Small-molecule Klotho enhancers as novel treatment of neurodegeneration

Abstract

The majority of neurodegenerative diseases have an important age component, and thus, understanding the molecular changes that occur during normal aging of the brain is of utmost relevance. In search for the basis of the age-related cognitive decline found in humans, monkeys and rodents, we study the rhesus monkey. Surprisingly, there is no loss of neurons in aged monkey brains. However, we reported white matter and myelin abnormalities in aged monkeys, similar to those observed in Alzheimer's disease and multiple sclerosis patients. In a microarray analysis comparing young and old monkey white matter, we discovered that Klotho is downregulated in the aged brain. We then asked whether there is a connection between the age-related cognitive decline, myelin abnormalities and Klotho downregulation. If such a connection is found, compounds that upregulate Klotho expression could become of therapeutic interest for the treatment of multiple sclerosis, and perhaps even Alzheimer's disease.

Figure 1. Sagittal view of Klotho mRNA distribution in mouse brain demonstrated by in situ hybridization

Note that the highest expression is in the choroid plexus, followed by hippocampal neurons, especially those in CA1. Reproduced from [102].

Figure 2. Compounds 21 and 25 induce Klotho mRNA expression

(A) The increase in luciferase signal is specific to KL promoter activation. (B) Time course of KL promoter activation in HEK293 cells stably transfected with a KL promoter-luciferase construct. q-PCR analysis of KL expression induced by the compounds in (C) primary hippocampal neurons and (D) in primary astrocytes. KL: Klotho.

Figure 3. Concentrated endogenously secreted Klotho and compounds 21 and 25 rescue co-cultures of oligodendrocyte precursor cells and astrocytes from TNF-α-induced cytotoxicity

Cells were pretreated with compounds for 24 h or with concentrated Klotho for 4 h and then exposed to 50 or 100 ng/ml of TNF-α for an additional 24 h. Cell cytotoxicity was assessed by CellTiter-Glo^® (Promega).