Elevated Hydrostatic Pressure Causes Retinal Degeneration Through Upregulating Lipocalin-2

Abstract

Elevation of intraocular pressure is a major risk factor for glaucoma development, which causes the loss of retinal ganglion cells (RGCs). Lipocalin 2 (Lcn2) is upregulated in glaucomatous retinae; however, whether Lcn2 is directly involved in glaucoma is debated. In this study, retinal explant cultures were subjected to increased water pressure using a two-chamber culture device, and Lcn2 protein levels were examined by immunoblotting. In situ TdT-mediated dUTP nick and labeling (TUNEL) and glial fibrillary acidic protein (GFAP) immunohistochemical assays were performed to assess apoptosis and gliosis, respectively. The neurotoxicity of Lcn2 in the retinal explant culture was determined with exogenous administration of recombinant Lcn2. The Lcn2 protein levels, percentage of TUNEL-positive cells, and GFAP-positive area were significantly higher in retinae cultured under 50 cm H2O pressure loads compared to those cultured under 20 cm H2O. We found that Lcn2 exhibited neurotoxicity in retinae at dose of 1 μg/ml. The negative effects of increased hydrostatic pressure were attenuated by the iron chelator deferoxamine. This is the first report demonstrating the direct upregulation of Lcn2 by elevating hydrostatic pressure. Modulating Lcn2 and iron levels may be a promising therapeutic approach for retinal degeneration.

Lipocalin 2 induces visual impairment by promoting ferroptosis in retinal ischemia-reperfusion injury

“…A recent study using retinal explant cultures in a 2-chamber culture device indicated that LCN2 is directly involved in RGC death ( 40 ). It was further found, by exogenous administration of recombinant LCN2, that elevated LCN2 was neurotoxic to the retinal explant culture.…”

Possible Therapeutic Utility of anti-Cell Adhesion Molecule 1 Antibodies for Malignant Pleural Mesothelioma

“…Total 3 × 10 4 cells of NCI-H28, NCI-H2052, NCI-H2452, MSTO-211H, MESO-1, MESO-1-CADM1, MESO-14, and EHMES10 cells; 8 × 10 4 of MESO-4, MESO-8D, MESO-9 cells; 1 × 10 5 of MESO-12 cells; and 6 × 10 4 of MeT-5A cells were seeded onto a culture insert bottomed with a Matrigel-coated semipermeable membrane (Transwell, transparent PET membrane, pore size 0.4 μm; Falcon, Corning, Tokyo, Japan) placed in a 12-well plate. After 2 days, the cells cultured on a semipermeable membrane were reached 100% confluence and lysed in a buffer containing 50 mM Tris-HCl (pH 8.0), 150 mM NaCl, 1% Triton X-100 and 1 mM phenylmethylsulfonyl fluoride, and after removal of impurities by centrifugation, were subjected to Western blotting analyses as described in our previous report ( Hagiyama et al, 2020 ; Yoneshige et al, 2021 ). Immunoreactive band intensities were quantified using ImageJ software (National Institutes of Health, Bethesda, MD, United States), as described previously ( Mimae et al, 2012 ).…”

Ferroptosis in Glaucoma: A Promising Avenue for Therapy

“…[152,153] Elevated intraocular hydrostatic pressure has been linked to increased Lipocalin-2 (LCN-2) expression, which fosters tissue inflammation and mediates apoptosis and glial cell activation in retinal ganglion cells (RGCs), an effect that can be countered by desferrioxamine. [62] Additionally, NF𝜅B upregulation is closely associated with ferroptosis and inflammatory injury, potentially representing a new target for anti-iron and antioxidant interventions. [156] While inflammation plays a vital role in combating infection, aiding in pathogen clearance and tissue repair, it tends to exacerbate injury and promote tissue sclerosis in non-infectious pathologies associated with glaucoma.…”

“…In DBA/2J mice models with secondary phIOP, a significant increase in lipocalin2 (Lcn‐2) content was observed, correlating with cell apoptosis and gliosis, indicating neurotoxicity. However, these adverse effects were mitigated by the iron chelator deferoxamine, [ 62 ] suggesting the involvement of iron‐dependent cell death. Cutting‐edge research, including in vitro and in vivo experiments with APACG patients, has revealed that retinal iron accumulation occurs abnormally within an 8‐h post‐damage period, mirroring changes in serum levels.…”

“…This effect could be blocked by the application of deferoxamine, confirming the presence of iron‐promoted inflammation in glaucoma. [ 62 ] Disrupted regulation leads to iron accumulation, acting as an active redox agent in the Fenton reaction, producing free radicals and ROS that cause lipid, protein, and DNA damage. [ 155 ] Furthermore, increased oxidative stress also elevates levels of tumor necrosis factor‐alpha (TNF‐alpha) and IL‐6, along with NF‐κB up‐regulation, intensifying the inflammatory state.…”