Selective suppression of the α isoform of p38 MAPK rescues late-stage tau pathology

BACKGROUND: Hyperphosphorylation and aggregation of tau protein are the pathological hallmarks of Alzheimer's disease and related tauopathies. We previously demonstrated that the microglial activation induces tau hyperphosphorylation and cognitive impairment via activation of p38 mitogen-activated protein kinase (p38 MAPK) in the hTau mouse model of tauopathy that was deficient for microglial fractalkine receptor CX3CR1. METHOD: We report an isoform-selective, brain-permeable, and orally bioavailable small molecule inhibitor of p38α MAPK (MW181) and its effects on tau phosphorylation in vitro and in hTau mice. RESULTS: First, pretreatment of mouse primary cortical neurons with MW181 completely blocked inflammation-induced p38α MAPK activation and AT8 (pS199/pS202) site tau phosphorylation, with the maximum effect peaking at 60-90 min after stimulation. Second, treatment of old (~20 months of age) hTau mice with MW181 (1 mg/kg body weight; 14 days via oral gavage) significantly reduced p38α MAPK activation compared with vehicle-administered hTau mice. This also resulted in a significant reduction in AT180 (pT231) site tau phosphorylation and Sarkosyl-insoluble tau aggregates. Third, MW181 treatment significantly increased synaptophysin protein expression and resulted in improved working memory. Fourth, MW181 administration reduced phosphorylated MAPK-activated protein kinase 2 (pMK2) and phosphorylated activating transcription factor 2 (pATF2), which are known substrates of p38α MAPK. Finally, MW181 reduced the expression of interferon-γ and interleukin-1β. CONCLUSIONS: Taken together, these studies support p38α MAPK as a valid therapeutic target for the treatment of tauopathies

Photoreceptor degeneration, azoospermia, leukoencephalopathy, and abnormal RPE cell function in mice expressing an early stop mutation in CLCN2.

PURPOSE: To determine the molecular basis and the pathologic consequences of a chemically induced mutation in a mouse model of photoreceptor degeneration, nmf240. METHODS: Mice from a G3 N-ethyl-N-nitrosourea mutagenesis program were screened by indirect ophthalmoscopy for abnormal fundi. A chromosomal position for the recessive nmf240 mutation was determined by a genome-wide linkage analysis by use of simple sequence length polymorphic markers in an F2 intercross. The critical region was refined, and candidate genes were screened by direct sequencing. The nmf240 phenotype was characterized by histologic analysis of the retina, brain, and male reproductive organs and by electroretinogram (ERG)-based studies of the retina and retinal pigment epithelium (RPE). RESULTS: Clinically, homozygous nmf240 mutants exhibit a grainy retina that progresses to panretinal patches of depigmentation. The mutation was localized to a region on chromosome 16 containing Clcn2, a gene associated with retinal degeneration. Sequencing identified a missense C-T mutation at nucleotide 1063 in Clcn2 that converts a glutamine to a stop codon. Mice homozygous for the Clcn2(nmf240) mutation experience a severe loss of photoreceptor cells at 14 days of age that is preceded by an elongation of RPE apical microvilli. Homozygous mutants also experience leukoencephalopathy in multiple brain areas and male sterility. Despite a normal retinal histology in nmf240 heterozygotes, the ERG light peak, generated by the RPE, is reduced. CONCLUSIONS: The nmf240 phenotype closely resembles that reported for Clcn2 knockout mice. The observation that heterozygous nmf240 mice present with a reduced ERG light peak component suggests that CLCN2 is necessary for the generation of this response component

Genetically enhancing the expression of chemokine domain of CX3CL1 fails to prevent tau pathology in mouse models of tauopathy

Abstract Background Fractalkine (CX3CL1) and its receptor (CX3CR1) play an important role in regulating microglial function. We have previously shown that Cx 3 cr1 deficiency exacerbated tau pathology and led to cognitive impairment. However, it is still unclear if the chemokine domain of the ligand CX3CL1 is essential in regulating neuronal tau pathology. Methods We used transgenic mice lacking endogenous Cx 3 cl1 (Cx 3 cl1 −/−) and expressing only obligatory soluble form (with only chemokine domain) and lacking the mucin stalk of CX3CL1 (referred to as Cx 3 cl1 105Δ mice) to assess tau pathology and behavioral function in both lipopolysaccharide (LPS) and genetic (hTau) mouse models of tauopathy. Results First, increased basal tau levels accompanied microglial activation in Cx 3 cl1 105Δ mice compared to control groups. Second, increased CD45+ and F4/80+ neuroinflammation and tau phosphorylation were observed in LPS, hTau/Cx 3 cl1 −/−, and hTau/Cx 3 cl1 105Δ mouse models of tau pathology, which correlated with impaired spatial learning. Finally, microglial cell surface expression of CX3CR1 was reduced in Cx 3 cl1 105Δ mice, suggesting enhanced fractalkine receptor internalization (mimicking Cx 3 cr1 deletion), which likely contributes to the elevated tau pathology. Conclusions Collectively, our data suggest that overexpression of only chemokine domain of CX3CL1 does not protect against tau pathology