Guanabenz Treatment Accelerates Disease in a Mutant SOD1 Mouse Model of ALS

<div><p>Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by loss of motor neurons. The mechanisms leading to motor neuron degeneration in ALS are unclear. However, there is evidence for involvement of endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) in ALS, notably in mutant SOD1 mediated models of ALS. Stress induced phosphorylation of the eIF2 alpha subunit by eukaryotic translation initiation factor 2-alpha kinase 3 Perk activates the UPR. Guanabenz is a centrally acting alpha2 adrenergic receptor agonist shown to interact with a regulatory subunit of the protein phosphatase, Pp1/Gadd34, and selectively disrupt the dephosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eif2alpha). Here we demonstrate that guanabenz is protective in fibroblasts expressing G93A mutant SOD1 when they are exposed to tunicamycin mediated ER stress. However, in contrast to other reports, guanabenz treatment accelerated ALS-like disease progression in a strain of mutant SOD1 transgenic ALS mice. This study highlights challenges of pharmacological interventions of cellular stress responses in whole animal models of ALS.</p></div

Guanabenz Treatment Accelerates Disease in a Mutant SOD1 Mouse Model of ALS - Fig 1

<p>(A) WST1 absorbance as an indicator of cell viability in a tunicamycin challenge assay using fibroblasts derived from G93A-SOD1 mice. (B) WST absorbance indicator a tunicamycin challenge assay using fibroblasts derived from non-transgenic mice. (C) Tunicamycin EC50s as a function of guanabenz concentration in G93A-SOD1 and non-transgenic mouse fibroblasts.</p

Average percent mouse body weight change after 28 days.

<p>Average percent mouse body weight change after 28 days.</p

Kaplan meier curves of results from efficacy study 4.0 mg/kg qod intraperitoneal injection of guanabenz compared to vehicle control in G93A-SOD1 mice (A) onset of paralysis of male G93A-SOD1 mice, (B) survival of G93A-SOD1 mice, (C) onset of paralysis of female G93A-SOD1 mice, (D) survival of G93A-SOD1 mice, (E) onset of paralysis of all G93A-SOD1 mice, (F) survival of all G93A-SOD1 mice.

<p>Kaplan meier curves of results from efficacy study 4.0 mg/kg qod intraperitoneal injection of guanabenz compared to vehicle control in G93A-SOD1 mice (A) onset of paralysis of male G93A-SOD1 mice, (B) survival of G93A-SOD1 mice, (C) onset of paralysis of female G93A-SOD1 mice, (D) survival of G93A-SOD1 mice, (E) onset of paralysis of all G93A-SOD1 mice, (F) survival of all G93A-SOD1 mice.</p

Guanabenz Efficacy Study Survival Results Summary.

<p>Age of ALS related death in 4.0 mg/kg qod efficacy study and 4.5 mg/kg/day efficacy study.</p

Guanabenz Efficacy Study Paralysis Onset Results Summary.

<p>Age at onset of paresis in 4.0 mg/kg qod efficacy study and 4.5 mg/kg/day efficacy study.</p

Guanabenz Treatment Accelerates Disease in a Mutant SOD1 Mouse Model of ALS - Fig 2

<p>a) Guanabenz plasma drug levels in G93A-SOD1 mice after i.p. bolus injection of 10 mg/kg guanabenz. b) Relative mRNA expression in spinal cord of mice after continuous subcutaneous infusion of guanabenz at 0.45, 1.5, or 4.5 mg/kg or vehicle control. c) Western blot analysis of Bip, Chop, Bcl2, and Ccnd1 in spinal cord samples from mice treated with 4.5 mg/kg/day guanabenz or vehicle control. d) Relative quantitation of Chop protein determined by western blot in 4.5 mg/kg/day guanabenz treated mice or vehicle treated mice.</p