FKBP51 and Methylene Blue as Neuroprotective Targets

Purpose: Neurodegenerative diseases and neurotraumas typically result in apoptosis of specific neurons leading to the pathology observed during the disease state. Existing treatments target the symptoms instead of preventing the death of these neurons. Although neuroprotective drugs should be useful as a treatment to prevent further loss of neurons, efficacious molecules are lacking. FK506 (tacrolimus), a widely used immunosuppressant drug, has significant neuroprotective and neuroregenerative properties throughout the central nervous system, including the eye. FK506 achieves these properties through interaction with FK506 binding proteins (FKBP), including FK506 binding protein 51 (FKBP51). In this study, we examine the effects of FKBP51 as a neuroprotective agent on a neuronal cell line. Methods: We cultured 661w cell cultures with or without FK506, or stably transfected them with an FKBP51 expression vector. These cells were then exposed to the apoptosis inducing agent staurosporine. Cell viability was determined using a calcein AM/propidium iodide assay. Protein levels and activation of nuclear factor kappa-light chain-enhancer of activated B cells (NF-κB) were determined by western immunoblot analysis. Results: FKBP51 overexpression significantly protected 661w cell cultures from staurosporineinduced apoptosis. FKBP51 overexpression also significantly increased NF-κB p65 protein 35 levels and activated NF-κB p65. FK506 treatment significantly protected 661w neuronal cultures from staurosporine-induced apoptosis. FK506 increased FKBP51, NF-κB p65, and levels of activated NF-κB p65 protein. Conclusions: These results suggest that FKBP51 protects 661w cell cultures from apoptosis induced by staurosporine. Additionally, FK506 protected 661w cell cultures from apoptosis and displayed a mechanism similar to that of FKBP51 overexpression. Both FK506 and FKBP51 appear to act through activation of NF-κB p65 protein, suggesting a common pathway for neuroprotection. These findings suggest that FKBP51 is a compound important to neuronal cell culture survival. FKBP51 may be a potential therapeutic drug target for preventing the neurodegeneration and neurotrauma that occur during neurodegenerative diseases.