A Dose-Response Study on Human FGF21 to Inhibit Necrosis, Spectrin Breakdown, and to Increase Intracellular Cold Shock Proteins in Cultured Cortical Neurons Subjected to Oxygen-Glucose Deprivation Injury.

The cold-stress hormone fibroblast growth factor 21 (FGF21) induces a broad spectrum of neuroprotective effects, including a blunting effect on α-II-spectrin breakdown product 145 (SBDP145) levels in models of hypoxia-ischemia (HI). Here, we studied the impact of FGF21 dosing on cell survival and on SBDP145 levels in normothermic male/female cortical neurons in an oxygen-glucose deprivation (OGD) injury model of necrosis. We also explored the impact of FGF21 dosing on cold-shock proteins RNA-binding motif 3 (RBM3) and cold-induced RNA-binding protein (CIRBP) in the OGD injury model. FGF21 concentrations ≥ 100 ng/mL attenuated postinsult increases in SBDP145 levels but had no effect on acute (24 h) or delayed (48-72 h) neuronal survival at normothermia. Further, FGF21 treatment at the highest dose tested (10 µg/mL) induced a sparing effect on postinsult RBM3 levels. This prompted follow-up studies to test if combination therapy with FGF21 and therapeutic hypothermia (TH)-induced synergistic benefits on cell survival. Only intraischemic TH increased 24-h cell survival in our model. FGF21 had no effect on cell survival when combined with intraischemic or posttreatment TH. Finally, we verified that necrosis was the primary mechanism of cell death induced by OGD injury in our model. Pretreatment with calpain inhibitors decreased markers of necrosis, but increased markers of autophagy/apoptosis, and had no effect on 24-h cell survival. In contrast, pretreatment with NMDA receptor antagonist MK801 robustly increased 24-h cell survival. In summary, FGF21 posttreatment (≥ 100 ng/mL) primarily alleviated α-II-spectrin disruption in an OGD model of excitotoxicity-induced necrosis.