Indoprofen upregulates the survival motor neuron protein through a cyclooxygenase-independent mechanism

Abstract

Most patients with the pediatric neurodegenerative disease spinal muscular atrophy have a homozygous deletion of the survival motor neuron 1 (SMN1) gene, but retain one or more copies of the closely related SMN2 gene. The SMN2 gene encodes the same protein (SMN) but produces it at a low efficiency compared with the SMN1 gene. We performed a high-throughput screen of approximately 47,000 compounds to identify those that increase production of an SMN2-luciferase reporter protein, but not an SMN1-luciferase reporter protein. Indoprofen, a nonsteroidal anti-inflammatory drug (NSAID) and cyclooxygenase (COX) inhibitor, selectively increased SMN2-luciferase reporter protein and endogenous SMN protein and caused a 5-fold increase in the number of nuclear gems in fibroblasts from SMA patients. No other NSAIDs or COX inhibitors tested exhibited this activity.

Figure 1

Indoprofen and Related Compounds: Chemical Structures and Maximum Percent Luminescence Enhancement from SMN1and SMN2 Minigene-Reporter Constructs for Treated versus Untreated Cells (A) Indoprofen; SMN1: 44%, SMN2: 184%. (B) Ibuprofen; SMN1: 5.6%, SMN2: −0.8%. (C) Ketoprofen; SMN1: −30%, SMN2: −21%. (D) Suprofen; SMN1: −4.0%, SMN2: −5.0%. (E) Aspirin; SMN1: −5.1%, SMN2: −3.0%. (F) Acetaminophen; SMN1: −17%, SMN2: −9.5%. (G) Isoindolinone; SMN1: 18%, SMN2: 21%. (H) Esterified indoprofen derivatives. R = methyl; SMN1: 38%, SMN2: 72%. R = ethyl; SMN1: 18%, SMN2: 98%. R = isopropyl; SMN1: 18%, SMN2: 70%. The isoindolinone group (“indo”) is shown in orange, and the phenylpropionic acid group (“profen”) is shown in blue. All chiral compounds were racemic mixtures.

Figure 2

Indoprofen Increases Minigene-Reporter Luminescence, SMN Protein Level, and Number of Nuclear Gems (A) C33a cells with a minigene-reporter construct containing either SMN1 (red) or SMN2 (blue) treated with indoprofen. A similar result was obtained in a mouse neuronal cell line NSC34) (data not shown). (B) Aspirin (acetylsalicylic acid), acetaminophen (4-acetamidophenol), and ibuprofen were tested in c33a cells with the same constructs as in (A). (C) Type I SMA patient fibroblasts (13) with no SMN1 have less SMN protein than carrier fibroblasts (14) that have 1 copy of SMN1. NSC34, a mouse neuronal cell line, cells (34) with two copies of SMN1 exhibit an effect that is visually indistinguishable from carrier fibroblasts. (D) Indoprofen-treated cells had a mean 13% increase in SMN protein production over untreated cells (independent, one-tailed t test; n = 17, ν = 15, p < 0.0139) as determined by densitometric analysis. Indoprofen-treated samples and control sample are noted. An initiation factor (eIF-4e) is shown as a loading control. (E) Indoprofen treatment of type I SMA patient fibroblasts (2806) results in an increase in gem count when compared to nontreated cells. Blue circles represent samples within each treatment. Red squares represent the mean number of gems per 100 nuclei within each treatment (0 µM: 1.3; 5 µM: 6.5; and 15 µM: 8.3).