Methotrexate carried in lipid core nanoparticles reduces microglial activation and is neuroprotective after ischemic cortical stroke

Methotrexate carried in lipid core nanoparticles (LDE-MTX) is a low toxicity compound effective in reducing inflammation and secondary damage in experimental models of arthritis, atherosclerosis, myocardial infarction, cardiac allograft vasculopathy and other pathological conditions. Nevertheless, whether it is neuroprotective after stroke is unknown. Here, we explored whether LDE-MTX could cross blood brain barrier (BBB) to exert anti-inflammatory and neuroprotecive effects after experimental cortical stroke in rats. Tissue uptake was assessed by injecting radioactively labeled-LDE through the caudal vein into both sham (n=18) and adult Wistar rats submitted to endothelin-1 (ET-1)-induced cortical stroke (n=11). To address possible neuroprotective effects of LDE-MTX after stroke, 10 adult male Wistar rats were randomly allocated in two groups: animals treated with LDE-MTX (1 mg/kg, i.v., n=5) or LDE-alone (i.v., n=5) at 4 hours after stroke induction. Animals were perfused with 0.9% saline and 4% paraformaldehyde at 7 days post-injury. Histopathology was assessed by cresyl violet staining. Mature neuronal bodies (anti-NeuN), astrocytes (anti-GFAP) and microglia (anti-Iba1) were immunolabeled by immunohistochemistry. Scintigraphy technique revealed accumulation of tritiated LDE in different brain regions and in non-neural organs without overt toxicity in both sham and ischemic rats. LDE-MTX treatment induced a 10-fold (1000%) reduction in microglial activation in the ischemic cortex and afforded a 319% increase in neuronal preservation in the ischemic periinfarct region compared to LDE-alone group. There was no effect of LDE-MTX treatment on primary infarct area and astrocytosis. The results suggest that LDE-MTX formulation must be considered a very promising neuroprotective agent for ischemic stroke. Future studies using different concentrations and longer survival times are needed before assessing the suitability of LDE-MTX as a neuroprotective agent for human stroke.