Effect of 308 nm excimer laser irradiation on retinal pigment epithelium cell viability in vitro

Protection of human γD-crystallin protein from ultraviolet C-induced aggregation by ortho-vanillin

Cataract is known as one of the leading causes of vision impairment worldwide. While the detailed mechanism of cataratogenesis remains unclear, cataract is believed to be correlated with the aggregation and/or misfolding of human ocular lens proteins called crystallins. A 173-residue structural protein human γD-crystallin is a major γ-crystallin protein in the human eye lens and associated with the development of juvenile and mature-onset cataracts. This work is aimed at investigating the effect of a small molecule, e.g., ortho-vanillin, on human γD-crystallin aggregation upon exposure to ultraviolet-C irradiation. According to the findings of right-angle light scattering, transmission electron microscopy, and gel electrophoresis, ortho-vanillin was demonstrated to dose-dependently suppress ultraviolet-C-triggered aggregation of human γD-crystallin. Results from the synchronous fluorescence spectroscopy, tryptophan fluorescence quenching, and molecular docking studies revealed the structural change of γD-crystallin induced by the interaction/binding between ortho-vanillin and protein. We believe the outcome from this work may contribute to the development of potential therapeutics for cataract.

A comparative study of UV-induced cell signalling pathways in human keratinocyte-derived cell lines

Ultraviolet (UV) radiation can activate the p38 mitogen-activated protein kinase (MAPK), Jun N-terminal kinase (JNK) and nuclear factor-κB (NFκB) pathways in skin cells. HaCaT cells are widely used as a primary keratinocyte substitute to study these pathways. However, like most squamous cell carcinomas (SCCs), it contains a dysfunctional p53. It is unclear if HaCaT cells activate these signalling pathways similarly to SCC cells (Colo16) or to primary human epidermal keratinocytes (HEK). In this study, the UV activation (UVA, UVB, UVA+B, UVB+A) of p38 MAPK, JNK and NFκB pathways, and TNFα secretion by HEK, HaCaT and Colo16 cells were investigated. The signalling pathway activation was UV-type and dose-dependent with UVB+A radiation inducing a high p38 and JNK activation. HaCaT cells exhibited 2- to 4-fold higher activity of the p38 (771% at 60 min) and JNK (794% at 30 min) pathways following UVB+A radiation than did HEK cells (p38: 367% at 15 min and JNK: 184% at 30 min). While both HaCaT and Colo16 cells did not activate the NFκB pathway, Colo16 cells had a lower p38 and higher JNK activity than HaCaT cells. Irradiated HaCaT cells produced less TNFα (UVB: 3.5 pg/ml), while HEK cells produced the most (UVB: 1,296 pg/ml). When co-exposed to IL1α, irradiated HaCaT had the greatest fold of TNFα release (UVB: 16.2-fold, UVA+B: 8.9-fold and UVB+A: 6.1-fold). The pattern of activation and TNFα secretion of HaCaT cells mirrored that of Colo16 cells. It is likely that the presence of molecular alterations in HaCaT cells may be responsible for its different responses to that seen for HEK cells. The results of this study suggest caution in using HaCaT cells as a substitute for normal keratinocytes in investigating UV-induced cells signalling pathways.

UVB-stimulated TNFα release from human melanocyte and melanoma cells is mediated by p38 MAPK

Ultraviolet (UV) radiation activates cell signaling pathways in melanocytes. As a result of altered signaling pathways and UV-induced cellular damage, melanocytes can undergo oncogenesis and develop into melanomas. In this study, we investigated the effect of UV-radiation on p38 MAPK (mitogen-activated protein kinase), JNK and NFκB pathways to determine which plays a major role in stimulating TNFα secretion in human HEM (melanocytes) and MM96L (melanoma) cells. MM96L cells exhibited 3.5-fold higher p38 activity than HEM cells at 5 min following UVA + B radiation and 1.6-fold higher JNK activity at 15–30 min following UVB+A radiation, while NFκB was minimally activated in both cells. Irradiated HEM cells had the greatest fold of TNFα secretion (UVB: 109-fold, UVA + B: 103-fold & UVB+A: 130-fold) when co-exposed to IL1α. The p38 inhibitor, SB202190, inhibited TNFα release by 93% from UVB-irradiated HEM cells. In the UVB-irradiated MM96L cells, both SB202190 and sulfasalazine (NFκB inhibitor) inhibited TNFα release by 52%. Although, anisomycin was a p38 MAPK activator, it inhibited TNFα release in UV-irradiated cells. This suggests that UV-mediated TNFα release may occur via different p38 pathway intermediates compared to those stimulated by anisomycin. As such, further studies into the functional role p38 MAPK plays in regulating TNFα release in UV-irradiated melanocyte-derived cells are warranted.

VEGF-A165b is cytoprotective and antiangiogenic in the retina

PURPOSE

A number of key ocular diseases, including diabetic retinopathy and age-related macular degeneration, are characterized by localized areas of epithelial or endothelial damage, which can ultimately result in the growth of fragile new blood vessels, vitreous hemorrhage, and retinal detachment. VEGF-A(165), the principal neovascular agent in ocular angiogenic conditions, is formed by proximal splice site selection in its terminal exon 8. Alternative splicing of this exon results in an antiangiogenic isoform, VEGF-A(165)b, which is downregulated in diabetic retinopathy. Here the authors investigate the antiangiogenic activity of VEGF(165)b and its effect on retinal epithelial and endothelial cell survival.

METHODS

VEGF-A(165)b was injected intraocularly in a mouse model of retinal neovascularization (oxygen-induced retinopathy [OIR]). Cytotoxicity and cell migration assays were used to determine the effect of VEGF-A(165)b.

RESULTS

VEGF-A(165)b dose dependently inhibited angiogenesis (IC(50), 12.6 pg/eye) and retinal endothelial migration induced by 1 nM VEGF-A(165) across monolayers in culture (IC(50), 1 nM). However, it also acts as a survival factor for endothelial cells and retinal epithelial cells through VEGFR2 and can stimulate downstream signaling. Furthermore, VEGF-A(165)b injection, while inhibiting neovascular proliferation in the eye, reduced the ischemic insult in OIR (IC(50), 2.6 pg/eye). Unlike bevacizumab, pegaptanib did not interact directly with VEGF-A(165)b.

CONCLUSIONS

The survival effects of VEGF-A(165)b signaling can protect the retina from ischemic damage. These results suggest that VEGF-A(165)b may be a useful therapeutic agent in ischemia-induced angiogenesis and a cytoprotective agent for retinal pigment epithelial cells.