Drug-Repurposing Strategy for Dimethyl Fumarate

Abstract

In the area of drug discovery, repurposing strategies represent an approach to discover new uses of approved drugs besides their original indications. We used this approach to investigate the effects of dimethyl fumarate (DMF), a drug approved for relapsing-remitting multiple sclerosis and psoriasis treatment, on early injury associated with diabetic retinopathy (DR). We used an in vivo streptozotocin (STZ)-induced diabetic rat model. Diabetes was induced by a single injection of STZ in rats, and after 1 week, a group of animals was treated with a daily intraperitoneal injection of DMF or a vehicle. Three weeks after diabetes induction, the retinal expression levels of key enzymes involved in DR were evaluated. In particular, the biomarkers COX-2, iNOS, and HO-1 were assessed via Western blot and immunohistochemistry analysis. Diabetic rats showed a significant retinal upregulation of COX-2 and iNOS compared to the retina of normal rats (non-diabetic), and an increase in HO-1 was also observed in the STZ group. This latter result was due to a mechanism of protection elicited by the pathological condition. DMF treatment significantly induced the retinal expression of HO-1 in STZ-induced diabetic animals with a reduction in iNOS and COX-2 retinal levels. Taken together, these results suggested that DMF might be useful to counteract the inflammatory process and the oxidative response in DR. In conclusion, we believe that DMF represents a potential candidate to treat diabetic retinopathy and warrants further in vivo and clinical evaluation.

Keywords: diabetic retinopathy; dimethyl fumarate; heme oxygenase-1; retina; streptozotocin.

Figure 1

HO-1, COX-2 and iNOS protein expression in the retina of the control group (CTRL), and diabetic rats (STZ) intraperitonially injected with only Vehicle or DMF. Representative Immunoblot of signals detected by HO-1, COX-2 and iNOS antibodies obtained using 32µg of tissue homogenate from whole-retina of non-diabetic (CTRL) and diabetic (STZ) rats following intraperitoneal injection of saline (Vehicle) or DMF (DMF). The bars show the data of three independent experiments. ImageJ software was used to quantify the relative band density. Results are representative of at least three independent experiments (n = 4). Data are expressed as Mean ± SEM * p < 0.05 or ** p < 0.01 vs. CTRL, † p < 0.05 vs. STZ, as determined by One-Way ANOVA followed by Tukey post hoc test.

Figure 2

Localization of HO-1 in the retina of the control group (CTRL), and diabetic rats (STZ) intraperitonially injected with Vehicle or DMF. Representative immunohistochemical staining of HO-1 in retina of non-diabetic (CTRL) and diabetic (STZ) rats following intraperitoneal injection of saline (Vehicle) or DMF (DMF). Retinal layers are indicated as follows: ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform (OPL), outer nuclear layers (ONL), photoreceptors layer (PR) and retinal pigmented epithelium (RPE). The bar graphs show the results of densitometric analyses. Vehicle (white bars) and DMF (gray bars). Results are representative of at least three independent experiments (n = 4). Data are expressed as Mean ± SEM * p < 0.05 vs. CTRL, † p < 0.05 vs. STZ, as determined by One-Way ANOVA followed by Tukey post hoc test.

Figure 3

Localization of COX-2 and iNOS in the retina of the control group (CTRL), and diabetic rats (STZ) intraperitonially injected with Vehicle or DMF. Representative immunohistochemical staining of COX-2 and iNOS in the retina of control animals or diabetic rats (STZ) injected with Vehicle or after DMF treatment. Retinal layers are indicated as follows: ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform (OPL), outer nuclear layers (ONL), photoreceptors layer (PR) and retinal pigmented epithelium (RPE). The bar graphs show the results of densitometric analyses. Vehicle (white bars) and DMF (gray bars). Results are representative of at least three independent experiments (n = 4). Data are expressed as Mean ± SEM *** p < 0.001 vs. CTRL, †† p < 0.01 vs. STZ, as determined by One-Way ANOVA followed by Tukey post hoc test.