Meilang Xue

Targeting matrix metalloproteases to improve cutaneous wound healing

Wound repair is a physiological event in which tissue injury initiates a repair process leading to restoration of structure and function of the tissue. Cutaneous wound repair can be divided into a series of overlapping phases including formation of fibrin clot, inflammatory response, granulation tissue formation incorporating re-epithelialisation and angiogenesis and finally, matrix formation and remodelling. Matrix metalloproteases (MMPs) are a family of neutral proteases that play a vital role throughout the entire wound healing process. They regulate inflammation, degrade the extracellular matrix (ECM) to facilitate the migration of cells and remodel the new ECM. However, excessive MMP activity contributes to the development of chronic wounds. Selective control of MMP activity may prove to be a valuable therapeutic approach to promote healing of chronic ulcers. Recent evidence indicates that the anticoagulant, activated protein C may be useful in the treatment of non-healing wounds by preventing excessive protease activity through inhibition of inflammation and selectively increasing MMP-2 activity to enhance angiogenesis and re-epithelialisation.

Activated protein C prevents inflammation yet stimulates angiogenesis to promote cutaneous wound healing

Activated protein C (APC) is a serine protease that plays a central role in physiological anticoagulation, and has more recently been shown to be a potent anti‐inflammatory mediator. Using cultured human cells, we show here that APC up‐regulates the angiogenic promoters matrix metalloproteinase‐2 in skin fibroblasts and umbilical vein endothelial cells, vascular endothelial growth factor in keratinocytes and fibroblasts, and monocyte chemoattractant protein‐1 in fibroblasts. In the chick embryo chorioallantoic membrane assay, APC promoted the granulation/remodeling phases of wound healing by markedly stimulating angiogenesis as well as promoting reepithelialization. In a full‐thickness rat skin‐healing model, a single topical application of APC enhanced wound healing compared to saline control. APC‐treated wounds had markedly more blood vessels on day 7 and a significantly lower infiltration of neutrophils at days 4 and 7. The broad spectrum matrix metallo‐proteinas, GM6001, prevented the ability of APC to promote wound healing. In summary, our results show that APC promotes cutaneous wound healing via a complex mechanism involving stimulation of angiogenesis and inhibition of inflammation. These unique properties of APC make it an attractive therapeutic agent to promote the healing of chronic wounds.

Activated protein C utilizes the angiopoietin/Tie2 axis to promote endothelial barrier function

Activated protein C (APC) is an anticoagulant, approved as a treatment for severe sepsis, that can prevent apoptosis, inflammation, and vascular leakage. The aim of this study was to investigate whether APC protects endothelial barrier function through the angiopoietin (Ang)/Tie2 axis. APC significantly up‐regulated gene and protein expression of Tie2 and Ang1 in a dose (0.01–10 μg/ml)‐ and time (0.5–24 h)‐dependent manner in human umbilical vein endothelial cells (HUVECs). Interestingly, it markedly inhibited Ang2 with an IC50 of ~0.1 μg/ml. HUVEC permeability, measured using Evans blue dye transfer, was significantly reduced in the presence of APC, and, in concordance, the tight junction associated protein zona occludens (ZO)‐1 was up‐regulated and localized peripherally around cells, compared with controls. Smooth muscle cell migration toward APC‐stimulated HUVECs was elevated compared with unstimulated cells. Blocking antibodies and small interfering (si) RNA treatment, compared with isotype (IgG) or scrambled siRNA controls, showed that APC requires 3 receptors, the endothelial protein C receptor, protease‐activated receptor 1, and Tie2 to perform all these barrier stabilization functions. In summary, this study demonstrates that APC has novel effects on the Ang/Tie2 axis, which enhance endothelial barrier function and are likely to contribute to its therapeutic effect in sepsis and other diseases associated with vascular leakage.—Minhas, N., Xue, M., Fukudome, K., Jackson, C. J. Activated protein C utilizes the angiopoietin/Tie2 axis to promote endothelial barrier function. FASEB J. 24, 873–881 (2010). www.fasebj.org

1α, 25-dihydroxyvitamin D3 inhibits pro-inflammatory cytokine and chemokine expression in human corneal epithelial cells colonized with Pseudomonas aeruginosa

The cytokines IL‐1β, IL‐6 and the chemokine IL‐8 are key mediators of host inflammation. 1α,25‐Dihydroxyvitamin D3 (VD3) has been shown to regulate host immune responses in vivo and in vitro. The purpose of this study was to investigate whether the addition of VD3 to human corneal epithelial cells colonized with Pseudomonas aeruginosa altered the expression of IL‐1β, IL‐6 and IL‐8. An immortalized human corneal epithelial (HCE) cell line was used in this study. After growth to confluency, HCE cells were challenged with P. aeruginosa strain 6294 in the presence or absence of 10−6 mol/L VD3 for 4 h, 8 h and 12 h. Gene expression of IL‐1β, IL‐6 and IL‐8 was detected by reverse transcription‐PCR (RT‐PCR) from total RNA extracted from HCE cells. Protein concentrations of IL‐1β, IL‐6 and IL‐8 in culture supernatants were measured by ELISA. Addition of VD3 to HCE cells colonized with P. aeruginosa significantly inhibited the expression of IL‐1β and IL‐8 mRNA and protein (P < 0.05). Although the expression of IL‐6 mRNA was stimulated at 12 h post‐challenge (P < 0.05), the expression of IL‐6 protein was inhibited at all time points after the addition of VD3. In conclusion, this study demonstrated that VD3 inhibited the P. aeruginosa‐induced expression of IL‐1β, IL‐6 and IL‐8 in HCE cells, suggesting that this vitamin may have the potential to become a novel anti‐inflammatory agent in ocular disease.

Protein C Is an Autocrine Growth Factor for Human Skin Keratinocytes

The protein C (PC) pathway plays an important role in coagulation and inflammation. Many components of the PC pathway have been identified in epidermal keratinocytes, including endothelial protein C receptor (EPCR), which is the specific receptor for PC/activated PC (APC), but the core member of this pathway, PC, and its function in keratinocytes has not been defined. In this study, we reveal that PC is strongly expressed by human keratinocytes at both gene and protein levels. When endogenous PC was blocked by siRNA the proliferation of keratinocytes was significantly decreased. This inhibitory effect was restored by the addition of recombinant APC. PC siRNA treatment also increased cell apoptosis by 3-fold and inhibited cell migration by more than 20%. When keratinocytes were pretreated with RCR252, an EPCR-blocking antibody, or PD153035, an epidermal growth factor receptor (EGFR) inhibitor, cell proliferation was hindered by more than 30%. These inhibitors also completely abolished recombinant APC (10 μg/ml)-stimulated proliferation. Blocking PC expression or inhibiting its binding to EPCR/EGFR decreased the phosphorylation of ERK1/2 but increased p38 activation. Furthermore, inhibition of ERK decreased cell proliferation by ∼30% and completely abolished the stimulatory effect of APC on proliferation. Taken together, these results indicate that keratinocyte-derived PC promotes cell survival, growth, and migration in an autocrine manner via EPCR, EGFR, and activation of ERK1/2. Our results highlight a novel role for the PC pathway in normal skin physiology and wound healing.

Activated protein C--an anticoagulant that does more than stop clots.

Activated protein C (APC) is a glycoprotein derived from its precursor, protein C and formed by the cleavage of an activation peptide by thrombin bound to thrombomodulin. Originally thought to be synthesized exclusively by the liver, recent reports have shown that protein C is synthesized by endothelial cells, keratinocytes and some hematopoietic cells. APC functions as a physiological anticoagulant with cytoprotective, anti-inflammatory and anti-apoptotic properties. In vitro and preclinical data have revealed that APC exerts its protective effects via an intriguing mechanism requiring endothelial protein C receptor and the thrombin receptor, protease-activated receptor-1. Remarkably, even though APC cleaves this receptor in an identical fashion to thrombin, it exerts opposing effects. Recently approved as a therapeutic agent for severe sepsis, APC is now emerging as a potential treatment for a number of autoimmune and inflammatory diseases including lung disorders, spinal cord injury and chronic wounds. The future pharmacologic use of APC holds remarkable promise.

Endogenous MMP-9 and not MMP-2 promotes rheumatoid synovial fibroblast survival, inflammation and cartilage degradation

OBJECTIVE The aim of this study was to investigate the effect of endogenous matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) on the invasive characteristics of RA synovial fibroblasts. METHODS Synovial fibroblasts isolated from patients with RA or OA were treated with MMP small interfering RNA (siRNA), inhibitors and recombinant proteins or TNF-α, with or without cartilage explants. Cell viability and proliferation were measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide and 5-bromo-2-deoxyuridine (BrdU) proliferation assays, respectively; apoptosis by an in situ cell death detection kit; migration and invasion by CytoSelect invasion assay, scratch migration and collagen gel assays; cartilage degradation by 1,9-dimethylmethylene blue assay; and inflammatory mediators and MMPs by ELISA, western blot and zymography. RESULTS MMP-2 was expressed by both OA and RA synovial fibroblasts, whereas only RA synovial fibroblasts expressed MMP-9. Suppressing MMP-2 or MMP-9 reduced RA synovial fibroblast proliferation equally. However, MMP-9 siRNA had greater effects compared with MMP-2 siRNA on promoting apoptosis and suppressing RA synovial fibroblast viability, migration and invasion. Suppression/inhibition of MMP-9 also decreased the production of IL-1β, IL-6, IL-8 and TNF-α, inactivated nuclear factor κB (NF-κB), extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) and suppressed RA synovial fibroblast-mediated cartilage degradation. In contrast, suppression/inhibition of MMP-2 stimulated TNF-α and IL-17 secretion and activated NF-κB, while recombinant MMP-2 (rMMP-2) inactivated NF-κB and suppressed RA synovial fibroblast-mediated cartilage degradation. Results using specific inhibitors and rMMPs provided supportive evidence for the siRNA results. CONCLUSION Endogenous MMP-2 or MMP-9 contribute to RA synovial fibroblast survival, proliferation, migration and invasion, with MMP-9 having more potent effects. Additionally, MMP-9 stimulates RA synovial fibroblast-mediated inflammation and degradation of cartilage, whereas MMP-2 inhibits these parameters. Overall, our data indicate that MMP-9 derived from RA synovial fibroblasts may directly contribute to joint destruction in RA.

Role and regulation of CXC-chemokines in acute experimental keratitis

The aim of this study was to elucidate the expression of chemokines, their role and regulation in bacterial corneal infection using three bacterial strains (Pseudomonas. aeruginosa- invasive, cytotoxic and contact lens induced acute red eye strains) which have been shown to produce three distinct patterns of corneal disease in the mouse. The predominant chemokine expressed in response to all three strains was MIP-2. Prolonged expression of high levels of MIP-2 was associated with increased severity of corneal inflammation. Significantly reduced disease severity upon administration of anti-MIP-2 antibodies suggested that MIP-2 may play an important role in the pathogenesis of Pseudomonas keratitis at least in part by being a major chemoattractant for polymorphonuclear leukocytes (PMN) recruitment. Interestingly, the numbers of bacteria in eyes with neutralized MIP-2 activity did not decrease even though the severity of the disease was decreased. This implies PMNs as the major destructive factor in microbial keratitis. Further, neutralization of IL-1beta activity alone using monoclonal antibodies resulted in significant reduction of both MIP-2 and KC activity indicating that chemokine levels were regulated by IL-1beta. These studies demonstrate that the regulation of MIP-2 activity may be beneficial in reducing corneal damage during microbial keratitis in rodents and perhaps that regulation of the human homologue of MIP-2, IL-8, may be useful for controlling keratitis in humans.

Activation of cartilage matrix metalloproteinases by activated protein C

OBJECTIVE To investigate the role of activated protein C (APC) in cartilage degradation. METHODS Chondrocyte expression of protein C, endothelial protein C receptor (EPCR), and thrombomodulin (TM) were evaluated by reverse transcription-polymerase chain reaction (RT-PCR). APC was immunolocalized in developing joints and in osteoarthritic (OA) cartilage from humans. The effect of APC on aggrecan and collagen degradation was examined in explant cultures of ovine cartilage in control cultures and in cultures stimulated with interleukin-1alpha (IL-1alpha), tumor necrosis factor alpha (TNFalpha), or retinoic acid (RetA), using colorimetric assays and Western blotting. Chondrocyte expression of matrix metalloproteinases (MMPs), ADAMTS, and tissue inhibitor of metalloproteinases (TIMPs) was measured by RT-PCR. MMP-2 and MMP-9 activity was evaluated by gelatin zymography and MMP-13 by fluorogenic assay. RESULTS Positive cellular immunostaining for APC was found at sites of MMP activity in developing joints and in OA, but not normal, cartilage. Chondrocytes expressed messenger RNA for protein C, EPCR, and TM, with the latter 2 levels increased by IL-1alpha and TNFalpha stimulation. APC augmented aggrecan release and initiated collagen breakdown in IL-1alpha-treated and TNFalpha-treated cartilage, but not in normal or in RetA-treated cartilage. APC-stimulated aggrecan and collagen breakdown were due to MMP activity but were not associated with modulation of MMP, ADAMTS, or TIMP expression. APC resulted in MMP-13 activation in cartilage cultures. APC could not directly activate proMMP-13, but it was associated with increased MMP-2 and MMP-9 activity. CONCLUSION APC may be a relevant activator of MMPs in cartilage and may play a role in progressive cartilage degradation in arthritis.

Treatment of Chronic Leg Ulcers With Topical Activated Protein C

BACKGROUND The treatment of skin ulcers frequently presents a management challenge. Nonhealing wounds with poor response to conventional wound management therapy represent a significant cause of disability, affecting approximately 1% of the global population. Activated protein C is a serine protease with anticoagulant, angiogenic, and anti-inflammatory properties that has shown efficacy in patients for the treatment of severe sepsis. We report 4 cases of nonhealing lower limb skin ulcers that were treated with activated protein C. OBSERVATIONS The study included 4 patients whose wounds were not improving despite standard wound treatment for 4 months or more. Activated protein C was applied topically to their wounds once weekly for 4 weeks. All 4 patients showed a rapid positive response to treatment that was maintained during a 4-month follow-up period. The treatment was well tolerated, with no remarkable adverse effects or complications. CONCLUSIONS Activated protein C can stimulate wound healing in patients with skin ulcers that are refractory to conventional wound-healing therapies. The likely mechanism of action is its recognized ability to stimulate angiogenesis and reepithelialization and to inhibit inflammation. Activated protein C has potential as a therapeutic option for patients with chronic skin ulcers.