Inhibiting Matrix Metalloproteinase 3 Ameliorates Neuronal Loss in the Ganglion Cell Layer of Rats in Retinal Ischemia/Reperfusion

Matrix Metalloproteinases in Glaucoma: An Updated Overview

Matrix metalloproteinases (MMPs) are important regulators of the extracellular matrix (ECM) and are involved in many stages of cellular growth and development. An imbalance of MMP expression is also the basis of many diseases, including eye diseases, such as diabetic retinopathy (DR), glaucoma, dry eye, corneal ulcer, keratoconus. This paper describes the role of MMPs in the glaucoma and their role in the glaucomatous trabecular meshwork (TM), aqueous outflow channel, retina, and optic nerve (ON). This review also summarizes several treatments for glaucoma that target MMPs imbalance and suggests that MMPs may represent a viable therapeutic target for glaucoma.

Apoptosis-associated speck-like protein containing a CARD-mediated release of matrix metalloproteinase 10 stimulates a change in microglia phenotype

Inflammation contributes to amyloid-β and tau pathology in Alzheimer's disease (AD). Microglia facilitate an altered immune response that includes microgliosis, upregulation of inflammasome proteins, and elevation of matrix-metalloproteinases (MMPs). Studies of cerebrospinal fluid (CSF) and blood in dementia patients show upregulation of two potential biomarkers of inflammation at the cellular level, MMP10 and apoptosis-associated speck-like protein containing a CARD (ASC). However, little is known about their relationship in the context of brain inflammation. Therefore, we stimulated microglia cultures with purified insoluble ASC speck aggregates and MMP10 to elucidate their role. We found that ASC specks altered microglia shape and stimulated the release of MMP3 and MMP10. Furthermore, MMP10 stimulated microglia released additional MMP10 along with the inflammatory cytokines, tumor-necrosis factor-α (TNFα), Interleukin 6 (IL-6), and CXCL1 CXC motif chemokine ligand 1 (CXCL1). A broad-spectrum MMP inhibitor, GM6001, prevented TNFα release. With these results, we conclude that MMP10 and ASC specks act on microglial cells to propagate inflammation.

Pre-Ischemic Hypothermic Oxygenated Perfusion Alleviates Protective Molecular Markers of Ischemia-Reperfusion Injury in Rat Liver

To expand the pool of organs, hypothermic oxygenated perfusion (HOPE), one of the most promising perfusion protocols, is currently performed after cold storage (CS) at transplant centers (HOPE-END). We investigated a new timing for HOPE, hypothesizing that performing HOPE before CS (HOPE-PRE) could boost mitochondrial protection allowing the graft to better cope with the accumulation of oxidative stress during CS. We analyzed liver injuries at 3 different levels. Histologic analysis demonstrated that, compared to classical CS (CTRL), the HOPE-PRE group showed significantly less ischemic necrosis compared to CTRL vs HOPE-END. From a biochemical standpoint, transaminases were lower after 2 hours of reperfusion in the CTRL vs HOPE-PRE group, which marked decreased liver injury. qPCR analysis on 37 genes involved in ischemia-reperfusion injury revealed protection in HOPE-PRE and HOPE-END compared to CTRL mediated through similar pathways. However, the CTRL vs HOPE-PRE group demonstrated an increased transcriptional level for protective genes compared to the CTRL vs HOPE-END group. This study provides insights on novel biomarkers that could be used in the clinic to better characterize graft quality improving transplantation outcomes.

Ocular TGF-β, Matrix Metalloproteinases, and TIMP-1 Increase with the Development and Progression of Diabetic Retinopathy in Type 2 Diabetes Mellitus

Diabetic retinopathy (DR) is a sight-threatening late complication of diabetes mellitus (DM). Even though its pathophysiology has not been fully elucidated, several studies suggested a role for transforming growth factor- (TGF-) β, matrix metalloproteinases (MMPs), and tissue inhibitors of matrix metalloproteinase (TIMP) in the onset and progression of the disease. Consequently, the aim of this study was to analyze the concentrations of TGF-β1, TGF-β2, TGF-β3, MMP-3, MMP-9, and TIMP-1 in patients with different stages of DR in order to identify stage-specific changes in their concentrations during the progression of the disease. Serum and aqueous humor (AH) samples were collected during intraocular surgery, and eyes were classified into the following groups: healthy controls (n = 17), diabetic patients with non-apparent DR (n = 23), mild/moderate nonproliferative DR (NPDR) (n = 13), and advanced NPDR/proliferative DR (PDR) without vitreal hemorrhage (n = 14). None of the patients had been under anti-VEGF or laser treatment within six months prior to surgery. In the AH, TGF-β1 levels increased in advanced NPDR/PDR by a factor of 5.5 compared to the control group. Similarly, an increase in MMP-3 and TIMP-1 levels in the AH was evident in the later stages of DR, corresponding to a 7.7- and 2.4-fold increase compared to the control group, respectively, whereas serum levels of the studied proteins remained similar. In conclusion, increased concentrations of TGF-β1, MMP-3, and TIMP-1 in the AH, but not in the serum, in advanced NPDR/PDR indicate that the intraocular regulation for these cytokines is independent of the systemic one and suggest their involvement in the progression of DR.

Knock-Out of Tenascin-C Ameliorates Ischemia-Induced Rod-Photoreceptor Degeneration and Retinal Dysfunction

Retinal ischemia is a common pathomechanism in various eye diseases. Recently, evidence accumulated suggesting that the extracellular matrix (ECM) glycoprotein tenascin-C (Tnc) plays a key role in ischemic degeneration. However, the possible functional role of Tnc in retinal ischemia is not yet known. The aim of our study was to explore retinal function and rod-bipolar/photoreceptor cell degeneration in wild type (WT) and Tnc knock-out (KO) mice after ischemia/reperfusion (I/R) injury. Therefore, I/R was induced by increasing intraocular pressure in the right eye of wild type (WT I/R) and Tnc KO (KO I/R) mice. The left eye served as untreated control (WT CO and KO CO). Scotopic electroretinogram (ERG) recordings were performed to examine rod-bipolar and rod-photoreceptor cell function. Changes of Tnc, rod-bipolar cells, photoreceptors, retinal structure and apoptotic and synaptic alterations were analyzed by immunohistochemistry, Hematoxylin and Eosin staining, Western blot, and quantitative real time PCR. We found increased Tnc protein levels 3 days after ischemia, while Tnc immunoreactivity decreased after 7 days. Tnc mRNA expression was comparable in the ischemic retina. ERG measurements after 7 days showed lower a-/b-wave amplitudes in both ischemic groups. Nevertheless, the amplitudes in the KO I/R group were higher than in the WT I/R group. We observed retinal thinning in WT I/R mice after 3 and 7 days. Although compared to the KO CO group, retinal thinning was not observed in the KO I/R group until 7 days. The number of PKCα⁺ rod-bipolar cells, recoverin⁺ photoreceptor staining and Prkca and Rcvrn expression were comparable in all groups. However, reduced rhodopsin protein as well as Rho and Gnat1 mRNA expression levels of rod-photoreceptors were found in the WT I/R, but not in the KO I/R retina. Additionally, a lower number of activated caspase 3⁺ cells was observed in the KO I/R group. Finally, both ischemic groups displayed enhanced vesicular glutamate transporter 1 (vGlut1) levels. Collectively, KO mice showed diminished rod-photoreceptor degeneration and retinal dysfunction after I/R. Elevated vGlut1 levels after ischemia could be related to an impaired glutamatergic photoreceptor-bipolar cell signaling and excitotoxicity. Our study provides novel evidence that Tnc reinforces ischemic retinal degeneration, possibly by synaptic remodeling.

Regional Expression of Act-MMP3 Contributes to the Selective Loss of Neurons in Ganglion Cell Layers following Acute Retinal ischemia/Reperfusion Injury

Purpose: Evidences suggest that during ischemia/reperfusion events, neuronal loss in ganglion cell layers (GCLs) occurs initially in the peripheral retinae followed by the central. However, which key molecule or factor mediates this selective loss needs elucidation. In the present study, we detected the regional expression of active matrix metalloproteinase 3 (Act-MMP3) in the central and peripheral rat retinae following acute retinal ischemia/reperfusion (RI/R) injury and explored the effects and mechanisms of this regional expression on the selective neuronal loss in GCLs.Methods: QPCR and Western Blotting were used to detect the expression of Act-MMP3 in the central part and peripheral part of the adult rat retinae. Immunofluorescence and double immunofluorescence were used to assess the number of NeuN-positive cells in the GCLs and Iba-1+CD 68-positive cells were determined. Additionally, the Linear-regression analysis was performed to test the correlation between the ODV of Act-MMP3 and the neuronal loss in the GCLs/Iba-1+CD 68 positive cells in retinae.Results: An evident up-regulation of active matrix metalloproteinase 3 (Act-MMP3) in peripheral retinae preceded to that in central region following acute RI/R. We found Act-MMP3 up-regulation to be associated with the selective neuronal loss in GCLs (central: r = 0.7566, p < .0001, r² = 0.5724; peripheral: r = 0.8241, p < .0001, r² = 0.6792). Suppressing Act-MMP3 ameliorated the selective neuronal loss in GCLs following acute RI/R. Furthermore, the activation of microglia in the peripheral retinae also preceded to that in the central and was found to be correlated with the regional expression of Act-MMP3 (Central: r = 0.8540, p < .0001, r² = 0.7294; Peripheral: r = 0.7820, p < .0001, r² = 0.6116). Suppressing Act-MMP3 ameliorated the microglia regional activation following acute RI/R.Conclusion: The regional expression of Act-MMP3 in the rat retinae may contribute to the selective neuronal loss in GCLs and microglia regional activation in acute RI/R.

MMP Inhibition Preserves Integrin Ligation and FAK Activation to Induce Survival and Regeneration in RGCs Following Optic Nerve Damage

Purpose

Integrin adherence to the extracellular matrix (ECM) is essential for retinal ganglion cell (RGC) survival: damage causes production and release of ECM degrading matrix metalloproteinases (MMPs) that disrupt integrin ligation, leading to RGC death. The interplay of MMPs, integrins, and focal adhesion kinase (FAK) was studied in RGCs after optic nerve injury.

Methods

Optic nerve transection and optic nerve crush were used to study RGC survival and regeneration, respectively. Treatments were administered intravitreally or into the cut end of the optic nerve. RGC survival was assessed by fluorescence or confocal microscopy; cell counting, peptide levels, and localization were assessed by Western blot and immunohistochemistry.

Results

MMP-9 was most strongly increased and localized to RGCs after injury. Pan-MMP, MMP-2/-9, and MMP-3 inhibition all significantly enhanced RGC survival and increased RGC axon regeneration. FAK activation was decreased at 4 days postaxotomy, when apoptosis begins. FAK inhibition reduced RGC survival and abrogated the neuroprotective effects of MMP inhibition, whereas FAK activation increased RGC survival despite MMP activation. Integrin ligation with CD29 antibody or glycine-arginine-glycine-aspatate-serine (GRGDS) peptide increased RGC survival after axotomy.

Conclusions

ECM-integrin ligation promotes RGC survival and axon regeneration via FAK activation.

Tissue Inhibitor of Metalloprotease-2 (TIMP-2): Bioprocess Development, Physicochemical, Biochemical, and Biological Characterization of Highly Expressed Recombinant Protein

Tissue inhibitor of metalloprotease-2 (TIMP-2) is a secreted 21 kDa multifunctional protein first described as an endogenous inhibitor of matrix metalloproteinases (MMPs) that prevents breakdown of the extracellular matrix often observed in chronic diseases. TIMP-2 diminishes the level of growth factor-mediated cell proliferation in vitro, as well as neoangiogenesis and tumor growth in vivo independent of its MMP inhibitory activity. These physiological properties make TIMP-2 an excellent candidate for further preclinical development as a biologic therapy of cancer. Here we present a straightforward bioprocessing methodology that yields >35 mg/L recombinant human TIMP-2 6XHis-tagged protein (rhTIMP-2) from suspension cultures of HEK-293-F cells. Enhanced rhTIMP-2-6XHis yields were achieved by optimization of both TIMP-2 cDNA codon sequence and cell culture conditions. Using a two-step chromatographic process, we achieved >95% purity with minimal processing losses. Purified rhTIMP-2-6XHis was free of mouse antigen contamination. Circular dichroism spectroscopy indicated a well-folded rhTIMP-2-6XHis that is highly stable and refractory to pH changes. Two-dimensional heteronuclear single-quantum coherence nuclear magnetic resonance of full length rhTIMP-2-6XHis also indicated a monodisperse, well-folded protein preparation. Purified rhTIMP-2-6XHis inhibited MMP-2 enzymatic activity in a dose-dependent fashion with an IC50 of ∼1.4 nM. Pretreatment of A549 lung cancer and JygMC(A) triple-negative breast cancer cells with rhTIMP-2-6XHis in low-nanomolar amounts inhibited EGF-induced proliferation to basal (unstimulated) levels. This study therefore not only offers a robust bioprocess methodology for rhTIMP-2 production but also characterizes critical physicochemical and biological attributes that are useful for monitoring quality control of the production process.