Tumor necrosis factor and nitric oxide production by retinal Müller glial cells from rats exhibiting inherited retinal dystrophy

Abstract

The primary cause of the inherited retinal dystrophy observed in Royal College of Surgeons (RCS) rats is located in the retinal pigmented epithelium, which is unable to phagocytize photoreceptor outer segments. We have demonstrated here that retinal Müller glial (RMG) cells obtained from RCS dystrophic rats and stimulated in vitro with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) accumulated higher levels of tumor necrosis factor (TNF) and inducible nitric oxide synthase (NOS II) mRNA and released in culture supernatants significantly higher amounts of TNF and nitrite compared to cells derived from nondystrophic controls. The TNF and NOS II mRNA expression and TNF and nitrite synthesis induced in RMG cells from both strains by LPS + IFN-gamma was significantly prevented by including transforming growth factor-beta (TGF-beta) in the culture medium. Coincubation of the stimulants with an inhibitor of NOS II, NG-monomethyl-L-arginine (L-NMMA), while inhibiting nitrite synthesis, induced an increase of TNF production in supernatants from RMG cells without increasing TNF mRNA levels. The retinal dystrophy observed in RCS dystrophic rats could result from an abnormal susceptibility of RMG cells form RCS dystrophic rats to produce TNF and NO in response to stimulants. Administration of the immunomodulatory cytokine TGF-beta or inhibitors of NOS II would provide additional research avenues for photoreceptor rescue.

Requirement for Nitric Oxide in Retinal Neuronal Cell Death Induced by Activated Müller Glial Cells

“…We demonstrated previously that treatment of RMG cells from the rat (Goureau et al, 1994 b ; Cotinet et al, 1997) with IFN‐γ in combination with LPS induced the expression of NOS‐2 and a subsequent large release of NO. A marked increase in levels of nitrites, an oxidation end product of NO, in cell culture medium provided evidence that NO production was also induced in RMG cells from C57BL/6×129SvEv mice exposed for 72 h to IFN‐γ and LPS (Table 1).…”

“…In the retina NOS‐2 is expressed in retinal pigmented epithelial, pericytes, and retinal Müller glial (RMG) cells in vitro after stimulation by cytokines (Goureau et al, 1993 a , 1994 a , b ; Liversidge et al, 1994; Sparrow et al, 1994; Chakravarthy et al, 1995; Cotinet et al, 1997). Furthermore, we have reported that NOS‐2 could be expressed in the retina from AIDS patients during cytomegalovirus retinitis (Dighiero et al, 1994) and in the rat retina during endotoxin‐induced uveitis (EIU) (Goureau et al, 1995; Jacquemin et al, 1996).…”

“…In this context, we have used cocultures of retinal neurons with RMG cells from the retina of wild‐type (WT) mice or of mice disrupted for the gene of NOS‐2 to clarify the role of NO in retinal neurotoxicity. Neuronal survival has been tested after treatment of RMG cells with lipopolysaccharide (LPS) and interferon‐γ (IFN‐γ), leading to NO release via the induction of NOS‐2 (Goureau et al, 1994 b ; Cotinet et al, 1997).…”

Cellular responses following retinal injuries and therapeutic approaches for neurodegenerative diseases

“…Some evidence indicates that in proliferative gliosis, Müller cells can promote neuronal cell death through the synthesis and secretion of TNF-a (Cotinet et al, 1997;Giaume et al, 2007;LebrunJulien et al, 2009;Tezel et al, 2001), monocyte chemoattractant protein-1 and NO (Cotinet et al, 1997;Giaume et al, 2007). Excess production of NO by Müller cells and the formation of free nitrogen radicals result in protein nitrosylation, which has toxic effects on surrounding neurons.…”

Chapter 18 Expression of nitric oxide synthase-2 in glia associated with CNS pathology

“…Inherited retinal dystrophy results from accumulation of cellular debris in the subretinal space and visual cell degeneration. Cotinet et al (1997) looked at the retinal Muller (astrocyte-like) cell from dystrophic rats and found that they produce abnormal amounts of TNFa and NOS-2 derived NO. As NO can decrease phagocytosis of photoreceptor segments, which underlies this dystrophy, they suggest that NO may disrupt transmission in retinal neurons.…”