP-13, IL-6, and TNF-α. In the tear fluid of patients with ocular rosacea, IL-1α and MMP-9 have been reported to be significantly elevated, and cases of inferior corneal thinning, resembling keratoconus, have been reported. We performed a literature review of published biochemical changes in keratoconus that would support that this could be, at least in part, an inflammatory condition.

Type I collagen accelerates the spreading of lens epithelial cells through the expression and activation of matrix metalloproteinases

PURPOSE

Matrix metalloproteinases (MMPs) are involved in posterior capsule opacification (PCO), but the mechanisms that promote MMP expression are yet to be determined. In this study, we investigated whether type I collagen, which is only detected in aged or cataractous lens capsules, affects the expression and activation of MMPs in primary-cultured chicken lens epithelial cells (LECs).

MATERIALS AND METHODS

Chicken LECs were isolated from chicken embryos and cultured in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum (FBS) on type I collagen-coated dishes. The activity of secreted MMPs was examined using gelatin zymography, and cell spreading was determined as the average area of randomly distributed cells. For some experiments, LECs were cultured in the presence of the broad-spectrum MMP inhibitor, GM6001. LECs cultured on uncoated dishes were used as controls. To examine the involvement of MMP in cell migration, a wound-healing assay was performed in the presence of the MMP inhibitor.

RESULTS

Chicken LECs constitutively express the pro-form of MMP-2. When LECs were cultured on type I collagen-coated dishes, they expressed the active form of MMP-2 and the pro-form of MMP-9. This expression and activation by type I collagen was also observed in the human LEC line SRA-01/04, but not the human Müller glial cell line, MIO-M1. Type I collagen enhanced cell spreading, which was suppressed by the MMP inhibitor. Type I collagen also accelerated α-smooth muscle actin expression. In addition, LEC migration was inhibited by the MMP inhibitor in a dose-dependent manner in the wound-healing assay.

CONCLUSION

Type I collagen promotes the expression and activation of MMPs in a LEC-specific manner. These results suggest that type I collagen may play a role in PCO development.

Immunohistochemical expression of matrix metalloproteinases in the rabbit corneal epithelium upon UVA and UVB irradiation

Matrix metalloproteinases (MMPs) are proteolytic enzymes involved in tissue remodeling and wound healing. These enzymes degrade and also synthesize components of the extracellular matrix. Overexpression of MMPs results in excessive extracellular matrix degradation and tissue destruction. In the cornea, destructive processes may lead to scarring and loss of vision. In this study MMPs (types 1, 2, 7, 8, 9 and 14) were examined immunohistochemically in the normal rabbit corneal epithelium and in epithelium irradiated in vivo with similar doses of UVB or UVA radiation (UVB rays 312 nm, UVA rays 365 nm, daily dose 1.01 J/cm(2) for four days). Results show that MMPs studied revealed low expression in the normal corneal epithelium, whereas after repeated UVB irradiation the expression of MMPs was significantly increased in the corneal epithelium, in ascending order: MMP-2, MMP-9, MMP-1, and MMP-7 with MMP-8. In contrast, compared to normal corneas, repeated UVA radiation did not significantly change the expression of MMPs in the irradiated corneal epithelium. MMP-14 was expressed at very low levels in all studied corneas, whereas no significant changes were detected upon UV exposure. In conclusion, UV radiation of shorter wavelength (UVB) induced an increase in expression of all MMPs except MMP-14. It is suggested that overexpression of MMPs in the corneal epithelium contributes to the damaging effect of UVB radiation to the cornea.

Interleukin-6: a growth factor stimulating collagen synthesis in human tendon

Human connective tissue, e.g., tendon, responds dynamically to physical activity, with collagen synthesis being increased after both acute and prolonged exercise or training. Markers of collagen synthesis and degradation as well as concentration of several potential growth factors have been shown to increase markedly in the peritendinous tissue around the human Achilles tendon following exercise. Of these potential growth factors interleukin-6 (IL-6) showed the largest fold increase, suggesting that IL-6 may be involved in transforming mechanical loading into collagen synthesis in human tendon tissue. In the present study the tissue levels of type I collagen turnover markers [procollagen type I NH(2)-terminal propeptide (PINP) and C-OOH terminal telopeptide of type I collagen (ICTP)] were measured by the use of microdialysis in peritendinous tissue of the Achilles tendon in 14 male volunteers, who had recombinant human IL-6 (rhIL-6) infused into the peritendinous tissue of the Achilles' tendon in one leg, with the other leg serving as control. Subjects were randomly assigned to either a resting group or an exercise group performing a 1-h treadmill run (12 km/h, 2% uphill) before infusion. In addition to IL-6, serum concentrations of collagen turnover markers PINP, ICTP, and COOH-terminal telopeptide of type I collagen (ICTX) were measured. The peritendinous concentration of PINP rose markedly in response to rhIL-6 infusion in both the exercise and the rest group, demonstrating that infusion of IL-6 significantly stimulates collagen synthesis in the peritendinous tissue in humans. Exercise alone did not result in an increased collagen synthesis. This indicates that IL-6 is involved in the collagen synthesis and supports the hypothesis that IL-6 is an important growth factor of the connective tissue in healthy human tendons.

Effect of anti-inflammatory medication on the running-induced rise in patella tendon collagen synthesis in humans

NSAIDs are widely used in the treatment of inflammatory diseases as well as of tendon diseases associated with pain in sports and labor. However, the effect of NSAID intake, and thus blockade of PGE(2) production, on the tendon tissue adaptation is unknown. The purpose of the present study was to elucidate the possible effects of NSAID intake on healthy tendon collagen turnover in relation to a strenuous bout of endurance exercise. Fifteen healthy young men were randomly assigned into two experimental groups, with one group receiving indomethacin (oral 2 × 100 mg Confortid daily for 7 days; NSAID; n = 7) and a placebo group (n = 8). Both groups were exposed to a prolonged bout of running (36 km). The collagen synthesis NH₂-terminal propeptide of type I (PINP) and PGE₂ concentrations were measured before and 72 h following the run in the patella tendon by microdialysis. The peritendinous concentrations of PINP increased significantly in the placebo group as a result of the run, as shown previously. PGE₂ levels were significantly decreased 72 h after the run compared with basal levels in the subjects treated with NSAID and unchanged in the placebo group. The NSAID intake abolished the adaptive increase in collagen synthesis in the patella tendon found in the placebo group in response to the prolonged exercise (P < 0.05). The present study demonstrates that intake of NSAID decreased interstitial PGE₂ and abolished the exercise-induced adaptive increase in collagen synthesis in human tendons.

Constitutive collagenase-1 synthesis through MAPK pathways is mediated, in part, by endogenous IL-1α during fibrotic repair in corneal stroma

Collagenase-1 is a protease expressed by active fibroblasts that is involved in remodeling of the extracellular matrix (ECM). In this study, we characterize the intracellular signaling mechanism of collagenase-1 production by IL-1alpha in subcultured normal fibroblasts (NF) from uninjured normal corneas, compared to that in repair wound fibroblasts (WF). In NF, collagenase-1 was induced specifically after the exogenous addition of IL-1alpha via activation of ERK and p38MAPK. Collagenase-1 expression was strongly suppressed upon treatment with either a MEK or p38MAPK inhibitor. In contrast, repair WF constitutively synthesized both IL-1alpha and collagenase-1. Combined treatment with both mitogen-activated protein kinase (MAPK) inhibitors dramatically reduced collagenase-1 synthesis, while individual MEK1 or p38 inhibitors weakly modulated the collagenase-1 level. The results indicate that both pathways are crucial in the regulation of collagenase-1 synthesis. Furthermore, an IL-1alpha receptor antagonist (IL-1ra) could not abolish constitutive collagenase-1 synthesis, even at high doses, suggesting that other cytokines/factors are additionally involved in this process. We propose that induction of collagenase-1 by IL-1alpha in both WF and NF depends on a unique combination of cell type-specific signaling pathways.

Relationship between IL-1A polymorphisms and gingival overgrowth in renal transplant recipients receiving Cyclosporin A

AIM

Levels of interleukin-1alpha (IL-1alpha) are elevated in periodontal inflammation. IL-1A gene polymorphisms are associated with inflammatory diseases. This study aimed to investigate IL-1A gene polymorphism in Cyclosporin A (CsA)-treated renal transplant patients and investigate the association between this polymorphism and gingival crevicular fluid (GCF) levels of several cytokines.

MATERIALS AND METHODS

Fifty-one renal transplant patients on CsA treatment (25 with and 26 without gingival overgrowth) and 29 healthy controls were recruited for the study. Demographic, pharmacological and periodontal parameters were recorded and gingival overgrowth was assessed.

RESULTS

Multiple regression analysis showed that genotype was significantly associated with gingival overgrowth (p=0.02). Carriage of the IL-1A (-889) T allele was strongly protective [95% confidence interval (CI): 0.046-0.77], although not significantly associated with IL-1alpha protein levels in GCF. IL-1alpha, IL-1beta and IL-8, but not IL-6, were detected in GCF of CsA-treated patients, but none of them was significantly associated with gingival overgrowth.

CONCLUSIONS

This study is the first to associate a gene polymorphism as a risk factor for CsA-induced gingival overgrowth in renal transplant patients, demonstrating that IL-1A polymorphism might alter individual susceptibility to CsA. However, there was no association between GCF cytokine levels and the presence of gingival overgrowth or patient IL-1A genotype.

How the cornea heals: cornea-specific repair mechanisms affecting surgical outcomes

In mammals, penetrating injuries typically heal by deposition of fibrotic "repair tissue" that fills and seals wounds but does not restore normal function. Excessive deposition of fibrotic repair tissue can lead to pathologies involving excessive scarring and contracture. In the cornea, fibrotic repair presents special challenges affecting both clarity and shape of the cornea. With the increasing popularity of surgical techniques that alter corneal refractive errors, understanding of cornea repair mechanisms has acquired new significance. The cornea has unique anatomic, cellular, molecular, and functional features that lead to important mechanistic differences in the process of repair in comparison with what occurs in skin and other organs. Moreover, corneal function calls for special outcomes. This review addresses these features from the viewpoint of the authors' research on factors of importance to understanding and improving surgical outcomes.

Wound healing in the cornea: a review of refractive surgery complications and new prospects for therapy

PURPOSE

The corneal wound healing response is of particular relevance for refractive surgical procedures since it is a major determinant of efficacy and safety. The purpose of this review is to provide an overview of the healing response in refractive surgery procedures.

METHODS

Literature review.

RESULTS

LASIK and PRK are the most common refractive procedures; however, alternative techniques, including LASEK, PRK with mitomycin C, and Epi-LASIK, have been developed in an attempt to overcome common complications. Clinical outcomes and a number of common complications are directly related to the healing process and the unpredictable nature of the associated corneal cellular response. These complications include overcorrection, undercorrection, regression, corneal stroma opacification, and many other side effects that have their roots in the biologic response to surgery. The corneal epithelium, stroma, nerves, inflammatory cells, and lacrimal glands are the main tissues and organs involved in the wound healing response to corneal surgical procedures. Complex cellular interactions mediated by cytokines and growth factors occur among the cells of the cornea, resulting in a highly variable biologic response. Among the best characterized processes are keratocyte apoptosis, keratocyte necrosis, keratocyte proliferation, migration of inflammatory cells, and myofibroblast generation. These cellular interactions are involved in extracellular matrix reorganization, stromal remodeling, wound contraction, and several other responses to surgical injury.

CONCLUSIONS

A better understanding of the complete cascade of events involved in the corneal wound healing process and anomalies that lead to complications is critical to improve the efficacy and safety of refractive surgical procedures. Recent advances in understanding the biologic and molecular processes that contribute to the healing response bring hope that safe and effective pharmacologic modulators of the corneal wound healing response may soon be developed.

Interleukin-1 (IL-1alpha and IL-1beta) and its receptors (IL-1RI, IL-1RII, and IL-1Ra) in prostate carcinoma

BACKGROUND

The principal components of the interleukin-1 (IL-1) family are two secreted factors (IL-1alpha and IL-1beta), two transmembrane receptors (IL-1RI [biologically active] and IL-1RII [inert receptor]), and a natural antagonist receptor of IL-1 function (IL-1Ra). Changes in the expression pattern of these IL-1 members have been reported to be related to disease progression. The objective of the current study was to evaluate these changes in prostatic tissue by means of immunohistochemistry and Western blot analysis.

METHODS

Immunohistochemical and Western blot analyses were performed in 20 normal samples, 35 samples of benign prostatic hyperplasia (BPH) and 27 samples from patients with prostate carcinoma (PC).

RESULTS

In normal prostate samples, immunoreactions to IL-1beta and IL-1RI were positive, whereas there were no immunoreactions observed to IL-1alpha, IL-1RII, or IL-1Ra. In BPH, in addition to immunoreactions to IL-1beta and IL-1RI, immunoreactions to IL-1alpha, IL-1RII, and IL-1Ra were observed in many samples. In samples of PC with low Gleason grade, most tumors had positive immunoreactions to IL-1alpha and IL-1RI. In samples of PC with high Gleason grade, immunoreactions were seen only to IL-1alpha, IL-1RI, and IL-1RII.

CONCLUSIONS

The current results suggested that high expression levels of IL-1alpha and IL1-RI in epithelial cells in BPH and PC samples were involved in cell proliferation and that the loss of immunoexpression of IL-1beta and IL-1Ra was a characteristic feature of PC compared with normal prostate samples and BPH. Because this loss is progressive up to a complete absence of immunoexpression in PC of high Gleason grade, the evaluation of IL-1beta and IL-1Ra in PC may be significant in assessing for malignancy.

Activity and expression ofXenopus laevis matrix metalloproteinases: Identification of a novel role for the hormone prolactin in regulating collagenolysis in both amphibians and mammals

Prolactin (PRL) has long been implicated in Xenopus metamorphosis as an anti-metamorphic and/or juvenilizing hormone. Numerous studies showed that PRL could prevent effects of either endogenous or exogenous thyroid hormone (TH; T(3)). It has been shown that expression of matrix metalloproteinases (MMPs) is induced by TH during Xenopus metamorphosis. Direct in vivo evidence, however, for such anti-TH effects by PRL with respect to MMPs has not been available for the early phase of Xenopus development or metamorphosis. To understand the functional role of PRL, we investigated effects of PRL on Xenopus collagenase-3 (XCL3) and collagenase-4 (XCL4) expression in a cultured Xenopus laevis cell line, XL-177. Northern blot analysis demonstrated that XCL3 and XCL4 expression were not detected in control or T(3)-treated cells, but were differentially induced by PRL in a dose- and time-dependent fashion. Moreover, treatment with IL-1alpha as well as phorbol myristate acetate (PMA), a protein kinase C (PKC) activator, or H8, a protein kinase A (PKA) inhibitor, augmented PRL-induced collagenase expression, suggesting that multiple protein kinase pathways and cytokines may participate in PRL-induced collagenase expression. Interestingly, XCL3 expression could be induced in XL-177 cells by T(3), but only when co-cultured with prometamorphic Xenopus tadpole tails (stage 54/55), suggesting that the tails secrete a required intermediate signaling molecule(s) for T(3)-induced XCL3 expression. Taken together, these data demonstrate that XCL3 and XCL4 can be differentially induced by PRL and T(3) and further suggest that PRL is a candidate regulator of TH-independent collagenase expression during the organ/tissue remodeling which occurs in Xenopus development.

Interleukin-1 beta promotes matrix metalloproteinase expression and cell proliferation in calcific aortic valve stenosis

Calcific aortic valve stenosis (AS), the main heart valve disease in the elderly, is characterized by extensive remodeling of the extracellular matrix. Matrix metalloproteinases (MMPs) are upregulated in calcific AS and might modulate matrix remodeling. The regulatory mechanisms are unclear. As recent studies have suggested that calcific AS might result from an inflammatory process involving leukocyte invasion and activation, the present study aimed to elucidate the role of the pro-inflammatory cytokine interleukin (IL)-1 beta on MMP expression and cell proliferation in human aortic valves. Immunohistochemistry for leukocytes, IL-1 beta and MMP-1 was performed on aortic valves with (n=6) and without (n=6) calcification obtained at valve replacement or autopsy. Stenotic valves showed marked leukocyte infiltration and associated expression of IL-1 beta and MMP-1. In control valves only scattered leukocytes, low staining for MMP-1 and no staining for IL-1 beta were present. Double-label immunostaining localized IL-1 beta expression mainly to leukocytes and MMP-1 expression to myofibroblasts. Stimulation of cultured human aortic valve myofibroblasts with IL-1 beta lead to a time-dependently increased expression of MMP-1 and MMP-2 by Western blotting and zymography, whereas MMP-9 remained unchanged. Cell proliferation was increased by IL-1 beta as determined by bromodesoxyuridine incorporation. Thus, IL-1 beta may regulate remodeling of the extracellular matrix in calcific AS.

Enhancement by neutrophils of collagen degradation by corneal fibroblasts

Activated corneal fibroblasts and infiltrated leukocytes are thought to contribute to corneal ulceration. The potential roles of neutrophil-fibroblast and cell-matrix interactions in the degradation of stromal collagen associated with corneal ulceration have now been investigated with the use of three-dimensional cultures of rabbit cells in collagen gels. Degradation of collagen fibrils during culture was measured by spectrophotometric determination of released hydroxyproline. Whereas corneal fibroblasts alone degraded collagen fibrils to a small extent, neutrophils did not. However, the addition of neutrophils or neutrophil-conditioned medium (CM) to cultures of corneal fibroblasts resulted in a marked increase in the amount of collagen degraded by the fibroblasts. The effect of CM from neutrophils cultured in collagen gels on collagen degradation by corneal fibroblasts was greater than that of medium conditioned by neutrophils in monolayer culture. Immunoblot as well as reverse transcription and real-time polymerase chain reaction analyses revealed that neutrophil-CM stimulated the synthesis of matrix metalloproteinase (MMP)-1 and MMP-3 by corneal fibroblasts. The stimulatory effect of neutrophils on collagen degradation by corneal fibroblasts was inhibited by the synthetic MMP inhibitor ilomastat and by interleukin-1 (IL-1) receptor antagonist. These results suggest that factors secreted by collagen-stimulated neutrophils augment collagen degradation by corneal fibroblasts through a stimulatory effect on MMP synthesis and that IL-1 released by neutrophils may contribute to this effect.

Role of protein kinase C signaling in collagen degradation by rabbit corneal fibroblasts cultured in three-dimensional collagen gels

PURPOSE

To understand the mechanism of corneal ulceration by characterizing the intracellular signaling pathways that regulate collagen degradation by corneal fibroblasts cultured in three-dimensional type I collagen gels. Specifically, the potential roles of protein kinase C (PKC) and protein kinase A (PKA) in collagen degradation were investigated.

METHODS

Rabbit corneal fibroblasts were cultured in three-dimensional type I collagen gels for 24 hours in the presence of plasminogen and in the absence or presence of activators or inhibitors of PKC or PKA. Degradation of collagen fibrils was then evaluated by measurement of released hydroxyproline, and the production of matrix metalloproteinases (MMPs) was assessed by gelatin zymography and immunoblot analysis.

RESULTS

The PKC activator phorbol 12-myristate 13-acetate (PMA) increased the extent of collagen degradation by corneal fibroblasts in a dose-dependent manner, with the maximal effect apparent at a concentration of 0.1 microM. The inactive analog 4alpha-PMA had no effect on collagen degradation. The PKC inhibitor H-7 reduced the extent of collagen degradation by corneal fibroblasts in the absence or presence of PMA. Phorbol 12-myristate 13-acetate also increased the production of proMMP-1, -3, and -9 by corneal fibroblasts, whereas H-7 inhibited this effect. Neither the PKA activators 8-bromo-cAMP, isobutylmethylxanthine, and forskolin nor the PKA inhibitor HA1004 affected collagen degradation by corneal fibroblasts.

CONCLUSION

These results demonstrate that PKC plays an important role in collagen degradation by corneal fibroblasts in three-dimensional type I collagen gels, whereas PKA does not appear to participate in this process.

MMPs in the eye: emerging roles for matrix metalloproteinases in ocular physiology

Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that function to maintain and remodel tissue architecture. Their substrates represent an astounding variety of extracellular matrix components, secreted cytokines and cell surface molecules, and they have been implicated in a wide range of processes and diseases. To date MMPs have been found in virtually every tissue of the eye under conditions of health and disease. Although their functions in vivo remain poorly understood, it is clear they impact on essentially every aspect of eye physiology. This chapter reviews the expanding literature on MMPs in the eye and attempts to place it in the context of basic MMP biology. A general overview of MMP functions is presented first, and then the discussion moves to examples of possible MMP roles in two eye structures. For the cornea, we present recent work on the roles of MMPs during various aspects of wound healing. For the retina, we describe the activities of MMPs in specific disease states from which common principles may emerge.

Trefoil peptides promote restitution of wounded corneal epithelial cells

The ocular surface shares many characteristics with mucosal surfaces. In both, healing is regulated by peptide growth factors, cytokines, and extracellular matrix proteins. However, these factors are not sufficient to ensure most rapid healing. Trefoil peptides are abundantly expressed epithelial cell products which exert protective effects and are key regulators of gastrointestinal epithelial restitution, the critical early phase of cell migration after mucosal injury. To assess the role of trefoil peptides in corneal epithelial wound healing, the effects of intestinal trefoil factor (ITF/TFF3) and spasmolytic polypeptide (SP/TFF2) on migration and proliferation of corneal epithelial cells were analyzed. Both ITF and SP enhanced restitution of primary rabbit corneal epithelial cells in vitro. While the restitution-enhancing effects of TGF-alpha and TGF-beta were both inhibited by neutralizing anti-TGF-beta-antibodies, trefoil peptide stimulation of restitution was not. Neither trefoil peptide significantly affected proliferation of primary corneal epithelial cells. ITF but not SP or pS2 mRNA was present in rabbit corneal and conjunctival tissues. In summary, the data indicate an unanticipated role of trefoil peptides in healing of ocular surface and demand rating their functional actions beyond the gastrointestinal tract.

Urokinase activity in corneal fibroblasts may be modulated by DNA damage and secreted proteins

Proteases like urokinase-type plasminogen activator (uPA) play an important role in tumor invasion. Cells derived from ultraviolet radiation (UVR)-induced corneal sarcomas of Monodelphis domestica produce relatively high levels of uPA compared to the untransformed keratocytes suggesting a mechanism for their invasiveness. Because UVR is known to stimulate uPA production in many cell types, UVR exposure may further increase uPA expression in corneal tumor cells, thus enhancing their ability to infiltrate. We investigated control of basal uPA levels and the induction of uPA by UVR in transformed and untransformed corneal keratocytes from Monodelphis. These studies took advantage of the fact that Monodelphis possesses an active photolyase that can be stimulated to remove UVR-induced pyrimidine dimers by exposure to long-wavelength visible photoreactivating light (PRL). Our studies showed that significant induction of uPA occurred in response to 200 J/m2 UVR. This induction was partially blocked by treatment with PRL, indicating that DNA damage, the pyrimidine dimer in particular, played a role in uPA induction. In untransformed cultured corneal fibroblasts, the heparin-binding protein inhibitor, suramin, reduced basal uPA levels, UVR-induced uPA production and cell proliferation. Basic fibroblast growth factor, a heparin-binding growth factor known to be UVR-inducible in mesenchymal cells, stimulated uPA production and cell proliferation; however, anti-bFGF antibodies did not significantly decrease proliferation or basal uPA production. These findings suggested that basal levels of uPA secretion were modulated in response to heparin-binding growth factors and that these growth factors may also have mediated the effect of UVR on uPA levels.

Matrix metalloproteinases correlate with alveolar-capillary permeability alteration in lung ischemia-reperfusion injury

BACKGROUND

Matrix metalloproteinases (MMPs) are able to degrade the endothelial basal lamina and increase vascular permeability.

METHODS

In a porcine model of isolated-reperfused lung, we studied the alveolar-capillary permeability and the zymographic expression of MMP-9 and MMP-2 in the bronchoalveolar lavage fluid of lungs submitted ex vivo to ischemia in three preservation solutions [modified Euro-Collins (EC), low-potassium-dextran, modified-blood]. Twenty-two pigs were randomly divided into three groups according to the preservation solution used. One lung of each pig was rapidly reperfused and analyzed (control lung) although the other lung was reperfused and analyzed after 8 hr of ischemia (ischemic lung).

RESULTS

Alveolar-capillary permeability, evaluated by the transferrin leak index, was increased after 8 hr of ischemia compared with controls in the three groups, but was significantly higher in the modified EC group. In the EC group, after 8 hr of ischemia, both proMMP-9 and MMP-9 increased significantly (8.8- and 22-fold, respectively) compared with controls and this increase correlated with the transferrin leak index. Neither proMMP-9 nor MMP-9 increased with the other two preservation solutions. The MMP-2 increase after ischemia was smaller and was also restricted to the EC group.

CONCLUSION

MMP expression is enhanced during lung ischemia-reperfusion, especially in the presence of EC and this phenomenon correlates with the alteration of alveolar-capillary permeability.

Monocyte chemoattractant protein-1 enhances gene expression and synthesis of matrix metalloproteinase-1 in human fibroblasts by an autocrine IL-1 alpha loop

Monocyte chemoattractant protein-1 (MCP-1), a member of the C-C chemokine superfamily, has recently been shown to be involved in the pathogenesis of tissue fibrosis. In vitro studies demonstrated that MCP-1 up-regulates type I collagen gene expression via endogenous production of TGF-beta in rat lung fibroblasts. We here show that recombinant human MCP-1 affects gene expression of interstitial collagenase (matrix metalloproteinase-1 (MMP-1)) in primary human skin fibroblasts and a stable fibroblast cell line. MMP-1 mRNA was induced by MCP-1 (10 ng/ml) as early as 6 h and reached a maximal expression at 24 h. MCP-1 also caused an increase of MMP-2 mRNA expression in both types of fibroblasts at 48 h. Interestingly, tissue inhibitor of metalloproteinase-1 (TIMP-1) mRNA was also up-regulated by MCP-1, and TIMP-1 mRNA expression peaked at 48 h in both types of fibroblasts. Immunoblot analysis demonstrated increased levels of MMP-1 and TIMP-1 protein in the culture supernatants of primary fibroblasts stimulated with MCP-1. In addition, MCP-1 strongly induced IL-1 alpha mRNA expression in dermal fibroblasts in parallel with the induction of MMP-1. Preincubation with IL-1 receptor antagonist almost completely abrogated the expression of MMP-1 mRNA, and partially inhibited MMP-1 synthesis induced by MCP-1. Transient transfection of primary skin fibroblasts with a MMP-1 promoter-reporter construct indicated a dose-dependent increase in promoter activity by MCP-1 stimulation. These data demonstrate that MCP-1 up-regulates MMP-1 mRNA expression and synthesis in human skin fibroblasts at a transcriptional level and provide evidence that this is mediated by an IL-1 alpha autocrine loop.

Macrophage migration inhibitory factor up-regulates expression of matrix metalloproteinases in synovial fibroblasts of rheumatoid arthritis

Neutral matrix metalloproteinases (MMPs) are responsible for the pathological features of rheumatoid arthritis (RA) such as degradation of cartilage. We herein show the up-regulation of MMP-1 (interstitial collagenase) and MMP-3 (stromelysin) mRNAs of cultured synovial fibroblasts retrieved from rheumatoid arthritis (RA) patients in response to macrophage migration inhibitory factor (MIF). The elevation of MMP-1 and MMP-3 mRNA was dose-dependent and started at 6 h post-stimulation by MIF, reached the maximum level at 24 h, and was sustained at least up to 36 h. Interleukin (IL)-1beta mRNA was also up-regulated by MIF. These events were preceded by up-regulation of c-jun and c-fos mRNA. Tissue inhibitor of metalloproteinase (TIMP)-1, a common inhibitor of these proteases, was slightly up-regulated by MIF. Similarly, mRNA up-regulation of MMP-1 and MMP-3 was observed in the synovial fibroblasts of patients with osteoarthritis. However, their expression levels were much lower than those of RA synovial fibroblasts. The mRNA up-regulation by MIF was inhibited by the tyrosine kinase inhibitors genestein and herbimycin A, as well as the protein kinase C inhibitors staurosporine and H-7. On the other hand, the inhibition was not seen after the addition of the cyclic AMP-dependent kinase inhibitor, H-8. The mRNA up-regulation of MMPs was also inhibited by curcumin, an inhibitor of transcription factor AP-1, whereas interleukin-1 receptor antagonist, an IL-1 receptor antagonist, failed to inhibit the mRNA up-regulation. Considering these results, it is suggested that 1) MIF plays an important role in the tissue destruction of rheumatoid joints via induction of the proteinases, and 2) MIF up-regulates MMP-1 and MMP-3 via tyrosine kinase-, protein kinase C-, and AP-1- dependent pathways, bypassing IL-1beta signal transduction.

Effect of galardin on collagen degradation by Pseudomonas aeruginosa

The authors examined the effect of a synthetic peptidyl hydroxamate inhibitor of matrix metalloproteinase, Galardin, on collagen degradation by Pseudomonas aeruginosa (P. aeruginosa) in the presence or absence of keratocytes. Type I collagen gels, with or without suspended keratocytes, were incubated under medium containing sterile P. aeruginosa culture broth and/or Galardin for 24 hr. Degradation of collagen fibrils during culture was measured by the release of hydroxyproline. The conditioned media were also subjected to gelatin zymography and Western blotting to analyse the activation, by P. aeruginosa factor(s), of matrix metalloproteinases (MMPs) released by keratocytes. The effects of protease inhibitors, aprotinin, leupeptin and pepstatin, on collagen degradation by P. aeruginosa were also examined. P. aeruginosa broth by itself induced collegen gel degradation. When keratocytes were present, P. aeruginosa broth increased the amount of degraded collagen even further. Galardin significantly reduced the amounts of collagen degraded by P. aeruginosa culture broth, whether keratocytes were present or absent in the gel. However, the protease inhibitors had no inhibitory effects on collagen degradation. Gelatin zymography and Western blotting revealed that inactive proMMP-1, -2 and -3, released by keratocytes, were converted to active forms in the presence of P. aeruginosa broth. Galardin decreased the amounts of active MMPs and increased those of inactive proMMPs, suggesting that Galardin inhibited the activation of proMMPs by P. aeruginosa. The present results suggest that Galardin inhibits the keratocyte-mediated collagen degradation by P. aeruginosa culture broth, resulting from preventing the conversion of proMMPs to active MMPs.

Effect of cell-cell interactions in preservation of cellular phenotype: cocultivation of hepatocytes and nonparenchymal cells

Heterotypic cell interaction between parenchymal cells and nonparenchymal neighbors has been reported to modulate cell growth, migration, and/or differentiation. In both the developing and adult liver, cell-cell interactions are imperative for coordinated organ function. In vitro, cocultivation of hepatocytes and nonparenchymal cells has been used to preserve and modulate the hepatocyte phenotype. We summarize previous studies in this area as well as recent advances in microfabrication that have allowed for more precise control over cell-cell interactions through 'cellular patterning' or 'micropatterning'. Although the precise mechanisms by which nonparenchymal cells modulate the hepatocyte phenotype remain unelucidated, some new insights on the modes of cell signaling, the extent of cell-cell interaction, and the ratio of cell populations are noted. Proposed clinical applications of hepatocyte cocultures, typically extracorporeal bioartificial liver support systems, are reviewed in the context of these new findings. Continued advances in microfabrication and cell culture will allow further study of the role of cell communication in physiological and pathophysiological processes as well as in the development of functional tissue constructs for medical applications.

Effect of magnesium sulfate pretreatment and significance of matrix metalloproteinase-1 and interleukin-6 levels in coronary reperfusion therapy for patients with acute myocardial infarction

Magnesium (Mg) inhibits the influx of calcium in vascular smooth muscle cells. The purposes of this study were to test the hypothesis that an intravenous administration of magnesium might effect the complement response and to determine the effects of a magnesium pretreatment of patients with acute myocardial infarction (AMI) on the incidence of reperfusion injuries. Thirty-eight AMI patients were treated with coronary reperfusion therapy within 6 hours of onset. They were randomly divided into two groups: group pretreated with intravenous magnesium sulfate (0.27 mmol/kg) (magnesium group, n = 19), and nonpretreated controls (placebo group). The reperfusion injuries observed within 1 hour after the coronary reperfusion included arrhythmias, aggravated chest pain, and ST segment elevation in 12-lead electrocardiograms. Coronary recanalization was performed in 36 patients. The incidence of reperfusion arrhythmia was significantly lower in the magnesium group than in the placebo group (17% vs 78%, p<0.001). At the postreperfusion stage, there was a tendency for the degree of ST segment reelevation in the magnesium group lower than in the placebo group (2.5 +/- 2.3 mm vs 4.7 +/- 3.8 mm, p = 0.07). No marked difference was observed in the incidence of chest pain aggravation between the two groups (67% vs 73%, ns). The peak serum levels of interleukin-6 (IL-6) were significantly lower in the magnesium group than those in the placebo group (38.9 +/- 25.0 vs 92.3 +/- 76.5 pg/mL, p = 0.016). The peak serum levels of matrix metalloproteinase-1 (MMP-1) were lower than those in the placebo group (16.2 +/- 4.8 vs 19.7 +/- 9.0 ng/mL, p = 0.09), but the difference was not significant. A positive correlation was observed between the peak MMP-1 values and the peak IL-6 values (r = 0.57, p = 0.001) in all patients. Increased serum ionized Mg2+ may inhibit arrhythmic recurrence and the production of IL-6 and MMP-1 after reperfusion and prevent the increase of myocardial lesions caused by calcium overload on myocytes. The increased IL-6 production may induce MMP-1, leading to tissue organ injury. Pretreatment with magnesium sulfate may protect the myocardium of AMI patients from reperfusion injuries.

Galardin inhibits collagen degradation by rabbit keratocytes by inhibiting the activation of pro-matrix metalloproteinases

We investigated the inhibitory action of a synthetic peptidyl hydroxamate inhibitor of matrix metalloproteinase (MMP), Galardin (GM6001), on collagen degradation by rabbit corneal stromal fibroblasts (keratocytes) cultured three-dimensionally in the type I collagen gel with medium containing interleukin 1alpha (IL-1alpha) and/or plasminogen. Degradation of collagen fibrils during culture was measured by the release of hydroxyproline, and activation of MMPs was also analyzed by gelatin zymography and Western blotting. Plasmin activity was measured using a synthetic substrate. In the absence of plasminogen, treatment of the cells with IL-1alpha in collagen gel greatly enhanced the production of proMMP-1, -3 and -9, but no significant degradation of collagen was detected. In the presence of plasminogen, IL-1alpha stimulated collagen degradation by keratocytes in a dose-dependent manner. This resulted from the plasminogen activator-plasmin system-dependent activation of proMMP-1, -3 and -9. Galardin inhibited the collagen degradation in a dose-dependent fashion in the presence of plasminogen, whether IL-1alpha was present or not. Galardin inhibited the activation of proMMP-3, and also prevented the activation of proMMP-9 and the conversion of MMP-1 intermediates to the fully active MMP-1. Galardin did not affect plasmin activity. The present results suggest that Galardin inhibits IL-1alpha-stimulated collagen degradation in the presence of plasminogen, resulting from not only inhibiting active MMPs but also preventing the conversion of proMMPs to active MMPs.

Keratinocyte collagenase-1 expression requires an epidermal growth factor receptor autocrine mechanism

In response to cutaneous injury, expression of collagenase-1 is induced in keratinocytes via alpha2beta1 contact with native type I collagen, and enzyme activity is essential for cell migration over this substratum. However, the cellular mechanism(s) mediating integrin signaling remain poorly understood. We demonstrate here that treatment of keratinocytes cultured on type I collagen with epidermal growth factor receptor (EGFR) blocking antibodies or a specific receptor antagonist inhibited cell migration across type I collagen and the matrix-directed stimulation of collagenase-1 production. Additionally, stimulation of collagenase-1 expression by hepatocyte growth factor, transforming growth factor-beta1, and interferon-gamma was blocked by EGFR inhibitors, suggesting a required EGFR autocrine signaling step for enzyme expression. Collagenase-1 mRNA was not detectable in keratinocytes isolated immediately from normal skin, but increased progressively following 2 h of contact with collagen. In contrast, EGFR mRNA was expressed at high steady-state levels in keratinocytes isolated immediately from intact skin but was absent following 2 h cell contact with collagen, suggesting down-regulation following receptor activation. Indeed, tyrosine phosphorylation of the EGFR was evident as early as 10 min following cell contact with collagen. Treatment of keratinocytes cultured on collagen with EGFR antagonist or heparin-binding (HB)-EGF neutralizing antibodies dramatically inhibited the sustained expression (6-24 h) of collagenase-1 mRNA, whereas initial induction by collagen alone (2 h) was unaffected. Finally, expression of collagenase-1 in ex vivo wounded skin and re-epithelialization of partial thickness porcine burn wounds was blocked following treatment with EGFR inhibitors. These results demonstrate that keratinocyte contact with type I collagen is sufficient to induce collagenase-1 expression, whereas sustained enzyme production requires autocrine EGFR activation by HB-EGF as an obligatory intermediate step, thereby maintaining collagenase-1-dependent migration during the re-epithelialization of epidermal wounds.

Probing heterotypic cell interactions: hepatocyte function in microfabricated co-cultures

Replacement of liver function using extracorporeal bioartificial systems has been attempted with limited success. The instability of the hepatocyte phenotype in vitro has restricted the useful lifetime of these devices. Co-cultivation of hepatocytes with mesenchymal cells is one method that has been widely utilized to stabilize the liver-specific function of isolated cells; however, co-culture has yet to be successfully incorporated in a bioreactor setting. In this study, we probed heterotypic cell interactions in co-cultures of hepatocytes and 3T3 in order to better understand the cellular microenvironment necessary to induce and stabilize liver-specific functions. Using microfabrication and conventional techniques to control the heterotypic interface, the effects of varying degrees of heterotypic interaction on tissue function (albumin and urea synthesis) were examined. Our data indicated maximal induction of liver-specific functions in cultures with maximal initial heterotypic interaction, and that induction of hepatic functions in hepatocytes was increased in the vicinity of fibroblasts as compared to hepatocytes far from the heterotypic interface. Furthermore, our data suggested that heterotypic cell contact is necessary for induction of these functions. These studies will aid in the formation of design criteria for a co-culture based bioartificial liver, as well as provide a useful tool to study the role of heterotypic and homotypic interactions in liver physiology and pathophysiology.

Imbalance between interstitial collagenase and tissue inhibitor of metalloproteinases 1 in synoviocytes and fibroblasts upon direct contact with stimulated T lymphocytes: involvement of membrane-associated cytokines

OBJECTIVE

To determine whether direct cell-cell contact with stimulated T lymphocytes (a) differentially modulates the production of interstitial collagenase (matrix metalloproteinase 1 [MMP-1]) and tissue inhibitor of metalloproteinases 1 (TIMP-1) on human synoviocytes and dermal fibroblasts, and (b) induces the production of prostaglandin E2 (PGE2); and to identify the membrane-associated factors on T cell surfaces involved in these mechanisms.

METHODS

Dermal fibroblasts and fibroblast-like synovial cells (synoviocytes) were cultured with fixed T cells, isolated plasma membranes from T cells, interleukin-1beta (IL-1beta; 250 pg/ml), or transforming growth factor beta (TGFbeta; 5 ng/ml). Culture supernatants were assayed for the production of MMP-1, TIMP-1, and PGE2. The expression of MMP-1 and TIMP-1 messenger RNA was analyzed by Northern blot of total fibroblast RNA.

RESULTS

Membranes of stimulated T cells, i.e., human peripheral blood T lymphocytes (PBTL) and the human T cell line HUT-78, induced the production of PGE2 and MMP-1 on both synoviocytes and dermal fibroblasts. TIMP-1 production was enhanced upon contact with PBTL stimulated for short periods of time (2-4 hours) but not for longer periods. Similar results were obtained with CD4+ and CD8+ synovial tissue T cell clones (TCCs), which induced the production of TIMP-1 by fibroblasts when stimulated for short (2-4 hours), but not long, periods of time. This time dependency was not observed with HUT-78 cells. The production of MMP-1 by fibroblasts and synoviocytes upon cellular contact with stimulated T cells was higher than that induced by an optimum concentration of IL-1beta, whereas the production of PGE2 was equivalent or slightly lower. Cell membrane-associated IL-1alpha and tumor necrosis factor a, but not CD69, CD40 ligand, or CD11b, were involved in the induction of MMP-1 and PGE2 production, as shown by blockade experiments using monoclonal antibodies and cytokine antagonists.

CONCLUSION

Synovial tissue TCCs and PBTL stimulated for long periods of time trigger the production of PGE2 and MMP-1, but not TIMP-1, in synoviocytes and dermal fibroblasts, thus inducing an imbalance between the metalloenzyme and its inhibitor. These results demonstrate that T cells may affect fibroblast and synoviocyte functions directly (i.e., by contact activation) and indirectly (i.e., by activation of cytokine production in monocyte/macrophages, which in turn, trigger stromal cell functions). Since the production of MMPs in monocyte/macrophages is also induced upon contact with stimulated T cells, our results strongly suggest that contact of synovial cells with chronically stimulated T lymphocytes favors matrix catabolism. By analogy, this mechanism may trigger tissue destruction in vivo and, thus, may potentiate tissue destruction in chronic inflammatory diseases such as RA.

Serotonin-mediated production of interstitial collagenase by uterine smooth muscle cells requires interleukin-1alpha, but not interleukin-1beta

The activation of the gene for interstitial collagenase in myometrial smooth muscle cells is absolutely dependent upon the presence of serotonin. Our previous studies investigating the mechanisms of this induction demonstrated that the mRNAs of both interleukin-1 (IL-1) isoforms, IL-1alpha and IL-1beta, are induced by serotonin and that the induction of IL-1 is required for the subsequent induction of collagenase. These data provided compelling evidence that serotonin-induced IL-1 acts via an autocrine loop in activating the collagenase gene. The experiments described here were designed to examine the potential role of each IL-1 isoform in collagenase production by using neutralizing antisera specific to each isoform of the cytokine. The antisera were examined for their ability to inhibit the serotonin-dependent production of the mRNA for collagenase and of the cytokines themselves. Neutralizing antiserum against IL-1alpha, but not against IL-1beta, inhibited the induction of the mRNA for collagenase and of the mRNAs for both IL-1alpha and IL-1beta. Western analysis indicated that detectable levels of IL-1alpha protein, but not that of IL-1beta, are produced at the time of serotonin-dependent collagenase induction. In contrast, significant levels of IL-1beta protein are detected only when bacterial lipopolysaccharide is added to the cells. Taken together, the results of our study indicate that IL-1alpha, but not IL-1beta, plays an obligatory role in multiple serotonin-mediated gene regulations in the myometrial smooth muscle cell. In addition, the data suggest that IL-1beta production has the potential for modifying myometrial function in pathological settings, particularly that of uterine infection.

An interleukin-1 loop is induced in human skin fibroblasts upon stress relaxation in a three-dimensional collagen gel but is not involved in the up-regulation of matrix metalloproteinase 1

The integrin-mediated stress relaxation as it occurs in a retracting three-dimensional collagen gel (RCG) is accompanied by a large up-regulation of the interstitial collagenase, matrix metalloproteinase 1 ((MMP-1), EC 3.4.24.7), regulated notably by interleukin-1 (IL-1), phorbol esters, and cytoskeleton-disrupting drugs as cytochalasin D (CD). The repression of MMP-1 up-regulation in RCG by cycloheximide suggested the participation in the regulation process of a de novo synthesized intermediary component. We demonstrate here that culture of human skin fibroblasts in RCG or in CD- and 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated monolayers resulted in the activation of an IL-1 autocrine feedback loop that was switched off by the naturally occurring IL-1 receptor antagonist (IL-1RA), a blocker of the common IL-1 receptor. The IL-1RA did not suppress the MMP-1 up-regulation induced in RCG nor in CD-treated cells, indicating that the up-regulation of MMP-1 and the IL-1 autocrine loop occurred in an independent way, while the TPA-induced MMP-1 expression was suppressed by the receptor antagonist. The RCG- as well as the TPA-, IL-1-, and CD-induced up-regulation of both MMP-1 and IL-1 was totally suppressed by protein tyrosine kinases inhibitors. In contrast bisindoylmaleimide, at a concentration (5 microM) that inhibits the TPA-induced protein kinase C activity, suppressed the CD-induced MMP-1 expression but did not or barely altered that induced in RCG or by IL-1. None of the other tested inhibitors of a variety of signaling pathways including those used by integrins was able to suppress the RCG or CD-induced MMP-1. These results point to a potent regulation of MMP-1 by mechanical stress relaxation, a process depending on de novo protein synthesis and occurring independently of the activation of an IL-1 autocrine feedback loop.

Role of serum amyloid A as an intermediate in the IL-1 and PMA-stimulated signaling pathways regulating expression of rabbit fibroblast collagenase

The matrix metalloproteinase collagenase is expressed by resident tissue cells only when needed for biological remodeling. Exogenous addition of inflammatory and growth-promoting cytokines stimulates collagenase expression in early passage fibroblast cultures. In addition, the signal for collagenase expression in response to phorbol-12 myristate-13 acetate (PMA) or to agents which alter cell shape in early passage fibroblast cultures is routed extracellularly to an autocrine cytokine intermediate, IL-1 alpha. Importantly, fibroblasts, when freshly isolated from the tissue, are not competent for IL-1 alpha gene expression and, therefore, cannot produce collagenase in response to shape change agents. However, they do make a small amount of collagenase in response to PMA via an IL-1-independent pathway that has not been further characterized. In this paper, we investigate the role of a second autocrine, serum amyloid A3 (SAA3), in IL-1-dependent and -independent collagenase gene expression. We demonstrate that SAA3 is required for effective stimulation of collagenase expression by either exogenous or endogenous IL-1. Furthermore, while freshly isolated fibroblasts cannot express IL-1 alpha they can express SAA3, and this autocrine mediator acts independently of IL-1 alpha to control the low level of collagenase expression that can be stimulated by PMA. These results provide further evidence for a newly emerging paradigm of collagenase regulation which emphasizes the requirement for extracellular routing of signals. They also suggest that SAA3 might be utilized independently of IL-1 alpha to control tissue remodeling in vivo.

Substance P induces the secretion of gelatinase A from human synovial fibroblasts

We investigated the secretion of the matrix metalloproteinases, interstitial collagenase (matrix metalloproteinase-1), gelatinase A (matrix metalloproteinase-2) and stromelysin-1 (matrix metalloproteinase-3) in human synovial fibroblasts after stimulation with the neuropeptide substance P. Human synovial fibroblasts were stimulated with substance P or interleukin-1 beta (IL-1 beta). In the cell culture media gelatinase A, interstitial collagenase and stromelysin-1 were identified and their activities towards different substrates were determined. Substance P in synovial fibroblasts induced an increase in the overall matrix metalloproteinase activity towards the dinitrophenyl-labelled peptide by 85%, against an increase of 124% after stimulation with IL-1 beta. In case of substance P stimulation, the increase in activity reflects a significantly enhanced secretion of gelatinase A, whereas no significant increase of stromelysin-1 and collagenase secretion could be observed. The matrix metalloproteinase pattern showing the highest gelatinase A secretion was obtained after stimulation with substance P. This pattern was very pronounced and differed very clearly from the pattern seen after IL-1 beta stimulation which caused a significant rise in collagenase and stromelysin-1 activity. We assume that distinct stimulation pathways are involved and that the neuropeptide (substance P), which is always present in the inflamed joint, plays its own and separate role in proliferative processes leading to the cartilage destruction.

Chemical injuries of the eye: current concepts in pathophysiology and therapy

Chemical injuries of the eye may produce extensive damage to the ocular surface epithelium, cornea, and anterior segment, resulting in permanent unilateral or bilateral visual impairment. Pathophysiological events which may influence the final visual prognosis and which are amenable to therapeutic modulation include 1) ocular surface injury, repair, and differentiation, 2) corneal stromal matrix injury, repair and/or ulceration, and 3) corneal and stromal inflammation. Immediately following chemical injury, it is important to estimate and clinically grade the severity of limbal stem cell injury (by assessing the degree of limbal, conjunctival, and scleral ischemia and necrosis) and intraocular penetration of the noxious agent (by assessing clarity of the corneal stroma and anterior segment abnormalities). Immediate therapy is directed toward prompt irrigation and removal of any remaining reservoir of chemical contact with the eye. Initial medical therapy is directed promoting re-epithelialization and transdifferentiation of the ocular surface, augmenting corneal repair by supporting keratocyte collagen production and minimizing ulceration related to collagenase activity, and controlling inflammation. Early surgical therapy if indicated, is directed toward removal of necrotic corneal epithelium and conjunctiva, prompt re-establishment of an adequate limbal vascularity, and re-establishment of limbal stem cell population early in the clinical course, if sufficient evidence exists of complete limbal stem cell loss. Re-establishment of limbal stem cells by limbal autograft or allograft transplantation, or by transfer in conjunction with large diameter penetrating keratoplasty, may facilitate development of an intact, phenotypically correct corneal epithelium. Limbal stem cell transplantation may prevent the development of fibrovascular pannus or sterile corneal corneal ulceration, simplify visual rehabilitation, and improve the visual prognosis. Advances in ocular surface transplantation techniques which allow late attempts at visual rehabilitation of a scarred and vascularized cornea include limbal stem cell transplantation for incomplete transdifferentiation and persistent corneal epithelial dysfunction, and conjunctival and/or mucosal membrane transplantation for ocular surface mechanical dysfunction. Rehabilitation of the ocular surface may be followed, if necessary, by standard penetrating keratoplasty if all aspects of ocular surface rehabilitation are complete, or by large diameter penetrating keratoplasty if successful limbal stem cell transplantation cannot be achieved but other ocular surface rehabilitation is complete.

Comparative study of the role of professional versus semiprofessional or nonprofessional antigen presenting cells in the rejection of vascularized organ allografts

The immune systems of transplant recipients are progressively challenged with exposure to the multiple lineages of donor cells that comprise the vascularized organ allograft. Each lineage of such donor tissue constitutively expresses or can be induced to express varying densities of MHC antigens ranging from no expression of MHC to MHC class I only to both MHC class I and class II. In addition, the cell surface expression of a diverse assortment of costimulatory and cell adhesion molecules also varies in density in a tissue specific fashion within the allograft. The MHC class I/II molecules displayed on the donor cells contain within their clefts a constellation of processed protein antigens in the form of peptides derived from intracellular and to some extent extracellular sources. Therefore, the potential for each cell lineage to induce alloactivation and serve as a target for allospecific immune responses is dependent on the diversity and density of peptide-bearing MHC molecules, costimulatory molecules, and cell adhesion molecules. In addition, the T cell receptor repertoire of the recipient also contributes to the magnitude of the allogeneic response. Consequently, the variety of clinical outcomes following organ transplantation even with the institution of potent immunosuppressive (drug) therapies is not surprising, as it appears reasonable for such therapies to influence the allogeneic response against distinct lineages differentially. Our failure to prevent chronic human allograft rejection may therefore be due to our limited appreciation of the full spectrum of alloactivating experiences encountered by host T cells as they interact with donor cells of diverse tissue lineages. Investigations by our laboratory of the immunopathogenesis of chronic cardiac allograft rejection have revealed an intrinsic inability of human cardiac myocytes to process and present antigens, not only for primary but also for secondary alloimmune responses. One obvious explanation for this phenomenon is the fact that cardiac myocytes do not constitutively express MHC class II molecules and express only low levels of class I molecules. However, this immunological unresponsiveness is maintained even after the induction of MHC class II and upregulation of MHC class I on these cells by interferon-gamma (IFN-gamma). Similar results have also been reported for cells of different tissue lineages (e.g. chondrocytes, keratinocytes, neural cells). Until now, cells have been defined as professional or nonprofessional for the purposes of defining their potential for antigen presentation to T cells. Professional antigen presenting cells have been identified as cells that are of haematopoietic origin, that constitutively express MHC class I and class II molecules as well as potent costimulatory molecules, and that are able to induce both primary and secondary immune responses, whereas nonprofessional antigen presenting cells are not bone marrow derived, do not constitutively express MHC class II, but may in some cases initiate primary and secondary immune responses after induction of MHC class II antigen by proinflammatory cytokines (e.g. IFN-gamma). The findings of our laboratory and others suggest that cells of certain lineages be considered in the separate class of 'nonantigen presenting cells'. Indeed, nonprofessional antigen presenting cells can be reclassified into three categories: semiprofessional-, nonprofessional-, or nonantigen presenting cells that are able to present antigen to and activate naive T cells, activated T cells, or no T Cells, respectively. The aim of this review is to identify and (re)examine the antigen presentation characteristics of cells of different tissue lineages in terms of their ability to activate different subsets of T cells. This approach is taken in an attempt to synthesize these concepts into a unified picture of T cell activation in the context of antigen processing and presentation by different cell types.

Regulation of plasminogen activation, matrix metalloproteinases and urokinase-type plasminogen activator-mediated extracellular matrix degradation in human osteosarcoma cell line MG63 by interleukin-1 alpha

Plasmin-mediated extracellular proteolysis has been implicated in the degradation of bone in normal and pathological conditions. Normal and malignant osteoblasts can produce both tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA). We have used the osteosarcoma cell line MG63 to address the question of whether the enhanced bone turnover in osteosarcomas is mediated by t-PA or by u-PAA and to study the effect of the cytokine interleukin-1 alpha (IL-1 alpha), known to influence bone degradation, on the plasminogen activator production and extracellular matrix degradation in malignant osteoblastic cells. Furthermore, the effect of IL-1 alpha on the synthesis of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) was analyzed. u-PA production by MG63 was high (approximately 180 ng/10(6) cells/24 h). Also t-PA and PAI-1 production was observed. u-PA production was rapidly increased in MG63 by IL-1 alpha (10 ng/ml), whereas an effect on t-PA production was only found after a prolonged incubation and hardly any effect of IL-1 alpha on PAI-1 production was observed. mRNA analysis revealed similar effects. u-PA receptor (u-PAR) mRNA was detectable in MG63 cells and could be increased by IL-1 alpha after 24 h. In MG63, u-PA-mediated extracellular matrix degradation was detectable, and IL-1 alpha increased the u-PA-mediated matrix degradation (approximately 2-fold). Under control conditions in MG63, only MMP-2, TIMP-1, and TIMP-2 mRNA could be observed. After the addition of IL-1 alpha, a very rapid increase in MMP-1 and MMP-3 mRNA could be observed as well as a moderate increase in TIMP-1 mRNA. The presence of MMP-2 was demonstrated by gelatin zymography. These results show that IL-1 alpha can stimulate u-PA production and can regulate extracellular proteolytic activity mainly via u-PA induction in the MG63 osteosarcoma cell line. Furthermore, IL-1 alpha has a strong stimulating effect on the production of MMP-1 and MMP-3. These findings suggest that u-PA and possibly MMP-1 and MMP-3 play an important role in the process of bone turnover in osteosarcomas.