Systemic Simvastatin Rescues Retinal Ganglion Cells from Optic Nerve Injury Possibly through Suppression of Astroglial NF-κB Activation

Abstract

Neuroinflammation is involved in the death of retinal ganglion cells (RGCs) after optic nerve injury. The purpose of this study was to determine whether systemic simvastatin can suppress neuroinflammation in the optic nerve and rescue RGCs after the optic nerve is crushed. Simvastatin or its vehicle was given through an osmotic minipump beginning one week prior to the crushing. Immunohistochemistry and real-time PCR were used to determine the degree of neuroinflammation on day 3 after the crushing. The density of RGCs was determined in Tuj-1 stained retinal flat mounts on day 7. The effect of simvastain on the TNF-α-induced NF-κB activation was determined in cultured optic nerve astrocytes. On day 3, CD68-positive cells, most likely microglia/macrophages, were accumulated at the crushed site. Phosphorylated NF-κB was detected in some astrocytes at the border of the lesion where the immunoreactivity to MCP-1 was intensified. There was an increase in the mRNA levels of the CD68 (11.4-fold), MCP-1 (22.6-fold), ET-1 (2.3-fold), GFAP (1.6-fold), TNF-α (7.0-fold), and iNOS (14.8-fold) genes on day 3. Systemic simvastatin significantly reduced these changes. The mean ± SD number of RGCs was 1816.3±232.6/mm2 (n = 6) in the sham controls which was significantly reduced to 831.4±202.5/mm2 (n = 9) on day 7 after the optic nerve was crushed. This reduction was significantly suppressed to 1169.2±201.3/mm2 (P = 0.01, Scheffe; n = 9) after systemic simvastatin. Simvastatin (1.0 µM) significantly reduced the TNF-α-induced NF-κB activation in cultured optic nerve astrocytes. We conclude that systemic simvastatin can reduce the death of RGCs induced by crushing the optic nerve possibly by suppressing astroglial NF-κB activation.

Statin Treatment in Multiple Sclerosis: A Systematic Review and Meta-Analysis

“…An indirect effect through effects on cardiovascular disease cannot be ruled out given that cardiovascular disease in itself has been shown to increase disability progression in progressive MS [64], possibly due to vascular disease-induced peripheral inflammation, which by itself has been linked to brain atrophy [65]. A possible explanation for a more marked effect of statins in neurodegeneration and atrophy in progressive MS than in RRMS may be a more marked effect on monocytes, rather than lymphocytes, as the presence of activated microglia is a pathological hallmark of progressive MS. A possible mechanism of effect of statins on monocyte-induced injury in the CNS has been outlined above [29].…”

“…However, a later murine study indicated a marked effect of statins on RGC survival after damage to the optic nerve. In this study, systemic simvastatin was shown to lead to local changes at the region of the optic nerve in the form of decreased levels of monocyte chemoattractant protein (MCP)-1 (an astrocytal chemokine involved in recruiting monocytes), suppressed numbers of monocytes, decreased upregulation of proinflammatory TNFa, and decreased TNFa-activated nuclear factor (NF)-jB astroglial activation [29].…”

Nitric Oxide Increases the Expression of Aquaporin-4 Protein in Rat Optic Nerve Astrocytes through the Cyclic Guanosine Monophosphate/Protein Kinase G Pathway

“…Astrocytes were isolated from the optic nerves of Wistar rats according to published procedures, with some modifications [25]. In brief, the left optic nerves of 6 rats were crushed under anesthesia with intraperitoneal pentobarbital sodium to make the astrocytes reactive.…”

“…The purity of the astrocytes of cells at passage 3 was determined by immunoreactivity to glial fibrillary acidic protein (GFAP) and flow cytometry (FACS). The results showed that >96% of the cells were GFAP positive, indicating that our cultures were nearly pure cultures of astrocytes [25]. The astrocytes at passages 3-6 were used in this study.…”

P7C3 Suppresses Neuroinflammation and Protects Retinal Ganglion Cells of Rats from Optic Nerve Crush

“…19,24 To quantify the degree of inflammation after the injury in each experimental group, we determined the changes in the expression of CD68 and MCP-1 in the optic nerve by real-time PCR (RT-PCR) on day 7 after the ONC. In addition, the mRNA level of TNF-a was determined because activated microglia and macrophages release inflammatory cytokines.…”