This study aimed to investigate the effect of OM-101 on the fibrotic response occurring in proliferative vitreoretinopathy (PVR) in an animal model.Antifibrotic effect of OM-101 was investigated in vivo. As control, eight weeks old c57black mice underwent intravitreal injection with Hepes (group A) or dispase (0.3 units), to induce retinal detachment (RD) and PVR. The dispase-injected mice were randomly divided into two groups B and C (N = 25 mice); in group C, the eyes were treated with intravitreal injection of OM-101 (3 μl), and group B with PBS, as a control. After additional five days, mice were injected with the same initial treatment. Three days later, mice were euthanized, and the eyes were enucleated and processed for histological analysis.Intravitreal injection of dispase caused RD in 64% of the mice in group B, and 93% of those mice had PVR. Only 32% of mice treated with OM-101 and dispase (group C) developed RD, and only 25% of those developed PVR.OM-101 was found effective in reducing the incidence of RD and PVR maintaining the normal architecture of the retina. This study suggests that OM-101 is a potentially effective and safe drug for the treatment of PVR patients.
Abstract Oocyte maturation in mammals is a multiple-stage process that generates fertilizable oocytes. Ovarian oocytes are arrested at prophase of the first meiotic division characterized by the presence of a germinal vesicle. Towards ovulation, the oocytes resume meiosis and proceed to the second metaphase in a process known as maturation; they undergo nuclear and cytoplasmic changes that are accompanied by translation and degradation of mRNA. Protein phosphatase 1A, magnesium dependent, alpha isoform (PPM1A), which belongs to the metal-dependent serine/threonine protein phosphatase family, is highly conserved during evolution. PPM1A plays a significant role in many cellular functions such as cell cycle progression, apoptosis and cellular differentiation. It works through diverse signaling pathways, including p38 MAP kinase JNK and transforming growth factor beta (TGF-β). Herein we report that PPM1A is expressed in mouse oocytes and that its mRNA level rises during oocyte maturation. Using quantitative real-time polymerase chain reaction (qPCR) and western blot analysis, we found that PPM1A mRNA is synthesized at the beginning of the maturation process and remains elevated in the mature oocytes, promoting the accumulation of PPM1A protein. Since PPM1A function is mainly affected by its level, we propose that it might have an important role in oocyte maturation.
Oxidative stress and cellular senescence are known to contribute to the development of AMD; however, the mechanism is not fully understood. This study investigated the role of TGF-β-activated kinase 1 (TAK1) in the senescence of RPE cells as a model for the development of dry AMD.Cultured human RPE cells were treated with the TAK1 inhibitor 5Z-7-oxozeaenol for 1 hour, and then treated with 200 μM hydrogen peroxide for 1 hour. Human RPE cells that were not pretreated with TAK1 inhibitor for 1 hour served as controls. Senescence-associated β-galactosidase (SA-β-gal) activity was detected by histochemistry, and p53 expression by immunoblotting. Cell-cycle and apoptosis rate in RPE cells were determined by flow cytometry.The TAK1 expression in human RPE cells was high and was altered on oxidative stress. Transforming growth factor-β-activated kinase 1 inhibition led to reduction in cell proliferation, cell-cycle arrest at G0/G1, and increased SA-β-gal expression, all known to be features of cell senescence. Exposure of cells to oxidative stress combined with inhibition of TAK1 activity decreased the expression of apoptotic proteins, such as p53, and promoted cellular senescence. Aberrant TAK1 activity in RPE cells triggered their secretion of factors that induced hypertrophy and fibrotic changes in neighboring cells.The in vitro evidence indicated a role for TAK1 in the onset of senescence in RPE cells. The data shown hereby demonstrated that TAK1 activity is essential for maintaining normal function of RPE cells. Elucidation of its role in mechanisms underlying RPE cellular senescence induction may potentiate development of powerful tools for halting the development of dry AMD.
Autophagy is an evolutionarily conserved mechanism for degrading long-lived or malfunctioning proteins and organelles, such as those resulting from oxidative stress. Several publications have demonstrated the importance of the autophagy process in the pathophysiology of dry age-related macular degeneration (AMD). Still, the mechanism underlying this process and its involvement in dry AMD are not fully characterized. Investigating the autophagy process in retinal pigment epithelial (RPE) cells, we identified transforming growth factor β activated kinase 1 (TAK1) as a key player in the process. We found increased TAK1 phosphorylation in ARPE-19 and D407 cells treated with different inducers of autophagy, such as oxidative stress and rapamycin. Moreover, utilizing TAK1 specific inhibitor prior to oxidative stress or rapamycin treatment, we found significant reduction in LC3A/B-II expression. These results point at the involvement of TAK1 in the regulation of autophagy in RPE cells. This study suggests that aberrant activity of this kinase impairs autophagy and subsequently leads to alterations in the vitality of RPE cells. Proper activity of TAK1 may be essential for efficient autophagy, and crucial for the ability of RPE cells to respond to stress and dispose of damaged organelles, thus preventing or delaying retinal pathologies.
Background and Aim Proliferative vitreoretinopathy (PVR) is an active process that develops as a complication upon retinal detachment (RD), accompanied by formation of fibrotic tissue. The main cells involved in the development of fibrotic tissue during PVR are the retinal pigment epithelial (RPE) cells. The RPE cells undergo epithelial-mesenchymal transition (EMT) which leads to complex retinal detachment and loss of vision. Transforming growth factor-β1 (TGF-β1) is considered as the main player in the EMT of RPE cells, even though the mechanism is not fully understood. This study was performed to determine the possible involvement of transforming growth factor β activated kinase 1 (TAK1) in the EMT process of the RPE cells. Methodology ARPE-19 Cells were treated with 5Z-7 oxozeaenol (TAK1 inhibitor) or SB431542 (TGF-β1 receptor kinase inhibitor) followed by TGF-β1 stimulation. Immunofluorescence, scratch assay Real time PCR and collagen contraction assay assessed the EMT features. The phosphorylation of Smad2/3 and p38 was examined using western blots analysis. Results This study demonstrates that stimulation of RPE cells with TGF-β1 increases α-SMA expression, cell migration and cell contractility, all of which are EMT features. Remarkably, addition of TAK1 inhibitor abolishes all these processes. Furthermore, we show hereby that TAK1 regulates not only the activation of the non-canonical cascade of TGF-β1 (p38), but also the canonical cascade, the Smad2/3 activation. Thus, the outcome of the TGF-β response in RPE cells is TAK1 dependent. Conclusions/Significance This work demonstrated TAK1, a component of the non-canonical pathway of TGF-β1, is a key player in the EMT process, thus provides deep insight into the pathogenesis of PVR. The ability to halt the process of EMT in RPE cells may reduce the severity of the fibrotic response that occurs upon PVR, leading to a better prognosis and increase the probability of success in RD treatment.
Transforming growth factor-β-activated kinase-1 (TAK1) is a mitogen activated protein kinase kinase kinase that is involved in diverse biological roles across species. Functioning downstream of TGF-β, TAK1 mediates the activation of the c-Jun N-terminal kinase (JNK) signaling pathway, serves as the target of pro-inflammatory cytokines, such as TNF-α, mediates NF-κβ activation, and plays a role in Wnt signaling in mesenchymal stem cells. Still, the expression of TAK1 in the retina has not been defined. In our study, pathological and immunohistochemical assessments indicate a link between retinal pathology and TAK1 phosphorylation. We observed similar TAK1 expression both in non-obvious and obvious retinal pathologies. However, the phosphorylated form of TAK1 in the segments of retina with obvious pathology was hardly detected compared to its expression in the segments with non-obvious pathology. This finding indicates, for the first time, a possible involvement of TAK1 in human retinal pathologies. Better understanding the expression pattern of TAK1 may serve as a new therapeutic avenue for retinal pathologies.
