Raquel Castellon

Overexpression of matrix metalloproteinase-10 and matrix metalloproteinase-3 in human diabetic corneas: A possible mechanism of basement membrane and integrin alterations

We have previously described decreased immunostaining of nidogen-1/entactin; laminin chains alpha1, alpha5, beta1,gamma1; and epithelial integrin alpha3beta1 in human diabetic retinopathy (DR) corneas. Here, using 142 human corneas, we tested whether these alterations might be caused by decreased gene expression levels or increased degradation. By semiquantitative reverse transcription-polymerase chain reaction, gene expression levels of the alpha1, alpha5, and beta1 laminin chains; nidogen-1/entactin; integrin alpha3 and beta1 chains in diabetic and DR corneal epithelium were similar to normal. Thus, the observed basement membrane and integrin changes were unlikely to occur because of a decreased synthesis. mRNA levels of matrix metalloproteinase-10 (MMP-10/stromelysin-2) were significantly elevated in DR corneal epithelium and stroma, and of MMP-3/stromelysin-1, in DR corneal stroma. No such elevation was seen in keratoconus corneas. These data were confirmed by immunostaining, zymography, and Western blotting. mRNA levels of five other proteinases and of three tissue inhibitors of MMPs were similar to normal in diabetic and DR corneal epithelium and stroma. The data suggest that alterations of laminins, nidogen-1/entactin, and epithelial integrin in DR corneas may occur because of an increased proteolytic degradation. MMP-10 overexpressed in the diabetic corneal epithelium seems to be the major contributor to the observed changes in DR corneas. Such alterations may bring about epithelial adhesive abnormalities clinically seen in diabetic corneas.

Alu DNA polymorphism in ACE gene is protective for age-related macular degeneration.

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. We report an association between an Alu polymorphism in the angiotensin-converting enzyme (ACE) gene with the dry/atrophic form of AMD. Using the polymerase chain reaction (PCR) on genomic DNA isolated from patients with AMD (n=173), and an age-matched control population (n=189), we amplified a region polymorphic for an Alu element insertion in the ACE gene. The Alu(+/+) genotype occurred 4.5 times more frequently in the control population than the dry/atrophic AMD patient population, (p=0.004). The predominance of the Alu(+/+) genotype within the unaffected control group represents a protective insertion with respect to the human ocular disease, dry/atrophic AMD. This is the first demonstration of an Alu element insertion exerting protective effects against a known human disease.

Oxysterol-induced toxicity in R28 and ARPE-19 cells.

Studies have shown an intimate relationship between cholesterol and retinal diseases; we examined the effects of cholesterol oxides on cultured cells. Using the rat retinal precursor cell line R28 and the human RPE cell line ARPE-19, we investigated the potential cytotoxicity of cholesterol oxides. Cultured R28 and ARPE-19 cells were treated with either 25-hydroxycholesterol and 7-ketocholesterol (0–50 µg/ml). Cell viability was determined by the WST-1 colorimetric assay. Production of reactive oxygen intermediate (ROI) was assessed by a fluorescent probe–based assay (2′,7′-dichlorodihydrofluorescein diacetate [H2DCFDA]). To detect the presence of apoptosis, DNA fragmentation gel analysis and Hoescht nuclear staining were performed. Both cholesterol oxides tested were toxic in a time- and dose-dependent fashion to the two cell lines used in this study. Treatment of R28 cells with either 25-hydroxycholesterol or 7-ketocholesterol at a concentration of 25 µg/ml resulted in greater than 50% loss of cell viability after 24 h. ARPE-19 cells were slightly less affected, with a loss of cell viability of approximately 20% and 40% after 24 h-exposure of 25-hydroxycholesterol and 7-ketocholesterol, respectively. DNA fragmentation and chromatin condensation demonstrated apoptotic events occurring in 7-ketocholesterol–treated cells. The fluorescent assay for ROI production showed that after an hour of exposure to 7-ketocholesterol, R28 cells responded with increased levels of ROIs, whereas no immediate production of ROIs were detected with treated ARPE-19 cells. These in vitro findings provide evidence that cholesterol oxides can directly damage cultured retinal and RPE cells. The oxysterol-induced oxidative stress in these cells may be a factor in the pathology of retinal degenerative diseases.

Demystifying the ACE polymorphism: from genetics to biology.

The angiotensin converting enzyme (ACE) I/D polymorphism has been one of the most studied genetic systems. It comprises hundreds of reports and a myriad of disease associations, including cardiovascular, metabolic, immune, cancer, aging, neurodegenerative and psychiatric diseases. Despite the wealth of information on the ACE polymorphism and the well-known functions of ACE, several questions arise. Why does the ACE polymorphism associate with so many diseases? What is its function? In this review, we summarize the current information on the ACE polymorphism and explain its function in the context of cell survival. We also provide a model to understand its role in biology and disease at the organism and population levels.

Nerve growth factor regulates neuroectodermal tumor cell responses to mitogenic growth factors

Previous studies showed that nerve growth factor (NGF) decreases the proliferation of neuroectodermal tumor (NET) cells (C‐1300 and Neuro2A murine neuroblastoma, PC12 rat pheochromocytoma) within 5–7 days in a dose‐dependent manner. This effect is regulated by the concentration of serum in the culture medium. Therefore, we hypothesized that NGF exerts its antimitogenic activities by interfering with the proliferative action of other growth factors. We studied the effects of short‐term vs. long‐term as well as endogenous vs. exogenous NGF on NET cell proliferation in response to various mitogenic growth factors. Retrovirus‐mediated transfer of the β‐NGF gene into NET cells activated TrkA and consistently decreased their proliferative responses to insulin‐like growth factor (IGF)‐I, IGF‐II, fibroblast growth factor‐2, and epidermal growth factor (EGF), down‐regulating EGF and IGF‐I binding sites. It also decreased tyrosine phosphorylation of ERK‐1, STAT3, and EGF or IGF receptors after treatment with IGF‐I or EGF. Long‐term incubation of NET cells with NGF mimicked the responses induced by β‐NGF gene transfer, albeit in a reversible manner. Short‐term NGF treatment augmented the proliferative responses to IGF‐I or EGF by enhancing cell survival. It also increased tyrosine phosphorylation of signal transducing proteins after exposure to IGF or EGF, an effect opposite to that of long‐term NGF treatments. Hence, long‐term NGF exposure in vitro might better reproduce the effects of NGF in vivo than short‐term treatments. Only long‐term exposure to NGF decreased the responses of NET cells to mitogenic growth factors by down‐regulating their receptors and attenuating signal transduction events required for cell proliferation. These results suggest that NGF could exert similar actions on cellular responses to growth factors in vivo.